Calcification roasting resource utilization process for polyaluminum chloride waste residues

Abstract

The invention discloses a calcium roasting resource utilization process for polyaluminum chloride waste residues, and belongs to the technical field of comprehensive utilization of solid wastes in the aluminum industry. The process comprises the following steps: mixing the polyaluminum chloride waste residue and calcium oxide according to a certain calcium-aluminum molar ratio, and adding a certain amount of water for wet grinding; after wet grinding is completed, the mixed materials are dried; crushing the dried material, and roasting in a resistance furnace; the clinker is leached by hydrochloric acid to separate acid leaching residues containing aluminum acid leaching liquid and magnesium aluminate spinel as main phases, the acid leaching liquid is cured to obtain a product, namely liquid polyaluminum chloride, and the acid leaching residues can be used as magnesium aluminate spinel industrial products. According to the method, part of aluminum resources in the polyaluminum chloride waste residues are converted into activated aluminum after being subjected to mechanical wet grinding assisted high-temperature calcification, the activated aluminum can be used for preparing aluminum-based products such as polyaluminum chloride through acid leaching, and the remaining aluminum resources are magnesium aluminate spinel resources. The method provided by the invention realizes full-quantitative recovery of aluminum resources in the polyaluminum chloride waste residues, effectively solves the problems of resource waste and environmental hazard caused by incapability of treating and utilizing aluminum-containing residues generated in the industrial production process of polyaluminum chloride, can improve the economic benefits of polyaluminum chloride production enterprises, and has important environmental protection significance and practical value.

Description

Technical Field

[0001] The present invention relates to the technical field of comprehensive utilization of solid wastes in the aluminum industry, and specifically to a process for resource utilization of calcined polyaluminum chloride waste residue by calcination. Background Art

[0002] With the country's initiative for environmental protection and "green" industrial development, the treatment of domestic sewage and industrial wastewater has gradually come into people's sight. As an efficient water treatment agent, polyaluminum chloride has been produced and applied in large quantities. Along with it, a large amount of waste residue is generated during the production process due to the presence of inert aluminum and impurities in the production raw materials, which is difficult to treat. The polyaluminum chloride waste residue contains corundum, magnesium aluminate spinel, aluminum hydroxide and various impurities. Corundum and magnesium aluminate spinel usually do not participate in the reaction, making it difficult to treat and utilize the polyaluminum chloride waste residue. Patent CN 118324276 A calcines the polyaluminum chloride waste residue at low temperature, and the insoluble solid obtained by acid leaching of the clinker is dried and crushed and used as cement aggregate, essentially ignoring the value of aluminum resources in the acid-insoluble substances. Patent CN 114655973 B mixes the polyaluminum chloride waste residue with calcium carbonate for calcination, the clinker is dissolved with sodium hydroxide and then solid-liquid separated, the leaching solution is used to prepare polyaluminum chloride, and the leaching residue is used as an auxiliary for building materials after being washed with water. Although this invention realizes the utilization of polyaluminum chloride waste residue, the overall process flow is long, the raw material economic cost is high, and the utilization of insoluble substances in the clinker is relatively low-level. Summary of the Invention

[0003] The present invention provides a process for resource utilization of calcined polyaluminum chloride waste residue by calcination, which can solve the problems raised in the above background art.

[0004] To achieve the above object, the present invention provides the following technical solutions: A process for resource utilization of calcined polyaluminum chloride waste residue by calcination, characterized in that the process comprises the following steps: S1 Mix calcium oxide and polyaluminum chloride waste residue in a certain proportion, and add an appropriate amount of water for wet grinding; S2 Dry and crush the wet-ground material; S3 Transfer the crushed material to an electric resistance furnace for calcination to obtain white clinker; S4 Leach the white clinker in an acidic environment, and perform solid-liquid separation on the leached slurry by pressure filtration to obtain a leaching solution and a leaching residue; S5 Age the leaching solution to obtain a polyaluminum chloride liquid; S6 Wash and dry the leaching residue in S4 and recycle it as magnesium aluminate spinel.

[0005] The process for resource utilization of polyaluminum chloride waste residue by low-temperature roasting according to any one of the steps S1-6 is characterized in that the mass percentage composition of each substance in the polyaluminum chloride waste residue in terms of oxides is as follows: Al 2 O 3 accounts for 50-80%, MgO accounts for 1-10%, SiO 2 accounts for 1-8%, and the remaining substances account for 1-15%.

[0006] In step S1, calcium oxide and polyaluminum chloride waste residue are mixed in a molar ratio of calcium oxide to reactive alumina in the waste residue (excluding aluminum in magnesium aluminate spinel, and the remaining aluminum is counted as reactive alumina) of 0.8-1.4. For example, it can be 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, etc., but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0007] In the wet grinding process in step S1, the water-to-material ratio is 1-3 L / Kg, preferably 2 L / Kg; the ball-to-material mass ratio is 2-10, preferably 6; the rotation speed is 200-500 rpm, preferably 300 rpm. Other unlisted values within the numerical range are equally applicable.

[0008] In step S1, the wet grinding time is 4-8 h. For example, it can be 4 h, 5 h, 6 h, 7 h, 8 h, etc., but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0009] In step S2, the drying temperature is 60-80 °C. For example, it can be 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, etc., but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0010] In step S3, the roasting temperature is 1000-1200 °C. For example, it can be 1000 °C, 1050 °C, 1100 °C, 1150 °C, 1200 °C, etc., but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0011] In step S3, the roasting time is 0.5-3 h. For example, it can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, etc., but not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0012] In step S4, the acid can be a 10-18% hydrochloric acid solution, and the leaching liquid-solid ratio is 4-10 L / kg, preferably 6 L / kg.

[0013] In step S4, the leaching temperature is 80-100 °C. For example, it can be 80 °C, 85 °C, 90 °C, 95 °C, 100 °C, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0014] In step S4, the leaching time is 0.5-2 h. For example, it can be 0.5 h, 1 h, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0015] In step S5, the curing temperature is 60-80 °C. For example, it can be 60 °C, 65 °C, 70 °C, 75 °C, 80 °C, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0016] In step S5, the curing time is 12-24 h. For example, it can be 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0017] The prepared polyaluminum chloride can meet the requirements of the national standard for water treatment agent polyaluminum chloride GB / T 22627-2022 after concentration or drying.

[0018] The main phase of the leaching residue obtained in step S4 is magnesium aluminate spinel, and the mass fraction is greater than 90%.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. This process for the resource utilization of polyaluminum chloride waste residue by low-temperature roasting uses industrial waste polyaluminum chloride waste residue as raw material to prepare valuable aluminum-based products such as polyaluminum chloride and magnesium aluminate spinel. The solid waste characteristics and low-cost characteristics of the raw materials make this process have practical environmental protection significance and can bring economic value. 2. This process for the resource utilization of polyaluminum chloride waste residue by low-temperature roasting activates the mixture of polyaluminum chloride waste residue and calcium oxide by mechanical wet grinding and then conducts roasting at 1000 °C - 1200 °C. Compared with simple sodium alkali roasting, the process of the present invention requires lower costs, and the roasting temperature is relatively low assisted by mechanical wet grinding activation, which can reduce economic costs while realizing waste utilization. 3. The resource utilization process of calcining the waste residue of polyaluminum chloride at low temperature, compared with other waste residue utilization processes of polyaluminum chloride such as Patent CN 118324276 A and the aforementioned Patent CN 118324276 A and Patent CN 114655973 B, makes more detailed use of the acid-insoluble substances leached after calcining the waste residue of polyaluminum chloride. Other existing processes often use them as cement doping agents or building materials, ignoring the aluminum resources in the acid-insoluble substances. However, the acid-insoluble substances separated by the process of the present invention are relatively pure magnesium aluminate spinel with a content of more than 90%, which can be reused as industrial raw materials. The process of the present invention makes more thorough use of the overall aluminum resources of the waste residue of polyaluminum chloride. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a process flow chart of the resource utilization of calcining the waste residue of polyaluminum chloride provided by the present invention.

[0021] Figure 2 It is an XRD pattern of the sintered clinker at different temperatures under the process of the present invention.

[0022] Figure 3 It is an XRD pattern of the magnesium aluminate spinel obtained after leaching and separation at the sintering temperature of 1200 °C under the process of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] In order to further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with the embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the invention. Those skilled in the art can draw on the content of this article and appropriately modify the process parameters to achieve it.

[0024] It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and those skilled in the art can obviously make changes or appropriate modifications and combinations to the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0025] The present invention provides a resource utilization process of calcining the waste residue of polyaluminum chloride, which is described in detail as follows in conjunction with the drawings: Figure 1 It is a process flow chart of the resource utilization of calcining the waste residue of polyaluminum chloride provided by the present invention. The process flow includes the following steps: (1) Mix the waste residue of polyaluminum chloride, calcium oxide and water for mechanical wet grinding, and obtain a mixed material after drying and pulverizing; (2) Sinter the mixed material obtained in step (1) at high temperature to obtain a clinker; (3) Leach the clinker obtained in step (2) with hydrochloric acid. After sufficient leaching, carry out solid-liquid separation to obtain a filtrate and a filter residue; (4) Let the filtrate in step (3) stand for ripening to obtain liquid polyaluminum chloride, and solid polyaluminum chloride can be obtained after drying. The filter residue in step (3) is magnesium aluminate spinel after washing and drying.

[0026] Example 1 This example provides a process for the resource utilization of polyaluminum chloride waste residue by calcination roasting, and the process includes the following steps: (1) Mix and wet-grind calcium oxide and polyaluminum chloride waste residue according to the molar ratio of calcium oxide to reactive alumina in the waste residue (excluding the aluminum in magnesium aluminate spinel, and the remaining aluminum is calculated as reactive alumina) of 1.3; (2) In the wet-grinding process in step (1), the water-to-material ratio is 2 L / Kg, the ball-to-material mass ratio is 6, and the rotation speed is 300 rpm; (3) Dry the wet-ground material in step (2) at 60 °C; (4) Crush the dried material in step (3) and sinter it at 800 - 1200 °C for 1 h; (5) The main reactions occurring during the sintering process in step (4) are as follows: Al 2 O 3 + CaO = CaAl 2 O 4 Al 2 O 3 + 2CaO + SiO 2 = Ca 2 Al 2 SiO 7 (6) Magnesium aluminate spinel in the polyaluminum chloride waste residue does not participate in the reaction during the sintering process in step (4); (7) Figure 2 is the XRD pattern of the clinker sintered at different temperatures under the process of the present invention. From Figure 2 it can be seen that the clinker mainly consists of calcium monoaluminate (CaAl 2 O 4 ), calcium aluminosilicate (Ca 2 Al 2 SiO 7 ), and magnesium aluminate spinel (MgAl 2 O 4)(It) consists of... and as the temperature rises, the composition of the clinker continuously decreases. When the roasting temperature reaches 1200 °C, there are almost only three phases in the clinker: calcium monoaluminate, calcium aluminosilicate, and magnesium aluminate spinel. The clinker obtained after high-temperature calcination roasting can recover acid-soluble aluminum salts such as calcium monoaluminate and calcium aluminosilicate through leaching and separation to realize the recycling of aluminum resources, and magnesium aluminate spinel remains stable during the leaching process; (8) Mix the clinker obtained by sintering in step (4) with 12% hydrochloric acid at a liquid-solid ratio of 6 L / kg and leach at 95 °C for 1 h; (9) The following reactions mainly occur during the leaching process in step (8): CaAl 2 O 4 +(8 - n)HCl = Al 2 (OH) n Cl 6-n +CaCl 2 +(4 - n)H 2 O Ca 2 Al 2 SiO 7 +(10 - n)HCl = Al 2 (OH) n Cl 6-n +2CaCl 2 +H 2 SiO 3 +(4 - n)H 2 O (10) Magnesium aluminate spinel in the sintered clinker does not participate in the reaction during the leaching process in step (8); (11) Filter the solid-liquid separation of the leached material in step (8). The liquid phase is polymerized aluminum chloride after ripening, and the solid phase is magnesium aluminate spinel after washing and drying; (12) Figure 3 This is the XRD pattern of magnesium aluminate spinel obtained after leaching and separation at a sintering temperature of 1200 °C in the process of the present invention. It can be clearly seen from Figure 3 that the characteristic peaks of magnesium aluminate spinel are obvious, and the miscellaneous peaks are almost absent, and the obtained magnesium aluminate spinel is relatively pure.

[0027] Example 2 This example provides a process for the resource utilization of calcination roasting of polyaluminum chloride waste residue. The process includes the following steps: (1) Mix calcium oxide and polyaluminum chloride waste residue according to a molar ratio of calcium oxide to reactive alumina in the waste residue (excluding aluminum in magnesium aluminate spinel, and the remaining aluminum is counted as reactive alumina) of 1.3, and wet grind for 4 h under the conditions of a water-to-material ratio preferably of 2 L / Kg and a ball-to-material mass ratio of 6; (2) Dry the wet-milled material in step (1) at 60 °C for 24 h; (3) Crush the dried material in step (2) and sinter it at 1200 °C for 1 h; (4) Mix the clinker obtained from sintering in step (3) with 12% hydrochloric acid at a liquid-solid ratio of 6 L / kg and leach it at 95 °C for 1 h; (5) Filter the material after leaching in step (4) to separate the solid and liquid. After the liquid phase is aged, it becomes polyaluminum chloride, and the solid phase is washed and dried to obtain magnesium aluminate spinel.

[0028] Example 3 The difference between this example and Example 2 is only that the sintering temperature in step (3) is 1100 °C.

[0029] Example 4 The difference between this example and Example 2 is only that the sintering temperature in step (3) is 1000 °C.

[0030] Example 5 The difference between this example and Example 2 is only that the molar ratio in step (1) is 1.4.

[0031] Example 6 The difference between this example and Example 2 is only that the molar ratio in step (1) is 1.2.

[0032] Example 7 The difference between this example and Example 2 is only that the molar ratio in step (1) is 1.1.

[0033] Comparative Example 1 This example provides a process for the resource utilization of polyaluminum chloride waste residue by calcination roasting, and the process includes the following steps: (1) Mix calcium oxide and polyaluminum chloride waste residue in a molar ratio of calcium oxide to reactive alumina in the waste residue (excluding aluminum in magnesium aluminate spinel, and the remaining aluminum is counted as reactive alumina) of 1.3; (2) Dry the mixed material in step (1) at 60 °C for 24 h; (3) Crush the dried material in step (2) and sinter it at 1200 °C for 1 h; (4) Mix the clinker obtained from sintering in step (3) with 12% hydrochloric acid at a liquid-solid ratio of 6 L / kg and leach it at 95 °C for 1 h; (5) The soluble alumina content in the sintered clinker is only 21.73%, and the insoluble content generated by leaching the clinker is 45.19%. The activation degree of corundum-type alumina in the polyaluminum chloride waste residue by roasting under wet ball milling is low, which is not conducive to the utilization of aluminum resources. At the same time, the generated insoluble content is high and impure and cannot be used as magnesium aluminate spinel.

[0034] Test method for soluble alumina in clinker fired in Examples 2-7 and Comparative Example 1: GB / T 29341-2022.

[0035] The content of soluble alumina in the clinker after roasting is a key index affecting the subsequent preparation of polyaluminum chloride and the purity of magnesium aluminate spinel. The content of soluble alumina in the clinker obtained in the above examples is shown in Table 1 below: Table 1 Soluble alumina content Example 2 40.85% Example 3 38.81% Example 4 34.12% Example 5 37.98% Example 6 39.17% Example 7 38.12% Comparative Example 1 21.73% Among them, the content of soluble alumina in the clinker obtained in Example 2 is the highest, which has a positive impact on both the preparation of polyaluminum chloride and the purity of magnesium aluminate spinel. The alumina content of the liquid polyaluminum chloride obtained by leaching the clinker under this condition reaches 8.36%, and the basicity reaches 33.48%. The alumina content of the solid polyaluminum chloride obtained after drying reaches 30.16%, and the basicity reaches 74.19%. The two main indexes of alumina content and basicity both meet the national standards of polyaluminum chloride for water treatment agents. In addition, the XRD pattern of the magnesium aluminate spinel obtained in Example 2 (i.e., Figure 3 ) was analyzed for its chemical composition by Rietveld refinement, and the mass fraction of magnesium aluminate spinel reached 93.41%. Under the conditions described in Example 2 in the examples of the present invention, the utilization of polyaluminum chloride waste residue reaches the optimal level, and the content of soluble alumina in the clinker obtained by calcination is the highest, which means that there is more active aluminum in the clinker that can be utilized. At the same time, a purer magnesium aluminate spinel can also be obtained by the process under this condition.

[0036] In summary, the present invention conducts secondary development and utilization of the aluminum-containing waste residue generated in the polyaluminum chloride process, extracts aluminum resources from the polyaluminum chloride waste residue for the production of polyaluminum chloride and magnesium aluminate spinel, improves resource utilization rate, and conforms to the general trend of sustainable green development.

[0037] This specific embodiment is only an interpretation of the present application, and it does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

Claims

1. A process for resource utilization of polyaluminium chloride waste slag by calcination and roasting, characterized in that: The process comprises the following steps: S1. Mix calcium oxide and polyaluminium chloride waste residue in a certain proportion, add a certain amount of water for wet grinding; S2. The wet-milled material in step S1 is dried and crushed; S3. The crushed material in step S2 is transferred to a resistance furnace for roasting to obtain a white clinker; S4. The white clinker obtained in step S3 is leached in an acidic environment, and the slurry after acid leaching is subjected to solid-liquid separation by filter pressing to obtain a leachate and a leach residue; S5. The leachate in step S4 is allowed to stand and mature to obtain a polyaluminium chloride liquid; S6. The leached residue in step S4 is recovered as magnesium-aluminum spinel.

2. The process for resource utilization of polyaluminium chloride waste slag by low temperature roasting according to any one of claim 1, characterized in that: The substances in the polyaluminium chloride waste residue are composed of the following substances in terms of mass percentage by oxide: Al2O3 accounts for 50-80%, MgO accounts for 1-10%, SiO2 accounts for 1-8%, and the remaining substances account for 1-15%.

3. The process for resource utilization of polyaluminium chloride waste slag at low temperature roasting according to claim 1, characterized in that: In step S1, calcium oxide and polyaluminium chloride waste slag are mixed in a molar ratio of 0.8-1.4 between calcium oxide and reactive alumina in the polyaluminium chloride waste slag (excluding the aluminium in magnesium aluminium spinel, the remaining aluminium is calculated as reactive alumina), the water-to-material ratio in the wet grinding process is 1-3 L / Kg, the ball-to-material mass ratio is 2-10, the wet grinding time is 4-8 h, and the rotation speed is 200-500 rpm.

4. The process for resource utilization of polyaluminium chloride waste slag at low temperature roasting according to claim 1, characterized in that: The drying temperature in step S2 is 60-80°C.

5. The process for resource utilization of polyaluminium chloride waste slag at low temperature roasting according to claim 1, characterized in that: The calcination temperature in step S3 is 1000-1200° C., and the calcination time is 0.5-3 h.

6. The process for resource utilization of polyaluminium chloride waste slag at low temperature roasting according to claim 1, characterized in that: The acid in step S4 includes a 10-18% hydrochloric acid solution, the leaching temperature is 80-100°C, the leaching time is 0.5-2 h, and the leaching liquid-solid ratio is 4-10 L / kg.

7. The process for resource utilization of polyaluminium chloride waste residue by low temperature roasting according to claim 1, characterized in that: The aging temperature in the step is 60-80° C., and the aging time is 12-24 h.

8. The process for resource utilization of polyaluminium chloride waste slag at low temperature roasting according to claim 1, characterized in that: The polyaluminium chloride prepared in step S5 can meet the requirements of the national standard for polyaluminium chloride for water treatment agents (GB / T22627-2022) after concentration or drying.

9. The process for resource utilization of polyaluminium chloride waste slag by low temperature roasting according to claim 1, characterized in that: The main phase of the leached slag obtained in step S4 is magnesia-alumina spinel.

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