Rotor bubbling

Rotor bubbling— the vortical device according contains the cylindrical chamber 1 with a tangential branch pipe 2 for input of cleared gas. Inside of the chamber on two support, the rotor 3 on which it is established installed screw 4, executed in the form of a brush from polyamide strings is placed. On an input entrance in the cylindrical chamber 1 the atomizers 5 directed towards to a stream of gas are established installed. The cylindrical chamber is attached with an inclination to a cyclone 6. Tap removal of disperse particles is carried out on a pipe of an overflow slim 7 in slim collector 8. 

Rotor bubbling—the vortical device works as follows. Dusty gas moves in the cylindrical chamber 1 on a tangential branch pipe 2 where under action of a rotating rotor 3 and screw 4 gets rotary screw movement. Simultaneously gas stream is irrigated with a liquid acting from atomizers 5. Jets of the liquid sprayed from atomizers 5, form a liquid veil, which... 

FIGURE 20.10 The longitudinal section rotor bubbling— the vortical device. 

Figure 5.123 a and b. Gas-liquid mixing modes a) bubble column behaviour (high gas flow, low rotor speed) b) circulating tank behaviour (high rotor speed, reduced gas flow). 

The skimmed oil Is collected and transferred to wet crude tank. Water from the SPI separator is discharged to induced air floatator. This unit is composed of four floatation cells. Each cell is equipped with a motor driven self-aerating rotor meonanistn. As the rotor spins, minute bubbles are generated ar.d oil and suspended solid particles attach to the gas bubbles as tney rise to the surface. Tne oil and suspended solids gather in a dense froth on the surface and are removed from the cell by skimmer paddles and collected in a scum tank. Then skum is pumped out of scum tank to the inlet of SPI separator by skum return pump. 

Dispcrscd-ga units. In these units, gas bubbles arc dispersed in the total stream either by the use of an inductor device or by a vortex set up by mechanical rotors. Fig. 8 shows schematic cross-section of such a unit. 

It can he shown mathematically that an efficient dis-persed-gas unit must have a high gas induction rate, a small-diameter-induced gas bubble, and a relatively large mixing zone Design of the induction nozzle or rotor and of internal baffles is critical to unit efficiency. 

Nozzles, rotors and baff les are patented designs. Field experiments indicate that these designs can be expected to have removal efficiencies of about 50% per cell, Each cell is designed for about 1-rnin retention time to allow gas bubbles to break free of the liquid and form the froth at the surface. Cell dimension and flowrate criteria vary somewhat between manufacturers... 

Interpretation of the multistage data is complicated by the fact that several rate processes occur simultaneously within each tank including drop removal by the air bubbles, drop production in the rotor s shear field, and drop aggregation/ coalescence. Thus, it was not possible to analyze completely the process with these data to determine the rate of removal for each drop size due to the air bubbles only. Accordingly, an experimental procedure was devised to isolate the rate of oil drop removal due to interactions between bubbles and oil drops only. 

Figure 19.8. The interaction of air and pulp in a froth flotation ceil and a series arrangement of such cells (a) Sectional schematic of flotation cell. Upper portion of rotor draws air down the standpipe for thorough mixing with pulp. Lower portion of rotor draws pulp upward through rotor. Disperser breaks air into minute bubbles. Larger flotation units include false bottom to aid pulp flow. (WEMCO Division, Envirotech Corp.). (b) A bank of three flotation cells. The floating concentrate is withdrawn continuously from each stage but the remaining pulp flows in series through the cells.

Fig. I. Flotation cell Upper portion of rotor draws air down the standpipe for rhomugh mixing with pulp. Lower portion of rotor draws pulp upward through roior. Disperser breaks air into minuie bubbles. Larger flotation units include false bnilom lo aid pulp flow...

Fig. 1. A Principle of flotation in a mechanical-type cell. The rotor and stator (which is here omitted for simplicity) keep the mineral particles and air bubbles in dispersion for adhesion. B Formation of hydrophobic and hydrophilic adsorption layer on solid in quartz-fluorite system...

In order to evaluate the VOC adsorbing capacity, several small ceramic rotor (10cm diameter, 40cm length) were prepared, and the adsorption and desorption characterstics were measured using static adsorption / desorption test equipment. In the experiment, VOC laden gas was artificially made and provided by bubbling air into VOC liquid. The concentration of the VOC was adjusted between 150 ad 420 ppm, and its flow rate was from 150 to 600 liter/min. 

The whipping process directly affects the amount of air incorporated into the matrix and therefore, variable process parameters should be selected in order to optimize foam quality and to avoid deterioration of the foam. A study by Hanselmann and Windhab (1999) showed that an increase in the rotor speed from 600 to 2000 rpm led to a decrease in bubble size and thus improved drainage stability. Lees (1991) demonstrated that at the upper limits of the beating temperature, aeration was faster and the volume of the foam increased as the temperature increased. This effect was attributed to the fact that higher temperatures lower the viscosity of the mixture and when the mixture is less viscous, more aeration is likely to occur. 

Hanselmann, W. and Windhab, E. Foam generation in a continuous rotor-stator mixer. Bubbles in Food, G.M. Campbell, C. Webb, S.S. Pandiella and K. Niranjan, eds., Eagan Press, USA, pp. 65 - 73,1999. 

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