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 = 100 L, k = 0.15 min⁻¹Q = 100 L/minCA0​ = 0.5 mol/LCA​ = ?

A liquid-phase first-order reaction A → B (k = 0.15 min⁻¹) runs in a 100 L continuous stirred-tank reactor (CSTR). The feed enters at 100 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 = 100 LQ = 100 L/mink = 0.15 min⁻¹CA0 = 0.5 mol/L
CA = mol/L
2.Easy
τ = ?k = 0.5 min⁻¹X = 50%

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 50% conversion?

k = 0.5 min⁻¹X = 50%
τ = min
3.Medium
Q = 50 L/minCA0​ = 2 mol/LCA​ = ?V = 50 L, k = 0.12 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.12 min⁻¹) runs in a 50 L plug-flow reactor (PFR). The feed enters at 50 L/min with CA0 = 2 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 50 LQ = 50 L/mink = 0.12 min⁻¹CA0 = 2 mol/L
CA = mol/L
4.Medium
QX = 80%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 80% 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 = 80%first order, same k and Q
VCSTR/VPFR =
5.Hard
V = 800 LV = 800 LQ = 20 L/minX = ?

A first-order liquid-phase reaction (k = 0.1 min⁻¹) runs in two equal CSTRs in series, each of 800 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 = 800 L (×2)Q = 20 L/mink = 0.1 min⁻¹
X = %
6.Hard
V = 800 LQ = 80 L/minX = ?

A first-order liquid-phase reaction (k = 0.25 min⁻¹) runs in an 800 L CSTR fed at 80 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 800 LQ = 80 L/mink = 0.25 min⁻¹
X = %

Answer key

  1. 1. CA = 0.4348 mol/L
  2. 2. τ = 2 min
  3. 3. CA = 1.774 mol/L
  4. 4. VCSTR/VPFR = 2.485
  5. 5. X = 96 %
  6. 6. X = 71.43 %

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