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 = 0.25 min⁻¹X = 95%

A first-order liquid-phase reaction with k = 0.25 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 95% conversion?

k = 0.25 min⁻¹X = 95%
τ = min
2.Easy
V = ?, k = 0.08 min⁻¹Q = 5 L/minX = 85%

A first-order liquid-phase reaction A → B with k = 0.08 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 = 0.08 min⁻¹X = 85%
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 = 40 L/minCA0​ = 2 mol/LCA​ = ?V = 400 L, k = 0.08 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.08 min⁻¹) runs in a 400 L plug-flow reactor (PFR). The feed enters at 40 L/min with CA0 = 2 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 400 LQ = 40 L/mink = 0.08 min⁻¹CA0 = 2 mol/L
CA = mol/L
5.Hard
V = 50 LV = 50 LQ = 20 L/minX = ?

A first-order liquid-phase reaction (k = 0.05 min⁻¹) runs in two equal CSTRs in series, each of 50 L. The feed rate is 20 L/min, the density is constant and the reactors are at steady state. Find the overall conversion X in percent.

V = 50 L (×2)Q = 20 L/mink = 0.05 min⁻¹
X = %
6.Hard
Q = 5 L/minX = ?V = 400 L

A first-order liquid-phase reaction (k = 0.05 min⁻¹) runs in a 400 L plug-flow reactor (PFR) 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 = 0.05 min⁻¹
X = %

Answer key

  1. 1. τ = 76 min
  2. 2. V = 354.2 L
  3. 3. VCSTR/VPFR = 3.909
  4. 4. CA = 0.8987 mol/L
  5. 5. X = 20.99 %
  6. 6. X = 98.17 %

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