RU2413808C1 - Method to produce cellulose - Google Patents

Abstract

FIELD: textile, paper.

SUBSTANCE: method is carried out by means of subsequent soaking of cellulose-containing herbal raw materials in alkaline solution, thermomechanical treatment, squeezing, washing, bleaching, squeezing, washing, squeezing and drying, besides, squeezing and washing are done in pulsating centrifuge.

EFFECT: higher yield of cellulose, reduced norms of consumption of initial reagents and water and reduced power inputs.

1 tbl, 3 ex

Description

The invention relates to the pulp industry, in particular to the production of cellulose from vegetable cellulose-containing material, and can be used for the production of cellulose intended for chemical processing, in the paper industry, etc.

A known method of producing cellulose by loosening plant materials, alkaline cooking using NaOH, a surfactant, T = 120-130 ° C for 1 hour, washing with 1-5 times the amount of clarified water, hydrocyclone treatment with clarified water, grinding , fine hydrocyclone treatment with clarified water, 2-fold NaOCl bleaching at pH = 9-11.5, T = 35-40 ° C for 1 hour, 2-fold washing with softened water, acidification with H ₂ SO ₄ at 15-40 ° C for 1 hour, rinsing with softened water, spin, air drying (Permanent Regulations №4-2 «Production of simple and cellulose esters", approved January 18, 1995 Gene. Director Engels JSC "Khimvolokno").

A known method of producing cellulose, including the mechanical treatment of cellulose-containing material by simultaneously loosening and cleaning it, cooking in an alkaline solution at a temperature of 130-140 ° C under a pressure of 3-4 atm for 180-210 minutes, washing, bleaching in an acidic solution with sodium hypochlorite, wringing, loosening and drying (RU 2078163, class D04H 1/02, publ. 1997).

The disadvantages of the above methods are: the alkaline cooking process in harsh conditions - at a temperature of T = 120-140 ° C, pressure P = 2-4 atm, the use of carcinogenic sodium hypochlorite for bleaching.

A known method of producing cellulose by simultaneous loosening and cleaning of cellulose-containing material, grinding, locks in a NaOH solution and cleaning, alkaline cooking for 1.5-3 hours with a hydraulic module 1: (5-20), containing additional surfactants, washing, bleaching in solution H ₂ O ₂ , washing, spinning and drying (RF Patent No. 2304647).

The disadvantages of this method is the inability to obtain cellulose from cellulose-containing raw materials with a high degree of pointedness and a high content of lignin.

The closest in technical essence and the achieved effect is a method of producing cellulose by simultaneously simultaneously loosening and cleaning the cellulose-containing material, washing and cutting the material, locking, thermomechanical processing, washing, bleaching, washing, spinning and drying. In an embodiment of the method, after thermomechanochemical processing, the material is left to ripen in an alkaline solution (RF Patent 2343241, D21C 5/00).

However, upon receipt of cellulose in a known manner, the washing process of the pulp is carried out by a displacement method, which takes a long time with significant losses of finely divided fibers (less than 1 mm) resulting from thermomechanical treatment, and also requires the use of a large amount of washing water.

The basis of the present invention is the task of creating an effective economical method of producing cellulose by using the forced filtration method at the washing stage. For this purpose, separation of liquid and solid phases in the centrifugal field of a pulsating centrifuge is used, as a result of which the process of displacing the spent reagents is accelerated and technological losses of finely dispersed fiber are eliminated, and the dosage coefficients of the starting reagents and water are reduced.

The problem is solved in such a way that in the method of producing cellulose by sequentially locking cellulose-containing raw materials in an alkaline solution, thermo-mechanochemical processing, washing, bleaching, washing, spinning and drying, spinning is carried out before washing, and the spinning and washing are carried out in a pulsating centrifuge, and as cellulose material is taken by herbaceous plants.

As a cellulose-containing material, herbaceous plants are used, for example: flax flax, -earth, curly, green, hemp, rapeseed, bulrush, sunflower, miscanthus, sweet clover, alfalfa, castor oil, Jerusalem artichoke, goatberry, Sosnovsky cowberry. n., of varying degrees of maturity, with a high content of bonfire, lignin, with a long aging period in warehouses and in the fields.

In the claimed method, the cellulose-containing raw materials from herbaceous plants are preliminarily locked in a cooking solution, which is prepared in circulating water with a NaOH content of 10-60 g / l and a surfactant of 0.2-0.8 g / l for 15-60 minutes at a temperature of 90-100 ° C. The hydraulic module is 1: (10 ÷ 20).

The cellulose-containing raw material impregnated with the cooking liquor enters through the receiving funnel - the batcher into the ASh-200 twin-screw apparatus heated to a temperature of 80-100 ° C, on the shafts of which alternating discharge screw and grinding cam nozzles are placed, shifted one relative to the other with the formation of a helical channel (A.с USSR No. 884715, 1981).

After thermomechanochemical activation, the processed pulp is pumped by a mass pump into a P-80 brand pulsating centrifuge to remove water-soluble substances sorbed from the fiber during fiber cooking.

A pulsating centrifuge consists of a perforated rotor placed in a casing, consisting of internal and external drums in the form of slotted metal screens; conical funnel; a loading nozzle for supplying a suspension and two flushing nozzles with nozzles for supplying hot and cold water; a collector divided into sections for the removal of the centrate and sediment (Passport P-80 Ferrum No. D11 of Bowas-Induplan Chemie GmbH).

The principle of operation of the centrifuge is as follows: an alkaline suspension of pulp continuously enters through a loading nozzle into a narrow part of the conical funnel, moves along its inner surface, gradually acquiring a speed equal to the rotor speed. Then the suspension is discarded on the surface of the inner drum, where the spent liquor is squeezed out and removed through the collector from the centrifuge. The squeezed pulp due to the pulsation of the centrifuge enters the outer drum for washing. Flushing is carried out by irrigation of the mass with water with a temperature of 70-90 ° C by injection through the nozzle of the flushing nozzle. The filtered solution is discharged through the collector. Then, as the centrifuge moves in the outer drum, the initially filtered mass is irrigated with water at a temperature of 30-40 ° C, which is injected through the nozzle of the second flushing nozzle. The washed pulp is discharged through the discharge channel of the centrifuge and transported to bleaching in bleaching towers.

Cellulose bleaching is carried out with a solution of hydrogen peroxide with a concentration of 5-10 g / l at a temperature of 85-95 ° C for 90 minutes. Hydraulic module - 1: (10 ÷ 20).

Washing from the bleaching solution is carried out in the same way as washing after alkaline thermomechanical activation.

Cellulose, squeezed to a moisture content of 30-40%, is fed by air transport for drying.

Cellulose is dried with flue gases at a temperature of 140-160 ° C on a vibrating dryer.

The dried cellulose is fed to a press and then to the packaging.

To prove the conformity of the claimed method to the criterion of "industrial applicability" we give specific examples of the method.

Example 1

1000 kg of unpacked and loosened rapeseed cross-section 2-3 cm in size and 10 m ^{3 of} cooking solution with a concentration of NaOH of 30 g / l in circulating water and 0.2 g / l of syntanol ALM-10 are fed to the storage reactor. The reaction mass in the storage reactor is heated to 100 ° C and maintained at this temperature for 30 minutes. The working temperature is maintained by heating the cooking solution with a tubular heat exchanger. The raw material impregnated with the cooking liquor from the storage reactor enters through a receiving funnel - dispenser into the ASh-200 twin-screw apparatus (capacity - 2.0 t / h), heated to a temperature of 100 ° C, and thermomechanical processing is carried out for 30 minutes while maintaining the temperature parameter .

At the end of the thermomechanochemical treatment, the processed pulp is pumped by a mass pump into a pulsating centrifuge, in which the spent alkaline solution is initially pressed. The squeezed pulp with a moisture content of 32% is washed by feeding 5 m ^{3 of} water with a temperature of 70-90 ° C and 5 m ^{3 of} water with a temperature of 30-40 ° C through the washing nozzles.

Next, the cellulose is mixed with an aqueous solution of hydrogen peroxide with a concentration of 5 g / l and fed by a screw conveyor to the bleaching tower. The mass is heated with hot steam to a temperature of 90-95 ° C and bleaching is carried out for 1.5 hours.

Washing from the bleaching solution is carried out in the same way as washing after alkaline thermomechanical activation in a pulsating centrifuge.

Cellulose, squeezed to a moisture content of 32%, is fed by air transport for drying.

Drying is carried out by feeding cellulose into a vibrating dryer. The temperature of the flue gas is 140-160 ° C.

The dried cellulose is fed into a horizontal press and then onto the packaging.

Cellulose is obtained in a yield of 48%.

Example 2-3 is carried out analogously to example 1, changing the process conditions. The data on examples are presented in the table.

As can be seen from the table, the claimed method is cost-effective, since it allows you to increase the yield of cellulose by 10% due to the catch of finely divided fiber, reduce the consumption rate of the starting reagents and water, reduce energy consumption by drying the product with a lower content of residual water in it.

Claims (1)

A method of producing cellulose by sequentially locking cellulose-containing raw materials in an alkaline solution, thermo-mechanochemical processing, washing, bleaching, washing, spinning and drying, characterized in that the presses are washed before washing, and the spinning and washing are carried out in a pulsating centrifuge, and as a cellulose-containing material plants.