Steam cracking method and plant using controlled injection of so

Details Steam cracking method and plant using controlled injection of so Steam cracking method and plant using controlled injection of so

1997-06-25

1999-10-12

Griffin, Walter D.

Mineral oils: processes and products

Chemical conversion of hydrocarbons

Cracking

208126, 208 48R, 585648, 585652, 585950, 422200, 422201, 422202, 422207, 422213, 422217, C10G 936, C10G 928, F28D 700, F28D 2100

Patent

active

059650133

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a facility for steam cracking of hydrocarbons and an implementation process, comprising a step of decoking by controlled injection of solid particles.
2. Description of the Prior Art
The prior art is illustrated by FR-A-1.433.702.
The steam cracking process is the basic process in the petrochemicals industry and consists of high temperature cracking then rapid cooling of a feed of hydrocarbons and steam. The main operating problem arises from the deposition of carbon-containing substances on the internal walls of the facility. These deposits, constituted by coke or condensed heavy pyrolysis tars, which are coagulated to a greater or lesser extent, limit the heat transfer in the cracking zone (coils of pyrolysis tubes) and the indirect cooling zone (effluent transfer line exchanger) necessitating frequent stoppages to decoke the facility.
The applicants have proposed (EP-A-419 643, EP-A-425 633 and EP-A-447 527) a decoking process for use during the operation of steam cracking facilities, by injection of solid erosive particles to overcome coking problems and to obtain continuous or substantially continuous steam cracking (for example with cycle periods of the order of one year).
The solid erosive particles can be injected upstream of the cracking zone of each furnace so that they scour the coke deposited in the pyrolysis tubes, then downstream that of the effluent transfer line exchangers.
Injections are carried out in line, that is to say either, preferably, during the normal operation of the furnace or during periods when the hydrocarbon feeding is interrupted briefly, the furnace then being swept by a delivery of steam and remaining connected to the downstream sections of the facility (primary furnace, cracked gas compression and so forth). This steaming, in the absence of oxygen, can also be used for steam decoking of the furnace tubes when it is carried out over longer durations.
To implement flexible steam cracking, compatible with the use of heavy feeds (gas oil, vacuum distillates) in an existing steam cracking facility designed for cracking naphtha, it was found essential to properly scour the coke deposited in the effluent transfer line exchangers and that decoking during operation of the transfer line exchangers allowed, in an unexpected manner, an existing steam cracking facility to be made compatible with a wide variety of feeds. It was also found, in an unexpected manner, that the coke deposited in the transfer line exchangers was far easier to remove by erosion than the coke deposited in the pyrolysis tubes, and that the process previously proposed for complete decoking of the facility using fine erosive particles was very difficult to implement in a reliable manner with flexible operation under necessarily variable conditions: the configuration of the pyrolysis tubes cannot be adapted for all of the feeds to ensure a correspondence between the local erosive intensity and the local speed of coking (the nature of the coke and its hardness possibly also being greatly varied from one feed to another); on the other hand, with flexible operation, that is with a variable regime of operating conditions, feed type and degree of dilution, the loss of feed and skin temperature of the tubes are no longer reliable indicators of the state of coking of a bundle of pyrolysis tubes, which therefore cannot be determined and controlled in real time.
In order to remedy these disadvantages, a new process linking at least preponderantly chemical decoking of the pyrolysis tubes with at least preponderantly erosive decoking of the transfer line exchangers is proposed. The process thus comprises erosive decoking of the transfer line exchangers, which requires means suitable for introducing the erosive particles into said exchangers.
For most facilities, these transfer line exchangers (TLE's) are of the multi-tube type with an inlet tube plate which can comprise, for example, 50 to 100 cracked gas circulation tubes, each tube being coole

REFERENCES:
patent: 5177292 (1993-01-01), Lenglet
patent: 5183642 (1993-02-01), Lenglet
patent: 5186815 (1993-02-01), Lenglet

Affiliated with

Also associated with

Rating

Steam cracking method and plant using controlled injection of so 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 method and plant using controlled injection of so, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Steam cracking method and plant using controlled injection of so will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-648820