Hydrogen and Electricity from Coal with Carbon Dioxide Separation

Jun 5, 2007 - Using FeO/Fe3O4 as an oxygen carrier, we propose a carbon-free coproduction system of hydrogen and electricity with chemical-looping rea...
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Energy & Fuels 2007, 21, 2272-2277

Hydrogen and Electricity from Coal with Carbon Dioxide Separation Using Chemical Looping Reactors Xiang Wenguo* and Chen Yingying Key Laboratory of Clean Coal Power Generation and Combustion Technology of Ministry of Education, Southeast UniVersity, Nanjing 210096, China ReceiVed October 17, 2006. ReVised Manuscript ReceiVed March 12, 2007

Concern about global climate change has led to research on low CO2 emission in the process of the energy conversion of fossil fuel. One of the solutions is the conversion of fossil fuel into carbon-free energy carriers, hydrogen, and electricity with CO2 capture and storage. In this paper, the main purpose is to investigate the thermodynamics performance of converting coal to a hydrogen and electricity system with chemical-looping reactors and to explore the influences of operating parameters on the system performance. Using FeO/Fe3O4 as an oxygen carrier, we propose a carbon-free coproduction system of hydrogen and electricity with chemicallooping reactors. The performance of the new system is simulated using ASPEN PLUS software tool. The influences of the chemical-looping reactor’s temperature, steam conversion rate, and O2/coal quality ratio on the system performance, and the exergy performance are discussed. The results show that a high-purity of H2 (99.9%) is reached and that CO2 can be separated. The system efficiency is 57.85% assuming steam reactor at 815 °C and the steam conversion rate 37%. The system efficiency is affected by the steam conversion rate, rising form 53.17 to 58.33% with the increase of the steam conversion rate from 28 to 41%. The exergy efficiency is 54.25% and the losses are mainly in the process of gasification and HRSG.

1. Introduction Concern about global climate change has led to research on low-CO2-emission energy systems. Various fossil fuel power plant concepts, which are intended to reduce CO2 emission in the process of energy conversion, are proposed. One such system is the conversion of fossil fuel into carbon-free energy carriers, H2, and electricity with CO2 capture and storage. Coal is a feedstock of particular interest because of its great abundance, widespread geographical distribution, and low cost. Coal-based hydrogen and electricity will play an important role during the transition to a hydrogen-based energy economy. Gasification of coal is a promising technology for the production of hydrogen and electricity. The coal is prepared and fed to the gasifier. In the gasifier, the feedstock reacts with steam and oxygen at high temperature and pressure. The resulting syngas is composed primarily of hydrogen, carbon monoxide, and smaller quantities of methane and carbon dioxide and then undergoes additional processing to separate and purify hydrogen with CO2 capture. A series of studies have investigated the thermodynamics and economics of converting coal to hydrogen and electricity with CO2 capture, including numerous plant designs, operating parameters, and choices of technology. Thomas Kreutz and Stefano Consonni, etc.1-4 studied performances, costs, and prospects of using commercially ready * Corresponding author. E-mail: [email protected]. (1) De Lorenzo, L.; Kreutz, T. G.; Chiesa, P.; Williams, R. H. Carbonfree hydrogen and electricity from coal: Options for syngas cooling in systems using a hydrogen separation membrane reactor. ASME Turbo Expo 2005, GT2005-68572. (2) Consonni, S.; Vigano, F. Decarbonized hydrogen and electricity from natural gas. Int. J. Hydrogen Energy 2005, 30, 701-718. (3) Chiesa, P.; Consonni, S.; Kreutz, T.; Williams, R. Co-production of hydrogen, electricity and CO2 from coal with commercially ready technology. Part A: Performance and emissions. Int. J. Hydrogen Energy 2005, 30, 747-767.

technology to convert coal to hydrogen and electricity with CO2 capture and storage. In the coproduction plants, coal is gasified to synthesis gas and then shifted to primarily H2 and CO2. CO2 is then removed from the syngas using Selexol; after being stripped from the solvent, the CO2 is dried and compressed for pipeline transport and underground storage. High-purity H2 is extracted from the H2-rich syngas via a pressure swing adsorption (PSA) unit and compressed for usage. The PSA purge gas is compressed and burned in a conventional gas turbine combined cycle, generating coproduct electricity. Results show that the technology allows transferring 57-58% of coal LHV to decarbonized hydrogen, whereas exporting decarbonized electricity to the grid amounted to 2-6% of coal LHV. Chemical-looping combustion (CLC) is a novel process for heat and power production with inherent CO2 capture. An oxygen carrier performs the task of bringing oxygen from the air to the fuel. Suitable oxygen carriers are small particles of metal oxide such as Fe3O4 (magnetite) and NiO (nickel oxide). A basic CLC system has two reactors, one for air and one for fuel. The oxygen carrier circulates between the reactors. In the fuel reactor, it is reduced by the fuel, which in turn is oxidized to CO2 and H2O (water vapor). In the air reactor, the reduced metal oxide is regenerated (oxidized) with oxygen from the combustion air. The CLC can also be used to generate hydrogen with inherent CO2 separation, as shown in Figure 1. Selecting iron oxides (magnetite Fe3O4, wuestite FeO) as the oxygen carrier, it circulates between two reactors, one for steam and one for fuel. In the fuel reactor, iron oxides (assuming (4) Kreutz, T.; Williams, R.; Consonni, S.; Chiesa, P. Co-production of hydrogen, electricity and CO2 from coal with commercially ready technology. Part B: Economic analysis. Int. J. Hydrogen Energy 2005, 30, 769784.

10.1021/ef060517h CCC: $37.00 © 2007 American Chemical Society Published on Web 06/05/2007

H2 and Electricity from Coal with CO2 Separation using CLC

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Figure 1. Chemical looping hydrogen reactors.

magnetite Fe3O4) are reduced to FeO or Fe. The following reactions occur (taking syngas as fuel)

Fe3O4 + 4H2 f 4H2O + 3Fe; ∆H298 ) 149.92 kJ/mol (1) Fe3O4 + H2 f H2O + 3FeO; ∆H298 ) 68.25 kJ/mol

(2)

Fe3O4 + 4CO f 4CO2 + 3Fe; ∆H298 ) -14.82 kJ/mol (3) Fe3O4 + CO f CO2 + 3FeO; ∆H298 ) 27.07 kJ/mol

(4)

In the steam reactor, hydrogen is produced and the wuestite FeO or Fe is reoxided according to the following reactions

3FeO + H2O f Fe3O4 + H2; ∆H298 ) -68.25 kJ/mol (5) 3Fe + 4H2O f Fe3O4 + 4H2; ∆H298 ) -149.92 kJ/mol (6) Hydrogen is produced with CO2 capture. The total amount of energy released in two reactors is the same as that of the watergas shift reaction as follows

CO + H2O f H2 + CO2; ∆H298 ) -41.20 kJ/mol (7) The chemical-looping hydrogen reactors have several potential benefits compared with the conventional water-gas shift reaction. The exhaust from the steam reactor consists mainly of hydrogen and remaining steam vapor. The gas from the reduction reactor consists of CO2 and H2O (steam vapor), so a condenser is the only equipment needed to obtain almost pure CO2 and H2. Viktor Hacker and S. D. Fraser, etc.,5-8 investigated hydrogen production by a steam-iron process. The process was studied in a laboratory fixed-bed reactor in the temperature range of 750-900 °C. The study shows that high operation temperatures are favored for high hydrogen productivity. Increasing the temperature results in a better redox potential of syngas and oxidation, which is not favored thermodynamically, yielding approximately similar H2:H2O ratios as with lower temperatures. (5) Hacker, V.; Fankhauser, R.; Faleschini, G.; Fuchs, H.; Friedrich, K.; Muhr, M.; Kordesch, K. Hydrogen production by steam-iron process. J. Power Sources 2000, 86, 531-35. (6) Hacker, V. A novel process for stationary hydrogen production: the reformer sponge iron cycle (RESC). J. Power Sources 2003, 118, 311314. (7) Hacker, V., Faleschini, G.; Fuchs, H.; Fankhauser, R.; Simader, G.; Ghaemi, M.; Spreitz, B.; Friedrich, K. Usage of biomass gas for fuel cells by the SIR process. J. Power Sources 1998, 226-230. (8) Fraser, S. D.; Monsberger, M.; Hacker, V. thermodynamic analysis of the reformer sponge iron cycle. J. Power Sources 2006, 161, 420-431.

Figure 2. Schematic layout of a chemical-looping-based hydrogen and electricity plant.

T. Akiyama9 studied the reactive property between steam and iron carbide by thermal analysis with a mass spectrometer. Luis G. Velazquez-Vargas10 pointed out that hydrogen production using a redox method to replace the conventional water-gas shift reaction could have a higher efficiency. Magnus Ryde´n11,12 proposed a natural-gas-fueled hydrogen production process by steam reforming with inherent capture of carbon dioxide by chemical-looping combustion. The process resembles a conventional circulating fluidized bed combustor with reforming taking place in reactor tubes located inside a bubbling fluidized bed. Process layout and expected performance were evaluated and a preliminary reactor design was proposed. It is found that it has potential to achieve better selectivity toward hydrogen than conventional steam reforming plants. In this paper, the main purpose is to investigate the thermodynamics performance of converting coal to hydrogen and electricity system with chemical-looping reactors and to explore the plant designs, operating parameters. The plant studied in this paper is shown schematically in Figure 2. Coal is gasified in the Shell gasifier (∼40 bar). The hot raw gas is cooled to ∼900 °C by recycling syngas and then cooled in convective heat exchangers to about 250 °C. The recovered heat is used to generate the steam necessary for the steam reactor and to heat up the resulting syngas before entering the fuel reactor, where syngas is converted to H2O and CO2 with iron oxides. After supplementary firing (SF1), the CO2 stream (9) Akiyama, T.; Miyazaki, A.; Nakanishi, H.; Hisa, M.; Tsutsumi, A. Thermal and gas analyses of the reaction between iron carbide and steam with hydrogen generation at 573 K. Int. J. Hydrogen Energy 2004, 29, 721724. (10) Velazquez-Vargas, L. G.; Li, F.; Gupta, P.; Fan, L.-S. Reduction of metal oxide particles with syngas for hydrogen production. http:// www.nt.ntnu.no/users/skoge/prost/proceedings/aiche2006/data/papers/ P61973.pdf. (11) Ryde´n, M.; Lyngfelt, A. Using steam reforming to produce hydrogen with carbon dioxide capture by chemical-looping combustion. Int. J. Hydrogen Energy 2006, 31, 1271-1283. (12) Ryde´n, M.; Lyngfelt, A. Hydrogen and power production with integrated carbon dioxide capture by chemical-looping reforming. Presented at the 7th International Conference on Greenhouse Gas Control Technologies, Vancouver, Canada, Sept 5-9, 2004; http://www.entek.chalmer.se/ anly/co2/co2.publ.htm.

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Table 1. Assumptions Adopted for Performance Simulation assumption gasification process

convective heat exchanger (clean syngas heater) convective heat exchanger (steam superheater) particulate removal desulferation

temperature 1400 °C, pressure 40 bar carbon conversion rate, 99.5%; O2/coal ratio, 1 pressure loss, 5%; heat loss, 0.5% of input LHV syngas outlet temperature, 900 °C pressure loss, 2% approach point, ∆T ) 100 °C pressure loss, 2% approach point, ∆T ) 10 °C

pressure loss, 6% MEDA method; removed sulfur, 98% pressure loss, 6% oxygen carrier Fe3O4/FeO steam reactor (SR) temperature, 815 °C; pressure loss, 6% thermal losses, 0.5% of thermal input fuel reactor (FR) temperature, 788 °C; pressure loss, 6%; thermal losses, 0.5% of thermal input turbine TIT, 1350 °C; air cooling fraction, 12% turbine polytropic efficiency, 90% mechanical/generator efficiency, 99%/99% HRSG approach point, ∆T ) 8 °C; pinch point, ∆T ) 10 °C pressure loss, 10%; exhaust gas temperature from the HRSG: from fuel reactor, 40 °C; from steam reactor, 88.2 °C HRSG thermal losses, 0.7% of thermal input CO2 compression single-stage compression ratio of CO2 compressor, 3.5 compressor stage isentropic efficiency, 82% cooling water inlet temperature, 15 °C pressure losses in the heat exchanger, 3% temperature at intercooler outlet, 30 °C mechanical/electric efficiency, 99%/99% liquid CO2 to disposal, 30 °C and 121 bar H2 compression single-stage compression ratio of H2 compressor, 3.5 compressor stage isentropic efficiency, 82% cooling water inlet temperature, 15 °C pressure losses in the heat exchanger, 3% temperature at intercooler outlet, 30 °C mechanical/electric efficiency, 99%/99% 99.9% pure hydrogen, 30 °C and 60 bar balance of plant (BOP) pump efficiency: 75%

Table 2. Proximate and Ultimate Analyses of Coal proximate analysis (%; mass, air-dry) M A V FC

C

ultimate analysis (%; mass,daf) H O N

S

0.81 7.49 39.28 52.42 73.64 5.24 9.81 1.13 2.63

Qnet,ad (MJ kg-1) 27.455

expands in a turbine and then the waste heat is recovered in the HRSG. After compression and removal of condensate, the CO2 stream is liquidized (∼120 bar) for piping. The overheated steam is led to the steam reactor where hydrogen is produced. The H2-rich stream from the steam reactor is expanded in a turbine and the heat is further recovered in HRSG. H2 is compressed to 60 bar for use. Because the recovery heat in the HRSG cannot supply enough steam for the steam reactor, supplementary firing (SF2) is needed in order to generate the needed overheated steam. 2. System Description The primary assumptions used to simulate plant performance are detailed in Table 1. Gasification Process. The coal data is shown in Table 2. The pretreated coal-powder is fed to the gasifier together with 95% pure oxygen from air separation unit (ASU) at a pressure of 48 bar. The ASU is not modeled here; rather, we adopt the composition and specific work (0.246 kWh/kg of 95% O2).13 And the work of compressing O2 to 48 bar is 0.125 kWh/kg. The mass ratio of O2 to coal is 1. Additional oxygen is needed in the supplementary combustors (SF1 + SF2). (13) Wang, B.; Jin, H.; Han, W.; Zheng, D. IGCC system with integration of CO2 recovery and the cryogenic energy in air separation unit. In Proceedings of ASME Turbo Expo, Vienna, Austria, June 14-17, 2004; International Gas Turbine Institute, The American Society of Mechanical Engineers: Atlanta, GA, 2004; paper GT-53723.

Coal (1 kg/s) is gasified at 40 bar in an entrained-flow Shell gasifier. Oxygen and steam are injected into the reaction chamber, where they react to produce syngas. The raw syngas (25.36 vol % H2, 65.59 vol % CO, 3.43 vol % H2O, 2.69 vol % CO2, and traces of Ar, COS, NH3, N2, and H2S) is cooled to ∼900 °C by recycling the clean syngas and further cooled to 250 °C in two convective heat exchangers. After particulate removal and desulfuration, the syngas can be used as the fuel of chemical-looping hydrogen reactors. Hydrogen Production. According to Viktor Hacker’s5-8 syngas experiment results, the iron ore is reduced to wuestite FeO in the fuel reactor and wuestite FeO is oxidized to magnetite Fe3O4 in the steam reactor assuming short residence time in the reactors. In the fuel reactor, the magnetite Fe3O4 is reduced to wuestite FeO as reactions 8 and 9 Fe3O4 + CO f 3FeO + CO2; ∆H298 ) 27.07 kJ/mol

(8)

Fe3O4 + H2 f 3FeO + H2O; ∆H298 ) 68.25 kJ/mol

(9)

In the steam reactor, the wuestite FeO is oxided to magnetite Fe3O4 according to reaction 10 3FeO + H2O f Fe3O4 + H2; ∆H298 ) -68.25 kJ/mol (10) The clean syngas is heated to 800 °C before entering the fuel reactor, which is at ∼785 °C, 32 bar. The steam is superheated to ∼600 °C before entering the steam reactor at ∼815 °C, 32 bar. To lower the unburnt syngas, we must keep the oxygen carrier (MFe3O4) excessive. The excessive oxygen coefficient R is defined as the ratio of mass flow of Fe3O4 and the minimum flow of Fe3O4 R ) MFe3O4/Mmin Fe3O4 In this system, R is selected as 1.3. According to the simulation, the stream from the fuel reactor mainly consists of 5.1 vol % CO, 65.75 vol % CO2, 2.18 vol % H2, and 24.77 vol % H2O. The H2 concentration in the steam reactor is the key parameter to the system efficiency. The parameter will be discussed in the following section. Power Island. The CO2-rich stream from the FR, which consists of unburnt fuel, is raised to 1350 °C through supplementary firing (SF1) with 95% oxygen. It can burn up the remaining fuel in a CO2-rich stream. The CO2-rich stream is then expanded in a turbine to a back pressure of 1.025 bar. The exhaust enters HRSG to generate steam. The H2-rich stream from the SR is also expanded in an expander to 1.025 bar and then to HSRG. Heat in the resulting syngas from Shell gasifier is also used to superheat the steam. However, the outlet gas from two turbines and resulting syngas cannot provide enough energy to produce steam to 600 °C, and supplementary firing (SF2) using oxygen and the resulting syngas is needed. CO2 Separation and H2 Compression. The H2-rich stream and the CO2-rich stream are compressed in stages and cooled through circulating water following each stage. Meanwhile, condensate is removed. H2 is compressed to 60 bar in 3 intercooled stages and CO2 is to 121 bar in 4 intercooled stages. System Efficiency. The system efficiency is defined as (LHV base) ηenergy )

LHVH2 + WNet LHVcoal

The system exergy efficiency is ηexergy )

ExH2 + WNet Ex0

3. Result and Discussion 3.1. Heat Energy Balance in Chemical-Looping Reaction. Between fuel reactor and steam reactor, the oxygen carrier is cycling in FeO and Fe3O4 forms. Simulation results show that

H2 and Electricity from Coal with CO2 Separation using CLC

Energy & Fuels, Vol. 21, No. 4, 2007 2275

Figure 3. The temperature relationship between the chemical-looping reactors.

Figure 5. H2 production and power with different temperatures at hydrogen reactors.

Figure 4. Fuel flow in different parts with different temperatures at steam reactors.

Figure 6. Efficiency of system and oxygen consumption with different temperatures at hydrogen reactors.

gas in the fuel reactor outlet contains unburnt CO (6-8 vol %) and H2 (∼6 vol %), which is consistent with the experimental results of Viktor Hacker.5,6 It has been discussed that the overall reaction between two reactors is the water-gas shift reaction 7, which is exothermic. However, because the reactors should be maintained at higher temperature, the temperature of inlet fuel and steam should be raised to certain values to satisfy the heat need of two reactors. Assuming that the two reactors are adiabatic and the fuel inlet temperature is 800 °C, SR temperature changes between 800 and 850 °C, and the temperature of the oxygen carrier to FR (Fe3O4) is the same. The reaction in FR is endothermic, so the temperature in FR cannot maintain the same value as in SR and varies between 771 and 812 °C, which increases along with SR. The temperature of steam to SR increases along with SR’s and the inlet temperature must be kept between 577 and 645 °C, as shown in Figure 3. As the SR temperature increases, the supplementary firing fuel flow (SF2) used to superheat the steam increases. On the other hand, the supplementary firing fuel flow (SF1) used to raise the TIT decreases because of the increase in FR temperature. The total supplementary firing fuel flow (SF1+SF2) increases and the FR fuel flow goes down as well (as in Figure 4), which leads to the decrease in H2 production, as shown in Figure 5. Decreasing FR fuel leads to the decrease in unburnt H2 and CO in FR outlet stream and the oxygen needed also decreases. But as the SR temperature goes up further, more heat is needed to superheat the steam and oxygen consumption goes up (as in Figure 6). The oxygen needed in this system decreases at first to a minimum and then increases. Because of the consumed work to produce oxygen and the change in H2 production, the system efficiency has an optimum value as

shown in Figure 6. When the SR temperature is 815 °C, the system has a highest efficiency of 57.85%. 3.2. The Effect of Different Steam Conversion Ratio on System Performance. The H2 concentration in the SR outlet stream is a key parameter to system efficiency. Viktor Hacker’s research5 showed that the steam conversion rate is ∼28% at 800 °C. S. D. Fraser8 made an explanation to the reaction between H2 and Fe3O4 to form FeO. The concentration of H2 on equilibrium is 40.9% and the concentration of H2O is 59.1%. It means that the concentration of H2 in SR will not be more than 40.9% after equilibrium of the reaction is reached. Meyer Steinberg14 indicated that the steam conversion rate is 37% when the reaction temperature is between 815 and 870 °C. Because different researchers have different data in their experiments, the effect of steam conversion rate is discussed here. The steam flow to SR decreases along with the increase of steam conversion rate. The steam temperature could be decreased because less heat is needed in two reactors. The exhaust temperature of the H2 turbine is changed because of the change in H2 and H2O concentration, as shown in Figure 7. At the same time, the fuel flow to SF2 to superheat the steam in HRSG decreases and the fuel flow to FR increases. As a result, the fuel flow to SF1 gets increased. The overall fuel flow for supplementary firing (SF1 + SF2) has a decreasing trend to the increase in conversion rate, as shown in Figure 8. The work of the CO2 turbine increases because the fuel flow to FR and SF1 increases. However, the decrease of steam to SR results in the decrease of work in the H2 turbine. The net (14) Steinberg, M.; Cheng, H. Modern and prospective technologies for hydrogen production from fossil fuels. Int. J. Hydrogen Energy 1989, 14, 797-820.

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Figure 7. Steam temperature in SR and turbine 2 outlet gas temperature with different steam conversion rates.

Figure 10. H2 production and efficiency of the system at different steam conversion rates.

Figure 8. The supplied gas flow with different steam conversion rates. Figure 11. Efficiency with different ratios of O2/coal.

Figure 9. Power of the system at different steam conversion rates.

work of the system decreases because the increasing work of the CO2 turbine is less than the decreasing work of the H2 turbine, as shown in Figure 9. The final H2 production and system efficiency increase along with the increase of steam conversion rate as shown in Figure 10. The system efficiency increases from 53.17 to 58.33% when the steam conversion rate increases from 28 to 41%. 3.3. Effect of O2/Coal Ratio on System Efficiency. The O2/ coal ratio is simulated here to detect the effect on the system

efficiency, as shown in Figure 11. Simulation results show that the raw gas consists of 25.36% H2, 65.59% CO, 3.43% H2O vapor, 2.69% CO2, and traces of Ar, COS, NH3, N2, and H2S when the O2/coal ratio is 1. As the ratio rises, the concentration of CO and H2 in the syngas decreases and leads to the decrease in H2 production and supplementary firing fuel. The system efficiency decreases as well, as can be seen in Figure 11. The results are not given when the O2/coal ratio is below 1.0. The gasification temperature cannot be kept at 1400 °C and will go down under the O2/coal ratio of 1.0. The carbon conversion rate decreases and the system efficiency becomes lower. 3.4. System Exergy Analysis. (1) Energy analysis. In this system, nearly all of the CO2 can be separated and captured. The air separation unit is not simulated, and 0.246 kWh/kg is selected as work consumption of oxygen production. The oxygen compression to 48 bar consumes 0.125 kWh/kg. Energy analysis of each part in the system is shown in Table 3. (2) Exergy analysis. The simulation results show that the system exergy efficiency is 54.25%. The exergy losses of the whole system mainly take place in the process of gasification and HRSG, as can be seen in Figure 12 and improvements should be made in gasification and waste heat recovery processes.

Table 3. Energy Balance of System energy input (MW)

H2 production (kg/h)

CO2 separation (MW)

H2 separation (MW)

O2 production and compression (MW)

net power (MW)

system efficiency (%)

27.455

433.590

1.049

0.943

1.784

1.310

57.85

H2 and Electricity from Coal with CO2 Separation using CLC

Energy & Fuels, Vol. 21, No. 4, 2007 2277 Acknowledgment. The authors thank to the National Natural Science Foundation of China for financial support of this project (90410009).

Nomenclature

Figure 12. Exergy flow of the hydrogen and electricity coproduction system.

4. Conclusions A CLC-based coproduction system of hydrogen and electricity is discussed and the system performance is simulated. Several conclusions can be derived: (1) CO2 in this system can be separated and captured. (2) The key parameter that impacts the system performance most is the steam conversion rate in SR. The system efficiency increases from 53.17 to 58.33% when the steam conversion rate increases from 28 to 41%. (3) The energy efficiency is 57.85% assuming that the SR temperature is 815 °C, the O2/coal quality ratio is 1, and the steam conversion rate is 37%. (4) The exergy analysis of the system shows that exergy losses of the system mainly take place in the process of gasification and HRSG.

ASU ) Air separation unit CLC ) Chemical Looping Combustion Ex ) exergy flow (MW) Ex0 ) Coal exergy flow, MW ExH2 ) H2 Exergy flow, MW FR ) Fuel reactor GT ) Gas turbine ∆H ) Heat of reaction at 25 °C, kJ/kmol Hx ) Heat exchanger HRSG ) Heat Recovery Steam Generation LHV ) Lower Heating Value, MW LHVH2 ) LHV of produced H2, MW LHVCoal ) LHV of Coal, MW M ) Mass flow, kg/s min ) minimum p ) Pressure, bar SR ) Steam reactor SF1 ) Supplementary firing before the turbine SF2 ) Supplementary firing after the turbine T ) Temperature, K TIT ) Turbine inlet temperature WNet ) Net work of the system, MW R ) Excessive oxygen coefficient EF060517H