A unique type of clean-burning combustion technology called, low-swirl injection (LSI), for fuel-flexible near-zero-emission gas turbines, developed by Robert Cheng and David Littlejohn of Berkeley Lab’s Environmental Energy Technologies Division, along with scientists from San Diego-based Solar Turbines. The technology is now entering the marketplace after years of research and development.
LSI technology, recently won a 2007 R&D 100 award for 2007 from R&D magazine as one of the top 100 new technologies of the year.
LSI is a technology that significantly reduces greenhouse gas emissions and pollution from gas turbines used to produce electricity, or from any stationary combustion system in which it is incorporated. Burners using this technology produce 10 to 100 times lower emissions of nitrogen oxides than conventional burners, making it easier and more economical for industries to meet clean air requirement.
In the 1980s, new combustion technologies reduced nitrogen oxides (NOx) from more than 100 parts per million (ppm) to the current standard of less than 25 ppm. Now, the low swirl Injector emits less than 2 ppm. It is the only technology that can affordably reduce NOx emissions to this near-zero level.
Per a 2003 article in Berkeley Labs science beat: Because conventional theory does not predict its features, new advances in combustion theory have been developed to explain the principles of this new combustion technology. LSI operates according to a novel combustion method that uses lean, premixed flames -- a type of combustion in which the appropriate ratios of air and fuel are mixed to burn completely when the mixture reaches the flame. Its operating principle, overall flame behavior, and turbulent-flow features have been studied using lasers.
The low swirl injector is a mechanically simple device with no moving parts that imparts a mild spin to the gaseous fuel and air mixture that causes the mixture to spread out. The flame is stabilized within the spreading flow just beyond the exit of the burner. Not only is the flame stable, but it also burns at a lower temperature than that of conventional burners. The production of nitrogen oxides is highly temperature-dependent, and the lower temperature of the flame reduces emissions of nitrogen oxides to very low levels. A distinct characteristic of the burner is a detached flame that is lifted above the burner.
Note that in the above photo Cheng is able to put his hand on the burner tube indicating there is little heat conducted from the flame to the tube, which, along with the excellent mixing prior to ignition, increases the efficiency of the burner.
Cheng, Berkeley Lab colleague David Littlejohn, and Kenneth Smith and Wazeem Nazeer from Solar Turbines Inc. of San Diego adapted the low-swirl injector technology to the Taurus 70 gas turbine that produces about seven megawatts of electricity. The team’s effort garnered them the R&D 100 honor. It is continuing the LSI development for carbon-neutral renewable fuels available from landfills and other industrial processes such as petroleum refining and waste treatments.
The technology is potentially scalable to turbines of all sizes and can burn almost any gaseous hydrocarbon, including landfill gases, biomass, refinery gases, and pure hydrogen. It requires no substantial redesign of gas turbines, nor does it need expensive catalysts. With further development, the technology can also be used in turbines designed for coal-derived syngas and hydrogen, commonly referred to as clean-coal power plants.
The Maxon Corporation of Muncie, Indiana, has licensed the, LSI technology for industrial process heaters. The Maxon MPAKT Ultra Low NOx Burner was the first product, in 2003, to use this technology. They call their technology using LSI as SLS™ Technology.
DOE’s Office of Fossil Energy is funding another project in which the LSI is being tested for its ability to burn syngas (a mixture of hydrogen and carbon monoxide) and hydrogen fuels in an advanced IGCC plant (Integrated Gasification Combined Cycle) called FutureGen, which is planned to be the world’s first near-zero-emissions coal power plant. The intention of the FutureGen plant is to produce hydrogen from gasification of coal and sequester the carbon dioxide generated by the process. The LSI is one of several combustion technologies being evaluated for use in the 200+- megawatt utility-size hydrogen turbine that is a key component of the FutureGen plant.
For more information about low-swirl combustion research, see: http://eetd.lbl.gov/aet/combustion/LSC-info/