US1754605A - Still - Google Patents

Description

Filed April '19 1927 '3 sheets-sheer @Zwar/7g.

Apral'w, 1930. y

J. A. CAMPBELL STILL lFiled Ap'ril 19,. 19'2'7 3 sheets-sheet 5 Patented riapre l@ mit@ A. CMEEELL, 0F LONG BEACH, CALIFORNIA application inea april ia,

This invention hasto do With devices which are variously known as stills, evaporators, strippers or separators their general function being the evaporation and separaa tion ot lower boiling constituents from a Vnoixdescribed are commonly used in evaporatingand separating od the light hydrocarbons from abody o't'absorbing oilof higher boil ing point; and the operation of the present.

invention will `theretne be. described as a plied to that particularusage, however Wit out limitation.

In absorption pla-anteior obtaining gasoline from casing head gas, the operations in general include lirst absorbing the gasoline 20 vapors trom the fixed gas into a heavier absorbing oil which is `delivered to the absorption apparatus iti-lean condition and cornes out ot the absorption apparatus in what 'is known as rich or at condition.

rlhe rich absorbing oil with its burden of absorbed gasoline is then passed to a still or stripper, usually being pre-heated before reaching the still, a great 'deal if not most of theheat tor evaporation being added to the oil before its release into the still, and Y evaporation taking place largely by release of pressure. ln these stills `it is aimed to maintain teinperatureand pressureA conditions such that all ot the desirable absorbed constituents are separated trom the absorbingr oil, leaving the absorbing oil clean to be used over again in the absorption'step. It is diicult, however, to maintain conditions such that While all the absorbed constituents are remove i, none of the absorbing oil is at the same time evaporated; and this diflliculty has led to the subsequent passage of the vapors through a dephlegrnator condenser for the purpose of more nearly stabilizing the product, separating and condensing out any absorbing oil vapors. So far as l am aware these two operations have usually been carried on in separate pieces of apparatus and the condensed absorbing! oil 'trom the dephleginator then returned to the inain body rear. sensi ne. rasees.'

of absorbing oil at some convenient point'in the lean oilV line. v

lt is an object of this invention `to carry out both the described operations in a single piece of apparatus, with attendant advantages and accomplishments that will be best 4understood'troni-the ollowin'ff detailed description 'of a specific and preferred form of apparatusA illustrative of the invention, reference for this purpose being had to the ,accompanying drawings, in which:

Fig. 1 1s a diagrammatic vertical central section of my improved apparatus;

Fig. 2 is an enlarged fragmentary central vertical section of the middle portion of the apparatus.

y 3 is a similar section .of the upper portion of the apparatus. i

Fig. 4 is a similar section of the lotte; portion of the'apparatus.

F ig. 5 is a horizontal section on line 5 5 of Fig. 1; l

Fig. 6 is a horizontal section on line 6-6 of Fig. l and Fig. 7 is a horizontal section on line 7-7 of Fig. l.

First to describe the structure of my iniproved apparatus; it is preierably in the form of an upright cylinder or tower having an outer shell'l() closed at its top with a suitable cap 11, having in its bottom suitable heatingv ineans,'asI steam heating coils 12, to maintain the desired operating temperatures Within thek apparatus.

Within the outer shell there is a number ofperforated plates or ioors, including several reflux plates 15, several oil plates 16 and also severalagitation plates 17, the oil platesl and agitation plates being assembled in pairs 4 as illustrated, To space these several dier ent plates apart there is an inner shell made up of sections 18, 19, 20,21, 22 and23, the lowerxnost inner shell section V18 resting upon an annular angleiron ilange 24 Welded to outer shell 10, and the uppermost inner shell section 23 preferablyhaving an angle iron flange 25 resting 'upon its upper. edge.l These' various inner shell sections and the floors supported and spaced thereby are all held together in superposed assembly relation by through all of the floors, is capped at 31' at its upper end,and has oil outlet slots 32- 4at a point above the uppermost` oil plate 16. Near its lower end there is a feed connection pipe 33`through which the rich oil is fed into the standpipe at a suitable temperature. Surrounding this central' standpipe and. also acting as spacers between the superimposed plates or floors, I provide spacer tubes 34 as illustrated, the standpipe being provided with collars 35 above and'below the floors that are spaced apart bythe tubes 34.` A reflux oil inlet pipe is provided at and delivers the reflux oil over the uppermost redux plate 15. Mounted above each reflux plate is one ormore froth breaking pans 41, each pan being mounted upon a liquid delivery tube 42 which extends through the corresponding reflux plate to deliver liquid to a point near the plate next below, a liquid sealing cup 43 being provided at the lower Vend of each tube 42 to prevent passage of gas or vapors upwardly through the tube andv also for the purpose of more or less spread ing the delivery of oil from each tube over the' perforated plate liust below. rlhe operation of these reflux plates is substantially that which has been described in my co-pending application Serial Number 79,073 filed January l, 1926 which matured'into Patent 1,643,696 on Sept. 27, 1927; and the froth breaking pans 41 may be either of the specilic construction described in that application or theymay be like the one described in'my co-pending application entitled Collector pans for absorbers, Serial Number 184,367, filed April 19, 1927. The operation at each of the. reflux plates is one that involves the formation of a mass of froth overl each reflux plate, by virtue of vapors passing up through the perforated plates and frothing the liquid which is delivered above the several plates, the body of froth rising to the level of the upper edges of the pan and the froth being broken 'up at those ,pan edges,'

which are preferably sharp, with the result ,that the freed oil iows over the pan edges into the pans and then down through tubes 42 to be delivered to the floor or plate' next below, where the operation is repeated. This operation puts the vapors and liquids into most intimate contact and repeatedly so, and as a result the vapors and liquids reach a condition of equilibrium, at the temperatures and pressures of operation. The final vapor flows olf through the vapor outlet 50 and the remaining liquid proceeds on downwardly to and through the lower perforated p ates.

At each of the upper plates at which the reflux liquid is being handled, the operations are characterized by having to do with a comparatively large amount of vapor and relatively small amount of liquid; and therefore the froth breaking pans may be relatively small and occupy arelatively smaller proportion of the total cross-sectional area of the tower. However, the operations in the lower parts of the apparatus characteristically involve a proportionately larger amount of. liquid and relatively smaller amount of vapor, and therefore the froth breaking pansabove the several oil floors or plates in the lower part of the apparatus are made comparatively large, with a comparatively long froth breaking edge, andoccupy a comparatively large proportion of the total cross-sectional area of the tower. This difference in relative areas covered by the pans,

and the corresponding diiferences in froth breaking capacity, may be attained in several different manners, For instance in my application Serial Number 184,867 filed April 19, `1927, mentioned above I show one improved arrangement for obtaining relatively large froth breaking capacity without the necessity of correspondingly increasing the total area occupied by the froth breaking pans; and such'an arrangementas there described may be used in this device if desired. However, because in the particular operations of mystill, lthe .lower sections are handling comparatively a large amount of liquid anda relatively small amount of vapor, the pau construction for the lower sections may be effectively made as I shall now describe; the presence of 'a relatively large amount of liquid making it desirable that the pans shall not only have a large froth breaking capacity, but that the pans themselvesshall be large, and the presence of a relatively small amount of vapor at that point making it unnecessaryt'o leave uncovered any large propotion of the upper surface area of the froth bo Cbnsequently as a preferred construction for this still l provide above each oil plate 16 a singlepan 55 of the shape and constructionshown in detail in Fig. 5. Each of these pans is of an exterior diameter somewhat smaller than the diameter of the inner shell of the tower, the pan having an exterior rim 56 which preferably has a sharp upper froth breaking edge. Within each pan there are several openings 57 of fairly large size each surrounded by a rim 58, also preferably sharp at its upper edge for froth breaking'purposes. Each of these pans also has in its bottom sevshoulders, as illustrated in Fig. 2, so that they form spacers between the adjacent plates; and these tubes also pass through the large openings 57 of the pan neat below. 'The lowf-zrmost` oil deliveryV tubes 60a have liquid seal cups 61 at their lower ends to prevent passage or gas directly up through the tubes and they deliver the liquid finally into the lower end oi?. the ap aratus directly above the steam heating coils 12, the liquid nding its nal outlet at 62 near the bottom of the apparatus but somewhat above the steam heating coils so that a body of oil is at all times maintained over those coils.

The rich oil that is delivered to the appa` ratus through pipe 33 will, in 'a typical case, be delivered at a temperature or about 320o F., and under' a pressure of 35 lbs. per square inch; this oil being delivered through the slots V32 in standpipe 30 directly over the uppermost oil plate 16 and over the u permost pan 55. The oil is spread outwardly under pressure, the operating premure within the apparatus being substantially lower than that at which the oil is delivered (a typical operating pressure in the apparatus is about 30 lbs. per square inch) @il is thus distributed over the uppermost oil plate 16 as well as over the uppermost pan 55. Whatever oil is delivered directl into this up ermost pan merely flows down t rough its tules 60 to the plate next below there to be frothed; and the oil that is delivered onto the uppermost oil plate 16 is frothed by the upwardly moving vapors. A typical froth forming operation takes place at the next set of plates 16, and 17 below. l-lere the clear oil is delivered between the two plates 16 and 17 s reading out over the perforated agitation late 17 and being agitated by the upwardly flowing vapors, and

then thevapors' and oil tcgether pass upward-= ly through the perforate Voil plate 16 more or less in the form of froth, and, in passing through the perforations of plate 16, a mass of froth containing bubbles of fairly -uniorm size is formed. This mass of froth builds up over plate 16 until the mass reaches the level of the pan just above, the froth is broken up at the several edges of the pan, the 'clear 011 flowing over into the panand then down through the tubes-60 to the plates next below, the vapors being released to pass on upwardly through the perforated lates next above. This operation is repeated or each set of periorated plates, theliquid being :Erothed and refrothed, the gas passing continuously upwardly and the oil passing continuously downwardly through the apparatus until the vapors are 'finally released from the froth formed with the absorbing oil and pass on up into the reflux operations, and the clear absorbing oil released of its burden finally .finding its outlet at the bottom of the apparatus.

lin order to increase the agitation within the apparatus steam may be admitted as at an inlet 65 belowL the lowermost plates, this steam passing upwardly with the vapors and increasing agitation. InV a typical operation this steam may be admitted'at about 280o F., and as the temperature at the iinal vapor outlet 50 will typically be about 300o F. the steam will-be taken o in vapor form and pass out with the vapors rather than passing out as water with the clean oil.

As l have said, my apparatus is not restricted to any particular useand although it' used forvstripping rich absorbing oil it is not necessarily limited to operation at the temperatures and pressures noted. l find it convenient merely for purposes of description to state such temperatures and pressures so that the operation may be well understood.` Using such temperatures and pressures'thus as a basis of description l shall now'proceed to describe how the deviceas a whole operates under typical conditions. The rich oil, as l have said, is introduced at a temperature of about 320J F. and the steam coil or other heating means at 12 is operated so that the lean oil leaves the apparatus at about 310 l?. The admission of agitating steam at 65 at its temperature of about 280 F. also has a bearing upon the operating temperature maintained in the lower part of the apparatus, But from what I have said it will be seen that throughout the lower part of the apparatus a fairly uniform temperature is maintained on the absorption oil, that temperature ranging only slightly, as between 310 and 32001?. The reflux oil is introduced at 40' at a temperature of about 200,o F., and as the temperature of iinal vapor take-oli is typically 300 E., 'the temperature of operation in the upper portion of the device ranges between those two'ligures.

Itv will be understood, of course, that in order to force thevaprs up through the successive plates there must be a fall of pressure as Vthe y vapors pass upwardly through the plates and' that generally speaking the pres- .sures in the sections between lower plates are peratures employed, by the nature of the volatile constituents (their vapor tension, etc.) and by the pressure maintained at the final vapor take-olf 50. With any eiven pressure iso i are maintained at theoil discharge at 32 a certain portion of the lighter constituents will be evaporated there; but evaporation from the absorbing oil continues the 'absorbing oil passes on down throughthe plates below, final evaporation of all the lighter constituents being accomplished by the time the oil is ready for final delivery into the lower part of the shell. Consequently as the oil passes down through the lower plates vapors .are

constantly releasedwhich,.under the pressures maintained by vapor generation, .f pass upwardly-through-the plates to froth the oil as before described. Under the maintained temperatures and pressures these vapors and the absorbing oil tend to come to a condition of equilibrium; so that all of the vapors. of lighter absorbed constituents are released to pass upwardlythrough the ytower while the whole bodyoffreed absorbing oil, cleared of its absorbed lighter constituents, finally' passes olf at the bottom.V However'in order to maintain ternperaure and pressure conditions that will cause a full evaporation and separation of the lighter absorbedV constio uents 1t is almost inevitable that the absorbing oil itself will have a sullicient vapor. 'tension that it `is Avaporized to some. small extent. and a small part of this vapo'r thus tends finally to pass upwardly from above the uppermost oil plate '16 into the refiunpart of the apparatus. Here the whole admixture of vapors comes linto frothing Contact with `the reflux oil, this reflux oil preferably being the oil which is being finally made, in this particular case the gasoline that is finally produced. This gasoline flowing down through v the reflux plates as a reflux liquid, and at the temperature and pressure ranges noted, tends to absorb and take up the vapors of the heavier absorbing oil and carry that absorbing voil down with it.' At the same time this reflux oil is being evaporated by being raised in temperature within the apparatus, the final vapor take-off temperaturebeing high enough to evaporate-'off all desirable constituents of the reflux oil, leaving substantially only the heaviest constituents of that reflux oil, and the absorbed oil that came from below, to linally be delivered fromthe 'reflux plates down into the absorption oilA which is flowing through the lower plates. The constituents of the reflux oil which are thus delivered to the lower parts of the apparatus will thus include some heavier and' un desirable portions of the reflux oil, some of the absorbing oil itself, and also perhaps some sees evaporated; and during their evaporation are intermittently '.commingled and contacted with the vapors of the lighter desirable con stituents, with the resultthat all the desirable constituents initially'present in or carried down by the reflux oil are re-evaporated; While only the heavy constituents which should finally come out with the absorption oil are not evapor:` ed.

` From what I have said it will be seen that my apparatus combines in a single operation and in a single device both -the' operation of vaporizing and separating the lighter constitutents from the absorbing oil and also the operation of refluxing those vapors with a re- -flux oil. The advantages of carrying these two operations out in a single procedure and in a single piece of apparatus lie largely in simplicity of operation as well as simplicity ofapparatus, and further peculiarly in the uniformity of operations and uniformity of results. Further I may speak oit'- thev convenience and simplicity of the direct delivery of the unvaporized remnants of the retluxed oil, togetherl with whatever constituents it yhas 'absorbed from the vapors, directly into the'body of absorption oil which is going.

through its evaporation process. The final result of the complete operation of the apparatus is a production of a very clean vapor product, substantially wholly clear of any of' closed at its upper end, liquid deliveryopenings in the stan-dpipe at an intermediate level adapted to deliver liquid into an intermediate part of the shell, a.serie's of perforated horizontal plates vertically spaced in the shell below said intermediate part, said plates surroundin th'e standpipe, froth-breaking pans arrange above sald plates', liquid deliverytubes yextending down from the frothbreakpoints above plates below, a series ,of horizontal perforated plates ,vertically spaced in the shellabove said intermediate part and surrounding the vertical standpfipe, froth breaking pans located above said last inentioned plates, liquid delivery tubes extending downwardly from said pans through the corresponding plates to deliver liquid above the plates next below, the liquid delivery tube of the lowernost one of said last men- 'apparatus,' comprising a ing'pans toI deliverfliquid from them to'120 tioned pans deliveringiiquid directly inte vertical shell, a vertical central standpipe extendlng through the length of the shell and i closed at its upper end, liquid delivery openings in the stand-pipe at an intermediate level adapted to deliver liquid into an intermediate p'art of the shell, a series of perforated horizontal plates vertically spaced in the shell below said intermediate part, said Vplates surrounding theV standpipe, frothbreaking pans arranged above said plates, liquid delivery tubes extending down from the froth-breaking pans Y to deliver` liquid fron them to points above plates below, a series of .horizontal perforated plates verti cally spaced in the shell above said intermediate part .and surrounding the vertical Vstandpipe, froth breaking pans located above said last mentioned plates, liquid delivery tubes extending downwardly from said pans through the corresponding plates to deliver 'liquid above the plates next below, the liquid delivery-tube vof the`lowerm0'st one of said last mentioned pans delivering li uid directly into said intermediate part o the shell,

and means to introduce a reflux liquid above the uppermost one of said last mentionedy plates, said first mentioned pans being relativelylarge in horizontal extent and occupying a relatively large portion of the horizontal sectional area of the shell, and said last mentioned pans being relatively smaller and occupying a relatively smaller .portion of the horizontal sectional area ofthe shell.

3. Fractionat'ing apparatus, comprising a vertical shell, means to introduce liquid to be vaporized at an intermediate level the shell, a series of perforated horizontall plates vertically spaced in the shell below said intermediate level, froth breaking'v pans arranged above the several plates, liquid dedown from the froth livery tubes extendin ver liquid to points breaking pans to de above plates below, perforated plates vertically spaced in. the shell above said intermediatedevel, 'froth breaking pans located above said last mentioned plates, liquid delivery tubes extending down from the froth breaking pans to dehver liquid over plates below, the liquid delivery tube of the lowermost one of said last mentioned pans delivering liquid directly ln the intermediate part of the shell and above the uppermost lone4 of the rst mentioned plates, and means to introduce a .reflux liquidv over the uppermost one of said last mentioned plates, said first mentioned pans being relatively large in cupying a relatively large portion of the horizontal sectional area of the shell, and said last mentioned pans being relatively smaller lhaving a sha a series of horizontal.

horizontal extent and ocand occup 'ng a relatively smaller portion of the horizontal sectional area of the shell.

4. In a deviceof the character described, the combination' of a shell, a series of horizontal perforated lates vertically spaced in .m the shell, froth reaking pans arranged above the platesfsaid pans com rising each 'a bottom and aeripheralraise `rim with a sharp froth brea ing-edge, the bottom having a plurality'of openingsthere'through andwith' 75 peripheral lraised rimsaroud said openings, said rims having sharp froth breaking edges, and liquid'l delivery tubes extending down-v wardly from the bottom of each an through Athe plate belowand throught e openingslgo in the .pan next below'to deliver liquid above S a platebelow the last mentioned pan.

5. A froth breaking device, comprising a flatbottompan with a raised vperip eral rim froth-breaking edge, openings S5 through the bottomof the` pan provided with i peripheral rims with shar frothbreaking edges, and liquid outlets' 1n the bottom of 5 the pan.

In witness that I claim'the foregoing I 9U have hereunto subscribed my name this 29th day of March, 1927.

JULIAN A. CAMPBELL.

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