Design And Experiment Of Carbonization Device With Afterheat For Corn Stalk

At present,there are many ways to comprehensively recycle straw,and biochar preparation is one of them.In order to improve the carbonization efficiency and provide technological basis for mobile carbonization,based on the internal carbonization method,the process of afterheat carbonization was studied and the process parameters were determined by the combination of spontaneous combustion and carbonization method.The main research contents are as follows:1)After analyzing various kinds of straw carbonization methods and combining the characteristics of spontaneous combustion and carbonized carbonization methods,the afterheat carbonization process was proposed.Under the condition of no external heat source,the straw combustion provides the heat required for the carbonization,and the carbonization is carried out in the anoxic environment in the carbonization chamber,which can save energy and improve the carbonization speed.2)The experimental system for straw carbonization with afterheat was determined and the parameters of the main components of the carbonization device are calculated,and the structures of the feeding system,combustion chamber,conveying device,carbonization chamber,control system and other systems of the straw afterheat carbonization device are determined.The calculation of the thermal insulation layer of furnace body shows that the temperature stress of aluminum silicate fiber insulation material is small and the periodic change is not big,which can make the carbonization chamber have good temperature stability and meet the needs of constant temperature carbonization chamber.3)The distribution of temperature field in the thermal insulation and carbonization chamber of the carbonization test device is studied by using ANSYS FLUENT software.The mathematical and physical models of temperature and fluid changes in the thermal insulation and carbonization chamber are established.The temperature changes in the thermal insulation and carbonization stage are analyzed.The effects of the thickness of thermal insulation materials and the structure of the carbonization chamber on the distribution of temperature field are studied.The influence mechanism is compared and discussed,and the carbonization chamber is optimized.4)The experiment was carried out through the designed afterheat carbonization test device,with feeding speed,spontaneous combustion time and feeding layer thickness as test factors,and carbonization rate and biochar yield as test indexes.The optimal range of each experimental factor was determined by single factor test: the thickness of feeding layer was controlled at 5cm-15 cm,the feeding speed was controlled at 6m/ min-14 m /min,and the spontaneous combustion time was controlled at 10s-20 s.The combined experiment was designed and carried out,and the design-Expert 8.06 software was used to analyze the influence parameters of corn stalk carbonization from large to small in order: feeding speed,feeding layer thickness and spontaneous combustion time.The effects of the factors on biochar yield were as follows: spontaneous combustion time,feeding layer thickness and feeding speed in descending order.Software Design-Expert8.06 was used for optimization to obtain the optimal process parameters of aferheat carbonization process.Considering the convenience of actual operation control,the optimized parameters were adjusted as follows:feeding speed of 8m/min,feeding layer thickness of 10 cm,spontaneous combustion time of20 s.Verification tests were carried out,and the errors between the experimental values and predicted values of each index were 3.2% and 4.1%,respectively,indicating that the regression model based on quadratic orthogonal rotation combination test has high accuracy and reproducibility.