JP4110629B2 - Powder heat treatment furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a granular heat treatment furnace for continuously heat treating a granular object, such as a heat treatment furnace for carbonizing carbon powder or a graphitization electric furnace for producing graphite powder.
[0002]
[Prior art]
As a furnace for heat-treating a granular object such as carbon powder, for example, in order to industrially produce carbonized powder or graphite powder, carbon powder or the like is heat-treated as raw material powder to be carbonized or graphitized. Heat treatment furnaces and graphitization electric furnaces are known.
[0003]
Conventionally, as a graphitization furnace, for example, a vertical shaft type heat treatment furnace as described in JP-A-2-14805 has been used. As shown in FIG. 5, the heat treatment furnace includes a hopper 2 in which an object 1 to be processed of raw material powder is stored, and a cylindrical heating tube 3 connected to the lower end of the hopper 2 and installed vertically. The heating tube 3 has an upper zone, an intermediate portion, and a lower portion, a charging zone A in which the workpiece 1 is fed from the hopper 2, a heating zone B in which the workpiece 1 is heated by an external heating source 4, and heating The processed object 1 to be processed is divided into cooling zones C.
[0004]
[Problems to be solved by the invention]
However, the following problems remain in the conventional heat treatment furnace. That is, in the conventional heat treatment furnace, when the gas G is generated from the workpiece 1 in the heating zone B, there is a problem that the workpiece 1 is blown up to the receiving hopper 2 of the workpiece 1 together with the generated gas G. . For example, when carbon powder is carbonized by heating to 1500 ° C as an object to be processed, a large amount of gas (mainly H ₂ (hydrogen), CH ₄ (methane), etc.) is generated in the temperature range of 800 ° C to 900 ° C. However, conventionally, since the workpiece 1 is filled in the upper part of the vertically long cylindrical heating tube 3, the generated gas G is difficult to escape, and the above-described blow-up occurs. Conventionally, the exhaust gas nozzle 5 for discharging the generated gas G to the charging zone A is connected. However, like the hopper 2, the exhaust gas nozzle 5 causes the above-mentioned blowing up.
If the inner diameter of the exhaust gas nozzle 5 is increased in order to improve gas venting, there arises an inconvenience that the workpiece 1 descending from the hopper 2 flows out of the exhaust gas nozzle 5.
In the case of a vertically long cylindrical heating tube, since the cross section is constant, if it is necessary to keep the temperature constant after a predetermined temperature, the workpiece 1 descends at the same speed, so the heating tube 3 is lengthened. There is a problem that the necessity arises and the equipment cost becomes high, and the equipment height becomes high, which is inconvenient in terms of maintenance. This is a more significant drawback when a long heat retention time is required in the heat treatment process.
[0005]
The present invention has been made in view of the above-described problems, and provides a granular heat treatment furnace that can prevent the granular object to be blown up by generated gas and can be made compact. With the goal.
[0006]
[Means for Solving the Problems]
The present invention employs the following configuration in order to solve the above problems. That is, in the first granular material heat treatment furnace, a furnace body that heat-treats the granular object to be processed, supply means for supplying the object to be processed to the furnace body, and heat treatment in the furnace body. And a granule heat treatment furnace provided with a cooling means for cooling the object to be processed, wherein the furnace body is installed in a substantially horizontal direction and heated while feeding the object to be processed supplied in the direction by the supplying means. A heating duct that vents the gas generated from the object to be processed, and a heat retaining duct that heats the object that has been degassed by the heating duct while maintaining the temperature at a constant temperature. A technique is adopted in which a discharge opening for discharging the generated gas to the outside is provided above the gas generation region where the generated gas is generated.
[0007]
In this granular heat treatment furnace, a furnace body is installed in a substantially horizontal direction and heated while feeding the object to be processed supplied by the supply means in this direction, and a heating duct for degassing the generated gas from the object to be processed And a heat retaining duct that heats while maintaining a constant temperature state while feeding the object degassed by the heating duct, and the heating duct generates gas at the upper part of the gas generation region where the generated gas is at a temperature. Since the gas is generated in the gas generation area, the gas generated in the gas generation area is easily escaped upward, and without being blown up the workpiece, the gas can be discharged smoothly from the discharge opening located above. Discharged.
[0008]
In the second granular heat treatment furnace, a technique is adopted in which, in the first granular heat treatment furnace, the heating duct has an internal shape wider than the vertical width.
[0009]
In this granular material heat treatment furnace, since the heating duct has an internal shape whose width is wider than the vertical width, the workpiece to be sent through the heating duct is easily heated and the gas is easily released.
[0010]
In the third granular material heat treatment furnace, in the first or second granular material heat treatment furnace, the discharge object is disposed in the discharge opening in a substantially horizontal direction so as to be processed in the heating duct. A technique is adopted in which a plurality of resistance plates are provided to suppress the upward swell.
[0011]
In this granular heat treatment furnace, a plurality of resistance plates are provided in the discharge opening so as to be spaced apart from each other in the substantially horizontal direction and prevent the workpiece in the heating duct from rising upward. The gas can escape upward through the resistance plates. However, even if an object to be processed fed into the heating duct rises upward, the resistance plate becomes an obstacle and cannot rise above the resistance plate.
[0012]
In the fourth granular heat treatment furnace, in any one of the first to third granular heat treatment furnaces, the heating duct introduces a gas that blows a gas different from the generated gas into the gas generation region from the outside. A technology equipped with a mechanism is adopted.
[0013]
In this granular heat treatment furnace, the heating duct is provided with a gas introduction mechanism that blows a gas different from the generated gas from the outside into the gas generation region, so that the gas generation region and the exhaust are discharged by the gas blown into the gas generation region. The vicinity of the opening for the use can be in a slightly positive pressure state, and the generated gas can be easily discharged to the outside.
[0014]
In the fifth granular heat treatment furnace, in any one of the first to fourth granular heat treatment furnaces, the heating duct has a divergent shape in which the internal shape in the gas generation region extends laterally toward the downstream side. Technology is adopted.
[0015]
In this granular heat treatment furnace, the heating duct has a divergent shape in which the internal shape in the gas generation region spreads laterally toward the downstream side, so the area increases toward the downstream side. As a result, the workpiece to be processed does not rise upward easily and flows smoothly.
[0016]
In the sixth granular material heat treatment furnace, in any one of the first to fifth granular material heat treatment furnaces, the heating duct has an inner bottom surface in the gas generation region on the downstream side of the object to be processed. A technology that has an inclined surface with an inclination below the angle of repose is employed.
[0017]
In this granular material heat treatment furnace, the heating duct has an inner bottom surface in the gas generation region with the downstream side facing downward and an inclined surface having an inclination equal to or less than the repose angle of the object to be processed. There is almost no upward swell of the workpiece to be processed. In addition, since the inclination is set to be less than the angle of repose, the object to be processed slips by itself due to the inclination, and it becomes impossible to sequentially move the object to be processed at low speed, or heating is not performed sufficiently. The inconvenience of insufficient gas venting can be prevented.
[0018]
In the seventh granular heat treatment furnace, in any one of the first to sixth granular heat treatment furnaces, the cooling means is connected to the downstream end of the heat retaining duct and cools while feeding the object to be processed. A technique is adopted in which a cooling duct is provided, and the heat retaining duct and the cooling duct are installed in a substantially vertical direction or in an inclined state with the downstream side facing downward.
[0019]
In this granular material heat treatment furnace, the cooling means includes a cooling duct that is connected to the downstream end of the heat retaining duct and cools the object to be processed, and the heat retaining duct and the cooling duct are substantially vertical with the downstream side facing downward. Since it is installed in a direction or in an inclined state, the object to be degassed is moved (down) by gravity to the downstream side (downward).
[0020]
In the eighth granular heat treatment furnace, in the seventh granular heat treatment furnace, the heat retaining duct is configured such that the cross-sectional area of the granular material is larger than that of the heating duct and the cooling duct. Is adopted.
[0021]
In this granular material heat treatment furnace, the flow passage cross-sectional area of the granular material in the heat retaining duct is set larger than that of the heating duct and the cooling duct, so that the descending speed of the object to be processed in the heat retaining duct is reduced. In other words, it is possible to sufficiently heat and heat the workpiece in the heat retaining duct, and to reduce the overall duct height of the heat retaining duct even when it is necessary to heat the workpiece for a long time. It becomes possible.
[0022]
In the ninth granular heat treatment furnace, in the seventh or eighth granular heat treatment furnace, the heating duct and the cooling duct can circulate the object to be processed at a heat insulating connecting portion formed of a heat insulating material. The technology connected to is adopted.
[0023]
In this granular heat treatment furnace, the heating duct and the cooling duct are connected so that the object to be processed can be circulated at the heat insulating connecting portion formed of the heat insulating material. Is not in direct contact and heat loss is reduced.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of a granular material heat treatment furnace according to the present invention will be described with reference to FIGS. 1 to 3.
In these drawings, reference numeral 11 denotes a furnace body, 12 denotes a supply means, and 13 denotes a cooling means.
[0025]
As shown in FIG. 1, the granular heat treatment furnace in this embodiment is a granular material to be processed 1 as a raw material powder, for example, an organic substance (or a precursor that is carbonized by heating or graphitized by further high-temperature heating. ) Powder (carbon powder or the like) for continuously producing carbonized powder or graphite powder, a furnace body 11 for heat-treating the workpiece 1 and supplying the workpiece 1 to the furnace body 11 Supply means 12 for cooling, and cooling means 13 for cooling the workpiece 1 heated in the furnace body 11.
[0026]
The supply means 12 is inserted at the lower end of the hopper 15 that is connected to the connection pipe portion 14 on the upstream side of the furnace main body 11 and stores the workpiece 1, and is movably inserted into the connection pipe portion 14 at the lower end of the hopper 15. A pusher 16 and a cylinder rod 17 having the pusher 16 attached to the tip thereof, and a cylinder 18 for moving the cylinder rod 17 back and forth.
That is, the cylinder rod 17 and the pusher 16 are moved forward and backward by the cylinder 18 so that the workpiece 1 is cut out from the lower end of the hopper 15 and supplied by being pushed into the heating duct 19 of the furnace body 11 through the connecting pipe portion 14. Is set to
[0027]
Thus, by providing the supply means 12 for the workpiece 1 at the inlet of the heating duct 19, the workpiece 1 can be reliably supplied without forming a bridge (arch). For example, a plurality of screw feeders arranged in a row may be adopted.
[0028]
The furnace body 11 is installed in a substantially horizontal direction and forms a heating zone a in which the object to be processed 1 supplied by the supply means 12 is heated in this direction while being heated to degas the generated gas G from the object to be processed 1. And a heat retaining duct 20 that forms a heat retaining zone b that heats the workpiece 1 degassed by the heating duct 19 while keeping it at a constant temperature while feeding.
Each of the heating duct 19 and the heat retaining duct 20 is entirely surrounded by a graphite heater 21 and is sequentially heated to a predetermined temperature as the workpiece 1 moves downstream in the duct. Is set to A heating source other than the graphite heater 21 may be employed.
[0029]
The heating duct 19 is provided with a degassing zone (exhaust opening) 23 that opens above the gas generation region 22 where the generated gas G is generated and discharges the generated gas G to the outside.
The heating duct 19 up to the degassing zone 23 has an internal shape that is wider in width than in the vertical width, and is set so as to facilitate heating and degassing.
[0030]
As shown in FIG. 3, the heating duct 19 has a divergent shape in which the internal shape of the gas generation region 22 spreads laterally toward the downstream side.
The gas vent zone 23 is provided with a plurality of louvers (resistive plates) 24 that are spaced apart from each other in a substantially horizontal direction and prevent the workpiece 1 in the heating duct 19 from rising upward.
Further, a gas collection hood 25 that collects one end of the generated gas G is installed on the upper part of the louver 24, and an exhaust gas duct 26 installed in a chimney shape is connected to the upper end of the gas collection hood 25. ing.
[0031]
Further, the heating duct 19 is a gas introduction mechanism for injecting a small amount of a blown gas N, for example, nitrogen, etc., which is different from the generated gas G, from the outside into the gas generation region 22 to bring the gas collection hood 25 into a slightly positive pressure state. 27. That is, the gas introduction mechanism 27 is provided with a blow nozzle 27a for blowing the blown gas N toward the gas generation region 22 at the downstream end of the heating duct 19, and a supply source of blown gas N (not shown) is supplied to the blow nozzle 27a. Connected and configured.
[0032]
The heat retaining duct 20 is connected to the downstream side of the heating duct 19, and further to the downstream side of the heat retaining duct 20 via a heat insulating connecting portion 28 formed of a heat insulating material, for example, carbon fiber. Is connected to the cooling duct 29 of the cooling means 13.
The heat retaining duct 20 and the cooling duct 29 are installed in the vertical direction with the downstream side facing downward.
[0033]
The heat retaining duct 20 is set so that the cross-sectional area of the workpiece 1 is larger than that of the heating duct 19 and the cooling duct 29.
The cooling means 13 includes a cooling duct 29 that is connected to the downstream end of the heat retaining duct 20 and cools the workpiece 1 while being sent, and a water cooling jacket 30 that surrounds the cooling duct 29. A cooling zone c is formed.
[0034]
At the lower end of the cooling duct 29, there is provided a resistance adding device 31 for applying a slight resistance to the workpiece 1 discharged and lowered downward. The resistance adding device 31 changes the lower end opening diameter of the cooling duct 29 by a remotely operated on-off valve 31a. The resistance adding device 31 prevents the workpiece 1 from flowing out without permission and adjusts the discharge amount. Is.
[0035]
Next, about the heat processing method of the to-be-processed object 1 by the granular material heat processing furnace of this embodiment, [Supply process], [Heating degassing process], [Heat-retaining carbonization process], [Cooling process], and [Discharge process] Each process will be described separately.
[0036]
[Supply process]
First, the workpiece 1 stored in the hopper 15 is cut out by a pusher 16 reciprocated by a cylinder 18 and sent to the upstream end of the heating duct 19 through the connecting pipe portion 14.
[0037]
[Heating degassing process]
The workpiece 1 sent to the heating zone a in the heating duct 19 is heated to a predetermined temperature at which gas is generated by the graphite heater 21 as it moves downstream.
That is, as the object to be processed 1 is heated in sequence, the temperature rapidly rises to a temperature range where gas is generated (800 ° C. to 900 ° C. in the case of carbon powder). Is generated.
The generated gas G escapes from the degassing zone 23 to the upper part through the louver 24, and is collected at one end by the gas collection hood 25 and processed (for example, diffused after being burned) after being collected by the exhaust gas duct 26. The
[0038]
The exhaust gas duct 26 has a chimney to generate a draft (upflow), and can easily discharge the generated gas G. However, the gas introduction mechanism 27 can capture the gas by the blowing gas N blown from the blowing nozzle 27a. Since the inside of the collection food | hood 25 will be in a some positive pressure state, discharge | emission from the exhaust gas duct 26 becomes still easier.
Therefore, the generated gas G easily escapes from the degassing zone 23 and the workpiece 1 does not blow up.
[0039]
Although the workpiece 1 supplied by the pusher 16 is opened in the degassing zone 23, it may be slightly raised, but the louver 24 becomes a resistance to prevent the rise. As described above, the generated gas G can easily escape to the upper part because of the louver structure.
Further, since the gas generation region 22 of the heating duct 19 becomes wider toward the downstream, the swell of the workpiece 1 generated by the supply by the pusher 16 is further suppressed, and the workpiece 1 flows smoothly. It has become.
[0040]
[Heat insulation carbonization process]
The to-be-processed object 1 degassed by the heating duct 19 is sent to the heat retention zone b in the heat retention duct 20 maintained at a temperature of 1100 ° C., and is heated and carbonized. At this time, the workpiece 1 in the heat retaining duct 20 is carbonized while being gradually lowered by gravity because the heat retaining duct 20 is configured vertically.
In addition, since the cross-sectional area of the heat retaining duct 20 is set larger than the front and rear ducts, that is, the heating duct 19 and the cooling duct 29, the workpiece 1 has a lower descending speed and is sufficiently heated. Carbonization takes place.
In addition, when obtaining graphite powder, it is also possible to graphitize the to-be-processed object 1 by maintaining the temperature state at 1500 ° C.
[0041]
[Cooling process]
The workpiece 1 carbonized in the heat retaining duct 20 descends due to gravity, and is sent to the cooling zone c in the cooling duct 29 via the heat insulating connecting portion 28. At this time, the workpiece 1 moving in the cooling duct 29 due to the cooling effect of the cooling jacket 30 is gradually cooled while being lowered. In addition, since the heat insulation connection part 28 is provided between the heat insulation duct 20 and the cooling duct 29, a high temperature heating zone and a low temperature cooling zone do not contact directly, and heat loss decreases.
[0042]
[Discharge process]
The cooled workpiece 1 is lowered and discharged from the lower end of the cooling duct 29. At this time, a slight amount of resistance is applied to the workpiece 1 by the resistance adding device 31, and the discharge amount is appropriately adjusted so as not to flow out without permission.
[0043]
Next, a second embodiment of the granular material heat treatment furnace according to the present invention will be described with reference to FIG.
[0044]
The difference between the second embodiment and the first embodiment is that the heating duct 19 of the first embodiment is horizontally installed throughout, whereas the heating duct 42 in the furnace body 41 of the second embodiment is As shown in FIG. 4, the inner bottom surface 42 a in the gas generation region 43 is an inclined surface having an inclination equal to or less than the repose angle of the workpiece 1 with the downstream side facing downward.
That is, in the granular material heat treatment furnace of the second embodiment, the heating duct 42 in the gas generation region 42 is inclined to the angle of repose or less so that the workpiece 1 is hardly raised by the supply by the pusher 16. be able to.
[0045]
In the present embodiment, since the repose angle of the workpiece 1 is 37 degrees, the inclination angle of the inner bottom surface 42a is set to 30 degrees or less.
If the inner bottom surface 42a is inclined more than the angle of repose, the workpiece 1 slips on its own, and the workpiece 1 cannot be moved sequentially at a constant speed, and the gas venting is insufficient. Inconvenience occurs.
[0046]
【The invention's effect】
The present invention has the following effects.
(1) According to the first particulate heat treatment furnace, the furnace body is installed in a substantially horizontal direction and heated while feeding the object to be processed supplied by the supply means in this direction, and the generated gas from the object to be processed A heating duct that degass the gas, and a heat retaining duct that heats the workpiece degassed in the heating duct while maintaining the temperature at a constant temperature, and the heating duct has a temperature at which generated gas is generated. Since a discharge opening for discharging the generated gas to the outside is provided at the top of the generation area, the gas generated in the gas generation area escapes upward from the discharge opening located at the top and is smoothly discharged to the outside. Therefore, it is possible to prevent the workpiece from being blown up and to perform stable operation.
[0047]
(2) According to the second granular heat treatment furnace, since the heating duct has an internal shape whose width is wider than the vertical width, it becomes easy to heat the object to be processed and facilitate gas escape. Can do.
[0048]
(3) According to the third granular heat treatment furnace, the plurality of resistance plates are arranged in the discharge opening so as to be spaced apart from each other in the substantially horizontal direction and prevent the workpiece in the heating duct from rising upward. Since it is provided, the resistance of the resistance plate can prevent the workpiece to be sent into the heating duct from rising, and the generated gas can escape upward from between the resistance plates.
[0049]
(4) According to the fourth granular heat treatment furnace, the heating duct is provided with a gas introduction mechanism for injecting a gas different from the generated gas from the outside into the gas generation region, so that it was blown into the gas generation region. With the gas, the gas generation region and the periphery of the discharge opening can be slightly positive pressured to facilitate the discharge of the generated gas to the outside.
[0050]
(5) According to the fifth granular heat treatment furnace, the heating duct has a divergent shape in which the internal shape in the gas generation region extends laterally toward the downstream side, so that the area becomes wider toward the downstream side. Therefore, the object to be processed sent into the heating duct is unlikely to rise upward and flows smoothly.
[0051]
(6) According to the sixth granular material heat treatment furnace, the heating duct has an inclined surface with an inner bottom surface in the gas generation region having an inclination below the repose angle of the workpiece with the downstream side facing downward. Therefore, the upward swell of the workpiece sent into the heating duct can be almost eliminated. In addition, it prevents the inconvenience that the object to be processed slips by itself due to the inclination, and the object to be processed cannot be moved sequentially at a low speed, or the gas is not sufficiently vented without being heated sufficiently. can do.
[0052]
(7) According to the seventh granular material heat treatment furnace, the cooling means includes a cooling duct that is connected to the downstream end of the heat retaining duct and cools the object to be processed, and the heat retaining duct and the cooling duct are disposed downstream. Since it is installed in a substantially vertical direction or in an inclined state with the side down, the degassed workpiece can be moved (down) by gravity to the downstream side (downward). In addition, the combination of a horizontally installed heating duct and a vertical or inclined heat retaining duct and cooling duct can reduce the overall height of the device, making it more compact and improving maintainability. To do.
[0053]
(8) According to the eighth granular heat treatment furnace, the cross-sectional area of the granular material in the heat retaining duct is set larger than that of the heating duct and the cooling duct. The descent speed is reduced, the workpiece can be sufficiently heat-treated and heat-treated, and the overall duct height of the heat-retaining duct can be reduced, so that it is inexpensive, further downsizing and improved maintainability. be able to.
[0054]
(9) According to the ninth granular heat treatment furnace, the heating duct and the cooling duct are connected to each other through the heat insulating connecting portion formed of a heat insulating material so as to be able to circulate. The duct and the low-temperature cooling duct are not in direct contact with each other, heat loss is reduced, and the heating efficiency in the heat retaining duct and the cooling efficiency in the cooling duct are improved.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a first embodiment of a granular material heat treatment furnace according to the present invention.
FIG. 2 is a perspective view showing a first embodiment of a granular material heat treatment furnace according to the present invention.
FIG. 3 is a cross-sectional view taken along line XX in FIG.
FIG. 4 is a longitudinal sectional view of an essential part showing a second embodiment of a granular material heat treatment furnace according to the present invention.
FIG. 5 is a longitudinal sectional view showing a conventional example of a granular material heat treatment furnace according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 To-be-processed object 11 and 41 Furnace main body 12 Supply means 13 Cooling means 19 and 42 Heating duct 20 Thermal insulation duct 22 and 43 Gas generation area 23 Degassing zone (exhaust opening part)
24 louvers
27 Gas introduction mechanism 28 Insulation connection part 42a Inner bottom G of gas generation region Generated gas N Blowing gas

Claims (8)

A furnace body for heat-treating the granular object,
Supply means for supplying the workpiece to the furnace body;
A granular heat treatment furnace provided with a cooling means for cooling an object to be processed heat-treated in the furnace body,
The furnace body is installed in a horizontal direction and heated while feeding the object to be processed supplied by the supply means in the direction, and a heating duct for degassing the generated gas from the object to be processed,
A heat-retaining duct that heats while keeping a constant temperature state while feeding the object degassed by the heating duct,
The heating duct includes a discharge opening for discharging the generated gas to the outside at the upper part of the gas generation region where the generated gas is generated .
The discharge opening is provided with a plurality of resistance plates that are arranged in the horizontal direction so as to be spaced apart from each other and prevent the workpiece in the heating duct from rising upward. Heat treatment furnace.   2. The granular heat treatment furnace according to claim 1, wherein the heating duct has an internal shape having a width wider than a vertical width. In the granular material heat treatment furnace according to claim 1 or 2,
The heating duct is equipped with a gas introduction mechanism for blowing a gas different from the generated gas from the outside into the gas generation region . In the granular material heat treatment furnace according to any one of claims 1 to 3,
The powder heat treatment furnace characterized in that the heating duct has a divergent shape in which the internal shape in the gas generation region extends laterally toward the downstream side . In the granular material heat treatment furnace according to any one of claims 1 to 4,
The heat treatment duct is a granular heat treatment furnace characterized in that an inner bottom surface in the gas generation region has an inclined surface with an inclination equal to or less than an angle of repose of the object to be processed with a downstream side downward . In the granular material heat treatment furnace according to any one of claims 1 to 5,
The cooling means includes a cooling duct that is connected to a downstream end of the heat retaining duct and cools the workpiece while being sent,
The heat- treating duct and the cooling duct are installed in a vertical direction or in an inclined state with the downstream side facing down, and a granular heat treatment furnace characterized by the above. In the granular material heat treatment furnace according to claim 6,
The heat retention duct is a granular heat treatment furnace characterized in that a flow passage cross-sectional area of the granular material is set larger than that of the heating duct and the cooling duct . In the granular material heat treatment furnace according to claim 6 or 7,
The heat treatment duct and the cooling duct are connected to each other by a heat insulation connecting portion formed of a heat insulating material so that the object to be treated can be distributed .

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