Field Study of the Factors Affecting the Fouling Tendency of Recovery Boilers, 1996 Engineering Conference Proceedings

K. Janka, M. Espo, J. Mäntnyniemi, R. Helke - Tampella Power Inc.

It is well known that the increased potassium and chloride concentrations in black liquor influence the fouling tendency of heat transfer surfaces in recovery boilers. In North America Tampella Power has previously carried out an extensive field study of the recovery boiler chemistry. The boilers included in the study were Tampella units in a capacity range from 3,500,000 lb/day to 4,650,000 lb/day. In this study three large Finnish recovery boilers have been investigated. The results have been compared to the results of the five North-American boilers in the earlier study /l/. The measured Finnish boilers have not experienced fouling prob-lems, although the potassium and chloride concentrations of the liquor do not differ essentially from the concentrations found in the liquor burned in the North American boilers of the earlier study. The main results are: 1) The enrichment of the potassium and chloride in the fly ash is affected by the wood species used in the cooking (hard/soft wood) and the floor heat load of the boiler. 2) Higher temperature of the lower furnace increases the amount of fume but also raises the melting points of the fume. 3) The chlorine in the black liquor may increase the enrichment of the potassium in the ESP-dust. The result is that by increasing the temperature of the lower furnace for example by increasing the dry solids content of the liquor, it seems to be possible to decrease the fouling tendency of the recovery boiler.