Zero- and negative-emissions fossil-fired power plants using CO2 capture by conventional aqueous amines

This work investigated the technical and economic feasibility of achieving zero and negative CO2 emissions in both pulverized coal (PC) and natural gas combined cycle (NGCC) power plants, using conventional amine scrubbing with 30 wt% aqueous monoethanolamine. In this work, we refer to “zero emissions” when the amount of CO2 in the exhaust flue gas is equal to that in the intake combustion air, and “negative emissions” when the amount of CO2 in the exhaust flue gas is less that in the intake combustion air. Increasing CO2 capture from 90% to that at zero-emissions for fossil-fired power plants can reduce global CO2 emissions by up to ∼1 Gt/y for the current global power generation mix. Even higher CO2 capture leads to negative emissions of the power plant with part of the CO2 from the intake air removed along with the fossil-fuel derived CO2. With an absorber configuration including a simple solvent intercooler, both PC and NGCC power plants can achieve zero-emissions with a ∼5% and ∼13% increase in CO2 avoidance costs, compared with the costs at 90% CO2 capture. The larger cost penalty for NGCC was mainly due to a temperature bulge at the absorber top. Replacing the simple solvent intercooler with a pump-around intercooler was able to reduce this cost penalty to ∼8%. Further decarbonization of flue gases from zero-emissions to direct air capture (DAC) -level of negative emissions (∼100 ppmv of CO2 in exhaust gases) has incremental costs of over 1000/t CO2 avoided for both PC and NGCC.