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 = 0.25 min⁻¹Q = 5 L/minX = 70%

A first-order liquid-phase reaction A → B with k = 0.25 min⁻¹ is carried out in a continuous stirred-tank reactor (CSTR) fed at 5 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 70% conversion of A.

Q = 5 L/mink = 0.25 min⁻¹X = 70%
V = L
2.Easy
V = 100 L, k = 0.25 min⁻¹Q = 50 L/minCA0​ = 0.5 mol/LCA​ = ?

A liquid-phase first-order reaction A → B (k = 0.25 min⁻¹) runs in a 100 L continuous stirred-tank reactor (CSTR). The feed enters at 50 L/min with CA0 = 0.5 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 100 LQ = 50 L/mink = 0.25 min⁻¹CA0 = 0.5 mol/L
CA = mol/L
3.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 =
4.Medium
Q = 100 L/minCA0​ = 1 mol/LCA​ = ?V = 250 L, k = 0.05 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.05 min⁻¹) runs in a 250 L plug-flow reactor (PFR). The feed enters at 100 L/min with CA0 = 1 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 250 LQ = 100 L/mink = 0.05 min⁻¹CA0 = 1 mol/L
CA = mol/L
5.Hard
Q = 40 L/minX = ?V = 500 L

A first-order liquid-phase reaction (k = 0.05 min⁻¹) runs in a 500 L plug-flow reactor (PFR) fed at 40 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 500 LQ = 40 L/mink = 0.05 min⁻¹
X = %
6.Hard
V = 200 LV = 200 LQ = 40 L/minX = ?

A first-order liquid-phase reaction (k = 0.12 min⁻¹) runs in two equal CSTRs in series, each of 200 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 = 200 L (×2)Q = 40 L/mink = 0.12 min⁻¹
X = %

Answer key

  1. 1. V = 46.67 L
  2. 2. CA = 0.3333 mol/L
  3. 3. VCSTR/VPFR = 6.342
  4. 4. CA = 0.8825 mol/L
  5. 5. X = 46.47 %
  6. 6. X = 60.94 %

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