US2978521A

US2978521A - Process and apparatus for treatment of hydrocarbons

Info

Publication number: US2978521A
Application number: US739553A
Authority: US
Inventors: Frederic F A Braconier; Jean J L E Riga
Original assignee: Societe Belge de lAzote et des Produits Chimiques du Marly SA
Current assignee: Societe Belge de lAzote et des Produits Chimiques du Marly SA
Priority date: 1957-06-07
Filing date: 1958-06-03
Publication date: 1961-04-04
Anticipated expiration: 1978-04-04
Also published as: DE1070167B; GB850420A

Description

April 4, 1961 F. F. A. BRACONIER ETAL 2,978,521

PROCESS AND APPARATUS FOR TREATMENT OF HYDROCARBONS Filed June 3, 1958 INVENTORS: v A'PvEP/c EA 5646mm? JA/l JAE. /P/ ,4

United States Patent PROCESS AND APPARATUS FOR TREATMENT OF HYDROCARBONS Frdric F. A. Braconier, Plainevaux, and Jean J. L. E. Riga, Liege, Belgium, assignors to Societe Belge de lAzote et des Produits Chimiques du Marly, Liege, Belgium Filed June 3, 1958, Ser. No. 739,553

Claims priority, application Austria June 7, '1957 7 Claims. (Cl. 260-679) This invention relates to a process and an apparatus for quenching hot gases, and is particularly applicable for quenching the hot reaction gases in the thermal decomposition of the hydrocarbons for production of acetylene and/ or olefines.

To prepare acetylene and/or olefines from more saturated hydrocarbons, these are heated in the gaseous or vaporized state at a high temperature. To obtain relatively high yields of unsaturated hydrocarbons, however, it is important to control the heating time within very narrow limits. It has been shown that, when pyrolyzing methane, the yield of ethylene was almost doubled by reducing the reaction time from 0.014 to 0.0023 sec., at 1400 C., and the yield of acetylene increased about 8% with a pyrolysis time of 0.0029 sec. instead of 0.0085 sec. (of. English Patent 709,035). At these high temperatures, the pyrolysis reaction tends to proceed beyond the formation of the desired unsaturated hydrocarbons, with resulting production of carbon, hydrogen, etc.

The pyrolysis time is limited by quenching the formed gases down to a temperature as low as 500 to 600 C., at which the desired unsaturated hydrocarbons are more stable.

Numerous processes have been proposed for that purpose. Transversely spraying cold water into the pyrolysis gases is the most economical method, although not always satisfactory on an industrial scale.

If the quenching water penetrates into the pyrolysis zone, some of the evolving gases are prematurely cooled and the yield of unsaturated hydrocarbons thereby reduced.

Thus, with a radial sprayer positioned axially at the end of the pyrolysis chamber, the projected water hits the wall of the pyrolysis chamber and splashes back in all directions. The kinetic energy of this Water suflicient to cause splashing is used to prevent serious deviation of the water jets by the gaseous stream.

Another problem is encountered, when jets from the periphery of the pyrolysis zone are used. These meet counter-current in a central area, where they tend to create eddies, by which a portion of the quenching liquid is drawn back into the pyrolysis zone in a pattern which may vary from a water cone to a mist of droplets depending upon whether the quench spraying is directed transversely or on slightly inclined directions with respect to the flow direction of the gaseous stream.

With previous devices, such eddies have been experienced even when said central spray is combined with the introduction of water through perforations situated along the wall of the pyrolysis zone or with a trickling of water therealong at the end of said zone.

According to the present invention, these shortcomings are overcome by a simple and original process and device, providing across the flow of hot gases, a full transverse sheet of water which iskept entirely beyond a clearly defined, two-dimensional boundary. A first water layer is formed by jets directed toward the longitudinal axis Patented Apr. 4, 19 1 of the pyrolysis zone, originating from sprayers peripherally situated at the end of said pyrolysis zone; and ad vantageously, a second water layer covers the first layer.

According to this invention, it is advantageous that the water sprayers should conform to the following when using a vertical furnace provided with a circular pyrolysis chamber.

(1) Slit openings for spraying water in blades towards the axis of the reaction zone, each blade having a spread of about 60.

(2) A truncated conical wall around the quenching zone and having a diameter greater than that of the When, respecting these conditions, the water jets originating from each sprayer under pressure, are arranged like the blades of a fan, overlapping horizontally they give a full and stable water layer, which extends slightly conically downward from the wall. From this water layer, emerges, at the bottom, a Water cone formed by the juncture of the several blades and, at the head of the cone, a very light mist of water droplets forms which has substantially no detrimental effect on the pyrolysis reaction.

These results are further improved if the first said water layer is covered with a second layer which prevents formation of the mist by an effect similar to a shearing. This second layer may originate most advantageously from the water screen which surrounds the reaction zone and protects the internal face of the wall of the pyrolysis chamber against carbon deposits(e.g., as described in the copending application, Serial No. 715,404, filed February 14, 1958).

'The accompanying drawings illustrate this invention 7 with the sprayers disposed therein.

distributor 1 having the form of a cylindrical refractory. disc traversed byparallel passages Z for distributing the reaction gaseous mixture into the combustion chamber within, and delimited by, an inner wall 4 of the doublewalled chamber. On its outer periphery, the distributor 1 is provided with a hollow metallic ring 5, having in its bottom an annular slit opening 6.

The inner wall 4 terminates at the bottom end of the combustion chamber.

diameter greater than that of the combustion zone and inclined on an angle of 15 with respect to the axis of I the pyrolysis furnace. Sprayers 7 are disposed around the periphery of this conical ring 8. As indicated in Fig-,

Below it, the outer wall 8 is. flared to form a truncated conical ring 8 having a mean ure 2, the injection orifice slits 7 of these sprayers are slightly inclined, advantageously on an angle of 2, with respect to the horizontal (normal) plane.

The preheated mixture of hydrocarbon and oxygen is introduced into the combustion zone 3 where it is ignited, through passages 2, from the usual mixing chamber or other reactant supply device. Water is injected under pressure through the hollow metallic ring and ejected through the slit 6, along the wall 4 of the combustion chamber. Water is supplied through suitable piping to the sprayers 7 under suflrcient pressure so that it fans out from the slit-orifices 7 in the form of thin blades having a 60 angle of spread, and slightly inclined downward, i.e., in the direction of the flow of the pyrolysis gases.

The sprayers 7 are spaced around the ring 8 to assure that the water blades overlap as indicated in Figure 3, thus forming a full and homogeneous layer of the coolant at least co-extensive with the cross section of the pyrolysis zone, as represented in Figure 3.

Water, supplied to the annular chamber 5 through pipe 5', passes out through slit 6 to form a liquid screen protecting the wall 4 against heat and/or carbon deposits. This water runs down onto said first layer, by which it is picked up and carried across the chamber, thereby obtaining a stable and fully efiicient sheet resulting from said both layers and having a substantially uniform upper surface. The water in said sheet is, of course, moving transversely of the gas flow and at such velocity that its path is little affected by the gas flow and gravity. The gas flows on through the interstices between the Water but is impelled by it toward the center, so that there is a greater exit velocity of the gas near the center, which aids the carrying olf of any splash formed by impinging of opposed blades in the control area. To the extent that the Water goes on to impinge on the opposite wall 8, it is below the jets from sprayers 7, so that splash does not get back into the pyrolysis zone.

In one example of using this process for quenching pyrolysis gases, at pyrolysis gas having an acetylene content of 8.4% (calculated on dry gas) was obtained by partial combustion of methane, while with previous quenching processes and apparatus, this content was only 8%.

What we claim is:

1. In a process for quenching hot pyrolysis gases in a vertically disposed cylindrical hydrocarbon pyrolysis reaction chamber to arrest a pyrolysis reaction therein at a predetermined level of said chamber with a transversely directed sprayed layer of water and while avoiding premature cooling contact of said gases above said predetermined level by upwardly diffusing or misting of water from said transverse layer resulting from eddying therein and impingement thereagainst by axially directed water flow in said reaction chamber, the steps which comprise establishing and surrounding said pyrolysis reaction in said reaction chamber with an axially and downwardly flowing screen of water extending substantially throughout the length of said chamber and at least to said predetermined level for quenching thereat, spraying a generally transversely directed continuous layer of water across said chamber toward the axis thereof from around the outside thereof and substantially at said predetermined level therein, said spraying being directed downwardly at an angle of about l015 with respect to a transverse plane through said chamber normal to the direction of flow of said gases therein for producing a generally depressed conical configuration in said transverse water layer whereby upward dilfusion of Water above said predetermined level and resulting from eddying and misting occurring at the center of said layer from the meeting of oppositely radially directed streams of fiow therein is avoided to prevent said premature cooling of said pyrolysis gases above said predetermined level in said chamber, and originating said spraying of said conical transverse water layer from a plurality of individual sprays spaced radially outside the periphery of said axially flowing screen of water for substantially complete consolidation of individual spray streams of water from said individual sprays into said continuous layer prior to impingement thereon of said axially flowing screen of water for entraining in said conical layer for transverse flow therewith water from said axial screen for avoiding additional upward eddying and misting at the juncture of said screen and said layer for also preventing said premature cooling contact of said pyrolysis gases above said predetermined level in said chamber, said plurality of individual sprays forming said conical transverse water layer being each formed as a separate fiat fan-like spray the cross section of Which is tilted about the radial axis thereof whereby the higher edge of one spray overlaps the lower edge of the adjacent spray prior to direct impingement or interference in a horizontal plane between water droplets in one spray with and against water droplets in the next adjacent spray.

2. A process as recited in claim 1 in which said individual fan-like sprays of water for forming said conical transverse water layer are directed radially inwardly of said chamber and axially downwardly thereof at an angle of about l0-15.

3. A process as recited in claim 1 in which the angle at which said cross section of each of said fan-like sprays is tilted about said radial axis thereof is approximately 2-5 with respect to said radial axis of each said spray.

4. A process as recited in claim 1 in which the angle at the radially outer apex of each of said individual fan-like sprays of water forming said conical transverse water layer is approximately 60 effecting substantially complete overlapping and consolidation of said individual sprays into said continuous transverse conical layer prior to impingement thereof on said axially flowing screen of Water within said combustion chamber.

5. In apparatus for controlling a pyrolysis decomposition reaction of hydrocarbons into less saturated hydrocarbons in a cylindrical pyrolysis reaction chamber and for quenching hot pyrolysis gases to arrest said pyrolysis reaction at a predetermined level in said reaction chamber, the combination which comprises means for forming a substantially continuous screen of Water within said reaction chamber for enclosing said pyrolysis gases and flowing axially Within said chamber in the same direction as the flow of said gases therein at least to said predetermined level for quenching said gases in said chamber, a plurality of radially inwardly directed water spray jet nozzles around said reaction chamber disposed on a transverse plane therethrough substantially at said predetermined quenching level axially thereof, said nozzles being disposed around said reaction chamber radially outside the periphery thereof defined by said axially flowing screen of water, means for mounting said plurality of nozzles in said apparatus for directing transversely overlapping sprays of water radially inwardly into said chamber and downwardly inclined therein at an angle of about 10-15 with respect to a transverse plane to said chamber normal to said flow of said gases therein, each of said plurality of radially inwardly directed jet nozzles having an outlet orifice having a narrow elongated transverse slot for producing said sprays of water in the form of a fiat fan-like spray into said chamber, and with each of said orifice slots angularly inclined about the axis of said orifice and with respect to a transverse plane through said chamber whereby individual sprays of water from said orifice slot into said chamber overlap before water from one said spray directly impinges upon water from an adjacent said spray.

6. Apparatus as recited in claim 5 in which the angle at which said orifice slots are inclined about said axis of said orifice is approximately 2-5 for effecting substantially complete overlapping of said fan-like sprays.

7. Apparatus as recited in claim 5 in which said spray orifice slots are configured to provide a substantially transverse spreading of said fan-like water sprays therefrom having an angle of about 60 at the radially outer apex of each spray effecting substantially complete overlapping of adjacent individual sprays from said orifices for forming a substantially continuous transverse layer of Water therefrom around said chamber at least in the area thereof where said axially flowing screen of water impinges upon said transverse layer of water formed from said individual sprays.

References Cited in the file of this patent UNITED STATES PATENTS Metzger Nov. 7, 1939 Jones Mar. 16, 1954 Kosbahn et a1 Sept. 27, 1955 Schutte Apr. 16, 1957 MacQueen Nov. 12, 1957 FOREIGN PATENTS Germany May 23, 1957

Claims

1. IN A PROCESS FOR QUENCHING HOT PYROLYSIS GASES IN A VERTICALLY DISPOSED CYLINDRICAL HYDROCARBON PYROLYSIS REACTION CHAMBER TO ARREST A PYROLYSIS REACTION THEREIN AT A PREDETERMINED LEVEL OF SAID CHAMBER WITH A TRANSVERSELY DIRECTED SPRAYED LAYER OF WATER AND WHILE AVOIDING PREMATURE COOLING CONTACT OF SAID GASES ABOVE SAID PREDETERMINED LEVEL BY UPWARDLY DIFFUSING OR MISTING OF WATER FROM SAID TRANSVERSE LAYER RESULTING FROM EDDYING THEREIN AND IMPINGEMENT THEREAGAINST BY AXIALLY DIRECTED WATER FLOW IN SAID REACTION CHAMBER, THE STEPS WHICH COMPRISE ESTABLISHING AND SURROUNDING SAID PYROLYSIS REACTION IN SAID REACTION CHAMBER WITH AN AXIALLY AND DOWNWARDLY FLOWING SCREEN OF WATER EXTENDING SUBSTANTIALLY THROUGHOUT THE LENGTH OF SAID CHAMBER AND AT LEAST TO SAID PREDETERMINED LEVEL FOR QUENCHING THEREAT, SPRAYING A GENERALLY TRANSVERSELY DIRECTED CONTINUOUSE LAYER OF WATER ACROSS SAID CHAMBER TOWARD THE AXIS THEREOF FROM AROUND THE OUTSIDE THEREOF AND SUBSTANTIALLY AT SAID PREDETERMINED LEVEL THEREIN, SAID SPRAYING BEING DIRECTED DOWNWARDLY AT AN ANGLE OF ABOUT 10$-15$ WITH RESPECT TO A TRANSVERSE PLANE THROUGH SAID CHAMBER NORMAL TO THE DIRECTION OF FLOW OF SAID GASES THEREIN FOR PRODUCING A GENERALLY DEPRESSED CONICAL CONFIGURATION IN SAID TRANSVERSE WATER LAYER WHEREBY UPWARD DIFFUSION OF WATER ABOVE SAID PREDETERMINED LEVEL AND RESULTING FROM EDDYING AND MISTING OCCURRING AT THE CENTER OF SAID LAYER FROM THE MEETING OF OPPOSITELY RADIALLY DIRECTED STREAMS OF FLOW THEREIN IS AVOIDED TO PREVENT SAID PREMATURE COOLING OF SAID PYROLYSIS GASES ABOVE SAID PREDETERMINED LEVEL IN SAID CHAMBER, AND ORIGINATING SAID SPRAYING OF SAID CONICAL TRANSVERSE WATER LAYER FROM A PLURALITY OF INDIVIDUAL SPRAYS SPACED RADIALLY OUTSIDE THE PERIPHERY OF SAID AXIALLY FLOWING SCREEN OF WATER FOR SUBSTANTIALLY COMPLETE CONSOLIDATION OF INDIVIDUAL SPRAY STREAMS OF WATER FROM SAID INDIVIDUAL SPRAYS INTO SAID CONTINUOUS LAYER PRIOIR TO IMPINGEMENT THEREON OF SAID AXIALLY FLOWING SCREEN OF WATER FOR ENTRAINING IN SAID CONICAL LAYER FOR TRANSVERSE FLOW THEREWITH WATER FROM SAID AXIAL SCREEN FOR AVOIDING ADDITIONAL UPWARD EDDYING AND MISTING AT THE JUNCTURE OF SAID SCREEN AND SAID LAYER FOR ALSO PREVENTING SAID PREMATURE COOLING CONTACT OF SAID PYROLYSIS GASES ABOVE SAID PREDETERMINED LEVEL IN SAID CHAMBER, SAID PLURALITY OF INDIVIDUAL SPRAYS FORMING SAID CONICAL TRANSVERSE WATER LAYER BEING EACH

5. IN APPARATUS FOR CONTROLLING A PYROLYSIS DECOMPOSITION REACTION OF HYDROCARBONS INTO LESS SATURATED HYDROCARBONS IN A CYLINDRICAL PYROLYSIS REACTION CHAMBER AND FOR QUENCHING HOT PYROLYSIS GASES TO ARREST SAID PYROLYSIS REACTION AT A PREDETERMINED LEVEL IN SAID REACTION CHAMBER, THE COMBINATION WHICH COMPRISES MENS FOR FORMING A SUBSTANTIALLY CONTINUOUS SCREEN OF WATER WITHIN SAID REACTION CHAMBER FOR ENCLOSING SAID PYROLYSIS GASES AND FLOWING AXIALLY WITHIN SAID CHAMBER IN THE SAME DIRECTION AS THE FLOW OF SAID GASES THEREIN AT LEAST TO SAID PREDETERMINED LEVEL FOR QUENCHING SAID GASES IN SAID CHAMBER, A PLURALITY OF RADIALLY INWARDLY DIRECTED WATER SPRAY JET NOZZLES AROUND SAID REACTION CHAMBER DISPOSED ON A TRANSVERSE PLANE THERETHROUGH SUBSTANTIALLY AT SAID PREDETERMINED QUENCHING LEVEL AXIALLY THEREOF, SAID NOZZLES BEING DISPOSED AROUND SAID REACTION CHAMBER RADIALLY OUTSIDE THE PERIPHERY THEREOF DEFINED BY SAID AXIALLY FLOWING SCREEN OF WATER, MEANS FOR MOUNTING SAID PLURALITY OF NOZZLES IN SAID APPARATUS FOR DIRECTING TRANSVERSELY OVERLAPPING SPRAYS OF WATER RADIALLY INWARDLY INTO SAID CHAMBER AND DOWNWARDLY INCLINED THEREIN AT AN ANGLE OF ABOUT 10$-15$ WITH RESPECT TO A TRANSVERSE PLANE TO SAID CHAMBER NORMAL TO SAID FLOW OF SAID GASES THEREIN, EACH OF SAID PLURALITY OF RADIALLY INWARDLY DIRECTED JET NOZZLES HAVING AN OUTLET ORIFICE HAVING A NARROW ELONGATED TRANSVERSE SLOT FOR PRODUCING SAID SPRAYS OF WATER IN THE FORM OF A FLAT FAN-LIKE SPRAY INTO SAID CHAMBER, AND WITH EACH OF SAID ORIFICE SLOTS ANGULARLY INCLINED ABOUT THE AXIS OF SAID ORIFICE AND WITH RESPECT TO A TRANSVERSE PLANE THROUGH SAID CHAMBER WHEREBY INDIVIDUAL SPRAYS OF WATER FROM SAID ORIFICE SLOT INTO SAID CHAMBER OVERLAP BEFORE WATER FROM ONE SAID SPRAY DIRECTLY IMPINGES UPON WATER FROM AN ADJACENT SAID SPRAY.