HEAT OF DILUTION AND ENTHALPY CONCENTRATION RELATIONS FOR SLASH PINE KRAFT BLACK LIQUORS

Abstract

Enthalpy-concentration charts have been developed for different black liquors from the results of statistically designed pulping experiments for pulping slash pine in a pilot scale digester. Black liquors were considered as pseudobinary solutions and enthalpy-concentration relations over wide ranges of temperature were developed by using heat capacity data and heal of solution data for the liquors. Heats of dilution of black liquors were determined by an absolute calorimetric method at 80°C and then were used to establish a thermodynamic reference state for enthalpy calculation of black liquors. Heats of dilution for diluting slash pine black liquors from 80% to 5% solids are 175-260 kJ/kg solids, depending upon the cooking conditions. The effects of pulping variables on heats of dilution of black liquors are discussed.

Keywords:

• Kraft liquors
• black liquors
• heat of mixing
• enthalpy
• dilution
• heat capacity
• heat effects