US2168875A - Method of treating oils - Google Patents

Description

Aug. 8, 1939. H. D. No| y 2,168,875

METHOD of' HEATING oILs Filed July 8, 1937 Ca s OMR, WATER f/VLETJ. 35F INVENTOR Patented Aug. s, 1939v UNITED STATES PATENT OFFICE cony-Vaeuum Oil Company,

Incorporated,

New York, N. Y., a. corporation of New York Application July 8, 1937, Serial No. 152,513

1 Claim.

This invention has to do with solvent refining of petroleum lubricant oil fractions to produce therefrom products of higher parafllnicity. Solvent refining is accomplished by mixing with the oil to be treated a solvent refining agent capable of exerting selective solvent power for one of the classes of constituents therein, allowing phase separation, and withdrawing the solvent and the extracted constituents dissolved therein. Either the extract or the non-dissolved portion may be the desired product depending upon the solvent.

Two solvents. one preferential for naphthenic constituents, and one preferential for paraflinic constituents, may be used simultaneously, in a similar manner. A modification of the double solvent process is one wherein a solvent preferentially dissolving oils of a 'parafilnic nature is passed through a series of treating stages, each composed of a mixing step and a settling step; a solvent preferentially dissolving naphthenic oils is passed through the same series in the opposite direction, and oil to be treated is introduced to some intermediate stage in the series. It is with such a system oi double solvent refining that this invention is specifically concerned.

In the usual commercial practice of this double solvent refining process, the parafflnic solvent used is a mixture of liquefied normally gaseous hydrocarbons consisting predominantly of propane with minor proportions of related compounds. This reagent is hereinafter referred to as propane. The usual naphthenic solvent isl a mixture of phenolic materials of the nature of tar acids, consisting mostly of cresylic acids, with smaller amounts of related phenols, hereinafter referred to as selecto.

The present commercial practice oi double solvent refining, the relation of this invention thereto, and the present invention may be understood most readily by reference to the drawing attached to this specification. In the drawing, Figure 1 indicates the present practice, and Figure 2 indicates practice according to my invention, both by diagrammatic ow sheets.

Referring now to Figure 1 of the drawing, showing present practice, the system consists of a container 3, housing a series of chambers 4, 5, 6, 1, 8, 9 separated by imperforate partitions I0, II, I2, I3, I4. A few more, or one or two less chambers may appear in any individual commercial setup, dependent upon its particular duty. Each of these chambers constitutes a settling zone wherein a mixture of oil, parafnic solvent, and naphthenic solvent may separate into an upper layer of rafnate composed of paraiiinic oil and paramnic solvent and `a lower layer of extract composed of naphthenic oils and naphthenic solvent, as shown by the arrows and liquid lining therein. Partitions Ii), I2, I3, I4

are equipped with a mixing jet as shown, de`

noted in each case by the numeral I5, which withdraws raiiinate layer from the preceding compartment over a Weir designated in each case by numeral- I6. Partition II and the end plate of chamber 4 are fitted with entry nozzles denoted by I1 for diffusion of outside formed mixtures. Naphthenic solvent is introduced by pipe I8 through jet mixer I5 intochamber 9, entraining and carrying with it raffinate from chamber 8. Settled, extract from chamber 9 passes through pipe I9, pump 20, and pipe 2| through a jet mixer into chamber 8, admixed with rainate from chamber 1. Extract from cham ber 8 similarly passes through 22, 23, 24 into chamber 1. Extract from chamber 1 passes through pipe 25 and pump 26 into mixer 21. Oil chargedv to the system for refining enters through pipe 28 and pump 29 to mixer 21. Railinate from chamber passes through pipe 30, pump 3| and pipe 32 to mixer 21, The mixture from 21 is passed through cooler 33 and pipe 34 into chamber 6. Extract from chamber 6 passes through pipe 35l pump 36, pipe 31 into chamber 5. Extract from chamber 5 passes through pipe 38, pump 39, pipe 40, and pipe 4I into chamber 4. Extract from chamber 4 is withdrawn by pipe 42, constituting the extract product of the system, and is an equilibrium mixture of naphthenic oils, naphthenic solvent, and some paraiiinic solvent. Paralnic solvent enters the system through pipe 4I, passes to the rafnate phase in chamber 4, thence to chamber 5 by 30, 3|, 32, 21, 33, 34, to chamber 6, to 1, 8, and 9, and raffinate withdrawn by pipe 43 from chamber. 9 constitutes the ralnate product of the system and is an equilibrium mixture of paralnic oils, paraiinic solvent, and some naphthenic solvent.

In the usual case the parailinic solvent and naphthenic solvent, propane and selecto respectively, are each applied in the amount of about four times the weight of the oil introduced. In such a system, with one part of oil per time unit at a temperature of about 180-190 F., about four parts of propane at a temperature of about 85- 95 F., and somewhat less than four parts of selecto at about 'T0-'75 F. the temperature in chamber 6 adjusted by the cooler 33 for best operation of chamber 6 and subsequent chambers 1 9, will be about 75-90" F. The temperature ."n chambers 5 and 6, as determined by the temperature in chamber 6 and the temperature of entering propane, will be about 77-90" F. in chamber 5 and 85-95 F. in chamber 4.

The system combines two functions. 'I'he first is that of separating naphthenic oils from parafnic oils, carried out in 6, 1, and subsequent chambers. The other is that of separating paraiiinic oils from extract, carried out in chambers 5 and 4. The deasphaltizing action of chambers 5 and 4 becomes more sharp and emof a system cient with increasing temperature. That is, for the same proportions of extract and propane, or oil and propane in the presence of selecto. a greater freedom of paraillnic fractions from extract will be attained with increasing temperature. The best temperature level is usually above 100 F. in the range 10D-120 F. In the upper end of the system, in chambers 6, 1, t, etc., the function of separation of naphthenic oils from paratflnic oils is made more eiiiclent by lower temperatures, of the order of rI590 F. and lower. If higher, too much propane is soluble in the extract layer, carrying with it valuable parafflnic oils. Since these two functions, of unlike temperature requirements, are practiced as connected portions of a unitary system, the control is for the more important function, that taking place in chambers 5, 1, 8, etc. This results in an undue loss of paralnic material in extract from chamber 4, and as well in a decrease of capacity for the system as a whole. This invention has for its object the provision which, while preserving those undoubted advantages arising from flowing a parafflnic solvent and a naphthenic solvent countercurrent through a series of stages each comprising a mixing and a settling step, and introducing oil at 'a` point intermediate the ends thereof, also permits the separation of the two functional parts thereof and their independent control in a manner best suited to the needs of each.

The invention may be understood by reference to Figure 2 of the drawing, and its comparison with Figure 1. In Figure 2, 44 is a container housing chambers 45 and 46, and 41 is another container housing chambers 48, 49, 50, 5I. As before, the number of chambers may vary slightly in response to the necessities of commercial design. The extract precipitation and stripping function is housed in 44 and the recovery of paraffinic from naphthenic oils is housed in 41. The separation is for the purpose of isolating 44 in a temperature sense from 41, and may be carried out equally well by joining 44 and 41 physically, as shown by dotted lines, but thoroughly insulating chamber 48 from chamber 46, as likewise shown in dotted lines. The internal functioning and the general arrangement of the chambers is the same as in Figure 1. Paraiinic solvent enters through pipe 52, passes into the raffinate phase, through chambers 45, 46, pipe 53, pump 54, pipe 55, mixer 56, cooler 51, pipe 58, chambers 48, 49, 50, 5|, and out with raffinate through pipe 59. Naphthenic solvent enters as before through pipe 60. Extract from 5I is transferred to 50 by pump 6l. Extract from 58 is transferred by pump 62 to 49. Extract from 49 is transferred by pump 63 to mixer 56. However, oil charge is not introduced to this mixer, and the chambers 48-51 inclusive are charged only with the duty of most efficiently separating a mixture of naphthenic and paraffinic oils, comparatively rich in paraffinic constituents, and the temperature therein, effected by use of cooler 51, is that best adapted for such operation. Oil charge introduced to the system by pump 64 passes through pipe 65 into chamber 46, in admixture with raffinate from chamber 45. There, at a comparatively high temperature level, in the presence of a relatively high proportion of propane and low proportion of selecto, it is effectively deasphaltized, to yield a comparatively parafiine-rich and comparatively asphalt-free mixture of parafllnic and naphthenic oils to pass as raffinate through pipe 53, pump 54, pipe 55, mixer 56 and cooler 51 into the upper portion of the system. Extract from chamber 48 passes through pipe 66, pump 61 and pipe 68 into pipe 52. Extract from chamber 46 passes through pipe 69, pump 10, and pipe 1i into pipe 52. These extracts admixed in pipe 52 with paratfinic solvent pass into chamber 45. In that chamber, due to the presence of propane, entirely free from paraflinic constituents of the oil, at a properly high temperature level, a. maximum separation from the extract of the paraffinic constituents entrained therein can be attained.

Thus it will be seen that without any sacriflce of the useful characteristics of the general system, my invention has enabled me to so separate the several functions thereof so as to best serve the demands of each and to secure the most efficient operation of each function. My system of operation, without substantial change in proportion of solvents applied will thus permit of an increase in the yield of paraflinic constituents. a greater parafiinicity of the raffinate, and a lower Conradson carbon content of the recovered refined oil. For a system housed in an apparatus of a given size, equipped with a given cooling capacity, the adoption of the method of operation disclosed herein, including the indicated heat insulation, will result in a material increase in daily through-put capacity.

As indicated, when operating according to this system, charging one part by weight of oil per unit time at a temperature of 180-190 F., and about four parts of selecto at about 'I0-'15 F., the temperature in chamber 48 would be about 15-90 F., while that in chambers 45 and 4B would be of the order of 10U-120 F., and would be effected by feeding propane at a higher temperature than before, say at about F. i

It will be understood that the numerical data given herein is set forth only by way of example, and' that the invention is not limited thereby or thereto, but is subject only to those limits expressly set forth in the following claim.

In the solvent treatment of petroleum lubricant fractions by counterflowing parafiinic and naphthenic solvents through a plurality of extractive stages and introducing oil to an inter- .mediate stage of the series, the improvement which comprises maintaining the oil introduction stage and all stages prior thereto in the direction of paraffinic solvent flow at a temperature level substantially higher than that obtaining in the stage next subsequent and in any other following stage in the direction of paraffinic solvent flow, while maintaining the same rate of paraflinic solvent flow throughout all stages of the series, and by-passing naphthenic solvent and extract from the first stage subsequent to oil introduction to the first stage prior to oil introduction, whereby enhanced separation of oil into parailinic and non-parafiinic oil constituents may be obtained for a given ratio of solvents.

HENRY D. NOLL.

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