基于温湿度控制的牛粪再生垫料生产工艺干燥特性研究

Temperature-humidity Controlled Drying Technology and Device Design for Producing Recycled Manure Solids

为解决奶牛场粪污处理的难题,同时为散栏饲养牛舍提供安全舒适的牛床垫料,以固液分离后的固体牛粪为研究对象,研究在不同干燥温度、相对湿度和物料厚度条件下,牛粪再生垫料的干燥特性和杀菌率,通过响应面分析得出最优干燥工艺参数,并进行装置设计与现场试验。结果表明:高温高湿干燥能有效杀灭牛粪中的无乳链球菌和大肠杆菌。响应面分析优化确定的最佳工艺参数为高温高湿(温度60℃、相对湿度60%)杀菌处理2 h+热风降湿(78℃)干燥处理4 h,物料厚度为4 cm,在此条件下得到的垫料产品含水率为(50.3±0.6)%,大肠杆菌和无乳链球菌的杀菌率分别为98.3%和99.5%。现场验证试验结果表明该方法生产牛粪再生垫料可行,其垫料成品的含水率为(50.2±1.0)%,大肠杆菌和无乳链球菌的杀菌率分别为95.3%和98.3%。

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.