Scaling Up Precipitated Silica Production: Two Critical Process Stages for Mixing Solutions

Precipitated silica is an essential reinforcing filler used in rubber, coatings, and personal care products. Although its industrial production technology is well established, many manufacturers encounter challenges when scaling up production, including inconsistent batch quality and difficulty improving product yield.

Addressing the challenges of industrial-scale precipitated silica production, GREATWALL MIXERS draws on years of practical project experience to develop customized mixing solutions for the entire process, meeting the distinct requirements of slurry dispersion and reaction mixing.

1. Slurry Preparation and Dispersion: Coaxial Dual-Speed Mixer to Minimize Powder Agglomeration at the Source

Precipitated silica powder readily agglomerates when it comes into contact with water, forming lumps that can compromise subsequent reaction efficiency and result in uneven particle size. Effective slurry preparation and dispersion are therefore critical to final product quality.

For high-solids, high-viscosity, and abrasive slurry applications, the solution features a coaxial dual-speed design that separates bulk circulation from intensive dispersion through two independent shafts.

Low-speed outer anchor frame impeller — Full-vessel circulation and wall scraping

The scraper blades cover the vessel wall below the maximum operating liquid level and the vessel bottom, mobilizing settled material and minimizing dead zones and material buildup. The removable scraper design also simplifies maintenance and replacement.

High-speed central inclined-blade impeller — Intensive dispersion and uniform suspension

Arranged in multiple stages, the central impellers generate strong circulation and dispersion, breaking down powder agglomerates and maintaining a uniform suspension. This helps prevent stagnant zones in the center of the vessel while the outer impeller continues to rotate.

The high-speed shaft is equipped with variable-frequency speed control, allowing operating parameters to be adjusted according to powder moisture content, feed quantity, and dispersion progress.

The design target is to complete dispersion and discharge from a single vessel within 30 minutes under high-solids conditions, while maintaining particle size and uniformity within the specified process requirements.

2. Reaction Mixing: High-Volume Axial Circulation for Uniform Reaction at 95°C

The reaction between sodium silicate and sulfuric acid is highly sensitive to temperature and concentration. A constant reaction temperature of 95°C is commonly used in industrial production, making temperature and concentration uniformity inside the reactor essential to consistent precipitated silica properties.

In large-scale reactors, localized temperature and concentration gradients are common challenges. These variations can result in uneven reactions and significant batch-to-batch differences.

The proposed solution uses multiple stages of hydrofoil-type axial-flow impellers to establish a complete vertical circulation pattern, with upward flow from the bottom and return flow through the upper section.

Operating at low speed with high pumping capacity, the system promotes thorough material turnover throughout the vessel, helping equalize temperature and concentration while minimizing localized overheating and incomplete reaction.

Combined with variable-frequency speed control, the mixing intensity can be adjusted to suit process conditions during the initial, intermediate, and final stages of the reaction, ensuring that mixing performance remains aligned with the requirements of the entire reaction cycle.

3. Integrated Process Solutions: From Individual Mixers to Complete, Ready-to-Install Systems

Mixing performance sets the potential for consistent precipitated silica quality. However, realizing that potential in actual production also depends on reliable installation, smooth commissioning, and stable long-term operation.

For the scale-up of precipitated silica production facilities, GREATWALL MIXERS offers more than individual mixing equipment.

a. Integrated Supply of Mixers, Vessels, and Structural Steelwork

The complete mixing assembly includes the shaft and impellers, pedestal, mechanical seal, drive system (motor and reducer), baseplate, coupling, baffles, and other associated components. The vessel and supporting steel structure can also be supplied as part of an integrated package.

Key interfaces—including discharge elevation, dust-control provisions, and structural dimensions—are coordinated during the design stage to minimize on-site modifications and installation work.

b. Materials and Service Life Designed for Abrasive, High-Solids Applications

All wetted components are manufactured from stainless steel. Internal surfaces undergo pickling and passivation, followed by a blue-point test to verify surface passivation quality.

To address abrasion in high-solids applications, the impeller surfaces receive a strengthening treatment using nickel-based alloy coating to help extend service life.

The design also considers the service life of critical components, including the shaft and impellers, drive system, motor, and bearings, supporting long-term equipment reliability.

c. More Than Equipment: A Complete Solution for Reliable Operation

Each delivery includes factory inspection records, assembly drawings, installation, operation and maintenance manuals, and a recommended spare parts list.

On-site services cover installation, commissioning, and trial operation. GREATWALL MIXERS also provides operator training in safe operation, routine maintenance, and troubleshooting.