Protecting Visibility in National Parks and Wilderness Areas (1993) / Chapter Skim
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Appendix D: Control Techniques
Appendix D: Control Techniques
Pages 407-440
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From page 407... ...
POWER PLANTS Increasing environmental regulation in many industrialized countries has spurred the advancement of power-plant pollution control technologies over We past two decades. Research and development to render the technologies more efficient, more reliable, and less costly has accelerated in We United States in anticipation of new emission reduction requirements for existing power plants resulting from the 1990 Clean Air Act Amendments (Torrens, 1990~.
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From page 408... ...
... : : Sulfur Dioxide Control Technologies Over 150 flue gas desulfurization (FGD)
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From page 409... ...
Wet Flue Gas Desulfurization The predominant scrubbing technology used by U.S. utilities is lime or limestone wet FGD (scrubbing)
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From page 410... ...
1:991~. : Spray Dry Flue Gas Desulfurization Spray dry FGD is the other principal method of SO2 control used today.
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From page 411... ...
At other utilities, with scrubbed or unscrubbed stack emissions, the visible emissions have been higher than expected, and there is concern about visibility reduction in the local environment. Unacceptable opacity may be caused by scrubber-generated particulate matter, condensible particulate matter such as sulfuric acid in the flue gas, fine particles penetrating the particulate control device, or colored gases such as NO2 in the flue gas.
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From page 412... ...
utilities. As a result of installing FGD systems in response to the Clean Air Act Amendments, plants burning high-sulfur coal are likely to form sulfuric acid mist under certain operating conditions.
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From page 413... ...
Reburning costs depend on the choice of reburning final, and capital costs are $25-$45/kW.
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From page 414... ...
Results with urea injection show the potential for NOX reductions of 30-50%, perhaps up to 75%, and NH3 emissions of 5-10 ppm or less. Capital costs are estimated to be $5-$15/kW, and operating costs of less than 3 milIs/kW-hr.
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From page 415... ...
Fluidized Bed Combustion Atmospheric fluidized bed combustion (AFBC) is now an established technology for industrial boilers (10-25 MW)
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Most processes are under development and are not commercially available, although several are being demonstrated in the DOE Clean Coal Technology Program (DOE, 1991~. Integrated Gasification Combined Cycle Several integrated gasification combined cycle LOGIC)
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From page 417... ...
. Alternative Emission Reduction Methods Switching to Low-Sulfur Coal The 1990 Clean Air Act Amendments have raised the question as to whether the supply of low-sulfur coals is adequate to meet substantially higher demands from electric utilities and others seeking to reduce emissions.
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From page 418... ...
. INDUSTRIAL BOILERS Much of the technology discussed above for power plants can also be used to control emissions from industrial combustion sources.
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From page 419... ...
About 90% removal efficiency is typical. Capital costs for the sodium solution method are $40-$60/kW of heat input; dual-alkali investment costs are about twice as high.3 Operating costs, including capital recovery, for sodium scrubbing are $400-$l,000Jton of SO2 removed by sodium scrubbing, depending on the sulfur content of the fuel.
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From page 420... ...
NOX control methods for industrial sources are similar to those for large sources: combustion modification and flue gas treatment. Flue gas recirculation involves returning a side stream of furnace exhaust to the burner.
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Use of sulfuric acid plants to recover SO2 has become common. Smelter acid plants are distinguished from commercial plants that burn sulfur by the wide variability in inlet SO2 concentration and the need for extensive gas cleaning.
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From page 422... ...
is broken down into products by the refining process, much of that sulfur is converted to either elemental sulfur or sulfuric acid, thereby reducing the potential for SO2 emissions to the atmosphere. However, sulfur recovery and sulfuric acid plants are not 100% efficient, and some emissions to the atmosphere do occur during sulfur recovery.
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From page 423... ...
. Elemental sulfur, H2S, or spent acid from refinery systems can be used as feedstock for sulfuric acid production (Hunter and Heigeson, 1976; EPA, 1985c)
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Because particles impair visibility and threaten human health, EPA has established limits on particle emissions from light- and heavy-duty diesel engines. Many of the limits were codified in altered form by the 1990 Clean Air Act Amendments.
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From page 425... ...
Trap Oxidizers A trap oxidizer consists of a durable particulate filter in the engine exhaust stream and some means of cleaning the filter by burning off the collected particulate matter. The most challenging problem in developing trap oxidizers has been devising a system to burn accumulated par
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Catalytic Converters Due to reductions in the solid soot fraction of particulate emissions from diesel engines, the soluble organic fraction now accounts for 3070% of the emitted particulate matter. A catalytic converter can be used to treat that emission.
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From page 427... ...
Additional emission reductions are expected as a result of lower trace lead levels in unleaded gasoline and more advanced emissions control components, particularly more durable catalysts, better air-fuel management systems, and improved electronics. The Clean Air Act Amendments also phase in a standard for NOX of 0.4 g/mile already in force in California.
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From page 428... ...
Those fuels, along with electrically heated catalysts and other improvements, are expected to allow compliance with the 0.2 g/mile standard for NOX. In addition, the 1990 Clean Air Act Amendments establish new requirements for reformulated gasoline, which are expected to lower emissions of VOCs.
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From page 429... ...
Its major disadvantage is the limited supply. I ike natural gas, liquid petroleum gas in spark ignition engines is expected to produce essentially no particulate emissions (except for a small amount of lubricating oil)
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Converted heavy-duty diesel engines using each of these methods have been developed and demonstrated. Methanol combustion does not produce soot, so particulate emissions from methanol engines are limited to a small amount of lubricating oil.
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From page 431... ...
Prescribed Forestry Burning Emission Control Measures Control measures to reduce prescribed burning emissions include (~) reduction of the number of acres burned; (2)
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Burning under conditions of increased fuel moisture has been shown to reduce emissions by about 30% (Sandberg, 1983~. In most cases, the land manager's intent is to eliminate small residue to create an adequate number of seedling planting spots.
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From page 433... ...
Agricultural Burning The burning of straw stubble following the harvesting of cereal grain, grass-seed fields, and other crops is different from forestry burning in Mat agricultural lands are more accessible, are typically level enough to be worked by farm machinery, and have much lighter fuel loading than forested lands. Large reductions in particulate emissions are possible through burning grass-seed fields on alternate years (rather than annually)
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From page 434... ...
for biomass burning, EPA's Office of Air Quality Planning and Standards has undertaken a program to describe BACM for biomass burning that affects serious PM nonattainment areas. Development of BACM documents is required by the 1990 Clean Air Act Amendments.
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From page 435... ...
· Wood Moisture Content. For wood stoves, cordwood that produces the lowest particulate emissions contains about 20-26% moisture.
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From page 436... ...
Public Education Programs Local programs to educate the public about the wood smoke problem, to promote good burning practices, to urge reduced reliance on wood as a space-heating fuel, and to promote compliance with voluntary and mandatory wood-burning curtailment programs are considered essential to any control of residential wood combustion. EPA guidance allows a 50% or more emissions reduction credit for mandatory curtailment and up to a 50% credit for voluntary programs.
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From page 437... ...
Further emission reductions are possible by increasing the durability of the stoves to reduce sheet metal warpage that allows flue gases to bypass catalytic converters and by increasing the durability of the converters themselves (Crane, 1989~. Reduced Dependence on Wood In some mountain communities, reduced dependence on wood through weatherization and fuel switching might be the only long-term strategy that will assure compliance with the PM~o NAAQS.
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From page 438... ...
FUGITIVE DUST Fugitive particulate emissions originating from a variety of sources can severely impair visibility in Class ~ areas in arid parts of the western United States or near major agricultural areas. Global emissions of wind-blown dust are estimated to be of the order of 2 million tons per day, or about one-tenth of total global tropospheric particle emissions.
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From page 439... ...
Control strategies for reducing paved road dust include road sweeping and flushing, reducing soil tracked out onto the road network from construction sites or unpaved roads, reducing spills from haul trucks, and reducing wind erosion from lands adjacent to the roadway. Unpaved road dust strategies include roadway surface improvements such as watering, chemical stabilization, and paving.
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From page 440... ...
estimated that wild and domestic animals and humans produce globally about 27-50 million metric tons/yr of NH3, but only a small faction of those emissions (2-7 million metric tons/yr) is attributable to wild animal wastes.
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