I was trying to get an appropriate definition of the term ‘
scale-up' which we we hear so often and find a very simple definition of the term to be ` an increase according to a fixed ratio’. I wish the technique of scaling up was as simple as the definition above. May I therefore write this blog on `scale-up’ , by defining scale-up to be an activity or a process which eventually results in an operation or a set of operations being carried out on a higher scale?
Requirement to scale-up a process or a machine becomes relevant when a Lab has successfully produced the end product on a small scale and now has the objective to produce the same on a higher scale. This is of great relevant when the process is novel, has many un-knowns, and is likely to require a high investment.
A process often involves more than one process variable which is known to affect the yield of the product, its purity, the batch time, temperature , pressure, agitator speed, to name a few. If one attempts to design the large scale reactor by merely multiplying all the numbers by a factor of 2 to double the production, all hell can break loose when the plant starts.
This is where a careful approach is necessary that analyses the inter-relation between the various process parameters that results in a achieving the required productivity in the larger scale plant.
We encounter challenging conditions for scaling up, for example, a jacketed reactor with agitator where an exothermic chemical reaction is carried out between two liquid reactants. The reactor is scaled-up for the required capacity through careful computation of the following parameters : heat load, flowrate of cooling medium in jacket, temperature of cooling medium at exit from jacket, heat transfer coefficients inside and outside the reactor wall, iteration to arrive at the optimum impeller diameter and RPM, optimum cooling water flowrate through jacket, etc.
The know-how for upscaling a process , an equipment or a machine helps in achieving the final result in a optimum manner at the least cost, rather than living with the compulsion to make adjustments in the scaled up plant or equipmemt that results in increased cost of operation, increased investment, high energy requirement , etc.