CN-117070700-B - Recycling method for directly using iron-rich red mud in converter steelmaking

Abstract

The invention relates to the technical field of comprehensive utilization of steel smelting resources, in particular to a recycling method for directly using iron-rich red mud in converter steelmaking, which comprises the following steps that slag for splashing slag to protect the converter is reserved in the converter, wherein the slag comprises MgO; adding small-granularity limestone into a converter, adding iron-rich red mud into the converter, shaking the converter for 2-3 times before and after the iron-rich red mud is added, vertically blowing nitrogen into the converter at least once by adopting a top blowing mode, wherein the nitrogen blowing time is 3-5s each time and the nitrogen blowing interval is 10s between two adjacent times, and fifthly, adding scrap steel into the converter, and after waiting for 0-5min, adding molten iron and starting blowing. According to the invention, the iron-rich red mud is directly applied to the converter steelmaking process, and dephosphorization of molten iron with higher phosphorus content can be realized without using fluxing agent.

Inventors

• WANG NIANXIN
• YUAN YUHAO
• WANG XUEBIN
• YANG GUANGYI
• WU JIANHUA
• WANG ZHONGXUE
• ZENG HUI
• ZHAO YUCHAO
• WANG XING
• LUAN JIYI
• ZHANG GE
• CHEN WANFU
• DONG HONGZHUANG

Assignees

• 山东钢铁股份有限公司

Dates

Publication Date

20260505

Application Date

20230726

Claims (4)

1. 1. The recycling method for directly using the iron-rich red mud in converter steelmaking is characterized by comprising the following steps of: firstly, reserving slag for splashing slag to protect the converter in the converter, wherein the slag comprises MgO; Step two, adding small-granularity limestone with the particle size of 5-15mm into the converter; Adding iron-rich red mud into the converter, and shaking the converter for 2-3 times back and forth after the iron-rich red mud is added; Fourthly, the converter is vertical, the oxygen lance is lowered to a converting waiting position, nitrogen is blown into the converter at least twice in a top blowing mode, the nitrogen blowing time is 3-5s each time, and the interval between two adjacent times of nitrogen blowing is 10s; Step five, adding scrap steel into a converter, adding molten iron after waiting for 1-5min and starting converting, wherein in the initial stage of converting, the converting gun is 100mm lower than the normal gun position, in the middle and later stages of converting, the converting gun position is 50-300mm higher than the gun position in the initial stage of converting, and before reaching the converting end point, the oxygen gun is lowered to a carbon pulling gun position; The mass of slag reserved in the converter is 5-9 tons, the capacity of the converter is 120-210 tons, the mass of the small-granularity limestone is 0.3-1 ton, the mass fraction of scrap steel in the fifth step is 10-35 percent of that of molten iron, a slag former is added in the initial stage of blowing, and the slag former comprises active lime.
2. 2. The recycling method for directly using iron-rich red mud in converter steelmaking as set forth in claim 1, wherein the iron-rich red mud is solid waste of alumina produced by a Bayer process, and the iron-rich red mud comprises the following components in mass fraction ：Fe 2 O 3 40%-60%,SiO 2 5%-20%,Al 2 O 3 15%-20%,CaO 5%-10%,Na 2 O 2%-10%,TiO 2 1%-10%.
3. 3. The recycling method for directly using iron-rich red mud in converter steelmaking as set forth in claim 1, wherein the nitrogen blowing times in the fourth step are 2-5 times.
4. 4. The recycling method for directly using iron-rich red mud in converter steelmaking as set forth in claim 1, wherein the flow rate of nitrogen in the fourth step is 15000-20000m 3 /h.

Description

Recycling method for directly using iron-rich red mud in converter steelmaking Technical Field The invention relates to the technical field of comprehensive utilization of iron and steel smelting resources, in particular to a recycling method for directly using iron-rich red mud in converter steelmaking. Background Red mud is an industrial solid waste discharged when alumina is extracted in the aluminum production industry, and is named as red mud because of the large content of ferric oxide and similar appearance to red mud. In recent years, along with the continuous development of aluminum industry in China, the red mud production is larger and larger, and the current red mud treatment method is mainly used for piling, and is also applied to preparing building materials, adsorption materials and silicon-calcium agricultural fertilizers. Because red mud is insoluble in water and is strongly alkaline, the red mud is required to be subjected to complex pretreatment in the fields of construction, environmental protection, agriculture and the like, the treatment process is long, and the energy consumption and the cost are high, so that the difficulty of industrialized large-scale digestion of the red mud is high, and the comprehensive utilization rate of the red mud is less than 5%. The largest alumina industrial system in the world is owned in China, 0.8-1.5 tons of red mud is produced every 1 ton of alumina, the annual output of the alumina in 2021 reaches 7748 ten thousand tons, meanwhile, the red mud is discharged by about 1 hundred million tons, and the pressure for absorbing the red mud is huge. In converter steelmaking, molten iron, scrap steel and ferroalloy are used as main raw materials, oxygen is blown into the molten raw materials, and impurities in the raw materials are oxidized. Because the impurities emit a large amount of heat in the oxidation process, the temperature in the furnace is high enough, and therefore, the converter steelmaking is completed without the help of external energy sources. With the development of the metallurgical industry, non-renewable resources are becoming depleted, and the phosphorus content in iron and steel raw materials is increasing, which results in higher phosphorus content in molten iron added to the converter. It is known that dephosphorization requires both oxidation of phosphorus and formation of stable phosphate in slag, dephosphorization is a slag-steel interface reaction, and must cause alkaline oxidation slag to dephosphorize, dephosphorization is a strong exothermic reaction, a lower temperature is favorable for dephosphorization, and reverse back-phosphorus reaction may occur when the temperature is too high. Therefore, the dephosphorization needs lower temperature, oxidizing atmosphere and alkaline environment, and the traditional converter steelmaking process cannot meet the dephosphorization of the molten iron with higher phosphorus content due to higher temperature in the converter. In order to remove higher content of phosphorus in molten iron, the prior art mostly adopts a method of adding a slag melting dephosphorizing agent in the converter steelmaking process. The slag-melting dephosphorizing agent generally comprises a plurality of components such as an oxidant, a slag-forming agent, a fluxing agent and the like, wherein the fluxing agent generally adopts fluorite, the fluorite is also called fluorite, the main component of the fluorite is calcium fluoride (CaF 2), and the fluorite has good slag-melting fluxing effect, but the calcium fluoride can generate a large amount of fluoride including HF, siF 4、MgF2 and the like at high temperature in a furnace. HF. Gaseous phase fluorides such as SiF 4 and the like can destroy an ozone layer when entering the atmosphere, and solid phase fluoride MgF 2 can exist in waste slag and enter soil, so that serious pollution is caused to the environment. The addition of the fluxing agent not only increases dephosphorization cost, but also introduces impurities containing fluorine elements, which is unfavorable for recycling waste steel, and at the same time, threatens environmental pollution. Disclosure of Invention Aiming at the problems that the recycling rate of the iron-rich red mud is not high and the harmless dephosphorization of the molten iron with higher phosphorus content is difficult to realize in the converter steelmaking process in the prior art, the invention provides a recycling method for directly using the iron-rich red mud in the converter steelmaking process, and the dephosphorization of the molten iron with higher phosphorus content can be realized without using fluxing agent. A recycling method for directly using iron-rich red mud in converter steelmaking comprises the following steps: firstly, reserving slag for splashing slag to protect the converter in the converter, wherein the slag comprises MgO; Step two, adding small-granularity limestone with the particle size of 5-15mm into the