US2222347A - Process for producing asphalt - Google Patents

Description

Nov. 39, 1940. E. W. GARD ET AL PROCESS FOR PRODUCING ASPHALT Filed July 20,- 1937 @a S e R han m 1 7e T, WA A m@ a; Bf .wmhm PQ., mw 5m um 2 QN E 1 FQ: .nl T .5 n@ j, @N @N NN NN w s Nl\ @www Patented Nov. 19, 1940 PATENT orifice PROCESS FOR PRODUCING ASPHALT Earle W. Gard, Palos Verdes Estates, and Blair G. Aldridge, Los Angeles, Calif., assignors to Union Oil Company of California, Los Angeles, Calif., a corporation f California Application `Iuly 20, 1937, Serial No. 154,606

9 Claims.

This invention relates to a process for treating petroleum Oils and in particular, the invention relates to the production of oxidized or air blown asphalt.

Itis an object of our invention t0 provide a simple, efficient and economical process by which petroleum oils may be converted into asphaltic products of desired penetration, melting point,

` ductility and solubility.

It is a further object of our invention to control the various characteristics of penetration, melting point, ductility and solubility of asphalt and to vary them independently and at will.

It is a further Object of our invention to control the oxidation of oil to produce asphalt so as to obtain a uniformly oxidized asphalt.

It is an important object of our invention to control the oxidation of the oil so as to partially oxidize the oil by contacting it with oxygen-containing gas, to accomplish substantially complete use of the oxygen under controlled conditions, to removethe undesirable gaseous and vaporous products of reaction, to prevent oxidation of vapors in the vapor space of the oxidizing still and to prevent formation of carbonaceous and coke-like materials in the still.

It is a further important object of our invention to reduce the time necessary to air-blow asphalt to the desired grade.

Another important object of our' invention is to reduce the distillation during oxidation of desirable oil fractions which impart the desired characteristics to the nal product.

It is a further object of our invention to prevent oxidation in the vapor space of the oxidizing still.

Other objects of our invention will appear from the included description of the preferred embodiment of our process appearing below.

The use of air has been employed for many years and is well known in the art of producing oxidized asphalt. However, in the past, it has been impossible to produce oxidized asphalts of desired melting point, penetr'ation and ductilities which have a high solubility in CS2, CCl4 and 80 gasoline. In these older methods, the penetration, melting point and ductility are not independently variable. If the melting point is increased, the penetration is decreased and the ductility is also decreased. This is due to the fact 'that the methods used cause some of the asphalt to become over-oxidized and part to be under-oxidized and also there is a considerable amount of distillation during the oxidation period. The air passes through the oil in large (Cl. ISG-'74) globules and is not intimately mixed with all of the cil. In .such methods, the rate of oxidation must be fairly slow, otherwise the temperature of the oil will rise too high, with the resultant low yield and poor quality of asphalt. 5

Also, in the manufacture of oxidized asphalt in the conventional spider and shell still, it has been found that the oxygen utilization is very poor and that the spent gases from the still will contain as high as 1'7 to 19% of oxygen showing 10' only a 2 to 4% reduction in the oxygen content of the air. This high oxygen content in the spent gases allows the vapors in the vapor space of the still and the vapor lines to undergo oxidation. This oxidation may carry on at such a rate that the Vapo-r temperatures will suddenly increase, say from 400 F. to as high as '700 or 800 F. This rapid increase in temperature quite often leads to vapor explosions with a resulting rupture of the still or explosion diaphragms built into the l2'() still. Also, when the oxygen content of the wasteA gases is high and oxidation takes place in the vapor space, vwe have found upon inspecting the still after completion of a run that large amounts of carbonaceous materials have been formed in the still and the vapor lines.

We have found, as will appear hereinafter, that by limiting the oxygen content of the waste gases to around 12%, the tendency to oxidize in y y the Vapor space is greatly reduced. When the oxygen content of the spentl gases is maintained at around 10%, we find that the oxidation in the vapor 'space is practically negligible and that the still and vapor lines are kept practically free of any carbonaceous deposits.

In our Patents 1,953,345, 1,953,346 and 1,999,018 we described methods for air blowing oils to' produce oxidized asphalts which methods have been largely responsible for correcting some of the foregoing evils with the result that a much better 40 product is produced in considerably less time. In these methods, the oil to be oxidized is circulated from a bulk supply maintained in a cylindrical still or container at an oxidizing temperature to a mixing jet, or other type of mixer known in the art for commingling a liquid and a gas into which a regulated quantity of air 0r oxygencontaining gas is admitted. The mixture of oil and air and also vapors are returned to the bulk supply container in which the air and vapors are separated from the partially oxidized charging stock. The latter is continuously recirculated to the mixer until the entire batch ofstock has been oxidized to the predetermined grade. By this procedure a superior asphaltic product is `440 gallons per cubic foot of air.

produced since the oxidation is not as severe, with the result that less caribonaceous material is produced and greater ductility and penetration is obtained at a given flash and melting point. In 5 this method of oxidation, a better utilization of air is obtained since the oil is more intimately.

commingled with the air with the attendant result that the oxidation is completedin considerably less time than that required by the older methods. The present invention relates particularly to improvements in the foregoing process of oxidation. y

Briefly stated, we have discovered that, in the foregoing method where circulation of the oil is employed in order to obtain substantially complete utilization of the oxygen in the air during oxidation, it is necessary to circulate the oil at a definite ratio per cubic foot of air continuously introduced into the mixer. In other words, we have discovered that the circulation of the oil from the bulk supply to the mixer where air is introduced must be controlled so that it exceeds at least a ratio of gallons per minute per cubic foot of air per minute injected into the mixer. We prefer, however, to operate the oxidation reaction with a circulation ratio within a range of 10 to 50 gallons per minute per cubic foot of air per minute with an optimum of -30 gallons per minute per cubic foot of air per minute. Stated differently, if air is injected into the mixer at a rate of 300 cubic feet per minute, it will be necessary to circulate the oil from the bulk supply at a rate between `3,000 to 15,000 gallons per minute with an optimum circulation of 7,500 to 9,000 gallons per minute. Under such conditions of operation, we have found that from to 80% or more of of the oxygen in the air is consumed by the mixture with an average of about 60 to '70% when the oil is circulated at a ratio of 30 In other words,

with a circulation ratio of approximately 10 gallons of Yoil per minute to one cubic foot of air per minute, the oxygen content of the spent gases will be in the neighborhood of -about 15% while 4 5 at an oil circulation ratio of about 45 gallons per cubic foot of air per minute, the oxygen content of the spent gases will fall to as low a figure as 3 or 5% and even as low as 1% of oxygen. Heretofore, with lower circulation ratios of four or five gallons per cubic foot of air, it has been impossible to utilize more than 20% of the oxygen in the air. Of course, the oil-air ratio and the oxygen consumption is a function of temperature and pressure of oxidation.

Under such increase conditions of oil circula.- tion ratios per cubic foot of air we have found that for a given maximum oxidation temperature and a given air rate per barrel of charging stock, increasing the circulation rate materially 60 decreases the time in which oxidation of the charge is completed. The increased efficiency of the air utilization results in a marked decrease in the amount of carbonaceous or coke-like materials in the final product.

Also, the increased circulation rate enables the oxidation to be effected at a lower temperature. We have found that the lower the temperature of oxidation, the better will be the air-blown characteristics of the final product or in other words, the asphalt will have a higher melting point for a given penetration and also a higher ductility. Stated differently, there are three fundamental occurrences duringY the oxidation. In the first place, the reaction of the air with the resinous fractions of the oil results in the production of additional bitumens. At the same time, the mutual solvency agents for the bitumens and cil are destroyed `so that the oil is transferred from a true solution to a colloidal mixture. In the second place, the oxidation of the low viscosity index (V. I.) fractions which flux the bitumens are converted into flux fractions of higher V. I. In the third place, distillation of the ux fractions takes place with the possibility that the distillation takes the form of a selective distillation of the high V. I. fractions. Generally speaking, the oxidation of the resins and the oxidation of the low V. I. flux fractions into fractions of higher V. I. increase the air blown characteristics of the asphalts. On the other hand, the distillation of the flux fractions retard such air blown characteristics. Consequently, by carrying out the oxidation reaction at higher temperatures, the tendency will be to distill considerably more of the high V. I. flux fractions. Yet, until recently, it has been impossible to obtain goody oxygen utilization at low temperatures due to the fact that the air does not react as readily with the hydrocarbons at low temperatures. With high circulation ratios, however, we have found that both good oxygen utilization and oxidation at lower temperatures may be obtained. The net results are y that the charge is oxidized in a much faster time with a lower consumption of power and the product will have a higher ductility than asphalts heretofore produced.

As stated heretofore,r the substantially complete utilization of the oxygen in the oxidation reaction resultsin less coking of the products than in cases where the utilization is not as complete. This is primarily due to the fact that less complete utilization of the oxygen and high temperatures of oxidation results in a combustion of the air and vapors at the surface of the bulk supply of charging stock with the result that some of the products are converted into coke-like and carbonaceous materials. In our process, we obtain a more complete utilization of the oxygen in the air and also carry out the oxidation reaction at a substantially lower temperature than temperatures heretofore employed. We have found it advisable to effect the oxidation reaction at a temperature not above about 475 F. with an optimum temperature of 450 to 460 F. Yet, we

can accomplish the completion of the oxidation reaction in less time than heretofore with a higher oxidation temperature but -a lower circulation ratio.

As a feature of our invention, we have found it to -be desirable to carry out the oxidation reaction at a lower temperature than the temperature employed for the greater part of the oxidation reaction. By maintaining a temperature of not greater than 400 to 415 F. for the first several hours and a temperature of not over 430 F. for the next hour, we have found that difficulties with the foaming of the contents in the still are eliminated. Operating in this manner, the still may be charged to as much as 65% of its capacity without trouble due to foaming. In some instances, it may be desirable to lower the rate 0f air introduction during the first 11/2 hours of operation in order to minimize foaming of the charge. Thus, on a 200 barrel charge, we may introduce air at a rate of about 120 cubic feet per minute for the first half hour which is gradually increased to about 200l cubic feet per minute by the end of the hour and to- 300 cubic feet by the end of the next half-hour.

The process will be better understood by reference to the drawing which contains a more or less schematic embodiment of the apparatus in which the process may be carried out. Fig. 1 is a full View of the apparatus with parts broken away. Fig. 2 is a cross-sectional View taken along line 2 2 of Fig. 1. Fig. 3 is a cross-sectional View 3 3 of Fig. 2.

In the drawing, Hl is a cylindrical still for containing the bulk supply of oil to be treated. Still Iii is positioned on a fire-box or furnace Il. Burners l2 are for supplying heat to the fire-box ll. Line i4, controlled by valve l5, serves to in-' troduce the oil tobe oxidized into the still l0. A horizontal baiiie plate I6, extends across the bottom of the still to form a passageway for the oil to the suctionof the pump to be described. The baiile plate I6 is joined to a vertical plate It at one end adjacent the pump so that all oil entering the passageway must be drawn into the pump. A small clearance may be left under the vertical member to keep a pocket of oil from forming between it and the pump end of the still.

A suction |8 extending into the passageway Il. leads to a pump I9 which is preferably of the vertical type and is provided with a stationary or adjustable screw type pump impeller I9. Pump i9 is provided with shaft 20 which is driven electrically by motor 2|. The pump is also provided with a plurality of straightening vanes 22 which serve to reduce the whirling motion imparted to the oil by the impeller. Provision is made for introducing steam and/ or air into the discharge side of the pump. This air may be introduced via line 23 controlled by valve 24 which passes through line 25 into a semi-circular spider 2t '.'hich terminates in each side of the pump casing into two nozzles 21. Likewise, steam may be introduced into the pump via line 28 controlled by valve 29. If desired, the air or steam may be introduced through these Vanes. The illustrated arrangement of nozzles in the pump permits an intimate adrnixture of the air and/or steam with the oil passing from the vanes 22. Openings 3i) are provided in the pump casing to allow the mixture of oil, vapors, air and/or steam to pass into the still.

The still i0 is provided with a vapor outlet 3| which is connected to a vapor line 32 controlled by valve 33. Condenser 34 serves to cool and condense vapors. Line 35 serves topass the cooled products into a separator SS'in which uncondensed gases and vapors may befwithdrawn in line 3l controlled by valve 38. Water `may be withdrawn from the bottom of the separator via f line 39 and oil distillate may be withdrawn from the side of the separator via line 48. Provision is mad-e for introducing chemicals into line 32 in order to prevent the oil from condensing as an emulsion. These chemicals may be introduced via line 52 provided with valve 53. The water containing the chemicals withdrawn from separator 35 via line 39 may be circulated back to line 52. As chemicals for preventing emulsilcation or for heating emulsions, we may employ any of the known materials employed for breaking oil emulsions, such as, for example, sulphonatedA oils, Turkey red oil or any of the known water softeners.

The still iii is also provided with line 4| controlled by valve 42 which is employed for pumping out or draining the still I0.

A cooling coil 43 is provided in the still for-cooling the charge during the oxidation. Preferably, cooling is obtained by introducing a cooling liquid such as oil taken from tank 44 via lin-e 45 pro` vided with valve 4t and pumping it by pump 41 through line 48 and through the coolingv coils 43. The cooling oil is circulated back to the tank 44 via line 49, cooler 5t and line 5|.

The vapor space of the still is also provided with perforated pipes 51 through which oil may be sprayed Via line 55 controlled by valve 56 in order to scour the sides of the still and the vapor space during the oxidation run and thus greatly reduce the carbonaceous formation. For this purpose, part ofthe oil undergoing oxidation in the still, particularly that portion which has passed through the pump casing, maybe circulated by means of a pump into line 55 and. thence through the perforated pipes 5l. It is preferable to spray the oil upwardly so that the top and sides of the still are sprayed with the oil. Instead of using part of the oil undergoing oxidation for this purpose, a blending oil may be used provided the proper type of blending oil is selected which when mixed with the oxidized asphalt results in a product having the desired characteristics. As blending oils, We may use steam blown asphalt, lubricating oil fractions, gas oil, sulphurized oil, vegetable and animal oils. 'The circulation of the'oil through the perforated pipe is not absolutely essential in cases where the oil-air circulation ratio is suiiiciently high to ensure substantially complete utilization of oxygen. However, with low circulation ratios and particularly in the conventional spider and shell still operation where air is introduced at a higher rate than can be utilized in the oxidation, we iind that scouring the sides of the still above the oil level is necessary'to prevent carbonaceous formation on the sides of the still. I

In operation, a hydrocarbon oil, preferably a residuum obtained by distilling voi tlie'lighter oils, such as kerosene and perhaps gas oils from asphaltic crude oil is introdueedvinto the still lil via lin'e i4 and valve l5. When a certain amount of the 'charge is in the still, pump i3 driven by shaft 20 and motor 2| is started and the oil in the still l is drawn from passageway through openings I8v in the suction side of the pump by impeller I9 which causes the oil to be whirled upwardly past the impeller. The oil then passes through straightening vanes 22 and back into the still via openings Si). rihe fire under the still I0 is lighted andthe oil is heated to an oxidation temperature, the temperature being controlled by burner 2. The oil is circulated until the required amount ofoil has been introduced into the still through line i4 and until the required oxidation p Lil, line 43, cooling coil d3, line 4i), cooler 'and line'i back to tank i4 in order to maintain the temperature oi the contents in the still at about 40o-4.1i? F. for the first two hours and at not over. 430 F. for the third hour. The lires in the furnace in the meantime have been turned oil. The balance of the oxidation operation carried out ata temperature of i-475 F. [is stated previously, it has been :found that still may be charged to capacity and all trouble with foam avoided if' the still temperature is held bei low 415 F. for the rst two hours and 430 F. for the third hour. Similarly, all trouble with loss of vapor temperature control can be avoided if the balance ofthe air blowing operation is carried out at temperatures below 475 F. or the oxygen content in the spent gases is kept below about 12%.

In still I0, the vapor and gases are separated from the oil and pass via outlet 3| and line 32 to condenser 34 and thence via line 35 into separator 36 where oil condensate may be separated from water and gases and which, if desired, the separated oil may be returned to the still for further oxidation. The rate of circulation of the oil through the pump may be controlled by varying vthe speed of the pump through shaft and motor 2 I. The cooling medium such as steam, air or water or oil in the heat exchanger or cooling coils 43 may be circulated in any desired amount l 20 in order to obtain the proper degree of cooling by heat exchange out of contact with the oil in the still.

When the charge has been oxidized to the desired degree, the air introduction via line 28is discontinued. Pump I9 continues to circulate the charge in the still. Steam is then introduced through the nozzle 2'I by opening valve 24 and the temperature of the charge is raised to about 490500 F. The circulation at about LSD-500 F.

i 30 through the pump and mixing section above the I drawn from still I0 via the drain 4I controlled by valve 42.

The following is a specific example for carrying out the present invention in order to produce an oxidized asphalt of coating grade: An asphaltic residuum obtained preferably by distilling from asphaltic base oil, the light oils and the intermediate boiling oils and specifically an Orcutt reduced residuum having an A. P. I. gravity of 10.6, a flash of 420 F. (Pensky-Martens closed cup) and a viscosity of 148 seconds Saybolt Furol at 210 F. is preferably preheated and then charged into the still via line I4 as previously described above. As soon as the oil is in the still, the circulating pump is started and the oil is circulated at a rate, for example, of 11,000 gallons per minute. The still is fired until the oil reaches a temperature of 350 F. When the still has been charged with 220 bbls. of oil and the charge has reached a temperature of 350 F., air is introduced into the mixing section of the pump via the nozzles 21 at a rate of 120 cubic feet per minute for about one-half hour. The air rate is then gradually increased until at the end of the next half hour it will be introduced at a rate of 200 cubic feet per minute. B-y the end o f the subsequent half-hour, the air rate will have increased to about 300 cubic feet per minute at which rate it is maintained until a melting point and penetration is reached which experience has shown it will subsequently produce as` phalt of approximately the desired specification. This will require about another 10 hours. During the air blowing, the temperature of the charge will have increased to about 410 F. This temperature is maintained for about the first two hours of the air blowing. It is then increased to about 430 F. during the next hour or air blowing at the end of which the temperature is increased to about 450460 F. where it is maintained for the balance of the oxidation period. The temperature is maintained and controlled by circulating a cooling medium such as oil through the cooling coils in the still to remove the heat of reaction.

When the charge has been brought to near the 5 desired melting point and penetration, which, as stated heretofore, will require about 11 to 12 hoursfrom the beginning of the air blowing, the air rate is reduced to about 165 cubic feet per minute where it is maintained for the next 2 10 hours to bring the asphalt to the desired melting point` and penetration preparatory to steam blowing.A It willv be observed at this point that the aforementioned reduction of air introduction is made necessary merely to allow the laboratory 15 to test samples of the charge to determine the melting point and penetration of the samples and to report the same to the vstill operator.v Thus, a better control may be had on the melting point and penetration characteristics of the 20 charge. Were it not for this factor, the air rate may be maintained at 300 cubic feet per minute until the completion of the reactionk in which case the reaction m-ay be completed in an additional hour instead of the 2' hours given above 25 which are vrequired subsequent to the reaction in air rate. 'The' above time may be greatly reduced by increasing the temperature of air rate or both. For some oils, this time will be only 5 or 6 hours.

When the charge has been brought to the 30 desired grade preparatory to steam blowing, the air supply is discontinued and the oxidized charge is heated to approximately 500 F. by re in the still and reducing the circulation of cooling oil through cooling coils and the oxidized charge is 35 subjected to steam blowing for about 2 hours. During the steam blowing period, the charge is continuously circulated as during the air blowing period, steam being introduced into the mixing section of the pump by opening valve 24. The '40 aforementioned temperature of 500 F. is maintained during the steam blowing period. The steaming,Y operation permits light oils to vaporize from the oxidized charge and thus bring the charge to proper specification. In the example W45 given above, the nal product will have a penetrationof 13 (200 gr. per 60 sec.) at 32 F., a penetration of 18 (100 gr. per 5 sec.) at 77 F. and a penetration of 33 (50 gr. per 5 sec.) at 115 F., a melting point (ball and ring) of 219 F., a ilash point (Pensky-Martens closed cup) of 445 F., a ductility of 2.2 cm. at 77 F. and solubilities of 99.1% in CS2 ,and CC14 and of 75.7% in 80 gasoline.

The :above description of our invention is not to '450 be considered as limiting but only as illustrative of the invention and as one mode of carrying it out. Many changes can be made within the scope of the invention which is set forth in the following claims.

We claim:

1. vA process for producing asphalt which comprises commingling oil with oxygen-containing gas at an elevated oxidizing temperature sufficient to oxidize said oil into asphalt, said oxidation being carried out while circulating said oil at a high rate from a bulk supply into a mixing device into which the oxygen-containing gas is introduced at a substantially constant rate for the greater part of said oxidation and maintaining a circulation ratio of 10 to 50 gallons of oil per minute per cubic foot of air per minute.

2. A process for producing asphalt which comprises circulating oil at an elevated oxidizing temperature, contacting said circulated Oil with free oxygen-containing gas at a rate of approximately 10-50 gallons per minute per cubic foot of free oxygen-containing gas per minute.

3. A process for producing asphalt which co-mprises circulating oil at an elevated oxidizing temperature, contacting said circulated oil with free oxygen-containing gas at a rate of approximately 10-50 gallons per minute per cubic foot of free oxygen-containing gas per minute and maintaining the temperature of said oil at below approximately 475 F.

4. A process forproducing asphalt which comprises maintaining a bulk supply of oil at an elevated oxidizing temperature, circulating said oil fromA said bulk supply through a mixing de- Vice and back to said bulk sup-ply and introducing air into said mixing device at a substantially constant rate to oxidize said o-il into asphalt, said circulation of oil through said mixing device during said oxidation being at a substantially constant rate of approximately 10-50 gallons per minute per cubicfoot of air .per minute introduced into said mixing device.

5. A process for producing asphalt which comprises circulating oil at an elevated oxidizing temperature, commingling said circulated oil with free oxygen-containing gas at a rate of approximately 10"-50 gallons per minute per cubic foot of free oxygen-containing gas per minute, whereby approximately 30 to 80% of the oxygen in said oxygen-containing gas is consumed by said commingling of oxygen-containing gas with said oil.

6. A process for producing asphalt which com prises circulating oil at an elevated oxidizing temperature, commingling said circulated oil with free oxygen-containing gas at a rate of approximately -50 gallons per minute per cubic foot of free oxygen-containing gas per minute, whereby approximately 30 to 80% of the oxygen in said oxygen-containing gas is consumed by said commingling of oxygen-containing gas with said oil, and maintaining the temperature of said oil below approximately 475 F.

7. A process as in claim 2 in which the oil is circulated at a rate of about 25-30 gallons per minute per cubic foot of oxygen-containing gas.

8. A process for producing asphalt which cornprises .commingling oil with free oxygen-containing gas at an elevated oxidizing temperature in a still and during said oxidation spraying the inner surfaces of said still above the oil level in said still with oil to prevent oil which has splattered on said surfaces during said oxidation from remaining on said surfaces for a sufficient period of time to form carbonaceous material.

9. A process as in claim 8 in which said sprayed oil comprises an oil which is adapted to be blended with the oil undergoing oxidation.

EARLE W. GARD. BLAIR G. ALDRIDGE..

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