EP0195129B1 - Reducing the temperature in a regeneration zone of a fluid catalytic cracking process - Google Patents

Reducing the temperature in a regeneration zone of a fluid catalytic cracking process Download PDF

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Publication number
EP0195129B1
EP0195129B1 EP85116235A EP85116235A EP0195129B1 EP 0195129 B1 EP0195129 B1 EP 0195129B1 EP 85116235 A EP85116235 A EP 85116235A EP 85116235 A EP85116235 A EP 85116235A EP 0195129 B1 EP0195129 B1 EP 0195129B1
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Prior art keywords
coke
catalyst
low
solid particles
make solid
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EP85116235A
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German (de)
English (en)
French (fr)
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EP0195129A1 (en
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Robert A. Lengemann
Gregory J. Thompson
Anthony G. Vickers
Raymond W. Mott
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Honeywell UOP LLC
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UOP LLC
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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
    • 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
    • C10G11/02—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils characterised by the catalyst used
    • C10G11/04—Oxides

Definitions

  • This invention relates to the reduction of the temperature in the regeneration zone of a fluid catalytic cracking process when it is operated with a high-coke-make feed stock. More specifically, the invention relates to reducing the maximum temperature reached in the regeneration zone of a fluid catalytic cracking process, without reducing the amount of coke burned therein, by simultaneously circulating, in admixture with the cracking catalyst, fluidizable low-coke-make solid particles, which have a surface area of less than 5 m 2 /g and which low-coke-make particles generate less than 0.2 weight percent coke in the ASTM standard method for testing fluid cracking catalyst by microactivity test (MAT).
  • MAT microactivity test
  • US-A-2889269 and -2894902 disclose methods wherein finely divided catalyst and inert, fluidizable heat transfer solid particles are circulated through a fluidized reactor-regenerator system for the purpose of removing heat from the regenerator. These methods are used primarily in conjunction with the fluid hydroforming of naphtha and are not concerned with high-coke-make feed stocks and the problems of lowering regenerator temperature without interfering with reactor-side operations and coke-burning capacity on the regenerator-side.
  • the above-mentioned patents do not disclose or teach the problems addressed by the present invention, nor the use of the low-coke-make solid particles employed therein.
  • US-A-4289605 discloses a fluid catalytic cracking process whereby a metal-containing hydrocarbon charge stock is contacted with a mixture of active cracking catalyst and inert porous solid particles.
  • Preferred inert porous solid particles have at least 50% of the pore volume comprising pores of at least 100 Angstroms (10OX10-l' m) in diameter and have a surface area of 10 to 15 square meters per gram.
  • a preferred type of inert porous solid particles is calcined kaolin clay.
  • the primary purpose of the large pore inert solid is selectively to accept the large molecules characteristic of the metal and Conradson Carbon content of the charge.
  • US ⁇ A ⁇ 4289605 does not address the problem of controlling the temperature of the regeneration zone with a high-coke-make charge without adversely affecting the reactor-side operation, nor does it suggest that the key is in the use of specific low-coke-make solid particles, which are added in amounts in addition to the established amount of catalyst needed to achieve the reactor-side objectives and not in place of catalyst.
  • GB-A-2116062 and -2116202 disclose a catalytic cracking composition
  • a catalytic cracking composition comprising a solid cracking catalyst and a diluent containing a selected alumina or a selected alumina in combination with one or more heat-stable inorganic compounds wherein the aluminaceous diluent has a surface area of 30-1000 m 2 /g and a pore volume of 0.05-2.5 cm 3 /gram.
  • the primary purpose of the high surface area diluent is to permit the catalyst system to function well, even when the catalyst carries a substantially high level of metal on its surface.
  • a common prior art method of heat removal provides coolant filled coils within the regenerator, which coils are in contact with the catalyst from which coke is being removed.
  • US-A-2819951, -3990992 and -4219442 disclose fluid catalytic cracking processes using dual zone regenerators with cooling coils mounted in the second zone.
  • These cooling coils must always be filled with coolant and thus be removing heat from the regenerator, even during start-up when such removal is particularly undesired, because the typical metallurgy of the coils is such that the coils would be damaged by exposure to the high regenerator temperature of up to 1350°F (732°C) without coolant serving to keep them relatively cool.
  • the cooling coils necessarily reduce the temperature of the regenerated catalyst which is circulated to the reaction zone. Therefore, in order to maintain a constant reaction zone temperature, additional catalyst must be circulated which in turn produces more coke thereby further reducing the yield of valuable liquid products.
  • the present invention provides a process for fluid catalytic cracking of a high-coke-make hydrocarbon feedstock having a 50 volume percent distillation temperature greater than 500°F (260°C) by contacting the feedstock at endothermic cracking conditions with a circulating, heated particulate, solid cracking catalyst in a reaction zone with concurrent cooling of the catalyst and deposition thereon of a deactivating carbonaceous contaminant, regenerating the catalytic cracking activity of the resulting contaminated catalyst by burning carbonaceous deposits therefrom in a regeneration zone under exothermic conditions, and thereafter circulating reheated regenerated catalyst from the regeneration zone to the reaction zone.
  • catalyst is employed in admixture with fluidizable low-coke-make solid particles of a refractory inorganic oxide having a surface area of less than 5 m 2 /g and which generate less than 0.2 weight percent coke in the ASTM standard method for testing fluid cracking catalysts by microactivity (MAT), in a ratio of low-coke-make solid particles to cracking catalyst from 1:100 to 10:1.
  • a refractory inorganic oxide having a surface area of less than 5 m 2 /g and which generate less than 0.2 weight percent coke in the ASTM standard method for testing fluid cracking catalysts by microactivity (MAT), in a ratio of low-coke-make solid particles to cracking catalyst from 1:100 to 10:1.
  • the regeneration zone temperature is maintained at a reduced temperature as compared to an equivalent operation without the use of the low-coke-make solid particles while simultaneously not reducing the coke burning capacity of the regeneration zone or adversely affecting the operation of the reaction zone.
  • the solid particles are advantageously present in an amount sufficient to result in lowering of the regeneration temperature from 10 to 250°F (6 to 139°C) while simultaneously not adversely affecting the operation of the reaction zone.
  • the drawing illustrates a preferred embodiment of the present invention and is an elevational view of apparatus suitable for use in accordance with the present invention. Other types of apparatus may also be suitable for use with the present invention.
  • FCC fluid catalyst cracking process
  • starting materials such as vacuum gas oils, and other relatively heavy oils
  • FCC involves the contact in a reaction zone of the starting material, whether it be vacuum gas oil or another oil, with a finely divided, or particulate, solid, catalytic material which behaves as a fluid when mixed with a gas or vapour.
  • This material possesses the ability to catalyze the cracking reaction, and in so acting, coke, a by-product of the cracking reaction, is deposited on its surface.
  • Coke comprises hydrogen, carbon and other material such as sulfur, and it interferes with the catalytic activity of FCC catalysts.
  • regenerators Facilities for the removal of coke from FCC catalyst, so called regeneration facilities or regenerators, are ordinarily provided within an FCC unit. Regenerators contact the coke-contaminated catalyst with an oxygen containing gas at conditions such that the coke is oxidized and a considerable amount of heat is released. A portion of this heat escapes the regenerator with the flue gas, comprised of excess regeneration gas and the gaseous products of coke oxidation, and the balance of the heat leaves the regenerator with the regenerated, or relatively coke free, catalyst. Regenerators operating at superatmospheric pressures are often fitted with energy-recovery turbines which expand the flue gas as it escapes from the regenerator and recover a portion of the energy liberated in the expansion.
  • the fluidized catalyst is continuously circulated from the reaction zone to the regeneration zone and then again to the reaction zone.
  • the fluid catalyst acts as a vehicle for the transfer of heat from zone to zone.
  • Catalyst exiting the reaction zone is spoken of as being “spent”, that is, partially deactivated by the deposition of coke upon the catalyst.
  • Catalyst from which coke has been substantially removed is spoken of as "regenerated catalyst”.
  • the rate of conversion of the feestock within the reaction zone is controlled by regulation of the temperature, activity of catalyst and quantity of catalyst (i.e., catalyst to oil ratio) therein.
  • the most common method of regulating the temperature is by regulating the rate of circulation of catalyst from the regeneration zone to the reaction zone which simultaneously increases the catalyst/oil ratio. That is to say, if it is desired to increase the conversion rate, an increase in the rate of flow of circulating fluid catalyst from the regenerator to the reactor is effected. Inasmuch as the temperature within the regeneration zone under normal operations is considerably higher than the temperature within the reaction zone, this increase in influx of catalyst from the hotter regeneration zone to the cooler reaction zone effects an increase in reaction zone temperature.
  • FCC units must now cope with feedstocks such as residual oils and in the future may require the use of mixtures of heavy petroleum oils with coal or shale derived oils.
  • Cooling coils which are associated with FCC regeneration zones must necessarily be constantly charged with a cooling medium and are considered to be a vulnerable link in the overall FCC process.
  • Objectives of the present invention are to reduce the temperature of the regeneration zone and to transfer heat from the regeneration zone to the reaction zone while simultaneously not affecting the operation of the reaction zone, or limiting the coke-burning capacity of the regeneration zone.
  • the present invention provides a process for the continuous catalytic conversion of a wide variety of hydrocarbon oils to lower molecular weight products, while maximizing production of highly valuable liquid products, and making it possible, if desired, to avoid vacuum distillation and other expensive treatments such as hydrotreating.
  • Feedstocks for the present invention include residual hydrocarbon oil or any other hydrocarbon feedstock having a 50 volume percent distillation temperature greater than 500°F (260°C).
  • residual hydrocarbon oil includes not only those predominantly hydrocarbon compositions which are liquid at room temperature, but also those predominantly hydrocarbon compositions which are asphalts or tars at ambient temperature but liquefy when heated to temperatures in the range of up to about 800°F (427°C) or more.
  • Suitable feedstocks for use in the present invention are residual oils whether of petroleum origin or not.
  • the invention may be applied to the processing of such widely diverse materials as heavy bottoms from crude oil, heavy bitumen crude oil, those crude oils known as "heavy crude” which approximate the properties of reduced crude, shale oil, tar sand extract, products from coal liquefaction and solvated coal, atmospheric and vacuum reduced crude, extract and/or bottoms from solvent de-asphalting, aromatic extract from lube oil refining, tar bottoms, heavy cycle oil, slop oil, other refinery waste streams and mixtures thereof.
  • Such mixtures can for instance be prepared by mixing available hydrocarbon fractions, including oils, tar, pitches and the like.
  • the invention may be applied to hydrotreated feedstocks, but it is an advantage of the invention that it can successfully convert residual oils which have had no prior hydrotreatment.
  • a preferred application of the process is the treatment of reduced crude, i.e., that fraction of crude oil boiling at and above 650°F (343°C), alone or in admixture with virgin gas oils. While the use of material, that has been subjected to prior vacuum distillation is not excluded, it is an advantage of the invention that it can satisfactorily process feedstock which has had no prior vacuum distillation, thus saving on captical investment and operating costs as compared to conventional FCC processes that require a vacuum distillation unit.
  • suitable feedstocks also include gas oil and vacuum gas oil.
  • An essential element in the process of the present invention is the circulation of low-coke-make solid particles of fluidizable particle size during the conversion of the hydrocarbon feedstock.
  • Suitable low-coke-make solid particles preferably comprise a refractory inorganic oxide such as corundum, mullite, fused alumina, fused silica, alpha alumina, low-surface area calcined clays or the like. Regardless of which type of low-coke-make solid particles are selected, these particles must exhibit very little tendency to enhance the amount of coke deposited on the solids (catalyst plus low-coke-make solid particles) which are present in the reaction environment.
  • the low-coke-make solid particles possess a surface area of less than 5 m 2 /g and generate less than 0.2 weight percent coke on the spent low-coke-make solid particles in the ASTM standard method for testing fluid cracking catalysts by microactivity test (MAT). If the additional solid particles were to contribute significantly to the formation of additional coke, then the additional heat release in the FCC regenerator would tend to nullify or inhibit the sought after regenerator temperature reduction.
  • the low surface area characteristic of the low-coke-make solid particles permits the rapid and complete stripping of hydrocarbonaceous reaction products from the low-coke-make solid particles in the reaction zone before particles are transferred to the regeneration zone thereby preventing the combustible hydrocarbons from entering the regeneration zone and producing additional heat release.
  • the low-coke-make solid particles must have no adverse effect upon the hydrocarbon conversion process, and be stable or resistant to physical breakdown due to the thermal and mechanical forces to which they are subjected in the process.
  • the size of the low-coke-make solid particles may vary from 5 to 2000 ⁇ m and are preferably in the shape of spherical or spheroidal particles.
  • the range of catalyst and low-coke-make particle size may, for example, be substantially the same, overlap, or be different.
  • the apparent bulk density of the low-coke-make solid particles may vary from about 0.3 g/ml to about 4 g/ml.
  • Low coke make solids which are essential in the process of the present invention are those materials which have a coke deposit of 0.2 weight percent coke or less on the spent low-coke-make solid after the solid alone has been subjected to the ASTM standard method for testing cracking catalyst by microactivity test (MAT).
  • MAT microactivity test
  • This microactivity test is more formally known as the Standard Method for Testing Fluid Cracking Catalysts by Microactivity Test and is designated as test D 3907-80.
  • This microactivity test is also mentioned in U.S. Patent No. 4,493,902.
  • the microactivity test is conducted in a laboratory test apparatus which is designed and operated in accordance with the Standard Method.
  • the microactivity test comprises loading a sample of particles weighing 4 grams into the reactor and injecting a standard batch of gas oil in an amount of 1.33 grams over a 75 second period into the reactor which is maintained at 900°F (482°C).
  • the resulting particles to oil weight ratio is about 3 and the weight hourly space velocity is about 16. Then the conversion of the feedstock and the coke remaining on the spent particles may be determined by standard techniques.
  • Another essential element of the process of the present invention is a fluidizable FCC catalyst.
  • a catalyst having an effective level of cracking activity providing high levels of conversion and productivity at low residence times.
  • That catalyst may be introduced into the process in its virgin form or, in other than virgin form; e.g., equilibrium catalyst which has been previously used.
  • One may employ any hydrocarbon cracking catalyst having the above-mentioned characteristics.
  • a particularly preferred class of catalysts include those which have pore structures into which molecules of feed material may enter for adsorption and/or for contact with active catalytic sites within or adjacent the pores.
  • Various types of catalysts are available within this classification, including for example the layered silicates, e.g., smectites.
  • the preferred zeolite-containing catalysts may include any zeolite, whether natural, semi-synthetic or synthetic, alone or in admixture with other materials which do not significantly impair the catalyst, provided the resultant catalyst has the activity and pore structure referred to above.
  • the catalyst may include the zeolite component associated with or dispersed in a porous refractory inorganic oxide carrier.
  • the catalyst may for example contain about 1% to about 60%, more preferably about 1% to about 40% and most preferably about 5% to about 25% by weight, based on the total weight of catalyst (water-free basis) of the zeolite, with the balance of the catalyst being the porous refractory inorganic oxide alone or in combination with any of the known adjuvants for promoting or suppressing various desired or undesired reactions.
  • zeolitic catalysts useful in the invention, attention is drawn to the disclosures of the articles entitled "Refinery Catalysts are a Fluid Business” and “Making Cat Crackers Work on a Varied Diet", appearing respectively in the July 26,1978 and September 13,1978 issues of Chemical Week magazine.
  • the zeolite components of the zeolite-containing catalysts will be those which are known to be useful in FCC processes. In general, these are crystalline aluminosilicates, typically made up of tetra coordinated aluminum atoms associated through oxygen atoms with adjacent silicon atoms in the crystal structure.
  • zeolite contemplates not only aluminosilicates, but also substances in which the aluminum has been partly or wholly replaced, such as for instance by gallium, phosphorus, and other metal atoms, and further includes substances in which all or part of the silicon has been replaced, such as for instance by germanium. Titanium and zirconium substitution may also be practical.
  • the zeolite may be ion exchanged, and where the zeolite is a component of a catalyst composition, such ion exchanging may occur before or after incorporation of the zeolite as a component of the composition.
  • Suitable cations for replacement of sodium in the zeolite crystal structure include ammonium (decomposable to hydrogen), hydrogen, rare earth metals, alkaline earth metals, etc.
  • Various suitable ion exchange procedures and cations which may be exchanged into the zeolite crystal structure are well known to those skilled in the art.
  • Examples of the naturally occurring crystalline aluminosilicate zeolites which may be used as or included in the catalyst for the present invention are faujasite, mordenite, clinoptilote, chabazite, analycite, erionite, as well as levynite, dachiardite, paulingite, noselite, ferriorite, heulandite, scolccite, stibite, harmotome, phillipsite, brewsterite, flarite, datolite, gmelinite, caumnite, leucite, lazurite, scaplite, mesolite, ptholite, nepheline, matrolite, offretite and sodalite.
  • Examples of the synthetic crystalline aluminosilicate zeolites which are useful as or in the catalyst for carrying out the present invention are Zeolite X, U.S. Patent No. 2,882,244; Zeolite Y, U.S. Patent No. 3,130,007; and Zeolite A, U.S. Patent No. 2,882,243; as well as Zeolite B, U.S. Patent No. 3,008,308; Zeolite D, Canada Patent No. 661,981; Zeolite E, Canada Patent No. 614,495; Zeolite F, U.S. Patent No. 2,996,358; Zeolite H, U.S. Patent No. 3,010,789; Zeolite J, U.S. Patent No.
  • the crystalline aluminosilicate zeolites having a faujasite-type crystal structure are particularly preferred for use in the present invention. This includes particularly natural faujasite and Zeolite X and Zeolite Y.
  • zeolite-containing catalysts are available with carriers containing a variety of metal oxides and combinations thereof, including for example silica, alumina, magnesia, and mixtures thereof and mixtures of such oxides with clays as e.g. described in U.S. Patent No. 3,034,948.
  • metal oxides and combinations thereof including for example silica, alumina, magnesia, and mixtures thereof and mixtures of such oxides with clays as e.g. described in U.S. Patent No. 3,034,948.
  • One may for example select any of the zeolite-containing molecular sieve fluid cracking catalysts which are suitable for production of gasoline from vacuum gas oils.
  • certain advantages may be attained by judicious selection of catalysts having marked resistance to metals.
  • a metal resistant zeolite catalyst is, for instance, described in U.S. Patent No. 3,944,482, in which the catalyst contains 1-40 weight percent of a rare earth-exchanged zeolite, the balance being a
  • catalysts having an overall particle size in the range of about 5 to about 160 and more preferably about 30 to about 120 pm.
  • the catalyst composition may also include one or more combustion promoters which are useful in the subsequent step of regenerating the catalyst. Cracking of residual oils results in substantial deposition of coke on the catalyst, which coke reduces the activity of the catalyst. Thus, in order to restore the activity of the catalyst the coke is burned off in a regeneration step, in which the coke is converted to combustion gases including carbon monoxide and/or carbon dioxide. Various substances are known which, when incorporated in cracking catalyst in small quantities, tend to promote conversion of the coke to carbon dioxide. Such promoters, normally used in effective amounts ranging from a trace up to about 10 or 20% by weight of the catalyst, may be of any type which generally promotes combustion of carbon under regenerating conditions, or may be somewhat selective in respect to completing the combustion of CO.
  • a stream is formed comprising a suspension of hydrocarbon feedstock, catalyst and low-coke-make solid particles.
  • the resulting suspension is conducted in a generally upward fashion to permit the desired hydrocarbon conversion to be performed.
  • diluent streams such as steam or light hydrocarbon gases, may also be introduced into the bottom of the reactor riser in order to maximize the degree of vaporization of the feed.
  • the apparatus for conducting the process of the present invention provides for rapidly vaporizing as much feed as possible and efficiently admixing the hydrocarbon feedstock, catalyst and low-coke-make solid particles thereby permitting the resultant mixture to flow as a dilute suspension in a progressive flow mode.
  • the catalyst and low-coke-make solid particles are separated from the hydrocarbons and it is preferred that all or at least a substantial portion of the hydrocarbons be abruptly separated from the catalyst and low-coke-make solid particles. This separation may be conducted in any convenient manner and may include the use of cyclones and the like.
  • the suspension as hereinabove described be transported in what is referred to as a reactor riser which is situated in a nearly vertical position as opposed to the horizontal and have a length to diameter ratio of at least about 10, more preferably about 20 to 25 or more.
  • the reactor riser can be of uniform diameter throughout or may be provided with a continuous or step-wise increase in diameter along the reactor path to maintain or vary the velocity along the flow path.
  • the reactor configuration is such as to provide a relatively high velocity of flow and dilute suspension of catalyst and low-coke-make solid particles.
  • the average velocity in the reactor riser will usually be at least about 25 (7.62 m/s) and more typically at least about 35 feet per second (10.7 m/s).
  • This velocity may range up to about 55 (16.8 m/s) or about 75 (22.9 m/s) feet per second or higher.
  • the velocity capabilities of the riser will in general be sufficient to prevent substantial build-up of a catalyst bed in the bottom or other portions of the riser, whereby the catalyst loading in the riser can be maintained below about 4 or 5 pounds (64.1 or 80.1 kg/m 3 ) and below about 2 pounds per cubic foot (32 kg/m 3 ), respectively, at the upstream (e.g. bottom) and downstream (e.g. top) ends of the riser.
  • the progressive flow mode involves, for example, flowing of catalyst, feed, low-coke-make solids, and products as a stream in a positively controlled and maintained direction established by the elongated nature of the reaction zone. This is not to suggest however that there must be strictly linear flow. As is well known, turbulent flow and "slippage" of catalyst and low coke make solids may occur to some extent especially in certain ranges of vapor velocity and some catalyst loadings, although it has been reported advisable to employ sufficiently low catalyst loadings to restrict slippage and back-mixing.
  • the reactor is one which abruptly separates a substantial portion of all of the vaporized cracked products from the catalyst and low-coke-make solids at one or more points along the riser, and preferably separates substantially all of the vaporized cracked products from the catalyst and low-coke-make solids at the downstream end of the riser.
  • the conversion of the hydrocarbon feedstock to lower molecular weight products may be conducted at a temperature of about 850° to about 1400°F (454 to 760°C) measured at the reactor vessel outlet. Depending upon the temperature selected and the properties of the feed, all of the feed may or may not vaporize in the reactor riser.
  • the pressure in the reactor vessel may range from about 10 to about 70 psia, (68.9 to 482.6 kPa), a preferred pressure range is from 15 to 55 psia (103.4 to 379.2 kPa).
  • the residence time of feed and product vapors in the reactor riser may be in the range of about 0.5 to about 6 seconds. The residence time is dependent upon the feed stock, type and quantity of catalyst and low-coke-make solid particles, the temperature and pressure. One skilled in the hydrocarbon processing art will readily be able to select a suitable residence time in order to enjoy the benefits afforded by the present invention.
  • the catalyst to oil ratios be maintained from 1 to 30 mass of catalyst per mass of feedstock and that the low-coke-make solid particles be present in an amount sufficient to result in a mass ratio of low-coke-make solid particles to cracking catalyst from 1:100 to 10:1.
  • the combination of catalyst to oil ratio, low-coke-make solids to oil ratio, temperatures, pressures and residence times should be such as to effect a substantial conversion of the residual hydrocarbon feedstock. It is an advantage of the process that very high levels of conversion can be attained in a single pass; for example, the conversion may be in excess of 60% and may range to about 90% or higher. Preferably, the aforementioned conditions are maintained at levels sufficient to maintain conversion levels in the range of about 60 to about 90% and more preferably about 65 to about 85%. The foregoing conversion levels are calculated by subtracting from 100% the percentage obtained by dividing the liquid volume of fresh feed into 100 times the volume of liquid product boiling at and above 430°F (221.1°C). These substantial levels of conversion may and usually do result in relatively large yields of coke, such as for example about 3.5 to about 20% by weight based on the fresh feed.
  • the present process preferably includes stripping of spent catalyst and low-coke-make solid particles after disengagement from the product vapors.
  • Persons skilled in the art are acquainted with appropriate stripping agents and conditions for stripping spent catalyst.
  • Substantial conversion of hydrocarbon oil to lighter products in accordance with the invention tends to produce sufficiently large coke yields and coke laydown on the catalyst and low-coke-make solids to require some care in regeneration thereof.
  • the amounts of coke which must therefore be burned off in the regeneration zone when processing residual oils are substantial.
  • Some coke will inevitably be deposited on the low-coke-make solid particles and the burning of this coke from the low-coke-make solid particles in the regeneration zone will herein be referred to as regeneration even though this burning is not an actual regeneration of catalytic activity.
  • coke when used to describe the present invention, should be understood to include any non-vaporized hydrocarbons present on the catalyst and low-coke-make solids after stripping.
  • Regeneration of the catalyst and low-coke-make solids by burning away of coke deposited on the catalyst and low-coke-make solids during the conversion of the feed may be performed at any suitable temperature in the range from about 1100°F to about 1600°F (593.3 to 871.1°C).
  • a stream of hot catalyst from the regenerator may be recycled to the regenerator inlet.
  • Heat released by combustion of coke in the regenerator is absorbed by the catalyst and the low-coke-make solid particles, and can be readily retained thereby until the regenerated mixture of solids are brought into contact with fresh feed.
  • Heat requirements for the reactor include heating and vaporizing the feed, supplying the endothermic heat of reaction for cracking, and making up heat losses from the reactor.
  • Heat from the regenerator is exported to the reactor via the circulation of the low-coke-make solid particles and catalyst. It is thus possible to control the regenerator temperature by varying the proportion of low-coke-make solids that are circulated between the regenerator and the reactor with the catalyst. This provides the opportunity to have independent control of the regenerator temperature by adjusting the quantity of low-coke-make solids in the circulating mixture of low-coke-make solids and catalyst.
  • a residual hydrocarbon feedstock enters into reactor riser 2 via conduit 1 and is contacted with an admixture of regenerated catalyst and low-coke-make solid particles which is supplied via conduit 13.
  • the resulting combination of hydrocarbon, catalyst and low-coke make solids travels in a generally upward fashion through reactor riser 2 wherein the majority of the hydrocarbon conversion occurs and enters reactor vessel 4 which has interior space 3.
  • Interior space 3 serves as a disengagement area wherein the catalyst and the low-coke-make solids are separated from the hydrocarbon vapors.
  • the spent catalyst and low-coke-make solids are collected in the bottom of reactor vessel 4 and subsequently removed therefrom via conduit 7.
  • Level sensing, recording and control device 20 maintains the flow rate in conduit 7 based on the differentials in pressures measured by pressure sensitive devices 18 and 19. Variations in particle inventory in reactor vessel 4 will be reflected in a varying pressure differential. Control device 20 will then maintain a predetermined particle inventory by controlling control valve 21.
  • the hydrocarbon vapors containing entrained fine particles of catalyst and low-coke-make solids are passed into cyclone separator 5 and the hydrocarbon vapors containing a reduced concentration of solids are removed from reactor vessel 4 via conduit 6.
  • the disengaged solids are returned to interior space 3 from the bottom of cyclone separator 5.
  • the spent catalyst and low-coke-make solid particles are contacted via conduit 7 with regeneration air (or oxygen) supplied via conduit 8.
  • the admixture of air, spent catalyst and low-coke-make solid particles is introduced into regenerator vessel 10 which has interior space 9 via conduit 8.
  • Conditions within regeneration vessel 10 are such that oxygen containing air and coke combine chemically to produce flue gas while leaving the catalyst and the low-coke-make solid particles relatively free from coke.
  • the resulting regenerated catalyst and low-coke-make solid particles are collected in an intermediate portion of regenerator vessel 10 and are subsequently removed via conduit 13 and introduced into reactor riser 2 as described hereinabove.
  • Control valve 14 is located in conduit 13 to control the flow of regenerated catalyst and low-coke-make solid particles in response to a temperature measurement, and control means 15 receives and transmits the appropriate signals via means 16 and 17.
  • temperature sensing means 16 is shown to be at the upper end of reactor vessel 4 near cyclone separator 5, any other suitable temperature associated with reactor vessel 4 may be selected to directly control valve 14. Flue gas exits regeneration vessel 10 via gas-catalyst separation means 11 and conduit 12.
  • Equation (1) may be used to estimate the fluid catalytic cracker (FCC) regeneration zone or regenerator temperature which will result when low-coke-make solid particles with known specific heat and coke making tendencies are circulated from the regeneration zone to the reaction zone:
  • FCC fluid catalytic cracker
  • regenerator temperature predicted by the hereinabove equation assumes that all of the independent operating variables of the FCC unit are held constant, while the low-coke-make solid particles are added into the circulating catalyst inventory.
  • These independent operating variables include feed temperature, feed composition, reactor temperature, extent of carbon monoxide combustion in the regeneration zone, plant pressure and catalyst type.
  • the only change which is allowed in the operation of the FCC unit is the addition of the low-coke-make solid particles to the circulating catalyst inventory.
  • the final regenerator temperature is a function of the quantity and specific heat of the low-coke-make solid particles, the specific heat of the FCC catalyst, the regenerator temperature before the addition of low-coke-make solid particles and the coke making tendency of the low-coke-make solid particles and the FCC catalyst.
  • any coke deposited on the low-coke-make solid particles will displace coke that formerly would have been generated by the circulation of FCC catalyst.
  • coke deposited on the low-coke-make solid particles will tend to reduce the number of catalyst particles delivered to the riser per pound of feed as defined as the catalyst to oil ratio.
  • the conversion observed in the FCC reactor will decrease. This is a strong incentive to select low-coke-make solid particles which make little or no coke in order to have the least detrimental impact on the performance of the FCC reactor.
  • Tests were conducted in a commercial fluid catalytic cracking plant to illustrate the advantages of the present invention. The tests were based upon cracking a blend of vacuum gas oil and atmospheric resid. Both the vacuum gas oil and the atmospheric resid were derived from a domestic crude oil and the blend contained 8.4 liquid volume percent atmospheric resid. An analysis of these feed components is presented in Table 1.
  • the tests were conducted in an upflow riser with a zeolite fluid cracking catalyst.
  • the operating conditions of both tests include a reactor pressure of 18 psig (1124 kPa gauge).
  • the first test was conducted as a base case and is representative of a conventional FCC unit processing a feedstock comprising atmospheric resid. This test was conducted at a catalyst to oil ratio of 6.7, a feed temperature of 441°F (227°C), and a reactor temperature of 972°F (521°C) with a resulting regenerator temperature of 1368°F (774°C).
  • the fresh feed conversion was 81.7 liquid volume percent while producing gasoline in an amount of 62.5 liquid volume percent and having a research octane number of 92.7.
  • the coke yield was 5.6 weight percent of the feed.
  • the second test was conducted as a comparative case and is illustrative of one embodiment of the present invention.
  • This test was conducted with the same feedstock comprising atmospheric resid as the first test.
  • This test was conducted at a catalyst to oil ratio of 6.5, a feed temperature of 475°F (246°C) and reactor temperature of 970°F (520°C).
  • the circulation catalyst stream to the reactor also contained low-coke-make inorganic oxide solid particles in an amount of 9 weight parts catalyst to one weight part low coke make solids or a catalyst to low-coke-make solids ratio of 9:1.
  • the low-coke-make inorganic oxide solid particles used in this test were alpha alumina particles which possessed a surface area of less than about 1 m 2 /g and which particles generate 0 weight percent carbon on the spent alpha alumina in the ASTM standard method for testing fluid cracking catalyst by microactivity test (MAT).
  • the resulting solids (catalyst plus low-coke-make solid particles) to oil ratio was therefore 7.5.
  • the regenerator temperature was found to be only 1337°F (725°C) as compared to 1368°F (742°C) for the first test.
  • the feed conversion was 80.5 liquid volume percent while producing gasoline in an amount of 62.7 liquid volume percent and having a research octane number of 92.5.
  • the coke yield was 5.6 weight percent.
  • the temperature of the feed in the second test was 475°F (246°C) while the feed temperature in the first test was 441°F (227°C) or 34°F (18.9°C) less. It is well known for this type of FCC operation that an increase in the feed temperature causes an increase in the regenerator temperature. Therefore, with a lower feed temperature in the second test, a correspondingly lower regenerator temperature would have been expected which would have demonstrated an even greater reduction in the regenerator temperature. The results of both tests are presented for ease of comparison in Table 2.
  • the resulting lower regenerator temperature helps to maintain the cracking activity of the catalyst, provides increased flexibility in the choice of operating conditions and eliminates, or at least reduces, the requirement to provide external cooling facilities for the catalyst regenerator.
  • the temperature of the regenerator may also be controlled independently by varying the proportion of low-coke-make solids in the catalyst plus low-coke-make solids mixture.
  • the hereinabove described gas oil feed which was used in this example was similar to, but not identical to, the ASTM standard feed referred to in the ASTM standard procedure and was selected in an attempt to duplicate the ASTM standard feed.
  • the present test comprises loading a sample of particles weighing 4 grams into the reactor and injecting the hereinabove described gas oil in an amount of 1.3 grams over a 75 second period into the reactor which is maintained at 900°F (482°C).
  • the resulting particles to oil weight ratio is about 3 and the weight hourly space velocity is about 15.4.
  • the gamma-alumina which was tested is representative of the alumina having a surface area of 30-1000 m 2 /g and a pore volume of 0.05­2.5 cm 3 /g and which is taught as a diluent for catalytic cracking catalyst in British Patent No. 2,116,062 (Occelli, et al.).
  • the data from Table 4 show that gamma-alumina demonstrates a conversion of 7.3 volume percent, accumulates 0.32 weight percent coke on the spent gamma-alumina particles and has a surface area of 205 m 2 /g.
  • the particles selected to perform the function of low-coke-make solid particles must necessarily produce less than about 0.2 weight percent coke on the spent particles in the ASTM standard method for testing cracking catalyst by microactivity test (MAT), have a surface area of less than about 5 m 2 /g and not substantially affect the operation of the reaction zone. Therefore, since the gamma-alumina accumulated a relatively substantial amount of coke and had a propensity to convert hydrocarbons thereby having the undesirable ability to affect the operation of an FCC reaction zone, gamma-alumina is not a satisfactory candidate for use as the low-coke-make solid particles in the present invention.
  • calcined kaolin clay which was tested as hereinabove described is believed to be representative of the calcined kaolin clay which is taught as a large pore inert material to be added with active catalyst in U.S. Patent No. 4,289,605 (Bartholic).
  • the data from Table 4 show that calcined kaolin clay demonstrates a conversion of 6.6 volume percent, accumulates 0.08 weight percent coke on the spent kaolin clay particles and has a surface area of 9 m 2 /g.
  • the particles selected to perform the function of low-coke-make solid particles must necessarily produce less than about 0.2 weight percent coke on the spent particles in the ASTM standard method for testing cracking catalyst by microactivity test (MAT), have a surface area of less than about 5 m 2 /g and not susbtantially affect the operation of the reaction zone. Therefore, since the calcined kaolin clay accumulated measurable coke, had a propensity to convert hydrocarbons thereby also having the undesirable ability to affect the operation of an FCC reaction zone and had a surface area of 9 m 2 /g, the calcined kaolin clay, as tested, is not considered to be a satisfactory candidate for use as the low-coke-make solid particles in the present invention.
  • MAT microactivity test
  • preferred low-coke-make particles are fluidizable alpha-alumina particles.
  • the data from Table 4 show that alpha-alumina demonstrates what is considered a minimal conversion of 4.1 volume percent, accumulates no detectable coke on the spent alpha-alumina in the ASTM standard method for testing fluid catalytic cracking catalyst by microactivity test and has a surface area of less than 1 m 2 /g.
  • the fludizable low-coke-make solid particles have a surface area of less than 5 m 2 /g and generate less than 0.2 weight percent coke on the spent low-coke-make solid particles in the ASTM standard method for testing fluid cracking catalyst by microactivity test (MAT).
  • Fluidizable low-coke-make solid particles which generate substantially less than 0.2 weight percent coke on the spent low-coke-make solid particles in the ASTM standard method for testing fluid cracking catalyst by microactivity test (MAT) are even more preferred.
  • Most preferred low-coke-make solid particles have a surface area of less than 5 m 2 /g and generate less than 0.05 weight percent coke on the spent low-coke-make solid particles in the ASTM standard method for testing fluid cracking catalyst by microactivity test (MAT).
  • any coke that is formed on the fluidizable solid particles added for purposes of temperature control is necessarily produced by nonselective cracking of the feed stream and thus has a significant adverse affect on the yield structure of the products from the reactor.
  • This adverse affect of the solid adjuvant is of course magnified as the level of coke formed increases and thus a low-coke-make characteristic is an essential feature both for proper operation of the reactor and for achieving temperature reduction in the regenerator.

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EP85116235A 1985-02-20 1985-12-19 Reducing the temperature in a regeneration zone of a fluid catalytic cracking process Expired EP0195129B1 (en)

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AT85116235T ATE36553T1 (de) 1985-02-20 1985-12-19 Temperaturverminderung in einer regenerationszone eines katalytischen fluid-crackingprozesses.

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CA1154735A (en) * 1978-09-11 1983-10-04 Stanley M. Brown Catalytic cracking with reduced emissions of sulfur oxides
US4311581A (en) * 1980-01-07 1982-01-19 Union Oil Company Of California Process for reducing CO and SOx emissions from catalytic cracking units
AU557769B2 (en) * 1981-09-14 1987-01-08 W.R. Grace & Co.-Conn. Catalytic cracking of sulphur-bearing hydrocarbon feedstocks and spinel component catalyst
GB2114146A (en) * 1982-01-29 1983-08-17 Engelhard Corp Preparation of FCC charge by selective vaporization
AU555438B2 (en) * 1984-01-04 1986-09-25 Mobil Oil Corp. Fcc process
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PL145514B1 (en) 1988-09-30
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AU5120985A (en) 1986-08-28
DD253576A5 (de) 1988-01-27
BR8600707A (pt) 1986-10-29
CN1004141B (zh) 1989-05-10
KR900000891B1 (ko) 1990-02-17
SU1436885A3 (ru) 1988-11-07
CA1264693A (en) 1990-01-23
ES8801359A1 (es) 1987-12-16
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HUT44066A (en) 1988-01-28
ZA859538B (en) 1986-08-27
AU572370B2 (en) 1988-05-05
NO855323L (no) 1986-09-02
EP0195129A1 (en) 1986-09-24
ATE36553T1 (de) 1988-09-15
CS112186A2 (en) 1987-09-17
ES550983A0 (es) 1987-12-16
CS257282B2 (en) 1988-04-15
NO166454B (no) 1991-04-15
KR860006526A (ko) 1986-09-11
GR860160B (en) 1986-05-21
NO166454C (no) 1991-07-24
JPH0349316B2 (el) 1991-07-29
DE3564445D1 (en) 1988-09-22

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