JP6985735B2 - Superheated steam furnace - Google Patents

Description

The present invention relates to a superheated steam furnace.

Heat treatment such as heating of an object by superheated steam is performed by accommodating the object in a furnace and introducing superheated steam into the furnace. Hereinafter, in the present specification, a furnace into which superheated steam is introduced is referred to as a superheated steam furnace.

This heat treatment with superheated steam is mainly for the purpose of (1) using the high heat transfer property of superheated steam to raise the temperature deep inside the object and rapidly, and (2) superheated steam. To realize an extremely low oxygen concentration atmosphere by introducing the above into a heating furnace, and to obtain reactivity under that atmosphere, and (3) to obtain both (1) and (2) above. It is roughly divided.

A large amount of superheated steam is required when the rapid temperature rise of the object is required as in (1) above, but a large amount of superheated steam is required when only the atmosphere of superheated steam is required as in (2). Not needed. Even in the case of (2), a constant temperature is often required together with the superheated steam atmosphere, and usually some kind of heating method is required.

When superheated steam is used as a heat source, the amount of superheated steam is required to maintain the temperature inside the furnace. The temperature at that time is also 100 ° C. or higher. Therefore, the latent heat (540 kcal / kg at 1 atm) released when the steam at 100 ° C becomes water at 100 ° C is discharged from the superheated steam furnace, and as a result, a large amount of heat is wasted. ..

In order to reduce the amount of wasted heat, it is conceivable to reduce the amount of superheated steam introduced into the superheated steam furnace and raise and adjust the temperature inside the furnace by another means. For example, many means are adopted in which an electric heater is installed inside or outside the furnace to raise and adjust the temperature inside the furnace.

However, since the electric heater has a small heat generation area, there is a problem in the controllability of the temperature inside the furnace. In addition, when the electric heater is installed in the furnace, the deterioration of the electric heater is promoted by the steam oxidation by superheated steam, so it is necessary to take measures such as housing the electric heater in a case where it is hard to deteriorate. .. As a matter of course, when the electric heater is installed outside the furnace, the influence of superheated steam can be avoided, but the heat transfer effect is significantly reduced.

Japanese Unexamined Patent Publication No. 2016-176613

Therefore, the present invention has been made to solve the above-mentioned problems, and its main task is to improve the controllability of the temperature inside the furnace.

That is, the superheated steam furnace according to the present invention includes a furnace body having a furnace chamber inside, a conductor pipe for introducing superheated steam into the furnace chamber, and a power supply circuit for applying an AC voltage to the conductor pipe. The main body has a metal furnace wall portion, and the conductor tube is spirally wound in the furnace chamber facing the furnace wall portion.

In such a superheated steam furnace, the conductor tube is energized and heated by energizing the conductor tube. The conductor tube heated by energization serves as a heating source in the furnace chamber. Further, the magnetic flux generated by energizing the spirally wound conductor tube passes through the furnace wall portion, and the furnace wall portion is induced and heated. The induction-heated furnace wall serves as a heating source in the furnace chamber. That is, in the present invention, both the conductor tube and the furnace wall portion serve as heating sources by the energization heating of the conductor tube and the induction heating of the furnace wall portion, so that the controllability of the temperature inside the furnace can be improved. In addition, since the temperature inside the furnace can be raised and adjusted by means other than superheated steam (conductor pipe and furnace wall), the amount of superheated steam introduced into the superheated steam furnace can be reduced to achieve significant energy savings. can do. Furthermore, since the conductor tube that introduces superheated steam into the furnace chamber is energized and heated, the temperature drop of superheated steam from the superheated steam generator installed outside the superheated steam furnace to the time when it is introduced into the superheated steam furnace is compensated. Can be maintained at the desired temperature.

Depending on the combined state of the amount of magnetic flux generated from the conductor tube and the metal furnace wall portion, the calorific value due to the induction heating of the furnace wall portion may not be sufficiently obtained. In this case, it is desirable that the conductor tube is made of copper or a copper alloy which is a low resistance material. With this configuration, a long conductor tube can be selected to obtain the same resistance value, so that the number of turns can be increased. Since the generated magnetic flux is proportional to the product of the number of turns and the flowing current value, the amount of generated magnetic flux increases, and the amount of heat generated by the induction heating of the furnace wall portion can be increased.

The energization heating of the conductor tube and the induction heating of the furnace wall portion are temperature controlled so that the temperature inside the furnace becomes constant regardless of the amount of superheated water vapor. That is, the temperature of the conductor tube and the temperature of the furnace wall portion are controlled to the values at which the temperature inside the furnace becomes a desired temperature. Here, it is desirable that the conductor pipe has one or a plurality of injection ports for injecting superheated steam toward the furnace wall portion. Since the temperature of the superheated steam ejected from the conductor tube is almost the same as the temperature of the conductor tube, the temperature of the furnace wall part is higher than the temperature of the conductor tube by injecting the superheated steam toward the furnace wall part. Even if it is low, it can be heated or cooled so as to approach the temperature of the conductor tube. Further, since the spouted superheated steam hits the furnace wall and is dispersed, it is possible to easily make the temperature in the furnace uniform. That is, (temperature of the conductor tube) ≈ (heated steam temperature) ≈ (temperature of the furnace wall portion) ≈ (temperature inside the furnace).

Since the furnace body requires heat resistance and steam resistance, metal or ceramic is used. Specifically, the furnace wall portion of the furnace body is configured such as ceramic / metal plate / heat insulating material / metal plate / ceramic from the furnace chamber side, or metal plate / heat insulating material / metal plate from the furnace chamber side. .. When the innermost portion (the innermost chamber side) of the furnace wall portion is a metal plate, the metal plate needs to be resistant to superheated steam. Therefore, it is desirable that the innermost portion of the furnace wall portion is formed of austenitic stainless steel or an inconel alloy, which is a material having high marketability and high resistance to superheated steam.

When the furnace wall portion is induced and heated, a high power factor can be obtained and the leakage flux can be reduced by constructing a magnetic circuit having a low magnetoresistance. Therefore, it is desirable that the portion different from the innermost portion of the furnace wall portion is formed of a magnetic material. Specifically, the innermost portion of the furnace wall portion is a non-magnetic metal such as austenitic stainless steel or inconel alloy having high steam resistance, and the portion different from the innermost portion of the furnace wall portion is iron or iron which is a magnetic metal. Martensitic stainless steel. As a result, the magnetic resistance can be lowered and the strength of the furnace body can be ensured.

The power supply circuit applies an AC voltage of 50 Hz or 60 Hz, which is a commercial frequency, to the conductor tube, and it is desirable to have a supersaturated reactor and a capacitor for improving the power factor.
The commercial frequency induction heating has a deeper induced current penetration than the high frequency induction heating, and can perform induction heating to a deep part in a thick furnace wall portion. In addition, the hypersaturated reactor has a smaller harmonic current than the semiconductor element, and the power factor can be improved without passing a large current through the power factor improving capacitor. Therefore, if this is used in the power supply circuit, a high power factor circuit can be constructed. Can be done. Further, a high frequency power supply is not required, the production can be performed at low cost, and the possibility of failure due to harmonics can be reduced.

According to the present invention configured as described above, both the conductor tube and the furnace wall portion serve as heating sources by the energization heating of the conductor tube and the induction heating of the furnace wall portion, so that the controllability of the temperature inside the furnace is improved. be able to.

It is a figure which shows typically the structure of the superheated steam furnace of this embodiment. It is sectional drawing of the furnace wall part which has the conductor tube and energization heating mechanism of the same embodiment. It is A arrow view which shows the structure of the conductor tube of the same embodiment. It is a schematic diagram which shows the power supply circuit of the same embodiment. It is a schematic diagram which shows the power supply circuit in a modification embodiment. It is a schematic diagram which shows the power supply circuit in a modification embodiment. It is a schematic diagram which shows the power supply circuit in a modification embodiment. It is a schematic diagram which shows the power supply circuit in a modification embodiment.

Hereinafter, an embodiment of the superheated steam furnace according to the present invention will be described with reference to the drawings.

The superheated steam furnace 100 according to the present embodiment is for performing heat treatment of an object using superheated steam of over 100 ° C. (200 ° C. to 2000 ° C.).

Specifically, as shown in FIG. 1, the superheated steam furnace 100 applies superheated steam to a conductor tube 3 and an AC voltage to the conductor tube 3 and a furnace body 2 having a furnace chamber 2S inside. It is equipped with a power supply circuit 4.

The furnace main body 2 has, for example, a rectangular parallelepiped housing main body portion 21 having an opening 2H on one surface, and a door portion 22 that closes the opening 2H so as to be openable and closable. The opening 2H of the present embodiment is provided on the front surface. Further, the furnace main body 2 is provided with a discharge unit (not shown) for discharging superheated steam to the outside.

Each furnace wall portion 21W of the accommodation main body portion 21 has an inner metal plate 211, a heat insulating material 212, and an outer metal plate 213 from the furnace chamber 2S side in this order. Similarly, the door portion 22 also has an inner metal plate, a heat insulating material, and an outer metal plate from the furnace chamber 2S side.

The inner metal plate 211 is made of austenitic stainless steel or an inconel alloy, which is a non-magnetic metal having high water resistance. As a result, the innermost portion of the furnace wall portion 21W becomes an austenitic stainless steel or an inconel alloy. The outer metal plate 213 is made of iron, which is a magnetic metal, or martensitic stainless steel. As a result, the outermost portion of the furnace wall portion 21W becomes iron or martensitic stainless steel.

The conductor tube 3 is provided so as to penetrate the furnace wall portion 21W of the accommodating main body portion 21, and is spirally wound in the furnace chamber 2S facing the furnace wall portion 21W. For the conductor tube 3, an austenitic stainless steel such as SUS304 having high water resistance and an alloy such as Inconel can be used. Note that FIG. 1 shows an example in which the conductor pipe 3 is provided in the two left and right furnace wall portions 21W of the accommodation main body portion 21 and the furnace wall portion 21W on the back side, but the present invention is not limited to this, and at least one of them is 1. It may be provided in one furnace wall portion 21W, may be provided in the upper furnace wall portion 21W, or may be provided in the lower furnace wall portion 21W.

Here, the conductor tube 3 is provided in a state of being insulated from the furnace wall portion 21W via an insulating member 5 such as an insulating insulator. In the present embodiment, an example of outer winding spirally wound outward from a portion introduced from the furnace wall portion 21W is shown, but the opposite, that is, a portion introduced from the furnace wall portion 21W. It may be an inward winding that is spirally wound inward from the starting point. The winding portion of the conductor tube 3 is provided substantially parallel to the facing furnace wall portion 21W, and a plurality of ejection ports 3x for ejecting superheated steam into the furnace chamber 2S are provided. The plurality of spouts 3x are provided on the opposite furnace wall portion 21W side in the outermost peripheral portion of the winding portion of the conductor tube 3. The plurality of spouts 3x may be provided in a portion other than the outermost peripheral portion. Further, a connection port 3P to which an introduction pipe for introducing superheated steam generated by an external superheated steam generator is connected is provided in a portion of the conductor pipe 3 located outside the furnace chamber 2S. The external superheated steam generator may be an induction heating method or an energization heating method.

The power supply circuit 4 applies an AC voltage to a first feeding terminal (energization electrode) 6 provided at one end of the conductor tube 3 and a second feeding terminal (energization electrode) 7 provided at the other end of the conductor tube. It is to be applied. The first power feeding terminal 6 is connected to a portion of the conductor tube 3 located outside the furnace chamber. Further, the second power feeding terminal 7 is connected to the winding end end of the winding portion of the conductor tube 3. The second power feeding terminal 7 extends out of the furnace chamber 2S in a state of being insulated from the furnace wall portion 21W via an insulating member 8 such as an insulator. The power supply circuit 4 is connected to this extended portion.

Specifically, as shown in FIG. 4, the power supply circuit 4 includes an AC power supply Es having a commercial frequency of 50 Hz or 60 Hz, and a saturable reactor SR that controls an AC current to the conductor tube 3.

The saturable reactor SR has a structure in which two types of windings, alternating current and direct current, are wound around an iron core having an electromagnetic induction action, and the product of the current flowing through the two wound windings and the number of turns is constant. in the range of the law of equal ampere-turns of equal relationship _{I L × N L = I DC} × N DC is established. Thus, by increasing or decreasing the DC current I _DC, can be controlled alternating current I _L, it is possible to control the output of the conductor tube 3.

Then, as shown in FIG. 4A, the power supply circuit 4 is provided with a power factor improving capacitor C and a protective capacitor C for protecting the power factor improving capacitor C between the saturable reactor SR and the conductor tube 3. The AC reactor CR is connected.

Specifically, the power factor improving capacitor C and the protective AC reactor CR are connected in series with the AC power supply Es, and one end of the protective AC reactor CR is connected to one end side of the conductor tube 4. A plurality of capacitors C for improving the power factor may be connected, or a plurality of protective AC reactor CRs may be connected. Further, as shown in FIG. 4B, a transformer VC is inserted between the conductor tube 3 and the AC power supply Es in order to obtain an appropriate voltage according to the resistance value and the number of turns of the conductor tube 3. You may. Note that FIG. 4B shows an example in which an autotransformer is inserted.

In this superheated steam furnace 100, the temperature inside the furnace is detected by a temperature detector (not shown) provided in the furnace chamber 2S, and a control signal corresponding to the deviation between the detected temperature and the target temperature is sent to the saturable reactor SR. The alternating current flowing through the conductor tube 3 is controlled by inputting to. Specifically, the temperature controller (not shown) that performs this control feedback-controls (for example, PID control) the temperature inside the furnace so that the deviation from the target temperature is less than ± 1 ° C.

Then, when an AC voltage is applied to the conductor tube 3 by the power supply circuit 4, the conductor tube 3 generates Joule heat (energized heating) due to the AC current flowing through the conductor tube 3. As a result, the conductor tube 3 becomes a heating source in the furnace chamber 2S. Further, the superheated steam introduced from the conductor pipe 3 is heated by the conductor pipe 3 and injected into the furnace chamber 2S. The injected superheated steam hits the furnace wall portion 21W and heats or cools the inner metal plate 211 of the furnace wall portion 21W to the same temperature as the temperature of the superheated steam.

Further, when an AC voltage is applied to the conductor tube 3 by the power supply circuit 4, a magnetic flux is generated from the wound portion of the conductor tube 3 and the magnetic flux passes through the inner metal plate 211 of the furnace wall portion 21W. Here, since the outer metal plate 213 is made of magnetic metal, the magnetic resistance is lowered and the amount of magnetic flux passing through the inner metal plate 211 can be increased. As a result, an induced current flows through the inner metal plate 211 of the furnace wall portion, and the induced current causes Joule heat generation of the inner metal plate 211 of the furnace wall portion 21W (induction heating). As a result, the inner metal plate 211 of the furnace wall portion 21W becomes a heating source in the furnace chamber 2S.

According to the superheated steam furnace 100 configured in this way, both the conductor tube 3 and the furnace wall portion 21W become heating sources in the furnace chamber 2S by the energization heating of the conductor tube 3 and the induction heating of the furnace wall portion 21W. Therefore, the controllability of the temperature inside the furnace can be improved. According to this embodiment, (temperature of conductor tube) ≈ (temperature of superheated steam) ≈ (temperature of furnace wall portion) ≈ (temperature inside furnace) can be set. Further, since the temperature inside the furnace can be raised and adjusted by means other than the superheated steam (conductor pipe 3 and the furnace wall portion 21W), the amount of superheated steam introduced into the superheated steam furnace 100 can be reduced to a large extent. Energy saving can be achieved. Further, since the conductor tube 3 for introducing superheated steam into the furnace chamber 2S is energized and heated, the superheated steam from the superheated steam generator provided outside the superheated steam furnace 100 until it is introduced into the superheated steam furnace 100. The temperature drop can be compensated and the desired temperature can be maintained.

<Other modified embodiments>
The present invention is not limited to the above embodiment.

For example, the material of the conductor tube 3 may be copper or a copper alloy which is a low resistance material. With this configuration, since a long conductor tube 3 can be selected to obtain the same resistance value, the number of turns to be wound can be increased. Since the generated magnetic flux is proportional to the product of the number of turns and the flowing current value, the amount of generated magnetic flux increases, and the amount of heat generated by the induction heating of the furnace wall portion 21W can be increased.

Further, the shape of the conductor tube 3 may be, for example, a shape spirally wound in a substantially circular shape as in the above embodiment, or a shape spirally wound in a substantially elliptical shape or a substantially rectangular shape. ..

Further, the plurality of spouts 21x provided in the conductor tube 3 may be provided on the side opposite to the furnace wall portion 21W facing each other in the winding portion, that is, on the central side, or may be provided at other positions. .. Further, the conductor tube 3 may have one spout 21x in addition to the configuration provided with a plurality of spouts 21x. In this case, it is conceivable to provide one ejection port 21x at the winding end end of the conductor tube 3.

Further, the furnace wall portion 21W has an inner ceramic plate, an inner metal plate 211, a heat insulating material 212, an outer metal plate 213, and an outer ceramic plate in this order from the furnace chamber side. You may.

In addition, in addition to the conductor tube 3 of the embodiment, a second conductor tube such as a straight tubular tube may be provided, and superheated steam may be introduced from the second conductor tube. It is desirable that the second conductor tube is energized and heated in the same manner as the conductor tube 3. Further, the second conductor tube is provided with a plurality of injection ports, and it is desirable to widen the introduction range of superheated steam.

Further, it may have a circulation flow path for returning the superheated steam discharged from the discharge portion of the furnace main body 2 to the inside of the furnace chamber 2S again. With this configuration, further energy saving can be realized.

For example, in the above embodiment, the power supply circuit 4 using the single-phase AC power supply Es has been described, but as shown in FIG. 5, the induction heating device 100 has a configuration including the power supply circuit 4 using the three-phase AC power supply Et. May be good. In this case, a conductor tube is connected between each phase of the three-phase AC power supply Et. Saturable reactors SR1 to SR3, power factor improving capacitors C1 to C3, and protective AC reactors CR1 to CR3 are connected to each of these three conductor tubes 3.

Further, as shown in FIG. 6, the first conductor tube 3 and the second conductor tube 3 may be Scott-connected. Specifically, one end of the first conductor tube 3 is connected to the first phase of the three-phase AC power supply Et via the first saturable reactor SR1, and the other end of the first conductor tube 3 is connected to the second induction coil. Connected to the center position of L2, one end of the second induction coil L2 is connected to the second phase of the three-phase AC power supply Et via the second saturable reactor SR2, and the other end of the second induction coil L2 is three-phase AC. Connect to the third phase of the power supply Et. With this configuration, the outputs of the first induction coil L1 and the second induction coil L2 are individually controlled while the two sets of induction heating circuits 31 and 32 balance the current of each phase of the three-phase AC power supply Et. Can be done.

Further, as shown in FIGS. 7 and 8, a conductor tube 3 may be connected to each of the two single phases on the output side by using a Scott connection transformer. Saturable reactors SR1 and SR2, power factor improving capacitors C1 and C2, and protective AC reactors CR1 and CR2 are connected to each of these two conductor tubes 3.

In addition, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

100 ... Superheated steam furnace 2S ... Furnace chamber 2 ... Furnace body 21W ... Furnace wall 21x ... Injection port 211 ... Inner metal plate (innermost part)
212 ・ ・ ・ Outer metal plate (part different from the innermost part)
3 ... Conductor tube 4 ... Power supply circuit SR ... Supersaturated reactor C ... Capacitor for improving power factor

Claims (6)

The main body of the furnace, which has a furnace chamber inside,
A conductor tube that introduces superheated steam into the furnace chamber,
A power supply circuit that applies an AC voltage to the conductor tube is provided.
The furnace body has a metal furnace wall portion and has a metal furnace wall portion.
The conductor tube is spirally wound in the furnace chamber facing the furnace wall portion .
The conductor tube is energized and heated by applying an AC voltage to the conductor tube by the power supply circuit, and the magnetic flux generated by applying the AC voltage to the conductor tube passes through the furnace wall portion. A superheated steam furnace in which the furnace wall is induced and heated. The superheated steam furnace according to claim 1, wherein the conductor tube is made of copper or a copper alloy. The superheated steam furnace according to claim 1 or 2, wherein the conductor pipe has one or a plurality of injection ports for injecting superheated steam toward the furnace wall portion. The superheated steam furnace according to any one of claims 1 to 3, wherein the innermost portion of the furnace wall portion is formed of austenitic stainless steel or an inconel alloy. The main body of the furnace, which has a furnace chamber inside,
A conductor tube that introduces superheated steam into the furnace chamber,
A power supply circuit that applies an AC voltage to the conductor tube is provided.
The furnace body has a metal furnace wall portion and has a metal furnace wall portion.
The conductor tube is spirally wound in the furnace chamber facing the furnace wall portion.
The portion different from the innermost portion of the furnace wall portion is a superheated steam furnace formed of a magnetic material. The power supply circuit is for applying an AC voltage of 50Hz or 60Hz is a commercial frequency to the conductor tube has a saturable reactor and the power factor improving capacitor, according to any one of claims 1 to 5 Superheated steam furnace.

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