chlorination of pulp under pressure and introduction of chlorine in blaeschen.

摘要

A method and apparatus are provided for increasing the efficiency of treatment of a paper pulp slurry with chlorine gas, such as in the bleaching or delignification of deciduous wood chemical pulps, coniferous wood chemical pulps, and non-wood fibrous chemical pulps. Chlorine gas is intimately mixed with the pulp in a fluidizing mixer (14), the pulp preferably having a consistency of about 7-12%, and then is passed to a retention vessel (20). The discharge of pulp from the mixer to the retention vessel, and from the retention vessel to other treatment structures, is throttled by valves (30, 31) so as to increase the pressure in both the mixer and the retention vessel to above atmospheric, and preferably in the range of about 15-150 psig (1 to 10 bar above atmospheric pressure). The chlorine gas is added to the mixer through one more discs (53) of porous materials having pore sizes in the range of about 5-175 microns, such as porous ceramic or sintered metal discs. The increased pressure during the chlorine treatment, and the introduction of the chlorine gas in the form of minute bubbles, improve the solubility of the chlorine in the pulp slurry and thereby increase the efficiency of treatment. (Figure 1).