Physical State of Fuels

Fuel is defined as any body whose chemical combination with another is exothermic. Based on their physical state, they can be classified into solids, liquids and gases.
Solid Fuels
They may have in their composition C, H₂, O₂, S (carbon, hydrogen, oxygen, sulfur), all of which are easily combusted. Among solid fuels we have firewood, sawdust, sugarcane bagasse, etc., which are used in industries to keep machines running.
The great inconvenience of this type of fuel is the erosion it causes on pistons, valves, cylinders, etc. This is because the combustion products contain very hard parts, which, when deposited in these places, cause damage.
Liquid Fuels

They can be found in mineral or non-mineral form. Mineral liquid fuels are obtained by refining petroleum, distilling oil shale or hydrogenating coal. The most used are gasoline with molecular formula C₈H₁₈ and diesel oil (C₈H₁₇).
Non-mineral liquid fuels are alcohols and vegetable oils. Among the alcohols, we have methyl and ethyl alcohol, while vegetable oils are formed from C, H

₂, O₂ and no₂.
Gaseous Fuels
In addition to having a low cost, because they are usually gases obtained as by-products, they are more homogeneous fuels because they mix better with air. This feature contributes to a better distribution in the cylinders, increasing engine efficiency and also facilitating cold starting.
Natural gas is a gaseous fuel found in sandy places that contain oil, this is stored deep underground. The main natural gases are: Methane (CH₄), Ethane (C₂H₆), carbon dioxide (CO₂), Nitrogen (N₂).
Through the petroleum refinery it is possible to obtain LPG (Liquefied Petroleum Gases), natural gases and distillation by-products: Propane (C₃H₈) and Butane (C₄H₁₀).

By Líria Alves
Graduated in Chemistry
Brazil School Team

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Fuels - Chemistry - Brazil School

Source: Brazil School - https://brasilescola.uol.com.br/quimica/estado-fisico-dos-combustiveis.htm