A high pressure membrane filtration system, recovery control and protection method

Abstract

The application discloses a high-pressure membrane filtration system, recovery rate control and protection method, the membrane filtration system comprises at least one membrane module, a high-pressure pump, a circulating pump, a raw water pipeline, a concentrated water pipeline, a high-pressure regulating valve and a PLC controller, the high-pressure pump is arranged on the raw water pipeline, a water inlet flowmeter is arranged on the raw water pipeline, a pressure transmitter S1 is arranged on the inlet end of the membrane module, a pressure transmitter S2 is arranged on the outlet end of the membrane module, the circulating pump is arranged on the concentrated water pipeline, a high-pressure regulating valve and a concentrated water flowmeter are arranged on the concentrated water pipeline, the high-pressure pump, the water inlet flowmeter, the concentrated water flowmeter, the pressure transmitter and the high-pressure regulating valve are connected with the PLC controller, and the PLC controls the recovery rate of the system and interlocks protection according to the system recovery rate H and the transmembrane pressure difference K. The application utilizes the method of fuzzy control to control the recovery rate of the system, can eliminate the phenomenon that the high-pressure regulating valve is frequently opened and closed, guarantees the stable operation of the membrane filtration system, and improves the recovery rate and filtration quality of the system.

Description

Technical Field

[0001] This invention relates to the field of membrane filtration technology, specifically to a high-pressure membrane filtration system and a method for controlling and protecting recovery rates. Background Technology

[0002] Membrane filtration is a pressure-driven membrane separation technology, also known as membrane filtration technology. It is an advanced method of water treatment. Depending on the selectivity of the membrane, it can be divided into reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF), and microfiltration (MF).

[0003] System recovery rate is an important indicator for evaluating the efficiency of a membrane filtration system. The control of system recovery rate is closely related to system pressure. Existing high-pressure membrane filtration systems generally regulate system pressure by adjusting the opening of the high-pressure regulating valve, thereby controlling the system recovery rate. Increasing the opening of the high-pressure regulating valve increases the concentrate flow rate, decreases the system pressure, and reduces the system recovery rate; decreasing the opening of the high-pressure regulating valve decreases the concentrate flow rate, increases the system pressure, and increases the system recovery rate.

[0004] Existing high-pressure regulating valves all use needle valves. Due to their small valve diameter and short stroke, the valve opening and closing or regulating speed is too fast, resulting in excessively rapid rises or falls in system pressure during valve regulation. The opening of existing high-pressure regulating valves is generally regulated using PID control. In actual operation, because the pressure rise or fall time in high-pressure systems is relatively slow, the instrument response is sluggish, and real-time pressure feedback is not available. This often leads to frequent opening and closing of the high-pressure regulating valve, causing frequent fluctuations in the pressure and recovery rate of the membrane filtration system. In some cases, the system pressure may even exceed safe limits due to the high-pressure regulating valve closing too quickly, posing a safety risk. Frequent fluctuations in the pressure and recovery rate of the membrane filtration system not only affect the filtration performance and lifespan of the membrane but also reduce the filtration quality and system recovery rate. Therefore, designing a safe, practical, and stable high-pressure membrane filtration system and a recovery rate control and protection method is of great significance. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides a high-pressure membrane filtration system, a recovery rate control and protection method.

[0006] The technical solution adopted in this invention is:

[0007] A high-pressure membrane filtration system includes at least one membrane module, a high-pressure pump, a circulating pump, a raw water pipeline, a concentrate pipeline, and a PLC controller. The high-pressure pump is installed on the raw water pipeline to input filtered raw water into the membrane filtration system. An inlet flow meter for detecting the inlet flow rate is installed at the inlet of the high-pressure pump. A pressure transmitter S1 for detecting the inlet pressure of the membrane module is installed at the inlet of the membrane module, and a pressure transmitter S2 for detecting the concentrate outlet pressure of the membrane module is installed at the outlet of the membrane module. The circulating pump is installed on the concentrate pipeline at the outlet of the membrane module to input the concentrate produced by the membrane module to the next membrane module or the next process step. A high-pressure regulating valve is installed at the concentrate outlet of the membrane filtration system, and a concentrate flow meter for detecting the concentrate outlet flow rate is installed at the outlet of the high-pressure regulating valve. The high-pressure pump, inlet flow meter, concentrate flow meter, pressure transmitter, and high-pressure regulating valve are all connected to the PLC controller. The PLC controls the system recovery rate H based on the system recovery rate and provides interlock protection based on the transmembrane pressure difference K.

[0008] The transmembrane pressure difference K = max(P2 - P1), and the system recovery rate H = (F1 - F2) / F1 × 100%; where...

[0009] P1 is the inlet water pressure value of the membrane module detected by pressure transmitter S1;

[0010] P2 is the membrane module outlet water pressure value detected by pressure transmitter S2;

[0011] F1 is the inlet flow rate of the high-pressure membrane filtration system detected by the inlet flow meter;

[0012] F2 is the concentrate effluent flow rate of the high-pressure membrane filtration system detected by the concentrate flow meter.

[0013] A method for controlling the recovery rate of the above-mentioned high-pressure membrane filtration system includes closing the valve according to the regulating valve closing step when the system recovery rate has a negative deviation and the negative deviation exceeds the allowable deviation range; and opening the valve according to the regulating valve opening step when the system recovery rate has a positive deviation and the positive deviation exceeds the allowable deviation range, until the system recovery rate is within the allowable deviation range, at which point the regulation stops.

[0014] Furthermore, the closing step of the regulating valve includes:

[0015] First, the regulating valve is quickly closed to its initial opening.

[0016] The second step is to quickly close the regulating valve to the initial opening, and then perform the closing action alternately according to the gain value and the pulse time. That is, after the opening of the regulating valve reaches a gain value, a pulse time is executed. After the pulse time ends, the closing action is performed according to the second gain value.

[0017] Third, repeat step two until the system recovery rate is within the allowable deviation range, then stop the shutdown action;

[0018] The initial opening refers to the valve opening of the high-pressure regulating valve when the system pressure is less than 4 bar; the gain value refers to the decrease in valve opening; the pulse time refers to the stop time between two closing actions performed in segments during the closing process of the high-pressure regulating valve.

[0019] Furthermore, the gain value is the percentage decrease in valve opening.

[0020] Furthermore, the step of opening the regulating valve includes:

[0021] The first step is to alternate between the gain value and the pulse time to perform the opening action. That is, after the opening of the regulating valve reaches a certain gain value, a pulse time is executed. After the pulse time ends, the opening action is executed again according to the second gain value.

[0022] The second step is to repeat step one until the regulating valve is opened to its initial opening.

[0023] The third step is to open the regulating valve to its initial opening degree, and then quickly open it until it is fully open.

[0024] The initial opening degree refers to the valve opening degree of the high-pressure regulating valve when the system pressure is less than 4 bar; the gain value refers to the increase in valve opening degree; the pulse time refers to the stop time between two opening actions when the high-pressure regulating valve performs the opening action in segments during the opening process.

[0025] Furthermore, the gain value is the percentage increase in valve opening.

[0026] A protection method for the above-mentioned high-pressure membrane filtration system includes: when any one of the system's high-pressure protection value, flow protection value, membrane flux protection value, or transmembrane pressure difference protection value reaches a set value, opening the valve according to the regulating valve opening procedure to promptly reduce the system operating pressure;

[0027] The high-pressure protection value is set as follows: P2 is greater than or equal to the design pressure × 120%;

[0028] The set value for the flow protection value is: F2 is less than or equal to 50% of the design concentrate flow rate;

[0029] The membrane flux protection value is set as follows: F1-F2) is greater than or equal to (design influent flow rate - design concentrate flow rate) × 120%;

[0030] The set value for the transmembrane pressure difference protection is: K is greater than or equal to the maximum transmembrane pressure difference that the membrane module designed by the system can withstand.

[0031] Furthermore, the valve opening procedure includes:

[0032] Step 1: Step 2 begins after the instrument signal continues to exceed the set response time;

[0033] The second step is to alternate between the gain value and the pulse time to perform the opening action. That is, after the opening of the regulating valve reaches a certain gain value, a pulse time is executed. After the pulse time ends, the opening action is executed again according to the second gain value.

[0034] Third, repeat step one until the regulating valve is opened to its initial opening degree;

[0035] Fourth step: After the regulating valve is opened to the initial opening degree, quickly open it until it is fully open;

[0036] The response time refers to the time it takes for the system instrument signal to remain stable at a certain value; the initial opening refers to the valve opening of the high-pressure regulating valve when the system pressure is less than 4 bar; the gain value refers to the increase in valve opening; the pulse time refers to the stop time between two opening actions performed in segments during the opening process of the high-pressure regulating valve.

[0037] Furthermore, the high-pressure pump is immediately stopped in a chain reaction.

[0038] The beneficial effects of this invention are:

[0039] 1. By setting parameters such as "recovery rate deviation", "gain value", "response time" and "initial opening", the recovery rate of the system can be controlled by using fuzzy control. This can eliminate the phenomenon of frequent opening and closing of the high-pressure regulating valve, ensure the stable operation of the membrane filtration system, improve the system's recovery rate and filtration quality, and at the same time extend the service life of the membrane and the high-pressure regulating valve.

[0040] 2. By setting parameters such as "high pressure protection value", "flow protection value", and "transmembrane differential pressure protection value", the high pressure regulating valve and high pressure pump are interlocked to ensure the safe and stable operation of the high pressure membrane system. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the high-pressure membrane filtration system according to the first embodiment of the present invention. Detailed Implementation

[0042] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0043] In the following embodiments:

[0044] Membrane module inlet water pressure value P1: The membrane module inlet water pressure value detected by pressure transmitter S1.

[0045] Membrane module outlet water pressure value P2: The membrane module outlet water pressure value detected by pressure transmitter S2.

[0046] The transmembrane pressure difference K = max(P2 - P1).

[0047] Valve opening degree D: refers to the degree to which the valve is open, usually expressed as a percentage, with 0 degrees indicating that it is fully closed.

[0048] Initial opening degree D0: refers to the valve opening degree of the high-pressure regulating valve when the system pressure is less than 4 bar.

[0049] Gain value D Z This refers to the increase or decrease in valve opening degree D.

[0050] Inlet flow rate F1: The inlet flow rate of the high-pressure membrane filtration system detected by the inlet flow meter F1.

[0051] Concentrate flow rate F2: The concentrate flow rate of the high-pressure membrane filtration system detected by the concentrate flow meter F2.

[0052] Actual recovery rate H S = (F1-F2) / F1×100%.

[0053] Target recovery rate H M This refers to the system's design recovery rate, which can be adjusted according to actual needs.

[0054] Recovery deviation HP = Actual recovery rate H S -Target recovery rate H M .

[0055] Pulse time S M : This refers to the time between two separate closing or opening actions performed by a high-pressure regulating valve during the closing or opening process.

[0056] Response time: refers to the time it takes for a system instrument signal to remain stable at a certain value.

[0057] The high-pressure protection setting value is P2, which is greater than or equal to the design pressure × 120%. This value can be modified as needed to prevent the risks caused by the membrane system operating under overpressure.

[0058] The flow protection value is set to F2, which is less than or equal to 50% of the design concentrate flow rate. This is used to prevent the risk of overpressure operation of the membrane system and to provide safety redundancy protection for the membrane system.

[0059] The membrane flux protection value is set at (F1-F2) greater than or equal to (design feedwater flow rate - design concentrate flow rate) × 120%, which is used to prevent the risk of membrane module damage due to excessive membrane flux.

[0060] The set value for the transmembrane pressure differential protection is: K is greater than or equal to the maximum transmembrane pressure differential that the membrane module designed for the system can withstand.

[0061] Implementation Method 1

[0062] See Figure 1 This embodiment provides a high-pressure membrane filtration system, including at least one membrane module M1, a high-pressure pump P1, a circulation pump P2, a raw water pipeline, a concentrate pipeline, and a PLC controller. The high-pressure pump P1 is installed on the raw water pipeline to input high-pressure filtered raw water into the membrane filtration system. An inlet flow meter F1 is installed at the inlet end of the high-pressure pump P1 to detect the inlet flow rate. A pressure transmitter S1 is installed at the inlet end of the membrane module M1 to detect the inlet pressure of the membrane module M1. A pressure transmitter S2 is installed at the outlet end of the membrane module M1 to detect the concentrate outlet pressure of the membrane module M1. The circulation pump P2 is installed on the membrane module M1... On the concentrate pipeline at the outlet of module M1, the concentrate produced by membrane module M1 is used to input to the next membrane module M1 or the next process. A high-pressure regulating valve VS1 is installed at the concentrate outlet of the membrane filtration system. A concentrate flow meter F2 is installed at the outlet of the high-pressure regulating valve VS1 to detect the concentrate flow rate. The high-pressure pump P1, the feed flow meter F1, the concentrate flow meter F2, the pressure transmitter S1, the pressure transmitter S2, and the high-pressure regulating valve VS1 are all connected to the PLC controller. The PLC controls the system recovery rate based on the system recovery rate H and provides interlock protection for the system based on the transmembrane pressure difference K.

[0063] The preferred types of influent flow meter F1 and concentrate flow meter F2 are electromagnetic flow meters or rotary flow meters; the pressure transmitters S1 and S2 are static pressure transmitters.

[0064] In this embodiment, two membrane modules M1 are provided. The concentrate from the first membrane module M1 is pumped into the second membrane module M1 through a first high-pressure pump P1, and the concentrate from the second membrane module M1 is pumped into the next process through a second high-pressure pump P1.

[0065] The design parameters and process operating parameters of the high-pressure membrane filtration system described in Example 1 are as follows:

[0066] Target recovery rate H M The acceptable recovery rate is 70%, with a negative deviation of HP. - The allowable positive deviation of HP recovery rate is -5%. + +5%;

[0067] When the valve opening degree D is 90%, it is fully open; the initial valve opening degree D0 is 60%; and the gain value D... Z It is 1%;

[0068] The pulse duration is 1 second, and the response time is 5 seconds.

[0069] The working pressure is 80 bar, and the high pressure protection value is set to: P2 is greater than or equal to 96 bar.

[0070] The set value for the transmembrane differential pressure protection value is set as follows: K is greater than or equal to 10 bar;

[0071] Design influent flow rate F J 10m 3 / h, Design concentrate flow rate F n 3m 3 / h, Flow protection setting: F2 less than or equal to 1.5m 3 / h, membrane flux protection setting value: (F1-F2) greater than or equal to 8.4m 3 / h.

[0072] Implementation Method 2

[0073] The recovery rate control method for the above-mentioned high-pressure membrane filtration system, when PIC detects a negative deviation HP in the system recovery rate. - When the response time of a signal greater than -5% lasts for 5 seconds, the PIC control regulating valve closes according to the following steps:

[0074] First, the regulating valve is quickly closed to its initial opening of 60%;

[0075] The second step is to quickly close the regulating valve to 60% opening, then the PIC controls the regulating valve to slowly close to 59% opening at the first gain value -1%, then stop the closing action for 1 second, and then execute the closing action at the next gain value -1%. In this way, the closing action is executed alternately at gain value -1% and pulse time of 1 second.

[0076] During the control valve closing process, the PIC monitors the system recovery rate in real time until a negative deviation HP in the system recovery rate is detected. - Stop the shutdown action when it is within the permissible range.

[0077] When PIC detects a positive deviation in recovery rate HP + When the response time of a signal greater than 5% is 5 seconds, the PIC-controlled regulating valve opens according to the following steps:

[0078] The first step is to alternate between a gain value of +1% and a pulse time of 1 second to perform the opening action. That is, after the opening of the regulating valve reaches a gain value of +1%, the opening action stops for 1 second, and then the opening action is performed at the second gain value of +1%, until the regulating valve is opened to the initial opening of 60%.

[0079] The third step is to open the regulating valve to 60% of its opening degree, and then quickly open it to 90% of its full opening degree.

[0080] During the opening of the regulating valve, the PIC monitors the system recovery rate in real time until a positive deviation of the system recovery rate from HP is detected.+ Stop opening the device when it is within the permissible range.

[0081] Implementation Method 3

[0082] A protection method for the high-pressure membrane filtration system described in Example 1, wherein when the PIC detects P2 ≥ 96 bar or (F1 - F2) ≥ 8.4 m 3 / h or F2≤1.5m 3 When / h or K≥10bar, open the valve and stop the system operation as follows;

[0083] Step 1: After the high-pressure regulating valve receives the open signal and responds continuously for 5 seconds, proceed to Step 2;

[0084] The second step is to alternate between the gain value +1% and the pulse time of 1 second to perform the opening action. That is, after the opening of the regulating valve reaches a gain value +1%, the opening action stops for 1 second, and then the opening action is performed at the second gain value +1% until the regulating valve is opened to the initial opening of 60%.

[0085] The third step is to open the regulating valve to 60% and then quickly open it to 90% full.

[0086] Implementation Method 4

[0087] Implementation Method 4: When the system detects that P2 ≥ 96 bar, the valve is opened according to the regulating valve opening procedure, and the high-pressure pump P1 is immediately stopped in a chain reaction to reduce the system operating pressure in a timely manner.

[0088] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling the recovery rate of a high-pressure membrane filtration system, characterized in that, The high-pressure membrane filtration system includes at least one membrane module, a high-pressure pump, a circulation pump, a raw water pipeline, a concentrate pipeline, and a PLC controller. The high-pressure pump is located on the raw water pipeline to supply raw water to the high-pressure membrane filtration system. An inlet flow meter is installed at the inlet of the high-pressure pump to detect the inlet flow rate. A pressure transmitter S1 is installed at the inlet of the membrane module to detect the inlet pressure, and a pressure transmitter S2 is installed at the outlet of the membrane module to detect the concentrate outlet pressure. The circulation pump is located on the concentrate pipeline at the membrane module outlet to supply the concentrate produced by the membrane module to the next membrane module or the next process step. A high-pressure regulating valve is installed at the concentrate outlet of the high-pressure membrane filtration system, and a concentrate flow meter is installed at the outlet of the high-pressure regulating valve to detect the concentrate outlet flow rate. The high-pressure pump, inlet flow meter, concentrate flow meter, pressure transmitter, and high-pressure regulating valve are all connected to the PLC controller. The PLC controls the system recovery rate H based on the system recovery rate and provides interlock protection based on the transmembrane pressure difference K. The transmembrane pressure difference K = max(P2-P1), and the system recovery rate H = (F1-F2) / F1×100%; Wherein, P1 is the inlet water pressure of the membrane module detected by pressure transmitter S1; P2 is the outlet water pressure of the membrane module detected by pressure transmitter S2; F1 is the inlet water flow rate of the high-pressure membrane filtration system detected by the inlet water flow meter; and F2 is the concentrate outlet water flow rate of the high-pressure membrane filtration system detected by the concentrate flow meter. When the system recovery rate shows a negative deviation and the negative deviation exceeds the allowable deviation range, close the valve according to the valve closing procedure; when the system recovery rate shows a positive deviation and the positive deviation exceeds the allowable deviation range, open the valve according to the valve opening procedure until the system recovery rate is within the allowable deviation range, then stop adjusting.

2. The recovery rate control method of the high-pressure membrane filtration system according to claim 1, characterized in that, The closing step of the regulating valve includes: First, the regulating valve is quickly closed to its initial opening. The second step is to quickly close the regulating valve to the initial opening, and then perform the closing action alternately according to the gain value and the pulse time. That is, after the opening of the regulating valve reaches a gain value, a pulse time is executed. After the pulse time ends, the closing action is performed according to the second gain value. Third, repeat step two until the system recovery rate is within the allowable deviation range, then stop the closing action; the initial opening degree refers to the valve opening degree of the high-pressure regulating valve when the system pressure is less than 4 bar; the gain value refers to the decrease in valve opening degree; the pulse time refers to the stop time between two closing actions performed in segments during the closing process of the high-pressure regulating valve.

3. The recovery rate control method of the high-pressure membrane filtration system according to claim 2, characterized in that, The gain value is the percentage decrease in valve opening.

4. The recovery rate control method of the high-pressure membrane filtration system according to claim 1, characterized in that, The steps for opening the regulating valve include: The first step is to alternate between the gain value and the pulse time to perform the opening action. That is, after the opening of the regulating valve reaches a certain gain value, a pulse time is executed. After the pulse time ends, the opening action is executed again according to the second gain value. The second step is to repeat step one until the regulating valve is opened to its initial opening. The third step is to open the regulating valve to the initial opening degree, and then quickly open it until it is fully open; the initial opening degree refers to the valve opening degree of the high-pressure regulating valve when the system pressure is less than 4 bar; the gain value refers to the increase in the valve opening degree; the pulse time refers to the stop time between two opening actions when the high-pressure regulating valve performs the opening action in segments during the opening process.

5. The recovery rate control method of the high-pressure membrane filtration system according to claim 4, characterized in that, The gain value is the percentage increase in valve opening.

6. A protection method for a high-pressure membrane filtration system, characterized in that, The high-pressure membrane filtration system includes at least one membrane module, a high-pressure pump, a circulation pump, a raw water pipeline, a concentrate pipeline, and a PLC controller. The high-pressure pump is located on the raw water pipeline to supply raw water to the high-pressure membrane filtration system. An inlet flow meter is installed at the inlet of the high-pressure pump to detect the inlet flow rate. A pressure transmitter S1 is installed at the inlet of the membrane module to detect the inlet pressure, and a pressure transmitter S2 is installed at the outlet of the membrane module to detect the concentrate outlet pressure. The circulation pump is located on the concentrate pipeline at the membrane module outlet to supply the concentrate produced by the membrane module to the next membrane module or the next process step. A high-pressure regulating valve is installed at the concentrate outlet of the high-pressure membrane filtration system, and a concentrate flow meter is installed at the outlet of the high-pressure regulating valve to detect the concentrate outlet flow rate. The high-pressure pump, inlet flow meter, concentrate flow meter, pressure transmitter, and high-pressure regulating valve are all connected to the PLC controller. The PLC controls the system recovery rate H based on the system recovery rate and provides interlock protection based on the transmembrane pressure difference K. The transmembrane pressure difference K = max(P2-P1), and the system recovery rate H = (F1-F2) / F1×100%; Wherein, P1 is the inlet water pressure of the membrane module detected by pressure transmitter S1; P2 is the outlet water pressure of the membrane module detected by pressure transmitter S2; F1 is the inlet water flow rate of the high-pressure membrane filtration system detected by the inlet water flow meter; and F2 is the concentrate outlet water flow rate of the high-pressure membrane filtration system detected by the concentrate flow meter. The protection methods include: when any one of the system's high pressure protection value, flow protection value, membrane flux protection value, or transmembrane pressure differential protection value reaches a set value, the valve is opened according to the regulating valve opening procedure to promptly reduce the system operating pressure; the set value of the high pressure protection value is: P2 is greater than or equal to the design pressure × 120%; the set value of the flow protection value is: F2 is less than or equal to the design concentrate flow rate × 50%; the set value of the membrane flux protection value is: (F1-F2) is greater than or equal to (design feedwater flow rate - design concentrate flow rate) × 120%; the set value of the transmembrane pressure differential protection value is: K is greater than or equal to the maximum transmembrane pressure differential value that the membrane module designed by the system can withstand.

7. The protection method according to claim 6, characterized in that, The steps for opening the regulating valve include: Step 1: Step 2 begins after the instrument signal continues to exceed the set response time; The second step is to alternate between the gain value and the pulse time to perform the opening action. That is, after the opening of the regulating valve reaches a certain gain value, a pulse time is executed. After the pulse time ends, the opening action is executed again according to the second gain value. Third, repeat step one until the regulating valve opens to its initial opening degree; fourth, after the regulating valve opens to its initial opening degree, quickly open it until it is fully open; the response time refers to the time it takes for the system instrument signal to remain stable at a certain value; the initial opening degree refers to the valve opening degree of the high-pressure regulating valve when the system pressure is less than 4 bar; the gain value refers to the increase in valve opening degree; the pulse time refers to the stop time between two opening actions when the high-pressure regulating valve performs the opening action in segments during the opening process.

8. The protection method according to claim 6, characterized in that, And execute the step of immediately stopping the high-pressure pump in a chain reaction.

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