Research in fibrous plant preparation for pressed solid biofuel and determination of pellet indicators

Abstract

In the development of economical and convenient renewable energy fuel in the last years, pelleting of biomass has become the most used technology for biomass processing. Fibrous plants were chosen for biofuel production – fibrous hemp (Cannabis sativa L.) and fibrous nettle (Urtica dioica L.) - for their high productivity and soil undemanding. Three sorts of fibrous hemp were chosen: Felina 32, USO 31, Finola and one sort of fibrous nettle. Laboratory trials with plant preparation and usage for energy purposes were carried out in the Aleksandras Stulginskis University and Lithuanian Energy Institute. Biometric features of plant stems were determined, and, later, the plants were chopped, milled and granulated into pellets of 6 mm diameter. For chaff milling a hummer mill Retsch SM 200 was used, and the mill fractional composition was determined. Mill was granulated by a small capacity granulator with a horizontal matrix. The pellet quality indicators – moisture content, density, and strength and heat value were determined. The fibre plant pellet moisture content ranged from 7.3 % to 10.0 % and pellet density reached 899.3 – 1221.6 kg·m-3 DM (dry matter). The strength of pellets was determined using the test equipment INSTRON 5960. Fibrous hemp USO 31 had the biggest strength (pressing force of pellet degradation) – 1223.21 N, Felina 32 – 1053.39 N, Finola – 854.19 N and fibrous nettle pellets – 1345.94 N. The heat value of the fibrous plant pellets varied from 17.1 MJ·kg-1 to 17.6 MJ·kg-1