Lean premixed (LP) combustion is a proven concept for NOx-reduction in gas turbine systems. Lean premixed liquid fuel systems, also known as LPP (lean premixed prevaporized) systems, however, are more complex, as the fuel has to be atomized, evaporated and premixed prior to combustion and there is a higher risk of autoignition and coking.

The Siemens LPP Hybrid burner, which was introduced into the Halmstadvaerket gas turbine of Sydkraft AB in Sweden in 1993, has since proven its reliability. As the primary design criteria have been maximum reliability and security against flashback, it still has a considerable potential for NOx-Emissions reduction.

The objectives of this paper are to summarize the activities connected with the further development of the LPP Hybrid burner based on the Halmstadvaerket operation experience. These include the introduction of the LPP burner into a new machine generation with ring combustors as well as investigations into the two phase flow phenomena inside the burner.

When the Model VX4.3A gas turbine family was introduced, the LPP Hybrid burner had to be scaled down to fit the different machine sizes. The paper reports on the development steps and first operation experiences with the LPP Hybrid burner system in HBR-combustor machines.

In a concluding chapter, the paper outlines the next steps in the LPP development program. These include further experimental and numerical studies which are partly conducted in a co-operation between Sydkraft AB and Siemens AG.

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