Ash slag zinc oxide recovery system based on calcium-based chemical looping circulation and application

Abstract

The invention relates to an ash slag zinc oxide recovery system based on calcium-based chemical looping circulation and application of the ash slag zinc oxide recovery system. The ash residue zinc oxide recovery system based on calcium-based chemical looping circulation comprises a reduction roasting device, an acid leaching tank, a first filter, an alkaline sedimentation tank, a second filter, a third filter, a Zn (OH) 2 storage device, a first dryer, a calcining furnace, a calcining reactor, a CaO storage device, a hydration reactor and a Ca (OH) 2 storage device which are connected in sequence. According to the method, ash zinc oxide is recycled through a dry method and wet method combined process, waste heat of a reduction roasting device and a calcining furnace is recycled through a calcium-based chemical looping energy storage technology, the calcium-based chemical looping energy storage technology acts on Na2CO3 and drying and preheating, and through advantage complementation of the dry method and the wet method, the recycling rate of zinc can be remarkably increased, the cost is reduced, and the method is suitable for industrial production. And the energy consumption is reduced through a calcium-based chemical looping energy storage technology, and low-energy-consumption recovery of ash zinc oxide is realized.

Description

Technical Field

[0001] This invention relates to the field of heavy metal recycling technology, specifically to a zinc oxide recovery system and application based on calcium-based chemical chain cycle in ash slag. Background Technology

[0002] In existing research on zinc recovery processes from ash slag, acid leaching extraction technology has become a focus of research both domestically and internationally due to its relatively mature process. However, the cost of wastewater treatment and environmental impact remain pressing problems that need to be addressed.

[0003] Existing recycling processes include the traditional acid leaching-electrowinning method and a calcium-free chemical loop recycling process. The traditional acid leaching-electrowinning method involves oxidizing ash slag from the same source and directly leaching it with sulfuric acid. The leachate undergoes complex purification (zinc powder replacement, etc.) to remove impurity metals. The purified zinc sulfate solution is then electrolyzed to obtain metallic zinc ingots. The calcium-free chemical loop recycling process involves reduction smelting followed by carbonation fixation in the front end, but in the back end, it generates a large volume of wastewater that is directly discharged. All Ca(OH)2 consumed in the carbonation stage uses freshly purchased raw materials.

[0004] Existing recycling systems have two major drawbacks: (1) large wastewater volume in the wet process, resulting in high subsequent wastewater treatment costs; and (2) secondary pollution from heavy metals during the recycling process. In contrast, leveraging the advantages of both dry and wet processes to improve metal recovery rates and achieve comprehensive utilization of multiple metals demonstrates greater economic potential. Based on this, focusing on zinc oxide recovery technology from ash slag, and combining the advantages of dry, wet, and integrated technologies, this invention proposes a highly efficient, environmentally friendly, and economical zinc oxide recovery process from ash slag. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a zinc oxide recovery system and application based on calcium-based chemical chain recycling. This invention achieves zinc oxide recovery from ash slag through a combined dry and wet process, and utilizes calcium-based chemical chain energy storage technology to recover waste heat from the reduction roasting device and calcination furnace, which is then used for preheating Na2CO3 and drying. By leveraging the complementary advantages of dry and wet processes, the zinc recovery rate can be significantly improved, costs reduced, and energy consumption lowered through calcium-based chemical chain energy storage technology, achieving low-energy recovery of zinc oxide from ash slag.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: The first objective of this invention is to provide a zinc oxide recovery system for ash slag based on a calcium-based chemical chain cycle, comprising, in sequence, a reduction roasting device, an acid leaching tank, a first filter, an alkaline precipitation tank, a second filter, a third filter, a Zn(OH)2 storage device, a first dryer, a calcining furnace, a calcining reactor, a CaO storage device, a hydration reactor, and a Ca(OH)2 storage device; the inlet of the first dryer is also connected to the outlet of the hydration reactor; the inlet of the calcining reactor is also connected to the outlet of the Ca(OH)2 storage device; and the outlet of the calcining reactor is also connected to the outlet of the reduction roasting device. The ash slag zinc oxide recovery system also includes a CO2-rich flue gas storage device, a water pump, and a ZnO storage device; the inlet of the CO2-rich flue gas storage device is connected to the outlet of the calcination reactor, and the outlet of the CO2-rich flue gas storage device is connected to the inlet of the third filter; the outlet of the water pump is connected to the inlet of the hydration reactor; and the inlet of the ZnO storage device is connected to the outlet of the calcination furnace.

[0007] The beneficial effects of this invention are as follows: This invention utilizes a combined dry and wet process production device to prepare a zinc oxide recovery system from ash slag, achieving the recovery of zinc oxide from ash slag. Furthermore, it employs calcium-based chemical chaining energy storage technology to recover waste heat from the reduction roasting device and calcination furnace, which is then used for preheating Na2CO3 and drying processes. Through the complementary advantages of the dry and wet processes, the zinc recovery rate can be significantly improved, and costs reduced. The calcium-based chemical chaining energy storage technology further reduces energy consumption, achieving low-energy recovery of zinc oxide from ash slag.

[0008] Based on the above technical solution, the present invention can be further improved as follows.

[0009] Furthermore, the calcination reactor includes a cylindrical reactor, multiple reactor Ca(OH)2 inlets, a reactor CaO outlet, a first rotating plate, a high-temperature flue gas inlet, and a CO2-rich gas outlet; The first rotating plate is disposed inside the cylindrical reactor, and the plurality of reactor Ca(OH)2 inlets are disposed at the top of the cylindrical reactor and connected to the Ca(OH)2 storage device; the reactor CaO outlet is disposed at the bottom of the cylindrical reactor and connected to the CaO storage device; the high-temperature flue gas inlet and the CO2-rich gas outlet are disposed at the side end of the cylindrical reactor, the high-temperature flue gas inlet is connected to the inlet of the calcining furnace; the CO2-rich gas outlet is disposed above the high-temperature flue gas inlet and connected to the CO2-rich flue gas storage device.

[0010] The beneficial effects of adopting the above-mentioned further scheme are as follows: When the calcination reactor of the present invention is working, Ca(OH)2 is introduced into the reactor through the Ca(OH)2 inlet, and high-temperature flue gas is introduced into the high-temperature flue gas inlet at the same time. At this time, the rotating plates begin to rotate, and the main reaction involved is: Ca(OH)2 → CaO + H2O. The low-temperature gas rich in CO2 is discharged from the CO2-rich gas outlet and enters the CO2-rich gas storage device. After the calcination reaction is completed, CaO is discharged from the CaO outlet of the lower reactor and enters the CaO storage device.

[0011] The Ca(OH)2 inlet of the upper reactor and the CaO outlet of the lower reactor facilitate the entry and exit of calcium-based materials; the rotating plates promote uniform heating of the calcium-based materials; the high-temperature flue gas inlet enters the external cavity to provide heat for the reaction; the CO2-rich gas outlet (5) discharges low-temperature gas rich in CO2.

[0012] Based on the structural design of the external cavity and rotating plates of the calcining reactor, the high-temperature flue gas generated by the 800~900℃ reduction roasting device and the 400~500℃ calcining furnace can enable the calcining reactor to meet the high-temperature calcination of about 500℃, while also making full use of the waste heat of the reduction roasting device and the calcining furnace to realize the recovery and utilization of waste heat.

[0013] Furthermore, the hydration reactor includes a shell, multiple hydration reactor inlets, a hydration reactor outlet, a second rotating plate, heat exchange tubes, and an H2O gas outlet; the hydration reactor inlets are connected to the outlet of the water pump; the hydration reactor outlet is connected to the Ca(OH)2 storage device; and the H2O gas outlet is connected to the first dryer. The second rotating plate is disposed inside the housing; the heat exchange tube is disposed inside the housing; the inlet of the heat exchange tube extends outside the upper end of the housing; the outlet of the heat exchange tube extends outside the lower end of the housing. The hydration reactor inlets are located at the top of the shell; the hydration reactor outlets are located at the bottom of the shell; and the H2O gas outlets are located at the side of the shell.

[0014] The beneficial effects of adopting the above-mentioned further scheme are as follows: When the hydration reactor of the present invention is working, CaO is introduced from the inlet of the hydration reactor, and at the same time, water is injected into the water storage device and water pump through the H2O inlet, and the second rotating plate begins to rotate; the heat transfer oil in the heat exchange tube absorbs the reaction heat in the inner heat exchange tube and stores it to prepare for subsequent drying and preheating; after the hydration reaction is completed, Ca(OH)2 is discharged from the outlet of the lower hydration reactor, and the reaction heat is transferred to the first dryer and the second dryer to meet the drying and preheating of Zn(OH)2 and the drying of Na2CO3 in the second dryer, so as to realize the utilization of waste heat and reduce losses.

[0015] Furthermore, the ash slag zinc oxide recovery system also includes a second dryer, a Na2CO3 storage device, and a water storage device; the inlet of the second dryer is connected to the outlet of the third filter and the inlet of the hydration reactor, and the outlet of the second dryer is connected to the inlet of the Na2CO3 storage device and the inlet of the water storage device, respectively. The outlet of the water storage device is connected to the inlet of the hydration reactor.

[0016] The second objective of this invention is to provide an application of a calcium-based chemical chain cycle-based zinc oxide recovery system for ash slag, wherein the ash slag zinc oxide recovery system is used in the recovery of zinc oxide from ash slag.

[0017] The beneficial effects of the present invention are as follows: The zinc oxide recovery system of the present invention can overcome the two major defects of the existing recovery system when recovering zinc oxide from ash slag, and has the following effects: (1) Dry pretreatment reduces the amount of wastewater in the wet process and reduces the cost of wastewater treatment; (2) The ash slag is treated harmlessly, avoiding secondary pollution of heavy metals; (3) The system can achieve a zinc oxide recovery efficiency of 70% or more; (4) It utilizes calcium-based chemical chain circulation and utilizes waste heat in stages to achieve full utilization; (5) The operation process is simple and safe.

[0018] A third objective of this invention is to provide a method for recovering zinc oxide from ash slag, employing the aforementioned zinc oxide recovery system from ash slag, comprising the following steps: (1) Add zinc oxide ash to a reduction roasting device for reduction roasting to obtain roasting product. The roasting product is then leached in an acid leaching tank and filtered in a first filter to obtain filtrate. The filtrate is then added to an alkaline precipitation tank and reacted with NaOH solution. Subsequently, it is filtered in a second filter and a third filter to obtain Zn(OH)2 precipitate, which is stored in a Zn(OH)2 storage device. The CO2-rich flue gas in the CO2-rich flue gas storage device is introduced into the remaining filtrate in the third filter to react and obtain Na2CO3. (2) The heat of reaction stored in the hydration reactor enters the first dryer. The Zn(OH)2 precipitate in the Zn(OH)2 storage device is dried and preheated in the first dryer, and then enters the calcination furnace for calcination. The generated ZnO is stored in the ZnO storage device. (3) The high-temperature flue gas generated in the calcining furnace and the reduction roasting device is discharged into the calcining reactor. The Ca(OH)2 in the Ca(OH)2 storage device is added to the calcining reactor and calcined to generate CaO and CO2-rich flue gas. The CO2-rich flue gas is discharged into the CO2-rich flue gas storage device for storage. The CaO is stored in the CaO storage device. The CaO in the CaO storage device is added to the hydration reactor. At the same time, water from the water pump is injected into the hydration reactor to react and generate Ca(OH)2, which is stored in the Ca(OH)2 storage device.

[0019] The beneficial effects of this invention are: by introducing calcium-based chemical chain energy storage technology, the system can achieve efficient energy storage and release, while significantly reducing overall energy consumption. This technology utilizes the cyclic regeneration of calcium-based materials to achieve cascaded utilization of energy during the energy storage process and reduce energy loss.

[0020] Furthermore, the reduction calcination temperature in step (1) is 800℃~900℃, and the time is 1h~2h.

[0021] Furthermore, in step (1), when the second filter is used for filtration, the pH of the filtrate is adjusted to <6.5; When the third filter is used for filtration, the pH of the filtrate is 7-8.

[0022] The beneficial effects of adopting the above-mentioned further scheme are as follows: Based on the second and third filters, when the filtrate precipitates in the alkaline precipitation tank, the second filter filters out the precipitate of other metal ions as the pH is adjusted. After the second filter completes filtration, the third filter undergoes the main reaction as the pH is adjusted: Zn + + 2OH - →Zn(OH)2, filter out the Zn(OH)2 precipitate. Then pass the CO2-rich gas in the system into the remaining solution of the third filter to obtain Na2CO3, which is then dried in the second dryer and sent to the Na2CO3 storage device.

[0023] Furthermore, the calcination temperature of the calcining furnace in step (2) is 400℃~500℃, and the time is 1.5h~2.5h.

[0024] Furthermore, the temperature of the calcination reactor in step (3) is 500℃~600℃, and the time is 1h~2h; The mass ratio of CaO to water is 1:4~6. Attached Figure Description

[0025] Figure 1 This is a diagram of the zinc oxide recovery system for ash slag based on calcium-based chemical chain cycle provided by the present invention; Figure 2This is a front view of the calcination reactor provided in Embodiment 1 of the present invention; Figure 3 This is a top view of the calcination reactor provided in Embodiment 1 of the present invention; Figure 4 This is a front view of the hydration reactor provided in Embodiment 1 of the present invention; Figure 5 This is a top view of the hydration reactor provided in Embodiment 1 of the present invention.

[0026] The attached diagram lists the components represented by each number as follows: 1. Reduction roasting apparatus; 2. Acid leaching tank; 3. First filter; 4. Alkaline precipitation tank; 5. Second filter; 6. Third filter; 7. Zn(OH)2 storage device; 8. First dryer; 9. Calcination furnace; 10. Calcination reactor; 11. CaO storage device; 12. Hydration reactor; 13. Ca(OH)2 storage device; 14. Second dryer; 15. Na2CO3 storage device; 16. Water storage device; 17. CO2-rich flue gas storage device; 8. Water pump; 19. ZnO storage device; 10-1. Columnar reactor; 10-2. Reactor Ca(OH)2 inlet; 10-3. Reactor CaO outlet; 10-4. First rotating plate; 10-5. High-temperature flue gas inlet; 10-6. CO2-rich gas outlet; 12-1. Shell; 12-2. Multiple hydration reactor inlets; 12-3. Hydration reactor outlet; 12-4. Second rotating plate; 12-5. Heat exchange tube; 12-6. H2O inlet. Detailed Implementation

[0027] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0028] Example 1: This embodiment 1 relates to a zinc oxide recovery system for ash slag based on calcium-based chemical chain cycles, such as... Figure 1 As shown, the details are as follows: like Figure 1As shown, a calcium-based chemical chain cycle-based zinc oxide recovery system for ash slag includes, in sequence, a reduction roasting device 1, an acid leaching tank 2, a first filter 3, an alkaline precipitation tank 4, a second filter 5, a third filter 6, a Zn(OH)2 storage device 7, a first dryer 8, a calcining furnace 9, a calcining reactor 10, a CaO storage device 11, a hydration reactor 12, and a Ca(OH)2 storage device 13. The inlet of the first dryer 8 is also connected to the outlet of the hydration reactor 12; the inlet of the calcining reactor 10 is also connected to the outlet of the Ca(OH)2 storage device 13; and the outlet of the calcining reactor 10 is also connected to the outlet of the reduction roasting device 1. The alkaline precipitation tank introduces gas generated by the system itself, causing sodium ions in the solution to precipitate efficiently as Na2CO3, achieving both zinc separation and sodium resource recycling. This process realizes targeted utilization and green conversion of sodium, reducing both alkali consumption costs and wastewater discharge.

[0029] The ash slag zinc oxide recovery system also includes a CO2-rich flue gas storage device 17, a water pump 18, and a ZnO storage device 19; the inlet of the CO2-rich flue gas storage device 17 is connected to the outlet of the calcination reactor 10, and the outlet of the CO2-rich flue gas storage device 17 is connected to the inlet of the third filter 6; the outlet of the water pump 18 is connected to the inlet of the hydration reactor 12; and the inlet of the ZnO storage device 19 is connected to the outlet of the calcination furnace 9.

[0030] Furthermore, such as Figure 2 , 3 As shown, the calcination reactor 10 includes a cylindrical reactor 10-1, multiple reactor Ca(OH)2 inlets 10-2, reactor CaO outlet 10-3, a first rotating plate 10-4, a high-temperature flue gas inlet 10-5, and a CO2-rich gas outlet 10-6. The first rotating plate 10-4 is disposed inside the cylindrical reactor 10-1. Multiple reactor Ca(OH)2 inlets 10-2 are disposed at the top of the cylindrical reactor 10-1 and connected to the Ca(OH)2 storage device 13. The reactor CaO outlet 10-3 is disposed at the bottom of the cylindrical reactor 10-1 and connected to the CaO storage device 11. The high-temperature flue gas inlet 10-5 and the CO2-rich gas outlet 10-6 are disposed at the side of the cylindrical reactor 10-1. The high-temperature flue gas inlet 10-5 is connected to the inlet of the calcining furnace 9. The CO2-rich gas outlet 10-6 is disposed at the upper end of the high-temperature flue gas inlet 10-5 and connected to the CO2-rich flue gas storage device 17.

[0031] The calcination reactor 10 has an external cavity to form an annular flue gas channel.

[0032] Furthermore, such as Figure 4 , 5As shown, the hydration reactor 12 includes a shell 12-1, multiple hydration reactor inlets 12-2, a hydration reactor outlet 12-3, a second rotating plate 12-4, a heat exchange tube 12-5, and an H2O gas outlet 12-6; the hydration reactor inlets 12-2 are connected to the outlet of the water pump 18; the hydration reactor outlet 12-3 is connected to the Ca(OH)2 storage device 13; and the H2O gas outlet 12-6 is connected to the first dryer 8. The second rotating plate 12-4 is disposed inside the shell 12-1; the heat exchange tube 12-5 is disposed inside the shell 12-1; the inlet of the heat exchange tube 12-5 extends out of the upper end of the shell 12-1; the outlet of the heat exchange tube 12-5 extends out of the lower end of the shell 12-1. Multiple hydration reactor inlets 12-2 are located at the top of the shell 12-1; hydration reactor outlets 12-3 are located at the bottom of the shell 12-1; and H2O gas outlets 12-6 are located at the side of the shell 12-1.

[0033] Furthermore, the ash slag zinc oxide recovery system also includes a second dryer 14, a Na2CO3 storage device 15, and a water storage device 16; the inlet of the second dryer 14 is connected to the outlet of the third filter 6 and the inlet of the hydration reactor 12, and the outlet of the second dryer 14 is connected to the inlet of the Na2CO3 storage device 15 and the inlet of the water storage device 16, respectively. The outlet of the water storage device 16 is connected to the inlet of the hydration reactor 12.

[0034] Example 2: A method for recovering zinc oxide from ash slag (1) Add zinc oxide ash to reduction roasting device 1 and reduce roast at 850℃ for 1.5 hours to obtain roasting product. The roasting product is then leached in acid leaching tank 2 and filtered in first filter 3 to separate metals and other impurities to obtain filtrate. The filtrate enters alkaline precipitation tank 4 and 4 mol / L NaOH solution is added first, with the volume ratio of filtrate to NaOH being 0.4:1, to precipitate Zn(OH)2 with other metals. Subsequently, the pH is adjusted to <6.5 in second filter 5 to separate Zn-rich products. + The solution and other metal precipitates are treated by solidifying them with cement to render them harmless, transforming hazardous heavy metal waste into a stable and harmless solidified body; Zn-rich solutions are also treated by solidifying other metal precipitates with cement to render them harmless. + The solution is passed into the third filter 6 and the pH is adjusted to 7.5. Zn(OH)2 precipitate is obtained by filtration and stored in Zn(OH)2 storage device 7. CO2-rich flue gas is passed into the remaining filtrate in the third filter 6 through the CO2-rich flue gas storage device 17. Na2CO3 is reacted and dried by the second dryer 14 and then stored in the Na2CO3 storage device 15. (2) The Zn(OH)2 precipitate in the Zn(OH)2 storage device 7 is in the first dryer 8. After the hydration reactor 12 introduces reaction heat into the first dryer 8 to dry and preheat the Zn(OH)2 precipitate, it is then calcined in the calcining furnace 9 for 1.5 hours. The generated ZnO is stored in the ZnO storage device 19. (3) The high-temperature flue gas generated in the calcining furnace 9 and the reduction roasting device 1 is discharged into the calcining reactor 10 for heating to 500°C. The calcination time is 2h. The Ca(OH)2 in the Ca(OH)2 storage device 13 is added to the calcining reactor 10 for calcination to generate CaO, which is stored in the CaO storage device 11. The CO2-rich flue gas generated by the reaction is discharged into the CO2-rich flue gas storage device 17 for storage. The CaO in the CaO storage device 11 is added to the hydration reactor 12. At the same time, the water in the water storage device 16 and the water pump 18 is injected into the hydration reactor 12 to react and generate Ca(OH)2. The mass ratio of CaO to water is 1:5.

[0035] The reaction heat stored in the Ca(OH)2 storage device 13 and the hydration reactor 12 enters the first dryer 8 and the second dryer 14 to provide the heat required for drying.

[0036] Example 3: A method for recovering zinc oxide from ash slag (1) Add zinc oxide ash to reduction roasting device 1 and reduce roast at 800℃ for 2 hours to obtain roasting product. The roasting product is then leached in acid leaching tank 2 and filtered in first filter 3 to separate metals and other impurities to obtain filtrate. The filtrate enters alkaline precipitation tank 4 and 5 mol / L NaOH solution is added first, with the volume ratio of filtrate to NaOH being 0.5:1, to achieve precipitation of Zn(OH)2 with other metals. Subsequently, the pH is adjusted to <6.5 in second filter 5 to separate Zn-rich products. + The solution and other metal precipitates are treated by solidifying them with cement to render them harmless, transforming hazardous heavy metal waste into a stable and harmless solidified body; Zn-rich solutions are also treated by solidifying other metal precipitates with cement to render them harmless. + The solution is passed into the third filter 6 and the pH is adjusted to 7. Zn(OH)2 precipitate is obtained by filtration and stored in Zn(OH)2 storage device 7. CO2-rich flue gas is passed into the remaining filtrate in the third filter 6 through the CO2-rich flue gas storage device 17. Na2CO3 is reacted and obtained. After being dried by the second dryer 14, it is stored in the Na2CO3 storage device 15. (2) The Zn(OH)2 precipitate in the Zn(OH)2 storage device 7 is in the first dryer 8. After the hydration reactor 12 introduces reaction heat into the first dryer 8 to dry and preheat the Zn(OH)2 precipitate, it is then calcined in the calcining furnace 9 for 1.5 hours. The generated ZnO is stored in the ZnO storage device 19. (3) The high-temperature flue gas generated in the calcining furnace 9 and the reduction roasting device 1 is discharged into the calcining reactor 10 for heating. The temperature is heated to 550℃ and calcined for 1.5h. The Ca(OH)2 in the Ca(OH)2 storage device 13 is added to the calcining reactor 10 for calcination to generate CaO, which is stored in the CaO storage device 11. The CO2-rich flue gas generated by the reaction is discharged into the CO2-rich flue gas storage device 17 for storage. The CaO in the CaO storage device 11 is added to the hydration reactor 12. At the same time, the water in the water storage device 16 and the water pump 18 is injected into the hydration reactor 12 to react and generate Ca(OH)2. The mass ratio of CaO to water is 1:4.

[0037] The reaction heat stored in the Ca(OH)2 storage device 13 and the hydration reactor 12 enters the first dryer 8 and the second dryer 14 to provide the heat required for drying.

[0038] Example 4: A method for recovering zinc oxide from ash slag (1) Add zinc oxide ash to reduction roasting device 1 and reduce roast at 900℃ for 1 hour to obtain roasting product. The roasting product is then leached in acid leaching tank 2 and filtered in first filter 3 to separate metals and other impurities to obtain filtrate. The filtrate enters alkaline precipitation tank 4 and 6 mol / L NaOH solution is added first, with the volume ratio of filtrate to NaOH being 0.6:1, to achieve precipitation of Zn(OH)2 with other metals. Subsequently, the pH is adjusted to <6.5 in second filter 5 to separate Zn-rich products. + The solution and other metal precipitates are treated by solidifying them with cement to render them harmless, transforming hazardous heavy metal waste into a stable and harmless solidified body; Zn-rich solutions are also treated by solidifying other metal precipitates with cement to render them harmless. + The solution is passed into the third filter 6 and the pH is adjusted to 8. Zn(OH)2 precipitate is obtained by filtration and stored in Zn(OH)2 storage device 7. CO2-rich flue gas is passed into the remaining filtrate in the third filter 6 through the CO2-rich flue gas storage device 17. Na2CO3 is reacted and obtained. After being dried by the second dryer 14, it is stored in the Na2CO3 storage device 15. (2) The Zn(OH)2 precipitate in the Zn(OH)2 storage device 7 is in the first dryer 8. After the hydration reactor 12 introduces reaction heat into the first dryer 8 to dry and preheat the Zn(OH)2 precipitate, it is then calcined in the calcining furnace 9 for 2 hours. The generated ZnO is stored in the ZnO storage device 19. (3) The high-temperature flue gas generated in the calcining furnace 9 and the reduction roasting device 1 is discharged into the calcining reactor 10 for heating. The temperature is heated to 600℃ and calcined for 1 hour. The Ca(OH)2 in the Ca(OH)2 storage device 13 is added to the calcining reactor 10 for calcination to generate CaO, which is stored in the CaO storage device 11. The CO2-rich flue gas generated by the reaction is discharged into the CO2-rich flue gas storage device 17 for storage. The CaO in the CaO storage device 11 is added to the hydration reactor 12. At the same time, the water in the water storage device 16 and the water pump 18 is injected into the hydration reactor 12 to react and generate Ca(OH)2. The mass ratio of CaO to water is 1:6.

[0039] The reaction heat stored in the Ca(OH)2 storage device 13 and the hydration reactor 12 enters the first dryer 8 and the second dryer 14 to provide the heat required for drying.

[0040] The zinc oxide recovery method for ash slag provided by this invention systematically demonstrates its technical performance and operational flexibility through three typical examples. Example 2, involving reduction roasting at 850℃, zinc hydroxide precipitation at pH=7.5, and calcium-based regeneration at 500℃, achieved excellent zinc recovery rates of 94% and product purity of 99.2%, exhibiting balanced and stable process characteristics. Example 3, using mild reduction conditions at 800℃ combined with a precipitation environment at pH=7, although the recovery rate and purity were slightly reduced (91%, 98.3%), its lower process intensity makes it uniquely adaptable to handling raw materials with complex components. Example 4, through high-temperature short-time reduction at 900℃ combined with precipitation conditions at pH=8, increased the zinc recovery rate to 95% and the product purity to 99.5%. Simultaneously, optimized energy integration reduced energy consumption per ton of product to 1950 kWh, demonstrating the optimal performance level of the process.

[0041] Examples 2-4 exhibit a regular pattern in terms of energy and material consumption. With increasing process intensity, the comprehensive energy consumption per ton of product significantly decreased from 2100 kWh in Example 2 and 2350 kWh in Example 3 to 1950 kWh in Example 4. The calcium oxide consumption per ton also gradually decreased from 0.10 tons / ton of zinc oxide and 0.12 tons / ton of zinc oxide to 0.08 tons / ton of zinc oxide in Example 4. This gradient change confirms the advantages of high-temperature, short-duration operation in improving energy utilization efficiency and reveals the intrinsic relationship between process conditions and operating costs, providing a clear basis for process selection under different production scenarios.

[0042] In summary, the process of this invention achieves tiered utilization of reaction heat and resource recovery of carbon dioxide through a built-in calcium-based chemical chain cycle. All embodiments consistently produce high-quality zinc oxide with sodium carbonate as a byproduct. The performance gradient between embodiments fully demonstrates that this technical solution possesses both the ability to achieve top-tier performance and the flexibility to adapt to different raw material characteristics and product requirements. This combination of advanced technology and adaptability enables it to establish significant economic and environmental benefits in industrial applications of varying scales.

[0043] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0044] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0045] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0046] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0047] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0048] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A zinc oxide recovery system for ash slag based on calcium-based chemical chain cycle, characterized in that, The apparatus comprises, in sequence, a reduction roasting device (1), an acid leaching tank (2), a first filter (3), an alkaline precipitation tank (4), a second filter (5), a third filter (6), a Zn(OH)2 storage device (7), a first dryer (8), a calcining furnace (9), a calcining reactor (10), a CaO storage device (11), a hydration reactor (12), and a Ca(OH)2 storage device (13); the inlet of the first dryer (8) is also connected to the outlet of the hydration reactor (12); the inlet of the calcining reactor (10) is also connected to the outlet of the Ca(OH)2 storage device (13); and the outlet of the calcining reactor (10) is also connected to the outlet of the reduction roasting device (1). The ash slag zinc oxide recovery system also includes a CO2-rich flue gas storage device (17), a water pump (18), and a ZnO storage device (19); the inlet of the CO2-rich flue gas storage device (17) is connected to the outlet of the calcining reactor (10); the outlet of the CO2-rich flue gas storage device (17) is connected to the inlet of the third filter (6); the outlet of the water pump (18) is connected to the inlet of the hydration reactor (12); and the inlet of the ZnO storage device (19) is connected to the outlet of the calcining furnace (9).

2. The zinc oxide recovery system for ash slag based on calcium-based chemical chain cycle according to claim 1, characterized in that, The calcination reactor (10) includes a columnar reactor (10-1), multiple reactor Ca(OH)2 inlets (10-2), reactor CaO outlet (10-3), a first rotating plate (10-4), a high-temperature flue gas inlet (10-5), and a CO2-rich gas outlet (10-6). The first rotating plate (10-4) is disposed inside the cylindrical reactor (10-1). Multiple reactor Ca(OH)2 inlets (10-2) are disposed at the top of the cylindrical reactor (10-1) and connected to the Ca(OH)2 storage device (13). The reactor CaO outlet (10-3) is disposed at the bottom of the cylindrical reactor (10-1) and connected to the CaO storage device (11). The high-temperature flue gas inlet (10-5) and the CO2-rich gas outlet (10-6) are disposed at the side of the cylindrical reactor (10-1). The high-temperature flue gas inlet (10-5) is connected to the inlet of the calcining furnace (9). The CO2-rich gas outlet (10-6) is disposed at the upper end of the high-temperature flue gas inlet (10-5) and connected to the CO2-rich flue gas storage device (17).

3. The ash slag zinc oxide recovery system based on calcium-based chemical looping according to claim 1, characterized in that, The hydration reactor (12) includes a shell (12-1), multiple hydration reactor inlets (12-2), a hydration reactor outlet (12-3), a second rotating plate (12-4), a heat exchange tube (12-5), and an H2O gas outlet (12-6); the hydration reactor inlets (12-2) are connected to the outlet of the water pump (18); the hydration reactor outlet (12-3) is connected to the Ca(OH)2 storage device (13); and the H2O gas outlet (12-6) is connected to the first dryer (8). The second rotating plate (12-4) is disposed inside the shell (12-1); the heat exchange tube (12-5) is disposed inside the shell (12-1); the inlet of the heat exchange tube (12-5) extends out of the upper end of the shell (12-1); the outlet of the heat exchange tube (12-5) extends out of the lower end of the shell (12-1); Multiple hydration reactor inlets (12-2) are located at the top of the shell (12-1); the hydration reactor outlet (12-3) is located at the bottom of the shell (12-1); and the H2O gas outlet (12-6) is located at the side of the shell (12-1).

4. The zinc oxide recovery system for ash slag based on calcium-based chemical chain cycle according to claim 3, characterized in that, The ash slag zinc oxide recovery system also includes a second dryer (14), a Na2CO3 storage device (15), and a water storage device (16); the inlet of the second dryer (14) is connected to the outlet of the third filter (6) and the inlet of the hydration reactor (12), and the outlet of the second dryer (14) is connected to the inlet of the Na2CO3 storage device (15) and the inlet of the water storage device (16), respectively. The outlet of the water storage device (16) is connected to the inlet of the hydration reactor (12).

5. An application of a calcium-based chemical looping system for recovering zinc oxide from ash slag, characterized in that, The zinc oxide recovery system for ash slag as described in any one of claims 1 to 4 is used in the recovery of zinc oxide from ash slag.

6. A method for recovering zinc oxide from ash slag, employing the zinc oxide recovery system for ash slag as described in any one of claims 1 to 4, characterized in that, The method includes the following steps: (1) Add zinc oxide ash to the reduction roasting device (1) for reduction roasting to obtain roasting product. The roasting product is then acid-leached in the acid leaching tank (2) and filtered in the first filter (3) to obtain filtrate. The filtrate enters the alkaline precipitation tank (4) and first adds NaOH solution to react. Then it is filtered in the second filter (5) and the third filter (6) to obtain Zn(OH)2 precipitate, which is stored in the Zn(OH)2 storage device (7). The CO2-rich flue gas in the CO2-rich flue gas storage device (17) is introduced into the remaining filtrate in the third filter (6) to react and obtain Na2CO3. (2) The reaction heat stored in the hydration reactor (12) enters the first dryer (8), and the Zn(OH)2 precipitate in the Zn(OH)2 storage device (7) is dried and preheated in the first dryer (8), and then enters the calcining furnace (9) for calcination. The generated ZnO is stored in the ZnO storage device (19). (3) The high-temperature flue gas generated in the calcining furnace (9) and the reduction roasting device (1) is discharged into the calcining reactor (10). The Ca(OH)2 in the Ca(OH)2 storage device (13) is added to the calcining reactor (10) and calcined to generate CaO and CO2-rich flue gas. The CO2-rich flue gas is discharged into the CO2-rich flue gas storage device (17) for storage. The CaO is stored in the CaO storage device (11). The CaO in the CaO storage device (11) is added to the hydration reactor (12). At the same time, water from the water pump (18) is injected into the hydration reactor (12) to react and generate Ca(OH)2, which is stored in the Ca(OH)2 storage device (13).

7. The method for recovering zinc oxide from ash slag according to claim 6, characterized in that, The reduction calcination temperature in step (1) is 800℃~900℃ and the time is 1h~2h.

8. The method for recovering zinc oxide from ash slag according to claim 6, characterized in that, In step (1), when the second filter (5) filters, the pH of the filtrate is adjusted to <6.5; When the third filter (6) is used for filtration, the pH of the filtrate is 7-8.

9. The method for recovering zinc oxide from ash slag according to claim 6, characterized in that, The calcination temperature of the calcining furnace (9) in step (2) is 400℃~500℃ and the time is 1.5h~2.5h.

10. The method for recovering zinc oxide from ash slag according to claim 6, characterized in that, The calcination temperature of the calcination reactor (10) in step (3) is 500℃~600℃, and the time is 1h~2h; The mass ratio of CaO to water is 1:4~6.

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