BE534641A - - Google Patents

Description

       

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   The present invention relates to an apparatus and a process for the preparation of coke in grains or elementary or base coke, intended for the coking of fluidized bed hydrocarbons, such as the coking of waste oils. and similar oils. The invention relates more especially to both an apparatus and a process for providing the required small coke particles to serve as cores for the deposition of coke formed during the process.



   An object of the invention is to replace the larger coke particles, which are removed from the system as produced coke, with smaller particles, so as to keep the total number of particles in the system at roughly constant. The invention presents an apparatus for breaking up large particles of coke so that the increase in the average particle size which occurs due to the deposition of coke is compensated for by the removal of the large coke particles. and replacing them with an equivalent number of small particles. The invention also relates to an efficient method of breaking up large particles and preferably returning the small particles to the coking zone for use as elemental coke.



   In the conversion of hydrocarbon oils, especially crude petroleum oils, it has been common practice for many years to remove the more volatile fractions by distillation and to subject the heavy residues to thermal cracking. in order to obtain motor fuel and other low boiling fractions in as high an amount as possible. In all prior processes there was a production of considerable amounts of pitch or waste, viscous, heavy oil. Although this pitch is usually of very low value, there is a fairly large market for this product in the field. steam locomotives, factory boilers, etc.

   Due, however, to the increase in the use of diesel engines in railroads, and the introduction of other improved heating and power supply facilities, the heavy waste oils market has grown. significantly decreased in recent years. At the same time, the demand for more volatile products, such as gasoline, heating oil, and products that can be converted into gasoline, diesel fuel, heating oil, etc., has greatly increased. Of great interest has been the conversion of crude oil residues by coking for years.



   Among the various processes which are used for coking, the recently developed solid-fluidity process appears to be among the most efficient and promises the greatest success. In this process, as is known, a mass of fluidized preheated solids, such as sand, metal particles, clay, alumina, pearls, and especially coke particles formed during the development of the process, is is used to provide the heat necessary for coking or conversion of the residue. A large proportion of the residue is normally converted into gas oil and other fractions of greater volatility than feed.



  A small proportion of the feed is converted to coke. Various solids, such as those mentioned above, can be used to provide the heat of conversion. As coke is a product of the process, it is obviously preferred.



   The present invention relates especially to means and methods for adjusting the particle sizes of circulating solids, especially those which consist entirely or mainly of coke, and this for maintaining a process capable of developing continuously. It should be understood that even when solids other than co-

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 ke are used to initiate the coking operation, they are coated with coke to such an extent that the particles removed from the coking system are largely coke.



   It has now been found that a fluidized coking system, using coke particles as heat transporting means, can best be kept in equilibrium by maintaining a relatively constant number of coke particles or other coking nuclei in the system. . As the particles steadily grow larger due to the deposition of heavy oil layers, and their conversion to coke layers on the initial particles in the coking zone, it has been found necessary to remove the large coke particles from the system. and replace them with an equivalent number of small particles.

   These, which serve as cores for new deposits of coke, can be considered "base coke" or "elemental coke", and these expressions apply even here when some of the particles, initially at least, are composed of other materials than coke, as indicated above.



   In the catalytic cracking of hydrocarbons, where masses of finely divided solids are used as catalysts, the number of particles can vary very widely. The catalyst particles can, on average, be much finer than the coke particles which are used in the fluidized solid coking process. In addition, the catalyst is not removed from the system as a product, but the coke is simply removed from this catalyst, by burning, and the catalyst is reused, as long as it retains its activity. Therefore, there is no problem of removing a solid product and keeping the number of particles constant in the overall solids charge.



   In accordance with the present invention, an important control feature is the maintenance, on a continuous basis, of a substantially constant total number of coke particles throughout the system. This includes the reaction vessel, the burner or heating vessel, and the connecting pipes between them, plus the solid and vapor separators, etc. There is much more coke produced than consumed, although coke is burned in order to provide heat for the entire operation. As a result, large particles of coke are removed, broken or otherwise used at a relatively constant rate. Particles removed from the system are digitally replaced with a substantially equivalent number of smaller particles. Very generally, these particles can be produced in various ways.

   However, in a more particular way, the small particles of coke or elemental coke are produced by attrition or breaking up particles which are already in the system. In particular, a preferred method of producing these particles is the shock-impact method. particles against each other, or, preferably by impacting against a solid hard surface, such as a target of metal or other hard material.



   Although the particles can be disrupted in various ways, it has been found, and it is an object of the invention, that attrition or disruption should be controlled and operated so as to occur in a relatively dilute portion. or dispersed from the coking system. The production of elemental coke or other particulate cores intended to serve as cores for the production of larger coke particles is, therefore, carried out in a preferred application form, by spraying the relatively large particles, or by spraying the relatively large particles. portion of the solids stream, at high speed. Impacting the particles against each other is effective, and impacting against a larger hard surface or target is even better at breaking them into smaller particles.

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   Although the degree of rupture of solid particles in the system may vary somewhat, the ratio of the average diameter of the broken particles or elemental coke to the diameter of the average particles in the system is preferably not less than 1 /. 5 to 1 / 1.3. It also appears that particles of about 1/5 in average diameter (1/125 of the average mass) are considered to be roughly small enough that they can be effectively handled for them. aims of the invention.



   Attrition to smaller dimensions consumes power without giving a compensatory improvement in the process. Elemental coke particles reduced only slightly in diameter, eg, down to 1 / 1.3 of the average particle diameter in the coking system, are roughly large enough to be supplied economically. However, rapid return of the coke is necessary when the reduction in size is only small.



   It will be seen, therefore, that the invention encompasses the general aspects of maintaining a balanced system with a relatively constant number as well as a relatively constant mass of heat-carrying and coke-accepting particles, even if these particles tend. to grow in the system. The invention also encompasses a more limited aspect of method and apparatus for providing in the system the small particles or cores to replace the large ones which are removed from the system.



   Other aspects of the invention are the discovery that it is very advantageous to recycle to the particle breaking or attrition means, particles which have already been partially broken. Also provided are means for selectively returning the elementary particles to the system and for preferably regrinding or subjecting to attrition the larger particles, and means for selectively rejecting from the system the particles of less utility.



   The invention will be better understood by reference to the accompanying drawings which show various methods of producing the small particles of elemental coke or coke, and various aspects of this method.



   Referring to the drawings, Fig. 1 shows, in elevation and partly in section, a coking apparatus or vessel, which may be a schematically shown coking reactor, in which coke or other system solids are converted into elementary particles.



   Figure 2 shows another shock or elemental coke forming system, in which the necessary small particles are provided by throwing the larger force particles against a shock target element, ¯ in an elutriation or separation zone, from which large and small particles can be separately removed.



   Figure 3 shows yet another system, in which small particles of coke or elemental coke are produced by the action of opposing jets entraining the larger particles and striking them against each other, in a relatively dispersed section of a conveyor or transfer line of a coking system.



   Figure 4 is a schematic elevational view of the main elements of a coking system, constituting a variant of the invention.



   Figure 5 is a graphical representation of the effect of particle velocity and apparatus characteristics on elemental coke yield.



   Referring in detail to the drawings, a reactor vessel 11, which may be of any suitable shape and size, is shown schematically in Figure 1. A crushing or impact attrition system is shown.

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 presented internally to this container. Coke particles or flowable, heat-transporting equivalents solids are brought into a vessel 11 by suitable means, such as a line 13 from a burner or heater, not shown, where the particles are fed. to a suitable coking temperature, for example, between 900 and 1250 F more or less.

   The particles can be brought through line 13 either in the fluidized state or in the dispersed state by means of a gas or an aeration or elevation vapor, such as vapor. It should be understood that the attrition mechanism can be placed in or connected to a transfer line, heater or burner, or other part of the system (see figure 4 and its description below). It is therefore obvious that Figure 1 is only illustrative.



   Steam or other gas-like fluidizing fluid, which may consist of hydrocarbon vapors, is introduced into the vessel 11 in the lower part thereof, to maintain the necessary fluidized movement of the solid particles in the bed 15 formed in the vessel. the recipient. Under these balanced conditions, this bed forms an intermediate surface or upper level 17, more or less stable. In this case, the steam or other gas used is used to fluidize the solids, to break up or induce attrition of the solid particles and thereby to provide the elemental coke or related solids discussed above.

   As shown here, two opposing jets of steam are introduced respectively through inlet conduits 19 and 21, and are directed through orifices or venturi nozzles 23 and 25 against the opposite faces of a shock member 27, such as 'a steel plate or similar piece. The shape and arrangement of the venturi elements are such that the solid particles, coke, or the like, surrounding the elements 23 and 25 are drawn into and through the venturis by the high velocity jets of steam or gas, and are thrown with considerable force against the plate 27.

   The space between the respective elements 23 and 25 and the plate 27 is such that the jet of steam plus the particles circulate up and down through the openings, with the result that these spaces are relatively clear and that a shock against the tray is not prevented. As soon as the solids are exhausted, they are removed through line 29. From there they can be returned to the burner. An oil supply can be introduced through suitable nozzles 31, as is known in the art. As will be seen below, the speed of the projection jets and the length of the acceleration tubes or nozzles have important effects on the efficiency of the grinding or the breaking of the particles.



   It should be understood that particles, for example coke ', are continuously removed from the container through line 29 and returned to it, also continuously, through line 13.



   The products of the coker, i.e., the volatile fractions produced by coking, are removed from the reactor vessel by a suitable gas and solids separator, the solid particles separated, for example, of coke. , being returned to bed 15 through the usual solids return line 37. Vaporous and / or gaseous products are removed at the top to go to a suitable recovery system through a discharge line 39.



   Obviously, if there is no addition or removal of particles, the total mass of coke in the system (when coke is used, which is usually the preferred case), would continue to grow, because coke is continuously deposited on the original elementary particles in the reactor, following coking of the oil supplied through the inlet lines 31. It is desirable to keep substantially constant in the system.

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 the mass or solids content, i.e., the total weight of coke, near a desired mass or operating level has been achieved.



   As noted above, the total number of particles in the system should be kept substantially constant when the system is in equilibrium. This is another way of saying that the average particle sizes of coke, etc., must be controlled because, for a given set of operating conditions, there is an optimum average particle size and distribution of. optimum particle sizes, at least generally, for the system solids. Therefore, relatively large particles must be continuously removed from the system, and new, smaller particles must be produced and / or introduced into the system at the same, or about the same. numerical speed than that of the removal of large particles.

   When this condition is satisfied, the operation continues continuously and without disturbing or interrupting. The degree and type of attrition, considered optimum, will be discussed below.



   Referring now to Figure 2, a different form or variant of the invention is shown therein, with respect to the breaking of coke particles by impact. In this representation, a combined system of elutriation or deposition separation apparatus and mill or attrition device is used to control the entry and removal of fine and coarse coke particles, respectively, so as to maintain the entire coking system in equilibrium.

   It should be understood that the combined unit of the attrition apparatus and the elutriation apparatus of figure 2 could be installed in the inlet duct 13 or the outlet duct 29 of a system. such as that shown in Figure 1, or it could be installed at any other suitable location in a solids circulation system, in which it is desired to control the particle size and replace the large particles removed with small particles. In Figure 4, described below, there is shown a similar system incorporated into a coking apparatus system of improved design.



   In the system of Figure 2, a stream of solid particles, having a larger average size than desirable in a coking reactor, can be fed through an inlet line 51 into a line 53. A A stream of fluid, such as vapor or gas, passes through line 53 at a rate high enough to cause the particles entrained therein to rupture when they strike an impact surface. This speed can be about 100 to 1000 feet per second, the range of 200 to 600 feet per second usually being preferable.



  The solids entering through line 51 are picked up in a high velocity gas stream or jet arriving through line 53, and forcibly taken against a shock target 55. The shock target, as shown in Figure 2, is formed by a concave impact surface. When properly shaped, the particles striking this surface bounce convergently so as to maintain a mat of particles on the concave face of the plate 55.

   With this arrangement, most of the impact force is spent on the particles rather than the impact plate, so that the latter does not wear out quickly by abrasion, as it could be, otherwise, the case if. hard particles were thrown into it at a high speed.However, in some cases, some wear is not so disadvantageous, as this element can easily be replaced, and impact against a smooth hard surface produces more efficient grinding depending. of steam consumption.



   When wear is not disadvantageous, a pla-

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 teau or flat target, such as the plate 27 of Figure 1. Conversely, a double concave type plate or target could replace the plate 27 of Figure 1, if desired.



   The shock plate 55 is disposed in a relatively large section of duct 57. This duct, however, is not of sufficiently large cross section to permit dense phase fluidization of the solids therein. The particles are preferably entrained in an upwardly circulating gas stream, i.e., in the dispersed phase, although this is not always necessary. Line 57 connects to a large elutriation or deposition separation section 59. The latter is of sufficient cross-section that the gas stream is unable to carry the heaviest or largest particles.

   All the particles, fine or coarse, leave the conduit 57 under the impulse of the fluid stream passing through the conduit 53, but the larger particles fall along the annular surface 60 outside the conduit 57 and inside the separation apparatus by deposit 59. A grid element 61 is disposed across the lower part of the annular section 60 of the ring 59, to separate the large particles by means of a chamber 63 into which a fluidizing gas can be introduced through a conduit 65.



   Thus, as soon as the particles emerge from the top of section 57, their speed is immediately reduced, and the heaviest particles fall back on or towards the grid 61. The fluid, for example steam or a hydrocarbon gas, introduced through line 65, forms a fluidized bed of these particles. The velocity of the aeration gas, in the separation apparatus 59, is sufficient to separate therein all the finer particles produced by impact against the plate 55. Most fine particles are carried by the top of the apparatus 59, directly from the duct 57. These fine particles escape through an outlet duct 69. From there, they can be returned to the coking system.

   The larger particles of coke fluidized in bed 60 can be removed from the system through an outlet line 71 regulated by a valve 74.



  The coarse particles of bed 60 are often partially broken up, and it is usually advantageous to recycle at least a portion of these particles to the mill or attritor 53, 55. This can be accomplished through a connecting line 75. , or a branch thereof, to line 51.



   Still another arrangement is shown in Figure 3; the solids are supplied by conduits 80 to two opposed jets 81 through which these solids are entrained in a large section 83. The particles are broken, in the respective jets, by mutual impact at high speed. The particles, after impact, are swept circularly and upwards, as shown by the arrows, under the impulse effect of a fluid current, and thanks to the guidance provided by the housing. 84, 85. At this time , the particul.es are preferably in the dispersed phase. Under the impulse of the gas stream, the particles rise, still in the dispersed phase, through a duct 87 in a dispersion zone located in the upper part of an elutriation or deposition separation vessel 89.

   The heaviest particles fall by gravity on a grid 90 supported in an annular space between the inlet duct 87 and the outer walls of the container 89. A fluidizing gas is supplied into the space below the grid 90, and this by a pipe 91. These gases pass through the grid to form a fluidized bed 92 with the large solids which are separated by gravity from the upward flow emerging from the pipe 87. The upper level of this bed is designated by 93. A withdrawal pipe 94 equipped with 'a valve 95, is, provided, and the large solids can be recycled to the attrition jets

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81, or removed as produced coke, or taken to a burner.



   Referring now to Figure 4, there is shown a fluidized bed coking system, comprising a burner or heater, with an elutriation and shock attrition device mounted in the transfer conduits. This coking vessel 101 is of the conical or frustoconical type. Feed, preferably preheated, is introduced through multiple feed lines 103,105 and a series of nozzles 107, 109, into a bed of fluidized, preheated solids which convey heat, particularly coke particles. of a size between about 40 and 500 microns in average particle diameter.



   These particles are normally preheated to a temperature above 1000 F, up to 1200 F or more, in a burner vessel III.



   Hot particles flow from the burner through line 113, relatively sharp bend 115, and steeply sloping elevation line)
117, under the control of valves 119, 121. The spent coke particles coming from the reactor vessel 101 pass through a coarse grain sieving device 123 in a separation or removal section or zone.
125, to go into a downcomer 127, a relatively sharp bend 129, a steeply sloped riser 131 with a control or cut-off valve 133; through an inlet 135, the particles go to a deflector 137 located in the burner vessel 111.



   Separation or stripping gas, such as steam, is introduced into zone 125 through line 141. Large parts or.! Agglomerated particles of coke, and other coke produced if desired, can be removed from the reactor vessel through an outlet 143 under the control of a valve 145.



   As the coke removed from the reactor descends, it can be at least partially aerated and impelled at the sharp bend 129 by a jet of steam or the like, introduced through line 147. D ' other aeration lines 149, 151, 153, 155 and 157 are provided for raising the coke in the burner vessel. Air can be supplied to some or all of these pipes to initiate combustion as soon as the coke flows to the burner. The burner container preferably comprises a combustion chamber, or starting device at its base, designated by 159, to which air and / or fuel can be supplied through line 161 for the initial heating of the burner. . The air and / or fuel supply to the burner can then be continued from this source, if desired.



   Hot coke or a portion thereof may be removed, as product, from the burner side of the vessel, if desired, through line 163 under the control of valve 165. Coke may be cooled, such as. removed, purifying it with a stream of water or steam, introduced through line 167. By operating the burner at a suitably high temperature, water gas can thus be formed, the temperature of the coke produced and / or coke returning to the coking reactor thus being brought back to the desired levels. This combustion gas and / or fuel gas from the burner pass through a stream solids separator 169. Entrained solids are returned to the fluidized bed 171 of the burner ¯ through a solids return line 173.

   The gases, substantially free of entrained solids, escape at the top through an outlet line 165 under the control of a valve 177, to a suitable heat recovery and / or exhaust system. The solids returning from the burner to the reactor are suitably aerated and supported or pushed by steam, hydrocarbon gas, or other inert gas-like fluid introduced through aeration valves 181, 183, 185.



  Since solid particles are much larger, on average, than

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 As the solids used in older fluidized bed systems, for example, catalytic cracking catalysts, they tend to deaerate quickly and lose their pushing force. For this reason, the risers 117 and 131 should be steeply sloping, ie at least 50 horizontally, preferably 60 or more.



   When the spent coke particles leave the reactor to go to the burner, their average particle size is significantly larger than when these same particles entered the reactor, as most of the particles have grown from the accumulation of coke deposited during the process. . At this point, they are less suitable for reuse because, for maximum coking efficiency, the number of particles and their total surface area should be as large as possible, due to considerations, such as their separation from the fluidized bed with the products. vaporous, etc. It is, therefore, desirable to replace the larger particles with an equivalent number of small particles of elemental coke.



   For this purpose, a small portion of the coke stream (or a greater portion or all of the stream in some cases, as will be explained) is diverted to a crushing or attrition device, referred to, in a fashion. In general, by reference 199. This apparatus, as shown, is substantially similar to that of Figure 2, although it can be modified to operate like those of Figures 1 or 3, if desired.



   The coke rises through line 191 under the driving force of a gas stream, injected through line 151. Line 151 may project through, at least partially, elevation line 131, or although another jet forming means may be introduced into line 191, above or below a control valve 193, so as to entrain the coke particles at high speed, 100 to 1000 feet per second , against a target plate 195, arranged in a large duct 197. The arrangement is practically identical to that of FIG. 2.



   The broken, partially broken, fine and coarse coke particles are all carried upward in a deposition separation vessel 199, where the fine particles continue to be entrained and carried upward by the impulse gas stream to exit through line 201. From there, they can pass through a valve 203 and a line 205 in the elevation line 117 and they are thus returned to the coker. Or, the fine particles, or a part thereof, may go to the burner, through line 207 and valve 209, with a suitable pulse jet of gas being provided, as indicated at 211.



   The heaviest particles fall back into an annular space 213 on a grid 215 through which a fluidizing gas supplied by a pipe 217 circulates from bottom to top. The fluidized particles, which are larger, can be withdrawn through line 219 under the control of a valve 221 and recycled to line 191 by a lifting or propulsion fluid injected through line 223. From line 191, the particles can be recycled to the crushing or impact attrition device 195, which is often desirable, since partially cracked particles usually break more easily than uncracked particles, or these particles can be fed back to the line. elevation 131 to go to the burner. If desired, produced coke can be removed at 225.



   The arrangement which has just been described is very flexible. It allows the replacement of large particles of coke produced by an equivalent number of small elementary particles at a constant and regular speed.

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 re, so as to keep substantially constant at all times the total number of particles, the particle size distribution, and the total solids content. The temperature of the coking bed can also be carefully controlled by adjusting the relative proportions of heated coke to unheated elemental coke (when using line 205).

   Or, the elemental coke can be sent to the burner through lines 207 and 135, with a view to further reduction in size by partial burning, and then returned through lines 113, 115, 117, to the coker with suitable proportions of larger particles.



   Vaporous products from the coker escape at the top of it through a conventional solids separator 221 with a solids return line 223 and a product outlet line 225.



   It should be understood that vaporous products can, if desired, go immediately to a washing machine or fractionator, or they can be taken directly to a non-condensing catalytic cracker.



   The design of the reactor, with its upper part of reduced cross section, does not constitute a part of the present invention.



   It should be understood that the grinding of the coke particles to reduce their size for reuse has already been described. The present invention encompasses not only an improved grinding technique, but also the design, noted above, of constantly replacing the large coke particles removed from the system with an equivalent number of small coke particles of the elemental coke, so as to maintaining the coke receiving or depositing surfaces substantially constant with respect to their total surface area, and keeping substantially constant the content or overall mass of coke in the coking apparatus.



   As suggested above, yet another feature of the present invention relates to the discovery that there is an optimum jet speed and an optimum design of the jet apparatus, for obtaining a high grinding efficiency. and coke attrition. In order to study these factors, different jet speeds and different lengths of accelerator tubes were tested by throwing the solids against a steel plate forming the target. The arrangement of the nozzles and the test target was practically that of Figures 1 and 2, i.e., the coke was supplied in a high velocity gas jet, and the length of the tube, the inlet of solids at the outlet of the tube was measured as the length of the accelerator tube.



   The coke tested - exhibited the following distribution of particle sizes, prior to crushing or attrition testing
TABLE I.
 EMI9.1
 
<tb>
<tb>



  Meshes <SEP> Tyler <SEP> Dimensions <SEP> of <SEP> particles <SEP>% <SEP> in <SEP> weight <SEP> remaining
<tb> ¯¯¯¯¯¯¯¯¯¯¯ <SEP> minima, <SEP> microns <SEP> on <SEP> the <SEP> sieve
<tb> 35 <SEP> 417 <SEP> 0.2
<tb> 48 <SEP> 295 <SEP> 10.5
<tb>, 60 <SEP> 246 <SEP> 42.7
<tb> 80 <SEP> 175 <SEP> 87.0
<tb> 100 <SEP> 147 <SEP> 95.4
<tb>
 
At a gas inlet velocity (at the point where coke was introduced into the acceleration tube) of 145 feet per second, there was only one

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 small amount of attrition. The number of particles smaller than 160 microns (about 90 meshes) increased by only 2.2% of the total mass.



   The number of particles larger than 240 microns (about 60 meshes) decreased by the same amount.



   At a gas velocity of 208 feet per second, there was a 9% increase in the total weight of material of less than 200 microns (approximately
68 stitches) and a 9% decrease in the material larger than 240 microns. At 246 feet per second there was a 21% increase in weight of material smaller than 200 microns in average diameter.



   The tests showed that there was an increase, in all cases, for material smaller than 200 microns, and a decrease for material larger than 200 microns. They also showed that, over the gas velocity range of 200 to 250 feet per second, there was no apparent significant difference in selectivity to fine material less than about 80 microns. -At 246 feet per second, 28% of the increase in weight of particles finer than 200 microns occurred in particles smaller than 80 microns. At 208 feet per second, 22% of the material was smaller than 80 microns (approximately 180 meshes).



   A preferred particle size of elemental coke appears to be in the general range of 50-200 microns. At 200 feet per second, the material passing through a 100 mesh per linear inch (about 150 microns) screen increased by 2%. At 250 feet per second, it increased by 14% by weight.



   Figure 5 graphically shows the relationship between the gas jet velocity in the tube, in feet per second, and the grinding efficiency, in horsepower (HP) hours required to produce one ton of elemental coke (passing through a sieve of 100 meshes per linear inch, that is, less than about 150 microns. At 230 feet per second, the power required, in an 8 inch accelerator tube, to produce one ton of elemental coke was not than 48 horsepower hour.At 160 feet per second, the power requirement was 115 horsepower hour.



   Figure 5 also shows the effect of the length of the accelerator tubes. The curve formed with the small circles refers to an accelerator tube 8 inches long. The curve formed with the small squares relates to a 24 inch long tube, and the curve formed with the small triangles relates to a 4 inch long tube. The 8 inch tube was much more efficient than the 4 or 24 inch tube, for the diameters: tested, and the diameter in the tester, i.e., 2 and 4 mm , did not appear to result in any measurable difference. In a larger scale apparatus, it appears that proportionately the above is also true.

   For small diameters *, the acceleration tube should be between about 4 and 24 inches long, with a length of about 8 inches being optimum for best performance. Apparently, the 4 inch tube is too short to bring the particles up to gas velocity due to slippage. The 24 inch tube caused too great a pressure drop, due to friction, to have efficient operation of a 4mm tube. With larger diameters, the optimum lengths are proportionately greater.



   In the range of 0.3 to 1.0 pounds of coke per standard cubic foot of gas, the solids loading rate appeared to be about optimum, and the variations were small. At a loading speed of less than 0.1 pounds per standard cubic foot, the power requirements increase.

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 were lying very strongly. The results are given in Table II, for which the use of the 8 inch throttle jet tube was intended.



   TABLE II.
 EMI11.1
 
<tb>
<tb>



  Loading <SEP> Speed <SEP> of <SEP> gas <SEP> in <SEP> HP.hour / ton <SEP> of <SEP> colivres <SEP> of <SEP> coke / foot <SEP> tube <SEP> acceleration <SEP> ke <SEP> through <SEP> sieve
<tb> cube <SEP> standard <SEP> of <SEP> gas <SEP> ¯¯¯¯¯¯¯¯¯¯¯¯¯¯ <SEP> of <SEP> 100 <SEP> meshes
<tb> 0.08 <SEP> 300 <SEP> 428
<tb> 0.38 <SEP> 246 <SEP> 48
<tb> 0.61 <SEP> 255 <SEP> 47
<tb>
 
Similar results were obtained, using a narrow range of coke particle sizes (48-60 mesh, 249-295 microns) for the feed. The ratio of gas velocity to yield was virtually unchanged. The power requirements were slightly higher than for the wider range of coke sizes in Table I.



   It should be noted that the power requirements drop and become relatively constant at 260-300 feet per second and above.



   For comparison, a ball mill required 97 horsepower hour of input power to crush one ton of coke, having roughly the same size distribution, to pass through a 100 mesh per linear inch screen, or roughly double the power requirements for the steam jet. Apart from the running cost, the investment costs are much higher for a ball mill. The impact attrition apparatus system operates even more efficiently on agglomerated coke particles and relatively large particles. With 20-35 mesh (400-800 micron) agglomerated coke, 96.7% by weight of coke was reduced in particle size in a lightly loaded jet at 250 feet per second.

   For comparison, a 48-60 mesh (246-295 micron) sample showed only a 26.2% size reduction in one pass.



   As mentioned above, it has been found advantageous to recycle the large size broken coke particles to the acceleration nozzle. Using an 8 inch long, 4mm inside diameter throttle tube with a load of 0.25 pounds per standard cubic foot of gas at 200 feet per second, it took 94 horsepower hour / ton to produce coke passing through a 100 mesh per linear inch screen. When the coke was recycled at 200 feet per second, the power required was reduced to 46 horsepower hour per tonne. The material discharged from both runs showed the following distribution of particle sizes.



   TABLE III.
 EMI11.2
 
<tb>
<tb>



  Weight <SEP> on <SEP> sieve <SEP> of <SEP> Test <SEP> A <SEP> - <SEP> coke <SEP> Test <SEP> B <SEP> - <SEP>
<tb> number <SEP> of <SEP> meshes <SEP> original <SEP> recycling
<tb> 35 <SEP> 5.6 <SEP> 0.9
<tb> 42 <SEP> 53.4 <SEP> 29.5
<tb> 48 <SEP> 71.4 <SEP> 50.5
<tb> 60 <SEP> 80.5 <SEP> 61.2
<tb> 80 <SEP> 89.8 <SEP> 73.6
<tb>
 

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 EMI12.1
 
<tb>
<tb> Weight <SEP> on <SEP> sieve <SEP> of <SEP> Test <SEP> A <SEP> - <SEP> coke <SEP> Test <SEP> B <SEP> number <SEP> of <SEP > meshes <SEP> of <SEP>:

   <SEP> originalrecycling
<tb> 100 <SEP> 93.6 <SEP> 80.7
<tb> 150 <SEP> - <SEP> 88.2
<tb> 200 <SEP> 99.2 <SEP> 93.4
<tb> 325 <SEP> - <SEP> 97.2
<tb>
 
Therefore, recycling the coarse coke from line 75 to line 51 in Figure 2, from line 94 to line 80 in Figure 3, or through line 219 in Figure 4, appears to be very advantageous in terms of regarding the grinding yield.



   In the separation or elutriation of fine particles, from the bed or mass of crushed or attritioned coke, the separation efficiency can be increased by filling the bed with Berl elements, Raschig rings, etc., such as This will easily be understood by specialists in this field. Beds 60 (Figure 2), 92 (Figure 3) and 213 (Figure 4) can be packed so, if desired, that the finely divided solids can be more efficiently separated from the larger solids.



   Various improvements and variants, such as the use of cyclones or other separation devices, instead of apparatus for separation by deposition or elutriation, will suggest themselves to technicians in this field, and it is quite obvious that the invention is not limited to the details described.



   CLAIMS.



   1. - In the process of coking heavy hydrocarbon oils by contacting a fluidized mass of preheated coke particles, a process in which the coke particles are sent, continuously, through a fluidized coking zone in order to grow by accumulation of coke on them, and in which at least part of your particles are continuously reheated and recycled via inlet and outlet pipes of the coking zone, the improvement which consists in maintaining a mass, a substantially constant number and size distribution of coke particles throughout the system, consistently removing relatively large coke particles from the system,

   and steadily replacing the removed particles with a substantially equal number of smaller particles.


    

Claims (1)

2. The method of claim 1, wherein the smaller replacement particles are produced by impacting the larger coke particles at high velocity against a hard material target in a relatively dispersed area of the system. 3. A method according to claim 1, wherein the smaller replacement particles are produced by impacting the larger particles of coke against other particles. 4. - The method of claim 1, wherein the replacement particles are projected against a hard fixed surface. 5. A method according to claim 2, wherein the smaller particles are produced by impacting the larger particles at high speed against a relatively fixed metal platen. 6. - The production process of "elementary coke" or "basic coke <Desc / Clms Page number 13> intended for use as coke deposition cores, in a fluidized bed oil coking system, which comprises establishing an artificially sparse zone in a dense mass of these particles, passing at high speed of a gas jet through this zone, the separation of the large particles, from this dense mass to go into the low density zone, and the projection of these large particles at high speed, thanks to said jet, against a hard impact surface to force these particles to break up into finer particles as a result of this impact. 7. - The method of claim 6, wherein the impact surface is a hard rigid target surface. 8. - A system for converting heavy hydrocarbon oils into relatively volatile products, which comprises a coking vessel, means for establishing and maintaining a fluidized bed of hot coke particles in this vessel; means for supplying oil in contact with these particles; means for supplying the oil in contact with these particles; means for reheating and recycling the particles to force them to grow due to the conversion of oil on contact with them, with formation of coke deposits thereon; means for continuously and selectively removing large particles of coke from the system; and means comprising high velocity fluid jet systems for breaking up relatively large coke particles into smaller elementary particles to numerically compensate for particles removed from the system. 9. - Apparatus according to claim 8, wherein said high speed jet systems consist of a pair of opposed jets. 10. - Apparatus according to claim 8 wherein said high speed jet systems consist of a pair of opposed jets with between them a rigid impact target. 11. - Apparatus according to claim 8, wherein said high speed jet systems consist of a separation jet by deposition or elutriation and a rigid impact target. 12. - Apparatus for adjusting the dimensions of particles in a system for contacting solids and a fluid, comprising in combination: means for classifying the solids by a thrust force, and comprising a conduit having longitudinal connection portions, of substantially different cross sections; a solid shock target, supported in the portion of smaller cross section :, high speed fluid jet means to project (The relatively large particles against this shock target with a speed high enough to break them into smaller particles This jet also has sufficient fluid circulation capacity for the fluid coming out of it to deposit the finer, larger particles in the portion of the apparatus of larger cross section. 13. - Apparatus according to claim 12, in which the target has a concave impact surface thanks to which the solid particles tend to accumulate therein in a mattress and to reduce the abrasion of this surface, caused by the impacts of the particles. particles. 14. - The process of breaking coarse solid particles of coke and the like into finer particles and separating coarse particles from fines, which includes the projection of these large particles, by a gas stream at high speed, against an impact surface with sufficient velocity to break them into smaller particles, and the simultaneous use of the blast gas stream to separate the larger ones <Desc / Clms Page number 14> fine particles of the largest, by elutriation or separation by deposition. 15. - The method of claim 14: wherein the flow of blast gas has a velocity of between about 150 and 1000 feet per second. 16. - The process of providing elemental coke for use as coke deposition cores in a bed of fluidized solid particles of coke, into which the heavy oil is fed for coking, which processes includes discharging of a current of these solids. of coke in an acceleration jet and the projection of these solids against a hard impact target at a speed of about 150 to 1,000 feet per second. 17. - The method of claim 16, wherein a hard platter is used as a target. 18. A method according to claim 16, wherein other coke particles are used as a target. 19. The process of claim 16, which comprises separating the larger sprayed particles from the smaller ones, passing the smaller particles to a coking reaction, and recycling the larger particles. 20. - Apparatus for keeping the coke content in equilibrium in a coking operation, which comprises: a coking reactor: attrition means comprising a high speed gas jet, intended to project the relatively large coke particles against a shock target; means for separating by deposit the fine particles produced by this shock and for carrying them into the coking zone of this reactor; means for recycling the larger particles to the attrition means; and means for removing large particles from the system at substantially the same rate as that of formation of the smallest particles. 21. - The process of coking hydrocarbon oils, which comprises: projecting relatively large particles of coke at a speed of 150 to 1000 feet per second, against a solid target, so. to produce small particles of elemental coke; the separation, by deposit or elutriation, of the small particles from the larger ones; passing the small particles to a coking reactor; supplying oil in contact with the small particles to remove this oil and cause coke to deposit on these particles, thereby forcing them to grow; and removing large coke particles from the system at a rate controlled to maintain substantially constant the total number and mass of coke particles in the system. in annex: 2 drawings.