RU2574385C1 - Some zones of catalyst burning out with independent circulation circuits - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to method of catalyst regeneration, which includes supply of waste catalyst stream into upper regeneration zone, supply of first regeneration gas flow, which contains oxygen, into upper regeneration zone with obtaining stream of partially regenerated catalyst as a result; transfer of stream of partially regenerated catalyst into lower regeneration zone and supply of stream of second regeneration gas into lower regeneration zone with obtaining stream of regenerated catalyst as a result; and stream of first regeneration gas and stream of second regeneration gas are independent streams.

EFFECT: improvement of catalyst regeneration process regulation.

10 cl, 1 dwg

Description

This application claims the priority of patent application US No. 13/327156 with a filing date 12/15/2011.

FIELD OF THE INVENTION

The invention relates to processes for converting a stream of feed hydrocarbons into useful hydrocarbon products. In particular, the invention relates to the continuous regeneration of spent catalyst for reuse in a hydrocarbon conversion process.

State of the art

Hydrocarbons and, in particular, oil are extracted from the bowels of the earth as a mixture. The produced mixture is subjected to conversion to obtain useful products by separation and processing of hydrocarbon streams in reactors. The conversion of hydrocarbon streams to useful products in most cases is a catalytic process carried out in a reactor. The catalyst may be solid or liquid and may contain supported catalyst materials. In particular, supported on a carrier are catalytic metals. Catalytic metals include platinum group metals, as well as other metals. During the processing of hydrocarbons, the catalysts deactivate over time. One of the main causes of decontamination is the formation and growth of coke deposits on the catalyst. The accumulation of coke deposits blocks access to the catalytic centers of the catalyst. Catalyst regeneration is usually done by removing coke, during which the coke is burned at high temperature using an oxygen-containing gas. These processes can be carried out either continuously with the catalyst circulating through the reactor and the regenerator, or the specified regeneration process can be carried out semi-continuously, for example, using a large number of fixed layers, from which one layer is previously removed from the catalyst stream for regeneration, while other catalyst beds continue to operate. During continuous regeneration, recirculation gas is continuously directed to the burner area of the regenerator, and the resulting exhaust gas containing combustion products is removed. The burning process is controlled by the oxygen content in the recycle gas. The recycle gas stream is formed by a part of the exhaust gas stream and an additional stream of fresh combustion gas, while another part of the exhaust gas is removed from the regenerator. This helps to maintain the temperature of the combustion gas, as well as ensuring a steady state of continuous input of spent catalyst and combustion gas into the regenerator with continuous removal of the regenerated catalyst and exhaust gas.

US Pat. No. 5,053,371 (Williamson) and US Pat. No. 6,048,814 (Capelle et al.) Describe methods for regenerating a catalyst produced to remove coke from catalyst particles by burning coke. The burning process can be harmful to the catalyst, and for the long life of the catalyst, which cyclically and sequentially moves through the reactor and regenerator, more important ways to control the process of burning carbon deposits are important. Creating a more advanced method provides an increase in the number of cycles of passage of the catalyst through the regenerator and increases the life of the catalyst. This can be achieved through improved workflow and control of the regenerator.

SUMMARY OF THE INVENTION

The present invention provides an improved catalyst regeneration method. The method includes supplying a spent catalyst stream to the first or upper regeneration zone for partial regeneration of the catalyst by means of a controlled process of burning coke deposits formed on the catalyst. The partially regenerated catalyst moves to the second, or lower, regeneration zone to completely regenerate the catalyst. The method includes supplying a first regeneration gas containing oxygen to the first or upper regeneration zone, and moving the second regeneration stream to the second or lower regeneration zone. The regeneration gas streams are independent gas streams, which makes it possible to control the amount and content of oxygen in individual gas streams.

Other objects, advantages, and applications of the present invention will become apparent to those skilled in the art from the following detailed description and drawings.

Brief Description of the Drawing

The drawing shows the regeneration zone and the flows of circulating oxidizing gas used to regenerate the catalyst passing through the regenerator.

DETAILED DESCRIPTION OF THE INVENTION

The object of the present invention is a method for continuous regeneration of the catalyst. The most typical example of the application of the invention is the removal of coke from catalyst particles that contain a platinum group metal, and the most typical process suitable for applying the invention is the catalytic process for the dehydrogenation of paraffins to produce olefins. The regenerator used in the conversion of olefins is described in patent document US 75858803 (Price and others), publication date September 08, 2009, which is fully incorporated into this description by reference.

The design of the known regenerator includes in the zone of complete burning two zones, namely the upper zone of burning and the zone of increasing oxygen concentration. With this design, the maximum oxygen concentration in the lower zone is limited by the total oxygen consumption and the relative size of the zone of increasing oxygen concentration in the complete burnout zone.

As a rule, this means that the maximum oxygen concentration in the zone of increasing oxygen concentration is 2% with the separation of the supplied combustion gas so that 70% of the combustion gas is supplied to the upper burning zone and 30% to the zone of increasing oxygen concentration. The process may be more resistant to deviations, and it is desirable to provide an increase in the concentration of oxygen supplied to the zone of increasing oxygen concentration. It may be preferable to increase the oxygen concentration in the zone of increasing oxygen concentration to 5% of the volume of the combustion gas.

In the case of the known design of the regenerator, the parts of the recycle gas stream, which are increased due to the additional introduction of oxygen or oxygen-containing gas, are directed into one channel of the zone of increasing oxygen concentration through the upper burning zone without depletion of oxygen flow. This leads to an increase in the oxygen concentration in the entire recycle gas leaving the regenerator body to a relatively high level compared to the upper burn zone. Said relatively high oxygen content is not acceptable for a properly controlled burning process in the upper burning zone. Therefore, an additional dilution gas is needed, which is introduced into the upper burning zone to reduce the oxygen concentration in the upper burning zone. The result is an increase in the amount of recirculation gas, removal and use of off-gas in energy supply systems. Separation of these two recirculation flows provides a greater degree of regulation.

The present invention is directed to improving the regulation of the catalyst regeneration process and improving catalyst regeneration. The method includes supplying a spent catalyst stream to a regenerator, which comprises an upper regeneration zone and a lower regeneration zone. The catalyst enters the upper regeneration zone and moves through it into the lower regeneration zone. The first regeneration gas stream is directed to the upper regeneration zone to burn off coke deposits on the catalyst, during which an exhaust gas is generated, consisting of combustion products, which are removed from the regenerator. The spent catalyst is partially regenerated in the upper regeneration zone and sent as a partially regenerated catalyst to the lower regeneration zone. The second regeneration gas stream is sent to the lower regeneration zone to obtain a regenerated catalyst stream. The streams of the first and second regeneration gas are independent streams, which provides regulation of the amount of oxygen in each stream and regulation of the burning process in each burning zone.

The process described above will be described in more detail below with reference to the drawing. A stream of spent catalyst particles 12 is continuously introduced into the regenerator 10. Although the term “continuously” is applied to the process in question, this process is more of a semi-continuous process in which small catalyst particles are discharged from the reactor and sent to the regenerator on a relatively continuous basis. The catalyst particles move downward through the annular zone 20 formed by the retaining mesh partitions 22 and 24 and located in the burning zone 30. The burnout zone 30 is divided into the upper burnout zone 32 and the lower burnout zone 34, which is also known as the oxygen concentration increase zone 34. The upper burning zone 32 is separated from the lower burning zone 34 by the baffles 40 and a separate downstream gas collecting device 42 located below. When moving the catalyst particles down through the upper burning zone 32, the first regeneration gas contacts the catalyst particles to burn off carbon deposits on the catalyst particles. The particles of the catalyst slowly move through the upper burning zone, which provides a sufficient period of time for burning carbon. The average residence time of the catalyst in the upper zone will be in the range from 3 to 5 hours, with a preferred period of time from 3.5 to 4.5 hours.

The first regeneration gas is circulated through the first regeneration gas circuit 50 by the first blower 52, which serves to promote the circulation of the regeneration gas, with the exhaust gas from the upper or first combustion zone 32 being directed to the first regeneration gas circuit 50. The flue gas consists of carbon monoxide, carbon dioxide, water, unreacted oxygen and other non-reactive gases generated in the burning area and discharged from the regeneration zone as flue gas. Regeneration gas is an off-gas that forms a recycle gas circuit, into which an off-gas stream is continuously discharged and oxygen-containing gas 54 is mixed thereto to compensate for oxygen consumed, after which this off-gas is returned to the initial burning section as the first regeneration gas. Part of the offgas is removed while maintaining a continuous steady state flow of regeneration gas. The off-gas, before being sent to the upper burning zone as a stream of the first regeneration gas, is heated to the burning temperature. The first burning temperature is in the range from 450 ° C to 600 ° C, preferably in the range from 470 ° C to 500 ° C, more preferably in the range from 470 ° C to 485 ° C, while the temperature is controlled at a temperature close to 477 ° C. Oxygen 54 is added to the regeneration gas stream to a level in the range of 0.5 vol.% To 2 vol.%, Preferably in the range of 0.5 vol.% To 1.5 vol.%. A regeneration gas containing recirculation gas with additional oxygen added is introduced into the upper burning zone. The oxygen content in the recycle gas is continuously monitored and, if necessary, additional oxygen is added so that the oxygen level corresponds to the desired intervals. The oxygen content is a parameter of the control of the burning process, carried out in order to prevent damage to the catalyst and equipment in which the burning is carried out. Further control of the gas composition includes the use of a nitrogen gas stream 56 to add diluent if the oxygen content needs to be further controlled. Alternatively, the oxygen-containing gas may be mixed with nitrogen before the gas stream is added to the first regeneration gas stream.

The upper burning zone is often not able to burn all coke deposits deposited on the catalyst. The present invention provides a lower burnout zone 34 into which a separate regeneration gas stream is directed to complete the combustion process and burn off the residual carbon deposits on the catalyst.

The catalyst is further processed and advanced from the upper burnout zone 32 to the lower burnout zone 34, in which the catalyst is in contact with the second regeneration gas stream to remove residual carbon deposits. The lower burning zone is also called the zone of increasing oxygen concentration. The second regeneration gas is circulated through the second regeneration gas circuit 60, in which a second blower 62 is used to circulate the regeneration gas, and off-gas from the lower or second burnout zone 34 is directed to the second regeneration gas circuit 60. The flue gas consists of carbon monoxide, carbon dioxide, water, unreacted oxygen and other non-reactive gases generated in the burning area and discharged from the regeneration zone as flue gas through a separate flue gas collecting device 42. The second regeneration gas is an exhaust gas forming a second recirculation gas circuit 60, into which a stream of exhaust gas is continuously discharged from the process, oxygen-containing gas 64 is mixed with it to compensate for the consumed oxygen, and then it is returned to the lower burning zone as a second regeneration gas. A portion of the offgas is removed while maintaining a continuous steady stream of a second regeneration gas. Before being fed to the lower burning zone, the exhaust gas is heated to a second burning temperature. The second burning temperature is in the range from 500 ° C to 600 ° C, preferably in the range from 550 ° C to 570 ° C, while the temperature is controlled at a temperature close to 560 ° C. Further control of the gas composition includes the use of a nitrogen gas stream 66 to add diluent in case it is necessary to further control the oxygen content. Alternatively, the oxygen-containing gas may be mixed with nitrogen before the gas stream is added to the second regeneration gas stream.

The lower burning zone, or the zone of increasing oxygen concentration, functions in such a way and is sized so that the catalyst is in the lower zone for a period of time from 1 hour to 3 hours, with a preferred average duration of this period being from 1.5 hours up to 2.5 hours. The oxygen concentration in the zone of increasing oxygen concentration is greater than in the upper burning zone, and is regulated to a level in the range from 2 vol.% To 5 vol.%.

After removing carbon deposits from the catalyst, the catalyst is further treated to redistribute the catalytic metal over the surface of the support. The process of burning during removal of carbon deposits from the catalyst leads to sintering of metal particles. As a result, the catalyst may become less efficient and its service life may be reduced. Metal particles can be redistributed over the surface of the catalyst due to contact with a halogen-containing gas. In this regard, the catalyst particles exiting from the oxygen concentration increase zone 34 are sent to the halogenation zone 36. The halogenation zone 36 is preferably located in the same regenerator housing to minimize external influences, as well as to minimize the amount of heating and cooling of the catalyst during its movement between the zones. The halogen-containing gas is supplied to the halogenation zone 36 through the inlet of the halogenation gas circulation loop 70. The halogen-containing gas contacts the catalyst and redistributes the catalytic metal over the surface of the catalyst. The gas flows upward through the halogenation zone 36 and is captured by the halogenation gas collecting device 72. The halogenation gas collecting device 72 is preferably an impermeable baffle attached to the lower end of the inner mesh baffle of the oxygen concentration increasing zone 34, and is provided with an outlet pipe 74 connected to the halogen-containing gas conduit 76. The halogen circulation system may include a separate gas blower to promote gas circulation, as well as appropriate desiccants to remove moisture and adsorbent layers to remove residual effluent from the catalyst as the catalyst passes through the halogenation zone 36. A preferred halogen-containing gas is chlorine contained in the gas as active halogen.

After regeneration, the catalyst is dried. During the combustion process, water is formed as one of the combustion products, and this water can be adsorbed by the regenerated catalyst. The presence of water negatively affects the process, and therefore, before returning the catalyst to the reactor, it is necessary to remove water from it. In one embodiment, the catalyst is dried in a regenerator 10. The catalyst moves from the halogenation zone 36 to the drying zone 38. A drying gas 80 is supplied to the drying zone 38, which passes through the catalyst and removes any residual water. The drying gas is heated to a temperature in the range from 390 ° C to 510 ° C before being fed to the drying zone 38. The drying gas is distributed throughout the drying zone 38 and flows upward through the catalyst, which moves downward through the drying zone 38. The drying time is determined mainly by the height of the zone 38. The dimensions of the drying zone are selected during design so as to provide an average residence time of catalyst particles in this zone of at least 4 hours. The drying gas passes through the drying zone 38 and the halogenation zone 36 upwards and exits the regenerator through the outlet pipe 74. The dried and regenerated catalyst is discharged through the catalyst outlet pipe 82, which is located in the bottom of the regenerator 10.

Although the present invention has been described above with the help of the considered embodiments of the invention, it should be understood that the invention is not limited to the described embodiments, and covers various modifications and equivalent embodiments included in the scope of the attached claims.

Claims (10)

1. The method of regeneration of the catalyst, including
supplying a spent catalyst stream to the upper regeneration zone;
supplying a first regeneration gas stream containing oxygen to the upper regeneration zone to form a partially regenerated catalyst as a result of the stream;
moving the stream of partially regenerated catalyst to the lower regeneration zone, and
supplying a stream of a second regeneration gas containing oxygen to the lower regeneration zone to obtain a regenerated catalyst as a result;
wherein the first regeneration gas stream and the second regeneration gas stream are independent streams, and the first regeneration gas stream is directed to the upper regeneration zone through the circulation circuit of the first regeneration gas, and the second regeneration gas stream is directed to the lower regeneration zone through the circulation circuit of the second regeneration gas. 2. The method according to p. 1, in which the flow of the first regeneration gas is sent to the upper regeneration zone using the first gas blower. 3. The method according to p. 1 or 2, in which the flow of the second regeneration gas is sent to the lower regeneration zone using a second gas blower. 4. The method according to p. 1 or 2, in which the upper regeneration zone operates at a temperature in the range from 450 ° C to 500 ° C. 5. The method according to p. 1 or 2, in which the lower regeneration zone operates at a temperature in the range from 500 ° C to 600 ° C. 6. The method according to p. 1 or 2, in which the average length of time the catalyst has been in the lower regeneration zone is from 1 to 3 hours. 7. The method according to p. 1 or 2, in which the average length of time spent by the catalyst in the upper regeneration zone is from 3 to 5 hours. 8. The method according to p. 1 or 2, further comprising transporting a stream of regenerated catalyst to the halogenation zone and contacting the catalyst with a halogen-containing gas. 9. The method according to p. 1 or 2, in which the oxygen concentration in the second regeneration gas stream is in the range from 2 vol.% To 5 vol.%. 10. The method according to claim 1 or 2, in which the first regeneration gas stream includes a first recirculation gas stream with added nitrogen to control the oxygen content in the first regeneration gas, and the second regeneration gas stream includes a second recirculated gas stream with added nitrogen to control the oxygen content in the second regeneration gas.

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