US2140574A - Process of desalting mineral oil - Google Patents

Description

Dec. 20, 1938 c. s. CERF 2,140,574

PROCESS OF DESALTING MINERAL OIL Filed Aug. 16, 1937 iepara/or 6 flrgsa/f M'rj era/ v free 0/'/ 22 2 Pack sa/f Wafer m P5 Wa/er Wafer I INVENTOR.

Cad/v; 5. Cerf ATTORNEY.

Patented Dec. 20, 1938 UNITED STATES mrsm orrica 11 Claims.

This invention relates to the desalting of mineral oils. The term mineral oil is used herein and in the claims as referring to petroleum hydrocarbons, as ordinarily produced after the petroleum has been largely separated from any attendant emulsion. This invention is not concerned with emulsion-breaking, but with the removal of those inorganic salts, usually sodium chloride, calcium chloride and magnesium chloride, which gasoline manufacturers have found such a problem. For a long time the oil industry was not cognizant of the fact that in adays operation there would be fed into a still, along with the crude petroleum, a mass of inorganic salts which could be readily measured in tons. These materials make their presence known by a high corrosion rate, by spotting of still bottoms, and by erosion. The mineral oilto which attention is directed herein is therefore relatively dry,

emulsion-free, but contains an undesirable salt content, including chlorides.

Prior to the filing of this application, it ha been proposed by the Petroleum Rectifying Co. that mineral oils, of the character dealt with in this application, be desalted by being contacted with water to the end that the salts be dissolved out. To remove the salts efiectually, it was found necessary to re-emulsify the oil. It appears that the salt is held in -the oil, often being surrounded by wax-like bodies which prevent water from gaining access to the salt and removing it by solution. Thereafter, in accordance with the Petroleum Rectifying Co. process, it was necessary to break the petroleum emulsion, thereby including the cost of a de-emulsification step in the desalting operation.

It is generally the broad object of the present invention to provide for the desalting of a mineral oil while obviating emulsification.

Another object of the present invention is to provide a new and novel process for desalting of a mineral oil.

A further object of the present invention is to provide a relatively simple process of low operating cost which can be effectively used to reduce the salt content of a mineral oil to the order of The invention includes other objects and features of advantage, some of which, together with the foregoing, will appear hereinafter wherein the present manner of practicing the process of this invention will be disclosed.

The drawing accompanying and forming a part hereof is a diagrammatic representation of the process of the present invention. v

As I have previously explained, this invention is concerned with a salt-containing mineral. oil which is relatively dry by reason of prior treatment or because it is so produced. I have been able to successfully reduce the salt content in mineral oils containing a small amount of water. For example, upon treatment of an emulsified crude from Section 5, Kern Front, Standard Oil Company of California, I was able to reduce the S. and W. (sediment and water) content from 6% 10 to 1% and to reduce the chlorine content to nil.

Referring, for example, to the operation as diagrammed in the drawing, the incoming oil was passed into the bottom of a tower 6 wherein a bed of mineral flooded with water was mainl5 tained. This mineral is fully disclosed in my co-pencling application Ser. No. 69,225, filed March 16, 1936, and my co-pending application with Conrad Ser. No. 131,198 filed March 16, 1937. The efiluent from the tower 6 was passed through 20 line 1 into a separator 8 wherein excess water was drawn off through line 9. To maintain the minerals water-flooded, in accordance with the teaching of my aforementioned application, water was introduced through line l0 into the base of the 25 tower, as was needed. The oil was introduced into the tower through line I l. The substantially dry oil passing out. from the separator through 9 line 12 was directed into the base of a tower I l filled with crude rock salt. The nearly dry oil 30 was passed upwardly through the rock salt and. water was drained ofi of the rock salt, as it accumulated, through line l6. Outlet I! provided for the drawing oif of substantially dry chloride- 7 free oil. 35

rifled clay. The surfaces of these materials af- 45 I forded by crushing the massive body and screening to suitable size ranges are usually the most desirable as well as the easiest to prepare, but

clay products with or without the additiq'i; of

oxides may be formed into pellets before or during 50 burning and such shaped materials are included in references to fraginental materials.

The physical structure of the bed proper is a matter of considerable importance. For xam-- ple, a sand bed is of such fine mesh that the chanemulsion through them. If the water is forced out, the grains become oil wet and nonfunctional for this purpose.

I have found that a bed of the fineness of sand can not be kept water-filled if any considerable quantity of emulsion is to be passed through it.

To keep the bed water-filled and also conductive to emulsion, the channels must be wide enough to permit the emulsion to pass the water inside the channels.

It is true that if any emulsion is resolved in the bed there will be a supply of water produced by the resolution, and if the water percentage is large and' the channels are sufliciently open this supply might be enough to keep the bed water'- wet. However, a relatively dry emulsion or oil will displace the water from a sand bed and cause it to become oil wet. I therefore flood the bed and keep it flooded, whether by means of the resolution water or by means of an added water supply.

In accordance with this invention I do not use material as fine as beach sand since that is not suitable. Instead I employ material of a size such that, when a bed thereof is flooded with water, the integrity of the water body filling the interstitial space is maintained. With particles the size of beach sand, this cannot be secured, oil fills the interstices, the solid material becomes oil wet and useless.

I prefer to use relatively coarse material and I have successfully used material wherein the sizes were between and of an inch. With different materials the coarseness can be varied and I do not wish to be limited to the sizes specified since the factor governing the selection as to size is to be sure that the material is always coarse enough so that the water body in the interstices is not displaced by oil and the material oil wetted.

In some cases it is desirable to place a layer of relatively coarse fragments (as for example about inch) on the foraminous support and to impose on this layer successive layers of progressively smaller fragments (as for example inch, M; inch, inchand 5 inch). The finest material should be appreciably coarser than. ordinary V sand in any case, and always coarse enough to ensure maintenance of the integrity of the water in the interstices. The above gradation is suggestive only and it is possible to make the entire bed of fragments of substantially one size, but for reasons which will appear a bed so constructed will have a reduced throughput. Successful results have been secured with a bed of particles of sizes between and of an inch.

In order to resolve the emulsion it is passed upwardly through this fragmental bed, but before the emulsion stream is introduced the vessel should be filled with water to a level sufiiciently high to cover the mineral. It is not suiflcient to merely wet the material with water as the oil phase of many emulsions will displace a water fllm if allowed to remain in contact with it, the effect of mass action reversing the normal selectivity of the solid surface. Once oil wet, the solid surface is thereafter inactive until it has been 2,140,574 nels between the sand grains are extremely narsubjected to a'cleaning process. I therefore introduce water, or material carrying a large percentage of water as an easily resolved emulsion, in advance, in quantity suflicient to completely submerge the mineral, and maintain this aqueous submergence at all times, both while the treatment is in progress and during any intermission between treatments.

The water liberated by the resolution of emulsion remains in part suspended in the oil and in part joins the initial water body, which overflows to a corresponding degree and keeps the vessel filled with water. It is necessary to bear in mind in this connection that if the channels through the mineral body be too narrow, or if the emulsion be too viscous for the width of the channels, the water liberated by resolution may remain completely suspended in the oil phase. In such case a gradual entrainment of the original water body may result, by which it will be in part or entirely carried into the overflow and replaced by oil, and to just that extent the bed will becomenonfunctional.

If this tendency should manifest itself there are three remedies available: (1) to reduce the velocity by lowering the throughput or by rebuilding the bed with larger fragments to afford wider channels; (2) to reduce the viscosity of the emulsion, as by predilution or heating; (3) to feed water continuously while feeding emulsion.

The choice between these alternatives for maintaining the integrity of the water body will depend on several conditions. First, resolution is usually accelerated by heating, and to such degree that it is economical and profitable to heat all except'the lightest emulsions. It is therefore usually the case that all the heat which the emulsion will tolerate is already being applied, so that a further heating effect is not available. The maximum permissible temperature is in all cases below the boiling point of water and, unless a condensing system is provided, is below the temperature at which appreciable vaporization losses are incurred.

Resolution is also accelerated by increase in the velocity of emulsion flowthrough the chan nels between the fragments, the limit to this increase being the point where turbulence sets in and tends to produce reemulsification. The acceleration of resolution with increasing velocity follows from the nature of the treatment, the effect of resolution being produced by the actual contact of the dispersed water particles with the water-wet solid surfaces. These particles, dispersed and suspended in the oil phase, arebrought into such contact by their inertia, which causes them to move in straight lines out of the narrow streams of oil asthese streams are deflected from straight lines in passing through tortuous channels. Such an inertia effect is afunction of velocity and while no numerical limits can be set, because of the extreme diversity in particle size, gravity difference and fluid friction, it will be found with any given emulsion that the rate of resolution at very low velocities is extremely small, that the rate increases rapidlyas the velocity increases, and that resolution ceases when the velocity of turbulence is reached.

Widening the channels by the use of larger fragments reduces velocity for any given throughput rate and therefore reduces the tendency toward entrainment of water. However, it also reduces the rate of resolution and is equivalent to or requires a reduction of throughput. This is intrinsically undesirable although in some cases it 75 ing a high vapor pressure.

is useful to reduce ebullition of gas from oils havin velocity. It may be said that the addition of water will seldom be required if the emulsion under treatment contains a large proportion of water. 1

The purpose served in using progressively smaller fragments in the upper layers of the mineral bed is to increase the velocity asthe emulsion is progressively resolved. Resolution consists es sentially in agglomerating fine water particles into larger drops, and as this efiect progresses the number of particles suspended in the oil phase becomes smaller and their spacing greater, requiring an increased inertia effect to bring a unit number of particles into contact with the solid surfaces. The same effect may be produced, though in a less desirable manner, by progres sively decreasing the cross sectional area of the bed in the direction of flow, thus accelerating the flow of the emulsion stream as a whole.

In no case should the channels through the bed be narrow enough or the velocity of the liquid high enough to cause the mineral to be lifted from its position or brought into any degree of suspension to any substantial extent. In order to produce the desired effect of resolution without loss of mineral agent and without oil wetting the agent the mineral bed should be fixed and permanent in position.

As was previously stated, the S. and W. content of the incoming mineral oil was 6%. That passing out through line I! carried only 1%. The incoming oil contained 0.04% of ash but this was reduced in the oil passing out through line I! to 0.026%. The oil passing through line l2 contained only 3% S. and W. while the ash content had been reduced to 0.033%. The treatment in only the mineral bed was effective to reduce the chlorine content to zero, but an appreciable calcium and sodium oxide content still remained in the oil, amounting to 12.5% on the basis of ash.

Passage through the rock salt reduced the sodium oxide content to zero.

In a similar operation, treating a crude oil for the Lion Oil Company of Arkansas, the oil in its wet condition contained0.0097% sodium chloride. The oil passing through line 12 had a salt content of 0.00594%, while that passing out of line H was reduced to 0.001451%. The other salts present of a deleterious nature were similarly reduced.

I have also been able to successfully desalt the oils utilizing rock salt alone, and upon the aforementioned oil from the Lion Oil Company the same wet oil was introduced through line l2, without previous treatment by the mineral. Passage through the rock salt bed alone reduced the salt content to 0.00105% and the other salts were likewise reduced.

The treatment accorded the oil in the waterfiooded mineral bed, I have determined upon study in glass, is such that although normally one would expect an emulsion to re-form, such is not apparently the case because of the presence of the mineral which, as I explain in my co-pending application, is effective to resolve a petroleum emulsion. Therefore, I can successfully contact the dry oil with water under such conditions of This objection does flow that ordinarily a petroleum emulsion would re-form. However, because of the presence of the water-flooded mineral, emulsion formation does not occur and instead the oil is so agitated and contacted with the water, scrubbed with the water, that sodium chloride and other watersoluble salts therein are effectively eliminated, particularly the chloride content.

I have successfully operated the mineral bed with water from which chlorides have been eliminated, and also with aconcentrated brine.

The action in this respect is hard to explain,

because I have secured successful results with both treatments. Possibly different explanations apply in each instance. While the preferred process is that disclosed, i. e., using both the water-flooded mineral bed and the rock salt column, either can be used, and I have successfully desalted oils using the water-flooded mineral bed and utilizing the rock salt tower separately. In place of rock salt, any other inorganic material of a water-soluble and highly ionizable nature can be employed.

I claim:

1. A process for desalting a substantially dry emulsion free mineral oil comprising passing said substantially dry emulsion free oil upwardly through a stationary bed of rock salt while maintaining said bed dry.

2. A process for desaltinga substantially dry emulsion free mineral oil containing only about 1% of water comprising passing said oil in the presence of only said 1% of water upwardly through a stationary bed of rock salt and-draining separated water off said bed.

3. A process for desalting a substantially dry emulsion free mineral oil comprising passing said substantially dry emulsion free oil upwardly through a substantially dry stationary mass of salt crystals, and draining separated water off adjacent the bottom of said mass.

4. A process for desalting a mineral 011 commaintained flooded with water, separating out free water to provide dry emulsion free oil and prising passing said oil through a mineral bed then passing the dry emulsion free oil through i a substantially dry mass of salt crystals.

5. A process for desalting a mineral oil comprising contacting the oil with water under conditions normally tending to emulsion formation but in the presence of a material effective to resolve an emulsionof said oil and water, and separating the oil from said water to provide substantially dry emulsion free oil and passing the so water-treated substantially dry emulsion free oil through a dry salt bed.

6. A process for desalting a mineral oil comprising contacting the oil with water carrying a relatively high salt concentration under conditions normally tending to emulsion formation but in the presence of a material effective to resolve an emulsion of said oil and water, and separating the oil from said water to provide substantially dry emulsion free oil and passing the so water-treated substantially dry emulsion free oilthrough a dry salt bed.

7. A process for reducing the salt content of a substantially dry emulsion free mineral oil to the order of 0.001% comprising contacting said oil containing an undesirably high-salt content with a relatively dry mass of an inorganic watersoluble highly ionizable material e. g. sodium chloride, removing said oil from the material and separating from said material any water liberated from said oil.

8. A process for reducing the salt content of a substantially dry emulsion free mineral oil .to the order of 0.001% comprising contacting said oil containing an undesirably high salt content with a relatively dry mass of an inorganic watersoluble highly ionizable material e. g. sodium chloride.

9. A process for desalting mineral oil comprising passing substantially waterand emulsionfree mineral oil through a substantially dry mass of rock salt.

10. .A method of treating an oil-water emulsion to rid the oil of emulsion and salt comprising treating the emulsion by passing said emulsion upwardly through 'a porous bed of fragm'ental,

solid, insoluble material in which the fragments are so large that the integrity of a water body filling the interstitial space in said bed is maintainable, continuously maintaining interstitial space in said bed substantially filled with water and the bed water flooded, permitting the sotreated emulsion to stand and separating ofi water to provide substantially dry emulsion-free oil, passing said substantially dry emulsion-free oil through a substantially dry rocl: salt mass, and maintaining said rock salt mass substantia1 ly-dry.

11. A method 'of treating an'oil-water emulfilling the interstitial space in said bed is maintainable, the fragments comprising said beds including those of a size between and 1%;

of an inch, continuously maintaining interstitial space in said bed substantially filled with water and the bed water flooded, permitting the so treated emulsion to stand and separating off water to provide substantially dry emulsion-free oil, passing said substantially dry emulsion-free oil through a substantially dry rock salt mass, and maintaining said rock salt'mass substantial- 1y dry.

CEDRIC S. CERF.

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