RU2746636C1 - Continuous vacuum freeze-drying unit for homogenized and liquid food products - Google Patents

Abstract

FIELD: drying equipment.SUBSTANCE: invention relates to drying equipment, in particular to equipment for vacuum freeze-drying, it can be used for the production of freeze-dried food products. The flow-line vacuum freeze drying unit for homogenized and liquid food products contains a sealed drying chamber and a sequentially connected frozen product preparation system, including a frozen granule-forming unit, loading gateway, a sealed drying chamber made in the form of a transport and drying system, including vacuum-treatment transport and drying pipes with a conveyor placed inside, ensuring continuous movement of the product, a heating unit, moisture desublimators connected to the transport and drying system and an unloading gateway. The frozen granule-forming unit, the entrance of the loading gateway and desublimators are connected to a two-circuit cooling system that provides the direction of generated heat to the heating unit of transport and drying pipes.EFFECT: invention is aimed at providing possibility of automating the continuous supply of raw materials and product unloading during the process of flow-line vacuum freeze-drying of the product, as well as improving the energy efficiency of the process.10 cl, 7 dwg

Description

The claimed invention relates to drying technology, in particular to equipment for vacuum-freeze drying, and can be used for the production of freeze-dried food products.

Known vacuum freeze dryer (RF patent No. 2395768, publ. 07/27/2010), containing a cylindrical chamber connected to a vacuum pump, a desublimator, trays for loading the product, in the double bottoms of which thermoelectric modules are installed, and in the lower part of the trays have ribbing for desublimation of the downstream cascade steam; the drying chamber is a sublimator consisting of two parts - a body and a hinged lid, made in the form of half-cylinders, cascades, which are baking trays with a developed surface (transverse partitions) to increase the heat exchange surface, in the double bottoms of which, made of material with a high coefficient of thermal conductivity , thermoelectric modules are hermetically installed, and in the lower part of the trays they also have a developed surface (ribbing) for desublimation of the steam of the downstream cascade, and along the periphery the chamber is equipped with two desublimators with a developed surface (ribbing), while the trays are installed in the sublimator using a stand.

The known device involves the use of manual labor for loading and unloading trays, placing them in a sublimator, which negatively affects the productivity of the process. The presence of voids between the trays, as well as around the stand with the trays installed on it, in which vacuum maintenance is also required, and the presence of a large number of non-target elements of the metal structure, increase energy consumption when heating the product on the trays.

Known complex for vacuum freeze drying according to RF patent No. 2705692, publ. 11.11.2019. The complex contains one or several drying chambers with a heat supply system and trays for dried material, as well as a vapor condensation system and a non-condensable gas suction system. The complex additionally contains an automated unloading system, a loading system, and each automated mobile drying chamber with trays for the material to be dried and a heat supply system located in it is made with the ability to move around the production room and alternately connect through sealed or non-sealed connectors with a loading system, with a stationary system condensation of vapors, as well as with the unloading system, after loading the raw material, the heat supply system of the drying chamber, if it is necessary to quickly freeze it, is connected with the help of sealed connectors to the system for preliminary freezing of the raw material, then, using a sealed connector, the inner volume of the chamber is connected to the inner volume of the stationary vapor condensation system and at the same time, using sealed connectors, the heat supply system of the drying chamber is connected to the heat generating system, and then the drying chamber is connected It can be connected with an automated unloading system using sealed or leaky connectors.

The presented solution has a sufficient degree of mechanization and automation, however, the loading / unloading process is clearly discrete and requires energy and time costs for cyclically repeating stages of preparation and completion of the process, such as vacuumization / de-vacuumization, heating / cooling, which inevitably increase the cost of the added value of the final product. ... In addition, the disadvantage of the proposed solution is the high capital cost of creating a production line.

Also known cryogenic vacuum-sublimation installation with the complex use of inert gas (RF patent No. 2458300, publ. 10.08.2012). The installation includes a device for preliminary freezing of the product, a vacuum freeze dryer with a sealed drying chamber, inside which a perforated drum and a heating element made in the form of a coil installed in the lower zone of the drum are located. The heating element is a cooler in relation to the refrigerant, its inlet branch pipe is connected to the discharge line of the desublimator refrigeration machine, and the outlet pipe is connected to the low pressure line of the refrigerant supply to the refrigeration machine. As a device for preliminary freezing of the product, a cryogenic quick-freezing unit of the tunnel type is used, the conveyor of which for feeding the frozen product is connected to the dispenser of the vacuum freeze dryer, the heating element of which is made of a material with a high coefficient of thermal conductivity or of a semi-permeable material, and as a refrigerating machine, a desublimator a gas liquefaction machine operating on the principle of the reverse Stirling cycle, the liquefied gas supply pipe of which is connected to a nitrogen trap used as a desublimator and to the nozzles of a quick-freezing unit.

The disadvantages of the known solution are the low productivity of the installation, the complexity of the equipment, and the complexity of setting up the technological process when switching to a new product. In addition, the vacuum freeze drying method using this unit has a high proportion of consumables / indirect costs such as nitrogen and liquid nitrogen. The use of infrared heating leads to high energy consumption and local overheating of the product.

The technical objective of the invention is to intensify the process of obtaining a freeze-dried powdery food product.

The technical result of the invention is to provide the possibility of automating the continuous supply of raw materials and unloading the product during the process of in-line vacuum freeze drying of the product, as well as increasing the energy efficiency of the process.

The technical result is achieved by the fact that the installation of vacuum-freeze drying of the in-line type of homogenized and liquid food contains a series-connected system for preparing a frozen product, including a unit for molding frozen granules; download gateway; a sealed drying chamber made in the form of a transport and drying system, including evacuated transport and drying pipes with a conveyor located inside, ensuring continuous movement of the product, and a heating unit; moisture desublimators connected to the transport-drying system and the unloading gateway, while the frozen granule molding unit, the inlet of the loading gateway and the desublimers are connected to a two-circuit cooling system, which ensures the direction of the generated heat to the heating unit of the transport-drying pipes.

Installation of vacuum freeze drying in accordance with the claimed invention allows deep processing of food products in order to remove water (deep drying), excluding thermal destruction of the micro- and macrostructure of food products. The initial product in the technological cycle of vacuum sublimation is a liquid or homogenized product (ground through a mixer / grinder). The end product is a dry powder of the raw material.

In the claimed installation, a quasi-continuous automated process for obtaining a finished sublimated product is implemented, including discrete loading, freezing, sublimation and discrete unloading of the product using a conveyor and mixing product screw.

Installation of vacuum-freeze drying of flow type homogenized and liquid foodstuffs contains systems for frozen product preparation, frozen product loading, transport and drying system, systems for sublimation and desublimation of moisture, unloading of sublimated product. The transport and drying system includes evacuated transport and drying pipes with a conveyor located inside and a heating unit for the sublimation system.

The frozen product preparation system includes a food product grinding unit that provides food product grinding to a powdery or dispersed state, a freezing unit and a frozen granule molding unit in a form convenient for transportation and sublimation. It is possible to use both a whole product and a pre-crushed one.

The freezing unit can be made in the form of a shock freezer or an acoustic freezing system.

Also, in one embodiment, a finger-type ice-granulator is used to pre-freeze the raw material.

In the particular case of execution, a pre-frozen product is fed to the preparation system, and in the frozen product preparation system, only the formation of frozen granules is realized by extrusion through a die or by rolling the frozen product through profiled rotating rolls (shafts).

In the system for preparing a frozen product, a product with a temperature of -50 to -18 ° C is formed in the form of granules of a cylindrical, cubic, spherical, drop-like shape, in the form of a parallelepiped or other volumetric figures. The frozen granules can be up to 50 mm in size.

Frozen product loading / unloading systems include batch, continuous or continuous batch locks. So, the sluice can be made of periodic action with butterfly valves to isolate the internal cavity. In another embodiment, a continuous gateway (dynamic seal) is used, while providing a continuous movement of the product with a continuous pressure gradient from atmospheric from the side of the product loading / unloading gateway to the operating pressure in the vacuum sublimation chamber. In the case of a continuous sluice, the working pressure in the vacuum chamber is ensured by using an extended sluice line representing a pipe (circular or rectangular section) which on one side faces the atmosphere, on the other hand - to the vacuum chamber, has many non-continuous partitions forming open volumes with intermediate pumping, through the gaps in the partitions, the product is transported, loaded into the vacuum chamber for subsequent freeze drying.

In another embodiment, a rotary sluice is used, which, in different phases of its movement, ensures that the product is captured into the working space of the sluice. At the same time, the working space of the lock with the product is evacuated, the product is unloaded into the vacuum chamber of the sublimation unit, followed by cyclic repetition of these operations.

The product transport system in the freeze-drying process includes a straight-line conveyor, such as a screw type, or a cascade system with parallel, serial or parallel-serial conveyors. The conveyor provides a linear speed of product movement from 0.25 to 3 m / h and a rotation frequency from 0.5 to 40 rpm. The choice of linear speed and rotational speed is selected depending on the processed product and its moisture content. In one embodiment, a rotary carousel conveyor with a rotational speed of 0.5 rpm to 40 rpm is used to move the product during the sublimation process, and the product is automatically applied to the belt in a layer of a predetermined thickness.

The product sublimation system contains an evacuation device and a heating unit. An ohmic heater, a Peltier element, a heat exchanger with a liquid or gaseous heat carrier can be used as a heating element of the heating unit. It is preferable to use a dry vacuum unit based on a screw and two-rotor booster pump in anticorrosive design as an evacuation device.

The system for desublimation of moisture evaporated from the surface of the product during the sublimation process contains a heat exchanger with a liquid or gaseous coolant or a Peltier element. In one embodiment, the implementation provides for the use of at least two alternately operating desublimers to ensure their periodic regeneration.

The frozen granule molding unit, the entrance of the loading lock and desublimers are connected with a two-circuit cooling system, which ensures the direction of the generated heat to the heating unit of the transport-drying pipes.

The claimed invention is illustrated by the following drawings:

Figure 1 shows a general view of a flow-type vacuum freeze drying unit with one transport and drying unit with a screw conveyor;

Figure 2 shows a general view of a flow-type vacuum-freeze drying unit with two transport-drying units with a screw conveyor;

Figure 3 shows a general view of the icemaker;

Figure 4 shows a block of pushers of the icemaker;

Figure 5 shows a freezing unit and an icemaker blade;

Figure 6 shows a two-circuit cooling scheme of the installation;

Figure 7 shows a diagram of the installation heating.

Examples of implementation of the invention

The vacuum-freeze drying unit of in-line type for homogenized and liquid foodstuffs contains a system for the preparation of a frozen product, transport and drying units connected to the loading and unloading units and desublimers.

Figure 1 shows an example of the implementation of a vacuum-freeze drying plant of the in-line type of homogenized and liquid food, equipped with a frozen product preparation unit (not shown in figure 1), one transport-drying unit, including a transport-drying pipe 1, equipped with a loading sluice 2, unloading gate 3 and desublimers 4. Figure 2 shows an example of implementation with two transport-drying units, each of which includes three horizontal transport-drying tubes 1, located one above the other and connected to a single transport unit, placed on the upper tube loading sluice 2, and at the bottom - unloading sluice 3. The transport and drying pipes are made with a double wall for supplying the heat carrier heated to 60 ° C to the inter-wall space. The movement and mixing of the dried material in each pipe is carried out by means of a screw conveyor. The screw is rotated by an asynchronous gear motor with frequency control of revolutions. Each transport-drying pipe has a branch pipe for connecting pressure sensors, as well as branch pipes for connecting loading and unloading locks.

The loading lock 2 is cylindrical, from above and below it is limited by disc valves 5 with flanges for connection to the transport-drying unit and the unit for molding frozen granules (icemaker) 6. In the side wall of the loading lock 2 there are two pneumatic ball valves connected through a pipeline with the main vacuum system and serving for pumping out and letting air into the loading lock. The loading gate 2 is made with a double wall for supplying liquid coolant to the inter-wall space to prevent the granules of the supplied raw material from sticking together (figure 1).

The frozen product preparation system is a finger-type ice maker 6 shown in FIGS. 3-5. The ice maker 6 is mounted to the loading sluice 2 through the flange. The icemaker includes a block of pushers 7, a freezing block 8 and a knife for cutting pellets of the required length.

The block of pushers 7 (Fig. 4) consists of a body 10, a pre-cooling coil 11, a plurality of pushers 12 attached to a pusher disk 13, the movement of which is upwardly limited by a flange 14. The pushers are calibrated stainless tubes. The disk 13, together with the pushers 12, is driven by a pneumatic cylinder.

Figure 5 shows a freezing unit 8 without an outer casing and an ice maker blade 6 without an outer plate. The freezing unit 8 consists of an outer casing 15, cooled tubes 16 in an amount corresponding to the number of pushers 12.

On the outer casing of the freezing unit 8 there are 2 branch pipes 17 for connection to the cooling circuit of the installation. The icemaker blade consists of a casing 18, inside of which the cutting disc 19 of the translational-guillotine or rotary type, which is driven by a pneumatic cylinder, moves progressively.

Pre-cooling of the block of pushers 7 is provided to reduce the energy load on the freezing cycle in the tubes 16, as well as to increase the viscosity of the homogenized product.

The pre-cooling coil 11 and the Ice Maker freezing unit are connected to the cooling circuit of the unit in parallel, which allows independent regulation of the pre-cooling temperature. In the pre-cooling coil, the flow rate of the propylene glycol solution is throttled, thereby ensuring a higher temperature of the coolant compared to circuit II.

The unloading gate 3 is cylindrical, from above and below it is limited by disc valves 5 with flanges for connection to the transport-drying unit and containers for collecting the finished product. In the side wall of the unloading lock 3, there are two pneumatic ball valves connected through a pipeline with the main vacuum system and serving for pumping and letting air into the unloading lock (Fig. 1).

For condensation of the evaporated moisture, two desublimators 4 are connected to each transport-drying pipe 1 by means of flanges 4 (Fig. 1, 2). During the drying process, the desublimators work alternately (one works, the other - for regeneration). The body of the desublimator is made in the form of a cylinder with a condenser located inside, on which moisture evaporated from the raw material is frozen. The condenser can be made in the form of a copper tube wound in one or more layers. A pipeline 20 for vacuum pumping is connected to the desublimator body by means of a branch pipe.

The vacuum system serves for pre-evacuation and removal of non-condensable gases. The evacuation device provides evacuation of loading locks 2 unloading 3, desublimator cavities 4.

An embodiment of the cooling system in the form of a double-circuit refrigeration unit 22 is shown in FIG. 6. In the first circuit I of the refrigeration unit, a refrigerant with a boiling point T = -40 ° C is used. The heat generated on the condenser 23 of the refrigeration unit is used to heat the transport-drying unit (Fig. 7). In this way, heat recovery is ensured, which reduces operating costs.

Desublimers 4 serve as evaporators, in which the temperature is maintained at -40 ° C. After the desublimator, on the first circuit of the refrigeration unit, there is a plate heat exchanger 24, which cools the coolant on the second circuit to -30 ° C. A propylene glycol solution is used as a coolant. The second circuit II cools the ice maker 6 and the loading sluice 2.

Description of device operation:

A homogenized product is supplied to the inlet of the icemaker 6 from the grinder (not shown in the figure), which fills the internal volume of the block of pushers 7, cooled to a temperature of (-10) - (-5) ° C by means of a pre-cooling coil 11.

Then the pneumatic cylinder of the pusher unit 7 is turned on and the disk 13 with the pushers 12 attached to it is brought into reciprocating motion. At the same time, when the pneumatic actuator is in the upper position, there is a gap between the pushers 12 and the freezing unit 8, which, during the movement of the disk 13 downward, provides filling tubes cooled to -30 ° C with raw materials 16.

The temperature of -30 ° C in the freezing block 8 of the icemaker 6 is provided by the secondary circuit II of the refrigeration unit with a circulating coolant (propylene glycol), which is cooled from the primary circuit I through the heat exchanger 24. The coolant is pumped by the circulation pump 25.

When the pushers 12 are lowered to a position corresponding to the beginning of the cooled tubes 16, the speed of movement of the pneumatic cylinder changes to a value at which the liquid raw material will be completely frozen. In this case, the cutting disc 19 of the ice maker 6 reciprocates and "chops off" the frozen product. The speed of movement of the cutting disc 19 is matched with the speed of movement of the pushers 12, which ensures that frozen granules of the required length are obtained. The length of the granules is determined by the stroke of the pushers 12, and their diameter by the diameter of the tubes 16.

Further, the frozen granules are fed through the loading gateway 2 to the entrance of the transport-drying unit. To prevent the frozen granules from sticking together, the loading gateway 2 is equipped with disc valves 5, the space between which is cooled to T = -30 ° C and additionally evacuated by a vacuum unit. In the transport-drying pipes 1 of the transport-drying unit, the process of sublimation of the product is carried out with its simultaneous linear movement and mixing by a screw mechanism. Heating of the transport-drying pipes 1 is carried out due to the heat generated on the primary circuit of the refrigeration unit 22. In the primary circuit of the refrigeration unit 22, freon is compressed in the compressor, which is part of the refrigeration unit. After compression, the freon temperature rises, and the heat from the compressed freon is transferred to the hydraulic circuit designed to heat the transport-drying pipes 1 (Fig. 7) through the chiller, including the heat exchanger 24 and the condenser 23. The heat carrier in this hydraulic circuit for heating the transport-drying pipes is injected circulation pump 26, the temperature is controlled by a temperature sensor 27, and maintaining the desired temperature of 60 ° C is carried out due to the provided possibility of dumping excess heat into the surrounding space. To compensate for the increase in volume in the system when the temperature rises, an expansion tank 28 is provided.

The water vapor generated during the drying process of the product enters the desublimators 4, where the transition of water from a gaseous state to a solid state is carried out, bypassing the liquid phase. In desublimers 4, ice crystals are frozen on the condenser tube by constantly maintaining a temperature of -40 °. The temperature in the desublimers is maintained by the primary circuit of the refrigeration unit. The freon compressed in the compressor enters the desublimators, which act as an evaporator, in which the adiabatic expansion of the medium is carried out, the freon is cooled to -40 ° C.

The advantages of the proposed solution are as follows:

The equipment allows for deep processing of food products in order to remove water (deep drying), excluding thermal destruction of the micro- and macrostructure of food products.

The use of a unit for molding frozen granules eliminates the effect of product inhomogeneity in composition and size and provides stable drying modes.

The equipment makes it possible to provide an automated continuous supply of raw materials to the installation.

Recovering the heat generated by the chiller to heat the pipe walls allows for high energy efficiency in the freeze drying process.

Claims (10)

1. Installation of vacuum-freeze drying in-line type homogenized and liquid food, containing a sealed drying chamber, characterized in that it includes a series-connected system for the preparation of a frozen product, including a unit for molding frozen granules; download gateway; a sealed drying chamber made in the form of a transport and drying system, including evacuated transport and drying pipes with a conveyor located inside, ensuring continuous movement of the product, and a heating unit; moisture desublimators connected to the transport-drying system and an unloading sluice, while the frozen granule molding unit, the loading sluice inlet and desublimers are connected with a two-circuit cooling system, which ensures the direction of the generated heat to the heating unit of the transport-drying pipes. 2. Installation according to claim 1, characterized in that the system for preparing the frozen product contains a preliminary freezing unit in the form of a shock or acoustic freezer. 3. Installation according to claim 1, characterized in that the unit for molding frozen granules comprises a finger-type icemaker-granulator, including a freezing unit with cooled tubes, a unit of pushers feeding raw materials into said tubes, wherein the unit of pushers is equipped with a pre-cooling coil, and block of freezing with a knife for cutting granules. 4. Installation according to claim 1, characterized in that the system for preparing the frozen product further comprises a grinder for the supplied raw materials. 5. Installation according to claim 1, characterized in that the loading gateway is made of periodic, continuous or continuous-periodic action. 6. Installation according to claim 1, characterized in that the loading and unloading locks are equipped with pneumatic ball valves connected through a pipeline with a vacuum system. 7. Installation according to claim 1, characterized in that the loading sluice is made with a double wall for supplying liquid coolant to the inter-wall space. 8. Installation according to claim 1, characterized in that the transport-drying system contains one conveyor or a cascade of conveyors with parallel, sequential or parallel-sequential placement of conveyors, wherein the conveyor is made of a screw or carousel type. 9. Installation according to claim 1, characterized in that the heating unit is made in the form of an ohmic heater, a Peltier element or a heat exchanger with a liquid or gaseous heat carrier. 10. Installation according to claim 1, characterized in that it contains two alternately operating desublimers connected to each transport-drying pipe, and the desublimers are made with the possibility of cooling by a cooling unit made in the form of a heat exchanger with a liquid or vapor heat carrier or a Peltier element.

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