燃煤烟气碳捕集系统压缩、干燥与液化设备选型

Research on compression,drying and liquefaction equipment selection in CO_(2)capture system of the coal-fired power plant

燃煤电厂烟气碳捕集系统的产品处理装置包括压缩、干燥和液化装置,其选型方案决定产品气质量。基于某1000 MW等级火力发电厂的50万t/a规模烟气二氧化碳湿法捕集项目,针对湿法吸收工艺CO_(2)气体含水率高、气量较大但压缩压力不高的特性,结合电厂发电、供热运行限制,对CO_(2)气体压缩系统压缩、液化及冷却工序所需CO_(2)压缩机、冷冻液化机等设备选型开展比型分析,并对化工系统设备应用于电力生产单位的适应性进行研究。结果表明,燃煤电厂烟气CO_(2)捕集装置设备选型与石油化工单位CO_(2)捕集装置设备选型差异极大。与化工单位的负荷追求稳定相比,现代火电厂调峰运行负荷波动性极强,火电厂CCUS项目采纳电厂排烟为原料,使用电厂余热蒸汽,占用厂用电份额,与电厂主系统共用循环水、闭式水、压缩空气等生产资料,导致火电厂CCUS项目所需烟气量、动力蒸汽参数、烟气CO_(2)浓度、冷却水源等处于波动状态,换热装置、压缩机等选型的设计边界条件与化工单位不同;一般情况下,燃煤电厂与化工企业所处区位不同,化工企业多为上下游企业同处一个化工区,火电厂周围一般不毗邻CO_(2)消纳单位,火电厂CCUS装置的产品气质量标准、气体封装及运输设备需结合区域及市场定位与化工单位相区别;与化工单位相比,燃煤电厂CCUS项目具有动力源成本较低等优势,电厂项目更多应考虑减少吸收剂损耗等成本,不必一味追求降低能耗成本。

The product processing devices of the flue gas carbon capture system of coal-fired power plants include compression,drying and liquefaction devices,and their selection determines the product gas quality.Based on the 500000 t/a flue gas CO_(2)wet capture project of a 1000 MW thermal power plant,this paper conducted a comparative study and analysis on the selection of CO_(2)compressors,refrigeration liquefiers and other equipment required for the compression,liquefaction and cooling processes of the CO_(2)gas compression system in view of the characteristics of the wet absorption process,such as high CO_(2)gas moisture content,large gas volume but low compression pressure,combined with the operating restrictions of power generation and heat supply of the power plant.The adaptability of chemical system equipment applied to power production units was also discussed.The results show that the type selection of CO_(2)capture device for flue gas of coal-fired power plants is greatly different from that of petrochemical units.Compared with the pursuit of stability of the load of petrochemical units,the load fluctuation of modern thermal power plants during peak shaving operation is extremely strong.The CCUS project of thermal power plants uses power plant smoke as raw material,uses power plant waste heat steam,takes up the share of power consumption,and shares circulating water,closed water,compressed air and other production materials,leading to the fluctuation of flue gas volume,power steam parameters,flue gas CO_(2)concentration,cooling water source,etc.The design boundary conditions for the selection of heat exchanger and compressor are different from those of petrochemical units.In general,coal-fired power plants and petrochemical enterprises are located in different locations.Most of the petrochemical enterprises are located in the same chemical industry zone as upstream and downstream enterprises.Thermal power plants are not adjacent to CO_(2)consuming units.The product gas quality standards,gas packaging and transportation equipment of CCUS units of thermal power plants need to be differentiated from chemical units based on regional and market positioning.Compared with chemical units,the CCUS project of coal-fired power plant has the advantage of lower power source cost.Power plant projects should consider reducing the cost of absorbent loss more,instead of blindly pursuing to reduce energy consumption costs.