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 = ?, k = 0.05 min⁻¹Q = 25 L/minX = 85%

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 25 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 85% conversion of A.

Q = 25 L/mink = 0.05 min⁻¹X = 85%
V = L
2.Easy
τ = ?k = 0.1 min⁻¹X = 60%

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 60% conversion?

k = 0.1 min⁻¹X = 60%
τ = min
3.Medium
QX = 80%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 80% 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 = 80%first order, same k and Q
VCSTR/VPFR =
4.Medium
Q = 5 L/minCA0​ = 1.5 mol/LCA​ = ?V = 50 L, k = 0.05 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.05 min⁻¹) runs in a 50 L plug-flow reactor (PFR). The feed enters at 5 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 = 50 LQ = 5 L/mink = 0.05 min⁻¹CA0 = 1.5 mol/L
CA = mol/L
5.Hard
V = 150 LV = 150 LQ = 40 L/minX = ?

A first-order liquid-phase reaction (k = 0.08 min⁻¹) runs in two equal CSTRs in series, each of 150 L. The feed rate is 40 L/min, the density is constant and the reactors are at steady state. Find the overall conversion X in percent.

V = 150 L (×2)Q = 40 L/mink = 0.08 min⁻¹
X = %
6.Hard
V = 400 LQ = 5 L/minX = ?

A first-order liquid-phase reaction (k = 0.4 min⁻¹) runs in a 400 L CSTR fed at 5 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 400 LQ = 5 L/mink = 0.4 min⁻¹
X = %

Answer key

  1. 1. V = 2833 L
  2. 2. τ = 15 min
  3. 3. VCSTR/VPFR = 2.485
  4. 4. CA = 0.9098 mol/L
  5. 5. X = 40.83 %
  6. 6. X = 96.97 %

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