Commissioning brown stock washing controls for an evaporator limited mill, 2015 PEERS Conference

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An automated shower water control system has been implemented to reduce the volume and variability of weak black liquor being sent from the pulp mill to the evaporators.  The washing controls attempt to balance the need for consistent and low soda carryover to the bleach plant with consistently high weak black liquor solids being sent to the evaporators.  The washer controls were implemented on two bleachable grade hardwood lines (one with oxygen delignification, one without oxygen delignification) and one pine line.  Implementation of the control program resulted in an increase in black liquor solids of 0.6 percentage point for the hardwood lines.  Significant foam reduction was realized on the pine line since the pine black liquor solids were able to be consistently maintained just below the soap separation point.