EP0425633A1 - Process for steam-cracking hydrocarbons. - Google Patents

Process for steam-cracking hydrocarbons.

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Publication number
EP0425633A1
EP0425633A1 EP90907103A EP90907103A EP0425633A1 EP 0425633 A1 EP0425633 A1 EP 0425633A1 EP 90907103 A EP90907103 A EP 90907103A EP 90907103 A EP90907103 A EP 90907103A EP 0425633 A1 EP0425633 A1 EP 0425633A1
Authority
EP
European Patent Office
Prior art keywords
installation
tubes
solid particles
particles
coke
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP90907103A
Other languages
German (de)
French (fr)
Other versions
EP0425633B1 (en
Inventor
Eric Lenglet
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Procedes Petroliers et Petrochimiques
Original Assignee
Procedes Petroliers et Petrochimiques
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from FR8904986A external-priority patent/FR2645873B1/en
Priority claimed from FR8909375A external-priority patent/FR2649761B1/en
Priority claimed from FR8913070A external-priority patent/FR2652817B1/en
Application filed by Procedes Petroliers et Petrochimiques filed Critical Procedes Petroliers et Petrochimiques
Publication of EP0425633A1 publication Critical patent/EP0425633A1/en
Application granted granted Critical
Publication of EP0425633B1 publication Critical patent/EP0425633B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G9/00—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
    • C10G9/002—Cooling of cracked gases
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G9/00—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
    • C10G9/14—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils in pipes or coils with or without auxiliary means, e.g. digesters, soaking drums, expansion means
    • C10G9/16—Preventing or removing incrustation
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G9/00—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
    • C10G9/28—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils with preheated moving solid material
    • C10G9/32—Thermal non-catalytic cracking, in the absence of hydrogen, of hydrocarbon oils with preheated moving solid material according to the "fluidised-bed" technique
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28G—CLEANING OF INTERNAL OR EXTERNAL SURFACES OF HEAT-EXCHANGE OR HEAT-TRANSFER CONDUITS, e.g. WATER TUBES OR BOILERS
    • F28G1/00—Non-rotary, e.g. reciprocated, appliances
    • F28G1/12—Fluid-propelled scrapers, bullets, or like solid bodies

Definitions

  • the invention relates to a process for steam cracking of hydrocarbons, making it possible in particular to avoid or at least limit the coking of the steam cracking installation.
  • Steam cracking of hydrocarbons consists in subjecting a charge of hydrocarbons mixed with steam to thermal cracking in an installation comprising in particular a tube furnace in which the charge is brought to a temperature of about 800 to 900 ° C. , then means for indirect quenching of the gaseous effluents leaving the furnace, making it possible to rapidly cool these effluents to stop the cracking reactions.
  • the main drawback of this process lies in the gradual fouling of the installation by the coke which is deposited in the oven and in the indirect quenching means.
  • Decoking processes have also been proposed which essentially consist in injecting solid particles into the steam cracking installation.
  • a first method consists in circulating a stream of neutral gas, conveying metal particles of relatively large size (250-2500 ⁇ m) in the oven previously connected to the atmosphere.
  • Another method proposes carrying out continuous sanding of the steam cracking installation, by injecting sand into the liquid hydrocarbon charge. The sand particles pass through the steam cracking furnace and the indirect quenching means and are finally trapped by the heavy oil used for the direct quenching of the gaseous effluents. As the sand particles generally have an average diameter of the order of a millimeter, this results in significant erosion of the tubes in which the charge and the steam cracking effluents circulate.
  • the subject of the invention is precisely a process for steam cracking of hydrocarbons which can be carried out continuously over very long periods, without it being necessary to stop the steam cracking in order to decoke the corresponding installation.
  • the invention also relates to a process of this type, making it possible to prevent or at least very strongly limit the coking of the installation, without risk of damaging the components of this installation.
  • it proposes a process for steam cracking of hydrocarbons, consisting in circulating a load of hydrocarbons and steam at high speed in an installation comprising at least one steam cracking oven with tubes, and indirect quenching means.
  • gaseous effluents leaving the oven and injecting into the installation erosive solid particles conveyed by a stream of gas at high speed to avoid or limit coking of the installation, characterized in that it consists in adding said solid particles to the load of hydrocarbons and water vapor circulating in the installation after a layer of coke of substantially determined average thickness has already formed on the internal walls of the installation, in particular on the internal walls of the tubes of the oven, the quantities, dimensions and / or masses of the solid particles being determined so that these particles circulating in the oven preserve sen said layer of coke and eradicate at least most of the coke which would tend to deposit, as it is formed, on the aforementioned coke layer.
  • the process according to the invention therefore makes it possible to carry out a continuous steam cracking of hydrocarbons, without it being necessary to stop this process in order to periodically decoke the steam cracking installation. Furthermore, the risks of deterioration of the components are avoided, thanks to the fact that the parts of these components, which are subjected to the action of erosive solid particles, are covered with a protective layer of a very hard material, which is advantageously constituted by the coke itself, and that it was left on purpose to form on the internal walls of the installation.
  • the quantities, dimensions and / or masses of the solid particles injected into the installation are determined so that the erosion of the coke layer by these particles is zero or substantially negligible, and the newly formed coke which becomes deposited on this layer of coke is eliminated as it is formed.
  • the coke precoat after a stay in the oven ranging from a few hours to a few days, at a temperature in the region of 1000 ° C., tends to harden by dehydrogenation and calcination, and is less easily erodable than the newly formed coke.
  • this method consists in measuring the pressure drops of at least certain tubes of the furnace, in measuring the flow rate of the hydrocarbon or steam charge, in correcting the measured values of the pressure losses in the tubes as a function of the measured flow rate of the hydrocarbon or water vapor load, and to regulate these pressure losses by varying the quantities of solid particles injected into the installation.
  • the average thickness of the hardened coke layer protecting the internal walls of the oven is preferably between approximately 0.5 and 4 mm.
  • This protective coke precoat protects the walls of the furnace tubes. It is not essential to also maintain a coke precoat on the walls of the quenching boiler, the risks of tube erosion being limited to this level due to the much lower circulation speeds.
  • this process also consists in increasing the hardness of said layer of coke, by subjecting it to a rise in temperature, possibly cyclic, for example between 20 and 140 ° C.
  • This rise in temperature above its temperature during subsequent steam cracking results in fact in an increase in the hardness of the coke layer.
  • the installation can also be operated with specific hydrocarbons different from those of the installation charge during the formation of this coke layer, for example with light hydrocarbons, of the C1 to C4 type, such as ethane. for example.
  • This operation results in the formation of a harder layer of coke on the internal walls of the installation.
  • the solid particles injected into the installation have an average diameter of less than approximately 250 ⁇ m, for example between 5 and 150 ⁇ m, the average flow rate of particles injected into the installation being less than 10% by weight of the flow of hydrocarbons and water vapor constituting the charge to be cracked.
  • These very fine particles in limited quantity, give the gas a slightly erosive character. allowing the removal of the newly formed coke by multiple low energy impacts, without fracturing the protective layer of hardened coke.
  • this process also consists in separating the solid particles from the gaseous effluents leaving the indirect quenching means, by means of gas-solid separation means of the cyclone type, in storing said solid particles in a tank. leaving the separation means, and periodically connecting this reservoir to a source of pressurized gas and to a pipe for injecting the particles into the installation, for recycling these particles.
  • the method according to the invention also provides for injecting the solid particles into a supply manifold for the tubes of the steam cracking furnace, to distribute the solid particles in these tubes by means of nozzles mounted at the end of the tubes and projecting in the manifold, these nozzles having an inlet section oriented upstream of the manifold, and to standardize the distributions of solid particles in the tubes by taking at the downstream end of the manifold a fraction of the gas-solid particle flow circulating in the collector.
  • gas-solid particles • flow rate which is sampled at the downstream end of the collector is advantageously recycled at the upstream end of this collector.
  • FIG. 1 schematically represents a steam cracking installation allowing the execution of the process according to the invention
  • FIG. 2 schematically represents, on a larger scale, an alternative embodiment of part of this installation
  • FIG. 3 schematically represents means for distributing erosive solid particles in the tubes of a steam cracking oven.
  • FIG. 1 The installation shown in FIG. 1 comprises an oven 10 with single-pass tubes 12 which are connected to a supply manifold 14 at one of their ends and which comprise, at their opposite ends, individual quenching boilers 16 connected to a outlet manifold 18.
  • the load of hydrocarbons to be cracked is brought to the liquid state by a line 20 in a convection zone 22 of the furnace, allowing its heating and its vaporization.
  • a pipe 24 for supplying steam is connected to the pipe 20 in this zone 22 of the oven 10.
  • a preheating duct 26 makes it possible to bring the mixture of vaporized hydrocarbons and steam to the manifold 14 supplying the tubes 12 of the furnace.
  • the outlet manifold 18 is connected to at least one cyclone 28 (or to several cyclones connected in series and / or in parallel), comprising an upper pipe 30 for the outlet of the gaseous effluents and a lower pipe 32 for the outlet of the solid particles.
  • the lower duct 32 is connected by a stop valve 34 and a shutter valve 36 to two particle storage tanks 38, which are arranged in parallel.
  • An isolation valve 40 is mounted between each tank 38 and the shutter valve 36.
  • Each reservoir 38 comprises means, such as for example a vibrating screen, for separating and retaining coarse solid particles as well as an orifice for discharging these particles (inspection hatch).
  • each reservoir 38 in which the fine solid particles collect, is connected by a motorized rotating member 42 (of the screw or rotary lock type) and by an isolation valve 44 to a conduit 46 for recycling the solid particles. in the installation.
  • a source 48 of pressurized gas supplies the conduit 46 with a gas flow at medium speed or relatively low (for example a flow of superheated water vapor circulating at 20 m / s).
  • a valve system 50 makes it possible to connect each reservoir 38, either to the source of pressurized gas 48, or to the conduit 30 by which the gaseous effluents leave the cyclone 28.
  • An independent reservoir 52 filled with new solid particles of determined average particle size , allows by means of a motorized rotating member and an isolation valve, to inject additional particles into the recycling duct 46.
  • the upper part of the reservoir 52 is connected to the exit from this tank via a pipe carrying out pressure balancing.
  • Each reservoir 38, or one of them, may comprise, in the lower part, a purge duct 54 making it possible to withdraw a certain quantity of spent solid particles.
  • the recycling duct 80 is connected by shut-off valves at different points of the steam cracking installation, in particular at the inlet of the duct 26, at the inlet of the indirect quench boilers 16, and to the duct 26 for clean the charge vaporization duct located in part 22 of the furnace 10 (for example at the point where the hydrocarbon charge is completely vaporized).
  • the installation of FIG. 1 also comprises means 56 for measuring the actual pressure drops in some of the tubes 12 of the furnace, in order to know the increase in these pressure drops which is due to the deposition of coke on the internal walls of the tubes .
  • the means 56 for measuring the pressure drops are connected, by a correction circuit 58 associated with means 60 for measuring the flow rate of the hydrocarbon (or water vapor) charge, to a logic control circuit 62 • making it possible to regulate the actual pressure drops in the furnace tubes to a value between approximately 130 and 300% of the value of these pressure losses in clean tubes, under the same operating conditions of the furnace (same hydrocarbon load and even water vapor flow).
  • the actual pressure drop in the furnace tubes, corrected according to the flow rate is maintained at a value between approximately 130 and 180% of the pressure drop in clean tubes.
  • the control circuit 62 can act on the following means: - the quantity of solid make-up particles delivered by the reservoir 52,
  • the operation of the installation is as follows: the load of hydrocarbons to be cracked is preheated, mixed with steam and vaporized in part 22 of the furnace, then it undergoes steam cracking in the tubes 12 with a residence time very brief in these tubes.
  • the gaseous steam cracking effluents then undergo indirect quenching in the boilers 16, pass through the cyclone 28 and gain means of direct quenching by injection of pyrolysis oil.
  • the hardness of this layer of coke can be increased by subjecting it to a temperature rise, possibly cyclic, of between 20 and 140 "C.
  • a temperature rise possibly cyclic, of between 20 and 140 "C.
  • the skin temperature of the tubes is allowed to increase, either by reducing the flow rate of the load to be cracked, ie by increasing the heating of the furnace. This results in an appreciable hardening of the coke layer.
  • an equivalent result is obtained by operating the installation with light hydrocarbons (of the Cl to C4 type) which are cracked at high temperature, or else by operating the installation with sulfur compounds.
  • the coke which is formed by cracking of ethane, ethylene, proprane, propylene, or sulfur compounds has in fact a hardness higher than that of the coke formed by cracking of more conventional fillers, such as naphtha and gas oil.
  • erosive solid particles are injected into this installation which will be entrained by the load of hydrocarbons and water vapor and which will remove the newly formed coke as it tends to settle on the aforementioned coke layer.
  • the quantities and dimensions and / or masses of the solid particles injected are determined to cause the elimination of the newly formed coke, while respecting the protective layer already deposited on the internal walls of the installation.
  • the flow rate of these particles is less than 10% by weight of the hydrocarbon and water vapor charge, and is between 0.1 and 8% by weight of this charge, preferably.
  • the heavier particles initiate the erosion of the newly deposited coke, while the finer and lighter particles propagate this erosion.
  • the solid particles used can be substantially spherical particles, for example of silica-alumina, such as particles of already used cathalytic cracking catalyst. It is also possible to use particles of metal, for example iron, steel, nickel, a nickel-containing alloy, etc., and other harder and more erosive particles (for example of cracking catalyst or of '' a refractory and hard metal alloy).
  • the solid particles circulating in the installation reach the cyclone (s) 28, where they are separated from the gaseous effluents with a very high efficiency, then leave each cyclone 28 by its lower duct 32 to gain alternately both tanks 38, the shutter valve 36 for selecting the tank in which the particles will be stored.
  • the other tank 38 can be used to reinject these particles into the installation.
  • the upper isolation valve 40 of this tank is closed, the upper part of the tank is isolated from the conduit 30 for the outlet of the gaseous effluents of the cyclone 28, and is connected to the source of pressurized gas 48, the rotating member 42 is rotated and the lower isolation valve 44 is open.
  • this tank When this tank is empty, it can be used again for the storage of the particles, while the solid particles stored in the other tank 38 are recycled in the installation.
  • FIG. 2 shows an alternative embodiment of the means for storing and recycling solid particles.
  • the means shown in Figure 2 different from those of Figure 1 in that the two tanks 38 are mounted in series, and no longer in parallel.
  • a three-way valve 64 makes it possible to connect the lower reservoir 38, ie to the source of pressurized gas 48 by means of a stop valve.
  • a conduit 68 is also provided for supplying a barrier gas which opens into the upper part of the upper reservoir 38.
  • This barrier gas is free of heavy aromatics and may be water vapor. It makes it possible to avoid coking of the upper reservoir 38 and of its filtering screen, by avoiding the presence of cracked gases.
  • the separation of solid particles in a cyclone can be done in two stages, in the case where the gaseous effluents entering the cyclone include traces of liquid:
  • a first step where the gaseous effluents are dried (for example at the outlet of a first cyclone by mixing with a stream of superheated gas and / or by recycling dry and hot particles) a second step, of separation of the dried particles.
  • the manifold 14 for supplying the tubes 12 receives at its upstream end a charge of vaporized hydrocarbons and of water vapor which is, for example, at a temperature of the order of 550 "C and into which a small amount of solid particles.
  • the tubes 12 of the furnace form one or more parallel rows and emerge at regular intervals into the collector 14.
  • the latter has a section which decreases progressively from its upstream end to its downstream end relative to the direction of flow of the charge, to maintain a minimum speed of the mixture in the collector and avoid deposits of solid particles.
  • each tube 12 opening into the manifold 14 comprises a supply nozzle 70 located in the manifold and the inlet section of which comprises an orifice 72 oriented towards the upstream end of the manifold.
  • Each tube 12 comprises, immediately downstream of the supply nozzle 70, a section restriction 74 such as a neck or a venturi, making it possible to standardize and make the constants substantially constant. Gas flows in the tubes 12.
  • a sonic venturi is used.
  • a settling chamber 76 is provided upstream of the last tube 12 and below the collector 14, to receive solid particles progressing along the lower generatrix of the collector 14.
  • the downstream end 78 of this manifold is connected by a duct 80 of suitable dimensions, to an ejector-compressor 82 comprising an axial duct 84 for supplying a flow of engine gas such as steam.
  • a valve 86 makes it possible to adjust the flow rate of engine gas.
  • the outlet of the ejector-compressor 82 is connected by a conduit 88 to the upstream end of the manifold 14 or to the conduit for supplying the hydrocarbon charge.
  • valve 86 for adjusting the engine gas flow rates can be controlled by a system 90 comprising means for detecting the skin temperature of the first and last tubes 12 of the furnace, in order to control the flow of engine gas unlike these temperatures.
  • This device operates as' follows: The mixture of vaporized hydrocarbons, water vapor and solid particles, flows with high turbulence in the manifold 14.
  • the mean flow velocity in the manifold is between 20 and 120 m / s, for example between 30 and 80 m / s and is notably lower than the circulation speed in the tubes 12 which is between 130 and 300 m / s approximately (in particular between 160 and 270 m / s ).
  • the flow speed in the collector 14 is sufficient to avoid any gas-solid separation in the collector, except for certain particles heavy, which can progress along the lower generator of the collector.
  • the system 90 makes it possible to adjust the flow rate of engine gas by action on the valve 86, which makes it possible to adjust the supply of solid particles to the first tubes relative to that of the last tubes and therefore to correct any irregularity in distribution detected. by differences between the skin temperatures of these tubes.
  • the section restrictions 74 formed at the upstream end of the tubes 12 have the effect of standardizing and making substantially constant the gas flow rates which circulate in these tubes. This results in a possibility of automatic regulation of the cleaning of these tubes by solid particles. Indeed, if a tube clogs abnormally, with partial obstruction by coke, the maintenance of the gas flow ensured by the restrictions 74 will lead to increasing the speed of circulation and therefore the erosive efficiency of the particles.
  • the first tubes 12 are thus, from the aerodynamic point of view, in the same situation as the following tubes.
  • the invention therefore makes it possible to make the operation of steam cracking installations continuous or substantially continuous, and is applicable to various types of ovens, in particular single-pass ovens, with straight tubes, and ovens with several passes, with elbows at right angles.

Abstract

PCT No. PCT/FR90/00273 Sec. 371 Date Dec. 12, 1990 Sec. 102(e) Date Dec. 12, 1990 PCT Filed Apr. 13, 1990 PCT Pub. No. WO90/12852 PCT Pub. Date Nov. 1, 1990.A method of steam cracking hydrocarbons in a steam cracking furnace (10) having tubes (12) connected to indirect quench menas (16) for the gaseous effluent leaving the furnace, the method consisting in allowing a layer of hard coke to form on the inside walls of the furnace tubes (12) and then in injecting a small quantity of solid erosive particles into the steam and hydrocarbon feedstock to be cracked, with the particles being separated from the gaseous effluent in a cyclone (28) provided at the outlet from the indirect quench means. The invention serves in particular to enable a steam cracking installation to operate continuously.

Description

PROCEDE DE VAPOCRAQUAGE D'HYDROCARBURES PROCESS FOR VAPOCRACKING HYDROCARBONS
L'invention concerne un procédé de vapocraquage d'hydrocarbures, permettant notamment d'éviter ou au moins de limiter le cokage de l'installation de vapocraquage.The invention relates to a process for steam cracking of hydrocarbons, making it possible in particular to avoid or at least limit the coking of the steam cracking installation.
Le vapocraquage des hydrocarbures consiste à soumettre une charge d'hydrocarbures mélangée avec de la vapeur d'eau à un craquage thermique dans une installation comprenant notamment un four à tubes dans lesquels la charge est portée à une température d'environ 800 à 900 ° C, puis des moyens de trempe indirecte des effluents gazeux sortant du four, permettant de refroidir rapidement ces effluents pour arrêter les réactions de craquage. L'inconvénient principal de ce procédé réside dans l'encrassement progressif de l'installation par le coke qui se dépose dans le four et dans les moyens de trempe indirecte.Steam cracking of hydrocarbons consists in subjecting a charge of hydrocarbons mixed with steam to thermal cracking in an installation comprising in particular a tube furnace in which the charge is brought to a temperature of about 800 to 900 ° C. , then means for indirect quenching of the gaseous effluents leaving the furnace, making it possible to rapidly cool these effluents to stop the cracking reactions. The main drawback of this process lies in the gradual fouling of the installation by the coke which is deposited in the oven and in the indirect quenching means.
Il se forme sur les parois internes de l'installation qui sont en contact avec la charge de craquage, une couche de coke dont l'épaisseur croit progressivement, qui est néfaste du point de vue du transfert thermique, et qui conduit à une augmentation des pertes de charge dans les tubes du four et à une réduction des rendements.There is formed on the internal walls of the installation which are in contact with the cracking charge, a layer of coke whose thickness gradually increases, which is harmful from the point of view of heat transfer, and which leads to an increase in pressure losses in the furnace tubes and reduced yields.
On est donc conduit à éliminer périodiquement le coke déposé dans ces installations.It is therefore necessary to periodically eliminate the coke deposited in these installations.
Pour cela, on a déjà proposé un procédé de décokage chimique oxydant par un mélange air-vapeur. La mise en oeuvre de ce procédé nécessite cependant d'arrêter le fonctionnement de l'installation de vapocraquage et de l'isoler des équipements situés en aval.For this, an oxidizing chemical decoking process has already been proposed by an air-vapor mixture. The implementation of this process however requires stopping the operation of the steam cracking installation and isolating it from the equipment located downstream.
On a également proposé de réaliser le décokage des moyens de trempe indirecte par sablage hydraulique ou au moyen de jets d'eau sous très haute pression. permettant de fracturer la couche de coke. Là encore, il faut arrêter complètement l'installation de vapocraquage.It has also been proposed to decoke the indirect quenching means by hydraulic sandblasting or by means of water jets under very high pressure. to fracture the coke layer. Again, the steam cracking installation must be stopped completely.
On a aussi proposé des procédés de décokage qui consistent pour l'essentiel à injecter des particules solides dans l'installation de vapocraquage. Un premier procédé consiste à faire circuler un courant de gaz neutre, véhiculant des particules métalliques de dimension relativement importante (250-2500 μm) dans le four préalablement relié à l'atmosphère. Un autre procédé propose de réaliser un sablage continu de l'installation de vapocraquage, par injection de sable dans la charge liquide d'hydrocarbures. Les particules de sable traversent le four de vapocraquage et les moyens de trempe indirecte et sont finalement piégées par l'huile lourde utilisée pour la trempe directe des effluents gazeux. Comme les particules de sable ont en général un diamètre moyen de l'ordre du millimètre, il en résulte une érosion importante des tubes dans lesquels circulent la charge et les effluents de vapocraquage. De plus, il est à peu près impossible de séparer économiquement les particules de sable de l'huile lourde de trempe directe, de sorte que les particules de sable ne sont pas recyclables et que l'huile de trempe devient inutilisable. II en résulte que les procédés connus de vapocraquage d'hydrocarbures sont exécutés de façon discontinue, les périodes de vapocraquage d'hydrocarbures alternant avec des intervalles de décokage des installations, ce qui entraîne des baisses de rendement et des augmentations de coût.Decoking processes have also been proposed which essentially consist in injecting solid particles into the steam cracking installation. A first method consists in circulating a stream of neutral gas, conveying metal particles of relatively large size (250-2500 μm) in the oven previously connected to the atmosphere. Another method proposes carrying out continuous sanding of the steam cracking installation, by injecting sand into the liquid hydrocarbon charge. The sand particles pass through the steam cracking furnace and the indirect quenching means and are finally trapped by the heavy oil used for the direct quenching of the gaseous effluents. As the sand particles generally have an average diameter of the order of a millimeter, this results in significant erosion of the tubes in which the charge and the steam cracking effluents circulate. In addition, it is almost impossible to economically separate the sand particles from the heavy direct quench oil, so that the sand particles are not recyclable and the quench oil becomes unusable. As a result, the known methods of steam cracking of hydrocarbons are carried out discontinuously, the periods of steam cracking of hydrocarbons alternating with decoking intervals of the installations, which leads to reductions in yield and increases in cost.
L'invention a précisément pour objet un procédé de vapocraquage d'hydrocarbures qui puisse être exécuté de façon continue sur de très longues périodes, sans qu'il soit nécessaire d'arrêter le vapocraquage pour procéder à un décokage de l'installation correspondante. L'invention a également pour objet un procédé de ce type, permettant d'empêcher ou au moins de limiter très fortement le cokage de l'installation, sans risque de détérioration des composants de cette installation. Elle propose à cet effet un procédé de vapocraquage d'hydrocarbures, consistant à faire circuler à vitesse élevée une charge d'hydrocarbures et de vapeur d'eau dans une installation comprenant au moins un four de vapocraquage à tubes, et des moyens de trempe indirecte des effluents gazeux sortant du four, et à injecter dans l'installation des particules solides érosives véhiculées par un courant de gaz à vitesse élevée pour éviter ou limiter le cokage de l'installation, caractérisé en ce qu'il consiste à ajouter lesdites particules solides à la charge d'hydrocarbures et de vapeur d'eau circulant dans l'installation après qu'une couche de coke d'épaisseur moyenne sensiblement déterminée se soit déjà formée sur les parois internes de l'installation, en particulier sur les parois internes des tubes du four, les quantités, dimensions et/ou masses des particules solides étant déterminées de façon à ce que ces particules circulant dans le four préservent sensiblement ladite couche de coke et éliminent par érosion au moins la plus grande partie du coke qui tendrait à se déposer, au fur et à mesure de sa formation, sur la couche de coke précitée.The subject of the invention is precisely a process for steam cracking of hydrocarbons which can be carried out continuously over very long periods, without it being necessary to stop the steam cracking in order to decoke the corresponding installation. The invention also relates to a process of this type, making it possible to prevent or at least very strongly limit the coking of the installation, without risk of damaging the components of this installation. To this end, it proposes a process for steam cracking of hydrocarbons, consisting in circulating a load of hydrocarbons and steam at high speed in an installation comprising at least one steam cracking oven with tubes, and indirect quenching means. gaseous effluents leaving the oven, and injecting into the installation erosive solid particles conveyed by a stream of gas at high speed to avoid or limit coking of the installation, characterized in that it consists in adding said solid particles to the load of hydrocarbons and water vapor circulating in the installation after a layer of coke of substantially determined average thickness has already formed on the internal walls of the installation, in particular on the internal walls of the tubes of the oven, the quantities, dimensions and / or masses of the solid particles being determined so that these particles circulating in the oven preserve sen said layer of coke and eradicate at least most of the coke which would tend to deposit, as it is formed, on the aforementioned coke layer.
Le procédé selon l'invention permet donc de réaliser un vapocraquage continu d'hydrocarbures, sans qu'il soit nécessaire d'arrêter ce procédé pour décoker périodiquement l'installation de vapocraquage. Par ailleurs, les risques de détérioration des composants sont évités, grâce au fait que les parties de ces composants, qui sont soumises à l'action des particules solides érosives, sont recouvertes d'une couche de protection en une matière très dure, qui est avantageusement constituée par le coke lui-même, et que l'on a laissée à dessein se former sur les parois internes de l'installation. Les quantités, les dimensions et/ou les masses des particules solides injectées dans 1'installation sont déterminées de façon à ce que l'érosion de la couche de coke par ces particules soit nulle ou sensiblement négligeable, et que le coke nouvellement formé qui se dépose sur cette couche de coke soit éliminé au fur et à mesure de sa formation.The process according to the invention therefore makes it possible to carry out a continuous steam cracking of hydrocarbons, without it being necessary to stop this process in order to periodically decoke the steam cracking installation. Furthermore, the risks of deterioration of the components are avoided, thanks to the fact that the parts of these components, which are subjected to the action of erosive solid particles, are covered with a protective layer of a very hard material, which is advantageously constituted by the coke itself, and that it was left on purpose to form on the internal walls of the installation. The quantities, dimensions and / or masses of the solid particles injected into the installation are determined so that the erosion of the coke layer by these particles is zero or substantially negligible, and the newly formed coke which becomes deposited on this layer of coke is eliminated as it is formed.
La précouche de coke, après un séjour dans le four allant de quelques heures à quelques jours, sous une température voisine de 1000'C tend à durcir par déshydrogénation et calcination, et est moins facilement érodable que le coke nouvellement formé.The coke precoat, after a stay in the oven ranging from a few hours to a few days, at a temperature in the region of 1000 ° C., tends to harden by dehydrogenation and calcination, and is less easily erodable than the newly formed coke.
Selon une autre caractéristique de l'invention, ce procédé consiste à mesurer les pertes de charge d'au moins certains tubes du four, à mesurer le débit de la charge d'hydrocarbures ou de vapeur d'eau, à corriger les valeurs mesurées des pertes de charge dans les tubes en fonction du débit mesuré de la charge d'hydrocarbures ou de vapeur d'eau, et à réguler ces pertes de charge par variation des quantités de particules solides injectées dans l'installation.According to another characteristic of the invention, this method consists in measuring the pressure drops of at least certain tubes of the furnace, in measuring the flow rate of the hydrocarbon or steam charge, in correcting the measured values of the pressure losses in the tubes as a function of the measured flow rate of the hydrocarbon or water vapor load, and to regulate these pressure losses by varying the quantities of solid particles injected into the installation.
On peut ainsi, simplement et de façon relativement précise, réguler l'épaisseur moyenne de la couche de coke déposée sur les parois internes de l'installation, et la maintenir sensiblement égale à une valeur prédéterminée.It is thus possible, simply and relatively precisely, to regulate the average thickness of the layer of coke deposited on the internal walls of the installation, and to keep it substantially equal to a predetermined value.
On peut pour cela maintenir les valeurs corrigées des pertes de charge dans les tubes sensiblement égales à une valeur comprise entre 130 et 300 % environ de la perte de charge corrigée dans un tube propre (non coke) .For this, it is possible to maintain the corrected values of the pressure losses in the tubes substantially equal to a value between approximately 130 and 300% of the pressure loss corrected in a clean tube (non-coke).
L'épaisseur moyenne de la couche de coke durcie protégeant les parois internes du four est de préférence comprise entre 0,5 et 4 mm environ. Cette précouche protectrice de coke protège les parois des tubes du four. Il n'est pas indispensable de maintenir également une précouche de coke sur les parois de la chaudière de trempe, les risques d'érosion des tubes étant limités à ce niveau en raison des vitesses de circulation beaucoup plus basses.The average thickness of the hardened coke layer protecting the internal walls of the oven is preferably between approximately 0.5 and 4 mm. This protective coke precoat protects the walls of the furnace tubes. It is not essential to also maintain a coke precoat on the walls of the quenching boiler, the risks of tube erosion being limited to this level due to the much lower circulation speeds.
Selon une autre caractéristique avantageuse de l'invention, ce procédé consiste également à augmenter la dureté de ladite couche de coke, en la soumettant à une élévation de température, éventuellement cyclique, comprise par exemple entre 20 et 140°C. Cette élévation de température au dessus de sa température lors du vapocraquage ultérieur se traduit en effet par une augmentation de la dureté de la couche de coke. On peut également faire fonctionner l'installation avec des hydrocarbures particuliers différents de ceux de la charge de l'installation pendant la formation de cette couche de coke, par exemple avec des hydrocarbures légers, du type Cl à C4, tels que de 1'éthane par exemple.According to another advantageous characteristic of the invention, this process also consists in increasing the hardness of said layer of coke, by subjecting it to a rise in temperature, possibly cyclic, for example between 20 and 140 ° C. This rise in temperature above its temperature during subsequent steam cracking results in fact in an increase in the hardness of the coke layer. The installation can also be operated with specific hydrocarbons different from those of the installation charge during the formation of this coke layer, for example with light hydrocarbons, of the C1 to C4 type, such as ethane. for example.
Ce fonctionnement se traduit par la formation d'une couche de coke plus dure sur les parois internes de 1'installation.This operation results in the formation of a harder layer of coke on the internal walls of the installation.
Ainsi donc, il est possible suivant l'invention d'obtenir une précouche de coke de dureté accrue, ce qui la rend moins fragile et augmente son effet protecteur du métal des tubes.Thus, it is possible according to the invention to obtain a coke precoat of increased hardness, which makes it less brittle and increases its protective effect from the metal of the tubes.
Selon encore une autre caractéristique de l'invention, les particules solides injectées dans l'installation ont un diamètre moyen inférieur à 250 μm environ, par exemple compris entre 5 et 150 μm, le débit moyen de particules injectées dans l'installation étant inférieur à 10% en poids du débit d'hydrocarbures et de vapeur d'eau constituant la charge à craquer. Ces particules très fines, en quantité limitée, confèrent au gaz un caractère légèrement érosif. permettant d'éliminer le coke nouvellement formé par de multiples impacts de faible énergie, sans fracturer la précouche protectrice de coke durci.According to yet another characteristic of the invention, the solid particles injected into the installation have an average diameter of less than approximately 250 μm, for example between 5 and 150 μm, the average flow rate of particles injected into the installation being less than 10% by weight of the flow of hydrocarbons and water vapor constituting the charge to be cracked. These very fine particles, in limited quantity, give the gas a slightly erosive character. allowing the removal of the newly formed coke by multiple low energy impacts, without fracturing the protective layer of hardened coke.
Selon une autre caractéristique de l'invention, ce procédé consiste également à séparer les particules solides des effluents gazeux en sortie des moyens de trempe indirecte, grâce à des moyens de séparation gaz-solide du type cyclone, à stocker dans un réservoir lesdites particules solides sortant des moyens de séparation, et à relier périodiquement ce réservoir à une source de gaz sous pression et à un conduit d'injection des particules dans l'installation, pour le recyclage de ces particules.According to another characteristic of the invention, this process also consists in separating the solid particles from the gaseous effluents leaving the indirect quenching means, by means of gas-solid separation means of the cyclone type, in storing said solid particles in a tank. leaving the separation means, and periodically connecting this reservoir to a source of pressurized gas and to a pipe for injecting the particles into the installation, for recycling these particles.
L'utilisation d'un ou de plusieurs cyclones en sortie des moyens de trempe indirecte permet de séparer les effluents gazeux et les particules solides avec une efficacité très élevée (qui peut atteindre 99% ou davantage) .The use of one or more cyclones at the outlet of the indirect quenching means makes it possible to separate the gaseous effluents and the solid particles with a very high efficiency (which can reach 99% or more).
Cela permet en outre de récupérer les particules solides et de les recycler ensuite dans l'installation, après avoir remonté leur niveau de pression.This also makes it possible to recover the solid particles and then recycle them in the installation, after having raised their pressure level.
Le procédé selon 1'invention prévoit également d'injecter les particules solides dans un collecteur d'alimentation des tubes du four de vapocraquage, à répartir les particules solides dans ces tubes au moyen d'embouts montés à l'extrémité des tubes et faisant saillie dans le collecteur, ces embouts ayant une section d'entrée orientée vers l'amont du collecteur, et à uniformiser les répartitions de particules solides dans les tubes en prélevant à l'extrémité aval du collecteur une fraction du débit gaz-particules solides circulant dans le collecteur.The method according to the invention also provides for injecting the solid particles into a supply manifold for the tubes of the steam cracking furnace, to distribute the solid particles in these tubes by means of nozzles mounted at the end of the tubes and projecting in the manifold, these nozzles having an inlet section oriented upstream of the manifold, and to standardize the distributions of solid particles in the tubes by taking at the downstream end of the manifold a fraction of the gas-solid particle flow circulating in the collector.
On évite ainsi des distributions irrégulières de particules dans les différents tubes du four de vapocraquage, et on assure un décokage uniforme des tubes, au fur et à mesure de la formation du coke.This avoids irregular distributions of particles in the different tubes of the steam cracking, and a uniform decoking of the tubes is ensured, as the coke is formed.
Par ailleurs, le débit gaz-particules • solides qui est prélevé à l'extrémité aval du collecteur, est avantageusement recyclé à l'extrémité amont de ce collecteur.Furthermore, the gas-solid particles • flow rate which is sampled at the downstream end of the collector, is advantageously recycled at the upstream end of this collector.
L'invention sera mieux comprise et d'autres caractéristiques, détails et avantages de celle-ci apparaîtront plus clairement à la lecture de la description qui suit, faite à titre d'exemple en référence aux dessins annexés dans lesquels : la figure 1 représente schématiquement une installation de vapocraquage permettant l'exécution du procédé selon l'invention; la figure 2 représente schématiquement, à une plus grande échelle, une variante de réalisation d'une partie de cette installation; la figure 3 représente schématiquement des moyens de répartition de particules solides érosives dans les tubes d'un four de vapocraquage.The invention will be better understood and other characteristics, details and advantages thereof will appear more clearly on reading the description which follows, given by way of example with reference to the accompanying drawings in which: FIG. 1 schematically represents a steam cracking installation allowing the execution of the process according to the invention; FIG. 2 schematically represents, on a larger scale, an alternative embodiment of part of this installation; FIG. 3 schematically represents means for distributing erosive solid particles in the tubes of a steam cracking oven.
L'installation représentée en figure 1 comprend un four 10 à tubes 12 monopasse qui sont reliés à un collecteur d'alimentation 14 à l'une de leurs extrémités et qui comprennent, à leurs extrémités opposées, des chaudières de trempe individuelles 16 reliées à un collecteur de sortie 18.The installation shown in FIG. 1 comprises an oven 10 with single-pass tubes 12 which are connected to a supply manifold 14 at one of their ends and which comprise, at their opposite ends, individual quenching boilers 16 connected to a outlet manifold 18.
La charge d'hydrocarbures à craquer est amenée à l'état liquide par une conduite 20 dans une zone de convection 22 du four, permettant son chauffage et sa vaporisation.The load of hydrocarbons to be cracked is brought to the liquid state by a line 20 in a convection zone 22 of the furnace, allowing its heating and its vaporization.
Une conduite 24 d'amenée de vapeur d'eau est raccordée à la conduite 20 dans cette zone 22 du four 10.A pipe 24 for supplying steam is connected to the pipe 20 in this zone 22 of the oven 10.
Un conduit de préchauffage 26 permet d'amener le mélange d'hydrocarbures vaporisé et de vapeur d'eau au collecteur 14 alimentant les tubes 12 du four. Le collecteur de sortie 18 est raccordé à au moins un cyclone 28 (ou à plusieurs cyclones montés en série et/ou en parallèle) , comprenant un conduit supérieur 30 de sortie des effluents gazeux et un conduit inférieur 32 de sortie des particules solides.A preheating duct 26 makes it possible to bring the mixture of vaporized hydrocarbons and steam to the manifold 14 supplying the tubes 12 of the furnace. The outlet manifold 18 is connected to at least one cyclone 28 (or to several cyclones connected in series and / or in parallel), comprising an upper pipe 30 for the outlet of the gaseous effluents and a lower pipe 32 for the outlet of the solid particles.
Le conduit inférieur 32 est relié par une vanne d'arrêt 34 et une vanne à volet 36 à deux réservoirs 38 de stockage de particules, qui sont agencés en parallèle. Une vanne d'isolement 40 est montée entre chaque réservoir 38 et la vanne à volet 36.The lower duct 32 is connected by a stop valve 34 and a shutter valve 36 to two particle storage tanks 38, which are arranged in parallel. An isolation valve 40 is mounted between each tank 38 and the shutter valve 36.
Chaque réservoir 38 comprend des moyens, tels par exemple qu'un tamis vibrant, de séparation et de retenue des particules solides grossières ainsi qu'un orifice d'évacuation de ces particules (trappe de visite) .Each reservoir 38 comprises means, such as for example a vibrating screen, for separating and retaining coarse solid particles as well as an orifice for discharging these particles (inspection hatch).
La partie inférieure de chaque réservoir 38, dans laquelle se rassemblent les particules solides fines, est reliée par un organe tournant motorisé 42 (du type vis ou écluse rotative) et par une vanne d'isolement 44 à un conduit 46 de recyclage des particules solides dans l'installation.The lower part of each reservoir 38, in which the fine solid particles collect, is connected by a motorized rotating member 42 (of the screw or rotary lock type) and by an isolation valve 44 to a conduit 46 for recycling the solid particles. in the installation.
Une source 48 de gaz sous pression alimente le conduit 46 par un débit de gaz à vitesse moyenne ou relativement faible (par exemple un débit de vapeur d'eau surchauffé circulant à 20 m/s) .A source 48 of pressurized gas supplies the conduit 46 with a gas flow at medium speed or relatively low (for example a flow of superheated water vapor circulating at 20 m / s).
Un système de vannes 50 permet de relier chaque réservoir 38, soit à la source de gaz sous pression 48, soit au conduit 30 par lequel les effluents gazeux sortent du cyclone 28. Un réservoir indépendant 52, rempli de particules solides neuves de granulométrie moyenne déterminée, permet par l'intermédiaire d'un organe tournant motorisé et d'une vanne d'isolement, d'injecter un appoint de particules dans le conduit de recyclage 46. La partie supérieure du réservoir 52 est reliée à la sortie de ce réservoir par un conduit réalisant un équilibrage de pression.A valve system 50 makes it possible to connect each reservoir 38, either to the source of pressurized gas 48, or to the conduit 30 by which the gaseous effluents leave the cyclone 28. An independent reservoir 52, filled with new solid particles of determined average particle size , allows by means of a motorized rotating member and an isolation valve, to inject additional particles into the recycling duct 46. The upper part of the reservoir 52 is connected to the exit from this tank via a pipe carrying out pressure balancing.
Chaque réservoir 38, ou l'un d'entre eux, peut comprendre, en partie inférieure, un conduit de purge 54 permettant de soutirer une certaine quantité de particules solides usées.Each reservoir 38, or one of them, may comprise, in the lower part, a purge duct 54 making it possible to withdraw a certain quantity of spent solid particles.
Le conduit de recyclage 80 est relié par des vannes d'arrêt à différents points de l'installation de vapocraquage, en particulier à l'entrée du conduit 26, à l'entrée des chaudières de trempe indirecte 16, et à la conduite 26 pour nettoyer le conduit de vaporisation de la charge situé dans la partie 22 du four 10 (par exemple au point où la charge d'hydrocarbures est entièrement vaporisée) . L'installation de la figure 1 comprend encore des moyens 56 de mesure des pertes de charge réelles dans certains des tubes 12 du four, pour connaître 1' augmentation de ces pertes de charge qui est due au dépôt de coke sur les parois internes des tubes. Les moyens 56 de mesure des pertes de charge sont reliés, par un circuit de correction 58 associé à des moyens 60 de mesure du débit de la charge d'hydrocarbures (ou de vapeur d'eau), à un circuit logique 62 • de commande permettant de réguler les pertes de charge réelles dans les tubes du four à une valeur comprise entre 130 et 300 % environ de la valeur de ces pertes de charge dans des tubes propres, dans les mêmes conditions de fonctionnement du four (même charge d'hydrocarbures et même débit de vapeur d'eau) . De préférence, la perte de charge réelle dans les tubes du four, corrigée en fonction du débit, est maintenue à une valeur comprise entre 130 et 180% environ de la perte de charge dans des tubes propres.The recycling duct 80 is connected by shut-off valves at different points of the steam cracking installation, in particular at the inlet of the duct 26, at the inlet of the indirect quench boilers 16, and to the duct 26 for clean the charge vaporization duct located in part 22 of the furnace 10 (for example at the point where the hydrocarbon charge is completely vaporized). The installation of FIG. 1 also comprises means 56 for measuring the actual pressure drops in some of the tubes 12 of the furnace, in order to know the increase in these pressure drops which is due to the deposition of coke on the internal walls of the tubes . The means 56 for measuring the pressure drops are connected, by a correction circuit 58 associated with means 60 for measuring the flow rate of the hydrocarbon (or water vapor) charge, to a logic control circuit 62 • making it possible to regulate the actual pressure drops in the furnace tubes to a value between approximately 130 and 300% of the value of these pressure losses in clean tubes, under the same operating conditions of the furnace (same hydrocarbon load and even water vapor flow). Preferably, the actual pressure drop in the furnace tubes, corrected according to the flow rate, is maintained at a value between approximately 130 and 180% of the pressure drop in clean tubes.
Le circuit de commande 62 peut agir sur les moyens suivants : - la quantité de particules solides d'appoint délivrées par le réservoir 52,The control circuit 62 can act on the following means: - the quantity of solid make-up particles delivered by the reservoir 52,
- la purge de l'un ou des réservoirs 38 par le conduit 54, - la fréquence des cycles et le débit de recyclage des particules solides à partir des réservoirs 38.the purging of one or more reservoirs 38 via the conduit 54; the frequency of the cycles and the recycling rate of solid particles from the reservoirs 38.
Le fonctionnement de 1'installation est le suivant : la charge d'hydrocarbures à craquer est préchauffée, mélangée à la vapeur d'eau et vaporisée dans la partie 22 du four, puis elle subit un vapocraquage dans les tubes 12 avec un temps de séjour très bref dans ces tubes. Les effluents gazeux de vapocraquage subissent ensuite une trempe indirecte dans les chaudières 16, passent dans le cyclone 28 et gagnent des moyens de trempe directe par injection d'huile de pyrolyse.The operation of the installation is as follows: the load of hydrocarbons to be cracked is preheated, mixed with steam and vaporized in part 22 of the furnace, then it undergoes steam cracking in the tubes 12 with a residence time very brief in these tubes. The gaseous steam cracking effluents then undergo indirect quenching in the boilers 16, pass through the cyclone 28 and gain means of direct quenching by injection of pyrolysis oil.
Au début du fonctionnement de l'installation, ou à l'issue d'un décokage réalisé par des moyens quelconques, on n'injecte pas de particules solides érosives dans la charge d'hydrocarbures et de vapeur d'eau circulant dans l'installation. La formation de coke sur les parois internes de la conduite 26 du collecteur 14, de tous les tubes 12 du four et des tubes des chaudières 16, est relativement importante et rapide. On laisse donc se former sur toutes ces parois une couche protectrice de coke, qui durcit rapidement et qui peut avoir une épaisseur moyenne comprise entre 0,5 et 4 mm, ou entre 1 et 3 mm. Le contrôle de l'épaisseur de cette couche de coke est réalisé grâce aux moyens précités 56 de mesure des pertes de charge dans des tubes 12, et de correction des valeurs mesurées en fonction du débit de la charge d'hydrocarbures ou de vapeur d'eau.At the start of operation of the installation, or after decoking by any means, no erosive solid particles are injected into the charge of hydrocarbons and water vapor circulating in the installation . The formation of coke on the internal walls of the pipe 26 of the manifold 14, of all the tubes 12 of the furnace and of the tubes of the boilers 16, is relatively large and rapid. A protective layer of coke is therefore allowed to form on all of these walls, which hardens rapidly and which can have an average thickness of between 0.5 and 4 mm, or between 1 and 3 mm. The thickness of this coke layer is controlled by the aforementioned means 56 for measuring the pressure drops in tubes 12, and for correcting the values measured as a function of the flow rate of the hydrocarbon or vapor charge. water.
Lorsque la perte de charge corrigée d'un tube du four a atteint une valeur prédéterminée, comprise entre 130 et 300% environ de la perte de charge d'un tube propre, on considère que la couche de coke formée sur les parois internes de l'installation a une épaisseur suffisante.When the corrected pressure drop of a furnace tube has reached a predetermined value, between approximately 130 and 300% of the pressure drop of a tube clean, it is considered that the coke layer formed on the internal walls of the installation has a sufficient thickness.
Avantageusement, on peut augmenter la dureté de cette couche de coke en la soumettant à une élévation de température, éventuellement cyclique, comprise entre 20 et 140"C. Pour cela, on laisse augmenter la température de peau des tubes soit en réduisant le débit de la charge à craquer, soit en augmentant le chauffage du four. Il en résulte un durcissement appréciable de la couche de coke.Advantageously, the hardness of this layer of coke can be increased by subjecting it to a temperature rise, possibly cyclic, of between 20 and 140 "C. For this, the skin temperature of the tubes is allowed to increase, either by reducing the flow rate of the load to be cracked, ie by increasing the heating of the furnace. This results in an appreciable hardening of the coke layer.
En variante, on obtient un résultat équivalent en faisant fonctionner l'installation avec des hydrocarbures légers (du type Cl à C4) qui sont craqués à haute température, ou bien en faisant fonctionner l'installation avec des composés soufrés. Le coke qui est formé par craquage d'éthane, d'éthylène, de proprane, de propylène, ou de composés soufrés a en effet une dureté supérieure à celle du coke formé par craquage de charge plus classiques, telles que du naphta et du gas oil.As a variant, an equivalent result is obtained by operating the installation with light hydrocarbons (of the Cl to C4 type) which are cracked at high temperature, or else by operating the installation with sulfur compounds. The coke which is formed by cracking of ethane, ethylene, proprane, propylene, or sulfur compounds has in fact a hardness higher than that of the coke formed by cracking of more conventional fillers, such as naphtha and gas oil.
Lorsque la couche de coke déposée sur les parois internes de l'installation a une épaisseur moyenne déterminée ou après que cette couche de coke ait éventuellement été durcie par l'un des procédés précités, on injecte dans cette installation des particules solides érosives qui vont être entrainées par la charge d'hydrocarbures et de vapeur d'eau et qui vont éliminer le coke nouvellement formé au fur et à mesure qu'il tend à se déposer sur la couche de coke précitée. Les quantités et dimensions et/ou masses des particules solides injectées sont déterminées pour provoquer l'élimination du coke nouvellement formé, tout en respectant la couche de protection déjà déposée sur les parois internes de l'installation. On utilise donc des particules solides érosives ayant un diamètre moyen inférieur à 250 μ environ de préférence compris entre 5 et 150 μm. le débit de ces particules est inférieur à 10% en poids de la charge d'hydrocarbures et de vapeur d'eau, et est compris entre 0,1 et 8 % en poids de cette charge, de préférence. On peut utiliser un mélange de deux types de particules, par exemple un premier type de particules ayant une masse moyenne et une granulométrie relativement faible (par exemple comprise entre 5 et 100 μm) le deuxième type de particules comprenant des particules de masse plus importante. Dans ce cas, les particules les plus lourdes amorcent l'érosion du coke nouvellement déposé, tandis que les particules les plus fines et les plus légères propagent cette érosion.When the layer of coke deposited on the internal walls of the installation has a determined average thickness or after this layer of coke has possibly been hardened by one of the abovementioned methods, erosive solid particles are injected into this installation which will be entrained by the load of hydrocarbons and water vapor and which will remove the newly formed coke as it tends to settle on the aforementioned coke layer. The quantities and dimensions and / or masses of the solid particles injected are determined to cause the elimination of the newly formed coke, while respecting the protective layer already deposited on the internal walls of the installation. We therefore use erosive solid particles having an average diameter less than 250 μ approximately preferably between 5 and 150 μm. the flow rate of these particles is less than 10% by weight of the hydrocarbon and water vapor charge, and is between 0.1 and 8% by weight of this charge, preferably. One can use a mixture of two types of particles, for example a first type of particles having an average mass and a relatively small particle size (for example between 5 and 100 μm) the second type of particles comprising particles of greater mass. In this case, the heavier particles initiate the erosion of the newly deposited coke, while the finer and lighter particles propagate this erosion.
Les particules solides utilisées peuvent être des particules sensiblement sphériques, par exemple de silice-alumine, telles que des particules de catalyseur de craquage cathalytique déjà usé. On peut également utiliser des particules de métal, par exemple de fer, d'acier, de nickel, d'un alliage contenant du nickel, etc, et d'autres particules plus dures et plus érosives (par exemple de catalyseur de craquage ou d'un alliage métallique réfractaire et dur) .The solid particles used can be substantially spherical particles, for example of silica-alumina, such as particles of already used cathalytic cracking catalyst. It is also possible to use particles of metal, for example iron, steel, nickel, a nickel-containing alloy, etc., and other harder and more erosive particles (for example of cracking catalyst or of '' a refractory and hard metal alloy).
Les particules solides circulant dans l'installation gagnent le ou les cyclones 28, où elles sont séparées des effluents gazeux avec une efficacité très élevée, puis sortent de chaque cyclone 28 par son conduit inférieur 32 pour gagner en alternance l'un et l'autre réservoirs 38, la vanne à volet 36 permettant de sélectionner le réservoir dans lequel les particules seront stockées. Quand l'un des réservoirs 38 est utilisé pour le stockage des particules solides, l'autre réservoir 38 peut être utilisé pour réinjecter ces particules dans l'installation. Pour cela, la vanne supérieure d'isolement 40 de ce réservoir est fermée, la partie supérieure du réservoir est isolée du conduit 30 de sortie des effluents gazeux du cyclone 28, et est reliée à la source de gaz sous pression 48, l'organe tournant 42 est entraîné en rotation et la vanne d'isolement inférieure 44 est ouverte.The solid particles circulating in the installation reach the cyclone (s) 28, where they are separated from the gaseous effluents with a very high efficiency, then leave each cyclone 28 by its lower duct 32 to gain alternately both tanks 38, the shutter valve 36 for selecting the tank in which the particles will be stored. When one of the tanks 38 is used for the storage of solid particles, the other tank 38 can be used to reinject these particles into the installation. For this, the upper isolation valve 40 of this tank is closed, the upper part of the tank is isolated from the conduit 30 for the outlet of the gaseous effluents of the cyclone 28, and is connected to the source of pressurized gas 48, the rotating member 42 is rotated and the lower isolation valve 44 is open.
Lorsque ce réservoir est vide, il peut être utilisé à nouveau pour le stockage des particules, tandis que les particules solides stockées dans l'autre réservoir 38 sont recyclées dans l'installation.When this tank is empty, it can be used again for the storage of the particles, while the solid particles stored in the other tank 38 are recycled in the installation.
Le fonctionnement de ces moyens de stockage et de recyclage de particules solides a été décrit plus en détail dans une autre Demande de Brevet des mêmes demandeurs déposée le même jour que la présente Demande de Brevet. En tant que de besoin, l'homme du métier pourra se reporter à cette autre Demande de Brevet, dont la description est incorporée ici par référence. On a représenté en figure 2 une variante de réalisation des moyens de stockage et de recyclage de particules solides. Les moyens représentés en figure 2 différent de ceux de la figure 1 en ce que les deux réservoirs 38 sont montés en série, et non plus en parallèle. En outre, une vanne à trois voies 64 permet de relier le réservoir inférieur 38, soit à la source de gaz sous pression 48 par l'intermédiaire d'une vanne d'arrêtThe operation of these means for storing and recycling solid particles has been described in more detail in another patent application from the same applicants filed on the same day as this patent application. If necessary, a person skilled in the art can refer to this other patent application, the description of which is incorporated here by reference. FIG. 2 shows an alternative embodiment of the means for storing and recycling solid particles. The means shown in Figure 2 different from those of Figure 1 in that the two tanks 38 are mounted in series, and no longer in parallel. In addition, a three-way valve 64 makes it possible to connect the lower reservoir 38, ie to the source of pressurized gas 48 by means of a stop valve.
66 soit au conduit 30 de sortie des effluents gazeux du cyclone 28 par l'intermédiaire d'une autre vanne d'arrêt 66.66 or to the conduit 30 for the outlet of the gaseous effluents from the cyclone 28 via another stop valve 66.
On a également prévu un conduit 68 d'amenée d'un gaz de barrage qui débouche en partie supérieure du réservoir supérieur 38. Ce gaz de barrage est exempt d'aromatiques lourds et peut être de la vapeur d'eau. Il permet d'éviter le cokage du réservoir supérieur 38 et de son tamis filtrant, en évitant la présence de gaz craqués.A conduit 68 is also provided for supplying a barrier gas which opens into the upper part of the upper reservoir 38. This barrier gas is free of heavy aromatics and may be water vapor. It makes it possible to avoid coking of the upper reservoir 38 and of its filtering screen, by avoiding the presence of cracked gases.
Pour le reste, les moyens sont les mêmes que ceux déjà décrits en référence à la figure 1 et le fonctionnement de cette variante de réalisation est sensiblement identique à celui des moyens correspondants de la figure 1, les deux réservoirs 38 étant toujours utilisés en alternance pour le stockage et le recyclage des particules solides.For the rest, the means are the same as those already described with reference to Figure 1 and the operation of this alternative embodiment is substantially identical to that of the corresponding means. of Figure 1, the two reservoirs 38 being always used alternately for the storage and recycling of solid particles.
La séparation des particules solides dans un cyclone peut être faite en deux étapes, dans le cas où les effluents gazeux pénétrant dans le cyclone comprendraient des traces de liquide :The separation of solid particles in a cyclone can be done in two stages, in the case where the gaseous effluents entering the cyclone include traces of liquid:
- une première étape où les effluents gazeux sont séchés (par exemple en sortie d'un premier cyclone par mélange avec un courant de gaz surchauffé et/ou par recyclage de particules sèches et chaudes) une seconde étape, de séparation des particules séchées.- A first step where the gaseous effluents are dried (for example at the outlet of a first cyclone by mixing with a stream of superheated gas and / or by recycling dry and hot particles) a second step, of separation of the dried particles.
La figure 3 représente des moyens de répartition ^ uniforme de particules solides dans les différents tubes 12 du four de vapocraquage. Le collecteur 14 d'alimentation des tubes 12 reçoit à son extrémité amont une charge d'hydrocarbures vaporisés et de vapeur d'eau qui se trouve par exemple à une température de l'ordre de 550"C et dans laquelle on a injecté une petite quantité de particules solides.3 shows means for distributing uniform solid particles ^ in the various tubes 12 of the steam cracking furnace. The manifold 14 for supplying the tubes 12 receives at its upstream end a charge of vaporized hydrocarbons and of water vapor which is, for example, at a temperature of the order of 550 "C and into which a small amount of solid particles.
Les tubes 12 du four forment une ou plusieurs rangées parallèles et débouchent à intervalles réguliers dans le collecteur 14. Celui-ci a une section qui décroit progressivement de son extrémité amont à son extrémité aval par rapport au sens d'écoulement de la charge, pour maintenir une vitesse minimum du mélange dans le collecteur et éviter les dépôts de -particules solides.The tubes 12 of the furnace form one or more parallel rows and emerge at regular intervals into the collector 14. The latter has a section which decreases progressively from its upstream end to its downstream end relative to the direction of flow of the charge, to maintain a minimum speed of the mixture in the collector and avoid deposits of solid particles.
L'extrémité de chaque tube 12 débouchant dans le collecteur 14 comprend un embout d'alimentation 70 situé dans le collecteur et dont la section d'entrée comprend un orifice 72 orienté vers l'extrémité amont du collecteur. Chaque tube 12 comprend, immédiatement en aval de l'embout d'alimentation 70, une restriction de section 74 telle qu'un col ou un venturi, permettant d'uniformiser et de rendre sensiblement constants les débits de gaz dans les tubes 12. Avantageusement, on utilise un venturi sonique.The end of each tube 12 opening into the manifold 14 comprises a supply nozzle 70 located in the manifold and the inlet section of which comprises an orifice 72 oriented towards the upstream end of the manifold. Each tube 12 comprises, immediately downstream of the supply nozzle 70, a section restriction 74 such as a neck or a venturi, making it possible to standardize and make the constants substantially constant. Gas flows in the tubes 12. Advantageously, a sonic venturi is used.
Une chambre de décantation 76 est prévue en amont du dernier tube 12 et en dessous du collecteur 14, pour recevoir des particules solides progressant le long de la génératrice inférieure du collecteur 14.A settling chamber 76 is provided upstream of the last tube 12 and below the collector 14, to receive solid particles progressing along the lower generatrix of the collector 14.
L'extrémité aval 78 de ce collecteur est reliée par un conduit 80 de dimensions appropriées, à un éjecto-compresseur 82 comprenant un conduit axial 84 d'alimentation d'un débit de gaz moteur tel que de la vapeur d'eau. Une vanne 86 permet de régler le débit de gaz moteur.The downstream end 78 of this manifold is connected by a duct 80 of suitable dimensions, to an ejector-compressor 82 comprising an axial duct 84 for supplying a flow of engine gas such as steam. A valve 86 makes it possible to adjust the flow rate of engine gas.
La sortie de 1'éjecto-compresseur 82 est raccordée par un conduit 88 à l'extrémité amont du collecteur 14 ou au conduit d'amenée de la charge d'hydrocarbures.The outlet of the ejector-compressor 82 is connected by a conduit 88 to the upstream end of the manifold 14 or to the conduit for supplying the hydrocarbon charge.
Avantageusement, la vanne 86 de réglage des débits de gaz moteur peut être commandée par un système 90 comprenant des moyens de détection de la température de peau des premiers et des derniers tubes 12 du four, pour asservir le débit de gaz moteur à la différence de ces températures.Advantageously, the valve 86 for adjusting the engine gas flow rates can be controlled by a system 90 comprising means for detecting the skin temperature of the first and last tubes 12 of the furnace, in order to control the flow of engine gas unlike these temperatures.
Ce dispositif fonctionne de' la façon suivante : le mélange d'hydrocarbures vaporisés, de vapeur d'eau et de particules solides, s'écoule avec une turbulence élevée dans le collecteur 14. La vitesse moyenne d'écoulement dans ce collecteur est comprise entre 20 et 120 m/s, par exemple entre 30 et 80 m/s et est notablement inférieure à la vitesse de circulation dans les tubes 12 qui est comprise entre 130 et 300 m/s environ (en particulier entre 160 et 270 m/s) .This device operates as' follows: The mixture of vaporized hydrocarbons, water vapor and solid particles, flows with high turbulence in the manifold 14. The mean flow velocity in the manifold is between 20 and 120 m / s, for example between 30 and 80 m / s and is notably lower than the circulation speed in the tubes 12 which is between 130 and 300 m / s approximately (in particular between 160 and 270 m / s ).
La vitesse d'écoulement dans le collecteur 14 est suffisante pour éviter toute séparation gaz-solides dans le collecteur, sauf pour certaines particules lourdes, qui peuvent progresser le long de la génératrice inférieure du collecteur.The flow speed in the collector 14 is sufficient to avoid any gas-solid separation in the collector, except for certain particles heavy, which can progress along the lower generator of the collector.
Le prélèvement d'une fraction du débit gaz- particules solides à l'extrémité aval du collecteur, transforme celui-ci en un collecteur de longueur infinie, d'où il résulte que l'extrémité aval du collecteur n'a plus* d'influence sensible sur la répartition du débit gaz-particules dans les différents tubes 12, qu'il soient proches ou éloignés de l'extrémité aval du collecteur. L'amenée d'un débit de gaz-moteur, par exemple de la vapeur d'eau, dans l'éjecteur 82 permet de prélever la fraction voulue du débit gaz-solides dans le collecteur et de recomprimer cette fraction pour la recycler par injection à l'extrémité amont du collecteur. Le système 90 permet de régler le débit de gaz moteur par action sur la vanne 86, ce qui permet de régler l'alimentation en particules solides des premiers tubes par rapport à celle des derniers tubes et donc de corriger une éventuelle irrégularité de répartition, décelée par des différences entre les températures de peau de ces tubes.Taking a fraction of the gas-solid particle flow rate at the downstream end of the collector transforms it into a collector of infinite length, from which it follows that the downstream end of the collector no longer * significant influence on the distribution of the gas-particle flow rate in the various tubes 12, whether they are close to or distant from the downstream end of the manifold. The supply of an engine gas flow rate, for example water vapor, into the ejector 82 makes it possible to take the desired fraction from the gas-solid flow rate in the manifold and to recompress this fraction for recycling by injection. at the upstream end of the manifold. The system 90 makes it possible to adjust the flow rate of engine gas by action on the valve 86, which makes it possible to adjust the supply of solid particles to the first tubes relative to that of the last tubes and therefore to correct any irregularity in distribution detected. by differences between the skin temperatures of these tubes.
Les restrictions de section 74 formées à l'extrémité amont des tubes 12 ont pour effet d'uniformiser et de rendre sensiblement constants les débits gazeux qui circulent dans ces tubes. Il en résulte une possibilité de régulation automatique du nettoyage de ces tubes par les particules solides. En effet, si un tube s'encrasse de manière anormale, avec obstruction partielle par du coke, le maintien du débit gazeux assuré par les restrictions 74 conduira à augmenter la vitesse de circulation et donc l'efficacité érosive des particules.The section restrictions 74 formed at the upstream end of the tubes 12 have the effect of standardizing and making substantially constant the gas flow rates which circulate in these tubes. This results in a possibility of automatic regulation of the cleaning of these tubes by solid particles. Indeed, if a tube clogs abnormally, with partial obstruction by coke, the maintenance of the gas flow ensured by the restrictions 74 will lead to increasing the speed of circulation and therefore the erosive efficiency of the particles.
On a prévu également, pour régulariser et répartir correctement le débit gaz-particules dans les différents tubes, un embout d'alimentation factice 92 placé en amont des premiers tubes, et qui est identique aux embouts d'alimentation 70 de ces tubes. Les premiers tubes 12 se trouvent ainsi, du point de vue aérodynamique, dans la même situation que les tubes suivants. L'invention permet donc de rendre continu ou sensiblement continu le fonctionnement des installations de vapocraquage, et est applicable à divers types de fours, en particulier les fours monopasses, à tubes rectilignes, et les fours à plusieurs passes, à coudes à angles droits. A dummy supply nozzle 92 placed upstream of the first tubes, and which is identical, is also provided, in order to regulate and correctly distribute the gas-particle flow in the different tubes. to the supply ends 70 of these tubes. The first tubes 12 are thus, from the aerodynamic point of view, in the same situation as the following tubes. The invention therefore makes it possible to make the operation of steam cracking installations continuous or substantially continuous, and is applicable to various types of ovens, in particular single-pass ovens, with straight tubes, and ovens with several passes, with elbows at right angles.

Claims

REVENDICATIONS
1. Procédé de vapocraquage d'hydrocarbures, consistant à faire circuler à vitesse élevée une charge d'hydrocarbures et de vapeur d'eau dans une installation comprenant au moins un four (10) de vapocraquage à tubes (12) et des moyens (16) de trempe indirecte des effluents gazeux sortant du four, et à injecter dans l'installation des particules solides érosives véhiculées par un courant de gaz à vitesse élevée pour éviter ou limiter le cokage de cette installation, caractérisé en ce qu'il consiste à ajouter lesdites particules solides à la charge d'hydrocarbures et de vapeur d'eau circulant dans l'installation, après qu'une couche de coke d'épaisseur moyenne sensiblement déterminée se soit déjà formée sur les parois internes de l'installation, en particulier sur les parois internes des tubes (12) du four, les quantités, dimensions et/ou masses de particules solides étant déterminées de façon à ce que ces particules circulant dans le four préservent sensiblement ladite couche de coke et éliminent par érosion au moins la plus grande partir du coke qui tendrait à se déposer, au fur et à mesure de sa formation, sur la couche de coke précitée.1. A method of steam cracking of hydrocarbons, consisting in circulating at high speed a charge of hydrocarbons and water vapor in an installation comprising at least one steam cracking oven (10) with tubes (12) and means (16 ) indirect quenching of the gaseous effluents leaving the oven, and to inject into the installation erosive solid particles conveyed by a stream of gas at high speed to avoid or limit the coking of this installation, characterized in that it consists in adding said solid particles charged with hydrocarbons and water vapor circulating in the installation, after a layer of coke of substantially determined average thickness has already formed on the internal walls of the installation, in particular on the internal walls of the tubes (12) of the furnace, the quantities, dimensions and / or masses of solid particles being determined so that these particles circulating in the furnace preserve sensitivity said coke layer and eradicate at least the greatest amount of coke which would tend to deposit, as it is formed, on the aforementioned coke layer.
2. Procédé selon la revendication 1, caractérisé en ce qu'il consiste à mesurer les pertes de charge d'au moins certains tubes du four, à mesurer le débit de la charge d'hydrocarbures ou de vapeur d'eau, à corriger les valeurs des pertes de charge mesurées dans les tubes en fonction du débit mesuré de la charge d'hydrocarbures ou de vapeur d'eau, et à réguler ces pertes de charge par variation des quantités de particules solides injectées dans l'installation.2. Method according to claim 1, characterized in that it consists in measuring the pressure drops of at least certain tubes of the furnace, in measuring the flow rate of the hydrocarbon or water vapor charge, in correcting the pressure drop values measured in the tubes as a function of the measured flow rate of the hydrocarbon or water vapor load, and to regulate these pressure drops by varying the quantities of solid particles injected into the installation.
3. Procédé selon la revendication 2, caractérisé en ce que les pertes de charge corrigées dans les tubes sont maintenues sensiblement égales à une valeur comprise entre 130 et 300 % environ de la perte de charge corrigée dans un tube non coke.3. Method according to claim 2, characterized in that the pressure losses corrected in the tubes are maintained substantially equal to one value between approximately 130 and 300% of the pressure drop corrected in a non-coke tube.
4. Procédé selon l'une des revendications précédentes, caractérisé en ce que l'épaisseur moyenne de4. Method according to one of the preceding claims, characterized in that the average thickness of
5 ladite couche de coke est comprise entre 0,5 et 4 mm environ.5 said layer of coke is between 0.5 and 4 mm approximately.
5. Procédé selon l'une des revendications précédentes, caractérisé en ce qu'il consiste à augmenter la dureté de ladite couche de coke en soumettant celle-ci 0 à une élévation de température comprise entre 20 et 140 °C au dessus de sa température lors du vapocraquage ultérieur.5. Method according to one of the preceding claims, characterized in that it consists in increasing the hardness of said coke layer by subjecting it 0 to a temperature rise between 20 and 140 ° C above its temperature during subsequent steam cracking.
6. Procédé selon l'une des revendications précédentes, caractérisé en ce qu'il consiste à faire 5 fonctionner l'installation avec des hydrocarbures particuliers différents de ceux de la charge de l'installation pendant la formation de ladite couche de coke pour augmenter la dureté de celle-ci.6. Method according to one of the preceding claims, characterized in that it consists in operating the installation with particular hydrocarbons different from those of the feed of the installation during the formation of said coke layer to increase the hardness of it.
7. Procédé selon la revendication 6, 0 caractérisé en ce que les hydrocarbures particuliers précités sont des hydrocarbures légers, du type Cl à C4 tels par exemple que de l'éthane.7. Method according to claim 6, 0 characterized in that the aforementioned particular hydrocarbons are light hydrocarbons, of the Cl to C4 type such as for example ethane.
8. Procédé selon l'une des revendications précédentes, caractérisé en ce que les particules solides 5 injectées dans l'installation ont un diamètre moyen inférieur à 250 μm environ, par exemple compris entre 5 et 150 μm, le débit moyen de particules injectées dans l'installation étant inférieur à 10% en poids du débit d'hydrocarbures et de vapeur d'eau à craquer.8. Method according to one of the preceding claims, characterized in that the solid particles 5 injected into the installation have an average diameter of less than approximately 250 μm, for example between 5 and 150 μm, the average flow rate of particles injected into the installation being less than 10% by weight of the flow of hydrocarbons and steam to be cracked.
30 9. Procédé selon l'une des revendications précédentes, caractérisé en ce qu'il consiste à séparer les particules solides des effluents gazeux en sortie des moyens (16) de trempe indirecte, grâce à des moyens (28) de séparation gaz-solides du type cyclone, à stocker dans9. Method according to one of the preceding claims, characterized in that it consists in separating the solid particles from the gaseous effluents at the outlet of the means (16) of indirect quenching, using means (28) of gas-solid separation. cyclone type, to be stored in
~~ un réservoir (38) lesdites particules solides sortant des moyens de séparation 28, et à relier périodiquement ce réservoir à une source de gaz sous pression (48) et à un conduit (46) d'injection des particules dans l'installation, pour le recyclage de ces particules. ~~ a reservoir (38) said solid particles leaving the separation means 28, and to periodically connect this reservoir to a source of pressurized gas (48) and to a pipe (46) for injecting particles into the installation, for recycling these particles.
10. Procédé selon la revendication 9, caractérisé en ce qu'il consiste à stocker les particules solides en sortie des moyens de séparation (28) dans deux réservoirs (38) agencés en série ou en parallèle.10. Method according to claim 9, characterized in that it consists in storing the solid particles at the outlet of the separation means (28) in two reservoirs (38) arranged in series or in parallel.
11. Procédé selon l'une des revendications précédentes, caractérisé en ce qu'il consiste à faire passer les particules solides dans un collecteur (14) d'alimentation des tubes (12) du four de vapocraquage, à répartir les particules solides dans ces tubes au moyen d'embouts (70) prévus à l'extrémité des tubes et faisant saillie dans le collecteur (14), ces embouts ayant une section d'entrée (72) orientée vers l'amont du collecteur, et à uniformiser les répartitions de particules solides dans les tubes en prélevant à l'extrémité aval du collecteur, une fraction du débit gaz-particules solides circulant dans le collecteur. 11. Method according to one of the preceding claims, characterized in that it consists in passing the solid particles through a collector (14) supplying the tubes (12) of the steam cracking oven, in distributing the solid particles in these tubes by means of end pieces (70) provided at the end of the tubes and projecting into the manifold (14), these end pieces having an inlet section (72) oriented upstream of the manifold, and to standardize the distributions of solid particles in the tubes by taking at the downstream end of the manifold, a fraction of the gas-solid particle flow circulating in the manifold.
12. Procédé selon l'une des revendications précédentes, caractérisé en ce qu'on fait circuler dans l'installation deux types de particules ayant des masses notablement différentes. 12. Method according to one of the preceding claims, characterized in that circulates in the installation two types of particles having significantly different masses.
EP90907103A 1989-04-14 1990-04-13 Process for steam-cracking hydrocarbons Expired - Lifetime EP0425633B1 (en)

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
FR8904986A FR2645873B1 (en) 1989-04-14 1989-04-14 METHOD FOR DECOKING A HYDROCARBON VAPOCRACKING PLANT, AND CORRESPONDING VAPOCRACKING PLANT
FR8904986 1989-04-14
FR8909375 1989-07-12
FR8909375A FR2649761B1 (en) 1989-07-12 1989-07-12 METHOD AND DEVICE FOR DISTRIBUTING A GAS FLOW CHARGED WITH SOLID PARTICLES
FR8913070A FR2652817B1 (en) 1989-10-06 1989-10-06 PROCESS AND PLANT FOR VAPOCRACKING HYDROCARBONS, WITH RECYCLING OF EROSIVE SOLID PARTICLES.
FR8913070 1989-10-06
PCT/FR1990/000273 WO1990012852A1 (en) 1989-04-14 1990-04-13 Process for steam-cracking hydrocarbons

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Publication Number Publication Date
EP0425633A1 true EP0425633A1 (en) 1991-05-08
EP0425633B1 EP0425633B1 (en) 1994-07-27

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EP90907103A Expired - Lifetime EP0425633B1 (en) 1989-04-14 1990-04-13 Process for steam-cracking hydrocarbons

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JP (1) JP2768553B2 (en)
AT (1) ATE109194T1 (en)
DE (1) DE69011037T2 (en)
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US7479537B2 (en) 1996-10-31 2009-01-20 Abbott Laboratories Inc. Reagents and methods useful for detecting diseases of the breast
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EP2311993A2 (en) 2002-07-26 2011-04-20 Abbott Laboratories Method of detecting and quantifying hepatitis C virus
WO2011068680A1 (en) 2009-12-03 2011-06-09 Abbott Laboratories Assay for diagnosis of cardiac myocyte damage
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WO2011068681A1 (en) 2009-12-02 2011-06-09 Abbott Laboratories ASSAY FOR CARDIAC TROPONIN-T (cTnT)
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US8173382B2 (en) 2006-10-26 2012-05-08 Abbott Laboratories Assay for cardiac troponin autoantibodies
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KR100877007B1 (en) * 2001-06-19 2009-01-07 지멘스 브이에이아이 메탈스 테크놀로지스 게엠베하 앤드 컴퍼니 Method and device for treating particulate material, and process for reducing the amount of gas which flows out of a separation chamber
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JP2768553B2 (en) 1998-06-25
ATE109194T1 (en) 1994-08-15
US5177292A (en) 1993-01-05
DK0425633T3 (en) 1994-11-28
WO1990012852A1 (en) 1990-11-01
EP0425633B1 (en) 1994-07-27
DE69011037D1 (en) 1994-09-01
ES2063353T3 (en) 1995-01-01
JPH03505605A (en) 1991-12-05
DE69011037T2 (en) 1994-11-24

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