Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With agitation or forced circulation
Patent
1979-06-15
1981-11-03
Bashore, S. Leon
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With agitation or forced circulation
162 65, D21C 910, D21C 528
Patent
active
042984270
ABSTRACT:
A wood pulp slurry is treated with oxygen in a mill with little change to the process or structure of the mill. No special pressure tanks are rquired. The consistency of the pulp need not be altered for the treatment step. It may be treated at the usual process consistency of the pulp; e.g., it may be treated at the usual consistency of the pulp leaving a washer or subsequent steam mixer without additional dewatering or additional dilution.
The oxygen is added into a closed section of the system so that it cannot immediately vent to the atmosphere. Alkali should also be present when the oxygen is mixed with the slurry. The mixing should occur near to the point of oxygen addition.
An existing extraction stage within the system may be used as a source of alkali. In an existing extraction stage, the mixer and upstream oxygen line would be placed in the line between the steam mixer and the extraction tower.
The mixing occurs in a relatively small mixer that intensively mixes the slurry and the gas. The mixer has a mixing zone with a swept area of 10,000 to 1,000,000 square meters per metric ton of oven-dry pulp. A preferred range is 25,000 to 150,000 square meters per metric ton of oven-dry pulp and an optimum range of around 65,400 square meters per metric ton of oven-dry pulp.
Other systems and specific mixer designs are also disclosed.
REFERENCES:
patent: 4023737 (1976-03-01), Leider et al.
patent: 4039154 (1977-08-01), Peterson
"The Asplund RL 50 S Raffinator", Bulletin, Oct. 1971.
"Raum Repola Double Shaft Mixer" (no date available).
Rapson, "The Bleaching of Pulp", TAPPI Monograph No. 27, 1963, p. 332, fig. 15.22.
Bentvelzen Jozef M.
Bepple Henry
Meredith Michael D.
Torregrossa Louis O.
Alvo Steve
Bashore S. Leon
Weyerhaeuser Company
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