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Show INTRODUCTION The manufacture of panel products, such as particle board, oriented strand board. or medium density fiberboard, result in large amounts of sanderdust, sawdust, and hog fuel waste. These waste products not only represent a source of free fuel to their producers, but also would require disposal in a land fill if they were not burned. Raw wood typically contains 0 to 0.25% nitrogen by weight. However, the glues used in manufacturing the panels can increase the nitrogen content of this waste to as high as 7%, with the largest FBN being observed with plants that are using new faster drying resins. The agricultural industry also produces a significant amount of biomass waste, such as rice husks or wheat straw, and increasing air quality regulations are greatly restricting the amount of field burning allowed. Plowing this waste material back into the soil can result in increased levels of crop disease and lower crop yields. These raw biomass materials can also contain comparatively high nitrogen levels, with typical values ranging from 0.5 to 2.5 % by weight. In order to utilize these materials as an industrial fuel one major concern is the effect that they may have on the amount of regulated emissions being generated. When these fuels are used to offset the use of natural gas, one area of major emissions increase is in the amount of NOx generated. NOx is a term that is used to refer to the sum total of nitric oxide (NO), nitrogen dioxide (NO2), and nitrous oxide (N20) emissions. When burning any fuel the two primary methods that result in the formation of NOx are termed "Thermal NOx" and "Fuel NOx". Thermal NOx results from the disassociation of the nitrogen molecules in the combustion air when they come into contact with the high temperature areas of the flame. Once the N2 molecule has split into two N molecules they will readily combine with the oxygen present to form NOx. Fuel NOx is formed by the nitrogen that is contained within the fuel itself, which is freed during the combustion process. As the fuel burns, this nitrogen that was chemically bonded as part of the fuel molecule is freed and can readily combine with any oxygen present. The conversion of this FBN to NOx is what results in dramatic increase in the NOx emissions of biomass fuels when compared with natural gas, which contains no FBN. Table 1 shows the typical uncontrolled NOx emission comparison of natural gas, fuel oil, and biomass of varying nitrogen levels. Table 1: Predicted Uncontrolled NOx Levels of Various Fuels Bound Nitrogen (% by weight) NOx Emissions (Ib/Mbtu) Natural Gas 0.0 0.18 #2 Fuel Oil 0.1 0.25 Wood Waste 0.5 0.80 Wood Waste 2.0 1.00 Wood Waste 7.0 2.19 2 |
