Search

A multi-stage fluidized bed process for CO 2 capture is a novel process for reducing regeneration energy. This process is consist of low-, mid-, and high-temperature stage. Each stage has an absorber and a regenerator. Solid absorbents circulating in these fluidized beds absorb and regenerate CO 2 by temperature swing. PEI-, MgO-, and Li 4 SiO 4 -based absorbents are utilized for low-, mid-, and high-temperature stage. The main feature of this process is a heat recovery scheme; i) an intra-stage heat exchanger, ii) an inter-stage heat exchanger. In the intra-stage heat exchanger, a sensible heat of lean and rich sorbents from regenerator and absorber is exchanged. In the inter-stage heat exchanger, a heat of absorption of mid- and high-temperature stage is supplied to a heat of regeneration of low- and mid-temperature stage. A bench-scale facility that can process 60 Nm 3 /hr flue gas is constructed for conducting a feasibility study of this process. From the experiments of the low-temperature stage, it can capture CO 2 with an efficiency of 80%, however, due to a low efficiency of intra-stage heat exchanger, the regeneration energy and total utility cost are estimated as 4.65 GJ and $36.9 per ton-CO 2 . The three-stage process is evaluated through a process simulation study based on the absorption performance measured at a lab-scale apparatus. The resulted regeneration energy is estimated as 2.37 GJ per ton CO 2 and total utility cost is $39.1 and $24.5 per ton CO 2 in the absence and in the present of steam-turbine, respectively. Finally, a parametric study of the absorption capacity of sorbents and MTA of intra-stage heat exchanger are also been conducted and discussed.

To reduce the energy required for CO 2 desorption, an energy exchangeable three-stage dry sorbent CO 2 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 Li 4 SiO 4 (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 CO 2 capture process was 1.68 GJ/ton-CO 2 , 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 Nm 3 /hr exhaust gas was constructed and in the step of operation.