Abstract:
This present invention relates to a method of recovering very efficiently the energy of a waste stream, which is a by product of the desalination process. More specifically, this present invention relates to a method of using the waste stream to pressurize the clean feed. It also uses the invention as a high pressure seawater pump using another fresh water pump as the pressure source. This invention uses as its core technology a removable pressurization element that enables the quick insertion and removal of the pressurization element via a peristaltic process.

Description:
[0001]    This present invention relates to a method of improving the efficiency of a reverse osmosis system by recovering very efficiently the energy of a waste stream, which is a by product of the desalination process. More specifically, this present invention relates to a method of using the waste stream to pressurize the clean feed and also a fresh water to seawater high pressure pump both by peristaltic compression 
         [0002]    Osmosis is a process by which a semi-permeable membrane, separating two fluid streams of different salinities, tends to ensure equilibrium of the two fluids, such that the less saline liquid tends to flow into the more saline liquid. Reverse osmosis is a ‘reversal’ of the osmosis process where by the more saline solution is ‘pressurized’ above the osmotic pressure across a semi-permeable membrane, thereby transferring a ‘permeate’ across the dividing membrane. 
         [0003]    For seawater, the osmotic pressure is approximately  60  bars and is dependant on the nature of concentration and composition of seawater. The ‘potable’ water obtained by this process is termed ‘permeate’ and the more concentrated water is termed ‘concentrate’ or ‘brine’. The ratio of the ‘feed’ liquid to the ‘permeate’ obtained is termed ‘recovery’ and typically 40-48%. 
         [0004]    The remaining liquid, which is still at a high pressure is termed ‘concentrate’ and its energy is available for recovery, which is essentially what this Invention relates to. 
         [0005]    Traditional methods of recovering this energy are,
       Hydraulic Recovery Turbines comprising of
           Impulse turbines with unit efficiencies of around 85%             eaction turbines with unit efficiencies of around 75%             urbo Chargers of reasonable efficiencies   
           Works Exchanger types       
 
         [0011]    Part of the present invention is a Work Exchanger type involves the pressurization of the feed using the waste energy of the concentrate. 
         [0012]    Typically these devices such as described in U.S. Pat. No 3,791,968 use opposed piston/diaphragm pumps and these arrangements have several drawbacks. The device described in U.S. Pat. No. 3,791,968 is also restricted in the quantity of fluid that can be handled and is suited to small installations. 
         [0013]    The Dual Work Exchanger Energy Recovery type also has several drawbacks, in that it is a piston accumulator type of device and having sliding components, is subject to wear, seawater has low lubricating properties. It also has to have valves and again prone to leaks and sealing is an issue. 
         [0014]    Other energy recovery devices employ pistons of different areas with connecting mechanisms as described in U.S. Pat. No. 3,558,242 and as with the above type has various seals to minimize leaks to atmosphere. 
         [0015]    Other energy recovery devices as described in Australian Patent No. 2011100390 while efficient does not allow for a modular extraction of the pressurization element. 
         [0016]    The principal behind the Invention is to provide a device for recovering the ‘waste’ or ‘Concentrate’ energy coming out of the reverse osmosis membranes and at the same time provide for a very simple removal and reinstallation of the main pressurization element that does not require the removal of the entire assembly. 
         [0017]    The fundamental principal behind this is the utilization of several technologies as briefly stated below.
       Utilization of ordinary polymer materials like PVC, gPVC for the Inner Containment Shell that is primarily there to cater to the corrosive nature of seawater.   Providing an Outer Containment Shell around this inner containment shell that is primarily there to cater to the high pressure that will be required for the process.   Filling the gap between the inner containment shell and the outer containment shell with a polymer that will support the pressure contained within the inner containment core and which in turn is supported by the outer containment core.       
 
         [0021]    The novel inventive step being the,
       The modular construction of the pressurization element that enables it to be removed and replaced as a single unit without disturbing much of the system piping using the peristaltic pressurization process for pressure transfer.       
 
     
    
     DETAILED DESCRIPTION 
     Reference Will Now be Made to FIG. 1 
       [0023]    The Outer Containment Shell  1  is provided with Flanges  5 . There are two Inner Containment Shell flanges  6  into which the Inner Containment Shell  3  is fixed into as shown. 
         [0024]    A cavity is formed between the outer diameter of the Inner Containment Shell  3  and the inner diameter of the Outer Containment Shell  1 . This cavity is filled with a fiberglass mat with resin and/or filled with resin or a polymer epoxy  2  which then forms a solid ‘shell’. Nozzles  12  &amp;  13  are provided into the Outer Containment Shell  1  and do not penetrate through to the inner diameter of the Inner Containment Shell  3 . 
       Reference Will Now be Made to FIG. 2 
       [0025]    There are two off Closing Flanges  7  one of which has attached the Feed Transfer Tube  20 , the Backing Flange  8 , Feed Transfer Coupling  9  and to the other the Concentrate Transfer Coupling  14 . 
         [0026]    The other end of the Feed Transfer Tube  20  is attached the feed transfer tube Holder  21  that has one end of a Elastomeric Containment Membrane  4  attached to it while the other end is fixed to the Plug Holder  24 . Encapsulating the Elastomeric Containment Membrane  4  is a Perforated Containment Tube  22  that which surrounds the Elastomeric Containment Membrane  4 . 
         [0027]    Attached to the Plug Holder  24  is a Deflector Plate  25 . The sealing between the 
         [0028]    Elastomeric Containment Membrane  4 , the Feed Transfer Tube Holder  21 , the Plug Holder  24  and the Perforated Containment Tube  22  is done by a flexible silicone/epoxy sealing. 
         [0029]    The Backing Flange  8  attaches to the Closing Flange  7  by means of Bolt  10  and Nut  11 . To the Perforated Containment Tube  22  are attached the Centralizers  23  that which ensures that&#39; the Perforated Containment Tube  22  is centralized within the Inner Casing Cover  3 . The Deflector Plate  25  serves to dissipate the impact energy of the Concentrate entering the Inner Containment Shell  3 . 
         [0030]    The entire assembly comprising the Deflector Plate  25 , the Perforated Containment Tube  22  the Plug Holder  24  the Elastomeric Containment Membrane  4  the Feed Transfer Tube Holder  21 , the Feed Transfer Tube  20  the Closing Flange  7  and the Backing Flange  8  are all removable as one element. This is achieved by removing the  120  Bolt  10  and Nut  11  on the Feed Transfer Coupling  9 . 
         [0031]    This assembly is called the Pressurization Element. 
         [0032]    The entire assembly mentioned above is easily introduced and removed into and from  125  the Inner Containment Shell  3 . 
         [0033]    This complete constructed component is termed the Pressure Exchanger. 
       Reference Will Now be Made to FIG. 3 
       [0034]    The entire system as shown in  FIG. 3  is assumed to be filled with clean filtered seawater, purged of all air and is ready for start. 
         [0035]    Pressure Exchangers  50  and  60  form the Energy Recovery circuit of the device. 
         [0036]    Stream  79  is clean, filtered and pretreated seawater that enters the suction of the LP Pump  300  and exits as stream  80  at a nominal pressure of 3 barg. 
         [0037]    This stream  80  splits into two streams, stream  81  &amp; stream  82 . 
         [0038]    Stream  82  enters the suction of the High Pressure Pump  400  and exits as stream  89  while stream  81  splits into two streams, stream  83  and stream  84 . 
         [0039]    Stream  83  enters the Pressure Exchanger  50  through check valve  53  and enters the elastomeric containment membrane  4  via the feed transfer tube  20 . As the Elastomeric containment membrane  4  expands and fills with stream  83 , it displaces an already filled volume of liquid which exits the pressure exchanger  50  via concentrate coupling  14  as stream  97 . 
         [0040]    Stream  97  splits into two streams  95  &amp;  96 . 
         [0041]    Stream  95  enters the transfer valve  170  via port  190 . As the position of the block  180  is downstream of port  200 , the stream  95  exits the transfer valve  170  via this exhaust port  200  as stream  94 . 
         [0042]    Stream  96  does not flow as port  110  is closed. 
         [0043]    Stream  84  does not flow as the check valve  65  is closed due to the downstream pressure. 
         [0044]    Stream  89  combines with stream  88  and becomes stream  90  and enters the reverse osmosis membrane  800 . The stream is split in two and the permeate stream  92  exits as desalinated water and the concentrate exits as stream  91 . Stream  90  is at a nominal pressure of 60 barg 
         [0045]    Stream  91  at a nominal pressure of 58 barg enters the transfer valve  100  at port  140  and exits as stream  92  as the position of the block  120  opens port  130 . Stream  92  enters the pressure exchanger  60  through the concentrate coupling  14  as Stream  98  and pressurizes the elastomeric containment membrane  4  to the pressure of 58 barg and the liquid inside the elastomeric containment membrane  4  now exits as stream  86  via the check valve  66 . Check valve  65  is closed as the pressure is greater than 3 barg. 
         [0046]    Stream  93  does not flow as port  210  on Transfer Valve  170  is closed by the position of block  200 . 
         [0047]      175  Stream  86  becomes stream  87  and enters the suction of the circulation pump  500  and exits as stream  88  at a nominal pressure of 60 barg flowing through check valve  30  and control valve  31  and joins stream  89  to become stream  90 . 
         [0048]    The position of the block  120  on transfer valve  100  and the position of block  180  on  180  transfer valve  170  control&#39;s the flow of concentrate through the pressure exchangers. 
         [0049]    Block  120  and block  180  are joined by rods  240  and  150 . The transfer valves  100  &amp;  170  are then sequenced by an actuator  230  that is coupled to the rods  240  and  150  by link  220 . 
         [0050]    The entire sequence is reversed when the Block  120  and block  180  are repositioned by the actuator  230  such that port  210  and port  110  are open 
         [0051]    The Casing can also be produced by using an ordinary grade of carbon steel or  190  stainless that which is suitably coated in a polymer coat or rubber. 
       Reference Will Now be Made to FIG. 4 
       [0052]    The workings of the Transfer Valve  100  &amp;  170  will now be explained. 
         [0053]    Each Transfer Valve  100  &amp;  170  essentially consists of a Cylinder Body  70 , Piston  71 , Piston Rings  72 , Piston Rod  73 , Piston Rod Packing  74 . On the Body  70  are provide three nozzles that serve as ports for the seawater to flow through depending on the position of the Piston  71 . 
         [0054]    The Piston Rod  73  of the two Transfer Valves  100  &amp;  170  are joined together with a Coupling  75  with the position of the Piston  71  in the position as shown in each Transfer Valve  100  &amp;  170 . 
         [0055]    To the Coupling  75  is attached a Link  220  that is also attached to an Actuator  230 . 
         [0056]    Explanation of the pressure distribution within the two Transfer Valves  100  &amp;  170  is now made. 
         [0057]    Stream  91  at a pressure of 58 barg enters the Transfer Valve  100  at port  140 . This exerts a force on the Piston  71 . At the same time Stream  96  enters the Transfer Valve  100  at port  110  at a pressure of 3 barg and as a consequence the differential pressure tends to push the Piston  71  to the left. 
         [0058]    Stream  93  on port  210  on Transfer Valve  170  is also at the pressure of Stream  92  minus a very small pressure drop as it is exposed to Stream  91  which is at 58 barg and tends to push the Piston  71  of the Transfer Valve  179  to the right. 
         [0059]    The net result the above is that the forces acting on the Pistons  71  of the Transfer Valves  100  &amp;  170  are very little and consequently the force required to change the position of the Pistons  71  for the next sequence of operation is small. 
         [0060]    The above Transfer Valve  100  &amp;  170  is essentially constructed in Carbon Steel with an electroless nickel coating or can be manufactured in seawater resistant materials  225  like Stainless Steel, Duplex and or Super Duplex Stainless Steels, Titanium 
       Reference Will Now be Made to FIG. 5 
       [0061]    In this figure as can be seen the Transfer Valve  100  &amp;  170  Cylinder Body is fabricated and is actually an Outer Containment Shell  1  and the Piston  71  is provided with Piston Rings  72 . 
         [0062]    The Pistons Rings  72  can seal along the inner diameter of the Cylinder Body  70  and also seal at the end face of the cylinder as well. Both Transfer Valves  100  &amp;  170  are connected together with Piston Rods  73   
         [0063]    A Flange  76  provides for port  210  stream  93   
       Reference Will Now be Made to FIG. 6 
       [0064]    In this Figure the construction of the Transfer Valve body is as described earlier. 
         [0065]    In this construction, the Cylinder Body consists on an Outer Containment Shell  1  provided with flanges  5 . It is also provided with an Inner Containment Shell  3  that which has flanges  6 . The cavity formed between the inner diameter of the Outer Containment Shell  1  and the Inner Containment Shell  2  is filled with a fiberglass resin  2  or a Polymer Epoxy or a Polyurethane material via the nozzle  12  &amp;  13  as shown. 
         [0066]    The Transfer Valves  100  &amp;  170  contain the Pistons  71  is provided with Piston Rings  72 . 
         [0067]    The Piston Rings  72  seal at the face of the flange  6 .