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Show AFRC90-PAPER #2B incandescently, the inner structures of the burner are maintained at temperatures only slightly elevated above that of the combustion reactants. In fact, with Pyrocore and Pyromat radiant burners, it is only the final surface layer that reaches these incandescent tern peratures. The key operational differences which Pyrocore and Pyromat burners exhibit over other radiant burners, are: • the uniformity of surface temperatures over a wide variety of shapes and sizes, • the ability to turn on and off instantly, • the absence of aerodynamic combustion noise, and • the lack of any susceptibility to thermal shock Most importantly, it is the ability to control heat transfer from the combustion reaction by geometrically matching the shape of the burner to that of the load that creates unique opportunities to obtain process benefits beyond the intrinsic low NOx emISSIOns of these burners. Pyrocore Burners A Pyrocore burner typically consists of a fuel/ air mixing section, ducting, and the active burner element. The element is fabricated by vacuum casting a ceramic matrix against a steel support structure. The Pyrocore burner operates at a nominal heat release rate of 100,000 Btu/hr-ft2 of burner surface area, with a turn-down as high as 4: 1 in some applications. The pressure loss across the ceramic matrix is less than 0.5" w.c. under nominal load conditions, and, when combined with the fuel/air mixing section and other components that make up the burner, the total pressure loss is still less than 2" w.c. Forced draft fans are typically used to maintain a stable supply of combustion air to these burners. Since the dynamics of the combustion reactions occurring on the surface of the burner are controlled by surface area phenomenon, the burner is easily scalable. Burners ranging in size from 15,000 Btu/hr up to 15 million 2 Btu/hr are commonly made using the same type of support structures and forming techniques. The steel support structures of smaller burners are constructed as single elements, while larger burners are constructed of multiple flanged segments to facilitate fabrication and handling. Burners assembled from cylindrical segments with both circular and diamond cross sectional geometries are in service, some with length-to-diameter ratios as high as 32: 1. The natural flexibility of the ceramic matrix permits reliable cyclic operation without thermal shock damage. Typical life expectancy of the product IS m excess of 20,000 hours of actual service and is unaffected by cyclic operation. Pyromat Burners Pyromat burners differ from Pyrocore burners in that the vacuum formed ceramic fiber matrix is replaced with a sintered metal fiber pad. This pad can be formed into flat and curved surfaces as appropriate to the application. Operationally, Pyromat burners demonstrate significantly improved surface durability compared to Pyrocore burners. Field data establish that these burners can readily withstand direct mechanical contact, abrasion, the impact of a high pressure water spray, and other similar abuse. Performance characteristics of Pyromat burners are roughly equivalent to those of Pyrocore burners. Radiant output and pollutant emissions of these burners are comparable over their normal operating range. In contrast, the pressure loss across the porous pad of the burner element is slightly higher with the Pyromat. Pyromat burners have been fabricated in modular elements that range from 1/3 ft2 to 8 ft2 of active burner surface area. This corresponds to burner ratings from 30,000 Btu/hr to 800,000 Btu/hr. MUltiple burner arrays can extend the rating of these burner systems to over 10 million Btu/hr. |
