OBTAINING PULP FROM WHEAT STRAW IN A TWO-STAGE SYSTEM “ACETIC ACID – HYDROGEN PEROXIDE – WATER – ETHANOL”
Authors:   National Technical University of Ukraine «Igor Sikorsky Kyiv Polytechnic Institute», Trembus Irina , Semenenko Nina ,   National Technical Uni-versity of Ukraine «Igor Sikorsky Kyiv Polytechnic Institute»
Published: August 2021

Urgency of the research. Involvement of secondary raw materials in the form of agricultural waste and development of new ecologically safe ways of delignification of vegetable raw materials to solve problems of environmental pollution.Target setting. Available methods of delignification of vegetable raw materials using oxidant - hydrogen peroxide allow to obtain a fibrous semi-finished product with a high yield, but with strength values of 15-30% lower compared to fibrous semi-finished products obtained bycooking solutions at pH > 7. Therefore, it is necessary to improve existing methods. hydrogen peroxide in acetic acid.Actual scientific researches and issues analysis. The latest available domestic and foreign publications on oxidative-organosolvent methods of delignification of plant raw materials using peroxyacids and alcohols were considered in detail.Uninvestigated parts of general matters defining. Research of technology of oxidative-organosolvent delignification of vegetable raw materials with useof alcohol as a part of a cooking solution and definition of optimum values of technological parameters (temperature and duration) of process of reception of straw fibrous semi-finished products.The research objective. Investigation of technological parameters of straw cellulose production in the system acetic acid-hydrogen peroxide-water-ethyl alcohol in order to increase the physical and mechanical parameters and the yield of the target product.The statement of basic materials.A two-stage method for producing straw pulp from wheat straw at the first stage has been investigated. Delignification was carried out in the “acetic acid-hydrogen peroxide-water” environment at a hydrogen peroxide consumption of 50% of the mass of absolutely dry raw material (a.d.r.m.) and at the second stage of cooking, 40 volume% of ethyl alcohol was added to the cooking solution to replace the same amount of spent cooking solution after the first stage. The content of the main components in the original plant raw materials isdetermined. The influence of delignifica-tion conditions, namely temperature and duration of cooking on the yield of fibrous semi-finished product, the content of re-sidual lignin, cellulose content and strength indicators was studied. It is shown that the temperature increase at the first stage of the process from 50 ºС to 70 ºС, at the second stage from 80 to 100 ºС and the duration of processing of vegetable raw materials from 60 to 120 min. and from 60 to 180 minutes, according to the stages of the delignification process, leads to a decrease in yield by 7.9-18.9%, the residual lignin content by 4.27-9.11%, while the cellulose content in the fibrous semi-finished product increases by 10.1-15.8%. It is investigated that the indicators of mechanical strength of the obtained fibrous semi - finished products increase with increasing temperature and duration of processing of raw materials. Regression equa-tions for each stage of cooking are calculated, which adequately describe the experimentaldata and can be used as a mathe-matical model of the process of delignification of wheat straw with hydrogen peroxide in acetic acid. The method of multicrite-ria optimization of delignification conditions determines the optimal values of technological parameters of the wheat straw cooking process. The lignin-carbohydrate diagram of delignification of vegetable raw materials is offered. The number in which various methods of delignification of wheat straw are located on efficiency is defined.Conclusions. The technology of obtaining straw fibrous semi-finished products in the system "acetic acid-hydrogen per-oxide-water-ethanol" has been developed. Regression equations are calculated that adequately describe the experimental data and can be usedas a mathematical model of the investigated method of obtaining straw fibrous semi-finished product. The optimal technological parameters are established, which ensure the production of the final product with high quality indicators. The lignin-carbohydrate diagram of delignification of wheat straw stalks by different cooking methods is given.