Foaming liquid systems

Loiseau et al. (100) have proposed to use empirical Michel and Miller (103) types of correlations to fit e qperiinental data concerning water and aqueous, organic and foaming liquid systems inside two fully baffled small vessels (5.5 and 8.9 litres) agitated by a six flat-blade Rushton types of disk turbine. 

In a gas and liquid system, when gas is introduced into a culture medium, bubbles are formed. The bubbles rise rapidly through the medium and dispersion of the bubbles occurs at surface, forming froth. The froth collapses by coalescence, but in most cases the fermentation broth is viscous so this coalescence may be reduced to form stable froth. Any compounds in the broth, such as proteins, that reduce the surface tension may influence foam formation. The stability of preventing bubbles coalescing depends on the film elasticity, which is increased by the presence of peptides, proteins and soaps. On the other hand, the presence of alcohols and fatty acids will make the foam unstable. 

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. 

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. 

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. 

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. 

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. 

G. Tosun, A study of cocurrent downflow of non-foaming gas-liquid systems in packed beds, Ind. Eng. Chem. Proc. Des. Dev., 23 (1984) 29-35. 

In fact, extremum tendencies expressing the dominant mechanisms in systems like turbulent pipe flow (Li et al, 1999), gas-liquid-solid flow (Liu et al, 2001), granular flow, emulsions, foam drainages, and multiphase micro-/nanoflows also follow similar scenarios of compromising as in gas-solid and gas-liquid systems (Ge et al., 2007), and therefore, stability conditions established on this basis also lead to reasonable descriptions of the meso-scale structures in these systems. We believe that such an EMMS-based methodology accords with the structure of the problems being solved, and hence realize the similarity of the structures between the physical model and the problems. That is the fundamental reason why the EMMS-based multi-scale CFD improves the... 

The stabilizing function of macromolecular surfactants in solid-liquid systems is exercised through protective colloid action. To be effective, they must have a strong solution affinity for hydrophobic and hydrophilic entities. In liquid-liquid systems, surfactants are more accurately called emulsifiers. The same stabilizing function is exercised in gas-liquid disperse systems where the surfactants are called foam stabilizers. 

Syntactic Foam. Hollow glass, ceramic, or plastic spheres are dispersed in the reactive liquid system before it is cast. When the liquid is polymerized and cured, the hollow spheres make it a unicellular foam. The air bubbles in the cells make it low-density, low dielectric constant and loss, and very resistant to compressive forces such as hydrostatic head in deep-sea equipment. 

Liquid products are approximately 50 to 60 percent water, with the remainder being a combination of surfactants, builders, foam regulators, enzymes and enzyme stabilizers, hydrotropes, antiredeposition polymers, optical brighteners, corrosion inhibitors, dye, and perfume. Two-in-one formulations also contain antistatic and fabric softening ingredients. Liquid systems require careful selection and blending of raw materials to achieve a stable product. Special attention is necessary for the following items. 

Any areas which have flammable liquids are equipped with a foam fire fighting system. The foam system is activated by fusible links or manually. The fire truck has a foam eductor system which can be used to extinguish flammable liquid, or Class II fires. The foam is educted out of five gallon buckets and mixed with the water stream in the eductor. 

From Equation 6.23.6, the tray spacing is 1.5 ft (0.467 m), and from Equation 6.23.4, k, equals 0.018 m/s (0.05906 ft/s). Because there is no information on foaming for this system, select the lower value of ky for a foaming liquid. This choice results in a larger column diameter than for a nonfoaming liquid. From Equation 6.23.5,... 

Elucidation of the electroconductivity mechanism and accurate calculation of the electroconductivity of highly foamed RO systems is of considerable interest. Important relevant information is provided by electroconductivity studies of liquid foams with a high foaming degree, e.g. based on surfactants. 

Weir heights of 2 in. are fairly standard and weir lengths about 75% of the tray diameter. For normal conditions downcomers are sized so that the depth of liquid in them is less than 50% and the residence time more than 3 sec. For foaming and foam-stable systems, the residence time may be two to three times this value. The topic of tray efficiency is covered in detail in Section 13.6, but here it can be stated that they are 80-90% in the vicinity of F = = 1.0(ft/sec)(lb/cuft) for mixtures similar to water... 

Just as the products of polycondensation are greatly varied, so are the reaction conditions used in their production. Some are produced in the melt (many polyamides and polyesters), some initially in the melt but with extensive polymerization continuing in the solid state (polyurethane foams and elastomers), in solution (some polyurethane fibres) or in non-homogeneous liquid systems (some polycarbonates, very high melting polyamides). 

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