US2953501A

US2953501A - Apparatus for extraction by the double solvent method

Info

Publication number: US2953501A
Application number: US710496A
Authority: US
Inventors: Mignone Tomaso
Original assignee: R O M AZIONARIA RAFFIN Soc
Current assignee: R O M AZIONARIA RAFFIN Soc; Sarom Azionaria Raffinazione Olii Minerali Soc
Priority date: 1957-07-18
Filing date: 1958-01-22
Publication date: 1960-09-20
Anticipated expiration: 1977-09-20
Also published as: DE1090360B; FR1206997A

Description

Sept. 20, 196 T; MIGNONE 2,953,501

APPARATUS FOR EXTRACTION BY THE DOUBLE SOLVENT METHOD Filed Jan. 22, 1958 APPARATUS FOR EXTRACTION BY THE DOUBLE SOLVENT METHOD Tomaso Mignone, Ravenna, Italy, assignor to S.A.R.O.M. Societa Azionaria Raflinazione Olii Minerali, Milan, Italy Filed Jan. 22, 1958, Ser. No. 710,496

Claims priority, application Italy July 18, 1957 2 Claims. (Cl. 196-1452) oils of which one component consists of paraflin oils and the other of aromatic i.e. non-paraffin oils. It is to be understood, however, that, selecting suitable solvents, the invention may also be applied to other homogeneous mixtures (solutions) as for example a mixture of acetoneacetic acid (using chloroform as a solvent for the acetone and water as a solvent for the acetic acid), or a mixture of parachloronitrobenzol orthochloronitrobenzol (in which the first is dissolved with heptane and the latter with methane). This specification, however, is particularly concerned with mineral lubricating oils.

As is Well-known it is frequently necessary in the production of lubricating oils to separate the paraifin hydrocarbons from the aromatic and asphaltic hydrocarbons, and as the viscosity of the former is much less afiected by temperature than is the case with the latter, paraflin oils present far superior properties as lubricants.

The term paraifin as used in this connection is not to be interpreted literally, but is intended to imply a phase composed of hydrocarbons in which aliphatic chains largely preponderate; the same applies by analogy to the terms aromatic and asphaltic respectively.

The separation of a crude oil into its paralfin and non-parafiin phases is effected industrially by means of solvent extraction operations. A large number of chemical'compounds are known to be suitable solvents, each nn'der certain conditions of application and for specific types of operations. Some of these solvents have a highly polar molecule e.g. phenol, cresols, furfural, sulphurous acid, nitrobenzol and aniline: these solvents present good solubility with non-parafiin hydrocarbons, but are barely soluble in parafiin hydrocarbons. A crude oil, if mixed ;with one of these solvents, will separate out into a layer composed of the solvent with incorporated non-paraffin hydrocarbons, and a layer composed of paraffin hydrocarbons containing a small quantity of the solvent.

In the case of certain crude oils, e.g. all oils rich in -asphaltic products and composed of vacuum distillation residues, treatment with a single solvent (as referred to above) is no longer adequate, as it is first necessary to feliminatethe asphalt content of the oil. This is generally :done'by precipitating out the asphalt with a mixture of liquefied propane and propylene. i

According to 'the method as practised at :the present time, a crude oil containing, asphaltic components is first jsubjectedto treatment with propane toxremove the asphalt, and then to successive extraction with one of the solvents mentioned-abovefor the separation of the paraf- -fin oils on the one hand, and of the aromatic 'oilson the other; As will be seen in the following, the yields result ingfrom such a process are unsatisfactory, and one'of the principal purposes of this invention is toprovide a process and apparatus afiording better yields. 1

tltCS ;:l AQQ hQI. di advantage, of the processes epiployednpltill J 1 Patented Sept. 20, 1960 now resides in the fact that neither the refined product (paraflin oils) nor the extract (non-paraffin oils) are ob tained in a sufliciently pure state and their coloration reveals the existence of impurities that can be eliminated only by the use of decolorising earths. Accordingly, another purpose of the invention is to provide means for remedying these disadvantages. 3

A further purpose of this invention is to simplify the technique of extraction by the double solvent method, independently of the type of the crude mixture to be separated into its components, so as to altord aprocess and apparatus of general application.

According to one form, the present process for the extraction of a homogeneous mixture of two liquid components by means of two solvents is principally characterised by the operations of: providing a refining zone and an extraction zone, both extending in a substantially vertical direction and each capable of bringing'about a descending flow of one liquid in contact with a rising flow of a second liquid having a specific gravity lower than that of the first liquid, feeding in a refining solvent at an upper part of the refining zone and producing a descending flow of the said refining solvent through the said refining zone; feeding in an extraction solvent at a lower part of the extraction zone and producing a rising flow of the said extraction solvent through the said extraction zone: taking from the bottom of the refining zone the bottom product of such zone, taking from the top of the extraction zone the top product of such zone and mixing the said bottom and top products with the aforementioned homogeneous liquid mixture to obtain a nonhomogeneous liquid mixture; decanting by gravity the non-homogeneous mixture, separating it into a heavy phase and a light phase; feeding in the light phase at a lower part of the refining zone to produce a rising flow of the light phase through the refining zone in refining contact with the descending flow of the refining solvent: feeding in the heavy phase at any upper part of the extraction zone to produce a descending flow of the heavy phase through the extraction zone in contact with the rising flow of the extraction solvent; taking from the top of the refining zone a product predominantly consisting of one component of the aforementioned homogeneous mixture and of the extraction solvent, and taking from the bottom of the extraction zone a product predominantly consisting of a second component of the aforementioned homogeneous mixture and of the refining solvent.

According to a further form, applied to a homogeneous mixture of mineral oils, the process according to the invention is characterised by the operations of: providing a refining and an extraction zone, both extending in a substantially vertical direction and each capable of bringing about a descending flow of one liquid in contact with a rising flow of a second liquid having a specific gravity lower than that of the first liquid; feeding in at an upper part of the refining zone a refining solvent, capable of dissolving the non-paralfin oils, and producing a descending flow of the said refining solvent through the refining zone; feeding in at a lower part of the extraction zone an extraction solvent capable of dissolving the parafifin oils, and producing a rising flow of the said extraction solvent through the extraction zone; taking from the bottom of the refining zone the bottom product of such zone, taking from the top of the extraction zone the top product of such zone, and mixing the said bottom and top products with the homogeneous mixture of parafiin oils and non-paraffin oils to obtain a non-homogeneous liquid mixture comprising a light phase and a heavy phase; decanting by gravity this non-homogeneous mixture, separating the said light and heavy phases; feeding refining zone in refining contact with the descending flow of the refining solvent; feeding in the heavy phase at an upper part of the extraction zone to produce a descending flow of the heavy phase through the extraction zone in contact with the rising flow of the extraction solvent; taking from the top of the refining zone a product predominantly consisting of the parafiin oils and of the extraction solvent; and taking from the bottom of the extraction zone a product predominantly consisting of the non-paraffin oils and of the refining solvent.

Furthermore, according to this invention, an apparatus for the extraction of a homogeneous mixture of two liquid components by means of two solvents is characterised by the feature of comprising in combination: a refining column and an extraction column; means in both columns capable of producing an intimate contact between a liquid rising and a liquid descending through the column; means for feeding in a refining solvent at an upper part of the refining column; means for feeding in an extraction solvent at a lower part of the extraction column; a mixing receptacle in communication with a bottom zone of the refining column and with a top zone of the extraction column; means for feeding the aforesaid homogeneous mixture into the mixing receptacle; a separator receptacle capable of being fed from the said mixing receptacle and having a lower zone in communication with an upper zone of the extraction column, and an upper zone in communication with a lower zone of the refining column; and means branching from the top of the refining column and from the bottom of the extraction column for taking from the said columns the refined and extracted products respectively.

Further details of the invention will be evident from the description given below with reference to the accompanying drawing which represents diagrammatically one form of application of the invention for the extraction of lubricating oils.

According to the drawing, the refining column 1 and the extraction column 2 which extend in a vertical direction contain means, 3 and 4, capable of producing an intimate contact between a descending liquid and a rising liquid respectively. Such means, as far as column 1 is concerned, preferably consists of a series of plates and, as regards column 2, of a large number of horizontally disposed angular sections, whereby in both columns the descending liquid may be intimately mixed with the rising for the necessary reciprocal transfer of the extracted and refined products respectively, in a manner well-known per se in the art.

A tank 5, which contains a refining solvent well-known in the art and composed of equal parts of phenol and cresol, is connected by means of a pipe 6, incorporating a pump 7 and a control valve 8, with an upper part 9 of column 1 through which the refining solvent-aforementioned can be fed into the column under volume and pres sure control.

A tank 10 containing an extension solvent comprising liquid propane is connected by means of apipe 11, incorporating a pump 12 and a control valve 13, with a lower part 14 of the extraction column 2 through which liquid propane may be fed into the column under volume and pressure control.

A mixing apparatus 15, comprising a unit separate from the two

columns

1 and 2, is fed with crude oil through a pipe .16 which incorporates a pump 17 and a control valve 18. A tube 19 leading from the bottom of the refining column 1 and incorporating a control valve 20 joins pipe 16 at section 16a which is located between the valve 18 and the mixer 15, whereby, subject to appropriate regulation of

valves

18, 20, the bottom product in column 1 may be brought into the mixer together with the crude oil. Furthermore, the top product in the extraction column 2, the top of which communicates with section 16a of pipe 16 through a tube 21, is also fed into the mixer 15.

The mixer 15 is connected by a pipe 22 with a gravity separator, or decanter 23, of any suitable type. As is well-known in the art, a classical form of separator comprises a bottom zone in which a heavy phase is deposited and a top zone in which a light phase is collected. The separator shown in the accompanying drawing is of a horizontal type comprising a vertical partition 24 extending from the bottom wall up to a point at close proximity to the upper wall of the separator, so that the interior of the separator is subdivided into two chambers 23a, 23b, the end of the first chamber, remote from the partition 24, being fed from the mixer 15 through tube 22. The heavy phase collects on the bottom of chamber 23a, While the light phase passes over the partition 24 and collects in chamber 23b, the separation level between the two phases being shown at 25 Therefore, considered in relation to a vertical separator of the classical type, the chamber 23b of separator 23 may be defined as the top zone of the separator and that part of chamber 23a situated below the level 25 may be defined as the bottom zone of the separator.

It will further be seen from the drawing that the bottom zone of separator 23 is connected via pipe 26 with an upper part 27 of extraction column 2, the pipe 26 aforesaid incorporating a pump 28 and a control valve 29. This valve 29 is automatically controlled by an apparatus 30 which is associated with chamber 23a of the separator and sensitive to variations in the interphase level 25. Apparatus of this kind is Well-known in the art and does not therefore call for specific description.

The top zone 23b of separator 23 is connected via pipe 31 with a lower part 32 of the refining column 1. The pipe 31 incorporates a pump 33 and a valve 34 which is automatically controlled by an apparatus 35 sensitive to the pressure obtaining in chamber 23b, in such a manner that valve 24 is largely opened or largely closed respectively, according to the increase or diminution, as the case may be, of the pressure in the separator 23. The extract, comprising in this case non-paraflin oil, is taken from the bottom of the extraction column 2 through a pipe 36, incorporating a control valve 37, which is automatically controlled by an apparatus 38 associated with the bottom zone of column 2 and sensitive to variations in the level of the non-paraffin oil which is collected in this zone of column 2.

Finally, the refined product, comprising in this case parafiin oil, is taken from the top of column 1 through a pipe 39 incorporating a control valve 40 which is automatically controlled by an apparatus 41 associated with the top zone of column 1 and sensitive to the pressure in that zone.

As will be readily understood from this description of the apparatus according to the invention, the apparatus in question necessarily operates under super-atmospheric pressure in order to maintain the propane in the liquid state. It will also be understood that in using solvents which are liquid under ordinary temperature and pressure conditions, the pressures inside the various parts of the apparatus will only be those necessary for maintaining the individual liquid phases in motion, and that they are therefore very substantially different from the pres sures required for the liquefaction of propane which may amount to as much as 25-30 atmospheres effective pressure or more.

As already stated above, the crude oil, which consists of a mutual solution of various non-parafiin and paraflin oils, is fed through the pipe 16. As is the case with all known processes, the purpose of this process is to trans.- form this solution (homogeneous mixture) into a nonhomogeneous mixture of two phases and to separate the two phases from one another by decantation. Finally, the solvents are recovered by a process which is known per se, but which is outside the scope of this invention.

In the normal operation of the apparatus here concerned, and considering primarily the two columns 1 and-2, it is clear that in each of these columns opposite flows of two liquid phases'in contact with one another are stabilized, the lighter phase, comprising propane in which paraflin oils are dissolved, rising to the top of each column, and

the heavier phase comprising the phenol-cresol solvent "5 in which non-paraflin oils are dissolved, descending to the bottom. The bottom product of column 1 therefore contains a substantial proportion of phenol-cresol solvent, while the product at the top of column 2 contains a substantial proportion of propane. These two products are 'taken from the respective columns through

pipes

19 and 21, added to the crude'oil in pipe 16aand conveyed to the mixer 15, which as has been shown, constitutes a manifestly composed of a non-homogeneous mixture in the two columns operates only on a part of the crude oil, i.e. that part which has been pre cleansed from the unwantedcomponent. The mixer and the separator 23 may therefore be regarded as an intermediate separation stage, outside the two columns and operating to provide through the pipes 31, 32 'a reflux for column 1, and through the pipes 26, 27 a reflux for column 2. In their turn, the

columns

1, 2 with

pipes

19, 21 respectively, produce a kind of reflux for the mixer-

separator group

15, 23. The interconnection between this group and the columns is regulable by means of the

valves

20, 29 and 34 incorporated in the pipes 19, 2-6 and 31 respectively, so that the entire process of extraction may easily be controlled to 'aiford the most favourable results.

The table below shows the composition in kilo-grammes per'hour of the phases at the salient points of the installation, designated at the top of the individual columns by the-same reference numerals as those used in the drawing.

Table I Operation Position Com- 16 14 9 39 36 21 19 27 32 ponent With crude 011 1,000 281 719 230 170 949 451 P 011 type Prnnano 2,000 1,490 510 2, 500 140 1,010 1,630

.1 Phenol-Cresol solven 1,500 225 1,275 270 1, 540 1,545 265 1 Density at 15 0.- 1.003 0. 508 1. 050 0. 576 0. 863 0. 553 0.92 0. 800 0. 595 With crude Oil 1,000 342 658 235 315 893 657 oil type Prnnsme 2,000 1,640 360 2, 300 230 660 1,870

...... Phenol-Cresol solvent 1, 000 350 750 290 1, 210 1, 040 460 Density 0. 998 0. 508 1.050 0. 592 0. 865 0. 549 0. 916 0. 811 0. 619 With crude Oil 1,000 552 448 438 390 886 942 oil type Propane"-.. 1,800 1, 510 290 2,080 110 570 1,620 3 Phenol-Cresol solvent 1, 800 350 1, 450 320 1, 740 1, 770 290 Density 0. 931 0. 508 1. 050 0. 619 0. 915 0. 681 0. 980 0. 870 0. 631

which particles or droplets of phenol-cresol solvent with their non-paraflin oil content are finely dispersed among particles or droplets of propane with their content of paraflin oils. By force of gravity, therefore, the heavy phase containingjaf little paraffin oil will accumulate at 40 the bottom of chamber 23a, while the light phase containing a little non-parafiin oil will accumulate in chamher 2312. The heavy,-or bottom, phase is then conveyed to "the top of column 2 throughpipe26, while the light,

or top, phase in the separator-23 isconveyed to the bot- F tom of column 1 through pipe 31. i

The light phase introduced at 32 into the refining column 1 will rise in that column in counter-current to the descending dispersed flow of phenol-cresol solvent,

whereby the solvent will remove from the light phase its content of non-paraflin oils, while, on the other hand, the propane contained in the-light phase will keep the parafiin oils sufliciently diluted so as not to be dissolved in the descending phase to any remarkable extent.

Finally, a product predominantly composed of par-afiin oils and propane will be collected at the top of column 1.

The heavy phase introduced at 27 into column 2 will descend in counter-current to the rising dispersed flow of liquid propane, whereby the latter will remove from the heavy phase its content of paraffin oils. product predominantly composed of non-paraflin oils and of phenol-cresol solvent will be collected at the bottom of column 2.

The bottom product of column 1 is predominantly composed of phenol-cresol solvent which carries along with it comparatively small quantities of non-paraflin oil and propane, while the product at the top of column 2 is predominantly composed of propane which carries along with it comparatively small quantities of paraffin oils and phenol-cresol solvent. These two products are taken from the columns and, as stated above, added to and vigorously remixed with the crude oil in the mixer 15 whereby the entire amount of incoming crude oil in the separator 23 is rapidly and eificiently separated into two rough phases Finally, a 0

i From this table it will be seen, for example, that in the case of operation with crude oil of type 1 there are obtained 281 liters per hour of paraffin oil leaving the topof column 1' through the pipe 39 and 719 liters per through the pipe 36.

The characteristics of the crude oil, parafiin oil and non-parafiin oil respectively in relation to the table given above will be seen from the Table II below in which the columns marked A refer to extraction according to the present process and the columns marked B refer to one of the processes ordinarily employed, comprising a preliminary asphalt-removal phase using propane, followed by extraction with phenol, while the column marked C refers to the treatment of crude oil type 3 in an ordinary extraction plant using phenol. It should be noted that the crude oil type 3 is a vacuum-distilled oil.

In the case of all the operations conducted in the apparatus as described above, all the valves shown in the diagram were so regulated as to aiford the following internal pressures:

Atm. effective pressure At top of column 1 24.5 At bottom of column 1 26.0 At top of column 2 23.0 At bottom of column 2 24.0 At separator 23 22.0

The temperature at which the process takes place ranges between 20 and 50 C., and amounts on the average to about 35 C.

The advantages of the invention will be immediately evident upon comparing columns B and C with columns A in Table II for each type of crude oil dealt with, and there is therefore no need to emphasize them further here.

It is also obvious that the invention is in no way restricted to the embodiment here described with reference to the accompanying drawing, but that various alternative modifications within the limits of technical equivalent may be applied thereto without exceeding the scope of the even before entering the columns, In this Way each of invention as defined in the following claims.

hour of non-paraffin oil leaving the bottom of column 2 Table II Operation with Operation with Operation with crude oil type 1 crude oil type 2 crude oil type 3 A B A B A 0 Crude oil:

Supply kg. per hT- 1000 1000 1000 1000 1000 1000 Density at 15 C 1. 0030 1. 0030 0. 9980 0.9980 0. 9315 0. 9315 Viscosity at 210 F. in centistokes 365 365 280 280 11.35 11.35 Paraffin oil:

Supply kg. per hr 281 218 342 273 552 425 Percentage yield by weight 28.1 21. 8 34. 2 27. 3 55. 2 42. 5 Density at 15 C O. 8990 0.8985 0. 9050 0. 9049 0.8652 0. 8654 Viscosity at 100 F. in centl- Y okes 408 421 464 473 Viscosity at 210 F. in centistokes 28. 3 28. 3 29. 4 29. 4 9. 9. 35 i c ity 1n e 102 100 97 96 115 115 Viscosity index after deparatfin i0n 100 98. 5 95 94 Oarbonicresid'ue acc. to Conradson (percentage 7 by Weight) 0.4 0.5 0.4 0.55 Oolor (Union)- .1 3% 5 Non-paraflin oil: ,7 Supply kg. per hr. 719 782 658 727 448 575 Percentage yield by weight 71. 78. 2 65. 8 721 7 44. 8 57. 5' Density at 15 C 1.052 1.036 1.058 1.040 1.026 0. 9861 Viscosity at 210 F. in centistokes 1700 850 1750 930 18. 1 15. 9

What I claim is:

1. An apparatus for the extraction by means of two solvents of a homogeneous mixture of two liquid components comprising in combination: a refining column and an extraction column; means in both columns for producing intimate contact between a liquid rising and a liquid descending through said columns; means for feeding a refining solvent into an upper part of the refining column; means for feeding an extraction solvent into a lower part of the extraction column; a mixing receptacle in communication with a bottom zone of the refining column and with a top zone of the extraction column; means for feeding the aforementioned homogeneous mixture 'into'the mixing receptacle; a separator receptacle connected to be fed from said mixing receptacle and having a lower zone in communication with an upper zone of the extraction column and an upper Zone in communication with a lower zone of the refining column; and means branching from the top of the refining column andfrom the bottom of the extraction columnfor taking from the said columns the refined and extracted products respectively. 1

2. An apparatus for the extraction by means'of two solvents of a homogeneous mixture of two liquid components comprising in combination: a refining column and an extraction column; means in both columns for producing intimate contact between a liquid rising and a liquid descending through said columns; means for feeding a refining solvent into an upper part of the refining column; means for feeding an extraction solvent into a lower part of the extraction column; a mixing receptacle in communication with a bottom zone of the refining column and with a top zone of the extraction column; means for feeding the aforementioned homogeneous mixture into the mixing receptacle; a separator receptacle connected to be fed from said mixing receptacle and having a lower zone in communication with an upper zone of the extraction column and an upper zone in communication with a lower zone of the refining column; valve means associated with the upper zone of the separator receptacle sensitive to pressure prevailing in the separator thereby to control light phase flow from said upper zone of the separator to the refining column; valve means associated With the separator receptacle sensitive to the phase separation level in the receptacle to control heavy phase flow from the lower zone of the separator to the extraction column, and means branching from the top of the refining column and from the bottom of the extraction column 'for taking from the columns the refined and extracted products, respectively. 9

References Cited in the file of this patent UNITED STATES PATENTS Lewisfi. Oct. 31, 1944

Claims

1. AN APPARATUS FOR THE EXTRACTION BY MEANS OF TWO SOLVENTS OF A HOMOGENEOUS MIXTURE OF TWO LIQUID COMPONENTS COMPRISING IN COMBINATION: A REFINING COLUMN AND AN EXTRACTION COLUMN, MEANS IN BOTH COLUMNS FOR PRODUCING INTIMATE CONTACT BETWEEN A LIQUID RISING AND A LIQUID DESCENDING THROUGH SAID COLUMNS, MEANS FOR FEEDING A REFINING SOLVENT INTO AN UPPER PART OF THE REFINING COLUMN, MEANS FOR FEEDING AN EXTRACTION SOLVENT INTO A LOWER PART OF THE EXTRACTION COLUMN, A MIXING RECEPTACLE IN COMMUNICATION WITH A BOTTOM ZONE OF THE REFINING COLUMN AND WITH A TOP ZONE OF THE EXTRACTION COLUMN, MEANS FOR FEEDING THE AFOREMENTIONED HOMOGENEOUS MIXTURE INTO THE MIXING RECEPTACLE, A SEPARATOR RECEPTACLE CONNECTED TO BE FED FROM SAID MIXING RECEPTACLE AND HAVING A LOWER ZONE IN COMMUNICATION WITH AN UPPER ZONE FOR THE EXTRACTION COLUMN AND AN UPPER ZONE IN COMMUNICATION WITH A LOWER ZONE OF THE REFINING COLUMN, AND MEANS BRANCHING FROM THE TOP OF THE REFINING COLUMN AND FROM THE BOTTOM OF THE EXTRACTION COLUMN FOR TAKING FROM THE SAID COLUMNS THE REFINED AND EXTRACTED PRODUCTS RESPECTIVELY.