Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With agitation or forced circulation
Patent
1979-06-15
1981-10-20
Bashore, S. Leon
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With agitation or forced circulation
162 65, 162243, D21C 910, D21D 528
Patent
active
042959268
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 required. 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 the 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.
The oxygen is inserted into the pulp slurry and mixed with the pulp slurry between a pair of washers. The second washer may be a vacuum, pressure or diffusion washer.
The mixing occurs in a relatively small mixer that intensively mixes the slurry and 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 65,000 square meters per metric ton of oven-dry pulp.
Other systems and specific mixer designs are also disclosed.
REFERENCES:
patent: 3293117 (1966-12-01), Pennington et al.
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patent: 3832276 (1974-09-01), Roymoulik et al.
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patent: 4039154 (1977-08-01), Peterson
patent: 4082233 (1978-04-01), Reinhall
patent: 4093506 (1978-06-01), Richter
Kleppe et al., "Oxygen/alkali delignification at Kanya digester blowline consistency", TAPPI, vol. 59, No. 11, Nov. 1976.
Jamieson et al., "Mill Scale Application of Oxygen Bleaching in Scandanavia", 1973 Tappi Alkaline Pulping Conference.
Kishner et al., "Low Consistency Oxygen Delignification in a Pipeline Reactor--A Pipeline Study".
Rapson, "The Bleaching of Pulp", Tappi Monograph Series No. 27, 1963, p. 332, Fig. 15.22.
"The Asplund RL 50 S Raffinator", 10-1971, Defibrator.
"Rauma-Repola double-shaft mixer", Bulletin.
Battan Howard R.
Bentvelzen Jozef M.
Bepple Henry
Justice Dennis H.
Meredith Michael D.
Alvo Steve
Bashore S. Leon
Weyerhaeuser Company
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