Refinery Distillation Extension: Practical Tools and Techniques

Refinery Fractionators: Zones and Operation

Simple columns: stages, reflux, stages-reflux relationship. Complex (muti-side-draw) columns: are they simple columns stacked on top of each other? Cut points, overlaps, gaps: how they reflect separation quality. Functions of the different sections of refinery fractionators: fractionation, pumparound, wash, stripping. Which sections are prone to damage, coking, salting out and which are generally well-behaved. Why preflash drums are used. Similarities and differences between atmospheric crude, FCC, and coker fractionators. Absorbers and strippers: what drives these columns (temperature, L/V, steam)

Refinery Fractionator Optimization

To what extent does improving separation enhance yield of a desirable product? Colder and warmer temperatures: how do they correlate to product composition? Changes in cut point: how do they affect a fractionator? Can they lead to flooding or aggravate a condenser limitation? Maximizing pumparound duty: how does it affect the tower and what are the constraints? Some rules of thumb for main fractionators: stripping rates, tray efficiencies.

Concepts Unique To Vacuum Crude Towers

Zones of a vacuum tower and their function. Vacuum tower wash zones: the most troublesome zone of refinery fractionators. Why must a minimum overflash be maintained. How poor flash zone simulation can lead to wash zone coking. True vs. Measured overflash: what is worthless wash? Maximizing gas oil yield. Can tall or efficient wash beds impair capacity or lead to coking? Sprays: good and bad practices. Conventional vs. new vapor horns: to replace or not?

Troubleshooting Techniques Unique To Refinery Towers

Mass and heat balance troubleshooting: how these detect leaks, overflows. Drawing out heat and mass envelopes for multi-draw towers. Leak/overflow/excess weep detection: the symptom of low temperature while making more heavy distillate. Simple tests that teach a lot about the nature of the bottleneck.

Turnaround Inspection of Refinery Fractionators

The most common assembly mishaps: installation of distributors, packing, tray panel and downcomer clearance assembly, loose bolts, nuts, manways, leaking collectors, obstruction and mis-orientation of feed and draw pipes: "musts" on the inspection list. Inspection tools, techniques, what to look for in an inspection.

Debottlenecking Refinery Towers

Do all sections of the fractionator need modification in a revamp? Factors that favor trays and factors that favor packings: why packings win in vacuum towers and in compressor suction. Should packings or trays be used in fouling services? What happens to structured packings at high pressure? High-capacity trays (e.g. MVG, Nye, Superfrac, Hi-Fi): do they really give 30% more capacity than conventionals? Some simple schemes that successfully debottlenecked complex fractionators: preflash towers, HAGO draw.

Note: This program is based on material presented in the past and may be modified by the presenter. A final program will be available prior to the course.