Techno-economic comparison of the thermodynamic system at lignite-fired boiler's cold-end for recovering waste heat of exhaust gases

doi:10.16085/j.issn.1000-6613.2016.12.050

Abstract

Abstract: It is an important way to increase the efficiency of a thermal power plant by recovering the waste exhaust gas heat at boiler cold-end with a stepwise integration with the heat regenerative system of steam turbines. In this paper,an in-service 600MW lignite-fired supercritical power unit was used as a reference unit to calculate and compare the thermal economy and techno-economic performances of three kinds of typical heat recovery processes at boiler cold-ends:low-temperature economizer,segmented air heating and bypass flue. The results showed that,with the recovery of boiler exhaust heat from 148℃ to 90℃,the three above-mentioned processes can make the net standard coal consumption rate reduced by 4.43g/(kW·h),5.84g/(kW·h) and 6.48g/(kW·h),respectively. Meanwhile,25.62 million CNY,23.48 million CNY and 22.61 million CNY are needed as the initial costs of the three heat recovery projects. If the 600MW unit runs 5500 hours per year with the rated load,the three processes can annually increase the earning of the unit by 9.94 million CNY,13.50 million CNY and 15.14 million CNY from coal savings,meaning that their dynamic payback periods are 3.12 years,2.00 years and 1.71 years,respectively. Those results indicate that the efficiency of a lignite-fired power unit can be significantly increased via an exhaust heat recovery process. Among the three processes,the bypass flue process shows the best thermal economy and techno-economic performance,therefore,it is recommended for preferential applications.

Key words: lignite, thermal power plant, flue gas, waste heat recovery, techno-economic analysis

摘要： 对电站锅炉排烟余热进行回收，使一部分锅炉冷端烟气热能梯级利用于汽轮机回热系统，是燃煤电厂增效减排的重要途径。以某600MW超临界燃褐煤机组为例，对低温省煤器、送风分段预热和旁通烟道3种锅炉冷端优化热力系统进行了热经济性与技术经济性比较。结果表明，由上述3种系统回收锅炉排烟由148℃降温至90℃余热，机组供电标准煤耗率分别减小4.43g/（kW·h）、5.84g/（kW·h）和6.48g/（kW·h），项目投资分别为2562万元、2348万元和2261万元。以机组在THA工况下年运行5500h计，3种系统每年由节煤增加净收益994万元、1350万元和1514万元，动态投资回收期分别为3.13年、2.00年和1.71年。可见褐煤锅炉排烟余热回收可明显提高电厂效率。3种冷端优化热力系统中，旁通烟道系统展示出最优的热经济性和技术经济性，建议对其进一步研究和应用。

关键词: 褐煤, 火力发电厂, 烟道气, 余热利用, 技术经济性分析

CLC Number:

O656.22
TE8

MA Youfu, YANG Lijuan. Techno-economic comparison of the thermodynamic system at lignite-fired boiler's cold-end for recovering waste heat of exhaust gases[J]. Chemical Industry and Engineering Progree, 2016, 35(12): 4088-4095.

马有福, 杨丽娟. 褐煤锅炉冷端优化热力系统技术经济性比较[J]. 化工进展, 2016, 35(12): 4088-4095.

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