Abstract: Energy saving technologies for CO2 capture systems are receiving extensive attentions from both academic researchers and industries. However，most of these researches focused on the CO2 capture systems，instead of the waste heat utilization of the flue gas and practical recovery schemes. However，in order to improve the energy efficiency of the CO2 capture systems，it was very important to recover the thermal energy from the flue gas. This paper took the flue gas processing system coupled with a 660MW coal-fired power plant as an example，the temperature of pinch point was determined by use of “problem table” method. The initial heat exchanger network （HEN）was optimized by matching hot flows and cold flows. And three new retrofit schemes were obtained：The one-stage HEN for energy recovery of the flue gas was to use the flue gas to heat the makeup mono ethanol amine (MEA) solvent；the two-stage HEN could be further divided into two networks - the first one recovered the heat of the flue gas directly by letting the flue gas heat the rich solvent and the makeup MEA solvent sequentially，the second one recovered the heat of flue gas indirectly，letting the flue gas heat water first and then the heated water was sent to heat both the rich and the makeup MEA solvent. The three new HENs were compared in terms of investment cost，and it was found that the most cost effective method was one-stage HEN.

Key words: flue gas, CO2 capture, pinch technology, optimization, recovery, investment cost

摘要： 二氧化碳捕集系统节能技术受到了人们的广泛关注，但基本上集中在系统本身，鲜见有关烟气余热回收利用方面的研究报道，缺少具体的应用方案。然而，要进一步提高二氧化碳捕集系统的效率，就必须对烟气余热进行有效利用。为此，本文以某发电厂与660MW热电联产装置相配套的烟气处理系统为研究对象，首先采用问题表法确定了换热网络的夹点温度，然后通过冷、热物流间的“新”匹配对原换热网络进行改造，得出3种改造方案：烟气余热回收一级换热网络是高温烟气与胺补液之间进行匹配；烟气余热直接回收二级换热网络是高温烟气依次与富液、胺补液之间进行匹配；而烟气余热间接回收二级换热网络包括高温烟气与富液之间的间接换热。通过对以上3种改造方案投资费用的比较，发现烟气余热回收一级换热网络的投资成本最低，是最优改造方案。

关键词: 烟道气, 二氧化碳捕集, 夹点技术, 优化, 回收, 投资成本