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Show Background and Objectives The overall objective of this program is to develop and demonstrate an advanced, high-efficiency, 10w-NOx burner for commercial chillers in order to remove environmental barriers to the increased use of natural gas for space conditioning. To achieve this objective, we established a project goal of attaining NOx emissions at or below 15 ppm. Important supporting objectives that are intended to produce a successful commercial product are as follows: • • • • • To develop a burner design that is applicable to a wide range of new chiller equipment; To develop a burner design that is retrofittable to the majority of existing chillers; To achieve burner performance that provides high chiller thermal efficiency; To incorporate burner modifications such that the burner cost is competitive with conventional burner technology, and To provide a safe and reliable burner design. Arthur D. Little, working with its partners, Power Flame and Trane, is conducting a multi-phase program to develop the proposed 10w-NOx' high-efficiency burner. We developed the initiallow-NOx burner design by modeling the combustion characteristics of the baseline Power Flame NOV A burner, and by investigating the impact of key design and operating characteristics on NOx formation. Subsequently, we fabricated a prototype 1.1 MW (3.8 MMBtuIhr) burner and conducted parametric tests at Power Flame's test facilities to optimize its performance. Final testing was conducted in a fully instrumented chiller at Trane Company's test facilities to assure that integrated performance satisfied all program goals. Burner Concept Selection of NOz-Control Method. Of the many possible combustion modification methods for controlling NOx' staged fuel with flue gas recirculation is best suited for direct-fired commercial chiller applications, especially when retrofit capability is essential. We selected this method because it has been proven to be highly effective in controlling NOx to low levels and it results in combustion characteristics (high heat release per unit volume, low excess air) that are compatible with chiller combustion chamber geometry and high-efficiency operation. Low-NOz Combustion Process. The burner technology incorporates staged fuel combustion with flue gas recirculation to achieve very low NOx levels. The 10w-NOx combustion process is illustrated schematically in Figure 1. Natural gas is introduced at two locations: primary gas is mixed with all of the combustion air and the recirculated flue gas to produce a lean, relatively low-temperature first combustion 2 |
