Is Your Formula Well Suited to Continuous In-Line Blending and Mixing?

This article will explore some of the various considerations when moving from batch processing to continuous in-line blending and mixing. The first issue is solids and their impact on continuous blending and mixing.

As of today, the holy grail of mixing has not been discovered.

What is the holy grail of mixing?

Accurately mixing a powder into a fluid stream.

Yes, there are eduction and vacuum systems, but these rely on a fixed amount of liquid and a fixed amount of powder.  Therefore, they are not true metering. Next, there are systems which mix a small amount of liquid with powder to create a paste. The paste is then ‘metered’ into the liquid. While close, this last option is just a glorified premix.

All Liquid Continuous Mixing and Blending

Next, if your product formula is all liquids (varying viscosities are tolerated) blending via a static mixer is not a problem. There are various options in the marketplace for equipment that can operate automatically with all liquid streams.

For more vigorous mixing than a static mixer, Sonic is the only manufacturer that is able to build multiple-feed automated homogenizer systems. The Sonolator homogenizer is a device which can accept a number of feeds. Sonic will, at times, custom build special manifolds to combine the various streams to be efficiently mixed in the homogenizer. Sonic’s homogenizer utilizes an orifice and blade combination operating at up to 5,000 PSI providing high shear for emulsions, dispersions and deagglomerations. Sonolator mixing results can match many single-feed homogenizers operating at much higher pressures.

Blending Skid

Above is a TechBlend continuous in-line blending system for all liquid inputs. Notice the input rack with automated valving behind the system. Fully automated TechBlend system used to produce over 12 different products utilizing up to six inputs in various combinations and ratios.

A problematic issue for multiple-feed in-line continuous blending and mixing or homogenizing is the overall number of feeds. Sometimes formulas will contain multiple fraction of a percentage streams. Any number of small inputs can be incorporated into a multiple-feed systems using small dosing pumps. If the number of fractional feeds is extreme, there may be a point at which the cost to incorporate all the small bits and pieces is just too great to be feasible. Therefore, a semi-continuous in- line solution makes sense.

Semi-Continuous Mixing and Blending

After overcoming the customary barriers to liquid formulas the inclusion of powders and solids within the formulation needs to be addressed. Specifically, the personal care industry utilizes formulas that have powders, waxes and other solids. With an eye toward efficient continuous production, many manufacturers approach Sonic to explore mixing and blending with formulas containing more than just liquids.

Since the holy grail of mixing has yet to be discovered, how can producers who utilize formulas with solids move to continuous in-line processing? At Sonic we call this mode of operation semi-continuous.

Here is how a semi-continuous system works. Powders, waxes, other solids and small bits and pieces are combined with the smallest possible amount of water or other medium into a premix. These premixes become one or more of the various phases of the multiple-feed system. Similar to a batch method the semi-continuous method limits the run size to the available premix. However, many of our customers will utilize two small tanks per premix stream. These smaller premix tanks are easier and faster to compound than a large batch tank. While the first tank is running the second is compounded. When the first tank is empty a valve is thrown and the second tank feeds the system. Thereby, the toggling back and forth between the two ‘limiting’ premix tanks in essence creates continuous processing or as we like to call it: semi-continuous in-line processing.

Post Additions

Another approach to handling some of the minor ingredients is via post additions. For example, given a common base, variations are added downstream from the main skid. Metering pumps would handle things like fragrance, color and/or other pluses. In this case, the variations would have dedicated small metering pumps downstream of the skid. Now, cleaning would be from the metering pump to the destination instead of through the entire skid to destination.

Benefits of post addition:

  • Dedicated pump for fragrance, color, etc.
  • Easier cleaning from metering pumps to destination
  • Faster changeovers


Above: Summary of how formula conditions lead to continuous or semi-continuous in-line mixing and blending.

In summary, moving from batch to continuous processing may require formula adjustments. Although some lab work may be required, the payoff is usually significant. Here is a summary of the benefits of moving from batch to continuous or semi-continuous processing:

  • Large and costly batch tank eliminated
  • Smaller more manageable premix tanks
  • Higher product yield for the tank and floor space
  • Post addition means dedicated pumps, easier cleaning and faster changeovers

As manufacturers within the personal care, chemical, food and pharmaceutical industries search for more process efficiencies they will inevitably drive toward continuous processing. Increasing demand in many sectors will compel producers to attempt to leverage economies of scale. This demand will require more product within a finite space and fixed amount of time. Increased demand and efficient production will always put pressure on manufacturers to move from batch production to more efficient continuous production.

At Sonic we have been helping our customers move their operations from batch to continuous and semi-continuous in-line production for over 75 years. Custom designed and built multiple-feed continuous and semi-continuous mixing and blending systems are our specialty. How well suited is your formula to continuous production? Contact Sonic today to find out!