Comparing Membrane Reactors with PFRs, Part 2

Changing F_A0

Let's take a look at the effects of changing the inlet flowrate, F_A0, and how it affects our individual flowrates and the conversion:

As expected, our flowrates increase as F_A0 increases. Interestingly though, conversion actually decreases as F_A0 increases. Why? Even though more of reactant A enters the reactor as the flowrate increases, it spends less time in the reactor, which causes the decrease in conversion.

Changing k_m

Now let's see what happens when we vary k_m:

The transport coefficient, k_m, is a measure of how easily a species will pass through a given substance (i.e., the membrane). The lower the value of k_m, the more difficult it will be for species B to pass through the membrane, so it makes sense that our highest conversion occurs when k_m is highest. (See the page on flux for more information.)

The resulting effect on our flowrates is also no surprise, since the removal of species B through the membrane will drive our reaction equilibrium to the right. In our extreme case of large k_m, species B is removed as quickly as it is produced.