US1869008A - Process and apparatus for dehydrating oils - Google Patents

Description

July 26, 1932 L. 1 DAVIS 1,869,008

PROCESS AND APPARATUS FOR DEHYDRATING OILS Filed Feb. ll. 1929 IN VEN TOR Q01/.0 L HAI/JJ y (tm EY Patented July 26, 1932 curr STATES PATENT OFFECE LLOYD L. DAVIS, OF PONGA CTY, OKLAHOMA, ASSIGNOR TO CONTINENTAL OIL COM- PANY, OF EONCA CITY, OKLAHOMA, A CORPORATION OF DELAWARE PROCESS AND yAPPARATUS FOR `l'JIEIEIYDRATCNGr OILS Application led February 11, 1929. Serial No. 339,034.

This invention relates to the dehydration of refined and unrefined petroleum lubricants in such a manner that the water may be completely removed from the rened lubricants for loading into tank cars for shipment and that the unrefined petroleum lubricants may be freed of water which improves the stock for further processing.

n The primary object of this invention is to provide a process and apparatus for the complete removal of water from refined lubricants prior to shipment. The usual method of dehydrating lubricants prior to shipment nis to blow the oil with air until all of the i5,j moisture is removed. The air causes the oil V,to lose color and to become unstable, whereas the use of my process and apparatus for` dehydrating oils completely eliminates l the loss and any increase in unstability of the '2d product otherwise brought about by the old methods. The air blowing method of dehydrating involves both chemical and physical action. `My method eliminates the chemical action which is injurious to the oil andeffects dehydration of the oil without injurious effects to the oil and withoutobjectionable changes in color. Another object is to completely dehydrate unrefined petroleum lubricants and bring about an improvement in the condition of such products which will enable reiining processing, as acid treatment, Contact and percolating filtration, etc., to be carried out more effectively and economical- `ly. Still another object of the invention is to provide a process and apparatus in which the `separation of water is continuously and completely edected, thus obviating the use of tanks required in the old and well-known method of drying the oil by air blowing.

The principles involved in this proc-ess and apparatus `are heat, vacuum and distribution of the oil in thin films so that the forces opposing the evaporation of the water are 'lessened. The waterin the oil is thought to be usually in the form of minute droplets,'com pletely surrounded by a film of oil, although at times it may also be present in the form of a film surrounding minute droplets of oil. Theeifect of heat, vacuumand thin film disv tribution is to reduce the surfacetension of both oil and water droplets; to effect vaporization at comparatively low temperatures of such water as may be present; the temperature of the mass being raised to a point higher than the boiling temperature of the moisture at the vacuum carried is thought to reduce the surface tension of the bubble film and cause the bubble to increase in size until the expanding water vapor breaks the film and escapes. The action is not instantaneous, a more or less definite time being required for it to take pla-ce. Sulflciently high temperatures must be used to bring about a` fairly quicker rupture of the films and consequent release of the water and water vapor present, as too slow a release of the water and water vapor will .result in a foaming action of the combined Water vapor and oil. Let it be understood that the process is independent of any projected theory, but is the result of tests on oils. lf a droplet of water is enclosedl in a body o-f oil, its tendency to vaporize or to change from liquid to vapor is lessened. If the oil is distributed in a thin film on a plate and if the oil has been heated so that the viscosity and surface tension are lowered, the oil will drain away from the bubbles and the resistance to evaporation of-v fered by the surface tension of the oil will be lessened. If the conditions are such that the water is in the form of vapor, or in other words` a foam, then the spreading of thel mixture in a thin film on a plate will permit,

the liquid oil to drain away from the bubbles and the water vapor to escape.

Usually on viscous lubricants such as bright stock, a temperature of 150 to 200o F. and a vacuum of 27 to 28 inches ona mercury gauge are required. I do not limit myself to the exact vacuum and temperature to be used in this process and apparatus, as this must be determined for each specic oil to be dehydrated.

'The invention possesses other advantageous features, some of which, with the foregoing, will be set forth at length in the following description, where I shall outline that form of the apparatus which I have selected for illustration in the drawing accompanying and forming part of the present specification, In

mediate pipes 8 storage tank, 2 is a drawoif pipeconnectedl with the suction side of a pump- 3. Thedischarge from the pump l4 is connected to a heat exchanger 5. A line from the discharge end of the heat exchanger -connects into a perforated pipe 14 positioned in the` vacuum tower 7. rlhe lines 6 are connectedby'interto the semi-circular perforated pipes 14 shown diagrammatically by a dotted line in the drawing. Y

At 9is shown a plurality of plates orbafle Y conesover which the oil sprayed from the perforated pipes 14 flows in its passage downwardly 'through the tower. l0 and 11 designate two liquid level control devices which are. placed on the vacuum chamber 7. The control 10 communicates with thepower supu ply to the pump 3, while the control 11 is connected to Vthe power supply to the pump 20. Thebottom head of the vacuum tower isidesignated'as 12 and the top head as 13. 14,. as suggested, is thev perforated pipe by means ofV which the oil is introducedinto the tower from the line 6, and 15 are the oil outlet pipes at the bottomV of the vacuum tower andV 16 is the top vapor withdrawalY A' line which ispreferably welded to the center ff of the removable head 13.

A two-stagey ejector is shown at 17, with thev necessary inlet and voutlet connections for. maintaining the desired v'acuumf on the system. 18 is a vacuum eolualizing*` line which is connected tothe removable head 18 and to a small intermediate discharge tank 19.V

2O is an automatically controlled pump for removing liquid from the tower and 21 isa cooler through which the discharged oil mayV ben circulated from the pump 20 when the.V

valve 25 is closed and the valve 24 open. 22

is a recirculating line by means of which the oil may be returned to the storage-tank when the Valve 24 is closed and the valve 25 open;

A? pipe 26 is used for introducing a heating medium to the heat exchanger v5, which medium is discharged from the heat exchanger through the pipe 27. In a like mannera cooling'medium is introduced to the cooler 21 through the pipe 28 and discharged through the line' 29. Intermediate connections and necessary bypasses have been omitted from the description in the interest of simplicity.

rIhe dehyrator consists of a circular tower 7 which 's closed at the bottom by a bumped Y head l2 and on top by a removable head 13 providing entrance to the interior of the tower. This constitutes the vacuum chamber. At the center of this chamber 7, shell angles are welded to the shell, upon which rests a series of conical plates 9. These conical plates 9 are-arranged alternately,` one being placed with the apex upward which flows the oil over the outer surface of the cone, and

the second arrangedv with the apex down- Ward, the oilfrom theupper cone draining olf the rim and flowing down the inside of the reverse cone and againdraining off through a hole provided in the bottom of the reverse cone for that purpose, to the next plate which is again turned with. the coneupward, and soV on. down throughthe series. of plates. A

preferred form for theseplates 9 provides a slope to the cone of.15 to the horizontal, although variations from this are. permissible, the` object being to have such a steepness of slope that thenatural flow of the oil film thereon will provide the proper length of time4 to permit the proper water release to take place. VI have found that various forms of plates as well as chemical Crockery willV have the sameeifect as the conical plates, and I do notlimit; myself to the conical plates, as other means have been` found` to distribute the oil ina multiplicity of evaporating surfaces. 'Ihese cones arey for the. purpose of causing the oil to flow in a thin film and they are equivalent to added height of the tower in that they lengthen theY time that the oil is exposed to the. influence ofthe vacuum. The

oil inlets 8,.two in number, are placed aboveV theI 4cone plates 9. They are welded to the inside shell of the tower and consi-st of a pipe witha companion flange. To the vinlet' pipes Y 8 arey attached two` semi-circular pipes 14 which are perforated and which are held in place by Hanges fastened to the companion flange at the shell of the vacuum drum 7. The-perforations are placed on the bottom of the= semi-circular pipe, so as to spray the oil upward. 'Ihe oil. outlet pipe 15 at the bottom is weldedtangentially to thebottom head` 12 so; asv to--permit complete drainage. 'Ihe steam and airoutlet 16v at thetop'of the vacuum chamber is welded in the center of the removable head 13. Baiiles 23 are suspended from thisremovable head to. collect and return the oil which is entrained in the escaping steam. Vaccum ismaintained by two stage ejectors; 17 with jet condensers be* tween the first; andsecond stages and onev after the: 'second' stage. This. ejector syst-.em

17 is connected to the steam and air outlet of the'tower. It is not:desired'to'limitthe invention to this means for obtaining the vacuum and any other suitable means may be used. Y

Two liquid level controllers. 1()Y and 11 are pllaced on the vacuum-chamber 7 just below t e cone. plates 9. Theone level controller 11 stops the discharging pump when the oil level falls below this level and the other controller causes the charging pump to stop `when the oil level rises above this level. This control prevents the tower from becoming inundated with the consequent loss of oil through the ejector. These liquid level con trollers are actuated by means of throttled compressed air as the pumps are at some distance from the controlling ball floats. The

vacuum equalizing line 18 is connected to the removable head 13 and to the small intermediate discharge tank 19 so as to permit the oil to flow out from the bottom of the chamber 7. The remainder of the equipment consists` of the usual heat exchangers, coolers, etc.

The following is a description ofv one of the preferred methods of operation of the process and is offered in the interest of clari tying the disclosure.

The oil to be dehydrated is pumped from storage into the tank 1. The steam is then chamber 7. When the controlled lower level of the vacuum chamber 7 is passed, the discharging pump 20 is automatically started by the lower liquid level controller 11, the valve 24 to the tank car or other iinished oil receptacle closed, and the valve 25 on the recirculating line open. The oil then passes throughline 22 to tank 1. The circulation is `continued until the system is dry and a sample of the oil shows dry. If the sample is dry, the water is turned into the cooler 21 on the loading line. The valve to the circulating line is closed and the valve on the loading line is opened and the loading of cars is begun. There is a relief valve placed between theloading line and recirculating line so that when loading from car to car, the operation of the dehydrator continues uninterrupted by discharging back to tank 1. To dry up the system and get it settled requires about one-half hour. After this the only attention required is that the supply of oil in tankl is not exhausted and continuous dehydration may be carried out.

In actual commercial operation of this process and apparatus described in the foregoing, 200 barrels per hour was completely dehydrated and loaded into cars and no detectable water was found. During one days operation, not running the 24 hours, 3,302 barrels of D stock (heavy viscous lubricant) were loaded into cars.

It has been found in actual practice in the dehydrating of normal mid-continent lubricating stocks that the temperature in the dehydrator runs approximately 190 F. and the temperature of the oil after going through the cooler 21 into the tank cars or into storage is 140 more or less. The normal pressure on the charging pump to the dehydrator is in the neighborhood of 150 pounds and the pressure on the pump pumping from the dehydrator runs from 50 to 55 pounds.

The vacuum maintained on the equipment is an average of 27 to 28% inches of mercury. In the case of dehydrating certain neutral oils which have a much lower viscosity than lubricating stocks it will be necessary to carry the temperature as high as that ordinarily used with high viscosity oils such as bright stocks. Temperatures from 150 to 200 F. would include the normal range necessary for dehydrating mid-continent lubricants.

In actual practice the oil is circulated through the system until the oil in the charging tank has reached a temperature of 130 to 140O F. Vacuum is then imposed on the system and the operation carried out as previously described. The temperatures and average vacuum maintained have been designated merely for the purpose of giving a typical example of the operation of the method constituting the invention, but it is not intended to limit the invention to these particular ranges, as diierent types of oils will require varying conditions and the process adapts itself readily to these necessary variations. The use of high temperatures obviously reduces the surface tension, producing a thinner lm and allowing more rapid escape of the moisture. At the same time temperatures must be properly limited to prevent degrading of the oil due to excessive temperatures.

I claim as my invention:

A process for dehydrating petroleum oils which contain substantially no low boiling hydrocarbons including the steps of heating the oil to be dehydrated to a temperature not in excess of substantially 200 F., spraying the oil so heated into a zone maintained at sub-atmospheric pressure, said heating step being performed completely without said sub-atmospheric pressure Zone, spreading the sprayed oil into a plurality of films within said zone, whereby the vacuum `is adapted to rupture the iilm surfaces to liberate the moisture, withdrawing the moisture in the form of vapor separately from and out of contact with the oil being dehydrated, and separately withdrawing the oil being dehydrated.

LLOYD L. DAVIS.

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