Sulphur addition to control dioxins formation in salt-laden power boilers - Co-firing of CNCGs with salt-laden wood waste is effective

In full-scale trials at a BC coastal mill, dioxins formation under typical baseline operating conditions was compared to that observed with the co-fir ing of sulphur in the form of concentrated non-condensible gases (CNCGs). T o reduce "memory effects," CNCGs were fired in the power boiler for over si x days during each test series. The average concentration of dioxin TEQs in ESP ash dropped from 5.7 ng/g for the baseline operation to 0.55 ng/g with co-firing of CNCGs. Of greater significance was the fact that dioxins form ation was still very effectively attenuated at a chlorine-to-sulphur ratio of one. While the effects of sulphur addition on boiler fouling and corrosi on are not entirely clear, it would appear, from a survey of mills that hav e burnt CNCGs in the power boiler, that the sticky temperature of the ash m ay not be exceeded under normal operating conditions in lower pressure boil ers and that fouling and plugging may be prevented by sootblowing.