CA2057239A1 - Process and apparatus for removal of carbonaceous materials from particles containing such materials - Google Patents
Process and apparatus for removal of carbonaceous materials from particles containing such materialsInfo
- Publication number
- CA2057239A1 CA2057239A1 CA 2057239 CA2057239A CA2057239A1 CA 2057239 A1 CA2057239 A1 CA 2057239A1 CA 2057239 CA2057239 CA 2057239 CA 2057239 A CA2057239 A CA 2057239A CA 2057239 A1 CA2057239 A1 CA 2057239A1
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- Prior art keywords
- reactor
- particles
- gas
- solids
- riser
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Classifications
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G11/00—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
- C10G11/14—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils with preheated moving solid catalysts
- C10G11/18—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils with preheated moving solid catalysts according to the "fluidised-bed" technique
- C10G11/182—Regeneration
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- Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Devices And Processes Conducted In The Presence Of Fluids And Solid Particles (AREA)
- Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
Abstract
A B S T R A C T
PROCESS AND APPARATUS FOR REMOVAL OF CARBONACEOUS
MATERIALS FROM PARTICLES CONTAINING
SUCH MATERIALS
Process and apparatus for the removal of carbonaceous materials from particles containing such materials, comprising introducing said particles into the lower part of a first, riser-type reactor, into which lower part also an oxygen containing gas is introduced, the reactor being operated under entrainment conditions with a relatively high density phase in the lower part and with a relatively low density phase in the upper part at a temperature suitable to burn off carbonaceous materials, separating solids and gas at the top of the reactor, introducing the separated particles into the upper part of a second, fluidized bed-type reactor while introducing an oxygen containing gas into the lower part of the second reactor, the reactor being operated under fluidized bed conditions at a temperature suitable to burn off carbonaceous materials, removing processed particles from the lower part of the reactor, and recirculating a part of the processed particles to the lower part of the riser-type reactor.
PROCESS AND APPARATUS FOR REMOVAL OF CARBONACEOUS
MATERIALS FROM PARTICLES CONTAINING
SUCH MATERIALS
Process and apparatus for the removal of carbonaceous materials from particles containing such materials, comprising introducing said particles into the lower part of a first, riser-type reactor, into which lower part also an oxygen containing gas is introduced, the reactor being operated under entrainment conditions with a relatively high density phase in the lower part and with a relatively low density phase in the upper part at a temperature suitable to burn off carbonaceous materials, separating solids and gas at the top of the reactor, introducing the separated particles into the upper part of a second, fluidized bed-type reactor while introducing an oxygen containing gas into the lower part of the second reactor, the reactor being operated under fluidized bed conditions at a temperature suitable to burn off carbonaceous materials, removing processed particles from the lower part of the reactor, and recirculating a part of the processed particles to the lower part of the riser-type reactor.
Description
20~723~
- 1 .
T SOOl PROCESS AND APPARATUS FOR REMOVAL OF CARBONACEOUS
MATERIALS FROM PARTICLES CONTAINING
SUCH MATERIALS
The invention relates to a process and an apparatus for the removal of carbonaceous materials from particles containing such materials Fluid catalytic cracking (FCC) processes are used to convert relatively heavy hydrocarbon products obtained from crude oil processing into lighter hydrocarbon products. The catalyst particles used in these processes become very quickly contaminated with carbonaceous materials. These hydrocarbonaceous materials have to be removed in a regeneration process in order to permit reuse of the catalyst particles. To regenerate the catalyst, the catalyst is contacted with an oxygen containing gas in a fluidized bed at a temperature suitable to burn off the carbonaceous materials, thus restoring thc activity of the catalyst.
Reference herein to a reactor is made in relation to a regeneration reactor, unless otherwise stated.
Suitable FCC-feeds are gas-oils boiling in the range from 250-590 C, especially 370-540 C. However, at the present moment there is a tendency to use heavier feeds, such as atmospheric and vacuum residual oils, often mixed with gas-oils. As these residuaL
feeds usually contain considerable amounts of asphaltenes, which compounds have a high tendency to form coke during the cracking operation, a larger amount of coke will be deposited on the catalyst. This holds especially when only residual feeds are used without mixing with lighter gas-oil fractions. In regenerating these heavily coked spent catalyst particles it may be difficult to burn off enough coke to provide a suitable low concentration of carbon on the regenerated catalyst. To overcome these difficulties regenerators are suggested in which the coke is burned to carbon 20~7239 monoxide, thus limiting the formation oi` heat in the regenerator.
The carbon monoxide may be use~ as fuel gas, for instance for the production of electricity or steam. Alternatively, a carbon monoxide boiler may be included after the regenerator to complete S combustion of carbon monoxide to carbon dioxide.
A process and an apparatus for the regeneration of spent FCC
catalyst particles by burning off the carbon under the formation of carbon monoxide are described in US patent 4,260,475. The first stage of this regeneration process is performed in a riser-type reactor employing an entrained bed of upwardly moving catalyst particles in cocurrent flow with regeneration gas. The second stage of the regeneration is performed in a staged fluidized bed of catalyst particles in net downward movement countercurrent to regeneration gas. The process of the before-mentioned US patent has a number of clear advantages over other known regeneration processes, as has been described in its specification.
A disadvantage of the process as described in the above-mentioned ~S patent, is that the riser reactor has to be of an extremely large height in order to obtain a reasonable removal of carbonaceous materials in the first stage. This is due to the fact that the temperature of the spent catalyst particles initially is too low for a rapid combustion.
An optimum performance of the catalytic cracking process is obtained when the starting reaction mixture of hydrocarbons and catalyst particles in the lower end of the riser cracking reactor has a temperature of 520 to 560 C. During the cracking process in the riser cracking reactor, the temperature decreases 20 to 30 C
due to the endothermic character of the reaction, thus resulting in a temperature of the spent catslyst particles of 490 to 540 C.
During the usual stripping of the catalyst, the temperature will fall another 5 C. Thus, the spent catalyst particles introduced into the riser regeneration reactor usually will have a temperature between 485 and 535 C. This temperature is far too low for an efficient combustion of the carbonaceous materials deposited on the catalyst particles during the cracking process. Efficient 20~7239 combustion takes place at a temperature of at least 650 C.
Therefore, the slowly oxidizing mixture of spent catalyst and oxygen has to be transported over a long distance in the riser regeneration reactor before a sufficiently high temperature i.s attained - due to the exothermal oxidation - at which combustion can take place at a reasonable velocity. As a result, riser regeneration reactors of an extremely large height are necessary, leading to increasing construction costs and a large catalyst inventory, thus resulting in high material, maintenance and operating costs of the unit.
It has now been found that the disadvantages of the before-mentioned process for the removal of carbonaceous materials from particles containing such material may be overcome by introducing said particles into the lower part of a first, riser-type reactor, into which lower part also an oxygen containing gasis introduced, the reactor being operated under entrainment conditions with a relatively high density phase in the lower part and with a relatively low density phase in the upper part at a temperature suitable to burn off carbonaceous materials, separating solids and gas at the top of the reactor, introducing the separated particles into the upper part of a second, fluidized bed-type reactor while introducing an oxygen containing gas into the lower part of the second reactor, the reactor being operated under fluidized bed conditions at a temperature suitable to burn off carbonaceous materials, removing processed particles from the lower part of the reactor, and recirculating a part of the processed particles to the lower part of the riser-type reactor.
The process may be operated by supplying substoichiometric or excess amounts of oxygen containLng gas to eLther or both reactor Ln such a way that the flue gases at the top of the reactors are substantially free of oxygen.
In the process as described above, the disadvantages of the prior art process as discussed hereLnbefore, have been overcome. By cLrculation of regenerated catalyst particles from the second reactor to the first reactor an increase of the temperature of the 2~57239 particles in the first reactor takes place. As a result thereof, and due to the fact that the lower part of the first reactor is operated in a relatively dense phase - and therefore a longer residence time as compared with a relatively low density phase - a considerable part of the carbonaceous materials is already burned off in the lower part of the reactor. Thus, the height of the riser-type reactor may be brought back to a more practical height.
In the process operated by supplying substoichiometric amounts of oxygen-containing gas to the first or both reactor, recirculation of regenerated catalyst particles from the second reactor to the first is partlcularly beneficial as compensation for the limited heat formation in the first reactor.
It is observed that due to the fact that the operation of the second reactor, at least within certain boundaries, is independent from the operation of the first reactor, the system has a great flexibility, and thus the amount of circulating particles may be varied over a wide range. This holds especially when the particle inventory of the second reactor is relatively large when compared with the first reactor. The ratio of the amount of particles which are removed from the second reactor and the amount of particles which are introduced again in the first reactor may vary between 0.1 and 10, and is preferably between 0.2 and 5, more preferably between 0.3 and 1. The recirculated particles have to be introduced into the relatively high density phase in the first reactor.
Recirculated particles may be removed via one or more outlets in the second reaetor at different heights.
The process of the present inventlon is especially suitable for the regeneration of spent FCC-catalyst particles, although it also may be used for other processes, as for instance the combustion of retorted oil shale particles. The amount of carbon on the FCC-catalyst particles is suitably between 0.5 and 4 %wt, preferably between 0.3 and 1.5 %wt. The particles are introduced into the relatively high density phase of the first reactor.
The process of the present invention is suitably carried out at a temperature in the first reactor of 525 C to 725 C, 2~723~
preferably 550 to 650 ~CI and at a temperature in the second reactor of 625 to 950 C, preferably 700-800 C. The substoichiometrical amount of oxygen introduced in the first reactor may be from 20-/0% of the amount necessary to burn all the carbonaceous materials, and is preferably from 40 to 60%, most preferably 50%. The pressure in both reactors is suitably between 1 and lO bar, preferably between 1.5 and 4 bar. The pressure drop over the first reactor is suitably between 0.1 and 2 bar, preferably between 0.3 and l bar. The pressure drop over the second reactor is suitably between 1 and 5 bar, preferably 1.5 and 4 bar.
The second reactor to be used in the process according to the present invention is preferably a staged fluidized bed.
As indicated above, the proces.s of the present invention is especially suitable for the regeneration of spent FCC-catalyst particles. The feed for the FCC-process is suitably a hydrocarbon fraction boiling between 250 and 590 C, especially between 370 and 540 C. Preferred feeds are atmospheric and vacuum residual fractions and socalled synthetic feed, such as coal oils, bitumen, shale oils and high boiling fractions thereof. Usually the boiling range is between 250 and 600 C, or higher, and preferably a substantial amount boils above 4S0 C. The conversion conditions include a temperature in the range from about 425 C to about 625 C, preferably from about 510 C to about 610 C. Cracking conditions also preferably include a pressure in the range from about atmosphsric to about 4 atmospheres or more, particularly preferably about 2 atmospheres to about 3 atmospheres. In cracking using a fluidlzed bed of partlculates, a catalyst/hydrocarbon weight ratio of about 2 to about 50, preferably 3 to about 10 is usually quite suitable. A hydrocarbon weight hourly space velocity in the cracking operation of about 5 to about 50 per hour is preferably used The cracking zone ernployed may be of conventional design and may use dilute-phase fluidized solids contact, riser-type entrained solids contact, dense-bed fluidized solids contact, countercurrent contact, a moving, packed bed of solids or a combination thereof, 2~7239 between the feed hydrocarbons and the catalyst particles. Catalyst fluidization, entrainment, etc. may be assisted by gases such as steam or nitrogen. Conventional spent solids stripping means for removing volatiles from the spent solids may also suitably be employed.
The particulate solids to be used in the cracking process may optionally be catalytically active or may simply act as a heat carrier and sorbent for the hydrocarbons. Essentially, the particulate solids employed must be suitably attrition resistant and refractory to the high temperatures and to steaming which are characteristic of the process, so that the particles can be circulated for a practical period of time in a fluidized system.
Conventional particulate cracking catalysts and heat transfer solids can be used in the present process. Suitable cracking catalysts may include a zeolitic crystalline aluminosilicate component.
Particulate solids other than active, acidic cracking catalyst may alternatively or additionally be circulated in the cracking system. For example, alumina particles may be included in the particulate solids inventory for the control of sulphur oxides and/or particles containing a highly active combustion promoting metal, such as a Group VIII noble metal, may be mixed with the catalyst or heat carrier particles. Likewise, particles having a heat carrying capacity but low intrinsic acidic cracking activity may be circulated either alone or mixed with more active and acidic cracking catalyst to provide heat for elther acidic or essentially thermal cracking of the hydrocarbons.
~ ccording to the invention, coke contaLning particles which result from cracking of hydrocarbons are re8enerated in two steps:
(1) an entralned bed step, in which particles and regeneration gas move in cocurrent, upward flow; and a (2) fluidized bed step, in which particles and regeneration gas move in generally countercurrent flow.
The first regeneration ~one, in which particles are partially regenerated in entrained flow in upwardly moving gases, may 7 20~7%39 .
suitably be defined by any vessel, conduit, reactor or the like capable of containing the upwardly moving gases and solids at the temperatures and pressures employed in the first regeneration stage. Riser-type vessels or transfer line vessels of the type used conventionally in carrying out riser-cracking in fluidized catalytic cracking systems are suitable for use as the first regeneration zone in the present process. The vessels or conduit used to provide the riser-type regeneration zone can be sized in length and cross-sectional area to provide the desired gas and solids flow rates and residence times in order to create the relatively high density phase in the lower part of the zone, and a relatively low density phase in the upper part of the zone.
Suitable measures to create the differences in density are introduction of sufficient amounts of gas at a certain height, or decreasing the cross-sectional area, thus increasing the gas velocity In case of a smaller cross-sectional area, the cross-sectional area of the relatively high density phase zone is suitably between 4-100 times as large as the cross-sectional area of the relatively low density zone, preferably 5-50, more preferably 9-25.
The riser reactor is preferably equipped with means for introducing molecular oxygen into the entraining gas stream at a plurality of vertically spaced levels ln the first regeneration zone.
The second regeneration zone, in which fluidized particles move generally downwardly, countercùrrent to upwardly moving gases, may likewise be defined by any vessel, conduit, reactor or the like capable of containing the fluidized particles in flowing gases at the temperatures and pressures used in the second, fluidized stage of regeneration. Preferably, the second regeneration zone comprises a vertically elongated vessel having a length and diameter suitably ad~usted for providing gas and solids residence times and solids fluidization according to the parameters of the process. In order to prevent gross back-mixing of generally downwardly moving particles in the second regeneration stage, the vessel employed 20~7~3~
should be equipped with some sort of means for impeding back-mixing such as barriers, baffles, solids or gas dispersing means, redistribution means, or the like. For example, perforated plates, bars, screens, packing material, or other suitable internals may be used to impede back-mixing.
The catalyst entrainment-regeneration gas introduced, in addition to the desired amount of molecular oxygen, may include such relatively inert gases as nitrogen, steam, carbon monoxide, carbon dioxide, etc. The composition of the entraining gases will, of course, vary along the gas flow path through the regeneration zone, as the gases pass from the upstream end to the downstream end of the ri.ser reactor. The amount of entraining gas and its pressure and superficial velocity in the riser are maintained at levels such that the particles present in the riser are entrained upwardly through the riser.
A solids residence time in the relatively low density phase zone of the riser reactor of about 3 to 6 seconds and a gas residence time of about 2 to 4 seconds are generally suitable.
Preferably, when the entraining gas is recovered from the riser reactor, it has a sufficiently high fuel value to have utility as a fuel. gas. The utility of the effluent gas from the riser reactor as a fuel gas will depend primarily on the carbon monoxide content of the gas. This may vary according to the oxygen and steam partial pressures, the total pressure, the gas and solids residence times and the exact temperature maintained in the riser reactor. The amount of molecular oxygen (free oxygen) introduced into the first stage regeneration zone is preferably conerolled to provide the desired degree of coke burn off in the entrained bed reactor, whether all the oxygen is introduced at the downstream end of the reactor or some is introduced further along the entraining gas path. The entraining gas exiting the first regeneration zone should generally have an oxygen concentration of not more than 0.5 volume percent. Preferably, the effluent gas contains not more than 0.1 volume percent molecular oxygen. Where it is desired to operate the 2~7239 riser reactor to obtain a high fuel value flue gas, the first and second reactors suitably have separate flue system~
After the partially regenerated particles have been removed from the riser reactor and separated from the entraining gas stream, the particles are subject to a second stage of regeneration in a fluidized bed, wherein the particles moved generally downwardly in countercurrent flow relative to a fluidizing stream of gases. In carrying out the second stage of regeneration, particles are passed into the upper end of a generally vertically extending regeneration zone, in which the particles are fluidized by an upwardly flowing stream of gases. Coke-free, regenerated particles are withdrawn from the lower end of the regeneration zone for reintroduction into, the cracking process of which a part is recirculated to the first reactor.
The invention also relates to an apparatus for the removal of carbonaceous materials from particles containing such materials. In this respect reference is made to Figure l, representing an apparatus according to the invention, comprising a first, riser-type reactor (l) comprising a normally vertical, elongated reactor provided with solids inlet means (2) and gas inlet means (3) at the lower part of the reactor, means for separating solids and gas (4) having an inlet (5) connected with the upper part of the first reactor, and having a gas (6) and a solids outlet (7), a second, fluidized bed reactor (8), comprisLng a normally vertical reactor connected with the solids outlet (7) of the gas/solids separation means and provided with gas inlet means (9) at the lower part oP the reactor and with solid outlet means (lO), the first and the second reactor being connected with means (ll) for the recirculation of solids from the second reactor to the first reactor.
In a preferred embodlment the lower part of the riser reactor has a larger diameter than the upper part of the reactor, as is shown in Figure 1. Further details on this feature have been described above. Also conical reactors may be used.
20~72~
In another preferred embodiment one or more additional ~as inlet means (12) are present above the lower part of the reactor.
Preferably the solids outlet means of the gas/solids separation means are connected with the upper part of the second reactor.
Suitably one or more cyclones may be used. The solids outlet means of the second reactor are preferably present at the lower part of the reactor. The second, fluidized bed-type reactor is preferably provided with internals (13) making it possible to create a staged fluidized bed. Plates, gauges, trays etc. may be used. The solids recirculation means is preferably provided with a valve, making adjustment of the recirculation ratio possible. The second reactor may be provided with a separated gas outlet at the upper part of the reactor, or the gas outlet may be combined with the gas outlet of the gas/solids separation means as for instance has been described in European patent application No. 0206399. The second reactor may be provided with heat exchanging means in the lower part of the reactor. Preferably a cooling heat exchange device is provided at the bottom of the reactor as for instance has been described in European patent application No. 340852.
- 1 .
T SOOl PROCESS AND APPARATUS FOR REMOVAL OF CARBONACEOUS
MATERIALS FROM PARTICLES CONTAINING
SUCH MATERIALS
The invention relates to a process and an apparatus for the removal of carbonaceous materials from particles containing such materials Fluid catalytic cracking (FCC) processes are used to convert relatively heavy hydrocarbon products obtained from crude oil processing into lighter hydrocarbon products. The catalyst particles used in these processes become very quickly contaminated with carbonaceous materials. These hydrocarbonaceous materials have to be removed in a regeneration process in order to permit reuse of the catalyst particles. To regenerate the catalyst, the catalyst is contacted with an oxygen containing gas in a fluidized bed at a temperature suitable to burn off the carbonaceous materials, thus restoring thc activity of the catalyst.
Reference herein to a reactor is made in relation to a regeneration reactor, unless otherwise stated.
Suitable FCC-feeds are gas-oils boiling in the range from 250-590 C, especially 370-540 C. However, at the present moment there is a tendency to use heavier feeds, such as atmospheric and vacuum residual oils, often mixed with gas-oils. As these residuaL
feeds usually contain considerable amounts of asphaltenes, which compounds have a high tendency to form coke during the cracking operation, a larger amount of coke will be deposited on the catalyst. This holds especially when only residual feeds are used without mixing with lighter gas-oil fractions. In regenerating these heavily coked spent catalyst particles it may be difficult to burn off enough coke to provide a suitable low concentration of carbon on the regenerated catalyst. To overcome these difficulties regenerators are suggested in which the coke is burned to carbon 20~7239 monoxide, thus limiting the formation oi` heat in the regenerator.
The carbon monoxide may be use~ as fuel gas, for instance for the production of electricity or steam. Alternatively, a carbon monoxide boiler may be included after the regenerator to complete S combustion of carbon monoxide to carbon dioxide.
A process and an apparatus for the regeneration of spent FCC
catalyst particles by burning off the carbon under the formation of carbon monoxide are described in US patent 4,260,475. The first stage of this regeneration process is performed in a riser-type reactor employing an entrained bed of upwardly moving catalyst particles in cocurrent flow with regeneration gas. The second stage of the regeneration is performed in a staged fluidized bed of catalyst particles in net downward movement countercurrent to regeneration gas. The process of the before-mentioned US patent has a number of clear advantages over other known regeneration processes, as has been described in its specification.
A disadvantage of the process as described in the above-mentioned ~S patent, is that the riser reactor has to be of an extremely large height in order to obtain a reasonable removal of carbonaceous materials in the first stage. This is due to the fact that the temperature of the spent catalyst particles initially is too low for a rapid combustion.
An optimum performance of the catalytic cracking process is obtained when the starting reaction mixture of hydrocarbons and catalyst particles in the lower end of the riser cracking reactor has a temperature of 520 to 560 C. During the cracking process in the riser cracking reactor, the temperature decreases 20 to 30 C
due to the endothermic character of the reaction, thus resulting in a temperature of the spent catslyst particles of 490 to 540 C.
During the usual stripping of the catalyst, the temperature will fall another 5 C. Thus, the spent catalyst particles introduced into the riser regeneration reactor usually will have a temperature between 485 and 535 C. This temperature is far too low for an efficient combustion of the carbonaceous materials deposited on the catalyst particles during the cracking process. Efficient 20~7239 combustion takes place at a temperature of at least 650 C.
Therefore, the slowly oxidizing mixture of spent catalyst and oxygen has to be transported over a long distance in the riser regeneration reactor before a sufficiently high temperature i.s attained - due to the exothermal oxidation - at which combustion can take place at a reasonable velocity. As a result, riser regeneration reactors of an extremely large height are necessary, leading to increasing construction costs and a large catalyst inventory, thus resulting in high material, maintenance and operating costs of the unit.
It has now been found that the disadvantages of the before-mentioned process for the removal of carbonaceous materials from particles containing such material may be overcome by introducing said particles into the lower part of a first, riser-type reactor, into which lower part also an oxygen containing gasis introduced, the reactor being operated under entrainment conditions with a relatively high density phase in the lower part and with a relatively low density phase in the upper part at a temperature suitable to burn off carbonaceous materials, separating solids and gas at the top of the reactor, introducing the separated particles into the upper part of a second, fluidized bed-type reactor while introducing an oxygen containing gas into the lower part of the second reactor, the reactor being operated under fluidized bed conditions at a temperature suitable to burn off carbonaceous materials, removing processed particles from the lower part of the reactor, and recirculating a part of the processed particles to the lower part of the riser-type reactor.
The process may be operated by supplying substoichiometric or excess amounts of oxygen containLng gas to eLther or both reactor Ln such a way that the flue gases at the top of the reactors are substantially free of oxygen.
In the process as described above, the disadvantages of the prior art process as discussed hereLnbefore, have been overcome. By cLrculation of regenerated catalyst particles from the second reactor to the first reactor an increase of the temperature of the 2~57239 particles in the first reactor takes place. As a result thereof, and due to the fact that the lower part of the first reactor is operated in a relatively dense phase - and therefore a longer residence time as compared with a relatively low density phase - a considerable part of the carbonaceous materials is already burned off in the lower part of the reactor. Thus, the height of the riser-type reactor may be brought back to a more practical height.
In the process operated by supplying substoichiometric amounts of oxygen-containing gas to the first or both reactor, recirculation of regenerated catalyst particles from the second reactor to the first is partlcularly beneficial as compensation for the limited heat formation in the first reactor.
It is observed that due to the fact that the operation of the second reactor, at least within certain boundaries, is independent from the operation of the first reactor, the system has a great flexibility, and thus the amount of circulating particles may be varied over a wide range. This holds especially when the particle inventory of the second reactor is relatively large when compared with the first reactor. The ratio of the amount of particles which are removed from the second reactor and the amount of particles which are introduced again in the first reactor may vary between 0.1 and 10, and is preferably between 0.2 and 5, more preferably between 0.3 and 1. The recirculated particles have to be introduced into the relatively high density phase in the first reactor.
Recirculated particles may be removed via one or more outlets in the second reaetor at different heights.
The process of the present inventlon is especially suitable for the regeneration of spent FCC-catalyst particles, although it also may be used for other processes, as for instance the combustion of retorted oil shale particles. The amount of carbon on the FCC-catalyst particles is suitably between 0.5 and 4 %wt, preferably between 0.3 and 1.5 %wt. The particles are introduced into the relatively high density phase of the first reactor.
The process of the present invention is suitably carried out at a temperature in the first reactor of 525 C to 725 C, 2~723~
preferably 550 to 650 ~CI and at a temperature in the second reactor of 625 to 950 C, preferably 700-800 C. The substoichiometrical amount of oxygen introduced in the first reactor may be from 20-/0% of the amount necessary to burn all the carbonaceous materials, and is preferably from 40 to 60%, most preferably 50%. The pressure in both reactors is suitably between 1 and lO bar, preferably between 1.5 and 4 bar. The pressure drop over the first reactor is suitably between 0.1 and 2 bar, preferably between 0.3 and l bar. The pressure drop over the second reactor is suitably between 1 and 5 bar, preferably 1.5 and 4 bar.
The second reactor to be used in the process according to the present invention is preferably a staged fluidized bed.
As indicated above, the proces.s of the present invention is especially suitable for the regeneration of spent FCC-catalyst particles. The feed for the FCC-process is suitably a hydrocarbon fraction boiling between 250 and 590 C, especially between 370 and 540 C. Preferred feeds are atmospheric and vacuum residual fractions and socalled synthetic feed, such as coal oils, bitumen, shale oils and high boiling fractions thereof. Usually the boiling range is between 250 and 600 C, or higher, and preferably a substantial amount boils above 4S0 C. The conversion conditions include a temperature in the range from about 425 C to about 625 C, preferably from about 510 C to about 610 C. Cracking conditions also preferably include a pressure in the range from about atmosphsric to about 4 atmospheres or more, particularly preferably about 2 atmospheres to about 3 atmospheres. In cracking using a fluidlzed bed of partlculates, a catalyst/hydrocarbon weight ratio of about 2 to about 50, preferably 3 to about 10 is usually quite suitable. A hydrocarbon weight hourly space velocity in the cracking operation of about 5 to about 50 per hour is preferably used The cracking zone ernployed may be of conventional design and may use dilute-phase fluidized solids contact, riser-type entrained solids contact, dense-bed fluidized solids contact, countercurrent contact, a moving, packed bed of solids or a combination thereof, 2~7239 between the feed hydrocarbons and the catalyst particles. Catalyst fluidization, entrainment, etc. may be assisted by gases such as steam or nitrogen. Conventional spent solids stripping means for removing volatiles from the spent solids may also suitably be employed.
The particulate solids to be used in the cracking process may optionally be catalytically active or may simply act as a heat carrier and sorbent for the hydrocarbons. Essentially, the particulate solids employed must be suitably attrition resistant and refractory to the high temperatures and to steaming which are characteristic of the process, so that the particles can be circulated for a practical period of time in a fluidized system.
Conventional particulate cracking catalysts and heat transfer solids can be used in the present process. Suitable cracking catalysts may include a zeolitic crystalline aluminosilicate component.
Particulate solids other than active, acidic cracking catalyst may alternatively or additionally be circulated in the cracking system. For example, alumina particles may be included in the particulate solids inventory for the control of sulphur oxides and/or particles containing a highly active combustion promoting metal, such as a Group VIII noble metal, may be mixed with the catalyst or heat carrier particles. Likewise, particles having a heat carrying capacity but low intrinsic acidic cracking activity may be circulated either alone or mixed with more active and acidic cracking catalyst to provide heat for elther acidic or essentially thermal cracking of the hydrocarbons.
~ ccording to the invention, coke contaLning particles which result from cracking of hydrocarbons are re8enerated in two steps:
(1) an entralned bed step, in which particles and regeneration gas move in cocurrent, upward flow; and a (2) fluidized bed step, in which particles and regeneration gas move in generally countercurrent flow.
The first regeneration ~one, in which particles are partially regenerated in entrained flow in upwardly moving gases, may 7 20~7%39 .
suitably be defined by any vessel, conduit, reactor or the like capable of containing the upwardly moving gases and solids at the temperatures and pressures employed in the first regeneration stage. Riser-type vessels or transfer line vessels of the type used conventionally in carrying out riser-cracking in fluidized catalytic cracking systems are suitable for use as the first regeneration zone in the present process. The vessels or conduit used to provide the riser-type regeneration zone can be sized in length and cross-sectional area to provide the desired gas and solids flow rates and residence times in order to create the relatively high density phase in the lower part of the zone, and a relatively low density phase in the upper part of the zone.
Suitable measures to create the differences in density are introduction of sufficient amounts of gas at a certain height, or decreasing the cross-sectional area, thus increasing the gas velocity In case of a smaller cross-sectional area, the cross-sectional area of the relatively high density phase zone is suitably between 4-100 times as large as the cross-sectional area of the relatively low density zone, preferably 5-50, more preferably 9-25.
The riser reactor is preferably equipped with means for introducing molecular oxygen into the entraining gas stream at a plurality of vertically spaced levels ln the first regeneration zone.
The second regeneration zone, in which fluidized particles move generally downwardly, countercùrrent to upwardly moving gases, may likewise be defined by any vessel, conduit, reactor or the like capable of containing the fluidized particles in flowing gases at the temperatures and pressures used in the second, fluidized stage of regeneration. Preferably, the second regeneration zone comprises a vertically elongated vessel having a length and diameter suitably ad~usted for providing gas and solids residence times and solids fluidization according to the parameters of the process. In order to prevent gross back-mixing of generally downwardly moving particles in the second regeneration stage, the vessel employed 20~7~3~
should be equipped with some sort of means for impeding back-mixing such as barriers, baffles, solids or gas dispersing means, redistribution means, or the like. For example, perforated plates, bars, screens, packing material, or other suitable internals may be used to impede back-mixing.
The catalyst entrainment-regeneration gas introduced, in addition to the desired amount of molecular oxygen, may include such relatively inert gases as nitrogen, steam, carbon monoxide, carbon dioxide, etc. The composition of the entraining gases will, of course, vary along the gas flow path through the regeneration zone, as the gases pass from the upstream end to the downstream end of the ri.ser reactor. The amount of entraining gas and its pressure and superficial velocity in the riser are maintained at levels such that the particles present in the riser are entrained upwardly through the riser.
A solids residence time in the relatively low density phase zone of the riser reactor of about 3 to 6 seconds and a gas residence time of about 2 to 4 seconds are generally suitable.
Preferably, when the entraining gas is recovered from the riser reactor, it has a sufficiently high fuel value to have utility as a fuel. gas. The utility of the effluent gas from the riser reactor as a fuel gas will depend primarily on the carbon monoxide content of the gas. This may vary according to the oxygen and steam partial pressures, the total pressure, the gas and solids residence times and the exact temperature maintained in the riser reactor. The amount of molecular oxygen (free oxygen) introduced into the first stage regeneration zone is preferably conerolled to provide the desired degree of coke burn off in the entrained bed reactor, whether all the oxygen is introduced at the downstream end of the reactor or some is introduced further along the entraining gas path. The entraining gas exiting the first regeneration zone should generally have an oxygen concentration of not more than 0.5 volume percent. Preferably, the effluent gas contains not more than 0.1 volume percent molecular oxygen. Where it is desired to operate the 2~7239 riser reactor to obtain a high fuel value flue gas, the first and second reactors suitably have separate flue system~
After the partially regenerated particles have been removed from the riser reactor and separated from the entraining gas stream, the particles are subject to a second stage of regeneration in a fluidized bed, wherein the particles moved generally downwardly in countercurrent flow relative to a fluidizing stream of gases. In carrying out the second stage of regeneration, particles are passed into the upper end of a generally vertically extending regeneration zone, in which the particles are fluidized by an upwardly flowing stream of gases. Coke-free, regenerated particles are withdrawn from the lower end of the regeneration zone for reintroduction into, the cracking process of which a part is recirculated to the first reactor.
The invention also relates to an apparatus for the removal of carbonaceous materials from particles containing such materials. In this respect reference is made to Figure l, representing an apparatus according to the invention, comprising a first, riser-type reactor (l) comprising a normally vertical, elongated reactor provided with solids inlet means (2) and gas inlet means (3) at the lower part of the reactor, means for separating solids and gas (4) having an inlet (5) connected with the upper part of the first reactor, and having a gas (6) and a solids outlet (7), a second, fluidized bed reactor (8), comprisLng a normally vertical reactor connected with the solids outlet (7) of the gas/solids separation means and provided with gas inlet means (9) at the lower part oP the reactor and with solid outlet means (lO), the first and the second reactor being connected with means (ll) for the recirculation of solids from the second reactor to the first reactor.
In a preferred embodlment the lower part of the riser reactor has a larger diameter than the upper part of the reactor, as is shown in Figure 1. Further details on this feature have been described above. Also conical reactors may be used.
20~72~
In another preferred embodiment one or more additional ~as inlet means (12) are present above the lower part of the reactor.
Preferably the solids outlet means of the gas/solids separation means are connected with the upper part of the second reactor.
Suitably one or more cyclones may be used. The solids outlet means of the second reactor are preferably present at the lower part of the reactor. The second, fluidized bed-type reactor is preferably provided with internals (13) making it possible to create a staged fluidized bed. Plates, gauges, trays etc. may be used. The solids recirculation means is preferably provided with a valve, making adjustment of the recirculation ratio possible. The second reactor may be provided with a separated gas outlet at the upper part of the reactor, or the gas outlet may be combined with the gas outlet of the gas/solids separation means as for instance has been described in European patent application No. 0206399. The second reactor may be provided with heat exchanging means in the lower part of the reactor. Preferably a cooling heat exchange device is provided at the bottom of the reactor as for instance has been described in European patent application No. 340852.
Claims (15)
1. Process for the removal of carbonaceous materials from particles containing such materials, comprising introducing said particles into the lower part of a first, riser-type reactor, into which lower part also an oxygen containing gas is introduced, the reactor being operated under entrainment conditions with a relatively high density phase in the lower part and with a relatively low density phase in the upper part at a temperature suitable to burn off carbonaceous materials, separating solids and gas at the top of the reactor, introducing the separated particles into the upper part of a second, fluidized bed-type reactor while introducing an oxygen containing gas into the lower part of the second reactor, the reactor being operated under fluidized bed conditions at a temperature suitable to burn off carbonaceous materials, removing processed particles from the lower part of the reactor, and recirculating a part of the processed particles to the lower part of the riser-type reactor.
2. Process according to claim 1, for the removal of carbonaceous materials from particles containing such materials, comprising introducing said particles into the lower part of a first, riser-type reactor, into which lower part also a substoichlometrical amount of an oxygen containing gas is introduced, the reactor being operated under entrainment conditions with a relatively high density phase in the lower part and with a relatively low density phase in the upper part at a temperature suitable to burn off carbonaceous materials, at such a rate that the flue gas at the top of the reactor does not contain any substantial amount of oxygen, separating solids and gas at the top of the reactor, introducing the separated particles into the upper part of a second, fluidized bed-type reactor while introducing an oxygen containing gas into the lower part of the second reactor, the reactor being operated under fluidized bed conditions at a temperature suitable to burn off carbonaceous materials, the amount of oxygen containing gas being established in such a way that the flue gas at the top of the reactor is substantially free of oxygen, removing processed particles from the lower part of the reactor, and recirculating a part of the processed particles to the lower part of the riser-type reactor.
3. Process according to claim 1 in which the carbonaceous materials containing particles are spent FCC-catalyst particles.
4. Process according to claim 1 in which the temperature in the riser-type reactor is between 525 °C and 725 °C, and the temperature of the fluidized bed reactor is between 625 °C and 950 °C
5. Process according to claims 1-4 in which the substoichiometrical amount of oxygen introduced in the first reactor is sufficient to burn off 20-70% of the carbonaceous materials.
6. Process according to any one of claims 1-5, wherein as second reactor a staged fluidized bed reactor is used.
7. Process according to claims 1-6 in which the ratio of the densities of the relatively high density phase and the relatively low density phase is between 5 and 50, preferably between 10 and 30, more preferably about 20.
8. Process according to any one of claims 1-7, wherein the ratio of the amount of particles which are removed from the second reactor and the amount of particles which are recirculated to the first reactor is between 0.1 and 10.
9. Apparatus for the removal of carbonaceous materials from particles containing such materials, comprising a first, riser-type reactor comprising a normally vertical, elongated reactor provided with solids and gas inlet means at the lower part of the reactor, means for separating solids and gas having an inlet connected with the top of the first reactor, and having a gas and a solids outlet, a second, fluidized bed-type reactor, comprising a normally vertical reactor connected with the solids outlet of the gas/solids separation means and provided with gas inlet means at the lower part of the reactor and with solids outlet means, the first and the second reactor being connected with means for the recirculation of solids from the second reactor to the first reactor.
10. Apparatus according to claim 9, in which the lower part of the riser reactor has a larger diameter than the upper part of the reactor.
11. Apparatus according to claim 10, in which additional gas inlet means are present above the lower part of the reactor.
12. Apparatus according to any of claims 9-11, in which the solids outlet means of the gas/solids separation means are connected with the upper part of the second reactor.
13. Apparatus according to any of claims 9-12, in which the solids outlet means of the second reactor are present at the lower part of the reactor.
14. Apparatus according to any of claims 9-13, in which the second reactor is provided with internals making it possible to create a staged fluid bed.
15. Apparatus according to any of claims 9-14, in which the solids recirculation means is provided with a valve making adjustment of the recirculation ratio possible.
D11/t5001FF
D11/t5001FF
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB909027038A GB9027038D0 (en) | 1990-12-13 | 1990-12-13 | Process and apparatus for removal of carbonaceous materials from particles containing such materials |
| GB9027038.0 | 1990-12-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2057239A1 true CA2057239A1 (en) | 1992-06-14 |
Family
ID=10686934
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2057239 Abandoned CA2057239A1 (en) | 1990-12-13 | 1991-12-06 | Process and apparatus for removal of carbonaceous materials from particles containing such materials |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0490453A1 (en) |
| JP (1) | JPH04322747A (en) |
| AU (1) | AU8892191A (en) |
| CA (1) | CA2057239A1 (en) |
| GB (1) | GB9027038D0 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2784602B1 (en) * | 1998-10-20 | 2002-04-12 | Eurecat Europ Retrait Catalys | PROCESS FOR TREATING A CATALYST OR ADSORBENT IN A FLUIDIZED BED |
| US7935245B2 (en) | 2007-12-21 | 2011-05-03 | Uop Llc | System and method of increasing synthesis gas yield in a fluid catalytic cracking unit |
| US7699975B2 (en) | 2007-12-21 | 2010-04-20 | Uop Llc | Method and system of heating a fluid catalytic cracking unit for overall CO2 reduction |
| US7932204B2 (en) * | 2007-12-21 | 2011-04-26 | Uop Llc | Method of regenerating catalyst in a fluidized catalytic cracking unit |
| US7811446B2 (en) | 2007-12-21 | 2010-10-12 | Uop Llc | Method of recovering energy from a fluid catalytic cracking unit for overall carbon dioxide reduction |
| US7699974B2 (en) | 2007-12-21 | 2010-04-20 | Uop Llc | Method and system of heating a fluid catalytic cracking unit having a regenerator and a reactor |
| US7767075B2 (en) | 2007-12-21 | 2010-08-03 | Uop Llc | System and method of producing heat in a fluid catalytic cracking unit |
| BRPI0905257B1 (en) * | 2009-12-28 | 2018-04-17 | Petroleo Brasileiro S.A. - Petrobras | FLOW CATALYTIC CRACKING PROCESS WITH REDUCED CARBON DIOXIDE EMISSION |
| EP3040401A1 (en) * | 2014-12-30 | 2016-07-06 | Shell Internationale Research Maatschappij B.V. | An oxygenate to olefins conversion reactor system and process for use thereof |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3926778A (en) * | 1972-12-19 | 1975-12-16 | Mobil Oil Corp | Method and system for controlling the activity of a crystalline zeolite cracking catalyst |
| US4822761A (en) * | 1986-05-13 | 1989-04-18 | Ashland Oil, Inc. | Method and apparatus for cooling fluid solid particles used in a regeneration system |
| US4849091A (en) * | 1986-09-17 | 1989-07-18 | Uop | Partial CO combustion with staged regeneration of catalyst |
| US4917790A (en) * | 1989-04-10 | 1990-04-17 | Mobil Oil Corporation | Heavy oil catalytic cracking process and apparatus |
| US5011592A (en) * | 1990-07-17 | 1991-04-30 | Mobil Oil Corporation | Process for control of multistage catalyst regeneration with full then partial CO combustion |
-
1990
- 1990-12-13 GB GB909027038A patent/GB9027038D0/en active Pending
-
1991
- 1991-12-06 AU AU88921/91A patent/AU8892191A/en not_active Abandoned
- 1991-12-06 CA CA 2057239 patent/CA2057239A1/en not_active Abandoned
- 1991-12-10 EP EP91203247A patent/EP0490453A1/en not_active Withdrawn
- 1991-12-13 JP JP35119691A patent/JPH04322747A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| AU8892191A (en) | 1992-06-18 |
| JPH04322747A (en) | 1992-11-12 |
| EP0490453A1 (en) | 1992-06-17 |
| GB9027038D0 (en) | 1991-02-06 |
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