Slagging is the formation of molten, partially fused or re-solidified deposits on furnace walls and other surfaces exposed to radiant heat. Over a period of time, a base deposit of slag may also form on boiler tubes. The base deposit may be initiated by the settling of fine ash particles or the gradual accumulation of particles with very low melting-point constituents. As the base deposit thickens, the temperature at its outside face increases significantly above the tube surface temperature. Eventually, the melting point of the ash constituents is exceeded and the deposit surface becomes molten. The process then becomes self-accelerating, with the molten slag trapping essentially all of the impinging ash particles.
Steam- or air-driven sootblowers are commonly used to remove ash and slag deposits from external tube surfaces, but their effectiveness varies. Also, sootblowing may cause localized erosion and corrosion in areas swept too clean by the blowing medium. This problem is often mitigated by installing shields on all tubes adjacent to sootblowers. However, sometimes the slag formation can’t be reached using conventional cleaning techniques.
Post time: Oct-16-2018