PROCESSES OF RETAINING CHELANT-CONTAINING EFFLUENT WITHIN PULP BLEACH PLANTS

摘要

Improved environmentally acceptable process for retaining chelant-containingeffluent within pulp bleach plants, particularly total chloride-free bleaching sequenceplants using a chelating agent closed re-cycle process. The process involves treating apulp liquor in an acidic or near neutral stage with an effective chelating amount of achelating agent to form a soluble, chelated metal species; removing the pulp to provide achelated metal species-containing solution; treating this solution in an alkaline stage inthe presence of sufficient Ca ions with an effective amount of an alkaline liquor to effectdisplacement of metals from the chelated metal species and precipitation of the metals assolids in alkaline solution; removing the solids from the alkaline solution to provide ametal-free, chelating agent-containing solution; and recycling the metal-free solution tothe pulp liquor.