Source: http://www.google.com/patents/US5296099?dq=7,172,682
Timestamp: 2014-03-13 20:10:12
Document Index: 321710834

Matched Legal Cases: ['art 2', 'art 2', 'art 2', 'art 2', 'art 1', 'art 1']

Patent US5296099 - Environmentally improved process for bleaching lignocellulosic materials ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA process for delignifying and bleaching a lignocellulosic pulp without the use of elemental chlorine by partially delignifying the pulp to a K No. of about 10 or less and a viscosity of greater than about 13 cps; and further delignifying the partially delignified pulp with an effective amount of ozone...http://www.google.com/patents/US5296099?utm_source=gb-gplus-sharePatent US5296099 - Environmentally improved process for bleaching lignocellulosic materials with oxygen, ozone and chlorine dioxideAdvanced Patent SearchPublication numberUS5296099 APublication typeGrantApplication numberUS 07/938,736Publication dateMar 22, 1994Filing dateAug 28, 1992Priority dateMay 17, 1990Fee statusPaidAlso published asUS5164044Publication number07938736, 938736, US 5296099 A, US 5296099A, US-A-5296099, US5296099 A, US5296099AInventorsThomas P. Gandek, Bruce F. Griggs, Michael A. Pikulin, Allen RosenOriginal AssigneeUnion Camp Holding, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (77), Non-Patent Citations (110), Referenced by (16), Classifications (10), Legal Events (7) External Links: USPTO, USPTO Assignment, EspacenetEnvironmentally improved process for bleaching lignocellulosic materials with oxygen, ozone and chlorine dioxideUS 5296099 AAbstract A process for delignifying and bleaching a lignocellulosic pulp without the use of elemental chlorine by partially delignifying the pulp to a K No. of about 10 or less and a viscosity of greater than about 13 cps; and further delignifying the partially delignified pulp with an effective amount of ozone for a sufficient time to obtain a substantially delignified pulp having a K No. of about 5 or less, a viscosity of greater than about 10, and a GE brightness of at least about 50%. The substantially delignified pulp may be brightened by the addition of a bleaching agent such as chlorine dioxide or a peroxide to obtain a final product having a GE brightness of at least about 65%, preferably above 70% to as high as 90%. Because of the absence of elemental chlorine in this sequence, filtrate from all stages but the chlorine dioxide stage (if used) can be recovered without sewering. Major environmental improvements are thus achieved.
We claim: 1. A process for delignifying and bleaching a lignocellulosic material which comprises the following steps in the order stated without additional intervening delignification or bleaching steps:partially delignifying a lignocellulosic material by pulping to form a pulp, washing said pulp, and delignifying said pulp with oxygen to form a partially delignified pulp having a first K No. of about 10 or less and a first viscosity of greater than about 13 cps; washing the partially delignified pulp; further delignifying said partially delignified pulp at a consistency of at least about 20% by treating the particles with a gaseous mixture containing ozone in an amount sufficient to remove a substantial portion, but not all, of the lignin remaining in the pulp by intimately contacting and turbulently mixing the discrete particles with the ozone containing gaseous mixture in a dynamic reaction zone for a sufficient time and at a temperature sufficient to allow access of the ozone to substantially all surfaces of the pulp particles for reaction therewith while advancing the pulp particles through substantially all of the reaction zone to obtain a substantially delignified pulp having a second K No. of about 5 or less, a viscosity of greater than about 10 cps and a GE brightness of at least about 50%; washing the substantially delignified pulp; combining the substantially delignified pulp with an effective amount of alkaline material in an aqueous alkaline solution for a predetermined time and at a predetermined temperature correlated to the quantity of alkaline material to solubilize a substantial portion of any lignin which remains in the pulp; extracting a portion of the aqueous alkaline solution so as to remove substantially all of the solubilized lignin therefrom and form a substantially lignin-free pulp; washing the substantially lignin-free pulp; bleaching the substantially lignin-free pulp with chlorine dioxide to raise the GE brightness thereof to at least about 70%; and washing the bleached pulp; wherein at least a portion of the wash water effluent from one or more of the partially delignified pulp washing step, the substantially delignified pulp washing step, the substantially lignin free pulp washing step or the bleached pulp washing step is recycled countercurrently to a previous pulp washing step, and further wherein the effluent from washing the bleached pulp has an amount of total organic chlorides of no more than about 2 pounds per ton prior to any treatment steps for organic chloride removal. 2. The process of claim 1 wherein the GE brightness is raised to at least about 80%.
13. The process of claim 5 wherein the discharge effluent has a color of no greater than about 2 pounds per ton, a BOD.sub.5 value of no greater than about 2 pounds per ton and an amount of total organic chlorides of no greater than about 0.18.
21. The process of claim 1 wherein the oxygen delignification step is conducted by:decreasing the consistency of said pulp to about 1 to 10% by weight: treating the decreased consistency pulp with a quantity of alkaline material in an aqueous alkaline solution having a concentration of alkaline material of between about 20 and 120 g/l, for a time of between about 1 and 15 minutes and at a temperature of between about 90 and 150 decreased consistency pulp during this treating step ranges from 6.5 to 13 g/l, so as to substantially complete a substantially uniform distribution of the alkaline material throughout the pulp; increasing the consistency of the alkaline treated pulp to between about 20 to 35% by weight to generate pressate while retaining at least about 1.4% by weight based on oven dry pulp of alkaline material on the increased consistency pulp; and subjecting the increased consistency pulp to high consistency oxygen delignification without substantially changing the viscosity of the pulp to form the partially delignified pulp. 22. The process of claim 21 wherein the consistency of the pulp in the oxygen stage, prior to treatment with alkaline material, is reduced to less than about 5% by weight, and further wherein substantially all of the liquid removed from the consistency increasing step is directly recycled to the pulp treating step.
Moreover, the preferred alkaline treatment of pulp according to the present invention may be carried out over a wide range of temperature conditions. According to a preferred practice, the treatment step is carried out at a temperature of from about room temperature to about 150 temperatures ranging from about 90 being even more preferred. Atmospheric pressure or elevated pressure may be employed. The treatment step is completed when the aqueous alkaline solution is substantially uniformly distributed throughout the low consistency pulp. The amount of aqueous alkaline solution present in the treatment step can vary greatly according to the particular process parameters of the delignification reaction. The amount of the alkaline solution effective for the purpose of the present invention will depend primarily upon the extent of delignification desired in the oxygen bleaching step and the strength of the particular solution being used. The aqueous alkaline solutions preferably used comprise a sodium hydroxide solution having a concentration of from about 20 to about 120 g/l. This solution is mixed with the low consistency pulp, so that the overall mixture has a concentration of alkaline material of between about 6.5 and 13.5 g/l, and preferably around 9 g/l. Thus, for a 5 to 15 minute treatment of a 3 to 5 percent consistency pulp at temperatures between 120 material, a uniform distribution of such alkaline material is obtained throughout the pulp.
TABLE I______________________________________LOBLOLLY PINE KRAFT PULPING CONDITIONSCONDITION/STEP           PARAMETER______________________________________PRESTEAM TIME (min.)      2.5TIME TO TEMPERATURE - 175                    1 hourTIME AT TEMPERATURE - 175                    1 hourLIQUOR:WOOD ratio        4:1SULFIDITY (%)            25.8ACTIVE ALKALI (%)        17.4% AA FROM BLACK LIQUOR FILLBACK                     0.43K NO.                    22.6VISCOSITY (cps)          27.1______________________________________
TABLE II______________________________________PINE TYPICAL CONVENTIONALO STAGE BLEACHING CONDITIONS                             PULPPRESSURE %                  TEMP  CONSISTENCY(PSIG)   CHEMICAL    pH     (                             (%)______________________________________80       2.5 NaOH    10.2   110   27*    0.1 MgSO.sub.4______________________________________ *both for alkali addition and oxygen delignification
TABLE III______________________________________PINE TYPICAL C/DED BLEACHING CONDITIONS                            PULP  CHEMICAL            TEMP  CONSISTENCYSTEP   (%)        pH       (                            (%)______________________________________C/D    3.6 Cl.sub.2             1.8      50    3.15  0.6 ClO.sub.2E      1.5 NaOH   11.6     70    12D      0.3 ClO.sub.2             4.2      60    12______________________________________
TABLE IV______________________________________PINE TYPICAL ACIDIFICATION CONDITIONS                             PULP                       TEMP  CONSISTENCYSTEP     % CHEMICAL   pH    (                             (%)______________________________________Acidification    to pH 2      2     22    3-4(H.sub.2 SO.sub.4)Chelation    0.11         2     22    3-4(oxalic acid)______________________________________
TABLE XIII______________________________________TYPICAL MODIFIEDOXYGEN (O.sub.m) STAGE CONDITIONS    %    CHEMICAL                 PULP    USED ON OD         TEMP  CONSISTENCYSTEP     FIBERS      pH     (                             (%)______________________________________Treatment    30%         --      22   3-4(NaOH)Oxygen (O.sub.2)    80 psig     10.2   110   27(MgSO.sub.4)    0.1______________________________________
TABLE XVIII______________________________________HARDWOOD TYPICALC/DED BLEACHING CONDITIONS                            PULP  CHEMICAL           TEMP.  CONSISTENCYSTEP   (%)        pH      (                            (%)______________________________________C/D    1.6 Cl.sub.2             1.8     50     3.15  0.26 ClO.sub.2E      1.0 NaOH   11.9    70     12D      0.35 ClO.sub.2             4.2     60     12______________________________________
TABLE XX______________________________________ED TYPICAL BLEACHING CONDITIONSUSED ON OZ.sub.m HARDWOOD PULP  CHEMICAL           TEMP.  PULPSTEP   (%)        pH      (                            CONSISTENCY______________________________________E      1.0 NaOH   12.0    70     12D      0.35 ClO.sub.2             4.36    60     12______________________________________
EXAMPLE 13 Southern softwood, i.e., loblolly pine, was bleached to target brightness of 83 GEB using the conventional CEDED sequence as shown in Table XXVI, using the conventional OC/DED sequence as shown in Tables II and III above and using the OZ.sub.m ED sequence as shown in Tables IV and V above. Wood based dirt was refined and added to the OZ.sub.m ED starting brownstock at a level of 0.75% by weight to examine the ability of this sequence to remove dirt compared to CEDED and 0C/DED bleaching. Dirt properties of the three sequences, measured as Effective Black Area, bark and shives, were equivalent.
TABLE XXX__________________________________________________________________________OZ.sub.M ED BLEACHING CONDITIONS                   PULP    CHEMICAL   TEMP.               TIME                   CON.                       GEB                          K NO.                              VISCOSITY*STEP    (%)    pH  (               (min.)                   (%) (%)                          (40 ml)                              (cps.)__________________________________________________________________________O.sub.m    [Conditions given in TABLE XIII]                       40 8.5 12.5Z.sub.m    0.43   2   22   1.5 43  50 --  10E   1.5    11.5          70   60  12  -- --  9.8D   0.5    4 to 5          70   180 12  65 --  9.6    0.7                     70     9.6__________________________________________________________________________ *Viscosity values after the O.sub.m stage are interpolated values based o established data.
It has been conventional for many years to delignify and bleach wood pulp by using elemental chlorine. Exemplifying the bleaching of lignocellulosic pulps are the processes disclosed in, for example, U.S. Pat. Nos. 1,957,937 to Campbell et al., 2,975,169 to Cranford et al. and, 3,462,344 to Kindron et al.; and Handbook For Pulp and Paper Technologists--Chapter 11: Bleaching (
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