Processing of sunflower hulls and peat with production of melanin and composite fuel briquettes

The article discusses production of composite peat fuel briquettes from butter-making waste represented by sunflower hulls. The experiments prove manufacturability of briquettes at the quality of the standard first-grade peat fuel briquettes. The specific heats of sunflower hulls and composite briquettes are determined. Furthermore, the experimental tests show that ultrasonic treatment used to extract melanin from sunflower hulls changes the chemical composition of the raw material and its reactivity worth, as well as promotes an increase in the specific heat of sunflower hulls from 17.5 to 19.7 MJ/kg. The ultrasonic treatment degrades lignified tissue matrix of sunflower hulls. The Fouriertransform infrared spectra of lignin from sunflower hulls are analyzed before and after the ultrasonic treatment. Despite the strong resemblance, the spectra display differences in the structure of lignin, as well as in the ranges of fluctuation of methyl and methylene groups. It is shown that the yield of melanin from sunflower hulls in the optimized extraction conditions in the ultrasonic field (temperature 60 0С, extraction time 25 min, density 414 W/cm2, sunflower hulls : extractant ratio 1 : 40) totals 7.6% of the biomass of sunflower hulls. The size of melanin particles is 457–465 nm. The accomplished research proves feasibility of the integrated approach to processing of sunflower hulls to produce bio-active melanin and composite peat fuel briquettes.The study was supported by the Russian Science Foundation, Project No. 20-69-47084.