Sparger details

Three different spargers were used in the experiments. Details are given in Table I. The experimental arrangement and sparger details are shown in Figures 1 and 2, respectively. 

Fig. 13. Examples of pipe gas distributors (a) simple sparger, (b) details of the pipe, (c) wagon wheel, and (d) multilevel distributor.

The gas dispersion ring or sparger can be a special design with holes or a single pipe entering the underside of the impeller, and there will be very little differences in mass transfer performance. References [25] and [29] provide valuable detail for considering design for gas dispersion/ mass transfer. 

The nozzle or shroud details inside a sparger pipe grid are illustrated in Fig. 7. 

The detailed experimental set-up is shown in Figure 2. Simulated flue gas (92% nitrogen and 8% SO2) is passed through a sparger of sintered glass placed inside an absorption tank, where it comes into contact with the liquor from the crystallizer, liquor continuously recirculates from the crystallizer through the adsorption tank. lime is pumped in slurry form directly into the crystallizer. 

When tank mixes were evaluated, the BALAN Dry Flowable was first dispersed in the spray water (328 ppm hardness with iron) and then the other product was added. Table V describes the details of testing at a rate of 2.5 Ib/acre at 20 gal/acre with sparger-pipe agitation. After four repetitive evaluations in which the contents were sprayed out and in which there was no clean out between tankfuls, the screens were clear and there was no residue in the bottom of the tank. The system was not cleaned out between runs to better simulate continuous spraying in actual use. Table V also describes the same type of evaluation with a jet agitator rather than a sparger pipe. This resulted in little residue in the in-line screens and none on the bottom of the tank. 

Sparger pipes are discussed in detail in Sec. 4.2. That discussion also applies to a sparger pipe introducing an intermediate feed. 

Even less is known about the liquid-solid transfer in bubble columns. Ghosh [83] has recently studied the liquid-solid mass transfer by monitoring the rate of dissolution of benzoic acid pellets suspended in a bubble column. He elucidated the effect of gas velocity (air), axial position of pellet and the types of sparger. Figure 8 shows the effect of gas velocity on the interphase mass transfer coefficient (k ) in a 1% aqueous CMC solution when the solute particles are positioned at various heights from the distributor. Within the narrow range of conditions, he found that the type and details of the sparger did not exert any influence on the value of the mass transfer coefficient. He presented his results in terms of Stanton number. 

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