JPS5821191B2 - Multi-stage continuous vacuum drying equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to a multi-stage continuous vacuum drying apparatus.

In general, the continuous vacuum drying method for food products was used to dry whole fat concentrated milk, concentrated fruit juice, etc. in the United States about 20 AM from now.

The characteristics of this drying method are that highly viscous heat-sensitive substances that cannot be processed by spray drying can be dried, and the resulting product is instant and has excellent flavor.

The normal operating pressure is in the range of 3 to 50 Torr, making continuous supply easier and cheaper than the freeze-drying method.

However, at the current state of the art, this method is slightly more expensive than the spray drying method.

This is mainly due to the large equipment investment due to the large volume of the vacuum chamber relative to the throughput (however, it is less compared to the freeze-drying method) and the thermal efficiency [-(heat required for drying / calorific value) x
Loo%" is at a low point.

In the conventional belt-type continuous vacuum drying method (hereinafter referred to as method A) as shown in FIG. 1, an endless metal belt 4 is stretched between rollers 2 and 3 installed at both ends of a vacuum chamber 1.

The raw material is guided under vacuum by a high viscosity pump through an orifice or slit-shaped nozzle, and is coated on a moving endless belt 4, and is heated by the radiant heat of heaters 5 (electric, heat medium, etc.) placed above and below the belt. It is dried, peeled off from a doctor blade 6 provided on the roller at the other end, discharged alternately into the atmosphere from two product hoppers 7 provided at the bottom, and then crushed, filled and packaged to become products.

However, as is clear from the figure, in this method, the space that is effectively utilized in the vacuum chamber is extremely small, and most of it can be said to be dead space.

In this way, the required vacuum chamber becomes large in relation to the throughput, so the equipment investment amount becomes large in relation to the throughput.

The reason for this is that if the vacuum chamber becomes larger, the thickness of the material used will increase in terms of strength according to design calculations, which will lead to an increase in the weight of the material and an increase in the capacity of the vacuum pump.

When scaling up according to this method, the only way to secure the required belt area is to install a large number of dryers.
There is little hope for economies of scale.

Regarding thermal efficiency, in this method, the heaters placed above and below the belt emit radiation to the top and bottom, respectively.

Reflectors are placed above the upper heater and below the lower heater to prevent heat from being released to the outside.However, these alone cannot completely block out the heat, and may vary depending on the heating temperature, vacuum, etc. Thermal efficiency is in the range of 30 to 50 degrees, although it varies depending on temperature conditions.

As mentioned above, in the conventional belt-type vacuum drying method, the volume of the vacuum chamber is large in relation to the throughput, and therefore the equipment investment is large, and the low thermal efficiency also increases the manufacturing cost of the vacuum drying method. It is also the cause.

In order to reduce this dead space, the dryer is made into a rectangular shape, but although this method contributes to a slight reduction in dead space, it cannot essentially solve this problem.

Technically, it is possible to manufacture a vacuum chamber that is quite large, but from an economic standpoint, it is more advantageous to install it in several units.

If the design is proceeded according to the conventional method (Method A) as described above, it is extremely difficult to make the belt type continuous vacuum drying method into a practical scale device.

The second method was devised to improve the drawbacks of this method.
The method shown in the figure (hereinafter referred to as method B) has a large number of rollers and belts arranged in one vacuum chamber as shown in the figure.

According to this method, a slight reduction in the volume of the vacuum chamber was achieved compared to Method A, but no improvement was achieved in terms of thermal efficiency.

In this way, Method B does not fundamentally solve the deficiencies of Method A.

The present invention aims to compensate for the drawbacks of the conventional methods as described above, to reduce the size of the vacuum chamber in a vacuum drying apparatus, and to improve thermal efficiency.

In order to achieve this purpose, the multi-stage continuous vacuum drying apparatus of the present invention has an endless conveyor belt system stretched in an annular manner between belt rollers, which is stacked vertically in multiple stages in one vacuum chamber, and the raw material supplied to each belt is stacked in multiple stages. In a vacuum drying device that peels the product by heating and drying it from a belt and converting it into a product, the belts that make up the endless conveyor belt device are arranged in an annular multistage manner, and the raw material conveying section is connected to the raw material conveying section, and the non-conveying section is connected to the raw material conveying section. The non-transporting parts are stacked together, and the heating device placed for the raw material transporting part is an intermediate heater shared by the upper and lower belts interposed between each belt, and a belt on the top or bottom stage. It consists of a heater that heats the

Since the multi-stage continuous vacuum drying apparatus of the present invention has the above-described structure, it has the advantage of greatly reducing the vacuum drying volume relative to the throughput and dramatically increasing the thermal efficiency.

The reason for this is that the belts constituting the endless conveyor belt device are arranged in an annular multi-stage manner, and the raw material conveying parts are stacked together, and the non-conveying parts are stacked together. Belts can be placed as close to each other as possible in both the non-conveying section and the non-conveying section.In particular, since no heaters are placed in the non-conveying section, it is possible not only to place the belts as close to each other as possible, but also to make it possible to place the belts as close as possible to each other. Since the intermediate heater can be shared by the upper and lower belts, there is no need to provide upper and lower heating heaters for each belt in the raw material conveyance section, unlike conventional belts, and the number of heaters can be reduced accordingly. The space for installing the heater can be saved, and the volume of the vacuum chamber in which the endless conveyor belt device is placed can be reduced.
In addition, the intermediate heater effectively applies heat to the upper and lower raw materials, and unlike conventional heaters, heat is not obstructed by the non-conveying area, making it possible to dramatically increase thermal efficiency. be.

In addition, by adopting the device of the present invention, it is possible to reduce the scale of the practical device (lton
Even if the scale-up is to the extent of 100 g product/Hr), it is possible to install equipment with the same capital investment as spray drying equipment, and continuous vacuum drying that integrates the process of spray drying and granulation will be used in the future industry. Not only can the method be modified, but by adopting the device of the present invention, the continuous vacuum drying method can be widely used in the industrial world, and high-quality products can be delivered to the world at low cost.

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 3 shows a continuous vacuum drying device with a five-stage belt arranged in an annular multi-stage manner.

As the number of stages increases, a system is adopted in which only the non-conveying part of the belt is returned from the bottom as shown in Figure 4. This should be decided in consideration of economic efficiency in each case, and is the basic principle of the present invention. My way of thinking hasn't changed.

In Figure 3, a special resin belt 8 made of a blend of five sheets of Teflon and glass wool and subjected to antistatic surface treatment is placed in a vacuum chamber 1.
It is located within 5.

The special resin belt is used here because it has high heat resistance and peelability, and unlike metal belts, it does not generate metal powder due to friction with the heater.

The second stage belt is arranged inside the first stage belt, and the third stage belt is arranged inside the second stage belt.

Therefore, the total length of the belt is the longest in the first stage belt and becomes shorter toward the inside.

Reference numeral 9 denotes their driving rollers, which are adapted to interlock with each other in a manner to be described later.

Reference numeral 10 indicates a presser roller corresponding to the drive roller 9, and the heald is stretched between the drive roller 9, the feed rollers 11, 12, and the jacket roller 130.

14 is a supply nozzle.

This supply nozzle 14 has a width slightly narrower than the belt width and is designed to be able to apply the raw material to the endless belt in a uniform thickness.

As shown in FIG. 5, the raw material sent from a high viscosity pump 16 installed outside the vacuum chamber 15 is transferred through an endless belt that moves through a slit-like supply nozzle 14 (with a gas injection step if necessary). It is applied onto the raw material conveying section 8a of No.8.

In this case, the second stage supply nozzle 14 is located between the first stage and second stage belts.

Further, a pipe connecting the high viscosity pump 16 and the supply nozzle 14 is led from the side of the vacuum chamber 15.

The raw material sent out from the high viscosity pump 16 is branched into the required number of supply nozzles, and a flow rate adjustment valve 17 is attached to all the branched piping so that the flow rate to each supply nozzle 14 is evenly distributed. It has become.

The raw materials supplied at each stage are transported by a moving endless belt 8
It is applied to a uniform thickness and dried to a predetermined moisture content while passing through a heating section.

In this case, all the heaters 28 except the top and bottom heaters supply heat to the belt passing through the top by conduction and radiation.

The lower part can be used as radiant heat to the raw material coated on the belt.

In this way, more than 90% of the heat generated by the intermediate heater is effectively utilized.

This is the reason why the present invention dramatically increases thermal efficiency.

The product passed through the heating section and dried into a porous layer on the endless belt is ground to a predetermined particle size by a grinding roller 18 provided at the exit of the heating section.

In this case, a Teflon belt support 19 is installed below the belt, and the particle size can be varied by changing the clearance between the crushing roller 18 and the support 19.

Thereafter, the pulverized product is peeled off from the belt 8 as shown in FIG. 7 by a scraper 20 coated with Teflon, and distributed to both sides of the belt as shown in FIG. The product falls into the tank.

In this case, a guide 21 is provided to prevent falling powder from adhering to the lower belt.

Products are alternately discharged into the atmosphere from two product take-out tanks located at the bottom.

The product is then packaged and filled.

An enlarged view of the five drive rollers 9 provided on the right side of FIG. 3 is shown in FIG.

The five driving rollers 9 all have the same diameter, and the number of gears 22 connecting them is also the same, and these are connected by a chain 23.
It is tied with

Therefore, it is only necessary to drive one roller from the outside, and only one shaft sealing mechanism is required.

In this manner, the rotational speed of all rollers is constant, and therefore the moving speed of the belt is also constant, and thus the product moisture content in each stage is constant.

Next, an automatic meandering prevention device 24 is attached to the non-conveying portion 8b of each belt at the lower part, as shown in FIG. 3, to prevent the belt from meandering.

This device has a structure in which a belt is passed between two rollers.

The endless belt that has passed through the meandering prevention device 24 is then cleaned with a cloth cleaner 25 such as a rasher to remove fine powder that could not be removed with a scraper to prevent trouble in the next supply process.

With such a system, stable porous powder foods can be obtained after long and stable feeding and drying.

In addition, 29 in FIG. 3 is a device or a flutter installed above the first stage belt and below the fifth stage belt, and 26 and 27 are the exhaust port and product outlet of the vacuum chamber 15.

In addition, the scraper 20 may be provided at a lower portion of the drive roller 9 other than the location shown in the drawing.

When provided in the lower portion of the drive roller 9 in this way, it is necessary to provide a guide of a different type from the guide 21 shown in FIG.

As is clear from the above explanation, the intermediate heater 28 of the present invention applies heat to the upper and lower raw materials more effectively than that of method B, and the return belt returns the heat as in method B. There is no such thing as obstruction.

In addition, the vacuum chamber 15 shown in FIG. 4 has an annular shape, but it has the same effect as the vacuum chamber 15 in FIG.
The same parts as in the figures are given the same reference numerals.

Next, how effective the method of the present invention is compared to methods A and B will be explained using specific numerical values.

The following numerical values show the cases where the apparatus for producing 1 ton/hr of full-fat condensed milk powder was implemented using Method A, Method B, and the method of the present invention, respectively.

A method was adopted in which the heating temperature was lowered in four stages as the drying progressed.

According to the results of this experiment, the drying time was 344 seconds.Based on the above specifications, the effective belt length (the length of the belt in the drying section) was 100 m.

The dimensions and capacity of the drying tank in each case are as follows.

From the above, if the tank volume in case of method A is 100, then B
Dharma is 67 and nature is 39.

The experimental results using one type of heat medium boiler are as follows.

As described above, compared to the conventional method, the method of the present invention can reduce the volume of the vacuum chamber (in the case of the same treatment), and can also dramatically increase thermal efficiency.

The heat transfer area of the heater is only about 60% of the conventional method because the intermediate heater can be shared by the upper and lower belts.

In this way, the scale of capital investment will be reduced in all aspects.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing a conventional drying device, FIGS. 3 and 4 are explanatory diagrams showing a drying device of the present invention according to different embodiments, and FIG. 5 is a sectional view taken along the line A-A in FIG. 6 is a sectional view taken along line BB in FIG. 3, FIG. 1 is a plan view of a portion of the scraper, and FIG. 8 is a partial side view showing the drive mechanism of the drive roller. 8...Belt, 9...Drive roller,
11゜12...Feed roller, 13...
- Jacketed roller, 14... Supply nozzle, 15... Vacuum tank, 18... Grinding row-y-, 20... Scraper.

Claims (1)

[Claims] 1 Endless conveyor belt devices stretched in a ring between belt-like rollers are stacked in multiple layers above and below in one vacuum chamber, and the raw materials supplied to each belt are heated and dried, and the product is peeled from the belt and manufactured. In a vacuum drying apparatus, the belts constituting the endless conveyor belt device are arranged in an annular multistage manner, and the raw material conveying parts are stacked together, the raw material conveying parts are stacked together, and the non-conveying parts are stacked together, and the raw material The heating device placed for the conveyance section is a multi-stage continuous vacuum dryer consisting of an intermediate heater that is interposed between each belt and shared by the upper and lower belts, and a heater that heats the top or bottom belt. Device.