Mist Eliminators

Mist eliminators effectively separate mist from a gas stream, aiding in the recovery of valuable products, enhancing emissions control, protecting downstream equipment, and raising product purity. The image below depicts fiber bed mist eliminators.

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Wire-Mesh

Among the most prevalent types, wire-mesh mist eliminators utilize knitted wire mesh pads to eliminate entrained liquid droplets from gas streams.

General Information

Wire-mesh mist eliminators, like the one depicted here, consist of knitted metal mesh. This type is highly effective for removing liquid droplets as small as 3mm in diameter from gas streams with velocities exceeding 1 ft/s. While primarily used in vertical flows, wire-mesh can also be employed horizontally.

The effectiveness of wire-mesh mist eliminators can be attributed to their operational efficiency, minimal pressure drop, and low costs associated with capital and operation.

Equipment Design

Impingement mist eliminators extract liquid droplets from gas streams through three mechanisms: inertial impaction, direct interception, and Brownian diffusion. All methods necessitate that the mist contacts the wire mesh, allowing for the separation of liquid droplets from the gas stream.

(Animation based on schematic courtesy of Amistco Separation Products Inc., Alvin, TX)

The mesh is crafted from woven metal fibers, often layered for enhanced permeability control. A typical mesh pad measures approximately six inches thick, with diameters generally three to five percent greater than the equipment's diameter, minimizing bypass fog.

Usage Examples

Wire-mesh mist eliminators are commonly utilized within gas-liquid contacting towers. For instance, the fume hoods shown below, integrated with mesh pad mist eliminators, effectively eliminate 99% of mists down to 2 microns.

Advantages

• Exceptional efficiency.
• Economical to purchase and operate.
• Compatible with existing equipment.
• Customizable pads to achieve target efficiencies.

Disadvantages

• Higher pressure drop compared to baffle-type eliminators.
• Not efficient for droplets smaller than 3mm in diameter.
• Efficiency declines as the droplet size increases.
• Possible clogging issues with pads.

Fiber-Bed

Fiber-bed mist eliminators feature columns of fibrous materials that effectively extract mist from a gas stream as it flows through.

General Information

These eliminators are adept at removing minute liquid droplets from gas streams and are particularly advantageous for substantial liquid flow rates and droplets smaller than 3mm in diameter. However, fiber beds are restricted to gas flow rates between 3 to 10 m/min and entail a significant pressure drop.

Designed to facilitate horizontal, concurrent gas stream flow through the bed, fiber beds are unsuitable for upward gas flow.

Equipment Design

Similar to wire-mesh mist eliminators, fiber beds operate by promoting contact between liquid droplets and fibrous material via inertial impaction, direct interception, or diffusion.

As illustrated by the vent system shown here, two fiber beds treat incoming air mixed with mist, eliminating and collecting liquid before ejecting clean exhaust. The drained liquid can be repurposed based on its nature.

With a competitive price and prompt delivery, ZHUAN LV aims to be a trusted supplier and partner.

Usage Examples

Fiber beds predominantly serve to eliminate very fine mists, often produced from shock-cooling condensable vapors. These systems are widely utilized for acid mist removal, such as within sulfuric acid plants.

Advantages

• Capable of removing droplets smaller than 3 micrometers in diameter.
• Consistently achieves efficiencies between 95% to 99.9%.
• Large surface area facilitates the removal of high liquid volumes.

Disadvantages

• Results in significant pressure drops.
• Only suitable for vapor flow rates below 10 m/min.
• Potential drainage issues can lead to clogging.
• Infeasible for vertical gas flow applications.

Baffle-Type

Baffle-type mist eliminators, known also as chevron or vane eliminators, alter the gas flow’s direction to capture liquid droplets on the baffle surface.

General Information

These devices are suitable for both vertical and horizontal gas flows. Baffle-type mist eliminators generate minimal pressure drop, rendering them favorable for processes prioritizing pressure conservation. However, they primarily handle droplets larger than 3 micrometers in diameter and effective velocities surpassing 500 ft/min.

Equipment Design

Baffle-type mist eliminators prompt gas flows to change direction, leading to droplets contacting surfaces for separation via inertial impaction, direct interception, or diffusion. Although they may be less effective for minute droplets, they incur little pressure drop.

Typically favored in high-flow horizontal gas applications, these eliminators excel in scenarios where the entrained liquid includes undissolved solids.

Usage Examples

Louver-type baffle mist eliminators, characterized by multi-row blades angled between 30° to 60°, are commonplace in cooling towers, adept at removing moisture from exiting air.

Should you desire additional information on fiber bed mist eliminators, please feel free to contact us.

Advantages

• Extremely low pressure drop.
• No clogging; effective for streams with solid particulates.
• Adjustable blade spacing for desired outcomes.
• Simple fabrication process.
• Capable of handling high volumes.

Disadvantages

• Ineffective for droplets smaller than 3mm in diameter.
• Gas velocity regulation is necessary to prevent re-entrainment.

Acknowledgements

References

• Brunazzi, Elisabetta and Alessandro Paglianti. "Design of Wire Mesh Mist Eliminators." AIChE Journal March: 505-512. Print.
• Capps, Ronald W. "Properly Specify Wire-Mesh Mist Eliminators." Chemical Engineering Progress Dec.: 49-55. Print.
• Fabian, Paul, and Roger Cusack. "Demystifying The Selection of Mist Eliminators: Part 1." Chemical Engineering Nov.: 148-156. Print.
• Fabian, Paul, and Roger Cusack. "Demystifying The Selection of Mist Eliminators: Part 2." Chemical Engineering Dec.: 106-111. Print.
• McKetta, John J. "Mist Removal Equipment, Design, and Selection." Encyclopedia of Chemical Processing and Design. 1st ed. Print.

Developers

• Daniel Viaches
• Christy Charlton
• Steve Wesorick
• Kelsey Kaplan