Low-Emissions Renewable Power Generation Using Liquid Fuels

Abstract

A Lean, Premixed, Prevaporized (LPP) combustion technology has been developed that converts liquid biofuels, such as biodiesel or ethanol, into a substitute for natural gas. This fuel can then be burned with low emissions in virtually any combustion device in place of natural gas, providing users substantial fuel flexibility. A gas turbine utilizing the LPP combustion technology to burn biofuels creates a “dispatchable” (on-demand) renewable power generator with low criteria pollutant emissions and no net carbon emissions. Natural gas, petroleum based fuel oil #1 and #2, biodiesel and ethanol were tested in an atmospheric pressure test rig using actual gas turbine combustor hardware (designed for natural gas) and achieved natural gas level emissions. Both biodiesel and ethanol achieved natural gas level emissions for NOx, CO, SOx and particulate matter (PM). Extended lean operation was observed for all liquid fuels tested due to the wider lean flammability range for these fuels compared to natural gas. Autoignition of the fuels was controlled by the level of diluent (inerting) gas used in the vaporization process. This technology has successfully demonstrated the clean generation of green, dispatchable, renewable power on a 30kW Capstone C30 microturbine. Emissions on the vaporized derived from bio-ethanol are 3 ppm NO(x) and 18 ppm CO, improving on the baseline natural gas emissions of 3 ppm NO(x), 30 ppm CO. Performance calculations have shown that for a typical combined cycle power plant, one can expect to achieve a two percent (2%) improvement in the overall net plant heat rate when burning liquid fuel as LPP Gas™ as compared to burning the same liquid fuel in traditional spray-flame diffusion combustors. This level of heat rate improvement is quite substantial, and represents an annual fuel savings of over five million dollars for base load operation of a GE Frame 7EA combined cycle plant (126 MW). This technology provides a clean and reliable form of renewable energy using liquid biofuels that can be a primary source for power generation or be a back-up source for non-dispatchable renewable energy sources such as wind and solar. The LPP technology allows for the clean use of biofuels in combustion devices without water injection or the use of post-combustion pollution control equipment and can easily be incorporated into both new and existing gas turbine power plants. No changes are required to the DLE gas turbine combustor hardware.