(52d) Scaling Two Phase Batch and Semi-Batch Chemical Processes from Laboratory Scale to Commercial Scale

The heart of a chemical process is its reactor. In many cases, the reactor contains two phases, each with one or more reactants in them. These phases are mixed to induce the desired chemical reaction, thereby producing marketable product. The semi-batch gas-liquid reactor is an example of such a process. A batch reactor containing two immiscible phases is another example of such a process. In most cases, agitator tip speed is used when scaling such reactors from laboratory size to commercial size. These relationships are used to scale the reaction rate of the chemical process. However, gas-liquid and immiscible liquid-liquid chemical processes have significant mass transfer resistances. Unfortunately, agitator tip speed scale-up correlations have little to do with mass transfer resistance. This paper reviews the foundations for scaling two phase chemical reactions in batch and semi-batch reactors and describes how mass transfer resistance arises in each situation. Methods for reducing each mass transfer resistance will be discussed. This paper concludes by proposing the use of mass transfer coefficient as the scaling factor rather than agitation tip speed or one to the numerous power to volume relationships available in the open literature.