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(11) | EP 1 591 719 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
| published in accordance with Art. 158(3) EPC |
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| (54) | SUPERHEATED STEAM PRODUCING DEVICE |
| (57) The invention provides a process and apparatus for facilitated generation of large
amounts of high-temperature overheated water vapor from water. The overheated steam generator comprises a cylindrical housing 1 of a heat-resistant material having a water injection inlet port 1a at one end and an overheated steam injection outlet port 4 at an opposite end, an exciting coil 6 wound around the outer periphery of the cylindrical housing 1, and an air-permeable assembly 4 to be heated, which is housed in the cylindrical housing 1 and formed of an electrically conductive material. Water is injected into the cylindrical housing 1 from one end 1a. The cylindrical housing 1 receives the air-permeable assembly 4 that is to be heated and is formed of an electrically conductive material. Then, the air-permeable assembly 4 housed in the cylindrical housing 1 is heated by high-frequency induction to inject large amounts of high-temperature overheated water vapor out of the outlet port 3 at the opposite end 1b of the cylindrical housing 1. |
ART FIELD
[0001] The present invention relates generally to a technology for generation of overheated steam, and more particularly to the provision of a technology for facilitated generation of large amounts of overheated steam.
BACKGROUND ART
[0002] Overheated steam, because of being a high-temperature water vapor free of any harmful components, lends itself well to disinfection, sterilization or the like of foodstuffs.
[0003] One known technology for generation of overheated steam, for instance, is set forth in JP(A)8-135903. While an AC current conducts through a coil to generate heat from a metal body by virtue of electromagnetic induction, water vapor is in contact with the surface of that heat-generation body, passing around it, thereby generating water vapor of 100°C or higher (overheated water vapor). With other known technology as shown typically in JP(A)9-241734, water is evaporated in a steam boiler and the resulting water vapor is heated to high temperatures by combustion of fuel.
[0004] With the prior art electromagnetic induction heating technologies, however, it is not easy to generate large amounts of high-temperature overheated steam, and it is difficult to generate high-pressure overheated steam, either.
SUMMARY OF THE INVENTION
[0005] The primary object of the invention is to provide a solution to the aforesaid problems of the prior art. The invention is embodied in the form of the overheated steam generator and the process of generating high-pressure overheated steam as given below.
(1) An overheated steam generator, characterized by comprising a cylindrical housing of a heat-resistant material having a water injection inlet port at one end and an overheated steam injection outlet port at an opposite end, an exciting coil wound around an outer periphery of said cylindrical housing, and an air-permeable assembly to be heated, which is housed in said cylindrical housing and formed of an electrically conductive material.
(2) An overheated steam generator, characterized by comprising a cylindrical housing of a heat-resistant material having a water injection inlet port and a water vapor inlet port at one end and an overheated steam injection outlet port at an opposite end, an exciting coil wound around an outer periphery of said cylindrical housing, and an air-permeable assembly to be heated, which is housed in said cylindrical housing and formed of an electrically conductive material.
(3) An overheated steam generator, characterized by comprising a cylindrical housing of a heat-resistant material, in which water is injected through one end and out of which overheated steam is injected through an opposite end, and electromagnetic induction heating means including an air-permeable heat-generation unit of an electrically conductive material which generates heat by electromagnetic induction for heating water charged in said cylindrical housing.
(4) An overheated steam generator, characterized by comprising a cylindrical housing of a heat-resistant material having a water injection inlet port at one end and an overheated steam injection outlet port at an opposite end, a refractory that is applied over an outer periphery of said cylindrical housing and formed of a heat-resistant material, an exciting coil wound around an outer periphery of said refractory, and an air-permeable assembly to be heated, which is housed in said cylindrical housing and formed of an electrically conductive material.
(5) The overheated steam generator according to any one of (1) to (4) above, characterized in that the heat-resistant material is a ceramic material.
(6) The overheated steam generator according to any one of (1) to (5) above, characterized in that the one end of the cylindrical housing is additionally provided with an injection inlet port for introduction of a liquid other than water.
(7) The overheated steam generator according to any one of (1) to (5) above, characterized in that the one end of the cylindrical housing is additionally provided with an injection inlet port for introduction of fluid comprising water and other liquid.
(8) The overheated steam generator according to any one of (2) to (7) above, characterized in that the one end of the cylindrical housing is additionally provided with an inlet port for introduction of water vapor and other gas.
(9) The overheated steam generator according to any one of (6) to (8) above, characterized in that the liquid other than water or the gas contains an organic chlorine compound.
(10) The overheated steam generator according to any one of (1) to (9) above, characterized in that overheated steam injected out of the outlet port at the opposite end of the cylindrical housing of a heat-resistant material has a temperature of 120 to 800°C.
(11) The overheated steam generator according to any one of (1) to (10) above, characterized in that the heat-generation unit of an electrically conductive material housed in the cylindrical housing comprises elements formed of one or more materials selected from the group consisting of a rod material, a wire material, sheet material, a honeycomb material, a network material, a spherical material, a hollow spherical material and an amorphous bulk material.
(12) The overheated steam generator according to any one of (1) to (11) above, characterized in that the heat-generation unit of an electrically conductive material housed in the cylindrical housing is formed of a magnetic material.
(13) The overheated steam generator according to any one of (1) to (12) above, characterized in that the cylindrical housing of a heat-resistant material is formed of a non-magnetic material.
(14) An overheated steam generation process, characterized by injecting water in a cylindrical housing of a heat-resistant material from one end, wherein said cylindrical housing houses therein an air-permeable assembly that is formed of an electrically conductive material and is to be heated, and then heating said air-permeable assembly housed in said cylindrical housing by means of high-frequency induction, thereby injecting high-temperature overheated steam out of an opposite end of the cylindrical housing.
(15) An overheated steam generation process, characterized by injecting water and water vapor in a cylindrical housing of a heat-resistant material from one end, wherein said cylindrical housing houses therein an air-permeable assembly that is formed of an electrically conductive material and is to be heated, and then heating said air-permeable assembly housed in said cylindrical housing by means of high-frequency induction, thereby injecting high-temperature overheated steam out of an opposite other end of the cylindrical housing.
(16) The overheated steam generation process according to (14) or (15) above, characterized in that the cylindrical housing of a heat-resistant material is formed of a non-magnetic material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006]
Fig. 1 is illustrative in schematic of one embodiment of the overheated steam generator according to the invention, and Figs. 2 (a), 2(b), 2(c) and 2(d) are illustrative of four shapes of an element forming a part of the air-permeable assembly to be heated, which is used in the invention.
EXPLANATION OF THE REFERENCE NUMERALS
[0007]
1: cylindrical housing,
1a: one end of the cylindrical housing 1,
1b: the opposite or other end of the cylindrical housing 1,
2: inlet nozzle for injection of water,
3: outlet port out of which overheated steam is injected,
4: element that forms a part of air-permeable assembly to be heated,
5: exciting coil,
6: covering material,
7: conduit,
8: pressurized water vapor generation unit,
40: punching metal sheet,
41: keeper formed of a punching metal sheet,
HV: overheated steam,
V1, V2: on-off valves, and
V3, V4: check valves.
BEST MODE FOR CARRYING OUT THE INVENTION
[0008] The invention is now explained more specifically with reference to the accompanying drawings.
[0009] Fig. 1 is illustrative in schematic of one embodiment of the overheated steam generator according to the invention, and Figs. 2(a), 2(b), 2(c) and 2(d) are illustrative of four embodiments of an element forming a part of the air-permeable assembly to be heated.
[0010] As mentioned above, the reference numerals are:
1: cylindrical housing,
1a: one end of the cylindrical housing 1,
1b: the opposite or other end of the cylindrical housing 1,
2: inlet nozzle for injection of water,
3: outlet port out of which overheated steam is injected,
4: element that forms a part of the air-permeable assembly to be heated,
5: exciting coil,
6: covering material,
7: conduit,
8: pressurized water vapor generation unit,
40: punching metal sheet,
41: keeper formed of a punching metal sheet,
HV: overheated steam,
V1, V2: on-off valves, and
V3, V4: check valves.
[0011] Referring first to Fig. 1, one end 1a of the cylindrical housing 1 of an electrically conductive material is provided with the inlet nozzle 2 of injection of water and the other end 1b with the port 3 out of which overheated steam is injected.
[0012] The cylindrical housing 1 is provided over its outer periphery with the covering material 6 formed of a castable refractory ceramic material for the purpose of heat insulation. The exciting coil 5 for conduction of a high-frequency current is wound around the outer periphery of the ceramic covering material 6, and connected with a high-frequency current power source, not shown.
[0013] The cylindrical housing 1 receives the air-permeable assembly 4 that is formed of an electrically conductive material and is to be heated, wherein, as shown in Fig. 1, the air-permeable assembly 4 is made up of stainless steel balls, one of which is shown in Fig. 2(a). The assembly 4 is heated by electromagnetic induction by the exciting coil 5 to generate heat, so that water or water vapor passing through it can be heated to high temperatures into overheated steam HV that is injected out of the outlet port 3 at the other end 1b. Reference numeral 40 stands for a punching metal sheet.
[0014] It is noted that the water injection inlet nozzle 2 at the one end 1a of the cylindrical housing 1 is connected to a water feed pump P via the conduit 7, and to the pressurized water vapor generation unit 8 as well.
[0015] To inject water from the inlet nozzle 2 into the cylindrical housing 1, the on-off valve V2 provided on the way of a conduit from the pressurized water vapor generation unit 8 remains closed and the on-off valve V1 is opened. To inject water and pressurized water vapor into the cylindrical housing 1, not only the on-off valve V2 but also the on-off valve V1 is opened. It is noted that V3 and V4 are the check valves.
[0016] In the embodiment of the invention, water, or water and water vapor are injected into the cylindrical housing 1 from its one end 1a, in which the air-permeable assembly 4 to be heated, formed of an electrically conductive material, is housed. Then, water or water vapor makes its way through the air-permeable assembly 4 to be heated, housed in the cylindrical housing 1. In the meantime, the air-permeable assembly 4 is heated with heat generated by electromagnetic induction by the exiting coil 5, so that the water or water vapor passing through it is heated to high temperature into overheated steam HV that is injected out of the outlet port 3 at the other end 1b of the cylindrical housing 1.
[0017] It is noted that reference numeral 40 is the punching metal sheet that is provided for prevention of the elements in the air-permeable assembly 4 housed in the cylindrical housing 1 from coming out. Reference numeral 41 is the keeper formed of a punching metal sheet that has preferably high thermal conductivity and good heat resistance (e.g., a copper or silver sheet). In the embodiment shown, the keeper 41 formed of copper has a vertically double-sheet structure, in which sheets 41a and 41b are joined together via a bridging sheet 41c. The sheet 41b has a long leg 41d that extends between the elements of the air-permeable assembly 4.
[0018] Accordingly, the high heat of the air-permeable assembly 4 always conducts to the long leg 41d to maintain 41b, 41c and 41a at so high temperature that the water injected from the inlet nozzle 2 can be immediately and continuously vaporized without undergoing temperature drops.
[0019] As the air-permeable assembly 4 to be heated, housed in the cylindrical housing 1, is heated by high-frequency induction with water injected into it, it allows overheated water vapor to be generated in an amount of about a few tens to thousand times as much as that generated by introduction of water vapor into the cylindrical housing. Accordingly, high-pressure overheated water vapor can be easily injected out of the other end of the cylindrical housing.
[0020] In other words, 22.4-liter water vapor is 18 grams, but 18-ml water is 18 grams. Theoretically, if 18-ml water is injected in the cylindrical housing 1, 22,400-ml water vapor will occur with the result that 22,400 ml÷18 ml≒1,240. To put it another way, as water is injected and heated, pressurized water vapor is obtained in an amount of about 1,200 times as much as that obtained by the introduction and heating of water vapor. Thus, the resulting pressurized water vapor, too, is brought up to a very high pressure.
[0021] It is noted that while water or water vapor passes through the cylindrical housing 1, it comes in contact with the heated air-permeable assembly, where it is further heated into overheated steam, which makes its way toward the discharge side of the cylindrical housing 1 while it expands slowly.
[0022] Even with the power source for the exciting coil 5 put off as the internal temperature of the cylindrical housing 1 rises, much time is taken for cooling, because the air-permeable assembly 4, kept in a high-temperature state, cools off, ending up with a decrease in the internal temperature of the cylindrical housing 1.
[0023] For the electrically conductive material of the air-permeable assembly 4, use could be made of metals of strong magnetism such as iron and metals of weak magnetism such as stainless steels SUS430 and SUS403, nickel and titanium as well as carbon ceramics such as carbon and silicon carbide.
[0024] The magnetic metal material, especially the soft magnetic material is preferable for the electrically conductive material of the air-permeable assembly 4 to be heated.
[0025] A requirement for the air-permeable assembly 4 to be heated is that vapors pass smoothly through it in a tank, and it could be made up of a rod material, a wire material, a sheet material, a honeycomb material, a network material, a spherical material, a hollow spherical material, an amorphous bulk material or the like. These materials could be provided with through-holes.
EXAMPLE
[0026] Overheated water vapor was generated, using the overheated steam generator of Fig. 1, in which the air-permeable assembly 4 to be heated was comprised of hollow sphere elements, each having some openings as shown in Fig. 2(b).
[0027] First, water was injected into the cylindrical housing 1 from the inlet nozzle 2 located at its one end 1a at an injection pressure of 4 to 6 kg/cm2 and in an amount of 6 to 10 kg/h. However, the pressurized water vapor generation unit 8 was not used; the on-off valve V2 remained closed and the on-off valve V1 was set at an open position.
[0028] The cylindrical housing 1 had an inside diameter of 20 cm and a length of 40 cm. The assembly to be heated was comprised of elements made of a ferritic stainless steel (SUS430) that was a magnetic metal material (carbon steel in a preferable embodiment), and the cylindrical housing 1 was made of an austenitic stainless steel (SUS304).
[0029] A high-frequency current having a frequency of 20 kHz was fed to the exciting coil 5 at 25 to 30 kw/h.
[0030] As a result, overheated water vapor having a temperature of as high as 320°C was continuously injected out of the overheated steam outlet port.
POSSIBLE APPLIATIONS TO THE INDUSTRY
[0031] According to the invention, water or water and water vapor are injected into a cylindrical housing from its one end, wherein the cylindrical housing receives an air-permeable assembly of an electrically conductive material to be heated, and the air-permeable assembly received in the cylindrical housing is heated by high-frequency induction, so that overheated water vapor in an amount of about a few tens to thousand times as much as that obtained by heating water vapor introduced in the cylindrical housing and, hence, at a high pressure, can be easily injected out of the other end.
[0032] The high-temperature overheated water vapor obtained in the invention could be utilized for disinfection of cereals such as wheat, buckwheat and beans and fruits and vegetables such as strawberry and tomato or roasting of tee leaves and coffee beans, purification of contaminated soils by gasification and isolation of volatile harmful substances (e.g., organic chlorine base harmful products) from them, or the like.