Method for constructing hot air stove and hot air stove

Abstract

To provide a construction method of a hot air furnace and a hot air furnace capable of reliably suppressing fatigue of mixed cold air piping even when cold air supplied to a blast mixer is preheated.SOLUTION: In a construction method of a hot air furnace 1, when upper mixed cold air piping 7 and lower mixed cold air piping 8 are connected by an expansion joint 9, the axial positions of a mounting part 7b of the upper mixed cold air piping 7 and a mounting part 8b of the lower mixed cold air piping 8 are adjusted to secure an axial length L of the expansion joint 9 so that the expansion joint 9 is able to tolerate the axial displacement of mixed cold air piping 6 caused by the switching of the hot air furnace 1 during operation. Further, a position of the mounting part 8b of the lower mixed cold air piping 8 in the axial normal direction with respect to the mounting part 7b of the upper mixed cold air piping 7 is adjusted so that a distance Δ between a center line CL2 of the repeated displacement of a lower part 9b of the expansion joint 9 and a center line CL1 of an upper part 9a of the expansion joint 9 due to the switching of the hot air furnace 1 during operation is 10% or less of the axial length L of the expansion joint 9.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for constructing a hot stove and a hot stove used, for example, in the steel industry, and is suitable for hot stoves that generate hot air to be blown into blast furnaces, for example. [Background technology]

[0002] A hot stove is a facility that blows air (hot air) heated to about 1200°C to a blast furnace. A hot stove repeats the process of storing heat in a heat storage material by burning fuel gas and heating (blowing) air using the heat storage material. Three or more hot stoves are provided for each blast furnace, and hot air is continuously blown to the blast furnace by switching between the hot stoves during operation. The temperature of the hot air coming out of the combustion chamber of the hot stove is not constant, and for example, it drops in accordance with the decrease in the amount of stored heat after switching between the hot stoves. For this reason, in order to keep the temperature of the hot air supplied to the blast furnace constant, the temperature is adjusted by mixing cold air with the hot air in a blast mixer. The cold air mixed in the blast mixer is not necessarily at room temperature, and is often preheated to about 200°C, for example, by heat exchange with the exhaust gas from the hot stove. This preheated cold air is supplied to the blast mixer through a mixed cold air piping.

[0003] A method for constructing such a hot stove is known in the art, for example, as shown in Patent Document 1. The method of constructing a hot stove shown in Patent Document 1 is a method of constructing a hot stove in which the heat storage chamber, combustion chamber, and blast mixer are separate, no expansion joints are used in the connecting parts, the upper end of the heat storage chamber and the upper end of the combustion chamber are connected with a connecting pipe, the middle part of the combustion chamber and the upper end of the blast mixer are connected with an outlet pipe, and the lower end of the blast mixer is connected to a hot air valve via a lower hot air branch pipe. In this method of constructing a hot stove, the dimensions of the shells of the heat storage chamber, combustion chamber, and blast mixer are adjusted at the time of initial installation according to the amount of deflection of the combustion chamber frame due to the brickwork inside the combustion chamber, the relative difference in thermal expansion between the combustion chamber and the blast mixer when the bricks are dried and heated, and the amount of expansion of the lower hot air branch pipe when the bricks are dried and heated.

[0004] According to the method of constructing a hot stove shown in Patent Document 1, even in an external combustion type hot stove in which the regenerator, combustion chamber, and blast mixer are separate, the level difference between each part can be kept within the allowable limit for cracking of brick joints. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-53030 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional method for constructing a hot stove shown in Patent Document 1 has the following problems. That is, the method of constructing a hot stove shown in Patent Document 1 does not mention a mixed cold air piping that supplies preheated cold air to a blast mixer. When the cold air supplied to the blast mixer is preheated, repeated thermal expansion and contraction of the mixed cold air piping occurs each time the hot stove is switched, and the mixed cold air piping may become fatigued and damaged. The method of constructing a hot stove shown in Patent Document 1 does not mention a mixed cold air piping that supplies preheated cold air to a blast mixer, and it is not possible to suppress fatigue of the mixed cold air piping caused by repeated thermal expansion and contraction that occurs each time the hot stove is switched.

[0007] Therefore, the present invention has been made to solve the problems in the conventional art, and an object of the present invention is to provide a method for constructing a hot air stove and a hot air stove that can reliably suppress fatigue in the mixed cold air piping even when the cold air supplied to the blast mixer is preheated. [Means for solving the problem]

[0008] In order to solve the above problems, a method for constructing a hot stove according to one aspect of the present invention is a method for constructing a hot stove in which a regenerator, a combustion chamber, and a blast mixer are configured as separate entities, and which includes a mixed cold air piping that supplies preheated cold air to the blast mixer, the mixed cold air piping including an upper mixed cold air piping that supplies cold air to the blast mixer, and a lower mixed cold air piping that extends in the horizontal direction and has a horizontal piping section supported by a slide saddle, the upper mixed cold air piping and the lower mixed cold air piping being connected by an expansion joint that is displaceable in the axial direction and in the same axial perpendicular direction as the horizontal direction, and when the upper mixed cold air piping and the lower mixed cold air piping are connected by the expansion joint, The gist of this invention is to adjust the axial positions of the mounting part of the upper mixed cold air piping to which the upper part of the expansion joint is attached and the mounting part of the lower mixed cold air piping to which the lower part of the expansion joint is attached so as to ensure an axial length of the expansion joint that enables the expansion joint to absorb axial displacement of the mixed cold air piping associated with switching of the hot stove during operation, and to adjust the axial position of the mounting part of the lower mixed cold air piping to which the lower part of the expansion joint is attached relative to the mounting part of the upper mixed cold air piping in the direction perpendicular to the axis so that the distance between the center line of the repeated displacement of the lower part of the expansion joint associated with switching of the hot stove during operation and the center line of the upper part of the expansion joint is 10% or less of the axial length of the expansion joint.

[0009] Furthermore, a hot stove according to another aspect of the present invention has a regenerator, a combustion chamber, and a blast mixer that are constructed as separate entities, and is equipped with a mixed cold air piping that supplies preheated cold air to the blast mixer, the mixed cold air piping comprising an upper mixed cold air piping that supplies cold air to the blast mixer, and a lower mixed cold air piping that extends in the horizontal direction and has a horizontal piping section supported by a slide saddle, the upper mixed cold air piping and the lower mixed cold air piping being connected by an expansion joint that is displaceable in the axial direction and in the same axial perpendicular direction as the horizontal direction, and when the upper mixed cold air piping and the lower mixed cold air piping are connected by the expansion joint, The gist of this invention is that the present invention includes a position adjustment means for adjusting the axial position of the mounting part of the upper mixed cold air piping to which the upper part of the expansion joint is attached and the mounting part of the lower mixed cold air piping to which the lower part of the expansion joint is attached so as to ensure an axial length of the expansion joint that enables the expansion joint to absorb axial displacement of the mixed cold air piping caused by switching of the hot stove during operation, and for adjusting the axial position of the mounting part of the lower mixed cold air piping to which the lower part of the expansion joint is attached in the direction perpendicular to the axis relative to the mounting part of the upper mixed cold air piping so that the distance between the center line of the repeated displacement of the lower part of the expansion joint caused by switching of the hot stove during operation and the center line of the upper part of the expansion joint is 10% or less of the axial length of the expansion joint. Effect of the Invention

[0010] According to the hot air stove construction method and hot air stove of the present invention, even if the cold air supplied to the blast mixer is preheated, the expansion joint connected between the upper mixed cold air piping and the lower cooling piping can absorb displacement due to thermal expansion and contraction in the axial and perpendicular directions of the mixed cold air piping, thereby reliably suppressing fatigue of the mixed cold air piping. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a hot stove according to one embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged view of the vicinity of the expansion joint in the hot stove shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments shown below are merely examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention is not limited to the following embodiments in terms of the materials, shapes, structures, arrangements, etc. of the components. In addition, the drawings are schematic, and therefore, it should be noted that the relationship between thickness and planar dimensions, ratios, etc. may differ from the actual relationship between thickness and planar dimensions, and the drawings may include parts in which the relationship between dimensions and ratios differ from one another. Fig. 1 shows a schematic configuration of a hot stove according to one embodiment to which the hot stove construction method of the present invention is applied. The hot stove 1 shown in Fig. 1 is an external combustion (coppers type) hot stove, and is a facility for blowing hot air to a blast furnace (not shown) in a steelworks. This hot stove 1 comprises a regenerator 2, a combustion chamber 3, and a blast mixer 4, which are separate bodies. The upper end of the regenerator 2 and the upper end of the combustion chamber 3 are connected by a connecting pipe 5a, and the middle part of the combustion chamber 3 and the upper end of the blast mixer 4 are connected by an outlet pipe 5b.

[0013] The combustion chamber 3 burns fuel gas inside to heat the inside of the furnace. The heat storage chamber 2 stores the sensible heat inside the furnace that has been heated by the combustion chamber 3. The hot blast stove 1 repeats the process of storing heat in the heat storage chamber 2 by burning the fuel gas in the combustion chamber 3 and heating (blowing) air by the heat storage chamber 2. The hot air (having a temperature of 1200°C or higher) heated in the heat storage chamber 2 is blown through the combustion chamber 3 in the direction indicated by arrow A and supplied to the blast mixer 4. In addition, in the blast mixer 4, in order to keep the hot air supplied to the blast furnace at a constant temperature (about 1200°C), the hot air is mixed with preheated cold air supplied in the direction indicated by arrow B from a cold air mixing pipe 6 described later to adjust the temperature. The cold air mixed in the blast mixer 4 is not necessarily at room temperature, but is preheated to about 200°C, for example, by heat exchange with the exhaust gas from the combustion chamber 3. Then, as shown by arrow C, hot air whose temperature has been adjusted (to about 1200°C) is sent from the blast mixer 4 towards a blast furnace (not shown). Three or more hot stoves 1 are provided for each blast furnace, and hot air is continuously sent to the blast furnace by switching between the hot stoves 1 during operation. In other words, the temperature of the hot air sent from the heat regenerator 2 gradually decreases as the air is sent, and when the temperature has dropped to a predetermined level, the other hot stove 1 is switched to, the air is stopped, and heat storage begins. For this reason, the cold air mixed with the hot air in the blast mixer 4 to adjust the temperature of the hot air is repeatedly sent in large quantities immediately after switching, and stopped before switching to the other hot stove.

[0014] The hot stove 1 is equipped with a cold air mixing pipe 6 that supplies preheated cold air to the blast mixer 4. The cold air that is mixed with the hot air in the blast mixer 4 is preheated to about 200°C. The cold air is supplied to the blast mixer 4 via the cold air mixing pipe 6. The mixed cold air piping 6 includes an upper mixed cold air piping 7 that supplies cold air to the blast mixer 4, a lower mixed cold air piping 8, and an expansion joint 9 that connects the upper mixed cold air piping 7 and the lower mixed cold air piping 8. The upper mixed cold air piping 7 extends vertically in the direction indicated by Y in Fig. 1 beside the blast mixer 4, has a bent pipe section 7a at its upper end, and supplies cold air from above the blast mixer 4. The lower end of the upper mixed cold air piping 7 is provided with an attachment section (flange section) 7b for attaching the upper section (flange section) 9a of the expansion joint 9.

[0015] The lower mixed cold air piping 8 has a horizontal piping section 8a that extends horizontally as indicated by X in Fig. 1 and is supported by a slide saddle 10. The lower mixed cold air piping 8 curves vertically upward from the end of the horizontal piping section 8a, and at its upper end is provided an attachment section (flange section) 8b for attaching the lower section (flange section) 9b of the expansion joint 9. Here, the cold air supplied to the blast mixer 4 is preheated, and the mixed cold air piping 6 undergoes repeated thermal expansion and contraction as the flow rate of the cold air increases and decreases and is stopped repeatedly each time the hot air stove 1 is switched on and off. The horizontal piping section 8a provided in the lower mixed cold air piping 8 can be as long as 10 m or more due to restrictions on the horizontal arrangement of the equipment, and has large amounts of thermal expansion and contraction, so it is supported by a slide saddle (a support base that is not fixed; also known as a thrust saddle) 11.

[0016] The expansion joint 9 is a so-called bellows type expansion joint, and connects the upper mixed cold air pipe 7 and the lower mixed cold air pipe 8 with its axial direction being vertical. The expansion joint 9 can be displaced in the axial direction (the same direction as the vertical direction indicated by Y) and the axial direction perpendicular to the direction (the same direction as the horizontal direction indicated by X). The upper part (flange part) 9a of the expansion joint 9 is attached to the mounting part 7b of the upper mixed cold air pipe 7 by welding or the like, and the lower part (flange part) 9b of the expansion joint 9 is attached to the mounting part 8b of the lower mixed cold air pipe 8 by welding or the like. As described above, the cold air supplied to the blast mixer 4 is preheated, and the mixed cold air pipe 6 repeats thermal expansion and thermal contraction with the repeated increase and decrease in the flow rate of the cold air and stoppage each time the hot stove 1 is switched. The expansion joint 9 absorbs the vertical thermal expansion and thermal contraction of the mixed cold air pipe 6 by displacing in the axial direction. Moreover, the expansion joint 9 absorbs the thermal expansion and contraction in the horizontal direction of the mixed cold air piping 6 by displacing in the direction perpendicular to the axis.

[0017] In this hot stove 1, as described above, the cold air supplied to the blast mixer 4 is preheated, and the mixed cold air piping 6 undergoes repeated thermal expansion and contraction as the flow rate of the cold air increases and decreases and is stopped repeatedly each time the hot stove 1 is switched. This can cause the mixed cold air piping 6 to fatigue and become damaged. In order to suppress fatigue of the mixed cold air piping 6, the hot stove 1 is provided with the expansion joint 9 described above that connects the upper mixed cold air piping 7 and the lower mixed cold air piping 8 that constitute the mixed cold air piping 6, and is also provided with a position adjustment means 12 for connecting the expansion joint 9, which will be described later, as shown in FIG. 2. The position adjustment means 12 adjusts the axial positions of the mounting portion 7b of the upper mixed cold air piping 7 to which the upper portion 9a of the expansion joint 9 is attached and the mounting portion 8b of the lower mixed cold air piping 8 to which the lower portion 9b of the expansion joint 9 is attached, so as to ensure an axial length L of the expansion joint 9 that enables the expansion joint 9 to absorb the axial (vertical) displacement of the mixed cold air piping 6 due to thermal expansion and thermal contraction accompanying switching of the hot air stove 1 during operation, when connecting the upper mixed cold air piping 7 and the lower mixed cold air piping 8 with the expansion joint 9. When it is not possible to secure the axial length L of the expansion joint 9 that enables the expansion joint 9 to absorb the axial (vertical) displacement of the mixed cold air piping 6 due to thermal expansion and contraction accompanying switching of the hot stove 1 during operation, the axial position of the mounting portion 7b of the upper mixed cold air piping 7 and the mounting portion 8b of the lower mixed cold air piping 8 can be adjusted by processing the upper mixed cold air piping 7 and the lower mixed cold air piping 8, changing the thickness of the mounting portions (flange portions) 7b, 8b, or using a different expansion joint.

[0018] 2, the position adjustment means 12 adjusts the position of the mounting part 8b of the lower mixed cold air piping 8, to which the lower part 9b of the expansion joint 9 is attached, in the axial direction (horizontal direction) relative to the mounting part 7b of the upper mixed cold air piping 7, so that the distance Δ between the center line CL2 of the repeated displacement of the lower part 9b of the expansion joint 9 accompanying switching of the hot stove 1 during operation and the center line CL1 of the upper part 9a of the expansion joint 9 is 10% or less of the axial length L of the expansion joint 9. If the aforementioned distance Δ is greater than 10% of the axial length L of the expansion joint 9, there is a disadvantage that the load applied in the shear direction rather than the original expansion and contraction direction of the expansion joint becomes excessive, which may damage the expansion joint. The position of the mounting portion 8b of the lower mixed cold air piping 8 in the axial direction relative to the mounting portion 7b of the upper mixed cold air piping 7 is adjusted by moving the position of the mounting portion 8b of the lower mixed cold air piping 8 in the axial direction (horizontal direction) relative to the mounting portion 7b of the upper mixed cold air piping 7 using the slide saddle 11 when the aforementioned distance Δ is not less than 10% of the axial length L of the expansion joint 9.

[0019] Here, the repeated displacement of the lower part 9b of the expansion joint 9 caused by switching of the hot stove 1 during operation is within the range from the center line CL1 of the upper part 9a of the expansion joint 9 to the "stroke at which the number of repetitions to failure Nf calculated from the Kellogg formula shown in the following equations (1), (2), and (3) is the design number of repetitions." The Kellogg formula is a formula for predicting the life of an expansion joint (bellows) from operating conditions such as stroke, which is described in the literature "Cryogenics Engineering, Vol. 28, No. 12 (1993) P. 663." The design repetition number is the number of hot stove switching cycles assumed within the period of the air suspension period during which planned repairs of the mixed cold air piping 6 can be made.

[0020] σa=3EtS / 2nH 2 ,σp=PH 2 / 2t 2 (1) σm = σa + σp (2)

[0021]

number

[0022] Here, σa: stretching stress [MPa], σp: pressure stress [MPa], σm: stiffness stress [MPa], E: Young's modulus [MPa], t: plate thickness [mm], D O :Outer diameter [mm], D i : Inner diameter [mm], S: Stroke [mm], n: Number of threads, H: Height of thread [mm] = (D O -D i ) / 2, P: Pressure [MPa], Nf: Number of repetitions The upper and lower parts 9a and 9b of the expansion joint 9 are attached to the mounting parts 7b of the upper mixed cold air piping 7 and the mounting parts 8b of the lower mixed cold air piping 8, respectively, after adjusting the axial positions of the mounting parts 7b of the upper mixed cold air piping 7 and the mounting parts 8b of the lower mixed cold air piping 8 and the axial perpendicular position of the mounting part 8b of the lower mixed cold air piping 8 relative to the mounting part 7b of the upper mixed cold air piping 7 using the position adjustment means 12.

[0023] This allows the expansion joint 9 to have an axial length L that can absorb the axial (vertical) displacement of the mixed cold air piping 6 caused by thermal expansion and contraction accompanying switching of the hot stove 1 during operation. Also, the distance Δ between the center line CL2 of the repeated displacement of the lower part 9b of the expansion joint 9 accompanying switching of the hot stove 1 during operation and the center line CL1 of the upper part 9a of the expansion joint 9 is 10% or less of the axial length L of the expansion joint 9. As a result, even if the cold air supplied to the blast mixer 4 is preheated, the expansion joint 9 connected between the upper mixed cold air piping 7 and the lower mixed cold air piping 8 can absorb displacement due to thermal expansion and contraction in the axial and perpendicular directions of the mixed cold air piping 6, thereby reliably suppressing fatigue of the mixed cold air piping 6.

[0024] Furthermore, the hot stove 1 is provided with an anti-sway member 11 that fixes the mounting portion 7b of the upper mixed cold air piping 7, to which the upper portion 9a of the expansion joint 9 is attached, to the blast mixer 4 when the upper mixed cold air piping 7 and the lower mixed cold air piping 8 are connected by the expansion joint 9. This makes it possible to regulate the axial and axially perpendicular positions of the mounting portion 7b of the upper mixed cold air piping 7 when the upper mixed cold air piping 7 and the lower mixed cold air piping 8 are connected by the expansion joint 9, and allows the expansion joint 9 to be more reliably attached between the upper mixed cold air piping 7 and the lower mixed cold air piping 8. Next, a method for constructing the hot stove 1 will be described with reference to FIGS. First, the heat storage chamber 2, the combustion chamber 3, and the blast mixer 4 are installed. At that time, the upper end of the heat storage chamber 2 and the upper end of the combustion chamber 3 are connected by a connecting pipe 5a, and the middle part of the combustion chamber 3 and the upper end of the blast mixer 4 are connected by an outlet pipe 5b. When installing the heat storage chamber 2, the combustion chamber 3, and the blast mixer 4, it is preferable to take into consideration the deflection caused by the brickwork inside the combustion chamber 3.

[0025] Next, the mixed cold air piping 6 is connected to the blast mixer 4. At this time, the bent pipe section 7a of the upper mixed cold air piping 7 of the mixed cold air piping 6 is connected to the upper part of the blast mixer 4, the horizontal pipe section 8a of the lower mixed cold air piping 8 is supported by a slide saddle 10, and the mounting section 7b of the upper mixed cold air piping 7 and the mounting section 8b of the lower mixed cold air piping 8 are opposed to each other with a gap therebetween for attaching an expansion joint 9. Thereafter, when connecting the expansion joint 9 between the upper mixed cold air piping 7 and the lower mixed cold air piping 8, the position adjustment means 12 adjusts the axial positions of the mounting part 7b of the upper mixed cold air piping 7 to which the upper part 9a of the expansion joint 9 is attached and the mounting part 8b of the lower mixed cold air piping 8 to which the lower part 9b of the expansion joint 9 is attached, so as to ensure the axial length L of the expansion joint 9 that enables the expansion joint 9 to absorb the axial (vertical) displacement of the mixed cold air piping 6 due to thermal expansion and thermal contraction accompanying switching of the hot stove 1 during operation. When the axial position of the mounting portion 7b of the upper mixed cold air piping 7 and the mounting portion 8b of the lower mixed cold air piping 8 cannot be secured such that the expansion joint 9 can absorb the axial (vertical) displacement of the mixed cold air piping 6 caused by thermal expansion and thermal contraction accompanying switching of the hot stove 1 during operation, adjustment of the axial position of the mounting portion 7b of the upper mixed cold air piping 7 and the lower mixed cold air piping 8 can be performed by processing the upper mixed cold air piping 7 and the lower mixed cold air piping 8, changing the thickness of the mounting portions (flange portions) 7b, 8b, or using a different expansion joint.

[0026] In addition, the position of the mounting part 8b of the lower mixed cold air piping 8, to which the lower part 9b of the expansion joint 9 is attached, in the axis-perpendicular direction (horizontal direction) is adjusted relative to the mounting part 7b of the upper mixed cold air piping 7 so that the distance Δ between the center line CL2 of the repeated displacement of the lower part 9b of the expansion joint 9 accompanying switching of the hot stove 1 during operation and the center line CL1 of the upper part 9a of the expansion joint 9 is 10% or less of the axial length L of the expansion joint 9 by the position adjustment means 12. When the aforementioned distance Δ is not 10% or less of the axial length L of the expansion joint 9, the adjustment of the axis-perpendicular direction position of the mounting part 8b of the lower mixed cold air piping 8 relative to the mounting part 7b of the upper mixed cold air piping 7 can be performed by moving the axis-perpendicular direction (horizontal direction) position of the mounting part 8b of the lower mixed cold air piping 8 relative to the mounting part 7b of the upper mixed cold air piping 7 by the slide saddle 11.

[0027] As described above, the repeated displacement of the lower part 9b of the expansion joint 9 caused by switching of the hot stove 1 during operation is within the range from the center line CL1 of the upper part 9a of the expansion joint 9 to the "stroke at which the number of repetitions to failure Nf calculated from the Kellogg formula shown in the above-mentioned equations (1), (2), and (3) is the design number of repetitions." Furthermore, when connecting the expansion joint 9 between the upper mixed cold air piping 7 and the lower mixed cold air piping 8, the mounting portion 7b of the upper mixed cold air piping 7 to which the upper portion 9a of the expansion joint 9 is attached is fixed to the blast mixer 4 by the anti-vibration member 11. This makes it possible to regulate the axial and axial-perpendicular position of the mounting portion 7b of the upper mixed cold air piping 7.

[0028] Next, an expansion joint 9 is connected between the upper cold air mixed piping 7 and the lower cold air mixed piping 8. At this time, the upper part 9a of the expansion joint 9 is fixed to the mounting part 7b of the upper mixed cold air piping 7 by welding or the like so that the axial direction of the expansion joint 9 is the vertical direction indicated by Y, and the lower part 9b of the expansion joint 9 is fixed to the mounting part 8b of the lower mixed cold air piping 8 by welding or the like. In this way, when the expansion joint 9 is connected between the upper mixed cold air piping 7 and the lower mixed cold air piping 8, the axial positions of the mounting portion 7b of the upper mixed cold air piping 7 and the mounting portion 8b of the lower mixed cold air piping 8 are adjusted by the position adjustment means 12 so as to ensure the axial length L of the expansion joint 9 that enables the expansion joint 9 to absorb the axial (vertical) displacement of the mixed cold air piping 6 due to thermal expansion and thermal contraction associated with switching of the hot stove 1 during operation, so that the expansion joint 9 can ensure the axial length L that enables the expansion joint 9 to absorb the axial (vertical) displacement of the mixed cold air piping 6 due to thermal expansion and thermal contraction associated with switching of the hot stove 1 during operation.

[0029] Furthermore, the position of the mounting part 8b of the lower mixed cold air piping 8 in the axial direction (horizontal direction) relative to the mounting part 7b of the upper mixed cold air piping 7 is adjusted by the position adjustment means 12 so that the distance Δ between the center line CL2 of the repeated displacement of the lower part 9b of the expansion joint 9 due to switching of the hot stove 1 during operation and the center line CL1 of the upper part 9a of the expansion joint 9 is 10% or less of the axial length L of the expansion joint 9. Therefore, in the expansion joint 9, the distance Δ between the center line CL2 of the repeated displacement of the lower part 9b of the expansion joint 9 due to switching of the hot stove 1 during operation and the center line CL1 of the upper part 9a of the expansion joint 9 is 10% or less of the axial length L of the expansion joint 9. As a result, even if the cold air supplied to the blast mixer 4 is preheated, the expansion joint 9 connected between the upper mixed cold air piping 7 and the lower mixed cold air piping 8 can absorb displacement due to thermal expansion and contraction in the axial and perpendicular directions of the mixed cold air piping 6, thereby reliably suppressing fatigue of the mixed cold air piping 6.

[0030] Furthermore, according to the method for constructing the hot stove 1 according to this embodiment, when connecting the expansion joint 9 between the upper mixed cold air piping 7 and the lower mixed cold air piping 8, the mounting portion 7b of the upper mixed cold air piping 7 to which the upper portion 9a of the expansion joint 9 is attached is fixed to the blast mixer 4 by the anti-sway member 11. This makes it possible to regulate the position of the mounting portion 7b of the upper mixed cold air piping 7 in the axial direction and in the axial direction perpendicular direction, and the expansion joint 9 can be more reliably attached between the upper mixed cold air piping 7 and the lower mixed cold air piping 8. Although the embodiment of the present invention has been described above, the present invention is not limited to this and various modifications and improvements can be made.

[0031] For example, an expansion joint 9 is connected between the upper mixed cold air piping 7 and the lower mixed cold air piping 8, but this connection work may be performed before the mounting portion 7b of the upper mixed cold air piping 7 is fixed to the blast mixer 4 by the anti-vibration member 11. [Explanation of symbols]

[0032] 1 hot stove 2 Heat storage chamber 3. Combustion chamber 4. Blast Mixer 5a Connecting pipe 5b Outlet pipe 6 Mixed cold air piping 7 Upper mixed cold air piping 7a Bent pipe section 7b Mounting part (flange part) 8 Lower mixed cold air piping 8a Horizontal piping section 8b Mounting part (flange part) 9 Expansion Joints 9a Upper part (flange part) 9b Lower part (flange part) 10 Slide Saddle 11 Anti-vibration member 12 Position adjustment means

Claims

1. A method for constructing a hot stove, comprising: a regenerator, a combustion chamber, and a blast mixer that are constructed separately; a mixed cold air piping that supplies preheated cold air to the blast mixer; the mixed cold air piping that supplies cold air to the blast mixer; and a lower mixed cold air piping that extends horizontally and has a horizontal piping section supported by a slide saddle; and the upper mixed cold air piping and the lower mixed cold air piping are connected by an expansion joint that is displaceable in an axial direction and in a direction perpendicular to the same axis as the horizontal direction, When connecting the upper mixed cold air piping and the lower mixed cold air piping by the expansion joint, the axial positions of the mounting part of the upper mixed cold air piping to which the upper part of the expansion joint is attached and the mounting part of the lower mixed cold air piping to which the lower part of the expansion joint is attached are adjusted so as to ensure an axial length of the expansion joint that allows the expansion joint to absorb the axial displacement of the mixed cold air piping caused by switching of the hot stove during operation, and the center line of the repeated displacement of the lower part of the expansion joint caused by switching of the hot stove during operation, i.e., the center line of the lower part of the expansion joint in the axis-perpendicular direction caused by switching of the hot stove during operation, is adjusted so as to be aligned along the axis of the expansion joint. a position of a mounting part of the lower mixed cold air piping for mounting the lower part of the expansion joint relative to the mounting part of the upper mixed cold air piping in the axis-perpendicular direction is adjusted so that, when the expansion joint is repeatedly displaced in the axis-perpendicular direction from the position of the center line of its upper part, the distance between a center line in the axis-perpendicular direction of the lower part of the expansion joint when the lower part of the expansion joint is displaced the largest, and a center line in the axis-perpendicular direction of the center line of the lower part of the expansion joint when the lower part of the expansion joint is displaced the smallest, and the center line of the upper part of the expansion joint, is 10% or less of the axial length of the expansion joint.

2. The method for constructing a hot air stove according to claim 1, characterized in that, when connecting the upper mixed cold air piping and the lower mixed cold air piping with the expansion joint, the mounting portion of the upper mixed cold air piping to which the upper part of the expansion joint is attached is fixed to a blast mixer with an anti-vibration member, and the axial and axial perpendicular positions of the mounting portion of the upper mixed cold air piping are regulated.

3. 3. A method for constructing a hot stove as claimed in claim 1 or 2, characterized in that the repeated displacement of the lower part of the expansion joint caused by switching of the hot stove during operation is within a range of "a stroke at which the number of repeated strokes to failure calculated by the Kellogg formula is the design number of repeated strokes" from the center line of the upper part of the expansion joint.

4. A hot air stove in which a regenerator, a combustion chamber, and a blast mixer are constructed separately, and which is provided with a mixed cold air piping for supplying preheated cold air to the blast mixer, the mixed cold air piping including an upper mixed cold air piping for supplying cold air to the blast mixer, and a lower mixed cold air piping having a horizontal piping section extending in a horizontal direction and supported by a slide saddle, the upper mixed cold air piping and the lower mixed cold air piping being connected by an expansion joint which is displaceable in an axial direction and in a direction perpendicular to the same axis as the horizontal direction, When connecting the upper mixed cold air piping and the lower mixed cold air piping by the expansion joint, the axial positions of the mounting part of the upper mixed cold air piping to which the upper part of the expansion joint is attached and the mounting part of the lower mixed cold air piping to which the lower part of the expansion joint is attached are adjusted so as to ensure an axial length of the expansion joint that enables the expansion joint to absorb the axial displacement of the mixed cold air piping accompanying switching of the hot stove during operation, and the axial positions of the mounting part of the lower mixed cold air piping to which the lower part of the expansion joint is attached are adjusted so as to ensure an axial length of the expansion joint that enables the expansion joint to absorb the axial displacement of the mixed cold air piping accompanying switching of the hot stove during operation, i.e., when the center line of the repeated displacement of the lower part of the expansion joint accompanying switching of the hot stove during operation, i.e., when the center line of the lower part of the expansion joint in the axis-perpendicular direction is repeatedly displaced in the axis-perpendicular direction from the position of the center line of the upper part of the expansion joint in the axis-perpendicular direction accompanying switching of the hot stove during operation, the lower part of the expansion joint is displaced the largest. a position adjusting means for adjusting the position of a mounting portion of the lower mixed cold air piping to which the lower part of the expansion joint is attached in the axis-perpendicular direction relative to the mounting portion of the upper mixed cold air piping so that a distance between a center line in the axis-perpendicular direction of the lower part of the expansion joint when the lower part of the expansion joint is displaced most slightly and a center line in the axis-perpendicular direction of the center line of the lower part of the expansion joint when the lower part of the expansion joint is displaced the smallest, and a center line of the upper part of the expansion joint is 10% or less of the axial length of the expansion joint, the position adjusting means comprising a slide saddle which supports a horizontal piping portion provided in the lower mixed cold air piping and moves the position of the mounting portion of the lower mixed cold air piping in the axis-perpendicular direction relative to the mounting portion of the upper mixed cold air piping.

5. The hot air stove according to claim 4, characterized in that when the upper mixed cold air piping and the lower mixed cold air piping are connected by the expansion joint, a vibration prevention member is provided for fixing the mounting portion of the upper mixed cold air piping to which the upper part of the expansion joint is attached to a blast mixer.

6. A hot stove as claimed in claim 4 or 5, characterized in that the repeated displacement of the lower part of the expansion joint caused by switching of the hot stove during operation is within the range of "a stroke at which the number of repeated strokes to failure calculated by the Kellogg equation is the design number of repeated strokes" from the center line of the upper part of the expansion joint.

Images