JP4977087B2 - System for measuring the concentration of volatile components in an aqueous solution of volatile components - Google Patents

Description

  In the present invention, the concentration of the volatile component in the volatile component aqueous solution is very simply measured using a gas sensor. There are a wide variety of fields that handle aqueous solutions of volatile components such as aqueous solutions of alcohol, such as chemicals, food, fermentation, biotechnology, energy, and electronic components, but their application range is expected in all fields. A preferred application example of the present invention relates to a method for controlling a hydrogen donating state (mainly methanol) to be added in a biological denitrification process in which nitrate or nitrite nitrogen is denitrified by microorganisms. The biological denitrification process is a process in which nitrate or nitrite nitrogen is reduced to nitrogen gas by the action of denitrifying bacteria in an anaerobic state (anoxic state) where a hydrogen donating state exists.

  Analytical instruments such as liquid chromatography, gas chromatography, and NMR are used to measure the concentration of the volatile components in the volatile component aqueous solution. However, instrumental analysis poses significant problems in terms of operability, versatility, and cost. An analysis method using physical properties such as refractive index and specific gravity is also used, but it cannot be said to be a simple analysis and there is a problem in its accuracy. In particular, with respect to alcohol gas concentration, a simple detector using a sensor is commercially available, but there is no method for simply measuring the concentration of an aqueous alcohol solution.

In particular, the present invention can be expected to be applied in biological denitrification processes. In this reaction, the existence of a hydrogen donor state is essential, but wastewater (treated water) containing almost no organic matter is added by adding a hydrogen donor state from the outside. Usually, this hydrogen donor state is volatile. Methanol is used.
^{_{6NO 3- + 5CH 3 OH → 3N}} 2 + 5CO 2 + 7H 2 O + 6OH -

  It can be seen that the amount of methanol required for the reaction is 5/6 moles per mole of nitrate nitrogen and 1.9 times the weight of methanol by the above theoretical formula. However, in reality, not all of the added methanol is used for the reduction reaction, and a part is also used for cell synthesis of denitrifying bacteria.

  If the amount of methanol added is insufficient, the denitrification performance will be degraded. Conversely, if the amount of methanol added is excessive, not only will it be a waste of methanol cost, but it will also be used to treat BOD / COD of methanol. This will increase the burden on the re-aeration tank. Therefore, the optimal addition of methanol is very important.

  Here, as a method of optimal addition of methanol, a method of controlling by measuring the oxidation-reduction potential (ORP) of a denitrification treatment tank (reactor tank) as disclosed in JP-A-7-256290, There is a method of controlling by measuring methanol in a denitrification tank (reactor tank) as shown in Open 2003-71492. However, the above-mentioned method using the liquid directly, such as measuring predetermined physical properties of the liquid or measuring methanol from the liquid, has the following problems.

  First, in the method of controlling the optimal amount of methanol by measuring the oxidation-reduction potential (ORP) of the denitrification treatment tank (reactor tank), methanol is not directly measured, so accurate control of the amount of methanol is very Have difficulty. Further, the ORP value is easily influenced by the influence of temperature, wastewater (treated water) concentration fluctuations, etc. and the active state of microorganisms, and methanol control using only the ORP value is likely to cause problems. Although there is a method of controlling by measuring methanol in a denitrification treatment tank (reactor tank) as disclosed in JP-A-2003-71492, gas-liquid separation by aeration is performed as a measurement method of methanol. The collected methanol gas is heated and a vaporization tank is provided separately from the reactor tank. In these methods, the energy cost by aeration and heating, the burden of providing an additional vaporization tank, etc. will be applied. Further, in the method of measuring gas by gas-liquid separation, the presence or absence of methanol in the reactor tank can be determined, but the methanol concentration cannot be measured. Therefore, accurate methanol control is difficult. These problems occur because the methanol concentration of the aqueous methanol solution cannot be directly measured with a sensor.

  Therefore, a method for measuring the volatile component concentration in the gas phase in a gas-liquid equilibrium state using a gas sensor and indirectly determining the volatile component concentration in the liquid based on Henry's law is disclosed in No. 64-6854 and JP-A-62-200241.

  However, these methods all estimate the volatile component concentration in the liquid based on the volatile component concentration in the gas phase when the vapor-liquid equilibrium state is reached. Therefore, as described in Japanese Patent Application Laid-Open No. 64-6854, measurement cannot be performed until a sufficient time has passed (the last line in the upper right column on page 2 to the seventh line in the lower left column). Further, in order to achieve a vapor-liquid equilibrium state in a short time, it is necessary to employ a method of bubbling gas through a liquid system as described in JP-A-62-200241 ( (Claim 5), page 3, lower right column, lines 4-7). However, even in this case, it is necessary to install bubble means, which causes great problems in operability, versatility, and cost.

Therefore, the present invention is a method for estimating the volatile component concentration in the liquid after measuring the volatile component concentration in the gas phase using a gas sensor. It is an object of the present invention to provide a means capable of measuring the concentration of a volatile component in a liquid without having to wait until the vapor-liquid equilibrium state is reached, without having to forcibly construct the vapor-liquid equilibrium state in a short time.
JP-A-7-256290 JP 2003-71492 A JP-A 64-6854 JP-A-62-200241

  Therefore, as a result of intensive studies, the present inventors have observed changes over time until the equilibrium between the gas phase and the liquid phase is reached, and found that there is a certain law, and the following inventions (1) to (4) ) Completed.

The present invention (1) relates to a volatile component concentration-related parameter value measured over time in a system for measuring the volatile component concentration in a volatile component aqueous solution. When the differential value reaches the maximum value, the estimated value of the concentration-related parameter value of the volatile component in the equilibrium state based on the concentration-related parameter value of the time when the maximum value is reached It is a system characterized by computing.
More specifically, the present invention (1) is a system for measuring the concentration of the volatile component in the volatile component aqueous solution.
An outer body capable of forming an airtight space when brought into contact with the volatile component aqueous solution, and capable of reaching a gas-liquid equilibrium state between the airtight space and the volatile component aqueous solution (for example, , Outer body 11),
A volatile component concentration-related parameter value measurement unit (for example, a gas sensor 12) that measures a concentration-related parameter value of the volatile component in the hermetic space;
Based on the volatile component concentration-related parameter value measured in the non-equilibrium state, the estimated value of the volatile component concentration-related parameter value in the equilibrium state is calculated. (For example, volatile component concentration calculation execution means 174);
A volatile component concentration calculation unit (for example, volatile component concentration calculation execution means 174) that calculates the volatile component concentration in the volatile component aqueous solution based on the parameter value and temperature related to the estimated volatile component concentration in the equilibrium state. And
The equilibrium state volatile component estimated concentration-related parameter value calculation unit (for example, the volatile component concentration calculation execution unit 174)
With respect to the volatile component concentration-related parameter value measured over time, a volatile component concentration-related parameter value time differential value acquisition unit that acquires a time-dependent differential value of the volatile component concentration-related parameter value. When,
A maximum value attainment determination unit for determining whether the differential value has reached a maximum value;
When the maximum value determination unit determines that the maximum value has been reached, the following formula:
F (x) = F (x: t (start)) + {F (x: t (max)) − F (x: t (start))} × A
{Where F (x) is the estimated value of the volatile component concentration related parameter value in the equilibrium state, t (start) is the time at the start of measurement, and t (max) is the maximum value. F (x: t (start)) is a measured value of the volatile component concentration related parameter value at t (start), and F (x: t (max)) is t (max) Is a measured value of the parameter value related to the concentration of the volatile component in A, and A is a constant}
A system for calculating an estimated value of a concentration-related parameter value of a volatile component in an equilibrium state by substituting each parameter value in an equilibrium state, It is.

The present invention (2) further includes a storage unit in which the constant A associated with temperature or the constant A associated with a combination of temperature and the volatile component is stored. System.

The present invention (3)
A constant A calculation unit (for example, constant A determination processing execution means 173) that calculates the constant A based on the maximum value obtained for the volatile component aqueous solution having a known concentration of a plurality of patterns;
The system according to the invention (1) or (2) further including a temporary storage unit (for example, temporary storage means 15) for temporarily storing the calculated constant A.

  This invention (4) further has the temperature measurement part (for example, temperature sensor 13) which measures the temperature in the said airtight space, or the temperature of the said volatile component aqueous solution directly or indirectly, The said invention (1)-( 3) One of the systems.

  Hereinafter, definitions of each term in the claims and the specification will be described. First, the “system” is not particularly limited as long as a plurality of elements can function integrally to achieve a desired purpose, and is not limited to a device in which all or most of the elements are integrated. It is also a concept that encompasses a remote plant. The “airtight space” is not a concept that is physically completely airtight, but a concept that allows some open state such as a cord hole of a sensor. The “density-related parameter value” refers to any parameter value related to the density, and includes not only the output value (voltage) corresponding to the density but also the density value itself.

  According to the present invention (1), the aqueous solution is not directly measured, but the gas phase volatile component concentration-related parameter value is measured using a simple gas sensor, and the volatile component in the aqueous solution is measured based on the measured value. Since the method of estimating the concentration is adopted, it is excellent in operability, versatility, and cost, and there is no problem that it cannot be measured until it reaches the gas-liquid equilibrium state as before, so the gas-liquid equilibrium state Thus, it is possible to avoid the situation of waiting for the measurement until tens of hours, and there is an effect that special equipment such as bubble means is not required.

  According to the present invention (2), in addition to the above effect, the constant A is read from the storage unit based on the temperature (or the temperature and the type of the volatile component to be measured). In addition, there is an effect that it is possible to save the labor of specifying the constant A using the standard solution.

  According to the present invention (3), in addition to the above-described effect, since the operation for specifying the constant A using the standard solution is performed in the field, the temperature (or the temperature and the volatile component to be measured) There is an effect that it is not necessary to store the constant A for each type).

  According to the present invention (4), in addition to the above-described effect, the temperature is automatically measured, so that it is not necessary to input temperature information every measurement.

"System configuration"
FIG. 1 is a schematic diagram of a volatile component concentration measurement system 1 according to the best mode. The system 1 stores an outer body 11, a gas sensor 12 attached to the outer body 11, a temperature sensor 13, and various data (programs and various parameter values) for calculating volatile component concentrations. A storage unit 14; a temporary storage unit 15 for temporarily storing various data when calculating the concentration of volatile components; and an input unit 16 capable of inputting a start signal and various types of information (for example, volatile component type information). , Comprising a display unit 18 for displaying various displays (volatile concentration values and various messages), and the above-described sensors 12 and 13, the input means 16, and the display unit 18 connected to be able to transmit information. Is done. The main elements are described in detail below.

(Outer body)
First, the outer body 11 is not particularly limited as long as it can form an airtight space inside the outer body 11 when part or all of the outer body 11 is submerged in an aqueous solution (for example, a liquid container having an opening such as a beaker). A member made of a permeable member and having shape retaining properties). For example, in the figure, an airtight space is created by covering the volatile component aqueous solution with an outer body and half-immersing it in the aqueous solution. Here, the airtight space is a space for the volatile component to reach vapor-liquid equilibrium, and may not be completely sealed. For example, a measured value is obtained when a very small hole for passing a copper wire connected to the sensor is opened in the outer body 11 and the hole is covered with clay and completely sealed, and when the very small hole is left as it is. There will be no slippage.

  Here, FIG. 6 is a diagram illustrating a modification example of the outer body 11. The outer body 11 (2) is devised so that the gas sensor 12 (2) can be directly measured into the volatile component aqueous solution for measurement. Specifically, the outer body 11 (2) has a configuration in which the periphery is made of a liquid non-permeable member such as glass and the opening (bottom) is covered with the waterproof moisture permeable membrane 11a (2). Yes. With this configuration, only the vapor of the volatile component is introduced into the hermetic space of the outer body 11 (2) through the waterproof and moisture permeable membrane 11a (2) while preventing water from entering. The waterproof and moisture permeable material may be any material as long as it passes volatile component gas without passing water, for example, Gore-Tex (made by Japan Gore-Tex). it can. Moreover, in the said figure, although only the aspect which provided the waterproof moisture-permeable film only in the opening part was shown, it is not limited to this, All or most may be comprised from the waterproof moisture-permeable film.

Furthermore, although the form of FIG.1 and FIG.6 constructs airtight space by making direct contact with aqueous solution, it is not limited to this, As shown in FIG. 7, it is airtight without making direct contact with aqueous solution. You may take the structure which builds space.
(Gas sensor)

  Next, the gas sensor 12 is not particularly limited as long as it can measure the gas concentration in the gas phase of the volatile component to be measured. For example, when the measurement object is methanol, a gas sensor using tin oxide can be used. However, any sensor can be used as long as it is a sensor that reacts with methanol gas. For example, a gas sensor using a metal oxide semiconductor other than tin oxide or a crystal resonator can be used. In the figure, two types of sensors with different sensitivities are used. This is because the concentration of the aqueous volatile component solution can be measured from a low concentration to a high concentration. Naturally, since the gas concentration changes depending on the volume of the airtight space in the outer body, a sensitivity corresponding to the volume of the air chamber is required. Therefore, it is preferable to use two or more types of sensors having different sensitivities as necessary. There are various types of tin oxide gas sensors available on the market depending on the type of gas to be detected. Taking advantage of the sensor characteristics, the sensitivity to notanol varies from high sensitivity to low sensitivity. Can be prepared. For example, it has been confirmed that a commercially available sensor for alcohol detection has high methanol sensitivity, and a commercially available sensor for detecting an amine-based sensor has low methanol sensitivity. By combining a high sensitivity and a low sensitivity, it is possible to measure both at high and low concentrations.

  Some types of gas sensors are affected by humidity. In this case, a configuration may be adopted in which a humidity sensor is provided to correct the influence of the humidity. For example, a capacitive sensor using a polymer, a metal oxide, or an electrolyte, or a humidity sensor using a crystal resonator can be used.

(Temperature sensor)
Next, the temperature sensor 13 is not particularly limited as long as the temperature of the hermetic space can be directly or indirectly measured, and any type can be used. For example, a temperature sensor using a thermocouple, thermistor, side temperature resistor or the like can be used. Here, in the figure, a method for indirectly measuring the temperature of the airtight space, that is, assuming that the temperature of the aqueous solution is substantially the same as the temperature of the airtight space, the temperature sensor 13 is immersed in the volatile component aqueous solution. I am letting. The reason is that when the gas sensor is accompanied by heat generation, the temperature in the airtight space cannot be measured accurately due to the influence of the heat generation. However, if the heat generation amount of the gas sensor is small, the temperature sensor 13 may be arranged in the airtight space. Further, even if the heat generation amount is not small, the temperature is located at a position away from the sensor in the airtight space. A sensor 13 may be installed. In addition, it is necessary to grasp the temperature when calculating the concentration of the volatile component, but the temperature sensor is not necessarily provided when the operator inputs the current temperature without installing the temperature sensor 13. It does not have to be.

(Memory means)
Next, the storage unit 14 is not particularly limited as long as it can store a program for executing various processes related to measurement and a display control process to be described later, and various parameter data necessary for executing the program. Specifically, it is a ROM. Here, various parameter data stored in the storage unit 14 is not particularly limited, but in the present embodiment, the following data is stored.

(1) “Constant A” used when estimating the volatile component (gas) concentration parameter value at equilibrium from the volatile component (gas) concentration parameter value at non-equilibrium state
In the present invention, the following equation (1) is used to estimate the volatile component (gas) concentration parameter value at equilibrium from the volatile component (gas) concentration parameter value at non-equilibrium state.

  In Formula (1), F (x) is an estimated value of the volatile component concentration-related parameter value in the equilibrium state, t (start) is the time at the start of measurement, and t (max) is F ( x) is a time until the differential value reaches the maximum value, and F (x: t (start)) is a measured value of the parameter value related to the volatile component concentration at t (start), and F (x: t (Max)) is a measured value of the volatile component concentration-related parameter value at t (max), and A is a constant. Here, the constant A is a constant found by the present inventors, and is a constant substantially specified by the type of volatile component, the type of solvent (water in the present invention), and temperature. Therefore, the constant A at various temperatures is stored for each volatile component so that the concentration measurement of various volatile components can be handled under various temperature conditions. Here, the constant A is a numerical value acquired experimentally in advance according to a method described later for each volatile component and temperature to be measured. Even if the constant A is not stored, the constant A may be obtained on-site using a standard solution with a known concentration.

(2) By using the estimated volatile component (gas) concentration parameter values at various constants used in calculating the volatile component concentration in the liquid using the estimated volatile component (gas) concentration parameter values at equilibrium In calculating the volatile component concentration in the liquid, various known methods can be employed.

(2-1) When performing the calculation based on Raoul's law First, the relationship between the gas sensor output (mV) and the volatile component (gas) concentration is calculated according to the following formula (2).

  Here, in formula (2), B and C are constants substantially specified by the type and temperature of the volatile component, and x is the gas sensor output. Therefore, constants B and C at various temperatures are stored for each volatile component so that the concentration measurement of various volatile components can be handled under various temperature conditions.

Next, the saturated vapor pressure and partial pressure of the volatile component at the gas phase temperature are calculated using the Antoine equation. At this time, the constant value in the equation of Antoine is a constant substantially specified by the type of the volatile component. Therefore, the constant value is stored for each volatile component so that it can cope with the concentration measurement of various volatile components.
(2-2) When performing the calculation based on Henry's law First, the relationship between the gas sensor output (mV) and the volatile component (gas) concentration is calculated according to the above equation (2). Next, the volatile component concentration of the solution is calculated using the Henry constant. At this time, the Henry constant is a constant substantially specified by the kind and temperature of the volatile component. Therefore, Henry's constants at various temperatures are stored for each volatile component so that the concentration measurement of various volatile components can be handled under various temperature conditions.

(Temporary storage means)
Next, the temporary storage unit 15 is not particularly limited as long as it has a function of temporarily storing various data when calculating the volatile component concentration, and examples thereof include a RAM. As the data, the output value transmitted from the gas sensor 12 over time, the time differential value of the output value, the ID information specifying the type of the volatile component to be measured, and the temperature sensor 13 are transmitted. In addition to the temperature value, on / off information of various processing flags is also included.

(Input means)
Next, the input means 16 is a means for inputting various parameter values necessary for calculation in addition to operation start and end instructions, for example. Specifically, a measurement start instruction unit and a selection unit that selects a volatile component to be measured from a plurality of lists can be exemplified. Furthermore, although the temperature sensor 13 exists in this form, the temperature input part which inputs the present temperature when it does not exist is included. In addition, in this embodiment, constant values (A, Antonio constants, Henry constants, etc.) necessary for various calculations are already stored in the ROM. If they are not stored, constants for inputting these constant values are stored. Includes an input section.

(Processing part)
Next, the processing unit 17 is a CPU that can execute arithmetic processing using various parameter values. An input / output circuit and an A / D converter are provided so that the CPU can communicate information with an external device.

<Functional configuration>
Next, the functional configuration of the system (processing unit 17) according to the present embodiment will be described with reference to the functional block diagram of FIG. In this embodiment, the constant A may or may not be stored (in this case, the constant A is input, or a standard solution with a known concentration is used in the field). To obtain the constant A). Below, the type which acquires the constant A on-site using a standard solution with a known concentration will be taken as an example, and the functional configuration (and subsequent processing) will be described in detail.

  First, as described above, the processing unit 17 is connected to peripheral devices (the gas sensor 12, the temperature sensor 13, the input unit 16, and the display unit 18) so that information can be transmitted. Here, the processing unit 17 includes a receiving unit 171 for receiving output information from peripheral devices (the gas sensor 12, the temperature sensor 13, and the input unit 16), and a display control unit 172 that controls display control on the display unit 18. A constant A determination processing execution unit 173, a volatile component concentration calculation execution unit 174 for calculating a volatile component concentration in the aqueous solution from various parameter values, the storage unit 14 described above, and the temporary storage unit 15 described above. And having. Although only elements particularly related to the present invention are shown, it should be understood that elements not shown are not present, and elements existing in the well-known technology basically exist.

"processing"
Next, the volatile component concentration measurement process executed by the system according to the present embodiment will be described in detail with reference to the flowcharts of FIGS. First, FIG. 3 is a main flow of volatile component concentration measurement processing executed in the system according to the present embodiment. First, in step 1000, the processing unit 17 executes a constant A determination process using a standard solution having a known concentration. Next, in step 2000, the processing unit 17 executes a process for determining the volatile component concentration in the sample liquid related to the measurement target. Hereinafter, the processing of these subroutines will be described in detail.

  First, FIG. 4 is a flowchart relating to a subroutine of the constant A determination process 1000 using a standard solution. First, in step 1001, the constant A determination process execution unit 173 accesses the reception unit 171 and determines whether or not the constant A determination start button has been pressed. In the case of Yes in step 1001, the constant A determination processing execution unit 173 accesses the flag area of the temporary storage unit 15 and turns off the constant A determination flag. Next, in step 1005, the display control means 172 controls to display “Start constant A determination processing” on the display unit 18. Next, in step 1007, the display control means 172 controls to display “Please input density” on the display unit 18. Here, the concentration is a concentration of a volatile component aqueous solution (standard solution) to be measured, which has a known concentration. Next, in step 1009, the constant A determination process execution unit 173 accesses the reception unit 171 and determines whether or not a density value has been input by the operator. In the case of Yes in Step 1009, the constant A determination processing execution unit 173 temporarily stores the input density value data in the temporary storage unit 15 in Step 1011. Next, in step 1013, the display control means 172 controls to display “Please put the sensor on the liquid” on the display unit 18. Subsequently, in step 1014, the constant A determination process execution unit 173 accesses the reception unit 171 and determines whether or not the start signal is recognized. Here, examples of the start signal include a signal input by an input device immediately after the measurer immerses the sensor in the liquid. If yes in step 1014, the measurement is started. In step 1015 and step 1017, the constant A determination processing execution unit 173 accesses the reception unit 171, acquires the output value (mV) of the concentration related parameter value from the gas sensor 12, and then temporarily stores the data. Temporarily stored in the storage means 15. The output value acquired immediately after the start of measurement is assumed to be V (start).

  Next, in step 1019, the constant A determination process execution unit 173 temporarily stores n = 1 in the temporary storage unit 15. Next, in step 1021, the constant A determination processing execution unit 173 determines whether Δt (for example, 0.5 minutes) has elapsed. The time Δt (the same applies to Δt described later) is 0.5 minutes in this example, but can be set as appropriate, and may be shorter or longer. In the case of Yes in step 1021, in steps 1023 and 1025, the constant A determination processing execution unit 173 accesses the reception unit 171 and outputs the output value V1 (mV) of the concentration related parameter value from the gas sensor 12 at time t1. After acquisition, the data is temporarily stored in the temporary storage unit 15. Next, in step 1027 and step 1029, the constant A determination processing execution unit 173 substitutes the V0 and V1 values temporarily stored in the temporary storage unit 15 into the expression V1 ′ = (V1−V0) / Δt. A differential value V1 ′ is calculated, and the differential value is temporarily stored in the temporary storage means 15.

Subsequently, the constant A determination processing execution unit 173 executes the same processing as the above-described steps 1021 to 1029 in steps 1031 to 1041, and temporarily stores V (n) ′ in the temporary storage unit 15. Subsequently, in step 1043, the constant A determination processing execution unit 173 determines whether V (n−1) ′ − V (n) ′> [sensor measurement error]. Here, as the measurement error of the sensor, for example, it is possible to set an error of the differential value that may be generated due to the measurement error of the sensor. In the case of No in step 1043, the process proceeds to step 1045, and V (n) ′ is obtained again in steps 1033 to 1041. In the case of Yes in step 1043, the constant A determination executing means 173, the V (n-1) at step 1047 as _{V max,} temporarily stored in the temporary storage unit 15.

Next, the constant A determination processing execution means 173 executes the same processing as the above steps 1021 to 1029 in steps 1049 to 1059 and temporarily stores V (n) ′ in the temporary storage means 15. Subsequently, the constant A determination processing execution unit 173 determines whether V (n) ′ ≦ 0 at Step 1061. In the case of No in step 1061, the process proceeds to step 1063, and V (n + 1) ′ is obtained again in steps 1049 to 1059. In the case of Yes in step 1061, the constant A determination processing execution unit 173 temporarily stores V (n) as V _fin in the temporary storage unit 15 in step 1065.

Subsequently, the constant A determination processing execution means 173 calculates the constant A by substituting each parameter into the formula of A = {V _fin −V (start)} / {V _max −V (start)} in step 1067. Then, in the next step 1069, it is temporarily stored in the temporary storage means 15. Subsequently, in step 1071, the constant A determination processing execution unit 173 accesses the flag area of the temporary storage unit 15 and turns on the constant A determination flag.

  Next, FIG. 5 is a flowchart relating to a subroutine of Step 2000 for executing a process for determining the concentration of the volatile component in the sample liquid relating to the measurement target. First, in step 2001, the volatile component concentration calculation execution means 174 accesses the flag area of the temporary storage means 15 and confirms whether the constant A determination flag is on. When step 2001 is No, the display control unit 172 controls the display unit 18 to display “Please execute the constant A determination process using the standard solution”, and the volatile component concentration calculation execution unit. In step 174, the process proceeds to subroutine constant A determination processing 1000. When step 2001 is Yes, the display control means 172 controls to display “Start volatile component determination processing in the sample liquid” on the display unit 18 in step 2003. Next, in step 2005, the display control means 172 controls to display “Please put the sensor on the liquid” on the display unit 18. Subsequently, in step 2009, the volatile component concentration calculation execution unit 174 accesses the reception unit 171 and determines whether or not the start signal is recognized. Here, examples of the start signal include a signal input by an input device immediately after the measurer immerses the sensor in the liquid. In the case of Yes in step 2009, this starts the measurement. Then, in step 2011 and step 2013, the volatile component concentration calculation execution means 174 accesses the reception means 171 to acquire the output value (mV) of the concentration related parameter value from the gas sensor 12, and then the data is obtained. Temporary storage in the temporary storage means 15. The output value acquired immediately after the start of measurement is assumed to be V (start).

  Next, in step 2015, the volatile component concentration calculation execution unit 174 temporarily stores n = 1 in the temporary storage unit 15. Next, in step 2017, the volatile component concentration calculation execution means 174 determines whether or not Δt (for example, 0.5 minutes) has elapsed. The time Δt (the same applies to Δt described later) is 0.5 minutes in this example, but can be set as appropriate, and may be shorter or longer. In the case of Yes in step 2017, in steps 2019 and 2021, the volatile component concentration calculation execution means 174 accesses the reception means 171 and outputs the concentration related parameter value output value V1 (mV) from the gas sensor 12 at time t1. Then, the data is temporarily stored in the temporary storage unit 15. Next, in step 2023 and step 2025, the volatile component concentration calculation execution unit 174 substitutes the V0 and V1 values temporarily stored in the temporary storage unit 15 into the equation V1 ′ = (V1−V0) / Δt. The differential value V1 ′ is calculated by the above, and the differential value is temporarily stored in the temporary storage unit 15.

Subsequently, the volatile component concentration calculation execution unit 174 performs the same processing as in steps 2015 to 2025 in steps 2027 to 2037 and temporarily stores V (n) ′ in the temporary storage unit 15. Subsequently, in step 2039, the volatile component concentration calculation execution means 174 determines whether V (n−1) ′ − V (n) ′> [sensor measurement error]. Here, as the measurement error of the sensor, for example, it is possible to set an error of the differential value that may be generated due to the measurement error of the sensor. In the case of No in step 2039, the process proceeds to step 2041, and V (n) ′ is obtained again in steps 2029 to 2037. In the case of Yes in step 2039, the volatile component concentration calculation execution unit 174 temporarily stores the temporary storage unit 15 with V (n−1) as V _max in step 1047.

Next, in step 2045, the volatile component concentration calculation execution means 174 substitutes each parameter value into an expression of V _{fin (estimate)} = V (start) + {V _max −V (start)} × A. _{fin (estimate)} is calculated and stored in the temporary storage unit 15 in the next step 2047. Subsequently, the volatile component concentration calculation execution means 174 accesses the reception means 171 in step 2049, acquires the temperature (° C.) from the temperature sensor 13, and then in the next step 2051, volatilizes from the formula of Antoine. The saturated vapor pressure of the sex component is calculated, and the data is temporarily stored in the temporary storage means 15.
Next, in step 2051, the volatile component concentration calculation execution means 174 accesses the temporary storage means 15 to acquire the estimated output value, and then obtains an expression obtained in advance {eg, volatile component (gas concentration) = B The volatile component gas concentration is calculated from exp (Cx), constants B and C are calculated by experiment}, and in the next step 2055, the volatile component concentration gas partial pressure is calculated, and the data is stored in the temporary storage means 15. Memorize temporarily. Subsequently, in step 2057, the volatile component concentration calculation execution unit 174 accesses the temporary storage unit 15 to read necessary information, and calculates the molarity according to the equation [partial pressure] / [saturated water vapor pressure] = [molar fraction]. The fraction is calculated, and in the next step 2059, a value converted from the molar fraction to the weight% is calculated, and the data is temporarily stored in the temporary storage means 15. Subsequently, the display control unit 172 controls to display the calculation result on the display unit 18.

<Application example>
FIG. 8 shows a methanol concentration management system in a biological denitrification process in which nitrate or nitrite nitrogen is denitrified by microorganisms, which is an application example of the concentration measurement system according to the present invention. is there. In the figure, 100 is a denitrification tank (reactor tank), 101 is a methanol pump, 102 is a stirrer, and 103 is a nitrogen measuring device. The control unit 19 executes control of the overall methanol concentration management system such as methanol supply control in addition to the above-described control of the concentration measurement system.

  By adding methanol to the denitrification treatment tank 100 (reactor tank) as a hydrogen donating state, the reduction reaction from nitrate or nitrite nitrogen to nitrogen gas by the microorganism (denitrification bacteria) proceeds. The treatment tank may be a combination of the nitrification tank and the re-aeration tank. In addition, there are various processes such as the presence / absence of a carrier and combined use with phosphorus removal during the treatment.

  The control part 19 calculates | requires the amount of residual methanol in water in a denitrification processing tank by performing the above processes. Then, the control unit 19 controls the methanol supply pump 101 based on the calculated amount of residual methanol in water (and possibly nitrogen concentration) to execute supply or stop of methanol. Here, there are various standards for supply and supply stoppage. As an example, 2.8 times the amount of nitrogen concentration (weight conversion) is set as the amount of methanol in the denitrification tank (reactor tank), and this amount of residual methanol is If it falls below the value, a method of controlling the methanol supply pump can be mentioned.

  As the nitrogen measuring device 103, an existing device can be used. For example, an online total nitrogen / total phosphorus meter (manufactured by Shimadzu Corporation) can be used. In addition, regarding the nitrogen concentration measurement method, various analysis methods such as nitrate ion / nitrite ion meter measurement, nitrogen measurement using a TOC meter, titration method, and absorptiometry can be used. Nitrogen concentration measurement can be used because the penetration rate of on-line nitrogen concentration measurement devices is high due to the total amount regulation. However, it is not always necessary to measure the nitrogen concentration. In order to control the amount of residual methanol in the denitrification tank (reactor tank) more precisely, grasp the nitrogen concentration and manage it with a methanol amount that is 2.8 times (weight conversion) the nitrogen concentration (TN). Is desirable. In a denitrification tank (reactor tank) where the nitrogen concentration cannot be measured, it is possible to control only the amount of methanol.

  Next, the functional configuration of the system (control unit 19) according to the present embodiment will be described with reference to the functional block diagram of FIG. In this embodiment, the volatile component concentration measurement processing unit described in detail above is included.

  First, as described above, the control unit 19 is connected to peripheral devices (the gas sensor 12, the temperature sensor 13, the input unit 16, the display unit 18, the methanol supply pump 101, the nitrogen concentration measuring device 103) so as to be able to transmit information. Yes. Here, the control unit 19 includes a receiving unit 171 for receiving output information from peripheral devices (gas sensor 12, temperature sensor 13, input unit 16, nitrogen concentration measuring device 103), and display control on the display unit 18. Display control means 172 for controlling the above, constant A determination processing execution means 173, volatile component concentration calculation execution means 174 for calculating the volatile component concentration in the aqueous solution from various parameter values, methanol supply pump control means 175, A nitrogen concentration determination unit 176, a methanol addition amount determination unit 177, the storage unit 14 described above, and the temporary storage unit 15 described above. Although only elements particularly related to the present invention are shown, it should be understood that elements not shown are not present, and elements existing in the well-known technology basically exist.

  Next, the humidity control process according to the best mode will be described in detail with reference to the flowchart of FIG. First, in step 3001, the nitrogen concentration determination unit 176 accesses the reception unit 171, accesses the nitrogen concentration measurement device 103, reads the nitrogen concentration, and stores it in the temporary storage unit 15. Next, in step 3002, the nitrogen concentration determination unit 176 accesses the temporary storage unit 15, reads the end set value input by the measurer, and determines whether or not the measured value exceeds the set value. In the case of Yes in step 3002, in step 1000, the constant A determination processing execution unit 173 and the volatile component concentration calculation unit 174 perform an alcohol concentration measurement process and store the processing result in the temporary storage unit 15. In step 1000, the alcohol concentration is calculated by the same method as the volatile component concentration measurement described above. On the other hand, if No in step 3002, that is, if the density is equal to or lower than the end set value, the control is stopped and the operation is ended. Subsequently, in step 3003, the methanol addition amount determining unit 177 reads and compares the alcohol concentration and the nitrogen concentration stored in the temporary storage unit 15 and compares the alcohol concentration with the set value (for example, 2. 8 times) or less. If step 3003 is Yes, in the next step 3004, the methanol addition amount determination means 177 determines the methanol addition amount. If NO in step 3003, the process returns to the beginning of the process. In the next step 3005, the methanol addition amount determining means 177 executes the alcohol addition according to the alcohol addition amount determined in step 3004, and returns to the beginning of the processing.

  In the biological denitrification process in which nitrate or nitrite nitrogen is denitrified by microorganisms by using the system according to the present invention, the residual hydrogen donating state (mainly methanol) of the denitrification tank (reactor tank) ) Is directly measured, it becomes possible to accurately control the hydrogen donating state (mainly methanol) to be added. The hydrogen donating state can be measured in alcohols other than methanol, but methanol is generally used because methanol is inexpensive and the reaction rate is high. Since the residual methanol in the denitrification tank (reactor tank) is directly measured, it is possible to control the added methanol more accurately than the method of measuring the oxidation-reduction potential (ORP). Further, methanol can be measured without gas-liquid separation of residual methanol in the denitrification treatment tank (reactor tank) by aeration and the like and without heating methanol gas. This method eliminates the need for extra energy costs.

Example 1 (Alcohol sensor output value estimation)
Using the volatile component concentration measurement system (sensor type: tin oxide) shown in FIG. 7 (container: 1 L), an experiment for estimating the alcohol concentration output value was performed. Here, 1000 ppm of methanol aqueous solution was prepared, and the time when the airtight space was set under the condition of 25 ° C. was set as the initial time for each solution, and the output value of the alcohol gas sensor was recorded. As a result, the data shown in Table 1 below could be obtained.

From the above results, the constant A is obtained by the following equation.
A = ([value at equilibrium]-[initial value]) / ([value at maximum differential value]-[initial value])
Here, the maximum differential value 348 was obtained at time 4.5 min. That is, [maximum differential value] = 451 mV. Further, the value at the time of 27 min was selected as the value at the time of equilibration, and [value at the time of equilibration] = 1156 mV. The initial value is 116 mV. Therefore, A = 3.10.

Example 2 (Comparison experiment of estimated value and actual value)
Based on the value of the constant A obtained in Example 1 and the gas sensor output value at the time when the differential value is maximum, the gas sensor output estimated value was obtained using the following gas sensor output value estimation formula at equilibrium. .
[Gas sensor output estimated value] = [Gas sensor initial value] + A {[Gas sensor output value at the time when the differential value is maximum] − [Gas sensor initial value]}
Here, 100, 500, and 5000 ppm methanol aqueous solutions were prepared, and for each solution, the gas sensor output value at the time when the initial value and the differential value were maximum was measured, and the gas sensor output value at equilibrium was estimated. . Furthermore, sufficient time was taken until the gas-liquid equilibrium was reached, and the output value (actually measured value) of the alcohol gas sensor at the time of equilibrium was measured. The validity of the equation was examined by comparing these estimated values and actual measured values. The results are shown in Table 2. As can be seen from the table, the estimated gas sensor output value at equilibrium was within about 15% of the gas sensor output value at equilibrium. In addition, the solution concentration value derived based on the estimated output value also has an error of about 30% of the solution concentration value derived based on the output value at equilibrium at the maximum (calculated based on Raoul's law: Activity coefficient = 1, B = 11.13, C = 0.008, temperature = 25 ° C.).

Example 2 (Methanol supply amount control)
FIG. 11 shows the experimental results with the apparatus shown in FIG. The treated water used was 1000 mg / L wastewater with nitrate / nitrite nitrogen as TN. Microorganisms were carried out at a sludge concentration of 6000 mg / L in MLSS using a carrier. The temperature of the denitrification tank (reactor tank) was controlled at 25 ° C., and PH was controlled at 8.0 with sulfuric acid and sodium hydroxide. The method for controlling the addition of methanol was performed so that the amount of the nitrogen concentration measured was 2.8 times (weight conversion). As a comparative example, the result of controlling the addition amount of methanol so that the ORP is −50 to −200 mV as conventionally performed is shown.
The horizontal axis shows the processing time, the vertical axis shows the TN value (line graph), and the vertical axis shows the residual methanol amount (bar graph). In addition, the amount of residual methanol here is a value measured by TOC and gas chromatography analysis separately from the alcohol concentration measurement method according to the present invention. Looking at the figure, there was no significant difference between the two in the amount of denitrification. However, when looking at the residual methanol (bar graph), there was a marked difference between the two. In the examples, the residual methanol amount decreased with a decrease in the TN value, and after 7 days, the residual methanol amount was 1/3 of the comparative example. Usually, it is necessary to treat BOD / COD of residual methanol in a re-aeration tank. However, when the amount of residual methanol becomes 1/3, the equipment burden and the energy burden of aeration can be significantly reduced. Furthermore, the amount of methanol used in the examples is less than half that of the comparative example, and the methanol cost can be greatly reduced.

FIG. 1 is a diagram showing an embodiment of a volatile component concentration measurement system. FIG. 2 is a functional block diagram of the volatile component concentration processing unit. FIG. 3 is a main flowchart of the processing unit of the volatile component concentration measurement system. FIG. 4 is a diagram showing one subroutine of the volatile component concentration measurement system. FIG. 5 is a diagram showing one subroutine of the volatile component concentration measurement system. FIG. 6 is a diagram showing an embodiment of a sensor of the volatile component concentration measurement system. FIG. 7 is a diagram showing an embodiment of a sensor of the volatile component concentration measurement system. FIG. 8 is a diagram illustrating an embodiment of a gas sensor in a biological denitrification process. FIG. 9 is a functional block diagram of the methanol supply amount control unit. FIG. 10 is a flowchart of the main routine of the methanol supply amount control unit. FIG. 11 is a graph showing changes over time in the TN value and the amount of residual methanol in Examples and Comparative Examples.

Claims (4)

In a system for measuring the concentration of volatile components in an aqueous solution of volatile components,
An outer body capable of forming an airtight space when brought into contact with the volatile component aqueous solution, the outer body capable of reaching a gas-liquid equilibrium state between the airtight space and the volatile component aqueous solution;
A volatile component concentration-related parameter value measuring unit for measuring a concentration-related parameter value of the volatile component in the airtight space;
Based on the volatile component concentration-related parameter value measured in the non-equilibrium state, the estimated value of the volatile component concentration-related parameter value in the equilibrium state is calculated. When,
A volatile component concentration calculator that calculates the concentration of the volatile component in the aqueous solution of the volatile component based on the parameter value related to the estimated concentration of the volatile component in the equilibrium state and the temperature;
The equilibrium state volatile component estimated concentration-related parameter value calculation unit,
With respect to the volatile component concentration-related parameter value measured over time, a volatile component concentration-related parameter value time differential value acquisition unit that acquires a time-dependent differential value of the volatile component concentration-related parameter value. When,
A maximum value attainment determination unit for determining whether the differential value has reached a maximum value;
When the maximum value arrival determination unit determines that the maximum value has been reached, the following formula (1):

{Where F (x) is the estimated value of the volatile component concentration related parameter value in the equilibrium state, t (start) is the time at the start of measurement, and t (max) is the maximum value. F (x: t (start)) is a measured value of the volatile component concentration related parameter value at t (start), and F (x: t (max)) is t (max) Is a measured value of the parameter value related to the concentration of the volatile component in A, and A is a constant}
A system for calculating an estimated value of a concentration-related parameter value of a volatile component in an equilibrium state by substituting each parameter value in an equilibrium state, . The system according to claim 1, further comprising a storage unit in which the constant A associated with a temperature or the constant A associated with a combination of a temperature and the volatile component is stored. A constant A calculation unit for calculating the constant A based on the maximum value obtained for the volatile component aqueous solution having a known concentration of a plurality of patterns;
The system according to claim 1, further comprising a temporary storage unit for temporarily storing the calculated constant A.   The system according to any one of claims 1 to 3, further comprising a temperature measuring unit that directly or indirectly measures the temperature in the airtight space or the temperature of the volatile component aqueous solution.

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