JPH0334916B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a vacuum belt dryer, and more particularly to a vacuum belt dryer for vacuum drying liquid, slurry, or paste raw materials and removing them as granular dry products. It is related to the device. BACKGROUND ART In recent years, with the diversification of dietary habits, many types of processed food materials and instant foods have become commercially available. In this field of food processing, it is important to maintain the solubility and ready-to-ready properties at a specified level when consumers use the product as a cooking ingredient, and to ensure that the final product does not suffer from deterioration in quality or alteration of ingredients. Various normal pressure drying devices and vacuum drying devices are used for the purpose of imparting restorability. Among such drying devices, attention has been paid to the fact that it is relatively easy to maintain the solubility of products as cooking ingredients at a good level, and the field of use of vacuum drying devices is rapidly increasing.
Spray dryers and freeze dryers are known as general-purpose vacuum drying equipment, but while the former has low drying costs, it has somewhat poor performance in maintaining product solubility and quality or preventing changes in components. On the other hand, the latter method employs a freezing/sublimation process, resulting in problems such as a complicated structure and a rise in drying costs. At this time, there has been a demand for the development of a vacuum belt dryer as a means of solving the practical problems observed in the above-mentioned spray dryers and freeze dryers. A vacuum belt dryer is equipped with a heating zone and a belt conveying device in a vacuum container, and supplies food material in the form of a liquid, slurry, or paste onto an endless conveyor belt in the form of a thin film. Thus, the food material is introduced into the heating zone and vacuum dried under drying conditions at a relatively low temperature. At this time, the food material placed in a thin film form on the belt undergoes a strong evaporation phenomenon of the water contained inside, causing the food material to swell and form numerous ventilation holes inside. , and sent to the crusher as a porous intermediate product. Vacuum belt dryers are thus increasingly being recognized as an alternative technology to conventional spray dryers and freeze dryers. Problems to be Solved by the Invention Vacuum belt dryers have performance that significantly exceeds known spray dryers and freeze dryers in terms of quality retention, prevention of component changes, and reduction of drying costs. However, in order to respond to the diversification of food materials to be subjected to drying processing, there are many points that require further improvements in terms of structure and function. For example, at the end of the endless conveying means,
A grinding device such as a rotating blade for intermediate products is provided, but the grinding capacity may be insufficient if only one stage of such grinding device is arranged. Measures were taken, such as slowing down the transport speed of intermediate products. However, the increase in drying time as described above may cause other problems such as deterioration of the product and reduction in productivity due to excessive drying.
On the other hand, if the drying rate is too fast, the final product will have a large particle size, and the granular product removed from the vacuum belt dryer must be pulverized under atmospheric pressure.
Such pulverization under atmospheric pressure sometimes causes more serious problems such as deterioration of the product due to moisture absorption and a reduction in the operating rate of the vacuum drying process. The main purpose of the present invention is to solve the above-mentioned problems found in conventional vacuum belt dryers.
An object of the present invention is to provide a vacuum belt dryer having a simple structure and a stable crushing function. Means for Solving the Problems In order to achieve the above object, the present invention provides a vacuum belt dryer for vacuum drying raw materials prepared in liquid, slurry, or paste form and taking out dry products in the form of granules. In this process, a precrusher consisting of a fluid pressure silling mechanism and a shearing blade is disposed at the raw material discharge end of an endless conveyor belt rotatably mounted in a vacuum container, and a rotary blade and a rotary blade are disposed below the precrusher. A main crusher made of a mesh wire mesh surrounding the main crusher approximately halfway around the main crusher is arranged in multiple stages. gradually decreases, and
The present invention provides a vacuum belt dryer configured with a multistage crushing mechanism in which the number of rotations of a rotary blade and the tooth width measured along the direction of rotation gradually increase. Function Processed food raw materials prepared in liquid, slurry, or paste form are spread on an endless conveyor belt and dried under vacuum, after which they are passed through a pre-crusher, a rotary blade, and its surroundings for approximately half a circumference. It is crushed in stages by a main crusher with multiple structures consisting of surrounding mesh wire mesh.
The product falls as a granular product into a product removal chamber equipped with a vacuum lock mechanism, and is taken out of the system in batches. Embodiment FIG. 1 is a partially sectional front view illustrating the overall structure of the apparatus of the present invention. Further, FIGS. 2 to 4 are explanatory diagrams of the main structure of the apparatus of the present invention. In FIG. 1, the main body of the vacuum vessel 18 is equipped with a vacuum generator 2, which includes a known vacuum pump 19, a cold trap 20, and a chiller unit 21.
By operating this vacuum generator, a vacuum level of around 10 Torr is maintained inside the main body 18 of the vacuum container during drying of raw materials. The first belt 1 has a flow path for hot water formed in the movement path of the belt 1 from the raw material supply side to the product delivery side.
to third heating plates 6a, 6b, 6c, and a cooling plate 7 having a cooling water flow path formed therein;
are arranged in sequence, and correspondingly, in order to supply hot water and cooling water adjusted to a predetermined temperature to the vacuum drying device 8 constituted by the heating plate and the cooling plate, the vacuum vessel 18 The main body includes a known tube or plate heat exchanger 22, which functions as a hot water circulation line heater.
A heating medium and cooling medium circulation device is connected, which includes an expansion tank 23 that promotes circulation of hot water by pressurizing air, and a circulation pump 24 connected to a temperature control circuit (not shown). As shown in FIG. 2, the endless conveyance device basically consists of a motor (not shown), a drive roller 26,
It is composed of a driven roller 27 and a mesh belt 1 formed by endlessly connecting knitted or woven fabrics of synthetic fiber threads, for example, polyester fiber threads, and this mesh belt is connected to the drive roller 2.
6 and driven roller 27 to form a drive system, a constant speed conveyance device having a conveyance speed of 0.05 to 0.5 m/min is formed. The mesh belt 1 is manufactured from a knitted fabric made of synthetic fiber yarn with excellent strength, coefficient of friction, heat resistance, and heat conductivity in consideration of the general characteristics required for an endless conveying device. In order to maintain the peelability of vacuum-dried intermediate products, the leakage prevention of raw materials and intermediate products from weaves and stitches, and the washability at a specified level, we use endless conveyance from a woven fabric of polyester multifilament yarn. We are making belts. Note that, in view of the above-mentioned required characteristics, the mesh belt 1 is preferably surface-treated with a resin such as silicone or polytetrafluoroethylene. The processed food raw materials supplied onto the mesh belt 1 from the nozzle 3 of the raw material supply device 5 move within the vacuum container 18 in a state of being spread on the mesh belt moving at a constant speed, and during this time, the processed food raw materials are subjected to a vacuum drying process using hot water circulation. A vacuum drying process is performed by the cooling device 8. Although the thin film raw material introduced into the first heating zone constituted by the first heating plate 6a contains a large amount of water, thermal energy is transferred from the high temperature hot water flowing inside the heating plate 6a. As the raw material is dried, water begins to evaporate on the surface and inside at the same time, so the raw material spread into a thin film is subjected to vacuum drying while expanding vigorously. Since this first heating zone is maintained in a constant dry state, the temperature of the raw material itself hardly rises, and the raw material is sent to the subsequent second heating zone in a state in which approximately half of its retained moisture has been evaporated. Hot water at a slightly lower temperature than the hot water supplied to the first heating plate 6a is introduced into the second heating plate 6b forming the second heating zone, and the raw materials are subjected to constant rate drying. Most of the retained moisture is evaporated. Therefore, the expanded thickness and surface shape of the raw material hardly change, the surface of the raw material hardens to some extent, and the temperature of the raw material itself begins to rise. In this first heating zone, the thermal conductivity of the raw material decreases to some extent, so the temperature of the hot water introduced into the heating plate 6b is set slightly lower than that in the first heating zone, and the heat flux is also set to a certain level. Adjust the drying conditions so that the size is reduced by 30 minutes. In this way, the raw material is sent from the first heating zone to the subsequent second heating zone in a state in which approximately 90 percent of the moisture content has been evaporated. The raw material introduced into the third heating zone formed by the third heating plate 6c has a lower moisture content than the first heating zone and the third heating zone, and has a final moisture content without swelling phenomenon. It is vacuum dried slowly until the end. That is, in the first heating zone, the raw material is dried at a reduced rate, hardening the surface and raising its own temperature. Since the thermal conductivity of the raw material in this first heating zone is significantly reduced, the heating plate 6c is lower than that in the first heating zone and the third heating zone.
The temperature of the hot water introduced into the chamber is set even lower, and the raw material is subjected to vacuum drying under the influence of a small heat flux and sent to the subsequent cooling zone. The raw material fed into the cooling zone is cooled by low-temperature water introduced into the cooling plate 7, lowering the temperature of the raw material itself and increasing its hardness, thereby improving the peelability of the intermediate product. as well as obtaining a final drying condition suitable for reducing hygroscopicity. The intermediate product, that is, the expanded product heated and cooled under vacuum in this manner becomes a multi-layered cake and reaches the end of the endless conveyance path while leaving a trace corresponding to the shape of the supplied liquid on the mesh belt 1. Here, at the end of the endless conveyance path,
As seen in FIG. 2, the hydraulic cylinder mechanism 9
and the reciprocating piston 3 of this fluid pressure cylinder mechanism.
A pre-crusher 11 consisting of a shearing blade 10 fixedly attached to the shaft 8 is provided. Therefore, the intermediate product that has reached the end of the endless conveyance path is primarily crushed by the vertical movement of the shearing blade 10 while protruding from the reversing part of the mesh belt 1, and the crushed pieces of the porous cake are sent into the outlet duct 39 at the bottom of the main body. fall as.
Incidentally, a scraper 40 is provided at the end of the endless conveyance path for peeling off residual cake adhering from the surface of the mesh belt 1 which has been inverted while rotating from above to below. As illustrated in FIG. 3, the scraper 40 includes a shaft 42 rotatably supported via a Rulon bearing 49 on a support bracket 41 fixed to the main body of the vacuum vessel 18, and arms 43, 44 extending from the shaft.
A cake scraping blade 46 made of fluororesin is fixed to the mesh belt 1 through a blade holding plate 45, and in order to elastically press the cutting edge of the cake scraping blade 46 against the mesh belt 1, It consists of a tension spring 48 suspended between a base plate 47 that supports the end of the mesh belt 1, and the cake scraping blade 46 is moved slightly below the reversed portion of the mesh belt 1 under the bias of the tension spring 48. The remaining cake is peeled off from the surface of the mesh belt 1 by pressing it over the entire width. On the other hand, in the main body lower outlet duct 39 located below the pre-crusher 11, there are shafts 51a, which are rotated at different speeds by motors (not shown) attached as shown in FIG.
51b, 51c, support plates 52a, 52
plate-shaped rotary blades 13a, 13b, 13c made of fluororesin fixed via b, 52c; and mesh wire meshes 14a, 14 arranged at a predetermined interval.
A main crusher 15 consisting of b and 14c is provided. In the main crusher 15 having a multi-stage structure according to the present invention, mesh wire meshes 14a, 14 are arranged from the dry product introduction side to the discharge side.
Multi-stage pulverization is achieved by gradually making the meshes of b and 14c denser and gradually increasing the number of rotations of the rotary blades 13a, 13b, and 14b as well as the blade widths W ₁ , W ₂ , and W ₃ measured along the rotation direction. It constitutes a mechanism. The intermediate product, that is, the crushed pieces of the porous cake, which have been primarily crushed by the pre-crusher 11, are introduced into the main crusher 15 equipped with the multi-stage crushing mechanism, and are crushed into a predetermined shape by the rotation of the rotary blades 13a, 13b, and 13c. Mesh wire mesh 1 having a mesh size of
4a, 14b, and 14c, and fall as secondary pulverized granules into a product take-out chamber 17 equipped with a vacuum locking mechanism 16, where they are stored while maintaining a vacuum state. Table 1 below shows the rotary blades 13a, 13b, 13c that constitute the multi-stage main crusher 15.
Also, the dimensional characteristics of the mesh wire meshes 14a, 14b, and 14c are illustrated.

[Table] Rotary blades 13a, 13b, 13 in this embodiment
The blade width of c is the same in any of the first to third stages, but as an alternative, the shaft 51
By gradually increasing the number of rotary blades fixed to the mesh wire meshes 14a, 14b, 1 from the dry product introduction side to the dry product discharge side.
4c and the rotary blades 13a, 13b, 13c, thereby forming a multi-stage crushing mechanism that cooperates with the wire mesh and the gradual increase in the rotational speed of the rotary blades. ing. On the other hand, the vacuum lock mechanism 16 is composed of a product take-out chamber 17, a first air lock valve 53 provided above the product take-out chamber 17, and a second air lock valve 54 provided at the bottom of the product take-out chamber 17. Furthermore, if necessary, a supply valve for supplying an inert gas such as nitrogen gas is attached to the product take-out chamber 17 as a means for preventing moisture absorption or oxidation of the product. The product pulverized into granules is stored in the product take-out chamber 17, which is maintained in a vacuum state by opening the first airlock valve 53 and closing the second airlock valve 54. When the amount reaches a predetermined level, the first airlock valve 53 is closed and the second airlock valve 54 is opened to release the vacuum state in the product removal chamber 17, and the product is removed under atmospheric pressure. Start the extraction work. When this product removal work is completed, the main body of the vacuum container 18 is cleaned, and then the first airlock valve 53 and the second airlock valve 54 are operated to bring the inside of the product removal chamber 17 into a vacuum state. At the same time, the vacuum pump 1
9. The vacuum generator 28 consisting of the cold trap 20 and the chiller unit 21 is activated to adjust the degree of vacuum within the main body 18 of the vacuum container to a predetermined level necessary for restarting the vacuum drying process. In this state, the drying conditions of the vacuum drying/cooling device 8 are adjusted according to the same operating procedure as described above, and the vacuum drying operation of the raw materials is resumed. Although preferred embodiments of the present invention have been described above based on the illustrations of the drawings, the gist of the present invention should not be construed as limited by such illustrative descriptions, but rather should be A variety of applications can be included based on the basic building blocks identified. For example, if the main crusher 15 is configured as a multi-stage crusher with two or four or more stages, or if the capacity of the product take-out chamber 17 is large, air from outside the system may enter the vacuum vessel 18 from the product take-out chamber. In order to prevent the inflow of the product, a second vacuum generator can be provided specifically for the product removal chamber 17. Furthermore, a steam heating sterilizer or a cleaning device may be attached to sterilize or clean the inside of the vacuum container 18 when changing the product in progress. In carrying out the present invention, the capacity of the vacuum pump 19, cold trap 20, chiller unit 21, vacuum drying/cooling device 8, etc. is determined not only to maintain the degree of vacuum and dryness, but also to maintain the inside of the main body of the vacuum container 18. It is desirable to make a decision taking into consideration the dew condensation prevention mechanism. Further, as an application example of the present invention, a vacuum belt dryer having a plurality of drying stages can be constructed by mounting a plurality of stages of endless conveyor belts 1, 1, . . . inside the vacuum container 18. Effects of the Invention As can be understood from the above explanation, the apparatus of the present invention has a pre-crusher at the end of the endless conveying means, and a main crusher with a multi-stage structure consisting of multiple stages of rotating blades and a mesh wire mesh. established,
By cooperating with a vacuum drying/cooling device, a granulation/pulverization device is constructed that allows easy particle size adjustment and has a function to gradually reduce the crushing load. By using the apparatus of the present invention, final products of uniform particle size, such as granular processed foods such as instant coffee, powdered soup, powdered miso, etc., can be produced under stable load sharing conditions. Thus, the vacuum belt dryer according to the present invention has the following features:
As a device that can completely eliminate the drawbacks of conventional equipment, such as overload during crushing and uneven particle size,
It can have a remarkable effect on improving the quality of processed foods and reducing manufacturing costs.

[Brief explanation of drawings]

FIG. 1 is a partially sectional front view illustrating the overall structure of the device of the present invention. FIGS. 2 to 4 are explanatory diagrams of the main structure of the apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Endless conveyor belt, 9... Fluid pressure cylinder mechanism, 10... Shearing blade, 11... Precrusher, 13n... Rotating blade, 14n... Mesh wire mesh, 15... Main crusher, 16... Vacuum Lock mechanism, 17...Product removal chamber.

Claims (1)

[Claims] 1. In a vacuum belt dryer for vacuum drying raw materials prepared in liquid, slurry, or paste form and extracting them as granular dry products,
At the raw material discharge end of an endless conveyor belt rotatably mounted in a vacuum container, a pre-crusher consisting of a fluid pressure silling mechanism and a shearing blade is installed.
Below this pre-crusher, a main crusher consisting of a rotary blade and a mesh wire mesh surrounding the rotating blade approximately half its circumference is arranged in multiple stages, and the main crusher is arranged from the inlet side to the discharge side of the dried product in this main crusher. A vacuum belt dryer comprising a multistage crushing mechanism in which the mesh spacing of the mesh wire mesh gradually decreases, and the rotational speed of the rotary blade and the tooth width measured along the rotation direction gradually increase.