Look at with examples the advantages and disadvantages of liquid and gaseous fuels

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Look at with examples the advantages and disadvantages of liquid and gaseous fuels.

Different types of fuels have been used throughout out time, because of their properties, or the technology needed to make them usable. The term fuel is generally limited to those substances that burn readily in air or oxygen, emitting large quantities of heat. Fuels are used for heating, for the production of steam for heating and power purposes, for powering internal-combustion engines, and for a direct source of power in jet and rocket propulsion.

Gaseous fuels

Fuel gases consist principally of hydrocarbons, that is, of molecular compounds of carbon and hydrogen. The properties of the various gases depend on the number and arrangement of the carbon and hydrogen atoms within their molecules. All these gases are odorless in the pure state, and carbon monoxide is toxic. It is therefore common practice to add sulphur compounds to manufactured gas; such compounds, which are sometimes normally present in the gas, have an unpleasant smell and serve to give warning of a leak in the supply lines or gas appliance. In addition to their combustible components most gases have varying amounts of noncombustible nitrogen and water as their end products, which are pollutants.

Fuel gases still in use are coal gas, made by the destructive distillation of coal; producer gas and blast-furnace gas, made by the interaction of steam, air, and carbon; natural gas, drawn from gas deposits in the earth; and bottled gases, made from the lighter hydrocarbons.

Coal Gas

The most important coal-gasification processes aim chiefly at production of so-called pipeline-quality gas, which is roughly equivalent in its properties to natural gas. Gas from coal, besides meeting pumping and heating specifications, must satisfy strict limits on content of carbon monoxide, sulphur, inert gases, and water. To meet these standards, most coal-gasification processes culminate with gas cleanup and methanation operations. Various hydrogasification processes, in which hydrogen reacts directly with coal to form methane, are used today; these processes bypass the indirect step of producing synthesis gas, hydrogen and carbon monoxide, before an upgrading yields methane. Other coal-gas processes include the carbon dioxide acceptor process, employing the lime-bearing material dolomite, and the molten salt process. These processes work indirectly, synthesis gas being produced first. Other gases manufactured formerly from coal and coke, such as illumination gas and coke-oven gas, are of little or no importance today.

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Producer and Blast-Furnace Gases

Producer gas is a form of water gas, a term applied to steam-process gases. It is made by burning low-grade fuel (such as lignite or bituminous coal) in a closed vessel, called a producer, while passing a continuous stream of steam and air through the producer. The resulting gas is approximately 50 per cent incombustible nitrogen derived from the air present in the producer, and is low in fuel value, having only about 28 per cent of the heating value of coke-oven gas.

Blast-furnace gas, which results from the interaction of limestone, iron ore, and ...

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