RU2493308C1 - Production method of sulphite pulp of mixture of different wood species chips - Google Patents

Abstract

FIELD: woodworking industry.

SUBSTANCE: method includes the use of three batch cookers sequentially interconnected by liquid-phases, loading them with a mixture of chips of different species of wood, including wood of larch, pine, spruce, birch, aspen, preliminary two-stage treatment of the mixture of chips with the aqueous medium at elevated temperature at the first stage to produce an extract and with the hot solution of lignosulphonates at the second stage by successive filling the cookers with the aqueous medium, the solution of lignosulphonates and cooking liquor and discharge from the cookers of the aqueous medium by its displacement with the solution of lignosulphonates, the discharge of this solution by its displacement with the cooking liquor. The aqueous extract discharged from the process is used for production of arabinogalactan and flavonoids. Pulp cooking is carried out by bisulfite method.

EFFECT: improvement of pulp quality, simplification of processing the extract to obtain arabinogalactan and flavonoids due to their increase in the extract.

7 cl, 2 tbl

Description

The method relates to technologies for the production of pulp from wood raw materials and may find application in the pulp and paper industry.

It is known that when cooking cellulose from a mixture of wood chips of different wood species, to obtain homogeneous pulp quality, it is advisable to use certain methods of preliminary processing of the mixture, the purpose of which is to equalize the characteristics of the components of such wood chips. Pretreatment of the chip mixture is especially important when the mixture contains larch wood chips. This wood contains arabinogalactan (AG) and flavonoids. AG complicates the process of wood delignification during cooking and, therefore, pre-treatment conditions should ensure the removal of AG from wood chips to the greatest possible extent. Another factor is important. AG and flavonoids are valuable products and, accordingly, in the process of processing chips, it is desirable to obtain these substances in the form of marketable products.

A known method of producing cellulose for the manufacture of paper and cardboard (and.with. 1601256, IPC D21C 1/04, 3/02, publ. 23.10.1990). The method is implemented by pre-processing chips from larch wood with an impregnating solution, which is used as an aqueous bisulfite solution with a concentration of bisulfite of 3.5-40.0 g / dm ³ , removal of the spent solution, subsequent cooking by the sulfate method. Chips are pretreated at 25-100 ° C for 20-70 minutes.

The disadvantage of this method is the low quality of the resulting pulp. The closest analogue of the invention is a method for producing sulfate cellulose from larch chips (SU No. 1595977, IPC D21C 3/02, 1/02, publ. 30.09.1990). This method using a batch boiler includes loading it with chips from larch wood, its water treatment at a temperature of 100-120 ° C, removing the spent solution from the boiler, processing it to produce arabinogalactan and flavonoids, feeding the cooking solution to the boiler, cooking chips, removing from the boiler of cooking products.

Essentially, the liquid phase (water) used to process the chips can be called an extractant, the processing operation is the extraction of chips, and the liquid phase after processing is an extract.

This method is intended for the production of cellulose for various purposes from larch wood chips, as well as AG and flavonoids extracted from wood chips. The disadvantage of this method is that when processing larch wood chips as part of a mixture of wood chips from different types of wood, the effectiveness of water treatment in terms of leveling the characteristics of all wood chips in the mixture before it is small. In addition, the concentrations of AG and flavonoids in the extract are small and it is difficult to extract them from the extract.

New technical results from the use of the present invention are to improve the quality of cellulose due to the equalization of the characteristics of wood chips from different wood species during the preliminary processing of the mixture, as well as to simplify and reduce the cost of the processing of the extract to obtain AG and flavonoids due to an increase in their concentration in the extract.

These results are achieved by the fact that in the method of producing sulfite cellulose from a mixture of wood chips of different types of wood, including the use of a boiler of periodic action, loading wood chips from a number of species containing larch, the level of extraction of wood chips by processing it with an aqueous medium at an elevated temperature for a specified time with obtaining the extract, removing it and processing it with obtaining arabinogalactan and flavonoids, feeding the cooking liquor to the boiler, cooking chips, removing cooking products from the boiler, with According to the invention, a number of species additionally includes pine, spruce, birch, aspen wood, a wood mixture after treatment with an aqueous medium is additionally subjected to hydrolysis treatment with a solution of lignosulfonates, both treatments being carried out in three boilers connected in liquid phases by filling each of the liquid phases with the withdrawal of the aqueous extract by its displacement from the boilers by a solution of lignosulfonates and the withdrawal of this solution by its displacement by a cooking solution and pulping is carried out according to the bisulfite method Sobu. The share of larch wood chips in the total mass of chips is 20-80%. Chips are treated with an aqueous medium and a solution of lignosulfonates at a temperature of 95-98 ° C. As a solution of lignosulfonates, hot spent sulfite liquor from pulping is used. An aqueous medium containing arabinogalactan and flavonoids, for example, a previously obtained extract from processing wood chips with an aqueous medium, is fed to the processing of wood chips. Processing the extract removed from the process includes the operation of purifying it by filtration and / or pressure flotation.

When chips are treated with spent sulfite liquor containing free sulfur dioxide, hydrolysis of polysaccharides occurs, including AG of larch chips, leaching of hydrolysis products and AG itself from chips into the liquid phase volume, as well as sulfonation of wood lignin. These factors contribute to the alignment of the characteristics of wood chips from different types of wood, facilitate the process of delignification of chips during cooking.

The proposed method can be implemented as follows. A mixture of wood chips is prepared from different species of wood, including larch. The content of AH and flavonoids in larch chips is determined. In laboratory conditions, water treatment of this woodchip is carried out at a temperature of 95-98 ° C, and the duration of effective AG extraction (τ _eff ), as well as its degree of extraction for this period of time, is determined by the dependence of the concentration of AG in the extract on the duration of extraction. Teff is taken equal to 25 minutes, the degree of extraction of AG - 40%. The same values of τ _eff and the degree of extraction are taken for the extraction of flavonoids. The residual content of AH and flavonoids in the chips is estimated.

Next, the same portion of the chips is treated with a solution of lignosulfonates at a temperature of 95-98 ° C for τ _eff . The degree of AH extraction by this extractant is determined, the final AH content in the chips after both treatments and the degree of “cleansing” of the chips from AG are evaluated. The degree of extraction of AG and the products of its hydrolysis with a solution of lignosulfonates is 52%, calculated on its content in the chips after aqueous extraction. The total degree of "cleaning" is 70-72%. The total degree of extraction of flavonoids can be considered equal to ~ 70%.

In an industrial process for the production of cellulose, a mixture of wood chips with a known fraction of larch wood chips is loaded with compaction and wetted by spray into three digesters of periodic action, interconnected by liquid phases. Water is supplied to the first boiler at a speed that ensures filling the boiler with wood chips in 25 minutes and in an amount that provides a hydraulic module value of not more than 1: 3, calculated on dry wood chips. After the first boiler is completely filled with water, it continues to be supplied for another three minutes. After that, the spent sulfite liquor begins to be fed into the first boiler at the same speed. A layer of water added over 3 minutes (this is ~ 12% of the volume of the liquid phase in the boiler) serves as a buffer between the liquor and the extract and eliminates its contamination with lignosulfonates.

When the first boiler is filled with liquor, its supply is stopped and the bisulfite cooking solution begins to be fed, which displaces the liquor from the first boiler into the second. In this case, the liquor displaces the extract and the buffer layer of water from the second boiler into the third boiler. When the boilers are sequentially filled with cooking liquor, at the outlet of the third boiler, first extract the aqueous extract, which is sent to the storage tank, then the buffer layer, which can be used, for example, to wash the cooked cellulose and, finally, the spent sulfite liquor, which is sent to the system processing.

When the liquid phase is transferred from the boiler to another boiler, each liquid phase is heated to 95-98 ° C.

When filling the third boiler with the cooking solution, its supply is stopped. Boilers are ready for pulping. As a result, the chips in all the boilers went through the same treatment in two stages. As a result of water treatment of a triple volume of chips, an extract with a high concentration of AG and flavonoids is obtained. It is sent to the storage tank. In boilers, wood chips are poured with the same cooking solution. Cellulose is cooked in predetermined identical or different modes with separate recirculation of the cooking solution in each of the boilers. After cooking, the boilers are empty. Part of the spent liquor is sent to a storage tank. The rest is sent to the processing system. After emptying the boilers, they begin the second cycle of the boiler. The boilers are reloaded with wood chips. Filtered extract from the storage tank (for example, with the addition of water) is supplied to the first boiler for water treatment. Using this technique allows you to increase the concentration of AG and flavonoids in the extract or to maintain it at a high level with the maximum degree of extraction of these components from the chips with water and the possibility of selecting part of the extract for processing. Spent sulfite liquor to the second stage of processing chips is fed from the storage tank. The remaining operations of the pulp production process are similar to those described above.

All subsequent boiler cycles are also identical.

The following examples illustrate the possibilities of the proposed method. When they are used, a laboratory setup is used, which includes an autoclave with liquid phase recirculation systems, heating the contents of the autoclave and liquid phases to a predetermined temperature, removing each liquid phase from the autoclave by displacing it with another phase, providing the specified parameters of the cooking modes, as well as storage tanks for the extract and spent sulfite liquor. In all examples, the processing of wood chips before cooking is carried out with a hydraulic module of 1: 3, calculated on dry wood, the temperature of the extractants 95-98 ° C, the extraction time for each of the extractants is 25 minutes, and the humidity (averaged) of chips loaded into the autoclave is 50%. Samples processed in two steps of chips are cooked with recirculation of the cooking liquid. Each processing cycle includes sequential processing of three identical portions of chips (a, b, c). Control boiling samples of treated chips are carried out according to known technologies.

Example 1. To obtain cellulose, a mixture of wood chips from pine, birch and larch is taken with a mass fraction of larch wood chips with an AH content of 19.8% and flavonoids 1.1%. With a sequential extraction of 25 minutes in a recycle mode of the extractant of three portions of wood chips (this is an analogue of the process in an installation of 3 boilers), the concentration of AG in the extract reaches 15.05 g / l and flavonoids 0.83 g / l. The residual concentration of AG in the chips is 9.8%. The same portions of chips are sequentially treated with spent sulfite liquor. After this treatment, the AG content in larch chips is below 5.0%.

In the second cycle of testing the method, as well as in the subsequent ones, using 3 portions of the same chips, an extract from the first cycle or a mixture of extracts from previous cycles are fed to the water treatment of the first portion. Otherwise, all operations are similar to operations in the first cycle. The concentration of AH in the extract after the second cycle is 29.35 g / l, after the third - 42.93 g / l, after the fourth - 55.74 g / l, after the fifth - 64.3 g / l. In the sixth and subsequent cycles, a mixture of extracts with the addition of fresh water is fed to the chip processing, and an extract with an AG content of 72 g / l is obtained at the outlet of the third boiler.

The concentration of flavonoids in the extracts of successive cycles increases with the same pattern and reaches in the steady state 3.9-4.1 g / l.

Example 2. To obtain cellulose, a mixture of wood chips from spruce, aspen, and larch is taken with a mass fraction of 50% and an AG content of 13% and flavonoids 0.7%. After the first cycle, an extract is obtained with an AH content of 24.7 g / l, after the second - 48.1 g / l, after the third - 48 g / l. Accordingly, in the following cycles, an extract with the addition of water is fed to the first stage of chip processing. The flavonoid content in the extracts of the last cycles reaches 2.6-2.7 g / l.

Example 3. To obtain cellulose, they take larch chips with the addition of 20% birch chips. The AH content in larch chips is 6%, and flavonoids are 0.3%. The extract after the first cycle contains 18.24 g / l AG and 1.02 g / l flavonoids. The calculated concentration of AH inside the larch chips is 24 g / l. In this case, already in the second cycle, a mixture of extract and water in a ratio of 30:70 is fed to the wood chips.

In the examples, cellulose is cooked using known techniques. Technology I (RU, Pat. No. 2106448, IPC D21C 3/06, 9/00, publ. 10.03.1998) is designed to produce cellulose for chemical processing. Its variant according to example 1 from the description is used for cooking portions of wood chips (a, b, c), processed in two stages in cycles 1 and 5 of example 1, in cycles 1 and 2 of example 2, in cycle 1 of example 3. As comparison parameters samples of cooked cellulose use the Kappa number of unbleached pulp, the whiteness of the cellulose and the content of α-cellulose after bleaching. The test results are shown in table 1.

Technology II (RU, Pat. No. 201068, IPC D21C 3/06, publ. 08/08/1992) is designed to produce unbleached pulp. Its variant according to example 2 from the description is used for cooking portions of wood chips (a, 6, c) in cycles 2 and 6 of example 1, in cycles 1 and 3 of example 2, in cycle 2 of example 3. As the comparison parameters, the pulp yield is used; whiteness and kappa number. The test results are shown in table 2.

The data in the tables indicate a high degree of leveling of the characteristics of wood chips of different types of wood as a result of its two-stage processing.

Derived from the processes of the extract is processed according to known technologies as follows. First, it is cleaned of resinous substances on the filter or by pressure flotation, then it is concentrated by ultrafiltration to obtain a concentrate and a filtrate until the AG content in the concentrate is 25-26%. Then, AG is planted in acetone. The precipitate was separated from the water-acetone mixture, washed with acetone, dried and pure AG was obtained. Flavonoids are obtained from the filtrate using reverse osmosis technology.

Table 1 Pulp Characteristics Example 1 Example 2 Example 3 Cycle 1 Cycle 5 Cycle 1 Cycle 2 Cycle 1 a b at a b at a b at a b at a b at Kappa number, units 18.6 18,4 18.9 18.8 18.1 18,4 19.3 18.8 18.8 19.1 18.8 18.6 18.0 18,4 19,4 White,% 89 87 87 87 88 89 88 88 91 90 88 87 87 87 88 The content of α-cellulose,% 91 90 90 90 89 91 90 90 89 90 90 90 88 90 90

table 2 Pulp Characteristics Example 1 Example 2 Example 3 Cycle 2 Cycle 6 Cycle 1 Cycle 3 Cycle 2 but b at but b at but b at but b at but b at Exit, % 51.9 52.9 52.7 52.7 53.0 52.3 53.3 53,4 52.8 53,4 52.1 53.0 53.3 52.7 53.0 White,% 57.3 56.3 56.7 56.7 56.3 56.0 56.4 56.8 55 57.3 57.1 56.8 56.8 57.8 57.8 Kappa number, units 30,2 31.3 31,0 31,0 31.3 30,0 31.3 31.7 30.8 31,2 30,2 30.8 31.3 32,0 31.9

Claims (7)

1. A method of producing sulfite cellulose from a mixture of wood chips of different wood species, including the use of a boiler of periodic action, loading wood chips from a number of species containing larch, extraction of wood chips by treating it with an aqueous medium at an elevated temperature for a predetermined time to obtain an extract, removing its processing with the production of arabinogalactan and flavonoids, supplying a cooking solution to the boiler, cooking chips, removing cooking products from the boiler, characterized in that a number of rocks are additional includes wood of pine, spruce, birch, aspen, the mixture of wood chips after treatment with an aqueous medium is additionally subjected to hydrolysis treatment with a solution of lignosulfonates, while both treatments are carried out in three boilers connected by liquid phases by sequentially filling each of the liquid phases with the conclusion of its aqueous extract displacing lignosulfonates from the boilers and discharging this solution by displacing it with a bisulfite cooking solution and pulping is carried out using the bisulfite method. 2. The method according to claim 1, characterized in that the proportion of wood chips of larch in the total mass of wood chips is 20-80%. 3. The method according to claim 1, characterized in that the chips are treated with an aqueous medium and a solution of lignosulfonates at a temperature of 95-98 ° C. 4. The method according to claim 1, characterized in that as the solution of lignosulfates use hot spent sulfite liquor from pulping. 5. The method according to claim 1, characterized in that the processing of wood chips with an aqueous medium serves a medium containing arabinogalactan and flavonoids. 6. The method according to claim 1 or 5, characterized in that the extract is used as an aqueous medium containing arabinogalactan and flavonoids. 7. The method according to claim 1, characterized in that the processing of the extract extracted from the process includes the step of purifying it from the resinous components using filtration and / or pressure flotation.