A method for the continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag.

Abstract

This invention discloses a method for the continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag, comprising the following steps: S1, adding water-quenched slag to a reaction apparatus; S2, adding EDTA and water to the reaction apparatus, stirring, and allowing it to stand to obtain a trace element-rich EDTA chelated iron solution and wet slag; S3, retaining the wet slag in the reaction apparatus; removing the EDTA chelated iron solution and drying it to obtain EDTA chelated iron powder; S4, adding water to the reaction apparatus, adding concentrated sulfuric acid while maintaining stirring, reacting fully, and allowing the solution to separate into layers within the reaction apparatus; S5, removing the upper slag layer after solution separation, drying it to obtain porous semi-coke; removing the middle solution layer after solution separation, and drying it to obtain ferrous sulfate. This invention, through continuous production, can prepare trace element-rich EDTA chelated iron fertilizer and efficiently improve the iron recovery rate from water-quenched slag.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment technology, and in particular to a method for the continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag. Background Technology

[0002] Under current technological conditions, the utilization of mineral resources by humans inevitably generates a large amount of waste, such as water-quenched slag. Improper handling of water-quenched slag can cause significant harm to the natural ecosystem and human society: 1. Large-scale dumping of water-quenched slag occupies arable land and covers vegetation, preventing the effective use of land resources; 2. It severely damages the ecological environment surrounding mining areas, affecting the living environment of residents. Leakage from some water-quenched slag ponds can have a serious impact on surrounding villages and farmers; 3. It is highly likely to trigger geological disasters. Water-quenched slag piles in spoil heaps often have steep slopes at their leading edges, which are highly susceptible to slope instability during heavy rains, leading to landslides, collapses, and other geological disasters, and providing material for debris flows. Along major rivers, much water-quenched slag either has heavy metal content exceeding leaching toxicity standards or contains hazardous components with acute toxicity. Some water-quenched slag ponds lacking proper treatment are like time bombs; once they encounter geological disasters such as flash floods, the hidden dangers could lead to accidents.

[0003] Resource utilization of water-quenched slag is an important way to solve the above problems. Currently, water-quenched slag is mainly used in building materials and agricultural production, but both have many problems. Water-quenched slag often contains a lot of free calcium oxide and magnesium oxide, making it unstable in volume and unsuitable as cement, building materials, and engineering backfill materials. Furthermore, water-quenched slag is not easy to grind, and direct use in cement production will reduce production capacity, and the fineness of cement is difficult to guarantee, affecting cement quality. When water-quenched slag is used directly as agricultural fertilizer and soil conditioner, it mainly relies on some of its effective components, such as MgO, CaO, and SiO2, resulting in low fertilizer efficiency and a limited range of applications.

[0004] In summary, the development and utilization of water-quenched slag is of great significance for environmental protection and energy conservation; however, the resource utilization of water-quenched slag is still in the preliminary research stage. Therefore, there is an urgent need for a treatment method that can effectively handle water-quenched slag in metallurgy and mining. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention provides a method for the continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag.

[0006] The technical solution of this invention is as follows: A method for continuously preparing chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag includes the following steps: S1, add water-quenched slag to the reaction apparatus; S2, EDTA and water are added to the reaction apparatus, stirred and allowed to stand to obtain a trace element-rich EDTA chelated iron solution and wet residue. S3, the wet residue is retained in the reaction apparatus; the EDTA chelated iron solution is taken out and dried to obtain EDTA chelated iron powder. S4, add water to the reaction apparatus, add concentrated sulfuric acid while maintaining stirring, and let it stand until the solution in the reaction apparatus completes the separation of layers after the reaction is fully completed; S5, after the solution is separated into layers, the upper scum layer is removed and dried to obtain porous semi-coke; the middle solution layer after the solution is separated is removed and dried to obtain ferrous sulfate.

[0007] Furthermore, the water-quenched slag is ground to a mesh size of 60.

[0008] Furthermore, the EDTA-chelated iron powder also contains nitrogen (N) element.

[0009] Furthermore, the EDTA chelated iron powder also contains C, Na, O, N, Al, Si, and S elements.

[0010] Furthermore, in steps S1 and S2, the addition ratio of the water-quenched slag, EDTA, and water is: 1kg:0.3~0.5kg:25~40L.

[0011] Furthermore, in steps S1 and S2, the addition ratio of the water-quenched slag, EDTA, and water is 100g: 20g: 2L; the reaction conditions are ultrasonic stirring at 500 r / min for 10 min.

[0012] Furthermore, in steps S4 and S5, the ratio of the wet residue to concentrated sulfuric acid is 50g:35ml.

[0013] Furthermore, in steps S4 and S5, the reaction conditions are: stirring speed of 600 r / min; stirring temperature of 120℃; stirring time ≥ 4H; and concentrated sulfuric acid dropping rate of 2.5 ml / min based on 100 g of wet residue.

[0014] Furthermore, the EDTA chelated iron solution is dried at 60°C to obtain EDTA chelated iron fertilizer powder; the scum layer is dried at 60°C to obtain porous semi-coke; the middle solution layer is evaporated and concentrated to saturation at 70°C, then cooled and crystallized at 4°C, and centrifuged to obtain ferrous sulfate heptahydrate crystals, which are then dried at 60°C to obtain ferrous sulfate product.

[0015] Furthermore, this method also includes the following steps: Elemental analysis revealed that zinc-smelting water-quenched slag rich in Fe and C was selected; the Fe and C content was defined as follows: Fe content ≥ 10 w.t.%; C content ≥ 3 w.t.%.

[0016] The beneficial effects of this invention are as follows: 1. The EDTA chelated iron fertilizer prepared by the method of this invention, in addition to having the basic characteristic of being easily soluble in water, is also rich in elements, as well as trace elements such as N, Al, Si, S, Na, and O. When used as fertilizer for crops, it can not only supplement iron but also nitrogen, and the other trace elements also have a certain promoting effect on plant growth.

[0017] 2. In the method described in this invention, after preparing EDAT chelated iron fertilizer and removing the EDTA iron solution, the EDTA solution will partially remain in the wet slag. In the subsequent preparation of ferrous sulfate, EDTA can act as a catalyst to promote the reaction between the wet slag and sulfuric acid, efficiently prepare ferrous sulfate, and improve the iron recovery rate in the water-quenched slag.

[0018] 3. The method described in this invention enables continuous and large-scale processing of zinc smelting quenching slag, thereby reducing frequent material transfers during the operation, reducing the workload of personnel, and achieving the goal of increasing production and efficiency. Attached Figure Description

[0019] Figure 1 : A schematic diagram of the workflow of the method of the present invention; Figure 2 Schematic diagram of EDS spectrum of zinc smelting water-quenched slag; Figure 3 Schematic diagram of XRD pattern of zinc smelting water-quenched slag; Figure 4 : Schematic diagram of SEM image of the prepared EDTA chelated iron fertilizer; Figure 5 Schematic diagram of the EDS spectrum of the prepared EDTA chelated iron fertilizer; Figure 6 : Schematic diagram of SEM image of the prepared porous semi-coke; Figure 7 Schematic diagram of the EDS spectrum of the prepared porous semi-coke; Figure 8 Schematic diagram of the EDS spectrum of the prepared ferrous sulfate. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and by way of embodiments.

[0021] This invention discloses a method for the continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag. The method includes the following steps: S1, zinc slag quenched in water is ground and then added to the reaction vessel.

[0022] Grinding can increase the specific surface area of ​​zinc smelting slag, which is beneficial for continuous production operations. Preferably, the zinc smelting slag should be ground to at least 60 mesh.

[0023] S2, Preparation of EDTA-chelated iron fertilizer rich in trace elements, including the following steps: S21. Add the set amount of EDTA and water to the reactor, stir and let stand to obtain a trace element-rich EDTA chelated iron fertilizer solution and wet residue.

[0024] S22, the wet residue is retained in the reactor; the trace element-rich EDTA chelated iron solution in the reactor is taken out and dried at 60℃ to obtain trace element-rich EDTA chelated iron fertilizer powder.

[0025] EDS spectrum analysis of EDTA-chelated iron fertilizer rich in trace elements is shown in the attached figure. Figure 4 It is known that this chelated iron fertilizer, in addition to Fe, is also rich in elements such as C, Na, O, N, Al, Si, and S, with Fe accounting for approximately 20%. The EDTA chelated iron fertilizer prepared in this step has a high iron content and is also rich in trace elements such as N. When used as fertilizer for crops, it can not only supplement iron but also nitrogen, and the other trace elements also have excellent promoting effects on plant growth.

[0026] S3, Preparation of porous semi-coke and ferrous sulfate solution, including the following steps: S31, add a set amount of water to the reactor containing wet slag, and stir thoroughly to form a wet slag suspension or wet slag slurry; S32, while maintaining stirring, add concentrated sulfuric acid dropwise to the wet sludge suspension or wet sludge slurry as required; S33, continue stirring for ≥4 hours, then let stand and cool to room temperature. A scum layer, a solution layer, and a precipitate layer will form inside the reactor. The scum layer is the porous semi-coke layer, and the solution layer is the ferrous sulfate solution layer.

[0027] S34. The porous semi-coke from the scum layer is removed, washed with water, and dried at 60°C to obtain the porous semi-coke product. This porous semi-coke product can be further processed by crushing, grinding, or purification, depending on its intended use.

[0028] S35, take out the ferrous sulfate solution and evaporate and concentrate the solution to saturation at 70℃; Then, the crystals were cooled and crystallized at 4°C, and centrifuged to obtain ferrous sulfate heptahydrate crystals. Dry it at 60°C to obtain ferrous sulfate product.

[0029] Appendix Figure 7The figure shows the EDS spectrum of ferrous sulfate. As can be seen from the figure, the main elements contained in the prepared ferrous sulfate are Fe, O, S, C and Si, and the ferrous sulfate product was successfully prepared.

[0030] In the above steps: I. In step S3, The principle of preparing porous semi-coke is briefly described below: After being crushed to a certain mesh size, zinc slag quenched in water takes the form of granules or granules. Since metallic elements exist in zinc smelting quenching slag in the form of elements, oxides or compounds, this form of existence will cause them to be partially or completely eliminated or peeled off from the quenching slag after the continuous reaction of EDTA and sulfuric acid, thus making the quenching slag porous. Because the zinc slag has a small particle size, some of the slag particles are mainly composed of elemental carbon. These slag particles float on the surface of the solution after forming a porous structure, forming a slag layer, i.e., a porous semi-coke layer.

[0031] II. In step S2, 1. As a preferred option: a. Mass of zinc smelting water-quenched slag: Mass of EDTA: Volume of water = 1kg: 0.3~0.5kg: 25~40L; b. Ultrasonic stirring is used inside the reactor, with the stirring speed set to 500 r / min; c. Stirring time ≥ 10 min.

[0032] 2. Further: To obtain EDTA-chelated iron fertilizer with uniform particle size and rich in trace elements, the ratio of the mass of zinc smelting slag, the mass of EDTA, and the volume of water, as well as the stirring speed, can be further adjusted. This adjustment can be different from the above-mentioned preferred ratio of the mass of zinc smelting slag, the mass of EDTA, and the volume of water.

[0033] By analyzing the SEM images of the EDTA chelated iron powder obtained from each comparative experiment, the optimal experimental data for obtaining EDTA chelated iron powder with relatively uniform size and an average particle size of about 6 μm were determined.

[0034] The comparative experiment can be set up as follows: Experiment 1: a. Take 100g of zinc smelting water quenching slag, crush it and sieve it to 60 mesh, and put it into the experimental reaction vessel; b. Add 20g EDTA and 2L water; c. Stir with ultrasound at 500 r / min for 10 min; d. Take out the EDTA chelated iron solution and dry it at 60°C to obtain EDTA chelated iron powder; e. Determine the particle size distribution of EDTA-chelated iron based on the SEM image of the EDTA-chelated iron powder.

[0035] Experiment 2: a. Take 200g of zinc smelting water quenching slag, crush it and sieve it to 60 mesh, and put it into the experimental reaction vessel; b. Add 20g EDTA and 2L water; c. Stir ultrasonically at 650 r / min for 10 min; d. Take out the EDTA chelated iron solution and dry it at 60°C to obtain EDTA chelated iron powder; e. Determine the particle size distribution of EDTA-chelated iron based on the SEM image of the EDTA-chelated iron powder.

[0036] Experiment 3: a. Take 150g of zinc smelting water quenching slag, crush it and sieve it to 60 mesh, and put it into the experimental reaction vessel; b. Add 20g EDTA and 2L water; c. Stir ultrasonically at 600 r / min for 10 min; d. Take out the EDTA chelated iron solution and dry it at 60°C to obtain EDTA chelated iron powder; e. Determine the particle size distribution of EDTA-chelated iron based on the SEM image of the EDTA-chelated iron powder.

[0037] In summary, based on the SEM chart analysis, the data from Experiment 1 were scaled up or down proportionally to guide continuous production operations.

[0038] III. In step S3, To ensure that the porous semi-coke product has a uniform, loose, porous structure and that the carbon content meets the standard requirements (e.g., the mass fraction of carbon in the porous semi-coke is ≥75%), the following comparative experiments can be conducted to set the ratio of wet slag mass to concentrated sulfuric acid volume, the concentrated sulfuric acid addition rate, the stirring speed in the reactor, and the reaction temperature, as detailed below: Experiment 1: a. Take 50g of wet residue and put it into the experimental reaction vessel; b. Add 100ml of water and stir at 500 r / min to form a slurry; c. While maintaining a stirring speed of 500 r / min, add 50 mL of concentrated sulfuric acid (98 w.t.%) to the reactor at a dropping rate of 3 mL / min; d. Stir at 500 r / min at 100℃ for ≥4 hours; e. Dry at 60℃ to obtain porous semi-coke product; f. Determine the microstructure of porous semi-coke based on the SEM image; Determine the mass fraction of carbon in porous semi-coke based on its EDS diagram.

[0039] Experiment 2: a. Take 50g of wet residue and put it into the experimental reaction vessel; b. Add 100ml of water and stir at 600 r / min to form a slurry; c. While maintaining a stirring speed of 600 r / min, add 35 mL of concentrated sulfuric acid (98 w.t.%) to the reactor at a dropping rate of 2.5 mL / min; d. Stir at 120℃ for ≥4 hours at a stirring speed of 600 r / min; e. Dry at 60℃ to obtain porous semi-coke product; f. Determine the microstructure of porous semi-coke based on the SEM image; Determine the mass fraction of carbon in porous semi-coke based on its EDS diagram.

[0040] Experiment 3: a. Take 50g of wet residue and put it into the experimental reaction vessel; b. Add 100ml of water and stir at 400 r / min to form a slurry; c. While maintaining a stirring speed of 400 r / min, add 45 mL of concentrated sulfuric acid (98 w.t.%) to the reactor at a dropping rate of 3 mL / min; d. Stir at 400 r / min at 130℃ for ≥4 hours; e. Dry at 60℃ to obtain porous semi-coke product; f. Determine the microstructure of porous semi-coke based on the SEM image; Determine the mass fraction of carbon in porous semi-coke based on its EDS diagram.

[0041] Experiment 4: a. Take 50g of wet residue and put it into the experimental reaction vessel; b. Add 100ml of water and stir at 500 r / min to form a slurry; c. While maintaining a stirring speed of 500 r / min, add 65 mL of concentrated sulfuric acid (98 w.t.%) to the reactor at a dropping rate of 4 mL / min; d. Stir at 500 r / min at 140℃ for ≥4 hours; e. Dry at 60℃ to obtain porous semi-coke product; f. Determine the microstructure of porous semi-coke based on the SEM image; Determine the mass fraction of carbon in porous semi-coke based on its EDS diagram.

[0042] In summary, based on the SEM and EDS images of porous semi-coke, the data from Experiment 2 were scaled up or down proportionally to guide continuous production operations.

[0043] In this embodiment, preferably, the following steps are also included: S0, through elemental composition analysis, was selected as zinc smelting water quenching slag rich in Fe and C elements.

[0044] The richness of Fe and C elements mentioned in this step refers to an Fe element content of ≥10 w.t.% and a C element content of ≥3 w.t.%.

[0045] For zinc slag with Fe and / or C content lower than the standard, it is treated by other solid waste treatment methods, such as for use in building material production and cement production.

[0046] EDS (Electro-Derivatives Spectroscopy) is the preferred method for elemental analysis of zinc smelting quenched slag.

[0047] Appendix Figure 1 The EDS spectrum of zinc quenching slag from Xinjiang Zijin Nonferrous Metals Co., Ltd. is shown. From the spectrum, it can be seen that the zinc quenching slag of the company includes elements such as O, Fe, S, C, Si, Al, Cl, Zn, and Pb, which can be used as raw materials for the method of the present invention.

[0048] Furthermore, as a further preferred method, the content of Fe and C elements in the zinc slag can be determined by performing crystal form analysis on the zinc slag, with XRD pattern analysis being the preferred method.

[0049] Appendix Figure 2 The XRD pattern of zinc quenching slag from Xinjiang Zijin Nonferrous Metals Co., Ltd. is shown. From the pattern, it can be determined that the main crystalline component of the quenching slag is Fe3O4 (JPCDS card number: 89-0950). In addition, it also contains amorphous carbon, i.e., a broad diffraction peak at about 2θ=25°, as well as SiO2, etc.

[0050] Because zinc ore raw materials vary geographically, with different components in different regions, this method can accurately and quickly determine the components in zinc slag quenching, thus allowing for the selection of a more economical zinc slag treatment method.

[0051] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for the continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag, characterized in that, Includes the following steps: S0, through elemental analysis, zinc smelting water-quenched slag rich in Fe and C was selected; the Fe and C content is ≥10 w.t.% and C content ≥3 w.t.%. S1, add water-quenched slag to the reaction apparatus; S2, EDTA and water are added to the reaction apparatus, stirred and allowed to stand to obtain a trace element-rich EDTA chelated iron solution and wet residue. S3, the wet residue is retained in the reaction apparatus; the EDTA chelated iron solution is taken out and dried to obtain EDTA chelated iron powder. S4, add water to the reaction apparatus, add concentrated sulfuric acid while maintaining stirring, and let it stand until the solution in the reaction apparatus completes the separation of layers after the reaction is fully completed; S5, after the solution is separated into layers, the upper scum layer is removed and dried to obtain porous semi-coke; the middle solution layer after the solution is separated is removed and dried to obtain ferrous sulfate.

2. The method for continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag according to claim 1, characterized in that, The water-quenched slag is ground to 60 mesh before being added to the reaction device.

3. The method for continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag according to claim 2, characterized in that, The EDTA-chelated iron powder also contains nitrogen (N).

4. The method for continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag according to claim 2, characterized in that, The EDTA-chelated iron powder also contains C, Na, O, N, Al, Si, and S elements.

5. The method for continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag according to claim 2, characterized in that, In steps S1 and S2, the addition ratio of water-quenched slag, EDTA and water is 1kg:0.3~0.5kg:25~40L.

6. The method for continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag according to claim 2, characterized in that, In steps S1 and S2, the addition ratio of water-quenched slag, EDTA, and water is 100g:20g:2L; the reaction conditions are ultrasonic stirring at 500 r / min for 10 min.

7. The method for continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag according to claim 2, characterized in that, In step S4, the ratio of wet residue to concentrated sulfuric acid is 50g:35ml.

8. The method for continuous preparation of chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag according to claim 7, characterized in that, In step S4, the reaction conditions are as follows: stirring speed is 600 r / min; stirring temperature is 120℃; stirring time is ≥4h; and concentrated sulfuric acid is added at a rate of 2.5 ml / min per 100g wet residue.

9. A method for continuously preparing chelated iron fertilizer, ferrous sulfate, and semi-coke from zinc smelting water-quenched slag according to any one of claims 2 to 8, characterized in that, The EDTA chelated iron solution was dried at 60°C to obtain EDTA chelated iron fertilizer powder. The slag layer is dried at 60°C to obtain porous semi-coke; The middle solution layer is evaporated and concentrated to saturation at 70°C, then cooled and crystallized at 4°C. The resulting ferrous sulfate heptahydrate crystals are obtained by centrifugation and dried at 60°C to obtain the ferrous sulfate product.

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