Page 340 - Handbook of Thermodynamic Diagrams 1 : Organic Compounds C1 to C4

Appendix C

Examples for Thermodynamic Diagrams

Example 1 - Vessel Pressure

A vessel containing ethylene (C2H4) at 300 psia and 0 F is exposed to a fire in the process area. The
temperature in the vessel is 600 F when the fire is extinguished. Estimate the final pressure in the vessel.

Since the vessel size does not change appreciably, this situation maybe approximated by a constant volume
A
process. Using the thermodynamic diagram, the initial volume is about 0.43 ft 3/lb. At this same volume and final
temperature of 600 F, the pressure is:

P finttL_=_90Q_psia

Example 2 - Reactor Size

A batch reactor is to contain 2,000 Ib of ethylene (C2H4) at 1,000 psia and 200 F. Estimate the reactor
size.

A
Using the thermodynamic diagram, the volume is about 0.2 ft 3/lb of ethylene at these conditions.
Substitution of this into the equation below for the reactor size provides:
A
A
Reactor Size = (2.000 Ib) (0.2 ft 3/lb) = 400 ft 3

Example 3 - Process Vessel Size

A process vessel is to contain 500 Ib of ethylene (C2H4) at 200 psia and 0 F. Estimate the process vessel
size.

A
Using the thermodynamic diagram, the volume is about 0.75 ft 3/lb of ethylene at these conditions.
Substitution of this into the equation below for the process vessel size provides:
A
A
Vessel Size = (500 Ib) (0.75 ft 3/lb) = 375 ft 3

Example 4 - Heat Exchanger Duty

Ethylene (C2H4, 30,000 Ib/hr) at 1,000 psia and 0 F is heated to 600 F and then fed to a plug-flow reactor.
Estimate the heat exchanger duty necessary to accomplish the heating.

Substitution of mass flow and enthalpies from the thermodynamic diagram into the equation below provides:

Heat Exchanger Duty = mass flow (H, - H.) = (30.000 lb/hr)(240 - (-180)) BTU/lb

= 12.6 million BTU/hr

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