Brown Stock Washing
Agro designs and implements brown stock washing systems.
Once the Pulping stage is complete, the unbleached pulp is screened, cleaned and washed. The pulp is washed using drum washers in three/four different stages, with washing done in counter current direction.
The third or fourth stage Brown Stock Washing is typical for pulp made from biomass or non-wood materials. The stock is spread over a rotating drum and the black liquor is removed from the pulp using vacuum generated by a vacuum leg or a vacuum pump. The filtrate or black liquor is concentrated as it moves from the last to the first stage. The filtrate from the first stage is then sent to the Chemical Recovery System.