OCR Text |
Show 4 energy of combustion as surface radiation, while also transferring energy by the gas phase radiation and convection mechanisms. A prototype refinery heater developed by Alzeta to effectively utilize porous surface burners demonstrated that radiant section efficiency was significantly higher than that of a conventional heate~. Porous surface burners are presently used in low temperature industrial applications. The prototype refinery heater discussed in the previous paragraph was demonstrated in heaters where peak process temperatures are 400 to 600°F. Higher temperature process heating applications, and high heat flux requirements, will require burners to operate at higher surface temperatures. Since the ceramic and metal fiber surfaces presently used as porous radiant burners degrade with prolonged use at surface temperatures above 1900°F, increased durability at high temperature is required. The ARCS combines high temperature porous surface radiant burners with a process control system designed to provided uniform and controlled heat flux to process tubes simultaneously with low emissions of NOx, CO, and air toxies. The benefits provided by porous surface radiant burners can best be utilized through a close interaction between the burners and the furnace control system, and this concept provides the basis for the ARCS. The ability to provide uniform and controllable radiant transfer and to shape burner surface geometry to meet load requirements provides the incentive to accurately monitor process temperatures along the entire length of a furnace. Based on localized process needs, heat flux to the load can be controlled by adjusting the firing rate of individual burners or banks of burners. This level of localized flux control is not possible with conventional burner systems. The ARCS will include: • High temperature porous surface burners to provide high heat flux while radiating to process temperatures up to 1800°F. • Uniform radiant energy transfer with no visible flame • Radiant surface geometry shaped to process load requirements • Localized control of energy transfer to the process in response to discrete process temperature measurements • Low emissions of NOx, CO, and air toxies |