FOAM BLANKETING FOR SPILL

The foam scrubbing technique is effective because it brings the hazardous material into close contact with the foam by getting it into the bubbles. This is different from using a foam blanket as a cover for spills (see Chapter 3). With the large internal surface area of the foam available for absorption or mass transfer, an equilibrium concentration between the contaminated air inside the bubble and the foam cell wall liquid can be developed rapidly. Unabsorbed gas that is still in the foam bubbles when they collapse is released. This results in the slower release of a smaller quantity of hazardous material, which should result in a reduced hazard zone downfield. 

High-expansion foam can be used as an effective vapor suppressant on LNG spills. It adds heat from the water in the foam to the vapors as they pass through the blanket. This procedure induces buoyancy which can reduce downwind concentrations at ground level. Expansion ratios of 750 1 to 1000 1 have been found to be particularly effective (NFPA 11 A, 1988). At the same time, a low-expansion foam in the 20 1 range would be effective for a hydrocarbon spill. As this shows, selection of the actual foam to be used must be based on the intended application and on the foam supplier s test data and recommendations. 

SPILL CLEAN-UP Ventilate area of spill or leak use appropriate foam to blanket release and suppress vapors absorb small quantities of liquid on paper towels and evaporate in fume hood allow solid form to melt and cover in noncombustible material for proper disposal atomize large amounts in a suitable combustion chamber equipped with an effluent gas cleaning device remove all sources of ignition. 

SPILL CLEAN-UP approach release from upwind use appropriate foam to blanket release and suppress vapors absorb in noncombustible material for proper disposal. 

SPILL CLEAN-UP evacuate danger area ventilate area of leak or spill stop or control the leak, if possible use appropriate foam to blanket release and suppress vapors absorb liquid in noncombustible materials (e.g., dry earth, sand, vermiculite) for proper disposal remove all sources of ignition. 

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