Retrograde Phenomena In Fluid Phase Equilibria

Occasionally the occurrence of retrograde condensation phenomena is encountered in the design of refineries and gas processing plants.  In this paper, we analyze retrograde phenomena in a typical natural gas mixture and then specifically address the occurrence of this phenomenon in hydrogen-containing systems.  It will be demonstrated that a very small change in the concentration of hydrogen can have a dramatic effect on the shape and location of the P-T phase envelope, especially on the bubble point locus.

 In light of the above analyses, we then provide an explanation to the observations made for two case histories reported for a naphtha unifiner reactor effluent stream and a high pressure bottoms liquid stream involved in a hydro-desulfurizing unit.  Both cases histories studied here involve petroleum fraction-rich streams containing a rather small concentration of hydrogen.

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