JP2000009388A - Melting furnace for incineration residue - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the lifetime of melting furnace while stabilizing the structure of the furnace by employing a high SiC based reduction firing refractory brick having SiC content of specified level or above at the furnace side wall part coming into face contact with a molten produced in the furnace. SOLUTION: A melting furnace for incineration residue, i.e., an arc furnace, comprises a furnace body 11, a furnace cover 12 applied thereto, and an electrode 13 inserted into the furnace from the furnace cover 12. A molten 21 comprising a lower molten metal layer 22, an upper molten slag layer 23 and a thin uppermost molten salt layer 24 is produced in the furnace when incineration residue is melted. The furnace side wall part (lower part of the side wall of the furnace body 11) coming into face contact with the molten 21 in the furnace is constructed, sequentially from the inside toward the outside of the furnace, of a high SiC based reduction firing refractory brick 31 having SiC content of 92 wt.% or above and apparent porosity of 12% or less, a refractory heat insulating material 32, and a steel plate 33 (furnace shell). The furnace side wall part coming into face contact with gas 26 is constructed sequentially of an irregular refractories 41, a refractory heat insulating material 42, and the steel plate 33 furnace shell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a melting furnace for incineration residues. When various types of waste, such as municipal solid waste, sewage sludge, and industrial waste, are incinerated in an incinerator, they remain in the incinerator and are scattered together with the incineration ash discharged from the bottom of the incinerator and the exhaust gas from the incineration. Fly ash is captured in the exhaust gas treatment system connected to the furnace. The incineration residue roughly classified into such incineration ash and fly ash is melted in a melting furnace in order to reduce the volume and stabilize it for the purpose of extending the life of the landfill site and preventing environmental pollution. The present invention relates to an improvement of such a melting furnace for incineration residues.

[0002]

2. Description of the Related Art Conventionally, arc furnaces, plasma furnaces, plasma arc furnaces, resistance furnaces, burner furnaces and the like have been used as melting furnaces for incineration residues. In these melting furnaces, an Al side is provided on the side wall of the furnace in contact with the melt generated in the furnace.
The ₂ O ₃ those using Al ₂ O ₃ -SiC refractory bricks composed primarily has been proposed (JP-A 5-118522, JP-A-9-318275). However, such conventional incineration residue melting furnaces have a correspondingly long service life when incinerated ash is melted as incineration residue, but a mixture of incineration ash and fly ash or fly ash is melted as incineration residue. In this case, there is a problem that the service life is extremely short. When a mixture of incinerated ash and fly ash or fly ash is melted, the molten metal is formed in the furnace as a molten metal layer in the lower layer, a molten slag layer in the upper layer,
A thin molten salt layer is formed on the uppermost layer, and the molten slag layer and the molten salt layer contain alkali components such as K ₂ O, Na ₂ O, and CaO in fly ash at a considerably high concentration. The alkali component reacts with the Al ₂ O ₃ -SiC-based refractory brick mainly composed of Al ₂ O ₃ used for the furnace side wall portion in contact with the molten slag layer and the molten salt layer, and the refractory brick is damaged. And the service life is significantly shortened.

Generally, an incinerator including an incinerator is set to have a periodic repair period once a year. Therefore, a melting furnace for melting and processing incineration residues generated from such an incinerator is also once a year. It is advantageous to have a service life such that the periodic repair period can be set. However, the above-mentioned conventional incineration residue melting furnace does not have such a long service life, and is very inconvenient.

As refractory bricks resistant to alkali components in fly ash as described above, MgO-Cr ₂ O ₃ -based and Al ₂ O _3-
Cr ₂ O ₃ refractory bricks are known. Therefore, it is conceivable to use these refractory bricks for the furnace side wall to extend the service life of the incineration residue melting furnace. However, since these refractory bricks have a large coefficient of thermal expansion, they have a problem that they are easily cracked due to a temperature change, and that the piled refractory bricks protrude from the furnace side wall to the inside of the furnace. These refractory bricks have a serious defect in that when they are used for the furnace side wall, the furnace construction becomes unstable.

[0005]

The problem to be solved by the present invention is that the conventional incineration residue melting furnace has a short service life or an unstable furnace construction.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a melting furnace for melting and processing incineration residues, wherein a SiC content of 92 wt. % Of a high-SiC reduction fired refractory brick.

[0007] The melting furnace for incineration residues which is the subject of the present invention is an arc furnace, a plasma furnace, and a plasma arc for melting and processing incineration residues obtained by incinerating various kinds of wastes such as municipal waste, sewage treatment sludge, and industrial waste. Furnace, resistance furnace, burner furnace and the like. When the incineration residue as described above is melt-processed, a molten metal layer is formed in the lower layer, a molten slag layer is formed in the upper layer, and a thin molten salt layer is formed in the uppermost layer. , A part of which is also contained in the molten metal layer, but is contained in the molten slag layer and the molten salt layer at a high concentration, and in particular, melts a mixture of incinerated ash and fly ash or fly ash as incineration residue. In the case of treatment, the fly ash contains an alkali component at a higher concentration than the incineration ash, so that the fly ash is contained at a considerably higher concentration in the molten slag layer and the molten salt layer. Since the formation of such a molten slag layer and a molten salt layer and the liquid level thereof vary depending on the actual melting conditions, in order to extend the useful life of the incineration residue melting furnace in view of such fluctuations, it is necessary to use a furnace. It is necessary to use refractory bricks, which are unlikely to react with alkali components, on the furnace side wall in contact with the melt generated at the same time. Therefore, it is necessary to use a refractory brick having a low coefficient of thermal expansion in the furnace side wall portion which comes into contact with the melt generated at the time.

[0008] Therefore, in the present invention, a high SiC reduction fired refractory brick having a SiC content of 92% by weight or more is used for the furnace side wall in contact with the melt generated in the furnace. High SiC reduction fired refractory bricks having an SiC content of 92% by weight or more are:
Al mainly composed of Al ₂ O ₃ having an Al ₂ O ₃ content of 50% or more
_{It is} less susceptible to reaction with alkali components than ₂ O ₃ —SiC refractory bricks, and MgO—Cr ₂ O ₃ or Al ₂ O ₃ —C
It has a lower coefficient of thermal expansion than r ₂ O ₃ refractory bricks. A SiC content of 9 is provided on the side wall of the furnace in contact with the melt generated in the furnace.
When a high SiC-based refractory fired refractory brick of 2% by weight or more is used, the service life of the incineration residue melting furnace is prolonged, and the furnace construction is stabilized.

According to the present invention, high Si having a SiC content of 92% by weight or more is provided on the side wall of the furnace in contact with the melt generated in the furnace.
C-based refractory fired refractory bricks are used, preferably SiC
Those having a content of 95% by weight or more, more preferably those having an apparent porosity of 14.5% or less, particularly preferably those having an apparent porosity of 12% or less are used. Thus, the dense high Si with higher SiC content and lower apparent porosity
The use of C-based reduced firing refractory bricks not only makes it less likely to react with alkali components, but also prevents the molten material from penetrating into the bricks and changing the structure. Longer service life,
The furnace construction becomes more stable.

[0010] Mortar is used for joint bonding between high SiC reduction fired refractory bricks having an SiC content of 92% by weight or more as described above. Although the material of the mortar to be used is not particularly limited, it is preferable to use a mortar having an Al ₂ O ₃ content of 90% by weight or more and a Cr ₂ O ₃ content of 3% by weight or more.
More preferably, a mortar having an l ₂ O ₃ content of 92% by weight or more and a Cr ₂ O ₃ content of 5% by weight or more is used. High SiC
When a mortar with a high SiC content is used, as in the case of the system-reduced fired refractory brick, SiC for the mortar material has fine particles and a large specific surface area, and the apparent porosity of the mortar itself is large. It oxidizes when exposed to the atmosphere, and the generated oxide reacts with the alkali component in the melt when the joints come into contact with the melt, so that the melting loss increases. The use of mortar in which certain Al ₂ O ₃ is combined with Cr ₂ O ₃ that is strong against alkali components in the melt can suppress such melting.

In order to more effectively suppress the erosion of the mortar used for joint bonding, it is necessary to increase the liquid level of the molten material, which fluctuates depending on the actual melting conditions, between the high SiC reduction fired refractory bricks stacked vertically. It is desirable not to come into the joint area of. For this purpose, a high SiC reduction fired refractory brick having a large solid height, for example, 150 to 230 mm
The high-SiC reduced-fired refractory bricks having a solid height of are vertically stacked, and the fluctuation of the liquid level of the melt generated in the furnace is covered within the solid height range of the high-SiC reduced-fired refractory bricks. It is advantageous to do so.

[0012] The high SiC reduction fired refractory brick piled on the furnace side wall comes into contact with the melt generated in the furnace, but a part of the brick also comes into contact with the furnace atmosphere. High S in contact with furnace atmosphere
iC-based reduced firing refractory brick is usually 1000-130
When the temperature rises to 0 ° C., the surface is oxidized. On the other hand, the alkali component in the incineration residue is present not only in the melt generated in the furnace, but also partially as a gas in the furnace atmosphere. The oxide generated on the surface of the high SiC reduction fired refractory brick in contact with the furnace atmosphere reacts with the alkali component in the furnace atmosphere, and as a result, the surface is melted. Such surface erosion is the same as the erosion of the joint as a result when a mortar having a high SiC content is used for the joint. In order to suppress such surface erosion, the surface of the high-SiC-based reduced-fired refractory brick which is in contact with the furnace atmosphere is made of a refractory mainly composed of an oxide such as Al _2.
It is advantageous to cover with an O ₃ —SiO ₂ or Al ₂ O ₃ —Cr ₂ O ₃ refractory brick or irregular refractory.

[0013]

FIG. 1 is a longitudinal sectional view schematically showing an embodiment of a melting furnace for incineration residues according to the present invention. The illustrated melting furnace is an arc furnace, which has a furnace body 11 and
The furnace includes a furnace lid 12 attached to a furnace body 11, and an electrode 13 inserted into the furnace from the furnace lid 12. In the furnace, a lower molten metal layer 22, an upper molten slag layer 23, and an uppermost thin molten salt layer 24 are generated as a melt 21 generated by the melting treatment of the incineration residue. There is an unmelted incineration residue 25 in the upper part of the furnace, and a space in the furnace above the molten salt layer 24 is filled with a gas 26 generated by melting the incineration residue. The molten slag layer 23 and the molten salt layer 24 contain a considerably high concentration of an alkali component originating from the incineration residue 25, and a gas 26.
Also contains a gasified alkali component at a corresponding concentration. Although not shown, a discharge port for the molten slag 23 is provided on the back side of the furnace body 11, and an incineration residue charging port and an exhaust port are provided on the furnace lid 12. Is equipped with a water granulator, and a dust collector is connected downstream of the exhaust port.

The furnace side wall portion (furnace main body 1) in contact with the melt 21
1 from the inside of the furnace toward the outside of the furnace.
High SiC-based reduced firing refractory brick 31 having a C content of 92% by weight or more and an apparent porosity of 12% or less, refractory heat insulating material 32 in contact with high SiC-based reduced firing refractory brick 31, and refractory heat insulating material 3
The steel plates 33 (furnace shell) in contact with 2 are constructed in this order. Further, the furnace side wall portion in contact with the gas 26 (upper side wall of the furnace body 11)
Is from the inside of the furnace toward the outside of the furnace,
It is constructed in the order of the refractory heat insulating material 42 in contact with the irregular refractory 41 and the steel plate 33 (furnace shell) in contact with the refractory heat insulating material 42.
The irregular-shaped refractory 41 is supported by a ceramic anchor 43 screwed to a metal rod welded to a steel plate 33.

The hearth is constructed of a refractory brick 51 having an inverted arch structure, and an expansion absorption board 52 is incorporated around the outer periphery of the refractory brick 51 in contact with a steel plate 33 (furnace shell). Further, the furnace lid 12 is constructed in substantially the same manner as the furnace side wall portion which comes into contact with the gas 26 as described above. An air passage 61 for air cooling is formed outside the steel plate 33 corresponding to the furnace shell of the furnace body 11 so as to cover the furnace wall and the hearth. It is also provided in
The furnace main body 11 and the furnace lid 12 are air-cooled.

In the embodiment schematically shown in FIG. 1, the high SiC reduced fired refractory bricks 31 are vertically stacked in three stages, and the high SiC reduced fired refractory bricks 31 stacked vertically are disposed between the high fired refractory bricks 31. Mortar 34 having an Al ₂ O ₃ content of 90% by weight or more and a Cr ₂ O ₃ content of 3% by weight or more is used for joint bonding. Each high SiC-based reduced fired refractory brick 31 has a relatively large solid height, and the liquid level of the melt 21 (the liquid level of the molten salt layer 24) is the high SiC-based reduced fired refractory brick stacked on the top. It is located almost in the center.

FIG. 2 is a longitudinal sectional view schematically showing another embodiment of the incineration residue melting furnace according to the present invention. 2 except for the letter a in FIG. 2 correspond to the same reference numerals in FIG. 1, and their configurations are the same as those in FIG. 1. In the embodiment schematically illustrated in FIG. 2, the surface of the high-SiC-based reduced-fired refractory brick 31 a stacked in three stages in the vertical direction (the surface inside the furnace in contact with the melt 21 a and the gas 26 a) is made of oxide. It is covered with an Al ₂ O ₃ —Cr ₂ O ₃ -based irregular refractory 35 as a main material.

FIG. 3 shows the high-SiC reduction fired refractory brick P (SiC content 95% by weight, SiO ₂ content 3% by weight, Al ₂ O ₃ content 2% by weight, apparent porosity 12) used in the present invention.
% Or less) and the conventional Al ₂ O ₃ —SiC refractory brick R
(Al ₂ O ₃ content 55% by weight, SiC content 38% by weight, SiO ₂ content 6% by weight, C content 1% by weight) with respect to the basicity (CaO / SiO ₂ ) of the test molten slag. It is a graph which illustrates the result of having calculated the erosion rate (%). FIG. 4 is a graph illustrating the results of determining the maximum pit depth (mm) of the test refractory bricks P and R with respect to the basicity (CaO / SiO ₂ ) of the test molten slag. FIGS. 3 and 4 show the results when each refractory brick was immersed in a test molten slag in which the basicity was adjusted by adding CaO to the molten slag of municipal waste incineration ash and left at 1650 ° C. for 3 hours, The erosion rate (%) in FIG. 3 was determined by (volume of eroded portion / original volume) × 100.

FIGS. 5 to 8 show furnace side walls which are in contact with the melt when the municipal waste incineration residue (mixture of incineration ash and fly ash) is melted for one year in an arc furnace as shown in FIGS. It is a schematic diagram which illustrates the erosion state of the refractory brick used for (a). Among them, FIG. 5 shows a high SiC reduction fired refractory brick P (Si
C content 95% by weight, SiO ₂ content 3% by weight, Al ₂ O
FIG. 6 shows a high SiC-based refractory fired refractory in a case where high SiC-based mortar S (SiC content: 93% by weight) was used for jointing the joints ( ₃ % content: 2% by weight). The bricks P are stacked in four layers, and the joints are bonded with Al ₂ O ₃
-Cr ₂ O ₃ based mortar T (Al ₂ O ₃ content of 92 wt%, Cr ₂ O ₃ content of 5 wt%) is used (Example equivalent), 7 high SiC-based reduction firing refractory bricks and Masonry P 4 stages, with Al ₂ O ₃ -Cr ₂ O ₃ mortar T of their joint adhesive, further 4-stage stacked, high-SiC-based reduction firing refractory bricks P Al ₂ O ₃ surface of -Cr Amorphous refractories mainly composed of ₂ O ₃ -based oxides (Al ₂ O ₃ content 92% by weight, C
r ₂ O ₃ content 5% by weight) (corresponding to Examples)
FIG. 8 shows an Al ₂ O ₃ —SiC refractory brick R mainly composed of Al ₂ O ₃ (Al ₂ O ₃ content 55% by weight, SiC content 38).
Weight%, SiO ₂ content 6 weight%, C content 1 weight%)
Are stacked in four stages, and high SiC-based mortar S is used for bonding these joints. In FIG. 5 to FIG. 8, the eroded portion is indicated by oblique lines.

[0020]

As is clear from the above, the present invention described above has the effects that the service life of the melting furnace for incineration residues can be extended and the furnace construction can be stabilized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing an embodiment of a melting furnace for incineration residues according to the present invention.

FIG. 2 is a longitudinal sectional view schematically showing another embodiment of the incineration residue melting furnace according to the present invention.

FIG. 3 is a graph illustrating the erosion rate with respect to the basicity of molten slag for a high SiC reduction fired refractory brick or the like used in the present invention.

FIG. 4 is a graph illustrating the maximum erosion depth with respect to the basicity of molten slag for a high SiC reduction fired refractory brick or the like used in the present invention.

FIG. 5 is a schematic view illustrating the state of erosion of a high SiC reduction fired refractory brick in one embodiment of the present invention.

FIG. 6 is a schematic view illustrating the erosion state of a high SiC-based reduced-fired refractory brick in another embodiment of the present invention.

FIG. 7 shows a high SiC in still another embodiment of the present invention.
FIG. 2 is a schematic view illustrating a erosion state of a system reduction fired refractory brick.

FIG. 8 is a schematic view illustrating the erosion state of an Al ₂ O ₃ —SiC refractory brick in a conventional example.

[Explanation of symbols]

11, 11a ... furnace body, 12, 12a ... furnace lid,
13, 13a ... electrodes, 21, 21a ... melts,
26, 26a: gas, 31, 31a: high SiC
System reduction firing refractory brick, 33 ... steel plate, 34, 34a
... Mortar, 35 ... Fixed refractories

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor ▲ Hiro ▼ Ichiro 215 F-term at 3-1-1 Akatsukidai, Yokkaichi-shi, Mie 4K051 AA00 AA05 AB03 BD05 BE03 DA13 DA18

Claims (4)

[Claims] In a melting furnace for melting and processing incineration residues, Si is provided on a side wall of a furnace in contact with a melt generated in the furnace.
A melting furnace for incineration residues, characterized by using a high SiC reduction fired refractory brick having a C content of 92% by weight or more. 2. An Al ₂ O ₃ content of not less than 90% by weight and Cr ₂ O _{3 for} bonding joints between high SiC-based reduced firing fire-resistant bricks.
The melting furnace for incineration residue according to claim 1, wherein a mortar having a content of 3% by weight or more is used. 3. A high SiC reduction firing having a corresponding solid height so that the liquid level of the melt generated in the furnace is not located at the joint between the high SiC refractory bricks stacked vertically. The melting furnace for incineration residues according to claim 1, wherein a refractory brick is stacked. 4. The melting furnace for incineration residue according to claim 1, wherein the surface of the high-SiC reduced-fired refractory brick which is in contact with the atmosphere in the furnace is covered with a refractory mainly composed of an oxide. .