Advanced Fossil Energy Technology Research, Subtopic d – "Corrosion and Erosion Resistant Surface Features for High Pressure Supercritical Carbon Dioxide Heat Exchangers"

Advanced highly efficient and compact, supercritical carbon dioxide power plants are being developed to replace Rankine based steam cycles in industrial and utility applications. They promise to be more efficient and compact, as well as lower in cost than current power systems. Heat exchangers for these plants represent approximately one third of the plant cost. Given the high temperatures of operation, corrosion and erosion can degrade these heat exchangers and drive up maintenance and replacement costs. This will reduce the commercial potential of this promising power system to replace waste heat, fossil, nuclear and concentrating solar energy driven power systems. The proposer has identified an innovative technology that leverages the current heat exchanger bonding process to also improve the heat exchanger surface characteristics to address corrosion and erosion as a result of operation with supercritical carbon dioxide. By going to this one step process, heat exchanger corrosion and erosion resistance can be improved, at low cost. Furthermore, the base structural strength of the heat exchanger will remain unchanged. Lastly, the process is applicable to moderate temperature waste heat applications, as well as higher temperature fossil, nuclear and concentrated solar power systems. During the effort, the proposer will prepare batches of test coupons prepared from intermediate and high temperature heat exchanger materials. These coupons will include additives to promote corrosion and erosion resistance. These coupons will then be furnace bonded to create structural strength, as in a full scale heat exchanger, and then tested for integrity. Tests will consist of measuring weight changes due to corrosion and erosion and metallography inspection of the base metal and surface zones to characterize and quantify corrosion and erosion effects. In addition, a pull test will be used to determine the bond strength. An analysis will then be conducted to determine the optimum additives to create both the needed strength and corrosion and erosion resistance. High temperature heat exchangers represent up to one third the cost of efficient advanced utility power cycles. A method is proposed to greatly increase the high temperature durability of the heat exchangers, which will reduce maintenance and replacement costs and thereby realize the potential of these power systems. Commercial Applications and Other Benefits: The proposed concept applies to waste heat, fossil, nuclear and concentrating solar energy driven supercritical carbon dioxide power plants of industrial and utility scales. The concept will improve the durability and reduce the maintenance of heat exchangers that represent one third the cost of these advanced super critical carbon dioxide power plants.