JP2002303416A - Induction heating type continuous melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating type continuous melting furnace which is optimum to melt in a small scale and which can continuously melting without necessity of a special knowledge and a skill by a simple operation of the furnace. SOLUTION: The induction heating type continuous melting furnace inputs a material to be melted from one end of the furnace, melts the material to be melted therein and discharges the molten material from another one end of the furnace. The furnace comprises a tubular heating material 1 containing ZrB2 of 50 mass% or more. In this furnace, the length of the tube of the heating material is 5 times as large as the inner diameter of the tube of the heating material or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace for melting waste and the like, and more particularly to a ash melting furnace suitable for small-scale continuous processing.

[0002]

2. Description of the Related Art Dioxins and harmful metals are contained in fly ash collected from dust collectors of municipal waste and industrial waste incinerators, and ashes (main ash) discharged from under incinerators. Ash melting furnaces are attracting attention as a means for reducing the volume and detoxifying the ash.

[0003] As a ash melting furnace, a gasification melting furnace in which a part of refuse is gasified and separated by heating in an oxygen-deficient atmosphere, and the ash is melted by burning the gas,
Combustion melting furnace that burns heavy oil and fuel gas and melts by the radiant heat, electric melting furnace that uses arc and plasma,
Alternatively, a coke bed type melting furnace or the like is known.

[0004] These melting furnaces are suitable for continuously processing a large amount of material to be melted, but there is a problem when used as a small melting furnace having a throughput of several tons per day. For example, combustion-type melting furnaces have a problem in that a large amount of exhaust gas is emitted, which increases equipment costs and operating costs for the treatment.In addition, gasification and melting furnaces, plasma-type melting furnaces, and arc-type melting furnaces have problems. Furnaces are difficult to make on a small scale because of the equipment.
Because it requires coke, it is not practical on a small scale.

As a method suitable for small-scale melting, there is an induction heating type melting furnace. Although the induction heating type melting furnace has the advantage of being easy to control, it is necessary to put a heating element such as carbon or a carbon-SiC composite into the furnace to melt electric insulators such as incineration ash by induction heating. is there. Such a heating element introduced into the furnace has a problem in that the running element is quickly worn out. Furthermore, since the structure of the furnace is limited to a crucible shape in order to put the heating element into the furnace, continuous melting is difficult,
There was also a problem in terms of throughput.

In order to solve the problem of introducing a heating element into a furnace, Japanese Patent Application Laid-Open No. 9-206797 discloses an induction heating method in which the furnace body is made of conductive ceramics and made of ZrB ₂ having corrosion resistance, and the furnace body is a heating element. There has been proposed a method of melting and solidifying sludge using the above method.

However, in the proposed apparatus, the heating element has a crucible shape instead of a cylindrical shape, so that it cannot be continuously melted and has a problem in terms of processing amount. Visual confirmation work is required, and there is a problem in operation costs such as labor costs. Furthermore, since the process is a batch process rather than a continuous process, there is a problem that the amount of heat for raising the temperature each time is lost, and the power consumption per melt is increased.

[0008]

DISCLOSURE OF THE INVENTION The present invention relates to a tubular heat generating apparatus which is most suitable for small-scale melting, is simple in furnace operation, does not require special knowledge and skill, and can be continuously melted. An object of the present invention is to provide an induction heating continuous melting furnace made of a body.

[0009]

The present invention SUMMARY OF] is a induction heating type continuous melting furnace which the melt is discharged from another end of which is melted internally enters from one end of the furnace the furnace, the ZrB ₂ 50
A tubular heating element containing at least 5% by mass of the heating element, wherein the length of the tube of the heating element is at least 5 times the inner diameter of the tube, and the material to be melted is melted on the inner wall surface of the heating element. An induction heating type continuous melting furnace is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The induction heating type continuous melting furnace of the present invention (hereinafter simply referred to as the present melting furnace) has a tubular heating element containing 50% by mass or more of ZrB ₂ (hereinafter simply referred to as “%”). And melting the object to be melted on the inner wall surface of the heating element.

The content of ZrB _{2 in} the tubular heating element is 50%
If it is less than 3, the conductivity may be insufficient. Zr
It is preferable that the content of B ₂ is 50 to 99.5%. More preferably a content of ZrB ₂ 70 to 99%. As ZrB ₂ , a sintered body is preferable in terms of corrosion resistance, conductivity, mechanical strength, and the like, and castable or the like may be used in combination.

FIG. 1 shows the basic configuration of the present melting furnace. FIG. 1 is a schematic diagram of a vertical sectional view of the present melting furnace. In the figure, 1 is Z
a tubular heating element containing 50% or more of rB ₂ (hereinafter referred to as the present heating element); In general, cooling water flows inside the copper tube. 5 is a heat insulating material, 6 is an outer furnace body. It should be noted that the material to be melted, such as main ash and fly ash, is supplied in a fixed amount by a supply device (not shown). FIG. 1 shows a case where the heating element is divided into four parts in the axial direction.

In the melting, an electric current is caused to flow through the induction coil 4 to cause an induced current to flow through the heating element 1 so that the material to be melted is set to 1300 to 1300.
Heat to 1500 ° C. Note that dioxin in the ash is decomposed, and harmful metals are dissolved in glass to make them harmless. Further, after being discharged, the melt is quenched and solidified with water as required, and becomes slag. The unburned components in the ash are burned in the melting process to generate exhaust gas, but the exhaust gas is exhausted downstream.

In the present heating element, the length of the tube is at least five times the inner diameter of the tube. If the length of the tube is less than 5 times the inner diameter of the tube, it is difficult for the ash melted on the surface of the tube to mix with the unmelted ash near the center of the tube, and the unmelted ash may be discharged. Yes, it must be melted longer than necessary to prevent it.

The heating element is preferably a straight pipe in order to prevent stagnation inside the pipe, but is not necessarily limited to this. In this heating element,
The inner diameter of the tube is preferably between 20 and 160 mm. More preferably, it is 40 to 100 mm. The inner diameter of the tube is 20
If the diameter is less than mm, the amount of processing is reduced and the number of heating elements is required accordingly, the ash charging device becomes complicated, and there is a problem of aggregation of the melt. On the other hand, when the inner diameter exceeds 160 mm, it becomes difficult to manufacture the pipe, and thus each is not preferable.

The heating element may be formed as a single unit, but the heating element may be divided to reduce thermal stress and to reduce the manufacturing cost of the heating element. When the heating element is divided, it is preferable to divide the tube into a ring shape (ring shape) in a direction perpendicular to the axis as illustrated in FIG. 1 since the induction current flowing in the circumferential direction is not affected. In addition, it is preferable to divide in advance in the direction perpendicular to the axis, because even if one of them breaks in the direction parallel to the axis and the induced current stops flowing and no heat is generated, the influence is not exerted on the whole.
When divided, the length of the pipe refers to the combined length.

When the inner diameter of the heating element is large, the heating element
May also be divided into a plurality in the circumferential direction. An example is shown in FIG.
You. In FIG. 2, a rod-shaped conductive refractory 7 is arranged in parallel to a cylinder.
And is surrounded by a non-conductive refractory 8. Conductivity
Refractory 7 is ZrB_TwoIs preferably 55% or more.
ZrB when conductive refractory 7 and non-conductive refractory 8 are combined
_TwoMust be contained at least 50%. In this case,
It may be divided in the direction perpendicular to the axis as needed.

If an uneven surface or a baffle plate is provided on the inner surface of the heating element for efficient melting, mixing of the molten material with the unmelted material is promoted, and the unmelted material is accelerated. It is preferable because the residual of the melt can be prevented.

In the present invention, the number of the heating elements is not limited to one, and two or more heating elements may be used in parallel in accordance with the processing amount. In this case, as shown in FIGS. 3 and 4, a plurality of main heating elements can be arranged in one induction coil. 3 and 4 show the case where the number of the heating elements is four. FIG. 3 is a schematic view of a transverse sectional view of the present melting furnace, and FIG. 4 is a schematic view of a longitudinal sectional view of the present melting furnace.

When a plurality of the heating elements are used side by side, if the frequency and voltage of the induction coil are appropriately selected, the plurality of heating elements can be simultaneously heated at a uniform temperature. Further, it is preferable to arrange a plurality of heating elements at the same distance from the induction coil, that is, on the same circumference, because a difference in temperature between the heating elements can be reduced.

In the present invention, the heating element is used in a nearly horizontal state, but it is arbitrarily selected depending on the viscosity of the melt and the fluidity of the ash, such as a downward slope or an upward slope. Also,
In the present invention, it is not necessary to put the heating element into the furnace, but a heating element such as carbon or metal may be partially mixed into the material to be melted for auxiliary purposes.

Further, when operating the present melting furnace, it is preferable to increase the flow rate of the material to be melted to the heating element because heat exchange between the material to be melted and the heating element is promoted. There is no particular limitation on the heat insulating material outside the heating element,
Examples thereof include silicon carbide, silicon nitride, carbon, high-zirconia electroformed refractories, alumina-based refractories, and magnesia-based refractories.

The outer furnace body outside the heat insulating material is not particularly limited, and examples thereof include silicon carbide castables, alumina castables, aluminum mullite castables, heat-insulated chamotte castables, and heat-insulated bricks.

[0024]

EXAMPLE Zirconium boride (including 98% of ZrB ₂ ) has an outer diameter of 100 mm, an inner diameter of 78 mm, and a length of 150 m.
Four pipes of m were connected in series to prepare a heating element having a length of 600 mm. Note that a compressive force was applied in the axial direction so that the melt did not leak from the joint of the pipes. The tubular heating element was held substantially horizontally, and incineration ash of industrial waste was charged at 15 kg / h from one end, and the molten material was discharged as molten slag (about 400 ° C.) from the other end. A high-frequency current having a frequency of 3 kHz was passed through the induction coil.

For comparison, the same material has an inner diameter of 200 mm,
A crucible having an outer diameter of 224 mm and a depth of 240 mm was manufactured.
The inner surface area of the crucible and the inner surface area of the pipe are almost the same.

In order to check the influence of the residue, the starting and stopping and reheating were repeated 5 times while leaving a part of the melt. As a result, when the pipe was used, reheating could be performed without any problem. However, when the crucible was used, it took time for the residue near the center to melt, and several small cracks entered the crucible during the fifth heating. In addition, when the both apparatuses were operated for 5 hours and the processing amounts were compared, the processing amount of the pipe was about 3 when the processing amount of the crucible was set to 1.

[0027]

According to the present invention, the heating element is composed of 5 ZrB ₂ .
Since it contains 0% or more, it has excellent corrosion resistance and also has conductivity, so that a melting furnace can be configured as a tubular heating element. Therefore, the continuous melting process by the induction heating method can be performed, and the processing amount is large.

Furthermore, since the length of the tubular heating element is set to be at least five times the inner diameter, heat exchange between the object to be melted and the heating element is promoted, and the heating and melting can be performed efficiently. The amount of the melt remaining in the melting furnace can be reduced. Further, since the molten material can be continuously discharged, the container does not need to be tilted every time the molten material is charged and discharged, unlike the crucible method, so that the productivity is high.

Further, by dividing the heating element in the axial direction, damage due to thermal stress or the like is prevented, and even if the element is damaged, the influence is localized and the entire furnace cannot be induction-heated. prevent.

Further, since the melting method is of the induction heating type, the melting state can be easily controlled by adjusting the output of the control panel, so that special knowledge and skill are not required for the operation as in the past.
It can be operated with simple operation.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a melting furnace using divided heating elements.

FIG. 2 is a schematic perspective view of a heating element divided in a circumferential direction.

FIG. 3 is a schematic cross-sectional view of a cross section of the present melting furnace using an undivided heating element.

FIG. 4 is a schematic cross-sectional view of a vertical section of the present melting furnace using a heating element that is not divided.

[Explanation of symbols]

 1: Tubular heating element 2: Injection direction of ash (molten material) 3: Discharge direction of melt 4: Induction coil 5: Insulation material 6: External furnace body 7: Conductive refractory 8: Non-conductive refractory

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) H05B 6/10 371 H05B 6/10 371 F term (reference) 3K059 AA08 AB16 AD03 AD32 AD40 3K061 AB03 AC03 NB01 4K050 AA07 BA06 CA05 CD07 CD08 CF01 CF11 CG27 4K063 AA04 AA12 AA19 BA13 CA08 FA36 FA43

Claims (2)

[Claims] 1. A induction heating type continuous melting furnace is discharged from another end of the melt is melted internally enters from one end of the furnace the furnace, heating elements of the tubular containing ZrB ₂ 50 mass% Wherein the length of the tube of the heating element is at least 5 times the inner diameter of the tube, and the material to be melted is melted on the inner wall surface of the heating element. 2. The induction heating type continuous melting furnace according to claim 1, wherein the tubular heating element is divided.