High-temperature hot air furnace with regenerator structure

Abstract

The present invention relates to a high-temperature hot blast furnace with a heat storage chamber structure, comprising a hot blast furnace body, a heat storage chamber structure disposed within the hot blast furnace body, at least one partition disposed within the heat storage chamber structure, and at least two heat storage chambers formed by the partition; each heat storage chamber sequentially comprises a low-temperature zone, a medium-temperature zone, and a high-temperature zone, each heat storage chamber being filled with spherical multi-stage heat storage bodies in a partitioned manner; each high-temperature zone is interconnected, the hot blast furnace body being located below each heat storage chamber and interconnected with a cold air inlet, and each low-temperature zone of each heat storage chamber being interconnected with a hot air outlet; when the cold air inlet corresponding to a heat storage chamber is opened, the hot air outlet connected to it is closed, and the hot air outlet of another heat storage chamber is opened. The heat storage chamber structure of the present invention is provided with partitions to form multiple heat storage chambers, enabling efficient heat storage and heat exchange, and achieving an increase in the supply air temperature under conditions of non-rich coal gas and non-oxygen-enriched combustion air, thus having significant industrial value.

Description

Technical Field

[0001] The present invention relates to the technical field of ironmaking equipment, and in particular to a high-temperature hot blast furnace provided with a regenerator structure. Background Art

[0002] With the continuous advancement of blast furnace ironmaking technology, hot air has evolved from early external- and internal-combustion methods to the now widely used top-combustion method. Air supply temperatures have continued to rise. According to statistics, for every 100°C increase in air supply temperature, the coke ratio decreases by 25 kg / t, molten iron production increases by 2%-3%, and the amount of ash injected increases, generating positive economic benefits. However, as the coke ratio in the ironmaking process continues to decrease, the CO content in blast furnace gas also decreases, reducing the calorific value of the gas and making it more difficult to maintain the air temperature in hot blast furnaces fueled by blast furnace gas. In engineering applications, air preheating or oxygen-enriched combustion air are often used to increase flue gas temperature, but these measures significantly increase the operating costs of the hot blast furnace.

[0003] In existing technology, the air supply temperature of blast furnace hot blast stoves is generally below 1250℃ (most of them are 1200℃ or lower). Increasing the air temperature of hot blast stoves can replace part of the coke with injected coal as the furnace charge. The cost of coke per ton is more than 400 yuan higher than that of injected coal, which is undoubtedly a huge economic burden. In addition, the traditional preheating system and oxygen-enriched gas system also have many problems:

[0004] 1. The preheating system contains a large number of pipes and heat exchange systems, and the device occupies a large area. If the existing hot air furnace is modified, it will inevitably lead to construction site.

[0005] 2. The air temperature of the hot blast furnace is much higher than that of the general heat exchange facilities, which will inevitably lead to a larger volume of conventional heat exchangers, reduced heat exchange efficiency, and a significant shortening of the life of the heat exchanger and piping system.

[0006] 3. The preheating system has a large laying area, which will cause a large amount of heat energy loss; the oxygen-enriched gas-enriched system will greatly increase the cost of fuel and combustion-supporting gas.

[0007] Therefore, the inventors, relying on their many years of experience and practice in related industries, have proposed a high-temperature hot blast furnace with a heat storage chamber structure to overcome the defects of the prior art. Summary of the Invention

[0008] The purpose of the present invention is to provide a high-temperature hot blast furnace provided with a heat storage chamber structure to overcome the problems existing in the prior art. The heat storage chamber structure of the present invention is provided with partitions to form multiple heat storage chambers, which can efficiently store and exchange heat, and achieve an increase in the supply air temperature under the conditions of non-rich coal gas and non-oxygen-enriched combustion air, and has significant industrial value.

[0009] The object of the present invention is achieved in this way. A high-temperature hot blast furnace with a heat storage chamber structure comprises a hot blast furnace body, a heat storage chamber structure is arranged in the hot blast furnace body, at least one partition is arranged in the heat storage chamber structure, and the heat storage chamber structure forms at least two heat storage chambers through the partition; each of the heat storage chambers is sequentially composed of a low-temperature zone, a medium-temperature zone and a high-temperature zone from bottom to top, and each of the heat storage chambers is filled with spherical multi-stage heat storage bodies according to the low-temperature zone, the medium-temperature zone and the high-temperature zone; each of the high-temperature zones is arranged to be connected, the hot blast furnace body is located below each of the heat storage chambers and is respectively connected to a cold air inlet, and the low-temperature zone of each of the heat storage chambers is respectively connected to a hot air outlet, when the cold air inlet corresponding to one of the heat storage chambers is opened, the hot air outlet connected to it is closed and the hot air outlet of the other heat storage chamber is opened.

[0010] In a preferred embodiment of the present invention, a combustion chamber is formed within the hot blast stove body above the regenerator structure, and a gas inlet and an air inlet are arranged opposite to each other on the side walls of the combustion chamber; a conical wall with a diameter gradually increasing from top to bottom is arranged within the combustion chamber below the gas inlet and the air inlet; a grate is arranged within the hot blast stove body at the bottom of the regenerator structure, and the cold air inlet is arranged on the hot blast stove body below the grate; a flue gas outlet is arranged within the hot blast stove body below the cold air inlet.

[0011] In a preferred embodiment of the present invention, the low temperature zone is filled with a first heat storage sphere, the medium temperature zone is filled with a second heat storage sphere, and the high temperature zone is filled with a third heat storage sphere, and the materials of the first heat storage sphere, the second heat storage sphere and the third heat storage sphere are set differently.

[0012] In a preferred embodiment of the present invention, the diameters of the first heat storage sphere, the second heat storage sphere, and the third heat storage sphere are all greater than or equal to 10 mm.

[0013] In a preferred embodiment of the present invention, the first heat storage sphere is made of clay balls, the second heat storage sphere is made of high-aluminum balls, and the third heat storage sphere is made of andalusite balls.

[0014] In a preferred embodiment of the present invention, the hot blast stove body is located above the regenerator structure and communicates with a ball inlet, and the hot blast stove body is located below the regenerator structure and communicates with a ball outlet.

[0015] In a preferred embodiment of the present invention, a plurality of communication holes are provided at the position of the partition located in the high temperature zone.

[0016] In a preferred embodiment of the present invention, the opening rate of the partition located in the high temperature zone is greater than or equal to 60%.

[0017] In a preferred embodiment of the present invention, pillars for supporting the grate are provided in the hot blast furnace body, and both the grate and the pillars are made of high-temperature resistant materials.

[0018] In a preferred embodiment of the present invention, the dome temperature of the hot blast stove body is greater than or equal to 1400°C, and the air temperature of the hot blast outlet is greater than or equal to 1250°C.

[0019] As described above, the high-temperature hot blast furnace provided with a regenerator structure provided by the present invention has the following beneficial effects:

[0020] In the high-temperature hot blast furnace provided with a regenerator structure of the present invention, partitions are provided in the regenerator structure to form multiple regenerator chambers. The multiple regenerator chamber design can double the distance of cold air passing through the regenerator structure, which is more conducive to increasing the wind temperature. By alternately blowing cold air through the multiple regenerator chambers, high and low temperature zones in the regenerator structure can be alternately changed. Compared with unidirectional air inlet, the heat stored in the spherical multi-stage regenerator can be more efficiently utilized.

[0021] The use of spherical multi-stage heat storage bodies instead of checker brick heat storage has stronger heat storage and heat exchange capabilities, further improving the heat storage and heat exchange efficiency, and greatly improving the air supply temperature of the hot blast furnace fueled by low calorific value blast furnace gas;

[0022] This invention uses a non-preheating, oxygen-enriched, and coal-gas-rich method to increase air temperature, resulting in a relatively low cost. It also improves the heat storage capacity of the hot blast furnace's regenerator during the combustion phase and the heat exchange capacity during the air supply phase, effectively raising the air supply flue gas temperature to over 1250°C. Every 100°C increase in air supply temperature reduces the ironmaking coke ratio by 25kg / t, increases the amount of pulverized coal injected, and effectively improves the economic efficiency of the ironmaking process.

[0023] The present invention can improve the air supply temperature under the conditions of non-rich coal gas and non-oxygen-enriched combustion air, and has significant industrial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following drawings are only intended to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.

[0025] in:

[0026] Figure 1 : It is a structural diagram of a high-temperature hot blast stove provided with a regenerator structure of the present invention.

[0027] Figure 2 : is a schematic diagram of a separator of the present invention.

[0028] In the picture:

[0029] 100. A high-temperature hot air furnace equipped with a regenerator structure;

[0030] 1. Hot air furnace body;

[0031] 11. Cold air inlet; 12. Hot air outlet; 13. Gas inlet; 14. Air inlet; 15. Smoke outlet; 16. Ball inlet; 17. Ball outlet; 18. Conical wall;

[0032] 2. Thermal storage chamber structure;

[0033] 21. Low temperature zone; 22. Medium temperature zone; 23. High temperature zone;

[0034] 3. partition; 31. communicating hole;

[0035] 4. Combustion chamber;

[0036] 5. Grate;

[0037] 61. First heat storage sphere; 62. Second heat storage sphere; 63. Third heat storage sphere. DETAILED DESCRIPTION

[0038] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described with reference to the accompanying drawings.

[0039] The specific embodiments of the present invention described herein are intended only to illustrate the present invention and are not to be construed as limiting the present invention in any way. In light of the present invention, a skilled person may conceive of any possible variations based on the present invention, all of which should be considered to fall within the scope of the present invention. It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected" to another element, it may be directly connected to the other element or there may be an intermediate element at the same time. The terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to mechanical or electrical connections, or to internal communication between two elements, and may be directly connected or indirectly connected through an intermediate medium. A person of ordinary skill in the art can understand the specific meanings of the above terms based on the specific circumstances. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are intended only to describe specific embodiments and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0041] like Figure 1 、 Figure 2 As shown, the present invention provides a high-temperature hot blast furnace 100 with a heat storage chamber structure, comprising a hot blast furnace body 1, a heat storage chamber structure 2 is arranged in the hot blast furnace body 1, and at least one partition 3 is arranged in the heat storage chamber structure 2. The heat storage chamber structure 2 forms at least two heat storage chambers through the partition 3; each heat storage chamber is sequentially formed from bottom to top into a low-temperature zone 21, a medium-temperature zone 22 and a high-temperature zone 23, and each heat storage chamber is divided into the low-temperature zone 21, the medium-temperature zone 22 and the high-temperature zone 23 and filled with a spherical multi-stage heat storage body; each high-temperature zone 23 is arranged to be connected, and the hot blast furnace body 1 is located below each heat storage chamber and is connected to a cold air inlet 11, and the low-temperature zone of each heat storage chamber is connected to a hot air outlet 12. When the cold air inlet 11 corresponding to a heat storage chamber is opened, the hot air outlet 12 connected to it is closed and the hot air outlet 12 of the other heat storage chamber is opened.

[0042] In a specific embodiment of the present invention, there is one partition, and the heat storage chamber structure 2 forms two heat storage chambers through the partition 3. When in use, when the cold air inlet 11 corresponding to the first heat storage chamber is opened, the hot air outlet 12 connected thereto is closed, and the hot air outlet 12 of the second heat storage chamber is opened, providing a double stroke for the cold air.

[0043] During the air supply phase, the present invention allows cold air to enter the hot blast furnace body 1 from the cold air inlet 11 corresponding to one heat storage chamber, move upward on one side of the partition 3, and sequentially exchange heat with the spherical multi-stage heat storage bodies in the low-temperature zone 21, medium-temperature zone 22, and high-temperature zone 23. The cold air is heated to hot air, which then passes through the high-temperature zone 23 of the heat storage chamber and enters the high-temperature zone 23 of another heat storage chamber. The hot air then passes from top to bottom through the spherical multi-stage heat storage bodies in the high-temperature zone 23, medium-temperature zone 22, and low-temperature zone 21 of the other heat storage chamber, and is finally discharged through the hot air outlet 12 of the other heat storage chamber. This lengthens the flue gas travel, which is more conducive to increasing the air temperature. This allows the air supply temperature to be increased even without using coal gas or oxygen-enriched combustion air, and has significant industrial value. Alternating cold air into each heat storage chamber causes the high and low temperature zones in the heat storage chamber to alternate, making more efficient use of the heat stored in the heat storage balls compared to unidirectional air intake.

[0044] In the high-temperature hot blast furnace provided with a regenerator structure of the present invention, partitions are provided in the regenerator structure to form multiple regenerator chambers. The multiple regenerator chamber design can double the distance of cold air passing through the regenerator structure, which is more conducive to increasing the wind temperature. By alternately blowing cold air through the multiple regenerator chambers, high and low temperature zones in the regenerator structure can be alternately changed. Compared with unidirectional air inlet, the heat stored in the spherical multi-stage regenerator can be more efficiently utilized.

[0045] The use of spherical multi-stage heat storage bodies instead of checker brick heat storage has stronger heat storage and heat exchange capabilities, further improving the heat storage and heat exchange efficiency, and greatly improving the air supply temperature of the hot blast furnace fueled by low calorific value blast furnace gas;

[0046] This invention uses a non-preheating, oxygen-enriched, and coal-gas-rich method to increase air temperature, resulting in a relatively low cost. It also improves the heat storage capacity of the hot blast furnace's regenerator during the combustion phase and the heat exchange capacity during the air supply phase, effectively raising the air supply flue gas temperature to over 1250°C. Every 100°C increase in air supply temperature reduces the ironmaking coke ratio by 25kg / t, increases the amount of pulverized coal injected, and effectively improves the economic efficiency of the ironmaking process.

[0047] The present invention can improve the air supply temperature under the conditions of non-rich coal gas and non-oxygen-enriched combustion air, and has significant industrial value.

[0048] Further, if Figure 1 As shown, the high-temperature hot blast furnace 100 with a regenerator structure of the present invention is a top-fired hot blast furnace. A combustion chamber 4 is formed within the hot blast furnace body 1 above the regenerator structure. A gas inlet 13 and an air inlet 14 are disposed on the sidewalls of the combustion chamber 4. Below the gas inlet 13 and the air inlet 14, a tapered wall 18 with a gradually increasing diameter from top to bottom is disposed within the combustion chamber 4. A grate 5 is disposed within the hot blast furnace body 1 at the bottom of the regenerator structure. A cold air inlet 11 is disposed within the hot blast furnace body 1 below the grate. A flue gas outlet 15 is disposed below the cold air inlet. In a specific embodiment of the present invention, the dome temperature of the hot blast furnace body 1 is greater than or equal to 1400°C, and the air temperature at the hot air outlet is greater than or equal to 1250°C.

[0049] During the combustion stage, coal gas (fuel) and air (combustion-supporting gas) enter the combustion chamber 4 from the coal gas inlet 13 and the air inlet 14 respectively. The coal gas inlet 13 and the air inlet 14 are respectively located on both sides of the combustion chamber. The gases are mixed by convection and fully burned in the combustion chamber 4. After combustion, the high-temperature flue gas moves to the lower heat storage chamber structure 2, causing the spherical multi-stage heat storage body to store heat, and the flue gas is finally discharged through the flue gas outlet 15.

[0050] Further, if Figure 1 As shown, the low temperature zone 21 is filled with the first heat storage sphere 61, the medium temperature zone 22 is filled with the second heat storage sphere 62, and the high temperature zone 23 is filled with the third heat storage sphere 63. The materials of the first heat storage sphere 61, the second heat storage sphere 62 and the third heat storage sphere 63 are set differently.

[0051] In this embodiment, the diameters of the first heat storage sphere 61 , the second heat storage sphere 62 and the third heat storage sphere 63 are all greater than or equal to 10 mm.

[0052] In a specific embodiment of the present invention, the first heat storage sphere 61 is made of clay balls, the second heat storage sphere 62 is made of high-aluminum balls, and the third heat storage sphere 63 is made of andalusite balls.

[0053] Furthermore, although the heat storage spheres (the first heat storage sphere 61, the second heat storage sphere 62 and the third heat storage sphere 63) have higher heat exchange and heat storage capabilities than the checker bricks, they also need to be replaced more frequently. To facilitate the replacement of the heat storage spheres, the hot blast furnace body 1 is located above the heat storage chamber structure 2 and is connected to a ball inlet 16, and the hot blast furnace body is located below the heat storage chamber structure and is connected to a ball outlet 17.

[0054] Further, if Figure 2 As shown, in order to give full play to the high heat storage density advantage of the high temperature zone 23, the partition 3 is provided with a plurality of connecting holes 31 at the position of the high temperature zone. In a specific embodiment of the present invention, the diameter of the connecting holes is 5 mm.

[0055] In this embodiment, the opening ratio of the partition plate 3 located in the high temperature zone is greater than or equal to 60%.

[0056] During the air supply stage, the gas inlet 13, the air inlet 14, and the flue gas outlet 15 are closed, the cold air inlet 11 corresponding to one heat storage chamber is opened and the hot air outlet 12 connected thereto is closed, and the hot air outlet 12 of the other heat storage chamber is opened (only one of multiple cold air inlets is open, and only one of multiple hot air outlets is open, and the hot air outlet and the cold air inlet do not belong to the same heat storage chamber). The cold air enters the hot blast furnace body 1 from the cold air inlet 11, moves upward in the heat storage chamber on one side of the partition 3, and exchanges heat with the spherical multi-stage heat storage bodies of different materials in the low temperature zone 21, the medium temperature zone 22, and the high temperature zone 23 in turn. The cold air is heated to hot air, and the hot air enters the high temperature zone 23 of the other heat storage chamber through the connecting hole of the high temperature zone 23 of the heat storage chamber. The hot air passes through the spherical multi-stage heat storage bodies in the high temperature zone 23, the medium temperature zone 22, and the low temperature zone 21 of the other heat storage chamber from top to bottom, and is finally discharged through the hot air outlet 12 of the other heat storage chamber. The air temperature can reach above 1250°C.

[0057] Furthermore, pillars for supporting the grate are provided in the hot blast stove body 1, and both the grate and the pillars are made of high-temperature resistant materials.

[0058] Specific embodiment 1: Establish an experimental device to simulate 2000m 3 The blast furnace provides hot air, and its length, width and height are all 1 / 10 of the actual size. The height of the hot blast furnace in the simulation experiment is 2.8m, of which the height of the heat storage section is 1.6m. Only this hot blast furnace is tested.

[0059] experiment:

[0060] The combustion stage lasted for 2 hours. During this stage, the gas inlet and air inlet were opened, and blast furnace gas (35℃, 120Nm 3 / h, 17.5% CO2, 21.1% CO, 3.3% H2, 53.1% N2, 5% H2O, CH4 detection content is very low and not considered), and combustion air (25℃, 21% O2, 84Nm 3 / h), ignite and burn in the combustion zone, the temperature of the combustion zone can be maintained at 1420℃, and exhaust gas is discharged at the waste outlet, the exhaust gas temperature is 400℃, and it is necessary to use internal high-temperature resistant grate and support.

[0061] The air supply phase lasts for 1 hour. During this phase, the gas inlet and air inlet are closed, and one side of the cold air inlet and the opposite side of the hot air outlet are opened. After 30 minutes, the cold air inlet on one side and the opposite side of the hot air outlet are opened. The air supply temperature can be maintained above 1300℃, but the temperature of the grate and support position can reach 450℃, which requires the support of high temperature resistant materials. The air supply volume of this equipment during the air supply phase is about 730Nm 3 / h.

[0062] As described above, the high-temperature hot blast furnace provided with a regenerator structure provided by the present invention has the following beneficial effects:

[0063] In the high-temperature hot blast furnace provided with a regenerator structure of the present invention, partitions are provided in the regenerator structure to form multiple regenerator chambers. The multiple regenerator chamber design can double the distance of cold air passing through the regenerator structure, which is more conducive to increasing the wind temperature. By alternately blowing cold air through the multiple regenerator chambers, high and low temperature zones in the regenerator structure can be alternately changed. Compared with unidirectional air inlet, the heat stored in the spherical multi-stage regenerator can be more efficiently utilized.

[0064] The use of spherical multi-stage heat storage bodies instead of checker brick heat storage has stronger heat storage and heat exchange capabilities, further improving the heat storage and heat exchange efficiency, and greatly improving the air supply temperature of the hot blast furnace fueled by low calorific value blast furnace gas;

[0065] This invention uses a non-preheating, oxygen-enriched, and coal-gas-rich method to increase air temperature, resulting in a relatively low cost. It also improves the heat storage capacity of the hot blast furnace's regenerator during the combustion phase and the heat exchange capacity during the air supply phase, effectively raising the air supply flue gas temperature to over 1250°C. Every 100°C increase in air supply temperature reduces the ironmaking coke ratio by 25kg / t, increases the amount of pulverized coal injected, and effectively improves the economic efficiency of the ironmaking process.

[0066] The present invention can improve the air supply temperature under the conditions of non-rich coal gas and non-oxygen-enriched combustion air, and has significant industrial value.

[0067] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principle of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A high-temperature hot blast furnace with a regenerator structure, characterized in that: The invention comprises a hot blast furnace body, wherein a heat storage chamber structure is provided in the hot blast furnace body, wherein at least one partition is provided in the heat storage chamber structure, and the heat storage chamber structure forms at least two heat storage chambers through the partition; each of the heat storage chambers is sequentially formed from bottom to top into a low-temperature zone, a medium-temperature zone and a high-temperature zone, and each of the heat storage chambers is filled with a spherical multi-stage heat storage body according to the low-temperature zone, the medium-temperature zone and the high-temperature zone; each of the high-temperature zones is arranged to be connected, and the hot blast furnace body is located below each of the heat storage chambers and is respectively connected to a cold air inlet, and each of the low-temperature zones of the heat storage chambers is respectively connected to a hot air outlet, and when the cold air inlet corresponding to one of the heat storage chambers is opened, the hot air outlet connected to it is closed and the hot air outlet of the other heat storage chamber is opened; A combustion chamber is formed within the hot blast stove body above the regenerator structure, and a gas inlet and an air inlet are disposed on side walls of the combustion chamber opposite to each other; a conical wall with a diameter gradually increasing from top to bottom is disposed within the combustion chamber below the gas inlet and the air inlet; a grate is disposed within the hot blast stove body at the bottom of the regenerator structure, and the cold air inlet is disposed within the hot blast stove body below the grate; a flue gas outlet is disposed within the hot blast stove body below the cold air inlet; The low temperature zone is filled with a first heat storage sphere, the medium temperature zone is filled with a second heat storage sphere, and the high temperature zone is filled with a third heat storage sphere. The materials of the first heat storage sphere, the second heat storage sphere, and the third heat storage sphere are different. The partition is provided with a plurality of communication holes at a position where the partition is located in the high temperature zone; The diameters of the first heat storage sphere, the second heat storage sphere, and the third heat storage sphere are all greater than or equal to 10 mm.

2. The high-temperature hot blast furnace with a regenerator structure according to claim 1, characterized in that: The first heat storage sphere is made of clay balls, the second heat storage sphere is made of high-aluminum balls, and the third heat storage sphere is made of andalusite balls.

3. The high-temperature hot blast furnace with a regenerator structure according to claim 1, characterized in that: The hot blast stove body is located above the heat storage chamber structure and is communicated with a ball inlet. The hot blast stove body is located below the heat storage chamber structure and is communicated with a ball outlet.

4. The high-temperature hot blast furnace with a regenerator structure according to claim 1, characterized in that: The opening rate of the partition located in the high temperature zone is greater than or equal to 60%.

5. The high-temperature hot blast furnace with a regenerator structure according to claim 1, characterized in that: Support pillars for supporting the grate are arranged in the hot blast furnace body, and both the grate and the support pillars are made of high-temperature resistant materials.

6. The high-temperature hot blast furnace with a regenerator structure according to claim 1, characterized in that: The dome temperature of the hot blast stove body is greater than or equal to 1400°C, and the air temperature of the hot blast outlet is greater than or equal to 1250°C.

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