CN1286544C - On-line defect diagnosis method for rolling type reverse osmosis membrane device - Google Patents

Abstract

The present invention relates to an on-line defect diagnosing method for rolled reverse osmosis membrane devices. A method of residence time distribution is adopted to diagnose fluid defects of a rolled reverse osmosis membrane device. NaCl is used as tracer agents and is injected into an inlet of a running rolled reverse osmosis membrane device to be detected through high voltage pulse injecting technique, and then, a conductivity meter is utilized at an outlet of the membrane device to detect a curve of the NaCl concentration varying with the time. A computer is utilized to carry out value conversion according to the curve, defect characteristic parameters D/uL of the membrane device can be obtained, and then, the defect information of the membrane device can be obtained. The present invention has the advantages of simple and convenient diagnosis programs and low cost of devices and can rapidly diagnose the flow pattern in a rolled reverse osmosis membrane device and the deflection degree of ideal piston flow to determine the defects of fluid flows to provide references for the optimization of membrane device design.

Description

On-line Diagnosis Method for Defects of Roll-type Reverse Osmosis Membrane Unit

technical field

The invention relates to an online diagnosis method for defects of a roll-type reverse osmosis membrane device, which uses a residence time distribution technology to diagnose fluid flow defects in the membrane device, detect fouling conditions, and improve the overall operating performance of the roll-type reverse osmosis membrane device. Membrane design provides a basis. The invention belongs to the technical field of membrane separation in chemical engineering science.

Background technique

Reverse osmosis (RO) water treatment technology has outstanding advantages such as operation at room temperature, low energy consumption, compact equipment structure, and economical operating costs. It has become the most economical seawater and brackish water desalination technology, and is widely used in ultrapure water Preparation, desalination and purification of high-pressure boiler water in power plants, industrial wastewater treatment, food and beverage processing, and concentration, separation and purification processes in various chemical fields will become one of the leading high-tech in the 21st century.

The coil type reverse osmosis membrane device has become the most used membrane device due to its good performance indicators, high membrane packing density, high desalination rate and long life. Although the roll-type reverse osmosis membrane device has a high comprehensive desalination performance, there is still a lot of room for development in reducing costs. Studies have shown that there are still many defects in the existing roll-type reverse osmosis membrane device, such as dead volume in operation, uneven distribution of fluid flow, fouling is easy to occur at the contact point between the membrane and the separator, and the study also shows that there is mass transfer The phenomenon of the maximum value of the coefficient. The existence of these defects greatly reduces the overall performance of the membrane device.

One of the main goals of the design of the roll-type reverse osmosis membrane device is to make the flow distribution of the feed water in the channel uniform. The existing design of the reverse osmosis system and the critical limit conditions of membrane fouling are based on the assumption that the fluid distribution in the membrane device is uniform. Yes, there are no defects such as dead volume. However, the above-mentioned defects exist in the membrane, thereby reducing the performance of the membrane. Relevant studies have shown that the uneven flow of this fluid can cause a great negative impact. Research on the scaling of CaSO ₄ and CaCO ₃ in roll-type reverse osmosis membranes has shown that the most prone to scaling is the surface of the membrane and the spacer. Fouling of the membrane at the point of contact, even when the bulk solution is not saturated. Therefore, the development of on-line diagnosis technology for the defects of the roll-type reverse osmosis membrane device will provide a basis for optimizing and improving the comprehensive performance of the entire membrane device, and it is of great significance to ensure the normal operation of the system.

Contents of the invention

The purpose of the present invention is to address the deficiencies in the prior art, to provide an online diagnosis method for the defects of the coiled reverse osmosis membrane device, to diagnose the fluid defects existing in the operation of the new and old coiled reverse osmosis membrane devices, to detect the fouling condition, and to timely Adjust the operating parameters to ensure the normal operation of the system; at the same time optimize and improve the design of the membrane.

In order to achieve such a purpose, in the technical solution of the present invention, the method of residence time distribution is adopted to diagnose the fluid defect of the roll-type reverse osmosis membrane device, NaCl is used as a tracer, and it is injected into the operation through high-pressure pulse injection technology. The inlet of the roll-type reverse osmosis membrane device to be tested, and then use the conductivity meter to detect the change curve of NaCl concentration with time at the outlet of the membrane device, and use the computer to perform numerical transformation according to the curve to obtain the membrane defect characterization parameter D/uL, In this way, the information of membrane defects can be obtained.

The specific implementation steps of the inventive method are as follows:

1. Install the tracer NaCl solution injection container and injection valve at the inlet of the roll-type reverse osmosis membrane device, and connect it with a 60bar high-pressure air bottle; install a high-speed response conductivity meter at the outlet of the roll-type reverse osmosis membrane device and communicate with the computer connected.

2. Adjust the water inlet pressure and water flow rate of the membrane device to stabilize to the set value, and use the pulse mode to conduct the residence time distribution test. Open the injection valve for 1 second, and use 60bar high-pressure air to inject the NaCl in the injection container into the roll-type reverse osmosis membrane device. The NaCl concentration used is 5g/L-300g/L. The tracer outlet concentration value corresponding to every 0.1 second is collected at the outlet of the membrane device, and the residence time distribution test is carried out. During the test, the temperature was controlled at 28-33°C. Then keep the inlet water pressure constant, change the inlet water flow in order from small to large, and conduct a residence time distribution test for each value of the inlet water flow.

3. Change the inlet water pressure to another set value, and keep the pressure constant, then change the inlet water flow in the order of small to large, and conduct a residence time distribution test for each inlet water flow value. The test is repeated in this way until the residence time distribution of different influent flows corresponding to each set influent pressure is determined.

4. The numerical conversion of the residence time distribution data collected by the test to the axial diffusion model can be used to obtain the characterization parameters of the membrane defect. In the present invention, the dispersion number D/uL is used to characterize the internal flow pattern of the coiled reverse osmosis membrane device, and the defect of the coiled reverse osmosis membrane device is determined according to the deviation degree between the value of D/uL and the ideal plug flow, and the online diagnosis is completed. The smaller the value of D/uL, the closer the flow pattern in the membrane is to ideal plug flow, the better the performance and the fewer defects; on the contrary, the larger the value of D/uL, the worse the performance of the membrane and the more defects.

The diagnosis program adopted by the method of the invention is simple and convenient, and the equipment cost is low, and the degree of deviation between the flow pattern in the roll-type reverse osmosis membrane device and the ideal plug flow can be diagnosed quickly, so as to determine the fluid flow defect. Wide range of applications, for example, it can be used for defect diagnosis of membrane devices such as new membrane devices, old membrane devices, and fouled membrane devices; it is also suitable for small membrane devices such as 2.5 inches for laboratory use and large membrane devices for industrial use such as 8 inches Device defect diagnosis. The invention provides a reliable basis for the safe operation of the roll-type reverse osmosis system widely used in the current industry and the optimized design of the membrane device.

Description of drawings

Fig. 1 is the processing result of embodiment 1-2 of the present invention.

Fig. 2 is the processing result of embodiment 3-5 of the present invention.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Example 1

In this example, a diagnostic test is performed on a new SWC1 roll-type reverse osmosis membrane device with a diameter of 8 inches from Hyde Energy.

Install the tracer NaCl solution injection container and injection valve at the inlet of the roll-type reverse osmosis membrane device, and connect it to a 60bar high-pressure air bottle; install a high-speed response conductivity meter at the outlet of the roll-type reverse osmosis membrane device and connect it to the computer.

Adjust the inlet water pressure and the inlet water flow rate of the membrane device to stabilize to the set value. When performing the residence time distribution test, the pulse mode is used. Open the valve for 1 second, and use 60bar high-pressure air to inject the NaCl injected into the container into the roll-type reverse osmosis membrane device. The NaCl concentration used was 300 g/L. The tracer outlet concentration value corresponding to every 0.1 second is collected at the outlet of the membrane device, and the residence time distribution test is carried out. Keep the inlet water pressure constant, change the inlet water flow in the order of small to large, and conduct a residence time distribution test for each value of the inlet water flow.

Change the water inlet pressure to another set value (the test pressure of this embodiment is 10bar, 20bar, 30bar respectively), and keep the pressure constant, and then change the water inlet flow in order from small to large (the test flow of this embodiment is 1 -10m ³ /h, the corresponding Reynolds number is 50-370), and for each influent flow value, the residence time test is carried out. The test is repeated in this way until the residence time distribution of different influent flows corresponding to each set influent pressure is determined. The test temperature is controlled at 28-33°C.

The residence time distribution data collected in the test is transformed into the axial diffusion model to obtain the characteristic parameter D/uL of the membrane defect.

The results are shown in the lower set of data points in Figure 1. It can be seen from the figure that the dispersion number D/uL decreases when the influent flow is increased, indicating that the flow pattern changes to a direction close to the ideal plug flow and the defects decrease. That is, the performance of the new industrial-scale roll-type reverse osmosis membrane device increases with the increase of the feed water flow rate. At the same time, it can be seen from the figure that when the pressure increases from 10bar to 30bar, the dispersion number does not change, indicating that the pressure change has no effect on the flow channel geometry in the roll-type reverse osmosis membrane device, that is, the pressure change has no effect on the new roll reverse osmosis membrane device. The change of the flow pattern in the reverse osmosis membrane device has no effect.

This example shows that the residence time distribution technology can conveniently and accurately diagnose the change of the flow pattern with the influent flow rate in the industrial-scale roll-type reverse osmosis membrane device, detect the change of the flow pattern defect, and detect the influence of the pressure change on the flow pattern defect. New industrial-scale coiled reverse osmosis membrane devices (D/uL=0.045-0.065) have significant deviations from ideal plug flow (D/uL<0.001), and there are obvious fluid flow defects.

Example 2

In this example, a diagnostic test is performed on an old 8-inch-diameter SWC1 roll-type reverse osmosis membrane device of Hyde Energy Company.

Install the tracer NaCl solution injection container and injection valve at the inlet of the roll-type reverse osmosis membrane device, and connect it to a 60bar high-pressure air bottle; install a high-speed response conductivity meter at the outlet of the roll-type reverse osmosis membrane device and connect it to the computer.

Adjust the inlet water pressure and the inlet water flow rate of the membrane device to stabilize to the set value. When performing the residence time distribution test, the pulse mode is used. Open the valve for 1 second, and use 60bar high-pressure air to inject the NaCl injected into the container into the roll-type reverse osmosis membrane device. The NaCl concentration used was 300 g/L. The tracer outlet concentration value corresponding to every 0.1 second is collected at the outlet of the membrane device, and the residence time distribution test is carried out. Keep the pressure constant, change the influent flow rate from small to large, and conduct a residence time distribution test for each value of the influent flow rate.

Change the inlet water pressure to another set value (the test pressure of this embodiment is 10bar, 20bar, 30bar, 40bar respectively), and keep the pressure constant, and then change the inlet water flow in order from small to large (this embodiment tests the flow rate is 1-10m ³ /h, and the corresponding Reynolds number is 50-370), and for each influent flow value, the residence time test is carried out. The test is repeated in this way until the residence time distribution of different influent flows corresponding to each set influent pressure is determined. The test temperature is controlled at 28-33°C.

The residence time distribution data collected in the test is transformed into the axial diffusion model to obtain the characteristic parameter D/uL of the membrane defect.

The results are shown in the upper set of data points in Figure 1. It can be seen from the figure that the dispersion number D/uL decreases when the influent flow is increased, indicating that the flow pattern changes to a direction close to the ideal plug flow and the defects decrease. That is, the performance of the old industrial-scale roll-type reverse osmosis membrane device increases with the increase of the influent flow rate. At the same time, it can be seen from the figure that when the pressure increases from 10bar to 40bar, the dispersion number does not change, indicating that the pressure change has no effect on the flow channel geometry in the roll-type reverse osmosis membrane device, that is, the pressure change has no effect on the new roll reverse osmosis membrane device. The change of the flow pattern in the reverse osmosis membrane device has no effect. Figure 1 also shows that compared with the data points in the new roll-type reverse osmosis membrane device (embodiment 1), the dispersion number D/uL of the old membrane device increases when other conditions are the same. This shows that the fluid flow defect in the old membrane device is larger than that of the new membrane device.

This example shows that the residence time distribution technology can conveniently and accurately diagnose the change of the flow pattern with the influent flow rate in the industrial-scale old roll-type reverse osmosis membrane device, detect the change of the flow pattern defect, and detect the influence of the pressure change on the flow pattern defect. The old industrial-scale roll-type reverse osmosis membrane device (D/uL=0.09-0.12) has a major deviation from the ideal plug flow (D/uL<0.001), and it is also larger than the new industrial-scale roll-type reverse osmosis membrane device (D/uL= 0.045-0.065) have greater fluid flow defects.

Example 3

In this example, a diagnostic test is performed on a new 2.5-inch TW30-2514 roll-type reverse osmosis membrane device from Dow Company.

Install the tracer NaCl solution injection container and injection valve at the inlet of the roll-type reverse osmosis membrane device, and connect it to a 60bar high-pressure air bottle; install a high-speed response conductivity meter at the outlet of the roll-type reverse osmosis membrane device and connect it to the computer.

When performing the residence time distribution test, the pulse mode is used. Open the valve for 1 second, and use 60bar high-pressure air to inject the NaCl injected into the container into the roll-type reverse osmosis membrane device. The NaCl concentration used was 20 g/L. The tracer outlet concentration value corresponding to every 0.1 second is collected at the outlet of the membrane device, and the residence time distribution test is carried out.

Adjust the inlet water pressure of the membrane device to stabilize at a set value (20bar), and then change the inlet water flow rate from small to large (the flow rate is 200-950L/h), and the corresponding Reynolds number changes to 50-220. Water flow values, were tested for residence time distribution.

During the test, the temperature was controlled at 28-33°C.

The residence time distribution data collected in the test is transformed into the axial diffusion model to obtain the characteristic parameter D/uL of the membrane defect.

The results are shown in the bottom set of data points in Figure 2. It can be seen from the figure that the dispersion number D/uL decreases when the influent flow is increased, indicating that the flow pattern changes to a direction close to the ideal plug flow and the defects decrease. That is, the performance of the new roll-type reverse osmosis membrane device increases with the increase of the feed water flow.

This example shows that the residence time distribution technology can conveniently and accurately diagnose the change of the flow pattern with the influent flow rate in the laboratory-scale roll-type reverse osmosis membrane device, and detect the change of the flow pattern defect. New laboratory-scale coiled reverse osmosis membrane devices (D/uL=0.012-0.04) have significant deviations from ideal plug flow (D/uL<0.001), and there are obvious fluid flow defects.

Example 4

In this example, a new fouled 2.5-inch Dow TW30-2514 spiral reverse osmosis membrane device is used for diagnostic testing. This fouled membrane was known to drop the permeate flow by 14%.

Install the tracer NaCl solution injection container and injection valve at the inlet of the roll-type reverse osmosis membrane device, and connect it to a 60bar high-pressure air bottle; install a high-speed response conductivity meter at the outlet of the roll-type reverse osmosis membrane device and connect it to the computer.

When performing a dwell time diagnostic test, it is performed in pulse mode. Open the valve for 1 second, and use 60bar high-pressure air to inject the NaCl injected into the container into the roll-type reverse osmosis membrane device. The NaCl concentration used was 20 g/L. The tracer outlet concentration value corresponding to every 0.1 second is collected at the outlet of the membrane device, and the residence time distribution test is carried out.

Adjust the inlet water pressure of the membrane device to stabilize at a set value (20bar), and then change the inlet water flow rate from small to large (the flow rate is 200-950L/h), and the corresponding Reynolds number changes to 50-220. Water flow values, were tested for residence time distribution.

During the test, the temperature was controlled at 28-33°C.

The residence time distribution data collected in the test is transformed into the axial diffusion model to obtain the characteristic parameter D/uL of the membrane defect.

The results are shown in the middle set of data points in Figure 2. It can be seen from the figure that the dispersion number D/uL decreases when the influent flow is increased, indicating that the flow pattern changes to a direction close to the ideal plug flow and the defects decrease. That is, the performance of the scaled roll-type reverse osmosis membrane device increases with the increase of the feed water flow rate.

This example shows that the residence time distribution technology can conveniently and accurately diagnose the change of the flow pattern with the influent flow rate in the fouling coil type reverse osmosis membrane device, and detect the change of the flow pattern defect. The laboratory-scale roll-type reverse osmosis membrane device (D/uL=0.025-0.045) with a 14% scaling reduction in permeate has a significant deviation from the ideal plug flow (D/uL<0.001), and there are obvious fluid flow defects. In conjunction with Example 3, it can be seen that the D/uL value of the scaled membrane device is larger than that of the non-fouled roll-type reverse osmosis membrane device (D/uL=0.012-0.04), that is, there is a larger fluid volume in the fouled membrane device flow defect.

Example 5

In this example, a new fouled 2.5-inch Dow TW30-2514 spiral reverse osmosis membrane device is used for diagnostic testing. This fouled membrane was known to drop the permeate flow by 36%.

Install the tracer NaCl solution injection container and injection valve at the inlet of the roll-type reverse osmosis membrane device, and connect it to a 60bar high-pressure air bottle; install a high-speed response conductivity meter at the outlet of the roll-type reverse osmosis membrane device and connect it to the computer.

When performing the residence time distribution test, the pulse mode is used. Open the valve for 1 second, and use 60bar high-pressure air to inject the NaCl injected into the container into the roll-type reverse osmosis membrane device. The NaCl concentration used was 20 g/L. The tracer outlet concentration value corresponding to every 0.1 second is collected at the outlet of the membrane device, and the residence time distribution test is carried out.

Adjust the inlet water pressure of the membrane device to stabilize at a set value (20bar), and then change the inlet water flow rate from small to large (the flow rate is 200-950L/h), and the corresponding Reynolds number changes to 50-220. Water flow values, were tested for residence time distribution.

During the test, the temperature was controlled at 28-33°C.

The residence time distribution data collected in the test is transformed into the axial diffusion model to obtain the characteristic parameter D/uL of the membrane defect.

The results are shown in the top set of data points in Figure 2. It can be seen from the figure that the dispersion number D/uL decreases when the influent flow is increased, indicating that the flow pattern changes to a direction close to the ideal plug flow and the defects decrease. That is, the performance of the scaled roll-type reverse osmosis membrane device increases with the increase of the feed water flow rate.

This example shows again that the residence time distribution technique can conveniently and accurately diagnose the change of the flow pattern with the influent flow rate in the fouled coiled reverse osmosis membrane device, and detect the change of the flow pattern defect. Permeate drops 36% Fouling lab-scale roll-type reverse osmosis membrane device (D/uL=0.036-0.056) has a significant deviation from ideal plug flow (D/uL<0.001), and there are obvious fluid flow defects . In conjunction with Examples 3 and 4, it can be seen that the fouling membrane device has larger fluid flow defects than the non-scaling roll type reverse osmosis membrane device (D/uL=0.012-0.04); and the permeate drops by 14% scaling (D/uL=0.025-0.045) compared with the diagnosis, the amount of fouling increased by 36% in permeate, and its D/uL also increased, that is, the defect of flow pattern also increased with the amount of fouling.

Claims (1)

1, a kind of inline diagnosis method of rolling type reverse osmosis membrane device defective is characterized in that comprising the steps:

1) the injection container of tracer NaCl solution is installed and is injected valve at the rolling type reverse osmosis membrane device entrance point, and link to each other, high-speed response conductivity gauge and continuous with computer is installed in the rolling type reverse osmosis membrane device exit with the high pressure air bottle of 60bar;

2) regulate the stable extremely setting value of film device intake pressure and flow of inlet water, adopt pulse mode to carry out time of staying distribution tests, open and inject 1 second of valve, utilize the pressure-air of 60bar will inject the NaCl injection rolling type reverse osmosis membrane device of container, used NaCl concentration is 5g/L-300g/L; Gather per 0.1 second pairing tracer exit concentration value in film device exit, carry out time of staying distribution tests, temperature is controlled at 28-33 ℃ during test; Keep intake pressure constant then, press from little extremely big order change flow of inlet water, and, all carry out time of staying distribution tests each feed water flow value;

3) change intake pressure to another setting value, and it is constant to keep-up pressure, press again from little extremely big order change flow of inlet water, and each feed water flow value is carried out time of staying distribution tests, set intake pressure time of staying distribution of the different flow of inlet water of correspondence down until having measured each;

4) will test the time of staying distributed data that is collected and carry out the axial dispersion model numerical transformation, obtain the characterization parameter of film device defective, D/uL is counted in the dispersion that promptly characterizes flow pattern in the rolling type reverse osmosis membrane device, according to the numerical value of D/uL and the departure degree of desirable piston flow, determine the defective of rolling type reverse osmosis membrane device, finish inline diagnosis.