Cost-effective stripper designs for CO2 capture on a 460 MW NGCC using piperazine

Abstract

Three stripper configurations that used a direct contact condenser (DCC) instead of a gas-liquid CO2 exchanger were designed, costed, and compared to the base case Front-End Engineering Design (FEED) for the Piperazine Advanced Stripper (PZAS) process. The designs were also compared to two other stripper configurations that used a low pressure (2 bar)/low temperature (120 ℃) stripper. Replacing the CO2 exchanger with a DCC enhanced gas cooling and water condensation in the stripper regardless of stripper pressure. The DCC preheated the cold rich bypass solvent and pre-stripped the solvent prior to entry into the stripper, but this required a bottom-side temperature pinch in the column, which was only achieved using a high-pressure stripper. The low-pressure stripper used a large amount of cold rich bypass which gave a top-side temperature pinch in the DCC, resulting in poor preheating of the solvent at the bottom. With the DCC, both capital expenditure (CAPEX) and operating expenditure (OPEX) were lower than for the base case with a high-pressure stripper. The total cost of capture was $3.30–4.00/tonne lower than the base case of $190.56/tonne when the DCC was used with a high-pressure stripper. The economic benefits of the DCC are suppressed with the low-pressure stripper due to larger stripper diameter and higher heat duty, resulting in a total cost of capture that is $6.30/tonne higher than the base value. The use of a DCC will therefore benefit solvents that can be stripped at high pressure and temperature.

Keywords

• CO2 capture
• Process configurations
• Rate-based modeling
• Process economics
• Piperazine
• Stripper