Advanced Modelling of IGCC-Power Plant Concepts

Transcription

1 Institut für Energieverfahrenstechnik und Chemieingenieurwesen Advanced Modelling of ICC-Power Plant Concepts Effects of ASU-Integration on Plant Performance and as Turbine Operation Dipl.-Ing. Mathias Rieger, Dipl.-Ing. Robert Pardemann, Prof. Dr.-Ing. Bernd Meyer, TU Bergakademie Freiberg Dr.-Ing. Alexander Alekseev, Linde Engineering TU Bergakademie Freiberg I Institut für Energieverfahrenstechnik und Chemieingenieurwesen Reiche Zeche I 9596 Freiberg I Tel. +49()3731/ I Fax +49()3731/ evt@iec.tu-freiberg.de I Web

2 P-471 Coal based ICC with CO 2 -capture asification mill and feeding system feedstock B HP-steam to CC clean gas saturator O2 saturated clean gas to CC clean dry gas CO2 coal excess N2 to environment pure AN A IP-steam from CC gasifier quench room raw gas scrubber CO-shift stage 1 CO-shift stage 2 condensate from CC make up H2S to Claus-plant Air Separation Unit slag discharge acid gas removal discharge make up discharge N2 to CC ambient air to MAC T-extraction air O2 to CC (preheating) make up cooling make up F E F E D C D B C saturated, diluted, preheated fuel gas Diluent N2 from ASU A 2

3 asifier unit Boundary conditions Main reactions within gasifier: C + O 2 CO 2 C + CO 2 2 CO C + 2 H 2 CH 4 CO + H 2 O H 2 + CO 2 Feedstock information: Pittsburgh No. 8 Proximate Analysis Ultimate Analysis (waf) Fixed Carbon (wt %) 5.15 C (wt %) 83.4 Volatile Matter (wt %) H (wt %) 5.7 Moisture (wt %) 5.5 O (wt %) 6.38 Ash (wt %) 7.37 N (wt %) 1.56 Total 1. Cl (wt %).6 S (wt %) 3.26 LHV (MJ/kg) Total 1. Modelling principle: - Thermodynamic equilibrium assumed - Steam/Oxygen ratio is adjusted to a specified carbon conversion rate at a given gasifier temperature 3

4 asifier unit Results and interface parameters asification temperature: 15 C 19.5 Sm³/J 4 kg/j η Cold gas 82.8 % 157 Sm³/J (wet) 73 Sm³/J (dry) as composition [mol %] CO 27.6 N H Ar.4 CH 4.1 CO 2.9 H 2 S.4 H 2 O 53.3 LHV kj/kg 235 C S/ ratio = J/J mol H2O S/ ratio = mol dry syngas 4

5 asifier unit Results quench temperature [ C] Steam / Dry gas ratio gasification temperature [ C] Conclusions: - Increasing quench temperature and increasing gasification temperature cause a higher steam / dry gas ratio => important for design of CO-shift cycle!! 5

6 P-471 Coal based ICC with CO 2 -capture as conditioning mill and feeding system feedstock B HP-steam to CC clean gas saturator O2 saturated clean gas to CC clean dry gas CO2 coal excess N2 to environment pure AN A IP-steam from CC gasifier quench room raw gas scrubber CO-shift stage 1 CO-shift stage 2 condensate from CC make up H2S to Claus-plant Air Separation Unit slag discharge acid gas removal discharge make up discharge N2 to CC ambient air to MAC T-extraction air O2 to CC (preheating) make up cooling make up F E F E D C D B C saturated, diluted, preheated fuel gas Diluent N2 from ASU A 6

7 as conditioning section Overview Main oals: - Recovery of CO-shift reaction heat => HP-steam generation - Recovery of evaporation enthalpy => Quench and saturation preheating - As little as possible interfaces to other ICC-sections HP-steam generation 8.4 % heat recovery based on gasifier input Quench preheating 7.8 % heat recovery based on gasifier input Saturation preheating 5.1 % heat recovery based on gasifier input η en 91 % 7

8 P-471 Coal based ICC with CO 2 -capture as turbine mill and feeding system feedstock B HP-steam to CC clean gas saturator O2 saturated clean gas to CC clean dry gas CO2 coal excess N2 to environment pure AN A IP-steam from CC gasifier quench room raw gas scrubber CO-shift stage 1 CO-shift stage 2 condensate from CC make up H2S to Claus-plant Air Separation Unit slag discharge acid gas removal discharge make up discharge N2 to CC ambient air to MAC T-extraction air O2 to CC (preheating) make up cooling make up F E F E D C D B C saturated, diluted, preheated fuel gas Diluent N2 from ASU A 8

9 as turbine Model and boundary conditions after H 2 O-dilution H N CO 2.5 Ar.6 CH 4.2 CO 2.7 H 2 O 2.3 LHV 25 MJ/kg Composition after AR H N CO 3.1 Ar.8 CH 4.3 CO 2.9 H 2 O.4 LHV 49 MJ/kg Turbine Loss Characteristics Main parameters for model tuning: P el,ref = MW η el,ref = 39.5 % π compressor,ref = 17.9 T hot gas,ref = 1425 C TIT ref = 124 C cool frac = 2.9 % TOT ref = C T blade,ref = 9 C Δη turbine 1 Ma relative Cooling fraction for off-design calculations is determined by combustion chamber pressure loss and throttle coefficient for the cooling air ducts! 9

10 as turbine Effects of N 2 -dilution (no air extraction) N 2 -dilution hot gas mass flow cooling effort, but cooling fraction const. blade temperature De-rating hot gas temperature! ΔT blade = T blade,syngas T blade,ref

11 as turbine Effects of N 2 -dilution (no air extraction) N 2 -dilution hot gas mass flow π compressor Surge margin! ΔT blade = T blade,syngas T blade,ref -2 Δπ compr = π compr,syngas / π compr,ref

12 as turbine Effects of N 2 -dilution (no air extraction) N 2 -dilution hot gas mass flow P el,t Limitations through shaft limit or generator capacity! ΔT blade = T blade,syngas T blade,ref -2 Δπ compr = π compr,syngas / π compr,ref -4 ΔP el = ΔP el,syngas / ΔP el,ref

13 as turbine Effects of N 2 -dilution (no air extraction) P el,syngas > 1.2 * P el,ref Operating window with possible operating points! ΔT blade = T blade,syngas T blade,ref T blade,syngas > T blade,ref -2 Optimization: m& compr Δπ compr = π compr,syngas / π compr,ref -4 ΔP el = ΔP el,syngas / ΔP el,ref Limitations for example gas turbine: 1. T blade,syngas,max T blade,ref 2. π compr,syngas,max 1.7 * π compr,ref P el,syngas,max 1.2 * P el,ref π compr,syngas > 1.7 * π compr,ref 13

14 as turbine Effects of N 2 -dilution and air extraction Air extraction hot gas mass flow T blade ; π compressor ; P el,t Operating window without air extraction

15 as turbine Effects of N 2 -dilution and air extraction Air extraction hot gas mass flow T blade ; π compressor ; P el,t Operating window at 4 % air extraction

16 as turbine Effects of N 2 -dilution and air extraction Air extraction hot gas mass flow T blade ; π compressor ; P el,t Operating window at 8 % air extraction

17 as turbine Effects of N 2 -dilution and air extraction -2-4 Air extraction hot gas mass flow T blade ; π compressor ; P el,t Operating window at 12 % air extraction Conclusions: Air extraction extends gas turbine operating window Air extraction reduces the amount of hot gas temperature de-rating - Air extraction reduces the need for blading/stage modifications Air extraction requires turbine modification and increases complexity

18 as turbine Effects of integration to -/steam cycle as turbine behavior for selected operating points air extraction rate [% of compressor mass flow] Relative exhaust gas mass flow (related to natural gas) depending on air extraction rate and syngas dilution (LHV) P el,steam turbine air extraction rate [% of compressor mass flow] Turbine Outlet Temperature change (related to natural gas) depending on air extraction rate and syngas dilution (LHV) η steam cycle ; P el,steam turbine

19 P-471 Coal based ICC with CO 2 -capture Water-/steam cycle mill and feeding system feedstock B HP-steam to CC clean gas saturator O2 saturated clean gas to CC clean dry gas CO2 coal excess N2 to environment pure AN A IP-steam from CC gasifier quench room raw gas scrubber CO-shift stage 1 CO-shift stage 2 condensate from CC make up H2S to Claus-plant Air Separation Unit slag discharge acid gas removal discharge make up discharge N2 to CC ambient air to MAC T-extraction air O2 to CC (preheating) make up cooling make up F E F E D C D B C saturated, diluted, preheated fuel gas Diluent N2 from ASU A 19

20 Water-/steam cycle Configuration and interfaces Three-pressure reheat -/steam cycle Interfaces for: - syngas-, diluent- and oxygen-preheating - extraction air cooling - gasifier steam supply - CO-shift steam superheating 2

21 ICC-Performance and concept evaluation OutputICC,net [MW] ICC-Output depending on ASU-integration level reduced % air integration 22 % air integration 44 % air integration 68 % air integration compressor mass flow (IV) ICC-Output depending on ASU-integration level % air integration Auxiliary load ICC [MW] H2-content [Vol. -%] ICC-auxiliary load depending on ASU-integration level reduced % air integration 22 % air integration 44 % air integration 68 % air integration compressor mass flow (IV) Output ICC,net [MW] % air integration 44 % air integration 68 % air integration η ICC,net [% ] H2-content [Vol. -%] ICC-Efficiency depending on ASU-integration level H 2-content [Vol. -%] 68 % air integration 44 % air integration 22 % air integration % air integration reduced compressor mass flow (IV) reduced H 2 -content [Vol. -%] compressor mass flow (IV) Air- and N 2 -integration Output 21

22 ICC-Performance and concept evaluation OutputICC,net [MW] Auxiliary load ICC [MW] η ICC,net [% ] ICC-Output depending on ASU-integration level reduced H2-content [Vol. -%] ICC-auxiliary load depending on ASU-integration level reduced compressor mass flow (IV) H2-content [Vol. -%] % air integration 22 % air integration 44 % air integration 68 % air integration compressor mass flow (IV) % air integration 22 % air integration 44 % air integration 68 % air integration ICC-Efficiency depending on ASU-integration level H 2-content [Vol. -%] 68 % air integration 44 % air integration 22 % air integration % air integration reduced compressor mass flow (IV) Auxiliary load ICC [MW] ICC-auxiliary load depending on ASU-integration level High pressure ASU reduced compressor mass flow (IV) Low pressure ASU H 2 -content [Vol. -%] % air integration 22 % air integration 44 % air integration 68 % air integration Air- and N 2 -integration Output Air-integration ; N 2 -integration Aux load 22

23 ICC-Performance and concept evaluation OutputICC,net [MW] ICC-Output depending on ASU-integration level reduced 35 % air integration 22 % air integration 44 % air integration 68 % air integration compressor mass flow (IV) ICC-Efficiency depending on ASU-integration level Auxiliary load ICC [MW] H2-content [Vol. -%] ICC-auxiliary load depending on ASU-integration level reduced % air integration 22 % air integration 44 % air integration 68 % air integration compressor mass flow (IV) ηicc,net [%] % air integration 44 % air integration 22 % air integration % air integration η ICC,net [% ] H2-content [Vol. -%] ICC-Efficiency depending on ASU-integration level H 2-content [Vol. -%] 68 % air integration 44 % air integration 22 % air integration % air integration reduced compressor mass flow (IV) reduced H 2 -content [Vol. -%] compressor mass flow (IV) Air- and N 2 -integration Output Air-integration ; N 2 -integration Aux load Marginal efficiency spread (for optimized concepts) 23

24 Conclusion and outlook Optimized and harmonized operating concepts yield to highest efficiencies for coal based CCS-ICC! Non or low integrated ICC concepts do not necessarily lead to poor plant-efficiencies! Further optimization and concept simplification should improve economics and push ICC to commercialization! Thank you for your attention! 24