Abstract
Agri-food waste is generated at various food cycle stages and is considered to be a valuable feedstock in energy systems and chemical syntheses. This research identifies the potential and suitability of a representative agri-food waste sample (i.e., plum stones) as a solid fuel. Ground plum stones containing 10, 15, and 20 wt.% of rye bran were subjected to pelletization. The pelletizer was operated at 170, 220, and 270 rpm, and its power demand for the mixture containing 20 wt.% of rye bran was 1.81, 1.89, and 2.21 kW, respectively. Such pellets had the highest quality in terms of their density (814.6 kg·m−3), kinetic durability (87.8%), lower heating value (20.04 MJ·kg−1), and elemental composition (C: 54.1 wt.%; H: 6.4 wt.%; N: 0.73 wt.%; S: 0.103 wt.%; Cl: 0.002 wt.%; O: 38.2 wt.%). Whole plum stones and pellets were subjected to combustion in a 25 kW retort grate boiler in order to determine the changes in the concentrations of NO, SO2, CO, CO2, HCl, and O2 in the post-combustion flue gas. Collected results indicate that plum stone–rye bran pellets can serve as effective substitutes for wood pellets in prosumer installations, meeting the Ecodesign Directive requirements for CO and NO.
Highlights
Improving the energy efficiencies of thermally operated waste conversion processes has lately become a trending topic worldwide [1,2]
Rye bran contains around four times the amount ofash that plum stones do. This indicates that rye bran has a higher amount of mineral salts, which could have been natural ashes chemically linked to the carbon structure or as so-called foreign ashes, that can be considered as mineral soil particles, that were absorbed by the plant while its state of vegetation or transferred to the biomass during harvesting and transport [71]
Being an agri-food waste, plum stones are feedstock with high calorific value and lower contents of nitrogen, sulfur, and chlorine. These properties make plum stones cleaner and alternative solid fuels for combustion. When they are pelletized without any additives, pellets with low kinetic durability are obtained, mainly due to the higher fat contents of plum stones
Summary
Improving the energy efficiencies of thermally operated waste conversion processes has lately become a trending topic worldwide [1,2]. Combustion the most preferred industry and in low- andinstallations; medium-power installations; so-called prosumer energy.isCombustion is the technology due to its high market availability and low installation and operating costs, most preferred technology due to its high market availability and low installation andcompared operating to that of gasification and pyrolysis Both woody and non-woody biomass pellets need to meet costs, compared to that of gasification and pyrolysis. It has pellets need to meet high-quality of current which was, in detail, described to be emphasized that the to method of energythat generation highly depends on the type of depends availableon fuel in Reference [45] It has be emphasized the method of energy generation highly the type of available fuel (woody biomass (woody biomass and agri-food waste).
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