Melting furnace

Abstract

To provide a melting furnace, even if low melting point metals such as copper and aluminum are included in a treatment object of a melting furnace, capable of preventing such a situation that the low melting metals and slag infiltrate to the depths through a joint part of a refractory brick in a furnace bottom part at high precision.SOLUTION: A melting furnace 1 is obtained by forming side walls 2 and a bottom wall 3 with prescribed thicknesses at the inside of an outer steel shell 6 formed into a bottom cylindrical shape with a prescribed size. Then, a furnace bottom part of the melting furnace 1 is buried with a circumferentially weir-fitted large sized precast block 4 as a recessed integrated refractory having a planer area larger than that of circumferential refractory blocks and provided with a weir at an outer circumference.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an industrial furnace (i.e., a melting furnace) such as a dielectric heating type or a gas burner type used for melting waste or incineration ash of waste.

Background Art

[0002] Waste is incinerated, and the incineration ash is finally discarded in a landfill or the like. However, since the disposal sites such as landfill are limited, it is desired to reduce the volume of the incineration ash before disposal. Therefore, a melting furnace for melting incineration ash of waste is widely used. Further, as such a melting furnace, a cylindrical side wall having a certain thickness is formed by assembling refractory bricks inside the peripheral surface of a bottomed cylindrical metal container (outer shell iron skin), and a bottom wall is formed by assembling refractory bricks on the furnace bottom of the metal container by a construction method such as "hollow stacking" of refractory bricks. Dielectric heating type and gas burner type melting furnaces are known.

[0003] In addition, among melting furnaces for melting waste or incineration ash of waste, in order to prevent damage to the furnace bottom and consumption in a short period due to harmful substances such as heavy metals and chlorine contained in the incineration ash with an inexpensive configuration, the bottom wall is made of a first layer composed of refractory bricks of a refractory material excellent in heat resistance, wear resistance, etc., and a second layer composed of refractory bricks of a refractory material cheaper than the first layer. A two-layer structure is also known (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in conventional melting furnaces like the one described in Patent Document 1, although damage to refractory bricks by harmful substances and rapid wear can be suppressed, if the material being processed in the melting furnace contains low-melting-point metals such as copper and aluminum, the molten material and slag of these low-melting-point metals can penetrate deep into the joints between the refractory bricks in the bottom wall (usually formed by mortar or castable material), potentially damaging the metal container.

[0006] Another method to prevent such a situation is to place large precast blocks in the bottom wall to eliminate joints in a certain area. However, this method cannot prevent molten material or slag of low-melting-point metals accumulated on the large precast blocks from moving horizontally (flowing sideways) and penetrating deep into the joints on the sides of the large precast blocks.

[0007] The object of the present invention is to solve the problems of the conventional melting furnaces described above and to provide a practical melting furnace that can prevent, with high precision, the molten material and slag of low-melting-point metals such as copper and aluminum from penetrating deep into the furnace through the joints of the refractory bricks at the bottom, even when these metals are included in the material being processed. [Means for solving the problem]

[0008] The invention described in claim 1 of the present invention is a melting furnace for melting waste or incinerated waste ash, characterized in that a bottom wall is provided at the bottom of the furnace by assembling refractory bricks, and a large, integrated refractory material with a periphery weir is embedded in the bottom wall, which is formed in a concave shape with a weir on its outer circumference and has a larger surface area than the refractory bricks assembled around it.

[0009] The invention described in claim 2 is characterized in that, in the invention described in claim 1, the large, integrated refractory structure with a surrounding weir is a precast block.

[0010] The invention described in claim 3 is characterized in that, in the invention described in claim 1 or 2, a porous refractory layer is formed in the concave portion of the large, integrated refractory material with a surrounding weir.

[0011] The invention described in claim 4 is, Claim 3 The invention described herein is characterized in that the thickness of the porous refractory layer is the same as the height of the weir of the large, integrated refractory structure with a surrounding weir. [Effects of the Invention]

[0012] The melting furnace described in claim 1 has a large, integrated refractory material with a concave outer weir, equipped with a weir on its outer circumference, positioned at the bottom of the furnace. Therefore, even when the material being processed contains low-melting-point metals such as copper and aluminum, the molten material and slag of these low-melting-point metals are dammed up on the large, integrated refractory material with a outer weir and prevented from leaking to the outside. This effectively prevents the molten material and slag of low-melting-point metals from penetrating deep into the furnace through the joints of the refractory bricks at the bottom of the furnace, thereby preventing damage to the outer shell and other issues.

[0013] The melting furnace described in claim 2 has a large, integrated refractory structure with a surrounding weir made of precast blocks, which makes on-site work easier when constructing a new furnace or performing maintenance. In addition, the large, integrated refractory structure with a surrounding weir has excellent durability and can be used for a long period of time, thus reducing the frequency of maintenance.

[0014] In the melting furnace described in claim 3, a porous refractory layer is formed in the concave portion of the large, one-piece refractory with a surrounding weir. As a result, molten low-melting-point metals and slag are adsorbed onto the porous refractory layer on the large, one-piece refractory with a surrounding weir (accumulated in the pores of the porous refractory layer), thus very effectively preventing molten low-melting-point metals and slag from penetrating deep into the furnace through the joints of the refractory bricks at the bottom. Furthermore, since the porous refractory layer is embedded in the refractory bricks together with the large, one-piece refractory with a surrounding weir, it is resistant to damage and does not need to be replaced for a long period of time.

[0015] In the melting furnace described in claim 4, since the thickness of the porous refractory layer is the same as the height of the weir of the precast block, even when refractory blocks are assembled (furnace construction) at the bottom of the furnace, there is no need to cut the refractory blocks around the large, integrated refractory structure with a surrounding weir, so the furnace construction work can be easily carried out. [Brief explanation of the drawing]

[0016] [Figure 1] This is an explanatory diagram showing a melting furnace (a vertical cross-section drawn through a vertical plane passing through the center). [Figure 2] This is an explanatory diagram showing the installation (buried portion) of the large precast block with a surrounding weir for the bottom wall. [Figure 3] This is an explanatory diagram showing a large precast block with a surrounding weir (a is a front view, b is a top view, and c is a perspective view with the porous refractory layer separated). [Modes for carrying out the invention]

[0017] Hereinafter, one embodiment of the melting furnace according to the present invention will be described in detail with reference to the drawings.

[0018] <Structure of a melting furnace> Figures 1 and 2 show a melting furnace, in which a melting furnace 1 is formed by creating a bottomed cylindrical outer shell 6 of a predetermined size (for example, inner diameter = approximately 2,000 mmφ × height = approximately 2,000 mm), and forming side walls 2 and a bottom wall 3 of a predetermined thickness inside.

[0019] The side wall 2 is formed into a hollow cylindrical shape with a predetermined thickness by assembling a plurality of refractory bricks formed of an alumina-chromium-based refractory material into a predetermined shape (such as a shape obtained by dividing a flat cylindrical body in the radial direction with respect to the central axis) inside the upper part of the peripheral surface of the outer shell iron sheet 6. And, an amorphous refractory (castable material) is filled between the assembled side wall 2 and the outer shell iron sheet 6. Further, the side wall 2 is provided with a slag discharge port (not shown) for discharging slag or the like accumulated inside to the outside, an inlet (not shown) for charging waste or incineration ash, and the like.

[0020] On the other hand, the bottom wall 3 has a two-layer structure of an upper layer 3a and a lower layer 3b. The upper layer 3a of the bottom wall 3 is formed into a disk shape with a predetermined thickness by assembling a plurality of refractory bricks formed of a refractory material excellent in heat resistance, abrasion resistance, and erosion resistance (for example, alumina-chromium, alumina carbon, silicon carbide, chromemagnesia) into a predetermined shape (such as a shape obtained by dividing a flat cylindrical body in the radial direction with respect to the central axis) in multiple layers from the center toward the outer shell iron sheet 6 by a construction method such as "ajiro stacking" or "ring stacking".

[0021] Also, the lower layer 3b of the bottom wall 3 is formed into a disk shape with a predetermined thickness (a curved surface shape with the central part bulging downward) by assembling a plurality of refractory bricks formed of a refractory material smaller than the precast blocks constituting the upper layer 3a of the bottom wall 3 and less expensive than the refractory bricks constituting the upper layer 3a in multiple layers from the center toward the outer shell iron sheet 6 by a construction method such as "ajiro stacking" or "ring stacking". Note that the precast blocks constituting the upper layer 3a of the bottom wall 3 and the refractory bricks constituting the lower layer 3b of the bottom wall 3 have substantially equal coefficients of thermal expansion. And, a large precast block 4 with a peripheral weir, which is a large integral refractory with a peripheral weir, is provided at the center (slightly above the vicinity of the axis) of the lower layer 3b of the bottom wall 3.

[0022] <Structure of the large precast block with a peripheral weir> Figure 3 shows a large precast block 4 with a surrounding weir, which is integrally formed from an alumina-based refractory material (for example, one consisting of 70-95% by mass of alumina and 5-30% by mass of magnesia). A surrounding weir 4b having a certain height and thickness is provided around the outer periphery of a substantially square flat plate section 4a having a predetermined thickness, with its plate surface perpendicular to the flat plate section 4a.

[0023] Furthermore, the height of the outer perimeter weir 4b of the large precast block 4 with a surrounding weir is approximately the same as the thickness of the flat plate section 4a (that is, the height of the large precast block 4 with a surrounding weir is approximately twice the thickness of the flat plate section 4a). In addition, the left and right width of the large precast block 4 with a surrounding weir is an integer multiple (for example, 13 times) of the left and right width of the firebricks assembled to the lower layer 3b of the bottom wall 3 (around the large precast block 4 with a surrounding weir), and the depth of the large precast block 4 with a surrounding weir is an integer multiple (for example, 26 times) of the depth of the firebricks assembled to the lower layer 3b of the bottom wall 3 (around the large precast block 4 with a surrounding weir). In addition, the height of the large precast block 4 with a surrounding weir (thickness of the flat plate section 4a + height of the outer weir 4b) is an integer multiple (for example, 2 times) of the height of the firebricks assembled to the lower layer 3b of the bottom wall 3 (around the large precast block 4 with a surrounding weir).

[0024] Furthermore, a porous refractory layer 5 is formed inside the large precast block 4 with a surrounding weir (the portion closed off by the outer weir). This porous refractory layer 5 is mainly composed of alumina and magnesia-based refractory materials, formulated to intentionally create pores, and formed by press molding, resulting in countless pores with an average pore diameter of approximately 100 μm.

[0025] <Function of a melting furnace> The melting furnace 1, configured as described above, can melt waste and incineration ash (C in Figure 1) after incineration of waste by raising the internal temperature using a heating device (such as a burner or dielectric heating device) not shown. Furthermore, when melting waste in this manner, if low-melting-point metals such as copper or aluminum are included, or if slag is generated after melting, the molten material and slag of these low-melting-point metals may penetrate downwards through the joints of the upper layer 3a of the bottom wall 3. However, even in such cases, most of the molten material and slag of these low-melting-point metals are dammed up on the large precast block 4 with a perimeter weir and accumulated in the pores of the porous refractory layer 5. Therefore, the molten material and slag of low-melting-point metals do not leak out from the lower side of the large precast block 4 with a perimeter weir.

[0026] <Effects of using a melting furnace> As described above, the melting furnace 1 has a bottom wall 3 at the bottom of the furnace, formed by assembling refractory bricks. Within the bottom wall 3, a large precast block 4 with a periphery weir is embedded, which is a large, integrated refractory material with a periphery weir, formed in a concave shape with a weir on its outer circumference and having a larger surface area than the refractory bricks assembled around it. Therefore, even if the material being processed contains low-melting-point metals such as copper and aluminum, the molten material and slag of these low-melting-point metals are dammed up on the large precast block 4 with a periphery weir and are not allowed to leak to the outside. Thus, the melting furnace 1 can effectively prevent molten material and slag of low-melting-point metals from penetrating deep into the furnace through the joints of the refractory bricks at the bottom of the furnace, and can prevent damage to the outer shell 6.

[0027] Furthermore, since the melting furnace 1 is a single unit formed by precasting a large precast block 4 with a surrounding weir, which is a large, one-piece refractory structure with a surrounding weir, on-site work during new construction and maintenance can be easily performed. In addition, the large precast block 4 with a surrounding weir has excellent durability and can be used for a long period of time, making it possible to keep the frequency of maintenance low.

[0028] Furthermore, in the melting furnace 1, since a porous refractory layer 5 is formed in the concave portion of the large precast block 4 with a surrounding weir, molten low-melting-point metals and slag are adsorbed onto the porous refractory layer 5 on the large precast block 4 with a surrounding weir (accumulated in the pores of the porous refractory layer 5), thus very effectively preventing molten low-melting-point metals and slag from penetrating deep into the furnace through the joints of the refractory bricks at the bottom.

[0029] Furthermore, in the melting furnace 1, since the thickness of the porous refractory layer 5 is the same as the height of the large precast block 4 with a surrounding weir (thickness of the flat plate section 4a + height of the outer weir 4b), even when assembling refractory blocks to the bottom of the furnace (constructing the furnace), there is no need to cut the refractory blocks around the large precast block 4 with a surrounding weir, so the furnace construction work can be carried out easily. In addition, in the melting furnace 1, if the large precast block 4 with a surrounding weir is in good condition (undamaged, etc.) during maintenance, it is possible to replace only the porous refractory layer 5 and reuse it.

[0030] <Examples of modifications to the melting furnace> The melting furnace according to the present invention is not limited in any way to the embodiments described above, and the materials, shapes, sizes, and other configurations of the outer shell, side walls, bottom walls, large integrated refractory material with surrounding weir, etc., can be appropriately changed as necessary without departing from the spirit of the present invention.

[0031] For example, the melting furnace according to the present invention is not limited to one in which a large precast block with a surrounding weir is laid within the bottom wall of the furnace bottom, as in the above embodiment. It is also possible to modify it to one in which a large, integrated refractory structure with a surrounding weir is constructed within the bottom wall of the furnace bottom using an amorphous refractory material (such as castable material) at the construction site to create a weir on its outer circumference. Furthermore, the melting furnace according to the present invention is not limited to one in which the shape of the large, integrated refractory structure with a surrounding weir is square in plan view, as in the above embodiment. It is also possible to modify the shape of the large, integrated refractory structure with a surrounding weir to one that is rectangular in plan view, or circular in plan view, etc.

[0032] Furthermore, in the melting furnace according to the present invention, the porous refractory layer is not limited to one that fills the internal space of the large, one-piece refractory with a surrounding weir by itself, as in the above embodiment. It may also be a combination of multiple layers that fill the internal space of the large, one-piece refractory with a surrounding weir, or it may be a material that fills the internal space of the large, one-piece refractory with a surrounding weir with an amorphous refractory material and then stamps it at the furnace construction site.

[0033] Furthermore, the melting furnace according to the present invention is not limited to having a two-layer structure for the bottom wall of the furnace, as in the above embodiment, but may also have a single-layer structure or a multi-layer structure of three or more layers. Also, as in the above embodiment, the upper layer of the bottom wall of the furnace is formed of a refractory material with excellent heat resistance, abrasion resistance, and corrosion resistance, and the lower layer is formed of a refractory material that is less expensive than the refractory material of the upper layer, or the large integrated refractory structure with a surrounding weir is formed of an alumina-based refractory material, but the materials used to form the refractory bricks of the bottom wall, the large integrated refractory structure with a surrounding weir, and the porous refractory layer can be changed as needed. [Industrial applicability]

[0034] As the melting furnace according to the present invention exhibits the excellent effects described above, it can be suitably used as an industrial furnace for melting waste and waste incineration ash. [Explanation of symbols]

[0035] 1. Melting furnace 2...side wall 3. Bottom wall 3a...upper layer 3b...lower layer 4...Large integral refractory with surrounding weir 4a. Plate-like part 4b. Outer perimeter weir 5. Porous refractory layer

Claims

1. A melting furnace for melting waste or waste incineration ash, A bottom wall is provided at the bottom of the furnace by assembling refractory bricks, Inside its bottom wall, A melting furnace characterized by having a concave shape with a weir on its outer perimeter, and by having a large, integrated refractory structure with a perimeter weir embedded within it, having a larger surface area than the refractory bricks assembled around it.

2. The melting furnace according to claim 1, characterized in that the large, integrated refractory material with a surrounding weir is a precast block.

3. The melting furnace according to claim 1 or 2, characterized in that a porous refractory layer is formed in the concave portion of the large, integrated refractory material with a surrounding weir.

4. The melting furnace according to claim 3, characterized in that the thickness of the porous refractory layer is the same as the height of the weir of the large, integrated refractory structure with a surrounding weir.

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