热电联产系统集成蒸汽喷射器性能分析

Performance analysis of integrated steam injectors in cogeneration systems

基于某典型超临界600 MW燃煤热电联产机组提出集成蒸汽喷射器和外置式蒸汽冷却器的新型系统。其中,新型系统Ⅰ通过蒸汽喷射器利用再热蒸汽回收乏汽余热;新型系统Ⅱ进一步集成外置式蒸汽冷却器降低混合蒸汽过热度并减少给水在锅炉的吸热量。基于EBSILON professional建模,对系统在最大供热工况(供热抽汽量800 t/h)和变工况进行调峰性能和热力学性能分析,并探讨混合蒸汽压力和换热器端差对系统性能的影响。结果表明:在最大供热工况下,新型系统Ⅰ和新型系统Ⅱ的供热量较参考系统分别提高21.59百分点和14.47百分点,发电效率提高2.48百分点和2.78百分点;在供热量为300 MW时,新型系统Ⅰ和新型系统Ⅱ的发电负荷调节率较参考系统提高了6.00百分点和3.91百分点,发电量下限降幅达84.75MW和74.32MW;混合蒸汽压力由50k Pa提高到85k Pa,新型系统I和新型系统Ⅱ的总效率分别提高3.02百分点和2.65百分点;上端差由1℃提高到9℃,新型系统Ⅰ和新型系统Ⅱ的总效率分别降低1.67百分点和1.51百分点。研究结果可为燃煤热电联产机组扩大供热和深度调峰提供技术选项。

Based on a typical 600 MW coal-fired cogeneration unit,novel systems with integrated steam jet and external steam cooler are proposed.In novel system I,the waste heat from exhaust steam is recovered through a steam jet,in which reheat steam is chosen as the working fluid.In novel system II,an external steam cooler is used to reduce the superheat of the mixed steam and the heat load of the boiler.Based on EBSILON professional modeling,the system is analyzed considering the peak shaving performance and thermodynamic performance under the maximum heating condition(extracted steam for heating:800 t/h)and variable conditions.Moreover,the effects of mixed steam pressure and heat exchanger end difference on the system performance are also investigated.The results show that,under the maximum heating condition,compared with those of the reference system,the heating capacities of the novel system I and II increase by 21.59 and 14.47 percentage points,and the power generation efficiencies are increase by 2.48 and 2.78 percentage points,respectively.With the heating load of 300 MW,the power load regulation ratios of the novel system I and II improve by 6.00 and 3.91 percentage points compared with the reference system,and the lower limits of generation reduce by 84.75 MW and 74.32 MW.The gross efficiency of the novel system I and II improve by 3.02 and 2.65 percentage points,respectively,when the mixing steam pressure is increased from 50 kPa to 85 kPa.With the upper temperature difference increasing from 1℃to 9℃,the gross efficiencies of the novel system I and II decrease by 1.67 and 1.51 percentage points,respectively.The result can provide technical references for expanding heating capacity and deep peaking of coal-fired cogeneration systems.