Method for preparing composite calcium ferrite from phosphogypsum and calcium-process vanadium extraction tailings

Abstract

The invention discloses a method for preparing composite calcium ferrite from phosphogypsum and calcium-process vanadium extraction tailings, and belongs to the technical field of metallurgy. The invention relates to a method for preparing composite calcium ferrite from ardealite and calcium-process vanadium extraction tailings. The method comprises the following steps: drying the ardealite and the calcium-process vanadium extraction tailings; uniformly mixing and grinding the dried material and carbon-containing reducing agent powder to obtain a mixed and ground material; adding water into the mixed and ground material, pressing the mixed and ground material into material ball blocks, and drying the material ball blocks under preset conditions; placing the dried material ball block in a reactor for calcining, and cooling to obtain a sample which is composite calcium ferrite in the reaction container; according to the method, sulfur in the ardealite and the vanadium extraction tailings is removed in the form of sulfur dioxide at high temperature through external carbon, the removal rate of sulfur reaches 95% or above, calcium ferrite with the effective content being 50% or above and a small part of sulfur dioxide flue gas in the prepared composite calcium ferrite are prepared, and calcium, sulfur and iron resources in the ardealite and the vanadium extraction tailings can be fully recycled.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy, and in particular to a method for preparing composite calcium ferrite from phosphogypsum and calcium-process vanadium extraction tailings. Background Art

[0002] my country's vanadium-titanium magnetite deposits are widely distributed and rich in reserves. The reserves and mining volume rank third among iron ores in the country. The proven reserves are 9.83 billion tons, and the prospective reserves are more than 30 billion tons. There are more vanadium ore resources, with a total V2O5 reserve of 25.96 million tons, ranking third in the world. According to statistics, the comprehensive utilization of phosphogypsum resources in my country will be 45 million tons in 2023, and the comprehensive utilization rate of phosphogypsum resources will reach 55.6%. Every ton of phosphoric acid produced will produce about 4.8-5.0 tons of phosphogypsum. The global stockpile of phosphogypsum is as high as 6 billion tons, and it is increasing at a rate of 100-280 million tons per year. The stacking and treatment of phosphogypsum is a global problem, but its comprehensive utilization is also being explored and promoted. For example, it is used in packaging materials, mine restoration, building materials and other fields, which effectively improves its utilization rate, but it causes a great waste of resources such as calcium, iron, and sulfur, and brings environmental pollution risks. Because of its iron content, phosphogypsum has problems such as high processing costs, narrow application range, and difficulty in large-scale disposal. Long-term storage also imposes a heavy economic burden and environmental risks on enterprises.

[0003] At present, the solid waste resources generated by phosphogypsum have not been effectively utilized, and are mainly stored or sold at a subsidy, resulting in a waste of calcium, iron and sulfur resources and bringing about environmental pollution risks. Therefore, the present invention provides a method for preparing composite calcium ferrite from phosphogypsum and calcium-process vanadium tailings. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the solid waste resources generated by phosphogypsum in the prior art have not been effectively utilized, resulting in a waste of calcium, iron and sulfur resources and bringing about environmental pollution risks, and a method for preparing composite calcium ferrite from phosphogypsum and calcium-process vanadium tailings is proposed.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing composite calcium ferrite from phosphogypsum and calcium-process vanadium extraction tailings comprises the following steps:

[0007] Step 1: Drying the phosphogypsum and calcium vanadium extraction tailings;

[0008] Step 2: fully mix and grind the dried phosphogypsum, calcium vanadium tailings and carbonaceous reducing agent powder to obtain a mixed grinding material;

[0009] Step 3: Add water to the mixed and ground materials and press them into material balls, and then dry them under preset conditions;

[0010] Step 4: placing the dried material pellets in a reactor for calcination, during which sulfur-rich flue gas that can be used to prepare sulfuric acid is generated. After cooling, the sample obtained in the reaction container is composite calcium ferrite.

[0011] Preferably, in step 1, the drying condition is that the drying temperature is 120-150° C., the phosphogypsum is dried to hemihydrate gypsum or anhydrous gypsum, and the vanadium-extracting tailings are dried to ferric oxide monohydrate.

[0012] Preferably, in step 2, the mass ratio of vanadium-extracted tailings to phosphogypsum is 1-2.5.

[0013] Furthermore, in step 2, the reducing agent is coal powder or coke powder, and the amount of the reducing agent added is 1-8% of the total mass of the mixed material.

[0014] Furthermore, in step 2, the carbon content in the reducing agent is greater than 85%.

[0015] Furthermore, in step 2, the material is ground to a size below 200 mesh.

[0016] Preferably, the amount of water added in step 3 is 5%-10% of the mass of the mixed and ground material.

[0017] Furthermore, in step 3, the mixed and ground material is added with water and pressed into material balls with a diameter of 1-3 cm.

[0018] Furthermore, the preset conditions in step three are that the drying temperature is 80-120° C. and the drying time is 1-2 hours.

[0019] Preferably, in step 4, the calcination temperature is 1000-1300° C., the calcination time is 0.5-2 h, and the reactor is in a negative pressure state during calcination.

[0020] Compared with the prior art, the present invention provides a method for preparing composite calcium ferrite from phosphogypsum and calcium-process vanadium extraction tailings, which has the following beneficial effects:

[0021] 1. The method for preparing composite calcium ferrite by using phosphogypsum and calcium-process vanadium tailings, wherein phosphogypsum and vanadium tailings can be decomposed into calcium oxide, ferric oxide, sulfur dioxide and oxygen at high temperature, the addition of a reducing agent can lower the decomposition temperature, and the sulfur dioxide produced by the decomposition can be diffused and discharged in time by controlling the slightly negative pressure state, thereby promoting the decomposition reaction to proceed in a positive direction, and the decomposed solid-phase calcium oxide reacts with ferric oxide to form composite calcium ferrite.

[0022] 2. The method for preparing composite calcium ferrite from phosphogypsum and calcium-process vanadium tailings fully mixes and contacts the materials by ball milling and briquetting, which is beneficial to the full contact of solid-phase reactants, thereby reducing the calcination temperature and improving the conversion rate.

[0023] The parts not involved in the device are the same as the existing technology or can be implemented by using the existing technology. The present invention removes sulfur in phosphogypsum and vanadium tailings in the form of sulfur dioxide at high temperature by external carbon, and the sulfur removal rate reaches more than 95%, and calcium ferrite with an effective content of more than 50% in the composite calcium ferrite and a small amount of sulfur dioxide flue gas is obtained, so that the calcium, sulfur and iron resources in the phosphogypsum and vanadium tailings can be fully utilized and the risk of environmental pollution can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention proposes a method for preparing composite calcium ferrite by using phosphogypsum and calcium vanadium extraction tailings Figure 1 ;

[0025] Figure 2 The present invention proposes a method for preparing composite calcium ferrite by using phosphogypsum and calcium vanadium extraction tailings Figure 2 . DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0027] In addition, reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] Embodiment 1:

[0029] Reference Figure 1-Figure 2 A method for preparing composite calcium ferrite from phosphogypsum and calcium vanadium extraction tailings, comprising the following steps:

[0030] Step 1: Dry the phosphogypsum and calcium vanadium tailings at a temperature of 120-150°C to dry the phosphogypsum to hemihydrate gypsum or anhydrous gypsum, and dry the vanadium tailings to monohydrated ferric oxide;

[0031] Step 2: fully mix the dried phosphogypsum and calcium vanadium tailings with the carbonaceous reducing agent powder and grind them to a size of less than 200 meshes to obtain a mixed grinding material;

[0032] Step 3: Add water to the mixed and ground material and press it into material balls with a diameter of 1-3 cm, and dry it at a temperature of 80-120°C for 1-2 hours;

[0033] Step 4: Place the dry material pellets in a negative pressure reactor and calcine them at a temperature of 1000-1300°C for 0.5-2h. During the process, sulfur-rich flue gas that can be used to prepare sulfuric acid is generated. After cooling, the sample obtained in the reaction container is composite calcium ferrite.

[0034] In step 2, the mass ratio of vanadium-extracted tailings to phosphogypsum is 1-2.5.

[0035] In step 2, the reducing agent is coal powder or coke powder, and the amount of the reducing agent added is 1-8% of the total mass of the mixed material.

[0036] In step 2, the carbon content in the reducing agent is greater than 85%.

[0037] The amount of water added in step 3 is 5%-10% of the mass of the mixed and ground material.

[0038] In the present invention, Figure 2 As shown, the dried phosphogypsum and calcium vanadium tailings are treated with carbon-containing reducing agent powder and then put into a mixer for full mixing and grinding to obtain a mixed material. The mixed material is pressed into a ball block in a ball press with water, and then transferred to a rotary kiln for calcination. During the process, sulfur-rich flue gas that can be used to prepare sulfuric acid is generated. The material block is then transferred to a cooling kiln for cooling to obtain a composite calcium ferrite. After the prepared composite calcium ferrite is used for sintering or pelletizing, the calcium ferrite can improve the strength and reducibility of the sintered and pelletized ore. Calcium ferrite is a product of a solid phase reaction. , which has the characteristics of low melting point and fast generation speed, can be generated at a lower temperature, inhibiting the formation of fayalite, thereby improving the strength and reducibility of sintered and pelletized ores; at the same time, calcium ferrite has good reducibility, which can reduce the free CaO and calcium orthosilicate in sintered and pelletized ores, and further improve the quality of sintered and pelletized ores; the preparation of composite calcium ferrite using the above two solid wastes as the main raw materials can not only effectively alleviate the environmental hazards caused by stockpiling, but also realize its high added value utilization, thereby achieving the purpose of efficient, harmless, resource-based and high added value utilization of solid wastes.

[0039] In step 1, phosphogypsum is a by-product gypsum of phosphoric acid. The physical properties of phosphogypsum include grayish white or grayish black, an attached water content of 10-30%, a particle diameter of generally 5-50 μm, and a pH value of 1.9-5.323; its chemical composition is complex, containing residual organic phosphorus and inorganic phosphorus, fluoride and fluorine, potassium, sodium and other components, as shown in Table 1 by weight percentage, and the main component is calcium sulfate dihydrate (CaSO4·2H2O). In addition, it also contains a small amount of impurities such as phosphorus, fluorine, silicon dioxide, organic matter, etc., calcium process vanadium tailings, as shown in Table 2 by weight percentage, and other impurities. During the drying treatment, the drying temperature is 120-150° C., and the phosphogypsum is dried to semi-hydrated gypsum or anhydrous gypsum.

[0040] Table 1 Main chemical components of phosphogypsum / %

[0041] <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> CaO MgO <![CDATA[TiO2]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> <![CDATA[SO3]]> 1-4 0-1 0-1 30-32 0-1 0-1 0-1 0-1 35-44

[0042] Table 2 Composition of calcium vanadium tailings / %

[0043] TFe <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> <![CDATA[V2O5]]> MgO <![CDATA[TiO2]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> <![CDATA[SiO2]]> CaO <![CDATA[SO3]]> 20-30 35-40 1-3 1-3 1-2 3-8 0-1 0-1 2-5 5-10 10-20

[0044] Embodiment 2:

[0045] The following is a guide to Example 1, using phosphogypsum and calcium vanadium tailings used by a chemical company. Figure 2 As shown, the phosphogypsum and calcium vanadium tailings are first dried at a temperature of 150°C, and the main chemical components thereof are measured as shown in Table 3 and Table 4:

[0046] Table 3 Main components of phosphogypsum

[0047] <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> CaO MgO <![CDATA[TiO2]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> <![CDATA[SO3]]> 4.23 0.053 0.18 31.06 0.058 0.022 0.014 0.16 43.46

[0048] Table 4 Main components of calcium vanadium tailings

[0049] TFe <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> <![CDATA[V2O5]]> MgO <![CDATA[TiO2]]> <![CDATA[K2O]]> <![CDATA[Na2O]]> <![CDATA[SiO2]]> CaO <![CDATA[SO3]]> 30.15 35.89 1.98 2.44 1.02 7.85 0.15 0.37 4.85 9.97 17.81

[0050] The phosphogypsum and vanadium tailings can be decomposed into calcium oxide, ferric oxide, sulfur dioxide and oxygen at high temperature. The addition of a reducing agent can reduce the decomposition temperature. The sulfur dioxide produced by the decomposition can be diffused and discharged in time by controlling the slightly negative pressure state, so as to promote the decomposition reaction to proceed in a positive direction. The decomposed solid-phase calcium oxide reacts with ferric oxide to form a composite calcium ferrite. The materials are fully mixed and contacted by ball milling and briquetting, which is conducive to the full contact of the solid-phase reactants, thereby reducing the calcination temperature and improving the conversion rate. The external carbon can remove the sulfur in the phosphogypsum and vanadium tailings in the form of sulfur dioxide at high temperature, and the sulfur removal rate reaches more than 95%. The composite calcium ferrite is obtained with an effective content of more than 50% of calcium ferrite and a small amount of sulfur dioxide flue gas, so that the calcium, sulfur and iron resources in the phosphogypsum and vanadium tailings can be fully utilized and the risk of environmental pollution can be reduced.

[0051] The phosphogypsum in Table 1 and Table 2 is mixed with the calcium vanadium tailings and carbon powder. The mass ratio of the calcium vanadium tailings to the phosphogypsum and the amount of carbon powder added are shown in Table 5. The mixture is ball-milled in a ball mill to a particle size of less than 200 meshes.

[0052] Add water to the mixed and ground materials and press them into material balls, and dry them at 80-120℃ for 1-2h;

[0053] After drying, the mixture is placed in a reactor for calcination. The calcination temperature and calcination time conditions are shown in Table 5. During the process, sulfur-rich flue gas that can be used to prepare sulfuric acid is generated. After cooling, the sample obtained in the reaction container is composite calcium ferrite.

[0054] Table 5 Test conditions

[0055] Serial number Toner added amount / % Mass ratio of vanadium tailings to phosphogypsum Calcination temperature / ℃ Calcination time / h 1 1 1 1000 0.5 2 2 1 1100 1 3 4 2 1200 1.5 4 6 2 1250 2 5 8 2.5 1250 2

[0056] The product quality results of the composite calcium ferrite are shown in Table 6. The calcium ferrite with a calcium ferrite content greater than 50% is obtained, and the product quality meets the requirements of the standard YB / T 4266-2011.

[0057] Table 6 Product quality / %

[0058] Serial number Total Calcium Ferrite <![CDATA[Fe2O3]]> CaO <![CDATA[SiO2]]> MgO <![CDATA[Al2O3]]> S 1 51.6 51.7 39.5 2.3 0.8 1.7 0.14 2 53.8 54.9 37.6 2.4 0.7 1.5 0.12 3 55.5 58.4 33.1 2.5 0.6 1.6 0.11 4 59.5 61.6 29.7 2.2 0.7 1.4 0.09 5 65.6 74.1 18.6 2.1 0.8 1.3 0.1

[0059] The reaction principle of the present invention is as follows: phosphogypsum and calcium-process vanadium tailings can be decomposed into calcium oxide, ferric oxide, sulfur dioxide and oxygen at high temperature; the addition of a reducing agent can lower the decomposition temperature; the sulfur dioxide produced by the decomposition can be diffused and discharged in time by controlling the slightly negative pressure state, thereby promoting the decomposition reaction to proceed in a positive direction; the decomposed solid-phase calcium oxide reacts with ferric oxide to form composite calcium ferrite.

[0060] The present invention removes sulfur in phosphogypsum and calcium-based vanadium tailings in the form of sulfur dioxide at high temperature by externally adding carbon, and the sulfur removal rate reaches more than 95%, thereby obtaining calcium ferrite with an effective content of more than 50% in the composite calcium ferrite and a small amount of sulfur dioxide flue gas, so that calcium, sulfur and iron resources in the phosphogypsum and calcium-based vanadium tailings can be fully utilized as resources, and various materials are fully mixed and contacted by ball milling and ball pressing, which is beneficial to the full contact of solid-phase reactants, thereby reducing the calcination temperature and improving the conversion rate.

[0061] The above are exemplary embodiments disclosed in the present invention, but it should be noted that various changes and modifications may be made without departing from the scope disclosed in the embodiments of the present invention as defined in the claims. The functions, steps and / or actions of the method claims according to the disclosed embodiments described herein do not need to be performed in any particular order. In addition, although the elements disclosed in the embodiments of the present invention may be described or required in individual form, they may also be understood as multiple unless explicitly limited to the singular.

[0062] It should be understood that, as used herein, the singular forms "a", "an" are intended to include the plural forms as well, unless the context clearly supports an exception. It should also be understood that, as used herein, "and / or" refers to any and all possible combinations including one or more of the associated listed items.

[0063] The serial numbers of the embodiments disclosed in the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0064] A person skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples; under the concept of the embodiments of the present invention, the technical features in the above embodiments or different embodiments can also be combined, and there are many other changes in different aspects of the embodiments of the present invention as above, which are not provided in detail for the sake of simplicity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included in the protection scope of the embodiments of the present invention.

Claims

1. A method for preparing composite calcium ferrite from phosphogypsum and calcium vanadium extraction tailings, characterized in that: The steps include: Step 1: Drying the phosphogypsum and calcium vanadium extraction tailings; Step 2: fully mix and grind the dried phosphogypsum, calcium vanadium tailings and carbonaceous reducing agent powder to obtain a mixed grinding material; Step 3: Add water to the mixed and ground materials and press them into material balls, and then dry them under preset conditions; Step 4: placing the dried material pellets in a reactor for calcination, during which sulfur-rich flue gas that can be used to prepare sulfuric acid is generated. After cooling, the sample obtained in the reaction container is composite calcium ferrite.

2. The method for preparing composite calcium ferrite from phosphogypsum and calcium vanadium extraction tailings according to claim 1, characterized in that: The drying conditions in step 1 are as follows: the drying temperature is 120-150° C., the phosphogypsum is dried to hemihydrate gypsum or anhydrous gypsum, and the vanadium-extracting tailings are dried to monohydrated ferric oxide.

3. The method for preparing composite calcium ferrite from phosphogypsum and calcium vanadium extraction tailings according to claim 1, characterized in that: In step 2, the mass ratio of vanadium-extracted tailings to phosphogypsum is 1-2.

5.

4. The method for preparing composite calcium ferrite from phosphogypsum and calcium vanadium extraction tailings according to claim 1 or 3, characterized in that: In step 2, the reducing agent is coal powder or coke powder, and the amount of the reducing agent added is 1-8% of the total mass of the mixed material.

5. The method for preparing composite calcium ferrite from phosphogypsum and calcium vanadium extraction tailings according to claim 1 or 3, characterized in that: In step 2, the carbon content in the reducing agent is greater than 85%.

6. The method for preparing composite calcium ferrite from phosphogypsum and calcium vanadium extraction tailings according to claim 1 or 3, characterized in that: In step 2, the materials are ground to a size of less than 200 mesh.

7. The method for preparing composite calcium ferrite from phosphogypsum and calcium vanadium extraction tailings according to claim 1, characterized in that: The amount of water added in step 3 is 5%-10% of the mass of the mixed and ground material.

8. The method for preparing composite calcium ferrite from phosphogypsum and calcium vanadium extraction tailings according to claim 1 or 7, characterized in that: In step 3, the mixed and ground materials are added with water and pressed into material balls with a diameter of 1-3 cm.

9. The method for preparing composite calcium ferrite from phosphogypsum and calcium vanadium extraction tailings according to claim 1 or 7, characterized in that: The preset conditions in step 3 are a drying temperature of 80-120°C and a drying time of 1-2h.

10. The method for preparing composite calcium ferrite from phosphogypsum and calcium vanadium tailings according to claim 1, characterized in that: In step 4, the calcination temperature is 1000-1300° C., the calcination time is 0.5-2 h, and the reactor is in a negative pressure state during calcination.

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