LIQUOR CONCENTRATION MEASUREMENT FOR CAUSTICIZING CONTROL

In this study, variations in the concentrations of sodium carbonate, s odium sulfide and sodium hydroxide in green liquor are quantified on t he basis of data collected from two mills. A method is also adapted to measure the concentrations of the components in the green liquor. Thi s technique involves the use of density, conductivity and ultraviolet absorbance to measure the concentrations of chemicals in green liquor with good accuracy. A correlation is developed to predict the caustici zing efficiency based on conductivity measurements of green liquor and the causticized liquor. This developed correlation has temperature co mpensation enabling its use at any process temperature. The model pred ictions are within 1% of the measured causticizing efficiency. The mea surement technique used along with a kinetic model developed at Auburn University, allows closing of the control loop without the need to me asure the lime quality. This enables better control of the causticizin g operation to produce uniform white liquor with improved causticizing efficiency.