System for improving calorific value of injection feed gas of low-carbon blast furnace

Abstract

The utility model relates to a system for improving the calorific value of low-carbon blast furnace injection feed gas, and belongs to the technical field of steel smelting. A converter gas holder (1), a first pressurization system (2), a heat exchange system (3), a decarburization system (4), a second pressurization system (5), a drying system (6), a precooling system (8), a liquefaction rectification system (9), a storage system (11), a vaporization system (12) and a converter sealing system (14) are sequentially arranged. And the liquefaction rectification system (9) is connected back to the precooling system (8) and then connected back to the decarburization system (4) to recover and reduce the reducing components again, so that the reducing components in the converter gas are recovered by 100%. According to the method, liquid carbon dioxide and low-carbon blast furnace injection reducing gas are separated and extracted by mainly utilizing a decarburization and low-temperature liquefaction rectification coupling process system, a nitrogen medium of each sealing system of a converter is replaced by a carbon dioxide product, and the reducing gas is used for a blast furnace injection system.

Description

Technical Field

[0001] The utility model belongs to the technical field of iron and steel smelting, and relates to a system for improving the calorific value of raw material gas blown into a low-carbon blast furnace. Background Technique

[0002] At present, 90% of China's iron and steel industry adopts the long process of blast furnace-converter production. Therefore, for a long time to come, China will still be based on the blast furnace-converter production process, and most iron and steel enterprises are relatively new and difficult to eliminate in a short time. In the comprehensive utilization of gas in iron and steel enterprises at present, except for special processes such as coke oven gas to hydrogen and LNG with relatively high utilization added value, other heat energy utilization methods such as blast furnace gas, converter gas, or a mixture of blast furnace gas and converter gas with coke oven gas as fuel gas, and CCPP power generation have relatively low added value.

[0003] Research shows that injecting hydrogen-rich and CO-rich gases into the blast furnace can effectively reduce the coke ratio and coal ratio of the blast furnace, which is the main way for traditional blast furnaces to achieve low-carbon emission reduction. In view of the urgent need of iron and steel enterprises for low-carbon smelting technology, after purifying and decarbonizing and separating the blast furnace gas or converter gas used for power generation, it is used for blast furnace injection, and more use of the chemical energy of gas to improve the utilization efficiency of fossil energy. This can not only effectively balance the gas fluctuations of the whole plant, but also reduce the coke ratio and coal ratio of the blast furnace at the source. While meeting the requirements of low-carbon emission reduction, it has good economic efficiency and can bring certain economic benefits to enterprises.

[0004] At present, the decarbonization systems and denitrification systems on the market cannot remove carbon dioxide and nitrogen components in gas at low cost at the same time. In addition, the converter gas in iron and steel enterprises has high economic and environmental benefits when recycled as energy. The statistical methods of converter gas recovery data in China's iron and steel enterprises are very irregular. Many enterprises only provide the gas recovery volume and do not provide the calorific value data of the recovered gas. At present, the converter gas recovery volume in steel mills generally can reach 100 - 120 Nm 3 / t, but the calorific value of the gas is relatively low because the gas contains a large amount of nitrogen components. Through investigation, it is found that during the converter steelmaking process, nitrogen is used as the sealing medium in the converter sealing systems such as the converter oxygen lance nozzle, the charging opening, the bunker, and the movable hood. The nitrogen consumption is relatively large, which is the main position of nitrogen consumption in the whole steelmaking process. Through the measurement of the flowmeter in the 120t converter steelmaking workshop of a certain iron and steel enterprise, the actual consumption of the sealing system is 6000 - 12000 Nm 3 / h. At present, after some iron and steel enterprises have taken a series of new processes, new technologies, technical transformations, and precise control of the micro differential pressure at the furnace mouth for the sealing systems of the converter oxygen lance nozzle and the charging opening, the nitrogen consumption of the sealing system also exceeds 6000 Nm 3above. Therefore, iron and steel enterprises should increase their research efforts on converter gas recovery technology, further explore the potential of converter gas recovery, and at the same time, combine other process technologies to significantly reduce the nitrogen content in converter gas.

[0005] Based on the above situation, how to reduce the nitrogen component in the converter gas of iron and steel enterprises and increase the converter gas recovery as much as possible, while the most important purpose is to increase the calorific value of the injected reducing gas and the production cost cannot be significantly increased. However, the current converter gas recovery process and decarbonization system in industry cannot meet the requirements of blast furnaces for injecting reducing gas. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a system for increasing the calorific value of the raw material gas for injecting into a low-carbon blast furnace, which simultaneously decarbonizes and denitrifies the converter gas.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A system for increasing the calorific value of the raw material gas for injecting into a low-carbon blast furnace is successively provided with a converter gas holder, a first pressurization system, a heat exchange system, a decarbonization system, a second pressurization system, a drying system, a precooling system, a liquefaction and rectification system, a storage system, a vaporization system, and a converter sealing system; the liquefaction and rectification system is connected back to the precooling system, and then connected back to the decarbonization system to recover the reducing components again so that 100% of the reducing components in the converter gas are recovered.

[0009] Optionally, the decarbonization system is connected back to the heat exchange system.

[0010] Optionally, the heat exchange system is connected to the blast furnace through an injection system.

[0011] Optionally, the outlet end of the drying system is connected back to the drying system through a heater.

[0012] Optionally, the liquefaction and rectification system is connected in a cycle to a refrigeration unit system.

[0013] Optionally, the converter sealing system includes an oxygen lance nozzle sealing system, a charging opening sealing system, a silo and movable hood sealing system, and a converter bottom blowing system.

[0014] Optionally, the converter sealing system is connected back to the converter gas holder.

[0015] The beneficial effects of the present invention are as follows:

[0016] At present, the recovery amount of converter gas in the converter steelmaking process of iron and steel enterprises is relatively low, and the nitrogen content is relatively high, resulting in generally low calorific value of converter gas. If the converter gas only undergoes decarbonization separation to obtain the blown reducing gas, the nitrogen content is relatively high, which not only affects the normal operation of the blast furnace, but also, since the nitrogen component is an ineffective gas component for the reduction reaction in the blast furnace, significantly reduces the energy efficiency of the blown reducing gas. If the converter gas is decarbonized and denitrified simultaneously, not only is the operating cost relatively high, but the investment also increases significantly. The present invention provides a process system and method for increasing the calorific value of the raw gas for blowing in a low-carbon blast furnace. Firstly, it can increase the recovery amount of converter gas in converter steelmaking and reduce the consumption of fossil fuels in iron and steel enterprises. Secondly, by using carbon dioxide as the sealing medium for each sealing system of the converter and for bottom blowing of the converter, the nitrogen component in the converter gas can be significantly reduced. Thirdly, the converter gas recovered after replacing the sealing medium in each sealing system of the converter only needs to undergo decarbonization separation to obtain a blown reducing gas with a relatively low nitrogen component content and a relatively high calorific value. Fourthly, the blown reducing gas prepared by this process system not only has relatively high energy efficiency, but also can reduce the adverse impact on the normal operation of the blast furnace.

[0017] Other advantages, objectives and features of the present utility model will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present utility model. The objectives and other advantages of the present utility model can be realized and obtained through the following specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the objectives, technical solutions and advantages of the present utility model clearer, the present utility model will be described in detail preferably with reference to the accompanying drawings, where:

[0019] Figure 1 is a schematic diagram of the system of the present utility model.

[0020] Reference numerals: 1 converter gas holder, 2 first pressurization system, 3 heat exchange system, 4 decarbonization system, 5 second pressurization system, 6 drying system, 7 heater, 8 precooling system, 9 liquefaction rectification system, 10 refrigeration unit system, 11 storage system, 12 vaporization system, 13 blast furnace, 14 converter sealing system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The following describes the implementation modes of the present utility model through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present utility model from the content disclosed in this specification. The present utility model can also be implemented or applied through other different specific implementation modes. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present utility model. It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present utility model in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0022] Among them, the attached drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to the present utility model; in order to better illustrate the embodiments of the present utility model, some components in the attached drawings will be omitted, enlarged or reduced, which does not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the attached drawings may be omitted.

[0023] In the attached drawings of the embodiments of the present utility model, the same or similar reference numerals correspond to the same or similar components; in the description of the present utility model, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc. indicating the orientation or positional relationship, they are based on the orientation or positional relationship shown in the attached drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the attached drawings are only for illustrative purposes and should not be construed as a limitation to the present utility model. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0024] Please refer to Figure 1 , the present utility model discloses a system for improving the calorific value of raw gas blown into a low-carbon blast furnace. The key lies in that converter gas successively passes through a first pressurization system 2, a heat exchange system 3, and a decarbonization system 4 for removing CO2 components. A part of the gas separated by the decarbonization system 4 is the blown reducing gas, and this gas is sent to the blast furnace 13 for low-carbon blast furnace injection after heat supplementation. Another part of the gas separated by the decarbonization system 4 is the desorbed gas. The desorbed gas is subjected to pressurization treatment by a second pressurization system 5, drying treatment by a drying system 6, temperature reduction treatment by a precooling system 8, deep temperature reduction liquefaction and rectification separation by a liquefaction rectification system 9. The rectification tail gas discharged from the top of the rectification tower of the liquefaction rectification system 9 recovers cold energy and then returns to the decarbonization system 4 to recover reducing components again, so that 100% of the reducing components in the converter gas are recovered. The liquefaction rectification system 9 exchanges heat with the refrigeration unit system 10 in a cycle.

[0025] Part of the dried gas flowing out of the outlet of the drying system 6 is reheated by the heater 7 and refluxed to the inlet of the drying system 6. The liquid carbon dioxide obtained from the bottom of the rectification column of the liquefaction and rectification system 9 is sent to the storage system 11, and finally taken out from the storage system 11 according to the demand of the converter sealing system 14, vaporized by the vaporization system 12 and then sent to each converter sealing system 14 and the bottom blowing of the converter. The surplus carbon dioxide is used for other users or sold externally.

[0026] The converter gas is pressurized by the first pressurization system 2, and the gas is pressurized to 600 - 1600 kPa. The pressurized converter gas exchanges heat with the blown reducing gas in the heat exchange system 3, and the temperature drops below 80°C, while the temperature of the blown reducing gas rises to between 70 - 82°C. The heat exchange system 3 can recover more than 12% of the shaft power heat of the compressor, and reduce the cooling water consumption by more than 12%.

[0027] The main processes of the decarbonization system 4 include chemical absorption process, physical solvent absorption process, adsorption separation method, membrane separation method, low-temperature rectification separation method, and combined processes of the above processes. Commonly used absorbents for the chemical absorption process include aqueous solutions of alkali metal carbonates, aqueous solutions of alkanolamines, ammonia water, ionic liquids, etc. Commonly used absorbents for the physical solvent absorption process include methanol, N-methylpyrrolidone, propylene carbonate, polyol ether, and sulfolane, etc. The adsorption separation method is mainly pressure swing adsorption separation, and adsorbents with high selectivity, high adsorption capacity, and strong desorption ability are selected.

[0028] The pressure of the blown reducing gas separated by the decarbonization system 44 is 550 - 1500 kPa, the CO content is greater than 80%, the CO2 content is less than 2%, and the nitrogen content is less than 15%. The coupling process of the decarbonization system 4 and low-temperature liquefaction and rectification achieves a 100% CO recovery rate in the converter gas. The desorbed gas is pressurized to 2500 - 3000 kPa. The drying system 6 uses a fixed-bed dryer. The operation mode of the dryer can be in series or in parallel. After drying, the water content of the desorbed gas is less than 10 mg / kg, and the static water adsorption capacity of the desiccant filled in the dryer is not less than 20%. In the process of cooling and liquefying the desorbed gas, the desorbed gas is first precooled to 10 - 30°C by the rectification tail gas, and then deeply cooled and liquefied to -30 - -40°C by a refrigeration unit.

[0029] The purity of the liquid carbon dioxide obtained from the bottom of the rectification column is 99.5% and above, the pressure is 2200 kPa - 2700 kPa, and the temperature is between -10 - -25°C. The liquid carbon dioxide is stored in a high-pressure and low-temperature spherical tank. The liquid carbon dioxide is led out of the spherical tank, vaporized and sent to each converter sealing system such as the converter oxygen lance nozzle, charging opening, bin, and movable hood as a sealing medium to replace the existing nitrogen medium, and is also used for the bottom blowing of the converter.

[0030] Example 1

[0031] 1. In this embodiment, there are 4 converters with a capacity of 120 t each. The effective operating days of the converter are 310 days / year, the C content in hot metal is 0.0465, and the recovery amount of converter gas per ton of hot metal is 100 Nm 3 , and the consumption of nitrogen as the sealing medium for each converter is 6000 Nm 3 / h. The specific parameter properties of the converter gas are as follows: its volume fraction is 12.00% carbon dioxide, 52.96% carbon monoxide, 2.10% hydrogen, 32.74% nitrogen, and 0.20% oxygen; the pressure is 10 kPa, the temperature is 40 °C, and the flow rate is 60000 Nm 3 / h.

[0032] 2. Process system: Please refer to the attached Figure 1 . The converter gas sequentially passes through the first pressurization system 2, the heat recovery system, and the decarbonization system 4 for removing CO2 components. A part of the gas separated by the decarbonization system 4 is the blown reducing gas, which is sent to the low-carbon blast furnace blowing system after heat supplementation. Another part of the gas separated by the decarbonization system 4 is the desorbed gas. The desorbed gas is subjected to pressurization treatment, drying treatment, pre-cooling and temperature reduction, deep cooling and liquefaction, and rectification separation. The rectification tail gas discharged from the top of the rectification column recovers cold energy and then returns to the decarbonization system 4 to recover the reducing components again, so that 100% of the reducing components in the converter gas are recovered. The liquid carbon dioxide obtained from the bottom of the rectification column is sent to the storage system 11, and finally, according to the demand of the converter sealing system 14, it is taken out from the storage system 11, vaporized, and then sent to the converter sealing system 14 and the bottom blowing of the converter. The surplus carbon dioxide is used for other users or sold externally.

[0033] 3. Treatment results:

[0034] 1) After using carbon dioxide instead of nitrogen as the sealing medium for each converter sealing system, the parameter properties of the converter gas are as follows:

[0035] A. When the proportion of C in hot metal converted to CO is 80% and the amount of the sealing medium entering the converter gas is 60% of the total sealing gas volume, the specific parameter properties of the converter gas are as follows: its volume fraction is 36.00% carbon dioxide, 52.96% carbon monoxide, 2.10% hydrogen, 8.74% nitrogen, and 0.20% oxygen; the pressure is 10 kPa, the temperature is 40 °C, and the flow rate is 60000 Nm 3 / h.

[0036] B. The parameters of the blown reducing gas are: its volume fraction is 81.58% carbon monoxide, 13.46% nitrogen, 1.41% carbon dioxide, 3.23% hydrogen, and 0.31% oxygen; the pressure is 550 - 1500 kPa, the temperature is 40 °C, and the flow rate is 38947 Nm 3 / h.

[0037] C. The parameters of liquid carbon dioxide are as follows: the volume fraction of carbon monoxide is 0.01% and that of carbon dioxide is 99.99%; the pressure is 2200 - 2700 kPa, the temperature is -13°C, and the flow rate is 41.25 t / h.

[0038] Example 2

[0039] 1. In this example, there are 4 converters with a capacity of 120 t each. The effective operating days of the converters are 310 days / year, the C content in hot metal is 0.0465, and the recovery amount of converter gas per ton of hot metal is 120 Nm 3 , and the consumption of nitrogen as the sealing medium for each converter is 6000 Nm 3 / h. The specific parameter properties of the converter gas are as follows: the volume fraction of carbon dioxide is 18.00%, that of carbon monoxide is 55.08%, that of hydrogen is 2.10%, that of nitrogen is 24.62%, and that of oxygen is 0.20%; the pressure is 10 kPa, the temperature is 40°C, and the flow rate is 72000 Nm 3 / h.

[0040] 2. Process system: Please refer to the appendix Figure 1 . The converter gas successively passes through the first pressurization system 2, the heat recovery system, and the decarbonization system 4 for removing CO2 components. A part of the gas separated by the decarbonization system 4 is the blown reducing gas, which is sent to the low-carbon blast furnace blowing system after heat supplementation. Another part of the gas separated by the decarbonization system 4 is the desorbed gas. The desorbed gas undergoes pressurization treatment, drying treatment, pre-cooling and temperature reduction, deep cooling and liquefaction, and rectification separation. The rectification tail gas discharged from the top of the rectification column recovers cold energy and then returns to the decarbonization system 4 to recover the reducing components again, so that 100% of the reducing components in the converter gas are recovered. The liquid carbon dioxide obtained from the bottom of the rectification column is sent to the storage system 11, and finally, it is taken out from the storage system 11 according to the demand of the converter sealing system 14, vaporized, and then sent to the converter sealing system 14 and the bottom blowing of the converter. The surplus carbon dioxide is used for other users or sold externally.

[0041] 3. Treatment results:

[0042] 1) After using carbon dioxide instead of nitrogen as the sealing medium in each converter sealing system, the parameter properties of the converter gas are as follows:

[0043] A. When the proportion of C in hot metal converted to CO is 90% and the amount of the sealing medium entering the converter gas is 60% of the total sealing gas volume, the specific parameter properties of the converter gas are as follows: the volume fraction of carbon dioxide is 38.00%, that of carbon monoxide is 55.08%, that of hydrogen is 2.10%, that of nitrogen is 4.62%, and that of oxygen is 0.20%; the pressure is 10 kPa, the temperature is 40°C, and the flow rate is 72000 Nm 3 / h.

[0044] B. The parameters of the injected reducing gas are as follows: the volume fraction is 87.55% carbon monoxide, 7.34% nitrogen, 1.44% carbon dioxide, 3.34% hydrogen, and 0.32% oxygen; the pressure is 550 - 1500 kPa, the temperature is 40°C, and the flow rate is 45290 Nm 3 / h.

[0045] C. The parameters of liquid carbon dioxide are as follows: the volume fraction is 0.01% carbon monoxide and 99.99% carbon dioxide; the pressure is 2200 - 2700 kPa, the temperature is -13°C, and the flow rate is 52.35 t / h.

[0046] Example 3

[0047] 1. In this example, there are 4 converters with a capacity of 120 t each. The effective operation days of the converter are 310 days / year, the C content in the hot metal is 0.0465, the recovery amount of converter gas per ton of iron is 100 Nm 3 , and the consumption of nitrogen as the sealing medium for each converter is 6000 Nm 3 / h. The specific parameter properties of the converter gas are as follows: the volume fraction is 12.00% carbon dioxide, 52.96% carbon monoxide, 2.10% hydrogen, 32.74% nitrogen, and 0.20% oxygen; the pressure is 10 kPa, the temperature is 40°C, and the flow rate is 60000 Nm 3 / h.

[0048] 2. Please refer to the appendix Figure 1 . The converter gas successively passes through the first pressurization system 2, the heat recovery system, and the decarbonization system 4 for removing the CO2 component. A part of the gas separated by the decarbonization system 4 is the injected reducing gas, which is sent to the low-carbon blast furnace injection system after heat supplementation. Another part of the gas separated by the decarbonization system 4 is the desorbed gas. The desorbed gas undergoes pressurization treatment, drying treatment, pre-cooling and temperature reduction, deep cooling and liquefaction, and rectification separation. The rectification tail gas discharged from the top of the rectification column recovers the cold energy and then returns to the decarbonization system 4 to recover the reducing components again, so that 100% of the reducing components in the converter gas are recovered. The liquid carbon dioxide obtained from the bottom of the rectification column is sent to the storage system 11, and finally, it is taken out from the storage system 11 according to the demand of the converter sealing system 14, vaporized, and then sent to the converter sealing system 14 and the bottom blowing of the converter. The surplus carbon dioxide is used for other users or sold externally.

[0049] 3. Treatment results:

[0050] 1) After using carbon dioxide instead of nitrogen as the sealing medium for each converter sealing system, the parameter properties of the converter gas are as follows:

[0051] A. When the conversion ratio of C in molten iron to CO is 80% and the amount of converter gas entering the sealed medium is 70% of the total sealed gas volume, the specific parameter properties of the converter gas are as follows: its volume fraction is 40.00% carbon dioxide, 52.96% carbon monoxide, 2.10% hydrogen, 4.74% nitrogen, and 0.20% oxygen; the pressure is 10 kPa, the temperature is 40 °C, and the flow rate is 60000 Nm 3 / h.

[0052] B. The parameters of the injected reducing gas are: its volume fraction is 86.87% carbon monoxide, 7.77% nitrogen, 1.58% carbon dioxide, 3.44% hydrogen, and 0.33% oxygen; the pressure is 550 - 1500 kPa, the temperature is 40 °C, and the flow rate is 36576 Nm 3 / h.

[0053] C. The parameters of liquid carbon dioxide are: its volume fraction is 0.01% carbon monoxide and 99.99% carbon dioxide; the pressure is 2200 - 2700 kPa, the temperature is -13 °C, and the flow rate is 45.91 t / h.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the present technical solution, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A system for increasing the calorific value of the raw material gas for low-carbon blast furnace injection, characterized in that: A converter gas holder (1), a first pressurization system (2), a heat exchange system (3), a decarbonization system (4), a second pressurization system (5), a drying system (6), a pre-cooling system (8), a liquefaction and rectification system (9), a storage system (11), a vaporization system (12), and a converter sealing system (14) are sequentially arranged; the liquefaction and rectification system (9) is connected back to the pre-cooling system (8), and then connected back to the decarbonization system (4) to recover and reduce the reducing components again so that 100% of the reducing components in the converter gas are recovered.

2. The system for increasing the calorific value of the raw gas injected into the low-carbon blast furnace according to claim 1, characterized in that: The decarbonization system (4) is connected back to the heat exchange system (3).

3. The system for increasing the calorific value of the raw gas injected into a low-carbon blast furnace according to claim 1, characterized in that: The heat exchange system (3) is connected to a blast furnace (13) through a blowing system.

4. The system for increasing the calorific value of the raw gas for injection into a low-carbon blast furnace according to claim 1, characterized in that: The outlet end of the drying system (6) is connected back to the drying system (6) through a heater (7).

5. The system for increasing the calorific value of the raw gas for low-carbon blast furnace injection according to claim 1, characterized in that: The liquefaction and rectification system (9) is connected in a cycle to a refrigeration unit system (10).

6. The system for increasing the calorific value of the raw material gas for low-carbon blast furnace injection according to claim 1, wherein: The converter sealing system (14) includes an oxygen lance nozzle sealing system, a charging opening sealing system, a bin and movable hood sealing system, and a converter bottom blowing system.

7. The system for increasing the calorific value of the raw gas for injection into a low-carbon blast furnace according to claim 1, characterized in that: The converter sealing system (14) is connected back to the converter gas holder (1).

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