Method and device for synergistically recovering fluorine and aluminum elements by using fluorine-containing sludge

Abstract

The invention provides a method and a device for synergistically recovering fluorine and aluminum elements by using fluorine-containing sludge. The method for synergistically recovering fluorine and aluminum elements by using fluorine-containing sludge provided by the invention comprises the following steps: mixing fluorine-containing sludge with a calcium source to obtain a mixed material; sequentially carrying out granulation treatment, dehydration treatment, fluorine fixation treatment and sintering treatment on the mixed material to obtain a recovery product; the dehydration treatment, the fluorine fixing treatment and the sintering treatment jointly form three-section calcination treatment, and the treatment temperatures of the dehydration treatment, the fluorine fixing treatment and the sintering treatment are sequentially increased; the recovery product comprises calcium fluoride and calcium aluminate. According to the method for synergistically recovering fluorine and aluminum elements by using the fluorine-containing sludge, provided by the invention, the fluorine-containing sludge is recycled, and the problems of environmental pollution and high treatment cost in the treatment of the fluorine-containing sludge in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of sludge resource utilization technology, and in particular to a method and apparatus for the co-recovery of fluorine and aluminum elements using fluorine-containing sludge. Background Technology

[0002] The purification and treatment of fluoride-containing wastewater in industries such as electrolytic aluminum, photovoltaics, semiconductors, and fluorochemicals generates sludge with high aluminum and fluoride content. Currently, the main methods for treating this type of sludge are incineration or landfill, but these methods are not only costly and occupy land resources, but also cause secondary pollution to the environment.

[0003] The existing technology for preparing slag-forming agents such as calcium fluoride and calcium aluminate mainly relies on non-renewable mineral resources, which results in high raw material extraction costs and poor industrial economics.

[0004] Therefore, there is an urgent need to utilize fluorine-containing sludge to prepare slag-reducing agents. Summary of the Invention

[0005] This invention provides a method and apparatus for the co-recovery of fluorine and aluminum elements from fluorine-containing sludge. The method, as provided by this invention, enables the recycling and reuse of fluorine-containing sludge. After sequentially subjecting the mixed material to granulation, dehydration, fluorine fixation, and sintering, the recovered products include calcium fluoride and calcium aluminate. This method solves the problems of environmental pollution and high treatment costs associated with existing fluorine-containing sludge treatment technologies.

[0006] Furthermore, in the method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided by the present invention, fluorine elements are fixed in the form of calcium fluoride before calcium aluminate is generated by segmented temperature control, and then compounded with the calcium aluminate obtained in the subsequent stage, so that the final co-recovered product can be used as a slag-reducing agent, realizing the positive utilization of fluorine impurities in the original fluorine-containing sludge, avoiding the complicated treatment of hydrogen fluoride gas and corrosion of pipelines and other equipment.

[0007] In a first aspect, embodiments of the present invention provide a method for the co-recovery of fluorine and aluminum elements using fluorine-containing sludge, comprising the following steps:

[0008] Fluorine-containing sludge is mixed with a calcium source to obtain a mixture.

[0009] The mixture is subjected to granulation, dehydration, fluorine fixation, and sintering processes in sequence to obtain the recovered product.

[0010] The dehydration treatment, solidification treatment, and sintering treatment together constitute a three-stage calcination process, with the treatment temperature of the dehydration treatment, solidification treatment, and sintering treatment increasing sequentially.

[0011] The recovered products include calcium fluoride and calcium aluminate.

[0012] In some embodiments of the present invention, the calcium source includes calcium oxide;

[0013] And / or, the fluoride-containing sludge includes calcium, the calcium source includes supplementary calcium, and the calcium in the recovered product includes calcium from the fluoride-containing sludge and the supplementary calcium;

[0014] And / or, the mixture includes calcium and aluminum, wherein the molar ratio of calcium to aluminum is (1.4~2.2):1;

[0015] And / or, the mass ratio of the fluoride-containing sludge to the calcium source is (1~1.6):1.

[0016] In some embodiments of the present invention, the dehydration treatment temperature is 350℃~450℃ and the treatment time is 0.5h~2h.

[0017] In some embodiments of the present invention, the solid fluoride treatment is carried out at a temperature of 800°C to 900°C for a time of 0.5 h to 2 h.

[0018] In some embodiments of the present invention, the sintering temperature is 1350℃~1400℃ and the processing time is 1h~3h.

[0019] In some embodiments of the present invention, the granulation process includes granulating the mixture using a briquetting machine;

[0020] And / or, after the granulation process, the particle size of the mixture is 5mm to 15mm.

[0021] In a second aspect, embodiments of the present invention provide an apparatus for implementing the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge as described in any embodiment of the first aspect, the apparatus comprising a dewatering treatment unit, a solid fluorine treatment unit, and a sintering treatment unit;

[0022] The outlet of the dehydration unit is connected to the inlet of the solid fluorine treatment unit, and the outlet of the solid fluorine treatment unit is connected to the inlet of the sintering treatment unit.

[0023] In some embodiments of the present invention, the dehydration treatment unit includes a dehydration chamber and a heat recovery component, wherein the heat recovery component includes a hot air nozzle, a hot air recovery pipe, and a hot air fan;

[0024] The hot air nozzle is connected to the dehydration chamber;

[0025] The hot air blower is connected to the hot air nozzle through the hot air recovery pipe.

[0026] In some embodiments of the present invention, the solid fluoride treatment unit includes a solid fluoride chamber, the inlet of which is connected to the outlet of the dehydration chamber.

[0027] In some embodiments of the present invention, the sintering processing unit includes a sintering chamber and an auxiliary component, the auxiliary component being located above the sintering chamber;

[0028] The inlet of the sintering chamber is connected to the outlet of the solid fluorine chamber;

[0029] The auxiliary components include an auxiliary fuel inlet and a supplementary fuel nozzle;

[0030] The auxiliary fuel inlet is connected to the supplementary fuel nozzle;

[0031] The supplementary fuel nozzle is connected to the sintering chamber.

[0032] This invention provides a method and apparatus for co-recovering fluorine and aluminum elements from fluorine-containing sludge. By utilizing fluorine-containing sludge for co-recovery, the resource recovery and reuse of fluorine-containing sludge is effectively achieved. The recovered products include calcium fluoride and calcium aluminate, which can be directly used as slag-forming agents in metallurgical and other industrial applications. This method not only successfully solves the problems of secondary pollution and high cost in existing fluorine-containing sludge treatment technologies, but also reduces the raw material cost in the slag-forming agent production process through a "waste-to-waste" resource recovery path, significantly improving the economic viability of the slag-forming agent for industrial application. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A process flow diagram of a method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in an embodiment of the present invention;

[0035] Figure 2 The left view is a schematic structural diagram of the apparatus for implementing the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge, as provided in an embodiment of the present invention.

[0036] Figure 3 This is a schematic front view of the apparatus for implementing a method of co-recovering fluorine and aluminum elements using fluorine-containing sludge, as provided in an embodiment of the present invention.

[0037] Figure 4 The images show the XRD patterns of the recovered products of Example 1 and Comparative Example 1 of the present invention, wherein the left image is the XRD pattern of the recovered product of Example 1 and the right image is the XRD pattern of the recovered product of Comparative Example 1.

[0038] Figure 5 The image shows the XRD pattern of the recovered product of Comparative Example 2 of this invention.

[0039] Figure 6 The images show the melting of the recovered product and simulated industrial slag at 1400°C in Test Example 2 of this invention. The left image shows the melting of the product and simulated industrial slag in Example 1 at 1400°C, and the right image shows the melting of the product and simulated industrial slag in Comparative Example 1 at 1400°C.

[0040] The attached diagram is labeled as follows: 1-Combustion chamber; 2-Firing zone; 3-Thermocouple; 4-Fuel inlet; 5-Hot air outlet; 6-Fluoride fan; 7-Dehydration chamber; 8-Fluorine solidification chamber; 9-Sintering chamber; 10-Cooling chamber; 11-Hot air nozzle; 12-Exhaust duct; 13-Insulation door lifting switch; 14-Insulation door; 15-Auxiliary fuel inlet; 16-Auxiliary combustion nozzle; 17-Supplementary fuel nozzle; 18-Residual fuel and combustible gas outlet; 19-Tail gas outlet; 20-Cold air nozzle; 21-Cold air fan; 22-Cooling conveying duct; 23-Hot air outlet; 24-Hot air fan; 25-Hot air recovery duct; 26-Kiln car; 27-Calcinated material; 28-Tail gas treatment chamber. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] In existing technologies, the fluoride-containing sludge generated after the purification treatment of fluoride-containing industrial wastewater is usually disposed of through incineration or landfill. However, this treatment method is costly and occupies land resources. Furthermore, the leaching of fluoride ions from the sludge poses a risk of secondary pollution. In addition to fluoride, fluoride-containing sludge also contains high levels of aluminum. Current methods for recovering fluoride-containing sludge focus only on the recovery of a single element, making it difficult to achieve the synergistic recovery and utilization of both elements simultaneously, resulting in low industrial economics.

[0043] Calcium fluoride and calcium aluminate are both common slag-forming agents in industrial production. The slag-forming agent formed by combining calcium fluoride and calcium aluminate can achieve rapid slag formation and more thorough slag formation, offering advantages over single-component slag-forming agents. However, current slag-forming agent production mainly relies on non-renewable mineral resources, resulting in high raw material extraction costs and poor industrial economics. Therefore, the inventors envisioned that if fluorine and aluminum elements could be synergistically recovered from fluoride-containing sludge, and the recovered products applied as a slag-forming agent, the environmental pollution and high treatment costs associated with existing fluoride-containing sludge treatment technologies could be solved, while also improving the industrial economics of slag-forming agent production.

[0044] Based on the above research, this invention provides a method for the synergistic recovery of fluorine and aluminum elements using fluorine-containing sludge, comprising the following steps: mixing fluorine-containing sludge with a calcium source to obtain a mixture; subjecting the mixture to granulation, dehydration, fluorine fixation, and sintering processes sequentially to obtain a recovered product; wherein the dehydration, fluorine fixation, and sintering processes constitute a three-stage calcination process, with the processing temperatures of the dehydration, fluorine fixation, and sintering processes increasing sequentially; wherein the recovered product includes calcium fluoride and calcium aluminate.

[0045] The method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this invention embodiment achieves the recycling and reuse of fluorine-containing sludge through a three-stage calcination process consisting of granulation, dehydration, fluorine fixation, and sintering (dehydration, fluorine fixation, and sintering constitute a three-stage calcination process). This solves the problems of environmental pollution and high treatment costs in the treatment of fluorine-containing sludge in the prior art. At the same time, through the co-recovery of fluorine and aluminum elements, the recovered products include calcium fluoride and calcium aluminate, which can be used as slag-reducing agents. This achieves the "harmlessness, reduction, and resource utilization" of fluorine-containing sludge, reduces the production cost of slag-reducing agents, and forms a green circular economy model of "treating waste with waste," thereby improving the environmental friendliness and industrial economy of this invention.

[0046] Fluorine, a conventionally unfavorable element, has been the subject of previous studies, which have mostly involved direct, one-step high-temperature production of calcium aluminate or the addition of defluorinating agents (such as those found in aluminum tailings with bound water). Under heating conditions, the bound water generates water vapor, which reacts with fluoride salts to produce gaseous hydrogen fluoride, which then volatilizes. This study utilizes solid fluoride treatment to generate calcium fluoride from the calcium source, which is then used to form a slag-reducing agent with calcium aluminate. This not only effectively avoids equipment damage caused by hydrogen fluoride volatilization but also achieves full recovery and utilization of fluorine.

[0047] In the method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this invention embodiment, the fluorine-containing sludge mainly provides fluorine and aluminum elements for the recovered products, while the calcium source additionally supplements calcium. Granulation treatment makes the morphology of the mixture more favorable for subsequent processing; dehydration treatment removes free water from the mixture, facilitating further solidification treatment; solidification treatment converts fluorine into calcium fluoride; sintering treatment generates calcium aluminate, and the auxiliary combustion during sintering allows for the efficient removal of other impurities (such as sulfur) under a reducing atmosphere. After the above treatments, the three-stage treatment with progressively increasing temperatures better reduces unnecessary energy consumption. Simultaneously, some impurities in the fluorine-containing sludge are removed, and recovered products, including calcium fluoride and calcium aluminate, are obtained, which can be used as slag-reducing agents for industrial reuse.

[0048] In existing technologies, fluoride-containing sludge is mostly directly recycled into calcium aluminate, without utilizing the fluorine element. Specifically, existing technologies often directly discharge fluoride-containing gas during the one-step sintering process to produce calcium aluminate, or mix the fluoride-containing sludge with a defluorinating agent before heating to allow water vapor to react with fluoride salts to generate volatile gaseous hydrogen fluoride, thus releasing the fluorine element. In this embodiment of the invention, solid fluoride treatment is used to generate solid calcium fluoride from fluorine and calcium. The resulting calcium fluoride is an effective component of the recovered product when used as a slag-reducing agent. This not only effectively avoids equipment damage caused by hydrogen fluoride volatilization but also achieves more complete recovery and utilization of fluorine, further improving the industrial economics of the method for co-recovering fluorine and aluminum elements using fluoride-containing sludge in this embodiment of the invention.

[0049] The embodiments of the present invention do not impose any special limitations on the composition of the fluoride-containing sludge to be treated. The fluoride-containing sludge used in the embodiments of the present invention can be derived from solid waste generated after the purification treatment of industrial wastewater. After the solid waste is preliminarily dried, the fluoride-containing sludge to be recycled is obtained. The above-mentioned drying treatment is a conventional technical means in the art. Exemplarily, the drying temperature is 100℃~150℃ and the time is 4h~24h.

[0050] Exemplary examples, in some embodiments of the present invention, after preliminary drying, the fluorinated sludge includes solid components and still contains a small amount of water. The specific components of the aforementioned fluorinated sludge are as follows: the water content in the fluorinated sludge is 10wt%~15wt% (including free water and water of crystallization); in the solid components, the mass fraction of aluminum hydroxide + aluminum fluoride complex is 60wt%~80wt% (of which the mass fraction of fluorine accounts for 1.5wt%~2wt% of the solid components), the mass fraction of calcium sulfate accounts for 6wt%~10wt% of the solid components, the mass fraction of silicon dioxide accounts for 3wt%~9wt% of the solid components, and in addition, the aforementioned solid components also contain 7wt%~15wt% of Mg, Fe, and Na compound impurities.

[0051] The method for co-recovering fluorine and aluminum elements using fluorine-containing sludge in this invention embodiment can also recover fluorine and aluminum elements from common industrial wastewater.

[0052] In some embodiments, industrial wastewater contains silicon. The wastewater can be desiliconized first to further improve the purity of the recovered products. Specifically, the industrial wastewater can be mixed with lime, and the resulting calcium silicate precipitate can be collected under a pH of 10-11 to achieve initial desiliconization. The desiliconization treatment in the above embodiments not only further reduces the silicon content in the fluorinated sludge but also further increases the calcium content, which is more conducive to the subsequent method of co-recovering fluorine and aluminum elements using fluorinated sludge as described in this invention. It also helps to increase the content of calcium fluoride and calcium aluminate in the recovered products, thereby improving the product performance when used as a slag-reducing agent and further enhancing industrial economics.

[0053] In some embodiments, after desilication treatment, industrial wastewater can be subjected to fluoride precipitation treatment to further increase the calcium fluoride content in the recovered product. Specifically, industrial wastewater can be mixed with an aluminum-based defluorination agent to obtain fluoride-containing sludge, and then the mixture including the fluoride-containing sludge and a calcium source can be recovered to obtain a recovered product, in which the calcium fluoride content is further increased.

[0054] The composition of fluoride-containing sludge can be tested using conventional testing methods and instruments. For example, XRF testing can be used.

[0055] In one specific implementation, the test can be conducted as follows: A semi-quantitative XRF assay is performed on a fluoride-containing sludge sample using an instrumental method. This involves irradiating the fluoride-containing sludge sample with high-energy X-rays (or gamma rays) to excite electrons within the sample atoms. When the excited atoms return to a stable state, they release secondary X-rays (i.e., fluorescent X-rays) with the characteristic energy of the element. By detecting and analyzing the characteristic X-rays, the element present in the sample can be determined, and its content can be calculated.

[0056] In some embodiments of the present invention, the calcium source includes calcium oxide (commonly known as "quicklime"). In the above embodiments, by using calcium oxide, which has higher reactivity and is easier to obtain, as the calcium source, the industrial economics of the method for co-recovering fluorine and aluminum elements using fluorine-containing sludge can be further improved.

[0057] In some embodiments of the present invention, the fluoride-containing sludge includes calcium, the calcium source includes supplementary calcium, and the calcium in the recovered product includes both the calcium from the fluoride-containing sludge and the supplementary calcium. That is, in the above embodiments, the calcium source added to the mixture is a supplementary calcium source, thus achieving the additional supplementation of the required calcium in the recovery method of the embodiments of the present invention.

[0058] In some embodiments of the present invention, the mixture includes calcium and aluminum elements, and the molar ratio of calcium to aluminum elements is (1.4~2.2):1.

[0059] In some embodiments of the present invention, the mass ratio of fluoride-containing sludge to calcium source is (1~1.6):1.

[0060] In the above embodiments, the calcium element comes from a calcium source and fluoride-containing sludge, while the aluminum element comes from the fluoride-containing sludge. The theoretical molar ratio of calcium to aluminum in the generated calcium aluminate is used as a benchmark in these embodiments, taking into account the fluoride content in the fluoride-containing sludge, to calculate the actual amount of calcium source to be added. By controlling the actual amount of calcium source added, the purity of calcium fluoride and calcium aluminate in the recovered product can be further improved, while also considering the cost of calcium source addition. Ultimately, this better enhances the performance of the recovered product when used as a slag-reducing agent, further improving industrial economics.

[0061] For example, the molar ratio of calcium to aluminum in the mixture is, for example, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1, or any combination thereof.

[0062] For example, the mass ratio of fluorinated sludge to calcium source is, for example, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1 or any combination thereof.

[0063] In some embodiments of the present invention, by subjecting the mixture to dehydration, solidification, and sintering treatments at gradually increasing temperatures, the dehydration treatment can further remove residual free water from the mixture, the solidification treatment can generate calcium fluoride, and the sintering treatment can generate calcium aluminate, which is more conducive to obtaining the target recovery product. At the same time, the three-stage calcination treatment with gradually increasing temperatures can further reduce the energy consumption of the calcination treatment, which is more conducive to improving the industrial economy of the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge in the embodiments of the present invention.

[0064] In some embodiments of the present invention, the dehydration treatment temperature is 350℃~450℃ and the treatment time is 0.5h~2h.

[0065] In the above embodiments, by controlling the processing temperature of the dehydration treatment, the residual free water in the mixture can be further removed, thereby further improving the processing efficiency of the remaining calcination stages.

[0066] It is worth noting that the dehydration treatment in the above embodiments is only to further remove free water from the fluoride-containing sludge. After the dehydration treatment, a small amount of crystal water still exists in the fluoride-containing sludge, which will be removed in subsequent calcination treatments.

[0067] For example, in some embodiments of the present invention, the water content of the fluoride-containing sludge after dehydration is 1wt% to 5wt%.

[0068] In some embodiments of the present invention, common testing methods in the art can be used to demonstrate that the dehydrated fluoride-containing sludge still contains a small amount of water of crystallization. For example, the fluoride-containing sludge after separate dehydration treatment can be subjected to ignition experiments at 300°C, 600°C, and 1000°C, and the weight can be measured. The tests show that the fluoride-containing sludge subjected to the ignition experiment at 1000°C has a significantly higher weight loss than the fluoride-containing sludge subjected to the ignition experiments at 300°C and 600°C, which further proves that a small amount of water remains after dehydration treatment.

[0069] For example, the dehydration treatment temperature is, for example, a range of 350°C, 360°C, 370°C, 380°C, 390°C, 395°C, 400°C, 405°C, 410°C, 420°C, 430°C, 440°C, 450°C, or any combination thereof.

[0070] In the above embodiments, by controlling the processing time of the dehydration treatment, it is more conducive to increasing the calcium fluoride content in the recovered product, and further improves the industrial economy of the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge in the present invention.

[0071] For example, the dehydration treatment time is, for example, a range of 0.5h, 1h, 1.5h, 2h, or any combination thereof.

[0072] In some embodiments of the present invention, the solid fluoride treatment temperature is 800℃~900℃ and the treatment time is 0.5h~2h.

[0073] In this embodiment of the invention, solid calcium fluoride is generated by reacting easily overflowing hydrofluoric acid gas with calcium oxide. This is more conducive to increasing the calcium fluoride content in the recovered product, thereby improving the product performance when used as a slag-reducing agent and enhancing the industrial economics of the invention. Furthermore, the addition of a calcium source ensures that the number of molar calcium molecules in the mixture exceeds the number of molar fluoride molecules, guaranteeing that the fluorine in the fluorine-containing sludge is completely converted into calcium fluoride, rather than escaping as HF gas.

[0074] During the aforementioned solid fluoride treatment stage, the water of crystallization in the fluorinated sludge that was not completely removed during the dewatering stage is released during the solid fluoride treatment stage. It reacts with the fluorinated compounds in the fluorinated sludge to generate HF, and at the temperature of the aforementioned solid fluoride treatment, it reacts more quickly and directly with the calcium source to generate calcium oxide. Therefore, it further reduces the overflow of gaseous hydrofluoric acid and further enhances the protection of the calcination equipment (taking aluminum fluoride, which is more common in fluorinated sludge, as an example, the above reaction process is AlF3+3H2O(g)=Al(OH)3+3HF(g), CaO+2HF=CaF2+H2O).

[0075] In the above embodiments, by controlling the processing temperature of the solid fluoride treatment, the fluorine-containing compounds in the fluorine-containing sludge can be further decomposed to produce hydrofluoric acid, which further promotes the reaction between hydrofluoric acid and calcium oxide to obtain calcium fluoride, thus improving the industrial applicability of the recovered products obtained in the embodiments of the present invention.

[0076] For example, the processing temperature of the solid fluorine treatment is, for example, a range of 800°C, 810°C, 820°C, 830°C, 840°C, 845°C, 850°C, 855°C, 860°C, 870°C, 880°C, 890°C, 900°C, or any combination thereof.

[0077] In the above embodiments, by controlling the processing time of solid fluoride treatment, it is more conducive to increasing the calcium fluoride content in the recovered product, and further improves the industrial economy of the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge in the present invention.

[0078] For example, the treatment time for solid fluorine treatment is, for example, a range of 0.5h, 1h, 1.5h, 2h, or any combination thereof.

[0079] In some embodiments of the present invention, the sintering temperature is 1350℃~1400℃ and the processing time is 1h~3h.

[0080] In the above embodiments, by controlling the temperature of the sintering process, the reaction to generate calcium aluminate can be further promoted, which is more conducive to improving the industrial applicability of the recycled products obtained in the embodiments of the present invention.

[0081] In addition, in the above embodiments, "oxygen-deficient" combustion (i.e., air coefficient λ < 1, such as 0.8~0.9) can be achieved in the sintering process. Since sulfate decomposition temperature is high and decomposition is difficult, it is often difficult to remove it completely. The reducing atmosphere created by "oxygen-deficient combustion" can ensure complete desulfurization in this section, further enhance the effective component content of the obtained slag-reducing agent, and further improve the industrial economy.

[0082] Furthermore, unlike the general calcium aluminate production process that uses the addition of CaS, charcoal, or other auxiliary reduction pyrolysis methods, this invention generates a reducing atmosphere through oxygen-deficient combustion during the sintering stage. The advantage is that it does not require the introduction of other auxiliary materials and only uses natural gas for combustion. Compared with the method of adding CaS, it is more economical, and the natural gas is pure and does not introduce other impurities like CaS and charcoal.

[0083] For example, the sintering temperature is a range consisting of any two of the following: 1350°C, 1355°C, 1360°C, 1365°C, 1370°C, 1375°C, 1380°C, 1385°C, 1390°C, 1395°C, and 1400°C.

[0084] In the above embodiments, controlling the sintering time is more conducive to increasing the calcium aluminate content in the recovered product, and further improves the industrial economy of the method for co-recovering fluorine and aluminum elements using fluorine-containing sludge in the present invention.

[0085] For example, the sintering process time is, for example, a range of 1h, 1.5h, 2h, 2.5h, 3h, or any combination thereof.

[0086] In some embodiments of the present invention, the granulation process includes granulating the mixture using a briquetting machine.

[0087] In the above embodiments, the fluorinated sludge after preliminary drying is ground with a calcium source and then proportioned according to the required feeding ratio described in the embodiments of the present invention. The fluorinated sludge and calcium source are mixed evenly to obtain a mixture (the mixing method can be any common technique in the art, such as ball milling). The mixture is then poured into a briquetting machine (YQJ-290 briquetting machine) and pressed into blocks under constant pressure. The particle size of the briquetting mixture is 5mm to 15mm. In the above embodiments, granulating the mixture into spheres within this particle size range is more conducive to improving the heat transfer efficiency and reactivity of subsequent dehydration, solidification, and sintering processes. It is also more conducive to improving the efficiency of synergistic recovery of fluorine and aluminum elements from the fluorinated sludge, thereby improving the product performance when the recovered product is used as a slag-reducing agent and enhancing the industrial economics of the present invention.

[0088] The particle size of the mixture can be verified using conventional testing methods and instruments. For example, it can be verified using a standard sieve sieving method.

[0089] In one specific implementation, verification can be performed as follows: Select a set of standard sieves with apertures of 4mm, 5mm, 10mm, 15mm, and 16mm, and assemble them from top to bottom in descending order of aperture size. Place the briquetting-treated mixture sample in the top 16mm sieve and fix the sieve assembly on a vibrating sieve machine for sieving. After sieving for 10 minutes, collect and weigh the material on each sieve layer, and calculate the mass percentage of the mixture in different particle size ranges.

[0090] In some embodiments of the present invention, sulfur in fluorinated sludge can be removed during the heating period of sintering. The desulfurization method provided in these embodiments does not require the addition of auxiliary reducing materials such as carbon sulfide or charcoal. During sintering, excessive combustion creates an oxygen-deficient atmosphere in the sintering chamber, which further facilitates the removal of sulfur from the fluorinated sludge. In the above embodiments, desulfurization is achieved by utilizing the environment of calcium aluminate production through calcination, eliminating the need for additional pretreatment desulfurization processes for the fluorinated sludge. This further simplifies the production process of utilizing fluorinated sludge for the co-recovery of fluorine and aluminum, thereby improving industrial economics.

[0091] Furthermore, compared to traditional desulfurization methods that add auxiliary reducing materials (the specific chemical reaction is: 2CaSO4→2CaO+2SO2↑+O2↑, and the reaction to generate sulfur dioxide needs to be achieved at 1400℃), the desulfurization method provided by the embodiments of the present invention can further reduce the desulfurization temperature (the specific chemical reactions are: CaSO4+4CO→CaS+4CO2, 3CaSO4+CaS→4CaO+4SO2↑, and the reaction to generate sulfur dioxide can be achieved at 1100℃), thereby ensuring more thorough desulfurization during the sintering heating period.

[0092] In some embodiments of the present invention, after the mixture is sintered, the resulting recycled product can be cooled, and then the cooled recycled product can be subjected to subsequent processing such as crushing and grinding. In the above embodiments, by processing the recycled product to a specific fineness (such as 80 mesh to 400 mesh), the industrial applicability of the recycled product is further improved.

[0093] The process flow diagram of the method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this embodiment of the invention is shown below. Figure 1 Specifically, the process flow of the method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this embodiment of the invention is as follows: after mixing fluorine-containing sludge with a calcium source, it is subjected to granulation treatment, dehydration treatment, fluorine fixation treatment, sintering treatment in sequence, and then cooled to obtain the recovered product of this embodiment of the invention.

[0094] This invention also provides a slag-reducing agent, which is prepared by the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge according to any embodiment of the first aspect.

[0095] The present invention also provides an apparatus for implementing the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge in any of the above embodiments. The apparatus includes a dewatering unit, a solid fluorine treatment unit, and a sintering unit; the outlet of the dewatering unit is connected to the inlet of the solid fluorine treatment unit, and the outlet of the solid fluorine treatment unit is connected to the inlet of the sintering unit.

[0096] By using the apparatus provided in this embodiment of the invention (commonly known in the art as a "tunnel kiln"), only one feeding step is needed to achieve the sequential dehydration, solidification, and sintering treatments of the mixture in the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge in this embodiment of the invention. The residual free water in the mixture can be removed in the dehydration unit, calcium fluoride can be generated in the solidification unit, and calcium aluminate can be generated in the sintering unit. The recovered products in this embodiment of the invention can be obtained through simple operation using this apparatus, which has high industrial applicability.

[0097] In some embodiments of the present invention, the dehydration treatment unit includes a dehydration chamber and a heat recovery component. The heat recovery component includes a hot air nozzle, a hot air recovery pipe, and a hot air fan. The hot air nozzle is connected to the dehydration chamber. The hot air fan is connected to the hot air nozzle through the hot air recovery pipe.

[0098] In some embodiments of the present invention, the solid fluoride treatment unit includes a solid fluoride chamber, the inlet of which is connected to the outlet of the dehydration chamber.

[0099] In some embodiments of the present invention, the sintering processing unit includes a sintering chamber and an auxiliary component, the auxiliary component being located above the sintering chamber; the inlet of the sintering chamber is connected to the outlet of the solid fluorine chamber; the auxiliary component includes an auxiliary fuel inlet and a supplementary fuel nozzle; the auxiliary fuel inlet is connected to the supplementary fuel nozzle; the supplementary fuel nozzle is connected to the sintering chamber.

[0100] In some embodiments of the present invention, the above-mentioned apparatus further includes a cooling unit, the inlet of which is connected to the outlet of the sintering treatment unit. In these embodiments, the mixture is sintered and then cooled in the cooling unit to ultimately obtain the recovered product obtained in the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge according to the embodiments of the present invention.

[0101] This invention designs a tunnel kiln for recovering fluorine-containing sludge. The tunnel kiln can achieve overall temperature control or three-stage temperature control, and can achieve "oxygen-deficient" combustion in the third stage area (i.e., sintering treatment unit) through excessive combustion, so that the corresponding position in the kiln is in a reducing atmosphere, in order to further ensure complete desulfurization.

[0102] For example, Figure 2 The left view is a schematic structural diagram of the apparatus for implementing the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge, as provided in an embodiment of the present invention. Figure 3 This is a schematic front view of the apparatus for implementing a method of co-recovering fluorine and aluminum elements using fluorine-containing sludge, as provided in an embodiment of the present invention.

[0103] like Figure 2 , Figure 3 As shown, the specific structure of the device provided by the present invention includes a combustion chamber 1, a firing zone 2, a thermocouple 3, a fuel inlet 4, a hot air outlet 5, a flue gas fan 6, a dehydration chamber 7, a fluorine solidification chamber 8, a sintering chamber 9, a cooling chamber 10, a hot air nozzle 11, a flue gas exhaust pipe 12, a door insulation lifting switch 13, a door insulation 14, an auxiliary fuel inlet 15, an auxiliary combustion nozzle 16, a supplementary fuel nozzle 17, a residual fuel and combustible gas outlet 18, a tail gas outlet 19, a cold air nozzle 20, a cold air fan 21, a cooling conveying pipe 22, a hot air exhaust outlet 23, a hot air fan 24, a hot gas recovery pipe 25, a kiln car 26, calcined material 27, and a tail gas treatment chamber 28.

[0104] In the device (i.e., tunnel kiln) provided by this invention, the combustion chamber 1 is heated by natural gas to provide heat for the three-stage calcination process of this invention embodiment. A thermocouple 3 is connected to the upper side of one side of the combustion chamber 1 to monitor the real-time temperature of the three-stage calcination process. Fuel inlets 4 are connected to both sides of the combustion chamber 1 for adding fuel. A hot air outlet 5 is connected to the inner side of the combustion chamber 1 for delivering hot air. A flue gas fan 6 is connected to the combustion chamber 1 to guide the flue gas in the tunnel kiln. An exhaust pipe 12 is connected to the top of the kiln body for exhausting the flue gas. The lower part of the insulation door lifting switch 13 is connected to the insulation door 14, which can divide the kiln body into three sections, realizing the implementation of this invention. In the example of the three-stage calcination process, the insulation door 14 is made of refractory material to ensure that the temperature of the three-stage calcination process can be independent. The hot air nozzle 11 is connected to the hot air blower 24 through the hot air recovery pipe 25. The other end of the hot air blower 24 is connected to the exhaust air port 23. Under the action of the hot air blower 24, the hot exhaust gas is returned to the hot air nozzle 11 through the hot air recovery pipe 25 to realize the recovery and utilization of heat energy. The kiln car 26 carries the calcined material 27 (the calcined material is the mixture material in the embodiment of the present invention that has undergone three-stage calcination processes of dehydration treatment, solidification treatment and sintering treatment in sequence). The kiln car 26 realizes the inward movement of the material in the kiln in the firing zone 2.

[0105] In the above-mentioned device, the dehydration treatment of the mixture can be realized in the dehydration chamber 7; the solidification treatment of the mixture can be realized in the solidification chamber 8; and the sintering treatment of the mixture can be realized in the sintering chamber 9. The outlet of the dehydration chamber 7 is connected to the inlet of the solidification chamber 8, and the outlet of the solidification chamber 8 is connected to the inlet of the sintering chamber 9. Above the sintering chamber 9 are auxiliary components, including an auxiliary fuel inlet 15, a supplementary fuel nozzle 17, an auxiliary combustion nozzle 16, a residual fuel and combustible gas outlet 18, a tail gas outlet 19, and a tail gas treatment chamber 28. The auxiliary fuel inlet 15 is connected to two outlets, one of which is the supplementary fuel nozzle 17, and the other is the auxiliary combustion nozzle 16. The supplementary fuel nozzle 17 sprays supplementary fuel into the sintering chamber 9, causing excessive combustion in the sintering chamber 9, thereby generating a reducing atmosphere, achieving desulfurization and generating sulfur dioxide gas in this embodiment of the invention. The residual tail gas enters the tail gas treatment chamber 28 through the residual fuel and combustible gas outlet 18, and the trace amounts of unreacted reducing gas are further converted into carbon dioxide through the auxiliary combustion nozzle 16. Finally, carbon dioxide and sulfur dioxide are discharged together through the tail gas outlet 19 for centralized treatment.

[0106] In the above-mentioned device, the cooling chamber 10 can be used to cool the mixed materials. The inlet of the cooling chamber 10 is connected to the outlet of the sintering chamber 9. A cooling assembly is located above the cooling chamber 10, including a cold air nozzle 20, a cold air fan 21, and a cooling conveying pipe 22. One end of the cold air fan 21 is connected to the cold air nozzle 20, and the other end is connected to the cooling conveying pipe 22. Cooling air is sprayed into the cooling chamber 10 through the cold air nozzle 20 to cool the calcined material 27. At the same time, the cooling air is sprayed from top to bottom. After contacting the hot gas, the hot gas will rise and be recovered to the hot gas recovery pipe 25 by the hot air fan 24, so as to realize the recovery and utilization of heat energy.

[0107] After the mixture undergoes dehydration, solidification, sintering, and cooling in the above-mentioned apparatus, the recovered product obtained in the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge according to the present invention can be obtained. This recovered product includes calcium fluoride and calcium aluminate, which can be used as a slag-reducing agent, thereby improving the industrial economy of the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge according to the present invention.

[0108] To further understand the present invention, the technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0109] Unless otherwise specified, the testing methods involved in this invention are all conventional methods used in the art; the reagents involved in the embodiments of this invention are all commercially available products and can be purchased through commercial channels.

[0110] Example 1

[0111] The method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this embodiment includes the following steps:

[0112] 1) Fluorine-containing sludge and calcium source (calcium oxide) are mixed at a mass ratio of 1:1 (the molar ratio of calcium to aluminum is 1.4:1) and then pressed into raw material balls in a briquetting machine (granulation process).

[0113] 2) Place the raw material pellets in a tunnel kiln and sequentially perform dehydration treatment (temperature 400℃, time 0.5h), solidification treatment (temperature 900℃, time 1h), and sintering treatment (temperature 1400℃, time 2h). After cooling, the recovered product is obtained.

[0114] Example 2

[0115] The method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this embodiment can be referred to in Embodiment 1. The difference is that the mass ratio of fluorine-containing sludge to calcium source is different in step 1). In this embodiment, the mass ratio is 1.2:1 and the molar ratio of calcium and aluminum is 1.6:1.

[0116] Example 3

[0117] The method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this embodiment can be referred to in Embodiment 1. The difference is that the mass ratio of fluorine-containing sludge to calcium source is different in step 1). In this embodiment, the mass ratio is 1.4:1 and the molar ratio of calcium to aluminum is 1.8:1.

[0118] Example 4

[0119] The method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this embodiment can be referred to in Embodiment 1. The difference is that the mass ratio of fluorine-containing sludge to calcium source is different in step 1). In this embodiment, the mass ratio is 1.5:1 and the molar ratio of calcium to aluminum is 2:1.

[0120] Example 5

[0121] The method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this embodiment can be referred to in Embodiment 1. The difference is that the mass ratio of fluorine-containing sludge to calcium source is different in step 1). In this embodiment, the mass ratio is 1.6:1 and the molar ratio of calcium to aluminum is 2.2:1.

[0122] Example 6

[0123] The method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this embodiment can be referred to in Embodiment 1. The difference lies in the different parameters of dehydration treatment, solid fluoride treatment, and sintering treatment in step 2) of this embodiment. In this embodiment, the dehydration treatment temperature is 350℃ and the time is 0.5h; the solid fluoride treatment temperature is 800℃ and the time is 0.5h; and the sintering treatment temperature is 1350℃ and the time is 1h.

[0124] Example 7

[0125] The method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this embodiment can be referred to in Embodiment 1. The difference lies in the different parameters of dehydration treatment, solid fluoride treatment, and sintering treatment in step 2) of this embodiment. In this embodiment, the dehydration treatment temperature is 450℃ and the time is 2h; the solid fluoride treatment temperature is 900℃ and the time is 2h; and the sintering treatment temperature is 1400℃ and the time is 3h.

[0126] Comparative Example 1

[0127] The method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this comparative example includes the following steps:

[0128] 1) Fluorine-containing sludge and calcium source (calcium oxide) are mixed at a mass ratio of 1:1 (the molar ratio of calcium to aluminum is 1.4:1) and then pressed into raw material briquettes in a briquetting machine;

[0129] 2) The raw material pellets were calcined in a muffle furnace at 1400℃ for 2 hours, and the recovered product was obtained after cooling.

[0130] Comparative Example 2

[0131] The method for co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in this comparative example includes the following steps:

[0132] 1) Fluoride-containing sludge is directly pressed into raw material pellets in a briquetting machine without the addition of a calcium source;

[0133] 2) The raw material pellets were placed in a tunnel kiln for three-stage calcination treatment with progressively increasing temperatures. The treatment temperature and time for each stage were the same as in Example 1.

[0134] Test Example 1

[0135] The components of the recovered products in Example 1 and Comparative Examples 1 and 2 were tested.

[0136] The test content is as follows: XRD was used to test the recovered product components in Example 1, Comparative Example 1, and Comparative Example 2. The test results are as follows. Figure 4 , Figure 5 As shown, where Figure 4 The left figure is the XRD pattern of the recovered product from Example 1. Figure 4 The right figure shows the XRD pattern of the recovered product from Comparative Example 1. Figure 5 The XRD pattern of the recovered product of Comparative Example 2 is shown in Table 1. The components of the recovered products in Example 1 and Comparative Example 1 were detected by XRF, and the results are shown in Table 1. The sulfur content in Comparative Example 1 was tested by infrared carbon-sulfur analysis.

[0137] Table 1:

[0138]

[0139] Depend on Figure 4 As can be seen, after the three-stage calcination treatment in the embodiments of the present invention, the obvious peak of the recovered product in Example 1 is only the diffraction peak of the calcium aluminate phase, and the sulfur-containing phase in the product completely disappears. That is, the present invention also has excellent desulfurization effect. However, due to the small content of calcium fluoride, the results cannot be directly obtained from XRD. The XRF detection results in Table 1 can further prove that the solid fluoride treatment in the present invention can fix fluorine in the form of calcium fluoride in the recovered product.

[0140] Depend on Figure 4 It can be seen that the main phase in the recovered product of Comparative Example 1 is Ca. 12 Al 14 O 33 It also contains small amounts of calcium silicate and calcium aluminate sulfate. Infrared carbon-sulfur analysis revealed that 1.35 wt% of sulfur remained in the recovered product. This is because sulfur reacted during the calcination process at 1400℃, forming the difficult-to-remove Ca₄(Al₆O₃)₂. 12 (SO4) phase. As shown in Table 1, the recovered product in Comparative Example 1 does not contain calcium fluoride, which further proves the necessity of the solid fluoride treatment of the present invention.

[0141] Depend on Figure 5 It can be seen that the recovered products obtained in Comparative Example 2 are almost entirely aluminum oxide. In the absence of a calcium source, the recovered product samples will hardly generate calcium aluminate.

[0142] Test Example 2

[0143] The effect of the recycled products in the examples and comparative examples on reducing the melting point of the auxiliary slag was tested, and the test method is as follows:

[0144] The recovered products from Examples and Comparative Example 1 were mixed with simulated industrial slag (50wt% CaO, 30wt% SiO2, 10wt% Al2O3, 10wt% MgO) at a mass ratio of 1:10. The mixtures were then placed in crucibles and heated in a muffle furnace at a rate of 10℃ / min. The melting temperatures of the corresponding mixtures were observed and recorded. The simulated industrial slag was used as a reference, and the same test was performed. The test results for the above melting temperatures are shown in Table 2.

[0145] Table 2:

[0146]

[0147] The image shows the actual melting process of the recovered product mixed with simulated industrial slag at 1400℃ for 1.5 hours. Figure 6 As shown, the left figure is a physical image of the melting of Example 1 and simulated industrial slag at 1400°C, and the right figure is a physical image of the melting of Comparative Example 1 and simulated industrial slag at 1400°C.

[0148] Depend on Figure 6 It can be seen that at 1400℃, the slag-forming effect of the recycled product in Example 1 is better, and the mixture can be completely melted after being mixed with the simulated industrial slag; while the slag-forming effect of the recycled product in Comparative Example 1 is not ideal. After being mixed with the simulated industrial slag, the melting effect of the mixture is not good, and only a certain melting shrinkage can be observed. The mixture cannot be completely melted at this temperature.

[0149] As shown in Table 2, the recovered products obtained by the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge provided in the embodiment can significantly reduce the melting temperature of industrial slag when used as a slag-reducing agent, thus achieving the transformation of slag into a low-melting-point and high-fluidity product.

[0150] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for co-recovering fluorine and aluminum elements using fluorine-containing sludge, characterized in that, Includes the following steps: Fluorine-containing sludge is mixed with a calcium source to obtain a mixture. The mixture is subjected to granulation, dehydration, fluorine fixation, and sintering processes in sequence to obtain the recovered product. The dehydration treatment, solidification treatment, and sintering treatment together constitute a three-stage calcination process, with the treatment temperature of the dehydration treatment, solidification treatment, and sintering treatment increasing sequentially. The recovered products include calcium fluoride and calcium aluminate.

2. The method according to claim 1, characterized in that, The calcium source includes calcium oxide; And / or, the fluoride-containing sludge includes calcium, the calcium source includes supplementary calcium, and the calcium in the recovered product includes calcium from the fluoride-containing sludge and the supplementary calcium; And / or, the mixture includes calcium and aluminum, wherein the molar ratio of calcium to aluminum is (1.4~2.2):1; And / or, the mass ratio of the fluoride-containing sludge to the calcium source is (1~1.6):

1.

3. The method according to claim 1, characterized in that, The dehydration process is carried out at a temperature of 350℃ to 450℃ for a duration of 0.5h to 2h.

4. The method according to claim 1, characterized in that, The solid fluoride treatment is carried out at a temperature of 800℃~900℃ for a time of 0.5h~2h.

5. The method according to claim 1, characterized in that, The sintering process is carried out at a temperature of 1350℃ to 1400℃ for 1 hour to 3 hours.

6. The method according to claim 1, characterized in that, The granulation process includes granulating the mixture using a briquetting machine; And / or, after the granulation process, the particle size of the mixture is 5mm to 15mm.

7. An apparatus for implementing the method of co-recovering fluorine and aluminum elements using fluorine-containing sludge as described in any one of claims 1-6, characterized in that, The device includes a dehydration treatment unit, a solid fluoride treatment unit, and a sintering treatment unit; The outlet of the dehydration unit is connected to the inlet of the solid fluorine treatment unit, and the outlet of the solid fluorine treatment unit is connected to the inlet of the sintering treatment unit.

8. The apparatus according to claim 7, characterized in that, The dehydration treatment unit includes a dehydration chamber and a heat recovery component, which includes a hot air nozzle, a hot air recovery pipe, and a hot air fan. The hot air nozzle is connected to the dehydration chamber; The hot air blower is connected to the hot air nozzle through the hot air recovery pipe.

9. The apparatus according to claim 8, characterized in that, The solid fluoride treatment unit includes a solid fluoride chamber, the inlet of which is connected to the outlet of the dehydration chamber.

10. The apparatus according to claim 9, characterized in that, The sintering processing unit includes a sintering chamber and auxiliary components, with the auxiliary components located above the sintering chamber; The inlet of the sintering chamber is connected to the outlet of the solid fluorine chamber; The auxiliary components include an auxiliary fuel inlet and a supplementary fuel nozzle; The auxiliary fuel inlet is connected to the supplementary fuel nozzle; The supplementary fuel nozzle is connected to the sintering chamber.

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