Fossil combustibles

In this process, nuclear energy can effectively be utilised, avoiding the C02 emission from any biomass or fossil combustion. Thus, a significant amount of C02 can efficiently be removed from the atmosphere by processing a part of annual growth of biomass, which leads to the decrease of atmospheric C02 concentration. 

The carbon source for the synthetic fuels is primarily the CO2 from flue gas of fossil combustion, but finally, perfect recycling CO2 will be supplied without any fossil fuel. 

There are many possibilities to reduce carbon dioxide emissions caused by fossil combustibles as caibon or hydrocarbons ... 

Replacement of fossil combustibles by other energy sources, especiaUy by renewable energies... 

Fossil combustibles. Emissions of carbon dioxide or sequestration of carbon dioxide (availability of secure and tight caverns) or carbon. 

Selection of pollution control methods is generally based on the need to control ambient air quaUty in order to achieve compliance with standards for critetia pollutants, or, in the case of nonregulated contaminants, to protect human health and vegetation. There are three elements to a pollution problem a source, a receptor affected by the pollutants, and the transport of pollutants from source to receptor. Modification or elimination of any one of these elements can change the nature of a pollution problem. For instance, tall stacks which disperse effluent modify the transport of pollutants and can thus reduce nearby SO2 deposition from sulfur-containing fossil fuel combustion. Although better dispersion aloft can solve a local problem, if done from numerous sources it can unfortunately cause a regional one, such as the acid rain now evident in the northeastern United States and Canada (see Atmospheric models). References 3—15 discuss atmospheric dilution as a control measure. The better approach, however, is to control emissions at the source. 

Physical Properties. Physical properties of waste as fuels are defined in accordance with the specific materials under consideration. The greatest degree of definition exists for wood and related biofuels. The least degree of definition exists for MSW, related RDF products, and the broad array of ha2ardous wastes. Table 3 compares the physical property data of some representative combustible wastes with the traditional fossil fuel bituminous coal. The soHd organic wastes typically have specific gravities or bulk densities much lower than those associated with coal and lignite. 

Temperatures Associated with Combustion. The temperatures achieved by soHd waste combustion are typically lower than those associated with fossil fuel oxidation, and are governed by the following general equation (1) ... 

Given the mechanisms and temperatures, waste combustion systems typically employ higher percentages of excess air, and typically also have lower cross-sectional and volumetric heat release rates than those associated with fossil fuels. Representative combustion conditions are shown in Table 11 for wet wood waste with 50—60% moisture total basis, municipal soHd waste, and RDF. 

Combustion. Coal combustion, not being in the strictest sense a process for the generation of gaseous synfuels, is nevertheless an important use of coal as a source of gaseous fuels. Coal combustion, an old art and probably the oldest known use of this fossil fuel, is an accumulation of complex chemical and physical phenomena. The complexity of coal itself and the variable process parameters all contribute to the overall process (8,10,47—50) (see also COLffiUSTION SCIENCE AND technology). 

Natural gas is attractive as a fuel ia many appHcatioas because of its relatively clean burning characteristics and low air pollution (qv) potential compared to other fossil fuels. Combustion of natural gas iavolves mixing with air or oxygen and igniting the mixture. The overall combustion process does not iavolve particulate combustion or the vaporization of Hquid droplets. With proper burner design and operation, the combustion of natural gas is essentially complete. No unbumed hydrocarbon or carbon monoxide is present ia the products of combustioa. 

Of all the fossil fuels, the use of natural gas results ia the formation of the least amouat of CO2 per unit of heat energy produced. On a constant energy basis, natural gas combustion produces approximately 30% less CO2 than Hquid petroleum fuels and approximately 45% less CO2 than coal and other soHd fossil fuels. 

In the fuel cell hydrogen is used two to three times as efficiendy as in an internal combustion engine. Hence, when utilized in a fuel cell, hydrogen can cost two to three times that of more conventional fossil fuels and stiU be competitively priced, ie, as of this writing the market price for hydrogen when used in a fuel cell and produced by electrolysis is competitively priced with gasoline. 

Hydrogen Internal Combustion Engine. Standard gasoline and diesel-powered internal combustion engine vehicles can be converted to mn on hydrogen. These vehicles have often been found considerably less polluting, safer, and more efficient than their fossil fuel-burning counterparts. 

Nuclear power plants of the future are to be designed and operated with the objective of better fiilfiUing the role as a bulk power producer that, because of reduced vulnerabiUty to severe accidents, should be more broadly accepted and implemented. Use of these plants could help stem the tide of environmental damage caused by air pollution from fossil-fuel combustion products (64). 

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