SU374403A1 - METHOD OF OUTPUT CONTROL AND DEGREE OF PROTECTION OF SOFT AND MEDIUM SULPHITE CELLULOSE - Google Patents

Description

one

The invention relates to a method of controlling the degree of penetration and the yield of medium and soft cellulose during its acid sulphite method of cooking on sodium, ammonium and magnesium bases. The method of controlling the cooking process may be applied both in batch and in continuous sulphite cooking, as well as in the production of ioluse cellulose and bisulfite and neutral sulphite methods.

The known method of controlling the degree of penetration of cellulose to the pH of the cooking solution does not provide accurate control, which is due to the considerable complexity of sulphite cooking processes, in which the acidity of the pan is not in any definite dependence on the degree of penetration, yield or other important pulp indicators.

According to the proposed control method, in order to increase the accuracy of control of the degree of penetration and yield of pulp during sulphite pulping (which ALLOWS, in turn, accurately determine the end of cooking and will provide an opportunity to obtain higher quality pulp without undue loss in its output) the degree of decomposition of sulfuric acid and bisulfite in the liquor and by this value, using a pre-built curve, determine the degree of penetration OR the yield of pulp at the moment of cooking.

The degree of decomposition of sulfurous acid and bisulfite is characterized by one of two methods:

1. According to the total content of thiosulfate (one of the main decomposition products), both in the liquor and formed from tetra- and pentathionate (also contained in the liquor) as a result of exposure to sulfite:

 + sol 8zOG + 8.0h. (1)

 + 2SOl

 S, Ol + 2S, Ol. (2)

In turn, the thiosulfate found in the liquor and formed by the reaction (1) n (2) can be easily and quickly determined by the usual 20 iodometric titration:

28.0 d -f I,

(3)

 + 2G

Thus, the flow rate of 0.01 n. B the final titration is proportional to the degree of decomposition of the cooking liquor.

2. According to the content of sulfate ions in liquor at this stage of cooking. The content of sulfation can be determined relatively quickly by conductometric titration. Moreover, in this case it is better to use directly the value of the obtained flow rate of 0.1 n. BaCU for titration of sulfate ions in a sample of liquor, did not resort to calculating the content of sulfate ions.

The first of the two proposed methods for determining the degree of cracking is accurate, fast enough, simple, and does not require special equipment. If there is some skill in titration, it can be easily mastered by both laboratory technicians and work foremen. Therefore, this method can be used not only for the control of laboratory and experimental cooking, but above all - directly for production control.

The second method, with an accuracy not inferior to the first, is somewhat longer (about 10 minutes), and also requires a titration system with a conductometer. This method is easier to implement in the laboratory than under production conditions. However, this method can serve as a good basis for creating semi-automatic or automatic devices for determining the level of decomposition of the cooking liquor and thus for semi-automatic and automatic monitoring of the pulping process.

Example. A series of acidic sulphite pulps is carried out on a sodium base of soft and medium hard pulp. Determination of the degree of penetration and the yield of the obtained cellulose, as well as the degree of decomposition of sulfurous acid and bisulfite in the liquors corresponding to the obtained cellulose. The degree of decomposition of sulfurous acid and bisulfite in the liquors is determined both by the total amount of thiosulfate and by the amount of sulfate ions in the liquor.

The total thiosulfate content is determined as follows.

1, a) In a flask with a capacity of 200-250 ml, 50 ml of distilled water is poured and 2.00 ml of the analyzed liquor is pipetted. Further titrated with 0.1 n. iodine (indicator: 1% starch solution), add 5 ml of 0.4 M. Na2503, alkalinize with 1N. NaOH

(indicator: phenolphthalein alcohol solution) and incubated for 1-2 minutes. Then 1 ml of formalin was added to the sample and, after stirring, 10 ml of 10% CH 2 COOH. After that, add 2 ml of 1% p. Akhmal kr solution and titrate at a rate of 2-3 drops per second 0.01 n. iodine with continuous stirring prior to dyeing the entire volume of the sample with a grayish-blue color. The total determination time is 4-5 minutes.

1, b) This variant differs from variant a by the absence of preliminary titration of the 0.1 n sample. iodine, which is necessary in order to reduce the possibility of interaction with 0.01. iodine (at the final titration) of organic matter liquor. If the equivalence point is clearly obtained without this preliminary titration, it can be omitted. In this example, the definition was carried out in both variants.

The content of sulfate ions in the liquor was determined by conductometric titration using a known method, but somewhat modified. The modification consists in the refusal of ion exchange (ion exchange is necessary only in the case of analysis of liquors on a calcium or magnesium base), by introducing a liquor neutralization operation 1 n. NaOH to pH 4-5, by varying the magnitude of the sample of liquor in the range of 2-10 ml so that

so that the initial resistance is not less than 1000 ohms, as a result of which the equivalence point becomes more noticeable (the end result unconditionally recalculates the same sample volume).

The data obtained for determining the degree of decomposition of liquor by both methods are presented in Table. one.

Table 1

According to the table. 1, the curves shown in FIG. 1 and 2.

FIG. 1 shows the dependence of the degree of penetration of cellulose on the degree of decomposition of liquor; in fig. 2 shows the dependence of the yield of cellulose on the degree of decomposition of the liquor.

Pa figs. 1 and 2, the following notation is accepted: curve / flow rate 0.01 n. iodine with pre-treatment samples of 0.1 n. iodine (option, a); curve 2 flow 0.01 n. iodine without pre-processing samples 0.01 n. iodine (version 1.6); curve 3 consumption 0.1 n. barium chloride on conductometric titration of sulfate ions (method 2); points O, corresponding to the results of the first series of cooking; points X, corresponding to the results of the second series of cooking. A second, similar to 5 degree of decomposition, corresponding to the cellulose of the second brewing series (see Table 2) was then carried out, and using the curves previously obtained from the results of the first brewing series (see fig. 1 and 2), the degree of penetration is determined and output10 celluloses of the second series, cooking.

Penetration rate, kapp number

Subject invention

The method of controlling the yield and degree of penetration of soft and medium sulfite pulp in the process of its production by treating the initial cellulose-containing raw material with cooking liquor containing sulfuric acid and

table 2

Yield,% of a. with. wood

Bisulphite, characterized in that, in order to increase the accuracy of control, the degree of decomposition of sulfurous acid and bisulphite is determined by known methods and the amount of decomposition is judged on the yield of pulp and the degree of its penetration. the first, a series of cooking in which the same were obtained, as well as slightly different in the degree of penetration and yield of cellulose (due to a change in the standing time at the final temperature), see table. 2. The degree of penetration and the yield of cellulose, determined by the proposed method, coincide well with the experimentally determined degree of penetration and the yield of cellulose (see Table 3), Table 3

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