Natural gas is natural inflammable gas used as important fossil fuel. It was produced millions years ago by transformation of organic material. Natural gas is a mixture of gaseous hydrocarbons with methane as main component. Beside of methane, it contains propane, butane and other substances. It is lighter than air and non-toxic. It is colourless and without natural smell, so for safety reasons a substance must be added to give natural gas a typical alarming smell for it to be easily identifiable. This process is called odorization of gas. Burning natural gas does not produce any combustion gases harmful to human health, it produces less harmful substances and less greenhouse gases than other fossil fuels and creates no mechanical impurities (soot), thanks to which it is regarded as ecological fuel friendly to the environment.
In the combustion process a large amount of thermal energy is released from natural gas, so it has large importance as fuel. However, natural gas is also used as basic raw material for production of various synthetic polymers and other chemical products, e.g. in production of nitrogenous fertilizers.
Natural gas is used as fuel for heating, cooking and preparation of domestic hot water, and in the form of compressed natural gas (CNG) as alternative fuel for vehicle engines.
Only exceptionally natural gas has a quality allowing its commercial use without further treatment. It usually contains many substances with potential negative effects on gas pipeline systems. Water, sulphur substances and carbon dioxide can cause corrosion and dust contained in gas can cause failure of compressor and regulation stations. In sites where oil occurs together with natural gas extracted natural gas must be deprived of liquid hydrocarbons.
Slovakia has insignificant natural gas deposits – in the region of Záhorie and in East Slovakia – so this country imports gas.
Europe has a dense network of international gas pipelines and their length is increasing. Operating pressure in the most modern pipelines achieves the value of 100 bar (10 MPa) and gas pipeline diameters often exceed 1 m. Long-distance transport of natural gas is economically the most demanding link of gas transport chain, due to the distance between the place of gas production and place of its final consumption.
Natural gas supplies from the individual producers are characterized by minimum fluctuations during year. Natural gas consumption particularly depends on external temperature, so the highest consumption of natural gas is registered in the winter period.
Differences between summer and winter consumption are compensated by production of gas that was held in underground storages during the period of lower consumption. Underground storages are therefore an important part of the gas system.
The transport network of the Slovak Republic is a part of the international gas network. This network is connected to main European transport systems and reliably serves for important gas companies. Natural gas from the transport network flows through domestic offtake stations to the system of distribution networks. Through this network natural gas is transported to final customers. Slovakia ranks among the most gasified countries in Europe with 77 per cent of gasified municipalities from the total number of municipalities in Slovakia.
The company SPP – distribúcia that owns and operates the gas distribution network distributes nearly 98% of total distributed volume of natural gas in the Slovak Republic for approximately 1.5 million customers. More than 94 % of all inhabitants of Slovak have access to natural gas.
Natural gas is distributed to the individual gasified municipalities through the system of high-pressure gas pipelines. In regulation stations the operating pressure of gas is decreased. Gas distribution pipelines in municipalities can be of low-pressure type (gas pressure is suitable for operation of gas appliances without further processing) or medium-pressure type (the individual buildings have their own regulators for adjustment of gas pressure to a value required for the operation of gas appliances). The advantage of medium-pressure distribution pipelines is the large capacity of networks.