US2322087A

US2322087A - Eductor tank mixer

Info

Publication number: US2322087A
Application number: US468508A
Authority: US
Inventors: Edwin H Atwood
Original assignee: Socony Vacuum Oil Co Inc
Current assignee: ExxonMobil Oil Corp
Priority date: 1942-12-10
Filing date: 1942-12-10
Publication date: 1943-06-15
Anticipated expiration: 1960-06-15

Description

June 15, 1943. E. H. ATwoon EDUCTOR TANK MIXER mea uw. 1o, 1942 2 Sheets-Sheet 1 FUD UD U w mm mm WH. lm W fm E. mm E HQ m/ l J j. ,ML .Ww f A@ June l5, 1943. E. H 'rwoon' EDUGTOR TANK MIXER Filed nec. 1o, "1942 2 Sheets-Sheet 2` l lNvENToR EDWIN H. ATwooD A oRNEY Patented June l5, 1943 A EDUCTOR TANK MIXER y Edwin -HfAtwooa Woodbury, N. J., assignor to S'ocony-Vacuum Oil Company Incorporated,

-New York, N. Y., afcorporation of New York. Y Application Dooomber 10, 1942, Vserial No. 468,508

8 Claims.

In the mixing ofv large quantities of crude petroleum oils or petroleum products whereoils of different gravityv are put in tanks it is observed that there is a marked. tendency. for the oils to separate by strati'iicationinto layers of different gravity. Even in a product of extremely high fluidity, such as gasoline, specific gravity differences amounting to one degree of A. P. I. gravity and sometimes more have been noted ina tank 30 feet `in height when filled and allowed to stand for a week or so.' These diierences are particularly acute and of importance with heavier, more viscous oils. customary in many reiineries to blend several diierent crude oils, of different properties, together to assure a uniform charging stock for continuous distilling operations. In some such cases, these blends give great -diiiiculty in arriving at uniformity. 'Also, in preparing products for market, much blending is done, such as cutting back a a heavy fuel oil stock with a lighter gas oil. 'Many of these blending operations, particularly in the case of preparing crude oilblends for distillation, take place in quite large tanks. The standard"55, that is a ytank holding 55,000 barrels of 42 gallons each, which is almost uniformly used throughout the industry for crude and major product storage, is a tank of about 11'7 feet diameter and 30 feet of height. It can readily be appreciated that assuring adequate mixing in vessels of proportions such as these is no mean problem. Even in muchsmaller tanks,

ksuch as those of 5, or 20 thousand barrels For examplait is pumping time is many hours-K-15 to 24--andfre-,- e,

quently a couple of days circulation is necessary.y Impeller or propeller type mixers driven by a` shaft extending through the side of the tank are frequently used, but are highly consumptivegof power, and can be operated with assurance only in quite small tanks or if rapid and complete mixing.

in large tanks is to be assured, three or more large propellers and motors must be installedper tank at an excessive installation cost.

Some eductor type tank mixers' have been pro-` posed and used, wherein an incoming stream of oil, either oil coming to be stored or a circulation stream rwithdrawn fromA the tank itself isgused,v

-designed as to entrain oil in any. other layer than thosefnear the bottom ofthe tank except to the smalldegree obtained by turbulence of an inclined discharge. While such mixers are more eiiicient than plain turnover-f pumping, the present design still requires long pumping times and large power expenditures. l

The objects of this invention are the provisionv of, an eductor type-tank mixer ,capable ofl effective mixing with small power expenditure, capable of effectively lmixingtwo ormore grades of oil in a tank during the lling operation' `by merelyjp'umping them -into the tank one after the other at the normal filling rate and with the existing lling pump, capableof complete mixing within a Wide range of level of oil'in tank, capable of complete mixing Vin a shorter length of time than by existing means, and capable of ready and cheap installation. l

These objects are accomplished by the applica-v tion of theV principle Olentraining a relatively greatvolume of tank vfluid inthe eductor; drawing that iiuid simultaneously from all levels of uid within the tank, regularly increasing the proportion drawn from each higher. level within the tank and by baiilingthe eductor discharge in such a way that one or more circulation'zones are created causing further mixingby turbulence in the tank Iand so arranged that the educted fluid is drawnfrom the relatively idle part of. thecirculation zone or zones.

The invention may be understood readily by pipev 1 which terminates in a nozzle 8 within an eductor 9 from which there extends a vertical intake4 pipe I0 having oriiices H1 The vertical pipe I0 is conveniently mounted by clamping to f the tank center post, l2, as shown. The eductor 9 is fitted with a Venturi-throat I3 and a dis-y charge tube I4. This tube is directed toward the tank wall and in front of it, against the tank wall there is placed a curved baille I5 adapted to to-V gether, there isA provided Awithin tank 6 an inlet change the course of the discharge stream into a swirling motion within the tank. This curved vertical baille I5 is associated with a curved lifting baille I 6, as may be clearly seen in Figure 3, which serves to lift the swirling tank liquid and in effect, to slide the mixed discharge stream under it. These baiiies may be effectively fixed in position by clamping to the inlet pipe 1 as may be clearly seen in Figure 3. Since in most tanks inlet and outlet pipes are adjacently located, as at the left side of Figure 2, it is usually convenient to provide that the tank outlet pipe I'I is located behind the bafiies I5 and I6.

In Figures 4 and 5, which should be read together, there is shown a slightly different; ar-

rangement to be used in tanks when the roof floats upon the stored liquid. In these figures the details of inlet piping are not shown, but, as before, the inlet pipe discharges through a nozzle I8 in a venturi I9 and mixer tube 20. Due to the large torsional effect that a single swirling motion would have on a oating roof, it appears best to use a double defiector baille 2I--2I to set up a double swirling motion to counteract the tendency the roof would otherwise have to stick on its vertical guide. 'I'he intake pipe in this case communicates with the eductor through a swing joint to which intake pipe 23 is affixed so that it mayrise with the roof 24 to the positions shown at 23 and 24. A good method of aflixing the pipe 23 to the roof 24 is by an enclosed trolley 25 operating in track 26. Pipe 23 is provided with orifices 2'I, and its end is closed by plate 28 in which there is an orice 29. There are also provided, in this tank, baiiies 30-30 to complete the double swirl, A double suction mixabout one-tenth to one-fifteenth the total being circulated.

'I'he arrangement of ports described above provides that the largest portion of fluid educted comes from horizontal layers farthest away from those which compose the jet or the freshly mixed uids, when mixing by recirculating, and draws back the largest portions of fluid first pumped in for mixing with that last pumped in thru the jet, when mixing during filling.

Third. Arranging the very large discharge from the mixer to flow tangentially to the tank shell creates a strong swirl which keeps the fresh- 1y mixed stocks near the shell and the least mixed stocks in each layer near the center. Locating the inlet mixing tube at the center draws to the mixer these least mixed stocks first.

Thus both vertically and horizontally the mixer automatically draws to it the least mixed stocks in the tank.

As an example of the comparative efficiency of this device, the vfollowing operation is cited, which was carried out with a very rudimentary form of jet and intake tube, capable of operating only in the lower range of efficiencies indicated. In

i this operation, no recirculation was performed,

ing tube could be used, each drawing from the center of one of the swirls, but the added efciency would not usually be suicient to justify the added complications. l

The efficiency of this device depends upon certain design factors. First the nozzle and eductor system are so designed as to secure a very high ratio ofentrained iiuid to nozzle-fluid, greater than 2 to 1 and preferably of the order of 5 to 1, with increasing efficiency as this ratio is increased. Due to the low differential heads, thesel ratios are obtained with comparative ease, and in some cases ratios of better than 10 to 1 have been attained.

Second, the location and proportioning of areas of the orifices in the intake mixingtube. These orifices are (a.) so located that oil is simultaneously withdrawn from all vertical levels in the tank, and (b) are so proportioned that the amount drawn from each level increases upwardly along the intake mixing tube. In most tank mixing problems it is usually convenient to have the rate of increase of amounts drawn from succeeding higher levels arranged in simple arithmetic progression. That is, it is convenient to arrange the areas of orifices in successive intervals of one foot each, taken upwardly, to have some such relationship to each other as 1: 2, 3: 4; etc., or 15: 16, 17: 18; etc.

The sum of the area of the orifices in the intake mixing pipe should be such that when the tank is full, all orifices are submerged, and the jet is entrained the full capacity for which it is designed, the velocity through the orifices is of the order of about two feet per second. In the swinging intake mixing tube for oating roof tanks, the end of the intake pipe should be closed except for an orifice capable of handling, at a velocity o1' about two feet per second, a ow o! the jet fluid being only the incoming crude on its way to storage in the tank. The tank was an 8000 barrel tank, 54 feet in diameter, 25 feet high. The following Coastal Naphthenic Crudes were pumped in one after the other.

l Approximately.

As soon as the filling was complete and without any other mixing, five samples were taken at different levels as follows:

Level Sayh.

Sample number 52210511 viscosity taken @me r.

The indicated viscosity of the blend of these Crudes in the proportion used, as read from a viscosity blending chart should have been about 245. This deviation from the average of the above is within the range of accuracy obtainable with such a chart.

Repeated tests on such mixtures in this tank confirmed the emciency of this equipment, so that two other tanks in the same service were equipped with similar jets and suction mixing tubes. About four batches per week were regularly made in these three tanks and previous to the mixer installation, each batch was circulated 15 to 20 hours after filling. In spite of this circulation the batches were very irregular, which caused much trouble in adjusting the still which was running this crude, with frequent slopping of off test stocks, resulting in extra re-running costs.

No recirculation is now necessary, less off test stock is produced. and the same three tanks now 52,322,087 vj handle about six batches per week and 'so supply feed to an additional distillation unit which has since been put in service.

Obviously, any device capable of handlinga` problem of this nature without pumping other than the normal pumping of each new batch of incoming stock into the tank has advantages overthe methods of mixing now prevalent.

I claim:

1. In a tank and mixer of the kind described a pipe for supplying fluid to the tank, an eductor in which the supply pipe terminates in a nozzle to supply jet fluid therefor, an upwardly extending intake pipe leading into said eductor, orifices so distributed along the length of that intake pipe that fluids may be drawn thereinto from all levels within the tank, and a discharge tube leading from the eductorand substantially horizontally mounted so as tocause circulatory motion of the uid within the tank about the vertical axis of` the latter.

2. In a tank and mixer of the kind described a pipe for supplying fluid to the tank, an eductor in which the supply pipe terminates in a nozzle to supply jet fluid therefor, an upwardly extending intake pipe leading into said eductor, orifices so distributed along the length of that intake pipe that uids may be drawn thereinto from all levels within the tank, the eductor, intake pipe, and orifices being so proportioned that the volume of entrained fluid is substantially in excess of the volume of nozzle fluid, and a dis.

charge tube leading from the eductor and substantially horizontally mounted so as to cause circulatory motion of the fluid within the tank about the vertical axis of the latter. 4

3. In a tank and mixer of the kind described a pipe for supplying fluid to the tank, an eductor in which the supply pipe terminates in a nozzle to supply jet fluid therefor, an upwardly extending intake pipe leading into said eductor, orifices so distributed along the length of that intake pipe that uids may be drawn thereinto from all levels within the tank, the eductor, intake pipe, and orifices being so proportioned that the ratio of the volume of entrained fluid to the volume of nozzle fluid is in excess oi 2:1; and a discharge tube leading from the eductor and substantially horizontally mounted so as to cause circulatory motion of the fluid within the tank about the vertical axis of the latter.

4. In a tank. and mixer of the kind described a pipe for supplying fluid to the tank, an eductor in which the supply pipe terminates in a nozzle to supply jet fluid therefor, an upwardly extending intake pipe leading intoA said eductor, orifices so distributed along the length of that intake pipe that fluids may be drawn thereinto from all levels within the tank, the eductor, in-

take pipe, and orifices being so proportioned that the ratio of the volume of entrained uid to the volume yof nozzle fluid is of the order of' 5:1: and a discharge tube leading from the eductor and substantially horizontally mounted so as to cause circulatory motion of the uid within the tank about the vertical axis of the latter.

5. In a tank and mixer of the kind described a pipe for supplying fluid to the tank, an eductor in which the supply pipe terminates in a nozzle to supply iet fluid therefor, an upwardly extending intake pipe` leading into said eductor, orifices so distributed along thelength of that intake pipe that fluids may be drawn thereinto from all levels within the tank, a discharge tube leadlng substantially horizontally from the eductor, and a baille mounted in the tank -in the path of the stream from the discharge tube to eil'ect that fluids may be drawn thereinto from all levelsv circulatory motion of the fluid within the tank about the vertical axis of the latter.

6. In a tank and mixer of the kinddescribed a pipe for supplying fluid to the tank, an eductor in which the supply pipe terminates in a nozzle to supply jet fluid therefor, an upwardly extendmg intake pipe leading into said eductor,-oriflces so distributed along the length of that intake pipe within the tank, the eductor, intake pipe, and orifices being so proportioned that the ratio of the volume of entrained fluid to the volume of nozzle fluid is in excess of 2:1, a discharge tube leading substantially horizontally from thev eductor, and a baille mounted in the tank in the path of the stream from the discharge tube to effect circulatory motion of the fluid within the tank about the vertical axis of the latter.

'7. In a tank and mixer of the kind described a pipe for supplying iluid to the tank, an eductorV l in which the supply pipe terminates in a nozzle to supply jet fluid therefor, an upwardly extending intake pipe leading into said eductor, orifices so distributed along the length of that intake pipe that fluids may be drawn thereinto from all levels within the tank, and a discharge tube leading substantially horizontally from the eductor and so mounted as to cause circulatory motion of the iiuid within the tank about the vertical axis thereof, in which the arrangement oi' the orifices in the intake pipe is such that greater f amounts of oil are withdrawn from tank levels most removed from the level to which the discharge tube leads..

8. In a tank and mixer of the kind described a pipe for supplying fluid to the tank, an eductor in which the supply pipe terminates in a nozzle to supply Jet fluid therefor, an upwardly extending intake pipe leading oriiices so distributed along intake pipe that fluids may from all levels Within the tube leading substantially the length of that tank, and a discharge to cause circulatory motion of the uid within .the tank about the vertical axis thereof, in which the arrangement -of the orifices in the intake pipe is such that greater amounts of oil are withdrawn from tank levels most removed from the level to which the dischargel tube leads and in which the intake pipe vis located at that portion of the tank in which said circulatory motion is lessA pronounced. n EDWIN H. ATWOOD.

into said eductor.

be 4drawn thereinto horizontally from the eductorand so mounted as