US1719235A - Apparatus for mineral oil distillation - Google Patents

Description

y 1929- A. E. PEW, JR., ET AL APPARATUS FOR MINERAL OIL DISTILLATION 5 Sheets-Sheet 1 Filed March 15, 1925 July 2, 1929.

A. E. PEW, JR., ET AL APPARATUS FOR MINERAL OIL DISTILLATION Filed March 13, 1925 5 Sheets-Sheet 2 W/IWESS:

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5 Sheets-Sheet mm MW M/VE/V rams Filed March 15, 1925 A. E. PEW, JR., ET AL u ll f--- I.-. :....:}..I.

July 2, 1929.

APPARATUS FOR MINERAL OIL mswnmu'rou July 2, 1929. w JR" E AL 1.719.235

APPARATUS FOR MINERAL OIL DISTILL ATION Filed March 15, 1925 5 Sheets-Sheet 4 y 1929. A. E. PEW, JR., ET AL 1.719.235

APPARATUS FOR MINERAL OIL DISTILLATION Filed March 13, 1925 5 Sheets-Sheet 5 s July '2, 192 1,719,235

UNITED STATESVLPVATENOT OFFICE.)

ARTHUR E. PEW, JIRh, OF IBR'YN MAWR, AND HENRY THOMAS, OF RIDLEY BARK,

PENNSYLVANIA, ASSIGNORS T SUN OIL COMPANY, OF PHILADELPHIA, PENNSYL- VANIA, A CORPORATION OF NEW JERSEY.

APPARATUS FOR MINERAL OIL DISTILLATION.

Application filed March 13, 1925. Serial No. 15,262.

' In the distillation of mineral oils by the capital charge of plant and cost of opermost commonly used processes, as, for examation. I 1 pie, where the oil is first topped to evap- Certain essential or important factors orate off the lighter fractions, such as gasocharacterize this process, which may be enuline and fuel oil, and then fractionally dismerated as follows: tilled for the purpose of producing various (1) Tile distribution of the oil in a thin grades of lubricating oil, it is difficult to layer, envelope or film over an extended surproduce the highest grades of refined prodface in heat-exchange relation, but out of aicts; and even to produce the ordinary contart, with the heating agent, thereby 10 grades of lubricating oils that are acceptable greatly expediting the rate of evaporation.

' as commercial products for most purposes, (2) The continuous inflow and outflow of it is necessary tosubject the distillates either ml o and from the locus of application of to treatment with sulphuric acid and caustic heat and the subjection of the oil to the soda. and washing with Water, or to filtra- 011011 of heat fora restricted time. 15 tion through fullcrs earth or some other (3) Provision for free escape ofthe oil clarifying and decolorizing agent, or both, Vapors immediately after vaporization with in order to remove from the oil contaminatv nc of s stant al Con act of the Va ing materials that have been produced in the 1301's With 1Il0l1r11l1g oil so as to avoid subdistillation process. I stantial refluxing, with resulting decompo- 7 20 Th t i tin t i l r th sition and cracking and entrainment of parproducts of decomposition and cracking ticles of incoming oil With-escaping vapors. which occur during distillation by reason. of (4:) Avoldance of the presence or leakage the high heat to which the oil is subjected of air into the oil vaponzatlng chambers and 7,5 to effect its evaporation, the considerable he oil vapor lines, regardless of the abso- 25 time to which any given quantity of oil is lute pressure that is malntalned 1n the oil exposed to such heat, and the pressure,.(ususystem. Air in small quantity H1. the 01], ally atmospheric) to which it is subjected system has an oxldlz ng efi'ect WlllCll seriduring evaporation, as hereinafter more ously contaminates the product. fully explained. If the heating agent could Th i ten ce sually) of 1 3o be maintained at such a temperature and fairly h gh, but no necessarily, and indeed applied in such a way and unde u h onnot preferably, an extremely high vacuum. ditions as to avoid this objectionable de- This requirement does not necessarily apply composition and cracking, there could be no Where the character of the crude oil is such occasion to subject the distillates to the exas not to be readily decomposible. In such 35 pensive, cumbersome, wasteful and time-concasethe vacuum may be low .or maybe su'ming chemical and physical purification absent altogether. Nor does the requirement processes which are now customarily'emnecessarily apply to the distillation of fracs, ployed. /t-ions lighter than lubricating fractions. In an application filed by us March 5, (6) The avoidance of direct heat-exchange 40 1925, Serial No. 13,040 we setforth a dis between the I heating medium and the oil tillation process wherein decomposition and vapors;

cracking are so entirely avoided that the (7) The indirect apphcation of the priproducts of distillation will, without further mary heating agent, and the direct transmistreatment, meet all the requirements of comsionof heat to the o l by means of a secmercial lubricating oil and even produce, ondary heating agent which boils, under -liycareful fractionation, the highest grade practicable absolute pressures,,at temperaproducts. The process is one adapted to tures desirable in oil distillation, and which, J produre such lubricating oils. by the use of in its vapor phase, flows into heat exchange plant units of reasonable size, in such large relation with the oil ,and is condensed to volume as to make the process much more thereby and gives up'its latent heat to the expeditious than the customary processes oil, the condensate returning to a liquid body 7 and much more economical with respect to of the substance, which is continually being heated by the primary heating agent and continually generating vapor. The direct heating agent must be one which is not 'merely theoretically, or even practically,

5' operative, but which, under the conditions above enumerated is also commercially practicable,-and adaptable to a plant that is not of impracticably large size.

In my said application, the secondary heating agent is a vaporized metallic liquid,

particularly mercury vapor. The use of mercury vapor as a heating agent for the vaporization of mineral oil has not been, it is believed, heretofore suggested; nor is any 1 known method of applying mercury vapor as a heating agent in any other art applicable to the art of'oil distillation; nor is any known method of applying other heating agents in the art of oil distillation applicable to mercury vapor.

We have devised a distilling apparatus which is admirably adapted to the successful practice of the process set forth in our said copending application, which apparatus I exhibits features of novelty, as well as new nally extending within this casing is a metal partition or pan which divides the easing into two chambers; an upper oil vaporizing chamber, which may be maintained under a high vacuum (say 28% inches), and a lower mercury vapor chamber. The oil to be distilled enters the upper chamber at the higher end and spreads itself over the pan or partition in the form of a thin envelope or film and flows rapidly down the same toward the lower end. Mercury vapor is admitted to one end ofthe lower chamber in regulatable quantities-preferably by flowing it in continuously at a regulatable rate. In the lower chamber the mercury vapor is condensed and in condensing gives up. itslatent heat to the oil. By reason of the distribution of the oil over an extended surface in the form of a thin film, every particle of the oil is subjected to this heat almost instantly. Although the flow of oil through the oil-vaporizing chamber is rapid, yet if the mean temperature difference between the oil-and' the condensation temperature of the mereuryvapor at the pressure at which it is under is sufiiciently great, a definitely calculable fraction of the-oil will be evaporated. The duration of e osure to heat, however, ifthe dimensions 0 the pan, slts inclination, rate of inflow of oil velocity of flow and thickness of film are carefully regulated, is not sufiiciently great to effect any substantial amount of cracking or decomposition. Provision is made for the escape of the oil vapors without substantial contact of same with incoming oils, thereby avoiding refluxing with resultant decomposition'and cracking, and avoiding, also, entrainment of oil with outgoing vapors.

The mercury vapor is conducted from a mercury boiler to the mercury vapor chamber through a valve, which is throttled to the extent required to admit the mercury vapor at the-rate required to cause a given volume of the vapor to be condensed in a given time, thus predetermining the amount of heat absorbed by the oil and the proportion thereof that will evaporate. This valve may be automatically controlled by a thermostat. in the mercury vapor chamber or in the oil vaporizing chamber or in the pipe through which the residual oil is discharged from the oil vaporizing chamber; but there are advantages in manual control, provided known means are provided to take temperature readings at one or all of these locations.

The drawings show, largely in diagram, a large plant capable of running 100 barrels of oil hourly. The plant is designed for the distillation of a reduced or topped crude oil from which it is desired to extract lubricating oils. In designing the plant, we have provided for ten units of uniform dimensions, and in describing the plant and its operation, we shall specify permissible (limensions and other structural features of different parts of the plant, and shall also specify permissible velocities of fiow, depths of films, absolute pressures in the mercury vapor system and in the oil system, temperatures of the oil and of the mercury vapor, mean temperature differences between oil and mercury, percentages vaporized in each unit, time during which the oil is subjected to heat in each unit, and other factors. It should be distinctly understood, however, that the plant may be of any size and capable of handling any desired volume of oil, that the units need not be of uniform construction, and that all the other factors specified may be varied within considerable limits. In fact, variations in one set of factors necessitate variations in other sets of factors. The specific data hereinafter given are, therefore, intended to be merely illustrative.

In the drawings:

Fig. 1 is a diagram, in plan, of the entire distilling plant.

Fig. 1 is a view of a part of Fig. 1, enlarged to show more details.

Fig. 2 is a diagram, in elevation, of part: of the plant.

Fig.3 is a view, in elevation, of one of the distilling units, comprising a mercury boiler, a vaporizer, a condenser, and a distillate tank; and the connection therewith of a vacuum pump for maintaining the oilcirculating system under vacuum.

Fig. 4 is a diagram, in elevation, ofthe mercury vapor circulating system.

Fig. 5 is a detail view, in elevation, of the means for maintaining constant the pressure in the mercury vapor system.

Fig. 6 is a longitudinal section through one of the Vaporizers.

Fig. 7 is a cross-section on the line 77 of Fig. 6.

Fig. 8 is a partial perspective view of the oil distributor in the oil chamber of the vaporizer. v

Fig. 9 is a longitudinal section view of a modified vaporizing unit. V

The oil to be distilled, preferablytopped crude oil containing all the lubricating fractions, is conveyed, by means of a pump or pumps a, through a pipe I), to the vaporizer of the first distilling unit of the plant, which may comprise any desired number of units, ten being shown. The ten Vaporizers are numbered 1 to 10 inclusive and the ten condensers are numbered 11 to 20 inclusive. Each vaporizer (see Figs. 6 and 7) comprises an oil vaporizing chamber 0 and a mercury vapor chamber d, separated one 'from another by a longitudinally extending pan or-partition 6. Each vaporizer is arranged to have a slight inclination to the horizontal.

' From the oil vaporizing chamber 0 of each vaporizer the residual oil flows,-through a pipe f, to the oil vaporizing chamber of the next. vaporizer. chamber of the last Vaporizer 10 the heavy residue flows, through a pipe 9, to a discharge tank, (tar tank) h. From the bottom of the tar tank is an outlet pipe having valved branch pipes 11 through which pumps j are adapted to draw the tarry residue from tank It to storage.

From the oil vaporizing chamber ofeach vaporizer extend multiple vapor outlet pipes k leading to a condenser. As hereinbefore stated. there are ten of these condensers, one for each vaporizer. Each condenser is connected, through a pipe m with a distillate receiving tank n. Suitable means should be provided for pumping the distillate from the tank. The drawings, which disclose one of many possible arrangements, show a valved pipe 0 leading from the bottom of each tank. The pipes 0 from a pair of adjacent tanks lead to a valved pipe p. There are five pairs of pipes 0 and five pipes 71. The pipes 72 connect with a valved manifold 1', which connects, through valved pipes s and pumps t, with another valved manifold a. from which extend valved pipes q to storage tanks (not shown). By this arrangcment, the distillate from any tank n may be pumped, through any of the pumps,

From the. oil vaporizing valved air exhaust pipe '0. The various pipes '0 may be connected to vacuum pumping means in any one of a number of different As shown, the pipes v from the ways. five tanks n connected with condensers 11 to 15 inclusive extend to one manifold and the pipes from the five tanks n connected with condensers 16 to 20 inclusiv extend to another manifold. Each of these manifolds is lettered w. Each manifold w connects with a pair of vacuum pumps 00. By means of these four vacuum pumps, or any one or more of them, the desired vacuum is maintained in the entire oil circulating system.

The pump and pumps t withdraw oil at intervals from tank It and tanks n while working against the vacuum in the oil circulating system; but the tanks may be made of such height that the head of the columns of oil in the tanks may in part, or even in whole, counterbalance the vacuum so as to reduce to the degree desired the power that mustbe expended by these pumps to withdraw the oil; it being understood that it is preferred to maintain the tanks nearly full so as to take advantage of the head of the oil columns.

From mercury boilers 30, 31, extend vapor outlet pipes 32 having ten branches 33 leading respectively through ten valves 34 (prefion erably manually operable) to the ten merpan 6 that separates chamber d from the oil vaporizing chamber 0. The mercury condensate flows out the lower ends of chambers (1 into pipes 35 connected with headers 36 that convey the mercury back to the boilers 30 and 31. g

It is not necessary to provide more than one mercury boiler; but in a large plant it is desirable to provide two or more. One mercury boiler may be connected with one set of Vaporizers and the other or others with another set or sets of Vaporizers. In the drawings, boiler 30 is connected with vaporizers 1 to 4 inclusive and boiler 31 with temperature for the mercury vapor which heats the oil containing the higher boiling point fractions.

Each of the several valves 34 are so set as to admit to the corresponding chamber d mercury vapor at such rate that on condensing it will liberate enough latent heat to drive off from the oil, in its passage through j chamber a, a predetermined percentage of the oil in the form of vapor. Once properly set, the valves 34 need not be adjusted during the distilling process. If, however, a different grade or quality of topped crude oil should be admitted to the distilling apparatus, the valves 34 should be adjusted to' properly regulate the percentage of oil vaporized in each vaporizer. The valves 34 may be controlled manually; or they may be controlled automatically by means of thermostats arranged in the residual oil outlet from each vaporizer and operable in accordance with the temperature of such escaping residual oil, or in any other way.

\Vhile the temperature of condensation in the several mercury vapor chamers d connected with each mercury boiler may be varied within somewhat wide limits, it is desirable that such temperatures shall be predetermined and remain constant during the distilling operation. It is, therefore, desirable that the pressure in each of the two mercury systems shall remain constant. This pressure maybe regulated in different ways. The volume of mercury generated, however, must be at least sufficient to supply the mercury vapor chambers of all the vaporizers at the rate required to liberate, by its condensation, the heat necessary to vaporize the predetermined percentages of oil. This will usually require that a slight encess of mercury vapor shall be generated. It is important that this vapor be condensed Without allowing the column of liquid mercury to rise and increase the boiler pressure. To effect this, I resort to the following simple expedient.

40 and 41 are two liquid mercury cups, which are; connected by a pipe 42. Into one of these cups 40 extends a pipe 43 from the boiler. Pipe 43 contains liquid mercury, and the height to which it extends in cup 40 -down its front face.

determines the level of mercury in both cups 40 and 41. Within cup 41 is a bubbler 44. The bubbler comprises a hollow openbottom chamber immersed in the mercury and provided with serrations in its lower edge. Bubbler 44 communicates with a bypass 45 connected with the main mercury vapor feed pipe 32. A vapor pipe 46 from cup 41 passes through a condenser 47 communicating with the header 36.

lVhn the pressure in the system exceeds the pressure desired to be maintained therein, mercury vapordiows through pipe 45 and bubbles up through the seal of liquid mercury in cup 41 and thence flows, through pipe 46, to condenser 47, from which the condensate returns to the boiler. By elevating overflow pipe 43, thus raising the level of the liquid mercury in cups 40 and 41, the pressure in the system may be increased. By lowering overflow pipe 43, the pressure in the system may be decreased.

One of the 'vaporizers 1 to 10 inclusive is shown in detail in Figs. 6-8. It comprises a long chamber of a height greater than its width, divided, as hereinbefore described, by a longitudinally extending partition 6, into an oil vaporizer chamber a and a mercury chamber or conduit cl. The oil inlet pipe extends into the upper end of the oil .vaporizer chamber a and has a down-turned discharge end. In front of the oil inlet pipe is a weir or distributor 50, which is corrugated across its upper edge and also vertically The oil rises in the space back of the distributor and flows over the distributor and down along its front face, thereby insuring a distribution of the oil equally across the chamber 0. The partition e is of considerable area, so that the oil flows down along the same in a shallow stream or thin film, thereby establishing excellent conditions for heat exchange with the mercury vapor in chamber (l. The front end of the oil vaporizing chamber a is closed by a cover plate 51.

A vacuum pump should be connected with the mercury vapor system in order to exhaust air therefrom prior to heating the mercury boiler. In the vaporization of mercury, certain fixed or permanent gases are formed which should be removed. The removal may be effected in different ways. \Ve prefer to so connect the vacuum pump with the mercury vapor system that these fixed gases may be removed by operating such vacuum pump at intervals. From the mercury vapor chamber of of each vaporizer extends a valved pipe connected with a pipe 71, which, through a pipe 72, connects with a condenser 73 (see Figs. 1 and 4). Through a condensate pipe 74, condenser 73 communicates with header 36. Pipe 74 connects, through pipe 75, with a vacuum pump 76. From time to time, the vacuum pump may be operated to withdraw from the mercury vapor system any fixed gases which have accumulated.

It is advisable to make' provision for deodorizing the oil in the process of distilla tion. Vapors that are driven off from the oil 1n the Oll vaporizing chambers and that, if

condensed, would contaminate the distillates,

dcnsed gases may be withdrawn, continuously or intermittently, from the oil system during operation.

Having described the construction of a plant embodying our invention, we shall now describe, in detail, the operation of the plant,

and shall give certain data with considerable particularity; it being understood, however, that great variation from the data given is permissible, and that any change in any of the factors involves a change in one or more of the other factors. The factors of most importance may be enumerated as follows: the capacity of the apparatus, the number of distilling units, the absolute pressure within each mercury vapor system (if there be more than one), the degree of vacuum in the oil system, the dimensions and degree of inclination of the Vaporizers, temperatures of the oil entering and leaving each vaporizer, the mean temperature difference between the mercury and the oil in each vaporizer, the velocity of flow of the oil through each vaporizer, the depth of the stream of oil flowing down through each vaporizer, the time during which the oil remains in each vaporizer, and the percentage of oil vaporized in each vaporizer.

As hereinbefore stated, we prefer to maintain a vacuum throughout the oil system of about 28% inches. This or any other desired absolute pressure is established and maintained by means of vacuum pumps :0. After the desired degree of vacuum is established in the oil system, the valves between tanks n and h and the pumps 00 should be maintained open just sufficiently to continuously withdraw the permanent gases driven off from the oil. It seems of importance, however, to seal the system against access of air, so as to avoid any circulation of air throughthe'oil vaporizer, however high a vacuum may be maintained therein. If the vacuum falls below a predetermined degree, the valves between the pumps :12 and the tanks 'n. and 71. may be opened more freely until the desireddegree of vacuum is established. It is unnecessary to secure an absolutely uniform vacuum in the oil vaporizing chambers of all ten oil distilling units, but it is desirable to maintain an approximately uniform vacuum therein. If the vacuum be maintained substantially below or above 28 inches, it will necessitate a change in many other factors in order to produce the same results. It will be understood, however, that my invention is not limited to any particular absolute pressure in the oil vaporizing chamber. Below a certain minimum, which We are not prepared to definitely fix, because it varies with the quality of the oil, but which is probably below twenty-five inches of vacuum even if the 011 contains decomposable constituents, there appears to be a decided fall in the quality of the distillates. Above a minimum degree of vacuum, which varies with the quality of the oil, there appears to be no improvement in the quality of the product, although it permits, obviousl of a reduction in the temperature of disti lation in each unit in order to secure the same yield.

In the mercury boiler 30 there is main tained a pressure slightly above atmospheric, so as to give a mercury condensation temperature of about 680 F. (Mercury vapor at atmospheric pressure condenses at 672 F.) In the mercury boiler 31 there is maintained a pressure of about thirty inches absolute, so as to give a temperature of condensation of about 750 F.

It is desirable to have all the still units of the same size. In' the apparatus herein de scribed, each vaporizer is five feet high and 2% feet wide. Of the specified height, about 1 foot 3 inches is occupied by the mercury vapor chamber d, and the remainder by theoil vaporizing chamber. The vaporizers are about twenty feet in length and are inclined so as, to have a fall of about one foot in thirty-four feet.

Assume that topped crude Texas oil having an average gravity of 17.5 136. and a temperature of 380 F. is admitted to the oil vaporizing chamber 0 of vaporizer 1 at the rate of one hundred barrels (4200 gallons) of oil per hour. Such oil will occupy 5.9 seconds in traversing the chamber from the top of pan 6 to the bottom. Its velocity of flow will be about 3.4 feet per second and the average depth of oil on the pan will be about 13-60th of an inch. About twelve per cent, or twelve barrels of oil per hour, will be vaporized and pass to the condenser. The residual oil that passes to the second still unit will have a temperature of about 400 F.

In the second vaporizer, the oil, entering at about 400, will traverse the pan in about 5.8 seconds, its velocity of flow will be about 3.4 feet per second and the average depth of oil in the pan will be something less than' a fifth of an inch. About sixteen barrels of oil per hour will be y The oil enters the other Vaporizers at progressively increasing temperatures. The times occupied in the flow of the oil through the Vaporizers progressively increase, and the depths of the streams of oil and its velocities of flow progressively diminish. The yield of distilled oil varies from nine to ten barrels per hour in the third'to sixth unit and then progressively falls in the succeeding units. The heavy residual oil enters vaporizer 10 at about 685 F. and the final tarry residue, amounting to about ten barrels per hour, leaves this vaporizer at a temperature of about 705 F. In this vaporizer, the time required for the oil to traverse it is about 15.5 seconds, while the velocity of flow falls to about 1.29 feet per second and the depth of the stream to less than a tenth of an inch. About four barrels of oil per hour are vaporized in this vaporizer.

It' is essential, in the later Vaporizers of the series, that the temperature of condensation should be substantially above that (672 F.) at which the mercury condenses at atmospheric pressure. The heaviest vaporizable constituents have a boiling point, even in a vacuum of 28 inches, in excess of the last mentioned temperature. Hence, it is essential that, in the later Vaporizers, the mercury vapor shall be generated at superatmosp eric pressure. In operating the ap- 'paratus herein described, mercury boiler 31 is at a pressure of about two atmospheres, which pressure corresponds to a condensa tion temperature of about 750 F., as hereinbefore stated; and we have connected this boiler with the last six Vaporizers of the series.

It is quite possible to carry on our process by means of a single mercury boiler at a pressure sufiicient to give a condensation temperature sufliciently high to furnish the heat required to vaporize the heaviest fractions which it is desired to distill, and to limit the transfer of heat to the oil containing the lighter constituents by more or less throttling the valves 34 controlling the admission of mercury vapor to the mercury chambers of the Vaporizers. The necessary control of the distillate yield in each distilling unit can also be eifectecl by varying the size or inclination, or both, of the vaporizing units, or by varying the rate of flow of oil into the distilling apparatus, and thereby controlling the depth and velocity of the running stream in each vaporizer and the time which the oil occupies in its traverse through each vaporizer; but the provision of two or more separate mercury boilers has distinct advantages in the way of simplification of the apparatus and the economical practice of the process.

The apparatus above described is admirably adapted to the use of mercury vapor as a direct heating agent to effect the vaporization of the oil. It distributes the oil over an extended area in a thin film and in heat exchange relation, but out of contact with the mercury vapor, and retains the oil within the heat zone for but a very short time,and allows the vapors to escape without contact with inflowing oil. It provides a simple means for regulating the rate of flow of the mercury vapor into the mercury chamber of each vaporizer, so as to control the number of heat units that are transmitted to the oil and thus predetcrmine the gravity of the cut that is obtained in each distilling unit. It provides for a rapid direct escape of oil vapors from the surface of the oil layer, thereby avoiding contact of the oil .vapors with entering or departing liquid oil and avoiding, also, such contact of the oil vapors with the liquid oil as occurs if the oil vapors, before escaping, were allowed to flow, through a space of restricted cross-section, in parallelism with the liquid oil flow. It avoids direct exchange of heat between the heating medium and the oil vapors, which is a condition promotive of cracking. The apparatus is adapted to continuous operation, which is a factor of great importance.

The apparatus has a large output relative to its size; it is cheap to construct, considering its great capacity; the temperatures are easy to control; and no difiiculty is experienced in maintaing it in continuous operation. The most considerable item of expense is the cost of the mercury, but there is no escape of mercury from thesystem, and consequently it is an item of capital expenditure and not an item of cost of operation.

The surface of the partition or tray in the vaporizer is not liable to cake, because of its proportions and the controllable velocity of the oil. If necessary to clean it, it is readily accessible and its fiat surface .facilitates cleaning.

It is obvious that the main item of operating expense is the cost of the fuel (preferably oil) required to heat the mercury boilers; but a very large proportion of the primary heat is converted into useful work.

The operation of the apparatus is so largely automatic that all the labor required is that of general supervision.

The capacity of the large commercial unit equals the capacity of a typical refinery covering some acres of ground, and comprising, besides large stills, tanks for chemcial treatment, filters and much other mechanism, requiring, for its operation, maintenance and repair, supervision and labor involving comparatively great expense.

An alternative, but less preferable, form ofvaporizer is shown in Fig. 9 in which headers 60, 60 are connected by a nest of tubes 61 within an enclosure 65. Mercury vapor is admitted to .one of the headers through a pipe 62 on which is a feed control valve 63. Pipe 64- aifords an outlet .for condensed mercury. The enclosure forms the oil vaporizer chamber, which has an inlet pipe 66 for oil, an outlet pipe 67 for residue and a vapor discharge pipe 68. The .Oil inlet pipe 66 communicates with a distributor 69 in the top of the oil vaporizing chamber 65, from which distributor the oil flows down over, the tubes (31. The oil spreads over the surfaces of the tubes in a thin layer so as to expose, to the greatest possible degree, every particle of the oil to the influence of heat and thereby effect a relatively rapid rise in its temperature; the oil flowing by gravity from tubes at a higher level to tubes at a lower level, the lighter fractions of the oil, in the course of its downward progress, being vaporized. At the same time mercury vapor flowing in the tubes 61 is condensed.

It will be understood that the tubes 61., or the tubes and headers 60, are the equivalent, in a broad sense, of the elongated narrow chamber (Z of any of the Vaporizers 1 to 10 inclusive and the chamber 6'3 is the equivalent of the oil vaporizing chamber 0 of such vaporizer.

The apparatus shown in Fig. 9, however, may not be practically operative to secure the objects of the invention unless sl'lbstantial condensation of driven-off vapors by downfiowing oil be avoided. In other words, a material amount of refluxing. if it results in substantial decomposition or cracking, must be avoided; and, therefore,-

it is distinctly preferred to use an appara tus, such as that shown in the preferred embodiment of the invention, wherein means are provided for the free escape of the oil vapors as soon asthey are formed.

While the apparatus has been described as more particularlyapplicable to the distilof the apparatus to any kind of distillation does not necessarily involve any change in the apparatus, although it would involve a suitable regulation of the various variable factors hereinbefore specified, which modifi- Cation is within the capacity of those skilled in the art of refining oil.

No claim is herein made to the process herein described, as this forms the subject matter of the copending application specified near the beginning of this specification.

\Vhere in the claims we specify a .inercury boiler, chamber or conduit, it is not intended to exclude as equivalents any boiler, chamber or conduit adapted to vaporize, condense or convey substances other than mercury that have qualities adapting them to be substituted for mercury and otherwise responding to the structural limitations of the claims.

A Where in the claims we refer to minimizing cracking we mean to. include the substantially absolute prevention of cracking as well as its reduction to an unobjectionable degree. Substantially an entire avoidance of cracking can be secured in those units in which, with a given absolute pressure on the oil, the vaporizing temperature of the fraction intended to be vaporized is below, or not materially above, a cracking temperature; it being possible, with mercury vapor, to effect such vaporization, without raising the temperature of the mercury vapor much above the temperature of vaporization of the oil. owing to the small required temperature difference between the heating and heated media that is possible where mercury vapor is the heating medium and it transfers its latent heat by condensation. Inasmuch. however, as the claims are directed to the apparatus, it is not intended to exclude such operation thereof as may not minimize cracking to the degree which is possible or desirable when the apparatus is operated under conditions of high efiiciency; the minimizing of cracking being an extremely valuable capacity of the apparatus as distinguished from a necessary incident of its operation.

Having now fully described our invention, what we claim and desire to protect by Letters Patent is:

1. An apparatus for distilling oil comprising an oil vaporizer having an oil vaporizing chamber and a mercury chamber in heat exchange relation therewith, a mercury boiler, a mercury vapor conduit from the boiler to the mercury chamber of the vaporizer, a mercury condensate conduit from said mercury chamber to the boiler, a liquid mercury holder, means connecting same with the boiler'and adapted to maintain a constant level of mercury-in the holder, a by-pass from the mercury vapor conduit to the mercury holder adapted to convey excess mercury vapor beneath the mercury level therein, a mercury vap'oroutflow passage from the mercury holder. and means to'condense the mercury vapor flowing out said passage.

2. In an apparatus for distilling oil, the combination of two series of oil vaporizing chambers, means to convey residual oil fromeach vaporizing chamber of a series except the last to the next vaporizing chamber of with the respective oil vaporizing chambers of the corresponding series, and two mercury boilers one for each set of mercury c0ndens ing chambers, whereby the condensing temperatures of the mercury vapor in the two sets of mercury condensing chambers may be independently regulated.

3. In an apparatus for distilling oil, the combination with an oil vaporizer compris ing an oil vaporizing chamber and a mercury vapor condenser in heat exchange relation therewith, of a mercury boiler and means affording passages for mercury vapor from the boiler to the mercury vapor condenser of the vaporizer and for condensed mercury from the latter to the boiler, the oil vaporizing chamber adapted to receive oil and to discharge residual oil and oil vapors,

a condenser communicating with the oil vapor outlet, an oil distillate tank communicating with the condenser and adapted to accumulate a column of distillate, a vacuum pump connected with the top of the distillate tank, and a'distillate discharge from the bottom of the distillate tank.

4'. In an apparatus for distilling oil, the combination with an oil vaporizer comprising an oil vaporizing chamber and a mercury Vapor condenser in heat exchange relation therewith, of a mercury boiler and means affording passages for mercury vapor from the boiler to the mercury vapor condenser of the vaporizer and for condensed mercury from the latter to the boiler, the oil vaporizing chamber adapted to receive oil and to discharge residual oil and oil vapors, a condenser communicating with the oil vapor outlet, an oil distillate tank communicating with the condenser, 21, by-pass for contaminating vapors carried ofi with the oil vapors, and vapor exhaust means connected with said by-pass.

5. In an apparatus for distilling oil, the combination with an oil vaporizer comprising an oil vaporizing chamber and a mercury vapor condenser in heat exchange relation therewith, of a mercury boiler and means affording passages for mercury vapor from the boiler to the mercury vapor condenser of the vaporizerand for condensed mercury from the latter to the boiler, the oil vaporizing chamber adapted to receive oil and to discharge residual oil and oil vapors, a condenser communicating with the oil vapor outlet, an oil distillate tank communicating with the condenser and adapted to accumulate a column of distillate, a by-pass for contaminating vapors carried oii with the oil vapors and extending through the condenser, a tank communicating with said by-pass and adapted to accumulate a column of condensed cont-rmiinating vapors, an air pump connected with the tops of said tanks, and liquid discharges at the bottoms of said tanks.

6. An apparatus for distilling lubricating oil comprising a mercury vapor generator, a number of oil vaporizing chambers arranged in series, each chamber comprising a wall over which the oil is adapted to flow in a thin sheet, and a number of mercury condensing chambers communicatingwith, and arranged in multiple with respect to, the mercury vapor generator, each of the several mercury condensing chambers being arranged in direct heat exchange relation with only that avail of the corresponding oil vaporizing chamber over which the oil is adapted to flow.

7. In an oil apparatus for distilling oil, the combination of a series of oil vaporizing chambers, an oil inlet pipe to the first vaporizer of the series, means to convey re sidual oil from each vaporizer except the last to the next vaporizer of the series, a set of mercury vapor chambers one for each oil vaporizing chamber, means to spread the oil in each vaporizing chamber, in its flow from inlet to outlet, over an extended surface in heat exchange relation with the corresponding mercury chamber, a mercury boiler, means arranged in multiple to admit mercury vapor generated by the boiler to each mercury chamber independently, independently regulable valves controlling the admission of mercury vapor to the several mercury chambers and adapted to be adjusted to permit mercury vapor to flow into the successive mercury chambers at progressively increasing rates and thereby establish in the successive mercury chambers progressively increasing pressures and temperatures of condensation.

8. An apparatus for distilling oil comprising an oil vaporizer having an oil vaporizing chamber and a mercury chamber in heat exchange relation therewith, a mercury boiler, a mercury vapor conduit from the boiler to the mercury chamber of the vaporizer, a mercury condensate conduit from said mercury chamber to the boiler, two holders for liquid mercur a connection between them forfiow of liquid mercury, a pipe connected with the boiler and extending into one holder and determining the level of liquid in both holders, and a by-pass from the mercury vapor conduit extending to the other holder.

9. An apparatus for distilling oil comprising an oil vaporizer having an oil vaporizing chamber and a mercury chamber in heat exchange relation therewith, a mercury boiler, a mercury vapor conduit from the boiler to the mercury chamber of the vaporizer, a mercury condensate conduit from said mercury chamber to the boiler, two holders for liquid mercury, a connection between them for flow of liquid mercury, a pipe connected witli'the boiler and extending into one holder and determining the level of liquid in both holders, a bubbler in the other holder. and a by-pass for mercury vapor from the mercury conduit to the bubbler.

10. An apparatus for distilling oil comprising an oil vaporizer having on oil vaporizing chamber and a mercury chamber in heat exchange relation therewith, a mercury boiler, a mercury vapor conduit from the boiler to the mercury chamber of the vaporizer, a mercury condensate conduit from said mercury chamber to the boiler,

two holders for liquid mercury, a connection between them for flow of liquid mercury, two pipes communicating with the boiler, one extending into one holder and determining the level of liquid therein and the other extending to the vapor space of the other holder, a bubbler in the last named holder, and a by-pass for mercury vapor from the mercury vapor conduit to the bubbler.

11. In an apparatus for distilling oil, the combination with a series of oil vaporizing chambers each comprising an elongated chamber inclined to the horizontal and provided with an inlet for oil at one end, an outlet for oil at the other end and means between the inlet and outlet for the escape of vapors, and means to convey residual oil from each oil vaporizing chamber except the last to the next oil vaporizing chamber of the series, of a set of mercury chambers in heat exchange relation with only the bottom walls of the respective oil vaporizing chambers over and along which thin sheets of oil are adapted to continuously flow, a mercury boiler, and means arranged in multiple to convey mercury vapor from the boiler to the several mercury chambers and to return mercury from the several mercury chambers to the boiler.

12. In an apparatus for distilling oil, the combination with a series of oil Vaporizers each comprising an elongated oil chamber inclined to the horizontal and provided with an inlet for oil at one end, an outlet for residual oil at the other end and means between the inlet and outlet for the escape of vapors and a mercury vapor chamber in heat exchange relation with only the bottom wall of said chamber over and along which a thin sheet of oil is adapted to continuouslyflow, of means adapted to convey residual oil from the oil chamber of one vaporizer to the oil chamber of the next vaporizer. means to generate mercuryvapor, means afiording passages for mercury vapor to, and to convey condensed mercury from. the several Vaporizers, and means to establish in the mercury chamber of a later vaporizer of the series an absolute pressure and temperature higher than in the mercury chamber of an earlier vaporizer of the series.

13. An apparatus for distilling oil while minimizing cracking comprising an elongated oil vaporizing chamber comprising a bottom wall over which the oil is adapted to flow in a thin sheet and having an oil inlet at one end and a residual outlet at the other end, and a mercury condensing chamber, having an inlet formercury vapor and an outlet for mercury condensate; such mercury vapor condensing chamber being arranged in direct heat exchange relation with only that wall of the oil vaporizing chamber over which the oil is adapted to flow in order to substantially prevent heat exchange between the mercury and the oil vapors; the oil vaporizing chamber being provided with a number of vapor outlets independent of said inlet and outlet arranged along the vaporizer between the oil inlet and residual outlet to allow the instant withdrawal of generated oil vapors from the oil vaporizing chamber.

14. In an apparatus for distilling oil, the combination of a series of mercury chambers, a series of oil vaporizing chambers each provided with. an inlet for liquid oil and an outlet for residual oil, each oil vaporizing chamber comprising a wall of extended area over which the liquid oil in its flow from inlet-to outlet is adapted to spread in a thin sheet, means to generate mercury vapor, means afi'ording passage for mercury vapor to, and to convey condensed mercury from, the several mercury chambers, means to establish in the mercury chamber of a later vaporizer of the series an absolute pressure and temperature higher than in the mercury chamber of an earlier vaporizer of the series, each oil vaporizingchamber having a separate outlet for oil vapor, means to convey residual oil from the residual oil outlet of one oil vaporizing chamber'to the inlet of the next oil vaporizing chamber, each of the several mercury chambers being arranged in direct heat exchange relation with only that wall ofthe corresponding oil vaporizing chamber over which the liquid oil is adapted to flow in a thin sheet and thereby prevent direct heat exchange between the mercury vapor and the generated oil vapor.

15. In an apparatus for distilling oil, the

combination of a series of oil vaporizing chambers each having a liquid oil inlet and a residual oil outlet,'an oil admission pipe to the inlet of the first vaporizing chamber of the series, means to convey residual oil from the outlet of each vaporizer except the last to the inlet of the next vaporizer of the series, each oil vaporizing chamber comprising a wall of extended area over which the liquid oil in its flow. between inlet and outlet is adapted to spread in a thin sheet, a 'set of mercury chambers in heat exchange relation with the walls of the respective oil vaporizing chambers over which the liquid oil is adapted to flow in a thin sheet, a mercury boiler, means arranged in multiple to convey mercury vapor from the boiler to the several mercury chambers and to return mercury from the several mercury chambers to the boiler, and means in each oil vaporizing chamber between and separate from said inlet and outlet to allow escape of oil vapor from the surface of the liquid oil sheet.

In testimony of which invention, we have hereunto set ourhands, at Marcus Hook, Pennsylvania, on this 12th day of March,

ARTHUR E. PEW, J12. HENRY THOMAS.

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