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Comprehensive surveys conducted at 5-yr intervals were used to estimate sulfur dioxide (SO,) and nitrogen oxides (NO.) emissions from U.S. pulp and paper mills for 1980, 1985, 1990, 1995, 2000, and 2005. Over the 25-yr period, paper production increased by 50%, whereas total SO, emissions declined by 60% to 340,000 short tons (t) and total NO, emissions decreased approximately 15% to 230,000 t. The downward emission trends resulted from a combination of factors, including reductions in oil and coal use, steadily declining fuel sulfur content, lower pulp and paper production in recent years, increased use of flue gas desulfurization systems on boilers, growing use of combustion modifications and add-on control systems to reduce boiler and gas turbine NO, emissions, and improvements in kraft recovery furnace operations.

Sulfur dioxide (SO2) and oxides of nitrogen (NOx) emissions from U.S. pulp and paper mills have been estimated from industry-wide surveys conducted every five years, beginning in 1980 and continuing through 2010. Between 1980 and 2010, total SO2 emissions declined by over 70%, while paper and paperboard production rose 35%. NOx emissions peaked in 1995, but fell by almost 40% over the next 15 years. Paper and paperboard production only declined 7% over the same period. These downward emission trends resulted from several factors, including reductions in oil and coal use, declining oil and coal sulfur content, increased use of add-on SO2 and NOx control systems on boilers, growing use of combustion modification techniques to minimize emissions, improvements in energy efficiency, and declining pulp, paper, and paperboard production over the past 15 years.

Coal dust is produced in coal mines during normal mining operations and by the movement of men and machines. This fine float coal dust, typically less then 74 pm, entrained in the ventiliating air is carried into the return airway, where it settles on exposed surfaces. In the event of an explosion this float dust can be re-entrained into the air, where it can propagate an explosion. The degree of combustion hazard associated with float coal dust is related to the surface density of the deposited coal dust, and the entry cross-sectional area. The operation of a prototype optical dust deposition meter used to measure the mass loading density of stratified coal and rock dust layers, to assess the float coal dust hazard, is described. The meter determines the surface loading density of a dust layer by measuring its optical reflectivity. The theory of the prototype unit's operation is developed and compared with experiment. The studies showed that the prototype unit is capable of measuring coal dust and rock dust surface loading densities of up to 7 mg/cm2 for coal and 10 mg/cm2 for rock dust. This is well within the hazard range, with an accuracy of about + 5 pct. The results of the laboratory and experimental mine testing of a second portable meter is also reported.