Microwave and low-pressure superheated steam combined drying test apparatus and drying method

Abstract

The present invention belongs to the technical field of material drying, and discloses a microwave and low-pressure superheated steam combined drying test apparatus and a drying method. The combined drying test apparatus is composed of a steam generator, steam opening valves, a heater, an inlet fan, an air velocity transducer, a temperature sensor, a microwave generator, a vacuum pump, an outlet fan, a net-shaped material tray, a weighing sensor, a running water valve and a drying box. The drying method comprises that low-pressure superheated steam is used as a drying medium of a closed drying system, and materials are dried by the superheated steam and microwave together. The interiors of agricultural products are heated, inside moisture transfer speed of the agricultural products is raised, drying of the agricultural products is accelerated, temperature difference between the inside and the surface is reduced, generation of thermal stress cracks is reduced, and the drying quality and the drying uniformity of the agricultural products are ensured. No dust or volatile substances are discharged into the air in the drying process, the exhaust gas is saturated steam and can be recycled, the heat utilization rate is raised and total energy consumption of drying is lowered.

Description

technical field [0001] The invention belongs to the field of material drying technology and drying method, in particular to a microwave-low pressure superheated steam combined drying test device and drying method. Background technique [0002] Drying is an indispensable link in the processing of agricultural products, and it is also a key step to ensure product quality. Commonly used drying methods include sun drying and shade drying. The cost of drying is low, but the drying time is relatively long, and product quality depends too much on the environment and climate. The change. At present, the commonly used drying methods for agricultural products in my country mostly use the hot air drying process. The principle is that the heat source heats the air, and the hot air is used as the drying medium to directly contact the agricultural products, and heat and moisture are exchanged through convective heat transfer and mass transfer diffusion between the two. The drying medium t...

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Problems solved by technology

[0002] Drying is an indispensable link in the processing of agricultural products, and it is also a key step to ensure product quality. Commonly used drying methods include sun drying and shade drying. The cost of drying is low, but the drying time is relatively long, and product quality depends too much on the environment and climate. The change

At present, the commonly used drying methods for agricultural products in my country mostly use the hot air drying process. The principle is that the heat source heats the air, and the hot air is used as the drying medium to directly contact the agricultural products, and heat and moisture are exchanged through convective heat transfer and mass transfer diffusion between the two. The drying medium transfers the heat carried to the wet material, and at the same time makes the moisture in the wet material absorb heat and gasify and expand, and the drying medium dries the wet material to obtain agricultural products with a certain moisture content. The disadvantages of hot air drying are: The thermal efficiency is very low, generally only 30-60%, and the second is that the quality of the dried product is not high, which cannot meet the modern people's pursuit of high-quality products

In the general drying process, if the drying temperature is too high, the starch in the agricultural product will be gelatinized, the structure of the plant will be destroyed, and even burnt and blackened; the drying speed of the surface of the agricultural product is faster than the internal speed, and the surface layer of the agricultural product and the internal cells will shrink inconsistently, and the material will Non-oxidative damage such as decomposition and denaturation of the heat-sensitive components contained in it, so normal pressure superheated steam is not suitable for heat-sensitive materials

Lead to cracks, broken and other quality degradation of agricultural products

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