CFB机组协同余热利用系统经济性分析

Economic analysis of the collaborative waste heat utilization system of the CFB unit

针对循环流化床(CFB)机组采用低温省煤器加滚筒冷渣器回收低温余热时存在凝结水流量分配不足问题,提出了一种冷渣器、暖风器与低温省煤器3个设备组成协同余热利用系统的新节能方法。该系统中冷渣器与暖风器为闭式循环,冷渣器将回收锅炉底渣的部分余热加热空气预热器进口的一、二次风冷风,由此增加的空气预热器出口烟气余热仍由低温省煤器回收。本文以山西某超临界350 MW CFB机组为例,将协同余热利用系统与传统的滚筒冷渣器、低温省煤器系统进行了经济性对比分析,结果表明协同余热利用系统较原有系统煤耗可降低0.83 g/(k W·h)以上,在CFB机组节能降耗方面有一定推广意义。

For the circulating fluidized bed（CFB） unit adopting the low-temperature economizer and the rolling slag cooler to recover the low-temperature waste heat, there is a problem of insufficient condensate flow distribution. To solve this problem, a new energy-saving method of a collaborative waste heat utilization system consisting of the slag cooler, air heater and low temperature economizer is proposed in this study. In this system,the slag cooler and air heater are closed cycles. The slag cooler recovers some of the residual heat from the bottom slag of the boiler, which is used to heat the first and second air of the air preheater inlet. And the increased waste heat of exhaust air flue gas at the outlet of the air preheater is recovered by the low-temperature economizer.Taking a supercritical 350 MW CFB unit in Shanxi province as an example, the economics of both the collaborative waste heat utilization system and the conventional rolling slag cooler and low temperature economizer system are compared and analyzed. The results show that, the coal consumption of the collaborative waste heat utilization system can be reduced by 0.83 g/（k W·h） compared with the conventional system, and this system has certain popularization significance in energy conservation and consumption reduction of the CFB unit.