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 = 0.2 min⁻¹X = 60%

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 60% conversion?

k = 0.2 min⁻¹X = 60%
τ = min
2.Easy
V = 400 L, k = 0.08 min⁻¹Q = 50 L/minCA0​ = 1.5 mol/LCA​ = ?

A liquid-phase first-order reaction A → B (k = 0.08 min⁻¹) runs in a 400 L continuous stirred-tank reactor (CSTR). The feed enters at 50 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 = 400 LQ = 50 L/mink = 0.08 min⁻¹CA0 = 1.5 mol/L
CA = mol/L
3.Medium
QX = 75%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 75% 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 = 75%first order, same k and Q
VCSTR/VPFR =
4.Medium
Q = 80 L/minX = 60%V = ?, k = 0.25 min⁻¹

A first-order liquid-phase reaction A → B with k = 0.25 min⁻¹ is carried out in a plug-flow reactor (PFR) fed at 80 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 = 80 L/mink = 0.25 min⁻¹X = 60%
V = L
5.Hard
Q = 25 L/minX = ?V = 200 L

A first-order liquid-phase reaction (k = 0.08 min⁻¹) runs in a 200 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 = 200 LQ = 25 L/mink = 0.08 min⁻¹
X = %
6.Hard
Q = 80 L/minX = ?V = 1000 L

A first-order liquid-phase reaction (k = 0.12 min⁻¹) runs in a 1000 L plug-flow reactor (PFR) fed at 80 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 1000 LQ = 80 L/mink = 0.12 min⁻¹
X = %

Answer key

  1. 1. τ = 7.5 min
  2. 2. CA = 0.9146 mol/L
  3. 3. VCSTR/VPFR = 2.164
  4. 4. V = 293.2 L
  5. 5. X = 47.27 %
  6. 6. X = 77.69 %

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