Enhancing Dust Control Efficiency with Chemical Foam
Foam Dust Suppression
Using surfactants with water enhances the likelihood of fines colliding with droplets, effectively suppressing dust. The goal is to maximize the surface area of water droplets to increase contact with dust fines, thus minimizing water usage. To achieve this, some suppliers offer dust suppression systems that create chemical foam. Foam, due to its expanded surface area, improves the chances of dust-water contact. Certain foam bubbles agglomerate and hold dust particles together, while others burst upon contact, releasing fine droplets that adhere to smaller, more hazardous dust particles that are harder to capture and pose greater risks to human health.
Foam systems typically add only 2 liters per ton (2 quarts per short ton) of material with moisture additions ranging from 0.2 percent to 0.4 percent. This amount is significantly less than what straight water spray systems apply, making foam systems ideal where water resources are scarce or excessive moisture could compromise material performance, such as in coal-fired power plants. Reduced water usage also mitigates issues like screen clogging and material adherence to mechanical components and enclosures.
The process of creating foam involves blending surfactants and water, then passing this mixture through a device that incorporates air, adjusting the air/water/chemical ratio to produce foam ranging from very wet to "shaving cream" dry. Established foam can increase water's surface area by 60 to 80 times, facilitating effective dust control with minimal moisture addition.
The foam application system begins with mixing water with the foam-generating chemical. This mixture is metered by a proportioning pump and regulated through a flow regulator before entering the system. Compressed air, controlled by a second flow regulator, is combined with the water/chemical solution at a foaming canister, where foam is generated and directed through hoses to application nozzles installed in equipment walls or ceilings, or at transfer points.
Limitations of Foam Suppression
While foam technology benefits many applications, it also has drawbacks. Surfactants that produce excellent foaming may not always be the best wetting agents for the materials treated. Some suppliers prioritize chemicals that create stable foam without ensuring its effectiveness in overcoming the hydrophobic nature of the material. Effective wetting of the material is crucial before considering foam generation.
Generating foam requires compressed air, necessitating the installation and maintenance of a compressor if air supply is not readily available at the application site.
In comparison to conventional water-spray equipment, foam application systems are slightly costlier and generally require more maintenance.
Lastly, generating foam requires a higher volume of surfactant compared to typical wet-spray systems. However, due to the foam's expansion, less moisture is applied to the material, potentially offsetting costs through reduced thermal penalties on fuel performance resulting from decreased moisture addition.