JPH0721381B2 - 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 a raw material supply device 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 reconstitution. Focusing on 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, 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 freezing and sublimation processes. 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 rapid evaporation phenomenon of the water contained therein, and the food material expands and forms a large number of vent holes inside. , 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, in the case of supplying a food material prepared in a slurry form or a paste form, in a conventional raw material supply device, the raw material discharge nozzle makes a swinging motion at a substantially constant rocking speed, and on the endless conveyor belt. Since the raw material is placed, a heavy portion of the raw material is formed at the turning point of the swinging motion as shown in FIG. In this way, when the raw material placed on the endless conveyor belt while forming a heavy portion having a larger thickness than other portions is subjected to a drying treatment according to the same heating condition as that of the other portion having a small thickness, Due to the increase in thickness, the drying effect of the heavy-duty portion decreases, and problems such as deterioration due to poor drying occur. On the other hand, if the heating temperature is set to a high value so as to fit the heavy portion, other thin portions fall into an excessively dry state, which causes problems such as deterioration of quality and deterioration.

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 vacuum belt dryer for vacuum-drying a raw material prepared in a liquid state, a slurry state or a paste state, and taking it out as a granular dry product. In addition, the swing of the raw material discharge nozzle (3) is detected on the rotary shaft of the motor (32) on the upper surface of the endless conveyor belt (1) rotatably mounted in the vacuum container (18) on the raw material introduction side. Swing speed in which a proximity switch (33) (34) for controlling the rotation and a forward / reverse rotary speed reducer (35) for converting the direction of the swing movement of the raw material discharge nozzle (3) by swing detection are connected. Rotating arm (2) and discharge nozzle (3) via control mechanism (4)
Is provided with a raw material supply device (5) which is swingably supported at a predetermined distance from the upper surface of the conveyor belt (1), and the endless conveyor belt ( 1) The purpose of the invention is a vacuum belt dryer that is placed in a meandering manner on top.

The raw material of the processed food prepared in the form of liquid, slurry or paste should be formed on the endless conveyor belt (1) with the increased thickness due to the heavy weight prevention function of the raw material supply device (5). It is supplied in a thin film while drawing a meandering trace, and in this state, it is vacuum-dried by the drying / cooling device (8) by the constant speed movement of the endless belt (1), and then the pre-crusher (11) and the main crusher (15). ) Is pulverized into granules by a) and is taken out of the system by a batch method from a product taking-out chamber (17) having a vacuum lock mechanism (16).

Example FIG. 1 is a front view with a partial cross section illustrating the overall structure of the device of the present invention, and FIG. 2 is a partial vertical cross-sectional view of a raw material supply device. 3 and 4 are plan views illustrating the meandering traces of the raw material supplied on the endless conveyor belt.

Referring to FIG. 1, a vacuum generator (28) including a known vacuum pump (19), a cold trap (20), and a chiller unit (21) is provided in the main body of the vacuum container (18). By operating the vacuum generator, a vacuum degree of about 10 Torr can be maintained inside the vacuum container (18) 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 .

The endless conveying device is basically a mesh (endlessly connecting a motor (not shown), a drive roller (26), a driven roller (27), and a synthetic fiber yarn, for example, a woven or woven fabric of polyester fiber yarn. It is composed of a belt (1), and the mesh belt is formed by the drive roller (26).
By constructing a drive system wound around the driven roller (27), a constant speed transport device having a transport speed of 0.05 to 0.5 m / min is formed. Mesh belt (1)
Considers the general characteristics required for endless conveyors,
It is manufactured from a knitted or woven fabric of synthetic fiber yarn having excellent strength, friction coefficient, heat resistance and heat transfer property.In the device of the present invention, the peelability of the vacuum dried intermediate product, the raw material from the weave and the stitch, and the Endless conveyor belts are manufactured from a woven fabric of polyester multifilament yarns in order to maintain the leakproofness and cleanability of intermediate products at a specified level. still,
In consideration 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 raw material supply device (5) is arranged on the most upstream side of the moving path of the endless conveyor belt (1), and has a nozzle (3).
As shown in FIG. 2, two sets of proximity switches (33), (34) for detecting the amplitude of the nozzle (3) are provided on the rotary shaft of the motor (32) as the swing speed control mechanism (4). ), And a forward / reverse rotational speed reducer (35) for converting the direction of the swinging motion of the nozzle (3) by detecting the amplitude of the proximity switches (33), (34). The rotating arm (2) and the nozzle (3) are swingably supported at a predetermined distance from the upper surface of the mesh belt (1) via the swing speed control mechanism (4) as described above. Tank (36)
The raw material stored therein reaches the nozzle (3) through the raw material supply valve (37) connected to the raw material tank, and is in a liquid, slurry or paste state due to the swinging motion of the nozzle. It is placed meanderingly on the mesh belt (1).

In the device of the present invention, in order to prevent an overlapping supply portion of the raw material, that is, an increased thickness portion due to the heavy-duty arrangement, from occurring at the turning point of the meandering supply trace, the two sets of proximity switches (33 ), (34) detects the direction change point of the swinging stroke of the nozzle (3), the forward / reverse rotation speed reducer (35) of the swing speed control mechanism (4) is temporarily stopped, and the third As shown in the figure, the raw material supplied to the edge portion of the mesh belt (1) is combined with the composite supply trace by the combination of the rotation of the mesh belt (1) and the temporary rest of the nozzle (3), That is, the shape of the meandering feed trace is controlled so that the feed trace oriented in the longitudinal direction of the mesh belt (1) is given to the raw material in the vicinity of the edge portion of the mesh belt (1).

Further, in the device of the present invention, the forward / reverse rotation speed reducer (35) is provided.
Even when the conventional feed trace shown in FIG. 4 is drawn by adjusting the speed reduction ratio of the mesh belt (1) to the traveling speed, it is caused by the disposition of the raw material at the turning point of the meandering feed trace. It is possible to obtain the meandering form of the raw material in which the increased thickness portion hardly occurs.

On the other hand, in the vacuum drying path formed by the endless conveyor belt, heating plates (6a), (6b) and (6c) having hot water passages built in along the lower surface of the mesh belt (1) and cooling water passages are provided. A hot water circulation type vacuum drying / cooling device (8) including a built-in cooling plate (7) is arranged.

The thin-film raw material introduced into the I-th heating zone constituted by the first heating plate (6a) contains a large amount of water, but was transferred from the high-temperature hot water flowing in the heating plate (6a). The raw material is dried by 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 I-th 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 subsequent II-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 raw 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 primary crushed by the vertical movement of the shear blade (10) of the pre-crusher (11) while protruding from the reversing part of the mesh belt (1), and then the rotating blade and the mesh. Main crusher (15) made of wire mesh (none shown)
Secondary crushed by. 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 As can be understood from the above description, by adopting the device of the present invention, the raw material of the processed food prepared in a liquid, slurry or paste form is at the direction change point of the swinging motion of the discharge nozzle. Moreover, the endless conveyor belt is arranged in a meandering manner without generating a heavy portion, and a substantially uniform spread thickness can be maintained over the entire surface of the endless conveyor belt. Therefore, according to the apparatus of the present invention, uniform heating / cooling conditions are maintained over the entire vacuum drying section, and it is noted that the quality of processed foods is improved as compared with the case where a conventional vacuum drying apparatus is used. The desired effect can be exhibited.

[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, and FIG. 2 is a partial vertical cross-sectional view of a raw material supply device. 3 and 4 are plan views illustrating the meandering traces of the raw material supplied on the endless conveyor belt. (1) ... Endless conveyor belt, (2) ... Rotating arm, (3)
... Discharge nozzle for raw material, (4) ... Swing speed control mechanism,
(5) ... Raw material supply device, (18) ... Vacuum container.

Claims (1)

[Claims] 1. A vacuum belt dryer for vacuum-drying a raw material prepared in a liquid form, a slurry form or a paste form, and taking it out as a granular dry product, which is rotatably mounted in a vacuum container. On the upper surface of the endless conveyor belt where the raw material is introduced, a proximity switch for detecting the swing of the discharge nozzle of the raw material on the rotation axis of the motor, and for changing the swinging direction of the discharge nozzle of the raw material by swing detection A raw material supply device is provided, which swingably supports the rotary arm and the discharge nozzle at a predetermined distance from the upper surface of the conveyor belt via a swing speed control mechanism in which a forward / reverse rotation speed reducer is continuously provided. A vacuum belt dryer, wherein raw materials are placed in a meandering manner on an endless conveyor belt by a swinging motion of the discharge nozzle.