Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Gas – vapor or mist contact
Patent
1990-01-29
1991-07-09
Alvo, Steve
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Gas, vapor or mist contact
162 66, 162 67, 162 88, 162 89, D21C 914, D21C 9147
Patent
active
050303244
ABSTRACT:
An improved process for bleaching cellulosic pulp in a first chlorination stage of a multi-stage bleaching process is provided, which involves an improved process for bleaching cellulosic pulp in a first chlorination stage of a multi-stage bleaching process, comprising: (a) admixing cellulosic pulp with a first chlorine dioxide charge and reacting the cellulosic pulp and said chlorine dioxide for a period of time ranging from about 1 second to about 10 minutes; (b) admixing the cellulosic pulp effluent obtained after step (a) wtih chlorine and chlorine dioxide and reacting the thus-obtained cellulosic pulp for a period of time ranging from 1 second to about 10 minutes; and then (c) admixing the cellulosic pulp effluent obtained after step (b) with a second chlorine dioxide charge and reacting the thus-obtained cellulosic pulp effluent for a period of time ranging from about 1 second to about 10 minutes, wherein the pH of the reaction mixture is maintained throughout the bleaching process at from about 5.0 to about 1.0, the temperature is maintained at from about 70.degree. to about 200.degree. C., and from about 10% to about 100% of total available chlorine is added as chlorine dioxide. The supply of chlorine dioxide can be varied for a particular process or mode of operation by causing up to substantially all of the chlorine dioxide to be supplied in the first chlorination stage to be supplied to the first and/or second and/or third step. It is also possible to regulate the process in order that the total available chlorine for the first stage is supplied as chlorine dioxide.
REFERENCES:
patent: 3433702 (1969-03-01), Jack et al.
Bugajer et al., "A Comparison Between Bleaching Sequences with Alkaline Extraction in the Presence of Oxidizing Agents", Pulp & Paper Canada, 88:12, (1987), p. 169-172.
Alvo Steve
Champion International Corporation
Sommer Evelyn M.
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