ITK-330 Chemical Reaction Engineering. Isothermal Reactor Design. Dicky Dermawan www.dickydermawan.net78.net firstname.lastname@example.org. Algorithm for Isothermal Reactor Design. Example of Application: First-order Gas Phase Reaction in PFR. An Example: Effect of Reactor Type.
The elementary gas phase reaction
2 A + B C
with rate constant k=10 L2/mol2.s
takes place in a CSTR at constant temperature (500 K) and constant pressure (16.4 atm). The feed is equal molar in A and B. The feed volumetric flow rate vo=25 L/s. In order to achieve 90% conversion:
In the past there have typically been six problems in a three hour segment of the California Professional Engineers Exam. Consequently one should be able to work each problem in 30 minutes or less. Many of these problems involve an intermediate calculation to determine the final answer.
1. Group unknown parameters/values on the same side of the equation
[unknowns] = [knowns]
2. Look for a Case 1 and a Case 2 (usually two data points) to make intermediate calculations
3. Take ratios of Case 1 and Case 2 to cancel as many unknowns as possible
4. Carry all symbols to the end of the manipulation before evaluating, UNLESS THEY ARE ZERO
The homogeneous gas reaction A 2B is run at 100oC at a constant pressure of 1 atm in an experimental batch reactor. The data in below were obtained starting with pure A.
What size plug flow reactor operated at 100oC and 10 atm would yield 90% conversion of A for a total feed rate of 10 mol/sec, the feed containing 40% inert?
Example for First Order Reaction
for small DP: P/P0 = 1
The combination results in 2 simultaneous differential equations
Reforming reactors are used to increase the octane number of petroleum. In a reforming process 20.000 barrels of petroleum are to be processed per day. The corresponding mass and molar feed rates are 44 kg/s and 440 mol/s, respectively. In the reformer, dehydrogenation reactions such as:
Paraffin Olefin + H2
occur. The reaction is first-order in paraffin with k’ = 0.02 L/kgcat.s. Assume that pure paraffin enters the reactor at a pressure of 2000 kPa and the corresponding concentration of 0.32 mol/L. This reaction is carried out in a tubular packed bed 2.4 m in diameter and 25 m in length containing 173870 kg catalyst
The hydrodemethylation of toluene is to be carried out in a packed bed reactor. Plot the conversion, pressure ratio P/P0, and the partial pressures of toluene, hydrogen, and benzene as a function of catalyst weight. The molar feed rate of toluene to the reactor is 50 mol/min and the reactor is operated at 40 atm and 640oC. The feed consist of 30% toluene, 45% hydrogen, and 25% inerts. Hydrogen is used in excess to help prevent coking. The pressure drop parameter is 9.8x10-5 kg-1. Also determine the catalyst weight in a CSTR with a bulk density of 400 kg/m3PBR Design
In some instance it is more convenient to work in term of
NA, NB,… (batch) or FA, FB,… (continue) rather than conversion.
for each species involved
only for A
The gas phase reaction:
A 2 B
is carried out isothermally at 500 K & 10 atm without pressure drop in a PFR and follows an elementary rate law.
kA = 2.7 min-1
KC = 1.2 mol/L
FA0 = 10 mol/min
Mole balances & stoichiometry:
Mole balances & stoichiometry: