Method of preventing cracking of a furnace shell by adding a furnace shell clamp

Abstract

A method for preventing cracking of a furnace shell by adding a furnace shell hoop, comprising the following steps: S1, first constructing a hoop device; S2, adding a plurality of layers of uniformly distributed first and second rib plates outside the hot blast furnace and the air mixing chamber in the circumferential direction, placing the first fixing member on the first rib plate, and placing the second fixing member on the second rib plate; S3, after the furnace is dried and the hot blast furnace and the air mixing chamber enter a normal production state, the segmented first and second fixing members are connected together by screwing, and then the first and second fixing members are connected together by a pull rod. The method is simple, convenient to operate, and low in cost, completely solves the design defects of the rigid hoop and the rigid connecting pull rod, the expansion and contraction of the furnace shell and the expansion and contraction of the furnace shell up and down are in a relaxed free state, completely solves the cracking of the furnace shell, avoids the cracking of the furnace shell, and has significant social and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of hot blast stoves, and in particular to a method for preventing furnace shell cracking by installing furnace shell clamps. Background Technology

[0002] Currently, the shells of high-pressure, high-temperature hot blast stoves in blast furnaces have all developed common cracks, which seriously affect the safety of the hot blast stoves and the personal safety of the workers. Besides the known defects in the furnace shell material, insufficient shell thickness, stress concentration, slight changes in yield strength and hardness in the welds and heat-affected zone, and the presence of nitrate ions (thousands of PPM) generated during the high-temperature air supply period, another factor overlooked by the industry is the rigid connection structure formed by welding reinforcing clamps firmly to the furnace shell to reduce shell deformation due to increased air supply pressure. This rigid clamp structure restricts the gradual expansion of the furnace shell from the heating and warm-up phase to normal production, while the shell outside the clamped area expands freely. Furthermore, the clamps and the tie rods of the rigid connection also restrict the overall upward expansion of the furnace shell. These two design flaws, along with the tie rods connecting the clamps to the transverse connections, are significant but often overlooked factors contributing to furnace shell cracking. Based on current cracking cases, the furnace shell expansion value is calculated according to the standard 12×10⁻⁶. -6 The calculation is as follows:

[0003] The circumferential expansion of the furnace shell is limited by the furnace shell clamps:

[0004] Case 1: The inner diameter of the furnace shell in the straight section of the hot air outlet of Angang is 11260mm. The circumferential expansion is 33.96mm when the furnace shell temperature is 80℃; 42.45mm when the furnace shell temperature is 100℃; 50.94mm when the furnace shell temperature is 120℃; and 63.67mm when the furnace shell temperature is 150℃.

[0005] Case 2: The inner diameter of the furnace shell of the straight section of the hot air outlet in Zhanjiang is 12590mm. The circumferential expansion is 37.97mm when the furnace shell temperature is 80℃; 47.46mm when the furnace shell temperature is 100℃; 56.96mm when the furnace shell temperature is 120℃; and 71.19mm when the furnace shell temperature is 150℃.

[0006] Case 3: The inner diameter of the furnace shell of the straight section of the hot air outlet of Jingtang is 13520mm. The circumferential expansion is 40.77mm when the furnace shell temperature is 80℃; 50.97mm when the furnace shell temperature is 100℃; 61.16mm when the furnace shell temperature is 120℃; and 76.45mm when the furnace shell temperature is 150℃.

[0007] The upward expansion of the furnace shell is limited by the furnace shell clamps:

[0008] For example: 1. The rigid connection between the hoop and tie rod of the hot blast stove of Angang 4747m³ blast furnace restricts the upward expansion of the furnace shell: Assuming an average furnace shell temperature of 70℃, the height from the furnace bottom to the hot blast outlet is 32.1m, with an expansion of about 26.96mm, and the height from the furnace bottom to the furnace top is 51.54m, with an expansion of 43.29mm; when the average furnace shell temperature is 100℃, the expansion from the furnace bottom to the hot blast outlet is about 38.52mm, and the expansion from the furnace bottom to the furnace top is 61.86mm.

[0009] 2. The rigid connection between the hoop and tie rod of the hot blast stove of Baosteel Zhanjiang 5050m³ blast furnace restricts the upward expansion of the furnace shell: Assuming an average furnace shell temperature of 70℃, the height from the furnace bottom to the hot blast outlet is 27.7m, with an expansion of approximately 23.27mm; the height from the furnace bottom to the furnace top is 48.3m, with an expansion of 40.57mm. With an average furnace shell temperature of 100℃, the expansion from the furnace bottom to the hot blast outlet is approximately 33.24mm, and the expansion from the furnace bottom to the furnace top is 57.96mm.

[0010] 3. The rigid connection between the blast furnace hot blast stove clamps and tie rods in the Jingtang 5500m³ blast furnace restricts the upward expansion of the furnace shell: Assuming an average furnace shell temperature of 70℃, the height from the furnace bottom to the hot blast outlet is 27.3m, with an expansion of approximately 22.96mm; the height from the furnace bottom to the furnace top is 49.7m, with an expansion of 41.75mm; with an average furnace shell temperature of 100℃, the expansion from the furnace bottom to the hot blast outlet is approximately 32.8mm. The expansion from the furnace bottom to the furnace top is 59.64mm.

[0011] Based on the temperature and corresponding expansion rate of the steel shell, the expansion amounts of the furnace shell diameter were calculated as follows: at 80 degrees Celsius, the expansion amounts were 33.96 mm, 37.97 mm, and 40.77 mm; at 100 degrees Celsius, the expansion amounts were 42.45 mm, 47.46 mm, and 50.97 mm; at 120 degrees Celsius, the expansion amounts were 50.94 mm, 56.97 mm, and 61.16 mm; and at 150 degrees Celsius, the expansion amounts were 63.67 mm, 71.19 mm, and 76.45 mm. These large circumferential expansions, constrained by the rigidity of the reinforced clamps, inevitably led to cracking in the welds and heat-affected zones of weak points outside the clamps. Currently, both domestic and international top-fired hot blast stove clamps are welded firmly to the furnace shell, forming rigid clamps. The overall upward expansion of the hot blast stove is also significant. For example, the calculated upward expansion from the furnace shell to the clamp in the Angang hot blast stove, based on an average furnace shell temperature of 70℃, results in an expansion of approximately 26.96mm from the furnace bottom to the hot blast outlet. With an average furnace shell temperature of 100℃, the expansion is approximately 43.29mm. Therefore, calculations show that both the rigid connection of the clamp and the rigid connection between the clamp and the tie rod limit the circumferential and upward expansion of the hot blast stove shell. This problem was encountered in actual production, and its severity was only discovered through calculations. Therefore, a new design is urgently needed to solve this problem and address the cracking issue in the weld seams and heat-affected zone of the top-fired hot blast stove shell. Summary of the Invention

[0012] In view of the above situation and to overcome the defects of the prior art, the purpose of this invention is to provide a method for preventing furnace shell cracking by adding furnace shell clamps, which can effectively solve the problem of furnace shell cracking caused by the existing rigid clamp structure in top-fired hot blast stoves.

[0013] To achieve the above objectives, the technical solution provided by this invention is a method for preventing furnace shell cracking by installing furnace shell clamps, comprising the following steps:

[0014] S1. First, construct a clamping device, which includes a first fixing component and a second fixing component. Both the first fixing component and the second fixing component are circular components composed of multiple arc plates connected by bolts. The arc plates opposite to the first fixing component and the second fixing component are respectively provided with a first connector and a second connector. The first connector and the second connector are connected together by a tie rod. Then, the clamp is installed in the following manner.

[0015] S2. Install multiple layers of evenly distributed first and second stiffening plates along the circumferential direction on the outer surface of the hot blast stove and mixing chamber. Place the first fixing member on the first stiffening plate and the second fixing member on the second stiffening plate. First, loosen the bolts. At this time, the first and second fixing members are loosely connected to the outer wall of the hot blast stove and mixing chamber. The formula for calculating the inner diameter of the first and second fixing members is:

[0016] Expansion amount = Temperature × Linear expansion coefficient α × Furnace shell circumference Equation 1

[0017] The inner diameter of the clamp D = (furnace shell circumference + expansion amount) / π (Equation 2)

[0018] Where expansion, D, and furnace shell circumference are in mm, temperature is in °C, and the linear expansion coefficient α = 12 × 10⁻⁶ -6 π is taken as 3.14;

[0019] S3. After the oven drying is completed and the hot air furnace and mixing chamber enter normal production, the first and second fixing parts of the segment are connected together by bolts. At this time, the first and second fixing parts are tightly connected to the outer wall of the hot air furnace and mixing chamber. Then, the first and second fixing parts are connected together with the tie rod to firmly install the clamping device on the furnace shell, effectively preventing the furnace shell from cracking.

[0020] The method of this invention is simple, easy to operate, and low in cost. It completely solves the design defects of rigid clamps and rigid connecting rods. The expansion and contraction of the furnace shell and the expansion and contraction of the upper and lower parts of the furnace shell are both in a relaxed and free state, which completely solves the limitation of furnace shell cracking and avoids the occurrence of furnace shell cracking. The social and economic benefits are significant. Attached Figure Description

[0021] Figure 1 This is a diagram of the existing clamp connection structure.

[0022] Figure 2 This is a schematic diagram (front view) of the installation structure of the present invention.

[0023] Figure 3 This is a schematic diagram (top view) of the installation structure of the present invention.

[0024] Figure 4 This is a top view of the clamping device of the present invention. Detailed Implementation

[0025] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples.

[0026] A method for preventing furnace shell cracking by installing furnace shell clamps includes the following steps:

[0027] S1. First, construct the clamping device, which includes a first fixing member 1 and a second fixing member 2. Both the first fixing member 1 and the second fixing member 2 are circular, composed of multiple arc plates connected by bolts 3. The arc plates opposite to the first fixing member 1 and the second fixing member 2 are respectively provided with a first connecting head 101 and a second connecting head 201. The first connecting head 101 and the second connecting head 201 are connected together by a tie rod 4. Then, the clamp is installed in the following way.

[0028] S2. Multiple layers of evenly distributed first stiffening plates 7 and second stiffening plates 8 are installed circumferentially on the outside of the hot blast stove 5 and the mixing chamber 6. The first fixing member 1 is placed on the first stiffening plate 7, and the second fixing member 2 is placed on the second stiffening plate 8. First, loosen the bolts 3. At this point, the first fixing member 1 and the second fixing member 2 are loosely connected to the outer walls of the hot blast stove 5 and the mixing chamber 6. The formula for calculating the inner diameter of the first fixing member 1 and the second fixing member 2 is:

[0029] Expansion amount = Temperature × Linear expansion coefficient α × Furnace shell circumference Equation 1

[0030] The inner diameter of the clamp D = (furnace shell circumference + expansion amount) / π (Equation 2)

[0031] Where expansion, D, and furnace shell circumference are in mm, temperature is in °C, and the linear expansion coefficient α = 12 × 10⁻⁶ -6 π is taken as 3.14;

[0032] S3. After the furnace drying is completed and the hot air furnace 5 and the mixing chamber 6 enter the normal production state, the first fixing part 1 and the second fixing part 2 of the segment are tightened together with bolts 3. At this time, the first fixing part 1 and the second fixing part 2 are tightly connected to the outer wall of the hot air furnace 5 and the mixing chamber 6. Then, the first fixing part 1 and the second fixing part 2 are connected together with the tie rod 4, and the clamping device is firmly installed on the furnace shell to effectively prevent the furnace shell from cracking.

[0033] Furthermore, the pull rod 4 includes a first connecting rod 401, a second connecting rod 402, a connecting shaft 403, and a double-ended bolt 404. The ends of the first connecting rod 401 and the second connecting rod 402 are respectively mounted on the first connecting head 101 and the second connecting head 201 via the connecting shaft 403. The other ends of the first connecting rod 401 and the second connecting rod 402 are connected to the double-ended bolt 404 via a threaded head.

[0034] The first fixing member 1 is a circle formed by connecting two or more arc-shaped plates with a first bolt 301, and the second fixing member 2 is a circle formed by connecting two or more arc-shaped plates with a second bolt 302.

[0035] The first connector 101 and the second connector 201 have the same structure, both being right-angled grooves. The two symmetrical side walls of the grooves are equipped with connecting shafts 403 for connecting the first connecting rod 401 and the second connecting rod 402.

[0036] The method of this invention is simple and ingeniously designed. Experiments in actual production have shown good results. Relevant information is as follows:

[0037] The outer diameter of the clamp for the hot blast stove is 11570mm, and the outer diameter of the clamp for the mixing chamber is 4060mm. The working temperature of the hot blast stove and the mixing chamber is 120℃. The first fixing member is divided into 4 sections, and the second fixing member is divided into 3 sections. They are installed on the first stiffening plate and the second stiffening plate respectively. At this time, the hot blast stove and the mixing chamber have not started working. The first fixing member and the second fixing member are loosely connected to the outer wall of the hot blast stove and the mixing chamber.

[0038] The expansion of the hot blast stove = 120 × 12 × 10 -6 ×11570×3.14=52.31mm;

[0039] Therefore, the inner diameter D of the first fastener is (52.31 + 11570 × 3.14) / 3.14 = 11586.66 mm;

[0040] Similarly, the inner diameter of the second fastener is D=4065.86. Its inner diameter is the inner diameter of the first and second fasteners after they are connected by bolts to form a whole circle. Its inner diameter is larger than the outer diameter of the furnace shell, which effectively prevents the furnace shell from cracking.

[0041] When the hot blast stove and mixing chamber are working normally, the furnace shell gradually expands from the heating and warming period of the hot blast stove to the normal production period. After the furnace drying is completed and the hot blast stove and mixing chamber enter the normal production state, the first and second fixed parts of the segment are connected end to end to form a whole by the first and second bolts respectively. At this time, the first and second fixed parts are tightly connected to the outer wall of the hot blast stove and mixing chamber. Then, the first and second fixed parts are connected together by tie rods. The first connecting rod and the second connecting rod can rotate around the connecting shaft, realizing the free expansion and contraction of the furnace shell. The loose connection between the first and second fixed parts and the furnace shell realizes the free circumferential expansion and contraction of the furnace shell.

[0042] This invention offers a simple, convenient, and low-cost method that completely solves the design defects of rigid clamps and rigid connecting rods. The loose connection between the clamp and the furnace shell not only strengthens the clamp but also allows for the free expansion of the top-fired hot blast stove shell. By optimizing the rigid connection between the clamp and the rod to an axial connection that allows the clamp and rod to expand upwards and contract downwards with the hot blast stove as a whole, the invention achieves free expansion and contraction of the furnace shell both vertically and horizontally. This completely solves the problem of furnace shell cracking and prevents furnace shell cracking, resulting in significant social and economic benefits.

[0043] It should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any person skilled in the art who can make changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preventing furnace shell cracking by installing furnace shell clamps, characterized in that, Includes the following steps: S1. First, construct a clamping device. The clamping device includes a first fixing part (1) and a second fixing part (2). The first fixing part (1) and the second fixing part (2) are both circular, consisting of multiple arc plates connected by bolts (3). The arc plates opposite to the first fixing part (1) and the second fixing part (2) are respectively provided with a first connector (101) and a second connector (201). The first connector (101) and the second connector (201) are connected together by a tie rod (4). Then, the clamp is installed in the following manner. S2. Install multiple layers of evenly distributed first stiffening plates (7) and second stiffening plates (8) around the outside of the hot blast stove (5) and the mixing chamber (6). Place the first fixing part (1) on the first stiffening plate (7) and the second fixing part (2) on the second stiffening plate (8). First loosen the bolts (3). At this time, the first fixing part (1) and the second fixing part (2) are loosely connected to the outer wall of the hot blast stove (5) and the mixing chamber (6). The formula for calculating the inner diameter of the first fixing part (1) and the second fixing part (2) is: Expansion amount = Temperature × Linear expansion coefficient α × Furnace shell circumference Equation 1 The inner diameter of the clamp D = (furnace shell circumference + expansion amount) / π (Equation 2) Where expansion, D, and furnace shell circumference are in mm, temperature is in °C, and the linear expansion coefficient α = 12 × 10⁻⁶ -6 π is taken as 3.14; S3. After the oven drying is finished and the hot air furnace (5) and the mixing chamber (6) enter the normal production state, the first fixing part (1) and the second fixing part (2) of the segment are tightened together with bolts (3). At this time, the first fixing part (1) and the second fixing part (2) are tightly connected with the outer wall of the hot air furnace (5) and the mixing chamber (6). Then, the first fixing part (1) and the second fixing part (2) are connected together with the tie rod (4) to firmly install the clamping device on the furnace shell and effectively prevent the furnace shell from cracking.

2. The method for preventing furnace shell cracking by installing furnace shell clamps according to claim 1, characterized in that, The tie rod (4) includes a first connecting rod (401), a second connecting rod (402), a connecting shaft (403), and a double-ended bolt (404). The ends of the first connecting rod (401) and the second connecting rod (402) are respectively mounted on the first connecting head (101) and the second connecting head (201) via the connecting shaft (403). The other ends of the first connecting rod (401) and the second connecting rod (402) are connected together with the double-ended bolt (404) via the threaded head.

3. The method for preventing furnace shell cracking by installing furnace shell clamps according to claim 1, characterized in that, The first fixing member (1) is a circle formed by connecting two or more arc-shaped plates end to end with the first bolt (301), and the second fixing member (2) is a circle formed by connecting two or more arc-shaped plates end to end with the second bolt (302).

4. The method for preventing furnace shell cracking by installing furnace shell clamps according to claim 2, characterized in that, The first connector (101) and the second connector (201) have the same structure, both being right-angled grooves. The two symmetrical side walls of the grooves are equipped with connecting shafts (403) for connecting the first connecting rod (401) and the second connecting rod (402).

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