Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – With regeneration – reclamation – reuse – recycling or...
Patent
1994-01-05
1997-01-21
Czaja, Donald E.
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
With regeneration, reclamation, reuse, recycling or...
162 29, 162 50, 162 72, 162 76, D21C 1104
Patent
active
055956289
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION OF THE PROCESS
The invention is related to a process which allows the production of pulp starting from different sorts of wood like hardwoods and softwoods and also from annual plants, with the possibility to recycle the cooking chemicals contained in the black liquors.
For the production of pulps, the Sulfate process (S. V. Rydholm, Pulping Processes (1965), p. 576 af) and the Sulfite process (S. V. Rydholm, Pulping Processes (1965) p. 439 af) are most frequently used. The Sulfite process has the disadvantage that technical data of pulps do not reach required quality levels; the Sulfate process has mainly the disadvantage of generation of bad smells. For all processes, special care has to be taken for the recovery of cooking chemicals so as to render complete process economical. The recovery of inorganic cooking chemicals is normally achieved by burning the organic compounds from the black liquor with subsequent preparation of the inorganic cooking chemicals.
During the last years, Organosolv processes have come to topic and partly also to realization (Pazner L. and Chang P. C., Canadian pat. 1,201,115, 1986, U.S. Pat. No. 4,470,851, 1984, (Kleinert, T. N. U.S. Pat. No. 3,585,104, Jun. 15, 1971), Dahlmann G., Schroeter M. C., Tappi Journal Vol. 73, No. 4, April 1990), (Cowan W. F. et al, German pat. 26 37 449, Dec. 15, 1988). The disadvantage of these processes is mainly the inflammable, volatile solvents like methanol and ethanol are used, which leads to relative high pressures in the cooking vessels and requires explosion-proof equipment. If sodium hydroxide is used in addition, it is necessary to use a recovery boiler for the recovery of inorganic cooking chemicals, which maintain high equipment costs. If no sodium hydroxide is used for the cooking, only hardwoods and annual plants can be treated.
Pulp processes where aqueous solutions with high concentrations of, for example, sodium benzoate or cymene sulfonate are used have as well to be mentioned. (Lindau, N. N., Naturwissenschaften, 20, 396 (1932); Pelipetz, M. G. Dissertation Columbia Univ. 1937). Recovery processes are particularly important for those highly concentrated cooking chemicals, but are up to now unknown. A further disadvantage of these hydrotropic processes is that lignin has the tendency to precipitate on the fibers during washing of the pulp with water. Organosolv processes also include pulping with organic carboxylic acids like formic acid or acetic acid (Buchholz und Jordan 1983. Nimz und Casten, 1986). The corrosive properties of the cooking chemicals are difficult to evaluate in this case.
Wet oxidation has already been proposed as a recovery process for the cooking chemicals of the Kraft process (F. J. Zimmermann, D. G. Diddams, TAPPI, Vol. 43, August 1960, No. 8) . Therein it was tried to burn completely, the organic compounds contained in the cooking liquors of the Sulfite resp. the Sulfate process, whereas all sulfites resp. sulfides were oxidized to sulfates, which sets the need for a reduction with BaS (barium sulfide) in the case of sulfate liquors to get back to the desired composition of the cooking liquor.
It was found surprisingly that wood could be pulped in an aqueous solution of the alkali salts of several alkyl benzol sulfonic acids, described as hydrotropic salts, and of sodium hydroxide, in conditions that are similar to the kraft process. The addition of anthraquinone up to 0,2% counted on wood is considered as well known for different pulp production processes. For example, for the soda process, for the Kraft process and for the Organocell process.
Anthraquinone is considered as a catalyst for the delignification. The advantages of this addition lies in the extent of the delignification, which eases the bleaching process.
The disadvantage of the anthraquinone addition is that no useful recovery process exists for anthraquinone.
The problem which appeared was to find an economical recovery process for sodium hydroxide, anthraquinone and the hydrotropic salts.
With the help of the partial aqueous ph
REFERENCES:
patent: 3490990 (1966-12-01), Johnson
patent: 4093508 (1978-06-01), Henricson
patent: 4138312 (1979-02-01), Gill et al.
patent: 4213821 (1980-07-01), Vanderhoek et al.
Zimmermann, F. J. "The Zimmermann Process . . . Paper Industry", Tappi vol. 43, No. 8, Aug. 1960, pp. 710-715.
Doppenberg Frank
Gordon Otto W.
Plattner Eric
Czaja Donald E.
Grant S.A.
Nguyen Dean T.
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