In pulp washing, the cooking chemicals used in the digester and the lignin obtained are separated from the pulp. In the process, washing water is passed countercurrent to the pulp through one or more washing units. In many cases, the pulp is then fed to a bleaching step.
The use of CO2 can improve the efficiency of alkaline washing stages. This technology can thus be considered for an optimisation of brown-stock washing or washing alkaline bleaching stages. If this technology is implemented correctly, many process parameters can be improved without investing heavily in new washing units:
- Lowering of washing water consumption
- Increase the capacity of the wash and the evaporation plant
- Increase in production amounts
- Reduction in alkali losses
- Lower bleaching agent usage
- Decrease in foam formation and less anti-foaming agent required
- For integrated factories, reduction in use of chemicals on the paper machine
- Reduction in COD in waste water
As hardware for the feed and dissolution of carbon dioxide, especially in highly viscous mixtures, especially designed nozzles must be used whose tendency to clog is as low as possible.