US1788947A - Apparatus for distilling oil - Google Patents

Description

R. F. GILDEHAUS, JR 1,788,947

APPARATUS FOR DISTILLING OIL Jan. 13, 1931.

Filed Augl I0. 1925 s Sheets-Sheet 1 i I Smamtoz Jan. 13, 1931. R. F. GILDEHAUS, JR

APPARATUS FOR DISTILLIPIG OIL ts-Sheet 2 Filed Aug.

J C M IINVENTOR fiz w/ N ATTORNEY Jan. 13, 1931. R. F. GILDEHAUSQJR APPARATUSFOR DISTILLING OIL F1196 Am 10. 1925 s Sheets- Sheet s z Z r i 2.

A3 U/FQZ 40.5

Patented Jan. 13, 1931 PATENT OFFICE RICHARD I. GILDEHAUS, JR, OF DALLAS, TEXAS APPARATUS FOR DISTILLING OIL Application flledAugust 10, 1925. Serial No. 49,221.

This invention relates to method of fractionally distilling crude oil and to apparatus therefor, the method and apparatus relating more particularly to carrying on continuous fractional distillation of crude oil under vacuum. r

The principal object of my invention is to provide an apparatus for recovering accurate and finely determined cuts from the oil distilled, and for carrying on such recovery continuously and without waste, and without the formation of carbon forming or other deleterious substances in the distillates, and to avoid discoloration and objectionable odor in the products. A further object of my invention is to provide a method and apparatus of the character described which will not result of the deterioration of or change in the character of the cuts should there be an interruption in the normal flow of oil to or through the apparatus. Other objects will be in part obvious and in part pointed out hereinafter.

In accordance with my invention, I provide 5 a battery of stills connected in series, so that oil is free to flow by gravityfrom an outlet at a certain level in each, still, except the last one, to the next still, the last still having a gravity outlet to waste oil tanks, which from now on I designate as receiving tanks. Each still has an individual furnace and condensing and cooling apparatus, individual means for maintaining positive directional circulation of oil through the still, means for maintaining recirculation of the oil through the still, and means for maintaining vacuum therein. The furnace or com bustion chamber of each ,still is arranged to prevent highly (heated prod- -al0 ucts of combustion from dontacting directly the walls of the parts whi h contain the oil, to insure against any cracking, which would otherwise be apt to resultfrom local or spot over-heating. The heat is transmit .3 ted to the oil by convection through the walls of refractory heat-retardant material and radiation from-the surfaces of the refractory material to the metal parts containing the oil. This furnace arrangement for indirect heat- 'ing of the oil is disclosed and claimed in an application for vacuum process for refining mineral crude oil and apparatus therefor, filed June 17, 1925, Serial No. 37 ,639.

A distinct feature of the present system is the positive directional recirculation of the oil within each still, combined with indirect heating of the oil by radiant heat and with gravity flow of the oil from one still to the next. This arrangement ves a high rate of heat absorption, a large'iiquid surface for 00 freeing the vapor and a large volume above the liquid (consequently low vapor velocity), which eliminates the carrying over of liquid by the vapor and so gives practically complete separation. Continuous fractional distillation is obtained by means of temperature regulation of the several stills.

In orderthat a clearerunderstanding of my invention may be had, attention is hereby directed to the accompanying drawings, 7 forming a part of this application and illustra-ting one possible embodiment of my invention.

Referring to the drawings, Fig. 1 is a diagrammatical top plan view of an apparatus embodying my invention and adapted to carry out the process; Fig. 2 is a diagrammatical side View, partly in section, of one of the cooling units, the view being taken on the line 2-2 of Fig. 1; Fig. 3 is a sectional so View through one of the still settings, showing the still therein, and is taken on the line 3-3 of Fig. 1; Fig. 4: is an enlarged sectional View of a fragment of the still and setting, and is taken on the line 44 of Fig. 3; and 35 Fig. 5 is a diagrammatical view showing the connections. between two intermediate stills, only fragments of the stills being shown. Similar reference characters refer to similar parts throughout the several views so of the drawings.

Referring to the drawings, there is shown 1 a battery of five similar stills A1, A2, A3, A4 and A5, each equipped with condensers C leading to one of the cooling units B1, B2,

B3, B4 and 135, which are similar to each other. I. 7

Each still is arranged to heat the oil therei in indirectly by means'of radiant heat. The

stillbody or retort 1 is suspended from the top 2 of the enclosing still setting 3. Below one end of the body 1 is a drum 4, connected to the .still body by conduit 5, and below the other end of the still is a drum 6, connected allel lines, and between which are the coils of pipes 8. The lower lines or tier of tilesare supported on bridge pieces 15, which provide a passage 16 beneath the tiles. The upper tiers of tiles rest on spacer blocks 17 placed on the next lower tier. The tiles form ducts for the products of combustion from the chamber 12. a, The arrangement is such that the highly heated .products from this chamber pass upwardly through a duct provided by the end tiles 18 of each line of tlles, then through ducts leading through each line 19 of the upper tier of tiles, then through ducts 20 leading through each line 21 of the second tier of tiles, then into ducts 22 leading through eaehline 23 of the lower .tier of tiles. The tiles of the lower tier have openings 24 in their bottom walls, and the products of combustion, now considerably reduced in temperature, then pass through these openings into passage 16 and up through the spaces 25 between the lines of tiles, and about the pipes 8. From here these products pass about the still body 1, and about its ends, and are discharged from the setting through opening 26.

At the usual rate of driving, practically all of the recoverable heat of combustion is removed from the gases by radiation through the ducts, so that the gases, upon leaving the ducts, have a temperature so low thatpractically no further transmission ofheat can take place from the gas to the oil on account of insuflicient temperature head.

Each still is equipped with a pump P,

V which is designed to receive oil from drum 6 through pipes 27 and 28 and to discharge the oil through pipe 29 into header I10. Pipes 27 and 28 have check valves 30; and pipe 106 connected near the pump P to relleve any vapor which may be carried with the liquid through pipes 28 and 27,.and so' prevent same from becoming -vapor-bound.

Pump Pmaintainscontinuous positive directional circulation of oil through thestill body and coilsS, and recirculation of the oil within each still when the supply of new oil to it is interrupted or is less than the capacity of the pump. 1

Each still has domes 31 provided with condensers C, which communicate with the still body .through conduits 32, and have water coils 33, connecting with water inlets 34 and water outlets 35 vapor baflles 36; vapor outlet 37; and liquid outlet 38. Pipe 39 leads from the vapor-outlet to the cooler unit, and pipe 40 leads from the liquid outlet to the cooler unit.

The oil supply line 110 is adapted to be connected with thecharging tanks D and D by the line 111 or it may be connected directly with pump P by line 112. Charging tanks .1) and D" are connected through lines 79 and 80 to a pump 80 for pumping out air, and with a vacuum equalizing line 81 which joins the line 39.

As distillation proceeds, the vapors and gases from the condensers G pass through lines 39 and 41 and valve 42 into a gas cooler J from where they pass through lines 43, 44 and 45 either through line 46 and valve 47 tovacuum pumpK or through line 48 and valve 49 to vacuum pump K, which pumps dischargerespectively through line 50 and valve 51 and'through line 52 and valve 53 into line '54 leading to look box L. A pipe 55 leadsuncondensable vapors and fixed gases from the top of the look box into a vented line 56 leading to a waste oil tank' (not shown).

Liquid products leave look box L through lines 57 and 58 to a header R and through valves 59 into storage tanks (not shown)- The look box has a tap 60 to permit the takand gases mix with the products coming over through line 39. Gas cooler J is by-passed by valved-line 68, so that upon closing valves 42 and 42 the cooler may be opened for cleaning or for any other purpose. The gas cooler J is drained through line 69 and the valve 70 into a container Q, which is connected to the line 43 by line 71, through valve 72. The container Q is drained by closing valves 70 and 72, and opening valve 73 to admit air, while its con tents is removed through valve 74. During operation, the valve 70 is partly opened to permit the condensation occurring in the cooler J to drain into contain er Q, except when Q, is emptied as described. Both J and Q are provided with gauge glasses J and Q, to

show the height of any liquid accumulating in them; The vacuum pumps K and K are cross-connected. as shown and described, so

The last still A5 has a discharge through line 75 and valve 76 to a pump X, which sends still through an equalizing line 90. vacuum is released and the oil is then pumped the liquid to the charging tanks D or D, or the liquid may be discharged through valve 77 and line 78 into receiving tanks Y; Tanks Y are connected by a vacuum equalizing line 90 which leads to the vapor line 39 of the last still. A line 91 also connects these tanks to an auxiliary vacuum pump, which may be the same pump 80' used for the charging tanks D and D. Line 91 has a valved vent 92 for admitting air when emptying either tank Y. A pump 93 is connected with the bottoms of tanks Y by valved lines 94 and 95 for pumping out either tank. Each tank Y contains coils 96 connecting with lines 97 and 98, and a pump 99 is provided in line 97 for circulating fuel oil, or crude oil, or any suitable medium through the coils within the tanks to cool the hot oil flowing into the tanks from the last still. valveddrain pipes 96 are provided for the coils. The heavy hot oil from the last still flows into the receiving tanks Y, which are maintained under the same vacuum as the last The from one receiving tank-through line 100 into a third tank or fuel tank 101, where it is diluted with light oil (usually the non-viscous fraction from the first still) to make fuel oil. There is also shown an elevated tank 102 with 'an overflow 103 to the fuel tank, from which the burners are supplied through line 104; while the bottoms and light oil are mixed in the fuel tank. The fuel oil may be pumped from the fuel tank through the coils in the receiving tanks, thence passing into the elevated tank through line 98, and flowing from it into the fuel tank, through the overflow line 103.

As stated above, any medium might be used to reduce the temperature of the hot oil in the receiving tanks, as may be required to prevent the oil. from igniting when coming in contact with air as either tank Y is emptied. In case'some medium other than the fueloil from tank 101 is used for cooling the oil'in tanks Y then of course the tank 101 is also elevated and serves alternately with tank 102 as a mixing tank or a supply tank to the oil burners, while pump 99 then connects to some other tank from which it would draw the cool ing medium to be pumped through the cooling coils in tank Y.

To begin operation, the crude oil, free of moisture and preferably hot (and treated where the crude requires it). is pumped into all of the stills to a suitable height in the drums, a valve 82' in the fiow line 83 from each still, except the last one, being closed. At the last si ill valves 76 and 77 are closed. The fires are-then started and the vacuum applied. The first cut is taken off each still, and additional crude oil is supplied by gravity to the pump of the first still, from one of the charging tanks D or D, which are also under the same vacuum, the rate of supply being regulated in accordance with the rate of distillation. After a suflicient quantity of oil has been reduced by one cut in the first still, all of the valves in the flow lines from the several stills are opened. Each succeeding still is then brought to its proper temperature as rapidly as conditions will permit, the oil from the last still being returned to one of the charging tanks, through valve 76 by pump X, until the last still reaches the required temperature. The charging tanks are filled alternately and then put under the same degree of vacuum as maintained in the distilling system, by a separate vacuum pump 80. These charging tanks are suitably heated for the purpose of heating the crude or to keep it hot if it has been previously heated.

In accordance with the laws of physics the vacuum is created by condensation, and the absolute pressure less than the barometer (degree of vacuum) is determined and is fixed by the temperature maintained within Y ihe condensers by the cooling medium. The vacuum pumps serve only to expel Vapors and gases which pass uncondensed through the condensers and such air as may have leaked into the-system.

In any system so operated and which is reasonably tight, the absolute pressure with in the condenser will be the vapor pressure of the condensate corresponding to the temperature within the condenser plus the partial pressures of any non-condensable gases which may be created in distillation. Now, in the particular case of distilling oil under absolute pressures less than atmospheric, the degree of vacuum? or more properly the absolute pressure, prevailing within the condenser is the sum of the vapor pressures of the oil and non-condensable gases created in distillation, corresponding to the temperature maintained by the cooling medium within the condenser. The vacuum, so-called, is independent of the rate of distillation as long as the rate of condensation is commensurate with it. I

In my vacuum oil distilling system, herein described, consisting of a number of like stills, if the system is reasonably tight the capacity of the vacuum pump or pumps for each still may be the same, inasmuch as the quantity of the non-condensable gases from each still does not vary enough to warrant different size pumps. Assuming for example, that the temperature of, the Water 1s the same to all condensers, the vacuum corresponding to this temperature will be great-.

er in each succeeding still and condenser depending on the gravity of the fraction being distilled in each case, since each heavier fraction has a correspondingly lower vapor pressure for the same temperature. In order that this difierence in absolute pressures may III" exist and be maintained between still units connected'm serles for contlnuous 'dIStIllapump of the following still unit. Thus the pressures on either side of the checks 30 are equalized so that oil will flow through them to the pump and be recirculated within a still unit when the fiow of oil to it from a preceding still unit (or from the charging tank to the first still unit, as the case'may be) is interrupted or ceases for a time. Under theconditions named, the vacuum on each still and condenser will of itself be fixed according to the partial pressures of the vapor and gas of the particular out taken from each still. Thus the lowest absolute pressure (highest vacuum) will prevail in the last still and the highest absolute pressure in the first still. This works out very well as the lightest fractions require relatively the least vacuum while the heavier fractions each'require a greater vacuum (lower absolute pressure) for safe distillatiomsince the temperature required to distill each succeeding fractiou is higher and nearer its critical temperature. This also aids the gravity'flow of oil from still to still as the difference in vacuum represents a ditference'in absolute pressure in favor of the flow. The same vacuum might be maintained in all the condensers, if the cooling medium toeach condenser were of correspondingly lower temperature, beginning with the last condenser. This would re quire a refrigerated medium for the first condenser, or for the first and second condenser depending on how light the first or first two outs may be. It, is cheaper to let these very light ends pass on as vapor and burn them under the still than to go to the expense of refrigerating the cooling medium for their recovery. When making a. re-run of the viscous fractions or when distilling a crude from which enough of the light ends has been stripped, practically the same vacuum (within one inch) can be maintained on all the stills with cold water having a temperature of Fahr. or less. In any event,-

, the desired vacuum can only be maintained III) on each condenser by controlling the temperature within each condenser.

As previously described, there are two vacuum pumps to each condenser, crossconnected and provided with variable speed drives. With this arrangement, either pump may be used to exhaust the vapors and gases oil out of each still and re-circulate it through the same still should the capacity of any removal in the least time while the pump handling the condensate is adjusted as to spleed so as to discharge a steady stream of o1 The desirable temperature for each still is determined by a trial run with one still operated as a batch still. Cuts of 10% or less if necessary are made and the temperature and degree of vacuum carefully noted for each cut. The'viscosity of each cut is subsequently found, and also the flash point; from which data an operating schedule is preared. p As before stated, the receiving tanks are discharged in succession after the bottoms so have been cooled sufficiently. When empty,

- The pump P is of the centrifugal type (or 1 I if reciprocal, it is properly by-passed) so that 5 the principal heating surface is always flooded," greatly facilitating temperature control, upon which depends 'the particular cut'recovered from each still. Thus, if the pump P should stop for any reason, the coils cannot be overheated or dried out for lack of oil, which minimizes carbon deposits therein and eliminates all'possibility of coking. In the usual arrangement the coils are fre-- quently'dried out and, become overheated, so that when circulation is re-es'tablished the oil is often badly cracked. Furthermore, in my' system, should the crudev supply to the first still, or the flow toa succeeding still, be interrupted for any reason, re-circulation will take place automatically in all the stills commencing with the one so affected, with the result that distillation will cease for a period of time, during which the conditions causing 'such interruption may be remedied..- If this condition prevails long enough, the oil may absorb sufficient heat to start evaporation again in one or more of the stills,. although in practical operation this will be of little consequence because the temperature head in any case will not be great enough to distill much of the oil which would otherwise be vaporized in the following still.

The several circulating pumps may be 115 roughly adjusted as to the quantity circulated in accordance with the extent of the cut taken from each still, but this is of no great im-' portance, since the pumps will simply take pump be greater than the quantity, flowing to it from the preceding still. Each pump must operate at a capacity equal to or greater than the flow of oil to it from the preceding still. A simple plan of operation would be to operate all pumps at the same capacity; and under such operation re-circulation would take place at an increased amountin each succeeding still, in accordance with the amount of oil vaporizedin the preceding still. Thus each heavier cut would be r e-circulated to a greater extent, insuring more complete evaporation of each fraction corresponding to the temperature maintained in each still.

A great many obvious supplementary valves and connections have been omitted so as to brin out clearly the movement of the oil throughout the system. A by-pass (not shown) is installed between the stills so that any still might be cut out of the system for any reason.

Each unit is provided with a complete vacuum condensing apparatus, as shown on drawings. Continuous fractional distillation is obtained by means of temperature re ulation.

t is to be understood that my process may be practiced with plants, appliances and apparatus which may difler widely from that described herein. It is also to be understood that as many changes could be made in the above constructional features and process and many widely difierent embodiments of this invention could be made without departmg from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What I claim is 1. An apparatus of the character described, comprising, in combination, a still having a vapor line, a plurality of charging tanks, an oil pump intermediate said tanks and still for transferring oil from said tanks to said still, means whereby oil may be introduced either to said still or to said tanks, an equalizing.

line between said tanks and said still vapor line, a vacuum pump connected to said-vapor line,'and an auxiliary vacuum pump connected to said tanks, whereby equal pressure conditions may be maintained in said still and said tanks.

2. A series of stills for oil or the like through which oil is adapted to pass successively, a separate condenser for each of such stills, means for introducing oil continuously into one of said stills, a closed U-pipe .between adjacent stills, enclosed means for causing the overflow from the first of said stills to pass to said U-pipe and enclosed means for causingthe overflow from said U-pipe to enter the second still, whereby the pressures in said stills may be separately varied without substantially afli'ecting rate of flow between the stills;

3. A. series of stills for oil or the like, each comprising a heat absorption portion, a convdenser for each still, a pump for each still adapted to recirculate oil through the heat absorption portion, overflow pipes connecting adjacent stills,'said pipes leading out of the stills from 'a oint substantially above the bottom thereo? and connected to the inlet side of said pump at a point below said liquid level, and a closed U-seal in each of said pipes, whereby oil may be caused to flow through said series of stills despite differences in absolute pressure therein.

4. A device as specified in claim'3, which further includes means for heating each still separately.

5. A device as specified in claim 3, which further includes means for separately controlliugthe condensing temperatures of each still. Y

6. A continuous closed distillation apparatus comprising two stills, an outlet for the first still running from a point substantially above the bottom thereof, a pump adapted to circulate liquid in theother still, a pipe connected with the outlet of the first still adapted to permit oil to flow by gravity to an intake for-said pump and a U-bend in over that removed as vapor may be permitted i to flow from the second still.

This specification signed this 3rd day of August, 1925.

RICHARD F. GILDEHAUS, JR.

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