Surgil ESIA Report - Volume III - EKN

Surgil ESIA Report - Volume III
A.3.2.7. Export Gas Compression Unit
The export gas compression unit will consist of a reciprocating export gas compressor which will export out
the sales gas (mainly methane) from the plant’s battery limits.
A.3.3.
Ethylene Plant
Ethane, LPG and NGL is delivered from the GSP via pipeline to the ethylene plant for production of high
purity ethylene and smaller amounts of propylene. The plant process will involve use of steam cracking
technology (thermal pyrolysis in the presence of steam) and reaction temperatures in the steam cracker will
be around 850 º C.
Within the steam cracking plant the saturated hydrocarbons are converted to smaller, often unsaturated
hydrocarbons, with ethylene as the key product. This plant will produce approximately 387 KTA of polymer
grade ethylene and 82 KTA of polymer grade propylene. Modern steam crackers such as those to be used
in this process ensure a short reaction time that improves yield and minimises the production of associated
by-products.
After the cracking temperature has been reached the gas is quickly quenched in the recovery section (coldend)
of the plant to stop the reaction in a transfer line heat exchanger. This process also recovers and
separates the olefin products produced and recycles saturated hydrocarbons to cracking. The recovery
section includes:
A compression unit to compress the cracked gas for the fractionation of hydrocarbon;
Caustic-washing in a caustic tower to remove acid gases, and
Drying prior to carrying out low temperature separation.
Separation of products will be conducted using demethaniser, deethaniser and depropaniser columns in a
sequence tailored to the feedstock being cracked.
In addition to the recovery of ethylene and propylene, the chilling train of the ethylene plant will produce a
mixed light hydrocarbon stream, hydrogen, pyrolysis gasoline and pyrolysis oil. The light hydrocarbon
stream is recycled to the plant furnace and cracked to extinction whilst the gasoline and oil is pumped to
the plant site boundary for export.
The steam cracking process results in the slow deposition of coke and de-coking is required every few
months. De-coking requires the furnace to be isolated 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 CO and CO 2 which are
vented to atmosphere.
The ethylene and propylene products of the ethylene plant, together with butene-1 and hydrogen are then
fed to two separate processes:
HDPE plant for the production of polyethylene pellets; and
PP plant for the production of PP pellets.
254793/RGE/GEV/03/01/03/08/2011
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