Mists and Aerosols
HOW Fiber Bed Filters and High-Efficiency Mist Eliminators Remove Liquid Emissions and Protect Industrial Operations
Mist elimination is the separation of liquid droplets from gas streams. Industrial mists and aerosols present a particular technical challenge because the droplet sizes span a wide range, from large visible droplets that are relatively straightforward to capture to submicron aerosol particles that require specialized high-efficiency collection technology. Selecting the right mist elimination technology requires understanding the droplet size distribution of the specific mist being controlled, the inlet liquid loading, the required outlet concentration and the chemical and physical properties of the liquid.
Condensable particulate matter forms when hot exhaust cools, creating fine liquid droplets that evade standard baghouse and cartridge dust collectors. CPM is subject to permit conditions requiring measurement and control using specialized technologies.
Fiber bed mist eliminators and wet electrostatic precipitators achieve up to 99.9% collection efficiency for submicron liquid aerosols, capturing the finest acid mist, oil mist and condensable particulate that conventional dry filtration cannot address.
Understanding Industrial Mist Emissions and Why They Require Control
Industrial mists are suspensions of fine liquid droplets in a gas stream. They are generated by a range of industrial processes including chemical reactions, evaporation and condensation, mechanical atomization from pumps and compressors, scrubbing operations and high-temperature process exhaust cooling.
Condensable Particulate Matter (CPM)
Condensable Particulate Matter (CPM) forms when hot exhaust cools creating fine particles that evade conventional dry filtration controls. Standard baghouse and cartridge dust collectors are designed to capture solid particles, they are not effective against liquid droplets and aerosols which pass through filter media or cause blinding and premature filter failure. CPM is regulated and is subject to permit conditions requiring measurement and control using specialized technologies.
Oil Mists
Oil mists from metalworking operations, rolling mills and compressed air systems are both a worker health hazard and a regulatory compliance issue. Oil mist from rolling mill operations also represents a recoverable product, as capturing and recovering rolling oil and recovering rolling oil reduces material costs and prevents environmental discharge.
Acid Mists
Acid mists including sulfuric acid mist, hydrofluoric acid mist, hydrochloric acid mist, phosphoric acid mist and nitric acid mist are among the most corrosive and heavily regulated industrial aerosols. They are generated in chemical manufacturing, fertilizer production, semiconductor fabrication and metal finishing operations. Acid mists cause rapid corrosion of unprotected downstream equipment and create serious worker health risks even at very low concentrations.
Fuming Acid Mist
Fuming acid mist from sulfuric acid, hydrofluoric acid, hydrochloric acid and other strong acid production processes must be controlled to meet environmental permit limits and protect both workers and surrounding communities from exposure to corrosive aerosols.
Mist Elimination Technology Comparison
| Criteria | Mist Eliminator | Fiber Bed Mist Eliminator | Venturi Scrubber | MicroMist Scrubber | WESP |
|---|---|---|---|---|---|
| Submicron collection | Low to moderate (primary collection of larger droplet) | 99.9%+ via Brownian diffusion | Moderate – above 1 micron | High – 99.9%+ | 99.9%+ via electrostatic |
| *Pressure drop | Low | Moderate | High | Low | Low |
| Liquid loading | Moderate – intermittent or lower liquid volume streams | Heavy liquid capable-continuous high liquid drainage without re-entrainment | High liquid loading | Low to moderate – low liquid waste generation | High liquid handling |
| Space requirement | Low – minimal footprint | Moderate – standard vessel sizing | Compact – smaller footprint suitable for retrofits | Compact – smaller footprint suitable for retrofits | Compact – smaller footprint suitable for retrofits |
| Best application | Scrubber outlet droplet separation | Acid mist, oil mist, CPM | CPM and particulate combined | Submicron CPM and trace metals | Submicron aerosol, sticky mist |
*specific pressure drop and efficiency values vary by application and system design
Technologies for Industrial Mist Elimination and CPM Control
Mist Eliminators
Mist eliminators remove entrained liquid droplets and aerosols from gas streams to meet environmental compliance and reduce corrosion. By separating liquid mist and soluble solid particulate from the gas stream before discharge, mist eliminators protect downstream equipment from liquid carryover and ensure clean gas output that meets regulatory requirements.
Fiber Bed Mist Eliminators (Candle Filters)
Fiber bed mist eliminators, also known as candle filters or fiber bed filters, are the highest-efficiency mist elimination technology available for industrial applications. They are specifically designed to capture and remove submicron liquid and soluble particulate from process gas streams using Brownian diffusion as the primary collection mechanism for the finest aerosol particles. Fiber bed mist eliminators achieve collection and removal efficiencies as high as 99.9% and enable recovery of valuable material even in heavy liquid loading situations.
MicroMist Scrubbers
MicroMist Scrubbers are specifically engineered to remove submicron particulate, condensable particulate matter and trace metals with low energy consumption and reduced liquid waste. They are designed for process-intensive industries where the combination of high collection efficiency, low operating cost and minimal liquid waste generation is a primary requirement.
Wet Electrostatic Precipitators (WESP)
Wet Electrostatic Precipitators remove fine particulates and acid aerosols using electrostatic collection rather than mechanical or diffusion mechanisms. The WESP charges particles and droplets electrostatically and collects them on grounded collection surfaces that are continuously wetted to flush collected material to the sump. WESPs achieve collection efficiencies over 99.9% for submicron aerosols and particulates in space-constrained installations where fiber bed systems cannot be accommodated.
CECO Environmental’s mist elimination systems are used across a broad range of industries. Turnkey package systems are designed to meet different capacities and eliminate process mist emissions for air pollution control. CECO provides complete mist elimination solutions including custom and standard fiber bed mist eliminator systems, repacking services, engineering consultancy and testing across the full lifecycle of the equipment.
More Than Equipment. Engineered for Industrial Air Excellence.
As the world’s most complete end-to-end industrial air quality platform, CECO Industrial Air spans every stage of the industrial air treatment process, from the point of generation through final compliance. We listen and solve, innovate and support, across every major global market, so nothing stands in the way of your operations.
