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Show -10- tion. Electronic Ignition of Flare Pilots For more than a decade, the trend has been toward electronic ignition. 8tateof- art, spark~ign.i~ed pil~ts u~ilize a high-energy excitor, originally developed for de~endable I~nltlo~ of Jet aircraft engines. With this high-energy excitor, any mOisture or dirt bUildup on a pilot tip will literally be blown off by the spark. The use of a direct spark at the top of the flare has been tried many times. It was abandoned in the late 1940s. Top-mounted ignitors will fail quickly because they are subjected to flame impingement. Remote-spark pilots, designed and manufactured to 180-9001 standards, offer fast paybacks for retrofit installations. Thousands are in service worldwide, including hundreds of replacements for defective, unreliable, short-life pilots. Complete Combustion of Waste Gases Typical flare combustion efficiencies are 99+% for hydrocarbons such as natural gas, ethane, propane and butane. Hydrocarbons such as ethylene and propylene will have similar efficiencies if smokeless operation is achieved through the use of steam, air blower or mUlti-tip designs. The combustion efficiency will be lower for gases having low-Btu heating value from high contents of nitrogen, carbon dioxide, water vapor or other inert media. For EPA compliance, if the heating value is below 300 Btu/scf3 (11.2 MJ/m3), some auxiliary fuel such as natural gas or propane must be utilized to increase the heating value. In some applications, particularly if H28 is present, the heating value must be further increased. When a gas contains considerable quantities of hydrogen a~d carbon monoxide (as is the case for steel plant gases) that are fast burning, the minimum heating value for complete combustion can be as low as 80 to 90 Btu/scf3 (3.4 MJ/m3); but those low-Btu gases must be enriched to comply with EPA regulations. If a flare requires steam or assist gas, one should consider using a low profile enclosed flare. An enclosed "ground flare," sometimes called a thermal oxidizer flare, will allow complete combustion of a gas at a lower calorific content without the use of any assist media. Burners are the key to reliability and performance of state-of-art low profile enclosed flares, which require no steam to maintain smokeless destruction of waste gases and waste liquids. With these flares, there are no visible flames, |