US1988004A - Distillation unit - Google Patents

Description

Jan. 15, c D GA DISTILLATION UNIT Filed July 11, 1932 INVENTOR. Clare [7 Gard BY wfila'w ATTORNEY.

Patented Jan. 15, 1935 UNITED STATES PATENT OFFICE? Application Julyll, 1932 Serial No. 621,952

3 Claims.

This invention is a continuation in part of my application Serial No. 457,656 filed May 30, 1930.

The present invention relates to a distillation unit which is adaptable for general distillation purposes. It is especially useful for the distillation of mineral oils and more particularly it may be employed as a conditioning still for the recovery of used absorption oil which has been circulated through an absorption plant for the recovery of natural gasoline.

It is an object of this invention to provide a useful and elficient distillation unit which is easily demountable so that any section which may require inspection, cleaning or replacement may be made available quickly and readily. v

It is a further object to provide an eflicient still for general distillation purposes such as for the distillation of mineral oils or for the conditioning of used absorption oil.

Referring to the drawing illustrating a preferred embodiment of the distillation unit, Fig. 1 is the distillation unit in elevation partly in vertical section. Fig. 2 is a horizontal section taken along the line 22 of Fig. l with head 52 partly broken away. Fig. 3 is a horizontal section taken along the line 33 of Fig. 1 with perforated plate or tray 14 partly broken away. Fig. 4 is a horizontal section along line 4 4 of Fig. 1. Fig. 5 is a more detailed view in vertical section of the mountingof coils 28 and 29 in still section A of the distillation unit. Fig. 6 is a more detailed View in vertical section of the structure atthe lower part of coils 28 and 29 disposed in still section A of the distillation unit. Fig. 7 is a vertical section of the tray assembly support in section A of the distillation unit.

The upper section A ofthe distillation unit illustrated by Fig. 1 may be denominated the still section. It extends from the top of the distillation unit to head 36. The central part B is a spacer section through whicha number of pipes enter the still. The spacer section is the space defined by heads 36 and 52. Section C is a preheater section between heads 52 and 60. Residuum drum section D is the space below head 60. The aforesaid heads are imperforate except, of course, for the passage of the various pipes therethrough as described below. It is preferred to weld the pipes to their respective heads in order to secure them firmly and to prevent leakage from the various sections. Thus the distillation unit comprises a residuum drum section, a preheating section, a spacer section and a still section disposed from the bottom to the top thereof in the order named and the connections and appurtenances therefor.

The shell 8 of the distillation unitcan be separated at the flanges 9, l0 and 11 and the piping can be separated at the unions 12. The flanges may be secured together by bolts, not shown. By positioning the flanges and pipe unions in the manner to be described, the entire distillation overflow pipes 15 and liquid seal caps 16. The perforated trays, overflow pipes and caps are in common use. in present day fractionation and dephlegmation apparatus. The entire tray assembly rests upon supports 13 secured to the shell. The trays are .properlyspaced in relation to one another by spacers held in place by rods 20. The lower ends of rods 20 are threaded and secured by nuts 21 below the lowest tray and the upper ends of rods 20 are also threaded and are screwed into ring 22. Fig. 7 shows the novel tray spacing structure in greater ,detail. Openings are provided in perforated plates 14 whereby rods 20 may be passed therethrough. The spacers 23 may simply be pipes of the desiredlength having an internal diameter greater than the diameter of rods 20 and thus each rod 20 may be passed through its respective spacer pipes 23 when said spacers are placed between their respective trays. The length of the spacer pipes determines the distance each tray is held apart from the others because the openingsin trays 14 for insertion of rods 20 are smaller than the diameter of the spacers 23. The tray assembly is madeintegral by tightening nuts 21 on the ends of rods 20 and by screwing rods 20 into ring 22. If desired, rods 20 may be provided with stops 24 welded thereon wherebythe tray assembly may be securely and firmly spaced alongrods 20. The trays 14 may be packed at their edges if they do not fit within shell 8 properly.

Any number of rods 20 may be provided although four are usually ,sufiicient. Fig. 3 illustrates one embodiment in'which fourrods 20 are employed. Four or more supports 13 may also be secured on the inner periphery of shell 8 to provide sufficient support for the entire tray assembly. I

The still section A is also provided with vapor outlet'7, oil inlet line l'land pipe 18 which is a pressure equalizing pipe connected with section D, described below. Lines 17 and 18 are provided with unions 12. It is preferred that oil line 1'1 should enter the still section A at a point above the uppermost tray 14. Valve 19 on pressure equalizing pipe 18 is normally open except when it is desired to blow out the residuum from the residuum drum section in the manner described below. Head 36 serves as the bottom of still section A.

The whole apparatus is designed to be taken apart easily so that the inside may be inspected, cleaned or that parts may be replaced if necessary. For instance, vapor line 7 may be disconnected at some point not shown and shell 8 may be disjoined at flange 9. The top of the distillation unit may then be removed and the entire tray assembly can be lifted in one integral piece from the shell by raising ring 22 to which the tray assembly is attached.

The heating coils in the still section A are also easily removable from the distillation unit. They are designed to carry steam or other heating medium. The outer coil 28 has coil turns which are slightly separated from each other while the inner coil 29 is a closed coil, i. e. there is substantially no space between the coil turns. The inner coil may extend some distance above the outer coil. Steam inlet pipe 30 is connected with coils 28 and 29 by pipes 31 and 32, respectively. Coil 29 is provided with outlet pipe 33 connecting with coil 28 and coil 28 is provided with outlet pipe 34 which discharges into a trap 35. Lines 31 and 34 are provided with unions 12 located at approximately the same elevation as flange 10.

Inner coil 29 is welded upon rods 40 and outer coil 28 is welded upon rods 41. Rods 40 and 41 may be bolted together as at 42 on top and at 43 at their bottoms. Fig. 5 illustrates this lower structure in detail. The coils are thus firmly secured to the rods and the lower ends of rods 41, in turn, may be attached to supports 44 by bolts 45. Supports 44 are securely attached to shell 8 as by welding. Fig. 4 shows a preferred embodiment in which three sets of rods 40 and 41 are employed but more or less may be used as desired.

In order to remove heating coils 28 and 29 from the distillation unit, it is merely necessary to disjoin shell 8 at flange l0 and to disconnect unions 12 on lines 1'7 and 18, respectively. The upper part of the shell may then be lifted oil, having first disconnected vapor line '7 at some point not shown, leaving the coils 28 and 29 exposed for inspection. If it is desired to remove the coils 28 and 29, unions 12 in pipes 31 and 34 may be disjointed and bolts 45 may be uniastened from supports 44, following which the coil assembly can be easily lifted from support 44 as an integral unit.

Steam may be directly introduced into the material to be distilled in the still section by perforated steam jet 46 connected with steam supply pipe 30 provided with valve 2'7, by line 47 controlled by valve 48. Referring to Figs. 4 and 6, it is preferred that the steam be introduced in the annular space between the concentric coils 28 and 29 as well as through approximately the middle area of the cylindrical space outlined by the inner coil 29. Perforations 50 are provided in jet 46 in order that the steam may flow through the space defined by coil 29 and perforations 51 are provided in order that the steam may flow between coils 28 and 29. By breaking the union 12 in pipe 47, the jet 46 may be removed from the still after the shell has been separated at flange 10 in the manner described above.

The bottom 36 of the still section A serves as the top of the central part B which is a spacer section provided for the purpose of conveniently locating the pipes connected with the distillation unit whereby the pipes may be quickly and easily reached for inspection and cleaning. An opening or manhole'54 is provided in shell 8 at spacer section B in order that the pipes disposed therein may be easily reached. Within section B is steam inlet line 31 which connects with coils 28 and 29 in section A, steam inlet line 4'? which is connected with steam jet 46, residuum draw-off line 55 provided with valve 25 and connected to the bottom of still section A, oil inlet pipe 56 provided with valve 26, said pipe 56 being connected with the preheater section C described below, oil pipe 1'7 which connects with still section A and steam exit pipe 34 connected with coils 28 and 29. It is preferred that these pipes be welded to the shell 8 and to the respective plates 36 and 52 through which they pass. Fig. 2 illustrates the arrangement of the pipes in the spacer section B.

The bottom head 52 of the spacer section B serves as the top of preheating section C. Preheater section C is provided with bottom head 60. Within this preheater section is preheating coil 61 through which oil may flow. It is connected with oil inlet 56, and with oil pipe 1'? through which the oil flows to still section A. Coil 61 is heated by heat exchange with steam furnished by pipe 62 connecting with steam inlet 30. Steam outlet 63 from the preheater section C communicates with steam outlet pipe 34. The coil 61 is thus maintained in an atmosphere of steam. If desired, other heating medium than steam may be employed.

Flange 11 is provided on shell 8 at the preheater section. If it is desired to gain entrance into the preheater section C without disjoining the other sections, unions 12 in pipes 30, 56, 55, 34 and 18, respectively may be disconnected and the distillation unit may be separated at flange 11 by lifting that section of the tower which is above said flange ll, first having disconnected vapor line '7 at some point not shown. Coil 61 will be carried with the upper part of the unit so raised and the coil is entirely open for inspection and repair. The entire preheating section is likewise conveniently exposed.

Section D of the distillation unit is the residuum drum section provided with head 60, which serves as the top of this section, bottom 64 and liquid draw-off 65 controlled by valve 66. Liquid drawoff line 55 from still section A communicates with section D. In order that pressure equilibrium may be maintained between sections A and D, equilibrium pipe 18 connects the vapor space of still section A with the vapor space of residuum drum section D. By maintaining equilibrium between sections A and D, the flow of oil from A via line 55 to section D is assured. Line 6'7 controlled by valve 68 is a gas or air pipe for blowing out the residuum section. In order to gain entrance into the residuum section, a manhole, not shown, may be provided therein.

This distillation unit is adapted for general distillation purposes but it is especially useful for the distillation of mineral oils and it is particularly eificient for the distillation of used or dirty lean absorption oil which is commonly circulated through absorption plants for the recovery of natural gasoline. The removal of. a relatively small proportion of dirty absorption oil fromzthecirculatory system of'an absorption plant, the distillation of the portion so removed and :the return to the circulating absorption oil stream of the distilled, clean absorption oilzis the subject of my application Serial No. 457,657, filed May 30th, 1930. Although the present distillation'unit is capable of a wide variety .of uses, its operation will be described as an absorption oil recovery still.

. It is well known to recover absorbable components from natural gas by subjecting such gas to intimate contact with an absorption oil. It is common practice to heat the absorption oil containing the absorbed fraction of the natural gas in order to drive off the lighter absorbed components. The absorption oil is then cooled and recirculated for additional intimate contact with more natural gas. Absorption oil which is relatively free of the lighter absorbable components is known as lean absorption oil.

After absorption oil has been circulated through an absorption plant over and over for a period of time it becomes dirty and heavy, collecting heavy hydrocarbons from the gas, making it inefiicient for gasoline recovery. When this distillation unit is connected to an absorption oil circulating system, the absorption oil is recovered by distillation leaving the heavy contaminating material as a residue. The clean absorption oil vapors are condensed and the recovered absorption oil is allowed to re-enter the absorption plant system. Its original absorption properties are regained. Operating costs are reduced because the oil may be used over and over instead of being thrown away. Only a small amount of new oil need be added from time to time to the absorption oil circulating system in order to keep the circulating system full, whereas before a distillation unit was installed all of the dirty oil had to be replaced.

When this distillation unit is used in connection with an absorption plant, only a portion of the circulating lean oil need be by-passed at any one time from the absorption plant circulatory system through this distillation unit in order to be cleaned, the return of recovered absorption oil being established so as to keep the oil in the circulating system in good condition.

Oil, such as dirty, lean absorption oil from an absorption plant for the recovery of natural gasoline, enters the distillation unit by line 56 which connects with coil 61 located in preheating section C. Any means for forcing the oil through line 56 may be employed as by use of a pump, not shown. As stated above, coil 61 is heated by anatmosphere of heating medium such as steam entering preheating section via line 62 connected with steam inlet 30 and exiting from the preheating section via line 53 connected with steam discharge pipe 34 which connects with trap 35. The preheated oil passes from coil 61 via line 17 into the still section A of the distillation unit and preferably the preheated oil enters above the uppermost perforated plate 14 in said still section. The liquid accumulates upon the perforated plates 14 and passes through overflow pipes 15 into the cups l6 situated on the next lower perforated plate or tray. Vapors generated pass upwardly through the perforations in plates 14. and intimately contact with the oil accumulated thereon whereby fractionation is accomplished. Vapors and gases from the still section A are conducted away via vapor outlet 7. In the application of the distillation unit to the recovery of absorption oil, the vatillation unit will operate under superatmospheric or atmospheric pressures or under vacuum.

Coils 28 and 29 situated in the lower-part of the still section A are connected with steam inlet 30 as above described and the steam passing through said coils heats the oil in the lower part of the still section. The oil descending from the lowermost overflow pipe accumulates upon the bottom of still section A. It is preferred to maintain the foam level in still section A at approximately the top inner coil 29. A liquid level indicator, not shown, may be provided. The amount of liquid in the still section can be controlled by regulating the amount of liquid entering the distillation unit via line 56 controlled by valve 26 and by regulation of the exit of residuum flowing through line 55 controlled by valve 25. Steam may be introduced directly into the oil by jet as. Part of the steam from jet 46 passes through the oil maintained within the space defined by inner coil 29. The oil within the annular space defined by outer coil 28 and inner coil 29 is also heated by steam arising from jet 46. In this manner, circulation is established Within the oil body maintained within the still unit. This circulation and steam distillation, together with contact of the oil with the heating coils 28 and 29 provides for very eiiicient distillation in the still unit. It will be noted that coils 28 may be slightly spaced apart whereby the oil may flow through these small spaces and heat exchange will be extremely efiicient. Exhaust steam from coils 28 and 29 passes via line 34 into steam trap 35.

Residuum from the still unit A exits therefrom via line 55 into residuum drum section D. In order that the oil may flow readily from A to D, pressure should be equalized between these two sections. For this reason, equalizing pipe 18 provided with valve 19 connects section A with section D. By opening valve 66 in residuum outlet 65 and valve 68 in gas or air pipe 67 after valves 19 and 25 in lines 18 and 55, respectively, are closed, the residuum may be blown out or the residuum section from time to time. A liquid level indicator, not shown, may be provided on the section D.

The above description is merely illustrative of a preferred embodiment of this invention and of oneof many applications for which this still is useful. Many variations thereof may be made within the scope of this invention.

I claim:

1. A distillation unit comprising a shell, 2. residuum drum section in said shell, a preheater section in said shell above said residuum drum section, means to heat said preheater section, a spacer section above said preheater section, a still section above said spacer section, means to heat said still section, a vapor outlet from said still section, a residuum outlet from said residuum drum section, a residuum conducting line connecting said still section with said residuum drum section to pass oil from said still section to said residuum drum section, an oil inlet to said preheater section and an oil conducting line connecting said preheater section with said still section to pass oil from saidpreheater section to said still section.

2. A distillation unit comprising a shell, aresiduum drum section in said shell, a preheater section in said shell above said residuum drum section, means to heat said preheater section, a spacer section above said preheater section, a still section above said spacer section, said still section including a liquid heating zone and a fractionating zone in open connection therewith, means to heat said still section, a vapor outlet from said still section, a residuum outlet from said residuum drum section, a residuum conducting line connecting said still section with said residuum drum section to pass oil from said still section to said residuum drum section, an oil inlet to said preheater section and an oil conducting line connecting said preheater section with said still section to pass oil from said preheater section to said still section.

3. A distillation unit comprising a shell, a residuum drum section in said shell, a preheater section in said shell above said residuum drum section, means to heat said preheater section, a spacer section above said preheater section, a still section above said spacer section, said still section including a liquid heating zone and a fractionating zone in open connection therewith, means to heat said still section, a vapor outlet from said still section, a residuum outlet from said residuum drum section, a residuum conducting line connecting said still section with said residuum drum section to pass oil from said still section to said residuum drum section, an oil inlet to said preheater section, and a pressure equilibrium line connecting said still section with said residuum drum section.

CLARE D. GARD.

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