NAELS: A New Method for Calculating Equilibrium Solubility of Burkeite and Sodium Carbonate in Black Liquor, 1998 International Chemical Recovery Conference Proceedings

Increasing levels of closure in’ pulp mills coupled with new evaporation technologies requires an improvement in our understanding of the solubility of inorganic constituents in black liquor. All current high-solids concentrator designs make use of crystallization technology to promote bulk crystallization and avoid scaling. Use of crystallization concepts implies a clear understanding of solubility. However, only limited information on the solubility of the inorganic compounds in black liquor has been available. With the development of NAELS (Non-ideal Aqueous Electrolyte Simulator), a chemical equilibrium calculator, we now have the ability to calculate the solubility of the major inorganic compounds in black liquor systems over a wide range of temperatures, and liquor solids and chemistries. This results in improved understanding necessary to avoid soluble scale in black liquor concentrators. This paper describes the development and application of NAELS to determine the solubility of inorganic compounds in black liquor (particularly sodium sulfate and sodium carbonate). The results from NAELS will be compared with the only black liquor solubility data available in the literature (Grace, 1976) and applied to data from current mill liquors. We will also show how calculations using NAELS helped us better understand soluble scaling problems in black liquor concentrators.