WO1997029049A1

WO1997029049A1 - Sea water reverse osmosis desalination system, with permanent renewal of the water to be de-salted

Info

Publication number: WO1997029049A1
Application number: PCT/ES1997/000028
Authority: WO
Inventors: Manuel Barreto Avero
Original assignee: Manuel Barreto Avero
Priority date: 1996-02-07
Filing date: 1997-02-06
Publication date: 1997-08-14
Also published as: AU1602997A

Abstract

The system is comprised of a high pressure intermediary chamber and two auxiliary side chambers which may be alternatingly pressurized or not with the prior chamber, said intermediary chamber communicating through its two extremities with the extremities of the auxiliary chamber. In the conduits which make the chambers communicate, there are provided valves which occupy different opening/closing positions so that when there is a pressurization in one of the auxiliary chambers of the sea water which is introduced in the intermediary chamber, the reverse osmosis desalination is performed through both chambers, while in the other auxiliary chamber the sea water is simultaneously renewed. In an alternative, the auxiliary chambers may be defined within a cylinder wherein a piston can slide, making these two chambers of the cylinder communicate with the high pressure intermediary chamber and with the tank of water to be de-salted, the corresponding communication conduits being provided with opening/closing valves.

Description

SEA WATER DESALINATION SYSTEM THROUGH REVERSE OSMOSIS, WITH PERMANENT RENEWAL OF WATER TO DESALINATE

The invention relates to a system for desalination of seawater by reverse osmosis, based on the fact that the pressure chamber in which the actual desalination is carried out is alternatively in communication with two other low pressure chambers, although the one If it is in communication with the first one, it will be pressurized, all in such a way that through such chambers a permanent renewal of the sea water is communicated, with a minimum energy consumption, using for this purpose properly designed valves to open and close in the opportune and required moments for the system to work correctly.

It is therefore an object of the invention, to provide a system based on chambers with compensated pressures that allow the operational and functional phases to be carried out with the minimum energy expenditure, therefore requiring a power much lower than that required in traditional systems and currently used for The same purposes.

It is also the object of the invention to provide a system that materializes in what can be considered as a brine water exchange pump for sea water in the process of reverse osmosis, based on producing a recirculation of water contained in the two chambers established in a cylinder that by one of its ends is in communication or connected with the pressure chamber in which the reverse osmosis occurs, which makes the piston of that cylinder is compensated by both sides, so that when it moves, Closed circuit water enters on one side and exits from the other side of the pressure chamber with no more effort than load losses and friction in ducts and in the corresponding osmosis membrane. The desalination of seawater, using the principle of reverse osmosis, requires complex and expensive facilities, to which the high energy cost necessary to pump large flows of water at high pressure must be added, taking advantage of a maximum of 40 percent. In addition, these desalination plants require a high maintenance cost. At this time, high-power and high-pressure pumps are used for reverse osmosis and are usually of different types: centrifugal, piston, screw, etc., capable of introducing the total gross flow that will be distributed in two parts, one will be the water to desalinate that is between 30 and 40 percent of the gross, and the remaining 70 or 60 percent, will revert to the sea in the form of brine. Throwing 60 percent of seawater is virtually unimportant, but losing the energy that has been spent on increasing the pressure to about 70 atmospheres is a great useless expense. Currently, this brine flow is used as much as possible, by very expensive systems and with low yields, such as putting a Kaplan or Pelton type turbine, at the outlet of the jet and connecting the turbine to an alternator to lighten the consumption of the pump, or also join it to the axis of the pump, with that of the turbine and thus some of this seventy percent of wasteful use is recovered. The yields of these expensive machines that do not exceed 20 percent are known. Other solutions for less important installations is to put an inverted centrifugal pump at the outlet on the input pump shaft. Of all the forms at the moment the systems of more performance are based on recovering the energy in the form of kinetic energy, reason why it is of interest speed in the water of exit, which is precisely the bad thing for the losses by friction.

The system that has been recommended has been designed to solve this problem to full satisfaction based on a simple and effective solution that, as a first advantage, can be mentioned energy saving, simplicity and low cost of installation, as well as low cost maintenance reduction of faults in the installation, since this is very simple.

In addition, the energy cost in the desalination itself is considerably reduced, since the use of pumps by sectors allows to control the yields in each sector. It can also be cited as a fundamental advantage to be able to use wind and photovoltaic energy for the operation of the installation or system itself, due to the low power that is needed.

The procedure that is recommended is based on pressurizing at high pressure the chamber where reverse osmosis occurs with another chamber, or nurse tank, which had been filled with low pressure seawater. Is Nursing chamber is used to exchange the brine produced in the osmosis chamber, for new water. This renewal will occur until the degree of salinity of the set reaches a certain value. At this time, a valve system incommunicates both chambers, osmosis and nurse. Then, at low pressure, the brine will be evicted by fresh seawater in the nurse tank. Simultaneously, another valve system will communicate the osmosis chamber with another parallel nurse tank filled with new seawater. Repeating the process described above. In addition to the water pump to the intermediate high pressure chamber, the system includes a sea water pump for renewal and a recycling pump so that the work done by such pumps is reduced and consequently the energy required small. On the other hand, and in relation to the loss of 60 to 70 percent of the remaining non-desalinated water, originated in traditional systems, it is resolved with the system of the invention, according to an alternative embodiment thereof.

More specifically, what is intended with the invention is to introduce without cost that 60 or 70 percent of water that will leave in the form of brine when leaving, without any energy or without pressure and supply the high pressure of reverse osmosis around 30 The remaining 40% at 70 atmospheres is the amount of water that will be desalinated, that is, the one that will cross the osmosis membrane. Only a separate pump, operating at high pressure, will be needed for the water that has to pass through the membrane, that is, the effective power for the water to be desalinated.

What may surprise most when building this pump is that the piston can be large diameter, because it is between two equal pressures (compensated) quite the opposite to conventional high pressure pumps that are trying to make a small diameter so that the product pressure per surface is small and that the rest of the mechanism, such as the connecting rod, crankshaft, bearings, brackets etc. do not be subjected to great efforts, and therefore affect the robustness and price. Only the cylinder will have to be sized for high pressure. The construction of the pistons for high pressures has to have a great adjustment and therefore a great friction with the cylinder walls. In the present case we can imagine, in a schematic way, a simple plastic disk of little thickness, more or less adjusted to the cylinder, which pushes the water as a paddle, since if it stops at any point there will be no leaks although the Adjustment is poor. Therefore, pistons with little friction can be designed.

In the system of the invention the low speed of the pump does not decrease the performance and this makes it particularly interesting to combine it with wind energy, since as we deal with pressures, a slow piston travel makes a displacement of the water, which does not happen with centrifugal pumps and turbines. The costs of the pump according to the invention are much lower than conventional.

The pump that materializes the system, according to what has just been exposed, also has special application to recirculate water from wells with large differences in dimensions, or renewal of pool water, counting on the difference in dimensions or the difference in Pressures between water containers is not a reason to increase engine power, although frictional load losses. Deposits that contain water can be opened or closed interchangeably. These and other particularities will be more easily understood based on the description that will then be made with the help of a set of drawings that accompany this descriptive memory, forming an integral part of it, and where with a merely indicative nature and not limiting the following has been represented: In Figure I ^a , the system is shown in the plant in the initial phase of operation, being able to see one of the side or nurse chambers with its valves open and the opposite with its valves closed.

In Figure 2 ^a , the same system as in the previous figure is shown with the valves in an inverted position, that is, those that were previously closed, are now open and vice versa.

In figure 3 ^a , a schematic view of an alternative embodiment of the system is shown, constituting in this case a brine exchange pump that originates in the process of reverse osmosis itself by the water to be desalinated. In figure 4 ^a , a schematic view is shown equal to the previous one, with the cylinder piston changed position like all the valves involved in the system.

According to and as can be seen in Figures I ^a and 2 ^a , the system of the invention comprises two nurse chambers (1 and 1 ') that on the one hand communicate through the conduits (2 and 2') with an inlet ( 3) of seawater, in which a pump (4) is intercalated with low pressure water renewal, while on the other hand those nurse chambers (1 and 1 ') are in communication with an outlet (5) through of respective pipes (6 and 6 '). In addition, such chambers (1 and 1 ') communicate with an intermediate chamber (7) of high pressure or osmosis through the pairs of conduits (8-8') and (9-9 ¹ ). This intermediate chamber includes an inlet (10) for seawater to be desalinated, as well as an outlet (1 1) for the desalinated water, a membrane (12) existing prior to said outlet (1 1). Seawater to be desalinated is propelled into the intermediate or osmosis chamber (7) by means of the high pressure pump (13), with a third recycling pump (14) existing in the intermediate chamber itself (7) with the nurse by the ducts (8-8 ') and (9-9').

In each of the intercom lines with the cameras there is a valve. Thus, in the pipes (2 and 2 ') the valves (15-15') are provided; valves (16-16 ') are provided in the pipes (6 and 6'); valves (17-17 ') are provided in the pipes (8-8'), and the valves (18-18 ') are provided in the pipes (9-9'). The operation is as follows:

Starting from the position represented in figure I ^a , and assuming that the entire system is loaded with seawater and with the primed pumps, if the pump operation starts (4), seawater will begin to be introduced by the conduit (2) to the chamber (1) at the same time as the eviction of the water that this chamber contains begins, and that evacuation of water is carried out through the conduit (6) towards the outlet (5). Such events occur as a consequence of the fact that the valves (15) and (16) are open and the valves (17), (18), (15 ') and (16') are closed. In this operation the pump (4) performs only the work necessary to overcome friction, as a result of the input (3) and output (5) are at the same level.

When all the water contained in the chamber (1) is finished, all the valves change position, the valves (17), (18), (15 ') and (16') are opened and the valves (15) are closed. , (16), (17 ") and (18 '), leaving the system as shown in Figure 2 ^a .

At that time the same operation starts in the chamber (1 '), that is, the renewal of the water in it starts as a result of the pump (4) still running, producing water from the sea into the chamber (T ) and leaving or discharging the water it contains (brine). Since the water entering the chambers (1) or (l ¹ ) and the water discharged from them must be the same, it will be necessary to control that equality by means of, for example, a flowmeter or by salinity controllers.

At the moment when the valves change position from figure I ^a to figure 2 ^a , the high pressure pump (13) is also put into operation, driving water from the sea through the inlet (10) to the chamber intermediate or osmosis (7). This water inlet will result in the chamber (1), which was previously at sea level pressure, being pressurized with the high pressure of the said pump (13), since the chambers (1) and (7) are communicated through the valves (17) and (18), but closed with respect to the outside because the valves (15), (16), (17 ') and (18') are closed.

The pump (13) is a pump that has to give a high pressure capable of overcoming the pressure of the reverse osmosis, so that the flow of water entering will leave through the membrane (12), that being the flow desalinated.

The brine that originates in the desalination and remains in the inner face or the pressure side of the membrane (12), logically remains in the chamber (7) and begins to renew with the flow provided by the pump (14) , this being a low pressure pump that only has to recirculate the water entering the chambers (7) and (1) that are pressurized with the high pressure of the pump (13). Therefore, the power of said pump (14) will only be that required to overcome the friction of the brine with the membrane (12) and to recirculate the water from the chamber (7) to the chamber (1). Desalinated water exits through the membrane (12) towards the conduit (1 1), while the brine passes through the conduit (8) and the valve (17) to the chamber (1), pushing the water without desalination of this through the valve (18) and the conduit (9) to the chamber (7) where the membrane desalination is performed (12).

In this way the water in the chamber (7) will be renewed with the water in the chamber (1). Now, as in the chamber (1) brine is entering through the valve (17), there will come a time when said brine begins to leave the chamber (1) through the valve (18), at which time a detector expected salinity around the valves (18) and (18 '), will give an order to an automated system to change the position of all the valves, repeating the desalination cycle now through the camera (l ¹ ). Keep in mind that while the desalination cycle is taking place in the chamber (7), according to figure 2 ^a , the seawater through the pump (4) will pass through the conduction

(2 ') to the chamber (1'), dislodging water (brine) through conduction

(6 '), being the amount of water that enters the same as that which comes out or is evicted.

It is obvious to say that the controls to change the position of the valves may be any, that is, they may be of the mechanical type or computerized, based, for example, on the salt concentrations at the strategic points of the system, the flows that pass through pumps, elapsed times, etc.

As you can see, the system can operate with only two chambers, one of them osmosis and the other one that is filled with seawater and closed to the outside, and both are pressurized, communicating with the appropriate valves. Although there would be the inconvenience of the lack of continuity in production, that is why three are incorporated into the scheme, but they may be more, the necessary ones to make it as continuous as you want. The size and shape of the nurse chambers that are loaded with salt water will be adequate for the capacity of the installation. The tubular cylindrical shape is suitable so that there is no turbulence, in this way the water that enters with the brine that comes out is not mixed. The smaller diameter also improves the mechanical resistance of the nurse chamber at the high pressure they are going to work on. The system can work with horizontal or vertical tanks. The valves can be simple multi-way valves to decrease the number of them.

In an alternative embodiment, shown in Figures 3 ^a and 4 ^a , the system determines what can be considered as a brine exchange pump for seawater, in this case comprising a high pressure chamber (20) containing the membrane of osmosis (21), and that communicates by two conduits (22) and (22 ') and through the respective valves of these (23) and (23') to one and another end of the cylinder (24). This cylinder (24) has a piston (25) that is driven by the rod (31) which in principle can be considered to be practically negligible in diameter and is supposed to go to an alternative power source, such as a connecting rod mechanism, crankshaft and engine. The cylinder (24) has two other ducts (26) and (26 '), which through their respective valves (27) and (27') communicate with the container (28) which may be the sea, a well. . etc. For the example we consider that the pump is at sea level. This mechanism is complemented by the entry of water to be desalinated by the duct (29), driven by the high pressure pump (30) to the described chamber (20) and which will pass through the osmosis membrane (21) and finally the duct (32) where the product or desalinated water comes out. To better understand the operation process, it is assumed that the entire system is loaded with seawater. Starting from Fig. 3 ^a , the valves (23) and (23 ') are closed, with high pressure in the osmosis chamber (20) due to the pressure supplied by the pump (30). The piston is to the left of the cylinder (24) and the valves (27) and (27 ') are open, as the pressure requested by the piston on both sides is that of sea level, and the high chamber pressure ( 20) it does not arrive because the valves (23) are closed and (23 ') the piston will be in total balance. If the piston is moved from left to right, water enters through the conduit (26) through the valve (27) that is open and the one to the right of the piston comes out down the conduit (26 ') through of the valve (27 ') which is also open. As you can see, there are no efforts due to water pressure, the work will only be friction and loss of loads. The piston stroke to the right ends, and at this time the valves (27) and (27 ') are closed and the pair (23) and (23') are opened, leaving everything as indicated in Fig. 4 ^a . Now in the cylinder (24) the pressure has changed since the high pressure arrives of the chamber (20) through the ducts (22) and (22 ') when the valves (23) and (23') are open; The piston (25) then has the same pressure on both sides and will be in equilibrium. If it is displaced to the left, the water that it took from the sea will introduce it into the chamber (20) through the conduit (22) and the brine will descend through the conduit (22 ') and will enter the cylinder (24) to the right of the piston (25) that moves to the left, without exercising more work, than to overcome friction and load losses. At this time the valves (23) and (23 ') are closed and then the valves (27) and (27') are opened, leaving the pump in the position of fig. 3 ^a , starting a new cycle.

For the recirculation to be continuous and non-intermittent, two cylinders must be placed in parallel, although they may be all the desired cylinders.

The placement of the same can be in the same rod, opposite 180 °, in V, radial, etc., that is, like any pump or explosion engine.

If a large diameter rod (31) is used with the consequent variation of the useful surface of the corresponding piston face (25), then the high pressure pump (30) could be suppressed, in which case the osmosis power would supply it the piston (25) by means of a greater alternative power source.

Claims

I ^a .- SEA WATER DESALINATION SYSTEM THROUGH REVERSE OSMOSIS, WITH PERMANENT RENEWAL OF WATER TO BE DESALINATED, based on the fact that only the flow of water to be desalinated is pumped at high pressure, introducing the rest of the desalinated water that intervenes to evacuate the brine, at low pressure and then pressurized with high pressure the water to be desalinated; with the particularity that the reverse osmosis is carried out in the corresponding high-pressure chamber, which is accessed by the same amount of water from the sea as the one in the form of brine is wasted in the desalination itself, the corresponding recirculation or exchange being carried out without more energy expenditure than that resulting from load losses and friction, characterized in that it includes three chambers interconnected with each other through respective conduits, in which valves are provided whose position is such that the intermediate chamber through which produces the osmosis can be in communication alternately with one or the other of the other two cameras or more considered as nurses, so that the nurse chamber that is not in communication with the intermediate chamber, considered the latter as a pressure chamber, is in communication with an entrance of the sea water and an exit, to get the renovation water ion in such a chamber while pressurization occurs and corresponding reverse osmosis in the intermediate chamber and the other nurse chamber; having provided that the two nurse chambers are communicated, through respective pairs of conduits, with a common inlet of seawater provided with a pump and with a common or independent outlet of the renewed water, existing in each of those pipes a valve ; with the particularity that the intermediate or pressure chamber includes a water recycling pump as well as a pressure pump to impel the sea water to be desalinated inside said chamber, the conduits communicating the ends of that intermediate chamber of pressure with the ends of the two nurse chambers, equipped with the corresponding valves. 2 .- WATER SYSTEM DESALINATION BY REVERSE OSMOSIS SEA WITH PERMANENT RENEWAL OF WATER A DES ALINIZAR of according to claim Ia, wherein the pump renewal planned water conducting common input for the two nurses chambers, forces water through one of said chambers and dislodges the water (brine) contained therein through of the corresponding common outlet, the valves being kept in the inlet and outlet ducts to such a nurse chamber in the open position; while the valves provided in the inlet and outlet ducts of the other nurse chamber are kept in a closed position, the communication of this second nurse chamber being established with the intermediate pressure chamber when the valves are open in the conduits between said nurse chamber and the intermediate pressure chamber, the valves provided in the conduits between said intermediate pressure chamber and the first nurse chamber being closed. 3 .- SYSTEM DESALINATION OF WATER SEA BY REVERSE OSMOSIS WITH RENEWAL PERM WATER desalinated according to claim I ^to wherein the Wetnurses chambers are constituted by a cylinder inside which is movable a piston connected to a shaft of negligible diameter, together with an alternative power source, establishing in said cylinder two independent chambers, one on each side of the piston, whose chambers and through independent ducts are in communication with the high pressure chamber in which the osmosis takes place ; with the particularity that said two cylinder chambers are in turn communicated, through independent ducts, with a low pressure container, such as the sea itself; having provided in each conduit a valve capable of closing / opening the communication between the chambers; with the particularity that the position of the valves corresponding to the communication conduits between the high pressure chamber and the cylinder is contrary to that of the valves provided in the communication conduits between the cylinder and the low pressure container, so that from a position of priming and equilibrium, and by moving on either side of the piston, the entry of seawater from the low pressure container to the cylinder and the brine output of the high chamber are alternately established pressure towards the cylinder, as well as the entry of that seawater from the cylinder to the high pressure chamber, and the brine outlet from the cylinder to the low pressure container.

4 .- SYSTEM DESALINATION OF WATER SEA BY REVERSE OSMOSIS WITH RENEWAL PERM WATER desalinated according to claim 3, wherein the water inlet of the sea from the container low pressure cylinder and brine outlet thereof to the low pressure container, the valves of the corresponding ducts are open, while the valves provided in the communication ducts with the high pressure chamber are in the closed position, and vice versa. 5 .- SYSTEM WATER DESALINATION SEA by osmosis

REVERSE, WITH PERMANENT RENEWAL OF THE WATER TO BE DESALINATED, according to claims 3 ^a and 4 ^a , characterized in that the high-pressure chamber has a water inlet to be desalinated, in which conduit a high-pressure discharge pump is provided , while the opposite part of such a chamber, following the membrane in which the reverse osmosis desalination occurs, has an outlet for desalinated water.

6 .- SYSTEM DESALINATION OF WATER SEA BY REVERSE OSMOSIS WITH RENEWAL PERM WATER desalinated according to claims 3, 4 ^th and 5, characterized in that two or more cylinders are arranged with a conventional arrangement including , to achieve continuous recirculation.

7 .- SYSTEM DESALINATION OF WATER SEA BY REVERSE OSMOSIS WITH RENEWAL PERM WATER desalinated according to claims 3 ^to to 6, characterized in that the rod to which is connected the piston of the cylinder is capable of being large diameter allowing the elimination of the high pressure pump provided in the inlet duct to the high pressure chamber, the osmosis power being supplied by means of the piston connected to a larger alternative power source.