利用电站锅炉耦合秸秆直燃炉提高再热汽温和SCR烟温经济性分析

Economic analysis of increasing reheat steam temperature and SCR flue gas temperature by coupling straw direct-fired boiler with utility boiler

针对电站锅炉普遍存在的再热蒸汽温度偏低和选择性催化还原(SCR)烟气脱硝系统低负荷下无法正常投运的问题,提出通过一种电站锅炉耦合秸秆绝热直燃炉,利用秸秆直燃的高温烟气显热直接提高锅炉尾部烟道烟气温度的技术方案。以某超临界350 MW机组锅炉为例,对不同负荷下将耦合秸秆绝热直燃炉高温烟气分别引入低温再热器进口烟道和SCR烟气脱硝系统前烟道的情况进行热力计算和经济性分析。结果表明:将1 000℃高温烟气引入低温再热器进口烟道时,100%负荷工况下,消耗秸秆3 749 kg/h,可将再热蒸汽温度升高13.5℃,节省供电标准煤耗1.86 g/(kW·h);50%负荷工况下,消耗秸秆3 749 kg/h,再热蒸汽温度升高33.3℃,节省供电标准煤耗7.39g/(kW·h);将1000℃高温烟气引入SCR烟气脱硝系统前烟道时,50%负荷工况下,消耗秸秆580 kg/h,SCR烟气脱硝系统入口烟温升高8.7℃,满足SCR烟气脱硝系统投运要求,供电标准煤耗增加0.84 g/(kW·h)。

In view of the common problems occur in utility boilers, such as low reheat steam temperature and failure operation of SCR flue gas denitration system at low load, a technical program of utility boiler coupling straw adiabatic direct combustion furnace was proposed. In this program, the flue gas temperature of boiler tail flue is directly increased by using the sensible heat of high temperature flue gas produced by straw combustion.Taking an ultra supercritical 350 MW unit boiler as the example, thermodynamic calculation and economic analysis were performed when the high temperature flue gas produced by straw combustion in adiabatic direct firing boiler was introduced to the inlet flue duct of the low temperature reheater and the flue duct in front of the SCR denitration system at different loads. The results show that, when the 1 000 ℃ high temperature flue gas was sent to the inlet flue duct of low temperature reheater at 100% load, the consumption of straw was 3 749 kg/h, the reheat steam temperature increased by 13.5℃ and the power supply coal consumption reduced by 1.86 g/(kW·h).At 50% load, the consumption of straw was 3 749 kg/h, the reheat steam temperature increased by 33.3℃ and the power supply coal consumption reduced by 7.39 g/(k W·h). When the 1 000 ℃ high temperature flue gas was sent to the flue duct in front of the SCR flue gas denitration system at 50% load, the consumption of straw was580 kg/h, the flue gas temperature at the SCR denitration system inlet increased by 8.7℃ and the power supply coal consumption increased by 0.84 g/(kW·h), which met the requirements of the SCR denitration system.