Steam Heat Treatment Hybrid Control Method in a Steam Heat Treatment System

Abstract

To provide a steaming processing hybrid control method in a steaming processing apparatus which uses two kinds of different heating means, and simultaneously achieves securing of quality of steaming processing and reduction of cost of the steaming processing.SOLUTION: A steaming processing apparatus comprises in a box-shaped casing 10: a vapor flow generation chamber 11; and a processing chamber 12. In the processing chamber, a steaming processing object is arranged, and a vapor flow is generated in the vapor flow generation chamber by humidification means 23 and heating means, then the vapor flow is supplied to a lower part of the processing chamber from a lower communication hole 24, for performing steaming processing to the steaming processing object arranged in the processing chamber. As the heating means, a hot water-based first heater 19, and an electric type second heater 20 are used. Measurement means 34 measures an inside temperature in the processing chamber, and after start of the steaming processing, in a first period until the inside temperature reaches a prescribed temperature before the steaming processing, only the first heater 19 is used for performing processing, and in a second period in which the inside temperature exceeds the prescribed temperature and until the inside temperature reaches a steaming processing temperature, the second heater 20 is used for performing processing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a steam heat treatment apparatus, and more particularly to a hybrid control method for controlling steam heat treatment using two different heating means.

Background Art

[0002] Sweet potatoes are cultivated throughout the country as important crops, have been popular for food since ancient times, and are widely used as raw materials for starch and shochu. The main production areas are Kagoshima Prefecture, Ibaraki Prefecture, Chiba Prefecture, Miyazaki Prefecture, Tokushima Prefecture, etc. Among them, Kagoshima Prefecture has extensive shirasu terraces suitable for the growth of sweet potatoes and is a production area accounting for about 40% of the national production volume.

[0003] However, recently, the occurrence of basal rot disease in sweet potatoes has been confirmed in Okinawa Prefecture, Kagoshima Prefecture, and Miyazaki Prefecture, and thereafter, its occurrence has also been confirmed throughout the country. The basal rot disease in sweet potatoes is caused by filamentous fungi. When this disease occurs, the leaves turn color and growth is poor, and the roots turn black and rot. In addition, the sweet potatoes growing underground also change color from the cut end. Therefore, the occurrence of basal rot disease causes problems such as a significant decrease in the yield of sweet potatoes and a shortage of raw materials for starch and shochu, and countermeasures against the basal rot disease of sweet potatoes have been an urgent issue.

[0004] The applicant has previously proposed an apparatus (Patent Document 1) for steam heat-treating fruits and vegetables at a low temperature (43°C) using saturated steam and heat to kill fruit flies and melon flies adhering to the fruits and vegetables, and an apparatus (Patent Document 2) for sterilizing bacteria generated on the surface of fruits and vegetables with steam heat at a high temperature (50°C or higher) to suppress the occurrence of diseases. Since it has been found that the same apparatus is effective in countermeasures against the basal rot disease of sweet potatoes, a steam heat treatment apparatus (Patent Document 3) for steam heat-treating sweet potatoes has also been proposed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] The apparatuses described in Patent Documents 1 to 3 use electric heaters as the heat source for steam treatment. While electric heaters have the advantage of enabling precise temperature control, they have the drawback of requiring large-capacity contracts. On the other hand, warm wastewater is discharged from factories and plant facilities, and although it is being effectively utilized in some fields, expanding the use of warm wastewater has long been a challenge from an environmental protection perspective. The applicant focused on the use of hot water as a heat source for steam treatment and discovered that by using hot water in the fuzzy temperature range of steam treatment and electric heaters in the critical temperature range of steam treatment—that is, by using two different heat sources—the above two problems can be solved simultaneously, leading to the completion of the present invention.

[0007] The present invention has been proposed in view of the above problems, and aims to provide a steam treatment hybrid control method for a steam treatment apparatus that uses two different heating means to simultaneously ensure the quality of the steam treatment and reduce the cost of the steam treatment. [Means for solving the problem]

[0008] To achieve the above objectives, the steam heat treatment hybrid control method in the steam heat treatment apparatus according to the present invention is In a steam heat treatment apparatus comprising a steam flow generation chamber and a treatment chamber inside a box-shaped casing, in which an object to be steam-treated is placed in the treatment chamber, steam flow generated in the steam flow generation chamber by humidification means and heating means is supplied to the lower part of the treatment chamber from a lower communication port, circulated so as to pass upward through the treatment chamber and return to the steam flow generation chamber from an upper communication port, and steam heat treatment is performed on the object to be steam-treated placed in the treatment chamber, The heating means includes a first heating means using hot water and a second heating means using electricity. A measuring means measures the internal temperature of the processing chamber. In the first phase, from the start of the steam treatment until the predetermined temperature before the steam treatment is reached, the processing is performed using only the first heating means. In the second phase, from the temperature above the predetermined temperature until the steam treatment temperature is reached, and after the steam treatment temperature is reached, the processing is performed using the second heating means. stomach, The first phase, from the start of the steam treatment until the predetermined temperature before the steam treatment is reached, is a fuzzy control phase. The second phase, from the point where the predetermined temperature is exceeded until the steam treatment temperature is reached, and after the steam treatment temperature is reached, is a precise control phase. Its main characteristic is this.

[0010] The steam heat treatment hybrid control method in the steam heat treatment apparatus according to the present invention is A third feature is that the system is equipped with a control means, which, based on a temperature signal from the measuring means, performs PID control on the flow rate of a flow control valve that supplies hot water to the first heating means and PID control on the heat source of the second heating means.

[0011] The steam heat treatment hybrid control method in the steam heat treatment apparatus according to the present invention is A fourth feature is that only the second heating means is used until the internal temperature of the processing chamber exceeds the predetermined temperature and reaches the steam treatment temperature, and after the steam treatment temperature is reached.

[0012] The steam heat treatment hybrid control method in the steam heat treatment apparatus according to the present invention is A fifth feature is that, until the internal temperature of the processing chamber exceeds the predetermined temperature and reaches the steam treatment temperature, and after reaching the steam treatment temperature, the second heating means is used as the main heat source and the first heating means is used as an auxiliary heat source.

[0013] The steam heat treatment apparatus according to the present invention is In a steam heat treatment apparatus comprising a steam flow generation chamber and a treatment chamber inside a box-shaped casing, in which an object to be steam-treated is placed in the treatment chamber, steam flow generated in the steam flow generation chamber by humidification means and heating means is supplied to the lower part of the treatment chamber from a lower communication port, circulated so as to pass upward through the treatment chamber and return to the steam flow generation chamber from an upper communication port, and steam heat treatment is performed on the object to be steam-treated placed in the treatment chamber, As the heating means, it is provided with a first heating means of a hot water system and a second heating means of an electric type. The in-chamber temperature in the processing chamber is measured by the measuring means. In the first stage until reaching a predetermined temperature before the steam heat treatment after the start of the steam heat treatment, only the first heating means is used. Fuzzy control The treatment is performed, and in the second stage until reaching the steam heat treatment temperature exceeding the predetermined temperature and after reaching the steam heat treatment temperature, the second heating means is used. By precise control It is configured to perform the treatment. The system includes a control means, which is configured to PID control the flow rate of a flow control valve that supplies hot water to the first heating means and to PID control the heat source of the second heating means based on a temperature signal from the measuring means. It is mainly characterized in that a blower, the first heating means, and the second heating means are provided in the steam flow generation chamber.

Effect of the Invention

[0014] As described above, according to the present invention, a first heating means of a hot water system and a second heating means of an electric type are used as heat sources. In the first stage, which is a fuzzy control region after the start of the treatment, the first heating means of the hot water system is used, and in the second stage, which is a precise control region from a temperature close to the steam heat treatment temperature to the steam heat treatment temperature, the second heating means of the electric type is used. Thus, it is possible to achieve an excellent effect of significantly reducing the cost of steam heat treatment while maintaining the high quality of the steam heat treatment.

[0015] In addition, it has an excellent energy-saving effect that high-temperature warm wastewater discharged from factories or plants or high-temperature groundwater heated by geothermal energy can be effectively utilized as a heat source for steam heat treatment.

Brief Description of the Drawings

[0016] [Figure 1] A longitudinal sectional view of the steam heat treatment apparatus according to an embodiment of the present invention, [Figure 2] A front view of the steam heat treatment apparatus of FIG. 1, [Figure 3] A plan view of the steam heat treatment apparatus of FIG. 1, [Figure 4] A view showing a state in which sweet potato-containing storage containers are stacked, (A) is a side view, and (B) is a plan view. [Figure 5] A sectional view showing the operation of the steam heat treatment apparatus of FIG. 1, [Figure 6]It is a diagram showing a hybrid control program for steam heat treatment.

Best Mode for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. FIGS. 1 to 3 are diagrams showing a steam heat treatment apparatus according to an embodiment of the present invention, and reference numeral S indicates the steam heat treatment apparatus.

[0018] The steam heat treatment apparatus S is an apparatus that steam-heat-treats objects to be treated such as fruits, horticultural crops, and tubers using steam and heat. In this embodiment, an example of using sweet potatoes as the object to be treated and using the apparatus to sterilize and disinfect the base rot pathogen infecting the sweet potatoes is shown.

[0019] As shown in FIG. 1, the steam heat treatment apparatus S includes a steam flow generation chamber 11 and a treatment chamber 12 inside a box-shaped casing 10. The steam flow generation chamber 11 and the treatment chamber 12 are partitioned left and right by a partition plate 13.

[0020] The casing 10 has an overall box shape and includes a top plate panel 10A, left and right side plate panels 10B, a bottom plate panel 10C, a front plate panel 10D, and a back plate panel 10E. As shown in FIG. 2, an airtight door 14 for sealing the opening of the treatment chamber 12 and an inspection door 15 are provided on the front surface. The casing 10 has a heat insulating panel attached to its inner surface and has a heat insulating structure. The bottom plate panel 10C is provided with a pair of insertion ports 16, 16 into which the claws of a forklift are inserted to lift the casing 10 from the floor surface G and make the casing 10 transferable.

[0021] The steam flow generation chamber 11 is a differential pressure chamber that generates a steam flow circulating within the casing 10, and is provided with an air intake 17 on its upper surface that opens after steam heat treatment. Inside the steam flow generation chamber 11 are a blower (differential pressure fan) 18, a hot water type first heater (hot water coil) 19, and an electric type second heater (electric heater) 20, which are arranged vertically with the first heater 19 on the bottom and the second heater 20 on the top. In the illustrated example, the first heater 19 and the second heater 20 are positioned directly below the blower 18, but the first heater 19 and the second heater 20 may be positioned upside down.

[0022] The first heater 19 consists of a hot water coil and is mainly used in the fuzzy control region of the first phase. The first heater 19 is located inside a box-shaped casing 19A and heats the airflow sent into the casing by a blower 18 in the heat exchange section (coil section). Hot water is supplied to the heat exchange section (coil section) from the outside through piping 21A, and after heat exchange, cooling water is sent to the outside through piping 21B. Fins are attached to the heat exchange section to increase the heat exchange rate.

[0023] As shown in Figure 3, the piping 21A that supplies hot water to the first heater 19 has a switching valve (three-way valve) 22 installed in the middle of the piping 21A. By switching the switching valve 22, the hot water heading towards the heat exchange section of the first heater 19 can be diverted through the bypass pipe 21C and drained from the bypass pipe 21C to the piping 21B. When only the second heater 20 is to be operated, the hot water flowing through the piping 21A is diverted to the bypass pipe 21C. The operation of the switching valve 22 is PID controlled by the control device 40, which will be described later.

[0024] The second heater 20 consists of an electric heater (such as a sheathed heater or ceramic heater) and is mainly used in the second phase of precision control. The second heater 20 is located inside a box-shaped casing 20A and heats the airflow sent into the casing by the blower 18 in the heat exchange section (electric heating wire). Fins are attached to the heat exchange section to increase the heat exchange rate. The heat source in the heat exchange section of the second heater 20 is PID controlled by the control device 40, which will be described later.

[0025] In this embodiment, the humidifier 23 used to generate saturated steam is located at the top of the processing chamber 12, but it may also be located at the top or bottom of the steam flow generation chamber 11.

[0026] The steam flow generation chamber 11 is connected to the lower communication space 25 directly below the processing chamber 12 through the lower communication port 24. When the blower 18 is operated, the steam flow in the steam flow generation chamber 11 is drawn into the lower communication space 25 through the lower communication port 24 and rises from the lower communication space 25 into the processing chamber 12 directly above.

[0027] The processing chamber 12 is where sweet potatoes 2 in storage containers 1, which are arranged in multiple rows and tiers within the processing chamber 12, are subjected to steam heat treatment by a steam flow rising from the lower communication space 25. The processing chamber 12 has an opening 26 at its front that is opened and closed by the airtight door 14. At the bottom of the processing chamber 12, a pair of transport rails (roller conveyors) 28, 28 are positioned on the inner side of the support 27, extending inward from the opening 26, and are fixedly supported by left and right support members 29.

[0028] The processing chamber 12 is connected to the steam flow generation chamber 11 through an upper communication port 30. The steam flow rising within the processing chamber 12 is drawn back into the steam flow generation chamber 11 from the upper space of the processing chamber 12 through the upper communication port 30 by the operation of the blower 18. An opening / closing damper 31 is positioned at the upper communication port 30. The opening / closing damper 31 is rotated by a motor (not shown), and the control device 40 opens the upper communication port 30 and closes the air intake port 17 during steam heat treatment, and closes the upper communication port 30 and opens the air intake port 17 after steam heat treatment.

[0029] An exhaust port 32 is provided in the upper space of the processing chamber 12. The exhaust port 32 opens when outside air is introduced from the intake port 17 after the steam heat treatment, allowing steam from inside the processing chamber 12 to be quickly discharged. A humidifier 23 used for generating saturated steam is also located in the upper space of the processing chamber 12. The humidifier 23 has piping 33 extending to the outer surface of the casing 10, and is powered by a compressor 41 to spray mist-like moisture from the upper space of the processing chamber 12 through the upper communication port 30 towards the upper space of the steam flow generation chamber 11.

[0030] A temperature and humidity measuring instrument 34 is located in the lower part of the steam flow generation chamber 11, near the lower communication port 24 (in the illustrated example, inside the lower communication space 25), to measure the temperature and humidity of the steam flow introduced into the processing chamber 12. The temperature and humidity measuring instrument 34 consists of a dry-bulb psychrometer capable of measuring dry-bulb and wet-bulb temperatures, and measures the temperature (dry-bulb temperature) and humidity (calculated from the difference between the dry-bulb and wet-bulb temperatures) of the generated steam flow.

[0031] Furthermore, the processing chamber 12 is equipped with an internal temperature measuring device 35 that measures the internal temperature of the sweet potatoes 2 in the storage container 1 located within the processing chamber 12. This internal temperature measuring device 35 is a needle-shaped temperature sensor that is inserted into the sweet potatoes 2 and transmits a temperature signal to the control device 40.

[0032] A control device 40 is installed in the casing 10. The control device 40 controls the switching operation of the blower 18 and the first heater (hot water coil) 19, the PID control of the second heater (electric heater) 20, the on / off operation, output adjustment, timer operation, and opening / closing of the humidifier 23 and compressor 41, based on input operations from the control panel.

[0033] Furthermore, the control device 40 controls the above-mentioned equipment based on signals from the temperature and humidity measuring instrument 34 and the internal temperature measuring instrument 35, and maintains the temperature and humidity of the steam flow circulating inside the casing 10 (steam flow rising inside the processing chamber 12) at the set state. The control device 40 has a steam treatment program set for each object to be processed, and can execute the steam treatment according to these steam treatment programs. Figure 6 shows an example of a steam treatment program.

[0034] As shown in Figure 4, the storage container 1 for storing the sweet potatoes 2 has an open top and numerous mesh-like ventilation holes 3 on each side and bottom. This storage container 1 can be the same mesh harvesting container or agricultural container made of lightweight plastic used for harvesting sweet potatoes 2.

[0035] Figure 4(A) shows a configuration in which storage containers 1 containing sweet potatoes 2 are arranged in multiple layers and rows on a pallet 4, and Figure 4(B) shows a plan view of these numerous storage containers 1. The entire area around the numerous storage containers 1, except for the top and bottom surfaces, may be covered with a flexible cover sheet. The pallet 4 is a lightweight, mesh-like material made of resin, and has numerous ventilation holes formed on its top and bottom surfaces to allow the flow to pass through vertically.

[0036] Next, the procedure for steaming (sterilizing) sweet potatoes using the steaming apparatus S configured as described above will be explained with reference to Figures 5 and 6, etc.

[0037] Referring to Figure 6, during the first phase (fuzzy control range) from the start of the steam treatment until the predetermined temperature (45°C) before the steam treatment is reached, only the first heater 19 is used. From the point where the temperature exceeds the predetermined temperature (45°C) until the steam treatment temperature (48°C) is reached, and after the steam treatment temperature is reached, the second heater 20 is used for the treatment.

[0038] First, the airtight door 14 is opened, and a pallet 4 containing storage containers 1 (see Figure 4(A)) with multiple layers and rows of sweet potatoes 2 at room temperature is placed on the transport rail 28 through the opening 26 and transported into the processing room 12.

[0039] Next, as shown in Figure 2, the airtight door 14 is closed to seal the inside of the casing 10, and the control panel of the control device 40 is operated to sequentially activate the blower 18, the first heater (hot water coil) 19, and the humidifier 23, setting the inside of the casing 10 to predetermined temperature and humidity conditions along with the processing time (required time). In this embodiment, the humidity inside the chamber is set to 95% or higher (97%), the temperature inside the chamber is set to a starting temperature of 31°C, a predetermined temperature (heat source switching temperature) of 45°C, and a steam treatment temperature of 48°C.

[0040] According to the program, when the switching valve 22 is opened by command from the control device 40, hot water (50-90°C) is supplied from the piping 21A to the first heater (hot water coil) 19, heating the airflow blown downward by the blower 18. As a result, the internal temperature of the casing 10 rises from room temperature to 31°C (time required: 0-1 hour).

[0041] (Acclimation treatment) The acclimatization process involves maintaining an internal humidity of 95% or higher while gradually increasing the internal temperature from 31°C to 41°C (as shown in Figure 6) at a constant rate (taking 3-4 hours). If the sweet potato 2 is immediately subjected to steam treatment (48°C) during the acclimatization process, damage may occur. To prevent this, the temperature of the sweet potato 2 is gradually increased as a preliminary step before steam treatment.

[0042] The control device 40 receives a temperature (dry-bulb temperature) signal from the temperature and humidity measuring instrument 34 and controls the amount of hot water supplied from the piping 21A to the first heater (hot water coil) 19 by opening the switching valve 22 using PID control so that the internal temperature of the chamber slowly rises from 31°C to 41°C over a certain period of time (3 to 4 hours). The hot water temperature ranges from 50 to 90°C depending on the hot wastewater or geothermal energy used. Fuzzy control by the first heater (hot water coil) 19 is suitable for controlling the internal temperature during this period, including the first half of the transition process described later, in order to slowly raise the internal temperature.

[0043] (Migration process) Next, the internal temperature of the chamber is transitioned over a certain period of time (0.5 to 1 hour) until it rises from 41°C to the steam treatment temperature of 48°C. When the internal temperature reaches 45°C, the control device 40 switches the heat source from the first heater (hot water coil) 19 to the second heater (electric heater) 20.

[0044] When the internal temperature reaches 45°C, the control device 40 operates the switching valve 22 to return the hot water flowing from pipe 21A to pipe 21B via bypass pipe 21C, and activates (turns on) the second heater (electric heater) 20. With the activation of the second heater (electric heater) 20, the internal temperature reaches 48°C over the remaining time required (0.5 to 1 hour).

[0045] The second heater (electric heater) 20 can precisely control the internal temperature through fine PID control, so when the internal temperature reaches 45°C to 48°C, and even after the internal temperature reaches 48°C, the temperature does not overshoot significantly, and the internal temperature can be stably maintained at around 48°C.

[0046] (Steam treatment) With the internal humidity maintained at 95% or higher, the second heater (electric heater) 20 is operated and controlled to maintain the internal temperature at 48°C. When the internal temperature (core temperature) of the sweet potato 2 reaches 47°C, the temperature of the sweet potato 2 is maintained at 47-48°C for a certain period of time (2-3.5 hours). Here, the internal temperature of the sweet potato 2 is measured in the storage container 1 at the top. In the case of seed potatoes, the total time required for acclimatization and steaming is shorter than the above, for example, set to 40 minutes. The total time required for acclimatization and steaming can also be shortened after verifying the effectiveness of disinfection and damage to the sweet potato. After a certain period of time has elapsed, the operation of the second heater (electric heater) 20 is turned off.

[0047] During the steam treatment period, it is necessary to maintain a stable internal temperature of around 48°C. Therefore, precise control using the second heater (electric heater) 20 is suitable, including during the latter half of the aforementioned transition treatment period.

[0048] Referring to Figure 5, during the acclimatization and steam treatment periods, the steam flow moves from the steam flow generation chamber 11 through the lower communication port 24 to the lower communication space 25 of the treatment chamber 12, as indicated by the arrows. It then rises from the lower communication space 25, passes through the interior of the lowest storage container 1 and the interior of the uppermost storage container 1, moves to the upper space of the treatment chamber 12, and returns to the steam flow generation chamber 11 through the upper communication port 30. The steam flow generated in the steam flow generation chamber 11 circulates between the chamber and the treatment chamber 12, performing steam treatment on the sweet potatoes 2 in each storage container 1 located within the treatment chamber 12, and sterilizing any basal rot bacteria that have invaded the sweet potatoes 2.

[0049] When the storage containers 1, which are arranged in multiple tiers and rows, are covered with a cover sheet except for the top and bottom surfaces, the steam flow introduced from below into the bottom storage container 1 does not escape to the sides but passes through the interior efficiently up to the top storage container 1 and escapes upward. This steam heat treatment device S uses a ventilation method called the differential pressure method to forcibly create airflow by utilizing differential pressure, so that steam heat passes through all the gaps between the sweet potatoes 2 in each storage container 1, and steam heat acts evenly on all the sweet potatoes 2.

[0050] (Post-processing) After the steaming process is complete, a post-processing step is performed to lower the core temperature of the sweet potato 2. After the second heater 20 (electric heater) stops operating, with the airtight door 14 closed, the opening / closing damper 31 is rotated counterclockwise to open the air intake 17 and close the upper communication port 30.

[0051] The control device 40 continues to operate the blower 18, introducing outside air into the steam flow generation chamber 11 through the intake port 17, and the high-temperature steam flow inside the steam flow generation chamber 11 and the processing chamber 12 is forcibly discharged through the exhaust port 32. The outside air introduced into the steam flow generation chamber 11 also enters the processing chamber 12 through the lower communication port 24, cooling the sweet potatoes 2 in each storage container 1, and is then exhausted to the outside through the exhaust port 32. The post-processing to lower the core temperature of each sweet potato 2 is carried out over approximately one hour.

[0052] After the post-processing is complete, the airtight door 14 is opened and the storage container 1 containing the steam-treated sweet potatoes 2 is removed along with the pallet 4. In this way, the first steam treatment of the sweet potatoes is completed and the temperature inside the casing 10 has decreased. Then, the second pallet containing the untreated sweet potatoes 2 is brought in, the airtight door 14 is closed again to seal the interior, and the interior of the casing 10 is returned to the initial set conditions (humidity of 95% or more, temperature of 31°C). Subsequent steam treatments of the sweet potatoes are then performed using the procedure described above.

[0053] According to this embodiment, the first phase (from the starting temperature until reaching a predetermined temperature (45°C) before the steam treatment temperature) is controlled using the first heater (hot water coil) 19, and the second phase (from the predetermined temperature (45°C) until reaching the steam treatment temperature (48°C) and after reaching the steam treatment temperature) is controlled using the second heater (electric heater) 20. By utilizing the control characteristics of each heater, it is possible to steam treat sweet potatoes with high quality, and by using this device S, the basal rot fungus on the sweet potatoes 2 can be effectively killed.

[0054] Furthermore, this device S can reduce the cost of steam treatment by using hot water as the heat source for the steam treatment. Hot water can be effectively utilized from sources such as hot wastewater discharged from factories, plants, power plants, and waste incinerators, as well as groundwater heated by geothermal energy, resulting in excellent energy-saving effects.

[0055] In the above embodiment, only the second heater 20 was used in the precision control range, but the second heater 20 may be used as the main heat source and the first heater 19 as an auxiliary heat source in combination.

[0056] As described above, according to the present invention, storage containers containing sweet potatoes are arranged in multiple tiers and rows within the processing chamber, and steam is circulated to steam-heat the sweet potatoes, thereby efficiently sterilizing the basal rot fungi that have invaded the sweet potatoes.

[0057] The materials that can be subjected to steam heat treatment according to this invention include not only sweet potatoes, but also fruits, horticultural crops, and tubers. The sweet potatoes can be of any use or variety, including seed potatoes, those for fresh consumption, starch production, and shochu production. It is suitable for controlling basal rot in all types of sweet potatoes. It can also be used for insecticidal and quarantine purposes. [Industrial applicability]

[0058] The present invention can be used as a method for controlling steam treatment in a steam treatment apparatus, and also as a method for controlling treatment for insecticidal or quarantine purposes. [Explanation of Symbols]

[0059] 1. Storage container 2 sweet potato 3. Ventilation holes 4 pallets 10, 19A, 20A casing 10A Top Panel 10B Side Panel 10C Bottom Panel 10D Front Panel 10E Back Panel 11. Steam flow generation chamber 12 Processing Rooms 13 Partition plates 14 Airtight door 15 Inspection door 16 outlets 17 Air intake 18. Blower (differential pressure fan) 19. First heater (hot water coil) 20. Second heater (electric heater) 21A, 21B, 33 Piping 21C Bypass Pipe 22 Switching valve 23 Humidifier 24 Lower communication opening 25 Lower communication space 26 Opening 27 Support 28 Transport Rails 29 Support member 30 Upper communication port 31 Opening / Closing Damper 32 Exhaust vents 34. Temperature and humidity measuring instrument (measuring means) 35 Internal temperature measuring instrument 40 Control device (control means) 41 Compressor S Steam Heat Treatment Equipment

Claims

1. In a steam heat treatment apparatus comprising a steam flow generation chamber and a treatment chamber inside a box-shaped casing, in which an object to be steam-treated is placed in the treatment chamber, steam flow generated in the steam flow generation chamber by humidification means and heating means is supplied to the lower part of the treatment chamber from a lower communication port, circulated so as to pass upward through the treatment chamber and return to the steam flow generation chamber from an upper communication port, and steam heat treatment is performed on the object to be steam-treated placed in the treatment chamber, The heating means comprises a first heating means using hot water and a second heating means using electricity. A measuring means measures the internal temperature of the processing chamber. During the first phase, from the start of the steam treatment until the predetermined temperature before the steam treatment is reached, the processing is carried out using only the first heating means. During the second phase, from the temperature above the predetermined temperature until the steam treatment temperature is reached, and after the steam treatment temperature is reached, the processing is carried out using the second heating means. A hybrid control method for steam treatment in a steam treatment apparatus, characterized in that the first phase, from the start of steam treatment until reaching a predetermined temperature before steam treatment, is a fuzzy control zone, and the second phase, from exceeding the predetermined temperature until reaching the steam treatment temperature and after reaching the steam treatment temperature, is a precision control zone.

2. A steam treatment hybrid control method in a steam treatment apparatus according to claim 1, characterized in that the control means provides control means that, based on a temperature signal from the measuring means, PID controls the flow rate of a flow control valve that supplies hot water to the first heating means and PID controls the heat source of the second heating means.

3. A steam heat treatment hybrid control method in a steam heat treatment apparatus according to claim 1, characterized in that only the second heating means is used during the second phase, until the internal temperature of the processing chamber exceeds the predetermined temperature and reaches the steam heat treatment temperature, and after the steam heat treatment temperature is reached.

4. The steam heat treatment hybrid control method in a steam heat treatment apparatus according to claim 1, characterized in that, in the second phase, until the internal temperature of the processing chamber exceeds the predetermined temperature and reaches the steam heat treatment temperature, and after reaching the steam heat treatment temperature, the second heating means is used as the main heat source and the first heating means is used as an auxiliary heat source.

5. In a steam heat treatment apparatus comprising a steam flow generation chamber and a treatment chamber inside a box-shaped casing, in which an object to be steam-treated is placed in the treatment chamber, steam flow generated in the steam flow generation chamber by humidification means and heating means is supplied to the lower part of the treatment chamber from a lower communication port, circulated so as to pass upward through the treatment chamber and return to the steam flow generation chamber from an upper communication port, and steam heat treatment is performed on the object to be steam-treated placed in the treatment chamber, The heating means comprises a first heating means using hot water and a second heating means using electricity. A measuring means measures the internal temperature of the processing chamber. During the first phase, from the start of the steam treatment until the predetermined temperature before the steam treatment is reached, processing is performed using fuzzy control with only the first heating means. During the second phase, from the temperature above the predetermined temperature until the steam treatment temperature is reached, and after the steam treatment temperature is reached, processing is performed using precise control with the second heating means. The system is equipped with a control means, which is configured to PID control the flow rate of a flow control valve that supplies hot water to the first heating means and to PID control the heat source of the second heating means based on a temperature signal from the measuring means. A steam heat treatment apparatus characterized by comprising a blower, the first heating means, and the second heating means in the steam flow generating chamber.

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