Energy recoverable multi-stage dry sorbent CO2 capture process

Abstract

To reduce the energy required for CO2 desorption, an energy exchangeable three-stage dry sorbent CO2 capture process was designed and in the step of efficiency evaluation. The process is composed of three stages working at different sorption- desorption temperatures to utilize the heat released at higher temperature absorption cycles for the regeneration of sorbent working at lower temperature cycles; low-, medium- and high-temperature stages. For this process three kinds of sorbents having different sorption-desorption temperatures were developed; amines supported on silica (low temperature), alkali-promoted MgO (medium temperature) and Li4SiO4 (high temperature). Based on the kinetic properties of these three types of sorbents, several process models were simulated and it was found that dilute-dilute sorption-desorption process is the most efficient. According to the simulation, the thermal energy demand for the three-stage CO2 capture process was 1.68 GJ/ton-CO2, which means about 60% of the thermal energy required for a single-stage dry sorbent process can be saved. To evaluate this concept, real facility which can treat 60 Nm3/hr exhaust gas was constructed and in the step of operation.