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 = 0.12 min⁻¹X = 85%

A first-order liquid-phase reaction with k = 0.12 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 85% conversion?

k = 0.12 min⁻¹X = 85%
τ = min
2.Easy
V = ?, k = 0.12 min⁻¹Q = 100 L/minX = 50%

A first-order liquid-phase reaction A → B with k = 0.12 min⁻¹ is carried out in a continuous stirred-tank reactor (CSTR) fed at 100 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 50% conversion of A.

Q = 100 L/mink = 0.12 min⁻¹X = 50%
V = L
3.Medium
Q = 25 L/minX = 50%V = ?, k = 0.3 min⁻¹

A first-order liquid-phase reaction A → B with k = 0.3 min⁻¹ is carried out in a plug-flow reactor (PFR) fed at 25 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 50% conversion of A.

Q = 25 L/mink = 0.3 min⁻¹X = 50%
V = L
4.Medium
QX = 50%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 50% 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 = 50%first order, same k and Q
VCSTR/VPFR =
5.Hard
Q = 10 L/minX = ?V = 250 L

A first-order liquid-phase reaction (k = 0.05 min⁻¹) runs in a 250 L plug-flow reactor (PFR) fed at 10 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 250 LQ = 10 L/mink = 0.05 min⁻¹
X = %
6.Hard
V = 800 LV = 800 LQ = 40 L/minX = ?

A first-order liquid-phase reaction (k = 0.25 min⁻¹) runs in two equal CSTRs in series, each of 800 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 = 800 L (×2)Q = 40 L/mink = 0.25 min⁻¹
X = %

Answer key

  1. 1. τ = 47.22 min
  2. 2. V = 833.3 L
  3. 3. V = 57.76 L
  4. 4. VCSTR/VPFR = 1.443
  5. 5. X = 71.35 %
  6. 6. X = 97.22 %

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