Techno-economic study of CO_2 capture from an existing coal-fired power plant: MEA scrubbing vs. O_2/CO_2 recycle combustion

摘要

The existing fleet of modern pulverised coal fired power plants represents an opportunity to achieve significant reductions in greenhouse gas emissions in the coming years providing that efficient and economical CO_2 capture technologies are available for retrofit. One option is to separate CO_2 from the products of combustion using conventional approaches such as amine scrubbing. An emerging alternative, commonly known as O_2/CO_2 recycle combustion, involves burning the coal with oxygen in an atmosphere of recycled flue gas. Both approaches can be retrofitted to existing units, however they consume significant amounts of energy to capture, purify and compress the CO_2 for subsequent sequestration. This paper presents a techno-economic comparison of the performance of the two approaches. The comparison was developed using the commercial process simulation packages, Hysys & Aspen Plus. The results show that both processes are expensive options to capture CO_2 from coal power plants, however O_2/CO_2 appears to be a more attractive retrofit than MEA scrubbing. The CO_2 capture cost for the MEA case is USD 53/ton of CO_2 avoided, which translates into 3.3 ￠/kWh. For the O_2/CO_2 case the CO_2 capture cost is lower at USD 35/ton of CO_2 avoided, which translates into 2.4 ￠/kWh. These capture costs represent an approximate increase of 20-30% in current electricity prices.