Atmospheric pollution fuel desulfurization

It is also doubtful that the industry will be in a position for many years to come to undertake sulfur removal from residual fuels solely to improve product quality. A number of consumer industries demand low sulfur fuel oils, but these special requirements can at present be met more appropriately by selection of crude rather than by adoption of desulfurization processes. In general industrial use, it is corrosion and atmospheric pollution that are the main disadvantages of high sulfur content. But there is no sign yet of the development of a cheap desulfurization process, the cost of which can be substantially offset by the gain in efficiency resulting from permissible lower stack temperatures or by the elimination of flue gas scrubbing equipment previously necessary for reduction of sulfur dioxide content. 

Of all the elements present in a normal residual fuel oil, vanadium, sodium, and sulfur contribute most to difficulties and problems that may arise in the industrial application of fuel oils. Sulfur contributes to the increasing problem of atmospheric pollution when sulfur oxides, produced on combustion of high-sulfur fuel oils, are emitted into the surrounding atmosphere of densely populated industrial areas or large towns. In specific applications fuel oil desulfurization may have to be used to comply with air pollution legislation. 

The total amount of vanadium in residual fuel oil is probably greater than in any other product of petroleum refining. About 668 million barrels of fuel oil were consumed in the United States in 1968, and this material is estimated to have contained nearly 19,000 tons of vanadium. At the current price, this amount of vanadium is worth about 100 million. Desulfurization of fuel Oil can reduce the vanadium content about proportionate to the reduction of sulfur.If fuel oil is desulfurized to reduce atmospheric pollution, can a significant amount of vanadium be recovered profitably from the catalysts used in the desulfurizing process or at some other stage in this process ... 

Sulfur Dioxide Emissions and Control. A substantial part of the sulfur dioxide in the atmosphere is the result of burning sulfur-containing fuel, notably coal, and smelting sulfide ores. Methods for controlling sulfur dioxide emissions have been reviewed (312—314) (see also Air POLLUTION CONTROL PffiTHODS COAL CONVERSION PROCESSES, CLEANING AND DESULFURIZATION EXHAUST CONTROL, INDUSTRIAL SULFURREMOVAL AND RECOVERY). 

The recovered sulfur industry exists primarily as a result of the necessity of removing sulfur values from hydrocarbon fuels before combustion so that sulfur emissions to atmosphere are reduced. In the case of sour gas, the principal source of recovered sulfur, the product that results from recovery of the sulfur is clean-burning, non-polluting methane. In the case of refineries handling high sulfur crude the product is low sulfur gasoline and oils. Thus every ton of sulfur recovered is a ton that is not added to the atmosphere. The recovery process itself however, is also the subject of optimization and recent developments in recovery efficiency have further ensured that the environmental impact in the immediate vicinity of these desulfurization facilities will be minimized. 

Sulfttr Content. The amount of sulfur in crude is important in terms of handling the crude within the refinery and the undesirable effects of sulfur in finished products. High-sulfur crudes require special materials of construction for refinery equipment because of their corrosiveness. Certain refinery processes require desulfurization of sour charge stocks prior to use as a feedstock, not only because of their corrosiveness, but also because of the effect of sulfur-bearing compounds on expensive catalysts, From the standpoint of the consumer, sulfurous gasoline has an unforgettably offensive odor unless specially sweetened and it may corrode the fuel system and engine parts, as well as pollute the atmosphere after it has been burned,... 

There are several approaches available to a utility to construct a boiler that will meet New Source Performance Standards. These approaches can be classified according to the position in the combustion system at which pollutant control technology is applied. Precombustion control involves removal of sulfur, nitrogen, and ash compounds from the fuel before it is burned. For coal combustion this approach involves the application of coal-cleaning technology. Combustion control relies on modifications to the combustion process itself or the addition of material to the combustion process to reduce pollutant formation or capture the pollutants formed in the combustion chamber. Examples of combustion control include staged combustion, boiler limestone injection, and fluidized-bed combustion with limestone addition. Post-combustion control involves removal of pollutants after they have been formed but before they are released into the atmosphere. Traditionally, flue gas desulfurization has meant the application of postcombustion control either alone or in conjunction with another... 

The environmental aspects of coal combustion have been a major factor in the various processes, and the movement of the fossil fuel base away from petroleum and natural gas to coal has increased the need for effluent/pollutant control for large, fossil-fueled power plants (Argonne, 1990). Very large amounts of coal are consumed in generating electricity and the emissions from power stations and similar industrial sources represent a potential, and considerable, environmental hazard. These power plants and the accompanying flue gas desulfurization processes emit effluents, which often are pollutants, and which by mere contact with the external environment or by (generally) simple atmospheric chemical transformations, may form secondary pollutants that are more harmful than the initial effluent/pollutant. 

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