Patent ID: 6336993
Filing Date: 2002-01-08
Classification: D21C

Abstract:
A method of treating a slurry comminuted cellulosic fibrous material using at least first and second series connected pumps, and at least first and second in-series stations, each with a solids/liquid separator, in which the metal content of the material is reduced, comprising:(a) pumping the slurry of comminuted cellulosic fibrous material using the series connected pumps; (b) separating some liquid from the slurry at each station to substantially isolate liquor circulations and streams, and to recirculate removed liquid from at least one of the stations to upstream of one of the pumps; and (c) adding to the slurry at or upstream of at least one of the pumps chemicals which dissolve or sequester metal containing compounds in the slurry, the chemicals including at least one chemical selected from the group consisting essentially of acids, chelating agents, and combinations thereof, so that at least some of the metals present in the material prior to the treatment are removed from the material.