FI20225392A1 - A reverse osmosis desalination method and apparatus for achieving high permeate recovery from low salinity raw water - Google Patents
A reverse osmosis desalination method and apparatus for achieving high permeate recovery from low salinity raw water Download PDFInfo
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- FI20225392A1 FI20225392A1 FI20225392A FI20225392A FI20225392A1 FI 20225392 A1 FI20225392 A1 FI 20225392A1 FI 20225392 A FI20225392 A FI 20225392A FI 20225392 A FI20225392 A FI 20225392A FI 20225392 A1 FI20225392 A1 FI 20225392A1
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- Prior art keywords
- concentrate
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- pressure
- raw water
- tube
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 54
- 239000012466 permeate Substances 0.000 title claims abstract description 31
- 238000011084 recovery Methods 0.000 title claims abstract description 22
- 238000010612 desalination reaction Methods 0.000 title claims abstract description 18
- 238000000034 method Methods 0.000 title claims abstract description 17
- 238000001223 reverse osmosis Methods 0.000 title claims abstract description 17
- 239000012141 concentrate Substances 0.000 claims abstract description 61
- 239000012267 brine Substances 0.000 claims abstract description 29
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical compound O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 claims abstract description 28
- 230000003044 adaptive effect Effects 0.000 claims abstract description 13
- 230000004087 circulation Effects 0.000 claims description 17
- 238000006073 displacement reaction Methods 0.000 claims description 2
- 239000012528 membrane Substances 0.000 abstract description 17
- 238000011010 flushing procedure Methods 0.000 abstract 1
- 239000000203 mixture Substances 0.000 abstract 1
- 235000008504 concentrate Nutrition 0.000 description 35
- 210000004379 membrane Anatomy 0.000 description 16
- 239000003673 groundwater Substances 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 239000000356 contaminant Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000000779 depleting effect Effects 0.000 description 1
- 238000009313 farming Methods 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/025—Reverse osmosis; Hyperfiltration
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/10—Accessories; Auxiliary operations
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
- B01D61/12—Controlling or regulating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2311/00—Details relating to membrane separation process operations and control
- B01D2311/14—Pressure control
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2311/00—Details relating to membrane separation process operations and control
- B01D2311/25—Recirculation, recycling or bypass, e.g. recirculation of concentrate into the feed
- B01D2311/252—Recirculation of concentrate
- B01D2311/2523—Recirculation of concentrate to feed side
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2209/00—Controlling or monitoring parameters in water treatment
- C02F2209/40—Liquid flow rate
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2301/00—General aspects of water treatment
- C02F2301/04—Flow arrangements
- C02F2301/046—Recirculation with an external loop
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A20/00—Water conservation; Efficient water supply; Efficient water use
- Y02A20/124—Water desalination
- Y02A20/131—Reverse-osmosis
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Water Supply & Treatment (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Nanotechnology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Organic Chemistry (AREA)
- Separation Using Semi-Permeable Membranes (AREA)
Abstract
Käänteisosmoosisuolanpoistomenetelmä ja -laitteisto korkean permeaatin talteenoton saavuttamiseksi matalasuolaisesta raakavedestä. Suurin osa käänteisosmoosimoduulista (4) ulosvirtautuvasta konsentraatista kierrätetään takaisin korkeapaineiseen tuloputkeen (3), jossa se sekoittuu raakaveden syöttövirtaan ja seos johdetaan moduuliin (4). Ylijäämäkonsentraatti, jota ei kierrätetä, virtaa adaptiivisen vakiopaineventtiilin (9) läpi ja rejektoidaan suolavetenä, kun taas adaptiivinen vakiopaineventtiili (9) ylläpitää moduulin (4) painetta vakiona. Permeaatin talteenotto määräytyy tämän paineen perusteella. Kalvon huuhteluvirtaus määräytyy permeaatin talteenottonopeuden ja jatkuvasti kiertävän konsentraattivirtauksen perusteella.Reverse osmosis desalination method and equipment to achieve high permeate recovery from low salinity raw water. Most of the concentrate flowing out of the reverse osmosis module (4) is recycled back to the high-pressure inlet pipe (3), where it mixes with the raw water feed stream and the mixture is fed to the module (4). The excess concentrate, which is not recycled, flows through the adaptive constant pressure valve (9) and is rejected as brine, while the adaptive constant pressure valve (9) maintains a constant pressure in the module (4). Permeate recovery is determined by this pressure. The membrane flushing flow is determined by the permeate recovery rate and the continuously circulating concentrate flow.
Description
A REVERSE OSMOSIS DESALINATION METHOD AND APPARATUS
FOR ACHIEVING HIGH PERMEATE RECOVERY FROM LOW SALINITY
RAW WATER
A reverse osmosis desalination method and apparatus for achieving high per- meate recovery from low salinity raw water. Improving a reverse osmosis system 's permeate recovery, especially in farming, is very important for sav- ing the scarce ground water resources from depleting.
Reverse osmosis is the current state-of-the-art method in water purification where water under pressure is forced through semipermeable thin film mem- brane element, producing clean water, and filtering out 99% of the impuri- ties. The clean product water is called permeate. Reverse osmosis is the only method that can effectively remove contaminants, heavy metals, and salt from the feed water.
In the following the thin film membrane element is called “membrane”.
Total dissolved solids (TDS) in a salty ground water are typically < 3000 mg/l. A conventional brackish water reverse osmosis (BWRO) unit has 60% recovery rate as maximum. Recovery rate means the percentage of perme- ate obtained from the treated raw water. The remaining 40% is concentrated
A water which is saltier than the raw water. It is rejected as waste, called
O “brine”. 3 25
S Flow in the following means in a time unit flowing liquid volume, for example
E m3/h. &
O In typical BWRO unit's membrane train there are 4 — 8 of membranes in se-
O 30 ries. The membranes are installed in a pressure vessel and to treat high vol- ume feed water flows there are several parallel pressure vessels.
The pressure vessel/membrane train combination is called module. Because the parallel modules are similar, for sake of clarity, in the following “module” means one module or several parallel modules.
The reason why the module cannot have higher recovery rate than 60% is because the membranes require a certain concentrate flush flow to stay in condition and with higher recovery rates than 60% this flush flow is not achieved.
The target of the present invention is to create a sufficient concentrate flush flow in the module to maintain the membranes in good condition while ob- taining a high permeate recovery.
A known method to increase a BWRO unit 's recovery rate is to treat the brine again, in a so called two stage system. The second stage requires a new membrane train, higher system pressure and more power, because the brine is saltier than the initial raw water. The two-stage configuration makes the unit more complicated, more expensive and reguires more space. It also must be noticed that because the feed water is saltier in the second pass, its recovery rate decreases to below 50% and the combined recovery rate hardly exceeds 80%.
A A known desalinating method and apparatus, resembling the present inven-
O tion, is presented in the publication: Patent No.: US 7.695,614 B2. This is a 3 25 closed cycle desalination CCD system. In the publication it is said that “the
S apparatus reguires periodical replacement of brine concentrate with fresh
E feed in the closed circuit at the desired system recovery level and this brief
N mode of operation is depicted in. Brine rejection from the closed circuit is i. achieved by diverting the concentrate flow to the outside through the three-
O 30 way valve. The control of the entire desalination process is achieved by means of "online' monitored conductivity with a signal form that manifests reaching the desired recovery level deactivating recycling in favor of brine re- jection; and likewise, a signal form that manifests brine rejection completion reactivating the recycling mode.”
Drawback in the above-mentioned method and apparatus is that the concen- trate is circulating back to the module 's inlet side intermittently, in cycles, resulting that mixed the feed water 's salinity is not constant but increases rapidly in every cycle. Pressure in the module gets quickly high, and the con- centrate circulation must be cut. There is a three-way valve which is then opened to let the concentrate (brine) out, and as a result only raw water en- ters the module. Water feed flow into the module and pressure in it drop im- mediately. The membranes which today are in use do not like this kind of changes. It also is hard to control this kind of operation and performance of the apparatus.
The present invention means a huge leap forward.
According to the present invention in the desalination process a high-pressure pump, preferably a positive displacement pump, feeds raw water into the module.
Major part from the module outflowing concentrate is continu-
A ously circulated back to the pressurized inlet side of the module,
O where it mixes with the raw water feed flow. Permeate is pro- 3 25 duced from this mixed flow. The concentrate flow, which is out-
S flowing from the module, is the sum of the brine and the con-
E centrate circulation flow. The rejected brine flow is the differ-
N ence between the raw water feed flow and the permeate flow.
O
X The concentrate circulation pump is preferably a positive dis-
S 30 placement pump and takes advantage of the concentrate 's pressure. The surplus part of the concentrate, which is not circulated, i.e., brine flow, is directed through an adaptive con- stant-pressure valve and rejected. Adaptive in this context means that the valve automatically adjusts itself according to the brine flow through itself while maintaining pressure in the mod- ule at the level which is pre-set with the adaptive constant-pres- sure valve.
The constant pressure in the module results constant permeate outflow and concentrate outflow from the module. Because also the raw water feed and concentrate circulation flow remain con- stant, the desalinating process stays in balance while the mem- brane flush flow is determined by the permeate recovery and the continuously circulating concentrate flow.
One adaptive constant-pressure valve implementing the method is described in the publication FI 20140049.
Fig.1 describes one desalinating apparatus implementing the method according to the present invention.
A In the following is presented a more detailed description of the operation of
O the desalinating apparatus implementing the method according to the pre- 3 25 sent invention with reference to the Fig.1. 3
E The desalinating apparatus comprises:
N i. - 1 Raw water inlet tube
O 30 - 2 High-pressure pump (HPP) - 3 High-pressure inflow tube
- 4 — Module - 5 Concentrate outflow tube - 6 Concentrate circulation tube - 7 Concentrate circulation pump (CCP) 5 - 8 Brine outflow tube - 9 Adaptive constant pressure valve (ACPV) - 10 Permeate outflow tube - 11 Waterdrain tube - 12 Two-way valve -
In the desalinating process raw water is continuously fed through the raw water inlet tube 1 to the HPP 2 which pumps it through the high-pressure in- flow tube 3 into the module 4. Concentrate flows out from the module 4 through the concentrate outflow tube 5 and major part of this concentrate is led through the concentrate circulation tube 6 to the CCP 7 which pumps it to the high-pressure inflow tube 3 where it mixes with the fed raw water flow.
The concentrate outflow tube 5 is also connected to a brine outflow tube 8 leading to an adaptive constant-pressure valve (ACPV) 9. The surplus con- centrate which cannot flow through the CCP 7 flows to the ACPV 9, which al- lows it flow through itself and be rejected as brine. The ACPV 9 is pre-set to
A open at the pressure at which the permeate flow is pre-calculated to be at
O the desired level. Once opened the ACPV 9 maintains pressure in the module 3 25 4 constant. As a result, the raw water feed flow, concentrate circulation flow,
S permeate flow, and brine flow stay constant and in balance. This balance is
E created and maintained by the ACPV 9, which stays open all the time during
N the desalination process.
S 30 The apparatus can also comprise for a desalination unit typical conventional devices, such as a safety valve and a pressure gauge in the high-pressure inflow tube 3, a pressure gauge in the concentrate outflow tube 5, and a wa- ter quality indicator in the permeate outflow tube 10. The water drain tube 11 is also supplementary and remains closed during the desalination process.
The following practical example illustrates the operation of one apparatus ac- cording to the present invention, in reference to the Fig.1. - Pressure at which the ACPV 9 is pre-set to open, 21bar - Raw water quality: TDS 1,400 mg/l; pH 7; T 25°C - Pressure vessels: 8 pcs parallel, type 80200 - Membranes per pressure vessel: 5pcs, type BW30HR-440 - Raw water feed flow 43 m3/h - HPP 2, capacity 43 m3/h at 50Hz - Permeate flow 39 m3/h - Permeate TDS 90 mg/l - Permeate recovery 90% - CCP7, capacity 36 m3/h at 50Hz - Mixed raw water and circulating concentrate flow 79 m3/h - Mixed water salinity 7,000 mg/l - Concentrate outflow from the module 4 is 40 m3/h - Brine outflow 4 m3/h (through the ACPV 9) - Brine TDS 13,900 mg/l
A - Used power 35kW
O - Specific energy 0.89 kWh/m3 3 25
S Raw water feed flow 43 m3/h proceeds through the raw water inlet tube 1
E into the HPP 2, which pumps it through the high-pressure inflow tube 3 into
N the module 4. From the module 4 outflowing concentrate 36 m3/h is circu- i. lated back into the high-pressure inflow tube 3 by means of the CCP 7, which
O 30 takes advantage of the concentrate 's pressure so that it must boost it only about 2bar. When the circulating concentrate 36 m3/h mixes with the raw water feed flow 43 m3/h in the high-pressure inflow tube 3 the total inflow into the module 4 increases to 79 m3/h and its TDS to 7000 mg/l. Because the raw water feed flow and the concentrate circulation flow are continuous and constant, the mixed water 's flow and salinity in the high-pressure inflow tube 3 remain constant. The ACPV 9 is pre-set to open at 21bar and the per- meate flow at this pressure can be calculated in advance. In this example case at the 21bar counter pressure the 8 membrane trains together are cal- culated to produce 39 m3/h permeate. This means that from the module 4 the outflowing concentrate is 40 m3/h and through the ACPV 9 rejected brine flow is 4 m3/h.
In the beginning of the desalination process the ACPV 9 opens at 21bar, and it will stay open and maintain the pressure in the module 4 at this level through the whole desalination process, day after day, maintaining the rela- tion between the raw water feed flow, concentrate circulation flow, permeate flow, and brine flow in balance. The 4 m3/h brine flow means that the per- meate recovery from the raw water feed flow is 90% and the total concen- trate outflow 40 m3/h from the module 4 means that the membrane flush flow in each of the 8 membrane trains is more than 35% greater than the recommended minimum 3.6 m3/h.
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Claims (6)
1. A reverse osmosis desalination method for achieving high permeate recov- ery from low salinity raw water, comprising a raw water feed flow tube (1) and a high-pressure pump (2), which pumps the fed raw water into a high- pressure inflow tube (3) leading to a reverse osmosis module (4) from which outflowing concentrate proceeds through a concentrate outflow tube (5) into a concentrate circulation tube (6) which leads to a concentrate circulating pump (7), which takes advantage of the concentrate 's pressure and boosts the circulating concentrate into the high-pressure inflow tube (3) where it mixes with the pressurized raw water feed flow increasing into the module (4) in a time unit inflowing water volume and salinity, a permeate outflow tube (10) and a brine outflow tube (8) characterized in that the concentrate outflow tube (5) - is openly connected to the brine outflow tube (8), which is - leading to an adaptive constant-pressure valve (9), which - is previously set to open at the pressure, at which permeate recovery from the raw water flow is calculated to be at the desired level, and - the surplus concentrate which cannot flow through the concentrate cir- culation pump (7) - is led through the brine outflow tube (8) to the adaptive constant-pres- sure valve (9), which A - allows the surplus concentrate flow through itself as brine, O - resulting that the pressure in the module (4) does not increase any 3 25 more but remains constant at the level which is determined and main- S tained by the adaptive constant-pressure valve (9), E - resulting that from the module (4) outcoming concentrate flow, the cir- N culating concentrate flow, the brine flow and the permeate flow remain i. constant and the desalinating process stays in balance. O 30
2. A reverse osmosis desalination method according to the claim 1, charac- terized in that the concentrate circulation flow is 30 — 90% of the raw water feed flow.
3. A reverse osmosis desalination apparatus for achieving high permeate re- covery from low salinity raw water, comprising a raw water inlet tube (1) and a high-pressure pump (2), which pumps the fed raw water flow into a high- pressure inflow tube (3) leading to a reverse osmosis module (4) from which outflowing concentrate proceeds through a concentrate outflow tube (5) into a concentrate circulation tube (6) which leads to a concentrate circulating pump (7), which takes advantage of the concentrate 's pressure and boosts the circulating concentrate into the high-pressure inflow tube (3) where it mixes with the raw water feed flow increasing into the module (4) in a time unit inflowing water volume and salinity, and a permeate outflow tube (10), and a brine outflow tube (8) characterized in that the concentrate outflow tube (5) is openly connected to the brine outflow tube (8), which leads to an adaptive constant-pressure valve (9), which automatically opens at the previously set pressure level al- lowing the surplus concentrate flow through itself as brine, resulting that that the pressure in the module (4) does not increase any more but remains con- stant at the level which is determined by the adaptive constant-pressure valve (9). N
S
4. A reverse osmosis desalination apparatus according to the claim 3, char- 3 25 acterized in that the concentrate circulation flow, determined by the con- S centrate circulation pump (7) is 30 — 90% of the raw water feed flow. j
N
5. A reverse osmosis desalination apparatus according to the claims 3 and 4,
i. characterized in that the concentrate circulation pump (7) is a positive dis- O 30 placement pump.
6. A reverse osmosis desalination apparatus according to the claims 3, 4 and characterized in that the high-pressure pump (2) is a positive displace- ment pump. 5
Ql N O N LÖ <Q O O I = N o 0 LO N N O N
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI20225392A FI20225392A1 (en) | 2022-05-06 | 2022-05-06 | A reverse osmosis desalination method and apparatus for achieving high permeate recovery from low salinity raw water |
| PCT/FI2023/050190 WO2023214111A1 (en) | 2022-05-06 | 2023-04-05 | A reverse osmosis desalination method and apparatus for achieving high permeate recovery from low salinity raw water |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI20225392A FI20225392A1 (en) | 2022-05-06 | 2022-05-06 | A reverse osmosis desalination method and apparatus for achieving high permeate recovery from low salinity raw water |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| FI20225392A1 true FI20225392A1 (en) | 2023-11-07 |
Family
ID=88646322
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| FI20225392A FI20225392A1 (en) | 2022-05-06 | 2022-05-06 | A reverse osmosis desalination method and apparatus for achieving high permeate recovery from low salinity raw water |
Country Status (2)
| Country | Link |
|---|---|
| FI (1) | FI20225392A1 (en) |
| WO (1) | WO2023214111A1 (en) |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4243523A (en) * | 1978-08-07 | 1981-01-06 | Allied Water Corporation | Water purification process and system |
| SE505028C2 (en) * | 1992-05-13 | 1997-06-16 | Electrolux Ab | Method and apparatus for purifying water |
| US20140061129A1 (en) * | 2012-09-04 | 2014-03-06 | Israel Aerospace Industries Ltd. | System and method of desalination of water |
| WO2020254268A1 (en) * | 2019-06-18 | 2020-12-24 | Baxter Healthcare Sa | A reverse osmosis apparatus, and a method for controlling a reverse osmosis apparatus |
-
2022
- 2022-05-06 FI FI20225392A patent/FI20225392A1/en not_active Application Discontinuation
-
2023
- 2023-04-05 WO PCT/FI2023/050190 patent/WO2023214111A1/en not_active Ceased
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| Publication number | Publication date |
|---|---|
| WO2023214111A1 (en) | 2023-11-09 |
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