A method for utilizing zinc ash polishing

Abstract

The application relates to a utilization method of polishing zinc ash, mainly comprising the following steps: firstly, screening and removing non-zinc garbage to obtain zinc ash A; then, drying and roasting the zinc ash A at a specific temperature, melting and separating zinc, crushing the remaining residue to prepare zinc ash B; finally, carrying out ammonia method positive pressure leaching of zinc at low temperature, negative pressure ammonia removal, and then preparing high-purity zinc oxide. Compared with similar applications, the process has high practicability, can be suitable for various polishing zinc ashes, has high zinc recovery rate, is low in energy consumption, does not need an oxidizing agent and extra zinc powder, and is low in cost.

Description

Technical Field

[0001] This invention relates to a method for utilizing polishing zinc ash, belonging to the field of environmental protection, specifically a method for enriching, extracting, and utilizing zinc in polishing zinc ash. Background Technology

[0002] Zinc, as a heat-resistant and decorative material, is widely used on the surfaces of various components, such as electroplating and hot-dip galvanizing. These processes generate a large amount of zinc-containing waste, such as typical hot-dip galvanizing ash and polishing zinc ash. The former, due to its huge production capacity and high added value, attracts significant research efforts and has led to a series of recycling and extraction processes, such as physical melting to prepare metallic zinc, chemical extraction to prepare zinc oxide, zinc sulfate, and electrolytic zinc. The latter, however, has relatively lower production capacity, more complex composition, and fewer related patents.

[0003] In actual production, high-content polishing zinc ash is mostly used as zinc-containing waste in rotary kilns for zinc oxide refining, which indirectly produces zinc-related products such as active zinc oxide, functional zinc oxide, zinc sulfate, and electrolytic zinc. Very little of the high-quality ash is used in hydrometallurgical zinc extraction, while low-grade ash (below 10%) is discarded due to its high impurity content, which easily affects furnace conditions and results in low leaching rates in hydrometallurgical extraction. Few manufacturers recycle it. Overall, the recycling process is characterized by high energy consumption, low efficiency, low utilization, and is uneconomical.

[0004] Ammonia extraction is a common and effective method for zinc extraction. Patent 202410428648.2 describes a preparation process for highly dispersed active zinc oxide powder. This method is innovatively applied to zinc ash, and a stator-rotor reactor is added to change the efficiency of ammonia stripping. From the perspective of chemical composition and process, it mainly focuses on the recycling of hot-dip galvanizing ash, because it does not involve the recovery and treatment of organic matter, metals, and inorganic non-metallic impurities in polishing zinc ash, nor does it involve the recovery of elemental metals.

[0005] Therefore, it is necessary to conduct research and propose a direct recycling method that can be adapted to various types of polishing zinc ash. Summary of the Invention

[0006] The present invention provides a method for utilizing polishing zinc ash, comprising the following steps: (1) Screening removes non-zinc waste to obtain zinc ash A; (2) Zinc ash A is dried and roasted at a specific temperature, then zinc is extracted by melting and precipitation, and the residue is crushed to prepare zinc ash B; (3) Zinc ash B is leached with zinc under low temperature and positive pressure by ammonia method, then deammoniated under negative pressure, and then high-purity zinc oxide is prepared.

[0007] In the aforementioned method for utilizing polishing zinc ash, step 1 preferably involves using a vibrating screen to remove non-zinc waste. In the method for utilizing polishing zinc ash, step 2: preferably, the drying temperature of zinc ash A is 40-100℃; In the method for utilizing polishing zinc ash, step 2: preferably, the calcination temperature of zinc ash A is 120-210℃; In the method for utilizing polishing zinc ash, step 2: preferably, the refining temperature for zinc extraction by melting is 450-600℃; In the method for utilizing polishing zinc ash, step 3: preferably, the leaching temperature of zinc ash B is 15-55℃. In the method for utilizing polishing zinc ash, step 3: preferably, the leaching pressure of zinc ash B is 0.1-0.5 MPa; In the aforementioned method for utilizing polishing zinc ash, step 3 preferably involves the removal of ammonia from the zinc ammonia solution using negative pressure ammonia removal, with a vacuum degree of 2000-20000 Pa.

[0008] Following the steps described above, zinc can be fully extracted from various polishing zinc ashes. Compared with existing processes, this process has the following advantages: First: This process is highly adaptable and can basically handle the polishing zinc ash from various process flows; Second: Low energy consumption, no need for high temperatures of over 1000 degrees Celsius; Third: Zinc has a high recovery rate and good economic benefits; zinc is sold directly in the form of metal and zinc oxide products. Fourth: No oxidant or additional zinc powder is required. Detailed Implementation

[0009] This invention provides a method for utilizing polishing zinc ash. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0010] The present invention will be described in detail below with reference to specific embodiments: 100 kg of polishing zinc ash was taken from a factory. After screening, 95 kg of zinc ash A remained, containing 8% Zn. Three 10 kg samples were then taken, hereinafter referred to as A1, A2, and A3. Example

[0011] Sample A1 was dried at 80℃ and normal pressure for 6 hours, leaving a residue of 8 kg; calcined at 180℃ for 4 hours, leaving a residue of 7.5 kg; then leached at 450℃ for 1 hour, yielding 148 g of crude zinc with a zinc content of 99.6%. The residue was crushed to obtain 7.32 kg of zinc ash B. Zinc ash B was leached at a liquid-to-solid ratio of 1:8, a pressure of 0.2 MPa, and a temperature of 30℃ for 6 hours. After leaching, the temperature was raised to 60℃, the pressure reduced to 5000 Pa, and ammonia was removed. The precipitated zinc salts were then filtered, dried, and calcined at 460℃, yielding 734.8 g of zinc oxide with a content of 99.5%, and a total zinc yield greater than 89%. Example

[0012] Sample A2 was dried at 80℃ under normal pressure for 4 hours, leaving a residue of 6 kg; calcined at 180℃ for 2 hours, leaving a residue of 7.5 kg; then leached at 450℃ for 1.5 hours, yielding 152 g of crude zinc with a zinc content of 99.6%. The residue was crushed to obtain 7.3 kg of zinc ash B. Zinc ash B was leached at a liquid-to-solid ratio of 1:8, a pressure of 0.2 MPa, and a temperature of 30℃ for 4 hours. After leaching, the temperature was raised to 60℃, and the pressure reduced to 5000 Pa to remove ammonia. The precipitated zinc salts were then filtered, dried, and calcined at 460℃, yielding 771 g of zinc oxide with a content of 99.5%, and a total zinc yield of over 94%. Example

[0013] Sample A3 was dried at 80℃ under normal pressure for 4 hours, leaving a residue of 6 kg; calcined at 180℃ for 1 hour, leaving a residue of 7.5 kg; then melted at 450℃ for 1.5 hours, yielding 151 g of crude zinc with a zinc content of 99.6%. The residue was crushed to obtain 7.3 kg of zinc ash B. Zinc ash B was leached at a liquid-to-solid ratio of 1:8, a pressure of 0.2 MPa, and a temperature of 30℃ for 8 hours. After leaching, the temperature was raised to 40℃, the pressure reduced to 3000 Pa, and ammonia was removed. The precipitated zinc salts were then filtered, dried, and calcined at 460℃, yielding 788 g of zinc oxide with a content of 99.5%, and a total zinc yield greater than 96%. As seen in the above implementation examples, the goal of extracting zinc products has been achieved in all cases. It should be understood that the above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Those skilled in the art can modify the technical solutions described in the above embodiments or make equivalent substitutions for some of the technical features; and all such modifications and substitutions should fall within the protection scope of the appended claims of this invention.

Claims

1. A method for utilizing polishing zinc ash includes the following steps: (1) Screening removes non-zinc waste to obtain zinc ash A; (2) Zinc ash A is dried and roasted at a specific temperature, then zinc is extracted by melting and precipitation, and the residue is crushed to prepare zinc ash B; (3) Zinc ash B is leached with zinc under low temperature and positive pressure by ammonia method, then deammoniated under negative pressure, and then high-purity zinc oxide is prepared.

2. The method for utilizing polishing zinc ash as described in claim 1, characterized in that, Step (1) The method for screening non-zinc waste is mechanical screening.

3. The method for utilizing polishing zinc ash as described in claim 1, characterized in that, In step (2), the drying temperature of zinc ash A is 40-100℃.

4. The method for utilizing polishing zinc ash as described in claim 1, characterized in that, In step (2), the roasting temperature of zinc ash A is 120-210℃.

5. The method for utilizing polishing zinc ash as described in claim 1, characterized in that, In step (2), zinc is extracted by melting and precipitation at a refining temperature of 450-600℃.

6. The method for utilizing polishing zinc ash as described in claim 1, characterized in that, In step (3), the leaching method for zinc ash B is ammonia positive pressure leaching, with a leaching temperature of 15-55℃.

7. The method for utilizing polishing zinc ash as described in claim 1, characterized in that, In step (3), the leaching method for zinc ash B is ammonia positive pressure leaching, with a leaching pressure of 0.1-0.5 MPa.

8. The method for utilizing polishing zinc ash as described in claim 1, characterized in that, In step (3), the method for removing ammonia from the zinc ammonia solution is negative pressure ammonia removal, with a removal vacuum degree of 2000-20000 Pa.