With the increase of people's demand for dairy products, the rapid development of dairy farming has made manure management attracting much attention. In order to solve the problem of manure treatment in large-scale dairy farms, and simultaneously provide safe and comfortable dairy bedding materials, the solid portion of dairy manure after solid-liquid separation was used as research object, and the sterilization rate during high-temperature and high-humidity drying process and the drying characteristics during the dehumidifying drying process under different temperature, relative humidity (RH) and material thickness conditions were investigated. The feasibility of producing recycled manure solids (RMS) by temperature-humidity controlled drying technology was analyzed. The optimal drying parameters were obtained through response surface analysis with drying temperature, drying time and material thickness as variables and final moisture content of RMS as response index. On this basis, temperature-humidity controlled drying device for producing RMS was designed and the on-site verification test was carried out under the optimized process conditions. The results indicated that high-temperature and high-humidity drying process can effectively kill Streptococcus agalactiae and Escherichia coli in dairy manure. Except for some conditions, the sterilization rate after 2 hours of drying can reach more than 99%. The higher the relative humidity of the environment during the high-temperature and high-humidity drying stage was, the less serious encrustation of dairy manure was, which was conducive to the moisture evaporation in the subsequent drying process and improving the drying efficiency. In the dehumidifying drying stage, under the same material thickness and drying time, the higher the drying temperature was, the more the moisture content drops were, and the faster the internal moisture migration speed was, however, it was not the higher drying temperature can make better. The results of response surface analysis showed that the intensity sequence of the parameters affecting the final moisture content was material thickness, drying time, and drying temperature. The optimal parameters were 2 h high-temperature and high-humidity (60℃, 60%RH) sterilization treatment +4 h dehumidifying drying (78℃), as well as the material thickness of 4 cm. Under this condition, the water content of the final product obtained was (50.3±0.6)%. The sterilization rate of Escherichia coli and Streptococcus agalactiae was 98.3% and 99.5%, respectively. The temperature-humidity controlled drying device was mainly composed of the feeding and discharging system, the heating and air supply system, the humidification and dehumidification system, etc. For the field verification test, the moisture content of the final product was (50.2±1.0)%, and the sterilization rates of Escherichia coli and Streptococcus agalactiae were 95.3% and 98.3%, respectively, meeting the safety requirements for RMS. The results showed that the temperature-humidity controlled drying technology was feasible to produce RMS quickly and safely. And the results can provide new method for producing RMS. © 2020, Chinese Society of Agricultural Machinery. All right reserved.
