Advanced materials that are expected to increase operating temperatures and therefore the efficiency of coal fired power plants are being evaluated by a consortium team under the technical direction of the Electric Power Research Institute in collaboration with the US Department of Energy.
Critical boiler components in existing older plants can be retrofitted with these advanced materials to allow for the continued use of the types of coal that are locally available, including high-sulphur coals. "Efficiency gains by as much as nine percentage points and CO2 reductions approaching 22 per cent are expected through the advanced materials technology being developed in this collaborative programme," said EPRI's Vis Viswanathan, overall technical manager for the project.
The five-year programme is being funded by DOE through the National Energy Technology Laboratory and co-funded by the Ohio Coal Development Office (OCDO). Consortium members are Alstom Power, Riley Power, Babcock & Wilcox, and Foster Wheeler. The increase in generating efficiency is to be achieved principally through the use of newly developed materials for piping, tubing, and waterwall panels that perform well under extremely high-temperature (ultrasupercritical) steam conditions. State-of-the-art supercritical plants operate at throttle steam conditions of approximately 1000°F-1100°F at pressures around 3600 psi. In contrast, the materials technology being developed envisages plant steam conditions approaching 1400°F at 5000 psi pressure. In the short term, these materials can also be used in existing older plants for selective retrofit of critical components, thus maximising plant reliability and availability.
The team has completed preliminary studies for two alternative ultrasupercritical boiler designs. Candidate materials have been identified, and corrosion studies have been conducted. Welding, fabrication, and coating trials are also in progress. Investigators have concluded that the capital cost of the boiler and steam turbine in an advanced supercritical plant can be 40 to 50 per cent higher than conventional components, and the ultrasupercritical plant will still be cost-competitive.
Even if construction of an ultrasupercritical plant costs 12 to 15 per cent more than a comparable-scale conventional facility the additional expense should be more than offset by fuel savings and reduction in balance-of-plant costs.
"This will enable coal-based electricity generation to continue at competitive rates, while substantially reducing emissions of carbon dioxide and fuel-related pollutants."
, as well as DOE's Oak Ridge National Laboratory.
"The efficiency advantages associated with higher-temperature operation will allow the US and other countries to continue using indigenous fuel supplies - including high-sulphur coals," says NETL's technology manager for Power Systems Advanced Research, Bob Romanosky.
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