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 = 0.25 min⁻¹X = 70%

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 70% conversion?

k = 0.25 min⁻¹X = 70%
τ = min
2.Easy
V = ?, k = 0.05 min⁻¹Q = 50 L/minX = 95%

A first-order liquid-phase reaction A → B with k = 0.05 min⁻¹ is carried out in a continuous stirred-tank reactor (CSTR) fed at 50 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 = 50 L/mink = 0.05 min⁻¹X = 95%
V = L
3.Medium
Q = 20 L/minCA0​ = 0.5 mol/LCA​ = ?V = 200 L, k = 0.4 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.4 min⁻¹) runs in a 200 L plug-flow reactor (PFR). The feed enters at 20 L/min with CA0 = 0.5 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 200 LQ = 20 L/mink = 0.4 min⁻¹CA0 = 0.5 mol/L
CA = mol/L
4.Medium
Q = 100 L/minCA0​ = 1.5 mol/LCA​ = ?V = 500 L, k = 0.5 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.5 min⁻¹) runs in a 500 L plug-flow reactor (PFR). The feed enters at 100 L/min with CA0 = 1.5 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 500 LQ = 100 L/mink = 0.5 min⁻¹CA0 = 1.5 mol/L
CA = mol/L
5.Hard
V = 400 LV = 400 LQ = 80 L/minX = ?

A first-order liquid-phase reaction (k = 0.12 min⁻¹) runs in two equal CSTRs in series, each of 400 L. The feed rate is 80 L/min, the density is constant and the reactors are at steady state. Find the overall conversion X in percent.

V = 400 L (×2)Q = 80 L/mink = 0.12 min⁻¹
X = %
6.Hard
V = 400 LQ = 10 L/minX = ?

A first-order liquid-phase reaction (k = 0.5 min⁻¹) runs in a 400 L CSTR fed at 10 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 400 LQ = 10 L/mink = 0.5 min⁻¹
X = %

Answer key

  1. 1. τ = 9.333 min
  2. 2. V = 19000 L
  3. 3. CA = 0.009158 mol/L
  4. 4. CA = 0.1231 mol/L
  5. 5. X = 60.94 %
  6. 6. X = 95.24 %

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