RU2018558C1 - Method for production of cellulose for chemical processing - Google Patents

Abstract

FIELD: production of cellulose for chemical processing. SUBSTANCE: alkali digestion of cellulose-containing raw material of hardwood is carried out on spent solution from stage of cold pulp purification with content of hemicelluloses amounting to 0.13-5.2 %. Cold purification is carried out with alkali reagent based on sodium-hydroxide. Used as alkali reagent is spent solution from mercerization stage with content of hemicelluloses of 0.1-3.2 % . Mercerization is accomplished directly after bleaching with dryness of bleached cellulose mass of 25-55 %. Mercerization is carried out with use of sodium hydroxide, white kraft liquor or their mixture or oxidized white kraft liquor. EFFECT: higher efficiency. 2 cl, 1 tbl

Description

 @ 400 = The invention relates to the pulp and paper industry and can be used in the manufacture of viscose fibers and films.

 Known methods for producing cellulose for chemical processing (Kosaya G.S. Production of sulphate viscose pulp, 1966; Rogovin Z.A. Cellulose chemistry, 1972.

 The closest analogue is a method of producing cellulose for chemical processing, including alkaline cooking of cellulose-containing raw materials from hardwood, cold dressing with an alkaline reagent based on sodium hydroxide, bleaching and mercerization with an alkaline solution based on sodium hydroxide (Sharkov V.I. and Kuibina N.I. Chemistry of hemicelluloses. M: Forest industry, 1972, S. 394-396).

 Mercerization of the dried pulp is carried out with an aqueous solution of sodium hydroxide at a concentration of 220-240 g / l. During subsequent extraction, part of the dissolved hemicelluloses leaves with squeezing liquor. The concentration of hemicelluloses in squeeze liquor is 2.0-3.0%.

 This liquor is unsuitable for reuse during mercerization and is sent for regeneration. Attempts are known to use isolated hemicelluloses (the chemical composition of these hemicelluloses: mannose, xylose, glucose), for example, for growing yeast.

 However, the presence of significant quantities of squeeze liquor, the need for its regeneration complicates and increases the cost of the method of producing cellulose for chemical processing. The appreciation of the method is explained by both an increase in the energy intensity of the process due to electrodialysis, and an increase in the content of fresh chemicals for mercerization. In addition, the presence of cellulose drying to a moisture content of 12% also increases energy costs.

 The aim of the invention is the reduction of alkaline reagents, energy and heat consumption. In addition, the ecology of the process is increased due to the lack of discharge of wastewater containing hemicelluloses.

 To do this, in the method of producing cellulose for chemical processing, including alkaline cooking of cellulose-containing raw materials from hardwood, cold dressing with an alkaline reagent based on sodium hydroxide, bleaching and mercing with an alkaline solution based on sodium hydroxide, alkaline cooking is carried out on the spent solution from the stage of cold treatment with the content of hemicelluloses is 0.13-5.2%, while the spent solution from the me stage is used as an alkaline reagent at the stage of cold upgrading mercerization with a content of hemicelluloses in it of 0.1-3.2%, and mercerization is carried out immediately after bleaching with dry bleached pulp 35-55%.

 In this case, the mercerization of the pulp is carried out with sodium hydroxide, white sulfite liquor or a mixture thereof or oxidized white sulfate liquor.

 The invention is illustrated by the following examples.

 PRI me R 1. The method of producing cellulose for chemical processing is as follows.

 Hardwood chips (a mixture of aspen and birch) are loaded into an autoclave, poured with soda liquor containing 0.13% hemicellulose, after the stage of cold treatment and boiled cellulose.

The consumption of alkali for cooking 19-20% Na ₂ O.

The resulting cellulose with a concentration of 8% is subjected to cold refinement (XO) with the spent solution from the mercerization stage containing 0.1% hemicellulose for 60 minutes. The concentration of the alkali in weight is 45 g / l, temperature 20 ^° C after cold Lye refining drained and used for cooking. Then the pulp is washed and subjected to bleaching according to the scheme: heat treatment at 95 ^about C - D / X-G-D-G-K.

Then bleached cellulose with a dryness of 35% is subjected to mercerization with sodium hydroxide according to the following regime: alkali concentration 268 g / l, duration 60 min, temperature 19 ± 1 ^о С.

 At the end of the mercerization, the alkali is squeezed out and used (with a hemicellulose content of 0.1%) at the XO stage.

 The test results of the target product, as well as indicators of the quality of the pulp after cooking, stages of the cold refinement and bleaching are shown in the table.

PRI me R 2. The method of producing cellulose for chemical processing is carried out analogously to example 1 with the only difference that at the stage of cooking the characteristics of the liquor are as follows: hemicellulose content of 5.2%, alkali consumption (in units of Na ₂ O) 22%

Before XO, unbleached cellulose is treated with oxygen in an alkaline medium (alkali ₂ ). In step CW characteristics following solution: 3.2% hemicellulose content, the alkali concentration of 45 g / l, the duration of CW 60 min, temperature 20 ^° C HO

 Bleaching is carried out according to the scheme: heat treatment - D-G-K.

At the stage of mercerization, cellulose with a dryness of 55% is treated with a mixture of sodium hydroxide and white sulfate liquor according to the regime: alkali concentration 237 g / l, duration 60 min, temperature 19 ± 1 ^о С.

 The test results of the target product, as well as indicators of the quality of the pulp after cooking, stage XO and bleaching are shown in the table.

PRI me R 3. The method of producing cellulose for chemical processing is carried out analogously to example 1 with the only difference that at the stage of cooking the liquor has the following characteristics: hemicellulose content of 2.31%, alkali consumption (in units of Na ₂ O) 21 %

Before XO, unbleached pulp is subjected to AHCO ₂ , at the XO stage, the characteristics of the solution are as follows: 1.86% hemicellulose content, liquor concentration 45g / l, XO duration 60 min, XO temperature 19 ± 1 ^о С.

 Bleaching is carried out according to the scheme: heat treatment - D-G-K.

At the mercerization stage, cellulose with a dryness of 43% is treated with a mixture of sodium hydroxide and oxidized white liquor according to the regime: alkali concentration 239 g / l, duration 60 min, temperature 19 ± 1 ^о С.

 The test results of the target product, as well as indicators of the quality of the pulp after cooking, stages of the cold refinement and bleaching are shown in the table.

 PRI me R 4 (according to the prototype method). A method of producing cellulose for chemical processing is as follows. Hardwood chips are loaded into an autoclave, white liquor is poured in an amount of 22% of a.s. wood and boil.

After separation of the fine fiber, the unbleached pulp is subjected to treatment with alkali oxide ₂ and XO (sodium hydroxide at a mass concentration of 8%, alkali concentration at a mass of 45 g / l, and a temperature of 20 ^{° C.} for 60 minutes). Then the pulp is washed and subjected to bleaching according to the scheme: heat treatment - D-G-K.

After bleaching the pulp is dried to a dryness of 95% and subjected to mercerization under the following conditions: the concentration of alkali 237-241 g / l, temperature 54-56 ^{° C,} the module 1:18 mercerization time 45 min.

 Their tables show that the properties of bleached cellulose after bleaching and the target product - alkaline cellulose - are almost the same for products obtained by the proposed and known methods (the yield of bleached cellulose obtained by the proposed method is higher than by the known). At the same time, the consumption of alkaline reagents, energy and heat consumption due to the processing of wet cellulose (without drying) are significantly reduced.

 In general, the proposed method is ecologically cleaner due to the lack of discharge of wastewater containing hemicelluloses.

Claims (2)

 1. METHOD FOR PRODUCING CELLULOSE FOR CHEMICAL PROCESSING, including alkaline cooking of cellulose-containing raw materials and hardwood, cold dressing with an alkaline reagent based on sodium hydroxide, bleaching and mercerization with an alkaline solution based on sodium hydroxide, characterized in that the alkaline cooking is carried out at the spent solution stage of a cold refinement with a hemicellulose content of 0.13 - 5.2%, the spent solution from the stage is used as an alkaline reagent at the stage of cold upgrading mercerizing the content of hemicelluloses therein 0.1 - 3.2%, and the mercerization is carried out immediately after bleaching with dry bleached pulp 25 - 55%.  2. The method according to claim 1, characterized in that the mercerization is carried out with sodium hydroxide, white sulfate liquor or a mixture thereof or oxidized white sulfate liquor.

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