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Practical Refinery Distillation Technology
3 Day Troubleshooting Program

Now Offering In Person Courses

About the Course

INTRODUCTION

  • This down-to-earth course gives comprehensive coverage of refinery distillation technology, with particular emphasis on the problems that can occur and how to solve them. 

  • It provides an excellent opportunity to develop a working knowledge of key techniques that can promote trouble-free operation and reduce distillation cost.

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WHO SHOULD ATTEND

  • Engineering and supervisory personnel who are involved in -

    • Operating

    • Troubleshooting

    • De-bottlenecking

    • Designing

    • Starting up of distillation processes​

YOU WILL LEARN HOW TO

  • Troubleshoot a distillation column and determine what may cause poor performance

  • Anticipate and address common problems in various sections of a main fractionator

  • Evaluate existing column performance and develop new designs

  • Avoid common causes of capacity bottlenecks, tray damage, downcomer unsealing problems, packed tower distributor malfunctions and many other operating difficulties

  • De-bottleneck a column to improve capacity and/or separation

  • Control and operate a distillation column

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CASE STUDIES

  • Case studies will be scattered throughout, brought in to illustrate the principles

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AFTER-HOURS INFORMAL SESSION

  • This optional session, which will be held following the program on day one, is an opportunity to discuss items that are not on the formal program and take longer to discuss.

  • Participants are encouraged to bring materials in a form that can be projected on the screen so that everyone in the audience can view and discuss.

  • Participants are also encouraged to bring with them backup material (tray and tower drawings, gamma scans), as often innocent-looking details turn to be major issues.

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Course Program

Day One

LESSONS FROM 50 YEARS OF TOWER MALFUNCTIONS

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  • What malfunctions should troubleshooters look for? Do the malfunctions repeat themselves?

  • The top 10 malfunctions experienced in distillation towers: plugging/coking, tower base, internals damage, startup/shutdown mishaps, installation mishaps, packing distributors, intermediate draws, misleading instrumentation, reboilers, controls. How can these malfunctions be alleviated?

  • Water in hot oil fractionators: the #1 cause of trays/packing damage.

  • Submerging feed and reboiler return inlets: how it induces premature floods, tray/packing damage or even overfills.

  • The plugging challenge: can it be alleviated?

         

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TRAY HYDRAULICS & LIMITS

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  • Visualization of flooding, entrainment, foaming, weeping, dumping, vapor-liquid dispersions on trays: how pumparound dispersion differs from wash-section dispersion?

  • Flood mechanisms: jet (entrainment), system limit, downcomer backup, downcomer choke: which one is likely to limit your column capacity? Do simulations contain trustworthy flood predictions?

  • C-factors: are they useful for operation?

  • Common tray types: sieve, moving valve, fixed valve, shed decks: pros and cons. Which works well in fouling services?

  • Small holes, valves: benefits and traps.

  • Hole area: can too much lead to troubleshooting assignments?

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TROUBLESHOOTING TRAY TOWERS

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  • Flooding symptoms: high dP’s, reduced bottoms, others. Which can be trusted?

  • Liquid and vapor-sensitivity field tests: identifying the likely flood mechanism.

  • dP plots: getting the most out of your plant data to diagnose floods.

  • Dealing with foams in amine, hydrocarbon absorption, and preflash units.

  • Downcomer unsealing: why many crude and FCC fractionators require excess wash and how to reduce.

  • Gamma scans: application for detecting flooding, missing and damaged trays, foaming, and downcomer flooding.

  • How to combine gamma scans with process checks to get the most out of the scans and avoid misinterpretation: the four keys to success.

Day Two

REFINERY FRACTIONATORS: ZONES AND OPERATION

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  • Complex (multi-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/ towers are used and what are their issues.

  • Similarities and differences between atmospheric crude, FCC, and coker fractionators.

  • Absorbers and strippers: what drives these columns (temperature, L/V, steam)

         

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REFINERY FRACTIONATOR OPTIMIZATION

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  • To what extent does improving separation enhance yield of a desirable product?

  • Changes in cut point: how do they affect a fractionator? Can they lead to flooding or aggravate a condenser limitation?

  • Maximizing pumparound (PA) duty: how does it affect the tower and what are the constraints? Should a product be drawn above or below the PA?

  • Shifting duty between PA’s: can maximizing PA destabilize a fractionator?

  • Some rules of thumb for main fractionators: stripping rates, tray efficiencies.

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CONCEPTS UNIQUE TO REFINERY VACUUM TOWERS

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  • Vacuum tower wash zones: the most troublesome zone of refinery fractionators. How much wash keeps packing wet?

  • 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?

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TROUBLESHOOTING TECHNIQUES UNIQUE TO REFINERY TOWERS

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  • Mass and heat balance troubleshooting: how these detect insufficient wash, overflows.

  • Drawing out heat and mass balance envelopes for multi-draw towers.

  • Leak/overflow/excess weep detection: the symptom of low temperature while making more heavy distillate.

  • Checking sprays: plugged? broken?

  • Simple tests that teach a lot about the nature of the bottleneck.

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TROUBLESHOOTING REFINERY PACKINGS

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  • Visualization of normal and flooded packing operation.

  • Rules of thumb for flood pressure drop and packing efficiency.

  • Simulation hydraulic calculation: to trust or not to trust?

  • Grid gamma scanning for detecting maldistribution, damage, distributor malfunction, distributor and collector overflows.

  • Distributor, collector, and parting box overflows: DEATH for packed beds. How to diagnose and how to avoid.

  • Can poor distributor feeding bottleneck towers?

  • Temperature surveys: application for simulation and maldistribution checks.

  • Neutron backscatter and CAT scans: what can they reveal that regular gamma scans cannot.

Day Three

DEBOTTLENECKING REFINERY TOWERS

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  • Factors that favor trays and factors that favor packings.

  • The pressure drop bonanza: why packings win in vacuum towers and in compressor suction, and in the path of a fan.

  • Should packings be used in fouling services, or are trays the better choice?

  • How do packings and trays compare on capacity and efficiency: can tray modification compete with packing atmospheric fractionators?

  • What happens to structured packings at high pressure?

  • Experience with structured packing fires in fractionators: what were some of the lessons learnt.

  • High-capacity trays (e.g. Superfrac®, VG Plus®, Hi- Fi®, MD®): principles, tricks and traps. Do they really give 30% more capacity than conventionals?

  • Some simple schemes that successfully debottlenecked complex fractionators: preflash towers, HAGO draw.

         

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DISTILLATION CONTROL

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  • Assembling control loops into an overall scheme: what works, what causes instability, and what impairs efficiency.

  • The 3 most common causes of control assembly failure: no material balance control, fighting between temperature controllers, and level control on a small stream.

  • The No. 1 control problem in refineries: is your fractionator immune? 

  • Best temperature control location: is there a reliable method that can find? 

  • Condenser and pressure controls: which loops work and which misbehave.

  • How dead pockets in vapor overhead lines interfere with controls.

  • Understanding hot vapor bypasses: why some work while others don’t. How to circumvent this No. 2 control problem in refineries. Good and bad practices.

  • Reboiler control: Does it make a difference if the control valve is in the steam or condensate?

  • Impact of valve location on energy efficiency, reboiler fouling and corrosion, loss of reboiler seal, hammering, reboiler stall, and tube leaks.

  • Control systems that did not work.

 

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IDENTIFYING AND REMOVING POTENTIAL TOWER MALFUNCTIONS

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  • This elaborates on the lessons learnt in the malfunctions survey (Day 1).

  • Points of transition (feeds, side draws, tower base): why these are some of the most severe tower bottlenecks.

  • Drawing sketches (to scale) to troubleshoot these internals: you need a sketch, not an expert.

  • High tower base levels: how they induce premature flood, tray/packing damage, tower overfills, and how to prevent.

  • Common instrument problems at the tower base: what to watch out for.

  • Examining operation charts: what happened first?

  • What are the common ways water finds its way into a fractionator.

  • Accumulator trays: do’s, don'ts, and how they bottleneck fractionators.

  • Common accumulator tray problems: overflow, hydraulic gradients, liquid bypassing.

  • Liquid outlets: choking in sidedraw rundown lines and how it restricts fractionator capacity.

  • Kettle reboilers and once-through thermosiphon reboilers: why are they common causes of bottlenecks.

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