JP5229058B2 - Refractory structure of cement manufacturing apparatus and method of using the same - Google Patents

Description

  The present invention relates to a fireproof structure of a cement manufacturing apparatus in which a refractory material is laid, and a method of using the cement manufacturing apparatus having the fireproof structure.

  FIG. 2 shows a schematic diagram of a normal cement baking apparatus. A refractory is applied to the inside of the ceiling portion 12 of the lowermost cyclone 11 of the preheating tower 10. FIG. 3 shows a cross-sectional view of the conventional lining refractory. This two-layered refractory structure includes a castable heat insulating layer 2 and a castable refractory layer 4. Studs 5 and 6 made of metal for fixing each refractory are welded to the iron skin 1 of the lowermost cyclone 11. Here, the stud is a kind of embedding rod for firmly fixing the castable refractory which is poured and solidified in the field to the inside of the furnace wall, and many studs are embedded in the castable. Studs are installed alternately for the purpose of preventing the fall of refractory materials, which are mixed alternately with either the Y-shaped stud 5 with the tip of the stud branched or the YY-shaped stud 6 with the stud branched in the middle. Has been.

  However, in recent situations where waste is effectively used as a raw material for cement, the refractory has come off as the amount of waste used gradually increases. As a result, the overall thickness of the refractory is reduced and the temperature of the iron skin 1 is increased. Therefore, the cement firing device had to be stopped and repaired.

  Patent Document 1 discloses a method for constructing two or three layers of refractories. However, the above-mentioned problem that seems to be caused by the gradual increase in the amount of waste used is not described, and a countermeasure for preventing the refractory from peeling off has been awaited. Since the thickness of the heat insulating layer and the refractory layer is based only on the refractory heat insulating performance, the stud is easily corroded under the use conditions such that the temperature of the boundary portion 13 of each layer of the refractory is 700 to 800 ° C. Peeling and falling of the inner lining refractory was inevitable.

JP-A-11-130485

  An object of the present invention is to provide a refractory structure for a cement manufacturing apparatus and a method for using the refractory for reliably holding the refractory without peeling or dropping.

The inventors of the present invention carefully observed the situation of the heat insulating layer 2 and the refractory layer 4 that are lining refractories, and as a result of various studies, the inventors have obtained the following knowledge.
First, in recent circumstances where waste is effectively used as a raw material for cement, the refractory has come off as the amount of waste used increases gradually. As a result of investigating the cause of the peeling, it was found that the studs 5 and 6 supporting and fixing the refractory were corroded and cut, and the refractory could not be held. In addition, the cut portion is seen at the boundary portion 13 between the heat-insulating layer 2 and the refractory layer 4 of the lining refractory. When the cut portion is analyzed, it is found that the main cause is metal corrosion. The temperature of the boundary portion 13 between the heat insulating layer 2 and the refractory layer 4 shown in FIG. 3 was 790 ° C. when thermal calculation was performed. In the region around this temperature, it was speculated that the chemical components potassium chloride (KCl) and sodium chloride (NaCl) in the cement raw material existed in a liquid state. When the temperature range is in the range of 700 to 800 ° C., KCl and NaCl, which are gaseous alkali salts that have entered from the inside of the furnace 7 through the gap formed at the boundary portion 13 between the heat insulating layer 2 and the refractory layer 4, are in the liquid phase. Become. This liquid phase condenses, corroding the metal studs 5 and 6 in the boundary portion 13 holding the heat insulating layer 2 and the refractory layer 4, and in some cases, the cutting 15 is likely to occur near the boundary portion 13. I guess it was. This temperature range is called the corrosion temperature range 9. Recently, wastes containing a large amount of chlorine have increased, and the chlorine concentration in the gas in the lowermost cyclone 11 shown in FIG. 2 has increased, and it is considered that such corrosion has increased. .

As shown in FIG. 7, a refractory is installed in a crack due to a thermal stress due to a difference in thermal expansion between the refractory layer 4 and the studs 5 and 6, and an inner cylinder portion 17 which is a lower end portion of the cyclone gas outlet 19 of the lowermost cyclone 11. It was estimated that KCl, NaCl, etc. vaporized in the furnace 7 invaded the boundary portion 13 through a portion in the vicinity of the area not to be used. This is caused by the gap between the sleeve 18 and the inner cylindrical portion 17 in the state where the hole is opened due to corrosion by the alkali salt corrosive gas contained in the furnace 7, the gap between the sleeve 18 and the refractory layer 4, and the like. It was considered that the liquid phase temperature region liquefied and entered at the boundary portion 13.
From these examinations, it is estimated that if the boundary portion 13 exists in the corrosion temperature region 9, the studs 5 and 6 are corroded and likely to be cut. As a result, the refractory layer 4 is peeled off, the overall thickness of the refractory is reduced, the temperature of the iron skin 1 rises, and it is estimated that the cement baking apparatus must be stopped and repaired. did.

The present inventors have found a refractory structure in which the boundary portion 13 does not exist in the corrosion temperature region 9 for the lining refractory in the preheating tower 10 of the cement firing apparatus.
That is, the present invention is as follows.
(1) A stud in which one end is fixed to the inner wall surface of the cement manufacturing apparatus that becomes a high temperature atmosphere and the other end extends toward the high temperature atmosphere, and a heat insulating layer in which a heat insulating board is laid along the inner wall surface, A refractory layer in which a refractory is laid in contact with the heat insulating boat layer, and a refractory structure of a cement manufacturing apparatus comprising:
The heat insulation layer has a thickness of 25 to 50 mm, the fireproof layer has a thickness of 200 to 300 mm, the stud is immersed in the heat insulation layer and the fireproof layer, and the heat insulation board and the fireproof layer. A fireproof structure for a cement manufacturing apparatus, characterized by having a structure for holding an object.
(2) The cement according to (1), wherein the high temperature atmosphere is at least one of a lowermost cyclone of a preheating tower, a calcining furnace, a rising duct, or a kiln bottom of a rotary kiln in a cement manufacturing apparatus. Fireproof structure of manufacturing equipment.
(3) The temperature when a high-temperature substance containing chloride is present in the high-temperature atmosphere and a part of the high-temperature substance containing chloride becomes gaseous and reaches the boundary between the refractory layer and the heat insulating layer, The method of using the cement manufacturing apparatus which has the fireproof structure of said (1) description which is the temperature below the solidification temperature of the high temperature substance containing a chloride.
(4) The method using the cement manufacturing apparatus having the fireproof structure according to (3), wherein the solidification temperature is 700 ° C. or less.

  According to the present invention, since the gap of the boundary portion 13 is not formed at the position of the refractory layer where the chemical components KCl and NaCl exist in a liquid state, corrosion of the studs 5 and 6 can be greatly reduced. As a result, the corrosion cutting 15 of the studs 5 and 6 is reduced, and the refractory can be prevented from falling into the furnace 7. Thereby, the frequency which repairs a refractory can fall significantly, and the operating degree of a cement baking apparatus can be improved.

The schematic of the structure of the refractory in this invention is shown. The schematic of an example of a normal cement baking apparatus is shown. The schematic of the structure of the conventional refractory is shown. The schematic of the structure of the Y-shaped stud in this invention is shown. The schematic of the structure of the YY-shaped stud in this invention is shown. A part of joint structure of the heat insulation board in this invention is shown. The schematic of the gap | interval which an alkali salt penetrate | invades into the boundary part of a refractory is shown. The laying figure of the heat insulation board and stud in the Example of this invention is shown.

In the present invention, the place where the cement production apparatus is in a high temperature atmosphere is the ceiling portion 12 of the lowermost cyclone 11 of the preheating tower 10, the lowermost cyclone 11, the calcining furnace 25, the rising duct 26, and the kiln of the rotary kiln. In at least one place such as the buttocks 27, there may be mentioned a ceiling portion or an inclined portion of the furnace where the castable of the furnace wall may be peeled off from the iron shell due to gravity.
As an example, two examples of the lining refractories to be constructed on the ceiling portion 12 of the lowermost cyclone 11 of the preheating tower 10 in the cement manufacturing apparatus will be described in detail. FIG. 1 shows a cross-sectional view of the lining refractory according to the present invention. This two-layer refractory structure is composed of a heat insulating board 3 having a thickness of 25 to 50 mm and a low thermal conductivity, and a castable refractory layer 4 having a thickness of 200 to 300 mm. By constructing with the thickness of such a heat insulation board 3 and the fireproof layer 4, the temperature of the boundary part 13 can be 700 degrees C or less. If the temperature is 700 ° C. or lower, the metal corrosive substance becomes a solid phase, and it is difficult to enter the position of the studs 5 and 6 from the gap of the boundary portion 13.

[Insulation board]
The thickness of the heat insulation board 3 used in the present invention is preferably 25 to 50 mm instead of the conventional heat insulation layer constructed by castable. If it is less than 25 mm, the temperature rise of the iron skin 1 (inner wall surface) is suppressed, so that the refractory layer 4 becomes too thick, which is not advantageous in terms of cost. Moreover, when it exceeds 50 mm, there exists a possibility that the fireproof layer 4 may become thin and a fireproof function may not be exhibited. Moreover, it is preferable that the shape of the heat insulation board 3 is a square or a rectangular board with one side having a length of 500 to 1000 mm. However, as long as the edges and corners of each side are arranged in contact with the adjacent heat insulating board so as not to form the joint 16 and the thickness is constant, any irregular shape may be used.

  As shown in FIG. 8, for the joint 16, the size of the heat insulating board 3 is determined so that the heat insulating board 3 hits the studs 5 and 6 and the width of all the joints 16 is about 0 to 5 mm. Also good. In this case, the dimension of one side of the heat insulating board 3 is increased by the length of the diameter of the studs 5 and 6. The heat insulating board 3 may be of any shape as long as it is a small piece of the heat insulating board 21 cut into small pieces. If it does in this way, the small-sized heat insulation board which will be discarded originally can be used effectively.

The material of the heat insulating board 3 is preferably a ceramic fiber board mainly composed of silica and alumina. As this heat insulation performance, a thermal conductivity of 0.1 to 0.2 W / (m · K) is preferable. For example, model number: SC board 1260 equivalent (SiO ₂ = 54% by mass, Al ₂ O ₃ = 46% by mass) manufactured by Shin-Nika Thermal Ceramics Co., Ltd. The heat insulating board 3 has a higher heat insulating effect than the conventional castable heat insulating layer, and when the thickness is 25 mm, the temperature is reduced by 250 to 300 ° C., or when the thickness is 50 mm, the temperature is reduced by 400 to 500 ° C. That is, since the heat insulation performance of the heat insulation board 3 is better than that of castable, the thickness can be reduced. For this reason, it becomes possible to separate the temperature in the vicinity of the boundary portion 13 from the corrosion temperature region 9 to the low temperature portion, and the liquid phase of the alkali salt hardly enters. Thereby, the corrosion of the studs 5 and 6 can be prevented.

At this time, the outside air temperature outside the furnace 8 is 30 ° C., the wind speed of the outside air is 1.0 m / second, and the temperature inside the furnace 7 is 900 ° C. By using the heat insulating board 3, the refractory layer 4 can be constructed with a high alumina castable. Further, since the heat insulation board 3 hardly undergoes drying shrinkage, cracks in the heat insulation layer 2 hardly occur.
As a method of laying the heat insulation board 3 on the iron skin 1 on the inner surface, a method of attaching the heat insulation board to the iron skin with an adhesive is simple.

[Stud and insulation board]
As shown in FIG. 4 and FIG. 5, the studs 5 and 6 for fixing each refractory are made of a round steel 22 welded to the iron shell 1 of the lowermost cyclone 11 by a welded portion 14. Only the Y-shaped stud 5 or the YY-shaped stud 6 is formed, or the two types of studs 5 and 6 are alternately arranged and mixed. Preferably, it is better in strength to include only the YY-shaped stud 6.

  The opening angle of the Y-shape is 55 to 80 degrees, and the materials of the studs 5 and 6 are stainless steel standards such as SUS304, SUS309S, and SUS310S, and the outer diameter is φ10 to 20 mm. If the outer diameter is less than φ10 mm, the castable can easily fall due to the weight of the refractory or the cutting due to corrosion of the studs 5 and 6. If the outer diameter exceeds 20 mm, the thermal performance specifications become excessive and the economy is inferior.

  The studs 5 and 6 have a square arrangement or a staggered arrangement, and the distance between the studs is 250 to 500 mm. However, as shown in the example of FIG. It is structurally good to set it as the dimension of the heat insulation board 3 which becomes the position where the joint 16 which is is. For this reason, since the dimension of the heat insulation board 3 is influenced and determined by the distance between the studs, it is preferable to determine the actual dimension of the heat insulation board 3 based on the thickness of the studs 5 and 6.

  As shown in FIG. 9, when the round steel 22 or the like is laid down and the surface of the heat insulating board 3 is pressed and welded to the studs 5 and 6, the fixing property of the heat insulating board 3 is further improved. When a small piece of heat insulating board 21 cut in small increments is used, it is preferable to press it with the pressing round steel 22.

[Castable refractories]
The refractory layer 4 is a high alumina castable. First, as shown in FIG. 6, a mold fixing bolt 25 having a diameter of φ5.5 to 6.5 mm for fixing the mold 23 is welded to the studs 5 and 6, and finally the mold 23 is assembled and fixed to the mold. The bolt 25 is fixed with a nut. Then, a castable refractory is poured into the mold 23 from the upper pouring opening 24, and is constructed as a refractory layer 4 as a refractory. After pouring the refractory, curing for 24 hours or more in the summer and curing for 48 hours or more in the winter, when the high alumina castable of the refractory layer 4 is condensed and solidified, the form 23 is disassembled. Removal of the refractory is completed. The thickness of the mold 23 is 12 mm, and the material is preferably a wood-based material, but may be a light metal-based or resin-based material having a strength sufficient to withstand the weight of the refractory.

  Regarding the thickness of the heat insulating board 3 and the thickness of the castable refractory described later, the inner wall surface is made of refractory according to the temperature in the furnace while preventing the liquid phase of the metal corrosive substance from being generated near the boundary between the layers. It is determined in consideration of protection and insulation from the outside of the furnace. The ratio of the thickness of the heat insulating board 3 to the thickness of the castable refractory is preferably in the range of 1: 4 to 1:12. Outside this range, it is not necessarily an advantageous method in terms of cost and construction. The thickness of the castable refractory is preferably 200 to 300 mm, and the thickness of the heat-insulating boat 3 is 25 to 50 mm, although it varies depending on the size and temperature of the high temperature atmosphere of the cement manufacturing apparatus.

The lining refractory in the preheating tower 10 is constructed with a two-layer structure in which the iron skin 1 side is composed of a heat insulating board 3 and the furnace inner side is composed of a castable refractory, that is, the heat insulating board 3 is a ceiling part of the furnace 7 12 is fixed to the iron skin 1 and castable work is performed by driving only one layer of the refractory layer 4. Since the castable layer of the refractory layer 4 is made thicker than in the prior art and the driving operation is performed in one layer, there is no gap between the castable boundary portions 13 in the corrosion temperature region 9 where the studs 5 and 6 may corrode. Therefore, a structure in which a liquid phase of an alkali salt such as KCl or NaCl as a chloride which is a metal corrosive substance is difficult to be formed can be obtained.
By adopting a refractory structure as in the present invention, it is difficult to form a liquid phase of a metal corrosive substance at the boundary portion 13 which is a gap between two refractories, and the corrosion cutting 15 of the stud can be greatly reduced. it can.

  A cement manufacturing apparatus is operated using the cement manufacturing apparatus having the above-mentioned fireproof structure. A high temperature material containing a chloride such as KCl or NaCl is present in the high temperature atmosphere. Regarding the mechanism in which high-temperature substances containing chlorides become gaseous and reach the boundary 13 between the heat insulating layer 2 and the refractory layer 4 and corrode the studs, the volatilized chloride becomes gaseous and passes through the clearance at the end of the refractory. It reaches the boundary portion 13 and becomes a liquid state here, and it is presumed that it spreads by capillary action and reaches the metal stud to be corroded.

  The temperature when a part of the high-temperature substance containing chloride becomes gaseous and reaches the boundary between the refractory layer and the heat insulating layer is a temperature equal to or lower than the solidification temperature of the high-temperature substance containing chloride. Thereby, corrosive substances such as KCl and NaCl can be prevented from contacting the stud in the liquid phase. When the corrosive substance is composed mainly of KCl, the solidification temperature can be effectively prevented by setting the solidification temperature to 700 ° C. or lower.

[Location of fireproof structure]
As the lining refractory of the ceiling portion 12 of the lowermost cyclone 11 in the cement-heated preheating tower 10, the castable refractory layer 4 of the present invention shown in FIG. The gas temperature at the ceiling portion 12 of the lowermost cyclone 11 was 900 ° C. on average, and the chlorine concentration at the chute portion 20 of the lowermost cyclone 11 was 2 mass%.

[Identification of corrosion temperature range]
A raw material with a chlorine concentration of 2 mass% sampled by the chute 20 of the lowermost cyclone 11 was subjected to a heating and heating test in an experimental rotary electric furnace. As a result, the respiration angle of the sample in the rotary electric furnace began to change at a temperature exceeding 700 ° C., and the dissolution of chloride in the sample became vigorous at around 750 ° C. and began to adhere to the furnace wall. Therefore, the start temperature of adhesion to the furnace wall (liquid phase start temperature) in this sample, that is, the boundary temperature between the solid phase and the liquid phase was 700 ° C., and the temperature exceeding 700 ° C. was specified as the corrosion temperature region. Thereby, if a boundary part can be set to 700 degrees C or less, it is anticipated that corrosion will be prevented.

[Identification of insulation board and refractory thickness]
As a result of heat conduction calculation, the thickness of the heat insulation board 3 and the fireproof layer 4 was determined as follows. The total thickness of the heat insulating board 3 and the refractory layer 4 does not affect the flow of the gas in the furnace, and thus is 275 mm, which is the design value of the cyclone 11 as before. Next, calculation is performed using a steady-state heat conduction calculation formula so that the internal temperature is 900 ° C., the temperature of the iron skin 1 (inner wall surface) is 150 ° C., and the temperature at the boundary between the heat insulation board 3 and the refractory layer 4 is 600 ° C. or less. did. From the 700 ° C. determined in the specification of the corrosion temperature region to the 100 ° C. margin, the temperature was set to 600 ° C. The heat insulation board 3 is a ceramic fiber board (model number: SC board 1260 manufactured by Nippon Kayaku Thermal Ceramics Co., Ltd.), and the main components are Al ₂ O ₃ = 46 mass%, SiO ₂ = 54 mass%, and the bulk specific gravity is 0.25 t / m ³ , heat resistant maximum temperature of 1260 ° C., and thermal conductivity of 0.17 W / (m · K) were used. The refractory layer 4 is a high alumina castable, the main components are Al ₂ O ₃ = 50 mass%, SiO ₂ = 42 mass%, the compressive strength is 48 MPa, the bending strength is 11.2 MPa, and the heat resistant maximum temperature is 1500 ° C. The thermal conductivity was 0.93 W / (m · K). From these thermal conductivities, the thickness of the heat insulating board 3 was 50 mm, and the thickness of the refractory layer 4 was 225 mm.

  The size of the heat insulation board 3 was set to a rectangular dimension of 616 × 900 mm as a reference dimension, and a rectangular piece of heat insulation board 21 was used in some constructions. The lining of the heat insulation board 3 on the iron skin 1 and the arrangement of the YY-shaped stud 6 were arranged as shown in FIG. At this time, the heat insulating boards 3 were arranged in contact with each other so that there was no gap between the edges. The adhesive between the heat insulating board 3 and the iron skin 1 was a synthetic resin bond.

  As for the dimensions of the stud, the height was 250 mm, and the YY-shaped stud 6 was used as the shape. The stud has a diameter of 16 mm, the opening angle of the Y-shape of the tip and the middle is 60 degrees, and the material is round steel 22 of SUS304. The distance between the studs was 450 mm in the long side direction of the heat insulating board 3 and 616 mm in the short side direction.

  FIG. 9 shows an example of the arrangement of the round steel bars 22 for holding the heat insulating boards 3 and 21. The heat insulating boards 3 and 21 were pressed using the round steel 22 welded to the YY-shaped stud 6 so that all the heat insulating boards 3 and 21 were pressed. The round steel 22 had a diameter of φ5.5 mm. The width of the joint 16 is 0 to 3 mm, and when the castable refractory is driven, one layer of the refractory layer 4 is driven and the construction process is performed. At this time, the material of the portion of the joint 16 is a high alumina castable.

As shown in FIG. 6, the castable refractory is pierced with an oxygen gas cutter at the predetermined interval, as shown in FIG. It was. Next, the studs 5 and 6 were welded and fixed to the inner surface of the iron skin 1 inside the furnace at the predetermined interval. In addition, in the part of the pouring opening 24, the heat insulation board 3 was previously drilled so that the heat insulation board 3 was not attached.
Then, in order to form a space into which castables having a thickness of 225 mm from the heat insulating boards 3 and 21 are poured, and to form the mold 23 so as to embed the studs 5 and 6, the mold fixing bolts 25 are connected to the nearby studs 5 and 6. And fixed by welding. Thereafter, the mold 23 having a thickness of 12 mm was fixed at a predetermined position while being passed through the mold fixing bolt 25 and tightened with a nut.
When all the setting of the mold 23 was completed, the castable refractory of the refractory layer 4 was poured from the pouring port 24 as shown in the figure.
When the castable curing was completed and cured, the formwork 23 was removed, and a lid was welded to the pouring port 24 to complete the construction of the refractory.

  The temperature inside the furnace 7 is 900 ° C. on the average, and the temperature of the contact portion between the iron skin 1 and the heat insulation board 3 is 130 ° C. Even if the construction is performed in this way, the iron skin 1 did not red heat during operation. . In the present embodiment of the present invention, as a result of continuous operation of the preheating tower for about one year, disassembling the castable and carrying out an inspection survey, the YY-shaped stud 6 was not subjected to corrosion cutting 15 at all. This is so that the temperature at the boundary between the heat insulation board 3 and the refractory layer 4 is 600 ° C. or lower, which is lower than the boundary temperature between the solid phase and the liquid phase of the raw material sampled by the chute 20 of the lowermost cyclone 11. This is because the thickness of the heat insulation board and the refractory is set.

  INDUSTRIAL APPLICABILITY The present invention can be used when a metal corrosive gas is present in a cement firing apparatus in which a refractory is constructed using a stud, and there is a temperature region that becomes a liquid phase inside the refractory layer. .

1 Iron skin (inner wall surface)
2 Insulating layer 3 Insulating board 4 Refractory layer 5 Y-shaped stud 6 YY-shaped stud 7 Inside the furnace 8 Outside the furnace 9 Corrosion temperature region 10 Preheating tower 11 Lowermost cyclone 12 Ceiling part 13 Boundary part 14 Welding part 15 Corrosion cutting 16 Joint 17 Inner cylinder part 18 Sleeve 19 Cyclone gas outlet 20 Chute part 21 Small piece of heat insulation board 22 Round steel 23 Mold frame 24 Pouring port 25 Mold frame fixing bolt

Claims (4)

One end is fixed to the inner wall surface of the location that becomes a high temperature atmosphere of the cement manufacturing apparatus, the other end extends toward the high temperature atmosphere, a heat insulating layer in which a heat insulating board is laid along the inner wall surface,
A refractory structure of a cement manufacturing apparatus comprising a refractory layer in which a refractory material is laid in contact with the heat insulating boat layer,
The heat insulation layer has a thickness of 25 to 50 mm, the fireproof layer has a thickness of 200 to 300 mm, the stud is immersed in the heat insulation layer and the fireproof layer, and the heat insulation board and the fireproof layer. A fireproof structure for a cement manufacturing apparatus, characterized by having a structure for holding an object. 2. The fire resistance of a cement production apparatus according to claim 1, wherein the high temperature atmosphere is at least one of a lowermost cyclone of a preheating tower in a cement production apparatus, a calcining furnace, a rising duct, or a kiln bottom of a rotary kiln. Construction. A temperature when a high-temperature substance containing chloride exists in the high-temperature atmosphere, and a part of the high-temperature substance containing chloride becomes gaseous and reaches the boundary between the refractory layer and the heat insulating layer, the chloride The method of using a cement manufacturing apparatus having a refractory structure according to claim 1, wherein the temperature is equal to or lower than a solidification temperature of a high-temperature substance including The method for using a cement manufacturing apparatus having a fireproof structure according to claim 3, wherein the solidification temperature is 700 ° C. or less.

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