AU2011100390B4

AU2011100390B4 - Peristaltic pressure exchanger in reverse osmosis desalination

Info

Publication number: AU2011100390B4
Application number: AU2011100390A
Authority: AU
Inventors: N. Jayaram
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-04-10
Filing date: 2011-04-10
Publication date: 2012-05-03
Anticipated expiration: 2019-04-10
Also published as: AU2011100390A4

Abstract

PERISTALTIC PRESSURE EXCHANGER IN REVERSE OSMOSIS DESALINATION 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 composite construction of a Casing as /0 described within which a confined flexible membrane is utilized to transfer the pressure from one liquid to the other via a peristaltic process.

Description

DESCRIPTION TITLE PERISTALTIC PRESSURE EXCHANGER IN REVERSE OSMOSIS DESALINATION 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 5 fresh water to seawater high pressure pump both by peristaltic compression 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 /0 '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. For seawater, the osmotic pressure is approximately 60 bars and is dependant on the /5 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%. .Jo 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. Traditional methods of recovering this energy are, 5 Hydraulic Recovery Turbines comprising of Impulse turbines with unit efficiencies of around 85% Reaction turbines with unit efficiencies of around 75% Turbo Chargers of reasonable efficiencies e Works Exchanger types Part of the present invention is a Work Exchanger type involves the pressurization of the feed using the waste energy of the concentrate. Typically these devices such as described in US Patent No 3,791,968 use opposed piston / diaphragm pumps and these arrangements have several drawbacks. The device described in US Patent No 3,791,968 is also restricted in the quantity of fluid that can be handled and is suited to small installations. 4) 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.

Other energy recovery devices employ pistons of different areas with connecting /5 mechanisms as described in US Patent No 3,558,242 and as with the above type has various seals to minimize leaks to atmosphere. The principal behind the Invention is to provide a device for both pressurizing treated seawater to the required osmotic pressure and a device that will recover the 'waste' or ro 'Concentrate' energy coming out of the reverse osmosis membranes The fundamental novel principal behind this is the utilization of several technologies as briefly stated below. r5 0 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 >0 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 e The separation of liquid contained within the elastomeric hose and the liquid 5 surrounding it and the Pressure exchange between the two liquids. .4. Detailed Description. Reference will now be made to Fig 1 The Outer Containment Shell (1) is provided with Flanges (5a). There are two Face Flanges (5) into which the Inner Containment Shell (3) is fixed into as shown. These Face Flanges (5) are also provided with a machined groove into which the 75 Outer Containment Shell (1) is fixed. Thus a cavity is formed between the outer diameter of the Inner Containment Shell (3) and the inner diameter of the Outer Containment Shell(l). This cavity is filled with a polymer epoxy (2) which then forms a solid 'shell'. Nozzles (9) are provided into the Outer Containment Shell (1) that penetrates through to the Inner Containment Shell (3) The above constructed component is termed the Casing. Reference will now be made to Fig 2 5 There are 2 off Sealing Flanges (6) to which the Inner Nozzle (7) and the Outer Nozzle (8) is fixed. An Elastomeric Containment Hose (4) length of which is equivalent to the length of the Casing, both ends of which are fixed to the Inner Nozzle (7) by means of a Circumferential Clamp (10) and now provides a passage for any liquid inside the Elastomeric Containment Hose (4). The Sealing Flanges (6) are (j fixed to the Face Flanges (5) by means on Bolts (11) and nuts (12) This constructed component is termed the Pressure Exchanger 3 Reference will now be made to Fig 3 95 Pressure Exchangers (20) and (21) form the High Pressure Pump circuit of the device while Pressure Exchangers (40) and (41) form the Energy Recovery circuit of the device. The LP Feed pump (30) provides low pressure pre-treated and filtered seawater to the 100 banks of the Pressure Exchangers (20), (21), (40) and (41) via the Pump Inlet Valves (3620) (3621) and the Energy Recovery Inlet Valves (4540) (4541)I Description of' the High Pressure Pump Circuit will now be made. 105 The high pressure is provided by the Fresh Water HP Pump (31) that which is capable of developing the required Osmotic Pressure. Into the Pressure Exchangers (20) and (21), Fresh Water Supply Valves (3520), (3521) and Fresh Water Return Valves (3320), (3321) are fitted. The Fresh Water Return Valves (3320) (3321) channel the fresh water into a Fresh Water Tank (32) which in turn supplies the Fresh Water HP 110 Pump (31). The Pump Inlet Valve (3620) fitted to Pressure Exchanger (20) allows low pressure Sea water to fill the Elastomeric Hose (4) and while this Elastomeric Hose (4) fills it displaces the fresh water through the Fresh Water Return Valve (3320) fitted to this 115 Pressure Exchanger (20). The Pump Inlet Valve (3621) fitted to Pressure Exchanger (21) is closed as is the Fresh Water Return Valve (3321) Simultaneously oin Pressure Exchanger (21) previously filled Seawater inside the Elastomeric Hose (4) of the Pressure Exchanger (21) is now subject the high pressure 120 fresh water flowing through the open Fresh Water Supply Valve (3521) thai squeezes the Elastomeric Hose (4) of the Pressure Exchanger (21),forcing the seawater out of the Pressure Exchanger (21) at the same pressure as the Fresh Water HP Pump (3 1) is putting out. Thus the low pressure seawater in the Elastomeric Hose (4) has been pressurized to the required osmotic pressure by the fresh water flowing in the fresh 125 water circuit. The now pressurized seawater flows out through the Pump Discharge Non Return Valves (3421) fitted to Pressure Exchanger (21) and enters the Reverse Osmosis membranes and is separated to the 'Permeate' and the waste 'Concentrate. Description of the waste Pressure Energy Exchange circuit will now be made. 130 The transfer of the concentrate pressure energy to the low pressure seawater is made by the Pressure Exchangers (40) & (41). The Pressure Exchangers are also fitted with Concentrate Inlet Valves (4440) (4441) and Exhaust Valves (4240) (424 1). 135 The Pressure Exchanger (40) had been previously filled with low pressure sea water via Valve (4540) which in now closed. The high pressure concentrate coming out of the RO Membrane enters the Pressure Exchanger (40) via the open Concentrate Valve (4440). The Valve (4441) is closed. This process pressurizes the low pressure sea water contained in the Elastomeric Hose (4) fitted in Pressure Exchanger (40) by 140 squeezing this hose (4) to the pressure of the Concentrate, forcing the seawater to flow through the open Non Return Valve (4340).

4 Simultaneously on Pressure exchanger (41) inlet valve (4541) is open allowing low pressure seawater to fill the Elastomeric I lose (4) also fitted inside this Pressure Exchanger (41). Concentrate Inlet Valve (4441) is closed and the Exhaust Valve (4241) is opera allowing the spent concentrate to exit from the Pressure Exchanger (41). The entire process is their reversed with the valves going to the opposite position and hence continuous production of high pressure seawater from both the high pressure pump circuit and the pressure energy recovery circuit The Casing can also be produced by using an ordinary grade of carbon steel or stainless that which is suitably coated in a polymer coat or rubber. The inlet valves (3620), (3621), (4540) and (4541) can also be non return valves.