The foaming tendency of seawater in distillation plants is unpredictable. It is generally thought that foam is formed when organic compounds are concentrated in the brine, giving rise to surface active effects which increase the liquid film strength at phase interfaces. Antifoam Defoamer AF10 is not soluble in water. At use concentrations (0.05 - 0.1 mg/l) Antifoam Defoamer AF10 forms a micro-emulsion and during evaporation is incorporated into the surface liquid film of bubbles where it acts as a surfactant and reduces the film strength. The result is that the film readily ruptures and a stable foam does not form. In this way a uniform boiling or flashing action is achieved and carry-over is minimised.

Where to use ANTIFOAM AF10 for foam knockdown?

• Reverse Osmosis (RO) Plants
• Multi-Stage Flash (MSF) Plants
• Multi-Effect Distillation (MED) Plants
• Hybrid Desalination Facilities

• Intake Channels
• Seawater Make-up Lines
• Pumping Stations
• Equalization Basins
• Clarifiers
• Dissolved Air Flotation (DAF) Units
• Pretreatment Systems

• Power Plant Cooling Water Intakes
• Refinery Seawater Systems
• Petrochemical Facilities
• Offshore Platforms
• LNG Terminals

• Add 50% - 70% of required distillate volume into dosing tank;
• Start the dosing tank agitator/mixer;
• Add the required Antifoam Defoamer AF10 volume into the dosing tank;
• Add the remaining volume of distillate to give the required concentration of Antifoam Defoamer AF10 solution;
• Continue agitation for a further 10 - 15 minutes;
• The resulting emulsion will be stable and will not normally separate

The dose level required will depend on the quality of the seawater feed (e.g. dissolved organics, suspended solids) but is typically found to be in the range 0.05 to 0.1 mg/l and is subject to optimisation as operating experience is gained. Dose level is not dependent on operating temperature of the distillation plant. Recommended injection points are either into the seawater make-up line after any external de-aeration and decarbonation equipment, or into the recycle brine stream at a suitable point after the blowdown and typically into the discharge of the recycle brine pump.

General-purpose antifoams have a wide range of applicability, but not all of them are suitable for use in the treatment. Some foam control agents can aggravate the problem. Foam control in gas scrubbers is only one of the process parameters to be monitored. It is equally important to prevent or slow the fouling of the unit, because dismantling of the gas-scrubbing units is manually intensive. Incorrectly specified antifoams can easily lead to increased fouling and clogging, particularly in the heat exchangers. Momentive Performance Materials RXSOL antifoams are designed to provide foam control with a minimum of such problems.

Dosing for Desalination plants/aqueous systems

• Organic loading
• Algal concentration
• Turbulence level
• Intake water quality
• Seasonal variations