JP2971111B2 - Cooking method for lignocellulosic material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for cooking lignocellulosic materials, and more particularly, to the modification of alkaline cooking of lignocellulosic materials by adding a cyclic keto compound (cyclic keto compound-based cooking aid). It relates to alkaline cooking.

[Conventional technology]

The mainstream of industrial pulp production methods from lignocellulosic materials such as wood, which has been conventionally industrially performed, is an alkaline cooking method using an alkaline cooking liquor, and in particular, a kraft method (sodium sulfate) using a sodium sulfide-containing cooking liquor. Law)
Has been implemented on a large scale because of the balance between pulp strength, pulp yield, and ease of recovery of chemicals in pulp production.

In recent years, A. Hartler of the Royal University of Technology in Sweden (KTH) and A. Teder of the Forestry and Forestry Research Institute (STFI) aim to improve the problems of the alkaline cooking method, especially the kraft method, for example, to improve the demand for further improvement in pulp strength. Suggest the possibility of reducing residual lignin while maintaining the viscosity of unbleached pulp [Svensk Papperstidn., 81 (15), 483 (197
8), Tappi, 62 (7), 49 (1979)]. The alkaline cooking method having delignification selectivity is generally called a modified alkaline cooking method (hereinafter sometimes referred to as an MCC method).

And this modified alkaline cooking method, in the permeation vessel, and in each digester zone of the digester, always replenish fresh cooking liquor, optimize the alkali concentration, carry out co-current cooking and countercurrent cooking inside the digester In other words, in other words, the point at which the alkali concentration in the infiltration vessel (infiltration stage) is lowered by circulation of the infiltration liquid, and in the cooking liquor at the end of cooking by countercurrent cooking (that is, used cooking liquor ...)
・ Black liquor) has the characteristic of lowering the alkali concentration, and the pulp obtained has a viscosity of more than 100 cP compared to the conventional digestion when measured at the same kappa number in the MCC method. What can be obtained, in other words, 5-7 points of N-wood (coniferous) and L-wood (hardwood) in the copper value after cooking without loss of pulp strength and viscosity
In this case, it is possible to pulverize by 3 to 4 points lower, and it is known that the merit of this MCC method is maintained in the subsequent bleaching step. (See Pulp and Paper Times, August 1990, pp. 55-59.) The modified alkaline digestion is described below with reference to the schematic diagram using a two-reactor continuous digester shown in FIG. The lignocellulosic material, specifically wood chips 1, is fed to a pressurized chip bin 2, heated and degassed in a steaming vessel 3, and then fed by a high-pressure feeder 4 through a conduit 5 to the top of an infiltration vessel 6. You. On the other hand, the main branch stream of the cooking liquor supplied from an alkaline cooking liquor (hereinafter referred to as cooking liquor) conduit 17 is supplied to the top of the permeation vessel 6 through a conduit 18. In the high-pressure feeder 4 the wood chips and the extract flowing in the extract conduit 7 from the top of the permeation vessel 6 are mixed, and this mixture is then fed through the conduit 5 to the top of the permeation vessel 6. The wood chips filled at the top of the infiltration vessel 6 descend together with the cooking liquor, during which a delignification reaction is partially started.

A strainer 39 is provided at an intermediate portion of the permeation vessel 6, and an extract from the strainer 39 is supplied to an extract conduit 40.
To the vicinity of the strainer 39 inside the infiltration vessel 6. The wood chips and the cooking liquor that passed through the strainer 39 reached the bottom of the permeation vessel 6 and
Is fed to the top of the digester body 8 through a transfer circulating fluid outgoing conduit 37 installed from the bottom of the digester 8 to the top of the digester 8. On the other hand, the cooking liquor branched from the cooking liquor introduction pipe 17 passes through a cooking liquor branch pipe 19, further branches and passes through a cooking liquor branch pipe 20, and is provided from the top of the digester 8 to the bottom of the permeation vessel 6. The circulating fluid 22 flowing through the circulating fluid return conduit 36 is combined with the circulating fluid 22 and supplied to the bottom of the permeation vessel 6. The heater 16 is installed in the middle of the transfer circulating fluid return line 36, and the heater 16 is heated by the medium-pressure steam 35 and the circulating fluid 22 is heated.

The digester main body 8 is roughly divided into four zones (zones) having different functions from the top to the bottom: an upper digestion trim zone A, an upper digestion zone B, a lower digestion zone C, and a washing zone D. A strainer 9 is provided at the boundary between the upper cooking trim zone A and the upper cooking zone B, a strainer 10 is provided at the boundary between the upper cooking zone B and the lower cooking zone C, and a lower cooking zone C and the washing zone are provided. A strainer 11 is provided at the boundary of D, and a strainer 12 is provided below the washing zone D, that is, near the bottom of the digester 8.

The extract extracted from the strainer 9 installed in the lower part of the upper digestion trim zone A passes through the extract conduit 38 and the transfer circulating liquid return conduit 36 provided from the top of the digester 8 to the bottom of the permeation vessel 6. Combined with the flowing circulating fluid 22.

The partially delignified wood chips descending from the digestion trim zone A enter the upper digestion zone B, where the wood chips are co-digested and the delignification reaction proceeds. The digested black liquor extracted from the strainer 10 provided in the lower part of the upper digestion zone B is transferred to the recovery step (not shown) through the extracted black liquor conduit 30.

The wood chips that have advanced from the upper digestion zone B and have undergone some delignification (digestion) are then converted to the lower digestion zone C.
And in this zone, the wood chips that have undergone delignification are subjected to countercurrent cooking,
The delignification reaction proceeds further. This lower cooking zone C
In the strainer installed at the bottom of this zone
The extract extracted from 11 is combined with the cooking liquor flowing through the branch pipe 21 further branched from the cooking liquor branch pipe 19 in the extract liquid conduit 24, and supplied by the medium pressure steam pipe 33 by the heater 14 provided in the flow path. Heated by medium-pressure steam. This circulating liquid is supplied via a circulating liquid conduit 27 in the lower part of the lower cooking zone, near the strainer 11. In this zone, the wood chips that have undergone delignification to some extent descend from the lower part of the strainer 10 toward the upper part of the strainer 11, during which time the cooking liquor supplied from the circulating fluid conduit 27 near the strainer 11 was replenished. The circulating liquid rises toward the strainer 10, and the delignification reaction proceeds further by the countercurrent cooking. strainer
The circulating liquor rising toward 10 becomes used cooking liquor, that is, black liquor, is mixed with the black liquor in the upper cooking zone B, and is transferred to the recovery step (not shown) through the extraction black liquor conduit 30. You.

The wood chips that have undergone further delignification by the countercurrent cooking in the lower cooking zone C descend into the washing zone D below the strainer 11. In this zone, the washing liquid introduced through the washing liquid conduit 29 at the bottom of the washing zone D, just above the bottom of the digester 8 rises towards the strainer 11. On the other hand, the extract extracted by the strainer 12 passes through the extract liquid conduit 25, and is heated by the medium-pressure steam supplied by the medium-pressure steam pipe 34 to the heater 15 installed in the flow path and washed through the circulating liquid conduit 28. The circulating liquid supplied near the strainer 12 provided at the lower part of the zone D is combined with the washing liquid supplied by the washing liquid conduit 29 and rises toward the strainer 11 to finish the delignified wood in this zone. The chips (pulp) are countercurrently washed. The washed pulp is sent through a cooking pulp discharge pipe 31 to a washing machine (not shown). In the steaming vessel 3, the pressure is 0.5 to 2.0 kg / cm ² (gauge pressure), and the temperature is 110 ° C to 130 ° C.
And the top pressure in the permeation vessel 6 is 12.0 to
14.0kg / cm ² (gauge pressure) temperature is about 110 ~ 130 ℃,
The partially delignified wood chips from the seepage vessel 6 have a kappa number of about 100 to 160.

In the digester body 8, the temperature in the upper digestion trim zone A is 145 to 165 ° C., and the upper digestion zone B
In the lower digestion zone C, the temperature is 150-170 ° C.
In the washing zone D, the circulating fluid extracted from the strainer 12 is heated by the heater 15, and the circulating fluid flowing through the circulating fluid conduit 28 is heated to 140 to 150 ° C.

The top pressure of the main body of the digester 8 is generally maintained at 10 to 13 kg / cm ² (gauge pressure). The temperature of the pulp discharged through the cooking pulp discharge pipe 31 is maintained at 75 to 95 ° C. The temperature of the black liquor discharged from the extraction black liquor conduit 30 is maintained at 150 to 170 ° C. Cooking liquid introduction pipe 17
Is supplied to the top of the permeation vessel 6 by the branch pipe 18 and to the bottom of the permeation vessel 6 by the branch pipe 20 of the branch pipe 19. The cooking liquor supplied by the branch pipes 18 and 20 is finally combined with the wood chips passing through the transfer circulating liquid outflow conduit 37 and fed to the top of the digester 8. Further, the cooking liquor flowing through the other branch pipes 21 of the branch pipes 20 of the branch pipes 19 is supplied to the lower cooking zone C at a lower portion, near the strainer 11, by a conduit 24, a heater 14,
It is supplied through a circulating fluid conduit 27.

Assuming that the cooking liquor supplied from the cooking liquor introduction pipe 17 is 100, the distribution ratio of the cooking liquor is 50 to 90% to the branch pipe 18, and
9 is supplied 10-50%. The cooking liquor introduced into the branch pipe 19 is further distributed by 5 to 45% by the branch pipe 20 and 5 to 45% by the branch pipe 21. As a result, 50 to 90% of the cooking liquor introduced from the cooking liquid introduction pipe 17 is obtained. % Of the cooking liquor is fed to the permeation vessel 6 via the inlet pipe 18, and 5 to 45% of the remaining 50 to 50% of the cooking liquor are fed to the upper cooking trim zone A via the inlet pipe 19, and 5 to 45% of the cooking liquor % Is generally supplied to the lower digestion zone C in a decomposed state.

FIG. 3 shows another embodiment of the modified alkaline cooking method. The difference from FIG. 2 is that the strainer 39 in the infiltration vessel 6 is used.
The extraction liquid conduit 40 through which the extraction liquid flows from the cooking liquid branch pipe 19
The cooking liquor introduced by the branch pipe 42 is introduced, the cooking liquor is not introduced into the transfer circulating liquid return line 36, and the extraction from the strainer 9 installed below the upper cooking trim zone A. The liquid is an extract conduit
23, is heated by the medium-pressure steam supplied by the medium-pressure steam pipe 32 by the heater 13 provided in the flow path, and supplied to the lower part of the upper digestion trim zone A and the vicinity of the strainer 9 through the circulating liquid conduit 26. And the extract is not combined with the circulating fluid flowing through the transfer circulating fluid return conduit 36.

Although FIGS. 2 and 3 show embodiments in which a washing zone D is provided inside the digester, this washing zone can be provided outside the digester 8 if necessary. Needless to say.

Since the above modified alkaline digestion method is composed of an infiltration vessel and a digester, it is generally used in a two-reactor continuous digester (TWO Vessel Type Continuo).
us Digestor).

The inventor conducted a modified alkaline cooking method, specifically a modified kraft cooking method, by continuous operation using the actual reactor shown in FIG. 2 of the above-described two-reactor type continuous digester, and found that the cooking liquor described above was obtained. The modified kraft digestion process, which belongs to the modified alkaline digestion process, can reduce the load of bleaching chemicals and drainage of unbleached pulp, but increases the cooking temperature and increases the amount of cooking liquor per lignocellulosic material. Learned that various problems occur.

[Problems to be solved by the invention]

It is an object of the present invention to provide an improved method for achieving a reduction in the cooking temperature in a modified alkaline cooking process, and another object of the present invention is to use an amount of alkaline cooking liquor per lignocellulosic material in a modified alkaline cooking process. Another object of the present invention is to provide an improved method for achieving an improvement in pulp yield in a modified alkaline cooking method, and another object of the present invention. The purpose is to provide an improved method for achieving a further improvement in the pulp strength obtained by the modified alkaline cooking method, and further objects will become clear from the description hereinafter.

[Means for solving the problem]

The present inventors have conducted intensive studies to solve the above-mentioned problems of the modified alkaline cooking method. As a result, in the modified alkaline cooking method, a cyclic keto compound (cooking aid) was added to the alkaline cooking liquor to digest the lignocellulosic material. The present invention has been completed based on the finding that various problems can be solved at once by doing so.

The digestion method of the lignocellulosic material of the present invention that achieves the above-mentioned object has an upper digestion zone A, an upper digestion trim zone A, in which an infiltration vessel is installed at an upper portion or a previous stage of the digester, and the inside of the digester extends from the top to the bottom. A cooking zone B, a lower cooking zone C, and optionally a washing zone D are provided, and an upper cooking trim zone A
In the digestion method using a one- or two-reactor continuous digester, a co-current digestion is performed in the upper digestion zone B, a countercurrent digestion is performed in the lower digestion zone C, and a washing is performed in the washing zone D. 50-90% of the alkaline cooking liquor containing the cyclic keto compound introduced into the vessel
Using an alkaline cooking liquor containing from 0.001 to 1.0% by weight, based on the lignocellulosic material, of a cyclic keto compound supplied to the digestion trimming zone A, 5-45% to the lower cooking zone C and 5-45%. It is characterized by cooking at ~ 75%.

To summarize the present invention, the alkaline cooking liquor used in the modified alkaline cooking method, soda cooking method,
The chemicals used in the Kraft cooking method (sulfate method), the polysulfide cooking method, the alkaline sulfite cooking method and the sodium carbonate cooking method can be used, but the two-reactor shown in FIG. 2 is preferred. It is a kraft cooking method and a polysulfide cooking method using a mold continuous digester, and has a sulfuration degree of 5 to 75%, preferably 5 to 50%. The effective alkali addition rate of the cooking liquor described above is 5 to 30%, preferably 10 to 20%.

Examples of the cyclic keto compound used in the present invention include benzoquinone, naphthoquinone, anthraquinone, anthrone, phenanthrenequinone and a nucleus-substituted quinone-based compound such as alkyl, alkoxy, amino,
Nitro, hydroxy or halogen or carboxy derivatives, sulphonates or carboxylates are suitable. A hydroquinone compound which is a reduced form of the quinone compound is used. Specifically, anthrahydroquinone, alkylanthrahydroquinone, alkoxyanthrahydroquinone, aminoanthrahydroquinone, haloanthrahydroquinone, hydroxyanthrahydroquinone, carboxyanthrahydroquinone and the above-mentioned anthrahydroquinone It is appropriately selected from tautomers of the hydroquinone compound and a mixture of any of the above compounds. Tautomers of the above compounds include 10-hydroxy-anthrone, 1- and 2-alkyl-10-hydroxy-anthrone, 1- and 2-amino-10-hydroxy-anthrone, 1- and 2-hydroxy-10 -Hydroxy-anthrone, 1- and 2-halo-10-hydroxy-anthrone and any mixtures of the aforementioned anthrone compounds.

The cyclic keto compound is further selected from the group consisting of a 9,10-diketohydroanthracene compound and a 9,10-dioxyhydroanthracene compound obtained as a stable compound as an intermediate in an anthraquinone synthesis method by the Diels-Alder method. One or more compounds can be used.

Examples of the 9,10-diketohydroanthracene-based compound include, for example, 1,4-dihydro-9,10-diketoanthracene, 1,2,3,4-tetrahydro-9,10-diketoanthracene, 4,4a, 9a-tetrahydro-9,10-diketoanthracene, 2-ethyl-1,4,4a, 9a-tetrahydro-9,10-
Diketoanthracene, 2,3-dimethyl-1,4,4a, 9a-tetrahydro-9,10-diketoanthracene, 1,3-dimethyl-1,4,4a, 9a-tetrahydro-9,10-diketo Anthracene, 1-methyl-1,2,3,4-tetrahydro-9,10-diketoanthracene, 1,2,3,4,5,8-hexahydro-9,10-
Diketoanthracene, 1,4,4a, 5,8,8a, 9a, 10a-Octahydro-9,10-diketoanthracene, 2,3,6,7-tetramethyl-1,4,4a, 5,8 , 8a9a, 10a-Octahydro-9,10-diketoanthracene, 1,2,3,4,5,6,7,8-octahydro-
Preferred is a mixture of 9,10-diketoanthracene, and 2,6- and 2,7-diethyl-1,4,4a, 5,8,8a, 9a, 10a-octahydro-9,10-diketoanthracene. Is a compound selected from unsubstituted and lower alkyl-substituted Diels-Alder adducts of naphthoquinone and benzoquinone, and from the viewpoint of effect and economy, 1,4-dihydro-9,10-diketoanthracene, 1,4, 4a, 9a-Tetrahydro-9,10-diketoanthracene and 1,4,4a, 5,8,8a, 9a, 10a-octahydro-9,10-diketoanthracene are suitable.

As the 9,10-dioxyhydroanthracene-based compound, 1,4-dihydro-9,10-dioxyanthracene,
4,5,8-tetrahydro-9,10-dioxyanthracene,
1,4,5,8,8a, 10a-Hexahydro-9,10-dioxyanthracene and the like, and sodium and potassium salts of 1,4-dihydro-9,10-dioxyanthracene can also be used.

In the present invention, the cyclic keto compound is used in an amount of 0.001 to 1.0% by weight, preferably 0.005% by weight, based on the lignocellulose material.
It is usually added to the cooking liquor, taking into account the liquor ratio (cooking liquor / lignocellulosic material) to be 0.001 to 1.0% by weight based on the lignocellulose material. A cyclic keto compound may be added to the cooking liquor.

Various lignocellulosic materials can be used to practice the pulping method of the present invention, for example, lignocellulosic materials for pulp production include softwood chips, hardwood chips, sawdust, and non-wood cellulose materials such as bagasse, kenaf , Straw, reeds and other annuals.

The present invention will be described with reference to examples, but the present invention is not limited to these examples.

Example Temporary piping of the actual two-reactor type continuous digester shown in FIG. 2 (Oji Paper Co., Ltd., Kasugai Mill, operation in February 1989, production capacity NUKP 800T / day), and the cooking liquor shown in FIG. The introduction pipe 42 was installed in the line 40 from the strainer 39 of the permeation vessel 6 to the extraction liquid conduit 40. Further, a strainer 9 → extract liquid conduit 23 → heater 13 → circulating liquid conduit 26 line was provided in the upper digestion trim zone as shown in FIG. 3, and a digest liquid branch pipe 44 was connected to the extract liquid conduit 23. With this piping, the branch pipe 21 of the cooking liquor was further branched into a branch pipe 43 and a branch pipe 44, and the branch pipe 43 was connected to the pipe 24 in the lower cooking zone. A cyclic keto compound introduction tube 45 was provided in the cooking liquor introduction tube 17.
FIG. 1 shows a system diagram of an apparatus provided with such piping. First
Modified Kraft cooking was performed using the apparatus shown in the figure.

The digestion rate of the cooking liquor, the top pressure of the permeation vessel 6, the temperature conditions, the temperature conditions of the upper cooking trim zone A, the upper cooking zone B, the lower cooking zone C, the washing zone D, and the top pressure conditions of the digester 8 are as follows. The results are shown in Table 1.

In FIG. 1, the cooking liquid branch pipe 42 and the branch pipe 44 are closed, and the strainer 9 → conduit 23 → heater 13 → conduit.
The line 26 was closed and the extract from the strainer 9 was combined with the circulating fluid flowing through the transfer circulating fluid return line 36 via the conduit 38.

Reference Examples 1 to 4 (conventional craft method) are shown in FIG.
This was performed using a reactor-type continuous digester. In FIG. 4, the inside of the digester is composed of an upper digestion trim zone A ', an upper digestion zone B', and a washing zone D. Both the A 'and B' zones are cocurrent digesters, and the cooking liquor is Infiltration vessel 6 with full digester introduction pipe 17
At the top.

The cyclic keto compound in the examples is 0.03 to chip
A total amount of the white liquor flowing through the digestion liquor introduction tube 17 was added from the cyclic keto compound introduction tube 45 so as to be 0.06% by weight.

In Comparative Example 1, Examples 1, 2, and 3, pine was cooked, in Comparative Example 2, Examples 4, 5, and 6, beech was cooked, and in Examples 7, 8, Douglas fir was cooked. .

In Examples 1, 2, 3, and 8, the cyclic keto compound was 9,
In Examples 4, 5, 6, and 7, the disodium salt of 1,4-dihydro-9,10-dioxyanthracene (DDA) was used as the 10-anthraquinone (AQ). In Comparative Examples, the cyclic keto compound was used. Not added. Therefore, it goes without saying that the division ratio of the cyclic keto compound is the same as the division ratio of the cooking liquor.

Regarding the physical properties of the pulp, the selected pulp (unbleached) from which the debris was removed was beaten to a Canadian freeness of 500 cc with a PFI mill, and hand-extracted according to TAPPI test method T205 _OS- 71 (JIS P8209) with a basis weight of 60 g / m ² . Measured on sheet. In addition, about each test method, it performed according to the following method.

Kappa number TAPPI test method T236m-60 Whiteness JIS P8123 The following measurement is based on the strength test method for paper pulp (JIS P8
In accordance with 210), the tear length was measured using each device of JIS P8113 specific rupture JIS P8112 specific tear JIS P8116.

Regarding the bleaching property test, the selected pulp from which the residue was removed was subjected to C (chlorine) -E (caustic soda) -H (hypo) -D (dioxide chloride) in the usual order.

 The results are shown in Tables 2 to 4.

The temperatures and times in Tables 2 to 4 used the following values.

The temperature is the average of the cooking temperatures of the upper cooking trim zone A and the lower cooking zone C.

Time is upper cooking trim zone A + upper cooking zone B +
Total value of each cooking time in the lower cooking zone C.

From the comparison with Examples 1 to 8 and Comparative Examples 1 to 3, the modified Kraft cooking by adding the cyclic keto compound of the present invention is more effective than the conventional modified Kraft cooking without adding the cyclic keto compound. The new thing is clear.

Further, it goes without saying that the present invention can be applied to a modified alkaline cooking method using a single-reactor continuous digester.

〔The invention's effect〕

As is clear from the above description, the modified alkaline cooking method by adding the cyclic keto compound has reduced the amount of cooking liquor added and improved the pulp yield. In addition, there is a secondary effect that pulp quality (pulp viscosity, pulp strength) is improved, and as a result, paper making speed is improved, and the present invention greatly contributes to the paper pulp industry.

[Brief description of the drawings]

FIGS. 1, 2 and 3 are system diagrams of an apparatus for carrying out the modified alkaline cooking method of the present invention, and FIG.
It is a system diagram of a reactor type continuous digester. 1 in the figure: wood chips, 6: seepage vessel, 8: digester, 9, 10, 11, 12, 39 ... strainer, A ...
… Top cooking trim zone, B …… Top cooking zone, C…
… Lower cooking zone, D …… Cleaning zone, 13,14,15,16…
… Heater, 17… cooking liquor introduction pipe, 18, 19, 20, 21, 42, 43,
44 …… Distillation liquid branch pipe, 45 …… Ring keto compound introduction pipe, 29
…… Cleaning liquid introduction pipe, 30… Extraction black liquor pipe, 31 …… Pulping pulp discharge pipe

Claims (1)

(57) [Claims] 1. An infiltration vessel is installed at the top or the front step of the digester, and the inside of the digester extends from the top to the bottom to form an upper cooking trim zone, an upper cooking zone, a lower cooking zone and optionally a washing zone. 1 or 2 wherein co-current cooking is performed in the upper cooking trim zone and the upper cooking zone, countercurrent cooking is performed in the lower cooking zone, and washing is performed in the washing zone.
In the digestion method using a reactor-type continuous digester, 50 to 90% of the alkaline cooking liquor containing the cyclic keto compound introduced into the digestion system is introduced into the permeation vessel, 5 to 45% is introduced into the upper digestion trim zone, and 5 to 45%. % Of the lignocellulosic material, which is supplied to the lower cooking zone and cooked at a sulfurization degree of 5 to 75% using an alkaline cooking liquor containing 0.001 to 1.0% by weight of the cyclic keto compound based on the lignocellulose material. Cooking method.