OCR Text |
Show combustion at the top of the furnace. After evaluating a number of configurations, a final configuration is obtained consisting of two overfire air ports above each burner with a diameter of 7.07 in and firing at a 10° angle toward the outer walls. The sander dust burners are configured with 1.92 m separation and fire straight into the furnace. In this arrangement, the average flue gas flow through the superheater has an oxygen concentration of 3.2% by volume. The effectiveness of the mixing from the fuel rich sander dust burners is shown in Figure 10 where sufficient residence time exists to allow the volatile F B N to evolve in an oxygen deficient environment. This is estimated to produce the required reductions in F B N conversion to N O x to bring the total boiler N O x emissions into compliance. The effects on the temperature contours within the furnace are indicated in Figure 11. These C F D data are then input to a particle combustion model which evaluate that the carbon loss and particulate emissions for the boiler are also within regulatory compliance. This project is currently undergoing field installation and actual emissions data will be obtained and compared with the results of this study. SUMMARY AND DISCUSSION T w o separate case studies for waste to energy solutions for industry have been presented and discussed. The first case study presents the application of gaseous and liquid waste, off-gas and PFO, in a tangentially fired boiler with a specially designed atomizer. The results of a combustion feasibility study are presented with acceptable features for (1) flame shaping, (2) excess air, (3) atomization quality, (4) particulate emissions, and (5) liquid firing range. The firing of these waste fuels provides tremendous cost advantages for the process and plant as a whole. A solid fuel case study is also presented. The description of the technique used to develop a low N O x sander dust cofired bark boiler is presented. The sander dust contains nitrogen from bonding glues and has a propensity for N O x formation when fired. A staged N O x reduction technique is employed where firing the sander dust burners with sub-stoichiometric amounts of air produces a fuel rich zone in the boiler. Finally, the design and effectiveness of overfire air ports above the sander dust burners was evaluated with C F D for penetration and mixing effectiveness. The use of waste products with calorific value for energy production means provides industry with a cost effective and environmentally sound technique of production. Further research is required on chemical kinetics, computer model development, pollutant formation mechanisms, and solid reaction kinetics are required. Such tools would be used by the industrial combustion designer in the development of more advanced techniques for handling difficult waste to energy applications. 9 |