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Microwave vacuum drying method achieving staging control

A microwave vacuum drying and vacuum drying technology, which is applied in the direction of static material drying machine, drying solid material, local stirring dryer, etc., can solve the problems of material overheating, surface cracking, coking, etc., to enhance the degree of automation and improve product quality Effect

Active Publication Date: 2016-07-20
SOUTH CHINA UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The three drying stages have their own characteristics, and the required microwave output power should also be changed accordingly. Especially in the drying stage of temperature rise and deceleration, if the operation is not properly controlled, the material is prone to partial overheating or even coking, surface cracking, and quality deterioration.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0029] The microwave vacuum drying device that present embodiment adopts is as figure 1 As shown, it includes drying box 1, magnetron 2, vacuum pump 3, infrared temperature measuring probe 4, air pressure measuring probe 5, data acquisition and processing system 6, PLC control system 7, ventilation valve 8, furnace door 9 and material tray 10. A plurality of magnetrons 2 are installed on the side and top of the drying box 1 to provide heat sources for the microwave drying process. There are vacuum holes on the side wall of the drying box 1, and the vacuum holes are connected with a vacuum pump 3 through a pipeline. The infrared temperature measuring probe 4 and the air pressure measuring probe 5 are located on the top of the drying box, and are used to measure the temperature of the material and monitor the vacuum degree in the cavity, and transmit the data to the data acquisition and processing system 6, and in the PLC control system 7 in real time.

[0030] The present em...

Embodiment 2

[0033] The present embodiment adopts the microwave vacuum drying method of the present invention to dry 5 kg of banana slices with a thickness of about 1 cm. After actual measurement, the initial water content of banana slices is 70.83% (calculated by weight M 初始 =242.82%), the moisture content of the expected dry product is 5% (M 终点 = 5.26%). Spread the radish slices evenly on the loading board, put them into the vacuum drying box, and close the oven door. Turn on the power of the equipment, enter the PLC control system, and set the power of the three stages of drying as p 1 =8kw,p 2 =14kw,p 3 =8kw; vacuum degree p 1 =p 2 =p 3 =0.95MPa (corresponding to the boiling point T of water p ≈37℃); processing time t 1 = 5min, t 2 = 30min, t 3 = 10min; temperature T in the drying stage of temperature rise and speed drop 3 =42℃; automatic conversion temperature T x1 =37°C, T x2 = 42°C. Turn on the vacuum pump until the vacuum reaches the set vacuum p 1When =0.95MPa, tur...

Embodiment 3

[0035] The present embodiment adopts the microwave vacuum drying method of the present invention to dry 5 kg of mango slices with a thickness of about 1 cm. After actual measurement, the initial water content of mango slices is 87.40% (calculated by weight M 初始 =693.63%), the moisture content of the expected dry product is 5% (M 终点 = 5.26%). Spread the mango slices evenly on the loading board, put them into the vacuum drying box, and close the oven door. Turn on the power of the equipment, enter the PLC control system, and set the power of the three stages of drying as P 1 =8kw,P 2 =14kw,P 3 =8kw; vacuum degree p 1 =p 2 =0.95MPa (corresponding to the boiling point T of water p1 ≈37℃),p 3 =0.97MPa; processing time t 1 = 5min, t 2 = 30min, t 3 = 10min; temperature T in the drying stage of temperature rise and speed drop 3 =40℃; automatic conversion temperature T x1 =37°C, T x2 = 40°C. Turn on the vacuum pump until the vacuum reaches the set vacuum p 1 When =0.95M...

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Abstract

The invention discloses a microwave vacuum drying method achieving staging control. In a heating temperature rise stage, a constant-temperature and constant-speed drying stage and a temperature rise and speed reduction drying stage, different microwave powers are adopted for being output; the temperature and air pressure of a material are monitored online, and the microwave output powers and vacuum degrees are controlled in a staging manner; automatic switching of the adjacent stages is achieved by setting the automatic switching temperature, and the automation degree of the microwave vacuum drying process is increased; and meanwhile the drying temperature is set, and therefore the operation temperature of the drying process is limited, the phenomena of surface seasoning cracking, local coking, quality dropping and the like caused to the material due to excessive heating are avoided, and the product quality is improved.

Description

technical field [0001] The invention relates to a microwave vacuum drying method, in particular to a stage-controlled microwave vacuum drying method. Background technique [0002] Microwave vacuum drying technology is a modern high-tech. It combines microwave drying and vacuum drying. It uses microwave to provide heat source for vacuum drying. The material can be dried at a lower temperature, which can better preserve the nutritional content of the material and improve other qualities of the dried product (such as browning), shorten the drying time and improve the production efficiency. Therefore, microwave vacuum drying technology has been more and more widely used. [0003] The microwave vacuum drying process can be divided into three stages according to the change of material temperature and water evaporation rate, namely, the heating and temperature rising stage, the constant temperature and constant speed drying stage, and the temperature rising and falling speed dryin...

Claims

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Application Information

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IPC IPC(8): F26B5/04F26B3/347F26B9/06F26B25/22
CPCF26B3/347F26B5/048F26B9/06F26B25/22
Inventor 孙大文韩忠曾新安余旭聪
Owner SOUTH CHINA UNIV OF TECH