FI65551B - FOERFARANDE FOER ATT SEPARERA KATALYTPARTIKLAR FRAON KOLVAETE-KONVERSIONSPRODUKTER - Google Patents

Description

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Patent and registration authorities ............

Patent · och registerstyralsan ^ A ^ MaM ^ SSuTodi utl.tkrtftan pubJkarad 29.02.84 (32) (33) (31) Requested utuolkuu * —Begtrd prtorkuc (71) Mobil Oil Corporation, 150 East 42nd Street, New York, New York 10017 , USA (US) (72) Conroy Donald Anderson, Wenonah, NJ, Paul W. Snyder, Jr., Joliet,

Illinois, Klaus Wilhelm Schatz, Wenonah, NJ, USA (74) Berggren Oy Ab (54) improved separation of dewes from gaseous reaction products. More specifically, the invention relates to a method and apparatus for improving the separation of suspended catalyst particles from a gas stream in a cyclone separation apparatus.

In a cyclone-type separator, a suspension consisting of a gaseous material carrying finely divided solid material is fed tangentially to the separator, which produces a helical or centrifugal vortex effect on the suspension. The central exhaust effect causes solids to splash onto the second wall of the cyclone separator and then drain down the wall of the cyclone into the solids collection funnel below it for removal by a vertical pipe or submersible device. The gaseous material thus separated from the solids is removed, for example, by a central open channel extending below the level of the tangential inlet pipe of the suspension upwards through the top of the cyclone separator. A particularly useful application of this apparatus is 2,6551 in connection with organic reactions using fluidizable catalyst particles, such as in the catalytic treatment of petroleum fractions by cracking, in the synthesis of hydrocarbons from carbon monoxide and hydrogen, in the conversion of methanol to liquid hydrocarbons or in other known fluidized bed catalysts.

In modern processes, such as catalytic riser cracking processes, huge amounts of catalyst suspended in gaseous materials are processed in catalytic riser cracking units and it is necessary to quickly separate

In particular, this invention relates to the improvement of a suspension separation technique to reduce losses in either the catalyst phase or the gaseous phase. More importantly, however, this invention relates to improving the separation of the gaseous product phase from the catalyst phase when one or more chemical reactions have been completed in the presence of a catalyst.

In particular, this invention relates to providing a rapid separation of a product suspension containing fluidized catalyst particles after passing the short contact time conversion zone normally in a period of less than about 15 seconds to avoid prolonging the desired conversion reactions excessively. In modern processes, it is not uncommon to use riser conversion zones to carry out catalytic cracking of relatively short contact time reaction series, such as petroleum fractions, and to discharge the suspension containing the reaction products directly into a cyclone separation device connected to the main riser conversion zone. However, current cyclone equipment allows for undesirably prolonged additional contact between the product phase and the catalyst phase in a portion of the removed suspension. This prolonged contact has been found to contribute to the loss of the desired product, which rises to as much as about 10 percent. Thus, it has been determined that the loss of gasoline yield due to over-cracking may be between 0.15 and about 1.5% by volume based on the fresh feed. Accordingly, it is an object of the present invention to provide a faster separation of catalytic cracking product vapors from suspended catalyst particles, particularly in a cyclone separation apparatus connected to the end of a relatively short contact time riser cracking process.

According to the present invention, the cyclone separators connected to the outlet of the riser are modified, as shown in Figure 1, to include a downwardly extending cylindrical insert comprising a lower cyclone. In this arrangement, the catalyst, which is separated in the upper cyclone from the gaseous material and which flows downwards along its wall, is scraped off the wall by a helical or annular baffle device separating the upper and lower cyclones. The catalyst recovered by the helical baffle is contacted with the water vapor fed tangentially, which substantially immediately further separates any entrained hydrocarbon product from the catalyst recovered from the upper cyclone. Stripping water vapor and stripped hydrocarbons are passed from the lower cyclone to the upper cyclone by a concentric, open-ended cylindrical tube device in direct line with the upper cyclone vapor outlet pipe, but spaced apart from it. The catalyst collecting portion is normally a conical portion between the cylindrical walls of the cyclone separator and the submerged branch of the catalyst through which the separated catalyst is removed.

Figure 1 is a schematic side view of a stripper cyclone of the present invention.

Figure 2 is a schematic side view of a riser reactor with the stripper cyclone of Figure 1 connected to the riser outlet. The combination is housed in a large vessel comprising a strip of catalyst at the bottom thereof and a cyclone separation device for separating the catalyst from the stripping gas at the top thereof.

Fig. 3 is a graph showing the amount of hydrocarbons removed by a conventional cyclone submerged branch with a catalyst, and shows that it decreases with the degree of catalyst loading.

Figure 4 is a graph showing that hydrocarbons can be displaced or stripped from the catalyst up to a high percentage by increasing the rate of water vapor and the flow rate of the catalyst.

Fig. 5 is a graph showing that the results shown in Fig. 4 can be implemented without significant loss of cyclone efficiency using the stripper cyclone combination of the present invention.

4 65551

Referring now to Figure 1, there is shown a stripper-cyclone combination of the present invention. It is apparent from the draft that a typical cyclone separator has been modified by extending the cyclone catalyst collection funnel to include the specific catalyst recovery stripping apparatus of this invention, with the second cyclone separation assembly being formed below the upper or first cyclone separation device. In the arrangement of Figure 1, a suspension of the catalyst and reaction products, such as catalytic crackers, is fed to the cyclone device via a tube 2, which may be a rectangular or round tube. The tubes 2 feed the suspension tangentially to the cylindrical part 4 of the cyclone, thus causing centrifugal separation of the solid catalyst particles from the vaporous or gaseous reaction products. As mentioned above, the separated solid particles flow down along the cylindrical wall 4 for recovery and / or stripping as described herein. The vaporous material separated from the solids or catalyst particles enters the open bottom inlet of the tube 6 and is removed by passing upwards through the tube 6 for recovery, as will be described in more detail in connection with Figure 2.

Centrifugally separated solids flowing down the wall of the cyclone separator are passed through an annular portion formed between the wall 10 and the other end-open cylindrical tube 8 having a diameter smaller than that of the cyclone hopper wall 10 and coaxially positioned therein, but set apart from its open lower end. A downwardly extending annular spacer plate device 12 or helical baffle 12 connected between the tube 8 and the wall 10 and completely surrounding the tube 8 forms a vertical opening 14 in one portion of the ring through which the separated solids must flow into another annular zone in contact with stripping water vapor. fed to it via a pipe 16. The tubes 16 may also be rectangular or circular to supply stripping water vapor tangentially to the cyclone below the baffle plate and catalyst inlet 14. The catalyst passing through the opening 14 is contacted with water vapor fed through the pipe 16 and then the mixture is separated by centrifugal action in an annular part below the guide plate 12 and between the lower part of the pipe 8 and the cylindrical wall 18 of the cyclone separator. The stripped and separated catalyst obtained as described above then flows down along wall 05551 05551 and is then collected in a conical supernatant formed by wall 20. The catalyst immersion branch 22 extends downwardly from the base of the wall 20 forming the conical part. The stripped hydrocarbons and stripping gas, water vapor separated from the catalyst, are introduced upwards at their ends through the open tube 8 and into the open lower end of the tube 6.

The schematic sketch of Figure 2 shows the stripper cyclone of Figure 1 connected to the outlet end of the riser conversion zone 24 and encapsulated in a large vessel 26. The lower portion of the vessel 26, and in particular the cylindrical portion 28, is normally used as a catalyst strip strip 36 and 34. water vapor is fed to its lower part through pipes 38 and 40. The level of catalyst maintained in the stripping section may be as high as approximately line 42, but will normally be kept as low as possible consistent with achieving the desired stripping of the catalyst. The plunger 22 may extend into the lower container as required by the situation. The stripped catalyst is removed from the stripping zone by means of a tube 44 for transfer to a catalyst regeneration zone, not shown. The suspension of hydrocarbons and catalyst passes upwardly through the riser 24 under the desired selected cracking conditions, usually at a temperature above 482 ° C and a residence time of the hydrocarbon with the suspended catalyst of less than about 15 seconds. The residence time of the hydrocarbon in the riser 24 can be limited to 2-8 seconds by operating at a reaction temperature of about 527 ° C or higher. The suspension in the riser 24 passes through an opening 2 adjacent its upper end to the stripper-cyclone assembly shown and specifically described in connection with Figure 1. The separated gaseous materials containing hydrocarbons and stripping gas pass upward through tube 6 to the top of vessel 26 or may pass directly to dome chamber 46 from where they are removed by tube 48 for transfer to a product fractionation apparatus not shown. When the vaporous material separated in the cyclone 4 is removed to the top of the vessel 26, it must then pass through the cyclone 52 and the tube 54 into the chamber 46.

In the stripping section 28 of the vessel 26, the stripped products and stripping gas pass through the spherical orifice 50 of the cyclone separator 52, where the entrained finely divided catalyst particles are separated from the stripping gas before the gas passes through the tube 54. Thus, an apparatus and method for implementing the concepts of this invention, particularly applied to the catalytic cracking of hydrocarbons, is set forth in the description of Figures 1 and 2.

Figure 3 is a graph of the values obtained showing the amount of hydrocarbons that can leave the cyclone separator with the catalyst through the immersion branches under different catalyst loading conditions. The curve is essentially self-explanatory and shows that as the catalyst load increases, the amounts of hydrocarbons leaving with it decrease.

Figure 4 is a graph of the values obtained showing the amount of all hydrocarbons exiting the plunger branch of the cyclone under various water-vapor stripping and catalyst loading conditions. Thus, as the amount of hydrocarbons increases, over-cracking of the products tends to progress, which reduces the yield of the desired gasoline product by up to 1.5% by volume based on the feed. This loss of yield is particularly accentuated by the curves in Figure 6 described below.

Figure 5 is a graph of values obtained showing the efficiency of water vapor stripping in a cyclone as a function of cyclone efficiency using the stripper-cyclone combination of the present invention. From these values, it is observed that the separation efficiency of the cyclone is not undesirably affected, but it decreases as the volume of stripping water vapor increases. In all cases, the cyclone efficiency is at least about 95%.

Figure 6 is a graph of the values obtained showing a comparison between a small pilot plant using the concepts of the present invention and a commercial process that does not utilize the stripper-cyclone concept. These values indicate an improvement in gasoline yield in a small pilot plant using the stripping cyclone concept and a decrease in dry gas yield.

Having thus generally described and described the specific embodiments and examples thereof, it is to be understood that no unreasonable limitations are to be imposed thereon unless otherwise specified in the following claims.

Claims (3)

7 65551 1. A method for separating suspended catalyst particles hydrocarbon conversion products, the conversion of hydrocarbons by catalytic fluidized catalyst through up-putkikonversiovyöhykkeessä, by passing the hydrocarbons and the catalyst in suspension up through the nousuputkikonversiovyöhykkeen elevated temperature conversion conditions, by passing the suspension nousuputkikonversiovyöhykkeestä directly syklonierotusvyöhyk-keeseen, wherein the first syklonierottaminen performed at the top zone of the fluidized catalyst and gaseous hydrocarbon products, passing the catalyst thus separated substantially immediately through the reduced orifice (14) to an annular zone at a separate lower part of the cyclone separation zone and in contact with the stripped gas tangentially introduced. ) through which is the same central with the annular zone and in open communication with the upper exhaust passage (6) for first removing the separated hydrocarbon gases from the top of the cyclone separation zone, and recovering the stripped catalyst from the cyclone separation zone below the annular zone. Process according to Claim 1, characterized in that the catalyst initially cyclically separated from the hydrocarbon gases is passed through a reduced vertical channel which is in open communication with the lower annular zone below the upper catalyst recovery zone in the cyclone separation zone. Method according to Claim 1, characterized in that the open-ended constricted duct (8) surrounded by an annular zone is smaller in diameter than the upper hydrocarbon gas outlet duct (6).