Corrosion electric utilities

Utilities Utilities consist of gas, water, electricity, and telecommunications services and account for the largest portion of industrial corrosion costs. The total direct corrosion costs amount to 47.9 billion. These costs are partitioned into sectors of gas distribution, drinking water and sewer systems, electrical utilities, and telecommunications (Fig. 2.4). 

Electrical Utilities There are seven generic types of electricitygenerating plants such as fossil fuel, nuclear hydroelectric, cogeneration, geothermal, solar, and wind. The major sources in use in the United States are fossil fuel and nuclear supply systems. The direct cost attributed to corrosion was 6.9 billion with the largest amount for nuclear power ( 4.2 billion), fossil fuel (1.9 billion), hydraulic power ( 0.15 billion), transmission, and distribution (0.6 billion). 

Areas of Major Corrosion Impact on Electric Utility Systems... 

The impact of corrosion on electric utility systems can be divided into the fraction of utility costs for depreciation, operation, and maintenance that are attributable to corrosion. The estimated costs discussed for this sector are based on detailed analysis of facilities and work activities, using input from Duke Power, an energy company serving more than two million people in North and South Carolina and the Electric Power Research Institute (EPRI) reports, technical literature, and other utilities. 

The total cost of electricity sold in the United States in 1998 was 3.24 million gigawatt hours at a cost to consumers of 218.4 billion. The electricity generation plants use fossil fuel, nuclear, hydroelectric, cogeneration, geothermal, solar, and wind energies. The major players are fossil and nuclear steam supply systems. The two types of nuclear reactors are boiling water and pressurized water reactors. Some relevant data on the costs of corrosion estimated in 1998 are as follows nuclear facilities 1,546 billion fossil fuel sector 1,214 billion transmission and distribution 607 million hydraulic and other power 66 million. The total cost of corrosion in the electrical utilities industry in 1998 is estimated at 6,889 billion/year. 

The resistance of ceramically bonded and recrystallized SiC to thermal shock, oxidation and corrosion is utilized in its use as a refractory construction material, for example, in the linings and skid rails for furnaces and hot cyclones, and as a kiln furniture, especially in saggars [164,552-556]. The good electrical conductivity of the material at high temperatures, coupled with its outstanding oxidation resistance, led to its early use in the electric heating industry [557-559], which markets its products... 

Jonas, O., "Cost of Corrosion and Scale in Electric Utilities, Paper presented at the EPRI Symposium on Fossil Utility Water Chemistry, Atlanta, 11-13 June 1985. 

Continuous, on-line corrosion monitoring can be used to operate FGD systems at optimal efficiency while avoiding high corrosion rates. Conventional corrosion monitors are designed for use in bulk liquids and do not function satisfactorily in the thin condensate films that form on the surfaces of FGD ducts. Recent EPRI research has made use of an advanced electrochemical method of corrosion surveillance developed by the Corrosion and Protection Centre Industrial Services (CAPCIS) in England [30]. This method allows on-line monitoring of corrosion activity in either thin condensate films or bulk liquids. EPRI introduced the CAPCIS system to the U.S. electric utility industry in 1985, sponsoring several field demonstrations. 

Polymer Electrolyte Membrane (PEM) Solid organic polymer poly-perflouro-sulfonic acid 60-100 Electric utility, transportation, portable power Solid electrolyte reduces corrosion, low temperature, quick start-up... 

The A" and B Monel alloys, supplied for the study by the electrical utility company, Ontario Hydro, were first characterized metallographically in this laboratory to ensure that each had the same metallurgical properties as. specimens studied in the past by Ontario Hydro corrosion engineers. 

Magnetic flow meters are sometimes utilized in corrosive Hquid streams or slurries where a low unrecoverable pressure drop and high rangeabiHty is required. The fluid is required to be electrically conductive. Magnetic flow meters, which use Faraday s law to measure the velocity of the electrically conductive Hquid, are relatively expensive. Their use is therefore reserved for special situations where less expensive meters are not appropriate. Installation recommendations usually specify an upstream straight mn of five pipe diameters, keeping the electrodes in continuous contact with the Hquid. 

Linear polarization instruments provide an instantaneous corrosion-rate data, by utilizing polarization phenomena. These instruments are commercially available as two-electrode Corrater and three electrode Pairmeter (Figure 4-472). The instruments are portable, with probes that can be utilized at several locations in the drilling fluid circulatory systems. In both Corrater and Pairmeter, the technique involves monitoring electrical potential of one of the electrodes with respect to one of the other electrodes as a small electrical current is applied. The amount of applied current necessary to change potential (no more than 10 to 20 mV) is proportional to corrosion intensity. The electronic meter converts the amount of current to read out a number that represents the corrosion rate in mpy. Before recording the data, sufficient time should be allowed for the electrodes to reach equilibrium with the environment. The corrosion-rate reading obtained by these instruments is due to corrosion of the probe element at that instant [184]. 

Aluminium and the aluminium alloys lend themselves to many engineering applications because of their combination of lightness with strength, their high corrosion resistance, their thermal and electrical conductivity and heat and light reflectivity, and their hygienic and non-toxic qualities. The variety of forms in which they are available also enhances their utility. 

The band edges are flattened when the anode is illuminated, the Fermi level rises, and the electrode potential shifts in the negative direction. As a result, a potential difference which amounts to about 0.6 to 0.8 V develops between the semiconductor and metal electrode. When the external circuit is closed over some load R, the electrons produced by illumination in the conduction band of the semiconductor electrode will flow through the external circuit to the metal electrode, where they are consumed in the cathodic reaction. Holes from the valence band of the semiconductor electrode at the same time are directly absorbed by the anodic reaction. Therefore, a steady electrical current arises in the system, and the energy of this current can be utilized in the external circuit. In such devices, the solar-to-electrical energy conversion efficiency is as high as 5 to 10%. Unfortunately, their operating life is restricted by the low corrosion resistance of semiconductor electrodes. 

Mitsubishi Electric Corporation investigated alloyed catalysts, processes to produce thinner electrolytes, and increases in utilization of the catalyst layer (20). These improvements resulted in an initial atmospheric performance of 0.65 mV at 300 mA/cm or 0.195 W/cm, which is higher than the IFC performance mentioned above (presented in Table 5-2 for comparison). Note that this performance was obtained on small 100 cm cells and may not yet have been demonstrated with full-scale cells in stacks. Approaches to increase life are to use series fuel gas flow in the stack to alleviate corrosion, provide well-balanced micro-pore size reservoirs to avoid electrolyte flooding, and use a high corrosion resistant carbon support for the cathode catalyst. These improvements have resulted in the lowest PAFC degradation rate publicly acknowledged, 2 mV/1000 hours for 10,000 hours at 200 to 250 mA/cm in a short stack with 3600 cm area cells. 

Clay filtration can be utilized to effectively remove polar compounds such as corrosion inhibitors, electrical conductivity improvers, and antioxidants from jet fuel. Also, more costly molecular sieve techniques can be utilized to remove contaminants from jet fuel. 

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