Manure drying optimization

Horse manure is a poor feedstock whose energetic content is comparable to that of herbaceous biomass. However, it can be effectively burnt provided that it is previously desiccated, being its moisture content very high (60% wb). This work reports an experimental investigation to identify optimal conditions for horse manure drying in a bench-scale direct heating rotary drier, to be sequentially combined with its combustion. The relative impact of the variables affecting the drying rate is assessed by an extensive sensitivity analysis which addresses both the role of solid motion and the drying fluid. Results show that the effectiveness of the gas-solid contact has a remarkable effect on the moisture release rate, and the drying air temperature is the controlling parameter. Tests using flue gases as drying medium confirm that they can be profitably used, without significant loss of drying capacity, suggesting that combined drying and combustion is a viable option. Setting a target residual moisture at 30% wb, by sensitivity analysis the time required could be cut to 12 min, for a reference quantity of 1.2 kg, with a maximum moisture removal capacity of 70 (kg/h)/m(3). (C) 2022 Published by Elsevier Ltd.