Designing Mixing Equipment for Creams, Gels, Adhesives, Pastes, Concentrates, and Other Viscous Products
High-viscosity products create some of the most demanding conditions in industrial mixing. Creams, gels, adhesives, pastes, concentrates, emulsions, and similar materials resist movement, require significant torque, and often behave differently as ingredients are added or temperatures change.
The challenge is moving the entire batch effectively and consistently.
A mixing system designed for high-viscosity production needs to account for the product throughout the complete batch cycle. Tank geometry, mixer horsepower, torque, impeller selection, wall scraping, heat transfer, and controls all contribute to the final result.
Getting these elements working together can improve batch consistency, reduce processing time, and protect the mechanical equipment from unnecessary stress.
Start with the Product’s Viscosity
Viscosity describes a fluid’s resistance to flow. As viscosity increases, moving material throughout a tank requires more energy.
Understanding the expected viscosity range is an important starting point when designing a mixing system. The product may enter the tank as a relatively thin liquid and become significantly thicker as powders, polymers, solids, or other ingredients are incorporated.
When evaluating a high-viscosity process, consider:
- Starting and maximum viscosity
- How viscosity changes during the batch
- Processing and storage temperatures
- Solids content and particle characteristics
- Required final product consistency
- Whether the material is shear-sensitive
The highest expected viscosity can be particularly important because it may establish the maximum mechanical load the mixer needs to handle.
Our guide to impeller and agitator types provides additional information about how mixer designs create different flow patterns for different products.
Torque and Horsepower Need to Match the Process
High-viscosity mixing requires enough power to move the product throughout the vessel.
Horsepower is part of that calculation, while torque becomes increasingly important as resistance to movement increases. Gear reducers are commonly used to provide the combination of lower mixer speed and higher torque required for viscous products.
Startup conditions also matter. A mixer starting in a tank filled with cold adhesive, gel, cream, or another thick product may experience a much greater load than a mixer starting with lower-viscosity raw ingredients.
The drive system should be selected around the expected operating range, including these demanding conditions. Proper motor and gearbox selection helps provide reliable performance while supporting longer equipment life.
Variable Frequency Drives can also provide useful control by allowing operators to adjust mixer speed for different stages of the batch.
Flow Through the Entire Vessel Matters
Successful mixing requires movement throughout the tank.
With low-viscosity liquids, an impeller can generate circulation relatively easily. As viscosity increases, energy dissipates more quickly and the product becomes harder to move over longer distances.
This can create areas where material moves slowly while the product immediately surrounding the impeller receives much more mixing energy.
High-viscosity systems may use several approaches to maintain effective circulation, including:
- Large-diameter anchor agitators
- Multiple impellers on a common shaft
- Helical or ribbon-style agitation
- Dual-agitation systems
- High-shear mixers combined with bulk agitation
The appropriate configuration depends on the product and what the process needs to accomplish. Mixing an adhesive may require a different approach than producing a cosmetic cream or incorporating powders into a concentrated food product.
Wall Scraping Supports Mixing and Heat Transfer
Anchor mixers are frequently used for viscous products because their large diameter allows them to sweep close to the vessel wall.
For some applications, scrapers can be incorporated into the agitation system. These help move product away from the vessel wall and back into the active mixing zone.
Wall scraping becomes particularly valuable when heating or cooling is part of the process. Product sitting against a heated or cooled vessel wall can create an insulating layer that reduces heat transfer. Keeping that material moving exposes new product to the heat-transfer surface and supports more uniform temperatures throughout the batch.
Scrapers can also help reduce material buildup and improve product recovery when the batch is discharged.
Heat Transfer and Viscosity Are Closely Connected
Temperature can dramatically affect the viscosity of many products.
Heating may make a thick product easier to mix and pump. Cooling can increase viscosity and place greater demands on the mixer. Some products also require controlled heating or cooling to achieve the desired formulation or physical properties.
A jacketed mixing tank can transfer heat through the vessel wall using steam, hot water, glycol, or another thermal medium. The effectiveness of that jacket depends partly on how well the mixer moves product across the heat-transfer surface.
Several factors should therefore be considered together:
- Required heat-up and cool-down times
- Product viscosity at different temperatures
- Available heating or cooling utilities
- Jacket design and available surface area
- Agitation near the vessel wall
- Temperature uniformity requirements
Thermal design, vessel geometry, and agitation should be developed as parts of the same process.
Tank Geometry Influences High-Viscosity Mixing
The dimensions of the vessel directly affect mixer performance.
Tall, narrow tanks can require longer shafts and multiple impellers to move viscous product from top to bottom. Wider vessels may allow larger-diameter agitation systems that create stronger bulk movement.
Working volume also matters. The mixer needs to perform across the actual batch range rather than at only one ideal fill level.
Our article on mixing tank sizing explains how working volume, diameter, and sidewall height influence the complete mixing system.
Consider Discharge and Product Transfer
Mixing the product successfully is only part of the process. The finished material also needs to leave the tank.
Viscous products can be difficult to drain and transfer. Bottom geometry, outlet size, valve selection, piping diameter, and pump design should reflect the characteristics of the finished product.
A system capable of producing a thick adhesive or gel efficiently also needs to move that product into storage, filling, packaging, or the next processing stage without creating another bottleneck.
This is why Mixing Tanks USA approaches these projects as complete liquid process systems, considering how each component affects the operation around it.
Design Around the Entire Batch
High-viscosity mixing systems perform best when they are engineered around the full range of conditions the product experiences.
Understanding how viscosity changes, where heat needs to move, how ingredients are incorporated, and how the finished product is discharged gives engineers the information needed to select the appropriate vessel, mixer, motor, gearbox, and controls.
If you are developing a new high-viscosity process, increasing production, or replacing existing equipment, contact Mixing Tanks USA for a quote on your next mixing and storage tank project. Our team can review your application and help design equipment around your product and production goals.
About Mixing Tanks USA
Mixing Tanks USA is an American manufacturer of stainless steel mixing and storage tanks and liquid process systems serving the food and beverage, life science, and industrial and chemical industries.
Our equipment is manufactured in Portland, Oregon, with a focus on precision engineering, quality fabrication, dependable performance, and long-term customer support. We design standard and custom equipment around the products, processes, facilities, and production goals of the manufacturers we serve.