CA1070909A - Nitrogen dioxide-oxygen delignification - Google Patents
Nitrogen dioxide-oxygen delignificationInfo
- Publication number
- CA1070909A CA1070909A CA251,752A CA251752A CA1070909A CA 1070909 A CA1070909 A CA 1070909A CA 251752 A CA251752 A CA 251752A CA 1070909 A CA1070909 A CA 1070909A
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- pulp
- oxygen
- consistency
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- treatment
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Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
- D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
- D21C9/10—Bleaching ; Apparatus therefor
- D21C9/1057—Multistage, with compounds cited in more than one sub-group D21C9/10, D21C9/12, D21C9/16
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Wood Science & Technology (AREA)
- Paper (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A process for delignification of lignocellulosic material such as wood pulp, employing treatment with nitrogen dioxide followed by treatment with gaseous oxygen in alkaline medium. Use of the process results in a reduction of polluting materials in the process effluent. The process is capable of removing 75% to 90% of the lignin residue of a conventional kraft wood pulp. Because of the chloride free nature of the process effluent, this can be recycled to the pulping chemicals recovery furnace in amounts related to the washing efficiency after the oxygen stage.
A process for delignification of lignocellulosic material such as wood pulp, employing treatment with nitrogen dioxide followed by treatment with gaseous oxygen in alkaline medium. Use of the process results in a reduction of polluting materials in the process effluent. The process is capable of removing 75% to 90% of the lignin residue of a conventional kraft wood pulp. Because of the chloride free nature of the process effluent, this can be recycled to the pulping chemicals recovery furnace in amounts related to the washing efficiency after the oxygen stage.
Description
1~;)7~
This invention relates to a process for the delignification of lignocellulosic material such as wood pulp, bagasse and straw, employing treatment with nitrogen dioxide and oxygen in sequence.
For many of the applications of lignocellulosic material a bleached product is required. Bleaching is basically a delignification process. commonly ligno-cellulosic material such as sulphate (kraft) wood pulp is bleached by treatment with chlorine and chlorine-containing compounds such as chlorine dioxlde or hypochlorite. A typical bleaching sequence for sulphate wood pulp is chlorination,caustic extraction, chlorine dioxide treatment, caustic extraction, and chlorine dioxide treatment, abbreviated C-E-D-E-D. The use of chlorine compounds, however, introduces difficulties in handling the effluent from the bleaching process. The chlorine-containing waste cannot be discharged into bodies of water because of its adverse effect on aquatic organisms.
If the chlorine-containing waste is recycled through the ; 20 sulphate process black liquor recovery system, damage to the evaporator and recovery furnace may result. In addition, a build-up of sodium chloride occurs in the recovery system, lowering the efficiency of the furnace. There is thus an advantage in the avoidance of chlorine compounds in bleaching processes, It is known to replace the chlorine ingredient of a pulp bleaching sequence by nitrogen dioxide, N02. In an article by G. L. Clarke in Volume 118 of the Paper Trade ~ournal, February 24, 1944 at page 62 entitled "The Action of Nitrogen Dioxide on Unbleached Pulp, Part I" a bleaching ~ , ........................................ . .
:
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sequence employing a first treatment with nitrogen dioxide followed by caustic extraction and treatment with hypochlor-ite is disclosed. This bleaching sequence had the disadvan-tage that it caused severe degradation of the pulp as indicated by a much lower viscosity value when compared with an analogous bleaching sequence, ch:Lorine, caustic extraction, hypochlorite. When applied to Western hemlock pulp the above nitrogen dioxide bleaching sequence gave a bleached product having a viscosity of 39 centipoise whereas with the analogous chlorine bleaching sequence a viscosity of 67 centipoise was achieved.
It has now been found that lignocellulosic material can be delignified to give a product of acceptable viscosity employing nitrogen dioxide as a first step in a sequence followed by alkali treatment and treatment with oxygen under supra atmospheric pressure, abbreviated N02-0. The novel sequence has an especial advantage in the abatement of pollution. It is capable of removing 75% to 90% of the lignin residue of a conventional kraft pulp and, because of the chloride-free nature of the effluent, the latter is capable of being recycled to the pulping chemicals recovery furnace in amounts related to the washing efficiencies after the oxygen stage.
Thus the main object of the invention is to provide a process for delignifying lignocellulosic material wherein the pollution load is reduced. Additional objects will appear hereinafter.
The novel process for the delignification of lignocellulosic material comprises the steps of ~l~7~909 (l) treating lignocellulosic material in aqueous medium with nitrogen dioxide,
This invention relates to a process for the delignification of lignocellulosic material such as wood pulp, bagasse and straw, employing treatment with nitrogen dioxide and oxygen in sequence.
For many of the applications of lignocellulosic material a bleached product is required. Bleaching is basically a delignification process. commonly ligno-cellulosic material such as sulphate (kraft) wood pulp is bleached by treatment with chlorine and chlorine-containing compounds such as chlorine dioxlde or hypochlorite. A typical bleaching sequence for sulphate wood pulp is chlorination,caustic extraction, chlorine dioxide treatment, caustic extraction, and chlorine dioxide treatment, abbreviated C-E-D-E-D. The use of chlorine compounds, however, introduces difficulties in handling the effluent from the bleaching process. The chlorine-containing waste cannot be discharged into bodies of water because of its adverse effect on aquatic organisms.
If the chlorine-containing waste is recycled through the ; 20 sulphate process black liquor recovery system, damage to the evaporator and recovery furnace may result. In addition, a build-up of sodium chloride occurs in the recovery system, lowering the efficiency of the furnace. There is thus an advantage in the avoidance of chlorine compounds in bleaching processes, It is known to replace the chlorine ingredient of a pulp bleaching sequence by nitrogen dioxide, N02. In an article by G. L. Clarke in Volume 118 of the Paper Trade ~ournal, February 24, 1944 at page 62 entitled "The Action of Nitrogen Dioxide on Unbleached Pulp, Part I" a bleaching ~ , ........................................ . .
:
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sequence employing a first treatment with nitrogen dioxide followed by caustic extraction and treatment with hypochlor-ite is disclosed. This bleaching sequence had the disadvan-tage that it caused severe degradation of the pulp as indicated by a much lower viscosity value when compared with an analogous bleaching sequence, ch:Lorine, caustic extraction, hypochlorite. When applied to Western hemlock pulp the above nitrogen dioxide bleaching sequence gave a bleached product having a viscosity of 39 centipoise whereas with the analogous chlorine bleaching sequence a viscosity of 67 centipoise was achieved.
It has now been found that lignocellulosic material can be delignified to give a product of acceptable viscosity employing nitrogen dioxide as a first step in a sequence followed by alkali treatment and treatment with oxygen under supra atmospheric pressure, abbreviated N02-0. The novel sequence has an especial advantage in the abatement of pollution. It is capable of removing 75% to 90% of the lignin residue of a conventional kraft pulp and, because of the chloride-free nature of the effluent, the latter is capable of being recycled to the pulping chemicals recovery furnace in amounts related to the washing efficiencies after the oxygen stage.
Thus the main object of the invention is to provide a process for delignifying lignocellulosic material wherein the pollution load is reduced. Additional objects will appear hereinafter.
The novel process for the delignification of lignocellulosic material comprises the steps of ~l~7~909 (l) treating lignocellulosic material in aqueous medium with nitrogen dioxide,
(2) washing the nitrogen dioxide-treated material with water,
(3) treating the washed material in aqueous medium with alkaline material, and
(4) treating -the alkaline treated material with oxygen or an oxygen-containing gas at supra atmospheric pressure.
In the first step the lignocellulosic material is treated in aqueous medium at a consistency in the range of 3.0% to 50%, preferably 30% to 50% by weight. The temperature employed in the first step is in the range of ambient to 120C., preferably 70C. to 90C. The concentration of nitrogen dioxide employed is 0O50/o to 10.0%
by weight, preferably 1.5% to 6.0% by weight. The first step treatment is carried out for a period of 5 to 60 minutes.
After the first step treatment with nitrogen dioxide the lignocellulosic material is diluted with water to a low consistency e.g. 3.0%. At this point the pH of the aqueous lignocellulosic pulp will usually be in the range 1.0 to 3Ø
The lignocellulosic material is then washed thoroughly with water. The lignocellulosic pulp is then pressed to a high consistency e.g. 35%.
Then in the third step of the process the lignocellulosic material is mixed with 1.0% to ~0.0% by weight of an alkali or alkaline earth base. Preferably there is also added at this stage 0.1% to 1.0% by weight _ 3 -:
1~7~:)9~9 of a magnesium salt such as magnesium chloride or magnesium sulphate.
Then in the fourth step of the process the lignocellulosic material in aqueous suspension at a consistency of 3.0% to 35.0% by weight i5 treated in a reactor with oxygen or an oxygen-containLng gas at a partial pressure of oxygen of 30 to 200 pounds per square inch at a temperature in the range 80C. to 200C. for a period of lO to 60 minutes. The ligno-cellulosic material is then diluted to low consistency and washed with water.
The above steps may be followed by conventional bleaching steps such as C-E-D or D-E-D. Employing bleaching sequences N0z-O-C-E-D or NO2-O-D-E-D final pulp properties can be obtained equivalent to or better than those fr~m a conventional sequence C-E-D-E-D. When this is done the conditions are as follows:
Chlorine treatment of C-E-D sequence. The lignocellulosic .
material in aqueous suspension at a consistency of 2.0%
to 35.0% by weight is treated with 0.5% to 5.0% by weight of chlorine. The treatment lasts from l to 60 minutes at a temperature of 15C. to 60C. The material is then washed with water.
First chlorine dioxide treatment of _-E-D sequenc_. The lignocellulosic material in aqueous suspension at a consistency of 3.0% to 35.0% by weight is treated with 0.5% to 1.5% by weight of chlorine dioxide and, optionally with sufficient base or other alkaline buffering agent, to give a pH of about 4 at the end of the chlorine dioxide - 30 treatment. The treatment lasts from 60 to 300 minutes at 1~7~09 a temperature of 60C. to 80C. The material is then washed with water. f Caustic extraction (C-E-D or D-E~D). The washed material in aqueous suspension at 3.0% to 35.0% consistency by weight i5 treated with 0.25% to 2.0% by weight of base for 60 to 120 minutes at 40C. to 70C. The material is then washed with water.
Chlorine dioxide treatment.__(Final step of C-E-D or D~E-D).
The washed material in aqueous suspension at 3.0% to 35.0%
consistency by weight is treated with 0.1% to 1.5% by weight of chlorine dioxide for 60 to 300 minutes at 60C. to 80C.
The material is then washed with water.
The base employed in the present process usual:Ly is sodium hydroxide. However, other materials such as potassium hydroxide, calcium hydroxide, sodium carbonate or potassium carbonate may be used. -The base employed in the third step of the present process, prior to treatment with oxygen, may be white liquor rom the alkaline recovery system of a wood pulping plant.
Instead of using fresh water as a washing medium "white water" available in pulp mills may be substituted.
The process of this invention has the advantage that the effluent from nitrogen dioxide and alkaline oxygen stages contains no chlorine compounds and so can be recycled through the recovery system of a pulp mill. This results in a reduction of polluting effluent from a pulp mill employing the process.
The N02-0 partial sequence of this invention has been found suitable for delignifying high yield kraft and soda pulps, resulting in yield advantayes normally associated with oxygen delignification but with added pollution abatement b~eits. Whexeas a single oxygen stage will delignify a high yield (50 to 100 Kappa number) pulp to a Kappa number in the vicinity of 20 to 30, the NO2-O
sequence delignifies to 10 to 15 Kappa numbex at viscosity levels equivalent to or better than those observed for single oxygen stage pulps. ~ larger portion of pulluting material can thus be returned to the recover~ system.
High yield pulps partially delignified by the N02-O partial bleaching sequence can be brought -to a fully bleached level by means of a C-E-D sequence. ~pplica-tion of the bleaching sequence N02 0-C-E-D to a high yield (Kappa number 50 to 100) pulp results in a fully bleached pulp with strength properties equivalent to or greater than those observed for the bleaching sequence C-E-D-E-D
on conventional kraft pulp of Kappa number 30.
In this specification all proportions and percentages are by weight of oven dried material, unless otherwise stated.
The tests characterizing the treated product of this invention were carried out by the following standard methods.
Kappa number TAPPI Method T-236 M-60 Viscosity TAPPI Method T-230 SU-66 Brightnass TAPPI Method T-217m, 218m Handsheet For~ation TAPPI T-205 M-58 (Hot disintegration) Freeness TAPPI T-227 M-58 Tear Factor TAPPI T-220 M-60 Burst Factor TAPPI T-220 M-60 Breaking Length TAPPI T-220 M-60 (Tensile) ~7vsvs Colour of the process effluent was measured by comparison wi-th colour standards prepared from potassium chloroplatinate and cobaltons chloride according to ASTM D-1209. The effluent colour is expressed as pounds of platinum per ton of ton.
The invention is illustrated additionally by the following Examples but its scope is not limited to the embodiments shown therein.
50 grams, oven dried basis, of a softwood ~mainly spruce species) kraft pulp of Kappa number 32.4 and viscosity 34.7 centipoise at 40.0% consistency were placed in a rotating reaction vessel. The pulp was preheated in the vessel to a temperature of 75C. Nitrogen dioxide (3.0% on pulp) was then distilled into the rotating pulp.
The reaction was allowed to proceed for an additional 30 minutes, after which the reactor was evacuated to remove any unreacted nitrogen dioxide. The pulp was then diluted to a consistency of 4.0% and the pH was found to ; 20 be 2.3. After thorough washing with distilled water, the pulp was pressed to 35% consistency in preparation for the oxygen stage.
To the washed pulp was added 2.6% by weight sodium hydroxide and 0.1% magnesium ion as magnesium sulphate and sufficient water to give a consistency of 27% while stirring in a Hobart mixer. The pulp was then transferred to an oxygen reactor. In the reactor the alkaline pulp was treated with oxygen gas at a pressure of 90 pounds per square inch gauge at 120C. temperature for a period of 30 minutes.
. .
9~9 The pulp was then diluted to a consistency of 4% and the pH was found to be 10Ø After washing with water the pulp had the following properties:
Kappa number 5.1 Visc05 ity 10.8 centipoise The oxygen treated pulp was then further bleached by the D-E-D sequence, the chemical charges and conditions being as follows:
D1 stage: 1.2% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
E staye: 0.6% sodium hydroxide at 65C. for 1.5 hour on pulp at 12.0% consistency.
D2 stage: 0.4% chlorine dioxide at 70C. for 3 hours on pulp at 6~0% consistency.
The pulp bleached by the ~02-O-D-E-D sequence had the follo~ing properties:
Brightness 90.1 Viscosity 9.7 centipoise Strength properties are shown in the accompanying Table.
Assuming return of the nitrogen dioxide and oxygen stage effluents to the kraft recovery system and an oxygen stage washing efficiency of 85% the combined D-E-D bleach effluent has the following properties:
Colour (pH 7) 17.7 lb/ton of pulp Total organic carbon 16.3 lb/ton of pulp Chlorine ion 14.0 lb/ton of pulp ~7~ 9 . ~`
The same softwood kraft pulp of Kappa number 32.4 and viscosity 34.7 centipoise was bleached by a conventional C-E-D-E-D bleaching sequence. The chemical charges and conditions of the various stages were as follows:
C stage: 6.9% chlorine at 21C. for 1 hour on pulp at 3.0% consistency.
El stage: 3.5% sodium hydroxide at 65C. for 1.5 hour on pulp at 12.0% consistency.
Dl stage: 1.0% chlorine dioxide at 70C. for 3 hours on pulp at 6~0% consistency.
E2 stage: 0.8% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
D2 stage: 0.3% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The pulp after the final chlorine dioxide stage had the following properties:
Brightness go,~
Viscosity 11.0 centipoise The stxength properties are shown in the Table. The combined effluents from the C-E-D-E-D bleaching sequence had the following properties:
Colour (p~ 7) 502 lb/ton of pulp Total organic carbon 53.3 lb/ton of pulp Chlorine ion 135 lb/ton of pulp It can be seen that by using the NO2-O-D-E-D rather than the C-E-D-E-D sequence there results a reduction of 96%, 70% and 90% in effluent colour, total organic carbon and chlorine ion respectively.
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The softwood pulp of Example 1 was subjected to a NO2-O bleaching sequence as in Example 1 except that the nitrogen dioxide concentration was 1.5% on pulp. The bleached pulp had the following properties:
~appa number 8.0 Viscosity 18.6 centipoise The NO2-O treated pulp was bleached further by a C-E-D sequence with chemical charges and conditions as follows:
C stage: 1.6% chlorine at 21C. for 1 hour on pulp at 3.0% consistency.
E stage: 0.8% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
D stage: 0.7% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The bleached pulp had the following properties:
Brightness 88.5 Viscosity lS.l centipoise The strength properties are shown in the Table. The combined C-E-D effluent from the bleach plant had the following properties:
colour (pH 7) 60 lh/ton of pulp Total organic carbon 21.4 lb/ton of pulp Chlorine ion 34~8 lh/ton of pulp Thus reductions of 88%, 61% and 74% in colour, total organic carbon and chlorine ion respectively were realized by using the sequence NO2-O-C-E-D rather than the sequence C-E-D-E-D.
9~9 A hardwood (mainly oak species) kraft pulp having a Kappa number of 19.0 and a viscosity of 25.7 centipoise was bleached by the NO2-0 sequence using the same conditions as in Example 1 except that -Nitrogen dioxide 2.0% on pulp 0xygen treatment Temperature 130C.
; Time 15 minutes % sodium hydroxide 2.0 The NO2-O bleached pulp had the following properties:
: Kappa number 5.8 ~: :
: Viscosity 19.1 centipoise ~-~
The hardwood pulp bleached by the N02-O pa~tial sequence was bleached further by a D-E-D sequence with chemical charges and conditions as ollows:
Dl stage: 1.2% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
E stage: 0.6% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistencyO :
: D2 stage: 0.4% chlorine dioxide at 70C. for 3 hours : on pulp at 6.0% consistency.
The resulting bleached pulp had the following properties~
Brightness 89.4 Viscosity 16.8 centipoise The same hardwood kraft pulp of Kappa number 19.0 ~ :~
and viscosity 25.7 centipoise was bleached by a conventional : .
C-E-D-E-D sequ~nce. The chemical charges and conditions of the various stages were as follows:
. .
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C stage: 3.6% chlorine at 21C~ for 1 hour on a pulp at 3.0% consistency.
El stage: 2.5% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
Dl stage: 0.7% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
E2 stage: 0.5% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
Dz stage: 0.28% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The bleached product had the following properties:
Brightness 88~6 Viscosity 18.2 centipoise The same hardwood kraft pulp of Example 3 having a Kappa number of 19.0 and a viscosity of 25.7 centipoise was subjected to a N02-0 bleaching sequence as in Example 3 except that -Nitrogen dioxide 1.5% on pulp Oxygen treatment Temperature 130C.
Time 15 minutes % sodium hydroxide 2.0 The bleached product had the following properties: - -Kappa number 6.0 Viscosity 19.8 centipoise The pulp bleached by the N02-0 partial sequence was bleached further by the sequence C-E-D.
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The chemical charges and conditions of the stages were as follows:
C stage: 1.24% chlorine at 21C. for l hour on pulp at 3.0% consistency.
E stage: 0.8% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
D stage: 0.5% chlorine dioxlde at 70C. for 3 hours on pulp at 6.0% consistency.
The bleached product had the following properties:
~rightness 88.8 Viscosity 16.5 centipoise E~MPLE S
A softwood (pine) kraft pulp of Kappa number 50 and viseosity 28 eentipoise was subjeeted to a N02-0 bleaching sequence as in Example l except that -Nitrogen dioxide 3.0% on pulp Oxygen stage Sodium hydroxide 3.0%
The bleached product had a Kappa number of 9.3 and a viseosity of 15.2 centipoise.
The product from the above N02~0 partial hleaching sequence was subjected to further bleaching by the sequence C-E-D. The chemical charges and conditions of the stages ~`
were as follows:
C stage: 1.9% chlorine at 21C. for 1 hour at a - pulp consistency of 3.0%.
E stage: 0.9% sodium hydroxide at 65C. for 1.5 hours at a pulp consistency of 12.0%.
D stage: 008% chlorine dioxide at 70C. for 3 hours at a pulp eonsistency of 6.0%.
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The bleached product had the following properties:
Brightness 88.1 - Viscosity 13.7 centipoise The same softwood kraft pulp was subjected to a single stage oxygen treatment under conditions identical to those given above in this example. The resulting oxygen treated pulp had a Kappa number of 22.4 and a viscosity of 17.2 c~ntipoise.
Thus it can be seen that the N02-0 sequence in this case allows 58% greater delignification than 0 alone.
The pulp treated by the single oxygen stage was subjected to the additional bleaching sequence C-E-D. The chemical charges and conditions of the stages were as follows:
C stage: 4.6% chlorine at 21C. for 1 hour on pulp at 3.0% consistency.
E stage: 3.3% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
D stage: 1.4% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The bleached product had the following properties:
Brightness 86.5 Viscosity 14.5 centipoise It can be seen that in order to attain a similar level of brightness the bleaching sequence 0-C-E-D requires the use of substantially more chlorine and chlorine dioxide than the sequence N02-0-C-E-D.
- 14 _ : `
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)9~9 A softwood (spruce-balsam fir) soda pulp having a Kappa number of 93 was refined to fiberiæe the rejects and then subjected to a N02-0 partial sequence as in Example 1 except that - :
Nitrogen dioxide 6.0% on pulp Oxygen stage % sodium hydroxide 7.5 The bleached product had a Kappa number of 17.G
and a viscosity of 16~6 centipoise. ~:
The N02-0 bleached material was then subjected to the further bleaching sequence C-E-D. The chemical charges ~ .
and conditions of the stages were as follows:
; C stage: 3.2% chlorine at 21C. for 1 hour on pulp at 3.0% consistency.
E stage: 1.8% sodium hydroxide at 65C. for 1.5 hours ~
on pulp at a consistency of 12.0%. ~;;
D stage: 0.6% chlorine dioxide at 70C. for 3 hours on pu}p at a consistency of 6.0%. :
The bleached product had the following properties:
Brightness 85.8 Viscosity 16.7 centipoise The same softwood soda pulp was subjected to a single stage oxygen treatment under conditions identical to those given above in this example. The resulting oxygen-treated pulp had a Xappa number of 32.4 and a viscosity o~ 11.8 centipoise.
15 _ ' '. , :
~L~7~9~9 The above soda pulp treated by the sinyle oxygen stage was subjected to the additional bleaching sequences C-E-D. The chemical charges and conditions of the stages were as follows:
C stage: 6.1% chlorine at 21C. for 1 hour on pulp at a consistency of 3O0%.
E stage: 3.4% sodium hydro~ide at 65C. for 1.5 hours on pulp a~ a consistency lf 12.0%.
D stage: 0.8% chlorine dioxide at 70C. for 3 hours on pulp at a consistency of 6.0%.
The bleached product had the following properties:
Brightness 84.8 Viscosity 11.2 centipoise A mixed hardwoods kraft pulp of ~appa number 46 w~s refined to fiberize rejects and then subjected to a ~2-partial bleaching sequence as in Example 1 except that -~itrogen dioxide 3.0% on pulp .
Oxygen stage % sodium hydroxide 4.0 on pulp The resulting bleached product had the Kappa number 8.2 and viscosity of 25.1 centipoise.
The above bleached pulp was subjected to the additional bleaching sequence C-E-D. The chemical charges and conditions of the stages were as follows:
C stage: 1.6% chlorine at 21C. for 1 hour on pulp at 3.0% consistency.
: E stage: 0.9% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
, . . .
~7~
D stage: 0.4% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The resulting product had the foLlowing properties:
Brightnass 88.8 Viscosity 24.3 centipoise Overall pulping and bleaching yield - 51.1% on wood.
The strength properties of this pulp are shown in the Table.
The above mixed hardwood kraft pulp was subjected to a single stage oxygen treatment under conditions identical to those given above in this example. The resulting oxygen-treated pulp had a Kappa number of 15.8 and a viscosity of 29.9 centipoise. ~
The above kraft pulp treated by the single oxygen -stage was subjected to the additional bleaching sequence ; C-E-D. The chemical charges and conditions of the stages were as follows:
C stage: 2.9% chlorine at 21C. for 1 hour ~
on pulp at 3.0% consistency. -E stage: 1.6% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
D stage: 0.4% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The resulting bleachecl pulp had the following properties:
Brightness 89.0 Viscosity 20.7 centipoise Overall pulpins and bleaching yield - 51.4% on wood.
The strength properties are shown in the Table.
Another portion of the mixed hardwood chips used in this example was pulped to a Kappa number of 14.8 and bleached by _ 17 - `
.
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a conventional C E~D E-D sequence. The chemical charyes and conditions of the stages were as follows:
C stage: 3.1% chlorine at 21C. for 1 hour on pulp at a consistency of 3.0%~
El stage: 1.7% sodium hydroxide at ~5C. for 1.5 hours on pulp at a consistency of 12~0%~
Dl stage: 0.7% chlorine dioxide at 70C. for 3 hours on pulp at a consistency of 6.0%.
E2 stage: 0.5 sodium hydroxide at 65C. for 1.5 hours on pulp at a consistency of 12.0%.
Dz stage: 0.3 chlorine dioxide at 70C. for 3 hours at a consistency of 6.0%.
The bleached pulp had the following properties:
Brightness 89.4 Viscosity 28.3 centipoise Overall pulping and bleaching yield - 47.8% on wood.
Strength properties are given in the Table.
EXAMpLE 8 A softwood (mainly spruce species) kraft pulp of Kappa number 32 was subjected to a NO2-O partial sequence as in Example 2 but in distinction to said Example, a low consistency pulp was employed in the oxygen stage. The conditions of treatment were as follows:
~itrogen dioxide stage: 1.5% NO2 at 7SC. for 30 minutes on pulp at 40% consistency.
Oxygen stage: oxygen gas at 90 pounds per square inch pressure for 15 minutes at 130C. on pulp at 3.0% consistency containing 3.0% sodium hydroxide.
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The product had the Kappa number of 9.8 and a viscosity of 23.1 centipoise.
The oxygen treated pulp was then fully bleached by a C-E~D sequence. The conditions and results were as follows:
C stage: 2.0% chlorine at 2LC. for 1 hour on pulp at 3.0% consistency.
E stage: 1.0% sodium hydroxide at 55C. for 1.5 hours ~ -on pulp at 12.0% consistency.
- 10 D stage: 0.6% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The bleached product had the following properties:
Brightness 88.2 Viscosity 16.5 centipoise ':
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In the first step the lignocellulosic material is treated in aqueous medium at a consistency in the range of 3.0% to 50%, preferably 30% to 50% by weight. The temperature employed in the first step is in the range of ambient to 120C., preferably 70C. to 90C. The concentration of nitrogen dioxide employed is 0O50/o to 10.0%
by weight, preferably 1.5% to 6.0% by weight. The first step treatment is carried out for a period of 5 to 60 minutes.
After the first step treatment with nitrogen dioxide the lignocellulosic material is diluted with water to a low consistency e.g. 3.0%. At this point the pH of the aqueous lignocellulosic pulp will usually be in the range 1.0 to 3Ø
The lignocellulosic material is then washed thoroughly with water. The lignocellulosic pulp is then pressed to a high consistency e.g. 35%.
Then in the third step of the process the lignocellulosic material is mixed with 1.0% to ~0.0% by weight of an alkali or alkaline earth base. Preferably there is also added at this stage 0.1% to 1.0% by weight _ 3 -:
1~7~:)9~9 of a magnesium salt such as magnesium chloride or magnesium sulphate.
Then in the fourth step of the process the lignocellulosic material in aqueous suspension at a consistency of 3.0% to 35.0% by weight i5 treated in a reactor with oxygen or an oxygen-containLng gas at a partial pressure of oxygen of 30 to 200 pounds per square inch at a temperature in the range 80C. to 200C. for a period of lO to 60 minutes. The ligno-cellulosic material is then diluted to low consistency and washed with water.
The above steps may be followed by conventional bleaching steps such as C-E-D or D-E-D. Employing bleaching sequences N0z-O-C-E-D or NO2-O-D-E-D final pulp properties can be obtained equivalent to or better than those fr~m a conventional sequence C-E-D-E-D. When this is done the conditions are as follows:
Chlorine treatment of C-E-D sequence. The lignocellulosic .
material in aqueous suspension at a consistency of 2.0%
to 35.0% by weight is treated with 0.5% to 5.0% by weight of chlorine. The treatment lasts from l to 60 minutes at a temperature of 15C. to 60C. The material is then washed with water.
First chlorine dioxide treatment of _-E-D sequenc_. The lignocellulosic material in aqueous suspension at a consistency of 3.0% to 35.0% by weight is treated with 0.5% to 1.5% by weight of chlorine dioxide and, optionally with sufficient base or other alkaline buffering agent, to give a pH of about 4 at the end of the chlorine dioxide - 30 treatment. The treatment lasts from 60 to 300 minutes at 1~7~09 a temperature of 60C. to 80C. The material is then washed with water. f Caustic extraction (C-E-D or D-E~D). The washed material in aqueous suspension at 3.0% to 35.0% consistency by weight i5 treated with 0.25% to 2.0% by weight of base for 60 to 120 minutes at 40C. to 70C. The material is then washed with water.
Chlorine dioxide treatment.__(Final step of C-E-D or D~E-D).
The washed material in aqueous suspension at 3.0% to 35.0%
consistency by weight is treated with 0.1% to 1.5% by weight of chlorine dioxide for 60 to 300 minutes at 60C. to 80C.
The material is then washed with water.
The base employed in the present process usual:Ly is sodium hydroxide. However, other materials such as potassium hydroxide, calcium hydroxide, sodium carbonate or potassium carbonate may be used. -The base employed in the third step of the present process, prior to treatment with oxygen, may be white liquor rom the alkaline recovery system of a wood pulping plant.
Instead of using fresh water as a washing medium "white water" available in pulp mills may be substituted.
The process of this invention has the advantage that the effluent from nitrogen dioxide and alkaline oxygen stages contains no chlorine compounds and so can be recycled through the recovery system of a pulp mill. This results in a reduction of polluting effluent from a pulp mill employing the process.
The N02-0 partial sequence of this invention has been found suitable for delignifying high yield kraft and soda pulps, resulting in yield advantayes normally associated with oxygen delignification but with added pollution abatement b~eits. Whexeas a single oxygen stage will delignify a high yield (50 to 100 Kappa number) pulp to a Kappa number in the vicinity of 20 to 30, the NO2-O
sequence delignifies to 10 to 15 Kappa numbex at viscosity levels equivalent to or better than those observed for single oxygen stage pulps. ~ larger portion of pulluting material can thus be returned to the recover~ system.
High yield pulps partially delignified by the N02-O partial bleaching sequence can be brought -to a fully bleached level by means of a C-E-D sequence. ~pplica-tion of the bleaching sequence N02 0-C-E-D to a high yield (Kappa number 50 to 100) pulp results in a fully bleached pulp with strength properties equivalent to or greater than those observed for the bleaching sequence C-E-D-E-D
on conventional kraft pulp of Kappa number 30.
In this specification all proportions and percentages are by weight of oven dried material, unless otherwise stated.
The tests characterizing the treated product of this invention were carried out by the following standard methods.
Kappa number TAPPI Method T-236 M-60 Viscosity TAPPI Method T-230 SU-66 Brightnass TAPPI Method T-217m, 218m Handsheet For~ation TAPPI T-205 M-58 (Hot disintegration) Freeness TAPPI T-227 M-58 Tear Factor TAPPI T-220 M-60 Burst Factor TAPPI T-220 M-60 Breaking Length TAPPI T-220 M-60 (Tensile) ~7vsvs Colour of the process effluent was measured by comparison wi-th colour standards prepared from potassium chloroplatinate and cobaltons chloride according to ASTM D-1209. The effluent colour is expressed as pounds of platinum per ton of ton.
The invention is illustrated additionally by the following Examples but its scope is not limited to the embodiments shown therein.
50 grams, oven dried basis, of a softwood ~mainly spruce species) kraft pulp of Kappa number 32.4 and viscosity 34.7 centipoise at 40.0% consistency were placed in a rotating reaction vessel. The pulp was preheated in the vessel to a temperature of 75C. Nitrogen dioxide (3.0% on pulp) was then distilled into the rotating pulp.
The reaction was allowed to proceed for an additional 30 minutes, after which the reactor was evacuated to remove any unreacted nitrogen dioxide. The pulp was then diluted to a consistency of 4.0% and the pH was found to ; 20 be 2.3. After thorough washing with distilled water, the pulp was pressed to 35% consistency in preparation for the oxygen stage.
To the washed pulp was added 2.6% by weight sodium hydroxide and 0.1% magnesium ion as magnesium sulphate and sufficient water to give a consistency of 27% while stirring in a Hobart mixer. The pulp was then transferred to an oxygen reactor. In the reactor the alkaline pulp was treated with oxygen gas at a pressure of 90 pounds per square inch gauge at 120C. temperature for a period of 30 minutes.
. .
9~9 The pulp was then diluted to a consistency of 4% and the pH was found to be 10Ø After washing with water the pulp had the following properties:
Kappa number 5.1 Visc05 ity 10.8 centipoise The oxygen treated pulp was then further bleached by the D-E-D sequence, the chemical charges and conditions being as follows:
D1 stage: 1.2% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
E staye: 0.6% sodium hydroxide at 65C. for 1.5 hour on pulp at 12.0% consistency.
D2 stage: 0.4% chlorine dioxide at 70C. for 3 hours on pulp at 6~0% consistency.
The pulp bleached by the ~02-O-D-E-D sequence had the follo~ing properties:
Brightness 90.1 Viscosity 9.7 centipoise Strength properties are shown in the accompanying Table.
Assuming return of the nitrogen dioxide and oxygen stage effluents to the kraft recovery system and an oxygen stage washing efficiency of 85% the combined D-E-D bleach effluent has the following properties:
Colour (pH 7) 17.7 lb/ton of pulp Total organic carbon 16.3 lb/ton of pulp Chlorine ion 14.0 lb/ton of pulp ~7~ 9 . ~`
The same softwood kraft pulp of Kappa number 32.4 and viscosity 34.7 centipoise was bleached by a conventional C-E-D-E-D bleaching sequence. The chemical charges and conditions of the various stages were as follows:
C stage: 6.9% chlorine at 21C. for 1 hour on pulp at 3.0% consistency.
El stage: 3.5% sodium hydroxide at 65C. for 1.5 hour on pulp at 12.0% consistency.
Dl stage: 1.0% chlorine dioxide at 70C. for 3 hours on pulp at 6~0% consistency.
E2 stage: 0.8% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
D2 stage: 0.3% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The pulp after the final chlorine dioxide stage had the following properties:
Brightness go,~
Viscosity 11.0 centipoise The stxength properties are shown in the Table. The combined effluents from the C-E-D-E-D bleaching sequence had the following properties:
Colour (p~ 7) 502 lb/ton of pulp Total organic carbon 53.3 lb/ton of pulp Chlorine ion 135 lb/ton of pulp It can be seen that by using the NO2-O-D-E-D rather than the C-E-D-E-D sequence there results a reduction of 96%, 70% and 90% in effluent colour, total organic carbon and chlorine ion respectively.
_ g _ :
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The softwood pulp of Example 1 was subjected to a NO2-O bleaching sequence as in Example 1 except that the nitrogen dioxide concentration was 1.5% on pulp. The bleached pulp had the following properties:
~appa number 8.0 Viscosity 18.6 centipoise The NO2-O treated pulp was bleached further by a C-E-D sequence with chemical charges and conditions as follows:
C stage: 1.6% chlorine at 21C. for 1 hour on pulp at 3.0% consistency.
E stage: 0.8% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
D stage: 0.7% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The bleached pulp had the following properties:
Brightness 88.5 Viscosity lS.l centipoise The strength properties are shown in the Table. The combined C-E-D effluent from the bleach plant had the following properties:
colour (pH 7) 60 lh/ton of pulp Total organic carbon 21.4 lb/ton of pulp Chlorine ion 34~8 lh/ton of pulp Thus reductions of 88%, 61% and 74% in colour, total organic carbon and chlorine ion respectively were realized by using the sequence NO2-O-C-E-D rather than the sequence C-E-D-E-D.
9~9 A hardwood (mainly oak species) kraft pulp having a Kappa number of 19.0 and a viscosity of 25.7 centipoise was bleached by the NO2-0 sequence using the same conditions as in Example 1 except that -Nitrogen dioxide 2.0% on pulp 0xygen treatment Temperature 130C.
; Time 15 minutes % sodium hydroxide 2.0 The NO2-O bleached pulp had the following properties:
: Kappa number 5.8 ~: :
: Viscosity 19.1 centipoise ~-~
The hardwood pulp bleached by the N02-O pa~tial sequence was bleached further by a D-E-D sequence with chemical charges and conditions as ollows:
Dl stage: 1.2% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
E stage: 0.6% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistencyO :
: D2 stage: 0.4% chlorine dioxide at 70C. for 3 hours : on pulp at 6.0% consistency.
The resulting bleached pulp had the following properties~
Brightness 89.4 Viscosity 16.8 centipoise The same hardwood kraft pulp of Kappa number 19.0 ~ :~
and viscosity 25.7 centipoise was bleached by a conventional : .
C-E-D-E-D sequ~nce. The chemical charges and conditions of the various stages were as follows:
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C stage: 3.6% chlorine at 21C~ for 1 hour on a pulp at 3.0% consistency.
El stage: 2.5% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
Dl stage: 0.7% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
E2 stage: 0.5% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
Dz stage: 0.28% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The bleached product had the following properties:
Brightness 88~6 Viscosity 18.2 centipoise The same hardwood kraft pulp of Example 3 having a Kappa number of 19.0 and a viscosity of 25.7 centipoise was subjected to a N02-0 bleaching sequence as in Example 3 except that -Nitrogen dioxide 1.5% on pulp Oxygen treatment Temperature 130C.
Time 15 minutes % sodium hydroxide 2.0 The bleached product had the following properties: - -Kappa number 6.0 Viscosity 19.8 centipoise The pulp bleached by the N02-0 partial sequence was bleached further by the sequence C-E-D.
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The chemical charges and conditions of the stages were as follows:
C stage: 1.24% chlorine at 21C. for l hour on pulp at 3.0% consistency.
E stage: 0.8% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
D stage: 0.5% chlorine dioxlde at 70C. for 3 hours on pulp at 6.0% consistency.
The bleached product had the following properties:
~rightness 88.8 Viscosity 16.5 centipoise E~MPLE S
A softwood (pine) kraft pulp of Kappa number 50 and viseosity 28 eentipoise was subjeeted to a N02-0 bleaching sequence as in Example l except that -Nitrogen dioxide 3.0% on pulp Oxygen stage Sodium hydroxide 3.0%
The bleached product had a Kappa number of 9.3 and a viseosity of 15.2 centipoise.
The product from the above N02~0 partial hleaching sequence was subjected to further bleaching by the sequence C-E-D. The chemical charges and conditions of the stages ~`
were as follows:
C stage: 1.9% chlorine at 21C. for 1 hour at a - pulp consistency of 3.0%.
E stage: 0.9% sodium hydroxide at 65C. for 1.5 hours at a pulp consistency of 12.0%.
D stage: 008% chlorine dioxide at 70C. for 3 hours at a pulp eonsistency of 6.0%.
7V~
The bleached product had the following properties:
Brightness 88.1 - Viscosity 13.7 centipoise The same softwood kraft pulp was subjected to a single stage oxygen treatment under conditions identical to those given above in this example. The resulting oxygen treated pulp had a Kappa number of 22.4 and a viscosity of 17.2 c~ntipoise.
Thus it can be seen that the N02-0 sequence in this case allows 58% greater delignification than 0 alone.
The pulp treated by the single oxygen stage was subjected to the additional bleaching sequence C-E-D. The chemical charges and conditions of the stages were as follows:
C stage: 4.6% chlorine at 21C. for 1 hour on pulp at 3.0% consistency.
E stage: 3.3% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
D stage: 1.4% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The bleached product had the following properties:
Brightness 86.5 Viscosity 14.5 centipoise It can be seen that in order to attain a similar level of brightness the bleaching sequence 0-C-E-D requires the use of substantially more chlorine and chlorine dioxide than the sequence N02-0-C-E-D.
- 14 _ : `
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)9~9 A softwood (spruce-balsam fir) soda pulp having a Kappa number of 93 was refined to fiberiæe the rejects and then subjected to a N02-0 partial sequence as in Example 1 except that - :
Nitrogen dioxide 6.0% on pulp Oxygen stage % sodium hydroxide 7.5 The bleached product had a Kappa number of 17.G
and a viscosity of 16~6 centipoise. ~:
The N02-0 bleached material was then subjected to the further bleaching sequence C-E-D. The chemical charges ~ .
and conditions of the stages were as follows:
; C stage: 3.2% chlorine at 21C. for 1 hour on pulp at 3.0% consistency.
E stage: 1.8% sodium hydroxide at 65C. for 1.5 hours ~
on pulp at a consistency of 12.0%. ~;;
D stage: 0.6% chlorine dioxide at 70C. for 3 hours on pu}p at a consistency of 6.0%. :
The bleached product had the following properties:
Brightness 85.8 Viscosity 16.7 centipoise The same softwood soda pulp was subjected to a single stage oxygen treatment under conditions identical to those given above in this example. The resulting oxygen-treated pulp had a Xappa number of 32.4 and a viscosity o~ 11.8 centipoise.
15 _ ' '. , :
~L~7~9~9 The above soda pulp treated by the sinyle oxygen stage was subjected to the additional bleaching sequences C-E-D. The chemical charges and conditions of the stages were as follows:
C stage: 6.1% chlorine at 21C. for 1 hour on pulp at a consistency of 3O0%.
E stage: 3.4% sodium hydro~ide at 65C. for 1.5 hours on pulp a~ a consistency lf 12.0%.
D stage: 0.8% chlorine dioxide at 70C. for 3 hours on pulp at a consistency of 6.0%.
The bleached product had the following properties:
Brightness 84.8 Viscosity 11.2 centipoise A mixed hardwoods kraft pulp of ~appa number 46 w~s refined to fiberize rejects and then subjected to a ~2-partial bleaching sequence as in Example 1 except that -~itrogen dioxide 3.0% on pulp .
Oxygen stage % sodium hydroxide 4.0 on pulp The resulting bleached product had the Kappa number 8.2 and viscosity of 25.1 centipoise.
The above bleached pulp was subjected to the additional bleaching sequence C-E-D. The chemical charges and conditions of the stages were as follows:
C stage: 1.6% chlorine at 21C. for 1 hour on pulp at 3.0% consistency.
: E stage: 0.9% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
, . . .
~7~
D stage: 0.4% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The resulting product had the foLlowing properties:
Brightnass 88.8 Viscosity 24.3 centipoise Overall pulping and bleaching yield - 51.1% on wood.
The strength properties of this pulp are shown in the Table.
The above mixed hardwood kraft pulp was subjected to a single stage oxygen treatment under conditions identical to those given above in this example. The resulting oxygen-treated pulp had a Kappa number of 15.8 and a viscosity of 29.9 centipoise. ~
The above kraft pulp treated by the single oxygen -stage was subjected to the additional bleaching sequence ; C-E-D. The chemical charges and conditions of the stages were as follows:
C stage: 2.9% chlorine at 21C. for 1 hour ~
on pulp at 3.0% consistency. -E stage: 1.6% sodium hydroxide at 65C. for 1.5 hours on pulp at 12.0% consistency.
D stage: 0.4% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The resulting bleachecl pulp had the following properties:
Brightness 89.0 Viscosity 20.7 centipoise Overall pulpins and bleaching yield - 51.4% on wood.
The strength properties are shown in the Table.
Another portion of the mixed hardwood chips used in this example was pulped to a Kappa number of 14.8 and bleached by _ 17 - `
.
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a conventional C E~D E-D sequence. The chemical charyes and conditions of the stages were as follows:
C stage: 3.1% chlorine at 21C. for 1 hour on pulp at a consistency of 3.0%~
El stage: 1.7% sodium hydroxide at ~5C. for 1.5 hours on pulp at a consistency of 12~0%~
Dl stage: 0.7% chlorine dioxide at 70C. for 3 hours on pulp at a consistency of 6.0%.
E2 stage: 0.5 sodium hydroxide at 65C. for 1.5 hours on pulp at a consistency of 12.0%.
Dz stage: 0.3 chlorine dioxide at 70C. for 3 hours at a consistency of 6.0%.
The bleached pulp had the following properties:
Brightness 89.4 Viscosity 28.3 centipoise Overall pulping and bleaching yield - 47.8% on wood.
Strength properties are given in the Table.
EXAMpLE 8 A softwood (mainly spruce species) kraft pulp of Kappa number 32 was subjected to a NO2-O partial sequence as in Example 2 but in distinction to said Example, a low consistency pulp was employed in the oxygen stage. The conditions of treatment were as follows:
~itrogen dioxide stage: 1.5% NO2 at 7SC. for 30 minutes on pulp at 40% consistency.
Oxygen stage: oxygen gas at 90 pounds per square inch pressure for 15 minutes at 130C. on pulp at 3.0% consistency containing 3.0% sodium hydroxide.
- læ -~7~
The product had the Kappa number of 9.8 and a viscosity of 23.1 centipoise.
The oxygen treated pulp was then fully bleached by a C-E~D sequence. The conditions and results were as follows:
C stage: 2.0% chlorine at 2LC. for 1 hour on pulp at 3.0% consistency.
E stage: 1.0% sodium hydroxide at 55C. for 1.5 hours ~ -on pulp at 12.0% consistency.
- 10 D stage: 0.6% chlorine dioxide at 70C. for 3 hours on pulp at 6.0% consistency.
The bleached product had the following properties:
Brightness 88.2 Viscosity 16.5 centipoise ':
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Claims (10)
1. A process for the deliynification of lignocellulosic material comprising the steps of 1) treating lignocellulosic material in aqueous medium with nitrogen dioxide, 2) washing the nitrogen dioxide-treated material with water, 3) treating the washed material in aqueous medium with alkaline material, and 4) treating the alkaline-treated material with oxygen or an oxygen-containing gas at supra atmospheric pressure.
2. A process as claimed in Claim 1 wherein the lignocellulosic material is treated in step 1) at a consistency of 3.0% to 50% by weight with 0.5% to 10.0%
by weight of nitrogen dioxide at 20°C. to 120°C. for a period of 5 to 60 minutes.
by weight of nitrogen dioxide at 20°C. to 120°C. for a period of 5 to 60 minutes.
3. A process as claimed in Claim 1 wherein the lignocellulosic material is treated in step 3) with 1.0%
to 20.0% by weight of an alkali or alkaline earth base.
to 20.0% by weight of an alkali or alkaline earth base.
4. A process as claimed in Claim 3 wherein in step 3) 0.1% to 1.0% by weight of magnesium ion is added to the lignocellulosic material.
5. A process as claimed in Claim 3 wherein the alkali base is sodium hydroxide.
6. A process as claimed in Claim 1 wherein the lignocellulosic material at a consistency of 3.0% to 35%
by weight is treated in step 4) with oxygen or an oxygen-containing gas at a partial pressure of oxygen of 30 to 200 pounds per square inch gauge at a temperature of 80°C. to 200°C. for a period of 10 to 60 minutes.
by weight is treated in step 4) with oxygen or an oxygen-containing gas at a partial pressure of oxygen of 30 to 200 pounds per square inch gauge at a temperature of 80°C. to 200°C. for a period of 10 to 60 minutes.
7. A process as claimed in Claim 1 wherein the oxygen-containing gas is air.
8. A process as claimed in claim 1 wherein the treatment defined therein is followed by additional treatment steps comprising in sequence a) treatment in aqueous medium with chlorine, b) extraction in aqueous medium with alkali base, and c) treatment in alkaline medium with chlorine dioxide.
9. A process as claimed in Claim 1 wherein the treatment defined therein is followed by additional treatment steps comprising in sequence a) treatment in aqueous medium with chlorine dioxide, b) extraction in aqueous medium with alkali base, and c) treatment in aqueous medium with chlorine dioxide.
10. A process as claimed in Claim 1 wherein the lignocellulosic material is wood pulp produced by the kraft or soda processes.
Priority Applications (12)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA251,752A CA1070909A (en) | 1976-05-04 | 1976-05-04 | Nitrogen dioxide-oxygen delignification |
| ZA00771424A ZA771424B (en) | 1976-05-04 | 1977-03-09 | Nitrogen dioxide-oxygen delignification |
| NZ183555A NZ183555A (en) | 1976-05-04 | 1977-03-09 | Nitrogen dioxide-alkali/oxygen treatment for lignocellulose delignification |
| AU23111/77A AU498646B2 (en) | 1976-05-04 | 1977-03-10 | Delignification |
| NO771297A NO771297L (en) | 1976-05-04 | 1977-04-14 | PROCEDURES FOR DELIGNIFICATION OF CELLULOSE MATERIAL USING NITROGEN DIOXIDE |
| DE19772717257 DE2717257A1 (en) | 1976-05-04 | 1977-04-19 | PROCESS FOR DEWESTING LIGNOCELLULOSE MATERIAL |
| BR7702713A BR7702713A (en) | 1976-05-04 | 1977-04-28 | PROCESS FOR DESIGNIFICATION OF LIGNOCELLULOSIC MATERIAL |
| FI771383A FI771383A (en) | 1976-05-04 | 1977-04-29 | |
| JP5003677A JPS52134690A (en) | 1976-05-04 | 1977-05-02 | Process for removing lignin from lignocellulose substance |
| SE7705136A SE7705136L (en) | 1976-05-04 | 1977-05-03 | PROCEDURE FOR DELIGNIFICATION OF CELLULOSA MATERIAL |
| FR7713425A FR2350421A1 (en) | 1976-05-04 | 1977-05-03 | Delignification of lignocellulose using nitrogen dioxide - and alkaline oxygen treatment to reduce pollution |
| ES458434A ES458434A1 (en) | 1976-05-04 | 1977-05-04 | Process for removing lignin from lignocellulose substance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA251,752A CA1070909A (en) | 1976-05-04 | 1976-05-04 | Nitrogen dioxide-oxygen delignification |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1070909A true CA1070909A (en) | 1980-02-05 |
Family
ID=4105864
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA251,752A Expired CA1070909A (en) | 1976-05-04 | 1976-05-04 | Nitrogen dioxide-oxygen delignification |
Country Status (12)
| Country | Link |
|---|---|
| JP (1) | JPS52134690A (en) |
| AU (1) | AU498646B2 (en) |
| BR (1) | BR7702713A (en) |
| CA (1) | CA1070909A (en) |
| DE (1) | DE2717257A1 (en) |
| ES (1) | ES458434A1 (en) |
| FI (1) | FI771383A (en) |
| FR (1) | FR2350421A1 (en) |
| NO (1) | NO771297L (en) |
| NZ (1) | NZ183555A (en) |
| SE (1) | SE7705136L (en) |
| ZA (1) | ZA771424B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4406735A (en) * | 1980-05-27 | 1983-09-27 | Mo Och Domsjo Aktiebolag | Process for alkaline oxygen gas bleaching of cellulose pulp |
| US4897156A (en) * | 1981-09-21 | 1990-01-30 | Mo Och Domsjo Aktiebolag | Process for activating cellulose pulp with NO and/or NO2 and oxygen in the presence of nitric acid and then delignifying bleaching the activated cellulose pulp |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE421938B (en) * | 1980-06-05 | 1982-02-08 | Mo Och Domsjoe Ab | PROCEDURE FOR TREATMENT OF CELLULOSAMASSA |
| SE445122B (en) * | 1980-12-17 | 1986-06-02 | Mo Och Domsjoe Ab | PROCEDURE FOR DELIGNIFICATION OF CELLULOSAMASSA IN THE PRESENTATION OF NITROGEN Dioxide |
| SE425674B (en) * | 1981-03-23 | 1982-10-25 | Mo Och Domsjoe Ab | PROCEDURE FOR DELIGNIFICATION OF CELLULOSAMASSA WITH NITROGEN Dioxide AND Oxygen |
| DE3118384C1 (en) * | 1981-05-09 | 1982-11-11 | Mannesmann AG, 4000 Düsseldorf | Process for bleaching chemically produced pulp with ozone |
| SE450394B (en) * | 1981-12-30 | 1987-06-22 | Mo Och Domsjoe Ab | PROCEDURE FOR BLACKING OF SIMILAR CELLULOSAMASSA |
| JP2002302888A (en) * | 2001-04-05 | 2002-10-18 | Oji Paper Co Ltd | Method of production for bleached pulp |
| FI20115754A0 (en) * | 2011-03-22 | 2011-07-15 | Andritz Oy | Process and arrangement for the treatment of chemical pulp |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1505070A (en) * | 1974-06-11 | 1978-03-22 | Canadian Ind | Process for bleaching of lignocellulosic material |
-
1976
- 1976-05-04 CA CA251,752A patent/CA1070909A/en not_active Expired
-
1977
- 1977-03-09 NZ NZ183555A patent/NZ183555A/en unknown
- 1977-03-09 ZA ZA00771424A patent/ZA771424B/en unknown
- 1977-03-10 AU AU23111/77A patent/AU498646B2/en not_active Expired
- 1977-04-14 NO NO771297A patent/NO771297L/en unknown
- 1977-04-19 DE DE19772717257 patent/DE2717257A1/en not_active Withdrawn
- 1977-04-28 BR BR7702713A patent/BR7702713A/en not_active IP Right Cessation
- 1977-04-29 FI FI771383A patent/FI771383A/fi not_active Application Discontinuation
- 1977-05-02 JP JP5003677A patent/JPS52134690A/en active Pending
- 1977-05-03 SE SE7705136A patent/SE7705136L/en unknown
- 1977-05-03 FR FR7713425A patent/FR2350421A1/en active Granted
- 1977-05-04 ES ES458434A patent/ES458434A1/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4406735A (en) * | 1980-05-27 | 1983-09-27 | Mo Och Domsjo Aktiebolag | Process for alkaline oxygen gas bleaching of cellulose pulp |
| US4897156A (en) * | 1981-09-21 | 1990-01-30 | Mo Och Domsjo Aktiebolag | Process for activating cellulose pulp with NO and/or NO2 and oxygen in the presence of nitric acid and then delignifying bleaching the activated cellulose pulp |
Also Published As
| Publication number | Publication date |
|---|---|
| ZA771424B (en) | 1978-02-22 |
| NO771297L (en) | 1977-11-07 |
| BR7702713A (en) | 1978-03-21 |
| FR2350421A1 (en) | 1977-12-02 |
| FI771383A (en) | 1977-11-05 |
| JPS52134690A (en) | 1977-11-11 |
| DE2717257A1 (en) | 1977-11-17 |
| NZ183555A (en) | 1978-11-13 |
| FR2350421B1 (en) | 1982-08-13 |
| SE7705136L (en) | 1977-11-05 |
| AU2311177A (en) | 1978-09-14 |
| AU498646B2 (en) | 1979-03-22 |
| ES458434A1 (en) | 1978-03-16 |
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