Working Principles, Material Selection, Applications, and Maintenance Guide

Working Principles of Demister Pads

Demister pads operate by intercepting liquid droplets in gas streams through inertial impaction, coalescence, and gravitational settling. The wire mesh structure creates a tortuous path for gas flow, forcing droplets to collide with the mesh wires. These droplets coalesce into larger masses, which then fall back into the system due to gravity. This process ensures purified gas exits the system while minimizing liquid carryover.

Key factors influencing efficiency include:

• Mesh density: Higher density increases droplet capture but raises pressure drop.

• Wire diameter: Thinner wires enhance surface area for droplet adhesion.

• Pad thickness: Optimal thickness balances separation efficiency and airflow resistance.

Material Selection for Wire Mesh

Material choice depends on operational environments and chemical compatibility:

1. Stainless Steel (SS 304/316): Ideal for general-purpose applications due to corrosion resistance and durability. Suitable for oil refineries and petrochemical plants.

2. Alloy Metals (Hastelloy, Monel): Used in highly corrosive environments (e.g., sulfuric acid production).

3. Polypropylene (PP) and PTFE: Lightweight, non-reactive options for pharmaceutical or food-grade applications.

Wire Specifications:

• Diameter: Ranges from 0.1 mm to 0.3 mm, balancing strength and surface area.

• Weave pattern: Standard plain weave for moderate efficiency; multi-layered designs for high-moisture conditions.

Industrial Applications

Demister pads are integral to:

1. Oil & Gas: Remove entrained hydrocarbons from gas streams in scrubbers and distillation columns.

2. Chemical Processing: Separate acid mists in sulfuric acid plants.

3. Power Generation: Capture moisture in flue gas desulfurization (FGD) systems.

4. Environmental Engineering: Mitigate aerosol emissions in wastewater treatment facilities.

Maintenance Best Practices

Proper maintenance ensures longevity and performance:

1. Regular Inspection: Check for clogging, corrosion, or physical damage. Use non-destructive testing (NDT) for high-risk environments.

2. Cleaning: Remove fouling with pressurized air or chemical solvents. Avoid abrasive methods that damage mesh integrity.

3. Replacement Indicators:

   • Persistent pressure drop increases (>15% baseline).

   • Visible deformation or broken wires.

4. Storage: Keep pads dry and coated with anti-corrosion agents if stored long-term.