WO1993008912A1 - Procede de regeneration d'un catalyseur use de craquage catalytique fluidifie - Google Patents

Procede de regeneration d'un catalyseur use de craquage catalytique fluidifie Download PDF

Info

Publication number
WO1993008912A1
WO1993008912A1 PCT/US1991/007980 US9107980W WO9308912A1 WO 1993008912 A1 WO1993008912 A1 WO 1993008912A1 US 9107980 W US9107980 W US 9107980W WO 9308912 A1 WO9308912 A1 WO 9308912A1
Authority
WO
WIPO (PCT)
Prior art keywords
catalyst
coke
flue gas
fluidized bed
regeneration
Prior art date
Application number
PCT/US1991/007980
Other languages
English (en)
Inventor
Hartley Owen
Paul Herbert Schipper
Original Assignee
Mobil Oil Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mobil Oil Corporation filed Critical Mobil Oil Corporation
Priority to PCT/US1991/007980 priority Critical patent/WO1993008912A1/fr
Priority to JP4500841A priority patent/JPH07500528A/ja
Priority to CA002122134A priority patent/CA2122134C/fr
Priority to AU90220/91A priority patent/AU658382B2/en
Priority to EP92900003A priority patent/EP0610186B1/fr
Priority to DE69132086T priority patent/DE69132086T2/de
Priority claimed from CA002122134A external-priority patent/CA2122134C/fr
Publication of WO1993008912A1 publication Critical patent/WO1993008912A1/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J38/00—Regeneration or reactivation of catalysts, in general
    • B01J38/04—Gas or vapour treating; Treating by using liquids vaporisable upon contacting spent catalyst
    • B01J38/12—Treating with free oxygen-containing gas
    • B01J38/30—Treating with free oxygen-containing gas in gaseous suspension, e.g. fluidised bed
    • B01J38/34—Treating with free oxygen-containing gas in gaseous suspension, e.g. fluidised bed with plural distinct serial combustion stages
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/90—Regeneration or reactivation
    • 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
    • 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
    • C10G11/187—Controlling or regulating

Definitions

  • This invention relates to a process for regenerating spent fluidized catalytic cracking * 5 catalyst.
  • Catalytic cracking is the backbone of many refineries. It converts heavy feeds to lighter products by cracking large molecules into smaller molecules. Catalytic cracking operates at low pressures, without 10 hydrogen addition, in contrast to hydrocracking, which operates at high hydrogen partial pressures. Catalytic cracking is inherently safe as it operates with very little oil actually in inventory during the cracking process. 15 There are two main variants of the catalytic cracking process: the moving bed process and the far more popular and efficient fluidized bed process.
  • catalyst circulates between a cracking reactor and a 20 catalyst regenerator.
  • hydrocarbon feed contacts a source of hot, regenerated catalyst, which vaporizes and cracks the feed at a temperature of 425-600°C, usually 460-560°C.
  • the cracking reaction deposits carbonaceous hydrocarbons or coke on the 25 catalyst, thereby deactivating the catalyst.
  • the cracked products are separated from the coked catalyst, which is then stripped of volatiles, usually with steam, in a catalyst stripper.
  • the stripped catalyst is then passed to the catalyst regenerator, where coke is burned 30 from the catalyst with oxygen containing gas, usually , air.
  • Decoking restores catalyst activity and simultaneously heats the catalyst to, for example, 500-900°C, usually 600-750°C. This heated catalyst is recycled to the cracking reactor to crack more fresh 35 feed. Flue gas formed by burning coke in the regenerator may be treated for removal of particulates and for conversion of carbon monoxide, after which the flue gas is normally discharged into the atmosphere.
  • Catalytic cracking has undergone progressive development since the 1940s, with the trend in fluid catalytic cracking being towards all riser cracking and use of zeolite catalysts.
  • riser cracking gives higher yields of valuable products than dense bed cracking.
  • Zeolite-containing catalysts having high activity and selectivity are now used in most FCC units. These catalysts work best when coke on the catalyst after regeneration is less than 0.2 wt %, and preferably less than 0.05 wt %.
  • U.S. Patent Nos 4,072,600 and 4,093,535 teach use of combustion-promoting metals such as Pt, Pd, Ir, Rh, Os, Ru and Re in cracking catalysts in concentrations of 0.01 to 50 pp , based on total catalyst inventory.
  • Steam is not intentionally added, but is invariably present, usually as absorbed or entrained steam from steam stripping of the catalyst or as water of combustion formed in the regenerator. Steam deactivation 10 becomes more of a problem as regenerators get hotter, since higher temperatures accelerate the deactivating effects of steam.
  • U.S. Patent No. 4,353,812 to Lomas et al discloses cooling catalyst from a regenerator by passing it through the shell side of a heat-exchanger with a cooling medium being passed through the tube side. This approach will remove heat from the regenerator, but will not prevent poorly, or even well, stripped catalyst from experiencing very high surface or localized temperatures in the regenerator.
  • the prior art also uses dense or dilute phase regenerated fluid catalyst heat removal zones or heat-exchangers that are remote from, and external to, the regenerator vessel to cool hot regenerated catalyst for return to the regenerator. Examples of such processes are found in U.S. Patent Nos. 2,970,117 to Harper; 2,873,175 to Owens; 2,862,798 to McKinney; 2,596,748 to Watson et al; 2,515,156 to Jahnig et al; 2,492,948 to Berger; and 2,506,123 to Watson.
  • Hot regenerated catalyst and flue gas from the coke combustor are discharged from the transport riser, separated, and the regenerated catalyst collected as a second, bubbling dense bed for return to the FCC reactor and recycle to
  • regenerators are now widely used. They typically are operated to achieve complete CO combustion within the dilute phase transport riser. They achieve one stage of regeneration, i.e., essentially all of the
  • coke is burned in the coke combustor, with minor amounts being burned in the transport riser.
  • the residence time of the catalyst in the coke combustor is on the order of a few minutes, while the residence time in the transport riser is on the order of a few seconds, so there is
  • Catalyst regeneration in such high efficiency regenerators is essentially a single stage process in that the catalyst and regeneration gas and produced flue gas remain together from the coke combustor through the dilute phase transport riser. Almost no further regeneration of catalyst occurs downstream of the coke combustor, because very little air is added to the second, bubbling dense bed used to collect regenerated catalyst for recycle to the reactor or the coke combustor. Usually enough air is added to fluff the catalyst, and allow efficient transport of catalyst around the bubbling dense bed. Less than 5 %, and usually less than 1 ., of the coke combustion takes place in the second dense bed.
  • Such units are popular in part because of their efficiency, i.e., the fast fluidized bed, with recycle of hot regenerated catalyst, is so efficient at burning coke that the regenerator can operate with only half the catalyst inventory required in an FCC unit with a bubbling dense bed regenerator.
  • the reducing flue gas from the coke combustor (with a C02/CO ratio of 0.7 to 2.0) is combined with the flue gas from the second dense bed, which operates with substantially complete CO combustion to produce a flue gas with at least 0.5% 0_.
  • the two flue gas streams are combined to form flue gas containing a C0-/C0 ratio from l to 5.
  • the present invention seeks to provide an improved process for effecting high efficiency multi-stage regeneration of spent FCC catalyst in which changes in coke make are dealt with either by changing the coke burning rates in both the coke combustor and the second dense bed, or at least in the coke combustor.
  • This is a preferred arrangement because the coke combustor is the most vigorously fluidized, and most robust place in the regenerator for coke combustion.
  • the fast fluidized bed region is not plagued by the presence of many large bubbles, unlike the second dense bed of many high efficiency regenerators.
  • the fast fluidized bed region is essentially entirely active, while much, and perhaps even a majority, of a bubbling dense phase fluidized bed is inactive.
  • the present invention resides in a process for regenerating spent fluidized catalytic cracking catalyst comprising the steps of: a) partially regenerating said spent cracking catalyst in a primary regeneration zone, comprising a fast fluidized bed coke combustor and a superimposed dilute phase transport riser, by charging said spent catalyst to said fast fluidized bed coke combustor having an inlet for spent catalyst, an inlet for recycled regenerated catalyst and an inlet for primary regeneration gas, to produce partially regenerated catalyst and flue gas comprising at least 1.0 mole % CO, which are passed up into the dilute phase transport riser and discharged therefrom to form a flue gas rich stream comprising at least 1 mole % CO and a catalyst rich stream comprising partially regenerated catalyst; and .--_.
  • a secondary regeneration zone comprising a second fluidized bed adapted to receive said partially regenerated catalyst and having means for adding additional regeneration gas to said second fluidized bed in an amount sufficient to complete the regeneration of said catalyst and produce regenerated catalyst and secondary flue gas; wherein: i) the CO-containing flue gas stream from the said dilute phase transport riser is combined with said secondary flue gas to produce a combined flue gas stream; ii) the conditions in said secondary regeneration zone are controlled such that said secondary flue gas contains less than 1 mole % CO and contains sufficient oxygen to react with the CO-containing flue gas stream from the said dilute transport riser; iii) at least one flue gas composition or a differential temperature in said combined flue gas stream is monitored; and iv) the amount of primary regeneration gas supplied to said fast fluidized bed coke combustor is controlled so as to maintain constant said monitored flue gas composition or differential temperature.
  • Figure 1 is a simplified schematic view of one example of the invention using flue gas composition, or a delta T indicating afterburning, to control air addition to the coke combustor of a multistage FCC high efficiency regenerator.
  • Figure 2 is a simplified view of the same regenerator using a flue gas analyzer, or temperature, to control total air flow, and a fluid bed dT controller to apportion air between the fluidized beds.
  • Figure 3 shows the same regenerator wherein a flue gas analyzer controller, and/or a delta T controller, changes feed preheat and/or feed rate.
  • the FCC reactor section in each example is the same and includes a riser reactor 4, into the lower end of which a heavy feed is charged via line 1.
  • Hot regenerated catalyst is added to the reactor 4 via standpipe 102 and control valve 104 to mix with the feed.
  • some atomizing steam is added via line 141 to the base of the riser, usually with the feed.
  • heavier feeds e. g. , a resid, 2-10 wt.% steam may be used.
  • a hydrocarbon-catalyst mixture rises as a generally dilute phase through riser 4. Cracked products and coked catalyst are discharged via riser effluent conduit 6 into first stage cyclone 8 in vessel 2.
  • the riser top temperature, the temperature in conduit 6, ranges between 480 and 615°C (900 and 1150 ⁇ F), and preferably between 538 and 595°C (1000 and 1050" F) .
  • the riser top temperature is usually controlled by adjusting the catalyst to oil ratio in riser 4 or by varying feed preheat.
  • Cyclone 8 separates most of the catalyst from the cracked products and discharges the separated catalyst via dipleg 12 to a stripping zone 30 located in a lower portion of vessel 2. Vapor and minor amounts of catalyst exit cyclone 8 via gas effluent conduit 20 and second stage reactor cyclones 14. The second stage cyclones 14 recover some additional catalyst which is discharged via diplegs to the stripping zone 30.
  • Stripping vapors enter the atmosphere of the vessel 2 and may exit this vessel via outlet line 22 or by passing through an annular opening in line 20, not shown, i.e. the inlet to the secondary cyclone can be flared to provide a loose slip fit for the outlet from the primary cyclone.
  • the coked catalyst discharged from the cyclone diplegs collects as a bed of catalyst 31 in the stripping zone 30.
  • Dipleg 12 is sealed by being extended into the catalyst bed 31, whereas the dipleg from the secondary cyclones 14 is sealed by a flapper valve, not shown.
  • Stripper 30 is a "hot stripper" in that spent catalyst is mixed and heated in bed 31 by hot catalyst from the regenerator. Catalyst from regenerator 80 enters vessel 2 via transfer line 106, and slide valve 108 which controls catalyst flow. Adding hot. regenerated catalyst permits first stage stripping at from 55"C (100°F) above the riser top temperature up to a temperature of 816"C (1500°F) . Preferably, the first stage stripping zone operates at at least 83°C (150°F) above the riser top temperature, but below 760°C (1400°F) .
  • a stripping gas preferably steam, flows countercurrent to the catalyst.
  • the stripping gas is preferably introduced into the lower portion of bed 31 by one or more conduits 341.
  • the stripping zone bed 31 preferably contains trays or baffles not shown.
  • High temperature stripping removes coke, sulfur and hydrogen from the spent catalyst. Coke is removed because carbon in the unstripped hydrocarbons is burned as coke in the regenerator. The sulfur is removed as hydrogen sulfide and mercaptans. The hydrogen is removed as molecular hydrogen, hydrocarbons, and hydrogen sulfide. The removed materials also increase the recovery of valuable liquid products, because the stripper vapors can be sent to product recovery with the bulk of the cracked products from the riser reactor. High temperature stripping can reduce coke load to the regenerator by 30 to 50% or more and remove 50-80% of the hydrogen and 35 to 55% of the sulfur, as well as a portion of nitrogen as ammonia and cyanides.
  • the present invention may also be used with conventional strippers, or with long residence time steam strippers, or with strippers having internal or external heat exchange means.
  • an internal or external catalyst stripper/cooler with inlets for hot catalyst and fluidization gas, and outlets for cooled catalyst and stripper vapor, may also be used where desired to cool the stripped catalyst before it enters the regenerator 80.
  • the regenerator 80 comprises two regeneration stages, that is a first coke combustor 62/transport riser 83 and a second fluidized bed 82, which is preferably a dense bed or bubbling fluidized bed. Partial CO combustion is maintained in the first stage while the second stage of catalyst regeneration operates in complete CO combustion mode.
  • the stripped catalyst passes through a conduit 42 into regenerator riser 60, where air from line 66 and stripped catalyst combine and pass up through an air catalyst disperser 74 into coke combustor 62.
  • a fast fluidized bed 76 of catalyst is thereby produced in the coke combustor so that combustible materials, such as coke on the catalyst, are burned by contact with air or oxygen containing gas.
  • the amount of air or oxygen containing gas added via line 66, to the base of the riser mixer 60, is preferably constant and preferably restricted to 10-95% of the total air addition to the first stage of regeneration. Additional air, preferably 5-50 % of total air, is added to the coke combustor via line 160 and air ring 167.
  • the partitioning of the first stage air, between the riser mixer 60 and the air ring 167 in the coke combustor, can be fixed or controlled by a differential temperature, e.g., the temperature rise in riser mixer 60.
  • the total amount of air addition to the first stage i.e., the regeneration in the coke combustor and riser mixer is controlled to maintain only partial coke removal and only partial CO combustion, so that the CO content of the first stage flue gas is in excess of 1 mole%.
  • the control method will be discussed in more detail later.
  • the temperature of fast fluidized bed 76 in the coke combustor 62 may be, and preferably is, increased by recycling some hot regenerated catalyst from the second fluidized bed 82 via line 101 and control valve 103. If temperatures in the coke combustor are too high, some heat can be removed via catalyst cooler 48, shown as tubes immersed in the fast fluidized bed in the coke combustor. Very efficient heat transfer can be achieved in the fast fluidized bed 76, so it may be beneficial to both heat the coke combustor (by recycling hot catalyst to it) and to cool the coke combustor (by using catalyst cooler 48) at the same time.
  • the combustion air regardless of whether added via line 66 or 160, fluidizes the catalyst in bed 76, and subsequently transports the catalyst continuously as a dilute phase through the regenerator riser 83.
  • the dilute phase passes upwardly through the riser 83, through riser outlet 306 into primary regenerator cyclone 308.
  • Catalyst is discharged down through dipleg 84 to form a second relatively dense bed of catalyst 82 located within the regenerator 80.
  • the hot, regenerated catalyst discharged from the various cyclones forms the second fluidized bed 82, which is hotter than any other fluid bed in the regenerator, and hotter than the stripping zone 30.
  • Bed 82 is at least 55°C (100°F) , and preferably at least 83 ⁇ C (150 ⁇ F), hotter than stripping zone 31.
  • the regenerator temperature is preferably no more than 870°C (1600°F) to prevent deactivating the catalyst.
  • some hot regenerated catalyst is withdrawn from dense bed 82 and passed via line 106 and control valve 108 into dense bed of catalyst 31 in stripper 30. Hot regenerated catalyst passes through line 102 and catalyst flow control valve 104 for use in heating and cracking of fresh feed.
  • Partial CO combustion is achieved in the first regeneration stage 62, 83 by control of temperature and residence time and by control of the air addition rate. There will always be large amounts of coke on catalyst exiting the riser. Combustion air to the second stage is maintained at a constant rate, or changed only infrequently to suit changing conditions.
  • the second stage flue gas, e.g., CO or 02 content controls the amount of air added to the first stage 62, 83.
  • air addition to the coke combustor 62 is controlled by a delta T controller 410 which is connected to thermocouples 400 and 405 in the outlet to the transport riser and the dilute phase region above the second fluidized bed respectively.
  • the output from the controller 410 is sent via control line 415 to alter air flow through valve 420 which supplies air to the coke combustor via line 160.
  • the air flow via line 78 to the upper dense bed is fixed, i.e., a conventional control means admits a fixed volume of air.
  • the second fluidized bed is not able to completely afterburn all the CO produced in the second fluidized bed.
  • the delta T observed by the thermocouples 400, 405 will drop and the dT controller 410 send a signal to the valve 420 to increase the air supply to the coke combustor 62.
  • second stage flue gas CO content decreases, e.g., to 0.05 mole %, or too much oxygen breaks through the second stage, this means the second stage is not being worked hard enough, so the amount of air added to the first stage will be decreased to shift more of the coke burning load to the second stage of regeneration.
  • a flue gas analyzer 625 is used in place of the dT controller 410 to measure the composition of the flue gas from the second regeneration stage.
  • the flue gas analyzer 625 sends a signal via signal transmission means 615 to valve 420 to control air flow to the coke combustor.
  • the embodiment shown in Figure 1 provides a relatively simple and reliable control scheme (use of a flue gas composition or delta T indicative of a composition of flue gas above the second fluidized bed) which can accommodate normal minor changes in operation, and even be adjusted to deal with major changes in operation. It will be beneficial in many refineries if the relatively large amount of coke burning in both the primary and secondary stage of the regenerator can be directly controlled.
  • the Fig. 2 embodiment provides a way to apportion and control the relative amount of coke burning that occurs in each stage of regeneration.
  • the Fig. 2 embodiment uses most of the hardware from the Fig. 1 embodiment, i.e., the regenerator flue gas streams are combined into a single flue gas stream.
  • the difference in the Fig. 2 embodiment is simultaneous adjustment of both primary and secondary air. This can be seen more easily in conjunction with a review of Figure 2.
  • Elements which correspond to Fig. 1 elements have the same reference numerals, and are not discussed.
  • Fig 2 also includes, besides reference numerals, symbols indicating temperature differences, e.g., dT. means that a signal is developed indicative of the temperature difference between temperature 1 and temperature 2.
  • the amount of air added to the riser mixer is fixed, for simplicity, but this is merely to simplify the following analysis.
  • the riser mixer air is merely part of the primary air, and could vary with any variations in flow of air to the coke combustor. It is also possible to operate the regenerator with no riser mixer at all, in which case spent catalyst, recycled regenerated catalyst, and primary air are all added directly to the coke combustor.
  • the riser mixer is, however, preferred.
  • the control scheme will first be stated in general terms, then reviewed in conjunction with Fig. 2.
  • the overall amount of combustion air i.e., the total air to the regenerator, is controlled based on either the composition or temperature of the combined flue gas or a differential temperature indicating afterburning downstream of the second fluidized bed. Controlling or apportioning the air added to each combustion zone allows unit operation to be optimized even when the operator does not know the individual optima for the first and second stages. If the second fluidized bed, typically a bubbling dense bed with fairly poor contacting efficiency, is being called on to do too much afterburning, an increased dT in the flue gas, will occur.
  • the unit can be controlled by increasing the air rate to the coke combustor and decreasing air flow to the second dense bed, and letting the controller keep the relative amount of coke burned in the first and second stages constant regardless of future fluctuations in coke make.
  • control scheme apportions air between the first and second stages of the regenerator. This is a more complicated control method than was used in Figure 1, but will usually allow better operation. An operator may specify e.g., that 40 % of the coke will be burned in the first stage and 60 % burned in the second stage, regardless of fluctuations in coke make.
  • control loops are needed, basically at least one loop to control total air addition to the regenerator based on a measurement of the flue gas from the unit, and one loop to shift air between the first and second stage to keep the relative amounts of coke combustion in each stage constant.
  • the total air flow in line 358 is controlled by means of a flue gas analyzer 361 or preferably by temperature controller 350 and thermocouple 336 which are in the dilute phase region above the second fluidized bed. Either temperature or flue gas composition can be used to generate a control signal which is transmitted via transmission means 352 or 362 (an air line, or a digital or analogue electrical signal or equivalent signal transmission means) to valve 360 which regulates the total air flow to the regenerator via line 358.
  • transmission means 352 or 362 an air line, or a digital or analogue electrical signal or equivalent signal transmission means
  • the apportionment of air between the primary and secondary stages of regeneration is controlled by the differences in temperature of the two relatively dense phase beds in the regenerator.
  • the temperature (Tl) in the coke combustor fast fluidized bed is determined by thermocouple 330.
  • the bubbling dense bed temperature (T2) is determined by thermocouple 332. Both temperature signals are sent to differential temperature controller 338, which generates a signal based on dT12, or the difference in temperature between the two beds. Signals are sent via means 356 to valve 372, which regulates primary air to the coke combustor and via means 354 to valve 72, which regulates secondary air to bubbling dense bed.
  • the delta T (dT12) becomes too large, it means that not enough coke burning is taking place in the coke combustor, and too much coke burning is occurring in the second dense bed.
  • the dT controller 338 will compensate by sending more combustion air to the coke combustor, and less to the bubbling dense bed.
  • the operation of the coke combustor can be measured by the fast fluidized bed temperature (as shown) , by the temperature in the dilute phase of the coke combustor or in the dilute phase transport riser, or the temperature measured in the primary cyclone or on a flue gas stream or catalyst stream discharged from the primary cyclone.
  • a flue gas or catalyst composition measurement can also be used to generate a signal indicative of the amount of coke combustion occurring in the fast fluidized bed, but this will generally not be as sensitive as simply measuring the bed temperature in the coke combustor.
  • primary air and secondary air do not require that a majority of the coke combustion take place in the coke combustor. In most instances, the fast fluidized bed region will be the most efficient place to burn coke, but there are considerations, such as reduced steaming of catalyst if regenerated in the bubbling dense bed, and reduced thermal deactivation of catalyst by delaying as long as possible as much of the carbon burning as possible, which may make it beneficial to burn most of the coke with the "secondary air”. This will usually require substantial unit modifications, to increase the size of the second fluidized bed, and to increase the bed superficial vapor velocity so that better fluidization is achieved.
  • the control method of Fig. 2. will be preferred for most refineries.
  • Another method of control is shown in Fig. 3, which can be used as an alternative to the Fig. 2 method.
  • the Fig. 3 control method retains the ability to apportion combustion air between the primary and secondary stages of regeneration, but adjusts feed preheat, and/or feed rate, rather than total combustion air, to maintain partial CO combustion in the coke combustor and complete CO combustion in the second fluidized bed.
  • the Fig. 3 control method is especially useful where a refiner's air blower capacity is limiting the throughput of the FCC unit. Leaving the air blower at maximum, and adjusting feed preheat and/or feed rate, will maximize the coke burning capacity of the unit by always running the air blower at maximum throughput.
  • the total amount of air added via line 358 is controlled solely by the capacity of the compressor or air blower.
  • the apportionment of air between primary and secondary stages of combustion is controlled as in the Fig. 2 embodiment, except that a flue gas dT, rather than a flue gas temperature, is used to adjust coke make.
  • Feed preheat and/or feed rate are adjusted as necessary to keep the coke make in balance with the coke burned in the first stage (partial CO combustion) and in the second stage (complete CO combustion) .
  • Each variable changes the coke make of the unit, and each will be reviewed in more detail below.
  • Feed preheat can control afterburning because of the way FCC reactors are run.
  • the FCC reactor usually operates with a controlled riser top temperature.
  • the hydrocarbon feed in line 1 is mixed with sufficient hot, regenerated catalyst from line 102 to maintain a given riser top temperature. This is the way most FCC units operate.
  • the temperature can be measured at other places in the reactor, as in the middle of the riser, at the riser outlet, cracked product outlet, or a spent catalyst temperature before or after stripping, but usually the riser top temperature is used to control the amount of catalyst added to the base of the riser to crack fresh feed. If the feed is preheated to a very high temperature, and much or all of the feed is added as a vapor, less catalyst will be needed as compared to operation with a relatively cold liquid feed which is vaporized by hot catalyst.
  • High feed preheat reduces the amount of catalyst circulation needed to maintain a given riser top temperature, and this reduced catalyst circulation rate reduces coke make.
  • a composition based control signal from analyzer controller 361 may be sent via signal transmission means 384 to feed preheater 380 or to valve 390. Decreasing feed preheat, i.e., a cooler feed, increases coke make. Increasing feed rate increases coke make. Either action, or both together, will increase the coke make, and bring flue gas composition back to the desired point.
  • a differential temperature control 350 may generate an analogous signal, transmitted via means 382 to adjust preheat and/or feed rate. The air is apportioned between the first and second stages as in the Fig.
  • a dT controller maintains a temperature difference, which indirectly sets the amount of coke burned in each stage.
  • the Fig. 3 embodiment provides a good way to accommodate unusually bad feeds, with CCR levels exceeding 5 or 10 wt %. Partial CO combustion, with downstream combustion of CO, in a CO boiler, and constant maximum air rate maximize the coke burning capacity of the regenerator using an existing air blower of limited capacity.
  • the high efficiency regenerator without departing from the scope of the present invention. It is possible to use the control scheme of the present invention even when additional catalyst/flue gas separation means are present.
  • the riser mixer 60 may discharge into a cyclone or other separation means contained within the coke combustor. The resulting flue gas may be separately withdrawn from the unit, without entering the dilute phase transport riser.
  • Such a regenerator configuration is shown in EP-A-0259115, published on March 9, 1988.
  • Any conventional FCC feed can be used.
  • the process of the present invention is especially useful for processing difficult charge stocks, those with high levels of CCR material, exceeding 2, 3, 5 and even 10 wt % CCR.
  • the process tolerates feeds which are relatively high in nitrogen content, and which otherwise might produce unacceptable NOx emissions in conventional FCC units, operating with complete CO combustion.
  • the feeds may range from the typical, such as petroleum distillates or residual stocks, either virgin or partially refined, to the atypical, such as coal oils and shale oils.
  • the feed frequently will contain recycled hydrocarbons, such as light and heavy cycle oils which have already been subjected to cracking.
  • Preferred feeds are gas oils, vacuum gas oils, atmospheric resids, and vacuum resids.
  • the present invention is most useful with feeds having an initial boiling point above 343 ⁇ C (650°F).
  • the catalyst can be 100% amorphous, but preferably includes some zeolite in a porous refractory matrix such as silica-alumina, clay, or the like.
  • the zeolite is usually 5-40 wt.% of the catalyst, with the rest being matrix.
  • Conventional zeolites include X and
  • Y zeolites being preferred. Dealuminized Y (DEAL Y) and ultrahydrophobic Y (UHP Y) zeolites may be used. The zeolites may be stabilized with Rare Earths, e.g., 0.1 to 10 Wt % RE.
  • Relatively high silica zeolite containing catalysts are preferred for use in the present invention. They withstand the high temperatures usually associated with complete combustion of CO to C02 within the FCC regenerator.
  • the catalyst inventory may also contain one or more additives, either present as separate additive particles or mixed in with each particle of the cracking catalyst.
  • Additives can be added to enhance octane (shape selective zeolites, i.e., those having a Constraint Index of 1-12, preferably ZSM-5) , adsorb SOX (alumina), and remove Ni and V (Mg and Ca oxides) .
  • the reactor may be either a riser cracking unit or dense bed unit or both.
  • Riser cracking is highly preferred.
  • Typical riser cracking reaction conditions include catalyst/oil ratios of 0.5:1 to 15:1 and preferably 3:1 to 8:1, and a catalyst contact time of 0.5-50 seconds, and preferably 1-20 seconds.
  • Hot strippers heat spent catalyst by adding some hot, regenerated catalyst to spent catalyst.
  • the hot stripper reduces the hydrogen content of the spent catalyst sent to the regenerator and reduces the coke content as well.
  • the hot stripper helps control the temperature and amount of hydrothermal deactivation of catalyst in the regenerator.
  • a good hot stripper design is shown in US 4,820,404 Owen.
  • the process and apparatus of the present invention can use many conventional elements most of which are conventional in FCC regenerators.
  • the present invention uses as its starting point a high efficiency regenerator such as is shown in the Figures.
  • the essential elements of such a regenerator include a coke combustor, a dilute phase transport riser and a second fluidized bed, which is usually a bubbling dense bed.
  • the second fluidized bed can also be a turbulent fluidized bed, or even another fast fluidized bed, but unit modifications will then frequently be required.
  • a riser mixer is used.
  • a significantly increased catalyst inventory in the second fluidized bed of the regenerator, and means for adding a significant amount of combustion air for coke combustion in the second fluidized bed are preferably present or added.
  • regenerator flue gas cyclones Each part of the regenerator will be briefly reviewed below, starting with the riser mixer and ending with the regenerator flue gas cyclones.
  • Spent catalyst and some combustion air are charged to the riser mixer 60.
  • Some regenerated catalyst, recycled through the catalyst stripper, will usually be mixed in with the spent catalyst.
  • Some regenerated catalyst may also be directly recycled to the base of the riser mixer 60, either directly or, preferably, after passing through a catalyst cooler.
  • Riser mixer 60 is a preferred way to get the regeneration started.
  • the riser mixer typically burns most of the fast coke (probably representing entrained or adsorbed hydrocarbons) and a very small amount of the hard coke.
  • the residence time in the riser mixer is usually very short. The amount of hydrogen and carbon removed, and the reaction conditions needed to achieve this removal are reported below.
  • the coke combustor 62 contains a fast fluidized dense bed of catalyst. It is characterized by relatively high superficial vapor velocity, vigorous fluidization, and a relatively low density dense phase fluidized bed. Most of the coke can be burned in the coke combustor. The coke combustor will also efficiently burn "fast coke", primarily unstripped hydrocarbons, on spent catalyst. When a riser mixer is used, a large portion, perhaps most, of the "fast coke" will be removed upstream of the coke combustor. If no riser mixer is used, relatively easy job of burning the fast coke will be done in the coke combustor.
  • the dilute phase transport riser 83 forms a dilute phase which efficiently transfers catalyst from the fast fluidized bed through a catalyst separation means to the second dense bed.
  • Additional air can be added to the dilute phase transport riser, but usually it is better to add the air lower down in the regenerator, and speed up coke burning rates.
  • the dilute phase mixture is preferably quickly separated into a catalyst rich dense phase and a catalyst lean dilute phase.
  • the quick separation of catalyst and flue gas sought in the regenerator transport riser outlet is very similar to the quick separation of catalyst and cracked products sought in the riser reactor outlet.
  • the most preferred separation system effects discharge of the regenerator transport riser dilute phase into a closed cyclone system such as that disclosed in US 4,502,947.
  • a closed cyclone system such as that disclosed in US 4,502,947.
  • Such a system rapidly and effectively separates catalyst from steam laden flue gas and isolates and removes the flue gas from the regenerator vessel. This means that catalyst in the regenerator downstream of the transport riser outlet will be in a relatively steam free atmosphere, and the catalyst will not deactivate as quickly as in prior art units.
  • Acceptable separation means include a capped riser outlet discharging catalyst down through an annular space defined by the riser top and a covering cap.
  • a reasonably efficient multistage regeneration of catalyst can be achieved by reducing the air added to the coke combustor and increasing the air added to the second fluidized bed. The reduced vapor velocity in the transport riser, and increased vapor velocity immediately above the second fluidized bed, will more or less segregate the flue gas from the transport riser from the flue gas from the second fluidized bed.
  • the transport riser outlet may be capped with radial arms, not shown, which direct the bulk of the catalyst into large diplegs leading down into the second fluidized bed of catalyst in the regenerator.
  • a regenerator riser outlet is disclosed in US Patent 4,810,360.
  • at least 90 % of the catalyst discharged from the transport riser preferably is quickly discharged into a second fluidized bed, discussed below.
  • At least 90 % of the flue gas exiting the transport riser should be removed from the vessel without further contact with catalyst. This can be achieved to some extent by proper selection of bed geometry in the second fluidized bed, i.e., use of a relatively tall but thin containment vessel 80, and careful control of fluidizing conditions in the second fluidized bed.
  • the second fluidized bed achieves a second stage of regeneration of the catalyst, in a relatively dry atmosphere.
  • the multistage regeneration of catalyst is beneficial from a temperature standpoint alone, i.e., it keeps the average catalyst temperature lower than the last stage temperature. This can be true even when the temperature of regenerated catalyst is exactly the same as in prior art units, because when staged regeneration is used the catalyst does not reach the highest temperature until the last stage.
  • the hot catalyst has a relatively lower residence time at the highest temperature in a multistage regeneration process.
  • the second fluidized bed bears a superficial resemblance to the second dense bed used in prior art, high efficiency regenerators. There are several important differences which bring about profound changes in the function of the second fluidized bed.
  • Catalyst temperatures were typically 680-730 ⁇ C (1250-1350°F) , with some operating slightly hotter, perhaps approaching 760"C (1400 ⁇ F) .
  • the average residence time of catalyst was usually 60 seconds or less.
  • the superficial gas velocity in the bed was typically less than 15 cm/s (0.5 fps) , usually 3cm/s (0.1 fps).
  • the bed was relatively dense, bordering on incipient fluidization.
  • the second fluidized bed plays a much more significant role in regenerating the catalyst.
  • the first step is to provide an increased residence time in the second fluidized bed, typically of at least 1 minute, and preferably much longer. This increased residence time can be achieved by adding more catalyst to the unit, and letting it accumulate in the second fluidized bed.
  • much more air is added to the second fluidized bed for several reasons. First, more carbon burning occurs in the second fluidized bed, so the air is needed for combustion. Second, to improve fluidization in the second fluidized bed, much higher superficial vapor velocities are necessary. Also the density of the catalyst in the second fluidized bed is decreased. This reduced density is a characteristic of better fluidization, and also somewhat beneficial in that although the present bed may be twice as high as a bed of the prior art it will not have to contain twice as much catalyst. SECOND DENSE BED CONDITIONS Good Preferred Best
  • CO combustion promoter in the regenerator or combustion zone is not essential for the practice of the present invention, however, it may be beneficial. These materials are well-known.
  • U.S. 4,072,600 and U.S. 4,235,754 disclose operation of an FCC regenerator with minute quantities of a CO combustion promoter. From 0.01 to 100 ppm Pt metal or enough other metal to give the same CO oxidation, may be used with good results. Very good results are obtained with as little as 0.1 to 10 wt. ppm platinum present on the catalyst in the unit. Pt can be replaced by other metals, but usually more metal is then required. An amount of promoter which would give a CO oxidation activity equal to 0.3 to 3 wt. ppm of platinum is preferred.
  • the control method of the present invention can be readily added to existing high efficiency regenerators. Most of the regenerator can be left untouched, as the modifications to install differential temperature probes in the regenerator cyclones, or flue gas analyzers, are minor. Usually only minor modifications will be needed in the second dense bed to accommodate the additional combustion air, and perhaps to add extra air rings, and new cyclones.
  • the riser mixer (if used) , the coke combustor, and the dilute phase transport riser require no modification.
  • the only modification that is strongly recommended for existing high efficiency regenerators is incorporation of a means at the exit of the dilute phase transport riser to rapidly and completely separate catalyst from steam laden flue gas.
  • the steam laden flue gas should be isolated from the catalyst collected in the second fluidized bed.
  • a closed cyclone system is used to separate and isolate steam laden flue gas from catalyst.
  • the coke combustion occurs in the dry atmosphere of the second fluidized bed. Temperatures in the second fluidized bed are high, so rapid coke combustion can be achieved even in a bubbling fluidized bed.
  • the process of the present invention permits continuous on stream optimization of the catalyst regeneration process. Achieving a significant amount of coke combustion in the second fluidized bed of a high efficiency regenerator also increases the coke burning capacity of the unit, for very little capital expenditure.
  • the process of the present invention gives refiners a way to achieve the benefits of multi-stage catalyst regeneration in a high efficiency catalyst regenerator. The process accommodates the inevitable changes in coke make that occur in FCC operation by forcing most of the change to be dealt with in the coke combustor, which is the most robust, and controllable, place to burn coke in an FCC regenerator.
  • Both coke combustion and afterburning in the coke combustor can be limited to a great extent by restricting the amount of combustion air added to the coke combustor, provided the unit does not contain excessive amounts of CO combustion promoter.
  • the coke burning characteristics of the coke combustor are varied directly, by controllably limiting the amount of hot regenerated catalyst recycled to the coke combustor from the second fluidized bed. In an extreme case, little or no hot regenerated catalyst is recycled to the coke combustor. Because the incoming catalyst is relatively cool, i.e., is merely at the temperature at which it is withdrawn from the catalyst stripper, carbon burning rates are very low even though there is intense fluidization in the coke combustor.
  • refiners will keep relatively constant operation in the second fluidized bed, and make most of the changes to unit operation occur in the coke combustor. It is also possible to change the operation of the primary and secondary stages of regeneration together, so that the relative amounts of coke burning in each stage remain constant.
  • refiners will be able to obtain the benefits of coke burning in a generally reducing atmosphere (less NOx, reduced formation of highly oxidized forms of vanadium, lower temperatures, greater coke burning capacity) while having a reliable and responsive way to control the unit which will deal with upsets and other changes which affect the units coke make.

Abstract

Dans un procédé de régénération contrôlé et comportant des étapes multiples d'un catalyseur de craquage catalytique fluidifié, un régénérateur de catalyseur modifié à efficacité élevée (80) comportant un brûleur de coke à lit fluidifié rapide (62), un riser de transport de phase dilué (83), ainsi qu'un deuxième lit fluidifié (82) régénère le catalyseur en au moins deux étapes. La première étape de régénération s'effectue dans le brûleur de coke (62), tandis qu'une deuxième étape de régénération du catalyseur s'effectue dans le deuxième lit fluidifié (82). La quantité de l'apport d'air de combustion au brûleur (62), ainsi que ses conditions d'opération, sont régulées, de façon à limiter la combustion de CO, tandis que la deuxième étape de régénération, effectuée dans le deuxième lit fluidifié (82), réalise la combustion complète du CO. La régénération contrôlée à étapes multiples réduit le stripping par injection de vapeur ou la désactivation du catalyseur pendant la régénération, augmente la capacité de combustion du coke et diminue les émissions de NOx.
PCT/US1991/007980 1991-10-30 1991-10-30 Procede de regeneration d'un catalyseur use de craquage catalytique fluidifie WO1993008912A1 (fr)

Priority Applications (6)

Application Number Priority Date Filing Date Title
PCT/US1991/007980 WO1993008912A1 (fr) 1991-10-30 1991-10-30 Procede de regeneration d'un catalyseur use de craquage catalytique fluidifie
JP4500841A JPH07500528A (ja) 1991-10-30 1991-10-30 使用済み流動接触分解触媒の再生方法
CA002122134A CA2122134C (fr) 1991-10-30 1991-10-30 Procede de regeneration du catalyseur use d'un lit catalytique fluidise
AU90220/91A AU658382B2 (en) 1991-10-30 1991-10-30 A process for regenerating spent fluidized catalytic cracking catalyst
EP92900003A EP0610186B1 (fr) 1991-10-30 1991-10-30 Procede de regeneration d'un catalyseur use de craquage catalytique fluidifie
DE69132086T DE69132086T2 (de) 1991-10-30 1991-10-30 Verfahren zur regenerieren von verbrauchtem fcc-katalysator

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
PCT/US1991/007980 WO1993008912A1 (fr) 1991-10-30 1991-10-30 Procede de regeneration d'un catalyseur use de craquage catalytique fluidifie
CA002122134A CA2122134C (fr) 1991-10-30 1991-10-30 Procede de regeneration du catalyseur use d'un lit catalytique fluidise

Publications (1)

Publication Number Publication Date
WO1993008912A1 true WO1993008912A1 (fr) 1993-05-13

Family

ID=25677215

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1991/007980 WO1993008912A1 (fr) 1991-10-30 1991-10-30 Procede de regeneration d'un catalyseur use de craquage catalytique fluidifie

Country Status (1)

Country Link
WO (1) WO1993008912A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20030010364A (ko) * 2001-07-26 2003-02-05 김동춘 촉매 하행식 크래킹반응 유화설비 및 이를 이용한휘발유·경유의 제조방법
KR100517898B1 (ko) * 2001-07-31 2005-09-30 김범진 폐합성수지를 원료로 하는 촉매 하행식 크래킹반응기 및 이를 이용한 휘발유·경유의 제조방법

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4211636A (en) * 1975-08-27 1980-07-08 Mobil Oil Corporation FCC Catalyst section control
US4448753A (en) * 1982-02-12 1984-05-15 Mobil Oil Corporation Apparatus for regenerating cracking catalyst
US4849091A (en) * 1986-09-17 1989-07-18 Uop Partial CO combustion with staged regeneration of catalyst
US4875994A (en) * 1988-06-10 1989-10-24 Haddad James H Process and apparatus for catalytic cracking of residual oils
US4917790A (en) * 1989-04-10 1990-04-17 Mobil Oil Corporation Heavy oil catalytic cracking process and apparatus
US5077251A (en) * 1990-07-17 1991-12-31 Mobil Oil Corporation Control of multistage catalyst regeneration with both partial and full co combustion

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4211636A (en) * 1975-08-27 1980-07-08 Mobil Oil Corporation FCC Catalyst section control
US4448753A (en) * 1982-02-12 1984-05-15 Mobil Oil Corporation Apparatus for regenerating cracking catalyst
US4849091A (en) * 1986-09-17 1989-07-18 Uop Partial CO combustion with staged regeneration of catalyst
US4875994A (en) * 1988-06-10 1989-10-24 Haddad James H Process and apparatus for catalytic cracking of residual oils
US4917790A (en) * 1989-04-10 1990-04-17 Mobil Oil Corporation Heavy oil catalytic cracking process and apparatus
US5077251A (en) * 1990-07-17 1991-12-31 Mobil Oil Corporation Control of multistage catalyst regeneration with both partial and full co combustion

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP0610186A4 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20030010364A (ko) * 2001-07-26 2003-02-05 김동춘 촉매 하행식 크래킹반응 유화설비 및 이를 이용한휘발유·경유의 제조방법
KR100517898B1 (ko) * 2001-07-31 2005-09-30 김범진 폐합성수지를 원료로 하는 촉매 하행식 크래킹반응기 및 이를 이용한 휘발유·경유의 제조방법

Similar Documents

Publication Publication Date Title
US5077252A (en) Process for control of multistage catalyst regeneration with partial co combustion
AU649268B2 (en) Process for control of multistage catalyst regeneration with full then partial CO combustion
EP0420967B1 (fr) Procede et appareil de craquage catalytique de petrole brut lourd
US5000841A (en) Heavy oil catalytic cracking process and apparatus
EP0493932B1 (fr) Procédé et appareillage pour le craquage catalytique d'huile lourde
US5077251A (en) Control of multistage catalyst regeneration with both partial and full co combustion
AU658382B2 (en) A process for regenerating spent fluidized catalytic cracking catalyst
US5128109A (en) Heavy oil catalytic cracking apparatus
US5126036A (en) Process and apparatus for split feed of spent catalyst to high efficiency catalyst regenerator
WO1992001511A1 (fr) Procede et appareil servant a commander la regeneration multiphase de catalyseurs avec combustion complete du co
WO1993008912A1 (fr) Procede de regeneration d'un catalyseur use de craquage catalytique fluidifie
WO1993000673A1 (fr) Procede de rectification et de regeneration d'un catalyseur de craquage catalytique fluidise
AU8221391A (en) A process for stripping and regenerating fluidized catalytic cracking catalyst

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AU CA JP

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB GR IT LU NL SE

DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
WWE Wipo information: entry into national phase

Ref document number: 2122134

Country of ref document: CA

WWE Wipo information: entry into national phase

Ref document number: 1992900003

Country of ref document: EP

WWP Wipo information: published in national office

Ref document number: 1992900003

Country of ref document: EP

WWG Wipo information: grant in national office

Ref document number: 1992900003

Country of ref document: EP