US1479776A - davidson - Google Patents

Description

Ian. 1 1924.

J. G. DAVIDSON APPARATUS FOR cmxcxme AND DISTILLING OILS Original Filed Aug. 23. 1920 2 Sheets-Sheet 1 .Jan. 1 1924. 1,479,776

J. G. DAVIDSON APPARATUYFOR CRACKING AND DISTILLING OILS Original Filed Aug., 23. .1920 2 Shg t-Shget 2 Patented Jan. 1, 1924.

UNITED STATES PATENT OFFICE.

JOSEPH GEORGE DAVIDSONLOF PITTSBURGH, PENNSYLVANIA, ASSIGNOB 1'0 CHARLES H. CONNER, 01 NEW YORK, N. Y.

APPARATUS FOR CRACKING AND DISTILLIH'G OILS.

Application filed August 28, 1920, Serial No. 405,281. Renewed January 28, 1928.

T all whom it may concern:

Be it known that I, JOSEPH Gannon DAVID- soN. a citizen of the United States, residing at Pittsburgh, in the county of Allegheny, State of Pennsylvania, have invented certain new and useful Improvements in Apparatus for Cracking and Distilling Oils; and I do hereby-declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

distilling operation.

This invention relates to an im roved apparatus for the distillation of oi s, such as petroleum oils, and for therthermal decomposition or cracking ofoils, such as the higher boiling petno euz'n fractions for the production therefrom of gasolene and other products. 1

In the cracking and distilling of petroleum oils, for the production of gasolene and other products, it has been proposed to. effect the crackin or distillation by heating the oil in a c osed retort b theapplication of external heat. In suc procedures the effective heat must pass through the walls of the still or retort, and the still walls must be heated to a much higher temperature than that required for the cracking or Moreover, the inner walls of the still, at the place where the heat is applied. becomes coated with a laver of carbon, which interferes with the effective heat transfer and results in further overheating of the still walls, causing buckling and warping of the still walls with consequent danger of explosion, particularly if the operation is carried out under a high pressure. Moreover, in such apparatus, the pressure which can safely be maintained in the still is limited, due to the weakening of the still walls when overheated.

The present invention overcomes such objections and disadvantages and provides an improved apparatus well adapted for use'in the distillation of oil. and in the thermal decomposition or cracking of oil, on a commercial scale. Accordio to the resent in-' vcntion. the heat n cessary for the cracking or distilling operation is generated by a heavy electric current of low voltage passing through one or more massive resistors, preferably of carbon, located awayfifrom able character to the temperature required for bringing about the distillation or the efi'ective cracking of the oil treated. The.

temperature of the resistors, in the process of the present invention, does not greatly exceed the temperature of the oil itself, although suilicient to heat the oil to the re uired temperature. The heat generated in t is way is substantially all effective in the distillin or crackin operation and substantial y all absorbe by the oil, the walls of the still remaining relatively cool. and

correspondingly reduces the internal pressure which t e still can safely withstand. In the apparatus of the present invention, the massive electrodes are spaced away from the walls of the still a suflicient distance to prevent heating of the still walls by induction. even though a heavy current is used, so that there is no cracking takin place where the oil contacts with the still walls, and therefore no objectionable deposition of carbon or coke on the still walls. Owing to the protection of the still walls from overheating,v it becomes possible to use a lighter and more economical construction than is possible in an externally heated stills It will also be evident that for a still of given construction and tensile strength a much greater pressure can be safely used than in an externally heated still.

I am aware that it has been pro osed to effect the cracking or conversion o1 oils by subjecting them to exceedin 1y high temperatures by means of an eectric heater, such temperatures being exceedingly high as compared with temperatures commercially used. In the process of the present invention. however, the temperatures to of. the resistors which are submerged in the the walls of the still, and such resistorsare' heatedby an alternating current of suit oil does not greatly exceed the temperature of the oil itself. and will usually-Jae lower the atmosphere and where any heavy material will be condensed and returned to the still. The uncondensed vapors will then go to the heat iuterchanger 9 yielding up part of their heat to the incomin oil and in part condensing to form a con ensate which may be removed from time to time through the pipe 10 while the still uncondensed vapors pass to the condenser 12 as above described. The valve in the pipe 15, or the other valve or valves in the system which control the pressure ar'preferably so regulated to permit of the permanent gas to escape at the same rate that vapor is generated in the still, thus maintaining the pressure in the system approximately constant.

The heating of the still is effected by the action of the massive resistors 6 which are in turn heated by alternating current. These resistors are preferably of graphite or amorphous carbon, although other suitable material can be used in their construction. They are of such massive construction as to permit the necessary cleaning thereof without removal from the still. The massive construction of the electrodes permits a very heavy current to be carried, for example, a current as high as 20,000 ampercs or higher. The massive construction of the electrodes permits them to be self-supporting and gives them great strength and rigidity so that they can be used time without danger of breaking even with repeated cleaning in a manner hereinafter described.

These resistors in the apparatus illustrated in Figs. 1 and 2, are three in number, and connected togther at one end b the connector and at the other end y means of connectors 27 with the leads 26 of copper or other suitable'metal. The connector 25, which may be a copper bar, and the copper leads 26, are so proportioned and connected that they will carry the current without danger of being heated to excessively high tern ratures.

ere the resistors are of massive construction and are intended to carry a very heavy current, it is important to arran e them remote from the walls of the sti 1, both to protect the walls of the still and to prevent short-circuiting by the growth of carbon deposit upon the resistors until it touches the still walls. If the resistors are in close proximity to the walls of the still the currents induced in the still walls will cause the walls to become very hot, with resulting heat loss and tendency toward objectionable carbon deposit on the still walls. So alsb, when used for the cracking of oils, carbon is deposited to a greater or less extent on the electrically heated resistors, and, it the resistors are in close proximity to the walls of the still. the

for long periods of growth of carbon deposit will tend to connect the resistors with the still, thus shortcircuiting the heating device and causing the current to pass in part through the still walls.

The proper construction and arrangement of the resistors is accordingly of importance where heavy currents are employed, while heavy currents are themselves important to obtain proper cracking and distillation due to the heat supplied thereby. F or example, the investigations that I have made indicate that with the use of currents in the neighborhood of 2,000 amperes, the distillation rate is only about to igallons per hour, which is too small for com merical operations unless the number of units were unreasonably multiplied. However, with a still of the construction illustrated in Fig. l, with massive resistors carrying a current of 20,000 amperes, the cracking operation can be carried on at the rate of from 200 to 350 gallons per hour; while with apparatus of larger size containing a plurality of heating devices of a similar character either in a still of larger construction or in separate individual stills, the yield or output can be correspondingly increased.

The proper arrangement of the leads or connections for the resistors is also of impor-.

tance. where heav currents are employed, in order to avoid objectionable losses of electrical energy due to impedance and hysteresis. With alternating current, and with the heavy amperage which I employ, a very considerable percentage of the total electrical energy would be lost if the properclectrical connections were not made, for example, if the leads were introduced at opposite ends of the still. However, by introducing the leads of the alternating current, whether single phase or poly-phase, at the same location, these losses are reduced to a minimum, and the current effectively applied in the resistors themselves.

It will thus be seen, from Figs. 1 and 2, that the three leads 26 at the same locality and with but a small distance between them. These leads or busbars must, of course, be properly insulated from each other and from the walls of the still where they pass through it, and the insulation must moreover be of such a character that it will withstand the high pressures maintained in the still and prevent leakage or escape of vapors therefrom. A suitable form of insulation and stuffing box is illustrated in Fi 3. In this figure the plate or portion 0 the still wall through which the leads pass is indicated at 30, and has welded thereto a tubular projection 31 externally threaded near its outer end. The conper lead 26 is closely wrapped with thin of the three-phast; alternating current supplied, enter the still sheets of mica 32 which extend below the lower end of the extension 31 and beyond the outer end of the clamping not 33 so that the lead is iIlSLiiitWtl hv thc inica both from the member 31 and the nut 33. i'isbcste; packing 34 is inserted in a recess in the bushing 31 and the nut 33 is then screwed down to clamp the asbestos packi 34 in place and form a tight joint, holding the mica sheets firmly against the copper lead and preventing escape of vapors from the still. \Vith a construction and arangement of this kind, pressures of around 200 pounds or more can readily be employed without dan er of leakage around the leads and while still obtaining the neccssar insulation for the heavy currents employcm I The plate 30, and also the extension 31., are advantageously made of non-ferrous metal of high resistance, such as Monel metal, in order to cut down the losses of electrical ener due to hysteresis and eddy currents, suc as would result if a steel plate were used.

\Vhen the apparatus is used for cracking oils, more or less carbon is separated from the oil and tends to deposit upon the resistors. These resistors should be spaced apart not. only from the still walls but also from each other to prevent the bridging over from one resistor to the other by carbon so doposited. After a certain time. however, the carbon deposit will become so great that it may seriously interfere with the operation of the electric heating device unless it is removed. It is not feasible to take the still apart and remove the resistors for the purpose of cleaning them, inasmuch as this would involve cooling the resistors to a sufiicicntly low temperature to permit them to be exposed to the atmosphere, and inasmuch as the massive electrodes are not read ily removed and would require a. considerable period of time before they could be safely removed. Accordingly, I provide for the cleaning of the resistors withoutremoving them from the still. This may be eil'ected by removing one of the heads and insorting a cleaning or scraping device for scraping the deposited carbon from the resistors. This can be done without permittin the still to cool and without any considerahlc loss of time for the cleaning operation. It is more advantageous, however, to provide cleaning means within the still itself which can be 0 rated periodically without opening the sti 1. Such cleanin devices are illustrated in Figs. 4 and 5, in w ich corresponding parts are indicated b the some reference numerals as in Fig. 1, with the surffix b and c appended thereto.

In'the construction of Fig. 4, the cleaning device consists of a series of thin sharpedged metal bars, equally as long as the re sisters and of somewhat greater height.

There are two of these bars 35 for each resister and they are all united at each end and supported by cross-bars 36 which are in turn suspended by rods 37 passing through stuffing boxes 33 and having handwheels or gears 39 for raising and lowering them. When (-xcessive amounts of carbon have been deposited upon the resistors, the current is interrupted and the gears or hand-wheels 39 are turned at the same rate, and in such a way that the bars 35 will be caused to rise parallel to the face of each resistor and only the fraction of an inch distance from it. The deposited carbon is thus brushed or broken from the resistors and falls to the bottom of the still. This cleaning movement can be repeated one or more times, after which the cleaning device is lowered to its original position, the current is agsin turned on, and the operation continued.

In the construction of Fig. 5, the cleaning device is operated by means of elcctro-magnets 40 having iron cores 41 secured to the lifting rods 37. The rods 37 pass through louse bearings having water-cooled devices 42 arranged to keopthe heat of the still from passing to the electromagnets, and the cores and lifting rods are suitably enclosed, as in a steel tube, to enable the pressure in the still to be, maintained. When it is desired to operate the cleaning device, the heating cutrent is interrupted, and a suitable current of electricity is caused to pass throu h the elccti'o-maguet 40. the magnetic fiel thus produced causing the front cover to raise the cleaning devices so that they operate as above described. On interrupting the magnctizing current of the electro-magnets, the cleaning device will resume its position of rest below the resistors. The heatin current is then reestablished through t e re sisturs and the process roceeds as before.

It will be evident tiat the provision of cleaning: devices for the resistors enables ilicsc resistors to be maintained in operation for long periods of time. with only infrequent stopping in operation for cleaning, and that such cleaning is eilccicd without opuninp the still and without the necessity for cooling of the still or of the resistors.

As the cracking operation proceeds, the amount of heavy residue and suspended carbon will increase. and it will usually be do sir-able from time to time to withdraw the heavy sludge and suspended carbon int-huh ing that broken oil by the resistors. This is accomplished by opening the draivm ti pipe 3, after which the pipe is closed and a fresh charge of oil introduced into the still.

In the operation of the still, the massive resistors will be maintained completely submerged in the oil, which should preferubl be maintained at such a level that the stil is about two-thirds full. It will be noted that the horizontal arrangement of the still gives a large surface of contact between the oil and the vapor therein, which is advantageous, and that this arrangement also provides a lar e vapor space within the still above the oil. The oil within the still is subjected to the heating action of. the massive resistors, and is thereby heated to the appropriate temperature, which, for cracking operations, will usually be between 700 and 900 F., although the particular temperature will vary with different oils. Inasmuch as the resistors themselves are completely immersed in the oil, the will be subjected to the coolin action of t e oil at the same time that the Oll is subjected to the heating action of the resistors. The resistors will thus be kept from attaining any undue temperatures materially in excess of that required for maintaining the oil at the lproper cracking temperature and effecting t e cracking and distillation at the proper rate. The 011, advantageously preheated as above described, is supplied tothe still in a continuous or intermittent manner, to make up for that which has been cracked and distilled, and to maintain the roper level within the still so that the resistors will be kept submerged in the oil.

In Figs. 1 and 2 the heating is efi'ccted by three-phase alternating current supplied from the transformer 29 through the leads 26 to the three resistors 6. By using a threephase current, each lead and each resistor will only carry a third of'the total current, for example, 6666 amperes where the total of 20,000 amperes is used. This arrangement permits theuse of smaller leads and distributes the current in a articularly advantageous manner. The c caning devices,

of the character illustrated'in Figs. 4 and 5, are omitted from the construction of Fig. 1, but even where such cleaning devices are not provided, the massive resistors can nevertheless be cleaned by removing one of the end plates 5 and inserting a cleaning device from outside, as above described.

A poly-phase current, such as the threephase current illustrated in Figs. 1 and 2, or the two-phase current illustrated in Figs. 4 and 5, is particularly advantageous and is to be more particularly recommended. A single-phase alternating current can, however, be used, although with less advantage.

\Vhere such a single-phase current is used, the leads should advantageously be introduced at the same location, the same as when a polybase current is used, for reasons previous fy stated, namely, to avoid the large losses 0 energy due to hysteresis and impedance which would result if the leads were introduced at opposite ends of the apparatus.

Th resistors themselves may vary in size and we, but in general they should advantagasmsly be 0 a considerable height and minimum width, for example, 2% inches wide, 8 inches high, and 8 to 10 feet long, and with the separate resistors spaced apart a suitable distance to permit the operation of the cleaning devices and reduce the danr of bridging over therebetween by caron deposit and resulting short-circuiting. That is, the resistors should be of massive construction and suitably arran ed and spaced apart from each other and mm the still walls and provided with leads of suitable construction arranged so that the enter the still at the same location. Wit resistors of the character described, a large heating surface is provided, and since this surface is in intimate contact with the oil it is itself cooled b the oil. The heat is thus effectively sulpphed to the oil, through the resistors, wit out objectionable overheating of either the oil or resistors.

In the operation of the apparatus of the present invention, for the cracking and distilling of oils, I recommend particularly the use of polybase current, such as t reephase current, which is economical and readily obtained, and the use of a heavy current of low voltage, for example, a. current of 15,000 to 20,000 amperes and 20m 50 volts, and with massive resistors of slablike construction, having a large heatiu surface in contact with the oil, and arrange to operate in the manner above described. A pressure of around 150 to 200 pounds is generally to be recommended for commercial practice in cracking oils, inasmuch as such pressures give greater yields of gasolene with smaller expenditure of energy per gallon of gasolene produced, while apparatus can readily be constructed capable of withstanding such pressures without daner. I also recommend such a rate of distillation that the time factor, that is, the still on acity in gallons divided by the rate of disti lation in gallons per hour, be maintained around 0.8 to 1.0, since at this rate there is an ap roximation to the minimum expenditure 0 energy per gallon of gasolene roduced. A more rapid rate of distillatlon may, however, be more advafl: tageous where a greater number of actual gallons of gasolenc per hour is more 1mportant and Where the other products of the cracking operation, mainly kerosene, are of equal or greater value than the material originally treated. I also recommend that the oil be ire-heated in a heat exchanger and in a preheating coil .to a temperature between 000 and 700 F. before it is introduced into the still so that little energy will he needed in the still to raise the oil to the retipired temperature.

tinuous operation it will be understood that the oil is supplied at substantially the rate cleaning of distillation to maintain the proper amount of oil in the still. It is also advsntageous to withdraw theheavy sludge and carbon periodically and at the time of the resistors of immediately thereafter and before the current is again turned on. The carbon broken or scraped ofi from the resistors can thus be removed together with the heavy sludge and a fresh charge can then he introduced into the still so that the cleaned electrodes operate upon fresh oil. Such periodic cleaning and withdrawal of sludge will. be more or less infrequent, depending upon the material treated and the manner of operation; but ordinarily cleaning will not be required until after the still has been in operation for several hours and with some oils the still can operate for relatively long periods of time before cleaning will be necessary.

When the apparatus is to be used for the distillation of petroleum oils without cracking, or with only such cracking as is incidental to the distillation under ordinary pressures, the apparatus can be somewhat simplified in construction, for example, the Still itself may be larger and need not be as strong, inasmuch as it is not required to withstand high internal pressure, while the cleaning devices and supplemental preheater 24% are of less importance and can be omitted.

From the foregoing description, it will be seen that the present invention provides an 'unproved apparatus well adapted for commercial operation, and that the invention resents various features of advantage and of novelty. The cracking and distilling operations are carried out with internal heating elements, heated by electricity, but with such size and construction of the heating elements and with such regulation of the current supplied thereto, that the oil is rapidlv and effectively heated to the required temperature without objectionable overheating. The current supplied may thus be a heavyfcurrent, but, owing to the nutssive character of the resistors-the heating effect of the heavy current is utilized in heating the oil, without objectionable overheat ingof the resistors. In fact, as above noted, the resistors have been found to have a relatirely low temperature not greatly exceedin% the temperature of ill( oil itself.

t will also be noted that. the apparatus of the present invention is adapted for the treatment of relatively large bodies of oil within which the resistors :lr'e submerged. as distinguished from processes involving a flow of oil passed heating elements heated to an exceedingly high temperature, that is, the apparatus of the present invention is one in which the resistors act directly upon the liquid oil and in which the oil itself is kept. in intimate contact with the resistors and actually penetrates the porous surface of the carbon resistors, where such porous resisters are used, as distinguished from 0peraiions involving the use oi such high temperatures that the oil can exist only in a vapor state lat the temperatures of the heat ing elements or surfaces. Owing to the intimate heating ellect obtained according to the present invention, the cracking and distilling operations can be effected without violent ebullit-ion of the oil, but nevertheless with rapid and effective cracking and distillation thereof. 7

It is a characteristic adie-ntagre oi the present invention when used h r the cracking of oils, that the amount. of pernmnent gas produced is very small. .1. have thus obtained cfi'cctive cracking of the oil with the conversion of as little as 1% or less of the original oil into permanent gas. it. also a characteristic advantage of the pr I vention that, with increased yields e; olene due to increased pressure, the loss does not correspondingly increase, ut remains only a small percentage of the original oil, even where the amount of gasoleue roduced is as high as 35 to or more o the original oil.

I claim 1. An apparatus for Li'lil-il and distilling oil, omnprl'. a still adapted to contain a relaln more massive ranged to hr; :uen and means is:

l y or oil, one or stars therein arvei in the body of oil, ecppl ing polyphasc alternatin current to said resistors.

2. in apparatus for cracking and distilling oil, comprising a still adapted to corn tain a. relatively large body of oil, one or more massive resistors therein adapted to be heated lay alternating current, the leads for the current all passing through the still sell at. 1.. locality.

3. An. apparatus for ling oil. comprising a still sdaptcd to contain u relsii'rcly large body of oil, a plureh ity of massive electrical resistors therein adopted in he heated lay l noting zli'r'ili. and lea said poly-please current to the r; to :z leads all passing through the still well at one locality.

4. An apparatus for cracking and distilling oil, comprising a still adapted to contain a relatively large body of oil, a plurality of massive resistors arranged to be immersed in said oil, said resistors being connected to each other at one end, and leads connected to the other ends of the resistors, one for each phase of the poly'phase current, allyof the leads entering the still at one 10 ca rtv.

5, An apparatus for cracking and diatil cracking and distih,

ling oil, comprising a still adapted to confrom the resistors, and means for operating tain a relatively large body of oil, one or said cleaning devices from outside the stil. more massive electrical resistors therein 7. An apparatus for cracking and distil- 15 adapted to heat the oil, and means within the ling oil, comprising a still adapted to con- 5 still for removing deposited carbon from tain a relatively large body of oil, one or the resistors from time to time. more massive resistors therein adapted to be '6. An apparatus for cracking and distilheated by alternating current, the leads for ling oil, comprising a still adapted to conthe current all passing throu h the still wall 20 tain a relatively large body of oil, one or at one locality, and the sti wall at such more massive electrical resistors therein locality being of non-ferrous metal.

adapted to heat the oil, resistor cleaning do In testimon whereof I afiix m signature. vices arranged to remove deposited carbon JOSEP GEORGE DA IDSON.

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