Chemical Reaction Engineering

Question 1

Why is the volume of a CSTR greater than the volume of a PFR for isothermal systems (and n>0)?

Answer 1

CSTR has a lower reaction rate

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Question 2

How (else) can a PFR be modelled?

Answer 2

As a large number of CSTRs in series.

Question 3

What does epsilon represent (in variable volume equations)?

Answer 3

Fractional change in volume between 0 and 100% conversion.

Question 4

What does RTD stand for?

Answer 4

Residence time distribution.

RTDs are used to model non-ideal reactor behaviour and to estimate the behaviour of the non-ideal reactor to get, for example, boundaries for the conversion that can be achieved in a particular behaviour. RTDs are measured with tracer experiments where a tracer is injected into the reactor at t = 0 and its concentration is measured in the effluent stream as function of time.

Question 5

What are properties of the tracer used for RTD experiments?

Answer 5

• Must be inert
• Easily detectable
• Has similar properties to the reacting mixture
• Is soluble in the reacting mixture

Question 6

What do E(t) and F(t) determine?

Answer 6

E(t) - Fraction of molecules leaving the reactor that has resided in reactor between t1 and t2

F(t) - fraction of effluent that has been in the reactor for less than time t