LearnChemE

Recycle Mass Balances: Screencasts

A chemical reactor system is fed 100. kmol/h of reactant A, which is then mixed with a recycle stream. In the reactor, 60.% of A that enters the reactor is converted to product B. The mixture exiting the reactor goes to a separation unit where all of product B plus 20.% of A is removed, and the rest of A is recycled and mixed with the fresh feed. How many kmol/h of reactant A enter into the reactor?


We suggest that after watching this screencast, you list the important points as a way to increase retention.

Explains the steps in crystallization that includes an evaporator, a crystallizer and filter, and a recycle stream.

We suggest that after watching this screencast, you list the important points as a way to increase retention.

Important Equations:

\[R = \frac{F_{T,R}}{F_f}\]

where \(R\) = recycle ratio,

\(F_{T,R}\) = total molar flowrate (or mass flowrate) in recycle stream, and

\(F_f\) = total molar flowrate (or mass flowrate) of fresh feed to system.

Overall conversion for a process with recycle

\[overall \, conversion \, = \frac{F_{A0} -F_{A,f}}{F_{A0}}\]

where \(F_{A0}\) = molar flowrate of reactant \(A\) into process (fresh feed, mol/h), and

\(F_{A,f}\) = molar flowrate of reactant \(A\) out of process (mol/h)

Conversion in reactor (single-pass conversion)

\[reactor \, conversion \, = \frac{F_{A,m} – F_{A,outlet}}{F_{A,m}}\]

where \(F_{A,m}\) = molar flowrate of reactant \(A\) in stream obtained by mixing fresh feed with recycle stream (mol/h), and

\(F_{A,outlet}\) = molar flowrate of reactant \(A\) in stream leaving reactor (mol/h).