Contactors operation

A differential countercurrent contactor operating with a dilute solution of the consolute component C and immiscible components A and B is shown in Figure 8. Under these conditions, the superficial velocities of the A-rich and B-rich streams can be assumed not to vary significantly with position in the contactor, and are taken to be and Ug, respectively. The concentration of C in the A-rich stream is and that in the B-rich stream is C-. ... 

The first set of 14 matched pairs of 2-h composites of GAC influent and effluent was concentrated on the first day of a 6-week GAC contactor operation cycle following regeneration, and the remainder of the sets were sampled throughout the rest of that cycle. No samples were collected during backwash operations. In a subsequent 6-week period, 10 matched pairs of GAC effluent composites were sampled before and after chlorination and were concentrated on the resin system. Chlorinated samples were stoichiometrically dechlorinated with ferrous ammonium sulfate prior to concentration. 

This subsection describes the design of a contactor stage and how that design affects contactor operation. It will be shown when to add or avoid a particular feature. The discussion follows the flow of the two immiscible liquids through a contactor stage liquid entry, mixing, separation, and liquid exit. Finally, criteria for motor selection are reviewed. 

In recent tests on a 5-cm contactor, the CINC V-2 model, estimates of the upper weir diameter indicated an apparent weir diameter much larger than the actual one (Leonard et al., 2002). As this contactor has a covered upper weir, a siphon probably formed to cause the unexpected results. Note that a siphon could also be formed over the LW as it is always closed. To the author s knowledge, this phenomenon has never been observed. For normal contactor operation, even with a closed upper weir, a siphon will probably not form, as it occurs only at very high flow rates. When a siphon is formed, the general contactor operation represented by Equation 10.5 no longer applies, since it is assumed that the pressure over the liquid surface on both weirs is the same. The formation of a siphon is an area where more research is needed. Some work has been started in this area. Experimental and modeling work by Wardle (2008) showed that a siphon can form above the upper weir on a 5-cm contactor when it is covered. Holes drilled in this cover reduced the effect of the siphon. 

The centrifugal contactor was first used to reprocess spent nuclear fuel at the SRS in 1966 (Webster et al., 1969). For almost 40 years, this 18-stage 25-cm SRL contactor was used for the extraction and scrub sections (the A-bank) of the PUREX (plutonium-uranium extraction) process at the SRS. Contactor operation stopped when the facility in which they were housed was shut down in 2003. This 18-stage contactor replaced a 24-stage mixer-settler. Mixer-settlers continued to be used for the rest of the processing, as most of the radiation was removed in the A-bank. The ability to... 

FIGURE 33.9 Schematic view of hollow fiber membrane contactor operated in recycling mode for U(VI) recovery from aqueous acidic waste (1) HFC module, (2) feed, (3) extractant, and (4) peristaltic pumps. 

Vajda M, Havalda I, Macek R. Membrane-based solvent extraction and stripping of zinc in a hohow-fiber contactor operating in a circulating mode. Desalination 2004 163 19-25. 

Continuous contactors operate as intermittently moving packed beds, as illustrated by the Higgins contactor " (Fig. 31), or as fluidized staged (compartmented) columns, as shown in Fig. 32, by the Himsley... 

Elegant slide valves are used to separate the adsorption, regeneration and resin backwash stages. The contactor operates in predetermined cycles and is an ideal process for feedstreams with no suspended solids. 

Air oxidation of aqueous sodium sulfide solution is encountered in the pulp and paper industry where the black liquor, which contains sodium sulfide (Na2S), is oxidized. In a typical process, 200 tons/day of an aqueous solution of sodium sulfide are oxidized with air at 75°C. The concentration of Na2S is to be reduced from 12 to 0.5 kg/m. The following contactors operated contin-... 

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