Energy requirement, fuel

In Sasolburg, South Africa, a commercial plant using the Fischer-Tropsch process was completed in 1950 and began producing a variety of Hquid fuels and chemicals. The faciUty has been expanded to produce a considerable portion of South Africa s energy requirements (15,16). 

Thermal decomposition of spent acids, eg, sulfuric acid, is required as an intermediate step at temperatures sufficientiy high to completely consume the organic contaminants by combustion temperatures above 1000°C are required. Concentrated acid can be made from the sulfur oxides. Spent acid is sprayed into a vertical combustion chamber, where the energy required to heat and vaporize the feed and support these endothermic reactions is suppHed by complete combustion of fuel oil plus added sulfur, if further acid production is desired. High feed rates of up to 30 t/d of uniform spent acid droplets are attained with a single rotary atomizer and decomposition rates of ca 400 t/d are possible (98). 

The gas turbine power plant which has revolutioni2ed aviation derives basically from the steam turbine adapted to a different working fluid. The difference is cmcial with respect to fuel because steam can be generated by any heat source, whereas the gas turbine requires a fuel that efficiently produces a very hot gas stream and is also compatible with the turbine itself. The hot gas stream results from converting chemical energy in fuel directly and continuously by combustion in compressed air. It is expanded in a turbine to produce useful work in the form of jet thmst or shaft power. 

Coal was the primary kiln fuel in 1989 as seen in Table 10. Energy from coal rose from 39 to 84% of the total energy required for cement production between 1972 and 1989. In the same time period, natural gas dropped to 9%, petroleum products to 1% of the total energy consumed. Waste fuels represented 5% of the energy consumed in 1989 cement production. 

Such a reference system is shown in Fig. 9.3a. The overall efficiency of the conventional electric power plant is (for simplicity the subscript O for overall efficiency is dropped from here onwards) the (demand) electrical load is unity. The ratio of heat to electrical demands is Ai>, so that the demand heat load is taken as Ajj. The efficiency of the heat only boiler is tjb so the fuel energy required for the boiler is i.e. there are heat losses ApKI/tjq)— 1 involved before heat is delivered to district or process heating. 

The total fuel energy required in the reference system is... 

The fuel energy savings ratio (FESR) is then defined as the ratio of the saving (AF) to the fuel energy required in the conventional plants,... 

Just as an internal combustion engine requires fuel to do work, animals need fuel to power their body processes. Animals Cake in complex molecules as food and break them down to release the energy they contain. This process is called catabolism. Animals use the energy of catabolism to do work and to assemble complex molecules of their own from simple building blocks, a process called anabolism. The sum of anabolism and catabolism is metabolism, a broad term that includes all chemical reactions in the body. 

The most important current technique for the thermal destmction of waste is incineration, where the energy required for destmction is provided by oxidation of the waste, sometimes supplemented with a fossil fuel. The major question about all thermal destmction techniques is whether products from the process—either traces of umeacted parent compound or compounds synthesized from the parent compound at high temperature— will pose a health hazard. 

Chemical energy fuels all human activity, whether it be work or play (Figure 6-81. In any physical activity, a person does work to accomplish movement, and the energy for this work comes from the chemical energy stored In food. Our explores human energy requirements. 

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