JPH0334917B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a vacuum belt dryer, and more particularly to a vacuum belt dryer for vacuum drying raw materials in the form of liquid, slurry or paste and extracting them as dried granular products. This invention relates to a raw material supply device in a vacuum belt dryer.

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 freezing and sublimation processes, 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 feeds food material in the form of a liquid, slurry, or paste onto an endless conveyor belt in the form of a thin film, and rotates the endless conveyor belt. The food material is introduced into a heating zone by means of a heating zone, and is 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, when feeding food raw materials prepared in the form of a slurry or paste, in a conventional raw material supply device, the raw material discharge nozzle swings at a substantially constant oscillating speed while moving the raw material onto an endless conveyor belt. As the raw material is placed, a striated portion of the raw material is formed at the point where the direction of the oscillating motion changes, as shown in FIG. In this way, if the raw material placed on the endless conveyor belt while forming a thickened part that is thicker than other parts is subjected to drying treatment under the same heating conditions as other thinner parts, Due to the increase in thickness, the drying effect of the keratinized portion decreases, and problems such as deterioration due to insufficient drying occur. On the other hand, if the heating temperature is set high to suit the above-mentioned keratinous portion, other thinner portions will become excessively dry, resulting in problems such as deterioration and deterioration of quality.

In addition, in a liquid supply device in which a large number of liquid supply nozzles are arranged in a line on a fixed header pipe, the raw material is discharged onto an endless conveyor belt in a linear liquid supply trajectory that is the same as the interval between the liquid supply nozzles. Therefore, the effective use of the liquid supply surface of the endless conveyor belt is considerably restricted.

The main object 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 drying function.

Means for Solving the Problems In view of the above object, the present invention provides a vacuum belt dryer for vacuum drying raw materials prepared in a liquid, slurry or paste form and taking out the dried product as granules. A header pipe having a plurality of liquid supply nozzles arranged in an array is installed on the upper surface of the raw material introduction side of an endless conveyor belt rotatably mounted in a vacuum container so as to be perpendicular to the traveling direction of the endless conveyor belt. A vacuum belt dryer is provided, in which a reciprocating swing device is connected to the header pipe to constitute a liquid supply device in which a liquid supply nozzle reciprocates along the width direction of an endless conveyor belt. .

Function Raw materials for processed foods prepared in liquid, slurry, or paste form can be drawn in a meandering trace on the endless conveyor belt without forming thickened areas by simultaneous swinging of multiple liquid supply nozzles. In this state, it is vacuum-dried in a subsequent drying/cooling device by constant speed movement of an endless belt, and then crushed into granules by a pre-crusher and a main crusher. The product is taken out of the system in batches from a product take-out chamber with a vacuum lock mechanism.

Embodiment FIG. 1 is a partially sectional front view illustrating the overall structure of the device of the present invention, and FIG. 2 is a schematic perspective view of the reciprocating liquid supply device. 3 and 4 are plan views illustrating the meandering trace of the raw material fed onto the endless conveyor belt.

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.
8 is disposed, and by operating the vacuum generator, a degree of vacuum of around 10 Torr can be maintained inside the vacuum container 18 during drying of raw materials.

On the other hand, inside the vacuum container 18, there is a first pipe which has a hot water flow path formed therein, extending along the movement path of the endless conveyor 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 and cooling device 8 constituted by the heating plate and the cooling plate, the vacuum vessel 18 is equipped with a known tube or plate heat exchanger 2 which functions as a hot water circulation line heater.
2. Expansion tank 23 that promotes circulation of hot water by pressurizing air, and temperature control circuit (not shown)
A heating medium and cooling medium circulation device consisting of a circulation pump 24 connected to is connected.

The endless conveyance device basically includes a motor (not shown), a drive roller 26, a driven roller 27,
and a mesh belt 1 formed by endlessly connecting knitted fabrics of synthetic fiber threads, such as polyester fiber threads, and a drive system in which the endless conveyor belt is wound around the drive roller 26 and the driven roller 27. By configuring
A constant speed conveying device having a conveying speed of 0.05 to 0.5 m/min is formed. The endless conveyor 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 endless conveyance devices. In order to maintain the releasability of vacuum-dried intermediate products, the prevention of raw materials and intermediate products from leaking from the fibers and stitches, and the washability at a specified level, endless fabrics made of polyester multifilament yarn are used. We manufacture conveyor belts. Note that, in view of the above-mentioned required characteristics, it is desirable that the endless conveyor belt 1 be surface-treated with a resin such as silicone or polytetrafluoroethylene.

The liquid supply device 5 is disposed at the most upstream side of the moving path of the endless conveyor belt 1, and includes a header pipe 4 formed by fixing a plurality of liquid supply nozzles 3a, 3b, 3c, . . . at a predetermined pitch. , and a reciprocating swing device 34 connected to this header pipe. To explain in more detail, the liquid supply device 5 is
As illustrated in FIG. 2, a plurality of liquid supply nozzles 3a, 3b, 3c...
Header pipes 4 are arranged perpendicularly to the traveling direction of the endless conveyor belt 1, and a drive shaft is supplied with power from a motor 31 and a forward/reverse rotary speed reducer 35 to make a vertical movement. A swinging arm 2 of a header pipe is fixed to the header pipe 32 to constitute a reciprocating swinging device 34 for the liquid supply nozzles 3a, 3b, 3c, . . . . On the other hand, header pipe 4
is swingably supported by guide members such as rollers 4a and guide rails 4b at a predetermined distance from the upper surface of the endless conveyor belt 1, and the raw materials stored in the raw material tank 36 are , 1st
As shown in the figure, the raw material flows into the header pipe 4 through the raw material supply valve 37 connected to the raw material tank, and becomes liquid, slurry, or paste due to the reciprocating movement of the header pipe along the axial direction of the endless conveyor belt 1. The liquid flows out from the respective liquid supply nozzles 3a, 3b, 3c, . . . and is placed on the endless conveyor belt 1 in a meandering manner.

In the device of the present invention, the forward/reverse rotation reducer 3
By adjusting the reduction ratio of 5 to the running speed of the endless conveyor belt 1, the increased thickness due to the striations of the raw material can be removed at the turning point of the meandering supply trace, as illustrated in FIG. The meandering supply conditions for the raw material are ensured so that almost no generation occurs and the entire surface of the endless conveyor belt 1 can function as a loading surface for the raw material.

On the other hand, in the vacuum drying path formed by the endless conveyor belt, heating plates 6a, 6b, 6 with built-in hot water channels are provided along the lower surface of the endless conveyor belt 1.
c, and a hot water circulation type vacuum drying cooling device 8 consisting of a cooling plate 7 having a built-in cooling water flow path.

The thin film-like raw material introduced into the first heating zone constituted by the first heating plate 6a contains a large amount of moisture, but due to the thermal energy transferred from the high temperature hot water flowing inside the heating plate 6a. As a result, the raw material is dried and 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 at a constant rate of dryness, the temperature of the raw material itself hardly increases, 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 flow rate 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 increasing its own temperature. In this first heating zone, the thermal conductivity of the raw material is significantly reduced, so the heating plate 6c is lower than that in the first heating zone and the second heating zone.
The temperature of the hot water introduced into the chamber is set even lower, and under the influence of a small heat flow rate, the raw material is subjected to vacuum drying 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 porous cake and reaches the end of the endless conveyance path while leaving a trace corresponding to the shape of the liquid supply on the endless conveyor belt 1. The intermediate product that has reached the end of the endless conveyance path is
It is first crushed by the vertical movement of the shearing blade 10 of the pre-crusher 11 in a state protruding from the reversing part of the endless conveyor belt 1, and then by the main crusher 15 consisting of a rotating blade and a mesh wire mesh (both not shown). It is then crushed for a second time. The granular product thus obtained is transferred to the vacuum lock mechanism 1.
6 into the product take-out chamber 17, and is taken out of the system in a batch manner.

Effects of the Invention As can be understood from the above explanation, by employing the apparatus of the present invention, raw materials for processed foods prepared in liquid, slurry, or paste form can be
The liquid is simultaneously supplied from a plurality of liquid supply nozzles onto the endless conveyor belt, and a plurality of meandering traces corresponding to the number of liquid supply nozzles are distributed over the entire surface of the endless conveyor belt. Therefore, according to the apparatus of the present invention, the entire surface of the endless conveyor belt can be effectively used as a loading surface for raw materials, and uniform heating and cooling conditions can be maintained throughout the vacuum drying section. As a result, the quality of the product and the productivity of the vacuum drying process are significantly improved compared to when conventional vacuum drying equipment is used.

[Brief explanation of drawings]

FIG. 1 is a partially sectional front view illustrating the overall structure of the device of the present invention, and FIG. 2 is a schematic perspective view of the reciprocating liquid supply device. 3 and 4 are plan views illustrating the meandering trace of the raw material fed onto the endless conveyor belt. DESCRIPTION OF SYMBOLS 1... Endless conveyor belt, 3a, 3b... Liquid supply nozzle, 4... Header pipe, 5... Raw material supply device, 18... Vacuum container, 34... Reciprocating rocking device.

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,
A header pipe consisting of a plurality of liquid supply nozzles arranged in an array is arranged on the upper surface of the raw material introduction side of an endless conveyor belt rotatably mounted in a vacuum container so as to be perpendicular to the traveling direction of the endless conveyor belt. A vacuum belt dryer characterized in that a reciprocating swinging device is connected to the header pipe to constitute a liquid supply device in which a liquid supply nozzle reciprocates along the width direction of the endless conveyor belt.