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Show • Nonuniform flux resulting in uneven heating and limited process throughput or efficiency • Inability to rapidly follow process load changes • High NOx and, in some cases, high CO emissions, which due to air quality constraints may prevent plant operation or expansion without costly retrofit controls such as Selective Catalytic Reduction (SCR). THE ARCS CONCEPT To improve the performance of high temperature process heaters, Alzeta is developing a combustion system based on advanced radiant burners and an integrated control system. 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. In addition to providing improved process temperature control, the ARCS will improve radiant section thermal efficiency and will provide reduced NOx emissions. Accurate stoichiometry control of individual burners will be achieved by remote sensing of burner output. This will guarantee that all burners are operating at optimum fuelj air ratios even though individual burners may be fired at different rates. Figure 2 shows the control system concept, where sensing of tube temperature at multiple elevations allows profiling of the radiant flux along the process tube length and sensing of burner output allows stoichiometry control. The combination of these concepts allows improved performance of the overall process. The ARCS will include: • High temperature porous surface burners to provide high heat output while radiating to process temperatures up to 180QoF. • Uniform radiant energy transfer with no attached flame • Radiant surface geometries shaped to process load requirements • Localized control of individual burners in a multiple burner system 4 |