管式GGH蒸汽吹灰器改造数值模拟及工程验证

Numerical simulation and practical verification of soot-blowing system retrofitting for tubular gas-gas heater

蒸汽吹灰器在燃煤电站锅炉的应用非常广泛,但由于蒸汽温度高、动量大,加上有时因过热度不足或疏水不充分使吹灰射流带水,因此对受热面热冲击较大,常发生吹损管壁等事故。对此,本文以浙江某电厂660 MW机组锅炉管式GGH烟气冷却器吹灰系统为研究对象,提出了将吹灰工质改为1.2 MPa压缩空气,并将喷嘴改为内径为14 mm的文丘里缩放喷嘴的改造方案。数值模拟结果表明,采用喉口直径为14 mm的文丘里喷嘴时,压缩空气射流刚性很强,最高速度为2.1马赫,有效吹灰距离可以达到改造前的80%。从实际运行数据看,采用压缩空气吹灰的换热器模块阻力小于蒸汽吹灰的模块阻力,吹灰系统运行良好,未再发生管壁吹损问题。

Steam soot blowing systems are widely applied in coal-fired boilers.However,due to high temperature,huge kinetic energy and sometimes entrained water droplets caused by insufficient superheat degree or insufficient drainage water,it will cause large thermal impact on the heating surface,which leads to frequent wear out of tube walls.To solve this problem,the soot-blowing system retrofitting for tubular gas-gas heater(GGH)of a 660 MW unit boiler in a Zhejiang power plant has been implemented.In the retrofitting,the compressed air(1.2 MPa)is employed in the soot blowing system instead of steam,and the spraying nozzle is changed into Venturi contraction and enlargement nozzle with inner diameter of 14 mm.The numerical simulation shows that,when using the Venturi nozzle with throat diameter of 14 mm,the jet air flow has a strong rigidity and a maximum velocity of 2.1 Mach.The efficient soot-blowing distance after the retrofitting reaches 80%of that before the retrofitting.The practical operation data indicate that the pressure drops of the tubular gas-gas heater using the compressed air soot-blowing system are less than that using the steam soot blowing system,the compressed air soot blowing system is in good operation and no pipe wall blowing loss occurs.