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 = 0.3 min⁻¹X = 85%

A first-order liquid-phase reaction with k = 0.3 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 85% conversion?

k = 0.3 min⁻¹X = 85%
τ = min
2.Easy
τ = ?k = 0.05 min⁻¹X = 50%

A first-order liquid-phase reaction with k = 0.05 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 50% conversion?

k = 0.05 min⁻¹X = 50%
τ = min
3.Medium
Q = 50 L/minX = 70%V = ?, k = 0.15 min⁻¹

A first-order liquid-phase reaction A → B with k = 0.15 min⁻¹ is carried out in a plug-flow reactor (PFR) fed at 50 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 70% conversion of A.

Q = 50 L/mink = 0.15 min⁻¹X = 70%
V = L
4.Medium
QX = 75%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 75% 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 = 75%first order, same k and Q
VCSTR/VPFR =
5.Hard
V = 150 LV = 150 LQ = 50 L/minX = ?

A first-order liquid-phase reaction (k = 0.4 min⁻¹) runs in two equal CSTRs in series, each of 150 L. The feed rate is 50 L/min, the density is constant and the reactors are at steady state. Find the overall conversion X in percent.

V = 150 L (×2)Q = 50 L/mink = 0.4 min⁻¹
X = %
6.Hard
Q = 50 L/minX = ?V = 1000 L

A first-order liquid-phase reaction (k = 0.12 min⁻¹) runs in a 1000 L plug-flow reactor (PFR) fed at 50 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 1000 LQ = 50 L/mink = 0.12 min⁻¹
X = %

Answer key

  1. 1. τ = 18.89 min
  2. 2. τ = 20 min
  3. 3. V = 401.3 L
  4. 4. VCSTR/VPFR = 2.164
  5. 5. X = 79.34 %
  6. 6. X = 90.93 %

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