Titanium Dioxide Production Process: Chloride Route & Grinding Mills for TiO2 Powder

Introduction to Titanium Dioxide Production

Titanium dioxide (TiO2) is one of the most important white pigments used globally across various industries including paints, coatings, plastics, paper, and cosmetics. The production of high-quality TiO2 requires sophisticated manufacturing processes and precise particle size control to achieve optimal opacity, brightness, and dispersion characteristics. This article explores the chloride route production method and examines the critical role of grinding mills in producing TiO2 powder with specific particle size distributions.

The Chloride Route Production Process

The chloride process has become the dominant method for TiO2 production due to its environmental advantages and ability to produce superior quality pigment compared to the older sulfate process. This continuous process involves several key stages:

1. Chlorination Stage

The process begins with high-titanium feedstocks such as rutile ore or synthetic rutile, which are reacted with chlorine gas in a fluidized bed reactor at temperatures between 900-1000°C. Carbon is typically added as a reducing agent to facilitate the reaction:

TiO2 + 2Cl2 + 2C → TiCl4 + 2CO

The resulting titanium tetrachloride (TiCl4) is separated from other metal chlorides through condensation and distillation processes.

2. Purification and Oxidation

Purified TiCl4 is vaporized and then oxidized in a specially designed reactor at temperatures around 1500°C with oxygen or air:

TiCl4 + O2 → TiO2 + 2Cl2

This reaction produces fine TiO2 particles and chlorine gas, which is recycled back to the chlorination stage. The oxidation conditions critically influence the crystal structure (rutile or anatase) and primary particle size of the TiO2 product.

3. Surface Treatment

The raw TiO2 pigment undergoes surface treatment with inorganic compounds (typically alumina, silica, or zirconia) to improve durability, dispersion, and weather resistance. This step is crucial for developing specific pigment grades for different applications.

The Importance of Grinding in TiO2 Production

Following surface treatment, TiO2 aggregates must be reduced to their optimal particle size distribution to maximize light scattering efficiency and opacity. The grinding process serves several critical functions:

• Deagglomeration: Breaking down aggregates formed during surface treatment
• Particle Size Control: Achieving the optimal particle size range of 0.2-0.3 μm for maximum light scattering
• Surface Area Optimization: Creating the appropriate specific surface area for different applications
• Dispersion Improvement: Enhancing the ability of particles to separate in application media

Grinding Mill Technologies for TiO2 Powder

Selecting the appropriate grinding technology is crucial for achieving the desired TiO2 particle characteristics while maintaining production efficiency and cost-effectiveness. Various mill types offer different advantages depending on the specific requirements of the TiO2 grade being produced.

Ultrafine Grinding Solutions

For high-value TiO2 grades requiring extremely fine particle sizes and narrow size distributions, advanced ultrafine grinding technologies are essential. The SCM Ultrafine Mill represents a cutting-edge solution specifically designed for challenging materials like titanium dioxide.

Our SCM Ultrafine Mill offers exceptional performance characteristics for TiO2 processing:

• Output fineness range of 325-2500 mesh (D97≤5μm) perfectly matches TiO2 pigment requirements
• Processing capacity from 0.5 to 25 tons per hour accommodates various production scales
• Vertical turbine classifier ensures precise particle size control with no coarse powder contamination
• Special material roller and grinding ring design provides extended service life
• Energy efficiency with 30% lower consumption compared to jet mills

The working principle involves main motor-driven multi-layer grinding rings rotating to disperse material into the grinding path by centrifugal force. Material undergoes roller compression and progressive grinding through multiple layers, with final powder collection accomplished by cyclone collector and pulse dust removal systems.

Medium-Fine Grinding Options

For TiO2 grades requiring less extreme fineness or for preliminary size reduction stages, the MTW Series Trapezium Mill provides an excellent balance of performance and operating economics.

Key advantages of the MTW Series for TiO2 applications include:

• Output fineness from 30-325 mesh (up to 0.038mm) suitable for many TiO2 pigment grades
• Processing capacity from 3 to 45 tons per hour for high-volume production
• Anti-wear shovel design with combined blades reduces maintenance costs
• Curved air channel optimization minimizes energy loss and improves transmission efficiency
• Integrated bevel gear transmission with 98% efficiency

The grinding mechanism employs a main motor driving grinding rollers to revolve around the central shaft while rotating themselves to generate centrifugal force. Shovels throw material between the grinding ring and rollers to form a material layer, achieving efficient crushing through extrusion, with the classification system precisely controlling final particle size.

Technical Considerations for TiO2 Grinding

Several technical factors must be considered when selecting and operating grinding mills for titanium dioxide:

Particle Size Distribution Requirements

Different TiO2 applications require specific particle size distributions. For maximum opacity in coatings and paints, the optimal particle size is approximately 0.24 μm, which corresponds to half the wavelength of visible light. Finer particles may be required for specialty applications such as cosmetics or high-performance plastics.

Contamination Control

Maintaining product purity is critical in TiO2 production. Grinding mills must be constructed with appropriate materials and sealing systems to prevent metallic contamination that could affect color and performance properties.

Energy Efficiency

Grinding represents a significant portion of TiO2 production costs. Modern mills incorporate energy-saving features such as optimized classifier designs, efficient drive systems, and intelligent control systems to minimize power consumption.

Temperature Control

Excessive heat generation during grinding can affect TiO2 surface treatments and potentially degrade organic additives. Advanced mills incorporate cooling systems and optimized grinding geometries to control operating temperatures.

Case Study: SCM Ultrafine Mill in TiO2 Production

A major TiO2 manufacturer implemented our SCM1680 Ultrafine Mill for their premium rutile pigment line. The results demonstrated significant improvements:

• Production capacity increased to 25 tons per hour with consistent D97 ≤ 5μm fineness
• Energy consumption reduced by 32% compared to their previous jet milling system
• Product quality improved with narrower particle size distribution and better dispersion characteristics
• Maintenance intervals extended due to the durable design with special material components
• Environmental performance enhanced with pulse dust collection efficiency exceeding international standards and noise levels below 75dB

The successful implementation highlights how advanced grinding technology can simultaneously improve multiple aspects of TiO2 production, from product quality to operational economics.

Future Trends in TiO2 Grinding Technology

The evolution of grinding technology for titanium dioxide continues to focus on several key areas:

Digitalization and Smart Control

Advanced control systems incorporating artificial intelligence and machine learning are being developed to optimize grinding parameters in real-time, adapting to variations in feed material and maintaining consistent product quality.

Sustainable Operations

Next-generation mills are being designed with enhanced energy recovery systems, reduced water consumption (for wet grinding applications), and improved environmental performance to meet increasingly stringent regulations.

Modular and Flexible Designs

Modular mill designs allow producers to quickly adapt to changing market demands and product specifications, reducing downtime and improving overall plant flexibility.

Conclusion

The chloride route for titanium dioxide production, combined with advanced grinding technologies, enables manufacturers to produce high-quality TiO2 pigments with precisely controlled particle characteristics. The selection of appropriate grinding equipment, such as our SCM Ultrafine Mill for premium grades or the MTW Series Trapezium Mill for standard applications, plays a critical role in determining final product performance and production economics.

As TiO2 applications continue to evolve and environmental regulations become more stringent, the ongoing development of grinding technology will remain essential for manufacturers seeking to maintain competitiveness while meeting increasingly demanding customer requirements. The integration of energy-efficient, precisely controllable grinding systems represents a significant opportunity for TiO2 producers to enhance both product quality and operational performance.