Method for promoting acidolysis of high-titanium slag for titanium extraction by using blast furnace desulfurization slag

Abstract

The application discloses a method for promoting acidolysis of high-titanium furnace slag by using blast furnace desulfurization slag, and belongs to the technical field of hydrometallurgy and comprehensive utilization of solid waste. The application provides a method for promoting acidolysis of high-titanium furnace slag by using blast furnace desulphurization slag, which comprises the following steps: mixing and grinding titanium-containing furnace slag, blast furnace desulfurization slag and carbonaceous reducing agent; roasting the mixture in a CO-containing weak reducing atmosphere at 850-980 DEG C to obtain porous modified roasted material; then, leaching the roasted material with dilute sulfuric acid to obtain a titanium-rich leaching solution; and purifying gaseous S2 produced in the roasting and hydrogen sulfide produced in the leaching by using caustic soda and H2O2 absorption liquid. In the application, CaS is used to replace elemental sulfur S2 produced in gasification to generate pores in situ by micro-blasting at grain boundaries, the prejudice of avoiding sulfur in the wet titanium extraction is overcome, the specific surface area of the roasted material is significantly increased, the diffusion resistance is reduced, low-temperature dilute acid leaching is realized, the titanium leaching rate and leaching efficiency are improved, and tail gas closed-loop oxidation treatment is realized.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgy and comprehensive utilization of solid waste, specifically relating to a method for synergistically promoting the acid hydrolysis of high-titanium slag to extract titanium using blast furnace desulfurization slag. Background Technology

[0002] The Panxi region of my country possesses extremely rich vanadium-titanium magnetite resources. During the smelting of vanadium-titanium magnetite (blast furnace or electric furnace), most of the iron and some vanadium enter the molten iron, while most of the titanium is enriched in the slag, forming titanium-bearing slag (such as high-titanium slag, where the TiO2 mass fraction is typically 35%–55%). Because this titanium-bearing slag is formed by rapid cooling at high temperatures, it has a high degree of internal crystallinity, and the titanium is mainly present as anosovite (its general chemical formula is often represented as Me). x Ti 3-x O5, where Me represents Fe 2+ Mg 2+ Al 3+ It exists in the form of a solid solution containing metal cations. This phase has extremely high lattice energy and low chemical reactivity. Conventional sulfuric acid extraction of titanium (dry acidolysis) requires high-temperature solid-phase acidolysis roasting at 150℃~220℃ using concentrated sulfuric acid of over 93%. This process consumes a huge amount of concentrated sulfuric acid and generates a large amount of acidic waste gas (SO₄²⁻). x The presence of difficult-to-treat acidic titanium gypsum wastewater severely restricts the green and sustainable development of the titanium industry.

[0003] CN102758030A discloses a seed crystal and method for promoting the growth of the perovskite phase in titanium-containing blast furnace slag, which utilizes a physical pretreatment process to promote the crystallization and growth of perovskite in a high-temperature molten state using specific seed crystals. CN108085505A discloses a method for efficiently extracting valuable titanium components from titanium-containing blast furnace slag, which involves mixing titanium-containing blast furnace slag with metal powder, roasting under a specific atmosphere, washing with water to remove salt, and dissolving in a weak acid to extract titanium. CN101812595A discloses a method for producing synthetic rutile from titanium slag, which uses a traditional technical route of mixing titanium slag with an alkaline additive, roasting to reconstruct the mineral phase, washing, and then leaching with dilute hydrochloric acid under normal pressure to produce synthetic rutile.

[0004] To lower the acidolysis temperature, existing technologies (such as CN101812595A) often involve adding alkaline calcium source additives (such as quicklime, calcium carbonate, or calcium salts) to titanium-containing slag and then modifying and roasting it at high temperatures. This remodels the insoluble black titanium stone phase into the acid-soluble perovskite (CaTiO3) phase. However, when using conventional quicklime or calcium carbonate for reconstruction, the perovskite crystals generated by the solid-phase reaction are dense and coarse-grained, lacking well-developed pores. During the dilute acidolysis process, as the surface perovskite dissolves, the fine calcium sulfate (titanium gypsum) generated by the reaction readily adheres and deposits on the surface of the particles, forming an insoluble barrier layer. This results in significant mass transfer resistance within the product layer when sulfuric acid molecules diffuse into the clinker particles from the reaction solution, transforming the leaching kinetics into a severely diffusion-controlled step. This makes the acid leaching process extremely slow. Typically, after 180 minutes of reaction, the leaching rate of titanium is only about 58%. The leaching reaction time must be significantly extended to achieve a leaching rate of over 75%, which severely limits the industrial promotion of titanium extraction using the atmospheric pressure dilute acid method.

[0005] Furthermore, the desulfurization pretreatment stage of molten iron in steel smelting generates a large amount of blast furnace desulfurization slag (also known as molten iron desulfurization slag). This type of desulfurization slag contains high concentrations of active free calcium oxide (CaO), calcium sulfide (CaS), and calcium sulfate (CaSO4). Due to its high sulfur content, it easily weathers in the air, releasing malodorous gases, and is unsuitable as a raw material for ordinary building materials. Currently, it is mostly stockpiled, causing serious secondary environmental pollution. More importantly, the sulfur element (especially CaS) in the desulfurization slag undergoes a transient metathesis reaction when it comes into contact with dilute acid, releasing high concentrations of the deadly toxic gas hydrogen sulfide (H2S). Hydrogen sulfide gas not only seriously endangers production safety, but also has a severe toxic effect on the color and purity of subsequent titanium dioxide (titanium dioxide) products. Therefore, there is a widespread industry bias among those skilled in the art of "avoiding sulfur," and for a long time, they have tried their best to avoid introducing any desulfurization slag or high-sulfur materials as modifying agents for titanium extraction. Summary of the Invention

[0006] The purpose of this invention is to address the technical challenges of low acidolytic activity of the black titanium stone phase in high-titanium slag, high energy consumption and significant environmental hazards associated with traditional high-temperature dry acidolysis using concentrated sulfuric acid, and the difficulty in utilizing and environmental pollution caused by the stockpiling of industrial blast furnace desulfurization slag. This invention provides a method for titanium extraction from high-titanium slag by synergistically promoting acidolysis using blast furnace desulfurization slag. This invention overcomes the industry's technical bias of "avoiding sulfur" in wet titanium extraction, cleverly transforming harmful sulfur into a grain boundary expansion and pore-forming agent. It achieves rapid one-step titanium extraction under mild, atmospheric pressure, and dilute sulfuric acid below 100°C. The process is highly simplified, the titanium yield is significantly and dramatically increased, and closed-loop oxidation treatment of highly toxic gases (S2 in the gaseous phase and H2S in the leaching section) is achieved, resulting in significant economic and environmental benefits.

[0007] To achieve the above objectives, this invention provides a method for synergistically promoting the acid hydrolysis of high-titanium slag using blast furnace desulfurization slag, based on the synergistic effect of "high-temperature solid-phase thermodynamic mineral phase reconstruction" and "lattice reconstruction in-situ gas phase expansion and pore formation," comprising the following steps:

[0008] A. Mix titanium-containing slag and blast furnace desulfurization slag at a mass ratio of 3~6:1, and add carbonaceous reducing agent at a total mass percentage of 2%~5% of the mixture, then grind to obtain mixed reaction material;

[0009] B. The mixed reactants are calcined in a weakly reducing atmosphere containing CO at a temperature of 850℃~980℃ to obtain porous modified calcined clinker.

[0010] C. After cooling the porous modified calcined clinker, grind it finely, then mix it with dilute sulfuric acid, and then carry out a leaching reaction under airtight, normal pressure and 75℃~95℃. After the reaction is completed, the solid and liquid are separated to obtain titanium-rich leachate.

[0011] In the above method, in step A, the carbonaceous reducing agent is at least one of reducing coal powder, coke powder, coke powder, or graphite powder.

[0012] Preferably, in the above method, in step A, the carbonaceous reducing agent is reduced coal powder.

[0013] In the above method, in step A, the high-titanium slag contains the following components by mass fraction: TiO2 35%~55%, TFe 5.0%~10.0%, SiO2 12.0%~22.0%, Al2O3 10.0%~15.0%, MgO 5.0%~10.0%, and CaO 4.0%~8.0%.

[0014] In the above method, in step A, the composition of the blast furnace desulfurization slag by mass fraction is: free CaO 20%~35%, CaS 10%~20%, CaSO4 5%~15%, SiO2 15%~25%, and the balance is calcium silicate.

[0015] In the above method, in step A, the particles are ground to a size of -0.074 mm or higher, accounting for 80% or more.

[0016] In the above method, in step B, the weakly reducing atmosphere is a mixture of CO with a volume percentage concentration of 2.0% to 5.0%, and the remainder is an inert gas mixture.

[0017] In the above method, in step B, the inert gas in the weakly reducing atmosphere is at least one of N2, He, Ne, and Ar.

[0018] Preferably, in the above method, in step B, the inert gas in the weakly reducing atmosphere is N2.

[0019] In the above method, in step B, the roasting time is 60 min to 120 min.

[0020] In the above method, in step B, the specific surface area of ​​the porous modified calcined clinker is not less than 0.42 m². 2 / g.

[0021] In the above method, in step C, the particles are ground to a size of -0.074 mm or higher, accounting for 80% or more.

[0022] In the above method, in step C, the mass percentage concentration of dilute sulfuric acid is 50%~70%.

[0023] In the above method, in step C, the liquid-solid ratio of dilute sulfuric acid to the finely ground porous modified calcined clinker is 3~5mL:1g.

[0024] In the above method, in step C, the leaching reaction time is 120 min to 240 min.

[0025] Furthermore, based on the above method, the present invention adds a tail gas absorption and emission step to achieve green emissions. In addition to steps A through C, it also includes the following steps:

[0026] D. Introduce the gaseous elemental sulfur S2 generated by roasting in step B and the hydrogen sulfide H2S generated by leaching in step C into a two-stage alkaline absorption tower. Use a mixed circulating absorbent of caustic alkali and H2O2 for spray oxidation absorption. Maintain the temperature of the mixed circulating absorbent at 40°C or below, and control the mass fraction of H2O2 in the circulating liquid to be within 1.0%~2.0%. After purification, exhaust the tail gas.

[0027] In the above method, in step D, the mass fraction of caustic alkali in the mixed circulating absorbent is 3%~8%, and the initial mass fraction of H2O2 is 1%~3%.

[0028] Preferably, in the above method, in step D, the mass fraction of caustic alkali in the mixed circulating absorbent is 4%~6%, and the initial mass fraction of H2O2 is 1.5%~2.5%.

[0029] In the above method, in step D, the caustic alkali is at least one of NaOH or KOH.

[0030] In the above method, in step D, the H2S concentration in the purified exhaust gas is less than 0.03 mg / m³. 3 .

[0031] The beneficial effects of this invention are:

[0032] This invention utilizes the elemental sulfur (S2) generated by CaS replacement gasification to create pores at grain boundaries through "in-situ micro-explosion," thereby increasing the specific surface area of ​​the clinker from 0.12 m² / g (pure quicklime calcification modification) to no less than 0.42 m² / g. 2 / g (0.42m) 2 / g~0.45m 2 / g), the high porosity greatly eliminates the mass transfer resistance of the calcium sulfate product layer generated in the reaction to the penetration of sulfuric acid molecules into the particle interior (the diffusion resistance is reduced by more than 80%), successfully transforming the dilute acid leaching kinetics process from the traditional "solid product layer diffusion mass transfer control step" to a highly active "interfacial chemical reaction control step", so that the leaching reaction can be completed extremely rapidly under mild atmospheric pressure dilute acid below 100℃ (75℃~95℃), the titanium leaching rate is stable at 90%~95%, the leaching time is reduced by half, and the equipment turnover rate is doubled.

[0033] This invention meticulously studied the sulfur phase transition law between the high-temperature S2 gas escaping from the roasting section and the trace amount of H2S gas escaping from the low-temperature acid leaching section. Employing a two-stage circulating cooling alkaline oxidation purification process, it not only completely eliminates the risk of highly toxic H2S leakage (the final exhaust gas emission concentration does not exceed 0.024 mg / m³), but also... 3 It is far superior to the national standard limit of 0.03 mg / m³. 3 It also recovers the byproduct Na2SO4 solution and high-value-added titanium gypsum filter residue, with a short process flow and significant economic benefits.

[0034] This invention uses two major industrial solid wastes, high-titanium blast furnace slag and blast furnace desulfurization slag, as raw materials, breaking the industry prejudice of "avoiding sulfur" and realizing waste treatment with waste: blast furnace desulfurization slag is used instead of purchased quicklime (or calcium carbonate) as a crystal lattice modifier. The leaching stage is optimized from the traditional high-temperature dry acid hydrolysis with concentrated sulfuric acid at 180℃~220℃ to a mild wet acid hydrolysis with dilute sulfuric acid at 75℃~95℃ under normal pressure, significantly reducing costs. It overcomes the technical prejudice of the titanium extraction industry to actively avoid sulfur due to fear of the release of highly toxic H2S and the toxicity of product color. It cleverly synergistically utilizes two major steel solid wastes, high-titanium blast furnace slag (high calcium and magnesium) and blast furnace desulfurization slag (rich in calcium and sulfur), and safely converts sulfur into the byproduct Na2SO4 for recovery through an alkaline hydrogen peroxide system. The process is green and environmentally friendly. Attached Figure Description

[0035] Figure 1 This is a flowchart of the synergistic titanium extraction process of the present invention.

[0036] Figure 2 This is a schematic diagram illustrating the principle of staged purification and absorption of exhaust gas in this invention. Detailed Implementation

[0037] Specifically, a method for synergistically promoting the acid hydrolysis of high-titanium slag using blast furnace desulfurization slag includes the following steps:

[0038] Step (1): Ingredients are mixed and ground together.

[0039] Titanium-containing slag and blast furnace desulfurization slag are mixed at a mass ratio of 3~6:1, and 2%~5% carbonaceous reducing agent is added to the total mass of the mixture. The mixture is then co-milled using a ball mill until the particle size is -0.074mm or more (80%) to obtain a mixed reaction material.

[0040] The synergistic reduction mechanism of step (1): The blast furnace desulfurization slag contains active free CaO, CaS, and CaSO4. During the heating stage of roasting, the added carbonaceous reducing agent acts as a strong reducing agent at high temperatures, reducing the calcium sulfate (CaSO4) in the desulfurization slag, which originally had no pore-forming activity, to calcium sulfide (CaS) with volatile expansion and cracking activity in situ, significantly increasing the total content of sulfides in the clinker that can be used for in-situ pore formation. The main chemical reduction reaction equations are as follows: ; .

[0041] In this invention, the main function of the carbonaceous reducing agent is to provide solid reduction during the roasting process and promote the conversion of CaSO4 in the desulfurization slag to low-valent sulfur components such as CaS. The carbonaceous reducing agent can be at least one of the following: reducing coal powder, coke powder, coke powder, or graphite powder; among these, reducing coal powder is the most effective.

[0042] Step (2): Medium-temperature synergistic modification and reduction calcination

[0043] The mixed reactant obtained in step (1) is fed into a calcining kiln and calcined at 850℃~980℃ for 60min~120min under a weakly reducing atmosphere containing CO (the volume percentage concentration of CO in the calcining atmosphere is controlled at 2.0%~5.0%, with the remainder being inert gases such as N2). This process transforms the insoluble black titanium stone phase in the high-titanium slag into the easily acid-soluble perovskite (CaTiO3) phase, resulting in a porous modified calcined clinker. The specific surface area of ​​the modified calcined clinker is controlled to be no less than 0.42m². 2 / g.

[0044] In this invention, based on the reduction of CaSO4 and the subsequent conversion reaction of sulfur-containing components, the oxygen potential of the CO / CO2 system and the sulfur-containing gas phase reaction pathway, a specific weakly reducing atmosphere of CO is adopted. In the weakly reducing atmosphere, the inert gas is used as the dilution gas and protective carrier gas of CO and does not participate in the target reaction.

[0045] The solid-phase reconstruction and grain boundary gas phase expansion cracking pore-forming mechanism in step (2):

[0046] Solid-phase mineral phase reconstruction reaction: At the solid-solid reaction interface between high-titanium slag and desulfurization slag, the active calcium oxide (CaO) in the desulfurization slag undergoes solid-phase lattice reconstruction with the insoluble anosovite (represented by its typical phase MeTi2O5) in the high-titanium slag, transforming into the acid-soluble perovskite main phase (CaTiO3) and releasing associated metal oxides. The main chemical reaction equations are as follows: Where Me represents Fe 2+ Mg 2+ (MeO represents the corresponding metal oxide).

[0047] In-situ gas-phase expansion and cracking reaction at grain boundaries: Under the combined action of a carbonaceous reducing agent and a controlled weakly reducing atmosphere, sulfur-containing components (such as CaS) in desulfurization slag undergo reduction, oxidation, and interconversion, and couple with silicate components (such as SiO2) in high-titanium slag, accompanied by the generation and escape of gaseous sulfur-containing components or elemental sulfur gas phases. At 850–980℃, the elemental sulfur gas phase can mainly exist in the form of oligosulfide molecules such as S2. The gaseous components escape from the interior of the clinker particles and grain boundaries, which is conducive to the formation of porous and fractured structures.

[0048] The net reaction formula may be: In CaS, sulfur (S) is oxidized from its -2 oxidation state to elemental sulfur, while carbon (C) in CO2 is reduced from its +4 oxidation state to CO. CO2 acts as an oxidant in this process. Although this invention employs a generally weak reducing atmosphere, the roasting system does not consist solely of reduction reactions. The reduction of CaSO4 by pulverized coal and CO both generate CO2 in situ. Therefore, components such as CO, CO2, CaS, and CaSO4 can coexist within the clinker particles and at the solid-gas interface. This invention uses controlled weak reducing conditions, rather than strong reducing conditions, and does not preclude the continued transformation of CaS under the influence of localized CO2.

[0049] Because the calcination temperature (850℃~980℃) is much higher than the boiling point of elemental sulfur (444.6℃), the newly generated S2 elemental sulfur, at the moment of nucleation and reconstruction of perovskite microcrystals, violently expands and escapes from the grain boundaries of the microcrystals with extremely high vapor pressure. This generates an in-situ "gas-phase micro-explosion and cracking" effect within the clinker matrix, spontaneously constructing high-density nanoscale (10nm~50nm) micropores and fissure channels. This results in a more than 3.5-fold increase in the specific surface area of ​​the modified clinker compared to that modified with pure quicklime (reaching 0.42m²). 2 The process (at least / g) completely breaks down the diffusion barrier of the acid leaching product layer, reducing the diffusion resistance of sulfuric acid molecules by more than 80%. The escaped gaseous elemental sulfur S2 is sent to the tail gas purification device through an airtight negative pressure exhaust system.

[0050] Step (3): Fine grinding of clinker and decomposition leaching with dilute acid under normal pressure

[0051] After cooling, the porous modified roasted clinker obtained in step (2) is ground to a particle size of -0.074 mm accounting for 80% or more. It is then sent to an airtight acid leaching reactor, and industrial dilute sulfuric acid with a mass percentage concentration of 50%~70% is added. The liquid-solid ratio (mL / g) is controlled to be 3~5:1. The leaching reaction is carried out under normal pressure and at 75℃~95℃ for 120min~240min. After filtration, titanium-rich leaching solution (mainly TiOSO2 solution) and leaching solid filter residue (mainly CaSO4·2H2O titanium gypsum) are obtained.

[0052] In this invention, the reaction vessel is kept airtight, and a tail gas outlet channel is provided and connected to the subsequent tail gas absorption system to prevent the direct escape of gases such as H2S. Therefore, the acid leaching process is a non-pressurized leaching process.

[0053] The acidolysis and sulfur side reaction mechanism in step (3):

[0054] Perovskite decomposition reaction under normal pressure with sulfuric acid: Due to the abundance of dense nanopores in the clinker, sulfuric acid molecules can penetrate deep into the clinker particles without hindrance, undergoing rapid metathesis acidolysis with the perovskite. The reaction formula is as follows: .

[0055] Residual calcium sulfide acidolysis reaction: Trace amounts of unreacted CaS remaining in the clinker react directly with dilute sulfuric acid, releasing trace amounts of highly toxic hydrogen sulfide (H2S) gas. .

[0056] In the acidolysis section, due to the low temperature (75℃~95℃), trace amounts of residual elemental sulfur safely precipitate and accumulate in the titanium gypsum solid filter residue as solid particles, without escaping into the gas phase. Under airtight negative pressure, the acid leaching reactor captures the trace amounts of escaping H2S gas and sends them to the tail gas purification device.

[0057] Step (4) involves the staged purification, absorption, and oxidation treatment of exhaust gas:

[0058] The gaseous elemental sulfur S2 discharged from the roasting kiln in step (2) and the hydrogen sulfide H2S tail gas captured in the acid leaching kettle in step (3) are uniformly sent to a two-stage alkaline absorption tower. A mixed circulating absorbent solution containing 3%~8% (preferably 4%~6%) of caustic alkali (at least one of NaOH or KOH) and 1%~3% (preferably 1.5%~2.5%) of H2O2 is used for spray oxidation absorption. During the absorption cycle, the temperature of the circulating liquid is maintained at 40℃ or below using a plate heat exchanger, and the mass fraction of H2O2 in the circulating liquid is controlled within the range of 1.0%~2.0% to ensure its thermodynamic safety. Hydrogen peroxide fully oxidizes H2S and S2 in situ in a strongly alkaline medium, converting them into a stable and harmless sodium sulfate (Na2SO4) solution for recovery. Finally, the H2S concentration in the exhaust gas is less than 0.03 mg / m³.3 This ensures that waste gas emissions meet standards and are safely discharged. The main chemical reaction equations for the absorption process are as follows: , .

[0059] In this invention, the circulating absorbent used in the absorption tower possesses both alkaline absorption and oxidation capabilities. That is, the circulating liquid contains both caustic alkali and H2O2. In actual production, the caustic alkali and H2O2 can be prepared into a mixed aqueous solution, or they can be prepared separately into aqueous solutions and then sprayed simultaneously. H2O2 is gradually consumed during the absorption and oxidation of sulfur-containing components. Therefore, during the circulating absorption process, it is necessary to replenish H2O2 according to its remaining concentration in the circulating absorbent to maintain the mass fraction of H2O2 in the circulating liquid within the range of 1.0% to 2.0% to ensure continuous oxidation capacity. Similarly, the caustic alkali is also gradually consumed during the absorption of acidic sulfur-containing gases such as H2S. Therefore, it is also necessary to replenish it according to changes in the pH or alkalinity of the circulating absorbent to maintain the mass fraction of caustic alkali in the circulating liquid within the range of 3.0% to 5.0% to maintain the alkaline absorption capacity of the circulating liquid.

[0060] In this invention, the two-stage absorption tower is a conventional tail gas absorption device in the field, which can be implemented by combining existing spray absorption towers, circulation tanks, circulation pumps, heat exchangers and tail gas pipelines.

[0061] This invention can use common high-titanium slag in the field, such as waste slag usually produced from electric furnaces or blast furnaces smelting vanadium-titanium magnetite in the Panzhihua-Xichang region. Its main components (by mass fraction) are: TiO2 35%~55%, TFe 5.0%~10.0%, SiO2 12.0%~22.0%, Al2O3 10.0%~15.0%, MgO 5.0%~10.0%, and CaO 4.0%~8.0%.

[0062] The present invention can use common blast furnace desulfurization slag in the field, whose composition is usually: 20%~35% free CaO, 10%~20% CaS, 5%~15% CaSO4, 15%~25% SiO2, and the balance is calcium silicate.

[0063] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the art or in the product manual.

[0064] Example 1

[0065] In this embodiment, the main chemical composition (mass fraction) of the high-titanium slag is: TiO2 45.20%, TFe 6.30%, SiO2 16.50%, Al2O3 12.10%, MgO 7.20%, CaO 5.40%.

[0066] The chemical composition (mass fraction) of the blast furnace desulfurization slag is as follows: free CaO 28.50%, CaS 15.30%, CaSO4 8.20%, SiO2 20.10%, with the balance being calcium silicate.

[0067] The specific process steps are as follows:

[0068] 1. Mixing the ingredients: Weigh 120g of dried high-titanium slag and 20g of blast furnace desulfurization slag (mass ratio 6:1), and add 2.80g of reducing coal powder (accounting for 2% of the total mass of the mixture of high-titanium slag and desulfurization slag). Co-mill and mix using a laboratory planetary ball mill for 30 minutes, until the particle size is -0.074mm or more (more than 85%), to obtain the mixed reaction material.

[0069] 2. Medium-temperature calcination: The mixed reactants are fed into a tubular resistance furnace and calcined at 880℃ in a weakly reducing atmosphere containing 3% CO and N2, holding the temperature for 100 minutes. The gaseous elemental sulfur (S2) generated during calcination is gas-tightly discharged. After calcination, the mixture is cooled to room temperature to obtain porous modified calcined clinker. The specific surface area of ​​this modified calcined clinker is measured to be 0.42 m². 2 / g. XRD analysis showed that the black titanium phase in the clinker had basically disappeared, and a large amount of easily acid-soluble perovskite (CaTiO3) main phase was reconstructed.

[0070] 3. Dilute acid atmospheric pressure decomposition leaching: The porous modified roasted clinker is finely ground to a particle size of -0.074mm or more (more than 80%). 100g of the finely ground clinker is weighed and placed in an airtight three-necked flask reactor. 300mL of industrial dilute sulfuric acid with a mass fraction of 50% is added (the volume-to-solid ratio is controlled at 3:1mL / g). The leaching reaction is carried out under atmospheric pressure and a constant temperature water bath at 75℃ for 240min with stirring.

[0071] 4. Tail Gas Absorption and Results: The gas escaping from the reactor during the acid leaching reaction (including highly toxic H2S gas produced by CaS acid hydrolysis), along with the gaseous S2 gas exiting the roasting section, was fed into a two-stage absorption tower. A mixed circulating liquid of 5% NaOH solution and 2% H2O2 was used for spray absorption. The temperature of the absorption circulating liquid was controlled below 40℃ using a plate heat exchanger, and the mass fraction of H2O2 in the circulating liquid was maintained within the range of 1.0%~2.0%. After the leaching reaction, vacuum filtration was performed, and the titanium leaching recovery rate was measured to be 91.20%. The H2S concentration in the tail gas emission was stable at 0.024 mg / m³. 3.

[0072] Example 2

[0073] In this embodiment, the chemical composition of the high-titanium slag and the blast furnace desulfurization slag is the same as that in Example 1.

[0074] The specific process steps are as follows:

[0075] 1. Mixing the ingredients: Weigh 100g of dried high-titanium slag and 25g of blast furnace desulfurization slag (mass ratio 4:1), and add 3.75g of reducing coal powder (accounting for 3% of the total mass of the mixture). Grind and mix the ingredients using a laboratory planetary ball mill for 30 minutes until the particle size is -0.074 mm or more, to obtain a mixed reaction material.

[0076] 2. Medium-temperature calcination: The mixed reactants are fed into a tubular resistance furnace and calcined at 920℃ in a weakly reducing atmosphere containing 3% CO and N2, holding the temperature for 90 minutes. The gaseous elemental sulfur (S2) generated during calcination is gas-tightly discharged. After calcination, the mixture is cooled to room temperature to obtain porous modified calcined clinker. The specific surface area of ​​this modified calcined clinker is measured to be 0.42 m². 2 / g, SEM microstructure shows that a large number of micropores and cracks of 10nm~50nm are uniformly distributed at the grain boundaries of its particles.

[0077] 3. Dilute acid atmospheric pressure decomposition leaching: The modified clinker is finely ground to a thickness of -0.074 mm or more (more than 80%). 100g of the finely ground clinker is weighed and placed in an airtight three-necked flask reactor. 400mL of industrial dilute sulfuric acid with a mass fraction of 60% is added (the volume-to-solid ratio is controlled at 4:1mL / g). The leaching reaction is carried out under atmospheric pressure and a constant temperature water bath at 85℃ for 180min with mechanical stirring.

[0078] 4. Tail Gas Absorption and Results: The escaping acidolysis tail gas and roasted S2 gas were fed together into a two-stage absorption tower for 5% NaOH + 2% H2O2 spray oxidation absorption (circulating liquid temperature below 40℃, hydrogen peroxide concentration controlled at 1.0%~2.0%). After the leaching reaction, vacuum filtration was performed, and the titanium leaching recovery rate was as high as 93.45%. The H2S concentration at the tail gas emission port of the purification system was 0.022 mg / m³. 3 This has achieved excellent results in the harmless recovery of sulfur.

[0079] Example 3

[0080] In this embodiment, the chemical composition of the high-titanium slag and the blast furnace desulfurization slag is the same as that in Example 1.

[0081] The specific process steps are as follows:

[0082] 1. Mixing the ingredients: Weigh 90g of dried high-titanium slag and 30g of blast furnace desulfurization slag (mass ratio 3:1), and add 6.00g of reducing coal powder (accounting for 5% of the total mass of the mixture). Co-mill and mix using a laboratory planetary ball mill for 30 minutes, until the particle size is -0.074 mm or more (more than 85%), to obtain the mixed reaction material.

[0083] 2. Medium-temperature calcination: The mixed reactants are fed into a tubular resistance furnace and calcined at 980℃ in a weakly reducing atmosphere containing 3% CO and N2, holding the temperature for 60 minutes. The gaseous elemental sulfur (S2) generated during calcination is gas-tightly discharged. After calcination, the mixture is cooled to room temperature to obtain porous modified calcined clinker. Testing shows that the specific surface area of ​​this modified calcined clinker reaches 0.45 m². 2 / g.

[0084] 3. Dilute acid atmospheric pressure decomposition leaching: The modified clinker is finely ground to a thickness of -0.074 mm or more (more than 80%). 100g of the finely ground clinker is weighed and placed in an airtight three-necked flask reactor. 500mL of industrial dilute sulfuric acid with a mass fraction of 70% is added (the volume-to-solid ratio is controlled at 5:1mL / g). The leaching reaction is carried out under atmospheric pressure and a constant temperature water bath at 95℃ with mechanical stirring for 120min.

[0085] 4. Tail Gas Absorption and Results: The acidolysis tail gas and calcination gaseous S2 were fed into a two-stage absorption tower for 5% NaOH + 2% H2O2 circulation absorption (temperature below 40℃, H2O2 mass fraction 1.0%~2.0%). After the leaching reaction, vacuum filtration was performed, and the titanium leaching recovery rate was measured to be 95.10%, with the H2S concentration at the tail gas emission point being only 0.020 mg / m³. 3 .

[0086] Comparative Example 1: Modification and roasting were carried out by adding an equivalent amount of pure quicklime with active calcium.

[0087] This comparative example uses the process parameters of Example 2 as a benchmark for comparison.

[0088] Calculation Basis: Example 2 used 25g of blast furnace desulfurization slag as a calcium source additive. The chemical composition of this blast furnace desulfurization slag is: free CaO 28.50%, CaS 15.30%, CaSO4 8.20%, SiO2 20.10%, with the balance being calcium silicate. At 920℃, calcium silicate (CaSiO3) is extremely stable in physicochemical properties and does not participate in the reconstruction reaction, making it an inert component. To ensure an equivalent level of calcium source addition, all calcium-containing mineral components (free CaO, CaS, CaSO4) in the desulfurization slag with mineral phase reconstruction activity must be equivalently converted to elemental CaO.

[0089] The conversion process is as follows: 28.50% + 15.30% × (56.08 / 72.14) + 8.20% × (56.08 / 136.14) = 28.50% + 11.90% + 3.38% = 43.78%. Therefore, the total mass of active CaO equivalent to 25g of blast furnace desulfurization slag is: 25g * 43.78% = 10.95g (take 10.9g).

[0090] Based on this, in this comparative proportion, the blast furnace desulfurization slag is replaced with an equal amount of pure quicklime (10.9g) with active calcium, and 3.75g of reducing coal powder and 100g of high-titanium slag are added (this formula does not contain sulfur). The remaining grinding parameters, roasting (920℃, 90min), dilute acid leaching (60% dilute sulfuric acid, liquid-solid ratio 4:1, 85℃, 180min) and tail gas circulation liquid preparation conditions are exactly the same as in Example 2.

[0091] Results: The clinker after reaction roasting was dense granular, and its specific surface area was measured to be only 0.12 m². 2 / g, the crystal surface has almost no nanopores. When leached with dilute sulfuric acid at 85℃ for 180 min, the titanium leaching recovery rate was only 58.30%; the reaction needed to be extended to 360 min for the titanium leaching recovery rate to reach 75.12%. This confirms that without the effect of CaS solid-phase displacement decomposition releasing elemental sulfur S2 gas phase in-situ expansion and pore-forming at grain boundaries, conventional quicklime modification results in extremely high mass transfer resistance due to the dense adhesion of the calcium sulfate product layer on the surface, leading to extremely poor acidolysis kinetics under normal pressure.

[0092] Comparative Example 2: Direct acid leaching with dilute acid without any additives

[0093] For comparison, 100g of high-titanium slag with the same composition was taken without adding any desulfurization slag or reducing coal powder. It was directly finely ground to a thickness of -0.074mm (more than 85%) and leached under the same atmospheric pressure acid leaching conditions (using 60% dilute sulfuric acid, a liquid-to-solid ratio of 4:1, and constant temperature mechanical stirring at 85℃ for 180min).

[0094] Results: Vacuum filtration analysis showed that the titanium leaching rate was only 12.30%. This indicates that, without modification and reconstruction by additives, the titanium phase in the high-titanium slag, existing as a black titanium solid solution, has an extremely stable lattice and is almost impossible to deconstruct and dissolve under normal pressure and dilute acid conditions below 100°C.

[0095] Comparative Example 3: No reducing coal powder added

[0096] Weigh out 100g of high-titanium furnace slag and 25g of blast furnace desulfurization slag, without adding reducing coal powder. Grind them together using a laboratory planetary ball mill for 30 minutes until the particle size is -0.074mm or more, to obtain a mixed reaction material.

[0097] The mixed reactants were fed into a tubular resistance furnace and heated to 920°C in a weakly reducing N2 atmosphere containing 3% CO, and then roasted for 90 minutes. Except for the absence of reducing coal powder, the roasting conditions were the same as in Example 2.

[0098] The results show that, since the blast furnace desulfurization slag itself contains CaS, and the external 3% CO weak reducing atmosphere can still promote the reduction and transformation of some CaSO4, the system can still undergo a certain degree of sulfur-containing component transformation and pore formation, but the degree of CaSO4 reduction is much lower than that in Example 2.

[0099] The BET specific surface area of ​​the roasted clinker is approximately 0.28 m². 2 / g. SEM microstructure still shows grain boundary pores and cracks, but the number of pores and the degree of connectivity are much lower than in Example 2; XRD shows that although the reconstructed perovskite product was generated, the residual CaSO4 phase was significantly increased compared to Example 2.

[0100] The obtained clinker was acid-leached under the same conditions as in Example 2, that is, using 60% sulfuric acid by mass, with a liquid-to-solid ratio of 4 mL:1 g, and leaching was carried out at 85°C with stirring for 180 min, and the titanium leaching rate was 79.0%.

[0101] Compared with 0.42m in Example 2 2 Compared to a titanium leaching rate of 93.45%, the clinker specific surface area and titanium leaching performance both decreased significantly after the removal of reducing coal powder, indicating that solid carbonaceous reducing agents are beneficial for promoting CaSO4 reduction and subsequent porous structure formation. However, since the desulfurization slag itself contains CaS and external CO still has a reducing effect, this comparative ratio will not completely lose its porous modification effect.

[0102] Comparative Example 4: Using a pure N2 inert atmosphere

[0103] Weigh 100g of high-titanium slag and 25g of blast furnace desulfurization slag, and add 3.75g of reducing coal powder, accounting for 3% of the total mass of the mixture of high-titanium slag and blast furnace desulfurization slag. Co-mill and mix using a laboratory planetary ball mill for 30 min, until the particle size is -0.074mm or more, to obtain a mixed reaction material.

[0104] The mixed reactants were fed into a tubular resistance furnace. The weakly reducing N2 atmosphere containing 3% CO in Example 2 was replaced with a pure N2 inert atmosphere. The temperature was raised to 920°C under the same gas flow rate conditions, and the furnace was held at that temperature for calcination for 90 minutes. Except for the absence of CO in the calcination atmosphere, all other conditions were the same as in Example 2.

[0105] The results showed that although external CO was eliminated, the system still contained 3.75 g of reduced coal powder. Under high-temperature conditions, the coal powder can directly participate in the carbothermic reduction of CaSO4 and can form a certain degree of localized reducing environment within the particles. Therefore, under pure N2 conditions, the conversion of CaSO4 to low-valent sulfur components does not completely stop. However, compared with Example 2 where 3% CO was introduced externally, the uniformity and stability of the overall reducing atmosphere of the system were significantly reduced, and the conversion of sulfur-containing components and the degree of porosity formation were somewhat affected.

[0106] The BET specific surface area of ​​the roasted clinker is approximately 0.29 m². 2 / g. SEM microstructure showed grain boundary pores and cracks, but the number of pores and the degree of connectivity were lower than in Example 2; XRD showed that a certain amount of reconstructed perovskite was generated, but the relative contents of sulfur-containing phases such as CaS and CaSO4 were significantly different from those in Example 2.

[0107] The obtained clinker was acid-leached under the same conditions as in Example 2, i.e., using 60% sulfuric acid at a liquid-to-solid ratio of 4 mL:1 g, and leaching with stirring at 85°C for 180 min. Based on the existing relationship between clinker specific surface area and acid leaching performance, the titanium leaching rate was simulated to be 80.0%.

[0108] Compared with 0.42m in Example 2 2 Compared to a titanium leaching rate of 93.45%, the clinker specific surface area and titanium leaching rate were significantly reduced after using a pure N2 inert atmosphere. This indicates that the weakly reducing atmosphere of external CO is beneficial for maintaining relatively stable and uniform roasting and reduction conditions, and promotes the conversion of sulfur-containing components and the formation of porous structures. However, since the reducing coal powder can still provide solid-phase reduction, the system can still maintain a certain degree of mineral phase reconstruction and porosity even after removing the external CO.

Claims

1. A method for synergistically promoting the acid hydrolysis and titanium extraction of high-titanium slag using blast furnace desulfurization slag, characterized in that: Includes the following steps: A. Mix titanium-containing slag and blast furnace desulfurization slag at a mass ratio of 3~6:1, and add carbonaceous reducing agent at a total mass percentage of 2%~5% of the mixture, then grind to obtain mixed reaction material; B. The mixed reactants are calcined in a weakly reducing atmosphere containing CO at a temperature of 850℃~980℃ to obtain porous modified calcined clinker. C. After cooling the porous modified calcined clinker, grind it finely, then mix it with dilute sulfuric acid, and then carry out a leaching reaction under airtight, normal pressure and 75℃~95℃. After the reaction is completed, the solid and liquid are separated to obtain titanium-rich leachate.

2. The method according to claim 1, characterized in that: In step A, the carbonaceous reducing agent is at least one of reduced coal powder, coke powder, coke powder or graphite powder; preferably reduced coal powder.

3. The method according to claim 1, characterized in that: In step A, the high-titanium slag contains the following components by mass fraction: TiO2 35%~55%, TFe 5.0%~10.0%, SiO2 12.0%~22.0%, Al2O3 10.0%~15.0%, MgO 5.0%~10.0%, and CaO 4.0%~8.0%.

4. The method according to claim 1, characterized in that: In step A, the composition of the blast furnace desulfurization slag by mass fraction is as follows: free CaO 20%~35%, CaS 10%~20%, CaSO4 5%~15%, SiO2 15%~25%, with the balance being calcium silicate.

5. The method according to claim 1, characterized in that: In step A, the particles are ground to a size of -0.074 mm or higher, accounting for 80% or more.

6. The method according to claim 1, characterized in that: In step B, the weakly reducing atmosphere is a mixture of CO with a volume percentage concentration of 2.0% to 5.0%, and the remainder is an inert gas mixture.

7. The method according to claim 1, characterized in that: At least one of the following must be met: In step B, the inert gas in the weakly reducing atmosphere is at least one of N2, He, Ne, and Ar; preferably N2. In step B, the roasting time is 60 min to 120 min; In step B, the specific surface area of ​​the porous modified calcined clinker is not less than 0.42 m². 2 / g.

8. The method according to claim 1, characterized in that: At least one of the following must be met: In step C, the particles are ground until the particle size is -0.074 mm or more, accounting for 80% or more. In step C, the mass percentage concentration of the dilute sulfuric acid is 50%~70%; In step C, the liquid-to-solid ratio of dilute sulfuric acid to the finely ground porous modified calcined clinker is 3-5 mL: 1 g; In step C, the leaching reaction time is 120 min to 240 min.

9. The method according to claim 1, characterized in that: It also includes the following steps: D. Introduce the gaseous elemental sulfur S2 generated by roasting in step B and the hydrogen sulfide H2S generated by leaching in step C into a two-stage alkaline absorption tower. Use a mixed circulating absorbent of caustic alkali and H2O2 for spray oxidation absorption. Maintain the temperature of the mixed circulating absorbent at 40°C or below, and control the mass fraction of H2O2 in the circulating liquid to be within 1.0%~2.0%. After purification, exhaust the tail gas.

10. The method according to claim 9, characterized in that: At least one of the following must be met: In step D, the mass fraction of caustic alkali in the mixed circulating absorbent is 3%~8%, and the initial mass fraction of H2O2 is 1%~3%; preferably, the mass fraction of caustic alkali is 4%~6%, and the initial mass fraction of H2O2 is 1.5%~2.5%. In step D, the caustic alkali is at least one of NaOH or KOH; In step D, the H2S concentration in the purified exhaust gas is less than 0.03 mg / m³. 3 .

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