Static Mixers, or Plug Flow Mixing:
Static, or Plug flow mixing, have physical limitations and are not capable of generating the same or even similar results that can be achieved using continuous stir flow reactors using top entering mixers.
Flash mixing process related problems can be numerous but the most common problems are related to improper or uncontrollable retention times in the flash mixing chamber. As an example, although in theory a certain G-factor, an outdated concept that is flawed, can be determined for a static mixer design at peak flow, it would take a very enlightened argument to explain exactly what portion of the G-Factors energy is attributable to frictional losses in an empty pipe, what is attributable to non-useful drag on the internal mixing elements, what is attributable to ineffective angular mixing (swirl) and what is attributable to actual preferred (radial) mixing. Again, this is assuming peak flow conditions. The reality is that most treatment plants almost never operate at peak flow, where flow turndown ratio, dependent on the season, may be anywhere from 2:1, and most often well beyond 2:1. Now it becomes necessary to have multiple static mixers to subdivide the total flow dependent to achieve and maintain optimal performance. The reality is the loss of process control, which can be compensated by elevating your chemical usage, or by changing to a potentially more expensive chemical source, or living with the result.