Energy Balance in Steady-State PFR: Example Problems
Try to solve these problems before watching the solutions in the screencasts.
Example Problem 1
A second-order endothermic reaction (ΔH = 25,000 J/mol) takes place in a steady-state, jacketed plug flow reactor.
A → B + C k = 1016e(-15,000/T) cm3/(mol min) T is in kelvin
The reactor feed contains A at 250°C and a concentration of 2.5×10-3 mol/cm3. The tubular reactor diameter is 8.0 cm, and the heat transfer coefficient through the walls is 30 J/(cm2 K min). The fluid in the jacket surrounding the reactor is at 300°C. Is the temperature of the reactor contents immediately downstream from the inlet higher or lower than the feed temperature?
Example Problem 3 (optional)
For the reversible, liquid-phase reaction A ↔ B, determine the adiabatic equilibrium temperature and conversion when pure A is fed to the reactor at 300. K.
CPA = CPB = 50. cal/(mol K). Heat capacities are independent of temperature. The equilibrium constant is 1 x 105 at 298 K; the heat of reaction is -2.0 x 104 cal/mol.
Example Problem 2
The gas-phase reaction A → B + C is carried out in an adiabatic 800-L PFR. The reaction is first-order in A and the rate constant is k = 60e(-5,000/T) s-1. The feed to the reactor is pure A at 15 bar and 450 K with a volumetric flow rate of 1.956 L/s. Heat of reaction = -12 kJ/mol. Heat capacities: CPA = 40 J/(mol K), CPB = 15 J/(mol K), CPC = 25 J/(mol K). Plot the molar flow rates of A and B as a function of cumulative volume down the reactor. Plot temperature versus volume.