JPH0749322B2 - Vacuum belt dryer - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a vacuum belt dryer, and more particularly to vacuum drying a liquid, slurry or paste raw material to obtain a granular dry product. The present invention relates to an attitude control device for an endless conveyor belt for a vacuum belt dryer.

2. Description of the Related Art In recent years, many kinds of processed food materials and instant foods have been marketed with the diversification of eating habits. In such a food processing field, the consumer maintains the solubility and instantness when using the product as a cooking ingredient at a predetermined level, and the final product is not deteriorated in quality and the components are not deteriorated. Various atmospheric dryers and vacuum dryers are used for the purpose of imparting restoration properties. Attention is paid to the fact that it is relatively easy to maintain the solubility of a product as a cooking ingredient at a good level among such dryers, and the fields of use of vacuum dryers are rapidly increasing. Spray dryers and freeze dryers are known as general-purpose vacuum dryers.
The former has a low drying cost, but the solubility and quality retention performance of the product or the component change prevention performance is somewhat inferior.
The latter is accompanied by problems of complicated structure and high drying cost due to the use of the freezing / sublimation process. Here, the development of a vacuum belt dryer has been demanded as a means for solving the practical problems recognized in the spray dryer and the freeze dryer. The vacuum belt dryer is provided with a heating zone and a belt transfer device in a vacuum container, supplies a liquid, slurry or paste food material in a thin film on the endless transfer belt, and rotates the endless transfer belt. The food material is guided to the heating zone by means of vacuum drying under relatively low temperature drying conditions. At this time, the food material placed in a thin film on the belt undergoes a vigorous evaporation phenomenon of water contained therein, and the food material swells and forms a large number of vent holes inside. . It is sent to the crusher as a porous intermediate product. Thus, the vacuum belt dryer is gradually recognized for its usefulness as an alternative technical means for the conventional spray dryer and freeze dryer.

Problems to be Solved by the Invention A vacuum belt dryer has a performance far exceeding that of a known spray dryer or freeze dryer in terms of quality retention performance, component change prevention performance, or drying cost reduction performance. However, in order to cope with the diversification of food materials to be dried, it is necessary to further improve the structure and function.

For example, the endless conveying means consisting of the endless conveying belt and its driving roller moves at a constant speed from the raw material supply station toward the drying station, and heats the thin film raw material supplied on the endless conveyor belt with thermal energy for drying. However, as a practical problem, the endless conveyor belt is made of a soft material, so that the conventional simple meandering prevention device is not effective, and the unstable driving state caused by meandering and warping is generated. In many cases it is placed. Once such a phenomenon occurs, the conditions for supplying the raw materials onto the endless conveyor belt become extremely unstable, and the final product may suffer defects such as deterioration of quality and alteration of components due to fluctuations in drying conditions.

A main object of the present invention is to provide a vacuum belt dryer having a simple structure and stability of a drying function, which can solve the above-mentioned problems recognized in a conventional vacuum belt dryer. It is in.

Means for Solving the Problems In view of such an object, the present invention provides a heating zone and an endless conveyor belt having a uniform thickness made of a soft material in a vacuum container, and is in a liquid form, a slurry form, or a paste form. The raw material prepared in (1) is supplied as a thin film on an endless conveyor belt, and vacuum dried by passing through a heating zone where a heating plate is arranged on the lower surface of the belt, and taken out as a granular dry product. In a belt dryer, left and right independent support structure that applies restoring force to the inside of the belt width direction is applied to both ends of the belt width direction on the belt retract side of the drive roller and driven roller of the endless conveyor belt. Door-shaped side push rollers are rotatably opposed to each other via a roller, and the upper end of the widthwise both edges of the endless conveyor belt is positioned above the widthwise both edges of the belt. A plurality of top presser roller to prevent the return, in which through another support bracket and the support arm of the press side roller and rotatably is supported by suitable intervals along the moving direction of the endless conveyor belt.

The endless conveyor belt of the present invention is installed in a vacuum container, and a means for supplying the raw material in a thin film form is installed on the upper surface of the starting end side of the belt, and in the heating zone, the lower surface of the belt is heated. A plate is arranged, and the raw material supplied in a thin film on the belt is heated to a low boiling point in a vacuum atmosphere by a heating plate to be used for efficient drying, so that the belt meanders and bends. The prevention mechanism should be a support structure that is as simple as possible, and prevent the belt made of a soft material from meandering without causing warping, and further, those mechanisms are provided in a thin film on the belt. Is required to be uniformly dried by heating, and the above means of the present invention satisfies these.

Therefore, when the endless conveyor belt made of a soft material tries to meander, the side surface pressing roller presses from the side,
Since the upper surface pressing roller prevents the belt from warping upward, it is possible to prevent the endless conveyor belt made of a soft material from meandering by the cooperation of these rollers, and to make the endless conveyor belt flat. It can be held to make the contact with the heating plate uniform in the width direction. As a result, the raw material of the processed food prepared in the form of liquid, slurry or paste moves in the vacuum container at a constant speed while being spread on the endless conveyor belt which is prevented from meandering and curling, and is dried and cooled. The product is vacuum dried in an apparatus, and thereafter, it is granulated into granules by a pre-crusher and a main crusher, and taken out of the system in a batch system from a product taking-out chamber having a vacuum lock mechanism.

Example FIG. 1 is a front view with a part in section illustrating the overall structure of the device of the present invention. Further, FIG. 2 is an explanatory view of the main structure of the device of the present invention.

In FIG. 1, a vacuum generator (28) including a known vacuum pump (19), a cold wrap (20), and a chiller unit (21) is provided in the main body (18) of the vacuum container. By operating the vacuum generator, the inside of the main body (18) of the vacuum container can maintain a vacuum degree of about 10 Torr when the raw material is dried.

On the other hand, in the vacuum container (18), first to third hot water flow passages are formed in the moving path of the endless conveyor belt (1) from the raw material supply side toward the product delivery side. The heating plates (6a), (6b) and (6c) and the cooling plate (7) having a flow path for cooling water inside are sequentially arranged. In order to supply hot water and cooling water adjusted to a predetermined temperature to a vacuum drying device (8) composed of a cooling plate, the main body (18) of the vacuum container functions as a hot water circulation line heater. Heating consisting of a tube or plate heat exchanger (22), an expansion tank (23) that promotes circulation of hot water by air pressurization, and a circulation pump (24) connected to a temperature control circuit (not shown). Circulation device for medium and cooling medium is connected .

As shown in FIG. 2, the endless conveying device basically comprises a motor (25), a drive roller (26), a driven roller (27), and a synthetic fiber yarn, for example, a polyester fiber yarn endless woven fabric. 0.05 to 0.5 m / m by comprising a mesh belt (1) which is connected in the shape of a circle, and a drive system formed by winding the mesh belt around the drive roller (26) and the driven roller (27). It forms a constant velocity transport device with a transport speed of min. The mesh belt (1) is manufactured from a knitted or woven fabric of synthetic fiber yarn having excellent strength, friction coefficient, heat resistance and heat transfer in consideration of 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 to a prescribed level, weaving of polyester multifilament yarn We manufacture endless conveyor belts. In view of the above-mentioned required characteristics, it is desirable that the mesh belt (1) be surface-treated with a resin such as silicon or polytetrafluoroethylene.

The drive roller (26) and driven roller (27)
It is necessary for the mesh belt (1) rotatably mounted inside the vacuum container (18) to be able to guarantee a stable conveyance posture without meandering. For this reason, the drive roller (26) and the driven roller (27) have their surfaces crowned so that the diameter of the center part is slightly larger than the diameter of the end parts, and the pivot of the driven roller (27) is fluidized. A tension adjusting mechanism for the mesh belt (1) is formed by being connected to a pressure cylinder mechanism (29), for example, a belt tension unit having an air cylinder mechanism. Further, on the side where the mesh belt (1) is drawn into the drive roller (26) and the driven roller (27), when a meandering phenomenon occurs in the mesh belt (1), the edge portion of the mesh belt (1), so-called, As shown in FIG. 3, one pair of four door roller-like side surface pushing rollers (30) for transmitting the inward restoring force to the ears are provided as shown in FIG.
They are rotatably opposed to each other via a). These constituent members are assembled into an integral structure to form a meandering prevention mechanism (12) for an endless conveyor belt.

On the other hand, when the mesh belt (1) is warped due to uneven tension or thermal contraction, the heating plate (6a),
The spacing between (6b), (6c) and the cooling plate (7) and the mesh belt (1) fluctuates along the width direction of the mesh belt (1), causing deterioration in quality of the product due to uneven drying. To do. In order to avoid such obstacles, the heating plate (6) is moved along the moving direction of the mesh belt (1).
As shown in FIG. 3, between the a), (6b), (6c) and the cooling plate (7), the mesh belt (1) is spaced from the raw material mounting surface of the mesh belt (1) at an appropriate distance. A plurality of pressing upper surface pressing rollers (31) are rotatably supported via a support bracket (not shown) with their axial directions aligned with the axial directions of the drive roller (26) and the driven roller (27). ing. The upper surface pressing roller (31) functions as a warp prevention member for the mesh belt (1) in cooperation with the meandering prevention mechanism (12).

The raw material supply device (5) supplies the raw material from the raw material tank (36) to the nozzle (3) through the raw material supply valve (37),
Moreover, the nozzle (3) is swung by the swing speed control mechanism (4) via the rotating arm (2), whereby the raw material is formed into a thin film from the nozzle (3) on the mesh belt (1). It is to be distributed and supplied to.

The raw material of the processed food supplied from the nozzle (3) of the raw material supply device (5) onto the mesh belt (1) moves at a constant speed under the posture control by the pressing roller (31) and the meandering prevention mechanism (12). While being carried by the mesh belt (1), it is moved inside the vacuum container (18), and during this, vacuum drying treatment is performed by a hot water circulation type vacuum drying / 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, it is transferred from the hot water of high temperature flowing in the heating plate (6a). The raw materials are dried by the generated heat energy,
Since moisture starts to evaporate at the same time on the surface and inside, the raw material spread in a thin film is vacuum-dried while swelling violently. Since the first heating zone is kept in a constant rate dry state, the temperature of the raw material itself hardly rises, and the raw material is sent to the succeeding second heating zone in a state where almost half of the water content is evaporated.

In the second heating plate (6b) forming the second heating zone, hot water having a temperature slightly lower than that of the hot water supplied into the first heating plate (6a) is introduced, and the raw material is Most of the retained water is evaporated by constant rate drying. Therefore, the expanded thickness and surface shape of the raw material hardly change, the surface of the raw material is slightly hardened, and the temperature of the raw material itself starts to rise. In this II heating zone, the thermal conductivity of the raw materials is somewhat reduced, so the temperature of the hot water introduced into the heating plate (6b) is set slightly lower than in the I heating zone, and The drying process conditions are adjusted so that the heat flux is also somewhat reduced. Thus, the raw material is allowed to evaporate approximately 90% of its water content from the second heating zone to the subsequent second.
III Delivered to heating zone.

The raw material introduced into the third heating zone formed by the third heating plate (6c) has a water content lower than those of the first heating zone and the second heating zone, and is free from swelling phenomenon. It is gently vacuum dried to the final moisture content. That is, in the III heating zone, the raw material is dried at a reduced rate, which hardens the surface and raises the temperature of itself. In this III heating zone,
Since the thermal conductivity of the raw material is significantly reduced, the heating plate (6c) is more than the first heating zone and the second heating zone.
The temperature of the hot water to be introduced therein is set lower, and the reduced material is vacuum-dried under the action of a small heat flux and sent out to the subsequent cooling zone.

The raw material fed into the cooling zone is cooled by the low temperature water introduced into the cooling plate (7), which lowers the temperature of the raw material itself and increases its hardness,
As a result, the final dry state suitable for improving the peelability of the intermediate product and reducing the hygroscopicity is obtained. In this way, the intermediate product heated and cooled under vacuum, that is, the expanded product, becomes a porous cake and reaches the end of the endless transfer path while leaving a trace corresponding to the liquid supply shape on the mesh belt (1). . The intermediate product reaching the end of the endless transport path is moved upward and downward by a fluid pressure cylinder mechanism (9) with a shear blade (not shown) of the pre-crusher (11) in a state of protruding from the reversal part of the mesh belt (1). Primary crushing is performed, and then secondary crushing is performed by a main crusher (15) composed of a rotating blade (14) and a mesh wire mesh (13). The granular product thus obtained falls into the product take-out chamber (17) having the vacuum lock mechanism (16) and is taken out of the system in a batch system.

EFFECTS OF THE INVENTION The side surface pushing roller of the present invention has a very simple structure in which a door roller is rotatably supported at the tip of a support arm having a left and right independent supporting structure. It does not hinder and does not cause uneven drying.

Further, the upper surface pressing roller is also rotatably arranged only on the upper surface side of both side edges in the width direction of the belt via a supporting bracket different from the supporting arm of the side surface pressing roller, and the heating plate of the heating zone is arranged in Has no hindrance, is in non-contact with the raw material supplied in a thin film on the belt, and has a uniform thickness, breathability and heat distribution characteristics from the center part in the width direction of the belt to both side edges. Thus, the raw materials can be uniformly heat-dried without uneven drying.

[Brief description of drawings]

FIG. 1 is a front view with a part in section illustrating the overall structure of the device of the present invention. 2 is a side view of the main structure of the device of the present invention, and FIG. 3 is a plan view thereof. (1) …… Endless conveyor belt, (12) …… Meandering and warping prevention mechanism, (18) …… Vacuum container.

Claims (1)

[Claims] 1. A vacuum zone is provided with a heating zone and an endless conveyor belt of uniform thickness made of a soft material, and raw materials prepared in a liquid, slurry or paste form are formed on the endless conveyor belt in a thin film form. In a vacuum belt dryer for supplying the powder to a vacuum belt dryer by passing through a heating zone in which a heating plate is arranged on the lower surface of the belt, and taking out as a granular dry product. Also, the door roller side push rollers are rotatably opposed to the driven roller at the belt retraction side both ends in the belt width direction through the support arms having left and right independent supporting structures that apply a restoring force to the inside in the belt width direction. Arranged and on the upper surface of the widthwise both side edges of the endless conveyor belt, a plurality of upper surface pressing rollers for preventing upward warping of the belt widthwise both side edges, Through another support bracket and the support arm of the flattened roller, vacuum belt dryer is characterized in that rotatably is supported by suitable intervals along the moving direction of the endless conveyor belt.