A Lean, Premixed, Prevaporized (LPP) combustion technology has been developed that converts liquid fuels into a substitute for natural gas. This gaseous fuel can then be burned with low emissions in place of natural gas in a wide range of combustion devices. The fuel preparation system overcomes the operational and emissions barriers associated with using liquid fuels in combustion turbines.
The technology has been adapted to fuel a 30 kW microturbine, with over 1,000 hours of operation logged to-date. The microturbine was initially designed for use with natural gas only, and can operate in both diffusion and premixed modes. No alterations were made to the combustion system on the turbine. Thirteen different liquid fuels, including bio-ethanol, naphtha, gasoline, kerosene, diesel, and biodiesel have been used in this study. The air emissions on gasoline measured at the conclusion of the 1,000 operating hours were less than 5 ppm NOx and 10 ppm CO (@15%O2), essentially unchanged from those measured at the commencement of the operating period. These emissions compare favorably to natural gas emissions of less than 5 ppm NOx and 50 ppm CO (@15%O2). The operating system was also designed to allow initial startup on the vaporized liquid fuel.
Detailed thermodynamic and system modeling has also been performed to investigate the effect of the LPP technology on overall combustion turbine plant efficiency and operation. GateCycle™, well-validated thermodynamic cycle modeling software, was used to determine the effect on overall plant heat rate and power production when utilizing an LPP system. Parasitic losses from the LPP hardware were accurately modeled, as were the performance benefits due to mass flow augmentation and the use of exhaust heat for vaporization. Overall heat rate improvements were found with judicious use of thermal energy from the gas turbine exhaust.