Experimental investigation of the strength characteristics of low‐temperature fouling containing ammonium bisulfate in boilers

Abstract

Low-temperature fouling is a severe problem in the heat recovery devices of coal-fired boilers; it is mainly caused by the condensation of ammonium bisulfate (ABS, NH 4 HSO 4 ) and is usually challenging to remove with soot-blowing equipment. This study investigates the strength of low-temperature fouling containing ABS, which is an essential indicator in soot blowing. The ash sample containing ABS with three different mass ratios was heated in a drop tube furnace (DTF) at several selected temperature conditions for different times.The compressive strength of ash blocks after heating was measured, and the energy-dispersive X-ray spectrometry (EDX) and scanning electron microscope (SEM) were used to clarify the relationship between ABS content with fouling strength. The results show that the higher content of ABS means higher fouling strength. The fouling strength could decrease by heating the fouling under the flue gas temperature is 350 C or more, and a higher heating temperature could result in lower strength of the fouling. To reduce the strength and maximize the removal of fouling effectively, taking into account the economy, the recommended heating condition is to heat the fouling for 5-20 min at a minimum temperature of 350 C.