Reaction in an Adiabatic Continuous Stirred-Tank Reactor

C_A0 (mol/L) 2.50

volumetric flow rate (L/s) 52.5

reaction

Directions

In this Demonstration, a liquid-phase reaction takes place in an adiabatic, continuous stirred-tank reactor (CSTR). Select an exothermic reaction, and then select the feed concentration of the limiting reactant A (C_A0) and the volumetric flow rate. Mass and energy balances are solved to determine the outlet reactant concentration and temperature. The color of the fluid in the reactor is correlated with the reactor temperature: lower temperature is blue, and as the temperature increases, the fluid becomes purple and then red. The fractional conversion of reactant A is represented by X_A.

Note that multiple steady states can exist in an adiabatic CSTR for certain feed conditions for hydrolysis of propylene oxide. Because of this, the outlet temperature can jump when the feed concentration increases above a certain value (ignition) and then drop when the feed concentration decreases below a certain value (not the same value for extinction). That is, the reactor exhibits hysteresis.

Details

At steady state, the rate of reaction is constant within the CSTR, so that the total moles reacted per time equals reaction rate times volume:

(F_A0 − F_A) = −r_AV

where F_A0 and F_A are the inlet and outlet molar flow rates of reactant A, r_A is rate of reaction (mol/L s) of A and V is reactor volume. This equation may be expressed in terms of residence time τ, conversion X_A and inlet concentration of A, C_A0:

−r_Aτ = C_A0X_A

The rate expression r_A is a function of reactant concentrations and the rate constant k:

r_A = f(k, C_A, C_B, …)

The rate constant k increases with temperature according to the Arrhenius equation:

k = A e^−E_A/(RT)

where A is the pre-exponential factor, E_A is the activation energy of the reaction, R is the gas constant and T is absolute temperature. Energy released from exothermic reactions causes the reactor contents (and the reactor effluent) to have a higher temperature than the inlet:

F_totC_p (T₀ − T) = ΔH_Rr_AV

where F_tot is the total molar flow rate at the inlet or outlet, C_p is the molar heat capacity of the mixture within the reactor, T₀ is temperature at the inlet and ΔH_R is the heat of reaction.

About

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 Neil Hendren. It was prepared with financial support from the National Science Foundation (DUE 2336987 and 2336988). Address any questions or comments to LearnChemE@gmail.com.