A system and method for synergistically processing secondary aluminum dross and desulfurization ash

Abstract

The application provides a kind of secondary aluminum ash and desulfurization ash resource system and method of synergistic treatment, the system includes along material flow closed circuit connection's pretreatment and batching system, thermal treatment system, flue gas purification and resource recovery system;Method includes: secondary aluminum ash is washed with water after and desulfurization ash is dosed according to calcium aluminum molar ratio 0.8-1.2, simultaneously generates the first flue gas containing ammonia;Mixed material is calcined to generate calcium aluminate product, simultaneously generates process flue gas rich in sulfur, process flue gas is reacted after dust removal, impurity removal with the first flue gas in liquid phase system and crystallization ammonium sulfate product is prepared, dust removal ash returns dosing.The application is converted into calcium aluminate and ammonium sulfate product by multistage synergy and full closed circuit circulation design, realizes that harmful substance is completely decomposed, pollutant near zero emission and resource depth recovery, and has significant environmental and economic benefits.

Description

Technical Field

[0001] This invention relates to the field of industrial waste solid waste treatment technology, specifically to a resource recovery system and method for the co-processing of secondary aluminum ash and desulfurization ash. Background Technology

[0002] With the rapid development of the electrolytic aluminum and aluminum alloy processing industries, the production of secondary aluminum ash is increasing daily. Secondary aluminum ash is classified as hazardous waste, containing components such as aluminum nitride (AlN), fluorides, chlorides, and residual metallic aluminum. These components cause it to react easily with water during storage and transportation, releasing ammonia gas, posing a dual risk of combustion, explosion, and environmental pollution. Currently, the resource utilization of secondary aluminum ash mainly falls into two technical paths: wet and pyrometallurgical processes. While wet processes (such as multi-stage washing and acid washing) can remove some soluble salts, they generate massive amounts of high-salt, high-ammonia-nitrogen wastewater, resulting in extremely high subsequent treatment costs. Furthermore, the process itself fails to effectively recover valuable aluminum components and nitrogen resources from the aluminum ash, making it economically unfeasible. Pyrometallurgical processes (such as high-temperature sintering and roasting) can decompose aluminum nitride through high temperatures, but this process consumes enormous amounts of energy, and the released ammonia content is complex and fluctuates greatly depending on its composition. Efficient recovery and purification technologies are still immature, and this process can easily cause secondary air pollution or generate new solid waste. Overall, existing technologies for treating secondary aluminum ash generally suffer from the bottleneck of "pollution control without resource utilization or resource utilization without economic benefits." The problems of incomplete harmlessness and low added value of resource-based products are prominent, making it difficult to meet the requirements of a green circular economy.

[0003] On the other hand, during flue gas desulfurization processes in industries such as steel and power, a large amount of desulfurization ash byproducts are generated. Its main components are calcium sulfite, calcium sulfate, and unreacted desulfurizing agents, along with soluble salt impurities such as chlorine, potassium, and sodium. Desulfurization ash is characterized by large fluctuations in composition, high moisture content, and unstable sulfite properties (e.g., it easily leads to volume expansion). Currently, its main utilization is limited to use as a building material admixture or roadbed material. However, due to its impurities and instability, it seriously affects the long-term durability and volume safety of building materials, resulting in low market acceptance and a comprehensive utilization rate far below expectations. Large stockpiles of desulfurization ash not only occupy land, but the leaching of its soluble salts also poses a potential threat to soil and groundwater.

[0004] Currently, the industry generally adopts a "divide and conquer" strategy for the treatment of two major industrial solid wastes: secondary aluminum ash and desulfurization ash. This strategy not only increases the individual treatment costs and environmental management difficulties, but also fails to achieve system-level coupling of components and energy between the wastes. In fact, simply considering the co-treatment of two wastes with vastly different physical properties and treatment objectives will face a series of insurmountable technical obstacles.

[0005] First, there are conflicts in physical properties and safety risks. Secondary aluminum ash is water-sensitive and reacts violently with water, releasing ammonia gas and posing a risk of combustion and explosion; while desulfurization ash has a high moisture content and is in a wet and sticky state. If the contradiction between moisture content and reactivity cannot be resolved during the pretreatment or mixing stage, it will directly lead to serious safety accidents, making co-processing impossible from the outset.

[0006] Secondly, there are obstacles to component interference and product degradation. High-temperature treatment of secondary alumina ash requires the introduction of specific additives to stabilize the aluminum and nitrogen components and directionally transform them into high-value products (such as calcium aluminate and spinel). However, the composition of desulfurization ash is extremely complex, containing not only calcium sources but also large amounts of sulfate, sulfite, chloride ions, and alkali metal impurities. During high-temperature processing, these impurities readily undergo uncontrollable and complex reactions with the main elements such as aluminum and silicon, interfering with the formation of the target mineral phase, leading to uneven product composition, performance degradation, and even loss of utilization value.

[0007] Thirdly, there are barriers to gas-solid utilization. The ammonia-containing flue gas released during secondary aluminum ash treatment has theoretical potential for combining with the resource utilization of sulfate components from desulfurization ash. However, in engineering, how to safely, efficiently, and economically transport and precisely apply the ammonia-containing waste gas, with unstable concentration and flow rate generated during the treatment of one hazardous waste, to the conversion process of another solid waste involves complex issues of gas purification, concentration control, multiphase reactor design, and system integration. Existing technologies are fragmented, lacking an integrated system solution capable of seamlessly coupling and stably operating two vastly different material flows, energy flows, and information flows.

[0008] Therefore, developing a disruptive technology and integrated system that can fundamentally resolve the aforementioned material property conflicts, avoid component interference, and break down the gas-solid barrier, thereby simultaneously achieving complete harmlessness and high value of all components in secondary aluminum ash and desulfurization ash, while ensuring a clean process and controllable energy consumption, has become a common key technical challenge restricting the green development of these two industries. Summary of the Invention

[0009] The purpose of this invention is to provide a resource utilization system and method for the synergistic treatment of secondary aluminum ash and desulfurization ash. This invention solves the disposal problems of secondary aluminum ash and desulfurization ash simultaneously through a highly integrated, closed-loop synergistic treatment system. On the basis of ensuring complete harmlessness, it realizes the deep resource utilization of all valuable components and maximizes energy utilization, resulting in outstanding environmental and economic benefits.

[0010] To achieve the above objectives, the present invention proposes the following technical solution:

[0011] A resource recovery system for the co-processing of secondary aluminum ash and desulfurization ash, the resource recovery system comprising:

[0012] The pretreatment and batching system is used to receive and process secondary aluminum ash and desulfurization ash, output a mixture containing aluminum and calcium, and generate the first flue gas containing ammonia.

[0013] A thermal treatment system is used to receive the mixture and sequentially preheat, calcine and cool the mixture to produce a first product and generate sulfur-containing process flue gas.

[0014] The flue gas purification and resource recovery system is used to receive and process the process flue gas. After dust removal and impurity removal, the flue gas is mixed with the first flue gas, so that the ammonia and sulfur oxides in the mixed flue gas react to prepare the second product. At the same time, the dust collected by the flue gas purification and resource recovery system during the dust removal process is returned to the pretreatment and batching system to participate in the preparation of the mixture.

[0015] As a preferred embodiment of the present invention, it also includes a water treatment system;

[0016] The water treatment system is used to receive the washing liquid from the pretreatment and batching system and the flue gas washing water from the flue gas purification and resource recovery system, and to produce circulating water.

[0017] The circulating water is returned to the pretreatment and batching system, as well as the flue gas purification and resource recovery system.

[0018] As a preferred embodiment of the present invention, the pretreatment and batching system includes a wet pretreatment system and a raw material mixing system connected in sequence;

[0019] The wet pretreatment system is used to wash the secondary aluminum ash to obtain an aluminum-containing slurry; the circulating water is returned to the wet pretreatment system.

[0020] The raw material mixing system is used to mix the aluminum-containing slurry with the desulfurization ash and the dust removal ash.

[0021] As a preferred embodiment of the present invention, the flue gas purification and resource recovery system includes a dust removal system, a dirt removal system, and an ammonium sulfate preparation system connected in sequence.

[0022] The dust removal system is used to remove dust from the collected process flue gas, and the collected dust is transported to the raw material mixing system.

[0023] The impurity removal system is used to perform wet impurity removal on the process flue gas after dust removal. The impurity-removed process flue gas enters the ammonium sulfate preparation system, and the flue gas washing water generated therefrom is discharged into the water treatment system.

[0024] The ammonium sulfate preparation system is used to receive the first flue gas and the process flue gas after impurity removal. Ammonia and sulfur oxides in the mixed flue gas react in a liquid phase system, and after crystallization, separation and drying, a second product mainly composed of ammonium sulfate is produced. The flue gas washing water generated is discharged into the water treatment system.

[0025] As a preferred embodiment of the present invention, the thermal system includes a preheating system, a calcination system, and a cooling system connected in sequence;

[0026] The heat source of the preheating system comes from the second flue gas generated by the roasting system and / or the third flue gas generated by the cooling system;

[0027] The calcination system is used to calcine the preheated mixture to allow the calcium and aluminum to react and obtain a first product mainly composed of calcium aluminate.

[0028] The cooling system is used to cool the first product from the roasting system and generates a heated third flue gas in the process. Part of the third flue gas enters the roasting system as secondary air and part of it enters the preheating system as a heat source.

[0029] The second and third flue gases generated by the preheating system, the calcination system, and the cooling system respectively are all incorporated into the dust removal system.

[0030] On the other hand, the present invention also provides a resource recovery system method for the synergistic treatment of secondary aluminum ash and desulfurization ash, implemented based on the resource recovery system as described in any one of claims 1 to 5, the method comprising the following steps:

[0031] S1. Water and secondary aluminum ash are pretreated and washed at a liquid-solid ratio of (1-5) L:1 kg to obtain aluminum slurry and dust- and ammonia-containing first flue gas.

[0032] The aluminum-containing slurry is either dehydrated or directly mixed with desulfurization ash and dust removal ash, wherein the calcium-aluminum molar ratio is controlled to be 0.8-1.2 to form a mixture.

[0033] S2. The mixture is preheated, calcined and cooled sequentially to obtain a first product mainly composed of calcium aluminate; wherein the reaction temperature during calcination is 800-1200℃ and the reaction time is 30-120 minutes.

[0034] S3. Collect the process flue gas generated during the preheating, calcination and cooling process of S2, and perform dust removal treatment on it. The collected dust is returned to S1 and mixed with the aluminum-containing slurry and the desulfurization ash.

[0035] The process flue gas after dust removal is washed to remove fluorine and chlorine impurities. Then, the process flue gas after impurity removal is mixed with the first flue gas, so that the ammonia and sulfur oxides in the mixed gas react in the liquid phase system. After crystallization, separation and drying, a second product with ammonium sulfate as the main component is obtained.

[0036] As a preferred embodiment of the present invention, S4 is also included:

[0037] S4. The washing liquid generated in S1, as well as the washing water generated in the flue gas washing and purification process and the ammonium sulfate preparation process in S3, are collected together, neutralized, precipitated and filtered to obtain purified circulating water. The circulating water is reused for the pretreatment washing in S1 and the flue gas washing and purification in S3.

[0038] As a preferred embodiment of the present invention, in step S2, the preheating temperature is 400-500°C.

[0039] As a preferred embodiment of the present invention, in step S2, the heat source for preheating is selected from at least one of the hot air generated during the roasting process and the cooling process;

[0040] All or part of the hot air generated during the cooling process is sent as secondary air into the roasting process, and / or

[0041] It is sent to the preheating process as a heat source.

[0042] As a preferred embodiment of the present invention, in step S3, when ammonia and sulfur oxides in the mixed gas are in a liquid phase system, the pH value of the reaction system is 2.5 to 4.0.

[0043] The crystallization is carried out by saturated crystallization or acid washing absorption crystallization, and the crystallization temperature is 50-70℃.

[0044] As can be seen from the above technical solutions, the technical solution of the present invention provides a resource utilization system and method for the synergistic treatment of secondary aluminum ash and desulfurization ash, which has the following beneficial effects compared with the prior art:

[0045] 1. Achieved full-component resource utilization and high-value conversion of solid waste. Through the main process of "pretreatment-batching-calcination," aluminum in secondary alumina ash and calcium in desulfurization ash are directionally converted into high-value-added calcium aluminate products, which can be used as raw materials for refractory materials or building materials. Simultaneously, through the secondary process of "flue gas purification-absorption crystallization," ammonia and sulfur elements escaping from the two solid waste streams are efficiently recovered and converted into pure ammonium sulfate products, which can be used as raw materials for fertilizers. Thus, two difficult-to-dispose-of industrial solid wastes are simultaneously transformed into two products with clear market value, achieving complete resource utilization of waste.

[0046] 2. A comprehensive closed-loop cycle is formed, achieving near-zero emissions. The dust collected by the flue gas purification and resource recovery system is returned to the batching process, where valuable components such as calcium and aluminum can be reused, improving the overall resource recovery rate and reducing the amount of final waste.

[0047] 3. All dust-, ammonia-, and sulfur-containing flue gas generated by the entire system is centrally purified. Among them, ammonia and sulfur oxides are selectively recovered to produce ammonium sulfate products; acidic pollutants (fluorine and chlorine) are specifically removed; and dust is collected and reused, ultimately achieving the unification of ultra-low emissions of waste gas and resource recovery of pollutants.

[0048] 4. Ensures thorough and harmless treatment, eliminating environmental risks. High-temperature calcination completely decomposes aluminum nitride in the secondary aluminum ash, which readily releases ammonia upon contact with water and poses a risk of combustion and explosion, eliminating safety hazards during storage and utilization at the source. The entire process is conducted in a closed system, ensuring that all potential pollutants are effectively collected and converted, resulting in thorough treatment.

[0049] 5. A highly efficient energy cascade utilization method has been established, resulting in significant energy savings and consumption reduction. Utilizing the high-temperature roasting flue gas and the hot air generated from cooling the finished product as a heat source for preheating the materials greatly reduces external energy consumption in the roasting process. The hot air generated by the cooling system can also be reused as secondary air for roasting or waste heat recovery. This integrated thermal management significantly improves the energy efficiency of the entire system.

[0050] In summary, secondary aluminum ash and desulfurization ash are not simply mixed in this process, but rather complement each other functionally. Desulfurization ash not only provides a calcium source, but its sulfates, when decomposed at high temperatures, can also provide a sulfur source for ammonium sulfate preparation. The pretreatment of secondary aluminum ash solves the problem of disposing of desulfurization ash separately. The synergy between the two overcomes the shortcomings of separate disposal, such as single product, high energy consumption, or toxic residues, achieving a synergistic effect of "treating waste with waste and turning waste into treasure."

[0051] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other.

[0052] The foregoing and other aspects, embodiments, and features of the teachings of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0053] The accompanying drawings are not drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0054] Figure 1 This is a schematic diagram of the resource utilization system for the coordinated processing of secondary aluminum ash and desulfurization ash according to an embodiment of the present invention. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art.

[0056] The terms "first," "second," and similar words used in the specification and claims of this patent application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "an," "a," or "the," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" indicate that the element or object preceding "comprising" encompasses the features, wholes, steps, operations, elements, and / or components listed following "comprising" or "including," and do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or sets thereof. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0057] This invention provides a resource recovery system for the co-processing of secondary aluminum ash and desulfurization ash. The system includes a pretreatment and batching system, a thermal treatment system, a flue gas purification and resource recovery system, and a water treatment system, all connected along the material flow to form a closed-loop cycle. Furthermore, the resource recovery system is mainly divided into three paths based on the material form: a first path primarily involving solid materials, a second path primarily involving gaseous materials, and a third path primarily involving circulating water. Specifically, the first path leads from the pretreatment and batching system to the thermal treatment system, completing the first product output; the second path leads from the pretreatment and batching system to the flue gas and resource recovery system, and from the thermal treatment system to the flue gas and resource recovery system, completing the second product output; the third path leads from the pretreatment and batching system to the water treatment system, and from the flue gas purification and resource recovery system to the water treatment system, completing the third product output.

[0058] Specifically, the pretreatment and batching system includes a wet pretreatment system and a raw material mixing system connected in sequence. The wet pretreatment system is used to pre-treat the secondary aluminum ash by washing, and then mix the desulfurization ash and dust removal ash according to the ratio to form a mixture.

[0059] To avoid the risk of deflagration when secondary aluminum ash comes into contact with water, this invention carries out safe treatment under controlled high liquid-to-solid ratio conditions, that is, the liquid-to-solid ratio (L / kg) of water to secondary aluminum ash is (1~5):1, and the amount of water used is much greater than the amount of aluminum ash. The large amount of water can quickly absorb and disperse the intense heat of reaction generated by the reaction between secondary aluminum ash and water, avoiding a sharp increase in local temperature, thereby effectively suppressing the risk of uncontrolled reaction and instantaneous large-scale release of ammonia.

[0060] like Figure 1As shown, the wet pretreatment system includes a first ash inlet, a first water inlet, a first water outlet, a first flue gas outlet, and a first discharge outlet. The first ash inlet receives secondary aluminum ash. The first water inlet connects to an external water supply system and a water treatment system, and is used to introduce washing water into the wet pretreatment system. During the secondary aluminum ash washing pretreatment, the circulating water treated by the water treatment system is mainly used, and the external water supply system can serve as a backup makeup water system. After the secondary aluminum ash comes into contact with water, it produces aluminum-containing slurry and a first flue gas containing dust and ammonia. The aluminum-containing slurry serves as a raw material for resource-recovered aluminum products, and the ammonia in the first flue gas serves as one of the raw materials for resource-recovered ammonium sulfate products. The aluminum-containing slurry can be directly introduced into the raw material mixing system through the first discharge outlet, where it is mixed with desulfurization ash. Alternatively, the aluminum-containing slurry can be dehydrated before being discharged into the raw material mixing system through the first discharge outlet. The washing liquid produced during dehydration can be discharged into the water treatment system through the first water outlet. The washing liquid is purified in the water treatment system and then recycled as washing water. The first flue gas enters the flue gas purification and resource recovery system through the first flue gas outlet. The dust contained in this first flue gas mainly refers to a small amount of droplets and fine particulate matter that are carried out during the escape of ammonia gas produced by the reaction of aluminum nitride and water. Figure 1 As shown, specifically, the first flue gas directly enters the ammonium sulfate preparation system at the back end of the flue gas purification and resource recovery system.

[0061] The main purpose of secondary aluminum ash washing is to safely remove soluble salts (fluorides, chlorides, potassium and sodium salts, etc.) to avoid these impurities interfering with the main reaction, corroding equipment, or causing complexity in flue gas treatment during subsequent high-temperature roasting processes.

[0062] like Figure 1 As shown, the raw material mixing system has a first feed inlet, a second ash inlet, a third ash inlet, and a second discharge outlet. The first feed inlet is connected to the first discharge outlet of the wet pretreatment system and is used to receive aluminum-containing slurry; the second ash inlet is used to receive desulfurization ash; the third ash inlet is connected to the dust removal system of the flue gas purification and resource recovery system and is used to receive dust generated from the dust removal system after the system's flue gas is dusted. The aluminum-containing slurry, desulfurization ash, and dust removal ash are uniformly mixed in this raw material mixing system to form a mixture; the second discharge outlet is connected to the thermal treatment system and is used to transport the mixture to the thermal treatment system for subsequent processing.

[0063] like Figure 1 As shown, the thermal treatment system includes a preheating system, a calcination system, and a cooling system connected in sequence, used to preheat, calcine at high temperature, and cool the mixture in sequence, and produce the first product calcium aluminate, while generating process flue gas rich in sulfur oxides.

[0064] The preheating system has a second inlet connected to the second outlet of the raw material mixing system. It receives the mixture from the raw material mixing system and preheats it to reduce energy consumption in subsequent roasting processes. Utilizing waste heat generated within the resource recovery system as a heat source, it achieves tiered energy utilization and system balance. Specifically, the heat source for the preheating system is selected from one of the following three methods: First, the heat source comes directly from the high-temperature flue gas of the roasting system. Furthermore, in this method, the third flue gas generated by the downstream cooling system is drawn out and transported to the roasting system via a flue gas pipeline as secondary air supplement. Second, the heat source comes directly from the third flue gas discharged from the cooling system, which is heated during the cooling of the high-temperature roasted products. Third, the heat source comes from the preheated mixed flue gas formed by the second and third flue gas. In this preferred method, the preheating system connects the roasting system and the cooling system in parallel via the second and third flue gas pipelines. The mixing ratio of the two flue gas can be adjusted by valves according to real-time operating conditions to obtain a stable and optimal mixed heat source with consistent temperature and flow rate. The preheated mixture is discharged into the roasting system through the third outlet of the preheating system.

[0065] The calcination system has a third feed inlet and a fourth discharge outlet. The third feed inlet is connected to the third discharge outlet of the preheating system to receive the preheated mixture. The fourth discharge outlet is connected to the cooling system to send the crude calcium aluminate product generated after calcination to the cooling system for cooling. In this calcination system, the reaction temperature is 800–1200℃, and the reaction time is 30–120 minutes.

[0066] The cooling system has a fourth inlet, which is connected to the fourth outlet of the roasting system, for receiving the preheated mixture. Specifically, the cooling system adopts counter-current cooling, with air as the cooling medium. The third flue gas generated during the cooling process can be entirely or partially sent into the roasting system as secondary air, or directly sent into the preheating system for utilization. Cooling can be carried out using indirect or direct cooling methods.

[0067] like Figure 1 As shown, the flue gas purification and resource recovery system includes a dust removal system, a dirt removal system, and an ammonium sulfate preparation system connected in sequence, which are used to treat the process flue gas rich in sulfur oxides generated by the entire system and recover the ammonium sulfate product.

[0068] Specifically, the first flue gas outlet of the wet pretreatment system is connected to the ammonium sulfate preparation system via a flue gas pipeline, thereby directly discharging the ammonia-containing first flue gas into the ammonium sulfate preparation system. Here, it merges with the process flue gas containing sulfur oxides that has undergone dust and impurity removal, and the ammonia and sulfur oxides in the mixed flue gas undergo an oxidation absorption reaction in the liquid phase system. This invention fully utilizes the characteristic of sulfur oxides in desulfurization ash decomposing and releasing sulfur dioxide at high temperatures, as well as the characteristic of ammonia released by the hydrolysis of secondary aluminum ash. The ammonia-containing first flue gas and the sulfur dioxide-containing process flue gas are directly mixed, and in an aerobic and liquid phase environment, the two spontaneously generate ammonium sulfate. This process does not require the addition of sulfuric acid and relies entirely on the reaction of sulfur and nitrogen elements within the solid waste, significantly reducing reagent costs, avoiding the introduction of external impurities, and demonstrating atom economy and advanced technology.

[0069] The preheating system has a second flue gas outlet and is connected to the dust removal system via another flue gas duct, thereby discharging the preheated mixed flue gas from the preheating system into the dust removal system. The preheated mixed flue gas is either the high-temperature second flue gas from the calcination system, the third flue gas from the cooling system, or a preheated mixed flue gas composed of the second and third flue gas. When the heat source for the preheating system is the preferred preheated mixed flue gas, the second flue gas from the calcination system and the third flue gas from the cooling system can be combined through the preheating system and then discharged into the dust removal system through the second flue gas outlet.

[0070] The dust removal system can be a bag filter or an electrostatic precipitator / bag filter hybrid dust collector. The collected dust is sent to the raw material mixing system through the return dust pipe and the third dust inlet.

[0071] To ensure that all flue gas generated by the preheating system can be treated by the dust removal system when the preheating system uses only the second or third flue gas as a single heat source, the calcination system and cooling system are each equipped with independent flue gas outlets, which are connected to the dust removal system through corresponding flue gas ducts. Thus, regardless of the heat source configuration used in the preheating system, all process flue gas generated by the calcination system, cooling system, and preheating system can be centrally treated by converging into the dust removal system through their respective flue gas ducts.

[0072] The impurity removal system is connected to the dust removal system and is used to receive the fourth flue gas that has already undergone dust removal treatment and perform impurity removal treatment. Specifically, the fluorine-containing and chlorine-containing impurities (such as sodium fluoride NaF and cryolite Na3AlF6) in the fourth flue gas are removed by wet process to obtain the fifth flue gas containing sulfur. The fifth flue gas is sent to the ammonium sulfate preparation system and mixed with the first flue gas containing ammonia from the wet pretreatment system. In this mixed gas, the ammonia and sulfur dioxide react in the liquid phase system. After crystallization, separation and drying, the second product ammonium sulfate is obtained.

[0073] The impurity removal system is also equipped with a second inlet and a second outlet. The second inlet is connected to the water treatment system or an external water supply system to receive the washing water. The second outlet is connected to the water treatment system to discharge the washed impurity removal water into the water treatment system for purification and recycling.

[0074] The ammonium sulfate preparation system can use existing technology, which will not be described in detail here.

[0075] The water treatment system includes a circulating water inlet, a circulating water outlet, and an evaporation and crystallization unit. The circulating water inlet is connected to the first outlet of the wet pretreatment system to receive the washing liquid from it. Simultaneously, the circulating water inlet is also connected via another pipe to the impurity removal system and the ammonium sulfate preparation system of the flue gas purification and resource recovery system to receive the flue gas scrubbing water containing trace amounts of ammonia and ammonium sulfate from these systems. The washing liquid and flue gas scrubbing water are treated in the water treatment system to produce circulating water, which is then returned to the first inlet of the wet pretreatment system and the second inlet of the impurity removal system, respectively, through the circulating water outlet. The concentrated brine produced after sedimentation and filtration enters the evaporation and crystallization unit for treatment to recover the third product, mixed salt.

[0076] This invention also provides a resource recovery system for the synergistic processing of secondary aluminum ash and desulfurization ash, specifically including the following steps:

[0077] S1. Pretreatment and Batching: Secondary aluminum ash and circulating water are mixed and washed at a liquid-to-solid ratio of (1-5):1 (L / kg) to obtain an aluminum-containing slurry and a first flue gas containing dust and ammonia. The aluminum-containing slurry obtained after washing is dehydrated or directly mixed with desulfurization ash and dust removal ash, controlling the calcium-aluminum molar ratio (CaO / Al2O3) between 0.8 and 1.2 to form a mixture. This calcium-aluminum molar ratio range is designed to ensure that after high-temperature calcination, the mixture mainly produces the target mineral calcium aluminate with high hydraulic activity. When the ratio is below 0.8, inert calcium dichlorate is easily formed; when it is above 1.2, other aluminate impurities may be formed. The preferred calcium-aluminum molar ratio of 1.0 provides a reasonable process control window to cope with fluctuations in raw material composition and ensure the stability of the final product performance.

[0078] To achieve precise control over the calcium aluminate phase in the final product, the aluminum content in the dehydrated secondary aluminum ash and the calcium content in the desulfurization ash must first be determined. XRF (Existing X-ray spectroscopy) is generally used for this purpose; it is a mature component analysis method in this field and will not be elaborated upon here. If the aluminum content in the secondary aluminum ash and the calcium content in the desulfurization ash are known, they can be used directly. Then, the mass ratio of the two materials is calculated based on the target calcium-aluminum molar ratio, and the materials are batched sequentially to form a mixture.

[0079] Dust collector ash is actually a mixture of secondary aluminum ash and desulfurization ash, which can be directly reused without further testing for the content of aluminum, calcium, etc.

[0080] S2. Thermal Treatment: The mixture is fed into a preheating system and preheated at a temperature of 300–600°C, with a preferred preheating temperature of 400–500°C. This preheating process serves as a buffer and preparation stage before the mixture enters high-temperature roasting, helping to ensure a uniform and stable increase in temperature, creating better conditions for the subsequent roasting reaction. It also helps to stabilize and regulate the temperature of the flue gas entering the subsequent flue gas purification and resource recovery system.

[0081] The preheated mixture is fed into the calcination system and calcined at 800–1200°C for 30–120 minutes, with the preferred calcination temperature being 900–1100°C.

[0082] This calcination temperature range represents the optimal kinetic temperature window required for the solid-state reaction between calcium oxide and alumina to generate the target product, ensuring high product activity. Furthermore, this calcination temperature is sufficient to decompose the sulfate components in the desulfurization ash, releasing sulfur oxides that can be subsequently recovered. Finally, this calcination temperature range achieves the aforementioned process objectives while avoiding excessive energy consumption and remains within the reliable operating range of conventional equipment.

[0083] The high-temperature material after roasting enters the cooling system and is cooled to below 80°C to obtain a product mainly composed of calcium aluminate.

[0084] S3. Flue Gas Purification and Resource Recovery: The sulfur-containing oxide process flue gas generated by the preheating system, calcination system and cooling system in S2 is introduced into the dust removal system. To ensure the long-term use of the dust collector and to meet the requirements of the subsequent wet impurity removal and ammonium sulfate preparation process for the inlet gas temperature, dust removal is carried out at a temperature ≤200℃. The collected dust is returned to S1 and mixed with aluminum-containing slurry and desulfurization ash to form a mixture.

[0085] After dust removal, the fourth flue gas is processed by an impurity removal system to remove fluorine and chlorine-containing impurities, resulting in the fifth flue gas. This fifth flue gas is then fed into an ammonium sulfate preparation system and mixed with the first flue gas. Ammonia and sulfur dioxide in the mixed flue gas undergo a contact reaction in a liquid phase system, with the pH of the reaction system controlled at 2.5–4.0. After crystallization, separation, and drying, ammonium sulfate is obtained. The ammonium sulfate preparation system employs either a saturated crystallization method or an acid washing absorption crystallization method, with a crystallization temperature of 50℃–70℃.

[0086] S4: Water recycling treatment: The washing liquid generated in S1, as well as the flue gas washing water generated in the flue gas purification and ammonium sulfate preparation process in S3, are sent to the water treatment system together. After neutralization, precipitation and filtration, the recycled water is obtained and reused for the pretreatment washing of S1 and the flue gas washing of S3.

[0087] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A resource recovery system for the co-processing of secondary aluminum ash and desulfurization ash, characterized in that, The resource recovery system includes: The pretreatment and batching system is used to receive and process secondary aluminum ash and desulfurization ash, output a mixture containing aluminum and calcium, and generate the first flue gas containing ammonia. A thermal treatment system is used to receive the mixture and sequentially preheat, calcine and cool the mixture to produce a first product and generate sulfur-containing process flue gas. The flue gas purification and resource recovery system is used to receive and process the process flue gas. After dust removal and impurity removal, the flue gas is mixed with the first flue gas, so that the ammonia and sulfur oxides in the mixed flue gas react to prepare the second product. At the same time, the dust collected by the flue gas purification and resource recovery system during the dust removal process is returned to the pretreatment and batching system to participate in the preparation of the mixture.

2. The resource recovery system for the synergistic treatment of secondary aluminum ash and desulfurization ash according to claim 1, characterized in that, It also includes water treatment systems; The water treatment system is used to receive the washing liquid from the pretreatment and batching system and the flue gas washing water from the flue gas purification and resource recovery system, and to produce circulating water. The circulating water is returned to the pretreatment and batching system, as well as the flue gas purification and resource recovery system.

3. The resource recovery system for the synergistic treatment of secondary aluminum ash and desulfurization ash according to claim 2, characterized in that, The pretreatment and batching system includes a wet pretreatment system and a raw material mixing system connected in sequence; The wet pretreatment system is used to wash the secondary aluminum ash to obtain an aluminum-containing slurry; the circulating water is returned to the wet pretreatment system. The raw material mixing system is used to mix the aluminum-containing slurry with the desulfurization ash and the dust removal ash.

4. The resource recovery system for the synergistic treatment of secondary aluminum ash and desulfurization ash according to claim 3, characterized in that, The flue gas purification and resource recovery system includes a dust removal system, a dirt removal system, and an ammonium sulfate preparation system connected in sequence. The dust removal system is used to remove dust from the collected process flue gas, and the collected dust is transported to the raw material mixing system. The impurity removal system is used to perform wet impurity removal on the process flue gas after dust removal. The impurity-removed process flue gas enters the ammonium sulfate preparation system, and the flue gas washing water generated therefrom is discharged into the water treatment system. The ammonium sulfate preparation system is used to receive the first flue gas and the process flue gas after impurity removal. Ammonia and sulfur oxides in the mixed flue gas react in a liquid phase system, and after crystallization, separation and drying, a second product mainly composed of ammonium sulfate is produced. The flue gas washing water generated is discharged into the water treatment system.

5. The resource recovery system for the synergistic treatment of secondary aluminum ash and desulfurization ash according to claim 4, characterized in that, The thermal system includes a preheating system, a calcination system, and a cooling system connected in sequence. The heat source of the preheating system comes from the second flue gas generated by the roasting system and / or the third flue gas generated by the cooling system; The calcination system is used to calcine the preheated mixture to allow the calcium and aluminum to react and obtain a first product mainly composed of calcium aluminate. The cooling system is used to cool the first product from the roasting system and generates a heated third flue gas in the process. Part of the third flue gas enters the roasting system as secondary air and part of it enters the preheating system as a heat source. The second and third flue gases generated by the preheating system, the calcination system, and the cooling system respectively are all incorporated into the dust removal system.

6. A resource recovery system method for the synergistic treatment of secondary aluminum ash and desulfurization ash, characterized in that, Based on the resource recovery system as described in any one of claims 1 to 5, the method includes the following steps: S1. Water and secondary aluminum ash are pretreated and washed at a liquid-solid ratio of (1-5) L:1 kg to obtain aluminum slurry and dust- and ammonia-containing first flue gas. The aluminum-containing slurry is either dehydrated or directly mixed with desulfurization ash and dust removal ash, wherein the calcium-aluminum molar ratio is controlled to be 0.8-1.2 to form a mixture. S2. The mixture is preheated, calcined and cooled sequentially to obtain a first product mainly composed of calcium aluminate; wherein the reaction temperature during calcination is 800-1200℃ and the reaction time is 30-120 minutes. S3. Collect the sulfur-containing process flue gas generated during the preheating, roasting and cooling process of S2, and perform dust removal treatment on it. The collected dust is returned to S1 and mixed with the aluminum-containing slurry and the desulfurization ash. The process flue gas after dust removal is washed to remove fluorine and chlorine impurities. Then, the process flue gas after impurity removal is mixed with the first flue gas, so that the ammonia and sulfur oxides in the mixed gas react in the liquid phase system. After crystallization, separation and drying, a second product with ammonium sulfate as the main component is obtained.

7. The resource recovery system method for co-processing secondary aluminum ash and desulfurization ash according to claim 6, characterized in that, Also includes S4: S4. The washing liquid generated in S1, as well as the washing water generated in the flue gas washing and purification process and the ammonium sulfate preparation process in S3, are collected together, neutralized, precipitated and filtered to obtain purified circulating water. The circulating water is reused for the pretreatment washing in S1 and the flue gas washing and purification in S3.

8. The resource recovery system method for co-processing secondary aluminum ash and desulfurization ash according to claim 6, characterized in that, In step S2, the preheating temperature is 400–500°C.

9. The resource recovery system method for co-processing secondary aluminum ash and desulfurization ash according to claim 6, characterized in that, In step S2, the heat source for preheating is selected from at least one of the hot air generated during the roasting process and the cooling process; All or part of the hot air generated during the cooling process is sent as secondary air into the roasting process, and / or It is sent to the preheating process as a heat source.

10. The resource recovery system method for co-processing secondary aluminum ash and desulfurization ash according to claim 6, characterized in that, In S3, when ammonia and sulfur oxides in the mixed gas are in a liquid phase system, the pH value of the reaction system is 2.5 to 4.

0. The crystallization is carried out by saturated crystallization or acid washing absorption crystallization, and the crystallization temperature is 50-70℃.

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