Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Charging and/or discharging fibrous material
Patent
1994-06-07
1996-11-05
Alvo, Steven
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Charging and/or discharging fibrous material
162 65, 162 76, 162 78, D21C 9153, D21C 916
Patent
active
055713777
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for chlorine-free bleaching of chemical pulp in association with production of the same, in which a suspension of the pulp preferably has a consistency exceeding 8% of cellulose-containing fibre material and in which the pulp entering into a bleaching line is preferably fed continuously through at least one bleaching vessel in the bleaching line, is treated with at least one acid for adjusting the pH to a value below 7 and with a chelating agent, and is subsequently bleached in at least one stage to a brightness exceeding 75% ISO, preferably exceeding 80%, using hydrogen peroxide or a corresponding quantity of another peroxide, added in a quantity exceeding 5 kg/BDMT.
Marketing and environmental considerations have demanded that extensive efforts be made to eliminate the use of chlorine-containing compounds for bleaching purposes. Using current technology, it is difficult to achieve complete bleaching of paper pulp prepared from soft wood sulphate pulp using oxygen, hydrogen peroxide and ozone.
There are a number of peroxide beaching processes of the Lignox and Macrox type in which a combination of EDTA treatment and peroxide addition is used. These processes require a minimum of a 4-hour reaction time at 90.degree. C. and, despite this, it is found that when a successful bleaching of oxygen-delignified softwood pulp has been carried out, with the pulp having a kappa of 12 and with a brightness of 77-79 ISO having been achieved, about half of the quantity of peroxide employed remains unused. The intention is that the latter should subsequently be returned to the process for reuse after the addition of fresh peroxide. As far as we know, this still does not take place on a factory scale. In some cases, the peroxide is returned to the oxygen reactor, with any possible brightness-increasing effect being negligible.
Through the Swedish Patent Application, laid open, 8503153-2 (Wagner-Biro AG), a process is known for delignifying pulp using oxygen and/or ozone with the possible addition of peroxide. In the said process, the pulp is placed in contact with oxygen, possibly in the presence of peroxide, at a temperature of 80.degree. C. to 150.degree. C. An alkalising supplement is then added to the pulp. The process can be repeated in several stages with increasing pressures and/or temperatures. This process is based on a two-stage process where the first stage takes place, in this case, at a consistency of 2.5-4.5% and the second stage is carried out at a consistency of 10%. The quantity of peroxide employed is 0-5 kg of H.sub.2 O.sub.2 per kg of ptp.
An approach which might seem to present itself immediately would be to raise the temperature and apply pressure in order to shorten the necessary reaction time and/or decrease the peroxide residue in order to achieve optimal utilisation of the hydrogen peroxide employed, and this suggestion is in fact included as a possibility in the Swedish Patent 8902058-0 (EKA Nobel AB) in which the so-called Lignox process is described. Experiments in this direction have been carried out, but have failed, the results in all respects being worse than those achieved with purely atmospheric peroxide bleaching. It has even been suggested that oxygen is of no value in bleaching by the Lignox method. The application of pressure is preferably carried out using an MC pump, with the pumped suspension having a consistency exceeding 8% and preferably less than 18%.
It should be noted that experiments to which reference has been made in the patent and other literature have, for understandable reasons, been carried out on a laboratory scale. Indications have been obtained that the results are worse if the temperature is increased (for example from 90.degree. C. to 95.degree. C.) and the conclusion has been drawn that peroxide bleaching should preferably take place at a temperature below 90.degree. C.
The object of the present invention is to produce a process of the type mentioned in the introduction which provides efficient and more homogeneous bleaching.
T
REFERENCES:
patent: 2516447 (1950-07-01), Burling et al.
patent: 3918898 (1975-11-01), Katz
patent: 4244778 (1981-01-01), Lindahl et al.
patent: 4410397 (1983-10-01), Kempf
patent: 4427490 (1984-01-01), Eckert
patent: 4568420 (1986-02-01), Nonni
patent: 4734160 (1988-03-01), Moldenius
patent: 4756798 (1988-07-01), Lachenal et al.
patent: 4804440 (1989-02-01), Liebergott et al.
patent: 5133946 (1992-07-01), Schwarzl
patent: 5171405 (1992-12-01), Torregrossa
patent: 5192397 (1993-03-01), Bohman
patent: 5266160 (1993-11-01), Hencrison et al.
patent: 5296099 (1994-03-01), Griggs et al.
patent: 5296100 (1994-03-01), Devic et al.
patent: 5310458 (1994-05-01), Lundgren et al.
Singh, "The Bleaching of Pulp", Tappi Press; Atlanta, Georgia; pp. 608-609, 1979.
Decision Concerning Cancellation of Patent dated Feb. 28, 1996.
Lachenal, et al., "The Potential of H.sub.2 O.sub.2 as delignifying and bleaching agent application to new bleaching sequences, " 1992 Pan Pacific Pulps and Paper Conference Proceedings, Sep. 8-10, 1992, pp. 33-38.
Official Gazette, vol. 1038, No. 4: Delignification and Bleaching Process for Lignocellulosis . . . of Metal Additives Abstract of U.S. Patent No. 4,427,490.
Alfthan, Carl-Johan, et al., "High-Temperature Peroxide Bleaching of Sulphate Pulp", Svensk Papperstidning (Ar 15 1977).
OZP-Bleaching of Kraft Pulps to Full Brightness (U. Germg.ang.ard and S. Norden) Sunds Defibrator.
"A Train of Developments Towards Chlorine Chemical Free Manufacturing of Bleached Kraft Pulps" K. Kovasin; L. Lindstrom, L. Sjodin (date unknown) .
"Mill Experiences of LIGNOX Bleaching" L. Igerud (date unknown).
Current State-of -the-Art of EO, EP and EPO Technologies: Non-chlorine bleaching conference, Mar. 1992, Hilton Head, SC, U.S.A.
A Handbook About Hydrogen Peroxide and How it Should be Handled-Eka Nobel Inc. 1991.
Delignification using hydrogen peroxide and oxygen under acidic conditions-the -POs-treatment-1985 Wood and Pulping Chemistry Symposium.
Degradation of carbonhydrates during oxygen bleaching, O. Samuelson and L. Stolpe, Chalmers University of Technology, Dept. of Engineering.
Semibleaching of kraft pulp using oxygen and hydrogen peroxide, H. U. Suss, W. Eul and O. Helming.
Proceedings-1991 Pulping Conference Book 1.
Production of Bleached Chemical Pulp in the Future-International Pulp Bleaching Conference 1991, Stockholm, Sweden Jun. 11-14, 1991 (vol. 3).
Non-Chlorine Bleaching Conference Proceedings-Emerging Technology Transfer Inc. (Pulp & Paper).
Improvement of Hydrogen Peroxide Delignification-Centre Technique du Papier-Forest Research Institute (1987).
Svensk Papperstidning-Swedish Paper Journal Nr. 18, Dec. 15, 1988 (w/translation).
High-temperature peroxide bleaching of sulphate pulp, Carl-Johan Alfthan et al, Swedish Forest Products Research Laboratory, Stockholm, Svensk Paperstidning Nr. 15, 1977.
Bleaching Technology, D. W. Reeve, Pulp and Paper Manufacture, vol. 5, 1989.
Proceedings-Emerging Technologies Today and in the Future Mar. 2-5 1992 Westin Resort-Hilton Head-South Carolina.
Modern Bleaching Technology, Kaj Henricson, Ahlstrom Machinery-Non-Chlorine Bleaching Conference 1993.
The Bleaching of Pulp, Third Edition, Revised-Pulp Manufacturer Division.
Pulping Processes, Sven A. Rydholm, 1965, Interscience Publishers.
Official Gazette, vol. 1038, No. 4: Delignification and Bleaching Process for Lignocellulosic . . . of Metal Additives Abstract of U.S. Pat. No 4,427,490..
The plants become larger and larger, Svenk Papperstidning Nr. 10, 1989 (translation).
Svenk Paperstidning-Nordisk Cellulose Nr. 18, Dec. 6, 1990 (translation).
Ekstroom Ulla
Larsson Lars-Ove
Nilsson Erik
Tibbling Petter
Alvo Steven
Kananen Ronald P.
Kvaerner Pulping Technologies AB
LandOfFree
Process for peroxide bleaching of chemical pulp in a pressurized does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for peroxide bleaching of chemical pulp in a pressurized, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for peroxide bleaching of chemical pulp in a pressurized will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2012393