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 = 0.1 min⁻¹X = 70%

A first-order liquid-phase reaction with k = 0.1 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 70% conversion?

k = 0.1 min⁻¹X = 70%
τ = min
2.Easy
τ = ?k = 0.4 min⁻¹X = 50%

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 50% conversion?

k = 0.4 min⁻¹X = 50%
τ = min
3.Medium
Q = 5 L/minCA0​ = 1 mol/LCA​ = ?V = 50 L, k = 0.4 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.4 min⁻¹) runs in a 50 L plug-flow reactor (PFR). The feed enters at 5 L/min with CA0 = 1 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 50 LQ = 5 L/mink = 0.4 min⁻¹CA0 = 1 mol/L
CA = mol/L
4.Medium
QX = 95%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 95% 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 = 95%first order, same k and Q
VCSTR/VPFR =
5.Hard
V = 200 LQ = 50 L/minX = ?

A first-order liquid-phase reaction (k = 0.5 min⁻¹) runs in a 200 L CSTR fed at 50 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 200 LQ = 50 L/mink = 0.5 min⁻¹
X = %
6.Hard
V = 100 LQ = 25 L/minX = ?

A first-order liquid-phase reaction (k = 0.2 min⁻¹) runs in a 100 L CSTR fed at 25 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 100 LQ = 25 L/mink = 0.2 min⁻¹
X = %

Answer key

  1. 1. τ = 23.33 min
  2. 2. τ = 2.5 min
  3. 3. CA = 0.01832 mol/L
  4. 4. VCSTR/VPFR = 6.342
  5. 5. X = 66.67 %
  6. 6. X = 44.44 %

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