Ultrafine Aluminum Hydroxide Production Process: An Overview of Vertical Roller Mill Technology

Introduction

The production of ultrafine aluminum hydroxide (ATH) is a critical process in various industrial applications, including flame retardants, fillers for polymers, and catalyst carriers. The demand for high-purity, consistently fine ATH powders has driven significant advancements in grinding technology. Among these, Vertical Roller Mill (VRM) technology has emerged as a superior solution for achieving the precise particle size distribution and high production efficiency required by modern industry. This article provides a comprehensive overview of the ultrafine ATH production process, with a specific focus on the application and benefits of VRM technology.

The Importance of Particle Size in Aluminum Hydroxide Applications

Aluminum hydroxide’s effectiveness is highly dependent on its particle size and distribution. For flame retardant applications, finer particles provide a larger surface area, leading to more efficient endothermic decomposition and release of water vapor. In polymer composites, a uniform, sub-micron particle size ensures better dispersion, improved mechanical properties, and a superior surface finish. Traditional grinding methods, such as ball mills, often struggle to achieve the desired fineness (commonly D97 ≤ 5μm) with high energy efficiency and consistent quality. This is where specialized vertical roller mills demonstrate their distinct advantages.

Vertical Roller Mill Technology: A Paradigm Shift in Ultrafine Grinding

Vertical Roller Mills represent a significant leap forward from conventional grinding systems. Unlike ball mills that rely on impact and attrition from tumbling media, VRMs utilize a bed compression principle. The core components include a grinding table (or磨盘) and rollers (or磨辊) that hydraulically press against the material bed on the rotating table. This method is inherently more efficient, as energy is directly applied to the particle layer rather than being dissipated through the motion of the entire grinding charge.

Key Advantages of VRM for ATH Production

• High Grinding Efficiency: The direct application of pressure to the material bed results in significantly lower energy consumption compared to ball mills, often by 30-50%.
• Precise Particle Size Control: Integrated dynamic classifiers allow for real-time adjustment of the product fineness, ensuring a tight particle size distribution critical for ATH applications.
• Drying Capability: VRMs can simultaneously grind and dry moist ATH filter cakes using hot gas, simplifying the process flow and reducing the need for separate drying equipment.
• Compact Design and Low Noise: The vertical arrangement and enclosed structure lead to a smaller footprint and considerably lower operating noise levels.
• Environmental Friendliness: The fully enclosed system, coupled with highly efficient pulse-jet baghouse filters, ensures dust emissions are kept well below international standards.

Critical Process Parameters in VRM Operation for ATH

Optimizing a VRM for ultrafine ATH production requires careful control of several parameters:

1. Grinding Pressure: The hydraulic pressure applied to the rollers is crucial for achieving the necessary comminution force without over-grinding, which can lead to excessive energy use and potential degradation of the ATH crystals.
2. Classifier Speed: The rotational speed of the integrated dynamic classifier is the primary control variable for product fineness. Higher speeds result in a finer cut-point.
3. Feed Rate and Bed Depth: A stable and consistent material bed is essential for smooth operation. The feed rate must be controlled to maintain an optimal bed depth for efficient grinding.
4. Gas Flow and Temperature: When used for drying, the volume and temperature of the hot gas must be balanced to achieve the desired moisture content without overheating the product.

Introducing the SCM Ultrafine Mill for Premium ATH Production

For producers aiming for the highest quality ultrafine ATH powders, selecting the right equipment is paramount. Our SCM Series Ultrafine Mill is specifically engineered to meet the rigorous demands of this application. This mill is designed to produce powders in the range of 325-2500 mesh (D97 ≤ 5μm) from feed material with a size of up to 20mm, with capacities ranging from 0.5 to 25 tons per hour depending on the model.

Why the SCM Ultrafine Mill Excels in ATH Grinding

The SCM Ultrafine Mill incorporates several advanced features that make it an ideal choice:

• Enhanced Energy Efficiency: With an energy consumption up to 30% lower than traditional jet mills and double the capacity, it offers significant operational cost savings.
• High-Precision Classification: The mill features a vertical turbine classification system that ensures precise particle size cuts, guaranteeing a uniform final product free of coarse particles.
• Durable and Stable Design: Key wear parts like rollers and grinding rings are made from special alloys, extending service life multiple times. The innovative bearing-free screw design in the grinding chamber enhances operational stability.
• Superior Environmental Performance: The integrated pulse dust collector exceeds international standards for efficiency, and the soundproof room design maintains noise levels below 75dB, ensuring a clean and quiet working environment.

The working principle involves a main motor driving multiple layers of grinding rings. Material is fed into the center, dispersed by centrifugal force to the grinding tracks, and subjected to rolling and crushing forces as it moves outward. The finely ground powder is then conveyed by an air stream to the cyclone collector and pulse dust removal system for final collection. Models such as the SCM1250 (2.5-14 t/h, 185kW) and SCM1680 (5.0-25 t/h, 315kW) are particularly well-suited for medium to large-scale ATH production lines.

Comparing VRM to Alternative Grinding Technologies

While ball mills are a common choice, they are less efficient for achieving ultrafine sizes. Jet mills, another alternative, can produce very fine powders but at a high energy cost and with limited capacity for moist materials. The VRM, particularly advanced models like the SCM Ultrafine Mill, strikes an optimal balance, offering high efficiency, precise control, and the ability to handle drying in a single unit operation. For coarser ATH grades or preliminary size reduction, our MTW Series Trapezium Mill presents an excellent solution. With an output fineness of 30-325 mesh (up to 0.038mm) and high capacity (3-45 t/h), it is perfect for applications where the extreme fineness of the SCM series is not required. Its advantages include an anti-wear shovel design, optimized curved air duct, and integrated cone gear transmission for high efficiency.

Conclusion

The adoption of Vertical Roller Mill technology, exemplified by advanced solutions like the SCM Ultrafine Mill, is revolutionizing the production of ultrafine aluminum hydroxide. By offering unparalleled energy efficiency, precise particle size control, and integrated processing capabilities, VRMs enable manufacturers to produce high-value ATH products that meet the stringent requirements of modern industries in a cost-effective and environmentally responsible manner. As the demand for finer and more consistent materials grows, the role of this technology will only become more central to the global ATH market.