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Kilns

NOx emission factors from kilns are reported as lbs per ton of product. Thus, a more efficient kiln (less fuel per ton of product) will result in lower emissions. As there are few manufacturing facilities building kilns, control technologies are most likely required in nonattainment areas for retrofit applications of major sources.

Tunnel kilns used in brick production use multiple burners similar to process furnaces. If required, commercially available technologies to retrofit tunnel kilns can be applied.

Rotary kilns are used to process asphalt, cement, lime and other mineral products. Facilities using rotary kilns are usually located in remote areas that are in attainment. A rotary kiln generally uses a large single burner that shoots a flame down a good portion of the kiln's length. There is little data available about low-NOx burner applications for rotary kilns. There have been some burner modifications and replacements in the U.S. and Canada that attempt to reduce excess air and stage combustion. These installations have achieved some success (up to 50% reduction). However, each retrofit must be adaptable to the heat transfer characteristics of the kiln.

A new burner on the market, the Gyro-Therm burner manufactured by FCT Combustion, employs a unique method of combustion to improve heat transfer and reduce NOx up to 50%. This burner uses a patented "precessing jet" technology. A newly discovered fluid flow phenomenon is generated by the nozzle design that produces a gas jet leaving the burner in a gyroscopic-like precessing motion.