Applications of Foams

An important application of foams arises in foam displacement, another means to aid enhanced oil recovery. The effectiveness of various foams in displacing oil from porous media has been studied by Shah and co-workers [237, 238]. The displacement efficiency depends on numerous physicochemical variables such as surfactant chain length and temperature with the surface properties of the foaming solution being an important determinant of performance. 

Generally two main types of foam detector are used. They work by detecting either changes in electrical capacitance or changes in electrical resistance. Table 4.2 shows the application of foam detectors based on various principles, such as conductance, thermal conductivity, capacitance, ultrasonic rotating disks. 

Likewise, the practical food foreman knows that by following certain manufacturer s recommendations and certain processing conditions in his plant, he is able to produce stabilized foam products to the satisfaction of his superiors and the public, most of the time yet when problems of instability and poor shelf life of the finished product are brought to his attention and all simple adjustments fail to produce a satisfactory result, he must turn to the food or colloid chemist for the theory and industrial application of foams. 

With foams, one is dealing with a gaseous state or phase of matter in a highly dispersed condition. There is a definite relationship between the practical application of foams and colloidal chemistry. Bancroft (4) states that adopting the very flexible definition that a phase is colloidal when it is sufficiently finely divided, colloid chemistry is the chemistry of bubbles, drops, grains, filaments, and films, because in each of these cases at least one dimension of the phase is very small. This is not a truly scientific classification because a bubble has a film round it, and a film may be considered as made up of coalescing drops or grains. ... 

In practically all our food products we have depended on the practical application of foam stability to solve our problems. The answer to many of our problems lies in the theoretical aspects of the stability and formation of foams. As yet, little time has been spent on the chemical and physical properties of foam. 

Typical fires involving floating roof tanks occur at the annular seal where the surface of the flammable liquid may be exposed or vapors may escape. Application of foam to smother a fire at the seal is a proven, effective fire extinguishment method. 

Gesser et al. initiated the application of polyurethane foam for the extraction of organic contaminants from water. Since then, several published investigations have described the application of foams as extractors for chlorinated organic compounds, polycyclic aromatic hydrocarbons (PAHs), and other organics. 

All of these cases considered have not been short term efforts. Market development requires at times infinite patience and understanding. The Goldline Camper from concept to commercial reality took just over one year. By comparison this is a very short time. The application of foamed ABS to the furniture industry is still in the process of commercial development. It has been in this process now for more than two years and will probably require one to two years more before it can be considered a commercial success. The study of electroplating on plastics has been under development for a period of at least seven years. It can now be considered to be a truly commercial product. Purafil, however, was discovered about ten years ago. It was first marketed by our Ingersoll Products Division as part of a line of hospital supplies. The next effort was an exclusive marketing arrangement by York Division as a filter for air condition-... 

Extruded polystyrene foam sheet is primarily produced in a single screw tandem extrusion line. Primary application of foam sheet is as a packaging material in items such as disposable dishes and food containers, trays for meal, poultry and produce products, and egg canons. 

Where the vapours to be controlled are flammable, many of these foams are quite similar to the protein, fluoroprotein, and aqueous-film-forming foams used in firefighting [590,594,598] (see also Section 12.9). Where longer-term odour and toxicity control are more important many of these foams are polymer-thickened and gelling foams [592-594]. Other applications of foam blankets are discussed in Sections 10.5 and 13. 

Froth flotation is an application of foams that is used to separate mineral components from each other based on their having different surface properties, typically their wettability and surface electrical charge. For example, froth flotation is the classic process used to separate copper from lead ore. The process involves having hydrophobic particles attach to gas bubbles which rise through a turbulent suspension to create a surface foam called a froth. Figure 10.2 shows an illustration of a mechanical flotation cell. This is the classic flotation device [53,91,625], First, the flotation feed particles are well dispersed into a particle suspension. Together with chemical flotation aids, such as collectors and frothers, this constitutes what is called the flotation pulp. In a mechanical flotation cell, air is fed in the form of fine bubbles and introduced near the impeller (see Figure 10.2). In addition to mechanical flotation cells, there are also pneumatic cells and cyclone flotation cells. Pneumatic... 

Other dust-suppressing applications of foam blankets include ... 

Other applications of foam blankets are discussed in Sections 9.7 and 13.9. 

Reservoir-foam applications may involve slug injection, in which foaming surfactant solution is injected into the gas stream at the well-head over a period of a few hours, semi-continuous injection, in which surfactant solution is injected at intervals over a period of a day or so, and continuous injection, in which surfactant solution is injected continuously for months or even years. Recently, much attention has been paid to near-well applications of foams [345,726-728],... 

Other agricultural applications of foam blankets include prevention of erosion and distribution of soil particulates by wind [589], and reducing ammonia and odour emissions from intensive feed-lot operations, such as in hog-farming operations, by blanketing waste slurries, both in animal houses and spread over fields. Here a cover is needed that will allow passage of fresh wastes, or rain, and that can be easily re-formed, although the foam has to be stable in the presence of ammonia. Applications of foam blankets in areas beyond the agricultural sector are discussed in Sections 9.7 and 10.5. 

A somewhat different application of foam is in blast and fire suppression during attempts to deactivate, or intentionally destroy, suspected terrorist bombs. When such a device, or even a small explosive device used to destroy the suspected item, explodes, severe damage can be caused by the compression wave emanating from the blast or from the fireball that may follow the blast. In Section 9.6 it was mentioned that foam blankets have been developed for blast noise and pressure wave... 

Olsen, D.K. Sarathi, P.S. (Eds.), Proceedings, Fidd Application of Foams for Oil Production Symposium, U.S. Department of Energy, Bartlesville, OK, 1993. 

Liu, P.C. Besserer, G.J., Application of Foam Injection in Triassic Pool, Canada Laboratory and Field Test Results in Proc., SPE 63rd Annual Technical Conf, Society of Petroleum Engineers Richardson, TX, 1988, SPE paper 18080. 

A., A Production Well Foam Pilot in the North Sea Snorre Field - Application of Foam to Control Premature Gas Breakthrough in Proc., 9th European Symposium on Improved Oil Recovery, The Hague, The Netherlands, 1997 paper 001. 

When considering the application of foam to hazardous material spills, key requirements include an adequate water supply, the foam concentrate, appropriate proportioning equipment, piping, foam makers, and discharge devices and protective equipment for the personnel involved. Activation may be automatic, but in most cases it is manual. There are four types of application systems. They include fixed, semifixed, mobile, and portable (NFPA 11, 1988). 

In order to develop efficient techniques for the preparation and application of foams in industry, agriculture, firefighting, etc., it is necessary to know the physicochemical parameters of surfactants and their relationship with the foam stabilising ability of the surfactant solutions. Usually the criterion of the surfactant foaming ability is the adsorption of these compounds at the solution/air interface and the related to it properties, such as decrease in surface tension, adsorption work, maximum adsorption T. [13,39,43]. CMC is often used as a characteristic of a foaming agent (if micellisation is possible in the surfactant solution). Parameters related to foam stability, such as foam lifetime and foam column height, are also employed [12,13,39],... 

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