Improving the Efficiency of Biowaste Torrefaction

Abstract

Russia faces an important environmental challenge associated with the accumulation of a large amount of biowaste due to the lack of technologies for their efficient processing. In particular, the intensive development of aviculture in Russia, including poultry farming, in the coming years will lead to the need of processing significant amounts of poultry manure and poultry litter. One of the options for litter disposal is its processing into biofuel suitable for the production of heat energy for the needs of poultry farms themselves and for outside consumers. However, with this option, the disposal of litter requires its disinfection, for example, by the method of torrefaction. However, the existing torrefaction technologies are characterized by a considerable process duration. A new method of torrefaction has been proposed and comparative studies have been carried out on the process of poultry litter torrefaction in a fixed bed under a nitrogen blanket (dry torrefaction) and in a fluidized manure bed pretreated in superheated steam (wet torrefaction). After both methods following heat treatment, manure samples are obtained, the mass of which is decreased twice due to an almost threefold decrease in the oxygen content, which, along with an increase in the carbon content and a decrease in the amount of moisture, causes the fuel efficiency of the manure. The manure torrefaction in a fluidized bed also makes it possible to significantly (four times) speed up the process. Technical solutions are proposed to solve the issues of full or partial recovery of energy costs related to the production of superheated steam due to the processing of gaseous torrefaction products into syngas using hot biochar thermal cracking.