Techno-Economic Evaluation of Different Post-Combustion CO2 Capture Process Flow Sheet Modifications

Publication Overview

This study evaluated different post combustion capture process modifications for SCPC and NGCC power plant. The study also evaluated the current state of process design improvements such as absorber intercooling, operation at higher stripper pressure and an advanced level of waste heat integration for the SCPC case. In order to identify the effect of future improvements in the solvent; a generic improved amine based solvent ‘Solvent 2020 was considered. Regarding to the different process modifications, matrix stripping was found to be having the highest efficiency penalty due to the increased energy requirement by compressors. Also the cost of electricity and cost of CO₂ avoided for this modification was found to be higher compared to other process modifications.

Publication Summary

• Post combustion capture process improvements that are already well established such as intercooling in the absorber and improved heat integration with power plant, combined with improved solvents typical of those that are expected to become available by 2020, should substantially reduce the efficiency penalty on power plant.
• Current stage of process design improvements and improvements in solvent properties leads to reducing efficiency penalty from 9.8% to 6.11% for super critical pulverised coal (SCPC) fired power plant with amine based solvent CO₂ capture process base case.
• In natural gas combined cycle (NGCC) power plant with improved solvent properties CO₂ Capture process base case, reductions in efficiency penalty from 7.8% to 5.93% are achieved by flue gas recirculation, process design improvements.
• The overhead condenser (OHC) process modification was found to be having the lowest efficiency penalty of 5.84% for SCPC case, due to the reduction in steam extraction penalty, and for NGCC case was found to be 5.28%.
• The heat integrated stripper + OHC heat integration process modification was found to have the second lowest efficiency penalty for SCPC and NGCC case.
• The process modifications such as improved split flow process, OHC heat integration, vapour recompression + split flow and heat integrated stripper + OHC heat integration showed reduced CoE (cost of electricity) and lower CO₂ avoidance cost for both SCPC and NGCC case.
• Overall it can be noticed from this study that once all current improvements have been implemented in the solvent based post combustion capture process, different process modifications for SCPC and NGCC only bring slight improvements in the power plant efficiency penalty.
• The performance and cost of different post combustion capture process modifications depend on the type of solvent used. Therefore, for new solvents further evaluation for all process modifications will be required.