Steam supply of soot blower
Steam supply of boiler soot blower is from the connecting pipe at inlet of super heater. Steam supply is at 26.41Mpa, 536℃.
Normally material of piping system of soot blower is 20G. The maximum temperature allowed is 450℃. If temperature is higher than 450℃ after steam is reduced to below 3Mpa, desuperheater water is used.
Desuperheating water is from main pipe of desuperheater system of reheater. Water supply is at 24Mpa, 210℃. Steam for air preheater is at 1.0Mpa, 350℃. Allowance of steam pressure and flow is around 10% to meet with the requirement of steam used for long retractable soot blower, short retractable, furnace wall soot blower and air preheater soot blower.
Impact of steam pressure
If steam pressure is too low, it can’t get satisfied cooling effect, and it would reduce the regidity of lance. Front end of lance would drop and bend. If steam pressure is too high, it could get satisfied cooling effect and maintain the rigidity of lance, but would damage the heating surface and cause broken pipe. Pressure could be adjusted by the regulating disc of poppet valve.
Impact of steam temperature
Temperature designed for long retractable soot blower is 440℃, but operating temperature is usually around 460℃. Moreover, flue gas from furnace is around 1100℃. The lance is not cooled well enough. By experience, temperature of the outer wall of lance must be higher than 500℃ in this case. Thickness of lance is reduced gradually under such circumstances. For example, thickness of lance of 19# soot blower in 6# boiler is only 2.5mm. By the thickness thinning ratio, the lance can’t be used anymore.
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