A method for preparing calcium sulfate whiskers from new liquid bottom stream filter residue of zinc smelting

Abstract

The present application relates to a kind of new liquid bottom stream filter residue of zinc smelting preparation calcium sulfate whisker method, belong to non-ferrous metal hydrometallurgy technical field, the preparation method of the present application includes six main steps such as pulping, acid leaching filtration, filter residue dissolution, calcium salt neutralization, cooling crystallization, filtration and drying, by pulping makes magnesium, manganese and other sulfate dissolution, by acid leaching makes colloidal substance dissolution, and generates calcium sulfate whisker after adding lime water;The present application not only can effectively recover zinc in new liquid bottom stream filter residue, and can prepare by-product calcium sulfate whisker, realizes the utilization of other resources while realizing the recovery of zinc, economic and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal hydrometallurgical technology, specifically, it relates to a method for preparing calcium sulfate whiskers from the bottom flow filter residue of zinc smelting liquid. Background Technology

[0002] In the hydrometallurgical zinc smelting process, the zinc sulfate solution used for electrolysis is referred to as the "new solution." Before use, the new solution is generally stored. During storage, solid phases precipitate at the bottom. Currently, filtration is commonly used to treat the underflow from the new solution storage tank. The clarified liquid obtained from filtration is sent to the zinc electrowinning process, and the underflow residue cannot be consumed. Attempts have been made to mix the new solution underflow residue with the acid leaching residue from zinc roasting ore and send it to a fuming furnace or rotary kiln to recover valuable metals. However, experiments have shown that the new solution underflow residue affects the recovery rate of valuable metals in the fuming furnace or rotary kiln. The new solution underflow residue contains a large amount of zinc. If it is directly piled up as waste, it not only pollutes the environment but also wastes zinc resources. Furthermore, this new solution underflow residue contains colloidal substances and has a high water content, making it difficult to wash clean. If piled up, the moisture will seep into the ground or be carried away by rainwater, polluting the environment. Therefore, there is an urgent need to develop an effective treatment method for the new solution underflow residue.

[0003] Based on the content of water of crystallization, calcium sulfate whiskers are classified into dihydrate, hemihydrate, and anhydrous calcium sulfate whiskers. Whiskers with different water of crystallization contents can be used in different industrial fields. Among them, dihydrate calcium sulfate whiskers are widely used in the papermaking industry. The preparation of dihydrate calcium sulfate whiskers requires high-purity calcium sulfate and has high requirements for preparation conditions. It usually needs to be reacted under high pressure, and calcium sulfate crystallization requires a certain aspect ratio. Summary of the Invention

[0004] In order to overcome the problems existing in the background technology, the present invention provides a method for preparing calcium sulfate whiskers from the bottom flow filter residue of zinc smelting liquid. This method can not only effectively recover zinc from the bottom flow filter residue, but also produce calcium sulfate whiskers as a by-product. It realizes the recovery of zinc and the utilization of other resources at the same time, which is economical and environmentally friendly.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: The method for preparing calcium sulfate whiskers from the bottom residue of zinc smelting liquid includes the following steps: (1) Pulping: Pulping the filter residue from the bottom of the new liquid.

[0006] (2) Acid leaching and filtration: Add dilute sulfuric acid to the slurry, filter, and obtain filtrate and filter residue.

[0007] (3) Dissolving the filter residue: Dissolve the filter residue from step (2) in water.

[0008] (4) Neutralization: After the filter residue has completely dissolved, add calcium oxide, calcium hydroxide or lime water to adjust the pH value to 7-9.

[0009] (5) Crystallization: Cool the solution from step (4) and age it to obtain calcium sulfate dihydrate crystals.

[0010] (6) Filtration and drying: Filtration, drying of filter cake to obtain calcium sulfate whiskers.

[0011] Furthermore, in step (2), dilute sulfuric acid is added to adjust the pH value to 0.5~2.

[0012] Furthermore, the dissolution temperature in steps (3) and (4) is 40℃~90℃.

[0013] Furthermore, the filter residue from step (2) is washed with water before being dissolved in step (3), and the wash water is returned to step (1).

[0014] Further, in step (1), water is used for slurry preparation, and the liquid-to-solid ratio of the slurry preparation is 7~10:1.

[0015] Furthermore, the zinc content in the filter residue of step (3) is less than 0.5 wt% on a dry basis.

[0016] Furthermore, in step (2), the filtrate is sent to a wet zinc smelting system to recover zinc.

[0017] The beneficial effects of this invention are: 1. The technical solution of the present invention not only realizes the recovery of zinc, but also prepares calcium sulfate dihydrate crystals, realizes the harmless treatment of the bottom flow filter residue of zinc smelting liquid, provides a new idea for the clean production of non-ferrous metal smelting, and expands the new method of bottom flow filter residue.

[0018] 2. This invention uses the bottom flow filter residue of zinc smelting liquid as raw material to prepare calcium sulfate dihydrate whiskers. After washing and acid leaching the bottom flow filter residue of zinc smelting liquid, zinc sulfate and other impurities remain in the filter residue. The residual substances increase the solubility of calcium sulfate, and the zinc sulfate and other substances play a catalytic role in the formation of calcium sulfate dihydrate whiskers. No pressure dissolution is required. Calcium sulfate dihydrate whiskers can be obtained through conventional cooling and aging. Attached Figure Description

[0019] Figure 1 This is a simplified process flow diagram of the present invention; Figure 2 This is a scanning electron microscope image of the calcium sulfate dihydrate whiskers prepared according to the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are all within the scope of protection of this invention.

[0021] The method for preparing calcium sulfate whiskers from the bottom residue of zinc smelting liquid includes the following steps: (1) Pulping: Add water to the new liquid bottom filter residue to slurry, and the liquid-solid ratio of slurry is 7~10:1.

[0022] (2) Acid leaching and filtration: Add dilute sulfuric acid to the pulping liquid to adjust the pH value to 0.5~2, filter, and obtain filtrate and filter residue.

[0023] (3) Dissolving the filter residue: Wash the filter residue from step (2) with water, return the wash water to step (1), and dissolve the washed filter residue with water at a temperature of 40℃~90℃.

[0024] (4) Neutralization: After the filter residue has completely dissolved, add lime milk to adjust the pH value to 7-9.

[0025] (5) Crystallization: Cool the solution from step (4) and age it for 3-5 hours to obtain calcium sulfate dihydrate crystals.

[0026] (6) Filtration and drying: Filtration, drying of filter cake to obtain calcium sulfate whiskers.

[0027] To illustrate the present invention more clearly, the following embodiments will be described in detail.

[0028] The main components of the new liquid bottom flow filter residue used in the following examples are as follows: Zn 28.28%; Ca 10.19%; Mg 0.73%; Mn 0.23%; SiO 20.34%. The above are the analysis results of the wet-based filter residue, and all are indicated by mass percentage. Example 1

[0029] The new liquid bottom flow filter residue is added to water at a liquid-to-solid ratio of 7:1 and stirred thoroughly. The slurrying process dissolves magnesium, manganese and other water-soluble sulfates.

[0030] Dilute sulfuric acid was added to the slurry-processed underflow filter residue to adjust the pH to 1.3 for acid leaching. Through extensive experimental research, the inventors discovered that the colloidal substance in the underflow filter residue mainly consists of basic zinc sulfate (Zn(OH)₂.ZnSO₄.5H₂O). Adding dilute sulfuric acid allows the basic zinc sulfate to dissolve in the form of zinc sulfate. Filtration yields a filter cake and filtrate. The filtrate contains 39.43 g / L of Zn. By weighing the untreated underflow filter residue and filtrate, a zinc recovery rate of 96.31% was calculated. The filtrate was then sent to a wet scrubbing system for zinc recovery.

[0031] The filter cake was washed with water, and the wash water was returned to the slurrying step. After washing, the filter cake was added to 70℃ hot water until it completely dissolved. The Zn content in the completely dissolved calcium sulfate solution was measured to be <0.01 g / L. After the filter cake was completely dissolved, the pH was adjusted to 7.8 with lime milk, and the solution was allowed to cool naturally to room temperature and aged for 4 hours. During aging, calcium sulfate dihydrate crystals were formed. The crystallized residue was filtered and dried in a forced-air oven at 60℃ for 12 hours to obtain calcium sulfate dihydrate whiskers. The scanning electron microscope image of the obtained calcium sulfate dihydrate whiskers is attached. Figure 2 The aspect ratio is 10-50.

[0032] Comparative Example 2 The new liquid bottom flow filter residue was directly added to dilute sulfuric acid to adjust the pH value to 1.3 for acid leaching, filtered, and the filtrate was found to contain 32.55 g / L of Zn. By weighing the new liquid bottom flow filter residue and filtrate before treatment, the zinc recovery rate was calculated to be 78.09%. The filtrate was sent to the hydrometallurgical zinc smelting system to recover zinc.

[0033] If the new underflow filter residue is directly leached with dilute sulfuric acid, the impurities in the new underflow filter residue cannot react fully with the acid, the impurity removal rate is reduced, and the formation of calcium sulfate whiskers is affected.

[0034] The filter cake was washed with water, and then dissolved in hot water at 70℃. The Zn content in the completely dissolved calcium sulfate solution was measured to be 0.42 g / L. After the filter cake was completely dissolved, it was naturally cooled to room temperature and aged for 4 hours. Crystals were formed during the aging process, and the resulting crystal residue was filtered. The crystal residue was dried in a forced-air drying oven at 60℃ for 12 hours, and the resulting product had an aspect ratio close to 5-15.

[0035] This comparative example shows that for the bottom flow of fresh zinc smelting liquid, pulping before acid leaching can effectively remove impurities that affect the formation of calcium sulfate whiskers. If acid leaching is performed directly, the impurities cannot be effectively removed, resulting in a decrease in the aspect ratio of calcium sulfate. Example 2

[0036] The new liquid bottom filter residue is added to water at a liquid-to-solid ratio of 10:1 and stirred thoroughly. The slurrying process dissolves water-soluble sulfates such as magnesium and manganese.

[0037] Dilute sulfuric acid was added to the slurry-processed underflow filter residue to adjust the pH to 1.1 for acid leaching treatment. After filtration, filter cake and filtrate were obtained. The filtrate contained 27.58 g / L of Zn. The zinc recovery rate was calculated to be 97.61% by weighing the underflow filter residue and filtrate before treatment. The filtrate was sent to a wet process system to recover zinc.

[0038] The filter cake was washed with water, and the wash water was returned to the slurry step. The washed filter cake was dissolved in 90℃ hot water. The Zn content in the completely dissolved calcium sulfate solution was measured to be <0.01g / L. After the filter cake was completely dissolved, calcium oxide was added to adjust the pH to 8.2. The solution was naturally cooled to room temperature and aged for 4 hours. During the aging process, calcium sulfate dihydrate crystals were formed. The crystallized residue was filtered and dried in a forced-air drying oven at 60℃ for 12 hours to obtain calcium sulfate dihydrate whiskers. The obtained calcium sulfate dihydrate whiskers had an aspect ratio of 10-50.

[0039] Example 3 (The effect of pH change in acid leaching on the preparation results) The new liquid bottom flow filter residue is added to water at a liquid-to-solid ratio of 8:1 and stirred thoroughly. Through slurrying, sulfates such as magnesium and manganese, which are easily soluble in water, are dissolved.

[0040] Dilute sulfuric acid was added to the filter residue of the new liquid bottom after slurrying to adjust the pH to 1-3 for acid leaching treatment. After filtration, filter cake and filtrate were obtained. After the filter cake was completely dissolved in 90℃ hot water, it was naturally cooled and aged to obtain crystals. The aspect ratio of the crystals was analyzed, and the zinc content, zinc recovery rate and crystals of the filtrate under different acid leaching pH values ​​are shown in the table below.

[0041]

[0042] The pH value of acid leaching affects the removal of impurities and the dissolution of zinc, and ultimately affects the purity of calcium sulfate dihydrate whiskers, resulting in calcium sulfate dihydrate being unqualified or unable to form whiskers.

[0043] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing calcium sulfate whiskers from the bottom residue of a fresh zinc smelting liquid, characterized in that, Includes the following steps: (1) Pulping: Pulping the filter residue from the new liquid bottom flow; (2) Acid leaching and filtration: Add dilute sulfuric acid to the pulping liquid to adjust the pH value to 0.5-2 for acid leaching. After acid leaching, filter to obtain filtrate and filter residue. (3) Dissolving the filter residue: Dissolve the filter residue from step (2) in water; (4) Neutralization: After the filter residue has completely dissolved, add calcium oxide, calcium hydroxide or lime water to adjust the pH value to 7-9; (5) Crystallization: The solution from step (4) is cooled and aged to obtain calcium sulfate dihydrate crystals; (6) Filtration and drying: Filtration, drying of filter cake to obtain calcium sulfate whiskers.

2. The method for preparing calcium sulfate whiskers from the bottom flow filter residue of zinc smelting liquid according to claim 1, characterized in that, The dissolution temperature for steps (3) and (4) is 40℃-90℃.

3. The method for preparing calcium sulfate whiskers from the bottom flow filter residue of zinc smelting liquid according to claim 1, characterized in that, The filter residue from step (2) is washed with water and then dissolved in step (3), and the wash water is returned to step (1).

4. The method for preparing calcium sulfate whiskers from the bottom flow filter residue of zinc smelting liquid according to claim 1 or 3, characterized in that, Step (1) Use water to slurry the mixture, with a liquid-to-solid ratio of 7-10:

1.

5. The method for preparing calcium sulfate whiskers from the bottom flow filter residue of zinc smelting liquid according to claim 1, characterized in that, The zinc content in the filter residue of step (3) is less than 0.5 wt% on a dry basis.

6. The method for preparing calcium sulfate whiskers from the bottom flow filter residue of zinc smelting liquid according to claim 1, characterized in that, The filtrate from step (6) is returned to step (3).

7. The method for preparing calcium sulfate whiskers from the bottom flow filter residue of zinc smelting liquid according to claim 1, characterized in that, Zinc is recovered by sending the filtrate of step (2) to a wet zinc smelting system.

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