Process simulation activities at Politecnico di Milano on Ca-based solid looping cycles

Transcription

1 1 st meeting of the high temperature Solid Looping Cycle Network Oviedo, September 2009 Process simulation activities at Politecnico di Milano on Ca-based solid looping cycles Matteo C. Romano Dipartimento di Energia, Politecnico di Milano

2 Summary 2 Summary of the presentation: - Introduction - Calcium-based plants with CO 2 capture assessed (or being assessed ) at Politecnico di Milano: Post-combustion capture plant Zecomix plant Sorption Enhanced - Steam Methane Reforming based plants

3 Introduction 3 GECOS (Group of Energy COnversion Systems): - Mechanical engineering background. - Large experience on turbomachineries and power systems modeling and simulation, thermodynamic analysis and plant optimization. Main calculation tool - GS code: - Developed at Politecnico di Milano - Modular structure: suitable for the simulation of complex plants - Built-in correlations for the prediction of turbomachinery performances: stage-by-stage steam turbine calculation and cooled gas turbine model

4 Post-combustion capture plant layout 4 carbonator calciner ECO+EVA+SH e.m. limestone coal ASU limestone coal blow off FF m.d. N2 ~ HP preheaters LP preheaters - heat from CO2 and air IC compressors

5 Post-combustion capture plant - carbonator 5 Application of Kunii-Levenspiel model for bubbling bed reactors proposed in literature, to calculate the carbonator estimation of bed height (and pressure drops) to obtain the selected carbon capture as a function of: (i) solids blow-off and (ii) fraction of active sorbent in carbonator blow off = 1% blow off = 5% xco f a = 10% Minimum CO 2 concentration f a = 5% f a = 2.5% z, m

6 Post-combustion capture plant - results 6 Results of sensitivity analysis, taking into account ash accumulation: low x b-o and f a bring about high bed heights, but low CaO export from the plant. Net efficiencies about 1% point higher than oxy-fuel PC steam cycle. Blow-off fraction x b-o, % Active CaO in carbonator f a, % Carbonator model output Maximum CaO utilization, % Actual CaO utilization, % Bed height, m Pressure loss, kpa Plant performance Net LHV efficiency η LHV, % Overall CO 2 captured, % Coal to main boiler, % CaO export, kg CaO /kg coal Circulating solids, kg/kg CO Romano M.: COAL-FIRED POWER PLANT WITH CALCIUM OXIDE CARBONATION FOR POST- COMBUSTION CO 2 CAPTURE; Energy Procedia, 1, , Work in progress: a similar study is being carried out, by considering a model for CFB carbonator.

7 The Zecomix project 7 Zero Emissions COal MIXed technology = ZECOMIX Project leaded by ENEA (Italian public agency operating in energy and environment) with industrial partner Ansaldo and some universities Syngas production: Hydro-gasifier (70 bar, 800 C): C + 2H 2 CH 4 Carbonator: CaO + CO 2 CaCO 3 CH 4 + H 2 O CO + 3H 2 CO + H 2 O CO 2 + H 2 CH 4 + 2H 2 O + CaO CaCO 3 + 4H 2 ΔH r =-74.6 kj/mole ΔH r = kj/mole ΔH r = kj/mole ΔH r =-41.2 kj/mole ΔH r =-14.5 kj/mole Calciner: a) Pressurized ( 1250 C) oxy-combustion of an ash-free fuel (i.e. TAR) b) Atmospheric ( 950 C) coal oxy-combustion, problems with solids pressurization Power island: Oxy-combustion of H 2 /H 2 O mixture high T, internal combustion steam cycle

8 Zecomix: plant layout 8 Chemical island 7 O2 ash recycle 14 4 HG Carb1 coal slurry tar 12 CaCO3 Cal Carb CaO 10 9 CEHR HP cyclone 11 Ex Oxygen island from HP eco HP O2 compr. 24 HP eco filter SC e.m. 20 ASU waste nitrogen 19 combustor air compr. Power island HTT HTT coolant 22 m.d. e.m. 16 incondensables 27 HP eco 23 SH/RH 25 liquid CO steam turbine LPT IPT HPT CO2 island e.m.

9 Zecomix simulations results 9 Romano M., Lozza G.: ZECOMIX: A ZERO-EMISSIONS COAL POWER PLANT, BASED ON HYDRO- GASIFICATION, CO 2 CAPTURE BY CALCIUM LOOPING AND SEMI-CLOSED HIGH TEMPERATURE STEAM CYCLE; Energy Procedia, 1, , 2009.

10 Zecomix simulations results 10 Sensitivity analysis: optimization of pressure ratio, turbine inlet temperature and minimum pressure Net efficiency, % TIT 1400 C - min. press. fixed TIT 1400 C - max. press. fixed TIT 1500 C - min. press. fixed Pressure ratio Romano M., Lozza G.: LONG-TERM COAL GASIFICATION BASED POWER PLANTS WITH NEAR-ZERO EMISSIONS. Under review for J. of Greenhouse Gas Control. Discussion on turbomachinery characteristics and comparison with other systems at the same technological level.

11 Zecomix main technical hurdles 11 Solids handling: Large amount of solids at high temperature and pressure circulates between the reactors. Investigate the possibility of keeping solids in the same vessel switched between carbonating and calcinating conditions. Hydrogen recycle compressor: Operates at high temperature and hot gas filtering is necessary. Syngas cleaning: Hot syngas filtering (and maybe desulfurization) on syngas before combustion. Large efficiency penalties occur by lowering filtering temperature. Development of new turbomachineries: Turbomachineries require a completely new design. Relevant technological development required for cooled turbine, operating with large heat fluxes.

12 Zecomix ENEA experimental facility 12 An experimental facility is under construction at the ENEA experimental site at Casaccia (near Rome): - Bench scale hydrogasifier, p= bar - Oxygen-blown, 50 kg/h gasifier and CH 4 addition in produced syngas - Atmospheric carbonator-calciner with cycling operation kw microturbine for syngas utilization (air combustion) - Separate O 2 /H 2 combustion bench scale facility

13 Zecomix ENEA experimental facility 13 For more information ask Antonio Calabrò of ENEA: Gasifier Hydrogasifier Carbonator flaring Microturbine: Modified Turbec T100 working with H 2 /H 2 O Developed by: Ansaldo Ricerche microturbine Steam generator Gasifier 50 kg/h Hydrogasifier: 5 Nm3/h H 2 Carbonatator with dolomite Developed by: ENEA/UNIVAQ Syngas cleaning Syngas cleaning Steam generator Syngas compressor Flaring Heaters Developed by: ENEA/CRIS Gas mixing

14 Sorption Enhanced SMR 14 Project still at a very preliminary stage, under the EERA (European Energy Research Alliance).

15 SE SMR 15 Assessment of SE-SMR reactor at equilibrium for two pressure levels: - 5 bars: suited for coupling with a SOFC-based hybrid cycle - 25 bars: suited for coupling with a gas turbine S/C = [%] Unconverted CH4 Carbon capture ratio 5 bar 25 bar Reactor temperature [ C]

16 SE SMR plant layout 16 LP drum HP drum heat recovery steam generator ~ - Heat pipes used to transfer heat from SOFC to calciner - Ejectors used for gas recirculation, to limit SOFC ΔT ~ LP HP - 5 bars, 650 C - Calciner T = 900 C Reformer CaO Calciner Heat pipes SOFC - SOFC T = 1100 C - Air side minimum ΔT in SOFC = 150 C CaCO3 - S/C = 4 CO2 compressor NG saturator NG e.m. condensate

17 SE SMR simulations results 17 After preliminary calculations: efficiency = 53.3%, CCR = 92.5%. - Large amount of heat must be generated for the calciner SOFC operates with low potential (and consequently low efficiency). - Large amount of steam required in the calciner heat from H 2 combustion used to generate the steam required (SOFC fuel utilization ~90%). benefits could be obtained by reducing maximum pressure below the optimal of hybrid cycles: lower amount of steam needed in the calciner higher consumptions for CO 2 compression

18 SE SMR GT-based plant 18 The other possible configuration (not investigated yet) is based on a combined cycle: - No critical components (no FC and heat pipes) - Calcination sustained by oxy-combustion of NG (ASU required) at high temperature (~ C) - Lower CO 2 capture in carbonator-reformer - Efficiency:?

19 19 Thank you for your attention