Improving the Quality of Hydroxyapatite Ashes from the Combustion of Meat-Bone Meal in an Industrial Rotary Kiln

Abstract

Research on the properties of hydroxyapatite ashes from an industrial unit burning meat and bone meal in an industrial rotary kiln is presented. High carbon content (10%), relatively low phosphorus (34%), and sulfides were found. The ash obtained was unsuitable for producing superphosphate fertilizer due to the emission of hydrogen sulfide in the reaction of the raw material with sulfuric acid. The research showed that decreasing the meat-bone meal calcining temperature below 950 °C and recycling the ashes, reusing them after mixing in a 1:1 ratio with dosed meat and bone meal, allows reducing the carbon content in the hydroxyapatite ash to the level of <0.2%, increases the P2O5 content in the ash to 39%, and eliminates hydrogen sulfide emissions. The improved parameters allow the production of hydroxyapatite ash that could be a substitute for phosphorites used in the production of fertilizers. Incineration of the meat-bone meal allowed the production of bioenergy and hydroxyapatite. This is an example of implementing a very profitable circular economy solution.