New Process for Metal Ion Chelation at Elevated pH in Pulp Production, 1994 Pulping Conference Proceedings
A. Nordgren, A. Elofson
Prior to peroxide bleaching of kraft pulps in ECF and TCF pulp productions, a pretreatment with a chelant, is a standard operation to control the metal profile of pulp, where a low manganese level is extremely important. This pretreatment operation has so far typically been carried out at a pH in the range of 4.5-6.
This presentation describes a new pretreatment process for metal ion chelation in pulps at pH 6-9.
In general terms the pulp is first treated in a process which includes evaporation and air oxidation at pH 4-5. Then the pH is raised to the desired upper pH and extractable species including chelated manganese are removed by dewatering and washing the pulp. This process is adding certain benefits to the pulp, such as improved bleach response and viscosity.
New Process for Metal Ion Chelation at Elevated pH in Pulp Production, 1994 Pulping Conference Proce