Two-step numerical procedure on the removal process of gaseous potassium chloride generated from waste incineration via the injection of sulfate-based additives

摘要

Gaseous potassium chloride (KCl) that constitutes a relatively large portion of the combustion gas of municipal solid waste can condense on the surface of boiler heat exchanger tubes, causing severe corrosion attacks. To reduce the chlorine-induced high-temperature corrosion, sulfate-based additives have been used. In this study, a two-step numerical procedure is proposed to quickly predict the effect of the injection of sulfate-based additives on the removal of gaseous KCl. A computational fluid dynamics (CFD) simulation is first carried out to obtain the temperature distribution. Then, the thermal decomposition of sulfate additives, sulfation of gaseous KCl, and condensation of K_2SO_4 are calculated to predict the species concentration profiles at the temperature conditions given by the CFD simulation. After validation with a laboratory-scale experiment using (NH_4)_2SO_4, the procedure is applied to a pilot-scale boiler to examine the effects of (NH_4)_2SO_4, Fe_2(SO_4)_3, and Al_2(SO_4)_3. The calculation results show that each additive has an optimal injection temperature range: approximately 800 °C for (NH_4)_2SO_4 and 1000 °C for both Fe_2(SO_4)_3 and Al_2(SO_4)_3, which are consistent with the values reported in the literature. The expressions for the stoichiometric KCl removal efficiency of each additive are derived and compared with the calculated efficiencies.