CN107441934B

CN107441934B - Reverse osmosis system and method for concentrating fluid using reverse osmosis system

Info

Publication number: CN107441934B
Application number: CN201610375454.6A
Authority: CN
Inventors: 翟建文; 张兴鹏; 潘炳梅
Original assignee: Suez Water Technologies Wuxi Co Ltd
Current assignee: Veolia Water Technologies and Solutions Wuxi Co Ltd
Priority date: 2016-05-31
Filing date: 2016-05-31
Publication date: 2020-01-31
Anticipated expiration: 2036-05-31
Also published as: CN107441934A

Abstract

The invention discloses reverse osmosis systems, which comprise n reverse osmosis units RO1, RO2, …, ROi, RO (i +1), … and ROn, wherein n is more than or equal to 2, i is more than or equal to 1 and less than or equal to n, each reverse osmosis unit ROi comprises an inlet, a permeate liquid outlet, a concentrated liquid outlet and at least membrane elements with water permeability coefficients of Ai and salt permeability coefficients of Bi, Ai is less than A (i +1), Bi is less than B (i +1), and the concentrated liquid outlet of ROi is connected with the inlet of RO (i + 1).

Description

Reverse osmosis system and method for concentrating fluid using reverse osmosis system

Technical Field

The invention relates to the technical field of fluid concentration, in particular to reverse osmosis systems and a method for concentrating fluid by using the reverse osmosis systems.

Background

Compared with the thermal method concentration process, the reverse osmosis concentration process has obvious advantages in terms of energy saving and equipment investment under the condition of a low concentration end point design corresponding to less than 10-15% of sodium chloride, but the traditional reverse osmosis concentration process is along with the design loop of a desalination treatment process, namely the operating pressure of the system is set to be higher than the osmotic pressure of a concentrated solution, for example, when the Total Dissolved Solids (TDS) of inlet water is low and the requirement on concentration rate is low, a brackish water reverse osmosis system (BWRO) is generally adopted, and when the TDS of inlet water is more than 10g/l, a seawater reverse osmosis System (SWRO) is generally adopted, so the highest design concentration end point of a BWRO + SWRO system adopting a reverse osmosis membrane is 70-80g/l, according to the traditional thought, for high TDS fluid, a higher concentration rate can be obtained, the reverse osmosis system must be adopted to complete the task of desalination, however, the operation cost and the investment of equipment investment are greatly increased, and the manufacturing cost of equipment manufacturing and the extra-high pressure operation is also set to be higher than the normal operation of a desalination disc type desalination membrane element , and the operation cost of a conventional reverse osmosis membrane element is set, and the requirement on the operating pressure of a high-operated super-pressure pipeline type desalination membrane element is also set up to be higher than the high-operated by the traditional design of a conventional desalination technology, and the high-operated super-pressure operation technology, and the high-pressure.

Therefore, there is a need for reverse osmosis systems capable of high-rate concentration of high-concentration fluids operating at lower operating pressures.

Disclosure of Invention

, the invention discloses reverse osmosis systems, which comprise n reverse osmosis units RO1, RO2, …, ROi, RO (i +1), … and ROn, wherein n is more than or equal to 2, i is more than or equal to 1 and less than n, each reverse osmosis unit ROi comprises an inlet, a permeate liquid outlet, a concentrate liquid outlet and at least membrane elements with water permeability coefficient of Ai and salt permeability coefficient of Bi, Ai is less than A (i +1), Bi is less than B (i +1), and the concentrate liquid outlet of ROi is connected with the inlet of RO (i + 1).

In another aspect, the invention discloses a method for concentrating fluids, which comprises introducing the fluids into a reverse osmosis system to obtain total permeate and total concentrate, wherein the reverse osmosis system comprises n reverse osmosis units RO1, RO2, …, ROi, RO (i +1), …, ROn, n is more than or equal to 2, i is more than or equal to 1 and less than or equal to n, each reverse osmosis unit ROi can generate ith permeate and ith concentrate, introducing the ith concentrate into RO (i +1), each reverse osmosis unit ROi comprises at least membrane elements with water permeability coefficient Ai and salt permeability coefficient Bi, Ai is less than A (i +1), and Bi is less than B (i + 1).

Drawings

FIG. 1 is a schematic diagram of reverse osmosis systems according to an embodiment of the invention;

fig. 2 is a schematic diagram of another types of reverse osmosis systems according to an embodiment of the invention.

Detailed Description

Unless defined otherwise, technical or scientific terms used herein should not be construed to have any order, quantity, or importance, but rather should be used to distinguish one element or group of elements from another, the use of "" or "" and the like herein is not intended to be limiting, but rather is intended to mean that there are at least such as "or" is not meant to be exclusive, but rather is intended to mean that there are at least of the referenced items (e.g., ingredients) and that "including," "comprises," "has," or "containing" and the like, where a combination of referenced items may be present.

As used herein, approximating language may be applied to quantitative terms indicating that a quantitative change in the quantity of may be permissible without changing basic function, and thus, a value corrected by a language such as "about", "left or right" is not limited to the precise value itself.

All numbers recited herein from lowest value to highest value refer to all numbers between the lowest value and the highest value in increments when there are more than two units between the lowest value and the highest value, for example, numbers of like elements such as temperature, pressure, time, etc. and process numbers when we say 1 to 90 refer to like enumerated numbers such as 15 to 85, 22 to 68, 43 to 51, 30 to 32, etc. when the numbers are less than 1, units may be 0.0001, 0.001, 0.01 or 0.1, as specific examples only.

In the reverse osmosis system and the fluid concentration method aiming at obtaining pure fluid, for example, desalination or purification of water flow, the design idea of the reverse osmosis system is that the water permeability coefficient A and the salt permeability coefficient B of the selected membrane elements are gradually reduced along with the increase of TDS of inlet water, for example, the A value and the B value of SWRO membrane for high-salinity inlet water such as seawater are the lowest, so that the requirement of low TDS of the permeate liquid can be ensured.

The reverse osmosis system and the fluid concentration method of the embodiment of the invention are suitable for the concentration of various fluids, the solvent of the fluids can be water or other solvents such as alcohols, and the solute of the fluids can be salts such as sodium chloride or small molecular organic matters.

, an embodiment of the invention relates to reverse osmosis systems, comprising n reverse osmosis units RO1, RO2, …, ROi, RO (i +1), …, ROn, wherein n is more than or equal to 2, 1 is more than or equal to i < n, each reverse osmosis unit ROi comprises an inlet, a permeate outlet, a concentrate outlet, and at least membrane elements with water permeability coefficient of Ai and salt permeability coefficient of Bi, Ai < A (i +1), Bi < B (i +1), and the concentrate outlet of ROi is connected with the inlet of RO (i + 1).

For the definition of the water permeability coefficient a value and the salt permeability coefficient B value, the explanation can be made with reference to the basic principle of the reverse osmosis process as shown in the following formulas (1) to (3).

J_a＝Q_p/S＝A(ΔP-Δπ) (1)

J_b＝(Q_pC_p)/S＝BΔC＝B(1/2(C_f+C_c)-C_p) (2)

Δπ＝θTΔC＝θT(1/2(C_f+C_c)-C_p) (3)

Wherein, J_aDenotes the permeate flux, Q_pDenotes the flow rate of the permeated liquid, S denotes the membrane area, A denotes the water permeability coefficient, Δ P denotes the pressure difference across the membrane, Δ π denotes the osmotic pressure difference, J_bRepresents the solute flux, C_pDenotes the permeate concentration, B denotes the coefficient of salt permeation,. DELTA.C denotes the difference in concentration between the two sides of the membrane,. theta.denotes the osmotic pressure coefficient, T denotes the temperature, C denotes the temperature_fDenotes the concentration of feed water, C_cDenotes the concentration of the concentrate, C_pIndicates the concentration of the permeated solution.

The basic principle of reverse osmosis process is described by formula (1) and formula (2), wherein formula (1) is solvent transfer process, solvent transfer is pressure driven, the difference between the pressure difference Δ P across the membrane and the osmotic pressure difference Δ π of the solution across the membrane is the net driving force of reverse osmosis process, and the permeate flow J per unit area of reverse osmosis membrane_aIs in direct proportion to the net driving force (delta P-delta pi), and the value of the proportionality coefficient A is the characteristic water permeability coefficient of the reverse osmosis membrane. Formula (2) is a solute transfer process, and solute transfer is concentration driven, i.e., the solute permeability J of the reverse osmosis membrane per unit area_bIs in direct proportion to the solute concentration difference delta C on the two sides of the membrane, and the value of the proportionality coefficient B is the characteristic salt permeability coefficient of the reverse osmosis membrane.

In the reverse osmosis system of the embodiment of the invention, the water permeability coefficient Ai and the salt permeability coefficient Bi of the membrane element in each reverse osmosis unit ROi have the relationship of Ai < A (i +1) and Bi < B (i +1) with the water permeability coefficient A (i +1) and the salt permeability coefficient B (i +1) of the membrane element in the next -stage reverse osmosis unit RO (i + 1). in embodiments, A (i +1) is 1.5 to 5 times, preferably 1.8 to 2.5 times, of Ai, and B (i +1) is 2 to 100 times, preferably 5 to 50 times, of Bi.

The reverse osmosis system of the present embodiment is capable of concentrating fluid at a high rate under conditions where the operating pressure of the system is less than the osmotic pressure of the total concentrate, in embodiments, the maximum operating pressure of the reverse osmosis system is 30-90%, preferably 50-70%, of the osmotic pressure of the total concentrate, for example, the reverse osmosis system of the present embodiment is capable of achieving a concentrate osmotic pressure of about 120bar (corresponding to a NaCl solution with a concentration of 125 g/l) at a maximum operating pressure of about 80bar, and a concentrate osmotic pressure of about 150bar (corresponding to a NaCl solution with a concentration of 160 g/l) at a maximum operating pressure of about 100 bar.

In , the reverse osmosis system further comprises a total liquid inlet pipe, a total permeate pipe and a total concentrate pipe, wherein an inlet of RO1 is connected with the total liquid inlet pipe, a permeate outlet of RO1 is connected with the total permeate pipe, and a concentrate outlet of RO1 is connected with an inlet of RO2, a permeate outlet of RO2 is connected with the inlet of RO1 or the total permeate pipe, and a concentrate outlet of RO2 is connected with the inlet of RO3, when 2< i < n, an inlet of ROi is connected with a concentrate outlet of RO (i-1), a permeate outlet of ROi is connected with an inlet of RO1, a concentrate outlet of ROi is connected with an inlet of RO (i +1), an inlet of ROn is connected with a concentrate outlet of RO (n-1), a permeate outlet of ROn is connected with the inlet of RO1 or the inlet of RO2, and a concentrate outlet of ROn is connected with the total concentrate pipe.

In , the reverse osmosis system uses spiral wound reverse osmosis membrane elements, which have the advantages of high packing density and easy operation compared with flat, tubular, hollow fiber membrane elements.

In examples, all of the membrane elements in each reverse osmosis unit have the same water permeability a value and the same salt permeability B value, further steps include the plurality of membrane elements in each reverse osmosis unit being the same membrane element.

In embodiments, each reverse osmosis unit comprises at least two reverse osmosis membrane sections in series, preferably 1-4 reverse osmosis membrane sections in series, more preferably 2-3 reverse osmosis membrane sections, each reverse osmosis membrane section comprising at least two parallel membrane modules (or pressure vessels), each membrane module comprising at least two membrane elements (typically comprising around 6 membrane elements).

, an embodiment of the invention relates to a method of concentrating a fluid using the foregoing reverse osmosis system, comprising passing the fluid through a reverse osmosis system to obtain a total permeate and a total concentrate, wherein the reverse osmosis system comprises n reverse osmosis units RO1, RO2, …, ROi, RO (i +1), …, ROn, n ≧ 2, 1 ≦ i < n, each reverse osmosis unit ROi capable of producing an ith permeate and an ith concentrate, passing the ith concentrate through RO (i +1), each reverse osmosis unit ROi comprising at least membrane elements having a permeability coefficient of Ai and a permeability coefficient of Bi, Ai < A (i +1), Bi < B (i + 1).

In , the method comprises introducing the fluid into RO1 to obtain a1 st permeate and a1 st concentrate, wherein at least parts of the total permeate come from the 1 st permeate, introducing RO2 to the 1 st concentrate to obtain a2 nd permeate and a2 nd concentrate, introducing RO1 to the 2 nd permeate or mixing the 2 nd permeate with the 1 st permeate to obtain the total permeate, introducing an i-1 st concentrate into ROi to obtain an i th permeate and an i th concentrate when 2< i < n, introducing the i th permeate into RO1, introducing the i th concentrate into RO (i +1), introducing an n-1 st concentrate into ROn to obtain an n th permeate and the total concentrate, and introducing an n th permeate into RO 1.

types of reverse osmosis systems 100 shown in fig. 1 comprise a reverse osmosis unit RO1 and a reverse osmosis unit RO2, wherein the water permeability coefficient of membrane elements in the RO1 is A1, the salt permeability coefficient is B1, the water permeability coefficient of membrane elements in the RO2 is A2, the salt permeability coefficient is B2, A1< A2 and B1< B2. the specific method for concentrating the feed water 111 by using the reverse osmosis system 100 comprises the steps of introducing the feed water 111 into the RO1 to obtain RO1 permeate 112 and RO1 concentrate 113, introducing the RO1 permeate 112 into the system total permeate, introducing the RO1 concentrate 113 into the RO2 to obtain RO2 permeate 122 and RO2 concentrate 123, mixing the RO2 permeate 122 with the feed water 111 and then introducing the RO1, and introducing the RO2 concentrate 123 into the system total concentrate.

The reverse osmosis system 200 shown in FIG. 2 comprises a reverse osmosis unit RO, a reverse osmosis unit RO and a reverse osmosis unit RO, wherein the water permeability coefficient of membrane elements in the RO is A, the salt permeability coefficient is B, A < A, B < B3. the specific method for concentrating the inlet water 211 by using the reverse osmosis system 200 comprises the steps of introducing the inlet water 211 into RO to obtain RO permeate 212 and RO concentrate 213, wherein the RO permeate 212 is the total permeate of the system 200, the RO concentrate 213 is introduced into RO to obtain RO permeate 222 and RO concentrate 223, the RO permeate 222 is mixed with the inlet water 211 and then introduced into RO, the concentrate 223 is introduced into RO to obtain RO permeate 232 and RO concentrate 233, the RO permeate 232 is mixed with the inlet water 211 and then introduced into RO, and the concentrate 233 is the total concentrate of the system.

The reverse osmosis system and the method for concentrating fluid by using the reverse osmosis system effectively overcome the design limitation of the traditional water purification or desalination reverse osmosis system, namely the requirement that the operating pressure of the reverse osmosis system is higher than the osmotic pressure of the concentrated solution, the reverse osmosis system of the embodiment of the invention can obtain the concentrated solution with higher concentration under lower operating pressure, and the reverse osmosis system has the advantages that , the reverse osmosis system of the embodiment of the invention adopts a conventional spiral-wound reverse osmosis membrane element, the manufacturing cost is greatly saved compared with high-pressure design of special structures such as high-pressure DTRO (direct-driven reverse osmosis) and pipe-network reverse osmosis (STRO), the manufacturing cost of various pumps, pipelines and valve control systems in the system is lower under the condition of not more than 100bar, and the energy consumption of the straight-through type step-up pressurization design under lower operating pressure is about 30% lower than that of a multistage pressurization cycle design such as DTRO and STRO is required.

Example 1

In example 1, the reverse osmosis system 100 as shown in FIG. 1 was used to concentrate feed water having a TDS of 30g/l NaCl equivalent concentration. The membrane elements in the reverse osmosis unit RO1 and the reverse osmosis unit RO2 were commercial membrane elements from GE corporation, and the specific product models are shown in table 1. The operating parameters of the reverse osmosis system 100 for the four operating conditions are set forth in table 1, which relates to the combination of different types of membrane elements used for RO1 and RO2, and the different maximum operating pressures of the system.

TABLE 1

Working conditions	1	2	3	4
					Model number of RO1 membrane element	INDRO5	AE	AE	INDRO5
Model number of RO2 membrane element	INDRO6	INDRO5	INDRO6	INDRO6
					A2/A1	2	2	5	2
B2/B1	5	10	50	5
					Maximum operating pressure (bar)	80	100	100	100
Incoming water TDS (g/l NaCl)	30	30	30	30
					Concentrate TDS (g/l NaCl)	120	130	150	160
TDS (g/l NaCl) as permeate	1	0.5	0.5	2

Example 2

In example 2, the reverse osmosis system 100 of FIG. 1 was used to concentrate feed water with a TDS of 30g/l NaCl equivalent concentration, with the operating parameters being as in condition 4 of Table 1. Wherein, the reverse osmosis unit RO1 includes three membrane sections, the reverse osmosis unit RO2 includes two membrane sections, a booster pump is arranged between the membrane sections, and the membrane elements in the reverse osmosis unit RO1 and the reverse osmosis unit RO2 adopt the commercial membrane elements of GE company, and the specific product model is shown in Table 2.

TABLE 2

Example 3

In example 3, the feed water with TDS of 30g/l NaCl normality was concentrated using a reverse osmosis system 200 as shown in fig. 2. Among them, the membrane elements in the reverse osmosis unit RO1, the reverse osmosis unit RO2 and the reverse osmosis unit RO3 were commercial membrane elements of GE corporation, and specific product models were as shown in table 3. The operating parameters of the reverse osmosis system 200 for the three operating conditions are listed in table 3, which relates to the combination of different types of membrane elements used for RO1, RO2, and RO3, and the different maximum operating pressures of the system.

TABLE 3

Working conditions	1	2	3
				Model number of RO1 membrane element	INDRO5	AE	INDRO5
Model number of RO2 membrane element	INDRO6	INDRO5	INDRO6
				Model number of RO3 membrane element	INDRO7	INDRO7	INDRO7
A2/A1	2	2	2
				B2/B1	5	10	5
A3/A2	2	4	2
				B3/B2	5	25	5
Maximum operating pressure (bar)	80	100	120
				Incoming water TDS (g/l NaCl)	30	30	30
Concentrate TDS (g/l NaCl)	150	200	200
				TDS (g/l NaCl) as permeate	1	0.5	1

This written description uses specific examples to describe the invention, including the best mode, and is intended to facilitate any experimentation by one skilled in the art. These operations include the use of any apparatus and system and with any embodied method. The patentable scope of the invention is defined by the claims, and may include other examples that occur in the art. Such other examples, if not structurally different from the literal language of the claims, or if they have equivalent structure to the description of the claims, are to be considered within the scope of the invention.

Claims

The reverse osmosis systems comprise n reverse osmosis units RO1, RO2, …, ROi, RO (i +1), … and ROn, wherein n is more than or equal to 2, i is more than or equal to 1 and less than n, each reverse osmosis unit ROi comprises an inlet, a permeate outlet, a concentrated solution outlet and at least membrane elements with water permeability coefficients of Ai and salt permeability coefficients of Bi, Ai is less than A (i +1), Bi is less than B (i +1), and the concentrated solution outlet of ROi is connected with the inlet of RO (i + 1).
2. The reverse osmosis system of claim 1, further comprising a total feed line, a total permeate line, a total concentrate line, wherein,

the inlet of RO1 is connected with the total liquid inlet pipe, the permeate outlet of RO1 is connected with the total permeate pipe, and the concentrate outlet of RO1 is connected with the inlet of RO 2;

the permeate outlet of RO2 is connected to the inlet of the RO1 or the total permeate tube, and the concentrate outlet of RO2 is connected to the inlet of RO 3;

when 2< i < n, the inlet of the ROi is connected with the concentrated solution outlet of the RO (i-1), the permeate outlet of the ROi is connected with the inlet of the RO1, and the concentrated solution outlet of the ROi is connected with the inlet of the RO (i + 1);

the inlet of ROn is connected with the concentrated solution outlet of RO (n-1), the permeate outlet of ROn is connected with the inlet of RO1 or the inlet of RO2, and the concentrated solution outlet of ROn is connected with the total concentrated solution pipe.
3. The reverse osmosis system of claim 1, wherein n ≦ 4.
4. A reverse osmosis system according to claim 1, wherein a (i +1) is 1.5 to 5 times Ai.
5. A reverse osmosis system according to claim 1, wherein a (i +1) is 1.8-2.5 times Ai.
6. A reverse osmosis system according to claim 1, wherein B (i +1) is 2-100 times Bi.
7. A reverse osmosis system according to claim 1, wherein B (i +1) is 5-50 times Bi.
8. The reverse osmosis system of claim 1, wherein the membrane element is a spiral wound reverse osmosis membrane element.
9. The reverse osmosis system of claim 1, wherein all membrane elements in each reverse osmosis unit have the same water permeability coefficient and the same salt permeability coefficient.
10. The reverse osmosis system of claim 1, wherein each reverse osmosis unit comprises at least two reverse osmosis membrane sections, each reverse osmosis membrane section comprising at least two parallel sets of reverse osmosis membranes, the sets of reverse osmosis membranes comprising at least two of the membrane elements in series.
11. A reverse osmosis system according to claim 10 further comprising a booster pump disposed before at least reverse osmosis membrane stages.
12. A reverse osmosis system according to claim 11 further comprising a booster pump disposed in front of each reverse osmosis membrane section.
13, fluid concentration method, which comprises the steps of leading the fluid into a reverse osmosis system to obtain total permeate and total concentrate, wherein the reverse osmosis system comprises n reverse osmosis units RO1, RO2, …, ROi, RO (i +1), … and ROn, n is more than or equal to 2, i is more than or equal to 1 and less than n, each reverse osmosis unit ROi can generate ith permeate and ith concentrate, the ith concentrate is led into RO (i +1), each reverse osmosis unit ROi comprises at least membrane elements with water permeability coefficient of Ai and salt permeability coefficient of Bi, Ai is less than A (i +1), and Bi is less than B (i + 1).
14. The method of fluid concentration of claim 13, further comprising:

passing the stream to RO1 to obtain a1 st permeate and a1 st concentrate, at least portion of the total permeate being from the 1 st permeate;

introducing RO2 into the 1 st concentrated solution to obtain a2 nd permeate and a2 nd concentrated solution, and introducing RO1 into the 2 nd permeate or mixing the 2 nd permeate with the 1 st permeate to obtain the total permeate;

when 2< i < n, introducing the i-1 th concentrated solution into ROi to obtain an i th permeating solution and an i th concentrated solution, introducing the i th permeating solution into RO1, and introducing the i th concentrated solution into RO (i + 1); and

and (3) introducing the n-1 concentrated solution into ROn to obtain an n-th permeating solution and the total concentrated solution, and introducing the n-th permeating solution into RO 1.