US2055896A - Conversion of hydrocarbon oils - Google Patents

Description

Sept. 29, 1936. J. B. HEID 2,055,896

' CONVERSION OF HYDROCARBON OILS Original Filed April 50, 1934 FRACTIONATOR l RECEIVER 47 9 HEAT EXCHANGER FURNACE INVENTOR JACOB BE IN HEID TORNEY Patented Sept. 29, 1936 CONVERSION OF HYDROCARBON OILS Jacob Benjamin Held, Chicago, 111., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application April 30, 1934, Serial No. 723,125 Renewed August 1, 1935 11 Claims. (CL 196-48) This invention particularly refers to an improved process for the conversion of hydrocarbon oils of the type wherein selected relatively low boiling and high boiling fractions of the intermediate conversion products of the process (reflux condensate) are each subjected to independently controlled conversion conditions in the same system. The improvements of the present invention comprise methods for subjecting normally gaseous products of the process, as well as, when desired, gases from any desired external source, to two-stage absorption, raw oil charging stock for the process being utilized as the absorber oil in one stage and the enriched raw oil being subjected to conversion, together with high boiling fractions of the intermediate conversion products of the process, while selected low boiling fractions of the intermediate conversion products are utilized as absorber oil in the other stage, the enriched oil from this stage being subjected to independently controlled more severe conversion conditions in the same system.

The advantages of recovering desirable high boiling components, such as propane, butane and their corresponding olefins, for example, from the gaseous products resulting from the pyrolytic conversion of hydrocarbon oils for the production of high yields of good quality motor fuel and subjecting the same to conversion, together with the absorbing menstruum utilized for their recovery, have already been demonstrated. I am aware that it has been the practice to utilize hydrocarbon oil charging stock of a relatively high-boiling nature as the absorber oiLin such processes and that selected low boiling fractions of the intermediate conversion products (reflux condensate) from within the system have also been successfully utilized for this purpose.

It is generally recognized that an absorbing medium only slightly higher in boiling characteristics than the material to be absorbed is ordinarily more eflicient than an absorbing medium of considerably higher boiling characteristics. For this reason a low-boiling fraction of the intermediate conversion products of the process is preferable for absorbing propane, butane and the like from the gaseous conversion products to higher boiling charging stock for the process.

I have also found that by the inclusion of addi-- tional quantities of the desirable high boiling components of the gases such as propane, butane and the like to the oils undergoing conversion, in excess of the propanes, butanes, etcetera, normally produced within the system, additional yields of motor fuel of improved quality may be produced.

This may be accomplished, for example, by supplying gases containing the desired materials from any suitable external source to the absorption stage of the process and, while I have not determined the exact limits within which improved results a-re obtainable from a commercial standpoint by the addition of increased quantities of normally gaseous material such as propane and butane to the oil undergoing conversion, I believe that the quantities of such materials which may be advantageously employed is relatively high and that it varies appreciably with different types of oil as well as with the conversion conditions to which they are subjected.

Furthermore, I have found that the same or an even greater increase in the yield of desirable light liquid products, such as motor fuel of high anti-knock value, may be obtained by the conversion of propanes, butanes and similar materials with a select low boiling fraction of the intermediate conversion products as compared to their conversion with hydrocarbon oil charging stock when the latter is of higher boiling characteristics comprising such materials as gas oil, fuel oil and the like. However, the volume of select low-boiling fractions of the intermediate conversion products in an operation of the character above mentioned is sometimes not suflicient to.

recover all of the available desired components of the gases, particularly when the gases produced within the system and subjected to absorption are augmented by gases from an external source. Therefore, in the present invention, in addition to subjecting the gases to adsorption with the relatively light intermediate conversion products, I employ another adsorption stage, utilizing hydrocarbon oil charging stock for the process as the absorber oil, subjecting the enriched hydrocarbon oil charging stock to conversion conditions of elevated temperature and superatmospheric pressure, together with high boiling fractions of the intermediate conversion products of the process and subjecting the enriched absorber oil from the other stage to independently controlled more severe conversion conditions of elevated temperature and superatmospheric pressure in the same cracking system. By this method of operation I am not only able to recover substantially all of the high boiling components of the gases but, due to the relatively large volume of total absorber oil available, I may, when desired, supply additional gases from any suitable external source to the system for absorption, thereby materially increasing the total quantity of normally gaseous material, such as propane and butane, subjected to conversion within the system together with the absorber liquid and increasing both the yield and quality of the motor fuel conversion products of the process.

The features of the present invention may be utilized to advantage in practically any type of cracking system wherein relatively low boiling and high boiling oils are subjected to independently controlled conversion conditions. It is within the scope of the invention to employ a selected low boiling fraction of the intermediate conversion products of the process as the absorber liquid in the first absorption stage, followed by subjection of the remaining gases to absorption with hydrocarbon oil charging stock for the process in the second absorption stage or, when desired, this order may be reversed, the raw oil being utilized as the absorption medium in the first stage and the selected low boiling fractions of the intermediate conversion products utilized as the absorption medium in the second stage.

Further details of the preferred operation of the process as well as alternatives which are permissible within the scope of the invention will be more apparent with reference to the accompanying diagrammatic drawing and the following description thereof. The drawing illustrates one specific form of apparatus in which the invention may be practiced.

Referring to the drawing, heating coil 4 is located within a furnace 2 of any suitable form and the oil supplied to this zone, as will be later more fully described, is subjected to the desired conversion temperature, preferably at a substantial superatmospheric pressure, the stream of heated oil being discharged from the heating coil through line 3 and valve 4 and introduced into reaction chamber 5.

Chamber 5 is also preferably maintained at substantial superatmospheric pressure and, although not indicated in the drawing, is preferably well insulated to prevent the excessive loss of heat by radiation so that conversion of the heated products supplied to this zone, and particularly their vaporous components, may continue therein. In the particular case here illustrated, both vaporous and liquid conversion products are withdrawn in commingled state from the lower portion of chamber 5, passing through line 6 and valve 1 into vaporizing chamber 8.

Chamber 8 is preferably maintained at substantially reduced pressure relative to that employed in the reaction chamber, by means of which further vaporization of the liquid conversion products supplied to this zone is accomplished. Residual liquid remaining unvaporized in chamber 8 may be withdrawn therefrom through line 9 and valve 10 to cooling and storage or to any desired further treatment or, when desired, the conditions of operation may be regulated to affect the production of substantially dry coke as the residual conversion product of the process. In the latter case the coke may be allowed to accumulate within chamber 8, or a similar coking zone of any desired form (not shown), to be removed therefrom after the operation of the chamber is completed and, when desired, a plurality of such zones may be employed and may be operated either alternately or simultaneously. When coke is produced in chamber 8 as the final residual product of the process line 9 and valve It! may serve as a drain line and as a means of introducing steam, water or other suitable cooling medium into the chamher after its operation is completed, in order to hasten cooling and facilitate cleaning of the chamber. The vaporous conversion products of the process pass, in the case illustrated, from chamber 8 through line H and valve l2 to fractionation in fractionator l3.

The components of the vaporous conversion products supplied to fractionator l3 boiling above the range of the desired final light distillate product of the process are condensed within this zone as reflux condensate and the reflux condensate is separated into selected low boiling and higher boiling fractions. The high boiling fractions of the reflux condensate may collect within the lower portion of fractionator I3 to be withdrawn therefrom through line [4 and valve l5 to pump I3, by means of which they are returned through line I! and valve I8 to further conversion in heating coil I. The selected low boiling fractions of the reflux condensate may be withdrawn from any suitable intermediate point or plurality of points in column l3, for example through line I9 and valve 20, to pump 2| by means of which they are fed through line 22 and may be directed through valves 23 and 24 in this line to absorber 55 or they may be subjected to cooling, when desired, prior to their introduction into the absorber in any suitable manner, for example, by passage through heat exchanger 25 and/or cooler 26.

Heat exchanger 25 serves as a means of obtaining indirect contact and heat exchange between low boiling fractions of the reflux condensate from fractionator l3 and enriched hydrocarbon oil charging stock for the process, which latter is supplied to this zone, as will be later more fully described. Lines 21 and 29, controlled by the respective valves 28 and 3D, serve, in conjunction valve 23 in line 22, to regulate the flow of low boiling reflux condensate through heat exchanger 25.

Cooler 25 which, in the case here illustrated, is of the immersed, open-coil type around which water or any other suitable cooling medium may be circulated by any suitable well known means (not shown). This zone serves as a means of further cooling the absorber oil supplied to column 55 to the desired degree and its flow through this zone is regulated by valves 32 and 36 in the respective lines 3! and 33 in conjunction with valve 24 in line 22.

Fractionated vapors of the desired end-boiling point are withdrawn, together with gaseous products produced by the process, from the upper portion of fractionator [3 through line 35 and valve 36 to be subjected to condensation and cooling in condenser 31. The resulting distillate and gas may pass through line 38 and valve 39 to collection and separation in receiver 40.

Distillate may be withdrawn from the receiver through line GI and valve 42 to storage or to any desired further treatment and, when desired, a regulated portion of the distillate collected in receiver may be withdrawn therefrom through line 33 and valve 44 to pump 45 by means of which it is recirculated through line 46 and valve l! to the upper portion of fractionator 13 to serve as a cooling and refluxing medium to assist fractionation of the vapors and to maintain the desired vapor outlet temperature from the fractionator.

The gaseous products of the process are withdrawn from receiver 40 through line 48 and valve 49 to pump or compressor 50 by means of which they are supplied through line 5| and valve 52 to absorber 55. When desired, gases of suitable composition, preferably containing desirable high boiling components such as propane, butane and the like from an external source may be supplied by means of line 53 and valve 54 to absorber 55, together with the gases produced within the system. Such external gases, when employed, may comprise, for example, gases recovered by the stabilization of distillate from receiver 40, gases from a separate cracking process or from any other suitable gas making process or natural gas. Preferably, however, the material selected for this purpose contains a considerable proportion of the desired high boiling components of the gaseous conversion products of the process such as propane, butane and/or the corresponding oleflns.

Absorption columns 55 and 55 are similar zones containing any suitable means (not shown), such as bubble trays, perforated pans, packing or the like or any desired combination of such means, whereby intimate contact is obtained between the gases and the absorber liquids. The gases not absorbed by contact with the selected low boiling fractions of the reflux condensate in column 55 pass from the upper portion of this zone through line 51 and valve 58 to be subjected to further absorption with raw oil charging stock for the process in column 56. The gases remaining after absorption in column 56 may be withdrawn from the upper portion of this zone and from the system through line BI and valve 82 to storage or elsewhere, as desired. The selected low-boiling fractions of the reflux condensate supplied as described to column 55and enriched therein by absorption of liquefiable components of the gases.

are withdrawn from the lower portion of column 55 through line 59 and valve 60 to pump 6! by means of which they are fed through line 62 and valve 63 to further conversion in heating coil 64.

Heating coil 64 is located within a furnace 65 of any suitable form by means of which the required heat is supplied to the oil passing through the heating coil to bring it to the desired conversion temperature preferably at a substantial superatmospheric pressure. The stream of highly heated oil is discharged from heating coil 64 through line 66 and may be directed through valve 61 in this line and line 3 into reaction chamber 5, together with heated products from heating coil I, or may be separately supplied to the reaction chamber at any desired point in this zone, by well known means (not shown). It is also within the scope of the invention, although not illustrated in the drawing, to supply a regulated portion or all of the hot conversion products from heating coil 64 to chamber 8 to serve as a means of assisting vaporization in this zone, particularly in case the process is operated for the pro duction of coke as the residual conversion product of the process in chamber 8.

Hydrocarbon oil charging stock for the process may be supplied through line 68 and valve 69 to pump 10 by means of which it is supplied, in the particular case here illustrated, through line H and valve 12 to column 56 to serve as an absorbing medium for the gases from column 55. The enriched hydrocarbon oil charging stock from column 56 may be withdrawn from the lower portion of this zone through line 13 and valve 14 to pump 15 by means of which it is fed, in the case here illustrated, through line 16, valve 11, heat exchanger 25, line 18, valve 19 and line l'l to conversion in heating coil i, together with high boiling fractions of the reflux condensate from fractionator II. It will be understood that, when desired, all or a regulated portion of the enriched charging stock may by-pass heat exchanger 25, by well known means (not shown) and also, when desired, only a regulated portion of the charging stock may be utilized as absorber oil in column 55, the remainder being supplied either to heating coil I or to fractionator i3, by well known means (not shown).

It is also within the scope of the invention, when desired, instead of supplying'selected low boiling fractions of the reflux condensate to column 55 and hydrocarbon oil charging stock to column 56 to reverse this arrangement by well known means (not shown) supplying hydrocarbon oil charging stock to the first absorption stage and selected low boiling fractions of the reflux condensate to the second absorption stage of the process.

It will be understood that the various alternative methods of operation mentioned are not to be considered equivalent but may be selected to suit requirements, the mode of operation being varied, for example, with different types of charging stock as well aswith variations in the cracking conditions employed within the system and the desired results.

In a process such as illustrated and above described the preferred range of operating conditions may be approximately as follows: The heating coil to which the enriched charging stock and high boiling fractions of the reflux condensate are supplied may utilize a conversion temperature, measured at the outlet from this zone, ranging, for example, from 850 to 950 F., or thereabouts, preferably with a superatmospheric pressure at thispoint in the system of from 100 to 500 pounds, or more, per square inch. The heating coil to which the selected enriched low boiling fractions of the reflux condensate are supplied preferably employs a higher conversion temperature than that utilized in the other heating coil ranging, for example, from 900 to 1050 F., or more, preferably with a superatmospheric pressure, measured at the outlet from the heating coil, of from 200 to 800 pounds, or more, per square inch. A pressure substantially equalized or somewhat reduced relative to that employed in the heating coil utilizing the lowest pressure, in case different pressure conditions are employed in the two heating coils, may be utilized in the reaction chamber, this pressure ranging, for example, from 100 to 500 pounds, or more, per square inch. The pressure employed in the vaporizing chamber, as already mentioned, preferably is substantially reduced relative to that employed in the reaction chamber and may range, for example, from 100 pounds, or thereabouts, per square inch, down to substantially atmospheric pressure. The pressures employed inthe fractionating, condensing and collecting portions of the cracking system may be either substantially equalized or somewhat reduced relative to the pressure employed in the vaporizing chamber. The two absorption stages of the system may utilize substantially the same or different pressures ranging, for example, from substantially atmospheric to 300 pounds, of thereabouts, per square inch. The relatively low boiling fractions of the reflux condensate selected as an adsorber oil may be within the boiling range of 350 to 650 F., for example, although a somewhat narrower boiling fraction within substantially this range is ordinarily preferred.

As a specific example of one of the many possible operations of the process of the present invention, as it may be practiced in an apparatus such as illustrated and above described, the charging stock is a Mid-Continent topped crude of about 30 A. P. I. gravity which, after being utilized as absorber oil in the second absorption stage of the process, is subjected while still in admixed form with components such as propane and butane absorbed from the gases to a conversion temperature of approximately 930 F., at a superatmospheric pressure of about 300 pounds per square inch. This pressure is substantially equalized in the reaction chamber and a pressure of approximately 30 pounds per square inch is employed in the succeeding vaporizing chamber wherein the residual conversion products of the process are reduced to coke. A pressure substantially equalized with that employed in the coking zone is utilized in the succeeding fractionating, condensing and collecting portions of the cracking system and high boiling fractions of the reflux condensate are returned to further conversion, together with the enriched charging stock. Selected low boiling fractions of the reflux condensate, boiling within the range of substantially 400 to 550 F., are utilized as absorber oil in the first absorption stage of the system. The gases subjected to absorption comprise uncondensable gases recovered from the receiver of the cracking system as well as gases recovered by stabilization of the light distillate product of the process and an approximately equal amount of similar gases from another cracking system. The enriched selected low boiling fractions of the reflux condensate are subjected in a separate heating coil to an outlet conversion temperature of approximately 995 F. at a superatmospheric pressure of approximately 800 pounds per square inch. A regulated portion of the heated products from this zone is introduced into direct contact with the residual products of the process undergoing coking for the purpose of assisting their reduction to coke and the remainder are supplied to the reaction chamber. This operation will produce, per barrel of charging stock, approximately 65% of motor fuel having an anti-knock value equivalent to an octane number of approximately 70 and about 70 pounds of coke of relatively low volatility, the remainder being chargeable principally to lean uncondensable gas.

I claim as my invention:

1. In a process for the conversion of hydrocarbon oils wherein the oil is subjected to conversion conditions of elevated temperature and superatmospheric pressure, the resulting vaporous and residual conversion products separated, the vapors subjected to fractionation whereby their insufliciently converted components are condensed as reflux condensate, fractionated vapors of the desired end boiling point subjected to condensation and the resulting distillate and gas collected and separated, the improvement which comprises separating the reflux condensate into selected low boiling and high boiling fractions, subjecting the latter to said conversion, subjecting the gas to absorption by intimate contact with selected low boiling fractions of the reflux condensate to recover desirable high boiling components of the gases such as propane and butane, subjecting the remaining gases to further absorption by intimate contact with hydrocarbon oil charging stock for the process whereby to recover additional quantities of desirable high boiling components of the gases, subjecting the charging stock enriched by said absorption to conversion, together with said high boiling fractions of the reflux condensate, subjecting the selected low boiling fractions of the reflux condensate enriched by said absorption to independently controlled conversion conditions of elevated temperature and superatmospheric pressure and commingling the vaporous products from both conversion stages, prior to their fractionation.

2. In a process for the conversion of hydrocarbon oils wherein the oil is subjected to conversion conditions of elevated temperature and superatmospheric pressure, the resulting vaporous and residual conversion products separated, the vapors subjected to fractionation whereby their insuflficiently converted components are condensed as reflux condensate, fractionated vapors of the desired end boiling point subjected to condensation and the resulting distillate and gas collected and separated, the improvement which comprises separating the reflux condensate into selected low boiling and high boiling fractions, subjecting the latter to said conversion, subjecting the gas to absorption by intimate contact with hydrocarbon oil charging stock for the process to recover desirable high boiling components of the gases such as propane and butane, subjecting the remaining gases to further absorption by intimate contact with selected low boiling fractions of the reflux condensate whereby to recover additional quantities of desirable high boiling components of the gases, subjecting the charging stock enriched by said absorption to conversion, together with said high boiling fractions of the reflux condensate, subjecting the selected low boiling fractions of the reflux condensate enriched by said absorption to independently controlled conversion conditions of elevated temperature and superatmospheric pressure and commingling the vaporous products from both conversion stages, prior to their fractionation.

3. In a process for the conversion of hydrocarbon oils wherein the oil is subjected to conversion conditions of elevated temperature and superatmospheric pressure, the resulting vaporous and residual conversion products separated, the vapors subjected to fractionation whereby their insufliciently converted components are condensed as reflux condensate, fractionated vapors of the desired end-boiling point subjected to condensation and the resulting distillate and gas collected and separated, the improvement which comprises separating the reflux condensate into selected low boiling and high boiling fractions, subjecting the gases to absorption for the recovery of their desirable high boiling components such as propane and butane in two separate absorbers connected in series, utilizing hydrocarbon oil charging stock for the process as absorber oil in one absorber, utilizing selected low boiling fractions of the reflux condensate as absorber oil in the other absorber, subjecting hydrocarbon oil charging stock enriched by said absorption to said conversion, together with the high boiling fractions of the reflux condensate, subjecting the selected low boiling fractions of the reflux condensate enriched by said absorption to independently controlled conversion conditions of elevated temperature and superatmospheric pressure and commingling the vaporous products from both conversion stages of the system, prior to their fractionation.

4. A process of the character defined in claim 3, wherein the selected low boiling fractions of the reflux condensate utilized as absorber oil are cooled to the desired degree, prior to their contact with said gases.

5. A process of the character defined in claim 3, wherein the selected low boiling fractions of the reflux condensate utilized as absorber oil are cooled to the desired degree, prior to their contact with said gases, said cooling being eflected, at least in part, by indirect contact and heat exchange with said enriched hydrocarbon oil charging stock.

6, A process of the character defined in claim 3, wherein hydrocarbon gases from an external source, containing desirable high boiling components such as propane and butane, are commingled in regulated amounts with the gaseous products of the process subjected to said absorption.

'7. A hydrocarbon oil conversion process which comprises fractionating craokedvapors, formed as hereinafter set forth, to separate heavier fractions thereof as reflux condensate, subjecting hydrocarbon gases, contaiing high boiling components such as propane and butane, to absorption in separate absorption stages, scrubbing the gases in one of said stages with charging oil to be cracked, scrubbing the gases in another of said stages with at least a portion of said reflux condensate, subjecting the enriched charging oil and the enriched reflux condensate to independently controlled cracking conditions of temperature and pressure in separate conversion zones, and supplying the resultant vaporous conversion products to the fractionating step as said cracked vapors.

8. A hydrocarbon oil conversion process which comprises fractionating cracked vapors, formed as hereinafter set forth, to separate heavier fractions thereof as reflux condensate, finally condensing the fractionated vapors and separating the condensed portion thereof from incondensable gases, subjecting the latter to absorption in separate absorption stages, scrubbing the gases in one of said stages with charging oil to be cracked, scrubbing the gases in another of said stages with at least a portion of said reflux condensate, subjecting the enriched charging oil and the enriched reflux condensate to independently controlled cracking conditions of temperature and pressure in separate conversion zones, and supplying the resultant vaporous conversion products to the fractionating step as said cracked vapors.

9. A conversion process which comprises heating hydrocarbon oil to cracking temperature of said reflux condensate and then with charging oil. for the process, supplying the enriched charging oil to said coil, subjecting the enriched reflux condensate in a second heating coil to independently controlled cracking conditions of temperature and pressure, and supplying vaporous products of this independent conversion to the fractionating step.

10. A conversion process which comprises heating hydrocarbon'oil to cracking temperature under pressure in a heating coil, fractionating the resultant vapors to separate reatively heavy and light reflux condensates therefrom, returning the heavy reflux condensate to the heating coil, finally condensing the fractionated vapors and separating the resultant final condensate from incondensable gases, scrubbing the gases first with the light reflux condensate and then Withcharging oil for the process, supplying the enriched charging oil to said coil, heating the enriched light reflux condensate in a second heating coil to higher cracking temperatures than the heavy reflux condensate and enriched charging oil in the first-named coil, and supplying vaporous conversion products of the enriched light reflux condensate to the aforesaid fractionating step.

11. In a hydrocarbon oil conversion process wherein charging oil for the process and reflux condensate are subjected to independently controlled cracking treatments, the improvement which comprises scrubbingincondensable gases produced in the process with the charging oil and with the reflux condensate in separate stages, and supplying high boiling components thus separated from the gases to said cracking treatments in admixture with the charging oil and reflux condensate. v

. JACOB BENJAMIN HEID.

Images