Runaway Reactions

Example - Using N/S vs. S Plot

The elementary gas phase reaction

is to be carried out in a PFR with external cooling. The entering pressure is 24.6 atm and the entering temperature is 227°C. The feed is 66.7% A and 33.3% inert. The ambient temperature in the heat exchange is constant at 500K. What is the largest tube diameter one can have and not have runaway.

Additional Information

Hint 1 - Calculate S

Hint 2 - Calculate N

Hint 3 - Find N/S for = 50

Hint 4 - Calculate d_t

Hint 1 Calculate S

at T = T₀

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Hint 2 - Calculate N

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Hint 3 - Find N/S for = 50

For S = 50 and a 2^nd order reaction (n=2) We find from Figure on the web  = 1.6

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Hint 4 - Calculate d_t

                                              One could have calculated the ratio.

                                                   One could have calculated the ratio.

                                                without calculating N separately.

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