JPH05163690A - Preparation of kraft pulp - Google Patents

Abstract

PURPOSE: To obtain a paper pulp having optimum viscosity/kappa and/or pulp strength property with high yield by making two kinds of white liquor having different sulfur content, sending a high sulfur content white liquor into impregnation process and a low sulfur content white liquor into digester process. CONSTITUTION: A relatively low sulfur content white liquor and a relatively high sulfur content liquor are arranged in white liquor manufacture process 23. The high sulfur content liquor is introduced into an impregnation vessel 37 and is used to impregnate crashed cellulose fiber material. The low sulfur content white liquor is introduced into a digester can 12 and is used to digester crashed cellulose fiber material under digester condition in a digester zone to obtain kraft pulp.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention provides an improved process for producing kraft pulp and the like from finely ground cellulosic fibrous material using white liquor.

[0002]

2. Description of the Related Art In the pulp and paper industry, increasing the concentration of sulfide in white liquor for kraft pulp (that is, white liquor with high sulfur content) has made it possible to produce kraft pulp with high viscosity and excellent physical properties for many years. Has been known. It is also known that the beneficial effects of high sulfur content white liquor are more pronounced in the first stage than in the later stages of Kraft cooking. However, in the past there have been many technical and practical concerns and conditions that have hindered the practical use of these concepts. Similarly, it maximizes the known ability of polysulfides to stabilize carbohydrates and wood against degradation during the production of chemical pulp by oxidatively converting the reducing end groups of cellulose and hemicellulose into carboxyl groups. This was not done commercially (see US Pat. No. 2,944.928).

[0003]

According to the most particular embodiment of the present invention, in order to obtain a kraft pulp with an optimum viscosity / kappa ratio and / or good strength properties in good yield. In fact, the above concept is actually used. The present invention is applicable to a wide variety of different kraft cooking processes, whether batch or continuous. For example, the invention can be used in continuous digesters with percolation zones, in cooking systems with separate infiltration tanks from continuous digesters, or in batch digesters. You can The present invention is directed to those in which white liquor and pulp move in co-current or in counter-current (e.g. under the trademark "MCC", Kamyr, Inc. of Glens Falls, NY). ), Such as those used in commercial cooking processes marketed by)).

White liquor is a processing liquid in the Kraft process, and is an active cooking chemical, that is, sodium hydroxide (NaO).
H) and sodium sulfide (Na ₂ S). In extreme cases, white liquor may contain essentially only NaOH as the active agent. According to conventional methods, the content of cooking sulfur in white liquor is 25-35% (this overall sulfur content is the amount of sodium sulfide relative to the sum of sodium sulfide and sodium hydroxide used in the total cooking process. 15%, according to standard practice of the technology.
Lower sulfur concentrations result in reduced cooking rates as well as pulp quality. During the production of kraft pulp, the residual liquid containing the reaction product of lignin solubilization, that is, "black liquor", is extracted from the digester tank, concentrated, and burned in a recovery furnace to obtain sodium carbonate and sodium sulfide. The inorganic dry matter of is obtained. This dry matter becomes green liquor when dissolved, and when reacted with slaked lime (CaO), sodium carbonate changes to sodium hydroxide and is thus regenerated as the first white liquor.

It has been found by the present invention that the white liquor feed or stream is two (or more) feeds or streams having different sulfur contents, which are applied to different parts of the craft cycle. This means that significantly improved results can be obtained. In fact, most of the sulphide (at least about 60-90%, actually almost all of the sulphide) in the total amount of white liquor (the total amount of cooking chemicals) is used in the initial steps of the craft cycle (eg during infiltration) Add
On the other hand, it has been found that it is highly desirable to add white liquor consisting almost exclusively of sodium hydroxide in the latter stage (for example in cocurrent or countercurrent digestion). In practicing the present invention, for a given level of sulfur concentration, the viscosity of the produced pulp /
It is possible to optimize the kappa ratio and / or the pulp strength properties. The degree of this improvement is extremely remarkable, and it is easy to add about 25% to multi-stage white liquor addition (concurrent flow) to conventional cooking, and modified continuous cooking (Trademark: Modified Continuous Cooking (trademark:
MCC)) can be increased to the same extent as above, but an increase of 15% or more can be achieved for strongly deformed continuous cooking (Extended Modified Continuous Cooking (trademark: EMCC)). Improvements comparable to these are also made for batch processing.

[0006] When 2% (based on sulfur alone) of white liquor with respect to wood is contained in a white liquor, a yield equivalent to a kappa ratio of about 18 to 20 in conventional kraft cooking is obtained with a kappa ratio of about 12.5. A pulp having a viscosity comparable to conventional cooked kraft pulp with a Kappa ratio of about 26 is obtained.
Elemental sulfur (either dry powder or slurry) can be used in place of polysulfide. However, the effect of elemental sulfur is about 60 to 75% of that of polysulfide.

The exact source of sulfur used to obtain a stream or feed of high sulfur white liquor according to the present invention is
One non-critical, but exceptionally good source that can be used for real, industrial scale processes is that shown in U.S. Pat.No. 4,929,307, which is sulfuric acid. Heating salt-containing black liquor above the cooking temperature,
It decomposes macromolecular lignin and produces sulfur-containing exhaust gas. When these exhaust gases are reacted, they mainly turn into methane and hydrogen sulfide. Then, when these are contacted with white liquor (a small amount of sulfur) from an ordinary chemicals manufacturing device in a pulp mill, white liquor with a very high sulfur concentration is obtained. Can be generated. Hydrogen sulfide is selectively absorbed by the white liquor. Next, by effectively using the white liquor with such a high sulfur content,
At least a substantial portion of polysulfide can be produced and then used in the initial steps of kraft cooking.

According to one embodiment of the present invention, there is provided a method of producing kraft pulp from finely ground cellulosic fibrous material using white liquor. This method includes the following steps. That is, (a) at least two types of white liquor streams are produced. The second stream should have a relatively low sulfur content. The first stream should have a relatively high sulfur content, which is considerably higher than the sulfur content of the second stream.
(b) The finely crushed cellulosic fiber material is impregnated with the first-stream white liquor. (c) In the cooking zone, finely crushed cellulosic fibrous material is cooked under cooking conditions with a cooking chemical for kraft pulp production. (d) A second stream of white liquor is fed to the digestion zone as a cooking chemical. Then, (e) the produced kraft pulp is washed.

According to another embodiment of the present invention, there is provided a kraft pulp manufacturing method including the following steps.
That is, (a) the slurry of the cellulosic fiber material is treated with white liquor in a plurality of continuous steps. There is at least a first step and a second step, the first step is the first supply of white liquor,
A second feed of white liquor is used for the second step. (b) In at least one stage of the above step, the material treated with the white liquor is brought to a cooking condition and kraft cooked to produce black liquor. (c) Recover sulfur from black liquor. And (d) adding the recovered sulfur to the white liquor first stream to increase its sulfur content, making the sulfur content of the first stream greater than that of the second feed stream.

According to still another embodiment of the present invention, there is provided a kraft pulp manufacturing method including the following steps. That is, (a) in the first step, the cellulosic fiber material is treated with the first feed stream of white liquor. (b) Treating the fibrous material with a second feed stream of white liquor in the second step. And
(c) Control the relative sulfur content of the first and second feeds of white liquor to optimize the viscosity / kappa ratio and / or physical strength properties of the resulting kraft pulp.

Although the present invention is described herein primarily with respect to kraft cooking, the present invention has a broader scope. According to a broader aspect of the invention, the agent which promotes the lignin reaction or which delays the degradation of carbohydrates can be one or more parts of the digestion, such as permeation, co-current processes,
Introduced into the countercurrent process. Therefore, the present invention can be applied not only to white liquor for kraft pulp, but also to sulfite cooking liquor (including a cationic base), anthraquinone, an anthraquinone derivative, or the like. Anthraquinone can replace all or part of the sodium sulfide in the NaOH-containing cooking liquor, or it can be used in other liquor compositions.

According to the broadest embodiment of the present invention,
There is provided a method of treating finely crushed cellulosic fiber material with a cooking liquor to obtain cellulosic pulp. This method includes the following steps. That is, (a) at least a first cooking liquor and a second cooking liquor are provided. The first cooking liquor contains a first concentration of an agent that promotes a lignin reaction or an agent that delays carbohydrate degradation, and the second cooking liquor contains a second concentration of an agent that promotes a lignin reaction or an agent that delays carbohydrate degradation. The second concentration is in the range of zero or less than the first concentration. (b) The finely crushed cellulosic fibrous material is cooked in several cooking steps. (c) The first cooking liquor is introduced into the cooking process of one or more (but less than the total) stages to provide the cooking liquor of one or more stages. And (d) the second cooking liquor is used in at least one cooking step in which the first cooking liquor is not used.

The cooking liquor used above may be a Kraft cooking smelt, a sulfite cooking liquor, or any other similar cooking liquor. The liquid may contain a cationic base, sodium sulfide, anthraquinone or a derivative thereof, or an equivalent product. Further, the first cooking liquor may be introduced into the infiltration step, the co-current cooking step, or the countercurrent cooking step.

The main object of the present invention is to provide a significantly improved cooking process for the production of paper pulp. This and other objects of the invention will be apparent upon examination of the following detailed description of the invention and the appended claims.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows an exemplary apparatus used in the Kraft pulp making process. However, the present invention is also applicable to other methods of making paper pulp from comminuted cellulosic fibrous material. In these methods, the agent that promotes the lignin reaction or the agent that delays carbohydrate degradation is incorporated into one or more parts of the cooking process, such as a permeation, co-current process,
Introduced into the countercurrent process.

In a typical kraft pulp making process as shown in FIG. 1, a digester 12 (a continuous digester such as the one sold by Kamaya Co. of Glens Falls, NY) is preferred, but a batch digester is also acceptable. There is a line that emits exhaust gas 13, and black liquor (white liquor residue containing reaction products of lignin solubilization) is withdrawn from an intermediate position indicated by 14, and the kraft pulp produced is 15
Taken out of. When discharging the black liquor in line 14,
It may be sent directly to the black liquor evaporator, but it is preferable to send it to the heat treatment process of step 17 to generate the exhaust gas in line 18 somewhere in the evaporator chain circuit. The heat treatment of block 17 is preferably that described in US Pat. No. 4,929,307. After the heat treatment at 17, the black liquor is sent to the evaporator group 19 (it is possible to concentrate the black liquor before the heat treatment 17 in another evaporator group), and the exhaust gas is also discharged from the line 20. The black liquor is further sent to a conventional recovery boiler 22 and white liquor reduced in sulfur in the conventional white liquor production process in block 23 is produced in line 24.

Exhaust gas in line 18 (exhaust gas from heat treatment 17 only, from evaporator line 13 only, from black liquor evaporator in line 20, or from two of these) (Including the case of combining
It is first subjected to a drying or absorption step (abbreviated as 27 in FIG. 1) to remove most of the water vapor. Removal of water vapor increases the concentration of organic sulfur gas. Process
27 is capable of drying the gas stream by conventional means and / or absorbing or adsorbing the organic portion of the exhaust gas into solids, or additionally absorbing the gas in a non-polar liquid (eg kerosene or mineral oil). It is achieved by doing. The subsequent treatment can be carried out in the state of a liquid mixture, but according to the present invention it is preferably carried out in the state of a concentrated gas.

The next step of the exhaust gas treatment shown in FIG.
Adding hydrogen and then flowing gas through the hydrodesulfurization catalyst in the presence of added hydrogen. This is, for example, hydrodesulfurization (H
DS) achieved in unit 28, hydrogen gas from line 29 is added to unit 28 with the gas in line 18. line
The 29 hydrogen gases may come from any source (eg purchased as a product or electrolyzed of water). The hydrodesulfurization catalyst preferably consists essentially of a transition metal-molybdenum alloy, especially a nickel molybdenum or cobalt molybdenum alloy.

Typically in gas processing, the line
The 30 product gas streams are further processed. The gas stream in line 30 contains primarily methane and hydrogen sulfide, with hydrogen also present. Preferably, this hydrogen sulfide is then separated from the gas in stream 30. The hydrogen sulfide may be separated as a gas and then used in its gaseous form in conventional pulp processing techniques, although it may be fed to the scrubber 32. In this wash tower, the gas is contacted with a caustic liquor, preferably a Kraft white liquor. The white liquor contains sodium hydroxide, and most often some sodium sulfide. Although white liquor is used in the preferred embodiment shown in the drawings, there are situations in which it is advantageous to use green liquor. In this case the white liquor will later be made from the green liquor.

The white liquor from line 24 flows into the inlet 33 of the scrubbing tower 32 and hydrogen sulphide is absorbed in the white liquor, thus significantly increasing the sulfur content. The white liquor with a significantly increased sulfur content then enters line 35 through outlet 34 of the wash tower and is used in the pulp treatment process. Preferably, the white liquor in line 35 is passed through a polysulfide treatment step as shown at 36 and then sent to a permeation tank 37 (if a separate permeation tank is used) or a similar tank for use in the pulp treatment cycle. To be done. Elemental sulfur may be added at 36 instead of polysulfide. The gas stream remaining in line 38 contains mainly methane but also some hydrogen. line
The gas of 38 can also be the source of hydrogen for line 29.

In the case of the present invention, the high-sulfur sulfur-containing white liquor in line 35 is used at an early stage of the cooking, for example at the beginning of the infiltration tank 37, or if infiltration takes place in the digester 12 itself. It is introduced in the infiltration step or at multiple points in the infiltration zone and / or tank 37. It is also possible to carry out the permeation countercurrently, in which case the high-sulfur sulfur-containing white liquor is added near the end of the permeation process. A portion of the white liquor depleted of sulfide in line 24 flows to line 41 and is then introduced into the digester, which is preferably a plurality of points as indicated by 42 and 43 in FIG. ..

According to the present invention, the place where the low-concentration sulfur-containing white liquor in the line 41 is introduced into the kraft cooking process can be various places. For example, one, two, or more co-current stages in the digester 12, or one, two, or one in a digester (eg, a digester for modified continuous cooking or strongly deformed continuous digestion) 12. In the above countercurrent stage, this can be added to the middle stage of the permeation tank 37. Of course, the liquid in line 41 can also be used in the batch method.

Although only two white liquor feeds or streams having different sulfur concentrations are shown in the drawings, 35 and 41, multiple streams of different sulfur concentrations can be made if desired. For example, two devices 32 connected in series can be used. The first device produces white liquor with the highest sulfur concentration, and the second device produces white liquor with a medium sulfur concentration (intermediate between those corresponding to lines 35 and 41). The white liquor of intermediate sulfidity is added to the digester prior to the white liquor in line 41.

The relative amount of sulfur concentration in the white liquor added at various stages within the Kraft process cycle can be varied in the present invention. For example, if the kraft pulp treatment is carried out in multiple stages of conventional cooking,
That is, when it is added to two or more places in the digester and flows in parallel with the pulp, about 60% of the total cooking chemical is added to the infiltration tank (for example, to line 35) and about 25% is added to the first cocurrent. It is added to the stage (eg at 42) and about 15% is added to the second co-current stage (eg at 43). Line 35 for this procedure
It is preferred that the amount of sulfide fed to is about 60-90% of the total sulfide in the total white liquor, and practically about 100%. That is, the white liquor of stream 41 is substantially sulfide-free. The flow in line 35 for this embodiment can be made by passing 35-65% of the total volume of white liquor through device 32. The remaining 65 ~ of white liquor
35% is added through line 41. According to another embodiment, about 35% of the total volume of white liquor is passed through device 32, and then this high sulfur content white liquor is added to the top circulation of conventional permeation tank 37. The low sulfide white liquor in line 41 is added to the intermediate circulation of tank 37, the amount of which is about 25 to about 25% of the total cooking chemical of white liquor.
35%, while about 20-25% of the total cooking chemical in the low sulphide white liquor in line 41 is added to the first digester cycle of continuous digester 12. Low sodium sulfide liquid in line 41 is also 44
Oxygen delignification or bleaching step 45 can be added at this location as a source of sodium hydroxide.

When the white liquor containing multiple concentrations of sulfides of the present invention is used in a modified continuous cooking or a strongly modified continuous cooking process, the viscosity / kappa ratio is such that almost all the amount of sulfide enters the permeation process (eg line 35). To tank 37) increases by about 0.2 to 0.3 units. Preferably,
At least about 60% (eg 60-90%) of the total sulfur content is added to the infiltration step (line 35). The total volume of white liquor added to line 35 is about 40-65% of the total volume of white liquor used in the pulp treatment process.

In step 36, polysulfide is added to the white liquor. For example, this is done by the Moxy (NOXY ™) method or other known polysulfide method where most of the sodium sulfide in the white liquor is partially oxidized to form polysulfide. Alternatively, step 36 may simply introduce polysulfide into the white liquor from an external source. For example, polysulfides are produced by reacting elemental sulfur with sulfide ions in an aqueous solution under suitable conditions. Alternatively, elemental sulfur can be added to the white liquor instead of polysulfide.

The amount of polysulfide produced or added in the step 36 is about 0.5 to the wood based on the elemental sulfur.
8%. Typically, about 2% polysulfide is desired. When 2% polysulfide is used in the severe deformation continuous cooking, it is possible to obtain kraft pulp with a kappa value of about 12.5, a viscosity of about 33.7 cp, and a yield of about 44.6%.
This yield is equal to the yield of a conventional cooking process or a high-deformation continuous cooking process with a Kappa value of about 18 to 20 without using polysulfide, and its viscosity is a conventional cooking process with a Kappa value of 26, or It is equal to the viscosity of the strong deformation continuous cooking process with a Kappa value of 17. When an amount of elemental sulfur corresponding to about 0.5-8% polysulfide is used, about 60-75% results with polysulfide are obtained.

With the apparatus schematically illustrated in the drawings, various methods can be implemented in accordance with the present invention. One of them is as follows. (a) Make two (or more) streams 35, 41 of white liquor.
The first stream (35) has a relatively high sulfur content and the second stream (41)
Has a relatively low sulfur content (sometimes close to zero). (b) The first stream 35 is infiltrated (eg in tank 37) into comminuted cellulose fiber material (eg wood chips). (c) This fibrous material is digested with cooking chemicals (sodium hydroxide and sodium sulfide in white liquor) in a cooking zone (in tank 12) under Kraft cooking conditions to produce Kraft pulp. (d) The second stream 41 of white liquor is supplied as a cooking chemical to the digestion zone (eg, digester 12). (e) Wash the kraft pulp (eg, in the wash zone in digester 12 and / or in a separate wash tank).

According to another aspect of the present invention, a slurry of wood chips has different sulfur contents in a plurality of sequential steps (eg, infiltration step, first and second cocurrent or countercurrent digestion step). Treated with first and second feed white liquor.
The wood chips are treated with white liquor under cooking conditions (eg, in the digester 12) in at least one step to perform their kraft cooking. Black liquor is withdrawn (at 14) and sulfur is recovered from the black liquor. At this time
It is heat treated (at 17) according to the method of 4,929,307, an evaporation operation is performed (at 19) and other steps (see 22 and 23 in FIG. 1) are performed. The recovered sulfur is added to the first feed of white liquor, as seen in apparatus 32, significantly increasing its sulfur content, with the result that the sulfur content of the liquor in line 35 is Significantly higher than that of the liquid in 24 (which has less sulfur and in some cases may be close to zero). The relative sulfur content of the white liquor in lines 35 and 24 is adjusted to optimize the viscosity / kappa ratio and / or physical strength properties.

The present invention makes it possible to carry out production of kraft pulp on an industrial scale while performing complete chemical recovery. By the way, the industrial scale is the scale at which production in the laboratory is more than reasonable.

The present invention can be described using various embodiments. Shown in Tables 1-5 are according to the invention:
Results of a lab-scale batch cooking with two white liquor streams with different sulfur contents, a conventional cooking is also shown for comparison. In these tables, "CK" means conventional kraft cooking, "MCK" means kraft cooking with white liquor introduced from a plurality of locations, and having two or more co-current cooking steps. "MCC" means the modified continuous cooking process (the white liquor is introduced from multiple points and has a countercurrent cooking process) which is the trademark of Kamaya, and "EMCC" is the trademark of Kamaya. Means a strong-deformation continuous cooking method (having a second countercurrent cooking step).

Table 6 shows the advantages of using polysulfide. For the cooks in Table 6, the liquor / wood ratios are all 4/1. "Sulfidity" means sodium sulfide content. The wood used in Tables 1-5 and Table 6 are all Southern Pine in the Mississippi region. However, these results are applicable to a wide range of tree types.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

[0036]

[Table 4]

[0037]

[Table 5]

[0038]

[Table 6]

As can be seen from the above examples, the process according to the invention optimizes the viscosity / kappa ratio and / or the strength properties of the produced kraft pulp, with further advantageous results. The yield is also significantly increased by using polysulfide or simple substance of sulfur as a part of the sulfide content of the white liquor.

Although the above tables describe the cooking and white liquor of the Kraft process, the invention is applicable to other cooking processes and cooking liquors for the production of paper pulp.
When a sulfite cooking liquor is used, and when an agent that promotes another lignin reaction or an agent that delays carbohydrate degradation, such as anthraquinone or a derivative or equivalent thereof, is used, one cooking liquor is used at a specific stage of the cooking process. Introducing into (including multiple stages) and using another cooking liquor in the part of the other stages can significantly increase the viscosity / kappa ratio or strength properties.

In general, the present invention provides a method for treating cellulosic fibrous material with a cooking liquor to obtain cellulosic pulp in the following steps. That is, (a) at least the first and second cooking liquors are prepared. The first cooking liquor contains a first concentration of an agent that promotes a lignin reaction or an agent that delays carbohydrate degradation (eg, in line 35), and a second cooking liquor contains an agent or carbohydrate that promotes a lignin reaction. It contains a second concentration of drug that delays degradation (eg, in line 41), which is a concentration that is much less than zero to the first concentration. (b) The crushed cellulose fiber material is cooked in several cooking steps (for example, in tanks 12 and 37).
(c) The first cooking liquor is introduced into the cooking process of one or more stages (however, less than the total number) to prepare cooking liquor for one or more stages (for example, co-current flow in tank 37). To the infiltration stage). And (d) the second cooking liquor is used in at least one cooking step in which the first cooking liquor is not used (for example, by introducing it into a cocurrent or countercurrent cooking stage at 42,43).

The preceding is a description and description of what is presently considered to be the most practical embodiment of the invention.
Those skilled in the art will appreciate that many variations are possible within the scope of the invention. Therefore, the scope of the present invention should be construed to include all equivalent methods and procedures by maximizing the scope of the claims.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an exemplary apparatus for implementing the exemplary method of the present invention.

[Explanation of symbols]

10 devices, 12 digesters, 13,14,15,18,20,24,29,30,35,3
8,39,41,42,43 lines, 17 heat treatment process, 19 evaporator, 22 recovery boiler, 23 white liquor production process, 27 drying or absorption process, 28 hydrodesulfurization equipment, 32 washing tower, 33 inlet, 34 outlet, 36 Polysulfide treatment process, 37 Infiltration tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Joe Earl Phillips United States, 12801-3686, Glens Falls, New York, Ridge Center (no address) in Kamaya Inc. (72) Inventor Brian F Greenwood United States, 12801-3686, Ridge Center, Grens Falls, N.Y., Ridge Center, Kamaya Incorporated (72) Inventor J. Robert Plough, United States, 12801-3686, Ridge Center, Grens Falls, N.Y. Kamaya Incorporated (72) Inventor Car Henrickson, United States, 12801-3686, New York, Lens Falls, Ridge Center (no house) in Kamaya Incorporated (72) Inventor Birchley Stromberg United States, 12801-3686, Glens Falls, New York, New York, No. House in Kamaya Incorporated (72) invention James W Smith, Canada, M58 1A4, Toronto, Ontario, University of Toronto (72) Inventor Rolf Leyham United States, 30077, Georgia, Rothwell, Mansell Court 30

Claims (10)

[Claims] 1. A kraft pulp from cellulosic comminuted fibrous material is prepared using white liquor by impregnating the pulp with white liquor, then cooking it under kraft cooking conditions and then washing it. In the method of manufacturing, the following steps are taken: (a) a second stream having a relatively low sulfur content and a relatively high sulfur content, substantially higher than the sulfur content of the second stream. Making at least two types of white liquor streams, including a first stream having a sulfur content, (b) allowing the first stream of white liquor to penetrate the comminuted cellulosic fibrous material, and (c) the first stream of white liquor. A craft characterized in that it comprises a step of producing a kraft pulp by digesting the finely ground cellulosic fiber material with a cooking chemical under cooking conditions in the cooking zone while supplying a second stream to the cooking zone as the cooking chemical. Pulp manufacturing method. 2. When carrying out steps (a) to (c),
A process according to claim 1, characterized in that about 60% of the total cooking chemical is added to (b) and about 40% to step (c). 3. The method according to claim 1, wherein the steps (a) to (c) and the washing step are continuously performed. 4. The steps (a)-(c) are carried out such that the first white liquor contains sodium sulfide and about 60-90% of the sodium sulfide from the white liquor is added to step (b). The method of claim 1 wherein the second stream of white liquor is substantially free of sodium sulfide. 5. The method of claim 1 wherein the sulfide in the first stream of white liquor contains about 0.5 to 8% polysulfide or elemental sulfur on wood based on elemental sulfur. 6. A method for producing kraft pulp by cooking crushed cellulosic fibrous material with white liquor to produce kraft pulp and black liquor, comprising the following steps: (a) at least The cellulosic fiber material slurry is treated with a white liquor in a plurality of continuous steps including one step and a second step, and the first step of the white liquor is performed in the first step, and the white step is performed in the second step. Using a second supply of liquid,
(b) In at least one stage of the above step, the material treated with white liquor is subjected to cooking conditions to carry out kraft cooking to produce black liquor, (c) sulfur content is recovered from the black liquor And (d) adding the recovered sulfur to the first feed stream of white liquor to increase its sulfur content and making the sulfur content of the first stream higher than that of the second feed stream. A method for producing kraft pulp, which is characterized by the above. 7. A method of producing kraft pulp using white liquor, comprising the following steps: (a) a first step of treating a cellulosic comminuted fibrous material with a first feed stream of white liquor. , (B) a second step of treating the fiber material with a second feed stream of white liquor, and (c) controlling the relative sulfur content of the first and second feed streams of white liquor. And a step of optimizing the viscosity / kappa ratio and / or the physical strength characteristics of the produced kraft pulp. 8. A method for producing cellulose pulp on an industrial scale using a cooking liquor, which comprises the following steps:
(a) a step of producing two types of cooking liquor, which is a cooking liquor having a high content of a sulfite drug and a cooking liquor having a low content of a sulfite drug, (b) at least two of the above two different liquids A step of treating the cellulose fiber material in different steps, and
(c) A method for producing cellulose pulp, comprising a step of recovering a cooking chemical after the treatment in two different steps and using the recovered chemical for carrying out the step (a). 9. A method for treating a pulverized cellulosic fiber material with a cooking liquor to obtain cellulosic pulp, comprising the following steps:
That is, (a) providing at least a first cooking liquor and a second cooking liquor, the first cooking liquor contains a first concentration of a drug that promotes a lignin reaction or a drug that delays carbohydrate decomposition,
The second cooking liquor contains a second concentration of an agent that promotes a lignin reaction or an agent that delays carbohydrate degradation, and the second concentration is in the range of zero or less than the first concentration. , (B) a step of cooking the crushed cellulose fiber material in several stages of cooking, (c) introducing the first cooking liquor into the cooking process of less than the total number of stages in one or more stages, and Or a step of providing as a cooking liquor of a greater number of stages, and (d) a step of using the second cooking liquor in at least one step of the cooking step in which the first cooking liquor is not used. Manufacturing method of cellulose pulp. 10. An agent which promotes a lignin reaction or an agent which delays carbohydrate degradation is selected from the group consisting essentially of anthraquinone or a derivative or equivalent thereof, sodium sulfide, and a cationic base. The method of claim 9.