Natural Gas Composition and Structures
Natural gas is a mixture of compounds composed primarily of hydrogen and carbon, but sometimes included other heavier components such as nitrogen, sulfur, and oxygen. The lightest component of natural gas is methane, which has one carbon and four hydrogen atoms, followed by ethane (with two carbons and six hydrogens), propane (three carbons, eight hydrogens), butane (four carbons, ten hydrogens), and pentane (five carbons, twelve hydrogens) as the most common components. Less common components such as pentane may also be present.
Natural gas has a low boiling point and therefore evaporates quickly, which makes it highly flammable. This means that when natural gas is released into the atmosphere, it can dissipate quickly, and thus reducing the risk of explosion or fire. The main component of natural gas, however, is methane, which does not burn with a bright flame, making it more difficult to detect when compared with other petroleum fuels such as petrol and diesel. As a result, natural gas is odorless, colorless and tasteless, making it difficult to detect a gas leak without dedicated equipment.
Natural gas is a naturally occurring fuel, produced underground from gas reservoirs, oil and coal bed formations, or compressed remains of ancient organisms such as plankton and bacteria. It can also be produced by a process called “fracking,” in which water, sand and chemicals are injected into rock formations deep underground to create fractures and release the natural gas. Natural gas is the cleanest burning of all fossil fuels, producing only half the carbon dioxide of petroleum, and less than 33 percent of emissions from coal.
At the molecular level, natural gas consists of either one single atom, or a combination of two or more elements. The most common elements found in natural gas are carbon (C) and hydrogen (H), and in some cases, nitrogen (N), oxygen (O), and/or sulfur (S). The ratio of these elements is what defines the “make-up” of the natural gas and can influence its properties and applications.
The properties of natural gas depend on the number and balance of the elements present. Natural gas is always a combination of molecules and these molecules can exist as individual molecules, known as “free molecules,” or they can form larger molecules, known as “complex molecules.” These molecules can form single molecules or clusters of molecules. The more complex the structure, the greater the number of elements and the higher the number of atoms, making the mixture more concentrated.
The compounds found in natural gas are generally of three types: hydrocarbons, nitrogen, and sulfur compounds. Hydrocarbons are compounds composed of molecules made up of just hydrogen and carbon atoms, while nitrogen and sulfur compounds are known as organic compounds, which contain an organic (carbon-based) molecule(s) along with the other elements. For example, methane is the simplest molecule composed of just one Carbon and four Hydrogen atoms, and is a hydrocarbon. When nitrogen or sulfur compounds are included in the natural gas, this will result in the formation of molecules known as “hydrocarbons compounds” such as methanethiol (a sulfur-containing methane molecule) and ethane nitrate (containing nitrogen and ethane).
The chemical structure of natural gas has a major influence on its physical characteristics. The size and configuration of the molecules will influence its viscosity, solubility and other properties. For example, natural gas with a high concentration of complex hydrocarbons will be ‘shaler’, or less dense, than natural gas with a lower concentration of complex hydrocarbons, which will be ‘higher’ or more dense. The quality of the natural gas will also be affected by the ratio of the components; a higher ratio of hydrocarbons will result in a better quality gas, while a higher ratio of nitrogen and sulfur compounds will reduce the quality.
The chemical structure of natural gas can also influence its burning characteristics. When natural gas is burned, the flame is considered “clean” if the ratio of hydrocarbons is high, as this will produce a flame that produces less smoke. Higher ratios of nitrogen and sulfur compounds will cause the flame to smoke and smother the fuel, reducing its efficiency.
In summary, natural gas is an abundant and versatile fuel, composed of substances composed mainly of hydrogen and carbon, but sometimes including other elements such as nitrogen, sulfur and oxygen. Its chemical structure has a major influence on its physical and burning characteristics, and the ratio of different elements present can affect the quality and efficiency of the fuel.
