Entrainment removal by a wire‐mesh separator

Abstract

The efficiency of a wire-mesh separator as an entrainment eliminator has been experimentally determined in an evaporator employing a sodium chloride brine to trace the entrainment throughout the system. Superficial linear velocities have been tested with efficiencies ranging from less than 80% at lower velocities up to 99.9% at 17 ft./sec. Higher superficial linear velocities were explored, but the results were erratic, with reentrainment from the separator visually evident. The experimental data have been correlated by the assumption, and development, of a proposed mechanip for the capture of the entrainment particles by the wires in the separator. This mechanism is developed from a theoretical derivation by Langmuir and Blodgett used for correlating the stoppage of mist particles by the leading edges of airplanes and has been found to correlate the experimental data very well, so that predictions in unworked ranges may be made. The separator as applied in this experimental work behaved as an impingement-type, inertial entrainment eliminator.The use of the presently developed equations permits the recommendation of specifications to be used in the fabrication of a separator for its most efficient performance if the nature of the entrainment and conditions of operation are known.Carryover, or carry along, of liquid particles (entrainment) in gas and vapor streams has been given much attention. Some of the recent and important studies evaluating the effect of entrainment in fractionating colunms are those of Souders and Brown ( 3 3 ) ; Holbrook and Baker (16) ; Rhodes (27,28) ; Sherwood and Jenny ( 3 2 ) ; Colburn ( 4 ) ; Rhodes and Slachman(29) ; Ashraf, Cubbage and Huntington (1) ; and Eduljee(6) ; and to evaluate the effect of entrainment in evaporators there have been the reports of Cessna and Badger (3) and O'Connell and Pettyjohn (25).More recently, however, methods for the removal of entrainment from gas and vapor streams has been the object of most study. These studies have involved the use of standard equipment such as the settling chamber, the cyclone separator, the centrifuge, screens, baffle plates, and their modifications. Typical of such studies are those of Pollak and Work(Z6), observing the performance of various types of cyclone separators; C. L. Carpenter is with Northern Chemical Industries, Inc., Searsport, Maine. Vol. 1, No. 4Campbell(2) the design and use of a special type of scrubber for the recovery of crude-oil mist from natural gas ; Lowrie-Fairs ( 2 3 ) the use of the Calder-Fox scrubber ; and Houghton and Radford(f7) the development of a new type of streamlined eliminator for removal of fine liquid droplets containing calcium chloride remaining in the air after local dissipation of natural fog by means of a spray of calcium chloride solution.Separators consisting of targets of fine wires or fibers upon which the droplets in a stream of entrainment-laden gas o r vapors are removed by filming on the filaments, have been found to be very effective. Hammond and Leary(l5) used a separator of...

Measurement of oil entrainment rates and drop size spectra from coalescence filter media

“…This has been done by electrostatic precipitation of the aerosol followed by gravimetric determination of the deposited mass (Conder and Liew, 1989;Raynor and Leith, 2000), or more recently by capturing the aerosol on a highefficiency filter placed further downstream (Contal et al, 2004;Mead-Hunter et al, 2013;Mullins et al, 2014). Others have used more indirect techniques such as condensation and weighing in the case of water mist (Carpenter and Othmer 1955;El-Dessouky et al, 2000), or even chemical precipitation and titration in the case of sulfuric acid (Bürkholz, 1970). In all these cases, the mass fraction actually obtained depends strongly on the placement of the capturing device downstream of the filter and there is no guarantee of collecting the entire size spectrum.…”

A high-precision method for calculating the pressure drop across wire mesh filters

“…Some methods for predicting the separation efficiencies of mesh pads were derived based on the droplet collection efficiency of a single wire, which was related to the Stokes number, Stk. However, in most cases, certain assumptions must be made Paglianti, 2000, 2001;Feord et al, 1993;Langmuir andBlodgett, 1944-1945;Carpenter and Othmer, 1955;Bradie and Dickson, 1969). With the advancements in measurement technologies, researchers have been able to experimentally investigate the relationship between separation efficiency and some macrostructural parameters (pad thicknesses, densities, specific surface areas, porosities, etc.).…”

Fog Water Collection Effectiveness: Mesh Intercomparisons

“…Models developed by Brunazzi and Paglianti (2000) following Langmuir and Blodgett efficiency equations (1946) and subsequent modifications (Carpenter and Othmer, 1955), to investigate demister efficiency revealed that calculation of Stokes number using diameter values underestimates collection efficiency of polypropylene strands and overestimates collection efficiency of metal strands.…”