管式换热器降温段堵灰原因分析及差压控制

Cause Analysis and Differential Pressure Control of Ash Blockage in Cooling Section of Tubular Heat Exchanger

浙江某燃煤电厂后置式烟气换热器出现腐蚀、堵灰现象,影响机组安全运行。为解决堵灰问题,结合堵灰样的成分分析、电除尘后烟气SO_(3)含量高、烟尘含量低的特点和换热器材质特性,得出换热器堵灰原因主要是烟气中SO_(3)结露导致管材腐蚀并吸附烟尘所致。在换热器差压控制试验中发现,积灰前期差压上升缓慢且加强吹灰效果较好;积灰后期差压快速上升但加强吹灰无明显效果。通过选用合适的脱硝催化剂,减少烟气SO_(3)浓度来提高灰硫比和考虑耐腐蚀材质是解决后置式管式换热器降温段腐蚀堵灰的重要手段。

The rear mounted flue gas heat exchanger of a coal-fired power plant in Zhejiang has corrosion and ash blockage, which affects the safe operation of unit. In order to solve ash plugging, combined with the composition analysis of ash plugging samples, the characteristics of high SO_(3)content and low smoke content of flue gas after electrostatic precipitation and the material characteristics of heat exchanger, it is concluded that the main reason for ash plugging of heat exchanger is the corrosion of pipes caused by SO_(3)condensation in flue gas and the adsorption of smoke. In the differential pressure control tests of heat exchanger, it is found that the differential pressure rises slowly in the early stage of ash deposition, and the effect of strengthening soot blowing is better. In the later stage of ash deposition, the differential pressure rises rapidly, but strengthening soot blowing has no obvious effect. Selecting appropriate denitration catalyst, reducing the amount of SO_(3)in flue gas, increasing ash sulfur ratio and considering corrosion-resistant materials are important means to solve the corrosion and ash blockage in the cooling section of post tubular heat exchanger.