A method for recovering copper and iodine from sinter machine head dust

Abstract

This invention belongs to the field of sintering process waste treatment technology, and provides a method for recovering copper and iodine from sintering machine head ash. The method involves using desulfurization wastewater to perform coordination leaching on the sintering machine head ash, utilizing the characteristic that ammonia nitrogen and chlorine in the desulfurization wastewater readily form complex ions with copper to selectively and efficiently dissolve copper from the machine head ash. The resulting copper-containing washing ash water is subjected to sulfidation precipitation, and the sulfidation precipitate is then subjected to oxidative acid leaching to obtain a copper-containing solution. The washing ash water after sulfidation precipitation is evaporated and desalted to obtain an iodine-rich evaporation mother liquor. Taking advantage of the low solubility of CuI, copper powder is added to the copper-containing solution to neutralize Cu. + The generated Cu + It can react with I in the iodine-rich mother liquor ‑ Direct precipitation is used to achieve efficient precipitation and recovery of iodine in the mother liquor, avoiding the problem of low recovery rate caused by multiple oxidation and precipitation processes in traditional iodine recovery processes.

Description

Technical Field

[0001] This invention relates to a method for treating waste in a sintering process, specifically a method for recovering copper and iodine from sintering machine head ash, belonging to the technical field of sintering process wastewater and waste treatment. Background Technology

[0002] Sintering machine head ash is a typical solid waste generated during the sintering process in steel production. It is mainly collected by electrostatic precipitators in the sintering machine head flue gas and contains various complex metals and halides. If not properly treated, it can easily cause equipment scaling, environmental pollution, and resource waste. Currently, the mainstream resource recovery approach is to achieve potassium and sodium separation and recovery through water washing, truly turning waste into treasure. Sintering machine head ash contains many valuable metal elements. Some steel companies, due to the large-scale use of copper-containing waste such as copper slag, produce head ash with high copper content. Since copper exists mostly in oxide form, it is extremely difficult to dissolve, making it difficult to dissolve copper in traditional head ash water washing processes, resulting in copper resource waste. On the other hand, sintering machine head ash generally contains iodine, although at a low content. This iodine can be enriched in the mother liquor through a head ash water washing-evaporation process, making it valuable for recycling.

[0003] Desulfurization wastewater is highly polluting wastewater generated by industrial enterprises such as coal-fired power plants and steel mills during the use of wet flue gas desulfurization (such as the limestone-gypsum method) or activated carbon desulfurization (SRG gas scrubbing wastewater). It contains high concentrations of ammonium and chloride ions; simultaneously, the desulfurization wastewater is acidic, with a pH value typically between 0 and 6, and is highly corrosive to equipment. It requires specialized treatment to meet environmental emission standards or achieve zero-emission targets. Current common methods involve adding lime slurry or sodium hydroxide to the wastewater to adjust the pH to 8.5-9.5, causing most heavy metals to precipitate as hydroxides; then adding organic sulfides (such as TMT-15) to remove metal ions that are difficult to precipitate.

[0004] Chinese patent CN120683364A discloses a method for efficient recovery and utilization of metals from sintering machine head ash leachate. This method involves oxidative acid leaching of the sintering machine head ash, followed by treatment of the leachate using displacement and precipitating agents, including displacement, acid dissolution, and reduction, to separate and recover metals such as silver, bismuth, and copper. While this technology improves copper leaching efficiency by leaching copper and other resources from the machine head ash through oxidative acid leaching, a large amount of iron also dissolves into the leachate, making subsequent impurity removal difficult. Chinese patent CN109250689A discloses a process for preparing calcium iodate using brine after zinc oxide rinsing as raw material. This method uses brine after zinc oxide rinsing as raw material and prepares calcium iodate through evaporation and concentration, iodine precipitation, purification, oxidation, and synthesis steps. It uses hydrogen peroxide to oxidize iodine, followed by alkali dissolution and chlorate oxidation, controlling pH and temperature to achieve stable iodine utilization. This technology achieves high-value iodine recovery, but the process involves multiple steps, including iodine oxidation, secondary precipitation of iodine sludge, and secondary oxidation leaching with iodine-rich solution. The process is lengthy and the overall recovery rate is low.

[0005] Existing technologies treat desulfurization wastewater and sintering machine head ash separately, and do not include technical solutions for the co-processing and resource utilization of copper and iodine in these two wastes. Summary of the Invention

[0006] To address the technical problems in existing technologies, such as the difficulty in efficiently and co-recovering copper and iodine from sintering mill head ash, and the low resource utilization rate, high processing costs, lengthy processes, and inability to recycle materials due to the separate treatment of desulfurization wastewater and sintering mill head ash, this invention provides a resource-based treatment method for the efficient recovery of copper and iodine through the co-processing of desulfurization wastewater and sintering mill head ash. This method uses desulfurization wastewater instead of pure water or pure acid for the initial water washing of the sintering mill head ash, utilizing its contained Cl... - NH4 + The weakly acidic environment enhances the dissolution kinetics of copper and iodine; the washing liquid is directionally enriched with copper through sulfide precipitation, and the liquid after copper precipitation is softened and hardened before entering the evaporation crystallization system, so that iodine is enriched in the mother liquor; the iodine-containing mother liquor is mixed with the acid leaching liquid of the copper precipitation sulfide slag, and reducing copper powder is added to react and generate cuprous iodide precipitate; after washing and drying, CuI product is obtained, and the filtrate is returned to the washing process for reuse.

[0007] According to the first embodiment of the present invention, a resource-based treatment method is provided that synergistically utilizes desulfurization wastewater and sintering machine head ash to achieve efficient recovery of copper and iodine.

[0008] A method for recovering copper and iodine from sintering mill head ash, the method comprising the following steps:

[0009] S1. Use desulfurization wastewater to wash the sintering machine head ash, control the pH of the final mixture at the end of the washing, and separate the solid and liquid to obtain copper-containing ash washing water and desalination filter cake.

[0010] S2. Sulfide precipitation is carried out on copper-containing washing ash water, and solid-liquid separation is performed to obtain precipitated liquid and copper-containing slag.

[0011] S3. The precipitated liquid is softened and hardened, and then evaporated and crystallized to obtain a chloride-containing salt and an iodine-containing mother liquor.

[0012] S4. The copper-containing slag obtained in step S2 is leached using a mixture of hydrochloric acid and hydrogen peroxide to separate the solid and liquid components, resulting in elemental sulfur and a copper-containing solution.

[0013] S5. Mix the iodine-containing mother liquor obtained in step S3 with the copper-containing solution obtained in step S4, add copper powder to the mixture, stir to react, let stand, and separate the solid and liquid phases. The solid phase is a mixture of cuprous iodide and copper powder, and the liquid phase is the liquid after copper precipitation.

[0014] In this invention, the desulfurization wastewater mentioned in step S1 is wet desulfurization wastewater or activated carbon desulfurization wastewater.

[0015] In this invention, the sintering machine head ash is dust collected from the sintering machine.

[0016] Preferably, the concentration of ammonium ions in the desulfurization wastewater in step S1 is 1~10 g / L, the concentration of chloride ions is 5~50 g / L, and the pH of the desulfurization wastewater is 0~6. The sintering machine head ash contains copper, iodine, potassium, sodium, chloride, iron, and calcium.

[0017] In this invention, the mixing ratio of desulfurization wastewater and sintering machine head ash is 2~5:1 L / kg.

[0018] In this invention, the pH of the final washing mixture is controlled to be 4-6.

[0019] In this invention, the sulfidation precipitation in step S2 specifically involves: adding a sulfiding agent to copper-containing washing ash water, stirring to carry out the reaction, allowing it to stand, separating the solid and liquid, and obtaining the precipitated liquid and copper-containing slag.

[0020] Preferably, the sulfiding agent is one or more of sodium sulfide, organic sulfur, and polysulfide-based descaling agents.

[0021] Preferably, the organic sulfur is at least one of TMT-15 and aminodithiocarbamate. The polysulfide-based sludge remover is at least one of sodium polysulfide and calcium polysulfide.

[0022] Preferably, the amount of sulfiding agent added is such that the molar ratio of copper ions to sulfur ions in the copper-containing washing ash water is 1:1 to 1.1.

[0023] Preferably, the softening and hardening process in step S3 specifically involves adding a softening agent to the precipitated liquid, stirring to carry out the reaction, and then separating the solid and liquid after the reaction is completed.

[0024] Preferably, the softening agent is sodium carbonate and / or liquid alkali. The amount of softening agent added is 0.5~10 g / L.

[0025] As a preferred embodiment, the evaporation and crystallization process in step S3 is specifically as follows: the liquid phase after the softening and hardening process is concentrated and crystallized by three-stage countercurrent evaporation to obtain chloride-containing salt, condensate, and iodine-containing mother liquor.

[0026] Preferably, the condensate is transported to the water washing process in step S1 and / or to the desulfurization and denitrification process.

[0027] In this invention, the chloride-containing salt is potassium chloride and / or sodium chloride.

[0028] In this invention, in step S4, the concentration of hydrochloric acid in the mixture of hydrochloric acid and hydrogen peroxide is 0.5~3 mol / L; the amount of hydrogen peroxide added is 10~50 mL / L.

[0029] In this invention, the liquid-to-solid ratio of the mixture of hydrochloric acid and hydrogen peroxide to the copper-containing slag is 3~6:1 L / kg.

[0030] In this invention, the mixing ratio of the iodine-containing mother liquor and the copper-containing solution in step S5 is such that the molar ratio of the concentration of iodine ions to the concentration of copper ions after mixing is 1:0.4~0.6.

[0031] In this invention, the amount of copper powder added is such that the molar ratio of copper to the concentration of copper ions in the mixture is 1:0.5-1.0, preferably 1:0.6-0.8.

[0032] In this invention, the reaction temperature of the sulfide precipitation in step S2 is 25~60℃.

[0033] In this invention, the process conditions for the softening and hardening process in step S3 are a reaction time of 10-30 min and a reaction temperature of 25-60℃.

[0034] In this invention, the evaporation crystallization process conditions are as follows: the softened and de-hardened liquid phase is passed sequentially through a triple-effect reactor, a double-effect reactor, and a single-effect reactor. The temperature in the triple-effect reactor is 20-60°C (preferably 30-50°C), the temperature in the double-effect evaporation is 40-90°C (preferably 50-80°C), and the temperature in the single-effect evaporation is 70-105°C (preferably 80-100°C). Condensate is obtained during the evaporation process. The purified liquid is concentrated and discharged from the single-effect reactor into a thickener, producing sodium chloride crystals and sodium mother liquor.

[0035] In this invention, the reaction temperature in step S5 is 60~90℃.

[0036] Preferably, the solid-liquid separation is performed by filtration, vacuum filtration, or centrifugation.

[0037] Preferably, the desalinated filter cake obtained in step S1 is used as a sintering raw material.

[0038] Preferably, the copper plating solution obtained in step S5 is returned to the water washing process in step S1.

[0039] The specific technical solution of this invention is as follows:

[0040] 1) Mix the desulfurization wastewater and sintering machine head ash to form a slurry, and obtain copper-containing ash washing water and desalination filter cake. The desalination filter cake is returned to the sintering feed. The desulfurization wastewater used includes at least one of wet desulfurization wastewater and activated carbon desulfurization wastewater.

[0041] 2) Use precipitants such as sodium sulfide, organic sulfur, and polysulfide-based precipitants to precipitate heavy metals such as copper in the washing water to obtain copper-containing slag and precipitated liquid.

[0042] 3) After softening and hardening the precipitate, multi-effect countercurrent evaporation is used to concentrate and separate and recover potassium chloride, sodium chloride and iodine-containing mother liquor. The condensate generated during the evaporation process is collected separately. The triple-effect condensate with high ammonia content is returned to step 1) as water washing makeup water. When the ammonia nitrogen reaches a certain concentration, it is opened for use in the desulfurization and denitrification process.

[0043] 4) Using hydrogen peroxide and hydrochloric acid, the copper-containing slag obtained in step 2) is oxidized and acid-leached to obtain copper-containing leachate and elemental sulfur slag. The sulfur slag can be sold directly for sulfur preparation.

[0044] 5) Mix the copper-containing leaching solution obtained in step 4) with the iodine-containing mother liquor obtained in step 3), add copper powder to precipitate, and obtain cuprous iodide product and copper precipitation liquid. The copper precipitation liquid is returned to step 1) as water replenishment for washing.

[0045] The technical principle of this invention is as follows:

[0046] 1) Coordination leaching of copper: Copper in the dust from the machine head generally exists in the form of oxides. Desulfurization wastewater is introduced as a leaching agent, utilizing the ammonia nitrogen and chlorine in the wastewater to perform coordination leaching of copper, resulting in copper as [Cu(NH3)4]. 2+ and CuCl4 2- The leaching process significantly improves the copper leaching rate. By controlling the pH of the final washing solution to 4-6, the problem of excessive iron and calcium leaching leading to difficulties in impurity removal is avoided.

[0047] 2) Oxidative leaching of copper sulfide slag: Copper sulfide slag is very stable and difficult to dissolve by conventional acid leaching. It usually requires desulfurization through oxidative roasting. By introducing hydrogen peroxide into the leaching process to oxidize the sulfur, efficient copper dissolution is achieved. The reaction process is as follows:

[0048] CuS + 2H + + H2O2 = Cu 2+ + S↓ + 2H2O.

[0049] 3) Precipitation of copper iodide: Cuprous iodide has extremely low solubility (Ksp = 1.1 × 10⁻⁶). -12 By adding copper powder and Cu in a copper-containing solution 2+ A disproportionation reaction occurs to give Cu + Then, it reacts with iodine in the iodine-containing mother liquor to undergo a precipitation reaction, ultimately yielding the CuI product. The reaction process is as follows:

[0050] Cu + Cu 2+ + 2I - = 2CuI.

[0051] In actual steel production scenarios, sintering machine head ash has a high copper content due to the presence of copper-containing waste in the raw materials. When treated using conventional water washing methods, copper oxides are difficult to dissolve, and the copper ion concentration in the washing liquid remains at a low level. At the same time, the desulfurization wastewater generated by this enterprise is weakly acidic and contains high concentrations of chloride and ammonium ions. In separate treatment processes, additional alkaline substances need to be added for neutralization, increasing the process steps and equipment maintenance difficulty. In this scenario, the water washing process cannot effectively extract copper resources. Although iodine can be enriched in the evaporation mother liquor, it requires multiple steps such as oxidation precipitation, secondary precipitation of iodine sludge, and secondary oxidation leaching with iodine-rich solution for recovery. Furthermore, the acidic nature of the desulfurization wastewater exacerbates scaling and corrosion problems in the treatment equipment, further limiting resource recovery efficiency.

[0052] Sintering machine head ash refers to the solid waste generated during the sintering process in steel production, primarily collected by an electrostatic precipitator for flue gas from the sintering machine head. This substance typically contains various metallic elements and halides, such as copper, iodine, potassium, sodium, chloride, iron, and calcium. Desulfurization wastewater refers to the wastewater generated during flue gas desulfurization processes in industrial enterprises such as coal-fired power plants and steel mills. This wastewater usually contains high concentrations of ammonium and chloride ions and is weakly acidic, exhibiting a certain degree of corrosiveness to equipment.

[0053] In this invention, sulfide precipitation is a method that removes metal ions from solution by reacting sulfides with metal ions to form insoluble metal sulfide precipitates. This method is commonly used in the treatment of heavy metal wastewater. Softening to remove hardness refers to the process of removing hardness ions such as calcium and magnesium from water using chemical methods. This is usually achieved by adding softening agents to cause hardness ions to precipitate or transform into other forms, thereby reducing water hardness. Evaporation crystallization is a process in which the solvent in a solution is evaporated by heating, causing the solute to reach a supersaturated state and precipitate crystals. This method is commonly used to recover salts from solution. Leaching refers to the process of separating and extracting components by contacting a solvent with a solid material, causing the target component in the solid to dissolve into the solvent. The leachate usually contains the dissolved target substance.

[0054] In this invention, in step S1, desulfurization wastewater is used to wash the sintering machine head ash. First, desulfurization wastewater with a pH of 0-6 is added, causing iodine in the sintering machine head ash to dissolve and combine with ammonium and chloride ions in the mixture to form a copper complex. The pH of the final washing mixture is controlled to be 4-6. Under this environment, the copper complex remains in the liquid phase, while iron and calcium ions hydrolyze and precipitate into the solid phase, achieving copper ion separation. Subsequently, solid-liquid separation is performed to obtain copper-containing ash wash water and desalination filter cake. This washing process can be achieved by mixing the sintering machine head ash and desulfurization wastewater in a stirred tank to ensure sufficient contact reaction. For example, the sintering machine head ash can be added in batches to a container containing desulfurization wastewater, and mechanical stirring can be used to ensure thorough solid-liquid mixing. Solid-liquid separation can be achieved using simple sedimentation separation, such as allowing the mixture to stand for a period of time to allow the solid particles to settle naturally, and then decanting the supernatant.

[0055] In this invention, in step S2, the copper-containing washing ash water undergoes sulfidation precipitation, followed by solid-liquid separation to obtain a precipitate and copper-containing slag. This sulfidation precipitation process can be achieved by adding a substance that can react with copper ions to the copper-containing washing ash water to form a sulfide precipitate.

[0056] In this invention, in step S3, the precipitated liquid undergoes a softening and hardening process, followed by an evaporation and crystallization process to obtain a chloride-containing salt and an iodine-containing mother liquor. The softening and hardening process can be achieved by adding a substance to the precipitated liquid that can react with hardness ions such as calcium and magnesium to form a precipitate. For example, calcium hydroxide or sodium carbonate solution can be added to cause calcium and magnesium ions to precipitate. The evaporation and crystallization process can be achieved by heating the softened and hardened liquid to evaporate its water content, thereby causing the salts in the solution to reach a supersaturated state and crystallize out.

[0057] In this invention, in step S4, the copper-containing slag obtained in step S2 is leached using a mixture of hydrochloric acid and hydrogen peroxide, followed by solid-liquid separation to obtain elemental sulfur and a copper-containing solution. This leaching process can be achieved by mixing the copper-containing slag with the mixture of hydrochloric acid and hydrogen peroxide in a reactor to allow for a complete reaction. For example, the copper-containing slag can be added to a container containing dilute hydrochloric acid and hydrogen peroxide solution, and stirring can be used to promote the dissolution of copper. Solid-liquid separation can be performed by centrifugation, for example, using a centrifuge to separate solid elemental sulfur from the copper-containing solution.

[0058] In this invention, in step S5, the iodine-containing mother liquor obtained in step S3 is mixed with the copper-containing solution obtained in step S4. Copper powder is added to the mixture, and the mixture is stirred to carry out the reaction. After standing, solid-liquid separation is performed, and the final solid phase is a mixture of cuprous iodide and copper powder, while the liquid phase is the liquid after copper precipitation. This mixing reaction process can be achieved by mixing the two solutions in a reaction vessel, adding copper powder, and promoting the reaction of iodine ions with copper ions and copper powder through stirring. For example, the iodine-containing mother liquor and the copper-containing solution can be mixed in a certain proportion, and then an appropriate amount of copper powder can be added, followed by stirring to carry out the reaction. After standing, solid-liquid separation can be performed by filtration, for example, by vacuum filtration to separate the solid mixture from the liquid.

[0059] In this invention, desulfurization wastewater refers to wastewater generated during industrial production processes, particularly in flue gas desulfurization processes at coal-fired power plants and steel mills. Wet desulfurization wastewater typically refers to wastewater generated after removing sulfur dioxide from flue gas using wet processes such as the limestone-gypsum method. Its composition is complex, potentially containing various ions such as chloride ions, sulfate ions, and calcium ions. Activated carbon desulfurization wastewater refers to wastewater generated during the regeneration process after activated carbon adsorption desulfurization. It is characterized by the potential presence of specific pollutants adsorbed by the activated carbon and regenerator residues. Both types of wastewater can be used as washing media. Their specific ionic composition and pH range provide a favorable chemical environment for the dissolution of copper and iodine in sintering machine head ash, while simultaneously achieving resource utilization of waste. Sintering machine head ash is industrial solid waste generated during the sintering process in steel production, primarily originating from dust carried by the flue gas during sintering. It is specifically defined as "dust collected from the sintering machine," including valuable elements such as copper and iodine. Ammonium and chloride ions can form complexes with copper ions or promote their dissolution in aqueous solutions. For example, chloride ions can form chloride complexes with copper, increasing its solubility; ammonium ions may also promote the dissolution of certain copper-containing compounds. Controlling the concentration of ammonium ions at 1–10 g / L and the concentration of chloride ions at 5–50 g / L can effectively enhance the leaching efficiency of copper. Maintaining the pH of the desulfurization wastewater at 0–6 provides a suitable acidic environment for the effective dissolution of copper and iodine, and also facilitates subsequent solid-liquid separation operations. The water-ash ratio is a key parameter in the washing process, directly affecting the solid-liquid contact efficiency and the dissolution balance of the target elements. Controlling the water-ash ratio within the range of 2–5:1 L / kg ensures sufficient contact between the desulfurization wastewater and the sintering machine head ash, allowing copper and iodine to effectively dissolve in the liquid phase, while avoiding excessive water volume leading to excessive load on subsequent evaporation and concentration, or insufficient water volume leading to incomplete leaching. Optimizing this ratio helps improve washing efficiency and economy.

[0060] In this invention, sodium sulfide is an inorganic sulfide with the chemical formula Na₂S, which can hydrolyze in aqueous solution to produce sulfide ions (S₂S). 2- ) and sulfide ions (HS) - These ions can react with copper ions (Cu). 2+The reaction produces copper sulfide (CuS) precipitate. Sodium sulfide has the advantage of being a sulfiding agent due to its relatively low cost and high reactivity, enabling rapid precipitate formation. The organic sulfur can be at least one of TMT-15 and 207A. Organic sulfur compounds are a class of organic compounds containing carbon-sulfur bonds, such as TMT-15 (tristaltitrile triazine trisodium salt) and aminodithiocarbamates (dithiocarbamates). These organic sulfur compounds typically have multiple active sulfur atoms, enabling them to form stable, insoluble chelates or precipitates with various heavy metal ions. They exhibit excellent heavy metal removal effects even at low concentrations, and the precipitates formed typically have good stability and filtration performance. The polysulfide-based heavy metal removal agent can be at least one of sodium polysulfide and calcium polysulfide. Polysulfide-based heavy metal removal agents refer to compounds containing multiple sulfur atoms, such as sodium polysulfide (Na2S). x ) and calcium polysulfide (CaS) x These compounds release polysulfide ions in aqueous solutions. These polysulfide ions possess strong redox activity and complexing ability, enabling them to form complex and highly stable sulfide precipitates with heavy metal ions. The advantage of polysulfide-based heavy metal removal agents lies in their broad-spectrum removal effect on a variety of heavy metal ions, and the resulting precipitates are typically dense and easy to separate from liquids.

[0061] In this invention, copper in sintering machine head ash generally exists in oxide form. To achieve copper leaching, existing technologies typically use acid as a leaching agent to directly wash the ash. However, other metallic elements (such as iron and calcium) contained in the sintering machine head ash also dissolve simultaneously, making subsequent separation difficult and hindering the high-value recovery of copper. Therefore, this invention creatively introduces desulfurization wastewater as a leaching agent, specifically using desulfurization wastewater for coordination leaching of the sintering machine head ash. The acidity of the desulfurization wastewater facilitates the dissolution of copper ions. Then, the ammonia nitrogen and chlorine in the desulfurization wastewater readily form complex ions with copper for coordination leaching, resulting in copper in the form of [Cu(NH3)4]. 2+ and CuCl4 2- The iron and calcium in the sintering machine head ash dissolve in their original form, while the iron and calcium in the mixed solution hydrolyze to form precipitates at the pH of 4-6 at the end of the water washing process, remaining in the solid phase. This selectively achieves efficient leaching of copper from the sintering machine head ash, significantly increasing the copper leaching rate. By controlling the pH of the mixed solution at the end of the water washing process, the problem of excessive leaching of iron and calcium, which would lead to difficulties in subsequent impurity removal, is avoided. It should also be noted that after being washed with desulfurization wastewater, the potassium, sodium, and chloride ions contained in the sintering machine head ash are basically removed into the liquid phase (i.e., the copper-containing ash washing water). This means that the resulting desalination filter cake not only retains a large amount of iron and calcium, which are beneficial to sintering, but also removes a large amount of potassium, sodium, and chloride, which are detrimental to sintering. In other words, after being washed with desulfurization wastewater, the sintering machine head ash is more suitable for use as a sintering feedstock, significantly avoiding or even eliminating the generation of secondary solid waste.

[0062] In this invention, if the content of ammonia nitrogen and chlorine in the desulfurization wastewater is low, the concentration of ammonia nitrogen and chlorine in the desulfurization wastewater can be increased by concentrating or adding substances containing ammonia nitrogen and chlorine (such as ammonium chloride). This invention uses desulfurization wastewater containing ammonia nitrogen and chlorine as a leaching agent. On one hand, it achieves selective leaching of copper from the head ash; on the other hand, it also washes away alkali metals (potassium, sodium) from the head ash, allowing the resulting desalination filter cake to be recycled as sintering raw material, thus avoiding or even eliminating the generation of secondary solid waste. Furthermore, the desulfurization wastewater also contains a certain amount of sulfite ions, which, together with ammonia nitrogen and a small amount of dissolved calcium ions, form calcium sulfite precipitate, and synergistically with ammonia and a small amount of dissolved iron ions, form ferrous ammonium sulfite precipitate, which enters the desalination filter cake. This helps to further prevent iron, calcium, and copper from entering the liquid phase (copper-containing ash washing water). In addition, using desulfurization wastewater as ash washing water consumes a large amount of desulfurization wastewater, significantly reducing the wastewater treatment volume of other desulfurization wastewater treatment processes. This reduction in volume and increase in efficiency aligns with the production concept of "treating waste with waste," making it environmentally friendly.

[0063] Compared with the prior art, the technical solution provided by the present invention has the following beneficial technical effects:

[0064] 1. By co-washing the sintering machine head ash with desulfurization wastewater, the strong coordination ability of ammonia nitrogen and chlorine in the desulfurization wastewater with copper is utilized to achieve efficient leaching of copper from the machine head ash, avoiding the difficulty of subsequent impurity removal caused by the dissolution of large amounts of impurities such as iron and calcium in the traditional acid leaching process.

[0065] 2. The copper-containing slag obtained from precipitation is subjected to secondary leaching to obtain a copper-containing solution. By adding copper powder, the monovalent copper generated is easily precipitated with iodine, and CuI product is recovered by precipitation, thus achieving high-value recovery of iodine and copper simultaneously.

[0066] 3. The water recycling rate throughout the entire process reaches over 95%, and the quality-based reuse of condensate and open-loop synergistic regulation significantly reduces the amount of wastewater discharged.

[0067] 4. The process conditions are mild, operating at normal pressure and temperature, without the need for high-temperature roasting or strong acid systems, which greatly reduces energy consumption and corrosion risk. Attached Figure Description

[0068] Figure 1 This is a schematic diagram of the process flow of the collaborative resource utilization method described in this invention. Detailed Implementation

[0069] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments.

[0070] This application proposes a method for recovering copper and iodine from sintering machine head ash, aiming to effectively recover copper and iodine from sintering machine head ash, and achieve resource recycling and environmental friendliness.

[0071] The specific steps are as follows: S1. Use desulfurization wastewater to wash the sintering machine head ash, control the pH of the mixed liquid at the end of the washing, separate the solid and liquid, and obtain copper-containing washing ash water and desalination filter cake.

[0072] Preferably, the desulfurization wastewater is wet desulfurization wastewater or activated carbon desulfurization wastewater, and the sintering machine head ash is dust collected from the sintering machine.

[0073] More preferably, the concentration of ammonium ions in the desulfurization wastewater is 1-10 g / L, the concentration of chloride ions is 5-50 g / L, and the pH is 0-6. The water-to-ash ratio is preferably 2-5:1 L / kg. The pH of the final washing mixture is controlled to be 4-6.

[0074] S2. The copper-containing washing water is subjected to sulfidation precipitation, and solid-liquid separation is performed to obtain the precipitated liquid and copper-containing slag.

[0075] Preferably, the vulcanizing agent is one or more of sodium sulfide, organic sulfur, and polysulfide-based de-weighting agent, the organic sulfur is at least one of TMT-15 and 207A, and the polysulfide-based de-weighting agent is at least one of sodium polysulfide and calcium polysulfide.

[0076] The preferred amount of sulfiding agent added is such that the molar ratio of copper ions to sulfur ions in the copper-containing washing ash water is 1:1-1.1.

[0077] The preferred reaction temperature for sulfide precipitation is 25~60°C.

[0078] S3. The precipitated liquid is softened and hardened, and then evaporated and crystallized to obtain a mother liquor containing chloride salt and iodine.

[0079] Preferably, the softening and hardening agent is sodium carbonate and / or liquid alkali, and the amount added is 0.5~10 g / L.

[0080] The preferred process conditions for the softening and hardening process are a reaction time of 10-30 min and a reaction temperature of 25-60°C.

[0081] The preferred process conditions for evaporation crystallization are to pass the liquid phase sequentially through a triple-effect reactor, a double-effect reactor, and a single-effect reactor, obtain condensate during the evaporation process, and then concentrate the purified liquid to produce sodium chloride crystals and sodium mother liquor.

[0082] The condensate is preferably returned to the water washing process in step S1 and / or transported to the desulfurization and denitrification process.

[0083] Chlorine-containing salts are preferably potassium chloride and / or sodium chloride.

[0084] S4. The copper-containing slag obtained in step S2 is leached using a mixture of hydrochloric acid and hydrogen peroxide to separate the solid and liquid components, resulting in elemental sulfur and a copper-containing solution.

[0085] The concentration of hydrochloric acid in the mixture of hydrochloric acid and hydrogen peroxide is preferably 0.5~3 mol / L, and the amount of hydrogen peroxide added is 10~50 mL / L.

[0086] The preferred liquid-to-solid ratio is 3~6:1 L / kg.

[0087] S5. Mix the iodine-containing mother liquor obtained in step S3 with the copper-containing solution obtained in step S4, add copper powder to the mixture, stir to react, let stand, and separate the solid and liquid phases. The solid phase is a mixture of cuprous iodide and copper powder, and the liquid phase is the liquid after copper precipitation.

[0088] The preferred mixing ratio of the iodine-containing mother liquor and the copper-containing solution is such that the molar ratio of the concentration of iodine ions to the concentration of copper ions after mixing is 1:0.4~0.6.

[0089] The amount of copper powder added is preferably such that the molar ratio of copper to copper ion concentration in the mixture is 1:0.5~1.0, more preferably 1:0.6~0.8.

[0090] The preferred reaction temperature is 60~90°C.

[0091] The beneficial effects of this application are that copper in the sintering machine head ash can be effectively recovered through water washing and sulfide precipitation of desulfurization wastewater, while iodine can be recovered through softening and evaporation crystallization, thereby realizing the recycling of resources and reducing environmental pollution.

[0092] The copper recovery rate is improved by leaching with a mixture of hydrochloric acid and hydrogen peroxide, and iodine is recovered by precipitating cuprous iodide.

[0093] The desalination filter cake obtained in step S1 is preferably used as a sintering raw material to realize the resource utilization of waste.

[0094] The copper plating solution obtained in step S5 is preferably returned to the water washing process in step S1 to achieve wastewater recycling.

[0095] Preferably, the solid-liquid separation in this application is achieved by filtration, vacuum filtration, or centrifugation, which is simple to operate and easy to implement.

[0096] The desalination filter cake obtained in step S1 is preferably used as a sintering raw material to realize the resource utilization of waste.

[0097] The copper plating solution obtained in step S5 is preferably returned to the water washing process in step S1 to achieve wastewater recycling.

[0098] Example 1

[0099] A method for recovering copper and iodine from sintering mill head ash includes the following steps:

[0100] S1. The sintering machine head ash is washed with desulfurization wastewater, and the pH of the final mixture is controlled at 4-6. Solid-liquid separation is performed to obtain copper-containing washing ash water and desalination filter cake. The desulfurization wastewater is wet desulfurization wastewater. The sintering machine head ash contains copper, iodine, potassium, sodium, chlorine, iron, and calcium. The mixing ratio of the added desulfurization wastewater to the sintering machine head ash is 5:1 L / kg.

[0101] S2. Add sodium sulfide to the copper-containing washing ash water, stir to react, let stand, and separate the solid and liquid to obtain the precipitated liquid and copper-containing slag; the amount of sulfiding agent added is such that the molar ratio of copper ions to sulfur ions in the copper-containing washing ash water is 1:1.

[0102] S3. The precipitated liquid is subjected to a softening and hardening process, followed by an evaporation and crystallization process to obtain a chloride-containing salt and an iodine-containing mother liquor; the softening and hardening agent is sodium carbonate.

[0103] S4. The copper-containing slag obtained in step S2 is leached using dilute hydrochloric acid and hydrogen peroxide to separate the solid and liquid, and to obtain elemental sulfur and copper-containing solution.

[0104] S5. Mix the iodine-containing mother liquor obtained in step S3 with the copper-containing solution obtained in step S4, add copper powder to the mixture, stir to react, let stand, and separate the solid and liquid phases. The solid phase is a mixture of cuprous iodide and copper powder, and the liquid phase is the liquid after copper precipitation.

[0105] Example 2

[0106] A method for recovering copper and iodine from sintering mill head ash includes the following steps:

[0107] S1. The sintering machine head ash is washed with desulfurization wastewater, and the pH of the final mixture is controlled at 4-6. Solid-liquid separation is performed to obtain copper-containing washing ash water and desalination filter cake. The desulfurization wastewater is activated carbon desulfurization wastewater. The sintering machine head ash contains copper, iodine, potassium, sodium, chlorine, iron, calcium, and / or the amount of desulfurization wastewater added and the mixing ratio of the sintering machine head ash are 2:1 L / kg.

[0108] S2. Add TMT-15 to the copper-containing washing ash water, stir to react, let stand, and separate the solid and liquid to obtain the precipitated liquid and copper-containing slag; the amount of sulfiding agent added is such that the molar ratio of copper ions to sulfur ions in the copper-containing washing ash water is 1:1.05.

[0109] S3. The precipitated liquid is subjected to a softening and hardening process, followed by an evaporation and crystallization process to obtain a chloride-containing salt and an iodine-containing mother liquor; the softening and hardening agent is sodium carbonate.

[0110] S4. The copper-containing slag obtained in step S2 is leached using dilute hydrochloric acid and hydrogen peroxide to separate the solid and liquid, and to obtain elemental sulfur and copper-containing solution.

[0111] S5. Mix the iodine-containing mother liquor obtained in step S3 with the copper-containing solution obtained in step S4, add copper powder to the mixture, stir to react, let stand, and separate the solid and liquid phases. The solid phase is a mixture of cuprous iodide and copper powder, and the liquid phase is the liquid after copper precipitation.

[0112] Example 3

[0113] A method for recovering copper and iodine from sintering mill head ash includes the following steps:

[0114] S1. The sintering machine head ash is washed with desulfurization wastewater, and the pH of the final mixture is controlled at 4-6. Solid-liquid separation is performed to obtain copper-containing washing ash water and desalination filter cake. The sintering machine head ash contains copper, iodine, potassium, sodium, chlorine, iron, calcium, and / or the amount of desulfurization wastewater added and the mixing ratio of the sintering machine head ash are 4:1 L / kg.

[0115] S2. Add sodium polysulfide to the copper-containing washing ash water, stir to react, let stand, and separate the solid and liquid to obtain the precipitated liquid and copper-containing slag; the amount of sulfiding agent added is such that the molar ratio of copper ions to sulfur ions in the copper-containing washing ash water is 1:1.1.

[0116] S3. The precipitated liquid is softened and hardened, and then evaporated and crystallized to obtain a chloride-containing salt and an iodine-containing mother liquor.

[0117] S4. The copper-containing slag obtained in step S2 is leached using dilute hydrochloric acid and hydrogen peroxide to separate the solid and liquid, and to obtain elemental sulfur and copper-containing solution.

[0118] S5. Mix the iodine-containing mother liquor obtained in step S3 with the copper-containing solution obtained in step S4, add copper powder to the mixture, stir to react, let stand, and separate the solid and liquid phases. The solid phase is a mixture of cuprous iodide and copper powder, and the liquid phase is the liquid after copper precipitation.

[0119] Example 4

[0120] A method for recovering copper and iodine from sintering mill head ash includes the following steps:

[0121] S1. The sintering machine head ash is washed with desulfurization wastewater, and the pH of the final mixture is controlled at 4-6. Solid-liquid separation is performed to obtain copper-containing washing ash water and desalination filter cake. The sintering machine head ash contains copper, iodine, potassium, sodium, chlorine, iron, calcium, and / or the amount of desulfurization wastewater added and the mixing ratio of the sintering machine head ash are 3:1 L / kg.

[0122] S2. Sulfide precipitation is carried out on copper-containing washing ash water, and solid-liquid separation is performed to obtain precipitated liquid and copper-containing slag.

[0123] S3. The precipitated liquid is softened and hardened, and then subjected to a three-stage countercurrent evaporation, concentration and crystallization process to obtain a mother liquor containing chloride salts and iodine; the softening and hardening agent is sodium carbonate and sodium hydroxide.

[0124] S4. The copper-containing slag obtained in step S2 is leached using dilute hydrochloric acid and hydrogen peroxide to separate the solid and liquid, and to obtain elemental sulfur and copper-containing solution.

[0125] S5. Mix the iodine-containing mother liquor obtained in step S3 with the copper-containing solution obtained in step S4, add copper powder to the mixture, stir to react, let stand, and separate the solid and liquid phases. The solid phase is a mixture of cuprous iodide and copper powder, and the liquid phase is the liquid after copper precipitation.

[0126] Example 5

[0127] The embodiment 1 is repeated, except that the condensate in step S3 is transported to the water washing process in step S1; the chloride-containing salt is potassium chloride and sodium chloride.

[0128] Example 6

[0129] Repeat Example 1, except that the condensate in step S3 is transported to the desulfurization and denitrification process.

[0130] Example 7

[0131] Example 4 is repeated, except that the reaction temperature of the sulfide precipitation in step S2 is 40°C; the process conditions for the softening and hardening process in step S3 are a reaction time of 20 min and a reaction temperature of 40°C; the process conditions for the evaporation and crystallization are that the liquid phase after softening and hardening is passed sequentially through a triple-effect reactor, a double-effect reactor, and a single-effect reactor, wherein the temperature in the triple-effect reactor is 40°C, the temperature of the double-effect evaporation is 60°C, and the temperature of the single-effect evaporation is 90°C. Condensate is obtained during the evaporation process, and the purified liquid is concentrated and discharged from the single-effect reactor into a thickener, producing sodium chloride crystals and sodium mother liquor; the reaction temperature in step S5 is 80°C.

[0132] Example 8

[0133] Repeat Example 1, except that the solid-liquid separation is filtration; the desalted filter cake obtained in step S1 is used as sintering raw material; the copper precipitated liquid obtained in step S5 is returned to the water washing process of step S1.

[0134] Application Example 1

[0135] 100 kg of sintering machine head ash from a steel plant (containing 0.82 wt% Cu, 0.15 wt% I, 28.6 wt% Fe, 12.3 wt% CaO, 20.35 wt% KCl, and 6.73 wt% NaCl) was mixed with 300 L of desulfurization wastewater (pH=1.2, Cl... -22.6 g / L, NH4 + 1.8 g / L, SO4 2- 2.4 g / L, Ca 2+ 0.9 g / L) was stirred and soaked at 25 ℃ for 60 min with a solid-liquid ratio of 1:3 (w / v). The pH of the final washing solution was controlled to be 4-5. The mixture was filtered to obtain copper-containing washing ash water and desalination filter cake. The sulfur content of the copper-containing washing ash water was adjusted with Na2S·9H2O. 2- / Cu 2+ The molar ratio was 1.05:1, pH=7.8, and the reaction was carried out at 60 ℃ for 30 min. Centrifugation was used to separate copper sulfide precipitate and the liquid after copper precipitation. The copper-containing slag was oxidized and leached with 30% H2O2 and dilute hydrochloric acid at 60 ℃ for 90 min. In the mixture of hydrochloric acid and hydrogen peroxide, the hydrogen peroxide concentration was 15 mL / L, and the HCl concentration was 1 mol / L. 2+ The leaching rate reached 99.3%. Filtration yielded a solid phase of elemental sulfur and a liquid phase of copper-containing leachate. After copper precipitation, the liquid was softened with lime and sodium carbonate to remove hardness, and then subjected to triple-effect countercurrent evaporation to precipitate potassium chloride and sodium chloride. The mother liquor volume was 15% of the original evaporation liquid, and the iodine concentration in the mother liquor reached 2.7 g / L. This mother liquor was then combined with the aforementioned copper-containing leachate (containing Cu... 2+ 8.3 g / L) were mixed at a volume ratio of 10:1, and 20 g of copper powder was added to each liter of the mixture. The mixture was reacted at 60 ℃ for 45 min to generate CuI precipitate. After vacuum filtration, washing three times with deionized water, and vacuum drying at 60 ℃, 1.14 kg of CuI product with a purity of 83.2% was obtained, with an iodine recovery rate of 94.6% and a total copper recovery rate of 81.3%.

[0136] Application Example 2

[0137] Take 120 kg of sintering machine head ash from another steel plant (Cu 0.67wt%, I 0.11wt%, Fe 31.2wt%, CaO 9.8wt%, KCl 16.87wt%, NaCl 3.54wt%) and mix it with 360 L of desulfurization wastewater (pH=2.0, Cl...). - 13.1 g / L, NH4 + 2.0 g / L, SO4 2- 2.9 g / L, Ca 2+ The sample was immersed in 1.1 g / L solution at 55 °C for 75 min, and the pH of the final washing solution was controlled to be 5-6. The remaining steps were the same as in Example 1. Finally, 1.01 kg of CuI product was obtained, with a purity of 81.3%, an iodine recovery rate of 93.8%, and a total copper recovery rate of 75.7%.

[0138] Application Example 3

[0139] Take 80 kg of sintering machine head ash from a steel plant (I 0.21 wt%, Cu 0.45 wt%, Fe 35.6 wt%, Al2O3 8.3 wt%, KCl 13.87 wt%, NaCl 2.86 wt%) and mix it with 240 L of desulfurization wastewater (pH=1.7, Cl...). - 12.8 g / L, NH4 + 4.5 g / L, SO4 2- 6.1 g / L, Ca 2+ The sample was washed at 58 °C for 65 min with 1.0 g / L of CuI at a solid-liquid ratio of 1:3. The pH of the final washing solution was controlled at 4.5–5.5. Subsequent processing was the same as in Example 1. The final yield was 0.87 kg of CuI product with a purity of 84.1%, an iodine recovery rate of 92.4%, and a total copper recovery rate of 85.5%.

[0140] Application Example 4

[0141] 100 kg of sintering machine head ash from a steel plant (I 0.18wt%, Cu 0.52wt%, Fe 33.4wt%, CaO 11.2wt%, KCl 15.3wt%, NaCl 3.1wt%) was mixed with 300 L of desulfurization wastewater (pH=2.6, Cl... - 13.5 g / L, NH4 + 3.2 g / L, SO4 2- 4.7 g / L, Ca 2+ The sample was immersed in 1.3 g / L solution at 56 °C for 70 min with a solid-liquid ratio of 1:3. The pH of the final washing solution was controlled to be 4-5. The remaining steps were the same as in Example 1. Finally, 0.95 kg of CuI product was obtained with a purity of 82.7%, an iodine recovery rate of 93.1%, and a total copper recovery rate of 79.6%.

Claims

1. A method for recovering copper and iodine from sintering machine head ash, characterized in that: The method includes the following steps: S1. Use desulfurization wastewater to wash the sintering machine head ash, control the pH of the final mixture at the end of the washing, and separate the solid and liquid to obtain copper-containing ash washing water and desalination filter cake. S2. Sulfide precipitation is carried out on copper-containing washing ash water, and solid-liquid separation is performed to obtain precipitated liquid and copper-containing slag. S3. The precipitated liquid is softened and hardened, and then evaporated and crystallized to obtain a chloride-containing salt and an iodine-containing mother liquor. S4. The copper-containing slag obtained in step S2 is leached using a mixture of hydrochloric acid and hydrogen peroxide to separate the solid and liquid components, resulting in elemental sulfur and a copper-containing solution. S5. Mix the iodine-containing mother liquor obtained in step S3 with the copper-containing solution obtained in step S4, add copper powder to the mixture, stir to react, let stand, and separate the solid and liquid phases. The solid phase is a mixture of cuprous iodide and copper powder, and the liquid phase is the liquid after copper precipitation.

2. The method according to claim 1, characterized in that: The desulfurization wastewater mentioned in step S1 is wet desulfurization wastewater or activated carbon desulfurization wastewater; the sintering machine head ash is dust collected from the sintering machine; Preferably, in step S1, the concentration of ammonium ions in the desulfurization wastewater is 1-10 g / L; the concentration of chloride ions is 5-50 g / L; the pH of the desulfurization wastewater is 0-6; and the sintering machine head ash contains copper, iodine, potassium, sodium, chloride, iron, and calcium; and / or The mixing ratio of desulfurization wastewater and sintering machine head ash is 2~5:1 L / kg (water-ash ratio); and / or Control the pH of the final washing mixture to 4-6.

3. The method according to claim 1, characterized in that: The sulfidation precipitation in step S2 specifically involves: adding a sulfiding agent to copper-containing washing water, stirring to carry out the reaction, allowing it to stand, separating the solid and liquid, and obtaining the precipitated liquid and copper-containing slag. Preferably, the vulcanizing agent is one or more of sodium sulfide, organic sulfur, and polysulfide-based deweighting agent; the organic sulfur is at least one of TMT-15 and aminodithiocarbamate; and the polysulfide-based deweighting agent is at least one of sodium polysulfide and calcium polysulfide.

4. The method according to claim 3, characterized in that: The amount of sulfiding agent added is such that the molar ratio of copper ions to sulfur ions in the copper-containing washing ash water is 1:1 to 1.

1.

5. The method according to claim 1, characterized in that: In step S3, the softening and hardening process specifically involves adding a softening agent to the precipitated liquid, stirring to carry out the reaction, and then separating the solid and liquid after the reaction is completed. Preferably, the softener is sodium carbonate and / or liquid alkali; the amount of softener added is 0.5~10 g / L.

6. The method according to claim 1, characterized in that: The evaporation and crystallization process in step S3 is as follows: the liquid phase after the softening and hardening process is concentrated and crystallized by three-stage countercurrent evaporation to obtain chloride salt, condensate and iodine mother liquor; Preferably, the condensate is transported to the water washing process in step S1 and / or to the desulfurization and denitrification process; the chloride-containing salt is potassium chloride and / or sodium chloride.

7. The method according to claim 1, characterized in that: In step S4, the concentration of hydrochloric acid in the mixture of hydrochloric acid and hydrogen peroxide is 0.5–3 mol / L; the amount of hydrogen peroxide added is 10–50 mL / L; and / or The liquid-to-solid ratio of the mixture of hydrochloric acid and hydrogen peroxide to the copper-containing slag is 3~6:1 L / kg.

8. The method according to claim 1, characterized in that: In step S5, the mixing ratio of the iodine-containing mother liquor and the copper-containing solution is such that the molar ratio of iodide ion concentration to copper ion concentration after mixing is 1:0.4~0.6; and / or The amount of copper powder added is such that the molar ratio of copper to copper ion concentration in the mixture is 1:0.5~1.0, preferably 1:0.6~0.

8.

9. The method according to any one of claims 1-8, characterized in that: The reaction temperature for the sulfide precipitation in step S2 is 25~60℃; and / or The softening and hardening process in step S3 has the following conditions: reaction time of 10-30 min and reaction temperature of 25-60℃; the evaporation and crystallization process involves sequentially passing the softened and hardened liquid phase through a triple-effect reactor, a double-effect reactor, and a single-effect reactor. The temperature in the triple-effect reactor is 20-60℃ (preferably 30-50℃), the temperature in the double-effect evaporation is 40-90℃ (preferably 50-80℃), and the temperature in the single-effect evaporation is 70-105℃ (preferably 80-100℃). Condensate is obtained during evaporation. The purified liquid is concentrated and discharged from the single-effect reactor into a thickener, producing sodium chloride crystals and sodium mother liquor; and / or The reaction temperature in step S5 is 60~90℃.

10. The method according to any one of claims 1-8, characterized in that: The solid-liquid separation is performed by filtration, vacuum filtration, or centrifugation; and / or The desalination filter cake obtained in step S1 is used as a sintering raw material; and / or The copper plating solution obtained in step S5 is returned to the water washing process in step S1.

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