US1666119A - Process for converting petroleum hydrocarbons - Google Patents

Description

Jamie/747395 w 7 Artemi V- A ma 17, 1928. 2,666.19

W. M. CROSS PROCESS FOR CONVERTING PETROLEUM HYDROCARBONS Filed July 20, .1925

mam-wax EVAPORAZ'DAS Patented Apr. 17, 1928.

PATENT OFFICE.

WALTER 1V1. CROSS, OF KANSAS CITY, MISSOURI.

PROCESS FOR CONVERTING PETROLEUM HYDROCARBONS.

Application filed July 20, 1925. Serial No. 44,781.

This invention relates to improvements in a process for convertlng petroleum hydrocarbons, and refers more particularly to a.

distillation process in which crude oil and the like is separated into a plurality of fractions of different boiling points, the separation being made in anefiicient manner and heat conserved throughout the system by are, to provide a process in which oil is pre liminarily heated in preheatingcoils positioned-in the top 'of refluxing towers, thence passed to a preliminary heating stage in which the oil is raised to a temperature sufiicient to vaporize certain of the lower boiling point fractions; to provide a process in which this preliminarily heated oil is thence passed to a vaporizing stage where a separation is made and the liquid bottom returned and reheated to temperature suflicient to drive off further fractions of relatively' higher boiling points; to provide a process in which'overhead material is taken from the separate stages of vaporization and separately subjected to dephlegmation, after which the products are combined, av final distillate recovered and intermediate cuts in the form of liquid condensates removed from the separate stages of treatment, and further, to provide an apparatus for carrying out this process.

The single figure is a diagrammatic side elevational view of the apparatus, with'parts in section and parts broken away. I

Referring to the drawing, at 1 is shown a furnace divided by a bafiie 2 into a combustion space 3 and a heating chamber 4. The combustion chamber is preferably heated by means of gas burners such as that diagram;

matically shown at 5. A heating coil comprising a lower preheating section 6 and an upper heating section 7 are positioned in the heating chamber and are there subjected to the high temperatures of, the combustion gases passing'from the combustionspace 3 through the heating ,chamber and out through the flue pi e 8. 'The tanks 9 and 10 are vaporizing c embers; 11 and 12 are fractionating towers in which the .vapor's from the separate vaporizing towers are treated. 13 is a condenser box in which is positioned a condenser coil 14:; at 15 is shown a receiving tank having a gas relief line 16 controlled by a valve- 17 and a liquid drawoff line 18 regulated by a valve 19.

At 20 is shown a charging pump by means of which crude oil, or any other suitable type of charging stock, is introduced from storage through the line 21 and is forced through the pipe 22 successively through the preheating coils 23 and 24 positioned in the towers 12 and 11, respectively. By circulation through these coils, the charging stock 1 is preheated by the hot hydrocarbon vapors in the separate towers and is passed thence through the line 25 to the preheating coil'6 in the lower part of the heating chamber of the furnace 1. In this coil 6 heat is added to the oil to raise it to a temperature at which the lighter fractions will vaporize. The discharge line 6 from the preheating coil, to-

gether with subsequent heating coils designated as 26 and positioned in the heating chamber between the preheating coil and the final heating coil 7, have their outer extremities connected into a header arrangement which consists of two vertical pipes '27 and 28 between which are intermediate connecting pipes 29 which constitute extensions.

ate these connecting lines, are valves 28 to 28, inclusive. In the vertical pipe 27 are corresponding valves numbered from 27 to 27, inclusive. The oil, on being preheated in the coil 6, may be discharged directly into the vaporizing chamber 9 through the line 6 by closing the valves 27 and 28 and opening the valve 29 fer-red directly to the vaporizing chamber 9 from which the volatilized material passes overhead through the vapor line 30 and is introduced into the bottom of the refluziing tower 11. This tower is preferably of the bubble tower type, but any suitable type of refluxing tower may be used in its stead. In this tower the vapors rise through a series.

of pools, passing off through the line 31 to the final condensing coil 14 and thence to the receiver 15. The unvaporized material or bottom chllecting in the chamber 9 is drawn The oil then is trans-' beyond the valve 29 off through the pipe 32 which is connected With the suction side of the pump 33. In this Withdrawal line from the chamber 9 may be interposed an automatic liquid level regulating device and a storage tank not shown which would serve to regulate the withdrawal from the chamber 9 and maintain at all times a head of oil for the pump 33. These details have purposely been omit ted for simplifying the drawings. The bottoms from the chamber 9 are discharged by thepump 33 through the line 34 which connects into the vertical pipe 28. In the event that the oil is being drawn from the preheating coils in the furnace through the discharge line 6, the valves in the header arrangement will be so arranged that the oil will travel downwardly through the pipe 28 and into the lowest intermediate connection 29 through the valve 29 which is open and into the lowest of the intermediate heating coils 26. It will then continue upwardly through the remaining coils 26 which are connected up as a continuous coil by closing the subsequent valves. 29 to 29, inclusive, and opening the valves 27 to 27?, inclusive. In a like manner, if the oil is not given sufficient heat by the lower preheating coil 6 by closing the valve 29 it may be circulated on up through the intermediate coils 26 by proper manipulation of the valves in the header arrangement and discharged from any one of these intermediate heating pipes through the header arrangement by directing the oil from the termination of any one of the coils 26 downwardly through the vertical pipe 28 and thence into the evaporating chamber through that portion of the line 6 When the oil is circuated in this manner, the bottoms returned to the pump 33 must be circulated back into the next succeeding coil 26 above that through which the oil .is discharged when passing through the vaporizing chamber 9. Thus, at all times the coils in the furnace will be maintained full of oil, preventing carbon accumulation and coking and failure of the tubes as a result of dryness. The upper extremity of the vertical line 27 is connected to the coil 7 which terminates in a transfer line 35 which is connected into the bottom of the evaporating chamber 10. Thus, the bottoms returned fromthe chamher 9 are given additional heat or are re- .heated to the extent that further of the relatively higher boiling point fractions are distilled off on their being discharged into the chamber 10. It will be noted that this upper coil 7 is in a hotter portion of the furnace and therefore the oil circulating therethrough receives considerably greater heat. The number of coils which will constitute the three stages of heating in the furnace, namely the preliminary stage, the

intermediate stage and the upper heating stage, is a lnatter of engineering and no attempt has been made in the drawings other than a diagrammatic showing of the manner in which the coils are connected up.

The material vaporized in the chamber 10 passes oif through the vapor line 36 and is discharged into the lower part of the tower 12 which is shown as a bubble tower of similar construction to the tower 11. In this tower the-vapors rise through a series of oil pools, being subjected to fractionation in their travel from the bottom of the tower to the top from which the still vaporized products pass off through the line 37 and are introduced near the bottom of the tower 11 where they are mixed and pass upwardly with the vaporized material arriving in this tower from the vaporizing chamber 9. The combined material passes olf through the line 31 to the condenser 13 and is finally collected in the receiving tank 15. The bottoms from the tower 10, which will consist of the heavier residual material unvaporized in the chamber, is drawn off through the line 38 regulated by a valve 39 which may be automatically controlled by a liquid level regulator, not shown, if desired. This highly heated material passes thence through a coil 40 positioned in the bottom of the tower 11 and is discharged therefrom through a line 41 regulated by a valve 42 to a cooler and thence to storage, or for subsequentrerunning and cracking or conversion in a separate apparatus.

The refluxed condensate collected inthe bottom of the tower 11 drawn-off through the line 43 regulated by a valve 43 which is preferably contrplled by-a liquid level regulating device (not shown) for thepurpose of maintaining the liquid level in the tower 11 above, in order to' maintain the coil 40 llO through the coil 44 is finally discharged through the line 45 controlled by a valve 46 into a cooler, storage tank or utilized as cracking stock. In order to maintain a proper flow of this condensate 'fromthe tower 11 through the tower 12, it may be necessary to lower the tower 12 somewhat in order that a proper gravitational flow will result or a suction pump may be put upon the discharge line to assure proper circu-- lation. Condensate separated out in the tower 12 is drawn ofl through the line 47 regulated by a valve 48. This latter valve I from the bottom of the tower 12 through the is preferably manipulated by an automatic liquid level regulatlng device to maintain a level of oil above the coil 44. J

In actual operation where crude oil is charged to the system, it will be preheated in the coils 23 and '24 in the tops of the towers 12 and 11 and in the coil 6 it will receive additional heat sufficient to vaporize the lighter fractions therefrom. On discharge to the vaporizing chamber 9 these lighter fractions will be taken overhead through the line 30 and subjected to a refluxing action in the tower 11. The returned bottoms from the chamber 9 will be circulated back through the coils 26 and 7 to receive further heating in order to vaporize additional fractions of relatively higher boiling point than those separated off in the chamber 9. This hot oil, on being discharged through the line 35 to the chamber 10, separates these fractions in the form of vapor which passes off through the line 36 to the tower 12 where they are separately fractionated from the vapors discharged from the chamber 9 while the bottoms from the chamber 10, which consists primarily ofa fuel oil bottom, passes off through the reboiling coil 40 in the bottom of the tower 11 and thence to storage. It may be necessary to' lower the tower*11 from the' position shown in the'drawing to assuregravitational flow or to interpose a positive circulating means such as a pump preferably in the discharge line 41 or beyond a fuel oil cooler (not shown).

Returning now to the material which is uncondensed in the tower '12, these vapors pass off through the line 37 into the bottom of tower 11 where they are combined and rise upwardly with the material transferred to the tower from the chamber 9 through the vapor line 30. The combined fractions are dephlegmated in the tower 11 and the still volatile material passes off through the line 31 to be collected as benzene or naphtha in the receiving tank 15. A condensate having the characteristics of gas oil is removed line 47, while a somewhat lighter cut, such as a kerosene distillate, is taken off from y the tower 11 through the line 43 and utilized as a reboiling agent in the tower. 12. In a process of this character, the distillat1on temperature to which the oil is raised in the coils in the furnace may be selected to give the most complete stripping of the initial-fraction, thus eliminating superheating of these fractions with the formation of unnecessary and objectionable amounts of mcondensible gas produced where the entire body of oil is raised to temperature sufiic ent to distill the higher boiling point fractrons. By treating the crude in this manner,

the equilibrium is immediately upset by removing the lighter gases and vapors in I the initial vaporizing stage so that material recovered from the remaining oil products such as the gas oil and\kerosene distillate or fuel oil recovered from the subsequent stages, produce a better crackmg stock WhlCh gives increased yields and a better final resulting distillate. Thus, a bigger yield of gasoline is obtained not only from the strip ping, but also from thecracking of the remaining petroleum hydrocarbons. The con servation of heat cuts down the fuel because superheating of the oil is eliminated. Furthermore, the elimination of the lighter fractions by the use of a vaporizing stage interposed between the separateheating stages,

friction loss, due to the accumulation of vapors and gases, is dispensed with. To overcome this friction loss, a certain amount of pressure must be maintained which increases the cost of theapparatus in recovering distillate not as good in uality as that recovered in thehereinbefore escribed proc bers and the bubble towers are heavily insulated to avoid loss of heat through radiation.

I claim: as my invention: 1. A process of distilling petroleum hydrocarbons, comprising the steps of heating the oil in a-prelimin'ary heating stage to a temperature to vaporize the lighter hydrocarbons, passing said heated oil to a, vaporizing stage and there separating the liquid and volatilized material, returning the liquid products for further heating to vaporize additional fractions of higher boiling points, and passing the reheated material to a separate vaporizmg stage and controlling the relative heating to which-the charging stock and recycled stock are subjected by limiting through the Heating zone.

2. A process of distilling petroleum hydrocarbons, comprising the steps of "heating extent of their circulationthe oil in apreliminary heatin stage to a temperature to vaporize the lig ter hydrocarbons, passing sai'd heate d oil to a vaporizing stage and there separating the liquid and volitized material, returning the liquid products for further heating to vaporize additional fractions of. higher boiling points,

and passing thereheated material to a sepa- 3. A process of distilling petroleum hy-- drocarbons, comprising the steps of heating the .oil to a. temperature to vaporize the light hydrocarbons, passin'githe heated oil to a vaporizing stage,-separatmg the hqmd and vapor, returning the liquid for fur ther heating to vaporize additional fractions of higher boiling point, passing the reheated materials to a separate vaporizing. stage, separately refluxing the volatized fractions and removing distillates having relatively difierent boiling point ranges, utilizing the heat contained in the liquid bottoms to redistill low boiling point products in the system ancl'controlling the relative heating 1 of the charging stock and recycled stock by the extent of circulation of said stocks through the heating zone.

WALTER M. GROSS.

Images