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 = 0.5 min⁻¹X = 60%

A first-order liquid-phase reaction with k = 0.5 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 60% conversion?

k = 0.5 min⁻¹X = 60%
τ = min
2.Easy
V = ?, k = 0.05 min⁻¹Q = 25 L/minX = 75%

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 75% conversion of A.

Q = 25 L/mink = 0.05 min⁻¹X = 75%
V = L
3.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 =
4.Medium
Q = 80 L/minCA0​ = 0.5 mol/LCA​ = ?V = 1000 L, k = 0.3 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.3 min⁻¹) runs in a 1000 L plug-flow reactor (PFR). The feed enters at 80 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 = 1000 LQ = 80 L/mink = 0.3 min⁻¹CA0 = 0.5 mol/L
CA = mol/L
5.Hard
V = 800 LV = 800 LQ = 25 L/minX = ?

A first-order liquid-phase reaction (k = 0.12 min⁻¹) runs in two equal CSTRs in series, each of 800 L. The feed rate is 25 L/min, the density is constant and the reactors are at steady state. Find the overall conversion X in percent.

V = 800 L (×2)Q = 25 L/mink = 0.12 min⁻¹
X = %
6.Hard
Q = 40 L/minX = ?V = 150 L

A first-order liquid-phase reaction (k = 0.15 min⁻¹) runs in a 150 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 = 150 LQ = 40 L/mink = 0.15 min⁻¹
X = %

Answer key

  1. 1. τ = 3 min
  2. 2. V = 1500 L
  3. 3. VCSTR/VPFR = 3.909
  4. 4. CA = 0.01176 mol/L
  5. 5. X = 95.73 %
  6. 6. X = 43.02 %

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