Investigating the influence of bed structure on pulp displacement washing using an in-situ measurement technique

The influence of bed structure on pulp washing was investigated in this work using an in situ measurement technique. The experimental equipment was a test piston filter press equipped with a γ-radiation source and a scintillation detector that was used to measure concentrations and porosity within the pulp bed during the washing process. Two types of pulp were investigated: groundwood and kraft pulp. Both the influence of flocculation and a porosity gradient on washing efficiency were examined. It was shown that washing efficiency was lower for a flocculated bed than for a corresponding non-flocculated bed. It was also shown that the porosity gradients obtained in this study virtually do not affect the washing efficiency. Local dispersion coefficients were also obtained and it was shown that they were within the experimental error independent of the measurement height