Energy recoverable multi-stage dry sorbent CO₂ capture process

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 sorptiondesorption 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.