类黄磷物料微波干燥特性及动力学研究

Microwave Drying Characteristics and Kinetics of Yellow phosphorus-like material

  • 摘要: 采用微波加热技术对类黄磷物料进行干燥实验,研究初始质量、初始含水率和微波功率对类黄磷物料微波干燥过程的影响,并计算微波干燥效率(η)和单位能耗(Qs)。结果表明,在质量为50 g,含水率为40%,微波功率为360 W的条件下微波干燥效率(η)最大为21.16%,单位能耗(Qs)最低为10.66 MJ·kg-1。采用四种薄层干燥动力学模型(Page、Modified Page、Simplified Fick’s diffusion和Wang and Singh)对黄磷物料的干燥实验数据进行拟合和分析,Modified Page模型最适合描述类黄磷物料微波干燥过程。通过菲克第二定律计算水分子在类黄磷物料中的有效扩散系数。当初始质量为50 g,初始含水率为30%,微波加热功率为540 W时,类黄磷物料的有效扩散系数为1.53×10-10 m2·s-1。根据微波功率与活化能的关系,计算出微波干燥类黄磷物料的活化能为5.95 W·g-1。利用COMSOL Multiphysics软件,研究不同微波功率和加热时间对类黄磷物料干燥特性的影响,模拟电磁场和温度场的分布情况,建立多物理场耦合有限元模型,随着物料厚度和微波功率的增加,电场强度随之增加。本文将实验研究与理论计算相结合,为高效干燥类黄磷物料提供一定的理论基础和参考价值。

     

    Abstract: In this paper, the effects of initial mass, initial moisture content, and microwave power on the drying process were investigated, and microwave drying experiments were carried out on materials using microwave drying technology. The effects of different initial mass, moisture content, and microwave power on the drying characteristics of the materials were explored, and the microwave drying efficiency (η) and unit energy consumption (Qs) were calculated under different conditions. The results show that with an increase in initial mass and initial moisture content, the microwave drying efficiency (η) increases and the unit energy consumption (Qs) decreases. However, with the increase in microwave power, the microwave drying efficiency (η) gradually decreased and the unit energy consumption (Qs) gradually increased. When the initial mass is 50 g, the initial moisture content is 40%, and the microwave power is 360 W, the microwave drying efficiency (η) is the largest and the unit energy consumption (Qs) is the lowest. Therefore, the initial mass and initial moisture content can be increased appropriately, and the microwave power can be reduced to improve the microwave drying efficiency (η) and reduce the unit energy consumption (Qs) to achieve the purpose of energy saving. Four thin-layer drying kinetic models were used to fit the relevant experimental data, and the results showed that Modified Page was most suitable for describing the material microwave drying process. The surface diffusion coefficients of water molecules under different conditions were also calculated, and the activation energy was further calculated through the diffusion coefficients. The maximum diffusion coefficient was 1.29×10-10 m2·s-1 for an initial mass of 40 g. The maximum diffusion coefficient was 1.53×10-10 m2·s-1 for an initial moisture content of 30%, and the maximum diffusion coefficient was 1.64×10-10 m2·s-1 for a microwave power of 900 W. The activation energy was calculated to be 5.95 W·g-1. COMSOL was used to model the microwave electric field strength and tangential resistance loss at 2.45 GHz for a range of power levels and layer thicknesses. The findings demonstrate that when microwave power increases, the electric field strength rises as well, from 8.13×104 V·m-1 to 9.96×104 V·m-1 and finally to 1.15×104 V·m-1. The electric field distribution in the cavity is more uniform, and the field strengths at the microwave feeder and the X-Y plane are higher. As layer thickness grows, the electric field strength rises as well, from 5.89×104 V·m-1 to 5.99×104 V·m-1 and finally to 8.13×104 V·m-1. It demonstrates how the microwave field intensity is affected by varying microwave powers and layer thicknesses. The temperature difference and temperature field distribution can be displayed by the temperature field simulation of materials with varying layer thicknesses under various microwave power settings.

     

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