Anode busbar

Anode head-bars rest on a busbar along one side of the cell and cathode head-bars rest on a busbar on the opposite side. Cells may be placed side by side, in which case the anode busbar for one cell serves as the cathode busbar for the adjacent cell. This means that cells are electrically connected in series with connections to the DC power supply only at the end of each cell bank. 

Busbars. Fitting the tank for d-c power is usually accompHshed usiag round copper busbars, both for supporting the anodes and the work or cathodes. Size of the copper bus is determined by the amount of current flow expected 1000 amperes requires about 6.5 cm of cross-sectional area. The bus is iasulated from the tank, and any other sources of grounding, and coimected to the d-c power supply. Shorter distances from the tank as well as fewer electrical connections keeps the voltage drop to a minimum. 

In a typical electrowinning or electrorefining operation, the electrolytic cells are rectangular tanks, and each contains 20-50 electrode pairs. An additional anode is required in each cell to ensure deposition on both sides of each cathode. The electrodes are designed to rest on busbars that supply electricity. The busbars are situated outside the top of each tank, one for the anodes and another for the cathodes. Thus, the electrode pairs in each tank operate in parallel. In the tankhouse, the cells are arranged in sections with the banks of cells connected in series and parallel to obtain optimum use of the electrical power, while keeping the voltage to earth at any point at a low level that is not a risk to the personnel. 

In the traditional parallel-plate cells, the Walker system is the most commonly used electrical arrangement (Fig. 13). In this system, the current flows from a copper busbar on one side of the cell to the anodes, and the cathodes are connected to another busbar on the opposing side of the cell. The second busbar feeds current to the anodes of the second cell, and so on. In the Walker system, only one side of each electrode is connected to the electric circuit. The intercell busbars do not require so much thickness as the end busbars as the current flows through the path of least resistance. 

Fig. 20 The arrangement of busbars and anode rods for six end riser cells mathematically modeled by Lympany and Evans. The cells are in two potlines and each cell has 18 anodes [50].

Because all electrochemical reactions involve anodic and cathodic reactions, polarization will have components for both reactions. As will be explained later, the electrode potentials have two terms for each electrode surface overpotential ija or ijc and concentration overpotential Apart from these overpotentials, electrical energy will also be expended due to the electrical resistance of the cell components such as electrolyte, diaphragm, busbar, etc. Thus the practical cell voltage (, when a net current is flowing through the cell, is the sum... 

With a theoretical 258.7 amp hours per kilogram of lead and a current efficiency of 95 per cent the actual current required is 272.3 amp hours per kilogram. For an average cell voltage of 0.5 over the anode cycle life the energy use is 136.2 DC watt hours per kg (or DC kilowatt hour per tonne of lead). With busbar and conversion losses of the order of ten per cent the AC energy consumption is close to 150 AC kWh per tonne of refined lead, which is a relatively low cost item. 

E ) is a thermodynamic component of the cell voltage, and are the cathodic and anodic overpotentials, Rcell rmstanoe of the electrolyte (plus any separator) and /taacuiT represents the resistance of electrical connections such as busbars. Equation (2.7) may be rewritten ... 

Voltage drop in the electrolyte cathode ovcrpotential due to organics and polarization Anode and cathode electrical connections Busbar and lead losses Anode polarization 0.11-X)J3 a04-0.08 0.03-0.06 0.01-0.02 0.0-0.01... 

Fig. 2.32 The FM21 SP Electrolyser. (a) The overall construction, (b) A single electrode, which has a nominal projected area of 0.21 on each face. The photograph shows the electrolyte ports and the current feeder busbar. A symmetrical lantern blade electrode is shown complete with its compression-moulded gasket, (c) An assembled, multi-electrode reactor, showing the electrolyte manifolds and the end plate. The electrolyser unit is capable of taking up to 60 electrode pairs, which would provide a projected cathode or anode area of up to 25 m. A double-pack version utilizes a central plate extending, the capacity to a maximum of 120 electrodes (50 m ). The construction of FM21 electrolysers for chloralkali production is considered in Chapter 3. (Photographs supplied by ICI Chemicals and Polymers Ltd.)...

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