Adam TATARCZUK, Marek ŚCIĄŻKO, Marcin STEC ? Institute for Chemical Processing of Coal, Zabrze, Poland; Stanisław TOKARSKI ? TAURON Wytwarzanie S.A.

Please cite as: CHEMIK 2013, 67, 5, 407?414

Introduction

According to Article 10 sec. 1 of the amended Directive EU ETS 2009/29/EC, in the third settlement period (2013÷2020) of the greenhouse gas emission allowance trading scheme, auctioning shall be the basic method of allocating emission allowances [1]. An exception to this rule are the energy-intensive industries (exposed to the so-called carbon leakage), other industries (pursuant to the principle of gradual derogation from free allocation of allowances), as well as power generation industry in certain Member States subject to derogation, i.e. Bulgaria, Cyprus, Czech Republic, Estonia, Hungary, Lithuania, Romania and Poland. In return, those industries shall be obligated to invest in industry modernisation equal to the value of allocated free allowances. This means that as of 1 January 2013 the national power sector, forced to incur environmental costs related to CO₂ emissions, will face a choice: to purchase allowances for CO₂ emission (100% of shares in the auctioning system after the derogation period) without investing in CCS (Carbon Capture and Storage) technologies, or to use the derogation period to field-test and deploy the CCS technology in the industry. Due to the nature of Polish power sector, which is based essentially on traditional coal combustion, with coal being the chief energy carrier, the technology that will most likely be used in the power units, will be based on the post-combustion CO₂ capture from exhaust gases (as they may be implemented in the existing power facilities without the need of any major technological modifications to the unit) [2].

Given the character of exhaust gases from coal power units (atmospheric pressure, CO₂ concentration up to 15%), the technology of chemical absorption of carbon dioxide in amine solution has been chosen for CO₂ capture. The process has been developed for the removal of acidic components (H₂S and CO₂) from natural gas, and then redesigned to capture carbon dioxide for carbonisation of saline solutions, for the production of dry ice, food industry applications and intensification of crude oil extraction. The existing CO₂ capture installations employing the amine method are usually much smaller that the scale of the power industry would require. Currently, the minimum capacity of new coal power units is 500 MWe (approx. 9,200 CO₂/day), but the operations in the chemical industry thus far have not exceeded the scale of a single sequence of 500 t of CO₂/day [3]. Dow Chemical Co. (the process was later acquired by Fluor Daniel, Inc.), Kerr-McGee Chemical Corp. and ABB Lummus Crest, Inc. have played a pivotal role in the development of technology of CO₂ capture from gases with the use of amine sorbents. This technology enables the capture of approx. 75?96% CO₂ and obtaining a nearly pure CO₂ stream (>99%). Commercially available CO2 separation technologies, used mainly in chemical and petrochemical installations, include: Econamine FG/ Econamine FG Plus, offered by Fluor, ABB Lummus Crest MEA, Mitsubishi Heavy Industries and Kansai Electric Power [4]. Analysing the available data on the on-going and planned research projects on the processes of CO₂ capture from gas streams, including exhaust gases, it can be concluded that the list of potential suppliers of CO₂ separation technologies will expand considerably [5÷7].

Strategic Programme ?Advanced Technologies for Energy Generation?

From the perspective of national needs of development of CCS technology, in the nearest future the key application factor for the national power sector will be the results of the Research task 1: ?Developing a technology for high efficient zero emission coal blocks integrated with CO₂ capture from exhaust gases? of the Strategic Research and Development Programme ?Advanced Technologies for Energy Generation?, implemented in the years 2010÷2015 [3]. The objective of the research task is to prepare the deployment of highefficiency almost zero-emission coal power unit in the Polish power generation system.

Under the research task, the Institute for Chemical Processing of Coal is the unit responsible for the research related to CO₂ capture from exhaust gases. Thus far, studies have included the characteristics of liquid sorbents and the analysis of CO₂ absorption and desorption processes in amine solution on the scale of 5 and 10 m3/h. The next stage will be the industrial analysis with the use of the Pilot Plant of nominal capacity of 200 m3 n/h. The plant was constructed in 2012 and funded by the project?s industrial partners: TAURON Polska Energia SA and TAURON Wytwarzanie SA It is the first plant of this type in Poland, designed for analysis of the process of CO₂ capture from actual exhaust gases of the coal power unit, using chemical absorption. Table 1 provides a list of similar pilot plants throughout the world.

As part of the preparation for industrial field-testing, the team at the Institute for Chemical Processing of Coal (ICPC) is researching the possibility of reducing the energy consumption of the process, i.a. by specific mixture of solvents and by reconfiguration of the technological systems used thus far. To date, amine mixture systems with the following compositions have been analysed in terms of kinetics and absorption balances:
? 30% MEA ? as reference solution
? MEA/MDEA/organic liquid/activator/H₂O
? primary amine/amine with steric hindrance/organic liquid/ activator/H₂O
? amine with steric hindrance/tertiary amine/organic liquid/ activator/H₂O
? MEA, ionic liquid. in accordance with the dominating global research trends [8].

Pilot Plant technological concept

According to the applicable norms, the concentration of sulphur oxides in exhaust gases for large power units should not exceed 200 mg/m3 n. This degree of desulphurisation is insufficient to ensure the correct operation of the available CO₂ capture technologies that are based on amine sorbents. Therefore, it has been stipulated that, in order to avoid considerable operational expenses related to sulphurinduced amine degradation, SO₂ concentration in exhaust gases directed to CCS system must be reduced to 20 mg/m3 n. In view of this stipulation, the Pilot Plan has been equipped with a deep desulphurisation module for exhaust gases in which SO₂ is absorbed in aqueous solution of sodium carbonate and sodium bicarbonate, producing acidic sodium sulphate (IV). Such a solution will enable the study of the impact of SO_x content in the exhaust gases directed to the absorber on the amine degradation process.

 

The basic technological system of the Pilot Plant is the CO₂ capture unit that removes carbon dioxide from exhaust gases using an amine solution and comprises a number of process nodes (Fig. 1). The key process node is the absorber to which exhaust gases are fed from the deep desulphurisation section, at the rate of approx. 208 m3 n/h. The gas, fed through the lower part of the column, rises, coming into contact with the aqueous solution of amine that flows down the lining. CO₂ is captured from the gas stream as a result of absorption and the accompanying chemical reactions (1) and (2) [10].

The next process node is the systemic heat recovery unit, located between the absorber and the desorber. The heat contained in the hot regenerated solution that leaves the desorber is returned to the saturated solution stream directed for regeneration. The heat recovery unit is crucial for the energy indicators characterising the entire process, reducing the heat demand in desorber evaporator, since the saturated solution that supplies it, is pre-heated in the cross-flow heat exchanger.

The CO₂ captured in the absorption node is released in the working solution regeneration node. The key element of the node is the desorption column in which the supplied heat triggers the release of CO₂ from the solution. The heat is supplied in the heater, through which the absorbent solution circulates. The hot vapours in the desorption column supply heat directly to the solution in counter-flow and partially condensate it. The mixture of vapour and CO₂ collected from the top of the column is cooled down and the released condensate is returned to the system.

Unlike in traditional configurations, the Pilot Plant employs a system of separated streams of the working solution, circulating between absorption and regeneration nodes. This solution has enabled redirecting some of the liquid from the central section of the regenerator (partially regenerated solution) and using it for provisional removal of CO₂ from the gas stream in the lower section of the absorber. In this arrangement, the absorber is divided into lower section for preliminary capture, and upper section for deep capture. The desorber is also divided into an upper section for partial regeneration, and lower section for deep regeneration. This solution, as evidenced by simulation, enables a reduction in the energy level required for amine solution regeneration by a few per cent [11].

Pilot Plant for CO₂ removal from exhaust gases

The Pilot Plant comprises three sections: technological, storage and supervision. Each section can be transported by vehicle in standard shipping containers. The process line for the removal of CO₂ from exhaust gases, comprising 40 devices, is located in the Technology Unit (Photo 1). Access to all devices and regulation systems is provided by lifted blinds installed on the side walls of the Unit.

The basic elements of the technological section are three sorption columns, up to 15 m high. Those devices, together with the support structures for shipping, are disassembled and stored in the Storage Unit. To ensure the correct operation of the system, monitor the key process parameters and collect the appropriate quantity of data for analysis, approx. 180 measuring points were installed in the system. The collected data are transmitted to the control system, located in the Supervision Unit, which also hosts a mobile laboratory and staff room. System visualisation is provided in Figure 2.

The chief objective of the planned study will be to confirm the usability of amine solutions in the CO₂ removal process from actual exhaust gases originating in coal boilers, and to determine the impact of basic operation parameters on process efficiency, as well as to verify the efficiency of the sorbents developed in the course of the study [10]. The expertise obtained from the study, together with data from the system, may contribute to future optimisation of systems for CO₂ removal from exhaust gases.

What will be analyses first are the exhaust gases from the pulverisedfuel boiler in TAURON Wytwarzanie SA power plant, Łaziska Power Plant Unit, where the system will be located and connected to the process line in the vicinity of Exhaust Gases Desulphurisation Unit, March 2013 (Fig. 3) [12].

Table 2 lists the designed balance parameters of supplied and treated exhaust gases, and the released CO₂ stream. In 2014 the system will be transported to TAURON Wytwarzanie SA Jaworzno Unit, where exhaust gases from fluidised-bed boiler will be analysed. Due to the nature of operation of this type of boiler and the applied exhaust gases desulphurisation method, the gas directed to the Pilot Plant will be characterised by higher sulphur compound content.

As part of the preparations for the planned pilot study, the Institute for Chemical Processing of Coal has been working on the development of the presented technology for several years, creating in the process i.a. the stationary CO₂ removal system with the capacity of 20?100 m3 n/h. On 13th December 2012 the team conducted a several-hours-long test of CO₂ removal from exhaust gases, the first on such scale in Poland, using amine absorption. Detailed data on the test are provided in Table 3. The tests are a unique source of invaluable experience in the industrial research of CCS technology, which will allow identification of key operational and technological problems and, to the extent possible, determine the methods of prevention and reduction of negative effects thereof.

Conclusion

The realisation of the research task and the need to confirm the technical capability to reduce the carbon dioxide emissions from the power units requires a shift of the conducted study from laboratory scale to pilot scale. For this purpose, the Project Industrial Partners, Tauron Polska Energia SA and Tauron Wytwarzanie SA, together with the Institute for Chemical Processing of Coal ? coordinator with factual knowledge for works concerning the methods of CO₂ removal from exhaust gases, have undertaken the task of designing, constructing and launching the Pilot Plant. The designed scale of the Plant allows the researchers to conduct their analyses at economically justified costs, providing an actual image of the course of CO₂ removal process by chemical absorption in liquid amine sorbents solutions. Determining the impact of basic operational parameters on the efficiency of the process and the possibility of obtaining the technical and ?operational? know-how (real-time process data) will allow the optimisation of the systems for CO₂removal from exhaust gases, and development of process principles for constructing such systems on a larger scale.

Acknowledgements

The results discussed in this paper were obtained through research cofinanced by the National Centre for Research and Development, under the agreement SP/E/1/67484/10 Strategic Programme ? Advanced Technologies for Energy Generation: Developing a technology for high efficient zero emission coal blocks integrated with CO₂ capture from exhaust gases.

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Adam TATARCZUK ? M.Sc., graduated from the Faculty of Chemistry at the Silesian University of Technology in Gliwice (2002). He is currently employed as the senior specialist in the Centre for Process Research at the Institute for Chemical Processing of Coal. Specialisation ? chemical and process engineering. e-mail: ; phone: + Marcin STEC ? M.Sc., graduated from the Faculty of Automatic Control, Electronics and Computer Science at the Silesian University of Technology in Gliwice (2003). He is currently employed in the Institute for Chemical Processing of Coal in Zabrze. Specialisation ? computer control systems.

Marek ŚCIĄŻKO, associate professor, Ph.D. Eng., graduated from the Silesian University of Technology (1975). In 1980 he was awarded a research internship at Pittsburgh Energy Technology Center in the U.S., where he studied the modelling of coal gasification at pressure, which he then presented and discussed in his doctoral thesis. In 1993 he was granted a scholarship for the management of investment projects in the power sector at the University of North Dakota. During 1987÷1993 he worked as project manager and deputy head of the Polish-German Research Centre which focused its work on the development of the technology of coal pyrolysis. Mr Ściążko has been the head of the Institute for Chemical Processing of Coal since 1991. He is also a member of the Advisory Group on Power ? DG RTD UE, the Committee on Energy and the Committee on Chemical and Process Engineering of the Polish Academy of Sciences, Member of the Supervisory Board of Tauron Group, and a professor at the AGH University of Science and Technology in Cracow. Co-author of 119 articles, 29 monographs and 52 patent applications.
e-mail: ; phone:

Marcin STEC ? M.Sc., graduated from the Faculty of Automatic Control, Electronics and Computer Science at the Silesian University of Technology in Gliwice (2003). He is currently employed in the Institute for Chemical Processing of Coal in Zabrze. Specialisation ? computer control systems.

 

Stanisław TOKARSKI ? M.Sc., graduated from the Faculty of Electrical Engineering, Automatics and Electronics at the AGH University of Science and Technology (1983). He is currently employed as the President of the Management Board of TAURON Wytwarzanie SA He was previously employed in TAURON Polska Energia SA as the Vice-president of the Board and Strategy & Development Manager. Mr Tokarski begun his professional career in PKE Elektrownia Jaworzno III (Jaworzno Power Plant) Since 1998, as the member of the international organisation UNIPEDE, later Eurelectric, in Brussels, which prepares the opinions for the European Commission on the key legal documents (Directives) on the power and fuels sector, he has participated in the works of numerous UE institutions. He is an active member of a number of organisations, among them Eurelectric, Polish Normalisation Committee and the Polish Member Committee of the World Energy Council. Mr Tokarski is also the member of the Managing Board of the Polish Electricity Association and the Board of Directors of VGB. He is also actively involved with KIC InnoEnergy, an international company dealing with research and development projects. Author of 11 chapters in monographs, 133 articles and 11 lectures.