XV Conference Environmental
Technological modifications in pilot research on CO2 capture process Tomasz SPIETZ*, Lucyna WIĘCŁAW-SOLNY, Adam TATARCZUK, Aleksander KRÓTKI, Marcin STEC – Institute for Chemical Processing of Coal, Zabrze, Poland Please cite as: CHEMIK 2014, 68, 10, 884–892
Introduction In recent years, there has been a growing interest in research regarding CO2 removal [1]. This is related to the implementation of energy and climate package by the European Union in 2008, which aims to reduce CO2 emissions from power facilities. Currently published papers present among others studies on new amine sorbents [2, 3], physicochemical data of amine solutions [4], analytical methods of determination of CO2 loadinge (α) and sorbent concentration [5], as well as model testing [6] and experimental data from research plants [7]. There are many pilot installations for CO2 capture from flue gas, both worldwide and in Poland – including Mobile Pilot Installation for CO2 removal from flue gas of TAURON group launched in 2010 and exploited by the Institute for Chemical Processing of Coal [8, 9]. Pilot installations operating with real flue gas allow thorough examination of the process, thus helping to choose optimum operation parameters, which cannot be measured on a laboratory scale, such as corrosion or effect of other acid flue gas components on sorbent operation. The barrier in applying chemical absorption method for CO2 removal from flue gas on industrial scale is the energy consumption of the process, mainly due to the high amount of energy required for sorbent regeneration. For achieving efficiency of 90% of captured CO2, energy supplied for installation operation is equivalent to the decrease in power plant efficiency by approx. 20% [10]. Decrease in the energy consumption can be achieved not only by changing the sorbent, but also through various technological modifications [11]. Classic system for amine CO2 removal Process diagram of amine installation for CO2 removal, showing classical processing system is presented in Figure 1. It shows only part related to CO2 absorption, without taking into account flue gas pre-treatment and desulphurization units. However, in each case, flue gas (input gas) entering the absorber is pre-cooled and dedusted in columns with water spray and then purified from excess SO2 and NOx. For that purpose absorption columns are most commonly used, in which flowing gas contacts alkaline solution [8, 12].
Fig. 1. Flow sheet of the standard amine CO2 capture process
Corresponding author: Tomasz SPIETZ – MSc., e-mail:
[email protected]
888 •
CO2 removal process in classic configuration of apparatus is carried out as follows. Pre-treated gas is directed to the absorber, where it contacts with counter-current flow of cooled and lean amine solution. In this column, amine reacts chemically with CO2 from flue gas and then gas purified from carbon dioxide leaves the column. Then, amine solution reach with CO2 is directed to the top of desorption column (regenerator), where it contacts hot vapours coming from heating the solution in the bottom part of the column, and CO2 desorption occurs. CO2 released from the reach solution leaves the desorption column. CO2 reach with water is cooled and the steam condesed in the cooler is collected in the separator and recirculated to the stripper. Hot lean solution is firstly directed to the heat exchanger, where it is partially cooled, transferring heat to the reach solution and then cooled to 40°C in aftercooler, after which it is recirculated to absorption column. This way absorption-desorption cycle occurs in a continuous manner. In order to improve CO2 capture process, numerous technological modifications are being implemented. Additional columns (strippers) are used, whose task is to ensure better regeneration of the solution. Moreover, except the main streams of amines from the columns – lean and reach amine – there can be two or only one additional split streams (semi-lean). Moreover, condensation heat of vapours generated in regenerator can be also used – by leading steam out of the column, letting it to expand and then compressing it, after which it is redirected to the column. Due to the vastness of discussed topic, only selected modifications are discussed in the paper. Other solutions can be found in the literature describing CCS installations [10, 12, 13]. Temperature modification in absorption column Modifications that allow temperature change inside absorption column may increase efficiency of absorption process. One of such technological modifications is the use of additional sorbent cooling system in absorption column. Solution from the bottom part of the absorber is pumped through the cooler and then recirculated to the column. It was found that cooling the solution taken from the bottom part of the column to 40°C gives the best results, in comparison with heating or cooling the solution from other parts of the column [10]. The modified installation is presented in Figure 2. The driving force of absorption process is the difference between partial pressure of CO2 at given column height (so-called operating line) and partial pressure of CO2, which settles at equilibrium (in the same column operating conditions). Solution cooling causes the decrease in equilibrium partial pressure of CO2 at the column height, at which cooled sorbent is recirculated into the column, which corresponds with the increase of driving force of absorption process. In the plot (Fig. 3) presenting the drop of CO2 partial pressure with the increase of column height, it may be seen that equilibrium curve shifts in place of applying additional sorbent cooling (1.78 m), and thus driving force increases. For the purpose of comparison, plot shows also equilibrium curve for reference system (i.e. classic configuration of installation) [10].
nr 10/2014 • tom 68
Fig. 2. Flow sheet of the absorber intercooling process
Fig. 4. Split-stream process flow sheet modification by Shoeld
Fig. 3. Operating and equilibrium lines for the intercooling process
Application of intercooling results also in the increase in sorbent absorption capacity and, therefore, CO2 loading of reach amine has higher values than for installation without cooling. Such a modification causes also the decrease in the amount of heat required for sorbent regeneration by approx. 6.4% in comparison with classical configuration. This is caused by the fact that in order to achieve the same efficiency as in classical configuration installation, lower solution circulation is applied. And the longer the residence time of the solution in the desorption column, the better sorbent regeneration. Split streams Another widely used modification in CO2 capture installations is the division of columns (absorber and desorber) into sections and isolation of additional sorbent streams. The first concept of split streams was suggested by Shoeld in 1934 (Fig. 4). He has divided absorber and desorption column into two sections, from which he had separated, respectively, streams: semireach amine – from the upper part of the absorber – and semi-lean amine – from the bottom part of regenerator [14]. Streams of semi-lean and semi-reach amine circulate between intermediate stages of columns, while streams of reach and lean amine remain in the classic circulation. This modification is to ensure optimum temperature profile in absorption column and increase absorption efficiency. Shoeld’s method provides the decrease of heating steam consumption by 50% reach and lean amine. However, such analysis is based on
nr 10/2014 • tom 68
The concept of split-stream operation is that the semi-lean amine solution directed to the bottom part of the absorber contacts gas of high concentration (high partial pressure of CO2) of acid component. At this stage, most of the CO2 is captured, and in the upper part of the absorber, lean amine stream purifies gas from remaining amounts of component, whose partial pressure is at this point rather low. Using of split flows equalize the driving force of absorption. Similar solution was applied in the testing plant of capacity of 100 m3/h launched in 2012 for studies on CO2 removal process in the Centre of Clean Coal Technology in the Institute for Chemical Processing of Coal (IChPW) in Zabrze [15, 16]. Towler [17] concluded, on the basis of model studies, that as a result of steam condensation in regenerator the solution becomes diluted, mainly at the tray below the inlet of reach amine stream. The researcher modified previously described process, removed stream of semi-reach amine solution and added heater on the pipeline of semi-lean amine, which was to maintain constant concentration of solution. He also suggested directing condensate from separator to the lower point of the column (evaporator). The entire process is presented in Figure 5. The system proposed by Towler was intended for selective removal of H2S from high-pressure systems, however Aroonwilas [12] has carried out model studies for such a system for removal of CO2 from flue gas, using 30% MEA solution and for CO2 removal efficiency of 95%. He has found that heat required for sorbent regeneration is lower by 17% – 62% (depending on the studied case) in comparison with system without split streams. However, the size of regenerator increases 2 – 4-fold.
Fig. 5. Process flow sheet modification introduced by Towler
• 889
XV Conference Environmental
absorption of acid gas using sorbent containing sodium phenolate, and the system was initially intended for purification of gas from high-pressure processes [14].
XV Conference Environmental
Stripping column with internal heat exchange Another process modification, which aims to decrease energy consumption in CO2 removal process, is the using a heat-integrated stripper (heat recorvery) [12]. Diagram of modified plant is presented in Figure 6. In this case, a hot solution of semi-lean amine, as well as lean amine is recirculated to the desorption column, where flowing through the part of column via spiral pipeline it transfers heat directly and then, after leaving the column, it is directed further to the absorber.
Fig. 6. Process flow diagram using a heat-intgerated stripper
This modification causes that heat of hot solution is transferred to the inside of stripping column, instead of being exchanged in heat exchangers outside the column, as for installation with classic configuration. Heat exchange outside the column is associated with higher losses to the environment. Heat transferred inside the desorption column results in the increase of column internal temperature and improves solution regeneration. IIn comparison with classic flow sheet configuration, reboiler heat duty is lower [12]. According to Oyenekan [18], the total energy expenditure of column (including CO2 compression) is lower by 17% in comparison with the desorption column without internal heat transfer. Experimental part In order to test effect of technological configuration on the process of CO2 removal from flue gas, number of research campaigns was carried out using Pilot Installation in Łaziska Power Plant – TAURON Wytwarzanie S.A. [19]. The Pilot Installation uses modified technology of amine absorption. One of the technological modifications in presented research installation is the division of the desorption column and separation of additional semi-lean amine stream (MRA) and system of (recovery) heat exchangers inside the regenerator, in analogy to the previously described solutions. The detailed description and operation of the Pilot Installation is presented in [20]. Below (Tab. 1) results obtained for system operation with flow of lean-amine (streamed to the top and middle of absorption column) are presented, along with operating energy recovery heat exchanger or without them – reference test. Average content of CO2 in flue gas, for both tests, was 11.2 % v/v; while 30% aqueous solution of monoethanolamine was used as sorbent. Most important data for reference test are presented in Table 1.
890 •
Table 1 Parameters of the reference test (without recovery heat exchangers) conducted on Pilot Installation in Łaziska Power Plant Parameter
Value
Unit
217
m3/h
CO2 concentration in flue gas
11.21
% v/v
CO2 concentration in purified flue gas
2.08
% v/v
CO2 removal efficiency
84.4
%
Flow of captured CO2
37.1
kg/h
Energy consumption for solution regeneration
3.90
MJ/kg CO2
Energy supplied to regenerator
50.4
kW
Flow rate of amine solution
1,400
kg/h
Pressure in absorption column
130
kPa (abs)
Pressure in desorption column
130
kPa (abs)
Liquid to gas ratio (L/G ratio)
4.63
kg/kg
CO2 loading of lean amine
0.320
mol/mol
CO2 loading of reach amine
0.438
mol/mol
Cooling water consumption
1,402
kg/h
Flow of flue gas streamed to absorber
Results presented in Table 1 show that the efficiency of the process is high; almost 85% of CO2 is removed from flue gas stream with energy consumption of solution regeneration equal to 3.9 MJ/kg CO2. This result is fully acceptable and similar to the results achieved in other operating installations in the world [21]. Application of internal heat exchange as a modification in regenerator allowed significant improvement of obtained parameters as shown in the graph (Fig. 7).
Fig. 7. Impact of the heat-integrated stripper on CO2 removal efficiency from flue gas. 1. standard process (reference) 2. heatintegrated stripper process
Experimental data show that the use of additional heat exchange inside the regenerator allows the improvement of CO2 removal process increase from 84.4% to 91.4% with simultaneous decrease in the energy consumption by approx. 2.5%. Hot and lean solution flowing through the recovery heat exchangers transfers heat in desorption column, heating the column and increasing the temperature of the liquid, especially in the upper part of the column. It helps to achieve better regeneration of reach solution streamed in the column, while deeper lean solution absorbs CO2 more efficiently and thus increases the efficiency of carbon dioxide removal.
nr 10/2014 • tom 68
Table 2 Comparison of solution carbonation levels for tests with recovery heat exchangers and without internal heat exchange αLA
αRA
mol CO2/mol amine
mol CO2/mol amine
Without recovery heat exchangers
0.438
0.320
With recovery heat exchangers
0.441
0.298
Test
Better desorption (decrease in saturation degree αRA by 6.9%) means greater stream of removed CO2 – increase in the stream of removed CO2 by 8.97%. For the same power supplied to regenerator, more carbon dioxide is removed. Table 3 Selected operation parameters of the Pilot Installation in 2013 Parameter
Value
Number of research campaigns
10
Number of conducted tests
118
Total plant operation time
550 hours
Amount of removed CO2
about 20,000 kg
Summary The paper presents selected technological modifications of installation for CO2 removal from flue gas, which aim to improve the process. Unfortunately, many of the described options has been tested only by means of model research. In order to verify presented solutions, experimental studies were carried out using the Pilot Installation, which due to its flexible technological structure allows to verify effect of internal heat exchange in regenerator and split streams on CO2 removal process. Test results (Fig. 7) show that applied heat recovery in desorption column helped to achieve better regeneration of sorbent – carbonation degree of lean amine solution decreased by 0.022 mol CO2/mol amine. Better regeneration of solution affected also the increase of CO2 capture efficiency by 7% and decrease in the energy consumption by 2.6% in comparison with reference test. The obtained results were in line with model tests. The efficiency increase, as well as the decrease in regeneration energy can be achieved by technological modifications of installations and by using different sorbents. The complex design of Pilot Installation allowed testing numerous technological variants of the process (i.a. by using recovery heat exchangers, split of absorption solution streams). Hundreds of hours of operation of the Pilot Installation (Tab. 3) has proven efficiency of selected technology under the conditions of real industrial facility. Tests using new sorbents are underway, which may help to increase CO2 capture efficiency, just as previous studies on technological configurations. The results presented in this paper were obtained from research work cofinanced by the National Centre of Research and Development in the framework of Contract SP/E/1/67484/10 – Strategic Research Programme – Advanced technologies for energy generation: Development of a technology for highly efficient zero-emission coal-fired power units integrated with CO2 capture.
nr 10/2014 • tom 68
Literature 1. The European Commission, Commission Decision of 3.11.2010. Bruksela, 2010. 2. Dubois L., Thomas D.: Postcombustion CO2 capture by chemical absorption: screening of aqueous amines(s)-based solvents. Energy Procedia 37, 2013, 1648-1657. 3. Wilk A., Więcław-Solny L., Tatarczuk A., Śpiewak D., Krótki A.: Wpływ zmiany składu roztworu absorpcyjnego na efektywność procesu usuwania CO2 z gazów spalinowych. Przem. Chem. 2013, 92, 1, 120. 4. Jayarathna S. A., Weerasooriya A., Dayarathna S., Eimer D. A., Melaaen C. A.: Densities and surface tensions of CO2 loaded aqueous monoethanoloamine solutions with r = (0.2 to 0.7) at T = (303.15 to 333.15) K. J. Chem. Eng. Data 2013, 58, 986-992. 5. Einbu A., Ciftja A. F., Grimstvedt A., Zakeri A., Svendsen H. F.: Online analysis of amine concentration and CO2 loading in MEA solutions by ATRFTIR spectroscopy. Energy Procedia 23, 2012, 55-63. 6. Stec M., Tatarczuk A., Wilk A.: Modeling of CO2 solubility in aqueous amine solutions using hybrid neural network. Power Engineering and Environment, Ostravice 2012, VŠB-TU Ostrava, pp. 157–160. 7. Śpiewak D., Krótki A., Tatarczuk A., Więcław-Solny L., Wilk A.: Badania procesu usuwania CO2 za pomocą wieloskładnikowych sorbentów aminowych. Inżynieria i Aparatura Chemiczna, 2014, 53, 3, 182-184. 8. Tatarczuk A., Więcław-Solny L., Stec M., Krótki A., Zdeb J., Janikowski J.: Mobile Pilot Plant for CO2 capture from flue gases. Clean Coal Technologies, Thessaloniki, Greece, 05/2013. 9. Artanto Y., Jansen J., Pearson P., Puxty G., Cottrell A., Meuleman E., Feron P. M.: Pilot-scale evaluation of AMP/PZ to capture CO2 from flue gas of Australian brown coal-fired power station. Int. Journal of Greenhouse Gas Control 2014, 20, 189-195. 10. Cousins A., Wardhaugh L. T., Feron P. M.: Preliminary analysis of process flow sheet modifications for energy efficient CO2 capture from flue gases using chemical absorption. Chem. Eng. Research and Design, 2011, 89, 1237-1251. 11. Szczypiński T., Tatarczuk A., Grudnik K.: Optymalizacja procesu aminowego wychwytu CO2 ze spalin poprzez zmianę konfiguracji układu technologicznego. Przemysł Chemiczny 2013, 92, 1, 106-110. 12. Cousins A., Wardhaugh L. T., Feron P. M.: A survey of process flow sheet modifications for energy efficient CO2 capture from flue gases using chemical absorption. Int. Journal of Greenhouse Gas Control, 2011, 5, 605-619. 13. Le Moullec Y., Kanniche M.: Screening of flowsheet modifications for an efficient monoethanoloamine (MEA) based post-combustion CO2 capture. Int. Journal Greenhouse Gas Control, 2011, 5, 727-740. 14. Shoeld M.: Purification and separation of gaseous mixtures. Patent No.US 1971798, The Koppers Co. 1934. 15. Krótki A., Śpiewak D., Więcław-Solny L., Spietz T., Tatarczuk A.: Badanie procesu usuwania CO2 metodą absorpcji aminowej w skali półtechnicznej. Inżynieria i Aparatura Chemiczna, 2014, 53, 4. 16. Lajnert R., Latkowska B.: Potencjał badawczy instalacji technologicznych Centrum Czystych Technologii Węglowych (CCTW) w Zabrzu. Przemysł Chemiczny 2013, 92, 215-221. 17. Towler G.P, Shethna H.K, Cole B., Hajdik B.: Improved absorberstripper technology of gas sweetening to ultra-low H 2S concentrations. Proceedings of the 76th GPA Annual Convention, 1997,Tulsa, OK, 93-100. 18. Oyenekan B. A., Rochelle G. T.: Alternative stripper configurations to minimize energy for CO2 capture. Proceedings of the 8th International Conference on Greenhouse Gas Control Technologies. Trondheim, 2006, Norwegia. 19. Tatarczuk A., Ściążko M., Stec M., Tokarski S.: Zastosowanie absorpcji aminowej do usuwania CO2 ze spalin w skali pilotowej. Chemik 2013, 67, 407-414
• 891
XV Conference Environmental
This is confirmed By values of CO2 loading of solution: reach and lean amine obtained in tests (Tab.2): reach amine (αLA) and deeply regenerated amine (αRA) solutions for the conducted tests (Tab. 2).
XV Conference Environmental
20. Tatarczuk A., Ściążko M., Stec M., Tokarski S., Janikowski J.: Carbon capture, wiedzieć jak najwięcej – nasz wspólny cel. CHEMIK 2013, 67, 10, 897-902. 21. Moser P., Schmidt S., Sieder G., Garcia H., Stoffregen T.: Performance of MEA in a long-term test at the post-combustion capture pilot plant in Niederaussem. Int. Journal of Greenhouse Gas Control, 2011, 5, 620-627.
Lucyna WIĘCŁAW-SOLNY – Ph.D., Eng., has graduated from the Faculty of Chemistry at Silesian University of Technology (1998). She has defended her doctoral thesis “Preparation of catalytic coatings on metallic substrates” in 2004. She specializes in the field of chemical and process engineering. She serves as the Deputy Director of the Centre for Process Research, Institute for Chemical Processing of Coal (IChPW).
Adam TATARCZUK – M.Sc., has graduated from the Faculty of Chemistry
Marcin STEC – M.Sc., has graduated from the Faculty of Automatic Control, Electronics and Computer Science at Silesian University of Technology in Gliwice (2003). He works at the Centre for Process Research, Institute for Chemical Processing of Coal (IChPW). Specialization – computerized control systems.
*Tomasz SPIETZ – MSc., has graduated from the Faculty of Chemistry at Silesian University of Technology in Gliwice (chemical and process engineering) (2012). He works as an Engineer at the Centre for Process Research, Institute for Chemical Processing of Coal (IChPW). e-mail:
[email protected], phone: +48 32 6216410
Aleksander KRÓTKI – M.Sc., has graduated from the Faculty of Chemistry at Silesian University of Technology in Gliwice (2010). Currently he works
at Silesian University of Technology in Gliwice (2002). He is a Senior Expert
as an Engineering and Technical Expert at the Centre for Process Research,
at the Centre for Process Research, Institute for Chemical Processing of Coal
Institute for Chemical Processing of Coal (IChPW). Specialization – techno-
(IChPW). Specialization – chemical and process engineering.
logies for CO2 removal from flue gas, chemical industry and environmental protection instruments.
Z prasy światowej – innowacje: odkrycia, produkty i technologie From the world press - innovation: discoveries, products and technologies Dokończenie ze strony 883 Bezpieczne tworzywa antybakteryjne w masowej produkcji Spółka Parx Plastics uruchamia produkcję materiału Saniconcentrate, który posłuży do wytwarzania bezpiecznych wyrobów samoodkażających się o dobowej skuteczności zwalczania bakterii wynoszącej 99%. Technologia opracowana przez Parx Plastics, to pierwsze rozwiązanie biobójcze, które nie opiera się na stosowaniu toksycznych chemikaliów, jak np. triklosan, metale ciężkie (np. srebro), biocydy, nanocząstki czy inne substancje o potencjalnie negatywnym wpływie na zdrowie człowieka. Właściwości antybakteryjne uzyskuje się w tym przypadku dzięki użyciu jednego z najważniejszych pierwiastków śladowych w organizmie ludzkim – cynku. Jest on obecny w pożywieniu i jest niezbędny do utrzymania poprawnego funkcjonowania systemu immunologicznego oraz utrzymywania włosów, paznokci i skóry człowieka we właściwej kondycji. Bezpieczeństwo technologii nie polega tylko na zgodności biologicznej, lecz także na tym, iż nie zachodzi tu zjawisko migracji substancji. Właściwości antybakteryjne uzyskuje się poprzez zmiany wewnętrzne, a nie poprzez ługowanie nałożonej na powierzchnię substancji. Pierwszymi materiałami wykorzystującymi nową technologię, które weszły do masowej produkcji we włoskiej fabryce w Bolonii, są Sani-ABS oraz Saniconcentrate oparty na kopolimerze Tritan produkowanym przez firmę Eastman. Uzyskany produkt końcowy w 3% zawierający nowe rozwiązanie Parx Plastics charakteryzuje się 99% skutecznością w zwalczaniu bakterii Staphylococcus Aurus oraz Escherichia Coli wg standardu ISO22196. (kk) (http://www.plastech.pl/, 12.09.2014)
Pszczeli antybiotyk Szwedzcy naukowcy z Uniwersytetu w Lund wykryli bakterie kwasu mlekowego, które mogą stać się alternatywą dla antybiotyków. Zbadali 892 •
oni żołądki pszczół miodnych, w których przechowują one miód i odkryli 13 bakterii kwasu mlekowego, które wytwarzają ogromną ilość związków przeciwbakteryjnych. W laboratoriach przeprowadzane są już badania nad działaniem tych bakterii wobec gronkowca złocistego odpornego na metycylinę (MRSA). Oprócz MRSA, badania dotyczą również pałeczki ropy błękitnej i szczepy bakterii typu VRE (odporne na jeden z antybiotyków, wankomycynę). Wyniki badań już teraz są obiecujące – bakterie pochodzące od pszczół wykazują bowiem właściwości zwalczające ludzkie patogeny. O ile badania nad wpływem na ludzki organizm wciąż są prowadzone w laboratoriach, o tyle działanie na zwierzętach już zostało sprawdzone. Bakterie kwasu mlekowego podano, wraz z miodem, dziesięciu koniom, które posiadały trwałe, trudno gojące się rany. W każdym przypadku zmiany zostały wyleczone. (kk) (http://biotechnologia.pl, 11.09.2014)
Nowa odmiana PE do produkcji rur w sieciach gazowych Koncern LyondellBasell wprowadził do swojej oferty nową odmianę polietylenu wysokiej gęstości Hostalen CRP 100 Resist CR Orange. Tworzywo przeznaczone jest do produkcji rur w sieciach gazowych instalowanych w nietypowy sposób – w technologii bezwykopowej lub rozwiązaniach bez obsypki piaskowej. Hostalen CRP 100 Resist CR Orange zapewnia długotrwałą wytrzymałość hydrostatyczną, potwierdzoną przez badania laboratoryjne. Rury wykonane z tworzywa posiadają wysoką odporność na zjawisko powolnego wzrostu pęknięcia (Slow Crack Growth). W teście NPT (Notched Pipe Pressure Test) uzyskano wynik 9,5 tys. godz., zaś w teście FNCT (Full Notch Creep Test) – 8760 godz. Tworzywo odznacza się wysoką lepkością i może być z powodzeniem przetwarzane w procesie ekstruzji, wtryskiwania oraz formowania tłocznego. (kk) (http://www.plastech.pl/, 3.09.2014)
nr 10/2014 • tom 68
