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 = 90%

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 90% conversion?

k = 0.4 min⁻¹X = 90%
τ = min
2.Easy
V = ?, k = 0.05 min⁻¹Q = 20 L/minX = 60%

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 20 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 = 20 L/mink = 0.05 min⁻¹X = 60%
V = L
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 = 100 L/minCA0​ = 2.5 mol/LCA​ = ?V = 1000 L, k = 0.25 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.25 min⁻¹) runs in a 1000 L plug-flow reactor (PFR). The feed enters at 100 L/min with CA0 = 2.5 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 1000 LQ = 100 L/mink = 0.25 min⁻¹CA0 = 2.5 mol/L
CA = mol/L
5.Hard
Q = 100 L/minX = ?V = 1500 L

A first-order liquid-phase reaction (k = 0.15 min⁻¹) runs in a 1500 L plug-flow reactor (PFR) fed at 100 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 1500 LQ = 100 L/mink = 0.15 min⁻¹
X = %
6.Hard
Q = 25 L/minX = ?V = 100 L

A first-order liquid-phase reaction (k = 0.5 min⁻¹) runs in a 100 L plug-flow reactor (PFR) 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 = 0.5 min⁻¹
X = %

Answer key

  1. 1. τ = 22.5 min
  2. 2. V = 600 L
  3. 3. VCSTR/VPFR = 1.443
  4. 4. CA = 0.2052 mol/L
  5. 5. X = 89.46 %
  6. 6. X = 86.47 %

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