System for sulfonating mechanical pulp fibers

Details System for sulfonating mechanical pulp fibers System for sulfonating mechanical pulp fibers

1989-11-03

1992-02-18

Hastings, Karen M.

Paper making and fiber liberation

Apparatus

Digester

162241, 162242, 162250, D21C 304

Patent

active

050890891

ABSTRACT:
A two stage sulfonation system includes a mixing tank, a retention tank, a thickening press, a pressurized vessel, and a liquor recovery press in series relation. A sodium sulfite generation unit is connected to maintain a supply of sodium sulfite solution in a holding tank from which a controlled quantity of said solution is metered and injected in the mixing tank. Liquor extracted in the thickening press is cycled back to the mixing tank. Liquor extracted in the recovery press is moved to an intermediate tank and then transferred to the sodium sulfite generation unit, there fortified with fresh sodium sulfite and forwarded to the holding tank to maintain therein an appropriate supply to service the system. The system is designed to receive mechanical pulp, in a slurry form, first introduced into the mixing tank simultaneously with a metered charge of sodium sulfite solution from the holding tank, the sodium sulfite content of which is at a level from about 40 to about 200 g/l. The solution is mixed into the slurry to provide a relatively uniform and intimate contact thereof with its fiber content. This slurry is transferred to the retention tank and there held subject to a sub-boiling temperature between 140 to 210 degrees F., producing a first stage sulfonation of the fiber content. The slurry is then passed to the pressurized vessel, in the course of which it is subjected to a pressing action, extracting liquor which inherently contains a majority of the original sodium sulfite charge directed to the mixing tank. A second stage sulfonation occurs in the pressurized vessel, producing a fiber which after refining is suited for use as reinforcing pulp in newsprint or specialty grade paper, without need for addition of conventional chemical pulp.

REFERENCES:
patent: 3016324 (1962-01-01), Textor
patent: 3186899 (1965-06-01), Madison et al.
patent: 3989588 (1976-11-01), Charters et al.
patent: 4152197 (1979-01-01), Lindahl et al.
patent: 4259148 (1981-03-01), Beath et al.
patent: 4502918 (1985-03-01), Mackie et al.

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