(40b) Estimating the Thermophysical Properties of Black Liquor from Kraft Pulping

Black liquor is a complex mixture that results from the kraft pulping process and is highly toxic and environmentally unsafe. Typically, black liquor is treated after digestion to recover and regenerate the cooking chemicals and liquor. There are three main components of black liquor: lignin, carbohydrate degradation products, and extractives, such as fatty acids and resin. The largest portion of black liquor contains high-molecular weight compounds which precipitate as the liquid is acidified. However, it is the low-molecular weight compounds left in solution that are of most concern when developing thermodynamic models. Even though the low-molecular weight portion of black liquor is minor, there have been hundreds of components identified within the remaining solution. Because of the diversity within the low-molecular weight components, identifying the correct thermophysical properties is crucial for obtaining a rigorous thermodynamic model of black liquor. This work aims to begin the process of identifying the necessary thermophysical properties from liquid-liquid and solid-liquid equilibrium data to initiate the process of building a rigorous thermodynamic model for the kraft pulping process.