Multi Component Control of Brownstock Washing, 1993 Environmental Conference Proceedings

Stringent effluent standards are resulting in the need for improved washing efficiency and control. The organic content of streams associated with the washing process has been shown to have a direct effect on the formation of chlorinated organics. However, present washing control strategies focus on the recovery of inorganic materials and measure organics recovery only inferentially.

Experiments using a laboratory displacement cell to simulate a washing stage were performed in order to compare the relative washing efficiency of organics and inorganics. Inorganics concentration, total dissolved solids and dissolved lignin in each liquor sample were measured using conductivity, refractive index and ultraviolet absorbance analysis respectively. Ultraviolet absorbance and refractive index were shown to be indicators of washing efficiency. Organics and inorganics were shown to possess different washing characteristics under certain conditions. An economic analysis indicated that control methods that prevent the change in washing conditions may be justifiable. Ultraviolet absorbance and refractive index techniques can be used to control brownstock washing.