二氧化碳捕集与地热发电全链能流分析

Energy flow analysis on the full-chain system of carbon dioxide capture and geothermal power generation

以CO_(2)为工质的增强型地热发电系统(CO_(2)-EGS)拓展了CO_(2)封存汇的种类,同时其从干热岩中获得的热量还可补充因捕集、输运和封存消耗的能量,有效提高了项目的经济性。但多大程度上可填补CO_(2)捕集及输运的能耗是该技术规模化应用与发展过程中亟需解决的关键问题之一。为此,通过对CO_(2)捕集电站与地热发电全链系统的解构和耦合,在降低了全链系统某些参数的敏感性基础上,编制了全链优化软件。然后以某超临界燃煤电站为参考电站(热效率设为42.30%,净功为590.8 MW),对4种捕集方法(燃烧后捕集、加压富氧燃烧、化学链燃烧、分级气化)对应的全链系统进行了能流分析。结果表明:①对于中等温度的热储,化学链燃烧和分级气化法与CO_(2)-EGS结合后,全链系统的净输出可超过无CO_(2)捕集的参考电站,即CO_(2)-EGS的输出功可以弥补因捕集和输运造成的能量损失;②对于高温热储,CO_(2)-EGS的净输出可补偿加压富氧、化学链和分级气化法捕集和输运能耗。最后,基于全链能量梯级利用理念,结合CO_(2)膨胀发电的特点,提出了热量反哺的全链能量优化利用方法。结论认为:①全链能耗的主要差异体现在捕集过程,具体数值可达到数量级的差别;②压缩和输运及CO_(2)-EGS的单位能耗差异因捕集气的组分差异导致,数值上相差不大;③热量反哺理念显示了基于全链系统的能量优化利用优势,使系统的能量分配得到了优化,燃烧后捕集和分级气化两种捕集方案的指标得以提高。

The enhanced geothermal power generation system taking CO_(2) as working fluid(CO_(2)-EGS)expands the types of CO_(2) storage sinks,and its heat from hot dry rocks can supplement the energy consumed by capture,transportation and storage,which improves the economics of the project effectively.However,to what extent this technology can supplement the energy consumption of CO_(2) capture and transportation is one of the key problems that need solving urgently in the process of its large-scale application and development.In this paper,the sensitivity of some parameters in the full-chain system is reduced by deconstructing and coupling the full-chain system of CO_(2) capture power plant and geothermal power plant.On this basis,the full-chain system optimization software is worked out.Then,energy flow analysis is carried out on the fullchain systems corresponding to four capture methods(post-combustion capture,pressurized oxygen combustion,chemical chain combustion and coal classification gasification)by taking one certain supercritical coal fired power plant as the reference power plant(heat efficiency 42.30%and net work 590.8 MW).And the following research results are obtained.First,for medium-temperature geothermal reservoirs,the net output of the full-chain system with the combination of chemical chain combustion and coal classification gasification methods and CO_(2)-EGS can exceed that of the reference power plant without CO_(2) capture,which means that the output work of CO_(2)-EGS can make up for the energy loss caused by capture and transportation.Second,for high-temperature geothermal reservoirs,the output work of CO_(2)-EGS can make up for the energy consumption of capture and transportation through pressurized oxygen,chemical chain and coal classification gasification methods.Finally,a full-chain energy optimization utilization method of heat feedback is put forward based on the concept of full-chain energy cascade utilization,combined with the characteristics of CO_(2) expanding power generation.In conclusion,the differences of full-chain energy consumption are mainly reflected in the capture process and the specific values of the differences can be in the order of magnitude.What's more,the difference of unit energy consumption in compression&transportation and CO_(2)-EGS is caused by the compositional difference of captured gas,and its value is not different greatly.Furthermore,the concept of heat feedback displays the advantages of energy optimization utilization based on full-chain system,which optimizes the distribution of system energy and improves the indicators of post-combustion capture scheme and coal classification gasification scheme.