Use of Borate Autocausticizing to Supplement Lime Kiln and Causticizing Capacities, 2003 Fall Technical Conference

This paper summarizes the research conducted at Western Michigan University to facilitate the commercialization of borate-based autocausticizing. Autocausticizing refers to non-conventional causticizing processes based on the use of amphoteric salts to release carbon dioxide (CO2) directly from sodium carbonate (Na2CO3) in the kraft furnace. Sodium hydroxide (NaOH) is then generated directly in the green-liquor dissolving tank. The most promising of the autocausticizing processes is boron-based autocausticizing. Boron-based autocausticizing can supply either part or all of the hydroxide requirements in the kraft pulping process. Where autocausticizing supplies the entire hydroxide requirement, the calcining/causticizing process is eliminated, and where autocausticizing supplies part of the hydroxide, the material and energy burden for calcining and causticizing are reduced. The major objectives of this project were to provide insight into the borate reactions occurring in the recovery boiler, to determine the effect of borate autocausticizing on the resulting black liquor behavior and to determine the effect of borate on the pulping reactions.