Energy-Saving Interstage Heating Process for CO2 Capture Based on Lean Solution Waste Heat Recovery

Traditional chemical absorption-based CO2 capture processes suffer from high consumption of regeneration energy, uneven temperature distribution inside the desorption column, and low waste heat utilization efficiency of lean solvent. With the aim of creating a 210,000 ton/year CO2 capture system for flue gas from coal-fired boilers, this study establishes a process model for CO2 capture using a blended methyldiethanolamine (MDEA)–piperazine (PZ) amine solvent via Aspen Plus software and systematically optimizes key parameters of the rich–lean heat exchanger and absorbent circulation rate. To address the bottleneck of overheating at the bottom and undercooling at the upper section of the desorption column, an interstage reheating process based on lean solvent waste heat recovery is proposed. The influences of the semi-lean solvent extraction position, extraction flow rate, and reinjection position on system energy consumption and hydrodynamic characteristics inside the column are comprehensively investigated. After optimization, the proposed interstage reheating process reduces energy consumption by 10.16% compared with the base MDEA-PZ process and achieves energy savings of 29.25% relative to the conventional monoethanolamine (MEA) process. This research provides theoretical foundations and technical data support for the engineering design and operational optimization of low-energy-consumption CO2 capture and desorption systems.