Residence Time Distribution

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The residence time distribution (RTD) of a chemical reactor or vessel is a description of the time that different fluid elements spend inside the reactor.

The concept was first proposed by MacMullin and Weber in 1935, but was not used extensively until P.V. Danckwerts analyzed a number of important RTDs in 1953.

[edit] Examples of RTDs

An ideal plug flow reactor has a fixed residence time: Any fluid that enters the reactor at time t will exit the reactor at time t + τ, where τ is the residence time of the reactor. The residence time distribution function is therefore a dirac delta function at τ.

An ideal continuous stirred-tank reactor has an exponential residence time distribution. The probability of a molecule of fluid that enters the reactor at time 0 exiting between times a and b is equal to \int_a^b \frac{e^{\frac{-t}{\tau}}}{\tau} \,dt, where τ is the mean residence time of the reactor.

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[edit] References

  1. R.B. MacMullin and M. Weber (1935). "The theory of short-circuiting in continuous-flow mixing vessels in series and kinetics of chemical reactions in such systems". Transactions of American Institute of Chemical Engineers 31 (2): 409–458.
  2. P.V. Danckwerts (1953). "Continuous flow systems. Distribution of residence times.". Chemical Engineering Science 2: 1–13.
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