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
V = 50 L, k = 0.05 min⁻¹Q = 10 L/minCA0​ = 0.5 mol/LCA​ = ?

A liquid-phase first-order reaction A → B (k = 0.05 min⁻¹) runs in a 50 L continuous stirred-tank reactor (CSTR). The feed enters at 10 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 = 50 LQ = 10 L/mink = 0.05 min⁻¹CA0 = 0.5 mol/L
CA = mol/L
2.Easy
τ = ?k = 0.2 min⁻¹X = 95%

A first-order liquid-phase reaction with k = 0.2 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 95% conversion?

k = 0.2 min⁻¹X = 95%
τ = min
3.Medium
QX = 50%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 50% 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 = 50%first order, same k and Q
VCSTR/VPFR =
4.Medium
Q = 20 L/minCA0​ = 1 mol/LCA​ = ?V = 1000 L, k = 0.08 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.08 min⁻¹) runs in a 1000 L plug-flow reactor (PFR). The feed enters at 20 L/min with CA0 = 1 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 1000 LQ = 20 L/mink = 0.08 min⁻¹CA0 = 1 mol/L
CA = mol/L
5.Hard
V = 500 LQ = 80 L/minX = ?

A first-order liquid-phase reaction (k = 0.5 min⁻¹) runs in a 500 L CSTR fed at 80 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 500 LQ = 80 L/mink = 0.5 min⁻¹
X = %
6.Hard
V = 2000 LQ = 80 L/minX = ?

A first-order liquid-phase reaction (k = 0.05 min⁻¹) runs in a 2000 L CSTR fed at 80 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 2000 LQ = 80 L/mink = 0.05 min⁻¹
X = %

Answer key

  1. 1. CA = 0.4 mol/L
  2. 2. τ = 95 min
  3. 3. VCSTR/VPFR = 1.443
  4. 4. CA = 0.01832 mol/L
  5. 5. X = 75.76 %
  6. 6. X = 55.56 %

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