Scale Up
A Definition

Edward T. Woodruff knows much about process Scale Up.  This sheet is informational and designed for your interest and edification.  For more information about our contributions and performance results please see Home and Accomplishments. 

The specific examples of Scale Up Edward T. Woodruff was directly involved with at Grace Research that come to mind are vinyl acetate process catalyst recovery, fixed and fluid be phthalic anhydride, sea water desalination, calcium nitrite, and the Grace sugar spray drying process.  All of these were of significance to the company as it allowed management to see technically how these projects would go commercially. 

The calcium nitrite scale up operates in the commercial plant right now.  The desalination work was scaled up to the pilot level from the bench and then to a much larger unit for San Diego, California. 

Beyond these specific examples, all the process designs we nave worked on, and the pilot plant studies we have been involved with include process scale up. 

Our process designs to project what a bench scale process might  look like in the commercial plant have involved scale up in that we designed the future commercial plant equipment so it could be scaled down at least to the pilot plant level. 

The term scale up literally means to make a plant bigger in size than the one a company had previously.  This includes moving from bench scale research to the pilot plant stage and from there to the commercial plant.  Sometimes companies take risks and scale directly from the bench to the commercial plant.

There is more to scale up than literally making something bigger.  The least risky scale up is where the next plant is 10 times or less bigger than the previous one.  For example, the commercial facility would be 10 times or less bigger than the pilot plant that was used to develop the process and the data necessary for scale up.

Scale up from the bench even to the pilot stage can cover several orders of magnitude in size difference.  Here scale up issues are not as important as going from the pilot to commercial plant simply because the pilot unit will cost much less than the commercial one.  If mistakes are made in going to the pilot plant they can be rectified via moderate costly equipment changes.  Changing mistakes here is much, much less expensive than changing them at the commercial plant level.

Gas / liquid or catalytic reactors are best scaled up by keeping the gas superficial velocity and the reactor bed height constant.  If there are heat transfer issues, these will have to be dwelt with as separate computations for the bigger plant.

Stirred tank reactors can be scaled over several orders of magnitude.  There is a great deal known about stirred tank reactors and how they correlate over various size ranges.  Having said this, however, heat transfer considerations are not quite so easy.  As the size gets bigger the surface area per unit volume gets smaller.  It is possible that heat transfer may ultimately limit the size that a particular system can be taken to.

Distillations and gas/liquid separations are well documented as far as their physical chemistry is concerned for many systems.  Modern day process simulators are quite capable of determining commercial scale equipment size.  Even with this widely used capability though there is sometimes need for experimental test work on large scale equipment.  If the behavior of the components, for example, are highly non ideal such testing may well be worth the while to reduce the risk in commercial plant design.

Also see Accomplishments.