A process for optimizing converter steelmaking by using ironmaking gas ash

Abstract

The present invention discloses a process for optimizing converter steelmaking by utilizing ironmaking gas ash, and involves three process contents: resource utilization technology of ironmaking gas ash and steel slag fine powder, and optimization of converter smelting process. The present invention utilizes ironmaking gas ash and steel slag fine powder as flux materials for converter after adding certain active materials. While utilizing ironmaking gas ash as resources, it plays the role of assisting melting slag in the early stage of converter blowing, suppressing slag splashing and metal splashing accidents in the early stage of converter smelting, and realizing the process purpose of recycling and resource utilization of solid waste within steel enterprises, with huge economic and environmental benefits.

Description

Technical Field

[0001] The invention relates to a process for optimizing converter steelmaking by utilizing ironmaking gas ash. Background Art

[0002] In the steel slag pretreatment process, the crushing and magnetic separation process can be used to recover iron-containing raw materials with a particle size greater than 5 cm in the steel slag. Most of the iron-containing substances in the steel slag are weakly magnetic substances, which are difficult to recycle using the magnetic separation process. The steel slag is crushed to less than 3 mm, and the iron-containing mineral phase in the steel slag can be separated from the silicate mineral phase in the steel slag. The crushed steel slag is passed through a strong magnetic field belt conveyor magnetic separation system to recover most of the iron-containing substances in the steel slag. The iron-containing substances obtained under this process are called steel slag concentrate. The main components of a factory's steel slag concentrate are shown in the following table:

[0003] ;

[0004] Steel slag concentrate is rich in various iron oxides, mainly in the form of calcium ferrite, ferromagnesian olivine, RO phase, etc., and the P and S contents in steel slag concentrate are relatively high. References (1) Li Xiaoli, Cui Zhijun, and Zhang Wenjia published a paper entitled "Research on the Sintering Addition Technology of Baosteel Steel Slag Magnetic Separation Powder" in the 4th issue of "Metallurgical Standardization and Quality" in 2015. The paper states: "The high P content of Baosteel steel slag magnetic separation powder has always been the main reason restricting its sintering application. This paper deduces the ratio of steel slag magnetic separation powder with different P contents for sintering through the requirements of steelmaking process for P content, which provides a theoretical and experimental basis for the addition of steel slag magnetic separation powder to sintering." (2) Qin Peng, Mao Youzhuang and Zhang Deqian published a paper titled “Research and Practice of Adding Steel Slag Powder to Sintering Production” in Laigang Science and Technology magazine in 2009. The paper stated, “In order to make full use of steel slag powder in sintering production, the physicochemical properties and sintering properties of steel slag powder were mastered through sintering cup test. In sintering production, adding 5% steel slag powder can effectively reduce solid fuel consumption, improve the yield of sintering production, and ensure that the sintered ore has better strength during low-temperature sintering, saving costs.”

[0005] According to the description in the above-mentioned documents, there is no mention of the process of using steel slag concentrate for converter slag smelting.

[0006] Blast furnace gas mud is a product obtained by wet dust removal from raw material dust carried by blast furnace gas and particles produced by intense reactions in high temperature areas during blast furnace smelting. As a by-product of the steel industry, ironmaking gas ash is mainly composed of iron and carbon, with an iron content of about 30% and a carbon content of about 20%. At the same time, since some iron ores used in blast furnaces contain a certain amount of non-ferrous metals, some low-boiling point non-ferrous metals enter the blast furnace gas after volatilization in the blast furnace, and are eventually enriched in the gas mud in the form of oxides. Xinjiang Bayi Iron and Steel Co., Ltd.2500m 3 The composition of ironmaking gas ash is shown in the following table:

[0007] ;

[0008] The resource utilization process of ironmaking gas ash is the rotary hearth furnace and vertical furnace process. After removing zinc, lead, potassium and sodium from the gas ash, the remaining iron-containing pellets are returned to the ironmaking process for resource utilization. In addition, there is currently no effective process method that can effectively treat all the ironmaking gas ash.

[0009] References (1) Liu Bingguo, Peng Jinhui, Zhang Libo et al. published a paper titled “Current Status of Research on Resource Recycling of Blast Furnace Gas Mud (Ash)” in the 5th issue of Mining Express in 2007. The paper states that “In 1976, the U.S. Environmental Protection Agency (EPA) enacted a law to classify steel mill dust containing lead and zinc as Class K061 substances (toxic solid waste). , requiring the lead and zinc in them to be recycled or passivated, otherwise they must be sealed and piled in designated areas. " (2) Shi Lei, Chen Ronghuan, and Wang Ruyi published a paper entitled "The Current Situation and Development Direction of Resource Utilization of Zinc Dust in the Iron and Steel Industry" in the 2nd issue of "China Resource Comprehensive Utilization" in 2009. The paper contains: "It compares the traditional treatment processes of zinc dust in the steel industry, introduces the research and utilization practices of zinc dust in Baosteel, investigates the utilization methods of zinc dust in foreign steel plants, lists the domestic and foreign progress of rotary hearth furnace treatment of zinc dust, and points out that pyrometallurgical recycling is the best way to properly treat zinc dust in the steel industry. The rotary hearth furnace has great potential in resource utilization of zinc dust in the steel industry and environmental protection."

[0010] According to the above description, there is no technological method for optimizing converter steelmaking by utilizing ironmaking gas ash.

[0011] Converter steelmaking is a process in which high-speed oxygen is blown onto the upper surface of liquid high-temperature iron to oxidize and remove harmful elements in the iron to make steel, and the chemical heat of the reaction process is used to heat the iron to a temperature suitable for tapping steel.

[0012] Sputtering is a phenomenon that occurs during the smelting process of oxygen top-blown converters. In the steelmaking industry, the phenomenon of overflowing and ejecting slag and metal from the furnace mouth is usually called splashing. During the blowing process, due to the impact of the oxygen stream on the molten pool and the escape of a large amount of CO gas produced by the decarburization reaction, the splashing of slag and molten metal is inevitable. Under normal circumstances, the height of the molten metal splashing generally does not exceed the furnace mouth, and no splashing will form. However, if a large amount of CO gas is produced in the converter in a short period of time when the decarburization reaction intensifies, the gas discharged to the furnace mouth will increase exponentially, and an explosive carbon-oxygen reaction will occur, bringing the slag and molten metal out of the furnace, thereby splashing. The converter splashing accident will not only pollute the environment, deteriorate the economic and technical indicators of steelmaking, and reduce production, but also cause damage to equipment. Common converter splashing is mainly divided into three types: explosive splashing, foam slag splashing and metal splashing.

[0013] In the top-blown oxygen converter steelmaking in the early stage of converter blowing, the oxygen stream first undergoes an oxidation reaction with the molten iron, and the generated iron oxide then reacts with other impurities in the order of affinity. If the primary reaction rate is greater than the secondary reaction, then the iron oxide in the slag accumulates, otherwise the iron oxide content in the slag decreases. After 1min to 3min of blowing, the oxidation reaction of elements such as Si and Mn is nearing its end. At this time, the accumulation and consumption of iron oxide depends on the CO reaction rate. The higher the temperature, the greater the driving force of the CO reaction, and the iron oxide in the slag is not easy to accumulate, otherwise it is easy to accumulate. Therefore, the temperature is low in the early stage, the CO reaction is delayed, and iron oxide accumulates in the slag. When the molten pool temperature rises to the temperature required for the CO reaction, the C in the molten pool begins to oxidize strongly, and the (FeO) accumulated in the slag provides a large additional oxygen supply for the CO reaction. The gas flow generated by the instantaneous reaction increases sharply, and at this time the basicity of the slag is low, and various splashes are prone to occur.

[0014] References (1) Yang Bo and Li Jun published a paper entitled “Control of Early Stage Splashing of 50t Converter” in the 4th issue of Shandong Metallurgy in 2013. The paper states that “In order to reduce the early stage splashing of 50t converter, the oxygen supply intensity was slowed down by adjusting the gun position, oxygen pressure and charging system, effectively controlling the change of FeO in slag and the foaming of early stage slag, thereby reducing the occurrence of splashing and reducing the splashing slag per ton of steel by 10kg.” (2) Xiao Hu published a paper entitled “Control of Early Stage Splashing of 50t Converter” in the 3rd issue of Metallurgical Journal in 2012. The paper titled "Control of Sputtering in the Early Stage of Converter Smelting" was published. The paper states that "Control of splashing in the early stage of converter smelting is an important link in the control of the entire smelting process. Reducing or even eliminating splashing in the early stage of smelting not only helps to smoothly control the entire smelting, but also improves various technical and economic indicators and smelting environment. Guanggang has effectively controlled splashing in the early stage of smelting by taking relevant measures such as raising the gun, reducing pressure and improving the slag in the furnace, making the smelting process stable, various consumption indicators significantly improved, and achieving safe and environmentally friendly production." According to the above literature statements, there is currently no mention of a process method for using ironmaking gas ash to prevent splashing in the early stage of the converter. Summary of the invention

[0015] The invention provides a process for optimizing converter steelmaking by utilizing ironmaking gas ash, which can completely solve the problem of ironmaking gas ash and has significant environmental benefits.

[0016] The technical solution adopted by the present invention is a process for optimizing converter steelmaking by utilizing ironmaking gas ash, which is implemented according to the following steps:

[0017] 1) Purchase heavy oil as a binder and transport it to the dry powder pelletizing production line for use;

[0018] 2) Transport the ironmaking gas ash and steel slag powder to the dry powder pelletizing production line for standby use;

[0019] 3) Mix the ironmaking gas ash and steel slag powder in a ratio of 70%:30% by mass, add the heavy oil as a binder, the amount of heavy oil added is 5% of the mass of the mixture of the ironmaking gas ash and steel slag powder, use a high-pressure dry powder pelletizing machine to press the mixture of the three substances into pellets with a diameter of 15 to 50 mm, and transport them to the converter smelting station for standby;

[0020] 4) When adding scrap steel to the converter, the pellets and scrap steel are added to the converter at an amount of 10-25 kg per ton of steel, wherein: the temperature of the molten iron smelted in the converter is normal, the scrap steel ratio is 10%-15%, and 15 kg-25 kg is added per ton of steel; the scrap steel ratio is 15%-20%, and 10 kg-15 kg is added per ton of steel;

[0021] 5) After adding the above pellets, the converter is smelted according to the normal smelting process.

[0022] The scrap steel ratio is the ratio of the scrap steel added to the total amount of steel material added.

[0023] The inventor used his research results on the performance of foamed slag and found that in the early stage of converter smelting, the melting speed of lime added to steelmaking was slow, and the slag operation was improper. The basicity of the slag in the early stage of converter blowing was between 1.6 and 2.5, which was the most suitable slag basicity for foaming. In the first 3 minutes of converter smelting, before the decarburization reaction started, if FeO was enriched in the slag, after the temperature of the converter molten pool reached the temperature at which the decarburization reaction started, a large number of bubbles were generated by the carbon-oxygen reaction. When the gas escaped, the foamed slag layer continued to expand and thicken. At this time, the gas generated by the metallurgical chemical reaction quickly escaped, which would push the slag out of the furnace mouth and cause explosion splashing. At this time, the probability of foam-type splashing and metal-type explosive splashing was higher. The inventor found that in the presence of foamed slag, the melting speed of the converter lime was accelerated, and the gas generated by the carbon-oxygen reaction could promote the virtuous cycle of slag breaking → slag foaming again → breaking → smelting end, which could greatly reduce the splashing accidents of the converter.

[0024] The inventor has designed a process to promote the rapid melting of lime and the formation of low-iron oxide foam slag in the initial stage of the reaction. That is, ironmaking gas ash and steel slag powder are produced into pellets in a dry powder pelletizing production line according to a certain ratio, and added together with scrap steel in the converter. In the early stage of converter smelting, the carbon element in the pellets can be used to react with the iron oxide in the pellets to form foam slag, optimize the early stage of converter smelting process, that is, the foam slag technology of electric furnace steelmaking is applied to converter steelmaking, reduce and suppress the occurrence of splashing accidents in the early stage of converter blowing. After the process technology was applied in a steel plant in Xinjiang, splashing accidents were reduced by more than 80%, and the consumption of steelmaking lime per ton of steel was reduced by more than 1.5kg.

[0025] The process principle of the present invention is:

[0026] 1. Use the iron oxides, sodium salts and potassium salts in the iron-making gas ash and the iron oxide in the steel slag powder to add into the converter in the early stage as flux to promote the melting of lime;

[0027] 2. Use the low melting point calcium ferrite in the steel slag powder as the slag in the early stage of converter blowing to form liquid basic slag, so that the lime added to the converter is immersed in the liquid basic slag to accelerate the melting of the lime;

[0028] 3. Utilize the carbon element in gas ash to form foam slag in the early stage of converter blowing to balance the FeO content in the slag and prevent the enrichment of iron oxide in the slag, which may cause splashing;

[0029] 4. Lead compounds in ironmaking gas ash are used as desiliconization and dephosphorization elements in the converter smelting process. After desiliconization and dephosphorization, most of them enter the molten steel to achieve harmless transformation of lead elements in gas ash;

[0030] 5. The carbon element in the gas ash is used to reduce part of the phosphorus and sulfur oxides in the slag to achieve the purpose of gasification desulfurization and gasification dephosphorization, weaken the reaction of phosphorus and sulfur in the steel slag concentrate that causes the molten steel to return to sulfur and phosphorus, and utilize the characteristics of potassium and sodium elements in the gas ash to increase the sulfur and phosphorus capacity of the slag, eliminating the shortcoming of increased phosphorus and sulfur content in molten steel caused by the use of steel slag concentrate in converter steelmaking;

[0031] The innovative features of the present invention are as follows:

[0032] 1. The inventors have discovered that low-melting-point minerals such as iron silicate in steel slag concentrate can form liquid basic slag after being added to the converter under the temperature conditions in the early stage of converter blowing, which can promote the melting of converter lime, so it can be used as a slag material resource for the converter;

[0033] 2. The inventors discovered that potassium and sodium elements in ironmaking gas ash are flux materials in the converter smelting process and are also elements that increase the sulfur and phosphorus content of slag. Based on this discovery, the inventors utilized ironmaking gas ash as a slag material and desulfurization and dephosphorization material for the converter;

[0034] 3. The inventor uses ironmaking gas ash and steel slag powder in a mass percentage ratio of 70%:30%, uses heavy oil as a binder to make balls, adds them into the converter along with scrap steel, and then adds molten iron. The characteristics of heavy oil are used to prevent flame and splash accidents caused by the breakage of the balls when adding molten iron;

[0035] 4. After adding the above pellets, foam slag can be formed in the early stage of converter blowing (1-3 minutes). The gas source of the foam slag is mainly provided by CO / CO2 produced by oxidation of carbon elements in gas ash. In the case of foam slag covering, the chemical reaction produced by oxygen blowing in the converter reacts rapidly at the interface of steel slag, which is conducive to the rapid melting of lime.

[0036] 5. The carbon element in the iron-making gas ash can reduce the iron oxide in the slag and prevent the enrichment of iron oxide in the slag, thereby preventing the explosive metal splashing caused by the enrichment of FeO in the slag;

[0037] 6. The carbon element in the gas ash reacts with the phosphorus and sulfur in the previous slag to achieve the purpose of gasification desulfurization and gasification dephosphorization, and the potassium and sodium elements are used to expand the phosphorus and sulfur capacity of the converter slag, eliminating the shortcoming of using steel slag fine powder to increase the phosphorus and sulfur content in the molten steel;

[0038] 7. Ironmaking gas ash contains zinc and lead compounds, which can undergo a reducing reaction in the early stage of converter smelting. Under the cover of foam slag, it can enter the molten steel and partially enter the dust removal ash, thus achieving harmless transformation of harmful substances;

[0039] 8. Using heavy oil as a binder can effectively enhance the strength of the pellets. After the pellets are added to the converter, the carbonized structure formed on the surface by the heavy oil cracking can prevent flame and splash accidents caused by adding molten iron to the converter.

[0040] According to the above innovations, the inventors process the ironmaking gas ash as follows:

[0041] 1. Mix the ironmaking gas ash and steel slag powder in a ratio of 70:30 by mass, use heavy oil as a binder, and press them into 30-50 mm pellets on a dry powder briquette machine. The carbon content in the pellets is greater than 10%. If the carbon content is insufficient, add carbonaceous materials to make up for it. There are no restrictions on other components.

[0042] 2. The above pellets are transported to the converter production line and added to the converter together with the scrap steel. The amount added is 10-25kg per ton of steel.

[0043] 3. The converter is smelted according to normal smelting process.

[0044] The beneficial contributions of the present invention are as follows: 1. Based on the principle of foam slag smelting technology of ultra-high power electric furnace, the present invention makes full use of the composition characteristics of ironmaking gas ash and steel slag powder to optimize the converter smelting process, prevent and suppress slag splashing accidents and metal splashing accidents in the early stage of converter blowing, and achieve the purpose of optimizing the converter steelmaking process by using solid waste. The converter smelting process platform is used to recycle ironmaking gas ash, which reduces the difficulty of converter smelting operation and accident losses, and saves gas ash processing costs; 2. The carbon element and potassium and sodium elements in the gas ash are used to achieve gasification desulfurization and gasification dephosphorization in the early stage of converter smelting, solve the problem of sulfur and phosphorus reversion of molten steel caused by the application of steel slag powder in converter, and solve the bottleneck problem of direct application of steel slag powder in converter smelting. 3. The current resource utilization process of ironmaking gas ash is the rotary hearth furnace and vertical furnace process. The above two processes are long, occupy a large area, require large investments, and have a long construction period, and are not suitable for urban steel mills and compact steel mills. The method of the present invention can completely solve the problem of ironmaking gas ash, which has great positive significance and significant environmental benefits. Implementation

[0045] The implementation process of the present invention is described by taking the converter production line of Yili Iron and Steel Company as an example. The configuration of the production line is: converter + LF molten steel refining + CCM continuous casting process, wherein the molten iron ratio of the converter is 80% to 85%, lime and dolomite are used for slag making of the converter, and the amount of ironmaking gas ash produced is 20kg per ton of steel. The carbon content in the ironmaking gas ash is 26%, and the TFe in the steel slag concentrate is 58%.

[0046] A process for optimizing converter steelmaking by utilizing ironmaking gas ash is implemented according to the following steps:

[0047] 1) Purchase heavy oil as a binder and transport it to the dry powder pelletizing production line for use;

[0048] 2) Transport the ironmaking gas ash and steel slag powder to the dry powder pelletizing production line for standby use;

[0049] 3) Mix the ironmaking gas ash and steel slag powder in a ratio of 70%:30% by mass, add the heavy oil as a binder, the amount of heavy oil added is 5% of the mass of the mixture of the ironmaking gas ash and steel slag powder, use a high-pressure dry powder pelletizing machine to press the mixture of the three substances into pellets with a diameter of 15 to 50 mm, and transport them to the converter smelting station for standby;

[0050] 4) When adding scrap steel to the converter, the pellets and scrap steel are added to the converter at an amount of 10-25 kg per ton of steel, wherein: the temperature of the molten iron smelted in the converter is normal, the scrap steel ratio is 10%-15%, and 15 kg-25 kg is added per ton of steel; the scrap steel ratio is 15%-20%, and 10 kg-15 kg is added per ton of steel;

[0051] 5) After adding the above pellets, the converter is smelted according to the normal smelting process.

[0052] The scrap steel ratio is the ratio of the scrap steel added to the total amount of steel material added.

Claims

1. A process for optimizing converter steelmaking using ironmaking gas ash, characterized in that Follow these steps to implement: 1) Purchase heavy oil as a binder and transport it to the dry powder pelletizing production line for use; 2) Transport the ironmaking gas ash and steel slag powder to the dry powder pelletizing production line for standby use; 3) Mix the ironmaking gas ash and steel slag powder in a ratio of 70%:30% by mass, add the heavy oil as a binder, the amount of heavy oil added is 5% of the mass of the mixture of the ironmaking gas ash and steel slag powder, use a high-pressure dry powder pelletizing machine to press the mixture of the three substances into pellets with a diameter of 15 to 50 mm, and transport them to the converter smelting station for standby; 4) When adding scrap steel to the converter, the pellets and scrap steel are added to the converter at an amount of 10-25 kg per ton of steel, wherein: the temperature of the molten iron smelted in the converter is normal, the scrap steel ratio is 10%-15%, and 15 kg-25 kg is added per ton of steel; the scrap steel ratio is 15%-20%, and 10 kg-15 kg is added per ton of steel; 5) After adding the above pellets, the converter is smelted according to the normal smelting process.