A method for preheating scrap steel using high-temperature converter gas

Abstract

The present invention relates to a method for preheating scrap steel by using high-temperature converter gas. By setting a converter gas preheating scrap steel device with a specific connection mode and using the device to perform specific process steps, the high-temperature converter gas is directly used for preheating the scrap steel, and the sensible heat of the converter gas completely enters the heating furnace for heating the scrap steel, which effectively saves fuel, efficiently utilizes the heat of the high-temperature converter gas, processes the carbon monoxide therein, avoids long-term heat preservation and long-distance transportation of the hot scrap steel, and makes converter smelting with a relatively high scrap steel ratio a reality.

Description

Technical Field

[0001] The present invention relates to the technical field of steelmaking and waste heat recovery, and in particular to a method for preheating scrap steel by utilizing high-temperature converter gas. Background Art

[0002] The converter is a metallurgical reactor that uses scrap steel, molten iron, etc. as raw materials, lime, dolomite, etc. as auxiliary materials, and oxygen, nitrogen, argon, etc. as energy media to achieve process goals such as decarbonization, dephosphorization, and heating. During converter smelting, a large amount of converter gas will be produced. The CO content in the converter gas is greater than 80%, and the calorific value is very high. After cooling and dust removal, it can be used as fuel gas. Conventional converter gas purification and dust removal processes (such as dry, semi-dry, wet processes, etc.) all cool the converter gas to below 200°C by directly spraying cooling water before dust removal. In this process, a large amount of sensible heat of the converter gas (about 7% of the total energy output of the converter process) is wasted.

[0003] The initial temperature of converter gas is as high as 1500℃, which is a high-grade heat source. In theory, it is suitable for producing steam for power generation through heat exchange. However, since converter smelting is not a completely continuous process, converter gas is produced intermittently. The amount of gas generated is not continuous and stable, which will cause the steam generation of the waste heat boiler to fluctuate violently, thus affecting the normal operation of the generator. At the same time, the dust content of converter gas is extremely high. The dust removal efficiency of conventional cyclone dust collectors is limited at high temperatures. The dust in the gas will cause serious dust accumulation in the heat exchanger and reduce the heat exchange efficiency. Therefore, there is currently no mature converter gas waste heat recovery process.

[0004] As for scrap steel, my country is the largest steel producer and also has abundant scrap steel resources. In 2020, my country's scrap steel output was about 210 million tons, and in 2025, the scrap steel output is expected to reach 270 million to 300 million tons, and in 2030, it is expected to reach 320 million to 350 million tons. The use of scrap steel can reduce the mining of iron ore, save raw coal, and reduce the emission of CO2 and a large amount of wastewater, waste gas, and solid waste. my country's steel production is mainly based on the long process of blast furnace-converter steelmaking, with a large amount of converter production capacity. Although scrap steel is the raw material for converter smelting, as a self-heating metallurgical reactor, if too much scrap steel is added, the tapping temperature will not meet the standard. Therefore, the converter's ability to consume scrap steel under conventional smelting processes is limited. If the scrap steel can be preheated before adding it to the converter, the energy input of the converter will be increased, and the technical problem of the steel tapping temperature not being able to meet the standard can be overcome to a certain extent. The scrap steel ratio of the converter can be increased, and more scrap steel can be absorbed. At the same time, the smelting cycle can be shortened, CO2 emissions can be reduced, and the steel output and economic benefits of the steel company can be increased.

[0005] If the high-temperature converter gas is directly used for scrap preheating, the sensible heat of the converter gas is fully utilized, the converter scrap ratio is improved, and the load and water consumption of the converter gas purification system are reduced. However, the high-temperature converter gas has a high temperature and a large dust content, and conventional induced draft fans cannot be used under this condition. New technical solutions are needed to achieve this process.

[0006] Chinese invention patent publication CN108398030A discloses a scrap steel preheating system, which solves the problem that scrap steel cannot be preheated directly in the kiln by preheating the scrap steel in the kiln before entering the converter. However, this technology also requires the preheated scrap steel to be transported, which will cause temperature loss. At the same time, this technology does not pay attention to the rational use of converter gas. Summary of the invention

[0007] In order to solve the above technical problems, the present invention uses high-temperature converter gas to directly burn and heat scrap steel, targeting the current situation that converter gas has high dust content and waste heat recovery is difficult. While utilizing the sensible heat of the converter gas, the scrap steel ratio of the converter is increased, thereby achieving better economic and environmental benefits.

[0008] The specific implementation is through the following technical solutions:

[0009] A method for preheating scrap steel using high-temperature converter gas is carried out using a converter gas preheating scrap steel device, the converter gas preheating scrap steel device comprising a scrap steel heating furnace, a scrap steel silo, a scrap steel tank, an air-to-gas heat exchanger, an air compressor, a gravity settling device, a gas filtering device, a gas dust removal device, and a low-temperature flue gas purification device.

[0010] A burner is arranged on the inner top of the scrap steel heating furnace, a scrap steel adding port is opened on the top of the scrap steel heating furnace, a scrap steel discharging port is opened on the bottom of the scrap steel heating furnace, a discharge valve is arranged on the scrap steel heating furnace, and a high-temperature flue gas discharging port is opened on the scrap steel heating furnace; the scrap steel silo is arranged above the scrap steel heating furnace, an openable and closable cold scrap steel discharging port is arranged on the bottom end of the scrap steel silo, a loading valve is arranged on the scrap steel silo, the scrap steel silo is used for temporarily storing cold scrap steel, and can control the cold scrap steel to be discharged into the scrap steel heating furnace through the cold scrap steel discharging port and the scrap steel adding port by opening the loading valve.

[0011] The burner comprises an air inlet of the burner and a gas inlet of the burner.

[0012] The air-to-flue gas heat exchanger includes a high-temperature flue gas flow area and an air flow area, and heat exchange is performed through a wall separating the two areas. The air flow area is provided with a cold air inlet and a hot air outlet, and the high-temperature flue gas flow area is provided with a high-temperature flue gas inlet and a low-temperature flue gas outlet, and the hot air outlet is connected to the air inlet of the burner of the scrap steel heating furnace; the air compressor compresses the air and discharges it through the compressed air outlet, and the compressed air outlet is connected to the cold air inlet.

[0013] The inlet end of the low-temperature flue gas purification device is connected to the low-temperature flue gas outlet of the heat exchanger through a pipeline, and the low-temperature flue gas purification device is used to purify the low-temperature flue gas after heat exchange.

[0014] The gravity sedimentation device includes a converter gas inlet, a first sedimentation gas outlet and a second sedimentation gas outlet. The converter gas inlet is connected to the gas outlet of the converter through a pipeline. The gravity sedimentation device is used to settle large particles of dust in the gas entering the interior under the action of gravity, and the settled gas is discharged through the first sedimentation gas outlet and / or the second sedimentation gas outlet; the gas filtering device is provided with a filtered gas inlet and a filtered gas outlet. The filtered gas inlet is connected to the first sedimentation gas outlet through a pipeline, and the filtered gas outlet is connected to the first inlet of a three-way pipeline through a pipeline, and the second inlet of the three-way pipeline is connected to the clean gas arranged outside, and the outlet of the three-way pipeline is connected to the gas inlet of the burner of the scrap steel heating furnace through a pipeline; a first stop valve is provided on the pipeline between the filtered gas outlet and the first inlet of the three-way pipeline, and a second stop valve is provided on the second inlet of the three-way pipeline.

[0015] The inlet end of the gas dust removal device is connected to the second settling gas outlet of the gravity settling device through a pipeline. The gas dust removal device is used to remove dust from the initial gas discharged from the gravity settling device and then discharge it into the gas pipeline network for subsequent treatment.

[0016] The scrap steel tank can control the heated scrap steel to be discharged into the scrap steel tank through the scrap steel discharge port by opening the discharge valve, and then discharge the heated scrap steel into the converter by moving and / or rotating the scrap steel tank.

[0017] The steps include:

[0018] (1) The cold scrap steel is loaded into the scrap steel silo for temporary storage, the loading valve is opened, and the cold scrap steel is added into the scrap steel heating furnace. When the scrap steel threshold of the scrap steel heating furnace is reached, the loading valve is closed.

[0019] (2) The converter starts blowing, and the generated converter gas is first discharged into the gravity settling device through the converter gas inlet of the gravity settling device for gravity settling. The converter gas after gravity settling is discharged into the gas dust removal device through the second settling gas outlet for dust removal and then discharged into the gas pipeline network for subsequent treatment. At the same time, the concentration of carbon monoxide in the converter gas is monitored. When the carbon monoxide concentration rises to the set carbon monoxide concentration threshold, the air compressor is turned on and the first stop valve is turned on, and the second settling gas outlet is closed at the same time. The converter gas after settling is discharged into the gas filter device through the first settling gas outlet, and then through the three-way pipeline. The gas inlet of the burner is discharged into the burner; the compressed air obtained by the air compressor is heat exchanged through the air-to-gas heat exchanger and then discharged into the air inlet of the burner through the hot air outlet. The high-temperature converter gas and the compressed air are mixed and burned in the burner to heat the cold scrap steel in the scrap steel heating furnace. The high-temperature flue gas generated after combustion is discharged from the high-temperature flue gas outlet of the scrap steel heating furnace into the air-to-gas heat exchanger, and after heat exchange with the compressed air, the compressed air is heated to obtain low-temperature flue gas. The low-temperature flue gas is discharged into the low-temperature flue gas purification device through the low-temperature flue gas outlet of the air-to-gas heat exchanger for purification and then discharged.

[0020] (3) In step (2), the temperature of the cold scrap steel is monitored while the scrap steel temperature is heated. When the scrap steel is heated to the preheating threshold, the air compressor is turned off and the first stop valve is closed. The heated scrap steel is temporarily stored in the scrap steel heating furnace. After the converter smelting is completed, the discharge valve is opened to discharge the heated scrap steel into the scrap steel tank. The scrap steel tank then transfers the scrap steel to the converter for a new cycle of converter smelting.

[0021] Preferably, a weighing sensor is provided on the base of the scrap steel silo, and the weighing sensor is used to accurately measure the mass of the scrap steel loaded into the scrap steel heating furnace.

[0022] Preferably, the scrap steel heating furnace is a vertical furnace, and the flame of the burner is set downward (to prevent damage to the burner when the scrap steel loading falls); the diameter or equivalent diameter of the bottom of the scrap steel heating furnace is smaller than the diameter or equivalent diameter of the middle of the scrap steel heating furnace (to facilitate unloading of the unloading valve).

[0023] Preferably, an air filter is provided at the front end of the air compressor, and the air filter is used to filter the external air and discharge it into the air compressor.

[0024] Preferably, the scrap steel threshold is 18-30wt.% of the nominal volume of the converter; the carbon monoxide concentration threshold is 58-65v.%, and the preheating threshold is 600-900°C (if the scrap steel heating temperature is too low, the energy-saving effect is not significant, and if the scrap steel temperature exceeds 900°C, the scrap steel burning loss will be aggravated).

[0025] Preferably, in step (2), the time length from opening to closing of the air compressor in each cycle is consistent with the recovery cycle of the converter gas, which is 9 to 13 minutes.

[0026] Preferably, a converter gas composition detector is provided between the converter and the gravity settling device, and the air compressor, the first stop valve and the converter gas composition detector are interlocked; when the converter gas composition detector detects that the carbon monoxide content reaches a set carbon monoxide concentration threshold, the air compressor and the first stop valve are opened at the same time; when it is detected that the carbon monoxide content is lower than the set carbon monoxide concentration threshold and at the same time the heating temperature of the scrap steel is lower than the preheating threshold, the first stop valve is closed, the second stop valve is opened, and the clean gas is discharged into the gas inlet of the burner.

[0027] Preferably, the burner is a self-priming burner, and the cone of the self-priming burner is configured to be automatically adjustable, and the air-fuel ratio is changed by adjusting the cone position (to adapt to the fluctuation of the CO content of the converter gas during the blowing cycle and ensure the efficiency of combustion); and the air inlet of the burner is arranged at the top of the cone, and the gas inlet of the burner is arranged at the side of the cone.

[0028] Preferably, the coal gas filtering device filters particulate matter from the coal gas through a filter screen, and the filter screen is a stainless steel wire mesh (since the main component of converter dust is metal oxides, the binding energy with the metal surface is very weak, and the adhered dust can be easily removed from the filter surface by vibration and backblowing, which can effectively avoid filter clogging); the wall of the air-to-gas heat exchanger used to separate the high-temperature flue gas flow area and the air flow area is a large-pore, low-resistance plate or tube wall made of stainless steel or ceramic material.

[0029] Preferably, the temperature of the low-temperature flue gas in step (2) is 150°C to 200°C, and the low-temperature flue gas purification device includes a bag filter and an SCR denitrification device (the dust in the flue gas is first removed by the bag filter, and if the flue gas contains NO x If the concentration is higher, it needs to be treated with SCR denitrification before it can be discharged).

[0030] The technical effects of the present invention are:

[0031] (1) The present invention sets a scrap steel heating furnace with a specific structure and a high-temperature gas treatment-related device and an air-gas heat exchange device, etc., so that the high-temperature converter gas is directly used for scrap steel preheating. At the same time, the further generated heat is retained in the system through the heat exchange device. The sensible heat of the converter gas completely enters the heating furnace for heating the scrap steel, which effectively saves fuel and avoids heat waste. Through the specific structure and process settings of the present invention, the high-temperature converter gas generated by the converter can be used on-site, and the disadvantages of high investment in insulation pipelines and large heat loss caused by long-distance transportation can be avoided, and the safety is also greatly improved.

[0032] (2) The present invention sets a burner with a specific structure (the conventional gas inlet position is interchanged with the air inlet position) in conjunction with the use of an air compressor. On the basis of using gravity sedimentation and filters for rough dust removal, the kinetic energy of the compressed air from the self-priming nozzle is used as a power source to suck the high-temperature, high-dust converter gas, thereby eliminating the need for power equipment in the gas passage. Such an arrangement avoids the influence of dust to the greatest extent and realizes the efficient and direct utilization of dusty high-temperature fuel gas.

[0033] (3) The present invention makes a specific arrangement so that the scrap steel heating cycle matches the converter gas generation cycle. The scrap steel heated by the converter gas of the current batch can be directly used for the production of the next batch after a short temporary storage, thereby avoiding the heat loss caused by long-term insulation of the hot scrap steel and long-distance transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a connection schematic diagram of a converter gas preheating scrap steel device according to an embodiment of the present invention.

[0035] Figure 2 It is a structural schematic diagram of the self-priming burner used in the scrap steel heating furnace.

[0036] Among them: 1-air filter; 2-air compressor; 3-air-smoke heat exchanger; 4-low-temperature flue gas purification device; 5-chimney; 6-scrap heating furnace; 7-scrap silo; 8-second stop valve; 9-charging valve; 10-second fan; 11-unloading valve; 12-scrap tank; 13-first stop valve; 14-gas filtering device; 15-gravity sedimentation device; 16-gas dust removal device; 17-first fan; 18-converter; A-air; B-high-temperature flue gas; C-low-temperature flue gas; D-cold scrap; E-clean gas; F-gas pipeline network; G-converter gas; X-high-temperature converter gas discharged through the three-way pipe; Y-compressed air after heat exchange; Z-high-temperature flue gas generated by burner combustion. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described with reference to the embodiments:

[0038] like Figure 1 As shown, the converter gas preheating scrap steel device includes a scrap steel heating furnace, a scrap steel silo, a scrap steel tank, an air-to-gas heat exchanger, an air compressor, a gravity settling device, a gas filtering device, a gas dust removal device and a low-temperature flue gas purification device.

[0039] A burner is arranged on the inner top of the scrap steel heating furnace, a scrap steel adding port is opened on the top of the scrap steel heating furnace, a scrap steel discharging port is opened on the bottom of the scrap steel heating furnace, a discharge valve is arranged on the scrap steel heating furnace, and a high-temperature flue gas discharging port is opened on the scrap steel heating furnace; the scrap steel silo is arranged above the scrap steel heating furnace, an openable and closable cold scrap steel discharging port is arranged on the bottom end of the scrap steel silo, a loading valve is arranged on the scrap steel silo, the scrap steel silo is used for temporarily storing cold scrap steel, and can control the cold scrap steel to be discharged into the scrap steel heating furnace through the cold scrap steel discharging port and the scrap steel adding port by opening the loading valve.

[0040] A weighing sensor is arranged on the base of the scrap steel silo, and the weighing sensor is used to accurately measure the mass of the scrap steel loaded into the scrap steel heating furnace.

[0041] The burner includes an air inlet of the burner and a gas inlet of the burner. Figure 2 The burner shown is a self-priming burner, and the cone of the self-priming burner is set to be automatically adjustable, and the air-fuel ratio is changed by adjusting the cone position; and the air inlet of the burner is set at the top of the cone, and the gas inlet of the burner is set at the side of the cone. The air moves downward from the top, forming a negative pressure on the side of the cone, sucking the gas flowing in from the side, and burning at the burner outlet.

[0042] The air-to-flue gas heat exchanger includes a high-temperature flue gas flow area and an air flow area, and heat exchange is performed through a wall separating the two areas. The air flow area is provided with a cold air inlet and a hot air outlet, and the high-temperature flue gas flow area is provided with a high-temperature flue gas inlet and a low-temperature flue gas outlet, and the hot air outlet is connected to the air inlet of the burner of the scrap steel heating furnace; the air compressor compresses the air and discharges it through the compressed air outlet, and the compressed air outlet is connected to the cold air inlet.

[0043] The inlet end of the low-temperature flue gas purification device is connected to the low-temperature flue gas outlet of the heat exchanger through a pipeline, and the low-temperature flue gas purification device is used to purify the low-temperature flue gas after heat exchange.

[0044] The gravity sedimentation device is provided with a converter gas inlet, a first sedimentation gas outlet and a second sedimentation gas outlet. The converter gas inlet is connected with the gas outlet of the converter through a pipeline. The gravity sedimentation device is used to settle large particles of dust in the gas entering the interior under the action of gravity, and the settled gas is discharged through the sedimentation gas outlet; the gas filtering device is provided with a filtered gas inlet and a filtered gas outlet. The filtered gas inlet is connected with the first sedimentation gas outlet through a pipeline, and the filtered gas outlet is connected with the first inlet of a three-way pipeline through a pipeline, and the second inlet of the three-way pipeline is connected with the clean gas, and the outlet of the three-way pipeline is connected with the gas inlet of the burner of the scrap steel heating furnace through a pipeline; a first stop valve is provided on the pipeline between the filtered gas outlet and the first inlet of the three-way pipeline, and a second stop valve is provided on the second inlet of the three-way pipeline.

[0045] The inlet end of the gas dust removal device is connected to the second settling gas outlet of the gravity settling device through a pipeline. The gas dust removal device is used to remove dust from the initial gas discharged from the gravity settling device and then discharge it into the gas pipeline network for subsequent treatment.

[0046] The scrap steel tank can control the heated scrap steel to be discharged into the scrap steel tank through the scrap steel discharge port by opening the discharge valve, and then discharge the heated scrap steel into the converter by moving and / or rotating the scrap steel tank.

[0047] like Figure 1 As shown, an air filter is also provided at the front end of the air compressor, and the air filter is used to filter the external air and discharge it into the air compressor.

[0048] Example 1

[0049] The above device was used to carry out this embodiment in a steel plant in Hebei Province. 20 tons of scrap steel at 900°C was added to a top and bottom double-blown converter with a nominal volume of 120 tons through a scrap steel tank, and then 100 tons of molten iron was added (the scrap steel ratio was 20% at this time). The scrap steel met the standard of "GB / T 4223-2017 Scrap Steel", and the composition and temperature indicators of the molten iron are shown in Table 1:

[0050] Table 1

[0051]

[0052] like Figure 1The converter gas preheating scrap steel device shown in the figure, when the scrap steel and molten iron are charged, the discharge valve is opened, and the scrap steel in the scrap steel silo enters the scrap steel heating furnace below. When the weight of the silo material decreases by 20t, the discharge valve is closed. After the scrap steel and molten iron are charged, the converter is shaken straight, the oxygen lance is lowered to start blowing, and the total blowing time is 17min. The mass of materials added during the blowing process is: 1t of iron ore, 300kg of fluorite, 3t of light-burned dolomite, and 5.6t of quicklime.

[0053] After the blowing starts, the first fan installed at the rear end of the gas dust removal device is turned on, and the generated converter gas enters the gravity settling device, and then passes through the gas dust removal device into the gas pipe network or is exhausted. After 2 minutes of blowing, the gas detector detects that the CO content of the converter gas reaches more than 60% (reaching the carbon monoxide threshold). At this time, the first stop valve is opened and the air compressor starts working. The compressed air generates negative pressure through the self-priming burner in the scrap steel heating furnace, and the converter gas sucked from the gravity settling device passes through the gas filter device and enters the burner to mix with the air and burn. The burner is Figure 2 The air inlet of the burner is arranged at the top of the cone, and the gas inlet of the burner is arranged at the side of the cone. The scrap steel is heated. When the scrap steel starts to be heated, the second fan arranged at the rear end of the low-temperature flue gas purification device is turned on to draw the flue gas generated by the combustion in the scrap steel heating furnace through the air-to-flue gas heat exchanger to preheat the compressed air. The low-temperature flue gas after waste heat recovery is cooled to about 170°C, and is discharged after being treated by the bag filter and SCR denitrification device in the low-temperature flue gas purification device to meet the standards.

[0054] When the blowing reaches 12 minutes, the gas detector detects that the scrap steel in the scrap steel heating furnace has been heated to about 920℃. At this time, the air compressor is turned off, the first stop valve is closed, and the second fan is turned off. The preheated scrap steel is temporarily stored in the scrap steel heating furnace. Under this condition, the amount of high-temperature converter gas used to heat each ton of scrap steel is 79.07Nm 3 .

[0055] After the converter has completed blowing, temperature measurement and sampling, it is measured that the tapping temperature of the converter under this working condition is about 1688℃, and the contents of carbon, manganese, phosphorus and sulfur meet the standards, meeting the tapping conditions, and the tapping port is opened to pour the furnace and tap the steel. After the tapping and slag splashing are completed, the discharge valve is opened, and the preheated scrap steel enters the scrap steel tank under the action of gravity, and then is added to the converter for the smelting of the next batch of converters.

[0056] Comparative Example 1

[0057] This comparative example is a conventional converter smelting example without preheating scrap steel. The difference is that the amount of scrap steel added is 12t, the molten iron temperature and the amount of addition remain unchanged (the scrap steel ratio is 12% at this time). The blowing process and material addition of this comparative example are the same as those of Example 1, except that the scrap steel preheating process is cancelled. Under this condition, the tapping temperature is also about 1690℃, and the carbon, phosphorus and sulfur elements of the molten steel meet the requirements. Although the tapping temperature and the quality of the molten steel are the same, the scrap steel ratio is significantly lower than that of Example 1, and the effect of scrap steel recycling is significantly reduced.

[0058] Comparative Example 2

[0059] This comparative example is a converter smelting example using a large scrap ratio without preheating scrap steel. The difference is that the 20t scrap steel added is room temperature scrap steel at 25°C, the molten iron temperature and the amount of addition remain unchanged (the scrap steel ratio is 20% at this time), and the blowing process and material addition of this comparative example are the same as those of Example 1, except that the scrap steel preheating process is cancelled. Under this working condition, the tapping temperature drops to 1600°C. When the amount of scrap steel in conventional smelting increases, the physical heat brought into the molten iron and the oxidation heat of carbon, sulfur, manganese, etc. in the molten iron are fixed, and the overall heat input of converter smelting remains unchanged, but the amount of scrap steel increases and the output of molten steel increases, resulting in the terminal temperature of the molten steel being too low, which is not conducive to later casting, and the effects of dephosphorization and decarburization are also poor. The carbon and phosphorus content of the molten steel is high, which affects the quality of the steel products. In addition, the amount of scrap steel increases, the melting slows down, and the smelting cycle will also be extended.

[0060] Comparative Example 3

[0061] This comparative example does not use high-temperature converter gas, but uses normal-temperature converter gas in the gas pipeline network for heating. Under this condition, the amount of converter gas used to heat each ton of scrap steel is 90.89Nm 3 In Example 1, since the sensible heat of the high-temperature converter gas is utilized, the amount of gas used is significantly reduced, thereby achieving a better energy-saving effect.

[0062] Comparative Example 4

[0063] This comparative example does not have an air-to-gas heat exchanger. The high-temperature flue gas generated by the scrap steel heating furnace is cooled to 170°C by a water-cooled heat exchanger and then directly discharged into the low-temperature flue gas purification device; the air generated by the air compressor directly enters the burner to mix with the high-temperature converter gas and burn. Other settings are the same as those in Example 1. Compared with Example 1, the amount of high-temperature converter gas used to heat each ton of scrap steel in this comparative example is 88.67Nm 3 In Example 1, the waste heat of the high-temperature flue gas is recovered by compressed air and then returned to the scrap steel heating furnace, which effectively reduces the consumption of gas. Although the water-cooled heat exchanger in Comparative Example 4 can recover part of the waste heat by generating hot water or low-temperature steam, they are all low-grade waste heat, which is not as scientific as directly saving fuel.

[0064] Comparative Example 5

[0065] The burner in this comparative example is a conventional gas burner, and the air uses a blower as the power source. A four-stage high-temperature resistant centrifugal fan is installed on the high-temperature gas pipeline to transport the high-temperature converter gas. The other settings are the same as those in Example 1. In this comparative example, since the high-temperature converter gas is only roughly dusted, the dust in the gas increases in viscosity at high temperatures and will adhere to the centrifugal fan impeller in large quantities, causing severe vibration of the fan impeller and bearing damage, making it difficult for the system to ensure stable operation. In Example 1, the high-temperature converter gas pipeline has no moving equipment, and the power is achieved through the burner negative pressure of the specifically set conversion inlet, which minimizes the impact of dust.

[0066] The above embodiments and comparative examples of the present invention are examples and do not limit the protection scope of the technical solution. The lack of comparison of technical features does not mean that there are no outstanding substantive features, but only uses text description to illustrate its setting method.

Claims

1. A method for preheating scrap steel using high-temperature converter gas, characterized in that: The process is carried out using a converter gas preheating scrap steel device, wherein the converter gas preheating scrap steel device comprises a scrap steel heating furnace, a scrap steel silo, a scrap steel tank, an air-to-gas heat exchanger, an air compressor, a gravity settling device, a gas filtering device, a gas dust removal device, and a low-temperature flue gas purification device; The scrap steel heating furnace is provided with a burner at the inner top, a scrap steel feeding port is provided at the top of the scrap steel heating furnace, a scrap steel discharge port is provided at the bottom of the scrap steel heating furnace, a discharge valve is provided on the scrap steel heating furnace, and a high-temperature flue gas discharge port is provided on the scrap steel heating furnace; the scrap steel silo is provided above the scrap steel heating furnace, an openable and closable cold scrap steel discharge port is provided at the bottom of the scrap steel silo, a charging valve is provided on the scrap steel silo, the scrap steel silo is used for temporarily storing cold scrap steel, and can control the cold scrap steel to be discharged into the scrap steel heating furnace through the cold scrap steel discharge port and the scrap steel feeding port by opening the charging valve; The burner includes an air inlet of the burner and a gas inlet of the burner; The air-smoke heat exchanger includes a high-temperature smoke flow area and an air flow area, and heat exchange is performed through a wall separating the two areas. The air flow area is provided with a cold air inlet and a hot air outlet, and the high-temperature smoke flow area is provided with a high-temperature smoke inlet and a low-temperature smoke outlet, and the hot air outlet is connected to the air inlet of the burner of the scrap steel heating furnace; the air compressor compresses the air and discharges it through the compressed air outlet, and the compressed air outlet is connected to the cold air inlet; The inlet end of the low-temperature flue gas purification device is connected to the low-temperature flue gas outlet of the air-to-flue gas heat exchanger through a pipeline, and the low-temperature flue gas purification device is used to purify the low-temperature flue gas after heat exchange; The gravity settling device comprises a converter gas inlet, a first settling gas outlet and a second settling gas outlet, the converter gas inlet is connected with the gas outlet of the converter through a pipeline, the gravity settling device is used to settle large particles of dust in the gas entering the interior under the action of gravity, and the settled gas is discharged through the first settling gas outlet and / or the second settling gas outlet; the gas filtering device is provided with a filtered gas inlet and a filtered gas outlet, the filtered gas inlet is connected with the first settling gas outlet through a pipeline, the filtered gas outlet is connected with the first inlet of a three-way pipeline through a pipeline, the second inlet of the three-way pipeline is connected with the external clean gas, and the outlet of the three-way pipeline is connected with the gas inlet of the burner of the scrap steel heating furnace through a pipeline; a first stop valve is provided on the pipeline between the filtered gas outlet and the first inlet of the three-way pipeline, and a second stop valve is provided on the second inlet of the three-way pipeline; The inlet end of the coal gas dust removal device is connected to the second settling coal gas outlet of the gravity settling device through a pipeline, and the coal gas dust removal device is used to remove dust from the initial coal gas discharged from the gravity settling device and then discharge it into the coal gas network for subsequent treatment; The scrap steel tank can control the heated scrap steel to be discharged into the scrap steel tank through the scrap steel discharge port by opening the discharge valve, and then discharge the heated scrap steel into the converter by moving and / or rotating the scrap steel tank; The steps include: (1) Load the cold scrap into the scrap silo for temporary storage, open the loading valve, add the cold scrap into the scrap heating furnace, and close the loading valve when the scrap threshold of the scrap heating furnace is reached; (2) The converter starts blowing, and the generated converter gas is first discharged into the gravity settling device through the converter gas inlet of the gravity settling device for gravity settling. The converter gas after gravity settling is discharged into the gas dust removal device through the second settling gas outlet for dust removal, and then discharged into the gas pipeline network for subsequent treatment. At the same time, the concentration of carbon monoxide in the converter gas is monitored. When the carbon monoxide concentration rises to the set carbon monoxide concentration threshold, the air compressor is turned on and the first stop valve is turned on, and the second settling gas outlet is closed at the same time. The converter gas after settling is discharged into the gas filter device through the first settling gas outlet, and then discharged through the three-way pipe. The compressed air obtained by the air compressor is discharged into the burner through the hot air outlet after heat exchange in the air-to-gas heat exchanger, and the high-temperature converter gas and the compressed air are mixed and burned in the burner to heat the cold scrap steel in the scrap steel heating furnace. The high-temperature flue gas generated after combustion is discharged from the high-temperature flue gas outlet of the scrap steel heating furnace into the air-to-gas heat exchanger, and after heat exchange with the compressed air, the compressed air is heated to obtain low-temperature flue gas, which is discharged into the low-temperature flue gas purification device through the low-temperature flue gas outlet of the air-to-gas heat exchanger for purification and then discharged; (3) In step (2), the temperature of the cold scrap steel is monitored while the scrap steel temperature is heated. When the scrap steel is heated to the preheating threshold, the air compressor is turned off and the first stop valve is closed. The heated scrap steel is temporarily stored in the scrap steel heating furnace. After the converter smelting is completed, the discharge valve is opened to discharge the heated scrap steel into the scrap steel tank. The scrap steel tank then transfers the heated scrap steel to the converter for a new cycle of converter smelting. The scrap steel threshold is 18-30wt.% of the nominal volume of the converter; the carbon monoxide concentration threshold is 58-65v.%, and the preheating threshold is 600-900°C; The time length from the start to the closing of the first stop valve in each cycle is consistent with the converter gas recovery cycle, which is 9 to 13 minutes; The burner is a self-priming burner, and the cone of the self-priming burner is configured to be automatically adjustable, and the air-fuel ratio is changed by adjusting the position of the cone to adapt to the fluctuation of the CO content of the converter gas during the blowing cycle; and the air inlet of the burner is arranged at the top of the cone, and the gas inlet of the burner is arranged at the side of the cone.

2. The method for preheating scrap steel using high-temperature converter gas according to claim 1, characterized in that: A weighing sensor is arranged on the base of the scrap steel silo, and the weighing sensor is used to accurately measure the mass of the scrap steel loaded into the scrap steel heating furnace.

3. The method for preheating scrap steel using high-temperature converter gas according to claim 1, characterized in that: The scrap steel heating furnace is a vertical furnace, and the flame of the burner is arranged downward; the diameter or equivalent diameter of the bottom of the scrap steel heating furnace is smaller than the diameter or equivalent diameter of the middle of the scrap steel heating furnace; An air filter is also provided at the front end of the air compressor, and the air filter is used to filter the external air and discharge it into the air compressor.

4. The method for preheating scrap steel using high-temperature converter gas according to claim 1, characterized in that: A converter gas composition detector is arranged between the converter and the gravity sedimentation device. The air compressor, the first stop valve and the converter gas composition detector are interlocked. When the converter gas composition detector detects that the carbon monoxide content reaches a set carbon monoxide concentration threshold, the air compressor and the first stop valve are opened at the same time; when it is detected that the carbon monoxide content is lower than the set carbon monoxide concentration threshold and at the same time the heating temperature of the scrap steel is lower than the preheating threshold, the first stop valve is closed and the second stop valve is opened to allow the clean gas to be introduced into the gas inlet of the burner.

5. The method for preheating scrap steel using high-temperature converter gas according to claim 1, characterized in that: The coal gas filtering device filters particulate matter from the coal gas through a filter screen, and the filter screen is a stainless steel wire mesh; the wall of the air-smoke heat exchanger used to separate the high-temperature smoke flow area and the air flow area is a large-pore, low-resistance plate or tube wall made of stainless steel or ceramic.

6. The method for preheating scrap steel using high-temperature converter gas according to claim 1, characterized in that: The temperature of the low-temperature flue gas in step (2) is 150°C to 200°C, and the low-temperature flue gas purification device includes a bag filter and an SCR denitrification device.

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