JP3978657B2 - Induction heating type distillation furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction heating type carbonization furnace used for carbonization treatment of polymer wastes, empty cans and the like.
[0002]
[Prior art]
Induction heating type carbonization furnaces are provided with an induction heating coil outside the furnace body. When the magnetic flux generated by the induction heating coil is linked to the furnace body, an induction current is generated in the furnace body so as to cancel the interlinkage magnetic flux. The furnace body generates heat due to the resistance loss due to the induced current. The to-be-distilled material in the furnace is heated and dried by radiant heat and heat conduction from the furnace body. FIG. 4 shows a conventional configuration of such an induction heating type carbonization furnace. FIG. 4 (A) is a longitudinal perspective view, and FIG. 4 (B) is a sectional view taken along the line BB. In FIG. 4, the dry distillation furnace includes an induction heating coil 2 that heats the furnace body 1 by induction heating outside the furnace body 1 that is a hollow cylindrical body with a bottom. After the to-be-distilled material 3 is put into the furnace body 1 and an inert gas such as nitrogen is sealed, when the furnace body 1 is induction-heated by the heating coil 2, the to-be-distilled object 3 is irradiated with heat or heat from the incubator. After being heated by conduction and reaching a predetermined temperature, for example, 550 ° C., it is subjected to dry distillation treatment by being held at that temperature for a certain period of time.
[0003]
[Problems to be solved by the invention]
FIG. 5 shows temporal changes in the temperature of the dry matter at the center P point and the outer periphery Q point in the furnace when the dry distillation object 3 is carbonized in the carbonization furnace of FIG. As shown in FIG. 5, the temperature of the to-be-dried product 3 is initially high on the outside and low on the inside. This is because the to-be-distilled material 3 at the outer peripheral portion is quickly heated by radiant heat and heat conduction from the furnace body 1, but the center is heated only by heat conduction from the surrounding to-be-dried material 3, so that the temperature rises. This is because a delay occurs. As time passes, the outside heat is transferred to the inside, and the to-be-dried product 3 has a uniform temperature distribution at substantially the same temperature as the furnace body 1. Incidentally, to-be-dried materials 3 such as polymer wastes (plastics and rubbers) and empty cans have poor thermal conductivity compared to solid metals. This temperature rise delay in the center of the furnace is related to the distance from the furnace wall, and becomes more noticeable as the distance from the furnace wall increases. For this reason, there is a problem that temperature control is difficult, the heating temperature and the holding time vary depending on the location, and the dry distillation becomes uneven.
[0004]
Accordingly, an object of the present invention is to promote the temperature rise of the material to be dried in the center of the furnace and increase the amount of heat transmitted to the material to be dried, thereby improving the quality of the dry distillation process and shortening the processing time.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention includes an induction heating coil outside the furnace body, and induction heating the furnace body by flowing an excitation current through the induction heating coil. An induction heating type dry distillation furnace in which a carbonized product is subjected to carbonization treatment, and the inert gas is forcibly circulated through the product to be distilled , between the induction heating coil and an outer wall surface of the furnace body A heat insulating wall that forms a gap is provided, and the inert gas that has flowed through in the axial direction of the furnace body through the to-be-dried product is recirculated to the to- be-dried product through the gap. 1). According to the present invention, the inert gas in the furnace is forcibly circulated, so that the heat of the hot part of the dry matter is taken away by this gas and moved to the low temperature part. Can raise the temperature. Moreover, the amount of heat transfer by radiation and heat conduction from a furnace body to a to-be-dried material increases because the temperature of the high-temperature to-be-dried material in contact with a furnace body falls.
[0006]
Furthermore, the heat insulating wall that forms a gap with the outer wall surface of the furnace body is heated to a high temperature by radiant heat from the furnace wall. Therefore, the reflux gas is heated to a high temperature by the high-temperature furnace wall and the heat insulation wall by refluxing the inert gas after passing through the to-be-distilled material through the gap between the outer wall surface of the furnace body and the heat insulation wall. The heating time of the to-be-distilled material by heat transfer from gas is shortened. Also, by circulating the inert gas after passing through the object to be dried through the gap outside the furnace, it is possible to prevent the circulating gas from recirculating through the shortcut and ensure that the heated gas is covered. Flow through the dry distillate.
[0007]
Fan for forced circulation of the inert gas, it is preferable for installation in the furnace (claim 2). Installing a fan outside the furnace increases heat loss and complicates the heat insulation structure. Further, the fan is preferably arranged so as to push and blow air against the material to be dried, so that the fan is less polluted by the reflux gas than the sucking air (Claim 3 ).
[0008]
Further, the induction heating type carbonization furnace of claim 1 is an upright cylindrical furnace body, a fan installed vertically with the discharge side facing up at the bottom of the furnace body, and a ventilation installed horizontally above the fan. A cylindrical heat insulating wall installed coaxially with the furnace body inside the induction heating coil by forming a gap between the support to be dried and the outer wall surface of the furnace body, and the suction side of the fan it is possible to adopt a configuration provided with a ventilation guide that communicates with the gap (claim 4).
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 shows a longitudinal sectional view of the induction heating type carbonization furnace according to the present invention. Before describing FIG. 2, for the sake of convenience of explanation, a configuration before reaching FIG. 2 excluding the requirement of “the heat insulating wall forming the gap” from the configuration of FIG. 2 will be described based on FIG. 1. In addition, the same code | symbol shall be used for the part corresponding to a prior art example. In FIG. 1, a furnace body 1 made of a magnetic material (steel) is an upright cylindrical body having a flange at an upper end portion, and is supported in a structure 4 that also serves as a heat insulating wall. The structure 4 is an upright cylindrical body with a bottom that is coaxial with the furnace body 1 and is made of, for example, a castable refractory. The upper surface of the furnace body 1 is closed with a lid 5 made of steel plate, and a suspension bolt 6 is attached to the lid 5. The outside of the lid 5 is covered with a heat insulating material 7.
[0010]
At the center of the bottom of the furnace body 1, a fan 8 is vertically installed with the discharge side facing up, and a to-be-dried object support 9 for supporting the to-be-dried object 3 is horizontally installed above the fan 8. The to-be-dried material support 9 is comprised, for example with a punching metal, a metal-mesh, a grating | lattice, etc. so that an inert gas may pass freely. The fan 8 is surrounded by a conical ventilation guide 10, and the ventilation guide 10 is opened at the lower side (suction side) of the fan 8, and the suction side of the fan 8 is dry-distilled between the peripheral edge and the furnace body 1. An annular air passage 11 communicating with the peripheral edge of the support 9 is formed. The fan 8, the to-be-dried material support 9, the ventilation guide 10, etc. are made of stainless steel. The fan 8 is driven from the outside of the structure 4 by a motor 12. The induction heating coil 2 is disposed outside the structure 4 and is excited by an excitation power source 13. The temperature of the furnace body 1 is detected by a temperature sensor 14 made of, for example, a thermocouple, and the excitation power source 13 is induction-heated so that the temperature of the furnace body 1 is maintained at a certain dry distillation temperature, for example, 550 ° C. based on the detection signal. The electric power supplied to the coil 2 is controlled.
[0011]
The operation of the carbonization furnace of FIG. 1 is carried out by loading an object 3 to be dried, such as an empty can, on the support 9 to be distilled, replacing the inside with an inert gas such as nitrogen or argon, and then induction heating coil. 2 is energized and at the same time the fan 8 is activated. The magnetic flux generated by the excitation of the induction heating coil 2 passes through the structure body 4 and is linked to the furnace body 1 to generate an induction current in the furnace body 1. Thereby, the furnace body 1 generates heat, and heats the dry matter 3 in the furnace. In that case, the to-be-dried product 3 adjacent to the furnace body 1 is heated by both radiant heat and heat conduction from the furnace body 1 and rapidly rises in temperature. On the other hand, since the to-be-distilled material 3 of the center part in a furnace is heated only by the heat conduction from the to-be-distilled material 3 of the outer side, it heats up late. The temperature increase delay is larger as the temperature is closer to the center of the furnace.
[0012]
On the other hand, when the fan 8 is started, the inert gas in the furnace flows in the axial direction (downward) of the furnace body 1 through the to-be-dried material 3 in the vicinity of the furnace wall as shown by the arrow in FIG. Then, the inert gas sucked into the fan 8 and discharged from the fan 8 flows in the reverse direction (upward) through the to-be-dried material 3 in the center of the furnace, and reverses again to pass through the to-be-dried material 3 near the furnace wall. It circulates so as to flow through in the axial direction (downward) of the furnace body 1. In this circulation, the inert gas that has taken heat from the high temperature dry matter 3 in the vicinity of the furnace wall gives this heat to the low temperature dry matter 3 in the center of the furnace by heat transfer to raise the temperature. As a result, heat transfer is performed from the high temperature dry matter 3 near the furnace wall to the low temperature dry matter 3 in the center of the furnace using an inert gas as a medium, and the rise of the dry matter 3 in the center of the furnace is increased. The temperature is urged.
[0013]
In addition, the to-be-dried product 3 in the vicinity of the furnace wall is cooled by the low-temperature circulating gas after flowing through the center of the furnace, and the temperature is lowered. As a result, the temperature difference between the dry distillation object 3 near the furnace wall and the furnace body 1 increases, and the amount of heat transfer from the furnace body 1 to the dry distillation object 3 by radiation and heat conduction increases. Since the exciting current for heating the furnace body 1 is controlled so as to maintain the temperature of the furnace body 1 at a constant (550 ° C.), the input power also increases as the amount of heat transfer from the furnace body 1 to the dry matter 3 increases. . From the above, the circulation of the inert gas in the furnace improves the heating rate of the to-be-dried product 3 in the center of the furnace, and the input power at the initial stage of operation is expanded. The carbonization time is shortened. Moreover, since the temperature of the dry distillation product in the vicinity of the furnace wall and the central part in the furnace is averaged through the circulating gas, a high quality dry distillation process with little dry distillation unevenness is achieved.
[0014]
Figure 2 is a longitudinal sectional view of an induction heating type dry distillation furnace showing an embodiment according to the present invention having an improved structure of FIG. 2 is different from FIG. 1 in that an annular gap 15 is formed between the outer wall surface of the furnace body 1 and the structure (heat insulating wall) 4. Square flow windows 16 and 17 communicating between the inside and the gap 15 are provided. A plurality of flow windows 16 and 17 are provided in the circumferential direction. The space between the peripheral edge of the ventilation guide 10 and the furnace body 1 is closed. In FIG. 2, when the fan 8 is driven, the inert gas circulates as shown by the arrows in the figure. That is, in this case, the inert gas that has flowed upward in the axial direction of the furnace body 1 through the to-be-dried product 3 in the center of the furnace returns to the furnace through the flow window 16, the gap 15, and the flow window 17. Sucked into fan 8.
[0015]
Thus, the heat insulating wall 4 facing the furnace wall is heated to a high temperature substantially equal to the furnace body temperature by radiant heat from the furnace wall that has been induction-heated. Therefore, the inert gas passing through the gap 15 receives heat from the two surfaces of the high-temperature furnace body 1 and the structure body 4 and is heated to a high temperature to enter the furnace. Accordingly, the to-be-dried product 3 in the center of the furnace through which the high-temperature gas flows is also heated more rapidly than the embodiment of FIG.
[0016]
Further, in the embodiment according to the present invention shown in FIG. 2, the circulation gas suction port (flow window) 16 is opened above the dry matter 3 so that the gas discharged from the fan 8 is always covered. It does not flow around the dry distillate 3 and short-circuit to the suction side of the fan 8 on the way. In FIG. 1, when the draft resistance of the to-be-distilled material 3 is large, as shown by the broken line arrow, before the discharge gas flows through the to-be-distilled material 3, it makes a U-turn on the way and goes to the suction side of the fan 8. there is a possibility. In that regard, in the embodiment shown in FIG. 2, the discharge side and the suction side of the fan 8 are completely separated via the gap 15, so there is no shortcut.
[0017]
FIG. 3 shows temporal changes in the temperature of the dry distillation product at the center P point and the outer periphery Q point (see FIG. 4B) in the dry distillation furnace of FIG. The conventional example of FIG. 4 (see FIG. 5) is also shown by a broken line. As shown by the solid line in FIG. 3, according to the embodiment of FIG. 2, the rise in temperature rise at the outer peripheral portion Q point becomes faster than before due to the increase in the initial input power, and from the vicinity of the furnace wall to the center of the furnace Due to the heat transfer using the circulating gas as a medium, the temperature rise at the center P point in the furnace rises at almost the same speed as that at the outer periphery Q point.
[0018]
Furthermore , in the embodiment of FIG. 2, the fan 8 is installed in a furnace. Therefore, heat loss is less than when the fan 8 is installed in, for example, a bypass duct outside the furnace, and heat insulation of the bypass duct is unnecessary. Further, the fan 8 is installed so that the air to be dried 3 is pushed into the dry matter 3, that is, the discharge side of the fan 8 faces the dry matter 3. Therefore, the fan 8 is less polluted by the reflux gas than the case where the suction air is blown, that is, the suction side of the fan 8 faces the dry distillation object 3.
[0019]
【The invention's effect】
As described above, according to the present invention, the inert gas is circulated in the furnace, thereby reducing the difference in the rate of temperature rise between the inner periphery of the furnace and the center part in the initial operation and increasing the input power. Thus, the carbonization time can be shortened. In addition, since the temperature difference between the inner and outer peripheral parts of the furnace is reduced, dry distillation unevenness is reduced, and high-quality dry distillation treatment is realized. Furthermore, the heat insulating wall that forms a gap with the outer wall surface of the furnace body is heated to a high temperature by radiant heat from the furnace wall. Therefore, the reflux gas is heated to a high temperature by the high-temperature furnace wall and the heat insulation wall by refluxing the inert gas after passing through the to-be-distilled material through the gap between the outer wall surface of the furnace body and the heat insulation wall. The heating time of the to-be-distilled material by heat transfer from gas is shortened. Also, by circulating the inert gas after passing through the object to be dried through the gap outside the furnace, it is possible to prevent the circulating gas from recirculating through the shortcut and ensure that the heated gas is covered. Flow through the dry distillate.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an induction heating type carbonization furnace relating to a configuration before reaching FIG. 2 of the present invention.
FIG. 2 is a longitudinal sectional view of an induction heating type carbonization furnace according to an embodiment of the present invention.
FIG. 3 is a diagram showing a temporal change in the temperature of a dry matter in the dry distillation furnace of FIG. 2;
4A is a longitudinal sectional view of a conventional induction heating type carbonization furnace, and FIG. 4B is a sectional view taken along the line BB of FIG.
FIG. 5 is a diagram showing a temporal change in the temperature of a material to be distilled in the carbonization furnace of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Furnace 2 Induction heating coil 3 To-be-dried thing 4 Heat insulation wall 8 Fan 9 To-be-dried object support 10 Ventilation guide 11 Ventilation path 13 Excitation power supply 14 Temperature sensor 15 Crevice 16 Flow-through window 17 Flow-through window

Claims (4)

An induction heating coil is provided outside the furnace body, and the furnace body is induction-heated by passing an exciting current through the induction heating coil, and a dry distillation treatment is performed on a dry matter in a furnace in an inert gas atmosphere, and the inert gas Is an induction heating type carbonization furnace in which forced circulation is performed through the to-be-distilled material ,
A heat insulating wall that forms a gap between the induction heating coil and the outer wall surface of the furnace body is provided, and the inert gas that has flowed in the axial direction of the furnace body through the dry matter is passed through the gap. An induction heating type carbonization furnace characterized by being refluxed to the dry distillation product . Induction heating type dry distillation furnace according to claim 1 Symbol mounting, characterized in that it has established a fan for forced circulation of the inert gas into the furnace. The induction heating type carbonization furnace according to claim 2, wherein the fan is arranged so as to be pushed into the dry matter and blown. An upright cylindrical furnace body, a fan installed vertically at the bottom of the furnace body with the discharge side up, a breathable dry matter support installed horizontally above the fan, and an outside of the furnace body A cylindrical heat insulating wall that is coaxially installed with the furnace body inside the induction heating coil with a gap formed between the wall surface and a ventilation guide that communicates the suction side of the fan with the gap. The induction heating type carbonization furnace according to claim 1 .

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