Chemical Reaction Engineering

Interlude III

Reactor design for thermodynamically limited reactions

We will continue the discussion of ammonia synthesis we briefly covered in the Overview.

N2 + 3H2 → 2NH3

(R1)

Understanding ammonia synthesis technology is important for several reasons:

1.   High pressures are necessary to drive a reaction of the net negative stoichiometry.

2.   The net exothermic reaction needs high temperatures for reasonable reaction rates.

3.   The reaction is mildly exothermic. Therefore, at temperatures the reaction rates are reasonable, the equilibrium conversions are quite low, imposing a thermodynamic limitation.

Once these restrictions are imposed on the reaction, the design of the reactor has to be optimized by taking all these effects ...