US2453205A - Controlled fractional distillation of petroleum - Google Patents

Controlled fractional distillation of petroleum Download PDF

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Publication number
US2453205A
US2453205A US473608A US47360843A US2453205A US 2453205 A US2453205 A US 2453205A US 473608 A US473608 A US 473608A US 47360843 A US47360843 A US 47360843A US 2453205 A US2453205 A US 2453205A
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Prior art keywords
column
feed
reflux
product
rate
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Expired - Lifetime
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US473608A
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English (en)
Inventor
Docksey Patrick
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Anglo Iranian Oil Co Ltd
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Anglo Iranian Oil Co Ltd
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Priority claimed from GB117242A external-priority patent/GB600801A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D3/00—Distillation or related exchange processes in which liquids are contacted with gaseous media, e.g. stripping
    • B01D3/42—Regulation; Control
    • B01D3/4211—Regulation; Control of columns
    • B01D3/425—Head-, bottom- and feed stream
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G7/00—Distillation of hydrocarbon oils
    • C10G7/02—Stabilising gasoline by removing gases by fractioning

Definitions

  • the invention has however among its objects to separate constituents of petroleum distillates closely related inboil-ing points, by greater preci'sion in fractionation than is possible by mere temperaturecontrol at the column head, to yield closely cut high grade fractions of high octane number.
  • the principle upon which the invention is based is the control of the quantity of one of the product streams withdrawn from the fractionating column as a fixed proportion of the feed, the quantity of the product withdrawn being determined by analysisof the feed. Only one of the twoproduct streams may-be controlled in this way, that is to say, either the overhead product orthe bottoms product.
  • The'other product is withdrawn from the column at such a rate as to :avoid the. accumulation of material in the column.
  • composition of "the feed may vary from time to time as indicat'ed by an'alysis of the products, small adjustments of the controls applied-to the column may be made in the course 1 tained, the heat'supplied to the column, the reflux and the'liquid level in the 'base of the column are constant.
  • Figure 1 illustrates a 'fractionating column in which the overhead is the product stream which is volume-controlled.
  • Figure 2 illustrates a 'fractionating column in Y which the bottoms product is the stream which is volume-controlled.
  • FIGS. 3 to 10 are diagrams hereinafter re- 'ferred to. I
  • the production of a narrow cut usually involves two steps of continuous distillation, in one of which separation is made between low boiling material and the desired narrow boiling range cut, and in the other between high boiling material and the narrow boiling range'cut.
  • the invention may be applied to one or both of these operations.
  • Figure 9 shows the true boiling point curve of the distillate and Figure 10 that of the residue. In both cases the true boiling point curve of the original feed in the cut point region is indicated by a dotted line.
  • Figure 9 has been drawn to cover a range of 0-62 gal. and Figure 10 to cover a range of 62-100 gal.
  • the imperfection of separation is measured on these diagrams by the amount of material boiling above "TQO C. in Figure 9 and the amount boilin below TQ C. in Figure 10, these amounts being QN gal. and RQ gal. respectively;
  • TQO C. the amount boilin below TQ C.
  • RQ gal. the amount of material boiling above
  • .It is the purpose of the invention to minimise the efiect due to the imperfection of control, so that the degree ofseparation obtained with any given practical column will approach more closely to that which is theoretically obtainable.
  • the petroleum distillate to be fractionated may be fed tothe fractiorl'ating column e from any one ofthree feed tanks a, b, c that are used successivelyor alternatively.
  • the feed tank a is being charged withth'edistillate to be fractionated; the distillate in the feed tanlgb is being stirred to ensure uniform composition and analysed, and the tank 0 contains distillate which has already been analysed and isready to be fed to the column.
  • the feed is in'this case delivered by thefeed pump d to the fractionating column e from the tank c.
  • the distillate in the tank b will be ready for feedingto'the column e, and the tank 0 may then be re-cllarged with distillate; The distillate after analysis may however be otherwise fed to the fractionating column.
  • Vapour is supplied at the bottomof thefractionating column e by a re-boiler m, and the bottoms productis delivered 'by the pump oto storlage, after passing throughthe cooler p.
  • the overhead vapour from the fractionating column e passes to the condenser f whence the liquid condensate flows to the intermediate storage or reflux tank g. From this tankthat'part of the overhead productto be withdrawn is passed to storage by the overhead pump Z, while theremainder ispassedback to'thefractionating column by means of the reflux pump it.
  • the plant conditions are as indicated in Figure :1 and as the amount of hereinafter described
  • the feed pump 11 is set'to deliver feed fromthe feed tank at a constant rate; which r'nay bacontrolledby a fiow controller of conventional'type.
  • the appropriate feed rate is dependent on the draw overhead product. from the tank g at a constant ratefand, may be controlled .by aLflow controller. The rate 'of withdrawal is determined from an" analysis of the feed, which determines .iiea 11 I :t he'proportion. of. theoverhead product it is desirodtoprnduce, and. the feed rate.
  • the quantity of steam to the re-boiler m. is maintained at a constant value determined to ivethemequired vapour. loading in the column.
  • the bottoms product withdrawal pump is operated under the. control of a level controller n coluninbase frornthe bottom tray of the column,
  • the former being. determined by the quantity of reflu -r turned y. t e ump it, and the latt r by the steam admit ed. to the re-boiler m.
  • the levelv in. the reflux tank g must be controlled within narrow limits, since at any given mom nt the e overhead product mad yt column is. the difference between the overhead nanour, passing. to the condenser f, and the liquidlretunnedto the. column e by the pump it. If the level in thereflux tank is rising, this difference is increasing, while if the level in the reflux tanleis v falling. this difierence is decreasing, as comparedwith average difference between these two. q antities- Such va iations of level are t us an indication. of corresponding undesirable variations in the quality of the product. However, the presence oi? large quantities of material both the re u tank. a and on t e trays.
  • the withdrawal of the product, the volume. of which is controlled shall be. efiected froma body of the product, the liquid levelor head. of which is maintained constant.
  • the quantity. thatiswithdrawn and is maintained constant may be taken from a tank, the liquid level in which may serve for the operation of a level controller determining the return of reflux to the column; while the bottoms product may be withdrawn under control of a level controller operating according to the liquid level to be maintained at the base. of the column.
  • the withdrawal of the overhead product from the tank may be effected by a level controller, while. the reflux may be supplied from the tank at a constant rate and the withdrawal of the bottoms product may be effected at a. constant rate from the base of the column, whereby the liquid level is determined by the heat supplied to the column which is controlled. by a level controller.
  • the feed pump at is set to pump at the desired rate.
  • steam is admitted at the determined rate to the re-boiler m. Further rise of level. in the column base is prevented by the controller n which determines the operation of;- the pump 0.
  • the hot vapours from the re-boiler m gradually warm up the entire column, and condensate then appears in the reflux tank.
  • the pump 1 is now operated at its deter-mined rate whereupon the level in the reflux tank g slowly rises. until; the pump it commences operation under the effect of the controller h. When thermal equilibrium has been attained, the pump it will be returning the determined amount of reflux to the column. During this period the products from the column withdrawn by the pumps 2 and 0 will pass either to waste or to whichever of the tanks a, b and c is being filled with the feed at the time.
  • the feed pump (1 is set to deliver feed from the feed tank at a steady. rate, controlled by a flow controller of conventional type.
  • the appropriate rate for feed admission is determined in the manner described with reference to Figure 1-on the basis of the characteristics of the column, the percentage overhead product it is desiredv to make andthe reflux ratio.
  • The. bottoms product pump 0. is set to withdraw bottoms at a steady rate, which may be controlled by a flow controller or otherwise.
  • the rate of withdrawal is determined from ananalysis of the feedwhich determines the percentage of bottoms product it is desiredto produce and the feed rate.
  • mea e 1? ..'.1,"Ih.ieflux.pump k is set to return reflux at the desired constant rate to give the desired 'vapounloading in the column.
  • the overhead product pump Z is controlled by the level controller h to maintain a constant level in the reflux tankg.
  • the admission of steam to the re-boiler mis controlled by level controller n to maintain a. constant level in the column base by ensuring the-necessary evaporation of the liquid.
  • volume control of the bottoms product is advantageous when that product is a small percentage of the feed, and when the column is operated under pressure controlled by a pressure controller in the vapour space of the reflux tank g, which operates by release of vapour and uncondensables from the reflux tank g through a valve.
  • the vapours so released are part of the overhead product, and if their quantity is not negligible it is evident that the volume control of the overhead product by means of pump Z, as in themodification described with reference to Figure 1 does not operate successfully.
  • the overhead product initially accumu- .lating in the reflux tank 9 is all returned to the column, thus increasing the load on the re-boiler. .It is preferable therefore to bring the column on stream by breaking the connection between the level controller n and the steam inlet to the reboiler m, and between the level controller h and the pump Z.
  • the feed pump (1 is started and feed introduced at the determined rate. When a determined level is attained in the column base, steam is admitted to the re-boiler m at about the rate indicated by the preliminary heat balance, and the pump 0 is started and hand controlled to maintain a proper level in the column base.
  • the pump Z is started and the overhead product is withdrawn at approximately the rate determined by analysis of the feed and feed rate.
  • the level is maintained by starting the pump it, and gradually increasing the flow.
  • the pump 0 is set to withdraw bottoms product at the desired rate, and the pump it to return reflux steadily at the desired rate. This method of bringing the column on stream is equivalent to control for a short time whilev approaching thermal equilibrium.
  • the feed in the example was found to have 12% by volume 11.22% by weight) boiling to this temperature.
  • the separation was carried out in a fractionating column with an operating vapour velocity of 150,000 lbs/hr. when taking-hexane overhead at atmospheric pressure. It was decided to operate at a re-boil ratio (lb. per hour of vapour from re-boiler: lb. per hour of bottoms product) of 3.8: 1.
  • the temperature at the column head and base were approximately 180 F. and 280 F. respectively, and the temperature of the'returm'ng reflux F. Steam supply to the re-boiler was duction of 39.5001bs./hr.
  • the content so determined, converted back to a percentage on the bottoms product, gives an indication as to whether the conditions are set correctly to give the desired normal hexane quantity in the bottoms, and allows a slight alteration to be made to the overhead product withdrawal rate, if necessary.
  • the process of the invention may be applied to the distillate in successive flow of material through a, number of columns in a manner such as described in the specification filed pursuant to the application Serial Number 428,530, dated January 28, 1942, (now abandoned) to yield for example isopentane. and isohexane fraction and an isoheptane fraction of high octane number, and for the segregation of low grade material, the fractiona tions being carried out in columns e, 1, g, h and i of such characteristics that fractionation may be carried out under superfractionation conditions in the use of a considerable number, such as 50 theoretical plates in the columns, whereby precision in fractionation is ensured.
  • the process may be applied to single or selected fractions, and the respective characteristics of the columns with respect to diameter and number of theoretical plates may vary according to the character of the crude oil from which the distillate is derived and its composition.
  • the distillate feed may be first stabilised and then de-butanised in columns in which the fractionation may be carried out in known manner, before subjection to iii) 10 the process of the invention, and the pentane content may be similarly fractionated for the separation of isopentane from n-pentane, as hereinbefore described.
  • a process of distillation for the production of closely out high grade fractions of a petroleum distillate in a fractionating column to yield an overhead product and a bottoms product comprising admitting a stream of the distillate to the column at a determined substantially constant rate by volume, withdrawing a stream of the overhead product from the column, condensing said overhead stream and introduicng the condensate into a reflux drum, withdrawing part of said condensate from the system as product at a substantially constant rate which is a determined substantially constant proportion of the distillate feed rate fixed by the cut point of the distillate as determined by analysis of the distillate from time to time, withdrawing a stream of the bottoms product from the column at such a rate as to maintain a substantially constant liquid level in the column base, maintaining a substantially constant determined vapour loading in the column by control of the heat applied to the column base, andv returning another part of the condensate from the reflux drum to the column as reflux at such a rate as to maintain a substantially constant liquid level in the reflux drum.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Engineering & Computer Science (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
US473608A 1942-01-28 1943-01-26 Controlled fractional distillation of petroleum Expired - Lifetime US2453205A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB117242A GB600801A (en) 1942-01-28 Improvements relating to the production of high grade aviation or motor fuels by fractional distillation

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2953524A (en) * 1956-04-25 1960-09-20 Jr Wilson C Rich Rectification process using cool shot in addition to reflux
US2990366A (en) * 1957-10-21 1961-06-27 Phillips Petroleum Co Method for control of dephlegmator in response to specific gravity measurements
US3309287A (en) * 1962-08-27 1967-03-14 Phillips Petroleum Co Controlling the operation of a train of distillation columns
US3361646A (en) * 1963-12-11 1968-01-02 Exxon Research Engineering Co Fractionation control system for controlling and optimizing fractionation tower material balance and heat input
US5876591A (en) * 1997-03-31 1999-03-02 Uop Llc Process for the production of lube oil

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE198804C (en(2012)) *
US1930166A (en) * 1930-07-14 1933-10-10 Union Oil Co Method and apparatus for rectification of hydrocarbons
US1940802A (en) * 1929-12-09 1933-12-26 Floyd L Kallam Control device for fractionators and the like
US1998123A (en) * 1932-08-25 1935-04-16 Socony Vacuum Oil Co Inc Process and apparatus for the distillation and conversion of hydrocarbons
US2029501A (en) * 1928-09-26 1936-02-04 Union Oil Co Method and apparatus for distillation of oil
GB476610A (en) * 1936-06-18 1937-12-13 Pintsch Julius Ag Fractional separation of crude hydrocarbon oil
US2104310A (en) * 1934-07-14 1938-01-04 Shell Dev Method of fractionation
US2109201A (en) * 1933-07-10 1938-02-22 Union Oil Co Process and apparatus for stabilizing hydrocarbons
US2246934A (en) * 1938-11-26 1941-06-24 Foster Wheeler Corp Fractional distillation
US2254387A (en) * 1939-03-11 1941-09-02 Charles A Olcott Means for conditioning sugar bearing materials
US2297098A (en) * 1940-03-23 1942-09-29 Phillips Petroleum Co Rectifying column control
US2340026A (en) * 1942-02-23 1944-01-25 Phillips Petroleum Co Fractionator control
US2357113A (en) * 1940-11-30 1944-08-29 Kellogg M W Co Apparatus for distillation control

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE198804C (en(2012)) *
US2029501A (en) * 1928-09-26 1936-02-04 Union Oil Co Method and apparatus for distillation of oil
US1940802A (en) * 1929-12-09 1933-12-26 Floyd L Kallam Control device for fractionators and the like
US1930166A (en) * 1930-07-14 1933-10-10 Union Oil Co Method and apparatus for rectification of hydrocarbons
US1998123A (en) * 1932-08-25 1935-04-16 Socony Vacuum Oil Co Inc Process and apparatus for the distillation and conversion of hydrocarbons
US2109201A (en) * 1933-07-10 1938-02-22 Union Oil Co Process and apparatus for stabilizing hydrocarbons
US2104310A (en) * 1934-07-14 1938-01-04 Shell Dev Method of fractionation
GB476610A (en) * 1936-06-18 1937-12-13 Pintsch Julius Ag Fractional separation of crude hydrocarbon oil
US2246934A (en) * 1938-11-26 1941-06-24 Foster Wheeler Corp Fractional distillation
US2254387A (en) * 1939-03-11 1941-09-02 Charles A Olcott Means for conditioning sugar bearing materials
US2297098A (en) * 1940-03-23 1942-09-29 Phillips Petroleum Co Rectifying column control
US2357113A (en) * 1940-11-30 1944-08-29 Kellogg M W Co Apparatus for distillation control
US2340026A (en) * 1942-02-23 1944-01-25 Phillips Petroleum Co Fractionator control

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2953524A (en) * 1956-04-25 1960-09-20 Jr Wilson C Rich Rectification process using cool shot in addition to reflux
US2990366A (en) * 1957-10-21 1961-06-27 Phillips Petroleum Co Method for control of dephlegmator in response to specific gravity measurements
US3309287A (en) * 1962-08-27 1967-03-14 Phillips Petroleum Co Controlling the operation of a train of distillation columns
US3361646A (en) * 1963-12-11 1968-01-02 Exxon Research Engineering Co Fractionation control system for controlling and optimizing fractionation tower material balance and heat input
US5876591A (en) * 1997-03-31 1999-03-02 Uop Llc Process for the production of lube oil

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Publication number Publication date
NL122134C (en(2012)) 1967-04-17
NL67785C (en(2012)) 1951-05-15
FR935749A (fr) 1948-06-29

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