WO2021173798A1 - Processus et appareil de séparation - Google Patents

Processus et appareil de séparation Download PDF

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Publication number
WO2021173798A1
WO2021173798A1 PCT/US2021/019608 US2021019608W WO2021173798A1 WO 2021173798 A1 WO2021173798 A1 WO 2021173798A1 US 2021019608 W US2021019608 W US 2021019608W WO 2021173798 A1 WO2021173798 A1 WO 2021173798A1
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WO
WIPO (PCT)
Prior art keywords
filter
xylene
solid
filtrate
reslurry
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PCT/US2021/019608
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English (en)
Inventor
Richard A. Wilsak
Brian BENJAMIN
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Ineos Us Chemicals Company
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Publication date
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Publication of WO2021173798A1 publication Critical patent/WO2021173798A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/50—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with multiple filtering elements, characterised by their mutual disposition
    • B01D29/52—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with multiple filtering elements, characterised by their mutual disposition in parallel connection
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D29/00—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor
    • B01D29/11—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements
    • B01D29/114—Filters with filtering elements stationary during filtration, e.g. pressure or suction filters, not covered by groups B01D24/00 - B01D27/00; Filtering elements therefor with bag, cage, hose, tube, sleeve or like filtering elements arranged for inward flow filtration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0004—Crystallisation cooling by heat exchange
    • B01D9/0013—Crystallisation cooling by heat exchange by indirect heat exchange
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0036—Crystallisation on to a bed of product crystals; Seeding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/004—Fractional crystallisation; Fractionating or rectifying columns
    • B01D9/0045—Washing of crystals, e.g. in wash columns
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0059—General arrangements of crystallisation plant, e.g. flow sheets
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/14—Purification; Separation; Use of additives by crystallisation; Purification or separation of the crystals

Definitions

  • the present disclosure relates generally to processes and apparatuses for separating p-xylene from a liquid feed stream.
  • centrifuge Typically, p-xylene is crystallized and then separated from mother liquor in a centrifuge to provide a product sufficiently pure for industrial applications. Centrifugation is a common solid-liquid separation technique, in which rapid rotation causes denser materials to move outward from the axis of rotation, while less-dense materials are displaced and move inward. Centrifuges are necessarily complex, involving moving parts that rotate at high speeds for extended periods of time. Accordingly, centrifuges can be costly to install and difficult to maintain.
  • the disclosure provides a method for recovering p-xylene, comprising in a crystallizer of a first crystallization zone, cooling a liquid feed stream comprising p-xylene to form a first solid/liquid mixture comprising solid p-xylene and mother liquor; transferring an effluent of the first crystallization zone to a second crystallization zone; in a crystallizer of the second crystallization zone, cooling at least a portion of the effluent to form a second solid/liquid mixture comprising solid p-xylene and mother liquor; transferring an effluent of the second crystallization zone to a third crystallization zone; in a crystallizer of the third crystallization zone, cooling at least a portion of the effluent to form a third solid/liquid mixture comprising solid p-xylene and mother liquor; transferring an effluent of the third crystallization zone to a recovery zone; in the recovery zone, filtering at least a portion of the efflu
  • the first solid/liquid mixture is filtered through at least one filter in a first filter column in the first crystallization zone to form a first filtrate comprising mother liquor and a first product stream comprising solid p-xylene, the filter having a first effective pore size larger (e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger) than the fourth effective pore size, and then the first product stream is slurried in a reslurry liquid to form a first reslurry stream; and the first crystallization zone effluent comprises the first filtrate.
  • a first effective pore size larger (e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger) than the fourth effective pore size
  • p-xylene is present in the first filtrate in an amount that is at least 1 wt.% (e.g., 1-5 wt.%) greater than the p-xylene solubility limit of the first filtrate.
  • the second solid/liquid mixture is filtered through at least one filter in a filter column in the second crystallization zone to form a second filtrate comprising mother liquor and a second product stream comprising solid p-xylene, the filter having a second effective pore size larger (e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger) than the fourth effective pore size, and then the second product stream is slurried in a reslurry liquid to form a second reslurry stream; and the second crystallization zone effluent comprises the second filtrate.
  • a second effective pore size larger (e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger) than the fourth effective pore size
  • p-xylene is present in the second filtrate in an amount that is at least 1 wt.% (e.g., 1-5 wt.%) greater than the p-xylene solubility limit of the second filtrate.
  • the third solid/liquid mixture is filtered through at least one filter in a filter column in the third crystallization zone to form a third filtrate comprising mother liquor and a third product stream comprising solid p- xylene, the filter having a third effective pore size larger (e.g., at least 25%, at least 50%, at least 100 at least 200%, or at least 300% larger) than the fourth effective pore size, and then the third product stream is slurried in a reslurry liquid to form a third reslurry stream; and the third crystallization zone effluent comprises the third filtrate.
  • the filter having a third effective pore size larger (e.g., at least 25%, at least 50%, at least 100 at least 200%, or at least 300% larger) than the fourth effective pore size
  • p-xylene is present in the third filtrate in an amount that is at least 1 wt.% (e.g., 1-5 wt.%) greater than the p-xylene solubility limit of the third filtrate.
  • p-xylene is present in the fourth filtrate in an amount that is at most 1 wt.% (e.g., 0.1-0.9 wt.%) greater than the p- xylene solubility limit of the fourth filtrate.
  • solid p-xylene is present in the fourth product stream in an amount that is at most 67% (e.g., at most 60% or at most 50%) of a total amount of solid p-xylene present in the first product stream, second product stream, third product stream, and fourth product stream.
  • At least a portion of the fourth reslurry stream and at least a portion of one or more of the first reslurry stream, second reslurry stream, and third reslurry stream are transferred to an efficiency-stage slurry drum of an efficiency zone.
  • At least a portion of an effluent of the efficiency-stage slurry drum is separated to form a fifth filtrate comprising reslurry liquid and a fifth product stream comprising solid p-xylene; at least a portion of the fifth product stream is slurried in a reslurry liquid to form a fifth reslurry stream; at least a portion of the fifth reslurry stream is transferred to a product-stage slurry drum of a product zone; and at least a portion of an effluent of the product-stage slurry drum is separated to form a sixth filtrate comprising reslurry liquid and a sixth product stream comprising p-xylene.
  • At least a portion of the fifth filtrate is transferred to the first crystallization zone.
  • the reslurry liquid of one or more of the first crystallization zone, second crystallization zone, third crystallization zone, and recovery zone comprises at least a portion of the fifth filtrate or sixth filtrate.
  • the reslurry liquid comprising the fifth reslurry stream includes at least a portion of the sixth filtrate.
  • the disclosure provides an apparatus for recovering p-xylene, comprising a first crystallizer; a second crystallizer in fluid communication with the first crystallizer; a third crystallizer in fluid communication with the second crystallizer; and a fourth filter unit comprising at least one filter column, each filter column in fluid communication with the third crystallizer, each filter column including at least one filter, each filter having a fourth effective pore size; and further comprising at least one of a first filter unit comprising at least one filter column, each filter column providing the fluid communication between the first crystallizer and the second crystallizer, each filter column including at least one filter, each filter having a first effective pore size; a second filter unit comprising at least one filter column, each filter column providing the fluid communication between the second crystallizer and the third crystallizer, each filter column including at least one filter, each filter having a second effective pore size; and a third filter unit comprising at least one filter column, each filter column providing the fluid communication between the third crystallizer and the fourth filter
  • the apparatus further comprises an efficiency-stage slurry drum in fluid communication with the fourth filter unit; a fifth filter unit comprising at least one filter column, each filter column in fluid communication with the efficiency-stage slurry drum, each filter column including at least one filter, each filter having a fifth effective pore size; a product-stage slurry drum in fluid communication with the fifth filter unit; and a sixth filter unit comprising at least one wash column, each wash column in fluid communication with the product-stage slurry drum.
  • the apparatus comprises the second filter unit, and the second effective pore size is larger (e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger) than the fourth effective pore size.
  • the second filter unit comprises 3-5 filter columns
  • the fourth filter unit comprises 3-5 filter columns
  • the apparatus comprises the first filter unit, and the first effective pore size is larger (e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger) than the fourth effective pore size.
  • the first filter unit comprises 2-4 filter columns, and the fourth filter unit comprises 4-8 filter columns.
  • FIG. 1 is a process flow diagram for the separation and recovery of p-xylene in accordance with one embodiment of the present disclosure.
  • FIG. 2 is a schematic view of a crystallization zone in accordance with one embodiment of the present disclosure.
  • FIG. 3 is a schematic view of a crystallization zone in accordance with one embodiment of the present disclosure.
  • FIG. 4 is a side view cross-section of a filter column in accordance with one embodiment of the present disclosure.
  • the processes of the disclosure provide for improved separation of p-xylene.
  • the present inventors have determined that high-purity p-xylene can be efficiently recovered by filtering crystallized p-xylene in a filter column having a relatively large pore size in one or more crystallization zones upstream of a recovery zone, and then filtering the crystallization zone effluent in the recovery zone, in a filter column having a relatively small pore size. Because the large-pore filter column can reliably recover substantial amounts of solid p-xylene at high throughput, the filtration duty of the small-pore filter column (which operates at lower throughput, and can be prone to failure) is desirably reduced. Surprisingly, then, filtering crystallized p-xylene at one or more stages of crystallization in addition to filtering in a downstream recovery zone can decrease the total number of filter columns necessary for an industrially useful p-xylene recovery process.
  • one aspect of the disclosure provides a process comprising, in a crystallizer of a first crystallization zone, cooling a liquid feed stream comprising p-xylene to form a first solid/liquid mixture comprising solid p-xylene and mother liquor; transferring an effluent of the first crystallization zone to a second crystallization zone; in a crystallizer of the second crystallization zone, cooling at least a portion of the effluent to form a second solid/liquid mixture comprising solid p-xylene and mother liquor; transferring an effluent of the second crystallization zone to a third crystallization zone; in a crystallizer of the third crystallization zone, cooling at least a portion of the effluent to form a third solid/liquid mixture comprising solid p-xylene and mother liquor; transferring an effluent of the third crystallization zone to a recovery zone; and in the recovery zone, filtering at least a portion of the effluent through at least one
  • the solid/liquid mixture is filtered through at least one filter in a filter column, the filter having an effective pore size larger than the fourth effective pore size, to form a filtrate comprising mother liquor and a product stream comprising solid p-xylene, and then the product stream is slurried in a reslurry liquid to form a reslurry stream, and the crystallization zone effluent comprises the filtrate.
  • the filter having an effective pore size larger than the fourth effective pore size, to form a filtrate comprising mother liquor and a product stream comprising solid p-xylene, and then the product stream is slurried in a reslurry liquid to form a reslurry stream, and the crystallization zone effluent comprises the filtrate.
  • the inventors have determined that using one or more larger- effective pore size filter columns in earlier filtering stages can provide improved process efficiency.
  • FIG. 1 is a process flow diagram for separating and recovering p-xylene from a liquid feed stream in accordance with one embodiment of the present disclosure.
  • a system for performing a method 100 includes a first crystallization zone 110 including at least one crystallizer (not shown) capable of cooling a liquid feed stream 101 comprising p-xylene to form a first solid/liquid mixture comprising solid p-xylene and mother liquor; a second crystallization zone 120 including at least one crystallizer (not shown) capable of cooling an effluent 111 of the first crystallizer zone 110 to form a second solid/liquid mixture comprising solid p-xylene and mother liquor; a third crystallization zone 130 including at least one crystallizer (not shown) capable of cooling an effluent 121 of the second crystallizer zone 120 to form a third solid/liquid mixture comprising solid p-xylene and mother liquor; a recovery zone 140 including a filter column 142 capable of filtering an effluent
  • reslurry liquids are provided by filtrates from the efficiency stage and/or the product stage.
  • Streams and materials used in the method represented in FIG. 1 may be directed and transferred through suitable transfer lines, conduits, and piping constructed, for example, from materials appropriate for process use and safety. It will be understood that particular elements may be physically juxtaposed and, where appropriate, may be have flexible regions, rigid regions, or a combination of both. In directed streams, intervening apparatuses and/or optional treatments may be included. By way of example, pumps, valves, manifolds, gas and liquid flow meters and distributors, sampling and sensing devices, and other equipment (e.g., for monitoring, controlling, adjusting, and/or diverting pressures, flows and other operating parameters) may be present.
  • a liquid feed stream 101 comprising p-xylene is transferred to the first crystallization zone 110.
  • the liquid feed stream comprises a product stream including p-xylene from a selective or non-selective toluene disproportionation reactor, a selective or non-selective alkylation reactor, a selective or non-selective transalkylation reactor, a catalytic reformer, or a distillation column capable of fractionating, for example, pyrolysis gasoline.
  • the liquid feed stream comprises a product stream including p-xylene from a reaction zone or a fractionation zone of a xylenes isomerization system.
  • the liquid feed stream comprises 10-70 wt.% p-xylene, e.g., 10-60 wt.%, or 10-50 wt.%, or 10-40 wt.%, or 10-30 wt.%, or 15-70 wt.%, or 20-70 wt.%, or 25-70 wt.%, or 15-60 wt.%, or 15-50 wt.%, or 15- 40 wt.%, or 15-30 wt.% p-xylene.
  • 10-70 wt.% p-xylene e.g., 10-60 wt.%, or 10-50 wt.%, or 10-40 wt.%, or 10-30 wt.%, or 15-70 wt.%, or 20-70 wt.%, or 25-70 wt.%, or 15-60 wt.%, or 15-50 wt.%, or 15- 40 wt.%, or 15-30 wt.
  • the liquid feed stream comprises 20-30 wt.% p-xylene, 40-60 wt.% m-xylene, and 20-30 wt.% o-xylene.
  • the feed stream comprises 40-99 wt.% xylenes (e.g., in a near-equilibrium distribution of p-xylene, m-xylene, and o-xylene) and 1- 60 wt.% of a combined amount of benzene, toluene, ethylbenzene, and Cg + aromatic compounds.
  • the liquid feed stream is substantially free (e.g., comprises less than 2 wt.%, or less than 1 wt.%, or less than 0.5 wt.%, or less than 0.1 wt.%) of solids.
  • the liquid feed stream comprises solid p-xylene (e.g., 2-5 wt.% solid p-xylene).
  • the first crystallization zone 110 the liquid feed stream 101 is cooled in a crystallizer to form a first solid/liquid mixture comprising solid p-xylene and mother liquor.
  • the first crystallization zone includes two or more (e.g., two or three) crystallizers configured to operate in parallel.
  • the liquid feed stream is cooled to a temperature below -40 °F (e.g., below -50 °F, or below -60 °F).
  • the first solid/liquid mixture comprises 5-15 wt.%, e.g., 5-12.5 wt.%, or 5-10 wt.%, or 7.5-15 wt.%, or 10-15 wt.%, or 7.5-12.5 wt.% solid p-xylene.
  • FIG. 2 is a schematic view of a crystallization zone in accordance with one embodiment of the present disclosure.
  • a crystallization zone in accordance with one embodiment of the present disclosure.
  • a liquid feed stream 201 is cooled in the crystallizer 212 to form a solid/liquid mixture, the solid/liquid mixture comprising the effluent
  • the effluent of the first crystallization zone comprises the first solid/liquid mixture (e.g., comprising 5-15 wt.% solid p-xylene).
  • FIG. 3 is a schematic view of a crystallization zone in accordance with another embodiment of the present disclosure.
  • a crystallization zone 310 includes a crystallizer 312 and a filter column 314.
  • a liquid feed stream 301 is cooled in the crystallizer 312 to form a solid/liquid mixture 311.
  • the solid/liquid mixture 311 is filtered in the filter column 314 to form a product stream (not shown) and a filtrate 313, and then the product stream is slurried to form a reslurry stream, the reslurry stream comprising the effluent 315 of the crystallization zone 310.
  • FIG. 4 is a side view cross-section of a filter column in accordance with one embodiment of the present disclosure.
  • a filter column 400 includes a substantially hollow cavity 402 having a closed end 404 and an open end 406.
  • the cavity 402 can be substantially tubular or cylindrical in shape.
  • at least one filter tube 408 extends in an axial direction, the filter tube 408 having a top portion 410 and a bottom portion 412.
  • the top portion 410 is closed.
  • the filter tube 408 is generally situated in substantial proximity to an inner wall 414 of the column 400.
  • the bottom portion 412 of the filter tube 408 extends through the closed end 404 of the substantially hollow cavity 402, the bottom portion 412 having an opening 416 at a terminal end.
  • the filter tube 408 includes at least one filter 418, attached, integrated, or otherwise affixed to the filter tube 408, forming a connection for flow of a substantially liquid portion of a solid/liquid mixture between the interior of the hollow cavity 402 and the interior of filter tube 408.
  • a product chute 426 extends from the open end 406 of the cavity 402, and includes a reslurry zone 428.
  • a stream 401 comprising a solid/liquid mixture is introduced into a filtration zone 420 of the hollow cavity 402 through an inlet 422.
  • the solid/liquid mixture moves towards the open end 406 of the hollow cavity 402.
  • a substantially liquid portion of the solid/liquid mixture passes through the filter 418 and through opening 416, and is removed from the filter column 400 through outlet 424 as filtrate stream 403.
  • a substantially solid portion of the solid/liquid mixture forms a packed bed within the hollow cavity 402.
  • the packed bed increases in size, filling the section between at least one filter tube 408 and the inner wall 414.
  • an “effective pore size” of a column is the 90 th percentile narrowest cross-sectional dimension of a pores (i.e. , as counted among all pores. This narrowest cross-sectional dimension would be, for example, 100 microns for a rectangular slot/pore that is 100 microns wide and 300 microns long. A circular pore 100 microns in diameter, would also have a pore size of 100 microns.
  • the first solid/liquid mixture is filtered through at least one filter in a first filter column in the first crystallization zone to form a first filtrate comprising mother liquor and a first product stream comprising solid p-xylene, the filter having a first effective pore size larger than the fourth effective pore size, and then the first product stream is slurried in a reslurry liquid to form a first reslurry stream.
  • the first crystallization zone effluent comprises the first filtrate.
  • the first effective pore size is at least 25%, or at least 50%, or at least 100%, or at least 200%, or at least 300% larger than the fourth effective pore size (i.e., of the at least one filter in a filter column of the recovery zone).
  • the first crystallization zone includes two or more (e.g., 2-4) filter columns configured to operate in parallel.
  • the at least one filter of the first filter column has a length (i.e., along a vertical axis of the filtration zone) of at least 4 in., e.g., at least 5 in., or at least 6 in., or 4-12 in., or 4-8 in., or 6-10 in.
  • the at least one filter comprises a filter tube having a length (i.e., along a vertical axis of the filtration zone) of at least 48 in., e.g., at least 60 in., or 48-96 in., or 48-84 in., or 48-72 in., or 60-96 in, or 72-96 in., or 60-84 in., or 60-72 in.
  • the first filter column includes one filter tube (e.g., comprising one filter).
  • the first filter column comprises two or more (e.g., 4-6) filter tubes, each filter tube comprising one or more (e.g., one) filters.
  • the at least one filter of the first filter column comprises rectangular pores having a length along a vertical axis of the filtration zone and a width perpendicular thereto.
  • the first pore height is 2-8 mm, or 2-6 mm, or 2-4 mm, or 4-8 mm, or 6-8 mm
  • the first pore width is 0.2-0.4 mm, or 0.2-0.3 mm, or 0.3-0.4 mm.
  • the at least one filter of the filter column of the recovery zone comprises rectangular pores having a fourth pore height of 1-7 mm, or 1-5 mm, or 1-3 mm, or 3-7 mm, or 5-7 mm, and a fourth pore width of 0.1-0.3 mm, or 0.1-0.2 mm, or 0.2-0.3 mm.
  • the area of at least a portion of the rectangular pores comprising the at least one filter of the first filter column is at least 200%, or at least 300% larger than that of the rectangular pores comprising the at least one filter of the filter column of the recovery zone.
  • p-xylene is present in the first filtrate in an amount that is at least 1 wt.%, e.g., 1-4 wt.%, or 1-3 wt.%, or 1-2 wt.%, or 2-5 wt.%, or 3-5 wt.%, or 4-5 wt.% greater than the p-xylene solubility limit of the first filtrate.
  • the person of ordinary skill in the art can determine the p-xylene solubility limit of a liquid (e.g., the first filtrate) based on its physical properties, such as chemical composition, temperature, etc.
  • the first solid/liquid mixture is filtered in a first filter column in the first crystallization zone to form a first filtrate comprising mother liquor and a first product stream comprising solid p-xylene, and the effluent of the first crystallization zone including the first filtrate is transferred to a crystallizer of the second crystallization zone.
  • transferring the filtrate to a downstream crystallizer desirably avoids p-xylene losses otherwise attributable to the relatively poor filtration efficiency of the first filter column, which can reliably separate solid p-xylene from the first solid/liquid mixture at a desirably high throughput (accordingly lowering the filtration duty of the downstream recovery zone).
  • the present inventors have determined that solid p-xylene present in the filtrate can “seed” the downstream crystallizer, advantageously improving the crystallization yield therein.
  • an effluent 111 of the first crystallization zone 110 (e.g., comprising the first solid/liquid mixture or the first filtrate) is cooled in a crystallizer to form a second solid/liquid mixture comprising solid p-xylene and mother liquor.
  • the second crystallization zone includes two or more (e.g., two or three) crystallizers configured to operate in parallel.
  • the effluent of the first crystallization zone is cooled to a temperature below -50 °F (e.g., below -60 °F, or below -70 °F).
  • the first crystallization effluent comprises the first solid/liquid mixture
  • the second solid/liquid mixture comprises 10-20 wt.%, e.g., 10-17.5 wt.%, or 10-15 wt.%, or 12.5-20 wt.%, or 15-20 wt.%, or 12.5-17.5 wt.% solid p-xylene.
  • the first crystallization effluent comprises the first filtrate
  • the second solid/liquid mixture comprises 2-10 wt.%, e.g., 2-8 wt.%, or 2-6 wt.%, or 4-10 wt.%, 6-10 wt.% solid p-xylene.
  • the effluent of the second crystallization zone comprises the second solid/liquid mixture (e.g., comprising 2-10 wt.%, or 10-20 wt.% solid p-xylene).
  • the second solid/liquid mixture is filtered through at least one filter in a second filter column in the second crystallization zone to form a second filtrate comprising mother liquor and a second product stream comprising solid p-xylene, the filter having a second effective pore size larger than the fourth effective pore size, and then the second product stream is slurried in a reslurry liquid to form a second reslurry stream.
  • the second crystallization zone effluent comprises the second filtrate.
  • the second effective pore size is at least 25%, or at least 50%, or at least 100%, or at least 200%, or at least 300% larger than the fourth effective pore size (i.e., of the at least one filter in a filter column of the recovery zone).
  • the second crystallization zone includes two or more (e.g., 3-5) filter columns configured to operate in parallel.
  • the at least one filter of the second filter column has a length (i.e., along a vertical axis of the filtration zone) of at least 4 in., e.g., at least 5 in., or at least 6 in., or 4-12 in., or 4-8 in., or 6-10 in.
  • the at least one filter comprises a filter tube having a length (i.e., along a vertical axis of the filtration zone) of at least 48 in., e.g., at least 60 in., or 48-96 in., or 48-84 in., or 48-72 in., or 60-96 in, or 72-96 in., or 60-84 in., or 60-72 in.
  • the second filter column includes one filter tube (e.g., comprising one filter).
  • the second filter column comprises two or more (e.g., 4-6) filter tubes, each filter tube comprising one or more (e.g., one) filters.
  • the at least one filter of the second filter column comprises rectangular pores having a length along a vertical axis of the filtration zone and a width perpendicular thereto.
  • the second pore height is 2-8 mm, or 2-6 mm, or 2-4 mm, or 4-8 mm, or 6-8 mm
  • the second pore width is 0.2-0.4 mm, or 0.2-0.3 mm, or 0.3-0.4 mm.
  • the at least one filter of the filter column of the recovery zone comprises rectangular pores having a fourth pore height of 1-7 mm, or 1-5 mm, or 1-3 mm, or 3-7 mm, or 5-7 mm, and a fourth pore width of 0.05-0.2 mm, or 0.05-0.1 mm, or 0.1-0.2 mm.
  • the area of at least a portion of the rectangular pores comprising the at least one filter of the second filter column is at least 200%, or at least 300% larger than that of the rectangular pores comprising the at least one filter of the filter column of the recovery zone.
  • p-xylene is present in the second filtrate in an amount that is at least 1 wt.%, e.g., 1-4 wt.%, or 1-3 wt.%, or 1-2 wt.%, or 2-5 wt.%, or 3-5 wt.%, or 4-5 wt.% greater than the p-xylene solubility limit of the second filtrate.
  • the second solid/liquid mixture is filtered in a second filter column in the second crystallization zone to form a second filtrate comprising mother liquor and a second product stream comprising solid p- xylene, and an effluent of the second crystallization zone including the second filtrate is transferred to a crystallizer of the second crystallization zone.
  • the first solid/liquid mixture is filtered in a first filter column in the first crystallization zone to form a first filtrate comprising mother liquor and a first product stream comprising solid p- xylene, and the effluent of the first crystallization zone including the first filtrate is transferred to a crystallizer of the second crystallization zone.
  • the effluent of the first crystallization zone including the first solid/liquid mixture is transferred to a crystallizer of the second crystallization zone.
  • an effluent 121 of the second crystallization zone 120 (e.g., comprising the second solid/liquid mixture or the second filtrate) is cooled in a crystallizer to form a third solid/liquid mixture comprising solid p-xylene and mother liquor.
  • the third crystallization zone includes two or more (e.g., two or three) crystallizers configured to operate in parallel.
  • the effluent of the second crystallization zone is cooled to a temperature below -60 °F (e.g., below -70 °F, or below -80 °F).
  • the second crystallization zone effluent comprises the second solid/liquid mixture
  • the third solid/liquid mixture comprises 10-20 wt.%, e.g., 10 17.5 wt.%, or 10-15 wt.%, or 12 5-20 wt.%, or 15-20 wt.%, or 12 5 17.5 wt.% solid p-xylene.
  • the second crystallization effluent comprises the second filtrate
  • the third solid/liquid mixture comprises 2-10 wt.%, e.g., 2-8 wt.%, or 2-6 wt.%, or 4-10 wt.%, 6-10 wt.% solid p-xylene.
  • the effluent of the third crystallization zone comprises the third solid/liquid mixture (e.g., comprising 2-10 wt.%, or 10-20 wt.% solid p-xylene).
  • the third solid/liquid mixture is filtered through at least one filter in a third filter column in the third crystallization zone to form a third filtrate comprising mother liquor and a third product stream comprising solid p-xylene, the filter having a third effective pore size larger than the fourth effective pore size, and then the third product stream is slurried in a reslurry liquid to form a third reslurry stream.
  • the third crystallization zone effluent comprises the third filtrate.
  • the third effective pore size is at least 25%, or at least 50%, or at least 100%, or at least 200%, or at least 300% larger than the fourth effective pore size (i.e. , of the at least one filter in a filter column of the recovery zone).
  • the third crystallization zone includes two or more (e.g., 2-6) filter columns configured to operate in parallel.
  • the at least one filter of the third filter column has a length (i.e., along a vertical axis of the filtration zone) of at least 4 in., e.g., at least 5 in., or at least 6 in., or 4-12 in., or 4-8 in., or 6-10 in.
  • the at least one filter comprises a filter tube having a length (i.e., along a vertical axis of the filtration zone) of at least 48 in., e.g., at least 60 in., or 48-96 in., or 48-84 in., or 48-72 in., or 60-96 in, or 72-96 in., or 60-84 in., or 60-72 in.
  • the third filter column includes one filter tube (e.g., comprising one filter).
  • the third filter column comprises two or more (e.g., 4-6) filter tubes, each filter tube comprising one or more (e.g., one) filters.
  • the at least one filter of the third filter column comprises rectangular pores having a length along a vertical axis of the filtration zone and a width perpendicular thereto.
  • the third pore height is 2-8 mm, or 2-6 mm, or 2-4 mm, or 4-8 mm, or 6-8 mm
  • the third pore width is 0.2-0.4 mm, or 0.2-0.3 mm, or 0.3-0.4 mm.
  • the at least one filter of the filter column of the recovery zone comprises rectangular pores having a fourth pore height of 1-7 mm, or 1-5 mm, or 1-3 mm, or 3-7 mm, or 5-7 mm, and a fourth pore width of 0.05-0.2 mm, or 0.05-0.1 mm, or 0.1-0.2 mm.
  • the area of at least a portion of the rectangular pores comprising the at least one filter of the third filter column is at least 200%, or at least 300% larger than that of the rectangular pores comprising the at least one filter of the filter column of the recovery zone.
  • p-xylene is present in the third filtrate in an amount that is at least 1 wt.%, e.g., 1-4 wt.%, or 1-3 wt.%, or 1-2 wt.%, or 2-5 wt.%, or 3-5 wt.%, or 4-5 wt.% greater than the p-xylene solubility limit of the third filtrate.
  • the third solid/liquid mixture is filtered in a third filter column in the third crystallization zone to form a third filtrate comprising mother liquor and a third product stream comprising solid p-xylene, and an effluent of the third crystallization zone including the third filtrate is transferred to a filter column of a recovery zone.
  • the first solid/liquid mixture is filtered in a first filter column in the first crystallization zone to form a first filtrate comprising mother liquor and a first product stream comprising solid p-xylene, and the effluent of the first crystallization zone including the first filtrate is transferred to a crystallizer of the second crystallization zone.
  • the effluent of the first crystallization zone including the first solid/liquid mixture is transferred to a crystallizer of the second crystallization zone.
  • the second solid/liquid mixture is filtered in a second filter column in the second crystallization zone to form a second filtrate comprising mother liquor and a second product stream comprising solid p-xylene, and the effluent of the second crystallization zone including the second filtrate is transferred to a crystallizer of the third crystallization zone.
  • the effluent of the second crystallization zone including the second solid/liquid mixture is transferred to a crystallizer of the third crystallization zone.
  • an effluent 131 of the third crystallization zone 130 (e.g., comprising the third solid/liquid mixture or the third filtrate) is filtered through at least one filter in a filter column to form a fourth filtrate 141 comprising mother liquor and a fourth product stream comprising solid p-xylene, the filter having a fourth effective pore size (i.e., smaller than the first effective pore size, the second effective pore size, and/or the third effective pore size), and then slurrying the fourth product stream in a reslurry liquid to form a fourth reslurry stream 143.
  • the recovery zone includes two or more (e.g., 3-8) filter columns configured to operate in parallel.
  • the at least one filter of the filter column of the recovery zone has a length (i.e., along a vertical axis of the filtration zone) of at least 4 in., e.g., at least 5 in., or at least 6 in., or 4-12 in., or 4-8 in., or 6-10 in.
  • the at least one filter comprises a filter tube having a length (i.e., along a vertical axis of the filtration zone) of at least 48 in., e.g., at least 60 in., or 48-96 in., or 48-84 in., or 48-72 in., or 60-96 in, or 72-96 in., or 60-84 in., or 60-72 in.
  • the filter column of the recovery zone includes one filter tube (e.g., comprising one filter).
  • the filter column of the recovery zone comprises two or more (e.g., 4-6) filter tubes, each filter tube comprising one or more (e.g., one) filters.
  • the at least one filter of the filter column of the recovery zone comprises rectangular pores having a length along a vertical axis of the filtration zone and a width perpendicular thereto.
  • the fourth pore height is 1-7 mm, or 1-5 mm, or 1-3 mm, or 3-7 mm, or 5-7 mm
  • the fourth pore width is 0.05-0.2 mm, or 0.05-0.1 mm, or 0.1-0.2 mm.
  • p-xylene is present in the fourth filtrate in an amount that is at most 1 wt.%, e.g., 0.1-0.9 wt.%, or 0.1-0.8 wt.%, or 0.1-0.7 wt.% greater than the p-xylene solubility limit of the fourth filtrate.
  • at least a portion of the fourth filtrate is transferred to a reaction zone of a xylenes isomerization system.
  • solid p-xylene is present in the fourth product stream in an amount that is at most 67% (e.g., at most 60%, or at most 55%, or at most 50%, or at most 45%) of a total amount of solid p-xylene present in the first product stream, second product stream, and/or third product stream, and the fourth product stream.
  • solid p-xylene is present in the fourth product stream in an amount that is at most 67% (e.g., at most 60%, or at most 55%, or at most 50%, or at most 45%) of a total amount of solid p-xylene present in the first product stream and the fourth product stream, or a total amount of solid p-xylene present in the second product stream and the fourth product stream, or a total amount of solid p-xylene present in the third product stream and the fourth product stream, or a total amount of solid p-xylene present in the first product stream, the second product stream, and the fourth product stream, or a total amount of solid p-xylene present in the first product stream, the third product stream, and the fourth product stream, or a total amount of solid p-xylene present in the second product stream, the third product stream, and fourth product stream, or a total amount of solid p-xylene present in the first product stream, the second product stream, the third product stream, and fourth product stream, or
  • the fourth reslurry stream 143 and the first reslurry stream, the second reslurry stream, and/or the third reslurry stream are transferred to an efficiency-stage slurry drum 152 of the efficiency zone 150.
  • the two or more reslurry streams are combined and then transferred to the efficiency-stage slurry drum.
  • each reslurry stream is individually transferred to the efficiency-stage slurry drum.
  • drums fed from filter columns as described herein can have less plugging and other operational problems than drums fed from centrifuges.
  • an effluent 151 of the efficiency-stage slurry drum 152 is filtered through at least one filter in a filter column 154 of the efficiency zone 150 to form a fifth filtrate 153 comprising reslurry liquid and a fifth product stream comprising solid p-xylene, the filter having a fifth effective pore size smaller than the first effective pore size, the second effective pore size, and/or the third effective pore size, and then the fifth product stream is slurried in a reslurry liquid to form a fifth reslurry stream 153.
  • the effluent of the efficiency-stage slurry drum comprises at least 40 wt.%, e.g., at least 45 wt.%, or at least 50 wt.%, or 40-70 wt.%, or 40- 60 wt.%, or 45-70 wt.%, or 50-70 wt.% p-xylene.
  • the efficiency zone includes two or more (e.g., two) filter columns configured to operate in parallel.
  • the at least one filter of the filter column of the efficiency zone has a length (i.e. , along a vertical axis of the filtration zone) of at least 4 in., e.g., at least 5 in., or at least 6 in., or 4-12 in., or 4-8 in., or 6-10 in.
  • the at least one filter comprises a filter tube having a length (i.e., along a vertical axis of the filtration zone) of at least 48 in., e.g., at least 60 in., or 48-96 in., or 48-84 in., or 48-72 in., or 60-96 in, or 72-96 in., or 60-84 in., or 60-72 in.
  • the filter column of the efficiency zone includes one filter tube (e.g., comprising one filter).
  • the filter column of the efficiency zone comprises two or more (e.g., 4-6) filter tubes, each filter tube comprising one or more (e.g., one) filters.
  • the at least one filter of the filter column of the efficiency zone comprises rectangular pores having a length along a vertical axis of the filtration zone and a width perpendicular thereto.
  • the fifth pore height is 1-7 mm, or 1-5 mm, or 1-3 mm, or 3-7 mm, or 5-7 mm
  • the fifth pore width is 0.05-0.2 mm, or 0.05-0.1 mm, or 0.1-0.2 mm.
  • p-xylene is present in the fifth filtrate in an amount that is at most 0.5 wt.%, e.g., 0.05-0.4 wt.%, or 0.05-0.3 wt.%, or 0.05-0.2 wt.% greater than the p-xylene solubility limit of the fifth filtrate.
  • at least a portion of the fifth filtrate is transferred to a crystallizer of the first crystallization zone.
  • the reslurry liquid of the first crystallization zone, the second crystallization zone, and/or the third crystallization zone comprises at least a portion of the fifth filtrate.
  • separating at least a portion of an effluent of the efficiency-stage slurry drum comprises filtering the effluent in a filter column.
  • separating at least a portion of an effluent of the efficiency-stage drum comprises separating in a centrifuge (e.g., a pusher centrifuge, or a screen-bowl centrifuge, or a solid-bowl centrifuge).
  • a centrifuge e.g., a pusher centrifuge, or a screen-bowl centrifuge, or a solid-bowl centrifuge.
  • the fifth reslurry stream 153 is transferred to a product-stage slurry drum 162 of the product zone 160.
  • an effluent 161 of the product-stage slurry drum 162 is separated in a wash column 164 of the product zone 160 to form a sixth filtrate 163 comprising reslurry liquid and a sixth product stream 165 comprising p-xylene.
  • the product zone includes two or more (e.g., 6-8) wash columns configured to operate in parallel.
  • a wash column (or a hydraulic wash column) is a solid-liquid separation apparatus for concentrating a suspension.
  • a wash column separates solids from a solid/liquid mixture by directing the mixture into a first end of a wash column and a wash liquid into a second end of the wash column in countercurrent flow to the suspension, forming a bed of the solids.
  • solid p-xylene of the bed is melted to form the sixth product stream 165.
  • separating an effluent of the product-stage slurry drum is separated using a centrifuge (e.g., a pusher centrifuge, or a screen-bowl centrifuge, or a solid-bowl centrifuge) to form the sixth filtrate and the sixth product stream.
  • a centrifuge e.g., a pusher centrifuge, or a screen-bowl centrifuge, or a solid-bowl centrifuge
  • the effluent of the product-stage slurry drum comprises at least 60 wt.%, e.g., at least 70 wt.%, or at least 80 wt.%, or 60-95 wt.%, or 60-90 wt.%, or 70-95 wt.%, or 08-90 wt.% p-xylene.
  • the sixth product stream comprises at least 97 wt.%, e.g., at least 98 wt.%, or at least 99 wt.%, or at least 99.5 wt.%, or at least 99.7 wt.%, or at least 99.8 wt.% p-xylene.
  • the sixth filtrate comprises 50-90 wt.%, e.g., 60-90 wt.%, or 70-90 wt.% p-xylene.
  • the reslurry liquid of the first crystallization zone, the second crystallization zone, the third crystallization zone, and/or the efficiency zone comprises at least a portion of the fifth filtrate.
  • Another aspect of the disclosure provides an apparatus for recovering p-xylene (e.g., according to a method described herein) comprising a first crystallizer; a second crystallizer in fluid communication with the first crystallizer; a third crystallizer in fluid communication with the second crystallizer; and a fourth filter unit comprising at least one filter column, each filter column in fluid communication with the third crystallizer, each filter column including at least one filter, each filter having a fourth effective pore size; and further comprising at least one of a first filter unit comprising at least one filter column, each filter column providing the fluid communication between the first crystallizer and the second crystallizer, each filter column including at least one filter, each filter having a first effective pore size; a second filter unit comprising at least one filter column, each filter column providing the fluid communication between the second crystallizer and the third crystallizer, each filter column including at least one filter, each filter having a second effective pore size; and a third filter unit comprising at least one filter column, each filter column providing
  • the apparatus comprises the first filter unit; or the second filter unit; or the third filter unit; or the first filter unit and the second filter unit; or the first filter unit and the third filter unit; or the second filter unit and the third filter unit; or the first filter unit, the second filter unit, and the third filter unit.
  • the properties of the various components of the apparatus can be as otherwise described above with respect to the methods of the disclosure.
  • the apparatus further comprises an efficiency-stage slurry drum in fluid communication with the fourth filter unit; a fifth filter unit comprising at least one filter column, each filter column including at least one filter, each filter having a fifth effective pore size; a product-stage slurry drum in fluid communication with the fifth filter unit; and a sixth filter unit comprising at least one wash column, each wash column in fluid communication with the product stage slurry drum.
  • the apparatus comprises the second filter unit, and the second effective pore size is larger (e.g., at least 25%, at least 50%, at least 100%, or at least 200% larger) than the fourth effective pore size.
  • the second filter unit comprises 3-5 filter columns
  • the fourth filter unit comprises 3-5 filter columns.
  • the apparatus comprises the first filter unit, and the first effective pore size is larger (e.g., at least 25%, at least 50%, at least 100%, or at least 200% larger) than the fourth effective pore size.
  • the first filter unit comprises 2-4 filter columns, and the fourth filter unit comprises 4-8 filter columns.
  • the p-xylene recovery process of FIG. 1 was modeled with ASPEN Plus (Aspen Technology Inc., Bedford, MA). Recovery processes 1-7, which included filtering in a filter column of one or more of the first crystallization zone, the second crystallization zone, and the third crystallization zone, were compared to a control process C, as shown in Table 1, below. The capacity of each process was 700 Ibs/hr.
  • Embodiment 1 A method for recovering p-xylene, comprising in a crystallizer of a first crystallization zone, cooling a liquid feed stream comprising p-xylene to form a first solid/liquid mixture comprising solid p-xylene and mother liquor; transferring an effluent of the first crystallization zone to a second crystallization zone; in a crystallizer of the second crystallization zone, cooling at least a portion of the effluent to form a second solid/liquid mixture comprising solid p-xylene and mother liquor; transferring an effluent of the second crystallization zone to a third crystallization zone; in a crystallizer of the third crystallization zone, cooling at least a portion of the effluent to form a third solid/liquid mixture comprising solid p-xylene and mother liquor; transferring an effluent of the third crystallization zone to a recovery zone; in the recovery zone, filtering at least a portion of the effluent through at least one filter
  • Embodiment 2 The method of embodiment 1, including filtering the first solid/liquid mixture through at least one filter in a first filter column in the first crystallization zone to form a first filtrate comprising mother liquor and a first product stream comprising solid p-xylene, the filter having a first effective pore size larger (e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger) than the fourth effective pore size, and then slurrying the first product stream in a reslurry liquid to form a first reslurry stream; wherein the first crystallization zone effluent comprises the first filtrate.
  • Embodiment 3 Embodiment 3.
  • Embodiment 4 The method of any of embodiments 1-3, including filtering the second solid/liquid mixture through at least one filter in a filter column in the second crystallization zone to form a second filtrate comprising mother liquor and a second product stream comprising solid p-xylene, the filter having a second effective pore size larger (e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger) than the fourth effective pore size, and then slurrying the second product stream in a reslurry liquid to form a second reslurry stream; wherein the second crystallization zone effluent comprises the second filtrate.
  • a second effective pore size larger e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger
  • Embodiment 5 The method of embodiment 4, wherein p-xylene is present in the second filtrate in an amount that is at least 1 wt.% (e.g., 1-5 wt.%) greater than the p-xylene solubility limit of the second filtrate.
  • Embodiment 6 The method of any of embodiments 1-5, including filtering the third solid/liquid mixture through at least one filter in a filter column in the third crystallization zone to form a third filtrate comprising mother liquor and a third product stream comprising solid p- xylene, the filter having a third effective pore size larger (e.g., at least 25%, at least 50%, at least 100 at least 200%, or at least 300% larger) than the fourth effective pore size, and then slurrying the third product stream in a reslurry liquid to form a third reslurry stream; wherein the third crystallization zone effluent comprises the third filtrate.
  • the filter having a third effective pore size larger (e.g., at least 25%, at least 50%, at least 100 at least 200%, or at least 300% larger) than the fourth effective pore size, and then slurrying the third product stream in a reslurry liquid to form a third reslurry stream; wherein the third crystallization zone efflu
  • Embodiment 7 The method of embodiment 6, wherein p-xylene is present in the third filtrate in an amount that is at least 1 wt.% (e.g., 1-5 wt.%) greater than the p-xylene solubility limit of the third filtrate.
  • Embodiment 8 The method of any of embodiments 1-7, wherein p-xylene is present in the fourth filtrate in an amount that is at most 1 wt.% (e.g., 0.1-0.9 wt.%) greater than the p-xylene solubility limit of the fourth filtrate.
  • Embodiment 9 The method of any of embodiments 1-8, wherein solid p-xylene is present in the fourth product stream in an amount that is at most 67% (e.g., at most 60% or at most 50%) of a total amount of solid p-xylene present in the first product stream, second product stream, third product stream, and fourth product stream.
  • Embodiment 10 The method of any of embodiments 1-9, further comprising transferring at least a portion of the fourth reslurry stream and at least a portion of one or more of the first reslurry stream, second reslurry stream, and third reslurry stream to an efficiency-stage slurry drum of an efficiency zone.
  • Embodiment 11 The method of embodiment 10, further comprising separating at least a portion of an effluent of the efficiency-stage slurry drum to form a fifth filtrate comprising reslurry liquid and a fifth product stream comprising solid p-xylene; slurrying at least a portion of the fifth product stream in a reslurry liquid to form a fifth reslurry stream; transferring at least a portion of the fifth reslurry stream to a product-stage slurry drum of a product zone; and separating at least a portion of an effluent of the product-stage slurry drum to form a sixth filtrate comprising reslurry liquid and a sixth product stream comprising p-xylene.
  • Embodiment 12 The method of embodiment 11, further comprising transferring at least a portion of the fifth filtrate to the first crystallization zone.
  • Embodiment 13 The method of embodiment 11, wherein the reslurry liquid of one or more of the first crystallization zone, second crystallization zone, third crystallization zone, and recovery zone comprises at least a portion of the fifth filtrate or sixth filtrate.
  • Embodiment 14 The method of any of embodiments 11-13, wherein the reslurry liquid comprising the fifth reslurry stream includes at least a portion of the sixth filtrate.
  • Embodiment 15 An apparatus for recovering p-xylene, comprising a first crystallizer; a second crystallizer in fluid communication with the first crystallizer; a third crystallizer in fluid communication with the second crystallizer; and a fourth filter unit comprising at least one filter column, each filter column in fluid communication with the third crystallizer, each filter column including at least one filter, each filter having a fourth effective pore size; and further comprising at least one of a first filter unit comprising at least one filter column, each filter column providing the fluid communication between the first crystallizer and the second crystallizer, each filter column including at least one filter, each filter having a first effective pore size; a second filter unit comprising at least one filter column, each filter column providing the fluid communication between the second crystallizer and the third crystallizer, each filter column including at least one filter, each filter having a second effective pore size; and a third filter unit comprising at least one filter column, each filter column providing the fluid communication between the third crystallizer and the fourth filter unit, each filter column
  • Embodiment 16 The apparatus of embodiment 15, further comprising an efficiency-stage slurry drum in fluid communication with the fourth filter unit; a fifth filter unit comprising at least one filter column, each filter column in fluid communication with the efficiency-stage slurry drum, each filter column including at least one filter, each filter having a fifth effective pore size; a product-stage slurry drum in fluid communication with the fifth filter unit; and a sixth filter unit comprising at least one wash column, each wash column in fluid communication with the product-stage slurry drum.
  • Embodiment 17 The apparatus of embodiment 15 or 16, comprising the second filter unit, wherein the second effective pore size is larger (e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger) than the fourth effective pore size.
  • the second effective pore size is larger (e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger) than the fourth effective pore size.
  • Embodiment 18 The apparatus of embodiment 17, wherein the second filter unit comprises 3-5 filter columns, and the fourth filter unit comprises 3-5 filter columns.
  • Embodiment 19 The apparatus of embodiment 15 or 16, comprising the first filter unit, wherein the first effective pore size is larger (e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger) than the fourth effective pore size.
  • the first effective pore size is larger (e.g., at least 25%, at least 50%, at least 100%, at least 200%, or at least 300% larger) than the fourth effective pore size.
  • Embodiment 20 The apparatus of embodiment 19, wherein the first filter unit comprises 2-4 filter columns, and the fourth filter unit comprises 4-8 filter columns.

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Abstract

La présente invention concerne de manière générale des processus et des appareils pour séparer le p-xylène d'un courant d'alimentation liquide. En conséquence, un aspect de l'invention concerne un processus comprenant, dans un cristalliseur d'une première zone de cristallisation, refroidir un courant d'alimentation liquide comprenant du p-xylène pour former un premier mélange solide/liquide comprenant du p-xylène solide et la liqueur mère ; transférer un effluent de la première zone de cristallisation à une seconde zone de cristallisation ; dans un cristalliseur de la seconde zone de cristallisation, à refroidir au moins une partie de l'effluent pour former un second mélange solide/liquide comprenant du p-xylène solide et de la liqueur mère ; transférer un effluent de la deuxième zone de cristallisation à une troisième zone de cristallisation ; dans un cristalliseur de la troisième zone de cristallisation, refroidir au moins une partie de l'effluent pour former un troisième mélange solide/liquide comprenant du p-xylène solide et de la liqueur mère ; transférer un effluent de la troisième zone de cristallisation à une zone de récupération ; et dans la zone de récupération, filtrer au moins une partie de l'effluent à travers au moins un filtre d'une colonne de filtration de la zone de récupération, le filtre ayant une quatrième taille de pore efficace, pour former un quatrième filtrat comprenant de la liqueur mère et un quatrième courant de produit comprenant du p-xylène solide, puis la mise en suspension du quatrième courant de produit dans un liquide de remise en suspension pour former un quatrième courant de remise en suspension. Dans une ou plusieurs de la première zone de cristallisation, la deuxième zone de cristallisation, et la troisième zone de cristallisation, le mélange solide/liquide est filtré à travers au moins un filtre dans une colonne de filtration, le filtre ayant une taille de pore efficace supérieure à la quatrième taille de pore efficace, pour former un filtrat comprenant une liqueur mère et un courant de produit comprenant du p-xylène solide, puis le courant de produit est mis en suspension dans un liquide de suspension pour former un courant de suspension, et l'effluent de zone de cristallisation comprend le filtrat.
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US8211319B2 (en) 2003-09-16 2012-07-03 Bp Corporation North America Inc. Solid-liquid separation process
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US8211319B2 (en) 2003-09-16 2012-07-03 Bp Corporation North America Inc. Solid-liquid separation process
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US8962906B2 (en) 2006-03-21 2015-02-24 Bp Corporation North America Inc. Apparatus and process for the separation of solids and liquids
US8530716B2 (en) 2008-08-14 2013-09-10 Bp Corporation North America Inc. Melt-crystallization separation and purification process
WO2014152762A1 (fr) * 2013-03-15 2014-09-25 Bp Corporation North America Inc. Procédé de récupération de paraxylène à partir d'au moins deux courants d'alimentation contenant des isomères de xylène

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