Bubble injection Design

Figures 4.35-4.40 show schematic arrangements and photographs of three of the numerous different cell designs which also differ in the arrangements of the individual flotation steps. The circular cell in Fig. 4.35 and 4.36 is dosed and pressurized. It is divided into 3-5 superimposed dementary cells. The suspension flows from top to bottom and is aerated after each dementary cell before being fed to the next lower one. Aeration is achieved by static mixers with self aspiration. The bubbles injected in each elementary cell ascend through the upper cells to the foam layer at the top. The foam is removed through pipes by pressure difference to the ambient. A reject valve allows control of the reject rate and composition in order to omit a secondary stage. Figures 4.37 and 4.38 show a flotation line with...

In order to verify the simulation results, experiments on bubble behavior in bubble columns are carried out under conditions similar to the simulations. A 3-D rectangular bubble column with the dimension of 8 x 8 x 20 cm3 is used for the experiments. Four nozzles with 0.4 cm I.D. and a displacement of 2.4 cm are designed in the experiments. For single-nozzle experiments, air is injected into the liquid bed through one of the orifices while the others are shut off. The outlet air velocity from the nozzle is approximated using the measured bubbling... 

In some multiphase reactors, stirring with an impeller or the flow pattern caused by gravity will control the interfacial area. By suitably designing and positioning propellers and reactant injection orifices or by using static mixers, it is possible to provide very efficient breakup of hquids into drops and bubbles. A factor of two decrease in drop or bubble size means a factor of four increase in interfacial area. 

Dissolvcd-gax units take a portion ol treated water effluent and saturate it with natural gas in a contactor. The higher the pressure, the more gas that can be dissolved in the water. Most units axe designed for a 2U to 40-psig contact pressure. Normally, 20 to 50% of treated water is rccircu iated for contact with gas. Gas-saturated water is then injected into a flotation tank as shown in Fig. 7. Dissolved gas breaks out of solution in small-diameter bubbles when flow enters the atmospheric flotation chamber. 

Figure 12.3 shows three microinjector designs that have been used for electrokinetic injection of very small samples, from microenvironments such as single nerve cells. The capillary tip diameters in these injectors are 10 pm o.d. or less, and can penetrate and sample from single cells. The design shown in Figure 12.3(c) has been shown to be the most effective, because electrolysis occurs away from the capillary tip and therefore does not introduce bubbles that would insulate the capillary ends from each other. 

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