Materials Performance

NOV 2018

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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22 NOVEMBER 2018 W W W.MATERIALSPERFORMANCE.COM FEATURE ARTICLE W Whether fueled by coal, gas, nuclear power, or geothermal energy, these types of power plants have one common feature: they use heat to generate electricity. Geothermal power plants use geothermal resources—reservoirs of hot water that exist at varying temperatures and depths below the Earth's surface—as a heat source. In the geothermal energy production process, heat from the Earth is accessed by drill- ing water or steam wells in a process similar to drilling for oil. A production well, which can be more than a mile (1.6 km) deep, is drilled into a known geothermal reservoir. The hot geothermal fluids then flow through pipes to a power plant where the hot, pressur- ized geothermal fluid or a secondary working fluid is allowed to expand rapidly and pro- vide rotational or mechanical energy to turn the turbine blades on a shaft for electricity generation. Typically, an injection well is also drilled to return used geothermal fluids to the geothermal reservoir. According to NACE International members W.D. MacDonald and J.S. Grauman with Titanium Metals Corp. (Exton, Pennsylvania, USA), tapping the energy potential in high- power geothermal wells can be restricted by the ability to specify materials that will with- stand the extreme environmental conditions. Geothermal brine reservoirs typically pose severe corrosion problems for operators—due to the combination of steam, water, and brine at elevated temperatures; the presence of hydrogen sulfide (H 2 S) and carbon diox- ide (CO 2 ); and high chloride content—yet these resources can also yield high-enthalpy steam that produces higher power outputs, so they have become very desirable fields to develop. 1 The Salton Sea Known Geothermal Resource Area (KGRA) is a high-enthalpy geother- mal field in the Salton Sea, the largest lake in California, USA, and saltier than the Pacific Ocean. Located ~60 miles (97 km) east of San Diego, California, the area contains one of Testing Corrosion- Resistant Alloys for Use in Geothermal Power Plants Utilizing the energy potential in high-power geothermal wells can be expanded with materials that withstand the extreme environmental conditions. Kathy Riggs Larsen

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