Liquid foams

Liquid argon Liquid asphalt Liquid atomizers Liquid-based foam Liquid butyl rubber Liquid carbon dioxide... 

Strigle [82] reports that there is no broadly documented agreement of the surface tension effects on the capacity of packed beds. Eckert [24, 82] concluded that surface tension of a non-foaming liquid had no effect on capacity. 

Solids (eg, suppositories, tablets), foams, liquids, and creams inserted into the vagina... 

Low-foaming liquid or powdered machine detergents are described using a surfactant system prepared from naturally based raw materials with good biodegradability and detergent properties [135]. These formulations are based on 5-30% alkylpolyglucoside, 5-30% alkyl ether carboxylate, 5-35% soap, and 0-3% of another surfactant. 

This has been verified for polydimethylsiloxanes added to crude oils. The effect of the dilatational elasticities and viscosities on crude oil by the addition of polydimethylsiloxanes is shown in Table 21-1. Under nonequilibrium conditions, both a high bulk viscosity and a surface viscosity can delay the film thinning and the stretching deformation, which precedes the destruction of a foam. There is another issue that concerns the formation of ordered structures. The development of ordered structures in the surface film may also stabilize the foams. Liquid crystalline phases in surfaces enhance the stability of the foam. 

High Expansion Efficient use of materials Expansion 400-800 1 (foam liquid volume)... 

Fluoroprotein foam is available as concentrates for proportioning with water to a concentration of 3% or 6%. The manufacturer should be consulted for the correct concentrate to be used in a particular system. Proportioners, the devices that meter the concentration, must be designed and set for the percent of foam liquid concentrate to be used. 

Fluoroprotein foam is produced through the turbulent mixing of atmospheric air into the foam solution (water and foam liquid concentrate). This turbulence is typically produced by air introduced into the solution by venturi action (foam maker). 

The minimum foam solution application rate for extinguishment of liquid hydrocarbons is 0.1 gpm/ft (0.3 Ipm/m ) of product surface areas. Foam liquid supplies must be sufficient to operate the system for a minimum period of time as required in Table 7-11 (modified from NFPA 11). 

The foam concentrate used with subsurface systems should be a fluoroprotein type for best results, although some AFFF foams are listed for substitutable application (because of their "fuel shedding" properties). The minimum foam solution rate should be 0.3 gpm/ft (12 Ipm/m ). The supply of foam liquid should be adequate to operate the system for 20 minutes. The foam injection point must be above the level of any residual water in the bottom of the tank. Subsurface foam application is not recommended for open or covered floating roof tanks or cone roof tanks with internal floating covers. 

The base quantity of foam liquid concentrate that should be stocked is the greatest amount calculated to be needed for any fire in a fire risk area. Normally, this involves either the largest cone roof tank or the seal of the largest floating roof tank and includes hose streams for ground fires around the tank. In addition, a supplementary supply of foam concentrate equal to 100% of the base supply should be readily available within 24 hours. 

In selecting the type of foam to be used in the system and also the amount of foam liquid concentrate to be maintained as a supplementary supply, consideration should be given as to what back-up compatible foam is available from nearby sources, such as other facilities, municipalities, the military, etc. This is especially desirable in areas where foam liquid concentrate may not be readily available from foam supply companies. If a facility is depending on back-up foam from other sources (other plants, military, etc.), it should be made certain that compatible foam is available. 

P.M. Kruglyakov, D. Exerowa, and K. Khristov New Possibilities for Foam Investigation Creating a Pressure Difference in the Foam Liquid Phase. Adv. CoUoid Interface Sci. 40, 257 (1992). 

However, Weaire et al. [41] have recently shown that it is possible to produce monodisperse dry foams containing Kelvin polyhedra. Upon addition of liquid, a structural rearrangement occurs at 0.87, to a system made up of mainly pentagonal faces. Thus, it would seem that a transition from pentagonal dodecahedral to tetrakaidecahedral packing may take place on reduction of foam liquid content. 

In addition to the film elasticity, other factors that may affect foam stability arc surface shear viscosity, bulk viscosity of the foaming liquid, and the presence of particulate matter. 

Liquid holdup was correlated in this work for both nonfoaraing and foaming liquids. 

These agents may operate via a number of mechanisms, but the most common ones appear to he those of entry and/or spreading. The defoamer must first of all he insoluble in the foaming liquid for these mechanisms to function. Second, the surface tension of the defoamer must be as low as possible. The interfacial tension between defoamer and foamer should be low. but not so low that emulsification of the defoamer may occur. Third, the defoamer should be dispersible in the foaming liquid. It was first shown in I fM8 that thermodynamically the entry of the defuamcr droplet into a bubble surface occurs when the entering coefficient has a positive value. The physics of bubbles is described in entry on Foam. 

Fig. 4.18. Flow regimes for co-current downwards flow of gas and liquid through a fixed bed of particles, (a) Non-foaming liquids. (b) Foaming liquids. L, G are liquid, gas flowrates per unit area (kg/mJs) X = Kpc/p.itH /pwater) ...

Projection Method for a Foam Liquid Explosive , PATR 2113 (195 5) 3) P. Tavernier,... 

In contrast, most of the conventional foam separation techniques use large bubbles, requiring relatively high gas flow rates to generate sufficient interfacial area for adhesion of solid particles to bubbles. This causes turbulence at the foam/liquid boundary and, in order to prevent redispersion of floated particles, a rather tall foam column is required (ref. 36). 

Disclaimer As in all theoretical variable determinations, these equations presented for Du calculation are subject to field-test verification. Equations (4.14) and (4.16) are not presented as being infallible or able to predict accurately every case of particle size with a given medium viscosity. For example, a crude with a high asphaltene content should be field tested before a final design for construction is issued on the basis of these equations. Small asphaltene crude contents (less than 2%) were used in deriving Eq. (4.16). More tests are needed for foam-liquid separations. Readers and users of this criterion, can perhaps contribute more data, and I indeed solicit such contributions of better methods and data as you may discover. 

The adsorption mechanisms of surfactant at interfaces have been extensively studied in order to understand their performance in many processes such as dispersion, coating, emulsification, foaming and detergency. These interfaces are liquid-gas (foaming), liquid-liquid (emulsification) and liquid-solid (dispersion, coating and detergency). 

In its physical sense and value the osmotic pressure is very closed to the excess pressure in foam liquid phase p L [108], In fact, the comparison of Eqs. (1.39) and (1.42) gives... 

There are at least three components in the foam liquid films, for example, water 1, surfactant 2 and electrolyte 3. The gas phase G is separated in two parts by the film and its pressure pc is usually determined by the pressure of the forth component an inert gas, practically insoluble in the bulk phase L (meniscus) that forms the film. The mechanical state of the foam film is determined by the normal (PN = pG) and tangential [Pj (z)] of the pressure tensor. The tension of the film y is calculated from the Bakker s integral... 

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