DE2326072C3 - Process for regenerating coke contaminated particulate exhausted cracking catalyst - Google Patents

Description

2. The method according to claim 1, characterized in that that the temperature of the regenerated catalyst by feeding a metered Amount of a flowable fuel, in particular heating gas and / or liquid hydrocarbons, in the first dense bed and / or the dilute phase transport riser is regulated.

3. The method according to claim 1 or 2, characterized in that the coke content of the regenerated Catalyst by limiting the amount of fresh fed to the comfortably dense bed Regeneration gas and / or the temperature in the first escaped bed is regulated.

4. The method according to any one of claims 1 to 3, characterized in that in the dilution phase transport riser pipe additional fresh regeneration gas is fed in.

5. The method according to any one of claims 1 to 4, characterized in that the operating conditions be chosen so that the residence time of the catalyst in the first dense bed is less than 2 minutes and / or in the second dense bed less than 1 minute, preferably less than 30 seconds, and / or the total residence time of the regeneration gas in the first sealed bed and in the Dilute phase transport riser is less than 10 seconds.

6. A method according to any one of claims 1 to 5, characterized in that in the first dense Beit the temperature in a range from 620 to 760 ^Q C, and the Global gas velocity in eintm range of 0.9 to 3.0 m / second, and / or the range 650-800 ⁰ C and the Global gas velocity in the ir Verdünntphasentransportsteigrohr temperature. second is maintained in a range of 3.0 to 7.5 m /.

7. The method according to any one of claims 1 to 6, characterized in that seal in the second Bed of regeneration gas stripped from the regenerated catalyst, preferably with superheated steam will.

The invention relates to a method of regeneration coke-contaminated particulate matter withdrawn from a hydrocarbon conversion zone! exhausted cracking catalyst by burning off coke with an oxygen-containing regeneration gas in a regenerator with two rows of dense beds of catalyst particles and a dilute phase wherein the spent catalyst fluidized in the first dense bed Particles from burning coke with simultaneous formation of partially used regeneration gas partially regenerated, carbon monoxide produced in the diluted phase when burning coke oxidized with oxygen from the regeneration gas to carbon dioxide (afterburning) and off the dilute phase separated into this entrained, regenerated catalyst and at least one the dense beds and the regenerated catalyst from the second dense bed for recycling withdrawn to the hydrocarbon conversion zone.

In the catalytic fluidized bed cracking, relatively high-boiling hydrocarbons increase lighter hydrocarbons boiling on or below the heating oil and gasoline range becomes the hydrocarbon feed in one or more reaction zones with a particulate cracking catalyst brought into contact, which is kept in a fluidized state. You can use

Dense catalyst fluidized beds are thus fluidized or with riser reactors in which the catalyst particles rise from the hydrocarbon vapors be carried through the riser and this is where cracking takes place. In each Trap will contain significant amounts of heavy hydrocarbon decomposition products coke-like substances, commonly referred to simply as coke, deposited on the catalyst particles, and these must for a continuous process implementation with constant circulation of the catalyst to be burned down from the catalyst particles to regenerate the catalyst.

The catalyst separated from the cracked hydrocarbon products is usually first guided through a stripping zone, in which a stripping gas, mostly water vapor, in countercurrent through the exhausted catalyst is passed to entrained hydrocarbons from the catalyst

rinse out. The catalyst then flows into a fluidized bed regeneration zone. There is the coke by means of a gas containing oxygen, in the Reeel Air, burnt down by the catalyst particles The flue gas formed, which is made up of carbon monoxide! Carbon dioxide, water vapor, nitrogen, and any residual amount of oxygen, is common burned in a steam generator. The regenerated catalyst becomes the cracking reaction zone returned. Typically the spent catalyst will contain 0.5 to 1.0 weight percent Coke and the regenerated catalyst about 0.2 to 0.4 percent by weight or in the case of modern known ones Plants only 0.01 to 0.05 percent by weight of coke.

In practice, the regeneration is mostly carried out in a single dense fluidized-bed catalyst carried out, which is arranged at the bottom of the regenerator. Catalyst, from which from the dense Sett entrained effluent flue gas is recovered by passing the flue gas through Cyclone! Rides in one over the dense bed located, fairly large separation space are arranged. Nevertheless, there is always something going out of the catalyst Lost regenerator.

During the regeneration is usually with a flow rate of the gas, based on the Total cross-sectional area of the regenerator (for simplification also as empty space or global flow velocity referred to), worked from about 0.45 to 1.8 and in particular 0.45 to 0.9 m / second. Such Global gas velocities are used to avoid excessive entrainment of catalyst particles from the dense fluidized bed into the flue gas. If the gas flow rate and the global gas velocity are determined, the minimum cross-sectional area of the regenerator is also determined. at For a given cross-sectional area, the dense bed height also determines the catalyst residence time for a given catalyst throughput through the reactor, assuming what is permissible, that the density of the dense bed is roughly constant. The catalyst residence time must be long enough to at given values with regard to regenerator dimensions, temperature and oxygen concentration to ensure that the desired amount of coke is burned off by the catalyst. The catalyst residence time in the regenerator is usually 2 to 5 and preferably 2 to 3 minutes, the residence time of the Gas in the regenerator usually about 10 to 20 seconds.

It is known to regulate the air flow to the regenerator in order to maintain a predetermined temperature difference between the gas separation space and the dense bed or to keep the excess oxygen in the flue gas as low as possible and thereby _{limit afterburning of CO to CO 2} in the separation space. Usually the oxygen content in the flue gas is only about 0.1 to 1 % in the known procedures, but considerable amounts of carbon monoxide are present in the flue gas.

In a fluidized bed cracking system with a regenerator, most of the total is in the Plant circulating catalyst in the regenerator. In modern systems with reactors with work for a short dwell time, e.g. B. with riser reactors, this is particularly pronounced. The ones in the regenerator The amount of catalyst located depends on the hydrocarbon flow rate: by the cracking plant and in particular on the expected coke yield, the coke yield in turn being dependent on the demand Determined fresh regeneration gas in the regeneration device. With the constant circulation of the catalyst goes lost catalyst due to attrition. The catalyst loss is roughly proportional to the catalyst use, d. H. the total amount of catalyst in the system. The ones necessary to compensate for the losses Amounts of catalyst are about 0.5 to 2% of the amount of catalyst used per day. Accordingly is a aim to use as little catalyst as possible. Since most of the catalyst use is in the regenerator Efforts have been made to reduce the amount of catalyst in the regenerator by inducing high rates of carbon burn to reduce. For this purpose, higher pressures and temperatures are used. Currently, regenerator pressures are from about 3 to 3.7 Atm and temperatures of about 620 to 675 ° C are common. This allowed some reduction the use of the catalyst can be achieved, however, as a result of the higher pressures with higher plant costs and due to the relatively long dwell time in the high-temperature regenerators with increased Catalyst deactivation had to be bought.

Furthermore, the temperature of the regenerated catalyst in the Rule not to be changed and also no nearly complete carbon monoxide combustion in the Regenerator brought about with simultaneous regulation of the residual coke content on the regenerated catalyst will.

In another known method, a countercurrent regeneration is used, in which exhausted catalyst is partially regenerated in a first fluidized bed with partially used regeneration gas, then regenerated in a transfer line with fresh regeneration gas and then passed into a second fluidized bed, in which a further regeneration with partially used Regeneration gas can take place. The preferred Global gas velocities are from 0.75 to 0.9 m / sec, the preferred temperatures of about 593-635 ⁰ C. A post-combustion of CO to CO ₂ is not mentioned. The aim is largely to remove the coke to a content of less than 0.2% and, if possible, 0.1 %. The regenerated catalyst can then be freed of gases with a high oxygen content in a separate stripping zone by stripping with steam or flue gas.

In another known method (DT-OS 19 64 647) the exhausted catalyst is in one first dense fluidized bed with a first oxygen-containing gas at a temperature of at least about 593 ° C, which is at least about 56 ° C above the inlet temperature of the catalyst lies in this bed, partially regenerated and then in a second dense Fluidized bed with another oxygen-containing gas at a temperature between 607 and 732 ° C, the is maintained at least about 14 ° C above the temperature in the first bed, is further regenerated. the Catalyst is continuously fed to the first bed and continuously from the first bed into the second bed initiated. A common dilute phase is located above both dense fluidized beds. Optionally, the one in the first fluidized bed

partially regenerated catalyst before it is introduced into the second fluidized bed in a middle one The fluidized bed is further in contact with an oxygen-containing gas to burn off carbonaceous material be brought, with the temperature in this middle fluidized bed between the temperature of the first and the temperature of the second bed and at least 14 ° C above the temperature of the first bed is held. The process operates at global gas velocities of about 0.38 to 1.8 and preferably 0.6 to 1.36 m / second. According to the information provided there, the ongoing The amount of catalyst in the regenerator is reduced to about 84% of that when working with only one dense fluidized bed amount required can be reduced. This is not yet a very drastic reduction. Furthermore, only a very limited afterburning of carbon monoxide in the upper Part of the regeneration zone can be tolerated, while the regeneration gas supply if the afterburning is too strong must be throttled. In this way, the heat of reaction of the partially consumed regeneration gas can also be used contained carbon monoxide only to a very small extent in the regeneration process can even be made usable for heating the regenerated catalyst. An almost complete one Carbon monoxide combustion in the regenerator with simultaneous regulation of the residual coke content on the regenerated catalyst is not possible.

The invention is based on the object of creating a method of the type specified at the outset which does not have the above-mentioned and similar shortcomings of known working methods, enables a large reduction in the amount of catalyst in each regenerator and thus a large reduction in the use of catalyst in the overall system, approximately complete carbon monoxide combustion in the regenerator even with at the same time very extensive and with regard to the residual coke content controllable burning of the coke from the catalyst allows, the carbon monoxide combustion heat can be used to a large extent for heating the regenerated catalyst, a control of the temperature of the regenerated catalyst allows and yet simple, reliable, failure-prone and can be carried out economically.

To achieve this object, the invention provides a process for the regeneration of particulate, exhausted cracking catalyst withdrawn from a hydrocarbon conversion zone and contaminated with coke by burning off coke with an oxygen-containing regeneration gas in a regenerator with two series-arranged dense beds of catalyst particles and one dilute one Phase, in which the exhausted catalyst in the first dense bed of fluidized particles is partially regenerated by burning coke with the simultaneous formation of partially used regeneration gas, in the dilute phase carbon monoxide formed when burning coke is oxidized with oxygen from the regeneration gas to carbon dioxide (post-combustion) and out separated from the dilute phase in this entrained, regenerated catalyst and fed to at least one of the dense beds and the regenerated catalyst from the second dense bed for recycling into the hydro is withdrawn material conversion zone, which is characterized according to the invention, «let

a) all of the catalyst partially regenerated in the first dense bed together with the partially spent regeneration gas directly in the diluted phase in and through a dilute phase transport riser pipe leads, in which he continues to burn coke to the desired final coke content is completely regenerated,

b) an afterburning is carried out in the dilute phase transport riser pipe in which the existing

ίο carbon monoxide almost completely to carbon dioxide is burned, and

c) the regenerated catalyst separated from the dilute phase to the second dense Bed feeds.

Further aspects, embodiments and technical advantages that come with the solution the technical advantages given above are related or in addition can be obtained from the following description of the drawings and the explanations that follow emerged.

F i g. 1 shows a schematic representation of a preferred one Device for carrying out the method.

The F i g. 2 and 3 show further advantageous embodiments of the device, FIG. 3 the implementation of the procedure with an already Existing conventional regeneration vessel explained.

In the case of the FIG. Regenerator 100 shown 1 is a first dense fluidized bed 1 connected via a tapered transition region 28 to the lower end of a vertical transport riser 2 for a dilute catalyst-gas phase. The transport riser pipe 2 has an outlet 7 to which a catalyst-gas separator 3 in the form of a cyclone is connected. Regenerating gas emerging from separator 3 passes into a separation space 5, from there into a fine separator 4, also in the form of a cyclone, and then through its outlet 26 into a chamber 27. The regeneration gas flows out of chamber 27 through outlets 8 and 8 ' . The catalyst separated off by the separator 3 and the fine separator 4 is fed to a second dense bed 6.

The exhausted cracking catalyst enters the first sealed container 1 through a catalyst supply line 9. The upper mirror or head 10 d; s bed 1 is located in the transition region 28 between the bed 1 and the transport riser 2. Fresh regeneration gas enters via a supply line H through a manifold 12 in the bed 1 a. Air is preferably used as the regeneration gas, and the term air is therefore used hereinafter, but other oxygen-containing gas mixtures, for example air enriched with or depleted of oxygen , can also be used. As a distributor 12 can ζ. Β a metal plate provided with holes or protectors or preferably a lattice tube should be provided . A controlled oxidation of the coke-like deposits takes place in the dense bed 1. The regeneration gas and the catalyst are carried out of the bed 1 through the transition area 28 into the transport riser 2, in which carbon monoxide oxidation takes place

The transport riser pipe 2 has its outlet 7 close to the head end. The outlet 7 can consist of one or more openings. The catalyst around

3

(U yj t * \ J \ J I

Jas's regeneration gas flow through the openings in the Catalyst gas separator 3. The separator 3 separates entrained catalyst essentially completely from the regeneration gas. The separator 3 can, for. B. off There are 1 to 4 cyclones. From the separator 3 passes through the outlet 13 essentially catalyst-free Gas off while the catalyst drains through a downcomer 14 to the second dense bed 6. The separator 3 can optionally be omitted, so that then from the transport riser pipe outlet 7 the gas and the catalyst reach the separation space 5 directly. In the separation space 5 occurs a separation of gas and Catalyst on, but not as completely as when using the separator 3.

The used regeneration gas and entrained gas enter the fine separator 4 through its inlet 16 Catalyst from the separation space 5 a. They are essentially completely separated from one another in the fine separator 4 separated. The gas then flows from regenerator 100 through fine separator outlet 26, the chamber 27 and outlets 8 and 8 '. The catalyst flows down through a downcomer 17 to the second tight bed 6. In the embodiment shown, only one fine separator 4 is provided, but can several can also be used. The downpipes 14 and 17 of the separators 3 and 4 preferably open above of the tight bed 6. The downpipe outlets can be equipped with flutter valves to prevent that gas and catalyst flow up through the downcomers. If the downpipes, as preferred, end above the dense catalyst bed, the cyclone separators work constantly even when the level of the tight bed changes.

In the Traruport riser pipe 2 can be via a supply line 20 and a manifold 21 a flowable fuel, e.g. B. a heating gas or a liquid hydrocarbon, be fed in. This is when the plant is started up and at the beginning of the CO post-combustion inexpensive in the transport riser. Au; h can thereby determine the temperature of the through the transport riser pipe 2 flowing catalyst to control the temperature of the regenerated catalyst can be increased.

A secondary air flow can enter the transport riser pipe 2 through a line 18 and a distributor 19 be fed in to support the combustion of additional fuel or CO.

The second tight bed 6 has up to its upper mirror 15 a sufficient height to the entire Pressure drop in the catalyst outlet line 22, a control valve 23 and others downstream arranged facilities to overcome and to ensure an unimpeded drainage of the catalyst.

The tight bed 6 can be arranged above, below or next to the tight bed 1. The whole Regenerator can be arranged above, below or alongside the reactor in which the regenerated Catalyst is used.

As in the embodiment shown, the tight bed 6 can be designed as a scraper or only serve to collect enough regenerated catalyst in dense phase.

The catalyst flows out through the outlet line 22 via the control valve 23. Mostly used as a control valve 23 a gate valve is provided, which is controlled by a reactor temperature or level measuring and control device is operated.

A stripping medium can be introduced into the second tight bed 6 via a line 24 and a distributor 25 are to be adsorbed and / oier in the spaces between the regeneration gas from the flush regenerated catalyst. Superheated steam is preferably used for this purpose.

The greater part of the total catalyst located in the regenerator 100 is preferably dense Bed 1 and only a smaller part is in the

ίο tight bed 6. When stripping with steam in the tight bed 6, the residence time of the catalyst in this bed should be less than 1 minute and preferably less than 30 seconds.
In the case of the FIG. In regenerator 2OD shown in FIG. 2, the spent cracking catalyst enters the first dense bed 201 through line 209. The upper mirror or head 210 of the first tight bed 201 lies in the transition area 228. The fresh regeneration gas is fed in through line 211 and manifold 212. In the dense bed 201 is a controlled oxidation of the carbonaceous deposits instead, which allows the reg Kaksgehalt the regenerated catalyst zi; ln. The regeneration gas and the catalyst flow from the dense bed 201 through the transition region 223 into the transport riser pipe 202, in which the CO post-combustion takes place.

The transport riser 202 has an outlet; 217 and 207 ' near the top, from the: nd; r catalyst and the Rejenerierga; occur in separators 203 and 203 ' in the form of cyclones. D'.e; e Cyclones almost completely separate the regeneration gas from the catalyst. The gas flows from the cyclones through outlets 213 and 213 ' into the separation space 205, which essentially contains gas and only a little entrained catalyst. The catalyst flows down from the cyclones through downcomers 214 and 214 ' into the second dense bed 205, the upper level of which is designated 215. If necessary, the downpipes 214 and 214 ′ can reach below the catalyst level 215 .

The separators 203 and 203 'can optionally be omitted. Then there is more catalyst in the separation space 205 and consequently the load on the fine separator 204 increases.

The spent regeneration gas and entrained catalyst from separation space 205 flows into fine separator 204, normally a cyclone, through inlet 216. After essentially complete separation, the gas leaves fine separator 204 and thus regenerator 200 through outlet 208. The catalyst flows out the fine separator 204 via a downpipe 217 down into the second sealed bed 206.
A flowable fuel can be fed into the transport riser 202 through the line 220 and the distributor 221. Secondary air can be introduced into the transport riser pipe 202 through the line 218 and the distributor 219. Optionally, a cooling gas can be fed in via line 218 in order to cool the catalyst to a predetermined temperature.

The catalyst level up to head 215 in bed 206 should be sufficient to overcome the pressure drop in the catalyst outlet line 222, the control valve 223 and downstream devices and ensure a smooth drainage of the regenerated catalyst zi.
The Katalysp'orstand can be regulated so that

ι · ■ · - »

3738

the desired catalyst residence time is provided in the second dense bed 206.

The regenerated catalyst flows out of the bed 206 and thus out of the regenerator 200 via the outlet line 222 and the control valve 223 downwards. The regulating valve 223 is preferably a gate valve which is operated by a reactor temperature or level measuring and regulating device.

In the bed 206 can be via lines 224 and 224 '

10

tolerate steam and the presence of metals in the cracking charge. With amorphous catalysts On the other hand, some advantages of the invention are particularly pronounced because of those applied here shorter catalyst residence times in the regenerator, their life is extended.

The improved regeneration according to the process of the invention allows the use of raw materials in the cracking which have a higher

as well as distributors 225 and 225 ' a stripping medium, vor- io content of impurities, z. B. coking back

preferably superheated steam, fed in to the adsorbed and in the interstices Remove regeneration gas.

As with the one shown in FIG. In the regenerator shown in Figure 1, most of the catalyst is in the first dense bed 201 and again the catalyst residence time in the second dense bed 206 when steam stripping is performed should be less than one minute, and preferably less than 30 seconds.

F i g. Figure 3 illustrates one possible modification of a conventional regenerator to create a regenerator suitable for carrying out the method of the invention. For this purpose, the according to Conradson and metals such as nickel, iron and vanadium than the usual ones Feedstocks, since the process of the invention increases the regeneration capacity.

In the method of the invention, the heat of combustion released by CO oxidation is from Catalyst added, the temperature of which is thereby increased considerably. Another increase the catalyst temperature can be adjusted by feeding a fuel into the dilute phase transport riser be effected. The combustion of CO or fuel that takes place there is one of their own effective heat transfer to the catalyst. Furthermore, despite the combustion of the

Regenerator 300 internals attached so that there is 25 CO in the regenerator, a controlled coke content on a first tight bed 301, a transport riser pipe 302, the regenerated catalyst are maintained.

This can be achieved by adding less than the stoichiometric amount of air to the first sealed bed feeds, so that noticeable amounts of coke remain on the catalyst, or by in the first dense bed maintains a relatively low temperature in order to limit coke burning. In the dilute phase transport riser pipe, more air is then preferably supplied, whereby the CO

is burned through the transition area 328 into the transport 35 there. The combustion of the coal riser pipe 302, in which carbon monoxide is oxidized. monoxyds in the transport riser runs very quickly,

'-''""'" ^j: ~ so that almost all of the CO is burned _{to CO 2,}

although the dwell time in the transport riser is short. There is also some residual coke in the transport riser burned, but the catalyst residence time in the transport riser is so short that despite the prevailing there the majority of the residual coke still present at the entry during high temperatures the passage of the catalyst through the

307 designed so that the catalyst and the gas 45 port riser pipe remain unburned, emerge in a downward jet, both coke and carbon monoxide react in the

to keep the catalyst-first dense bed entrained into the separation space 305 and in the amount of dilution phase as low as possible, transport riser pipe. with both competing for the oxygen in the fine separator 304 in the form of a cyclone. The relative reaction velocities through the inlet 316 gas and entrained 50 th are carried out by the prevailing temperatures and catalyst from the separation space 305. The gas leaves the availability of the reactants, affects the fine separator 304 and thus the regenerator 300 through the outlet 308, the catalyst flows through the Downpipe 317 down to the second dense bed 306. Its upper level 315 forms the boundary between the second dense bed 306 and the separation space 305. The regenerated catalyst flows downwards from the regenerator through the line 322 and the control valve 323, the latter in is operated in the manner already explained. Stripping medium, preferably superheated steam, may be fed into bed 306 through line 324 and manifold 325 to remove regeneration gas from the regenerated catalyst.

and a second dense bed 306 .

The exhausted catalyst flows through the pipe

309 into the first dense bed 301, its upper mirror

310 lies in the transition area 328 between the bed 301 and the transport riser pipe 302. Air is fed in via line 311 and manifold 312. In dense bed 301 , coke is oxidized. Gas and fluidized catalyst flow from bed 301

A flowable fuel can be fed into the transport riser pipe 302 through the line 320 and the distributor 321 and secondary air can be fed through the line 318 and the distributor 319.

The catalyst and gas exit the transport riser 302 through the outlet 307 into the separation space 305 . In this embodiment, no cycion is connected there. Preferably the outlet is

The process of the invention is suitable for the usual fluidizable cracking catalysts. Highly active zeolitic catalysts are preferred because they cause high temperatures, the action of water, the coke combustion and the CO afterburning are not mutually exclusive; rather, these terms denote which reaction is prevailing in each case.

If the regenerated catalyst is to contain as little coke as possible, almost all of the regeneration gas is fed into the first sealed bed. The temperatures there are lower than in the riser pipe, so that in this bed there is no considerable afterburning before carbon monoxide to carbon dioxide. In the transport riser there is less catalyst in contact with the regeneration gas, so that afterburning occurs. If necessary, the catalyst can be heated even further by adding the fuel, but this is usually not necessary.

This can be achieved in the manner explained above

Leaving some coke behind on the catalyst can be used to target the activity of the catalyst control, for example, the cracking from the highest possible gasoline yield to the highest possible convert high yield of fuel oil.

In the first dense bed, higher global gas velocities of the fresh regeneration gas than adhered to in known methods, preferably in the range from 0.9 to 3 m / second. The Catalyst from the first dense bed into the dilute phase transport riser in the manner illustrated carried. The global gas velocity in the dilute phase transport riser is preferably 3 to 7.5 m / second.

The higher gas velocities used in the regenerator of the invention create a more turbulent one Flow and lead to better mixing and more effective regeneration. Through the improved gas-solid contact, higher oxygen partial pressures and higher temperatures will be the Coke burning rate increased. As the coke is removed more quickly, the catalyst residence time can be increased from the previously usual 2 to 5 minutes to less than 2 minutes and the gas residence time usually from about 20 seconds to less than 10 seconds be reduced. Since the catalyst is only exposed to high temperatures for a short period of time, the catalyst activity is also retained for a longer period, as a result of which the required catalyst feed is reduced will. Shorter catalyst residence times also reduce the amount of catalyst required in the plant.

The use of catalyst only needs about 40 to 60 ° when using the process of the invention Catalyst use of currently common single or multi-stage regeneration processes to be. One Medium-sized fluidized bed cracking systems usually contain around 140 t of catalyst. By applying the procedure The invention saves the initial costs for about 70 tons of catalyst. The required Catalyst replenishment is also greatly reduced because the catalyst losses are a certain percentage of the catalyst use.

In the process of the invention, the regenerated catalyst can conveniently be flushed out, particularly with steam. Although steam basically has a somewhat deactivating effect, stripping with steam, contrary to previous methods, can be carried out without hesitation, since the effect of the steam on the catalyst is only short due to the short catalyst residence time in the second dense bed, small amounts of steam are sufficient and the steam with the catalyst is neither in the first tight bed still comes into contact in the dilute phase transport riser pipe, so that damage by water vapor in these zones is excluded. A steam stripping is desirable because the regenerated catalyst contains about 1 else to 3 parts by weight of flue gas components to 1000 parts by weight of catalyst In a medium fluidized bed cracking unit run per hour about \ 350 000kg catalyst is that per hour about 2000 kg Flue gas into the reactor einschleppt The reactor effluent thus contains about 1600 Nm ³ flue gas components per hour. These get into the gas from the conventional distillative work-up in conjunction with a gas concentration system comprising compressors, absorbers and fractionating columns

last absorber. The entrained flue gas (N ₂ , CO and CO ₂ ) then makes z. B. 31.1 mole percent of this product stream. Most of the flue gas in the regenerator can be removed by wiping off the regenerated catalyst with steam. This leads to considerable savings, since smaller compressors and absorbers can be used and the adsorber exhaust gas has a higher calorific value.

According to the method of the invention, most of the coke oxidation takes place in the first dense bed and most of the carbon monoxide oxidation in the transport riser. The temperatures occurring during carbon monoxide oxidation are higher than the temperatures required for coke oxidation. However, the catalyst residence time in the transport riser is very short. This minimizes the time during which the catalyst is exposed to very high temperatures. If the oxidation of CO in the sealed bed is to be kept as low as possible, a temperature of 620 to 675 ^° C. is expediently used there. In Tempera doors 675-695 ⁰ C a weak CO post-combustion takes place. Temperatures of 695 to 760 C are required for strong afterburning.

The almost complete afterburning of the carbon monoxide in the transport riser of the regenerator solves the air pollution problem without the previously required use of an additional one CO-heated boiler. The absorption of the carbon monoxide released during the combustion Heat through the catalyst in the transport riser creates a hotter regenerated one Catalyst, thereby the necessary preheating of the feed decreased during cracking.

In the regenerator, pressures from atmospheric pressure to 4.5 atm, preferably 2 to 3.5 atm, applied

The spent cracking catalyst entering the first dense bed can contain from a few tenths up to about 5 weight percent coke, usually it contains 0.5 to 1.5 weight percent coke. The regenerated catalyst will normally contain less than 0.5 and optionally less than 0.05 weight percent coke, depending on the operating conditions used in the regenerator and the conversion sought in the cracking reactor. In the case of the partially regenerated catalyst, part of the coke has burned off. The partially used regeneration gas which emerges from the first sealed bed has a reduced content of free oxygen and consists essentially of H ₂ O, N ₂ , O ₂ , CO and CO ₂ . The used regeneration gas contains almost no carbon monoxide, a few tenths up to 15 mol percent O ₂ and also CO ₂ , N ₂ and H ₂ O.

In the used for the gas-solid separation cyclones may each involve only one cyclone Odei several, arranged in parallel or in series Cyclone.

Example with comparative tests

A commercially available molecular sieve cracking catalyst was regenerated with air after being used to crack a vacuum gas oil in a cracking reactor and then steam stripped. The spent cracking catalyst contained 0.9 weight percent coke, which in turn contained 10.1 ge

3

Contained weight percent hydrogen. For the comparison used a conventional regenerator with a single dense bed over which a large dilute phase separation space was located. The results for the Vü driving execution after the The invention and the comparison are given in Table 1.

Table 1

State of
technology

invention

Temperature, "C 643 677 Dense Elett 641 Diluted phase - 741 Transportation management 674 738 Flue gas 727 Two dense beds 2.67 2.36 Pressure, atm 105 600 105 100 Air supply to the Re generator, kg / h 11.1.3 14.51 Air / coke weight ratio 6.61 5.05 Coke attack in the Cracking, weight percent of fresh loading (at 75 ° _o Conversion) 0.2 0.02 Coke in the rain rated catalyst. Weight percent 7.5 4.8 Regencytor Cross messcr, m 3 0.9 Catalyst retention time. Min. 15.5 5.5 Gas flow rate. Sec. Global gas fluctuations in digkeit, m / Siek. 0.72 1.5 Dense Etett 0.72 6.0 Diluted phase or trainsport riser pipe Flue gas analysis, Molecular Percentage 9.2 14.9 CO ₁ 1.1 1.0 argon 79.2 82.3 N, 10.2 (270 parts by volume CO per million) 0.2 1.8 O, 0.1 0 CH ₄ no Yes Stripping off the rain rated catalyst 211 136 Required Be sehickungsv heated mung during cracking to degree Cdsius 54 32 Catalvsatorcinsatz, t

3 °

35

40

45

55

In both procedures, dry air was used as the regeneration gas. In the method of the invention, there is a higher oxygen concentration in the regenerator, as can be seen from the higher flue gas oxygen concentration - 15 mol percent O ₅ compared to 0.2 mol percent O in the known method. The catalyst regenerated according to the invention is hotter, which means less catalyst circulation allowed and consequently a reduction in the coke accumulation from 6.61 to 5.05 percent by weight of coke with it. This in turn increases the yield of valuable products during cracking. In the process of the invention, less air is used at a lower pressure, but a regenerated catalyst with a lower coke content and a flue gas which contains almost no carbon monoxide is produced. The combustion of the carbon monoxide in the regenerator itself eliminates air pollution problems and, as a result of the higher catalyst heating, reduces the required preheating of the Kxack charge by around 75 ° C. The use of catalyst is around 40 % less than in the conventional process, so that the regenerator can also be smaller. Although this is not directly shown by the test results, it goes without saying that the lower use of catalyst and the shorter residence time of the catalyst lead to a reduction in the amount of catalyst required. The wear-off of the regenerated catalyst, which is harmless according to the invention, has the advantages explained.

The method of the invention also enables the temperature of the regenerated catalyst, and therefore the To regulate catalyst delivery temperature during cracking. It has been shown that the delivery temperature of the regenerated catalyst is an important reactor variable in catalytic fluidized bed cracking is. The regulation of the temperature of the regenerated catalyst, which is possible according to the invention, can a better distribution of yield and product quality can be achieved during cracking. The effect of the Temperature of the regenerated catalyst at constant reactor outlet temperature on the product yields for fluidized bed cracking is shown in Table II.

Table II

Operating conditions and
results

Catalyst regenerates

State of the invention technology

Reactor outlet temperature, 536 536 Temperature of regener 677 732 th catalyst, ⁰ C Feed preheating 364 316 to ³ C Gasoline yield (C ₅ to 90% 67.1 67.0 distilled at 193 ^° C.) Vo lum percent (liquid) Alkylation feed 25.1 27.1 yield (C ₃ to C ₄ ), Vo lum percent (liquid) K. Reislauf total oil yield, 21.3 23.5 Volume percentage (liquid) Coke yield, weight 5.3 3.8 percent Conversion. Volume pro 78.7 76.5 cent (liquid) Gasoline octane number (Re 93.0 93.3 search, unleaded)

The example shows that at the higher temperature of the catalyst according to the crfinduings regenerated the Conversion a little lower, but the product value is significantly higher. The gasoline yield is when using of the hotter catalyst is roughly the same, but the octane number is higher. More essential Advantages are the 1.0 volume percent higher alkylation feed yield and 2.3 volume percent higher higher total circulating oil yield and the 1.5 weight percent lower yield Coke. Furthermore, the hotter catalyst reduces the required feed preheat.

The method of the invention also enables one

Regulation of the residual coke content on the regenerated catalyst. At constant catalyst and reactor temperature An increase in the residual coke content on the regenerated catalyst reduces the conversion and the gasoline yield and increases the yield of cycle oil (fuel oil) in cracking. A reduction in the residual coke content increases the conversion at the expense of the fuel oil yield. A very low residual coke content increases the liquefied gas yield at the expense of the gasoline yield. Relevant Constant temperature results of the regenerated catalyst are given in Table III.

Table III

Operating mode for high yield LPG petrol

Fuel oil

Effect of the residual coke content LPG conditions

Reactor temp., ° C
Charge preheat temp., ⁰ C
Temperature of the rain. Catalyst,
Residual coke on the rain.
Catalyst weight percent

Yields, percent by volume (liquid),

based on fresh loading

conversion

LPG (C ₃ -C ₄ )

Gasoline (90% distilled at 193 ⁰ C)

Light circulation oil

Clarified mud oil

Coke, weight percent

521 521 521 521 191 316 316 191 732 732 732 732 <0.02 0.11 0.62 0.62 85.7 75.0 64.4 77.0 38.2 26.3 20.4 31.4 52.0 62.3 48.3 58.3 11.4 20.0 30.6 18.0 5.0 5.0 5.0 5.0 6.8 3.8 5.3 6.8

A maximum liquefied gas yield is achieved under these conditions when one of the invention Carries out regeneration of the catalyst down to a very low residual coke content. The catalyst with less than 0.02 weight percent coke gives the highest conversion and even cracks Petrol to LPG. The 0.11 weight percent residual coke catalyst gives less conversion and a lower liquid gas yield, but a higher gasoline yield. If you are at the regeneration leaves the residual coke content even higher, as in fuel oil operation with 0.6 percent by weight Residual coke, the conversion and the yields of liquefied petroleum gas and gasoline decrease, but the yield decreases to light circulation (fuel oil). The effect of the residual coke content on the product yields is on best seen by comparing the first and last columns of Table III. The respectively applied Operating conditions are with the exception of the

Residual coke content the same. The conversion and the liquefied gas yield are when the catalyst is regenerated to a residual coke content of 0.62 percent by weight, but the yields of gasoline are lower and cycle oil (fuel oil) higher.

The regeneration according to the process of the invention thus allows the product yields in the Cracking directly and conveniently by regulating the temperature of the regenerated catalyst and / or Adjusting its residual coke content to control and to

optimize. This makes it very easy to use the regeneration process of the invention Choice of fuel oil production, gasoline yield or liquefied gas production all in one Bring maximum value.

For this purpose 2 sheets of drawings

Claims (1)

Patent claims: 1. Process for the regeneration of withdrawn from a hydrocarbon conversion zone, particulate !, exhausted cracking catalyst contaminated with coke by burning off Coke with an oxygen-containing regeneration gas in a regenerator with two in series dense beds of catalyst particles and a dilute phase, the exhausted Catalyst in the first dense bed of fluidized particles by burning coke with simultaneous Formation of partially used regeneration gas partially regenerated, in the diluted Phase carbon monoxide formed during the burning of coke with oxygen from the regeneration gas oxidized to carbon dioxide (afterburning) and carried away from the dilute phase into this, separated regenerated catalyst and fed to at least one of the sealed beds towie the regenerated catalyst from the second straightening bed for recycling to the hydrocarbon Conversion zone is withdrawn by marked that one a) all of the catalyst partially regenerated in the first dense bed together with the partially used regeneration gas directly in the diluted phase in and through a dilute phase transport riser pipe leads, in which it regenerates completely by further burning off coke up to the desired final coke content will, b) an afterburning is carried out in the dilute phase transport riser, in which the existing carbon monoxide is practically completely burned to carbon dioxide, and c) the regenerated catalyst separated from the dilute phase to the second dense Bed feeds.