US2057923A - Oil refining process - Google Patents

Description

Patented Oct. 20, 1936 UNITED STATES PATENT OFFICE OIL REFINING PROCESS ration of New Mexico Application July 20, 1934, Serial No. 736,253

3 Claims.

This invention relates to an oil refining process, and more particularly to a novel process for the manufacture of lubricating oils or bright stock made from an oil product ordinarily known as cylinder stock.

One object, among others, of the invention is to dewax the cylinder stock before the latter is acid treated, neutralized, and clarified. This is found to result in a number of advantages, such as increasing the output of a given refinery plant, lowering the cost of manufacture, and enhancing the quality of the lubricating oil.

Another object of the invention is to so rearrange the conventional plant refinery equipment that a new relation exists in the order or sequence of steps taken in treating the oil. It is this new orderly arrangement and the discovery of the new results attained, coupled with the greatly improved character of the oil produced, which is an important feature of this invention.

It is a further important object to centrifuge the oil in the presence of the tarry body substances, and use these substances as carriers to rid the oil of wax and petrolatum matter.

The accompanying drawing is in the form of a flow sheet or diagram showing the various steps of the invention, and is used in connection with the following description in aid of a full understanding of this invention. The drawing is exemplary, and it is to be understood that changes or rearrangements of the stills, tanks, and other oil receiving and treating members may be made without departing from the principle of the invention; and likewise the same is true as regards the proportions of ingredients mentioned in the description to follow. As a convenience, a number of the elements, or diagrammatically shown parts, are lettered or named on the drawing, as Well as being referred to herein by reference characters.

In practicing this invention and new refining process, a vacuum still may be used exclusively for the initial distillation operations on the residual oil known as reduced crude and which is the result of a primary skimming operation in which is removed from the raw or natural oil all gasoline, kerosene, distillate, gas oil, and tar. This operation leaves the reduced crude for treatment in accordance with this invention.

The exclusive use of a vacuum still results in many advantages. Other types of stills may be used, but it is found preferable to treat the reduced crude in a vacuum still, thus producing a superior base for the manufacture of lubricating oils and bright stock, which base is commonly referred to as cylinder stock. By this invention it is now possible to dewax the cylinder stock before it is acid treated, neutralized, and clarified. This is found to produce a superior grade of lubricating oil and bright stock at lower cost in manufacture and which has higher heat resisting characteristics.

In practicing the invention, the reduced crude oil is first topped off preferably in a vacuum still indicated generally at l, although I may use a 10 pipe still, shell still, or any other type of still suitable for the purpose. The reduced crude is delivered from a source of supply, not shown, through a pipe 2 into the still I. An initial distilling action takes place in this still I to re- 15 move the gas oil content from the reduced crude, the gas oil being carried off through a pipe line 3. Furthermore, this first distillation also produces a product commonly called wax-distillate which is removed through a pipe line 4. Likewise, tar is ordinarily removed through a pipe line 5 from the still I. The gas oil and'the waxdistillate disposed of at 3 and 4 may be used for the further manufacture of light lubricating oils or for other products. Likewise, the tar is of course a Icy-product also capable of further use.

The foregoing distillation results in producing a cylinder stock or lubricating oil distillate, which is taken off through a pipe line B, and it is used for the manufacture of heavy lubricating oils and bright stock in practicing this invention, as will now be described.

The cylinder stock or lubricating oil distillate is drawn oif at 6 from the vacuum still I and may be cooled in coils I. It is then carried through a pipe 8 to a cylinder stock or lubricating oil distillate receiving or storage tank 9. From this tank 9, the cylinder stock is drawn as needed and carried through a pipe l0 and introduced into a solution mixing tank or tanks II where it is diluted with about to of gasoline by volume introduced through a pipe line l2 from a gasoline source of supply, say a gasoline storage tank l3 shown in the lower right hand portion of 45 the flow sheet. This gasoline diluent, just mentioned, causes the oil to run or feed more freely through a centrifuging plant hereinafter referred to.

This mixture or solution of cylinder stock or 50 lubricating oil distillate and gasoline is next passed from the solution mixing tank or means H through a pipe M to a chilling tank or tanks [5 Where the mixture is sometimes chilled to a temperature of about 20 to 45 degrees Fahrenheit be- 55 low zero, or such temperature as is necessary to cause the wax or petrolatum contained in this gasoline and oil mixture to crystallize, precipitate, or separate out from the oil and gasoline solution, though the lubricating oil itself remains in solution at this point, as will be understood. In some cases 20 to 50 degrees below zero are required to precipitate the wax, depending on the viscosity of the diluted oil and its wax content.

A pipe line I6 conveys this chilled mixture or solution, carrying the precipitated wax, to a centrifuging wax removing plant designated generally at H, where the bulk of the precipitated. wax and tarry substances are removed from the chilled mixture by a centrifuging process of conventional form. This invention may also be practiced, as to the removal of wax or petrolatum, by

means of solvents, pressing, cold-settling, orany;

dewaxing process suitable for the purpose, and discharged from the centrifuge plant Il through a pipe line I3. In other words, I designate generally (at I1, I8) the wax andpetrolatum extracting step, thus showing its relation to other steps in the process, prior to any sulphuric acid treatment. It is noted, therefore, that regardless of the de-waxing method used, the actual precipitation and removal of the wax and petrolatum from the chilled oil and gasoline solution, takes place at the chilling tanks I5 and centrifuge plant I1 before any clarification, acid treatment, or clay contacting treatment is carried out. This is an important and outstanding feature of the invention, as later explained.

The oil and gasoline mixture or blend (now free of Wax and-petrolatum) is now passed from the centrifuge plant I'I through a pipe line I9 to areceiving tank 20 for temporarily storing this Wax-free solution. This solution is drawn as needed through apipe 2i to a gasoline-recovery plant or still 22 where the gasoline, about 65% to 75% (by volume) heretofore introduced at I I, is now recovered or removed by distillation and carried through a pipe 23 back to the gasoline storage tank I3 for further use.

The resulting de-waxed gasoline-free and petrolatum-free oil may now be carried through a pipe 24 to a receiving or storage tank 25, and thence through a pipe 26 to an agitator plant 21 where the oil is now treated with sulphuric acid. The acid 'may be introduced into the agitator plant 2-? through a supply pipe line 28, and the oil and acid is then thoroughly agitated and treated as will be understood. From 2% to 3% of acid by weight of the oil is used and hence this process is economical in acid consumption. This acid treatment serves to remove such tar forming constituents as may have so far remained in the oil afterthe previous treatments and after leaving the centrifuging plant H. A pipe 29 is used to removethe sludge, resulting from the acid treatment, from the agitator 21. Since most of the tarry substances are already removed by the centrifuging plant Ii, a minimum amount of acid is required. This is explained as an important feature of economy in this new process.

The-sulphuric acid treatedoil is next treated in a contacting plant, and to this end it is now passed through a pipe line 30 toand treated in clay mixing tanks 3|, where the acid-treated oil is mixed with finely ground clay introduced into these tanks 3! through a supply means or conduit 32. The oil and clay mixture is heated in a pipe still 34, connected througha pipe 33 with the clay vmixing tanks 3 I, in order that this mixture, more particularly the clay, may come in intimate contact with the acid in the oil, to neutralize the acid and remove the impurities. Other agents for neutralizing the acid may be used, as for example, ammonia, soda ash, caustic soda, and alkali sub-, stances in general.

From the pipe still 34, the neutralized acid-free oil and clay mixture, at a suitably low temperature, next passes through a pipe 35 to gasoline solution mixing tanks 36 where the acid-free oil and clay is now mixed or diluted with a sufficient amount of gasoline, say about 35% to 50% by volume, introduced into said solution mixing tanks 36 through a pipe or pipes 31 running from the gasoline feed line I2 connected with the gasoline supply tank I3. Thus the oil and clay mixture isjthinned with gasoline for further treatment. The gasoline thins the oil to facilitate filtering out the clay, as next explained.

A pipe line 38 conveys the oil and gasoline solution containing neutralized acid-free oil with clay, to afilter 39 (say the Sweetland type) where the mixture is filtered to remove-all the clay from the oil and gasoline solution. The clay-free and. acidfree filtered mixture of oil and gasolineis now carried through a pipe line 40 to a receiving tank Al for temporary storage.

A pipe line 42 next carries this filtered mixture from the storage tank M to a shellor pipe still 43 where all the gasoline diluent (about 35% more or less) is now removed through a pipe 44 connected with the return gasoline recovery pipe line 23, and this recovered gasoline is re- 7 turned to the gasoline storage tank I3 for furvolves a new chemical and mechanical process and is found to react on the oil pro-duct in a new way, producing new results, and a better product.

The percentage of gasoline diluent used in the two instances referred to, as well as the chilling temperatures named, are not critical, and neither are these factors in themselves controlling features of the invention. These factors are well known in the art and are merely given by way of example to aid in understanding the invention as a whole. 7

Among other things, this process makes possible the exclusive use of a vacuum still, indicated generally at I, for the initial distillation of the previously reduced. crude oil. Prior to this invention it has been impossible to make exclusive use of a vacuum still for this initial'distillatio-n because of the large amount of crystalline wax which the vacuum still produces and leaves in the cylinder stock. This crystalline wax can, however, by this new process, be successfully centrifuged at I! prior to the acid treatment, since all the highly unsaturated and tarry or asphaltic substances are present in the oil to act as a carrier of the wax or petrolatum in extracting the latter by centrifugal force and disposing of it out through pipe I8. The vacuum still, being more efiicient, due to lower temperature to which the oil is heated, produces a much higher grade of lubricating oil and bright stock product than a pipe or shell still. My invention, therefore, finds a practical way to employ the vacuum still.

Heretofore, it has been impossible to use the cylinder stock from a vacuum still on a profitable commercial basis except When said stock was mixed with a residue having an amorphous wax content from a pipe or shell still. The reason for this condition was that the residue or cylinder stock from a Vacuum still contains principally a crystalline wax which will not completely separate by centrifuging under the old method. However, by using this new process, it is now possible to carry on the entire initial distillation of reduced crude in the vacuum still at I, since under this new process, the separation of the wax or petrolatum takes place before the highly unsaturated and tarry or asphaltic substances have been removed, due to which it is now found that crystalline wax will separate out completely without mixing it with an amorphous wax stock from pipe or shell stills. In other words, the asphaltic and tarry substances aid in carrying off the wax and petrolatum. I have found that it is entirely untrue that all tarry substances must be removed before the centrifuging process, as heretofore followed so consistently in the industry.

This process is also distinguished by a decrease in sludge which is a waste residue removed from the agitator 27 thru pipe 29. Old methods resulted in a residue of about 18% sludge, whereas by this invention the new method has decreased this residue to 9%. This new process uses less sulphuric acid, only about 2% to 3% by weight, and there is less tendency to acid burning the oil, and consequently the final lubricating oil has a higher heat resistance.

The finished lubricating oil and bright stock are of higher grade, of greater heat resisting characteristics, and have a lower carbon residue, say as low as 1.25%, hence superior to oils heretofore produced by prior methods. These finished oil products also have an improved viscosity index, and the flash and fire tests thereof are greatly improved. This is due to a more satisfactory removal of the impurities from the cylinder stock, especially the unsaturated hydrocarbons, and to less injury of the oil treated in a vacuum still at somewhat lower temperature than in other stills. These factors distinguish this new processed lubricating oil and bright stock from those heretofore produced.

There is a substantial saving in refining cost. It is pointed out that the oil stock flows more freely through the pipes and separating machines before acid treatment than after the wax has been removed, and so this improved process actually increases the output of the plant, and thus economizes by effecting a larger production in a refinery of given capacity, as compared to processes heretofore used. About one-third less acid and at least one-half less clay are used by my said improved process in contacting than previously practiced in the refining process, since in this new process the acid and clay are not Wasted by action on the petrolatum and wax because the latter is removed prior to acid and clay treatments.

Various modifications will occur to those skilled in the art in the processing, composition and disposition of the component elements or steps going to make up the method of the invention as a whole, as well as in the selective combination or application of the respective process steps, and no limitation is intended by the phraseology of the foregoing description or illustrations in the accompanying drawing.

What is claimed is:

1. In the art of producing lubricating oil from crude petroleum, the process which comprises performing on a petroleum oil of cylinder stock viscosity, and while the latter contains initially all of its naturally occurring asphaltic and unsaturated bodies, the following steps in the order named: forming a mixture of said oil with a normally liquid light hydrocarbon, chilling said mixture to thereby cause the precipitation of wax in the presence of said asphaltic and unsaturated bodies, removing precipitated wax by centrifuging, and removing asphaltic and unsaturated bodies from said so treated oil product by successive sulphuric acid and clay treatments.

2. In the art of producing lubricating oil from crude petroleum, the process which comprises performing on a vacuum distilled petroleum oil of cylinder stock viscosity, and while the latter contains initially all of its naturally occurring asphaltic and unsaturated bodies, the following steps in the order named: forming a mixture of said oil with a normally liquid light hydrocarbon, chilling said mixture to thereby cause the precipitation of wax in the presence of said asphaltic and unsaturated bodies, removing precipitated wax by centrifuging, and removing asphaltic and unsaturated bodies from said so treated oil product by successive sulphuric acid and clay treatments.

3. In the art of producing lubricating oil from crude petroleum, the process which comprises performing on a petroleum oil of cylinder stock viscosity, and while the latter contains initially all of its naturally occurring asphaltic and unsaturated bodies, the following steps in the order named: forming a mixture of said oil with a normally liquid light hydrocarbon, chilling said mixture to thereby cause the precipitation of wax in the presence of said asphaltic and unsaturated bodies, removing precipitated wax by centrifuging, removing asphaltic and unsaturated bodies from said so treated oil product by treatment with sulphuric acid, neutralizing said oil product, and removing the light hydrocarbon therefrom.

ERNEST J. SLATER.

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