Influence of the particle parameters on the properties of biomass briquettes

In the handling and usage processes, sufficient density and durability of biomass (straw, reed and hemp stalk) briquettes should be provided. For the briquettes density standards determined the value ρ is greater than 1.0 g⋅cmE-3. In the densification process, usually fine grinded particles are used, which significantly increases energy consumption for stalk material cutting. It is generally agreed that biomass material of 6-8 mm size with 10-20% powdery component (is less than 4 mesh) gives the best results. Calculated energy consumption for hemp stalk cutting to such size is greater than 12 kJ·kgE-1, but to the size of 100 mm – is less than 1 kJ·kgE-1. Calculated energy consumption for common reed cutting to sizes less than 3 mm was greater than 7 kJ·kgE-1 but to the size of 20 mm – approximately 1 kJ·kg-1. The goal of the investigation was to obtain the necessary density and durability of briquettes of larger biomass particles by arranging them. The orientation of the straw or reed or hemp stalks has to promote binding by the pressing operation. The article presents the investigation of straw, common reed and hemp biomass mechanical properties which influence the machine design and methods for biomass conditioning. The investigation of biomass briquetting energy and briquettes strength is also presented. Crushing force dependence on particle size for arranged structure briquettes was stated in laboratory experiments. The specific splitting force of arranged structure coarse chopped wheat straw and reed briquettes reached the value of 35 N·mmE-1. It is approximately the same as that of industrially produced wood briquettes. Splitting force of the hemp stalk briquettes reached 115 N·mmE-1. The density of the arranged reed and hemp stalk particles exceeds the recommended in the standards (1000 kg∙mE-3) and reaches – 1185 kg∙mE-3 for the arranged hemp stalk particles with the length of 150mm and briquetting pressure – 212 MPa. The specific briquetting energy of coarsely chopped arranged reed and hemp stalk particles varied from 51.61 kJ∙kgE-1 to 67.23 kJ∙kgE-1. For comparison, the finely chopped reed particle briquetting energy gave the maximum specific energy – 40 kJ∙kgE-1. The splitting force of the hemp stalk briquettes reached 133.33 N∙mmE-1.