High-stability foams for long-term suppression of hydrocarbon va

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...

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252 3, 252 805, 252307, 252382, 252605, 252610, 422 42, 521 65, 521 78, 530210, B01J 1300, B01J 1916

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active

054341922

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to dilute and concentrated foam formulations for the production of high-stability, high-expansion aqueous foams. Foams generated from the formulations may be used as a blanket to suppress the emission of volatile gases and vapors, such as hydrocarbon and polar organic vapors. More specifically, the present invention relates to aqueous foams for the suppression of hydrocarbon and polar organic vapors generated during loading of oil tankers, as well as during the transportation, transfer, storage, and accidental spillage of crude oil and lighter hydrocarbons. Foams according to the present invention can be prepared from fresh water, brackish water or sea water.
2. Description of the Prior Art
During loading of oil tankers, and during the transportation, transfer, storage, and accidental spilage of crude oil and lighter hydrocarbons, a large quantity of vapors may be released which poses a fire-hazard, as well as a threat to life or the environment. A hard-piped vapor-recovery system conventionally is used to remove the released hydrocarbon vapors for later incineration. This method however, is expensive and ultimately releases carbon dioxide, nitrogen oxides and sulfur oxides into the atmosphere as by-product of the hydrocarbon incineration.
Another possibility for handling such vapors is suggested by U.S. Pat. No. 3,639,258 to Corino which involves the use of a gelling material to create an integral roof by gelling the upper layer of the oil in a tank to provide a floating roof of the same material. This technique, while useful for some purposes, creates considerable difficulties in cleaning and maintaining tanks or tanker compartments.
Alternatively, as suggested in U.S. Pat. No. 3,850,206 to Canevari et al., a foamed vapor barrier can be used to suppress the release of volatile hydrocarbons. The vast majority of conventional aqueous foams and foams for fire-fighting/vapor suppression, however, do not persist for more than 30 minutes and only a few persist for up to 2 hours. Accordingly, conventional aqueous foams do not persist for a sufficient time to allow their use in connection with the suppression of the release of hydrocarbon vapors during a lengthy procedure such as the loading of a tanker which takes from 10 to 36 hours. Adding to the foam solution a water thickener such as a polysaccharide, polyacrylamide or sulfonated polystyrene, as prescribed in Canevari et al. '206, extends the foam stability to no more than a few hours, especially when the temperature exceeds 90.degree. F.
In general, protein and fluoroprotein foams are capable of suppressing vapors of non-polar hydrocarbons below the lower explosive limit (LEL), usually about 2% or less of hydrocarbon gas in the air, for up to a few hours, but are not very effective against polar compounds.
Likewise, high-expansion foams of synthetic detergents and aqueous film-forming foams (AFFF), which form a spreading protective film over the hydrocarbon surface, are also capable of suppressing vapors of non-polar hydrocarbons for up to a few hours, but are equally ineffective against polar hydrocarbons.
Other AFFF foams that include an insoluble polymer complex formed from anionic polysaccharides and perfluoroalkyl surfactant cations are effective fire fighting foams but do not have sufficient stability to persist for more than a few hours.
Similarly, alcohol-type foams (ATF) consisting of a protein, surfactant, fluoroprotein or AFFF base and a metal stearate or polymer additive are capable of being effective for up to a few hours against polar hydrocarbons. In contrast, AFFF coupled with a polyurethane foam, e.g. the Light Water.RTM. ATC product sold by the Minnesota Mining & Manufacturing Company, is very effective for longer suppression of polar and non-polar vapors. This product yields a semi-solid polyurethane foam with excellent mechanical strength. However, this type of foam leaves behind a non-collapsible polyurethane residue which is difficult to dispose of. F

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