玉米薄层变温干燥特性及工艺参数优化研究

Variable Temperature Drying Characteristics and Process Parameters Optimization of Maize Thin Layer

为提高玉米的干燥品质,降低干燥能耗,在前人研究谷物变温干燥基础上,探究变温干燥工艺对玉米干燥特性及品质的影响。分析初始干燥温度(45~70℃),转换温度含水率(18%~26%)、升温幅度(5~25℃)、缓苏比(1∶1、2∶1、3∶1、4∶1、5∶1)等实验因素对玉米干燥速率及外观品质(裂纹率增值、色差)的影响规律;采取多元二次回归正交旋转组合实验方法,以初始干燥温度、转换温度含水率、升温幅度及缓苏比为实验因素,裂纹率增值和色差值为目标响应值,通过建立回归模型和响应面图,分析玉米变温干燥特性并阐明产生的原因。通过单因素分析,结果表明:初始干燥温度为45~55℃、转换温度含水率为20%~24%、升温幅度为5~15℃、缓苏比为2∶1~4∶1条件下可获得较好的干燥品质;变温干燥的最佳工艺参数为初始温度为50.59℃、转换温度含水率为21.56%、升温幅度为5℃、缓苏比为3.8∶1.0,干燥后的玉米裂纹率增值为10.00%、色差值为2.056,实验值与预测值之间的相对误差为4.25%。

To improve the drying quality of corn and reduce the drying energy consumption,based on the previous research on grain drying,the influence of temperature change drying technology on the drying characteristics and quality of corn was studied.Initial drying temperature(45-70℃),moisture content of conversion temperature(18%-26%),temperature rise range(5-25℃),tempering ratio(1∶1,2∶1,3∶1,4∶1,5∶1)and other experimental factors on maize drying rate and appearance quality(crack rate and color difference);the multiple quadratic regression orthogonal rotating combination test method was adopted,with initial drying temperature,moisture content at transition temperature,temperature rise range and tempering ratio as test factors,crack rate and color difference as target response values.The regression model and response surface diagram were established to analyze the drying characteristics of maize at variable temperature and explain the causes of the results.Through single factor analysis,the results indicated that,the initial drying temperature was 45-55℃,the moisture content of the conversion temperature was 20%~24%,the temperature rise was 5-15℃,and the tempering ratio was 2∶1-4∶1.The optimum process parameter combination of variable temperature drying was the initial temperature of 50.59℃,the moisture content of the conversion temperature of 22.86%,the temperature rise of 5℃,and the tempering ratio of 3.8∶1.0.After drying,the crack growth rate of corn was 10.00%,the color difference value was 2.056,and the relative error between the experimental value and the predicted value was 4.25%.