1. Institute of Energy Systems Prof. Dr.-Ing. A. Kather Dipl.-Ing. Sören Ehlers Jan Mletzko, M.Sc. Comparison of natural gas combined cycle power plants with post combustion and oxyfuel technology at different CO 2 capture rates The 8th Trondheim Conference on Capture, Transport and Storage, Trondheim, 16 th -18 th June 2015

2. TCCS-8 Trondheim, 16 th -18 th June 2015 Institute of Energy Systems GuD-POXY project  NGCC (GuD) power plants with Post combustion and OXYfuel  Hamburg University of Technology – Institute of Energy Systems ▸ Overall process simulation for post-combustion and oxyfuel  University of the Federal Armed Forces Hamburg (Helmut-Schmidt- University) – Laboratory of Turbomachinery ▸ Investigation of turbomachinery ▸ Combustion experiments 2 Project partners

3. TCCS-8 Trondheim, 16 th -18 th June 2015 Institute of Energy Systems Motivation  NGCC power plants have the lowest specific CO 2 emissions of fossil fuelled power plants ▸ ~ 340 g CO 2 / kWh el (60 % net efficiency) ▸ Further reduction to << 100 g CO 2 / kWh el with CCS technologies  Studies of different capture processes assume different capture rates ▸ 90 % for post combustion / 100 % for Oxyfuel ▸ Net efficiency does not provide a common basis for comparison  Legislative framework could favour the focus on a CO 2 emission limit ▸ A limit of 100 g CO 2 / kWh el requires 90 % capture rate for coal but only 75 % for natural gas 3 Aim: Comparison of two NGCC options with post combustion and oxyfuel regarding the loss of electricity related to the amount of CO 2 captured!

4. TCCS-8 Trondheim, 16 th -18 th June 2015 Institute of Energy Systems Reference plant  Conventional NGCC power plant is taken as the reference plant for all processes of the project  2x ALSTOM GT26 with HRSG  1x steam turbine ▸ Triple pressure reheat steam cycle ▸ Once-through evaporator for the HP level ▸ Net power: 876 MW ▸ Gross/net efficiency: 59.8 % / 59.2 % 4 G HPSH CPH IPE1 HPB IPSH LPB RH IPB IPE2 HPE1HPE2HPE3 Air EV SEV Pressure levels (HP/IP/LP): 159 bar / 40 bar / 4.2 bar Live steam/reheat temperature: 585 °C

5. TCCS-8 Trondheim, 16 th -18 th June 2015 Institute of Energy Systems Post combustion capture for NGCC  Basic 30 wt.-% MEA capture unit (15 m absorber height) ▸ Steam extracted from crossover between the IP and LP steam turbine ▸ 90% capture rate in the base case ▸ CO 2 compression to 110 bar  Base case net efficiency 52.1 % (-7.1 %-pts.) ▸ Steam extraction  4.6 %-pts. ▸ CO 2 compression  1.6 %-pts. ▸ Additional auxiliary duty  0.9 %-pts. 5

6. TCCS-8 Trondheim, 16 th -18 th June 2015 Institute of Energy Systems Influence of the capture rate on the PCC unit  Specific heat duty increases sharply at capture rates above 85 % ▸ Efficiency penalty varies between 4.8 and 9.4 %-pts.  Same tendency for improved capture processes ▸ flue gas recycle shifts the sharp increase of the specific heat duty to higher capture rates (~ 90 %) 6 L/G adjusted to the lowest specific heat duty for each capture rate

7. TCCS-8 Trondheim, 16 th -18 th June 2015 Institute of Energy Systems NGCC with Oxyfuel  Semi-closed oxyfuel combustion combined cycle (SCOC-CC) ▸ Pressure ratio of 60 due to sequential combustion ▸ O 2 purity 95 vol.-% (0.202 kWh/kg O 2 ), 3 vol.-% O 2 (dry) in the flue gas ▸ 100 % CO 2 capture  Compression of the flue gas to 110 bar ▸ CO 2 purity of 86.5 vol.-% (dry)  Base case net efficiency 50.3 % (-8.9 %-pts.) ▸ O 2 production  5.9 %-pts. ▸ CO 2 compression  2.3 %-pts. ▸ Additional auxiliary duty  0.3 %-pts. ▸ Thermodynamics of the process  0.4 %-pts. 7

8. TCCS-8 Trondheim, 16 th -18 th June 2015 Institute of Energy Systems Influence of the capture rate on the SCOC-CC  Assumed CO 2 purity for transport and storage  96 vol.-% (dry) ▸ CO 2 purification (partial condensation)  Reduced capture rate ▸ Two condensation stages at -25 °C and -30 – -50 °C ▸ Only small effects  ASU loss independent of the capture rate  Alternative: High purity O 2, 1 vol.-% O 2 (dry) in flue gas ▸ Energy demand for the ASU (99.5 vol.-% O 2 ): 0.241 kWh/ kg O 2 ▸ 100 % Capture rate  Additional penalty 0.8 %-pts. 8

9. TCCS-8 Trondheim, 16 th -18 th June 2015 Institute of Energy Systems Specific electric loss  Post combustion capture for natural gas has a significantly lower loss for a wide range of capture ratios  Minimum at ~ 80 %  SCOC-CC only advantageous if full capture is required ▸ If purity is restricted high purity oxygen is necessary 9 SCOC-CC Base case  Purity not sufficient Coal-fired plants (90% CR) 0.26 – 0.36 kWh/kg CO 2

10. TCCS-8 Trondheim, 16 th -18 th June 2015 Institute of Energy Systems Conclusion 10  Post combustion capture for NGCC allows an adjustment of the capture rate to a required CO 2 emission limit for a wide range of capture rates ▸ Specific electric loss is approx. constant from 60 to 90 % at 0.38 kWh/kg CO 2 ▸ Sharp increase of the specific electric loss for higher capture rates ▸ Minimum specific loss at 80 % capture rate  The SCOC-CC leads to a higher specific electric loss of > 0.45 kWh/kg CO 2 ▸ Specific loss increases for lower capture rates because the ASU is independent of the capture rate ▸ Only at full capture case advantageous compared to post-combustion capture ▸ 96 vol.-% CO 2 purity at full capture is only achievable with high purity oxygen  Compared to coal-fired plants the specific electric loss due to CCS technologies is higher for NGCC plants

11. TCCS-8 Trondheim, 16 th -18 th June 2015 Institute of Energy Systems 11 Thank you for your attention! Questions?