Page 109 - Analysis, Synthesis and Design of Chemical Processes, Third Edition

where A and B are the two reactants, and A is the limiting reactant. The standard analysis for conversion
in a reactor yields

(E3.1f)

(E3.1g)

(E3.1h)

3
3
where C = (500 kg/100 kg/kmol)(875 kg/m )/5500 kg = 0.796 kmol/m . Because reactant B is present
Ao
in 60% excess, Θ = 1.6. The desired conversion, X final , is 0.94. Integration of Equation (E3.1h) with an
initial condition of zero conversion at time zero yields

(E3.1i)

When all of the values are inserted into Equation (E3.1i), the time (Δt) is found to be 7082 s, or 118 min,
which is just less than the desired two hours allotted for the reaction. For simplicity, the additional
reaction time that occurs after the mixture leaves the reactor until the catalyst is removed from the reacting
mixture has been ignored.

Step 3: Draining Reaction Vessel and Catalyst Filtration

This step will be modeled as a draining tank, which may significantly underestimate the actual required

time for draining and filtering. In reality, experimental data on the filter medium and inclusion of the exit
pipe frictional resistance would have to be included to determine the actual time for a specific tank.
Generally, the filter is the bottleneck in such a step. Here, a 2-in schedule 40 exit pipe, with a cross-
2
sectional area of 0.00216 m , is assumed.