A method for utilizing carbon dioxide in high-rich oxygen and all-oxygen blast furnace injection

Abstract

The present invention discloses a method for utilizing carbon dioxide by injecting it into a high-oxygen-enriched and all-oxygen blast furnace, belonging to the technical field of blast furnace ironmaking. In the present invention, the top gas discharged from the all-oxygen blast furnace is passed through a CO2 removal device to remove the CO2 component therein, and after the top gas with CO2 removed is heated, it is injected into the furnace from the tuyeres at the lower part of the furnace body; and a part of the CO2 separated from the top gas is heated and then blown into the blast furnace from the tuyeres of the blast furnace together with pure oxygen and pulverized coal, and this part of CO2 accounts for 5% to 8% of the total amount of CO2 separated from the top gas. The present invention aims to provide a method for utilizing carbon dioxide by injecting it into a high-oxygen-enriched and all-oxygen blast furnace, removing the CO2 in the top gas, heating a part of the separated CO2 and injecting it into the furnace from the tuyeres of the blast furnace together with oxygen and pulverized coal, on the one hand, solving the problem of "hot at the bottom and cold at the top" of the all-oxygen blast furnace, and on the other hand, increasing the concentration of reducing gas in the furnace and reducing the consumption of solid carbon.

Description

Technical Field

[0001] The present invention belongs to the technical field of blast furnace ironmaking, and more specifically, relates to a method for utilizing carbon dioxide in high oxygen enrichment and all-oxygen blast furnace injection. Background Art

[0002] The all-oxygen blast furnace (abbreviated as OBF) ironmaking process refers to a blast furnace ironmaking process that uses high oxygen enrichment or even all-oxygen blast to replace the traditional air blast operation. Under the condition of all-oxygen blast, it is also called the "nitrogen-free blast furnace" or "all-oxygen blast furnace". The all-oxygen blast furnace is generally combined with the top gas recycling process (abbreviated as TGR-OBF), called the "all-oxygen blast furnace top gas recycling". Due to the advantages of high coal injection rate, low coke ratio, strong reducibility of gas, high calorific value, high productivity, etc. in the all-oxygen blast furnace top gas recycling, it can be considered as a new ironmaking process for extremely efficient utilization of carbon, with a significant carbon reduction effect.

[0003] In the all-oxygen blast furnace top gas recycling process, in order to increase the CO concentration in the top gas, it is necessary to remove CO2 from the top gas. After removing CO2, the top gas is heated to above 900 °C and injected into the blast furnace from the tuyere or the lower part of the furnace body to enhance the reduction atmosphere in the furnace, improve the indirect reduction degree of iron ore, reduce the consumption of solid carbon (coke), thereby reducing the coke consumption and achieving the purpose of carbon reduction in blast furnace smelting.

[0004] For the CO2 product removed from the top gas, at present, a part can be used in the chemical industry, and most are planned to be buried underground or under the sea by means of sequestration, but there are certain environmental safety risks such as leakage. Therefore, how to solve the problem of the disposal of the CO2 removed in the all-oxygen blast furnace top gas recycling process is a huge challenge faced by the current industry.

[0005] After retrieval, relevant patent literatures on the utilization of CO2 in gas have been publicly disclosed. For example, the Chinese patent application number is: 201010199232.6, and the invention creation name is: A method for injecting carbon dioxide into a blast furnace. This scheme injects hot blast stove flue gas into the blast furnace, which has a high nitrogen content. After being injected into the blast furnace, it dilutes the concentration of the reducing gas, is not conducive to improving the indirect reduction degree of iron ore, and has limited carbon reduction and emission reduction effects, and is debatable.

[0006] Another example is the Chinese patent application number: 201010268748.1, and the invention creation name is: A method for injecting pulverized coal into a blast furnace using carbon dioxide as a transmission medium. This scheme uses carbon dioxide as the coal injection conveying gas for injection, which can reduce the amount of nitrogen entering the furnace. However, compared with the nitrogen amount in the conventional blast in the blast furnace, the reduced nitrogen amount is extremely small, and the effect of increasing the concentration of the reducing gas in the gas is extremely limited. In addition, the source of CO2 in this scheme is not described as separated from the top gas. Summary of the Invention

[0007] 1. Problems to be Solved

[0008] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, an object of the present invention is to propose a method for high-oxygen-enriched and all-oxygen blast furnace injection using carbon dioxide, which removes CO2 from the top gas of the blast furnace, and after heating a part of the separated CO2, injects it into the furnace together with oxygen from the tuyeres of the blast furnace. On the one hand, it solves the problem of "hot at the bottom and cold at the top" in the all-oxygen blast furnace, and on the other hand, it increases the concentration of reducing gas in the furnace, improves the indirect reduction degree of iron ore, reduces the consumption of solid carbon, and is beneficial to reducing the consumption of carbon fuel.

[0009] 2. Technical solution

[0010] To solve the above problems, the present invention adopts the following technical solutions.

[0011] A method for high-oxygen-enriched and all-oxygen blast furnace injection using carbon dioxide according to the present invention removes the CO2 component from the top gas discharged from the all-oxygen blast furnace through a CO2 removal device, heats the top gas after removing CO2, and injects it into the furnace from the tuyeres at the lower part of the furnace body; and heats a part of the CO2 separated from the top gas, and blows it into the blast furnace together with pure oxygen and pulverized coal from the tuyeres of the blast furnace. This part of CO2 accounts for 5% - 8% of the total CO2 separated from the top gas.

[0012] As a further improvement of the present invention, iron ore and coke are sent to the top charging device of the furnace through a feeding device, and the materials are distributed into the blast furnace through the charging device.

[0013] As a further improvement of the present invention, a part of the CO2 separated from the top gas is transported to the charging device through a CO2 pipeline for equalizing pressure, purging and cooling gas of the charging device. This part of CO2 accounts for 1% - 2% of the total CO2 separated from the top gas.

[0014] As a further improvement of the present invention, a part of the CO2 separated from the top gas is transported to the pulverized coal preparation device through a pipeline for protective gas of the pulverized coal preparation device and carrier gas for pulverized coal transportation and injection. This part of CO2 accounts for 2% - 3% of the total CO2 separated from the top gas.

[0015] As a further improvement of the present invention, a part of the CO2 separated from the top gas is introduced into a CO2 heating device and heated to 850 - 1350 °C, and then blown into the blast furnace from the tuyeres of the blast furnace.

[0016] As a further improvement of the present invention, the CO content in the top gas after being treated by the CO2 removal device reaches more than 90%, and is introduced into a gas heating device and heated to 850 - 1350 °C, and then injected into the blast furnace from the tuyeres at the lower part of the furnace body.

[0017] As a further improvement of the present invention, the CO2 concentration of the CO2 separated by the CO2 removal device from the top gas of the blast furnace reaches more than 95%.

[0018] As a further improvement of the present invention, the injection amount of the CO2 separated by the CO2 removal device and injected into the blast furnace is ≤ 30 Nm per ton of iron 3 .

[0019] As a further improvement of the present invention, the top gas discharged from the top of the all-oxygen blast furnace is successively treated by a dust collector, a TRT and a pressure reducing valve group, and then a part of it is subjected to CO2 separation treatment through a CO2 removal device, and the remaining part enters the gas pipeline network.

[0020] 3. Beneficial effects

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: the CO2 in the top gas of the blast furnace is removed, and its purity reaches more than 95%. It is recycled to the blast furnace system in three parts: a part of CO2 is heated to 850-1350 °C and then sprayed into the furnace from the tuyeres of the blast furnace together with oxygen and pulverized coal. By utilizing the characteristics of endothermic reaction and generating CO in the gasification reaction of CO2 and carbon, it not only solves the problem of "hot at the bottom and cold at the top" of the all-oxygen blast furnace, but also enhances the concentration of reducing gas in the furnace, improves the indirect reduction degree of iron ore, reduces the consumption of solid carbon, and is beneficial to reducing the consumption of carbon fuel; a part of CO2 is transported through a pipeline to the top charging equipment to replace compressed nitrogen for equalizing pressure, purging and cooling gas of the charging equipment; another part of CO2 is transported through a pipeline to the pulverized coal preparation device, also replacing compressed nitrogen, for protective gas of the pulverized coal preparation system and carrier gas for pulverized coal transportation and injection; the remaining CO2 is transported out for treatment. This solution can achieve the purpose of carbon and nitrogen oxide emission reduction, provide a way for CO2 emission reduction in the iron and steel industry, and can make the CO2 emission reduction rate reach more than 8%. Brief description of the drawings

[0022] Figure 1 It is a flow chart of a method for high oxygen enrichment and all-oxygen blast furnace injection and utilization of carbon dioxide of the present invention.

[0023] Reference numerals in the figure:

[0024] 1. Blast furnace; 11. Tuyeres at the lower part of the furnace body; 12. Blast furnace tuyeres; 13. Top gas outlet pipe; 2. Charging equipment; 21. Charging equipment; 22. CO2 pipeline; 3. Dust collector; 4. TRT and pressure reducing valve group; 5. Gas pipeline network; 6. CO2 removal device; 7. Gas heating device; 8. Pulverized coal preparation device; 9. CO2 heating device; 10. Pure oxygen pipeline. Detailed implementation manners

[0025] To further understand the content of the present invention, the present invention will be described in detail in combination with the accompanying drawings.

[0026] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention 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, it should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0027] The following further describes the specific implementation manners of the present invention in detail through the description of implementation examples.

[0028] Embodiment

[0029] A method for high-rich oxygen and all-oxygen blast furnace injection using carbon dioxide in this embodiment uses the top gas discharged from the blast furnace 1 for blast furnace circulating injection. The CO2 component in the top gas is removed by the CO2 removal device 6, and then the top gas after removing CO2 is heated to a certain temperature and injected into the furnace from the tuyere 11 at the lower part of the furnace body; a part of the separated CO2 is heated to a certain temperature and blown into the furnace together with pure oxygen and pulverized coal from the blast furnace tuyere 12. This part of CO2 accounts for 5% - 8% of the total amount of CO2 separated from the top gas, such as 5%, 6.5%, 7%, 8%, etc. In this embodiment, the concentration of CO2 separated by the CO2 removal device 6 reaches more than 95%. In this embodiment, the content of CO2 blown into the furnace together with pure oxygen and pulverized coal should be controlled within 5% - 8% of the total amount of CO2. If the content of CO2 blown into the furnace is too low, a good emission reduction effect cannot be achieved; if the content of CO2 blown into the furnace is too high, too much coke will be consumed, affecting the combustion situation in the furnace and increasing production costs. Therefore, the content of CO2 blown into the furnace needs to be controlled within an appropriate range to achieve a good CO2 emission reduction effect without affecting the fuel ratio in the furnace.

[0030] In this embodiment, the CO2 in the top gas is removed, and a part of the separated CO2 is heated and then blown into the furnace together with oxygen and pulverized coal from the blast furnace tuyere. On the one hand, it solves the problem of "hot at the bottom and cold at the top" of the all-oxygen blast furnace. On the other hand, it enhances the concentration of reducing gas in the furnace, improves the indirect reduction degree of iron ore, reduces the consumption of solid carbon, is beneficial to reducing the consumption of carbon fuel, and achieves the purpose of carbon and nitrogen oxide emission reduction, providing a way for the CO2 emission reduction in the steel industry. The CO2 used for circulating injection is the CO2 removed from the top gas of the all-oxygen blast furnace, and its purity reaches more than 95%.

[0031] In this embodiment, the blast furnace 1 can be an all-oxygen blast furnace or a high-oxygen-enriched blast furnace, wherein the high-oxygen-enriched blast furnace with an oxygen enrichment rate of 50% or more is basically close to the smelting process of the all-oxygen blast furnace. Specifically, the blast furnace 1 in this embodiment is all-oxygen blast injection, and there is no nitrogen in the blast furnace, that is, a "nitrogen-free blast furnace", and the nitrogen content in the top gas is only formed by the decomposition of nitrogen compounds in iron ore, coke and coal powder. In this embodiment, the iron ore and coke are transported to the top charging device 2 through the feeding device 21, and the materials are distributed into the blast furnace through the charging device 2.

[0032] In this embodiment, the CO2 separated from the top gas is divided into three parts for circulation in the blast furnace injection system, wherein one part of the CO2 is transported to the charging equipment 2 through the CO2 transport pipe 22, and is used for pressure equalization, purging and cooling of the charging equipment 2. This part of CO2 accounts for 1% to 2% of the total amount of CO2 separated from the top gas, for example, 1%, 1.5%, 2%, etc.; one part of the CO2 is transported to the coal powder preparation device 8, and is used as the protective gas of the coal powder preparation device 8 and the carrier gas for coal powder transportation and injection. This part of CO2 accounts for 2% to 3% of the total amount of CO2 separated from the top gas, for example, 2%, 2.6%, 3%, etc.; another part is passed into the CO2 heating device 9 and heated to 850 to 1350°C, and then blown into the furnace from the blast furnace tuyere 12 together with the oxygen from the pure oxygen pipeline 10 and the coal powder from the coal powder preparation device 8; the remaining CO2 is transported externally for treatment.

[0033] In this embodiment, in view of the problem of the destination of CO2 removed in the all-oxygen blast furnace top gas circulation process, a method for using CO2 removed in the all-oxygen blast furnace top gas circulation process in the blast furnace system is proposed. A part of CO2 replaces nitrogen and is used as pressure equalization, purging and cooling gas for the furnace top charging equipment and carrier gas for coal powder preparation and transportation injection; a part of CO2 is heated to a temperature within the range of 850 to 1350°C, such as 860°C, 980°C, 1250°C, etc., and then sprayed into the furnace from the blast furnace tuyere together with oxygen and coal powder, which is not only conducive to improving the gas volume and heat distribution in the all-oxygen blast furnace, but also can enhance the reducing atmosphere in the furnace, improve the indirect reduction degree and reduction speed of iron ore, reduce the heat loss per ton of iron, have a certain effect of reducing coke consumption, and also provide a way to reduce CO2 emissions in the steel industry.

[0034] In this embodiment, the top gas discharged from the top of blast furnace 1 passes through the deduster 3, TRT and pressure reducing valve group 4 in sequence through the top gas outlet pipe 13. After treatment, a part of it is introduced into the CO2 removal device 6 for CO2 separation treatment, and the remaining part enters the gas pipeline network 5. Among them, the CO content in the top gas after being treated by the CO2 removal device 6 reaches more than 90%. The treated top gas is introduced into the gas heating device 7 and heated to 850-1350 °C, such as 860 °C, 980 °C, 1250 °C, etc., and then sprayed into the furnace from the tuyere 11 at the lower part of the furnace body. In this embodiment, the appropriate amount of CO2 separated by the CO2 removal device 6 and sprayed into the furnace is that the injection volume of CO2 per ton of iron ≤ 30 Nm 3 .

[0035] Compared with the existing all-oxygen blast furnace and high oxygen enrichment blast furnace, this embodiment has the following effects:

[0036] 1) The CO2 sprayed from the blast furnace tuyere reacts with the hot coke in the tuyere raceway and all generates CO reducing gas. According to the reaction formula C (solid) + CO2 (gas) → 2CO (gas) - Q, it can be seen that spraying 1 volume of CO2 from the blast furnace tuyere reacts with coke to produce 2 volumes of CO, enhancing the reduction potential energy of the gas in the furnace, which is beneficial to improving the indirect reduction degree of iron ore; reducing the interfaces of solid-solid and solid-liquid reactions in the furnace is beneficial to improving the reduction speed of iron ore, thereby improving the production efficiency of the blast furnace and reducing the heat loss of the furnace shell radiation per ton of iron and the heat carried away by cooling water, having a certain energy-saving and consumption-reducing effect. Calculated according to the normal heat loss of 1 GJ per ton of iron in the blast furnace, if the production efficiency of the blast furnace is 25%, the heat loss of the blast furnace per ton of iron is reduced by 0.2 GJ, and the converted coke (calorific value 30 MJ / kg) is 6.7 kg.

[0037] 2) The above reaction of CO2 with coke is an endothermic reaction, which can effectively solve the "lower hot and upper cold" phenomenon of the existing all-oxygen and high oxygen enrichment blast furnaces, that is, due to all-oxygen and high oxygen enrichment combustion in the tuyere raceway area of the blast furnace, the reaction is intense and the temperature is too high, resulting in overheating problems, which are prone to accidents such as burning or burning through of the furnace shell in the tuyere and its nearby areas; on the other hand, due to the use of all-oxygen and high oxygen enrichment injection, the gas volume in the furnace is greatly reduced, and the heat brought to the upper burden column by the gas is also correspondingly reduced, resulting in a cooler upper burden column, reducing the reduction speed of the upper burden. By spraying an appropriate amount of CO2 in the all-oxygen and high oxygen enrichment blast furnace, the overheating phenomenon in the tuyere raceway can be reduced, and the heat in the lower part of the furnace body can be brought to the middle and upper parts of the furnace body by increasing the gas volume, strengthening the heat exchange in the lump burden column area.

[0038] 3) Reduce the CO2 emissions. According to the injection of 25 Nm of CO2 per ton of iron 3Estimation shows that the CO2 emissions are reduced by approximately 5%; considering a 25% increase in the blast furnace production efficiency, reducing the thermal loss per ton of iron by 6.7 kg of coke, and calculating based on a carbon content of 86%, the corresponding CO2 emissions are reduced by 10.7 Nm 3 , with a total reduction of CO2 emissions of 40.7 Nm 3 , resulting in a reduction of approximately 8.4%.

[0039] The examples described in the present invention are merely descriptions of the preferred embodiments of the present invention, and do not limit the concept and scope of the present invention. Without departing from the design idea of the present invention, various deformations and improvements made by those skilled in the art to the technical solutions of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for using carbon dioxide in the injection of a high-rich oxygen and all-oxygen blast furnace, characterized in that The top gas discharged from the blast furnace (1) is passed through a CO2 removal device (6) to remove the CO2 component in the top gas. After the top gas with CO2 removed is heated, it is injected into the furnace from the tuyeres (11) at the lower part of the furnace body. And a part of the CO2 separated from the top gas is heated and then blown into the furnace together with pure oxygen and pulverized coal from the blast furnace tuyeres (12). This part of CO2 accounts for 5% - 8% of the total amount of CO2 separated from the top gas. Among them, a part of the CO2 separated from the top gas is passed into a CO2 heating device (9), heated to 850°C - 1350°C, and then blown into the blast furnace (1) from the blast furnace tuyeres (12). After being treated by the CO2 removal device (6), the CO content in the top gas reaches more than 90%, and then it is passed into a gas heating device (7), heated to 850 - 1350°C, and then injected into the blast furnace (1) from the tuyeres (11) at the lower part of the furnace body.

2. The method for utilizing carbon dioxide in high-rich oxygen and all-oxygen blast furnace injection according to claim 1, characterized in that, Iron ore and coke are transported to the top charging device (2) of the furnace through a feeding device (21), and then the materials are distributed into the blast furnace (1) by the charging device (2).

3. A method for high-rich oxygen and all-oxygen blast furnace injection using carbon dioxide according to claim 2, characterized in that, A part of the CO2 separated from the top gas is transported to the charging device (2) through a CO2 pipeline (22) for equalizing pressure, purging, and cooling gas of the charging device (2). This part of CO2 accounts for 1% - 2% of the total amount of CO2 separated from the top gas.

4. A method for high-rich oxygen and full-oxygen blast furnace injection using carbon dioxide according to claim 3, characterized in that, A part of the CO2 separated from the top gas is transported to the pulverized coal preparation device (8) through a pipeline for protective gas of the pulverized coal preparation device (8) and carrier gas for transporting and injecting pulverized coal. This part of CO2 accounts for 2% - 3% of the total amount of CO2 separated from the top gas.

5. A method for high-rich oxygen and full-oxygen blast furnace injection using carbon dioxide according to claim 1, characterized in that The concentration of CO2 separated from the top gas by the CO2 removal device (6) reaches more than 95%.

6. A method for utilizing carbon dioxide in high-rich oxygen and all-oxygen blast furnace injection according to any one of claims 1-5, characterized in that, The injection rate of CO2 separated by the CO2 removal device (6) and injected into the blast furnace (1) is ≤ 30 Nm of CO2 per ton of iron 3 .

7. A method for high-rich oxygen and full-oxygen blast furnace injection using carbon dioxide according to claim 1, characterized in that, The top gas discharged from the top of the all-oxygen blast furnace (1) is successively treated by a dust collector (3) and a TRT and a pressure reducing valve group (4). A part of it is subjected to CO2 separation treatment through a CO2 removal device (6), and the remaining part enters the gas pipeline network (5).

Images