CN101824505A - Method for producing low-sulfur molten iron in one step by smelting and reducing copper slag - Google Patents

Abstract

The invention discloses a method for producing low-sulfur molten iron in one step through copper slag smelting reduction, which is characterized in that it contains the following process steps: the high-temperature molten copper slag is reduced by a reducing agent in a high-temperature reduction furnace before the iron reduction reaction is basically completed. , based on the existing slag system in the reduction furnace, combined with theoretical calculations, a certain additive is added to the molten pool. The blowing time is 30min-40min, and the desulfurization reaction is basically completed. The molten pool is left to stand until the slag and iron are completely separated, and the high-temperature low-sulfur molten iron and slag are released from the tap hole and the slag port respectively. In addition, the high-temperature flue gas passes through the secondary combustion chamber and then passes through the waste heat boiler for waste heat recovery, cyclone dust collection and washing. The invention makes full use of the high desulfurization of refining slag and the injection of carbon monoxide gas, and solves the disadvantage of high sulfur content in molten iron obtained from copper slag smelting reduction ironmaking; the process flow is short, the discharge of pollutants is less, and the applicability is wider.

Description

A method for producing low-sulfur molten iron in one step by smelting and reducing copper slag

technical field

The invention relates to a method for preparing low-sulfur molten iron in one step through copper slag smelting reduction, which belongs to the field of resources and environment.

Background technique

In recent years, China's iron and steel industry has developed rapidly. my country's iron and steel industry occupies a pivotal position in the world's iron and steel industry. For more than ten years, its total iron and steel production has always occupied the first place in the iron and steel industries of all countries in the world. However, my country's iron ore resources are far from meeting the needs of the iron and steel industry, and the distribution of resources has the following characteristics: first, there are many lean ores, and the reserves of lean ores account for 80% of the total reserves; The third is that my country's iron ore resources are scarce, the grade is low, and the production capacity of steel enterprises across the country is huge, the demand is increasing year by year, and the dependence on imports is increasing day by day. However, my country has no pricing power for imported iron ore. In recent years, iron ore The soaring price of iron and steel has directly led to a sharp increase in the cost of ironmaking, which has weakened the profit margins of the iron and steel industry and seriously affected the development of China's iron and steel industry.

Therefore, finding a supplementary resource of iron ore as a raw material for ironmaking is an effective solution to solve the long-term shortage of iron ore resources in China.

According to statistics, the production of one ton of copper produces 2.2 tons of copper slag. China's copper output in 2007 was 3.5 million tons, and the corresponding output of copper slag was 7.7 million tons. In 2008, China's copper output was about 3.71 million tons. The amount of copper slag produced is calculated to be 8.16 million tons. Copper slag contains about 40% iron, and this huge amount of copper slag contains iron with considerable recovery value.

Iron mainly exists in the form of 2FeO·SiO ₂ (fayalite) and Fe ₃ O ₄ (magnetite) in copper metallurgical slag. At present, there are two main methods for the recovery and enrichment of iron from copper slag:

First: The copper slag is oxidized and roasted in a non-melting state, and the iron in the copper slag mainly in the form of 2FeO·SiO ₂ (fayalite) is converted into the form of Fe ₃ O ₄ (magnetite) After that, the roasted copper slag is crushed and magnetically separated to separate the iron-rich phase from the rest of the slag phase to achieve the purpose of enriching iron. Relevant literature proves, reclaims the iron in the copper slag by this method, can make the enrichment degree of iron in the slag reach more than 85% in the magnetite, but there is following shortcoming in this kind method:

1. The water-quenched copper slag is cooled and then oxidized and roasted at high temperature, which causes waste of heat in the process. The furnace temperature of copper slag is 1150°C-1250°C, and the specific heat capacity of copper slag is about 1.1kJ·kg ^-1 ·k ^-1 . After calculation, when the copper slag is cooled from the furnace temperature to room temperature of 25°C, the copper smelter in China in 2008 The heat loss is about: 1.1×10 ¹³ -1.2×10 ¹³ kJ, and the calorific value is calculated economically, calculated according to the calorific value of standard coal: 29271.2kJ kg ^-1 , combined with the current price of standard coal, each year in China due to The economic loss caused by the heat loss of copper slag is at least 210 million yuan, and the economic loss will be even greater if it is extended to the world;

2. Iron is enriched in magnetite through oxidation roasting-crushing magnetic separation process. This process has the disadvantages of low iron recovery rate and complicated follow-up treatment process. Relevant documents confirm that the highest recovery rate of iron in copper slag is maintained at about 85% through this process, and the enriched iron is concentrated in magnetite, which needs to be put into the blast furnace for reduction and ironmaking For ironmaking, the whole process is too complicated.

Second: drawing on the idea of smelting reduction ironmaking, the iron mainly in the form of 2FeO·SiO ₂ (fayalite) and Fe ₃ O ₄ (magnetite) in the copper slag is directly smelted and reduced to metallic iron by using a reducing agent. A process for recovering iron from copper slag that realizes the separation of slag and iron in a molten state. However, this process has the disadvantage of high sulfur content (average content higher than 0.6%) in molten iron obtained after copper slag smelting reduction.

Contents of the invention

The object of the present invention is to provide a method for producing low-sulfur molten iron in one step through smelting reduction of copper slag. It makes full use of the characteristics of high desulfurization of the refined slag prepared after the iron reduction reaction and the carbon monoxide gas injected in the molten pool to reduce the oxygen potential in the molten iron and improve the reaction kinetics, greatly reducing the molten iron obtained by the smelting reduction of copper slag. of sulfur content.

Based on the copper slag smelting reduction ironmaking method, this process makes full use of the characteristics of high desulfurization of the prepared refining slag and the injection of carbon monoxide gas to reduce the oxygen potential in molten iron and improve the reaction kinetics, and solves the problem of copper slag smelting reduction. The disadvantage of high sulfur content in molten iron obtained from ironmaking provides a new method for the industrial application of the technology of copper slag smelting reduction of iron in the future.

The technical scheme of the method for producing low-sulfur molten iron in one step through copper slag smelting reduction of the present invention contains the following process steps: the high-temperature molten copper slag is reduced by the reducing agent before the reduction furnace, and when the reduction reaction of iron is basically completed, the For the existing slag system, add additives to the molten pool. After the additives are completely molten, insert the spray gun to the slag-iron interface, and spray carbon monoxide gas into the molten pool. The injection time is 30min-40min, and the desulfurization reaction is basically completed. After that, the injection is stopped; the molten iron is left to stand until the slag and iron are completely separated, and the high-temperature low-sulfur molten iron and slag are released from the taphole and slag outlet respectively; the high-temperature flue gas passes through the secondary combustion chamber and then passes through the waste heat boiler for waste heat recovery. It is dedusted by cyclone dust collection, and finally the harmful gases such as sulfur dioxide and nitrogen oxides contained in the flue gas are removed through the washing device, and discharged into the atmosphere after meeting the emptying requirements.

The injection pressure of the carbon monoxide gas is 0.5MPa～1.5MPa; the additives are CaO-CaCO ₃ , CaO-CaF ₂ , CaO-CaF ₂ -C (oil coke), CaO-BaO-CaF ₂ ; The broken particle size of the additive is 0.5mm-4mm; the temperature of the reaction furnace in the injection stage is kept at 1600°C-1700°C.

满足质量比

CaO-CaF₂，其加入量满足使渣的碱度为4.6-5.2，其中添加剂中CaF₂的质量百分含量为10％-13％；CaO-CaF₂-C(油焦)其加入量满足使渣的碱度为4.6-5.2，其中CaF₂的加入量为添加剂总质量的8.5％-9.5％，C(油焦)的加入量为添加剂总质量的10％-15％；CaO-BaO-CaF₂，CaO-BaO-CaF₂的加入量满足使渣的碱度为4.6-5.2，其中添加剂中CaF₂的质量百分含量为9.5％-12％，添加剂CaO、BaO的加入量m_CaO、m_BaO满足质量比 The addition amount of the additive should meet the following relationship according to the type: CaO-CaCO ₃ , the addition amount satisfies the alkalinity of the slag to be 4.6-5.2, wherein the addition amount of the additives CaO and CaCO ₃ m _CaO ,

Satisfy the quality ratio

CaO-CaF ₂ , its adding amount is enough to make the basicity of slag be 4.6-5.2, wherein the mass percentage of CaF ₂ in the additive is 10%-13%; its adding amount of CaO-CaF ₂ -C (oil coke) meets Make the basicity of slag be 4.6-5.2, wherein the addition of CaF ₂ is 8.5%-9.5% of the total mass of additives, the addition of C (oil coke) is 10%-15% of total mass of additives; CaO-BaO- The amount of CaF ₂ , CaO-BaO-CaF ₂ is enough to make the basicity of the slag be 4.6-5.2, wherein the mass percentage of CaF ₂ in the additive is 9.5%-12%, and the addition amount of CaO and BaO of the additives is m _CaO , m _BaO satisfies mass ratio

The smelting process of the present invention is as follows:

The high-temperature copper slag is smelted and reduced by the reducing agent before the reduction furnace. When the reduction reaction of iron is basically completed, the additives are ground to a particle size of 0.5mm-4mm and added to the reaction molten pool to prepare high-desulfurization refining slag. When the prepared refining slag is completely in the molten state, the gas spray gun is inserted into the slag-iron interface, and carbon monoxide gas is injected into the reaction molten pool to improve the reaction kinetics and reduce the oxygen potential in the molten iron. Taking the additive CaO-CaF ₂ -C (oil coke) as an example, after it is added into the molten pool, the reaction is as follows:

C(oil coke)＝[C]         (1)

CaO+[S]+[C]＝CaS+CO (2)

3CaO+[S]+[O]+[Si]=CaS+Ca ₂ SiO ₄ (3)

The addition of C (oil coke) in the additive effectively reduces the oxygen potential in molten iron. According to Le Chatelier’s principle, it promotes the desulfurization reaction. In addition, it can be seen from the reaction (3) that after adding CaO to the molten pool, the desulfurization Ca ₂ SiO ₄ will be generated during the process, and its melting point is relatively high, and it is easy to wrap on the surface of CaO particles, which hinders the contact between [S] and CaO particles, and is not conducive to the further progress of the desulfurization reaction. With the addition of CaF ₂ , the decomposed fluorine ions can destroy the chemical bonds on which 2CaO·SiO ₂ is combined, making it form pores, allowing sulfur to diffuse into the interior of CaO particles, and the desulfurization reaction can continue. At the same time, during the reaction process, the carbon monoxide spray gun goes deep into the reaction molten pool to stir the molten pool, so that the boundary layer of the solid-solid phase reaction becomes thinner, which promotes the improvement of the reaction speed. And the injection of CO gas also effectively reduces the oxygen potential in molten iron:

CO+[O]=CO ₂ (4)

Promote the desulfurization reaction.

After a period of time, the desulfurization reaction is basically completed. The generated molten iron quickly settles to the bottom of the molten pool due to its own gravity and higher density than the slag. The thick high-temperature slag covers the upper part of the molten iron pool, so that the reduced molten iron avoids the possibility of being oxidized again. The pool plays the role of heat preservation and realizes the separation of slag and iron. After the reaction is completed, the smelted high-temperature low-sulfur molten iron and slag are released from the tap hole and the slag port respectively.

Beneficial effects of the present invention:

Copper slag undergoes smelting reduction reaction in the reduction furnace, and when the smelting reduction reaction of iron is basically completed, use the high desulfurization of the prepared refining slag and inject carbon monoxide gas to reduce the oxygen potential in the molten iron and improve the reaction kinetics to reduce the iron. Sulfur content in water, this process has the following advantages:

1) By preparing high desulfurization refining slag, spraying carbon monoxide gas into the molten pool reduces the oxygen potential in the molten iron, improves the reaction kinetics, and effectively reduces the sulfur content in the molten iron;

2) This process is short and has less iron loss, which is beneficial to reduce investment costs and reduce environmental pollution;

3) The applicability of this process is relatively wide, and this technology can be indirectly extended to the effective recovery of iron resources from other non-ferrous metallurgical slags.

Description of drawings

Fig. 1 is a process flow diagram of the present invention.

Detailed ways

The substantive content of the present invention will be further described below with examples in conjunction with the accompanying drawings, but the content of the present invention is not limited thereto.

The high-temperature molten copper slag of the present invention is reduced by the reducing agent before the reduction furnace, and when the iron reduction reaction is basically completed, a certain additive is added to the molten pool based on the existing slag system in the reduction furnace, and the additive is completely in a molten state. , insert the spray gun to the slag-iron interface, spray carbon monoxide gas into the molten pool, and the injection time is 30min-40min, and the desulfurization reaction is basically completed. The molten iron is left to stand until the slag and iron are completely separated, and the high-temperature low-sulfur molten iron and the slag are released from the tap hole and the slag port respectively. In addition, after the high-temperature flue gas passes through the secondary combustion chamber, the waste heat is recovered by the waste heat boiler, and then it is dedusted by cyclone dust collection, and finally the harmful gases such as sulfur dioxide and nitrogen oxides contained in the flue gas are removed through the washing device to achieve emptying. On request, vent to atmosphere.

满足质量比

CaO-CaF₂，其加入量满足使渣的碱度为4.6-5.2，其中添加剂中CaF₂的质量百分含量为10％-13％；CaO-CaF₂-C(油焦)其加入量满足使渣的碱度为4.6-5.2，其中CaF₂的加入量为添加剂总质量的8.5％-9.5％，C(油焦)的加入量为添加剂总质量的10％-15％；CaO-BaO-CaF₂，CaO-BaO-CaF₂的加入量满足使渣的碱度为4.6-5.2，其中添加剂中CaF₂的质量百分含量为9.5％-12％，CaO、BaO的加入量m_CaO、m_BaO满足质量比

(5)CO气体的喷吹时间为30min-40min；(6)喷吹过程中反应炉温保持在1600℃～1700℃。The specific process parameters in the above process steps of the present invention are: (1) the injected gas is carbon monoxide, and the injection pressure is 0.5MPa～1.5MPa; (2) the additives are CaO-CaCO ₃ , CaO-CaF ₂ , CaO-CaF ₂ -C (oil coke), CaO-BaO-CaF ₂ ; (3) The crushing particle size of the additive is 0.5mm~4mm; (4) The amount of the additive should meet the following relationship according to the type: CaO-CaCO ₃ , the amount of the additive should meet the Make the alkalinity of slag be 4.6-5.2, the addition amount of CaO, CaCO ₃ m _CaO ,

Satisfy the quality ratio

CaO-CaF ₂ , its adding amount is enough to make the basicity of slag be 4.6-5.2, wherein the mass percentage of CaF ₂ in the additive is 10%-13%; its adding amount of CaO-CaF ₂ -C (oil coke) meets Make the basicity of slag be 4.6-5.2, wherein the addition of CaF ₂ is 8.5%-9.5% of the total mass of additives, the addition of C (oil coke) is 10%-15% of total mass of additives; CaO-BaO- The amount of CaF ₂ , CaO-BaO-CaF ₂ should be added to make the basicity of the slag 4.6-5.2, the mass percentage of CaF ₂ in the additives should be 9.5%-12%, the amount of CaO and BaO m _CaO , m _BaO satisfies mass ratio

(5) The injection time of CO gas is 30min-40min; (6) The temperature of the reaction furnace is kept at 1600°C-1700°C during the injection process.

Example 1

When the iron reduction reaction in the molten copper slag in the reduction furnace is basically completed [at this time, the composition of the slag is: CaO=33.708, SiO ₂ =28.09, S=0.58, FeO=2.85 (mass percentage), and the temperature of the molten pool is 1630°C], Grind the additive CaO-CaF ₂ -C (oil coke) to a particle size of about 0.6mm [the amount of CaO-CaF ₂ -C (oil coke) added is to make the ternary basicity of the slag 4.9, and the mass of CaF ₂ in the additive The percentage content is 9%, and the addition amount of C (oil coke) is 12% of the total mass of the additive], add it into the molten pool, and when it is completely melted, inject the carbon monoxide gas into the molten pool to the slag-iron interface to react The system is stirred to accelerate the desulfurization reaction, and the injection pressure of carbon monoxide gas is maintained at 1.2MPa. Under this condition, the carbon monoxide gas injection time is 30 minutes, and the spray gun is lifted out of the molten pool after the injection is stopped. The molten pool was left to stand for 20 minutes, and the molten iron and slag phases were completely separated. The resulting molten iron and slag phases are released from the tap hole and the slag port respectively. The S content in the obtained molten iron is analyzed to be 0.05%, which is far lower than the average sulfur content of 0.6% in the molten iron in this process, and meets the requirements of my country for steelmaking pig iron.

Example 2

When the reduction reaction of iron in the molten copper slag in the reduction furnace is basically completed [at this time, the composition of the slag is: CaO=32.02, SiO ₂ =29.39, S=0.62, FeO=2.74 (mass percentage), and the temperature of the molten pool is 1650°C] , grind the additive CaO- _CaF2 to a particle size of about 1mm (the amount of CaO- _CaF2 added is such that the ternary basicity of the slag is 5.2, and the mass percentage of _CaF2 in the additive is 10%), and add it into the molten pool , when it is in a molten state, the spray gun is deep into the molten pool to spray carbon monoxide gas at the slag-iron interface to stir the reaction system, reduce the oxygen potential in the molten iron, and accelerate the desulfurization reaction. The injection pressure of carbon monoxide gas is maintained at 1.32 MPa. Under this condition, the carbon monoxide gas injection time is 35 minutes, and the spray gun is lifted out of the molten pool after the injection is stopped. The molten pool was left to stand for 20 minutes, and the molten iron and slag phases were completely separated. The resulting molten iron and slag phases are released from the tap hole and the slag port respectively. The content of S in the obtained molten iron is analyzed to be 0.047%, which is far lower than the average sulfur content of 0.6% in the molten iron of this process, and meets the requirements of my country for steelmaking pig iron.

Example 3

)，加入到熔池内，其处于熔融状态时，将喷枪深入熔池至渣铁界面处喷吹一氧化碳气体对反应系统进行搅拌，加速脱硫反应的进行，一氧化碳气体的喷吹压力维持在1.18MPa。此条件下一氧化碳气体喷吹时间为32min，停止喷吹后将喷枪提出熔池。熔池静置25min，铁水和渣相完全分离。将所得铁水和渣相分别由出铁口和出渣口放出。所得铁水中S经分析其含量为0.045％，远远低于此工艺铁水的平均硫含量0.6％，符合我国对炼钢生铁的要求。When the reduction reaction of iron in the molten copper slag in the reduction furnace is basically completed [at this time, the composition of the slag is: CaO=35.31, SiO ₂ =26.34, S=0.54, FeO=2.73 (mass percentage), and the temperature of the molten pool is 1670°C] , the additive CaO-BaO- _CaF2 is crushed to a particle size of about 1.2mm (the addition of CaO-BaO- _CaF2 meets the basicity of the slag to be 4.9, wherein the mass percentage of _CaF2 in the additive is 10%, CaO, The amount of BaO added m _CaO and m _BaO meet the mass ratio

), into the molten pool, when it is in a molten state, the spray gun is deep into the molten pool to spray carbon monoxide gas at the slag-iron interface to stir the reaction system to accelerate the desulfurization reaction, and the injection pressure of carbon monoxide gas is maintained at 1.18MPa. Under this condition, the carbon monoxide gas injection time is 32 minutes, and the spray gun is lifted out of the molten pool after the injection is stopped. The molten pool was left to stand for 25 minutes, and the molten iron and slag phases were completely separated. The resulting molten iron and slag phases are released from the tap hole and the slag port respectively. The content of S in the obtained molten iron is analyzed to be 0.045%, which is far lower than the average sulfur content of 0.6% in the molten iron of this process, and meets the requirements of my country for steelmaking pig iron.

m_BaO是CaO、CaCO₃、BaO的质量。The above m _CaO ,

m _BaO is the mass of CaO, CaCO ₃ , BaO.

Claims (3)

1. A method for making low-sulfur molten iron in one step through copper slag smelting reduction is characterized in that it contains the following process steps: the high-temperature molten copper slag is reduced by a reducing agent before the reduction furnace, and when the reduction reaction of iron is basically completed, based on the reduction For the existing slag system in the furnace, add additives to the molten pool. After the additives are completely molten, insert the spray gun to the slag-iron interface, and spray carbon monoxide gas into the molten pool. The injection time is 30min-40min. The desulfurization reaction is basically After completion, the injection is stopped; the molten iron is left to stand until the slag and iron are completely separated, and the high-temperature low-sulfur molten iron and slag are released from the taphole and slag outlet respectively; the high-temperature flue gas passes through the secondary combustion chamber and then passes through the waste heat boiler for waste heat recovery After that, it is dedusted by cyclone dust collection, and finally the harmful gases such as sulfur dioxide and nitrogen oxides contained in the flue gas are removed through the washing device, and discharged into the atmosphere after meeting the emptying requirements. 2. The method for producing low-sulfur molten iron in one step through copper slag smelting reduction according to claim 1, characterized in that: the injection pressure of the carbon monoxide gas injection is 0.5MPa～1.5MPa; the additive is CaO -CaCO ₃ , CaO-CaF ₂ , CaO-CaF ₂ -C (oil coke), CaO-BaO-CaF ₂ ; the crushed particle size of the additive is 0.5mm~4mm; the temperature of the reaction furnace in the injection stage is kept at 1600℃~ 1700°C. 3. The method for producing low-sulfur molten iron in one step through copper slag smelting reduction according to claim 2 is characterized in that: the addition amount of the additive should satisfy the following relationship according to the type: CaO-CaCO ₃ , the addition amount satisfies The alkalinity of the slag is 4.6-5.2, wherein the addition amount of CaO and CaCO ₃ m _CaO ,

Satisfy the quality ratio CaO-CaF ₂ , its adding amount is enough to make the basicity of slag be 4.6-5.2, wherein the mass percentage of CaF ₂ in the additive is 10%-13%; its adding amount of CaO-CaF ₂ -C (oil coke) meets Make the basicity of slag be 4.6-5.2, wherein the addition of CaF ₂ is 8.5%-9.5% of the total mass of additives, the addition of C (oil coke) is 10%-15% of total mass of additives; CaO-BaO- The amount of CaF ₂ , CaO-BaO-CaF ₂ is enough to make the basicity of the slag be 4.6-5.2, wherein the mass percentage of CaF ₂ in the additive is 9.5%-12%, and the addition amount of CaO and BaO of the additives is m _CaO , m _BaO satisfies mass ratio

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