One of my great enthusiasms is the topic of small scale continuous synthesis. There has been some new thinking in this area recently. I don’t mean the use of robots to move material around- I mean continuous flow reactions. Our refinery friends have been doing this for a long time. It’s the reason gasoline isn’t $25/gallon. 

Many, if not most, supplies of bulk raw materials come from continuous process equipment. The economies of large scale may require custom reaction equipment dedicated to a given product. The problem for small scale production is the cost of custom designed equipmet is often large compared to the value of the production run. It is usually best to develop processes to operate in conventional, off-the-shelf pots & pans.

The availability of stirred tank reactors and their ease of use for small scale production has dominated the mode of specialty chemical process technology to the present day. Generations of chemists and engineers in fine and specialty chemicals know nothing other than batch reactor chemistry.

Easy, inexpensive continuous processing isn’t automaticaly suitable for every process. Transformations that are suitable for continuous flow processing may still be disqualitied by virtue of upstream or downstream processes that feed from or into transformations that must be done batchwise. There is the question of feed rates to and from the continuous transformative step and the extent to which non-continuous operations are compatible.

But back to basics. Why have continuous synthesizers at all in the small scale?  Why not just run the semi-batch process as may times as you need at the largest scale possible? Well, there is no reason not to. This is a tried and true business plan.  But what small scale continuous processing allows is the possibility of multiple parallel operations run by fewer staff. At the small scale, batch chemical production typically has a larger labor component than bulk or commodity scale production. Improvements to small scale process economics rests to a large extent on reducing the labor cost contribution.

By it’s nature, continuous processing is an intensified activity. The idea is to construct a minimum reactive volume and flow materials through the reaction or processing zone under intensified conditions for as short of a residence time as possible. At any given moment, there is a minimum mass of hazardous materials undergoing a potentially hazardous transformation. Or, intensification may mean the use of smaller ancillary equipment continuously, as in the case of continuous filtration vs batch filtration.

There are those who are making progress in this field. Recently I ran into a number of websites and files of Ashe Morris in the UK. These folks are operating a productive engine of development in regard to reactor design and innovative process chemistry improvemets. They have focused on process efficency and intensification. The question is, what shape will the IP take? Will users pay a royalty on their production or will it be limited to the purchase cost ofthe equipmet. How they do this will make all of the difference to the extent and rate of acceptance in the market.

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