US1958310A - Process for refining petroleum crude oil - Google Patents

Description

y 1934. M. c. MCDONALD 58,310

PROCESS FOR REFINING PETROLEUM CRUDE OIL Filed June 27. 1931 iNVENTOR; MEI-'11 E. MBDDTLElIi ATTORNEYS.

Patented May 8, 1934 UNITED STATES PROCESS FOR REFINING PETROLEUIVI CRUDE OIL Mei-t0. McDonald, Coffeyville, Kans.

Application June 27,

4 Claims.

This invention relates to improvements in processes for treating petroleum oils for the separation therefrom of amorphous wax, undea sirable hydrocarbons, coloring matter, sulphur compounds, and undesirable odors.

The primary object of this invention-is the provision of an improved process for the treatment pf petroleum oils, for the dewaxing and purification thereof, embodying improvements over the process set forth in prior U. S. Patent 141,791,329, dated Feb. 3, 1931, and granted to Horace B. Seltzer and Mert C. McDonald, in the specific treatment of the hydrocarbon product at a materially lower working temperature for m the production of a bright stock of good color and sweet odor having a pour test of from F. to 25 F.

A further object of this invention is the provision of an improved method for the efiicient chilling of hydrocarbon oils preparatory to treatment with sulphuric acid for purification.

A further object of this invention is the provision of an improved process for the treatment of petroleum oils, comprising generally the invention of U. S. Patent #1391329, heretofore referred to but differentiating thereover, in part,

by the chilling treatment of the oils with sulphuric acid at lower temperatures than set forth in said patent and under conditions which will prevent the absorption of moisture during treatment.

Other objects and advantages of this invention will be apparent during the course of the following detailed description.

r In the accompanying drawing, forming a part of this specification, similar reference characters designate corresponding parts throughout the View.

The view generally designates, in diagrammatic manner, the apparatus which is preferably used for the dewaxing and purification treatment of petroleum oils.

The apparatus consists of a storage tank A for receiving the crude petroleum oil, with which a discharge 1%ne is connected. A pump 11 45 in the line 1 pumps the oil through the line 10 and into atank 11. A main still 12 is provided, preferably of the horizontal tank type, into which the crude petroleum oil flows through a reflux tower 14 which has connec-. 50 tions 15 with the tank 11 thereabove, and which 1931, Serial No. 547,413

at its lower end has '-a conduit connection 18 with the still 12. If desired, the tower 14 may be provided with ordinary rectification or refiux bafiles. A vapor line 20 leading from the top of the still extends into the intermediate portion of the tower 14, and the vapors passing through the tower 14 and into the tank 11 will distill oil or vaporize from 5 to 10% of the initial stock, for the purpose of dehydration.

In the still 12 the petroleum oil is heated to substantially 250 F. and is then transferred to a cooler 21 including a casing 22 with a cooling coil 23 therein. The cooling coil 23 is connected by a conduit 24 with the lower portion of one end of the still 12, and' in this conduit 24 is disposed a pump 25 for pumping the heated oil through the coil 23. From the coil 23 the oil is pumped into a combination chiller and treating apparatus which includes a tank 31, of any approved metal, shaped with an upper cylindrical portion and a lower funnel-shaped bottom 33. Throughout its major height the tank 31 is surrounded with a jacket 34 spaced from the walls of the tank 31 to define a brine receiving jacket space 35 wherein brine is disposed, to surround the tank 31 below the bottom and throughout its major height. The tank 31 and its surrounding jacket 34 are entirely insulated externally, pref- 1 erably by means of cork 38.

.The discharge end .of the coil 23 enters the upper end of the tank 31 at 39, for depositing the pre-cooled petroleum oil into the compartment or chamber 40. r

The center of the tank bottom 33 has a discharge pipe or conduit 42 through which the sludge as well as the purified desirable oils, are withdrawn.

Sulphuric acid is introduced into the upper part of the tank through a conduit 45, and together with the petroleum oil is mixed within the chamber or compartment by an improved mechanical agitator. The latter includes a main shaft 43 extending axially through the tank. At its lower end it has a step bearing 44 in the tank upon the bottom 33; the same being supported by a suitable spider as shown in the drawing. The shaft 43 extends vertically through the tank and exits at the top therefrom. It has a main agitator 48 in the cylindrical portion of the tank, which consists of a plurality of paddles adapted to perform the main mixing action. In the conical space at the bottom of the tank there is a small agitating blade 49, in the shape of an ordinary propeller which accomplishes the flnal mixing of the petroleum and sulphuric acid.

Means is provided to drive the shaft 43 which consists of a motor 50 having a shaft 51 connected by bevel gearing 52 with the upper end of the shaft 43.

Brine cooling apparatus is provided for maintaining the brine in the space 35 at a predetermined temperature. This apparatus includes a cooling tank 55 having inlet and discharge conduits 56 and 57 for the cooling medium. A brine cooling coil 58 is disposed within the tank 55, having a discharge conduit 59 connected with the lower portion of the brine jacket space 35 for discharging the cold brine into the space 35. A brine discharge conduit 60 connects with the upper portion of the tank brine space 35, having a discharge end connected in the preferably insulated brine storage tank 61. The latter has a conduit connection 62 with the inlet end of the brine cooling coil 58, and in this conduit 62 is disposed a pump 63 for circulating the brine.

A conventional thermometer 65 may be provided on the apparatus 30 for designating the temperature of the contents within the compartment 40.

It is an important feature of the invention that the mixing of the sulphuric acid and petroleum oil shall take place within a comparatively airtight compartment. To that end the tank 31 is entirely enclosed during treatment, although it may have a man-hole construction 65 with a suitable cover 66 to seal over the same. At times it may be desirable to vent a small quantity of air into the compartment 40 to discharge vapor for reducing superatmospheric pressure in the compartment 40. To that end a vent conduit 67 is connected with the top of the tank having a weight controlled vent valve '70 communicating therewith which is operable responsive to pressures within the tank for the escape of air or gas for relieving such pressure. The conduit 67 may also have a low pressure valve 71, of the weight operated variety, which will open responsive to certain sub-atmospheric pressures within the tank to vent a small quantity of air into 'the tank. These vent valves prevent the rupture or collapsing of the tank under unusual circumstances.

The discharge line 42 has a branch connection for conveying the lighter oil constituents, afterdewaxing and purification, to any suitable location. The line 42 also enters the top of a sludge tank 77. This tank 77 has an external jacket 78 which provides a steam space 80 surrounding the lower portion of the tank for elevating the temperature of the sludge as it is received from the mixing apparatus 30. Suitable inlet and outlet connections 81 and 82 are provided, with valve controls for regulating the passage of steam through the jacket space 80. Stirring apparatus 85 is provided in the sludge tank 77 which is suitably operated by motor means 87 from externally of the tank. A conduit 90 connects with the upper portion of the tank 77 for conveying wax oil into a suitable storage tank 91; the line 90 having a pump 92 therein. The lower portion of the sludge tank 77 has a sludge line 93 connected therewith which is provided with a pump 94 therein for pumping the sludge to a suitable burner 97 beneath thestill 12, so that the sludge residue may be used as fuel for heating the still 12.

As before stated, the crude oil is charged into the still, after having distilled off from 5 to 10% of the light hydrocarbons, in order to insure that the oil to be later purified will be free of moisture. This vapor distillate passes off from the tank 11 through the line 100. The oil remaining in the still has a temperature of approximately 250 F. and is then conveyed through a cooling coil 23, wherein the temperature is gradually reduced to approximately 80 F. at the time that the same passes through the conduit 39 into the top of the compartment 40.

It is highly important in the improved process to prevent shock chilling. This for the reason that if the oil to be purified is chilled too rapidly it will requirea higher percentage of sulphuric acid for purification. I have found that it will require as much as 25 pounds more sulphuric acid per barrel of oil to be purified if the latter is subject to shock chilling instead of a gradual chilling. The oil to be purified as it enters the compartment 40 of the treating apparatus 30 is protected from exposure to the atmosphere, since the compartment 40 is air-tight. This prevents absorption of moisture from the atmosphere. Moisture will dilute sulphuric acid, generating heat and generally hindering the chilling for low temperature purification treatment.

The chilling apparatus 30 preferably has a motor 50 which is of a variable speed type in order that the agitator may be driven at a moderate speed while the oil is being cooled preparatory to sulphuric acid treatment, and later speeded up to increase the agitation while the purification treatment of the oil with concentrated sulphuric acid is being carried out.

The temperature at which the acid treatment of the oil in the tank 31 is carried out preferably ranges between -30 F. and 25 F. I have found these to be the most practical working temperature extremes in order to secure a purified oil which will respond to a desired flow test.

Assuming that the tank 31 is charged with 1000 barrels of mixed base crude oils that have substantially a gravity of 32 A. P. I. Assuming the same to have just entered the tank 31 and being at a temperature of 80 F. the variable speed motor 50 is set in operation, and the agitators 48 and 49 run at moderate speed. The brine is circulated through the jacket surroundingthe jacket 31, by the means above described, and precaution is taken to see that the temperature of the brine refrigerant is maintained within 15 F. to 20 F. of the actual temperature of the oil being chilled in the tank 31. This precaution is taken, at least until the oil in the tank 31 has reached a freezing temperature after which it is chilled down rapidly. This precaution'will prevent the shock chilling above referred to. The lowering of the temperature of the 1000 barrels of selected oil in the tank 31 will require approximately 12 hours. When the zero temperature, or the required low temperature of the oil in the tank 31 has been reached, the variable speed motor 50 is increased to speed up the agitators 48 and 49,

and the concentrated sulphuric acid is then bottom of the tank compartment 40 will form apor the like.

proximately 21% of the total charge. In the example above given this will comprise about 210 barrels. In this 210 barrels of sludge there are associated petrolatum, sulphur compounds, coloring matter, and other undesirable constituents and characteristics, such as the heavier ingredients and the odor attendant therewith. Approximately six hours after the agitators have been stopped, the sludge will represent approximately 220 barrels of the contents and may be readily drawn oil into the tank 77. The petrolatum will represent approximately barrels of the sludge residue thus obtained and may readily be separated from the remaining constituents of the sludge by agitation and mixing at a temperature of approximately 125 F. The latter elevation of temperature is of course obtained by passing steam through the jacket 78. The petrolatum is then conveyed into the wax tank 91 to be used as pressure still cracking stock, or for the removal of other ingredients and by-products. The residue sludge may be pumped through the line 93 and used as fuel for heating the still 12, as above mentioned.

After the sludge has been drawn ofi from the tank 31 there will remain substantially 780 barrels of dewaxed and purified petroleum oil. This is now discharged from the apparatus through the line and conveyed to a suitable agitator wherein the said oil is neutralized under temperatures of substantially 120 F. The neutralization treatment is carried out by agitating the oil and mixing therewith a suitable neutralizing agent such as fullers earth, soda ash, ammonia, In event fullers earth is used it will be required in the proportion of 15 pounds per barrel of oil, and subsequent to proper mixing and agitation the oil will be passed through a filter press for removing the neutralizing agent from the oil, which of course contains the acid which it has absorbed.

After the neutralizing treatment the residue oil may be distilled for removing the difierent hydrocarbons. ofi' will be commercially finished gasoline; the second group commercially finished kerosene; the third group commercially finished gas oil; the fourth group lubricating light motor oil. The residue heavier group of hydrocarbons, known as heavy commercial finished bright stock will have a very low pour test. Generally I have found that the cloud test on the dewaxed and purified petroleum oil will be approximately zero and the -color approximately 4 N. P. A. The distillation when carried out will result in approximately 20% gasoline; approximately 20% kerosene; ap proximately 15% gas oil; approximately 10% paraifin oil; approximately 15% low pour test light'motor oil, and the residue 20% of heavy bright stock product will have approximately a 160 to 165 viscosity at 210 F. with a pour test of from 5 F. to 15 F., abright color at 0 F., and a gravity of 5 N. P. A.

The principal advantage of the process and apparatus is the flexibility of operation which will enable a refiner to operate his plant according to the needs of a shifting market so far as pour tests of the lubricatting oils and bright stock are concerned. The public demands a much lower pour test oil in winter than in summer, and of course it is much less expensive to produce a bright stock with a pour test of 15 F. to 30 F. than to produce a bright stock ranging between 07 F. and 15 F. pour test.

To illustrate that various results are obtained The first group which may be distilled by using various temperatures, as well as by using difierent diluted oils after distilling ofi substantially 8% of light hydrocarbons, I have prepared a number of examples, which are as follows:- 80

Viscosity at 210 F. of

above 48 48 48 48 48 48 Gravity of above (A. -l 32 32 32 32 32 32 Temperature of oil (18- waxed 24 F. 14 F5 F 0 F5 20 F. 30 F.- Lbs. 98.8% sulphuric acid per bbl 40 38 36 31 23 20 sludge and wax loss... 28 27 24 21 18 17 Lbs. XXF 200-mesh fullers earth per bbl... l5 15 15 l5 l5 15 Color of treated and dewaxed oil (N. P. A).. -3% 3% 3% 4 4 4% Cloud test of lie-waxed oil (degrees F.) 1S -8 0 8 18 28 1;, light vapor hydrocarbous distilled 0a s2 52 52 52 a2 52 lubricant vapor hydrocarbons distilled ofi .V 26 27 27 20 26 28 Pour test of last above (degrees F.) 0 5 15 20 25 30/35 )5 bright stock remaining in bottom of still. 22 21 21 22 22 20 Viscosity at 210 F. of

last above 100 162 160 163 163 173 lour test of last above (degrees F.) -5/0 0/5 5/10 10/15 10/25 30/35 Bright test of last above (degrees F.) -l0 20 0 8 22 32 Cloud test of last above (degrees F.) 22 2 6 20 so Color of last above (N. I. A.) 5% 5% 5% 5% 5% 6 Viscosity at 210 F. of

above 96 78 51 49 43 Gravity of above (A. P. I. 28 29.6 30.6 31. 5 32.8 Temperature of oil dewaxed 10 F 10 F. 14 F. 6 F. 8 F. Lbs. 08.8% sulphu acid per bbl 34 40 38 34 40 sludge and wax loss 28 30 26 22 25 Lbs. XXF 200-mesh fullcrs earth per bbl 20 15 l5 l5 15 Color of treated and dewaxed oil (N. P. A.). 4% 2n 2% 3% 3% Color test of de-waxed oil (degrees F.) 16 6 6 16 0 light vapor hydrocarbons distilled off 37 50 55 54 56 )1; lubricant vapor hydrocarbons distilled 06...- 38 14 20 31 19 Your test of last above (degrees F.) 20/25 10/15 10/15 25 10 II, brightstock reluai ng in bottom of still 25 34 25 15 25 Viscosity at 210 F. of

last above 166 243 160 189 159 Your test 01 last above (degrees F.) 15/20 15/20 10/15 15/20 5/10 llright test of last above (degrees F.) l0 0 0 8 0 Cloud lost of lost above (degrees F.) 8 2 2 6 -2 (olor of last above (N. l. A.) 5% 5% 5 6 6 It will readily be understood that the above examples are not to be construed as a hmltation upon my improved process, for 11: 1s a fact that each particular treating temperature, and the characteristics of the crude 01]. require analysis for determining the amount of acid necessary. I do treat petroleum crude 0118 for dewaxmg and purification at temperatures below those previously used for the ob ect of producing commercially finished products, and motor 011s with a 1 low pour test.

Various changes in the steps of the method herein outlined, as well as changes to the arrangement of parts of the appara us, may be made to the method and apparatus as herem described, without departing from the spirit of the invention or the scope of the claims.

I claim:

1. Those steps in the method of treating petroleum oils containing amorphous wax, which consist in gradually reducing the temperature of the selected oil to between F. and 5 F.

with moderate agitation, treating the oil with the atmosphere, until the amorphous wax therein is precipitated. Y

3. The process of producing from a residue of crude oil a bright stock oil having a pour test between 0 F. and 25 F. which includes dehydrating and topping the crude oil, chilling the dehydrated and topped oil to an effective dewaxing temperature, subjecting the dehydrated chilled oil to a treatment with concentrated sulphuric acid while excluding air and moisture from the atmosphere therefrom until substantially all wax is precipitated, separating the wax from the treated residue, and neutralizing the treated residue.

4. The steps in the process of treating petroleum crude oil which consist in gradually chilling the crude oil in a chamber to an efiective dewaxing temperature, subjecting the oil to a treatment while in said chamber with concentrated sulphuric acid until substantially all wax has precipitated from the crude oil, and drawing ofi the sludge from the treated oil while maintaining the oil out of contact with the atmosphere from the beginning of chilling until substantially all wax is precipitated.

MERT C. McDONALD.

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