Washing Away Inefficiency

Brownstock Washing
Carbonic acid reduces pH in brownstock washing and forms when carbon dioxide is added to the water.
Unbleached pulp prior to Brownstock Washing
Lowering Chemical Costs with CO2

Carbon dioxide (CO2) acidification of brownstock washers is easily implemented and can reduce your pulp and paper operation’s chemical cost. It can clean up your pulp and reduce overall chemical usage, regardless of whether your operation produces white stock paper, brownstock paper or corrugated board.

Wood pulp in the washing phase of production
Carbonic Acid from CO2 Dissolution for pH Control

Brownstock washing involves the injection of carbon dioxide into the wash water for the final stage of the washing cycle. The CO2 dissolves in water to form carbonic acid, which works to reduce the pH levels in the brownstock. Lower brownstock pH reduces fiber swelling, which promotes better pulp drainage and results in improved washing efficiency. Lower pH levels in the pulp will also reduce sodium loss in the washing stage.

Brownstock Washing with Carbon Dioxide

The Benefits of in the Washing Step

Commercially-proven, brownstock washing technology can increase production rates of bleached and non-bleached kraft pulp through more efficient washing and recovery systems. At the same time, it can reduce effluent loadings and lower bleach plant chemical requirements. Brownstock washing technology can provide operational cost savings with minimal capital expenditures, using traditional or newly designed equipment, with or without oxygen delignification.


  • Increased production rates
  • Improved washing efficiency
  • Lower bleach plant chemical requirements
  • Reduced effluent loadings

Other benefits of adding CO2 include reduced bleach plant chemical requirements through lower chemical oxygen demand carry over, lower dilution factors, improved sheet consistency and higher sodium recovery levels.

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