US3367846A - Utilization of recovered steam heat for heating the distillation zone - Google Patents

Utilization of recovered steam heat for heating the distillation zone Download PDF

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Publication number
US3367846A
US3367846A US482685A US48268565A US3367846A US 3367846 A US3367846 A US 3367846A US 482685 A US482685 A US 482685A US 48268565 A US48268565 A US 48268565A US 3367846 A US3367846 A US 3367846A
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United States
Prior art keywords
column
steam
xylene
overhead
benzene
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Expired - Lifetime
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US482685A
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English (en)
Inventor
Kenneth D Uitti
Okuma Toshio
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Universal Oil Products Co
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Universal Oil Products Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Universal Oil Products Co filed Critical Universal Oil Products Co
Priority to US482685A priority Critical patent/US3367846A/en
Priority to IL26347A priority patent/IL26347A/xx
Priority to GB36518/66A priority patent/GB1149169A/en
Priority to AT793266A priority patent/AT272303B/de
Priority to DE19661593652 priority patent/DE1593652A1/de
Priority to ES0330435A priority patent/ES330435A1/es
Priority to NL6611788A priority patent/NL6611788A/xx
Priority to FR73967A priority patent/FR1490258A/fr
Priority to NO164422A priority patent/NO117538B/no
Priority to DK433966AD priority patent/DK117136B/da
Priority to CH1230666A priority patent/CH486400A/de
Priority to FI662226A priority patent/FI46732C/fi
Application granted granted Critical
Publication of US3367846A publication Critical patent/US3367846A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/04—Purification; Separation; Use of additives by distillation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S203/00—Distillation: processes, separatory
    • Y10S203/11—Batch distillation

Definitions

  • This invention relates to the separation of a mixture of aromatic hydrocarbons by fractional distillation. More particularly, our invention is directed to a process for the recovery of ortho-xylene from a feedstock comprising a major proportion of benzene and/ or toluene and a minor proportion of xylene isomers including ortho-xylene, utllizing a multiple column fractionator train in which heat is abstracted from the column requiring the highest heat duty and used to reboil a preceding column having a lower reboiler temperature.
  • such heat recovery is effected by condensing the overhead vapors of the high heat duty column in indirect heat exchange, in a steam generator, with boiling water under a regulated, preferably superatmospheric, steam pressure; this column 1s further refiuxed hot whereby the steam generator provides precise automatic control of refiux temperature, in addition to furnishing steam for the lower temperature column.
  • a typical feedstock to the fractionation unit which may comprise the product of an aromatics extraction plant, consists of 30%-47% benzene, 30%-47% toluene, 5 1% paraxylene, 15%-2.5% metaxylene, 5%-1% orthoxylene, %-1% ethylbenzene, 4%-0.5% C9 aromatics, and 1%0.05% diphenyl, all of the foregoing percentages being mol percentages.
  • the fractionation unit is usually designed to recover substantially pure benzene, nitration grade toluene, and ortho-xylene of at least 95% purity.
  • a preferred fractionation scheme removes first the lowest boiling component, benzene, followed by toluene removal in a second column.
  • These separations are relatively easy: for example, to recover a 100% benzene overhead fraction and a benzene-free bottoms fraction, the benzene column requires 45-60 trays, a heat flux of 20,000-33,200 B.t.u./lb.mol of feed, and an external reflux to feed mol ratio of from about 1:1 to about 2: 1; to recover a 100% toluene overhead fraction and a toluene free bottoms fraction, the toluene column requires 55- 70 trays, a heat flux of 212,200-28,400 B.t.u./lb.-Ino1 of feed, and an external reflux to feed m01 ratio of from about 1.00 to about 1.50.
  • the toluene column bottoms fraction consisting of a major proportion of C8 aromatics and a minor proportion of C9 aromatics and diphenyl is then distilled in a third 3,367,846 Patented Feb. 6, 1968 column designed to effect a precise split between metaxylene and ortho-xylene.
  • Light xylenes and ethylbenzene are taken overhead, while ortho-xylene, C9 aromatics and diphenyl constitute the bottoms fraction which is substantially free of light xylenes.
  • our invention affords significant operating economies in the overall fractionation process as well as improved control of the ortho-xylene column itself.
  • the quantity of steam so generated exceeds that required to run the benzene column which generally has the highest heat duty of all columns except the ortho-xylene column; therefore, the total reboil heat of the benzene column can be supplied by the heat of condensation of the orthoxylene column overhead vapors.
  • the excess steam generated by the ortho-xylene column overhead condenser permits independent control of steam pressure and temperature by a back-pressure regulator, and this in turn provides precise automatic stabilization of the orthoxylene column reflux temperature.
  • the ortho-xylene column is refluxed hot, meaning that the condensed overhead fraction leaving the tube side of the steam generator is returned to the top of the column without any appreciable additional cooling.
  • the refiux temperature will generally be at least 10 F. higher, and preferably 15 -50 F. higher, than the steam temperature depending upon design approach temperature of the condenser-steam generator.
  • One embodiment of our invention therefore provides a process for the separation of a hydrocarbon mixture comprising 'benzene and xylene isomers including ortho-xylene which comprises charging said mixture as feed to a first multistage distillation column; reboiling the first collumn bottoms -by indirect heat exchange in a reboiling zone with condensing steam obtained from a steam generation zone; recovering from the first column a benzenerich overhead fraction and a bottoms fraction which is substantially free of benzene; passing at least a portion of the first columns bottom fraction as feed to a second multistage distillation column operating under an overhead pressure in the range of -100 p.s.i.a.; passing the overhead vapors from the second column through said steam generation zone and therein condensing the overhead vapor by indirect heat exchange with boiling water under a regulated, preferably superatmospheric steam pressure and at a temperature higher than the temperature of said first column bottoms; recovering from the steam generation zone a condensed overhead fraction compris
  • an aromatic feedstock comprising benzene, toluene, ortho-xylene, paraxylene and/ or metaxylene, together with minor amounts of ethylbenzene, C9 aromatics and diphenyl, is charged to benzene column 10 through line 11.
  • Column 10 has 45-60 stages, which may be conventional bubble decks, sieve trays or valve trays.
  • Overhead vapors are removed therefrom through line 12, totally condensed in air condenser 13, and drained to receiver 14.
  • the liquid contents of receiver 14 are maintained under an atmosphere of suitable blanketing gas, such as sweet refinery gas, delivered from header 15 through line 16 at a regulated pressure.
  • the blanketing gas would be omitted and line 16 would instead connect with a steam jet ejector or vacuum pump.
  • Reiiux is returned to the column through line 17.
  • Net overhead liquid consisting essentially of 100% benzene, is removed from the column through a side-draw 18 several trays down from the top.
  • Column 10 is reboiled by an external thermosyphon reboiler 19.
  • Steam is supplied to the tubes of reboiler 19 from line 20 at a controlled rate of flow provided by flow controller 21 and motor valve 22.
  • Condensed steam is drained from reboiler 19 through line 23 to a condensate receiver 24.
  • Operating conditions for the benzene column are as follows:
  • the receiver pressure is desirably slightly above atmospheric, e.g. about 1 p.s.i.g. gas blanketing pressure.
  • the overhead vapor condensation pressure is then in the range of 20-16 p.s.i.a. corresponding to a condensation temperature of 195 175 F.
  • the benzene column bottoms, substantially free of benzene, is charged as feed to toluene column through line 25.
  • Column 30 has 55-70 stages which may be conventional bubble decks, sieve trays or valve trays. Overhead vapors are removed therefrom through line 32, totally condensed in air condenser 33 and drained to receiver 34. The liquid contents of receiver 34 are maintained under an atmosphere of blanketing gas delivered from header 15 to line 36. Reux is returned to column 30 via line 37, and net overhead liquid, consisting essentially of 100% toluene, is removed through line 38.
  • Column 30 is reboiled by an yexternal thermosyphon reboiler 39. High pressure refinery steam is supplied to the tubes of re- 4 boiler 39 through line 40, and condensate is removed therefrom through line 43. Operating conditions for the toluene column are as follows:
  • the receiver pressure is desirably slightly above atmosphere, e.g. about 1 p.s..i.g. gas blanketing pressure.
  • the overhead vapor condensatlon pressure is then in the range of 20-16 p.s.i.a. corresponding to a condensation temperature of 250-235 F.
  • Column 50 has 1Z0-160 stages and, while diagramatically illustrated as a single column, is usually composed of two side-by-side columns connected in series, one column serving as the upper rectification section and the other being the lower stripping section.
  • This column is designed and operated to separate ortho-xylene from meta-xylene or para-xylene; and net overhead product therefore comprises light xylenes and ethylbenzene, preferably containing less than about 1 mol percent of orthoxylene, and the bottoms product comprises ortho-xylene, C9 aromatics and diphenyl, preferably containing less than about 3 mol percent of light xylenes.
  • Overhead vapors are removed through line 51 and are totally condensed in the tubes of steam generator 53. Column pressure is controlled by a pressure controller 55 actuating motor 52 in the net overhead line. The condensed overhead fraction is drained through line 51-a to a subjacent hot receiver 54 maintained at column pressure by an equalizing line 56.
  • Hot reflux is returned to the column through line 57 and net overhead product is taken olf through line 58.
  • Column 50 is reboiled by a forced circulation gas-fired or oil-fired tube furnace 59.
  • the bottoms fraction, withdrawn through line 65, is passed to a finishing column (not illustrated) for heavy ends removal and recovery of 95% ortho-xylene.
  • Feedwater for steam generator 53 is supplied by line 71 from condensate receiver 24 to which make-up conf densate or treated deaerated feedwater is added via line 70.
  • Saturated steam is withdrawn from the generator through line 74, a portion thereof being diverted through line 20 to run the benzene column reboiler 19 and the re ⁇ mainder being discharged through valve 76 and line 77 for other uses such as dri-ving turbines or deaerating boiler feedwater.
  • Rate of feedwater addition is controlled by a conventional three element boiler feedwater computer actuating a motor valve 73.
  • Information transmitted to computer 80 consists of feedwater rate from flowmeter 72, steam demand from iiowmeter 75 and drum level from level transmitter 79.
  • Steam generation pressure is controlled by a pressure controller 78 actuating motor valve 76 in the net drawoff line. This fixes the shell side temperature of generator 53 and affords precise regulation of reflux temperature for column 50.
  • the steam temperature is at least 10 F. lower, and preferably 15-50 F. lower, than the reux temperature in order to provide optimum mean temperature difference.
  • the overhead vapor pressure of column 50 is so established in relation to the bubble point of the benzene column bottoms that the steam supplied to reboiler 19 is at a usefully high temperature; in general, thesaturated steam temperature should be at least 5 F, higher, preferably of the order of 20-60 F. higher, than the benzene column bottoms temperature.
  • the ortho-xylene column overhead condenser steam generator produces 97,400 lbs. per hour of saturated steam at 75 p.s.i.a. for a duty of 88,000,000 B.t.u. per hour; this represents a recovery of more than 99% of the heat input to the column supplied by the fired reboiler. Of this steam, 62,000 lbs.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Investigating Materials By The Use Of Optical Means Adapted For Particular Applications (AREA)
US482685A 1965-08-26 1965-08-26 Utilization of recovered steam heat for heating the distillation zone Expired - Lifetime US3367846A (en)

Priority Applications (12)

Application Number Priority Date Filing Date Title
US482685A US3367846A (en) 1965-08-26 1965-08-26 Utilization of recovered steam heat for heating the distillation zone
IL26347A IL26347A (en) 1965-08-26 1966-08-16 Process for the separation of a mixture of aromatic hydrocarbons by fractional distillation
GB36518/66A GB1149169A (en) 1965-08-26 1966-08-16 Heat utilization in aromatics fractionation
AT793266A AT272303B (de) 1965-08-26 1966-08-19 Verfahren zur Trennung eines Kohlenwasserstoffgemisches
DE19661593652 DE1593652A1 (de) 1965-08-26 1966-08-19 Verfahren zur Trennung eines Kohlenwasserstoffgemisches
ES0330435A ES330435A1 (es) 1965-08-26 1966-08-20 Un procedimiento para la separacion de una mezcla de hidrocarburos que comprende benceno e isomeros de xileno.
NL6611788A NL6611788A (no) 1965-08-26 1966-08-22
FR73967A FR1490258A (fr) 1965-08-26 1966-08-24 Procédé de séparation d'un mélange d'hydrocarbures aromatiques
NO164422A NO117538B (no) 1965-08-26 1966-08-25
DK433966AD DK117136B (da) 1965-08-26 1966-08-25 Fremgangsmåde til fraktioneret destillation af en carbonhydridblanding indeholdende benzen og xylenisomere.
CH1230666A CH486400A (de) 1965-08-26 1966-08-25 Verfahren zur Trennung von aromatischen Kohlenwasserstoffgemischen
FI662226A FI46732C (fi) 1965-08-26 1966-08-25 Menetelmä bentseeniä ja ksyleeni-isomeerejä sisältävän hiilivetyseokse n jakotislaamiseksi.

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US482685A US3367846A (en) 1965-08-26 1965-08-26 Utilization of recovered steam heat for heating the distillation zone

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US3367846A true US3367846A (en) 1968-02-06

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US (1) US3367846A (no)
AT (1) AT272303B (no)
CH (1) CH486400A (no)
DE (1) DE1593652A1 (no)
DK (1) DK117136B (no)
ES (1) ES330435A1 (no)
FI (1) FI46732C (no)
GB (1) GB1149169A (no)
IL (1) IL26347A (no)
NL (1) NL6611788A (no)
NO (1) NO117538B (no)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2706853A1 (de) * 1976-02-19 1977-08-25 Uop Inc Verbundverfahren zur xylolabtrennung und toluoltransalkylierung
US4555311A (en) * 1983-11-18 1985-11-26 Uop Inc. Integrated fractionation in the recovery of alkylaromatic hydrocarbons
US20060101852A1 (en) * 2004-11-18 2006-05-18 Porter John R Method for separating a multicomponent stream
CN110981835A (zh) * 2019-12-16 2020-04-10 江苏怡达化学股份有限公司 一种环氧丙烷生产中的甲醇回收方法

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1874387A (en) * 1922-11-13 1932-08-30 Semet Solvay Co Apparatus for the separation of liquids having different boiling points
US1882568A (en) * 1928-06-18 1932-10-11 E B Badger & Sons Company Method of distilling
US2325379A (en) * 1942-05-26 1943-07-27 Shell Dev Distillation process
USRE22379E (en) * 1943-09-28 Recovery of pure aromatics
FR912978A (fr) * 1944-03-29 1946-08-26 Woodall Duckham 1920 Ltd Distillation
US2406695A (en) * 1941-04-25 1946-08-27 Union Oil Co Separation of hydrocarbons by distillation
US2577701A (en) * 1946-05-20 1951-12-04 Shell Dev Fractionation process
US3254024A (en) * 1965-03-03 1966-05-31 Halcon International Inc Process for separating c8-aromatic hydrocarbons by series column distillation
US3265590A (en) * 1964-06-23 1966-08-09 Badger Co Apparatus and method of fractionation of ethyl benzene

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE22379E (en) * 1943-09-28 Recovery of pure aromatics
US1874387A (en) * 1922-11-13 1932-08-30 Semet Solvay Co Apparatus for the separation of liquids having different boiling points
US1882568A (en) * 1928-06-18 1932-10-11 E B Badger & Sons Company Method of distilling
US2406695A (en) * 1941-04-25 1946-08-27 Union Oil Co Separation of hydrocarbons by distillation
US2325379A (en) * 1942-05-26 1943-07-27 Shell Dev Distillation process
FR912978A (fr) * 1944-03-29 1946-08-26 Woodall Duckham 1920 Ltd Distillation
US2577701A (en) * 1946-05-20 1951-12-04 Shell Dev Fractionation process
US3265590A (en) * 1964-06-23 1966-08-09 Badger Co Apparatus and method of fractionation of ethyl benzene
US3254024A (en) * 1965-03-03 1966-05-31 Halcon International Inc Process for separating c8-aromatic hydrocarbons by series column distillation

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2706853A1 (de) * 1976-02-19 1977-08-25 Uop Inc Verbundverfahren zur xylolabtrennung und toluoltransalkylierung
US4555311A (en) * 1983-11-18 1985-11-26 Uop Inc. Integrated fractionation in the recovery of alkylaromatic hydrocarbons
US20060101852A1 (en) * 2004-11-18 2006-05-18 Porter John R Method for separating a multicomponent stream
US7249469B2 (en) 2004-11-18 2007-07-31 Exxonmobil Chemical Patents Inc. Method for separating a multicomponent stream
CN110981835A (zh) * 2019-12-16 2020-04-10 江苏怡达化学股份有限公司 一种环氧丙烷生产中的甲醇回收方法

Also Published As

Publication number Publication date
NL6611788A (no) 1967-02-27
GB1149169A (en) 1969-04-16
IL26347A (en) 1970-05-21
FI46732B (no) 1973-02-28
CH486400A (de) 1970-02-28
ES330435A1 (es) 1967-06-16
DE1593652A1 (de) 1972-04-20
FI46732C (fi) 1973-06-11
DK117136B (da) 1970-03-23
AT272303B (de) 1969-07-10
NO117538B (no) 1969-08-25

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