JP3758668B2 - Induction heating steam generator - Google Patents

Description

  The present invention relates to an induction heating steam generator that generates steam by heating water by induction heating.

As shown in Patent Document 1, an ordinary steam generator is configured to generate steam by heating water passed through a narrow tube by combustion gas generated by burning liquid fuel or gas fuel. In this conventional steam generator 110, in order to efficiently generate steam and obtain a desired steam pressure, the surroundings are covered with a heat insulating material 111 as shown in FIG. 6, and a gas or liquid fuel is burned by a burner 116 attached below. The high-temperature combustion gas generated by burning the gas is passed through the economizer 112, the evaporator 113, and the superheater 114, each of which is composed of thin tubes and provided in multiple stages, and supplies heat thereto.
The economizer 112 preheats the water W supplied to the evaporator 113 with the heat of the combustion gas of the burner 116. The evaporator 113 heats the water preheated by the economizer 112 and generates steam. Then, the superheater 114 reheats the steam S generated by the evaporator 113 and supplies it to the external load as the desired superheated steam S ′. The steam generated in the evaporator 113 is wet steam, but is separated into moisture and steam by the steam-water drum 115 that stores water and steam provided between the evaporator 113 and the superheater 114. Combustion exhaust gas is discharged to the outside through an exhaust pipe such as a chimney from above.

Since such a conventional steam generator using combustion gas requires an exhaust pipe such as a chimney because of the fuel burning, it must be installed only in a specially provided boiler room. For this reason, when a load that requires steam is placed at a location remote from the installation location of the steam generator, it is necessary to guide the steam through a long pipe insulated to this load installation location. Since it is as small as about 0.5 cal / g / deg, the drop in steam temperature increases due to heat loss in the piping. In order to improve this, it is necessary to reheat the steam by wrapping a ribbon heater in the middle of the piping or installing other heating means.
In order to eliminate such inconvenience, an induction heating type steam generator that generates steam by induction heating without using combustion gas has been proposed as disclosed in Patent Document 2.
As shown in FIG. 7, the induction heating type steam generator 120 disclosed in Patent Document 2 is provided with a steam generation container 121 and a steam superheat container 122 which are overlapped with each other, and the outside is provided by an induction heating coil 123. Surrounds and configures. In this apparatus, the conductive containers 121 and 122 are heated by electromagnetic induction by the induction heating coil 123, and the water W supplied from the water supply port 124 into the inner steam generation container 121 is heated by the heat to generate steam S. The steam S generated in the steam generating container 121 is guided into the outer steam superheated container 122, where it is heated again and taken out from the steam outlet 125 as superheated steam S ′.

According to such a configuration, since it is not necessary to burn the fuel, there is no restriction on the installation location, and it can be installed adjacent to the installation location of the load that requires steam. For this reason, since the pipe for introducing the steam from the steam generator to the load is shortened, heat loss in this pipe is reduced, so that it is not necessary to install a reheating device or the like, and the steam generator using the combustion gas heating device Can be eliminated.
JP 2001-033004 A JP 2002-022107 A

However, in the above-described conventional induction heating steam generator, the heat absorbed by the cooling water is only lost as a loss and is not recovered, which is a major factor for reducing the heating efficiency.
In addition, since the steam generation container and the steam heating container itself are heated by the induction heating coil and the water or steam supplied into the container is heated by the heat, the steam generation that is water or steam and the heating body is generated. Since the container and the heating steam generation container are only in contact with the inner wall of the container, the contact area between the two is small, the heat transfer efficiency from the container to water or steam is poor, and the overall heating efficiency cannot be increased. .
In addition, the boiler installed adjacent to the equipment that requires steam is different from the case where the steam generated in a large-capacity boiler placed in the boiler room is branched and supplied to each equipment. It is required to improve the follow-up performance to fluctuations in usage (load fluctuation).

  It is an object of the present invention to provide an induction heating steam generator that solves the above-described problems in the conventional induction heating steam generator and has high heating efficiency and can easily cope with fluctuations in the amount of steam used. To do.

In order to solve such problems, the invention of claim 1 is directed to an induction heating steam generator that generates steam by heating water by a heating container heated by an induction heating coil. A required number of shield coils made up of annular coils electrically closed at the upper or lower end portions are arranged, and a cooling water flow passage is provided in a conductor forming the shield coil.
The invention of claim 2 is characterized in that the steam generated in the heating vessel is taken out as superheated steam to the outside through the cooling water flow passage of the shield coil.
According to a third aspect of the present invention, in the induction heating steam generator according to the second aspect, the superheated steam is supplied to the container body.
A fourth aspect of the present invention is the induction heating steam generator according to any one of the first to third aspects, wherein a part or all of the conductor of the induction heating coil or shield coil is made of a highly conductive material such as copper or aluminum. It is characterized by comprising a composite conductor formed by integrally joining a conductive plate formed in (1) and a pipe formed of a non-rust material such as stainless steel forming a cooling water flow passage.

The invention according to claim 5 is the induction heating steam generator according to any one of claims 1 to 3, wherein the heating container is a container body formed of a non-magnetic non-conductive heat-resistant material, and the container body It is characterized by comprising a heating element composed of a number of small pieces of conductive metal filled therein.
When the heating container is made of a conductive metal material, an induced current flows on the outer peripheral side of the heating container, the magnetic flux density passing through the metal pieces in the container is reduced, the heat generation of the metal pieces is reduced, and the heating container also generates heat. Easily escape from the container, reducing heat generation efficiency.
According to a sixth aspect of the present invention, in the induction heating steam generator according to the fifth aspect, the heating element is formed of a small piece of stainless steel having magnetism.
The induced current induced in the heating element has a distribution that decreases exponentially from the surface of the heating element in the depth direction of the thickness. The total induced current can be regarded as a value obtained by multiplying the value of the current flowing on the surface by the penetration depth λ expressed by the following equation.

λ = (2 × ρ / (2πf × μ ₀ × μ _s )) ^1/2
Here, ρ: resistivity of the heating element, f: frequency, μ ₀ : permeability of vacuum, μ _s : relative permeability of metal For example, if f = 20 kHz and ρ = 100 μΩ · cm, λ is non-magnetic heat generation 3.6mm for the body and 0.1mm for the magnetic heating element, the penetration depth of the magnetic heating element is shallow, and the induced current flows near the surface of the heating element. Heating efficiency can be made higher than that of a magnetic heating element.
The invention of claim 7 is the induction heating steam generator according to any one of claims 1 to 3, wherein the container body is composed of a plurality of thin tubes formed of a non-magnetic non-conductive heat-resistant material. Features.
The invention according to claim 8 is the induction heating steam generator according to any one of claims 1 to 3, wherein a cooling water flow passage is provided in a conductor forming the induction heating coil, and water supplied to the heating container is supplied. And before supplying to this heating container, it supplies to a heating container through the cooling water flow path of the said induction heating coil, It is characterized by the above-mentioned.

In this invention, in the induction heating type steam generator, the shield coil is formed by arranging a required number of shield coils composed of annular coils electrically closed at the outer periphery or upper and lower ends of the induction heating coil. Since the cooling water flow passage is provided in the conductor, the resistance loss in the shield coil can be recovered, thereby improving the thermal efficiency.
And according to this invention, while forming a heating container with a nonmagnetic and nonelectroconductive heat-resistant material, it is filled with many heat generating bodies which consist of a small piece of conductive metal in this, and this heat generating body is comprised. When heat is generated by induction heating in the container and comes into contact with water supplied to the container, each heating element of the small piece comes into contact with water on the entire surface, so the contact area with water is expanded, and Heat transfer to water becomes good, and the thermal efficiency of the steam generator can be increased.
Furthermore, since this heating vessel is composed of a plurality of thin tubes formed of a non-magnetic non-conductive heat-resistant material, the amount of water in the boiler can be reduced, so that the structure becomes suitable for a simple boiler, Since the contact area is large, it is possible to provide an induction heating steam generator that can easily follow fluctuations in the amount of steam used.

In order to solve such problems, the invention of claim 1 is directed to an induction heating steam generator that generates steam by heating water by a heating container heated by an induction heating coil. A required number of shield coils made up of annular coils electrically closed at the upper or lower and lower ends, a cooling water flow passage is provided in a conductor forming the shield coil, and the steam generated in the heating vessel is It is characterized by taking out as superheated steam to the outside through the cooling water flow passage of the shield coil .

A second aspect of the present invention, in the induction heating steam generator according to claim 1, wherein the induction heating coil or the conductive plate forming part or all of the conductor of the shield coil in highly conductive material such as copper or aluminum And a pipe formed of a non-rust material such as stainless steel that forms the cooling water flow passage is integrally formed of a composite conductor formed by joining together.

Numerous invention of claim 3, in the induction heating steam generator according to claim 1, wherein the heating vessel comprises a container body formed with a non-magnetic non-conductive heat-resistant material, filled into the container body And a heating element made of a small piece of conductive metal.
When the heating container is made of a conductive metal material, an induced current flows on the outer peripheral side of the heating container, the magnetic flux density passing through the metal pieces in the container is reduced, the heat generation of the metal pieces is reduced, and the heating container also generates heat. Easily escape from the container, reducing heat generation efficiency.

According to a fourth aspect of the present invention, in the induction heating steam generator according to the third aspect , the heating element is formed of a small piece of stainless steel having magnetism.
The induced current induced in the heating element has a distribution that decreases exponentially from the surface of the heating element in the depth direction of the thickness. The total induced current can be regarded as a value obtained by multiplying the value of the current flowing on the surface by the penetration depth λ expressed by the following equation.

When high frequency power is supplied to the heating coil 2, Joule heat is generated by the current and resistance flowing in the coil conductor 21, and the magnetic material filled in the heating container 1 by the high frequency magnetic field generated by the induction heating coil 2. Eddy currents are respectively generated in the heating elements 13 made of small pieces, and Joule heat is generated by the currents. The water W supplied to the heating container 1 is preheated by absorbing the heat lost in the coil conductor 21 in the process of flowing through the cooling water flow passage in the heating coil 2 and cooling it to become the heating container 1. Supplied to. The water supplied to the heating container 1 comes into contact with a heating element 13 made of a small piece of magnetic material filled in the container 1 and is heated by the heat generated by the heating element to become steam S.
The steam S generated in the heating container 1 gathers in the upper space of the container, and is sent to the steam-water drum 5 through the steam extraction pipe 14 drawn from the upper space. Since the steam sent to the steam-water drum 5 is wet steam containing moisture, the steam and moisture are separated in the steam-water drum 5 and the moisture is stored in the drum 5. The steam from which moisture has been removed is guided to the inlet pipe of the cooling water passage of the annular conductor 34 at the lower end of the shield coil through the steam pipe 52 and flows through the cooling water passages of the four annular conductors (31 to 34). It flows to the superheated steam supply pipe 62 connected to the outlet pipe 3d of the annular conductor 31 at the upper end.

A fifth aspect of the present invention, in the induction heating steam generator according to claim 1, characterized by being composed of a plurality of tubules formed with the container body in a non-conductive heat-resistant material on the non-magnetic.

According to a sixth aspect of the invention, in the induction heating steam generator according to claim 1, the cooling water flow path in the conductor forming the induction heating coil is provided, the water supplied to the heating vessel, the heating vessel Before supplying, it supplies to a heating container after passing through the cooling water flow path of the said induction heating coil, It is characterized by the above-mentioned.

In such a case, as shown in FIG. 2, the heating coil is composed of a conductive plate 21a formed of copper, aluminum or the like having a low electrical resistance in the conductive portion inside the coil, and a cooling water flow passage is formed outside the heating coil. A composite conductor having a structure in which the stainless steel pipe 22a to be formed is joined by welding or the like is preferably used as the coil conductor 21. By doing so, since the conductive portion through which the current flows in the heating coil has a low resistance, the generation loss is reduced, and the portion through which the cooling water flows is constituted by a stainless steel pipe to prevent the occurrence of rust. be able to.
The shield coil 3 that heats the steam can change the amount of heat generated by changing the distance from the heating coil 2. When the shield coil 3 is brought close to the heating coil 2, the amount of heat generated in the shield coil 3 is increased, and the steam can be changed to a higher temperature superheated steam.

In order to suppress the temperature of the steam from becoming too high, the shield coil 3 may be installed at a distance from the heating coil 2. However, if the shield coil 3 is installed at a distance from the heating coil 2, the height of the apparatus is increased. There is an inconvenience that the size and the diameter are large and the apparatus becomes large.
In order to eliminate such inconvenience, it is necessary to reduce the resistance of the coil conductor of the shield coil 3. The resistance of the coil conductor is reduced by using a composite conductor formed by joining a low-resistance conductor plate and a non-rusting material pipe such as stainless steel as shown in FIG. Can be realized. By configuring the shield coil with such a composite conductor, the generation loss of the shield coil can be reduced, so that the shield coil can be arranged closer to the heating coil and the apparatus can be miniaturized.

Next, an embodiment when the present invention is applied to a once-through steam generator will be described.
4 and 5 show a once-through steam generator as a second embodiment of the present invention. 4 is a longitudinal sectional view thereof, and FIG. 5 is a plan sectional view taken along line VV in FIG.
As is clear from these drawings, the apparatus of the second embodiment is the same in shape and arrangement of the heating coil 2 and the shield coil 3 as the apparatus of the first embodiment.
Unlike the apparatus of the first embodiment, the heating container 1 includes lids 17a and 17b made of non-magnetic metal such as stainless steel that constitute the upper and lower steam and water headers, and a magnetic metal inside each of them. It is composed of a plurality of heating tubes 15 composed of thin tubes of nonmagnetic refractory material such as ceramic filled with a large number of heating elements 13 composed of small pieces. The plurality of heating tubes 15 are supported by being hermetically coupled to flanges 18 and 19 made of a nonmagnetic metal such as stainless steel at both upper and lower ends. The lids 16 and 17 are airtightly joined to the flanges 18 and 19 so that the entire heating container 1 is airtight.

Furthermore, if necessary, a heat insulating container 10 made of a non-conductive heat-resistant material is provided on the outer periphery of the entire heating tube 15, and the space between the heating tubes in the container and the space between the heating tube and the heat insulating container are provided. May be filled with a non-magnetic non-conductive heat insulating material 10a. Thereby, the heat radiation from the heating container 1 to the outside can be reduced and the heating efficiency can be increased.
The water supply pipe 41 is connected to the inlet 25 of the cooling water passage 22 of the lowermost coil conductor 21 of the heating coil 2, and the outlet 26 of the cooling water flow path 22 of the uppermost coil conductor 21 is connected to the lower water supply header by the connection pipe 42. It connects with the lid 17 which comprises a part. The steam extraction pipe 14 drawn out from the lid body 16 constituting the upper steam header is connected to the steam-water drum 5 installed outside the heating container 1. A water supply pipe 51 is drawn out from the air / water drum 5 and connected to the lower lid 17 to supply water from the drum 5 to the water supply header of the heating container 1. The amount of water in the heating container 1 is adjusted so as to always maintain a predetermined water level L so that the heating element 13 is not exposed from the water. Further, the steam pipe 52 drawn out from the air-water drum 5 is connected to the inlet pipe 3c of the cooling water passage of the uppermost annular conductor 31 of the shield coil 3, and is connected to the outlet pipe 3d of the cooling water passage of the lowermost annular conductor 34. The superheated steam supply pipe 62 is connected. The superheated steam supply pipe 62 is extended to an installation place of a load that requires steam, and supplies the steam S to the load.

The operation of the steam generator according to the second embodiment configured as described above is almost the same as that of the first embodiment.
In order to generate steam, high frequency AC power of about 30 kHz is supplied to the heating coil 2 from a high frequency AC power supply device (not shown). Then, water W is supplied from a water source such as a water storage tank 41 to the inlet 25 of the cooling water flow passage 22 formed in the conductor 21 of the heating coil 2 through the water supply pipe 41. This water flows through the cooling water flow passage 22 of the heating coil 2 and is injected from the outlet 26 into the water supply header portion below the heating container 1 through the connection pipe 42.
When high frequency power is supplied to the heating coil 2, Joule heat is generated by the current and resistance flowing in the coil conductor 21, and each heating tube 15 in the heating container 1 is filled by the high frequency magnetic field generated by the induction heating coil 2. An eddy current is generated in each of the heating elements 13 made of small pieces of magnetic metal, and Joule heat is generated by this current. The water W supplied to the heating container 1 is preheated by cooling the coil conductor 21 in the process of flowing through the cooling water flow passage in the heating coil 2 and supplied to the water supply header portion of the heating container 1 as hot water. Is done. The water supplied from here to the heating tube 15 comes into contact with the heating element 13 made up of a number of magnetic metal pieces filled in each heating tube, and is heated by the heat generated by the heating element to produce steam S and As a result, the inside of the heating pipe rises and gathers in the steam header portion formed by the lid 16 at the top of the heating container 1.

The steam in the upper steam header portion of the heating container 1 is sent to the steam drum 5 through the steam take-out pipe 14. Since the steam sent to the steam-water drum 5 is wet steam containing moisture, the steam and moisture (condensed liquid component) are separated in the steam-water drum 5 and stored in the drum 5. The steam from which moisture has been removed is guided to the inlet pipe 3c of the cooling water passage of the annular conductor 31 at the upper end of the shield coil through the steam pipe 52, and flows through the cooling water passages of the four annular conductors (31 to 34). Then flows to the superheated steam supply pipe 62 connected to the outlet pipe 3d of the annular conductor 34 at the lower end.
The shield coil 3 cancels out the magnetic flux leaking to the outside of the heating coil 2 by the magnetic flux generated by the circulating current generated by the magnetic flux generated by the heating coil 2 in each annular conductor, and suppresses the leakage of the magnetic flux to the outside. Work. The circulating current flowing in each annular conductor naturally generates Joule heat due to the resistance of the conductor itself, but the steam S is reheated in the process of flowing through the cooling water flow passage 3b in the shield coil 3 and dried overheated. Steam S ′ is obtained. The superheated steam S ′ generated in this way is transported to the installation location of the load that uses the steam by the superheated steam supply pipe 62.

When the heating container is constituted by a plurality of thin tubes as described above, the heating vessel is subdivided and the amount of water contained in one thin tube is reduced, so that the safety as a boiler can be improved.
Also in the second embodiment, the heating coil 2 and the shield coil 3 are provided with a low resistance conductive plate 21a such as copper or aluminum and a rust-free metal pipe 22b such as a stainless steel pipe as shown in FIG. It is preferable to use a composite conductor formed by bonding.

  As described above, the steam generator according to the present invention is configured to rust the generated steam by forming the heating element for heating water and the flow path through which water and steam are circulated with stainless steel or other non-metallic material. Therefore, it is suitable for use as a steam generation source for applications that do not like impurities such as food processing.

It is a longitudinal cross-sectional view which shows the structure of 1st Example of this invention. It is a perspective view which shows partially the Example of the coil conductor of the heating coil used for this invention. It is a top view which shows the coil conductor of the shield coil used for this invention. It is a longitudinal cross-sectional view which shows the structure of 2nd Example of this invention. It is a plane sectional view of the VV line of FIG. It is a block diagram which shows the example of the conventional combustion gas type steam generator. It is a block diagram which shows the example of the conventional induction heating type steam generator.

Explanation of symbols

1: Heating vessel 13: Heating body 15: Heating tube 2: Heating coil 21: Coil conductor 22: Cooling water flow passage 3: Shield coil 3a: Coil conductor 3b: Cooling water flow passage W: Water S: Steam S ': Superheated steam

Claims (6)

In an induction heating type steam generator that generates steam by heating water by a heating container heated by an induction heating coil,
A required number of shield coils made of an annular coil electrically closed at the outer periphery or upper and lower ends of the induction heating coil are disposed,
A cooling water flow passage is provided in the conductor forming the shield coil ,
An induction heating steam generator , wherein steam generated in the heating container is taken out as superheated steam to the outside through a cooling water flow passage of the shield coil . The induction heating steam generator according to claim 1 , wherein a part or all of the conductor of the induction heating coil or shield coil is formed with a conductive plate and a cooling water flow passage formed of a highly conductive material such as copper or aluminum. An induction heating steam generator characterized by comprising a composite conductor formed by integrally joining a pipe formed of a non-rust material such as stainless steel. In the induction heating type steam generator according to claim 1 ,
The heating container is composed of a container body formed of a non-magnetic, non-conductive heat-resistant material, and a heating element made up of a large number of conductive metal pieces filled in the container body. Steam generator. The induction heating steam generator according to claim 3 , wherein the heating element is formed of a small piece of magnetic stainless steel. 2. The induction heating steam generator according to claim 1 , wherein the container body is composed of a plurality of thin tubes formed of a non-magnetic non-conductive heat-resistant material. In the induction heating type steam generator according to claim 1 ,
A cooling water flow passage is provided in the conductor forming the induction heating coil;
An induction heating steam generator, wherein the water supplied to the heating container is supplied to the heating container through the cooling water flow passage of the induction heating coil before being supplied to the heating container.

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