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Calcimator

Reactor Sizing Calculator

Size CSTR and PFR reactors for first-order reactions using the design equation V = FA0·X/(−rA).

Inputs

L/min
mol/L
1/min
(1=CSTR, 2=PFR)

Results

Reactor Volume

400 L

≈ 5 wheelbarrows

Residence Time

40 min

Space Time (τ)40 min
Exit Concentration0.4 mol/L
How to Use This Calculator
  1. Enter the Feed Volumetric Flow Rate in L/min and the Feed Concentration in mol/L.
  2. Enter the Target Conversion as a decimal (e.g., 0.80 = 80% conversion of the reactant).
  3. Enter the First-Order Rate Constant (k) in 1/min at the operating temperature — obtain from kinetics experiments or literature.
  4. Select the Reactor Type: 1 for CSTR (Continuously Stirred Tank Reactor, well-mixed) or 2 for PFR (Plug Flow Reactor, unmixed axially).
  5. Read the Reactor Volume in liters — a PFR always requires less volume than a CSTR for the same conversion and first-order kinetics.
  6. Review the Residence Time (τ) in minutes and Exit Concentration in mol/L to confirm the design meets purity requirements.

How the result changes with Target Conversion

Target ConversionReactor VolumeResidence Time
0.1112.11 L1.21 min
0.3554.56 L5.46 min
0.65183.29 L18.33 min
0.89825.93 L82.59 min

What each input means

Feed Volumetric Flow Rate
Volumetric flow rate of the feed entering the reactor.
Feed Concentration
Molar concentration of the reactant in the feed stream (CA0).
Target Conversion
Desired fractional conversion of the reactant (0 to 1).
Rate Constant (k)
First-order reaction rate constant at operating temperature.
Reactor Type
Select 1 for CSTR (Continuously Stirred Tank Reactor) or 2 for PFR (Plug Flow Reactor).

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Feed Volumetric Flow Rate = 10, Feed Concentration = 2, Target Conversion = 0.8, Rate Constant (k) = 0.1 = 5 input(s) provided
  2. Calculate Reactor Volume
    Reactor Volume
    400 = 400
  3. Calculate Residence Time
    Residence Time
    40 = 40
  4. Calculate Space Time
    Space Time
    40 = 40
  5. Calculate Exit Concentration
    Exit Concentration
    0.4 = 0.4

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