1 reply to this topic

Dear All,

Seek assistance for calculating pressure drop in vacuum transfer line in Vac. Distillation Unit.
Given:
Flash zone pressure & temperatures and Furnace outlet temp (COT)

Delta P across box furnace is unknown. Required to calculate % vaporization at vacuum furnace outlet and velocity in transfer line.

Find difficulties to formulate the problem itself.

Any help will be solicited.

Thanks.

[djack77494]

If this is an actual design and not an academic exercise, I would tell you to seek expert help. Calculating the hydraulics of a vacuum tower transfer line is arguably the most difficult of all hydraulic problems. You are dealing with very low absolute pressures, so small inaccuracies are big errors. The distribution of your feed between the liquid and vapor phases varies a lot along the transfer line and is very sensitive to the pressure profile. Ditto for the velocities in the line. You cannot assume a single condition or estimate "an average" and do a straightforward calculation. Instead, you must divide the line into multiple segments or run it through a simulator. The issue is further complicated by the assertations of some experts that there is appreciable slip between the phases. This is a very interesting academic exercise, but don't hang your professional reputation on it if it's really more than an exercise.