WO2023029816A1

WO2023029816A1 - Low carbon blast furnace ironmaking method

Info

Publication number: WO2023029816A1
Application number: PCT/CN2022/107904
Authority: WO
Inventors: 邹忠平; 肖学文; 王刚; 李牧明; 赵运建; 徐灿; 郑军; 牛群; 翟晓波; 吴开基; 全魁; 许俊
Original assignee: 中冶赛迪工程技术股份有限公司; 中冶赛迪技术研究中心有限公司
Priority date: 2021-09-03
Filing date: 2022-07-26
Publication date: 2023-03-09
Also published as: CN113718074A

Abstract

The present invention provides a low carbon blast furnace ironmaking method, comprising: injecting heated and pressurized back-injection gas into a blast furnace, injecting pure oxygen into the blast furnace or injecting oxygen-enriched hot air into the blast furnace, spraying pulverized coal into the blast furnace, and alternately loading iron ore, coke and other furnace charges into the blast furnace; after the gas blown into the blast furnace undergoes a chemical reaction with the furnace charges and the like, forming a furnace top gas; after the furnace top gas undergoes a series of treatment processes, pressurizing and heating the furnace top gas and then injecting into the blast furnace as back-injection gas, and sending the remaining furnace top gas to a gas pipe network. According to the present invention, the oxygen-enriched smelting and furnace top gas circulation processes are adopted, the utilization rate of carbon in a blast furnace is greatly improved, the concentration of reducing gas in bosh gas is increased, the direct reduction degree in a blast furnace hearth is reduced, the fuel consumption is saved, the blast furnace fuel ratio is reduced, the blast furnace ironmaking efficiency is improved, and the emission of CO2 in the blast furnace ironmaking process is reduced.

Description

A low-carbon blast furnace ironmaking method

technical field

The invention belongs to the technical field of blast furnace ironmaking, in particular to a low-carbon blast furnace ironmaking method.

Background technique

Green and low-carbon development is the main theme of the development of the iron and steel industry in the world today, and the carbon emissions of the blast furnace ironmaking process account for more than 70% of the carbon emissions of the iron and steel metallurgical industry. Therefore, the development of low-carbon blast furnaces is the main direction to achieve carbon emission reduction in the iron and steel industry one. Today, major iron and steel enterprises have reduced the fuel ratio of blast furnaces to a relatively low level through technical means such as optimizing raw material conditions, optimizing furnace design, and strengthening smelting. However, it is found through theoretical calculations that due to the large amount of N ₂ in the bosh gas of traditional blast furnaces, the content of reducing gas that undergoes an indirect reduction reaction with iron ore is not high, and the gas is not fully utilized. When the iron ore reaches the reflow zone , still contains a large amount of iron oxides, and these iron oxides have a strong endothermic direct reduction reaction with the carbon in the coke, which further consumes the carbon to supplement this part of the heat, eventually reducing the fuel ratio of the traditional blast furnace ironmaking to 480 -490kg/thm is the limit, and the emission of carbon per ton of iron is still very high. Therefore, it is necessary to develop a new low-carbon blast furnace ironmaking technology that is different from the traditional blast furnace.

Today, the existing low-carbon blast furnace technologies include blast furnace injection of hydrogen-rich gas, oxygen blast furnace, and top gas circulation. Since the reduction of iron oxides by hydrogen will absorb a large amount of heat, the carbon reduction effect of blast furnace injection of hydrogen-rich gas is very limited, and the source of hydrogen-rich gas in China is limited, so the cost is high; oxygen blast furnace and furnace top gas circulation technology, the lower part The high oxygen concentration in the swirl area leads to a high temperature of the local combustion focus in the swirl area, and the reduction of the heat carrier-blast _N2 results in a significant reduction in the amount of gas per ton of iron, resulting in insufficient blast kinetic energy at the tuyere. In order to maintain the necessary blast kinetic energy, the tuyere has to be The diameter is greatly reduced; at the same time, the reduction in the amount of gas per ton of iron leads to insufficient heat supply in the upper part of the furnace, and it is forced to consider injecting hot reducing gas into the furnace body, which leads to further shrinkage of the combustion zone at the tuyere. As a result, it is difficult to ensure the stable operation of the blast furnace after the volume of the blast furnace is expanded appropriately.

Contents of the invention

In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a low-carbon blast furnace ironmaking method, which is used to solve the problems in the prior art that the ironmaking fuel ratio is limited and the carbon emission per ton of iron is high, so as to achieve The purpose of reducing the blast furnace fuel ratio, improving blast furnace ironmaking efficiency and reducing _CO2 emissions in the blast furnace ironmaking process.

In order to achieve the above purpose and other related purposes, the present invention provides a low-carbon blast furnace ironmaking method, comprising:

Inject the heated and pressurized re-injection gas into the blast furnace, inject pure oxygen into the blast furnace or inject oxygen-enriched hot air into the blast furnace, spray pulverized coal into the blast furnace, and alternately load iron ore and coke into the blast furnace;

Top gas is formed after the chemical reaction in the blast furnace;

After the furnace top gas has gone through a series of processing procedures, the top gas after pressurization and heat treatment is sprayed into the blast furnace as re-injection gas, and the remaining top gas is sent to the gas pipeline network.

The invention adopts the process of coupling oxygen-enriched smelting and furnace top gas circulation, injects pure oxygen at normal temperature, and resprays the heated and pressurized furnace top gas after desulfurization, CO ₂ and N ₂ removal into the blast furnace , thereby increasing the reducing gas content in the low-carbon blast furnace bosh gas. The bosh gas with high reducing gas content moves to the middle and upper part of the blast furnace, fully contacts with the iron ore moving to the lower part of the blast furnace, and develops an indirect reduction reaction.

Further, if pure oxygen is injected into the blast furnace, the treatment process includes dust removal, dehydration, desulfurization, and CO ₂ removal, the sum of the amount of pure oxygen injected per ton of iron and the amount of top gas re-injected per ton of iron and the amount of the same furnace capacity The amount of hot air consumed per ton of iron in a blast furnace is similar; if oxygen-enriched hot air is injected into the blast furnace, the treatment process includes dust removal, dehydration, desulfurization, CO ₂ removal, and N ₂ removal. The sum of the top gas re-injection amount is similar to the hot air consumption per ton of iron of a blast furnace with the same furnace capacity. Compared with the oxygen-enriched hot air injection process, the pure oxygen injection process can reduce N ₂ entering the blast furnace, increase the reducing gas content in the bosh gas, and increase the indirect reduction efficiency in the middle and upper parts of the blast furnace. If oxygen-enriched hot air is injected, N ₂ in the furnace top gas needs to be removed to increase the reducing gas content in the re-injection gas.

Further, the particle content of the top gas after dedusting is less than 20 mg/Nm ³ . The top gas after dedusting can directly enter the gas pipeline network on the one hand, and on the other hand, it can ensure that the subsequent top gas desulfurization and _CO2 removal processes will not be weakened or lose their effect due to particulate matter in the gas.

Further, the dehydration efficiency of the top gas after dehydration is greater than 95%.

Further, the desulfurized S content of the top gas is lower than 0.015%. The high sulfur content in the furnace top gas will cause corrosion to the pipeline on the one hand, and on the other hand, it does not meet the requirements of ultra-low emissions.

Further, the CO ₂ removal rate of the furnace top gas after CO ₂ removal is greater than 95%. The re-injection gas formed after _CO2 removal can increase the concentration of reducing gas in the re-injection gas on the one hand, ensuring that the indirect reduction reaction between H2 _and CO and iron oxides can be fully developed in the upper and middle parts of the furnace shaft, and on the other hand If the removal rate of CO ₂ in back injection gas is less than 95%, CO ₂ will undergo a large amount of carbon melting loss reaction with coke, resulting in an increase in fuel ratio.

Further, the back injection gas needs to be pressurized to above 0.5Mpa. The higher pressure back-injection gas can ensure that the wind speed and blast kinetic energy in the tuyere gyration area are equivalent to those of the conventional blast furnace of the same level, and ensure that the tuyere gyration area will not shrink greatly compared with the conventional blast furnace of the same level, and the active furnace Cylinders ensure high efficiency, stability and smooth operation of the blast furnace.

Further, the re-injection gas needs to be heated to above 950°C. The high-temperature gas can make up for part of the heat required for chemical reactions in the furnace and heating the furnace charge, so as to further reduce fuel consumption.

Further, the purity of the pure oxygen is greater than 99%. High-purity oxygen can strengthen smelting and improve the utilization factor of blast furnaces. In particular, the content of impurity elements in high-purity oxygen is relatively small, which can prevent other impurity gases from entering the furnace. It reacts with excessive coal powder and coke and other carbonaceous materials in the tuyere swirl area to produce CO and other reducing gases, ensuring the furnace The upper part of the body has a higher reducing gas content.

Further, the pure oxygen is injected into the blast furnace through the oxygen nozzle, and the injection pressure of the pure oxygen is higher than the injection pressure of the re-injection gas. On the one hand, the higher oxygen injection pressure can ensure that high-purity oxygen can be effectively injected into the center of the hearth, and on the other hand, it can prevent safety accidents such as tempering inside the oxygen pipeline.

Further, the pulverized coal is injected into the blast furnace through a coal gun by a coal carrier gas, and the coal carrier gas is CO ₂ gas removed from the furnace top gas. After _CO2 enters the tuyere area, it will react with the carbon in the hearth at high temperature to produce a reducing gas CO. Coal carrier gas using CO ₂ gas can on the one hand consume part of the CO ₂ removed from the top gas to achieve the purpose of CO ₂ circulation in the blast furnace, on the other hand it can prevent other components of the carrier gas from entering the blast furnace, reducing the bosh While reducing the reducing gas content in the coal gas, other subsequent gas removal processes are added.

Further, preferably, the pulverized coal is a high-volatile pulverized coal with a volatile content greater than 21%, and the H ₂ generated after volatile cracking and decomposition in the pulverized coal with high volatility is used to participate in the indirect reduction reaction. The H ₂ generated after volatile cracking and decomposition replaces part of the amount of CO that participates in the indirect reduction reaction, and finally achieves the purpose of reducing the generation and emission of CO ₂ .

Further, the iron ore is highly reducing iron ore, including one or more of sintered ore, pellet ore, lump ore and composite iron coke, its comprehensive furnace grade is greater than 58%, and its reduction index RI greater than 80%. If the furnace grade is greater than 58%, the production of slag can be reduced, and the heat consumption in the blast furnace can be reduced. A higher degree of reduction (RI>80%) can ensure that the iron ore in the middle and upper part of the furnace shaft fully undergoes indirect reduction reaction with the reducing gas.

As mentioned above, a low-carbon blast furnace ironmaking method of the present invention has the following beneficial effects:

On the premise of not making major changes to the traditional blast furnace system, the present invention adopts oxygen-enriched smelting and furnace top gas circulation technology to greatly increase the utilization rate of carbon in the blast furnace and increase the concentration of reducing gases in the bosh gas, Reduce the direct reduction degree inside the blast furnace hearth, save fuel consumption, reduce the blast furnace fuel ratio, improve the blast furnace ironmaking efficiency and reduce the CO ₂ emission in the blast furnace ironmaking process.

Description of drawings

Fig. 1 is a schematic diagram of a system used in a low-carbon blast furnace ironmaking method in Embodiment 1 of the present invention;

Fig. 2 is a schematic diagram of a system used in a low-carbon blast furnace ironmaking method in Embodiment 2 of the present invention.

Part number description

1-charge; 2-distributing components; 3-blast furnace body; 4-coal injection device; 5-oxygen device; 6-top gas pipeline; 7-top wet gas; 8-dust removal device; 9-dehydration device; 10-desulfurization device; 11-CO ₂ removal device; 12-gas pipe network; 13-pressurization device; 14-preheating device; Tuyere swirl area; 19-hot stove device; 20-N ₂ removal device; 21-air.

Detailed ways

The implementation of the present invention will be illustrated by specific specific examples below, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

It should be noted that the structures, proportions, sizes, etc. shown in the drawings attached to this specification are only used to match the content disclosed in the specification, for those who are familiar with this technology to understand and read, and are not used to limit the implementation of the present invention. Limiting conditions, so there is no technical substantive meaning, any modification of structure, change of proportional relationship or adjustment of size, without affecting the effect and purpose of the present invention, should still fall within the scope of the present invention. The disclosed technical content must be within the scope covered. At the same time, terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and are not used to limit this specification. The practicable scope of the invention and the change or adjustment of its relative relationship shall also be regarded as the practicable scope of the present invention without any substantial change in the technical content.

Please in conjunction with shown in Fig. 1, the present invention provides a kind of low-carbon blast furnace ironmaking method, comprising:

Inject the heated and pressurized re-injection gas 15 into the blast furnace, inject pure oxygen into the blast furnace or inject oxygen-enriched hot air into the blast furnace, inject pulverized coal into the blast furnace, and alternately load iron ore and coke into the blast furnace;

Top gas is formed after the chemical reaction in the blast furnace;

After the furnace top gas has gone through a series of processing procedures, the top gas after pressurization and heat treatment is sprayed into the blast furnace as back injection gas 15, and the remaining top gas is sent to the gas pipe network.

Specifically, the preheated and pressurized re-injection gas 15 is injected into the blast furnace through the tuyeres, pure oxygen is injected into the blast furnace through the oxygen nozzles through the tuyeres, oxygen-enriched hot air is injected into the blast furnace through the hot air surrounding pipes through the tuyeres, and the pulverized coal is carried by the coal The gas is blown into the blast furnace through the tuyere, and the charge 1 such as iron ore and coke is loaded into the blast furnace by the cloth assembly 2 .

Decomposition reaction of volatile components of coal powder, combustion reaction of carbon in pulverized coal and coke, carbon melting loss reaction, reduction reaction of C in molten iron and Si, Mn, S in slag, etc. mainly occur in the blast furnace; back injection of gas 15 and The gas formed by the chemical reaction in the blast furnace constitutes the bosh gas, and the sum of CO and _H2 in the bosh gas accounts for more than 90%. When the iron ore reaches the high temperature zone below the reflow zone 17, the metallization rate is higher than that of the conventional blast furnace, ensuring that the direct reduction reaction between C and iron oxide basically does not occur in the hearth of the blast furnace; the top gas after participating in the indirect reduction reaction is mainly The components are CO, H ₂ , CO ₂ and a small amount of N ₂ .

Wherein, if pure oxygen is injected into the blast furnace through the tuyeres through the oxygen nozzle, the treatment operations include dust removal, dehydration, desulfurization, and CO ₂ removal, the sum of the re-injection amount of furnace top gas per ton of iron and the amount of oxygen injection per ton of iron The amount of hot air consumed per ton of iron in a blast furnace with the same furnace capacity is similar; if the oxygen-enriched hot air is sprayed into the blast furnace through the tuyere through the hot air surrounding pipe, the treatment operations include dust removal, dehydration, desulfurization, CO ₂ removal and N ₂ removal, The sum of pure oxygen injection per ton of iron, oxygen-enriched hot air injection per ton of iron and furnace top gas re-injection per ton of iron is similar to the hot air consumption per ton of iron of a blast furnace with the same furnace capacity. In this way, the gas flow distribution and material layer distribution in the low-carbon blast furnace are close to those of the traditional blast furnace.

After a series of processing operations, the top gas is decomposed into three parts, one part is used to heat the other part of the top gas, and the remaining top gas is sent to the gas pipe network, and the heated top gas is passed through After pressurization, it is sprayed into the blast furnace as back injection gas 15 .

Compared with the conventional blast furnace, the low-carbon blast furnace ironmaking method can improve the utilization rate of the reducing agent in the blast furnace, and because the occurrence of the direct reduction reaction between the strongly endothermic carbon and the iron ore in the blast furnace is suppressed, thereby The blast furnace coke ratio can be controlled to be less than 220kg/thm (thm is ton of molten iron), and the fuel ratio is less than 400kg/thm.

Using the process of coupling oxygen-enriched smelting and top gas circulation, the top gas is dedusted, desulfurized, CO ₂ removed, N ₂ removed, pressurized and heated, and then sprayed back into the blast furnace to reduce the gas in the bosh gas The content is higher than that of conventional blast furnaces, and the indirect reduction reaction in the blast furnace is developed, so that the metallization rate of iron ore when it reaches the bottom of the reflow zone 17 is higher than that of conventional blast furnaces, so that high-endothermic C and iron oxides basically do not occur in the high-temperature zone of the blast furnace The direct reduction reaction can achieve the purpose of reducing the CO ₂ emission of blast furnace ironmaking.

Since the exothermic indirect reduction reaction is fully developed in the furnace, the direct reduction reaction between endothermic C and iron oxide is reduced, fuel consumption is reduced, and the purpose of carbon emission reduction is achieved. The purpose of strengthening smelting.

Example 1

In this embodiment, a blast furnace with a capacity of ¹⁵⁸⁰ m is taken as an example. Referring to Fig. 1, the low-carbon blast furnace ironmaking method as described above is adopted. The low-carbon blast furnace ironmaking system adopted in this embodiment includes a blast furnace body device, coal injection Device 4, oxygen generating device 5, dust removal device 8, dehydration device 9, desulfurization device 10, _CO2 removal device 11, pressurization device 13 and preheating device 14, wherein: blast furnace body device, including blast furnace body 3, is arranged in The cloth assembly 2 and the tuyere assembly 16 on the blast furnace body 3 are also provided with a top gas pipeline 6 on the top of the blast furnace body 3 . Moreover, the cloth assembly 2, the blast furnace body 3, the coal injection device 4, the oxygen making device 5, the furnace top gas pipeline 6, the dedusting device 8, the dehydration device 9, and the desulfurization device 10 are consistent with conventional blast furnaces.

The blast furnace body 3 is a cylindrical furnace body constructed on a foundation foundation. Different from the conventional blast furnace, the low-carbon blast furnace ironmaking system cancels the hot blast stove device, but uses the high-purity oxygen prepared by the oxygen generator 5 and the blast furnace top gas after removing _CO2 to replace the hot blast, which is transported by pipeline After reaching the blast furnace body 3, it is sprayed into the blast furnace through the tuyere assembly 16. In this way, on the one hand, the utilization rate of carbon in the blast furnace can be improved, and on the other hand, the concentration of reducing gas in the bosh gas can be further increased, so that the iron ore and reducing gas in the blast furnace can fully develop the indirect reduction reaction, so that the iron When the ore reaches the reflow zone 17, the metallization rate is close to 100%, so as to avoid the direct reduction reaction of iron oxide and carbon with strong endothermic heat, and reduce the consumption of carbon for direct reduction reaction heat. Ultimately, the blast furnace fuel ratio can be achieved below 370kg/thm, and the calculated theoretical coke ratio can reach below 200kg/thm.

The present invention has adopted following method in order to achieve the above object:

The bulk or spherical iron ore and coke and other charge 1 are alternately distributed into the blast furnace body 3 through the material distribution assembly 2, and the charge 1 moves from the upper part of the blast furnace body 3 to the lower part of the blast furnace body 3 under the action of gravity, and the tuyere swirl area 18 in the hearth is generated. A large amount of high-temperature bosh gas flows to the upper part of the furnace body. On the one hand, the high heat carried by it is transferred to the charge 1 such as iron ore and coke, so that the temperature of the iron ore can be raised to the temperature where the indirect reaction can fully occur with the reducing gas; on the other hand, the reducing gas in the bosh gas and the The iron ore undergoes an indirect reduction reaction, reducing the iron ore to metallic iron.

Oxygen with a purity of 99% produced by the oxygen generator 5 is injected into the blast furnace through the tuyere assembly 16 through the oxygen nozzle, and the injection volume is about 223 Nm ³ /thm.

The pulverized coal with a volatile content of 30% is blown into the blast furnace through the coal injection device 4 and the tuyere assembly 16. The coal injection amount per ton of iron is about 170kg/thm, and the coal carrier gas used for pulverized coal injection is CO ₂ gas. Methane, ethane, etc. in the pulverized coal volatiles undergo cracking reactions in the tuyere swirl zone 18 to produce CO and H ₂ , which can further increase the content of reducing gases in the bosh gas. At the same time, H ₂ can also replace part of CO to participate in the indirect reduction reaction with iron ore, which can further reduce the generation and emission of CO ₂ in the blast furnace smelting process.

The blast furnace top wet gas 7 in Example 1 is sprayed back into the blast furnace body 3 after dedusting, dehydration, desulfurization, CO ₂ removal, pressurization and heating, and the remaining top gas is sent to the gas pipe network 12 . In order to ensure the rationality of the gas flow distribution inside the lower blast furnace and the activity of the hearth, the calculated back injection gas volume is about 606Nm ³ /thm. The sum of the amount of oxygen injection and back-injection gas is about 829Nm ³ /thm, which ensures that the sum of pure oxygen injection per ton of iron and top gas re-injection per ton of iron is similar to the hot air consumption per ton of iron of a traditional blast furnace with the same furnace capacity.

In order to ensure that the back-injection gas 15 can be blown to the center of the hearth and improve the smelting efficiency, the back-injection gas 15 needs to be pressurized by the pressurizing device 13 to be equal to the air pressure of a conventional blast furnace, that is, more than 0.5Mpa. Simultaneously, in order to prevent safety issues such as tempering occurring in the oxygen nozzle, the injection pressure of pure oxygen is higher than the injection pressure of back-injection gas 15 .

According to the calculation of heat balance and material balance, in order to ensure sufficient heat supply, the re-injection gas 15 injected from the tuyere needs to be heated to above 950°C. Part of the pure oxygen injected into the tuyere reacts with the injected coal powder, and the other part undergoes a combustion reaction with part of the coke. Both of these two reactions release a large amount of heat, which is the decomposition of the volatile matter of the pulverized coal in the furnace and the molten iron and slag. Melting provides heat. The carbon in the remaining coke undergoes melting loss reaction with back injection gas 15 and CO ₂ in coal carrier gas, reduction reaction with SiO ₂ and MnO in slag, dissolves into molten iron as molten iron carburization, etc. The amount of bosh gas produced is about 1200Nm ³ /thm, and the composition of the bosh gas is shown in Table 1 below.

Table 1 Composition of bosh gas

The reducing gas content in the bosh gas is about 95%. Sufficient bosh gas volume and bosh gas with high reducing gas content can ensure that the metallization rate of iron ore is close to 100% when it reaches the reflow zone 17, and ensure that the direct reduction reaction of carbon and iron oxide does not occur in the high temperature zone of the blast furnace , the degree of direct reduction is reduced to close to 0. At this time, the molten iron and slag with low melting point are heated by the high heat generated by the tuyere swirl zone 18 of the hearth to become liquid, and the molten iron and liquid slag penetrate into the hearth through the coke layer, and the reflow zone 17 may not exist.

In order to ensure that the iron ore and reducing gas in the upper part of the blast furnace can fully develop the indirect reduction reaction, it is preferable to use iron ore with a reducing RI greater than 80 and a comprehensive furnace grade greater than 58%. The cold strength and The performance index of coke can meet the same level of blast furnace smelting.

After the indirect reduction reaction, the top dry gas volume is about 1119Nm ³ /thm, of which the CO ₂ content is about 38%, the CO content is about 31.6%, the H ₂ content is about 8.6%, and the N ₂ content is about 28.1%.

After the furnace top gas is dedusted, dehydrated, desulfurized and CO ₂ removed, the CO content in the furnace top gas is about 67%, the H ₂ content is about 24%, and the gas with high reducing gas content has a higher calorific value. After the above treatment process, the top gas is decomposed into three parts, of which 606Nm ³ /thm is used as back-injection gas 15, 110Nm ³ /thm is used for heating back-injection gas 15, and the remaining gas 15.2Nm ³ /thm is supplied to the gas pipe net12. The back-sprayed gas 15 can be back-sprayed into the blast furnace by the tuyere assembly 16 after being pressurized by the pressurizing device 13 . Such a cycle can achieve the goal of high-efficiency smelting in blast furnaces, an increase in production efficiency of blast furnace ironmaking by more than 20%, and a reduction in _CO2 emissions per ton of iron by 25%.

Example 2

In this embodiment, a blast furnace with a furnace capacity of 850 ^m3 is taken as an example. Referring to Figure 2, the low-carbon blast furnace ironmaking method as described above is adopted. The low-carbon blast furnace ironmaking system adopted in this embodiment includes a blast furnace body device, coal injection Device 4, dust removal device 8, dehydration device 9, desulfurization device 10, _CO2 removal device 11, pressurization device 13, preheating device 14, hot blast stove device 19 and _N2 removal device 20, wherein: blast furnace body device, It includes a blast furnace body 3 , a cloth assembly 2 and a tuyere assembly 16 arranged on the blast furnace body 3 , and a furnace top gas pipeline 6 is also arranged on the top of the blast furnace body 3 . And, cloth assembly 2, blast furnace body 3, coal injection device 4, furnace top gas pipeline 6, dedusting device 8, dehydration device 9, desulfurization device 10, _CO2 removal device 11, pressurization device 13, preheating device 14 and The low-carbon blast furnace ironmaking system in Embodiment 1 is consistent. In this embodiment, only 72% of the blast furnace top wet coal gas 7 is treated and sprayed back into the blast furnace. Therefore, in order to ensure sufficient air volume at the tuyere, it is necessary to use the hot blast stove device 19 and the oxygen generator 5 as in the conventional blast furnace. Oxygen is mixed into the air 21 and passed into the hot blast stove device 19 for heating to form oxygen-enriched hot air, and a N ₂ removal device 20 is added. The description of the common parts with the first embodiment will be omitted, and only the different parts will be described below.

The blast furnace top wet gas 7 in Example 2 is sprayed back into the blast furnace body 3 after dust removal, dehydration, desulfurization, CO ₂ removal, N ₂ removal, pressurization and heating, and the remaining top gas is sent into the gas pipe net12. Compared with Example 1, a gas removal N ₂ device needs to be added here to remove N ₂ brought in by the blast from the furnace top gas and increase the content of reducing gas in the re-injection gas 15 . The calculated back-injection gas volume is 376Nm ³ /thm. The temperature of back injection gas is 950℃.

Embodiment 2 adopts the hot blast stove device 19, and the blowing volume of the oxygen-enriched hot blast is 587.3Nm ³ /thm. The sum of oxygen-enriched hot air blowing volume and back-injection gas volume is about 963.3Nm ³ /thm, which ensures that the sum of oxygen-enriched hot air injection volume and top gas re-injection volume per ton of iron is comparable to that of a traditional blast furnace with the same furnace capacity. The amount is equivalent, and the operation and production operation of the blast furnace will not change significantly.

The blast oxygen enrichment rate is 17.9%. A higher oxygen enrichment rate can promote the full combustion of pulverized coal and improve the smelting efficiency. The blast temperature is 1200°C, which is close to that of a conventional blast furnace.

In order to ensure that the back-injection gas 15 can be blown to the center of the hearth and improve the smelting efficiency, the injection pressure of the back-injection gas 15 is equivalent to the air pressure of a conventional blast furnace, that is, more than 0.5 MPa. The pressure of oxygen-enriched hot air is below 0.35MPa～0.5MPa. In order to prevent safety problems such as tempering in the hot air surrounding pipe, the injection pressure of back-injected coal gas 15 should be higher than the injection pressure of oxygen-enriched hot air.

Because the oxygen content in the blast is less than that of the oxygen-enriched smelting method in Example 1, it is not suitable to use pulverized coal injection with too high volatile content in Example 2, so as to avoid a large amount of volatile substances decomposing and consuming heat, resulting in The theoretical combustion temperature is low. Therefore, in Example 2, pulverized coal with a volatile content of about 21% is selected for injection, and the amount of coal injected is about 180kg/thm. According to the heat balance calculation, the theoretical coke ratio is about 200.2kg/thm, and the theoretical fuel ratio is about 380.2 kg/thm.

The main chemical reactions and heat transfer in the blast furnace, the operation of charge 1 and gas are consistent with those in Example 1. The amount of bosh gas produced is about 1294Nm ³ /thm, and the composition of the bosh gas is shown in Table 2 below.

Table 2 bosh gas composition

The reducing gas content in the bosh gas is about 71.8%. Sufficient bosh gas volume and bosh gas with high reducing gas content can ensure the full development of the indirect reduction reaction in the middle and upper part of the blast furnace, and the final direct reduction degree is reduced to about 0.182.

The coal carrier gas used for pulverized coal injection and the metallurgical performance requirements of the iron ore fed into the furnace are consistent with those in Example 1. After the indirect reduction reaction, the top dry gas volume is about 1300.3Nm ³ /thm, of which the CO ₂ content is about 31.7%, the CO content is about 31.6%, the H ₂ content is about 8.6%, and the N ₂ content is about 28.1% .

The difference from Example 1 is that after dust removal, 316.3Nm ³ /thm of the top wet coal gas 7 in Example 2 is used to heat the re-injection coal gas 15 and oxygen-enriched hot air, of which 936.2Nm ³ /thm (accounting for furnace 72% of the total amount of top wet gas) The gas continues to go through the CO ₂ removal device 11 to remove CO ₂ , the N ₂ removal device 20 to remove N ₂ , the pressurizing device 13 to pressurize, and the preheating device 14 to heat and spray back into the After removing CO ₂ and N ₂ in the blast furnace, the back injection gas volume is 376Nm ³ /thm, and the remaining 47.8Nm ³ /thm top gas enters the gas pipe network 12 .

After CO ₂ and N ₂ are removed, the re-sprayed gas 15 contains about 78.7% CO and 21.3% H ₂ , and is re-sprayed from the tuyere assembly 16 into the blast furnace. Such a cycle can realize the high-efficiency smelting of blast furnaces, increase the production efficiency of blast furnace ironmaking by more than 12%, and reduce _CO2 emissions per ton of iron by 20%. Apparently, compared with Example 1, the effect of back-spraying only 72% top gas in Example 2 on strengthening blast furnace smelting and carbon emission is much lower.

Example 3

In this embodiment, a blast furnace with a furnace capacity of 2850 m ³ is taken as an example for illustration. The implementation of Example 3 is also shown in FIG. 2 .

The process flow of embodiment 3 is consistent with that of embodiment 2, the difference is that embodiment ³ is implemented based on a 2850m3 medium and large blast furnace, and it is difficult to change the operation method of a blast furnace with a larger furnace type, and the air volume required for the tuyeres is relatively high. If a high amount of back-injection gas is still maintained, on the one hand, the subsequent removal of CO ₂ and N ₂ , pressurization, and heating will require a larger amount of gas; on the other hand, a larger amount of gas back-injection into the blast furnace is safe Security and stability cannot be guaranteed. Therefore, in this embodiment, only 25% of the blast furnace top wet gas 7 is treated and sprayed back into the blast furnace.

The blast furnace top wet gas 7 in Example 3 is dedusted, dehydrated, desulfurized, CO ₂ removed, N ₂ removed, pressurized, heated and sprayed back into the blast furnace body 3, and the remaining gas is sent to the gas pipe network 12 . After removing CO ₂ and removing N ₂ , the amount of back injection gas is 126Nm ³ /thm. The temperature of back injection gas is 950℃.

The blowing volume of oxygen-enriched hot air in Example 3 is 813.3Nm ³ /thm. The sum of oxygen-enriched hot air blowing volume and back-injection gas volume is about 939.3Nm ³ /thm, which ensures that the sum of oxygen-enriched hot air injection volume and top gas re-injection volume per ton of iron is comparable to that of a traditional blast furnace with the same furnace capacity. The amount is equivalent, and the operation and production operation of the blast furnace will not change significantly.

The blast oxygen enrichment rate is 6.0%, and the blast temperature is 1200°C, which is close to that of a conventional blast furnace.

The pressure of the blast furnace oxygen-enriched hot blast is consistent with the requirements in Example 2. Simultaneously, the blowing pressure of back-spraying coal gas 15 also should be higher than the blowing pressure of oxygen-enriched hot blast.

Same as Example 2, Example 3 also uses pulverized coal with a volatile content of about 21% for injection, the amount of coal injection is about 170kg/thm, and the theoretical coke ratio is about 306.6kg/thm according to the heat balance calculation. thm, the theoretical fuel ratio is about 476.6kg/thm, which is slightly lower than that of conventional blast furnaces.

The main chemical reactions and heat transfer in the blast furnace, the operation of charge 1 and gas are consistent with those in Example 2. The amount of bosh gas produced is about 1379Nm ³ /thm, and the composition of the bosh gas is shown in Table 3 below.

Table 3 bosh gas composition

The content of reducing gas in bosh gas is about 52.4%. Sufficient bosh gas volume and bosh gas with high reducing gas content can ensure the full development of indirect reduction reaction in the middle and upper part of the blast furnace, and the final direct reduction degree is about 0.432.

The coal carrier gas used for pulverized coal injection and the metallurgical performance requirements of the iron ore fed into the furnace are consistent with those in Example 2. After the indirect reduction reaction, the top dry gas volume is about 1504Nm ³ /thm, of which the CO ₂ content is about 22.7%, the CO content is about 28.5%, the H ₂ content is about 5.0%, and the N ₂ content is about 43.7%.

Embodiment 3 is the same as Embodiment 2. After the furnace top wet gas 7 is dedusted, 455.3Nm ³ /thm of it is separated for heating back injection gas 15 and oxygen-enriched hot blast, wherein 376.1Nm ³ /thm (accounting for furnace top wet 25% of the total amount of gas) the gas continues to go through the CO ₂ removal device 11 to remove CO ₂ , the N ₂ removal device 20 to remove N ₂ , the pressurizing device 13 to pressurize, and the preheating device 14 to heat and spray back into the blast furnace. After removal of CO ₂ and N ₂ , the amount of re-injection gas is 126Nm ³ /thm, and the remaining 672.5Nm ³ /thm of furnace top gas enters the gas pipe network 12 .

The re-sprayed coal gas 15 after removal of CO ₂ and N ₂ contains about 85% CO and 15% H ₂ , and is re-sprayed into the blast furnace through the tuyere assembly 16 . Such a cycle can achieve the goal of reducing _CO2 emissions of 9 tons of iron by 9%. Since the blast oxygen enrichment rate is close to that of conventional blast furnaces, Example 3 does not have the effect of strengthening blast furnace smelting. Apparently, compared with Example 2, the effect of back-spraying only 25% top gas in Example 3 on strengthening blast furnace smelting and carbon emission is further reduced.

To sum up, in a low-carbon blast furnace ironmaking method provided by the embodiment of the present invention, the present invention adopts oxygen-enriched smelting and furnace top gas circulation technology without making major changes to the traditional blast furnace system to greatly improve the blast furnace The utilization rate of carbon in the furnace, and increase the concentration of reducing gas in the bosh gas, reduce the degree of direct reduction inside the blast furnace hearth, save fuel consumption, reduce the fuel ratio of the blast furnace, improve the efficiency of blast furnace ironmaking and reduce the Iron Process CO ₂ Emissions.

The above-mentioned embodiments only illustrate the principles and effects of the present invention, but are not intended to limit the present invention. Anyone skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical ideas disclosed in the present invention should still be covered by the claims of the present invention.

Claims

A low-carbon blast furnace ironmaking method, characterized in that it comprises:

Inject the heated and pressurized re-injection gas into the blast furnace, inject pure oxygen into the blast furnace or inject oxygen-enriched hot air into the blast furnace, spray pulverized coal into the blast furnace, and alternately load iron ore and coke into the blast furnace;

Top gas is formed after the chemical reaction in the blast furnace;

The top gas is sprayed into the blast furnace as respray gas after a series of treatment procedures, and then pressurized and heated, and the remaining top gas is sent to the gas pipe network.
A low-carbon blast furnace ironmaking method according to claim 1, characterized in that: if pure oxygen is injected into the blast furnace, the treatment process includes dust removal, dehydration, desulfurization, CO 2 removal, pure oxygen injection per ton of iron The sum of the blowing volume and the top gas re-injection per ton of iron is similar to the hot air consumption per ton of iron of a blast furnace with the same furnace capacity; if oxygen-enriched hot air is injected into the blast furnace, the treatment process includes dust removal, dehydration, desulfurization, and CO removal 2 and removal of N 2 , the sum of oxygen-enriched hot air injection per ton of iron and furnace top gas re-injection per ton of iron is similar to the hot air consumption per ton of iron of a blast furnace with the same furnace capacity.
A low-carbon blast furnace ironmaking method according to claim 2, characterized in that the particle content of the top gas after dedusting is less than 20 mg/Nm 3 .
A low-carbon blast furnace ironmaking method according to claim 2, characterized in that the dehydration efficiency of the top gas after dehydration is greater than 95%.
A low-carbon blast furnace ironmaking method according to claim 2, characterized in that: the S content of the top gas after desulfurization is lower than 0.015%.
A low-carbon blast furnace ironmaking method according to claim 2, characterized in that: the CO 2 removal rate of the top gas after CO 2 removal is greater than 95%.
A low-carbon blast furnace ironmaking method according to claim 2, characterized in that: the back injection gas needs to be pressurized to above 0.5Mpa.
A low-carbon blast furnace ironmaking method according to claim 2, characterized in that: the back injection gas needs to be heated to above 950°C.
A low-carbon blast furnace ironmaking method according to claim 2, characterized in that the purity of the pure oxygen is greater than 99%.
A low-carbon blast furnace ironmaking method according to claim 2, characterized in that: the pure oxygen is injected into the blast furnace through an oxygen nozzle, and the injection pressure of the pure oxygen is higher than the injection pressure of the back-injection gas .
A low-carbon blast furnace ironmaking method according to claim 2, wherein the pulverized coal is injected into the blast furnace by a coal carrier gas through a coal gun, and the coal carrier gas is removed from the furnace top gas of CO 2 gas.
A low-carbon blast furnace ironmaking method according to claim 2, wherein the pulverized coal is high-volatile pulverized coal with a volatile content greater than 21%, and the volatile pulverized coal in the high-volatile pulverized coal is decomposed The generated H2 is used to participate in the indirect reduction reaction, and part of CO is replaced by H2 to reduce carbon emissions.
A low-carbon blast furnace ironmaking method according to claim 2, characterized in that: said iron ore is highly reducing iron ore, including one of sintered ore, pellet ore, lump ore and composite iron coke One or several kinds, the comprehensive furnace grade is greater than 58%, and the reduction index RI is greater than 80%.