Solar Turbines Inc Calabasas Landfill Gas-To-Energy Facility, U.S.A.

Start-up phase for the Calabasas Landfill Gas-to-Energy Facility in Agoura, California, U.S.A., began on June 1, 2010. Commercial operation was declared on July 12, 2010. The plant broke new ground for operation on very low Btu landfill gas while simultaneously achieving industry-low emission levels.

Plant equipment consists of three Solar Turbines Inc. Mercury 50 gas turbines, ISO rated at 4.6 MW each, three 150% gas treatment, blending and compression skids, continuous emissions monitoring (NOx), and miscellaneous support equipment. Strict local landfill gas surface emission limits combined with local soil conditions result in landfill gas that averages only 30% methane, as compared to typical landfill gas, which usually runs around 50% methane.

In 2004, the fuel’s low quality posed a problem, as there were few technologies available that could burn the Calabasas landfill gas. There was not enough fuel to make a boiler/steam turbine plant economically feasible. Reciprocating engines could not operate with fuel of this low quality, which left industrial gas turbines as the most reasonable alternative. However, the South Coast Air Quality Management District’s emission restrictions for gas turbines provided no margin on actual performance.

Therefore, no manufacturers would guarantee their equipment to meet the set limits. The Los Angeles County Sanitation District (LACSD) became aware of Solar Turbines’ Mercury 50, a DOE-funded low-emission, high-efficiency gas turbine, and proposed using it at Calabasas. Though the Mercury had been designed strictly for natural gas, Solar took on the challenge of modifying it to burn landfill gas. Prior to this time, Solar required a minimum of 40% methane for its turbines.

After testing the Mercury 50 in the factory with simulated landfill gas (natural gas diluted with CO2), Solar guaranteed operation down to 32% methane. However, for initial plant start-up, 40% methane would be required; six months of on-site testing was stipulated to achieve operation on the 32% methane fuel. The facility air permit allowed the LACSD to blend up to 25% methane to the landfill gas’ methane. Slight adjustments to the landfill gas collection operation, plus the addition of natural gas, allowed the two parties to meet. The project was launched.

Six years after the original idea, plant start-up began. As initially planned, the turbines were initially lit off with fuel having 40% methane or more. Once the units were running, it was decided to attempt operation on lower quality fuel. Rather than taking six months to adapt the Mercury 50 to the 32% methane fuel, it was done in one day. A few days later, the turbines were starting and operating successfully on unblended fuel, which has been the case ever since, Solar said.

In addition, the Mercury’s emissions were unaffected by the fuel’s low quality, with emission source test results averaging 7 ppm NOx and 3 ppm CO (at 15% O2) on all three turbines.

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