燃煤电厂烟气MDEA/PZ混合胺法碳捕集工艺模拟分析

采用混合胺吸收剂替代传统一乙醇胺（MEA）吸收剂是降低有机胺法碳捕集工艺能耗的重要方法。利用Aspen plus软件模拟了以甲基二乙醇胺(MDEA)/哌嗪(PZ)混合胺为吸收剂的燃煤电厂每年百万吨CO₂捕集工艺系统,考察了贫液负荷、MDEA/PZ混合胺浓度、MDEA/PZ比例和解吸压力等因素对解吸塔再沸器热负荷和冷凝器冷负荷的影响。通过对这些影响因素下吸收塔内液相温度分布和CO₂负荷分布变化揭示了MDEA/PZ对CO₂的吸收特性。此外,进一步分析了不同影响因素下解吸塔内气液相CO₂浓度驱动力和气液相级间温度驱动力分布特性,发现了强浓度驱动力和低温度驱动力分布更有利于降低再生能耗。研究表明,由30%MDEA和20%PZ组成的混合胺液在贫液负荷为0.08和解吸压力为2.02×10⁵Pa时,再沸器热负荷和塔顶冷凝负荷分别为2.76GJ/tCO₂和0.60GJ/tCO₂,相比传统MEA吸收剂降低了20.92%和40.0%。

Simulation and analysis of carbon dioxide capture process using MDEA/PZ blend solution in a coal-fired power plant

Amine blend is recognized as a promising alternative to traditional MEA solution for reducing the energy cost of post-combustion chemical absorption CO₂ capture process. In this study, a coal-fired power plant CO₂ capture system using the blend of methyldiethanolamine (MDEA) and piperazine (PZ) as an absorbent was simulated by Aspen plus soft at a capacity of 1 million tons CO₂ one year. The effects of MDEA/PZ blend concentration, MDEA/PZ ratio, CO₂ load in lean solution and stripping pressure on the stripper reboiler heat duty and condenser cool duty were investigated. The liquid phase temperature and CO₂ load of the solution in the absorber under different conditions were analyzed to reveal the absorbing properties of MDEA/PZ blend. The CO₂ concentration driving force and temperature driving force for the stripping process were also studied. The results showed that strong concentration driving force and weak temperature driving force favored the decrease of energy cost. The heat duty and cold duty for CO₂ regeneration in stripper can be as low as 2.76GJ/tCO₂ and 0.60GJ/tCO₂, respectively under optimized conditions (30% MDEA and 20% PZ, 0.08 lean load, 2.02×10⁵Pa stripping pressure), which were reduced by 20.92% and 40.0% compared to using traditional MEA solution.