Method for improving stability of converter steel slag by using red mud

Abstract

The invention discloses a method for improving the stability of converter steel slag by using red mud, which comprises the following steps: adding waste coal tar into the red mud generated in the electrolytic aluminum industry, pressing into pellets, adding the pellets into converter liquid-state steel slag in the converter deslagging process link, and reacting Al2O3 and SiO2 in the red mud with f-CaO and f-MgO3CaO.SiO2 in the converter steel slag to obtain the stability of the converter steel slag. And meanwhile, the waste coal tar reacts with Fe2O3 in the red mud and the steel slag to recover the iron element in the red mud, so that the recovery efficiency of the iron element in the steel slag is improved, and the strength of cross innovation of technologies in different fields is manifested.

Description

Technical Field

[0001] The invention relates to a method for improving the stability of converter slag by utilizing red mud. Background Art

[0002] Red mud is the gray and dark red powder left after alumina is produced from bauxite. Its color varies depending on its iron content. Red mud is a porous structure with a large internal surface area and a porosity ratio of 2.53 to 2.95. A sludge-like, strongly alkaline solid waste, red mud is an essential byproduct of alumina production. Generally, 1.0 to 1.8 tons of red mud are produced for every ton of alumina produced. Currently, most companies first store red mud in open-air dams, then recycle it for resource utilization or disposal. References (1) Wang Lu, Hao Yanzhong, and Hao Zengfa published a paper titled "Progress in the Extraction and Comprehensive Utilization of Valuable Metals in Red Mud" in the 8th issue of the Journal of China Nonferrous Metals in 2018. The paper states: "The development and utilization of red mud is a global problem. The ideal utilization technology should achieve large processing capacity, simple process, and no secondary pollution. At present, the treatment of red mud is to use it as a raw material as a whole and to extract its useful components. The use of red mud as a mineral raw material as a whole has been applied in industrial production and has achieved certain results. However, As for high value-added products such as precious metals, their economic efficiency is poor due to the processing cost and product value. They have not been widely used in industrial production and remain at the research stage. The recovery of precious metals is mainly divided into pyrometallurgy and hydrometallurgy. Among them, pyrometallurgy was proposed by foreign scholars many years ago and has a relatively mature process. Its advantage is that it can recover metals such as iron, aluminum, titanium, and scandium in steps. However, it has the disadvantages of high energy consumption, complex process, and the generation of a large amount of waste gas causing secondary pollution, which is not in line with the concept of green environmental protection. "Content description; (2) Zhu Qiang, Qi Bo published a paper titled "Development and Current Status of Domestic Red Mud Comprehensive Utilization Technology" in the 8th issue of "Light Metals" magazine in 2009. The paper stated: "The comprehensive utilization of red mud is a technical challenge that spans multiple technical fields and disciplines. For a long time, professional workers at home and abroad have done a lot of work on the comprehensive utilization of red mud and achieved some application results. In particular, relatively successful applications have been achieved in technical fields such as red mud ingredients for cement production and red mud as road construction materials. The consumption of red mud is also relatively large, but most research results have not been realized in industry due to economic cost factors."

[0003] It can be seen from the above literature that there is currently no process for co-processing red mud using steel slag.

[0004] Steel slag is a by-product of the steelmaking process. It contains a large amount of waste heat that is difficult to utilize. In addition, the basicity of steel slag is relatively high. The presence of f-CaO and f-MgO in steel slag affects the safety of its resource utilization. Currently, there has been a large amount of scientific research on using steel slag modification technology to solve the problem of steel slag stability, but there has been no demonstration project introduction for industrial application. Literature review (1) Xu Ying, Wang Qiaoling, Hu Chenguang, and Zhang Zizi published a paper titled "Research Progress on Online Reconstruction Technology of Liquid Steel Slag" in the 2nd issue of "Comprehensive Utilization of Minerals" in 2019. The paper states: "This paper briefly describes the characteristics and existing problems of steel slag, and focuses on the effects of tempering components, temperature system, cooling system, atmosphere system, mixing system, process equipment, and thermodynamic and kinetic research on the gelling activity and volume stability of reconstructed steel slag in the online reconstruction of liquid steel slag; finally, the development trend of online reconstruction of steel slag is prospected based on the problems existing in online reconstruction of steel slag and the more advanced technologies in the steel industry." The paper does not mention the use of steel slag to treat Bayer red mud; (2) Yang Jun published a paper titled "Expansion phase of steel slag and its influence on the volume stability of cement" in the 10th issue of "Cement" in 2009. The following content states: "The lime and RO phases in steel slag dissolve some stable impurity ions, reducing their overall reactivity with water. However, due to the uneven slag formation process, the lime and RO phases contain varying amounts of stable impurity ions dissolved in their microcrystals, and their hydration abilities vary. The lime phase, composed primarily of CaO, has a high overall reactivity and can be hydrated under boiling conditions. The RO phase, composed primarily of MgO and FeO, has a low overall reactivity, and only a small portion hydrates under autoclaving conditions. The RO phase only affects the autoclave stability of cement and is not the primary cause of poor cement stability. The lime phase is the primary factor affecting the boiling and autoclave stability of cement. The boiling and autoclave stability of steel slag cement are related not only to the composition of the lime and RO phases in the slag but also to the slag dosage." The article also fails to mention the process technology for red mud stabilization of converter slag.

[0005] In summary, there is currently no process for treating converter slag using red mud stabilization. Summary of the Invention

[0006] The present invention aims to provide a method for improving the stability of converter slag by utilizing red mud, which can degrade f-MgO, f-CaO and 3CaO·SiO2 in the converter slag, reduce the f-MgO and f-CaO in the converter slag, and improve the safety of the converter slag resource utilization process.

[0007] The technical solution adopted by the present invention is a method for improving the stability of converter slag using red mud, which is implemented according to the following steps: 1) The red mud after filtration and dehydration is transported to the high-pressure dry powder briquetting machine production line for standby use; 2) Transport the waste coal tar to the high-pressure dry powder briquetting machine production line for standby use; 3) After mixing red mud and waste coal tar in a mass percentage of 85%:15%, press them into red mud pellets with a particle size of 15-30mm on a high-pressure dry powder pelletizer, and transport them to the steelmaking slag tapping point; 4) During the slag tapping process of the converter, add the red mud pellets into the slag pot along with the slag flow, adding 500kg to 800kg of red mud pellets per ton of liquid slag; 5) After the slag is discharged, keep the slag pot still for 120 to 180 minutes, and then treat it according to the traditional hot smoldering or hot pouring slag treatment; 6) After the slag treatment is completed, the iron-containing elements are recovered by magnetic separation on the magnetic separation production line, and the remaining tailings are normally used as raw material resources in the fields of building materials, cement production, road and bridge construction, etc.

[0008] This invention studies the main factors contributing to converter slag instability and the characteristics of red mud. It proposes a method for pelletizing red mud with waste coal tar and adding it to liquid high-temperature converter slag. The f-CaO, f-MgO, and 3CaO·SiO2 in the high-temperature converter slag react with Al2O3 and SiO2 in the red mud to form slag. The carbon and hydrogen elements from the cracked coal tar react with the RO phase to convert the red mud into components of the slag, eliminating the instability of the converter slag. Simultaneously, the high-valent iron oxides in the converter slag and red mud are reduced with coal tar, converting them into metallic iron or magnetic low-valent iron. The slag is then treated using standard water quenching or slow cooling processes. The treated slag is then subjected to magnetic separation to extract the iron-containing elements for recycling. The components of the Bayer process red mud are then converted into components of the slag, which can be used, along with the slag, as raw materials for building materials, cement, roads, and other applications. This technology not only eliminates instability factors for the resource utilization of slag but also recovers valuable components from the red mud. According to this technology, each ton of liquid steel slag can process 500kg to 800kg of Bayer red mud, enabling large-scale application of red mud.

[0009] The present invention uses red mud as the main raw material and adds some waste coal tar as a binder to form red mud into pellets. During the slag discharge process of converter steelmaking, the red mud is added to the slag pot along with the slag flow. The slag pot is then kept stationary for 120 to 180 minutes. The steel slag is then processed according to the traditional hot slagging process or hot slagging process. During the hot slagging process or hot slagging process, the iron-containing elements are magnetically separated and recovered on the magnetic separation production line according to the traditional magnetic separation process. The remaining tailings can be used as a raw material resource in the fields of building materials, cement, road construction, etc.

[0010] The innovative points of the present invention are as follows: 1. The inventors discovered that the alkali metal sodium oxides in red mud can chemically react with waste coal tar to form stable fatty acid salts, which serve the purpose of binding red mud powder into pellets. In addition, the waste coal tar is cracked upon heating to generate reducing substances that react with metal oxides in red mud and steel slag, thereby achieving the purpose of recovering metallic iron from the red mud and steel slag. 2. The present invention utilizes the heat energy of high-temperature steel slag as chemical heat for the slagging reaction between red mud and steel slag, thus achieving the goal of resource utilization of steel slag waste heat; 3. The present invention utilizes Al2O3 and SiO2 contained in red mud to react with f-MgO and 3CaO·SiO2 in converter slag, which is one of the most effective process methods for eliminating the unstable factors of converter slag; 4. After the sodium salt in red mud enters the steel slag, it can increase the activity of the hydration reaction of the converter steel slag, which is beneficial to the resource utilization of the steel slag; 5. The present invention applies the roasting magnetization and carbon thermal reduction reaction of the sintering process in the steel industry to steel slag to collaboratively treat red mud, which can achieve better process effects than the current use of rotary kilns to treat red mud.

[0011] 6. After the red mud is pelletized and the pellets are added to the liquid steel slag, the gaps between the pellets expand the reaction interface between the red mud and the steel slag for slagging reaction, which is beneficial to the chemical reaction between the liquid steel slag and the red mud.

[0012] The beneficial effects of the present invention are as follows: 1. The content of f-MgO and f-CaO in converter slag is currently high, and f-CaO is also precipitated during the phase transformation of 3CaO·SiO2 in converter slag to 2CaO·SiO2 during the cooling process. The present invention can effectively degrade f-MgO in converter slag. , f-CaO and 3CaO·SiO2, reducing f-MgO and f-CaO in converter slag, and improving the safety of the converter slag resource utilization process; 2. The present invention can make full use of the waste heat of converter slag, and apply the slag-forming reaction principle, roasting magnetization principle and carbon thermal reduction reaction principle of converter slag to the resource utilization of valuable elements in red mud. The above reactions can absorb a large amount of steel slag waste heat, which can reduce water consumption in the steel slag treatment process and help reduce the cost of steel slag treatment; 3. Red mud is a large amount of solid waste in the aluminum industry production process. The present invention uses steelmaking slag to treat red mud on a large scale. By adding 500kg to 800kg of red mud balls per ton of liquid slag, China's steel industry can collaboratively process more than 50 million tons of red mud each year, which can effectively alleviate the process difficulties in the resource utilization of red mud. DETAILED DESCRIPTION

[0013] Example

[0014] The present invention is described by taking a 250-ton converter production line of a certain factory as an example. The converter slag capacity per ton of the converter is 120 kg, the slag capacity per furnace is 30 tons, the tapping temperature during the smelting process is 1650°C, and the slag temperature is between 1700 and 1750°C.

[0015] A method for improving the stability of converter slag using red mud is implemented according to the following steps: 1) The red mud after filtration and dehydration is transported to the high-pressure dry powder briquetting machine production line for standby use; 2) Transport the waste coal tar to the high-pressure dry powder briquetting machine production line for standby use; 3) After mixing red mud and waste coal tar in a mass percentage of 85%:15%, press them into red mud pellets with a particle size of 15-30mm on a high-pressure dry powder pelletizer, and transport them to the steelmaking slag tapping point; 4) During the slag tapping process of the converter, add the red mud pellets into the slag pot along with the slag flow, adding 500kg to 800kg of red mud pellets per ton of liquid slag; 5) After the slag is discharged, keep the slag pot still for 120 to 180 minutes, and then treat it according to the traditional hot smoldering or hot pouring slag treatment; 6) After the slag treatment is completed, the iron-containing elements are recovered by magnetic separation on the magnetic separation production line, and the remaining tailings are normally used as raw material resources in the fields of building materials, cement production, road and bridge construction, etc.

Claims

1. A method for improving the stability of converter slag using red mud, characterized in that Follow these steps to implement: 1) The red mud after filtration and dehydration is transported to the high-pressure dry powder briquetting machine production line for standby use; 2) Transport the waste coal tar to the high-pressure dry powder briquetting machine production line for standby use; 3) After mixing red mud and waste coal tar in a mass percentage of 85%:15%, press them into red mud pellets with a particle size of 15-30mm on a high-pressure dry powder pelletizer, and transport them to the steelmaking slag tapping point; 4) During the slag tapping process of the converter, add the red mud pellets into the slag pot along with the slag flow, adding 500kg to 800kg of red mud pellets per ton of liquid slag; 5) After the slag is discharged, keep the slag pot still for 120 to 180 minutes, and then treat it according to the traditional hot smoldering or hot pouring slag treatment; 6) After the slag treatment is completed, the iron-containing elements are recovered by magnetic separation on the magnetic separation production line, and the remaining tailings are normally used as raw material resources in the fields of building materials, cement production, road and bridge construction, etc.