Use of Foam

Froth flotation (qv) is a significant use of foam for physical separations. It is used to separate the more precious minerals from the waste rock extracted from mines. This method reHes on the different wetting properties typical for the different extracts. Usually, the waste rock is preferentially wet by water, whereas the more valuable minerals are typically hydrophobic. Thus the mixture of the two powders are immersed in water containing foam promoters. Also added are modifiers which help ensure that the surface of the waste rock is hydrophilic. Upon formation of a foam by bubbling air and by agitation, the waste rock remains in the water while the minerals go to the surface of the bubbles, and are entrapped in the foam. The foam rises, bringing... 

Whilst initial development was primarily in the fields of fibres and rubbers, the presence of polyurethanes at about sixth position in the production league tables is largely due to the widespread use of foam materials. By 1980 global consumption was of the order of 3 X 10 tonnes per annum. 

Foam is gas-liquid dispersion in which the liquid is the continuous phase and the gas is the discontinuous phase. The first use of foam in drilling was reported in 1964. 

In oil-producing formations with high fluid loss, drilling in with foam and foam completion proves beneficial. Usually, these formations cannot stand a column of water—so it is impossible to establish returns with conventional mud. The use of foam for drilling in and completion results in substantial increases in production. 

Foam Systems. The preparation, composition, and maintenance of foam completion and workover fluids is similar to that of foam drilling fluids. The advantage of foam is the combination of low density and high lifting capacity at moderate flow rates. The use of foam as a completion fluid can be justified by. 

Addnl Refs 1) W.G. Joseph, Use of Foamed Polyurethane in Decreasing Erosion in Guns , PATR 2520 (1958) 2) Anon, Polymer,... 

The potential use of foams has also been demonstrated for the decontamination of nerve agents [80]. In these applications, the detoxification of the nerve agent was carried out by immobilizing the enzyme organophosphorous acid anhydrase within either a fire fighting or blast-containment foam carrier. 

The use of cooling tower basins and process water pumps as fire water supply is not recommended. This water is usually treated with chemicals or may be contaminated with hydrocarbons that interfere with the use of foam extinguishing agents. At best, this supply could serve as a secondary system, should the primary supply be interrupted, using emergency connections. 

Foam systems have more components requiring higher maintenance and have somewhat lower reliability than water-only systems. Low expansion foam systems do offer the advantage over high expansion foam of an effective "water only" discharge after the foam agent has been expended. "Water only" discharge can be detrimental in most situations that require foam application. Limitations on the use of foam include ... 

The system can be operated with fewer emergency responders and foam loss is minimized. Foam chambers cause the foam to flow down the tank shell and onto the liquid surface therefore, thermal updrafts have little effect on foam application. A similar effect is seen with the use of foam chambers to protect the seals on floating roof tanks. 

Despite the limitations, there are sufficient advantages in the use of portable foam monitors to justify consideration for tank fire extinguishment. Some foam trucks are equipped with a 1,000 gpm (3,800 Ipm) foam monitor or snorkel articulated boom with a 500 gpm (1,900 Ipm) monitor. In addition, a 1,000 gpm (3,800 Ipm) portable monitor is recommended and can be towed behind the foam truck for use on tank or spill fires. Monitors have the advantage of fire extinguishment without close approach, resulting in less personnel hazard than the use of foam hose lines. 

Foams are currently used by the oil industry to improve crude oil recovery, resulting in 20 to 50% higher recovery rates for oil in some applications. A field demonstration to investigate the use of foam for site remediation was planned for 1996by the U.S. Department of Energy. 

Researchers see several potential advantages in the uses of foams for remediation. They include ... 

Class A Fires Fires arising mainly because of paper, wood, textiles etc. are known as Class A fires. The use of foam extinguishers, water pumps, water sprays, and gas cartridges etc. is recommended to fight Class A fires. Further, experts are of the opinion that almost any type of extinguisher is satisfactory for such fires. 

Norman, E. C. 1987. A Guide to the Use of Foam on Hazardous Material Spills. Hazardous Materials and Waste Management Magazine, Sept/Oct. 

In this example the use of foam, which was described in Section 3.3.1, will be demonstrated as a postrelease mitigation agent. An accidental release of n-pentane, a flammable material, from a storage tank into a diked area, and a hazard zone to a concentration of one half the lower flammable limit (LFL/2) will be evaluated. For n-pentane the LFL is 1.4% by volume in air. Then the LFL/2 will be 0.7% by volume in air (GPSA, 1972). 

The surfactant systems used for mobility control in miscible flooding do not form a surfactant rich third phase, and lack its buffering action against surfactant adsorption. Furthermore, for obvious economic reasons, it is desirable to keep the surfactant concentration as low as possible, which increases the sensitivity of the dispersion stability to surfactant loss. Hence, surfactant adsorption is necessarily an even greater concern in the use of foams, emulsions, and dispersions for mobility control in miscible-flood EOR. The importance of surfactant adsorption in surfactant-based mobility control is widely recognized by researchers. A decision tree has even been published for selection of a mobility-control surfactant based on adsorption characteristics (12). 

In recent years there has been considerable interest in the use of foams in chemical steam flood, CO2, and low tension processes. To date, principal applications have been as diverting agents where the foam has been used to block high permeability, low oil saturation zones and hence force drive fluids through lower permeability, higher oil saturation zones. The utility of foams in more general mobility control roles has not been extensively... 

One important application method for chemical finishes is the use of foam to apply the finish to the fabric. By replacing part of the water in the chemical... 

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