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  • Demister Pad

Working Principle of Demister Pad

When mist in the gas rises at constant speed, then the mist eliminator works where, vapour strikes the mesh surface filament and liquid start coalescing. After some time, liquid droplet size goes up and it gets isolated from the filament

S CUBE Mist eliminator

Mist elimination, or the removal of entrained liquid droplets from a vapor stream, is one of the most commonly encountered processes regardless of unit operation. Unfortunately, mist eliminators are often considered commodity items and are specified without attention to available technologies and design approaches. The engineered mist eliminator may reduce liquid carryover by a factor of one hundred or more relative to a 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 maintenance cycles using proven and cost effective technologies and techniques. S cube mist eliminators offer a robust remedy for liquid entrainment challenges in various equipment, including:

  • Scrubbing, absorption, stripping, or distillation towers
  • Evaporators
  • Folling film condensers
  • Sedimentation vessels
  • Tri-phase separators
  • Desalination facilities
  • Cooling systems
  • Gas moisture removal plants
  • Compression mechanisms.
MistEliminitor_MisteliminatorTop

Working Principle of Demister Pad

When mist in the gas rises at constant speed, then the mist eliminator works where, vapour strikes the mesh surface filament and liquid start coalescing. After some time, liquid droplet size goes up and it gets isolated from the filament

MistEliminitor_SCUBEMisteliminator-2

Liquid entrainment within a process gas stream can originate from dynamic activities,like the interaction between gas and liquid phases during a mass transfer task, or from thermal actions such as condensation. For instance, droplets might emerge when bubbles burst or jet at a gas/liquid boundary, commonly seen in distillation columns, evaporators, bubble columns, and inundated packed bed scrubbers. High relative speeds between gas and liquid can also shear droplets from moistened surfaces, a scenario often witnessed in venturi scrubbers, dual-phase flow within pipes, and packings.

Advantages & Features

  • Can handle liquid volumes up to three times that of regular mesh pads.
  • Demonstrates a 20% higher vapor capacity compared to standard technology.
  • Compatible with all mesh pad varieties, even those made from combined materials.
  • Customizable to fit a variety of vessel dimensions and forms.
  • An economical and adaptable choice for numerous mist elimination needs.
  • Simple to manage and set up, seamlessly fitting between current double rings (both top and bottom supports).

Common Uses

  • Upgraded towers with the newest packings and trays requiring mist eliminators due to increased vapor flowrates or entrainment.
  • Enhancements to existing knock-out drums, eliminating the cost of buying a new vessel.
  • Scenarios with high pressure where the difference between vapor and liquid density is minimal.
  • Systems with low surface tension, like NGLs, where secondary droplet atomization is dominant.
  • Positioned beneath a high-capacity vane; the mesh pad readies and merges fine droplets for capture by the vane, while troughs channel the accumulated liquid to the vessel's edge.
  • In high turndown cases - up to 50% more than traditional pads - where superior droplet removal is crucial, even during plant initiation or transitional phases.

Primary Attributes

  • Achieves high-efficiency separation for droplets as small as 2 to 3 µm.
  • Usually experiences a pressure drop below 2.5 mbar.

Various mist eliminators exist for the task of separating entrapped liquids. When determining the right tool, it's essential to understand the four primary droplet capture methods:

Diffusional Deposition

Deposition is primarily effective for separating ultra-fine aerosols, typically those with droplets under 1µm in size. These droplets are minute enough to be influenced by Brownian Motion.

Direct Interception

operates on the idea that a droplet, with a specific diameter and negligible weight, will follow the gas flow around a 'target' wire or fiber. The droplet is then separated when it comes into contact with the target or collecting fiber.

Inertial Interception

takes into account the weight of the droplet, predicting how its momentum will cause it to diverge from the gas flow.

Gravitational Deposition

is based on the concept that large, slow-moving droplets might naturally separate from a gas flow due to gravity. However, this method is limited to bigger droplet sizes and minimal gas speeds, often resulting in impractically large and cost-inefficient separator dimensions.

The effectiveness of each mechanism heavily relies on the droplet size distribution specific to an application. For instance, in gas drying tasks using glycol contactors, droplet sizes typically range between 5-25 µm, and achieving a high separation efficiency is paramount. Under such conditions, direct and inertial interception prove to be the most suitable methods. The best separation results are obtained when droplets impact the wires of top-tier mesh mist eliminators.

Types of Mist Eliminator

MistEliminator_SCMPLAINVVNew

SCM PLAIN VV

Features plate-style vanes designed for separating entrained droplets.

MistEliminitor_SCMSINGLEHOOKEDV

SCM SINGLE HOOKED V

Equipped with an additional vane to enhance mass transfer efficiency.

MistEliminitor_SCMDOUBLEHOOKEDVNew

SCM DOUBLE HOOKED V

Incorporates two supplementary vane plates, adjusted for optimal vane angles, to achieve improved performance outcomes.

Subtypes of the Mesh Type Demister Pad

Different types of Mesh Type Demister pad are classified on the basis of mesh density has been mentioned in the below chart-

Style Material Application Wire

Diameter

mm

 Mesh density

Kg/m3

 Surface Area

m2/m3

 Voidage

%

 Nominal Micron Rating*
SCM-A1 Metals Very high efficiency in clean service 0.15 195 650 97.5 3µ
SCM-A2 Metals Fine droplet removal in clean service 0.15 145 480 98.2 4µ
SCM-A3 Metals General purpose, clean service 0.15 112 375 98.6 5µ
SCM-B1 Metals Optimum efficiency & pressure drop 0.275 195 355 97.6 5µ
SCM-B2 Metals General purpose, not totally clean 0.275 170 310 97.9 6µ
SCM-B3 Metals Heavy duty e.g. oil & gas separators 0.275 145 265 98.2 8µ
SCM-C1 Metals Light fouling 0.275 110 200 98.6 10µ
SCM-C2 Metals Moderate fouling 0.275 80 145 99.0 12µ
SCM-C3 Metals Heavy fouling e.g. evaporators 0.275 50 90 99.4 15µ
SCM-PP1 Polypropylene Acid mists 0.25 75 1120 93.0 3µ
SCM-PP2 Polypropylene Chemical Scrubber towers 0.25 50 750 95.3 6µ
SCM-T Teflon Very corrosive services 0.25 64 480 97.0 8µ
SCM-PP3 Polypropylene Low pressure drop e.g. air scrubbers 0.25 33 490 96.9 10µ
SCM-A1X Metal/PP Mix Mist removal of polar/Non- polar mixtures 0.25 200 625 95.6 5µ

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