FUME CHEMISTRY, MORPHOLOGY AND DEPOSITION IN A KRAFT RECOVERY BOILER

Fume deposits were collected from various locations of a recovery boil er. Lower furnace deposits contained 26 wt% alkali hydroxides, plus th e usual sodium and potassium salts. Upper furnace deposits contained n o hydroxide and had constant chloride and potassium contents. The carb onate content increased, at the expense of the sulphate content, from 5 wt% at the bullnose to 12 wt% in the superheater region, and remaine d constant from this location onward, except in the economizer where t he carbonate content was unusually high. Solid fume appeared to form a t the entrance to the generating bank. Deposition rate results were co nsistent with thermophoretic deposition mechanism.