Composite balling agent containing red mud and its use

Abstract

This invention discloses a composite pellet binder containing red mud and its application, belonging to the technical field of binders for metallurgical pelleting. The binder uses red mud, a waste residue from the alumina industry, as the main raw material, combined with functional additives. By mass percentage, red mud accounts for 73%~87%, with the remainder being functional additives. This invention, through multi-component synergistic formulation, solves the industry pain points of poor compatibility with strong alkalinity and insufficient self-binding performance of red mud. The prepared binder can directly replace bentonite used in pelleting, exhibiting superior pelletizing performance at the same addition amount. Simultaneously, it can increase the iron content of pellets by 0.248~0.62 percentage points, reduce ironmaking waste emissions, and possess significant environmental and economic benefits. It is compatible with existing pelleting production processes, requires no new equipment, and is easy to industrialize.

Description

Technical Field

[0001] This invention relates to the field of binders for metallurgical pelletizing, specifically to a composite pelletizing binder containing red mud, and to the application of this binder in the preparation of iron concentrate pellets. Background Technology

[0002] In the iron and steel metallurgical industry, oxidized pellets are one of the core raw materials for blast furnace ironmaking. The iron grade and metallurgical properties of the pellets directly determine the efficiency and production cost of blast furnace ironmaking. During the pellet preparation process, binders are the core auxiliary materials that ensure green pellet formation, improve green pellet strength and calcination performance. Currently, bentonite is the most widely used binder in the industry.

[0003] However, existing bentonite binders have insurmountable technical drawbacks: bentonite's main components are SiO2 and Al2O3, containing no iron. In pellet production, it is typically added at a rate of 1% to 2%, directly diluting the total iron content of the pellets. For every 1% of bentonite added, the iron content of the pellets decreases by approximately 0.6 percentage points. Simultaneously, it increases slag emissions from blast furnace ironmaking, raising energy consumption and costs. Furthermore, the reserves of high-quality metallurgical bentonite are limited, and procurement costs are rising year by year, further squeezing steel mills' profit margins.

[0004] Red mud is a highly alkaline industrial waste generated during the production of alumina. For every ton of alumina produced, 1.0 to 1.8 tons of red mud are generated. Most of the red mud is disposed of by building dams and stockpiling it, which not only occupies a large amount of land resources, but its highly alkaline leachate also causes soil and groundwater pollution, posing serious environmental and safety hazards. The high-value and large-scale resource utilization of red mud is an urgent problem to be solved in the industry.

[0005] Existing technologies include research on using red mud as a pellet binder, but they generally suffer from the following technical challenges: First, red mud itself has insufficient binding properties, requiring the addition of large amounts of bentonite or other binder materials, making it impossible to achieve a high proportion of red mud utilization and still diluting the iron content of the pellets. Second, the strong alkalinity of red mud affects pellet formation and green pellet performance. Existing solutions have not addressed the issue of adapting and adjusting the alkalinity of red mud, resulting in key indicators such as green pellet drop strength, compressive strength, and bursting temperature failing to meet the requirements of industrial production, leading to pelletizing effects far lower than those achieved with bentonite. Third, existing red mud-based binder preparation processes are complex, requiring modification and calcination of the red mud, necessitating the addition of specialized equipment, making them unsuitable for existing pelletizing processes in steel plants, and hindering industrial-scale promotion. Fourth, existing solutions fail to achieve efficient utilization of the iron-containing components in red mud, failing to simultaneously achieve the dual effects of solid waste disposal and pellet grade improvement, thus failing to balance economic and environmental benefits.

[0006] Based on this, developing a composite pellet binder with a high proportion of red mud, excellent bonding performance, complete replacement of bentonite, improved iron content of pellets, and compatibility with existing production processes is the core direction for solving the pain points of existing technologies. Summary of the Invention

[0007] The purpose of this invention is to address the aforementioned deficiencies of the prior art by providing a composite pellet binder containing red mud and its application, specifically achieving the following objectives: 1. Solve the technical problems of existing bentonite binders diluting the iron grade of pellets, increasing ironmaking waste and energy consumption, thereby improving the iron grade of pellets and reducing ironmaking production costs.

[0008] 2. Solve the environmental pollution problem caused by red mud stockpiling, and realize the high proportion and high value of red mud resource utilization. The proportion of red mud in binders can reach up to 87%.

[0009] 3. To address the issues of insufficient bonding performance, poor pelletizing effect, and inability of key performance indicators to meet the requirements of industrial production of existing red mud-based binders, a multi-component synergistic formulation is adopted to achieve bonding performance superior to that of bentonite of the same dosage.

[0010] 4. To address the issues of complex processes and incompatibility with existing pellet production processes of red mud-based binders, a binder solution with a simple preparation process that can directly replace bentonite and requires no additional equipment is provided, thereby reducing the difficulty of industrialization.

[0011] 5. Balancing environmental and economic benefits, it improves the economic benefits of steel plants while disposing of large quantities of solid waste.

[0012] To achieve the above objectives, the present invention provides the following technical solution: A composite pellet binder containing red mud, comprising the following components by mass percentage: 73%~87% red mud, 5%~10% sodium humate, 2%~4% sodium carbonate, 2%~5% starch, 2%~3% sodium polyacrylate, 1%~3% tripolymethicone, and 1%~2% carboxymethyl cellulose, with the sum of the mass percentages of each component being 100%. The red mud is an industrial waste residue generated during the alumina production process, in which the Fe2O3 mass content is 20%~55%.

[0013] Furthermore, the pretreatment parameters of the red mud are: initial moisture content of 18%~22%, moisture content controlled at 13%~15% after drying, and particle size of -200 mesh ≥70%.

[0014] The preparation method of the above-mentioned composite pellet binder containing red mud includes the following steps: S1 Red Mud Pretreatment: Red mud with an initial moisture content of 18%~22% is dried to control the moisture content after drying to 13%~15%. The particle size of the red mud is tested to ensure that the proportion of -200 mesh is ≥70%, without the need for additional crushing.

[0015] S2 ambient temperature mixing: According to the preset ratio, the pretreated red mud and all additives are added to the mixing equipment at ambient temperature and mixed until the materials are uniform to obtain a mixture.

[0016] S3 Grinding Process: The mixed materials are fed into a Raymond mill for grinding. The particle size of the material after grinding is controlled to be 93%~95% of -200 mesh, which yields the finished composite pellet binder, which is then packaged and stored.

[0017] The application of the above-mentioned composite pellet binder containing red mud is as follows: the composite pellet binder is applied to the preparation process of iron concentrate pellets. The amount of binder added is 0.8% to 2% of the total mass of iron concentrate. The binder directly replaces an equal amount of composite bentonite, is compatible with the existing production equipment and processes of the pellet plant, and does not require any new equipment.

[0018] Furthermore, the preparation process parameters of the iron concentrate pellets are as follows: pellet disc rotation speed 8~10 r / min, pellet disc angle 45°~47°, pelletizing time 10~12 min, green pellet moisture content controlled at 8.5%~10%, and green pellet roasting temperature controlled at 1000~1200℃.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention uses red mud, a major solid waste from the alumina industry, as the main binder. The red mud accounts for up to 87% of the binder, realizing the large-scale disposal of red mud and solving the environmental problems caused by red mud storage, such as land occupation, soil and groundwater pollution, from the source.

[0020] The red mud used in this invention contains 20%~55% Fe2O3. Replacing iron-free bentonite with this mud does not dilute the iron content of the pellets; on the contrary, it increases the total iron content. Actual test data shows that when the iron concentrate grade is 62% and the binder addition is 2%, the pellet grade using existing bentonite is only 60.76%, while the pellet grade using the binder from Scheme 1 of this invention can reach 61.008%~61.38%, an increase of 0.248~0.62 percentage points. Based on the average market price of 20 yuan per grade of pellet, each ton of pellets can directly generate an additional economic benefit of 4.96~12.40 yuan. For a steel plant producing 4,000 tons of pellets per day, this translates to an additional daily economic benefit of 19,840~49,600 yuan; for a steel plant producing 16,000 tons of pellets per day, this translates to an additional daily economic benefit of 79,360~198,400 yuan. At the same time, it can reduce the amount of ironmaking waste slag emissions by 0.248%~0.62%, reduce the energy consumption of blast furnace ironmaking, and improve both economic and production efficiency.

[0021] This invention addresses the shortcomings of red mud's strong alkalinity and binding performance by achieving synergistic effects through precise multi-component formulation: sodium carbonate and tripolymethicone can precisely adjust the pH value of the system to suit the strong alkalinity of red mud, eliminating the adverse effects of alkalinity on pelleting performance. Sodium humate, carboxymethyl cellulose, and sodium polyacrylate, three binding components, work synergistically to enhance the adhesive's bonding strength and improve the drop strength and compressive strength of green pellets. Starch optimizes the material's formability, resulting in smooth green pellet surfaces without water overflow, thus improving the green pellet yield. Experimental verification shows that, with the same 2% addition, the optimal solution of this invention achieves 9.2 drop cycles for green pellets, superior to 8.6 cycles for bentonite with the same dosage; the compressive strength of green pellets reaches 11-13 N / pellet, and there is no cracking at 600-700℃. All key performance indicators meet the requirements for industrial pellet production, and the pelleting effect is superior to existing composite bentonite.

[0022] The binder of this invention has a simple preparation process, requiring only three steps: drying, mixing, and grinding. It eliminates the need for complex treatments such as modification and calcination of red mud, and can be produced at room temperature with minimal equipment requirements. Furthermore, this binder can directly replace existing composite bentonite, with usage methods identical to existing bentonite. It is compatible with existing pelletizing equipment and processes in steel plants, requiring no additional equipment or modification investment. Industrialization is extremely easy, enabling rapid large-scale application.

[0023] The main material of this invention is industrial waste red mud, which has a wide range of sources and extremely low procurement costs, even to the point of being possible to purchase at negative costs. The additives are all common, conventional chemical raw materials available on the market, making them easy to procure. The overall production cost is far lower than that of existing high-quality metallurgical bentonite, which can further reduce the auxiliary material costs for steel mill pellet production. Attached Figure Description

[0024] Figure 1This is a process flow diagram for the preparation of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] The red mud used in the following examples is industrial waste residue produced by the Bayer process for alumina production. Its core component content is as follows: Fe2O3 45%, SiO2 18%, CaO 15%, Al2O3 10%, Na2O 5%, and TiO2 4%. The bentonite used is commercially available metallurgical composite bentonite. The additives used are all industrial-grade conventional products that are commercially available.

[0027] The performance testing methods of the following examples and comparative examples all follow the relevant industry standards for determining the compressive strength, drop strength, and bursting temperature of iron ore pellets.

[0028] Example 1: This embodiment provides a composite pellet binder containing red mud, which, by mass percentage, consists of: 80% red mud, 7% sodium humate, 3% sodium carbonate, 3% starch, 2.5% sodium polyacrylate, 2% tripolymethicone, and 1.5% carboxymethyl cellulose, with the sum of the mass percentages of each component being 100%.

[0029] The adhesive is prepared as follows: S1 Red Mud Pretreatment: Red mud with an initial moisture content of 20% is placed in a drying device and dried. The moisture content of the dried red mud is controlled to be 14%, and the particle size is tested to be -200 mesh, accounting for 75%. No additional crushing is required.

[0030] S2 ambient temperature mixing: According to the above ratio, add the pretreated red mud and all additives to the twin-shaft mixer and mix at ambient temperature for 15 minutes until the material is completely uniform to obtain the mixture.

[0031] S3 Grinding Process: The mixed materials are fed into a Raymond mill for grinding. The particle size of the material after grinding is controlled to be -200 mesh, accounting for 94%, to obtain the finished binder.

[0032] Application method of the binder: Take 2.5 kg of iron concentrate with a TFe grade of 62%, add 50 g of the above-mentioned finished binder (the amount added is 2% of the mass of iron concentrate), mix thoroughly, and then pelletize in a laboratory pelletizer. The pelletizing parameters are: pelletizer rotation speed 9 r / min, pelletizer angle 46°, pelletizing time 11 min, green pellet moisture controlled at 9.5%, and green pellet particle size 10~14 mm. After the green pellets are calcined at 1100℃, the finished pellets are obtained.

[0033] Example 2: This embodiment provides a composite pellet binder containing red mud, which, by mass percentage, consists of: 87% red mud, 5% sodium humate, 2% sodium carbonate, 2% starch, 2% sodium polyacrylate, 1% tripolyphosphate, and 1% carboxymethyl cellulose, with the sum of the mass percentages of each component being 100%.

[0034] The preparation and application methods of this adhesive are the same as in Example 1, only the raw material ratio is adjusted.

[0035] Example 3: This embodiment provides a composite pellet binder containing red mud, which, by mass percentage, consists of: 73% red mud, 10% sodium humate, 4% sodium carbonate, 5% starch, 3% sodium polyacrylate, 3% tripolymethicone, and 2% carboxymethyl cellulose. The sum of the mass percentages of each component is 100%. The preparation and application methods are the same as in Embodiment 1.

[0036] The following are the experimental data for the performance test results of the molded product: Red mud experiment results

Claims

1. A composite pellet binder containing red mud, characterized in that, By mass percentage, it consists of the following components: red mud 73%~87%, sodium humate 5%~10%, sodium carbonate 2%~4%, starch 2%~5%, sodium polyacrylate 2%~3%, tripolymethicone 1%~3%, and carboxymethyl cellulose 1%~2%, with the sum of the mass percentages of each component being 100%. The red mud is an industrial waste residue generated during the alumina production process, in which the mass content of Fe2O3 is 20%~55%.

2. The composite pellet binder containing red mud according to claim 1, characterized in that, The initial moisture content of the red mud is 18%~22%, and the moisture content is controlled to 13%~15% after pretreatment. The particle size is ≥70% of -200 mesh.

3. The composite pellet binder containing red mud according to claim 1, characterized in that, It consists of the following components by mass percentage: 80% red mud, 7% sodium humate, 3% sodium carbonate, 3% starch, 2.5% sodium polyacrylate, 2% tripolymethicone, and 1.5% carboxymethyl cellulose.

4. The composite pellet binder containing red mud according to claim 1, characterized in that, It consists of the following components by mass percentage: 87% red mud, 5% sodium humate, 2% sodium carbonate, 2% starch, 2% sodium polyacrylate, 1% tripolyphosphate, and 1% carboxymethyl cellulose.

5. The composite pellet binder containing red mud according to claim 1, characterized in that, It consists of the following components by mass percentage: 73% red mud, 10% sodium humate, 4% sodium carbonate, 5% starch, 3% sodium polyacrylate, 3% tripolymethicone, and 2% carboxymethyl cellulose.

6. A method for preparing a composite pellet binder containing red mud as described in any one of claims 1-5, characterized in that, Includes the following steps: S1 Red Mud Pretreatment: Red mud with an initial moisture content of 18%~22% is dried to control the moisture content after drying to 13%~15%. The particle size of the red mud is tested to ensure that the proportion of -200 mesh is ≥70%. S2 ambient temperature mixing: According to the preset ratio, the pretreated red mud and all additives are added to the mixing equipment at ambient temperature and mixed until the materials are uniform to obtain the mixture. S3 Grinding Process: The mixed materials are fed into a Raymond mill for grinding. The particle size of the material after grinding is controlled to be 93%~95% of -200 mesh, which yields the finished composite pellet binder.

7. The application of a composite pellet binder containing red mud as described in any one of claims 1-7, characterized in that, The binder is applied in the preparation process of iron concentrate pellets. The amount of binder added is 0.8% to 2% of the total mass of iron concentrate. The binder directly replaces an equal amount of composite bentonite and is compatible with existing pellet production equipment and processes.

8. The application according to claim 7, characterized in that, The preparation process parameters for iron concentrate pellets are as follows: pelletizing disc rotation speed 8~10 r / min, pelletizing disc angle 45°~47°, pelletizing time 10~12 min, green pellet moisture content controlled at 8.5%~10%, and green pellet roasting temperature controlled at 1000~1200℃.

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