Present Sources of Energy

Using the standard enthalpies of formation from Table 6.2 and Equation (6.1), we have 

Thus 1.45 X 10 kJ of heat is evolved when 2 moles of methanol bum. The molar mass of methanol is 32.04 g/mol. This means that 1.45 X 10 kJ of energy is produced when 64.08 g methanol bums. The enthalpy of combustion per gram of methanol is 

This is the amount of heat evolved when 2 moles of octane bum. Since the molar mass of octane is 114.22 g/mol, the enthalpy of combustion per gram of octane is 

Woody plants, coal, petroleum, and natural gas hold a vast amount of energy that originally came from the sun. By the process of photosynthesis, plants store energy that can be claimed by burning the plants themselves or the decay products that have been converted over millions of years to fossil fuels. Although the United States currently 

TABLE 9.5 Formulas and Names for Some Common Hydrocarbons 

Although how they were produced is not completely understood, petroleum and natural gas were most likely formed from the remains of marine organisms that lived about 500 million years ago. Petroleum is a thick, dark liquid composed mostly of compounds called hydrocarbons that contain carbon and hydrogen. Table 9.5 lists the formulas and names of several common hydrocarbons. Natural gas, usually associated with petroleum deposits, consists mostly of methane but also contains significant amounts of ethane, propane, and butane. 

The composition of petroleum varies somewhat, but it consists mostly of hydrocarbons having chains that contain from 5 to more than 25 carbons. To be used efficiently, the petroleum must be separated into fractions by boiling. The lighter molecules (having the lowest boiling points) can be boiled off, leaving the heavier ones behind. The uses of various petroleum fractions are shown in Table 9.6. 

As gasoline became more important, new ways were sought to increase the yield of gasoline obtained from each barrel of petroleum. William Burton 

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TABLE I. Present Sources of Energy Averaged over the Earth"... 

The civilised world is rapidly increasing its demands for more light, more heat, more electricity, and motive power in all forms. The sun is eventually the source of all this increased physical activity. Human progress and fuel consumption seem to go hand in hand. Coal, petroleum, vegetation, water power, and the sun B rays seem to be quite exclusively the present sources of energy. These sources represent in reality the sun s rayB, past and present. When the supply of coal, petroleum, and wood is consumed, many believe we will be restricted to the utilization of the annual fixation of energy from the sun s rays, in other words, annual crops. 

Chemical Insights Firewalking Magic or Science Standard Enthalpies of Formation 384 Present Sources of Energy 390... 

Characteristics of Enthaipy Changes Standard Enthalpies of Formation Present Sources of Energy Petroleum and Natural Gas Coal... 

The main commercial source of methane, ethane, and propane is natural gas, which is found ia many areas of the world ia porous reservoirs they are associated either with cmde oil (associated gas) or ia gas reservoirs ia which no oil is present (nonassociated gas). These gases are basic raw materials for the organic chemical industry as well as sources of energy. The composition of natural gas varies widely but the principal hydrocarbon usually is methane (see Gas, natural). Compositions of typical natural gases are Hsted ia Table 2. 

AUTO-iGNiTiON TEMPERATURE The minimum temperature required to initiate or cause self-sustained combustion of material in the absence of any external source of energy. (Values may change significantly with geometry, gas/vapour concentration, and if catalyst is present.)... 

An important addition to this list of fuels is electric energy which, when viewed as a source of heat is also identified as fuel. It bears the reputation of the cleanest source of energy. The advantages and disadvantages of the three types of fuels, solid, liquid, and gaseous fuels are presented in Tables 1.23 to 1.25, respectively. The main factors that come under consideration when a fuel or type of fuel is chosen for a particular purpose are presented in Table 1.26. These serve as useful guidelines. 

The present shortage of gas and the projected shortage of power has caused the chemical industry to become aware of how it can conserve the power it now has. For any new plants the process will be carefully scrutinized to see that power usage is minimized. To accomplish this, the design engineer must be aware of all the places within the plant where energy is needed and of all the sources of energy available. 

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