Failure Analysis of Fire-Tube Boiler Caused by Ash Accumulation During All-Sensible Heat Recovery for Primary Dust Removal of Converter Gas

Abstract

All-sensible heat recovery technology for converter gas is a new alternative process to the current oxygen converter gas recovery (OG) method and Lurgi-Thyssen (LT) method. However, the high-dust characteristics of converter gas lead to severe ash accumulation and clogging in fire-tube boiler, which cause the system to fail in the stable operation in actual applications. In this case, the accumulated ash from a fire-tube boiler of an all-sensible heat recovery system on an actual converter with a capacity of 100 tons was selected as the research object. The results show that exothermic reaction tends to increase the temperature of the accumulated ash, which causes fusion and sintering among the ash particles. The turbulent viscosity at the tube inlet is significantly increased with problem occurrence of ash accumulation, which improves the possibility of ash particles deposition. These processes contribute to the accumulation and adhesion of ash particles on the surfaces of the heat exchanger. In addition, ash accumulation can cause a decrease in the steam production by about 7.5%, and the high-pressure N2 pulse blowing combined audio method are proven to be effective in removing the ash.

Keywords: All-sensible heat recovery technology, fire-tube boiler, ash accumulation, fusion and sintering, failure mechanisms, ash removal