Design Manual Mist Eliminator - New

The Engineered Mist Eliminator

R EDUCE EDUCE COSTS INCREASE C APACITY  IMPROVE PERFORMANCE DEBOTTLENECK  EQUIPMENT SIMPLIFY  INSTALLATION CUSTOMIZE P ADS

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The Engineered Mist Eliminator

Table of Contents

Mist elimination, or the removal of entrained liquid droplets from a vapor stream, is one of the most commonly encountered processes regardless Introducti Introduction on . . . . . . . . . . . . . . . . . . . . . . . . . . .1 of unit operation. Unfortunately, mist eliminators are often considered commodity items and are specified without attention to available techDroplet Formation Formation and Size Distributions Distributions . . . .1 nologies and design approaches. The engineered mist eliminator may reduce liquid carryover by a factor of one hundred or more relative to a Mechanisms of Droplet Droplet Removal . . . . . . . . . .2 standard unit, drop head losses by 50% or more, or increase capacity by factors of three or four. This manual summarizes cost effective approaches to reducing solvent losses or emissions, extending equipment life and Types of Mist Eliminator Mesh & Materials . . .4 maintenance cycles using proven and cost effective technologies and techniques. Design Design Equations Equations . . . . . . . . . . . . . . . . . . . . . .6

Droplet Formation and Size Distributions

Entrained liquid does not consist of same-sized droplets, but as a broad range of droplet sizes that may be characterized with a Normal or Bell Distribution centered about some mean or average. The average droplet Inlet Diffusers . . . . . . . . . . . . . . . . . . . . . . . . . .7 size depends very much on the mechanism by which they are generated. Sizing equations are expressed in terms of the probability of removing a Vessel Vessel Configuration . . . . . . . . . . . . . . . . . . . .8 droplet of a given diameter, and mist eliminator performance is the integration or cumulative sum of individual removal efficiencies. It is Advanced Mist Eliminator Eliminator Designs . . . . . . . .10 therefore critical to know the approximate droplet size distribution in order to properly design a mist elimination system. Figure 1 show some typical size distribution Vane-Mesh Assemblies . . . . . . . . . . . . . . . . .11 FIGURE 1 curves from different sources. VOLUME FRACTION FREQUENCY DISTRIB DISTRIBUTIONS UTIONS Predicting Pressure Pressure Drop . . . . . . . . . . . . . . . .7

Use of Geometry . . . . . . . . . . . . . . . . . . . . . .11

FOR DISPERSIONS OF VARIOUS MATURITIES

In practice, designers or engineers do not MultiPocket™ Vanes . . . . . . . . . . . . . . . . . . .11 quantify or measure droplet size distribuCase Studies & Examples . . . . . . . . . . . . . .12 tions, rather they are assumed based on empirical data or expePlate-Pak Plate-Pak™ ™ and MistXper MistXpert™ t™ are trademar trademarks ks of rience. Fortunately, an ACS Industries, Inc. MaxFlow is a registered experienced engineer t r a de de m ar ar k o f AC AC S I n du du s t ri ri e s , LP LP a n d can assume an Mistermesh is a registered trademark of ACS Industries, Inc. Ripple Tray is a registered approximate distributrademark of Stone & Webster Engineering tion based on the Corporation. Kynar is a registered trademark of means or mechanism ELF Atochem North America, Inc. Teflon is a registered trademark of E.I. du Pont de Nemours by which the droplets are generated. Typical examples from common and Company. Hastelloy is a registered trademist sources are given to illustrate these concepts.  ® 

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mark of Haynes International, International, Inc. Goodloe ®  is a registered trademark of Koch-Glitsch, LP. ACS Industries presents the information in this publication in good faith, believing it to be accurate. However, nothing herein is to be construed as an express or implied warranty or guarantee regarding performance, merchantability, fitness for a

Fine droplet distributions, often called fogs  (