A production system and method for high-purity indirect zinc oxide using physical polymerization inhibition

Abstract

This invention discloses a physical inhibition method for producing high-purity indirect zinc oxide, belonging to the field of zinc oxide preparation technology. Addressing the technical challenge of preventing the use of chemical additives and agglomeration in high-end zinc oxide production, this invention proposes a solution combining three physical methods: gradient cooling, dry airflow purging, and electrostatic neutralization. Specifically, high-temperature zinc oxide powder is subjected to a three-stage gradient cooling process: 180℃→120℃→70℃→40℃, with dry, clean air (dew point ≤ -20℃) circulated throughout. During the cooling process, an electrostatic neutralization device eliminates static electricity from the particles. This system and method involve no chemical additives, effectively inhibiting thermal stress agglomeration and electrostatic adsorption. The resulting zinc oxide product exhibits high purity, good looseness, and excellent flowability, making it perfectly suitable for fields with stringent purity and safety requirements, such as food, pharmaceuticals, and cosmetics. This invention features a green process, low equipment modification costs, and is easily applied industrially.

Description

Technical Field

[0001] This invention belongs to the field of inorganic chemical material preparation technology, specifically relating to the production equipment and process of zinc oxide, and in particular to an additive-free physical anti-agglomeration system and method suitable for producing high-purity, high-flowability food, pharmaceutical and cosmetic grade zinc oxide. Background Technology

[0002] Zinc oxide, as an important inorganic functional material, is widely used in various industries such as rubber, coatings, pharmaceuticals, food, and cosmetics. For high-end applications in food, pharmaceuticals, and cosmetics, there are extremely strict requirements for the purity, safety, and physical properties (such as flowability and dispersibility) of zinc oxide, and the addition of any organic modifiers or chemical additives is strictly prohibited.

[0003] In the traditional indirect zinc oxide production process, high-temperature zinc oxide vapor is usually cooled rapidly after being condensed and collected. This method brings two main problems: (1) electrostatic adsorption: rapid cooling causes a large amount of static charge to be generated and accumulated on the surface of zinc oxide particles, causing the particles to adsorb each other and form soft agglomerates; (2) thermal stress agglomeration: the thermal stress generated by the large temperature difference will cause the particles to melt and form hard agglomerates that are difficult to disperse. These agglomerates seriously affect the bulk density, flowability and application performance of the final product.

[0004] To address the agglomeration problem, existing technologies often employ methods such as coating or adding surface modifiers like organosilicon or fatty acids to the zinc oxide surface. However, this method introduces foreign chemicals, leading to a decrease in product purity and making it unsuitable for high-end applications with strict limitations on additives. Therefore, there is an urgent need to develop a novel production process and equipment that can effectively prevent zinc oxide particle agglomeration while ensuring absolute product purity and the absence of any chemical additives. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a production system and method that inhibits zinc oxide particle agglomeration entirely through physical means without relying on any chemical additives. This method effectively eliminates particle static electricity and avoids thermal stress agglomeration, thereby producing high-purity, high-flowability, non-caking indirect zinc oxide products suitable for high-end applications such as food, pharmaceuticals, and cosmetics.

[0006] To achieve the above objectives, this invention provides a "triple physical coupling" anti-polymerization technology, the core of which lies in the systematic integration and synergistic effect of three physical means: gradient slow cooling, dry airflow purging, and electrostatic neutralization.

[0007] A method for producing high-purity zinc oxide using a physical anti-agglomeration indirect method includes: subjecting high-temperature zinc oxide powder collected by condensation to a three-stage gradient slow cooling process, while simultaneously introducing a dry and clean airflow throughout the cooling process, and applying electrostatic neutralization treatment to the zinc oxide powder during the cooling process, thereby achieving anti-agglomeration of zinc oxide particles without adding any chemical additives.

[0008] A more specific method is as follows: S1: Three-stage gradient slow cooling: The high-temperature zinc oxide powder (initial temperature approximately 180℃) after condensation and collection is gradually cooled through three slow cooling zones with different set temperatures. The specific cooling gradient is as follows: from the first zone of approximately 180℃ to the second zone of approximately 120℃, then to the third zone of approximately 70℃, and finally cooled to the discharge zone of approximately 40℃, which is close to room temperature. This gradient design aims to release heat smoothly and minimize thermal stress agglomeration caused by rapid temperature differences.

[0009] S2: Full-process dry airflow purging: Throughout the cooling process, dry, clean air (or inert gas such as nitrogen) with a dew point ≤ -20℃ is continuously introduced into the pipes or equipment through which the zinc oxide powder flows. This dry airflow serves a dual purpose: firstly, it removes trace amounts of moisture from the powder surface, preventing capillary agglomeration caused by moisture; secondly, it acts as a carrier gas and cooling medium, assisting in the uniform flow and heat exchange of the powder.

[0010] S3: Electrostatic Neutralization: Electrostatic neutralization devices (such as ionizers, radioactive electrostatic eliminators, etc.) are installed in key sections of the cooling process (preferably in areas where the temperature drops to approximately 70°C or below). These devices generate positive and negative ions that neutralize the static charge accumulated on the surface of zinc oxide particles, fundamentally eliminating the electrostatic attraction between particles.

[0011] By coupling the above-mentioned gradient cooling, drying and purging, and electrostatic neutralization triple physical measures, effective and long-term inhibition of zinc oxide particle agglomeration can be achieved without adding any chemical modifiers.

[0012] A production system for implementing the above method includes, in sequence along the material flow direction: (1) Feeding unit: a feed inlet for receiving high-temperature zinc oxide powder from the condensation process; (2) Gradient cooling unit: It consists of multiple cooling sections connected in series and independently temperature-controlled, used to achieve the three-stage gradient cooling (e.g., 180℃→120℃→70℃→40℃). This unit can be a jacketed screw conveyor, a multi-stage fluidized bed cooler, or a closed conveying pipeline with heat exchange fins. (3) Drying air system: including air purification device, deep drying device (such as adsorption dryer) and fan. This system is connected to the gradient cooling unit to generate and continuously introduce dry and clean airflow with dew point ≤-20℃ into the system; (4) Static neutralization device: Integrated and installed inside or near the outlet of the gradient cooling unit to eliminate static electricity generated during powder flow; (5) Discharge and collection unit: used to collect the final zinc oxide product after cooling and reaching the target temperature. Beneficial effects

[0013] Compared with the prior art, the present invention has the following significant advantages: 1. Absolutely pure and widely applicable: The entire process is free of any chemical additives, resulting in high product purity and no introduction of foreign impurities, fully meeting the extremely high safety requirements of industries such as food, medicine, and cosmetics.

[0014] 2. Advanced and effective anti-agglomeration mechanism: It innovatively combines three physical anti-agglomeration mechanisms: gradient slow cooling (controlling thermal stress), drying and purging (controlling humidity), and electrostatic neutralization (eliminating electrostatic force). It comprehensively solves the multiple physical factors that cause agglomeration from the root, and the anti-agglomeration effect is significant and long-lasting.

[0015] 3. Excellent product performance: The obtained zinc oxide product is free of static electricity, does not clump, has high looseness and excellent flowability, which significantly improves the efficiency of subsequent processing (such as mixing, packaging and transportation) and application performance.

[0016] 4. Green and environmentally friendly process and equipment: The entire process does not produce any chemical pollutants, and the dry air can be recycled, which is in line with the concepts of green manufacturing and sustainable development.

[0017] 5. Low modification cost and stable operation: This solution can be modified and upgraded based on the existing indirect zinc oxide production line, mainly by adding temperature control, drying and static elimination modules. The modification is simple, the operation is stable and reliable, and it is easy to promote industrially. Attached Figure Description Figure 1 This is a process flow diagram of the production system of the present invention. Detailed Implementation

[0018] The preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. This embodiment is intended to illustrate the technical solution of the present invention more clearly, rather than to limit the scope of protection of the present invention.

[0019] Example 1: Physical polymerization inhibition production of 5000 tons / year of food-grade indirect zinc oxide 1. System Configuration Adopting such Figure 1 The production system shown has the following specific equipment configuration: (1) Feeding unit: A closed star feeder is used, which is connected to the upstream condenser collector to receive high-temperature zinc oxide powder with a temperature of 180-190℃.

[0020] (2) Gradient Cooling Unit: In this embodiment, a three-section jacketed screw conveyor cooler is used as the core equipment. The equipment is 12 meters long, with a stainless steel outer shell and a slow-speed screw conveyor shaft (2-5 rpm) inside. The equipment is divided into three independent cooling sections along the material flow direction, and each jacket can be circulated with cooling media of different temperatures for independent temperature control: First cooling section: 4 meters long, with circulating heat transfer oil flowing through the jacket, and the material is slowly cooled from about 180°C to about 120°C through a temperature control system. Second cooling section: 4 meters long, with medium-temperature circulating water flowing through the jacket to cool the material from about 120°C to about 70°C; The third cooling section is 4 meters long. Low-temperature circulating water is introduced into the jacket to cool the material from about 70°C to below about 40°C.

[0021] (3) Drying air system: It consists of an oil-free air compressor, a refrigerated dryer, an adsorption dryer, and a high-efficiency filter. The system can provide dry and clean air with a pressure of 0.3-0.5 MPa and a dew point stability of ≤-25℃. The drying air is blown into the material layer in a counter-current or tangential direction through multiple airflow inlets (wind speed 0.5-1.0 m / s) evenly distributed in each section of the cooling unit.

[0022] (4) Static neutralization device: A set of rod-type ion wind static eliminators is installed at the end of the third cooling section and above the discharge port. The positive and negative ions generated by them can effectively neutralize the static charge accumulated on the surface of zinc oxide powder.

[0023] (5) Discharge and collection unit: The cooled zinc oxide powder enters the finished product silo through a closed rotary valve and is then automatically packaged.

[0024] 2. Production process steps According to the above system, perform the following operations: (1) System preparation: Start the drying air system and the cooling medium circulation system to ensure that the temperature of each cooling section reaches the set value (120℃ for the first section, 70℃ for the second section, and 40℃ for the third section), and continuously introduce dry air into the system for purging.

[0025] (2) Feeding and primary cooling: Start the feeding unit and screw conveyor to continuously feed the primary zinc oxide product from the indirect method at a rate of 500 kg / h, which is about 185°C. The material undergoes indirect heat exchange with heat transfer oil in the first cooling section, and the temperature drops to about 120°C after about 25 minutes. Most of the sensible heat is released slowly during this stage to avoid rapid cooling.

[0026] (3) Secondary and tertiary cooling: The material enters the second and third cooling sections, where it continues to cool down under the combined action of medium and low temperature circulating water and drying airflow. The drying airflow continuously removes trace amounts of water vapor and assists in powder flow. When the material reaches the end of the third cooling section, the temperature has dropped to approximately 65°C.

[0027] (4) Static neutralization: Zinc oxide powder at a temperature of about 65°C flows through the static neutralization device area, and the high-concentration ion flow generated by the rod ion fan neutralizes and eliminates the static charge on its surface.

[0028] (5) Discharge: The zinc oxide powder, after cooling and electrostatic neutralization, is discharged through the discharge unit at a temperature of 38-40℃ to obtain the final product.

[0029] 3. Summary of Process Parameters Processing capacity: 500 kg / h (based on zinc oxide) Cooling gradient: 185℃ → 120℃ → 70℃ → 40℃ Total cooldown time: Approximately 70-80 minutes Dry air dew point: ≤ -25℃ Screw conveyor speed: 3 rpm.

[0030] 4. Product performance testing The zinc oxide product produced using the method of this embodiment was tested and compared with zinc oxide produced by conventional quenching (without this system). The results are as follows: Table 1: Performance Comparison Table

[0031] This embodiment fully demonstrates that the "gradient slow cooling + dry airflow + electrostatic neutralization" triple physical coupling system and method of the present invention can effectively solve the agglomeration problem in the production of high-end zinc oxide without adding any chemical modifiers. The resulting product maintains extremely high chemical purity while its physical flowability and looseness are fundamentally improved, fully meeting the application requirements of the food, pharmaceutical, and other fields. The process is stable, easy to upgrade and modify on existing production lines, and has significant industrial application value.

Claims

1. A method for producing high-purity zinc oxide using a physical polymerization inhibition indirect method, characterized in that, The method includes: subjecting the high-temperature zinc oxide powder collected by condensation to a three-stage gradient slow cooling process, while simultaneously introducing a dry and clean airflow throughout the cooling process, and applying electrostatic neutralization treatment to the zinc oxide powder during the cooling process, thereby achieving anti-agglomeration of zinc oxide particles without adding any chemical additives.

2. The method for producing high-purity indirect zinc oxide using physical polymerization inhibition according to claim 1, characterized in that, The specific temperature ranges for the three-stage gradient slow cooling are: from about 180°C to about 120°C, then to about 70°C, and finally to about 40°C.

3. The method for producing high-purity indirect zinc oxide using physical polymerization inhibition according to claim 1, characterized in that, The dew point of the dry, clean airflow is ≤-20℃.

4. The method for producing high-purity indirect zinc oxide using physical polymerization inhibition according to claim 1, characterized in that, The electrostatic neutralization process is achieved by an electrostatic neutralization device installed in the cooling process.

5. A physical polymerization-inhibited high-purity indirect zinc oxide production system for implementing the method of any one of claims 1-4, characterized in that, The system, along the material flow direction, includes, in sequence: (1) Feeding unit: a feed inlet for receiving high-temperature zinc oxide powder; (2) Gradient cooling unit: A gradient cooling unit connected to the feed inlet for realizing the three-stage gradient slow cooling; (3) Drying air system: A drying air system connected to the gradient cooling unit for providing a dry airflow with a dew point ≤ -20℃; (4) Static neutralization device: a static neutralization device integrated on or inside the gradient cooling unit; (5) Discharge and collection unit: used to collect the final zinc oxide product after cooling and reaching the target temperature.

6. A high-purity indirect zinc oxide product prepared by the method according to any one of claims 1-4, characterized in that, The zinc oxide product contains no chemical additives, meets food or pharmaceutical grade purity standards, and has excellent flowability and dispersibility.

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