Method for rapidly producing zinc oxide through microwave heating

Abstract

The invention relates to the technical field of zinc oxide preparation, and discloses a method for rapidly producing zinc oxide through microwave heating, which comprises the following steps: pretreating zinc-containing metallurgical waste slag, and crushing the zinc-containing metallurgical waste slag until the particle size is less than 50 microns; placing the crushed metallurgical waste residues in a microwave reactor, and adding a proper amount of fluxing agent to promote volatilization of zinc; heating is conducted within the microwave power range of 500 W to 2500 W, the temperature is controlled to range from 600 DEG C to 1100 DEG C, and zinc elements in the metallurgical waste residues are evaporated to form zinc steam; keeping the oxygen concentration not lower than 20% in the reactor, and ensuring that the zinc steam fully reacts with oxygen to generate zinc oxide; and cooling the zinc oxide steam generated by the reaction step by step by using a multi-stage condensation system. Rapid and uniform heating is realized through a microwave heating technology, the reaction time can be remarkably shortened, and the volatilization temperature of zinc is effectively reduced, so that the energy consumption is reduced, and the generation efficiency of zinc oxide is improved.

Description

Technical Field

[0001] The invention relates to the technical field of zinc oxide preparation, in particular to a method for rapidly producing zinc oxide by microwave heating. Background Art

[0002] Zinc oxide is a functional material with a wide range of applications. It is widely used in electronic devices, photocatalysts, optoelectronic materials, rubber additives, cosmetics and other fields. Traditional methods for producing zinc oxide mainly include direct method, indirect method and hydrometallurgical method. Although these methods are relatively mature, there are still many technical deficiencies and limitations in practical applications, which are mainly manifested in the following aspects:

[0003] Existing zinc oxide production technologies usually rely on methods such as resistance furnaces or flame heating. These heating methods have problems such as low heat conduction efficiency and uneven heating, resulting in low zinc volatilization efficiency, long reaction time, and high energy consumption. At the same time, since heat energy is mainly transferred to the inside of the material from the outside, the temperature inside the material is difficult to control, which can easily lead to local overheating or underheating, reducing production efficiency.

[0004] In the traditional zinc oxide production method, the generated zinc oxide particles often have a wide particle size distribution, and it is difficult to obtain fine and uniform zinc oxide particles. Especially for the production of nano-scale zinc oxide, the existing process is prone to particle agglomeration or overgrowth, resulting in a limited application range of the final product, making it difficult to meet the strict requirements for zinc oxide particles in high-precision fields such as electronics and optics.

[0005] The existing technology is easily affected by material impurities during the production process, resulting in low purity of the generated zinc oxide, especially when extracting zinc from waste slag, the impurity content in the waste slag is high, and the process of removing impurities is complicated and the effect is limited. Therefore, the generated zinc oxide often needs to be further purified, which increases the process cost and affects the stability and applicability of the product quality.

[0006] The existing zinc oxide production process is usually relatively fixed, and it is difficult to customize the performance of the product according to the needs of different application fields. For example, some applications require zinc oxide products with specific optical or electrical properties, but traditional methods are difficult to achieve product performance improvements through simple process improvements, especially when doping or modification is required, the process is difficult and the cost is high.

[0007] To this end, those skilled in the art provide a method for rapidly producing zinc oxide by microwave heating to solve the problems raised in the above background technology. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention provides a method for quickly producing zinc oxide by microwave heating, which solves the problems of low efficiency of traditional heating methods, uneven distribution of zinc oxide particle size, high impurity content, insufficient process flexibility, and difficulty in meeting diversified needs in the prior art.

[0009] To achieve the above object, the present invention is implemented by the following technical scheme: A method for rapidly producing zinc oxide by microwave heating, comprising the following steps:

[0010] Pre-treating the zinc-containing metallurgical waste slag and crushing it to a particle size of less than 50 μm;

[0011] The crushed metallurgical waste slag is placed in a microwave reactor and a proper amount of flux is added to promote the volatilization of zinc;

[0012] Heating is performed within a microwave power range of 500W-2500W, and the temperature is controlled between 600°C-1100°C, so that the zinc element in the metallurgical waste slag evaporates to form zinc vapor;

[0013] Maintaining an oxygen concentration of not less than 20% in the reactor to ensure that zinc vapor fully reacts with oxygen to generate zinc oxide;

[0014] The zinc oxide vapor generated by the reaction is cooled step by step using a multi-stage condensation system to condense it into zinc oxide particles of different particle sizes;

[0015] The generated zinc oxide particles are graded and screened, and collected according to different particle size distributions;

[0016] The collected zinc oxide particles are purified to remove impurities.

[0017] Preferably, the flux is one or more of calcium oxide, boric acid or calcium fluoride.

[0018] Preferably, the pulverizing step of the metallurgical waste slag is carried out by wet grinding, and after pulverizing, a slurry with a particle size of less than 30 μm is formed.

[0019] Preferably, the microwave heating time is 10 min-60 min.

[0020] Preferably, the multi-stage condensation system comprises at least two stages of condensers with different temperatures, the temperature of the first condenser is 300°C-500°C, and the temperature of the second condenser is 100°C-200°C.

[0021] Preferably, the oxygen concentration is adjusted in real time by a gas flow control system in the reactor.

[0022] Preferably, the grading and screening step is performed by a multi-stage screening device, and the screening particle size range is 10nm-1μm.

[0023] Preferably, the purification treatment includes pickling and heat treatment steps, wherein the pickling is used to remove residual metal impurities and the heat treatment is used to improve the crystallinity of zinc oxide.

[0024] Preferably, a temperature sensor and a gas monitoring device are provided in the microwave reactor for real-time monitoring of the reaction temperature and reaction atmosphere composition.

[0025] Preferably, the zinc oxide particles may be further doped after being collected, and the doped elements include aluminum, magnesium, silver or titanium to improve their electrical, optical or catalytic properties.

[0026] The present invention provides a method for rapidly producing zinc oxide by microwave heating. It has the following beneficial effects:

[0027] 1. The present invention realizes rapid and uniform heating through microwave heating technology, which can significantly shorten the reaction time. By reasonably selecting flux (such as calcium oxide, boric acid, calcium fluoride) and optimizing microwave power, temperature and other parameters, the present invention effectively reduces the volatilization temperature of zinc, thereby reducing energy consumption and improving the generation efficiency of zinc oxide.

[0028] 2. The present invention adopts a multi-stage condensation system and a graded screening device, which can accurately control the particle size range of zinc oxide particles, from nanometers to micrometers. Through different condensation and screening steps, zinc oxide particles that meet the application requirements of electronics, optics, catalysis and other fields can be generated, and the product has uniform particle size distribution and stable quality.

[0029] 3. The present invention uses flux and multiple purification treatments (pickling and heat treatment) in the production process to effectively remove impurities and ensure the high purity of zinc oxide. In addition, by doping elements such as aluminum and magnesium, the performance of zinc oxide in optical, electrical and other properties can be further improved, increasing the application flexibility of the process and meeting the needs of high-performance products. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the steps of the present invention. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Embodiment 1: The zinc oxide production method based on calcium oxide flux

[0033] step:

[0034] The zinc-containing metallurgical waste slag is crushed and the particle size is controlled below 50μm.

[0035] Add 2% calcium oxide (CaO) as flux and mix well.

[0036] The mixed materials were placed in a microwave reactor, and the microwave power was set to 1500 W and the reaction temperature to 900° C.

[0037] The oxygen concentration in the reactor is maintained at 25%, and the zinc vapor fully reacts with the oxygen to generate zinc oxide vapor.

[0038] The temperature is gradually lowered through a multi-stage condensation system, with the first condenser temperature being 400°C and the second condenser temperature being 150°C, to condense the generated zinc oxide particles.

[0039] The condensed zinc oxide particles are screened, the screened particle size is controlled at 50nm-500nm, and zinc oxide particles of different particle sizes are collected.

[0040] The zinc oxide is pickled using dilute acid to remove impurities and heat treated at 120°C to improve crystallinity.

[0041] Summary: In this embodiment, the use of calcium oxide as a flux can effectively promote the volatilization of zinc elements and reduce the temperature required for the reaction. At the same time, the multi-stage condensation system achieves precise control of the particle size. The zinc oxide particles after screening have high purity and good particle size distribution. Calcium oxide flux not only has cost advantages, but also improves reaction efficiency and is suitable for large-scale production.

[0042] Example 2: Method for producing zinc oxide using boric acid flux

[0043] step:

[0044] The metallurgical waste slag is wet ground to control the particle size below 30μm to make a slurry.

[0045] Add 1.5% boric acid (H3BO3) as flux and mix well.

[0046] The slurry was placed in a microwave reactor, the microwave power was set to 2000 W, and the temperature was controlled at 800°C.

[0047] The oxygen concentration is maintained at 30%, and the evaporated zinc vapor reacts with oxygen to form zinc oxide.

[0048] Cooling is performed by a multi-stage condensation system, with the first condenser temperature being 450°C and the second condenser temperature being 120°C.

[0049] After grading and screening, zinc oxide particles with different particle size distributions are obtained, and the screening range is 10nm to 500nm.

[0050] Acid pickling and heat treatment are performed. Acid pickling is used to remove metal impurities, and the heat treatment temperature is set at 150°C.

[0051] Summary: This embodiment uses boric acid as a flux to further reduce the reaction temperature, making the volatilization and oxidation process of zinc more efficient. The role of boric acid is not only to accelerate volatilization, but also to optimize the uniformity of particles. Compared with calcium oxide, boric acid is more effective in the generation of small-particle zinc oxide and is suitable for applications requiring high precision, such as electronic materials and optical devices.

[0052] Example 3: Calcium fluoride flux and wet grinding method

[0053] step:

[0054] The metallurgical waste slag was crushed to less than 50 μm and 3% calcium fluoride (CaF2) was added as flux.

[0055] The mixed waste residue was placed in a microwave reactor, the power was set to 2500 W, and the temperature was maintained at 1000 °C.

[0056] The oxygen concentration is maintained at 20% to ensure that the zinc vapor reacts fully with oxygen to form zinc oxide.

[0057] A multi-stage condensation system was used, with the first condenser temperature set at 500 °C and the second condenser at 200 °C.

[0058] The condensed zinc oxide particles are screened in a size range of 10 nm to 1 μm.

[0059] The zinc oxide particles were purified by using hydrochloric acid in the pickling step and heat-treated at 160°C.

[0060] Summary: The use of calcium fluoride flux improves the stability of the reaction process and maintains high zinc volatilization efficiency under high temperature conditions. This example demonstrates the advantages of calcium fluoride in promoting high temperature reactions, which is particularly suitable for production environments with high requirements for material stability at high temperatures. The particle size is optimized through wet grinding, which improves the distribution control of zinc oxide particles and product quality.

[0061] Example 4: Zinc oxide production without flux method

[0062] step:

[0063] The zinc-containing metallurgical waste slag is crushed to a particle size of less than 50 μm.

[0064] The crushed waste residue is directly placed in a microwave reactor without adding any flux.

[0065] The microwave heating power was set to 1500 W and the reaction temperature was set to 900 °C.

[0066] The oxygen concentration was maintained at 22% so that the evaporated zinc fully reacted with oxygen to form zinc oxide.

[0067] The cooling temperatures of the multi-stage condensation system are 300°C and 150°C respectively, and zinc oxide particles are condensed.

[0068] The zinc oxide particles were screened and collected with a particle size range of 10 nm to 1 μm.

[0069] Acid washing and heat treatment were performed to improve crystallinity, and the heat treatment temperature was set at 120°C.

[0070] Summary: This example demonstrates a more traditional microwave heating process without a flux. Although this method can effectively generate zinc oxide, the reaction temperature and time requirements are high, and the particle size distribution is relatively wide. This method is suitable for applications with lower requirements for zinc oxide purity and particle size, but the efficiency and effect are not as good as the process containing a flux.

[0071] Embodiment 5: Production method of zinc oxide with doping treatment

[0072] step:

[0073] The metallurgical waste slag is crushed to less than 50 μm and 2% calcium oxide flux is added.

[0074] The heating was carried out in a microwave reactor with the power set at 1800 W and the reaction temperature at 950 °C.

[0075] The oxygen concentration was maintained at 25%, and the evaporated zinc vapor reacted with oxygen to generate zinc oxide vapor.

[0076] During the condensation process, the temperature is gradually lowered through a multi-stage condenser to obtain zinc oxide particles of different particle sizes.

[0077] After condensation, the collected zinc oxide particles were doped with 2% aluminum (Al) to improve their optical properties.

[0078] Acid washing, heat treatment and sieving steps are performed, the sieving range is 10nm to 500nm, and the heat treatment temperature is 140°C.

[0079] Summary: The optical properties of zinc oxide were improved by aluminum doping, demonstrating the technical path to optimize material performance through doping. Metal doping such as aluminum and magnesium improves the electronic properties of zinc oxide, making it have broad potential in semiconductor, photocatalytic and other applications. This process is particularly suitable for high-end applications that require customized performance.

[0080] Summary: In five examples, various technical paths for producing zinc oxide by microwave heating are demonstrated. The use of flux significantly reduces the volatilization temperature of zinc, improves the reaction efficiency, and optimizes the particle size distribution of zinc oxide particles. The choice of each flux has different effects on product quality and reaction conditions. Calcium oxide is suitable for large-scale production, boric acid is suitable for the production of small-particle zinc oxide, and calcium fluoride performs well under high temperature conditions. Through wet grinding and graded screening, the particle size of zinc oxide can be further controlled to ensure its suitability for different application scenarios. Finally, doping treatment expands the function of zinc oxide, making it more superior in the fields of optics and electronics.

[0081] Test experiments and data

[0082] Experimental conditions:

[0083] The metallurgical waste slag used has a zinc content of 15%, and the processing amount of each batch is 500g.

[0084] The microwave frequency was 2.45 GHz, and the reaction temperatures were set at 800°C, 900°C, and 1000°C, respectively.

[0085] The flux ratio is 2%.

[0086] Test experiment data table:

[0087]

[0088]

[0089] Data Analysis:

[0090] The use of fluxes (especially boric acid and calcium oxide) can significantly improve the purity of zinc oxide and shorten the reaction time.

[0091] The zinc oxide produced by calcium fluoride under high temperature conditions has slightly lower purity, but is suitable for production under high temperature and high load conditions.

[0092] In the absence of flux, the reaction time is longer and the particle size distribution is wider, indicating that the flux plays a significant role in this process.

[0093] Comparative Experimental Design

[0094] Experiment 1: Flux comparison experiment

[0095] Experimental design:

[0096] Compare the effects of using different fluxes (calcium oxide, boric acid, calcium fluoride) and no flux on zinc oxide production.

[0097] Controlled variables: microwave power 1500 W, temperature 900 °C, oxygen concentration 25%.

[0098]

[0099]

[0100] Experimental conclusion:

[0101] Boric acid has the best effect as a flux, which can not only improve the reaction efficiency but also significantly reduce the reaction temperature. Although zinc oxide can be produced without flux, the purity and particle size are not as good as those with flux.

[0102] Experiment 2: Microwave power comparison experiment

[0103] Experimental design:

[0104] The effects of different microwave powers (1000W, 1500W, 2000W, 2500W) on reaction time, zinc oxide purity and particle size distribution were compared.

[0105] Controlled variables: flux is calcium oxide, temperature is 900°C, oxygen concentration is 25%.

[0106]

[0107] Experimental conclusion:

[0108] As the microwave power increases, the reaction time is significantly shortened, the purity of zinc oxide is improved, and the particle size distribution is more concentrated. However, at 2500W power, too fast reaction may cause local overheating, which is suitable for scenarios with higher purity requirements.

[0109] Experiment 3: Temperature comparison experiment

[0110] Experimental design:

[0111] The effects of different temperatures (800℃, 900℃, 1000℃) on the purity, reaction efficiency and particle size of zinc oxide were compared.

[0112] Controlled variables: flux is calcium oxide, microwave power is 1500 W, and oxygen concentration is 25%.

[0113]

[0114] Experimental conclusion:

[0115] Increasing the temperature helps to improve the purity of zinc oxide and shorten the reaction time, but when the temperature is higher than 1000 °C, the particle size distribution becomes wider, indicating that the particle agglomeration phenomenon is more obvious at high temperature.

[0116] Summarize

[0117] Through multi-parameter comparative experiments, the advantages of microwave heating for rapid production of zinc oxide were demonstrated, such as fast reaction speed, high purity of zinc oxide and controllable particle size. Different process parameters (flux type, microwave power, reaction temperature, etc.) have a significant impact on the final product and can be adjusted according to actual needs to optimize production efficiency and product performance.

[0118] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for rapidly producing zinc oxide by microwave heating, characterized in that: The following steps are involved: Pre-treating the zinc-containing metallurgical waste slag and crushing it to a particle size of less than 50 μm; The crushed metallurgical waste slag is placed in a microwave reactor and a proper amount of flux is added to promote the volatilization of zinc; Heating is performed within a microwave power range of 500W-2500W, and the temperature is controlled between 600°C-1100°C, so that the zinc element in the metallurgical waste slag evaporates to form zinc vapor; Maintaining an oxygen concentration of not less than 20% in the reactor to ensure that zinc vapor fully reacts with oxygen to generate zinc oxide; The zinc oxide vapor generated by the reaction is cooled step by step using a multi-stage condensation system to condense it into zinc oxide particles of different particle sizes; The generated zinc oxide particles are graded and screened, and collected according to different particle size distributions; The collected zinc oxide particles are purified to remove impurities.

2. The method for rapidly producing zinc oxide by microwave heating according to claim 1, characterized in that: The flux is one or more of calcium oxide, boric acid or calcium fluoride.

3. The method for rapidly producing zinc oxide by microwave heating according to claim 1, characterized in that: The pulverizing step of the metallurgical waste slag is carried out by wet grinding, and after pulverizing, a slurry with a particle size of less than 30 μm is formed.

4. The method for rapidly producing zinc oxide by microwave heating according to claim 1, characterized in that: The microwave heating time is 10 min-60 min.

5. The method for rapidly producing zinc oxide by microwave heating according to claim 1, characterized in that: The multi-stage condensation system comprises at least two stages of condensers with different temperatures, the temperature of the first condenser is 300°C-500°C, and the temperature of the second condenser is 100°C-200°C.

6. The method for rapidly producing zinc oxide by microwave heating according to claim 1, characterized in that: The oxygen concentration is adjusted in real time by a gas flow control system in the reactor.

7. The method for rapidly producing zinc oxide by microwave heating according to claim 1, characterized in that: The grading and screening step is carried out by a multi-stage screening device, and the screening particle size range is 10nm-1μm.

8. The method for rapidly producing zinc oxide by microwave heating according to claim 1, characterized in that: The purification process includes pickling and heat treatment steps, wherein the pickling is used to remove residual metal impurities and the heat treatment is used to improve the crystallinity of zinc oxide.

9. The method for rapidly producing zinc oxide by microwave heating according to claim 1, characterized in that: The microwave reactor is provided with a temperature sensor and a gas monitoring device for real-time monitoring of the reaction temperature and reaction atmosphere components.

10. The method for rapidly producing zinc oxide by microwave heating according to claim 1, characterized in that: The zinc oxide particles may be further doped after being collected, and the doped elements include aluminum, magnesium, silver or titanium to improve their electrical, optical or catalytic properties.

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