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4. Foam Control Nozzles

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Foam is a dispersion of gas (typically air) in a liquid. Air/gas can be entrained via agitation at the surface, such as a spinning impeller partially out of the liquid or a stream entering the free surface of a liquid (e.g., where a waterfall meets the pool at its base) or be created by biological or chemical reactions or processes. Foam is undesirable because it can overflow vessels, create slippery and unsafe working conditions, interfere with processing, damage materials, and cause tanks to drain and dry slowly. Controlling foam can be accomplished by spraying liquid onto the surface of the pool, vessel or reservoir, and allowing the droplets of the spray to impact the foam bubbles, causing them to break.
 

Selecting a Foam Control Nozzle: 

Important factors to consider:

• Required coverage
• Static vs. moving fluids
  • If the contents of a tank, vessel are rotating, or the fluid is traveling in a trough or weir, a line of nozzles across the vessel can be used as the entire surface of the tank will pass under the line of nozzles after a complete rotation
• Available nozzle mounting locations
• Foam thickness and rate of build-up (required drop size for break-up and mitigation)
  • If the droplets are too small and have too little momentum they will bounce off the bubble surface with no effect
  • Similarly, if the droplets are too large and have too much momentum they will crash through the bubble and impact the liquid below, causing more foam to be generated
• Nozzle clog resistance
  • As the foam control fluid is commonly recirculated, containing solids or waste particles, selection of the nozzle with regard to clog resistance is important
• Available pressure drop (∆P) across the nozzle
  • ∆P = supply pressure at nozzle inlet - process pressure outside nozzle
  • Typical operating pressures range from 5-20 PSI (0.3-1.4 bar) to produce a suitble droplet size and velocity for effective foam mitigation
• Our experienced engineers can help determine which nozzle will perform as required with your design details

Common Foam Control Nozzle Uses and Industries:

• Waste management industry
• Pulp and paper industry
• Food processing industry
• Aeration and settling basins
• Aerobic and anaerobic digesters
• Mixing vessels
• Weirs and spillways
• Launders
• Seawater intakes