Steamcracked

Steamcracked refers to hydrocarbons that have been subjected to steam cracking, a high‑temperature thermal decomposition process used primarily to produce light olefins such as ethylene and propylene. In steam cracking, a hydrocarbon feed is heated with a controlled amount of steam to promote bond scission while suppressing excessive coke formation. The process is non‑catalytic, relying on heat rather than catalysts, and operates at very high temperatures.

The reactor design typically involves multi‑tubular furnace systems where the feed–steam mixture reaches approximately 750–900 degrees Celsius. Residence times are short, on the order of milliseconds to a few seconds. Diluting the hydrocarbon with steam lowers the partial pressure of reactive species, enhances cracking efficiency, and reduces coking. After cracking, the hot effluent gas is rapidly quenched to stop further reactions, then cooled and fractionated to separate desired products from byproducts such as hydrogen, methane, and heavier hydrocarbons.

Common feedstocks include light naphtha, gas oils, LPGs, ethane, and propane, with the choice of feed influencing the distribution of products. The primary product target is ethylene; propylene and other olefins (butenes, C4 hydrocarbons) are also formed, along with aromatics when heavier feeds are used. The resulting mixture, often called steamcracked gas, is processed further in downstream units for purification and separate refining of individual components.

Steamcracking remains a central technology in the petrochemical industry due to its ability to convert relatively inexpensive hydrocarbon feeds into essential building blocks for plastics and chemicals. It is energy‑intensive and coke management is a key operational concern.