Reactor sizing (CSTR & PFR) worksheet with answers

Free printable Reactor sizing (CSTR & PFR) worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
τ = ?k = 0.4 min⁻¹X = 80%

A first-order liquid-phase reaction with k = 0.4 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 80% conversion?

k = 0.4 min⁻¹X = 80%
τ = min
2.Easy
V = ?, k = 0.25 min⁻¹Q = 20 L/minX = 85%

A first-order liquid-phase reaction A → B with k = 0.25 min⁻¹ is carried out in a continuous stirred-tank reactor (CSTR) fed at 20 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 85% conversion of A.

Q = 20 L/mink = 0.25 min⁻¹X = 85%
V = L
3.Medium
QX = 60%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 60% conversion. How many times larger must a CSTR be than a PFR for the same feed rate, rate constant and conversion? Find the ratio VCSTR/VPFR.

X = 60%first order, same k and Q
VCSTR/VPFR =
4.Medium
Q = 40 L/minX = 95%V = ?, k = 0.25 min⁻¹

A first-order liquid-phase reaction A → B with k = 0.25 min⁻¹ is carried out in a plug-flow reactor (PFR) fed at 40 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 95% conversion of A.

Q = 40 L/mink = 0.25 min⁻¹X = 95%
V = L
5.Hard
V = 2000 LQ = 50 L/minX = ?

A first-order liquid-phase reaction (k = 0.5 min⁻¹) runs in a 2000 L CSTR fed at 50 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 2000 LQ = 50 L/mink = 0.5 min⁻¹
X = %
6.Hard
Q = 20 L/minX = ?V = 150 L

A first-order liquid-phase reaction (k = 0.2 min⁻¹) runs in a 150 L plug-flow reactor (PFR) fed at 20 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 150 LQ = 20 L/mink = 0.2 min⁻¹
X = %

Answer key

  1. 1. τ = 10 min
  2. 2. V = 453.3 L
  3. 3. VCSTR/VPFR = 1.637
  4. 4. V = 479.3 L
  5. 5. X = 95.24 %
  6. 6. X = 77.69 %

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