Influence of moisture on particle size of plant raw materials after grinding

Stem plant materials, as a common lignocellulosic raw material, are widely used both in agro-industrial production and in biofuel technologies. One of the main technological operations when using stem plant materials is grinding. The performed studies are dedicated to determining the influence of raw material moisture on the efficiency of grinding plant materials such as wheat straw, rape straw and corn stalks. A hammer grate crusher was used for the research. The diameter of the rotor was 520 mm, the diameter of the sieve holes was 7.25 mm, and the frequency of rotation of the rotor was 1470 rpm. In the upper part of the rotor, four knives are installed on a disk with slots, which preliminarily destroy the raw materials. Raw materials obtained after grinding were analysed using a sieve classifier. Grinding quality was assessed by the weighted average particle size. Experiments were conducted with wheat straw, rape straw and corn stalks with moisture obtained during crop harvesting, as well as additionally dried. Each type of raw material had three levels of moisture, and the repetition of the experiments was threefold. The moisture limits for each crop were individual and ranged from 8 to 30%. When analysing the results of the experiment, mathematical dependencies were obtained that describe the change in the weighted average length of the crushed raw material in the form of linear functions. It was established that when grinding wheat straw, rape straw, and corn stalks with a hammer crusher, an increase in their moisture content within the range of 8–30% leads to an increase in the weighted average length of particles from 1.6 to 2.4 mm, and the coefficient of determination of linear models of the influence of moisture on the change in weighted average length is in the range of 0.68–0.96.