Mole Balance

Shown above is a representation of a typical semibatch reactor. B is fed to A, which is already in the reactor, and there are no outputs (evporation included). To model a semibatch reactor, start with a mole balance on each species :

Starting with species A :

C and D are similar :

Species B is fed to the reactor making its mole balance equation slightly different :

We now have all the equations needed to describe the changes in concentration of the different species in the reactor over time. However, since there is a feed stream, the volume in the reactor will change. So, we need to develop an equation describing how the volume in the reactor changes with time.

Mass Balance

Starting with a mass balance and remebering that mass can neither be created nor destroyed :

The mass terms in the equation can be replaced by :

giving :

Assuming that the system is at constant density leads to :

That is the last equation needed to model the semibatch reactor.

Mole Balance			Mass Balance
			Rate Law

Now we can move on and talk about reactive distillation.