Höyrykrakkaus

Höyrykrakkaus, also known as steam cracking, is a petrochemical process in which hydrocarbons are broken down into smaller molecules by subjecting them to high temperatures in the presence of steam. This process is fundamental to the petrochemical industry, serving as the primary method for producing olefins, particularly ethylene and propylene. These olefins are essential building blocks for a vast array of plastics and other chemical products.

The feedstock for steam cracking can range from light hydrocarbons like ethane and propane, derived from natural gas, to heavier fractions such as naphtha and gas oils, which are byproducts of crude oil refining. The choice of feedstock influences the yield of different products. The process involves heating the hydrocarbon feedstock, often mixed with steam, in a furnace to temperatures typically between 750 and 950 degrees Celsius. The steam acts as a diluent, reducing the partial pressure of the hydrocarbons and minimizing unwanted side reactions like coke formation.

The high temperatures cause the hydrocarbon molecules to break apart, a process called pyrolysis. The cracked gases are then rapidly cooled to stop the reactions and prevent further degradation. Following cooling, a complex separation process, usually involving distillation, is employed to isolate the various products, including ethylene, propylene, butadiene, and aromatic compounds like benzene. The efficiency and product distribution of steam cracking are influenced by factors such as temperature, residence time, and the steam-to-hydrocarbon ratio.