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  CHEMICAL ENGINEERING WWW.CHE.COM APRIL 2014 73

Environmental Manager

In my October 2011 column (A

window into kettle reboiler se-crets, Chem. Eng. p. 28) I brieflydescribed FRI’s early work using

two windows on its industrial-sizekettle reboiler. Subsequent to that,FRI had performed appreciableheat-transfer work. All of that workwas reported to FRI’s members atall-day kettle-reboiler symposia,which were held in Galveston, Tex.on October 2 and in Tokyo on No- vember 20 (both 2013). All of thefeedback that was received during

those meetings was documentedand considered. Another sympo-sium will be held in Ludwigshafen,Germany, on September 25, 2014.Professors Ken Bell and Rob White-ley of Oklahoma State University,who were mentioned in the October2011 column, continue to consult forFRI regarding heat transfer work.

During the last two years, one ofFRI’s focus areas was the entrain-ment of liquid droplets out of the vapor product nozzle. FRI added

two new windows to the kettle, atthe steam-header end of the heatexchanger. Entrainment is now vis-ible from four different windows.Tracerco (Pasadena, Tex.; www.tracerco.com) personnel have col-lected gamma-scan data from the vertical and horizontal sections ofthe vapor-product piping. Thosedata were easily converted to liquidentrainment data [liquid(L)/vapor(V) basis]. Pressure drop data werecollected across that same pip-

ing and were compared againsttheoretical calculations. When thekettle was entrainment-flooded,according to visual observations,the measured pressure drops devi-ated from (became higher than) thetheoretical values.

Subsequent to the 2011 column,appreciable data were collected re-garding boiling pool depths and max-imum horizontal vapor velocities,in other words, the points at whichexcessive liquid droplets were sweptup from the boiling pool. Tony Caideveloped a boiling-pool depth corre-lation; the impact of steam rate (re-

boiler duty) was surprisingly weak.

Cai also developed a maximum,horizontal vapor-velocity correla-tion. Both of those correlations wereapplied to a literature kettle floodpoint (Kister, H.Z. and Chavez, M.A.,Kettle Troubleshooting, Chem. Eng.,February 2010, pp. 26–33). Cai’s cor-relations successfully predicted thatindustrial experience.

On four separate occasions, FRIattempted to run its kettle in “semi-thermosiphon mode.” Specifically,the liquid level in the bottom of the

column was raised until the vaporreturn nozzle (from the kettle) wascompletely flooded with liquid.FRI’s column has windows placedexactly opposite the kettle vapor-return nozzle. Video footage ofthat liquid-submerged nozzle was“amazing.” This semi-thermosiphon

mode of operation was performedwith three different binary systemsacross a broad range of pressures.The column proved to be easily con-trollable. Windows farther up on thecolumn were used to assure that theliquid level in the bottom of the col-umn was not so high as to reach the

packings that were located fartherup in the column.

FRI engineers will present apaper regarding this work on April2 at the AIChE Spring Meeting(New Orleans, La.; www.aiche.org). Video footage will be shown. ■

 Mike Resetarits

Fractionation Column

A better look into kettle reboilersMike Resetarits is the technical direc-tor at Fractionation Research, Inc. (FRI;

Stillwater, Okla.; www.fri.org), a distilla-tion research consortium. Each month,Mike shares his first-hand experiencewith CE  readers

For more information, call Wright’s Media at 877.652.5295 or visit our

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