Moving bed electrodes

Ftf, UT Dynamic, pe ticulmtc bed electrodes, (a) The inclined two-phase Parcl fluidized-bed electrode reactor, (b) The moving-bed electrode in a rectangular conflgurilioit. 

Many variants of fluidized or moving-bed electrodes have been proposed and operated at pilot or small commercial plant level. Such reactors have largely attempted to reduce the problems of bed agglomeration, poor bed-feeder contact and feeder deposition by controlling the dynamics of the mobile electrode phase. Several such cases are shown in Fig. 2.37, while Chapter 7 provides further examples. 

Three-dimensional electrodes are configured as static or solid electrodes (porous or packed bed), or as dynamic or fluid bed electrodes (fluidized bed and moving bed), cf. Table 6. 

Scott [11] compared three types of circulating particulate electrodes for copper recovery from dilute solutions (Fig. 1) spouted (circulating) beds, vortex beds, and moving beds. The beds contained 500— 700 pm spherical copper particles positioned on a stainless steel cathode feeder, and a platinized titanium anode. All electrodes performed similarly in terms of copper recovery current efficiencies. Recovery was found to be more efficient at low pH and high metal concentrations. The spouted bed electrode was preferred on the basis of scaleup. 

Fig. 1. A schematic of three types of circulating particulate-bed electrodes studied for copper recovery (a) spouted bed (b) vortex bed (c) moving bed. b bed region d diaphragm f feeder e electrolyte flow. (Adapted from [11]).

The moving electrodes include fluidized bed electrodes [25, 26], formed by individual carbon or metal particles fluidized by an appropriate flow of electrolyte, and also Circulating bed electrodes [26, 27] where the geometrical configuration promotes two differentiated zones concerning the relative motion of particles and solution one with both circulating in the same direction, the other with counter-current stream of each phase. Several less... 

To increase the efficiency for the electrochemical treatment of effluents rotating three-dimensional electrodes were also tested. Thus, a rotating packed bed electrode [44] and a vertically moving particle bed electrode were proposed [45, 46]. Plater barrels were also adapted for the removal of metals [47,48]. Likewise, rotating cylinder electrodes made of reticulated vitreous carbon [49], expanded metal sheets [50], woven wire meshes [51] and wedge wire screens [52] were also examined. 

The RF welding press has two platens—a move-able one, and a fixed one also called a bed. During the process, the press lowers the moveable platen and closes the electric circuit. The parts to be welded are placed in a set of metal dies or electrodes which are usually activated by a compressed air cylinder to apply a preset amount of pressure at the joint area. RF energy flows and the materials heat and melt. The joint cools under pressure and after the appropriate time the press opens and releases the welded assembly. 

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