Let us look at the scope for inventory reduction in the process operated
at Flixborough. The output of the plant was about 50 000 tonnes/year KA.
Assuming a linear velocity of 0.5 m/s, it could all have passed through a
pipe 1.6 inches diameter. Any larger pipe is a measure of the inefficiency
of the chemical engineering. Actual pipe sizes ranged up to 28 inches, so
the cross-section of the pipe, and thus the flow rate, was (28/1.6)
2 = 300
times greater than the theoretical minimum. This is a bit unfair as the 28
inch pipes were made larger than necessary for the liquid flow so that the
gas pressures in the reactors were the same. Photographs of the plant
suggest that liquid lines were at least 12 inches diameter. The ‘inefficiency’
or ‘hazard enhancement’ index was thus (12/1.6)2 = 56. Was it possible to
reduce it?