ABB Review

ABB Review 9/95

Thermonet® new energy technology for district heating More efficient and environmentally friendly screw compressors New process for recycling residues from solid waste incineration Optimization of automotive paint shop Operation Unconventional fuels no barrier to economic gas turbine Operation

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ABB is an international Company firmly committed to electrical engineering. It has industrial bases on all continents and is represented in over 140 countries. Its major businesses are power plants, power transmission, power distribution and industrial equipment; other important business activities are in the robotics and environmental sectors.

The ABB Review is published ten times a year in English, French, German, Spanish and Swedish. Publisher and Copyright © 1995 ABB Asea Brown Boveri Ltd. Zurich/Switzerland Publisher’s Office ABB Corporate Communications Ltd Rütistrasse 6 CH-5401 Baden Switzerland Tel. +41 56 205 48 36 Telex 755 749 abb ch Telefax +41 56 221 22 74

Thermonet is a new community

cooling and heat recovery are united by

energy System which reduces the cost

Thermonet in a single System. Thermal

of installing and operating district heating

utilization is improved by, among other

networks. The three separate heat-ex-

things, a low return water temperature.

changers normally used for the heating,

Page 4

Enquiries concerning the editorial content should be addressed to: The Editor ABB Review Rütistrasse 6 CH-5401 Baden Switzerland Subscription correspondence should be addressed to the nearest ABB representative or direct to the publisher’s Office. Notifications of change of address should include the address label from the most recent issue. Orders for the ABB Review may be placed direct with the publishers, ABB agents or representatives, or with appointed booksellers. Subscriptions/copy prices Annual subscriptions: SFr 110.00 (incl. regulär mailing to all countries) Airmail rates: Europe plus SFr 35.00 Overseas plus SFr 52.00 Single copies of back issues: SFr 15.00, incl. mailing Subscription Orders for the next 10 issues can be placed at any time. Lithography and Printers Vorarlberger Verlagsanstalt Aktiengesellschaft A-6850 Dornbirn Austria The ABB Review is printed on paper made from chlorine-free pulp. Partial reprints or reproductions are permitted subject to full acknowledgement. Complete reprints require the publisher’s written consent. ISSN: 1013-3119

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ABB

Review 9/1995

New screw compressors developed by ABB have special benefits for operators of large refrigeration and freezing units in the food and process industries. The

new-generation

compressors are

more compact, efficient and environmentally friendly than their predecessors. Page 10

CONTENTS

T H I S

I S S U E

Thermonet® System saves energy and lowers costs

Seppo Leskinen Eero Hätinen Kalevi Hyvärinen Page 4

New refrigeration compressors energy-efficient and environmentally sound Tommy Asplund Lennart Rolfsman Page 10 InRec™ is a new, modular process

the DryRec™ sorting System, a consider-

that answers the question of what to do

able improvement in residue quality is

with the residues left over from solid waste

achieved. The AshArc™ furnace can be

incineration. By combining the DryEx™

used for the treatment of the fine fraction.

discharge process with components from

Page 15

InRec™ process for recovering materials from solid waste incineration residues Dr. Franz-Georg Simon Karl-Hugo Andersson Page 15

Paint finishing is given a high priority by car makers. In just a few decades,

Optimization of automotive

paint spraying by hand has given way to

paint shop Operation

fully automated, high-performance paint

Dr. Dragoslav Milojevic

shops which are also environmentally

William Mainieri

compatible. ABB is a leading supplier of

Page 21

compiete paint finishing Systems to the automotive industry.

Experience

Page 21

with unconventional gas turbine fuels Dr. Dilip K. Mukherjee Page 29

News in brief ABB’s experience with unconventional gas turbine fuels enables it to deliver gas turbine power plants that can be fired on blast furnace gas, crude or residual oil, or syngas - gas from residual, biomass or coal gasification processes. Orders were received recently for gas tur­ bine and combined cycle power plants fired on blast furnace gas and residual gas. Page 29

100-MW adjustable-speed drive for NASA wind tunnel fan • LP turbine Upgrade boosts nuclear plant’s output by 40 MW • GE Orders 10,000 gate units • 400-kV XLPE cable System successfully tested • Blast furnace process control modernized • Hand-over of Escatrön PFBC power plant Page 38

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InRec™ process for recovering materials from solid waste incineration residues

ation Stacks are minimal today. And for the fly ash ABB has developed a process technology - called Deglor - which transforms it through melting into a harmless glass plus a salt mixture as byproduct [3], The Total Cleaning and Recycling (TCR) System [2], also developed by ABB, has likewise shown that end-products of the flue-gas cleaning process can be recovered

and

re-used

in various

industries

(eg, hydrochloric acid in the Chemical industry and gypsum in the construction sector). One major problem, however, has remained - recycling of the bottom ash, an inhomogeneous mixture of mineral (ash,

bricks,

glass,

etc) and

metallic

materials (iron scrap, elementary aluminInRec is a new process offering an answer to the increasingly urgent

ium, copper), is only possible to a limited

question of what to do with the residues left over from solid waste incin­

extent. Table 1 gives an OverView of the

eration. State-of-the-art incineration grate technology is the starting

solid residues that are left over from

point for InRec. Dry bottom ash is discharged from the furnace by the

municipal waste incineration.

DryEx™ System and sorted by DryRec™ - a dry process for separating

The composition of the ash dictates the

the iron, other metals and the mineral fraction. The untreated coarse

requirements which a process for treating

fraction can be used direct in road construction or landfilled. The fine

bottom ash must satisfy. Its main com-

fraction is melted in an AshArc™ furnace, if required with the fly ash

ponents are the oxides of Silicon, alumin-

from the particulate Separation process. Conditioning or solidification

ium and calcium (ie, quartz (Si02), clay

are possible as an alternative to energy-intensive melting.

(Al203) and Urne (CaO), all of which are constituents of rock. Besides these, there

^^^e long-term goal of the waste dis-

are several mineral components, some of 25 percent of the total - is discharged as

posal industry is to produce recyclable

which inhibit recycling.

O shows the

Chemical composition of the mineral frac­

bottom ash through a water bath.

materials for continual re-use, plus envi-

The combustion gases contain fine par-

tion contained in bottom ash.

ronmentally compatible materials which

ticles (fly ash), which are separated and

Fe203 originates mainly from iron that is

are suitable for landfilling. This goal is

collected by electrostatic precipitators or

oxidized during the combustion process.

feasible when solid muhicipal waste is

bag filters. Acidic gases released by the

burnt in state-of-the-art waste incineration

combustion, primarily hydrogen Chloride

plants. ABB öfters across-the-board incin­

and

eration plant technology, from the grate

scrubbers.

sulfur

dioxide,

are

removed

by

[1], boiler and steam turbines for energy

Modern technology has ensured that

recovery through the flue gas cleaning

pollutant emissions from waste inciner­

Systems [2] to the Controls.

Chemical composition of the mineral fraction of bottom ash

□

Zn, Cu, Waste incineration residues

Dr. Franz-Georg Simon

In thermal waste disposal, sorted solid

ABB Corporate Research

waste with a typical heating value of

Baden, Switzerland

between 8,000 and 12,000 kJ/kg is burnt

Karl-Hugo Andersson

in grate furnaces. The non-combustible

ABB W+E Umwelttechnik

CI, Na, K Fe203

portion of the waste - approximately

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Ca(OH)2 + nSi02 Ash, incl. 20% water

Fine fraction

-> CaO • nSi02 + H20

Bricks^^^\ASh These hydraulic reactions lead to min­

Ceramic^fcÄ3RE=sss=4 GlassW^|

eral attachments on the scrap iron, and these have to be removed mechanically

Al + Cu^™^^Oversize Zn

Iran

material

a

before recycling can begin. In addition, Nonferrous metals

Iran

Oversize material ^

the fine fraction is distributed over the coarser fractions with

Material fractions in dry (a) and wet (b) bottom ash. Besides allowing better Separation of the fractions, dry bottom ash ensures a higher purity for the metals.

0

their smaller

heavy-metal content, making it more difficult to recycle the mineral fraction (eg, as material for road construction). • It is no longer possible to differentiate

The alkaline earth metals calcium and

line environment with a pH-value of

between the different materials in the

magnesium may be partly present in the

about 12 is formed when the ash

bottom ash, eg, glass, bricks, ceramic,

form of their carbonates rather than their

becomes wet. Linder these conditions,

oversize material (offen large pieces of

oxides (eg, CaC03, limestone). Chlorides

many elementary metals (eg, iron and

scrap metal), sintered ash-like material

and sulfates of sodium and potassium

aluminium) are oxidized and can no

form the water-soluble fraction of the

longer be recycled.

bottom ash. The combustion efficiency achieved with the best technology avail-

and the fine fraction (0-2 mm). • A water content of approximately 20 percent increases the total mass that

2 AI + 6 H20 -> 2 AI(OH)3 + 3 H2

(1)

able today is so good that the residual

has to be landfilled. In the case of dry bottom ash (ie, ash

carbon content (CHX) is always lower

• The fine fraction of the bottom ash

which does not come into contact with

than 1 percent. The heavy metals zinc

(0 to 2 mm) contains a very large Pro­

water), neither oxidation reactions nor

(Zn), lead (Pb) and copper (Cu) are found

portion of calcium oxide. The heavy

hydraulic reactions take place. When the

in concentrations of between 500 and

metals are also found primarily in this

ash is dry it can be separated into different

4,000 mg/kg.

fraction. When the fine fraction comes

groups

of

materials.

0

shows

the

As already mentioned, the bottom ash

into contact with water the CaO which

respective material break-downs for dry

is discharged through a water bath. This

is present causes hydraulic reactions

and wet bottom ash.

has several consequences:

with other oxides simiiar to those

• Since the CaO reacts with the water to

occurring during the formation of con-

fractions by mechanical

crete.

as sieving. The fine fraction measuring

produce milk of lime (Ca(OH)2), an alka­

Dry bottom ash is easily divided into means,

such

0-2 mm is easily separated, since no hydraulic reactions take place. Because the heavy metals are concentrated in this Table 1: Residues from waste incineration and their treatment/recycling

fraction, further treatment is necessary. High-purity iron and nonferrous metals can be separated with the help of mag-

Bottom ash (25 - 30% by weight)

nets or eddy current technoiogy. The min­

Restricted recycling in road construction

eral fraction (> 2 mm) is for the most part inert and can be used direct as road con­

F/y ash (2.5 - 3% by weight)

struction material, etc.

Hazardous waste, disposal Underground, stabilization/solidification, melting (Deglor [3]) Flue-gas cleaning residues (1.5-3% by weight, depending on process)

InRec™ process

Dry and semi-dry flue-gas scrubbing:

The patented InRec process [4] was

Stabilization/solidification, landfilling

developed to take advantage of the bene-

Wet process: recycling as hydrochloric acid, industrial salt, gypsum

fits of the dry discharge of bottom ash. The modular design of the process, with

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DryEx for the dry discharge, DryRec for sorting the dry ash and AshArc for treating the fine fraction, is shown in 0 A more

Glass

detailed description of these modules is Metal concentrate

given in the following.

DryEx™ process Inert material

The bottom ash is discharged from the furnace dry, ie, a water bath is not used,

Iran

To operate the installation, the furnace has to be sealed off from the atmosphere. In

Nonferrous metals

conventional plants the water bath acts as the seal; in InRec the ash discharge process performs this function. The DryEx module begins separating the material into

InRec™ process configuration

0

two fractions (one larger than, one smaller than 40 mm) as soon as the ash is dis­ charged from the incineration grate. This

the nonferrous metals in the bottom ash

proven, having already been used suc-

takes place on a sieve conveyor of a type

(mainly

mechanical

cessfully on a large scale in other industrial

used widely in industry for separating min­

components of the DryRec process are

sectors. What is new is their use in Con­

eral materials. The topside material -

sieves, sorting belts, a mill for crushing the

nection with dry bottom ash. Initial tests

mostly scrap metal and stones larger than

mineral material and conveying equip-

with 2 to 5 tonnes of bottom ash have

about 40 mm - is discharged as usual

ment. □ Shows the flow chart for the

already been carried out by the manufac-

through a water bath as this fraction does

DryRec process.

turers of the flip-flop sieves, magnets and

aluminium).

Other

not react with water. The material smaller

The end-products of the DryRec mod­

eddy-current Separators. A pilot DryRec

than 40 mm contains the alkaline material,

ule are recyclable metals (iron and alumin­

process will also be installed at a Swiss

which is not allowed to come into contact

ium), a mineral fraction (approximately

waste incineration plant to produce a suffi-

with water and is discharged through a

2-40 mm) and the fine fraction (less than

cient amount of products for trying out dif­

cellular wheel sluice, etc. If Operation of

2 mm). Tests in the laboratory have shown

ferent recycling options for the mineral

the conveyor is disturbed for any reason,

that the coarse fraction (2-40 mm) hardly

fraction.

all of the material can be discharged

reacts with water since virtually no alkaline

through the water bath. A prototype of the

material is present. Heavy-metal leaching

DryEx System is currently being installed in

is shown by Standard leaching tests to be

AshArc™ process

a Swiss waste incineration plant, and first

so slight that is it possible to use this frac­

The fine fraction can be treated by melting

operating

tion as a construction material. Providing

in a furnace (AshArc process), solidifi-

the quality is good, the metal yield can be

cation

experience

should

become

available by the end of 1995.

by means of bonding

agents

sold on the scrap market - in Switzerland,

(admixture of cement or clay) or condition-

for example, approximately US$ 650 per

ing (wetting and storing). The AshArc pro­

DryRec™ process

tonne is

metals.

cess melts the bottom ash to produce

DryRec is a mechanical process for sort­

Further treatment of the fine fraction is

a glassified product which satisfies all

paid for nonferrous

ing the dry bottom ash discharged from

necessary betöre it can be re-used or

landfili requirements for inert materials.

the DryEx module. In a first Step, the fine

dumped on landfili sites. The methods that

Other recycling options also exist.

fraction smaller than 2 mm is separated by

can be used to treat the fine fraction are

sieving in Order to keep the dust load for

given under 'AshArc™ process’.

The furnace used in the AshArc pro­ cess is an ABB DC arc furnace which is

the rest of the installation to a minimum.

DryRec is a simple process designed

currently operating successfully in more

Iran is removed by means of a magnet

to sort dry bottom ash for the purpose of

than 30 installations in the metallurgical

drum and overhead magnets, an eddy-

recovering recyclable materials. The com­

industry [5], The ash is fed into the furnace

current Separator being used to extract

ponents that make up the process are all

through a hollow electrode and melted by

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an arc produced between the tip of the

can be recycled in the metallurgical indus-

justified providing the recyclable end-

electrode and a metal bath, on which the

try.

contains,

products replace materials which would

molten material, which is electrically con-

besides air and C02, S02 and HCl from

otherwise have to be produced by means

ductive, floats. The molten ash can be

the thermal decomposition of the Sulfates

of

either

and Chlorides. The exhaust gas finally

example,

batches from the furnace. As in other bot-

passes to a cleaning stage. 0 shows how

AshArc process can be used as glass

tom ash melting processes, the high

the AshArc furnace works.

discharged

continuously

or

in

temperature immediately decomposes the

The

exhaust

gas

now

The AshArc furnace is designed to

energy-intensive the vitrified

processes. product

For

of the

wool, cellular (foamed) glass or admixture for cement clinker. The cost of the AshArc

organic Compounds. The Chlorides are

handle ash at the rate of more than

process is approximately US$ 240/t of

largely evaporated, leaving the furnace

2 tonnes per hour. This allows the fine

ash.

through the exhaust-gas exit. Use of a

fraction of the bottom ash (some 8 per-

The process has been tested on a large

graphite electrode, which is consumed as

cent of the total waste) to be treated

scale to determine its suitability for melting

it is fed slowly into the furnace, produces

together with the filter ash from the flue-

bottom ash. In all, some 50 t of bottom

an atmosphere in the furnace in which the

gas cleaning process (about 2.5 percent

ash (fine fraction 0-2 mm), fly ash and a

heavy-metal compounds are reduced to

of the total waste). In very large waste

mixture of the two was melted. Tables 2

their elements and either sink into the

incineration plants, an AshArc installation

and 3 give the measured heavy-metal

metal bath, forming an alloy, or leave the

is used for the direct treatment of the

content in the glass and the measured

furnace as gas. To prevent toxic organic

residuals that are produced, the exhaust

leachate concentrations, and compares

compounds from reforming, the exhaust

gases passing to the flue-gas scrubber.

them with the limits for inert materials as

gas exiting the furnace is first passed

Alternatively, one AshArc furnace can be

prescribed by the Swiss authorities (TVA).

through a CO afterburner and then cooled

used for the centralized treatment of resid­

The measured values show that recycling

rapidly with water and air. The evaporated

uals from several smaller plants. The ener-

is possible, since they lie below the limits

Chlorides resublimate and are removed by

gy consumption of the AshArc process is

for inert materials.

bag filters. This heavy metal concentrate

0.8 to 1 kWh/kg. This high energy figure is

The DryRec™ process for sorting dry bottom ash

Inert material

18

ABB

Review 9/1995

In cases where vitrification is not de-

□

*

RESIDUE

m

TREATMENT

m ®

0

The AshArc™ furnace for melting ash 1 2 3

Fine fraction Fly ash Additive

4 5 6

Are furnace Vitrified slag Afterburning/quenching

7 8 9

Blower Bag filter Metal concentrate

sired (eg, where landfilling is more econ-

water transforms the lime into lime hydrate

can be achieved simply by combining the

omical), the InRec process offers alter­

(calcium hydroxide). The material is then

DryEx dry discharge process with some

native methods of treating the residuals.

amenable to the hydraulic reactions (reac-

components of the DryRec process (siev-

Mixtures of fly ash and the fine fraction

tion 2) mentioned earlier and can also

ing of the fine fraction, Separation of the

(0-2 mm) of the bottom ash can be com-

react better with the carbon dioxide in the

iron and nonferrous metals). The AshArc

pacted by admixing clay or cement. The

air or rain to form limestone (CaC03). This

furnace can be used for follow-up treat-

compacted material can be shaped into,

and other reactions reduce the alkaiinity of

ment of the fine fraction, which can be

eg, pellets, for easier handling. Compact-

the ash. Leaching tests Show the pH value

mixed with fly ash (decentralized for very

ing the material also strongly reduces the

to be between 11 and 11.5, the heavy-

large waste incineration plants or central-

risk of heavy metals being released in

metal compounds exhibiting only a very

ized for several smaller plants).

landfills. Table 4 shows the results of initial

slight solubility. After the bottom ash fine

The InRec process can also be retro-

tests with compacted products.

fraction has been conditioned in this way

fitted to existing incineration plants. In a

(wetting and storage), it is safe for land­

pilot project started this year (1995), a

The fine fraction contains far fewer heavy metals than the fly ash produced

filling.

waste incineration plant was equipped for the first time with a dry discharge System

by the particulate Separation process.

(DryEx) and components for dry sorting

Because of this, wetting of the fine frac­ tion, followed by storage for one to three

InRec - the flexible solution

(sieving of the fine fraction and Separation

months, causes the heavy metals to be

The InRec process is modular and com-

of iron and nonferrous metals).

largely immobilized, allowing landfilling of

prises independently operating System

InRec provides operators of waste

the conditioned bottom ash. Contact with

components. An improved residue quality

incineration plants with options that allow

ABB

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E

considerable flexibility in the handling of Table 2:

residues.

Heavy metals contained in the vitrified products of the AshArc

melting, the quantity of material treated is

process, and limits prescribed by the Swiss authorities (TVA) Inert materials

Vitrified products

Element G1

G2

(TVA)

[mg/g]

[mg/g]

[mg/g]

Zn

0.5

0.7

1.0

Cu

0.5

0.5

0.5

Pb

0.1

0.1

0.5

Cd

< 0.004

< 0.004

0.01

Ni

0.01

0.01

0.05

When the process

includes

small and requires only little energy since the majority of the bottom ash (coarse fraction in excess of 2 mm, about 60 percent of the bottom ash) is separated and can be recycled without prior treatment.

References [1] M. Künzli, E.W. Haitiner: The incineration grate’s central role in thermal waste

The base material for G1 and G2 was bottom ash fine fraction and a mixture

disposal. ABB Review 10/90, 17-22.

of bottom ash and fly ash (70:30), respectively.

[2] K. Carlsson: TCR for effective control

of flue gas emissions and Processing of reaction products for recycling. ABB Review 8-9/90, 11-16. Table 3:

[3] I. Joichi, J. Balg, C. Wieckert: De-

Heavy-metal concentrations measured during an elution test

toxification of municipal waste incineration

as per TVA for vitrified products from the AshArc process

residues

by vitrification.

ABB

Review

6-7/95, 9-16. Inert materials

Vitrified products

Element G1

G2

(TVA)

[mg/i]

[mg/l]

[mg/l]

[4] Process and apparatus for Processing slag from incinerators for refuse. European Patent 0372 039 B1 (1992)

0.1

[5] S. E. Stenkvist, H. Stickier: The DC

0.079

1.0

arc furnace - a low-cost melting unit. ABB

0.002

0.2

Review 10/92, 3-10.

0.01

0.2

< 0.005