Waste fuels properties

P. T. Williams S. Besler and D. T. Taylor, The batch pyrolysis of tyre waste - fuel properties of the derived pyrolytic oil and overall plant economics. Proceedings of the Institution of Mechanical Engineers Part A. Journal of Power and Energy, 207, 55-63 (1993). 

The fuel properties of wood can be summarized by ultimate and proximate analyses and deterrnination of heating value. The analytical procedures are the same as those for coal, but with some modifications. Analytical results generally vary about as much within a species as they do between species, except that softwood species generally have a higher carbon content and higher heating values than hardwood species because of the presence of more lignin and resinous materials in softwood species (see Fuels from waste). 

Table 7.6 Comparison of the calorific properties of coal and plastic waste fuels...

Gonz lez G6mez, M. E., Howard-Hildige, R., Leahy, J. J., and Rice, B. 2002. Winterization of Waste Cooking Oil Methyl Ester to Improve Cold Flow Temperature Fuel Properties. Fuel, 81,33-39. 

Table 2 Physical, chemical, and fuel properties of biomass, coal, and municipal solid waste...

Coal was added to the secondary fuels to balance out the significant fluctuations in fuel properties, e.g. heating value, and to provide residual char as energy source for the endothermic gasification process (autothermal operation). In 2007 the Swiss Sustec Industries AG, then owner of SVZ, put the gasification plant out of service and discontinued the waste conversion operation because of insufficient profitability. 

TaUe 17.7. Selected properties of solid fuels and waste fuels other than coals... 

Althongh the electrolyte of a fuel cell would have been chosen for its ion conducting properties, it will always be able to support very small amounts of electron conduction. The sitnation is akin to minority carrier conduction in semicondnctors. Probably more important in a practical fuel cell is that some fuel will diffuse from the anode through the electrolyte to the cathode. Here, because of the catalyst, it will react directly with the oxygen, producing no current from the ceU. This small amount of wasted fuel that migrates through the electrolyte is known as fuel crossover. 

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. 

Table 3. Physical Properties of Waste-Based Fuels ...

The primary issue is to prevent groundwater from becoming radioactively contaminated. Thus, the property of concern of the long-lived radioactive species is their solubility in water. The long-lived actinides such as plutonium are metallic and insoluble even if water were to penetrate into the repository. Certain fission-product isotopes such as iodine-129 and technicium-99 are soluble, however, and therefore represent the principal although very low level hazard. Studies of Yucca Mountain, Nevada, tentatively chosen as the site for the spent fuel and high level waste repository, are underway (44). 

H. Alter and J. J. Duim, Jr., Solid Waste Conversion to Energy Current European and U.S. Practices, Marcel Dekker, Inc., New York, 1980, Chapt. 5 H. Alter andj. A. CampbeU, in J. L. Jones and S. B. Radding, eds.. The Preparation and Properties ofDensified Refuse-Derived Fuel, Thermal Conversion of Solid Wastes andBiomass, American Chemical Society, Washington, D.C., 1980, pp. 127—142. 

Chemical Composition Information on the chemical composition of sohd wastes is important in evaluating alternative processing and recoveiy options. If solid wastes are to be used as fuel, the four most important properties to be known are ... 

Selected physical properties of oxygen are included in Table 9.24. It is a colourless, odourless and tasteless gas which is essential for life and considered to be non-toxic at atmospheric pressure. It is somewhat soluble in water and is slightly heavier than air. Important uses are in the steel and glass industries, oxyacetylene welding, as a chemical intermediate, waste-water treatment, fuel cells, underwater operations and medical applications. 

The heating value of a waste and/or fuel is one of its most important chemical properties. Tliis value represents the amount of heat evolved in tlie complete reaction (usually combustion) of a given quantity of the waste and/or fuel. 

Fhosphoric acid does not have all the properties of an ideal fuel cell electrolyte. Because it is chemically stable, relatively nonvolatile at temperatures above 200 C, and rejects carbon dioxide, it is useful in electric utility fuel cell power plants that use fuel cell waste heat to raise steam for reforming natural gas and liquid fuels. Although phosphoric acid is the only common acid combining the above properties, it does exhibit a deleterious effect on air electrode kinetics when compared with other electrolytes ( ) including such materials as sulfuric and perchloric acids, whose chemical instability at T > 120 C render them unsuitable for utility fuel cell use. In the second part of this paper, we will review progress towards the development of new acid electrolytes for fuel cells. 

Comparable fuels. In order to promote the recycling of materials with high fuel values, certain materials that are burned as fuels are excluded from the definition of solid waste, provided that they meet certain specifications (i.e., are of a certain degree of purity). This is to ensure that the material does not exceed certain levels of toxic constituents and physical properties that might impede burning. Materials that meet this specification are considered comparable to pure or virgin fuels. 

When an incinerator is designed, the waste to be burned must be characterized for properties such as heat content (fuel value), percent moisture, chlorine content, metals content, and physical characteristics. The size and physical layout of the incinerator should be based on those waste properties. 

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