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Show INTRODUCTION Bark is generally produced as a by-product in the Paper Industry. With increased energy costs, bark is now recognized as a valuable fuel to generate steam and power. Typical cost of bark is less than 1.0 dollars per million BTU (if purchased) compared to about 2.0 dollars per million BTU for coal and more than 4.0 dollars per million BTU for oil. Typical bark contains very little sulfur, low ash content, and more volatile matter in comparison with coal. Environmental regulations with respect to S0X are easy to meet because of the low sulfur. Bark quality is generally a variable. Moisture in the bark could vary anywhere from 30% to 70%. Because of this, heat content varies significantly. For example, at 70% moisture, the heat content of the bark is 2625 BTU per pound compared to 8750 for dry bark. The size of the bark is another major variable. The awkward shapes and sizes, along with high moisture content, pose difficult handling problems with this fuel. Major problems in the combustion of bark are particulate emissions, slagging, and high levels of unburned carbon in the fly ash. A product was developed in the laboratory to reduce particulate emissions and improve combustion of bark. This product was then field evaluated on a bark boiler, which was marginally out of particulate compliance. The product was very successful in reducing excess air required for combustion and in bringing the boiler into particulate compliance. 2,5.2 |
