A method for recycling and utilization of iron-rich red mud in the iron and steel industry

Abstract

The present invention discloses a method for recycling rich iron red mud in the iron and steel industry. The present invention innovatively proposes adding rich iron red mud into a slag ladle and / or a ladle, mixing it with recycled refining slag, and using the heat of the recycled slag for premelting to form complex calcium ferrite with a low melting point phase, thus realizing a new idea of "double recycling" of rich iron red mud and refining slag. The premelted slag formed in the slag ladle is added to the converter, which is beneficial to the rapid slag melting of the slag in the early stage of converter blowing, improving the dissolution rate of lime as a slag-making material and the converter dephosphorization rate, and reducing the consumption of slag-making materials such as lime; the premelted slag formed in the ladle can provide favorable conditions for slag melting in the ladle dephosphorization and refining processes. The present invention realizes the common recycling of refining slag and rich iron red mud, achieving the purpose of disposing of rich iron red mud and recovering the molten steel remaining in the ladle, iron resources, and valuable minerals.

Description

Technical Field

[0001] The present invention relates to the field of comprehensive utilization of iron and steel smelting resources, and specifically relates to a method for recycling rich-iron red mud in the iron and steel industry. Background Art

[0002] The solid waste discharged during the extraction of alumina from bauxite is commonly known as "red mud". Approximately 0.8 - 2.0 tons of red mud is generated for every 1 ton of alumina produced, and the global cumulative stockpile of red mud exceeds 5 billion tons. Alumina plants generally use methods such as building platforms on flat ground, damming river valleys, and filling depressions to store red mud. This not only occupies and pollutes a large amount of land, posing serious potential risks to the ecological environment, but also represents a waste of resources. Currently, the comprehensive utilization rate of red mud in China is less than 5%. Given the long process, high energy consumption, and high cost of the end-treatment methods for red mud, it is difficult to industrially dispose of red mud on a large scale. Adhering to the principle of circular economy, focusing on the clean production process of alumina, carrying out steel-aluminum collaboration, researching the reduction of red mud at the source and the high-quality recycling of valuable minerals, and realizing the disposal of rich-iron red mud in the iron and steel industry is an effective way to solve the "red mud problem".

[0003] The applicant's previous patent CN105238902A disclosed an iron melt pretreatment desiliconization / dephosphorization agent, which is composed of high-iron red mud and lime particles mixed in a mass ratio of 1:(0.2 - 0.3); the TFe content in the high-iron red mud is 40 - 50 wt%. The patent also disclosed the usage method of this iron melt pretreatment desiliconization / dephosphorization agent, and the steps are as follows: Determine whether to perform desiliconization operation alone, dephosphorization operation, or both operations according to the requirements of the steel grade for steelmaking and the conditions of the iron melt entering the station. When high-iron red mud is used as a desiliconization / dephosphorization agent for iron melt pretreatment, it can prevent the slag from foaming and prevent the slag from overflowing from the iron melt furnace, and has good desiliconization and dephosphorization effects. On this basis, the applicant continues to research the method for recycling rich-iron red mud in the iron and steel industry, with the expectation of obtaining more ways to recycle rich-iron red mud and improving the comprehensive utilization rate of red mud.

[0004] Converter slag formation is to add slag-making agents into the converter, and then melt the slag-making agents through the exothermic oxidation reaction to form a composite slag with high alkalinity and high oxidizing property for dephosphorization and desulfurization. The molten slag plays a huge role in refining the molten steel. Production practice has proved that forming a slag with relatively high alkalinity, strong oxidizing property, appropriate slag amount, good fluidity, and foaming is an important prerequisite for producing good-quality steel.

[0005] The refined slag after being treated by the LF refining furnace has the characteristics of high alkalinity, low oxidability, and low melting point. At the same time, due to its special composition, it is particularly prone to pulverization. The recycling of refined slag means that instead of pouring the steel slag in the ladle after continuous casting into the slag pot, it is directly poured into an empty ladle (or into the ladle after tapping) before tapping, for the recycling of the ladle pouring residue and refined slag, realizing the recycling of the so-called "waste slag". The recycling of refined slag can save slag-making materials, reduce the consumption of lime and fluorite; reduce the erosion of the furnace lining by the slag during the refining process, improve the ladle lining life and the desulfurization ability and deoxidation and inclusion adsorption ability of the next furnace. At the same time, the recycling of hot refined slag can also increase the slag formation speed, reduce the power consumption for melting slag materials, realize the recycling of the remaining molten steel after pouring, further improve the metal yield, and reduce the emission of industrial waste.

[0006] The iron-rich red mud contains components such as Fe2O3, CaO, Al2O3, SiO2, etc., and can form calcium ferrite under certain conditions and temperature. It is considered that the formation of calcium ferrite SFCA is the result of the following several reactions: the formation of CaO·Fe2O3 (1050 - 1150 °C); the reaction of Al2O3 with CaO to form calcium aluminate (1100 - 1150 °C); calcium aluminate melts in CaO·Fe2O3 (1100 - 1150 °C) to form monocalcium ferrite aluminate; monocalcium ferrite aluminate melts and reacts with Fe2O3 to form hemicalcium ferrite aluminate (1200 - 1250 °C); then it reacts with SiO2 to form SFCA (1200 - 1250 °C). When Mg is contained in the slag, the formed magnesium-containing calcium ferrite is called SFCAM, and the low-melting-point phases of SFCA and SFCAM are well-known good slagging agents and dephosphorizing agents.

[0007] Based on the above analysis, the recycling and utilization of iron-rich red mud in the iron and steel industry has high feasibility. Summary of the Invention

[0008] Aiming at the deficiencies of the above-mentioned prior art, the present invention provides a method for recycling and utilization of iron-rich red mud in the iron and steel industry. The present invention adds iron-rich red mud into the slag pot and / or the ladle, mixes it with the recycled refined slag, and uses the heat of the recycled slag for premelting to form low-melting-point calcium ferrite. Adding the premelted slag formed in the slag pot into the converter is beneficial to the rapid slag formation in the early stage of converter blowing, improving the dissolution rate of lime as the slag-making material and the converter dephosphorization rate, and reducing the consumption of slag-making materials such as lime; forming the premelted slag in the ladle can provide favorable conditions for slag formation in the ladle dephosphorization and refining processes. The present invention realizes the common recycling of refined slag and iron-rich red mud, achieving the purpose of disposing of iron-rich red mud and recycling the remaining molten steel, iron resources, and valuable minerals in the ladle.

[0009] The technical solution of the present invention is as follows: A method for recycling iron-rich red mud in the iron and steel industry, characterized in that the iron-rich red mud is added into a slag ladle and / or a ladle, and the refining slag and part of the molten steel remaining after continuous casting in the ladle are poured into it, mixed evenly, and pre-melted using the heat of the refining slag to form calcium ferrite with a low melting point phase.

[0010] The iron-rich red mud used in the present invention is a solid waste produced by the Bayer process for producing alumina, and its composition is: Fe2O3: 40-60 wt%, SiO2: 5-20 wt%, Al2O3: 15-20 wt%, CaO: 5-10 wt%, Na2O: 2-10 wt%, TiO2: 1-10 wt%, and the remaining components <5 wt%. Considering its physical properties, after air-drying or drying, it is packed in bags (10 kg or 20 kg per bag, convenient for manual input), ensuring convenient transportation, avoiding spillage during the transfer process, and at the same time saving the cost of pelletizing and briquetting in the traditional utilization of red mud.

[0011] The refining slag used in the present invention has a CaO content of 45-50 wt%, an MgO content of 5-10 wt%, and an SiO2 content of 6-9 wt%.

[0012] The iron-rich red mud in the present invention contains Fe2O3 and CaO, and the CaO content in the refining slag is high. At the same time, small-grained limestone decomposes upon heating to produce CaO. According to the composition of the iron-rich red mud and the number of cycles of the refining slag, it is calculated that after adding and pre-melting according to the molar ratio of Fe2O3 to CaO of 1:0.9-1, the optimal range and conditions for generating calcium ferrite can be ensured.

[0013] Among them, the method for recycling iron-rich red mud by adding it into a slag ladle is characterized by including the following steps:

[0014] 1) Uniformly spread small-grained limestone with a particle size of 5-15 mm at the bottom of the slag ladle; add bagged iron-rich red mud, level it, and evenly cover it on the small-grained limestone.

[0015] 2) After continuous casting is completed, slowly pour the refining slag and part of the molten steel remaining after casting in the ladle into the slag ladle; after the refining slag is poured out, cover the slag ladle with a ladle cover for heat preservation and pre-melting to prevent heat loss and waste.

[0016] 3) After 2-3 hours, knock out the pre-melted slag in the slag ladle; then directly load the poured red-hot pre-melted slag into a scrap steel bucket with a forklift and add it to the converter for smelting together with the scrap steel.

[0017] Further, during the process of pouring refining slag into the slag pot, the agitation of the slag is started, and the refining slag is mixed with iron-rich red mud. Meanwhile, small-sized limestone decomposes when heated to produce CaO and CO2, and the floating CO2 gas further plays a role in agitation. At the same time, it effectively avoids the sticking of slag to the slag pot, which is conducive to the separation of pre-melted ore and the slag pot. The heat, oxidizing property, relatively high slag basicity, relatively high contents of MgO and SiO2 in the slag, and relatively high content of Al2O3 in the iron-rich red mud, etc., form a low-melting-point red mud-based calcium ferrite pre-melted slag after pre-melting in the slag pot for a certain period of time.

[0018] Further, the pre-melted slag with a smaller particle size is packed in small bags and added into the ladle to promote slag melting during refining, realizing the efficient and full recycling of the pre-melted slag.

[0019] Further, the pre-melted red mud-based calcium ferrite has a relatively low melting point. After the converter starts blowing, a well-melted early slag is quickly formed. After adding active lime, it has a large contact area in the liquid slag and is easy to dissolve. At the same time, the relatively high iron oxide in the calcium ferrite can quickly reduce the melting point of calcium oxide, promoting the rapid dissolution of lime. Due to the active slag and good slag melting, the oxidation reaction is accelerated and the blowing efficiency is improved. At the same time, due to good slag melting, the relatively high slag basicity, fluidity and oxidizing property provide good conditions for phosphorus removal by the slag in the early stage of blowing, and the phosphorus removal rate is significantly increased.

[0020] Among them, the method for recycling iron-rich red mud by adding it into the ladle is characterized by including the following steps (taking a 120-ton converter as an example):

[0021] 1) Before tapping, first add bagged iron-rich red mud into ladle 1; turn on the bottom argon blowing of the ladle before pouring the refining slag, and control the gas flow rate at 30 - 40 L / min and the argon pressure at 0.5 - 0.6 MPa;

[0022] 2) After continuous casting pouring is completed, lift ladle 2 with refining slag and part of the remaining molten steel after pouring to above ladle 1;

[0023] 3) Slowly and steadily pour the molten slag in ladle 2 into ladle 1 in a small stream; at the same time, continuously put in bagged iron-rich red mud, and adjust the bottom argon blowing gas flow rate of the ladle to 50 - 60 L / min; after pouring, adjust the bottom argon blowing gas flow rate of the ladle to 10 - 20 L / min to reduce heat loss;

[0024] 4) Cover the ladle heat preservation cover for heat preservation and pre-melting, and wait for tapping;

[0025] 5) Before starting to tap, drive the ladle car to the specified position under the furnace, adjust the bottom argon blowing gas flow rate of the ladle to 60 - 80 L / min, and start tapping; during tapping, add active lime according to the process requirements;

[0026] 6) 10 - 20 seconds before the end of tapping, adjust the flow rate of argon blown from the bottom of the ladle to 10 - 20 L / min; after tapping ends, close the argon blown from the bottom of the ladle.

[0027] Furthermore, waiting for the tapping moment, conditions such as appropriate slag temperature in the ladle, relatively high slag basicity and oxidizability, relatively high contents of MgO and SiO2 in the slag, and relatively high content of Al2O3 in the red mud are all conducive to the formation of low - melting - point composite calcium ferrite. The waiting before tapping also provides sufficient pre - melting time, providing favorable conditions for dephosphorization in the ladle and slag melting in the subsequent refining process.

[0028] The technical principle of the present invention is:

[0029] Fe2O3, CaO, Al2O3, SiO2, etc. contained in the iron - rich red mud are all important components of converter slag. After the ladle is emptied after continuous casting, the refining slag in the ladle is poured into a slag basin and mixed with the iron - rich red mud. The temperature after mixing is basically 1200 - 1300 °C. Appropriate slag temperature, relatively high slag basicity and certain oxidizability in the refining slag, relatively high contents of MgO and SiO2 in the slag, and relatively high content of Al2O3 in the red mud provide good conditions for the formation of low - melting - point composite calcium ferrite SFCA (see the formation of the above - mentioned composite calcium ferrite SFCA). Al2O3 in the slag also plays a good role in promoting slag melting. In the present invention, the iron - rich red mud is mixed with the recycled refining slag in the slag basin and pre - melted using the heat of the recycled slag to form low - melting - point composite calcium ferrite SFCA. Then, this pre - melted slag is added to the converter, which is conducive to the rapid melting of the slag in the early stage of converter blowing, improving the dissolution rate of lime as a slag - forming material and the converter dephosphorization rate, reducing the consumption of slag - forming materials such as lime, and at the same time realizing the disposal of iron - rich red mud and the recovery and utilization of valuable minerals, with significant economic and social benefits.

[0030] In combination with the recycling of refining slag, the present invention directly adds iron-rich red mud into a ladle, mixes and co-melts it with the oxidizing refining recycled slag poured into the ladle, and uses the heat of the refining slag and the ladle to pre-melt to form red mud-based calcium ferrite, promoting slag melting in the ladle and refining molten steel, realizing the recycling of rich iron resources and valuable minerals in the red mud, achieving the purpose of disposing of the red mud, while improving the phosphorus removal effect of the ladle, improving the refining efficiency, and reducing the refining cost. After the continuous casting machine finishes pouring, the temperature of the ladle slag in the ladle is about 1300°C to 1400°C. Pour the ladle slag together with the remaining part of the residual molten steel after pouring into another ladle prepared for tapping, and at the same time manually add bagged iron-rich red mud, use the potential energy of the ladle slag during slag pouring to perform impact mixing and stirring evenly, and pre-melt in the ladle using oxidizing slag and the heat of the ladle, waiting for tapping. Components such as Fe2O3, CaO, Al2O3, and SiO2 contained in the iron-rich red mud are pre-melted with CaO, MaO, Al2O3, SiO2, etc. in the high-alkalinity recycled slag in an oxidizing slag atmosphere to form a composite calcium ferrite with a low melting point phase, which is beneficial to the rapid dissolution of the active lime added during tapping, providing favorable conditions for slag melting in the ladle phosphorus removal and refining processes.

[0031] The technical effects of the present invention are as follows:

[0032] 1. The present invention innovatively proposes the idea of "pre-melting and synthesizing red mud-based calcium ferrite by using the heat of refining slag and the conditions of iron-rich red mud". Add the iron-rich red mud into the slag pot and / or ladle, mix it with the recycled refining slag, and use the heat of the recycled slag for pre-melting to form a composite calcium ferrite with a low melting point phase, realizing the "dual recycling" of iron-rich red mud and refining slag, with significant economic and social benefits.

[0033] 2. The pre-melted slag generated by mixing the iron-rich red mud with the recycled refining slag in the slag pot is directly loaded into the scrap steel bucket for addition in converter steelmaking. This method is simple and efficient, reducing heat loss. The red mud-based calcium ferrite with a low melting point phase in the pre-melted slag is beneficial to the rapid slag melting of the slag in the early stage of converter blowing, improving the dissolution rate of the slag-making material lime, increasing the lime reaction rate and efficiency, reducing the consumption of other slag melting agents and fluxes, and being conducive to reducing the consumption cost of process auxiliary materials. Due to the rapid slag formation and good slag melting of the pre-melted slag in the converter, the slag has good fluidity, high oxidability and alkalinity, creating good phosphorus removal conditions, being conducive to rapid phosphorus removal in the early stage, and increasing the phosphorus removal rate. The slag has good slag melting, improved slag action efficiency, stable blowing, reasonable temperature rise, increased oxygen utilization rate and metal yield, reduced oxygen consumption, and shortened blowing time.

[0034] 3. In the present invention, iron-rich red mud and recycled slag are directly added to the ladle. Conditions such as the heat of the slag in the ladle, the relatively high basicity and oxidizability of the slag, the relatively high content of MgO and SiO2 in the slag, and the relatively high content of Al2O3 in the red mud are all conducive to the formation of calcium ferrite with a low melting point phase, providing favorable conditions for the recovery of iron resources and valuable minerals in the red mud, dephosphorization in the ladle, and slag melting in the subsequent refining process. The calcium ferrite with a low melting point phase is conducive to the dissolution of lime added during tapping, improving the tapping dephosphorization efficiency and the lime utilization rate, and reducing the lime consumption cost. The calcium ferrite with a low melting point phase is conducive to the fluidity of the ladle slag, improving the refining heating efficiency and the refining treatment efficiency, and reducing the consumption of refining slag-making materials and the refining power consumption.

[0035] 4. The addition method of iron-rich red mud is in bags for direct utilization, which is convenient for transportation and reduces spillage; it saves the processing costs of pelletizing and briquetting the red mud; and it improves the metal recovery rate. Specific Embodiments

[0036] The following examples are used to illustrate the effects.

[0037] The iron-rich red mud used in this example is a solid waste produced by the Bayer process for alumina production, with the following composition: Fe2O3: 40 - 60 wt%, SiO2: 5 - 20 wt%, Al2O3: 15 - 20 wt%, CaO: 5 - 10 wt%, Na2O: 2 - 10 wt%, TiO2: 1 - 10 wt%, and the remaining components < 5 wt%. After air-drying or drying, it is bagged, with each bag weighing 20 kg.

[0038] The refining slag in the ladle after continuous casting pouring in this example has a CaO content of 45 - 50 wt%, an MgO content of 5 - 10 wt%, and an SiO2 content of 6 - 9 wt%.

[0039] According to the composition of the iron-rich red mud and the number of recycling times of the refining slag, it is calculated and pre-melted after adding according to the molar ratio of Fe2O3 to CaO of 1:0.9 - 1.

[0040] Example 1: Adding iron-rich red mud to the slag pot

[0041] 1) Evenly spread 800 kg of small-sized limestone with a particle size of 5 - 15 mm at the bottom of the slag pot; add 3000 kg of bagged iron-rich red mud and also spread it flat (using a forklift), evenly covering the small-sized limestone;

[0042] 2) After continuous casting pouring, slowly pour about 5000 kg of the refining slag in the ladle (including a small amount of remaining molten steel after pouring) into the slag pot. When pouring, keep a small flow and pour slowly, and spread it back and forth to ensure the full mixing of the red mud and the refining slag; after pouring the refining slag, cover the slag pot with a pot cover for heat preservation and pre-melting to prevent heat loss and waste;

[0043] 3) After 3 hours, pour out the pre-melted slag in the slag pot. Since small-sized limestone has been spread on the bottom of the slag pot in advance, it is beneficial to the separation of the pre-melted slag from the slag pot and avoids adhesion to the slag pot.

[0044] 4) Use a forklift to directly load the poured red-hot pre-melted slag into the scrap steel bucket and add it to the converter together with the scrap steel (the mass ratio of the pre-melted slag to the scrap steel is 1:10), increasing the heat of the converter; after starting blowing, add lime as a slag-making agent according to the process requirements. The slag melting is good in the early stage, the blowing process is stable, and there is no phenomenon of splashing and back-drying; the blowing end temperature and carbon content are hit at one time. The end temperature is 1625 °C, the end carbon content is 0.08%, and the phosphorus content is 0.008%. The lime consumption is reduced by 0.2 kg / t of steel compared with the normal situation (if the red-hot pre-melted slag is not used, the normal lime consumption is 35 kg / t, and the actual consumption in this example is 34.8 kg / t), and the blowing time is shortened by 9 seconds (if the red-hot pre-melted slag is not used, the normal blowing time is 15 minutes, and the actual blowing time in this example is 14 minutes and 51 seconds).

[0045] Example 2: Adding iron-rich red mud to the slag pot

[0046] 1) Evenly spread 600 kg of small-sized limestone with a particle size of 5 - 15 mm on the bottom of the slag pot; add 4000 kg of bagged iron-rich red mud and also spread it flat (using a forklift), evenly covering the small-sized limestone.

[0047] 2) After continuous casting is completed, slowly pour about 6000 kg of refining slag (including a small amount of molten steel remaining after casting) in the ladle into the slag pot in a small stream as required; after pouring the refining slag, cover the slag pot with a pot cover for heat preservation and pre-melting.

[0048] 3) After 2.5 hours, pour out the pre-melted slag in the slag pot. Since small-sized limestone has been spread on the bottom of the slag pot in advance, it is beneficial to the separation of the pre-melted slag from the slag pot and avoids adhesion to the slag pot.

[0049] 4) Use a forklift to directly load the poured red-hot pre-melted slag into the scrap steel bucket and add it to the converter (the mass ratio of the pre-melted slag to the scrap steel is 1:15); after starting blowing, add lime as a slag-making agent according to the process requirements. The slag melting is good in the early stage, the blowing process is stable, and there is no phenomenon of splashing and back-drying; the blowing end temperature and carbon content are hit at one time. The end temperature is 1635 °C, the end carbon content is 0.085%, and the phosphorus content is 0.009%. The actual lime consumption is reduced by 0.3 kg / t of steel compared with the normal situation (if the red-hot pre-melted slag is not used, the normal lime consumption is 33 kg / t, and the actual consumption in this example is 32.7 kg / t), and the blowing time is shortened by 12 seconds (if the red-hot pre-melted slag is not used, the normal blowing time is 15 minutes and 20 seconds, and the actual blowing time in this example is 15 minutes and 8 seconds).

[0050] Example 3: Adding iron-rich red mud to the slag pot

[0051] 1) Evenly spread 700 kg of small-sized limestone with a particle size of 5 - 15 mm at the bottom of the slag pot; add 3500 kg of bagged iron-rich red mud and level it evenly (using a forklift), covering the small-sized limestone evenly on top;

[0052] 2) After continuous casting pouring is completed, slowly pour about 5000 kg of refining slag (including a small amount of remaining molten steel after pouring) in the ladle into the slag pot in a small stream as required; after pouring the refining slag, cover the slag pot with a pot lid for heat preservation and pre-melting;

[0053] 3) After 3 hours, knock out the pre-melted slag in the slag pot. Since small-sized limestone was spread at the bottom of the slag pot in advance, it is beneficial for the separation of the pre-melted slag from the slag pot and avoids adhesion to the slag pot;

[0054] 4) Directly load the poured red-hot pre-melted slag into the scrap steel bucket with a forklift and add it to the converter together with the scrap steel (the mass ratio of the pre-melted slag to the scrap steel is 1:13); after starting blowing, add lime as a slag-forming agent according to the process requirements. The slag melting is good in the early stage, the blowing process is stable, and there is no splashing or drying back phenomenon; the blowing end temperature and carbon content are hit at one time. The end temperature is 1636 °C, the end carbon content is 0.076%, and the phosphorus content is 0.010%. The lime consumption is reduced by 0.5 kg / t of molten steel compared with the normal situation (if the red-hot pre-melted slag is not used, the normal lime consumption is 34 kg / t, and the actual consumption in this example is 33.5 kg / t), and the blowing time is shortened by 10 seconds (if the red-hot pre-melted slag is not used, the normal blowing time is 15 minutes and 10 seconds, and in this example it is 15 minutes).

[0055] Example 4: Adding iron-rich red mud into the ladle

[0056] For a 120-ton converter, it specifically includes the following steps:

[0057] 1) Before tapping, use the overhead crane to lift the repaired ladle 1 to the ladle car for standby, and manually add 200 kg of bagged iron-rich red mud; turn on the bottom argon blowing of the ladle before pouring the refining slag, and control the argon gas flow rate at 30 L / min;

[0058] 2) After continuous casting pouring is completed, use the overhead crane to lift the ladle 2 with refining slag (including a small amount of remaining molten steel after pouring) above the ladle 1;

[0059] 3) Start the ladle car, and slowly and steadily pour the refining slag in ladle 2 into ladle 1 in a small stream to reduce the loss of red mud dust and environmental pollution. At the same time, manually add 300 kg of bagged iron-rich red mud in sequence. At the same time, adjust the flow rate of bottom blowing argon in the ladle to 50 L / min to prevent caking and hardening of the iron-rich red mud, which is beneficial to the uniform mixing of the iron-rich red mud and the refining slag and prevent the red mud from sticking to the bottom of the ladle. The mixing of the iron-rich red mud and the refining slag is in good uniformity. After pouring, adjust the flow rate of bottom blowing argon in the ladle to 10 L / min to reduce heat loss;

[0060] 4) Cover the ladle with a heat preservation cover for heat preservation and pre-melting. Conditions such as the appropriate slag temperature, higher slag basicity and oxidizability, higher content of MgO and SiO2 in the slag, and higher content of Al2O3 in the red mud in the ladle during the waiting time are all beneficial to the formation of low-melting-point composite calcium ferrite. The waiting before tapping also provides sufficient pre-melting time, providing favorable conditions for ladle dephosphorization and slag melting in the subsequent refining process;

[0061] 5) After 10 min, drive the ladle car to the specified position under the furnace, adjust the flow rate of bottom blowing argon in the ladle to 60 L / min, and start tapping. During tapping, add 300 kg of active lime according to the process requirements. Slag conditions such as high basicity, large slag volume, good fluidity slag and low-melting-point calcium ferrite effectively promote the removal of phosphorus from the ladle slag and inclusions in the molten steel;

[0062] 6) 10 seconds before the end of tapping, adjust the flow rate of bottom blowing argon in the ladle to 10 L / min. After tapping is completed, drive the ladle car to the hoisting position of the crane and wait for hoisting. Turn off the bottom blowing argon in the ladle before hoisting. The phosphorus content at the end of blowing is 0.010%, the phosphorus content after tapping is 0.009%, and the dephosphorization during tapping is 0.001%. The refining power consumption per ton of steel is reduced by 0.5 kW·h compared with the average value (if no iron-rich red mud and refining slag are added, the power consumption is 41.6 kW·h under normal conditions, and the actual power consumption in this example is 41.1 kW·h).

[0063] Example 5: Adding iron-rich red mud into the ladle

[0064] For a 120-ton converter, the specific steps are as follows:

[0065] 1) Before tapping, use the crane to lift the repaired ladle 1 to the ladle car for standby, and manually add 200 kg of bagged iron-rich red mud; open the bottom blowing argon in the ladle before pouring the refining slag, and control the argon gas flow rate at 40 L / min;

[0066] 2) After continuous casting pouring is completed, use the crane to lift ladle 2 with refining slag (including a small amount of remaining molten steel after pouring) above ladle 1;

[0067] 3) Start the ladle car, slowly and steadily pour the refining slag in ladle 2 into the ladle in a small stream, and at the same time, manually add 350 kg of bagged iron-rich red mud in succession. Adjust the flow rate of argon gas blown from the bottom of the ladle to 60 L / min so that the iron-rich red mud and the refining slag are well mixed. After pouring, adjust the flow rate of argon gas blown from the bottom of the ladle to 20 L / min;

[0068] 4) Cover the ladle with a heat-insulating cover for heat preservation and pre-melting, and wait for tapping. Conditions such as the appropriate slag temperature, relatively high slag basicity and oxidizability, relatively high content of MgO and SiO2 in the slag, and relatively high content of Al2O3 in the red mud in the ladle during the waiting period are all conducive to the formation of low-melting-point composite calcium ferrite. The waiting before tapping also provides sufficient pre-melting time, providing favorable conditions for dephosphorization in the ladle and slag melting in the subsequent refining process;

[0069] 5) After 8 minutes, move the ladle car to the specified position under the furnace, adjust the flow rate of argon gas blown from the bottom of the ladle to 70 L / min, and start tapping. During tapping, add 320 kg of active lime according to the process requirements;

[0070] 6) 20 seconds before the end of tapping, adjust the flow rate of argon gas blown from the bottom of the ladle to 10 L / min. After tapping is completed, move the ladle car to the position for hoisting by the crane and wait for hoisting. Turn off the argon gas blown from the bottom of the ladle before hoisting. The phosphorus content at the end of blowing is 0.012%, the phosphorus content after tapping is 0.010%, and the dephosphorization during tapping is 0.002%. The power consumption for refining per ton of steel is reduced by 0.6 kW·h compared with the average value (if iron-rich red mud and refining slag are not added, the power consumption is 41.1 kW·h under normal conditions, and the actual power consumption in this example is 40.5 kW·h).

[0071] Example 6: Adding iron-rich red mud into the ladle

[0072] For a 120-ton converter, it specifically includes the following steps:

[0073] 1) Before tapping, use the crane to hoist the repaired ladle 1 onto the ladle car for standby, and manually add 200 kg of bagged iron-rich red mud. Open the bottom argon blowing of the ladle before pouring the refining slag, and control the argon gas flow rate at 35 L / min;

[0074] 2) After continuous casting is completed, use the crane to hoist ladle 2 with refining slag (including a small amount of molten steel remaining after casting) above ladle 1;

[0075] 3) Start the crane, slowly and steadily pour the refining slag in ladle 2 into the ladle in a small stream, and at the same time, manually add 400 kg of bagged iron-rich red mud in succession. Adjust the flow rate of argon gas blown from the bottom of the ladle to 60 L / min so that the iron-rich red mud and the recycled slag are well mixed. After pouring, adjust the flow rate of argon gas blown from the bottom of the ladle to 20 L / min;

[0076] 4) Cover the ladle with a heat-insulating cover for heat preservation and pre-melting; Conditions such as appropriate slag temperature, high slag basicity and oxidizability, high contents of MgO and SiO2 in the slag, and high content of Al2O3 in the red mud in the ladle during the waiting period are all conducive to the formation of calcium ferrite with low melting point phases. The waiting before tapping also provides sufficient pre-melting time, providing favorable conditions for ladle dephosphorization and slag melting in the subsequent refining process;

[0077] 5) After 15 minutes, drive the ladle car to the specified position under the furnace, adjust the flow rate of bottom blowing argon in the ladle to 80 L / min, and start tapping; During tapping, add 260 kg of active lime according to the process requirements;

[0078] 6) 10 seconds before the end of tapping, adjust the flow rate of bottom blowing argon in the ladle to 20 L / min; After tapping is completed, drive the ladle car to the position for hoisting by the crane and wait for hoisting. Turn off the bottom blowing argon in the ladle before hoisting. The phosphorus content at the end of blowing is 0.013%, the phosphorus content after tapping is 0.009%, and the phosphorus removal during tapping is 0.004%. The power consumption for refining per ton of steel is reduced by 0.3 kW·h compared to the average value (if rich iron red mud and refining slag are not added, the power consumption is 40.8 kW·h under normal conditions, and the actual power consumption in this example is 40.5 kW·h).

Claims

1. A method for recycling and utilization of iron-rich red mud in the iron and steel industry, characterized in that, Add iron-rich red mud into the slag pot, pour the refining slag and part of the remaining molten steel in the ladle after continuous casting pouring into it, mix evenly, and use the heat of the refining slag for premelting to form calcium ferrite with low melting point phase; Specifically, it includes the following steps: 1) Uniformly lay small-grained limestone at the bottom of the slag pot, with the particle size of 5 - 15 mm; add bagged iron-rich red mud, spread it flat and evenly cover it on the small-grained limestone; 2) After continuous casting pouring is completed, slowly pour the refining slag and part of the remaining molten steel in the ladle into the slag pot; after pouring the refining slag, cover the slag pot with a pot cover for heat preservation and premelting to prevent heat loss and waste; 3) After 2 - 3 hours, knock out the premelted slag in the slag pot; then directly load the hot premelted slag poured out into the scrap steel bucket with a forklift and add it to the converter for smelting together with the scrap steel; The iron-rich red mud is a solid waste produced by the Bayer method for alumina production, and its components are: Fe2O3: 40 - 60 wt%, SiO2: 5 - 20 wt%, Al2O3: 15 - 20 wt%, CaO: 5 - 10 wt%, Na2O: 2 - 10 wt%, TiO2: 1 - 10 wt%, and the remaining components < 5 wt%; For the refining slag in the ladle after continuous casting pouring is completed, its CaO content is 45 - 50 wt%, MgO content is 5 - 10 wt%, and SiO2 content is 6 - 9 wt%; The dosages of the iron-rich red mud and the refining slag in the ladle after continuous casting pouring are compounded according to the molar ratio of Fe2O3 to CaO after compounding being 1:0.9 - 1.

2. The method for recycling iron-rich red mud in the iron and steel industry according to claim 1, characterized in that, The iron-rich red mud is used in bags after being air-dried or dried.

3. The method for recycling and utilization of iron-rich red mud in the iron and steel industry according to claim 1, characterized in that, In step 3), the premelted slag with smaller particle size is packed in small bags and added into the ladle to promote refining slag melting, realizing the efficient and full recycling of the premelted slag.

4. The method for recycling iron-rich red mud in the iron and steel industry according to claim 1, characterized in that, During the process of pouring the refining slag into the slag pot in step 2), start the stirring of the slag for flushing and mixing. The refining slag and the iron-rich red mud are mixed evenly. At the same time, the small-grained limestone decomposes when heated to produce CaO and CO2. The CO2 gas floats up to further play a stirring role, and at the same time effectively avoids the slag sticking to the slag pot, which is beneficial to the separation of the premelted ore and the slag pot.

5. A method for recycling rich iron red mud in the iron and steel industry, characterized in that, Add iron-rich red mud into the ladle, pour the refining slag and part of the remaining molten steel in the ladle after continuous casting pouring into it, mix evenly, and use the heat of the refining slag for premelting to form calcium ferrite with low melting point phase; Specifically, it includes the following steps: 1) Before tapping, first add bagged iron-rich red mud into ladle 1; open the bottom blowing argon of the ladle before pouring the refining slag, and control the gas flow rate at 30 - 40 L / min and the argon pressure at 0.5 - 0.6 MPa; 2) After continuous casting pouring is completed, lift ladle 2 with the refining slag and part of the remaining molten steel to above ladle 1; 3) Slowly and steadily pour the molten steel slag in ladle 2 into ladle 1 in a small stream; at the same time, continuously put in bagged iron-rich red mud, and adjust the bottom blowing argon gas flow rate in the ladle to 50 - 60 L / min; after pouring, adjust the bottom blowing argon gas flow rate in the ladle to 10 - 20 L / min to reduce heat loss; 4) Cover the heat preservation cover of the ladle for heat preservation and premelting, and wait for tapping; 5) Before starting to tap the steel, move the ladle car to the specified position under the furnace, adjust the flow rate of argon gas blown from the bottom of the ladle to 60 - 80 L / min, and start tapping the steel; during the tapping process, add active lime according to the process requirements. 6) 10 - 20 seconds before the end of tapping, adjust the flow rate of argon gas blown from the bottom of the ladle to 10 - 20 L / min; after the tapping is completed, turn off the argon gas blown from the bottom of the ladle. The iron-rich red mud is a solid waste produced in the production of alumina by the Bayer process, and its composition is: Fe2O3: 40 - 60 wt%, SiO2: 5 - 20 wt%, Al2O3: 15 - 20 wt%, CaO: 5 - 10 wt%, Na2O: 2 - 10 wt%, TiO2: 1 - 10 wt%, and the remaining components < 5 wt%. For the refining slag in the ladle after continuous casting pouring is completed, its CaO content is 45 - 50 wt%, MgO content is 5 - 10 wt%, and SiO2 content is 6 - 9 wt%. The dosages of the iron-rich red mud and the refining slag in the ladle after continuous casting pouring is completed are compounded according to the ratio that the molar ratio of Fe2O3 to CaO after compounding is 1:0.9 - 1.

6. The method for recycling rich iron red mud in the iron and steel industry according to claim 5, characterized in that, The iron-rich red mud is used in bags after being air-dried or dried.