Method and program for calculating separation performance of separation membrane

Abstract

The separation performance of the separation membrane is calculated by the following steps using the initial separation performance SP(0) of the separation membrane, the operation period D of the liquid treatment, the temperature T(t) of the treated liquid, and the pressure P(t) of the treated liquid. Step 1: When the separation performance of the separation membrane changed due to compaction after the operation period D has elapsed is SP(D), and an arbitrary time is t1, the equivalent operation period D' is determined for the separation performance SP(D) assuming that the temperature T(t) of the treated liquid is constant at t1. Step 2: The compaction coefficient m(T(t1),P(t1)) is determined using the temperature T(t1) of the treated liquid and the pressure P(t1) of the treated liquid at t1. Step 3: The equivalent operation period D' and the compaction coefficient m are used to calculate the separation performance correction coefficient M(D) corresponding to the ratio of the separation performance SP(D) to the initial separation performance. Step 4: The separation performance SP(D) is calculated using the separation performance correction coefficient M(D) and the initial separation performance.

Description

[Technical field]

[0001] The present invention relates to a method and a calculation program for calculating the separation performance of a separation membrane used in liquid treatment to obtain a treated liquid from a liquid to be treated. [Background technology]

[0002] There are various purification technologies for liquids containing dissolved solutes such as inorganic salts and organic salts. Among these, the use of membrane separation has expanded in recent years to various fields due to its advantages such as energy saving, space saving, and improved treated water quality.

[0003] According to the reverse osmosis method, which is an example of a membrane separation method, a liquid to be treated containing solutes such as salt can be separated into a treated liquid with reduced solute content and a concentrated liquid by passing the liquid through a reverse osmosis membrane with a pressure equal to or greater than the osmotic pressure of the liquid. This technology can produce drinking water from, for example, seawater, brackish water, or water containing harmful substances, and is also used for producing ultrapure water for industrial use, treating wastewater, recovering valuable materials, etc.

[0004] The performance of a separation membrane deteriorates over time, although the degree of deterioration varies depending on the type of separation membrane, the water quality of the liquid being treated, the operating method, etc. Therefore, in order to design a liquid treatment device and to achieve stable operation, it is desirable to know the change in separation performance of a separation membrane over time as accurately as possible.

[0005] There are various reasons why the separation performance of a separation membrane changes over time, including chemical damage caused by cleaning, scale accumulation of inorganic salts, and microbial fouling. One of these is known to be irreversible compaction of the separation membrane caused by the pressure difference between the liquid to be treated and the liquid to be treated.

[0006] Non-Patent Document 1 describes that the change over time in the separation performance of a separation membrane due to compaction depends on the material and specifications of the membrane, operating time, temperature of the treated liquid, and pressure of the treated liquid, and Non-Patent Document 2 describes a method of expressing the change over time in the separation performance of a separation membrane due to compaction using the compaction coefficient (m value).

[0007] In the empirical formula described in Non-Patent Document 2, the m value is treated as a constant if the operating conditions are constant, but in an actual liquid treatment device, the m value is not necessarily constant because the temperature of the treated liquid changes with the seasons and the pressure of the treated liquid changes accordingly. Non-Patent Document 3 describes a method for more accurately estimating the m value after a specified time has elapsed by sequential calculation based on the changes over time in the temperature and pressure of the treated liquid. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] Bernard Baum,1 Stanley A. Margosiak, and William H. Holley, Jr., Ind. Eng. Chem. Prod. Res. Dev., vol. 11, No. 2, 195 (1972) [Non-Patent Document 2] Takashi Kimura, Membrane, Vol. 6, No. 3, 83 (1981) [Non-Patent Document 3] Naohiko UKAWA, Ikuo NAKATANI and Hideo IWAHASHI, Journal of the Society of Sea Water Science, Vol. 43, No. 4, 218 (1989) Summary of the Invention [Problem to be solved by the invention]

[0009] However, the method described in Non-Patent Document 3 requires sequential calculations based on the time-dependent changes in the temperature and pressure of the treated liquid, and therefore may be difficult to apply in designing a liquid treatment device, which requires prediction of the time-dependent changes in the temperature and pressure of the treated liquid. In addition, the amount of calculation increases according to the operating time of the liquid treatment device, and the calculation takes a long time, so that this method is not necessarily practical.

[0010] Therefore, an object of the present invention is to provide a method for simply and accurately calculating the change over time in the separation performance due to compaction of a separation membrane used in a liquid treatment device. [Means for solving the problem]

[0011] In order to solve such problems, the present disclosure provides: The present invention provides a method for calculating the separation performance of a separation membrane used in liquid treatment to obtain a treated liquid from a liquid to be treated, the method being characterized in that the separation performance of the separation membrane is calculated using the initial separation performance SP(0) of the separation membrane, the operating period D of the liquid treatment, the temperature T(t) of the treated liquid during the operating period D (t is a certain time during the operating period D), and the pressure P(t) of the treated liquid by the following steps: Step 1: The separation performance of the separation membrane that has changed due to compaction after the operation period D has elapsed is defined as SP(D), Any time during the operation period D is t 1 When The temperature of the treated liquid T(t) is t 1 The temperature T(t 1 ) is assumed to be constant, a step of determining an equivalent operation period D' at which the separation performance becomes SP(D). Process 2: Temperature T(t 1 ) and t 1 The pressure of the treated liquid at P(t 1 ) is used to calculate the compaction coefficient m(T(t 1 ),P(t 1 ) determining the Step 3: Equivalent operation period D' and compaction coefficient m (T(t 1 ),P(t 1 ) to calculate a separation performance correction coefficient M(D) corresponding to the ratio of the separation performance SP(D) to the initial separation performance SP(0). Step 4: A step of calculating the separation performance SP(D) using the separation performance correction coefficient M(D) and the initial separation performance SP(0). Effect of the Invention

[0012] According to the method for calculating the separation performance of a separation membrane of the present invention, it is possible to simply and accurately calculate the change over time in separation performance due to compaction of a separation membrane used in a liquid treatment device, which can contribute to the accurate design and stable operation of liquid treatment devices. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a flow diagram showing an example of a liquid treatment apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a flow diagram illustrating an example of a calculation method according to an embodiment of the present invention. [Diagram 3] 4 is a graph showing an example of the relationship between operation time, temperature of treated liquid, and separation performance correction coefficient according to one embodiment of the present invention. [Figure 4] 11 is a graph showing another example of the relationship between operation time, temperature of treated liquid, and separation performance correction coefficient according to one embodiment of the present invention. [Diagram 5] 1 is a graph showing an example of the relationship between the ratio D' / D of the equivalent operation period and the operation period, and the difference ΔT in the temperature of the liquid to be treated between the high temperature period and the low temperature period according to one embodiment of the present invention. [Figure 6] FIG. 1 is a schematic diagram illustrating a configuration example according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention will be described in more detail below based on the embodiments shown in the drawings. Note that, although the following description will be given using a water treatment device using a reverse osmosis membrane as an example, the present invention is not limited to the following embodiments.

[0015] Figure 1 shows an example of a water treatment system in which raw water 1 is treated by a membrane treatment method using a reverse osmosis membrane 4 to obtain product water 5. In a water treatment process, there are always three types of water flow: raw water, product water, and wastewater. The raw water is treated in each water treatment system, and is finally separated into product water and wastewater. Raw water is the solution to be treated in the water treatment process, and examples include river water, groundwater, seawater, sewage treatment water, industrial wastewater, and culture liquid.

[0016] Reverse osmosis membranes are processed into reverse osmosis membrane elements and installed in the equipment. There are spiral elements in which a flat membrane is wrapped around a water collection pipe, plate-and-frame elements in which flat membranes are attached to both sides of a plate-type support plate and stacked at regular intervals via spacers to form a module, tubular elements using tubular membranes, and hollow fiber membrane elements in which hollow fiber membranes are bundled and stored in a case. The element may be in any form, but it is preferable to use a spiral element from the viewpoint of operability and interchangeability. The number of elements can be set arbitrarily depending on the membrane performance.

[0017] As the material of the reverse osmosis membrane, for example, polyamide, polypiperazine amide, polyester amide, or crosslinked water-soluble vinyl polymer can be used, and as the membrane structure, a membrane having a dense layer on at least one side of the membrane, with gradually increasing pores from the dense layer toward the inside of the membrane or toward the other side of the membrane (asymmetric membrane), or a membrane having a very thin separation functional layer made of another material on the dense layer of such an asymmetric membrane (composite membrane), etc. can be used. However, for high water production, a composite membrane is preferable, and among them, a polyamide composite membrane, and even more preferably a piperazine polyamide composite membrane, are preferable from the viewpoints of permeation amount, chemical resistance, etc.

[0018] Raw water 1 is pumped by a raw water pump 2, pressurized by a high-pressure pump 3, and then supplied to a reverse osmosis membrane 4. In the reverse osmosis membrane method, in order to obtain an effective osmotic pressure, it is necessary to sufficiently increase the supply pressure by the high-pressure pump 3 according to the salinity of the raw water; for example, if the raw water has a high salinity such as seawater, the pressure is increased to about 8 MPa. At this time, a large pressure difference occurs with the produced water 5, which is generally released to atmospheric pressure, and therefore the reverse osmosis membrane 4 becomes compacted.

[0019] FIG. 2 is a flow diagram showing an example of a method for calculating the separation performance of a separation membrane used in liquid treatment to obtain a treated liquid from a liquid to be treated. The method calculates the separation performance of the separation membrane in the following steps using the initial separation performance SP(0) of the separation membrane, the operation period D of the liquid treatment, the temperature T(t) of the treated liquid during the operation period D (t is a certain time during the operation period D), and the pressure P(t) of the treated liquid. Step 1: The separation performance of the separation membrane that has changed due to compaction after the operation period D has elapsed is defined as SP(D), and an arbitrary time during the operation period D is defined as t 1 When the temperature T(t) of the treated liquid is t 1 The temperature T(t 1 ) is constant, and step 2: determining an equivalent operation period D' for which the separation performance is SP(D); 1 ) and t 1 The pressure of the treated liquid at P(t 1 ) is used to calculate the compaction coefficient m(T(t 1 ),P(t 1 )) and step 3: determining the equivalent operation period D' and the compaction coefficient m (T(t 1 ),P(t 1 ) to calculate a separation performance correction coefficient M(D), which corresponds to the ratio of the separation performance SP(D) to the initial separation performance SP(0); and step 4: to calculate the separation performance SP(D) using the separation performance correction coefficient M(D) and the initial separation performance SP(0).

[0020] Here, the initial separation performance SP(0) and separation performance SP(D) of the separation membrane are membrane performances that are affected by compaction, and examples of these include the solvent permeability coefficient, solute permeability coefficient, and separation selectivity. However, it is particularly effective to apply the present invention to the solvent permeability coefficient or solute permeability coefficient, which are greatly affected by compaction.

[0021] The method for determining the initial separation performance SP(0) is not particularly limited, but the separation performance calculated by the method described below based on the product planning of the separation membrane, the test results during production of the separation membrane, the operating conditions at the start of liquid treatment operation, etc. can be used.

[0022] As an example of a method for calculating the separation performance, a method for calculating the solvent permeability coefficient and the solute permeability coefficient of a reverse osmosis membrane will be described.

[0023] The permeating substances in the separation membrane consist of a solvent and a solute. The solvent permeates the reverse osmosis membrane due to the pressure difference, and the solute permeates the reverse osmosis membrane due to the concentration difference. As shown in equation (1), the solvent permeation flux J v is the solvent permeability coefficient L specific to the reverse osmosis membrane. p and the effective pressure difference ΔP e and the solute permeation flux J s is the solute permeability coefficient P and the transmembrane concentration difference (C m -C p ) and

[0024]

number

[0025]

number

[0026] Here, C m is the solute concentration on the membrane surface on the treated liquid side, C p is the solute concentration in the treatment liquid, C s is the average solute concentration, π(C) is the osmotic pressure at concentration C, and σ is the reflectance.

[0027] Here, we assume that a membrane with high salt rejection is used, and the reflectance σ is very close to 1, and the solvent permeation flux J v and solute flux J s is given by equations (3) and (4).

[0028]

number

[0029]

number

[0030] Also, C p is given by equation (5).

[0031]

number

[0032] Solute concentration C on the membrane surface on the treated liquid side m It is desirable to take into consideration the concentration polarization phenomenon (the phenomenon in which the salt concentration on the membrane surface on the treated liquid side becomes higher than the salt concentration in the treated liquid bulk due to accumulation of solutes on the membrane surface).

[0033] This concentration polarization phenomenon is, for example, the movement of solutes accompanying the solvent permeation flux J v C and the diffusion of solutes on the membrane surface on the treated liquid side D C dC / dx and the amount of solute that permeated the membrane, J v C p This can be expressed by equation (6) using the three material balance equations above.

[0034]

number

[0035] Here, D C is the diffusion coefficient of the solute. By integrating the mass balance equation (6), we obtain the concentration polarization equation (7).

[0036]

number

[0037] Here, k=D C / δ, where k is the mass transfer coefficient and δ is the thickness of the layer through which mass transfer occurs.

[0038] The mass transfer coefficient k can be calculated, for example, as follows:

[0039] Mass transfer correlation (Sh=a·Re b·Sc c ) is an equation that shows the flow characteristics of the application form of reverse osmosis membrane (for example, a spiral-type reverse osmosis membrane element), and expresses the relationship between the Sherwood number (Nusselt number) Sh, the Reynolds number Re, and the Schmidt number Sc. The Sherwood number Sh is calculated by multiplying the mass transfer coefficient k by the flow channel thickness d of the layer in which the mass transfer takes place, using the solute diffusion coefficient D C The Reynolds number Re is a dimensionless quantity obtained by dividing the product of the flow velocity u, density ρ, and characteristic length d of the treated liquid by the viscosity coefficient η, and represents the influence of the flow velocity of the treated liquid. The Schmidt number Sc is the product of the viscosity coefficient η and the density ρ and the solute diffusion coefficient D C This is calculated by dividing by the product of x and y, and represents the influence of the physical properties of the treated liquid.

[0040]

number

[0041]

number

[0042]

number

[0043] In this embodiment, the exponents b and c of the Reynolds number Re and the Schmidt number Sc in the mass transfer correlation are set to predetermined fixed values. For example, the exponents b and c are set to, for example, 0.875 and 0.25, respectively, according to the Deissler equation, which is known as a mass transfer correlation for piping.

[0044] In this case, the mass transfer correlation equation is given by equation (11), and equation (12) is obtained from equations (8) and (11).

[0045]

number

[0046]

number

[0047] Here, the unknown coefficient a in the formula (12) can be found by conducting an experiment in which the flow rate u of the liquid to be treated is changed according to the usage form of the reverse osmosis membrane.

[0048] Solvent permeability coefficient L specific to reverse osmosis membrane p It is known that the solute permeability coefficient P and the solvent permeability coefficient P change reversibly due to the influence of temperature, pressure, etc. The above-mentioned reversible changes can be corrected by any method. For example, the solvent permeability coefficient and the solute permeability coefficient after the change can be calculated by subtracting L p ', P', the viscosity of the treated liquid is μ, the viscosity of the treated liquid at 25°C is μ25, and the temperature of the treated liquid is T f , the pressure of the treated liquid is P f , the standard operating pressure (e.g. the standard operating pressure stated in the product catalogue) is P s Let c be a constant specific to each film type. 1 ,c 2 ,d 1 ,d 2 Then, it can be determined by the following equations (13) and (14).

[0049]

number

[0050]

number

[0051] In this way, the solvent flux J v , and solute flux J s That is, the flow rate of the liquid to be treated Q f , processing liquid flow rate Q p , membrane area A, solute concentration of the treated liquid C f , solute concentration of the treated liquid C p , the pressure of the liquid to be treated P f , standard operating pressure Ps , the temperature of the liquid to be treated T f If the values ​​of are known in advance, then J v , J s Calculate backwards and then calculate the J v , J s Meet L p and P can be determined.

[0052] The operating period D of the liquid treatment may be any period from the start of operation, but considering that compaction of the separation membrane is initialized by replacement, the operating period D may be the average number of years that the separation membrane has been used in the liquid treatment.

[0053] In step 1, the separation performance of the separation membrane changed due to compaction at the time when the operation period D has elapsed is SP(D), and an arbitrary time in the operation period D is t1. When the temperature T(t) of the treated liquid is t 1 The temperature T(t 1 ) is constant, a process for determining an equivalent operation period D' at which the separation performance becomes SP(D).

[0054] As mentioned above, reverse osmosis membranes are often made of a polymer such as polyamide. In such cases, in addition to the pressure difference between the liquid to be treated and the liquid to be treated, the temperature of the liquid to be treated, which affects the hardness of the polymer itself, is also an important factor in consolidation; the higher the pressure of the liquid to be treated and the higher the temperature of the liquid to be treated, the faster the consolidation progresses.

[0055] On the other hand, the higher the temperature of the treated liquid, the lower the viscosity of the treated liquid, and therefore the lower the pressure of the treated liquid. In other words, the pressure of the treated liquid is low during high temperature periods and high during low temperature periods, resulting in a trade-off in terms of consolidation.

[0056] As a result of extensive research by the authors, it was found that the progress of densification is dominated by the effect of temperature rather than the effect of pressure, and that when densification progresses at a certain temperature, densification hardly progresses at all at temperatures lower than that temperature. In other words, the membrane performance SP(D) of the separation membrane after the operating period D has elapsed can be considered to have been affected mostly only by the high temperature period, and the period of the high temperature period during operating period D corresponds to the equivalent operating period D'.

[0057] The method of determining the equivalent operation period D' is not limited, but may be determined based on data on temperature changes in natural water in the area where the liquid treatment is performed or data on temperature changes in the liquid being treated measured during the liquid treatment, or may be determined by sequential calculation based on changes over time in the temperature and pressure of the liquid being treated. A certain time during the low temperature period in the operation period D is designated as t 2 Then, t 1 The temperature T(t 1 ) and t 2 The temperature T(t 2 An example of a method for determining the equivalent operation period D' will be described later.

[0058] Step 2 is to increase the temperature T(t 1 ) and t 1 The pressure of the treated liquid at P(t 1 ) is used to calculate the compaction coefficient m(T(t 1 ),P(t 1 ) is determined.

[0059] The consolidation coefficient m is a coefficient empirically determined based on the material and specifications of the membrane, the temperature of the treated liquid, the pressure of the treated liquid, etc., and according to the widely used definition of the consolidation coefficient m, the range of possible values ​​for the consolidation coefficient m is m≦0, with m=0 when consolidation does not progress, and the absolute value of the consolidation coefficient m increasing as the rate of consolidation progresses. There are no particular limitations on the method for determining the consolidation coefficient m, but it can be determined from a diagram or formula showing the relationship between the temperature of the treated liquid, the pressure of the treated liquid, and the consolidation coefficient m for each material and specification of the membrane.

[0060] As an example of a formula for determining the compaction coefficient m, it can be calculated, for example, by equation (15).

[0061]

number

[0062] Here, the coefficient b takes a specific value depending on the material and specifications of the membrane, and can be determined from an experimentally obtained correlation between the pressure of the treated liquid, operation period, and solvent permeability coefficient.

[0063] Step 3 is to determine the equivalent operation period D' and the compaction coefficient m(T(t 1 ),P(t 1 ) to calculate a separation performance correction coefficient M(D), which corresponds to the ratio of the separation performance SP(D) to the initial separation performance SP(0).

[0064] According to the above definition, the separation performance correction coefficient M(t) at a certain time t has an initial value M(0) = 1 at the start of operation, and decreases as compaction progresses. There are no particular limitations on the method of calculating the separation performance correction coefficient M(D) at t = D, but since the separation membrane becomes more dense and less susceptible to compaction as compaction progresses, it is predicted that the separation performance correction coefficient M(t) will form a curve that asymptotically approaches a certain value as the operating time t increases, and M(D) can be calculated by equation (16) as an example of a function that satisfies this.

[0065]

number

[0066] Step 4 is a step of calculating the separation performance SP(D) using the separation performance correction coefficient M(D) and the initial separation performance SP(0).

[0067] From the definition of the separation performance correction coefficient M(D) described above, the separation performance SP(D) can be calculated by the formula (17).

[0068]

number

[0069] An example of a method for determining the equivalent operating period D' will now be described.

[0070] Figure 3 is a graph showing an example of the relationship between operating time, temperature of the treated liquid, and separation performance correction coefficient in one embodiment of the present invention, and Figure 4 is a graph showing another example of the relationship between operating time, temperature of the treated liquid, and separation performance correction coefficient in one embodiment of the present invention.

[0071] For simplicity, in Figures 3 and 4, the change in the temperature of the treated liquid over time is expressed as a smooth waveform, and the separation performance correction coefficient M(t) is assumed to decrease linearly only during the high temperature period. In addition, the temperature T(t 1 ) and the temperature T(t 1 ) are considered equal.

[0072] Temperature during the high temperature period T(t 1 ) is equal in Fig. 3 and Fig. 4, while the temperature T(t 2 ) is the temperature T(t 2 ), the period of the high temperature period in Figure 4 is longer than that in Figure 3, and accordingly M(D) in Figure 4 is smaller than M(D) in Figure 3. This suggests that the period during which consolidation progresses is longer in the operating period D in Figure 4 than in Figure 3.

[0073] The above relationship is T(t 1 ) does not depend on the absolute value of T(t 1 ) and T(t 2 ) is ΔT, the relationship between ΔT and the ratio D' / D of the equivalent operating period D' to the operating period D is estimated to be as shown in the graph in Figure 5. Therefore, if the relationship between ΔT and D' / D is determined, it is possible to determine D' from ΔT. Note that in Figure 5, the horizontal axis of the graph is ΔT, but ΔT can also be expressed as T(t1 ) and T(t 2 ) may also be used as the rate of change.

[0074] The method for determining the relationship between ΔT and D' / D shown in Figure 5 is not particularly limited, but it may be determined based on data on temperature changes in natural water from around the world and data on temperature changes in the treated liquid measured in liquid treatment, as well as a separation performance correction coefficient M(D) determined by back-calculating from operating results measured in liquid treatment, or it may be determined based on a database of relationships between the treated liquid temperature T(t) and M(D) obtained from a plurality of liquid treatment devices.

[0075] For the sake of simplicity, the explanation has been given in Figs. 3 to 5 on the basis of a case where the temperature of the treated liquid over time is expressed as a smooth waveform. However, since the actual temperature of the treated liquid varies daily depending on the region and climate, the temperature of the treated liquid during both the high-temperature period and the low-temperature period will have a certain range of values, and it is not possible to express the temperature of the treated liquid as t 1 or 2 In some cases, it is difficult to determine t 1 But T(t 1 t) is determined so that the maximum temperature of the treated liquid during the operation period D is reached. 1-Tmax and t 2 But T(t 2 t) is determined so that the temperature of the treated liquid during the operation period D is the minimum temperature. 2-Tmin Then, t 1 and t 2 It is preferable to be able to determine

[0076] 3 to 5, for simplicity, the separation performance correction coefficient M(D) is explained based on the case where it decreases linearly, but as described above, as the compaction progresses, the density of the separation membrane increases and it becomes less susceptible to compaction, so the separation performance correction coefficient M(t) is predicted to be a curve that approaches a certain value as the operating time t increases, and the smaller the compaction coefficient m, that is, when the compaction progresses quickly, the separation performance correction coefficient M(t) approaches a certain value more quickly. When this asymptosis is slow, that is, when the separation performance correction coefficient M(t) decreases linearly, the relationship between ΔT and D' / D in FIG. 5 can be applied as it is, but when the asymptosis is fast, that is, when the separation performance correction coefficient M(t) decreases in a more curved manner, there is a risk that the calculation accuracy of the equivalent operating time D' and therefore the separation performance SP(D) will decrease if the relationship between ΔT and D' / D in FIG. 5 is applied as it is.

[0077] As described above, the compaction coefficient m is determined based on the membrane material, specifications, temperature of the treated liquid, pressure of the treated liquid, etc., and the separation performance correction coefficient M(t) calculated using the compaction coefficient m is also affected by the membrane material, specifications, temperature of the treated liquid, and pressure of the treated liquid. As described above, although temperature is more dominant than pressure in the progress of compaction, high-pressure operation in a low-temperature period does not necessarily have no effect on the progress of compaction. Therefore, the equivalent operating period D' can be further corrected based on one or more of the temperature T(t) of the liquid treatment device and the pressure P(t) of the treated liquid during the operating period D.

[0078] The method of further correcting the equivalent operation period D' is not particularly limited, but may be based on one or more of data on temperature changes of the treated liquid measured during liquid treatment, data on pressure changes of the treated liquid, and a separation performance correction coefficient M(D) determined by back-calculation from the operation results measured during liquid treatment. A database may be created of the relationships between the treated liquid temperature T(t), treated liquid pressure P(t), and M(D) obtained from a plurality of liquid treatment devices, and correction may be based on the database. T(t) which has a relatively large effect on the consolidation progress rate due to the high temperature or high pressure during the operation period D may be used. 1 ), t 1The pressure of the treated liquid at P(t 1 ), T(t 2 ), t 2 The pressure of the treated liquid at P(t 2 ) may be corrected based on one or more of the following:

[0079] In this way, the method for calculating the separation performance of a separation membrane, which is composed of steps 1 to 4, can simply and accurately calculate the change over time in separation performance due to compaction of a separation membrane used in a liquid treatment device, and can contribute to the accurate design and stable operation of liquid treatment devices.

[0080] Another embodiment of the present invention is a separation membrane separation performance calculation program as shown in Fig. 6, which causes a computer 10 to function as an operation information input means 11 for inputting operation information including at least the initial separation performance SP(0) of the separation membrane, an operation period D in liquid treatment, the temperature T(t) of the liquid being treated during the operation period D (t is a certain time during the operation period D), and the pressure P(t) of the liquid being treated, an operation information storage means 12 for storing the operation information, an operation information retrieval means 13 for retrieving the operation information from the operation information storage means, a separation performance calculation means 14 for calculating the separation performance of the separation membrane using the operation information in the following steps, a separation performance storage means for storing the separation performance in the separation performance storage means, and a separation performance storage means. Here, the steps are as follows: Step 1 is a step in which the separation performance of the separation membrane that has changed due to compaction after the operation period D has elapsed is SP(D), and an arbitrary time in the operation period D is t1, and the temperature T(t) of the liquid being treated is t 1 The temperature T(t 1 Step 2 is a step of determining the equivalent operation period D' for which the separation performance becomes SP(D) when the temperature T(t 1 ) and t 1 The pressure of the treated liquid at P(t 1 ) is used to calculate the compaction coefficient m(T(t 1 ),P(t 1 Step 3 is a step of determining the equivalent operation period D' and the compaction coefficient m(T(t 1 ),P(t 1) to calculate a separation performance correction coefficient M(D), which corresponds to the ratio of the separation performance SP(D) to the initial separation performance SP(0). Step 4 is a step of calculating the separation performance SP(D) using the separation performance correction coefficient M(D) and the initial separation performance SP(0). When t1 is a time in a high temperature period in the operating period D and t2 is a time in a low temperature period in the operating period D, step 1 of determining the equivalent operating period D' may determine the equivalent operating period D' based on information calculation means that calculates the difference or rate of change between the temperature T(t1) of the treated liquid and the temperature T(t2) of the treated liquid at t2 from information recorded in the operating information storage means. Furthermore, when T(t 1 ), T(t 2 ), t 1 The pressure of the treated liquid at P(t 1 ), t 2 The pressure of the treated liquid at P(t 2 It is preferable that the information calculation means functions as an equivalent operation period correction means for further correcting the equivalent operation period D' by using one or more of the above. In the information calculation means, t1 and t2 are t1-Tmax, which is determined so that T(t1) is the maximum temperature of the treated liquid in the operation period D, and t2 is t2-Tmin, which is determined so that T(t2) is the minimum temperature of the treated liquid in the operation period D, to uniquely determine t 1 and t 2 It is preferable to be able to determine

[0081] In step 2, the compaction coefficient m(T(t 1 ),P(t 1 In step 3, a separation performance correction coefficient calculation means is provided for calculating a separation performance correction coefficient M based on the formula (16), and in step 4, a separation performance calculation means is provided for calculating the separation performance SP(D) based on the formula (17).

[0082] In the embodiment of the present invention, the membrane performance calculation method of the separation membrane as described above may be stored as a computer-readable program in a computer-readable recording medium on which the program is recorded. In this case, the membrane performance calculation program is stored in a recording medium such as a hard disk of the computer.

[0083] Although various embodiments have been described above, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present invention. Furthermore, the components in the above-mentioned embodiments may be arbitrarily combined within the scope of the invention.

[0084] This application is based on a Japanese patent application (Patent Application No. 2023-37302) filed on March 10, 2023, the contents of which are incorporated by reference into this application. [Explanation of symbols]

[0085] 1: Raw water 2: Raw water pump 3: High pressure pump 4: Reverse osmosis membrane 5: Produced water 6: Drainage 10: Computer 11: Driving information input means 12: Driving information storage means 13: Means for extracting driving information 14: Separation performance calculation means 15: Process 1 16: Process 2 17:Process 3 18:Process 4 19:Separation performance preservation means 20: Separation performance storage means 21: Separation performance output means

Claims

1. A method for calculating the separation performance of a separation membrane used in liquid treatment to obtain a treated liquid from a treated liquid, the method comprising the steps of: calculating the separation performance of the separation membrane using an initial separation performance SP(0) of the separation membrane, an operating period D of the liquid treatment, a temperature T(t) of the treated liquid during the operating period D (t is a certain time during the operating period D), and a pressure P(t) of the treated liquid, by the following steps: Step 1: The separation performance of the separation membrane changed due to compaction after the operation period D has elapsed is defined as SP(D); Any time during the operation period D is t １ When The temperature T(t) of the liquid to be treated is １ The temperature T(t １ ) determining an equivalent operation period D' at which the separation performance becomes SP(D) when the separation performance is assumed to be constant. Step 2: Temperature T (t １ ) and the t １ The pressure P(t １ ) is used to calculate the compaction coefficient m (T(t １ ), P(t １ ) determining the Step 3: The equivalent operating period D′ and the compaction coefficient m (T(t １ ), P(t １ ) to calculate a separation performance correction coefficient M(D) corresponding to the ratio of the separation performance SP(D) to the initial separation performance SP(0). Step 4: A step of calculating the separation performance SP(D) using the separation performance correction coefficient M(D) and the initial separation performance SP(0).

2. Said t １ is a certain time during the high temperature period in the operating period D, A certain time during the low temperature period in the operation period D is t ２ When The equivalent operation period D' is defined as the temperature T(t １ ) and the t ２ The temperature T(t ２ 2. The method for calculating the separation performance of a separation membrane according to claim 1, wherein the separation performance is determined based on a difference or rate of change from the measured value.

3. Said T(t １ ), the T(t ２ ), the above t １ The pressure P(t １ ), the above t ２ The pressure P(t ２ 3. The method for calculating the separation performance of a separation membrane according to claim 2, further comprising correcting the equivalent operation period D' determined in step 1 based on at least one of the following:

4. Said t １ is the T(t １ t) is determined so that the temperature of the treated liquid during the operation period D is the maximum temperature. １－Ｔｍａｘ and Said t ２ is the T(t ２ t) is determined so that the temperature of the treated liquid during the operation period D is the minimum temperature. ２－Ｔｍｉｎ The method for calculating the separation performance of a separation membrane according to claim 2,

5. The compaction coefficient m (T(t １ ), P(t １ 2. The separation performance calculation method of claim 1, wherein the separation performance correction coefficient M(D) and the separation performance SP(D) are calculated based on one or more of the following formulas: (15), (16), and (17). [0010]

6. 2. The method for calculating the separation performance of a separation membrane according to claim 1, wherein the separation performance SP(D) is a solvent permeability coefficient or a solute permeability coefficient.

7. A computer is used to calculate the separation performance of a separation membrane used in liquid treatment to obtain a treated liquid from a treated liquid, an operation information input means for inputting operation information including at least the initial separation performance SP(0) of the separation membrane, an operation period D in the liquid treatment, a temperature T(t) of the liquid to be treated during the operation period D (t is a certain time during the operation period D), and a pressure P(t) of the liquid to be treated; A driving information storage means for storing the driving information; a driving information retrieval means for retrieving the driving information from the driving information storage means; A separation performance calculation means for calculating the separation performance of the separation membrane using the operating information in the following steps: A separation performance storage means for storing the separation performance in a separation performance storage means; The separation performance storage means, A program for calculating the separation performance of separation membranes to function as a filter. Step 1: The separation performance of the separation membrane changed due to compaction after the operation period D has elapsed is defined as SP(D); Any time during the operation period D is t １ When The temperature T(t) of the liquid to be treated is １ The temperature T(t １ ) determining an equivalent operation period D' at which the separation performance becomes SP(D) when the separation performance is assumed to be constant. Step 2: Temperature T (t １ ) and the t １ The pressure P(t １ ) is used to calculate the compaction coefficient m (T(t １ ), P(t １ ) determining the Step 3: The equivalent operating period D′ and the compaction coefficient m (T(t １ ), P(t １ ) to calculate a separation performance correction coefficient M(D) corresponding to the ratio of the separation performance SP(D) to the initial separation performance SP(0). Step 4: A step of calculating the separation performance SP(D) using the separation performance correction coefficient M(D) and the initial separation performance SP(0).

8. Said t １ is a certain time during the high temperature period in the operating period D, A certain time during the low temperature period in the operation period D is t ２ When The step 1 of determining the equivalent operating period D' comprises: From the information recorded in the operating information storage means, the temperature T(t １ ) and the t ２ The temperature T(t ２ ) based on an information calculation means for calculating a difference or a rate of change from 8. The separation membrane performance calculation program according to claim 7, further comprising a means for determining the equivalent operation period D'.

9. The step 1 of determining the equivalent operating period D' comprises: From the information stored in the driving information storage means, the T(t １ ), the T(t ２ ), the above t １ The pressure P(t １ ), the above t ２ The pressure P(t ２ 9. The separation membrane separation performance calculation program according to claim 8, further comprising an equivalent operation period correction means for further correcting the equivalent operation period D' using one or more of the above.

10. Said t １ is the T(t １ t) is determined so that the temperature of the treated liquid during the operation period D is the maximum temperature. １－Ｔｍａｘ and Said t ２ is the T(t ２ t) is determined so that the temperature of the treated liquid during the operation period D is the minimum temperature. ２－Ｔｍｉｎ The separation performance calculation program according to claim 8,

11. The step 2 calculates the compaction coefficient m (T(t １ ), P(t １ ) a compaction factor determining means for determining a compaction factor of the The step 3 includes a separation performance correction coefficient calculation means for calculating a separation performance correction coefficient M based on the formula (16), 8. The separation performance calculation program for a separation membrane according to claim 7, wherein the step 4 includes a separation performance calculation means for calculating the separation performance SP(D) based on the formula (17). [0025]

12. A computer-readable recording medium having recorded thereon the separation performance calculation program for the separation membrane according to any one of claims 7 to 11.

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