A method for co-processing and resource utilization of overhaul slag, fly ash, and desulfurized gypsum

Abstract

The present invention relates to a method for co - processing and resource utilization of overhaul slag, fly ash, and desulfurized gypsum. The method comprises the following steps: Step 1) dehydrate and then dry the desulfurized gypsum, add calcium carbonate to the dried desulfurized gypsum, and collect SO3 gas; Step 2) carry out an autoclave reaction on the SO3 gas obtained in Step 1, water, and fly ash. After solid - liquid separation, silicon dioxide and an aluminum sulfate solution are obtained; Step 3) crush and ball - mill the overhaul slag, and carry out first - stage roasting with a peroxide at high temperature to obtain clinker 1; leach out sodium fluoride from clinker 1 by water immersion, and then add it to the aluminum sulfate for second - stage roasting to obtain clinker 2; Step 4) mix clinker 2 with water for leaching to obtain a filtrate and a filter residue; Step 5) calcine calcium oxide and the filter residue to obtain calcium aluminate. The beneficial effect of the present invention aims to synergistically utilize the sodium, aluminum, fluorine, and lithium elements, the aluminum and silicon elements of fly ash, and the calcium element in desulfurized gypsum to achieve the purpose of resource conversion.

Description

Technical Field

[0001] The present invention relates to the technical field of resource utilization of industrial solid waste, and particularly relates to a method for co-processing and resource utilization of overhaul slag, fly ash, and desulfurized gypsum. Background Art

[0002] Overhaul slag is a large amount of solid waste generated in the process of electrolytic aluminum production. It contains a high concentration of fluorides, mainly Na3AlF6 and NaF, and belongs to hazardous waste. The soluble fluorine content exceeds 60 times the national standard value. Its harmful substances enter the human body through polluting air, water, soil, and crops, which will aggravate diseases such as Alzheimer's disease and skeletal fluorosis. The overhaul slag has a complex composition, with sodium, aluminum, fluorine, oxygen, and carbon wrapped around each other, making it difficult to treat. It has the dual characteristics of "hazardous waste" and "fluorine-containing secondary resource", and its resource utilization is extremely urgent.

[0003] Desulfurized gypsum is a by-product formed after desulfurizing sulfur-containing flue gas in industries such as coal-fired power, aluminum smelting, fluorine chemical industry, and cement using the limestone-gypsum method or the calcium hydroxide solution leaching method. Its main component is CaSO4·2H2O, with a content of about 90% - 93%. Other components are CaO, Ca(OH)2, and CaCO3. The annual production of gypsum in China is hundreds of millions of tons, and resource utilization is urgently needed.

[0004] The main components of fly ash are silicon dioxide (SiO2), aluminum oxide (Al2O¬3), calcium oxide (CaO), and iron oxide (Fe2O3); fly ash is a waste residue generated after coal combustion, and its impact on the environment is relatively serious, and resource utilization is also urgently needed.

[0005] At present, a large number of patent documents provide resource utilization of overhaul slag. For example, CN101134595A discloses a method for producing calcium fluoride, which uses fluorosilicic acid and calcium oxide as raw materials, filters after reaction to obtain calcium fluorosilicate solid, and then decomposes it at high temperature to produce calcium fluoride. CN101891231A discloses a method for preparing analytically pure calcium fluoride, which uses analytically pure hydrofluoric acid and ammonia dissolved in water, and then reacts with calcium nitrate aqueous solution, and then dries, calcines, and crushes to obtain analytically pure calcium fluoride. CN114804179A discloses a method for recovering high-purity calcium fluoride from fluorine-containing waste slag, wherein the fluorine-containing waste slag contains calcium fluoride and calcium carbonate. The powdered fluorine-containing waste slag is first calcined to cause calcium fluoride crystals to grow and the calcium carbonate to decompose into calcium oxide to obtain a calcined product; the calcined product is sequentially subjected to calcium oxide flotation treatment and calcium fluoride capture treatment in an aqueous solution to obtain a recovered product. CN 115338238 A discloses a fluorine-fixing agent and a fluorine-fixing method for aluminum electrolytic cell overhaul slag. The fluorine-fixing agent comprises calcium sulfate. The fluorine-fixing method comprises: 1) crushing and ball-milling the electrolytic cell overhaul slag; 2) adding desulfurized gypsum to a rotary calcining kiln for heating, calcining the desulfurized gypsum in the kiln to remove water adhering to the desulfurized gypsum, and oxidizing the calcium sulfite in the desulfurized gypsum to calcium sulfate or decomposing it into calcium oxide and sulfur dioxide at high temperature; maintaining a stable temperature, converting the calcium sulfate dihydrate in the desulfurized gypsum into calcium sulfate hemihydrate; 3) adding water to a reaction chamber, adding the powdered overhaul slag obtained in step 1), and stirring to leach out all soluble fluorides in the overhaul slag; and 4) adding the desulfurized gypsum powder obtained in step 2) to the mixture obtained in step 4), stirring the mixture thoroughly, and converting all toxic and harmful soluble fluorides in the overhaul slag into calcium fluoride.

[0006] In view of the fact that none of the above technologies have carried out the coordinated utilization of overhaul slag, fly ash and desulfurization gypsum, it is necessary to provide a method for the coordinated treatment and resource utilization of overhaul slag, fly ash and desulfurization gypsum to meet the demand for resource utilization of overhaul slag, fly ash and desulfurization gypsum. Summary of the Invention

[0007] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a method for the coordinated treatment and resource utilization of overhaul slag, fly ash and desulfurization gypsum, aiming to achieve the purpose of resource conversion by synergistically utilizing the sodium, aluminum, fluorine and lithium elements in overhaul slag, the aluminum and silicon elements in fly ash and the calcium element in desulfurization gypsum.

[0008] The present invention is achieved through the following technical solutions: On the one hand, a method for the coordinated treatment and resource utilization of overhaul slag, fly ash, and desulfurization gypsum is provided, which comprises the following steps:

[0009] Step 1) Dehydrate and dry the desulfurized gypsum, add calcium carbonate to the dried desulfurized gypsum, grind it into a uniform mixture, preheat it and then calcine and decompose it to obtain the product calcium oxide and SO2 flue gas. After the SO2 flue gas is dust-removed and oxygen-enriched, a high-temperature oxidation reaction is carried out to collect SO3 gas;

[0010] Step 2) Carry out an autoclave reaction on the SO3 gas obtained in Step 1 with water and fly ash. After solid-liquid separation, silica and aluminum sulfate solution are obtained;

[0011] Step 3) Crush and ball-mill the overhaul slag to below 150 mesh, and carry out one-stage roasting of the crushed and ball-milled overhaul slag with peroxide at high temperature to obtain clinker 1; leach and separate sodium fluoride from clinker 1 with water, and then add it to the aluminum sulfate prepared in Step 2, and at the same time add soluble calcium salt for two-stage roasting to obtain clinker 2;

[0012] Step 4) Mix and leach the clinker 2 obtained in Step 3 with water, and carry out solid-liquid separation to obtain a filtrate and a filter residue; the filter residue is dried to obtain a material containing alumina;

[0013] Step 5) After calcining the calcium oxide obtained in Step 1 and the filter residue obtained in Step 4, calcium aluminate is obtained.

[0014] Through the above technical solutions, the present invention is based on the co-preparation of aluminum sulfate from desulfurized gypsum and fly ash. Aluminum sulfate reacts with the overhaul slag to extract fluorine and lithium, and the calcium element of the desulfurized gypsum and the fluorine-aluminum elements of the overhaul slag react to prepare calcium aluminate, thereby realizing the co-utilization of secondary resources.

[0015] Among them, in Step 2), alumina, iron oxide and calcium oxide in the fly ash enter the solution to obtain crude silica, achieving the purpose of effective separation of aluminum and silicon elements in the fly ash.

[0016] In Step 4), the lithium recovery rate of the obtained lithium-containing solution is greater than 99%. Compared with the prior art, the recovery rate is increased by 20%.

[0017] Furthermore, in Step 2), the temperature of the autoclave reaction is 80-150 °C, and the reaction time is 60-90 min.

[0018] Even further, in Step 2), the main reactions in the autoclave process are as follows:

[0019] 3SO3 + 3H2O + Al2O3 = Al2(SO4)3 + 3H2O;

[0020] 3SO3 + 3H2O + Fe2O3 = Fe2(SO4)3 + 3H2O;

[0021] SO3 + H2O + CaO = CaSO4 + H2O.

[0022] Through the above technical solution, compared with the conventional reaction, the autoclave reaction increases the activation energy of the reactants, and the reaction efficiency is increased by more than 20%.

[0023] Further, in step 3), at least one of sodium peroxide and potassium peroxide is selected as the peroxide; the addition amount of the peroxide accounts for 5% - 10% of the mass of the overhaul slag.

[0024] Through the above technical solution, the peroxide of the present invention can promote the rapid oxidative decomposition of cyanides, nitrides, and carbides in the overhaul slag, avoid the subsequent release of toxic and harmful gases, and at the same time the clinker becomes porous, and sodium fluoride is easily leached, improving the recovery rate of sodium fluoride in the solution. Compared with no addition, the reaction time is shortened by 25%, and the recovery rate of sodium fluoride in the solution is increased by 10%. Sodium peroxide is preferably used. For clinker 1, adding sodium peroxide can not only provide oxygen and promote the decomposition of cyanides / nitrides / carbides, but also avoid reacting with soluble fluorides to consume fluorine elements. Potassium peroxide is preferably used. For clinker 1, the function of adding potassium peroxide is similar to that of sodium peroxide. It can not only provide oxygen and promote the decomposition of cyanides / nitrides / carbides, but also avoid reacting with soluble fluorides to consume fluorine elements.

[0025] Further, in step 3), the temperature of the first-stage roasting is 500 - 700 °C, and the roasting time is 30 - 60 min; the temperature of the second-stage roasting is 600 - 800 °C, and the roasting time is 2 - 4 h.

[0026] Through the above technical solution, the first-stage roasting removes the cyanides, nitrides, and carbides in the overhaul slag. The escape of gases makes the clinker 1 porous, and sodium fluoride is easily leached by water, and no toxic and harmful gases are released. The second-stage roasting decomposes cryolite in the overhaul slag, enabling lithium elements to enter the solution, which is beneficial for lithium extraction in subsequent processes.

[0027] Further, in step 3), the specific preparation process of the clinker 2 is as follows: The clinker 1 is leached with water, and solid-liquid separation is performed to obtain a sodium fluoride solution and a filter cake. The filter cake is dehydrated and dried and then mixed with the aluminum sulfate solution prepared in step 2), and at the same time, a soluble calcium salt is added for second-stage roasting to obtain the clinker 2.

[0028] Through the above technical solution, the main components of the clinker 1 of the present invention are mullite, alumina, cryolite, and sodium fluoride; the soluble calcium salt and aluminum sulfate react with lithium cryolite and sodium cryolite, that is, the soluble calcium salt can react with the fluorine element in the overhaul slag to form calcium fluoride, effectively promoting the decomposition of sodium cryolite and lithium cryolite in the overhaul slag. Adding the soluble calcium salt preferentially decomposes sodium cryolite, and the encapsulated lithium cryolite is freed, thus promoting the decomposition of lithium cryolite. The main components of the obtained clinker 2 are lithium sulfate, sodium salt, mullite, alumina, and calcium fluoride.

[0029] Further, in step 3), the soluble calcium salt is at least one of calcium chloride, calcium sulfate, and calcium nitrate, and the addition amount of the soluble calcium salt accounts for 5% to 10% of the mass of the overhaul slag.

[0030] Further, in step 3), the soluble calcium salt cannot be calcium carbonate or calcium bicarbonate to avoid generating insoluble substances of lithium, resulting in a decrease in the yield of the lithium solution.

[0031] Further, in step 3), adding a soluble calcium salt is beneficial to improving the yield of lithium in the solution. Compared with not adding, the yield of lithium in the solution is increased by 15%.

[0032] Further, in step 3), the main reactions in the secondary roasting process are as follows:

[0033] 3CaCl2 + Na3AlF6 → 3CaF2 + 3NaCl + AlCl3;

[0034] 6CaSO4 + 2Na3AlF6 → 6CaF2 + 3Na2SO4 + Al2(SO4)3;

[0035] 3Ca(NO3)2 + Na3AlF6 → 3CaF2 + 3NaNO3 + Al(NO3)3;

[0036] Al2(SO4)3 + 2LiNa2AlF6 → 4AlF3 + 2Na2SO4 + Li2SO4;

[0037] CaCl2 / Ca(NO3)2 + AlF3 → CaF2 + AlCl3 / Al(NO3)3.

[0038] Further, in step 1), the addition amount of the calcium carbonate accounts for 5% to 10% of the mass of the desulfurized gypsum.

[0039] Through the above technical solution, the calcium carbonate of the present invention improves the dispersibility of the desulfurized gypsum, has a mineralization effect on the desulfurized gypsum, and avoids incomplete decomposition of the gypsum; the calcium carbonate is preferentially decomposed into calcium oxide and CO2, and the release of CO2 makes the gypsum loose and porous, promoting the decomposition of the gypsum and shortening the gypsum decomposition time; at the same temperature, compared with not adding calcium carbonate, the gypsum decomposition time is shortened by 30%, which is beneficial to energy conservation and carbon reduction.

[0040] Further, in step 1), the calcination temperature is 1000 to 1200 °C, and the calcination time is 1 to 3 h.

[0041] Through the above technical solution, when calcined at 1000-1200°C, the decomposition rate of gypsum is increased by 10% compared with that when calcined at a temperature lower than 1000°C.

[0042] The beneficial effects of the present invention are as follows:

[0043] ① Prepare aluminum sulfate from desulfurized gypsum and fly ash. React aluminum sulfate with overhaul slag to extract fluorine and lithium. Prepare calcium aluminate from calcium oxide obtained by the decomposition of desulfurized gypsum and the filter residue obtained after extracting fluorine and lithium from overhaul slag, thereby realizing the collaborative utilization of secondary resources.

[0044] ② Calcium carbonate improves the dispersibility of desulfurized gypsum and has a mineralization effect on desulfurized gypsum. The escape of CO2 gas makes the gypsum loose and porous, promoting the decomposition of gypsum and avoiding incomplete decomposition of desulfurized gypsum; peroxides promote the de-cyanation and de-nitrification of overhaul slag. The escape of gas makes the overhaul slag loose and porous, which is beneficial to the water leaching of sodium fluoride and effectively avoids the generation of toxic and harmful gases; soluble calcium salts react with cryolite sodium preferentially, and the encapsulated cryolite lithium is freed, promoting the reaction between aluminum sulfate and cryolite lithium. Description of the Drawings

[0045] Figure 1 To show the process flow chart of the present invention. Detailed Embodiments

[0046] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the invention embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0047] The experimental methods without specific conditions in the following embodiments are usually carried out according to conventional conditions or according to the conditions recommended by the manufacturers. Unless otherwise stated, all percentages, ratios, proportions or parts are by weight; the raw materials involved are all obtained commercially.

[0048] Example 1

[0049] As Figure 1As shown in the figure, a certain amount of desulfurized gypsum is weighed, 5% calcium carbonate is added, and they are mixed and ground to obtain gypsum. The gypsum is heated and decomposed at 1000 °C for 3 h, and the decomposition rate of the gypsum is 99.3%, obtaining calcium oxide and SO2. The SO2 gas is dedusted and oxidized to obtain SO3 gas. The SO3 gas is collected and introduced into an autoclave containing fly ash and water, and autoclaved at 150 °C for 60 min. After solid-liquid separation, crude silica and aluminum sulfate solution are obtained. The aluminum sulfate solution is concentrated and dried to obtain aluminum sulfate. The overhaul slag is crushed and ground to less than 150 mesh, 5% sodium peroxide is added, and they are mixed evenly. The mixture is calcined at 600 °C for 60 min to obtain overhaul slag clinker 1. Sodium fluoride is separated by water leaching, and the fluorine recovery rate is 98.3%. Aluminum sulfate is fully mixed with overhaul slag clinker 1 and 5% calcium chloride, and the mixture reacts at 600 °C for 4 h to obtain overhaul slag clinker 2. The clinker is leached with water and filtered to separate the lithium-containing solution and the filter cake. The lithium recovery rate in the solution is 97.1%. The filter cake and calcium oxide are calcined together to obtain calcium aluminate, and the product meets the requirements of standard GB201-2000.

[0050] On the basis of the above scheme, the main components of the filter cake are mullite, alumina, and calcium fluoride.

[0051] Comparative Example 1

[0052] As Figure 1 shown in the figure, a certain amount of desulfurized gypsum is weighed, 5% calcium carbonate is added, and they are mixed and ground to obtain gypsum. The gypsum is heated and decomposed at 1000 °C for 3 h to obtain calcium oxide and SO2. The SO2 gas is dedusted and oxidized to obtain SO3 gas. The SO3 gas is collected and introduced into a reactor containing fly ash and water, and reacts at 150 °C for 80 min. After solid-liquid separation, crude silica and aluminum sulfate solution are obtained. The aluminum sulfate solution is concentrated and dried to obtain aluminum sulfate. The operations of other steps are the same as those in Example 1.

[0053] Comparative Example 11

[0054] As Figure 1 shown in the figure, a certain amount of desulfurized gypsum is weighed, mixed and ground to obtain gypsum. The gypsum is heated and decomposed at 1000 °C for 4 h to obtain calcium oxide and SO2. The SO2 gas is dedusted and oxidized to obtain SO3 gas. The SO3 gas is collected and introduced into an autoclave containing fly ash and water, and autoclaved at 150 °C for 60 min. After solid-liquid separation, crude silica and aluminum sulfate solution are obtained. The aluminum sulfate solution is concentrated and dried to obtain aluminum sulfate. The operations of other steps are the same as those in Example 1.

[0055] Example 2

[0056] As Figure 1As shown in the figure, a certain amount of desulfurized gypsum is weighed, 7.5% calcium carbonate is added, and they are mixed and ground to obtain gypsum. The gypsum is heated and decomposed at 1100 °C for 2 h, and the decomposition rate of the gypsum is 99.5% to obtain calcium oxide and SO2 gas. The SO2 gas is dedusted and oxidized to obtain SO3 gas. The SO3 gas is collected and introduced into an autoclave containing fly ash and water, and autoclaved at 115 °C for 75 min. After solid-liquid separation, crude silica and aluminum sulfate solution are obtained. The aluminum sulfate solution is concentrated and dried to obtain aluminum sulfate. The overhaul slag is crushed and ground to less than 150 mesh, 7.5% potassium peroxide is added, and they are mixed evenly. The mixture is calcined at 650 °C for 45 min to obtain overhaul slag clinker 1. Sodium fluoride is separated by water leaching, and the fluorine recovery rate is 98.6%. Aluminum sulfate is fully mixed with overhaul slag clinker 1 and 10% calcium sulfate, and the mixture reacts at 700 °C for 3 h to obtain overhaul slag clinker 2. The clinker 2 is leached with water and filtered to separate the lithium-containing solution and the filter cake. The lithium recovery rate in the solution is 96.4%. The filter cake and calcium oxide are calcined together to obtain calcium aluminate, and the product meets the requirements of standard GB201-2000.

[0057] On the basis of the above scheme, the main components of the filter cake are mullite, alumina, and calcium fluoride.

[0058] Comparative Example 2

[0059] The overhaul slag is crushed and ground to less than 150 mesh, and calcined at 650 °C for 60 min to obtain overhaul slag clinker 1. Sodium fluoride is separated by water leaching, and the fluorine recovery rate is 88.6%. Aluminum sulfate is fully mixed with overhaul slag clinker 1 and 10% calcium sulfate, and the mixture reacts at 700 °C for 3 h to obtain overhaul slag clinker 2. The operations of other steps are the same as those in Example 2.

[0060] Comparative Example 22

[0061] The overhaul slag is crushed and ground to less than 150 mesh, 7.5% potassium peroxide is added, and they are mixed evenly. The mixture is calcined at 650 °C for 45 min to obtain overhaul slag clinker 1. Aluminum sulfate is fully mixed with overhaul slag clinker 1, and the mixture reacts at 700 °C for 3 h to obtain overhaul slag clinker 2. The clinker 2 is leached with water and filtered to separate the lithium-containing solution and the filter cake. The lithium recovery rate in the solution is 81.2%. The filter cake and calcium oxide are calcined together to obtain calcium aluminate, and the product meets the requirements of standard GB201-2000. The operations of other steps are the same as those in Example 2.

[0062] Example 3

[0063] As Figure 1As shown, a certain amount of desulfurized gypsum was weighed, 10% calcium carbonate was added, and they were mixed and ground to obtain gypsum. The gypsum was heated and decomposed at 1200 °C for 1 h, and the decomposition rate of the gypsum was 99.8% to obtain calcium oxide and SO2 gas. The SO2 gas was dedusted and oxidized to obtain SO3 gas. The SO3 gas was collected and introduced into an autoclave containing fly ash and water, and digested at 80 °C for 90 min. After solid-liquid separation, crude silica and aluminum sulfate solution were obtained. The aluminum sulfate solution was concentrated and dried to obtain aluminum sulfate. The overhaul slag was crushed and ground to less than 150 mesh, 10% of a mixture of sodium peroxide and potassium peroxide was added, and they were mixed evenly. The mixture was calcined at 700 °C for 30 min to obtain overhaul slag clinker. Sodium fluoride was separated by water leaching, and the yield of sodium fluoride was 98.8%. Aluminum sulfate was fully mixed with the overhaul slag clinker and 7.5% calcium nitrate. The mixture reacted at 800 °C for 2 h to obtain clinker 2. Clinker 2 was leached with water and filtered to separate the lithium-containing solution and the filter cake. The yield of lithium in the solution was 96.1%. The filter cake and calcium oxide were calcined together to obtain calcium aluminate, and the product met the requirements of Standard GB201-2000.

[0064] On the basis of the above scheme, the main components of the filter cake are mullite, alumina, and calcium fluoride.

[0065] Comparative Example 3

[0066] As Figure 1 shown, a certain amount of desulfurized gypsum was weighed, 10% calcium carbonate was added, and they were mixed and ground to obtain gypsum. The gypsum was heated and decomposed at 1000 °C for 1 h, and the decomposition rate of the gypsum was 89.7% to obtain calcium oxide and SO2 gas. The SO2 gas was dedusted and oxidized to obtain SO3 gas. The SO3 gas was collected and introduced into an autoclave containing fly ash and water, and digested at 80 °C for 90 min. After solid-liquid separation, crude silica and aluminum sulfate solution were obtained. The aluminum sulfate solution was concentrated and dried to obtain aluminum sulfate. Other operation steps were the same as those in Example 3.

[0067] Effect Example

[0068] The data measured for Examples 1-3 and Comparative Examples 1, 11, 2, 22, and 3 based on the existing experimental process and the following experimental conditions are shown in Table 1 below.

[0069] Table 1 Process parameters used in the experiment

[0070]

[0071] In summary, as can be seen from a comparison between Example 1 and Comparative Example 1 and Comparative Example 11, without carrying out the autoclave reaction, the reaction time is 80 min; by using the autoclave reaction, the activation energy is increased, the reaction time is shortened to 60 min, and the reaction efficiency is increased by more than 20%, with obvious effects. Without adding calcium carbonate, the decomposition time of gypsum is 4 h; with the addition of calcium carbonate, the decomposition time of gypsum is 3 h. Compared with the case without adding calcium carbonate, the decomposition time of gypsum is shortened by about 30%, with obvious effects. As can be seen from a comparison between Example 2 and Comparative Example 2 and Comparative Example 22, without adding potassium peroxide, the first-stage roasting time is 60 min and the sodium fluoride yield is 88.6%; with the addition of potassium peroxide, the first-stage roasting time is 45 min and the sodium fluoride yield is 98.6%. The time is shortened by 25% and the sodium fluoride yield is increased by 10%, with obvious effects. Without adding calcium sulfate, the lithium yield in the solution is 81.2%; with the addition of calcium sulfate, the lithium yield in the solution is 96.4%; with the addition of calcium sulfate, the lithium yield is increased by about 20%, with obvious effects. As can be seen from a comparison between Example 3 and Comparative Example 3, when gypsum is heated and decomposed at 1000 °C for 1 h, the gypsum decomposition rate is 89.8%; when gypsum is heated and decomposed at 1200 °C for 1 h, the gypsum decomposition rate is 99.8%; by using a suitable temperature, the decomposition rate of gypsum is increased by 10%.

[0072] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for co - treating and resource utilization of overhaul slag, fly ash, and desulfurized gypsum, characterized in that, The method comprises the following steps: Step 1) Dehydrate and dry the desulfurized gypsum, add calcium carbonate to the dried desulfurized gypsum, grind it into a uniform mixture, calcine and decompose it after preheating to obtain the product calcium oxide and SO2 flue gas. After the SO2 flue gas is dust-removed and oxygen-enriched, a high-temperature oxidation reaction is carried out to collect SO3 gas; Step 2) Carry out an autoclave reaction on the SO3 gas obtained in Step 1) with water and fly ash. After solid-liquid separation, silica and an aluminum sulfate solution are obtained; Step 3) Crush and ball-mill the overhaul slag to less than 150 meshes, and carry out a first-stage roasting of the crushed and ball-milled overhaul slag with a peroxide at a high temperature to obtain clinker 1; Leach and separate sodium fluoride from clinker 1 with water, and then add it to the aluminum sulfate prepared in Step 2), and at the same time add a soluble calcium salt for a second-stage roasting to obtain clinker 2; Step 4) Mix and leach clinker 2 obtained in Step 3) with water, and carry out solid-liquid separation to obtain a filtrate and a filter residue; The filter residue is dried to obtain a material containing alumina; Step 5) Calcine the calcium oxide obtained in Step 1) and the filter residue obtained in Step 4) to obtain calcium aluminate; Wherein, in Step 2), the temperature of the autoclave reaction is 80-150 °C, and the reaction time is 60-90 min; In Step 2), the main reactions during the autoclave process are as follows: 3SO3 + 3H2O + Al2O3 = Al2(SO4)3 + 3H2O; 3SO3 + 3H2O + Fe2O3 = Fe2(SO4)3 + 3H2O; SO3 + H2O + CaO = CaSO4 + H2O; In Step 3), the main reactions during the second-stage roasting process are as follows: 3CaCl2 + Na3AlF6 → 3CaF2 + 3NaCl + AlCl3; 6CaSO4 + 2Na3AlF6 → 6CaF2 + 3Na2SO4 + Al2(SO4)3; 3Ca(NO3)2 + Na3AlF6 → 3CaF2 + 3NaNO3 + Al(NO3)3; Al2(SO4)3 + 2LiNa2AlF6 → 4AlF3 + 2Na2SO4 + Li2SO4; CaCl2 / Ca(NO3)2 + AlF3 → CaF2 + AlCl3 / Al(NO3)3.

2. The method for co-processing and resource utilization of overhaul slag, fly ash, and desulfurized gypsum according to claim 1, characterized in that, In Step 3), the peroxide is at least one of sodium peroxide and potassium peroxide; The addition amount of the peroxide accounts for 5%-10% of the mass of the overhaul slag.

3. The method for co-processing and resource utilization of overhaul slag, fly ash, and desulfurized gypsum according to claim 1, wherein In Step 3), the temperature of the first-stage roasting is 500-700 °C, and the roasting time is 30-60 min; The temperature of the second-stage roasting is 600-800 °C, and the roasting time is 2-4 h.

4. The method for co-processing and resource utilization of overhaul slag, fly ash, and desulfurized gypsum according to claim 1, characterized in that In Step 3), the specific preparation process of clinker 2 is as follows: Leach clinker 1 with water, carry out solid-liquid separation to obtain a sodium fluoride solution and a filter cake, dehydrate and dry the filter cake, mix it with the aluminum sulfate solution prepared in Step 2), and at the same time add a soluble calcium salt for a second-stage roasting to obtain clinker 2.

5. The method for co-processing and resource utilization of overhaul slag, fly ash, and desulfurized gypsum according to claim 4, wherein In Step 3), the soluble calcium salt is at least one of calcium chloride, calcium sulfate, and calcium nitrate, and the addition amount of the soluble calcium salt accounts for 5%-10% of the mass of the overhaul slag.

6. The method for co-processing and resource utilization of overhaul slag, fly ash, and desulfurized gypsum according to claim 1, characterized in that In step 1), the addition amount of the calcium carbonate accounts for 5% to 10% of the mass of the desulfurized gypsum.

7. The method for co-processing and resource utilization of overhaul slag, fly ash, and desulfurized gypsum according to claim 1, wherein In step 1), the calcination temperature is 1000 to 1200 °C, and the calcination time is 1 to 3 h.

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