Intercell Contact Bar

COMPARISON OF INTERCELL CONTACT BARS FOR ELECTRO WINNING PLANTS... 

Hatch has completed a study to compare a number of intercell contact bar designs currently available in the market for their use in electrowinning and electrorefining plants. The different designs have been compared on a number of bases to determine their ability to produce consistent product and minimize operating costs. 

This paper presents the theory that governs calculation of resistive drop and power consumption for intercell contact bars and the electrode header bars that rest on them. A comparison is then made of the different contact systems to assess their relative efficiency with particular reference... 

It is important that the different types of contacts used in all of these systems can be classified as either line contacts or point contacts according to the shape of the interface between the electrode header bar and the intercell contact bar. 

A line contact occurs when the electrode header bar and intercell contact bar form a contact interface on an edge. This occurs when the flat surface of one member contacts the edge of the other. A point contact occurs when the two contacting items contact at a point. This can only occur when an edge from one member contacts the edge of another member or when an edge from one member contacts a convex surface of another member. 

Intercell Bar - Standard Walker System, The Walker System uses continuous intercell contact bars which electrically connect adjacent cell electrodes in a parallel fashion. This system was patented in 1901 [1] and appears to be the basis of the more refined contact bar arrangements developed over time. The typical Walker system bars are generally of a dog-bone or triangular profile [2]. 

DoubleContact - Outotec. Outotec s DoubleContact intercell contact bar system is designed so that all electrodes have an electrical contact on each end. These electrical contacts are all line contacts. Outotec has claimed that the principal benefit of using the double contact system is a more even current distribution [4]. The basis of this design is that if there is a poor contact between an electrode and the contact bar, the electrode will still receive current from the contact on the other end of the electrode from the equalizer bar. Outotec claims that a more even current distribution is likely to reduce energy consumption and lead to better quality cathodes [4]. In this paper, the impact of the equalizer bars is not considered. This results in this system being considered as a simple dog-bone system. 

Spool system - Cominco. The spool or sloping-tangent contact bar was developed in the 1970s by Cominco Ltd and utilizes a contact bar similar to that shown in Figure 4. This bar is claimed to provide excellent electrical contact via the notched portion of the header bars [5]. In theory this arrangement results in each electrode having four points of contact with the intercell contact bar. 

Notehed Intereell Contaet Bar. The notched intercell contact bar provides a double line contact for the cathode at the primary current transfer end as detailed in Figure 5. 

Table I provides a summary of the intercell contact bars described above and their typical applications. 

The total resistance of the intercell contact bar network is the sum of the contact resistances between the electrodes and the intercell contact bar, and the bulk resistance, as shown in Figure 7. 

Contact Resistance. To enable calculation of the cathode and anode contact resistances for each of the intercell contact bar systems, the equations presented in the literature have been assessed. For the case of two items being brought into contact, the area in apparent contact is much smaller than would be expected due to the microscopic high points (asperities) on each face. The resistance due to this smaller than expected area, is called the constriction resistance [7]. Additional resistance can occur due to thin films such as oxide deposits occurring on the contact surfaces. The sum of the constriction resistance and film resistance makes up the contact resistance for a particular contact. 

The major components of the resistance and differences between their values for the various intercell contact bar types are reviewed below. 

The rule-of-thumb lA/mm was used to determine an initial cross-sectional area of the intercell contact bar - cross-sectional area was 400mm. ... 

Table II compares the different intercell contact bars mentioned, and displays the contact resistances that have been calculated for each ICCB system on the basis of no anode bags being used.

The contact resistances are dominant over the bulk resistance of the intercell contact bar at between 95 and 98% of the total resistance. 

This paper described the most common intercell contact bars currently available. These bars have been analyzed to determine how much electrical resistance can be expected due to the intercell contact bar system and have also been compared on the basis of other practical plant considerations. It was found that ... 

This paper introduces the concept of determining the contact resistance of an intercell contact bar interface, and to use this information along with other parameters to develop the most efficient solution in the future. In future work the following additional aspects will be considered ... 

Comparison of Intercell Contact Bars for Electrowinning Plants.177... 

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