JP2006300357A - Refractory structure of waste melting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refractory structure improving the durability of a refractory of a furnace lower part particularly severe in wear in a waste melting furnace. <P>SOLUTION: A silicon carbide castable refractory 1 containing at least 30 mass% of silicon carbide is used as a furnace wall refractory at the furnace wall of a part in contact with molten slag in the waste melting furnace, and cooling water pipes 2 are embedded inside. A silicon carbide refractory 3 containing at least 30 mass% of silicon carbide is used as a first layer refractory in contact with a molten material at a hearth of the waste melting furnace. A high alumina refractory 4 containing at least 50 mass% of alumina is used as a second layer refractory at the back face of a first layer. A heat insulating refractory 5 is further disposed at the back face of a second layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a refractory structure of a waste melting furnace for melting waste such as general waste and industrial waste in a shaft furnace.

  As one of the waste processing methods, there is a waste melting processing method in which waste is dried, pyrolyzed, burned and melted in a shaft furnace type waste melting furnace to form slag and metal.

  FIG. 2 is a sectional view of a general waste melting furnace. In order to melt the waste, oxygen-enriched air is blown into the furnace from the blower tuyere 30 at the lower part of the furnace, and the waste 50 is charged into the furnace together with coke and limestone from the upper part of the furnace. Then, drying and dry distillation gasification (thermal decomposition) proceed while the waste 50 descends in the furnace, and the remaining ash is melted by the combustion heat of the furnace bottom coke 60 forming a coke bed near the blower tuyere 30. The molten slag and molten metal descend to the hearth surface. The molten material in the hearth is discharged from a hot water outlet 40 that leads from the hearth surface to the outside of the furnace. The in-furnace process of such a waste melting furnace is disclosed in Patent Document 1.

  However, in a waste melting furnace where such an in-furnace process occurs, particularly in the lower part of the furnace, the refractories (the furnace wall refractory 10 and the hearth refractory 20 shown in FIG. 2) are placed in a very harsh environment. For example, refractory repairs and replacements were required every year.

  In other words, high-alumina refractories have been used in the lower part of the furnace to withstand high temperatures, but in the upper part of the blower tuyere, the furnace on the blower tuyere is slag generated by the active combustion of coke at the upper part of the blower tuyere. Wall refractories are eroded. Similarly, the hearth is eroded by high-temperature slag.

In order to prevent erosion caused by slag, it is conceivable to use a silicon carbide refractory having low reactivity with slag. However, in the furnace wall directly above the blowing tuyere, CO generated by combustion of oxygen and coke from the blowing tuyere _{With two} gases, the silicon carbide refractory is easily oxidized and worn.

  Also, in the hearth, the hearth surface is always covered with slag, so there is no oxidation by the gas in the furnace, but silicon carbide refractories have high heat transfer, so the temperature rises to the back, and refractory joints and cracks From the above, a metal such as iron or copper penetrates to the heat insulating layer on the back surface in a molten state, and enters the pores of the porous heat insulating material, thereby remarkably deteriorating the heat insulating property. In this case, the iron skin at the bottom of the furnace rises in temperature, and the heat dissipation of the furnace bottom increases, the hearth is cooled, the melt is solidified on the hearth surface, and it is difficult to discharge the melt.

  On the other hand, in order to improve the slag resistance, there is an example of using a chrome refractory, but the durability is not sufficient, and in use, harmful hexavalent chromium may be generated from this refractory, There is a drawback that it requires careful handling.

In addition, for the purpose of extending the life of these refractories, a method of cooling with a jacket or a cooling pipe has been proposed (see Patent Document 2). However, high alumina refractories and chrome refractories have thermal conductivity. It is difficult to obtain a practical refractory life without being sufficiently cooled to the operating surface in the furnace.
Japanese Patent Publication No.55-21923 JP 2004-156875 A

  The problem to be solved by the present invention is to provide a refractory structure capable of improving the durability of the refractory in the lower part of the furnace, particularly in a waste melting furnace, and more specifically, slag. A refractory structure for a waste melting furnace is provided that uses a silicon carbide refractory that has low reactivity with the heat conductivity and that can solve the above-mentioned problems such as high-temperature oxidation, which is a weak point of silicon carbide refractories. There is.

In order to prolong the durability of the refractory in the lower part of the waste melting furnace, the furnace wall refractory structure of the present invention includes at least 30% by mass or more of silicon carbide as the furnace wall refractory in the furnace wall at the portion in contact with the molten slag. A silicon carbide castable refractory is used, and a cooling water pipe is embedded inside. In this way, by burying the cooling water pipe inside the silicon carbide castable refractory material having high slag resistance and high thermal conductivity and cooling it, the furnace gas (which is a major weak point of the silicon carbide refractory material ( The problem of wear due to high temperature oxidation due to O ₂ , CO ₂ ) can be eliminated. Further, since the molten slag is solidified on the surface of the cooled silicon carbide castable refractory, the molten slag becomes a surface-coated state and is protected from the furnace gas. Here, since the oxidation of the silicon carbide refractory with O ₂ and CO ₂ gas starts at 1000 ° C. or higher, the silicon carbide castable refractory on the furnace wall is cooled so that the operation surface in the furnace becomes less than 1000 ° C. It is preferable.

  Furthermore, the hearth refractory structure of the present invention uses a silicon carbide refractory containing at least 30% by mass or more of silicon carbide as the first layer refractory in contact with the melt in the hearth of the waste melting furnace, A high-alumina refractory containing at least 50% by mass or more of alumina is used as the second layer refractory on the first layer back surface, and a heat insulating refractory is further disposed on the back surface of the second layer. In other words, the surface of the hearth is always covered with the melt, and oxidation by the gas in the furnace can be prevented. Therefore, as the first layer refractory in contact with the melt, the carbonization of high SiC content with excellent slag resistance is achieved. Use silicon refractories. Since silicon carbide refractories have high thermal conductivity, the temperature rises to the back. However, as the refractories for the second layer on the back of the first layer, the refractories have high fire resistance and low thermal conductivity compared to silicon carbide refractories. By using the alumina refractory, the temperature of the back surface of the second layer can be made below the freezing point of the melt, and the melt can be prevented from entering the heat insulating refractory of the back surface of the second layer.

  According to the furnace wall refractory structure of the present invention, by cooling the silicon carbide castable refractory used as the furnace wall refractory, high temperature oxidation by the furnace gas of the silicon carbide castable refractory is prevented. The slag resistance effect by the silicon castable refractory can be sufficiently exhibited.

  According to the hearth refractory structure of the present invention, by disposing the second layer made of the high alumina refractory on the back surface of the silicon carbide refractory used as the first layer refractory in contact with the melt, While being able to improve the slag resistance of a floor part, it can prevent that a molten material penetrate | invades into the heat insulation refractory material of a 2nd layer back surface, and can prevent that a heat insulation function lose | disappears.

  As described above, according to the present invention, it is possible to remarkably improve the durability of the refractory in the lower part of the furnace that is particularly worn out in the waste melting furnace. can do.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a sectional view of a lower part of a waste melting furnace to which the refractory structure of the present invention is applied. The structure of the waste melting furnace shown in the figure is the same as that of the conventional one shown in FIG. 2, and in order to melt the waste, oxygen-enriched air is supplied from the blower tuyere 6 at the lower part of the furnace. Blowing into the furnace, waste is charged into the furnace together with coke and limestone from the top of the furnace. Then, drying and dry distillation gasification (pyrolysis) proceed as the waste descends in the furnace, and the remaining ash is melted by the combustion heat of the bottom coke forming a coke bed not shown near the blower tuyere 6. Then, it falls as molten slag and molten metal to the hearth surface. The molten material in the hearth is discharged from a hot water outlet 7 that leads from the hearth surface to the outside of the furnace.

  In the furnace wall refractory structure of the present invention, the silicon carbide castable refractory 1 is used as the furnace wall refractory in the furnace wall at the portion in contact with the molten slag, and the cooling water pipe 2 is provided inside the silicon carbide castable refractory 1. Buried. Here, the furnace wall in contact with the molten slag is generally the furnace wall of the combustion melting zone that melts the ash remaining after dry distillation gasification (pyrolysis) of the waste. It is a furnace wall below the part 8.

  The silicon carbide castable refractory 1 needs to have high thermal conductivity in order to sufficiently exhibit the cooling effect by the cooling water pipe 2, and for this purpose, it is a material containing at least 30% by mass of silicon carbide. In this example, a silicon carbide castable refractory containing 70% by mass of silicon carbide, alumina + silica = 29% by mass as the other components, and 1% by mass of the remaining calcium oxide was used.

In the portion (combustion melting zone) where the silicon carbide castable refractory 1 is used, coke combustion is actively performed in the vicinity of the blower tuyere 6 and immediately above it, and reaches 1700 ° C to 1800 ° C. When exposed to this high temperature atmosphere, the silicon carbide refractory is usually easily oxidized, and SiC becomes SiO ₂ , causing structural changes and wear. On the other hand, in the present invention, the silicon carbide castable refractory 1 is cooled by the cooling water pipe 2, and the silicon carbide castable refractory 1 has high thermal conductivity, so that the oxidation starts to the operation surface in the furnace. The temperature is kept at about 400 ° C. to 500 ° C., which is lower than the temperature (1000 ° C.), and high temperature oxidation by the furnace gas is prevented.

  This furnace wall refractory structure makes it possible to use silicon carbide castable refractories that could not be used on the furnace wall in contact with the molten slag, making use of the slag resistance of silicon carbide castable refractories Refractory life is greatly improved. In this part, erosion progresses mainly due to melting loss due to contact with molten slag and spalling due to rapid temperature change, but silicon carbide castable refractories have good durability in any respect. The conventional high-alumina castable refractory can have a service life of 5 years or more, which was normally about 1 year.

  On the other hand, in the hearth refractory structure of the present invention, the silicon carbide refractory 3 having high slag resistance is disposed as the first layer in contact with the melt, and the high alumina refractory 4 as the second layer on the back surface thereof. A refractory layer is provided. Further, a heat insulating refractory 5 is disposed on the back surface to prevent a temperature drop of the hearth portion.

  Since the hearth surface is always covered with slag, there is no risk of oxidation due to the gas in the furnace. Therefore, the silicon carbide refractory 3 of the first layer sufficiently exhibits slag resistance. A material containing silicon carbide is used. In this example, a silicon carbide castable refractory containing 70% by mass of silicon carbide, alumina + silica = 29% by mass as the other components, and 1% by mass of the remaining calcium oxide was used.

  However, since the silicon carbide refractory 3 of the first layer has high thermal conductivity as described above, the entire first layer is maintained at a high temperature, and the molten metal (Fe, Cu) Easy to penetrate through cracks. When this molten metal reaches the adiabatic refractory 5, the heat insulation is lost, the hearth is cooled, the melt (slag, metal) is solidified on the hearth surface, and the discharge of the melt from the tap 7 is not possible. It becomes possible.

  Therefore, in order to prevent the molten metal from reaching the adiabatic refractory 5, in the present invention, as described above, the high alumina refractory 4 is provided as the second layer on the back surface of the silicon carbide refractory 3 of the first layer. It arrange | positions and it prevents that a molten metal osmose | permeates the adiabatic refractory 5 by making the back surface temperature of a 2nd layer become 1000 degrees C or less below the solidification temperature of a molten metal. In this case, the alumina content of the high-alumina refractory 4 is 50% by mass or more in terms of fire resistance. In this example, a high-alumina castable refractory containing 93% by mass of alumina, 6% by mass of silica and 1% by mass of calcium oxide as other components was used. Further, as the heat insulating refractory 5, a heat insulating castable refractory was used. In the present embodiment, the castable refractory is used for the hearth, but it is also possible to use a pre-castable refractory or a fixed refractory that has been molded into a predetermined shape in advance.

It is sectional drawing of the melting furnace for wastes to which the refractory structure of this invention is applied. It is sectional drawing of a general waste melting furnace.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Silicon carbide castable refractory 2 Cooling water pipe 3 Silicon carbide refractory 4 High alumina refractory 5 Thermal insulation refractory 6 Blower tuyeres 7 Hot water outlet 8 Morning glory 10 Furnace wall refractories 20 Hearth refractories 30 Blower wings Mouth 40 Hot spring outlet 50 Waste 60 Furnace bottom coke

Claims (3)

  In the furnace wall at the site in contact with the molten slag of the waste melting furnace, a silicon carbide castable refractory containing at least 30% by mass of silicon carbide is used as the furnace wall refractory, and a cooling water pipe is embedded inside. The furnace wall refractory structure of the waste melting furnace.   In the hearth of the waste melting furnace, a silicon carbide refractory containing at least 30% by mass of silicon carbide is used as the first layer refractory in contact with the melt, and the second layer refractory on the back of the first layer is used. A hearth refractory structure for a waste melting furnace, wherein a high-alumina refractory containing at least 50% by mass or more of alumina is used, and an adiabatic refractory is disposed on the back surface of the second layer.   In a waste melting furnace, a silicon carbide castable refractory containing at least 30% by mass of silicon carbide is used for a furnace wall at a site in contact with the molten slag, and a cooling pipe is embedded in the furnace wall. The first layer in contact with the silicon carbide refractory containing at least 30% by mass of silicon carbide, the second layer on the back side of the first layer being a high alumina refractory containing at least 50% by mass of alumina, and the second layer A refractory structure for a waste melting furnace, characterized in that an adiabatic refractory is disposed on the back surface of the waste melting furnace.

Images