花椒真空干燥动力学模型及干燥工艺研究

发布时间：2018-03-22 11:36

  本文选题：花椒　切入点：真空干燥　出处：《西南大学》2017年硕士论文　论文类型：学位论文

【摘要】：新鲜花椒采收后含水率高达200%.d.b,在贮藏过程中极易受外界条件的影响,发生质变,造成巨大损失。干燥是花椒收获后重要的处理环节,对花椒的运输、贮藏等起到重要的作用,但若干燥处理不当,则会造成花椒品质严重受损,营养物质流失严重,降低其经济效益。传统的干燥方式存在干燥效率低、干燥品质差等缺点,而真空干燥是一种新型热门的干燥技术,具有节能、环保、干燥品质好等优点。本文将采用真空干燥对花椒进行以下几个方面的研究:(1)研究了花椒的真空干燥特性。选取温度(50、60、70℃)、真空度(-0.02、-0.04、-0.06Mpa)和载重量(30、40、50g)对花椒进行三水平三因素的全面试验研究。对不同温度、真空度和载重量条件下花椒的真空干燥特性进行研究;选取决定系数R2、残差平方和SSE和卡方χ2作为模型评价指标对水分比-时间干燥曲线进行了7种经典数学模型的拟合,结果表明三次多项式模型具有较大的决定系数和较小的误差值,是最适合描述花椒真空干燥的数学模型。(2)建立花椒真空干燥BP神经网络模型。以时间、真空度、温度和载重量为输入神经元,水分比为输出神经元,利用Matlab神经网络工具箱对全面试验的25组896个试验数据作为训练样本进行训练,再把另外2组试验作为检验样本进行拟合检验,结果表明BP神经网络模型拟合性很高,两个检验样本的平均相对误差分别为8.698%和6.593%,通过BP神经网络能直接准确的预测花椒真空干燥过程中的水分比变化。(3)基于Weibull函数的花椒真空干燥模型建立及过程解析。利用Weibull函数及其尺度参数α和形状参数β在干燥理论中的意义对花椒真空干燥进行解析及模型建立。结果表明,Weibull函数模型对花椒真空干燥过程拟合度高;温度是影响花椒真空干燥的主要因素,随着温度的升高,Weibull模型的尺度参数α值减小,有效水分扩散系数增大,说明干燥速率增大,所用的干燥时间缩短;Weibull函数的形状参数β大于1表明花椒真空干燥过程中有明显的升速阶段。(4)本论文以开口率和色差值为花椒真空干燥评价指标初探花椒真空干燥品质。试验结果表明干燥温度越高,花椒色差值越大;干燥温度和真空度越高,开口率越高。为了获得高品质的花椒制品,在进行花椒干燥时尽量采用低温干燥。(5)花椒真空干燥工艺优化。选取三个因子和三个指标进行了三元二次旋转回归组合试验设计,借助Design-Expert 8.0软件工具,通过响应面法进行单指标参数优化,再通过加权评分法进行多指标综合优化最终确定花椒真空干燥的最佳工艺参数为:温度62.18℃,真空度-0.054Mpa,装载量37.23g。在此试验条件下,各个指标的相对误差均小于10%,可靠度高。
[Abstract]:The moisture content of fresh Zanthoxylum bungeanum after harvest is as high as 200.d.b. it is easy to be affected by external conditions during storage, resulting in great loss. Drying is an important process after harvest and plays an important role in transportation and storage of Zanthoxylum bungeanum. However, if the drying process is not proper, the quality of Zanthoxylum bungeanum will be seriously damaged, the loss of nutrients will be serious, and its economic benefit will be reduced. The traditional drying method has the disadvantages of low drying efficiency and poor drying quality. Vacuum drying is a new and popular drying technology with energy saving and environmental protection. The vacuum drying characteristics of Zanthoxylum bungeanum were studied by vacuum drying in the following aspects: 1) the vacuum drying characteristics of Zanthoxylum bungeanum were studied. A comprehensive experimental study of three factors. For different temperatures, The vacuum drying characteristics of Zanthoxylum bungeanum under vacuum and deadweight conditions were studied, and seven classical mathematical models were fitted with the determination coefficient R2, residual square and SSE and chi-square 蠂 2. The results show that the cubic polynomial model is the most suitable mathematical model to describe the vacuum drying of Chinese prickly ash, and the cubic polynomial model has a large determining coefficient and a small error value, and the BP neural network model for vacuum drying of Chinese prickly ash is established. The time, vacuum degree and vacuum degree are used to establish the BP neural network model for vacuum drying of prickly ash. The temperature and deadweight were input neurons and the water ratio was output neurons. The Matlab neural network toolbox was used to train 896 experimental data of 25 groups. Then the other two groups of experiments were used as test samples to carry out fitting test. The results show that the BP neural network model has high fitting ability. The average relative error of the two test samples is 8.698% and 6.593respectively. BP neural network can directly and accurately predict the change of water ratio in the vacuum drying process of prickly ash.) based on Weibull function, the vacuum drying model of Chinese prickly ash and its process solution can be established. Using the meaning of Weibull function and its scale parameter 伪 and shape parameter 尾 in drying theory, the vacuum drying of prickly ash was analyzed and the model was established. The results showed that the Weibull function model had high fit for the vacuum drying process of prickly ash. Temperature is the main factor affecting vacuum drying of Zanthoxylum bungeanum. With the increase of temperature, the scale parameter 伪 value of Weibull model decreases and the effective moisture diffusion coefficient increases, which indicates that the drying rate increases. The shape parameter 尾 of Weibull function is greater than 1, which indicates that there is a significant increasing speed stage in vacuum drying of Chinese prickly ash.) in this paper, the opening rate and color difference value are used as the evaluation index of vacuum drying of Chinese prickly ash. Drying quality. The test results show that the higher the drying temperature, The greater the color difference value, the higher the drying temperature and vacuum, the higher the opening rate. The vacuum drying process of Zanthoxylum bungeanum was optimized by using low temperature drying. Three factors and three indexes were selected to design the three dimensional quadratic rotation regression test, and the software Design-Expert 8.0 was used to design the optimal vacuum drying process of Zanthoxylum bungeanum L. The single parameter is optimized by response surface method, and the optimum technological parameters of vacuum drying of Chinese prickly ash are determined by weighted scoring method. The optimum technological parameters are: temperature 62.18 鈩，

本文编号：1648476