WO1993005870A1

WO1993005870A1 - Pump assembly

Info

Publication number: WO1993005870A1
Application number: PCT/DE1992/000782
Authority: WO
Inventors: Jürgen BLANKE
Original assignee: Blanke Juergen
Priority date: 1991-09-18
Filing date: 1992-09-15
Publication date: 1993-04-01
Also published as: AU2549092A; DE4131095A1

Abstract

Proposed is a pump assembly designed to generate pressure for an incompressible-fluid consumer unit in which the resistance to fluid flow can vary, in particular for supplying the reverse-osmosis membrane of a sea-water desalination plant. The assembly includes a high-pressure pump (1) with a low-pressure pump connected in series with it on the aspiration side. The invention calls for the low-pressure pump to be a jet pump (7') whose driving-jet inlet is connected to the pressure side of the high-pressure pump by a line (9) and a tee-junction (11). The assembly includes at least one pressure-control valve (14, 17).

Description

Pump arrangement

The invention relates to a pump arrangement for generating a pre-pressure for a consumer of an incompressible medium with variable flow resistances with a high-pressure pump and with a low-pressure pump connected in series with this on the suction side.

A consumer for whom a generic pump arrangement is used to generate a pre-pressure is, in particular, the membrane of a seawater desalination plant working according to the principle of urine osmosis.

As shown in Figure l ^'._., Supplied at a Meerwasserent- the prior art εalzungsanlage according to one driven by a motor 2 Hochdruckverdrängerpumpe 1 via a line 3 a diaphragm 4 with sea water, which has passed through a previously Fil¬ ter. 5 A throttle which is higher than the osmotic pressure of the salt solution is built up in the membrane by a throttle or a pressure control valve 6 connected downstream of the membrane. In the membrane there is a reversal of the osmosis principle, water from the salt solution (the sea water) passing through the membrane and being supplied as a product stream to storage tanks or the like. In terms of quantity, the product flow is about 1/4 of the total seawater flow used and conveyed by the high-pressure displacement pump. The remaining 3/4 of the sea water originally used leaves the membrane in concentrated form as brine or concentrate stream and is returned to the sea. In order to overcome the resistance of the fine filter, a high-pressure displacement pump or low-pressure pump 7 is connected upstream of the high-pressure displacement pump, which is driven either by its own motor 8 or by a gear via the motor 2.

The degree of implementation, i.e. the ratio between the product flow and the raw water flow used, the membrane, is dependent on the type of membrane and a predetermined size that must be observed. The working pressure of the membrane to be set to maintain the degree of conversion is usually in the range from 55 to 70 bar for the desalination of sea water. However, the temperature and the salt content of the raw water and thus the osmotic pressure on the one hand and aging and pollution mechanisms of the membrane on the other hand represent disturbances which influence the degree of conversion and the working pressure. In order to ensure a constant product flow or a constant degree of conversion, it is therefore necessary to readjust the pressure control valve or the throttle 6.

The latter is done manually in smaller systems, such as those installed on board yachts. While large, stationary seawater desalination plants are particularly concerned with good efficiencies, smaller seawater desalination plants, which operate on the principle of reverse osmosis, have other technical requirements. In the case of systems designed for lower power, which are installed in particular on board ships or the like, it is particularly important that they are inexpensive to manufacture, have a low overall weight and small installation dimensions, are insensitive to contamination in the raw water stream, and if possible, only need one drive shaft in order to enable direct drive through an internal combustion engine without any problems and at low cost. In particular, in the case of smaller systems which are not operated by specialist personnel, it is also important that they are easy to operate and that incorrect operation does not lead to total system failure, for example on board a ship, with catastrophic consequences.

In the case of pump arrangements for smaller seawater desalination plants, the admission pressure or low pressure pump in the state of the art is designed as an impeller pump or as a side channel pump. Both have the disadvantage that they are comparatively complex and thus increase the investment costs of such a system. Furthermore, overall efficiencies of less than 10% are the normal case in the two embodiments mentioned, so that the specific energy requirement is increased. Furthermore, only one unsatisfactory delivery head can be achieved with single-stage impeller pumps given the small volume flows in the context of a sea water desalination plant.

Side channel pumps, on the other hand, reach large delivery heights even with small volume flows, but they are extremely sensitive to contamination in the raw water, since their design has narrow gaps that can easily become dirty.

Furthermore, the known pump forms used as a pre-pressure or low-pressure pump are disproportionately expensive, increase the overall weight and enlarge the dimensions of a pump arrangement for the special purpose mentioned.

The invention is therefore based on the object of developing a purapen arrangement for building up a pre-pressure which is particularly suitable for use in a seawater desalination plant and is simpler, cheaper, smaller and more reliable than the previously known pump arrangements. The solution to the problem consists first of all in that, in a manner known per se, a jet pump is used as the low-pressure pump, which is connected in series with the high-pressure pump, and draws its propellant flow from the pressure side of the high-pressure pump.

Such a circuit, which is shown in principle in FIG. 2, is known in order, for example, to convey water, oil or the like from greater depths. The pump arrangement as such, on the other hand, is not known in order to generate a pre-pressure for a consumer of an incompressible medium which is subject to variable flow resistances.

In the simple embodiment shown in FIG. 2, it is not yet suitable for this purpose.

2, the jet pump 7 'is supplied with the necessary propellant flow via a line 9. Line 9 is connected on the pressure side of the high pressure pump, i.e. the propellant flow is branched off from the flow to be conveyed. The propellant flow does not flow until a counterpressure is present in the pressure-side line 10 when the high-pressure pump is started.

In the pump arrangement, as used according to the prior art for pumping water, for example from the shaft of a mine, a static back pressure is present, since the outlet is usually arranged higher than the pressure port of the high pressure pump.

With the intended use for the pump arrangement to be invented, namely in particular the supply of a membrane of a seawater desalination plant with raw water while building up a pre-pressure, this necessary back pressure is not given under all circumstances. In the latter systems will _. the back pressure is built up by a throttle or pressure control valve in the concentrate line. The back pressure is dependent on the valve position and increases approximately in square with the throughput. Since there is no back pressure when starting with the throttle or pressure control valve open, the necessary propellant flow does not occur through line 9. The result is that the high-pressure pump draws in against the resistance of the fine filter 5, causing harmful cavitation on the suction side in the high-pressure displacement pump .

A further problem which complicates the use of a pump arrangement according to FIG. 3 and which has to be solved in order to be able to use a jet pump for the stated purpose is that - as already explained - changes in the temperature and the salt content of the raw water and Aging and pollution mechanisms of the membranes must be compensated by adjusting the control valve 6 or the throttle, which is connected in series after the membrane.

As a result of the latter, the back pressure prevailing in the line 10 changes. This leads to the fact that the propellant flow through line 9 becomes smaller or larger and the operating point of the jet pump is shifted. In the worst case, a large part of the raw water flow conveyed by the high-pressure pump circulates via the propellant flow line 9, the jet pump 7 'and the filter 5, while only a small part is supplied to the membrane 4 through the line 10 as intended becomes.

The originally intended purpose of keeping the product stream which is separated in the membrane 4 constant by adjusting the control valve or the throttle 6 is therefore not achieved. The invention is therefore also based on the object of designing a generic pump arrangement using a jet pump as a pre-pressure or low-pressure pump in such a way that it can be controlled in terms of control technology if it is used to generate a pre-pressure for a consumer of an incompressible person with variable flow resistances Medium, in particular for the membrane of a seawater desalination plant working according to the reverse osmosis principle.

The solution to the problem is characterized in a generic pump arrangement characterized in that the low-pressure pump is a jet pump (ejector), the drive flow inlet of which is connected via a line and a pipe branch to the pressure side of the high-pressure pump, and that the arrangement has at least one pressure control valve.

In a particularly preferred embodiment, a pressure-limiting valve is provided, which is arranged on the pressure side of the high-pressure pump after the pipe branch and whose opening pressure is less than the working pressure of the consumer, while a pressure-reducing valve is arranged in front of the jet pump's propellant inlet .

In a further particularly preferred embodiment, only one pressure control valve is provided, which is a pressure limiting valve, which is arranged on the pressure side of the high-pressure pump after the pipe branch in front of the membrane, and whose opening pressure is greater than the working pressure of the consumer or the membrane.

In a further preferred embodiment of the invention, the high-pressure pump is connected in parallel with a short-circuit line (by-pass line) which is used to start up the arrangement by hand or, can be opened by an actuator and connects the suction and pressure side of the high pressure pump.

Furthermore, it is preferably provided to connect the throttle valve in parallel to ensure that a certain percentage of the delivered volume is exchanged even when the pressure relief valve is closed and an inadmissible heating of the delivered volume or raw water is prevented.

Further preferred embodiments are described in the subclaims and are explained in more detail in the drawings.

The drawing shows:

1 shows a pump arrangement for supplying the membrane of a seawater desalination plant according to the prior art,

2 shows a pump arrangement consisting of jet pump and high pressure pump according to the prior art,

3 shows a pump arrangement according to FIG. 2 for supplying the membrane of a sea water desalination plant, a filter being connected between the jet pump and the high pressure pump,

4 shows a first embodiment of a pump arrangement according to the invention with a pressure limiting valve (DBV) and a pressure reducing valve (DNV),

5 shows a second embodiment of a pump arrangement according to the invention with only one pressure relief valve (DBV), 6 shows a pump arrangement according to FIG. 4 with an additional buffer (memory),

7 shows a pump arrangement according to FIG. 4 with an additional line connecting the high-pressure pump on the suction side and the concurrent flow outlet,

8 shows a pump arrangement according to FIG. 5, in each of which a throttle is integrated in the jet pump and in the pressure limiting valve,

FIG. 9 shows a pump arrangement according to FIG. 5, in which all components belonging to the actual pump arrangement are integrated in a housing, and

10 shows a section through a pressure relief valve with an integrated, parallel-connected throttle for use in a pump arrangement according to the invention.

1 and 2 have already been recognized in the discussion of the prior art. 3 shows a high-pressure pump 1 which draws in raw water through a filter 5, the jet 5 being connected upstream of a jet pump 7 'for generating a pre-pressure. The jet pump 7 'obtains its propellant flow via a line 9 which branches off from the raw water line 10 on the pressure side of the high-pressure pump at a pipe branch 11. The raw water line 10 leads to the membrane, ie to a consumer whose flow resistance is changeable. A product stream is separated in the membrane 4. The concentrate leaves the membrane via a line 12 and is returned to the sea. A control valve 6 or a throttle is inserted into line 12. The necessary back pressure changes, for example because brackish water is treated with a correspondingly lower osmotic pressure the control valve is to be adjusted accordingly in order to ensure the degree of conversion or back pressure required for the membrane. The pressure in line 10 changes accordingly, and with it the propellant flow led through line 9, and as a result thereof the operating point of jet pump 7 '. A pump arrangement according to FIG. 3 is therefore not yet suitable for the intended purpose.

Furthermore, starting up a pump arrangement according to FIG. 3 is not possible. When starting, there are no appreciable resistances in the raw water flow line 10, since the control valve 6 does not yet build up any back pressure. Accordingly, a sufficient motive current is not branched off via line 9, with the result that the jet pump 7 'does not build up a pre-pressure. As a result, the high-pressure pump 1 sucks in against the resistance of the filter 5 and cavitation occurs in the suction area 13 of the pump.

The disadvantages of the pump arrangement according to FIG. 3 are avoided in the pump arrangement according to FIG. 4.

A pressure limiting valve (DBV) 14 is initially arranged in the raw water line 10 leading from the high pressure pump 1 to the membrane 4. The opening pressure of the pressure relief valve 14 is less than the normal working pressure of the diaphragm 4, e.g. 50 bar.

Furthermore, a short-circuit or by-pass line is connected in parallel to the high-pressure pump 1, which connects the pressure and suction side of the high-pressure pump to one another. A by-pass valve, not shown, is arranged within the by-pass line. This arrangement serves to load the membrane 4 slowly and continuously when starting up. The by-pass valve of the by-pass line 15 is opened to start up the system. When the high-pressure pump begins to be pumped, most of the pumped raw water volume is pumped through the by-pass line. Through the line 9, part of the delivered volume of the jet pump is supplied as a motive flow, whereupon the latter builds up a pre-pressure. The pressure relief valve 14 is closed and ensures that a back pressure is present which enables the system to be started up. A throttle 16, which allows a small part of the pumped raw water flow to pass, is connected in parallel with the pressure limiting valve. If the by-pass valve is gradually closed, the pressure rises and the volume flow that flows through the jet pump increases. As a result, the jet pump builds up a correspondingly higher pre-pressure. If the limit pressure of the pressure relief valve is reached, it opens and allows a partial flow to flow through the membrane and the open throttle valve or pressure control valve 6. In this position of the by-pass valve, the raw water that is still in the membrane is exchanged without permeation and thus production of pure water. If the by-pass valve is closed further, a pressure builds up in the membrane when the throttle or pressure control valve is set accordingly, permeation occurring when the osmotic pressure is exceeded. When the by-pass valve is completely closed and the throttle or pressure regulating valve 6 is set accordingly, a pressure builds up which is above the limit pressure of the pressure limiting valve. The latter thereby opens completely and allows the raw water flow to flow to the membrane almost without loss.

If the seawater desalination plant is used for desalting brackish water which has a lower osmotic pressure, so that the throttle 6 or the control valve 6 has to be opened widely, the high-pressure displacement pump enters Nevertheless, there is no cavitation on the suction side, since the pressure relief valve ensures that there is sufficient back pressure and thus a propellant flow for operating the jet pump and for generating a pre-pressure.

On the other hand, if the pressure required in the membrane rises sharply and is well above the pressure to which the pressure limiting valve 14 is set, a pressure reducing valve 17 inserted into the propellant flow line 9 ensures that the pressure supplied to the jet pump on the propellant side is constant remains constant.

A throttle 18 is furthermore arranged in front of the propellant connection of the jet pump, which ensures that signs of aging of the jet pump are eliminated. This is because contamination of the raw water, such as sand, for example, can lead to wear on the nozzle, which results in a change in the characteristics of the jet pump. This effect is compensated for by the throttle 18.

The limit pressure of the pressure reducing valve is preferably also lower than the working pressure of the membrane 4.

Since the high-pressure pump is usually designed with a small number of pistons or plungers and accordingly inadmissibly high fluctuations occur in the delivery flow, a pulsation damper 19 in the form of a reservoir ensures that the delivered raw water flow is evened out. The pulsation damper 19 is usually designed in the form of a bladder accumulator with a gas bubble which is filled with a filling pressure which is approximately 2/3 of the working pressure, that is to say approximately 40 bar, for example. When starting and switching off as well as when sowing brackish water, seawater desalination plants which correspond to the state of the art according to FIG. ble on that the osmotic pressure or the pressure occurring in the membrane is lower than the filling pressure in the gas bubble of the pulsation damper, which is why damping is not possible.

4 takes the place of the pressure prevailing in the membrane, the limit pressure of the pressure relief valve, so that the filling pressure of the gas bubble is in any case lower than the prevailing working pressure. In this way it is ensured that apart from a small raw water stream flowing through the throttle 16, only a smoothed raw water stream reaches the membrane.

The aforementioned throttle 16, which is connected in parallel with the pressure limiting valve 14, also fulfills further tasks in the arrangement according to the invention of pumps according to FIG. 4. If the seawater desalination system is operated for a longer period at a pressure below the limit pressure of the pressure relief valve, the raw water contained in the line circulates and heats up. The throttle 16 ensures that a small volume flow of the pumped raw water flow flows through the membrane and at the same time a small volume flow can be sucked in by the jet pump. In this way, thermal equilibrium is ensured.

The throttle 16 connected in parallel to the pressure relief valve 14 also serves to automatically vent the seawater desalination plants. If the system is put into operation again, the high pressure positive displacement pump is filled with raw water manually. Then it is started with the by-pass valve wide open. Depending on the position of the by-pass valve, the raw water with the air still contained is circulated through the by-pass line and the jet pump. However, a partial flow also flows through the throttle of the membrane Suck in the raw water jet pump, which contains no air. Through this process, the entire system is vented after a certain time.

Instead of the pressure reducing valve 17 and the throttle 18, a constant flow valve (flow control valve) can also be connected in the line to the jet pump 9. A constant flow valve can also be used instead of the pressure limiting valve 14 and the throttle 16.

FIG. 5 shows a pump arrangement according to the invention, in which the pressure reducing valve 17 in the propellant flow line of the jet pump 7 'has been omitted.

To compensate for this, the pressure relief valve 14 is designed such that its opening pressure is greater than any working pressure to be expected in the membrane 4. This ensures that all changes in the membrane 4 are kept away from the pump arrangement. With an expected working pressure in the membrane in a range between 55 bar and 70 bar, the pressure limiting valve can be set to an opening pressure of 75 bar, for example.

The disadvantage of this arrangement is that the high-pressure pump has to be pumped against the maximum conceivable pressure in any case and the specific energy consumption is accordingly too high if, for example, sea water with a low salt content is reacted in the membrane.

The advantage of the arrangement is that the structure and thus the manufacturing costs are considerably simplified. Any incorrect operation of the control valve 6 by an unskilled operator does not damage the high-pressure pump due to cavitation in this arrangement. In the case of a pump arrangement according to FIG. 6, according to the invention, care is also taken to ensure that incorrect operation of the by-pass line 15 does not damage the system.

A buffer or memory 20 is arranged on the suction side of the high-pressure pump. If the system is started, i.e. the motor 2 is switched on, although the by-pass line 15 is closed, the buffer 20 provides a volume which can be sucked in by the high-pressure pump until a sufficient pre-pressure has been built up by the jet pump, so that harmful cavitation is avoided becomes.

FIG. 7 shows an alternative pump arrangement to that shown in FIG. 6. Instead of the buffer 20, a line 21 is provided which connects the suction side of the high-pressure pump to the line 22 discharging the concentrate. If the motor 2 is switched on, even though the by-pass line 15 is closed, the high-pressure pump can draw in concentrate through the line 21, so that harmful cavitation is prevented. In order to prevent sea water from being sucked in, a check valve 23 is arranged in line 22.

Furthermore, a check valve 24 is arranged in line 21 itself, which ensures that the pre-pressure generated by jet pump 7 'after the system has started up cannot be reduced by line 21.

FIG. 8 shows a pump arrangement according to the invention according to FIG. 5, various components having been integrated.

The throttle 18 has been integrated into the jet pump 7 'in such a way that a single component, ie a jet pump 7 ", is produced. In the same way, the throttle 16 connected in parallel with the pressure relief valve 14 is integrated in the former. Fig. 10 shows an embodiment of a pressure relief valve, in which a parallel throttle in the form of a bore 16 is integrated.

10 consists of a valve seat 26, in which a valve body 27 is seated. The valve body 27 is connected via a piston rod 28 to a piston 29, which is loaded by a spring 30. Below the piston 29 there is a Cavity 32, which is connected to the fluid, the pressure of which is to be limited, via an inflow 33. The fluid flowing in via the inflow 33 exerts a pressure on the annular surface A of the piston 2. If the pressure force generated exceeds the spring force 30, then the valve body 27 is lifted off the valve seat 26 and releases an annular gap through which the fluid can flow off.

If the pressure prevailing in the cavity 32 is too low to raise the piston 29, the valve body 27 closes the valve seat 26. The bore 16 in the valve body 27 then acts as a throttle connected in parallel, whereby fluid can flow through the bore 16.

FIG. 9 shows an embodiment of the invention in which all hydraulic parts are integrated in the head of the high-pressure pump 1. The jet pump 7 'and the throttle 18, like the by-pass line 15, pressure relief valve 14 and throttle 16, can be accommodated in a common housing 40. Only the motor 2 and the pulsation damper 19 then have to be flanged on. The entire unit or the housing 40 has only five connections 41 to 45, with which it must be connected to the filter 5, the membrane 4 and the pulsation damper 19. The connection 41 leading out of the housing 40 serves for the supply of raw or sea water. The filter 5 is connected to the connections 42 and 43. connected and the terminal 44 is used to connect with the Mem bran ^¬ 4. The connector 45 serves to mount the Pulsationsdämp- fers 45th

The pump arrangement according to the invention makes it possible to construct a compact unit which is excellently suitable for generating a form for a consumer with variable flow resistances. The pump arrangement according to the invention is inexpensive to manufacture, has small dimensions and is insensitive to operator errors.

The pump arrangement according to the invention is therefore particularly suitable for supplying a membrane to a smaller seawater desalination plant operating according to the reverse osmosis principle, in particular on board ships or the like

Reference list

Cavity connecting piece housing raw water connection filter connection filter connection raw water connection pulsation damper connection circular surface

Claims

1. Pump arrangement for generating a pre-pressure for a consumer of an incompressible medium with variable flow resistances, in particular for the membrane of a sea water desalination plant working according to the reverse osmosis principle, with a high pressure pump and with a low pressure pump connected in series with this on the suction side, characterized in that that the low-pressure pump (7) is a jet pump (7 ') (ejector), the drive current inlet of which is connected to the pressure side of the high-pressure pump (1) via a line (9) and a pipe branch (11), and that the arrangement has at least one pressure control valve (14, 17).

2. Pump arrangement according to claim 1, characterized in that the high-pressure pump (1) is a pump operating according to the displacement principle.

3. Pump arrangement according to claim 2, characterized in that the pressure control valve (14) is a pressure relief valve (DBV) which is arranged on the pressure side of the high-pressure pump (1) after the pipe branch (11).

4. Pump arrangement according to claim 3, characterized in that the opening pressure of the pressure relief valve (DBV 14) is greater than the working pressure of the consumer (4-).

5. Pump arrangement according to claim 1 or 2, characterized gekenn¬ characterized in that the pressure control valve (17) is a Druckminder¬ valve (DMV), which is arranged before the drive flow of the jet pump (7 ').

6. Pump arrangement according to claim 5, characterized in that the limit pressure of the pressure reducing valve (DMV 17) is smaller than the working pressure of the consumer (4).

7. Pump arrangement according to one or more of the preceding claims, characterized in that a pressure relief valve (14) is arranged on the pressure side of the high-pressure pump (1) after the pipe branching (11) and that a pressure is present before the jet pump's drive current occurs reducing valve (17) is arranged.

8. Pump arrangement according to claim 7, characterized in that the opening pressure of the pressure relief valve (14) is less than the working pressure of the consumer (4).

9. Pump arrangement according to one of claims 7 or 8, da¬ characterized in that the limit pressure of the Druckminder¬ valve (17) is less than the working pressure of the consumer (4).

10. Pump arrangement according to one or more of the preceding claims, characterized in that the high-pressure pump (1) connects a short-circuit line (by-pass line) (15) connecting its suction and pressure sides in parallel.

11. Pump arrangement according to claim 10, characterized in that the short-circuit line (11) contains a shut-off valve.

12. Pump arrangement according to one or more of the preceding claims, characterized in that the pressure limiting valve (14) has at least one throttle (16) connected in parallel.

13. Pump arrangement according to one or more of the preceding claims, characterized in that a throttle (18) is connected in series with the drive current entry of the jet pump (7 ').

14. Pump arrangement according to claim 13, characterized in that the throttle (18) in the jet pump (7- ^* ) is integrated.

15. Pump arrangement according to one or more of the preceding claims, characterized in that at least one buffer (memory) (20) is connected to the suction side of the high-pressure pump (1).

16. Pump arrangement according to one or more of the preceding claims, characterized in that the suction side of the high-pressure pump (l) is connected via a line (21) to the outlet side of the consumer (4).

17. Pump arrangement according to claim 16, characterized in that a check valve (24) is arranged in the line (21).

18. Pump arrangement according to claim 17 or claim 16, da¬ characterized in that a check valve (23) is arranged downstream of the connection point of the line (21) with the outlet side of the consumer (4).

19. Pump arrangement according to claim 12, characterized in that the throttle (16) is integrated in the pressure relief valve (14).

20. Pressure relief valve for use in a pump arrangement according to claim 19, with a conical seat (26) and a closing, spring-loaded Ventilkör¬ per (27), which is pressurized via a piston rod (28) with a fluid to be controlled by a pressure Piston (29) is connected, characterized in that the valve body (27) has at least one throttle bore (16).

21. Pump arrangement according to the preamble of claim 1, characterized in that the high-pressure pump (1) is a pump operating on the displacement principle and is driven by a motor (2), the speed of which can be regulated depending on the pressure prevailing on the pressure side of the high-pressure pump.

22. Pump arrangement according to the preceding claims, characterized in that the high pressure pump (1) and parallel-connected short-circuit line (15), jet pump (7 ') and series-connected throttle (18) as well as pressure relief valve (14) and parallel-connected throttle (16) are designed as an integrated unit.

23. Pump arrangement according to claim 1, characterized in that the pressure control valve is a constant flow valve.