Advanced Fossil Fuel Energy Technologies:
The Materials Demand
Fossil fuels currently provide a significant amount of the worldwide energy and chemical needs because of their high energy density, availability, relatively low cost, ease of utilization with current technology, and highly developed distribution intrafracture. Increased reliance on fossil fuels, however, has created a number of questions, the most pressing of which is the impact of their utilization on the environment. Advanced combustion technologies and gasification-based systems can increase the efficiency and decrease the environmental impact associated with producing energy from carbon-containing materials, as well as provide an opportunity for CO2 capture and sequestration. In addition to electricity, the synthesis gas produced by the gasification of fossil fuels can provide the building blocks for synthetic fuels for the transportation sector, or be a source of hydrogen for fuel cells. Gasification is also fuel-flexible, so that mixed feedstocks – such as biomass combined with coal – can be gasified to produce energy products that are essentially carbon neutral, if CO2 sequestration is also employed.
of these advanced technologies will be required to enable fossil fuels as a viable transition technology in the coming decades while alternative, sustainable energy technologies are developed and realized at commercial scale. However, implementation of advanced fossil fuel energy technologies will not occur without simultaneous advances in materials science and engineering. Higher efficiencies in combustion and gasification processes typically mean higher operating temperatures and more aggressive service environments, placing a huge stress on materials of construction. Mixed feedstocks require more robust, impurity tolerant membranes and catalysts. Reliability and availability requirements by plant operators demand materials that are stable for thousands of hours in environments that are high temperature, corrosive, and potentially subject to thermal cycling. Reliable performance is expected of these materials without high cost. In some cases, meeting these requirements will call for new, high performance materials to be developed, in others, protection strategies will be needed to extend service life.
In conventional pulverized coal combustion (PCC),
for example, higher efficiencies are being sought through an increase in the temperature and pressure of the product steam. Ultra supercritical (USC) power plants, operating at temperatures in excess of 700 º C, will require material shifts from iron-based alloys to nickel-based superalloys for the components exposed to the higher steam temperatures and pressures. Coating and/or cladding strategies are being explored that may enable existing components to achieve the necessary performance criteria. Other research efforts focus on reducing the environmental impact of PCC, such as developing new chemical processes and/or absorbent materials for pre- and post-combustion CO2 capture; and “oxy-fuel” combustion, which utilizes oxygen to combust the fuel, thereby reducing NOx emissions and facilitating CO2 capture. Oxy-fuel combustion, whether in a retrofit or new construction, changes the operating environment of the boiler, potentially exasperating fireside corrosion and increasing wall temperatures. In addition, oxyfuel combustion requires an affordable and reliable source of oxygen, which could be provided by ion transport membranes capable of sustained operation at 800-900 °C, and capable of producing oxygen from compressed air.
To reach increased efficiency
and reliability of IGCC plants, efforts are currently ongoing to develop materials and new coatings for the hot sections of gas turbines able to support the operation with syngas or other fuels more aggressive than natural gas. Also the much higher water content of the combustion gases will create new material problems to be solved in the design of hot sections of future gas turbines.
Other materials issues exist in gasification plants, including the reliability of the refractories used to line air cooled slagging gasifiers that operate between 1325-1600 °C, with a variety of feedstocks, and the lack of reliable temperature and gas sensors for gasifiers that are responsive and selective over a wide temperature range and in molten slag. To satisfy the needs of industry, materials must provide sufficiently long and predictable service life at an affordable cost.
Materials challenges are not limited to boilers, turbines and gasifiers, but extend to hydrogen and fuels production from synthesis gas. Improved, robust catalysts for the water-gas shift reaction and for fuels production; sulphur-, ammonia- and chloride-tolerant hydrogen separation membranes with high throughput and selectivity; high performance, defect-free, inorganic, and organic or hybrid CO2 selective membranes; and high temperature seals for membrane assemblies are among the research needs.
aims at discussing the materials challenges imposed by the operating environments necessary for advanced fossil fuel energy systems, and the materials solutions that can be implemented to effectively address them. Goal will be defining these new systems needs, and the necessary research (testing and development) of materials to meet these needs, while achieving the performance characteristics necessary to reliably maintain the conversion of carbon-containing materials to energy in an efficient and environmentally benign way. Sessions will encompass all major aspects concerning the science and characterisation of materials, advanced processing technologies that can economically produce components at the required scale, and their evaluation in service; linked to a deeper understanding of the underlying physics and chemistry of materials such as catalysis, membrane separation mechanisms, and materials/environment interactions.
Topics will feature, but are not limited to, advances in:FA-1 Fossil Fuel Combustion
FA-1.1 Improved or new materials (steels, ODS alloys, Ni and Co based superalloys, aluminides, ceramic-matrix composites)
FA-1.2 Membranes for oxygen separation. Adsorbents for CO2 capture
FA-1.3 Thermal and protective coating
FA-1.4 Long-term creep and fatigue
FA-1.5 Corrosion and erosion
FA-2 Gasification and gas clean-up
FA-2.1 Catalysts for water-gas shift and catalysts for fuels production
FA-2.2 Membranes for H2 separation and CO2-selective membranes
FA-2.3 High temperature seals