Techno-economic analysis of a hybrid CO2 capture system for natural gas combined cycles with selective exhaust gas recirculation

Abstract

This work analyses the implementation of CO2 capture in natural gas combined cycle (NGCC) power plants using a hybrid system integrated by an amine scrubbing plant and a CO2 selective membrane. In this configuration, the membrane unit operates at close to atmospheric pressure and it is used to selectively recycle CO2 back to the inlet of the compressor, therefore increasing the CO2 content of the flue gas entering the capture system. A novel integration between the amine capture plant and the selective membrane is analysed here, which aims at exploiting the benefits of both the parallel and series selective exhaust gas recirculation (S-EGR) existing options. The mass and energy balances performed on this system indicate that the new configuration generates a flue gas with a CO2enhanced concentration of 18%vol., which leads to a decrease in the energy demand in the reboiler by 6% with respect to an amine scrubbing system coupled to a conventional NGCC plant without S-EGR. Moreover, a reduction of 77% is achieved in the gas flowrate fed to the absorber of the amine plant, thus significantly reducing its size and cost. The calculated net electrical efficiency of the plant is 50.3%, which is 0.5 net percentage points higher than that of a conventional NGCC with amine-based capture and slightly lower than that of a reference plant with exhaust gas recirculation (EGR). These values are dependent on the pressure drop associated with the membrane system, which has a large influence on the energy balance of the plant. Therefore, higher efficiency improvements can be achieved if membrane module designs with reduced pressure drop are used. A techno-economic evaluation reveals that the cost of the membrane system has a strong effect on the capital costs of the plant and thus, on the cost of electricity and the cost of CO2 avoided.

Evaluation of the Performance and Economic Viability of a Novel Low Temperature Carbon Capture Process

“…The largest column size is required for the absorber of the oil-fired boiler case, as this case deals with the largest volume of flue gas, with the absorber diameter being 9.9 m, which is comparable to results from similar studies (Nwaoha et al, 2018). At large scales, amine capture plants will be designed with two columns to avoid oversized units and provide operating flexibility, however the columns for these cases are smaller than units typically designed for two-absorber column capture plants on industrial scale plants (Agbonghae et al, 2014;Diego et al, 2018), so a one-absorber design was maintained for consistency throughout the cases. Costs of the MEA reference cases are detailed in Table 6.…”

Efficiency Improvement of Chemical Looping Combustion Combined Cycle Power Plants

“…The energy penalty for carbon capture in an NGCC power plant with post‐combustion capture ranges from 7.6 to 8.4 %‐points . This includes the energy required for separation of CO 2 from the flue gas and the compression to a supercritical state.…”

Gas switching reforming (GSR) for power generation with CO2 capture: Process efficiency improvement studies

“…Case 5 shows an efficiency penalty of only 7.2 %-point when compared to reference NGCC plant with more than 95% CO2 avoided. This outperforms post-combustion CO2 capture systems with 7.6-8.4 %-point energy penalty and 88% CO2 avoidance [32,33].…”