Crossflow CO ₂ Absorber Design for Gas-Fired Combined Cycles

Crossflow CO2 absorbers were designed for a 110 MW Natural Gas Combined Cycle power plant with a height limitation of 7 m. Five molal piperazine (PZ) (30 wt %) was simulated in Aspen Plus with a lean solvent loading of 0.2 mol CO2/equiv N at 90% CO2 removal. A simple absorber and an absorber with pump-around intercooling were modeled. All configurations used a crossflow water wash to maintain the water balance around the absorber. Sulzer MellapakPlus 252Y structured packing was used. All crossflow configurations underperformed compared to analogous countercurrent designs. An analysis of the interfacial temperature and CO2 flux profiles showed that crossflow absorbers developed multiple mass transfer pinches and CO2 stripping by the flue gas, despite the relatively low temperature. These represent a fundamental shortcoming unique to the crossflow absorber. If performance costs can be tolerated, crossflow can be attractive alternative to countercurrent units when height constraints are present.