US2685938A

US2685938A - Emulsion treater

Info

Publication number: US2685938A
Application number: US220476A
Authority: US
Inventors: Jay P Walker; Clarence O Glasgow; Jr Alex W Francis
Original assignee: National Tank Co
Current assignee: Cameron Solutions Inc
Priority date: 1951-04-11
Filing date: 1951-04-11
Publication date: 1954-08-10
Anticipated expiration: 1971-08-10

Description

Aug. 10, 1954 Filed April 11, 1951 J. P. WALKER ET AI.

EMULSION TREATER 4 Sheet-Sheet 1 Jay P. Walker Clarence 0; Glasgow Alex W. Franc/'s,J/:

\ eg; N ATTORNEYS 10, 1954 J. P. WALKER ET AL 2,685,938

EMULSION TREATER Filed April 11 1951 4 Sheets-Sheet 3 R wk mm m Wm Qk m R I K mm mm mm \m wm mm v mm mm mm Jay P. Wa/ke) Clarence 0. Glqsgow Alex W Franc/3,0

ATTO R N EYS'.

Aug. 10, 1954 J. P. WALKER ET AL 2,585,933

EMULSION TREATER I Filed April 11, 1951 4 Sheets-Sheet 4 y 0 Jay R Walker Clarence 0. Glasgow Qfl Alex W Franc/8,115

2 5 ATTOR N EYS .of the treater,

, .Fig. 6 is a front elevation of Patented Aug. 10, 1954 EMULSION TREATER Jay P. Walker, Clarence 0. Glasgow, and Alex W. Francis, J12, Tulsa, Okla, assignors to National Tank Company, Tulsa, Okla., a corporation of Nevada Application. April 11, 1951, Serial No. 220,416

14 Claims.

This invention relates. to new and useful improvements in emulsion treaters.

One object of the invention is to provide an improved emulsion treaterof the horizontal type involving certain features and arrangements which make for more efiicient and. economical treating. Y

A particular object of the invention is to pro.- vide an improved treater arranged to effectively separate free water, treat the emulsion to efficiently segregate the oil and water components thereof and release .the gas therefrom, as well as to scrub such gas so as to delete entrained oil.

A further object of the invention is to provide a heated emulsion treating chamber in the front end of the horizontal tank with a water knockout immediately preceding the treating chamber, whereby the infiuent. stream is denuded of free water just before passing into the treating chamber, in combination with means for diverting the rearward fiOW of the treated oil, and some water, into the immediate vicinity of the knockout, and flowing the same rearwardly, thereby preventing stagnation of liquids above the knockout and setting up flowing currents through the oil zone, which will be substantially free from gas and undue agitation.

Still another object of the invention is to provide an improved treater wherein substantially all of the gas is evolved at the treating chamber and such gas is carried off in heat exchangerslation with the inflowing influent and thereafter scrubbed to remove moisture therefrom.

A construction designed. to carry out the invention will be hereinafter described together the line 22 of 4:,

Fig. 3 is a similar view taken on the line of Fig. i,

Fig. 4 is a iongitudinal, vertical sectional view Fig. 5 is a longitudinal, vertical sectional View of the volume tans,

the treater, '1 is a, rear elevation. of thesanie, portions for theheat. exchanger being insection,

Fig. 9 is a detailed elevation of the rear end portion of the treater from the opposite side to Fig. i.

In the drawings the numeral i9 designates an elongate cylindrical tank, seated, and supported horizontally, in transverse standards ii, adjacent each end. The lower transverse bottoms of the standards are supported at each side upon longitudinal frame skids i2, connectedv by cross members l3, welded thereto, whereby a substantial base frame is provided. The standards are suitably fastened on the base frame. A crowned head 14 is secured to the. front end of the tank and a similar head i5 is fastened to the rear end of said tank.

A horizontal return-tube heater is is insered through a transversely elongated collar i? mounted in the head M','j.ust below the center. As is best shown in Figs. 1, s, 6 and 8, this collar extends across. the head and is flanged whereby a flanged adapter [8 may be secured thereto. This adapter has outwardly extending, transversely spaced, flanged collars is and it To the right hand collar 19, Fig; 6, a gas burner mounting 21 is secured; the details of this structure being unimportant. A flue-elbow connection 22 is secured to the other or left hand collar 2% (Fig. 6).' The burner details are subject to considerable variation and no claim is made thereto.

The heater it extendsv rearwardly in the front end of the tank and has its inner or rear end adjacent an upright, transverse partition 23, having its top spaced below the top of the tank and its bottom Well above the bottom of the tank. This partition defines in the front end of the tank, aheating and separating chamber A. A hood or free water compartment is formed in'th'e medial portion of the tank in rear of the chamber A. The hood is formed by a verse, top' sheet 24 across the tank. having its ends secured to the tank wall, at the central portion.

A'transverse, vertical partition is spaced a short distance from the partition 23, forming a fiumel 26 therebetween, transversely of the tank.

The partition 25 has its top edge a shortdistance 7 torn'of' the hood is open to-the tank and there below...

ihe infiuent which enters the downcomer pipe or flume 2i flows down into the compartment B, wherein the free water settles out and flows down into the body of water, toward the bottom of the tank. The emulsion accumulates in the com-- partment and overflows the top edge of the par tition into the broad fiume 2G. Elongate perforated spreaders 29, each triangular in crosssection (Fig. 2) have their forward ends supported on an angular cross bar, under the heater tube 15 at the front end of the chamber A. The bottom of each spreader is open and its rear is secured in the bottom edge of the partition to one side of the center so as to be open to the fluids flowing from the fiume 26.

Since more or less sand flows into the compartment B, with the influent stream, and settles downward, where it is accumulated along the bottom of the tank, under the chamber A and compartment B, steam nozzle or

jet heads

39 and 3| are disposed relatively between and below the Spreaders 2i) and under the compartment B, respectively. The heads and 3i are disposed in alignment along with the longitudinal center of the bottom of the tank and each has a longitudinal manifold pipe 32 provided with inwardly and downwardly directed curved jets 33 at each end. Each pipe 32 is supported in clips 3 5, welded to said bottom. Each head rests in a transverse dam strip 35 at its center, supported upon the bottom of the tank.

Each dam strip extends across a drainage sump 36 in the bottom of the tank, having a flanged outlet 3'3, adapted to be bolted to a suitable outthe head 3| by an inlet pipe 40, the rear end of The the pipe 32 being closed (Figs. 4 and 8).

pipes

39 and 40 are bent right-angularly so as to extend through the side wall of the tank and are connected with a suitable source of water or gas supply (not shown).

The sand being precipitated and washed out by the

heads

39 and 3| and through the sunips 36, the water being knocked out in the compart ment B and commingling with the body of water W, and the influent flowing down the fiume 26, as

hereinbefore set forth, is spread across this rela-' i tively narrow fiume and enters the rear open ends of the spreaders 29. The perforations of the spreaders being relatively small, said infiuent is discharged in numerous and closely spaced, small streams. Since a water level is maintained longitudinally throughout the length of the tank, slightly above the heater 16, forming the zone W, the streams from the perforations are discharged into this body of heated water.

The emulsion streams are discharged from the spreaders 23 (Fig. 2), one under the burner leg [6a and the other under the return leg 13?). These discharged streams flow outwardly and upwardly on the inner and outer sides of the legs, whereby the emulsion is thoroughly heated and the oil, gas and water separated in the usual manner. The oil flows up into the oil zone 0 to oil level; while the gas escapes into the gas zone G along the top of the tank.

Spaced rearwardly of the partition 23, is an Each manifold pipe 32 is Water or gas is upright transverse bailie 4i, which has its top edge above the oil level in the gas zone and below the top of the tank; while its bottom edge is some distance below the oil level, but above the water level. Theoretically, the oil which passes over the partition 23 and under, the baffle 44, will have been dewatered to a large or maximum extent and substantially all of the gas will have been released. The flow rearwardiy is largely through the oil zone. An upright perforated partition ii? is mounted transversely in the tank immediately in the rear of the head 3i and spaced rearwardly is a second perforated partition 43. Filtering material i -l is disposed between the partitions and supported on a cross shelf 45, spaced above the bottom of the tank in the water zone. Where tighter emulsions are being handled, the space S below the partition may be filled with filtering material.

The partition 43 is spaced a short distance from the rear head i5 and an outlet compartment F is formed therebetween. In the bottom of the compartment is a steam head 5%, constructed along the lines of the heads and 3i, and mounted over an outlet til having connection with suitable piping (not shown). A water dis-- charge pipe t8 (Figs. 3 4) inclined downwardly from a horizontal outlet pipe ii! extend ing through a nianway 5G to the lower side of a water siphon column 5i, closed at its top and bottom. The lower end of the inclined pipe 48 terminates close to the head 46. The pipe :19 is aligned with the water level in the tank, whereby the latter is maintained.

A pressure equalizing pipe 52 leads from the gas zone at the top of the tank, through the tank wall to the upper end of the column An overflow pipe nipple 52" is mounted in the bottom or" the column, having its upper end somewhat above the water level in the tank. The body of oil and mixture of oil and water supported on the body of water in the tank will depress the water level therein, so that the water in the column 5! will rise much higher than in the tank. A discharge pipe 53 (Figs. 3, 7 and 9) leads from the bottom of the nipple 52' and is directed horizontally to a water valve E i, which has a suitable outlet pipe connection 55.

The well emulsion is conducted by a pipe 55 to one end of the lower leg of a heat exchanger 57 (Figs. 1, 4 and 7). The upper and lower legs of the exchanger are of standard construction and are supported across the rear end of the tank, enteriorly thereof. The emulsion flows through tubes 58 (Fig. 7) to a chamber 59 at the opposite end of the leg from which it escapes through a pipe 6! to the chamber 62 of the upper leg. From the chamber E2 the emulsion passes back through tubes 63 to a chamber at the opposite end of the upper leg and is discharged through a nipple 65 into an angular pipe 58 (Figs. 1, 7 and 8). The angular pipe 65 leads to discharges into the side of the horizontal exterior tank 23.

The dewatered and degassed or clean oil, from the zone 0, overflows into the outlet box iii, at the oil level in the compartment 1. The oil filling this box escapes through an angular outlet pipe 68, which enters the top of a volume tank 69 (Figs. l, 5 and 7). This tank is mounted transversely above the heat exchanger 5? and is sup ported thereon at one end by a bracket it, carried at one end of the upper leg of the heat exchanger; while at its opposite end the volume tank is supported by and connected with, the upper leg of the exchanger 5i by an outlet pipe assume 5. ll connected with the heat exchangezsectiom of the lowerleg by-a pipe 'lt- Thecooledoil escapes from" the exchanger: through tan: outlet pipe t2 (Figs. 1, 7 and? 81).. This-outletpipe E2; hasal diaphragm outlet: yalvefl$t-fEi=gs 7.; 8; h). connected thereinl ":III the: volume tank Eh a float; is: mounted on the end. or an; arnrll'fimounted; on arrock: shaft (Figfilvwhich ishoused. in a. bonnet. la. A

'lever arrn re (Figs. '7; and 3): ishingcd cn-the. rock shaitsll: and connected. with; valve arm to of a control :valve 8 l A. gas line 3-2. leadsfrom; .the tank; 28 and is; bent at. right. angle so asto extend downztorthc basexof the! (Fig, 9) where it is connected.- to ahorizontal pipe 833 connected with a. diaphragm valvetlkhaving aseitabl'e disposal "connection.

A. gasisupplyelbowta': (Big 9'). is mounted on thesideof. the gas pipe 82; and a gas. supply line *85- is'conneeted .thereto-.. :Thisline leads to and connects with the valve fli anal-.with-the bowl: of a diaphragm pressure.responsive-member d9. Ihe member as is mounted on steam pipe. 89 mount ed on the water outlet. pipe-53 and controls the Water. outlet-valve; 54. The. valve fi ih-as the usual lilting arm linked to aweighted lever arm 32 motm-ted on and controlledby the-diaphragm member 83. A gas supply line 86 leads from the valve 8| to the'lower bowl of the diaphragm l3 'Qfathe-oi-l valve 12:, andv a. second gas supplyline 81-. leads from; the line ditto. the upper bowl or the: diaphragm of. thegas valve 84 The infiuent. stream from the. heat. exchanger 51 (Figs. 1,. .6. and. 7.) which isc-onducted b the pipe.- 5.6, is discharged. into. a jacket or shell 9.3., dis.- .posed axially in the. gas separator-tank. 28. This shell. (Figs. .4. and 7) is mounted toward the. front endi'o-f the tank, has its. inner endcloscd and is provided With cross partition 94,, whereby a. box 185' is formed at the inner or rear end of said shell. The influent oil. pipe 66' discharges into the shell in front of the partition (Fig. 7') A gas discharge pipe 95 leads from the top'of the tank ill-and is'bent and directed axially through the shell and the partition 94, so as to discharge into the b02195 which has outlets 91, whereby the gas may escape into the tank 2-3 aroundtheshell.

The oil which enters the rear end portion of the shell 93 flows forwardly therein, around the 'gas pipe Si-i, inhea-t exchange relation with the gas flowing rearwarclly in said pipe. This emulsified oil stream from the shell discharges into the tank 2 3 and exits by way of the pipe-2?. The gas 'which is discharged-intothe separator tanlr' 28 passes rearwardly between the inclined scrubbed plates: 98 to the rear of said tan-k whereit escape 1 by way of the pipe- $2.

. Inoperation the influe-nt from the well is conpointed out, the incoming infiuent flow-s in heat exchange relation with the outflowingwarm clean toil and is thereby heated or'warmecl. I

"Thepinfluent flows up the pipefid and thenhorizontally (Figs. 1 and '8) and entersthetank '18. thr ugh. the side thereoli to the shell. 93, into which it discharges. (Bias. 4 and 7 in fnont of the artition 9; l.. The.influentthenfiows. iorward-ly g in. the .-shell and being. cooler than .theahotgases flowing rearwamily;"through the pipe 916;, .will cause condensation of any heavy hydrocarbons in the gas stream. The influentfiow. discharging "fromthe front end of the shell, accumulates. on the. .bottom'o'f theta-11k 2.8 and discharges down into the downcomer pipe 2t into the free water compartmentB. In this compartment, the free water settles out; of the influent and flows along the bottom of thetank Hi, commingling withthe body of water maintained therein.

- In'order-ztotassure the settling out of substantially-all freewater, the uprightv partition 25 (Fig. 4) is employed. Since the top edge ofv said partition is. quite close to the top sheet ZG (usually about 2 inches) only emulsion from immediately under saidsheet. escapes intothe i'iume 25. This will give the free water flowing into the chamber B, aufulli opportunity to settle out. The down flowing infiuentemulsion, which has been dowatered, upon reaching the bottom of the fiunie,

. will flow intot'herear ends of the two perforated spreaders 29 (Figs. 2: and 4) and forwardly therein. I It might be well at this stage to point out the disposition of the sand. In some inlluents large quantities. of sand are suspended in the influent and-are carried thereby. By reason of the retardation and settling afforded in the compartment B, sand will drop out and spread along the bottom of the tank under the nozzles and 35. Water or gasbeing ejected by the jets 33 and 3-8, the sand will be impelled toward and into the sumps 36', iro-mwhich it is periodically withdrawn.

. Since. thepartition 25 terminates on a level with the bottoms of the triangular spreaders 29, "entry of the iniiuent into the Spreaders, is assured. The influent flowing forwardly in the spreadcrs is discharged in upwardly flowing, closely spaced, small streams which impinge the bottoms of the burner legs Ilia and b- (Fig. 2), longitudinally thereof soas to flow upwardly around each side of each leg in the body of water W. This thoreagle-hea ing; not only maintains a warm body of water W around the heater, but causes the emulsified constituent to break down, whereby the oil'and water are separated, the water tending to settle and the oil rising.

Where gas is in solution with the emulsion, it will bereleased when the emulsion is broken around the heater and as the oil and oil-gas globules flow upwardly inot the oil zone 0. The

oillevel is controlled by out-let box at the .rearnendouf' the tank. Gas rises from the oil into the gas zone G along the top of the tank. it will be noted that a the partition 23 and baths. 2 l' are sopdisposed as to cause the oil, in itsrearward :movernent towardthe outlet box iii, to flow over the top of the partition and down under the lower i'ecl ge or the bafil e it, just above the waterlevel. Substantially all-oi the gas is evolved in this area.

By: causingthe-rearwardly flowing oil in the ZOCEIG Q totake path between the partition. 23' and baffie t? under thelatter, the effect ist'o reduce the temperature of such oil,

' upto several'degrees, Fahrenheit. I

needed, the space below the shelf can be filled with filtering material. The filtered oil and water stratify in the outlet compartment F.

As some sand may precipitate in the compartment F, arrangement is made to drive it out by means of a water or gas head lt, and an outlet 41. A water level is maintained in the tank by the means shown in Figs. 3 and l. The inclined pipe leg d8 carries water up and out through the pipe 49 into the lower end of the water syphon column 5!, from which it escapes into the nipple 52 and thence out through the pipe 523 to the water valve 54 (Fig. 9).

The warm clean oil which overflows into the box t! is carried out through a pipe 65 (Figs. 4, 5 and '7) to the volume tank 59 from which it escapes down through the pipe H. An oil level is carried in this tank by means of the float 75 (Fig. 5) which controls the gas supply through the elements ill and 86 to the diaphragm it of valve 12. The gas supply to the gas outlet valve as is also controlled by the valve iii. The warm oil escaping through the pipe ll (Fig. 7) flows into the upper leg of the heat exchanger El and around the tubes 63 therein, escaping from the bottom through a pipe i l into the top of the lower leg around the tubes 58, thereof and finally escaping through the valve 72.

The gas escaping from the zone G by way of the pipe 95 flows through the shell t3 and discharges into the box 95. Some cooling may take place in the pipe to within the shell, and these heavier hydrocarbon condensates will escape through the lower opening 9? into the tank and flow to the pipe 2's. The gaseous fluids will flow between the inclined scrubber plates and escape by way of the pipe 82.

It is pointed out that the partition 23 and baffle dl directing the flow downwardly, prevent a layer of stagnant oil overlying the top sheet 24 of the water knock-out B. This flow of oil causes sufiicient agitation through the oil zone to maintain the grade of oil. Since all the separable gas evolves at the heater and the oil being immediately cooled by flowing adjacent the top of the water knock-out, substantially no more gas is evolved, during the rearward travel of the oil and consequently there is no more agitation.

The foregoing description of the invention is explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claims, without departing from the spirit of the invention.

What we claim and desire to secure by Letters Patent is:

1. An emulsion treater including, an elongate horizontal treating tank having a front end and a rear end, a treating chamber in the front end of the treating tank, a return-tube heater disposed longitudinally in the front portion of the tank, a transverse upright partition across the tank immediately in rear of the heater, water and oil zones longitudinally in the tank from one end to the other end thereof, said partition having its lower end in the water zone above the bottom of the treating tank and its upper end in the oil zone, a pair of Spreaders having inlets at the bottom of the partition and extending forwardly under the heater, a water-v knock-out hood contiguous to the partition having its bottom open in the water zone above the bottom of the tank, an infiuent inlet leading into the tank to the top of the hood, and oil and water outlets from the tank.

2. An emulsion treater as set forth in claim 1, with a transverse flume in the hood having a narrow transverse inlet at its top and discharging into the spreaders at its bottom.

3. An emulsion treater including, an elongate horizontal treating tank having a front end and a rear end, a treating chamber in the front end of the treating tank, a return-tube heater disposed longitudinally in the front portion of the tank, a water knock-out hood adjacent the heater in the tank, Spreaders extending from the hood under the heater, an influent conductor connected with the hood, a gas outlet in the top of the tank, an oil outlet in the rear end of the tank at the oil level, a water outlet at the rear end of the tank, an exterior volume tank at the rear end of the treating tank having a float therein, a heat exchanger, an oil outlet from the volume tank to the heat exchanger, an oil outlet valve connected with the heat exchanger having a diaphragm operator, a gas line c0nnect ing the gas zone of the treating tank with the diaphragm operator including a valve and connected with the tank float, an influent inlet to the heat exchanger, and an influent conductor leading from the heat exchanger and having connection with the infiuent conductor connected with the hood.

l. An emulsion treater as set forth in claim 3 with an oil and gas separating tank connected with the influent conductors and having a gas inlet from the treating tank and a gas outlet.

5. An emulsion treater including, an elongate horizontal treating tank having a front end and a rear end, a heating chamber in the front end of the tank having a heater therein and an influent spreader below the heater having an entrance at its rear end, a water knockout compartment in the tank intermediate the ends thereof and having an open bottom spaced at its rear edge from the bottom of the tank whereby fluid may escape into the tank from the rear edge of the compartment, the spreader being connected to the front edge of the compartment whereby fluid normally escapes from the compartment to said spreader, an influent conductor leading to the knock-out chamber, and gas, water and oil outlets from the tank.

6. An emulsion treater as set forth in claim 5, a plurality of nozzles under the spreader and the knock-out compartment, means for supplying a flushing fluid to said nozzles, and sediment outlets from the bottom of the tank adjacent said nozzles.

7. An emulsion treater including, an elongate horizontal tank having a front end and a rear end, a treating chamber in the front end of the tank having heating means therein and an influent spreader below the heating means having an entrance at its rearward end, a water knockout compartment immediately in rear of the chamber and having a wall in common with the chamber, the knockout compartment having an outlet directly to the spreader, an influent conductor leading through the tank to the knockout compartment, an elongate horizontal stratifying chamber extending from the treating chamber over the knockout compartment to the rear end of the tank providing an elongate horizontal flow path and separating zone with large liquid surfaces whereby full Stratification and separation of the oil and water and gas are enhanced, an oil outlet in the rear end of the tank maintaining an oil level in the tank, a gas outlet from the tank above the oil level therein, and

a water outlet from the tank maintaining a water level therein, whereby oil and water and gas zones are provided in the tank, the tank having an open continuous space extending along its bottom wall from beneath the treating chamber through the bottom of the stratification chamber and passing beneath the knockout compartment, the bottom of the knockout compart ment opening into said space, whereby an elongate continuous water accumulation and flow space is provided in the bottom of the tank.

8. An emulsion treater as set forth in claim '7 wherein the wall common to the treating chamber and the knockout compartment is formed by an upright partition having its upper edge adjacent and below the oil level.

9. An emulsion treater as set forth in claim 8, and a transverse upright bafiie in the tank over the knockout compartment and spaced rearwardly from the partition, the baffle extending from above the oil level to a point spaced above the top of the knockout compartment whereby heated liquids flowing from the treating chamber must pass downwardly and under the bafile in close proximity to the top of the knockout compartment.

10. An emulsion treater as set forth in claim with a vertical flume leading from the top portion of the knockout compartment to the entrance of the spreader.

11. An emulsion treater as set forth in claim 7, with an oil and gas separating tank exterior of the treating tank, a gas conductor leading from the gas outlet of the treating tank into the separating tank, an influent pipe leading into the separating tank, a conductor in the separating tank connected to the influent inlet pipe and in heat exchange relation with the gas conductor, and an outlet from the separating tank connected with the influent conductor of the treating tank.

12. An emulsion treater as set forth in claim 7. with an oil and gas separating tank exterior of the treating tank, a gas conductor leading from the gas outlet of the treating tank into the separating tank, an influent'pipe leading into the separating tank, a conductor in the separating tank connected to the influent inlet pipe and in heat exchange relation with the gas conductor, an

outlet from the separating tank connected with the influent conductor of the treating tank, a scrubber in the separator tank disposed beyond the gas conductor, and-a gas outlet pipe leading from the separating tank beyond the scrubber.

13. An emulsion treater as set forth in claim 7 e wherein the oil outlet includes an oil discharge conductor leading from the tank, and a volume tank into which the oil discharge conductor is connected, a float in the volume tank and an oil drain valve connected to the volume tank and having an actuating connection with the float.

14. In an emulsion treater, an elongated horizontal treating tank having a front end and a rear end, a treating chamber in the front end of the tank having a heater therein and an influent spreader below the heater having an entrance at its rear end, a water knockout compartment immediately in rear of the chamber having an outlet directly to the spreader, an influent conductor leading through the tank to the compartment, an elongate horizontal stratifying chamber extending from the treating chamber over the knockout compartment to the rear end of the tank providing an elongate horizontal flow path and separating zone with large liquid surfaces whereby full stratification and separation of the oil and water and gas is enhanced, an oil outlet in the rear end of the tank maintaining an oil level in the tank above the compartment, a gas outlet from the tank above the oil level therein,

a water outlet from the tank maintaining a water level therein, whereby oil and gas zones are provided in the treating tank, a filter in the tank contiguous to the oil outlet and extending downwardly through the oil level, a pair of spaced vertical foraminou partitions in the stratifying chamber adjacent the oil outlet, said partitions extending substantially from the bottom of the tank to the top thereof, and a fllter support between the latter partitions below the water level,

the filter being disposed between the partitions and in at least the space above the support.

References Cited in the file of this patent UNITED STATES PATENTS