Hydrocracking process and apparatus for removing heavy polynuclear aromatic hydrocarbons

Abstract

An exemplary embodiment may be a process for processing a hydrocracking fraction. The process can include obtaining a bottoms stream from a fractionation column, stripping the HPNA from the bottoms stream, and adsorbing the HPNA from the stripped stream to provide an adsorbed stream that can meet a desired HPNA concentration specification. The adsorption step may be adjusted to achieve an adjusted HPNA concentration.

Description

[0001] This application is a divisional application of a patent application with application number 201880014261.5, application date February 27, 2018, and invention name “Hydrocracking method and equipment for removing heavy polynuclear aromatic hydrocarbons”.

[0002] This patent application claims priority to U.S. Patent Application No. 15 / 445,681, filed on February 28, 2017, the contents of which are hereby incorporated by reference in their entirety. Technical Field

[0003] The field generally relates to methods and apparatus for removing HPNA from hydrocracked streams. Background Art

[0004] Typically, heavy polynuclear aromatic hydrocarbons (HPNA) compounds can be minor by-products from the hydrocracking process. HPNA compounds can be a problem, especially for high conversion hydrocracking units, and are present in the reactor product. Recycling unconverted oil to increase the yield of distillate products can cause the HPNA compounds to accumulate in the recycled oil. The HPNA compounds accumulated in the recycled oil can be deposited on the catalyst in the form of coke, which can reduce catalyst performance and cause the catalyst recycle length to be shortened. For hydrocracking units processing heavier feeds, the generation of undesirable HPNA compounds may be more significant. Therefore, it is desirable to remove HPNA compounds from unconverted oil to minimize catalyst deactivation.

[0005] One way to remove HPNA is to reduce the conversion rate by pumping a portion of the unconverted oil to limit the accumulation of HPNA compounds. Unfortunately, this is generally undesirable due to economic and logistical considerations because of the loss of yield and the lack of a market for the unconverted oil. In order to minimize the pumping rate of the unconverted oil, schemes such as carbon bed adsorption of circulating oil streams to remove HPNA and stripping towers to concentrate HPNA in unconverted oil waste streams have been commercially implemented. It may be problematic to handle HPNA concentrated streams within a refinery. If the refinery does not have an outlet for a fuel oil system or heavy bunker fuel oil, there may not be a good outlet for the HPNA concentrated stream due to the increasing environmental restrictions on the use of heavy fuel oil or FCC units and the decreasing demand for them.

[0006] Attempts to recycle unconverted oil through the crude vacuum distillation column and coker unit in some cases result in the recycling of HPNA back to the hydrocracking unit where accumulation of HPNA leads to increased fouling and catalyst deactivation. Furthermore, if unconverted oil with a high HPNA content must be stored and transported to a suitable location, the storage and transfer temperatures must be maintained at a level to prevent the HPNA from precipitating out of solution and depositing on pipelines or equipment.

[0007] It is desirable to control the HPNA content of the unconverted oil stream so that it can be properly processed within a refinery at low cost. Summary of the invention

[0008] A method and apparatus provides an unconverted oil stream from a hydrocracking reactor having an adjusted concentration of HPNA. In one aspect, the adsorption zone can provide a variable space velocity to maintain the HPNA concentration within a specific range. In another aspect, multiple adsorption beds in a series can be utilized, where the stream enters only one bed or some beds and then enters other adsorption beds in the series when the HPNA concentration of the adsorbent stream exceeds a predetermined maximum value.

[0009] definition

[0010] As used herein, the term "stream" may include various hydrocarbon molecules such as linear, branched or cyclic alkanes, alkenes, alkadienes and alkynes, and optionally other substances such as gases, for example hydrogen, or impurities such as heavy metals, and sulfur and nitrogen compounds. The stream may also include aromatic hydrocarbons and non-aromatic hydrocarbons. In addition, hydrocarbon molecules may be abbreviated as C1, C2, C3 ... Cn, where "n" represents the number of carbon atoms in one or more hydrocarbon molecules. In addition, the subscript "+" or "-" may be used to abbreviate one or more hydrocarbon symbols, for example C3 + or C3 - , preferably including one or more hydrocarbons abbreviated. As an example, the abbreviation "C3 + ” means one or more hydrocarbon molecules having more than three carbon atoms and preferably three or more carbons.

[0011] As used herein, the term "enriched" may identify a stream from a separation unit, such as a stripping column, that has a higher concentration of one compound or class of compounds than in the stream fed to the separation unit.

[0012] As used herein, the term "lean" may identify a stream from a separation unit, such as a stripping column, that has a lower concentration of a compound or class of compounds than in the stream fed to the separation unit.

[0013] As used herein, the term "substantially" may mean that the amount of a compound or class of compounds in a stream is generally at least 80 mole%, preferably 90 mole%, and optimally 99 mole%.

[0014] As used herein, the term "hydrocracking" may refer to a process of cracking hydrocarbons into lower molecular weight hydrocarbons in the presence of hydrogen and optionally a catalyst.

[0015] As used herein, the term "heavy polynuclear aromatics" may be abbreviated as "HPNA" and may characterize compounds having seven, and preferably ten or more "benzene rings" typically produced in a hydrocracking reaction zone.

[0016] As used herein, the term "fluid" may mean one or more gases, one or more liquids, and / or one or more vapors.

[0017] As used herein, the term "gas" may mean a single gas or a solution of multiple gases.

[0018] As used herein, the term "liquid" may mean a single liquid, or a solution or suspension of one or more liquids and one or more gases and / or solid particles.

[0019] As used herein, the term "vapor" may refer to a gas or dispersion that may include or consist of one or more hydrocarbons and / or water. The dispersion may include one or more of a gas, a liquid, and a solid, such as a dispersion of an aerosol and / or a mist.

[0020] As used herein, the term "top" can be at or near the top of a container.

[0021] As used herein, the term "bottom" may be at or near the bottom of a container.

[0022] As used herein, the term "non-distillable components" may include finely divided particulate matter that may tend to foul heat exchange surfaces, form coke on catalysts, deactivate catalysts and / or plug catalyst beds. Generally, the finely divided particulate matter may include polymerized organic matter.

[0023] As used herein, the term "space velocity" may include the ratio of the volume or mass of the treated material to the volume or mass of the adsorbent or catalyst, respectively.

[0024] As used herein, the term "kilopascal" may be abbreviated as "kPa" and all pressures disclosed herein are absolute pressures; the term "hour" may be abbreviated as "hr"; the term "kilogram" may be abbreviated as "kg"; the term "cubic meter" may be abbreviated as "m 3 ”; and the term “liquid hourly space velocity” may be abbreviated as “LHSV”.

[0025] As used herein, unless another method is specified, the boiling point of a stream may be determined by ASTM method D2887-97.

[0026] As shown in the drawings, the process lines in the drawings may be referred to interchangeably as, for example, lines, pipes, feeds, fractions, condensates, residues, mixtures, portions, hydrocarbons, effluents, products, or streams. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Attached Figure 1 is a schematic diagram of an exemplary embodiment. DETAILED DESCRIPTION

[0028] Referring to the Figure, there is shown an exemplary embodiment of an apparatus and process 10. The apparatus and process 10 may include a hydrocracking reactor 100, a heater 130, a fractionator 140, a recycle stripper 160, and an adsorption zone 200. A hydrocracking feed 60 may be provided to the apparatus and process 10.

[0029] The hydrocracking feed 60 may be a hydrocarbon-containing oil containing hydrocarbons and / or other organic substances to produce products containing hydrocarbons and / or other organic substances having a lower average boiling point and a lower average molecular weight. The hydrocracking feed 60 may include mineral oils and synthetic oils, such as shale oils, tar sand products, and fractions thereof. Exemplary hydrocracking feeds 60 include those containing components having an initial boiling point higher than 285°C, such as atmospheric diesel; vacuum gas oil; deasphalted vacuum and atmospheric residues; hydrotreated or mildly hydrocracked residual oils; coker fractions; straight run fractions; solvent deasphalted oils; pyrolysis derived oils; high boiling synthetic oils; cycle oils; and catalytic cracker fractions. An exemplary preferred hydrocracking feed 60 is a gas oil or other hydrocarbon fraction whose components boil at a temperature higher than the desired product endpoint, such as 360°C, of ​​at least 50% by weight. An exemplary hydrocracking feed 60 may include one or more hydrocarbon components having a boiling point greater than 285° C. and preferably includes at least 25% by volume of components having a boiling point of 310° C. to 540° C. The hydrocracking feed 60 may be combined with a recycle stream 158, as described below, to form a combined stream 64 and provided to the hydrocracking reactor 100. Hydrogen may be added to the combined stream 64 in line 66 or directly to the hydrocracking reactor.

[0030] The hydrocracking reactor 100 may include a single reactor or multiple reactors, and carry out methods such as hydrocracking and hydrotreating. The hydrocracking reactor 100 may include a hydrocracking catalyst, which utilizes an amorphous matrix or a low-content zeolite matrix of one or more metals of the 6th and 8-10th groups of the periodic table as a hydrogenation metal and a promoter. In another embodiment, the catalyst may include any crystalline zeolite cracking matrix, on which a small portion of the 8th-10th group metals of the periodic table are deposited. The hydrogenation component may also be selected from the 6th group metal of the periodic table of the periodic table incorporating a zeolite matrix. The hydrogenation metal may include one or more of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum, and may include molybdenum and tungsten. The amount of hydrogenation metal in the catalyst may vary over a wide range, such as 0.05 wt % to 30 wt % based on the weight of the catalyst. For precious metals such as platinum and palladium, 0.05 wt % to 2 wt % may be used.

[0031] Zeolite matrices may be referred to as molecular sieves and are composed of silicon dioxide, aluminum oxide, and one or more exchangeable cations such as sodium, magnesium, calcium, and at least one rare earth metal. They may also be characterized by having crystal pores of relatively uniform diameters of 4 to 14 angstroms. Suitable zeolites may include mordenite, stilbite, heulandite, ferrierite, cyclotite, chabazite, erionite, and faujasite, as well as β, X, Y, and L crystal types, such as synthetic faujasite and mordenite. Generally, an exemplary zeolite is a synthetic Y molecular sieve.

[0032] The original zeolite monovalent metal may be ion exchanged with a multivalent metal and / or with an ammonium salt and then heated to decompose the ammonium ions associated with the zeolite, leaving in their place hydrogen ions and / or exchange sites deionized by further removal of water. Exemplary hydrogen or deionized Y zeolites are disclosed, for example, in US 3,130,006.

[0033] Mixed multivalent metal-hydrogen zeolites can be prepared by first ion exchanging with an ammonium salt, then partially back exchanging with a multivalent metal salt, and then calcining. In some cases, the hydrogen form can be prepared by direct acid treatment of an alkali metal zeolite.

[0034] A preferred method of incorporating the hydrogenation metal is to contact the zeolite matrix material with an aqueous solution of a suitable compound of the desired metal, wherein the metal may be present in cationic form. After adding the selected one or more hydrogenation metals, if desired, the resulting catalyst powder may then be filtered, dried, pelletized with added lubricants, binders, etc., and calcined in air at a temperature of, for example, 370° C. to 650° C. to activate the catalyst and decompose the ammonium ions. Alternatively, the zeolite component may first be pelletized, then the hydrogenation component may be added and activated by calcination. The above catalyst may be used in an undiluted form, or a powdered zeolite catalyst may be mixed with other relatively less active catalysts, diluents or binders such as alumina, silica gel, silica-alumina co-gels and activated clays in a ratio ranging from 5% to 90% by weight and pelletized. These diluents may be used as is, or they may contain a smaller proportion of the added hydrogenation metals of the 6th and 8-10th groups of the periodic table.

[0035] Additional metal-promoted hydrocracking catalysts may also be utilized and may include aluminophosphate molecular sieves, crystalline chromosilicates, and other crystalline silicates. Such crystalline silicates are disclosed, for example, in US 4,363,718.

[0036] The hydrocracking feed may be hydrocracking with a hydrocracking catalyst in the presence of hydrogen and preferably under hydrocracking reactor conditions at a temperature of 230°C to 470°C, a pressure of 3,450 kPa to 20,690 kPa, 0.1 hr -1 Up to 30 hours-1 LHSV and 330 standard m 3 / m 3 Up to 25,000 standard m 3 / m 3 Such feed and hydrocracking reactors are disclosed, for example, in US 4,447,315 and US 6,379,535.

[0037] The hydrocracked stream in the hydrocracking effluent line 110 may be provided to a heater 130 and heated to any suitable temperature, such as 140° C. to 400° C., and provided to a fractionation column 140 in downstream communication with the hydrocracking reactor 100 for fractionating the hydrocracked stream. The hydrocracked stream may first be separated in a series of separators 120 to provide one or two hydrocracked liquid streams in lines 122 and / or 123, and stripped in a stripper 124 by an inert gas such as steam to remove gases (including light hydrocarbons and hydrogen sulfide), and provide a stripped liquid hydrocracked stream in line 126 before heating in the heater 130. More than one stripper 124 may be used.

[0038] The fractionation tower 140 may include one or more trays, which may include bubble caps or other suitable vapor / liquid contacting devices. The tower 140 may be operated at a flash zone temperature of 330° C. to 390° C. and a pressure of 13 kPa to 138 kPa (absolute). The fractionation tower 140 may include two fractionation towers, one of which is operated at vacuum pressure. The heated hydrocracked stream in line 132 may be provided to the fractionation tower 140, wherein the lighter components pass upward and the lighter products are further withdrawn from the tower 140, and the heavier components such as in the fractionation tower bottom stream in the bottom line 152 leave the tower 140. The diesel stream may be removed from one side of the fractionation tower in line 154.

[0039] The bottoms stream 152 can be divided into a process fractionation bottoms stream in process line 156 and a recycle stream 158 that is recycled to the hydrocracking reactor 100. The recycle stream in recycle line 158 can be combined with the hydrocracking feed 60 to provide a combined stream 64, as described above. The process fractionation bottoms stream in process line 156 can be provided to a recycle stripper 160, which can include a rotating drum. The recycle stripper 160 can be in downstream communication with the fractionation column 140 for stripping the fractionation stream in the bottoms line 152.

[0040] The recycle stripper 160 can be operated under any suitable conditions to fractionate the bottom stream with an inert gas, such as steam, stripping process to provide an HPNA-depleted top stream in an overhead line 164 and an HPNA-enriched stripping stream in a stripping line 168. In one embodiment, the stripper 160 can be disposed at the bottom of a fractionation column 140 that is configured to function as a split shell column, not shown. The top stream in the overhead line 164 can be returned to the fractionation column 140 to recover valuable products therefrom.

[0041] The stripping stream in stripping line 168 may include non-distillable components such as HPNA compounds, one or more C24 + The stripping stream may be transferred to an adsorption zone 200 to have HPNA adsorbed from the stripping stream to provide an adsorption stream having a desired HPNA concentration. The adsorption zone 200 may be in downstream communication with the recycle stripping column 160 for adsorbing HPNA in the stripping stream in line 168.

[0042] The adsorption zone 200 may include a plurality of adsorption beds 22-25 in series, so the stripping stream in the stripping line 168 may be adsorbed on a plurality of beds in series. The stripping stream in the stripping line 168 may contain 500 wppm to 3000 wppm of HPNA, and suitably 900 wppm to 1500 wppm of HPNA. The stripping stream may be combined with the recycle stream in line 30 before being fed to the adsorption line 34. Alternatively, all or a portion of the stripping stream may be diverted to the bypass line 32. The plurality of adsorption beds 22-25 may be housed in the same vessel 20 as shown. It is also contemplated that the series of adsorption beds 22-25 may be housed in one or more separate vessels not shown.

[0043] Each adsorption bed 22-25 may have an extraction line 22a-25a in communication with the respective bed and a control valve on the extraction line. The extraction line 22a-25a may be located in a volume in the vessel 20, preferably just below the respective bed 22-25, and have an inlet for extracting adsorption liquid that has contacted the adsorbent in the respective bed and may have left the respective bed. The extraction line 22a-25a may include a pipe and have an opening in the pipe in communication with the respective bed 22-25 for extracting the adsorption liquid. The adsorption liquid in the extraction line 22a-25a may be collected in the manifold line 28.

[0044] The adsorption zone 200 can be operated to change the space velocity during the adsorption process. The stripping stream in the pipeline 34 can be directed to the first adsorption bed 22, in which HPNA is adsorbed from the stripping stream through the adsorption feed pipeline 26, which has an open control valve. The first adsorption bed 22 can be an upstream adsorption bed 22 of the plurality of adsorption beds 22-25. Under initial conditions, the control valve on the extraction line 22a can be an upstream control valve on the upstream extraction line 22a, which is open when the downstream control valves on the downstream extraction lines 23a, 24a and 25a are closed. Under initial conditions, the stripping liquid from the adsorption feed line 26 will fill the container 20, but will only leave through the extraction line 22a, so the additional stripping liquid entering the container 20 after the container is filled will only flow through the upstream adsorption bed 22. The HPNA concentration measurement device 36 on the product pipeline 50 connected downstream to the manifold line 28 can be used to measure the concentration of HPNA in the product pipeline 50. Alternatively, the HPNA concentration may be determined manually by taking a sample from the product line 50 for laboratory HPNA concentration analysis. The HPNA concentration measuring device may notify the computer 40 of the measured HPNA concentration value by sending a signal. The computer or operator may determine whether the measured HPNA concentration of the adsorbent stream in the product line 50 exceeds a predetermined maximum HPNA concentration. If the measured HPNA concentration of the adsorbent stream exceeds the predetermined maximum HPNA concentration, the computer 40 or the operator may send a signal to close, or the operator may close the upstream control valve on the upstream extraction line 22a and send a signal to open, or the operator may open the downstream control valve on the downstream extraction line 23a of the downstream adsorbent bed 23 for multiple adsorbent beds. The adjustment from the initial condition to the adjusted condition is used to change the space velocity because the stripping stream effectively contacts the adsorbent in the two adsorbent beds 22 and 23 under the adjusted condition compared to only the single bed 22 under the initial condition to adjust the HPNA concentration of the adsorbent stream back to or below the predetermined concentration. Preferably, the downstream adsorption bed 23 is an adsorption bed in the downstream series and adjacent to the upstream adsorption bed 22. Under the adjusted condition, the control valve on the extraction line 23a can become an upstream control valve on the upstream extraction line 23a, which is open when the downstream control valves on the extraction lines 24a and 25a are closed. In addition, the last upstream control valve on the last upstream extraction line 22a under the initial condition remains closed.

[0045] If the measured HPNA concentration of the adsorbent stream exceeds a predetermined maximum HPNA concentration under the adjusted conditions, the computer 40 or the operator may send a signal to close, or the operator may close, the upstream control valve on the upstream extraction line 23a, and the computer 40 or the operator may send a signal to open, or the operator may open, the downstream control valve on the downstream extraction line 24a for the downstream adsorbent bed 24 of the plurality of adsorbent beds. The adjustment from the adjusted conditions to the second adjusted conditions serves to change the space velocity because the stripping stream effectively contacts the adsorbent in three adsorbent beds 22, 23, and 24 under the second adjusted conditions compared to only two beds 22, 23 under the adjusted conditions to adjust the HPNA concentration of the adsorbent stream back to at or below the predetermined concentration. Preferably, the downstream adsorbent bed 24 is the adsorbent bed in the downstream series and adjacent to the upstream adsorbent bed 23. Under the second adjusted conditions, the control valve on the extraction line 24a may become the upstream control valve on the upstream extraction line 24a, which is open when the downstream control valve on the extraction line 25a is closed. In addition, the last upstream control valve on the last upstream extraction line 22a, 23a under the regulated condition remains closed.

[0046] If the measured HPNA concentration of the adsorbent stream at the second conditioned condition exceeds the predetermined maximum HPNA concentration, the computer 40 or the operator sends a signal to close, or the operator closes, the upstream control valve on the upstream extraction line 24a, and the computer 40 or the operator sends a signal to open, or the operator opens, the downstream control valve on the downstream extraction line 25a for the downstream adsorbent bed 25 of the plurality of adsorbent beds. The adjustment from the second conditioned condition to the final conditioned condition serves to change the space velocity because the stripping stream effectively contacts the adsorbent in four adsorbent beds 22, 23, 24, and 25 at the final conditioned condition, as compared to only three beds 22, 23, and 24 at the second conditioned condition, to adjust the HPNA concentration of the adsorbent stream back to at or below the predetermined concentration. Preferably, the downstream adsorbent bed 25 is the adsorbent bed in the downstream series and adjacent to the upstream adsorbent bed 24. At the final conditioned condition, the control valve on the extraction line 25a is open. In addition, the last upstream control valve on the last upstream extraction line 22a, 23a, 24a in the second regulated condition remains closed.

[0047] An additional renewal adsorbent bed 44 is disposed in parallel with the plurality of adsorbent beds 22-25 for adsorbing HPNA from the stripping stream when the flow of the stripping stream to the plurality of adsorbent beds is shut off. If the measured HPNA concentration of the adsorbent stream in the product line 50 at the final conditioned condition exceeds a predetermined maximum HPNA concentration, the computer or operator sends a signal to close, or the operator closes, the control valve on the adsorbent feed line 26, and the computer or operator sends a signal to open, or the operator opens, the control valve on the renewal line 42 to the renewal adsorbent bed 44, which is not in series with the plurality of adsorbent beds 22-25 but may be in parallel thereto. The renewal adsorbent bed 44 may be in a separate vessel. The flow of the stripping stream in line 168 to the plurality of adsorbent beds 22-25 in series is stopped or shut off to effectuate replacement or regeneration of one or more of the plurality of adsorbent beds 22-25. To enable the hydrocracking process to continue, the stripping stream is fed to the renewal adsorption bed 44 through the pipeline 42 to continue to adsorb HPNA from the stripping stream when the flow to the plurality of adsorption beds 22-25 is shut off. Once the measured HPNA concentration in the product pipeline 50 exceeds the predetermined maximum HPNA concentration and the regeneration or replacement of the adsorption beds 22-25 is completed, the computer 40 or the operator sends a signal to close, or the operator closes the control valves on the renewal pipeline 42 and the extraction pipeline 23a-25a, and the computer 40 or the operator sends a signal to open, or the operator opens, the control valves on the adsorption feed pipeline 26 and the extraction pipeline 22a, and the process continues. The pipeline 30 can recycle the adsorption liquid to the stripping line 168 through a pump to ensure adequate distribution of the liquid on the adsorption beds 22-25 and 44.

[0048] When the measured HPNA concentration value of the adsorbent stream in the product line 50 drops below a predetermined minimum value, the computer 40 or the operator may send a signal to close or partially close, or the operator may close or partially close a control valve on the adsorbent feed line 26 or on the renewal line 42, and the computer 40 or the operator may send a signal to open or partially open, or the operator may open or partially open a control valve on the bypass line 32 to allow a portion or all of the stripping stream in the stripping line 168 to bypass the adsorbent beds 22-25 and 44. It may be advantageous to open a downstream control valve on the extract lines 22a-25a or on the renewal line 42 to allow the downstream adsorbent beds to be combined with fresh adsorbent, which may adsorb more HPNA than is required to meet the HPNA specification of the adsorbent stream. Once the HPNA concentration of the adsorbent stream in the product line 50 exceeds a predetermined minimum value on the adsorption feed line 26 or the refresh line 42 (whichever was most recently closed to allow bypassing), the computer or operator may send a closure or partial closure signal, or the operator may close or partially close the control valve on the bypass line 32. The mentioned valves may be partially closed or opened to more accurately control the HPNA concentration of the adsorbent stream in the product line 50.

[0049] The measuring and adjusting steps in the method can be performed manually or automatically.

[0050] The adsorbent stream in product line 50 may have an HPNA concentration between 150 wppm and 600 wppm. Because the HPNA concentration of the adsorbent stream is low enough, the stream may be used as a lubricant, FCC feed, or coker feed, or fed to a crude tower, returned to the hydrocracking reactor 100, or cooled and sent to storage or transport for future use without concern for contamination of the equipment.

[0051] In adsorption zone 200, the stripping stream may be contacted with a suitable adsorbent that selectively retains HPNA compounds. Suitable adsorbents may include one or more of molecular sieves, silica gel, activated carbon, activated alumina, silica-alumina gel, and clay. The adsorbent may be installed in each adsorption bed 22-25 and 44 in any suitable manner, such as a fixed bed arrangement. The adsorption beds 22-25 and 44 may be maintained at a pressure of 170 kPa to 4,300 kPa, a temperature of 10° C. to 370° C., and a 0.1 hr -1 Up to 500hr -1 The flow of hydrocarbons through the vessel 20 may be carried out in an upflow, downflow or radial flow manner, wherein the hydrocarbons are in the liquid phase.

[0052] Specific implementation plan

[0053] While the following is described in conjunction with specific embodiments, it should be understood that this description is intended to illustrate and not to limit the scope of the foregoing description and the appended claims.

[0054] The first embodiment of the present invention is a method for hydrocracking, which includes hydrocracking a hydrocarbon feed stream over a hydrocracking catalyst in the presence of hydrogen to provide a hydrocracking stream; separating the hydrocracking stream to provide a liquid hydrocracking stream; fractionating the liquid hydrocracking stream to provide a fractionation tower bottom stream; stripping at least a portion of the bottom stream to provide a HPNA-rich stripping stream and an HPNA-depleted stream; adsorbing HPNA from the stripping stream to provide an adsorption stream having a certain HPNA concentration; measuring the HPNA concentration of the adsorption stream; and adjusting the HPNA concentration of the adsorption stream. One embodiment of the present invention is one, any one, or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, which also includes adsorbing the stripping stream on a plurality of adsorption beds in series. One embodiment of the present invention is one, any one, or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, wherein the plurality of adsorption beds are in the same container. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, which also includes changing the space velocity of the adsorption step. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, wherein each adsorption bed has an extraction line in the bed and a control valve on the extraction line. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, which also includes feeding a stripping stream to an upstream adsorption bed of a plurality of adsorption beds, wherein the upstream control valve on the upstream extraction line for the upstream adsorption bed is opened, and when the measured HPNA concentration of the adsorption stream exceeds a predetermined value, the upstream control valve is closed and the downstream control valve on the downstream extraction line for the downstream adsorption bed of the plurality of adsorption beds is opened. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, which also includes shutting off the flow of the stripping stream to a plurality of adsorption beds in series to replace or regenerate one or more of the plurality of adsorption beds. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, which also includes feeding the flow of the stripping stream to another adsorption bed while shutting off the flow to multiple adsorption beds. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, which also includes recycling a portion of the adsorption stream to the adsorption step. One embodiment of the present invention is one, any or all of the previous embodiments of this paragraph to the first embodiment of this paragraph, wherein the HPNA concentration of the stripping stream is 900 wppm to 1500 wppm, and the HPNA concentration of the adsorption stream is 150 wppm to 600 wppm.An embodiment of the invention is one, any or all of prior embodiments in this paragraph through the first embodiment in this paragraph further comprising bypassing the stripping stream around the adsorption bed when the HPNA concentration of the adsorption stream drops below a predetermined value.

[0055] A second embodiment of the present invention is a method for hydrocracking, which includes hydrocracking a hydrocarbon feed stream over a hydrocracking catalyst in the presence of hydrogen to provide a hydrocracking stream; fractionating the liquid hydrocracking stream to provide a fractionation tower bottoms stream; stripping at least a portion of the bottoms stream to provide a HPNA-rich stripping stream and an HPNA-depleted stream; adsorbing HPNA from the stripping stream on a plurality of adsorption beds in series to provide an adsorption stream having a certain HPNA concentration. One embodiment of the present invention is one, any one, or all of the previous embodiments of this paragraph to the second embodiment of this paragraph, which further includes measuring the HPNA concentration of the adsorption stream and adjusting the HPNA concentration of the adsorption stream. One embodiment of the present invention is one, any one, or all of the previous embodiments of this paragraph to the second embodiment of this paragraph, wherein the plurality of adsorption beds are in the same container. One embodiment of the present invention is one, any one or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, which also includes feeding a stripping stream to an upstream adsorption bed of the plurality of adsorption beds, wherein an upstream control valve on an upstream extraction line for the upstream adsorption bed is opened, and then closing the upstream control valve and opening a downstream control valve on a downstream extraction line for a downstream adsorption bed of the plurality of adsorption beds. One embodiment of the present invention is one, any one or all of the previous embodiments in this paragraph to the second embodiment in this paragraph, which also includes shutting off the flow of the stripping stream to the plurality of adsorption beds in series to replace or regenerate one or more of the plurality of adsorption beds; and feeding the flow of the stripping stream to another adsorption bed while shutting off the flow to the plurality of adsorption beds.

[0056] The third embodiment of the present invention is an apparatus for hydrocracking, which includes a hydrocracking reactor; a fractionation tower connected to the hydrocracking reactor for fractionating a hydrocracked stream; a stripper connected to the fractionation tower for stripping the fractionated stream; and an adsorption zone connected to the stripper for adsorbing HPNA in the stripping stream on a plurality of adsorption beds in series. One embodiment of the present invention is one, any one, or all of the previous embodiments of this paragraph to the third embodiment of this paragraph, wherein the plurality of adsorption beds are in the same container. One embodiment of the present invention is one, any one, or all of the previous embodiments of this paragraph to the third embodiment of this paragraph, further comprising an extraction line on each of the plurality of adsorption beds and a control valve on each extraction line. One embodiment of the present invention is one, any one, or all of the previous embodiments of this paragraph to the third embodiment of this paragraph, further comprising an additional adsorption bed in parallel with the plurality of adsorption beds for adsorbing HPNA from the stripping stream when the flow of the stripping stream to the plurality of adsorption beds is shut off.

[0057] Although there is no further detailed description, it is believed that those skilled in the art can utilize the present invention to the greatest extent by using the foregoing description and can easily ascertain the essential characteristics of the present invention without departing from the spirit and scope of the present invention to make various changes and modifications of the present invention and adapt it to various usages and conditions. Therefore, the aforementioned preferred specific embodiments should be understood as merely illustrative and not limiting the rest of the present disclosure in any way, and are intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0058] In the foregoing, all temperatures are set forth in degrees Celsius and all parts and percentages are by weight unless otherwise indicated.

Claims

1. A method for hydrocracking, comprising: hydrocracking a hydrocarbon feed stream over a hydrocracking catalyst in the presence of hydrogen to provide a hydrocracked stream; separating the hydrocracked stream to provide a liquid hydrocracked stream; fractionating the liquid hydrocracked stream to provide a fractionation column bottoms stream; stripping at least a portion of the bottoms stream to provide a stripped stream rich in HPNA and a stream lean in HPNA; adsorbing HPNA from the stripping stream to provide an adsorption stream having a HPNA concentration; measuring the HPNA concentration of the adsorption stream; and The HPNA concentration of the adsorption stream is adjusted.

2. The method of claim 1 further comprising adsorbing the stripping stream on a plurality of adsorption beds in series.

3. The method of claim 2, wherein the plurality of adsorption beds are in the same vessel.

4. The method of claim 2, further comprising varying the space velocity of the adsorption step.

5. The process of claim 4 wherein each adsorbent bed has an extraction line in the bed and a control valve on the extraction line.

6. The method of claim 5, further comprising feeding the stripping stream to an upstream adsorption bed of the plurality of adsorption beds, wherein an upstream control valve on an upstream extraction line for the upstream adsorption bed is opened, and when the measured HPNA concentration of the adsorption stream exceeds a predetermined value, the upstream control valve is closed and a downstream control valve on a downstream extraction line for a downstream adsorption bed of the plurality of adsorption beds is opened.

7. The method of claim 6, further comprising shutting off the flow of the stripping stream to the plurality of adsorbent beds in series to replace or regenerate one or more of the plurality of adsorbent beds.

8. The method of claim 7, further comprising feeding the flow of the stripping stream to another adsorption bed while shutting off the flow to the plurality of adsorption beds.

9. The process of claim 2, further comprising recycling a portion of the adsorption stream to the adsorption step.

10. An apparatus for hydrocracking, comprising: Hydrocracking reactor; a fractionation tower in communication with the hydrocracking reactor, for fractionating the hydrocracking stream; a stripping tower in communication with the fractionation tower, for stripping the fractionated stream; as well as An adsorption zone is in communication with the stripping column for adsorbing HPNA in the stripping stream on a plurality of adsorption beds in series.

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