Process Scale-Up Dos & Don'ts

Session Chair:

• Noel Sutton, Amway Corporation

Session Description:

The goal of scale-up is to identify & develop a process that will successfully produce a desired product when manufactured at a commercial scale.  To successfully move from the small scale to the large, one must understand how size changes impact a number of physical & chemical phenomena.  This session will focus on things that should be done, and avoided, to prevent costly errors and delays during process development. 

Schedule:

The Dos and Don’ts of Fluidized Bed Scale-Up

Ray Cocco, Particulate Solid Research, Inc.

Fluidized beds are commonly used for the manufacturing of a wide range of products including syngas, fuels including gasoline, acrylonitrile, polyolefins, and ultra-high purity silicon. These units provide unsurpassed heat transfer along with  the ability to flow solids during operation.  However, scale-up of these units can be challenging with respect to productivity and reliability.  For fast reactions, the fluidized bed is usually mass-transfer limited and mass-transfer is strongly dependent on bed hydrodynamics.  Thus, scale-up parameters need to include gas compression, bubble growth, solids mixing, and particle cohesive forces all of which need to be obtained on a large-scale.  Many of the available correlations were either obtained on too small of a test unit to be relevant with commercial application, or simply don’t consider parameters that affect to mass transfer. 

Unit reliability also needs to be addressed in the design stage of fluidized bed scale-up.  Particle-particle collisions and particle wall collisions need to be managed to ensure low particle attrition and limited vessel erosion.  Thus, areas of high particle shear such as that from gas jets and cyclone separators need to be understood.  The addition of shrouds and vortex stabilizers can extend the lifetime of a unit by years.

Thus, understanding key hydrodynamic parameters such as bed density profiles, bubble hydrodynamics, pressure loop profiles and jet-penetration lengths can yield a commercial-scale design that mimics pilot-plant performances with reliability goals similar to other unit operations.  Details of these parameters and how they can be obtained are discussed.

Ultrasonics / High Shear in Polymerization

Sohan Khungar, Middough

Use of ultrasonics and high shear for polymer breakdown (degradation) is widely published. However, publications of their use during polymerization are not of consistent quality. The presenter’s work on mass (bulk), solution, and micro-suspension and emulsion polymerization, using ultrasonics / high shear will be reported and compared with the published work. Scientific explanations will be given for the differences. The presenter has successfully developed processes which have saved millions of dollars. Examples will be given of lessons learned, including the following DOs and DON’Ts:

DOs:

1. Make good, accurate, scientific observations and repeat your work.
2. Find explanation for observed differences from your hypothesis, and change your hypothesis if needed, in view of the above scientific observations.
3. Make final 10-25% payment contingent on equipment performance validation.
4. Note surprising observations, find explanation and think of exploiting these.
5. Provide for contingencies, e.g., 10-50% extra horsepower for pumps, agitators, mixers, for future higher throughputs or higher viscosities, and consider the use of variable frequency drives (VFDs).
6. Work with willing equipment vendors to resolve in constructive ways, with creative solutions if the equipment underperforms.
7. Use established scale up parameters, such as constant tip speed (other choices are shear number or horsepower per unit volume).
8. Be open minded and receptive to input from others.

DON’Ts:

1. Trust all claims of equipment vendors without doing performance tests.
2. Trust all published work without duplicating or analyzing it carefully (DO challenge it where it seems wrong).
3. Believe in hearsay or opinions without corroborating from reliable sources.
4. Despair if you get negative/unexpected results (DO look for explanations).
5. Generalize, or get emotionally attached to a particular type of equipment for all applications, just because it worked wonderfully for one application. It may not work for the new application, or there may be a lower cost/ better alternative.

The Dos and Don’ts of Scaleup

Gary Tatterson, North Carolina A&T State University

The softer side of scaleup is reviewed in Do's and Don'ts of Scaleup.  The important starting point, the importance of recognizing scale effects, different attitudes, approaches, methods and heuristics are presented. The scaleup ratio, geometric similarity, effective geometries, use of pilot plants, analogies, retrofits and myths are specifically examined.