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 = 85%

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 85% conversion?

k = 0.4 min⁻¹X = 85%
τ = min
2.Easy
V = 150 L, k = 0.3 min⁻¹Q = 80 L/minCA0​ = 1 mol/LCA​ = ?

A liquid-phase first-order reaction A → B (k = 0.3 min⁻¹) runs in a 150 L continuous stirred-tank reactor (CSTR). The feed enters at 80 L/min with CA0 = 1 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 150 LQ = 80 L/mink = 0.3 min⁻¹CA0 = 1 mol/L
CA = mol/L
3.Medium
Q = 25 L/minX = 90%V = ?, k = 0.4 min⁻¹

A first-order liquid-phase reaction A → B with k = 0.4 min⁻¹ is carried out in a plug-flow reactor (PFR) fed at 25 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 90% conversion of A.

Q = 25 L/mink = 0.4 min⁻¹X = 90%
V = L
4.Medium
Q = 10 L/minX = 60%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 10 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 60% conversion of A.

Q = 10 L/mink = 0.05 min⁻¹X = 60%
V = L
5.Hard
V = 50 LV = 50 LQ = 50 L/minX = ?

A first-order liquid-phase reaction (k = 0.2 min⁻¹) runs in two equal CSTRs in series, each of 50 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 = 50 L (×2)Q = 50 L/mink = 0.2 min⁻¹
X = %
6.Hard
V = 150 LV = 150 LQ = 10 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 10 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 = 10 L/mink = 0.4 min⁻¹
X = %

Answer key

  1. 1. τ = 14.17 min
  2. 2. CA = 0.64 mol/L
  3. 3. V = 143.9 L
  4. 4. V = 183.3 L
  5. 5. X = 30.56 %
  6. 6. X = 97.96 %

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