SYSTEM AND METHOD FOR MOVEMENT OF FLUID IN A TANK

Abstract

A system for movement of fluid in a tank comprises: a tank; at least two pumping sets, each pumping set comprising: a pumping line external to the tank and in fluidic communication with the interior of the tank at two separate points of the tank via the two ends of said pumping line, and a pump configured to circulate fluid through the pumping line, wherein each pumping set is configured to collect fluid from the tank at one end of its respective pumping line, circulate the fluid through its respective pumping line and discharge the fluid into said tank through the other end of its respective pumping line, and wherein each pumping set is configured such that the flow of fluid in its respective pumping line is reversible.

Claims

1. A system for movement of fluid in a tank, the system comprising: a tank; at least two pumping sets, each pumping set comprising: a pumping line external to the tank and in fluidic communication with the interior of the tank at two separate points of the tank via the two ends of said pumping line, and a pump configured to circulate fluid through the pumping line, wherein each pumping set is configured to collect fluid from the tank at one end of its respective pumping line, circulate the fluid through its respective pumping line and discharge the fluid into said tank through the other end of its respective pumping line, and wherein each pumping set is configured such that the flow of fluid in its respective pumping line is reversible.

2. The system of claim 1, wherein at least one end of each pumping line extends towards the interior of the tank.

3. The system of claim 1, wherein at least one end of each pumping line comprises the shape of a hydrodynamic nozzle.

4. The system of claim 1, wherein the system comprises four pumping sets.

5. The system of claim 4, wherein the pumping sets are positioned around the tank in pairs, each pair being positioned opposite to the other pair.

6. The system of claim 5, wherein the pumping sets of a particular pair are configured to have their flows of fluid inside their pumping lines in the same direction around the tank.

7. The system of claim 5, wherein the pumping sets of a particular pair are configured to have their flows of fluid inside their pumping lines in opposite directions around the tank.

8. The system of claim 5, wherein the pumping sets of each pair are configured to have their direction of fluid flows around the tank mirror the direction of fluid flows of the opposite pair.

9. The system of claim 5, wherein the pumping sets of each pair are configured to have their direction of fluid flows around the tank be inverted compared to the direction of fluid flows of the opposite pair.

10. The system of claim 1, wherein the ends of the pumping lines extend towards the interior of the tank parallel to one another.

11. The system of claim 1, wherein the system comprises three pumping sets.

12. The system of claim 1, wherein at least one of the ends of the pumping line comprises two or more outlets/inlets.

13. The system of claim 1, wherein each pumping set further comprises at least one blocking valve positioned in the pumping line on each side of the pump.

14. The system of claim 13, wherein each pumping set comprises a blocking valve positioned in each inlet/outlet of the ends of the pumping line.

15. The system of claim 1, wherein the tank is a storage tank.

16. A method of moving fluid in a tank, using at least two pumping sets external to the tank, the method comprising: with each pumping set, collecting fluid from the tank through a pumping line and discharging the fluid back into the tank through the other end of the pumping line; and for at least one pumping set, reversing the direction of flow through the pumping line.

17. The method of claim 16, wherein a flow of fluid in each of the pumping lines is from 0.5 to 5 m/s.

18. The method of claim 17, wherein the flow of fluid in each of the pumping lines is from 1 to 3 m/s.

19. The method of claim 16, wherein the flow velocity of fluid in each of the pumping lines is one of substantially the same or not substantially the same.

20. (canceled)

21. The method of claim 16, further comprising at least one of: reversing the direction of flow through the pumping line of at least one pumping set; or changing the fluid flow speed through at least one pumping set as part of a mixing routine.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0042] The detailed description presented hereunder refers to the appended figures and their respective reference numbers.

[0043] FIG. 1 shows a schematic top view of a storage tank comprising the external system for movement of fluids in an embodiment where four pumping sets are provided.

[0044] FIG. 2 shows a schematic top view of one of the pumping sets in FIG. 1. FIG. 3 shows a detailed top view of the left side of the pumping set in FIG. 2.

[0045] FIG. 4 shows an isometric view of one end of a pumping line comprising a hydrodynamic format.

[0046] FIG. 5 shows a schematic isometric view of a storage tank comprising the external system for movement of fluids in an embodiment where four pumping sets operate with combined flows.

[0047] FIG. 6 presents results obtained by CFD numerical simulations for the operation with combined flows in FIG. 5 in a first configuration of flows.

[0048] FIG. 7 presents results obtained by CFD numerical simulations for the operation with combined flows in FIG. 5 in a second configuration of flows.

[0049] FIG. 8 shows a schematic isometric view of a storage tank comprising the external system for movement of fluids in an embodiment where four pumping sets operate with opposite flows.

[0050] FIG. 9 presents results obtained by CFD numerical simulations for the operation with opposite flows in FIG. 8.

[0051] FIG. 10 shows a schematic top view of a storage tank comprising the external system for movement of fluids in an embodiment where three pumping sets are provided.

[0052] FIG. 11 shows a detailed top view of one of the sides of two of the pumping sets in FIG. 10.

[0053] FIG. 12 shows a detailed front view of one of the sides of two of the pumping sets in FIG. 10.

DETAILED DESCRIPTION OF THE INVENTION

[0054] Firstly, it is emphasized that the following description will be based on preferred embodiments of the invention. As will be obvious to a person skilled in the art, however, the invention is not limited to these particular embodiments.

[0055] The present disclosure provides an external system for movement of fluids in a tank such as a storage tank 10. They system comprises at least two pumping sets 20. As an example, FIG. 1 illustrates a schematic top view of a cylindrical storage tank 10, provided with a cylindrical side wall 12. However, although tanks such as storage tanks 10 are commonly cylindrical, the present invention could be utilised with tanks of any shape. In any case, returning to FIG. 1, the tank 10 is provided with an external system for movement of fluids of the present invention in an embodiment where four pumping sets 20 are provided. That is, the system is external in the sense that the movement is achieved by removing fluid, pumping it externally around the tank 10 and then re-injecting it into the tank 10 at a different point (this is in contrast, for example, to internal mixer propellers or equivalents which are positioned within the tank). As such, any parts expected to require regular maintenance are external to the tank 10.

[0056] As illustrated in the details in FIGS. 2 and 3, each pumping set 20 comprises a pumping line 30. The pumping line 30 is external to the storage tank 10. The pumping line 30 is in fluidic communication with the interior of the storage tank 10 at at least two separate points of the storage tank 10 via two ends 32, 34 of said pumping line 30. That is, the ends of ends 32, 34 of each pumping line 30 are spaced apart from each other and connect to the interior of the tank 10. At least one of the ends 32, 34 of the pumping line 30 can extend towards the interior of the storage tank 10. In embodiments where the storage tank is cylindrical, all the ends 32, 34 of the pumping lines 30 can be directed substantially towards the centre of the tank, as illustrated in FIG. 1. In other embodiments where the storage tank is cylindrical, all the ends 32, 34 of the pumping lines 30 can be directed into the tank substantially parallel to each other, as illustrated in FIG. 5 (and discussed in more detail later).

[0057] The ends 32, 34 of the pumping line 30 of each pumping set 20 can be a nozzle. The nozzle can have the shape of a hydrodynamic nozzle, as illustrated in FIG. 4. This specific shape was developed to promote even more effective movement of the flow in the layer of fluid near the bottom of the tank. The shape is that of a cylindrical tube which tapers (in a first direction) and broadens (in a perpendicular direction to the first direction) into a substantially rectangular slot. The inlet/outet of the nozzle (depending on the direction of fluid flow) is slightly convex when viewed from the endthat is the rectangular slots curves backwards such that the narrow ends of the slot are behind the centre. Experimental tests and results of numerical modelling of fluid dynamics (CFD: Computational Fluid Dynamics) showed the considerably higher efficiency of this design of hydrodynamic nozzle for the application in question.

[0058] Irrespective of the particular shape, the ends 32, 34 of the pumping line 30 of each pumping set 20 function as both outlets and inlets for the pumping line 30. As explained in more detail below, flow can go in either direction through the pumping line 30, and thus the skilled person will understand that the terms outlet and inlet can be used interchangeably. In view of this, this document refers to outlets/inlets in the following description and claims.

[0059] In addition, as illustrated in FIGS. 1 to 3, each pumping set 20 of the system of the present invention comprises a pump 40 suitable for circulating fluid through the pumping line 30. Thus, fluid from inside the storage tank 10 is collected by one of the ends 32, 34, circulated through the pumping line 30 and discharged at the opposite end 32, 34.

[0060] Each pump can be provided with a velocity control system. This could be, for example, by means of a frequency inverter. This means that the direction of the flow and the value of the operating flow rate of each pumping set 20 can be adjusted independently of the others. Thus, this means that the flow of fluid in the pumping line 30 of each pumping set 20 is controlled in its intensity. This is also one way of making the flow of fluid in each pumping line 30 reversible.

[0061] The system allows a routine of alternation of flow directions and velocities to be established for a particular storage tank 10, meaning that there is maximum elimination of permanent regions with low velocity, as observed in the systems of the prior art. That is, a routine can be set that sets and changes the directions of flows of fluid through the pumping sets 20, thus varying the velocity profiles within the tank 10.

[0062] FIGS. 5 and 8 illustrate an embodiment of the system of the present invention comprising four pumping sets 20a, 20b, 20c, 20d. The four pumping sets 20a, 20b, 20c, 20d are positioned in the storage tank 10 in pairs. Each pair is positioned opposite to the other pair. That is, the pumping sets are arranged with two sets 20a, 20b (forming a first pair), on one side of the tank 10 and two sets 20c, 20d (forming a second pair) on the opposite side (in this example using a substantially cylindrical tank 10, the sets are radially opposite each other). In other words, the arrangement of one pair of sets 20 mirrors the arrangement of the other across the centre of the tank 10. In the embodiment depicted, the directions in which the ends 32, 34 of all the pumping lines 30 are pointing into the storage tank 10 are parallel to one another. In the embodiment depicted, the ends 32, 34 of all the pumping lines 30 are at substantially the same height in the tank.

[0063] Still referring to FIGS. 5 and 8, two combinations of flows are illustrated, among numerous that are possible. For ease of comprehension, since the storage tank 10 used as the example in the figures is cylindrical, we shall use the designations clockwise flow when the direction of the flow around the tank in a particular pumping line 30 is clockwise with respect to a view from above the depicted storage tank 10 (i.e. from end 32 to end 34 in FIG. 5) and anti-clockwise flow when the direction of the flow around the tank in a particular pumping line 30 is anti-clockwise with respect to a view from above the depicted storage tank 10 (i.e. from end 34 to end 32 in FIG. 5).

[0064] Based on the foregoing, FIG. 5 presents an example of configuration of flows called operation with combined flows. This is so-called because each pair of pumping sets 20 are operated such that flow through the closest pump line ends within each pair is in the same direction, and such that flow through the pump line ends opposite each other (i.e. in opposite pairs) are in the same direction with respect to the tank (and thus the flows of the pumping set pairs are inverted with respect to each other). In this way the pumping sets 20 can be viewed as cooperating to form large combined circulating cells within the tank 10.

[0065] In more detail, in this configuration, a first pumping set 20a has the flow in its pumping line clockwise. The flow in the pumping line of the second 20b pumping set (forming a first pair with set 20a) is anti-clockwise. As shown in FIG. 5, this effectively results in fluid being drawn from the two edges of the tank and being injected more centrally. In contrast, third 20c and fourth 20d pumping sets (forming the second pair) have anti-clockwise and clockwise flows respectivelyand are thus inverted compared to the first pair, drawing fluid from the centre of the tank and injecting it at the sides. Thus, in the operation with combined flows of the example above, quicker flows are created in central and lateral lines parallel to the direction in which the ends 32, 34 of the pumping lines 30 are pointing.

[0066] FIGS. 6 and 7 present results obtained by CFD numerical simulations for two configurations of operation with combined flows. The colour gradient legend shows the velocity of the flow lines in metres per second (m/s) at a level 0.7 m above the bottom of the storage tank. More specifically, FIG. 6 illustrates results for a configuration of operation with combined flows where the flow in each pumping line is 2.0 m/s. In its turn, FIG. 7 illustrates results for a configuration of operation with combined flows where the flow in the pumping lines of the first 20a and third 20c sets is 2.0 m/s and the flow in the pumping lines of the second 20b and fourth 20d sets is 1.0 m/s.

[0067] FIG. 8 presents an example of a configuration of flows called operation with opposite flows. This is so-called because each pair of pumping sets 20 are operated such that flow through the closest pump line ends within each pair is in the same direction, and such that flow through the pump line ends opposite each other (i.e. in opposite pairs) are in opposite directions with respect to the tank (and thus the flows of the pumping set pairs are mirrored with respect to each other). In this way the pumping sets 20 are can be considered to be working against each other (drawing fluid from opposite positions and injecting fluid at opposite positions).

[0068] In more detail, in this configuration, a first pumping set 20a has the flow in its pumping line clockwise. The flow in the pumping line of the second 20b pumping set (forming a first pair with set 20a) is anti-clockwise. As shown in FIG. 8, this effectively results in fluid being drawn from the two edges of the tank and being injected more centrally. Similarly, third 20c and fourth 20d pumping sets (forming the second pair) have clockwise and anti-clockwise flows respectivelyand are thus mirror the flows of the first pair, drawing fluid from the sides of the tank and injecting it more centrally. Thus, in the operation with opposite flows of the above example, generally more turbulent flows are created near the bottom of the storage tank.

[0069] FIG. 9 presents results obtained by CFD numerical simulations, in the same conditions as in FIGS. 6 and 7, for two configurations of operation with opposite flows. In this simulation, the flow in each pumping line is 2.0 m/s.

[0070] Thus, as already mentioned above, the system means that a routine of alternation of flow directions and velocities (opposite and combined, for example) can be established in a specified cycle of movement for a specified storage tank. This means that regions of high and low velocity vary their positions inside the tank along with the variations of the cycle. Moreover, these alternations in a specified cycle allow better adjustment of the velocities of the fluid so that they adapt to any shape and size of storage tank.

[0071] It should be emphasised that although the opposite and combined flow patterns have been discussed in detail, other patterns are also possible and could be used in a varying routine of flow patterns. For example, whilst the pumping sets 20 within each pair have opposite flow directions around the tank (i.e. one clockwise, one anti-clockwise) in the opposite and combined flow patterns, they may have the same flow direction around the tank in other patterns.

[0072] In some embodiments, illustrated by a top view in FIG. 10, three pumping sets 30 can be employed. Another feature illustrated in this embodiment, so as to increase the angular amplitude of the flow injected into the tank, is that each end of the pumping line comprises two or more separate outlets and inlets (e.g. two hydrodynamic nozzles) pointing in different directions, as illustrated in detail in FIG. 11. It should be emphasized that this configuration of two outlets/inlets at each end of the pumping line 30 may be employed in any possible embodiment, regardless of the number of pumping sets 20.

[0073] A blocking valve 50, with automatic or manual drive, can be provided downstream and upstream of the pump 40 (i.e. on each side of the pump), optionally at each end 32, 34 of each pumping line 30. This makes it possible for each pumping set 20 to be isolated or disconnected independently of the others for maintenance of the pump 40 or to reduce the number of pumping sets 20 in operation (for example to reduce the energy consumption for a period of time).

[0074] In the embodiment illustrated in FIGS. 10, 11 and 12, two outlets/inlets are provided at each end of the pumping line 30, and each of the two outlets/inlets may comprise a blocking valve 50. Besides allowing closure of the entire pumping set 20, as mentioned above, this arrangement makes it possible for just one outlet/inlet at each end of the pumping line 30 to be closed, meaning that in certain situations the pumping set 30 can operate with just one inlet and one outlet, thus giving greater configurability for the different flow patterns available.

[0075] Optionally, as illustrated in FIG. 12, the central portion of the pumping lines 30 (i.e. the portions at the edges of FIG. 12) may be buried, i.e. positioned below ground level. This avoids a concentration of parts and components around the storage tank 10 and possible damage to the pipelines.

[0076] Accordingly, based on the above description, the present disclosure provides an external system for movement of fluids in storage tanks. The system does not require any failure-prone components positioned inside the tank, any servicing and maintenance being carried out on components outside the tank. The system still possesses high efficiency of movement and low energy consumption, and can be adapted to the most varied types of design of the storage tank.

[0077] In addition, owing to the possibilities of implementation of routines with variation of direction and intensity of flow in each of the pumping sets 20, the system allows very high efficiency of mixing inside the tank, so that the power used is considerably less than in systems of the prior art. As an example, compared to the systems of the jet mixer type cited in the background section of the present description, the difference in operating power is quite significant. Taking as a reference the J200 model from the company Mixrite, which operates in maximum conditions of 722.2 m.sup.3/h at 7.0 bar, a value of operating power of the order of 26 hp is estimated for these conditions (assuming a typical value of efficiency of the pump equivalent to 70%). Assuming the condition of optimum cost/benefit is achieved, the system of the present disclosure has a power consumption of approximately 9 hp, for a flow rate of the order of 2190 m.sup.3/h. Thus, in the present comparative example, the system of the present disclosure achieves a flow rate approximately three times greater while the power consumption is practically three times smaller. The significantly higher efficiency of the present system relative to the systems in the prior art is thus confirmed.

[0078] Numerous variations falling within the scope of protection of the present application are permitted. This reinforces the fact that the present invention is not limited to the particular configurations/embodiments described above. As such, modifications of the above-described apparatuses and methods, combinations between different variations as practicable, and variations of aspects of the invention that are obvious to those of skill in the art are intended to be within the spirit and scope of the claims.