Batch Reactor Design Questions and Answers

Answer: A

Correct answer: an inflow and a generation term

A semi-batch reactor is fed but not discharged, so the balance keeps the accumulation, the generation and the inflow, and loses only the outflow: \[ \frac{\mathrm{d}N_i}{\mathrm{d}t} = F_{i0} + r_iV. \] The volume changes as the feed enters, which must be allowed for when concentrations are computed from mole numbers.

Answer: B

A batch reactor is unsteady by definition, since everything changes with time. The other three are the practical consequences that follow from that. Nothing in a batch vessel is at steady state. Time is the independent variable throughout.

Answer: C

The first two are correct and are the two real difficulties. The third is wrong, since the chemistry is unchanged and it is the physical environment that differs between the laboratory and the plant. Chemistry is scale independent.

Answer: D

Reaction calorimetry gives the heat output against time and can be compared with what the jacket can actually remove. This comparison is what a proper scale-up assessment rests on. Peak heat release is the number that matters.

Answer: A

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

Both are true and the reason gives the purpose. A reaction calorimeter measures the heat release rate against time on a laboratory scale, and that curve can be compared directly with what the plant vessel’s jacket can remove - which the scaling item shows will be proportionally less. If the peak release exceeds the cooling, the process must be changed to semi-batch, diluted or run cooler before it goes anywhere near a plant.

Answer: B

For second order the time is the conversion divided by the rate constant times the initial concentration times one minus the conversion, that is four over point one. The dependence on initial concentration is what distinguishes second order.

Answer: C

The rate depends on concentration squared, so a more concentrated start reaches a given conversion sooner. For first order the time is independent of the starting concentration. Order decides whether concentration enters.