Biofuel Alternative to Natural Gas

liquid biofuel
LPP Combustion’s process allows unmodified natural gas turbines to run on biofuel made from food waste.
(cc) Steve Jurvetson

LPP Combustion, a Columbia, Maryland-based innovator of liquid fuel technology, has successfully demonstrated clean and green generation of renewable electric power using both bio-ethanol and bio-diesel. LPP Combustion has developed a Lean, Premixed, Prevaporized (LPP) combustion technology that converts liquid fuels, including bio-ethanol and biodiesel, into a substitute natural gas called LPP Gas™. The LPP Gas has been used to fuel a commercial Capstone 30 kW gas turbine designed for operation on natural gas, allowing the gas turbine to burn these liquid bio-fuels with natural gas level performance and emissions. The LPP Combustion fuel processing skid is designed to enable real-time operation of gas turbines on liquid fuels without requiring any modifications of the combustion system.

Currently, combustion of bio-fuels in gas turbines is accomplished by burning these liquids as a spray. This spray flame mode of combustion generates much higher emissions of pollutants such as NOx, CO, and particulates than the burning of natural gas. However, the LPP Combustion system allows these bio-fuels to be burned in the same lean, premixed combustion system that provides extremely low emissions from natural gas operation. Emissions from the Capstone gas turbine, operating in low emissions mode at 25 kW on LPP Gas derived from these bio-fuels, are less than 5 ppm NOx and less than 20 ppm CO, at 15%O2, with no observable particulate emissions. These emissions were lower than those obtained during operation of the gas turbine on natural gas. In addition, no problems with combustion instabilities, flashback, or autoignition have been observed.

The bio-ethanol fuels tested range from pure alcohol with no water to ethanol containing over 30% water. Although the presence of even small amounts of water in ethanol used for blending with gasoline causes problems for automotive engines, the presence of up to 30% water mixed with the ethanol had no significant effects on performance or emissions from the gas turbine. The bio-ethanol was provided by Dubay Biofuels, a Stratford, Wisconsin company. Dubay has developed a proprietary process to create ethanol from waste streams of food manufacturers.

The biodiesel fuels tested in the 30 kW gas turbine included both a canola-based diesel fuel that meets the ASTM specification for biodiesel and a less expensive to produce, off-spec form of biodiesel not suitable for use in diesel engines. Both biodiesel formulations also provided performance and emissions in the gas turbine similar to natural gas, with less than 5 ppm NOx and less than 20 ppm CO, at 15%O2, and with no observable particulate emissions.

These biodiesel fuels were provided by Northern Biodiesel, an Ontario, NY company. According to Northern Biodiesel, the off-spec biodiesel can be produced at a substantially lower cost than traditional biodiesel since the off-spec fuel can be made from a wider variety of feedstocks, including beef tallow and chicken waste.

Clean operation of gas turbines on biofuel provides a reliable alternative to wind or solar power for renewable electric power generation. Gas turbines equipped with LPP Combustion fuel skids can provide “dispatchable” (available on demand) renewable power to complement new or existing wind or solar farms. LPP Combustion enables the cleanest use of renewable fuels by using existing or new gas turbine infrastructure while providing dispatchable, green energy. The LPP Combustion system allows for fuel flexibility, improved heat rate, and reduced maintenance for gas turbine operation on liquid fuels without the usual 80% increase in emissions associated with conventional burning of liquid fuels. The LPP System can be integrated into new combustion systems or deployed as a self-contained hardware skid that can be easily retrofitted into existing natural gas-fired equipment without modification of the combustion hardware. This ease of installation makes LPP Systems using liquid bio-fuels an exciting option for industrial and utility scale power markets.

Read Biofuels and Bioenergy: Processes and Technologies from Amazon.

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