US2082034A - Apparatus for countercurrent contact treatment of liquids - Google Patents

Description

June 1, 1937. R B SWTH 2,082,034

APPARATUS FOR GOUNTERCURRENT CONTACT TREATMENT OF LIQUIDS Filed Dec. lO, 1935 Haff/ha:

aff/haie ayer l eve! ATTORNEYS Patented June l, 1937 PATENT oFFlcE APPARATUS FOR COUNTERCURRENT CON- TACT TREATIWENT' OF LIQUIDS Reading B. Smith, Hammond, Ind., assignor to Sinclair Refining Company, New York, N. Y.,

a corporation of Maine v Application December 10, 1935, Serial No. 53,705

3 Claims.

This invention'relates to improvements inapparatus for countercurrent contact treatment of one liquid with anothersubstantially immiscible liquid of different specific gravity. It is an object of the presentinvention to provide anl apparatus adapted to'. subject two immiscible liquids of .different specific igravities, passing in countercurrent relation, to a serieslof alternate mixing'and settlingoperations. The invention provides an apparatus adapted for kthis .purposewhich is of simple: andarugged construction. Its operation also is simple and does not require expensive and complicated control mechanism.

The apparatus of the present invention is of special value and utility in solvent-extraction rening operations, which are now excessively used in the petroleum rening art, wherein a lubricating .oil fraction, for example, is treated lwith a solvent such. as'nitrobenzene, furfural, or the like. In such processes the solvent selectively extractsundesirable constituents frointhe lubricating oil fraction and improves the properties of the treated oil. However, the apparatus of the invention is .of general utility foreffeoting efcient l-countercurrentfcontact of any liquid with any other. substantially immiscible liquid of different specific gravity.

The apparatus of thepresent invention com- V prises. a vertically elongated housing' divided transversely into aseries of superimposed compartments. Connectionsare provided for supplying arelatively heavy` liquid to an upper compartmentk and for discharging. a relatively light liquid fromv the upper portion, thereof. Similarly, connections .are provided for supplying a relatively light liquidto a lowercompartment and` for discharging a relatively heavy liquidfrom the lower portion thereof. ducts, shaped to prevent a liquid lighter than that withinxthe pipes fromlentering theirlower ends. and'flowing. upwardly therethrough, lead' from the lowerportion of each compartment, ex-

cept the lower-most, to the central portion of the next lower compartment ofthe series. Similarly, ay plurality of pipesor ducts', shaped to prevent a liquid heavier than that within the pipes from entering thcirnpper'ends and flowing downwardlyftherethrough, lead fromthe upper portion of eachyci `the compartments, except the uppermost, to -thefcentral portion of the next higher compartment of the series. In each of the intermediate compartments theoutlet ends of the pipesy or ducts leading-downwardly from the next higher compartment are disposed in immediate juxtaposition to the outlet ends of the corresponding pipes or ducts leadingupwardly from the next lower compartment.

. Inttheopgeration of such'a device, when a heavy liquid is continuously supplied to annpper. compartmentancla relatively lighter vliquid is sup- A plurality of pipes orr plied to a lower compartment, the difference of speciiic gravity will cause the lighter liquid to workits way upwardly through the series of superimposed compartments -and the heavier liquid to work its way downwardly through the series ,of compartments. In any one of the intermediate compartments the heavier liquidirom the next higher compartment and the lighterliquid from the next lower compartment will be brought into contact with each other as oppositely liowing streams and intimately admixed in the central portion vof the intermediate compartment. lighter components of the mixture then will separate because of the difference in their specic gravity, the lighter liquid accumu-y lating in the upper portion of the compartment and then passing upwardlyV to the central portion of the next higher compartment while the heavier liquidv accumulates in the lower portion'oi the intermediate compartment and then passes to the central portionxof-the next lower compartment. This procedure of alternate admixing vand settling is repeated in each of the series of compartments as the heavier liquid flows downwardly andthe lighter liquid iiows upwardly through'the apparatus.

The invention will be further described in connection with the accompanying drawing which illustrates one form of apparatus embodying the invention.

Fig. l of the drawing is a sectional elevation of a countercurrent liquid contacting column embodying the invention; and

Fig.v 2 shows, in section, a fragmentary elevation of a modied arrangement for conveying heavier liquid from an upper compartment and lighter liquid from a lower compartment into an intermediate compartment insuch a-way that the two liquids will be brought into intimate admixture and `discharged into the intervening com..-

partment while at the `same time preventing short-circuiting, of either the heavier orV lighter liquid, through the intervening compartment.

The countercurrent contacting column shown in Fig. 1 comprises a vertically elongated housing I provided with a plurality of vertically-spaced trays 2, 3, and 4 which extend transversely acrosskv the housing I and divide it into a series of compartments A, B,f-,C, and D. An inlet connection 5 communicates with the uppermost compartment A and is adapted to supply a relatively` municates with the upper end of the uppermostV compartment A and a discharge connection` 8' The heavier and communicates with the lower end of the lower compartment D. Pipes 9 lead from each of the compartments A, B and C, through the partitions 2, 3, and d, respectively, into the next lower compartment B, C or D. The pipes Q advantageously are shaped in the form of a U near their.

lower ends and terminate at their lower ends at a level approximating the middle of the compartments into which they depend. Similarly, pipes lli lead from each of the compartments D, C, and B, through the partitions il, 3, and t, into the next higher compartment C, B or A, respectively. The pipes lll are shaped in the form of a U at their upper ends and similarly terminate at a level approximating the middle of the upper compartment into which they extend. Each of the pipes 9 depending into anyone of th'e intermediate compartments is positioned so that its lower end will terminate in immediate juxtaposition to the upper end of one of the pipes It! extending upwardly from the next lower compartment. With this construction, for example, a relatively heavy liquid passing downwardly through pipes 9 from compartment A will be brought into intimate admixture with a relatively light liquid passing upwardly through the pipes I0 from compartment C, and the mixture will be discharged into the central portion of the intervening compartment B. However, the heavy liquid passing downwardly through one of the pipes 9 cannot short-circuit through the corresponding pipe it and pass to the next lower compartment without intervening admixture and settling in the intermediate compartment. Similarly, it is not possible for the lighter liquid passing upwardly through any one of the pipes HJ toy short-circuit through the corresponding line 9' and pass upwardly to the next higher compartment without intervening admixture and settling in the intermediate compartment.

The inlet line 5 through which the lighter liquid is supplied to the upper compartment advantageously may be divided into branches at its discharge end the discharge end of each branch positioned to register with the upper end of one of the pipes i@ leading into the uppermost compartment from the next lower compartment. Similarly, line E, through which the lighter liquid is supplied to the lowermost compartment, may be divided into branches and the discharge end of each branch positioned so as to register with the lower end oi one of the lines 9 depending into the lowermost compartment.

A mechanical level controlling-device Il arranged to control the rate of discharge from the lowermost compartment through line 8, so as to maintain approximately constant the upper surface of a body of the heavier liquid in the lower portion of the lowermost compartment, advantageously may be provided. No level controls are necessary in any of the other compartments, however, as the proper direction of ow in each of the other sections will be maintained by the gravity differential.

In the modied form of duct arrangement shown in Fig. 2, the pipes @a and ltd correspond respectively to the pipes t? and i@ in the apparatus shown in Fig. l. However, the lower bent end of the pipe da is enlarged and the upper bent end of the pipe ita extends into it. By this arrangement, any short-circuiting through pipe Illa of the heavier liquid flowing downwardly through pipe 9a or vice versa is effectively precluded. However, the heavier liquid flowing downwardly through one of pipes 9a and the lighter liquid flowing upwardly through the corresponding pipe lila are admixed before they are discharged into the intervening compartment.

In the operation of the apparatus illustrated inFig. l for the treatment of a lubricating oil fraction with a solvent heavier than the oil (nitrobenzene or furfural, for example), the raw lubricating oil fraction is supplied through connection 6 and the solvent through connection 5. The lubricating oil fraction which is lighter than the solvent passes upwardly through the housing I and eventually is discharged through connection 1, while the heavier solvent with the extracted material dissolved therein passes downwardly through the housing l and eventually is discharged through connection 8. In each of? the compartments a stratification of the liquid body occurs. The upper stratum .consists of. treated or partially treated oil with a minor amount of the solvent dispersed therein. This substance, in the rening art, is known as the rainate. The lower stratum consists of a layer of the solvent with the extracted material selectively dissolved therein. In the rening art this substance is known as the extract. The inter-- mediate layer consists of a mixture of raffinate particles and extract particles.

In operation, the lower or extract layer in the compartment A, for example, is heavier than the mixture of rainate and extract particles in the intermediate portion of the compartment B and therefore the extract ilows downwardly from compartment A to compartment B through the lines 9. Similarly, the upper raffinate layer in the compartment C is lighter than the mixture of rainate and extract particles in the intermediate portion of compartment B and it therefore flows upwardly from compartment C to compartment B' through pipes I0. The extract entering compartment B from compartment A, through lines El, and the raffinate entering compartment B from compartment C, through line I 0 are brought into intimate admixture as they are discharged from pipes S and Hl, respectively, into the intermediate portion of compartment B. the gravity diierential again effects separation of the mixture into an upper layer of the lighter raiinate and a lower layer of the heavier extract. The same procedure occurs in each of the other compartments of the series. Thus the device of the present invention provides for a definite mixing and settling zone in each compartment or section, and accordingly a more eilcient extraction is obtained than is possible in the ordinary packed type of column or in the normal bubble tower type of apparatus both of which have been employed to some extent for this type of operation.

It will be apparent that the details of construction can be modiiied without departure from the spirit of the invention. For example, the housing can be divided into any number of superimposed compartments. Similarly, the number, arrangement and shape of the pipes 9 and l0 can be varied so long as ducts are provided for bringing a lighter liquid from the upper portion of a lower compartment and a heavier liquid from the lower portion of a higher compartment into intimate admixture in the central portion of an intervening compartment, and so long as means are provided for preventing short-circuiting of either of the liquids through the intervening compartment. For example, the pipes 9 and I0 need not be bent in the form of a U if a balanced check valve is arranged in each pipe to permit flow In compartment Bi therethrough only in the desired direction. Similarly, if the housing l is divided'into a relatively large number of superimposed compartments, the heavier liquid (the solvent for example) may be initially supplied to one of the upper compartments below the uppermost compartment, if desired, and the lighter liquid (the oil fraction for example) may be initially supplied to one of the lower compartments above the lowermost compartment. The uppermost and lowermost compartments in such an arrangement will function principally as stripping compartments promoting a more complete nal separation of extract and raffinate.

I claim:

l. In apparatus for countercurrent contact treatment of one liquid with another substantially immiscible liquid of different specific gravity, the improvement comprising a series of superimposed compartments, connections for supplying a relatively light liquid to and for discharging a relatively heavy liquid from the lowermost compartment of the series, connections for supplying a relatively heavy liquid to and for discharging a relatively light liquid from the uppermost compartment of the series, a plurality of generally downwardly extending ducts connecting the lower portion of each compartment of the series except the lowermost and the central portion of the next lower compartment, said ducts being arranged to provide free and open communication into the lower compartment with which they connect from the next higher compartment, a plurality of generally upwardly extending ducts connecting the upper portion of each compartment of the series except the uppermost and the central portion of the next higher compartment, said last-mentioned ducts being arranged to provide free and open communication into the upper compartment with which they connect from the next lower come partment, the said downwardly extending ducts and the said upwardly extending ducts extending into each of the intermediate compartments of the series being arranged with their lower ends and upper ends respectively in immediate juxtaposition and shaped to prevent short-circuiting of a heavier liquid downwardly through the upwardly extending ducts and short-circuiting of a lighter liquid upwardly through the downwardly extending ducts, whereby in any intermediate compartment of the series liquid passing upwardly through the upwardly extending ducts from the next lower compartment and liquid passing downwardly through the downwardly extending ducts from the next higher compartment will be brought into intimate contact and discharged into the central portion of the said intermediate compartment, and means for controlling the rate of discharge of liquid through said connection for discharging heavy liquid from the lowermost compartment.

2. In apparatus for countercurrent contact treatment of one liquid with another substantially immiscible liquid of different specific gravity, the improvement comprising a series of superimposed compartments, connections for supplying a relatively light liquid to and for discharging a relatively heavy liquid from the lowermost compartment of the series, connections for supplying a relatively heavy liquid to and for discharging a relatively light liquid from the uppermost compartment of the series, a plurality of generally downwardly extending ducts connecting the lower portion of each compartment of the series except the lowermost and the central portion of the next lower compartment, the lower ends of said downwardly extending ducts being bent to provide relatively short upwardly extending portions, a plurality of generally upwardly extending ducts connecting the upper end of each compartment except the uppermost and the central portion of the next higher compartment, the upper ends of said upwardly extending ducts being bent to provide relatively short downwardly extending portions, the upturned lower end of each of the said downwardly extending ducts in any one of the intermediate compartments being positioned so as to register with and adjacent to the downturned lower end of one of the upwardly extending ducts in said intermediate compartment.

3. In apparatus for countercurrent contact treatment of one liquid with another substantially immiscible liquid of different specific gravity, the improvement comprising a vertically elongated housing, a series of vertically-spaced trays extending transversely across said housing and dividing it into a plurality of superimposed compartments, a plurality of pipes depending from each tray of the series into the next lower compartment, said pipes terminating at their lower ends at a level approximating the center f of the compartment immediately below the tray from which they depend and communicating through said trays with the lower portion of the next higher compartment, a plurality of pipes extending upwardly from each tray of the series into the next higher compartment, said lastmentioned pipes terminating at their upper ends at a level approximating the center of the compartment immediately above the tray from which they extend and communicating through said trays with the upper portion of the next lower compartment, means for supplying a liquid of relatively light specific gravity to the lowermost compartment of the series, means for supplying a liquid of relatively heavy specic gravity to the uppermost compartment of the series, the lower end of said depending pipes and the upper end of said upwardly extending pipes terminating in each intermediate compartment being positioned in close juxtaposition and oppositely directed, whereby a relatively heavy liquid flowing downwardly from an upper compartment and a relatively light liquid owing upwardly from a lower compartment will be admixed as they are discharged into the intermediate compartment, means for preventing short-circuiting of heavier liquid from the depending pipes through the upwardly extending pipes and for preventing shortcircuiting of lighter liquidl from the upwardly extending pipes through the depending pipes, connections for supplying a relatively heavy liquid tothe uppermost compartment and a relatively light liquid to the lowermost compartment, a discharge connection communicating with the upper end of said housing, a discharge connection leading from the lower end of said housing and means for controlling the rate of discharge of liquid through the last-named connection.

READING B. SMITH.

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