What to do with natural gas?

Gazprom has reported that approximately half of Russia’s gas supplies are sent to energy companies and public utilities and plays a big part in fuelling homes. Natural gas is well known as being the most environmentally friendly fossil fuel as it only emits carbon dioxide and water during combustion whilst other products such as oil and coal emit other pollutants. Also, gas is a popular fuel for the power industry due to its high environmental performance as cities and companies seek to meet the ever more stringent environmental policies and regulations.

Below are some of the products that natural gas can be manufactured from natural gas, according to Gazprom.

Transport fuels

Natural gas is becoming more widely used as a transport fuel. Compressed methane, according to Gazprom, costs approximately half as much as petrol and has an octane number of 76, it is reported to extend the service life of engines, and improve the urban ecology. Also, engines that are fuelled by natural gas met the Euro 4 environmental standards.

Liquid motor fuels can also be produced from natural gas via gas to liquids (GTL). Due to natural gas being relatively inert, it is almost always converted into a more reactive mixture in the form of syn gas which is a mixture of CO and H₂. It is the syn gas that is converted in to a liquid fuel such as diesel and paraffin.

Fuel facts

• Compressed natural gas (CNG) for fuelling vehicles is supplied at filling stations through pipelines.
• In 1923, German chemists Franz Fischer and Hans Tropsch were the first people to produce liquid hydrocarbons from syn gas.
• The Fischer-Tropsch method now has various modifications and is applied to varied processes for gas to liquid conversions.

Separation and feedstocks

When it comes to gasoline separation, gas processing always takes place in a gas processing plant. Due to the admixtures in natural gas, it must go through a separation process to extract nitrogen, methane, carbon dioxide, hydrogen sulfide, helium and water vapours. This is interpreted as the natural gas being cleaned and dried in the plant. Following this gas is compressed for processing.

In a gasoline extraction unit, gas is separated to take the unstable natural gasoline and lean gas apart. Lean gas is pumped as gas in to trunk lines. The cleaned gas can also be supplied to chemical plants as a feedstock for methanol and ammonia. Following separation, unstable gasoline is put through fractionation units to extract the light hydrocarbons, ethane, propane, butane and pentane which are products used as feedstocks for further processing. Light hydrocarbons are often used to make polymers and the propane/butane mixture is a finished product in its own right so is often used as household fuel.

Everyday objects

Natural gas produces Methanol through a process similar to the Fischer-Tropsch, discussed above. Methanol is used in a variety of ways, as an agent to prevent hydrate plugs that are formed in low pipeline temperatures, as a feedstock for manufacturing chemicals such as formaldehyde, paints, glues, fuel additives and varnishes.

Fertilisers can also be produced from natural gas through a series of conversions. At stage one, it is ammonia which is produced in a similar method to GTL. The variances come when looking at catalysts, pressure and temperature. Ammonia alone is a type of fertiliser, however it is also used as a refrigerant coolant and as a feedstock for producing nitrogen compounds including nitric acid and carbamide.

Ammonia production

When it comes to producing ammonia, the natural gas is first stripped of sulfur. Following this it is combined with heated water vapour and passed through catalyst beds in a reactor, a process known as primary reforming. After reforming, a mixture of hydrogen, methane, carbon dioxide, and carbon oxide is emitted. This mixture is sent for secondary reforming and is mixed with atmospheric oxygen, vapour and nitrogen in specific proportions. In the penultimate stage, the CO and CO₂ are removed. The final stage sees the hydrogen and nitrogen mixture sent for ammonia synthesis.

Source: Gazprom

Adapted by Claira Lloyd

Read the article online at: https://www.hydrocarbonengineering.com/gas-processing/06082014/gazprom-gas-manufacturing/