Page 152 - Materials Chemistry, Second Edition

Mass-Balance Concept and Reactor Design 135

(c) The required reactor volume, V = (τ)Q (from Equation 4.27)
= (64 min)(30 gal/min) = 1,920 gal

Discussion:
A minimum of three reactors are needed in this case. The reactors are
operated in different phases; while two are in loading or unloading
phases, the other one will be in active reaction phase. Consequently,
the influent flow will not be interrupted.

Example 4.16: Sizing a CFSTR
A soil slurry reactor is used to treat soils that contain 1,200 mg/kg of TPH.
It is required to treat the slurry at 30 gal/min. The required final soil TPH
concentration is 50 mg/kg. From a bench-scale study, the rate equation was
found to be

γ = −0.05C in mg / kg / min

The contents in the reactor are fully mixed. Assume that the reactor behaves
as a CFSTR. Size the CFSTR for this project.

Solution:
(a) Insert the known values into Equation (4.20) to find the value of τ:

50 1
C out
= =
C in 1200 1(0.05)+ τ
τ = 460 min

(b) The required reactor volume, V = (τ)Q (from Equation 4.27)
= (460 min)(30 gal/min) = 13,800 gal

Example 4.17: Sizing a PFR

A soil slurry reactor is used to treat soil that contains 1,200 mg/kg of TPH.
It is required to treat the slurry at 30 gal/min. The required final soil TPH
concentration is 50 mg/kg. From a bench-scale study, the rate equation was
found to be

γ = −0.05C in mg / kg / min

Assume that the reactor behaves as a PFR. Size the PFR for this project.