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 = 150 L, k = 0.5 min⁻¹Q = 20 L/minCA0​ = 0.5 mol/LCA​ = ?

A liquid-phase first-order reaction A → B (k = 0.5 min⁻¹) runs in a 150 L continuous stirred-tank reactor (CSTR). The feed enters at 20 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 = 150 LQ = 20 L/mink = 0.5 min⁻¹CA0 = 0.5 mol/L
CA = mol/L
2.Easy
V = ?, k = 0.5 min⁻¹Q = 5 L/minX = 85%

A first-order liquid-phase reaction A → B with k = 0.5 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 85% conversion of A.

Q = 5 L/mink = 0.5 min⁻¹X = 85%
V = L
3.Medium
Q = 20 L/minX = 80%V = ?, k = 0.2 min⁻¹

A first-order liquid-phase reaction A → B with k = 0.2 min⁻¹ is carried out in a plug-flow reactor (PFR) fed at 20 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 80% conversion of A.

Q = 20 L/mink = 0.2 min⁻¹X = 80%
V = L
4.Medium
QX = 90%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 90% 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 = 90%first order, same k and Q
VCSTR/VPFR =
5.Hard
V = 250 LQ = 80 L/minX = ?

A first-order liquid-phase reaction (k = 0.4 min⁻¹) runs in a 250 L CSTR fed at 80 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 250 LQ = 80 L/mink = 0.4 min⁻¹
X = %
6.Hard
V = 1000 LV = 1000 LQ = 50 L/minX = ?

A first-order liquid-phase reaction (k = 0.05 min⁻¹) runs in two equal CSTRs in series, each of 1000 L. The feed rate is 50 L/min, the density is constant and the reactors are at steady state. Find the overall conversion X in percent.

V = 1000 L (×2)Q = 50 L/mink = 0.05 min⁻¹
X = %

Answer key

  1. 1. CA = 0.1053 mol/L
  2. 2. V = 56.67 L
  3. 3. V = 160.9 L
  4. 4. VCSTR/VPFR = 3.909
  5. 5. X = 55.56 %
  6. 6. X = 75 %

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