BE511161A - - Google Patents

Description

       

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  IMPROVEMENTS IN CIRCULATION METHODS AND DEVICES
OF SOLID GRANULAR SUBSTANCES.



   The present invention relates to a method and apparatus for the conversion of hydrocarbons in the presence of a moving catalyst bed. It relates more particularly to improvements to the processes and devices operating in a circuit, in which the conversion of the hydrocarbons and the regeneration of the catalyst, with a view to eliminating the carbonaceous deposit formed on this catalyst during the conversion, s' perform in superimposed reaction and regeneration zones through which the catalyst moves successively by gravity in a continuous manner, in the form of a compact moving bed,

   said data lyser then being transported from the lower end of its downward stroke to the upper end thereof by a pneumatic elevator.



   In the preferred embodiment of the invention, the tram- port of the catalyst, or of any other circulating granular solid substances to which the said invention also applies, from the lower end of its downward stroke to at the upper end thereof is effected in a number of parallel and separate riser conduits under conditions which minimize the wear of catalyst or other granular solids.



   Although the invention is described below in its application to a catalytic cracking process, and that the improvements in the apparatus relate more specifically to a catalytic cracking installation, it must be understood that the invention no is by no means limited to this particular application. It can in fact be applied to other processes or devices operating in a circuit and using superimposed zones in which reactions take place in the presence of a downwardly mobile layer of granular contact mass.

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   The catalyst or other contact substance to be treated is in the form of elements of relatively large dimensions or of agglomerates such as pellets, raw grains, etc., the dimensions of which are between approximately 1 mm and 1 cm. In the case of a device for the conversion of hydrocarbons, the granular substance is preferably a catalyst, and the gaseous medium used for the pneumatic transport can comprise either flue gas, water vapor or any other inert gas, either gaseous or vaporized hydrocarbons, air etc ...



   The present invention is more particularly applicable to hydrocarbon conversions as described in an article entitled "Houdriflow New Design in Catalytic Cracking" published in the journal "The Oil and Gas' Journal" of January 13, 1949.



   The devices used 9 for this purpose have superimposed zones; for the conversion reaction of the hydrocarbons and the regeneration of the catalyst., the communication between these zones being obtained by suitable devices, forming, pressure seals, that is to say allowing the passage of solids d zone to zone while preventing gases or vapors from one zone from mixing with those from the other zone.



  From the lowest processing zone the catalyst is discharged into the introduction zone of the pneumatic lifting device, where the solid substance is contacted with the lifting gas which carries it upwards to a release zone where the lifting gas is collected. separates from the solid substance, the latter then resuming its downward course.



   Such pneumatic elevating devices overcome certain drawbacks inherent in mechanical bucket elevating devices previously employed, particularly when applied to units in which relatively large quantities of catalyst or other granular material circulate;

   however, the operation of pneumatic lifting devices poses particular problems, relating in particular to the elimination of excessive wear of the catalyst and the erosion of the mechanical parts of the apparatus, on the one hand and maintaining uniform flow of catalyst through the riser This latter problem is particularly acute in multiple riser arrangements where the catalyst is supplied to the various riser tubes from a common distribution source .

   In such devices, accidental alterations in operation. inside one of the riser tubes may cause pressure fluctuations at the lower end thereof of sufficient magnitude to create a differential back pressure between the inlet end of the malfunctioning riser tubes and the ends of the risers. introduction of adjacent riser tubes.

   In this case the lift gas introduced in the vicinity of the inlet of the malfunctioning riser tube may be diverted through the compact catalyst mass to the inlet of the adjacent riser tube, resulting in a faulty operation of the latter and consequently of the lifting system as a whole. The problem is particularly serious when the shortest possible path for gas flow through the catalyst compact, from an inlet port to an adjacent inlet port, does not provide. sufficient resistance to oppose the differential back pressure existing between respective inlet ports of the risers.

   Experience has shown that, for various reasons, it is inevitable that small fluctuations will occur in the flow of catalyst within the various riser tubes during normal operation of the riser. -When the inlet ends of the various riser tubes are not sufficiently separated within the mass of catalyst which flows downwards, it is inevitable that a migration of gas will occur from the region which surrounds a malfunctioning riser tube to 19, the inlet port of one or more adjacent tubes having a substantially lower inlet pressure.

   The effects of this migration of ele-

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 Vator which tends to remove this gas from the malfunctioning tube are cumulative.



  If the migration continues, it can cause a complete interruption of the flow of catalyst in the malfunctioning tube, and can affect the operation of the remaining riser tubes by increasing the flow rate of the catalyst beyond acceptable limits.



   On the other hand, the amount of solids that can be drawn upward through a tube of any given diameter is limited by practical pressurizing conditions, and by other considerations such as the disproportionate increase. wear and structural complications which are then necessary to bring the lift gas into contact with the catalyst and then to release the latter from said gas. As the dimensions of the tube are increased, maintaining the desired flow conditions favorable to a low rate of wear becomes more difficult to achieve, so that in processing larger quantities of solids it has often been found it is preferable and more economical to use one or more smaller tubes rather than a single riser tube of larger diameter.



   There are also other factors which must be taken into consideration in order to achieve proper operation of single or multiple tube elevators, in order to achieve such low wear rates of granular solids in practice. as possible. For example, as the catalyst moves upward through the riser tube, it normally experiences acceleration along its flow path until it reaches its discharge velocity at the top of the riser tube from where it is then projected a considerable distance inside the release chamber arranged above this tube.

   Catalyst grain breaks due to the impact of this catalyst against the top wall and the side walls of the release chamber can be avoided by giving the release chamber the proper dimensions; however, this expedient does not take into account the damage to the catalyst falling back in free fall from the highest point that it has reached on the base of the release chamber or on the surface of the catalyst layer which is therein. bedroom.



   The present invention makes it possible to eliminate for the most part the malfunctions described above of the solids circulation devices as well as all other factors which contribute to the wear of these solid substances during the operation of these devices.



  This invention comprises for this purpose the use of new operating techniques as well as the production of improved apparatus. Various embodiments employed in the present invention have been described below by way of nonlimiting examples with reference to the accompanying drawings.



   In these drawings, Figure 1 is a schematic elevation of a device comprising a number of riser tubes symmetrically disposed around and in the vicinity of the chamber; some connections for gases and solids have not been shown to make the drawing clearer.



   Figure 2 is a partial elevation on a larger scale, partially in section, of the lower end of the lifting device shown in Figure 1.



   Figure 3 is a plan view from above Figure 1.



   Figure 4 is a horizontal section taken along line 4-4 of Figure 1.



   Figure 5 is an enlarged horizontal section taken along line 5-5 of Figure 1.



   Figure 6 is an enlarged vertical elevation (partially in section) of the upper part of a unit reaction chamber showing slight modifications from that of the fi

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 gure 1.



   Figure 7 is a similar view of a modified chamber showing the lower part of this chamber continuing below the part shown in Figure 6.



   Figure 8 is an enlarged fragmentary view of a solids discharge device having a different shape from that of Figure 7.



     FIG. 9 is a vertical elevation, partially in section, showing the arrangement of the fines separator in the apparatus, and the conduits connecting this separator to the upper hopper shown in FIG. 60
Figure 10 is a vertical sectional view of a modified embodiment of the release chamber in the case of using multiple riser tubes.
Figure 11 is a horizontal section taken along line 11-11 of Figure 10.



   Figure 12 is a fragmentary view on a larger scale, in vertical elevation and partly in section, of an elevator engagement hopper having a shape different from that shown in Figures 1 and 2.



   Referring more particularly to Figure 1, the bead-shaped catalyst is continuously discharged from the base of the upper hopper 11 and flows by gravity downward through the pressure seal 12 to. the upper end of a processing chamber indicated generally at 13 and which comprises a reaction zone and a regeneration zone or furnace.

   Passing through the whole of the treatment chamber 13, the catalyst flows downwards by gravity in the form of a compact moving bed and successively first passes through the reaction zone where it is brought into contact with the particles. hydrocarbons, in liquid phase or in vapor phase under conditions suitable for carrying out the desired conversion, then an intermediate zone in which the gaseous conversion products are separated from the catalyst which has been contaminated by a deposit of coke, then the regeneration zone in which the catalyst is freed of its carbonaceous deposit, by combustion of the latter in a gas containing oxygen,

     for example
The reactivated catalyst then flows downward from the bottom of chamber 13 through a vertical conduit 14 to the interior of a catalyst distribution chamber 15 whose axis is aligned with that of chamber 13. The catalyst flows directly from the lower end of conduit 14 onto a compact moving bed 16 (Figure 2) maintained within the distribution chamber. This bed 16 is not required for catalyst engagement, but is only of sufficient size to allow uniform flow of catalyst to the various riser tubes.



   From the lower end of the distribution chamber 15 the catalyst flows downwardly and radially outward through a number of supply conduits 17 which lead it to various corresponding engagement chambers 18. - to the various lifting tubes and where it is brought into contact with the lifting gas. These chambers 18 are clustered below and around chamber 13 and the catalyst flows downward into each of them in the form of a compact moving column.



  The introduction ducts 17 have a substantially uniform length and, together with the distributor bed 16 and the vertical duct 14, they constitute the gas seal between the lower end of the chamber 13 and the engagement chambers 18. Each vertical riser tube 20 extends upward from a low point within the corresponding engagement chamber 18, the lower end of said riser tube being immersed in the catalyst layer. contained therein. The

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 elevator tubes 20 are distributed around the periphery of the chamber 13 and arranged as close as possible thereto.

   In the particular embodiment of the invention shown in Figures 1 to 4, twelve elevator tubes have been shown arranged in a group of three diametrically opposed. Of course, any other number and any other arrangement of the lifting tubes can be provided. At the top of the elevator, each group of three tubes enters a common release chamber and the four release chambers are arranged so that the conduits which start from their lower part and which lead to the upper loading hopper have a substantially uniform length.



  If preferred, however, one could use a single large relief chamber which can incorporate loading facilities, or separate relief chambers for each riser tube.



   Referring to the part of the lifting device where the catalyst is introduced, and which has been shown clearly in the large-scale partial section of FIG. 2, it can be seen that each engagement device has a cylindrical chamber. close 21 concentrically surrounding the lower end of the lifting tube 20. The duct 17 is laterally connected to the cylindrical chamber 21 so that the granular substance which is introduced therein and which flows downwards in the form of a The compact mass may have a free surface in the upper region of the chamber 21. A cylindrical sleeve member 22 concentrically disposed between the riser tube and the wall of the chamber 21 extends upwardly beyond the chamber. upper end of the chamber.

   A seal 23 closes the upper end of the annular space 24 formed between the lifting tube 20 and the sleeve 22.



   The lift gas is introduced into the annulus 24 through an inlet pipe 25 opening at the upper end of the sleeve 22 and the lift gas flows downward through the annulus 24 to be discharged as a gasket. annular current around the lower periphery of the riser tube. The annular flow of lift gas engages the catalyst which flows inwardly below the lower end of the sleeve and carries this catalyst into the inlet of the riser tube. The lower end of the sleeve 22 may terminate at the lower end of the riser tube or slightly higher or slightly lower if desired.

   The desired setting of the sleeve can be determined in advance, and the sleeve constructed for this purpose; it is also possible to provide an additional adjustable sleeve element, not shown, which is then adapted to the lower end of the sleeve 22 so as to make the position of said sleeve adjustable. The lift gas is supplied to the port 25 by a manifold 26 in the form of an annular tube connected to the various gas inlet ports of the remaining engagement chambers. Preferably, the annular manifold 26 is arranged concentrically to the axis of the chamber 13.



   Additional lift gas can be supplied to the engagement chamber through an inlet duct 27, in the lower part of said engagement chamber.



   The discharge port of conduit 27 is preferably axially aligned with the riser tube and is arranged to discharge a stream of riser gas at a point disposed below and some distance from the mouth of the riser. riser tube, so that this riser gas is introduced into the bed of substance formed below the end of the riser, and diffuses upward through a layer of this bed in the direction of the orifice of the riser tube. Normally most of the lift gas will be introduced through the inlet 25 and a relatively small amount, not exceeding about 25% of 1% overall of the lift gas will be introduced through the port 27.



   However, in some cases it may be desirable to introduce all the lift gas or most of it at least by.

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 The inlet 27, and in this case the sleeve 22 can be omitted and the catalyst which enters the engagement chamber 18 through the inlet duct 17 can flow downwardly as a stream. annular, remaining in contact with the outer surface of the riser tube.

   The vertical end of the inlet duct 27 may be made adjustable so as to allow modification of the space between the end 27 and the bottom of the riser tube 200
Additional elevator gas may be introduced at or above the elevator inlet or above, and at some distance therefrom, so that this gas flows downward or sideways concurrently with it. the catalyst to the inlet of the elevator, which facilitates its flow while supplementing the quantity of elevator gas introduced at other points. For example, this additional elevator gas can be introduced through orifice 28 to 1. upper end of engagement chamber 18.

   It is also possible to eliminate the introduction of secondary gas through line 27, in which case the entrainment will be effected by the primary gas introduced through line 25 and the annular space 24, increased by small quantities of gas introduced through the orifi - this inlet 28 and diffusing downwardly through the catalyst bed into the engagement chamber 18.



   FIG. 12 shows a variant of the device for introducing the lifting gas into the engagement chamber. In this embodiment, the engagement chamber 18a comprises a flared lower part 19 which surrounds the lower end of the cylindrical part 21a, and which forms therewith, at an intermediate level, a annular space 19a communicating with the gas inlet duct 28a, so that the gas introduced by this duct enters the annular space 19a and diffuses laterally through the catalyst layer towards the orifice of the riser tube 20 .

   A sleeve 22a concentrically surrounds the riser tube 20 creating an annular space 24a between itself and the outer wall of the riser tube; this space communicates with the gas inlet tube 25 which operates in a manner analogous to that of FIG. 2.



  In operation, the primary gas which constitutes the major part is introduced through line 25 while a small fraction of auxiliary gas is admitted through line 28a; this fraction serves to release the catalyst bed and to push it towards the orifice of the sleeve 22a which is open at its base, and to facilitate the entrainment of the catalyst in the riser tube by the main gas discharged by the space ring finger 24a. As can be seen in Fig. 12, a PC pressure controller can be provided to adjust the rate of admission of gases through conduit 28a to maintain a fixed differential pressure with respect to a determined point at advance of the elevator tube 20.



   The lift gas introduced either from the bottom or from the side, concurrently with the catalyst, in any of the embodiments described, serves primarily to exert catalyst flow rate control as it is known that even relatively small amounts of gas flowing downwardly or laterally with the catalyst in the engagement chamber can allow regulation of the flow of catalyst within the riser tube. It is then evident that the flow in each riser tube can be controlled by controlling the passage of small quantities of gas through either orifice 27 or 28 or both, or through the. 'orifice 28a.

   The lift gas can, of course, be added in a relatively quantity. low amount of gas introduced in excess to form a seal at a point disposed in the path of the catalyst going to the engagement chamber, and for example to the inlet port 29 (Figure 2) at the upper end of the chamber. distribution 15. Gas may be supplied to the engagement ports 27 by a manifold 30 in the form of an annular tube, and also disposed concentrically to the axis of the chamber 13.

   Lift gas introduced through the various inlet ports can be made to flow into the engagement chamber by keeping the source of ele-

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 release a pressure higher than that which is necessary in the engagement member of the elevator; the lift gas can also come from a low pressure source and be delivered into the engagement chamber of the lift by a thermocompressor as shown at 34. In the latter case, the lift gas introduced into the chamber engagement will include a large fraction of the compression gas used by the thermo compressor ... -. - -.

   The elevator tube 20 extends upwardly to a substantial distance above the end of the loading treinea 11 and protrudes into a clearance chamber 3 1. (Figure 1), a separate release chamber being provided in this embodiment for each group of three riser tubes 20 (Figure 3). Within the release member 31 the catalyst is released in a known manner from the lift gas and the latter is discharged from the release chamber through the orifice 32. The released catalyst collects at the base of the gasket. release chamber 31 which it leaves through flow conduits 33 directed radially downward and inward in the direction of the common axis of the assembly.

   The conduits 33 are connected to the upper end of the loading hopper 11 and they discharge the released catalyst onto the catalyst bed which is maintained to ensure flow.



   Although the illustrated embodiment shows individual release chambers for each group of three riser tubes it should of course be understood that the invention also covers the use of a single large-sized release member. a diameter sufficient to receive the ends of all the riser tubes or, on the contrary, individual clearance chambers for each of the individual tubes. In the case of a single and larger release chamber, the catalyst released from the lift gas streams collects at the base of said chamber and flows downward and inward. , in the central outlet orifice arranged along the axis of the apparatus.

   The released catalyst can then flow vertically downward through a single feed conduit opening out at the center of the base of the release chamber. There is shown in Figures 10 and 11 and will be described hereinafter another embodiment comprising several elevator tubes discharging into a single release chamber.



   The dimensions and arrangement of the elevator apparatus and of the transfer conduits which are connected are established so that the pressure fluctuations which occur at the lower end of any of the elevator conduits, as a result of accumulation of catalyst in these tubes, have no influence on the inlet orifices of one or more of the other elevators Thanks to the relatively long flow path that any fraction of gas should follow. would seek to move from a region surrounding one of the riser tube orifices to another, sufficient resistance is imposed on the gas flow to prevent migration of that gas, for all pressure fluctuations to which one can normally expect.



  Thanks to the noticeable pressure drop that occurs across the mass of the catalyst on the path from one elevator inlet port to another inlet port, there is a sufficient period of time for everything malfunction occurring in one elevator can correct itself before the resulting pressure fluctuations at the base of the malfunctioning elevator can influence other elevator inlet ports .



   In the embodiment which has just been described, it has been assumed that the primary lift gas, which may for example be a flue gas, comes from a source maintained at a pressure lower than the pressure required in the pipes. elevator engagement chambers 18. To induce the flue gases supplied by the manifold 26 into the sleeve 22 of the elevator engagement chamber to the desired high pressure, a jet compressor 34 is disposed in the gas inlet duct 25. This

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 The jet compressor is supplied with relatively high pressure water vapor through line 35 connected to a water vapor collector 36.

   The flue gases from the manifold 26 are fed to the jet compressor through line 370.
Each of the gas conduits to the elevator engagement chambers has a control valve disposed in the usual manner.



  If desired, however, an automatic adjustment device can be provided for separately adjusting selective adjusting valves according to the pressure variations in the lifting system. Any malfunction in one of the risers, liable to cause pressure fluctuations in this riser will consequently cause the automatic adjustment system to regulate the entry of gases into the malfunctioning riser so as to correct this. malfunction., in a manner analogous to what has been shown in figure 12.



   It should be understood that when the regeneration zone of a unitary process chamber is operated at a sufficiently high pressure, flue gases can be withdrawn from this zone and conducted directly to the elevator engagement chambers without causing any damage. 'Additional devices such as jet compressors 34 should be used.



   By using a multiplicity of riser tubes the relatively high rates of wear heretofore encountered when only one large diameter riser tube was used for the circulation of large amounts of solids through it. industrial operations, can be reduced considerably. Further elimination of possible causes of wear of solids in a single or multiple elevator system is also achieved by the construction and arrangement described below.



   Although the riser tubes 20 discharge in a large area within the clearance chamber 31, which results in a reduction in the gas velocity and hence the separation of solids and gases., The solid particles discharged from them. The elevators still retain, at the point of loading, such a living force that these particles are thrown upwards to a certain distance above the top of the elevator. Unless special devices are provided, some or all of these solid particles can strike the top or side walls of the release chamber with sufficient force to cause the particles to break and wear.

   Broken particles and finess if allowed to remain and accumulate in the mass of circulating solids would interfere in various ways. proper functioning of the system; even if these fines are removed there is also a loss of expensive substances which adversely affects the general economy of the system. The impact on the top and the side walls of the release member can be largely eliminated by making the chamber 31 of suitable dimensions so that these walls are out of the path traveled by the solid particles at a minimum. noticeable speed.

   However, there is another important factor which contributes to the wear of the solid particles, and which is not removed by the increase in the height and diameter of the chamber, and that is the wear due to the impact of the chambers. particles of catalyst falling under the effect of the acceleration of gravity from the maximum level which they could reach.



   The catalyst particles having the dimensions indicated., When raised to a height of 33 m. or more in tubes of suitable diameter can reach at the discharge end of the elevator an average speed of 10 mb / s or more and they can therefore be thrown over the discharge end of the elevator. riser tube up to 7 mb high and sometimes even 10 mb or more before starting to descend.

   To minimize the wear due to this factor, the solids discharge rate and hence their lift height into the discharge chamber will be effectively reduced by flaring the top of the elevator:

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 the solid particles are then transported by the gas stream over
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 most of the distance traveled through the elevator (in the non-flared part of the riser tube) at sufficiently high speeds to allow smooth flow and then they undergo regular deceleration in the upper part of the riser tube. so as to be discharged into the release chamber at low speed.

   To get
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 This smooth deceleration without the risk of causing intermittent agglutination or tendency to flow intermittently 1 -'an¯kle of the riser tube flaring must be very small. It has been found that an angle of less than 7 and even preferably at 5 and for example between 0.15 and 3 gives the desired regular deceleration without causing too much relaxation
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 sudden surge of lift gas, which would tend to develop "localized" concentrations of particles at or above the expansion point which would lead to the formation of agglomerates or unwanted irregular flow which could cause increased wear.

   When using the flowing angles indicated the diameters of the non-flared part of the riser tube and the top of the flared section have the following relationships between them: the ratio of the square of the last to the square of the first is approximately included '
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 be 193/1 and 5s0 / ls, this ratio being equal to the ratio of the horizontal cross sections at the points indicated on the lifting tube.

   In most industrial installations (that is, for elevators between 30 and 100MB high), the length of the flared portion will be approximately 7 to 15MB.
In the embodiment which has been shown in particular in Figures 1 and 2, the elevator tubes 20 enter the release chamber 31 at a location arranged along a cord spaced a certain distance from the center of the chamber. This method of construction allows a more compact arrangement of the various clearance chambers around the periphery of the hopper 11 and facilitates the construction.
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 tion of the installation support.

   To prevent the flow of solids discharge against part 38 (Figure 5) of the chamber wall,
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 The relief tube, which is closest to the riser tubes. The top end of each tube is eccentrically flared, so that the portion of the riser tube wall (S) which is closest to the wall 38 of the clearance chamber, is substantially rectilinear. and parallel to the vertical axis of the clearance chamber while the opposite wall of the riser tube (T) widens upward, in the direction of the axis of the clearance chamber at the previous angle. - indicated.

   Due to this eccentric flaring, the flow of solids
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 discharged is pushed back through the chamber from wall 38 of the release chamber and directed toward the portion of wall 39 which is furthest from the line of the riser tubes.



   While the velocity of each of the streams of emerging solids and gases discharged into the various release chambers 31 is thus reduced by a flaring of the upper part of the riser tube 20 and at least the major part of the solid particles contained in it. the current is thus projected upwardly into the evacuation chamber at a reduced height, which offers additional safeguard against the breaking of the discharged particles and gives greater operational flexibility allowing the efficient use of a speed.
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 Higher discharge at the top of the elevator 9 is provided in the release chamber 31 to effectively reduce the maximum speed in free fall likely to be reached by the granular downward solids,

   thereby reducing their impact force against the base of the release chamber or against the particles which rest on this base. This result is obtained, as has been shown in Figures 1 and 5, for example, by interrupting the already started fall of the solid substances released at an intermediate point of their downward stroke.

   For this purpose an inclined plate 40 forming a baffle is disposed on the side of the solids discharge stream which is adjacent to the part of the wall 38 of the clearance chamber and another series of plates.

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 analogues 41, 42 and 43 protrude inwards and upwards on the diametrically opposed wall o These trays have such dimensions and are arranged so that their inner edges are placed just outside the path followed by the current ascending solids.



  Each of the trays further, has openings adjacent to the respective walls to allow the solid particles it has collected to discharge to a lower level. The openings 44 formed in the series of vertical plates 41, 42 and 43 are preferably offset with respect to one another. In order to allow a layer of solid granules to accumulate and be maintained in a substantially continuous manner practically on the whole of the upper surface of each tray 40 to 43, provision is made on the upper surface of each of these plates one or more ribs 45.

   The particular, non-symmetrical arrangement of the plates on their respective walls, in the embodiment shown in Figures 1 and 5 has been adopted due to the nature of the path followed by the stream of solids discharged in this mode of discharge. achievement, itself due to the arrangement of the lifting tubes. In the release chamber 31 are provided vertical separations 46 which extend from the wall 38. To the wall 39 so as to constitute separate chambers into which the various elevator tubes 20 are discharged.

   With the release chambers in operation as just described, the mixture of granular particles and gases discharged at the top of each of the elevator tubes continues its upward movement due to the live force which is communicated to it by the lifting gas, towards the top of the release chamber, \) and the stream of solid substances moves outwards with respect to the axis of the rising current o The periphery of this stream thus forms an angle about 7 to 15 with respect to the axis of the current.

   As the force of the upwardly rising solids decreases, the particles spread even wider and then fall downward in a form similar to that of an open umbrella formed from the granular particles. falling under the influence of gravityeuro Some of these particles rise higher than the others and falling are picked up by the highest plate 43 while the particles which arrive lower fall on the surfaces of the plates T lower 41 and 420
The solid particles are thus damped in their descent by falling on a layer of solids, then they are discharged through the orifices 44 to finally reach the base of the chamber 31.



   In the modified embodiment, shown in Figures 10 and 11, one can see a device using only four elevator tubes.



  This embodiment is not, however, of course restricted to a determined number of riser tubes. All the elevator tubes 20a discharge into a common release chamber 31 and are distributed concentrically around the longitudinal axis of this chamber. The lower ends of riser tubes 20a (not shown) receive catalyst from engagement chambers similar to chambers 18 of Figures 1 and 2 but which are arranged differently with respect to the axis of reaction chamber 13.

   These engagement chambers, in this embodiment, are aligned with the corresponding tubes 20a which are directed vertically upward towards the single release chamber 3a. Furthermore, the operation is substantially similar to that previously described, the gas being discharged through a pipe 32a and the granular solids released accumulated at the base of this chamber are discharged through a pipe 33a (also corresponding to the pipe 33 of the embodiment described above)
The clearance chamber 3 1a also includes drop-interrupting devices in order to reduce the wear of the solids by impact, canopy this chamber. As shown, a separation surface 50 extends horizontally through the clearance chamber, inside the lower half of it,

   and it separates the clearance area

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 EMI11.1
 proper which is above the portion of the water bed disposed below. Four pentagonally shaped baffles 51 arranged at right angles to each other divide the clearance space into equal sectors. so that each of the riser tubes 20a discharges into one of the respective sectors. The baffles are carried on the longest side of each of them by a pillar 52 which is itself carried by supports.
 EMI11.2
 soles attached to the base plate.

   A series of trays 539 54s 55 extend inward and upward from the outer wall of the clearance chamber 31a; plates are spaces vertically with respect to one another and each of them terminates in an interior circular rim and parallel to that of the other plate, and arranged on a frustoconical surface, coinciding with the inclined edges of the baffles 51
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 which support the interior arenas of the platforms. Thanks to this arrangement. ,, as in the case of the embodiment previously ''
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 described the trays are kept out of the way of the current. ascent of solids but remain on the path of the released solids which fall
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 bent.

   These trays are also provided with discharge ports 56 along their outer peripheries, the orifices of each tray being offset from those of the next adjacent tray. These trays can also be provided with retaining ridges for the solids analogous to the ridges 45 previously described. The base plate 50 is provided with a
 EMI11.6
 symmetrically arranged series of tubular members 57 directed downwards and through which the solids which finally reach this plate are discharged onto the layer arranged below. The operation of this embodiment is quite similar to that of the embodiment described above.



   The guide baffles 51 serve primarily to separate the individual streams emerging from the riser tubes as the streams ascend through the frustoconical passage limited by the inner ridges of the trays, reducing any tendency to turbulence which might be caused by the possible influence of one current on the other. If desired the individual tubes 20a can go into
 EMI11.7
 their upper part widens at a low angle, so as to reduce the discharge speed; the flaring may also be provided only along the part of the wall of the riser tube which is furthest from the pillar 52.



   Referring more particularly to FIGS. 6 and 7, the arrangement and operation of the conversion and regeneration zones of the device will now be described in more detail. The catalyst which leaves the release chamber 31 through the conduits 33 is discharged at the top of the hopper 11 from where it passes through the gas seal 12 into the unit reaction chamber 13.

   When using the release chamber shown in Figure 10 for example, the flow capacity is provided at the base of the release chamber 31a, so that the flow control hopper 11 (Figure 6) can be omitted and that the solids discharge conduits 33a can terminate directly at the top of the reaction chamber 13. At the top of this reaction chamber 13 is provided at 59 an inlet conduit for the gas forming a seal. (figure 6). .



   The chamber 13 is surrounded by a cylindrical envelope allon-
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 gée-unique9 of stepped shape, comprising sections of gradually increasing diameters from top to bottom. The uppermost and narrower section 60 contains the reaction zone. Intermediate section 61 comprises, from top to bottom, the vapor development zone, the purge zone, the catalyst transfer zone and the first stage of the regeneration zone. The lower and wider section 62 contains the area corresponding to the second regeneration stage.

   It will be understood that the invention is not limited to the provision of two regeneration stages and that a larger number of intermediate regeneration stages can be provided if desired or if necessary in accordance with the requirements. depending on availability

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 general position which is described and shown.

   In addition 5) - as has been shown in Figure 1, the widening of the lower regeneration zone can be suppressed., From the bottom of the regeneration zone, the catalyst is discharged by a device. special designed to ensure uniform discharge over the entire section of the chamber, and it is discharged into a suitable receiving device-such as a hopper 15 (Figure 1) which distributes the catalyst through different conduits 17 to the different chambers of engagement 18 of the elevator
The catalyst which enters the upper part of section 60 is received on a tube holder or distributor plate 65 and forms a compact bed flowing by gravity above the plate.

   Most of the catalyst from this bed is discharged through a series of distributor conduits 68 which empty inside section 60 onto the surface of a bed disposed below plate 65, if although there is a vapor receiving space which surrounds the conduits 68 and which is disposed between the underside of the plate 65 and the upper surface of the catalyst bed disposed below o A fraction of the catalyst originated from the bed which resting on the plate 65 flows into a cylindrical sleeve 67, open at its ends and which passes through an opening made in the plate 65 so as to discharge into a cylindrical chamber 66 arranged concentrically and mounted below the plate.

   A hydrocarbon introduction conduit 69 passes through the central portion of the sleeve 67 and terminates in a spray head 70 through which the liquid hydrocarbons can be introduced alone or mixed with water vapor or vaporized hydrocarbons. This duct is surrounded and protected inside the sleeve 67 by a casing 71 which is provided at its lower end, below the discharge port of the sleeve 67, with a portion which recedes towards the end. exterior 72 and which is extended by an inwardly flared portion disposed below, and intended to conform to the exterior periphery of the spray head 70.

   The casing 66 has at its lower end an inwardly directed rim which is disposed at a level substantially coinciding with that of the lower end of the outwardly flared portion 72, thus creating a narrow annular passage. 73 through which the catalyst flows as an annulus curtain falling freely past the jets of liquid discharged from the head 70, onto the surface of the compact bed disposed below. The spray head may be of a type suitable for converting into mist, spray, or any other liquid particles of suitable size, the liquid hydrocarbon which is introduced.

   The inner rim of the flange is spaced from portion 72 by an appropriate amount so as to allow the formation of a relatively thick curtain of free-falling catalyst particles so as to stop completely or at least in some way. sufficient passage of all the atomized liquid particles projected onto this curtain by the spray head 70.- 'By virtue of this arrangement, any migration of atomized liquid particles which would be liable to be deposited on the interior surfaces in the chamber is reduced to a minimum. part 60 of the chamber, which prevents any harmful formation of carbonaceous deposit on these surfaces.

   A jet of water vapor or inert gas, not shown, is directed downwards just above the spray head 70 and constitutes a further safeguard against the accumulation of carbon on this head.



   Through the wall of the section 60 of the reaction chamber passes a tube 74 which communicates with the vapor receiving space disposed below the plate 65 and which allows the introduction of additional hydrocarbon vapors to be converted. . The liquid hydrocarbon feed vaporizes or is converted, at least partially, into vaporized products on contact with the curtain of chaid catalyst, and these vapors, together with those which have been admitted through line 74, flow downward. ., through the compact falling bed of catalyst, in section 60.



  In a known manner, this section maintains the conditions desired to effect the desired conversion - cracking for example - of

 <Desc / Clms Page number 13>

 hydrocarbon vapors passing through this catalyst bed.



   From the lower end of the hydrocarbon contact zone, inside section 60, the catalyst flows outward as a compact moving mass so as to constitute an enlarged bed supported by the baffle plate or tube holder plate 75 and limited at its outer periphery by the walls of section 61, thus constituting an annular sloping surface 76 for the release of gases, surface disposed between the wall of section 60 and the wall of section 61. Passing from the bottom of section 60 to section 61, the mixture of catalyst and reaction gas products flows downwardly through the section. clearance region indicated generally at 77 and which extends through the bottom of section 60.

   This clearance section 77 comprises three groups of elongated channels 78 and 78a which extend laterally through the lower portion of section 60, at three different vertical levels, the lower channels 78a being considerably deeper than that. others. These channels are reversed-and horizontally spaced at each level to allow free passage of the catalyst between them. Each group contains the same number of channels and the corresponding channels are aligned vertically.

   Ducts 79 constitute passageways between the vertically aligned channels of each group for the gases given off from the catalyst below each inverted channel; these conduits open into the inverted channels 78a and comprise openings suitable for receiving gases below the channels 78. The channels 78a, arranged at the lowest level, pass through the wall of the section 60 so as to constitute an outlet allowing to discharge into the annular space 60a which surrounds the wall of the section 60, the gases collected by the channels 78 and 78a. A vapor discharge duct 80, communicating with the gas collecting space 60a, discharges therefrom the vapors discharged through the lower channels 78a as well as the vapors which enter this space by being released at the surface of the gas. catalyst 76.



   Tube plate 75 supports a shallow catalyst bed and carries a series of evenly distributed conduits 81 which pass through it upwardly. The catalyst disposed above the tube carrier plate 75 is discharged in the form of compact streams through the tubes 81 onto the surface of a lower bed carried by a similar tube carrier plate 82. The catalyst which rests on the plate tube holder 75 and that which passes through the tubes 81 is purged by water vapor or by another inert gas introduced through a conduit 83 which communicates with the vapor collecting space surrounding the tubes 81.

   The purge gas flows upwardly through the shallow bed disposed above the tube plate 75 and escapes within the lower channels 78 to be discharged with the hydrocarbon reaction products through the cone. - discharge pipe 80.



   From the tube holder plate 82 the catalyst flows downwards in the form of compact mobile columns through a series of joint tubes 84, the upper ends of which are mounted in the tube holder plate 82. These joint tubes are distributed. uniformly on the plate 82 so that the catalyst can be drained from the purge zone and distributed evenly over the entire cross section of the upper part of the regeneration zone without the need for special collectors and redistributors. The lower ends of the seal tubes 84 determine the upper level of the catalyst bed within the regenerator (Figure 7).



   The sealant catalyst tubes 84 are of sufficient size and number to assure passage of the catalyst between the reaction and regeneration sections with the maximum flow rate desired. The joint tubes are of such length that the compact columns of catalyst passing through them cause a drop; pressure-sufficient to prevent unwanted migration of

 <Desc / Clms Page number 14>

 gaseous reaction products between the reaction chamber and the regeneration chamber.



   The regeneration zone or furnace which is contained in sections 61 and 62 may be of any known conventional type and therefore has not been shown in detail in the drawings. In the embodiment shown schematically in Figure-7, two regeneration stages are provided. At the upper stage, a combustion gas such as air is introduced through a pipe 85 and flows upwards in countercurrent with respect to the catalyst. The gaseous regeneration products or flue gas are released from the catalyst at the surface 86 of the regeneration bed. These evolved gases enter the space surrounding the seal tubes 84 and are discharged from there through the flue gas discharge port 87 (Figure 6).

   A lower regeneration stage of air or other oxidizing gases is introduced through port 88 and flows upward in a manner which will be described hereinafter through a catalyst bed in section 62 to a separating release region. the upper and lower floors, none of which has been shown. The gaseous regeneration products from the lower stage are discharged through the outlets 89.



   At the base of the lower section 62 the catalyst bed is carried by a flat horizontal partition wall 90 forming a tube holder, which is disposed adjacent to the base of the chamber and is supported therein. an appropriate way. In the embodiment shown in Fig. 7 the partition wall 90 is removably disposed in an arcuate plate 91 having the shape of a flat and which is preferably rigidly attached to the wall of the chamber. This wall 90 then rests on said arcuate portion 91 in an appropriate manner by means for example of a ring (not shown) which is associated with it and from which it can be easily released.

   Vertical conduits 92 for 1-evacuation of the solids pass vertically, on the one hand through the wall 90 in holes provided in this wall, and on the other hand through the arched part 91. Below the wall 91 these conduits communicate with Individual conduits 93 inclined downwards converge towards the axis of the apparatus and which discharge into an exhaust manifold indicated generally at 94. An intermediate support for the wall 90 is formed by providing clamps or supports 95 at the bottom. vicinity of the upper ends of the conduits 92 and rigidly fixing conduits to the arched part 91. The conduits 92 thus transmit the load of the bed of granular solids to the part 91 which is better adapted by its curved shape to bear this load.

   By giving the holes formed in the partition wall 90 slightly too large dimensions, a sliding assembly is allowed for the passage of the upper ends of the conduits 92 which makes it possible to keep irremovability while preventing the solid particles from entering. the chamber formed below the partition wall 90 if not within the ducts 92. As can be seen in FIG. 7, the plate 90 defines with the base of the unitary chamber a wide chamber which is divided by the arched part 91 into a lower chamber 96 and an upper chamber 97 (included between elements 90 and 91).



   The arcuate piece 91 has orifices 98 through which the gas introduced into the lower chamber 96 through the conduit 88 enters the interior of the chamber 97. The gas from the chamber 97 flows upwards into the bed of catalyst disposed at the- above the flat plate 90 by short vertical tubes 99 which extend a short distance above the plate 90 into the movable cones of catalyst which discharge into the conduits 92 (compare with FIG. 8).



   At a certain distance above the upper ends of the tubes 99 and concentrically with these tubes are placed deflector devices generally indicated at 1000. Devices constituted, for example, by slotted cylindrical caps of the type employed.

 <Desc / Clms Page number 15>

 in the distillation columns, or by hemispherical caps can be used to divert the flow of granular solid particles so as to form in the mass of the solids free surfaces limiting spaces not containing solids but filled with gas.

   The gas which discharges upwards through the tubes 99 enters the free spaces thus formed, then passes through the free surface of the solids, which flow over the caps 100 to then flow upwardly through the layer of catalyst arranged. above. As has been shown (see in particular Figure 8) the caps 100 which serve to divert the flow of solids have the form of a series of truncated baffles overlapping one another and whose diameters decrease. as one rises, the whole being surmounted by a substantially conical cap and its cohesion being obtained by bars or supports 10. These caps are carried to the tops of the tubes 99 by - many 102.



   Thanks to the arrangement which has just been described, the catalyst or any other granular substance is discharged at the base of the regeneration zone in the form of a bed flowing downwards, uniformly, while the gas introduced at the bottom. the base of the bed flows upward spanning substantially the same vertical distance, minimizing the height required for the chamber.



   Since the desired regeneration of the catalyst has been carried out in the various regeneration zones as described above, the regenerated catalyst particles which can, if desired, carry a small deposit of residual coke are removed from the regeneration zone. lowest regeneration by vertical conduits 92 which are distributed in a substantially uniform manner over the horizontal cross section of the catalyst bed, which ensures a uniform downward flow of solids above the catalyst bed. horizontal section of the lita The inclined conduits 93 are arranged angularly with respect to the corresponding vertical conduits which communicate with them and this so that the granular solid substances can flow freely inside,

   that is, they form an angle of 45 or less with the vertical. These conduits '93 pass through the rounded or generally hemispherical surface which constitutes the upper part of the discharge device 94 and enter it to a shallow depth. The interior of the discharge device 94 is arranged, being welded. for example at the lower surface of this device, a series of funnels 105 which terminate in a common horizontal plane inside the duct 106;

   generally corresponds to the conduit 14 of figure 1, and discharges into the hopper of the elevator or into an intermediate catalyst distribution chamber such as chamber 15 (figure 2) which itself communicates with a certain number of catalyst engagement chambers. The funnels 105 are constructed and arranged so that there is a uniform flow of the solid granular substances, in the conduits 92 and 93. When the gas introduced into the lower chamber 96 is relatively cold it serves usefully to keep the cold. conduits 92 and 93 and consequently cooling by indirect heat exchange the granular solids which flow through these conduits.



   In the modified embodiment shown in Fig. 8, the flat partition wall 90 is omitted, and the vapor tubes 99 pass through the arcuate piece 91a in which they are mounted; this part 91a moreover corresponds to the head 91 of FIG. 7. The vapor tubes 99 are consequently in direct communication with the lower chamber 96. The arcuate part 91a thus serves both as a support for the bed of substances. solids and as a partition wall to prevent the admission of solids into chamber 96 except in conduits 91 and 93 which pass through this chamber.

   In this variant, the part of the volume of the furnace represented by 1-space 97 of FIG. 7 is oc-

 <Desc / Clms Page number 16>

   cupped by a non-mobile mass of catalyst; could also be filled, at least in part, with a ceramic or other, less expensive material.



   The differences in structure which exist in the various embodiments do not appreciably modify the operation of the assembly. In both cases there is a gas-tight chamber below the catalyst bed in which the gas introduced is not not exposed to contact with granular solids. The initial contacting of the gas with the bed of solids which moves by gravity takes place in the zone of contact whose lower limit is approximately at the level of the deflector devices 100. As these devices are arranged short only away from the introduction orifices going to the vertical conduits 92, the gas does not pass through a significant mass of solids, which is not actually in motion.

   Thus in the embodiment of Figure 7 there is no noticeable mass of standing solids on the partition wall 90. In the embodiment of Figure 8 although there is a layer of solids. immobile surrounding the conduits 92 and the lower part of the vapor tubes 99, this layer is below the zone of contact of the gaso The possibility that a zone is created opposing a high localized resistance to the flow as a result the accumulation of fines in this region is thus avoided. The contacting of the oxygen-containing gas with the granular solids and the evacuation of the granular solids takes place in the embodiment described, under advantageous distribution conditions,

   and simultaneously in substantially the same part or volume of the regeneration chamber, while the uniform downward flow of the moving bed of solid particles continues. Thanks to the device described, it is possible to save considerably on the height of the regeneration chamber, from 60 cm to lm 50, and even more compared to the known installations where the devices for contacting the gases are placed at a certain distance. distance from the level where solid particles are discharged from the bed.



   In the particular mode of construction of the regeneration section shown in Fig. 7, there are certain advantages that the operation can be carried out with a relatively low pressure drop per unit depth of gas passing through the zone. the lower of the furnace and a relatively higher pressure drop on the contrary per unit depth, through the catalyst layer in the highest regeneration zone.

   By operating in this manner the flue gases discharged from the lower zone through line 89 are at a pressure high enough to be used in the upward entrainment of the catalyst. Thus the flue gases coming from the conduit 89 can be sent to a manifold 26 (Figure 2) and if desired, also, partially to manifold 30 to ultimately arrive at the different elevator engagement chambers. It is of course not necessary to discharge the flue gases through line 89 at pressures in themselves sufficiently high to allow the desired upward entrainment operation, since provision is made to re- increase the pressure of the lift gas by means of the jet compressor 34.



  As the major part of the most easily combustible or distillable hydrocarbon or other components is discharged during the first stages of combustion in the upper zone of the furnace, the flue gases which are available in the ducts 89 are relatively free of vapors. Deleterious such as sulfur which can be detrimental to the activity of the catalyst.

   Because the smallest pressure drop occurs at the base of the regeneration zone, a relatively high average pressure and a relatively high discharge pressure are maintained for a given introduction pressure, and there is therefore a given introduction pressure, and there is therefore a higher oxygen pressure in the area where it is most necessary to facilitate combustion of the residual carbon which is most difficult to remove.



   In the regeneration section described, all areas of

 <Desc / Clms Page number 17>

 combustion works with a counter-current flow of the regeneration gas. The passage of gas from one regeneration zone to the other is easily prevented by maintaining the outlet pressure of the flue gases from one of the zones substantially equal to or slightly lower than the inlet pressure of the regeneration gas. in the area directly above.



  With all the zones operating against the current the pressure drops of the gases flowing upwardly through the different zones of the furnace add up, and the total pressure drop can then be used advantageously to compensate for the pressures. that prevail in the rest of the system which results in a reduction of the sealing requirements and allows to reduce the total height of the system
With the introduction of cold regeneration gas, such as atmospheric air at the temperature resulting from its compressions some of the sensible heat of the catalyst is removed by direct heat exchange which reduces and sometimes eliminates the need to use coils. coolers,

   and the space which would otherwise be required to accommodate the additional cooling equipment can be beneficially used to increase the volumetric capacity useful for combustion.



  It should be understood, however, that if considerations of thermal balance require additional cooling, cooling coils comprising a fluid for indirect heat exchange may be placed in one or more of the regeneration zones, or between these zones, as required. the construction method shown in Figures 6 and 7, all the well-known advantages due to the superposition of the hydrocarbon conversion zone and the coke combustion zones in a unit structure are retained, but the vertical distance that maintenance between incompatible areas to achieve joints is significantly reduced by the replacement of the single compact column forming joint with a number of relatively short compact columns having a relatively narrow cross section.

   In this way an appreciable reduction in height is also obtained, with the elimination of the devices which are necessary in the known devices for collecting and redistributing the catalyst as it passes from one zone to another.



   There has thus been fully described the construction and operation of a device for circulating catalyst or other granular contact mass in which said granular substance flows downward in the form of a moving bed through a hydrocarbon conversion zone and one or more reheating or regeneration zones to be finally brought back to the top of the device for restarting a new cycle by means of a pneumatic conveyor system.



  The device is designed to minimize the various factors which may contribute to the wear of the granular substance through the different sections of the reaction chamber 13 as well as within the chambers of the reaction chamber. engagement 18 and disengagement 31 of the pneumatic lifter. Despite this reduction in the possible causes of wear, there will nevertheless necessarily be formation of some fines in the continuous recirculation of granular substances; these fines must be removed to maintain proper functioning of the device.



  It is this operation which will now be described.



   Referring now to Figure 6 it can be seen that the loading hopper 11 has a bypass duct 200 through which a suitable fraction of the catalyst is withdrawn from the main circuit, the remainder of the catalyst maintained in the system being discharged from the hopper. - Mie by the conduit forming a seal 12. The fraction of catalyst thus drawn by the conduit 200 is fixed or regulated by means of appropriate throttling devices arranged in the conduit 200 or in a connection communicating with it, and by in practice, about 5% of the catalyst in circulation is thus withdrawn through line 2000
This catalyst withdrawn through line 200 is brought to a separate.

 <Desc / Clms Page number 18>

 rator which has been shown in general in FIG. 9 and whose operation will now be described.



   In bypass on the duct 200 is disposed a vertical duct 201 which communicates with the separator device indicated generally at 202. When this device is in operation, the catalyst coming from the duct 201 enters the separator via a connection. 203, with a determined flow rate, regulated by a device 204 which can be constituted by a diaphragm provided with a calibrated orifice, by a sliding valve or any other adjustment device. The duct 203 discharges into the upper section 205 of the separator in the form of a stream of freely falling particles which are traversed by gas,

   countercurrently flowing itself introduces at the base of this section through conduit 206. The upward flowing gas through section 205 collects dust and the most finely divided particles, which are discharged with it. the gas, through a conduit 207, in a cyclone 208, which, in the present case, has been shown mounted above the separator proper.



   The larger particles are discharged from section 205 of the separator into an enlarged hopper 210 disposed below, so as to constitute in this hopper a compact bed maintained at a certain level, indicated at 211, and which is at a height. a certain distance below the base of section 205. This bed level is maintained regardless of the amount of catalyst entering the separator through line 203, by separate introduction of catalyst into hopper 210.

   To this end, as has been shown, section 210 of the hopper is supplied directly by a branch 212 which communicates with the inlet duct of the catalyst 201 so that the level of the bed in the hopper 210 can be kept substantially constant regardless of the fraction of catalyst admitted to section 205 'under the control of device 204.



  The flow of catalyst through line 212 is determined only by the rate of discharge at the base of hopper 210.



   From the hopper 210, the larger catalyst particles, recovered after having been freed of fines in the separator, are returned to the device by means, for example, of a discharge duct 213 communicating with any suitable point of the system. The main catalyst circulation device C9 is thus that the catalyst in question can be sent directly to one or more of the engagement chambers 18 of the elevator or that the catalyst can be introduced at the top of the elevator. highest regeneration zone, and for example in the space included :! between the tubes forming a seal 84.



   Conduit 200 is shown as provided with an extension 215 communicating with suitable catalyst storage devices (not shown). This extension is used to bypass the separator as for example in the case where it is desired to evacuate the catalyst from the main circuit in order to stop the operation of the apparatus to allow periodic inspections or repairs.



   To replace the catalyst removed from the system in the form of fines, or in other cases where it is desired to add fresh catalyst to the system, for example to maintain equilibrium inactivity, a catalyst introduction line 216 is provided, communicating with a source of fresh catalyst (not shown) and discharging into a hopper 210 below the level 211 of the catalyst therein. The amount of fresh catalyst thus added to the system is determined by the dimensions of the discharge port of the inlet conduit 216 relative to the total cross section of the moving catalyst column, where this conduit 216 discharges into the system. this column.



   The catalyst discharge line 213, which discharges the separated catalyst and fresh catalyst, has a shut-off valve 218 and a suitable flow control device which may be in the form of a valve. diaphragm 219 provided with an orifice.

   he

 <Desc / Clms Page number 19>

 It should be noted that the flow-regulating device, 219, is arranged in a vertical part of the pipe through which the catalyst passes, because it has been observed that the arrangement of a diaphragm pierced with an orifice, a sliding valve or other device for regulating the flow in an inclined duct often caused a fine and uncontrollable flow of solids particularly in the case where there was a flow of gas through this regulator in the opposite direction to that of the solids.

   In addition, in order to prevent the accumulation of condensate moisture which could cause blockage or clogging of the pipe, devices are provided which allow a small quantity of gas to be introduced through the diaphragm 2190 For this purpose as this is shown, the duct 213 empties into an enlarged section 220 up to a level disposed below the top of this enlarged section so as to constitute an annular space free of solid, which surrounds this part of the duct 213 within the enlarged section 220;

   this space is located above the catalyst layer discharged into the extended section. Gas is supplied in small quantities to this free space of solid particles, through a line 221, for example by means of a pressure relief valve. Throttling This assures a positive flow of gas through diaphragm 219 and therefore aids in the flow of catalyst through the orifice of the diaphragm, or at least compensates for the antagonistic pressure gradient which occurs. would otherwise occur by the flow of gas in the opposite direction through the diaphragm.

   This positive flow of gas through the diaphragm in the same direction as the flow of the catalyst serves to maintain a substantially uniform flow of catalyst through the throttle orifice and tends to prevent the catalyst from jamming. where the flow of catalyst can be temporarily stopped, for example when closing valve 218, maintaining a positive gas pressure in the duct prevents gas leakage upward into the duct and the adverse effects that could be caused. then cause the moisture that this gas contains to condense.



   For the same reason, members indicated at 225 are provided to maintain a differential flow of gas through diaphragm 204 of branch 203. Again it may be desirable to locate perforated diaphragm 204 in a vertical portion of conduit 203 rather than in. an inclined part as has been shown.



   In the device for supplying fresh catalyst, shown in Fig. 9, the catalyst thus added is well distributed in the system because it is initially mixed with the spent catalyst from the separator and is in the form of of mixture that it is introduced into the main mass of catalyst in circulation; Relatively slow heating of the cool, relatively cold catalyst thus occurs which avoids thermal shock breakage, as well as the formation of localized concentrations of fresh catalyst at the point of introduction into the system, which would constitute a another factor liable to cause operating problems which may lead to the breaking of the catalyst grains.



   From what has just been said, it can be appreciated that the arrangement and operation of the system described as well as of the various accessory devices all cooperate to reduce or eliminate the possible causes of rupture and wear of the catalyst and all help to keep the resulting total catalyst wear in the system as low as possible.


    

Claims (1)

ABSTRACT. 1 - Process applicable to devices for converting hydrocarbons using a catalytic or other contact substance, kept in circulation and which moves downwards in the form of a compact mass through an apparatus comprising one or more zones of <Desc / Clms Page number 20> treatment, to be taken up at the base of this apparatus and retransported upwards by means of a carrier gas, the said method making it possible to operate the devices in question under conditions of low wear of the granular substance, and consisting in continuously flowing this granular substance downwardly from the lowest processing zone to several grouped engagement zones of the elevator, each of these engagement zones being associated; with one or more long elevator ducts of reduced diameter, directed upwards, and to maintain in each of these engagement zones a compact bed, flowing downwards, of granular materials, thanks to a constant supply produced from of the lowest treatment zone, the inlet orifices of the different lifting ducts being arranged in such a way inside the bed of granular substances that there are sufficiently elongated communication paths between these different orifices of 'inlet so that there is sufficient resistance to the migration of gases from one of these inlet ports to the other, the entraining gas being introduced into the said zones of engagement at one or more regions. , through the compact bed therein, and in particular in regions adjacent to said inlet openings, so as to engage the granular substance and carry it upwards, through the elevator ducts, to one or more several discharge chambers, the granular substances being separated from the lift gas in each of these discharge regions, to again run their downward flow path through the various processing zones and so on. . 2 - Particular embodiments of this process which may comprise separately or in combination the following characteristics: a) - The granular substances pass from the lowest treatment zone to a widened intermediate distribution zone arranged below and from where they are distributed to the different engagement zones of the lifting conduits by one or more conduits, substantially radial which cause them to flow downward and outward. b) - Each of the elevator engagement zones is associated with a corresponding single elevator duct c) - The granular substances flow downward in each elevator engagement zone in the form of an elongated and compact mobile column - surrounding the lower part of the elevator duct, the major part, held constant, of all the elevator gas being introduced into the movable column along the lower perimeter of the elevator duct, while a variable and smaller fraction of this assembly of the lifting gas is introduced peripherally into said mobile column at an intermediate level, the quantity of this smaller fraction of lift gas being regulated according to the pressure variations at the lower end of said lift duct, the variations of this quantity being in the opposite direction of the pressure changes. d) - The granular substances coming from a group of elevator conduits are discharged in a common release region for the whole group. e) - A number of separate release regions receive the granular material from different groups of risers, and the granular material from all of these release regions is fed to a common flow bed from where it is directed to. the highest treatment area. f) - The major part of the lifting gas is brought in the form of an annular current directed downwards, and free of solid substances, this current surrounding the inlet orifices of each of the lifting ducts, and being diverted so as to penetrate inside the elevator, entraining the granular substance with which it is brought into contact. <Desc / Clms Page number 21> g) - In each of the discharge regions., at the top of the elevator ducts, the granular substance rises to a certain distance above the outlet of the elevator ducts and its descent in free fall from the highest point reached is interrupted in one or more levels so as to reduce its momentum when it reaches the base of the discharge region. h) - A feed layer of granular substance is maintained at the base of the discharge region and the falling granular substance comes to rest on the top of this layer. i) - Hydrocarbons for conversion flow downward through the compact bed of granular substances flowing by gravity into the higher of the processing zones and gaseous conversion products are released from the granular substance in a a number of levels within and near the base of this uppermost processing zone, these products flowing downward in the form of streams directed into relatively deep gas collection zones, espa - horizontally open and open at the bottom, a spreading and relatively shallow layer of granular material being maintained below these deep areas and flowing down to a lower level as short columns of granular substance, the purge gas passing through to the bottom. up these columns to flow into the said shallow layer, and to emerge on the surface of the latter, with the residual hydrocarbons in the form of vapors, to penetrate into deep zones, all the vaporized products collected in these deep zones being then evacuated outside the treatment area, whereby the velocity of the gas and vapors given off from the granular substance is maintained at an insufficient value to cause the lifting and impacting of the granular substances within this bed at any level of gas evolution. j) - The total height of the system is kept as low as possible thanks to the provision of a unitary chamber comprising separate zones where the conversion of the hydrocarbons in contact with the granular catalytic substance is carried out respectively, and the combustion of the carbonaceous substance deposited on said substance said zones being separated from one another by a number of compact and narrow columns of granular catalysts moving downwards said columns being distributed over the section cross section of the unit chamber at an intermediate level, while gasketing gas is introduced into these compact and narrow columns o k) - The granular substance is discharged at the base of the lower processing zone as a a number of streams coming from a number of discharge points arranged above the horizontal cross section of this base so as to cause a uniform flow towards the base of the bed of granular substance in the treatment zone, these streams passing through an equal number of conduits extending downwardly through a gas distribution space located below the treatment zone and kept out of direct contact with the granular substance, the treatment gas being introduced into this distribution space and flowing upwards therefrom at a certain number of places communicating with the bottom of the bed of granular substance, said places being distinct from the points of discharge previously indicated ., said gas then flowing upwardly through at least a portion of said bed to a release chamber. 1) - The gas enters the bed at a level higher than that where a certain number of streams of granular substance enter the said conduits so that the gas is brought directly to a moving part of the bed. m) - The various ducts of limited dimensions which allow the passage of granular substances empty into a concentric group of <Desc / Clms Page number 22> tumblers which discharge the granular substance into a common duct. n) - A relatively small fraction of the circulating granular substance containing fines is laterally withdrawn from the main circuit at a relatively high level but below the discharge regions indicated above, this lateral or secondary current being then divided so that one part of it is made to constitute a continuous compact bed moving by gravity, in a region separated from the treatment zones, while the other part of this current the secondary is discharged in the form of a mass falling freely into a separation zone arranged directly above this bed flowing by gravity, a separation gas being caused to pass through the freely falling mass at a speed sufficient to entrain the fines therein in suspension, the said gas containing these fines in suspension then being evacuated at the top of the separation zone , while the largest particles collect on the surface of the bed which moves by gravity, all the granular substances constituting the said bed then being brought to join the main circuit. o) - Fresh granular substances are introduced into the system through a conduit communicating with the compact bed placed below the separation zone and they are discharged into this bed at a level located below the top of the latter, the rate of introduction of this fresh substance being determined by the cross-sectional ratio of 19, discharge port of this duct to that of the compact bed at the level of this discharge porta 3 - Apparatus for carrying out the method described above comprising a unitary chamber formed of separate treatment zones through which the granular substance is liable to flow downwards a certain number of riser tubes distributed. peripherally around said chamber and a distribution hopper arranged above this chamber, the lifting tubes communicating at their lower ends with transfer chambers connected to the distribution hopper by solids flow conduits, and to their upper ends with discharge chambers extending to a certain height above the upper ends of said elevator tubes, these discharge chambers comprising trays making it possible to delay the free fall of granular substances inside said chambers. In appendix 4 drawings.