The following example illustrates an ammonia synthesis process in which an inert gas (I) is present, necessitating a purge stream. The fresh feed to the process contains nitrogen and hydrogen, as well as an inert gas (I). The feed is combined with a recycle stream containing the same three species, and the combined stream is fed to a reactor. The reactor effluent flows to a condenser. A liquid stream containing all of the ammonia formed in the reactor and a gas stream containing all the inerts and the unreacted nitrogen and hydrogen leave the condenser. The gas stream is split into two fractions with the same composition: one is removed from the process as a purge stream, and the other is the recycle stream, which is subsequently combined with the fresh feed. In every stream containing nitrogen and hydrogen, the two species are in stoichiometric proportion. Let yI0 be the mole fraction of inerts in the fresh feed, f the single-pass conversion of nitrogen in the reactor, and p the fraction of the gas leaving the condenser that is purged (mol purged/mol total).
Draw and fully label a process flowchart, and using stoichiometric ratios, physical constraints and simple material balances in your head, try to introduce the fewest possible variables. In other words express as many quantities as possible in terms
of yI0, f and p. Given yI0 = 0.01, f = 0.20, and p = 0.10, solve for the total moles fed to the reactor (nr), moles of ammonia produced (np), and overall nitrogen conversion (fov).