Solid fuels chemical availability

In addition to rotary and vertical kilns, hearth furnaces or fluidized-bed reactors may be used. These high-temperature reactors convert minerals for easier separation from gangue or for easier recovery of metal. Fluidized beds are used for the combustion of solid fuels, and some 30 installations are listed in Encyclopedia of Chemical Technology (vol. 10, Wiley, 1980, p. 550). The roasting of iron sulfide in fluidized beds at 650 to 1100°C (1202 to 2012°F) is analogous. The pellets have 10-mm (0.39-in) diameter. There are numerous plants, but they are threatened with obsolescence because cheaper sources of sulfur are available for making sulfuric acid. 

The removal of both mineral matter and sulfur species to very low values would provide premium solid fuels and possibly new chemical feedstocks. Several techniques are being explored to achieve these goals. The mineral matter in a physically cleaned coal can be further reduced by the solubilization of the aluminosilicate minerals. This can technically be accomplished with the use of alkaline and then acid treatments. A variety of studies are under way to define the conditions required for effective removal of the mineral matter and establish the amount of sulfur reduction that can be accomplished. Others involve the use of fine grinding to liberate the coal from the mineral matter. Then an agglomerant is used to separate the coal matter from the aqueous phase containing suspended mineral matter. A new approach uses microwave energy to selectively decompose the clays into species that can be solubilized and removed. Still another technique involves treatment with carbon dioxide to reduce the particle size and permit the liberation of the mineral matter. Over the next few years these will be studied further and it is hoped that coal will become available in a form with less of these interesting, but not entirely desirable mineral species. 

Some partial contributions to the total availability are then considered. Thus, a simple expression for the pressure availability of an incompressible fluid is developed. Formulae for the chemical availability of hydrocarbon fuels obtained by Szargut and Styrylska are then discussed and summarized in a separate table. Equations for the average value of the specific heat of various solid fuels between some fixed temperature and some other variable one are also given, as is a technique to estimate the lower heating value of a fuel of known atomic composition. Finally, a simplified approach used in approximating the thermal availability of tars is described. 

Using equation [24], the chemical availability of many fuels with known values of LHV and sg was computed by Szargut and Styrylska and a correlation established in terms of their atomic ratios or corresponding mass ratios. Three categories of fuels were studied, namely, solid fuels containing no sulfur, sulfurbearing solid fuels, and fluid fuels. 

In order to handle this group of solid fuels, they ignore the bond availability of sulfur in the fuel that is, they treat sulfur as a free species. Next they calculate the difference between sulfur s chemical availability and its lower heating value, given by... 

Note The authors being discussed seem to base some of their numerical values on a set of tables different from reference (3). The value of ac given here is the one listed on table I, resulting from reference (3) values, while the LHV of sulfur has been taken from Chemical Engineer s Handbook (7).) From this they reason that the chemical availability of solid fuels containing sulfur can be obtained from the expressions... 

Solid-fueled and liquid-fueled rockets were developed because of the characteristics of travel beyond the Earth s atmosphere. First, a spacecraft must develop a speed of more than 25,000 mile per hour to break the gravitational puU. Second, in space oxygen is absent, so turbojet engines and internal-combustion engines will not operate. Therefore, alternative types of propulsion needed to be developed, which is why solid-fueled and liquid-fueled rockets were developed. Rockets develop thrust without having oxygen available to burn. Engineers term the types of chemical mixtures used in rockets that produce thrust as propellants. 

Fuels for combustion are initially gases, liquids, or solids. A fuel initially in one phase may be transformed into another during the burning process (i.e., liquids vaporized to gases). The factors involved in the selection of the fuel phase or its physical and chemical characteristics for an application such as burning in an automobile or jet aircraft involve many different considerations such as price, availability, and source. 

This paper is concerned with the potential for production of liquid fuels from biomass in Canada. To this end, the availability and cost of wood wastes, surplus roundwood, bush residues, energy plantation trees, and municipal solid wastes (mostly cellulosic) are assessed and promising thermal, chemical and biochemical conversion processes reviewed. 

Direct Reduction. Direct reduction processes are distinguished from other ironmaking processes in that iron oxide is converted to metallic iron without melting. Because this product, called direct reduced iron (DRI), is solid, it is most suitable for melting in an electric arc furnace (EAF) as a substitute for scrap (see Furnaces, electric). The briquetted form of DRI, hot briquetted iron (HBI) is used when the product is to be transported. Briquetting increases density and chemical stability. The predominant direct reduction processes (MIDREX and HyL III) are based on natural gas as a fuel and reductant source. They are economically attractive in regions where natural gas is cheap and abundant, especially if iron ore is available nearby (see Iron BY DIRECT REDUCTION). 

Cellulosic wastes have great potential as a feedstock for producing fuels and chemicals. Cellulose is a renewable resource that is inexpensive, widely available and present in ample quantities. Large amounts of waste cellulose products are generated by commercial and agricultural processes. In addition, municipal facilities must treat or dispose of tremendous quantities of cellulosic solid waste. 

Explosives in which the oxidizer and fuel portions come from different molecules are called composite explosives because they are a mixture of two or more chemicals. A classic industrial example is a mixture of solid ammonium nitrate (AN) and liquid fuel oil (FO). The common designation for this explosive is the acronym, ANFO. The oil used (typically 2 diesel fuel) is added in sufficient quantity to react with the available oxygen from the nitrate portion of AN. The redox reaction of ANFO is as follows ... 

Hexamine forms colorless, odorless, or white granules, powder, or crystals. It sublimes at 263 Celsius without melting, but is volatile below this temperature. Hexamine bums with a smokeless flame, and is used in solid camping fuel pellets (in high purity). 1 gram of hexamine dissolves in 1.5 milliliters water, and 12.5 milliliters of alcohol. It is insoluble in ether. Hexamine is a widely available, and cheap commercial chemical. 

Originally confined to the shipment of crude raw materials and fuels, the term transportation of bulk solids now applies also to manufactured products, which often become raw materials for other industries. In recent years, increasing tonnages of highly processed, finished chemical products have moved to customers in large bulk units. A useful definition of a bulk shipment is any unit greater than 2000 kg (4000 lb) or 2 m (70 ft ). The containers available range from small portable hoppers of 2-m (70-ft ) capacity to railroad cars of 255-m (9000-ft ) capacity. 

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