Section 4.14 Foam Fractionation

Cost as a vessel. Section 10.1 and add blowers. Section 2.1 and other auxiliaries. Installed unit for waste water treatment Installed cost 450 000 at waste water capacity = 44 L/s with n = 0.8. 

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A separation can sometimes be obtained even in the absence of any foam (or any floated floe or other surrogate). In bubble fractionation this is achieved simply by lengthening the bubbled pool to form a vertical column [Dorman and Lemlich, Nature, 207, 145 (1965)]. The ascending bubbles then deposit their adsorbed or attached material at the top of the pool as they exit. This results in a concentration gradient which can serve as a basis for separation. Bubble fractionation can operate either alone or as a booster section below a foam fractionator, perhaps to raise the concentration up to the foaming threshold. 

By using an anionic collector and external reflux in a combined (enriching and stripping) column of 3.8-cm (1.5-in) diameter with a feed rate of 1.63 ni/n [40 gal/(h ft )] based on column cross section, D/F was reduced to 0.00027 with C JCp for Sr below 0.001 [Shou-feld and Kibbey, Nucl. AppL, 3, 353 (1967)]. Reports of the adsubble separation of 29 heavy metals, radioactive and otheiwise, have been tabulated [Lemlich, The Adsorptive Bubble Separation Techniques, in Sabadell (ed.), Froc. Conf. Traces Heavy Met. Water, 211-223, Princeton University, 1973, EPA 902/9-74-001, U.S. EPA, Reg. 11, 1974). Some separation of N from by foam fractionation has been reported [Hitchcock, Ph.D. dissertation. University of Missouri, RoUa, 1982]. 

In this section the laboratory measurements of CC -foam mobility are presented along with the description of the experimental procedure, the apparatus, and the evaluation of the mobility. The mobility results are shown in the order of the effects of surfactant concentration, CC -foam fraction, and rock permeability. The preparation of the surfactant solution is briefly mentioned in the Effect of Surfactant Concentrations section. A zwitteronic surfactant Varion CAS (ZS) from Sherex (23) and an anionic surfactant Enordet X2001 (AEGS) from Shell were used for this experimental study. 

Conditions sometimes exist that may make separations by distillation difficult or impractical or may require special techniques. Natural products such as petroleum or products derived from vegetable or animal matter are mixtures of very many chemically unidentified substances. Thermal instability sometimes is a problem. In other cases, vapor-liquid phase equilibria are unfavorable. It is true that distillations have been practiced successfully in some natural product industries, notably petroleum, long before a scientific basis was established, but the designs based on empirical rules are being improved by modern calculation techniques. Even unfavorable vapor-liquid equilibria sometimes can be ameliorated by changes of operating conditions or by chemical additives. Still, it must be recognized that there may be superior separation techniques in some cases, for instance, crystallization, liquid-liquid extraction, supercritical extraction, foam fractionation, dialysis, reverse osmosis, membrane separation, and others. The special distillations exemplified in this section are petroleum, azeotropic, extractive, and molecular distillations. 

Figure 34-4. Plateau borders in cross section, (a) two capillaries with a film between them, (b) magnified view of one capillary showing the six fold symmetry. (Courtesy - Lemlich, R.. Principles of Foam Fractionation, Wiley-Interscience, New York, NY, 1968)...

Foam fractionation. Section 4.14, uses differences in surface activity to effect the separation. 

In Figure 8, the experimental results from the (4 m/day frontal advance rate, oil free) short core flood are compared to the simulated pressure drops which were based on the limiting capillary pressure principle. In this particular case was chosen at 0.35 over a range of water fractional flows from 0.01 to 0.15 to closely match the experimental data. For Sw > a fractional flow curve was chosen which matched the experimental data closely by appropriately adjusting the gas phase relative permeability curve. The water relative permeability curve remains the same as defined in the Appendix under gas/water relative permeabilities. The composite foam fractional flow curve can be seen in Figure 9. Notice the vertical section in the curve for the foam flow case lies at = 0.35. 

In much of the work on rheology, foams and HIPEs have been considered as analogous. The expressions derived are applicable to both systems, only the actual values are different. Consequently, workers in this area choose to study either emulsions or foams (or both) and so, in this section, the rheological properties of HIPEs and high gas-fraction (or dry ) foams will be discussed jointly. 

As discussed in Section 1.2.2 the bubble shapes in fairly dry foams and froths (4 gas > 0.83, approximately) are not spheres or distorted spheres, but polyhedrons. In practice there will be distributions of both gas-cell sizes and shapes. In addition to the gas bubbles, froth contains the floated particles, pulp liquor, and a fraction of (hydrophilic) particles that did not float due to bubble attachment, but which were mechanically entrained in the froth. The pulp liquor and these latter particles all have to be allowed to drain back out of the froth. The rate of this drainage will be greatest at the froth-pulp interface (i.e., the bottom of the froth layer) and slowest near the top of the froth layer. Froth drainage equations are discussed elsewhere [53]. The froth needs to be a stable enough foam that some time can be allowed for these drainage processes, and also so that the upper layer(s) of the froth can be swept out of the flotation cell. On the other hand, the froth should not be too stable as a foam so that it will break easily after collection. In addition to the role of the frother, froth stability is also promoted by increasing liquid viscosity. 

Sharovamikov and Tsap [66] have proposed another way to measure the liquid distribution in a foam based on the evaluation of the geometric coefficient B. The dependence of the film liquid volume fraction on the total foam liquid volume (ft = cp/( +(p) can be expressed by two almost equivalent formulae (see Section 8.3.)... 

The casein retentate, when used as cheese milk, can almost be fully depleted of all whey proteins through a sufficient number of diafiltration volume turnovers. In contrast to conventional cheese technology, it is then possible to UHT treat the cheese milk in order to destruct spore formers. The whey proteins can be used as a WPG or WPI product or treated further in order to fractionate the whey proteins in their main components. Alternatively the whey proteins can particulated to form WPP see Section 19.5.1. Both approaches are options to build a platform for novel product matrices with specific properties such as gelling, foaming or emulsification. 

Comparing the fractional flow curves. Figures 8 and 10 show that oil and CO2 production are delayed since the entire core cross section is swept and additional brine is displaced. Note the second hump in the brine production curve after 0.7 HCPV when foam is present. Without foam, brine production stops and oil production drops rapidly when CO2 breaks through. 

Certain smaller suboxic environments within larger estuarine systems also show unbioturbated sections of sediments. Because of their generally rapid rate of accumulation, the cosmogenic nuclide Be (53 d half-life) may be used in addition to °Pb for sediment accumulation rate assessment for the more recently deposited sediments. Similarly the pattern of bomb-produced Cs in sediments can serve as a chronometer. In addition, radiocarbon ages commonly can be obtained from calcareous fractions in the accumulating sediment. All these approaches were used at the FOAM site in Long Island Sound by Krishnaswami et al. (1984). 

Multiple layers of low conductivity phenolic foam insulation and small temperature differences between the primary coolant and the ambient minimized the heat loss from the primary loop to the ambient. Also, the heat addition to this loop was minimized by using a recirculation pump with an extremely low heat dissipation rate, which was calculated from the pump curves supplied by the manufacturer. With the pump heat dissipation and the ambient heat loss being small fractions of the secondary loop duty, the test section heat load was relatively insensitive to these losses and gains. Local heat transfer coefficients were therefore measured accurately in small increments for the entire saturated vapor-liquid region. Additional details of this thermal amplification technique are provided in the paper by Garimella and Bandhauer [32]. 

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