Answers to 10 common questions about batch mixing

Proper mixing is one key to control quality in many processing operations. In this first of a question-and-answer series on common powder and bulk solids handling problems, VORTEX engineer answers 10 of the batch mixing questions which are commonly asked.

Choosing a batch mixer

1. I am confused by the variety of mixers available. How do I know which type to choose for my batch process?

Determining mix quality

2. How can I tell when my materials has been adequately mixed?

Segregation problems

3. We use a bumble blender. I’ve heard that if you mix too long, you can undo the mixing results. What is this “de-mixing” and what causes it?

4. Can Demixing occur in an impeller-driven or multiple motion mixer?

5. When I analyze material samples taken from our mixer vessel, the mixing quality is okay, but I find mixing quality and weight variations in the final packages. How Can I avoid this?

Other mixing problems

6. What’s the quickest way to determine if my mixer is causing particle degradation?

7. My materials goes through a wet granulation step in a tumble blender to avoid segregation downstream. But the granulated material contains agglomerates, formed by liquid droplets in the blender, and I have to treat the agglomerates before I can use the material downstream. How can I avoid the agglomerates.

Choose a mixer that can handle dry materials and pastes

8. Most of the processes in my specialty chemical company are batch and handle only dry materials. However, some materials go through a phaste phase. Can one mixer handle both dry materials and pastes?

9. To properly package our material, we add an active ingredient in less than 5 percent concentration to a carrier that acts almost like a diluent. What kind of mixer should we use, and how should we add the ingredients to get good mixing?

Mixing and direct compression

10. Our pharmaceutical process currently requires a granulation step. We’d like to skip this step and the processing and equipment it requires and go to direct compression. What should we consider before making this change?