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 = 0.5 min⁻¹X = 75%

A first-order liquid-phase reaction with k = 0.5 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 75% conversion?

k = 0.5 min⁻¹X = 75%
τ = min
2.Easy
τ = ?k = 0.25 min⁻¹X = 75%

A first-order liquid-phase reaction with k = 0.25 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 75% conversion?

k = 0.25 min⁻¹X = 75%
τ = min
3.Medium
Q = 80 L/minX = 85%V = ?, k = 0.05 min⁻¹

A first-order liquid-phase reaction A → B with k = 0.05 min⁻¹ is carried out in a plug-flow reactor (PFR) fed at 80 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 = 80 L/mink = 0.05 min⁻¹X = 85%
V = L
4.Medium
QX = 70%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 70% 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 = 70%first order, same k and Q
VCSTR/VPFR =
5.Hard
V = 100 LV = 100 LQ = 5 L/minX = ?

A first-order liquid-phase reaction (k = 0.15 min⁻¹) runs in two equal CSTRs in series, each of 100 L. The feed rate is 5 L/min, the density is constant and the reactors are at steady state. Find the overall conversion X in percent.

V = 100 L (×2)Q = 5 L/mink = 0.15 min⁻¹
X = %
6.Hard
Q = 50 L/minX = ?V = 100 L

A first-order liquid-phase reaction (k = 0.15 min⁻¹) runs in a 100 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 = 100 LQ = 50 L/mink = 0.15 min⁻¹
X = %

Answer key

  1. 1. τ = 6 min
  2. 2. τ = 12 min
  3. 3. V = 3035 L
  4. 4. VCSTR/VPFR = 1.938
  5. 5. X = 93.75 %
  6. 6. X = 25.92 %

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