Combustible gases: names, properties and applications

Combustible gases are substances with a low threshold of heatcombustion. This is the main component of gaseous fuel, which is used for gas supply to cities, in industry and other spheres of life. The physico-chemical characteristics of such gases depend on the presence of noncombustible components and harmful impurities in their composition.

Types and origin of combustible gases

Combustible gases contain methane, propane, butane, ethane,hydrogen and carbon monoxide, sometimes with impurities of hexane and pentane. They are obtained in two ways - from natural deposits and artificially. Gases of natural origin - fuel, the result of a natural biochemical process of organic decomposition. Most of the deposits are located at a depth of less than 1.5 km and consist mainly of methane with small impurities of propane, butane and ethane. With increasing depth, the percentage of impurities increases. Obtained from natural deposits or as associated gases from oil fields.

The most common deposits of natural gasare concentrated in sedimentary rocks (sandstones, pebbles). Covering and underlaying layers are dense clay rocks. As a sole, oil and water are mainly used. Artificial - flammable gases produced by the thermal processing of various types of solid fuels (coke, etc.) and derivatives of oil refining.

The main component of natural gases producedin dry deposits, is methane with a small amount of propane, butane and ethane. Natural gas is characterized by constancy of the composition, it belongs to the dry category. The gas composition obtained from oil refining and from mixed gas and oil deposits is unstable and depends on the size of the gas factor, the nature of the oil and the conditions for the separation of oil and gas mixtures. It includes a significant amount of propane, butane, ethane, as well as other light and heavy hydrocarbons contained in oil, up to kerosene and gasoline fractions.

The production of combustible natural gases isextracting it from the bowels, collecting, removing excess moisture and preparing for transportation to the consumer. The peculiarity of gas production is that at all stages from the formation to the end user the whole process is sealed.

Combustible gases and their properties

Heat output - maximumthe temperature released by the complete combustion of dry gas in the theoretically necessary amount of air. In this case, the heat released is expended on heating the combustion products. For methane, this parameter in ° C is 2043, butane - 2118, propane - 2110.

Ignition temperature - lowestthe temperature at which a spontaneous ignition process occurs without the influence of an external source, spark or flame, due to the heat of the gas released by the particles. This parameter is especially important for determining the permissible surface temperature of apparatus used in hazardous areas, which should not exceed the ignition temperature. For such equipment, a temperature class is assigned.

Flash point is the lowest temperature, withwhich emits sufficient vapor (on the surface of the liquid) to ignite from the smallest flame. This property should not be generalized to the ignition temperature, since these parameters can differ to a great extent.

Density of gas / steam. It is determined in comparison with air, whose density is equal to 1. The gas density <1 - increases,> 1 - decreases. For example, for methane, this figure is 0.55.

Danger of flammable gases

Flammable gases present a hazard with three of their properties:

1. Flammability. There is a risk of fire caused by uncontrolled ignition of gas;
2. Toxicity. The risk of poisoning with gas or products of its burning (carbon monoxide);
3. Strangulation due to oxygen deficiency, which can be replaced by another gas.

The combustion process is a chemicalreaction, which includes oxygen. At the same time, energy is released in the form of heat and flame. A gas acts as a flammable substance. The process of gas combustion is possible if there are three factors:

• Source of ignition.
• Flammable gases.
• Oxygen.

The purpose of fire protection is to eliminate at least one of the factors.

Methane

It is a colorless, light, flammable gas that does not smell. Non-toxic. Methane accounts for 98% of all natural gases. It is considered to be the main one that determines the properties of natural gas. 75% consists of carbon and 25% hydrogen. Weight cube. meter - 0.717 kg. It is liquefied at a temperature of 111 K, while its volume decreases 600 times. Has low reactivity.

Propane

Propane gas is a combustible gas, without color and odor. It has a greater reactivity than methane. The content in natural gas is 0.1-11% by weight. In associated gases from mixed gas and oil fields up to 20%, in products of processing of solid fuels (brown and hard coal, coal tar) up to 80%. Propane gas is used in various reactions to produce ethylene, propylene, lower olefins, lower alcohols, acetone, formic and propionic acid, nitroparaffins.

Butane

Combustible gas without color, with a peculiar smell. Butane gas is easily compressed and volatile. Contained in petroleum gas up to 12% by volume. Also obtained as a result of cracking of oil fractions and laboratory by the reaction of Wurz. Freezing point -138 ^aboutC. Like all hydrocarbon gases, it is flammable. Harmful to the nervous system, if inhaled, causes dysfunction of the respiratory apparatus. Butane (gas) has narcotic properties.

Ethane

Ethane is a gas without color and odor. Representative of hydrocarbons. Dehydrogenation at 550-650⁰ C leads to ethylene, over 800⁰ C - to acetylene. Contained in natural and associated gases up to 10%. It is distinguished by low-temperature rectification. Significant amounts of ethane are released during oil cracking. In laboratory conditions, they are prepared according to the Wurz reaction. It is the main raw material for the production of vinyl chloride and ethylene.

Hydrogen

Transparent, odorless gas. Non-toxic, 14.5 times lighter than air. By nature, hydrogen does not differ from air. Has a high reactivity, wide limits of ignition, very explosive. It is part of almost all organic compounds. The most difficult compressible gas. Free hydrogen in nature is extremely rare, but in the form of compounds is very common.

Carbon monoxide

Colorless gas, without taste and smell. Weight 1 cu. m - 1.25 kg. Contained in high-calorie gases along with methane and other hydrocarbons. An increase in the proportion of carbon monoxide in a combustible gas lowers the heat of combustion. Has a toxic effect on the human body.

Application of flammable gases

Combustible gases have a high calorific value,and therefore are highly energy-efficient fuel. Widely used for domestic needs, power plants, metallurgy, glass, cement and food industries, as a motor fuel, in the production of building materials.

Use of combustible gases as raw materials forproduction of organic compounds such as formaldehyde, methyl alcohol, acetic acid, acetone, acetaldehyde, is due to the presence of hydrocarbons in their composition. Methane, as the main component of combustible natural gases, is widely used for the production of various organic products. To produce ammonia and various kinds of alcohols, synthesis gas is used - the product of conversion of methane by oxygen or water vapor. Pyrolysis and dehydrogenation of methane produce acetylene, along with hydrogen and soot. Hydrogen, in turn, is used for the synthesis of ammonia. Combustible gases, and especially ethane, are used in the production of ethylene and propylene, which are subsequently used as raw materials for the production of plastics, synthetic fibers and synthetic rubbers.

A promising fuel for many spheresof the national economy is liquefied methane. The use of liquefied gases in many cases gives a great economic benefit, allowing to reduce the material costs for transportation and solve the problems of gas supply in certain regions, allows the creation of stocks of raw materials for the needs of the chemical industry.