Continuous Processing Systems
Particle size reduction in many emulsions and dispersions can be achieved by processing with EnSight’s in-line wet mixers and colloid mills. All the user needs to do is introduce a crude premix of the product into the EnSight mixer/mill processing chamber, and then collect the finished product at the discharge. The two most common ways to accomplish this are:
- Batch System – A complete premix is made in an agitated batch tank and is then fed to the mixer/mill for processing. This method is discussed in detail in a separate EnSight article.
- Continuous System – The premix is formed by injecting one or more minor ingredients in the appropriate ratio into a stream of the main carrier liquid immediately ahead of the inlet connection to the mixer/mill. Finished product is discharged on a continuous basis, as long as the flow of raw materials is maintained.
One method for premixing ingredients continuously is an injection manifold on the inlet to the mixer/mill. This device allows the injection of minor ingredients directly into the center of a stream of the main carrier liquid. The picture to the right shows a EnSight in-line mixer with a dual side-port injection manifold installed at its inlet. The main carrier liquid is connected to the front port, which is aligned with the mixer inlet, while two additional ingredients are injected into the side ports and carried into the center of the mainstream. The flow rates of the three ingredients may be controlled to establish the desired ratio of the three components.
The injection manifold approach in a continuous processing system is very commonly used because it offers several advantages over alternative methods.
- As the injection manifold performs its task just outside of the processing chamber, it may be used with any EnSight in-line mixer or colloid mill with no modifications to the standard mixer/mill.
- Because of the simple design, it is easy to construct such a manifold with the exact number of injection ports required for the application. The maximum number of ports possible is only limited by the size of the ports, which must fit in a 360° circle around the main pipeline.
- The external nature of the injection manifold means that it is still possible to install any combination of the many different types of rotors and stators that EnSight offers for its mixers and mills. The injection system and the processing elements remain completely independent of each other, as separate processing variables.
Note: As the minor ingredients are injected by pumping them into the side ports at a controlled rate, all of them must be able to flow. Any powders must first be made into a slurry before they can be injected.