Method for treating red mud and steel desulfurization waste

Abstract

According to the method for treating the red mud synergistic steel and iron desulfurization waste, the red mud and the steel and iron desulfurization waste are cooperatively treated, so that synergistic absorption of various solid wastes is realized, the problem of separation of elements such as aluminum, iron, calcium and titanium in the red mud is solved, and meanwhile, the problem of treatment of harmful elements such as sulfur and chlorine in the steel and iron desulfurization waste is also solved; the efficient resource utilization of the solid waste is realized. In the treatment process, waste water and waste gas are not generated, and clean production is achieved. By optimizing process conditions, the invention provides the red mud synergistic steel desulfurization waste disposal method, and the method has the advantages of simple process, convenience in operation, high resource utilization rate, small environmental pollution and the like, and has wide application prospects and market values.

Description

Technical Field

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

[0002] Red mud is a highly alkaline solid waste produced in the process of producing 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 to achieve its bulk consumption. But at the same time, 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, the problems of iron-aluminum separation and iron-titanium separation in high-iron red mud must be solved. 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, there are bottlenecks in their consumption and utilization.

[0003] Chinese patent CN115261540A discloses a method for recovering iron and tailings from red mud. In this method, red mud, solvent and reducing agent are pressed into balls, and then directly reduced at high temperature in a rotary kiln after drying to reduce the iron in the red mud to elemental iron, thereby realizing the separation of iron and aluminum in red mud. However, this method has the disadvantages of high energy consumption and large consumption of reducing agent. Chinese patent CN112410559A discloses a method for separating and recovering aluminum and iron from high-iron red mud. This technology mixes high-iron red mud with sodium salt and calcium salt, and roasts the mixture at 800~1200℃ for 0.5~3h. The obtained clinker can separate about 70% of the aluminum in the red mud after water immersion, thereby realizing the separation of iron and aluminum. Although the reaction conditions of this method are relatively simple, there are still problems such as rotary kiln ring formation, large water volume and large alkali consumption in the process of engineering amplification that have not been solved.

[0004] Chinese patent CN109850922A discloses a method for resource utilization of baking soda desulfurization ash, which comprises mixing baking soda desulfurization ash with lime and introducing CO 2 and O 2 This method converts the sulfur in the baking soda desulfurization ash into calcium sulfate and then recovers the baking soda. It has the advantage of simple operation, but there is a problem of untreated chlorine in the baking soda desulfurization ash during application.

[0005] Chinese patent CN110404936A discloses a method for comprehensive treatment of semi-dry desulfurization ash, which converts sulfur in the semi-dry desulfurization ash into sulfur dioxide after reduction roasting, and further uses it for acid production, while calcium is recovered in the form of calcium oxide, and the iron therein is returned as a sintering raw material. This method can achieve harmless treatment of semi-dry desulfurization ash and recover sulfur, calcium and iron therein respectively, but has the disadvantages of high operating cost, low sulfur concentration in flue gas, and difficulty in resource recovery.

[0006] In the existing technology, solid waste generated by the steel industry is mostly treated in a single way. First, in order to treat the solid waste, additional chemical reagents need to be added, which increases the harmful components in the treatment object; secondly, the process route of solid waste treatment is relatively simple, and the components in the solid waste are not completely extracted, resulting in a waste of valuable components; thirdly, the existing process does not completely separate the aluminum, iron, calcium and titanium in the red mud, resulting in a low purity of the obtained product. Summary of the invention

[0007] In view of the technical problems existing in the prior art for solid waste, especially red mud, the inventors proposed a technical route for the coordinated disposal of red mud and various desulfurization by-products based on multiple experiments. First, the present invention realizes the coordinated disposal of various solid wastes by coordinating the treatment of red mud and steel desulfurization waste, which not only solves the separation problem of aluminum, iron, calcium, titanium and other elements in red mud, but also solves the disposal problem of harmful elements such as sulfur and chlorine in steel desulfurization waste, and realizes the efficient resource utilization of solid waste. Secondly, the present invention does not produce wastewater and waste gas during the disposal process, and realizes clean production. By optimizing the process conditions, the present invention realizes the 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 by drying, grinding, and pelletizing, so that subsequent roasting, cooling, magnetic separation and other processes can be carried out smoothly, and the recovery rate and purity of each element in the product are also improved. 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 coordination with steel desulfurization waste is proposed.

[0009] A method for disposing red mud and steel desulfurization waste, the method comprising the following steps: 1) Dry the red mud, then mix it with semi-dry desulfurization ash and baking soda desulfurization ash, grind it into powder, and then mix it with iron and calcium containing solution to make balls; 2) The mixed material after ball making is transported to the rotary kiln for roasting; 3) Dry-cooling the kiln slag obtained by the rotary kiln treatment; after dry-cooling, further cooling by water cooling is performed to separate 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, and the iron-rich phase is returned to the sintering process for consumption; 5) The titanium-rich phase obtained in step 4) is subjected to an acidification reaction with an acid solution, and solid-liquid separation is performed after acidification, the obtained solid phase is titanium-containing slag, and the obtained liquid phase contains a solution of iron and calcium; 6) conveying the cooling 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 an activated carbon dry method, and the obtained purified gas is introduced into the washing tower described in step 6) to obtain a suspension; 8) The suspension obtained by the reaction in step 7) is transported to a clarifier, and solid aluminum hydroxide precipitate and alkali solution are separated in the clarifier; a part of the alkali solution is returned to step 3) for use as a coolant, and the remaining part of the alkali solution is used in the 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) The sulfur-rich gas obtained in step 9) reacts with the alkali solution obtained in step 8), and after the reaction, the solution is separated by crystallization to obtain a finished product of sodium metabisulfite.

[0010] 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.

[0011] In the present invention, in step 1), the particle size of the mixed material after pelletizing is 2-10 mm, preferably 3-8 mm.

[0012] 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.

[0013] In the present invention, the calcination time in step 2) is 10-240 min, preferably 20-120 min, and more preferably 30-60 min.

[0014] Preferably, an ultrasonic generator is provided in the rotary kiln, and the ultrasonic generator inputs ultrasonic waves into the rotary kiln.

[0015] Further preferably, the ultrasonic generating device is arranged in the temperature zone of 950-1050°C in the rotary kiln.

[0016] Preferably, before dry cooling in step 3), coal powder is sprayed on the slag obtained by the rotary kiln treatment, and then dry cooling is performed.

[0017] Preferably, the amount of coal powder sprayed is 2-10% of the weight of the slag, preferably 3-5%.

[0018] In the present invention, the slag is cooled to 200-500°C, preferably 300-400°C by dry cooling.

[0019] Preferably, the water-cooled slag is ground before magnetic separation in step 4).

[0020] Preferably, the water-cooled slag is ground to a particle size of 50-200 um.

[0021] Preferably, the solid-liquid separation in step 3) is carried out by a grab bucket.

[0022] 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; the obtained liquid phase contains a solution containing iron and calcium, and the solution containing iron and calcium is returned to step 1) for pelletizing.

[0023] Preferably, the separation is filtration.

[0024] Preferably, the acid solution is derived from the acidic washing wastewater obtained in step 9).

[0025] Preferably, 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 washing is performed by using the power wave washing tower.

[0026] Preferably, the purified gas obtained in step 9) is introduced into the dynamic wave washing tower described in step 6).

[0027] Preferably, 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 subjected to desulfurization by an activated carbon dry method.

[0028] Preferably, the waste heat is utilized by a heat exchanger.

[0029] Preferably, the dust removal process uses a bag dust collector.

[0030] In the present invention, step 11) is specifically: 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, 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.

[0031] 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.

[0032] In the present invention, the red mud is first dried to remove the moisture therein and ensure the smooth progress of subsequent processing. The drying process can be achieved by various known drying techniques, such as using a hot air dryer, a microwave drying device, etc. The dried red mud will enter the next step, that is, it will be mixed with semi-dry desulfurization ash and baking soda desulfurization ash. The purpose of mixing is to make these materials achieve a certain uniformity in physical and chemical properties, so that a more uniform powder can be obtained in the subsequent grinding process. The grinding process can use a ball mill, a Raymond mill or other types of grinding equipment to ensure that the material is fully crushed to form 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 waste liquid or other solutions containing iron and calcium ions. The mixed material will be subjected to a balling process, and the balling is to make the mixed material into spherical particles through a specific balling machine or balling process, so as to facilitate subsequent use or processing. Preferably, the particles after balling are dried and sieved to ensure that their size and strength meet the requirements.

[0033] Then, the spheroidized mixture is safely and efficiently transported to the rotary kiln through the conveying system for the next roasting process. In the rotary kiln, the material undergoes a high-temperature roasting process, which is achieved by precisely controlling the temperature and atmosphere in the kiln to ensure that the material is evenly heated to achieve the desired physical and chemical changes. The roasted material is cooled to stabilize its physical properties.

[0034] Next, the slag obtained from the rotary kiln is dry-cooled; during this process, the temperature of the slag will drop significantly, thus reaching a relatively stable temperature state. Subsequently, in order to further reduce the temperature of the slag and ensure that it meets the standards for safe handling, the dry-cooled slag is further cooled by water cooling. Through water cooling, the heat in the slag is absorbed by water, and at the same time, the easily soluble component aluminum in the slag is also separated from the slag, making it easier to obtain aluminum hydroxide later. Aluminum can be separated from the slag directly through solid waste separation. Finally, two main products, water-cooled slag and cooling solution, are obtained.

[0035] The water-cooled slag is magnetically separated to obtain an iron-rich phase and a titanium-rich phase, and the iron-rich phase is 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 can not only realize the recycling of resources, but also reduce the impact on the environment. At the same time, the titanium-rich phase is also effectively separated, which provides convenience for subsequent treatment and utilization. In the washing tower, the cooling solution undergoes a series of chemical reactions and physical processes, and the harmful substances in it are effectively removed, meeting the environmental emission standards. After purification, the cooling solution can be recycled as liquid alkali for process use, which saves resources and reduces costs. The titanium-rich phase can be used to prepare high-value-added titanium products, further improving resource utilization. Through this series of refined treatment processes, the resource utilization, reduction and harmlessness of waste are realized, laying a solid foundation for green and sustainable development.

[0036] The titanium-rich phase obtained in step 4) is subjected to an acidification reaction with an acid solution, and solid-liquid separation is performed after acidification. The solid phase obtained is titanium-containing slag, and the liquid phase obtained is a solution containing iron and calcium. The titanium-containing slag is further processed to extract high-purity titanium resources, which are widely used in aerospace and other fields.

[0037] Further processing of titanium-containing slag can produce titanium products with higher purity, providing an effective way to recycle titanium resources. The iron and calcium in the titanium-rich phase easily react with acid and enter the liquid phase, thereby reducing the iron and calcium content in the titanium-containing slag. After solid waste separation, the solution containing iron and calcium is used as the pelletizing water in step 1) to improve the pelletizing performance and strength of the pellets. This step not only realizes the effective extraction of titanium resources, but also ensures the environmental friendliness of the entire treatment process. Through recycling, production costs are reduced and resource utilization efficiency is improved. The entire process is closely linked, which is both efficient and environmentally friendly, setting an example of sustainable development for the industry.

[0038] The suspension obtained by the reaction in step 7) is transported to a clarifier, and the solid aluminum hydroxide precipitate and alkali solution are separated in the clarifier; a part of the alkali solution is returned to step 3) for use as a coolant, and the remaining part of the alkali solution is used for subsequent steps to react with sulfur-rich gas. Furthermore, after washing and drying, the solid aluminum hydroxide precipitate is obtained to obtain a high-purity aluminum hydroxide product, which is widely used in the fields of chemical industry, medicine, etc. After the remaining alkali solution is treated to remove harmful components, it can be recycled as industrial liquid alkali, further reducing production costs and improving resource utilization efficiency.

[0039] In the scrubber, the scrubbing liquid is in full contact with the cooling solution, and the residues, impurities and harmful substances in the cooling solution are effectively removed through chemical reactions and physical effects. The design of the scrubber allows the scrubbing liquid and the cooling solution to fully mix and react, ensuring the efficiency and stability of the scrubbing effect. The cleanliness and environmental performance of the solution treated by the scrubber are significantly improved, providing a strong guarantee for subsequent treatment and utilization. At the same time, the operation of the scrubber is stable and reliable, easy to operate, and easy to maintain and maintain, ensuring the smooth progress of the entire treatment process. The efficient operation of the scrubber not only improves the cleanliness of the solution, but also reduces the equipment maintenance cost and extends the service life. The treated solution is recycled again, further reducing waste liquid discharge and maximizing the utilization of resources.

[0040] The sulfur-rich gas obtained in step 9) reacts with the alkali solution obtained in step 8), and the solution is separated by crystallization after the reaction to obtain the finished sodium metabisulfite. This reaction process not only makes full use of the sulfur-rich gas and the alkali solution, but also efficiently obtains the finished sodium metabisulfite through the crystallization separation technology. As an important chemical raw material, sodium metabisulfite is widely used in many fields, such as food preservation, bleaching, and pharmaceuticals. Through this step, not only the effective conversion of resources is achieved, but also the economy and practicality of the entire treatment process are improved. At the same time, the reaction process is stable and controllable, and the operation is simple, which provides strong support for large-scale industrial production. The finished sodium metabisulfite has high purity, stable quality, and large market demand, which creates significant economic benefits for the enterprise. In addition, the process reduces sulfur emissions, meets environmental protection requirements, and enhances the social responsibility of enterprises. The optimization and innovation of the entire process provides a reference template for the green development of the industry and promotes the in-depth practice of resource recycling.

[0041] In the present invention, the mass ratio of the dried red mud to the semi-dry desulfurization ash and the 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 materials in the subsequent treatment process are ensured, thereby improving the overall treatment efficiency. The selection of this ratio is based on an in-depth study of the properties of the raw materials and the analysis of a large amount of experimental data, aiming to maximize the utilization of resources and optimize the treatment. At the same time, the particle size control of the mixed materials 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 can be ensured that the materials are evenly heated in the rotary kiln, the roasting efficiency is improved, and the strength and stability of the product are guaranteed. In addition, the temperature and time of the roasting treatment are also key factors affecting the quality of the product. By accurately controlling these factors, it can be ensured that the materials undergo the expected physical and chemical changes during the roasting process, thereby obtaining high-quality products. The introduction of an ultrasonic generator is the key to preventing ring formation 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.

[0042] In the present invention, before dry cooling in step 3), coal powder is sprayed on the slag obtained by the rotary kiln treatment, and then dry cooling is performed. The purpose of spraying coal powder is to reduce the slag by utilizing the heat generated by the combustion of coal powder, and to utilize the high temperature condition 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 the treatment efficiency, but also reduces energy consumption and production costs, creating greater economic benefits for the enterprise.

[0043] Preferably, the amount of coal powder sprayed is controlled to be 2-10% of the weight of the slag, preferably 3-5%. By accurately controlling the amount of coal powder, the optimization of the slag pre-reduction effect is ensured, and the iron-aluminum separation efficiency is further improved. At the same time, the dry cooling process effectively reduces the slag temperature, reduces heat loss, and optimizes the overall energy consumption.

[0044] 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, wherein the suspension containing salt crystals obtained in the first stage is separated by centrifugation, the solution separated by centrifugation is returned for three-stage countercurrent alkali solution absorption, and the solid separated by centrifugation is the finished product sodium metabisulfite. The three-stage countercurrent absorption technology not only improves the utilization efficiency of resources, but also ensures the economy and environmental protection of the treatment process. By accurately controlling the pH value and solution temperature in each stage of the absorption tank, the chemical reaction can be promoted to the maximum extent, thereby improving the purity and quality of the product.

[0045] In the present invention, 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. Through this precise pH value and temperature control, the chemical reaction in each stage of the countercurrent absorption tank is ensured to be carried out efficiently, and the purity and stability of sodium metabisulfite are further improved. At the same time, the optimized process significantly reduces the emission of waste gas and waste liquid, reaches higher environmental protection standards, and provides a strong guarantee for the sustainable development of the enterprise.

[0046] The inventor studied the production practice of the steel industry for many years and found that the traditional process had problems such as high energy consumption and heavy pollution. After repeated experiments and optimization, this innovative treatment method was finally determined. 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. The inventor fully analyzes the characteristics of three solid wastes, red mud, semi-dry desulfurization ash, and baking soda desulfurization ash, and their chemical reaction mechanisms. The inventor cleverly combines the three, and through precise control of the reaction conditions, the efficient utilization of resources and the effective transformation of waste are achieved, further improving the environmental protection and economy of the overall process, and providing 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, and the resource recovery rate is significantly improved. At the same time, the emission of harmful substances is reduced and the production environment is optimized. At the same time, the 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 finally converted into products. Through this innovative process, not only the resource utilization of solid waste is achieved, but also the production cost is greatly reduced and the market competitiveness of the enterprise is improved.

[0047] In the present invention, the materials involved mainly include red mud, semi-dry desulfurization ash, and baking soda desulfurization ash. The red mud mainly contains aluminum goethite, hematite, quartz, rutile, etc. The semi-dry desulfurization ash mainly contains calcium oxide, calcium sulfite, calcium sulfate, and calcium chloride. The baking soda desulfurization ash mainly contains sodium carbonate, sodium sulfite, sodium sulfate, and sodium chloride.

[0048] In the technical solution proposed by the present invention, 1. High-strength pelletizing of red mud: The particle size of red mud is relatively fine, generally 0.002-0.05 mm. The pellets obtained by conventional pelletizing technology have low strength and are prone to pulverization in the rotary kiln, increasing the risk of ring formation. The present invention utilizes the mixed solution of calcium and iron obtained by acid hydrolysis of red mud roasting material for mixing and pelletizing, which can improve the strength of the pellets through the bridging of iron and calcium and the strengthening of flocculation, ensuring that the red mud pellets are not pulverized in the rotary kiln, and that iron resources can be fully utilized without waste of iron resources.

[0049] 2. Low-cost pyrometallurgical treatment of red mud: The iron and aluminum in red mud mainly exist in the form of aluminum goethite. After the red mud and baking soda desulfurization ash are mixed and roasted (>1000℃), the sodium carbonate in the baking soda desulfurization ash can be used to convert the aluminum goethite into iron oxide and sodium aluminate. However, since red mud also contains silicon dioxide, it will react with sodium aluminate in the high temperature process and convert into sodium aluminosilicate. Since the semi-dry desulfurization ash contains a large amount of calcium oxide, it can react with silicon dioxide under high temperature conditions, so that it is preferentially converted into calcium silicate, while avoiding its reaction with sodium aluminate. Through effective mixing and roasting, the low-cost pyrometallurgical separation of red mud iron and aluminum can be achieved by using low-cost waste desulfurization by-products, and the sulfur and chlorine ash in baking soda desulfurization ash and semi-dry desulfurization ash enter the flue gas during the high temperature process, which does not affect the composition of the kiln slag. In addition, since the reaction is carried out at high temperature, red mud will melt during the high-temperature reaction process, which will cause the rotary kiln equipment to form rings, resulting in a high failure rate. The present invention adopts the method of adding 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.

[0050] 3. Low-cost magnetization of iron in red mud: In order to avoid the incomplete reaction of aluminum, titanium and alkali during the red mud alkali roasting process, which leads to high aluminum and titanium content in the obtained hematite, coal injection cooling is carried out on the slag after roasting in the rotary kiln, so that the iron in the slag clinker is reduced from hematite to magnetite, further realizing the separation of iron and aluminum and titanium components. This process does not require additional heating, and uses the heat of the slag itself for reaction, which is low in cost.

[0051] 4. Wet separation of iron and aluminum from red mud: After calcination by fire, the iron in the red mud exists as iron oxide and the aluminum exists as sodium aluminate. Since sodium aluminate has good water solubility, the slag can be separated by water cooling. After the slag is dissolved, a highly alkaline solution will be obtained, which is mainly composed of sodium aluminate and sodium carbonate. Since the purified flue gas is mainly CO 2 Mainly, CO 2Direct discharge will not only increase carbon emissions, but also waste resources. When alkaline solution is used to absorb flue gas, the pH of the solution will gradually decrease. When the pH of the solution drops to 10-11, the aluminum in the sodium aluminate will be converted into aluminum hydroxide and precipitated, thereby achieving the separation of aluminum and sodium. The Al content in the treated red mud can be less than 1%.

[0052] 5. Separation of iron and titanium in red mud and recycling of chlorine: Titanium in red mud mainly exists in the rutile phase, which is tightly wrapped with iron, and the Ti content is generally 2-4%. Since the ironmaking process does not have the ability to absorb titanium, its addition amount 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 a titanium-rich phase and an 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 steel sintering for absorption. The titanium-rich phase contains 40% iron and 10% titanium, and direct discarding causes 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.

[0053] 6. Resource utilization of sulfur in desulfurization by-products and recycling of waste alkali: Sodium sulfate, sodium sulfite and calcium sulfite in baking soda desulfurization ash and semi-dry desulfurization ash will decompose into sulfur dioxide under high temperature conditions. After sulfur dioxide is treated by activated carbon method, high-concentration sulfur-rich gas (sulfur dioxide concentration>5%) can be obtained by regeneration, while the waste alkali liquor after aluminum sodium separation is mainly composed of sodium hydroxide and sodium carbonate. The high-concentration sulfur-rich gas is reacted with the waste alkali liquor in countercurrent, that is, the waste alkali liquor enters the tertiary reactor, SO 2 The gas enters from the primary reactor. By controlling the pH and temperature of each reaction, the directional conversion of sulfur dioxide can be achieved. For example: the pH of the primary and secondary reactors is 4.1, and the pH of the tertiary reactor is 7~8. The temperature of the primary reactor is 65℃, and the temperature of the secondary and tertiary reactors is 73~75℃. The reaction of sulfur dioxide converting to sodium sulfite mainly occurs in the tertiary reactor, the reaction of sodium sulfite converting to sodium bisulfite occurs in the secondary reactor, and the reaction of sodium bisulfite converting to sodium pyrosulfite mainly occurs in the primary reactor, and precipitates in a crystalline state.

[0054] 7. Recycling of chlorine in desulfurization byproducts: Analysis of the acidic washing wastewater shows that its cations are relatively simple, mainly ammonia nitrogen and hydrogen ions, and its anions are chloride ions and sulfate / sulfite. The present invention uses calcium oxide or calcium hydroxide to adjust the pH of the acidic washing wastewater so that the solution is mainly calcium chloride. The wastewater obtained after calcium precipitation is spray-dried to obtain high-purity calcium chloride.

[0055] Compared with the prior art, the technical solution proposed by the present invention has the following beneficial technical effects: 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 a low cost.

[0056] 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.

[0057] 3. The disposal cost of the present invention is low. 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 the cost of raw materials; in addition, red mud is cooled for magnetization, which can also reduce the disposal cost; and acid wastewater is used for red mud acidification, which can reduce acid consumption.

[0058] 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

[0059] 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

[0060] The technical solution of the present invention is illustrated below by way of example, and the scope of protection requested by the present invention includes but is not limited to the following embodiments. Example 1

[0061] A method for disposing red mud and steel desulfurization waste, characterized in that the method comprises the following steps: 1) Dry the red mud, then mix it with semi-dry desulfurization ash and baking soda desulfurization ash, grind it into powder, and then mix it with iron and calcium containing solution to make balls; 2) The mixed material after ball making is transported to the rotary kiln for roasting; 3) Dry-cooling the kiln slag obtained by the rotary kiln treatment; after dry-cooling, further cooling by water cooling is performed to separate 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, and the iron-rich phase is returned to the sintering process for consumption; 5) The titanium-rich phase obtained in step 4) is subjected to an acidification reaction with an acid solution, and solid-liquid separation is performed after acidification, the obtained solid phase is titanium-containing slag, and the obtained liquid phase contains a solution of iron and calcium; 6) conveying the cooling 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 an activated carbon dry method, and the obtained purified gas is introduced into the washing tower described in step 6) to obtain a suspension; 8) The suspension obtained by the reaction in step 7) is transported to a clarifier, and solid aluminum hydroxide precipitate and alkali solution are separated in the clarifier; 60% by volume of the alkali solution is returned to step 3) for use as a coolant, and 40% by volume of the alkali solution is used in subsequent steps to react with 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, 50% by volume is returned to step 5) as an acid solution to undergo an 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; 11) The sulfur-rich gas obtained in step 9) reacts with the alkali solution obtained in step 8), and after the reaction, the solution is separated by crystallization to obtain a finished product of sodium metabisulfite. Example 2

[0062] Example 1 was repeated, except that the mass ratio of the dried red mud to the semi-dry desulfurization ash and the baking soda desulfurization ash was 10:3:2. The particle size of the mixed material after balling was 5 mm. Example 3

[0063] Example 2 was repeated, except that an ultrasonic generator was provided in the rotary kiln, and the ultrasonic generator inputted ultrasonic waves into the rotary kiln; the temperature of the roasting treatment in step 2) was 1050°C; the roasting treatment time was 45 minutes. The ultrasonic generator was set in the temperature section of 950-1050°C in the rotary kiln. Example 4

[0064] Example 3 was repeated, except that before dry cooling in step 3), coal powder was sprayed on the slag obtained after the rotary kiln treatment, and then dry cooling was performed; the amount of coal powder sprayed was 4% of the weight of the slag; and the slag was cooled to 350° C. by dry cooling. Example 5

[0065] 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 um; and in step 3), the solid-liquid separation was performed by a grab bucket. Example 6

[0066] Example 5 is repeated, except that 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 2, 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; the obtained liquid phase contains a solution containing iron and calcium, and the solution containing iron and calcium is returned to step 1) for pelletizing; the acid solution comes from the acidic washing wastewater obtained in step 9). Example 7

[0067] Example 6 is repeated, 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 the power wave washing tower is used for washing; the purified gas obtained in step 9) is introduced into the power wave washing tower described in step 6). Example 8

[0068] Example 7 is repeated, except that 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 subjected to dry desulfurization by activated carbon method; the waste heat utilization adopts a heat exchanger; the dust removal treatment adopts a bag filter. Example 9

[0069] Example 8 is repeated, except that step 11) is specifically as follows: 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, 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; 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.

[0070] Application Example 1 A method for treating red mud and steel desulfurization waste, the process flow is as follows: 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, 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 min 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 water-cooled slag is separated by a grab bucket, and then the slag is separated by magnetic separation to obtain an iron-rich phase which is returned to the sintering process for consumption, and a titanium-rich phase is obtained for subsequent acidification treatment; 5) The titanium-rich phase obtained in step 4) reacts with the dilute acid water obtained subsequently, and the pH of the solution is controlled to be 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 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 treated with bag dust removal, and then activated carbon is used. The desulfurization is carried out by dry method, 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 the clarification tank, and the solid aluminum hydroxide precipitate can be separated through the clarification tank. The liquid with a volume ratio of 60% is returned to step 3) for cooling and use, and the liquid with a volume ratio of 40% is used for the subsequent step to react with high concentration sulfur dioxide; 9) the saturated activated carbon obtained by step 8) is regenerated by high temperature, and the regenerated carbon obtained is used in the cycle step 7), and the desorbed gas obtained is washed to obtain acidic washing wastewater and sulfur-rich gas; 10) the acidic washing wastewater obtained by step 9) is recycled. After the washing wastewater is discharged, 50% by volume is used to return to step 5) for acidification reaction with the titanium-rich phase, and 50% by volume of water enters the calcium precipitation process. The supernatant after the calcium precipitation is concentrated by step circulation and coupled with calcium chloride anti-dissolution, and added to the atomizer after conditioning, and the finished product anhydrous calcium chloride is obtained by spray drying; 11) the sulfur-rich gas obtained by step 9) reacts with the alkali solution obtained by 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 for three-stage countercurrent alkali solution absorption, and the solid is the finished product sodium metabisulfite.

[0071] The obtained products were analyzed, among which the purity of calcium chloride was 98.4%, the purity of sodium metabisulfite was 96.4%, the purity of aluminum hydroxide was 99.5%, the iron content in titanium-containing slag was 20.8%, the calcium content in titanium-containing slag was 10.5%, and the titanium content in titanium-containing slag was 25.2%. The iron grade in the iron-rich phase was 62%, and the titanium content in the iron-rich phase was 0.4%. The purity of each product meets industrial standards, the process is efficient and environmentally friendly, and the resource utilization rate is significantly improved.

[0072] Application Example 2 A method for treating red mud and steel desulfurization waste in combination, the specific process flow is: 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, 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) passing the kiln slag obtained after the rotary kiln treatment into a coal injection cooling device, spraying 5 kg of coal powder into the kiln slag, cooling the kiln slag and the coal powder together, and then further cooling it with water. Cooling; 4) The water-cooled slag obtained in step 3) is separated by a grab bucket, and then the slag is separated by magnetic separation to obtain an iron-rich phase, which is returned to the sintering process for consumption, and a titanium-rich phase is obtained for subsequent acidification treatment; 5) The titanium-rich phase obtained in step 4) reacts with the dilute acid water obtained subsequently, and the pH of the solution is controlled to be 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 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 desulfurization is then carried out by dry activated carbon method, and the purified gas is then introduced into the power wave washing tower described in step 6); 8) the suspension obtained by the reaction in step 7) enters the clarification tank, and the solid aluminum hydroxide precipitate can be separated through the clarification tank. The liquid with a volume ratio of 60% is returned to step 3) for cooling and use, and the liquid with a volume ratio of 40% is used for the subsequent step to react with high-concentration sulfur dioxide; 9) the saturated activated carbon obtained by step 8) is regenerated by high temperature, and the regenerated carbon obtained is used in the recycling step 7), and the desorbed gas obtained is washed to obtain acidic washing wastewater and sulfur-rich gas; 10) the obtained by step 9) 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 by step circulation and coupled with calcium chloride anti-dissolution, and added to the atomizer after conditioning, and the finished product anhydrous calcium chloride is obtained by spray drying; 11) the sulfur-rich gas obtained by step 9) reacts with the alkali solution obtained by 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 for three-stage countercurrent alkali solution absorption, and the solid is the finished product sodium metabisulfite.

[0073] The obtained products were analyzed, among which the purity of calcium chloride was 98.5%, the purity of sodium metabisulfite was 96.3%, the purity of aluminum hydroxide was 99.8%, the iron content in titanium-containing slag was 16.5%, the calcium content in titanium-containing slag was 8.8%, and the titanium content in titanium-containing slag was 31.4%. The iron grade in the iron-rich phase was 71%, and the titanium content in the iron-rich phase was 0.1%. The purity of each product meets industrial standards, the process is efficient and environmentally friendly, and the resource utilization rate is significantly improved.

Claims

1. A method for treating red mud in cooperation with steel desulfurization waste, characterized in that: The method comprises the following steps: 1) Dry the red mud, then mix it with semi-dry desulfurization ash and baking soda desulfurization ash, grind it into powder, and then mix it with iron and calcium containing solution to make balls; 2) The mixed material after ball making is transported to the rotary kiln for roasting; 3) Dry-cooling the kiln slag obtained by the rotary kiln treatment; further cooling by water cooling after dry cooling, solid-liquid separation, and obtaining 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, and the iron-rich phase is returned to the sintering process for consumption; 5) The titanium-rich phase obtained in step 4) is subjected to an acidification reaction with an acid solution, and solid-liquid separation is performed after acidification, the obtained solid phase is titanium-containing slag, and the obtained liquid phase contains a solution of iron and calcium; 6) conveying the cooling 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 an activated carbon dry method, and the obtained purified gas is introduced into the washing tower described in step 6) to obtain a suspension; 8) The suspension obtained by the reaction in step 7) is transported to a clarifier, and solid aluminum hydroxide precipitate and alkali solution are separated in the clarifier; a part of the alkali solution is returned to step 3) for use as a coolant, and the remaining part of the alkali solution is used in the 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) The sulfur-rich gas obtained in step 9) reacts with the alkali solution obtained in step 8), and after the reaction, the solution is separated by crystallization to obtain a finished product of sodium metabisulfite.

2. The method according to claim 1, characterized in that: 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 10:1-5:1.5-3; and / or In step 1), the particle size of the mixed material after balling is 2-10 mm, preferably 3-8 mm.

3. The method according to claim 1 or 2, characterized in that: The calcination temperature in step 2) is 900-1250°C, preferably 950-1200°C, more preferably 1000-1100°C; the calcination time is 10-240min, preferably 20-120min, more preferably 30-60min; and / or An ultrasonic generator is provided in the rotary kiln, and the ultrasonic generator inputs ultrasonic waves into the rotary kiln; Preferably, the ultrasonic generator is arranged in the temperature zone of 950-1050°C in the rotary kiln.

4. The method according to any one of claims 1 to 3, characterized in that: In step 3), before dry cooling, coal powder is sprayed on the slag obtained after the rotary kiln treatment, and then dry cooling is performed; preferably, the amount of coal powder sprayed is 2-10% of the weight of the slag, preferably 3-5%; and / or Dry cooling cools the slag to 200-500°C, preferably 300-400°C.

5. The method according to any one of claims 1 to 4, characterized in that: Step 4) grinding the water-cooled slag before magnetic separation; preferably, grinding the water-cooled slag to a particle size of 50-200 um; and / or Step 3) The solid-liquid separation is carried out by a grab bucket.

6. The method according to any one of claims 1 to 5, characterized in that: 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; the obtained liquid phase contains a solution containing iron and calcium, and the solution containing iron and calcium is returned to step 1) for pelletizing; and / or The acid solution comes from the acidic washing wastewater obtained in step 9).

7. The method according to any one of claims 1 to 6, characterized in that: Step 6) specifically comprises: conveying the cooling solution obtained in step 3) to a power wave washing tower through a booster pump, and washing the solution with the power wave washing tower; Preferably, the purified gas obtained in step 9) is introduced into the dynamic wave washing tower described in step 6).

8. The method according to any one of claims 1 to 7, characterized in that: 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 subjected to desulfurization by an activated carbon dry method; Preferably, the waste heat is utilized by a heat exchanger; and the dust removal treatment is carried out by a bag filter.

9. The method according to any one of claims 1 to 8, characterized in that: Step 11) is specifically as follows: 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, 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.

10. The method according to claim 9, characterized in that: In the three-stage countercurrent absorption, the pH in the first-stage countercurrent absorption tank is controlled at 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 at 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 at 7-8, and the temperature of the solution in the third-stage countercurrent absorption tank is 70-85°C.

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