Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By c content reduction – e.g. – cracking – etc.
Patent
1999-03-08
2000-12-12
Griffin, Walter D.
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By c content reduction, e.g., cracking, etc.
585648, 585950, 208 48R, 208126, 208130, 422200, 422201, 422202, 422207, C07C 404, C10G 916, C10G 920, F28D 700
Patent
active
061601926
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a hydrocarbon steam-cracking unit and an operating process that comprises a decoking stage with controlled single injection of solid particles.
BACKGROUND OF THE INVENTION
The technological background is illustrated by Patents FR-A-1,433,702 and WO-A-96 20259.
The steam-cracking process is the basic process of the petrochemical industry and consists in cracking a feedstock of hydrocarbons and water vapor at high temperature and then abruptly cooling it. The main operating problem arises from the deposition of carbon-containing products on the inner walls of the unit. These deposits, which consist of coke or heavy pyrolysis tars that are condensed and more or less agglomerated, limit heat transfer in the cracking zone (in a pyrolysis pipe coil) and the indirect quenching zone (effluent quenching exchanger), thus requiring frequent shutdowns to decoke the unit.
In patents EP-A-419 643, EP-A-425 633 and EP-A 447 527 there is proposed a process for in-service decoking of steam-cracking units by injecting erosive solid particles in order to solve coking problems and to obtain continuous or approximately continuous steam cracking (for example, cycle periods on the order of 1 year).
The erosive solid particles can be injected upstream from the cracking zone of each furnace in order to scrape out the coke that is deposited in the pyrolysis pipes, and then downstream, the coke that is deposited in the effluent quenching exchangers.
The injections are carried out on line, i.e., either, preferably, during the normal operation of the furnace or during times when the hydrocarbon supply is interrupted briefly, whereby the furnace is then flushed with a stream of water vapor and is connected to the downstream sections of the unit (primary furnace, compression of cracked gases, etc.) This passage under vapor, in the absence of oxygen, can also be used for vapor decoking of the pipes of the furnace when it is carried out over longer periods of time. It is also possible to inject particles during air decoking periods, as air or air/vapor mixtures are being circulated in the unit.
To provide flexible steam cracking that is compatible with the use of heavy feedstocks (gas oil, distillate under vacuum) or olefinic feedstocks in an existing steam-cracking unit that is provided for cracking naphtha, it was found that it is essential to scrape out the coke that was deposited in the effluent quenching exchangers well and that in-service decoking of these quenching exchangers made it possible, unexpectedly, to make an existing steam-cracking unit compatible with a very wide variety of feedstocks and operating conditions. It was also found, unexpectedly, that the coke that was deposited in the quenching exchangers was much easier to eliminate by erosion than the coke in the pyrolysis pipes and that the previously proposed complete process for decoking of the unit by fine erosive particles was very difficult to implement in a reliable manner with flexible operation under inevitably variable conditions: the geometry of the pyrolysis pipes cannot in fact be suitable for all of the feedstocks to ensure correspondence between the erosive local intensity and the local coking speed (whereby the nature of the coke and its hardness can furthermore vary very greatly from one feedstock to the next); in contrast, with flexible operation, i.e., with variable operating conditions, type of feedstock and degree of dilution, the loss of load and the skin temperature of the pipes are no longer reliable indicators of the coking state of a bundle of pyrolysis pipes, and said coking state therefore cannot be known and monitored in real time.
SUMMARY OF THE INVENTION
To eliminate these drawbacks, a new process is proposed that combines at least predominantly chemical decoking (for example with air) of the pyrolysis pipes with decoking, at least partially by erosion, of quenching exchangers. This process therefore comprises erosive decoking of the quenching exchanger pipes, which requires suitable mea
REFERENCES:
patent: 5177292 (1993-01-01), Lenglet
patent: 5183642 (1993-02-01), Lenglet
patent: 5186815 (1993-02-01), Lenglet
patent: 5820747 (1998-10-01), Lenglet et al.
patent: 5965013 (1999-10-01), Lenglet et al.
patent: 5972206 (1999-10-01), Lenglet et al.
Burzynski Jean-Pierre
Courteheuse Gerard
Gougne Yves
Huin Roland
Lenglet Eric
Griffin Walter D.
Institut Francais du Pe'trole
LandOfFree
Steam cracking installation and method with single controlled in does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Steam cracking installation and method with single controlled in, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Steam cracking installation and method with single controlled in will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-219811