Graymont’s plant is a major manufacturer of quicklime, supplying quality pulverized limestone. Since 2013, the plant has had two Metso Outotec kilns in operation. One of the kilns had a DFN burner while the other had a next generation burner, the DFN-X. At the time of installation, the DFN-X was an untested design with the inclusion of improved gas injection technology for enhanced heat flux manipulation when firing on natural gas. Since then, many DFN-X burners have been installed across the lime industry and, with appropriate tuning, significantly outperforms older generations of burner.
The challenge of optimizing from a distance
Each year, Graymont switches its kilns from solid fuel to natural gas which can cause a 28% derating of production. Historically, the main limitation of switching from solid fuel to natural gas is elevated feed-end temperatures as a result of the properties of the fuel. Preheater lime kilns can be susceptible to build-up in the preheater when temperatures are high and other conditions are met. The challenge was to increase production when transitioning to gas firing without exceeding the temperature limit through process and combustion optimization.