JP2008249317A - Furnace bottom structure of waste melting furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent stopping of a facility by melting damage of a shell caused by permeation of a melt, particularly, metal such as Fe and Cu, while reducing consumables required for hot water outlet work, the quantity of utility used and also the number of persons required for hole opening/blocking-up work, by largely increasing a hot water outlet interval by restraining a temperature drop in slag, in a furnace bottom part of a waste melting furnace for performing continuous operation. <P>SOLUTION: This furnace bottom structure of the waste melting furnace is composed of a multilayered structure of laminating a refractory material on a shell upper surface. The furnace bottom structure of the waste melting furnace is characterized by forming a first layer being the uppermost layer as a castable layer composed of a silicon carbide refractory material 4, a second layer of a first layer back face as a castable layer composed of an alumina refractory material 5, a third layer of a second layer back face as a layer composed of a heat insulating refractory material 6 and a fourth layer of a third layer back face as a heat insulating layer composed of a high functional heat insulating material 7 being a micro-porous mold mainly composed of a silica particulate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a bottom structure of a waste melting furnace for melting waste such as general waste and industrial waste, and more particularly, a bottom of a waste melting furnace having a laminated structure that is optimal for improving heat retention of the melt. Concerning structure.

  In waste melting furnaces that melt waste such as general waste and industrial waste, it has been a very important issue to prevent erosion of the bottom of the furnace and to control the temperature drop of the melt. As a furnace bottom structure of a melting furnace, a structure in which refractories having excellent slag penetration resistance, spalling resistance, fire resistance, and the like are laminated in a layered manner on the upper surface of the iron skin is frequently used (for example, Patent Document 1). reference).

  The bottom structure of the waste melting furnace disclosed in Patent Document 1 is shown in FIG. The waste material charged into the melting furnace together with coke and limestone is dried and dried in the process of descending the melting furnace by blowing oxygen-enriched air from the blower tuyere provided on the lower side of the furnace. The pyrolysis reaction proceeds, and the remaining ash is melted by the combustion heat of the bottom coke forming a coke bed near the blower tuyere.

  Molten metal and the molten material that has fallen to the bottom of the furnace as molten slag are discharged (discharged) from a hot water outlet that leads to the outside of the furnace. Here, the present situation is that the hot water discharge operation of the slag stored in the furnace bottom is performed at intervals of approximately 60 minutes. This is because, in a waste melting furnace having this kind of furnace bottom structure, a silicon carbide refractory having high thermal conductivity and excellent slag penetration resistance is provided in the first layer in contact with the melt as shown in FIG. 4, the high-alumina refractory 5 is generally used for the second layer on the back side, and the heat-insulating refractory 13 is used for the third layer on the back side. Since the rate λ is about 0.2 to 11 W / m · K, there is a limit to the suppression of the slag temperature drop, and the slag solidifies and the melt is discharged unless the hot water is discharged at intervals of about 60 minutes. This is because it becomes difficult.

  Further, in a waste melting furnace having this kind of furnace bottom structure, mud opening work and closing work are required each time the hot water is discharged. Therefore, as described above, the hot water discharge operation is performed at intervals of approximately 60 minutes, and therefore it is necessary to perform the mud opening and closing operations at the intervals as well, which requires a great deal of human cost. Similarly, the rods, bits, etc. that make up the hole opening machine come into contact with high-temperature slag each time the hot water is discharged, so the cost as a consumable item increases, and it is necessary to operate the hole opening machine. Service costs for air, oxygen, water, etc. are also costs that cannot be ignored.

Further, in the configuration of the above prior art, in a long-term continuous operation, for example, the first layer of silicon carbide refractory 4 and the second layer of high alumina refractory 5 are melted from the crack of the refractory or the joint of the refractory. If a metal such as Fe, Cu or the like enters, the heat-insulating refractory 13 provided on the back surface of the second layer is low in fire resistance, so it is melted by the melt 1, and in some cases, the iron core at the bottom of the furnace May melt and cause melting furnace equipment to stop.
JP 2006-300377 A

  The object of the present invention is to solve the problems of the prior art, and at the bottom of a waste melting furnace that is continuously operating, greatly increases the interval between tapping by suppressing the decrease in the temperature of the slag, The purpose of this is to reduce the amount of consumables and utilities used for the hot water work, as well as the personnel required for opening and closing work, and to prevent the equipment from shutting down due to molten iron skin erosion. .

  As a result of repeating the bottom structure analysis and heat transfer calculation of the waste melting furnace in order to solve the above problems, the present inventor has obtained the following technical knowledge.

(A) As described above, the primary purpose of the present invention is to suppress the temperature drop of the slag, and in order to realize this, the waste melting furnace having the optimum laminated structure for improving the heat retaining property of the melt When creating a new bottom structure, it has a high thermal conductivity λ of 0.05 W / m · K or less on the bottom layer of the refractory layer that constitutes the bottom structure, that is, on the upper surface of the iron shell. By forming a heat insulating layer, more specifically, a heat insulating layer made of a high-performance heat insulating material, which is a microporous molded body mainly composed of silica fine particles, the amount of heat conduction to the iron skin can be suppressed, thereby It can greatly improve the heat retention of the melt.

(B) It should be noted that a heat-resistant temperature of a high-performance heat insulating material having a thermal conductivity λ of 0.05 W / m · K or less that is currently commercially available or currently available is about 1100 ° C. For this reason, although the possibility is extremely low, if a melt, particularly a metal such as Fe or Cu, has penetrated into the heat insulating layer made of the high-performance heat insulating material, the iron skin on the lower surface of the heat insulating layer Is not without risk of red heat and melting. Therefore, when there is a concern about the penetration of the melt into the heat insulation layer, or when the probability of iron skin erosion due to the melt penetration is to be zero, the gap between the heat insulation layer and the iron skin. A fireproof refractory layer should be formed as a backup. In other words, by forming a refractory refractory layer on the top surface of the iron skin and a heat insulating layer made of a high-performance heat insulating material on the top surface, the heat retention of the melt can be improved by suppressing the amount of heat conduction to the iron skin. In addition to being able to completely prevent equipment stoppage due to iron skin erosion.

(C) On the other hand, the first layer, which is the uppermost layer, is always in contact with the high-temperature slag, so that a castable layer made of a silicon carbide refractory having excellent slag penetration resistance and spalling resistance should be formed.

(D) However, since the silicon carbide refractory of the first layer has a high thermal conductivity λ, the entire first layer is maintained at a high temperature, and the melt, particularly metal such as Fe, Cu, etc. There is a risk of penetration into the lower layer easily. Therefore, a castable layer made of an alumina refractory having excellent slag penetration resistance and spalling resistance should be formed as a second layer on the back of the first layer for backup.

  Based on the above findings, the present inventor has conceived a furnace bottom structure of a waste melting furnace having a laminated structure that is optimal for improving the heat retention of the melt. That is, according to the present invention, in the bottom structure of a waste melting furnace having a multilayer structure in which refractories are laminated on the upper surface of the iron skin, the first layer, which is the uppermost layer, is a castable layer made of silicon carbide refractory, the first layer Castable layer made of alumina refractory on the second layer on the back side, heat insulating refractory layer on the third layer on the back side of the second layer, and microporous molding on the fourth layer on the back side of the third layer mainly composed of silica fine particles It is a furnace bottom structure of a waste melting furnace characterized by being a heat insulating layer made of a high-functional heat insulating material as a body.

(1) In the bottom structure of the waste melting furnace according to the present invention, a high-performance heat insulating material having a thermal conductivity λ of 0.05 W / m · K or less as the fourth layer of the refractory layer constituting the bottom structure. Since the heat insulating layer made of is used, it is possible to suppress the heat conduction amount to the iron skin, and hence the heat dissipation amount from the hearth, thereby greatly improving the heat retention of the melt. Accordingly, the hot water discharge interval can be greatly extended, and, for example, the conventional hot water discharge operation at 60 minute intervals can be performed at 90 minute intervals. As a result, the human cost of the work personnel can be greatly reduced. Moreover, since the hot water discharge interval can be greatly extended, the required number of consumables such as rods and bits can be reduced and the utility cost can be reduced.

(2) In other words, the bottom structure of the waste melting furnace according to the present invention consisting of the first to fourth layers can maximize the advantages of each refractory, and each refractory. Because it has a laminated structure that takes into account the layer order of refractories so as to compensate for the shortcomings, the heat retention of the melt is greatly improved by suppressing the amount of heat conduction to the iron skin, which could not be achieved with the prior art. Can do.

(3) Further, in the bottom structure of the waste melting furnace according to the present invention in which a refractory refractory layer is formed as a fifth layer on the back surface of the fourth layer, it is temporarily melted to the fourth layer made of a high-functional heat insulating material. Even if a metal such as Fe, Cu penetrates, the fifth layer of the refractory refractory layer can completely prevent the melt from entering the iron skin, so only the heat retention of the melt is improved. In addition, it is possible to completely prevent the equipment from being stopped due to the iron skin melting.

The best mode for carrying out the present invention will be described below with reference to FIGS.
FIG. 1 is a cross-sectional view showing an example of a bottom structure of a waste melting furnace according to the present invention. In this example, four layers of refractories are laminated on the upper surface of an iron shell 9. Hereinafter, the action of each layer and the selection basis will be described in detail.

  First, since the first layer, which is the uppermost layer, is always in contact with the high-temperature melt 1, a castable layer made of a silicon carbide refractory 4 having excellent slag penetration resistance and spalling resistance is formed. In this case, a castable layer made of a silicon carbide refractory 4 containing at least 30% by mass or more of silicon carbide is desirable. By using a material containing 30% by mass or more of silicon carbide, the slag penetration resistance can be sufficiently exhibited. Moreover, thermal conductivity (lambda) becomes high by containing 30 mass% or more of silicon carbide. For example, when silicon carbide refractory 4 having 70% by mass of silicon carbide, alumina + silica = 29% by mass and the remaining calcium oxide of 1% by mass is used as the other components, the thermal conductivity λ is 11.3 W / m · It is about K.

  However, since the silicon carbide refractory 4 used for the first layer has a high thermal conductivity as described above, the entire first layer is maintained at a high temperature. As a result, the melt 1, particularly Fe, Cu, etc. There is a risk that metal may penetrate through joints and cracks in the first layer. When the melt 1 reaches the layer made of the heat insulating refractory 6, the heat insulation is lost, the hearth is cooled, the melt is solidified on the hearth surface, and the discharge of the melt from the tap 2 is not possible. It becomes possible.

  For this reason, as the second layer on the back surface of the first layer, a castable layer made of the alumina refractory 5 having excellent slag penetration resistance and spalling resistance is formed, whereby the melt 1 is formed from the heat insulating refractory 6. To penetrate into the layer. In addition, since the original purpose of the second layer is fire resistance, the alumina refractory 5 is desirably an alumina refractory containing at least 50% by mass or more of alumina in order to exhibit fire resistance. It is desirable to select a material having a thermal conductivity λ smaller than that of the first layer. For example, an alumina refractory 5 containing 93% by mass of alumina, 6% by mass of silica and 1% by mass of calcium oxide as other components can be used, and its thermal conductivity λ is 2.1 W smaller than that of the first layer. / M · K or so.

  Next, as for the third layer on the back surface of the second layer, as described above, the thermal conductivity λ of the first layer and the second layer is large, and the amount of heat held by the melt 1 such as slag is transmitted to the next layer. Since it is easy, in order to reduce this heat transfer amount, a refractory layer using a heat insulating refractory 6 having a thermal conductivity λ smaller than that of the first layer and the second layer is formed. For example, it is desirable to use a heat-insulating refractory 6 having a wavelength of λ = 0.26 W / m · K.

  Next, as the fourth layer on the back surface of the third layer, in order to minimize the amount of heat transfer from the heat insulating refractory layer of the third layer to the iron skin, the thermal conductivity λ is 0.05 W / m · K or less. Although the heat insulating layer made of the high-functional heat insulating material 7 is formed, it is desirable to select a material that satisfies about λ = 0.02 W / m · K, which is about 1/10 of the heat insulating refractory layer of the third layer. For example, POREXTHERM WDS (registered trademark) sold by Kurosaki Harima Co., Ltd. can be used. The high-performance heat insulating material 7 is made of fumed silica and a substance that does not transmit infrared rays, has a fine micropore structure that regulates the movement of air molecules, and differs from conventional heat insulating materials that simply take in air. It is a microporous molded body mainly composed of silica fine particles that achieves thermal conductivity exceeding that of still air by controlling heat transfer such as solid heat transfer, air molecule transfer, and infrared ray transmission.

  As described above, the primary object of the present invention is to create a new bottom structure of a waste melting furnace having a laminated structure that is optimal for suppressing the temperature drop of the slag, that is, for improving the heat retention of the melt 1. In particular, by forming a heat insulating layer made of the high-performance heat insulating material 7 having a thermal conductivity λ of 0.05 W / m · K or less as the fourth layer, the amount of heat conduction to the iron skin 9 can be suppressed, Thereby, the heat retention of the melt 1 can be significantly improved. The thermal conductivity λ at the maximum use temperature of about 1000 ° C. or more of conventional heat-insulating refractories is about 0.2 to 0.5 W / m · K, and in order to secure a very large heat insulation effect using these It is necessary to greatly increase the layer thickness. However, increasing the layer thickness greatly has a limit from the viewpoint of the structural stability of the refractory and is difficult in practice. Therefore, in the present invention, in order to obtain a high heat insulation effect without increasing the layer thickness, that is, while ensuring the structural stability of the refractory, the maximum use temperature of the conventional heat-insulating refractory is about 1000 ° C. or more. The target is about 1/10 of the thermal conductivity λ, and λ = 0.05 W / m · K is set as the upper limit.

  The thickness of the fourth layer is preferably 3 to 20 mm. Since the high-performance heat insulating material 7 used in the fourth layer has high compressibility, it compresses and shrinks due to the weight of a refractory and a slag melt laminated on the upper part of the fourth layer, so that the thickness of the fourth layer is 20 mm. Exceeding this may cause excessive shrinkage and the surrounding refractories may collapse. On the other hand, if the layer thickness is 20 mm or less, the shrinkage is about 3 mm, which is equivalent to the thickness of the joint material (mortar) between the layers. However, there is little influence on the entire refractory structure, and there is no sinking or instability due to depression. However, if the layer thickness is less than 3 mm, a sufficient heat insulating effect cannot be obtained.

  Moreover, it is desirable to construct mortar with a layer thickness of about 3 mm on the front and back of the heat insulating layer made of the high-performance heat insulating material 7 of the fourth layer. By applying mortar on the front and back of the heat insulation layer, it is possible to secure a shrinkage allowance when the highly functional heat insulating material 7 is compressed and shrunk, thereby increasing the stability of the entire structure. Moreover, the function as an expansion allowance and contraction allowance when the highly functional heat insulating material 7 expands by heat can be expected. The layer thickness itself of the fourth layer is 3 to 20 mm, and the shrinkage allowance when the high-performance heat insulating material is compressed and shrunk is about 3 mm. Therefore, the thickness of the mortar is preferably about 3 mm. .

  However, the heat resistance temperature of the high-performance heat insulating material 7 having a thermal conductivity λ of 0.05 W / m · K or less that is currently commercially available or currently available is about 1100 ° C. For this reason, although the possibility is extremely low, if the melt 1, especially a metal such as Fe or Cu, has penetrated into the fourth layer, the penetration of the melt 1 into the fourth layer itself There is no ability to prevent it, and it is not without the fear that the iron skin 9 will be red hot and melted down, resulting in equipment shutdown due to iron skin melt damage.

  For this reason, when there is a concern about the penetration of the melt 1, particularly metal such as Fe, Cu, into the fourth layer, or when it is desired to reduce the probability of iron skin melting due to the melt penetration to zero as much as possible. As shown in FIG. 2, a refractory refractory layer made of a refractory refractory 8 is formed as a fifth layer on the back surface of the fourth layer as a backup, so that the melt 1 such as slag and metal is applied to the iron skin 9. Intrusion can be prevented.

FIG. 3 is a model diagram used for heat transfer calculation of the bottom structure of a waste melting furnace, and the heat transfer amount of the bottom structure according to the present invention comprising the bottom structure according to the prior art and the first to fourth layers. Are shown for comparison. The conditions used for heat transfer calculation are shown below.
(1) Furnace heat transfer coefficient: 850 W / m ² · K
(2) External heat transfer coefficient: 8W / m ² · K
(3) Slag temperature: 1500 ° C
(4) Outside temperature: 30 ° C

  As a result of the heat transfer calculation using the above model, in the bottom structure according to the prior art shown on the left side of FIG. 3, the boundary temperature (the temperature at point A in FIG. 3) between the core 9 of the furnace bottom and the heat insulating material is It became 280 degreeC. In contrast, in the furnace bottom structure according to the present invention shown on the right side of FIG. 3, the boundary temperature (the temperature at point B in FIG. 3) between the iron core 9 and the heat insulating material at the furnace bottom was 155 ° C. That is, the boundary temperature of the bottom structure according to the present invention consisting of the first to fourth layers is 125 ° C. lower than the boundary temperature of the bottom structure according to the prior art, and the adiabatic drop rate is about 55%. became. This remarkably shows the effect of the furnace bottom structure according to the present invention.

It is sectional drawing which shows an example of the furnace bottom structure of the waste melting furnace which concerns on this invention. It is sectional drawing which shows another example of the furnace bottom structure of the waste melting furnace which concerns on this invention. It is the model figure used for the heat transfer calculation of the furnace bottom structure of a waste melting furnace. It is sectional drawing which shows the furnace bottom structure of the waste melting furnace which concerns on a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Melt of slag, metal, etc. 2 Hot water outlet 3 Opening rod / bit 4 Silicon carbide refractory 5 Alumina refractory 6 Heat insulation refractory 7 High performance heat insulation 8 Refractory refractory 9 Iron skin 10 Furnace bottom 11 Blower tuyere 12 Thermometer 13 Insulating refractory

Claims (5)

In the bottom structure of a waste melting furnace consisting of a multilayer structure with refractories laminated on the upper surface of the iron skin,
A castable layer made of a silicon carbide refractory, the first layer being the uppermost layer;
A castable layer made of alumina refractory on the second layer on the back of the first layer;
The third layer on the back of the second layer is a heat insulating refractory layer,
A furnace bottom structure for a waste melting furnace, wherein the fourth layer on the back surface of the third layer is a heat insulating layer made of a high-functional heat insulating material that is a microporous molded body mainly composed of silica fine particles.
The furnace bottom structure of a waste melting furnace according to claim 1, further comprising a refractory refractory layer formed as a fifth layer on the back surface of the fourth layer.
The bottom structure of the waste melting furnace according to claim 1 or 2, wherein the thickness of the fourth layer is 3 to 20 mm.
The first layer is a castable layer made of a silicon carbide refractory containing at least 30% by mass of silicon carbide,
The bottom of the waste melting furnace according to any one of claims 1 to 3, wherein the second layer is a castable layer made of an alumina refractory containing at least 50 mass% of alumina. Construction.
The bottom structure of a waste melting furnace according to any one of claims 1 to 4, wherein mortar is applied to the front and back of the fourth layer.

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