Trapping of Organically Bound Chlorine During Burning of Concentrates from Ultrafiltration of Bleached-Kraft Effluents, 1991 Forest Products Symposium Proceedings

Data are reported showing the fate of organically bound chlorine during burning of bleach plant concentrates. The concentrates were produced by ultrafiltration of C/D and El effluents from a bleached kraft mill and contained 8-20% (weight percentage of dry solids) total chlorine, a substantial part of which was organic. Upon rapid heating in air at oven temperatures of 600-800 degrees Celsius, the organic chlorine in both C/D and El concentrates was thermally

destroyed. For the El concentrates which contained a molar excess of Na over Cl, the organic chlorine was trapped as NaCl, such that approximately 100% of the total chlorine was accounted for in the unburned residue. This trapping was not observed for C/D concentrates having a molar excess of Cl over Na, showing that chlorine trapping was dependent on molar ratio of Na/Cl. The rate of chlorine trapping was independent of the mass of chlorinated organics, independent of oxygen concentration in the combustion air, and occurred rapidly (during devolatilization). The rate increased with increasing temperature, showing an activation energy of approximately 9 kcal/gmol.