Texts for educational purposes Types of fuel

Petroleum is a naturally occurring oil that consists chiefly of hydrocarbons with some other elements, such as sulphur, oxygen and nitrogen. In its unrefined form petroleum is known as crude oil (sometimes rock oil). Petroleum is believed to have been formed from the remains of living organisms that were deposited, together with rock particles and biochemical and chemical precipitates, in shallow depressions, chiefly in marine conditions. Under burial and compaction the organic matter went through a series of processes before being transformed into petroleum, which migrated from the source rock to become trapped in large underground reservoirs beneath a layer of impermeable rock. The petroleum often floats above a layer of water and is held under pressure beneath a layer of natural gas. Petroleum reservoirs are discovered through geological exploration: commercially important oil reserves are detected by exploratory narrow-bore drilling. The major known reserves of petroleum are in Saudi Arabia, Russia, China, Kuwait, Iran, Iraq, Mexico, USA, United Arab Emirates, Libya and Venezuela. The oil is actually obtained by the sinking of an oil well. Before it can be used it is separated by fractional distillation in refineries. The main fractions obtained are:

1. Refinery gas is a mixture of methane, ethane, butane and propane used as a fuel and for making other organic chemicals.

2. Gasoline is a mixture of hydrocarbons containing from 5 to 8 carbon atoms, boiling in the range of 40 - 180°C. It is used for motor fuels and for making other chemicals.

3. Kerosene (or paraffin oil) is a mixture of hydrocarbons having 11 or 12 carbon atoms, boiling in the range of 160 - 250°C. Kerosene is a fuel for jet aircraft and for oil-fired domestic heating. It is also cracked to produce smaller hydrocarbons for use in motor fuels.

4. Diesel oil (or gas oil) is a mixture of hydrocarbons having from 13 to 25 carbon atoms, boiling in the range of 220 - 350°C It is a fuel for diesel engines.

The residue is a mixture of higher hydrocarbons. The liquid components are obtained by vacuum distillation and used in lubricating oils. The solid components (paraffin wax) are obtained by solvent extraction. The final residue is a black tar containing free carbon.

Classification of fuels

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The principal fuels used at present for making steam are coal, coke, wood, charcoal, peat, mineral oil, natural and artificial gas. All kinds of fuel may, in fact, be virtually subdivided into three classes: solid, liquid and gaseous. All coals seem to be derived from vegetable origin and their differences appeared as a result of the varying conditions under which they were formed. Anthracite coal consists almost entire­ly of carbon and inorganic matters; it contains little or no hy­drocarbon at all. Some varieties appear to approach graphite in their characteristics and are burnt with difficulty unless at first mixed with other coals. Good anthracite is hard, compact and lustrous. It burns with very little flame unless it is moist, and gives a very intense fire, free of smoke. Even when carefully used, it is liable to break up at high temperatures and, in this way, the fine pieces may be lost with the ash. Semianthracite contains some hydrocarbon, is less dense than anthracite, ignites at once, and burns readily with a short flame. Bituminous coals contain a large and varying percents of hydrocarbons or bituminous matter. Their physical properties and behavior, when burning, vary widely so that classification is difficult, though at least three kinds may be distinguished : dry bituminous coals, caking bituminous coals and, at last, long-flaming bituminous coals. The latter has a strong ten­dency to produce smoke; some do and some do not cake at all while burning. Charcoal is made by charring wood; it is no longer used for making steam but is widely applied for special metallurgical purposes.

Lesson 12

Part 1

The gerundial constructions

The gerund and the words relating to it form gerundial constructions that usually begin with a preposition, a possessive pronoun or a noun. Gerundial constructions can be of two types:

1. Dependent gerundial constructions;

2. Absolute gerundial constructions.

Dependent gerundial constructions

Dependent gerundial constructions are constructions which don’t have a word denoting a doer before gerund. These gerundial constructions are translated into Russian by a subordinate clause and gerund itself is translated by a predicate, e.g.:

This polymer differs from that one by having absorption properties - Этот полимер отличается от того тем, что он обладает адсорбционными свойствами.