“Black pellets” is the generic name for a range of thermally-treated biofuel pellets intended for substitution of fossil-origin material in heat and power production. Woody biomass or agricultural residues can be processed into black pellets via various methods, including hydrothermal carbonization, torrefaction (mild pyrolysis) and steam treatment.
Black pellets characteristics, such as durability, moisture resistance, grindability, heating value and (bulk) density vary, depending on which method is used for thermal treatment. The steam treatment process, compared to torrefaction or hydrothermal carbonization, produces very durable pellets with good moisture resistance. Steam treatment gives an improvement in the heating value of the pellets but, more importantly, the process yield is high which means low loss of biomaterial during processing.
Valmet Pretreatment BioTrac system may be applied in the production of black pellets as well. A BioTrac steam treatment process is easily integrated into existing pulp mills or CHP-plants (Combined Heat and Power plants) thereby offering low energy use and unsurpassed environmental performance.