US2420185A - Process for producing asphaltic materials - Google Patents

Description

May 6, 1947. H. E. MEssMoRE PROCESS FOR PRODUCING ASPHALTIC MATERIALS Filed Jan lINVENTOR.

ATTORNEYS.

HAROLD E. MESSMORE #ww-fn, r W

Patented May 6, 1947 PROCESS FR PROIUCING ASPHALTIC MATERIALS Harold E. Messmore, Bartlesville, Okla., assigner to Phillips Petroleum Company, a corporation of Delaware Application January 4, 1943, Serial No. 471,299

(Cl. ISG- 74) 1 Claim.

This invention relates to the manufacture of asphalt stocks or blended asphalt containing oils from asphaltic or mixed base crude oils by the phenomenon known as retrograde vaporization. ln the manufacture of certain types of asphalts, asphalt stocks and certain blended asphaltic oils, such as cut-back road oils; straight run petroleum residual stocks are used.

Heretofore in the preparation of these stocks the asphaltic base or mixed-base crude oil was distilled in conventional apparatus for removal of gasoline, kerosene, and distillates, by the use of iire and steam in a shell type still. This latter o; ration was slow and tedious in that oils of h; her boiling points and lower Volatilities were ciiiicult to remove. Overheating of the asphaltic residue was not uncommon.

The introduction of continuous processes for the refining of petroleum along with the advent of the vacuum still resulted in important advancements in vthe technique of asphalt making. The use of the vacuum still permitted the removal of the heavy oil fractions at much reduced temperatures and therefore reduced the possibility ot cracking of the residue. Steam distillation in the vacuum still was a further advance in the art in that the asphaltic residues could be stripped of the relatively high boiling waxy and oily materials at still lower temperatures. For many' purposes asp-halts and asphalt stocks must not contain appreciable cracked material since stocks containing such frequently possess undesirable properties as evidenced by failure to pass specilication tests, such as, for example, penetration, ductility, spot test, etc.

"he use of steam distillation in conjunction with a vacuum usually overcomes the aforementioned difficulty. Vacuum stills, however, consume excessively large amounts of steam, the steam consumption being directly proportional to the vacuum maintained.

I have found that heavy, high boiling hydrocarbons of a parafiinic and/or less. asphaltic nature may be separated from the more asphaltic materials at relatively low temperatures by application of the principles of retrograde VaporiZation and condensation. By the application Vol' these retrograde principles asphalt-.ic stocks may be prepared at such low temperatures as 50 to. 506 or even lower, the lower limit being apparently dependent upon the melting point and duid properties of the asphalt. By my process there is no. overheating with resultant cracking of the hydrocarbons, since the separation may be efficiently and Completely carried out at temperatures below which cracking occurs.

object of this invention is to provide a process for the manufacture` of asphalt and asphalt containing stocks from certain crude oils.

Another object of this invention is to provide a process for the manufacture of asphalt and asphalt containing stocks at sufficiently low temperatures as to avoid the detrimental effects of cracking.

Still another object of this invention is to provide a continuous process for making essentially any type of asphaltic stock at a Suiciently low temperature as to avoid the detrimental elects of high temperature processes.

Still other objects and advantages will be apparent to those skilled in the art from a careful` study of the following detailed disclosure.

The figure is a diagrammatic illustration of one form of apparatus in which my process may be carried out. Y

Referring now to the ligure, numeral l represents a storage tank or other source of crude oil suitable for use in my process. Gas from whatever source enters through line il, is raised to pressure by pump l2 on passage to vaporizer 4. The pressure maintained in this vaporizer, 9,050-i90 pounds per square inch, for example, is controlled by the back pressure regulator 5 in the vapor line Asphalt containing crude oil stock from source l passes through exchanger 2 and is pumped by pump 3 into vaporizer al against the above mentioned gas pressure. The gas from line l l and the crude oil from source l pass through the vaporizer, preferably in countercurrent relation. This vaporizer may be essentially type ci Vessel in which intimate contact of gas and oil may be eiected and which, of course, is sufficiently heavy to withstand the operating pressures. I have found that a bubble plate column having a few plates, say live or six, for example, is satisfactory.

The resulting vapor phase from the vaporizer 4 passes through vapor line 5, back pressure regulator t, exchanger l and into condensate separator S. The pressure maintained in this condensate separator is determined by the setting of the back pressure regulator 9 in the wet gas line Ill. Retrograde condensation, supplemented by normal condensation resulting from cooling in exchanger l and/or the Joule-Thompson effect through expansion at the back pressure regulator E, takes place in the condensate recovery tank. The amount of condensate recovered and its nature depends to a considerable extent upon the pressure maintained in this recovery tank. The condensate collects in the bottom of said recovery tank and is removed therefrom by levcl controller valve 35, and passes through line 35 into flash chamber 3i. From this chamber ilashed gases issue through line 33 for disposal as desired. The residual condensate is withdrawn through level controller valve dll and line 4| and passed to intermediate storage, not shown, to be treated further as desired. Back pressure regulator 39 in gas line 38 controls the pressure in this flash chamber.

The' residual' asphalt containing liquid from the vaporizer 4 is Withdrawn through level controller valve I3 and passed through exchanger I4 and line l5 into vent tank i6. The pressure on this tank is held at any desired pressure, say 800 to 2000 lbs. per square inch for example, by back pressure regulator l1. from the 9,000-10,000 pounds in vaporizer 4 to say 1000 pounds in this Vent tank, the major portion of the dissolved gases is evolved and separated from the asphaltic stock. During this flashing operation considerable heat is absorbed and in order to prevent congelation or undesirable thickening of the asphaltic stock, exchanger I4 supplies heat thereto. The flashed gases exit through line I8 and may be repressured by pump 33 and recycled into the gas line Il for reuse in the system.

The asphaltic bottoms from the vent tank IS .are removed through level controller valve .and passed through line I9 and heater 2| into 'the blending tank 22. In this vessel from 100 lbs. to 300 pounds pressure per square inch, for example, is maintained. Suicient heat is added by heater 2l to maintain the asphalt in a fluid condition. Upon pressure reduction in this blending tank, as controlled by back pressure regulator 23, additional dissolved gases are ashed and pass upward to be disposed of through vapor line 24. Blending naphtha, such as is used in making cut-back road oils, enters through line 32 and mixes with the asphalt stock in the upper portion of this blending tank. The evolving hydrocarbon gases assist in effecting a mixing or blending of the blending naphtha with the asphalt. Due to the relative viscous nature of asphalt, further blending or mixing may be necessary. Thus the at least partially mixed asphalt stock and naphtha are Withdrawn through level controller valve and passed through line 25 and heater 2l into the gas separator 28 wherein final mixing is carried out along with removal of the remainder of the dissolved gas at atmospheric pressure. The completely mixed product is Withdrawn through level controller valve and passed through line 3l to storage, not shown. The separated gas leaves the separator 28 by way of line 28 for disposal as desired.

The Wet gas leaving condensate separator' 8 through line l0 may be recycled through recycle gas line 42, and pressured by pump 34 for reuse in my system. Or, if desired, the said Wet gas from line I0 may be stripped of its condensible hydrocar-bons as in a high pressure absorption system, which is known in the art, and the resulting high pressure dry gas recycled through said line 42.

By operating according to my process, many types or kinds or asphaltic products may be made. Numerous blending naphthas may be added through blending naphtha line 32 depending upon the iinal blended product desired.

Another embodiment of my invention comprises the making of basic asphaltic stock containing no blending naphtha. In such an operation no blending naphtha is added through line 32 While the asphalt is maintained in a iluid condition in vessel 22 by heating coil 43, and in the final gas separator 28 by heating coil 44. In this operation relatively high melting asphalt is Withdrawn through line 3l. It may be advantageous in this operation to operate vessel 22 at atmospheric pressure to remove completely the dissolved gas and eliminate the necessity for the use of vessel 28.

The type of asphalt stock made by my process may be varied by control of operating conditions,

By the drop in pressure especially those affecting `the vaporizer 4. By increasing the operating temperature thereof higher molecular Weight hydrocarbons may be removed by retrograde vaporization. By increase of the gas-to-oil ratio more nearly complete removal of the desired fractions may be obtained. Higher operating pressures facilitate removal of higher molecular weight compounds. The composition of the high pressure gas is also pertinent to the operation, for example a gas containing methane and 20% propane will remove higher molecular weight hydrocarbons by vaporization than will a gas containing 80% methane and 20% ethane at the same pressure.

As an example of my invention a Mid-Continent crudeioil was contacted at F. with a natural gas in the proportion of 8.086 mols of gas to 1 mol of crude oil. rFhis gas to oil is in the ratio of 5,120 cubic feet to 1 barrel (42 gals.) of oil.

The gas and crude oil of this example have the following compositions:

Gas, Mol Per cent Crude Oil, Mol Per cent Under a contacting pressure of 9,374 pounds per square inch at 120 F., approximately 75% of the C7 and heavier fraction of the crude oil was vaporized. Since the crude oil according to the above given analysis contained 79.8% C1 and heavier, the total fraction of crude oil vaporized was (79.8 .75) +(100--79.8), or 80.0 mol per cent. The factor (100-79.8) or 20.2% of the crude oil was Cs and lighter, and all this material was vaporized.

The residue from this vaporization, constituting 20 mol per cent of the crude oil was a black and viscous asphaltic mass. 'I'his residue was distilled at 580 F. yielding a residue of 61% (39.0% evaporated), which had a specific gravity of 0.916, and viscosities of 299 seconds Saybolt at F. and 832 seconds at 100 F.

In the operation of my invention, essentially any gas or preferably hydrocarbon gas may be used, providing the gas is chemically inert to the oils being treated. The available pressure on the gas is an important factor because of the economics of compression to high pressures. In case fluid from a so-called distillate or condensate type well is available at a high pressure, for example from 1,000 to 6,000 pounds pressure, this fluid may be advantageously used as the contacting gas in the vaporizer 4. By variation of the gas-to-oil ratio as may conveniently be carried out in the countercurrent vaporizer 4, at a given temperature, hydrocarbons up to a given molecular weight or of a given type may be removed by the retrograde vaporization. If a certain amount of gas does not completely vaporze the desired hydrocarbons at a given temperature, additional gas may be passed until such hydrocarbons are removed. In case the asphaltic residue contains relatively low molecular Weight, paramnic material, this may be vaporized at higher temperatures, for example, at 200 to 300 F., or even as high as 400 to 600 F., providing that such high temperatures are not employed as would cause cracking of the asphaltic material. Ordinarily it is not necessary to carry the vaporizer (4) temperature as high as 500 F., which then classes my process as an extraordinarily low temperature asphalt making process.

By employment of one or more high pressure gas streams as recycle gas, compression costs are materially lessened. v

Some asphalt or mixed base crude oils may be treated according to my process at pressures considerably lower than the aforegiven 9,000 to 10,000 pounds pressure and yet vaporiZe essentially all materials excepting the asphaltic. This operation may be carried out at lower pressures, for example, 5000 to 6000 pounds per square inch, but at temperatures considerably above that given in the included example. At temperatures as high as 400 to 500 F., and at relatively high gas-tooil ratios, my process may be practiced for the preparation of good quality asphalts and asphaltic stocks.

The pressure maintained in vent tank I8 may best be determined by trial since the pressure should be suiciently low to permit flashing off oi appreciable quantities of the dissolved hydrocarbon gas and yet high enough that the flashed gases may be economically recompressed for recycling into the retrograde vaporizer 4. From 1000 to 2000 pounds pressures on this vent tank have been found to be satisfactory under many conditions.

The asphaltic oil containing considerable amounts of dissolved hydrocarbon gas at the above said vent tank (i6) pressure is vented of much of its remaining dissolved hydrocarbon gas on passage through valve 20 into blending tank or vessel 22. The pressure on this blending tank 22 may be ordinarily maintained at about atmospheric or some above. However, the blending of the asphalt with the blending naphtha must be carried out at a pressure less than the retrograde vaporization pressure so that the hydrocarbon' gas will not remove the added blending naphtha by retrograde vaporization. The minimum pressure at which retrograde vaporization occurs, of course, varies with temperature, coinposition of the hydrocarbon gas, etc., so that definite and exact pressures cannot be given. However, under normal operating conditions, the pressure on this blend tank may safely be held at any value below approximately 600 to 700 pounds without fear of loss of blending naphtha by retrograde vaporization into the evolving hydrocarbon gas. Normally this blending tank pressure is maintained around atmospheric to say 100 pounds. The evolving hydrocarbon gas frequently furnishes sufficient agitation for complete and thorough mixing' of the asphalt with the blending naphtha; however, if necessary, additional means for mixing may be installed in the bottom of vessel 22, vessel 28 or in line 28 connecting vessel 22 with vessel 28.

Temperatures at various stages of the process need not ordinarily be carried especially high, essentially the only requirement being the maintenance of sufficient temperature to impart uidity to the asphaltic stock for transfer purposes and to prevent chilling due to the internal evaporation of the dissolved hydrocarbon gas during the pressure reduction steps. However, the temperature maintained in the vaporizer 4, discussed heretofore, is dependent upon the pressure carried therein and the extent of separation by retrograde vaporization desired.

The vaporized non-asphaltic materials are separated from the hydrocarbon gas in one or more steps involving successive pressure reductions in one or more vessels 8. That is, the said non-asphaltic materials vaporized in vaporizer 4 may be fractionally condensed in a series of retrograde condension steps, the nal gaseous efuent being stripped of its condensible vcontents by essentially any conventional method, as desired.

Pressures, temperature, gas-to-oil ratio in the retrograde vaporizer, number of vent steps as in vent tank i8, etc., may be varied to suit the conditions most suitable to smooth and economic operation, taking into consideration the said economies of the operation, the asphalt containing stock available, the hydrocarbon gas available and the asphaltic product desired to be manufactured, and yet remain Within the intended spirit and scope of my invention.

I claim:

A continuous process for preparing a blended asphaltic oil from a crude oil stock containing asphaltic and non-asphaltic materials comprising contacting said oils countercurrently with a continuous stream of natural gas at a pressure between approximately 9,000 and 10,000 pounds per square inch and at a temperature of approximately F. whereby the non-asphaltic materials are vaporized into the natural gas and the asphalt with natural gas dissolved therein remains as a liquid phase; removing the gaseous phase and the liquid asphaltic phase; separating the natural gas from the non-asphaltic materials in said gaseous phase and recycling the said separated gas into the original contacting step; reducing the pressure on the liquid asphaltic phase containing dissolved natural gas to release at least a portion of said dissolved natural gas; further reducing the pressure on said liquid asphaltic phase to a pressure below approximately 1,000 pounds per square inch to release a further quantity of said dissolved natural gas and simultaneously adding a blending naphtha; still further reducing and essentially lto atmospheric the pressure on the blended liquid asphaltic oil to release the remaining dissolved natural gas; compressing to approximately 9,000 to 10,000 pounds pressure per square inch the natural gas first separated from the liquid asphaltic phase and recycling the compressed gas into the original contacting step.

HAROLD E. MESSMORE.

REFERENCES CITED The following-references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,944,491 Bray Jan. 23, 1934 1,948,296 Haylett Feb. 20, 1934 1,988,715 Bray et al Jan. 22, 1935 2,151,165 Slatineau Mar. 21, 1939 2,166,160 King July 18, 1939 2,188,012 Pilat et al Jan. 23, 1940 2,220,092 Evering et al Nov. 5, 1940 2,249,885 Carney July 22, 1941 2,188,018 Pilat et al Jan. 23, 1940 OTHER REFERENCES Ind. and Eng. Chemistry, vol. 29, (1937) pp. 1072-1077, article by KatZ-Hachmuth.

Ind. and Eng. Chemistry, vol. 32, (1940) pp. 817-827, article by KatZ-Kurata.

Petroleum Technology, Am. Inst. Min. & Met. ngsineers Tech. Paper No. 1269 (Jan. 1941), pp.

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