EP0187032A1 - Improved fluid catalytic cracking process and apparatus - Google Patents
Improved fluid catalytic cracking process and apparatus Download PDFInfo
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- EP0187032A1 EP0187032A1 EP85309354A EP85309354A EP0187032A1 EP 0187032 A1 EP0187032 A1 EP 0187032A1 EP 85309354 A EP85309354 A EP 85309354A EP 85309354 A EP85309354 A EP 85309354A EP 0187032 A1 EP0187032 A1 EP 0187032A1
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- catalyst
- stripper
- stripping
- hot
- regenerator
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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
Definitions
- This invention relates to methods and apparatus for fluid catalytic cracking, FCC, of hydrocarbons with subsequent regeneration of catalyst particles.
- the oil is catalytically cracked, thereby deactivating the catalyst with coke.
- Deactivated catalyst is stripped, and then regenerated by burning coke from catalyst with air.
- Multistage stripping is disclosed in U. S. Patent No. 4,043,899 to Anderson et al.
- a catalyst riser terminating in a cylindrical vessel and a riser comprising baffles is disclosed by U.S. Patent No. 4,206,174 to Heffley et at and risers attached to conduits are disclosed by U. S. Patent No. 4,219,407 to Haddad et al.
- catalyst passing from a fluid catalytic cracking stripper to a fluid catalytic cracking regenerator contains hydrogen-containing components, such as coke, adhering thereto. This causes hydrothermal degradation when the hydrogen reacts with oxygen in the regenerator to form water.
- the present invention provides a process for fluid catalytic cracking (FCC) of a hydrocarbon feed, by passing a mixture of catalyst and feed up through a conventional FCC riser and discharging from the riser a mixture of coked catalyst and cracked product, separating coked catalyst from cracked product, stripping coked catalyst to remove strippable hydrocarbons and regenerating the stripped catalyst by burning coke from catalyst, characterized by heating the coked catalyst by combining with a hot regenerated catalyst from the FCC regenerator and stripping the heated coked catalyst by contact with a stripping gas before regeneration of the hot stripped catalyst in the FCC regenerator.
- FCC fluid catalytic cracking
- the present invention provides an apparatus for fluid catalytic cracking of oil by adding oil and catalyst to an upstream end of a riser reactor, and discharging spent catalyst and cracked product at a downstream end, separating catalyst from product, and the spent catalyst is stripped and then regenerated, characterized by a two stage regenerator including a verticai, dilute phase first stage regenerator, receiving stripped catalyst and discharging partially regenerated catalyst into a second stage dense bed regenerator.
- Fig. 1 shows a riser reactor of a vertical elongated tube 1 having an upstream end 3 wherein hydrocarbon feed from line 7 and hot regenerated catalyst from line 37 are introduced and a downstream end 5 where a mixture of spent catalyst and cracked hydrocarbons exit.
- the riser is preferably a short contact time riser reactor 0.1 to 10 seconds, preferably 0.2 to 5 seconds gas residence time, having a multiple point feed injection nozzle and an acceleration zone.
- the gas catalyst mixture exiting conduit 1 is deflected downwardly by, e.g., deflector 51, to separate a major portion of the catalyst from the cracked hydrocarbons.
- deflector 51 is shown, a cyclone may also be used.
- the riser reactor terminates within elongated enclosed vessel 11, which has a substan- tally continuous sidewall 13 attached to bottom member 15 and top member 9 which can function with deflector 51 to deflect catalyst in the gas catalyst mixture exiting riser conduit 1 to separate a portion of the catalyst from the cracked hydrocarbons.
- One or more perpendicular conduits 19 provide an exit from vessel 11 for the mixture of hydrocarbon product and entrained catalyst Stripping medium from the stripping regions 17 and 23 also exits vessel 11 via conduits 19. Deflection can also be accomplished by means of an inertial separator or other equivalent means.
- Vessel 11 includes a stripping zone with a primary stripping region 17 and a secondary stripping region 23.
- Primary stripping region 17 is formed in an upper portion of vessel 11 and receives the downwardly deflected catalyst.
- a stripping medium is introduced into primary stripper 17 via line 53 to contact the downwardly deflected catalyst to separate entrained hydrocarbons from the catalyst
- the stripped hydrocarbon ascends with the stripping medium to exit vessel 11 through conduits 19 to external closed cyclone system 21 and then via line 61 to conventional product recovery and fractionators (not shown).
- Secondary stripping region 23 is formed in a lower portion of vessel 11 and receives stripped catalyst from primary stripper 17, stripped catalyst from one or more diplegs 25 associated with cyclone system 21 and hot regenerated catalyst along conduit 27 which is connected to a bottom portion of second stage regenerator 29.
- the secondary region 23 is a hot stripping zone because the recycle of hot regenerated catalyst directly to the region 23 allows the catalyst within region 23 to be at a temperature greater than that at which it is discharged from the riser 1.
- the catalyst in region 23 is at a temperature between 56°C (100°F) above that at which it exits the riser 1 and 871 °C (1600°F).
- the catalyst in the region 23 is at a temperature between 83°C (150°F) above that at which it exits the riser 1 and 871 °C (1600°F).
- Mixing means in a form of mixing tray 31, is disposed between primary stripper 17 and secondary stripper 23 for mixing stripped catalyst from stripper 17, cyclone diplegs 25 and hot regenerated catalyst from second stage regenerator 29, prior to passage of this mixed catalyst into secondary stripper 23.
- a stripping medium is introduced into secondary stripper 23 via line 55 to separate additional entrained hydrocarbon from the catalyst This latter stripping medium can be light hydrocarbon gas, inert gas or steam.
- Hot regenerated catalyst from second stage regenerator 29 is recycled to mixing tray 31 and then into secondary stripping region 23, to provide more complete removal of hydrocarbons from the spent catalyst.
- First stage regenerator 33 which is preferably a fast fluidized bed regenerator, receives stripped catalyst leaving secondary stripper 23 to bum off additionally entrained coke deposits by contact with a rapidly ascending stream of air at, e.g., 4 to 20 ft/sec, which is provided via air inlet 35.
- First stage regenerator 33 passes regenerated catalyst output into second stage regenerator 29 via conduit 57.
- Second stage regenerator 29 includes a first conduit 27 for recycling hot regenerated catalyst onto mixing tray 31, and then to secondary stripper 23, and a second conduit 37 for recirculating hot regenerated catalyst into upstream end 3 of riser conversion zone conduit 1 where it is mixed with hydrocarbon feed from feed source 7.
- Air distributor header 49 distributes air from conduit 59 to a bottom region of catalyst bed 45 in second stage regenerator 29.
- Second stage regenerator 29 can include a cyclone system having a primary cyclone 39 and a secondary cyclone 41.
- the secondary cyclone includes dipleg 43 for fines removal from catalyst bed 45 of second stage regenerator 29.
- thermofor catalytic cracking (TCC) system to fluid catalytic cracking operation.
- TCC thermofor catalytic cracking
- This is beneficial in that numerous thermofor catalytic cracking units are presently idle, with restarting in a thermofor catalytic cracking mode of operation being uneconomical.
- conversion to fluid catalytic cracking operation by the method and apparatus of the present invention would be very economical.
- Fig. 2 illustrates a second embodiment of a fluid catalytic cracking system of the present invention.
- a hydrocarbon feed passes from a hydrocarbon feed source (feeder) 7 to the lower end of a riser conversion zone 104 which is a vertically elongate tubular conduit.
- Regenerated catalyst from a standpipe 202, having a control valve 20 4 is combined with the hydrocarbon feed in the riser 104, such that a hydrocarbon-catalyst mixture rises in an ascending dispersed stream until it is discharged at a riser discharge temperature into a reactor vessel 102, and passes through a riser effluent conduit 106 into a first reactor cyclone 108.
- the riser discharge temperature defined as the temperature at which the mixture is discharged from the riser 104 to conduit 106, may be any suitable temperature but preferably ranges from 482 0 to 593°C (900 0 to 1100°F), and most preferably 538° to 566°C (1000° to 1050°F).
- Riser effluent conduit 106 is attached at one end to the riser 104 and at its other end to the cyclone 108.
- the first reactor cyclone 108 separates a portion of catalyst from the catalyst-hydrocarbon mixture and passes this catalyst down a first reactor cyclone dipleg 112 to a preliminary stripping zone 130 located therebelow.
- the remaining gas and catalyst pass from the first reactor cyclone 108 through a gas effluent conduit 110.
- the conduit 110 is provided with a connector 111 to allow for thermal expansion.
- the catalyst passes through the conduit 110, into a second reactor cyclone 114 as part of a closed cyclone system.
- the second cyclone 114 separates the stream to form a catalyst stream, which passes through a second reactor cyclone dipleg 118 to the preliminary stripping zone 130 located therebelow.
- a second cyclone overhead stream which contains the remaining gas and catalyst, passes through a second cyclone gaseous effluent conduit 116 to a reactor overhead port 120. Gases from the atmosphere of the reactor vessel 102 may pass through a reactor overhead conduit 122 into the reactor overhead port 120. The gases which exit the reactor 1 02 through the second cyclone gaseous effluent conduit 116 and the reactor overhead conduit 122 are combined and exit through the reactor overhead port 120 as reactor overhead stream 124. It will be apparent to those skilled in the art that although only one series connection of cyclones 108, 114 is shown in the embodiment, more than one series connection and/or more or less than two consecutive cyclones in series connection could be employed.
- the mixture of catalyst and hydrocarbons passes through the first reactor cyclone oerhead conduit 110 to the second reactor cyclone 114 as part of a closed cyclone system without entering the reactor vessel 102 atmosphere.
- the connector 111 may provide an annular port to admit stripping gas from the reactor vessel 102 into the conduit 110 to aid in separating catalyst from hydrocarbons adhering thereto.
- the closed cyclone system and annular port is described more fully in U. S. Patent No. 4,502,947 to Haddad et al.
- the separated catalyst from cyclones 108, 114 pass through respective diplegs 112, 118 and are discharged therefrom after a suitable pressure is generated within the diplegs by the buildup of the catalyst.
- the catalyst falls from the diplegs into a bed of catalyst 131 located in the stripping zone 130.
- the first dipleg 112 and second dipleg 118 are sealed by being extended into the catalyst bed 1 31.
- diplegs 112, 118 could instead be sealed by trickle valves (not shown).
- the separated catalyst is passed to a preliminary stripping zone 130 where it is contacted with stripping gas.
- the stripping gas is introduced into the lower portion of the stripping zone 130 by one or more conduits 134 attached to a stripping gas header 136.
- the preliminary stripping zone 130 strips portions of coke, sulfur and hydrogen from the separated catalyst at conventional stripping conditions, such as temperature, pressure, gas residence time and solids residence time as known in the art.
- the stripping zone 130 may also be provided with trays (baffles) 132.
- the trays 1 32 may be disc- and doughnut-shaped and may be perforated or unperforated.
- the preliminary stripped catalyst passed from the zone 130 through a reactor effluent conduit 138 and combines with hot regenerated catalyst
- the conduit 138 is provided with a valve 139.
- the regenerated catalyst has a temperature between 56°C (100°F) above that of catalyst 142 in a hot stripping zone 143 and 871 °C (1600°F) to heat the preliminarily stripped catalyst.
- the regenerated catalyst passes from the regenerator 180 to the reactor effluent conduit 138 through a transfer line 206 attached at one end to the regenerator vessel 80 and at another end to the reactor effluent conduit 138.
- the transfer line 206 is provided with a slide valve 208.
- the hot stripping occurs at a temperature between 56°C (100°F) above the riser exit temperature and 8 1 6°C (1500°F).
- the catalyst in the hot stripping zone 143 has a temperature from 83°C (150°F) above the riser exit temperature to 760°C (1400°F).
- the hot catalyst stripping zone 143 has a temperature between 593° and 760°C (1100° and 1400 ° F).
- the catalyst 142 in the hot stripping zone 143 is contacted at high temperature, discussed above, with a stripping gas, such as steam, flowing countercurrently to the direction of flow of the catalyst
- the stripping gas is introduced into the lower portion of the hot stripping zone 143 by one or more conduits 146 each attached to a stripping gas injection point 148.
- the catalyst residence time in the hot stripping zone 143 ranges from 2.5 to 7 minutes.
- the vapor residence time in the hot stripping zone 143 ranges from 0.5 to 30 seconds, and preferably 0.5 to 5 seconds.
- the hot stripping zone 143 removes coke, sulfur and hydrogen from the separated catalyst which has been combined with the regenerated catalyst.
- the sulfur is removed as hydrogen sulfide and mercaptans.
- the hydrogen is removed as molecular hydrogen, hydrocarbons, and hydrogen sulfide.
- the hot stripping zone 143 is maintained at desired conditions sufficient to reduce coke load to the regenerator by about 50% and strip away 70-80% of the hydrogen as molecular hydrogen, light hydrocarbons and other hydrogen-containing compounds.
- the hot stripping zone 1 4 3 is also preferably maintained at conditions sufficient to remove 45 to 55% of the sulfur as hydrogen sulfide and mercaptans, as well as a portion of nitrogen as ammonia and cyanides.
- the stripped hydrogen-, coke, sulfur- and nitrogen-containing compounds pass from the hot stripping vessel through a gaseous effluent conduit 150 as a stream 149.
- the hot stripping zone 143 may also be provided with trays (baffles) 144.
- the trays 144 may be disc- and doughnut-shaped and may be perforated or unperforated.
- the hot stripping vessel 140 is located directly underneath the regenerator vessel 180. In the embodiment shown in Fig. 2, the hot stripping vessel 140 is attached to the regenerator vessel 180. The atmosphere of vessel 140 is separated from that of vessel 180 by a hot stripping vessel top wall 141. Locating vessel 140 below the vessel 180 results in an economical long catalyst residence time hot stripper. It is cheaper to stack a long residence time hot stripper in this fashion than to build a separate vessel. It would also be more desirable to build a hot stripper under the regenerator than under the reactor vessel 1 02 for ease of catalyst circulation.
- the hot stripped catalyst passes from the hot stripping vessel 140 through an effluent conduit 152 and into a regenerator riser 160. Conduit 152 is attached to the hot stripping vessel 140 and riser 160 and provided with a slide valve 154.
- regenerator riser 160 In the regenerator riser 160, lift air from a conduit 166 and the hot stripped catalyst combine and pass upwardly as a dilute phase to the regenerator vessel 180. In the riser 160, combustible materials such as coke which adheres to the cooled catalyst are burned off the catalyst by contact with the air. The dilute phase passes upwardly through the riser 160, through a radial arm 184 attached to the riser 160, and then passes downwardly to a relatively dense bed of catalyst 182 located within the regenerator vessel 180.
- the major portion of catalyst passes downwardly through the radial arms 184, while the gases and remaining catalyst pass into the atmosphere of the regenerator vessel 180.
- the gases and remaining catalyst then pass through an inlet conduit 189 into the first regenerator cyclone 186.
- the first cyclone 186 separates a portion of catalyst and passes it through a first dipleg 190, while remaining catalyst and gases pass through an overhead conduit 188 into a second regenerator cyclone 192.
- the second cyclone 192 separates a portion of catalyst and passes the separated portion through a second dipleg 196, with the remaining gas and catalyst passing through a second overhead conduit 194 into a regenerator vessel plenum chamber 198.
- a flue gas stream 201 exits from the regenerator plenum chamber 198 through a regenerator flue gas conduit 200.
- the regenerated catalyst settles to form the bed 182, which is dense compared to the dilute catalyst passing through the riser 160.
- the regenerated catalyst bed 182 is at a substantially higher temperature than the stripped catalyst from the hot stripping zone 143, due to the coke burning which occurs in the riser 160 and regenerator 180.
- the catalyst in bed 182 is at least 56°C (100°F) hotter than the temperature of the catalyst 142 in the hot stripping zone 143, preferably at least 83°C (150°F) hotter than the temperature of the catalyst 142 in the hot stripping zone 143.
- the regenerator temperature is, at most, 87PC (1600°F) to prevent deactivating the catalyst.
- Air also passes through an air transfer line 170, to an air header 174 located in the regenerator 180. This provides for additional regeneration in the regenerator 180.
- the regenerated catalyst then passes from the relatively dense bed 182 through the conduit 206 to conduit 138 to combine with and heat the catalyst from the preliminary stripping zone 130.
- Fig. 3 shows a third embodiment of the present invention. This third embodiment is an optional modification of the second embodiment of Fig. 2.
- the hot stripped catalyst passes through the conduit 152 into a lift pot (preheat chamber) 155.
- a portion of hot regenerated catalyst passes through a conduit 156, provided with a control valve 158, into the lift pot 155.
- These catalyst streams form a catalyst bed 153.
- the air from a conduit 168 passes through a nozzle 162, fluidizes the catalyst in the bed 153, and subsequently transports the catalyst continuously as a dilute phase through the regenerator riser 160.
- Any conventional fluid catalytic cracking catalyst can be used in the present invention.
- Use of zeolite catalysts in an amorphous base is preferred.
- Many suitable catalysts are discussed in U. S. Patent No. 3,926,778 to Owen et al.
- the catalyst should not contain any agents designed to absorb or react with SO x in the fluid catalytic cracking regenerator.
- the countercurrent hot stripping zone 143 shown in Figs. 2 and 3 is replaced by a fluidized bed hot stripping zone 243 contained within a hot stripping vessel 240.
- the hot stripping vessel 240 contains a fluidized, dense phase catalyst bed 242.
- the spent catalyst 236 is fluidized and stripped by contact with stripping gas provided by a stripping gas conduit 246 through injection points 248.
- Hot regenerated catalyst passes from the regenerator vessel 180 through a catalyst conduit 306, provided with a slide valve 308, into the hot stripping vessel 240 to mix with the spent catalyst.
- hydrogen-, sulfur-, and nitrogen-containing compounds are separated from the spent catalyst 236 and are discharged from the hot stripping vessel 240 as a gaseous effluent stream 249 through a gaseous effluent conduit 250.
- the stripped catalyst is discharged from the stripping vessel 240 by passing into a catalyst effluent conduit 252 where it combines with lift air provided by a conduit 266 and passes upwardly in dilute phase through a regenerator riser 260.
- the dilute phase catalyst then discharges from the regenerator riser 260 through radial arms 184 and is regenerated in the regenerator vessel 180 as described above for the embodiments shown by Figs. 2 and 3.
- a regenerated catalyst stream 304 is discharged from the regenerator vessel 180 through the catalyst conduit 202 and passes to the riser conversion zone 104 (shown on Fig. 2).
- the fluidized hot stripping zone 243 operates under the same ranges of temperature and gas residence time as the countercurrent stripping zone 143 shown in Figs. 2 and 3.
- a fifth embodiment of the present invention employs the reactor vessel as shown by Figs. 2 and 3.
- catalyst passes from the preliminary stripping zone 130 through a preliminary stripper effluent conduit 310 into a hot stripping zone 317 comprising a hot stripping riser 316.
- riser 316 the preliminarily stripped catalyst from zone 130 combines with a regenerated catalyst stream 314 which passes through a conduit 312 from a fluid catalytic cracking regenerator (not shown) into the hot striping riser 316.
- the fluid catalytic cracking regenerator operates at the temperature conditions outlined for the fluid catalytic cracking regenerator 180 of Figs. 2 and 3.
- These temperature conditions include a fluid catalytic cracking temperature between 56°C (100°F) above the temperature of catalyst in the hot stripping riser 158° and 871 °C (316° and 1600°F), preferably a temperature between 83°C (150°F) above the temperature of catalyst in the hot stripping riser 158° and 871 °C (316° and 1600°F).
- the combined catalyst passes in dilute phase through the riser 316 for a gas residence time 0.5 to 30 seconds and preferably 0.5 to 5 seconds.
- the combined catalyst is hot stripped in the riser 316 and is discharged from the riser 316 into a gas disengaging vessel 320.
- the gas continues upwardly and exits through an overhead conduit 322 as an overhead stream 324 while the solids drop downwardly to form a relatively dense bed of catalyst 326 in a lower portion of the vessel 320.
- the catalyst from the dense bed 326 then exits from the vessel 320 as a hot stripped catalyst stream 328 which passes through conduit 330 to a fluid catalytic cracking regenerator (not shown).
- Figs. 6 and 7 disclose a sixth embodiment of the present invention in which preliminary stripping and catalyst separation occur in a reactor vessel 342.
- a hydrocarbon-catalyst mixture passes through a riser conversion zone 340, at suitable catalytic cracking temperature conditions as described for riser 10 4 discussed above.
- the mixture of catalyst and cracked hydrocarbons is deflected by a frusto conical deflector 390, as shown by Fig. 7, attached to a conical deflector 392 and thus deflected through a conduit 344 into a cyclone portion 345 of a short contact time stripper 347.
- the cyclone 345 is a centrifugal separator.
- the short contact time stripper 347 includes a preliminary stripping vessel 349 which defines a preliminary stripping zone located adjacent a barrel 346 of the cyclone separator 345. This construction is such that extensions of the exit barrel walls 346 make up the walls of the preliminary stripping vessel 349.
- the preliminary stripping vessel 349 operates at preliminary stripping conditions as discussed in regard to the previous embodiments.
- Fig. 7 illustrates the details of the short contact time stripper 347.
- the hydrocarbon catalyst mixture ascends vertically through the riser conversion zone 340, and enters the cyclone 345 located in the upper portion of the short contact time stripper 347 and descends towards a lower portion thereof.
- Baffles 402 and 404 serve to direct the descending separated catalyst particles toward perforated conical diffusers 332 and 334.
- Steam is provided by inlets 398 and 400 and travels through only a portion of the flowing separated catalyst particles. The portion referred to is that catalyst located between the steam injection point and the intake of the baffles 402 and 404 which are inverted funnels.
- the separated catalyst passes from the cyclone 345 to the baffle 404 through a conduit 394.
- the catalyst from the second conical diffuser 334 passes through a conduit 396 to a bed of catalyst 410 located therebelow.
- the catalyst in bed 4 10 is discharged from the short contact time stripping vessel 347 into an exit conduit 414 which is inserted into a seal pot 348.
- the catalyst exits the seal pot 348 by overflowing through an annulus between conduit 414 and the seal pot 348 as well as through drain holes 412 provided at the bottom of the seal pot 348.
- the drain holes 412 allow 10-90% of the catalyst to flow therethrough.
- the seal pot provides a catalyst seal as opposed to extending the conduit 414 into a catalyst bed 362, shown on Fig. 6, located therebelow or providing the conduit 414 with a trickle valve.
- the overhead from the short contact time stripper 347 passes through an overhead conduit 350 into a second cyclone 354 which separates a second portion of catalyst from the short contact time stripper overhead and passes the separated portion of catalyst through a dipleg 358 to catalyst bed 362 therebelow.
- the overhead conduit 350 may be provided with a connector 352 which may have an annulus as described above in relation to connector 24 of Figs. 2 and 3.
- Catalyst from the seal pot 348 passes to the catalyst bed 362 located in a hot stripping zone 363 defined by the lower portion 360 of the reactor vessel 342.
- the preliminarily stripped catalyst from the seal pot 348 combines with hot regenerated catalyst from conduit 382.
- the conduit 382 is provided with a slide valve 38 4 .
- the regenerated catalyst is provided by passing a regenerated catalyst air mixture upwardly through a riser 372 which discharges the regenerated catalyst air mixture into a disengaging vessel 374. Gasiformed material continues upwardly and exits vessel 374 through an overhead conduit 378 as an overhead stream 376. Solids separated from the regenerated catalyst air mixture drop through the vessel 374 to form a dense catalyst bed 380.
- the regenerated catalyst from bed 380 passes through the conduit 382 into the reactor vessel 342, at the temperature conditions outlined for regenerated catalyst in the previous embodiments.
- the regenerated catalyst from the conduit 382 provides heat to the hot stripping zone 363.
- the combined catalyst within the lower portion 360 of the reactor vessel 342 passes countercurrentty to stripping gas provided by a stripping gas conduit 366 which feeds a stripping gas header 368.
- the hot stripping zone 363 may be provided with baffles (trays) 364 which are disc- and doughnut-shaped and may be perforated or unperforated.
- the hot stripped catalyst is discharged from the hot stripping zone 363 through a conduit 370 and passes to a fluid catalytic cracking regenerator (not shown).
- Hot stripper As a high temperature (hot) stripper has the advantage that it separates hydrogen, as molecular hydrogen as well as hydrocarbons, from catalyst. Hydrogen removal eliminates hydrothermal degradation, which typically occurs when hydrogen reacts with oxygen in a fluid catalytic cracking regenerator to form water.
- the hot stripper also removes sulfur from coked catalyst as hydrogen sulfide and mercaptans, which are easy to scrub. By removing sulfur from coked catalyst in the hot stripper, the hot stripper prevents formation of SO X in the regenerator. It is more difficult to remove SO X from regenerator flue gas than to remove hydrogen sulfide and mercaptans from a hot stripper effluent.
- the hot stripper enhances removal of hydrocarbons from spent catalyst, and thus prevents bum- ing of valuable hydrocarbons in the regenerator. Furthermore, the hot stripper quickly separates hydrocarbons from catalyst to avoid overcracking.
- the hot stripper is maintained at desired conditions sufficient to reduce coke load to the regenerator by about 50% and strip away 70-80% of the hydrogen as molecular hydrogen, light hydrocarbons and other hydrogen-containing compounds.
- the hot stripper is also maintained at conditions sufficient to remove 45 to 55% of the sulfur as hydrogen sulfide and mercaptans, as well as a portion of nitrogen as ammonia and cyanides.
- the hot stripper controls the amounts of carbon removed from the catalyst in the stripper. Accordingly, the hot stripper controls the amount of carbon (and hydrogen, sulfur) remaining on the catalyst to the regenerator. This residual carbon level controls the temperature rise between the reactor stripper and the regenerator. The hot stripper also controls the hydrogen content of the spent catalyst sent to the regenerator as a function of residual carbon. Thus, the hot stripper controls the temperature and amount of hydrothermal deactivation of catalyst in the regenerator. This concept may be practiced in a multistage, multi- temperature stripper or a single stage stripper.
- the degree of regeneration desired is set by the CO/CO, ratio desired, the amount of carbon bum-off desired, the catalyst recirculation rate from the regenerator to the hot stripper, and the degree of desulfurizationldenitrificationldecarbonization desired in the hot stripper.
Abstract
Description
- This invention relates to methods and apparatus for fluid catalytic cracking, FCC, of hydrocarbons with subsequent regeneration of catalyst particles.
- Hot catalyst contacts oil in a riser reactor. The oil is catalytically cracked, thereby deactivating the catalyst with coke. Deactivated catalyst is stripped, and then regenerated by burning coke from catalyst with air.
- Large amounts of catalyst are suspended in gas materials in the riser. It is necessary to separate rapidly the suspension into a spent catalyst phase and a gas phase after catalytic cracking in the riser.
- Various attempts have been made to improve suspension separation techniques to decrease losses in the catalyst phase or the gas phase resulting from overcracking. Multistage stripping is disclosed in U. S. Patent No. 4,043,899 to Anderson et al. A catalyst riser terminating in a cylindrical vessel and a riser comprising baffles is disclosed by U.S. Patent No. 4,206,174 to Heffley et at and risers attached to conduits are disclosed by U. S. Patent No. 4,219,407 to Haddad et al.
- Along with the development of process modifications and catalysts, which could accommodate heavier, dirtier feeds, there has been a growing concern about the amount of sulfur contained in the feed that ended up as SOx in the regenerator flue gas. Higher sulfur levels in the feed, com- bined with a more complete regeneration of the catalyst in the fluid catalytic cracking regenerator, tended to increase the amount of SOx contained in the regenerator flue gas. Some attempts have been made to minimize the amount of SOx discharged to the atmosphere through the flue gas by providing agents to react with the SOxin the flue gas. These agents pass along with the regenerated catalyst back to the fluid catalytic cracking reactor, where the reducing atmosphere releases the sulfur compounds as H,S. Suitable agents for this purpose have been described in U. S. Patent Nos. 4,071,436 and 3,834,031. Use of a cerium oxide agent is shown in U. S. Patent No. 4,001,375.
- Unfortunately, the conditions in most fluid catalytic cracking regenerators are not the best for SOx adsorption. The high temperatures encountered in modem fluid catalytic cracking regenerators (up to 871 °C [1600°F]) tend to discourage SOxadsorption. One approach to overcome the problem of SOx in flue gas is to pass catalyst from a fluid catalytic cracking reactor to a long residence time steam stripper. After the long residence time steam stripping, the catalyst passes to the regenerator, as disclosed by U. S. Patent No. 4,481,103 to Krambeck et sl. However, it preferably steam strips spent catalyst at 500° to 550°C (932° to 1022°F), which is not sufficient to remove some undesirable sulfur- or hydrogen- containing components. Furthermore, catalyst passing from a fluid catalytic cracking stripper to a fluid catalytic cracking regenerator contains hydrogen-containing components, such as coke, adhering thereto. This causes hydrothermal degradation when the hydrogen reacts with oxygen in the regenerator to form water.
- U. S. Patent No. 4,336,160 to Dean et at attempts to reduce hydrothermal degradation by staged regeneration. However, this process has the disadvantage that the flue gas from both stages of regeneration contains SOx, which is difficult to clean.
- It would be desirable to separate hydrogen from catalyst to eliminate hydrothermal degradation. It would be further advantageous to remove sulfur-containing compounds prior to regeneration to prevent SOx from passing into the regenerator flue gas.
- Accordingly, the present invention provides a process for fluid catalytic cracking (FCC) of a hydrocarbon feed, by passing a mixture of catalyst and feed up through a conventional FCC riser and discharging from the riser a mixture of coked catalyst and cracked product, separating coked catalyst from cracked product, stripping coked catalyst to remove strippable hydrocarbons and regenerating the stripped catalyst by burning coke from catalyst, characterized by heating the coked catalyst by combining with a hot regenerated catalyst from the FCC regenerator and stripping the heated coked catalyst by contact with a stripping gas before regeneration of the hot stripped catalyst in the FCC regenerator.
- In another embodiment, the present invention provides an apparatus for fluid catalytic cracking of oil by adding oil and catalyst to an upstream end of a riser reactor, and discharging spent catalyst and cracked product at a downstream end, separating catalyst from product, and the spent catalyst is stripped and then regenerated, characterized by a two stage regenerator including a verticai, dilute phase first stage regenerator, receiving stripped catalyst and discharging partially regenerated catalyst into a second stage dense bed regenerator.
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- Fig. 1 illustrates a fluid catalytic cracking reactor- regenerator system according to the present invention;
- Fig. 2 illustrates a hot stripping vessel below the regenerator of the present invention;
- Fig. 3 illustrates the system of Fig. 2 further, including a means for mixing hot stripped catalyst and regenerated catalyst
- Fig. 4 illustrates a fluidized hot stripping vessel of the present invention;
- Fig. 5 illustrates a riser hot stripper of the present invention;
- Fig. 6 ittustrates a stripping vessel, seal pot and hot stripper located in a reactor vessel of the present invention; and
- Fig. 7 illustrates details of the stripping vessel and seal pot of Fig. 6.
- Fig. 1 shows a riser reactor of a vertical elongated tube 1 having an upstream end 3 wherein hydrocarbon feed from line 7 and hot regenerated catalyst from
line 37 are introduced and adownstream end 5 where a mixture of spent catalyst and cracked hydrocarbons exit. The riser is preferably a short contact time riser reactor 0.1 to 10 seconds, preferably 0.2 to 5 seconds gas residence time, having a multiple point feed injection nozzle and an acceleration zone. Atdownstream end 5 the gas catalyst mixture exiting conduit 1 is deflected downwardly by, e.g.,deflector 51, to separate a major portion of the catalyst from the cracked hydrocarbons. Although adeflector 51 is shown, a cyclone may also be used. The riser reactor terminates within elongated enclosed vessel 11, which has a substan- tallycontinuous sidewall 13 attached tobottom member 15 andtop member 9 which can function withdeflector 51 to deflect catalyst in the gas catalyst mixture exiting riser conduit 1 to separate a portion of the catalyst from the cracked hydrocarbons. One or moreperpendicular conduits 19 provide an exit from vessel 11 for the mixture of hydrocarbon product and entrained catalyst Stripping medium from the stripping regions 17 and 23 also exits vessel 11 viaconduits 19. Deflection can also be accomplished by means of an inertial separator or other equivalent means. - Vessel 11 includes a stripping zone with a primary stripping region 17 and a secondary stripping region 23. Primary stripping region 17 is formed in an upper portion of vessel 11 and receives the downwardly deflected catalyst. A stripping medium is introduced into primary stripper 17 via
line 53 to contact the downwardly deflected catalyst to separate entrained hydrocarbons from the catalyst - The stripped hydrocarbon ascends with the stripping medium to exit vessel 11 through
conduits 19 to external closedcyclone system 21 and then vialine 61 to conventional product recovery and fractionators (not shown). - Secondary stripping region 23 is formed in a lower portion of vessel 11 and receives stripped catalyst from primary stripper 17, stripped catalyst from one or more diplegs 25 associated with
cyclone system 21 and hot regenerated catalyst alongconduit 27 which is connected to a bottom portion ofsecond stage regenerator 29. - The secondary region 23 is a hot stripping zone because the recycle of hot regenerated catalyst directly to the region 23 allows the catalyst within region 23 to be at a temperature greater than that at which it is discharged from the riser 1. Preferably the catalyst in region 23 is at a temperature between 56°C (100°F) above that at which it exits the riser 1 and 871 °C (1600°F). Most preferably the catalyst in the region 23 is at a temperature between 83°C (150°F) above that at which it exits the riser 1 and 871 °C (1600°F).
- Mixing means, in a form of mixing tray 31, is disposed between primary stripper 17 and secondary stripper 23 for mixing stripped catalyst from stripper 17, cyclone diplegs 25 and hot regenerated catalyst from
second stage regenerator 29, prior to passage of this mixed catalyst into secondary stripper 23. A stripping medium is introduced into secondary stripper 23 vialine 55 to separate additional entrained hydrocarbon from the catalyst This latter stripping medium can be light hydrocarbon gas, inert gas or steam. Hot regenerated catalyst fromsecond stage regenerator 29 is recycled to mixing tray 31 and then into secondary stripping region 23, to provide more complete removal of hydrocarbons from the spent catalyst. -
First stage regenerator 33, which is preferably a fast fluidized bed regenerator, receives stripped catalyst leaving secondary stripper 23 to bum off additionally entrained coke deposits by contact with a rapidly ascending stream of air at, e.g., 4 to 20 ft/sec, which is provided viaair inlet 35.First stage regenerator 33 passes regenerated catalyst output intosecond stage regenerator 29 viaconduit 57.Second stage regenerator 29 includes afirst conduit 27 for recycling hot regenerated catalyst onto mixing tray 31, and then to secondary stripper 23, and asecond conduit 37 for recirculating hot regenerated catalyst into upstream end 3 of riser conversion zone conduit 1 where it is mixed with hydrocarbon feed from feed source 7. Air distributor header 49 distributes air fromconduit 59 to a bottom region ofcatalyst bed 45 insecond stage regenerator 29. -
Second stage regenerator 29 can include a cyclone system having aprimary cyclone 39 and asecondary cyclone 41. The secondary cyclone includesdipleg 43 for fines removal fromcatalyst bed 45 ofsecond stage regenerator 29. - The apparatus and process of the first embodiment of the present invention are particularly adapted for conversion of a thermofor catalytic cracking (TCC) system to fluid catalytic cracking operation. This is beneficial in that numerous thermofor catalytic cracking units are presently idle, with restarting in a thermofor catalytic cracking mode of operation being uneconomical. However, in many instances, conversion to fluid catalytic cracking operation by the method and apparatus of the present invention would be very economical.
- Fig. 2 illustrates a second embodiment of a fluid catalytic cracking system of the present invention. In Fig. 2, a hydrocarbon feed passes from a hydrocarbon feed source (feeder) 7 to the lower end of a
riser conversion zone 104 which is a vertically elongate tubular conduit. Regenerated catalyst from astandpipe 202, having a control valve 204, is combined with the hydrocarbon feed in theriser 104, such that a hydrocarbon-catalyst mixture rises in an ascending dispersed stream until it is discharged at a riser discharge temperature into areactor vessel 102, and passes through ariser effluent conduit 106 into afirst reactor cyclone 108. The riser discharge temperature, defined as the temperature at which the mixture is discharged from theriser 104 toconduit 106, may be any suitable temperature but preferably ranges from 4820 to 593°C (9000 to 1100°F), and most preferably 538° to 566°C (1000° to 1050°F).Riser effluent conduit 106 is attached at one end to theriser 104 and at its other end to thecyclone 108. - The
first reactor cyclone 108 separates a portion of catalyst from the catalyst-hydrocarbon mixture and passes this catalyst down a first reactor cyclone dipleg 112 to a preliminary strippingzone 130 located therebelow. The remaining gas and catalyst pass from thefirst reactor cyclone 108 through agas effluent conduit 110. Theconduit 110 is provided with a connector 111 to allow for thermal expansion. The catalyst passes through theconduit 110, into asecond reactor cyclone 114 as part of a closed cyclone system. Thesecond cyclone 114 separates the stream to form a catalyst stream, which passes through a second reactor cyclone dipleg 118 to the preliminary strippingzone 130 located therebelow. - A second cyclone overhead stream, which contains the remaining gas and catalyst, passes through a second cyclone
gaseous effluent conduit 116 to areactor overhead port 120. Gases from the atmosphere of thereactor vessel 102 may pass through areactor overhead conduit 122 into thereactor overhead port 120. The gases which exit the reactor 102 through the second cyclonegaseous effluent conduit 116 and thereactor overhead conduit 122 are combined and exit through thereactor overhead port 120 asreactor overhead stream 124. It will be apparent to those skilled in the art that although only one series connection ofcyclones 108, 114 is shown in the embodiment, more than one series connection and/or more or less than two consecutive cyclones in series connection could be employed. - The mixture of catalyst and hydrocarbons passes through the first reactor
cyclone oerhead conduit 110 to thesecond reactor cyclone 114 as part of a closed cyclone system without entering thereactor vessel 102 atmosphere. However, the connector 111 may provide an annular port to admit stripping gas from thereactor vessel 102 into theconduit 110 to aid in separating catalyst from hydrocarbons adhering thereto. The closed cyclone system and annular port is described more fully in U. S. Patent No. 4,502,947 to Haddad et al. - The separated catalyst from
cyclones respective diplegs catalyst 131 located in the strippingzone 130. Thefirst dipleg 112 andsecond dipleg 118 are sealed by being extended into the catalyst bed 131. However, diplegs 112, 118 could instead be sealed by trickle valves (not shown). - The separated catalyst is passed to a preliminary stripping
zone 130 where it is contacted with stripping gas. The stripping gas is introduced into the lower portion of the strippingzone 130 by one ormore conduits 134 attached to a strippinggas header 136. The preliminary strippingzone 130 strips portions of coke, sulfur and hydrogen from the separated catalyst at conventional stripping conditions, such as temperature, pressure, gas residence time and solids residence time as known in the art. - The stripping
zone 130 may also be provided with trays (baffles) 132. The trays 132 may be disc- and doughnut-shaped and may be perforated or unperforated. - The preliminary stripped catalyst passed from the
zone 130 through areactor effluent conduit 138 and combines with hot regenerated catalyst Theconduit 138 is provided with avalve 139. The regenerated catalyst has a temperature between 56°C (100°F) above that ofcatalyst 142 in a hot strippingzone 143 and 871 °C (1600°F) to heat the preliminarily stripped catalyst. The regenerated catalyst passes from theregenerator 180 to thereactor effluent conduit 138 through atransfer line 206 attached at one end to the regenerator vessel 80 and at another end to thereactor effluent conduit 138. Thetransfer line 206 is provided with aslide valve 208. - Combining the separated catalyst with the regenerated catalyst heats the separated catalyst to promote subsequent hot stripping in the hot stripping
zone 143 defined by a hot strippingvessel 140. The hot stripping occurs at a temperature between 56°C (100°F) above the riser exit temperature and 816°C (1500°F). Preferably, the catalyst in the hot strippingzone 143 has a temperature from 83°C (150°F) above the riser exit temperature to 760°C (1400°F). Most preferably, the hotcatalyst stripping zone 143 has a temperature between 593° and 760°C (1100° and 1400 ° F). - The
catalyst 142 in the hot strippingzone 143 is contacted at high temperature, discussed above, with a stripping gas, such as steam, flowing countercurrently to the direction of flow of the catalyst The stripping gas is introduced into the lower portion of the hot strippingzone 143 by one ormore conduits 146 each attached to a strippinggas injection point 148. The catalyst residence time in the hot strippingzone 143 ranges from 2.5 to 7 minutes. The vapor residence time in the hot strippingzone 143 ranges from 0.5 to 30 seconds, and preferably 0.5 to 5 seconds. The hot strippingzone 143 removes coke, sulfur and hydrogen from the separated catalyst which has been combined with the regenerated catalyst. The sulfur is removed as hydrogen sulfide and mercaptans. The hydrogen is removed as molecular hydrogen, hydrocarbons, and hydrogen sulfide. Preferably, the hot strippingzone 143 is maintained at desired conditions sufficient to reduce coke load to the regenerator by about 50% and strip away 70-80% of the hydrogen as molecular hydrogen, light hydrocarbons and other hydrogen-containing compounds. The hot stripping zone 143 is also preferably maintained at conditions sufficient to remove 45 to 55% of the sulfur as hydrogen sulfide and mercaptans, as well as a portion of nitrogen as ammonia and cyanides. The stripped hydrogen-, coke, sulfur- and nitrogen-containing compounds pass from the hot stripping vessel through agaseous effluent conduit 150 as a stream 149. - The hot stripping
zone 143 may also be provided with trays (baffles) 144. Thetrays 144 may be disc- and doughnut-shaped and may be perforated or unperforated. - The hot stripping
vessel 140 is located directly underneath theregenerator vessel 180. In the embodiment shown in Fig. 2, the hot strippingvessel 140 is attached to theregenerator vessel 180. The atmosphere ofvessel 140 is separated from that ofvessel 180 by a hot stripping vesseltop wall 141. Locatingvessel 140 below thevessel 180 results in an economical long catalyst residence time hot stripper. It is cheaper to stack a long residence time hot stripper in this fashion than to build a separate vessel. It would also be more desirable to build a hot stripper under the regenerator than under the reactor vessel 102 for ease of catalyst circulation. The hot stripped catalyst passes from the hot strippingvessel 140 through aneffluent conduit 152 and into aregenerator riser 160.Conduit 152 is attached to the hot strippingvessel 140 andriser 160 and provided with aslide valve 154. - In the
regenerator riser 160, lift air from aconduit 166 and the hot stripped catalyst combine and pass upwardly as a dilute phase to theregenerator vessel 180. In theriser 160, combustible materials such as coke which adheres to the cooled catalyst are burned off the catalyst by contact with the air. The dilute phase passes upwardly through theriser 160, through aradial arm 184 attached to theriser 160, and then passes downwardly to a relatively dense bed ofcatalyst 182 located within theregenerator vessel 180. - The major portion of catalyst passes downwardly through the
radial arms 184, while the gases and remaining catalyst pass into the atmosphere of theregenerator vessel 180. The gases and remaining catalyst then pass through aninlet conduit 189 into thefirst regenerator cyclone 186. Thefirst cyclone 186 separates a portion of catalyst and passes it through afirst dipleg 190, while remaining catalyst and gases pass through anoverhead conduit 188 into asecond regenerator cyclone 192. Thesecond cyclone 192 separates a portion of catalyst and passes the separated portion through asecond dipleg 196, with the remaining gas and catalyst passing through a secondoverhead conduit 194 into a regeneratorvessel plenum chamber 198. Aflue gas stream 201 exits from theregenerator plenum chamber 198 through a regeneratorflue gas conduit 200. - The regenerated catalyst settles to form the
bed 182, which is dense compared to the dilute catalyst passing through theriser 160. The regeneratedcatalyst bed 182 is at a substantially higher temperature than the stripped catalyst from the hot strippingzone 143, due to the coke burning which occurs in theriser 160 andregenerator 180. The catalyst inbed 182 is at least 56°C (100°F) hotter than the temperature of thecatalyst 142 in the hot strippingzone 143, preferably at least 83°C (150°F) hotter than the temperature of thecatalyst 142 in the hot strippingzone 143. The regenerator temperature is, at most, 87PC (1600°F) to prevent deactivating the catalyst. - Air also passes through an
air transfer line 170, to anair header 174 located in theregenerator 180. This provides for additional regeneration in theregenerator 180. The regenerated catalyst then passes from the relativelydense bed 182 through theconduit 206 toconduit 138 to combine with and heat the catalyst from the preliminary strippingzone 130. - Fig. 3 shows a third embodiment of the present invention. This third embodiment is an optional modification of the second embodiment of Fig. 2. In the embodiment shown on Fig. 3, if the temperature of the hot stripped catalyst from the conduit 152 is less than 593°C (1100°F), the hot stripped catalyst passes through the
conduit 152 into a lift pot (preheat chamber) 155. A portion of hot regenerated catalyst passes through aconduit 156, provided with acontrol valve 158, into thelift pot 155. These catalyst streams form acatalyst bed 153. The air from a conduit 168 passes through anozzle 162, fluidizes the catalyst in thebed 153, and subsequently transports the catalyst continuously as a dilute phase through theregenerator riser 160. - Any conventional fluid catalytic cracking catalyst can be used in the present invention. Use of zeolite catalysts in an amorphous base is preferred. Many suitable catalysts are discussed in U. S. Patent No. 3,926,778 to Owen et al. The catalyst should not contain any agents designed to absorb or react with SOx in the fluid catalytic cracking regenerator.
- In the fourth embodiment of the present invention, shown by Fig. 4, the countercurrent hot stripping
zone 143, shown in Figs. 2 and 3, is replaced by a fluidized bed hot strippingzone 243 contained within a hot strippingvessel 240. The hot strippingvessel 240 contains a fluidized, densephase catalyst bed 242. A stream of spentcatalyst 236 containing catalyst from the preliminary strippingzone 130 of Fig. 2 or separated catalyst taken directly from a fluid catalytic cracking reactor vessel without preliminary stripping, passes through a hotstripper inlet conduit 238 into the hot strippingvessel 240. The spentcatalyst 236 is fluidized and stripped by contact with stripping gas provided by a stripping gas conduit 246 through injection points 248. Hot regenerated catalyst passes from theregenerator vessel 180 through acatalyst conduit 306, provided with a slide valve 308, into the hot strippingvessel 240 to mix with the spent catalyst. - In the hot stripping
vessel 240 hydrogen-, sulfur-, and nitrogen-containing compounds are separated from the spentcatalyst 236 and are discharged from the hot strippingvessel 240 as agaseous effluent stream 249 through agaseous effluent conduit 250. The stripped catalyst is discharged from the strippingvessel 240 by passing into acatalyst effluent conduit 252 where it combines with lift air provided by aconduit 266 and passes upwardly in dilute phase through aregenerator riser 260. The dilute phase catalyst then discharges from theregenerator riser 260 throughradial arms 184 and is regenerated in theregenerator vessel 180 as described above for the embodiments shown by Figs. 2 and 3. A regeneratedcatalyst stream 304 is discharged from theregenerator vessel 180 through thecatalyst conduit 202 and passes to the riser conversion zone 104 (shown on Fig. 2). - The fluidized hot stripping
zone 243 operates under the same ranges of temperature and gas residence time as thecountercurrent stripping zone 143 shown in Figs. 2 and 3. - A fifth embodiment of the present invention, as shown by Fig. 5, employs the reactor vessel as shown by Figs. 2 and 3. However catalyst passes from the preliminary stripping
zone 130 through a preliminarystripper effluent conduit 310 into a hot strippingzone 317 comprising a hot strippingriser 316. Inriser 316 the preliminarily stripped catalyst fromzone 130 combines with a regeneratedcatalyst stream 314 which passes through aconduit 312 from a fluid catalytic cracking regenerator (not shown) into thehot striping riser 316. The fluid catalytic cracking regenerator operates at the temperature conditions outlined for the fluid catalytic crackingregenerator 180 of Figs. 2 and 3. These temperature conditions include a fluid catalytic cracking temperature between 56°C (100°F) above the temperature of catalyst in the hot strippingriser 158° and 871 °C (316° and 1600°F), preferably a temperature between 83°C (150°F) above the temperature of catalyst in the hot strippingriser 158° and 871 °C (316° and 1600°F). - The combined catalyst passes in dilute phase through the
riser 316 for a gas residence time 0.5 to 30 seconds and preferably 0.5 to 5 seconds. The combined catalyst is hot stripped in theriser 316 and is discharged from theriser 316 into agas disengaging vessel 320. Invessel 320 the gas continues upwardly and exits through anoverhead conduit 322 as anoverhead stream 324 while the solids drop downwardly to form a relatively dense bed ofcatalyst 326 in a lower portion of thevessel 320. The catalyst from thedense bed 326 then exits from thevessel 320 as a hot strippedcatalyst stream 328 which passes throughconduit 330 to a fluid catalytic cracking regenerator (not shown). - Figs. 6 and 7 disclose a sixth embodiment of the present invention in which preliminary stripping and catalyst separation occur in a
reactor vessel 342. In this embodiment, a hydrocarbon-catalyst mixture passes through ariser conversion zone 340, at suitable catalytic cracking temperature conditions as described for riser 104 discussed above. The mixture of catalyst and cracked hydrocarbons is deflected by a frusto conical deflector 390, as shown by Fig. 7, attached to aconical deflector 392 and thus deflected through aconduit 344 into acyclone portion 345 of a shortcontact time stripper 347. Thecyclone 345 is a centrifugal separator. The shortcontact time stripper 347 includes a preliminary strippingvessel 349 which defines a preliminary stripping zone located adjacent abarrel 346 of thecyclone separator 345. This construction is such that extensions of theexit barrel walls 346 make up the walls of the preliminary strippingvessel 349. The preliminary strippingvessel 349 operates at preliminary stripping conditions as discussed in regard to the previous embodiments. - Fig. 7 illustrates the details of the short
contact time stripper 347. The hydrocarbon catalyst mixture ascends vertically through theriser conversion zone 340, and enters thecyclone 345 located in the upper portion of the shortcontact time stripper 347 and descends towards a lower portion thereof.Baffles conical diffusers inlets baffles vessel 347. - The separated catalyst passes from the
cyclone 345 to thebaffle 404 through aconduit 394. The catalyst from the secondconical diffuser 334 passes through aconduit 396 to a bed ofcatalyst 410 located therebelow. The catalyst in bed 410 is discharged from the short contacttime stripping vessel 347 into anexit conduit 414 which is inserted into aseal pot 348. The catalyst exits theseal pot 348 by overflowing through an annulus betweenconduit 414 and theseal pot 348 as well as throughdrain holes 412 provided at the bottom of theseal pot 348. The drain holes 412 allow 10-90% of the catalyst to flow therethrough. The seal pot provides a catalyst seal as opposed to extending theconduit 414 into acatalyst bed 362, shown on Fig. 6, located therebelow or providing theconduit 414 with a trickle valve. - As further seen on Fig. 6, the overhead from the short
contact time stripper 347 passes through anoverhead conduit 350 into asecond cyclone 354 which separates a second portion of catalyst from the short contact time stripper overhead and passes the separated portion of catalyst through adipleg 358 tocatalyst bed 362 therebelow. Theoverhead conduit 350 may be provided with aconnector 352 which may have an annulus as described above in relation to connector 24 of Figs. 2 and 3. - Catalyst from the
seal pot 348 passes to thecatalyst bed 362 located in a hot strippingzone 363 defined by thelower portion 360 of thereactor vessel 342. - In the hot stripping
zone 363 the preliminarily stripped catalyst from theseal pot 348 combines with hot regenerated catalyst fromconduit 382. Theconduit 382 is provided with a slide valve 384. The regenerated catalyst is provided by passing a regenerated catalyst air mixture upwardly through ariser 372 which discharges the regenerated catalyst air mixture into a disengagingvessel 374. Gasiformed material continues upwardly and exitsvessel 374 through anoverhead conduit 378 as anoverhead stream 376. Solids separated from the regenerated catalyst air mixture drop through thevessel 374 to form adense catalyst bed 380. The regenerated catalyst frombed 380 passes through theconduit 382 into thereactor vessel 342, at the temperature conditions outlined for regenerated catalyst in the previous embodiments. The regenerated catalyst in the previous embodiments. The regenerated catalyst from theconduit 382 provides heat to the hot strippingzone 363. - The combined catalyst within the
lower portion 360 of thereactor vessel 342 passes countercurrentty to stripping gas provided by a strippinggas conduit 366 which feeds a strippinggas header 368. The hot strippingzone 363 may be provided with baffles (trays) 364 which are disc- and doughnut-shaped and may be perforated or unperforated. The hot stripped catalyst is discharged from the hot strippingzone 363 through aconduit 370 and passes to a fluid catalytic cracking regenerator (not shown). - Operating the stripping zone as a high temperature (hot) stripper has the advantage that it separates hydrogen, as molecular hydrogen as well as hydrocarbons, from catalyst. Hydrogen removal eliminates hydrothermal degradation, which typically occurs when hydrogen reacts with oxygen in a fluid catalytic cracking regenerator to form water. The hot stripper also removes sulfur from coked catalyst as hydrogen sulfide and mercaptans, which are easy to scrub. By removing sulfur from coked catalyst in the hot stripper, the hot stripper prevents formation of SOX in the regenerator. It is more difficult to remove SOX from regenerator flue gas than to remove hydrogen sulfide and mercaptans from a hot stripper effluent. The hot stripper enhances removal of hydrocarbons from spent catalyst, and thus prevents bum- ing of valuable hydrocarbons in the regenerator. Furthermore, the hot stripper quickly separates hydrocarbons from catalyst to avoid overcracking.
- Preferably the hot stripper is maintained at desired conditions sufficient to reduce coke load to the regenerator by about 50% and strip away 70-80% of the hydrogen as molecular hydrogen, light hydrocarbons and other hydrogen-containing compounds. The hot stripper is also maintained at conditions sufficient to remove 45 to 55% of the sulfur as hydrogen sulfide and mercaptans, as well as a portion of nitrogen as ammonia and cyanides.
- The hot stripper controls the amounts of carbon removed from the catalyst in the stripper. Accordingly, the hot stripper controls the amount of carbon (and hydrogen, sulfur) remaining on the catalyst to the regenerator. This residual carbon level controls the temperature rise between the reactor stripper and the regenerator. The hot stripper also controls the hydrogen content of the spent catalyst sent to the regenerator as a function of residual carbon. Thus, the hot stripper controls the temperature and amount of hydrothermal deactivation of catalyst in the regenerator. This concept may be practiced in a multistage, multi- temperature stripper or a single stage stripper.
- The degree of regeneration desired is set by the CO/CO, ratio desired, the amount of carbon bum-off desired, the catalyst recirculation rate from the regenerator to the hot stripper, and the degree of desulfurizationldenitrificationldecarbonization desired in the hot stripper.
- Employing a hot stripper, to remove carbon on the catalyst, rather than a regeneration stage reduces air pollution, and allows all of the carbon made in the reaction to be burned to CO,, if desired. In contrast, the process of U. S. Patent No. 4,336,160 to Dean et at (also known as the TOTAL process) employs two flue gas streams, and only one of these flue gas streams is combustible to CO,.
Claims (15)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US68680084A | 1984-12-27 | 1984-12-27 | |
US686800 | 1984-12-27 |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0187032A1 true EP0187032A1 (en) | 1986-07-09 |
Family
ID=24757820
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP85309354A Withdrawn EP0187032A1 (en) | 1984-12-27 | 1985-12-20 | Improved fluid catalytic cracking process and apparatus |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0187032A1 (en) |
JP (1) | JPS61157580A (en) |
AU (1) | AU5115885A (en) |
CA (1) | CA1261774A (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0275158A2 (en) * | 1987-01-15 | 1988-07-20 | Mobil Oil Corporation | Short contact time fluid catalytic cracking process and apparatus |
US4988430A (en) * | 1989-12-27 | 1991-01-29 | Uop | Supplying FCC lift gas directly from product vapors |
EP0456924A1 (en) * | 1986-05-29 | 1991-11-21 | Uop | Side-to-side FCC stripping apparatus with baffle-skirts having stripping gas injection ports |
EP0702077A3 (en) * | 1994-09-13 | 1996-03-27 | Bar Co Processes Joint Venture | |
US7276210B2 (en) | 2003-08-20 | 2007-10-02 | Petroleo Brasileiro S.A. -Petrobras | Stripping apparatus and process |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2610638B1 (en) * | 1987-02-11 | 1990-04-13 | Total France | IMPROVEMENTS TO METHODS AND DEVICES FOR CATALYTIC CRACKING OF HYDROCARBON FEEDSTOCKS |
US7622625B2 (en) * | 2004-11-01 | 2009-11-24 | Uop Llc | Purge gas streams to stagnant zones within oxygenate-to-olefin reactor |
Citations (7)
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US2526881A (en) * | 1948-05-17 | 1950-10-24 | Shell Dev | Catalytic conversion of hydrocarbons to produce alkyl naphthalenes |
US2944963A (en) * | 1958-03-03 | 1960-07-12 | Shell Oil Co | Conversion of heavy oils to gasoline using the fluidized catalyst technique |
US3008896A (en) * | 1959-09-21 | 1961-11-14 | Phillips Petroleum Co | Catalytic cracking of residual oils |
US3821103A (en) * | 1973-05-30 | 1974-06-28 | Mobil Oil Corp | Conversion of sulfur contaminated hydrocarbons |
US4419221A (en) * | 1981-10-27 | 1983-12-06 | Texaco Inc. | Cracking with short contact time and high temperatures |
US4424116A (en) * | 1982-03-25 | 1984-01-03 | Ashland Oil, Inc. | Converting and stripping heavy hydrocarbons in two stages of riser conversion with regenerated catalyst |
US4435281A (en) * | 1980-09-15 | 1984-03-06 | Standard Oil Company (Indiana) | Catalytic cracking with reduced emission of noxious gas |
-
1985
- 1985-12-12 AU AU51158/85A patent/AU5115885A/en not_active Abandoned
- 1985-12-18 CA CA000498002A patent/CA1261774A/en not_active Expired
- 1985-12-20 EP EP85309354A patent/EP0187032A1/en not_active Withdrawn
- 1985-12-21 JP JP28912185A patent/JPS61157580A/en active Pending
Patent Citations (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2526881A (en) * | 1948-05-17 | 1950-10-24 | Shell Dev | Catalytic conversion of hydrocarbons to produce alkyl naphthalenes |
US2944963A (en) * | 1958-03-03 | 1960-07-12 | Shell Oil Co | Conversion of heavy oils to gasoline using the fluidized catalyst technique |
US3008896A (en) * | 1959-09-21 | 1961-11-14 | Phillips Petroleum Co | Catalytic cracking of residual oils |
US3821103A (en) * | 1973-05-30 | 1974-06-28 | Mobil Oil Corp | Conversion of sulfur contaminated hydrocarbons |
US4435281A (en) * | 1980-09-15 | 1984-03-06 | Standard Oil Company (Indiana) | Catalytic cracking with reduced emission of noxious gas |
US4419221A (en) * | 1981-10-27 | 1983-12-06 | Texaco Inc. | Cracking with short contact time and high temperatures |
US4424116A (en) * | 1982-03-25 | 1984-01-03 | Ashland Oil, Inc. | Converting and stripping heavy hydrocarbons in two stages of riser conversion with regenerated catalyst |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0456924A1 (en) * | 1986-05-29 | 1991-11-21 | Uop | Side-to-side FCC stripping apparatus with baffle-skirts having stripping gas injection ports |
EP0275158A2 (en) * | 1987-01-15 | 1988-07-20 | Mobil Oil Corporation | Short contact time fluid catalytic cracking process and apparatus |
EP0275158A3 (en) * | 1987-01-15 | 1988-10-05 | Mobil Oil Corporation | Short contact time fluid catalytic cracking process and apparatus |
US4988430A (en) * | 1989-12-27 | 1991-01-29 | Uop | Supplying FCC lift gas directly from product vapors |
US5584986A (en) * | 1993-03-19 | 1996-12-17 | Bar-Co Processes Joint Venture | Fluidized process for improved stripping and/or cooling of particulate spent solids, and reduction of sulfur oxide emissions |
EP0702077A3 (en) * | 1994-09-13 | 1996-03-27 | Bar Co Processes Joint Venture | |
US7276210B2 (en) | 2003-08-20 | 2007-10-02 | Petroleo Brasileiro S.A. -Petrobras | Stripping apparatus and process |
Also Published As
Publication number | Publication date |
---|---|
JPS61157580A (en) | 1986-07-17 |
CA1261774A (en) | 1989-09-26 |
AU5115885A (en) | 1986-07-03 |
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