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CN109289530B - Method for judging reverse cleaning critical time of flat ceramic membrane - Google Patents

Method for judging reverse cleaning critical time of flat ceramic membrane Download PDF

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CN109289530B
CN109289530B CN201811324110.8A CN201811324110A CN109289530B CN 109289530 B CN109289530 B CN 109289530B CN 201811324110 A CN201811324110 A CN 201811324110A CN 109289530 B CN109289530 B CN 109289530B
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CN109289530A (en
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王海桥
孙传文
陈世强
谢星明
李轶群
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Hunan University of Science and Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
    • B01D63/08—Flat membrane modules
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/02—Membrane cleaning or sterilisation ; Membrane regeneration

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Abstract

本发明公开了一种平板陶瓷膜反清洗临界时间的判定方法，包括以下步骤：步骤一：分析陶瓷膜本身参数对渗透通量的影响，得到陶瓷膜本身参数对渗透通量影响的表达式；步骤二：拟合修正得到膜通水量随时间变化的函数式，通过膜通水量随时间变化规律的函数式来确定不同时刻膜通水量的变化情况。本发明能用于确定平板陶瓷膜反清洗临界时间的适用条件，能够根据膜参数和压差等参数，在不考虑滤液颗粒粒径大小的情况下确定膜通量随时间的变化规律，避免膜阻力和滤液颗粒粒径的繁琐计算，可迅速确定膜通量在不同时间的变化情况，实现平板陶瓷膜反清洗临界时间的确定，为膜的反清洗时间的确定提供理论支持。

Figure 201811324110

The invention discloses a method for judging the critical time of reverse cleaning of a flat ceramic membrane, comprising the following steps: Step 1: analyzing the influence of the parameters of the ceramic membrane itself on the permeate flux, and obtaining an expression of the influence of the parameters of the ceramic membrane itself on the permeate flux; Step 2: Fitting and correcting to obtain the functional formula of the membrane water flow rate changing with time, and determining the change of the membrane water flow rate at different times through the functional formula of the membrane water flow rate changing with time. The invention can be used to determine the applicable conditions of the critical time of the back-cleaning of the flat ceramic membrane, and can determine the variation law of the membrane flux with time according to parameters such as membrane parameters and pressure difference without considering the particle size of the filtrate particles, so as to avoid membrane The tedious calculation of resistance and particle size of filtrate can quickly determine the change of membrane flux at different times, realize the determination of the critical time of back-cleaning of flat ceramic membrane, and provide theoretical support for the determination of the back-cleaning time of the membrane.

Figure 201811324110

Description

Method for judging reverse cleaning critical time of flat ceramic membrane
Technical Field
The invention relates to a method for judging the backwashing critical time of a flat ceramic membrane.
Background
The ceramic material is one of three major pillars in the global material industry, and plays a very important role in daily life and industrial production. Inorganic ceramic membranes formed by inorganic ceramic materials through a special process are widely applied to the fields of food, biomedicine, fine chemical industry, environment and the like due to excellent performance. The research on the change rule of the water flow of the ceramic membrane along with time is particularly important as one of important parameters in application, and the blockage condition of membrane holes can be known by knowing the change rule of the water flow of the membrane at different times, so that theoretical support is provided for determining the backwashing time of the membrane.
In practical application, the determination of the membrane water flow is generally to determine the membrane resistance according to a membrane blocking theory, and then calculate the water flow according to a Darcy law expression, but the calculation is carried out by using the method, because the blocking process is carried out in real time, the blocking degree is different at different moments, and the membrane resistance at each moment cannot be accurately determined; and the particle size of different filter liquor is also greatly different, so that the filtration of membranes with different parameters is also greatly different. Because of the influence of multifactorial changes during membrane filtration, it is difficult to calculate a definite functional formula for the membrane flux at different times during actual filtration, which makes it difficult to effectively grasp the determination of the membrane backwashing time.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for judging the reverse cleaning critical time of the flat ceramic membrane, which has a simple algorithm and a wide application range.
The technical scheme for solving the problems is as follows: a method for judging the backwashing critical time of a flat ceramic membrane comprises the following steps:
the method comprises the following steps: analyzing the influence of the ceramic membrane parameters on the permeation flux to obtain an expression of the influence of the ceramic membrane parameters on the permeation flux;
step two: and fitting and correcting to obtain a function expression of the membrane water flow changing along with time, and determining the change condition of the membrane water flow at different times through the function expression of the membrane water flow changing along with time.
The method for judging the backwashing critical time of the flat ceramic membrane comprises the following specific steps:
a) calculating the specific filtration resistance alpha of the fixed bed formed by stacking the particles:
Figure BDA0001858243530000021
correcting the specific resistance to filtration:
Figure BDA0001858243530000022
in the formula: alpha is the specific resistance of filtration and has no dimensional number; dpIs the film layer particle size, m; k is a radical of1And k2The undetermined parameters of the model are dimensionless numbers; epsilon is the porosity of the bed layer and is a dimensionless number;
b) calculating the membrane resistance, wherein the membrane resistance is expressed as the product of the specific filtration resistance and the membrane thickness, and the calculation formula is as follows:
Figure BDA0001858243530000023
in the formula: rmM is film resistance-1(ii) a L is the film thickness, m;
c) taking the particle size d of the film layerpIs the average membrane pore diameter dm4 times of that of:
dp＝4·dm (4)
d) substituting the formula (3) into the formula (4) to obtain a relation between the film resistance and the film microstructure parameters as follows:
Figure BDA0001858243530000031
the merging constant term reduces equation (5) to:
Figure BDA0001858243530000032
e) substituting the formula (6) into the Darcy law expression to obtain an expression J of the influence of the parameters of the ceramic membrane on the permeation flux, wherein the expression J is as follows:
Figure BDA0001858243530000033
in the formula, J is an expression function of the influence of the parameters of the ceramic membrane on the permeation flux, and delta P is the operation pressure difference, kPa; μ is the liquid viscosity, Pa · s.
In the method for determining the backwashing critical time of the flat ceramic membrane, in the second step, the function formula of the water flow of the membrane, which is obtained by fitting and correcting, along with the change of time is as follows:
Figure BDA0001858243530000034
in the formula: j (t) is a function of the permeation flux as a function of time, L/h.m2(ii) a t is time, s; a, b and c are fitting parameters respectively.
The invention has the beneficial effects that: the method can be used for determining the application condition of the back washing critical time of the flat ceramic membrane, can determine the change rule of the membrane flux along with the time under the condition of not considering the particle size of the filtrate particles according to the parameters such as the membrane parameters, the pressure difference and the like, avoids the complex calculation of the membrane resistance and the particle size of the filtrate particles, can rapidly determine the change condition of the membrane flux at different times, realizes the determination of the back washing critical time of the flat ceramic membrane, and provides theoretical support for the determination of the back washing time of the membrane.
Drawings
FIG. 1 is a schematic structural diagram of an experimental apparatus for measuring permeation flux according to the present invention.
FIG. 2 is a graph of experimental data and a graph fitted thereto (pore size 0.1 μm, pressure difference 20 kPa).
FIG. 3 is a graph of experimental data and a fit thereof (pore size 0.1 μm, differential pressure 30 kPa).
FIG. 4 is a graph of experimental data and a fit thereof (pore size 0.1 μm, differential pressure 40 kPa).
FIG. 5 is a graph of experimental data and a fit thereto (pore size 1.0 μm, pressure difference 20 kPa).
FIG. 6 is a graph of experimental data and a fit thereof (pore diameter 1.0 μm, pressure difference 30 kPa).
FIG. 7 is a graph of experimental data and a fit thereof (pore diameter 1.0 μm, differential pressure 40 kPa).
In the figure: 1. a valve I; 2. a valve II; 3. a suction pump; 4. a pressure controller; 5. a flat ceramic membrane module.
Detailed Description
The invention is further described below with reference to the figures and examples.
As shown in fig. 1, a specified pressure difference is set by a pressure controller 4, a plurality of groups of flat ceramic membrane assemblies 5 with different apertures are respectively filtered under different pressure differences, the water yield and the corresponding time within a certain period of time are recorded at intervals, the suction pump 3 is controlled to be reversely rotated and the valves I1 and II 2 are controlled to be opened and closed after one experiment is finished, and the filtered water is used for reversely cleaning the flat ceramic membrane assemblies 5; then, the pressure controller 4 is adjusted to set the pressure difference, and a plurality of groups of flat ceramic membranes with different apertures are subjected to experiments again, so that the experiments are carried out under different required pressure differences. And correcting and fitting the data obtained by the experiment by taking the expression of the influence of the parameters of the membrane on the permeation flux as a basis function, and verifying the fitting function by using other groups of experimental data to prove the universality of the fitting function.
A method for judging the backwashing critical time of a flat ceramic membrane comprises the following steps:
the method comprises the following steps: and analyzing the influence of the ceramic membrane parameters on the permeation flux to obtain an expression of the influence of the ceramic membrane parameters on the permeation flux. The method comprises the following specific steps:
a) calculating the specific filtration resistance alpha of the fixed bed formed by stacking the particles:
Figure BDA0001858243530000041
in the ceramic membrane separation layer, since particles in the ceramic membrane are deformed at high temperature, the specific filtration resistance is corrected:
Figure BDA0001858243530000051
in the formula: alpha is the specific resistance of filtration and has no dimensional number; dpIs the film layer particle size, m; k is a radical of1And k2The undetermined parameters of the model are obtained through fitting of experimental data, and dimensionless numbers are not obtained; epsilon is the porosity of the bed layer and is a dimensionless number;
b) calculating the membrane resistance, wherein the membrane resistance is expressed as the product of the specific filtration resistance and the membrane thickness, and the calculation formula is as follows:
Figure BDA0001858243530000052
in the formula: rmM is film resistance-1(ii) a L is the film thickness, m;
c) because the average grain diameter of the film layer particles prepared by the particle sintering method is generally 3-5 times of the average pore diameter of the sintered film, the size d of the film layer particles is taken by analyzing SEM (scanning electron microscope) pictures and pore diameter distribution of the filmpIs the average membrane pore diameter dm4 times of that of:
dp＝4·dm (4)
d) substituting the formula (3) into the formula (4) to obtain a relation between the film resistance and the film microstructure parameters as follows:
Figure BDA0001858243530000053
the merging constant term reduces equation (5) to:
Figure BDA0001858243530000054
e) substituting the formula (6) into the Darcy law expression to obtain an expression J of the influence of the ceramic membrane parameters on the permeation flux, wherein the expression J is as follows:
Figure BDA0001858243530000055
in the formula, J is an expression function of the influence of the parameters of the ceramic membrane on the permeation flux, and delta P is the operation pressure difference, kPa; μ is the liquid viscosity, Pa · s.
Step two: and fitting and correcting to obtain a function expression of the membrane water flow changing along with time, and determining the change condition of the membrane water flow at different times through the function expression of the membrane water flow changing along with time. And fitting the function formula of the water passing capacity of the membrane, which is obtained by correction, along with the change of time, wherein the function formula is as follows:
Figure BDA0001858243530000061
in the formula: j (t) is a function of the permeation flux as a function of time, L/h.m2(ii) a t is time, s; and a, b and c are fitting parameters respectively and are obtained by fitting experimental data.
Regarding the fitting parameters a, b, c: by using the function formula (8) obtained by fitting correction as a basis function and by fitting data to the experimental data measured when the pore diameter and the differential pressure are determined, the parameters a, b, c in the experimental state can be obtained.
With respect to fitting parameter k1、k2: selecting a plurality of ceramic membranes with the same pressure difference, consistent porosity and different apertures to carry out a pure water permeation experiment, measuring the change condition of pure water permeation flux along with the thickness of the membrane under different apertures, fitting the measured experimental data to obtain a undetermined parameter k of the model1And k2。
And performing fitting verification on the obtained functional expression by utilizing other groups of experiments to obtain figures 3-7, wherein the obtained experimental data curve has certain deviation around the fluctuation of the function curve, but the general trend is consistent with the function curve, and the obtained correlation coefficient R2All are above 0.97, and have better correlation.
By analyzing the specific embodiments, the following summary is made: firstly, a relational graph of experimental data and a function curve is obtained through fitting verification, the correlation coefficient of the relational graph is reasonable, and the universality of the functional formula is proved. The method defines a function formula of the change rule of membrane water flow along with time under the condition of not researching the particle size of filtrate particles, and can provide theoretical support for determining the backwashing time of the membrane.

Claims (1)

1. A method for judging the backwashing critical time of a flat ceramic membrane comprises the following steps:
the method comprises the following steps: analyzing the influence of the ceramic membrane parameters on the permeation flux to obtain an expression of the influence of the ceramic membrane parameters on the permeation flux;
the first step is as follows:
a) calculating the specific filtration resistance alpha of the fixed bed formed by stacking the particles:
Figure FDA0002792824810000011
correcting the specific resistance to filtration:
Figure FDA0002792824810000012
in the formula: alpha is the specific resistance of filtration and has no dimensional number; dpIs the film layer particle size, m; k is a radical of1And k2The undetermined parameters of the model are dimensionless numbers; epsilon is the porosity of the bed layer and is a dimensionless number;
b) calculating the membrane resistance, wherein the membrane resistance is expressed as the product of the specific filtration resistance and the membrane thickness, and the calculation formula is as follows:
Figure FDA0002792824810000013
in the formula: rmM is film resistance-1(ii) a L is the film thickness, m;
c) taking the particle size d of the film layerpIs the average membrane pore diameter dm4 times of that of:
dp＝4·dm (4)
d) substituting the formula (3) into the formula (4) to obtain a relation between the film resistance and the film microstructure parameters as follows:
Figure FDA0002792824810000014
the merging constant term reduces equation (5) to:
Figure FDA0002792824810000015
e) substituting the formula (6) into the Darcy law expression to obtain an expression J of the influence of the ceramic membrane parameters on the permeation flux, wherein the expression J is as follows:
Figure FDA0002792824810000021
in the formula, J is an expression function of the influence of the parameters of the ceramic membrane on the permeation flux, and delta P is the operation pressure difference, kPa; μ is the liquid viscosity, pas;
step two: fitting and correcting to obtain a function expression of the membrane water flow changing along with time, and determining the change condition of the membrane water flow at different times through the function expression of the change rule of the membrane water flow along with time;
and fitting the function formula of the water passing capacity of the membrane, which is obtained by correction, along with the change of time, wherein the function formula is as follows:
Figure FDA0002792824810000022
in the formula: j (t) is a function of the permeation flux as a function of time, L/h.m2(ii) a t is time, s; a, b and c are fitting parameters respectively.
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JP7168102B2 (en) * 2019-10-29 2022-11-09 三菱電機株式会社 Water treatment equipment design support device and water treatment equipment design support method
US20230121715A1 (en) * 2020-03-30 2023-04-20 Toray Industries, Inc. Method and program for determining cleaning trouble in fresh water generator

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EP1174177A2 (en) * 2000-07-18 2002-01-23 Nitto Denko Corporation Spiral wound membrane element, spiral wound membrane module and treatment system employing the same as well as running method and washing method therefor
CN103120900A (en) * 2011-11-18 2013-05-29 东丽纤维研究所（中国）有限公司 Membrane module operation designing method
CN103619761A (en) * 2011-06-13 2014-03-05 普莱克斯技术有限公司 Control system for wastewater treatment plants with membrane bioreactors
CN104524844A (en) * 2014-12-31 2015-04-22 上海市安装工程集团有限公司 Method for cleaning filter tank
CN105642124A (en) * 2016-02-02 2016-06-08 北京金泽环境能源技术研究有限公司 Offline cleaning method for immersion type ultrofiltration membrane stack

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1174177A2 (en) * 2000-07-18 2002-01-23 Nitto Denko Corporation Spiral wound membrane element, spiral wound membrane module and treatment system employing the same as well as running method and washing method therefor
CN103619761A (en) * 2011-06-13 2014-03-05 普莱克斯技术有限公司 Control system for wastewater treatment plants with membrane bioreactors
CN103120900A (en) * 2011-11-18 2013-05-29 东丽纤维研究所（中国）有限公司 Membrane module operation designing method
CN104524844A (en) * 2014-12-31 2015-04-22 上海市安装工程集团有限公司 Method for cleaning filter tank
CN105642124A (en) * 2016-02-02 2016-06-08 北京金泽环境能源技术研究有限公司 Offline cleaning method for immersion type ultrofiltration membrane stack

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