燃煤电厂配置二氧化碳捕集系统需消耗大量蒸汽用于吸收剂再生与循环利用,蒸汽消耗降低机组发电效率和发电量。机组热力系统和二氧化碳捕集系统的跨界区能量耦合利用是减少发电效率损失的重要途径。以全容量二氧化碳捕集的630MW机组为对象,构建全容量烟气的二氧化碳捕集系统模型和汽轮机组热力系统热平衡图,借助等效焓降法研究碳捕集系统工艺参数选择及多种余热利用方法对汽轮机组发电效率的影响。结果表明:全容量二氧化碳捕集系统后需消耗569.18t/h蒸汽,导致原机组循环效率从43.84%降至35.74%。再沸器凝结水余热用于富液加热时,再生热耗降低0.2GJ/t,节约蒸汽用量43.05t/h,机组循环效率升至36.35%,和余热用于机组回热系统效果相当,但前者系统更简单。再生气余热和二氧化碳压缩机级间余热可用于机组凝结水加热,节约机组低压缸抽汽,提高循环效率;再生气温度、流量和余热量与碳捕集系统富液分流工艺的分流比有关,随着冷富液流量增加,碳捕集系统能耗和机组发电效率损失均呈先降低再升高趋势,当冷富液、主富液、凝结水加热富液质量比0.20∶0.75∶0.05时,机组发电效率最高;二氧化碳压缩机级数越少可利用的热量越大,机组发电效率越高,但同时消耗更多电能。通过优化,配置全容量二氧化碳捕集系统的630MW机组发电功率由无优化时的510.09MW增至528.96MW。

Deployment of carbon capture system to coal-fired power plant consumes large amount steam for solvent regeneration andcyclic utilization. Steam consumption reduces the power generation efficiency and output of the plant. The trans-system utilization ofenergy between power system and carbon capture system is vital to decrease the efficiency penalty. By analyzing the flowsheet model offull-scale flue gas carbon capture and the heat balance diagram of steam turbine units,the effect of carbon capture system parameterselection and waste heat utilization on turbine efficiency of a 630 MW plant were studied by equivalent enthalpy theory. 569.18 t/h steamwas consumed in full-scale carbon capture system for solvent regeneration,resulting in the decrease of turbine efficiency from 43.84% to35.74%. Utilization of re-boiler condensate waste heat on heating rich solvent,reducing 0.2 GJ/t regeneration duty and saving 43.05 t/hsteam consumption,exhibits the same outcomes as on regenerative feedwater heating system,while the former choice can be reached witha simpler system. The waste heat from CO2 compressor and regenerated gas,which is related to the rich split ratio of carbon captureprocess,can be recycled by condensate water from turbine to reduce the steam extraction from low pressure turbine to enhance efficiency.The best performance of turbine is reached at mass ratio of 0.2∶0.75∶0.05 (cold rich solvent∶rich solvent mainstream∶rich solventheated by re-boiler condensate). Cutting stages of CO2 compressor increases the recyclable heat at the expense of higher electricityconsumption. After optimization, the power generation of a 630 MW plant with full-scale flue gas carbon capture increases from510.09 MW to 528.96 MW.

0 引言

1 研究方法与模型

   1.1 二氧化碳捕集系统流程

   1.2 等效焓降理论

2 机组及碳捕集系统性能

3 碳捕集系统和机组系统的耦合利用

   3.1 无余热利用

   3.2 凝结水余热利用

   3.3 再生气余热利用

   3.4 压缩机级间余热利用

4 结论