Production of fibrous materials by combined cooking of technical hemp processing waste

The purpose of the work is to evaluate the effectiveness of testing combined two– stage sodium oxidative-organosolvent cooking of industrial hemp processing waste for the production of cellulose. The component composition of the raw material: the mass fraction of resins and fats is 1.9%, substances soluble in hot water are 3.4%, cellulose is 56.7%, lignin is 21.7%, ash is 1.1%. Conditions of sodium cooking: hydromodule – 5:1; consumption of NaOH – 20...24% in units of Na₂O, % of abs. dry raw materials; temperature rise to 170 °C – 40 min; cooking at 170 °C – 120 min. Conditions of oxidative-organosolvent delignification: consumption of equilibrium peracetic acid – 0.8 g/g abs. dry raw materials, hydraulic module – 10:1, temperature rise to cooking – 15 min, cooking temperature – 90°C, duration – 90 min. At the first stage (alkaline cooking), 2.8 to 3.2% of carbohydrates are destroyed per one percent of the removed lignin, depending on the consumption of active alkali. At the second stage, during the temperature rise to the cooking point, there is a significant decrease in the concentration of cooking components: RPA decreases by 2.5-3.9 times, and H₂O₂ by 1.6-2.3 times, depending on the consumption of RPA for an absolutely dry soda semi- finished product. The main stage of delignification is characterized by the complete expenditure of RPA. For all variants of oxidative-organosolvent delignification, the reaction rate constant is (2.8 ± 0.2) × 10^–1 s^–1. During step-by-step cooking of cannabis processing waste with an alkaline cooking duration of 120 minutes at an alkali consumption of 24% in units of Na₂O from abs. dry. raw materials and subsequent oxidation-organosolvent delignification within 30 minutes can produce technical cellulose with a yield of 54.9% of the mass of abs. dry raw materials with a mass fraction of lignin of 3% and alpha-cellulose of 88.9% of technical cellulose.

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