Definition - What does Thermal Cracking mean?
Thermal cracking or simply cracking is a process of breaking down the larger and heavier nonvolatile molecules of hydrocarbons (primarily crude oil) into smaller and lighter molecules by application of heat at high temperatures and pressures in the presence of a catalyst. This process is sometimes also called pyrolysis of oil. This process helps in extracting the lighter petroleum fractions such as gasoline and diesel fuel.
Petropedia explains Thermal Cracking
Thermal cracking is one of the most important procedural steps in the refinery for converting crude oil into the lighter and valuable petroleum products such as gasoline (or petrol), diesel fuel, residual heavy oil, coke, and many gases such as C1, C2, C3, C4 (methane, ethane, propane, butane). In the thermal cracking process, the heavier crude oil molecules that need to be cracked are subjected to high heat and pressure in the oil refinery. Sometimes a catalyst is added to control the chemical reactions which occur during the process, with the goal of promoting the development of specific molecules. Petroleum fractions which have a low boiling point, such as gasoline and the lighter gases are released first. The residual is further heated in other processes in order to yield more lighter fractions. As the cracking proceeds, fractions of various molecular weights can be extracted and processed further for additional uses, or packaged for transport and sale.