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.