JPS60134088A - Production of sulfite pulp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to a method for producing sulfite pulp.

According to the present invention, when the cooking liquid is absorbed into the chips, the weight ratio of cooking liquid to wood becomes 2.6:1 due to the reduction of the cooking liquid.
or less, i.e. the initial ratio of about 4:l is 35
% or more. After reduction, the weight ratio of cooking liquor to wood is preferably 2.jll. 10 chips
% or more, the weight ratio is further increased to 2.2:
can be reduced to less than l. The cooking liquor can be circulated through a calorizator so that the ♀- cooking liquor remains in the cooker, and the circulating acid raises and regulates the cooking temperature. Direct addition of steam, as required in so-called gas-phase valving, is therefore not necessary. Since the chips are thus partially immersed in the cooking liquid, the process of the invention can be called a semi-vapor phase pulp process.

In the method of the present invention, the SO2 and base content remaining in the digester after the absorption stage and the reduction of the cooking liquor are supplied at the beginning of the cooking so that they are sufficiently high for a proper cooking process. It is necessary to increase the acid chemical content of the sulfite cooking liquor. This is true if the base in the initial acid is bound to at least 13 g/50 ml of S02 and the total amount of S02 is more than 80 g/l, i.e. the S02 bound to the base is
o Achieved when rats account for 16% or more of all SO2 stars. If the pressure during proper steaming is kept as high as possible,
That is, if the amount of gas discharged is reduced depending on the pressure resistance of the steamer, the SO2 content remains at an appropriate value.

The sulfite cooking liquor is absorbed by the chips at a temperature range of 80°C to 110°C and reduces the cooking liquor at this same temperature range. at a temperature higher than the absorption stage, i.e. 120°C to 150°C.
Steaming takes place properly at ℃.

As the base, known bases for sulfite cooking, such as calcium sulfite, ammonium sulfite, magnesium sulfite or sodium sulfite, or mixtures thereof can be used.

The purpose of the initial part of the cooking in the method of the invention is primarily to absorb the cooking liquor into the chips, and not for proper sulfonation and/or dissolution of the lignin. The reason for this is that it is desirable that the acid removed by the reduction of the cooking liquor contain only a small amount of organic matter when returned to the acid system.

As is well known, the SO2 concentration can be increased by introducing liquefied SO2 into the steamer. On the other hand, the basicity can be increased by adding suitable carbonic acid 11X, hydroxides or oxides to the so-called tower acids. The base may also be added as the corresponding basic compound directly to the depth charged to the digester.

The second important point of the present invention is that by adding soluble calcium salts directly to the sulfite cooking liquor, the amount of cooking liquor can be significantly reduced in calcium sulfite cooking if the calcium content in the liquor is also sufficiently increased. be.

For example, addition of luciram acetate can similarly sufficiently increase the calcium content in the sulfite cooking liquor.

Furthermore, the method of the present invention provides the following advantages.

The sulfite cooking liquor can be heated with less energy than with the prior art.

The black liquor is received in the evaporator at a concentration of 4% higher. That is, evaporation can be performed with less energy.

Steaming occurs rapidly, resulting in high pulp yield and whiter pulp.

The sulfonate molecules in the black liquor are larger than in the conventional method.

It is known to produce sulfite salts by two-stage steaming, as described in Finnish Patent No. 35.726. That is, steaming is carried out at a temperature of 100 to 130 °C in the first stage and at a higher temperature in the second stage, and after the end of the first stage, about 172 of the volume of the cooking liquor is removed and the central calorizer is heated. ) in the process of the invention, no central calorizator is used and the temperature of the absorption stage is only between 80°C and 11°C.
The temperature is approximately 0°C, and heating is performed by circulating the cooking liquid in both the first and second stages.

Therefore, during steaming, a small amount of liquid is sufficient, and no condensation of heated steam occurs in the steamer. Despite this, fiber disintegration results are at least as good as prior art methods.

Finnish Patent No. 54,938 discloses a method for reducing heating costs in pulp production. It can be seen from the embodiment that it relates to sulfuric acid steaming, but on the other hand, the steaming of the present invention relates to sulfite steaming,
Both methods are completely different. This prior art method also uses pressurization techniques to enhance absorption.

Another method of reducing heating costs in the production of sulfuric acid pulp is known, as described in Finnish Patent Application No. 81-2102. Similar to Finnish Patent No. 54.938 of No.-h, this method is also quite different from the method of the present invention. To enhance absorption, pressure treatment is applied at the beginning of the absorption stage and vapor phase pulping is carried out at the final stage.

From Swedish Patent No. 175,684 a two-stage steaming process for pine wood chips is known, in which sodium is used as the base (calcium is not suitable at a pH of 4 to 7). After the completion of one stage, the cooking liquid is almost completely removed, and then the liquefied S02 and/or
Or an aqueous solution of S02 is added.

EXAMPLES A series of batch cooking experiments were carried out on both laboratory and industrial scales, varying the initial acid composition and concentration and, in particular, the reduced cooking liquor temperature. In industrial-scale experiments, the cooking liquid should be reduced from the usual 25% to 35-41% based on the total liquid volume.
20% to 40% on a laboratory scale.
It was reduced to 45%.

In addition to calcium oxide, calcium acetate was added to the cooking liquor in order to increase calcium to the extent necessary to significantly reduce the cooking liquor, and laboratory-scale batch cooking experiments were conducted. The results are shown in Table 1.

Table 1 Explanation of Table 1 l) Increase in temperature 50-85℃ for 2 hours Temperature increase 85-130℃ for 3.5 hours 2) Base amount corresponding to 4.3g/l of bond S02 Calcium acetate was added.

3) +11 groups of calcium acetate were added, corresponding to 7.0 g/crosslinked SO2.

4) A jl base amount of ammonium acetate corresponding to 4.3 g/l of bound S02 was added.

5) No acetate was added. That is, a small amount of base was used.

El) An amount of 111 bases of ammonium acetate corresponding to 4.7 g/cross bond S02 was added.

Patent Applicant Ge, A, Cellulasehiusoi Representative Person Originated from Patent Attorney m: E (1 other person) Ji゛, -゛+1. ,・Continued from page 1 0 Inventor Simo Hyverinen Twitch 4 @ Inventor Eero Szostlö Finnram Arionund Republic, 35800 Mentte, Republic of Hallitouskund, 02170 Nispo 17. Pitken Power Tanfa 3

Claims (10)

[Claims] (1) At the initial stage of steaming, thick steaming liquor is absorbed into the chips so that an amount of steaming liquor remains in the steamer pot to indirectly increase the steaming temperature at the final stage by circulating the M-point liquor through the calorizer. , A method for producing sulfite pulp, characterized by reducing the total amount of cooking liquor by 35% or more. (2) The weight ratio of the cooking liquid to the wood is changed to a range of 2.6:1 to 2.2=1, or lower, preferably to a range of 2.4:1, by reducing the cooking liquid. The method according to claim 1, characterized in that: (3) The SO2 concentration of the cooking liquid is higher than 80g7m, and the base concentration of the cooking liquid is 5O2f! :
2. A method according to claim 1, characterized in that it is so high as to bind at least 16% of the (4) The method according to claim 1, characterized in that the sulfite cooking liquor is absorbed in a temperature range of 80°C to 110°C and the cooking liquor is reduced in the same temperature range. (5) The method according to claim 1, characterized in that the concentration of the steaming liquid is increased by adding liquid SO2 to the steaming pot. (6) f! 4. The method according to claim 1, wherein the W-based gold compound is added to the sulfite cooking liquor or the chips to increase the base content in the cooking liquor. (7) The method according to any one of claims 1 to 3, characterized in that the base content of the cooking liquor is increased by adding a soluble calcium salt. (8) A method according to claim 7, characterized in that calcium acetate, calcium nitrate or calcium formate is added to the sulfite cooking liquor or the chips. (9) The method according to any one of claims 1 to 8, characterized in that the chips are densified with wk in order to reduce the ratio of the cooking liquid to the wood to 2.2 or less. (10) The method according to claim 9, characterized in that the chip is densified by 10% or more by applying pressure.