Induced air flotation

Alternatively, induced air flotation (lAF) can be employed, in which air bubbles are generated through an inductor. The removal mechanism is the same as the DAF. 

Dissolved Air Flotation ODispersed Air Flotation Induced Air Flotation O Diffused Air Flotation... 

Zlokarnic, M. Separation of activated sludge from purified waste water by induced air flotation. Water Research, Vol. 32, No. 4, pp. 1095-1102, 1998. 

In Oil/Water Separation by Induced-Air Flotation by Sylvester and Byeseda, an induced-air flotation pilot unit was used to study the separation of oil from bnne solutions. Variations in the inlet oil concentration, vessel, residence time, air flow rate, bubble diameter, oil-drop diameter, temperature. NaCI concentration, and cationic polyelectrolyte concentration were evaluated. On a multistage unit, the majority of the oil removal occurred in the first stage. Oil-drop and air-bubble diameters have the most significant effects on oil-removal rates. 

Combination Crossflow Pliue-Pack Coalescer and Induced-Air Flotation System. This in-scrics combination was offered with a recycled portion of the effluent from the plate coalescer being injected into the influent stream. Very little field experience is available on this design. Also, when the dissolved air breaks out of solution, turbulence is created. This can adversely affect the action of the plate-pack coalescer. Also, the system is very expensive it costs more than twice the other acceptable altcmauvcs. This system, therefore, was not accepted. 

This research focuses on the induced-air flotation process for the removal of dispersed oil droplets. The industrial use of induccd-air flotation devices for oil wastewater separation began in IW9. Basset1 provides the process development history, equipment description, and operating experience lor an induced air unit similar to the design used in the experiments described here. Although induced-air flotation equipment is simple, the fluid mechanics of the process are not and the arrangement of the turbine, sleeve, and perforations have been determined necessarily by trail-and-crror experimentation with small-scale units. 

Since dissolved-air flotation has been used successfully for oily-waste separation for 20 years, the bulk of the published literature treats the dissolved-air process. No study has been published for either dissolved- or induced-air flotation of oily wastes that considers in detail the effect of bubble or particle size... 

The effects of residence time (1.0 to 6.2 min/cell), air flow rate (40 to 190 mL/s, cell) and feed-oil concentration (35-190 ppm by weight) on oil removal as a function of the oil droplet size for the three-stage induced-air flotation process were evaluated in the overall performance studies. A feed emuison of No. 

For flotation of oil drops by bubbles with diameters from 0.2 to 0.7 mm. the surface chemistry of drop/drop interactions as it relates to liquid coalescence and droplet breakup governs the overall performance of flotation. As the rate of dispersed oil coalescence increases, the overall oil removal efficiency for the process increases. Thus, if process improvement is desired, one should concentrate on pretreatrnent of the emulsion to improve the oil s coalescing properties. These ohservalins are consistent with Leech el at.1 who found that the most important variables governing induced-air flotation were chemical treatment (type and dose) and the system residence lime. Smaller air bubbles also increased the removal rate in our experimental range however, bubble si2e is not independently variable in the field. 

In the range of practical operation of the induced-air flotation process, the air flowrate had no effect on the removal rate constants. 

The authors thank the U.S. National Science Foundation (Grant No. ENG 76-02866) and the sponsoring companies of the U. of Tulsa Environmental Protection Projects (UTEPP) program for financial support. The authors also thank C-E Natco for providing the induced-air flotation equipment. 

Bycscda. J.J. Induced-Air Flotation of Oil-Water Emulsions. PhD dissertation. U. of Tulsa(l980). 

In this example, the development of a new flotation technique for waste water treatment is discussed. Dimensional analysis has been used since the onset of this work. It concerns the so-called Induced Air Flotation, IAF, which is an alternative to the well-known Dissolved Air Flotation, DAF, the latter being already discussed in Example 7. 

Fig. 56 a - c Differentdesignsofthe funnel-shaped nozzle for induced air flotation from [80, 81,82],... 

Zlokamik, M., J. Susa, Chem.-Ing.-Techn. 68 (1996) 12,1572-1574 Selbstansaugende und radialstrahlende Trichterdiise Zlokamik, M., Int. Application Number PTC/EP98/00375, 23 January 1998 Apparatus and Method for Induced Air flotation... 

Zlokamik, M., Water Research 32 (1998) 4, 1095-1102 Separation of activated sludge from purified waste water by Induced Air Flotation (IAF)... 

Three general methods are used in forming the minute air bubbles. One involves aerating the stream through submerged diffuser plates. The second, called induced air flotation, uses an agitator to physically beat the air into the water. In the third method, a sidestream of dissolved air-flotation effluent is aerated under 2 to 3 atm of pressure and then fed to the incoming contaminated stream. The sudden decrease in pressure on the sidestream causes breakout of minute bubbles, which attach to contaminants in the stream. 

Dispersed air flotation (or induced air flotation) Example Deinking flotation... 

All the aforementioned process terms can simply be called foam separation. It is important to note that although any type of technique can be used for bubble generation in a foam separation system, the most common bubble generation technique for a foam separation system is dispersed air flotation, which is also known as induced air flotation. 

To start the SBR foam separation (or dispersed air flotation, or induced air flotation) experiments, sufficient volume of raw water is adjusted to the desired pH with 1.0 A sodium hydroxide or 1.0 A sulfuric acid, an appropriate amount of surfactant is added to the raw water, and the ntixture is poured into the Foamer Tester (Fig. 7). Compressed air is then diffused through the liquid ntixture by means of a plastic cloth grid (Fig. 8). Foam is withdrawn from the top and collected in a container. The run is allowed to proceed until no additional foam is formed. A sample of the bulk liquid near the reactor bottom is analyzed for pH, color, turbidity, and other water quality parameters. The foam is collapsed in a beaker and its volume is measured. 

The dispersed air flotation (or induced air flotation) de-inking process allows the use of a wider range of printed waste paper. The amount of dirt in the finished paper is reduced, thereby improving quality and reducing the amount of reject paper. The brightness of the finished paper is improved without the use of chlorine bleaching. 

Y. D. Yan, Simultaneous Algae and Phosphorus Removal from Wastewaters Using Induced Air Flotation, Centre for Mnltiphase Processes, Department of Chemical Engineering, University of Newcastle, Callaghan, Anstralia, 1999. 

Dissolvnd air flotation or induced air flotation are commonly used techniques in the oil refining Industry for the removal of both oils and suspended solids. The coal industry has been invastigeting fonm flotation technology as well. One use would inclode cleaning the wet scrubber air pollution control devices used in oonl-burning power plants.9... 

In today s world of waste treatment, bubble and foam separations lemain lelatively little used techniques. Dissolved or induced air flotation is the most commonly used variation, havii been enqiloyed for many years in the treatment of wastewaters for the separation of suspended sc, oils, greases, fibeis, and other iow-density solids as well as fbr the thickening of activated sludge and flocculated chemical sludges. The most active commercial use was and is in ore flotation—as discussed in Chapter 16. The potential Cor the use of these separation techniques, however, is veiy high in both the areas of traditional and hazardous waste management. 

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