Isopropanol.
Acetone is to be produced by the dehydrogenation of an aqueous solution of
isopropanol according to the reaction:
The effluent from the reactor enters a phase separator that separates vapor from
liquid. The liquid contains the bulk of the product, and the vapor is a waste
stream. The vapor stream is at a temperature of 30ºC and an absolute pressure of
1.1 bar. The component flowrates in the vapor stream are given in Table 3,
together with their raw material values and fuel values. Three options are to be
considered:
a) Burn the vapor in a furnace
b) Recover the acetone by absorption in water recycled from elsewhere in the
process with the tail gas being burnt in a furnace. It is expected that 99% will be
recovered by this method at a cost of 1.8 $/ Kmol acetone recovered.
c) Recover the acetone by condensation using refrigerated coolant with the tail
gas being burnt in a furnace. It is anticipated that a temperature of –10ºC willneed to be achieved in the condenser. It can be assumed that the hydrogen is an
inert gas that will not dissolve in the liquid acetone. The vapor pressure of
acetone is given by:
The cost of refrigerant is 11.5 $·GJ–1, the mean molal heat capacity of the vapor is
40 kJ·kmol–1·K–1, and the latent heat of acetone is 29,100 kJ·kmol–1. Calculate the
economic potential of each option given the data in Table 3.
Table 3
