JP5525499B2 - Method and apparatus for grasping inhibitor concentration in absorbent, and absorption chiller / heater equipped with the apparatus - Google Patents

Description

  The present invention relates to an inhibitor concentration grasping method and apparatus in an absorbent for grasping the concentration of a corrosion inhibitor (inhibitor) in the absorbent, and an absorption chiller / heater equipped with the apparatus.

  Conventionally, absorption chiller / heater using water as a refrigerant and lithium bromide (LiBr) aqueous solution as an absorbent does not require large electric power for operation, supports various heat sources for heating, and demand decreases in summer It is used for large-scale building due to various circumstances such as the use of natural gas, kerosene, etc., which can be used for air conditioning in summer. In this way, the absorption chiller / heater can be said to be an air-conditioning heat source that attracts attention, particularly in the current situation where power supply and demand in summer is tight.

  By the way, in such an absorption chiller / heater, since a concentrated lithium bromide (LiBr) aqueous solution is used as an absorbent, there is a problem of corrosion of the materials constituting the absorption chiller / heater, and how to prevent corrosion. Is important in guaranteeing the reliability and longevity of equipment.

  In order to prevent corrosion of the materials constituting the absorption chiller / heater, it is common to add an inhibitor, which is a corrosion inhibitor, to the absorbing solution, and the amount of addition (concentration) of the inhibitor is properly controlled. This makes it possible to put an absorption chiller / heater with high corrosion resistance into practical use. Usually, an oxidant is used as the inhibitor, and a stable oxide film is formed on the surface of carbon steel, which is the main component of the absorption chiller / heater, to suppress corrosion and at the same time prevent the generation of hydrogen gas due to corrosion. To do. In addition, the absorption chiller / heater is made of carbon steel and copper pipes with high thermal conductivity. However, since copper pipes have low durability against strong oxidants, carbon steel and Molybdate is frequently used to effectively prevent corrosion of both copper tubes.

  However, molybdate has a high corrosion prevention effect, but its solubility in a concentrated lithium bromide (LiBr) aqueous solution is small, so it is generally added up to the solubility limit. However, the lower limit of the concentration necessary for corrosion prevention is still present. It is about a level. For this reason, in order to prevent corrosion of the absorption chiller / heater and maintain stable operation, it is necessary to finely control the concentration of molybdate.

  Therefore, a technique has been proposed in which an electrode is installed at an appropriate location in the absorption chiller / heater and the concentration of the inhibitor is electrochemically measured. For example, as a well-known technique related to this, an inhibitor in the absorbent is used. The absorption concentration is determined by the potential difference between the member that causes the oxidation-reduction reaction and the reference electrode (see Patent Document 1), dissolved in the absorbing solution from the potential difference between the oxide electrode and the reference electrode. “Absorption refrigerator” (see Patent Document 2) that determines the oxygen concentration, and “Absorption refrigerator” that measures the current flowing between a pair of iron electrodes to detect the formation of the anticorrosive film ( For example, see Patent Document 3).

JP 7-35434 A JP 2006-57895 A JP 2008-286441 A

  The technique for electrochemically measuring the concentration of an inhibitor according to Patent Documents 1 to 3 described above has the following problems. Specifically, in the technique according to Patent Document 1, the concentration of the inhibitor is obtained by the potential difference between the reference electrode and the member that causes an oxidation-reduction reaction with respect to the inhibitor in the absorbing solution. Since an oxide is generated by the oxidizing action of an oxidizing agent, which is an inhibitor, on the surface of the metal, the potential changes with time, so that it is difficult to know the concentration of the inhibitor accurately.

  Moreover, in the technique which concerns on patent document 2, it calculates | requires the dissolved oxygen concentration in absorption liquid from the electric potential difference between an oxide electrode and a reference electrode, and also in the technique which concerns on patent document 3, it flows between a pair of iron electrodes. The current is measured to detect the state of formation of the anticorrosion film. In any case, when the inhibitor in the absorbing solution to which the inhibitor mainly composed of molybdate is added is targeted, There is a problem that it is difficult to grasp the concentration with high accuracy.

  The present invention has been made to solve such problems, and a first technical problem thereof is that the concentration of the inhibitor in the absorbing solution to which an inhibitor mainly composed of molybdate is added is highly accurate. It is an object of the present invention to provide a method for grasping an inhibitor concentration in an absorbing solution that can be grasped easily.

  A second technical problem of the present invention is to provide an inhibitor concentration grasping device having a simple configuration capable of grasping with high accuracy the concentration of an inhibitor in an absorbing solution to which an inhibitor mainly composed of molybdate is added. is there.

  The third technical problem of the present invention is that the concentration of the inhibitor in the absorbing solution to which the inhibitor mainly composed of molybdate is added can be grasped with high accuracy and the corrosion in the apparatus can be effectively prevented. It is to provide a water chiller / heater.

In order to achieve the first technical problem, the first means of the present invention is to determine the concentration of the inhibitor in the absorbing solution to which an inhibitor mainly composed of molybdate is added. Concentration grasping method , which includes two working electrodes composed of any one of glassy carbon, carbon, platinum, and molybdenum inserted so as to be immersed in the absorbing solution, and a reference electrode / counter electrode composed of molybdenum . Apply a voltage between the electrodes or supply a current and measure the current in response to the concentration of molybdate ion flowing between the two electrodes when the voltage is applied, or apply the current Measure the voltage in response to the molybdate ion concentration between the two electrodes, and grasp the concentration of the inhibitor in the absorbent based on the measured current value or voltage value And wherein the door.

In order to achieve the second technical problem described above, the second means of the present invention is to determine the concentration of the inhibitor in the absorbing solution to which an inhibitor mainly composed of molybdate is added. a concentration determination apparatus, the installed reference electrode as immersed in the absorbing solution, the working electrode, and a counter electrode, or a voltage is applied between the working and counter electrodes, or to supply current, of the working electrode A polarization function that performs cathode polarization that shifts the potential in the negative direction and anode polarization that shifts the potential of the working electrode in the positive direction, a first measurement function that measures the cathode current or the cathode voltage when the cathode is polarized, and A potentiostat having a second measurement function for measuring an anode current or an anode voltage when the anode is polarized, and the reference electrode and the counter electrode are shared Characterized in that it is a reference electrode and a counter electrode that.

In order to achieve the second technical problem, a third means of the present invention is characterized in that, in the second means, the reference electrode / counter electrode is composed of a molybdenum metal electrode .

In order to achieve the second technical problem, the fourth means of the present invention is the second means or the third means, wherein the working electrode is any one of glassy carbon, carbon, platinum, and molybdenum. It is composed of two .

In order to achieve the third technical problem, the fifth means of the present invention absorbs the inhibitor concentration grasping device in the absorption type according to any one of the second means to the fourth means. It is characterized by the fact that it is equipped with a water chiller .

According to the present invention, two electrodes are composed of a working electrode composed of any one of glassy carbon, carbon, platinum, and molybdenum inserted so as to be immersed in the absorbing solution, and a reference and counter electrode composed of molybdenum. Apply a voltage between them or supply a current and measure the current in response to the concentration of molybdate ion flowing between the two electrodes when a voltage is applied, or molybdenum flowing between the two electrodes when a current is supplied In order to measure the voltage in response to the acid ion concentration and grasp the concentration of the inhibitor in the absorbent based on the measured current value or voltage value, The concentration of the inhibitor can be grasped with high accuracy.

It is the figure which showed schematic structure of the double effect absorption type | mold cold / hot water machine provided with the inhibitor density | concentration grasping | holding apparatus in the absorption liquid which concerns on Example 1 of this invention. Diagram showing the experimental results relating to the polarization characteristics of the relationship of current density versus voltage in the case of cathode polarization at the absorption solution containing lithium molybdate (Li ₂ MoO ₄₎ as the absorption chiller machine inhibitor shown in FIG. 1 It is. The experimental result regarding the polarization characteristic by the relationship of the current density with respect to the voltage at the time of anodic polarization after cathodic polarization in an absorption liquid containing lithium molybdate (Li ₂ MoO ₄ ) as an inhibitor in the absorption chiller / heater shown in FIG. FIG. FIG. ₄ is a diagram showing the relationship of the anode peak current density to the concentration of lithium molybdate (Li ₂ MoO ₄ ) described in FIG. 3. It is the diagram which showed the experimental result by the relationship of the voltage with respect to time at the time of the constant current polarization to the working electrode in the absorption-type cold / hot water machine shown in FIG. FIG. 6 is a diagram showing an experimental result based on a relationship of a voltage with respect to a concentration of lithium molybdate (Li ₂ MoO ₄ ) after elapse of a predetermined time due to constant current polarization described in FIG. A plurality of absorbing liquids in the case where the concentration of lithium molybdate (Li ₂ MoO ₄ ) in the absorbing liquid is different when the reference electrode and counter electrode in the absorption chiller / heater shown in FIG. It is the diagram which showed the experimental result by the relationship of the current density with respect to the electric potential at the time of the cathode polarization to the working electrode of, and an anode polarization.

  Hereinafter, an inhibitor concentration grasping method and apparatus in an absorbing solution of the present invention and an absorption chiller / heater equipped with the apparatus will be described in detail with reference to the drawings.

  First, a technical outline of the method for grasping the inhibitor concentration in the absorbing solution of the present invention will be briefly described. The method for determining the inhibitor concentration in the absorption liquid of the present invention is to determine the concentration of the inhibitor in the absorption liquid to which an inhibitor mainly composed of molybdate is added, and its technical outline is immersed in the absorption liquid. Apply a voltage between at least two electrodes inserted so as to supply current or measure the current in response to the molybdate ion concentration flowing between the two electrodes when voltage is applied, or The voltage in response to the molybdate ion concentration between the two electrodes when supplied is measured, and the concentration of the inhibitor in the absorbing solution is grasped based on the measured current value or voltage value.

Specifically, cathodic reduction is effected by cathodic polarization in which a voltage is applied between a working electrode and a counter electrode installed so as to be immersed in the absorbing solution, or current is supplied and the potential of the working electrode is shifted in the direction of the negative electrode. after allowed to occur to precipitate molybdenum dioxide (MoO ₂₎ to the working electrode, the molybdenum dioxide is deposited on the working electrode by rise to anode oxidation by anodic polarization shifting the potential in the direction of the positive electrode (MoO ₂₎ The cathode current or cathode voltage when eluting and cathodic polarization is measured, and the current value or voltage value by the anode current or anode voltage when anodic polarization is measured, and the measured cathode current value or cathode voltage value and anode current value or The concentration of the inhibitor in the absorbent is determined based on at least one measured value of the anode voltage value. It is. However, it is preferable here to repeat cathodic polarization and anodic polarization multiple times. It is also preferable to measure the potential of the working electrode when a constant current is supplied to the working electrode to perform constant current polarization, and to determine the inhibitor concentration in the absorbing solution based on the measured potential.

  By applying such a method, the concentration of the inhibitor in the absorbing solution to which the inhibitor mainly composed of molybdate is added can be grasped with high accuracy.

  FIG. 1 is a diagram showing a schematic configuration of a double-effect absorption chiller / heater equipped with an inhibitor concentration grasping device in an absorbent according to Example 1 of the present invention. This double-effect absorption chiller / heater has a high temperature regenerator 1, a low temperature regenerator 2, a condenser 3, an evaporator 4, an absorber 5, a heat exchanger 6, a solution pump 7, a heating source such as a boiler, A potentiostat provided with a refrigerant pump 8, a pipe line connecting these devices, and connected to a reference electrode 11, a working electrode 12, and a counter electrode 13 installed so as to be immersed in the absorbing liquid in the high-temperature regenerator 1. 14.

  Among these, the reference electrode 11, the working electrode 12, the counter electrode 13, and the potentiostat 14 serve as an inhibitor concentration grasping device to which the above-described inhibitor concentration grasping method in the absorption liquid is applied. A polarization function that applies a voltage or supplies a current between the electrode 12 and the counter electrode 13 to perform cathode polarization that shifts the potential of the working electrode 12 toward the negative electrode and anode polarization that shifts the potential of the working electrode 12 toward the positive electrode A first measurement function for measuring the cathode current or the cathode voltage when the cathode is polarized, and a second measurement function for measuring the anode current or the anode voltage when the anode is polarized.

  The low temperature regenerator 2 has a heating pipe 2A that uses the refrigerant vapor generated in the high temperature regenerator 1 as a heating source, the condenser 3 has a cooling water pipe 3A through which cooling water flows, and the evaporator 4 A cold water pipe 4A in which cold water (medium to be cooled) flows in the pipe and a distribution header 4B for distributing refrigerant liquid fed from the refrigerant pump 8 to the cold water pipe 4A. The absorber 5 is a cooling water pipe for cooling water pipe 5A through which cooling water flows, and a concentrated absorbent (absorbent having a relatively high concentration of absorbent) returned from the high temperature regenerator 1 and the low temperature regenerator 2. It has the distribution header 5B distributed to 6A.

  The heat exchanger 6 in the double-effect absorption chiller / heater according to the first embodiment is discharged from the solution pump 7 and sent to the high-temperature regenerator 1 and the low-temperature regenerator 2 (low-temperature and dilute absorbent) and high temperature. Heat exchange is performed with the absorption liquid (absorption liquid concentrated at high temperature) returned from the regenerator 1 and the low-temperature regenerator 2 to the absorber 5. This heat exchanger 6 has a high-temperature heat exchanger function for exchanging heat between the absorbing liquid sent to the high-temperature regenerator 1 and the absorbing liquid returned from the high-temperature regenerator 1, and the absorbing liquid and low-temperature regenerator sent to the low-temperature regenerator 2. Generally, it has a low-temperature heat exchanger function for exchanging heat with the absorbing liquid returning from 2.

  Further, the solution pump 7 sucks a diluted absorbent from the absorber 6 and supplies it to the high temperature regenerator 1 and the low temperature regenerator 2 via the heat exchanger 6. Incidentally, a pipe line connected to the distribution header 5B may be branched from the discharge side of the solution pump 7, and a part of the absorbent may be led to the distribution header 5B of the absorber 5 and distributed in the absorber 5.

  In the double-effect absorption chiller / heater having the above-described configuration, the inside of the chamber is maintained at a high vacuum, and the absorbing liquid is injected into the high-temperature regenerator 1. In this absorbing solution, an aqueous solution of lithium bromide (LiBr) using water as a refrigerant is used as an absorbent, and an inhibitor mainly composed of lithium molybdate (molybdate) is added.

  The operation of the double-effect absorption chiller / heater will be described. The refrigerant in the high-temperature regenerator 1 is heated by the combustion heat of the boiler to generate refrigerant vapor, and the refrigerant vapor is heated to the heating pipe of the low-temperature regenerator 2. 2A, the absorption liquid in the low-temperature regenerator 2 is heated to generate refrigerant vapor. The refrigerant in the heating pipe 2A and the refrigerant vapor generated in the low temperature regenerator 2 flow into the condenser 3 and are cooled by the cooling water flowing through the cooling water pipe 3A to become a cooled refrigerant liquid. This refrigerant liquid is distributed from the distribution header 4B of the evaporator 4 to the cold water pipe 4A, and takes the latent heat of vaporization from the cooling medium flowing in the cold water pipe 4A to cool the cooling medium. This cooled medium to be cooled is circulated to an indoor fan coil unit schematically shown for cooling and air conditioning.

  The refrigerant vapor evaporated in the evaporator 4 flows into the absorber 5 and directly contacts the absorbing liquid (concentrated absorbing liquid) distributed from the distribution header 5B, and is cooled by the cooling water passing through the cooling water pipe 5A. As a result, the refrigerant vapor is absorbed by the absorption liquid, and becomes a diluted absorption liquid having a low concentration (in other words, the refrigerant has increased in number). The diluted absorbent generated in the absorber 5 is sent to the low temperature regenerator 2 and the high temperature regenerator 1 by the solution pump 7.

  Furthermore, in the inhibitor concentration grasping device according to the first embodiment, a case where various electrodes are installed so as to be immersed in the absorbing solution in the high temperature regenerator 1 will be described. Of course, the inside of the low-temperature regenerator 2, the absorber 5, or the conduit through which the absorbing liquid circulates may be used. Examples of the various electrodes include a reference electrode 11 made of a silver-silver chloride electrode with a cooling jacket, a working electrode 12 made of glassy carbon, and a counter electrode 13 made of platinum. The potentiostat 14 has a function of applying a voltage or supplying a current between the working electrode 12 and the counter electrode 13 as described above, and a cathode polarization function for shifting the potential of the working electrode 12 in the negative direction. It has an anode polarization function that shifts in the direction of the positive electrode, a first measurement function that measures the cathode current or cathode voltage during cathode polarization, and a second measurement function that measures the anode current or anode voltage during anode polarization. .

  About the reference electrode 11, the working electrode 12, and the counter electrode 13 installed so that it may be immersed in the absorption liquid of the high temperature regenerator 1, although the reference electrode 11 is connected to the potentiostat 14, it does not flow an electric current. It is installed to obtain the reference potential. The working electrode 12 and the counter electrode 13 are connected to a potentiostat 14 so that a voltage (potential difference) or a current can be applied.

When the current or voltage is measured by the first measurement function or the second measurement function in order to grasp the concentration of the inhibitor, the first measurement function uses a cathode polarization that shifts the potential of the working electrode 12 in the negative electrode direction. A reduction action is caused to deposit molybdenum dioxide (MoO ₂ ) on the working electrode 12. In the second measurement function thereafter, anodic oxidation is caused by anodic polarization that shifts the potential of the working electrode 12 toward the positive electrode, and molybdenum dioxide (MoO ₂ ) deposited on the working electrode 12 is eluted. In short, after the working electrode 12 is cathodic polarized, an anodic polarization operation is performed, but it is desirable to repeat the operation twice or more. The potentiostat 14 measures the cathode current or cathode voltage when the cathode is polarized by the first measurement function, and the anode current or anode voltage when the anode is polarized by the second measurement function.

  The relationship between each current value or each voltage value and the inhibitor concentration based on at least one of the cathode current value and anode current value measured by the potentiostat 14 or at least one of the cathode voltage value and the anode voltage value. Referring to the curve, it is possible to accurately detect and grasp the concentration of the inhibitor in the absorbing solution in the double-effect absorption chiller / heater.

In the example described above, the case where the current value or the voltage value is measured has been described. However, as the constant current density supplied to the working electrode 12, for example, a constant current of 141 μA (microampere) / cm ² is supplied. By measuring the time-dependent change of the electrode potential (voltage between the working electrode 12 and the counter electrode 13) and referring to the relationship curve between the voltage value and the inhibitor concentration based on the measured voltage value, a double-effect absorption formula It is also possible to detect (obtain) the concentration of the inhibitor in the absorption liquid in the cold / hot water machine.

  Although the double-effect absorption chiller / heater according to the first embodiment is a three-electrode system, in this case, there is a problem that a reliable reference electrode 11 must be inserted into the device, and thus a simpler configuration. If the concentration of an inhibitor containing molybdate can be detected (ascertained) as a two-electrode system, the practicality is expected to be higher. A three-electrode system is the most desirable embodiment for measuring the current or voltage corresponding to the inhibitor concentration in the absorbing solution. However, when operating at a high temperature such as an absorption chiller / heater, Therefore, the reference electrode 11 that responds stably has a complicated structure. Therefore, in practice, it is desirable to use a two-electrode system that includes the counter electrode 13 and the reference electrode 11 serving both as the reference electrode 11 and the working electrode 12.

  In the case of a two-electrode system, when the shape of the polarization curve of the counter electrode 13 does not depend on the concentration of molybdate inhibitor in the absorbing solution, the potential of the counter electrode 13 becomes constant at a steady value if the current density is made constant. Therefore, the potential of the working electrode 12 can be controlled by so-called voltage control, and the counter electrode / counter electrode can be used as the counter electrode 13 and the reference electrode 11. In addition, when a current is passed through the working electrode 12, if the area of the counter electrode 13 is made sufficiently large, the current density becomes small and the polarization is substantially small and the potential is kept constant. Therefore, the counter electrode 13 and the reference electrode 11 are used together. The reference electrode and counter electrode can be used.

  Incidentally, it has already been confirmed through experiments that each voltage value and molybdate inhibitor concentration have a certain relationship between each voltage value and molybdate inhibitor concentration. The relationship between the current value or each voltage value and the inhibitor concentration will be described.

FIG. 2 shows the experimental results regarding the polarization characteristics based on the relationship between the current density and the voltage in the case of cathodic polarization in an absorbing solution containing lithium molybdate (Li ₂ MoO ₄ ) as an inhibitor in the absorption chiller / heater described above. FIG. FIG. 3 shows an experiment on the polarization characteristics based on the relationship between the current density and the voltage when cathodicly polarized in an absorbing solution containing lithium molybdate (Li ₂ MoO ₄ ) as an inhibitor in the absorption chiller / heater described above. It is the diagram which showed the result. FIG. 4 is a graph showing the relationship between the anode peak current density and the concentration of lithium molybdate (Li ₂ MoO ₄ ) described in FIG. FIG. 5 is a diagram showing experimental results based on the relationship of voltage with respect to time during constant current polarization to the working electrode 12 in the absorption chiller / heater described above. FIG. 6 is a diagram showing experimental results based on the relationship of voltage to the concentration of lithium molybdate (Li ₂ MoO ₄ ) after a predetermined time has elapsed due to the constant current polarization described in FIG. FIG. 7 shows a plurality of cases where the concentration of lithium molybdate (Li ₂ MoO ₄ ) in the absorbing solution is different when the reference electrode 11 and the counter electrode 13 are combined in the absorption chiller / heater as described above. It is the diagram which showed the experimental result by the relationship of the electric current density with respect to the electric potential at the time of the cathode polarization to the working electrode 12, and the anode polarization about the absorption liquid.

However, in FIGS. 2 to 6, a basic solution, an aqueous solution was added lithium bromide (LiBr) of 17.3mol · ^{kg -1} of lithium bromide (LiBr) 0.1mol · ^{kg -1} in aqueous solution, which 1 × 10 ^{−4 to} 3 × 10 ⁻³ mol · kg ⁻¹ lithium molybdate (Li ₂ MoO ₄ ) as an inhibitor is added as necessary. 2, 3, 5, and 7, curve A shows the case of an absorption solution to which an inhibitor is not added, and curve B shows an inhibitor concentration of 1 × 10 ⁻⁴ · mol · kg ⁻¹ . The case of the absorbing solution is shown, curve C shows the case of the absorbing solution having an inhibitor concentration of 5 × 10 ⁻⁴ · mol · kg ⁻¹ , and curve D shows the inhibitor concentration of 1 × 10 ⁻³ · mol · kg ⁻¹ . The case of the absorbing solution is shown, and the curve E shows the case of the absorbing solution having an inhibitor concentration of 3 × 10 ⁻³ · mol · kg ⁻¹ . Curves A to E show the measurement results for the same inhibitor concentration in each figure, but the types of lines used vary from figure to figure even for the same curve A. The same applies to the curves B, C, D, and E. 2 and 3, the voltage (potential difference) represents the difference from the reference electrode 11.

Referring to FIG. 2, here, specifically, argon gas was blown into the absorbing solution and degassed, and in the absorbing solution at 40 ° C., the working electrode 12 was glassy carbon, the counter electrode 13 was a platinum plate, and the reference electrode 11. Shows the relationship between the inhibitor concentration of lithium molybdate (Li ₂ MoO ₄ ) and the cathodic polarization characteristics in the case of cathodic polarization by the electrokinetic method using a silver (Ag) -silver chloride (Agcl) electrode having a water-cooled jacket ing. Regarding the cathode polarization characteristics, the vertical axis represents current density (i / μAcm ⁻² ), the horizontal axis represents potential (E / V vs. Ag / Agcl) as voltage (potential difference), and curve A represents the addition of an inhibitor. shows the case of a non-absorbing liquid, curve B is the inhibitor concentration shows a case of the absorbing liquid of ^{1 × 10 -4 · mol · kg} -1, the curve C is the inhibitor concentration ^{5 × 10 -4 · mol · kg} - ¹ shows the case of the absorbing solution, curve D shows the case of the absorbing solution having an inhibitor concentration of 1 × 10 ⁻³ · mol · kg ⁻¹ , and curve E shows the inhibitor concentration of 3 × 10 ⁻³ · mol · kg ⁻ The case of ¹ absorption liquid is shown.

  FIG. 2 shows that the current density clearly depends on the inhibitor concentration when the voltage is -1.2 volts or less. This is because reduction products of molybdenum dioxide in the absorbing solution are formed on the glassy carbon. Thus, in the cathode polarization characteristics, if the current density at −1.2 volts or less is measured, the concentration of the inhibitor in the absorbing solution can be detected (understood).

Referring to FIG. 3, here, the same absorbing solution as that described in Example 1 above was used, and after cathodic polarization at 150 ° C., the anode was subsequently turned back from −1.4 volts toward the anode. The relationship between the lithium molybdate (Li ₂ MoO ₄ ) concentration (inhibitor concentration) and the polarization characteristics in the case of polarization is shown. Regarding the polarization characteristics in FIG. 3, the vertical axis, the horizontal axis, and the curves A, C, D, and E are the same as those described in FIG.

From FIG. 3, it can be seen that with respect to the polarization characteristics, the cathode current once turns to the anode current and shows a peak when the voltage is around -0.6 volts, and then the anode current becomes near 0 volts or more. This is because the anode current peak at a voltage of around -0.6 volts is eluted by reoxidation of molybdenum dioxide (MoO ₂ ), which is a reduction product of MoO ₄ ²⁻ deposited on the glassy carbon by cathodic polarization. Although the potential indicating the peak current slightly shifts depending on the temperature of the absorbing solution, there is substantially no problem. As is clear from FIG. 3, the peak current density near −0.6 volts is clearly dependent on the inhibitor concentration. Therefore, if this peak current density is measured, the concentration of the inhibitor in the absorbing solution can be detected. (Understand).

Referring to FIG. 4, the relationship between the peak current density and the inhibitor concentration shown in FIG. 3 is arranged and the vertical axis is current density (i / μAcm ⁻² ), and the horizontal axis is molybdic acid. Lithium (Li ₂ MoO ₄ ) concentration (inhibitor concentration) (m / mol · kg ⁻¹ ). From FIG. 4, as described above, the inhibitor concentration is almost linearly related to the peak current density, and the concentration of the inhibitor in the absorbing solution can be detected (obtained) by performing anodic polarization in the anode direction after cathodic polarization. it can.

Referring to FIG. 5, here, a case where a constant current density of 141 μA / cm ² is applied to the working electrode (glassy carbon electrode) 12 at 25 ° C. using the same absorbing liquid as in FIGS. The electrode potential (voltage) of the electrode is shown to change with time, the vertical axis is the potential (E / V vs. Ag / Agcl) as the voltage (potential difference), and the horizontal axis is the time (second t / s). . From FIG. 5, it can be seen that for each of the curves B, C, D, and E, the voltage (potential difference) of the working electrode (glassy carbon) 12 shows a clear difference depending on the inhibitor concentration.

Referring to FIG. 6, the relationship between the voltage (potential difference) of the working electrode (glassy carbon) 12 and the inhibitor concentration after 150 seconds from the state shown in FIG. 5 is shown. The vertical axis indicates the voltage (potential difference). As a potential (E / V vs. Ag / Agcl), and the horizontal axis represents a lithium molybdate (Li ₂ MoO ₄ ) concentration (inhibitor concentration) (m / mol · kg ⁻¹ ). From FIG. 6, since the inhibitor concentration and the voltage (potential difference) of the working electrode (glassy carbon) 12 are in a substantially linear relationship, the inhibitor concentration in the absorbing solution is obtained by constant-current polarization of the working electrode 12 by the glassy carbon. It can be detected (understood).

Referring to FIG. 7, a two-electrode system in which the anode is a reference electrode / counter electrode composed of a molybdenum metal electrode and the cathode is a working electrode 12 composed of a glassy carbon electrode is specifically described here. inhibitor concentration is zero at each curve a lithium molybdate absorbing solution _(Li 2 MoO ₄₎ of ^{(40 ℃), 1 × 10} -4 · mol · kg -1 by curve B, and curve C 5 × 10 ^- The current-potential curve in the case of ⁴ · mol · kg ⁻¹ , curve D is 1 × 10 ⁻³ · mol · kg ⁻¹ , and curve E is 3 × 10 ⁻³ · mol · kg ⁻¹ is shown. In FIG. 7, the vertical axis represents current density (i / μAcm ⁻² ), the horizontal axis represents potential as potential (E / V vs. Ag / Agcl), and the left side is when the working electrode 12 is cathodic polarized. The cathode polarization characteristic showing the cathode current of the reference electrode, and the right side shows the anode polarization characteristic showing the anode current of the reference electrode and the counter electrode when the working electrode 12 is anode-polarized.

From FIG. 7, the shape of each curve in the cathode polarization characteristics shows that the cathode current increases and increases depending on the inhibitor concentration when the inhibitor concentration is in the range of zero to 3 × 10 ⁻³ · mol · kg ^−1. It can be seen that the degree tends to vary depending on the inhibitor concentration. On the other hand, the shape of each curve in the anodic polarization characteristics is almost the same in any case without depending on the inhibitor concentration, and it can be seen that it is constant. Therefore, the potential difference D between the anode and the cathode when electrolyzed at the same current density (the value is arbitrary) (the interval between the anodic polarization characteristic and the cathode polarization characteristic at the same current density shown in FIG. 7) varies depending on the inhibitor concentration. Therefore, the concentration of the inhibitor in the absorbing solution can be detected (understood) by the potential difference D. That is, by using a two-electrode system in which the reference and counter electrode is a molybdenum metal electrode, it is possible to detect (understand) the concentration of the inhibitor in the absorbing solution to which the inhibitor containing molybdate is added.

  In the double-effect absorption chiller / heater according to Example 1, the case where a glassy carbon electrode is used as the working electrode 12 has been described. However, the working electrode 12 is not limited to glassy carbon, and lithium bromide (LiBr). Other materials can be used as long as they are inert and stable to the aqueous solution. For example, carbon, molybdenum, platinum, or the like can be used. In this case, the same effects as those described in the first embodiment can be obtained. can get.

In any case, according to the double-effect absorption chiller / heater according to the first embodiment, between the two electrodes (working electrode 12 and counter electrode 13) installed so as to be immersed in the absorbing liquid in the high-temperature regenerator 1. A voltage is applied to the working electrode 14 by a potentiostat 14 or an electric current is supplied to the working electrode 12 by a cathode polarization that shifts the potential of the working electrode 12 in the negative direction by a polarization function. ₂ ) After depositing, anodic oxidation is caused by anodic polarization shifted in the positive direction, and molybdenum dioxide (MoO ₂ ) deposited on the working electrode 12 is eluted. At this time, in the potentiostat 14, at least one current value or the cathode current or the cathode voltage when the cathode polarization is performed by the first measurement function and the anode current or the anode voltage when the anode polarization is performed by the second measurement function. Since the voltage value is measured, the voltage between the working electrode 12 and the counter electrode 13 corresponding to the concentration of the inhibitor whose main component is molybdate is applied almost without being affected by the formation of an oxide film on various electrodes. Current corresponding to the molybdate ion concentration flowing between the two electrodes (cathode current, anode current), or voltage corresponding to the molybdate ion concentration flowing between the two electrodes when current is supplied (cathode voltage, anode voltage) ) Can be measured. As a result, the inhibitor concentration can be detected (obtained) with high accuracy. In addition, since a two-electrode system comprising a reference electrode and counter electrode that also serves as the reference electrode 11 and the counter electrode 13 and the working electrode 12 is configured and the inhibitor concentration can be detected (obtained) with high accuracy, the number of electrodes can be reduced. Since it can be easily mounted on a device, it is extremely effective in practice. Furthermore, since the inhibitor concentration can be detected (obtained) with high accuracy, an absorption chiller / heater with high corrosion resistance and reliability can be provided.

DESCRIPTION OF SYMBOLS 1 High temperature regenerator 2 Low temperature regenerator 3 Condenser 3A, 5A Cooling water pipe 4 Evaporator 4A Cold water pipe 4B, 5B Distribution header 5 Absorber 6 Heat exchanger 7 Solution pump 8 Refrigerant pump 11 Reference electrode 12 Working electrode 13 Counter electrode 14 Potentiometer Stat

Claims (5)

A method for grasping an inhibitor concentration in an absorbing solution for grasping a concentration of the inhibitor in an absorbing solution to which an inhibitor mainly composed of molybdate is added,
A voltage is applied between two electrodes by a working electrode made of any one of glassy carbon, carbon, platinum, and molybdenum inserted so as to be immersed in the absorbing solution and a reference electrode / counter electrode made of molybdenum. Or current is supplied and the current in response to the concentration of molybdate flowing between the two electrodes when the voltage is applied is measured or the molybdic acid between the two electrodes when the current is supplied A method for grasping an inhibitor concentration in an absorbing solution, comprising: measuring a voltage in response to an ion concentration, and grasping the concentration of the inhibitor in the absorbing solution based on the measured current value or the voltage value. An inhibitor concentration grasping device in the absorbing solution for grasping the concentration of the inhibitor in the absorbing solution to which an inhibitor mainly composed of molybdate is added,
The installed reference electrode as immersed in the absorbing solution, the working electrode, and a counter electrode, or a voltage is applied between the working electrode and the counter electrode, or to supply current, the negative electrode potential of the working electrode A polarization function for performing cathode polarization shifted in the direction and anodic polarization for shifting the potential of the working electrode in the positive direction, a first measurement function for measuring a cathode current or a cathode voltage when the cathode is polarized, and the anode polarization A potentiostat having a second measurement function for measuring the anode current or anode voltage of the case,
The inhibitor concentration grasping device in the absorbing solution, wherein the reference electrode and the counter electrode are a combined reference electrode and counter electrode . In inhibitor concentration determination apparatus of the absorbing solution according to claim 2, wherein the reference electrode and the counter electrode, the inhibitor concentration determination apparatus of the absorbing fluid and characterized in that it is composed of molybdenum metal electrodes. The inhibitor concentration grasping device in the absorbing solution according to claim 2 or 3 , wherein the working electrode is composed of any one of glassy carbon, carbon, platinum, and molybdenum. Grasping device . An absorption chiller / heater having the inhibitor concentration grasping device in the absorbent according to any one of claims 2 to 4 .

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