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 = 1000 L, k = 0.25 min⁻¹Q = 5 L/minCA0​ = 1 mol/LCA​ = ?

A liquid-phase first-order reaction A → B (k = 0.25 min⁻¹) runs in a 1000 L continuous stirred-tank reactor (CSTR). The feed enters at 5 L/min with CA0 = 1 mol/L. The density is constant and the reactor is at steady state. Find the outlet concentration CA.

V = 1000 LQ = 5 L/mink = 0.25 min⁻¹CA0 = 1 mol/L
CA = mol/L
2.Easy
V = ?, k = 0.08 min⁻¹Q = 20 L/minX = 70%

A first-order liquid-phase reaction A → B with k = 0.08 min⁻¹ is carried out in a continuous stirred-tank reactor (CSTR) fed at 20 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 = 20 L/mink = 0.08 min⁻¹X = 70%
V = L
3.Medium
QX = 50%same Q, k and X as the CSTR

A first-order liquid-phase reaction must reach 50% 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 = 50%first order, same k and Q
VCSTR/VPFR =
4.Medium
Q = 80 L/minCA0​ = 2.5 mol/LCA​ = ?V = 250 L, k = 0.25 min⁻¹

A liquid-phase first-order reaction A → B (k = 0.25 min⁻¹) runs in a 250 L plug-flow reactor (PFR). The feed enters at 80 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 = 250 LQ = 80 L/mink = 0.25 min⁻¹CA0 = 2.5 mol/L
CA = mol/L
5.Hard
V = 1500 LV = 1500 LQ = 25 L/minX = ?

A first-order liquid-phase reaction (k = 0.05 min⁻¹) runs in two equal CSTRs in series, each of 1500 L. The feed rate is 25 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 = 25 L/mink = 0.05 min⁻¹
X = %
6.Hard
V = 250 LQ = 80 L/minX = ?

A first-order liquid-phase reaction (k = 0.12 min⁻¹) runs in a 250 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 = 250 LQ = 80 L/mink = 0.12 min⁻¹
X = %

Answer key

  1. 1. CA = 0.01961 mol/L
  2. 2. V = 583.3 L
  3. 3. VCSTR/VPFR = 1.443
  4. 4. CA = 1.145 mol/L
  5. 5. X = 93.75 %
  6. 6. X = 27.27 %

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