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Show Cooperative in Pennsylvania has produced very solid results: N O x levels of 30 p p m at efficiencies up to 87 percent over a 6:1 turndown ratio. A n 1800-hp unit entered field testing at a paper processing plant in eaelier this year. Testing of a 3000-hp unit at a chemical processing plant is planned to begin shortly. Another low-NOx technology for steam boilers uses a ceramic fiber matrix material to support flameless combustion with a temperature of only 1800°F at the burner surface. Pyrocoretm burners, developed for GRI by Alzeta Corporation, are available in cylindrical shapes for retrofit installation in existing firetube boilers. Emitting less than 25 ppm NOx, the burners have been designated as meeting criteria for best available control technology (BACT) in California. Pyrocoretm burners have also been applied to heat asphalt storage tanks as well as in low-temperature drying and heating applications. Pulse combustion, originally developed for GRI for use in residential furnaces, is another effective N O x reduction technology for industrial boilers. Pulse combustion is the sequential combustion of fuel and air charges in a closed chamber. As each charge-or pulse-ignites, rising pressure forces hot gases out of the burner and draws in more fuel and air to sustain the process. The strong turbulence of the combustion gases transfer heat rapidly to the heat exchanger or work load, thus quickly reducing temperature and N O x levels. Fulton Boiler Company offers a range of sizes up to 750,000 Btu/hr and has completed development for GRI of a 5 million Btu/hr prototype. N O x levels of available units range from 35 to 55 ppm, depending on the boiler's size. It is expected that regulators will require even lower N O x emissions from industrial boilers in the future. In anticipation of this, GRI is funding Altex Technologies and Cleaver Brooks to develop a fire-tube boiler that will achieve less than 15 ppm NOx. Tests at Altex in a simulated 350-hp boiler have achieved the targeted N O x level. Work is now underway at Cleaver Brooks' facility in Miwaukee to confirm these results in commercial 350- and 500-hp units. Hioh-Temperature Heating and Melting High-temperature processes represent the greatest challenge to combustion system designers as well as the greatest need for innovative products. Because N O x formation 3 i-l |
