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 = 0.08 min⁻¹X = 50%

A first-order liquid-phase reaction with k = 0.08 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 50% conversion?

k = 0.08 min⁻¹X = 50%
τ = min
2.Easy
τ = ?k = 0.15 min⁻¹X = 95%

A first-order liquid-phase reaction with k = 0.15 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 95% conversion?

k = 0.15 min⁻¹X = 95%
τ = min
3.Medium
Q = 80 L/minX = 80%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 80 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 = 80 L/mink = 0.4 min⁻¹X = 80%
V = L
4.Medium
QX = 95%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 95% 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 = 95%first order, same k and Q
VCSTR/VPFR =
5.Hard
V = 100 LQ = 10 L/minX = ?

A first-order liquid-phase reaction (k = 0.25 min⁻¹) runs in a 100 L CSTR fed at 10 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 100 LQ = 10 L/mink = 0.25 min⁻¹
X = %
6.Hard
V = 500 LV = 500 LQ = 20 L/minX = ?

A first-order liquid-phase reaction (k = 0.1 min⁻¹) runs in two equal CSTRs in series, each of 500 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 = 500 L (×2)Q = 20 L/mink = 0.1 min⁻¹
X = %

Answer key

  1. 1. τ = 12.5 min
  2. 2. τ = 126.7 min
  3. 3. V = 321.9 L
  4. 4. VCSTR/VPFR = 6.342
  5. 5. X = 71.43 %
  6. 6. X = 91.84 %

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