LPG Petrochemical
LPG Petrochemical steam cracking is the common process in petrochemical industries.
Steam cracking is a petrochemical process in which saturated hydrocarbons are broken down into smaller, often unsaturated, hydrocarbons.
It is the principal industrial method for producing the lighter alkenes (or commonly olefins), including ethene (or ethylene) and propene
(or propylene).
In steam cracking, a gaseous or liquid hydrocarbon feed like naphtha, LPG or ethane is diluted with steam and briefly heated in a furnace
without the presence of oxygen. Typically, the reaction temperature is very high, at around 850°C, but the reaction is only allowed to take place very briefly. In modern cracking furnaces, the residence time is reduced to milliseconds to
improve yield, resulting in gas velocities faster than the speed of sound. After the cracking temperature has been reached, the gas is quickly
quenched to stop the reaction in a transfer line heat exchanger or inside a quenching header using quench oil.
The products produced in the reaction depend on the composition of the feed, the hydrocarbon to steam ratio and on the cracking temperature and
furnace residence time.
Light hydrocarbon feeds such as ethane, LPG Petrochemical or light naphtha give product streams rich in the lighter alkenes, including ethylene, propylene, and butadiene. Heavier hydrocarbon (full range
and heavy naphthas as well as other refinery products) feeds give some of these, but also give products rich in aromatic hydrocarbons and
hydrocarbons suitable for inclusion in gasoline or fuel oil. The higher cracking temperature (also referred to as severity) favors the production
of ethene and benzene, whereas lower severity produces higher amounts of propene, C4-hydrocarbons and liquid products. The process also results in the slow deposition of coke, a form of carbon, on the reactor walls. This degrades the
efficiency of the reactor, so reaction conditions are designed to minimize this. Nonetheless, a steam cracking furnace can usually only run for a few
months at a time between de-cokings. Decokes require the furnace to be isolated from the process and then a flow of steam or a steam/air mixture is passed through the furnace
coils. This converts the hard solid carbon layer to carbon monoxide and carbon dioxide. Once this reaction is complete, the furnace can be returned to
service.