OCR Text |
Show difference between compliance with Rule 1109 and non-compl iance. . ULTRALO'V NOX™ theory analyzes the macroscopic effects caused by the ability (or lack of it) of a flame burst to radiate energy to its surroundings. It takes into account the time and temperature effects at the macroscopic level based on horizontal and vertical placement and distance of the burners from the heat transfer surface area. This is very important because the macroscopic effects greatly influence NOx production for NOx levels below 50ppmv. Therefore, a thorough and complete understanding of the mechanism of flame burst heat transfer for the specific system of burners and heat transfer equipment is required. The IT-McGill NOx prediction program has proven to be a necessary tool in the evaluation of the overall heater and boiler performance after the installation of NOx reducing burners. It will also properly select the number, size and location of burners that will meet both the NOx specifications and operational requirements of the equipment. An IT-McGill study will serve as an example of the importance of analyzing any NOx reduction project as a system as opposed to merely replacing burners. A 1963 vintage heater was to have premix style burners removed and replaced with NOx reducing burners utilizing natural flue gas recirculation. The heater was operating at 120 % of original design duty and the stack temperature was above 800oP. The convection section was undersized by today's standards. The IT-McGill NOx prediction program evaluated the entire system for the following three cases; Case 1 Replacement of burners, one for one, to meet new NOx criteria. Case 2 Minimize load shift and meet new NOx criteria with onl y changes in burner location, number and size. Case 3 Minimize load shift and meet new NOx criteria with additional convection section 5 surface area and changes in burner location, number and size. Each of the three cases were analyzed and each analysis included an economic evaluation of the cost versus the benefits. Specifically, higher first costs for cases 2 & 3 were evaluated for the positive return on investment associated with increased run time, reduced coking rates, reduced radiant section tube metal temperatures, and potential for increased capacity without exceeding existing tube metal temperatures. Case three was selected based on achieving NOx reduction goals and demonstrating less than a 2 year return on investment. It represented the highest first cost option, but also the lowest NOx production with an associated increase in capacity. Summary Analyzing the complete system, as opposed to merely replacing burners, can result in operational improvements and economic incentives for installing NOx reducing burners. Each heater or boiler must be individually computer modeled in order to determine the potential for improvement and the economic incentives for NOx reduction. ULTRALOW NOX™ technology is proven and field results from operating ULTRALOW NOX™ systems are available upon written request. By June of 1991, five major users will be operating ULTRALOW NOX™ systems with a combined heat release in excess of 600MM BTU/HR. |