Current Trends in Evaporator Fouling, 1998 International Chemical Recovery Conference Proceedings

A second IPST survey of evaporator fouling in the North American kraft pulping industry was conducted in 1997. The objective was to assess the nature and extent of these fouling problems, and the changes since the first survey conducted by Grace in 1974-75. A questionnaire and a request for black liquor and scale samples were distributed to 40 kraft pulp mills. This questionnaire requested detailed information on the nature of the wood supply, the pulping process and conditions; liquor processing; a description of the evaporator equipment configuration, performance characteristics, and scaling conditions of the evaporator system; and the liquor and scale composition. 25 mills returned a completed questionnaire, and 19 submitted liquor samples. The black liquor samples were analyzed for total solids content, total carbon, hydrogen, oxygen, sulfur, metals content, anions, residual active alkali, fiber, and residual soap content. The scale samples were analyzed for inorganic phase composition by X-ray diffraction.