630 MW级亚临界燃煤机组余热深度利用方案研究

Research on Deep Utilization Scheme of Waste Heat of 630 MW Class Subcritical Coal-Fired Unit

目前燃煤电厂的排烟温度在设计和运行工况下尚存一定偏差,一般高于设计值。为了有效利用烟气余热从而提高燃煤机组能量利用效率,以某630 MW亚临界燃煤机组为例,建立烟气余热深度利用模型,对2种余热利用方案进行优化设计及对比分析。研究结果表明:方案二通过对低压省煤器凝结水进水接入点、空气预热器旁路中间点烟气温度、烟气旁路比例等的优化设计,具有最佳的节能效果和经济性,在选择从6号低压加热器入口作为低压省煤器凝结水进水接入点、空气预热器旁路中间点烟气温度选择204.8℃、烟气旁路比例选择20%时,方案二可以使汽轮机热耗降低123 kJ/(kW·h),节能效果为4.92 g/(kW·h)。可为燃煤机组烟气余热深度利用的工程改造设计提供一定的参考依据。

At present,the flue gas temperature of coal-fired power plants still has a certain deviation under the design and operating conditions,which is generally higher than the design value.In order to effectively use the waste heat of flue gas and improve the energy utilization efficiency of coal-fired units,a 630 MW subcritical coal-fired unit is taken as an example to establish a deep utilization model of flue gas waste heat,and to optimize the design and to comparatively analyze two waste heat utilization schemes.The research results show that Option 2 has the best energy-saving effect and economy by optimizing the design of the low-pressure economizer condensate water inlet access point,the air preheater bypass intermediate point flue gas temperature,and the flue gas bypass ratio.When the 6#low pressure feedwater heater inlet is selected as the low-pressure economizer condensate water inlet access point,the air preheater bypass intermediate point flue gas temperature as 204.8℃,and the flue gas bypass ratio as 20%,the Option 2 can make the heat consumption of the steam turbine to be reduced by 123 kJ/(kW·h),and the energy saving effect to be 4.92 g/(kW·h).This paper can provide a reference for the engineering retrofit design of the deep utilization of the flue gas waste heat of coal-fired units.