Steam cracking
Steam cracking is a
Process description
General
In steam cracking, a gaseous or liquid hydrocarbon feed like
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
A higher cracking
Process details
The areas of an ethylene plant are:
- steam cracking furnaces:
- primary and secondary heat recovery with quench;
- a dilution steam recycle system between the furnaces and the quench system;
- primary compression of the cracked gas (3 stages of compression);
- hydrogen sulfide and carbon dioxide removal (acid gas removal);
- secondary compression (1 or 2 stages);
- drying of the cracked gas;
- cryogenic treatment;
- all of the cold cracked gas stream goes to the demethanizer tower. The overhead stream from the demethanizer tower consists of all the hydrogen and methane that was in the cracked gas stream. Cryogenically (−250 °F (−157 °C)) treating this overhead stream separates hydrogen from methane. Methane recovery is critical to the economical operation of an ethylene plant.
- the bottom stream from the demethanizer tower goes to the deethanizer tower. The overhead stream from the deethanizer tower consists of all the C2's that were in the cracked gas stream. The C2 stream contains acetylene, which is explosive above 200 kPa (29 psi). If the partial pressure of acetylene is expected to exceed these values, the C2 stream is partially hydrogenated. The C2's then proceed to a C2 splitter. The product ethylene is taken from the overhead of the tower and the ethane coming from the bottom of the splitter is recycled to the furnaces to be cracked again;
- the bottom stream from the de-ethanizer tower goes to the depropanizer tower. The overhead stream from the depropanizer tower consists of all the C3's that were in the cracked gas stream. Before feeding the C3's to the C3 splitter, the stream is hydrogenated to convert the allene) mix. This stream is then sent to the C3 splitter. The overhead stream from the C3 splitter is product propylene and the bottom stream is propane which is sent back to the furnaces for cracking or used as fuel.
- The bottom stream from the depropanizer tower is fed to the debutanizer tower. The overhead stream from the debutanizer is all of the C4's that were in the cracked gas stream. The bottom stream from the debutanizer (light pyrolysis gasoline) consists of everything in the cracked gas stream that is C5 or heavier.
Since ethylene production is energy intensive, much effort has been dedicated to recovering heat from the gas leaving the furnaces. Most of the energy recovered from the cracked gas is used to make high pressure (1200 psig (8300 kPa)) steam. This steam is in turn used to drive the turbines for compressing cracked gas, the propylene refrigeration compressor, and the ethylene refrigeration compressor. An ethylene plant, once running, does not need to import steam to drive its steam turbines. A typical world scale ethylene plant (about 1.5 billion pounds (680 KTA) of ethylene per year) uses a 45,000 horsepower (34,000 kW) cracked gas compressor, a 30,000 hp (22,000 kW) propylene compressor, and a 15,000 hp (11,000 kW) ethylene compressor.
Even though the thorough energy integration within a steam cracking plant, this process produces an unsurmountable amount of carbon dioxide. Per
Steam cracking furnaces licensors
Several proprietary designs are available under a license that must be purchased from the design developer by any petroleum refining company desiring to construct and operate a Steam Cracking unit of a given design.
These are the major steam cracking furnaces designers and licensors:
See also
Notes and references
- ^ Giovanni Maggini (2013-04-17). "Technology Economics: Propylene via Propane Dehydrogenation, Part 3". Slideshare.net. Retrieved 2013-11-12.
- ^ ISBN 978-3527306732.
- .
- ^ a b c "Dream or Reality? Electrification of the Chemical Process Industries". www.aiche-cep.com. Retrieved 2021-07-05.
- ^ "BASF, SABIC and Linde join forces to realize the world's first electrically heated steam cracker furnace". www.basf.com/.
- ^ "Petrochemical companies form Cracker of the Future Consortium and sign R&D agreement". www.borealisgroup.com/.
- ^ "Pyrolysis/Steam Cracking | Lummus Technology". www.lummustechnology.com. Retrieved 2020-07-16.
- ^ "Ethylene - Technip Energies plc". www.technipenergies.com. Retrieved 2021-10-27.
- ^ "Cracking furnace technology". Linde Engineering. Retrieved 2020-01-13.
- ^ "Petrochemical Technologies | KBR". www.kbr.com. Retrieved 2020-01-27.