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 = 0.2 min⁻¹X = 90%

A first-order liquid-phase reaction with k = 0.2 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 90% conversion?

k = 0.2 min⁻¹X = 90%
τ = min
2.Easy
τ = ?k = 0.1 min⁻¹X = 85%

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 85% conversion?

k = 0.1 min⁻¹X = 85%
τ = min
3.Medium
QX = 70%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 70% 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 = 70%first order, same k and Q
VCSTR/VPFR =
4.Medium
Q = 40 L/minX = 60%V = ?, k = 0.4 min⁻¹

A first-order liquid-phase reaction A → B with k = 0.4 min⁻¹ is carried out in a plug-flow reactor (PFR) fed at 40 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 60% conversion of A.

Q = 40 L/mink = 0.4 min⁻¹X = 60%
V = L
5.Hard
V = 2000 LV = 2000 LQ = 80 L/minX = ?

A first-order liquid-phase reaction (k = 0.3 min⁻¹) runs in two equal CSTRs in series, each of 2000 L. The feed rate is 80 L/min, the density is constant and the reactors are at steady state. Find the overall conversion X in percent.

V = 2000 L (×2)Q = 80 L/mink = 0.3 min⁻¹
X = %
6.Hard
V = 400 LV = 400 LQ = 40 L/minX = ?

A first-order liquid-phase reaction (k = 0.1 min⁻¹) runs in two equal CSTRs in series, each of 400 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 = 400 L (×2)Q = 40 L/mink = 0.1 min⁻¹
X = %

Answer key

  1. 1. τ = 45 min
  2. 2. τ = 56.67 min
  3. 3. VCSTR/VPFR = 1.938
  4. 4. V = 91.63 L
  5. 5. X = 98.62 %
  6. 6. X = 75 %

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