MODELING AND STOCHASTIC SIMULATION OF ...

· Delft University of Technology Department of Chemical Engineering

MODELING AND STOCHASTIC SIMULATION OF THE REACTIONS AND ABSORPTION OF NO x IN WATER

.'.

Thesis by: Michiel Spoor Laveibos 177 2715 RK Zoetenneer The Netherlands

24th august 1992 TU Delft

Directed by: Dr.Ir. P.l.T. Verheijen, Ir. V. de Leeuw (AspenTech) and under the responsibility of the section Process Integration.

Absorption of NO x in Water

Summary This work discusses the absorption of NOX in an absorption column. This is of relevance to the production of nitric acid and the fertilizer industry. Non-reacted NOx, released with stack-gases, plays an important role in environmental pollution problems. NOX absorption characterizes itself as a very complex system that is difficult to describe or to model. Up to forty equilibrium reactions exist and describe the system together with some irreversible kinetic reactions. Mass and heat transport limitation plays an important role in this reaction model. This complex model results in a complex simulation of a NOx absorption column. Simulations have been done with a simplified model (only four reactions) and an enhanced model (with eight reactions and two more components). This enhanced model requires extra parameters to describe the physical and chemical properties of the components and reactions that were added to this model. The parameters that were needed in the enhanced model were found in literature, calculated with appropriate correlations, or some had to be guessed. Introducing uncertain parameters to the model meant that uncertainties were added to the results. A method of simulation has been evolved, called stochastic simulation, which enables to translate the uncertainties in model parameters to uncertainties in the results. Several simulations have been done with the flowsheeting program ASPEN PLUS, where different classes of parameters have been varied to study their effects on the results. It is found that uncertainties in reaction parameters are less important then uncertainties in pure component parameters and thermodynamic parameters. If operating parameters are stochastic (like temperatures, pressures and feed compositions) then uncertainties in model parameters have no or little effect, taking realistic estimates for these uncertainties. In this thesis the modeling of NOx absorption and the concept of stochastic simulation is discussed. It is found that stochastic simulation is a useful tool in chemical process engineering. Also, recommendations are made to enhance the simulation model of NOx absorption. A good knowledge of the model and its uncertainties gives the possibility to optimize absorption column performance and design.

Summary

page iii


Summary

page iv

Absorption of NOx in Water

Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 What is NOx? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1.2 The production of nitric acid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . " 1.3 Modeling absorption columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Problem identification for modeling NOx absorption ................

1 2 3 6 6

2 Reactions of NOx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.1 Reactions of NOx in the gas phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Acid-dissociation Equilibria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.3 Heterogeneous equilibria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.4 Aqueous-phase equilibria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.5 Mass transfer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2.6 Simulation models .......................... . . . . . . . . . . . . ..

9 9 11 12 14 14 16

3 Reactive absorption with ASPEN PLUS ........ . . . . . . . . . . . . . . . . . . . . . . . 3.1 The physical properties of NOx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3.2 The electrolyte NRTL model ......................... , ..... " 3.3 Modeling a reactive absorption with ASPEN PLUS ................. 3.4 Modeling NOx absorption with ASPEN RATEFRAC ............... ,

19 20 25 27 32

4 Stochastic simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 4.1 Stochastic process simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , 4.2 Incorporating stochastic simulation in ASPEN PLUS ................ 4.3 Stochastic simulation of NO x absorption . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Other uses of stochastic process simulation . . . . . . . . . . . . . . . . . . . . . ..

33 33 36 38 40

5 Results of the simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 The standard simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5.2 The stochastic simulations ............... . ................... 5.3 Convergence characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,

43 43 47 S3

6 Conclusions and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Modeling of NOx absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6.2 Stochastic versus standard simulation .. . . . . . . . . . . . . . . . . . . . . . . . " 6.3 Recommendations for work to be done ...... '. . . . . . . . . . . . . . . . . . ..

SS 56 57

Literature ....... .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . List of symbols ................... .. ........ .. .................. , List of figures .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. List of tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Appendixes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

59 63 65 67 69

Contents

S5

page v


Contents

page vi


1 Introduction

Absorption of NO x gas in aqueous solutions plays an important role in several processes. First, in the manufacture of nitric acid and secondly, the r~moval of NOx from the flue gases that have received considerable attention due to strict regu1ations on a clean environment. Absorption of NOx gases is probably the most complex case in all absorption operations. Joshi (1985) gives therefore the following reasons: The NO x gas is a mixture of several components, all nitrogen oxides. The absorption of NO x gas in water results in two oxyacids, nitric acid and nitrous acid. Several equilibria exist between the nitrogen oxides and oxyacids, both in liquid and gas phase. The number of equilibrium reactions is more then forty. Absorption and desorption occur simultaneously. Further the absorption is accompanied by chemical reaction and the desorption is preceded by chemical reaction. All kinds of reactions undergo .in this system. They occur in both phases and include parallel, reversible and consecutive reactions. The knowledge of physical and chemical data such as diffusivity, solubility, equilibrium and rate constants are still incomplete. In this thesis a mathematical model will be examined for the absorption and reactions of NO x , based on the current knowledge about the subject in literature. This model will be restricted by the limitations that the simulation program (here ASPEN PLUS) possesses. Nitric acid is a very common chemical compound and numerous companies produce this acid. Because the model of NO x absorption is so complex, there is no adequate simulation model available yet to simulate this process with a commercial flowsheet simulation program. Venkataraman (1990) introduced an ASPEN PLUS simulation model for the absorption of NO x , but in this model the reactions are simplified and the results of this simulation are difficult to verify with experimental data. With Valentijn de Leeuw from Aspen Technology there is decided to derive a model for the absorption of NO x in water and to simulate this with ASPEN PLUS.

Introduction

page 1

Absorption of NO x in Water In this first chapter some background information will be provided on the subject of NOx

absorption. The nitric acid production will be discussed, and finally a problem identification and definition will be given. Chapter two will describe the reactions and reaction equilibria that the NOx absorption system describes. It also gives some information on the mass transport limitations between the vapor and liquid phase. Three reaction models that can be simulated will be presented here. Chapter three describes the flowsheet simulation program ASPEN PLUS and how it is used to simulate reactive absorption. Chapter four will introduce a rather new concept in process simulation, stochastic simulation. The purpose of stochastic simulation and the implementation is described here. Finally the results of the (stochastic) simulations will be presented, and the last chapter discusses and comments the results and will give· some recommendations for further research on this subject.

1.1 What is NO X ? According to the definition given in Ullmann (Thieman, 1991) NO x is defined as the compound of oxygen with nitrogen. Because nitrogen can exist in several oxidation states (+ 1 to +6) numerous compounds of nitrogen oxide exist. The oxides known are: (+1) (+2) (+3) (+4)

(+5)

(+6)

N 20

NO

N 20 2 N 20 3

N0 2

N 20 4 N 20 S

N03

N 20 6

dinitrogen monoxide Oaughing gas), nitrogen monoxide, dinitrogen dioxide, dinitrogen trioxide, nitrogen dioxide, dinitrogen tetroxide, dinitrogen pentoxide, nitrogen trioxide, dinitrogen hexoxide.

Very little is known of N03 and its dimeric form N20 6. In the case of NO x absorption not all compounds are of equal importance. In this project only NO, N02, N20 4 and N20 3 are considered so NOx in this thesis will denote those four compounds.

Introduction

page 2

Absorption of NOx in Water For the simulation model more compounds are relevant. These include of course the oxyacids: nitrous acid, nitric acid, nitrate, nitrite, hydrogen-ion, and further: H20 02 N2

water, oxygen, nitrogen.

Nitric acid is classified as a hazardous substance. It reacts with and causes spontaneous ignition of organic substances. Its MAC value (Maximum Allowable Concentration) is 10 ppm. At room temperature nitrous gases are released from nitric acid. Nitrous acid is toxic because it decomposes to form nitric acid and nitrogen monoxide. Nitrogen monoxide does not have irritating effects. It reacts, however, with hemoglobin and can cause possibly death. Nitrogen dioxide is an irritant gas. Its MAC value is 5 ppm. Inhalation of a lethal dose of 200 ppm of nitrogen dioxide may result in death (Thieman, 1991).

1.2 The production of nitric acid One of the major applications for NOx absorption is the production of nitric acid. Nitric acid is a very important industrial compound. Figure 1 shows the top ten of industrial important chemicals where nitric acid ranks tenth. Originally sodium nitrate was used to produce nitric acid. When at the beginning of the 20th century the sodium nitrate reserves were thought to be exhausted, new processes were

developed: Production of nitrogen monoxide by reacting atmospheric nitrogen and oxygen at temperatures higher then 2000 QC (direct process). Production of ammonia by hydrolysis of calcium cyanamide under pressure. Production of ammonia from nitrogen and hydrogen. The last process, ammonia produced from nitrogen and hydrogen (Haber-Bosch process) is still used as a feedstock for nitric acid production. The most critical part in nitric acid production is the combustion of ammonia with oxygen (Ostwald process). This catalytic oxidation of ammonia, used to produce nitrogen monoxide, is: 4 ~ + 5 02 .... 4 NO + 6 ~O .

Introduction

(1)

page 3


Chemicals top 1 0 Top ten of chemicals in 1 9 gland 1 9 6 9 H2S04

N2 02

C2H4 NH3

NaOH

-

----

-

-

~

11-

--

C2H6 -~ Cl2

Soda HN03

1991

-

o

5

1969

10 15 20 25 30 Production in mln kg/year in the VS

35

40

Figure 1 Top ten of industrial chemicals. As can be seen. nitric acid ranks loth.

The next step in the acid production is the oxidation of nitrogen monoxide: (2)

and the last step is the absorption of the nitrogen oxides to obtain nitric acid: 3 N02 +

~O

... 2 HN03 + NO .

(3)

These steps can be implemented in several ways. There are the low pressure, medium pressure, high pressure and dual pressure processes. Although the low pressure plants are not longer built, the other processes still are. The choice between those processes is based on plant capacity, energy costs and environmental aspects. In Europe the dual pressure process is more popular. The combustion process takes place at medium pressure (4-6 bar) and the absorption at high pressure (9-14 bar). Figure 2 shows a simplified flowsheet of a dual pressure nitric acid production plant. This process combines the favorable economics of medium pressure combustion with the efficiency of high-pressure absorption. Dual pressure processes are used when large capacities are needed. Single train plants can produce up to 2000 ton of nitric acid per day.

1ntroduction

page 4

Absorption of NO x in Water High-pressure steam

d

Ammon~ia_ _--1~=r-

Process water

Low-pressure steam _ _" , - - _ - - - J ~

Air

Tail gas

L--'------Demineralized water

FIpre 29. Simplified flow sheet of a dual-pressure process a) Ammonia evaporator: b) Ammonia stripper: c) Ammonia gas IiIter: d) Ammonia preheater: e) Ammonia-air mixer: I) Air filter: g) Air compressor: h) Reactor: i) Waste-heat boiler: j) Tail-gas preheater Ill: k) Economizer: I) Tail-gas I'fdteater 11: ml Feedwater preheater: n) Cooler-condenser I: 0) Cooler-condenser 11 : p) Nitrous gas compressor: q)Tail-gas preheater I; r) Cooler-condenser Ill: s) Absorption tower : t) Tail-gas expansion turbine: u) Feedwater tank with cleaerator: V) Steam drum: w) Steam turbine : Xl Steam turbine condenser: y) Bleacher

Figure 2 Flowsheet of a dual pressure nitric acid plant_ Adoptedfrom Thieman (1991)-

Industrially produced mtrIc acid contains 50-70 wt % HN03, which is high enough for fertilizer production_ Nitric acid needed for nitration processes in organic chemistry calls for higher HN03 concentrations (98-100%). However, it is not possible to distill nitric acid because it fonns an azeotrope with water (68.4%, 1 atm). To produce pure nitric acid, nitrous gases can be reacted with azeotropic acid to fonn a concentrated acid that can be distilled in pure nitric acid and azeotropic acid. The azeotropic acid can be completely recycled. Waste-water problems will be overcome by appropriate design of the nitric acid plant. A more serious problem is the environmental pollution with NOx gases. Some stack gases of older plants contain up to 3000 ppm NO x. In the last decade regulations have been issued to restrict the NOx concentrations of stack gases. The concentration of NO x has to be lower then 240 ppm and further on the stack-gas may be discharged only if colorless. A practical limit used is a NOx concentration lower then 200 ppm (Thieman, 1991). To improve NO x absorption and especially to purify tail gases, a number of methods have been developed_ Some methods use scrubbing solvents other then water. These include ammonia, hydrogen peroxide or a solution of urea and nitric acid in water. Other methods to reduce the NO x content in stack gases are adsorption by molecular sieves and catalytic reduction of NO x. All methods reduce the NO x content to approximate 50 ppm.

Introduction

pageS


1.3 Modeling absorption columns Several aspects for NO x absorption tower design have to be noted. The tower can be a packed column or a plate column. Most modem absorption towers have sieve plates. Figure 3 is an example of a packed absorption column. To handle packed columns in a process simulation program, the program uses equivalent tray-heights. The equivalent tray-height is the height of the package with the same results as would be obtained with one equilibrium tray for tray columns. For sieve tray columns the tray height increases while NOx content decreases. This is because the NOx reacts slower when its content decreases. Acid formation chiefly takes place at the lower third of the column, while NO x is reduced in the upper twothirds. As a result most of the heat must be withdrawn in the lower third. The top of the column contains a demister to remove the entrained acid droplets.

it ~

coolant

I

I

tail gas ~ water

I

I

I

coolant

coolant

m

iIII2\XI

~

m

NOXvapor

nitric acid Figure 3 Example of a packed NOx absorption tower

1.4 Problem identification for modeling NOx absorption One of the goals of this project is to define a model for the reactions and absorption of NOx in water. As a starting point a model has been provided by Aspen Technology (Venkataraman, 1990). Objective for this project was to: enhance this model by introducing extra components and adding extra reactions, take account for mass transport limitations and use the ASPEN PLUS program RATEFRAC to simulate this model, verify the results of the simulations with experimental data and use this data to reconsolidate the NOx absorption model, optimize column performance by increasing nitric acid concentration and decreasing stack gas NOx content.

Introduction

page 6

Absorption of NO x in Water During this project some extra problems appeared. Starting with the first simple model, some components and reactions had to be added. The pure component data for these extra components were difficult or even impossible to find and in some cases had to be estimated. Also kinetic data for these reactions and thermodynamic binary parameters were uncertain. Therefore additional goals have been defined: Try to find pure component data, thermodynamic binary data and reaction data for the components added to the simulation model. If not found use a correlation model to estimate these properties else estimate the properties by comparing them with properties of other components. Evolve a method to translate these uncertainties in model parameters to uncertainties in results. To accomplish this, a new method (new in process simulation) has been evolved called stochastic simulation. This provides the tool to translate process model uncertainties to uncertainties in simulation results. This research project has been done in order to graduate on the subject of this thesis. The research took place at the section: Process Integration at the Department of Chemical Engineering at Delft University of Technology.

Introduction

page 7


Introduction

page 8


2 Reactions of NO x

The reaction system of the NOx reactions and absorption in water is very complex. Joshi (1985) reports more then forty equilibrium reactions that occur both in liquid and vapor phase. In this chapter the reactions that play an important role in NO x absorption, are outlined. Three models are given who can be used to simulate this absorption.

2.1 Reactions of NOx in the gas phase The nitrogen monoxide gas enters the absorption column at the bottom. Oxygen and nitrogen and other nitrogen oxides enter the column with the monoxide. SeveraJ reactions occur in the gas phase. It is believed that the rate limiting reaction is the oxidation of nitrogen monoxide (Thieman, 1991):

(4) Several equilibrium reactions occur in the gas phase. The most important are the dimerisation of nitrogendioxide:

(5) the formation of nitrogen trioxide:

(6) the formation of nitrous acid: (7)

Reactions of NOx

page 9

Absorption of NOx in Water and the fonnation of nitric acid: 3 N02 +

~O

.. 2 HN03 + NO .

(8)

Table 1 gives a detailed description of all equilibrium reactions in the gas phase. To describe the kinetics of (4) a third order rate equation is used (Thieman, 1991): le, 2 r = RT PNOPOz

where r

i

T

P

(9)

[kmol m- 3 s-l], = reaction rate constant [atm-2 s-l], = universal gas constant [m3 atm kmor l K- l ], = temperature [K] and = partial pressure [atm].

= reaction rate

The rate constant for reaction (4) is given by:

log le, = 652.1 - 1.0366 . T

(10)

This reaction goes faster at low temperature then at high temperature. Bodenstein (1922) assumed that the oxidation occurred in two steps:

2 NO .. (NO)2 (NO)2 + 02 .... N20 4 .. 2 N02 .

(11)

Because the dimerisation of nitrogen oxide is exothermic, the equilibrium of the first reaction of (11) will be to the left at higher temperatures. The equilibrium for reaction (5) is reached very quicldy and the dimerisation rate is virtually independent of temperature. Hoftyzer (1972) gave the following equation for the equilibrium constant:

K,

= fPH-O = O.698xlO-9 exp (6866) T .

(12)

PNO.z

= equilibrium constant [atm-l]. The same equilibrium constant can be written for dinitrogen trioxide fonnation: (13)

Jethani (1992) reported the equilibrium constant for the formation of nitrous acid in the gas phase:

Reactions of NO x

page 10


Table 1 Gas-phase equi/ibria involving nitrogen oxides and oxyacids (Adapted from Joshi (1985)).

1.38 10. 2 [-] 3.18 [-] 2 HN03 /

P

PN2oSPiuo

2

Kp

=

PIIlG

= 1.8S01xlo-7

PHo PNOz PHp

exp (4723) ,

(14)

T

and for the fonnation of nitric acid in the gas phase: (15)

2.2 Acid-dissociation Equilihria Nitric acid and nitrous acid dissolves in water where it is ionized. The following equilibria can be written: (16)

(17)

Reactions of NO x

page 11


The equilibrium constant for the nitric acid dissociation is defined by: ~.~-

(18)

Koq = - - ~o,

= activity for component i. The value for Keq for the acid dissociation is 15.4±2.1 kmole/m3 (Joshi, 1985). The same can be written for the dissociation of nitrous acid: (19)

(20)

with a value for the Keq of about 6x 10-4 kmole/m3. It has been found that the value for the equilibrium constant for the dissociation of nitrous acid strongly depends upon the pH of the aqueous solution. Because HN02 is a weak acid it doesn't dissolve in water as well as nitric acid does. So the formation of nitrous acid in the gas phase plays a more important role then its formation in the liquid phase.

2.3 Heterogeneous equilibria If you consider equilibrium (7), (19) and (20) then you can write down the following overall reaction:

NOCg) + N02 Cg) +

~o(g)

... 2H + + 2N02-

•

(21)

The equilibrium constant can be computed by multiplying the equilibrium constants of the corresponding three reactions. Several equilibria are listed in table 2 and values are given for dilute aqueous solutions. An important parameter in describing heterogeneous reactions is the Henry's-law constant defmed as:

.

H =lim. P, ' %.-0 x,

(22)

= Henry's-law constant [m3 atm/kmol],

= partial pressure of component i [atm] and = concentration of component i [kmol/m3].

Reactions of NO x

page 12

Absorption of NOx in Water Table 2 Heterogeneous equi/ibria (Adapted from Joshi (1985». Superscript W means that water is involved in the reaction.

3.28 lO-s

3.56 10 1 6.141O-S 4.25 1017 2.27 1011

4.78

105

1.26

102

6.98 104 2.38

102

3.01 10 1

a in [kmole/m3], p in [atm]

The Henry's-law constant is often taken constant for low concentrations and a small temperature region. When the following reaction is considered (Thieman, 1991): (23)

Its kinetics can be described by: 4

k

CHNo"

(24)

2

CNO

Reactions of NO x

page 13


where the rate constant k is defined by:

log k

6200 T

= --- +

(25)

20.1979 .

A value for the Henry's law constant for NO is given by Emig (1979) and is 518 m3atm/kmol.

2.4 Aqueous-phase equilihria The large number of components and reactions in the gas phase suggests that there is also a complicated reaction scheme in the liquid phase. In principle all the reactions in the gas phase also happen in the liquid phase and vice versa (except the ionic reactions). The main route for the formation of nitric acid is according to the following reaction: (26)

The dinitrogen tetroxide dissolves in the water and reacts with the water to produce nitric acid and nitrous acid. The nitric acid is a strong electrolyte and dissolves into H30+ and N03-. Nitrous acid then dissociates to nitric acid, water and nitrogen monoxide. Because the nitrogen monoxide partly dissolves, it will be transported to the vapor phase. Its kinetics is described in (24) and (25). In Thieman a relation for the first order kinetics of (26) is given: (27)

A complete reaction scheme is given by Joshi (1985) and is summarized in table 3.

2.5 Mass transfer Many studies have been done on the subject of mass transfer of NOx in aqueous systems. A variety of mechanisms have been proposed depending on the gas composition and acid concentration. It is believed that the physical absorption of dinitrogen tetroxide to the aqueous phase is the rate limiting step in nitric acid formation. The rate of transport depends primarily on the N0 2-N20 4 equilibrium (Thieman, 1991): (28)

= absorption rate [kmoVm2/s], = gas-side mass-transfer coefficient of component i [m/s],

= partial pressure of component i in the bulk gas [atm] and = partial pressure of component i in the interface [atm].

Reactions of NOx

page 14


Table 3 Aqueous phase equilibria. Adaptedfrom Joshi (1985).

4.52106

H

The following equation can be written for the absorption rate of dinitrogen tetroxide (Thiemann, 1991): (29)

where k D

= rate constant [/s] and = diffusion constant [m/s2].

Several correlations have been developed for the mass transfer coefficient. Miller (1987) found for sieve trays:

for

WHNO, > 0.05

1500 .... ,2 ----2.7648-39.614WHNO +181.98wHNO T 3 3

-429.65W~3 +496.99w'HNO3 -223.24WHNO3 and for

(30)

,

WRNa < 0.05

1500 -r -0.2548 - 315.73 2

WHNo, 3

+92S6.2WHNO3 -223.24WHNO3 where W H

= mass fraction and

= Henry' s-law constant [m3kPa/kmol].

Reactions of NO x

page 15


_ 1

and for bubble-cap trays:

1500

HN"o.

-4.3790-23.279WBNO

Jk DN"o. = e T '

+130.42w~1

(31)

, .

-370.87~BNo, +486.94~HNO, -236.54YBNo,

2.6 Simulation models Hoftyzer (1972) fonnulated an absorption model for the NO x absorption with the main components and reactions. Figure 4 summarizes Hoftyzer's model.

iT

,,

,, I~--~:--------~.

:

--------7-----.~ N204----!~~ N204+H20~HN03+HN02!1

r

N02

~

N02

i~

2N02+H20

-'HNba.HN02~

i

i"

HN03

! 3HN02---. HN03+2NO+H20 ! ~

1At02+NO .~---:---~ NO+N02+H20 :

.ii

2HN02--~-~_ _•

NO+N02

11

N203 ------+-------:---.... ~ N203

gas-bulk

interface

+. N203+H2O2HN02 1

nquid-film

_'-----.J

liquid-bulk

Figure 4 Absorption model for the formation of nitric acid, according to Hoftyzer and Kwanten. Reproducedfrom Hoftyzer (1972). This model describes the absorption problem with the most important reactions. It takes into account for the mass transfer limitation by defining a gas-bulk, interface, liquid-film and liquid bulk phase. Heterogeneous reactions take place at the interface, the fast liquid phase reactions take place in the liquid mm and the slow liquid phase reactions occur in the liquid-bulk phase. The gas phase is homogeneous. This model further will be denoted as the Hoftyzer model.

Reactions of NO x

page 16

Absorption of NO x in Water Because the ASPEN RADFRAC unit operation module does not have the possibility to use a mass transport rate based approach, the model used for simulation with ASPEN PLUS only has a gas and liquid bulk: phase. The original ASPEN PLUS model (further denoted as the ASPEN model) for the simulation of NOx absorption incorporates some simplifications (Venkataraman, 1990). Most notable in this model is that the nitric acid is fonned in the vapor phase. Also, the nitric acid dissociation has been taken into account. Figure 5 shows the ASPEN model. The ASPEN model has been extended and most of the reactions from the Hoftyzer model have been used to define the Enhanced model. Figure 6 shows the Enhanced model. It does not describe liquid-film and interface reactions, but it does define nitrous acid and dinitrogen trioxide as reacting compounds.

N204

~i

N02

r

'h02+NO 3N02+H20

l.i

2HN03 .~_ _ _ _ _ _ _ _--:--.~ HN03 HH+ + N03-

gas-bulk

liquid-bulk

Figure 5 Basic model for the simulation of NOx absorption (ASPEN model).

Reactions of NO x

page 17


iT

I

~

r

N02

..

r 3H~

.~------~~N204+H20 ...1 1 H l t l + H+ + 1102-

HN03

1

HN03+2NO+H20

~+N04~~-----------------7--------------------~~~------~1 NQ+N02+H20

Ii

2HN~.~

'-

...

__________________+-__________________

~

NO+N02

ti

N203 .4- - - - - - - - -.........~ N203

gas-bulk

liquid-bulk

Figure 6 Enhanced model for the simulation of NOx absorption (Enhanced model).

Reactions of NOx

page 18


3 Reactive absorption with ASPEN PLUS

ASPEN PLUS is an advanced steady state flowsheeting program. It got its power from the flexible way of defIning your process, a comprehensive set of thermodynamic models and a complete set of unit operations. It also has possibilities of optimizing your flowsheet and performs sensitivity studies. You can add your own thermodynamic or unitoperation models by writing user subroutines in FORTRAN. ASPEN PLUS runs on several platforms, from PC's to supercomputers and under different operating systems like MS-DOS, VMS or unix. There are some disadvantages, such as its difficult user interface and the 'feeling' that you easily can get 'lost' in the program, lacking information on all the possibilities in it. For the different available flowsheet simulators (like ChemCad U, PRO/ll, Hysim, ASPEN PLUS), ASPEN PLUS is the most adequate for simulating the NOx absorption because of its capability to handle reactions in absorption and distillation columns. For this problem the flowsheet simulator must contain: a complete set of physical properties for all the components (02' N2, NO, N0 2, N20 3 , N20 4 , H20, HN02, HN03 , H+, N02- and N03-). Thermodynamic models to describe the correct vapour-liquid behavior. These models are: an equation of state for the vapour-phase, Henry's-law for the solubility of the non-condensable gases, an electrolyte model for the dissociation of HN02 and HN03 and a model for the activity constants of the liquid components. A unit operation model for the simulation of simultaneous absorption and reactions on every stage and the possibility to enter duties on every tray. A correct way to defme a complete set of reactions. There are equilibrium and kinetic reactions, in the liquid and vapor phase. Mass-transport models for the simulation of mass-transfer limitation between the liquid and vapor phase. Heat-transport models for the simulation of heat-transfer limitation in both phases. The temperature does not have to be uniform on one tray. In this chapter the different requirements are discussed and is shown how these are

implemented with respect to the NOx absorption.

Reactive absorption with ASPEN PLUS

page 19


3.1 The physical properties of NO x In Chemical Engineering flowsheeting it is important to provide a rigorous way to

calculate the properties of various streams. These include compositions, liquid/vapor equilibria, enthalpies, entropies, densities etc. Most flowsheeting programs provide a variety of models to calculate these. These models require parameters for every component in a stream. For example, for liquid/vapor equilibria one needs an equation of state. A commonly used equation of state is the Redlich-Kwong equation:

p=

{t

RT _

v-b.

v (v+b,..)

,;a.. = E x, ra, I

(32)

aI = b, =

where T v P

R

is is is is is is is

the the the the the the the

0.08664035 R Ta

------~

Pa

temperature, volume, pressure, gas-law constant, mole-fraction of component i, critical temperature of component i and critical pressure of component i.

In order to use this equation, the critical properties of all the components involved have to be provided.

ASPEN PLUS provides a databank for the properties of the often used chemical components. An additional package, the DIPPR-databank provides the properties of more than a thousand components. Unfortunately, none of the databanks has information about the components HN02 and N20 3. These where just the components that were used in the additional series of reactions for the NOx-model. Literature was searched for the necessary properties, but only limited information could be found. Table 4 summarizes the various constants for HN02 and N20 3 that were used for simulating the NOx absorption.

Reactive absorption with ASPEN PLUS

page 20

Absorption of NO x in Water Table 4

Values for the pure component data for HN02 and N 20 3 used in the ASPEN PLUS simulation of the NOx absorption.

Standard heat of formation· [J/kmol]

-79.53 106

83.72 106

Joshi, 1985

Standard energy of formation· [J/kmol]

-46.05 106

139.41 106

Joshi, 1985

Normal boiling point [K]

295.7

263

estimated

Critical temperature [K]

444.3

400

estimated

Critical pressure [Pa]

58 105

80 105

estimated

Critical volume [m3/kmol]

0.160

0.102

estimated

Critical compressibility factor

0.2516

0.2456

from definition

Pitzer acentric factor

0.493

0.567

estimated

Antoine vapor-pressure constants In(p)=A +B/f+Cln(T)+DTE F 2 N02 2 N02 N204 NO + N02 N203 NO + N02 + H20 K, N204 + H20 -> HN03 K, 3 HN02 -> HN03 + ...

Figure 18 contents of the file with stochastic parameters that have been varied for the simulation of NOx absorption.

Figure 19 demonstrates the effect when the Arhenius constant and pre-exponential factor are uncoupled, so the reaction rate constant is nonnal distributed.

Stochastic simulation

page 39

Absorption of NO x in Water rr

aU5

p

=

0

n

~---r---r--~--~--~--~~--~--r---~~

Arn-nlus Dlat "'aaur--.t. :2 R-I.tlu. .1~:0.01

\

Fr_.

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r~tar

:100

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T_.

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rr~

:2'73.15

to

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:8.462S

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2.7

2.8

2.9

3.0

3.1 1/1"

3.2

3.3

(/1E-3)

3.4

3.5

3.6 "ichi.1 Spoor.

199

Figure 19 Stochastic simulation of the reaction rate. The reaction constants are fictive and exaggerated to demonstrate the fact that the Arhenius constant and pre-exponential factor are correctly varied.

4.4 Other uses of stochastic process simulation In the stochastic simulation of NOx absorption it was the intention to translate the uncertainty in model parameters to uncertainty in the results. This is of course a sensible use of stochastic simulation and a lot of infonnation can be retrieved with it. More uses for stochastic simulation has been mentioned previously and will be summarized in this paragraph.

Of great importance is the ability to simulate the stochastic vanatlons in operating parameters and stream specifications like temperatures, pressures and compositions. This gives you the opportunity to detect processing limits and can be an aid in process optimization. A more advanced approach would be the design and optmuzation of a process when uncertainties in operating parameters, stream, parameters and unit operation models are considered. For examples a design specification for a distillation column could be: ' given all uncertainties, estimate with a certainty of 95%, the number of required trays in a the distillation column.' In this way the possibility for overdesign is minimized.


page 40

Absorption 01 NO x in Water

Stochastic simulation can also be used in process economics (Holland, 1984). When estimating Discounted Cash Flow Rates of Return (DCFRR) and Net Present Values (NPV)l of future projects, uncertainties in future sales volumes, interests and other parameters can be translated to uncertainties in the DCFRR and NPV. Probability data for these factors supports decisions whether to continue a project or not. One last example for stochastic simulation is its use for testing flowsheet convergence. During a calculation the process simulators spend most of their time solving very large systems of equations. The user can enter convergence specifications which are used to detennine if a system of equations is solved. Numerically it is possible for a specific system of equations to have multiple solutions or to have solutions which are insensitive for convergence specifications. By varying the estimations made in process simulation models, one can test the capability and precision of the flowsheet simulator.

IThe Discounted-Cash-Flow Rate of Return (DCFRR) and Net Present Value (NPV) of a project are defined at the following manner: The Present Value (PV) of a future sum of money (F) after n years is given by:

PV = F Id Id =

1 (1 +i)n

where i is the interest rate. Thus cash flow in the early years of a project has a greater value then the same amount in the later years of a project. The annual discounted-cashflow (A DCF) is related by the annual cash flow (~) by: A DCF = ACF

Id

The sum of the annual discounted cash flows over n years is known as the Net Present Value. The interest rate i which makes the NPV equal to 0 is called the Discounted-CashFlow Rate of Return.


page 41



page 42


·5 Results of the simulations

Several simulations have been realised and they can be arranged in two categories. First there are the standard simulations. By this a simulation is meant with one given set of input parameters and then one solution. These include the simulation with the ASPEN model and the simulation with the Enhanced model. Secondly stochastic simulations have been completed with both models. For a stochastic simulation a set of simulations is done with stochastically varied input parameters. With the Enhanced model also stochastic simulations have been done to determine the influence of two classes of model parameters and the influence of stochastic varying operating parameters and feed compositions. The results of both the standard as the stochastic simulations will be presented in this chapter. Statistical interesting observations will be given in the last part of this chapter.

5.1 The standard simulations As discussed in chapter 2 there are several models one can fonnulate to define the reactions of NOx that take place on an absorption tray. For two models (ASPEN and Enhanced) simulations have been completed with ASPEN PLUS. The program cumulates its results in a report file which is added to this thesis in appendix C for the ASPEN model and appendix D for the enhanced model. Several problems concerning the simulation of the Enhanced model have been resolved. Adding reactions to the ASPEN model showed that every additional reaction makes the simulation more difficult to converge. A practical limit of eight reactions could be implemented. The original ASPEN model used an user kinetics routine for the NO oxidation. The disadvantage of this approach is that no other kinetic reactions can be added to the model. The NO oxidation in the Enhanced model is taken to the input me where its kinetics is described with a standard powerlaw equation. One other disadvantage of the kinetic user routine for the NO oxidation is the empirical factor X in this model (;(=0.5) that accounted for the pressure and other 'effects' (Venkataraman, 1990). To be

Results of the simulations

page 43

Absorption of NO x in Water able to converge the Enhanced model, the temperature had to be controlled in the column. Best results have been obtained by using the COOLANT option in a figurative way. By defming huge coolant flows on each tray, the temperatures could be fixed at the same temperature of the coolant. Some experiments with the different convergence methods in ASPEN PLUS have been done and the Newton method seemed to converge better than other methods. In order to compare the results of the two simulations, the temperature profIles of the absorption columns for both simulation models have been fixed (figure 20). With fixed temperatures reaction rates only depend on tray composition.

Figure 20

Temperature profile in NO x absorption column for both ASPEN and Enhanced model. First some dependent variables have to be chosen to compare the different models. One of the goals was to minimize the NOx flowrate out of the absorption column. It is interesting to examine the NO flowrate of the vapor phase on every tray. Another goal is to maximize the nitric-acid production, or to obtain nitric-acid in a significant high concentration. Both results are shown in figure 21 and figure 22. Another aspect in NOx absorption is amount of heat to be remove in the column. A duty profIle for both simulations is provided in figure 23. It can be concluded that the mtnc acid production takes place on lower third of the column, while the nitrogen oxide concentration decreases slowly in the upper two third of the column. The largest differences of the simulations are in the nitric acid production Results of the simulations

page 44

Absorption of NO x in Water phase. Probably the factor X in the user supplied kinetics of the ASPEN model plays an important role with respect to the differences in nitric acid fonnation.

Figure 21 Nitrogen monoxide jlowrate on every tray in the NOx absorption column. The results of two models (ASPEN and Enhanced) are compared.

Figure 22 Flowrate of HjO+ in NOx absorption column. The HjO+ jlowrate represents the nitric acid jlowrate. Two models are compared (ASPEN and Enhanced).


page 45

Absorption of NOx in Water Another consideration with NOx absorption is its environmental aspect Some older nitric acid plant produce stack gases with up to 3000 ppm NOx. A regulation issued in Germany under The Federal Pollution Control Act (TA-Luft) states that the NOx content must not exceed 0.45 g/m3 (1 atm, 298 K) (Thieman, 1991). In the usual concentration units for waste gases (ppm) the norm of 0.45 g/m3 equals to 240 ppm. A proper defmition of the NOx concentration is: (49)

Figure 23 Duty profile for NOx absorption column. The duty on each tray for both models (ASPEN and Enhanced) are compared.


page 46


Figure 24 concentration of NOx in the NO x absorption column. NOx is defined here as (NO/+{N02/+{HN02/+2([N20J+{N203J). Figure 24 shows the NOx concentration in the absorption column. For both simulation models the NOx concentration on top of the column is about 375 ppm.

5.2 The stochastic simulations Several stochastic simulations have been done and these will be described below: Firstly a stochastic simulation has been done with the ASPEN model where only kinetic constants have been varied. Pure component data for the participating components (H20, HN03, N03-, H30+, NO, N0 2, N20 4 , 02 and Nz) among then thermodynamic binary data have been held constant for this simulations. It is assumed that uncertainties in pure component and thermodynamic data of these well known components just adds little to the overall uncertainty in the results. The kinetic constants for the reactions have been varied in such way, that correlation between the coefficients, is taken into account. Secondly for the enhanced model the additional parameters are stochastic varied, especially pure component data and thermodynamic data for HN02 and N20 3 have been varied. For the reactions, taken over from the ASPEN model, the reaction constants are varied with the same variances. Additional reactions have also stochastic variables. To investigate the significance of the two categories of parameters (thermodynamic/pure component and kinetic data) two sets of simulations have been done where the parameters of one category have been held constant while the others vary.


page 47

Absorption of NOx in Water Finally a stochastic simulation have been done on the Enhanced model where

operating parameters and feed compositions, temperatures and pressures have been varied. In appendix E an overview is given with the specifications for these stochastic simulations. Results that have been monitored are the NO vapor fraction and the duty on each, the H30+, HN02 and HN03 bottom flowrate and the NO and N02 top flowrate.

Figure 25 Frequency histogram for the top column NO flowrate for both simulation models.


page 48


Figure 26 Frequency histogram for the bottom column jlowrate of H30+ for both simulation models.

For the simulation of the ASPEN model and the Enhanced model the NO flowrate is shown in figure 25. The Enhanced model predicts a NO flowrate of 0.54 kmol/h (0'=4.7 10-3) and the ASPEN model predicts a flowrate of 0.65 kmol/h (0'=1.6 10-3). Distance between the two values of the flowrates is 24="[0'1 2

+O'ln.

The same histogram can be made for the acid production. Figure 26 shows the H30+ flowrate. For the Enhanced model the H30+ flowrate equals to 134.36 kmol/h (cr=0.031) and for the ASPEN model 135.05 kmollh (0'=8.2 10-3). Distance between these values is 21 observed )

(50)

= QnLastSim then LastSim:=i; end; lotusEOF ,seek(ResF,FilePos(ResF)-4-1en), end; until (typ=lotusEOF)or eof(ResF), if len>O then FreeMem(data,len); WriteLog(IF,'Simulations begin from loop '+intstr(LastSim); end; end; if reuse option is not set then create new results file in WKS-format if Reuse'YES' then begin assign(ResF,ResFile); rewrite(ResF,l); if IOresultO then Error('Cannot create Results file'); lotus123BOF(ResF), lotus123LABEL(ResF,1,1,'loop'), offset, =0, for i,=l to NumStoch do beqin lotus123LABEL(ResF,1,1+i+offset,Stoch(i).s), if Stoch(i).datanil then beqin inc(offset) ; lotus123LABEL (ResF, 1. l+i+offset, 'B (' +Stoch (i) . s+' ) , ) , end; end, for i,=l to NumMon do lotus123LABEL(ResF.1,1+NumStoch+i+offset,Mon(i).s), solve base-case first Write parameters used for this run Run aspen plus If converged parse the summary file and write the results lotus123INTEGER(ResF,2,1,0); offset ,.0, for i,=l to NumStoch do begin lotus123NUMBER(ResF,2,i+1+offset,stoch(i).def); if stoch(i) .data nil then beqin inc (offset), lotus123NUMBER(ResF,2.i+1+offset,stoch(i).data'.b); end, end; WriteLog(IF, 'Executing '+runasp+' for base case'+' on '+intstr(hh)+': '+intstr(mm»; ·· Window(1,16,80,2S),) Clrscr,) {W_}Exec(GetEnv('COMSPEC'),'/C '+runasp+' '+RunDir+' '+RunID+' '+tplfile+' '+Sumfile'+"·· '+ConvFile), if (DosErrorO)or(DosExitCodeO) then Error('Error executing '+runasp}; if Converged then begin ParseResultsFile; for i,=l to NumMon do lotus123NUMBER(ResF,2,i+1+NumStoch+offset,mon(i) .curval), end else Error('Base case did not converge')j end; Initialize normal-distribution object New(Dis,SetConstants); Main loop, 'Numsim' times for Counter:=l+LastSim to NumSim+LastSim do begin WriteLog(IF,'»»»»»»»»» Loop '+intstr(counter}+' «««««««« 2 N02 2 N02 N204 NO + N02 N203 NO + N02 + H20 N204 + H20 -> HN03 3 HN02 -> HN03 + ...

g

"~"

:l" 00

. ~.

>< ~

,IV

*!/bin/csh • script file to run aspen-plus • arguments:

* • • • •

•

$1 $2 $3 $4 $S

run-directory run-ID dos-format input file dos-format summaryfile file containing one line with convergence check

echo stochasp . csh

setenv ASPDIR '/bin/cat /users/bin/setup_aspen+' set path: ( $path $ASPDIR/aspenplus $ASPDIR/aspupdate rehash cd $1 getridof $2 if ( -w $4 ) then rm $4 endif if ( -w $5 then rm $5 endif if ( -w core ) then rm core

endif echo converting $3 to S2 . inp

dos2ux $3 > $2 . inp e cho starting aspen plus

aspen $2 $2 echo converting $2.sum to $4

ux2dos $2.sum > $4 grep -i completed $2.rep > $5

Monitor file for Stochastic simulation.

created 17 june 1992, by Michiel Spoor for use with stochasp Use GETDSETS to delete IDSET's and LSET's from summary file and to number the DSET's Format:

Set no Set id

DSET number (n th DSET) Set id (first id after DSET);

Var pos: position of variable --> De~cr description of variable ;Set no

21 21 21 21 21 21 21 21 21 21 30 30 30 30 30 30 30 30 30 30 39 39 39 40 40

Set id BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK BLOCK STREAM STREAM STREAM STREAM STREAM

Var pos 1 2 3 4 5 6 7 9 9 10 7 19 31 43 55 67 79 91 103 115 2 3 10 7 9

n th variable after ( Descr

DUTY [CALlS) TRAY 1 DUTY [CAL/S] TRAY 2 DUTY [CALlS] TRAY 3 DUTY [CI.L/S) TRAY 4 DUTY [CALlS) TRAY 5 DUTY [CALl S] TRAY 6 DUTY [CALlS) TRAY 7 DUTY [CALlS] TRAY 9 DUTY [CALlS] TRAY 9 DUTY [CALlS) TRAY 10 Y NO, TRAY 1 Y NO, TRAY 2 Y NO, TRAY 3 Y NO, TRAY 4 Y NO, TRAY 5 Y NO, TRAY 6 Y NO, TRAY 7 Y NO, TRAY 9 Y NO, TRAY 9 Y NO, TRAY 10 RATE HN03 [KMOL/H) BOTTOM RATE H30. [KMOL/H] BOTTOM RATE HN02 [KMOL/H) BOTTOM RATE NO [KMOL/H) TOP RATE N02 [KMOL/H] TOP

TITLE "HNO) OXIDATION-ABSORPTION"

MOLE-FLOW H20 9

DESCRIPTION " SIMULATION OF NITRIC ACID ABSORPTION TOWER. THE PURPOSE OF THE TOWER IS TO OXIDIZE THE NO IN THE VAPOR PHASE AND TO FORM HNO) IN THE LIQUID. HNO) IS REMOVED IN THE RAW ACID STREAM WHILE THE NOX CONCENTRATION IN THE TAIL GAS SHOULD BE AS LO AS POSSIBLE. THE REACTION OCCURING IN THE ABSORPTION TOWER ARE: (1) NO OXIDATION, (2) N02 DIMERZATION, ()) HNO) FORMATION AND (4) HNO) DISSOCIATION IN WATER. SINCE THE REACTIONS ARE HIGHLY EXOTHERMIC, COOLING IS REQUIRED ON EVERY STAGE OF THE COLUMN . •

I

N2 1690

I

02 105

I

NO 27

I

N02 71

I

N204 29

STREAM WATER SUBSTREAM MIXED TEMP=20 PRES=11 . 0 MOLE-FLCM H20 400 BLOCK TOWER RADFRAC PARAM NSTAGE=10 ALGORITHH=NONIDEAL MAXOL=50 MAXIL=9 DIAGNOSTICS MAIN=9 FEEDS NOX-GAS 11 I WATER 1 PRODUCTS TAIL-GAS 1 V I RAW-ACID 10 L P-SPEC 1 11.0 COL-SPECS Q1=10 QN=-355000 MASS-RDV=1.0 HEATERS 2 -1770 I 3 -2600 I 4 -4060 I 5 -7150 I 6 -15000 I 7 -40000 I 9 -135000 I 9 -300000 REAC-STAGES 1 10 NITRIC 1 10 VOL-VHLDP=6500 . 0 HOLD-UP 1 25.0 I 10 37.0 T-EST

IN-UNITS MET TEMPERATURE=C RUN-CONTROL MAX-TIME=10000

STREAM-REPORT MOLEFLOw MASSFLOW MOLEFRAC MASSFRAC DIPPRPCD I AQUEOUS

DATA BANKS ASPENPCD COMPONENTS H2O H2O HNO) HNO) H)O+ H)O+ NO)- NO)N2 N2 02 02 NO NO N02 N02 N204 N204

H2O HN03 H30+ N03N2 02 NO N02 N204

REACTIONS NITRIC DESCRIPTION "OXIDATION REACTIONS AND NITRIC ACID HYDROLYSIS" PARAM SUBROUTINE=NOX REAL VALUE-LIST=0.5 REAC-DATA 1 KINETIC PHASE=V STOIC 1 02 -1 . 0 I NO -2 . 0 I N02 2.0 REAC-DATA 2 EQUIL PHASE=V KBASIS=P K-STOIC 2 A=-33.0 B=6991 . 0 C= . O D=.O STOIC 2 N02 -2 . 0 I N204 1.0 REAC-DATA 3 EQUIL PHASE=V KBASIS =P K-STOIC 3 A=-17.0 B=3625 . 0 C=-2.0 D=.O STOIC 3 H2o -1.0 I N02 -3 . 0 I NO 1.0 I HN0 3 2.0 REAC-DATA 4 EQUIL STOIC 4 HN03 -1.0 I H20 -1.0 I H30+ 1.0 I N03- 1.0

I I I I I I I I

PROPERTIES SYSOP15M HENRY-COMPS=GAS CHEMISTRY=HNO) HENRY-COMPS GAS N2 02 NO N02 N204 CHEMISTRY HNO) STOIC 1 HN03 -1.0

I

H20 -1.0

I

H)O+ 1.0

I

NO)- 1.0

PROP-DATA IN-UNITS SI PROP-LIST DHFORM I DGFORM PVAL HNO) -1.3506E9 I -7.472E7 PROP-LIST MW I TB I TC PC I VC I ZC PVAL HN03 63 . 0129 I 356.15 I 520 6.9901E6 I 0 . 145 I 0.231 PROP-LIST DGAQFM PVAL NO)- -1 . 0974E9 PROP-LIST VLBROC PVAL HNO) 0 . 041771 PROP-LIST DHVLWT PVAL HNO) 3 . 904E7 299.15 PROP-LIST PLXANT PVAL HNO) -291.9727 0 0 -0.1)59019 59 . 15114 0 0 231.55 376 . 1 PVAL H20 72 . 55 -7206.7 0 0 -7.1395 4.046E-6 2 PROP-LIST CPIG PVAL HN03 53350 PROP-LIST CPAQO PVAL N03- -96600.0 191.90 PROP-LIST HENRY BPVAL N02 H20 )0.5647 -2972.96 -0.30299 0 293 396 BPVAL N204 H20 27.5647 -2972.96 -0.30299 0 293 396 PROP-LIST GMELCC I GMELCD PPVAL H20 ( H30+ N03-) 7.0790 I 154.40 PPVAL ( H30+ N03- ) H20 -3.2960 I -215.70 PPVAL HN03 ( H30+ N03- ) 7.5430 I 447.70 PPVAL ( H30+ N03- ) HN03 -2.9940 I -225.30 FLCMSHEET BLOCK TOWER IN=NOX-GAS WATER OUT=TAIL-GAS RAW-ACID STREAM NOX-GAS SUBSTREAM MIXED TEMP=40.0 PRES=11.0

OMEGA 0.7144

.

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U U U U U U U U UUUUU

ASPEN PLUS IS A TRADEMARK OF ASPEN TECHNOLOGY, INC. 251 VASSAR STREET CAMBRIDGE, MASSACHUSETTS 02139 617/497-9010

HOTLINE: U.S.A. 617/497-9010 EUROPE (32) 2/732-6300

VERSION: HP-PA RELEASE: 8.5-4 INSTALLATION: DUTSCH5

AUGUST 14, 1992 FRIDAY 2:32:20 P.M.

SSSSS S

SSSSS S

SSSSS

ASPEN PLUS

VER: HP-PA

REL: 8.5-4 INST: DUTSCH5 HN03 OXIDATION-ABSORPTION

08/14/92

PAGE

ASPEN PLUS(TM) IS A PROPRIETARY PRODUCT OF ASPEN TECHNOLOGY, INC. (ASPENTECH), AND MAY BE USED ONLY UNDER AGREEMENT WITH ASPENTECH. RESTRICTED RIGHTS LEGEND: USE, DUPLICATION, OR DISCLOSURE BY THE GOVERNMENT IS SUBJECT TO RESTRICTIONS AS SET FORTH IN DEAR AND DFAR 252-227-7013 (C) (1) (11) OF THE RIGHTS IN TECHNICAL DATA AND COMPlITER SOFTWARE CLAUSES OR OTHER SIMILAR REGULATIONS OF OTHER GOVERNMENTAL AGENCIES WHICH DESIGNATE SOFTWARE AND DOCUMENTATION AS PROPRIETARY .

ASPEN PLUS

VER: HP-PA

REL: 8.5-4 INST: DUTSCH5 HN03 OXIDATION-ABSORPTION RUN CONTROL SECTION

08/14/92

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RlIN CONTROL INFORMATION THIS VERSION OF ASPEN PLUS LICENSED TO Delft University of Technology THE FOLLOWING LAYERED PRODUCTS HAVE BEEN INSTALLED: RATEFRAC RELEASE 1.5-4 INSTALLED ON 07/21/92 AT 19:51:30:00 TYPE OF RUN: NEW

TABLE OF CONTENTS INPUT PILE NAME: aspnox.inp RUN CONTROL SECTION...... . .. .. . ... . ............ RUN CONTROL INFORMATION ......... . . . ...... . DESCRIPTION. . .. . . . . ... . . . . . .... . . . . . . . . .. . BLOCK STATUS....... ......... .. ... . .. ... ...

1 1 1 1

FLOWSHEET SECTION.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLOWSHEET CONNECTIVITY BY STREAMS . . . .... .. FLOWSHEET CONNECTIVITY BY BLOCKS . ..... . ... COMPUTATIONAL SEQUENCE.. . .... .... .. ... . . .. OVERALL FLOWSHEET BALANCE ............ .... .

3 3 3 3 3

PHYSICAL PROPERTIES SECTION ............... ... . . COMPONENTS ........ ... ........• ..... .... .. . U-O-S BLOCK SECTION ................... .. ... . .. .

BLOCK:

TOWER

OUTPUT PROBLEM DATA FILE NAME: aspnox VERSION NO. LOCATED IN: /disc/users/spoor/aspen/base

PDF SIZE USED FOR INPUT TRANSLATION: NUMBER OF FILE RECORDS (PSIZE) 9999 NUMBER OF IN-CORE RECORDS 400 PSIZE NEEDED FOR SIMULATION 100 CALLING PROGRAM NAME : LOCATED IN :

aspnox /disc/users/spoor/aspen/base

MODEL: RADFRAC ..... . . . . . .

STREAM SECTION................................ . 11 NOX-GAS RAW-ACID TAIL-GAS WATER ......•.. . . 11

.SIMULATION REQUESTED FOR ENTIRE FLOWSHEET DESCRIPTION SIMULATION OF NITRIC ACID ABSORPTION TOWER . THE PURPOSE or THE TOWER IS TO OXIDIZE THE NO IN THE VAPOR PHASE AND TO FORM HN03 IN THE LIQUID . HN03 IS REMOVED IN THE RAW ACID STREAM WHILE THE NOX CONCENTRATION IN THE TAIL GAS SHOULD BE AS LO AS POSSIBLE . THE REACTION OCCURING IN THE ABSORPTION TOWER ARE : (1) NO OXIDATION, (2) N02 DIMERZATION, (3) HN03 FORMATION AND (4) HN03 DISSOCIATION IN WATER. SINCE THE REACTIONS ARE HIGHLY EXOTHERMIC, COOLING IS REQUIRED ON EVERY STAGE OF THE COLUMN. BLOCK STATUS

• ALL UNIT OPERATION BLOCKS WERE COMPLETED NORMALLY

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BLOCK STATUS (CONTINUED)

REL , 8 . 5-4 INST, DUTSCH5 HN03 OXIDATION-ABSORPTION RUN CONTROL SECTION

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oUHJI f'I. U.i

VI' ,

H~

a[l.• 8 . S·. l/lST : DUTSCH5 HHVl OIlDATlOII-ABSORPTION fLOWSHEET SECTION

PA

08/14/92

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FLOWSHEET CONNECTIVITY BY STREAMS STREAM WATER TAIL-GAS

SOURCE

DEST TOWER

TOWER

STREAM NOX-GAS RAW-ACID

SOURCE

DEST TOWER

TOWER

FLOWSHEET CONNECTIVITY BY BLOCKS BLOCK TOWER

INLETS NOX-GAS WATER

OUTLETS TAIL-GAS RAW-ACID

COMPUTATIONAL SEQUENCE SEQUENCE USED WAS: TOWER

OVERALL FLOWSHEET BALANCE MASS AND ENERGY BALANCE IN OUT GENERATION RELATIVE DIFF . CONVENTIONAL COMPONENTS (KHOL / HR ) H2O 409.000 197 . 781 -211.219 -.353930E-11 HN03 . OOOOOOE+OO 17.2699 17.2699 -.617152E-15 H30+ .OOOOOOE+OO 135.056 135.056 . OOOOOOE+OO N03.OOOOOOE+OO 135.056 135.056 .OOOOOOE+OO N2 1680.00 1680.00 .OOOOOOE+OO .125962E-11 02 105 . 000 53.7443 -51.2557 .492969E-09 NO 27.0000 .651618 -26.3484 .387512E-08 N02 71 . 0000 .464790E-01 -70.9535 - .147472E-08 N204 28.0000 .487908 -27.5121 .126883E-15 TOTAL BALANCE MOLE(KHOL/HR ) 2320.00 2220.09 -99.9067 . 225659E-10 ) MASS (KG/HR 64442 . 8 64442.8 .238647E-06 ENTHALPY(CAL/SEC - . 734791E.07 -.820848E.07 .104839

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REL, 8 . 5-4 INST , DUTSCH5 HNO) OXIDATION-ABSORPTION PHYSICAL PROPERTIES SECTION

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COMPONENTS

ASPEN PLUS

BLOCK,

----------

TOWER

VER, HP-PA

H2O HNO) H)O+ NO)N2 02 NO N02 N204 LISTID GAS

TYPE C C C C C C C C C

FORMULA H2O HNO) H)O+ N03N2 02 NO N02 N204

NAME OR ALIAS H2O HNO) H)O+ NO)N2 02 NO N02 N204

SUPERCRITICAL COMPONENT LIST N2 02 NO N02 N204

REPORT NAME H2O HNO) H)O+ N03N2 02 NO N02 N204

08/14/92

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MODEL, RADFRAC

INLETS

ID

REL, 8.5-4 INST, DUTSCH5 HN03 OXIDATION-ABSORPTION U-O-S BLOCK SECTION

- NOX-GAS WATER OUTLETS - TAIL-GAS RAW-ACID PROPERTY OPTION SET, HENRY-COMPS ID , CHEMISTRY ID ,

STAGE 10 STAGE 1 STAGE 1 STAGE 10 SYSOP15M

ELECTROLYTE NRTL I REDLICH-KWONG-SOAVE

GAS

HNO)

- TRUE SPECIES

MASS AND ENERGY BALANCE IN OUT TOTAL BALANCE MOLE(KMOL / HR ) MASS (KG / HR ) ENTHALPY(CAL / SEC

2)20.00 64442 . 8 - . 734791E+07

2220.09 64442 . 8 - . 820848E+07

GENERATION

RELATIVE DIFF .

-99 . 9067

.225659E-10 . 238647E-06 .104839

INPUT DATA INPUT PARAMETERS NUMBER OF STAGES ALGORITHM OPTION INITIALIZATION OPTION HYDRAULIC PARAMETER CALCULATIONS INSIDE LOOP CONVERGENCE METHOD DESIGN SPECIFICATION METHOD MAXIMUM NO . OF OUTSIDE LOOP ITERATIONS MAXIMUM NO. OF INSIDE LOOP ITERATIONS MAXIMUM NUMBER OF FLASH ITERATIONS FLASH TOLERANCE OUTSIDE LOOP CONVERGENCE TOLERANCE

10 NONIOEAL STANDARD NO NEWTON NESTED 50 8 50 0.00010000 0.000100000

r

COL-SPECS CONDENSER DUTY (W/O SUBCooL) REBOILER DUTY MASS VAPOR DIST I TOTAL DIST

CALl SEC CALl SEC

10.0000 -355,000. 1.00000

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REL : 8 . 5-4 INST : DUTSCH5 HN03 OXIDATION-ABSORPTION U-O-S BLOCK SECTION

08 / 14 / 92

MODEL : RADFRAC (CONTINUED)

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REL : 8.5-4 INST: DUTSCH5 HN03 OXIDATION-ABSORPTION U-O-S BLOCK SECTION

08 / 14/92

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MODEL: RADFRAC (CONTINUED)

REAC-STAGES SPECIFICATIONS •••• STAGE 1

TO

STAGE 10

RESULTS .•.•.....•.•.•.....

REACTIONS/CHEMISTRY ID NITRIC

TOP STAGE TEMPERATURE BOTTOM STAGE TEMPERATURE TOP STAGE LIQUID FLOW BOTTOM STAGE LIQUID FLOW TOP STAGE VAPOR FLOW BOTl'OM STAGE VAPOR FLOW MOLAR REFLUX RATIO MOLAR BOILUP RATIO CONDENSER DUTY (W/O SUBCOOL) REBOILER DUTY

HOLD-UP SPECIFICATIONS STAGE 1

TO

STAGE 10

LIQUID HOLDUP MISSING

VAPOR HOLDUP 6500.0000 L

HEATERS STAGE HEATERS

STAGE

2 3 4 5 6 7 8 9

RATE, CAL/ SEC

-1,770.00 - 2,600.00 -4,060.00 -7,150.00 -15,000.0 -40,000.0 -135,000. -300,000.

C

25.2364 37.3442 400.825 480.335 1,739.76 1.842.02 0 .2 3039 3.83488 10 . 0000 -355,000 .

C

KMOL / HR KMOL / HR KMOL/HR KMOL / HR CAL/SEC CAL/ SEC

MAXIMUM FINAL RELATIVE ERRORS BUBBLE POINT COMPONENT MASS BALANCE ENERGY BALANCE

.30133E-03 . 80627E-05 . 76872E-05

STAGE= 6 STAGE= 8 COMP=N204 STAGE= 10

PROFILES P-SPEC

STAGE

TEMP-EST

STAGE

1 10

PRES, ATM

11. 0000

TEMP, C

25.0000 37.0000

PROFILES

STAGE TEMPERATURE C 1 2 3 4 5 6 7 8 9 10 STAGE 1 2 3 4 5 6

25.236 27.359 28 . 350 28.854 29.182 29.552 30.380 33.137 36 . 374 37.344

PRESSURE ATM 11. 000 11.000 11.000 11. 000 11.000 11. 000 11.000 11. 000 11. 000 11.000

FLOW RATE KMOL/HR LIQUID VAPOR 400.8 1740. 401. 3 1741. 401.6 1741. 401 . 8 174 2. 402.3 1743. 403 . 1 1744 .

LIQUID

ENTHALPY CAL / MOL VAPOR

HEAT DUTY CAL/SEC

-170.65 -177.95 -180.77 -180.32 -177.10 -170.35 -156.49 -104.90 90.796 289 . 73

10.0000 -1770.0000 -2600.0000 -4060.0000 -7150.0000 -.15000+05 -.40000+05 - .13500+06 - . 30000+06 - . 35500+06

-68288. -68243 . -68214. -68187. -68151. -68084. -67898. -66734. -63349. -60903.

LIQUID 400 . 0000

FEED RATE KMOL/HR VAPOR

MIXED

PRODUCT RATE KMOL / HR LIQUID VAPOR 1739 . 7584

"'_.:"

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TOWER


08/14/92

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MODEL , RADFRAC (CONTINUED)

FLOW RATE KMOL/HR VAPOR LIQUID 1746 . 405.0 1752. 414.2 1777. 447 . 5 1842 . 480.3

LIQUID

BLOCK,


MIXED

1920 . 0000

STAGE 1 2 3 4 5 6 7 8 9 10

H2O .99927 . 99847 . 99731 .99550 .99241 . 98627 .96905 .86148 .57278 .40045

X-PROFILE HN03 H30. .33712E-08 .29857E-03 .18077E-07 .70199E-03 .57195E-07 . 12833E-02 .15476E-06 .21858E-02 .41685E-06 .37326E-02 .12764E-05 .68046E-02 .62277E-05 .15408E-01 .20151E-03 . 69099E-01 .85452E-02 .209l9 .35954E-01 .28117

STAGE 1 2 3 4 5 6 7 8 9 10

NO .58204E-10 .62991E-10 .73091E-10 .89386E-10 .11537E-09 .15928E-09 .24024E-09 .39532E-09 .60641E-09 .65758E-09

No2 .45095E-09 .14755E-08 .34068E-08 .71581E-08 .15252E-07 .36404E-07 .12507E-06 .17796E-05 .31837E-04 .96417E-04

X-PROFILE N204 .48297E-13 . 46851E-12 .23865E-11 .10297E-10 .46067E-10 .25815E-09 .29364E-08 . 51577E-06 .12481E-03 .10158E-02

STAGE 1 2 3 4 5 6 7 8 9 10

H2o .31210E-02 .35288E-02 .37318E-02 .38347E-02 .38958E-02 .39560E-02 .40759E-02 .41503E-02 .28720E-02 .19588E-02

HN03 .26729E-10 .16209E-09 .54359E-09 .15187E-08 .41933E - 08 .13272E-07 .69963E-07 .29097E-05 .12953E-03 .50285E-03

¥-PROFILE H30. .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO . OOOOOE.OO .OOOOOE.OO .OOOOOE.OO

ASPEN PLUS

N03.29857E-03 .70199E-03 .12833E-02 . 21858E-02 .37326E-02 .68046E-02 . 15408E-01 .69099E-01 .209l9 .28117

N03.OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO . OOOOOE.OO .OOOOOE.OO . OOOOOE.OO .OOOOOE.OO .OOOOOE.OO . OOOOOE.OO

PRODUCT RATE KMOL/HR LIQUID VAPOR

480 . 3348 N2 .12340E-03 . 11982E-03 .11823E-03 .11742E-03 .11686E-03 . 11619E-03 . 11481E-03 .11291E-03 .12363E-03 . 12817E-03

N2 .96562 .96510 . 96475 .96442 . 96401 .96335 .96204 .95882 .94549 .91204

02 . 76898E-05 . 74450E-05 . 73469E-05 . 73118E-05 . 73080E-05 . 73221E-05 . 73416E-05 . 74619E-05 .9 1126E-05 .11933E-04

02 .30889E-01 .30924E-01 .30983E-01 .31072E-01 .31214E-01 .31458E-01 .31938E-01 .33101E-01 .36680E-01 .44806£-01

VER, HP-PA

TOWER


08/14/92

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MODEL, RADFRAC (CONTINUED)

STAGE 1 2 3 4 5 6 7 8 9 10

NO .37454E-03 .44285E-03 .53526E-03 .66832E-03 .87442E-03 .12260E-02 . 19132E-02 .3449lE-02 .52234E-02 . 54165E-02

N02 .95686E-07 .33392E-06 .79435E-06 .16946E-05 .36471E-05 .88051E-05 .31019E-04 .46969E-03 .80386E-02 .23161E-01

¥-PROFILE N204 .50907E-12 .52667E-11 .27640E-10 .12108E-09 .54714E-09 .31014E-08 .36172E-07 .67610E-05 .15651E-02 . 12119E-01

STAGE 1 2 3 4 5 6 7 8 9 10

H2O . 31232E-02 .35342E-02 . 37419E-02 .38520E-02 . 39256E-02 . 40111E-02 . 42060E-02 .48176E-02 .50142E-02 .489l5E-02

HN03 .79287E-02 .89667E-02 .95039E-02 .98132E-02 .10059E-01 .10398E-01 .11234E-01 . 14439E-01 . 15158E-01 . 13986E-01

K-VALUES H30. .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO . OOOOOE.OO .OOOOOE.OO .OOOOOE.OO . OOOOOE.OO

STAGE 1 2 3 4 5 6 7 8 9 10

NO .64350E.07 .70299E.07 . 73226E.07 .74760E.07 . 75782E.07 .76965E.07 . 79626E.07 .87238E.07 .86132E.07 .82367E.07

N02 212 . 19 226.29 233.13 236.70 239.08 241.83 247 . 97 263.90 252.48 240.19

K-VALUES N204 10 . 541 11 . 240 11. 580 11 . 757 11.875 12 . 012 12.316 13 .107 12 . 539 11.930

STAGE 1 2 3 4 5 6 7 8 9 10

H2O -.1795 -.2430 -.3505 -.5446 -.9348 -1.862 -5.245 -33.50 -99.01 -69.35

HN03 .1116E-05 .5238E-05 .1401E-04 .3456E-04 .8966E-04 .2478E-03 -.2968E-02 -.1441 3.044 14 . 37

N03.OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO .OOOOOE.OO

RATES OF GENERATION KMOL/HR N03H30. .1197 .1197 . 1620 .1620 .2337 .2337 . 3630 .3630 . 6232 .6232 1.241 1. 241 3 . 498 3 . 498 22.38 22.38 64 . 99 64.99 41. 44 41.44

N2 7825.1 8053 . 2 8157 . 7 8211.1 8246 . 8 8288.4 8377 . 0 8489 . 5 7646 . 9 7114 . 8

02 4016.8 4153.1 4216.2 4248 . 5 4270.0 4295.1 4349 . 1 4434.9 4024.8 3754.2

.

N2 . OOOOE.OO . 0000£.00 . 0000£.00 .0000£.00 .OOOOE.OO .OOOOE.OO .0000£+00 .OOOOE+OO .OOOOE.OO . 0000£.00

02 -.8955E-01 -.1211 -.1745 -.2706 -.4629 - . 9118 -2.225 -7.178 -17.36 -22.47

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6

ASPEN PLUS

VER, HP-PA

TOWER

STAGE 1

2 3 4

5 6 7 8 9 10

NO - .1193 -.1612 -.2321 -.3597 -.6142 - 1. 203 -2.702 -3.238 - . 6963 -17.02


MODEL, RADFRAC (CONTINUED) RATES OF GENERATION KHOL/HR N02 N204 -.4146E-03 -.8263E-08 -.8016E-03 -.3879E-07 -.1568E-02 -.1620E-06 -.3402E-02 - . 7394E-06 -.8996E-02 -.4441E-05 -.3880E-01 - . 5767E-04 -.7688 - .1178E-01 -13.46 - 2 . 769 -28.37 -19.49 -28.31 -5.244

08/14/92

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REL, 8.5-4 INST, DUTSCH5 HN03 OXIDATION-ABSORPTION STREAM SECTION

08/14/92

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NOX-GAS RAW-ACID TAIL-GAS WATER

-------------------------------

STREAM ID FROM TO

,

SUBSTREAM, MIXED PHASE, COMPONENTS, KHOL/HR H2O HN03 H30+ N03N2 02 NO N02 N204 COMPONENTS, MOLE FRAC H2O HN03 H30+ N03N2 02 NO N02 N204 COMPONENTS, KG/HR H2O HN03 H30+ N03N2 02 NO N02 N204 COMPONENTS , MASS FRAC H2 O HN03 H30+ N03N2 02 NO N02 N204 TOTAL FLOW, KHOL/HR KG/HR L/MIN

NOX-GAS

RAW-ACID TOWER

TAIL-GAS TOWER

TOWER VAPOR

WATER TOWER

LIQUID

VAPOR

LIQUID

9.0000 0.0 0.0 0.0 1680.0000 105.0000 27.0000 71.0000 28 . 0000

192.3510 17.2698 135 . 0562 135.0562 6.1563-02 5.7318-03 3.1586-07 4.6313-02 0.4879

5 . 4297 4.6503-08 0.0 0.0 1679.9384 53.7385 0.6516 1. 6647-04 8.8567-10

400 . 0000 0 .0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

4.6875-03 0.0 0.0 0.0 0.8750 5.4688-02 1.4063-02 3.6979-02 1. 4583-02

0.4004 3 . 5954-02 0.2811. 0 . 2811 1.2817-04 1.1933-05 6.5758-10 9.6417-05 1.0158-03

3 . 1210-03 2.6729-11 0.0 0.0 0.9656 3.0889-02 3.7454-04 9.5686-08 5.0907-13

1 . 0000 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

162.1350 0.0 0.0 0.0 4.7062+04 3359.8950 810.1620 3266.4260 2576.3108

3465.2040 1088.2250 2569.1742 8374.1467 1.7245 0.1834 9 . 4776-06 2 . 1306 44.8929

97.8160 2.9303-06 0.0 0.0 4.7060+04 1719 . 5800 19.5524 7.6587-03 8.1491-08

7206.0000 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

2.8327-03 0.0 0.0 0.0 0.8222 5.8702-02 1.4155-02 5.7069-02 4 . 5011-02

0.2229 7.0002-02 0.1652 0.5386 1 . 1094-04 1.1798-05 6 . 0966-10 1. 3706-04 2.8878-03

2.0004-03 5.9927-11 0.0 0.0 0.9624 3.5167-02 3 . 9987-04 1.5663-07 1.6666-12

1. 0000 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

1920 . 0000 5.7237+04 7.4752+04

480.3348 1. 5546+04 154.4122

1739.7584 4.8897+04 6.4541+04

400.0000 7206.0000 120.2472

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TITLE "HN03 OXIDATION-ABSORPTION" DESCRIPTION " SIMULATION OF NITRIC ACID ABSORPTION TOWER. THE PURPOSE OF THE TOWER IS TO OXIDIZE THE NO IN THE VAPOR PHASE AND TO FORM HN03 IN THE LIQUID. HN03 IS REMOVED IN THE RAW ACID STREAM WHILE THE NOX CONCENTRATION IN THE TAIL GAS SHOULD BE AS LO AS POSSIBLE . THE REACTIONS OCCURING IN THE ABSORPTION TOWER ARE : (1) NO OXIDATION, (2) N02 DIMERlZATION , (3) N203 FORMATION , (4) HN02 FORMATION, (5) HN03 FORMATION, (6) HN03 AND HN02 DISSOCIATION IN WATER. SINCE THE REACTIONS ARE HIGHLY EXOTHERMIC, COOLING IS REQUIRED ON EVERY STAGE OF THE COLUMN . " IN-UNITS MET PRES=ATM TEMPERATURE=C RUN-CONTROL MAX-TIME=1000

BPVAL N204 H20 27 . 56470 -2872.960 - . 302880 .0 283.0 386.0 BPVAL N203 H20 27.5647 -2872 . 960 -.302880 .0 283.0 386.0 GMELCC I GMELCD PROP-LIST PPVAL H20 ( H30+ N03- ) 7.0780 I 154 . 4 PPVAL ( H30+ N03- ) H20 -3.2960 I -215.7 PPVAL HN03 ( H30+ N03- ) 7.5430 I 447.7 PPVAL ( H30+ N03- ) HN03 -2.9840 I -225.3 PPVAL H20 ( H30+ N02- ) 7.0780 I 154.4 PPVAL ( H30+ N02- ) H20 -3.2960 I -215.7 PPVAL HN02 ( H30+ N02- ) 7.5430 I 447.7 PPVAL ( H30+ N02- ) HN02 -2.9840 I -225.3 FLOWS MEET BLOCK TOWER IN=WATER NOX - GAS OUT=TAIL-GAS RAW-ACID STREAM NOX-GAS TEMP=40.0 MOLE-FLOW H20 9.0 N2 1680.0 02 105.0 NO 27.0 N02 71.0 N204 28.0

PRES=11.0 I I I I I

DATABANKS DIPPRPCD I AQUEOUS COMPONENTS H20 H20 HN03 HN03 H30+ H30+ N03- N03N2 N2 02 02 NO NO N02 N02 N204 N204 HN02 HN02-1 N02- N02N203 • N203

STREAM WATER TEMP=20 . 0 PRES=11.0 MOLE-FLOW H20 400.0

I I I I I I I I I I I

PROPERTIES SYSOP15M HENRY-COMPS=GAS CHEMISTRY=HNOX TRUE-COMPS=YES HENRY-COMPS GAS N2 02 NO N02 N204 N203 CHEMISTRY HNOX PARAM KBASIS=MOLAL STOIC 1 HN03 -1 I H20 -1 I H30+ 1 I N03K-STOIC 1 15.098 -738.88 0 -0.031534 STOIC 2 HN02 -1 I H20 -1 I H30+ 1 ! N02PROP-DATA IN-UNITS SI PROP-LIST MW PVAL N203 76 PROP-LIST VLBROC I DHFORM I DGFORM PVAL HN03 .041771 I -135. 06E6 I -74 . 72E6 PVAL N203 • I 83. 72E6 I 139 . 41E6 PVAL HN02 • I -79.53E6 I -46 . 05E6 I OMEGA PROP- LIST TB I TC PC I VC I ZC PVAL HN03 356.15 I 520 68 . 901E5 I 0.145 I 0 . 231 I 0 . 7144 PVAL HN02 295.7 I 444.3 58E5 0.2516 I 0 . 493 I 0 . 160 I PVAL N203 263 I 400 80E5 I 0.102 I 0 . 2456 I 0 . 567 PROP-LIST PLXANT PVAL H20 72.55 -7206 . 7 0 0 -7.1385 4 . 046E- 6 2 PVAL HN03 -281.8727 0 0 -.1358019 58 . 15114 0 0 231.55 376 . 1 PVAL HN02 21.00814 -3000 0 0 -3E-6 8E-6 2 275 340 PVAL N203 22 . 3847 -2996.63 0 0 9 . 672E-3 7E-6 2 275 340 PROP-LIST CPIG I DHVLWT PVAL HN03 53350 I 39.04E6 298.15 PVAL HN02 45606 I 39E6 298 PVAL N203 65605 I 39.3E6 263 PROP-LIST DGAQFM I CPAQO PVAL N03- -1 . 0874E8 I -86600.0 591.8 PROP-LIST HENRY BPVAL N02 H20 30 . 56470 -2872 . 960 -.302880 .0 283.0 386 . 0

BLOCK TOWER RADFRAC PARAM NSTAGE=10 ALGORITHM=NEWTON MAXOL=50 MAXIL=20 & FLASH-MAXIT=200 DSMETH=NESTED MAIN=8 OLVAR1=4 OLVAR2=4 CMBAL=4 EMBAL=4 DIAG FEEDS WATER 1 I NOX-GAS 11 PRODUCTS TAIL-GAS 1 V RAW-ACID 10 L P-SPEC 1 11 . 0 COL-SPECS Q1 =-387 & QN =-670780 & MOLE-RDV=1.0 1 H20 TEMP=25.1 MOLE-FLOW=lE12 UA=lE10 PRES=l COOLANT 2 H20 TEMP=27 . 3 MOLE-FLOW=lE12 UA=lE10 PRES=l 3 H20 TEMP=28 . 3 MOLE-FLOW=lE12 UA=lE10 PRES=l 4 H20 TEMP=28 . 8 MOLE-FLOW=lE12 UA=lE10 PRES=l 5 H20 TEMP=29 . 2 MOLE-FLOW=lE12 UA=lE10 PRES=l 6 H20 TEMP=29 . 6 MOLE - FLOW=lE12 UA=lE10 PRES=l 7 H2o TEMP=30 . 4 MOLE-FLOW=lE12 UA=lE10 PRES=l 8 H20 TEMP=33 . l MOLE-FLOW=lE12 UA=lE10 PRES=l 9 H20 TEMP=36 . 4 MOLE-FLOW=lE12 UA=lE10 PRES=l 10 H20 TEMP=37 . 4 MOLE-FLOW=lE12 UA=lE10 PRES=l T-EST 1 25 . 1 I 10 37.4 REAC-STAGES 1 10 NITRIC HOLD-UP 1 10 VOL-VHLDP=6500 VOL-LHLDP=20

I I I I I I I I I

REACTIONS NITRIC DESCRIPTION "OXIDATION REACTIONS AND NITRIC ACID HYDROLYSIS" GAS-PHASE REACTIONS: 02 + 2 NO ---> 2 N02 2 N02 N204 NO + N02 N203 NO + N02 + H20 2 HN02 LIQUID-PHASE REACTIONS: N204 + 3 HN02 HN03 + HN02 +

H20 ---> HN02 + ---> HN03 + H20 H20 H30+ + H2o H30+ +

REAC-DATA STOIC RATE-CON POWLAW-EXP

1 1 1 1

HN03 + 2 NO N03N02-

KINETIC V CBASIS=MOLEFRAC 02 -1 I NO -2 I N02 2 5594.16 -2284.306 -1 02 1 I NO 2

REAC-DATA STOIC K-STOIC

2 EQUIL V KBASIS=P 2 N02 -2 / N204 1 2 -33 6891

PRESENT IN ORIGINAL NOX-INPUT FILE BUT ELIMINATED. THIS REACTION IS AN OVERAL REACTION AND NITRIC ACID IS FORMED HERE IN VAPOR PHASE, WHAT IS NOT THE CASE REAC-DATA 3 EQUIL V KBASIS=P STOIC 3 H20 -1 / N02 -3 / NO 1 / HN0 3 2 K-STOIC 3 -17 3625 -2 REAC-DATA STOIC K-STOIC REAC-DATA STOIC K-STOIC REAC-DATA STOIC REAC-DATA STOIC REAC-DATA STOIC RATE-CON POWLAW-EXP REAC-DATA STOIC RATE-CON POWLAW-EXP STREAM-REPORT

4 4 4 5 5 5 6 6 7 7 8 8 8 8 9 9 9 9

EQUIL V KBASIS=P NO -1 / N02 -1 / N203 1 -28.183 4771 EQUIL V KBASIS=P NO -1 / N02 -1 / H20 -1 HN02 2 -27.029 4723 EQUIL L KBASIS=MOLAL HN03 - 1 / H2 0 -1 / H3 0 + N03EQUIL L HN02 -1 / H20 -1 / H30+ No2KINETIC L CBASIS=MOLAR N2 0 4 -1 / H20 -1 / HN0 3 HN02 2.19533E16 18938.8 N204 1 KINETIC L CBASIS=MOLAR HN02 -3 / HN03 1 / H2O 1 / NO 2 I.SE8 28369 . 3 HN0 2 4 / NO -2 MOLEFLOW MASSFLOW MOLEFRAC MASSFRAC

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U U U U U U U U UUUUU

ASPEN PLUS IS A TRADEMARK OF ASPEN TECHNOLOGY, INC. 251 VASSAR STREET CAMBRIDGE, MASSACHUSETTS 02139 617/497-9010

HOTLINE, U.S . A. 617/497-9010 EUROPE (32) 2/732-6300

VERSION, HP-PA RELEASE , 8.5-4 INSTALLATION , DUTSCH5

AUGUST 14, 1992 FRIDAY 3 , 35,47 P.H.

SSSSS S

SSSSS S

SSSSS

ASPEN PLUS

VER : HP-PA

REL : 8.5-4 INST: DUTSCH5 HNO) OXIDATION-ABSORPTION

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ASPEN PLUS

VER : HP-PA

REL: 8.5-4 INST: DUTSCH5 HN0 3 OXIDATION-ABSORPTION RUN CONTROL SECTION

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RUN CONTROL INFORMATION ASPEN PLUS(TM) IS A PROPRIETARY PRODUCT OF ASPEN TECHNOLOGY, INC. (ASPENTECH), AND MAY BE USED ONLY UNDER AGREEMENT WITH ASPENTECH . USE, DUPLICATION, OR DISCLOSURE BY THE RESTRICTED RIGHTS LEGEND: GOVERNMENT IS SUBJECT TO RESTRICTIONS AS SET FORTH IN DEAR AND DFAR 252-227-7013 (C) (1) (11) OF THE RIGHTS IN TECHNICAL DATA AND COMPUTER SOFTWARE CLAUSES OR OTHER SIMILAR REGULATIONS OF OTHER GOVERNMENTAL AGENCIES WHICH DESIGNATE SOFTWARE AND DOCUMENTATION AS PROPRIETARY.

THIS vERSION OF ASPEN PLUS LICENSED TO De1ft University of Technology THE FOLLOWING LAYERED PRODUCTS HAVE BEEN INSTALLED: RATEFRAC RELEASE 1 . 5 - 4 INSTALLED ON 07 / 21 / 92 AT 19 : 51 : 30 : 00 TYPE OF RUN : NEW

TABLE OF CONTENTS INPUT FILE NAME: nox . inp RUN CONTROL SECTION ......... . ......... . . ... RUN CONTROL INFORMATION ..... . .... . . . .. DESCRI PTION .............. . .... .... .. . . BLOCK STATUS .... ... . . .. . .. .. .... ......

.. . .. . . .. ...

. . . .

FLOWSHEET SECTION ... . . . . . . . . . . . . . . . . . . . . . . . . • . . FLOWSHEET CONNECTIVITY BY STREAMS . . .. .. .. . FLOWSHEET CONNECTIVITY BY BLOCKS . . . .. .... . COMPUTATIONAL SEQUENCE . . . . .. . ....... .. . .. . OVERALL FLOWSHEET BALANCE ............ .. ...

OUTPUT PROBLEM DATA FILE NAME: nox VERSION NO . LOCATED IN: /disc/users/spoor/aspen 3 3 3 3 3

PHYSI CAL PROPERTIES SECTION.......• . .. . ... .... . COM PONENTS . .. .. .. .. . . .. . .. ... .. .. . . . . .. . . . U-O- S BLOCK SECTION.. . . . . . . . . . . . . . . . . . . . . . . . . . . BLOCK: TOWER MODEL : RADFRAC . ........ . .

5 5

STREAM SECTION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 11 NOX-GAS RAW-ACID TAIL - GAS WATER ........... 11

PDF SIZE USED FOR INPUT TRANSLATION: NUMBER OF FILE RECORDS (PSIZE) 9999 NUMBER OF IN-CORE RECORDS 400 PSIZE NEEDED FOR SIMULATION 2000 CALLING PROGRAM NAME: LOCATED IN :

apmod / disc / users / aspr85 / aspenp1us

SIMULATION REQUESTED FOR ENTIRE FLOWSHEET DESCRIPTION SIMULATION OF NITRIC ACID ABSORPTION TOWER. THE PURPOSE OF THE TOWER IS TO OXIDIZE THE NO IN THE VAPOR PHASE AND TO FORM HN03 IN THE LIQUID. HN03 IS REMOVED IN THE RAW ACID STREAM WHILE THE NOX CONCENTRATION IN THE TAIL GAS SHOULD BE AS LO AS POSSIBLE. THE REACTIONS OCCURING IN THE ABSORPTION TOWER ARE: (1) NO OXIDATION, (2 ) N02 DlHERIZATION, (3) N203 FORMATION, (4) HN02 FORMATION, (5) HN03 FORMATION, (6) HN03 AND HN02 DISSOCIATION IN WATER. SINCE THE REACTIONS ARE HIGHLY EXOTHERMIC, COOLING IS REQUIRED ON EVERY STAGE OF THE COLUMN . BLOCK STATUS

• ALL UNIT OPERATION BLOCKS WERE COMPLETED NORMALLY

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REL, 8.5-4 INST, DUTSCH5 HN03 OXIDATION-ABSORPTION RUN CONTROL SECTION

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...........................•.............................•.................•

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FLOWSHEET CONNECTIVITY BY STREAMS STREAM NOX-GAS TAIL-GAS

SOURCE

DEST TOWER

TOWER

STREAM WATER RM1-ACID

SOURCE

DEST TOWER

TOWER

FLOWSHEET CONNECTIVITY BY BLOCKS BLOCK TOWER

INLETS WATER NOX-GAS

OUTLETS TAIL-GAS RAW - ACID

COMPUTATIONAL SEQUENCE SEQUENCE USED WAS, TOWER

OVERALL FLOWSHEET BALANCE MASS AND ENERGY BALANCE IN OUT GENERATION RELATIVE DIFF. CONVENTIONAL COMPONENTS (KMOL/HR ) H2o 409 . 000 197.965 -211. 035 . 291861E-14 HN03 .OOOOOOE+OO 17.0284 17.0284 .605042E-13 H30+ . OOOOOOE+OO 134.352 .OOOOOOE+OO 134.352 N03. OOOOOOE+OO 134.352 134.352 .OOOOOOE+OO N2 1680.00 1680.00 .OOOOOOE+OO -.270683E-15 02 105 . 000 54.4211 -50 . 5789 . 994760E-14 NO 27 . 0000 .536836 -26.4632 .810545E-13 N02 71.0000 .801806E-01 -70.9198 .100076E-14 N204 28.0000 .565017E-02 -27.9943 .304518E-14 HN02 .OOOOOOE+OO 1. 98632 1.98632 - .175025E-11 N02. OOOOOOE+OO .132135E-05 .132135E-05 -.833346E-14 N203 .OOOOOOE+OO .248689E-02 .248689E-02 -.261580E-14 TOTAL BALANCE MOLE(KMOL/HR ) 2320.00 2220.73 -99.2703 . 502280E-15 MASS (KG/HR ) 64442 . 8 64442.8 . 234073E-06 ENTHALPY(CAL/SEC -.734791E+07 -.818982E+07 .102799

... . '

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COMPONENTS

ASPEN PLUS

BLOCK:

----------

TOWER

VER: HP-PA

LISTID GAS

TYPE C C C C C C C C C C C C

FORMULA H2O HN03 H30+ N03N2 02 NO N02 N204 HN02-1 N02MISSING

NAME OR ALIAS H2O HNO) H30+ N03N2 02 NO N02 N204 HN02-1 N02MISSING

REPORT NAME H2O HNO) H30+ N03N2 02 NO N02 N204 HN02 N02N203

08/14/92

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MODEL: RADFRAC

INLETS

ID H2O HN03 H30+ N03N2 02 NO N02 N204 HN02 N02N203

REL: 8.5-4 INST: DUTSCHS HN03 OXIDATION-ABSORPTION U-O-S BLOCK SECTION

- WATER NOX-GAS OUTLETS - TAIL-GAS RAW-ACID PROPERTY OPTION SET: HENRY-COMPS ID: CHEMISTRY ID:

STAGE 1 STAGE 10 STAGE 1 STAGE 10 SYSOP1SM ELECTROLYTE NRTL / REDLICH-KWONG-SOAVE GAS HNOX - TRUE SPECIES MASS AND ENERGY BALANCE IN OUT

TOTAL BALANCE MOLE (KMOL/HR ) MASSIKG/HR ) ENTMALPY(CAL/SEC

2320.00 64442.8 -.734791E+07

2220.73 64442.8 - . 818982E+07

GENERATION

RELATIVE DIFF.

-99.2703

.S02280E-1S .234073E-06 .102799

SUPERCRITICAL COMPONENT LIST N2 02 NO N02 N204 N203 INPUT DATA INPUT PARAMETERS NUMBER OF STAGES ALGORITHM OPTION INITIALIZATION OPTION HYDRAULIC PARAMETER CALCULATIONS DESIGN SPECIFICATION METHOD MAXIMUM NO . OF NEWI'ON ITERATIONS MAXIMUM NUMBER OF FLASH ITERATIONS FLASH TOLERANCE COLUMN EQUATIONS CONVERGENCE TOLERANCE

10 NEWI'ON STANDARD NO NESTED 50 200 0 . 00010000 0.100000-06

COL-SPECS MOLAR VAPOR DIST / TOTAL DIST CONDENSER DUTY IW/O SUBCOOL) REBOILER DUTY

CAL/SEC CAL/SEC

1 . 00000 -387 . 000 -670,780.

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REAC-STAGES SPECIFICATIONS •••• STAGE 1

TO

RESULTS

REACTIONSICHEMISTRY ID NITRIC

STAGE 10

HOLD-UP SPECIFICATIONS STAGE 1

TO

LIQUID HOLDUP 20.0000 L

STAGE 10

VAPOR HOLDUP 6500 . 0000 L

COOLANT SPECIFICATIONS STAGE 1 2 3 4 5 6 7 8 9 10

COMP ID

OPTN SET

PHASE

H2O H2O H2O H2O H2o H2o H2o H2O H2o H2o

SYSOP15M SYSOP15M SYSOP15M SYSOP15M SYSOP15M SYSOP15M SYSOP15M SYSOP15M SYSOP15M SYSOP15M

LIQUID LIQUID LIQUID LIQUID LIQUID LIQUID LIQUID LIQUID LIQUID LIQUID

STAGE AV. HEAT CAP. CAL/MOL-K 16.6029 1 17.1377 2 17.2326 3 17.9660 4 19.0797 5 6 19.0664 7 17'.9199 17.9730 9 17.9675 9 17.9758 10

HT COEF*AREA CAL/SEC-K 1.0000+10 1.0000+10 1.0000+10 1.0000+10 1.0000+10 1.0000+10 1. 0000+10 1.0000+10 1.0000+10 1.0000+10

PRESSURE ATM 1 . 0000 1 . 0000 1.0000 1.0000 1 . 0000 1.0000 1 . 0000 1.0000 1. 0000 1. 0000

TEMPERATURE C 25.1000 27.3000 29.3000 29 . 8000 29 . 2000 29 . 6000 30 . 4000 33.1000 36 . 4000 37.4000

STAGE

TEMP-EST

STAGE

1 10

KMOL/HR KMOL/HR KMOL/HR KMOL/HR CALl SEC CALl SEC

MAXIMUM FINAL RELATIVE ERRORS .33999E-13 .12630E-09 .22102E-07

BUBBLE POINT COMPONENT MASS BALANCE ENERGY BALANCE

1 2 3 4 5 6 7 9 9 10

PRES, ATM

11. 0000

TEMP, C

25 . 1000 37 . 4000

STAGE; STAGE; STAGE;

5 8 COMP;HN03 5

PROFILES

STAGE TEMPERATURE C

KMOL/HR KMOL/HR KMOL/HR KMOL/HR KMOL/HR KMOL/HR KMOL/HR KMOL/HR KMOL/HR KMOL/HR

25.1000 37.4001 400.974 490.332 1. 740.40 1. 769. 73 0.23033 3.69439 -385.014 -670,749.

C C

FLOW RATE 1. 0000+12 1.0000+12 1. 0000+12 1. 0000+12 1. 0000+12 1.0000+12 1.0000+12 1. 0000+12 1. 0000+12 1.0000+12

PROFILES P-SPEC

TOP STAGE TEMPERATURE BOTTOM STAGE TEMPERATURE TOP STAGE LIQUID FLOW BOTTOM STAGE LIQUID FLOW TOP STAGE VAPOR FLOW BOTTOM STAGE VAPOR FLOW MOLAR REFLUX RATIO MOLAR BOILUP RATIO CONDENSER DUTY (W/O SUBCooL) REBOILER DUTY

STAGE 1 2 3 4 5 6

25 . 100 27 . 300 29 . 300 29 . 900 29 . 200 29.600 30.400 33.100 36 . 400 37.400

PRESSURE ATM 11 . 000 11 . 000 11.000 11 . 000 11 . 000 11.000 11 . 000 11. 000 11.000 11. 000

FLOW RATE KMOL/HR VAPOR LIQUID 1740. 400 . 9 401. 3 1741. 401. 6 1742 . 1742. 401. 9 402.3 1743. 402.9 1744.

LIQUID

ENTHALPY CALl MOL VAPOR

HEAT DUTY CAL l SEC

-171. 73 -179.16 -192.58 - 183.11 -192 . 14 -179.40 -175 . 52 -176 . 92 -150 . 93 137 . 53

-385 . 0139 - 1315 . 9720 -1994 .0 968 -3337.9954 -4926 . 4307 -9455 . 5819 - . 23567+05 - . 39799+05 - . 973 79+05 - . 67075+06

-69294 . -69237. -69209. -69196 . -69156. -69111. - 69025 . -67912 . -67060. -60759 .

LIQUID 400.0000

FEED RATE KMOL / HR VAPOR

MIXED

PRODUCT RATE KMOL/HR LIQUID VAPOR 1740 . 3971

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FLOW RATE KMOL/HR VAPOR LIQUID 1745. 404.7 1749. 407.4 1755. 409.1 1770. 480.3

LIQUID

ASPEN PLUS

BLOCK,


MIXED

1920.0000

PRODUCT RATE KMOL/HR LIQUID VAPOR

480.3324

STAGE 1 2 3 4 5 6 7 8 9 10

H2O .99930 .99863 .99770 .99635 .99427 .99075 .98410 .96841 .90321 .40092

HN03 .11629E-08 .92863E-08 .32245E-07 .86295E-07 .21463E-06 .54712E-06 .15874E-05 .66467E-05 .84189E-04 .35451E-01

X-PROFILE H30+ .17215E-03 .492 56E-03 .94248E-03 .15921E-02 .25977E-02 .42979E-02 .75390E-02 .15265E-01 .47563E-01 .27971

N03.17014E-03 .49165E-03 .94190E-03 .1591 7E-02 .25974E-02 .42976E-02 .75388E-02 .15265E-01 .47562E-01 .27971

N2 .12359E-03 .11989E-03 .11830E-03 .11751E-03 .11686E-03 .11620E-03 .11493E-03 .11114E-03 .10767E-03 .13321E-03

02 .78012E-05 .75401E-05 .74363E-05 .73954E-05 .73728E-05 .73620E-05 .73318E-05 .71656E-05 .71573E-05 .99014E-05

STAGE 1 2 3 4 5 6 7 8 9 10

NO .48210E-10 .54547E-10 .61854E-10 .73035E-10 .89569E-10 .11505E-09 . 15568E-09 .21718E-09 .34853E-09 .94812E-09

N02 .20465E-06 .23852E-06 .26199E-06 .30352E-06 .36718E-06 .46509E-06 .61010E-06 .78208E-06 .12971E-05 .10240E-04

X-PROFILE N204 .10011E-07 .12274E-07 .14143E-07 .18554E-07 .26666E-07 .42023E-07 .69765E-07 .10162E-06 .24023E-06 .11382E-04

HN02 .22436E-03 .25879E-03 .28927E-03 .33844E-03 .41214E-03 .52524E-03 .69856E-03 .93091E-03 .14683E-02 .40441E-02

N02.20060E-05 .91251E-06 .58423E-06 .43892E-06 .35468E-06 .29589E-06 .24228E-06 .16849E-06 .68026E-07 .27509E-08

N203 .72739E-08 .93495E-08 . 11511E-07 .15657E-07 .23124E-07 .37461E-07 .65908E-07 .11428E-06 .29089E-06 .49027E-05

STAGE 1 2 3 4 5 6 7 8 9 10

H2O .30962E-02 .35174E-02 .37226E-02 .38259E-02 .39066E-02 .39835E-02 .41421E-02 .47427E-02 .52644E-02 .19578E-02

HN03 .91433E-11 .82918E-10 .30516E-09 . 84215E-09 .21509E-08 .56461E-08 .17343E-07 .86384E-07 .14061E-05 .49379E-03

Y-PROFILE H30+ .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO

N03.OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO

N2 .96526 .96473 .96440 .96412 .96379 .96332 .96249 .96063 .95712 .94929

02 .31267E-01 .31286E-01 .31328E-01 .31391E-01 .31485E-01 .31631E-01 .31880E-01 .32352E-01 .33486E-01 .37223E-01

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STAGE 1 2 3 4 5 6 7 8 9 10

NO .30846E-03 .38252E-03 .45199E-03 .54475E-03 .67915E-03 .88690E-03 .12400E-02 .19270E-02 .34923E-02 .78357E-02

N02 .43244E-04 .53877E-04 .60985E-04 .71721E-04 .87818E-04 .11260E-03 .15131E-03 .21001E-03 .38046E-03 .24530E-02

Y-PROFILE N204 .10508E-06 .13772E-06 .16353E-06 .21777E-06 .31678E-06 .50533E-06 .85938E-06 .13553E-05 .34993E-05 .13540E-03

HN02 .25173E-04 .31472E-04 .36480E-04 .43463E-04 .53704E-04 .69452E-04 .95099E-04 .13954E-03 .24537E-03 .55531E-03


N203 .75816E-07 .10419E-06 .13220E-06 .18254E-06 .27289E-06 .44749E-06 .80656E-06 .15145E-05 .42117E-05 .57977E-04

STAGE 1 2 3 4 5 6 7 8 9 10

H2O .30983E-02 .35222E-02 .37311E-02 .38399E-02 .39292E-02 .40207E-02 .42090E-02 .48974E-02 .58285E-02 .48832E-02

HN03 .78622E-02 .89290E-02 .94638E-02 .97589E-02 .10021E-01 .10320E-01 .10926E-01 .12997E-01 .16702E-01 . 13929E-01

K-VALUES H30+ .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO .OOOOOE+OO


N2 7810.1 8046.8 8152.1 8204.7 8247.2 8290.2 8374.8 8643.3 8889.1 7126.2

02 4007.9 4149.2 4212.8 4244.7 4270.4 4296.6 4348.1 4514.9 4678.6 3759.4

STAGE 1 2 3 4 5 6 7 8 9 10

NO .63981E+07 .70126E+07 .73074E+07 .74589E+07 .75825E+07 .77086E+07 .79651E+07 .8872 7E+07 .10020E+08 .82645E+07

N02 211.31 225.88 232.78 236.30 239.17 242.09 248.00 268.53 293.31 239.54

K-VALUES N204 10.497 11.220 11.562 11. 737 11. 880 12.025 12.318 13.337 14.566 11. 896

HN02 .11220 .12161 .12611 .12842 .13031 .13223 .13614 .14990 .16711 .13731


N203 10.423 11.144 11.485 11.659 11.801 11.945 12.238 13.253 14.479 11. 826

H2O -.1430 -.1956 -.2713 -.3930 -.6088 -1. 031 -1.976 -4.706 -19.27 -182.4

RATES OF GENERATION KMOL/HR HN03 H30+ N03.6821E-01 .3377E-06 .6901E-01 .1291 .2873E-05 .1287 .1810 .8287E-05 .1808 .2614 .1945E-04 .2614 .4051 .4556E-04 .4051 .6868 .1137E-03 .6868 .3012E-03 1. 320 1. 319 3.168 -.2516E-03 3.168 13 .24 -.8397 13 .24 114.9 17.87 114.9

STAGE 1 2 3 4 5 6 7 8 9 10

...

.

N2 .OOOOE+OO .OOOOE+OO .OOOOE+OO .OOOOE+OO .OOOOE+OO .OOOOE+OO .OOOOE+OO .OOOOE+OO .OOOOE+OO .OOOOE+OO

02 -.6178E-01 -.9174E-01 -.1262 - .1823 -.2823 -.4807 -.9351 -2.197 -7.098 -39.12

",

... .1

>

."0 .•

. -g··r

=: 9:1 >
.::: ..

:::.:.:.::::::-.;.::::;::;:.:.:

2.195EI6, 18939 10,0.01 298-378

2.195EI6, 18939 10,0.01 298-378

1.5E8, 28369 10,0.05 298-378

1.5E8, 28369 10,0.05 298-378

-17,3625 10,0.05 298-378 40

± 5%

11

± 5%

9

± 5%

1680

± 5%

105

" , ...:.:...:.... :. . .:.::-

.: stnd) D 0.016391 Qks(D6N) 0.955505

Rale NO [kmollhJ

Column top vapor flowrate NO


Epanechnikov estimate

Probability curve

250r-----------:IIII:""'""---------. 0.9 200

0.8 ------- ..... ------------------ - ----

0.7 .. -- _............... -- .... -- -_ .. --- -_..........

-------.-.-----------

.. -- -- .. -_ .. -_ .. _... -_ .. -- .. --

~150

'a ~

lOO 0.3 -- ... -----_ .. _--_ .. -------

50

-- ..... -------- ....... -_ .. ----------

0.2

O+---~~~-~-~---r_-~~~--~

0.642

0.646

0.644

0.65

0.648 0.652 Rate NO [kmollhJ

0.654

0.658

0.656

0.1 O+-----~~-r_--r_-~~-~~-~

0.644

Rate NO [kmollhJ

count sum avg vars min max median lekw 3ekw sids h glow ghigh gpoints gwidth

372 200.0503 0.53777 2.24E-05 0.526758 0.563509 0.537435 0.534289 0.540547 0.004737 0.003 0.522021 0.568247 50 0.000943

Column top flowrate NO Rate NO [kmol/h] Epanechnikov estimate Probability curve Density histogram, 25 classes

Column top flowrate NO Density histogram, 25 classes 90.-------------------------------------_.

Basic run for changed input file All parameters varied Compensation done for kinetics

hpoints hwidth

25 0.001926

80 ------------------

--------------------------------------

70 ------------------

----------------------------------

60 ----------------

----------------------------------

50 ----------------

--------------------------------

40 ----------------

--------------------------------

30 ----------------

------------------------------

20 --------------

------------------------------

10 --------------

1----------

------------------

or--,~a~II~~~~~~~~~~~~--~ 5.220E'{)1 5.432E'{)1 5.644E'{)1 IlI

Kolmochorov-Smimov test (prob D > stnd) D 0.048192 Qks(DBN) 0.353318

Rate NO [kmolJbJ

Column top flowrate NO



Probability curve

80r---------~=-._--------------------_.

0.9

70

0.8 _••• ------------------

60

c

0.7 --------------------

50

cO.6

a

·240

"

-------------------------------._--------._----------------------

~

.Ll

"0

0.5

~0.4

30 20

0.3 -------------

10

0.2 -----------

-----------------------------------------------------------------------------------

0.1 8.52

0.53 0.525

0.54 0.535

0.55

0.545 0.555 Rate NO [kmolJbJ

0.56

0.57

0.565

o+---=r--_.----r---~--~----r_--,_--~

0.25

Rate NO [kmollhJ

count sum avg vars min max median le kw 3ekw stds h glow ghigh gpoints gwidth

372 49981.74 134.3595 0.000987 134.2689 134.4757 134.3595 134.3392 134.3803 0.031413 0.02 134.2374 134.5071 50 0.005503

Column bottom flowrate H30+ Rate H30+ [kmol/h] Epanechnikov estimate Probability curve Density histogram, 25 classes

Column bottom flowrate H30+ Density histogram, 25 classes 14r-------------~__------------------~

12 ------------------------

Basic run for changed input file All parameters varied Compensation done for kinetics

10 ------------------------

8 ------------------------

6 - ••••••••••••••••••• 4 •••••••••• -.- •••••• -

hpoints hwidth

25 O.ot1234

2

····-----·······1

o

.11.1

Kolmochorov-Smirnov test (prob D> stnd) D 0.024589 Qks(DBN) 0.978079

1.342E+02

111·················_--_·

Ill. 1.344E+02 Rate H30+ [kmolJhl

RI

1.345E+02

Column bottom flowrate H30+



Probability curve 0.9 •••••••••••••••••••••••••••••••••

12

0.8 •••••••••••••••••••....••••••. - .-.--.. -- .. - ••.•.• -.•.••

10

0.7 ------_ •• _._.----------- •• -

-------.-.-----------------

cO.6

r3

-ii 0.5

.rJ

~0.4 0.3 _._-----------.----- -----.----------.------------------

0.2

2 O~--~~~--~r---~~~--~~~

134.2

134.4

134.25

134.35 134.45 Rate H30+ [kmolJhJ

134.5

134.55

0.1

l~

.25 Rate H30+ [kmolJhJ

1000 134352.2 134.3522 5.92E-05 134.3231 134.3771 134.3523 134.3469 134.3571 0.007696 0.003848 134.3154 134.3848 50 0.001417


Column bottom liquid flowrate H30+ Rate H30+ [kmol/h] Epanechnikov estimate Probability curve Density histogram, 25 classes

Column bottom liquid flowrate H30+ Density histogram, 25 classes ~.-----------------------------------~ 50 .--.--.--.--.-----------......

Basic run for changed input file Only kinetics varied

• ••••• - •• --- •••••••••• -- ••

40 .- •••••••• -.- ••• -- •• - •• -..

--- •• -.--.-- ••••••••••••

30 ••••• - ••••• - •••••••• --.-..

..-•••••••• -----.-.- •• -.

20 ---------.---.----------

hpoints hwidth

25 0.002892

------------ •• --- ••• --

i

1:+--_---_--T"'--r;-- -1"'"1--""T---1--~I YI ~ I,,.I~r.yy.Y¥JipII,.IIII,.llllyl -I -~.,.~~~-- -r;--,....., •• -• • '-'.-1. llY

Kolmochorov-Smirnov test (prob 0 > stnd) 0.015406 Qks(DBN) 0.97155

1.343E+02

o

1.343E+02 Rate H30+ [kmolA1J

1.344E+02

.,:.-"

Column bottom liquid flowrate H30+

Column bottom liQ uid flowrate H30+

Epanechn&ov estimate

Probability curve

~.---------------------------------~

0.9 •••••••••••••••••••••••••••••••••••••• 50 ----------------------------

-

-----.- •• --.-.---.-.-- ••

0.8 0.7 -_ . . -_ .. _...... -- --- .. -_ .. _.. --- -_ .. --- ---

40

.. --- --- ........ -- --- .. - .. _..

?;> 0.6

a

il 0.5 .&l

~0.4

20

0.3 .. -- --- .. -- -_ .. --- --- --- ---..

10

------ _.. - --- .... - .. -- --- --- --_ ....

02 -•• -••• -•••••• -••. -.--- .••••••• --------.•• --.- •••••••• 0.1

134.33 134.32

134.35 134.34 134.36 Rate H30+ [kmol/hJ

134.37

134.39 134.38

194.32 Rate H3O+ [kmolJhJ

count sum avg vars min max median lekw 3ekw stds h glow ghigh gpoints gwidth

1000 536.8462 0.536846 1.25E-06 0.533711 0.539893 0.536822 0.536077 0.537649 0.001118 0.000559 0.532593 0.54101 50 0.000 172

Column top vapor flowrate NO Rate NO [kmol)h] Epanechnikov estimate Probability curve Density histogram. 25 classes

Column top vapor flowrate NO Density histogram. 25 classes 350r------------------~

300 - - - -- - - - - - -- - -- - -- - -- ----.

Basic run for changed input file Only kinetics varied

250 ----------------------200 -----------------------

150 -------------------., 100 ---------.---------

hpoinls hwidth

25 0.000351

5: -----·--------~-I

Kolmochorov-Smimov test (prob D > slnd) D 0.01795 Qks(DBN) 0.904032

5.326E-01

·lrii-~------------5.365E-01

• 5.403E-01

Rate NO [kmol/h)




Probability curve

350.-------------------,

0.9 •••••••• ------ •••••••••••• --------- ••••••

300

0.8 250

0.7 ~O . 6

i"= 0.5

••••••••••••••••••••••••••••••••

• __ •••••••••••••••••••

---- ••• -._---- ••••••• _•••• _.-- -----.--_.--------- ••• _.-

.&l

~0.4

100

0.3

50

0.2

0~532

0.1 0.534 0.533

0.536 0.535

0.538 0.537

Rate NO (kmolftl]

0.54 0.539

0.542 0.541

O+---~~~~-~--~--~--,_-~

O. 33

Rate NO [kmol/h)

. ~.


771 414.1936 0.537216 2.07E-05 0.526259 0.56259 0.537141 0.533796 0.540634 0.004554 0.002277 0.521705 0.567143 50 0.000927

Column top flowrate NO Rate NO [kmol/h] Epanechnikov estimate Probability curve Density histogram, 25 classes

Column top flowrate NO Density histogram, 25 classes 80.-------------------------------------~

70 ------------------

Basic run for changed input file Pure component parameters varied component interaction parameters varied

··--_·_------T----------------------

60 ---------------50 ---------------40 ---------------30 ----------------

hpoints hwidth

20 ----------------

25 0.001893

----------~

10

o


II

5.217E-OI

5.425E-Ol Rate NO [kmolAtJ

5.634E-OI




Probability curve

80r-----------------------------------~

0.9

70

0.8 0.7 -------------------- -----------------------------------

2;> 50 I.------------ ------------ -------------------------------

'240 -----------

"

------------- ------------------------------

."

30 ----------- ---------------

----------------------------

2;>0.6

a

i.&> 0.5

~0.4

20

0.3 ------------

10

0.2 ----------

------------------------------------------

--------------------------------------------

0.1 8.52

0.53 0.525

0.54 0.535

0.55 0.545 0.555 Rate NO [kmolAtJ

0.57

0.56 0.565

O+-~_r--~----r_--~--_r--_,._--~--~

0.25

Rate NO [kmolAtJ

771 103587.1 134.3543 0.001027 134.2545 134.4989 134.3529 134.3323 134.3761 0.032043 0.016022 134.2224 134.5309 50 0.006296


Column bottom liquid flowrate H30+ Rate H30+ [kmol/h] Epanechnikov estimate Probability curve Density histogram. 25 classes

Column bottom liquid flowrate H30+ Density histogram. 25 classes 14r-----------------------------------~

Basic run for changed input file Operating parameters varied Feed composition varied

hpoints hwidth

25 0.012854

12 ------------------------

--------------------------------

10 ------------------------

--------------------------------

8 --------------------

----------------------------

6 --------------------

----------------------------

4 --------------------

--------------------------

:+-------~-----

I

~ ~1.fI¥¥I'T1.~-

--r-r-r-- - - - - . . -. -- r-- r - -- r-- - - -- .--, -

-rl"-I'Y'-


1.342E+02

1.344E+02

1.345E+02

Rate H30+ [krno\ftlJ

Column bottom liquid flow rate H30+

Column bottom liquid flowrate H30+


Probability curve

14r---------------------------------~

0.9 12 ----------------------

- ------------------------------0.8

10

0.7 --- •• ---._ ••••• _••••••• _.-

•••• _----------._.----------

cO.6

a

~

0.5

e

c..0.4

0.3 0.2

2 O~--~-c--~--~----~--~~--~--~

134.2

134.3

134.25

134.4

134.35 Rate H30+ [krno\ftlJ

134.5

134.45

134.55

0.1

I~

.25 Rate H30+ [kmolJhJ

count sum avg vars mm max median lekw 3ekw stds h glow ghigh gpoints gwidth

937 511.8905 0.546308 0.008104 0.298336 0.851518 0.537242 0.486166 0.600072 0.090022 0.036009 0.208313 0.941541 50 0.014964

Rate NO in column top Rate NO [kmol}h] Epanechnikov estimate Probability curve Density histogram, 25 classes

Rate NO in column top Density histogram, 25 classes 6.---------------------------------------~


5 ------------------------

-----------------------------------

4 ------..................

• ••••••••••••••••• - ••••••••••••

3 ----------------------

2 ---------------- ••• -

hpoints hwidth

-------------------- •• - ••••

25 0.030551 O+----rTO~~~~py~~~~~~~~_r~----;


2.083E-OI

5.444E-OI

8.804E-Ol

Rate NO [krnolJh]

Rate NO in column top

Rate NO in column top


Probability curve

5.-------------------------------------,

0.9 ••••••••••••••••••••••••••••••••••••

4.5 4

C

-------------.---------.-.- ••

0.8

3.5

0.7

3

cO.6

;;

'22.5 ."" 2

~ 0.5

~0.4

1.5

0.3 -- - - -- -- - --- -- - -- - - -- -- --- - -- --- -- - - -- - -- - -- --- -- - -----

I

0.2

0.5 O~--~--_r--~----r_--~--~~~--~

0.2

0.6

0.4

0.3

0.5

0.8

0.7

Rate NO [krnolJh]

0.9

0.1 O+-----r-~~r---~-----r-----r----~--~

0.2 Rate NO [kmolJb]


937 125686.9 134.1376 13.11342 120.5496 144.6695 134.164 131.8082 136.6465 3.621246 1.448498 116.9284 148.2907 50 0.640048

Rate H30+ in column bottom Rate H30+ [krnol/h] Epanechnikov estimate Probability curve Density histogram, 25 classes

Rate H30+ in column bottom Density histogram, 25 classes

O.l2T""-------------------. -----------·---------·--·· · ·~I.~····-····-·-······-··--


hpoints hwidth

•••••••••••••••••••••••••• ~f g,lIiH1-ll11- •••••••••••••••••••••

25 1.306765


I.

Rate H30+ Ikmol/hJ

Rate H30+ in column bottom

Rate H30+ in column bottom


Probability curve

0.12T"'*--------------------. 0.9 ••••••••••••••••••••••••••••••••••••••••

0.8 0.7 --_.-_ •• _•••••••• _------ •••• --.----

----.--_.-._.------

~0.6

a

~

.t>

0.5

~0.4

»-

0.3

.~. .

0.2

g.

0.1 125 120

135 130 Rate H30+ IkmollhJ

145 140

150

.~ ..........

, ~ ,. " ,

0 120 Rate H30+ [kmollhJ

..\.1\ .

424 227.6138 0.536825 4.6lE-08 0.535217 0.538108 0.53684 0.536822 0.53686 0.000215 6.44E-05 0.535002 0.538323 50 6.78E-05


Column top flowrate NO Rate NO [kmoVs] Epanechnikov estimate Probability curve Density histogram, 25 classes

Column top flowrate NO Density histogram, 25 classes

6OOOr------------------------------------,

Basic run for changed input file Start estimations varied Check for convergence accuracy

hpoints hwidth

25 0.000138

5000 ••••••••••••••••••••••••••••••

• ••••••••••••••••••••••••

4000 ••••••••••••••••••••••••••••••

• ••••••••••••••••••••••••

3000 ••••••••••••••••••••••••••••••

• ••••••••••••••••••••••••

2000 ••••••••••••••••••••••••••••••

• ••••••••••••••••••••••••

1000 ••••••••••••••••••••••••••••••

• ••••••••••••••••••••••••

o~--~-rrr~~TT~~·I~I~_~I-~~~-rrT,_--~ 5.350E-Ol 5.365E-Ol 5.380E-Ol

Kolmochorov-Smirnov test (prob D > stnd) D 0.313966 Qks(DBN) 9.95E-37

Rate NO [kmoVsl

.

.;"




Probability curve

8~r----------------------------------'

7~ ---------------------------

-------------------------

0.9 ----------------------- ••••• -- -- •••••••••• _------_ •••• 0.8 --.---- •••••••••••••• ---....... ----_ ••• _-_ ....... _. . _---

6000 --------------------------5~ •••••••••••• -•••• -.........

----------------- •. -.... • ••••••••••••••••••••••••

0.7 .. -- --- --- --- . . -- --- --- -- ..... -_ .....

c '2 4~

..,u

cO.6

........ -... -.. -•..••.•••. -

.. -.. - ....• - ••• -••••••• -

3~

•••••••••••••••••••••••••••••••••• - •••••••••••••••••

2~

-..•••..•.• -..............

l~

••••••••••••••••••••••

. ....•..••.•••••••••••..•

-;J .. ...................... ~

:3

j

0.5

~0.4 0.3 -----------_ . . ------- ... ---.- . . -------------------------0.2 ----------------._-------

..

--_._---------------------

0.1

&535

0.536 0.5355

0.537 0.5365 0.5375 Rate NO [kmolls I

0.538 0.5385

O~--_r----P_~~-----_,r_-----,_-----_,-----~

O. 35

Rate NO [kmolls I


424 56965.12 134.3517 5.6E-05 134.2791 134.3945 134.3519 134.3511 134.3524 0.007484 0.001 134.2716 134.402 50 0.002662

Column bottom flowrate H30+ Rate H30+ [kmoVs] Epanechnikov estimate Probability curve Density histogram, 25 classes

Column bottom flowrate H30+ Density histogram, 25 classes

IW,-------------------------------------, 140 ---------------------------------

120 ---------------------------------


lOO --------------------------------80 ---------------------------------

w --------------------------------hpoints hwidth

40 ---------------------------------

25 0.005434

20 --- --- --- --- ------ --- --- ------ ~~ II~

--------------------

O+---~rr~~rr~rr~~~~~~~rr~--;

Kolmochorov-Smirnov test (prob D> stnd) D 0.300425 Qks(DBN) 1.15E-33

1.343E+02

l.343E+02

l.344E+02

Rate H30+ [kmol/s)




Probability curve

350~--------------------------------~

0.9 ---------- ........................... .

300 ------------------------------- -----------------------

0.8 250 ------------------------------- -----------------------

0.7 ~0.6

~200

'a

;3

i 0.5

~ 150

~c.0.4

lOO ------------------------------

----------------------

50 ------------------------------ - ----------------------

\

134.3 134.28

134.34 134.32

134.36

0.2 --- .. ----------------------- .. ------ .. - .. -----------_ .. -_ .. -

0.1 ••••• -- ••• ------- ••• -- ••••••••••• -

134.42

134.38

Rate H30+ [kmol/.)

0.3 • __ .................................. ..

134.4

I~

.26 Rate H30+ [kmol/s)

_... --- •••• _.-------

424 823.5806 1.942407 4.26E-06 1.921226 1.954481 1.942472 1.942259 1.942607 0.002064 0.00031 1.919162 1.956545 50 0.000763


Column bottom flowrate HN02 Rate HN02 [kmoVs] Epanechnikov estimate Probability curve Density histogram, 25 classes

Column bottom flowrate HN02 Density histogram, 25 classes

4OOr-------------------------------------, 350 --------------------------------300 ---------------------------------


250 --------------------------------200 --------------------------------150 ---------------------------------

hpoints hwidth

lOO ---------------------------------

25 0.001558

50 ---------------------------------

OT---"rr~on".,~~~·-~~I·~~~~rr--~

Kolmochorov-Smirnov test (prob D > stnd) D 0.289303 Qks(DBN) 3E-31

1.919E+00

1.936E+00

1.953E+00

Rate HN02 [krnoUs)

Column bottom flowrate HN02

Column bottom flowrate HN02


Probability curve 0.9 ------------------------------------ - --------------0.8 ------------------------------------ .. -----------------

:::t::::::::::::::::::::::::::::::::: :::::::::::::::::::: I

300 -------------------------------c250

0.7

--------------------

cO.6

a

·2

~2oo

150 -------------------------------- -

-------------------

1

0.5

0.4 0.3 .. -- -_ .. -_ .. -_ .. --- .. -- --- .. -_ .. -- --- ---

lOO -------------------------------- - ------------------50 -------------------------------

-- -------------------

0.2 -------------------------------0.1 ------------------------------- --

1.925 1.92

1.935 1.93

1.945 1.94

Rate HN02 [krnoUs]

- ---------------------------------------

1.955 1.95

1.96

?92 Rate HN02 [krnoUs]

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