JP7549967B2 - Method for recycling fluid catalytic cracking residual oil in fluid catalytic cracking process and method for producing refined oil - Google Patents

Description

The present invention relates to a method for recycling fluid catalytic cracking residual oil in a fluid catalytic cracking process and a method for producing refined oil.

Fluid catalytic cracking is a reaction in which feedstock oils, including heavy oil, are cracked at high temperatures in a fluid catalytic cracking unit by contacting the feedstock oils with a fluid catalytic cracking catalyst to produce high-value-added cracked oils such as gasoline, kerosene, and diesel.

When fluid catalytic cracking is carried out using heavy oil as the feedstock, the following cracked oils are produced: Liquid Petroleum Gas (LPG), whose main components are propane and butane; gasoline; Light Cycle Oil (LCO); Heavy Cycle Oil (HCO); and Fluid Catalytic Cracked Residual Oil (SLO).

The cracked oil is transferred from the fluid catalytic cracking unit to a distillation tower where it is distilled at atmospheric pressure to separate the atmospheric distillate fractions LPG, gasoline, LCO, and HCO, and the residual oil SLO. SLO is the heaviest fraction of the cracked oil, and is then used as a heavy oil base material for bunker C heavy oil and other products.

As a fluid catalytic cracking unit, one that includes a riser that brings a feedstock oil into contact with a fluid catalytic cracking catalyst to crack the feedstock oil and produce cracked oil, a reaction tower that separates the cracked oil from the fluid catalytic cracking catalyst, and a regeneration tower that regenerates the catalyst by burning carbon (coke) that has accumulated on the separated fluid catalytic cracking catalyst (for example, Patent Document 1) is well known.

Fluid catalytic cracking catalysts are powdered solid catalysts, and for example, solid catalysts containing zeolite as a main component are widely used (for example, Patent Document 2). In the fluid catalytic cracking reaction, coke is formed on the fluid catalytic cracking catalyst as a by-product, and it is known that this coke covers the active sites of the fluid catalytic cracking catalyst and blocks the pores, thereby reducing the catalytic activity (cracking activity).

In a fluid catalytic cracking unit, the fluid catalytic cracking catalyst, whose activity has been reduced by coke, is transferred to a regeneration tower, where the coke is burned off at high temperatures under air flow to regenerate the fluid catalytic cracking catalyst and reuse it in the reaction. The temperature of the regeneration tower during regeneration of the fluid catalytic cracking catalyst depends on the coke content in the fluid catalytic cracking catalyst transferred to the regeneration tower. A regeneration tower usually has a maximum operating temperature set according to its material and structure, and is restricted to operating at or below this maximum operating temperature. Therefore, if too much coke is brought into the regeneration tower, the load on the regeneration tower increases, and the regeneration process becomes a bottleneck. In this case, the feedstock oil supply may have to be reduced, reducing the efficiency of the fluid catalytic cracking process.

Japanese Patent Application Publication No. 11-102204 JP 2008-173583 A

As mentioned above, the fluid catalytic cracking catalyst is in powder form, so when the cracked oil is transferred from the fluid catalytic cracking unit to the distillation tower, some of the fluid catalytic cracking catalyst scatters from the fluid catalytic cracking unit and is sent to the distillation tower together with the cracked oil. When the cracked oil containing the fluid catalytic cracking catalyst is distilled, almost the entire amount of the fluid catalytic cracking catalyst contained in the cracked oil sent to the distillation tower is contained in the fluid catalytic cracking residual oil.

As mentioned above, the fluid catalytic cracking residual oil obtained by distillation is used to produce products such as bunker C heavy oil, but these products have standard values for the impurity content, and the fluid catalytic cracking catalyst content in the product is one of them. Normally, the fluid catalytic cracking residual oil obtained by distillation contains fluid catalytic cracking catalyst in excess of the standard values, so the fluid catalytic cracking catalyst must be separated by separation processing using a liquid cyclone, settler, etc.

However, it is virtually impossible to completely separate the fluid catalytic cracking residual oil from the fluid catalytic cracking catalyst by the above separation process, and the above separation process results in a fluid catalytic cracking residual oil fraction that is a product with a fluid catalytic cracking catalyst content below the above-mentioned standard value, and a fluid catalytic cracking residual oil fraction that exceeds the above-mentioned standard value.

Such fluid catalytic cracking residual oil fractions that exceed the standard value are either returned to the distillation tower of the fluid catalytic cracking unit, or sent to upstream units such as atmospheric distillation units that refine crude oil, where they are subjected to the refining process again.

In the former case, the returned fluid catalytic cracking residual oil fraction is simply circulated with almost no change in properties, while in the latter case, since the processing capacity of the unit is fixed, it is necessary to reduce the amount of raw material supplied by the amount of fluid catalytic cracking residual oil returned. Therefore, one method is to recycle (recycle) the fluid catalytic cracking residual oil fraction that exceeds the above-mentioned standard value back to the fluid catalytic cracking unit.

The inventors of the present application have investigated a method for resupplying fluid catalytic cracking residual oil fractions exceeding the above-mentioned standard value to a fluid catalytic cracking unit, and have found the following problems.

When the fluid catalytic cracking residual oil fraction exceeding the standard value is fed back to the fluid catalytic cracking unit, the fluid catalytic cracking residual oil fraction cracks to some extent, but contains a large amount of residual carbon, which increases the production of coke, and therefore reduces the activity of the fluid catalytic cracking catalyst and increases the load on the regeneration tower (specifically the temperature and air supply load). In such cases, it is necessary to either reduce the processing ratio of feedstock oil containing a large amount of residual carbon and metals, or to lower the reaction temperature to lower the cracking rate and reduce the cracked coke, but either of these measures is inefficient as they have disadvantages in terms of profits.

The present invention has been made in consideration of the above circumstances, and aims to provide a method for recycling fluid catalytic cracking residual oil that can reduce the amount of fluid catalytic cracking residual oil recycled and improve the efficiency of the fluid catalytic cracking process in which fluid catalytic cracking residual oil is recycled, a method for controlling the amount of fluid catalytic cracking residual oil recycled, and a method for producing refined oil.

In order to solve the above problems, the present invention has the following aspects.
[1] A method for recycling fluid catalytic cracking residual oil in a fluid catalytic cracking process in which a feed oil is contacted with a fluid catalytic cracking catalyst in a fluid catalytic cracking unit to obtain a cracked oil, and the cracked oil is separated in a distillation column to obtain a refined oil, the method comprising the step of re-supplying fluid catalytic cracking residual oil containing the fluid catalytic cracking catalyst, which is a type of the refined oil, to the fluid catalytic cracking unit, wherein the wear resistance of the fluid catalytic cracking catalyst is 2 to 5%.
[2] The method for recycling fluid catalytic cracking residual oil according to [1], wherein the proportion of the fluid catalytic cracking catalyst having a particle size of 50 μm or less is 15 to 23 mass %.
[3] The method for recycling fluid catalytic cracking residual oil according to [1] or [2], wherein a fluid catalytic cracking residual oil containing the fluid catalytic cracking catalyst is subjected to a separation treatment by a separation device, and among the fluid catalytic cracking residual oil after the separation treatment, a fluid catalytic cracking residual oil having a fluid catalytic cracking catalyst content exceeding a product specification value is directly supplied again from the separation device to the fluid catalytic cracking unit.
[4] In a fluid catalytic cracking process in which a feed oil is contacted with a fluid catalytic cracking catalyst in a fluid catalytic cracking unit to obtain a cracked oil, and the cracked oil is separated in a distillation column to obtain a refined oil, a method for controlling the amount of fluid catalytic cracking residual oil recycled when fluid catalytic cracking residual oil, which is a type of refined oil and contains the fluid catalytic cracking catalyst, is supplied again to the fluid catalytic cracking unit, the method for controlling the amount of fluid catalytic cracking residual oil recycled being carried out by changing the wear strength of the fluid catalytic cracking catalyst.
[5] A method for producing a refined oil, comprising contacting a feed oil with a fluid catalytic cracking catalyst in a fluid catalytic cracking unit to obtain a cracked oil, and separating the cracked oil in a distillation column to obtain a refined oil, the method further comprising a fluid catalytic cracking residual oil recycling step of re-supplying a fluid catalytic cracking residual oil, which is a type of the refined oil and contains the fluid catalytic cracking catalyst, to the fluid catalytic cracking unit, and wherein the wear resistance of the fluid catalytic cracking catalyst is 2 to 5%.

According to the present invention, in a fluid catalytic cracking process in which fluid catalytic cracking residual oil is recycled, it is possible to provide a method for recycling fluid catalytic cracking residual oil that can reduce the amount of fluid catalytic cracking residual oil recycled and improve the efficiency of the fluid catalytic cracking process, a method for controlling the amount of fluid catalytic cracking residual oil recycled, and a method for producing refined oil.

FIG. 1 is a block diagram showing the configuration of an apparatus used in a fluid catalytic cracking process for recycling fluid catalytic cracking residue according to one embodiment of the present invention. FIG. 1 is a diagram showing the configuration of an abrasion strength measuring device capable of measuring the abrasion strength of a fluid catalytic cracking catalyst.

The following describes in detail the embodiments of the present invention. However, the following description is merely an example of the embodiments of the present invention, and the present invention is not limited to these contents, and can be modified and implemented within the scope of the gist of the invention.

The definitions of terms used in this specification are as follows.
Fluid catalytic cracking residual oil (hereinafter sometimes referred to as "SLO") is the residual oil obtained by distilling cracked oil obtained by contacting feed oil with a fluid catalytic cracking catalyst in a fluid catalytic cracking unit, and refers to a fraction having a boiling point range of 200 to 600°C and a flash point of 85 to 100°C.
The term "product SLO" refers to a fraction obtained by separating the upper layer of the treated liquid obtained by subjecting the SLO to a separation process using a separation device, the fraction having a fluid catalytic cracking catalyst concentration equal to or lower than the product specification value. Product SLO is usually used as a heavy oil base material.
The recycled SLO means the treated liquid after separation of the product SLO, which is re-supplied to the fluid catalytic cracking unit as part of the feedstock. The concentration of the fluid catalytic cracking catalyst in the recycled SLO usually exceeds the product specification value.

The abrasion strength [%] of a fluid catalytic cracking catalyst is a value measured as follows, in accordance with the abrasion strength measuring method described in Catalyst and Chemical Engineering Report Vol. 13, No. 1 (1996), using an abrasion strength measuring device simulating the catalyst tube and cyclone of a fluid catalytic cracking apparatus shown in Figure 2. The following description will be given with reference to Figure 2.
After the FCC catalyst to be measured is dried at 500°C for 5 hours, 3 g of the dry weight is measured, 0.3 g of added water is added, and the catalyst is introduced into the catalyst tube 66 of the abrasion strength measuring device. The flow rate (linear velocity) of the nitrogen in the catalyst tube 66 is then adjusted to 0.104 m/s using the flow rate regulator 63, and measurement is started. The amount [g] of the fine particles of FCC catalyst scattered from the cyclone 67 and collected by the receiver 68 between 12 hours and 42 hours after the start of measurement is measured, and this is taken as the average abrasion amount. Using this value, the value calculated using the following formula is the abrasion strength.
Abrasion strength (%) = average abrasion amount ÷ amount of catalyst put into abrasion strength measuring device (3 g) × 100
That is, the lower the abrasion strength value, the higher the abrasion strength of the FCC catalyst.

The particle size distribution of fluid catalytic cracking catalysts can be measured in accordance with JIS Z8815.

In the method for recycling fluid catalytic cracking residual oil of this embodiment, in a fluid catalytic cracking process in which a feedstock oil is brought into contact with a fluid catalytic cracking catalyst in a fluid catalytic cracking apparatus to obtain a cracked oil, and the cracked oil is separated in a distillation column to obtain a refined oil, the fluid catalytic cracking residual oil containing the fluid catalytic cracking catalyst, which is one type of the refined oil, is fed back to the fluid catalytic cracking apparatus. This embodiment is characterized in that the wear strength of the fluid catalytic cracking catalyst is 2 to 5%.
The fluid catalytic cracking catalyst, the fluid catalytic cracking unit, the distillation column, and the separation unit will be described below.

<Fluid catalytic cracking catalyst>
The fluid catalytic cracking catalyst (hereinafter also referred to as "FCC catalyst") of this embodiment has an attrition strength of 2 to 5%. The attrition strength is preferably 2 to 4%, and more preferably 2 to 3%. It is even more preferable.
When the abrasion strength is equal to or less than the upper limit of the above range, cracking or chipping of the FCC catalyst is unlikely to occur when the FCC catalyst collides with itself in the fluid catalytic cracking reaction, and the FCC catalyst transported to the distillation tower together with the cracked oil is unlikely to be broken or chipped. It is possible to reduce the amount of catalyst. When the amount of FCC catalyst transferred to the distillation column is reduced, the content of FCC catalyst contained in the SLO is reduced. As a result, the yield of the product SLO is This improves the efficiency of the process, and therefore the amount of recycled SLO can be reduced. By reducing the amount of recycled SLO, it is not necessary to reduce the amount of normal raw oil to be processed. The decomposition process becomes more efficient.
When the abrasion strength is at least the lower limit of the above range, damage due to abrasion to the pipe walls in the FCC unit and the inner walls of the separation unit can be suppressed.

The FCC catalyst of the present embodiment is a powdered solid catalyst, and contains zeolite as a main component. The zeolite preferably contains zeolite having a sodalite cage structure, β zeolite, ZSM-5 type zeolite, or the like, and more preferably contains zeolite having a sodalite cage structure.
The content of the zeolite relative to the total mass of the FCC catalyst is preferably 23 to 40 mass %, more preferably 25 to 38 mass %, and even more preferably 28 to 35 mass %.

In this specification, a zeolite having a sodalite cage structure means a zeolite having a sodalite cage structure, i.e., a tetradecahedral crystal structure defined by four-membered rings or six-membered rings, in which the vertices of a three-dimensional regular octahedral crystal structure formed by aluminum and silicon tetrahedrons as basic units and sharing the oxygen at the vertices with aluminum or silicon, is cut off, and which has voids formed by the tetradecahedral crystal structure defined by four-membered rings or six-membered rings, and which has various pore structures, skeletal densities, and channel structures due to changes in the locations and methods in which the sodalite cages are bonded to each other.

The zeolite having the sodalite cage structure may be one or more selected from sodalite, A-type zeolite, EMT, X-type zeolite, Y-type zeolite, stabilized Y-type zeolite, etc., and is preferably stabilized Y-type zeolite.

Stabilized Y-type zeolite is synthesized using Y-type zeolite as a starting material, and is more resistant to deterioration in crystallinity than Y-type zeolite. In general, stabilized Y-type zeolite is prepared by subjecting Y-type zeolite to steam treatment at high temperatures several times, and then, if necessary, treating it with a mineral acid such as hydrochloric acid, a base such as sodium hydroxide, a salt such as calcium fluoride, or a chelating agent such as ethylenediaminetetraacetic acid.
The stabilized Y-type zeolite obtained by the above method can be used in a form in which it has been ion-exchanged with a cation selected from hydrogen, ammonium, or a polyvalent metal. Also, as the stabilized Y-type zeolite, a heat shock crystalline aluminosilicate zeolite (see Japanese Patent No. 2544317) having superior stability can be used.

The FCC catalyst of the present embodiment preferably further contains a binder, a clay mineral, and the like.
An example of the binder is silica sol. By using silica sol, the moldability during granulation of the FCC catalyst is improved, and it is possible to easily form the catalyst into a spherical shape. In addition, the flowability and abrasion resistance of the granulated FCC catalyst can be easily improved. The content of the binder relative to the total mass of the FCC catalyst is preferably 15 to 35 mass%, more preferably 18 to 32 mass%, and even more preferably 20 to 30 mass%.

Examples of clay minerals include montmorillonite, kaolinite, halloysite, bentonite, attapulgite, bauxite, etc. In the FCC catalyst of this embodiment, known inorganic oxide fine particles used in normal FCC catalysts, such as silica (excluding silica added in the form of the above-mentioned sol), silica-alumina (excluding the above-mentioned zeolite), alumina, silica-magnesia, alumina-magnesia, phosphorus-alumina, silica-zirconia, and silica-magnesia-alumina, can be used in combination with the above-mentioned clay minerals.
The sum of the contents of the clay mineral and the inorganic oxide relative to the total mass of the FCC catalyst is preferably 40 to 55 mass %, more preferably 43 to 52 mass %, and even more preferably 45 to 50 mass %.
The content of the clay mineral relative to the total mass of the FCC catalyst is preferably 30 to 50 mass %, more preferably 32 to 47 mass %, and even more preferably 34 to 45 mass %.

The FCC catalyst of this embodiment may also contain a zeolite stability improver. The zeolite stability improver has the function of suppressing the collapse of zeolite crystals. Examples of zeolite stability improvers include phosphorus-based zeolite stability improvers such as phosphoric acid, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, aluminum monophosphate, and other water-soluble phosphates, and rare earth metal-based zeolite stability improvers such as scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, dysprosium, and holmium. When the FCC catalyst contains a zeolite stability improver, the content of the zeolite stability improver relative to the total mass of the FCC catalyst is preferably 0.1 to 5 mass%.

The FCC catalyst is granulated to a certain size and then used in the fluid catalytic cracking reaction.
The ratio of the FCC catalyst having a particle size of 50 μm or less to the total mass of the FCC catalyst is preferably 15 to 23 mass%, more preferably 15 to 22 mass%, and even more preferably 15 to 21 mass%. By setting the ratio of the FCC catalyst having a particle size of 50 μm or less to the upper limit value of the above range or less, it is easy to suppress the amount of scattering of the FCC catalyst and to reduce the amount of FCC catalyst in the fluid catalytic cracking residual oil. By setting the ratio of the FCC catalyst having a particle size of 50 μm or less to the lower limit value of the above range or more, it is possible to maintain good catalyst fluidity.

<Method of producing fluid catalytic cracking catalyst>
The FCC catalyst of the present embodiment can be produced by a conventionally known method. When the FCC catalyst contains zeolite, a binder, a clay mineral, and a zeolite stability improver, the catalyst can be produced by drying a slurry containing a predetermined amount of each of the zeolite, the binder, the clay mineral, and the zeolite stability improver.

In this production method, first, an aqueous slurry containing zeolite, a binder, a clay mineral, and a zeolite stability improver is prepared.
The solid content of the aqueous slurry is preferably 5 to 60% by mass, more preferably 10 to 50% by mass. When the solid content of the aqueous slurry is within the above range, the amount of water evaporated during drying of the aqueous slurry becomes appropriate, and drying can be easily performed. In addition, the slurry can be easily transported without increasing its viscosity.

The aqueous slurry is then dried to obtain the microspheres.
The aqueous slurry is preferably dried using a spray dryer under conditions of a gas inlet temperature of 200 to 600°C and a gas outlet temperature of 100 to 300°C.

In this manufacturing method, the microspheres obtained by the drying process may be further washed and ion-exchanged by known methods as necessary to remove excess alkali metals and soluble impurities that may be brought in from the various raw materials.

Specifically, the washing process can be carried out with water or aqueous ammonia, and washing with water or aqueous ammonia can reduce the content of soluble impurities.

Specifically, the ion exchange treatment can be carried out using an aqueous solution of ammonium salts such as ammonium sulfate and ammonium sulfite, and this ion exchange can reduce the amount of alkali metals such as sodium and potassium remaining in the microspheres.

The above-mentioned cleaning treatment is usually carried out prior to the ion exchange treatment, but the ion exchange treatment may be carried out first as long as the cleaning treatment and the ion exchange treatment are carried out appropriately.

The above-mentioned washing process and ion exchange process are preferably carried out until the content of alkali metals and the content of soluble impurities are below the desired amount. By keeping the content of alkali metals and the content of soluble impurities below the desired amount, the catalytic activity can be improved.

The microspheres preferably have an alkali metal content of 1.0% by mass or less, more preferably 0.5% by mass or less, based on the dry catalyst. The soluble impurity content is preferably 2.0% by mass or less, more preferably 1.5% by mass or less.

The microspheres that have been subjected to the above-mentioned washing and ion exchange treatments are preferably dried again at a temperature of 100 to 500° C. until the moisture content of the microspheres reaches 1 to 25% by mass.
In this manner, the FCC catalyst of this embodiment can be produced.

<Fluid catalytic cracking equipment>
The fluid catalytic cracking unit of this embodiment is equipped with the above-mentioned FCC catalyst.
The fluid catalytic cracking unit (hereinafter also referred to as "FCC unit") of this embodiment includes a riser that generates cracked oil by contacting a feedstock oil with a fluid catalytic cracking catalyst and cracking the feedstock oil, and a gas turbine engine that produces a gas turbine engine. The FCC catalyst is separated from the reaction tower, and the carbon (coke) deposited on the separated FCC catalyst is burned to regenerate the catalyst. An example of an FCC apparatus will be described below. Fig. 1 is a block diagram showing an example of an FCC apparatus. The FCC apparatus 1 includes a riser 10, a reaction tower 20, and a regeneration tower 30.

(Riser)
The riser 10 is a device that produces cracked oil by contacting the feedstock oil with an FCC catalyst and cracking the feedstock oil. The riser 10 is connected to, for example, a regenerated catalyst transfer line 34 that supplies the FCC catalyst regenerated in the regenerator 30, a feedstock oil supply line 11 that supplies the feedstock oil, and a recycled SLO supply line 51 that supplies recycled SLO described below. In addition, a preheating device 12 is provided on the feedstock oil supply line. Furthermore, the upper part of the riser 10 is connected to a reaction tower 20.

(Reaction tower)
The reaction tower 20 is a device for separating the cracked oil from the FCC catalyst. The reaction tower 20 includes, for example, a cyclone 21, a cracked oil discharge line 22, a stripper 23, and a post-reaction catalyst transfer line 24. The top of the cyclone is connected to the cracked oil discharge line 22. Furthermore, the bottom of the stripper 23 and the lower part of the regeneration tower 30 are connected by the post-reaction catalyst transfer line 24.

(Regeneration Tower)
The regenerator 30 is an apparatus for regenerating the catalyst by burning the coke on the FCC catalyst separated in the reaction tower 20. The regenerator 30 includes, for example, an air blower 31, an air grid 32, a cyclone 33, a regenerated catalyst transfer line 34, and an exhaust gas line 35. The bottom of the regenerator and the air blower 31 are connected via the air grid 32. Furthermore, a cyclone 33 is installed at the top of the regenerator, and the upper part of the cyclone is connected to the exhaust gas line 35.

<Distillation tower>
The distillation column 40 of this embodiment is a device that separates the cracked oil produced in the fluid catalytic cracking unit into liquefied petroleum gas (LPG), gasoline, light cracked gas oil (LCO), heavy cracked gas oil (HCO), and fluid catalytic cracking residual oil (SLO).
A distillation tower known in the art can be used as the distillation tower 40. The distillation tower 40 is connected to the reaction tower 20 via a cracked oil discharge line 22 near the middle of the tower. The distillation tower 40 is also connected to a fluid catalytic cracking residual oil transfer line 41 at the bottom of the tower. The detailed structures of the reflux line, preheater, bottoms discharge line, effluent discharge line, and the like of the distillation tower are not shown in FIG. 1, but as described above, the distillation tower 40 has a structure known in the art.

<Separation device>
The separation device 50 of this embodiment is a device that utilizes centrifugal force or the like to separate the FCC catalyst from the SLO containing the FCC catalyst separated by distillation.
As the separation device 50, a liquid cyclone, a settler, or the like known in the art can be used. The separation device 50 is connected to the distillation column 40 via a fluid catalytic cracking residual oil transfer line 41. The separation device 50 is also connected to the riser 10 via a recycle SLO supply line 51. The separation device 50 is further connected to a product SLO transfer line 52.

<Method for recycling fluid catalytic cracking residual oil in a fluid catalytic cracking process and method for producing refined oil>
The fluid catalytic cracking process of the present embodiment, the method for recycling the fluid catalytic cracking residue in the fluid catalytic cracking process, and the method for producing refined oil will be described below.
The fluid catalytic cracking process of the present embodiment is roughly divided into four steps: a fluid catalytic cracking reaction step, a distillation step, a separation step using a separation device, and a recycling step of recycled SLO. These steps will be described below.

(Fluid catalytic cracking reaction process)
In this embodiment, the fluid catalytic cracking reaction of the feedstock oil can be carried out by a method known in the art. The fluid catalytic cracking reaction of the feedstock oil can be carried out in an FCC unit by contacting the feedstock oil with an FCC catalyst at a high temperature.

In this embodiment, the raw oil to be cracked is not particularly limited, and may be a hydrocarbon oil (hydrocarbon mixture) that is liquid at room temperature and pressure.

Examples of the hydrocarbon oil include one or more selected from light oil fractions obtained by atmospheric or reduced pressure distillation of crude oil, atmospheric distillation residual oils, and reduced pressure distillation residual oils, and also include one or more selected from coker light oil, solvent deasphalted oil, solvent deasphalted asphalt, tar sands oil, shale oil, coal liquefied oil, GTL (Gas to Liquids) oil, vegetable oil, waste lubricating oil, waste edible oil, and the like.
Furthermore, the feedstock oil to be cracked in this embodiment may also include hydrotreated oil obtained by subjecting the above-mentioned hydrocarbon oil to hydrotreatment known to those skilled in the art, that is, hydrodesulfurization under high temperature and high pressure in the presence of a hydrotreatment catalyst such as a Ni-Mo based catalyst, a Co-Mo based catalyst, a Ni-Co-Mo based catalyst, or a Ni-W based catalyst.

In this embodiment, the cracking reaction of the feedstock oil can be carried out by continuously circulating an FCC catalyst in an FCC unit 1, which is typically composed of a vertically installed riser 10, a reaction tower 20, and a regenerator 30. In this specification, the term "fluid catalytic cracking unit" (FCC unit) also includes a residual oil fluid catalytic cracking unit (RFCC unit). In other words, in this specification, the term "fluid catalytic cracking reaction" also includes a residual oil fluid catalytic cracking reaction.

The fluid catalytic cracking reaction carried out by the FCC unit will now be described in detail.
A pumping fluid flows upward in the riser 10, and the FCC catalyst supplied from the regenerated catalyst transfer line 34 flows upward in the riser 10 together with the pumping fluid. The feed oil is heated to a predetermined temperature by the preheating device 12, steam is added, and then the feed oil is supplied to the riser 10 from the feed oil supply line 11. Similarly, recycled SLO is supplied to the riser 10 from the recycled SLO supply line 51. The feed oil and recycled SLO supplied to the riser 10 come into contact with the FCC catalyst, and a cracking reaction occurs. The cracked oil and FCC catalyst produced by the cracking reaction are transferred to the reaction tower 20.

As operating conditions for the riser 10, the reaction temperature is preferably 400 to 600°C, and more preferably 450 to 550°C. If the reaction temperature in the riser 10 is 400°C or higher, the cracking reaction of the feedstock oil and recycled SLO proceeds, improving the yield of cracked oil. Also, if the reaction temperature in the riser 10 is 600°C or lower, the amount of light gases such as dry gas and LPG produced by cracking can be reduced, making it easier to relatively increase the yield of gasoline fraction, which is more economical.

The reaction pressure is preferably from normal pressure to 0.49 MPa (5 kg/cm ² ), and more preferably from normal pressure to 0.29 MPa (3 kg/cm ² ). Since the decomposition reaction is a reaction in which the number of moles of the product increases relative to the number of moles of the reactants, it is thermodynamically (equilibrium-wise) advantageous for the reaction pressure in the riser 10 to be 0.49 MPa or less.

The mass ratio of FCC catalyst/(feedstock oil + recycled SLO) is preferably 2 to 20, and more preferably 4 to 15. When the mass ratio of FCC catalyst/(feedstock oil + recycled SLO) in the riser 10 is 2 or more, the catalyst concentration in the riser 10 can be kept at an appropriate level, improving the efficiency of cracking the feedstock oil. Even when the mass ratio of FCC catalyst/(feedstock oil + recycled SLO) in the riser 10 is 20 or less, the cracking reaction of the hydrocarbon oil proceeds effectively, making it easier to proceed with the cracking reaction commensurate with the increase in catalyst concentration.

The cracked oil produced by cracking the feedstock oil and recycled SLO in the riser 10 is supplied to the cyclone 21. The cyclone 21 separates the cracked oil from the FCC catalyst using centrifugal force. The cracked oil is then discharged from the reaction tower 20 via the cracked oil discharge line 22 and transferred to the distillation tower 40.

The FCC catalyst separated by the cyclone 21 is supplied to the stripper 23. Steam, nitrogen, etc. are supplied to the stripper 23. In the stripper 23, the hydrocarbons on the FCC catalyst are removed using the steam, nitrogen, etc. After the reaction, the FCC catalyst is discharged from the reaction tower 20 via the catalyst transfer line 24 and transferred to the regeneration tower 30.

The temperature during stripping in the stripper 23 is usually 470 to 530°C, preferably 480 to 520°C, and more preferably 490 to 510°C. The gas used for stripping is steam generated by a boiler or an inert gas such as nitrogen pressurized by a compressor, etc.

Air is supplied from the air blower 31 to the air grid 32, and from the air grid 32 to the inside of the regenerator 30, where the coke on the FCC catalyst after the stripping process transferred to the regenerator 30 is burned, and the FCC catalyst is regenerated. The regenerated FCC catalyst and the exhaust gas generated by the combustion of the coke are separated by the cyclone 33. The regenerated FCC catalyst is discharged from the regenerator 30 via the regenerated catalyst transfer line 34 and supplied to the riser 10. The exhaust gas is discharged from the regenerator 30 via the exhaust gas line 35.

As for the operating conditions of the catalyst regenerator, the regeneration temperature is preferably 600 to 800°C, and more preferably 700 to 750°C.
When the regeneration temperature in the catalyst regeneration tower is 600° C. or higher, the combustion of coke proceeds sufficiently and the catalytic activity is sufficiently restored. When the regeneration temperature in the catalyst regeneration tower is 800° C. or lower, the adverse effect on the equipment material is low.

(Distillation process)
The cracked oil is transferred from the reaction tower 20 to the distillation tower 40 via the cracked oil discharge line 22, and in the distillation tower 40, dry gas, LPG, and gasoline are distilled from the top of the tower, LCO and HCO are distilled from the middle of the tower, and SLO containing an FCC catalyst is distilled from the bottom of the tower, thereby producing various refined oils.

(Separation process by separation device and recycling process of recycled SLO)
The SLO containing the FCC catalyst obtained in the distillation step is transferred to the separation device 50 through the fluid catalytic cracking residual oil transfer line 41. The FCC catalyst in the SLO is settled by the separation process (centrifugation process) by the separation device. On the other hand, it is practically impossible to settle all the FCC catalyst in the SLO. Therefore, the FCC catalyst that has not settled is suspended in the treated liquid obtained by the separation process by the separation device. The content of the FCC catalyst in the treated liquid is lower in the upper layer and higher in the lower layer. Therefore, the upper layer of the treated liquid in which the content of the FCC catalyst is equal to or less than the product specification value is sent to the product SLO transfer line 52 as the product SLO. On the other hand, the treated liquid after separating the product SLO is sent to the recycled SLO supply line 51 as the recycled SLO and is supplied again to the fluid catalytic cracking device 1. Since the recycled SLO undergoes some cracking when used again in the fluid catalytic cracking reaction, thereby increasing the yield of light fractions, and since the catalyst contained in the recycled SLO can be returned to the FCC unit, in this embodiment, it is preferable to supply the recycled SLO again directly to the FCC unit 1 from the separation unit 50 through the recycled SLO supply line 51.

In addition, since the SLO product is used as a heavy oil base material, the FCC catalyst content (product standard value) is preferably 0.45 mass% or less in order to protect equipment that uses heavy oil C.

<Method for controlling the amount of fluid catalytic cracking residual oil recycled in a fluid catalytic cracking process>
Another aspect of the present invention is a method for controlling the amount of fluid catalytic cracking residual oil recycled when fluid catalytic cracking residual oil, which is a type of refined oil, containing the fluid catalytic cracking catalyst, is re-supplied to the fluid catalytic cracking unit in a fluid catalytic cracking process in which a feed oil is contacted with a fluid catalytic cracking catalyst in a fluid catalytic cracking unit to obtain a cracked oil, and the cracked oil is separated in a distillation tower to obtain a refined oil, by changing the wear strength of the fluid catalytic cracking catalyst.

In this embodiment, the fluid catalytic cracking catalyst and the equipment used in the fluid catalytic cracking process (fluid catalytic cracking unit, distillation column, and separation unit) are the same as those described above.

In this embodiment, the amount of SLO recycled in a fluid catalytic cracking process in which SLO is recycled is controlled by changing the wear strength of the FCC catalyst. Specifically, the amount of SLO recycled can be reduced by using a catalyst with a low wear strength value.

When changing the wear strength of the FCC catalyst in the FCC unit to control the amount of SLO recycled, all of the FCC catalyst in the FCC unit may be replaced at once with an FCC catalyst having the desired wear strength, or a portion of the FCC catalyst in the FCC unit may be replaced periodically or regularly with an FCC catalyst having the desired wear strength.

In fluid catalytic cracking reactions, the activity of the FCC catalyst is reduced not only by the above-mentioned coke, but also by the accumulation of heavy metals and hydrothermal degradation. As described above, FCC catalysts whose activity has been reduced by coke can be regenerated in the FCC unit by circulating air in the regeneration tower of the FCC unit and burning off the coke at high temperatures. On the other hand, FCC catalysts whose activity has been reduced by the accumulation of heavy metals and hydrothermal degradation cannot be regenerated in the FCC unit. For this reason, a method is adopted in which part of the FCC catalyst whose activity has been reduced by the accumulation of heavy metals and hydrothermal degradation is periodically or regularly removed and the required amount of new catalyst is introduced to maintain the activity of the FCC catalyst in the FCC unit (hereinafter referred to as "catalyst makeup treatment").

When controlling the amount of SLO recycled by periodically or steadily replacing a portion of the FCC catalyst in the FCC unit with an FCC catalyst having the desired wear strength, it is preferable to add an FCC catalyst having the desired wear strength as new catalyst for the above-mentioned catalyst makeup.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

<Measurement of Attrition Strength of FCC Catalyst>
The abrasion strength [%] of the fluid catalytic cracking catalyst was measured in accordance with the abrasion strength measurement method described in Catalysts and Chemical Engineers, Vol. 13, No. 1 (1996), as follows, using an abrasion strength measurement device simulating the catalyst tube and cyclone of a fluid catalytic cracking apparatus shown in Figure 2. The following will be explained with reference to Figure 2.
After the FCC catalyst to be measured was dried at 500°C for 5 hours, 3 g of the dry weight was measured, 0.3 g of added water was added, and the catalyst was introduced into the catalyst tube 66 of the wear strength measuring device. Next, the flow rate (linear velocity) of the nitrogen in the catalyst tube 66 was adjusted to 0.104 m/s by the flow rate regulator 63, and the measurement was started. The amount of the FCC catalyst particles scattered from the cyclone 67 and collected by the receiver 68 from 12 hours to 42 hours after the start of the measurement was measured and used as the average wear amount. Using this value, the wear strength was calculated using the following formula.
Abrasion strength (%) = average abrasion amount ÷ amount of catalyst put into abrasion strength measuring device (3 g) × 100
That is, the lower the abrasion strength value, the higher the abrasion strength of the FCC catalyst.

<Proportion of particle sizes of 50 μm or less>
The particle size distribution of the FCC catalyst was measured in accordance with JIS Z8815, and the proportion of particles having a particle size of 50 μm or less was determined from the particle size distribution obtained.

[Production Example 1]
42g (dry basis, _SiO2 equivalent) of silica sol (binder) was diluted with 25% sulfuric acid and stirred to obtain a silica sol suspension. 60g (dry basis) of stabilized Y-type zeolite was added to distilled water to prepare a zeolite slurry. 70.4g (dry basis) of kaolinite (clay mineral) and 26g (dry basis) of alumina hydrate oxide were added and mixed to the above silica sol aqueous solution, and the above _zeolite slurry and 1g of primary aluminum _phosphate (dry basis _{, Al2O3.2P2O5} equivalent) were added and stirred and mixed for 10 minutes using a disperser to prepare an aqueous slurry.
The obtained aqueous slurry was spray-dried under the conditions of an inlet temperature of 210 ° C. and an outlet temperature of 140 ° C. to obtain microspheres as a catalyst precursor. Then, it was ion-exchanged twice with 3 L of 5 mass% ammonium sulfate aqueous solution heated to 60 ° C., and further washed with 3 L of distilled water. Then, the washed microspheres were ion-exchanged for 15 minutes with an aqueous lanthanum nitrate solution so that the lanthanum oxide content on a dry basis was 0.3 mass%, and then washed with 3 L of distilled water. Then, it was dried overnight at 110 ° C. in a dryer to obtain FCC catalyst A. The wear strength and the proportion of particles with a particle diameter of 50 μm or less of FCC catalyst A were obtained by the above-mentioned method. Table 1 shows the composition of FCC catalyst A, its wear strength, and the proportion of particles with a particle diameter of 50 μm or less.

[Example 1]
The FCC catalyst A was packed in a fluid catalytic cracking unit (actual machine), and the feedstock oil shown in Table 2 was catalytically cracked under the conditions shown in Table 3. The obtained cracked oil was separated into LPG, gasoline, LCO, HCO, and SLO in a distillation tower (actual machine). This SLO was transferred to a liquid cyclone, and the product SLO with the FCC catalyst content shown in Table 4 was separated, and the SLO after separation of the product SLO was re-supplied to the fluid catalytic cracking unit as recycled SLO. As a result, in Example 1 using this FCC catalyst A, the recycled SLO amount could be reduced from 14.5 [KL/H] to 10.5 [KL/H] while maintaining the FCC catalyst content in the product SLO at 0.02 mass% or less, and the feedstock oil supply amount could be increased from 24,600 [BPD] to 25,200 [BPD] within the range not exceeding the upper limit of the air supply amount and the upper limit of the temperature of the regeneration tower.

[Comparative Example 1]
Fluid catalytic cracking reaction was carried out in the same manner as in Example 1, except that a commercially available FCC catalyst B containing stabilized zeolite as an active component like FCC catalyst A was used as the catalyst. The abrasion strength of catalyst B and the proportion of particles having a particle size of 50 μm or less were determined by the above-mentioned method. The abrasion strength of FCC catalyst B and the proportion of particles having a particle size of 50 μm or less are shown in Table 1.
Table 4 shows the content of FCC catalyst in the product SLO [mass %], the feed oil supply amount [BPD], and the amount of recycled SLO [KL/H].
In this comparative example, although the content of FCC catalyst in the product SLO was slightly higher than that in Example 1, the recycled SLO amount was 18.4 [KL/H], which was higher than that in Example 1. As a result, in order to keep the air supply amount and temperature in the regeneration tower within the upper limit, the feed oil supply amount had to be reduced to 24,000 [BPD], which was lower than that in Example 1.

The method for recycling fluid catalytic cracking residual oil in a fluid catalytic cracking process and the method for controlling the amount of fluid catalytic cracking residual oil recycled according to the present invention are useful because they can reduce the amount of fluid catalytic cracking residual oil recycled and improve the efficiency of the fluid catalytic cracking process.

1...Fluid catalytic cracking unit, 10...Riser, 11...Feedstock oil supply line, 12...Preheater, 20...Reactor, 21...Cyclone, 22...Cracked oil discharge line, 23...Stripper, 24...Post-reaction catalyst transfer line, 30...Regenerator, 31...Air blower, 32...Air grid, 33...Cyclone, 34...Regenerated catalyst transfer line, 35...Exhaust gas line, 40...Distillation tower, 41...Fluid catalytic cracking residual oil transfer line, 50...Separator, 51...Recycled SLO supply line, 52...Product SLO transfer line, 61...Solenoid valve, 62...Pressure control valve, 63...Flow regulator, 64...Pressure gauge, 65...Orifice plate, 66...Catalyst tube, 67...Cyclone, 68...Receiver, 69...Flow meter, 70...Sample

Claims (3)

A method for recycling fluid catalytic cracking residual oil, comprising the steps of: contacting a feedstock oil with a fluid catalytic cracking catalyst in a fluid catalytic cracking unit to obtain a cracked oil; separating the cracked oil in a distillation column to obtain a refined oil; separating a fluid catalytic cracking residual oil containing the fluid catalytic cracking catalyst, which is a type of the refined oil, in a separation unit; and directly supplying from the separation unit to the fluid catalytic cracking residual oil having a fluid catalytic cracking catalyst content exceeding a product standard value among the fluid catalytic cracking residual oils after the separation unit;
The method for recycling fluid catalytic cracking residual oil, wherein the attrition strength of the fluid catalytic cracking catalyst is 2 to 5%. The method for recycling fluid catalytic cracking residual oil according to claim 1, wherein the proportion of the fluid catalytic cracking catalyst having a particle diameter of 50 μm or less is 15 to 23 mass %. A method for producing a refined oil, comprising contacting a feedstock oil with a fluid catalytic cracking catalyst in a fluid catalytic cracking apparatus to obtain a cracked oil, and separating the cracked oil in a distillation column to obtain a refined oil, comprising:
The method for producing refined oil includes a step of recycling the fluid catalytic cracking residual oil, which is a type of the refined oil and contains the fluid catalytic cracking catalyst, by a separation device, and feeding the fluid catalytic cracking residual oil having a fluid catalytic cracking catalyst content exceeding a product standard value from the separation device back to the fluid catalytic cracking device, wherein the wear resistance of the fluid catalytic cracking catalyst is 2 to 5%.

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