Fate of NPEs During Evaporation of Bleach Plant Effluents, 1996 Minimum Effluent Mills Symposium Proceedings

Don Manolescu - Zerotech Technologies

Ernie Perkins, Ralph G. Jonasson, Bryan Fuhr - Alberta Research Council

This paper presents the results of experiments carried out by Zerotech and Alberta Research Council during their two year Joint Research Venture Program and proposes alternatives for control of NPE’s (non-process elements) for zero liquid effluent Kraft pulp mills using TCF or ECF bleaching technologies. A key element of the research program was to develop and confirm a computer model to predict the fate of NPE’s to avoid fouling of evaporator heat transfer surfaces and to provide a purge of unwanted elements for those technologies which propose to stabilize concentrate in the recovery boiler. It has been demonstrated that the solubility of compounds which can adversely affect mill operation are reduced by design and operating parameters such as pH, temperature, residence time and sodium concentration. The use of thermal deactivation as well as the addition of elements such as magnesium or aluminum can assist in determining the types of precipitates and their fate, fouling or formation in the bulk solution.