residence time (min) 1.7
initial reactant concentration (mol/L) 6

An irreversible reaction A → B is carried out in an isothermal, continuous stirred-tank reactor (CSTR). Select a plot with the three buttons at the top.

In rate vs. concentration, the green generation curve is the reaction rate and the blue removal line is the CSTR mass balance. Their intersections are the steady-state solutions. Drag the residence time slider: when three intersections exist, only two are stable (the middle one is unstable); at high and low residence times only one steady state remains.

In concentration vs. time and rate vs. time, also drag the initial reactant concentration slider to set the reactor's starting concentration, then watch how the reactor approaches steady state. When three steady states exist, starting above the middle steady-state concentration sends the reactor to the higher steady state; otherwise it settles to the lower one.

Rate equations:

τ = V / v ,

rA = − 25 CA 2 + CA + 5 CA2 ,

rA, r = ( CA, f − CA, s ) / τ ,

rA, g = − 25 CA, s 2 + CA, s + 5 CA, s2 ,

where τ is residence time (min), V is reactor volume (L), v is the volumetric flow rate (L/min), rA is reaction rate (mol/[L min]), rA, r is the steady-state removal rate (mol/[L min]) from a mass balance, rA, g is the transient generation rate (mol/[L min]), CA is the concentration of reactant A (mol/L), and CA, f is the feed concentration of A (mol/L).

The transient mass balance solved for each plot is

dCA/dt = ( CA, f − CA ) / τ + rA ,   CA(0) = CA, 0 ,

where CA, 0 is the initial concentration of A in the reactor (mol/L). Here V = 5.5 L and the feed concentration CA, f = 6.0 mol/L.

This simulation was created in the Department of Chemical and Biological Engineering at University of Colorado Boulder for LearnChemE.com by John L. Falconer using Claude AI. It is a JavaScript/HTML5 implementation of a Mathematica simulation by Rachael L. Baumann. It was prepared with financial support from the National Science Foundation (DUE 2336987 and 2336988) in collaboration with Washington State University. Address any questions or comments to LearnChemE@gmail.com.