EFFECT OF CATALYSTS AND CHLORINE SOURCE ON THE FORMATION OF ORGANIC CHLORINATED COMPOUNDS

Two series of catalyzed incineration tests were performed in a 32 kW laboratory pilot plant to study the effect of metal catalysts on the formation of chlorobenzenes, chlorophenols and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). In the first series, iron(III), tin(II) and copper(II) chlorides were added to the flame as catalysts and the combustion parameters were adjusted for optimum and incomplete combustion. The aim was to study the distribution of organic chlorinated compounds between particles and the gas phase in the flue gases when the combustion parameters were varied. Concentrations of particle-bound PCDD/Fs were high in the incomplete combustion tests, and those in the gas phase were still high even in the optimum combustion tests. In the second test series, copper(II), iron(III) and manganese (II) nitrates were added to the flame. Sodium chloride, representing inorganic chlorine, and tetrachloroethylene representing organic chlorine, were used as chlorine sources in the basic fuel with the different catalysts. Metals and chlorine accounted for 0.5 weight-% of the total fuel flow. The basic fuel used in these investigations was an aliphatic liquid free of aromatic hydrocarbons. Organic chlorine with the catalyst promoted the formation of particle-bound PCDD/Fs, whereas inorganic chlorine was observed to promote the formation of PCDD/Fs more effectively in the gas phase than in the particle phase. Consequently, different mechanisms of formation may be involved in the gas phase and on particle surfaces.