BE475366A - - Google Patents

Description

       

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  "Improvements in a method of cracking hydrocarbons or relating to this method."
The present invention relates to the cracking of hydrocarbons and, more particularly, to a novel thermal cracking method and pulley apparatus of normally liquid hydrocarbons as well as normally gaseous hydrocarbons.

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   In the art of hydrocarbons for high olefin production, the fear of serious carbon deposition together with the fear of ethylene polymerization has resulted in delaying improvements and, consequently, this technique is appreciably behind the technique quite similar to the cracking of hydrocarbons with a view to the manufacture of hydrogen. The processes for the manufacture of ethylene are, in fact ,. conditioned by the use of the most favorable raw materials: generally propane, kerosene and diesel or at most steam distillates of heavier oils.

   The processes using "whole" petroleum oils are clearly lacking, and the reaction control facilities which exist in the art of hydrogen production are not found in the majority of the processes for the production of hydrogen. manufacture of ethylene, due to the possibly unverified opinion that ethylene is more difficult to obtain. The technique therefore lacks a practical and flexible process similar to that employed in the production of hydrogen and capable of adapting to the use of "whole" petroleum oils to produce compounds. liquids as well as olefins by controlling the reactions.



   In the art of ethylene production, typical processes are those of NAGEL (US Patent No. 2,111,899) and GREBE (US Patent No. 2,176,962) based on the principles of instant mixing and reaction. separate streams of hydrocarbon and steam preheated to an elevated temperature so as to provide all the heat required.

   Another typical process for the manufacture of ethylene is carried out in some type of refractory regenerative apparatus, such as, for example, that shown in US Pat. No. 2,208,123 to DUNCAN. not

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In opposition to the instantaneous heating method of NAGEL and GREBE or the regenerative types of DUNCAN, there are processes of the tubular type, in which one obtains: olefins from hydrocarbons containing sulfur and steam in chrome nickel alloy tubes under controlled temperature conditions.

   The patents granted to WIETZEL (1,934,836) and BALCAR (2,218,495) and the complementary patent to 21,521 granted to J.H. SHAPLEIGH disclose representative processes of this type. WIETZEL patents the use of the chromium nickel alloy in the catalytic cracking of hydrocarbons with steam according to a technique using gases containing sulfur within the limits permitted by the catalysts in use.

     SHAPLEIGH patents a process for treating fluid reactants in a tubular furnace heated at a number of spaced points, so as to achieve counter current heating and dual temperature control of the fluid products entering the reaction. BALCAR teaches a way to prepare a steam distillate but also gives all the important details concerning the operation of the furnace to avoid carbon deposition and for the control of the reaction.



   The tubular-type process has received highly developed applications, particularly with regard to hydrogen, and the few people well acquainted with its use know how well it is in controlling the temperature of the fluids which enter into reaction. Even so, oa recognizes that by treating the hydrocarbons and particularly by subjecting them to a preliminary heating in a temperature zone which is a few hundred degrees below that necessary for a good reaction rate, there is a large tendency for a deposit of carbon to occur, the importance of this deposit depending on the product which feeds the furnace.

   It is also possible to prolong the contact of hydrocarbons with fully heated surfaces to the detriment of eco-friendly cracking.

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   mics of petroleum oil if the operation is not done by skilled technicians. This lack of habit from the point of view of the operation of the tube furnace has greatly contributed to the fear of carbon deposition, excess cracking, polymerization and all mechanical difficulties, such as the short duration of use of the tube. This may explain the inflexibility of the instant heating type process.



   Now, in accordance with the present invention, it has been found that if petroleum oil or oil mixtures are atomized in the vapor state at temperatures not giving condensation and at a pressure substantially equal to that of the atmosphere and if one injects very quickly into a mixture of vapor in an alloy tube heated on the outside, the mixture can be charged with heat during its subsequent passage through the rest of the tube. to produce satisfactory cracking of petroleum oils with minimum carbon deposition and maximum flexibility of temperature, time and pressure control.

   the process of this invention constitutes an improvement not only in the manufacture of the olefin, but also in the cracking of oils and gaseous hydrocarbons to obtain the maximum value of total products and to achieve selective production of particular products. "Total" petroleum oils that is, those containing asphalt and heavy hydrocarbons, as well as light hydrocarbons and normally gaseous hydrocarbons, can be used without substantial carbon deposition. In fact, the presence of any carbon deposit in the cracking tube was not observed in the application which was made of the process on an industrial scale.

   This constitutes a clear and important improvement which was not possible until then without running the risk of putting the carbon in

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In practice, hydrocarbons such as light petroleum hydrocarbons, including deasphalted oils and crude oils, for example East Texas crudes are atomized with steam (or other similar gas) without heating. up to the thermal decomposition temperature and then injected in a new way into a stream of superheated vapor (another suitable gaseous medium containing the same quantity of sensible heat) at one end of an externally heated alloy tube to vaporize petroleum oil substantially completely and form a gas mixture of hydrocarbon and vapor,

   after which this mixture is immediately passed through the remainder of the tube which is maintained at the desired temperature by direct heating.



   The hydrocarbons are thus "cracked" to give a mixture of components comprising the olefins which can then be treated in a suitable manner to retard polymerization, to separate liquid components from normally gaseous components and / or to separate liquid streams. and / or gaseous in their components. The process is continuous and gives a product with a high olefin content.



   Having now generally indicated the nature and object of the present invention, a more detailed description of the invention is given in the following, with reference to the accompanying drawing, in which: FIG. . 1 schematically represents the succession of operations in the production of olefins or other products by thermal cracking of a petroleum oil, in the presence of steam, and FIG. 2 is a modification of the novel injection and mixing devices of this invention.



   Referring to fig. 1 of the drawing, it can be seen that the petroleum oil is supplied by means of a pump 1 from a suitable petroleum oil tank to a preheater 2, where

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 it can be heated with steam by indirect heat exchange up to a temperature determined in advance and depending on the raw material used. The preheated oil is sent, through a valve measuring device 6, to a mixer 4 where it is atomized and vaporized in part by a primary stream of saturated or superheated steam (called primary steam), which is supplied to the mixer. by an atomized valve measuring device 5.

   The / and partially vaporized mixture of petroleum oil and primary vapor is% when injected into the mass of a secondary vapor stream (called secondary vapor), moving in a corres- ponding manner and arranged concentrically and this by means of an injection tube 6, The injection tube 6 penetrates at a predetermined depth through the inlet end of a reaction tube 1 heated externally by a furnace 10 and carries a rounded end 8 pierced with holes 9, The mixture of petroleum oil and primary atomized and partly vaporized vapor is kept in the injection tube until it reaches its outlet end 8 and then it passes through the holes 9 forming a number of currents.

   Thus, it is heated to a predetermined temperature by indirect passage of heat from the oven.



   The secondary vapor is supplied to the reaction tube 7 by means of a line 11 controlled by a metering valve 12. It flows concurrently but outside direct contact with the primary oil-vapor mixture, the primary oil-vapor mixture. being inside and the secondary vapor being outside the injection tube. The primary vapor petroleum oil mixture exits the injection tube through the holes 9 and enters the annular stream of the secondary vapor.

   In this way the primary vapor petroleum oil mixture is intimately and rapidly mixed with the secondary vapor and rapidly heated by direct temperature exchange of the secondary vapor which has been heated in the section.

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 superior of. reaction tube.



   . The atomized and already partially var porized petroleum oil continues to vaporize and the intimate gas mixture of hydrocarbons and vapor passes rapidly through the indirectly heated annular reaction space between the walls of the reaction tube. and a tubular space reducer 13 axially disposed within the reaction tube.



   The tubular space reducer 13 is provided at its upper part with a closure 14 and, at its lower end, with a perforated plate 15. Steam can be introduced into the space reducer 13 by means of 'a pipe 16 regulated by a valve 17, When the appliance is working, a small quantity of steam is admitted into the space reducer
13 to maintain complete separation of any hydrocarbons which would otherwise enter the interior through the perforated plate 15. The adjustment of the vapor passing through the member 13 further helps to control the temperature of the hydrocarbon vapor mixture. passing through the reaction tube.



   The reaction product, containing the olefins, is withdrawn from the reaction tube by means of a line 14 cooled by liquid hydrocarbons and the mixture passes through a tray column to separate and recover the normally gaseous products from the normally liquid products. . This cooling, this separation and this recovery can be carried out by the means known to this technique. The products from the tray column can then be disposed of as they are or mixed with the materials supplied to the apparatus or otherwise reintroduced into the cycle of operations.



   In the modification of the invention shown in Figure 2, a part of the injection tube 6 is surrounded by a concentric tube or jacket 18 having its upper part open as seen at 19. The space between the reaction tube - tion 7 and the tube or jacket 18 is filled with ring packing or other suitable materials 20 to obtain the

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 passage of heat to secondary steam and / or to reduce heat radiation to the injection tube. The packing material 20 is suitably carried on a perforated plate or screen 21 mounted beside the outlet end of the injection tube.

   The steam pipes 22 and 23 are connected to the steam supply line 24 and serve to introduce the secondary superheated steam respectively to the lower part of the tube 18 and to the upper part of the reaction tube 7. .



   Appropriate metering valves 25 and 26 selectively control the passage of steam through pipes 22 and 23.



   In the operation of this form of the invention all or part of the secondary vapor can be introduced into the lower part of the tube or jacket 18 and sent against the current to flow inside the tube. to be injected before entering the outer concentric space. The vapor passing through tube 18 leaves it through the open end 19 and mixes with any secondary vapor introduced through pipe 23.

   The mixture passes downwardly through the packing material 20 and mixes with the hydrocarbon-vapor mixture as it exits the injector tube? This arrangement allows very efficient temperature control of the vapor-hydrocarbon mixture flowing through the injector tube, while at the same time allowing secondary vapor passing through the packing material to be heated rapidly to the desired degree.



   In accordance with this invention and to illustrate more specifically the method of producing olefins and other products by thermal cracking of hydrocarbons in the presence of heat, several examples are given below in tabular form. . These examples clearly show the results obtained by the use of different

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 types of petroleum oil when the whole cracking tube is supplied with petroleum oil, that is to say without prior separation of the isolated favorable components / unfavorable components. Asphalt and other products that are part of the composition of each petroleum oil enter the cracking tube.

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   TABLE ------------- Results of tests on different petroleum oils
 EMI10.1
 
<tb> Residue <SEP> Gross <SEP> from <SEP> Texas
<tb>
 
 EMI10.2
 Disaster fuel ha7ted from ItEst (a) Qombustible (b)) ## i ## jr - ####
 EMI10.3
 
<tb> gas <SEP> to <SEP> the <SEP> outlet
<tb>
<tb> in <SEP> m3 <SEP> by <SEP> 45, <SEP> 34 <SEP>
<tb>
<tb> kgs <SEP> of oil <SEP> sub-
<tb>
<tb> setting <SEP> to <SEP> cracking
<tb>
<tb> S.TP. <SEP> and <SEP> base
<tb>
<tb> dry <SEP> 5I, 8 <SEP> 56 <SEP> 39.7 <SEP> 42.7 <SEP> 50.8 <SEP> 43.5 <SEP> 63.8
<tb>
<tb>
<tb>
<tb>
<tb>% <SEP> Olefins <SEP> 46.3 <SEP> 41.7 <SEP> 61.7 <SEP> 57.4 <SEP> 46.0 <SEP> 53.3 <SEP> 41, < SEP> 0 <SEP>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Report <SEP> in
<tb>
<tb> weight <SEP> oil <SEP> of
<tb>
<tb> petroleum <SEP> at
<tb>
<tb> Steam:
<tb>
<tb>
<tb>
<tb> - <SEP> Primary:

   <SEP> 1.0 <SEP> 0.9 <SEP> 0.6 <SEP> 0.6 <SEP> 0.6 <SEP> 0.9 <SEP> 0.9
<tb>
 
 EMI10.4
 - Secondary: o, 9 1.0 2.0 1.4 1.9 2.0 2.1 Total: 1.9 1.9 2.6 2.0 2, S 2.9 3.0
 EMI10.5
 
<tb> Temperatures <SEP> eu
<tb>
<tb>
<tb>
<tb> C; <SEP> to:
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> <SEP> output of the <SEP> tube
<tb>
<tb>
<tb>
<tb>
<tb> injector: <SEP> 1400 <SEP> I43 <SEP> 1430 <SEP> 1650 <SEP> 165 <SEP> I59 <SEP> 1700
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Steam <SEP> secon-
<tb>
<tb>
<tb>
<tb> daire <SEP> at the <SEP> point
<tb>
<tb>
<tb>
<tb> injection <SEP> to <SEP> 6320 <SEP> 599 <SEP> 6980 <SEP> 706 <SEP> 720 <SEP> 7200 <SEP> 7590
<tb>
<tb>
<tb>
<tb> metal <SEP> wall
<tb>
<tb>
<tb>
<tb> from <SEP> tube:

   <SEP> 9070 <SEP> 9070 <SEP> 8710 <SEP> 8850 <SEP> 9020 <SEP> 8800 <SEP> 907
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Oil <SEP> from <SEP> petroleum
<tb>
<tb>
<tb>
<tb> in <SEP> Kgs <SEP> provided
<tb>
<tb>
<tb>
<tb> by <SEP> tubeet <SEP> by
<tb>
<tb>
<tb>
<tb>
<tb> time: <SEP> 56.17 <SEP> 70.19 <SEP> 66.13 <SEP> 69.76 <SEP> 69.76 <SEP> 46.2 <SEP> 46, <SEP> 2 <SEP>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Injection <SEP> type: <SEP> Angular <SEP> penetration <SEP> of <SEP> the <SEP> secondary <SEP> steam
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>% <SEP> of <SEP> oil supplied
<tb>
<tb>
<tb>
<tb> undergoing <SEP> on
<tb>
<tb>
<tb>
<tb>
<tb> cracking <SEP>: <SEP> 54 <SEP> 48 <SEP> 47 <SEP> 49 <SEP> 51 <SEP> 64 <SEP> 73
<tb>
 

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The preceding examples do not represent maximum or optimum values.

   The process is flexible, the feed rates of the apparatus can be significantly increased, the percentage of petroleum oil, subjected to cracking can be increased or decreased and the gas produced by 45.34 kgs. petroleum oil increased or decreased. Quantities of gas corresponding to 112 m 3 were obtained per 45.34 kg of petroleum oil, the olefin content being 18% with a good percentage of C2 H2 and 105 m 3 with 20% of C2H2 plus C2H4. This represents a quantity of gas of the order of 342 m3 per barrel. The figures in the above table represent an amount of gas produced on the order of 114-213 m3 per barrel of petroleum oil supplied to the apparatus.



   Likewise, it has been found that certain petroleum oils can be advantageously subjected to 100% cracking, thus yielding 30% or more of total olefins and by eliminating the phase of separation by fractionation of the gas and of 1. petroleum oil which has not been cracked. Thus, for example, the product from the reaction column can be cooled with intermediate hydrocarbon fractions or with water and the gas sent directly to the liquefaction plant. fractionation and absorption under pressure at low temperature or absorption methods for the separation of the gaseous part entering into the composition.



   Depending on the petroleum oil subjected to the cracking and the precise conditions of application of the process, under the conditions of partial cracking and after cooling and condensation, a liquid product is obtained which may be lighter than water, while under other conditions the unfractionated condensed product may be a liquid having the consistency of cream and heavier than water. The components of non-oracked oil vary, but the conditions under which cracking occurs will influence the percentage of each group of components and each of them in particular.

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   The liquid part may contain, for example, butadix, isoprene, styrene, indeh, naphthalin and acidic fractionation resins more normally provided. This invention therefore comprises not only an advantageous process for the economical manufacture of olefins, but also a process for cracking petroleum oils so as to obtain the maximum value from the point of view of industrial uses and, particularly. for use in the chemical industry.



   The success of the cracking of hydrocarbons with the production of olefins or other products which accompany it by thermal cracking of the hydrocarbons in a tubular cracking furnace in the presence of steam depends first of all:
1 - the proper preparation and introduction of the vapor-hydrocarbon mixture into the alloy cracking tube and,
2 - passing the mixture through the rest of the tube under controlled conditions of temperature, reaction time and pressure to achieve the desired result.



   The novel method of preparing and suitable introduction of the vapor-hydrocarbon mixture according to the present invention consists in atomizing and partially vaporizing the hydrocarbon, preferably with vapor, to pass and the atomized / partially vaporized mixture of hydrocarbon and of steam through an injector fitting extending into the cracking tube and rapidly injecting the atomized and partially vaporized mixture into a stream of superheated steam. The hydrocarbons are subjected if desired to preheating beforehand by means of any type of suitable device, for example an indirect temperature exchanger,

   the degree of heat desired varying according to the type of raw material and the heat being supplied in an insufficient amount to bring about appreciable decomposition of the hydrocarbon.

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  Desirable hydrocarbon preheating temperatures at this point are on the order of about 137 ° C but may range from 110 to 275 ° C under different operating conditions and when processing different kinds of hydrocarbons. Preheating is not necessary when using light or gaseous hydrocarbons and relies on heat in the secondary steam plus indirect heat at the injection tube.



   The hydrocarbon when it is in liquid form is atomized and vaporized in part with the primary vapor under high pressure, the objective which is sought being to bring the hydrocarbon either to the vapor state or to the state of very deep division. Easily volatile hydrocarbons such as ethane and propane can be supplied to the injection tube completely in the vapor state. With petroleum oils the role of the primary vapor is to prepare the oil by bringing it to the state of fine division by means of a mixer or atomizer to delay the reunion of the particles before injection into the secondary vapor. and to cause partial vaporization.

   The lowering of the partial pressure of the petroleum oil by the vapor in the injection tube decreases the boiling point and promotes vaporization. Up to the limit that this vaporization can reach without depositing carbon, it is favorable to this process.



   The higher the vaporization in the injection tube, the more heat units must be supplied to the primary vapor. This is favored by the preheating of the oil, by the use of superheated steam and by conditions of the injection tube giving a high heat passage such as for example a great speed, the use of fins, etc. to increase area and turbulence. The steam to petroleum oil ratio can also be changed to help achieve the best conditions.

   The exact temperature conditions of petroleum oil and steam, the way

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 How they are mixed and the ratio in which this mixture is made to obtain an atomized and partially vaporized mixture of petroleum oil and primary vapor will depend on the characteristics of the given hydrocarbon and the processing conditions as will be appreciated by those skilled in the art.



   The atomized and partially vaporized mixture of hydrocarbon and primary vapor is then sent through the injection tube where. it is heated by the superheated steam flowing outside the tube and by the indirect heat from the wall of the reaction tube. The temperature of the mixture at the point where it exits the injection tube can vary from about 137 C to about 440 C but preferably should not exceed about 330 C to 355 C. The temperature chosen depends on the volatility. the hydrocarbon, its heat stability, the ratio of hydrocarbon to vapor and the passage time.

   A temperature is chosen which results in partial vaporization of the hydrocarbon as it leaves the injection tube but which does not result in substantial thermal decomposition of the constituents of the hydrocarbon within the tube. injection. It will be understood that it is the hydrocarbons from the low boiling petroleum fractions which are most readily volatilized but at the same time which are more stable at elevated temperature than are the high boiling fractions.



   The heated mixture of petroleum oil and primary steam in which the petroleum oil has been partially vaporized is then injected into a superheated mass of secondary steam moving in the same direction retained inside the reaction tube. The objective at this time is to suddenly heat up and mix the vapor and the hydrocarbon particles by quickly injecting the hydrocarbon into the hot secondary vapor without hitting or. by striking as little as possible at this high temperature the wall of the cracking tube which in this zone is at a temperature of 8250 A ---

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 at 1045 C.

   The secondary vapor stream serves to dampen the vapors and the sprayed particles and to deflect the trajectories of the hydrocarbons in a turbulent stream and on axis in a zone of reaction temperature. In this way the vaporization of petroleum oil is quickly terminated while at the same time hydrocarbons are suddenly heated to substantially the temperature of the reaction and the mixture receives the heat of reaction from the furnace along the chimney. min it runs through in the reaction. These conditions minimize the type of thermal decomposition of the hydrocarbons which produces carbon and results in the removal of carbon which may have formed.



   There is a large choice as to the method of injecting the primary vapor-hydrocarbon mixture into the secondary vapor stream. The mixture can be injected at any angle into the side stream. It can be injected at multiple points per side and / or in the direction of the axis. It can be introduced tangentially or by any other means meeting the objective that is proposed. It is preferred to inject at an angle of about 60 to the axis with a small amount 0 to the axis and with a conical or spherical end.



   The position of the injection point can be varied along the axis along the cracking tube. For example, with heavy petroleum oil, the preference is given to a point placed at a distance of about 2 meters from the arch of the wall or from the sheet metal of the furnace closest to the gas inlet end of furnace. However, for a petroleum oil of the Diesel type, good results are obtained using the distance of about one meter.



     The injection tube may or may not be jacketed depending on other factors. For example, when no packings are employed in the secondary vapor space it may be advantageous to reduce the effect of radiation between the vapor tube.

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 cracking and the walls of the injection tube, so as to allow control of the injection temperature.

   This can be achieved by means of a jacket on the injection tube and with all or part of the secondary vapor circulating in the jacket against the current to the flow of the primary vapor, hydrocarbon and eusuite mixture. in the secondary steam channel. In other cases it may be advantageous to use both the jacket and the packing material as shown in fig. 2 of the drawing.



   The secondary steam is supplied to the reaction tube as shown in fig. 1 or in fig. 2, the object being to prepare a secondary stream of steam at temperatures preferably ranging from about 550 ° C to 880 ° C. C at the point where the mixture is made with the primary vapor / hydrocarbon mixture leaving the injection tube. The temperature to be reached in each particular case depends on the relative amounts of secondary vapor and primary vapor petroleum oil mixture just before mixing with secondary vapor, the thermal stability of the hydrocarbons and the like. The above objective can be achieved by using the superheated steam and then heating the steam as it passes through the reaction tubes.

   Various methods can be used if desired to effect and / or accelerate the passage of heat from the reaction tube or cracking tube. One of these methods involves the use within the cracking tube of surfaces exposed to radiant heat. Another method involves the use of strong metal packing carried on a perforated plate attached to the injection tube as shown in Figure 2.

   If desired the packing can be assembled in a metal tube forming a container concentric with the cracking tube and suspended in a suitable manner from an end plate of the latter or mounted in a suitable manner.

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 alternatively on the injection tube and / or on the perforated plate so as to form a removable packing assembly.



   By mixing the primary vapor petroleum oil with the secondary vapor there is an instantaneous lowering of the partial pressure of the hydrocarbon together with instantaneous heating and subsequent heating of the cracking tube wall and soon afterwards. after by the wall of the inner tube of the spacer. The combination of the low partial pressure and the temperature immediately or rapidly thereafter creates a condition in which all hydrocarbons, except extremely small quantities of high boiling point hydrocarbons, must be in the state. vapor and may be subjected to the reaction.

   The higher the temperature at the time of mixing the primary petroleum-vapor oil and the secondary vapor, the more complete the vaporization of the hydrocarbon is at the time of flash mixing.



   The most satisfactory conditions as to temperatures at the ratio of primary steam to petroleum oil, to the ratio of secondary steam to primary steam, etc., etc. will be determined by experience for each particular petroleum oil and simultaneously with other conditions such as feed speed of the device, type of petroleum oil, etc.



   The total amount of steam employed, primary plus secondary, depends on a number of considerations. Since in the process of this invention the vapor serves primarily as a mass medium of heat, as a partial pressure reducer for hydrocarbons and as a material acting against carbon deposition, where it can be varied with respect to the amount. petroleum oil supplied under different time, contact or temperature conditions, to adjust the injection temperature conditions and the curves A

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 temperature on the reaction path,

   both radially and along the axis? The steam to hydrocarbon ratio can be varied so as to have high or low ratios as desired for more difficult or less difficult materials to be processed, but normally this ratio will be between 0.1 to 1 and 5 to 1.



   It is preferable to use vapor to hydrocarbon ratios varying from 1 to 1 to 3 to 1.



   The exact way to proportion primary vapor to secondary vapor varies depending on a number of factors. In certain cases, it may be advantageous to atomize the hydrocarbon in a medium other than steam, for example in hydrogen, nitrogen, combustion gases, etc. under pressure. In this type of case all the steam is supplied as secondary steam. On the other hand, all the vapor can be introduced into the atomization and the other heated gaseous media in addition to the vapor can be used for heating and dilution in the secondary gas stream. Hot combustion gases, heated hydrogen or nitrogen, etc. can be used.



   An important part of the present invention which greatly assists in achieving the objective of cracking hydrocarbons in the presence of steam to take place in good yields is the formation of an atomized and / or vaporized mixture. of high molecular weight hydrocarbon with steam by maintaining the product in a state such that there is a minimum of cohesion of the hydrocarbons and by heating the mixture all at once to the cracking temperature without depositing appreciable carbon.



   Although it is preferable to make the desired mixture of vapor and vaporized hydrocarbons within the cracking tube as shown and as described, it may in some circumstances be desirable.

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 and advantageous to make this mixture separately and then send it to pass through the reaction tube. This can be achieved by placing a separate injection and mixing device based on the principles already described and connecting it to the reaction tube by a flanged coupling, pipe or other system. suitable for connecting these parts.



   The important thing is to obtain a gas mixture comprising vapor and vaporized hydrocarbons from high molecular weight petroleum hydrocarbons and in particular particularly liquid petroleum oils containing about 0.1 to 5 parts by weight of vapor per weight. each part by weight of petroleum oil, at a temperature ranging from about 550 ° C to 880 ° C not containing substantially free carbon.



   The gas mixture of vapor and vaporized hydrocarbons which must be $. a temperature of at least about 38500 and preferably from about 550 C to about 880 C is immediately passed through the remainder of the cracking tube. The factors which are of primary importance in this phase of the working process are the temperature of the vapor-hydrocarbon gas, the temperature of the metal wall in relation to the temperature curve and the duration of contact or reaction. These factors depend on the characteristics of the hydrocarbon to be cracked, the ratio of the amount of petroleum oil to the amount of steam and / or other gas, the percentage of cracking desired, etc. ..

   In general, temperatures of the vapor-hydrocarbon mixture varying from about 605 ° C to about 935 ° C provide the best results and are preferred. These temperatures, however, are not critical and can be extended to provide more favorable conditions for a particular petroleum oil or such or such.

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 The desired products. The temperatures of the metal walls are controlled with respect to the other processing conditions so as to give the desired temperature and the desired temperature curve within the reaction zone.



   The duration of the reaction under the given treatment conditions will depend on the temperature chosen and the partial pressure of the hydrocarbon. As the temperature increases the reaction time correspondingly decreases and vice versa. Or has generally found that relatively short reaction times of about 0.1 to 5 seconds and particularly about 0.1 to 1 second are most advantageous.



   The reaction products from the cracking tube are preferably cooled by the use of liquid hydrocarbons and the cooled gaseous stream is passed to a fractionation column top to separate the normally liquid products from the gases. gaseous products.



   The flexibility of the process of the present invention derives in part from the possibility that it offers to control the temperature curves and the temperature itself both in the axis and in the radial direction of the cracking tube.



   This is done in the radial direction with respect to a point or a zone on the wall of the tube, by heating the furnace so as to have a specific temperature of the furnace wall and by controlling the passage of heat to the gas stream, for example by changing the speed of the gas, by changing the surfaces for the passage of the gas or by increasing the supply of the gases, by changing the ratio of the outer surface to the inner surface of the tube, by the use of wings, baffle partitions etc. to increase turbulence, changing the ratio of steam to petroleum oil

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 or generally, the ratio of the medium diluting petroleum oil and using a packing material.



   In the direction of the axis, the control can be carried out in different ways. One of the methods is to use a furnace in which heat is applied selectively at spaced points along the periphery of the reaction tube with the hot combustion gases rising up the counter tube. current with respect to the flow of the vapor-hydrocarbon mixture in the same apparatus and emerging through an outlet flue placed very close to the end towards which the vapor-hydrocarbon mixture is injected into the secondary vapor.

   In this way, the temperatures of the furnace zone can be regulated at will, but a temperature curve falling sharply, i.e. a high temperature at the injection zone and a low temperature at the gas outlet becomes more and more difficult to obtain the more the curve is inclined.



   In a slightly different process, the hot combustion gases are sent up and down around the reaction tube parallel and concurrently with the circulation of the vapor-hydrocarbon mixture in this tube and they are discharged through an exhaust flue placed very close to the tube. The end of the tube opposite to that in which the hydrocarbon vapor is mixed with the secondary vapor, the heat being applied at spaced points along the tube as before. This process gives good control, particularly when a high temperature is required in the injection zone and a low temperature is required in the reaction zone.



   Either of the above methods can be varied by heating near the end of the tube rather than at spaced points along the tube.

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   In a still different process, the transverse radiation can be significantly reduced and benefit greatly from a selective heating plan achieved when using a single chamber furnace, in this case by using one or more partitions along the length of the furnace. 'axis of the tube, zones are formed which help to improve control of the curve. The products of the tubes and of the combustion pass through these partition walls by means of suitable openings.



   These processes can be applied in a vertical furnace or in a horizontal furnace with any combination of injection tube location and gas outlet, with or without multiple chambers along the tube axis and with curves. rising or falling tube temperature or combinations of both.



   This flexibility, combined with other factors, such as the temperature level, the ratio of diluent gas to petroleum oil or the ratio of vapor to petroleum oil, contact time and pressure. , makes it possible to improve in a marked way the control of the yield of products which one wishes to obtain. Significant control is achieved by employing the multi-point heater of Patent No. 2I.52I redelivered to James H. SHAPLEIGH which can be modified in this process by obtaining either countercurrent or parallel flow of the process. and combustion gases.



   The reaction tube of the present invention preferably consists of a spacer tube and an outer cracking tube arranged concentrically, as shown in Fig. 1 and made of a steel or chromium alloy, containing about 25 chromium. , 20% nickel, l of columbium, the remainder being substantially constituted by iron. These specific proportions are given only as a guide and it will be understood that other suitable alloys can be used. The reaction tube can be vertical, horizontal or inclined depending on the

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 conditions of use, the space available, etc.



  Very effective temperature control is achieved by the direct heat applied to the exterior of the outer tube as heretofore has been indicated and by the additional surface area provided by the spacer tube.



   If desired, the inner spacer tube can be replaced with packing or other suitable materials or the spacer tube is removed and the empty reaction tube used. In each case, however, the conditions must be such as to give the required heat transfer and passage time within the reaction zone.



   The vapor-hydrocarbon mixture can be injected into the reaction tube via either end, that is to say at the end through which the combustion gases exit or at the opposite end. As can be seen applied in fig. 1 for example, the injection can take place either near the top of the tube as shown, or near the base of the tube, the combustion gases flowing countercurrently or parallel to the tube. vapor-hydrocarbon mixture and being vented near either end of the tube as desired.



   Although it is desirable in most cases to achieve a high percentage of hydrocarbon cracking, it is possible and sometimes desirable to achieve partial cracking, i.e. ranging from about 50% to 75%. % and to put into circulation in the operating cycle parts of non-cracked products with the petroleum oil which feeds the apparatus, so as to end up having a product to be treated of a lower viscosity, which constitutes a favorable condition. Another advantage of the process is the efficient use of the recirculating petroleum oils to cool the reaction products from the process.

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 cracking tube.



   The present process is most advantageously applied at atmospheric pressure, although pressures somewhat above or below atmospheric pressure can be employed with satisfactory results. In addition, pressures of 1.75 / kg per square centimeter can be used successfully to adjust the types and proportions of products obtained, it is possible to operate at pressures of this order by placing a valve adjustment at the end of the cracking system.



   In the injection and instantaneous heating process according to this invention, it will be noted that liquid hydrocarbons containing sulfur do not come into contact with the metal wall in any case, except perhaps for traces of oil. high boiling petroleum and yet not in any appreciable and serious way. The hydrocarbons in the cracking tube itself are above the dew point. In addition, the sulfur-containing hydrocarbon vapors are out of contact with the metal wall at the temperatures at which precipitation of the carbides occurs or any concomitant attack of the sulfur normally occurs in serious fashion.

   Under the injection conditions, the mercaptans which are present are transformed into H2S t do not cause any difficulty under the conditions of temperature and of condensation points of the hydrocarbons which prevail in the apparatus.



   The process of this invention can be adapted to the injection of emulsions, petroleum oils containing catalysts and petroleum oil containing anti-carbon products. It is applicable to the treatment of normally gaseous hydrocarbons as well as normally liquid hydrocarbons. Although the preferred form of apparatus and method have been described, it will be appreciated that much can be done.

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 change to both without departing from the objective of the invention.



   A particular advantage of the present invention lies in the fact that better yields of olefins and liquid products of commercial value are obtained with less trouble than with regard to varbone than has been hitherto possible. in the cracking of hydrocarbons in tube furnaces. Another advantage is that 'whole' petroleum oils are successfully and economically processed into heavier liquid petroleum hydrocarbons, deasphalted oils, and crude oils containing asphalt. This makes it possible to take advantage of the possible use and the economy of these raw materials and without being limited by the geographical positions of the factories, considered until now as necessary.



   The words "counter-current" and "parallel" as used in the description and summary apply to the flow of fluids and mean parallel flow in the same direction as opposed to "counter-current" which means parallel flow in opposite directions.



   CLAIMS
I - Hydrocarbon cracking process which comprises the injection of a hydrocarbon in gaseous or atomized form into a vapor stream inside a cracking tube through which the vapor mixture is immediately passed and hydrocarbon through the remainder of the tube as it is supplied with heat to produce a satisfactory hydrocarbon cracking without appreciable carbon deposition.


    

Claims (1)

II - A cracking process according to claim I wherein a liquid hydrocarbon can be mixed with a gaseous substance such as vapor to form a gaseous mixture of vapor and hydrocarbon. <Desc / Clms Page number 26> III - A cracking process according to claims I and II in which the atomized mixture is heated to partially vaporize the hydrocarbon; IV - A cracking process according to claims I to III wherein the mixture of vapor and atomized hydrocarbons is simultaneously heated and mixed with the vapor stream in the cracking tube; V - Cracking process according to claims 1 to IV wherein the vapor stream is superheated steam and the cracking tube is an alloy tube heated externally; VI - Cracking process according to claims I to V wherein the hydrocarbon is a volatile petroleum hydrocarbon containing more than two carbon atoms, heated to a temperature not greater than about 460 C and the vapor stream in which the hydrocarbon is injected is heated to a temperature above about 550 ° C, thereby forming a gaseous mixture of hydrocarbon and vapor at a temperature above about 440 ° C. VII - Cracking process according to claims I to VI, in which a hydrocarbon in gaseous form is heated to a temperature at which vaporization takes place without appreciable thermal decomposition before injection into the vapor stream. inside said cracking tube. VIII- A cracking process according to claims I to VII in which the reaction products coming from the cracking tube are suddenly cooled and the products formed are separated and recovered. IX - A cracking process according to claim I applied by circulating a hydrocarbon in gaseous or atomized form along a path, by circulating superheated steam parallel to the previous one <Desc / Clms Page number 27> along a second path concentric with the first, causing the hydrocarbon to mix with the steam and immediately sending the mixture of steam and hydrocarbon into a cracking tube while it is supplied with steam to provide satisfactory cracking of the hydrocarbon without appreciable carbon deposition. X - A cracking process according to claims I e @ IX wherein the steam is superheated by applying indirect heat to the second pathway. XI - A cracking process according to the preceding claims in which the hydrocarbon flows through an elongated injection tube and the superheated vapor flows along the exterior of the injection tube over a substantial part of the tube. its length in a direction parallel to that of the flow of the hydrocarbon, the vapor mixing with the hydrocarbon as it exits the injection tube. XII - Cracking process according to the preceding claims, in which a liquid petroleum hydrocarbon is mixed with vapor to form a mixture of vapor and atomized hydrocarbon. XIII - Cracking process according to the preceding claims wherein the steam before being superheated flows along a countercurrent pathway relative to the pathway of the hydrocarbon and concentrically relative to this and then flows along a parallel path while being indirectly heated. XIV - A cracking process according to claim XIII in which additional steam is mixed with the steam which flows countercurrently to the flow of the hydrocarbon. <Desc / Clms Page number 28> XV - Installation for cracking hydrocarbons in a furnace according to the preceding claims, which comprises a device for injection, a device for circulating the steam along the injector and outside it and a device for passing a hydrocarbon partially vaporized in the injector device and injecting it into the vapor which circulates so as to form a gas mixture of hydrocarbon and vapor. XVI - Installation according to claim XV comprising a device for heating the steam as it flows along the injector device. XVII - Installation according to claims XV and XVI wherein the injector device comprises an elongated tube penetrating into one end of a cracking tube. XVIII - Installation marketed above comprising a device for immediately passing the hydrocarbon vapor mixture through a cracking tube. XIX - Installation as claimed above comprising a device for circulating the steam along a first path limited in counter-current with respect to the path of the hydrocarbon through the injector device and concentrically relative to it, and then following a second limited path parallel to the hydrocarbuxe pathway and concentrically with respect to it. XX - Installation as claimed above comprising a device for mixing additional steam with the steam which circulates from the first to the second pathway. EMI29.1 <Desc / Clms Page number 30> EMI30.1