A method for establishing a model to predict the service life of porous filter membranes; a method for predicting the service life of porous filter membranes.

Abstract

This invention belongs to the field of filter membrane technology, specifically relating to a method for establishing a model to predict the service life of porous filter membranes, and a method for predicting the service life of porous filter membranes. This invention provides a method for establishing a model to predict the service life of porous filter membranes, using the length change rate and porosity change rate as sensitive parameters for predicting service life. Based on the time-temperature equivalence principle, a time-temperature model is fitted. This invention calculates the aging time at a specific temperature using the established time-temperature model, as the predicted service life of the porous filter membrane.

Description

Technical Field

[0001] This invention belongs to the field of filter membrane technology, specifically relating to a method for establishing a model for predicting the service life of porous filter membranes and a method for predicting the service life of porous filter membranes. Background Technology

[0002] Membrane distillation is a technology that uses porous membranes to purify and reduce the volume of wastewater, especially radioactive wastewater, by allowing only volatile components such as water vapor to pass through the membrane pores. Polytetrafluoroethylene (PTFE) possesses high chemical and thermal stability, can withstand high and low temperatures, and is virtually insoluble in any strong acids, strong alkalis, and strong oxidizing agents, making it a suitable material for preparing porous membranes. In practical applications, because porous membranes operate in high-temperature environments for extended periods, they require a long service life resistant to high temperatures.

[0003] Traditional high-temperature life estimation of materials is generally based on the principle of "time-temperature equivalence," which estimates the life at the operating temperature by estimating the weight change corresponding to accelerated aging at different high temperatures. For example, Shen Shizhao (Shen Shizhao, Tao Zhaozeng, Guo Chengrui, et al. Study on long-cycle life of aerospace wires based on thermal decomposition kinetics [J]. Optical Fiber and Cable and its Application Technology, 2020(2):6) started from the theory of thermal decomposition kinetics, used the Kissinger maximum weight loss rate method and the Ozawa et al. weight loss percentage method to calculate the decomposition activation energy of polytetrafluoroethylene, and based on the principle of "time-temperature equivalence," estimated that the maximum operating temperature of polytetrafluoroethylene is 250℃, and the life at the operating temperature of 250℃ is 2.33 years.

[0004] However, porous filter membranes primarily utilize their tiny pores and hydrophobic properties to allow gas to pass through while preventing water penetration, making them ideal for membrane distillation to purify wastewater. Their pore structure is crucial to their successful application. Therefore, the traditional method of estimating lifespan based on weight changes is not applicable to porous filter membranes. Furthermore, there are no reports in the current technology regarding the prediction of the lifespan of porous filter membranes. Summary of the Invention

[0005] The purpose of this invention is to provide a method for establishing a model to predict the service life of porous filter membranes, and a method for predicting the service life of porous filter membranes. The model established by the method provided by this invention can predict the service life of porous filter membranes.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for establishing a model to predict the service life of porous filter membranes, comprising the following steps:

[0008] (1) Set n temperature values ​​T1 to T2 within a range below the melting point of the porous filter membrane. nAging tests were conducted at the set temperature values, and samples were periodically taken to test the length change rate and porosity change rate of the porous filter membrane; n≥3;

[0009] (2) Using a length change rate of no more than 10% at each temperature as the range, different length change rates are selected within the range to obtain the temperature value T for each length change rate. n The corresponding aging time t n ; with the aging time t n The logarithm of the value is on the ordinate, and the temperature value T is on the ordinate. n Using the reciprocal of the x-axis as the horizontal axis, we fit the time-temperature model for each rate of change of length: logt n =A+B / T n ;

[0010] (3) Taking a porosity change rate of no more than 10% at each temperature as the range, different porosity change rates are selected within the range to obtain the temperature value T for each porosity change rate. n 'Corresponding aging time t n ';With the aging time t n The logarithm of ' is the ordinate, and the temperature value T is the ordinate. n Using the reciprocal of ' as the x-axis, we fit the time-temperature model for each porosity change rate: logt n =A'+B' / T n ';

[0011] There is no time order restriction for steps (2) and (3).

[0012] Preferably, in step (1), the maximum value T among the n set temperature values ​​is... max and the melting point T of the porous filter membrane 熔点 Satisfy: T max <T 熔点 -30℃.

[0013] Preferably, the value range in step (2) is 5% to 10% of the length change rate.

[0014] Preferably, the value range in step (3) is 5% to 10% of the porosity change rate.

[0015] This invention also provides a method for estimating the service life of a porous filter membrane, comprising the following steps:

[0016] a. Substitute the service environment temperature T0 of the object under test into the time-temperature model obtained by the method described above for each length change rate, and calculate the aging time for each length change rate. Take the minimum value as the aging time t determined by the length change rate. c ;

[0017] b. Substitute the service environment temperature T0 of the object under test into the time-temperature model for each porosity change rate obtained by the method described above, and calculate the aging time for each porosity change rate. Take the minimum value as the aging time t determined by the porosity change rate. k ;

[0018] c. Comparison of t c and t k The smaller value is used as the estimated service life of the porous filter membrane at the service environment temperature T0.

[0019] There is no time order requirement for steps a and b.

[0020] This invention provides a method for establishing a model to predict the service life of porous filter membranes, comprising the following steps: (1) setting n temperature values ​​T1 to T2 within a range below the melting point of the porous filter membrane. n Aging tests were conducted at the set temperature values, and samples were taken periodically to test the length change rate and porosity change rate of the porous filter membrane; n≥3; (2) Taking the length change rate at each temperature as the range, different length change rates were selected within the range to obtain the temperature value T at each length change rate. n The corresponding aging time t n ; with the aging time t n The logarithm of the value is on the ordinate, and the temperature value T is on the ordinate. n Using the reciprocal of the x-axis as the horizontal axis, we fit the time-temperature model for each rate of change of length: logt n =A+B / T n (3) Taking a porosity change rate of no more than 10% at each temperature as the range, different porosity change rates are selected within the range to obtain the temperature value T for each porosity change rate. n 'Corresponding aging time t n ';With the aging time t n The logarithm of ' is the ordinate, and the temperature value T is the ordinate. n Using the reciprocal of ' as the x-axis, we fit the time-temperature model for each porosity change rate: logt n =A'+B' / T nSteps (2) and (3) are not restricted by time order. This invention uses the length change rate and porosity change rate as sensitive parameters for estimating the service life of porous filter membranes, and fits a time-temperature model based on the time-temperature equivalence principle. This invention also provides a method for estimating the service life of porous filter membranes. The aging time at a specific temperature is calculated using the established model, and this can be used as the estimated service life of the porous filter membrane. Attached Figure Description

[0021] Figure 1 The graph shows the length change rate versus time obtained after aging tests on the porous polytetrafluoroethylene tubular membrane in Example 1.

[0022] Figure 2 The graph shows the change rate of porosity over time after an aging test of the porous polytetrafluoroethylene tubular membrane in Example 1.

[0023] Figure 3 The equation for the time-temperature relationship under the rate of change of length obtained in Example 1 is shown.

[0024] Figure 4 The equation representing the time-temperature relationship linear equation obtained by fitting the porosity change rate in Example 1 is shown. Detailed Implementation

[0025] This invention provides a method for establishing a model to predict the service life of porous filter membranes, comprising the following steps:

[0026] (1) Set n temperature values ​​T1 to T2 within a range below the melting point of the porous filter membrane. n Aging tests were conducted at the set temperature values, and samples were periodically taken to test the length change rate and porosity change rate of the porous filter membrane; n≥3;

[0027] (2) Using a length change rate of no more than 10% at each temperature as the range, different length change rates are selected within the range to obtain the temperature value T for each length change rate. n The corresponding aging time t n ; with the aging time t n The logarithm of the value is on the ordinate, and the temperature value T is on the ordinate. n Using the reciprocal of the x-axis as the horizontal axis, we fit the time-temperature model for each rate of change of length: logt n =A+B / T n ;

[0028] (3) Taking a porosity change rate of no more than 10% at each temperature as the range, different porosity change rates are selected within the range to obtain the temperature value T for each porosity change rate. n'Corresponding aging time t n ';With the aging time t n The logarithm of ' is the ordinate, and the temperature value T is the ordinate. n Using the reciprocal of ' as the x-axis, we fit the time-temperature model for each porosity change rate: logt n =A'+B' / T n ';

[0029] There is no time order restriction for steps (2) and (3).

[0030] This invention sets n temperature values ​​T1 to T2 within a range below the melting point of the porous filter membrane. n Aging tests were conducted at the set temperature values, and samples were taken periodically to test the length change rate and porosity change rate of the porous filter membrane; n≥3.

[0031] This invention does not have any special requirements regarding the type of porous filter membrane; any type of porous filter membrane can be used. In a specific embodiment of this invention, the porous filter membrane is preferably a porous polytetrafluoroethylene tubular membrane.

[0032] In this invention, the maximum value T among the n set temperature values ​​is... max and the melting point T of the porous filter membrane 熔点 Preferred condition: T max <T 熔点 -30℃.

[0033] In this invention, n is preferably ≥3.

[0034] The present invention does not impose any special limitations on the process of the aging test, and any process known to those skilled in the art can be used.

[0035] This invention does not specify the interval and total time for the periodic sampling tests; any method well-known to those skilled in the art can be used. In a specific embodiment of this invention, the interval for the periodic sampling tests is 24 hours, and the total time is 288 hours.

[0036] After the periodic sampling test is completed, the present invention uses a length change rate of no more than 10% at each temperature as the value range, selects different length change rates within the value range, and obtains the temperature value T at each length change rate. n The corresponding aging time t n ; with the aging time t n The logarithm of the value is on the ordinate, and the temperature value T is on the ordinate. n Using the reciprocal of the x-axis as the horizontal axis, we fit the time-temperature model for each rate of change of length: logt n =A+B / T n .

[0037] In this invention, the value range is preferably 5% to 10%.

[0038] After the periodic sampling test is completed, the present invention uses a porosity change rate of no more than 10% at each temperature as the value range, selects different porosity change rates within the value range, and obtains the temperature value T at each porosity change rate. n 'Corresponding aging time t n ';With the aging time t n The logarithm of ' is the ordinate, and the temperature value T is the ordinate. n Using the reciprocal of ' as the x-axis, we fit the time-temperature model for each porosity change rate: logt n =A'+B' / T n '.

[0039] In this invention, the value range is preferably 5% to 10%.

[0040] In this invention, there is no time order restriction for steps (2) and (3).

[0041] This invention also provides a method for estimating the service life of a porous filter membrane, comprising the following steps:

[0042] a. Substitute the service environment temperature T0 of the object under test into the time-temperature model obtained by the method described above for each length change rate, and calculate the aging time for each length change rate. Take the minimum value as the aging time t determined by the length change rate. c ;

[0043] b. Substitute the service environment temperature T0 of the object under test into the time-temperature model for each porosity change rate obtained by the method described above, and calculate the aging time for each porosity change rate. Take the minimum value as the aging time t determined by the porosity change rate. k ;

[0044] c. Comparison of t c and t k The smaller value is used as the estimated service life of the porous filter membrane at the service environment temperature T0.

[0045] There is no time order requirement for steps a and b.

[0046] To further illustrate the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, provides a method for establishing a model for predicting the service life of a porous filter membrane and a method for predicting the service life of a porous filter membrane, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0047] Example 1

[0048] Taking porous polytetrafluoroethylene tubular membranes as an example:

[0049] Aging tests were conducted at four temperatures—250°C, 270°C, 290°C, and 300°C—below the melting point of the porous PTFE tubular membrane by 30°C. The length and porosity changes of the porous PTFE tubular membrane were measured every 24 hours, for a total testing time of 288 hours. The resulting curves of length change versus time are shown below. Figure 1 As shown in the figure, the curve of porosity change rate versus time is as follows: Figure 2 As shown;

[0050] With a length change rate of 5%, the corresponding aging times at the four temperatures were 24.45 h, 13.92 h, 9.02 h, and 5.39 h, respectively. Using the logarithm of the aging time t1 (logt1) as the ordinate and the reciprocal of the corresponding temperature value T (1 / T) as the abscissa, a time-temperature model was fitted: logt1 = -5.71 + 3724 / T, with a linear correlation coefficient of 98.6%. The fitted linear equation for the time-temperature relationship under the length change rate is as follows: Figure 3 As shown; the service life at 90℃ is calculated to be 3.87 years according to the model.

[0051] With a porosity change rate of 8.5%, the corresponding aging times at the four temperatures were 281.96 h, 144.5 h, 70.6 h, and 30.6 h, respectively. Using the logarithm of the aging time t1' (logt1') as the ordinate and the reciprocal of the corresponding temperature value T (1 / T) as the abscissa, a time-temperature model was fitted: logt1' = -7.966 + 5477 / T, with a linear correlation coefficient of 100.0%. The fitted linear equation for the time-temperature relationship under the porosity change rate is as follows: Figure 4 As shown; the calculated service life at 90℃ is 1442 years according to the model;

[0052] The smaller value (i.e., the aging time calculated based on the length change rate) was selected as the estimated service life of the porous PTFE tubular membrane.

[0053] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for predicting the service life of a porous filter membrane, characterized in that, The steps are as follows: a. Substitute the service environment temperature T0 of the object under test into the time-temperature model obtained by the model establishment method for estimating the service life of the porous filter membrane at each length change rate, and calculate the aging time at each length change rate. Take the minimum value as the aging time t determined by the length change rate. c ; b. Substitute the service environment temperature T0 of the object under test into the time-temperature model obtained by the model establishment method for estimating the service life of the porous filter membrane at each porosity change rate, and calculate the aging time at each porosity change rate. Take the minimum value as the aging time t determined by the porosity change rate. k ; c. Comparison of t c and t k The smaller value is used as the estimated service life of the porous filter membrane at the service environment temperature T0. There is no time order requirement for steps a and b; The steps for establishing the model for predicting the service life of porous filter membranes are as follows: (1) Set n temperature values ​​T1~T within the range below the melting point of the porous filter membrane. n Aging tests were conducted at the set temperature values, and samples were periodically taken to test the length change rate and porosity change rate of the porous filter membrane; n≥3; the maximum value T among the set n temperature values. max and the melting point T of the porous filter membrane 熔点 Satisfy: T max <T 熔点 -30℃; (2) Taking a length change rate of no more than 10% at each temperature as the range, different length change rates are selected within the range to obtain the temperature value T for each length change rate. n The corresponding aging time t n ; with the aging time t n The logarithm of the value is on the ordinate, and the temperature value T is on the ordinate. n Using the reciprocal of the x-axis as the horizontal axis, we fit the time-temperature model for each rate of change of length: logt n =A+B / T n ; (3) Taking a porosity change rate of no more than 10% at each temperature as the range, different porosity change rates are selected within the range to obtain the temperature value T for each porosity change rate. n 'Corresponding aging time t n ';With the aging time t n The logarithm of ' is the ordinate, and the temperature value T is the ordinate. n Using the reciprocal of ' as the x-axis, we fit the time-temperature model for each porosity change rate: logt n =A'+B' / T n '; There is no time order restriction for steps (2) and (3).

2. The prediction method according to claim 1, characterized in that, The value range in step (2) is the length change rate of 5% to 10%.

3. The prediction method according to claim 1, characterized in that, The value range in step (3) is the porosity change rate of 5% to 10%.

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