Design of Anodes

The installation costs for a single impressed current anode of high-silicon iron can be taken as = DM 975 ( 550). This involves about 5 m of cable trench between anodes so that the costs for horizontal or vertical anodes or for anodes in a common continuous coke bed are almost the same. To calculate the total costs, the annuity factor for a trouble-free service life of 20 years (a = 0.11, given in Fig. 22-2) should be used. For the cost of current, an industrial power tariff of 0.188 DM/kWh should be assumed for t = 8750 hours of use per year, and for the rectifier an efficiency of w = 0.5. The annual basic charge of about DM 152 for 0.5 kW gives about 0.0174 DM/kWh for the calculated hours of use, so that the total current cost comes to 

The wattage i I is directly proportional to the grounding resistance of the whole anode bed and therefore to the specific soil resistivity. Equation (9-5) gives the grounding resistance of the anode installation which either consists of n horizontal or vertical single anodes or of anodes with a horizontal continuous coke bed of total length I ns. The total cost function is given by [1]  

Differentiating with respect to n gives the desired minimum cost for the economical number of anodes, n  

It must be emphasized that areas with low soil resistivity should be chosen for siting the anode beds. 

The current requirement of the protected object basically determines the design of the anode bed. For example, for a pipeline requiring 10 A with horizontal anodes laid in soil with p = 45 m, according to Fig. 9-14, eight anodes are necessary. The grounding resistance of one anode amounts to / = 14 12. From Fig. 9-8, the grounding resistance of the anode bed with an interference factor F = 1.34 for 8 anodes spaced at 5 m comes to Fg = 2.34 Q.. 

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Design of Anode Electrocatalysts for the CO-Tolerant H2 Oxidation and CH3OH Oxidation... 

T. F. Hung, H. Wong, and Y. C. Cheng, A new design of anodic oxidation reactor for high-quality gate oxide preparation, J. Electrochem. Soc. 138, 3747, 1991. 

Forming bipolar plates from stamped metal sheets imposes constraints in the design of the gas distribution structures. Furthermore, the design of anode, cathode and coolant flow fields no longer is independent. Careful design of the flow structures is required to avoid media bypassing the intended distribution channels as well as imeven media supply across the active area. 

Proper design of the flow zones is of particular importance in the case of metallic bipolar plates since the design of anode, cathode and coolant flow field cannot be optimized individually. Furthermore, when using a bead seal concept, coolant flow diversion in the bead needs to be taken into account. 

Fig 1. Comparison of design of Anode Supported SOFC and Metal Supported SOFC... 

As already mentioned, no general principles concerning the design of anodic protection systems have been prepared up to now. Such problems as the number and location of cathodes and reference electrodes are solved experimentally. However, on the basis of information obtained for many industrial objects with anodic protection, some principles may be established concerning the method of polarization of the structure (Foroulis, 1980). 

One important application of amperometry is in the construction of chemical sensors. One of the first amperometric sensors to be developed was for dissolved O2 in blood, which was developed in 1956 by L. C. Clark. The design of the amperometric sensor is shown in Figure 11.38 and is similar to potentiometric membrane electrodes. A gas-permeable membrane is stretched across the end of the sensor and is separated from the working and counter electrodes by a thin solution of KCl. The working electrode is a Pt disk cathode, and an Ag ring anode is the... 

In electrolytic processes, the anode is the positive terminal through which electrons pass from the electrolyte. Anode design and selection of anode materials of constmction have traditionally been the result of an optimisation of anode cost and operating economics, in addition to being dependent on the requirements of the process. Most materials used in metal anode fabrication are characteristically expensive use has, however, been justified by enhanced performance and reduced operating cost. An additional consideration that has had increasing influence on selection of the appropriate anode is concern for the environment (see Electrochemical processing). 

Metal anodes using platinum and precious metal oxide coatings are also incorporated into a variety of designs of impressed current protection for pipeline and deep weU appHcations, as weU as for protection of condenser water boxes in power generating stations (see Pipelines Power generation). 

Designed to accommodate rectifier amperages from 30 to 150 kA. Cells of various kA ratings vary in the length of cell and number of anodes and cathodes. Operating characteristics vary with current density (30). 

Examples of the Design of Protective Installations 11.3.3.1 Equipment Using Galvanic Anodes... 

Chemical analyses should be provided for all anodes used in the offshore and harbor area, together with results for current content in A h kg and current output in amperes [2,3]. The geometric shape and the number of anodes required is determined by these parameters. Expensive calculations for design based on grounding resistances are made only in exceptional cases because in practice there are too many uncertainties and the number and mass of the anodes have to be quoted with a corresponding safety factor. 

Production platforms are coated only in exceptional cases or for the purposes of investigation because the life of the structure is greater than the life of the coating. Therefore in the design of the cathodic protection, only the protection potential Us of the steel need be considered. Steels with an ultimate tensile strength of up to 350 N mm are used for these structures, which are weldable even in thick sections, and the hardness of the welded material can be kept to 350 HV (see Section 2.3.4 [2,10]). Aluminum anodes with the same protection effect and life as zinc anodes have much less weight. This is a very important advantage for... 

The required number, n, of anodes can be calculated using Eq. (17-2) from the current requirement, together with the maximum current output 1 of the anodes. The arrangement of the anodes is dealt with in Section 17.3.2.2. Galvanic protection systems are usually designed to give protection for 2-4 years. After this period, a maximum of up to 80% of the anodes should be consumed. 

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