| OCR Text |
Show The primary fuels of concern to EPA (in all phases of the program) are coal and heavy fuel oils, including synfuels. A number of efforts within the FCR program are addressing particular aspects of burning these fuels. MIT and Institut Francais du Petrole have shown that coal char and soot (respectively) may play an important role in determining exhaust N0X levels from furnaces and boilers. It has been shown that both char and soot react with NO, even at low temperatures, and that such reactions may represent an important step in determining exhaust NO levels and may even be utilized to gain a significant level of emission control. MIT has applied for a patent based on their EPA sponsored studies of char/NO reduction. Other studies are also being pursued to determine the rate of evolution and fate of nitrogeneous species as they evolve from coal particles or oil droplets. Results from these studies are being directly used in the development of new low emission burners, particularly heavy oil burners for package boilers. Identification of primary pyrolysis products and speciation of secondary pyrolysis products may be the key to explaining variations in the effectiveness of staged combustion as physical characteristics of fuels are needed. An example of this is shown in Figure 18 where the achievable, N0X reduction with staged combustion is plotted versus a defined fuel nitrogen volatility. The volatility is based on the fraction of the fuel nitrogen in the original fuel that could be evolved as HCN during inert pyrolysis at 1373K. The highest HCN yield was from the crude shale oil which gave a 93 percent reduction under staged combustion conditions. The reductions achievable from petroleum oils decreased as the fuel nitrogen volatility decreased. Although the data are limited, this graph shows the potential for correlation of the previously presented pilot scale data (Figure 12) with results of fundamental experiments. Several additional studies are being pursued to investigate aspects of furnace aerodynamics. Turbulence, fuel ballistics, and numerical analysis of boiler type flow fields are being considered. By incorporating the aerodynamics, gas phase chemistry, and fuel chemistry studies into an integrated program package, significant input is being made to development of emerging control technology and suggestions are forthcoming on approaches to realizing advanced pollution control techniques. 3-51 51 |
