Non-isothermal Reactor Design Questions and Answers

Answer: A

The rise is proportional to the conversion, so half of two hundred kelvin is one hundred. The linear relation between temperature and conversion is what makes adiabatic operation so easy to analyse. The line has a slope set by the adiabatic rise.

Answer: B

The balances cannot be written without the kinetics and the heat of reaction, and the hazard assessment must precede any decision about cooling. Specifying the hardware is the last step. Hazard assessment comes before hardware.

Answer: C

Correct answer: generation peaks where concentration is high

Reactant concentration is highest at the inlet, so that is where heat is generated fastest, while the cooling capacity per unit length is the same all along. The temperature therefore peaks somewhere near the front, and because the rate rises with temperature the peak can reinforce itself. Diluting the feed, staging the injection or grading the catalyst activity along the tube all flatten the profile.

Answer: D

The first two are correct and are what makes such reactors demand careful design. The third is exactly the danger, since the change can be abrupt and leaves little warning time. Design margins are set with this in mind.

Answer: A

Correct answer: True

Parametric sensitivity means the reactor’s behaviour depends discontinuously on a parameter - coolant temperature, feed concentration, flow rate - so that a small change past a critical value moves it from a bounded temperature profile to a runaway. It matters practically because the safe and unsafe conditions are not separated by any gradual worsening that would give warning.

Answer: B

A feed effluent heat exchanger returns the reaction heat to the incoming stream, so no external heating is needed once running. Starting such a system up requires an auxiliary heat source. The exchanger returns heat to the incoming feed.

Answer: C

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason is the difficulty. An autothermal system uses the product stream to preheat the feed, so once running it needs no external heat - but that arrangement provides nothing at all when the reactor is cold, since there is no reaction heat to recover. A start-up heater brings the feed to ignition temperature and is then withdrawn, and the same problem recurs after any shutdown.