Studies on the Heat Capacity of Slash Pine Kraft Black Liquors: Effects of Temperature and Solids Concentrations

Heat capacities of different kraft black liquors from statistically designed experiments for pulping slash pine were measured as a function of solids concentrations over a temperature range of (313.2 to 393.2) K using differential scanning calorimetry. The dependency of heat capacity on temperature and solids concentrations is described in detail. The results indicate that kraft black liquors are nonideal solutions, and their thermal properties cannot be predicted from the properties of pure water and solids. The excess heat capacities were determined using a binary solution assumption and are defined with a single correlation as a function of temperature and solids mass fraction for every single liquor. An empirical method is developed that can be applied to describe the heat capacity behavior of a single liquor as a function of temperature and solids concentrations. The results of this work show that the heat capacities are directly proportional to the organic-to-inorganic ratio in the liquor.