Ultra-high oxygen enrichment type low-carbon smelting method

Abstract

There is provided an ultra-high oxygen enrichment type low carbon smelting method, which includes a charging step and a blast furnace smelting step, in which the blast furnace oxygen enrichment rate is 40% to 50%, the oxygen enrichment rate of the hot stove portion reaches 15 to 20%, the air temperature is in the range of 900 to 1000°C, and for the portion that is insufficient, cold oxygen is blown in from the blowing port, and pulverized coal, highly reducing coal gas, and coke oven gas are blown in from the blowing port to maintain the theoretical combustion temperature at the blowing port in the range of 2350 to 2500°C, and during that period, the blowing coal ratio is 0.3 to 0.35 kg / m of coke oven gas. 3 or the coke rate is reduced to 0.28-0.3 kg / m of decarbonized coal gas. 3 By lowering the replacement rate to 210 kg / t or less at the high oxidation enrichment stage in the blast furnace, the problem of "cold at the top and hot at the bottom" that occurs is solved, and the goal of reducing coke consumption is achieved.

Description

[Technical Field]

[0001] This invention belongs to the technical field of blast furnace steelmaking, and more specifically, relates to an ultra-high oxygen enrichment type low-carbon smelting method. [Background technology]

[0002] Since 70% of energy consumption in the steel industry is concentrated in the steelmaking process, reducing carbon consumption in the steelmaking process is the primary means of reducing coal use in the steel industry. Currently, reducing carbon emissions is a technical bottleneck in the development of blast furnace technology. The space available to further reduce fuel consumption in molten iron is very limited, and there are limits to increasing the size of blast furnaces and improving production efficiency. Currently, fuel consumption in blast furnace molten iron smelting is often around 550 kg per ton of molten iron, but given China's progress in decarbonization and low-carbon initiatives, it seems there is still a long way to go to achieve the goal of reducing carbon emissions from conventional blast furnaces.

[0003] The conventional blast furnace ironmaking process is mainly as follows: A charge is formed by mixing sintered ore, pellets, coke, and solvent in a fixed ratio. The charge is then fed into the furnace from the top, and humidified by blowing hot air, oxygen gas, and pulverized coal from the blast furnace vent. As the charge moves in contact with the hot air inside the blast furnace, heat conduction and oxidation-reduction reactions occur, generating coal gas. The coal gas moves upward and leaves the blast furnace through the riser pipe. The blast furnace raw materials melt during the reaction process, dripping out as molten iron and slag, and the liquid slag is discharged from the blast furnace through the pigsty nozzle. In conventional blast furnaces, when oxygen is highly enriched, the temperature inside the furnace is distributed so that "the top is cold and the bottom is hot," making it difficult to develop the smelting process. At the same time, since approximately 35% to 40% of the iron elements in the furnace depend on direct reduction by carbon, the coke consumption is large. [Overview of the project]

[0004] The present invention aims to provide an ultra-high oxygen enrichment type low-carbon smelting method that can reduce the amount of coke consumed in the process by reducing the proportion of direct reduction and increasing the proportion of indirect reduction, in order to solve the problem of the temperature distribution inside the furnace being "colder at the top and hotter at the bottom" as mentioned in the background technology above.

[0005] To achieve the above objective, the present invention provides the following technical solutions.

[0006] An ultra-high oxygen enrichment type low-carbon smelting method, The preparation process (S1) involves filling the blast furnace in layers with an ore charge having a composition of 60-80% sintered ore, 20-40% pellets, and 0-5% raw ore and coke. The amount of blast furnace injection per ton of molten iron is 570-690 m³. 3 The blast furnace is controlled to maintain a temperature within the range of 900-1000°C, and pure oxygen is blown into the blast furnace to create an ultra-high oxygen enrichment smelting environment. Here, 15-20% oxygen enrichment is achieved before the hot blast furnace, but to compensate for the deficiency, cold oxygen is blown in from the vent. Fine coal, highly reducible coal gas, and coke oven gas are blown in from the vent to maintain a theoretical combustion temperature of 2350-2500°C at the vent. During this period, the coal-injection ratio is set to 0.3-0.35 kg / m³ for the coke oven gas. 3 The coal gas replacement rate is reduced, or the coke ratio is set so that the decarbonized coal gas is 0.28-0.3 kg / m³. 3 The process includes a blast furnace smelting process (S2) in which the substitution rate is reduced to 210 kg / t or less.

[0007] The pure oxygen blown into the blast furnace is divided into two parts. One part of this is oxygen gas heated by the hot blast furnace, accounting for 15-20% of the total amount of gas blown in. The furnace inlet temperature is 900-1000°C, and the oxygen content of the total amount of oxygen blown in is 40-50%. The remaining part of the oxygen gas is cold oxygen. The highly reducing coal gas is blast furnace coal gas from which CO2 has been removed, with a composition of CO: 65-75%, H2: 10-18%, N2: 6-15%, and others: 5-12%. Since CO2 accounts for the majority of the blast furnace coal gas, after the CO2 is removed, the proportion of reducing gases such as CO and H2 is significantly increased, and the amount of this gas blown in per ton of molten iron is 200-300 m³. 3 The rate of coke oven gas blown in per ton of molten iron is 210-230 m³ / t. 3 / t is the case.

[0008] Compared to conventional technology, the beneficial effects of the present invention are as follows:

[0009] When the blast furnace oxygen enrichment rate is 40-50%, the intensity of blast furnace smelting is increased, and the production volume is increased by 20%. Moreover, since the hot blast furnace oxygen enrichment rate reaches 15-20%, it is equivalent to the oxygen gas in that part being introduced at a temperature of 900-1000°C, increasing the amount of heat generated by oxygen enrichment and effectively reducing carbon consumption in the blast furnace. By injecting highly reducing coal gas and coke oven gas from the vent, they can participate in the reduction reaction in the furnace, increasing the calorific value of the coal gas, strengthening the preheating and reduction reaction of the charge in the upper part, and preventing the "cold top, hot bottom" situation. In addition, by injecting highly reducing coal gas from the vent, the theoretical combustion temperature at the highly oxygen-enriched vent can be adjusted, ensuring that the furnace process runs smoothly. Furthermore, since coke oven gas is primarily composed of hydrogen gas, has a small molecular weight, excellent permeability, and is more readily reduced with iron oxides than CO, it increases the degree of indirect reduction and reduces coke consumption. In addition, some of the highly reducing coal gas and coke oven gas can be burned as a heat source to release heat, thus achieving the objective of reducing coke consumption. As a result, overall coke consumption can be reduced by 10-15%. Moreover, since a large amount of highly reducing coal gas and coke oven gas was blown in through the vents, sufficient indirect reduction occurred in the upper part of the blast furnace, and the carbon consumption for indirect reduction in the lower part of the blast furnace was significantly reduced. Consequently, the objectives of reducing carbon emissions from the blast furnace and lowering the fuel ratio were achieved, and the blast furnace production was increased by 20% while maintaining a 50% high-oxygen enrichment smelting operation, resulting in an overall carbon consumption reduction of 15%. [Modes for carrying out the invention]

[0010] The following clearly and completely describes the technical concepts of embodiments of the present invention. It is clear that the embodiments described are only a subset of, and not all, embodiments of the present invention. All other embodiments that can be obtained based on the embodiments of the present invention, without requiring any creative effort from those skilled in the art, are all within the scope of the protection of the present invention.

[0011] The present invention provides the following technical solutions.

[0012] In the ultra-high oxygen enrichment type low-carbon smelting method, An ore charge having a composition of sinter ore: 60-80%, pellet: 20-40%, and raw ore: 0-5% is raised to the furnace top and charged, and a charging step (S1) is controlled such that the depth of the charge line is 1.1-1.6 m. The blast volume of the blast furnace is 500-600 m 3 / min, and the blast temperature is controlled within the range of 900-1000 °C. Here, 15-20% oxygen enrichment is gradually increased in front of the hot blast stove so that the total oxygen enrichment rate is about 40-50%. After the oxygen enrichment of the hot blast stove reaches the standard, for the insufficient part, cold oxygen is blown from the tuyere. From the tuyere, pulverized coal and coke oven gas (0-250 m 3 / t) are blown in to increase the oxygen enrichment in front of the hot blast stove. At the same time, the blowing amount of high-reducing coal gas (0-250 m 3 / t) is synchronously increased so that the theoretical combustion temperature at the tuyere is within the range of 2250-2350 °C, and the amount of coal gas in the furnace is maintained at 1200-1400 m 3 / t. During that period, the blowing coal ratio is reduced at a coal gas substitution rate of 0.3-0.55 kg / m 3 or the coke ratio is reduced at a substitution rate of 0.25-0.5 kg / m 3 This includes a blast furnace smelting step (S2).

[0013] By blowing in high-reducing coal gas, the theoretical combustion temperature at the tuyere can be adjusted so that the temperature at the lower part of the furnace body is not too high. Also, the purpose of introducing coke oven gas is to make the coke oven gas participate in the reduction reaction of iron and reduce the consumption of coke directly reducing iron. Since the coke oven gas contains a large amount of CO, it may be used for the reaction with iron ore instead of some coke.

[0014] In the case of oxygen enrichment, the oxygen enrichment before the hot blast stove should be preferentially increased. By doing so, the oxygen gas in that part is equivalent to being introduced into the furnace at a blast temperature of 900 - 1000 °C or higher, the amount of heat brought by injection increases, and the carbon consumption in the blast furnace process can be effectively reduced. After the oxygen enrichment before the hot blast stove reaches 20%, cold oxygen is blown from the tuyere.

[0015] [Examples] The control parameters of the conventional blast furnace smelting method are as follows.

[0016] [Table 1] The blast furnace economic and technical indicators in the conventional smelting method are as follows.

[0017] [Table 2] The blast furnace control parameters when the method according to the present invention is used are as follows.

[0018] [Table 3] The blast furnace economic and technical indicators controlled by the method according to the present invention are as follows.

[0019] [Table 4] When comparing the economic and technical indicators in the conventional blast furnace control method with those of the blast furnace economic and technical indicators controlled by the method in the present invention, it was found that when the method in the present invention was used, when high-reducing coal gas or coke oven gas was blown from the tuyere of the blast furnace, the blown coal gas immediately contacted the charge in the upper part of the blast furnace and a reduction reaction occurred, strengthening the indirect reduction reaction in the furnace and effectively reducing the fuel consumption in the blast furnace smelting process. Also, according to the oxygen enrichment in the blast furnace, when the smelting was strengthened and the coke ratio and fuel ratio in the blast furnace were significantly reduced, the production volume of the blast furnace molten iron was also increased. That is, it became clear that even when the fuel decreased, the production volume of the molten iron was slightly higher than that of the conventional blast furnace ironmaking method.

[0020] What should be explained here is that in this specification, terms such as "comprising", "including" or other variations are intended to cover non-exclusive "including", whereby a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or elements inherent to such a process, method, article or device. Without too many restrictions, for an element limited by the phrase "comprising one...", it cannot be excluded that there are further similar elements in the process, method, article or device comprising said element.

[0021] The above description is only for explaining the technical solution of the present invention and is not restrictive. Other corrections or equivalent replacements of the technical solution of the present invention by those skilled in the art should fall within the scope claimed by the present invention as long as they do not depart from the spirit or scope of the technical solution of the present invention.

Claims

1. An oxygen-enriched smelting method comprising a mashing process and a blast furnace smelting process, The preparation process (S1) involves filling the blast furnace in layers with an ore charge having a composition of 60-80 wt% sintered ore, 20-40 wt% pellets, and 0-5 wt% raw ore and coke. The amount of blast furnace injected per ton of molten iron is 570-690 m³. ３ The process includes a blast furnace smelting process (S2) in which the air temperature is controlled to be within the range of 900 to 1000°C, and pure oxygen is blown into the blast furnace to create an oxygen-enriched smelting environment in the blast furnace, where oxygen enrichment is performed in front of the hot blast furnace to an oxygen enrichment rate of 15 to 20%, but oxygen is blown in from the vent to make up for the insufficient amount, and pulverized coal, highly reducible coal gas, and coke oven gas are blown in from the vent to maintain the combustion temperature at the vent in the range of 2350 to 2500°C, The aforementioned blast furnace injection volume refers to the total amount of gas injected into the blast furnace, and is expressed as the gas volume per ton of molten iron (m³ / t). The total amount of the aforementioned gas includes pure oxygen (oxygen gas), highly reducing coal gas, and coke oven gas, but does not include solid pulverized coal. The aforementioned "insufficient portion" refers to the remaining portion of the pure oxygen, which is divided into two parts, after excluding the oxygen gas heated by the hot air furnace (the portion accounting for 15-20% of the total amount of gas blown in), and which corresponds to the unheated oxygen blown in from the air outlet. An oxygen-enriched smelting method characterized by the following features.

2. The oxygen enrichment rate in the total amount of air blown in reaches 40% to 50%. The total amount of gas injected refers to the total amount of gas, The aforementioned oxygen enrichment rate refers to the oxygen content (volume percentage) (%) in the total amount of material blown into the furnace. The oxygen-enriched smelting method according to feature 1.

3. The oxygen-enriched smelting method according to claim 1, characterized in that the 15-20% oxygen enrichment is achieved by heating to a temperature of 900-1000°C via a hot blast furnace heating system.

4. The amount of highly reducing coal gas injected per ton of molten iron is 200-300 m³. ３ The oxygen-enriched smelting method according to claim 1, characterized in that the value is / t.

5. The amount of coke oven gas blown in per ton of molten iron is 210 to 230 m³. ３ The oxygen-enriched smelting method according to claim 1, characterized in that the value is / t.

6. The composition of the aforementioned highly reducing coal gas is CO: 65-75 vol%, H ２ :10-18vol%, N ２ : 6-15 vol%, other: 5-12 vol. The oxygen-enriched smelting method according to feature 1.

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