RU2827396C1 - Universal vacuum drying cabinet - Google Patents

Abstract

FIELD: chemistry; microbiology; food industry.

SUBSTANCE: invention relates to food, chemical and chemical industry and can be used for vacuum sublimation and vacuum low-temperature drying of both frozen and non-frozen products of animal and vegetable origin, which are in non-liquid aggregate state. In process of vacuum sublimation or vacuum low-temperature drying for supply of heat energy to dried product in vacuum drying chamber instead of rigid heat-conducting shelves is used soft vapour-permeable fabric with heating elements, on which the dried product is placed. Electrically heated fabric with the unfolded product is rolled up, placed into the drying chamber and connected to the power supply.

EFFECT: increased area of heat exchange surface, simplified performance of operations of loading and unloading of product, as well as design of vacuum chamber, which together increases technological effectiveness of drying process.

1 cl, 3 dwg

Description

The invention relates to the field of food, microbiological and chemical industries and can be used for vacuum sublimation and vacuum low-temperature drying of both frozen and non-frozen products of animal and plant origin that are in a non-liquid aggregate state.

There are many known vacuum drying or vacuum sublimation units of various types. The classic design of such a unit is presented in (Lekae V.M., Lekae A.V. Processes and apparatuses of the chemical industry. - M.: Vysshaya shkola, 1977. - 256 p.) in the catalog (Dryer-Yimin Drying [online]. Changzhou Yimin Drying Equipment Co., Ltd [found 2023-11-07] - Found in <https://www.ymdrying.com/products/138/>) presents cylindrical vacuum drying chambers of the FZG and YZG series from Yimin (PRC), which are intended for heat treatment of products in a vacuum state.

As a rule, in vacuum and sublimation units containing a vacuum chamber, a vacuum pump, an ice evaporator (desublimator) connected to a refrigeration machine, the dried product is placed on heat-conducting trays, which, in turn, are installed on heated (in one way or another known) shelves. The disadvantage of such a product arrangement is air (vacuum) layers of significant volume that arise between the heating shelves and the trays with the product when the configurations of the contacting surfaces at the bottom (between the tray and the shelf) and at the top (above the product under the shelf located above) slightly mismatch. These layers have low thermal conductivity, as a result of which the dried material is heated unevenly, which worsens the quality of the finished product and increases the duration of the entire drying process. Also known is a vacuum freeze-drying unit (Vacuum freeze-drying unit: patent 2776402 Russian Federation: IPC F26B 5/06 / S.A. Ermakov, G.V. Semenov, I.S. Krasnova - No. 2020131235; declared 10.02.2021; published 19.07.2022, Bulletin No. 20. - 8 p.), in which the authors attempted to improve the uniformity of heating of the product being dried and intensify the mass transfer process by installing an additional gas blower device, which should ensure the forced movement of the vapor-gas medium filling the evacuated system from the product being dried to the condenser (desublimator), cooled by a refrigeration unit. This solution greatly complicates the design of the device and its maintenance, and also increases the overall cost and operating costs.

The closest technical solution is a vacuum drying oven (Vacuum drying oven: patent 2326312 Russian Federation: IPC F26B 9/06, F26B 5/06 / S.A. Ermakov - No. 2006142974/06; declared 04.12.2006; published 10.06.2008, Bulletin No. 16. - 7 p.), adopted as a prototype, containing a vacuum chamber with heating/cooling plates with thin deformable walls and with thick non-deformable walls, as well as heat-transfer trays formed into stacks with reinforcing heat-transfer partitions, filled with the material to be dried.

The disadvantage of this technical solution is that the walls of the plates in contact with the baking trays experience constant multidirectional deformation under the influence of the pressure difference between the internal environment of the heating plates and the atmosphere of the vacuum drying oven, which leads to rapid wear of the wall material and a reduction in the service life of the unit.

In addition, joining trays filled with product into a single package complicates and increases the cost of the device’s design, and also complicates loading and unloading operations during its operation.

The aim of the proposed invention is to intensify the heat and mass transfer drying process, simplify the design of the vacuum drying apparatus and loading and unloading operations.

The technical result of the invention is a device that ensures the almost complete elimination of air gaps between the heating element and the product being dried, uniformity of two-sided heating of the product, reduction of the duration of the drying process, simplification of the loading and unloading operation, as well as an increase in the useful heated area for placing the product (compared to the possible placement of the product on baking sheets and on heated shelves in a cylindrical chamber of the same volume).

The technical result of the invention is ensured by the fact that inside the vacuum chamber there is a device consisting of a flexible vapor-permeable material compatible with the food product, containing heating elements evenly distributed over the entire area, which is rolled into a multi-layer roll, between the layers of which the product to be dried is placed, and the vacuum chamber contains an electrical connector for connecting the device, wherein the length and diameter of the roll with the product are at least 10 mm less than the internal length and diameter of the vacuum chamber.

Fig. 1-3 schematically depicts the stages of placing a food product to be dried (for example, an apple slice) in a universal vacuum oven: placing the product on an elastic, washable, vapor-permeable material with electrical heating (Fig. 1); rolling it into a “roll” (Fig. 2); placing it in a vacuum chamber (Fig. 3).

1 – elastic, washable, vapor-permeable material with electrical heating; 2 – product to be dried; 3 – electrical connector of electrically heated material; 4 – “Velcro” for fixing the roll; 5 – cylindrical vacuum chamber with electrical connector 6; 7 – rolled up roll with product; 8 – connection pipe with vacuum pump; 9 – sealed door of vacuum chamber.

The universal vacuum drying cabinet works as follows.

The product to be dried 2, preliminarily prepared (cut) in a manner corresponding to the general requirements of sublimation and vacuum drying, is placed on an elastic, washable, vapor-permeable material with electrical heating 1 (Fig. 1) and rolled into a roll (Fig. 2). In this case, the product can be either frozen or unfrozen . For the convenience of placing the product to be dried on an elastic, washable, vapor-permeable material with electrical heating and its subsequent rolling into a roll, the product can be preliminarily placed in a perforated polyethylene (or other similar and food-compatible material) bag. After rolling the roll, the product is between layers of electrically heated material, tightly adjacent to the product to be dried from above and below, which ensures its effective and uniform heating during the entire vacuum drying process. After forming a roll 7 with the product using the provided "Velcro" 4, the latter is placed in a cylindrical vacuum chamber 5, the electrical connector of the electrically heated material 3 is connected to the electrical connector in the vacuum chamber 6 and the sealed door 9 is closed (Fig. 3). The vacuum pump (not shown) is switched on, which creates the required vacuum value in the chamber 5 through the branch pipe 8, the control panel (not shown) switches on the heating elements, and the vacuum drying process occurs according to the specified program until its completion. After the vacuum (or sublimation) drying process is completed, the pressure in the chamber 5 is equalized to atmospheric, the sealed door 9 is opened, the electrical connector 3 is disconnected from the connector 6, the roll 7 with the dried product is removed from the chamber 5, the roll is unrolled, the finished product is removed and packed in a sealed container (not shown).

It should be noted that the product to be dried can be either frozen or unfrozen. The vacuum drying cabinet is universal, since it can carry out both sublimation and low-temperature vacuum drying processes.

The economic effect from the use of the declared universal vacuum drying cabinet is obtained by eliminating heated shelves with a heating system and circulation of the coolant in them and trays, reducing the duration of the drying process and simplifying loading and unloading operations, as well as increasing the useful heated area for placing the product in the cylindrical chamber.

Claims (1)

A universal vacuum drying cabinet containing a vacuum pump, a cylindrical vacuum chamber, inside which there is a sealed door for loading and unloading, characterized in that inside the vacuum chamber there is a device consisting of a flexible vapor-permeable material compatible with the food product, containing heating elements evenly distributed over the entire area, which is rolled into a multi-layer roll, between the layers of which the product to be dried is placed, and the vacuum chamber contains an electrical connector for connecting the device, wherein the length and diameter of the roll with the product are at least 10 mm less than the internal length and diameter of the vacuum chamber.