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 = 0.4 min⁻¹X = 70%

A first-order liquid-phase reaction with k = 0.4 min⁻¹ runs in a CSTR at steady state. What space time τ is needed to reach 70% conversion?

k = 0.4 min⁻¹X = 70%
τ = min
2.Easy
V = 200 L, k = 0.08 min⁻¹Q = 20 L/minCA0​ = 1.5 mol/LCA​ = ?

A liquid-phase first-order reaction A → B (k = 0.08 min⁻¹) runs in a 200 L continuous stirred-tank reactor (CSTR). The feed enters at 20 L/min with CA0 = 1.5 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 200 LQ = 20 L/mink = 0.08 min⁻¹CA0 = 1.5 mol/L
CA = mol/L
3.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 =
4.Medium
Q = 25 L/minCA0​ = 2.5 mol/LCA​ = ?V = 400 L, k = 0.1 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.1 min⁻¹) runs in a 400 L plug-flow reactor (PFR). The feed enters at 25 L/min with CA0 = 2.5 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 400 LQ = 25 L/mink = 0.1 min⁻¹CA0 = 2.5 mol/L
CA = mol/L
5.Hard
V = 1500 LV = 1500 LQ = 80 L/minX = ?

A first-order liquid-phase reaction (k = 0.12 min⁻¹) runs in two equal CSTRs in series, each of 1500 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 = 1500 L (×2)Q = 80 L/mink = 0.12 min⁻¹
X = %
6.Hard
Q = 50 L/minX = ?V = 1500 L

A first-order liquid-phase reaction (k = 0.08 min⁻¹) runs in a 1500 L plug-flow reactor (PFR) fed at 50 L/min. The density is constant and the reactor is at steady state. Find the conversion X in percent.

V = 1500 LQ = 50 L/mink = 0.08 min⁻¹
X = %

Answer key

  1. 1. τ = 5.833 min
  2. 2. CA = 0.8333 mol/L
  3. 3. VCSTR/VPFR = 2.485
  4. 4. CA = 0.5047 mol/L
  5. 5. X = 90.53 %
  6. 6. X = 90.93 %

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