This is a model of the partial oxidation of o-xylene in a large excess of oxygen in a 1.5 m long plug flow reactor.
The first-order rate expression:
is rate of reaction (
is the pre-exponential factor in the rate constant (1/s),
is activation energy (kJ/mol),
is the ideal gas constant (kJ/[mol K]),
is absolute temperature in the reactor (K),
is pressure (atm),
is the ideal gas constant (
is the molar flow rate of the reactant o-xylene (kmol/s), and
is the total molar flow rate of the feed (kmol/s).
Mole balance as a function of reactor length:
is distance down the PFR (m),
is the cross section area of the PFR (
is the PFR radius (m).
Energy balance as a function of length:
are simplification terms,
is the temperature of heat transfer fluid surrounding the reactor (K),
is heat of reaction (kJ/kmol),
is mass flow rate (kg/s),
is the mass heat capacity of gas in reactor (kJ/[kg K]), and
is the overall heat transfer coefficient (
At the PFR inlet (
is the feed temperature (K) and
is the mole fraction of reactant in the feed.
The screencast video at  explains how to use this Demonstration.
 J. B. Rawlings and J. G. Ekerdt, Chemical Reactor Analysis and Design Fundamentals
, Madison, WI: Nob Hill Publishing, 2002 pp. 323–326.