US 1666597 A
Description (OCR text may contain errors)
April 17, 1928.
A. E; HARNSBERGER PROCESS FOR DISTILLING oILs Filed NOV. l2, 1926 Patented Apr. 17, 1928.
AUDLEY E. HARNSBERGER, OF COLUMBUS omo, AssIGNon To THE PURE 01T. com- PANY, OF CHICAGO, ILLINOIS, A CORPORATION 0F OHIO.
l PROCESS FOR DISTILLING OILS.
Application lc-d November 12,1926. Serial No. 148,060.
This invention relates to a new and improved process for eii'ecting a continuous distillation of mineral oil or petroleum under substantially vacuum conditions, whereby the oil under treatment is separated into two or more fractions. Dist-illation f under vacuum conditions is of fundamental uum, so
importance in preventing the cracking or molecular decomposition of certain hydrocarbons which ldestroy .the viscosity and color of the oil. Distillation can be carried on when a vacuum is present at a considerably lower temperature than. when ordinary atmospheric pressures or superatmospheric pressures are employed, and distillation at or above atmospheric pressure requires ordinarily such high temperatures that the cracking of the oil is apt to occur, suchhigh temperatures frequently resulting in depriving the oil of its' desired color and viscous properties. Again, distillation under vacuum has the advantage of overcoming this tendency toward cracking because of the -fact that lower temperatures may lbe utilized, but in prior apparatus and methods, of which I now have knowledge, the apparatus has been costly to install and expensive and difficult to regulate and operate, and it is, therefore, an outstanding object of the present invention to tem of distillation of simple yet efficient form and wherein investment and operating costs may be maintained at a comparatively low level.
Another object of the invention resides in the provision of distilling apparatus formed to include a primary oil heater in the form of a continuous pipe coil wherein the latter is of such form that the vacuum present in the system will penetrate back to the point of introduction of the oil into the coil,`or to such other location wherein the oil would be subjected possibly to dangerous overheating were the vacuum not present, the design of the coilxbeing su v,h that by enlarging the internal diameter thereof. either continuously or intermittently, at various points throughout the length thereof the friction loss of the oil,passing be such -as to allow the vacuum the coil or tube bank oil approaches cracking temperature.
to penetrate The higher temperature` the oil obtains in the` the greater will be the vacheater where primary that at the polni' of outlet,
provide a vacuum sys-v through the coil, will to a point where thev the oil temperature is the highest, the vacuum will be the greatest. This construction of the coil .or the tube bank in the primary heater or still is one of the fundamental features of this invention, since experience has shown that when oil in tube stills vaporizes, very great back pressures are formed due to the vaporization of the oil, unless increased area is provided to take care of the vapor volume.
My invention vision of a process vacuum conditions, wherein the construction of the apparatus employed is such as to permit the vacuum to penetrate to a point below that where the temperatures are suiiiciently.high to bring about the decomposition of the hydro-carbon were. the vacuum conditions not present. This result being attained primarily in this instance by the variations in the cross-sectional diameter of therefore consists in the prothe coils or tubes constituting the primary heater or still. I
The invention further consistsv in a vacuum system of oil distillation wherein a primaryheating element of improved eiiiciency is provided permitting the system to operate under lower temperatures than those used in present systems with consequent saving in the vamount of fuel required and also in generally simplifying and reducing the amount of apparatus required in carrying out the system.
For a further understanding of my invention reference is to be description wherein further features and objects ofthe invention will be in part described and in part obvious, reference being had to the accompanying drawing wherein:
Figure 1 represents diagrammatically theapparatus which may be employed for carrying out the invention. l
Figure 2 is a detail view on an enlarged scale ofthe primary heating coil.
Figure 3 is a similar view of a modiiied form thereof.
Referring now to the drawings wherein I have illustrated more or less diagrammatically one form of apparatus which can be successfully employed to carry out the invention, and wherein the reference numeral 1 designates the setting of a primary heater of the: type commonly known as a tube still. This heater includes the usual combustion chamber 2 and a tube chamber 3,
for distilling oil under' hadA to the following the chambers 2 and 3 being separated by means of a bridge wall 4. Within the chamber 3 are upper` and lower tube banks 5 and 6 respectively, and the lower bank has connected therewith a supply pipe 7, leading from a source of oilsupply, and through which pipe the cold or preheated oil is pumped to the heater. After circulating through the lower bank of tubes the temperature of the oil is raised, for example, from atmospheric to substantially 600 degrees F., wherein the lighter fractions of the oil are allowed to readily vapo1ize,witl1 out danger cf cracking the unvaporized portion of the oil. and pass from the heater by way of an outlet pipe 9 which leads to a vapor chamber 10 provided in a. vaporizer 11. The gases and vapors generated by this initial heat-ing step pass upwardly through the separator and are preferably passed through a cooling coil 12a, Where the vapors are reduced to liquid form and suitably stored for future use.
The heavier or unvaporized fractions of the oil collect in the bottom of the separator and are removed therefrom by Way of a pipe line 13, in which is situated a pump 14 of any suitable type. This condensate is then forced through the line 14 to the inlet side of the upper tube bank 5, where the oil is subjected to the higher temperatures prevailing in the tube still or primary heater, but wherein provision is made in the construction and form of the coil comprising the upper bank 5 to prevent the decomposi tion or cracking of the oil.
As an illustration of a specific form which the upper bank of tubes may take, it is calculated that the tube bank 5 having tubes of one inch internal diameter at` `the point Where the oil enters, that is, at the bottom of the bank, should have approximately tubes of six inches internal diameter at the oil exit, or at the upper end of the bank, stepping up the sizes at intermediate points in the bank. The increase in diameter `may be of a gradual tapered form, as shown in Figure 2or may be of an intermittent, ab-
- ruptly stepped form as shown in Figure 3.
The preferred method is to increase the diameter of the individual tubes comprising the upper bank successively in an upward direction. B v this construction the design of the still will be such that by the enlargement of the tube diameters at variousvpoints in the still, friction loss of the oil passing through the tubes will be such as to allow the vacuum to penetra-te the tube bank toa point Where the oil approaches cracking temperatures.A It is believed'that without the enlargement of areal as the oil progresses through the tube bank, highest etliciency would not be obtained from a vacuum tube .tilL since the oil being under pressure could not vaporize except at a high temperature,
bank as disclosed resides in the fact that experience has shown that when oil in tube stills vaporizes, very great back pressures are formed due to the vaporization of the oil, and the increased area is provided to take care of the vapor volume and to allow for its proper circulation bank without local overheating.
The increasing pipe area from the inlet to the out-let end of the pipe still 5 is suiiicient so that by the resulting decrease of pipe friction or back pressures of oil traveling in the still, four inches of mercury absolute of vacuum on the outlet of the still will penetrate to the `inletof the still, the above-mentioned vacuum reducing gradually toward the inlet end of the still. For example, it has been found that the process will produceunusual distillates such as of cylinder stock grade having a Baume gravity of 20.3 and a viscosity in excess of 150 seconds Saybolt Fah.) with a flash test of 560 Fah. and a fire test-of 625 Fahand of good color vvhen operating with a vacuum of 1.75 inches of mercury absolute on the outlet of the still, and showing 12 inches of mercury ab- 'solute on the inlet side, the temperature of the outlet oil being 690 Fah. Various lighter distillates can be produced by reduction in the outlet temperature of the still, these latter distillates showing superior yields, color, Hash and fire tests than those produced by ordinary methods.
The oil having been brought up to the dcsired temperature in the still is discharged through the tube y from the upper bank 5 of the tubes and isv conducted through t-he vapor line 15 to a vapor chamber 16 provided in a separator 17. In the particular form of the invention illustrated the heavier fractions are collected in liquid form inthe bottom of the separator and are permitted to pass through a cooling coil 18 and removed from the still by a condensate pump4 19, which may be of the centrifugal or direct acting type, either steam orI electric driven.
To further f fractionate the discharged vapors, the top of the separator 17 is provided With a scrubber or dephlegmator 20, in which the vapors are scrubbed and then passed through the vapor line 21 to a second separator 22. which includes the usual separating chamber 23 and a superposed scrubber 24. The bottom of the separator 22 lrater 29. The coil 30 is connected with a condenser and a discharge pump 26 by means ofa pipe line 27 through which the condensate formed in the separator 22 is circulated. The vapors present in the hydrocarbons led to the separator 22 are permitted to pass to the scrubber 24 and thence by way of a pipe line 28 =to a third separator 29, in which is provided a cooling or refluxing coil 30., through which cold oil may be circulated so as to eifect the condensing of the vapors within the sepaextends also to a similar coil 31 arranged in the Asecond separator 22, and from this coil a pipe line 32 extends to the pipe line entering the tube bank 6. It will be apparent that by the provision of suitable valves the flow of oil through t-he coils and 31 may be readily regulated so as to control the heat exchanging operation thereof in the separators 22 and 29. The final condensate collected in the separator 29 is led through a condenser 33 to a. pump S4 which may be of'the types indicated at 19 and 26. Additional cooling coils 29b and 29C are provided in the separator 29 to insure final condensation, through which may be circulated oil, water or brine.
The vacuum in the system may be governed by means of a vacuum pump 35, which communicates with the chamber 29 by way of a pipe 36, the 'latter having at its inlet end the coil 29, through which a cold liquid will be circulated to provide maximum cooling of non-condensable vapors: formed during the operation. It will be understood that as many of the fractionating separators may be provided in the system as desired depending upon the number of' cuts or fractions wanted and that the specific form and arrangement of the fractionating equipment lmay be varied from that herein conventionally illustrated Without departing from the principles of the invention. Any non-condens-able vapors which may be formed in the operation of the system will be removed by means of the vacuum pump 35, which may be of the displacement type, hurling water type or steam ejected. The pump 35 thus serves to place theA entire system under vacuum conditions as far back as tlie inlet end of the tube bank 5. v
lt will he seen that by the present invention a vacuum system of oil distillation is provided b v which the operating temperalures may be maintained at safe levels to prevent the cracking or molecular decomposition of the oils handled by the system.
The system thus produces distillates of im proved viscosity and color, particularly well adapted for use 1n the formation and production of lubricating oils. I 'am aware that the general advantages accruing from vacuum distillation systems have been recognized and in a measure developed by prior patentees, however, to the best of my knowledge such prior systems have never employed the principle of extending the vacuum back to the point of introduction of the oil into the lprimary heater or to such positions Where the temperatures employed might have the eEect of cracking the-oil were the vacuum not present.
Iiurthermore, the use of a tube type of heater, instead of a shell or drum type,rhas the advantage that the oil exposed to hot metal travels at high velocities; increasing heat transfer and minimizes to a great eX- tent the likelihood of local overheating due to the turbulent flow. This is also accomplished Without the use of steam, thereby reducing throughout the system the size of vapor lines, containers and other fractionating equipment necessary per unit of capacity. Also it is well known that tube heaters can be operated with greater fuel economy than the shell or ldrum type heaters. Again. by employing the tube type of primary heater the vapor pressures will be reduced on the oil circulated therethrough, as compared with the drum or shell type of heater, by the elimination of the hydrostatic head. This head, in a drum or shell type of still, causes pressure on the oil at the bottom of the container and thereby renders the vacuum less effective.
What is claimed is:
l. The method of vacuum distillation of mineral oil, which consists in drawing a qu'ant1ty of oil without reduction in its total weight through a heated pipe still of progressively increasing cross-sectional pipe area from the inlet to the outlet ends thereof, said increasing pipe area permitting such reduction in ba'ck pressure due to pipe friction of the oil and vapors drawn through the still to allow a vacuum carried on the outlet end of the still to penetrate back to the inlet end thereof.
2. The method of vacuum distillation of mineral oil, which consists in drawing a quantity of oil Without reduction in its total weight through a heated pipe still of progressively increasing cross-sectional pipe area fromthe inlet to the outlet ends thereof, said mereasing pipe area permitting s'uclrreduction in back pressure due to pipe friction of the oil and vapors drawn through the still to allow a'vacuum carried on the outlet end of the stillto penetrate back to the inlet end thereof, said vacuum being sufliciently high to permit vaporization of the 'oil1 lto take place in the heating zones of the sti outlet ends thereof, said increasing pipel area permitting suehreduction in back-pressure'of the oil and .vapors drawn through a The method of distini'ng minerai Oil,A
the still to allow a vacuum carried on the.
out et end of the still to penetrate back to the inlet end thereof, theY oil being dra-Wn through said still at progressively increasing velocities as said oil reaches zones 0f higher temperature as a result of vaporization of the oil within the heating zonesof the still.
4 The method of distilling mineral oil,-
which consists in the step of drawing a quantity of oil through a heated pipe stilllpossessing a progressively increasing pipe area from the oil inlet to the oil outlet ends thereof, said increasing pipe area permitting such reduction in back pressure on the oils yand vapors drawn through the still to allow a .Vacuum carried on the outlet end of the still to penetrate back to the inlet end thereof, said vacuum being sufficiently high to permit vaporization of the yoil to take place in the heating zones of the still, the temperature of the oil and vapors passing through the still being prevented from exceeding the temperature of the oil and vapors issuing from the outlet- .of the still.
In testimony whereof I affix my signature.
AUDLEY E. HARNSBEBGER.