Simulation Optimization of a New Ammonia-Based Carbon Capture Process Coupled with Low-Temperature Waste Heat Utilization

Although ammonia-based CO₂ capture has attracted global research attention, several inherent issues with this technology remain to be resolved. To address these problems, a new design for carbon capture using ammonia is proposed on the basis of anti-solvent crystallization, also known as precipitation crystallization. The crystallization of a low carbonized absorbent was found to be enhanced in the crystallizer using an anti-solvent process, which can maintain a high absorption rate and simultaneously prevent crystallization from occurring in the absorption tower. Energy consumption for sorbent regeneration is reduced by regenerating the crystal product rather than the rich solution. Energy-cascade utilization is an effective way to improve the use of energy. In this work, steam was used to drive a heat pump that extracts energy from discharged flue gas from a wet flue gas desulfurization system in a power plant to enable the recovery of low-temperature residual energy; this energy can be used in the crystal regeneration process, thereby further reducing the energy required for regeneration. Aspen Plus (version 8.4) software was adopted to simulate the flue gas condensation, heat-pump circulation, and steam drive subsystems. The simulation results showed that 10 heat pumps (6.04 MW) can meet the regeneration energy requirement of the CO₂ capture process in a 300 MW coal-fired unit and recycle 40.6 MW of low-temperature heat. The extraction steam requirement is low, which reduces the impact on power generation.