JPH0211637B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for fluid catalytic cracking of a hydrocarbon feedstock in a reactor system comprising an interconnected cracking zone and a regeneration zone. Fluid catalytic cracking has long been considered one of the primary gasoline production methods in the refining industry. Typically, the feedstock used is a distillate, such as gas oil, and the operating conditions are for relatively high conversions of the gas oil feedstock to allow maximum yield of gasoline. has been selected. The cracking of gas oil to gasoline is well understood and the limits placed on the feedstock gas oil are well defined. The main limitations currently placed on gas oil feedstocks are the amount of carbon or "coke" precursors and the amount of metal compounds included in the feedstock. These coke formers or precursors, which are typically high molecular weight fused ring hydrocarbons, are primarily a function of the crude feed type and boiling range of the material. Results obtained by Conradson or Ramsbottom carbon residue analysis indicate the approximate extent of the coking tendency of these compounds and feedstocks. It is generally desirable to limit the amount of these compounds in the gas oil feed to 0.5% by weight or less by Conradson method. The reason is that if the coke precursor compounds in the gas oil are allowed to increase, more coke can deposit on the catalyst in the hydrocarbon reaction zone than is required for the heat balance of the process. Because it will be. Coke is CO and/or _CO2
The temperature in the regeneration zone where the catalyst is oxidized to can become too high and the catalyst grain temperature can rise to such a temperature that the catalyst structure is harmed or destroyed resulting in a loss of activity. The second major limitation imposed on gas oil is the presence of organic nickel (Ni)-containing compounds, organic vanadium (V)-containing compounds and organic iron (Fe) in gas oil.
This is the content of the contained compounds. These compounds, commonly called "porphyrins", distill out in the high boiling fraction of vacuum gas oil. Additionally, inorganic metal compounds may also be present. Typically, the metal content is
Weight ppm determined by the formula NE=Ni+0.3×V
The nickel equivalent given by should be limited to less than 0.4. The circulating catalyst absorbs the metals almost completely and its performance decreases. These metals in an active state on the catalyst can reduce the yield of the main gasoline product, promote various dehydrogenation reactions, and produce large amounts of hydrogen and coke. This leads to a large buildup of undesired gases, leading to rapid overloading of the gas compressor and gas recovery equipment. Residual oils such as whole crudes or atmospheric reduced crudes
In addition to being more difficult, if not impossible, to completely vaporize, the residual oil has a higher amount of “coke” than typical gas oil.
precursors (measured by Conradson or Ramsbottom carbon residues) and large amounts of metallic Ni,
It is clear that it contains V and Fe. Despite the potential processing difficulties posed by the presence of such contaminants, refiners are encouraged by the frugality of crude oil supplies to move beyond the relatively clean nature of distillates such as gas oil. , attempts have been made to expand the nature of the feedstock charged to fluid catalytic cracking processes.
To increase the availability of feedstocks to meet gasoline and fuel oil demands, high boiling point feedstocks, previously considered minimal or unsuitable due to such contaminants, are increasingly being considered. It's starting to look like this. The reaction conditions for the fluid catalytic cracking process typically consist of a temperature range of 425°C to 550°C, a pressure range of atmospheric to 4 bars absolute, and a catalyst to oil ratio of less than 7. The catalyst-to-oil ratio is the quotient of the catalyst circulation rate and the hydrocarbon oil feed rate (expressed in the same mass units). In a fluid catalytic cracking unit, to maintain equilibrium cracking conditions it is necessary to remove heat at a controllable rate from the regeneration zone where the carbon deposits are combusted and the spent catalyst is regenerated by an oxygen-containing gas such as air: This is because the regeneration heat added to the catalyst is transferred to the fresh oil feed to the cracking reactor. Continuous heat removal is also necessary to prevent excessive regeneration temperature levels that tend to sinter and deactivate the catalyst due to surface area reduction. Heavy hydrocarbon feedstocks, such as atmospheric residues, vacuum
residues), and heavy crude oils
When catalytically cracking , more carbon is deposited on the catalyst particles than in the case of cracking feedstocks such as gas oil. The problem of heat removal becomes even worse when the spent catalyst from catalytic cracking of such heavy hydrocarbon feeds is regenerated by combustion with oxygen-containing gas in a regeneration zone: since in this way This is because more heat than is used is released in the regenerator. With the introduction of more active zeolite-based cracking catalysts, the above-mentioned problems regarding heat balance, especially at maximum yield conditions, are becoming more critical:
This is because maximum product yields are now achieved with low coke formation and the heat balance is again disturbed. To avoid excessive cracking of the feedstock, it is necessary to reduce the severity of cracking when using more selective and active zeolite-based cracking catalysts. The severity of the decomposition is usually
“severity parameter”
(C/O/S _V ) where C is the catalyst circulation rate, O is the oil feed rate, and S _V is
space velocity). The C/O is
It is commonly referred to as the catalyst-to-oil ratio. All rates are given in mass units, usually tons/day. Reducing intensity can be accomplished in several ways.
One way to reduce the severity of decomposition is to reduce the catalyst circulation rate C. however,
This results in an increase in the temperature of the catalyst in the regeneration zone: since the reduced amount of catalyst provides the necessary heat for the endothermic cracking reaction, the same amount of coke in the exothermic regeneration reaction This is because approximately the same amount of heat that is emitted must be absorbed. As already acknowledged, excessive regenerator temperatures can spoil the catalyst and even damage the regenerator itself due to the resulting high catalyst particle temperatures. Further reduction in the severity of decomposition will therefore be limited by the maximum permissible regeneration temperature. Increasing the oil feed rate O, on the other hand, takes place by direct contact with the regenerated high-temperature catalyst and also by the mixing of the feedstock, which usually takes place in the so-called liftpot and in the so-called riser zone. This will cause problems with vaporization. Since the high temperature regenerated catalyst coming from the regeneration zone is used to provide the necessary heat for vaporization of the feedstock, lowering the catalyst-to-oil ratio typically reduces the temperature of the regeneration zone and the feedstock temperature. Vaporization may be adversely affected. Particularly with the heavy hydrocarbon feedstocks mentioned above, this poses a problem as insufficient vaporization of the feedstock leads to increased coke formation in the cracking zone. Although some coke production is required in fluid catalytic cracking processes due to the desired heat for feed vaporization, excessive coke production results in catalyst temperatures that are too high during regeneration. Another possible way to reduce the severity of decomposition is to reduce the severity of decomposition, e.g.
catalyst inventory).
The goal is to increase the space velocity S _V (ie, oil feed rate/reactor catalyst residual amount). however,
This results in the same problems discussed above with respect to reducing the catalyst to oil ratio. Furthermore, the need to maintain an upper level of the fluidized bed above the reactor draw-off standpipe limits the ability to reduce catalyst residuals. In catalytic cracking reactor systems, it is naturally desirable to regenerate the catalyst particles as completely as possible and to utilize all of the heat released by completely burning off the coke deposits. However, in practice, combustion is often incomplete: the carbon burns to carbon monoxide in the regeneration zone. The carbon monoxide is then oxidized to carbon dioxide in a separate flue gas combustor combined with a waste heat boiler to recover the chemicals and sensible heat present in the flue gas. The reason for this complex mechanism is that complete combustion in the direct regeneration zone is
This is because a large amount of heat will be released and the catalyst and/or regenerator material will be damaged. If it were possible to maintain the temperature of the regeneration zone below the normally accepted upper limit of 725°C while achieving so-called "complete CO combustion", this would represent a great simplification of the catalytic cracking process. Become. Unfortunately, most currently used heavier feedstocks produce so much coke deposits on the catalyst that complete CO combustion is not possible with these feedstocks. From the foregoing, it can be seen that the operation of a thermally balanced fluid catalytic cracking unit is constrained by several interacting operating conditions and that there is little flexibility left for changing the feedstock and/or catalyst. It is clear that this has not been done. It is better to operate the process to produce the optimum amount of middle distillate or the optimum amount of gasoline according to market demand, so the maximum regenerator temperature, the minimum regenerator temperature, the capacity of the equipment used, the catalyst The total heat balance requirements of the process, as determined by parameters such as activity and coking tendency of the feedstock,
There is clearly a need for an improved fluid catalytic cracking process that does not limit operational flexibility. It is therefore intended to provide a method for fluid catalytic cracking of hydrocarbon oils, and more particularly for treating more difficult to crack and/or more coking feedstocks. Such feedstocks include “residual oils,” meaning all hydrocarbons, regardless of initial boiling point.
There are heavy residual oils, such as tar,
Asphalt (bityumen), asphalten,
Contains resin, etc. Therefore, the remaining oil is the total crude oil,
It may be an atmospheric crude oil or even a residual oil fraction (having a boiling point above about 570-600° C. that remains after vacuum column distillation). However, some unusual feedstocks are also included, such as propane and butane deasphalted oils, extractives and pyrolyzed and flashed distillates. Usually the average carbon residue (the Conradson Carbon Residue of petroleum product test ASTM designation D18965)
Petroleum Productstest，ASTM designation
Feedstocks and/or feedstock mixtures having a nickel equivalent (as defined above) of less than 1.4 ppm can be treated according to the method according to the invention. It is intended to process a wide range of feedstocks, and the use of a wide range of catalysts is also contemplated. conventional cracking catalyst,
For example, crystalline aluminosilicates or iron silicates complexed with siliceous matrices such as silica-alumina, silica gel, etc., although amorphous catalysts based on natural or synthetic clays or on silica-alumina may be used. The use of preferably more active and/or more selective cracking catalysts comprising zeolates is contemplated. The process of the invention therefore allows a very wide variation of feedstocks, catalysts and products. The activity/selectivity of a particular catalyst composition is
It is conveniently expressed by its zeolite content.
The zeolite content is determined, for example, by French patent specification no.
It can be conveniently measured as described in US Pat. No. 2,330,756. The zeolite-containing catalyst is preferably a zeolite, in particular a natural or synthetic alkali metal aluminosilicate zeolite such as type X, type Y or type L, where at least
Most of the alkali metals are replaced by hydrogen or other metal ions, and the remainder is silica-alumina). The zeolite content is preferably between 1 and 10% by weight, based on the total catalyst composition, since application of too much zeolite leads to excessive decomposition, ie excessive gas formation. Accordingly, the object of the present invention is a method for fluid catalytic cracking of hydrocarbon feedstocks, in particular heavy residue hydrocarbon feedstocks, in which the heat balance of the reactor system as defined below is such that from the regeneration zone to the cracking zone The object is to provide a method that does not rely exclusively on heat transfer through circulating catalysts. A further object is to provide a process which makes it possible to obtain optimal yields of gasoline or middle distillates, depending on market demand, from heavy hydrocarbon feedstocks, in particular by applying catalysts based on zeolites. It is to be. Yet another object is to provide a fluid catalytic cracking process that can be operated with complete CO combustion when regenerating spent coke-containing catalysts. The general object of the present invention is to increase the operational flexibility of the process, regardless of the type of feedstock being treated or the type of catalyst used. These objectives are achieved in accordance with the present invention by removing heat from the bed of regenerated catalyst by indirect heat exchange with the fresh hydrocarbon feedstock to be treated to maintain the temperature of the regeneration zone below 725°C. achieved. Accordingly, the present invention provides a method for fluid catalytic cracking of a hydrocarbon feedstock in a reactor system comprising at least a cracking zone and a regeneration zone in communication with each other, the method comprising:
The hydrocarbon feedstock is contacted with a hot cracking catalyst in a cracking zone, thus at temperatures ranging from 425°C to 550°C.
at least a portion of the feedstock is vaporized and subsequently cracked into low-boiling hydrocarbon products under cracking conditions at a pressure range of atmospheric to 4 bar absolute and a catalyst-to-oil ratio of less than 7; The hydrocarbon products are separated and recovered from the spent catalyst, while the spent catalyst containing coke deposits is passed to a regeneration zone in which oxygen-containing gas is passed through the catalyst bed, thus A new method for fluid catalytic cracking of hydrocarbon feedstocks comprising oxidizing coke deposits with the generation of heat to regenerate and heat the catalyst, and then returning the hot regenerated catalyst to the cracking zone. Maintaining the regeneration zone temperature below 725°C by removing heat from the bed of regenerated catalyst by indirect heat exchange with the hydrocarbon feedstock, thus
heating the feedstock to a temperature of at least 200°C;
The present invention relates to a method for fluid catalytic cracking of a hydrocarbon feedstock, characterized in that the feedstock is then introduced into a cracking zone and brought into direct contact with a hot regenerated catalyst and vaporized at a temperature above 200°C. The main advantage of the process according to the invention is that the heat balance no longer depends solely on the heat transfer from the regeneration zone to the cracking zone due to the catalyst circulation. The possibility of extracting heat from the circulating catalyst by preheating the feedstock in the regeneration zone has been proposed, which is then fed to the endothermic cracking reaction. Thus, the method of the present invention allows greater flexibility in decomposition severity without exceeding regeneration zone temperature limitations. Vaporization by contacting the preheated feedstock with the hot catalyst occurs substantially quickly, thus minimizing the amount of liquid hydrocarbons in the pores of the catalyst. Liquid hydrocarbons remaining in the pores of the catalyst are a major source of excessive coke deposits when using heavy feedstocks. It is known per se to extract the heat generated during catalyst regeneration: e.g. in a bed of catalyst to generate high-pressure steam by indirect heat exchange with water or steam fed to coils e.g. several interconnected tubes. It is known to cause However, in such devices heat is irreversibly extracted from the reactor system. In the present invention, such heat generated is
It is used in the reactor system by reheating the feedstock to be treated in the same system. The products of the cracking process according to the invention are typically comprised of lower molecular weight and lower boiling point compounds than found in the initial feedstock. These products have particular use as feedstreams for the production of petrochemicals, polymers, gasoline and alkylates. The cracking method uses middle distillates, namely kerosene and gas oil (approximate boiling range 140-300°C and
180-370°C) and for maximum production of gasoline and naphtha in the boiling range of about 30-200°C, although some gaseous compounds such as lower olefins are always produced. . It is possible to perform indirect heat exchange between the beds of regenerated catalyst with fresh hydrocarbon feed in several ways. For example, it is possible to circulate the heat exchange fluid through heat exchange tubes located in the regeneration zone and then through a heat exchanger into which the feedstock is also led. However, this solution requires considerable investment and is usually not preferred. Typically, indirect heat exchange of the regenerated catalyst with fresh hydrocarbon feed is accomplished by passing the feed through one or more heat exchange tubes located in the bed of catalyst to be regenerated. be exposed. It has surprisingly been found that the presence of tubes in the fluidized bed (occupying approximately 20% of the bed area) has a further positive influence on the air bubble size and bubble distribution in the bed. The horizontal tube breaks up the bubble growth by splitting the rising bubble into a large number of smaller bubbles, which results in an increase in the mass transfer coefficient from the air to the catalyst particles: i.e. more coke , meaning that it can be burned with the same throughput of air. The dimensions and thickness of such tubes, as well as the type of material to be used, will be apparent to those skilled in the art of designing heat exchange equipment for the petroleum processing industry. During normal operation, the average temperature of the feedstock is 200℃
While increasing to higher temperatures, it has been found that rate regulation of the feedstock in the heat exchange tubes and heat transfer within the hydrocarbon feedstock prevents the temperature of the feedstock from rising too high anywhere. Although the maximum film temperature at the inner tube surface, about 400 °C, still occurs, such temperatures do not lead to appreciable thermal decomposition of the hydrocarbons: because the heat is immediately transferred to the bulk oil and the resulting This is because the temperature drops to The initial temperature of the feedstock to be processed in the catalytic cracking unit, ie before preheating according to the invention, depends on its source and the degree of cooling it undergoes during its production. In refineries, it is normal practice to minimize heat losses, so that the cracked feedstock, for example the residue of an atmospheric distillation unit or a vacuum reduction unit, is processed as soon as it is obtained.
Preferably, it is conveyed to the fluid contact unit via an insulated line. The (initial) feedstock temperature is then approximately 200°C or 250°C. The same applies to other feedstocks such as gas oil, deasphalted oil, etc. Sometimes oil-burning charge-preheaters will have to be used; for example, the initial temperature of the feedstock may be so low that the feedstock, even when preheated according to the invention, will have to be heated to a high temperature. is not heated to vaporization temperature by direct contact with freshly regenerated catalyst. On the other hand, sometimes a charge cooler will have to be used: for example, if the feedstock is difficult to decompose,
This is when a high degree of coking occurs which leads to too high a temperature of the catalyst particles. Preheating the charge material is expensive, and precooling the charge material, apart from being labor intensive, reduces vaporization of the feed material on contact with the hot catalyst. As mentioned above, if vaporization is poor,
Coke formation will increase and product yield will decrease. Therefore, hydrocarbon feeds with very high coke-forming properties, which are not amenable to catalytic cracking according to conventional methods of the art, can be cracked by preheating the charge in the regeneration zone according to the present invention. can be done. According to a preferred embodiment of the process of the invention, the fresh hydrocarbon feedstock prior to indirect heat exchange with the regenerated catalyst will have a temperature of at least 80°C and no higher than 250°C. Preferably, the fresh feedstock is heated by said heat exchange to a temperature in the range 250-425°C. Feedstocks between 80 and 150°C are said to be relatively cold, and feedstocks between 150 and 250°C are said to be relatively hot. The new feedstock is prepared according to the method of the invention, preferably at a temperature range of
Heated to 325-400℃. Temperatures in the range 350-400° C. should not be maintained for too long, since thermal decomposition can then begin.
However, this risk is minimal as long as the preheated feedstock is fed directly to the reaction zone. As previously mentioned, it is desirable but often impossible to perform fluid catalytic cracking with complete CO combustion. This is particularly difficult when attempting to process heavy coking feedstocks in reactor systems designed for light feedstocks such as gas oil. The method of the present invention in which heat is withdrawn from the regeneration zone allows operation with full CO thermal calcination using a wide range of feedstocks. Therefore, the present invention oxidizes the coke deposited on the spent catalyst to complete carbon dioxide and increases the temperature of the regeneration zone to 725
It also relates to a method of keeping the temperature below ℃. Although a temperature of 725°C may be considered as an upper limit for the temperature of the regeneration zone, it is clear that operating at a temperature below 725°C, for example keeping the upper limit at 700°C, is perfect. On the other hand, the temperature in the regeneration zone should not be too low, for example below 610 °C, because in this case the combustion of the coke precipitates would be too slow and furthermore the catalyst would not be hot enough to reach the cracking zone. Unable to vaporize charge material. It is within the scope of this invention to cool a portion of the preheated feedstock by indirect heat exchange with a suitable cooling medium, such as water, to remove excess heat that cannot be stored in the reactor system. This may be the case with very high coke-forming feedstocks,
Particularly, the present invention provides for complete recovery during spent catalyst regeneration.
This is the case when it is operated with CO combustion. In such a case, at least a portion of the preheated hydrocarbon feedstock would be cooled by a cooling medium such as water, since a large amount of heat would have to be extracted from the catalyst bed to prevent the temperature from rising above 725°C. It would have to be cooled again externally by indirect heat exchange with The heat thus contained in the cooling medium can be used in other units of the refinery in which the catalytic cracking unit is located. That is, in a special example of the process of the invention, at least a portion of the feedstock after being heated by indirect heat exchange with the catalyst to be regenerated is cooled outside the regeneration zone by indirect heat exchange with the cooling medium. be done. The feedstock preheated in this way and further partially recooled can be fed directly to the reaction zone, if only part of the feedstock is recooled.
It is not recooled after mixing with other parts of the feedstock. However, once a certain amount of recirculation takes place,
The temperature stability of the feedstock entering the reaction zone and the flexibility of the process are increased. Preferably, a portion of the feedstock heated and then cooled as described above is
Combine with fresh feedstock to be heated by indirect heat exchange with the regenerated catalyst. It has been found that when (some) feedstock is heated and cooled again, it is uneconomical for the feedstock to be cooled to be cooled to a temperature higher than the temperature of the fresh hydrocarbon feedstock: because This is because the feedstock itself can be easily cooled, for example by simply mixing the fresh feedstock and the heated feedstock. It is therefore preferred that at least a portion of the heated feedstock is cooled to a temperature no higher than the temperature of the feedstock to be heated. In the latter case, at least a portion of the heated feedstock is cooled to a temperature preferably in the range of 80° to 150°C, depending on the particular temperature of the feedstock to be heated. As mentioned above, all or a portion of the heated feedstock will be cooled after being heated in the regeneration zone. However, for process economics, 1/3 to 1/1 of the heated feedstock
Preferably, the 0 is cooled before being mixed with fresh feedstock. This amount results in a recycle ratio of 0.11:0.50, where the recycle ratio is defined as the ratio of recycled feed to fresh feed. In some cases it is advantageous to burn so-called "torch oil" in the regeneration zone. This oil, in contrast to so-called cycle oils, is part of the reaction products which are very difficult to decompose and are not suitable for recycling with fresh feedstock. It is advantageously used, for example, as heating oil in regeneration zones, especially when optimum yields of middle distillates are aimed at. The extra heat added is easily transferred to the feedstock according to the method of the invention. The invention therefore also relates to a method in which a hydrocarbon fuel is combusted in a regeneration zone. The present invention will be explained in more detail below with reference to the drawings. FIG. 1 is a simplified process diagram of a fluid catalytic cracking reactor system. FIG. 2 is a graph of the effect of feedstock preheating on the regeneration reactor and catalyst to oil ratio and is detailed in Example 2. Described with reference to FIG. 1, fresh feedstock is fed through tube 1 and via tube 17 with regenerator coil 16 and heat exchanger 18 the feedstock is heated and directed to tube 3. It is also possible to pass a portion of the feedstock back through the regenerator coil 16 via tube 19, resulting in a more stable temperature of the feedstock in tube 17 and a more stable temperature of the fluidized bed 13. The regenerator coil 16 is surrounded by a fluidized bed 13 of catalyst particles to be regenerated. In some cases it may be advantageous to provide another heat exchanger in the tube 1 before or after the branch 2 in order to cool or heat the fresh feedstock which is too hot or cold. Particularly when processing very heavy coking feedstocks, the recirculation line 19
It is also possible to provide a heat exchanger 18 in the tubes 3 or 17, since the high temperature of the feedstock in tubes 3 or 17 (to accelerate the vaporization of the heavy feedstock in the lift pot) is due to the excess coke being combusted. This is because it must be combined with a large cooling effect in the regenerator. The feedstock is passed via pipe 3 to a liftpot 4 where it is brought into contact with high pressure regenerated catalyst fed through standpipe 5. The feedstock is vaporized and passes in an upward plug flow through the vertical tube reactor 6 into the fluidized bed 7 of the reactor 8 along with the catalyst particles. The gaseous vaporized liquid decomposition products are passed from the top of the container 8 into a conduit 9.
It is removed after Conduit 9 is connected to a cyclone (not shown) which removes entrained solid catalyst particles from the gas stream and returns these particles to fluidized bed 7 via a date preg (not shown). The spent catalyst particles are stripped from the adhering hydrocarbons in a stripper vessel 10 located below the reactor vessel 8.
Next, the removed spent catalyst particles are transported to the vertical pipe 11.
It is supplied to the regenerator vessel 12 through the. In this vessel, a fluidized bed 13 of catalyst particles is maintained by a stream of oxygen-containing gas, usually oxygen, supplied via a nozzle tube 14. The carbon deposits on the catalyst particles are combusted in the bed 13 and the regenerated catalyst particles pass through the standpipe 5 and return to the lift pot 4. Combustion gases are removed from the top of the regenerator vessel 12 through conduit 15 . In the method according to the invention, the tube 2 is not used, or at least not necessarily required. If present as a remainder of a conventional reactor system (when a conventional system is modified to carry out the process of the invention), this
It may be advantageous to use it for starting purposes or as a safety relief line. For this purpose, a valve (not shown) is provided at the connection between pipes 1 and 2, so that the feedstock can be directed in whole or in part to pipe 2 as desired. Example 1 A fluid catalytic cracking unit in a refinery is first operated normally, but with complete CO combustion. However, in this form of operation, an increase in the feed temperature results in an unacceptable increase in the regenerator temperature, so low temperatures (50-80
℃) range). In the regenerator, a high oxygen slip (excess oxygen) must be retained to cool the regenerator bed. In order to apply the method of the invention, this unit has been modified by providing a preheating coil in the regenerator. Due to the particular size and shape of this regenerator, two parallel sets of these coils in series are provided. The coil occupies the cross section of the vessel between the lowest level of the drawoff bin and the top of the manhole. Each coil has its own supply inlet and outlet, and each coil constitutes a self-supporting beam requiring only end supports. Additionally, each coil is configured to extend through the manhole. The selected tube alloy allows operation at maximum reactor temperatures of 700° C. and design pressures of 25 bar absolute. In the design, necessary attention has been paid to thermal expansion. The total length of the piping inside the reactor is approximately
Enough to heat up to 370℃. The reaction conditions and results of the steps taken are shown in the following table:

Table: Clearly, the operational flexibility is increased by carrying out the preheating according to the invention. Table 3 according to the invention
Two cases are shown: 1 Feedstocks that produce more coke can be processed. 2 Feedstocks containing more metals can be processed. 3 More active/selective catalysts may be used. Additionally, less oxygen is used in the regenerator for cooling purposes, warmer feedstock can be processed, and the need to pre-chill the feedstock is avoided. Example 2 FIG. 2 shows the effect of preheating the feed material in the regenerator coil 16 according to the invention. Regeneration zone temperature Treg is plotted as a function of catalyst to oil ratio C/O. Clearly, a reduction in catalyst feed rate C results in an increase in Tregs, which should be kept below 725°C. However, a reduction in C is necessary to reduce the severity of decomposition, for example when using more active/selective catalysts. Two cases are shown for a fluid catalytic cracking reactor system according to FIG. Series A is a conventional heat-balanced catalytic cracking operation using tube 2, and series B is a recirculation through tube 19 or exchanger 1.
According to the invention, the feedstock is preheated in the regeneration zone 12 and the tube 2 is bypassed, without the heat exchange of 8. For all measurements, the feed material was tube 1
was introduced at a temperature of 200°C, and the reactor/standpipe outlet temperature was maintained at 520°C. Curve A shows the results of series A heat-balanced operation, and curve B
shows the results of a series B heat-balanced operation, with the regenerator coil preheating the feed to 400°C. Curve B is shifted to lower C/O ratios and lower regenerator temperatures so that in the process according to the invention a more selective/active catalyst and/or a more coking-forming feedstock is maximally regenerated. It can now be used without the temperature exceeding 725°C.

[Brief explanation of drawings]

FIG. 1 shows a simplified flow diagram of a fluid catalytic cracking reactor system. FIG. 2 graphically illustrates the effect of preheating the feedstock on catalyst-to-oil ratio and regenerator temperature. 4... Lift pot, 6... Standpipe reactor, 7... Fluidized bed, 8... Reactor container, 10... Stripper container,
12... Regenerator container, 13... Fluidized bed, 16... Regenerator coil, 18... Heat exchanger.

Claims (1)

[Scope of Claims] 1. A method for fluid catalytic cracking of a hydrocarbon feedstock in a reactor system including at least a cracking zone and a regeneration zone that communicate with each other, the method comprising: subjecting the hydrocarbon feedstock to high-temperature cracking in the cracking zone; brought into contact with a catalyst, and
At least a portion of the feedstock is vaporized and subsequently cracked into low-boiling hydrocarbon products under cracking conditions at a temperature range of 425° C. to 550° C., a pressure range of atmospheric pressure to 4 bar absolute, and a catalyst-to-oil ratio of less than 7. , the low-boiling hydrocarbon products are then separated and recovered from the spent catalyst while simultaneously passing the spent catalyst containing coke deposits to a regeneration zone where an oxygen-containing gas is passed through the catalyst bed. The hydrocarbon feedstock is subjected to fluid catalytic cracking by oxidizing the coke deposits with the generation of heat to regenerate and heat the catalyst, and then returning the hot regenerated catalyst to the cracking zone. In a method of
After this, the feedstock is introduced into a cracking zone and in direct contact with the hot regenerated catalyst to a temperature of 200 °C.
A method for fluid catalytic cracking of the hydrocarbon feedstock, characterized in that the hydrocarbon feedstock is vaporized at a temperature higher than °C. 2. indirect heat exchange between the regenerated catalyst and fresh hydrocarbon feedstock is carried out by passing the feedstock through one or more heat exchange tubes located in the bed of the regenerated catalyst; Claim 1
The method described in section. 3. The fresh hydrocarbon feedstock is heated at a temperature of at least 80 °C and 250 °C prior to indirect heat exchange with the regenerated catalyst.
3. A method according to claim 1 or 2, having a temperature not higher than 0.degree. 4 The new feedstock is brought to temperature by said indirect heat exchange.
A method according to any one of claims 1 to 3, wherein the method is heated to a temperature in the range of 250 to 425°C. 5. The method of claim 4, wherein the fresh feedstock is heated to a temperature in the range 325-400C. 6 The temperature in the regeneration zone is 725°C while the coke deposits on the spent catalyst are completely oxidized to carbon dioxide.
Claims 1 to 5 are maintained at a temperature below °C.
How to describe any one of the sections. 7. The method according to any one of claims 1 to 6, wherein the temperature of the regeneration zone is maintained in the range of 610 to 700°C. 8. Claims 1 to 7, wherein at least a portion of the feedstock after being heated by indirect heat exchange with the catalyst to be regenerated is cooled outside the regeneration zone by indirect heat exchange with a cooling medium. The method described in any one of the following. 9. At least a portion of the heated feedstock is cooled and then recombined with fresh feedstock to be heated by indirect heat exchange with the regenerated catalyst. the method of. 10 At least a portion of the heated feedstock is
10. Process according to claim 8 or 9, characterized in that it is cooled to a temperature no higher than the temperature of the fresh feedstock to be heated. 11 At least a portion of the heated feedstock is 80
11. The method of claim 10, wherein the method is cooled to a temperature in the range -150<0>C. 12 1/3 to 1/10 of the heated feedstock is
cooled and then mixed with fresh feedstock,
A method according to any one of claims 7 to 11. 13. A method according to any one of claims 1 to 12, wherein the hydrocarbon fuel is combusted in a regeneration zone.