A first-order reaction is carried out in an isothermal plug flow reactor (PFR) with recycle. The fresh feed concentration and volumetric flow rate (
) are known. In order to calculate the concentration of the reactant entering the PFR, the outlet concentration (
) must be known. Thus,
is guessed, and then changed using the slider until the calculated value of
(the black arrow on the left) equals the known value of the feed concentration of 0.185 mol/L (the green circle). This simulates solving the system iteratively. The concentration of the reactant down the PFR is plotted based on the guessed value of
. The reactor volume and the recycle ratio
can be varied. For larger values of
, the PFR simulates the behavior of a continuous-stirred tank reactor (CSTR).