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 = 0.15 min⁻¹X = 70%

A first-order liquid-phase reaction with k = 0.15 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 70% conversion?

k = 0.15 min⁻¹X = 70%
τ = min
2.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
3.Medium
Q = 80 L/minCA0​ = 1 mol/LCA​ = ?V = 150 L, k = 0.4 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.4 min⁻¹) runs in a 150 L plug-flow reactor (PFR). 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 = 0.4 min⁻¹CA0 = 1 mol/L
CA = mol/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
Q = 50 L/minX = ?V = 200 L

A first-order liquid-phase reaction (k = 0.4 min⁻¹) runs in a 200 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 = 200 LQ = 50 L/mink = 0.4 min⁻¹
X = %
6.Hard
V = 250 LQ = 25 L/minX = ?

A first-order liquid-phase reaction (k = 0.05 min⁻¹) runs in a 250 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 = 250 LQ = 25 L/mink = 0.05 min⁻¹
X = %

Answer key

  1. 1. τ = 15.56 min
  2. 2. τ = 9.333 min
  3. 3. CA = 0.4724 mol/L
  4. 4. VCSTR/VPFR = 1.938
  5. 5. X = 79.81 %
  6. 6. X = 33.33 %

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