Evaluation of the condensation behavior of lead and zinc in BFB combustion of recovered waste wood

The chemistry of lead and zinc in the bubbling fluidized bed combustion of recovered waste wood (RWW) was studied based on advanced thermodynamic equilibrium calculations. The condensation behavior of zinc and lead compounds in different parts of the boiler was evaluated, and the dependence of the fuel composition on the condensation behavior was investigated. Zinc and lead were found to vaporize mainly as Zn(g) and Pb(g) in the lower, reducing part of the furnace. In this area condensation of metallic Pb and Zn and PbS can be expected. Condensation of PbCl2 and ZnCl2 can be expected on heat transfer surfaces later in the convection section. The theoretical results were supported by long-term deposits from full-scale boilers burning fuel mixtures containing RWW.