FI60403C - REGENERERINGSPROCESS OCH -ANORDNING - Google Patents

Description

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U.S. Patents and Patent Publications U.S. Patent No. 30.09-81 (32) (33) (31) Required Utility - Begird Prlorltet 28.12.73 28.12.73, 28.12.73 USA (US) 429423, 429422, 429421 (71) Universal Oil Products Company, Ten U0P Plaza - Algonquin & Mt. Prospect Roads, Des Plaines, Illinois, USA (72) Algie James Conner, Downers Grove, Illinois, Daniel Dudych, Des Plaines, Illinois, Richard Paul Pulak, Palatine, Illinois, Willas Leon Vermilion, Arlington Heights, Illinois, USA (US) (74) Berggren Oy Ah (54) Regeneration Process and Equipment - Regenereringsprocess och -anordning This invention relates to the regeneration of coke-contaminated catalysts, in particular to catalysts from an FCC unit or a fluidized catalytic cracking unit.

In most regeneration processes, the oxidation of coke from the spent catalyst is performed in a regenerator in which one or more dense layers are placed on the bottom of the vessel and in which a large dilute-phase release space is above the dense layer. The dense layer is held at the bottom of the vessel by limiting the velocity along the surface of the incoming fresh Regeneration gas. Typical speeds are less than about 0.9 m per second, with speeds of 0.45-0.75 m / s being common. Any catalyst trapped in the flue gas leaving the dense bed is recovered by passing the flue gas through the cyclones in the exit space and returning the catalyst to the dense bed. The average residence time of the catalyst in the regenerator per cycle is about 2-5 minutes. The gas residence time is usually 10-20 seconds. All regenerated catalyst is returned directly to the reaction zone.

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Most conventional regenerators operate to avoid complete combustion of the C0 formed in the oxidation of coke. This is usually done by adjusting the oxygen-containing gas stream fed to such a regeneration zone, which is directly sensitive to a relatively small temperature difference between the combustion gas and the dense bed, to minimize excess oxygen in the regenerator and severely limit C0 afterburning.

It has recently been found that it is possible to "afterburn" CO obtained from the combustion of coke into CO 2 inside the regenerator · It is known to use a combustion chamber with a dense catalyst bed for coke combustion followed by a dilute phase transfer shaft where C0 combustion is completed and followed by a collector chamber with a second sealed bed in which the regenerated catalyst is collected for return to the FCC reactor.

Unfortunately, the known process described above was not as inexpensive as was once thought. It was difficult to control the temperature of the combustion zone of the burner or coke and this also affected the efficiency of CO combustion in the transfer shaft.

It has now been found that by returning part of the hot regenerated catalyst to the combustion chamber, a method is provided for controlling the temperature of the burner and thus the reaction rate of coke oxidation. An increase in reaction rate and catalyst residence time results in a regenerated catalyst with lower residual coke levels. In addition, the burning rate of CO in the C0 conversion zone also increases due to the higher inlet temperature, so lower CO concentrations are obtained at the outlet of the zone. The regenerated catalyst, which is not recycled to the burner, is returned to the reaction zone at a higher temperature, allowing reduced feed preheating requirements.

The invention thus relates to a process for regenerating a spent coke-containing catalyst, in which the catalyst used and the fresh regeneration gas are continuously passed from the reaction zone to a combustion zone comprising a first dense catalyst bed regenerator and regenerated is introduced into the CO conversion zone and 3 60403 is converted to CO to produce CC regeneration gas and a regenerated catalyst at a higher temperature, and the regenerated catalyst is separated from the regeneration gas used and passed to a collector comprising a second dense catalyst bed, from a regenerated catalyst at a higher temperature in a dense catalyst bed and another portion of the catalyst is returned to the reaction zone.

The invention also relates to an apparatus for regenerating a spent catalyst, the apparatus comprising a) a combustion chamber containing a dense catalyst bed and having a spent catalyst inlet and a fresh regeneration gas inlet and a combustion chamber outlet for regenerating the regenerated catalyst and regenerating; (b) a transfer tube having a substantially vertical portion having an inlet connected to the outlet of the combustion chamber and a horizontal portion having an outlet; (c) a collector chamber having a side inlet connected to the transfer tube outlet and comprising a dense bed of regenerated catalyst and having a regenerated catalyst outlet and a spent regeneration gas outlet and the collector chamber having a collector above; and the apparatus according to the invention is characterized by a regenerated catalyst recycling device which allows the regenerated catalyst to flow directly from the collection chamber to the combustion chamber.

The special embodiment shown in the drawing is best suited for modifications of previous regenerators in the art, but the invention can be applied equally well to the new structure.

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The attached schematic drawing shows the main features of the process as follows: Coke Combustion Chamber 1. CO Conversion Zone 2, Regenerated Catalyst Collector Zone 2, and Catalyst Recycling Plant 6.

The spent catalyst from the reaction zone and the fresh regenerated gas are fed to the combustion chamber or coke oxidation zone 1 via pipes 7 and 10, respectively,

The combustion chamber 1, shown in the left corner of the drawing, has a dense catalyst layer 4, the level or distribution surface 8 of which is maintained inside the chamber.

Typically, fresh regeneration gas is fed through the decomposer 11. Oxidation of the coke on the catalyst takes place in the dense layer 4 of the catalyst in the burner, producing partially spent regeneration gas and regenerated catalyst.

The partially spent regeneration gas and the regenerated catalyst travel out of the combustion chamber to the transfer tube 3 from its lower part. In tube 3 a substantially complete conversion of CO to CCl takes place and regeneration gas is obtained. At least a portion of the heat of combustion of CO is transferred to the regenerated catalyst, which is transferred through the zone.

The transfer tube 3 has a substantially vertical portion 3A and a substantially horizontal portion 3B connected to each other at a substantially right angle and has an interior 30. The substantially vertical portion 3A has an inlet 9 at its lower end connected to the burner 1. The inlet of the transfer tube 3 is also a burner outlet.

The mixture of regeneration gas and regenerated catalyst passing through the part 3A of the transfer tube 3 is directed through a rectangular bend to the substantially horizontal part 3B of the transfer tube 3. The substantially horizontal part 3B extends through the wall of the collector device 2. The horizontal part 3B has an outlet opening 16, which may include one or more openings located inside the collector device 2 and allowing the catalyst and regeneration gas to escape from the transfer tube 3.

The lid 3D is placed at the upper end of the vertical portion 3A and positioned so that a certain volume of the vertical portion is included above the upper portion of the horizontal portion 3B. This provides a space that can be filled with catalyst and gas, creating a buffer layer that prevents abrasion at the upper end of the vertical portion as the catalyst particles are directed from the vertical portion of the transfer tube to the horizontal portion.

An external combustible liquid such as fuel gas or liquid carbon hydrogen stream may be introduced into the space 30 in the pipe 3 through an optional combustible liquid supply port 12 and an optional decomposer 13. Combustion of such a liquid may be necessary to raise the temperature at start-up in state 3C sufficiently to initiate CO oxidation or to raise the temperature of the catalyst particles passing through the tube beyond what could be achieved by CO combustion alone. Although not shown in the figure, more combustible liquid could be added to chamber 1 for any or all of the above reasons.

Additional fresh regeneration gas can be added to space 3C through an optional fresh regeneration gas supply port 14 and an optional decomposer 15. This gas can supply oxygen to support the combustion of the external combustible liquid or to supplement the combustion of CO inside the transfer tube 3.

The regenerated catalyst collection chamber 2, which contains a dilute phase separation space 17 at the top of the chamber in which the cyclone separators are located, contains a dense layer 5 of regenerated catalyst, the level or interface of which is at 26 at the bottom of the chamber. The collector chamber 2 is very similar to the commonly used single-vessel regenerators. The process of the present invention can be accomplished by converting a prior art regenerator to a regenerated catalyst receiving chamber and adding a combustion chamber, transfer tube, and regenerated catalyst recycling device.

The substantially horizontal part 3B of the tube 3 extends inside the space 17. The outlet 16 of the transfer tube is located in the chamber 2 above the interface 26 of the sealed layer 5. The outlet 16 is connected to or communicates with a catalyst and regeneration gas separator, such as an intermediate space or cyclone separators, located in parallel or series flow, or a combination thereof. The drawing uses a combination of the exit space 17 and the cyclone separators 19 and 23. The guide plate 18 directs the flow of catalyst and gas from the outlet 16 to the vessel. The spent regeneration gas enters the cyclone separator 60403 19 through the inlet 20. The gas from the cyclone 19 enters the cyclone 23 via a pipe 22. The separated catalyst passes through immersion tubes 21 and 25 to a dense bed 5. The spent regeneration gas exits the cyclone 23 and the vessel 2 through the outlet 24.

This cyclone arrangement makes it possible to use the cyclones in an existing regenerator at their original location, which simplifies the change required to replace an existing regenerator to use the method and apparatus of the present invention.

The reason that the transfer tube has both a substantially vertical and a substantially horizontal portion and that the horizontal portion enters from the side is that existing single vessel regeneration equipment can be used without having to be displaced as the regenerated catalyst receiving chamber of the invention. Being able to use existing single-vessel regeneration equipment at its former location means savings in construction costs.

More specifically, it is necessary for the collector device to be positioned relative to the combustion chamber so that at least a portion of the dense catalyst bed in the collector remains above the dense catalyst layer in the combustion chamber to maintain the pressure necessary to ensure hot regenerated catalyst flow from the collector to the combustion chamber. This requirement, combined with the fixed position of the old single-vessel regeneration equipment, determines the current configuration of the transfer tube or CO combustion zone and its flow from the side to the collector device. This structure achieves an elevated position without having to reposition the old regenerator, which is now used as a collector.

Of course, the special arrangement described above is not necessary for carrying out the process of this invention. Also shown is another apparatus in which the collector device is directly above the combustion chamber instead of above and on the side as shown in the drawing.

A dense catalyst bed is maintained in the collector for sealing purposes and to provide sufficient pressure to ensure a one-way flow of regenerated catalyst from the collector 2 to the combustion chamber 1 and the reaction zone (not shown). The regenerated catalyst can, although not necessary, be washed countercurrently from the adsorbed and porous regeneration gas by passing it over the spacers in the stripping zone shown at number 27 as the wash medium enters the zone through line 29. The detergent is usually superheated steam.

The hot regenerated catalyst generally moves downward and exits the regenerated catalyst through an optional funnel 30 and return pipe 6 and valve 31. The hot regenerated catalyst is returned to the combustion chamber 1 to control the temperature therein and the oxidation rate of the coke.

Valve 31 is usually a spool valve and can be operated by means of a coke oxidation zone temperature controller. The return pipe 6 can be a series of pipes with or without valves and can generally be any device capable of conducting the catalyst from the collector device 2 to the combustion chamber 1 at an adjustable speed.

The rest of the catalyst from the collector 2 is returned to the reaction zone via a pipe 32 and a valve 33, which is typically a spool valve.

In an alternative apparatus embodiment, the collector device may be above and vertically aligned with the combustion chamber and the CO oxidation zone. In this type of arrangement, the CO oxidation zone must join the bottom of the collector device and extend inside it. Preferably, the outlet of the CO oxidation zone is connected directly to the inlet of the cyclone. The hot regenerated catalyst is in a dense layer at the bottom of the collector. The arrangements for external recycling of the catalyst may resemble the arrangements of the apparatus embodiment described above, i. an optional funnel in the tight catalyst hot bed of the collector leads to a catalyst return pipe that includes a flow control valve. Arrangements for washing the regenerated catalyst with steam can also be made. Of course, in this alternative embodiment, where the collector device is aligned with the combustion chamber, there is no rectangular bend in the center of the CO conversion zone. Instead, the CO conversion zone is a substantially vertical tube, although at the outlet of the CO conversion zone, the catalyst and gas may make a rectangular bend to enter the cyclone separator.

"Spent catalyst" means a catalyst that has been removed from the reaction zone due to a decrease in activity caused by coke deposits. The catalyst used may contain from a few tenths of a weight of about 5% by weight of coke, typically about 0.5-1.5% by weight of coke.

"Regenerated catalyst" means a catalyst from which most of the coke has been burned off. The regenerated catalyst produced by the process of our invention typically contains about 0.01 to 0.20% by weight of coke and even more typically about 0.01 to 0.1% by weight of coke.

"Regeneration gas" means any gas that contacts a catalyst in a regeneration process and includes oxygen-containing gases such as air and oxygen-enriched or oxygen-deficient air that enters the regenerator, oxidizing coke from the surface of the spent catalyst. A "partially spent regeneration gas" is a gas that has been in contact with a catalyst and contains a reduced amount of free oxygen compared to fresh regeneration gas. Typically, the partially used regeneration gas contains water, oxygen, carbon monoxide, and carbon dioxide.

"Substantially complete combustion of CO" means that the CO content of the exhaust gas is less than about 2000 ppm and generally less than about 500 ppm.

"Spent regeneration gas" means a regeneration gas that exits the regeneration process and contains less than about 2000 ppm of carbon monoxide, carbon dioxide, nitrogen, water, and from a few tenths of a percent up to 15 moles of free oxygen. Generally, the regeneration gas used contains less than about 500 ppm CO.

"Combustion chamber" means a zone containing one or more dense catalyst layers in which most of the coke is oxidized. "C0 conversion zone" means a zone in which the conversion of C0 takes place to produce spent regeneration gas. "Collector" means a zone in which regenerated catalyst is kept in one or more dense layers primarily for sealing and differential pressure purposes. A portion of the regenerated catalyst from this zone is recycled back to the combustion chamber and the remainder is returned to the reaction zone.

The catalyst used in the process of this invention is efficiently regenerated to a very low level of residual coke and the CO thus produced is burned substantially completely to CO 2. The spent catalyst is introduced into the combustion chamber to produce regenerated catalyst and partially spent regeneration gas. The regeneration gas and the regenerated catalyst then enter the CO conversion zone, where oxidation of CO takes place and where at least part of the heat of combustion of CO2 is transferred to the catalyst. The residence time of the catalyst in the CO conversion zone is short enough to prevent further substantial oxidation and the formation of additional CO with residual coke. The catalyst leaving the CO conversion zone and the spent regeneration gas are separated and the hot regenerated catalyst is passed to a collector. A portion of the hot regenerated catalyst is then recycled from the collector to the combustion chamber to raise the combustion chamber temperature and increase the oxidation rate of the coke and indirectly to increase the oxidation rate of CO in the CO conversion zone. The rest of the regenerated catalyst is returned from the regenerated catalyst zone to the reaction zone. The regenerated catalyst may optionally be stripped of adsorbed and pore-retained regeneration gas in the regenerated catalyst zone.

Thus, the process of this invention not only eliminates the problem of C0 contamination without requiring a CO evaporator, but also recovers at least a portion of the heat of combustion of C0 for useful purposes within the process. Recirculation of the hot regenerated catalyst back to the combustion chamber increases the oxidation and CO conversion rate of the coke, thus enabling smaller equipment. Returning the hotter-than-usual regenerated catalyst to the reaction zone makes it possible to reduce the preheating requirements for the feed. In addition, separating the oxidation of coke from the oxidation of CO makes it possible not only to produce a regenerated catalyst with a lower residual coke content and thus higher activity, but also to recover at least part of the CO capture heat for use in the FCC process. It is well known in the art that the residual coke content of the regenerated catalyst has a large effect on the conversion and product yield achieved in the reaction zone, especially when using coke-sensitive zeolite-containing catalysts in short dilution phase reaction zones.

60403 The catalyst in the coke oxidation zone of the present invention does not remain in this zone, so the velocity along the surface of the fresh regeneration gas as it enters the zone is not limited to the critical velocity. Surface velocities in the coke oxidation zone can be 0.9-3 m / s so that the catalyst can be transported to the CO conversion zone. The velocities in the CO conversion zone are usually about 3-7.5 m / s.

Since the surface velocity in the combustion chamber is not limited to the transfer rate, but is in fact 2-3 times the critical velocity, significant reductions in catalyst storage can now be achieved, as regenerated catalyst stocks are directly proportional to the surface velocities used in the combustion chamber. The catalyst stocks used in the process and apparatus of this invention are about 40-60% of the stocks of current single or multi-stage regeneration processes. By using the regeneration process and equipment of the present invention in a reasonably sized PCC process, the refinery can save about 75 tons of catalyst cost.

The amounts of catalyst replenishment required to compensate for losses and maintain activity are also reduced, as such amounts tend to be a percentage of the total catalyst stock.

Due to the higher temperatures resulting from the recirculation of the hot regenerated catalyst, the better gas-solid contact due to the higher speeds now allowed, and the higher oxygen partial pressures, the combustion rate of coke increases and the residence times of the catalyst can therefore be shortened. The residence times of the catalysts passing through once can be shortened from the current 2-5 minutes to less than 2 minutes and the residence times of the regeneration gas can be reduced from about 20 seconds to less than 10 seconds.

Another important result of the shorter catalyst residence time is that steam washing of the flue gas components from the regenerated catalyst is now possible. Steam washing of the regenerated catalyst has generally not been carried out due to the long residence time of the catalyst in conventional regeneration processes. Exposing the catalyst to steam for long periods of time increases the rate of catalyst deactivation.

When washing the regenerated catalyst is carried out in the process of the present invention, the volume of the bed must be made such as to allow a minimum exposure of the catalyst to steam.

The pressures intended for use in the process and equipment in question may range from about normal pressure to 4.4 atm, the absolute pressure being in the recommended range of about 1.7 to 3.7 atm.

Recommended operating conditions for the combustion chamber include a residence time of the single pass catalyst of less than about 2 minutes, a temperature of about 675-760 ° C and a surface gas velocity of about 0.9_3 m / s. The amount of catalyst recycled from the collector to the combustion chamber is about 5-150% of the spent catalyst entering the combustion chamber, and preferably about 25-100%.

Recommended operating conditions for the CO conversion zone include a temperature of about 690-775 ° C and a surface gas velocity of about 3-7.5 m / s.

A single cyclone can be used to separate the regenerated catalyst from the gas, but more than one such cyclone is preferably used as a parallel or series flow arrangement to achieve the desired degree of separation.

Example

The following example illustrates the benefits of recycling hot regenerated catalyst from a collector to a combustion chamber. The information in the table below is for commercial FCC regenerator processes with and without reclaimed catalyst recycling.

Summary of regeneration processes

Recycling of reclaimed catalyst No Yes

Reaction zone temperature, ° C 520 518

Conversion of the reaction zone,% by volume 74.0 76.5

Regeneration process temperatures, ° C

Combustion chamber 629 674 CO conversion zone inlet 653 699 CO conversion zone outlet 728 745

Collector 706 743 Used regeneration gas 791 759 60403

Surface velocity in the combustor, m / s 1.0 1.1

Dense bed density in the incinerator, kg / l 0.096 0.104

Carbon with regenerated catalyst,% by weight 0.14 0.04

Burner oil, 1 / h 26 0 Analysis of spent regeneration gas CO mol ppm 1520 60 CO2 mol-ϊ 15.9 16.0 02 mol% 0.3 1.6

The effects observed from recycling the regenerated catalyst from the regenerated catalyst zone to the coke oxidation zone were: increased temperatures in the combustion chamber, the CO conversion zone, and the catalyst zone of the collector; increased combustion chamber bed density and decreased amount of residual coke with regenerated catalyst due to higher rate of coke oxidation.

As can be seen from the table, the temperature differences are significant; the temperature of the combustion chamber and the inlet of the CO conversion zone both rose by about 45 ° C. The outlet temperature of the CO conversion zone increased by 17 ° C; the temperature of the collector or regenerated catalyst zone increased by 37 ° C and the temperature of the flue gas decreased by 32 ° C.

Due to the higher combustion chamber temperatures and the resulting higher oxidation rate of coke, the amount of residual carbon with the regenerated catalyst decreased from 0.14 wt.% To 0.04 wt.% To 55 wt.%. The density of the dense layer of the combustion chamber increased by about 8%.

Due to the higher rate of oxidation of CO in the CO conversion zone caused by higher temperatures, the concentration of CO in the combustion gas decreased from 1520 ppm to 60 ppm. The lower CO concentration was also evidenced by the smaller temperature difference between the outlet of the CO conversion zone and the regeneration gas used, which indicated less combustion of C0. The recycle of the regenerated catalyst also raised the temperatures sufficiently so that the addition of burner oil could be stopped when the recycle of the regenerated catalyst was carried out. The overall operation with this catalyst recycling was more stable and smoother than the operation without it.

Claims (6)

A process for regenerating a coke-containing spent catalyst, in which process the spent catalyst and fresh regeneration are carried out continuously from a reaction zone to a combustion zone comprising a first dense catalyst bed and the coke is oxidized therein to obtain regenerated catalyst and spent regeneration gas containing CO, the regenerated catalyst and the partially consumed regeneration gas are introduced into a zone for converting CO and CO into this CO to obtain spent regeneration gas and regenerated catalyst at higher temperature, and the regenerated catalyzed regenerated catalyst the regenerating gas and entering a collection zone comprising a second dense catalyst bed, characterized in that a portion of the higher dense catalyst bed present in the second dense catalyst bed is recirculated to the combustion zone and another portion of the catalyst is recirculated to the reaction zone. Process according to claim 1, characterized in that the temperature in the combustion zone is controlled by controlling the recirculation of the regenerated catalyst from the collection zone to the combustion zone.