The NETL Advanced Turbines Program manages a research, development, and demonstration (RD&D) portfolio designed to remove environmental concerns over the future use of fossil fuels by developing revolutionary, near-zero-emission advanced turbines technologies. In response to the Nation’s increasing power supply challenges, NETL is researching next-generation turbine technology with the goal of producing reliable, affordable, diverse, and environmentally friendly energy supplies. Program and project emphasis is on understanding the underlying factors affecting combustion, aerodynamics/heat transfer, and materials for advanced turbines and turbine based power cycles. The Advanced Turbines Program currently has three technology areas:
ADVANCED COMBUSTION TURBINES
Advanced Combustion Turbines for Combined Cycle Applications area is focused on components and combustion systems for advanced combustion turbines in combined cycle operation that can achieve greater than 65% combined cycle efficiency (LHV, natural gas benchmark) and support load following capabilities to meet the demand of a modern grid. To achieve this target, emphasis will be placed on advanced turbine concepts that are fueled with natural gas and coal derived fuels, including hydrogen and syngas, and higher firing temperatures (3,100 F).
Component R&D is being conducted that will allow higher turbine inlet temperatures, manage cooling requirements, minimize leakage, advance compressor and expander aerodynamics, advance the performance of high temperature load following combustion systems with low emissions of criteria pollutants including oxides of nitrogen (NOx), and overall lead to improved efficiency of the gas turbine machine in a combined cycle application. Projects in this topic area include research on pressure gain combustion systems, ceramic matrix composite components, and advanced turbine configurations for improved cooling and efficiency.
SUPERCRITICAL CO2 TURBOMACHINERY
The supercritical carbon dioxide power cycle operates in a manner similar to other turbine cycles, but it uses CO2 as the working fluid in the turbomachinery. The cycle is operated above the critical point of CO2 so that it does not change phases (from liquid to gas), but rather undergoes drastic density changes over small ranges of temperature and pressure. This allows a large amount of energy to be extracted at high temperature from equipment that is relatively small in size. SCO2 turbines will have a nominal gas path diameter an order of magnitude smaller than utility scale combustion turbines or steam turbines.
The Advanced Turbines Program at NETL conducts R&D for directly and indirectly heated supercritical carbon dioxide (CO2) based power cycles for fossil fuel applications. The focus is on components for indirectly heated fossil fuel power cycles with turbine inlet temperature in the range of 1300 - 1400ºF (700 - 760ºC) and oxy-fuel combustion for directly heated supercritical CO2 based power cycles.
The turbomachinery R&D focuses on advancing technologies and designs of turbomachinery to be used in the supercritical CO2 power cycle. Operating power cycles, either directly or indirectly, with supercritical CO2 offers potential for further improvements in power cycle efficiencies and lower costs. However, the utilization of supercritical CO2 as the working fluid must be considered when designing the turbines. Extremely compact turbine sizes are possible for use in the supercritical CO2-based power cycles. These turbines will have high power density, lower peripheral speeds, high blade loading, and high shaft speeds, all of which will factor into the final turbine designs. The high pressure, relatively high temperature, uncertainty of the CO2 state near the critical point, and high power density create design challenges for the supercritical CO2 turbomachinery. The R&D will consider all aspects of the turbomachinery, including the turbo-expander, compressors, pumps, airfoils, turbine coupling with the motor/generator, seals, casings, bearings, shafts, and valves.
PRESSURE GAIN COMBUSTION
Pressure gain combustion (PGC) has the potential to significantly improve combined cycle performance when integrated with combustion gas turbines. While conventional gas turbine engines undergo steady, subsonic combustion, resulting in a total pressure loss, PGC utilizes multiple physical phenomena, including resonant pulsed combustion, constant volume combustion, or detonation, to affect a rise in effective pressure across the combustor, while consuming the same amount of fuel as the constant pressure combustor. The methodology resulting in a pressure-gain across the combustor relies on the Humphrey (or Atkinson) cycle and is seen to have great potential as a means of achieving higher efficiency in gas turbine power systems, potentially reaching 4-6% for simple cycle systems and 2-4% in combined cycle systems. At the power system level this efficiency increase would reduce the cost and performance penalty incurred by capturing carbon. The high reactivity of hydrogen fuels from an IGCC with pre-combustion capture is particularly attractive to certain PGC concepts.
Pursuing PGC as a method for realizing a step-change in efficiency provides another approach to the 65 percent combustion turbine combined cycle efficiency goal. Historically, efficiency gains in combustion turbines have been realized by demonstrating higher and higher turbine inlet temperatures. Pressure gain combustion provides alternative pathway to the ultrahigh efficiency target that bypasses the material limitations currently faced by technology developers. Additionally, advanced materials and cooling schemes can still be pursued along with PGC providing the potential for ultrahigh efficiency combustion turbines for IGCC. Potential technical challenges include fuel injection, fuel and air mixing, backflow prevention, detonation initiation, wave directionality, maintaining a pressure gain, controlling emissions of NOx and CO, as well as unsteady heat transfer and cooling flow challenges resulting from integration with the turbine hot gas path expansion components.
The goal of this key technology is to develop PGC systems designed for potential integration with combustion gas turbines in combined cycle applications. The research is focused on combustion control strategies and fundamental understanding of pressure wave-flame interaction that will lead to lab-scale testing and component prototyping for turbine integration with PGC.
The 10 largest coal producers and exporters in the Indonesia:
- Bumi Resouces
- Adaro Energy
- Indo Tambangraya Megah
- Berau Coal
- Bukit Asam
- Baramulti Sukses Sarana
- Harum Energy
- Mitrabara Adiperdana
- Samindo Resources
- United Tractors
Source: US National Energy Technology Laboratory
