Reverse osmosis desalination system adapting to wide-range change of salinity of raw water and control method

Abstract

The invention discloses a reverse osmosis desalination system adapted to wide-range change of raw water salinity and a control method.The system is characterized in that a raw water pipe provided with a raw water conductivity instrument is connected with a raw water pump, then is connected with a high-pressure pump, a medium-pressure pump and a low-pressure pump through pipelines, and then is connected with a reverse osmosis membrane group; a pressure transmitting instrument is arranged on a pipeline in front of a water inlet of the reverse osmosis membrane group, a fresh water outlet of the reverse osmosis membrane group is connected with a fresh water pipe, a first flow meter is arranged on the fresh water pipe, a concentrated water outlet of the reverse osmosis membrane group is connected with a concentrated water pipe, and an adjusting valve and a second flow meter are sequentially arranged on the concentrated water pipe along the flow direction of the concentrated water; and the computer control system is electrically connected with the raw water conductivity instrument, the pressure transmitting instrument, the first flow meter, the second flow meter, the raw water pump, the high-pressure pump, the medium-pressure pump, the low-pressure pump and the adjusting valve respectively. The invention relates to a reverse osmosis desalination system adaptive to wide-range change of salinity of raw water.

Description

Technical Field

[0001] The invention belongs to the technical field of seawater or brackish water desalination, and in particular relates to a reverse osmosis desalination system and a control method which are adaptable to wide-range changes in raw water salinity. Background Art

[0002] The stable operation of the reverse osmosis desalination system is greatly affected by the fluctuation of the salinity of the raw water (including seawater and brackish water). In actual projects, the salinity of the raw water often fluctuates greatly with seasonal or environmental changes, especially for some sea areas near estuaries. Under the dual effects of the influx of freshwater from the estuary and the changes in ocean tides, the salinity of the raw water often fluctuates violently in a short period of time. This huge salinity fluctuation is extremely unfavorable for the regulation of the high-pressure pump of the reverse osmosis system, and may even cause the high-pressure pump to exceed the operating pressure range and cannot be used normally. Therefore, it is of great significance to develop a reverse osmosis desalination system and control method that can adapt to the wide range of salinity changes of raw water such as seawater or brackish water to solve this problem. Summary of the invention

[0003] The purpose of the present invention is to overcome the problem in the prior art that the drastic fluctuation of the salinity of raw water such as seawater or brackish water affects the stable operation of the reverse osmosis system, and to provide a reverse osmosis desalination system that is adaptable to a wide range of raw water salinity changes.

[0004] The second object of the present invention is to provide a control method for a reverse osmosis desalination system that is adaptable to a wide range of changes in raw water salinity.

[0005] The technical solution of the present invention is summarized as follows:

[0006] A reverse osmosis desalination system adapted to a wide range of raw water salinity changes, comprising a raw water pump 1, a high-pressure pump 2, a medium-pressure pump 3, a low-pressure pump 4, and a reverse osmosis membrane group 5. A raw water pipe 6 provided with a raw water conductivity meter 9 is connected to the raw water pump 1, and then connected to the water inlets of the high-pressure pump 2, the medium-pressure pump 3, and the low-pressure pump 4 through pipelines, respectively; the water outlets of the high-pressure pump 2, the medium-pressure pump 3, and the low-pressure pump 4 are connected to the water inlet of the reverse osmosis membrane group 5 through pipelines, and a pressure transmitter is provided on the pipeline before the water inlet of the reverse osmosis membrane group 5 Table 10, the fresh water outlet of the reverse osmosis membrane group 5 is connected to the fresh water pipe 7, and the first flow meter 11 is arranged on the fresh water pipe 7; the concentrate water outlet of the reverse osmosis membrane group 5 is connected to the concentrate water pipe 8, and the regulating valve 13 and the second flow meter 12 are arranged in sequence along the concentrate water flow direction in the concentrate water pipe 8; the computer control system 14 is electrically connected to the raw water conductivity meter 9, the pressure transmitter 10, the first flow meter 11, the second flow meter 12, the raw water pump 1, the high pressure pump 2, the medium pressure pump 3, the low pressure pump 4, and the regulating valve 13 respectively.

[0007] A control method for a reverse osmosis desalination system adapting to wide-range changes in raw water salinity comprises the following steps:

[0008] (1) using a reverse osmosis desalination system adapted to a wide range of raw water salinity changes;

[0009] (2) The computer control system 14 receives signals from the raw water conductivity meter 9, the pressure transmitter 10, the first flow meter 11 and the second flow meter 12, and controls the raw water pump 1, the high pressure pump 2, the medium pressure pump 3 and the low pressure pump 4 with variable frequency, and controls the opening of the regulating valve 13;

[0010] (3) Raw water is divided into the following categories according to different electrical conductivity: high-salinity water greater than 25,000 μS / cm; medium-salinity water greater than 10,000 μS / cm and less than or equal to 25,000 μS / cm; and low-salinity water less than or equal to 10,000 μS / cm.

[0011] The selected pressure ranges of the high-pressure pump 2, the medium-pressure pump 3, and the low-pressure pump 4 correspond to the operating pressure ranges of the reverse osmosis membrane group 5 of high-salinity water, medium-salinity water, and low-salinity water, respectively;

[0012] (4) When the raw water enters the raw water pipe 6, the computer control system 14 controls the raw water pump 1 to deliver the raw water to the high-pressure pump 2, the medium-pressure pump 3 or the low-pressure pump 4 according to the conductivity value monitored by the raw water conductivity meter 9, and further boosts the pressure to deliver the raw water to the reverse osmosis membrane group 5, so that the value of the first flow meter 11 reaches the expected value, and controls the opening of the regulating valve 13 so that the value of the second flow meter 12 reaches the expected value; the fresh water of the reverse osmosis membrane group 5 is delivered to the outside through the fresh water pipe 7, and the concentrated water of the reverse osmosis membrane group 5 is delivered to the outside through the concentrated water pipe 8;

[0013] When the raw water conductivity value monitored by the raw water conductivity meter 9 fluctuates within the respective numerical ranges of high-salinity water, medium-salinity water or low-salinity water, the computer control system 14 frequency-controls the high-pressure pump 2, the medium-pressure pump 3 or the low-pressure pump 4, and controls the regulating valve 13 to keep the values ​​of the first flow meter 11 and the second flow meter 12 stable, and the pressure transmitter 10 transmits the pressure signal to the computer control system 14 for monitoring the operating pressure change of the reverse osmosis membrane group 5;

[0014] When the raw water conductivity meter 9 detects that the raw water conductivity decreases from high salinity to medium salinity, or from medium salinity to low salinity, the computer control system 14 frequency conversion controls the high pressure pump 2 to switch to the medium pressure pump 3, or the medium pressure pump 3 to switch to the low pressure pump 4;

[0015] When the raw water conductivity meter 9 detects that the raw water conductivity increases from low salinity to medium salinity, or from medium salinity to high salinity, the computer control system 14 frequency conversion controls the low-pressure pump 4 to switch to the medium-pressure pump 3, or the medium-pressure pump 3 to switch to the high-pressure pump 2. The beneficial effects of the present invention are:

[0016] (1) By configuring three pumps with different operating pressure ranges, namely, a high-pressure pump, a medium-pressure pump and a low-pressure pump, the reverse osmosis desalination system of the present invention can adapt to a wide range of raw water salinity changes and can operate normally regardless of the raw water salinity conditions of seawater or brackish water, thereby improving the scope of application of the present invention.

[0017] (2) The computer control system 14 is used to receive signals from the raw water conductivity meter 9, the pressure transmitter 10, the first flow meter 11 and the second flow meter 12, and to control the raw water pump 1, the high-pressure pump 2, the medium-pressure pump 3 and the low-pressure pump 4 by frequency conversion, and to control the opening of the regulating valve 13 by adjusting the opening of the regulating valve 13; online automatic operation is realized, thereby improving the convenience and accuracy of the control of the system of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a reverse osmosis desalination system that can adapt to a wide range of changes in raw water salinity. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0020] Example 1

[0021] A reverse osmosis desalination system that adapts to a wide range of raw water salinity changes, see Figure 1 , including a raw water pump 1, a high-pressure pump 2, a medium-pressure pump 3, a low-pressure pump 4, and a reverse osmosis membrane group 5. A raw water pipe 6 provided with a raw water conductivity meter 9 is connected to the raw water pump 1, and then connected to the water inlets of the high-pressure pump 2, the medium-pressure pump 3 and the low-pressure pump 4 through pipelines respectively. The water outlets of the high-pressure pump 2, the medium-pressure pump 3 and the low-pressure pump 4 are connected to the water inlet of the reverse osmosis membrane group 5 through pipelines. A pressure transmitter 10 is provided on the pipeline before the water inlet of the reverse osmosis membrane group 5. The fresh water outlet is connected to the fresh water pipe 7, on which a first flow meter 11 is arranged; the concentrate outlet of the reverse osmosis membrane group 5 is connected to the concentrate pipe 8, and a regulating valve 13 and a second flow meter 12 are sequentially arranged on the concentrate pipe 8 along the direction of the concentrate water flow; the computer control system 14 is electrically connected to the raw water conductivity meter 9, the pressure transmitter 10, the first flow meter 11, the second flow meter 12, the raw water pump 1, the high-pressure pump 2, the medium-pressure pump 3, the low-pressure pump 4, and the regulating valve 13 respectively.

[0022] Example 2

[0023] A control method for a reverse osmosis desalination system adapting to wide-range changes in raw water salinity comprises the following steps:

[0024] (1) using a reverse osmosis desalination system adapted to a wide range of raw water salinity changes according to Example 1;

[0025] (2) The computer control system 14 receives signals from the raw water conductivity meter 9, the pressure transmitter 10, the first flow meter 11 and the second flow meter 12, and controls the raw water pump 1, the high pressure pump 2, the medium pressure pump 3 and the low pressure pump 4 with variable frequency, and controls the opening of the regulating valve 13;

[0026] (3) Raw water is divided into the following categories according to different electrical conductivity: high-salinity water greater than 25,000 μS / cm; medium-salinity water greater than 10,000 μS / cm and less than or equal to 25,000 μS / cm; and low-salinity water less than or equal to 10,000 μS / cm.

[0027] The selected pressure ranges of the high-pressure pump 2, the medium-pressure pump 3, and the low-pressure pump 4 correspond to the operating pressure ranges of the reverse osmosis membrane group 5 of high-salinity water, medium-salinity water, and low-salinity water, respectively;

[0028] (4) When raw water (seawater or brackish water) enters the raw water pipe 6, the computer control system 14 controls the raw water pump 1 to deliver the raw water to the high-pressure pump 2, the medium-pressure pump 3 or the low-pressure pump 4 according to the conductivity value monitored by the raw water conductivity meter 9, and further boosts the pressure to deliver the raw water to the reverse osmosis membrane group 5, so that the value of the first flow meter 11 reaches the expected value, and controls the opening of the regulating valve 13 so that the value of the second flow meter 12 reaches the expected value; the fresh water of the reverse osmosis membrane group 5 is delivered to the outside through the fresh water pipe 7, and the concentrated water of the reverse osmosis membrane group 5 is delivered to the outside through the concentrated water pipe 8;

[0029] When the raw water conductivity value monitored by the raw water conductivity meter 9 fluctuates within the respective numerical ranges of high-salinity water, medium-salinity water or low-salinity water, the computer control system 14 frequency-controls the high-pressure pump 2, the medium-pressure pump 3 or the low-pressure pump 4, and controls the regulating valve 13 to keep the values ​​of the first flow meter 11 and the second flow meter 12 stable, and the pressure transmitter 10 transmits the pressure signal to the computer control system 14 for monitoring the operating pressure change of the reverse osmosis membrane group 5;

[0030] When the raw water conductivity meter 9 detects that the raw water conductivity decreases from high salinity to medium salinity (or medium salinity to low salinity), the computer control system 14 controls the high-pressure pump 2 to switch to the medium-pressure pump 3 (or the medium-pressure pump 3 switches to the low-pressure pump 4) by frequency conversion;

[0031] When the raw water conductivity meter 9 detects that the conductivity of the raw water increases from low salinity to medium salinity, or from medium salinity to high salinity, the computer control system 14 frequency conversion controls the low-pressure pump 4 to switch to the medium-pressure pump 3, or the medium-pressure pump 3 to switch to the high-pressure pump 2.

[0032] This embodiment takes the gradual change of seawater into brackish water as an example to explain in detail:

[0033] Assumption: The expected values ​​of the first flow meter 11 and the second flow meter 12 are 1000m3 / h and 1200m 3 / h. The operating pressure range of the high-pressure pump 2 is 35-65 bar, the operating pressure range of the medium-pressure pump 3 is 20-40 bar, and the operating pressure range of the low-pressure pump 4 is 5-25 bar;

[0034] When the raw water conductivity meter 9 detects that the raw water conductivity is 45000 μS / cm, the computer control system 14 controls the raw water pump 1 and the high-pressure pump 2 to start, and the frequency of the high-pressure pump 2 is controlled by frequency conversion so that the value of the first flow meter 11 reaches 1000m / s. 3 / h (expected), and control the opening of the regulating valve 13 so that the value of the second flow meter 12 reaches 1200m 3 / h (expected), at this time, the pressure transmitter 10 transmits the operating pressure value (about 58 bar) of the reverse osmosis membrane group 5 to the computer control system 14;

[0035] When the raw water conductivity meter 9 detects that the raw water conductivity drops to 35000 μS / cm, the computer control system 14 frequency-converting controls the high-pressure pump 2 and the regulating valve 13 to keep the values ​​of the first flow meter 11 and the second flow meter 12 stable, and the pressure transmitter 10 transmits the operating pressure value (about 45 bar) of the reverse osmosis membrane group 5 to the computer control system 14 to monitor the operating pressure change of the reverse osmosis membrane group 5;

[0036] When the inlet water conductivity meter 9 detects that the raw water conductivity drops to 25000 μS / cm, the computer control system 14 starts the medium-pressure pump 3 by frequency conversion, stops the high-pressure pump 2 by frequency conversion, and controls the regulating valve 13 to keep the values ​​of the first flow meter 11 and the second flow meter 12 stable. At this time, the pressure transmitter 10 transmits the operating pressure value (about 35 bar) of the reverse osmosis membrane group 5 to the computer control system 14;

[0037] When the inlet water conductivity meter 9 detects that the raw water conductivity drops to 15000 μS / cm, the computer control system 14 frequency-converts and controls the medium-pressure pump 3 and the regulating valve 13 to keep the values ​​of the first flow meter 11 and the second flow meter 12 stable, and the pressure transmitter 10 transmits the operating pressure value (about 25 bar) of the reverse osmosis membrane group 5 to the computer control system 14;

[0038] When the inlet water conductivity meter 9 detects that the raw water conductivity drops to 10000 μS / cm, the computer control system 14 starts the low-pressure pump 4 by frequency conversion, stops the medium-pressure pump 3 by frequency conversion, and controls the regulating valve 13 to keep the values ​​of the first flow meter 11 and the second flow meter 12 stable. At this time, the pressure transmitter 10 transmits the operating pressure value (about 22 bar) of the reverse osmosis membrane group 5 to the computer control system 14.

[0039] When the inlet water conductivity meter 9 detects that the raw water conductivity drops to within the range of 5000 μS / cm, the computer control system 14 frequency-controls the low-pressure pump 4 and the regulating valve 13 to keep the values ​​of the first flow meter 11 and the second flow meter 12 stable, and the pressure transmitter 10 transmits the operating pressure value (about 18 bar) of the reverse osmosis membrane group 5 to the computer control system 14.

[0040] The above is only a typical implementation of the present invention, but the present invention is not limited to the above implementation. Under the guidance of the present invention, ordinary technicians in this field can also make many forms of specific changes without departing from the scope of protection of the present invention and the claims, all of which belong to the protection scope of the present invention.

Claims

1. A reverse osmosis desalination system adapted to a wide range of raw water salinity changes, comprising a raw water pump (1), a high-pressure pump (2), a medium-pressure pump (3), a low-pressure pump (4), and a reverse osmosis membrane group (5), characterized in that: After the raw water pipe (6) provided with the raw water conductivity meter (9) is connected to the raw water pump (1), it is then connected to the water inlets of the high-pressure pump (2), the medium-pressure pump (3) and the low-pressure pump (4) through pipelines. The water outlets of the high-pressure pump (2), the medium-pressure pump (3) and the low-pressure pump (4) are connected to the water inlet of the reverse osmosis membrane group (5) through pipelines. A pressure transmitter (10) is provided on the pipeline before the water inlet of the reverse osmosis membrane group (5). The fresh water outlet of the reverse osmosis membrane group (5) is connected to the fresh water pipe (7). A first flow meter (11) is arranged on the top, the concentrated water outlet of the reverse osmosis membrane group (5) is connected to the concentrated water pipe (8), and a regulating valve (13) and a second flow meter (12) are arranged in sequence on the concentrated water pipe (8) along the concentrated water flow direction; the computer control system (14) is electrically connected to the raw water conductivity meter (9), the pressure transmitter (10), the first flow meter (11), the second flow meter (12), the raw water pump (1), the high-pressure pump (2), the medium-pressure pump (3), the low-pressure pump (4), and the regulating valve (13) respectively.

2. A control method for a reverse osmosis desalination system that is adaptable to a wide range of raw water salinity changes, characterized in that The steps include: (1) A reverse osmosis desalination system adapted to a wide range of raw water salinity changes according to claim 1; (2) The computer control system (14) receives signals from the raw water conductivity meter (9), the pressure transmitter (10), the first flow meter (11) and the second flow meter (12), and performs frequency conversion control on the raw water pump (1), the high pressure pump (2), the medium pressure pump (3) and the low pressure pump (4) and adjusts the opening of the regulating valve (13); (3) Raw water is divided into the following categories according to different electrical conductivity: high-salinity water greater than 25,000 μS / cm; medium-salinity water greater than 10,000 μS / cm and less than or equal to 25,000 μS / cm; and low-salinity water less than or equal to 10,000 μS / cm. The selected pressure ranges of the high-pressure pump (2), the medium-pressure pump (3), and the low-pressure pump (4) correspond to the operating pressure ranges of the reverse osmosis membrane group (5) for high-salinity water, medium-salinity water, and low-salinity water, respectively; (4) When the raw water enters the raw water pipe (6), the computer control system (14) controls the raw water pump (1) to deliver the raw water to the high-pressure pump (2), the medium-pressure pump (3) or the low-pressure pump (4) according to the conductivity value monitored by the raw water conductivity meter (9), and further boosts the pressure to deliver the raw water to the reverse osmosis membrane group (5), so that the value of the first flow meter (11) reaches the expected value, and controls the opening of the regulating valve (13) so that the value of the second flow meter (12) reaches the expected value; the fresh water of the reverse osmosis membrane group (5) is delivered to the outside through the fresh water pipe (7), and the concentrated water of the reverse osmosis membrane group (5) is delivered to the outside through the concentrated water pipe (8); When the raw water conductivity value monitored by the raw water conductivity meter (9) fluctuates within the respective numerical ranges of high-salinity water, medium-salinity water or low-salinity water, the computer control system (14) frequency-converts and controls the high-pressure pump (2), the medium-pressure pump (3) or the low-pressure pump (4), and controls the regulating valve (13) to keep the numerical values ​​of the first flow meter (11) and the second flow meter (12) stable, and the pressure transmitter (10) transmits the pressure signal to the computer control system (14) for monitoring the operating pressure change of the reverse osmosis membrane group (5); When the raw water conductivity meter (9) detects that the raw water conductivity decreases from high salinity to medium salinity, or from medium salinity to low salinity, the computer control system (14) controls the high pressure pump (2) to switch to the medium pressure pump (3), or the medium pressure pump (3) to switch to the low pressure pump (4) by frequency conversion; When the raw water conductivity meter (9) detects that the raw water conductivity increases from low salinity to medium salinity, or from medium salinity to high salinity, the computer control system (14) controls the low-pressure pump (4) to switch to the medium-pressure pump (3), or the medium-pressure pump (3) to switch to the high-pressure pump (2).

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