INFLUENCE OF COMPLEX HYDROMECHANICAL TREATMENT ON THE DISPERSION OF PLANT RAW MATERIAL IN THE TECHNOLOGY OF OBTAINING FUEL ETHANOL

In the energy sector, particularly, the transport sector, biomass of plant origin is associated with additives to motor fuels with biodiesel and bioethanol. The main purpose of the pretreatment of lignocellulosic raw materials for hydrolysis is to destroy the heterogeneous matrix, increase the surface area and porosity of the cellulose material, and free carbohydrates from lignin bonds. One of the key factors affecting the efficiency of pretreatment and subsequent hydrolysis is the size of the raw material particles obtained at the stage of mechanical grinding. During subsequent processing in rotary reactors based on centrifugal pumps, the raw material is subjected to additional influence of thermophysical factors, which contribute to a further increase in the degree of dispersion of the raw material, increasing the specific surface area of the cellulose material. The work aimed to determine the influence of the complex thermophysical phenomena of hydromechanical processing on the particle size of plant raw materials during their pretreatment for hydrolysis in the technology of obtaining fuel ethanol. The feedstock was wheat straw and corn stalks, chopped on a straw cutter, and once processed in a disintegrator. The determination of the plant raw material particle size distribution was carried out using sieve analysis. The processing of the suspension of plant raw materials was carried out on experimental setup with a reactor mixer, which is a rotor-pulsation apparatus. The particle size distribution in the range of 0.001-0.08 mm was determined using a laser particle size analyzer Microsizer 201 A. Further crushing of the straw was carried out on experimental setup. It was determined that with an increase in the solid : liquid ratio from 1 : 5 to 1 : 15, the size of the parts decreases by 35–40 %, and when increasing the solid : liquid ratio from 1 : 5 to 1 : 10 — by 3–5 %. Changing the solid : liquid ratio from 1 : 15 to 1 : 10 for 10 cycles of processing the dispersion in the reactor-mixer until the temperature drops from 47 to 42 °C, at which the productivity of the equipment increases in 1.5–2 times, energy consumption changes by 25–30 %. The temperature of an aqueous dispersion of wheat straw (corn stalk) at a ratio of 1 : 15, mixed in the reactor-mixer for 10 cycles, moves from 17 to 22 °C, at the same time at solid : liquid ratio 1 : 10 at 17 to 42 °С, at solid : liquid ratio 1 : 5 at 17 to 47 °С. When processing an aqueous dispersion with wheat straw in a reactor mixer with a pulsation frequency of 1 kHz, 42 cycles are required to achieve 100 % frequency in less than 80 µm. When the pulsation frequency increases from 1 to 3 kHz, the number of cycles changes to 30. When the pulsation frequency changes from 1 to 5 kHz, the number of cycles decreases to 27. Changing the shear rate of the flow has a more significant effect on particle dispersion than the pulsation frequency. The number of processing cycles is reduced by 5–7 %. Bibl. 15, Fig. 8.