WO2021047417A1 - Pressure energy composite desalination process - Google Patents

Abstract

Disclosed is a pressure energy composite desalination process, comprising the steps: 1) initial liquid feeding, and specifically, feeding saline water into a pressure energy recovery container (1) through a saline water pre-liquid inlet (11) by using a water feeding and draining pump M1; 2) reverse osmosis, wherein after the pressure energy recovery container (1) is filled with the saline water, a circulating pump M2 delivers the saline water in the pressure energy recovery container into a general saline water inlet (21) of a membrane assembly (2) with a plurality of reverse osmosis membranes (22) connected in parallel, fresh water resulting from treatment flows out through a general fresh water outlet (23), concentrated water returns to the pressure energy recovery container (1) through a general concentrated water outlet (25), and in addition, a high-pressure pump M3 supplements saline water from a saline water normal liquid inlet (31) of a liquid supplementing pipeline (30) to the pressure energy recovery container (1) to maintain the system pressure for normal operation; 3) drainage, wherein after multiple cycles of the reverse osmosis in step (2) are performed to reach preset circulation time T2, concentrated brine in the pressure energy recovery container (1) is completely drained by the water feeding and draining pump M1 via a drainage port (43); and repeating steps 1) to 3).

Description

Pressure energy composite desalination process

Technical field:

The invention relates to the technical field of desalination, in particular to a pressure-energy composite desalination process.

Background technique:

The world's fresh water resources that can be directly used by humans are less than 0.3% of the total water resources, and population growth, agriculture and industrial development have led to a rapid decrease in fresh water, especially clean fresh water. At present, about 300 million people need to rely on the desalination of salt water or saline groundwater to obtain domestic water, so desalination has strategic significance and development prospects.

At present, desalination has formed industrialized technologies mainly represented by multi-stage flash evaporation (MSF), low-temperature multi-effect distillation (MED), electrodialysis (EDI) and reverse osmosis (RO). Mainly these technologies, but the proportion of reverse osmosis will gradually increase.

In recent years, reverse osmosis technology has rapidly occupied the market due to its advantages of low power consumption, simple equipment, easy maintenance and modular equipment, gradually replacing the flash method, becoming the most widely used method, and obtaining rapid development. At present, almost all domestic industrial wastewater, desalination and other desalination processes use reverse osmosis membranes to work in series. Figure 1 shows a traditional production process of reverse osmosis membranes arranged in series. In this process, brine is fed into the membrane module 100 from the brine inlet 110, and then passes through the primary membrane 101, secondary membrane 102, tertiary membrane 103, The fourth-stage membrane 104, the fifth-stage membrane 105, and the sixth-stage membrane 106 perform reverse osmosis, the fresh water produced by the reverse osmosis flows out through the fresh water outlet 120, and the concentrated water produced by the reverse osmosis is discharged through the concentrated brine outlet 130. The disadvantages of this process are as follows: ①The membrane module occupies a large area and the capital investment cost is high; ②The pressure in the reverse osmosis membrane is gradually reduced, and the water output of the osmosis membrane is gradually reduced, and the desalination efficiency is low; Different, the service life is different; ④ The reverse osmosis membrane is embedded in the same membrane shell, which is not conducive to monitoring and maintenance.

In general, the traditional desalination process is divided into two types: one is a process without an energy recovery machine, for example, brine enters the ultrafiltration device through a lift pump, then pressurized by the booster pump into the security filter, and then through the high pressure Pumped into the traditional reverse osmosis membrane unit; the other is a process containing a typical imported PX energy recovery machine, for example, the brine enters the ultrafiltration device through a lift pump, then pressurized by the booster pump into the security filter, and then through the high-pressure pump and The energy recovery machine connected to the high-pressure pump is sent to the traditional reverse osmosis membrane unit. After the traditional reverse osmosis membrane unit reverse osmosis, the fresh water flows out directly, and the high-pressure concentrated water returns to the energy recovery machine to convert the pressure energy into the kinetic energy of the high-pressure pump, and Drain the low-pressure concentrated water whose energy has mostly been converted.

However, for the above-mentioned traditional process without an energy recovery machine, about 60% of the influent residual pressure energy contained in the high-pressure concentrated water discharged in the reverse osmosis desalination process will be wasted, making the entire fresh water production process energy consumption. Too large; and for the above-mentioned traditional process using energy recovery machines, although the high-pressure concentrated water in the reverse osmosis desalination process will be returned to the energy recovery machine for energy recovery, there is still low-pressure concentrated water containing part of the energy that will be discharged The process also discharges this part of the energy. In addition, the energy recovery machine used in the traditional process is mainly imported from abroad, and its cost is relatively high. These factors greatly increase the cost of production.

In addition, in the traditional process, the brine is reverse osmosis through the reverse osmosis membrane in series, but because the energy will gradually attenuate in this process, the pressure of the brine passing through the first stage membrane will be set much higher than the osmotic pressure. Ensure that the osmotic pressure is still higher than the last stage of the membrane. In addition, in many cases in the traditional process, the pump and the piping system cannot be perfectly matched, so the valve of the last-stage concentrated water outlet needs to be adjusted to maintain the pressure of the system, which causes a lot of energy loss.

Summary of the invention

In order to overcome the above shortcomings, the present invention will be advantageous to provide a pressure-energy composite desalination process with compact structure, low cost and low energy consumption.

To this end, the present invention provides a pressure-energy composite desalination process, which includes the following steps:

1) Initial liquid inlet: use the water supply and drainage pump M1 to send the brine from the brine pre-liquid inlet of the liquid inlet pipe into the pressure energy recovery container;

2) Reverse osmosis: After the pressure energy recovery container is filled with salt water, the circulating pump M2 is used to send the salt water in the pressure energy recovery container to the total salt water inlet of the membrane module in which multiple reverse osmosis membranes are arranged in parallel through the circulation pipeline. The fresh water generated by the components flows out through the total fresh water outlet, and the concentrated water produced is returned to the pressure energy recovery container through the total concentrated water outlet. At the same time, the high-pressure pump M3 is used to supplement the salt water from the salt water normal inlet of the replenishing pipeline to the pressure energy recovery container. System pressure to maintain normal work;

3) Draining: After the reverse osmosis in step 2) performs multiple cycles and reaches a predetermined cycle time, the water supply and drainage pump M1 is used to drain the concentrated brine in the pressure energy recovery container through the drain port of the drain pipeline;

Repeat steps 1) to 3).

In the present invention, by setting up separate initial liquid feeding steps and liquid draining steps, the salt water supply time and the concentrated salt water discharge time can be saved, and the work efficiency can be improved; the normal working system pressure is maintained by using the high-pressure pump M3, and the circulating pump is used M2 supplies brine to the membrane module and recovers the concentrated brine through the pressure energy recovery container. In the reverse osmosis step, as long as the initial pressure of the brine can be higher than its osmotic pressure, the higher the circulation pressure, the higher the pressure, there is no serial reverse osmosis membrane structure at all The pressure of the secondary membrane may not meet the osmotic pressure, so the entire process does not require a valve to adjust the system pressure. Moreover, the concentrated brine with residual pressure at the outlet of the membrane module is directly recovered and enters the pressure energy recovery container without energy conversion. Energy recovery efficiency As high as 99%-99.5%; and, the present invention discharges after multiple cycles of reverse osmosis and reaches a predetermined cycle time, so that the concentration of concentrated salt water and fresh water can be flexibly adjusted in a larger range, and the residual pressure of concentrated salt water follows The production cycle of fresh water is reused to realize system energy recovery. Compared with the desalination process that is generally equipped with imported PX energy recovery machines, it can save electricity by 10%-20%.

Furthermore, the pressure-energy composite desalination process further includes step 4) washing after step 3): using the circulation pump M2 and the high pressure pump M3 to flush the fresh water inlets of the respective circulation pipelines and the replenishment pipelines respectively by using the circulation pump M2 and the high pressure pump M3. Inhale fresh water to flush the membrane module and the pressure energy recovery container. After the flushing is performed for a predetermined flushing time, the water supply and drainage pump M1 is used to flush the flushing water collected into the pressure energy recovery container through the drain line The above-mentioned drain port is discharged, and then steps 1) to 4) are repeated.

In the above-mentioned washing steps, the high-pressure pump M3, the circulating pump M2, the water supply and drainage pump M1, the membrane module, and the pressure energy recovery container are completely cleaned by the fresh water, which can improve the working reliability and service life of the entire unit.

Furthermore, in the above step 1), the salt water enters the pressure energy recovery container from the salt water pre-liquid inlet through the solenoid valve X1, the one-way valve C1, the water supply and drainage pump M1, and the solenoid valve X2 on the liquid inlet pipeline. .

Still further, in the above step 2), the brine in the pressure energy recovery container enters the membrane module through the solenoid valve X3, the circulating pump M2, and the total brine inlet on the circulation pipeline for reverse osmosis, and from the membrane module The concentrated water from the above-mentioned total concentrated water outlet continues to return to the above-mentioned pressure energy recovery container through the manual valve H1 and the one-way valve C2 on the above-mentioned circulation pipeline. At the same time, the above-mentioned brine from the above-mentioned high-pressure pump M3 passes through the above-mentioned brine on the above-mentioned replenishing pipeline. The normal liquid inlet, the solenoid valve X4, the above-mentioned high-pressure pump M3, the one-way valve C3, and the manual valve H2 enter the above-mentioned pressure energy recovery container.

Still further, in the above step 2), the salt water from the total salt water inlet first enters the salt water inlet of each of the multiple reverse osmosis membranes, and the fresh water produced by the permeation of the membrane module passes through the multiple reverse osmosis membranes. Each sub-fresh water outlet enters the above-mentioned total fresh water outlet and flows out, and the concentrated water produced by the permeation of the above-mentioned membrane module enters the above-mentioned total concentrated water outlet through the sub-concentrated water outlet on each of the plurality of reverse osmosis membranes and then returns to the above-mentioned pressure energy. Recycle the container.

Still further, in the above step 3), the concentrated brine in the pressure energy recovery container passes through the solenoid valve X5, the one-way valve C1, the water supply and drainage pump M1, and the solenoid valve X6 on the drain line, and finally drains from the above The liquid port is discharged.

Still further, in the above step 4), the fresh water from the flushing fresh water inlet of the circulation pipeline enters the membrane module through the solenoid valve X7 and the circulation pump M2 for flushing, and the flushing water returns to the main concentrated water outlet through the total concentrated water outlet. The pressure energy recovery container; the fresh water from the flush fresh water inlet of the replenishment pipeline enters the pressure energy recovery container through the solenoid valve X8, the high pressure pump M3, the one-way valve C3, and the manual valve H2, and is finally used to the station The drain pump M1 allows the flushing water in the pressure energy recovery container to be discharged through the solenoid valve X5, the one-way valve C1, and the solenoid valve X6 to complete the system flushing.

Further, the above-mentioned solenoid valves and the above-mentioned pumps are fully automatically linked and controlled by a PLC controller.

These and other aspects of the present invention will be explained more clearly by referring to the embodiments described below.

Description of the drawings:

The structure and further objects and advantages of the present invention will be better understood through the following description in conjunction with the accompanying drawings, in which the same reference signs identify the same elements:

Figure 1 is a schematic diagram of a traditional production process of reverse osmosis membranes arranged in series;

2 is a schematic diagram of a pressure-energy composite saltwater desalination unit used in a pressure-energy composite saltwater desalination process according to a specific embodiment of the present invention, and arrows in the figure show the flow of liquid in each step of the process;

Fig. 3 is a schematic diagram of the parallel arrangement structure of the membrane modules of the pressure-energy composite salt water desalination unit shown in Fig. 2.

detailed description:

The specific embodiments of the present invention will be described below with reference to the accompanying drawings. However, it should be understood that the embodiments disclosed herein are merely typical examples of the present invention, which can be embodied in various forms. Therefore, the specific details disclosed herein are not considered to be restrictive, but merely serve as a basis for the claims and as a representative basis for teaching those skilled in the art to apply the present invention in any appropriate manner in practice.

The "desalination" referred to in this article includes seawater desalination, brackish water desalination, industrial wastewater desalination, etc.; the "brine water" referred to in this article includes seawater, brackish water, industrial wastewater and other water with high salt content.

Referring to Figures 2 and 3, the present invention according to a specific embodiment of the present invention provides a pressure-energy composite desalination process, which includes the following steps:

1) Initial liquid inlet: use the water supply and drainage pump M1 to send the brine from the brine pre-liquid inlet 11 of the liquid inlet pipe 10 into the pressure energy recovery container 1;

2) Reverse osmosis: After the pressure energy recovery container 1 is filled with salt water, the circulating pump M2 is used to send the salt water in the pressure energy recovery container 1 to the membrane module 2 in which the multiple reverse osmosis membranes 22 are arranged in parallel through the circulation pipeline 20. The total salt water inlet 21, the fresh water produced by the membrane module 2 flows out through the total fresh water outlet 23, and the produced concentrated water is returned to the pressure energy recovery vessel 1 through the total concentrated water outlet 25. At the same time, the high-pressure pump M3 is used to remove the salt water from the salt water in the replenishing pipeline 30. The normal liquid inlet 31 is supplemented to the pressure energy recovery container 1 to maintain the normal working system pressure;

3) Draining: After the reverse osmosis of step 2) performs multiple cycles and reaches the predetermined cycle time T2 (the salt content of concentrated brine and fresh water can be flexibly adjusted through T2), the pressure energy in the container 1 is recovered by the water supply and drainage pump M1 The concentrated brine is completely discharged through the discharge port 43 of the discharge pipe 40;

4) Flushing: Use the circulating pump M2 to suck in fresh water from the flushing fresh water inlet 27 of the circulating pipe 20 to flush the membrane module 2 and the pressure energy recovery container 1, and at the same time to use the high-pressure pump M3 to suck in from the flushing fresh water inlet 37 of the replenishing pipe 30 The pressure energy recovery container 1 and the membrane module 2 are washed with fresh water. After the washing is carried out for a predetermined washing time T4, the water supply and drainage pump M1 is used to flush the washing water collected into the pressure energy recovery container 1 through the drain pipe 40 The drain port 43 is discharged.

Then repeat the above steps 1) to 4).

It should be understood that in the above-mentioned washing process, the circulating pump M2, the high-pressure pump M3, and the water supply and drainage pump M1 are naturally cleaned during the process of sucking or discharging fresh water. The water supply and drainage pump M1, circulating pump M2, high-pressure pump M3, pressure energy recovery container 1, and membrane module 2 have been completely cleaned with fresh water, which can improve the reliability and service life of the entire unit.

Specifically, in the above step 1), the brine enters the pressure energy recovery container 1 from the brine pre-inlet port 11 on the inlet pipe 10 through the solenoid valve X1, the one-way valve C1, the water supply and drainage pump M1, and the solenoid valve X2; In step 2), the brine in the pressure energy recovery container 1 enters the membrane module 2 through the solenoid valve X3, the circulating pump M2, and the total brine inlet 21 on the circulating pipeline 20 for reverse osmosis, and from the total concentrated water outlet of the membrane module 2 The concentrated water discharged from 25 continues to return to the pressure energy recovery vessel 1 through the manual valve H1 and the one-way valve C2 on the circulation pipeline 20, and at the same time, the brine from the high-pressure pump M3 is on the replenishment pipeline 30 through the brine normal inlet 31, The solenoid valve X4, the high-pressure pump M3, the one-way valve C3, and the manual valve H2 enter the pressure energy recovery container 1.

As shown in Figure 3 and with reference to Figure 2, in step 2), the brine from the total brine inlet 21 first enters the split brine inlet 221 on each of the multiple reverse osmosis membranes 22, and the fresh water produced by the permeation of the membrane module 2 passes through more The sub-fresh water outlet 223 on each of the reverse osmosis membranes 22 enters the total fresh water outlet 23 and flows out. The concentrated water produced by the permeation of the membrane module 2 enters the total concentrated water outlet through the sub-concentrated water outlet 225 on each of the multiple reverse osmosis membranes 22 25 and then return to the pressure energy recovery container 1.

Specifically, in step 3), the concentrated brine in the pressure energy recovery container 1 passes through the solenoid valve X5, the one-way valve C1, the water supply and drainage pump M1, and the solenoid valve X6 on the drain line 40, and finally from the drain port 43 Discharge; In step 4), the fresh water from the flushing fresh water inlet 27 of the circulating pipeline 20 enters the membrane module 2 through the solenoid valve X7 and the circulating pump M2 for flushing, and the flushing water returns to the pressure energy recovery vessel 1 through the total concentrated water outlet 25 (The flushing pressure is much lower than the osmotic pressure of the salt water, so no fresh water is produced during the flushing process, that is, no water is discharged from the total fresh water outlet); the fresh water from the flushing fresh water inlet 37 of the refill pipe 30 passes through the solenoid valve X8 and the high-pressure pump M3 , Check valve C3, manual valve H2 enter the pressure energy recovery container 1, and finally use the water supply and drainage pump M1 to make the flushing water in the pressure energy recovery container 1 drain through the solenoid valve X5, the one-way valve C1, and the solenoid valve X6 to complete the system flushing .

It should be noted that the pressure energy recovery container 1 is also provided with a mechanical pressure relief valve 14 (when the electronically controlled pressure relief is abnormal, that is, the pressure relief through the solenoid valve is abnormal, the mechanical pressure relief valve 14 will ensure the safety of the system). Exhaust or intake to help the pressure energy recovery container 1 is filled with salt water or emptied of concentrated brine solenoid valve X9 and pressure sensor P1 for high-pressure protection; in addition, it should be noted that in this embodiment, in the system Before starting, solenoid valve X1 to solenoid valve X9 is normally closed, manual valve H1 and manual valve H2 are normally open (the setting of each manual valve is for the maintenance of the unit). The solenoid valves are closed and opened by the PLC controller, the pumps are started and stopped by the PLC controller, and the solenoid valves and pumps are linked through the PLC controller to realize fully automatic control.

The pressure-energy composite desalination process of the present invention has the following characteristics:

1) Reverse osmosis is carried out with membrane modules arranged in parallel with reverse osmosis membranes, which occupies a small area and the system pressure is convenient to control;

2) The salt content of concentrated brine and fresh water can be flexibly adjusted by controlling the cycle time of reverse osmosis;

2) Through the PLC controller to intelligently control the electronic control components (such as solenoid valves, pumps, etc.) involved in the entire process, and then control the various steps of the process (that is, each process: initial liquid inlet process, reverse osmosis process, liquid discharge Process, flushing process);

3) With automatic flushing function, the reliability of the use of reverse osmosis membranes, etc. is good, and the service life is long;

4) The normal pressure of the system is maintained by the high-pressure pump replenishment and the reverse osmosis is performed through the parallel reverse osmosis membrane, which greatly reduces the energy loss.

5) The system energy recovery technology is adopted, which is different from the traditional energy recovery machine in which the energy is recovered in a single link. The overall energy recovery efficiency is higher and the cost is lower.

The technical content and technical features of the present invention have been disclosed as above. However, it is understood that under the creative idea of the present invention, those skilled in the art can make various changes and improvements to the above structure, including the technologies separately disclosed or claimed herein. Combinations of features, and other combinations that obviously include these features. These modifications and/or combinations all fall into the technical field involved in the present invention and fall into the protection scope of the claims of the present invention.

Claims (8)

A pressure-energy composite desalination process, which is characterized in that it comprises the following steps: 1) Initial liquid inlet: use the water supply and drainage pump M1 to send the brine from the brine pre-liquid inlet of the liquid inlet pipe into the pressure energy recovery container; 2) Reverse osmosis: After the pressure energy recovery container is filled with salt water, the circulating pump M2 is used to send the salt water in the pressure energy recovery container to the total salt water inlet of the membrane module in which multiple reverse osmosis membranes are arranged in parallel through the circulation pipeline. The fresh water generated by the components flows out through the total fresh water outlet, and the concentrated water produced is returned to the pressure energy recovery container through the total concentrated water outlet. At the same time, the high-pressure pump M3 is used to supplement the salt water from the salt water normal inlet of the replenishing pipeline to the pressure energy recovery container. System pressure to maintain normal work; 3) Draining: After the reverse osmosis in step 2) performs multiple cycles and reaches the predetermined cycle time, the water supply and drainage pump M1 is used to discharge the concentrated brine in the pressure energy recovery container through the drain port of the drain pipeline; Repeat steps 1) to 3). The pressure-energy composite desalination process according to claim 1, characterized in that it further comprises step 4) washing after the step 3): using the circulating pump M2 and the high-pressure pump M3 from the respective corresponding The flushing fresh water inlets of the circulation pipeline and the replenishing pipeline suck in fresh water to flush the membrane module and the pressure energy recovery container. After the flushing is performed for a predetermined flushing time, the water supply and drainage pump M1 is used to After flushing, the flushing water merged into the pressure energy recovery container is discharged through the drain port of the drain pipe, and then steps 1) to 4) are repeated. The pressure-energy composite desalination process according to claim 2, characterized in that, in the step 1), the brine is in the inlet pipeline from the brine pre-liquid inlet through the solenoid valve X1 and the single The direction valve C1, the water supply and drainage pump M1, and the solenoid valve X2 enter the pressure energy recovery container. The pressure-energy composite desalination process according to claim 2, characterized in that, in the step 2), the brine in the pressure-energy recovery container passes through the solenoid valve X3, the The circulating pump M2, the total brine inlet enters the membrane module for reverse osmosis, and the concentrated water from the total concentrated water outlet of the membrane module continues to pass through the manual valve H1 and the one-way valve C2 on the circulating pipeline. Return to the pressure energy recovery container, and meanwhile, the brine from the high-pressure pump M3 passes through the brine normal inlet, solenoid valve X4, high-pressure pump M3, one-way valve C3, The manual valve H2 enters the pressure energy recovery container. The pressure-energy composite desalination process according to claim 4, characterized in that, in the step 2), the brine from the total brine inlet first enters the fraction on each of the plurality of reverse osmosis membranes. Salt water inlet, the fresh water produced by the permeation of the membrane module enters the total fresh water outlet through the sub-fresh water outlet on each of the plurality of reverse osmosis membranes, and the concentrated water produced by the permeation of the membrane module passes through the plurality of fresh water outlets. The concentrated water outlet on each of the reverse osmosis membranes enters the total concentrated water outlet and then returns to the pressure energy recovery container. The pressure-energy composite desalination process according to claim 2, characterized in that, in the step 3), the concentrated brine in the pressure-energy recovery container passes through the solenoid valve X5, the The one-way valve C1, the water supply and drainage pump M1, and the solenoid valve X6 are finally discharged from the drain port. The pressure-energy composite desalination process according to claim 2, characterized in that, in the step 4), the fresh water from the flushing fresh water inlet of the circulation pipeline passes through the solenoid valve X7, the circulation The pump M2 enters the membrane module for flushing, the flushing water returns to the pressure energy recovery container through the total concentrated water outlet; the fresh water from the flushing fresh water inlet of the replenishing pipeline passes through the solenoid valve X8, The high-pressure pump M3, the one-way valve C3, and the manual valve H2 enter the pressure energy recovery container, and finally use the drain pump M1 to make the flushing water in the pressure energy recovery container pass through the solenoid valve X5 and the single Discharge to valve C1 and solenoid valve X6 to complete system flushing. The pressure-energy composite desalination process according to any one of claims 3 to 7, characterized in that each solenoid valve and each pump are fully automatically linked through a PLC controller.

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