DE2328679A1 - METHOD FOR CONTROLLING A CATALYTIC FLUIDED BED CRACK SYSTEM - Google Patents

Description

Patent assessor Hamburg, May 31, 1973

Dr. G-. Schupfner T 73048 (D TO, 960-P)

GERMAN TEXACO AG 769 / HH

2000 Hamburg 76 9 ^ 28679

Sextuple gate 2

TEXACO DEVEIOPMENT CORPORATION

135 East 42nd Street

New York, N.Y. 10017

UNITED STATES.

Method for controlling a catalytic fluidized bed

Cracking plant

The present invention relates to fluid catalytic cracking. In particular, this invention relates to a method for controlling fluidized catalytic cracking to to obtain a desired product distribution.

In a fluid catalytic cracking process, hydrocarbon oil reacted with a catalyst in a reaction zone under conditions such that the hydrocarbon in desired products is converted with simultaneous coke deposition on the catalyst. The one removed from the reaction zone Catalyst can come into contact with a stripping medium in a stripping zone to remove entrapped hydrocarbon oil remove the same. The stripping medium and removed carbon • '-2-

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hydrogen can be introduced into the reaction zone from the stripping zone. The stripped catalyst can leave the stripping zone are fed into a regeneration zone in which the stripped catalyst is burned off the coke therefrom using an oxygen-containing gas such as e.g. air is regenerated. Hot, regenerated catalyst can be withdrawn from the regeneration zone and with more Hydrocarbon are reacted in the reaction zone. Hydrocarbon vapors from the reaction zone can be in a Fractionation zone are given, in which the vapors are separated into fractions according to their boiling range. A fraction consisting of G-asolin and lighter components, can be drawn off overhead and a heavy circulating gas oil fraction as bottom product from the fractionation zone. One light cycle gas oil fraction, useful as fuel oil, can be recovered as a liquid side stream from the fractionation zone will. A medium circulating gas oil fraction can be collected in an enrichment section in the fractionation zone, from which a second circulating gas oil stream can be drawn off. All or part of the mean cycle gas oil flow can be returned from the fractionation zone to the reaction zone for further conversion into desired products.

The yield of desired products from such a fluidized catalytic cracking process can be within one specific range can be controlled by selecting the hydrocarbon conversion conditions in the reaction zone and / by selecting the circulation speed of the middle circle

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Running gas oil stream from the fractionation into the reaction zone. For example, the product speed may be light Circuit gas at the expense of the other products during the Months in which the demand for heating oil is high can be increased and decreased with a simultaneous increase in the Gasoline production during the months when gasoline demand is high.

The hydrocarbon oils entered into the reaction zone are heated to temperatures of about 232 to about 399 ⁰ C. Preferably the preheat temperature of the hydrocarbon oils does not exceed the temperature at which significant thermal cracking begins to occur. Such hydrocarbon preheating temperatures are generally below the desired reaction temperature. The additional heat required to raise the hydrocarbon temperature in the reaction zone to the desired reaction temperature is provided by the hot, regenerated catalyst. As the coke is burned off the stripped catalyst in the regeneration zone, the temperature of the regenerated catalyst rises to about 593 to about 677 C. A desired temperature of the regenerated catalyst can be obtained by controlling the amount of heat withdrawn from the regeneration zone.

The preferred reaction temperature for hydrocarbon conversion is about 471 to about 53O ⁰ C. The hydrocarbon oil is heated to a temperature so that the regenerated catalyst

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_y can be added lyst in a catalyst-oil weight ratio of about 3 to about 15 to the hydrocarbon temperature to the selected reaction zone temperature to increase, while an acceptable regeneration zone temperature is maintained.

A well-known fluidized bed catalytic cracking process to To obtain desired products in a selected ratio, the hydrocarbon feed to a to .heat selected temperature to control the addition of regenerated catalyst to hydrocarbon to maintain a selected reaction temperature and an average Recycle gas oil at a selected rate. Gasoline and lighter products are removed from the fractionation zone immediately removed after their creation. The heavy cycle gas oil fraction also becomes immediately after generation removed from the fractionation zone. The light cycle gas oil is extracted from the fractionation zone at a rate of around one constant level of medium circulating gas oil in the approach section to maintain the fractionation zone, decreased, The circulation rate of the medium circulation gas oil and the reaction zone temperature can be varied to the desired one Obtain product distribution. For example, increasing the reaction zone temperature leads to an increase in the Production of lighter products and it leads to increasing the cycle speed of the middle cycle gas oil a decrease in the yield of the light cycle gas oil, since a jeil of light cycle gas oil a collection on that

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Trapping soil for the middle cycle gas oil must be allowed, to maintain the liquid level on the floor. By suitable selection of the cycle speed of the mean cycle gas oil and the reaction zone temperature a "broad product distribution between light products, the gasoline and the light recycle gas oil fraction can be obtained. A disadvantage with this method of controlling a fluidized bed catalytic cracking plant is that both The reaction zone temperature and the cycle speed of the middle cycle gas oil must be regulated at the same time, to get the mixed product distribution.

There has now been an improved method of controlling a catalytic Fluidized bed cracking plant to obtain a desired product distribution found. This new procedure concerns withdrawing light cycle gas oil from a fractionation zone at a selected rate, recycling medium Gas oil from the fractionation zone into the reaction zone at a given rate and maintaining a substantially constant gas oil liquid level in an enrichment section the fractionation zone by adjusting the ratio of regenerated catalyst to hydrocarbon in the reaction zone.

The advantage of this process is that it is easy to cycle gas oil is produced at a rate that corresponds to the market demand for this product and the product distribution between gasoline and lighter products can be within

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a wide range by changing the circulatory speed of the middle cycle gas oil can be set.

The accompanying drawing is a schematic diagram of a fluidized bed catalytic cracking plant and gives the improved, control method according to the invention again.

Fluidized bed catalytic cracking plants and processes are known. Fresh hydrocarbon feeds for such a plant, such as distillate fractions from crude oil, are also known. A wide range of catalysts, such as synthetic SiOp / aluminum oxide, synthetic SiOg / MgO, SiOp / Alumina Zeolite, Natural Clays, Acid Treated natural clays, etc., are available for use in such facilities.

With the development of vortex catalytic power cracking, it has been found that an improved yield of gasoline and light cycle gas oil by applying a relatively short Contact period with good contact of hydrocarbon and Catalyst is obtained in the reaction zone. An improved contact between hydrocarbon and catalyst can by. Using a reaction zone structure, consisting of a reactor, an adjacent and above-arranged regeneration zone and a riser line. at Using this setup, hydrocarbon enters at the bottom of the riser and regenerated catalyst becomes the Steiger fed from the regeneration zone. Catalyst and

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Hydrocarbon fHessen through the riser under reaction conditions, so that a substantial part of the hydrocarbon conversion occurs in the riser, upwards. The catalyst hydrocarbon -Mixture flows from the riser into the reactor. In the reactor, the catalyst inventory is in the fluidized bed state kept by the fact that hydrocarbon vapors from the Risers and other vapors, such as primary stripping steam, flow through the catalyst. The arrangement of the riser outlet in the reactor is chosen so that the discharged Hydrocarbon vapors in contact with the catalyst inventory in the reactor for a period of time which is further desired Hydrocarbon conversion in the reactor is sufficient, occur can. The desired amount of catalyst in the reactor is maintained by discharging catalyst into a stripping zone. In the stripping zone, trapped hydrocarbons are separated from the catalyst with the aid of stripping steam. Of the Stripping steam and the separated hydrocarbons are fed into the reactor and the stripped catalyst into the regeneration zone. The carbonaceous deposits known as coke are stripped of the catalyst using oxygen-containing gas, such as air, burned off in the regeneration zone. Regenerated catalyst is from the regeneration zone to react with other hydrocarbons in the Steiger led.

Hydrocarbon vapor is withdrawn from the reactor and passed into an Eraktionierzone, in which the steam in a Gasoline and lighter fraction, in a light cycle gas

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oil fraction ₉ as a liquid side stream of the fractionation zone, and is separated _{into a heavy cycle gas oil fraction 9 as the bottom product of the fractionation zone.} The Fraktionier ™ zone is equipped with facilities, such as a collecting floor, for collecting a volume of medium circulating gas oil in an enrichment section of the fractionating zone. A recycle stream of medium recycle gas oil is withdrawn from the Praktierzone at a selected rate and fed into the reaction zone for further conversion in the presence of regenerated catalyst.

When the process according to the invention is applied to a catalytic fluidized bed cracking process, the precipitation zone can be provided with a level indicator ^ um the proportion of the middle cycle gasölS; which is in the enrichment. section has accumulated to determine, the gasoline and lighter The fraction containing products is taken off from the Praktierzone as it was produced, "the light circulating gas oil removed from the fractionation zone at a selected rate and the recycle stream of the middle recycle gas oil adjusted to a desired "rate of the fractionator in the reaction zone. Catalyst from the Regeneration zone is introduced into the reaction zone with the catalyst-oil ratio adjusted to a desired one The product distribution is to be maintained to maintain the liquid level of the medium circulating gas oil in the enrichment section between gasoline and lighter products, the desired range is achieved through a suitable selection of the circulation speed.

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ness of the heavy cycle gas oil fraction of the set, the heavy cycle gas oil _s such as it is created withdrawn from the fractionation · and may be recycled for further conversion or in the reaction zone are discharged as product _o

In developing the fluidized catalytic cracking process was found _s that the circulation materials heat-resistant and thus more difficult than the fresh feedstocks to be converted _"P To get a better product distribution, the more refractory circuit materials under more severe Bediigrngen are cracked as the fresh feedstocks"

Advantageously, two risers can be used in the catalytic fluidized bed cracking process _o Preheated fresh hydrocarbon feed and regenerated catalyst from the regeneration zone are introduced into a first riser. An optimal conversion of the fresh feed to desired products can be obtained by controlling the reaction conditions "off are obtained in the first riser to the first riser enters the content in.'den reactor at an intermediate point, which is arranged in such a _s that of the emitted hydrocarbon in contact with the catalyst component during a relatively short period of time occurs, a ₀ For example, may be bent to the output of the first riser down and can phase immediately above the surface of the dense fluidized bed catalyst "that exists in the reactor _{s o} be disposed by this

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Arrangement, the downwardly directed hydrocarbon output of the first riser only comes into contact with the catalyst inventory of the reactor for a short time are relatively stricter than the reaction conditions used in the first riser for the fresh feed ₀ The contents of the second riser can be discharged into the reactor at a point below the discharge of the first riser The area of the catalyst stock in the reactor occurs as the hydrocarbon released from the first riser * This additional contact of the circulating hydrocarbon with the catalyst in the reactor increases the conversion of the circulating hydrocarbon.

When applying the inventive method to a fluid catalytic cracking process in which two separate risers for fresh hydrocarbon feed and for cycle material can be used Modification of the tax procedure can be made. In one embodiment, a G-asolin and lighter products are developed, holding fraction as generated, sucked out of the fractionation zone, light cycle gas oil at a selected one Speed decreased and medium cycle gas

oil from the fractionation zone into the second riser at a ■ ■ -. -11-

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Target velocity returned a üiveauanzeigeeinriehtung _s is used agree to loading ■-liquid level cycle gas oil in the enrichment section .the fractionation around. The heavy cycle gas oil fraction is, as it was created _a from fractionation withdrawn Preferably reaction conditions are maintained in the first Steiger to ensure optimal conversion to receive fresh feed to desired products "A method ^ to this optimal conversion to obtain _{s 9} is to monitor the reaction temperature in the first riser and the ratio of regenerated catalyst to the oil einzustellenj to obtain the optimum conversion temperature for the fresh Beschikkung. The conversion of the middle cycle gas oil recirculation in the second riser is done by entering regenerated catalyst. the regeneration zone into the second riser "in a catalyst ~ oil ~ Yerhältnis _Q which is sufficiently ₉ to the cycle gas oil fluid level in the enrichment section of the fraction! pedestrian area to maintain ,, controlled. The conversion rate of the fresh feed is adjusted to the desired product distribution between advertising Where to get gas oil and lighter products "By applying this embodiment des.erfindungsgemäßen Terfahrens an optimum yield of desired products from fresh charges related to a conversion step · to ₀ shares desired products in a ausgewähl-. th product distribution can from the repayment medium cycle gas oil are obtained,

• · - 12 -

The inventive method is based on the drawing showing an embodiment explained in more detail ι A preheated Frisehgasöl-Beschickungj boiling point 232-566 ⁰ C, from the line (10) with hot, regenerated catalyst entstammend the standpipe (H) _5, brought at about 582 ⁰ C at the entrance part of the fresh raw material riser (12) in contact. The resulting catalyst-oil vapor mixture with a temperature of about 493 C and an average speed of about 12.2 m / sec, producing a residence time of about 4 seconds, flows up through the riser (12) into the reactor ( 13), the riser (12) ending in a downwardly directed outlet. The catalyst-oil G-ewichtsverhältnis in Steiger (12) is about 9 _S 8 j 1. A substantial conversion of the fresh material occurs in the riser (12) and at these conditions, about 30 parts by volume of fresh feed in Jo below 221 ⁰ C boiling products converted. The desired reaction temperature in the upper part of the riser (12) is obtained by using a temperature response device (15) to adjust a slide valve (19) so that the proportion of regenerated catalyst which is fed from a regeneration zone (20) into the riser (12) is controlled. The slide valve (19) controls the speed of the proportion of regenerated catalyst entering the riser (12) in such a way that a desired reaction temperature is maintained in the upper part of the riser (12). Regenerated catalyst from the regenerator (20) flows through the standpipe (52), through the slide valve

(19) into the standpipe (11) _e The

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regenerated catalyst in the riser (12) _o The feedback of the average cycle gas oil takes place via the line (21) in the inlet part of the circulation riser (22) _s in which the mean cycle gas oil with the regenerated catalyst from a second standpipe (23) at about 582 ° C in contact trittο the resulting catalyst cycle gas oil steam mixture flowing at 510 ⁰ C upwardly through the riser (22) at an average speed of about 9 _S 15 m / sec and an average residence time of about 5 seconds * the other conditions in the Steiger (22) contain a catalyst to oil weight ratio of ΙΟ.2; 1 and a space velocity (based on weight) of 45 °, about 60 VoI, -% of the cycle gas oil are converted to below 221 ⁰ C boiling products in the riser (22) "

The riser (22) ends in a downwardly directed outlet in the reactor (13). The hydrocarbon vapor outflow from the riser (22) pours into the reactor (13) and rises up through the dense fluidized bed of the catalyst _? which brings about a further conversion of cycle _{gas oil in about 74 5} 5 % of products boiling below 221 G. The reaction conditions in the reactor fluidized bed are 504 ° C. and a space velocity of 12.8 (based on weight). The cracking of fresh feed and recycle gas oil in the risers ^ and the cracking in the reactor bed resulting in a total conversion of about 65.2 VoI .-% of the fresh feed in below 221 C boiling products and the yield of light cycle gas oil from 24 "6 VoI _o -% (based on fresh loading).

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Be the vapor velocities in the reactor (13) O ₉ 46 m / sec at the point at which the riser (22) empties, I ₉ O m / sec at the point at which the riser (12) exhausts' and 0 , 49 m / sec in the upper part of the reactor, above the fluidized bed phase »

Evaporated products separate from the dense ones at level (25) Catalyst phase with a steam velocity of about 0.24 m / sec. Vapors and entrained catalyst flow through a cyclone (26) in which the entrained catalyst is separated off and through the dip tube (27) into the catalyst bed is returned »Although only one cyclone is shown, it is evident that several cyclones can also be interconnected for essentially complete separation to achieve, and it can be used several cyclone interconnections to control the steam volumes that occur. The outflow vapors from the cyclone (26) flow through the line (28) into a collection chamber (29) in which the Vapors from the other cyclone interconnections (not shown) are collected and withdrawn from the reactor (13) via line (30) will. The steam line (30) conveys the reaction products into a fractionation column (54).

Steam coming from line (31) is sent through the steam ring (32) and into the lower part of the reactor (13) a point below the exit of the riser (22) is, entered ,, the dense catalyst phase in the lower part of the reactor is stripped by the steam and flows down

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through the standpipe (33) and the catalyst valve (34) into the stripping zone (35). Steam coming from the line (37) entered through the steam ring (38) in the lower part of the stripper (35). The steam rising through the stripper (35) removes trapped and entrained hydrocarbon vapors and rises up through the stripper exhaust line (39) in the upper part of the reactor (13) «

G-stripped catalyst is drawn off at the bottom of the stripper (35) through the standpipe (40) for used catalyst at a rate controlled by the slide valve (41) and fed into the regenerator (20) through line (42). 20) the spent catalyst is contacted with by the line (43) and the air ring (44) introduced air ο oxygen from the air operates the combustion of the accumulated on the stripped catalyst coke _s wherein the catalyst is regenerated ,, the regeneration in The catalyst underlying the regenerator (20) forms a dense fluidized bed with the level (45) ° The flue gas from the coke combustion flows upwards and enters the cyclone (46) _? in which entrained catalyst is separated and through the dip tube. (47) is returned to the dense bed. Although only one cyclone (46) is shown _8, a series of cyclones connected in parallel or in series ^ are arranged "so as to substantially complete removal of the entrained solids from the flue gas to cause" exhaust gas from the cyclone (46) flows through the Line (48) into the collecting chamber (49) and from there through the flue gas line (50) into the exhaust gas device

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services (not shown). Regenerated catalyst is at the bottom of the regenerator (20) through the standpipes (51) and (52) at the speed controlled by the slide valves (19) and (53) withdrawn ^ to supply the standpipes (11) and (23) with hot, regenerated catalyst *

Product vapor in the line (30) flows into a fractional distillation column (54) _s in which the product vapor is separated into desired fractions. A vapor fraction consisting of gasoline and lighter hydrocarbons is taken off at the top of the column (54) via line (55). The vapor fraction flows from the line (55) into the condenser (56), in which essentially all of the gasoline is condensed. From the condenser (56), condensate and non-condensed vapors flow through line (57) into a tank (58) in which the non-condensed vapors are separated from the condensate. The non-condensed vapors "containing material such as gasoline, are withdrawn from the collector (58) via the line (59) for further treatment". A third of the condensate, containing gasoline, is returned from the collector (58) through the line (60) as overhead reflux into the column (54). Product gasoline is withdrawn from the collector (58) through line (61) for further treatment. Water; which consists of condensed stripping steam from the reactor (13) is collected in the immersion tube connected to the collector and from there via line (63) removed.

A liquid! Fraction consisting of light cycle gas0I ₉

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\ iird from the column (54) through the line (64) into a storage facility withdrawn »A selected rate of decrease of the light cycle gas oil is achieved by the appealing • flow control device (65) maintained

A heavy recycle gas oil precaution is made at the bottom of the column (54) withdrawn through line (66)

In the column (54), a liquid Praktion ,, containing medium Kreislaufgasölj collected on a Pangboden (67) 0 a recycle stream ₉ containing mid-cycle gas oil j, via the line (68) at a through from the bottom (67) the responsive flow control device (69) controlled target speed subtracted From the device (69) the gas oil circuit stream flows at about 332 ⁰ C through the line (21) to the inlet part of the riser (22) "The temperature ₉ at which circuit stream of the middle circuit gas oil is transferred , is about the boiling point temperature of the medium circulating gas oil collected on the Pangboden (67) = Praction ₀ If desired, a product from the medium circulating gas oil can be withdrawn through the line (71) to a storage facility.

The level (72) of the accumulated gas oil is controlled by controlling the conversion of the intermediate cycle gas oil in the riser (22) maintained a level response control means (70) represents the gate valve (53) "through which the regenerated catalyst through the standpipe (23) in the riser ( 22) a '

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occurs, a "The degree of conversion of the circulation in the riser (22) v / ill be determined by the ratio of regenerated catalyst for circulation in the riser (22) ,, For example, the" catalyst-oil ratio in riser (22) 'increases _s growing the conversion of intermediate cycle gas oil and the proportion of non-converted circuit ₉ of the collecting tray _s returns decreases. Since the velocity of circulation of the intermediate cycle gas oil is given, thus lowering the level (72) ₀

The product distribution between gasoline and lighter products can be determined by a suitable selection of the circulation speed of the medium circulating gas oil to be regulated «To achieve a material equilibrium To maintain in the catalytic fluidized bed cracking process, the middle cycle gas oil must be used in the Net speed at which it is generated and on the collecting tray (67) collects, are consumed «, the proportion middle Recycle gas oil, which must be converted per pass through the reaction zone, is determined by the net velocity the accumulation of medium circulating gas oil on the collecting tray (67) is determined. At relatively high rotational speeds the fraction of the circulating flow which has to be converted per passage through the system “to keep the system in equilibrium to keep it low. This means that relatively mild cracking conditions can be used in the riser (22). Under relatively mild ' Cracking conditions, the ratio of light cycle gas oil increases too light hydrocarbons «,

At relatively low circulation rates, the fraction is

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to maintain the recycle stream, which must be converted per pass to the system equilibrium ,, grown and will be sharper Crackledingungen _s required to collect the fraction ¹ of the converted recycle stream to increase ,, under stringent Grackbedingungen the conversion is the circuit in lighter hydrocarbons increasingly preferred at the expense of the light cycle gas oil. Thus, a product distribution range between light circulating gas oil, gasoline and lighter products can be obtained through a suitable selection of the circulation speed of the medium circulating gas oil «,

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Claims (4)

. - 20 - T 75048 P a t ent an. s' ρ r ü c Ii e J) Method for controlling a catalytic fluidized bed cracking plant, consisting of a reaction zone, a regeneration zone and a zone for fractional distillation, in which carbon oil with regenerated catalyst from the regeneration zone in the reaction zone under reaction conditions to convert part of the hydrocarbon oil into desired products comes into contact, product hydrocarbon vapors from the reaction zone in the distillation zone are separated into gasoline and lighter products, a light cycle gas oil and a heavy cycle gas oil fraction, a medium cycle gas oil fraction is collected in an enrichment section of the distillation zone and a cycle flow of the middle cycle gas oil into the reaction zone is returned, characterized in that a product stream of the light cycle gas oil is removed from the distillation zone at a selected rate, at a set speed, a flow of the middle cycle gas oil is returned from the enrichment section to the reaction zone
and the hydrocarbon conversion is adjusted to a 4098 8 1/0 539 Volume of medium cycle gas oil in the enrichment section to obtain. 2.) Method according to claim 1, characterized in that that the hydrocarbon conversion is adjusted by controlling the proportion τοη in the Regenerated catalyst introduced into the reaction zone. 3.) Method according to claim 1 or 2, characterized that a selected product distribution between light gas oil and lighter hydrocarbons by choosing an appropriate circulation rate of the middle cycle gas oil is obtained. 4.) Method according to one of claims 1 to 3, characterized in that the addition is regenerated Catalyst to the reaction zone by means of a to the level of the accumulated medium cycle gas oil in the enrichment section appealing facility is controlled, 409881/0 539 3Z Blank page