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Show watertube and firetube boilers. Performance characteristics of porous radiant burners that make their use preferable in these applications are: • Uniform, controllable, and compact radiant heat transfer • Stable and safe operation over a wide range of operating conditions • Simultaneous low emissions of NOx and CO • Scalability to various sizes (250 to 1) • Absence of aerodynamic combustion noise • Compact equipment design Petrochemical process heaters, which require controlled radiant heating of process fluids flowing inside of tube coils, provide an excellent example of the operational benefits provided by radiant Gumers. Typical flame burner furnaces operate at low volumetric heat release rates. The heat absorbed in the radiant section of conventional heaters comes from either direct gas phase radiation or is emitted by the refractory walls of the heater. Very little of the total energy is transferred by convection. In a prototype advanced refinery heater (process temperatures of 600°F) developed by Alzeta with porous surface radiant burners, the radiant section efficiency increased dramatically over that of a conventional heater (Reference 2). As shown in Table 1, the heater's radiant section performed at up to twice the volumetric heat release rate of conventional units, resulting in a more compact design with a consequent capital cost savings of 10 percent. TABLE 1. RADIANT SECTION THERMAL PERFORMANCE FOR REFINERY PROCESS HEATERS Burner Type Heat Release Rates Radiant Section Efficiency (MBtu/hr-ft3) (percent) Flame Burners 5 to 10 55-65 Radiant Burners 10 to 20 65-73 Although porous surface burners are currently used in low temperature industrial applications, higher process load temperatures with high heat flux requirements will result in increased burner surface temperatures. Since the ceramic and metal fiber surfaces currently used in porous radiant burners degrade with prolonged use at surface temperatures above 1900°F, increases in their durability are required. For applications requiring high heat fluxes at high temperatures, factors that limit process improvement using conventional burner technologies include: 3 |