Parameter optimization on mechanical coating processing of rotary table-roller coating machine for peanut seeds

Abstract: In order to improve both poor coating qualified rate and high breakage rate of peanut seeds caused by unreasonable working parameters of rotary table-roller coating equipment, the single factor and central composite experiments were conducted. The effects of the main working parameters, including ratio of seeds weight to coating volume, dilution ratio of seed coating, speed of roller, on coating qualified rate and breakage rate of peanuts coating were analyzed by means of the rotary table-roller coating test rig. The study object was "Huayu 33", which was 16.22-19.16 mm in length, 8.06-10.36 mm in width, and 7.16-8.36 mm in thickness and whose moisture was 11.6%, and thousand kernel weight was 812.1 g. The single factor experiments were firstly conducted, and the results showed the influence laws of the 3 main working parameters on coating qualified rate and breakage rate, which were necessary to determine zero level of each parameter in the quadratic regression revolution design. And then the composite experiment methods of quadratic orthogonal rotation were adopted, the data were analyzed based on the Design-Expert software, the mathematical regression models of peanuts coating rate and breakage rate were built, and their corresponding variance analysis were conducted too. A regression equation of the relationship between variation coefficient of the 3 main working parameters was obtained. Through the analysis of variance, the results showed that the most influential factor for the coating qualified rate was the ratio of seeds weight to coating volume, and the minimum impact factor was the dilution ratio of seed coating; regarding to the breakage rate, the most influential factor was the speed of roller, and the minimum impact factor was the ratio of seeds weight to coating volume. The response surface method was utilized to analyze the effects of factors' interaction on the coating qualified rate and breakage rate, and the multi-objective optimizations were conducted for the regression models. The optimal combination working parameters of the drum coating test rig were the roller speed of 18.32 r/min, ratio of seeds weight to coating volume of 31.73 g/mL, and dilution ratio of seed coating of 4.76. All of those were obtained by the optimization solution of all factors with the quadratic regression model equation of performance evaluation indices in the range of experimental parameters constraints. Under the condition of the optimal combination working parameters, the coating qualified rate and the breakage rate were 97.35% and 0.37%, respectively. This coating quality met the need of peanut seeds processing industry. The results of verification test were consistent with those of optimization solution. Production verification test was conducted with the 5BY-500-J coating machine (the productivity was 5 t/h when it was used for corn seeds coating operation) in Nanjing Agricultural Machinery Factory. The coating machine worked the same as the rotary table-roller coating test rig, but the working parameters were not reasonable for peanut coating. In the experiment, the working parameters of 5BY-500-J coating machine were adjusted according the optimization results by variable frequency regulation of the drum and the control of feeding parts of seeds coating. With the optimal parameters applied by the coating machine, the coating quality was improved greatly, and the coating qualified rate and breakage rate were 97.05% and 0.40%, respectively, which were very close to those obtained from the previous model results. The results of verification showed that the coating machine could be used for peanut seeds processing after working parameters optimization. The study provides the scientific basis for the working parameter optimization of rotary table-roller coating machine for peanut seeds.