Page 171 - CW E-Magazine (4-6-2024)

Special Report

Box 2: Steam cracking
Steam cracking is a process in which a hydrocarbon feedstock, such as ethane, propane or naphtha is converted to olefins
(ethene, propene and butadiene). The raw material input is ‘cracked’ in high temperature furnaces in the presence of steam.
CHAPTER ONE
Typically, to achieve the high temperatures required – in the range of 800-1,000°C – significant quantities of fuel, such
as methane, are burned. This leads to significant CO emissions, in the range of 0.5-1.5 tonnes of CO per tonne of olefin
2
2
product, depending on the feedstock used.
The cracking reactions occur very rapidly, in the order of fractions of a second. The range of products that are obtained
depend on the feed composition, the hydrocarbon to steam ratio, and on the temperature of the furnace. Lighter hydrocarbon
feeds, such as ethane or liquified petroleum gas, will crack to give light olefins (ethene, propene and butene) as products.
Cracking of heavier, liquid feeds such as naphtha, will give aromatic hydrocarbons as well as olefins.

FIGURE 4
A modern steam cracker is a large plant with a high degree of heat integration that can have the capability of producing
more than 1.5-mt of olefins each year. As such, steam cracking is the core technology for producing large quantities of
Simplified flow diagram displaying the route from fossil feedstocks to benzene to end products,
many primary chemicals. A facility of this size can cost around US$2-5 billion.
highlighting the complexity of the chemical industry.
Cups insulation,
KEY Polystyrene
food service / packaging
Methanol Propene
Ethene Butadiene ABS resins Auto parts,
consumer electronics

Housewares,
Ethylbenzene Styrene SAN resins appliances parts,
cosmetic packaging

Carpet backing,
SB latex paper coating

SB rubber Tyres, adhesives

Crude oil
Phenol PF resins Wood adhesives

Epoxy resins,
Benzene Cumene BPA polycarbonates Coatings, medical

Automotive panels,
Acetone MMA medical equipment,
baseball helmets
Coal

MDI

Rubber chemicals
Nitrobenzene Aniline
Dyes, pigments

Herbicides

Cyclohexane Nylon fibres
Fig. 4: Simplified flow diagram displaying the route from fossil feedstocks to benzene to end products, highlighting the complexity of the chemical industry.
ABS resins = Acrylonitrile-Butadiene-Styrene resins SAN resins = Styrene acrylonitrile resin SB latex = Styrene-Butadiene Latex
SB rubber = Styrene-butadiene rubber PF resins = Phenol formaldehyde resins MMA = Methyl methacrylate BPA = bisphenol A
MDI = Methylene diphenyl diisocyanate
Chemical Weekly June 4, 2024 171

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