Membrane technology for CO2 capture: From pilot-scale investigation of two-stage plant to actual system design

A versatile pilot-scale two-stage membrane plant for CO2 capture from different simulated exhaust gases was designed and constructed. The capture efficiency was investigated in detail under different operating pressures, humidifier temperatures, and stage-cuts based on the graded CO2 contents of the initial feed gas (i.e., 14%, 25%, and 35%), which were similar to the typical CO2 contents of industrial exhaust gas emitted from coal-fired power plants, steel mill/cement plants, and factories associated with high–CO2–concentration operations, respectively. When the CO2 capture rates were 61.3%, 60.7%, and 53.9% in the three cases, the product gas CO2 purities could reach 78.5%, 87.2%, and 96.3%, respectively. This study also represents the first instance of developing an actual design and layout of a three-stage and three-step membrane plant, which will be built in early 2021 in Nanjing, China, and is expected to achieve the targets of 95% CO2 product purity and 90% CO2 capture rate. The experience gained through this study could accelerate the industrial application of membrane technology for CO2 capture.