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
V = 400 L, k = 0.3 min⁻¹Q = 10 L/minCA0​ = 0.5 mol/LCA​ = ?

A liquid-phase first-order reaction A → B (k = 0.3 min⁻¹) runs in a 400 L continuous stirred-tank reactor (CSTR). The feed enters at 10 L/min with CA0 = 0.5 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 400 LQ = 10 L/mink = 0.3 min⁻¹CA0 = 0.5 mol/L
CA = mol/L
2.Easy
τ = ?k = 0.5 min⁻¹X = 75%

A first-order liquid-phase reaction with k = 0.5 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 75% conversion?

k = 0.5 min⁻¹X = 75%
τ = min
3.Medium
QX = 75%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 75% 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 = 75%first order, same k and Q
VCSTR/VPFR =
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 = 400 LQ = 10 L/minX = ?

A first-order liquid-phase reaction (k = 0.25 min⁻¹) runs in a 400 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 = 400 LQ = 10 L/mink = 0.25 min⁻¹
X = %
6.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 = %

Answer key

  1. 1. CA = 0.03846 mol/L
  2. 2. τ = 6 min
  3. 3. VCSTR/VPFR = 2.164
  4. 4. VCSTR/VPFR = 6.342
  5. 5. X = 90.91 %
  6. 6. X = 98.62 %

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