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 = 60%

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 60% conversion?

k = 0.2 min⁻¹X = 60%
τ = min
2.Easy
V = ?, k = 0.15 min⁻¹Q = 10 L/minX = 90%

A first-order liquid-phase reaction A → B with k = 0.15 min⁻¹ is carried out in a continuous stirred-tank reactor (CSTR) fed at 10 L/min. The density is constant and the reactor is at steady state. Find the reactor volume V in litres for 90% conversion of A.

Q = 10 L/mink = 0.15 min⁻¹X = 90%
V = L
3.Medium
Q = 25 L/minX = 70%V = ?, k = 0.25 min⁻¹

A first-order liquid-phase reaction A → B with k = 0.25 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 70% conversion of A.

Q = 25 L/mink = 0.25 min⁻¹X = 70%
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 = 50 LV = 50 LQ = 100 L/minX = ?

A first-order liquid-phase reaction (k = 0.3 min⁻¹) runs in two equal CSTRs in series, each of 50 L. The feed rate is 100 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 = 100 L/mink = 0.3 min⁻¹
X = %
6.Hard
V = 250 LQ = 10 L/minX = ?

A first-order liquid-phase reaction (k = 0.2 min⁻¹) runs in a 250 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 = 250 LQ = 10 L/mink = 0.2 min⁻¹
X = %

Answer key

  1. 1. τ = 7.5 min
  2. 2. V = 600 L
  3. 3. V = 120.4 L
  4. 4. VCSTR/VPFR = 6.342
  5. 5. X = 24.39 %
  6. 6. X = 83.33 %

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