蓄热元件动态壁温控制技术解决空预器堵灰问题研究

Study on dynamic wall temperature control technology of thermal storage element in solving the problem of ash blockage in air preheater

随着“双碳”政策的逐步推进与深入,燃煤机组长期处于灵活性运行方式下,空预器堵灰问题越发突出。为解决空预器堵灰难题,以某600 MW机组空预器为研究对象,结合硫酸氢铵的物理特性,提出对空预器增设“分环轮循升温模块”和“分环轮循吹扫模块”的防堵改造技术方案。根据空预器设计参数以及常规运行方式和分环轮循升温运行方式下不同的边界条件,分别建立空预器换热模型进行计算,并对两种运行方式下蓄热元件壁面温度场和气体温度场进行对比分析。结果表明:升温环冷端端面壁温较常规运行方式提高约115℃,冷端蓄热元件壁温整体可提升至200℃以上,高于空预器内硫酸氢铵沉积温度区间(约150~190℃);温度可达到237℃左右的升温环出口烟气,与非升温环出口烟气在空预器与除尘器之间的烟道内掺混后,平均排烟温度仅比常规运行方式提升16℃左右。该技术方案可使空预器冷端蓄热元件壁温短时间高于硫酸氢铵沉积温度区间,便于定期清理位于空预器蓄热元件内部的粘结性积灰,同时运行方式灵活、对锅炉燃烧稳定性和下游设备安全性影响较小。

With the gradual advancement and deepening of the " Carbon neutrality and Emission peak ", under the long-term flexible operation mode of coal-fired units, the problem of air preheater ash blockage has become more prominent. In order to solve the problem of ash blockage, a single air preheater of a 600MW unit was taken as the research object. Combined with the physical properties of ammonium bisulfate, a technical plan for anti-blocking transformation is proposed to add a "split cycle heating module" and "split cycle purging module" to the air preheater. According to the design parameters of the air preheater and the different boundary conditions in the conventional operation mode and the sub-cycle heating operation mode, the air preheater heat exchange model is established for calculation, and the temperature field of the wall surface of the heat storage element and the temperature field of the gas under the two operation modes are analyzed. The wall temperature of the end face of the cold end of the heating ring is increased by 115℃ compared with the conventional operation mode, and the wall temperature of the cold end heat storage element can be raised to above 200℃ as a whole,which is higher than the ABS deposition temperature range(150~190℃) in the air preheater;After the flue gas at the outlet of the heating ring whose temperature can reach about 237℃ is mixed with the flue gas at the outlet of the non-heating ring in the flue between the air preheater and the dust collector, the average exhaust gas temperature is only about 16℃ higher than that in the conventional operation mode. The analysis shows that, the technical solution can make the wall temperature of the heat storage element at the cold end of the air preheater higher than the deposition temperature range of ABS for a short time, which is conducive periodically to the treatment of the cohesive fouling inside the heat storage element. And boiler combustion stability and downstream equipment safety are less affected..