A method for disposing red mud and steel desulfurization waste in combination

Abstract

The present invention proposes a method for the coordinated disposal of red mud and steel desulfurization waste. By co-processing red mud and steel desulfurization waste, the coordinated disposal of multiple solid wastes is achieved, which not only solves the problem of separating elements such as aluminum, iron, calcium, and titanium in red mud, but also solves the problem of disposing of harmful elements such as sulfur and chlorine in steel desulfurization waste, thereby achieving efficient resource utilization of solid waste. The present invention does not generate wastewater or waste gas during the disposal process, thus achieving clean production. By optimizing the process conditions, the present invention provides a method for the coordinated disposal of red mud and steel desulfurization waste. The method has the advantages of simple process, easy operation, high resource utilization, and low environmental pollution, and has broad application prospects and market value.

Description

Technical Field

[0001] The present invention relates to a solid waste disposal method, in particular to a method for the coordinated treatment of multiple solid wastes in the steel industry, and belongs to the technical field of solid waste treatment environment. Background Art

[0002] Red mud is a highly alkaline solid waste generated during the production of alumina from bauxite, and there is currently no effective solution. Red mud is rich in iron resources, and using it as a raw material for steel smelting is an effective means of achieving its bulk disposal. However, the aluminum content in red mud is also high, which limits its direct use as a raw material for steel smelting. The current addition amount does not exceed 2%. To achieve high-value utilization of iron in high-iron red mud, it is necessary to solve the problems of iron-aluminum separation and iron-titanium separation in high-iron red mud. In addition, steel mills also have a large amount of desulfurization solid waste, such as semi-dry desulfurization ash, baking soda desulfurization ash, etc. Because they contain unstable sulfur, chlorine and other harmful elements, their disposal and utilization also face bottlenecks.

[0003] Chinese patent CN115261540A discloses a method for recovering iron and tailings from red mud. This method involves briquetting red mud with a solvent and a reducing agent, drying it, and then directly subjecting it to high-temperature reduction in a rotary kiln. This reduces the iron in the red mud to elemental iron, thereby separating the iron and aluminum in the red mud. However, this method suffers from high energy consumption and high reducing agent consumption. Chinese patent CN112410559A discloses a method for separating and recovering aluminum and iron from high-iron red mud. This technique involves mixing high-iron red mud with sodium and calcium salts, calcining the mixture at 800–1200°C for 0.5–3 h, and then leaching the resulting clinker in water. This method can separate approximately 70% of the aluminum in the red mud, achieving iron-aluminum separation. Although this method has relatively simple reaction conditions, issues such as rotary kiln ringing, high water consumption, and high alkali consumption remain unresolved during scale-up.

[0004] Chinese patent CN109850922A discloses a method for resource utilization of baking soda desulfurization ash. This method involves mixing baking soda desulfurization ash with lime and introducing CO2 and O2 to convert it into calcium sulfate and baking soda. This method converts the sulfur in the baking soda desulfurization ash into calcium sulfate and then recovers the baking soda. While this method offers the advantage of simple operation, it also poses the problem of untreated chlorine in the baking soda desulfurization ash.

[0005] Chinese patent CN110404936A discloses a method for the comprehensive treatment of semi-dry desulfurization ash. This method converts the sulfur in the ash into sulfur dioxide after reduction roasting, which is then used to produce acid. Calcium is recovered as calcium oxide, and the iron is returned as a sintering raw material. This method can achieve harmless treatment of the semi-dry desulfurization ash and recover the sulfur, calcium, and iron elements separately. However, it suffers from high operating costs, low sulfur concentration in the flue gas, and difficulty in resource recovery.

[0006] Existing technologies mostly treat solid waste generated by the steel industry in a single way. First, additional chemical reagents are needed to treat the solid waste, which increases the hazardous components in the treatment object. Second, the process route for solid waste treatment is relatively simple, and the components in the solid waste are not completely extracted, resulting in the waste of valuable components. Third, the existing process does not completely separate the aluminum, iron, calcium, and titanium in red mud, resulting in a low purity of the obtained product. Summary of the Invention

[0007] In response to the technical problems existing in the prior art regarding solid waste, especially red mud, the inventors have proposed a technical route for the coordinated disposal of red mud and various desulfurization by-products based on multiple experiments. First, the present invention achieves the coordinated disposal of various solid wastes by co-processing red mud and steel desulfurization waste, which not only solves the problem of separating elements such as aluminum, iron, calcium, and titanium in red mud, but also solves the problem of disposing of harmful elements such as sulfur and chlorine in steel desulfurization waste, thereby achieving efficient resource utilization of solid waste. Secondly, the present invention does not produce wastewater or waste gas during the disposal process, thus achieving clean production. By optimizing the process conditions, the present invention achieves efficient utilization of waste heat, reduces energy consumption, and improves economic benefits. Furthermore, the present invention improves the reactivity of red mud by pre-treating it through drying, grinding, and pelletizing, so that subsequent roasting, cooling, magnetic separation, and other processes can be carried out smoothly, while also improving the recovery rate and purity of various elements in the product. In addition, the present invention further optimizes the process conditions and improves the quality and output of the product by adopting advanced technologies such as ultrasonic generators and waste heat utilization devices. In summary, the present invention provides a method for the coordinated disposal of red mud and steel desulfurization waste, which has the advantages of simple process, convenient operation, high resource utilization, and low environmental pollution, and has broad application prospects and market value.

[0008] According to a first embodiment provided by the present invention, a method for disposing red mud in conjunction with steel desulfurization waste is proposed.

[0009] A method for disposing red mud in conjunction with steel desulfurization waste, the method comprising the following steps:

[0010] 1) The red mud is dried, then mixed with semi-dry desulfurization ash and baking soda desulfurization ash and ground into powder, and then mixed with iron and calcium containing solution to form balls;

[0011] 2) The mixed material after ball making is transported to the rotary kiln for roasting;

[0012] 3) Dry-cooling the kiln slag obtained from the rotary kiln treatment; further cooling the slag with water after dry cooling, and separating the solid and liquid to obtain water-cooled slag and cooling solution;

[0013] 4) Magnetic separation is performed on the water-cooled slag to obtain an iron-rich phase and a titanium-rich phase. The iron-rich phase is returned to the sintering process for disposal;

[0014] 5) The titanium-rich phase obtained in step 4) is subjected to an acidification reaction with an acid solution, followed by solid-liquid separation. The obtained solid phase is titanium-containing slag, and the obtained liquid phase is a solution containing iron and calcium;

[0015] 6) transporting the cooled solution obtained in step 3) to a washing tower for washing;

[0016] 7) The flue gas generated by the roasting in step 2) is desulfurized by a dry activated carbon method, and the resulting purified gas is passed into the scrubbing tower described in step 6) to obtain a suspension;

[0017] 8) The suspension obtained by the reaction in step 7) is transported to a clarifier, where it is separated into a solid aluminum hydroxide precipitate and an alkaline solution; a portion of the alkaline solution is returned to step 3) for use as a coolant, and the remaining portion of the alkaline solution is used in a subsequent step to react with the sulfur-rich gas;

[0018] 9) The saturated activated carbon obtained in step 8) is regenerated by high temperature, and the regenerated carbon is circulated to step 7) for desulfurization; the desorbed gas is washed to obtain acidic washing wastewater and sulfur-rich gas;

[0019] 10) After the acidic washing wastewater obtained in step 9) is discharged, a portion is returned to step 5) as an acid solution for acidification reaction with the titanium-rich phase, and the remaining portion enters the calcium precipitation process; after the calcium precipitation, the finished product anhydrous calcium chloride is obtained by drying;

[0020] 11) reacting the sulfur-rich gas obtained in step 9) with the alkaline solution obtained in step 8), and separating the solution by crystallization to obtain finished sodium metabisulfite.

[0021] In the present invention, in step 1), the mass ratio of the dried red mud to the semi-dry desulfurization ash and the baking soda desulfurization ash is 10:0.5~10:1-4, preferably 10:0.6~8:1.2~3.5, and more preferably 10:1~5:1.5-3.

[0022] In the present invention, in step 1), the particle size of the mixed material after pelletizing is 2-10 mm, preferably 3-8 mm.

[0023] In the present invention, the temperature of the calcination treatment in step 2) is 900-1250°C, preferably 950-1200°C, and more preferably 1000-1100°C.

[0024] In the present invention, the calcination treatment time in step 2) is 10-240 min, preferably 20-120 min, more preferably 30-60 min.

[0025] Preferably, an ultrasonic generator is provided in the rotary kiln, and the ultrasonic generator inputs ultrasonic waves into the rotary kiln.

[0026] More preferably, the ultrasonic generating device is arranged in a temperature zone of 950-1050°C in the rotary kiln.

[0027] Preferably, before dry cooling in step 3), coal powder is sprayed onto the slag obtained by the rotary kiln treatment, and then dry cooling is performed.

[0028] Preferably, the amount of coal powder sprayed is 2-10% of the weight of the kiln slag, preferably 3-5%.

[0029] In the present invention, the dry cooling is used to cool the slag to 200-500°C, preferably 300-400°C.

[0030] Preferably, the water-cooled slag is ground before magnetic separation in step 4).

[0031] Preferably, the water-cooled slag is ground to a particle size of 50-200 μm.

[0032] Preferably, the solid-liquid separation in step 3) is performed by a grab bucket.

[0033] Preferably, step 5) is specifically as follows: adding an acid solution to the titanium-rich phase obtained in step 4), controlling the pH of the acid solution to be 1-3, reacting the acid solution with the iron and calcium in the titanium-rich phase, separating after the reaction, and obtaining a solid phase as titanium-containing slag for titanium resource utilization; and obtaining a liquid phase containing an iron- and calcium-containing solution, and returning the iron- and calcium-containing solution to step 1) for pelletizing.

[0034] Preferably, the separation is filtration.

[0035] Preferably, the acid solution comes from the acidic washing wastewater obtained in step 9).

[0036] Preferably, step 6) specifically comprises: transporting the cooling solution obtained in step 3) to a power wave washing tower through a booster pump, and washing is performed using the power wave washing tower.

[0037] Preferably, the purified gas obtained in step 9) is introduced into the dynamic wave scrubbing tower described in step 6).

[0038] Preferably, before the desulfurization process is carried out in step 7), the flue gas generated by the roasting in step 2) is firstly utilized by waste heat, then subjected to dust removal treatment, and then desulfurized by a dry activated carbon method.

[0039] Preferably, the waste heat is utilized by a heat exchanger.

[0040] Preferably, the dust removal process uses a bag dust collector.

[0041] In the present invention, step 11) specifically comprises: reacting the sulfur-rich gas obtained in step 9) with the alkali liquor obtained in step 8) through three-stage countercurrent absorption, wherein the suspension containing salt crystals obtained in the first stage is separated by centrifugation, and the solution separated by centrifugation is returned to the three-stage countercurrent alkali liquor absorption, and the solid separated by centrifugation is the finished product sodium metabisulfite.

[0042] Preferably, in the three-stage countercurrent absorption, the pH in the first-stage countercurrent absorption tank is controlled to be 3-5, and the temperature of the solution in the first-stage countercurrent absorption tank is 60-70° C. The pH in the second-stage countercurrent absorption tank is controlled to be 3.5-6, and the temperature of the solution in the second-stage countercurrent absorption tank is 70-80° C. The pH in the third-stage countercurrent absorption tank is controlled to be 7-8, and the temperature of the solution in the third-stage countercurrent absorption tank is 70-85° C.

[0043] In the present invention, the red mud is first dried to remove moisture and ensure smooth subsequent processing. The drying process can be achieved using various known drying techniques, such as hot air dryers and microwave drying equipment. The dried red mud is then mixed with semi-dry desulfurization ash and baking soda desulfurization ash. The purpose of mixing is to achieve a certain degree of uniformity in the physical and chemical properties of these materials, thereby producing a more uniform powder during the subsequent grinding process. The grinding process can be performed using a ball mill, Raymond mill, or other type of grinding equipment to ensure that the materials are thoroughly pulverized into a fine powder suitable for pelletizing. Finally, the ground powder is mixed with a solution containing elements such as iron and calcium. This solution can be natural mineralized water, industrial wastewater, or other solutions containing iron and calcium ions. The mixed materials are then pelletized. Pellets are formed using a specific pelletizing machine or process to form spherical particles for subsequent use or processing. Preferably, the pelletized particles are dried and sieved to ensure that their size and strength meet the requirements.

[0044] The spheroidized mixture is then safely and efficiently transported to the rotary kiln via a conveying system for the next step in the roasting process. Inside the rotary kiln, the material undergoes a high-temperature roasting process. This process is achieved by precisely controlling the temperature and atmosphere within the kiln to ensure uniform heating of the material, thereby achieving the desired physical and chemical changes. The roasted material is then cooled to stabilize its physical properties.

[0045] Next, the slag obtained from the rotary kiln is dry-cooled. During this process, the slag temperature drops significantly, reaching a relatively stable state. Subsequently, to further reduce the slag temperature and ensure that it meets safe handling standards, the dry-cooled slag is further cooled using water cooling. This water cooling absorbs the heat from the slag and simultaneously separates the soluble aluminum component from the slag, facilitating the subsequent production of aluminum hydroxide. Aluminum can be separated from the slag directly through solid waste separation. Ultimately, the two main products are water-cooled slag and cooling solution.

[0046] Magnetic separation is performed on the water-cooled slag to produce an iron-rich phase and a titanium-rich phase. The iron-rich phase is then returned to the sintering process for disposal. The iron-rich phase obtained after magnetic separation is rich in iron and has a high recycling value. Returning it to the sintering process for disposal not only recycles resources but also reduces environmental impact. Simultaneously, the titanium-rich phase is effectively separated, facilitating subsequent processing and utilization. In the scrubbing tower, the cooling solution undergoes a series of chemical reactions and physical processes to effectively remove harmful substances, meeting environmental emission standards. After purification, the cooling solution can be recycled as liquid caustic soda for process use, conserving resources and reducing costs. The titanium-rich phase can be used to produce high-value-added titanium products, further improving resource utilization. This refined treatment process achieves waste resource recovery, volume reduction, and harmlessness, laying a solid foundation for green and sustainable development.

[0047] The titanium-rich phase obtained in step 4) is subjected to an acidification reaction with an acid solution. After acidification, solid-liquid separation is performed to obtain a titanium-containing slag as the solid phase and a solution containing iron and calcium as the liquid phase. The titanium-containing slag is further processed to extract high-purity titanium resources, which are widely used in aerospace and other fields.

[0048] Further processing of the titanium-containing slag yields titanium products of higher purity, providing an effective path for the recycling of titanium resources. The iron and calcium in the titanium-rich phase readily react with acid, entering the liquid phase and reducing the iron and calcium content in the titanium-containing slag. After solid waste separation, the iron- and calcium-containing solution is used as the pelletizing water in step 1), improving the pelletizing performance and strength of the resulting pellets. This step not only effectively extracts titanium resources but also ensures the environmental friendliness of the entire process. Recycling reduces production costs and improves resource efficiency. The entire process is seamlessly integrated, efficient, and environmentally friendly, setting a new example of sustainable development for the industry.

[0049] The suspension obtained in step 7) is transported to a clarifier, where it is separated into a solid aluminum hydroxide precipitate and an alkaline solution. A portion of the alkaline solution is returned to step 3) as a coolant, while the remaining portion is used in subsequent steps to react with the sulfur-rich gas. The solid aluminum hydroxide precipitate is then washed and dried to produce a high-purity aluminum hydroxide product, which is widely used in the chemical and pharmaceutical industries. The remaining alkaline solution, after treatment to remove harmful components, can be recycled as industrial caustic soda, further reducing production costs and improving resource utilization efficiency.

[0050] In the scrubber, the scrubbing liquid and the cooling solution come into full contact, effectively removing residues, impurities, and harmful substances from the cooling solution through chemical and physical reactions. The scrubber's design allows for thorough mixing and reaction between the scrubbing liquid and the cooling solution, ensuring efficient and stable scrubbing. The solution treated in the scrubber exhibits significantly improved cleanliness and environmental performance, providing strong support for subsequent processing and utilization. Furthermore, the scrubber's stable and reliable operation, simple operation, and easy maintenance ensure smooth operation of the entire treatment process. The scrubber's efficient operation not only improves solution cleanliness but also reduces equipment maintenance costs and extends its service life. The treated solution is recycled, further reducing waste discharge and maximizing resource utilization.

[0051] The sulfur-rich gas obtained in step 9) reacts with the alkaline solution obtained in step 8), and the resulting solution is separated by crystallization to produce the finished sodium metabisulfite. This reaction process not only fully utilizes the sulfur-rich gas and alkaline solution, but also efficiently produces the finished sodium metabisulfite through crystallization separation technology. As an important chemical raw material, sodium metabisulfite is widely used in various fields, such as food preservation, bleaching, and pharmaceuticals. This step not only achieves efficient resource conversion but also improves the economics and practicality of the entire process. Furthermore, the reaction process is stable, controllable, and easy to operate, providing strong support for large-scale industrial production. The finished sodium metabisulfite is of high purity and stable quality, enjoying high market demand, generating significant economic benefits for the company. Furthermore, this process reduces sulfur emissions, complies with environmental requirements, and enhances the company's sense of social responsibility. The optimization and innovation of the entire process provides a valuable model for green development in the industry and promotes the in-depth practice of resource recycling.

[0052] In the present invention, the mass ratio of the dried red mud to the semi-dry desulfurization ash and baking soda desulfurization ash is controlled to be 10:0.5~10:1-4, preferably 10:1~5:1.5-3. By finely controlling the mixing ratio of the raw materials, the stability and uniformity of the mixed material during the subsequent processing process are ensured, thereby improving the overall processing efficiency. The selection of this ratio is based on in-depth research on the properties of the raw materials and analysis of a large amount of experimental data, aiming to maximize resource utilization and optimize processing. At the same time, the control of the particle size of the mixed material after pelletizing is also crucial, which directly affects the effect of the subsequent roasting process and the quality of the product. By optimizing the particle size, it is possible to ensure that the material is evenly heated in the rotary kiln, improve the roasting efficiency, and at the same time ensure the strength and stability of the product. In addition, the temperature and time of the roasting process are also key factors affecting product quality. By precisely controlling these factors, it is possible to ensure that the material undergoes the expected physical and chemical changes during the roasting process, thereby obtaining a high-quality product. The introduction of an ultrasonic generator is key to preventing ringing during the treatment process, further improving the treatment effect and making the entire process more efficient and environmentally friendly. Fine control not only improves product quality but also reduces energy consumption.

[0053] In the present invention, before dry cooling in step 3), coal powder is sprayed onto the slag obtained by the rotary kiln treatment, and then dry cooling is performed. The purpose of spraying coal powder is to use the heat generated by the combustion of coal powder to reduce the slag, and to use the high temperature conditions of the slag to cause a reduction reaction between the coal powder and the iron phase in the slag, thereby promoting the separation of iron and aluminum. The combustion of coal powder also produces a certain reducing atmosphere, which helps to reduce the oxide content in the slag and improve the quality and stability of the product. This innovative treatment method not only improves treatment efficiency, but also reduces energy consumption and production costs, creating greater economic benefits for the enterprise.

[0054] Preferably, the amount of pulverized coal sprayed is controlled to 2-10% of the slag weight, preferably 3-5%. Precisely controlling the amount of pulverized coal ensures optimal slag pre-reduction and further improves iron-aluminum separation efficiency. Furthermore, the dry cooling process effectively lowers slag temperature, reduces heat loss, and optimizes overall energy consumption.

[0055] In the present invention, the sulfur-rich gas obtained in step 9) reacts with the alkali solution obtained in step 8) through three-stage countercurrent absorption. The suspension containing salt crystals obtained in the first stage is separated by centrifugation. The centrifuged solution is returned to the third-stage countercurrent alkali solution absorption, and the solid separated by centrifugation is the finished product, sodium metabisulfite. The use of three-stage countercurrent absorption technology not only improves resource utilization efficiency but also ensures the economic and environmental performance of the treatment process. By precisely controlling the pH value and solution temperature in each absorption tank, the chemical reaction can be maximized, thereby improving the purity and quality of the product.

[0056] In the present invention, during the three-stage countercurrent absorption, the pH in the first-stage countercurrent absorption tank is controlled to be 3-5, and the temperature of the solution in the first-stage countercurrent absorption tank is 60-70°C; the pH in the second-stage countercurrent absorption tank is controlled to be 3.5-6, and the temperature of the solution in the second-stage countercurrent absorption tank is 70-80°C; the pH in the third-stage countercurrent absorption tank is controlled to be 7-8, and the temperature of the solution in the third-stage countercurrent absorption tank is 70-85°C. This precise pH and temperature control ensures that the chemical reactions in each stage of the countercurrent absorption tank proceed efficiently, further improving the purity and stability of sodium metabisulfite. At the same time, the optimized process significantly reduces the emission of waste gas and waste liquid, meets higher environmental protection standards, and provides a strong guarantee for the sustainable development of the enterprise.

[0057] After studying the production practices of the steel industry for many years, the inventors found that the traditional process had problems such as high energy consumption and heavy pollution. After repeated experiments and optimization, they finally determined this innovative treatment method. This method not only solves the pain points of the industry, but also brings significant economic and environmental benefits to enterprises, and opens up a new path for the green development of the steel industry. After fully analyzing the characteristics of three solid wastes, red mud, semi-dry desulfurization ash, and baking soda desulfurization ash, and the chemical reaction mechanisms between them, the inventors cleverly combined the three. By precisely controlling the reaction conditions, they achieved efficient resource utilization and effective conversion of waste, further improved the environmental protection and economy of the overall process, and provided a new technical solution for the field of solid waste treatment. Through the process scheme provided by the present invention, the iron, calcium and aluminum elements in red mud can be efficiently separated, significantly improving the resource recovery rate. At the same time, the emission of harmful substances is reduced and the production environment is optimized. At the same time, elements such as chlorine, sulfur, and sodium in semi-dry desulfurization ash and baking soda desulfurization ash are fully utilized as beneficial components in the process of the present invention and are ultimately converted into products. Through this innovative process, not only is the resource utilization of solid waste achieved, but the production cost is also greatly reduced and the market competitiveness of the enterprise is improved.

[0058] The materials involved in this invention mainly include red mud, semi-dry desulfurization ash, and baking soda desulfurization ash. Red mud mainly contains aluminum goethite, hematite, quartz, rutile, etc. Semi-dry desulfurization ash mainly contains calcium oxide, calcium sulfite, calcium sulfate, and calcium chloride. Baking soda desulfurization ash mainly contains sodium carbonate, sodium sulfite, sodium sulfate, and sodium chloride.

[0059] In the technical solution proposed by the present invention,

[0060] 1. High-strength red mud pelletizing: Red mud has a relatively fine particle size, typically 0.002-0.05 mm. Conventional pelletizing techniques produce pellets with low strength and are prone to pulverization in the rotary kiln, increasing the risk of ring formation. The present invention utilizes a calcium and iron mixed solution obtained by acid hydrolysis of calcined red mud for pelletizing. This solution improves pellet strength through the bridging effect of iron and calcium and enhanced flocculation, ensuring that the red mud pellets do not pulverize in the rotary kiln and fully utilizing iron resources without wasting them.

[0061] 2. Low-cost pyrometallurgical treatment of red mud: The iron and aluminum in red mud are primarily present as aluminous goethite. After mixing red mud with baking soda desulfurization ash and calcining it (>1000°C), the sodium carbonate in the baking soda desulfurization ash can be used to convert the aluminous goethite into iron oxide and sodium aluminate. However, since red mud also contains silica, it reacts with sodium aluminate at high temperatures to form sodium aluminosilicate. Semi-dry desulfurization ash contains a large amount of calcium oxide, which reacts with silica at high temperatures, preferentially converting it into calcium silicate while avoiding reaction with sodium aluminate. Through effective mixing and calcination, low-cost waste desulfurization byproducts can be utilized to achieve low-cost pyrometallurgical separation of iron and aluminum from red mud. The sulfur and chlorine in baking soda desulfurization ash and semi-dry desulfurization ash enter the flue gas during the high-temperature process, without affecting the composition of the kiln slag. Furthermore, since the reaction occurs at high temperatures, red mud can melt, causing ringing in the rotary kiln equipment and leading to high failure rates. The present invention adopts the addition of 500-2000 Hz ultrasonic waves in the temperature zone of 950-1050° C. to prevent the molten sodium ferrite formed in the high temperature process from sticking to the inside of the rotary kiln, thereby preventing ringing and ensuring the stable operation of the reaction.

[0062] 3. Low-cost magnetization of iron in red mud: To prevent incomplete aluminum-titanium-alkali reaction during the red mud alkaline roasting process, which results in high aluminum and titanium contents in the resulting hematite, coal injection is used to cool the slag after rotary kiln roasting. This reduces the iron in the slag clinker from hematite to magnetite, further separating the iron from the aluminum and titanium components. This process does not require additional heating, utilizing the slag's own heat for the reaction, resulting in a low-cost solution.

[0063] 4. Wet Separation of Iron and Aluminum from Red Mud: After pyrolysis, the iron in the red mud exists as iron oxide and the aluminum as sodium aluminate. Since sodium aluminate is highly water-soluble, the slag can be separated by water cooling. Dissolving the slag produces a highly alkaline solution, primarily composed of sodium aluminate and sodium carbonate. Since the purified flue gas primarily consists of CO2, direct emission of CO2 not only increases carbon emissions but also wastes resources. When the alkaline solution is used to absorb the flue gas, the pH of the solution gradually decreases. When the pH drops to 10-11, the aluminum in the sodium aluminate is converted to aluminum hydroxide and precipitated, thus separating the aluminum from the sodium. The aluminum content in the treated red mud can be less than 1%.

[0064] 5. Separation of iron and titanium in red mud and recycling of chlorine: Titanium in red mud mainly exists in the rutile phase, tightly wrapped with iron, and the Ti content is generally 2-4%. Since the iron-making process does not have the ability to absorb titanium, its addition is limited. The present invention realizes the effective separation of iron and titanium through magnetic separation coupled with acidification process. Magnetic separation is performed on the red mud roasted water-cooled material to obtain titanium-rich phase and iron-rich phase. The Fe content in the iron-rich phase can be greater than 60%, and the Ti content can be less than 0.6%, which can be returned to the steel sintering for absorption. The titanium-rich phase, which contains 40% iron and 10% titanium, is directly discarded, resulting in a waste of iron resources. The present invention uses the acidic washing wastewater generated in the flue gas treatment process to dissolve the iron in the titanium-rich phase, and returns it to the front end for enhanced pelletizing, which not only improves the iron recovery rate, but also effectively improves the strength of the pellets and realizes the enrichment of titanium resources.

[0065] 6. Resource Utilization of Sulfur in Desulfurization Byproducts and Recycling of Waste Alkali: Sodium sulfate, sodium sulfite, and calcium sulfite in baking soda desulfurization ash and semi-dry desulfurization ash decompose into sulfur dioxide under high temperature. After sulfur dioxide is treated with activated carbon, it can be regenerated to produce a highly concentrated sulfur-rich gas (sulfur dioxide concentration >5%). The waste alkali liquor after aluminum sodium separation is primarily composed of sodium hydroxide and sodium carbonate. The highly concentrated sulfur-rich gas and waste alkali liquor are reacted in a countercurrent fashion, with the waste alkali liquor entering the tertiary reactor and the SO2 gas entering the primary reactor. Controlling the pH and temperature of each reaction achieves targeted conversion of sulfur dioxide. For example, the pH in the primary and secondary reactors is 4.1, and the pH in the tertiary reactor is 7-8. The temperature in the primary reactor is 65°C, and the temperatures in the secondary and tertiary reactors are 73-75°C. The reaction of converting sulfur dioxide into sodium sulfite mainly occurs in the tertiary reactor, the reaction of converting sodium sulfite into sodium bisulfite occurs in the secondary reactor, and the reaction of converting sodium bisulfite into sodium metabisulfite mainly occurs in the primary reactor, and precipitates in the form of crystals.

[0066] 7. Resource Utilization of Chlorine from Desulfurization Byproducts: Analysis of acidic scrubbing wastewater reveals a relatively simple composition of cations, primarily ammonia nitrogen and hydrogen ions, while anions are primarily chloride and sulfate / sulfite. This method uses calcium oxide or calcium hydroxide to adjust the pH of the acidic scrubbing wastewater, resulting in a solution primarily composed of calcium chloride. The wastewater obtained after calcium precipitation is then spray-dried to yield high-purity calcium chloride.

[0067] Compared with the prior art, the technical solution proposed in the present invention has the following beneficial technical effects:

[0068] 1. The present invention proposes for the first time a process route for the coordinated disposal of red mud and steel desulfurization by-products, which can dispose of multiple solid wastes at low cost.

[0069] 2. The present invention is reasonable, simple to operate, does not produce three wastes, and realizes the resource utilization of iron, sulfur, chlorine, aluminum, sodium, titanium and calcium.

[0070] 3. The present invention has low disposal costs. On the one hand, the strength of red mud pellets is effectively improved; on the other hand, alkaline substances in the waste are used for alkaline roasting of red mud, which reduces raw material costs; in addition, the red mud is cooled and magnetized, which can also reduce disposal costs; and the acidification of red mud using acidic wastewater can reduce acid consumption.

[0071] 4. The rotary kiln ultrasonic device designed in the present invention can effectively avoid the risk of kiln calcination during the red mud treatment process and ensure stable operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 This is a process flow chart of a method for disposing red mud in coordination with steel desulfurization waste provided by the present invention. DETAILED DESCRIPTION

[0073] The technical solutions of the present invention are illustrated below with examples, and the scope of protection requested by the present invention includes but is not limited to the following embodiments. Example 1

[0074] A method for disposing red mud and steel desulfurization waste in combination, characterized in that the method comprises the following steps:

[0075] 1) The red mud is dried, then mixed with semi-dry desulfurization ash and baking soda desulfurization ash and ground into powder, and then mixed with iron and calcium containing solution to form balls;

[0076] 2) The mixed material after ball making is transported to the rotary kiln for roasting;

[0077] 3) Dry-cooling the kiln slag obtained from the rotary kiln treatment; further cooling the slag with water after dry cooling, and separating the solid and liquid to obtain water-cooled slag and cooling solution;

[0078] 4) Magnetic separation is performed on the water-cooled slag to obtain an iron-rich phase and a titanium-rich phase. The iron-rich phase is returned to the sintering process for disposal;

[0079] 5) The titanium-rich phase obtained in step 4) is subjected to an acidification reaction with an acid solution, followed by solid-liquid separation. The obtained solid phase is titanium-containing slag, and the obtained liquid phase is a solution containing iron and calcium;

[0080] 6) transporting the cooled solution obtained in step 3) to a washing tower for washing;

[0081] 7) The flue gas generated by the roasting in step 2) is desulfurized by a dry activated carbon method, and the resulting purified gas is passed into the scrubbing tower described in step 6) to obtain a suspension;

[0082] 8) The suspension obtained by the reaction in step 7) is transported to a clarifier, where it is separated into a solid aluminum hydroxide precipitate and an alkaline solution; 60% by volume of the alkaline solution is returned to step 3) for use as a coolant, and 40% by volume of the alkaline solution is used in a subsequent step to react with the sulfur-rich gas;

[0083] 9) The saturated activated carbon obtained in step 8) is regenerated by high temperature, and the regenerated carbon is circulated to step 7) for desulfurization; the desorbed gas is washed to obtain acidic washing wastewater and sulfur-rich gas;

[0084] 10) After the acidic washing wastewater obtained in step 9) is discharged, 50% by volume is returned to step 5) as an acid solution for acidification reaction with the titanium-rich phase, and 50% by volume enters the calcium precipitation process; after the calcium precipitation, the finished product anhydrous calcium chloride is obtained by drying;

[0085] 11) reacting the sulfur-rich gas obtained in step 9) with the alkaline solution obtained in step 8), and separating the solution by crystallization to obtain finished sodium metabisulfite. Example 2

[0086] Example 1 was repeated except that the mass ratio of the dried red mud to the semi-dry desulfurization ash and baking soda desulfurization ash was 10:3:2. The particle size of the mixed material after pelletization was 5 mm. Example 3

[0087] Example 2 was repeated, except that an ultrasonic generator was installed in the rotary kiln to input ultrasonic waves into the rotary kiln. The calcination temperature in step 2) was 1050°C, and the calcination time was 45 minutes. The ultrasonic generator was located in the 950-1050°C temperature range of the rotary kiln. Example 4

[0088] Example 3 was repeated, except that before dry cooling in step 3), pulverized coal was sprayed onto the slag obtained from the rotary kiln treatment, and then dry cooling was performed; the amount of pulverized coal sprayed was 4% of the weight of the slag; and the slag was cooled to 350°C by dry cooling. Example 5

[0089] Example 4 was repeated, except that in step 4), the water-cooled slag was ground before magnetic separation; the water-cooled slag was ground to a particle size of 95% less than 100 μm; and in step 3), the solid-liquid separation was performed by a grab bucket. Example 6

[0090] Example 5 was repeated, except that step 5) was specifically as follows: an acid solution was added to the titanium-rich phase obtained in step 4), the pH of the acid solution was controlled to 2, the acid solution reacted with the iron and calcium in the titanium-rich phase, and the reaction was separated. The solid phase obtained was titanium-containing slag, which was used for titanium resource utilization; the obtained liquid phase contained an iron- and calcium-containing solution, and the iron- and calcium-containing solution was returned to step 1) for pelletizing; the acid solution was derived from the acidic washing wastewater obtained in step 9). Example 7

[0091] Repeat Example 6, except that step 6) is specifically as follows: the cooling solution obtained in step 3) is transported to a power wave washing tower by a booster pump and washed by the power wave washing tower; the purified gas obtained in step 9) is introduced into the power wave washing tower described in step 6). Example 8

[0092] Example 7 was repeated, except that before the desulfurization process was carried out in step 7), the flue gas generated by the roasting in step 2) was first utilized for waste heat, then subjected to dust removal treatment, and then desulfurized by the activated carbon dry process; the waste heat was utilized using a heat exchanger; the dust removal treatment used a bag filter. Example 9

[0093] Example 8 was repeated, except that step 11) was specifically as follows: the sulfur-rich gas obtained in step 9) was reacted with the alkali solution obtained in step 8) through three-stage countercurrent absorption, wherein the suspension containing salt crystals obtained in the first stage was separated by centrifugation, the solution separated by centrifugation was returned to the three-stage countercurrent alkali solution absorption, and the solid separated by centrifugation was the finished product sodium metabisulfite;

[0094] Among them: in the three-stage countercurrent absorption, the pH in the first-stage countercurrent absorption tank is controlled to be 3-5, and the temperature of the solution in the first-stage countercurrent absorption tank is 60-70°C; the pH in the second-stage countercurrent absorption tank is controlled to be 3.5-6, and the temperature of the solution in the second-stage countercurrent absorption tank is 70-80°C; the pH in the third-stage countercurrent absorption tank is controlled to be 7-8, and the temperature of the solution in the third-stage countercurrent absorption tank is 70-85°C.

[0095] Application Example 1

[0096] A method for treating red mud in conjunction with steel desulfurization waste, the process specifically comprises the following steps: 1) drying 1000 kg of red mud, mixing it with 40 kg of semi-dry desulfurization ash and 20 kg of baking soda desulfurization ash, grinding it into powder, and then mixing it with the subsequent iron- and calcium-containing supernatant to form balls; 2) adding the balled mixture into a rotary kiln equipped with an ultrasonic device, and roasting it at 1000-1100°C for 40 minutes in the rotary kiln; 3) cooling the kiln slag obtained after the rotary kiln treatment by indirect heat exchange with dry cooling air, and then further cooling it by water cooling; 4) the slag obtained in step 3) is heated to 1000-1100°C for 40 minutes. The water-cooled slag is separated by a grab bucket, and then the slag is magnetically separated to obtain an iron-rich phase which is returned to the sintering process for disposal, and a titanium-rich phase is obtained for subsequent acidification treatment; 5) the titanium-rich phase obtained in step 4) reacts with the subsequently obtained dilute acid water, and the pH of the solution is controlled to 3. The solid phase obtained is titanium-containing slag, and the obtained solution is returned to step 1) for pelletizing; 6) the water-cooled solution obtained in step 4) enters the booster pump through overflow, and then enters the power wave washing tower through the pump; 7) the flue gas after the reaction in step 2) is utilized through waste heat, then subjected to bag dust removal treatment, and then activated carbon is used The desulfurization is carried out by dry method, and the purified gas obtained is then introduced into the dynamic wave washing tower described in step 6); 8) the suspension obtained by the reaction in step 7) enters the clarifier, and the solid aluminum hydroxide precipitate can be separated through the clarifier, and 60% of the liquid by volume is returned to step 3) for cooling and use, and 40% of the liquid by volume is used for the subsequent step to react with high concentration sulfur dioxide; 9) the saturated activated carbon obtained in step 8) is regenerated by high temperature, and the regenerated carbon obtained is recycled to step 7), and the desorbed gas obtained is washed to obtain acidic washing wastewater and sulfur-rich gas; 10) the acidic After the washing wastewater is discharged, 50% by volume is returned to step 5) for acidification reaction with the titanium-rich phase, and 50% by volume of the water enters the calcium precipitation process. The supernatant after the calcium precipitation is concentrated through a cascade circulation coupled with calcium chloride dissolution, and after conditioning, is added to an atomizer and spray-dried to obtain the finished product anhydrous calcium chloride. 11) The sulfur-rich gas obtained in step 9) reacts with the alkaline solution obtained in step 8) through three-stage countercurrent absorption, wherein the suspension containing salt crystals obtained in the first stage is separated by centrifugation, and the solution separated by centrifugation is returned to the three-stage countercurrent alkaline solution absorption, and the solid is the finished product sodium metabisulfite.

[0097] Analysis of the resulting products revealed a purity of 98.4% for calcium chloride, 96.4% for sodium metabisulfite, and 99.5% for aluminum hydroxide. The iron content of the titanium-bearing slag was 20.8%, the calcium content was 10.5%, and the titanium content was 25.2%. The iron grade of the iron-rich phase was 62%, and the titanium content was 0.4%. The purity of each product met industrial standards, and the process was highly efficient and environmentally friendly, significantly improving resource utilization.

[0098] Application Example 2

[0099] A method for the coordinated disposal of red mud and steel desulfurization waste, the process flow is as follows: 1) 1000kg of red mud is dried, mixed with 40kg of semi-dry desulfurization ash and 20kg of baking soda desulfurization ash, and then ground into powder, and then mixed with the subsequent iron- and calcium-containing supernatant to form balls; 2) the balled mixture is added to a rotary kiln equipped with an ultrasonic device, and roasted at 1000-1100°C for 40 minutes in the rotary kiln; 3) the kiln slag obtained after the rotary kiln treatment is passed into a coal injection cooling device, 5kg of coal powder is sprayed into the kiln slag, the kiln slag and coal powder are cooled together, and then further cooled by water cooling. Cooling; 4) The water-cooled slag obtained in step 3) is separated by a grab bucket, and then the slag is magnetically separated to obtain an iron-rich phase which is returned to the sintering process for disposal, and a titanium-rich phase is obtained for subsequent acidification treatment; 5) The titanium-rich phase obtained in step 4) reacts with the subsequently obtained dilute acid water, and the pH of the solution is controlled to 2. The solid phase obtained is titanium-containing slag, and the obtained solution is returned to step 1) for pelletizing; 6) The water-cooled solution obtained in step 4) enters the booster pump through overflow, and then enters the power wave washing tower through the pump; 7) The flue gas after the reaction in step 2) is utilized through waste heat, and then passes through a bag dust removal process. The activated carbon is then dry-processed for desulfurization, and the purified gas is then introduced into the dynamic wave washing tower described in step 6); 8) the suspension obtained by the reaction in step 7) enters a clarifier, and solid aluminum hydroxide precipitate can be separated through the clarifier. 60% of the liquid by volume is returned to step 3) for cooling and use, and 40% of the liquid by volume is used for the subsequent step to react with high-concentration sulfur dioxide; 9) the saturated activated carbon obtained in step 8) is regenerated by high temperature, and the regenerated carbon obtained is recycled for step 7), and the desorbed gas obtained is washed to obtain acidic washing wastewater and sulfur-rich gas; 10) the obtained activated carbon in step 9) is regenerated by high temperature, and the regenerated carbon obtained is recycled for step 7). After the acidic washing wastewater is discharged, 50% of the water by volume is used to return to step 5) for acidification reaction with the titanium-rich phase, and 50% of the water by volume enters the calcium precipitation process. The supernatant after the calcium precipitation is concentrated through a cascade circulation coupled with calcium chloride anti-dissolution, and after conditioning, it is added to an atomizer and spray-dried to obtain the finished product anhydrous calcium chloride; 11) the sulfur-rich gas obtained in step 9) reacts with the alkali solution obtained in step 8) through three-stage countercurrent absorption, wherein the suspension containing salt crystals obtained in the first stage is separated by centrifugation, and the solution separated by centrifugation is returned to the three-stage countercurrent alkali solution absorption, and the solid is the finished product sodium metabisulfite.

[0100] Analysis of the resulting products revealed a purity of 98.5% for calcium chloride, 96.3% for sodium metabisulfite, and 99.8% for aluminum hydroxide. The iron content of the titanium-bearing slag was 16.5%, the calcium content was 8.8%, and the titanium content was 31.4%. The iron grade of the iron-rich phase was 71%, and the titanium content was 0.1%. The purity of each product met industrial standards, and the process was highly efficient and environmentally friendly, significantly improving resource utilization.

Claims

1. A method for disposing red mud in conjunction with steel desulfurization waste, characterized by: The method comprises the following steps: 1) The red mud is dried, then mixed with semi-dry desulfurization ash and baking soda desulfurization ash and ground into powder, and then mixed with iron and calcium containing solution to form balls; 2) The mixed material after ball making is transported to the rotary kiln for roasting; 3) Dry-cooling the kiln slag obtained from the rotary kiln treatment; further cooling the slag with water after dry cooling, and separating the solid and liquid to obtain water-cooled slag and cooling solution; 4) Magnetic separation is performed on the water-cooled slag to obtain an iron-rich phase and a titanium-rich phase. The iron-rich phase is returned to the sintering process for disposal; 5) The titanium-rich phase obtained in step 4) is subjected to an acidification reaction with an acid solution, followed by solid-liquid separation. The obtained solid phase is titanium-containing slag, and the obtained liquid phase is a solution containing iron and calcium; 6) transporting the cooled solution obtained in step 3) to a washing tower for washing; 7) The flue gas generated by the roasting in step 2) is desulfurized by a dry activated carbon method, and the resulting purified gas is passed into the scrubbing tower described in step 6) to obtain a suspension; 8) The suspension obtained by the reaction in step 7) is transported to a clarifier, where it is separated into a solid aluminum hydroxide precipitate and an alkaline solution; a portion of the alkaline solution is returned to step 3) for use as a coolant, and the remaining portion of the alkaline solution is used in a subsequent step to react with the sulfur-rich gas; 9) The saturated activated carbon obtained in step 8) is regenerated by high temperature, and the regenerated carbon is circulated to step 7) for desulfurization; the desorbed gas is washed to obtain acidic washing wastewater and sulfur-rich gas; 10) After the acidic washing wastewater obtained in step 9) is discharged, a portion is returned to step 5) as an acid solution to undergo an acidification reaction with the titanium-rich phase, and the remaining portion enters the calcium precipitation process; after the calcium precipitation, the finished product anhydrous calcium chloride is obtained by drying; 11) reacting the sulfur-rich gas obtained in step 9) with the alkaline solution obtained in step 8), and separating the solution by crystallization to obtain finished sodium metabisulfite.

2. The method according to claim 1, wherein: In step 1), the mass ratio of the dried red mud to the semi-dry desulfurization ash and the baking soda desulfurization ash is 10:0.5 to 10:1-4; and / or In step 1), the pelletizing process is performed so that the particle size of the mixed material after pelletizing is 2-10 mm.

3. The method according to claim 2, wherein: In step 1), the mass ratio of the dried red mud to the semi-dry desulfurization ash and the baking soda desulfurization ash is 10:1~5:1.5-3; and / or After the pelletizing in step 1), the particle size of the mixed material is 3-8 mm.

4. The method according to claim 1, wherein: The calcination temperature in step 2) is 900-1250°C; the calcination time is 10-240 minutes; and / or An ultrasonic generator is provided in the rotary kiln, and the ultrasonic generator inputs ultrasonic waves into the rotary kiln.

5. The method according to claim 4, characterized in that: The calcination temperature in step 2) is 950-1200° C., and the calcination time is 20-120 minutes.

6. The method according to claim 5, characterized in that: The calcination temperature in step 2) is 1000-1100° C. and the calcination time is 30-60 minutes.

7. The method according to claim 4, characterized in that: The ultrasonic generating device is arranged in the temperature zone of 950-1050°C in the rotary kiln.

8. The method according to claim 1, wherein: In step 3), before dry cooling, pulverized coal is sprayed onto the slag obtained from the rotary kiln treatment, and then dry cooling is performed; and / or Dry cooling cools the kiln slag to 200~500℃.

9. The method according to claim 8, characterized in that: The amount of pulverized coal sprayed is 2-10% of the weight of the slag; and / or Dry cooling cools the kiln slag to 300~400℃.

10. The method according to claim 9, characterized in that: The amount of coal powder sprayed is 3~5% of the weight of the kiln slag.

11. The method according to claim 1, wherein: Step 4) Grinding the water-cooled slag before magnetic separation; and / or Step 3) The solid-liquid separation is carried out by a grab bucket.

12. The method according to claim 11, wherein: Grind the water-cooled slag to a particle size of 50~200um.

13. The method according to claim 1, wherein: Step 5) is specifically as follows: adding an acid solution to the titanium-rich phase obtained in step 4), controlling the pH of the acid solution to be 1-3, reacting the acid solution with the iron and calcium in the titanium-rich phase, separating the reactants after the reaction, and obtaining a solid phase as titanium-containing slag for titanium resource utilization; obtaining a liquid phase as a solution containing iron and calcium, and returning the solution containing iron and calcium to step 1) for pelletizing; and / or The acid solution comes from the acidic washing wastewater obtained in step 9).

14. The method according to claim 1, wherein: Step 6) specifically comprises: transporting the cooling solution obtained in step 3) to a power wave washing tower through a booster pump, and washing is performed using the power wave washing tower.

15. The method according to claim 14, characterized in that: The purified gas obtained in step 9) is introduced into the dynamic wave washing tower described in step 6).

16. The method according to claim 1, wherein: Before the desulfurization process is carried out in step 7), the flue gas generated by the roasting in step 2) is firstly utilized through waste heat, then subjected to dust removal treatment, and then desulfurized by a dry activated carbon method.

17. The method according to claim 16, wherein: The waste heat is utilized by a heat exchanger; the dust removal treatment is carried out by a bag dust collector.

18. The method according to claim 1, wherein: Step 11) specifically comprises: reacting the sulfur-rich gas obtained in step 9) with the alkali solution obtained in step 8) through three-stage countercurrent absorption, wherein the suspension containing salt crystals obtained in the first stage is separated by centrifugation, and the solution separated by centrifugation is returned to the three-stage countercurrent alkali solution absorption, and the solid separated by centrifugation is the finished product sodium metabisulfite.

19. The method according to claim 18, wherein: In the three-stage countercurrent absorption, the pH in the first-stage countercurrent absorption tank is controlled to be 3-5, and the temperature of the solution in the first-stage countercurrent absorption tank is 60-70°C; the pH in the second-stage countercurrent absorption tank is controlled to be 3.5-6, and the temperature of the solution in the second-stage countercurrent absorption tank is 70-80°C; the pH in the third-stage countercurrent absorption tank is controlled to be 7-8, and the temperature of the solution in the third-stage countercurrent absorption tank is 70-85°C.

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