RU2578737C1 - Method of vacuum-sublimation drying - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: method includes supply of a prepared product to the vacuum chamber on inclined to the horizontal vibration trays, movement over them, product sublimation by vacuum creation in the vacuum chamber, heat supply necessary for drying and condensate removal. For t vacuum-sublimation drying sections with thermal electric modules are used, to them ammonia is supplied, it ensures the cooling temperature of 30-70°C. The product is loaded in the vertical bucket conveyor, transferred by it to the top tray installed in the section with a thermal electric module, located at an angle α to the horizontal axis, moved along the tray and transferred to another tray, installed in the section with a thermal electric module under the previous section opposite inclined at the angle α to the horizontal axis, is passed along the carrying frame of the vacuum chamber until all trays loading, creating a fluidised flow inside it, with the further product delivery to the said vertical bucket conveyor, via which the product is delivered to the said top tray of the section with the thermal electric module. During sublimation a multiple round air flow is ensured until the achievement of a specified final humidity.

EFFECT: uniform drying, reduced duration of treatment process, and reduced power consumption.

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Description

The invention relates to drying equipment and can be used in the food and feed industry for drying plant products and components of animal feed.

The well-known "Vacuum freeze dryer" (US Pat. RU, 2183307, F26B 5/06, 06/10/2002), "Vacuum freeze dryer continuous cycle" (US Pat. RU, 2099658, F26B 5/06, 20.12. 1997), containing a vacuum chamber, a desublimator, hermetically connected sections, a vacuum pump and a heater.

The disadvantage of these dryers is the high energy intensity, the long cycle time (8-10 hours per cycle) and the unevenness of the drying process. The reason for this is a fixed, dense layer of the processed product with a thickness of 10-15 cm.

The closest in technical essence to the present invention is a freeze-drying method implemented in "Installation for freeze-drying granular food products" (Auth. Sv., 763658, F26B 5/06, 09/15/1980) - taken as a prototype that contains a vacuum chamber, loading and unloading devices, vibrating trays inclined to the horizontal, electric heaters, vibrators and desublimators.

The installation provides for the implementation of the sublimation process in one pass of granules on inclined trays. Due to the fact that the sublimation process lasts 8-15 hours, this can be done only with a large length of trays and a very low speed of movement of the processed material, which is not practical. The sublimation time of the product is not regulated, therefore it is difficult (impossible) to obtain the set drying temperature.

The task of the invention is to ensure uniformity of drying, reducing the duration of the cycle and reducing energy consumption.

The problem is achieved in that in the proposed method of vacuum freeze-drying, which includes supplying the prepared product to the vacuum chamber on vibrating trays inclined to the horizontal, moving along them, sublimation of the product by creating a vacuum in the vacuum chamber, supplying heat necessary for drying and removing condensate, new is that sections with thermoelectric modules are used for vacuum freeze drying, to which ammonia is supplied, providing a cooling temperature of 30-70 ° C, and the product is loaded They are moved into a vertical bucket conveyor, which is fed to the upper tray installed in the section with the thermoelectric module located obliquely at an angle α to the horizontal axis, moved along the tray and transferred to the next tray installed in the section with the thermoelectric module located under the previous section, anti-inclined under angle α to the horizontal axis, they are passed along the supporting frame of the vacuum chamber until all trays are filled, creating a fluidized stream inside it, with the subsequent receipt of the product in the mentioned a vertical ladle conveyor, through which the product is delivered to the aforementioned upper tray of the section with thermoelectric modules, while during the sublimation process, a uniform circular flow of the product is made repeatedly until it reaches the specified final moisture content.

The presence of vibrating sublimation sections with thermoelectric modules and a vertical bucket conveyor connected with them makes it possible to create a continuous, uniform circular flow of the processed product, and the installation of adjacent sublimation sections with thermoelectric modules on the inner surfaces of the opposite vertical walls of the vacuum chamber in a checkerboard pattern at an angle α to the horizontal axis gives the ability to exclude the static state of the processed product in the trays in the form of IG Petritskaya dense layer of 10-15 cm thick and create a fluidized flow, which causes the uniformity of the drying process reduces the processing time and energy costs. The slope of the angle α is 2-5 ° and depends on the processed product.

The drying limits can be intensified by optimizing the vacuum conditions for each type of product (<610 Pa and 250 ... 255 K, US Pat. RU 2183307, section work), while the final humidity should be 5-2%.

Thermoelectric modules provide cooling of the product to 23-28 ° C, therefore, to stimulate this process, ammonia is additionally supplied, providing a temperature in the range of 30-70 ° C, which allows vacuum-freeze-drying of various types of products.

The essence of the proposed method is implemented in a vacuum freeze dryer and is illustrated in FIG. - scheme of a vacuum freeze dryer.

The vacuum freeze dryer contains a vacuum chamber 1 (see Fig.), Inside which, from the loading side, a loading tray 2 is located, communicated through a shutter 3 with a vertical ladle conveyor 4 having a guide pipe 5 in the lower part connected to the bottom of the carrier frame 6 in the location area of the bottom (of the same type), inclined at an angle α to the horizontal axis, section 7 with a tray 8 filled with the processed product, a thermoelectric module 9 and a sublimator 10, mounted vertically on the opposite guide pipe 5 the front wall of the supporting frame 6. In the upper part, the vertical bucket conveyor 4 is equipped with a flexible rotary nozzle 11, brought from above to the supporting frame 6 in the area of the upper section 7, which is located obliquely relative to the lower section at an angle α to the horizontal axis and mounted on the adjacent to the rotary nozzle 11 of the vertical wall of the supporting frame 6. All sections 7 are rigidly mounted on opposite vertical walls of the supporting frame 6 in a checkerboard pattern and counter-inclined to each other. A vacuum wire 12 is connected to the area of each section 7, and pipes with liquid ammonia 13 are connected to each sublimator 10. An electric vibrator 14, coil springs 15, an electric heater 16 are installed at the bottom of the support frame 6. At the discharge site, next to the vacuum chamber, finished product reception capacity 17.

Vacuum freeze dryer operates as follows. When the electric vibrator 14 is turned on, the processed product pre-frozen to a predetermined temperature (-35 - 50 ° C) enters the loading tray 2 and when the shutter 3 is open and the vertical bucket conveyor 4 is working, it is captured by its buckets, it rises, then it is discharged through a flexible rotary pipe 11 the upper part of the tray 8 of the upper section 7, mounted at an angle α to the horizontal axis, on the vertical wall of the supporting frame 6. adjacent to the flexible rotary nozzle 11. Under the influence of the electric vibrator 14 and the spiral 15, due to the angle of inclination α, the frozen product is evenly distributed throughout the tray 8, moves along to the opposite edge and is poured down onto the upper part of the tray 8 of the lower section 7, which is installed at an angle α to the horizontal axis on the opposite vertical wall of the supporting frame 6 of the previous section 7, and so on until all trays are fully loaded 8. Then the shutter 3 closes, the vacuum is connected through the vacuum wire 12, which is brought to a value below the triple point for water (<610 Pa), ektroobogrevatel 16, a constant current source for supplying power to the thermoelectric modules 9 and 13 is passed through the pipes the liquid ammonia. Freeze-drying begins. Thermoelectric modules 9 heat the bottom of the tray 8 with the product located on it, to which heat is transferred, as a result of which frozen water molecules break out (“evaporate”) under the influence of vacuum, passing from a solid to a gaseous state, bypassing the liquid phase, which settle in the form of ice on the sublimator 10, upstream section 7 and at the same time cooled by the back of the thermoelectric module 9 to a temperature of -23 - 28 ° C, turning into ice, while continuously moving e first product stream being processed inside the supporting frame 6 from the section in section, further through the guide tube 5 in a vertical bucket conveyor 4, followed by the receipt of the flexible conduit 11, again turning on section 7 of the base frame 6 and etc. until the specified humidity of the processed product is reached. Upon completion, the drying process is stopped, the vacuum chamber 1 is evacuated, and the power supply and ammonia are turned off. A flexible rotary pipe 11 is set to the unloading position, and the dried product is discharged into the container 17. Then, the power supply polarity of the thermoelectric modules 9 of the sublimation sections 7 is changed, which leads to heating of the cold side and removal of ice from the sublimator 10. The installation is switched to the operating mode.

Thus, the use of the proposed method, implemented in a vacuum freeze dryer, allows for uniform drying, reduce the duration of the processing cycle and reduce energy consumption.

Claims (1)

The method of vacuum freeze-drying, including feeding the prepared product into a vacuum chamber on vibrating trays inclined to the horizontal, advancing through them, sublimating the product by creating a vacuum in a vacuum chamber, supplying heat necessary for drying and removing condensate, characterized in that for vacuum-freeze-drying drying uses sections with thermoelectric modules, to which ammonia is supplied, providing a cooling temperature of 30-70ºC, and the product is loaded into a vertical ladle conveyor, which is fed to the upper tray installed in the section with the thermoelectric module located obliquely at an angle α to the horizontal axis is moved along the tray and transferred to the next tray installed in the section with the thermoelectric module located under the previous section counter-inclined at an angle α to the horizontal axis, pass along the carrier the frame of the vacuum chamber until all trays are filled, creating a fluidized stream inside it, with the subsequent flow of the product into the aforementioned vertical ladle conveyor, through which pouring the product onto said upper tray of the section with thermoelectric modules, while in the process of sublimation, a uniform circular flow of the product is repeated several times until it reaches the specified final moisture content.