JPH0474397B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL FIELD OF APPLICATION The present invention relates to the catalytic cracking of hydrocarbon charges in a fluidized bed. The object of the invention is in particular a method for catalytic cracking by wetting the reaction products with a fluid and adjusting the reaction temperature, and a device for this purpose. Purpose of the invention Contact cracking (in English, FLUID
It is known that in a process known as CATAFYTIC CRAKING (FCC method), a hydrocarbon charge is completely vaporized by contacting it at high temperature with a suitable cracking contact which is kept in suspension. After achieving the desired molecular weight classification by cracking and lowering the temperature to the respective boiling point,
The resulting product is rapidly separated. In reality, the catalyst and the charge to be treated in the FCC method are the lower part of a reactor consisting of a circular column called the charge list, which engineers give the English technical term "RISER". can be contacted with. A list concentration vessel is attached to the top of the column. A centrifugal separator is housed in the upper part of this vessel and above the lift to recover the catalyst carried by the steam. Generally, a cyclone system is used. The charge is discharged at the top of the vessel mentioned above, but the catalyst grains that have become unreactive due to adhesion of coke are collected at the bottom of the vessel and sent to a regenerator for the purpose of regaining their activity by burning the coke. Before being discharged, it comes into contact with a stripping fluid, such as steam, which is injected into the bottom of the container. Combustion air is blown into the lower part of the regenerator, the upper part of which is equipped with a cyclone to separate entrained particles of regenerated catalyst from the combustion gases. The regenerated catalyst is discharged by the bottom of the regenerator and recycled to the bottom of the lift or riser. The lift is injected with the charge at a temperature of 80° C. to 400° C. and under a relative pressure of 0.7×10 ⁵ to 3.5×10 ⁵ Pascals. As another example, the catalyst can be charged together with the charge at the top of a reaction column that is essentially of the falling or dropper type. The spent catalyst is recovered from the bottom of the reactor, stripped and sent to a regeneration stage. Parallel to this regeneration, the depleted catalyst particles are subjected to stripping with a fluid, generally steam. The purpose of this is to remove hydrocarbons adsorbed between or on the surface of the catalyst particles. The inventors pursued work on catalytic cracking and investigated the possibility of adjusting the residence time of the hydrocarbons to be treated in the reaction zone. This is thus the time during which this charge is in contact with the catalyst, as a result of the study of the physical properties and conversion of the charge to be treated. The adjustment that was the object of this study is possible by correctly adjusting the temperature of the reaction zone at a higher temperature in the charge injection zone and at a lower temperature in the final zone of the lift, thus suppressing interfering reactions. I discovered that. Such adjustment is particularly useful in the case of charges that tend to cause adsorption of coke on the surface of the catalyst. This fact is evidenced by the concentration of compounds at high boiling points or by the presence of compounds with fundamental physical properties (nitrogenated aromatics, condensed aromatic hydrocarbons, etc.) that neutralize the acidic bed of the catalyst. It has a tendency to absorb and adsorb. Better vaporization of the charge and less adsorption of coke precursors
Accelerated by higher mixing temperatures. The mixing temperature is determined as the temperature generated by mixing the hot regenerated catalyst with the charge which has absorbed the required calories from the catalyst and is to be cracked after vaporization. If, due to the higher mixing temperature, coke deposition on the catalyst is reduced and the heaviest molecules of the charge to be cracked are thermally cracked in the reaction zone, It is necessary to adjust the contact time with the catalyst.
This is because if the reaction continues too long, this
This can lead to subsequent reactions and extend the thermal cracking reaction to such an extent that it becomes excessive, producing gas and coke at the expense of vaporizing the heavy charge of liquefied product with the aid of the catalyst. It is therefore an object of the present invention to provide a process for the catalytic cracking of a hydrocarbon or fluidized bed charge, in which the charge and a catalyst are catalytically cracked at a temperature high enough to form coke deposits on the catalyst. The goal is to bring them into contact in such a way as to perform them optimally. Another object of the invention is to control the contact time of the catalyst and the charge at these elevated temperatures in a manner that reduces secondary reactions and inhibits predicted thermal cracking. be. SUMMARY OF THE INVENTION The inventors have discovered that this result can be achieved by injecting a liquefied or gaseous fluid into the cracking column downstream of the contact zone between the hydrocarbon charge and the catalyst. Established. The temperature of the liquefied material or gas is such that the temperature at the reaction site can be lowered and the increased temperature can control the initial reaction time of catalytic cracking. The present invention is therefore directed to a method for the catalytic cracking of a hydrocarbon charge in a diluted fluidized bed, which method comprises combining the hydrocarbon charge and crackling catalyst particles in a cracking column under cracking conditions. separating the depleted catalyst and the cracked charge downstream of the charge injection zone; and stripping at least the depleted catalyst; Next, a method for cracking a hydrocarbon charge comprising the steps of regenerating the catalyst under conditions of combustion of coke adhering to the catalyst, and finally supplying the regenerated catalyst to the cracking tower for recycling. In the cracking column, an auxiliary fluid is injected downstream of the contact zone between the regenerated contact and the charge, and the injection causes the separation of the depleted contact and the products of the cracking reaction. It is characterized in that, before the step, the catalytic cracking reaction is carried out at a flow rate and temperature such that the reaction can be carried out under milder conditions. The injected fluid can be a liquid or a gas, especially water or steam. The injection of this fluid therefore has a selective quenching effect on the reaction mixture constituted by the inserts and the catalyst particles and on the injection flow rate of said fluid, which also has a catalytic cracking reaction temperature. of,
It must be possible to adjust to optimal conditions. This reaction temperature also ensures that the depleted catalyst is not significantly harmed in the subsequent stripping step and that the heaviest hydrocarbons present condense on the catalyst grains, i.e. appear as increased deposits of coke on the catalyst. We must take care not to cause this.
In practice, the fluid injection temperature must be such that it causes a reduction in the temperature of the reaction mixture by 10°C to 70°C. As will now be described in more detail, methods consistent with the invention can be applied equally well to rising fluid cracking towers (lifts, also called "risers") and descending fluid cracking towers ("droppers"). I can be there. An important advantage of the process according to the invention is that the temperature of the catalyst regeneration can be suppressed, which reduces the coke loading, but also the heavy charges, which are usually excluded in fluidized bed catalytic cracking processes. That is to say, it is possible to make a transformation. In this way, at the inlet of the reaction zone, the ratio C/O between the catalyst recycle flow rate and catalyst amount C and the cracked charge amount O approaches the "flash" condition, resulting in rapid and uniform vaporization of the charge. can be maintained at the desired value to ensure that the
Therefore, an optimum conversion rate can be obtained to obtain the desired product with a better octane number. Of course, the injection flow rate of the quenching auxiliary fluid has to be adjusted to the catalytic cracking reaction conditions and the desired temperature curve in relation to the physical properties of the charge and the catalyst. In order to determine this flow rate, effective parameters that can be used are the temperature of the cracked charge before the injection of the auxiliary fluid and the temperature after or during the separation of the catalyst grains. A preferred embodiment of the method according to the invention comprises adjusting the injection flow rate of said auxiliary body into the cracking column in such a way that the reaction temperature as a result of this injection is kept at a predetermined constant value. be.
However, this temperature needs to be high enough so that the stripping effect is not substantially impaired. The invention is also directed to a device for catalytic cracking of hydrocarbon charges. This device is
a fluid-rising cracking column; means for supplying the cracking column with a hydrocarbon charge and regenerated cracking catalyst particles under pressure; means for separating at least the depleted catalyst particles with at least one fluid; a device for regenerating the catalyst by burning coke deposited on the catalyst; and recycling the regenerated catalyst to the supply means. an apparatus for catalytic cracking of a hydrocarbon charge comprising means for discharging at least an auxiliary fluid in said cracking column downstream of the contact zone of the hydrocarbon charge and regenerated catalyst grains;
The apparatus is characterized in that it includes means for injecting the auxiliary fluid at a rate such that the temperature of the reaction zone immediately downstream of the contact zone is reduced. In a preferred embodiment, the device further includes means for adjusting the flow rate of said fluid such that the reaction temperature is predetermined and maintained at a constant value in the reaction zone. The means for injecting this auxiliary body can advantageously be placed at a distance within the reaction zone. This distance is 0.2 to 0.8 of the length of the reaction zone.
The distance can be increased by 0.4 to 0.6 times, more preferably 0.4 to 0.6 times this distance. This injection means is used for all parts of the reaction zone.
It is advantageously constructed with an injection device of a type known per se, which makes it possible to ensure uniform distribution of the fluid. If the temperature adjustment fluid consists of liquid water, the small amount of water required for temperature adjustment can be sprayed in the form of a very fine mist over all parts of the reaction zone using a sprayer. By doing so, it is injected.
In this way, in conventional production equipment, 20 to 150 liters of water in liquid form are injected per m ³ of the feedstock to be treated, and the temperature in the downstream reaction zone is adjusted. The temperature can be lowered by approximately 10 to 70℃. The invention will now be described in detail with reference to the accompanying schematic drawings. FIG. 1 depicts the application of the method according to the invention to a complete catalytic cracking in a fluidized bed in a cracking column of the fluid riser type. FIG. 2 depicts the application of the present invention to a complete fluid dropper type packing tower. In FIG. 1, the regenerated catalyst is injected by pipe 1 with carrier gas injected in line 3 into the lower part of cracking tower 2 of the rising fluid or lift. The hydrocarbon charge to be treated is
As such, it is injected with injection means 4 into the lower part of the cracking tower. Also, the hydrocarbon and catalyst particles are brought into contact in the area immediately below the charge injection. The mixing temperature of the catalyst and vaporized charge is between 525°C and 580°C, depending on the physical properties of the charge and the desired conversion purpose. At the upper part of the cracking tower 2, a separation vessel 6 for separating cracked products and spent catalyst particles is provided. At the bottom of this container 6 a stripping fluid injector 7 is attached. This fluid is
It is generally water vapor, which acts against the flow of separated catalyst particles. At the bottom of the vessel 6, the catalyst particles are discharged via a conduit 8 towards a secondary stripping or regeneration device. Meanwhile, the cracked product is in container 6.
(not shown). According to the invention, the auxiliary fluid for the quenching of the cracking product is introduced downstream of the contact zone between the catalyst grains and the vaporized charge, i.e. into the intermediate part 5 of the cracking column 2, by injection means 9. Injected. This auxiliary fluid, i.e. water, steam or other, is injected at a flow rate that lowers the mixing temperature by 10°C to 70°C depending on the desired result, with the aim of increasing the catalytic cracking reaction of the charge to the best efficiency. Ru. The temperature of the thus cooled mixture may be, for example, around 500° C., but must be higher than the boiling point of the heaviest hydrocarbon present. Therefore, the temperature measuring device 10 is placed inside the container 6.
A valve 12 with an actuator 11 installed to measure the temperature at the location and thereby control the flow rate of the auxiliary fluid in the supply line 13 of the injection means 9
is simultaneously controlled to maintain the temperature in vessel 6 above a target temperature appropriate for the type of charge being treated. Another temperature measuring device 14
is installed in the cracking tower 2 upstream of the auxiliary fluid injection means 9, that is, in the contact zone between the charge and the catalyst particles. On the other hand, the valve 12 can regulate the flow rate of the auxiliary fluid in the supply line 13 of the injection means 9 so as to be able to influence the injection flow rate of the regenerated catalyst and the temperature in the contact zone. Control as much as possible. In FIG. 2, the cracking tower 20 is a so-called
It is a DROPPER type. That is, the regenerated catalyst particles 21 are injected into the upper part of the cracking tower 20,
Due to gravity, it falls down the Kratzkig tower 20. The charge to be cracked is likewise injected by the injection means 22 in the upper part of the cracking column 20. Separation vessel 2 at the bottom of the cracking tower 20
3 pipes the effluent, i.e. the cracking product, to pipe 2.
4, the spent catalyst grains are also stripped at the bottom of this vessel 23 and then separated and discharged to be transported for regeneration. According to the invention, the cracking product quenching auxiliary fluid is injected by injection means 26 downstream of the charge injection means 22. The flow rate is such that the mixing temperature is lowered by about 10 DEG C. to 70 DEG C. so that the catalytic cracking reaction is carried out under the most efficient conditions. As in the previous case, a temperature measuring device 27 is mounted upstream of the pipe 24 and the temperature of the injection means 26 is adjusted so that the temperature measured by the measuring device 27 is always equal to or higher than the target temperature. A valve 29 with an operating part 28 in the supply pipe 30 controls the flow rate of the auxiliary fluid.
It can be controlled with. On the other hand, the temperature measuring device 31
is the injection temperature and injection means 26 in the reaction zone.
It works to adjust the injection flow rate. The following example illustrates the advantages of the method according to the invention. EXAMPLE A hydrodesulphurized residual charge having the following physical properties was processed in a cracking device comprising a short residence time lift and a two-layer catalyst regeneration system as described in French Patent Application No. 8418706. , handle cracking. Density: 0.930 Sulfur (wt%): 0.25 Kondrasson Carbon (wt%): 4.8 Nickel (wtppm): 10 Vanadium (wtppm): 24 Ultra-stable zeolite for cracking and the heaviest carbonization of cracking conditions A commercially available catalyst consisting of a matrix suitable for cracking hydrogen molecules is used. Two experiments were performed using the same charge.
One test was performed under normal cracking conditions, and the other test was performed with a quenching fluid consisting of liquid water injected at mid-lift height. The conditions for the two experiments were as follows.

【table】

[Table] The weight ratio at the inlet of the shows the resulting benefits. In the case of the process according to the invention, despite the lower stripping temperature of the catalyst (525° C. instead of 550° C.), the hydrogen content of the coke is lower and the delta coke is also slightly below. This shows that the heavy fractions were cracked efficiently and did not remain adsorbed on the exhausted catalyst. Here, the lower temperature for the exhausted catalyst, less delta coke, and lower hydrogen content bring the final regeneration temperature of the catalyst to 53°C.
I know that it is possible to reduce the level. This means that
There is an advantage of increasing the C/O ratio (in this case) or the temperature of the charge. This significantly improves the vaporization of the charge. Operation and Effects of the Invention The beneficial effects obtained by the method according to the invention are summarized as follows. Basically, it will be noted that improved conversion, better selectivity between gasoline and distillate, less generation of dry gas, and this suppresses thermal cracking and nickel effects. In other respects, the higher olefin and lower aromatic properties of the product lead to better octane numbers and better cetane numbers. Furthermore,
By having less high catalyst regeneration temperatures, the catalyst is more stable and the rate of replacement to maintain the desired performance can be reduced. The method according to the invention therefore makes it possible to improve the performance of cracking devices for certain charges of hydrocarbons. This is advantageously used to process heavier and dirtier charges with maximum efficiency. This process is likewise very attractive for the treatment of nitrogenated charges or charges rich in polar compounds (resins, asphalts). Because,
This is because if the amount of aromatic nitrogen compounds is large, the conversion rate will drop significantly. For example, for residues of Nigerian encore, the conversion rate in the process according to the invention is of the order of 5% by volume. This explains that very high mixing temperatures, ie, lower neutralization of the acidic sites of the catalyst, shift the adsorption balance of aromatic nitrogen compounds in favor.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a fluid-ascending type cracking tower, and FIG. 2 is a vertical cross-sectional view of a fluid-descending type cracking tower. 2, 20... Cracking tower, 9, 26... Auxiliary fluid injection means, 6, 23... Separation container, 1
2, 29... Valve, 11, 28... Operating unit, 1
0,27...Temperature measuring device.

Claims (1)

[Scope of Claims] 1. Contacting a hydrocarbon charge and cracking catalyst grains as rising or descending fluids in a cracking column under cracking conditions; separating the cracked catalyst from the cracked charge; and stripping at least the spent catalyst;
Next, under the combustion conditions of coke attached to the catalyst,
A method for cracking a hydrocarbon charge comprising the steps of regenerating the catalyst, and finally supplying the regenerated catalyst to the cracking tower for recycling, wherein the regenerated catalyst is regenerated in the cracking tower. An auxiliary fluid is injected downstream of the contact zone between the catalyst and the charge, the injection of which causes the catalytic cracking reaction to be more moderate before the separation stage of the depleted catalyst and the products of the cracking reaction. A method characterized in that the process is carried out at such flow rates and temperatures that the process can be carried out under suitable conditions. 2. A process according to claim 1, characterized in that the reaction temperature resulting from the contact of the regenerated catalyst with the charge to be cracked is 500° C. or higher. 3. A method according to claims 1 and 2, in which the amount of auxiliary fluid injected increases the mixing temperature of the vaporized charge and the catalyst grains compared to the temperature resulting from contact between the catalyst and the charge. , a method characterized in that the flow rate is lowered by about 10°C to 70°C. 4. A method according to any one of claims 1 to 3, in which the injection means for an auxiliary fluid making it possible to regulate the temperature are provided downstream from the injection zone of the charge to be cracked into the reaction zone. A method characterized by being placed at a distance between 0.2 and 0.8 times the length of. 5. A method according to any one of claims 1 to 4, characterized in that the auxiliary fluid is water or steam. 6. In the method according to claim 5, water is uniformly supplied with the aid of ^one or several injection devices in an amount of between 20 and 150 liters per cubic meter of charge injected into the reaction zone. A method characterized by being injected in such a way that 7. In the method according to any one of claims 1 to 6, for a particular type of charge, the temperature of the catalytic reaction is equal to the temperature resulting from the injection of the charge to be cracked with the catalyst. A method characterized in that the method is maintained independently of the user. 8. A cracking column of the fluid ascending type 2 or descending type 20, means for supplying said cracking column with a hydrocarbon charge and regenerated cracking catalyst particles under pressure, and a product of the cracked charge. means for separating spent catalyst particles; means for stopping at least the spent catalyst particles with at least one fluid; a device for regenerating the catalyst by burning coke deposited on the catalyst; An apparatus for catalytic cracking of a hydrocarbon charge, comprising means for recycling the hydrocarbon charge to the feed means, wherein at least an auxiliary fluid is provided in the cracking column downstream of the contact zone between the hydrocarbon charge and the regenerated catalyst particles. , comprising means 9, 26 for injecting this auxiliary fluid at a rate such that the injection of this auxiliary fluid lowers the temperature of the reaction zone immediately downstream of the contact zone. 9. The device according to claim 8, characterized in that the auxiliary fluid injection means are located downstream from the injection zone of the charge to be cracked at a distance of 0.2 to 0.8 times the length of the reaction zone. Featured device. 10. In the device according to claim 9,
means 10, 11, 12 for adjusting the flow rate of said auxiliary fluid so that the temperature of the reaction zone downstream of the injection of said auxiliary fluid is maintained at a target value specific to the physical properties of the charge to be cracked; , 27, 29.