JPS6244908B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is a continuous vacuum drying method in which a liquid raw material or a solid raw material is frozen to form a granular frozen raw material, and the frozen raw material is continuously placed in a vacuum drying chamber and sublimated and dried by heating. The present invention relates to a method and an apparatus for carrying out the method. [Prior Art] Liquid raw materials, such as extraction solutions for coffee, tea, pharmaceuticals, etc.; solid raw materials, such as fish and beef flakes;
Frozen raw materials such as braised meat, braised meat, strawberries, green peas, etc. are frozen, and the frozen raw materials are placed in a vacuum drying chamber and heated by sublimation drying at an appropriate temperature that matches the raw materials and the vacuum value at that time. Vacuum drying methods and devices are already known. By the way, most of the vacuum drying equipment currently in operation and of medium size or larger (1 to 10 ton/day) employs a stand-standing system. When using this method, vacuum drying is performed according to the following steps. (a) Raw materials are distributed and introduced into a large number of trays, for example, 300 to 500 trays. (b) Set the tray on the railing. (c) Preliminarily freeze the railings, trays, and raw materials in the freezing equipment. (d) Place the entire railing equipment into a vacuum dryer and rapidly create a high vacuum (0.1 to 1 torr). At this time, the freezing temperature of the raw material is maintained at an appropriate value until the inside of the apparatus reaches a high vacuum state. (e) Rapidly raise the temperature of the railing between 100 and 150°C to an appropriate temperature that suits the raw material and the vacuum value at that time. (F) 5 to 10 with the vacuum value and temperature of the fence constant.
Hold for a while and perform sublimation drying. (g) After drying is complete, gradually release the vacuum while lowering the temperature. (H) Remove the tray and railing from the vacuum dryer. (li) Transfer the dried raw materials from the tray to the crusher hopper. (NU) Particle size is adjusted using a crusher and becomes the final product. (l) Used trays are washed, dried and used again. However, in the case of this stand-standing method, tasks such as attaching and detaching the tray to and from the railing, putting the railing in and out of the vacuum drying chamber, and opening and closing the vacuum drying chamber must be done manually. Because of the cooling,
Vacuuming, heating, and releasing the vacuum must be repeated. Furthermore, when setting the tray on the railings, the material spills on the railings, so the railings must be cleaned, and especially when drying liquid materials, the spillage is violent and dirt is difficult to remove. If the next drying operation is carried out while the fence is still dirty, the quality will be impaired due to the generation of shoe-squeezing flavor due to the high temperature of the fence step for a long time. Furthermore, as an automated version of the above-mentioned fence stage stationary method, a tray moving method is known in which trays are sequentially dropped one by one onto a belt conveyor in a vacuum drying chamber and taken out one by one. When using this method, when loading and unloading trays, two preliminary vacuum chambers are provided and vacuum is maintained by opening and closing four gate valves, and dry goods are collected, trays are washed, and frozen raw materials are dropped and filled. ing. However, since this method is also a drying method using a tray, heat is transferred to the frozen raw material through the tray, and although the temperature of the raw material at the bottom of the tray rises, it does not sublimate because the frozen raw material is present in the vacuum atmosphere. It is difficult for the raw material on the upper part of the tray, which is in contact with the vacuum atmosphere, to rise in temperature due to the distance from the heating surface and the latent heat of sublimation, and therefore it takes a long time for sublimation drying. In addition, the entire surface of the conveyor could not be used effectively, and when it came to recovering dry goods, there were problems such as loss of residual quantity adhering to the inner surface of the tray. As for other vacuum drying methods, if the above-mentioned vacuum drying method uses the raw material stationary, dynamic drying methods include diaphragm, multi-stage scraping, rotary can, rotary blade, multi-stage inclined heating plate, slitting, etc. A batch-type operation that performs vacuum drying while stirring the frozen granule filling tank,
There is a method of drying frozen granules by continuously moving them on a plate. In the latter drying method, continuity is achieved by switching operation using a vacuum preliminary chamber and a gate valve, or by providing a special valve with a slit to maintain vacuum. However, most of the devices for dynamic drying methods are developed specifically for the shape and properties of a single raw material, and are not suitable for general drying processing. Therefore, the present applicant proposed a method of continuously drying a paste-like raw material in Japanese Patent Application Laid-Open No. 59-32775. However, even when attempting to apply this method to granular frozen raw materials, it has not been possible to continuously and uniformly place the frozen raw materials on the conveyor in the vacuum drying chamber. The device disclosed in Japanese Patent Application Laid-Open No. 59-32775 is extremely effective for drying paste-like raw materials, but when trying to continuously supply frozen solid materials into the drying chamber, the vacuum inside the drying chamber is insufficient. This is because it is easily destroyed and cannot maintain the vacuum that is essential for sublimation drying. [Object of the Invention] The present invention eliminates the above-mentioned drawbacks of conventional vacuum drying equipment, reduces equipment costs, reduces installation space, reduces utility costs, reduces production costs through unmanned automation, and makes quality uniform. The purpose of this work is to provide a continuous vacuum drying method and device for frozen raw materials that can be used for sanitary control. [Structure of the Invention] According to the method of the present invention, the frozen raw material is conveyed to the relay hopper, the raw material in the relay hopper is conveyed in a fixed quantity to the vacuum drying chamber in a sealed state by the quantitative conveying device, and the frozen raw material is transferred onto the conveyor. The frozen raw material on the conveyor is heated from above and below the conveyor to sublimate it, and the upstream, intermediate, and downstream regions are heated under independent temperature conditions to determine the characteristics of the raw material. In addition, drying on the conveyor leaves some moisture, and the sublimated semi-dry raw material is finished dried in a finishing drying room. According to the apparatus of the present invention, there is provided a relay hopper through which frozen raw materials are conveyed by a conveying device, a rotary leaf feeder that supplies a fixed amount of frozen raw materials from the relay hopper, and a fixed amount of frozen raw materials that are supplied by the rotary leaf feeder to a vacuum drying chamber. A quantitative conveyance device that conveys a fixed amount without breaking the vacuum in the chamber, and a distribution arrangement that is installed in the vacuum drying chamber and that makes the frozen raw material conveyed by the quantitative conveyance device uniform in thickness and width and places it on a belt conveyor. The machine is equipped with a belt conveyor that conveys frozen raw materials loaded with uniform thickness and width by the distribution and leveling machine into a vacuum drying chamber, and the quantitative conveyance device is equipped with a cylinder having a frozen raw material receiving port for receiving the frozen raw material and a frozen raw material discharge port for discharging the frozen raw material into a vacuum drying chamber; A continuous vacuum drying device is provided that includes a piston for quantitatively conveying a raw material to a raw material outlet. When carrying out the present invention, the pistons constituting the conveying device together with the cylinders may be a large number of pistons attached to a chain at predetermined intervals and run endlessly, or a large diameter portion at the tip and a large diameter portion at the base. Preferably, the reciprocating piston has a small diameter portion of a predetermined length between which the frozen raw material is received from the rotary feeder. [Operation of the Invention] Therefore, the relay hopper is at atmospheric pressure, and the frozen raw material is put therein, and a fixed amount is continuously sent from the relay hopper in a sealed state to the vacuum drying chamber by a piston. Therefore, the piston can provide a sufficient seal and the vacuum inside the drying chamber will not drop. By placing the frozen raw material uniformly on a conveyor and heating it from above and below, the temperature becomes uniform throughout and the frozen raw material can be sublimed and dried uniformly. This continuous system allows for more uniform products compared to known tray methods, etc.
There is no need for extra cooling of frozen raw materials and there is little heat loss. When heating on a conveyor, for example,
The upstream side is heated strongly and the downstream side is heated weakly to allow rapid sublimation drying in the early stages of drying when the moisture content of the raw material is high, and then drying is carried out at a temperature that suits the characteristics of the raw material. Further, drying on the conveyor is carried out in a state in which some moisture remains, for example, up to an intermediate dry area with a moisture content of about 8 to 10%. Therefore, the length of the conveyor inside the drying chamber can be shortened, and the entire apparatus can be made compact. Then, it can be sufficiently dried in the finishing drying room. Incidentally, in the drying process of frozen raw materials, sublimation drying is quick when the moisture content is relatively high, but from around 10%, it takes a long time compared to the remaining dry moisture content. [Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The variety to be dried may be a liquid raw material or a solid raw material. Liquid raw materials include coffee, black tea, matcha, pharmaceuticals, and other extraction solutions with a water content of 20~
90% of the substance, solid raw materials, are fish and beef flakes or braised meat, meat, fish, and shellfish such as strawberries, green peas, and corn, and fruits and vegetables. Prior to vacuum drying, the raw material is pre-frozen. In the case of liquid raw materials, the raw materials are pre-frozen in the form of granules or granules (about the size of soybeans). The freezing temperature at this time may be the minimum cooling temperature at which the raw material can maintain its solidified state.
For example, an ice maker is used as a pre-freezing device.
In the case of solid raw materials, the raw materials are pre-frozen as they are (while retaining their original shape). At this time, freeze the raw materials to prevent them from solidifying each other (to prevent large lumps from forming). As a pre-freezing device, for example, continuous freezing is carried out using a multi-stage screw conveyor device in a freezer. The frozen raw material pre-frozen according to the above-mentioned method is
As shown in the figure, the material is transported to a relay tank 3 equipped with a cooling jacket 2 by a transport device 1 such as a screw conveyor or a vibrator feeder. A rotary feeder, generally indicated by 4, is provided below the relay tank 3, and is adapted to supply a fixed amount of the frozen raw material in the relay tank 3 into the vacuum drying chamber 29 in a manner to be described in detail later. Figure 3 shows details of the rotary feeder 4,
The blade 5 is, for example, a rubber blade, and as shown in FIG. 2, is rotated by a variable speed reducer motor 6 at a predetermined rotation speed to supply a fixed amount of frozen raw material. Below the rotary leaf feeder 4, a vacuum drying chamber 2 is provided where the frozen raw material supplied in a fixed amount from the rotary leaf feeder 4 is placed in a vacuum drying chamber 2.
9 is provided with a transfer device that transfers a fixed amount without breaking the vacuum in the chamber. In this embodiment, the conveying device includes a cylinder having an inlet and a discharge port for the frozen raw material, and a piston that conveys the frozen raw material from the inlet to the discharge port while maintaining airtightness by sliding on the inner circumferential wall of the cylinder. It consists of a conveyor chain that is equipped with a large number of cylinders at predetermined intervals and moves within the cylinder. Details of this conveyance device will be described later. The rotary feeder 4 is covered with a cooling jacket 7, which is connected to the brine inlet 9.
As shown in FIG. 1, cooling liquid is circulated from the brine tank 11 through a line 13 by a brine pump 12, and this liquid is supplied to the cooling jacket 2 of the relay tank 3.
It also flows. The temperature of the coolant is -10°C to -40°C. Next, a conveying device for conveying a fixed amount of frozen raw material supplied from a rotary feeder to a vacuum drying chamber without destroying the vacuum in the chamber will be explained. As shown in FIG. 2, the conveying device is provided with a frozen raw material receiving port 14 for receiving the frozen raw material supplied in a fixed amount from the rotary feeder 4, and a frozen raw material discharge port 15 for discharging the frozen raw material into the vacuum drying chamber 29. A cylinder 16 is provided. As shown in FIG. 4, the cylinder 16 is lined with, for example, Teflon 17 to improve the sliding of a piston 19, which will be described later. Move inside the cylinder 16 and freeze the raw material receiving port 14.
The whole unit for conveying a fixed amount of frozen raw material from the frozen raw material discharge port 15 to the frozen raw material discharge port 15 is attached to a conveying chain 18, which is spanned by a pair of sprocket wheels 26a and 26b and runs endlessly in the direction of the arrow. . sprocket wheel 26
One of the sprocket wheels a and 26b is on the drive side, and the drive side sprocket wheel is driven by a prime mover (not shown). The conveyance chain 18 includes a piston 19 that is in sliding contact with the inner peripheral wall of the cylinder 16 and conveys the frozen raw material while maintaining airtightness. This piston 1
9, as shown in FIGS. 5A and 5B, a disk 20 made of polyethylene, for example, and a metal disk 21, which is slightly smaller in diameter than the disk 20 and to which a chain link 25 is connected, are integrated with screws 22. metal disk 2 to ensure a reliable seal.
A washer 23 made of polyethylene and an O-ring 24, for example, are fitted into the circumferential groove formed in 1.
The pistons 19 configured in this manner are connected by a chain link 25 at a predetermined interval to form a conveyance chain 18. A rubber guide plate 8 is provided at the frozen raw material receiving port 14 to prevent the piston 19 from fitting.
In this manner, the frozen raw material supplied from the rotary feeder 4 is conveyed in a fixed amount to the vacuum drying chamber 29 by the conveyance chain 18 to which the pistons 19 are attached at predetermined intervals. At this time, the piston 19 is in airtight sliding contact with the inner circumferential wall of the cylinder 16 and moves smoothly, so that the vacuum in the vacuum drying chamber 29 is not destroyed. A preliminary vacuum chamber 27 is provided in the middle of the cylinder 16, and this preliminary vacuum chamber 27 is connected to the vacuum drying chamber 2.
9 is connected to a vacuum equipment (not shown) of a different series, and the preliminary vacuum chamber 2 of the cylinder 16
7 portion is a perforated cylinder 28. The perforated cylinder 28 has a large number of holes of about 1φ to 3φ, and removes minute particles contained in the frozen raw material conveyed by the conveyance chain 18 at the same time as vacuuming. This perforated cylinder 28 is particularly effective in removing unnecessary fine particles in advance when drying solid raw materials to obtain a high-quality dried product and at the same time to avoid drying unnecessary materials. Next, the main body of the vacuum drying apparatus will be explained with reference to FIGS. 1 and 2. The vacuum drying apparatus is equipped with a vacuum drying chamber generally indicated by 29, and the chamber 29 has an opening 3.
It is connected to vacuum equipment (not shown) by 0. In addition, the vacuum drying chamber 29 has a frozen raw material outlet 15.
A viewing window 31 is provided above to view the state of raw material input. Furthermore, removable airtight lids 32 and 33 are provided on both sides of the vacuum drying chamber 29 so that a conveyor frame 35, which will be described later, can be pulled out from both sides of the chamber 29 for easy inspection and cleaning. There is. The frozen raw material conveyed by the conveyor 18 is transferred from the frozen raw material outlet 15 to the vacuum drying chamber 29.
A certain amount of the entire amount is dropped onto a distributing and arranging machine shown at 34. The distribution and sorting machine 34 has a roller 36 rotatably supported by a conveyor frame 35, and this roller 36 is rotated by a prime mover 37 via a chain 38. The frozen raw materials are transferred to a belt conveyor 41 (described later) by this distribution and sorting machine 34.
It is placed on top with uniform thickness and width. The frozen raw material discharge port 15 is provided with a flapper 39 and a flow divider plate 40, and the frozen raw material inputted from the discharge port 15 is dropped into the middle of the flow divider plate 40 by the flapper 39, and is diverted by the flow divider plate 40. It falls onto the distribution and sorting machine 34. It is equipped with a belt conveyor generally designated by 41, and this belt conveyor 41 is connected to a conveyor frame 35.
It has a pair of pulleys 42 and 43 supported by a conveyor belt 44 made of, for example, Teflon glass cloth. One of the pulleys 42 and 43
Reference numeral 2 denotes a drive pulley, which is driven by a prime mover 45 via a chain 46, thereby causing the conveyor belt 44 to run in the direction of the arrow. 47 is a tension pulley. Electric plate heaters 48, 49, and 50 are provided below the forward side of the conveyor belt 41.
The heaters 48, 49, and 50 are controlled to an appropriate temperature of 100° C. to 180° C., and for example, the temperature of the heater 48 can be high, the temperature of the heater 49 can be medium, and the temperature of the heater 50 can be low. Further, above the forward side of the conveyor belt 41, a far-infrared heater 51 and a radiant plate 52 are provided, which are set at a water absorption wavelength of 2.5 to 2.7 μm. The frozen raw material placed on the conveyor belt 44 and moved is heated by an electric plate heater 48,
49, 50 and the far infrared heater 51, approximately 6
It sublimates and dries to a moisture content of 8-10% in minutes (80% moisture raw material). A frame moving roller 53 is attached to the conveyor frame 35, and when inspecting or cleaning the apparatus, the above-mentioned lids 32 and 33 are opened and the conveyor frame 35 is pulled out for inspection and cleaning. A crusher 54 is provided below the belt conveyor 41 to adjust the particle size of the freeze-dried product sublimated and dried in the manner described above, and the crusher 54 adjusts the particle size of the freeze-dried product. In the case of solid freeze-dried products, do not pass through a crusher. The freeze-dried product whose particle size has been adjusted by the crusher 54 is transferred to the full port ball valve 5 by a screw conveyor 55 provided at the outlet of the vacuum drying chamber 29.
6 and are alternately filled into two finishing drying chambers 57. A jacket 58 is provided in the finishing drying chamber 57, and the inside of this jacket 58 is connected to a hot water tank 5.
Hot water from 9 to 70°C is circulated through a line 61 by a hot water pump 60.
Further, in the finishing drying chamber 57, a stirring blade is provided which is reversely rotated at a low speed by a reducer motor 62. The freeze-dried product filled in the final drying chamber 57 is inverted and stirred at low speed in a vacuum at a temperature of 20° C. to 70° C. for about 3 hours to obtain a dry product with a moisture content of 2% or less. The product is taken out by opening the lid 62 of the finishing drying chamber 57. In this way, it is possible to perform integrated production in a vacuum. By alternately operating the two finishing drying chambers, it is possible to take out the dried product using the automatic discharge mechanism while maintaining a high vacuum value (0.1 to 1 torr). FIG. 6 shows a second embodiment of the present invention, in which the first embodiment
In the embodiment, a conveying device for conveying a fixed amount of frozen raw material supplied from a rotary feeder to a vacuum drying chamber without breaking the vacuum of the chamber has a cylinder and a piston that slides on the inner circumferential wall of the cylinder, and is endless. However, in this embodiment, a reciprocating piston, generally designated by 63, is used instead of the conveying chain. This piston 63 has a large diameter portion 6 at the tip to receive the frozen raw material supplied in a fixed amount from the rotary feeder 4.
A small diameter portion 66 of a predetermined length is provided between the large diameter portion 65 of the base portion and the large diameter portion 65 of the base portion. Piston 63 and cylinder 6
7 is provided with an O-ring 68 for maintaining airtightness. The frozen raw material supplied quantitatively from the rotary feeder 4 is transferred to the small diameter portion 6 of the piston 63.
6, and by reciprocating the piston 63, the frozen raw material is transported in a fixed amount from the frozen raw material receiving port 14 to the frozen raw material outlet 15 without breaking the vacuum in the vacuum drying chamber 29. [Results of Experiments] A soluble starch solution containing 80% water and 20% solids was used as a raw material, frozen into a cylinder with a thickness of 6 mm, and cut into an average length of 5 mm. This was vacuum dried using the apparatus shown in FIG. The results are shown in Table 1.

[Summary of effects of the invention]

The present invention has the following excellent effects. 1 Reduction of equipment costs a. Omission of trays, railings, and their moving loading equipment b. Reduction of utility equipment Since there is no need to repeat cooling, vacuum, heating, and release of vacuum, load peaks are eliminated, and the refrigeration capacity is reduced to approx. /2, exhaust capacity will be reduced to approximately 1/3 including cold trap equipment. 2. Reduction of utility costs The equipment is significantly reduced and at the same time there is no need to cool or heat the trays, railings and the entire drying chamber. Furthermore, since it is continuous, there is no need for extra cooling during pre-freezing of raw materials, and utility costs can be greatly reduced. 3 Unmanned operation and production cost reduction can be achieved.Works that previously had to be done manually, such as attaching trays to the railings, moving the railings in and out of the drying chamber, and opening and closing the drying chamber, are omitted, making it unmanned. It is now possible to drive 24 hours a day and night.
This means that a large capacity can be obtained with a small device, resulting in an increase in productivity and a reduction in management, etc., resulting in a reduction in production costs. 4. Uniform quality and hygiene control can be achieved. Production of uniform quality can be achieved by shortening the sublimation time (approximately 6 minutes at 80% moisture) through continuous operation and eliminating artificial variations. Furthermore, it is hygienic because it is produced through integrated processing in a vacuum until the final product form. 5. Small installation space The size of the dryer itself is approximately 1/3 that of a fence type with the same capacity. In addition, the installation space for utility equipment is approximately 1/2, and since no steam is used, no boiler equipment is required, making it easy to operate day and night.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a side view of a continuous vacuum drying device, FIG. 2 is a front view showing the relationship among a rotary feeder, quantitative conveyance device, and vacuum drying device, and FIG. FIG. 4 is a longitudinal sectional view of the rotary feeder, FIG. 4 is a vertical sectional view of the cylinder of the quantitative conveying device, FIG. FIG. 2 is a vertical cross-sectional view showing a part of an example in a plan view. 1...Transfer device, 3...Relay tank, 4...Rotary feeder, 11...Brine tank, 1
4...Frozen raw material intake port, 15...Frozen raw material discharge port, 16...Cylinder, 18...Transportation chain,
19...Piston, 27...Preliminary vacuum chamber, 29...
...Vacuum drying room, 34...Distributing and sorting machine, 35...Conveyor frame, 41...Belt conveyor, 48,4
9, 50...Electric plate heater, 51...Far infrared heater, 52...Radiation plate, 54...Crusher, 55...Screw conveyor, 57...Finishing drying room, 59...Hot water tank, 63... Reciprocating piston, 67... cylinder.

Claims (1)

[Claims] 1. The frozen raw material is conveyed to a relay hopper, and the raw material in the relay hopper is continuously conveyed in fixed quantities to a vacuum drying chamber without damaging the vacuum state by a metering conveyance device, and the frozen raw material is transferred to a conveyor. A continuous vacuum drying method characterized in that the frozen raw material on the conveyor is heated from above and below the conveyor to sublimation dry. 2. The frozen raw material on the conveyor is heated from above and below the conveyor to sublimate and dry it to an intermediate drying area, and at this time, the strength of the heating from upstream to downstream of the conveyor is set, and the sublimated raw material is transferred to a vacuum finish drying room. 2. The continuous vacuum drying method according to claim 1, wherein final drying is carried out by drying. 3. A relay hopper to which the frozen raw material is transported by a conveying device, a rotary leaf feeder that supplies the frozen raw material in a fixed quantity from the relay hopper, and a vacuum drying chamber for the frozen raw material supplied in a fixed quantity by the rotary leaf feeder to break the vacuum in the chamber. A quantitative conveying device that conveys a fixed amount without drying, a distributing and sorting machine that is installed in a vacuum drying chamber and that makes the frozen raw material conveyed by the quantitative conveying device uniform in thickness and width and places it on a conveyor, and the distributing and sorting machine The apparatus is equipped with a conveyor that conveys frozen raw materials loaded with a uniform thickness and width in a vacuum drying chamber, and the quantitative conveyance device includes:
A cylinder having a frozen raw material receiving port that receives the frozen raw material supplied from the rotary feeder and a frozen raw material discharge port that discharges the frozen raw material into a vacuum drying chamber, and a cylinder that is in sliding contact with the inner circumferential wall of the cylinder and freezes while maintaining airtightness. A continuous vacuum drying device comprising a piston that conveys a fixed amount of raw material from the frozen raw material inlet to the frozen raw material outlet. 4. The continuous vacuum drying apparatus according to claim 3, wherein the pistons of the conveying device are pistons that are attached to a chain at predetermined intervals and run endlessly. 5. The piston of the conveying device is a reciprocating piston having a small diameter part of a predetermined length for receiving the frozen raw material from the rotary feeder between the large diameter part at the tip and the large diameter part at the base. A continuous vacuum drying apparatus according to claim 3.