Plate-in-tank cells

These limitations have encouraged developments in two directions. Improvements in conventional plate-in-tank cells have included ... 

Fig. 2.5 Elementary reactor geometries, (a) Parallel-plate cell, (b) Concentric rotating-cylinder cell, (c) Plate-in-tank cell, (d) Plate cell with non-parallel electrodes.

Tank Cells. A direct extension of laboratory beaker cells is represented in the use of plate electrodes immersed into a lined, rectangular tank, which may be fitted with a cover for gas collection or vapor control. The tank cell, which is usually undivided, is used in batch or semibatch operations. The tank cell has the attraction of being both simple to design and usually inexpensive. However, it is not the most suitable for large-scale operation or where forced convection is needed. Rotating cylinders or rotating disks have been used to overcome mass-transfer problems in tank cells. An example for electroorganic synthesis is available (46). 

Fig. 4.6 Methods of improving mass transport in vertical plate-in-tank electrowinning cells, (a) Tapered anode with mass transport improved by oxygen evolution at the. anode (cathodic hydrogen evolution may also enhance mass transport), (b) Air-sparging (electrolyte jetting may also be used electrolyte outlet is not shown.)...

Newt, Triturus cristatus, adults, held in tank with a zinc-plated base South African clawed frog, Xenopus laevis 200 to 3000 overa 7-day period Zinc-poisoned newts were lethargic, ate poorly, and had skin darkening prior to death. Zinc residues were elevated in kidney, brain, liver, and intestine, when compared to controls. The hippocampus region of the brain of poisoned newts contained zinc-rich cells 82... 

In this cell, mechanical vibration is applied to the cell housing to enhance the transfer in the parallel plate tank cell [248]. The vibrations are transfered to the electrolyte resulting in an increase of the mass-transfer coefficient. The cell is extensively used in industry for the pretreatment of higher and high metal concentrations which is finally purified by a packed bed electrolysor if the required conversion is not too high [247],... 

Stuart cell — Monopolar water - electrolysis tank cell employing plate electrodes with those of the same polarity connected in parallel resulting in a cell voltage of 1.7-2 V. Cells are connected in series, the inherent drawbacks of cells of the filterpress design (e.g., complicated sealing and interconnect devices) are avoided. 

The ideal cell in order to scale up an electrochemical reaction can depend on the reaction, the electroactivity of the substrate to convert, the concentration of the substrate, as well as the current density at the working electrode. The use of a separator is necessary when the electrode can affect the whole process negatively. With anodic oxidations, the reaction at the counter electrode is most frequently the cathodic formation of hydrogen. In these cases, a separator does not seem indispensable a tank cell (kind of Grignard type reactor equipped with cylindrical electrodes) or a capillary-gap cell (piling of bipolar electrodes in a cylinder-shaped vessel connected to an anodes and a cathode located at the top and the bottom of the cell) can be considered as suitable devices for anodic conversions. More generally, the so-called plate-and-frame cells (Fig. 4) are used in a battery. 

Electrochemical reactors are heterogeneous by their very nature. They always involve a solid electrode, a liquid electrolyte, and an evolving gas at an electrode. Electrodes come in many forms, from large-sized plates fixed in the cell to fluidizable shapes and sizes. Further, the total reaction system consists of a reaction (or a set of reactions) at one electrode and another reaction (or set of reactions) at the other electrode. The two reactions (or sets of reactions) are necessary to complete the electrical circuit. Thus, although these reactors can, in principle, be treated in the same manner as conventional catalytic reactors, detailed analysis of their behavior is considerably more complex. We adopt the same classification for these reactors as for conventional reactors, batch, plug-flow, mixed-flow (continuous stirred tank), and their extensions. 

The use of chromic acid as a depolariser instead of nitric acid was proposed by Bunsen," who later described a cell with zinc and carbon plates in chromic acid solution in glass tanks and an arrangement for lifting the plates out of the solution. Small bottle-shaped cells were popular in laboratories. Bunsen described a thermopile composed of copper and copper pyrites. ... 

Two-dimensional electrodes. Two-dimensional electrodes appropriate for metal recycling are typically based on the tank electrolyser to enable ready removal of metal plated electrodes. The simplest cells are the vertical, plate or mesh, electrode in tank units where turbulence is provided by using either inert fluidised beds [8] (Chemelec Cell, BEWT Water Engineers Ltd.) or air agitation (Reconwin cell), in conjunction with electrolyte pumping (see Figure 11.3). 

Classical electrochemical reactor designs invariably evolved from direct scale-up of simple laboratory electrolysis experiments. The most common example of this concept is the tank cell where an array of electrodes is immersed in a plastic or metal tank. More sophisticated versions involve a variety of approaches to enhancing convection, by rapid stirring, rotating or moving electrodes or improving geometry with plate and frame or filter-press-type cells. 

---