CFB锅炉低压省煤器余热回收及热力特性分析

Waste heat recovery and thermal characteristics analysis of low pressure economizer for CFB boiler

某热电厂1 025 t/h循环流化床锅炉机组在运行过程中排烟温度过高,导致排烟热损失增大。为提高机组热效率,在锅炉尾部安装了低压省煤器。将主机凝结水作为冷却水,吸收锅炉尾部烟道内烟气的余热。通过等效焓降法计算设计工况下锅炉尾部烟道加装低压省煤器前后汽机和锅炉有关参数及经济指标的变化,对机组进行性能测试和热力特性计算,验证低压省煤器的改造效果。结果表明:安装低压省煤器后,在试验工况下锅炉排烟温度降低了29. 6℃,机组煤耗降低了1. 6 g/(kW·h),并且保证了电袋除尘器的安全运行,未对机组的运行造成负面影响。

The exhaust gas temperature of 1 025 t/h circulating fluidized bed boiler unit in a thermal power plant is too high during operation, which leads to the increase of heat loss of exhaust gas. In order to improve the thermal efficiency of the unit, a low pressure economizer is installed at the rear of the boiler. The condensate of the main engine is used as cooling water to absorb the residual heat of the flue gas in the tail flue of the boiler. Based on the equivalent enthalpy drop method, the changes of relevant parameters and economic indexes of steam turbine and boiler before and after installing low-pressure economizer in the flue of boiler tail under design conditions are calculated. The performance test and thermodynamic characteristic calculation are carried out to verify the retrofitting effect of low-pressure economizer. The results show that after installing low-pressure economizer, the flue gas temperature of the boiler is reduced by 29.6℃, the coal consumption of the unit is reduced by 1.6 g/(kW ·h), and the safe operation of the bag filter is guaranteed. in such way, there is no negative impact on the operation of the unit.