RU2360055C2 - Method for cellulose production from technical hemp - Google Patents

Abstract

FIELD: textile fabrics.

SUBSTANCE: raw hemp is boiled. Boiling is carried out with addition of anthraquinone in amount of not more than 0.1% from raw material weight. Produced cellulose is bleached with oxygen and/or ozone. Alkaline boiling liquid is processed with the help of semi-permeable membranes of reverse or direct osmosis. Regenerated boiling liquid is returned to boiling stage in boiling vessel. At that temperature of boiling is maintained in interval of 125-145°C.

EFFECT: increased quality of cellulose products and improved economic and ecological parametres of cellulose production process.

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Description

The invention relates to the field of cellulose production and can be used to produce high quality cellulose from inexpensive and quickly reproducible grassy raw materials with minimizing the environmental load on the environment.

A known method of producing pulp from stalks of corn [1]. In this method, a short fiber of corn is used, which does not provide a paper with a tear resistance. In addition, corn is not grown in most regions of the Russian Federation, especially in the areas where the largest pulp and paper enterprises are located (the north of the European part of Russia, Siberia, Baikal).

Long since in Russia and then in the USSR, technical hemp was grown for the subsequent production of marketable fiber. Fiber was used to prepare ropes, ropes, canvas.

Currently, hemp varieties that do not possess, in contrast to Indian hemp, narcotic properties have been bred. At the same time, industrial hemp has a unique ability to tenfold excess fiber growth compared to wood pulp per unit planted area.

Also known is the closest to the claimed method of producing cellulose from industrial hemp, including drying the raw materials, grinding and classification of the obtained particles, cooking using alkaline cooking liquids with a concentration of not more than 18% mass sodium hydroxide in a digester, separating the resulting cellulose from the cooking liquid [2 ]. The disadvantages of the method are the significant content of lignin in cellulose, high energy consumption to create the necessary cooking temperature and a large amount of spent alkaline cooking liquid as production waste.

The objective of the invention is to reduce the lignin content in the resulting pulp and thereby increase the quality of cellulose products, reduce energy consumption for the cooking process and significantly reduce the environmental load on the environment due to a sharp reduction in production waste.

The problem is solved in that the cooking is carried out with the addition of anthraquinone in an amount of not more than 0.1% by weight of the raw material, the cellulose obtained is bleached with oxygen and (or) ozone, the alkaline cooking liquid is treated with semi-permeable reverse or direct osmosis membranes, the regenerated cooking liquid is returned at the stage of cooking in the digester, while the cooking temperature is maintained in the range of 125-145 ° C.

The invention is illustrated by the following examples.

Example 1 (prototype).

Cannabis was cooked in a digester under the following conditions. The consumption of active alkali to hemp is 16-18% by weight of NaOH, the ratio of the mass of the cooking solution to the mass of the sample (hydraulic module) is 6, the maximum cooking temperature is 145 ° C, the cooking time is 2 hours. The yield of technical pulp is 45.1%. In this case, all the cooking liquid goes into waste water, that is, cooking liquor is completely lost and cannot be reused.

Example 2

Cannabis was cooked in a digester under the following conditions. The consumption of active alkali to hemp is 15-16% by mass of NaOH, the hydromodule is 6, the consumption of anthraquinone is 0.1% to hemp, the maximum cooking temperature is 125 ° C, the cooking time is 2 hours. The yield of technical pulp is 55.3%.

Example 3

The same as in example 2, but at a maximum cooking temperature of 145 ° C. The yield of technical pulp is 61.5%.

Example 4

The cellulose obtained in examples 2 or 3 was bleached using oxygen and (or) ozone. The whitening results are shown in table 1.

Table 1. The dependence of the whiteness of the pulp from the bleaching method Bleaching reagent Cellulose mass concentration,% Consumption of O ₂ and O ₃ , kg / t White,% About ₂ 18-25 1,5 thirty 2.0 40 3.0 49 About ₃ 18-25 1,5 52 2.0 60 3.0 66 O ₂ + O ₃ in a ratio of 1: 1 18-25 1,5 42 2.0 53 3.0 60

Table 2 presents the results of processing alkaline cooking liquids using semi-permeable membranes reverse or direct osmosis. This treatment allows to minimize the loss of cooking liquor, drastically reduce the volume of wastewater and the environmental load on the environment, as well as reduce the cost of wastewater treatment.

Table 2. Cleaning the cooking liquor. Membrane Pressure, atm The concentration of NaOH,% Loss of cooking liquor at hydromodule 6,% Source liquor Filtrate Concentrate No. 1 reverse osmosis fifty 12 - 24.1 1,2 fifteen - 26.0 1.4 No. 1 reverse osmosis 75 12 26.1 1,0 fifteen - 28.1 1.3 No. 2 direct osmosis four 12 10.8 - 7.2 fifteen 14.0 - 6.0 No. 2 Direct Osmosis 5 12 11.0 - 6.0 fifteen 14.1 - 5,4

The treated alkaline cooking liquid (direct osmosis membranes) with the addition of fresh water or purified water with the addition of fresh cooking liquor (reverse osmosis membrane) is sent as a regenerated cooking liquid to the pulping stage in the digester.

The proposed method allows to improve the quality of cellulose products and to improve the economic and environmental indicators of the pulp production process.

Literature

1. RF patent No. 2249636, IPC 7 D21C 5/00, 3/00, D21H 11/12, 06/29/2000.

2. CORREIA, F., D.N. ROY and K.GOEL, “Chemistry and Delignification Kinetics of Canadian Indastrial Hemp (Cannabis sativa L.),” J. Wood Chem. Technol. 21 (2): 97-111 (2001).

Claims (1)

A method of producing cellulose from industrial hemp, including cooking using an alkaline cooking liquid with a concentration of not more than 18 wt.% Sodium hydroxide in a digester, separating the resulting cellulose from the liquid, characterized in that the cooking is carried out with the addition of anthraquinone in an amount of not more than 0, 1% of the mass of raw materials, the resulting cellulose is bleached with oxygen and / or ozone, the cooking liquid is treated with semi-permeable reverse or direct osmosis membranes, the regenerated alkaline cooking liquid returns t for cooking stage in the digester, the digestion temperature is maintained in the range 125-145 ° C.