Understanding heat and mass transfer processes during microwave-assisted and conventional solvent extraction
Understanding heat and mass transfer processes during microwave-assisted and conventional solvent extraction
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DOI：
10.1016/j.ces.2020.116418
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发表时间：
2021-04
影响因子：
4.7
通讯作者：
Yujie Mao;J. Robinson;E. Binner
中科院分区：
文献类型：
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作者：
Yujie Mao;J. Robinson;E. Binner
溶剂萃取是一个传质过程。在本文中，我们研究了传热学在溶剂萃取中的作用：特别是固体的传热性和加热方式(传统加热和微波加热)如何驱动这个传质过程。以橙皮、苹果渣、芒果皮和胡萝卜果肉为原料，采用水基溶剂萃取法提取果胶。当微波处理生物质的介电损耗明显高于水时(例如，从苹果渣中最佳提取果胶的时间从120min缩短到45min)，热导率和介电损耗可以很好地预测提取性能，随着传质速率的阶跃变化而增加。当损耗因子较低时，两种技术的提取性能没有差异(例如，两种情况下的胡萝卜浆提取时间都是60分钟)。在不同的加热速率下对常规提取和微波提取进行了进一步的研究，以使微波体积加热和选择加热的影响分离。结果表明，在一定的功率阈值下(在本实验的100-120W范围内)，微波与常规提取是等价的，而在阈值以上，微波的提取时间实现了阶跃变化。这些发现首次在实验上证实了微波生物质加工的最新理论进展，在该理论中，温度诱导的扩散驱动了传质。这也是第一篇能够识别最适合微波提取的生物量特征的论文。
Solvent extraction is a mass transfer process. In this paper, we investigate the role of heat transfer in solvent extraction: in particular, how the heat transfer properties of the solid and the heating method (conventional heating and microwave heating) drive this mass transfer process. Water-based solvent extraction of pectin from orange peel, apple pomace, mango peel and carrot pulp was carried out. The thermal conductivity and dielectric loss were shown as good predictors of extraction performance, with step change increases in mass transfer rates when microwave processing was applied to biomass with dielectric loss significantly higher than water (e.g. 120 mins reduced to 45 mins for optimal pectin extraction from apple pomace). When the loss factor was lower there was no difference in extraction performance between the two technologies (e.g. carrot pulp extraction time was 60 mins in both cases). Further investigations were carried out at different heating rates for both conventional and microwave extraction in order to decouple the effects of microwave volumetric and selective heating. It was shown that below a certain power threshold (within the range of 100–120 W in these experiments), microwave and conventional extraction are equivalent, while above the threshold, microwaves achieved a step-change in extraction time. These findings are the first experimental confirmation of recent theoretical advances in microwave biomass processing, in which Temperature-Induced Diffusion drives mass transfer. It is also the first paper to allow identification of biomass characteristics that will be most amenable to microwave extraction.