JP2010249643A - Method and device for measuring mercury concentration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly precisely detect mercury in exhaust gas according to individual chemical form by suppressing production of hardly-soluble mercury and reduction of oxidized mercury during sampling the exhaust gas. <P>SOLUTION: This method includes a first step in which a gas 11 sampled by introducing into a conduit 2 is contacted with a first solution 3 for absorbing oxidized mercury to collect the oxidized mercury in the gas, a second step in which gas out of the collection into the first solution in the first step is contacted with a mercury collector 5 for capturing metal mercury or a second solution 21 for absorbing metal mercury to collect metal mercury in the gas, and a third step in which the concentration of the oxidized mercury collected into the first solution in the first step and the concentration of the metal mercury collected into the solid or the second solution in the second step are respectively measured. In the first step, the gas flowing in the conduit is gradually cooled along the gas flow direction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for measuring the concentration of mercury in a gas and a measuring apparatus therefor, and in particular, mercury contained in exhaust gas discharged from a coal-fired thermal power plant is divided into oxidized mercury and metallic mercury. The present invention relates to a measurement method and a measurement apparatus thereof.

  In recent years, mainly in Europe and the United States, there is an increasing trend to tighten emission regulations on nitrogen oxides (NOx), sulfur oxides (SOx), and mercury (Hg) contained in exhaust gas from boilers for thermal power plants. In particular, mercury contained in exhaust gas is roughly classified into oxidized mercury and metallic mercury, and the exhaust gas temperature, the concentration of halogen compounds such as chlorine (Cl) and bromine (Br) in the exhaust gas, SOx concentration, moisture content, etc. Changes in the chemical form change greatly. Furthermore, since the amount of mercury contained in the exhaust gas is very small, in order to accurately grasp the behavior of mercury in a denitration device, dust collector, or desulfurization device, oxidized mercury and metallic mercury in the exhaust gas are used. A method that can accurately measure the chemical form is indispensable.

  As a method for measuring mercury in exhaust gas, a method specified in Japanese Industrial Standard (JIS K-0222) and a method called Ontario Hydro Method specified in American Materials and Testing Association (ASTM D6784-02) have been proposed. ing.

  In the measurement method stipulated in JIS, as a method of measuring the total mercury concentration in exhaust gas, the exhaust gas collected using a conduit is led to an absorption bottle containing a sulfuric acid potassium permanganate solution, and the mercury in the exhaust gas is removed. A method is shown in which absorption is carried out in a potassium permanganate solution, the absorption solution is reduced, and mercury is expelled from the absorption solution into the gas phase by air, and the amount of mercury in the gas phase is measured by atomic absorption spectrometry. Has been. As a method for measuring the concentration of metallic mercury in the exhaust gas, the exhaust gas collected using a conduit is passed through water or a phosphate buffer, and then the exhausted gas is introduced into a gold-amalgam collecting tube to exhaust the exhaust gas. There is shown a method of collecting metallic mercury therein, and then ventilating while heating the collecting tube, and measuring mercury transferred into the gas phase by atomic absorption spectrometry.

  On the other hand, in the Ontario hydro method, flue gas collected using a conduit is passed through an absorption bottle containing a KCl solution, a mixture of hydrogen peroxide and nitric acid, and a sulfuric acid potassium permanganate solution in order. After that, the mercury absorbed in the KCl solution is oxidized mercury, the mixture of hydrogen peroxide and nitric acid, and the mercury absorbed in the sulfuric acid potassium permanganate solution as metallic mercury and measured separately for each chemical form. Is.

JIS K0222-1997 ASTM D6784-02 (Standard Test Method for Elemental, Oxidized, Particle-Bound, and Total Mercury in Flue Gas Generated from Coal-Fired Stationary Sources)

  However, in the above method, insoluble gas is generated in the gas in the process from the collected gas flowing through the conduit to the absorption bottle, depending on the properties of the exhaust gas and the gas sampling conditions. I understand. For this reason, mercury may not be completely collected by the method of absorbing mercury using an absorbing solution.

In addition, when SO ₂ is present in the collected gas, SO ₂ is absorbed by the moisture condensed in the conduit to become sulfurous acid, and this sulfurous acid reacts with oxidized mercury, so that oxidized mercury becomes metal mercury. Reduced. For this reason, when measuring the mercury in exhaust gas according to the chemical form of oxidized mercury and metallic mercury, an error is likely to occur in the measured values of each form.

  Then, this invention makes it a subject to detect the mercury in waste gas with high precision according to chemical form by suppressing the production | generation of the hardly soluble mercury in the sampling of waste gas, and the reduction | restoration of oxidized mercury.

  As a result of intensive studies on the above problems, the present inventors have found that the following phenomenon occurs when measuring the gas sampled in the exhaust gas from the exhaust gas.

(1) Production of sparingly soluble mercury during sampling of exhaust gas occurs in a process in which the gas in the conduit from the exhaust gas sampling conduit to the absorption bottle is rapidly cooled by heat dissipation.
(2) When SO ₃ is present in the exhaust gas introduced into the conduit, the production of hardly soluble mist-like mercury in the process (1) is accelerated.
(3) The amount of mist-like mercury produced depends on the SO ₃ concentration in the gas introduced into the conduit, and tends to increase as the SO ₃ concentration increases.
(4) In the process in which the exhaust gas guided into the conduit flows toward the absorption bottle, when the temperature of the exhaust gas falls below the dew point of water, the water condenses in the conduit, and SO ₂ absorbed in the condensed water becomes sulfurous acid. As a result, sulfurous acid and oxidized mercury react to reduce oxidized mercury to metallic mercury (reaction formulas (1) to (3)).
SO ₂ + H ₂ O (l) → 2SO ₃ ²⁻ + 2H ⁺ (1)
HgCl ₂ + SO ₃ ²⁻ + H ₂ O → Hg + SO ₄ ²⁻ + 2H ⁺ + 2Cl ⁻ (2)
HgBr ₂ + SO ₃ ²⁻ + H ₂ O → Hg + SO ₄ ²⁻ + 2H ⁺ + 2Br ⁻ (3)

As described in the above (1) to (3), when the gas is rapidly cooled in the conduit during sampling of the exhaust gas, mercury in a form that seems to be solid fine particles is generated. Such mercury is considered to be a hardly soluble substance and is difficult to be absorbed and collected in a solution. In addition, when SO ₃ is present in the gas, the formation of this hardly soluble mercury is promoted. This is because mercury adsorbs to the slightly soluble SO ₃ mist of submicron order as the gas in the conduit is rapidly cooled. Or it is thought that it is taken in in the form included.

  From the above, when sampling was performed under the condition that the exhaust gas flowing through the conduit was cooled rapidly, the mercury in the gas was not detected even though the exhaust gas was passed through the oxidized mercury absorption liquid and the metal mercury absorption liquid in this order. All of them cannot be collected, making it difficult to measure with high accuracy.

  Therefore, in order to solve the above-described problems, the present invention provides a mercury concentration measurement method in which the mercury concentration in a gas is measured separately from oxidized mercury and metallic mercury. A first step of collecting oxidized mercury in the gas by bringing it into contact with a first solution that absorbs metal, and trapping metallic mercury in the gas that has not been collected in the first solution in the first step A second step of contacting the second solution that absorbs solid or metallic mercury to collect metallic mercury in the gas; and a concentration of oxidized mercury collected in the first solution in the first step; A third step of measuring the concentration of metallic mercury collected in the solid or the second solution in the second step, respectively, and the first step converts the gas flowing in the conduit into the direction of gas flow. It is characterized by being gradually cooled along.

  In this way, since the gas introduced into the conduit can be allowed to flow through the conduit while being gradually cooled without being rapidly cooled, the production of hardly soluble mercury and the process up to the first solution can be achieved. Reduction of oxidized mercury can be suppressed. For this reason, in the gas guided to the first solution through the conduit, all or most of the oxidized mercury is absorbed by the first solution, and all or most of the metal mercury is absorbed in the second solution. Therefore, it is possible to detect mercury in the gas with high accuracy by chemical form by detecting the amount of trapped mercury.

  In this case, the third step includes the measurement of the concentration of oxidized mercury deposited in the conduit. In this way, the measurement accuracy of the oxidized mercury concentration can be further enhanced.

More specifically, the gas flowing in the conduit is gradually cooled with a temperature gradient of 5 ° C./cm or less in the flow direction in a gas temperature range of 200 ° C. or lower, and at a temperature higher than the dew point temperature of water. Try to keep. In this way, it is possible to prevent the dew condensation of the gas flowing through the conduit, so that even if SO ₃ is present in the gas, the reduction of oxidized mercury can be efficiently suppressed, and the chemical The measurement accuracy for each form can be further increased.

  The present invention also relates to a mercury concentration measuring apparatus for measuring the mercury concentration in a gas by dividing it into oxidized mercury and metallic mercury, and a conduit for introducing the gas, and the gas and oxidized mercury collected through the conduit. A first reaction part that contacts the first solution to be absorbed and collects oxidized mercury in the gas, and a gas and metal mercury that are not collected in the first solution of the first reaction part. The second reaction part for collecting the solid metal to be captured or the second solution for absorbing the metal mercury to collect the metal mercury in the gas, and the first reaction part collected in the first solution. A first measuring means for transferring oxidized mercury to the gas phase and measuring the mercury concentration in the gas phase, and the metal mercury collected in the solid or the second solution in the second reaction section are gasified. And a second measuring means for measuring the mercury concentration in the gas phase, the conduit being provided along the longitudinal direction A plurality of heaters are provided, the heating temperature of the heater shall be set to decrease stepwise or continuously toward the gas passage direction.

Moreover, it is preferable that the conduit is formed so that components in the gas collide with the inner wall of the conduit. With such a conduit can be trapped by colliding the SO ₃ mist in the gas on the inner wall surface of the conduit, be recovered without missing even a small mercury was accompanied to the SO ₃ mist Therefore, the measurement accuracy can be further increased.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to detect the mercury in waste gas with high precision according to chemical form by suppressing the production | generation of the hardly soluble mercury during the sampling of waste gas, and the reduction | restoration of oxidized mercury.

It is a figure which shows the basic composition of the mercury concentration measuring apparatus which shows one Example of this invention. It is a figure explaining the structure of the conduit | pipe used for the mercury concentration measuring apparatus of this invention. It is a figure which shows the basic composition of the mercury concentration measuring apparatus which shows one Example of this invention. In Example 1 and Comparative Examples 1 and 2, it is a figure explaining the mode of the temperature change of the gas which flows through the inside of a conduit | pipe. It is a figure which shows the structure of the mercury concentration measuring apparatus which shows one practical example of this invention.

  Hereinafter, embodiments using the method and apparatus for measuring mercury concentration of the present invention will be described.

  FIG. 1 is a diagram for explaining a basic configuration of a mercury concentration measuring apparatus to which the present invention is applied. This mercury concentration measuring apparatus is configured to contact a cylindrical quartz high-temperature layer 1 through which a gas to be measured flows, a glass conduit 2 for collecting the gas to be measured, oxidized mercury and a solution 3. An absorption bottle 4 for absorbing oxidized mercury in the solution 3 and a metal mercury not absorbed in the solution 3 by introducing the gas to be measured extracted from the absorption bottle 4 and contacting the mercury collector 5 with the metal A gas sampling line is configured by sequentially connecting a collecting pipe 6 for capturing mercury, a suction pump 7 and a gas meter 8 as shown in FIG. Further, such a gas sampling line is connected to a detection unit (not shown) for detecting the oxidized mercury captured by the absorption bottle 4 and the concentration of metallic mercury captured by the collection tube 6.

  The periphery of the high temperature layer 1 is heated by an electric furnace 9 so that the inside of the furnace is maintained at a predetermined high temperature. The gas flow path in the furnace of the high temperature layer 1 is formed with a packed bed 10 of mercury oxidation catalyst, and a gas to be measured (hereinafter referred to as gas 11) is introduced into the furnace upstream of the packed bed 10. An inlet (not shown) is provided, and one end side of the conduit 2 is inserted downstream of the packed bed 10.

  The absorption bottle 4 is a sealed reaction tube for bringing the solution 3 and the gas 11 into contact with each other. The other end side of the conduit 2 is inserted into the absorption bottle 4, and the tip portion thereof is positioned in the solution 3. Here, as the solution 3, for example, a 1N-KCl solution (30 cc) can be used as a solution capable of absorbing oxidized mercury in the gas 11.

  The collection tube 6 is a sealed reaction tube that introduces the gas 11 taken out from the absorption bottle 4 and brings the mercury metal in the gas 11 not absorbed by the solution 3 into contact with the mercury collection agent 5. ing. The gas flow path of the collection tube 6 is filled with a mercury collection agent 5. Here, the mercury scavenger 5 is a solid capable of capturing metal mercury, and for example, a gold-amalgam (manufactured by Nippon Instruments, filling amount: about 30 mg) scavenger can be used.

  In the conduit 2, a plurality of flexible heaters 12 are wound along the longitudinal direction of the conduit 2 in a region from the outlet of the high temperature layer 1 to the inlet of the absorption bottle 4, that is, a region where the outer peripheral surface is exposed to the outside. Yes. Each flexible heater 12 is connected to a control means (not shown) so that the heating output is controlled. Here, five flexible heaters 12 are provided in the longitudinal direction of the conduit 2 in increments of 5 cm, for example, and the heating output of each flexible heater 12 can be adjusted. More specifically, the heating output of each flexible heater 12 is a gas flow so that the gas 11 emitted from the high temperature layer 1 is gradually cooled at a predetermined temperature gradient in a predetermined temperature range. It is set so as to decrease stepwise toward the direction.

  In the mercury concentration measuring apparatus configured as described above, the gas 11 is introduced from the inlet of the high temperature layer 1. The gas 11 introduced into the high temperature layer 1 is heated to about 400 ° C. in the high temperature layer 1, and further, a part of mercury in the gas 11 is oxidized when passing through the packed layer 10. Part of the gas 11 that has passed through the packed bed 10 is collected by the conduit 2 introduced into the high temperature bed 1 by suction of the suction pump 7. The hot gas 11 introduced into the conduit 2 is gradually cooled by temperature control of the flexible heater 12 when it flows out of the high temperature layer 1 and flows through the conduit 2. The gas 11 flowing in the conduit 2 and gradually cooled to a predetermined temperature is guided to the absorption bottle 4 where the oxidized mercury in the gas is absorbed by the solution 3. Subsequently, the gas 11 in which the oxidized mercury is absorbed flows into the collection tube 6, where the metallic mercury in the gas is captured by the mercury collection agent 5. In this way, the gas 11 in which the mercury by chemical form is captured is guided to the gas meter 8 via the suction pump 7 and the collected amount of exhaust gas is measured.

  Next, the concentration of mercury captured from the collected gas 11 is detected. First, the amount of mercury absorbed in the solution 3 of the absorption bottle 4, that is, oxidized mercury, is determined by adding a known reducing agent to the solution 3 and subjecting the oxidized mercury to gaseous metal. It can be detected by reducing to mercury and expelling it into the gas phase, and measuring the mercury concentration in the gas phase by atomic absorption spectrometry. The amount of mercury captured by the mercury collecting agent 5 in the collecting tube 6, that is, the amount of metallic mercury, is, for example, the amount of mercury trapped in the mercury collecting agent 5 by aeration while heating the collecting tube 6. It can be detected by driving out into the phase and measuring the mercury concentration in the gas phase by atomic absorption.

  Further, it has been confirmed by the inventors' investigation that mercury contained in the gas 11, specifically, oxidized mercury, adheres to the inner wall surface of the conduit 2. Therefore, in addition to the above detection method, mercury adhering to the conduit 2 is washed with a washing solution, and the mercury in the washing solution is expelled into the gas phase by, for example, the same reduction treatment as described above and measured by atomic absorption spectrometry. . In this way, the amount of mercury adhering to the inner wall surface of the conduit 2 is measured, the measured amount of mercury is regarded as the amount of oxidized mercury, and the total amount of oxidized mercury absorbed in the solution 3 is added. The concentration of oxidized mercury in the gas 11 can be detected more accurately. Here, as a cleaning liquid used for cleaning the inner wall surface of the conduit 2, for example, a potassium permanganate solution (1.5 g / L) and a hydroxylammonium chloride solution (20 g / L) can be used.

  In the present embodiment, the gas 11 heated to a high temperature in the high temperature layer 1 is sampled by the conduit 2, and the sampled gas 11 is gradually cooled stepwise or continuously at a predetermined temperature gradient in a predetermined temperature range. After that, it is guided to the absorption bottle 4 to absorb the oxidized mercury in the solution 3 and further guided to the collecting tube 6 so that the mercury collecting agent 5 captures the metallic mercury. That is, since the collected high-temperature gas 11 is allowed to flow through the conduit 2 while being gradually cooled without being rapidly cooled, the formation of the hardly soluble mercury and the oxidation state before the mercury is captured for each chemical form. Reduction of mercury can be suppressed. Therefore, all or most of the oxidized mercury contained in the collected gas 11 is absorbed by the solution 3, and all or most of the metallic mercury is absorbed by the mercury scavenger 5, so that it is absorbed by each solution. By measuring the concentration of the collected mercury, the mercury in the collected gas 11 can be measured with high accuracy for each chemical form. The slow cooling means for the gas 11 collected by the conduit 2 is not limited to the flexible heater 12.

Example 1
Next, specific examples of the present invention will be described. In this example, the mercury concentration measuring device shown in FIG. 1 was used to sample the gas 11 having the components shown in Table 1, and the mercury concentration contained in the gas 11 was measured for each chemical form. In this embodiment, the gas 11 collected from the conduit 2 is flexible so that the temperature from the high temperature layer 1 to the absorption bottle 4 decreases with a temperature gradient of 5 ° C./cm toward the gas flow direction. The control temperature (heating temperature) of the heater was set in the order of 175 ° C., 150 ° C., 125 ° C., 100 ° C., 75 ° C., and 50 ° C. in the gas flow direction. Moreover, the conduit | pipe 2 used the glass tube extended in a straight shape as shown to (a) of FIG.

(Example 2)
In Example 1, the collecting tube 6 filled with the mercury collecting agent 5 is replaced with an absorption bottle 22 containing 30 cc of a solution 21 (sulfuric acid potassium permanganate solution) (FIG. 3). 11 were collected and the mercury concentration was measured according to chemical form.

(Example 3)
In Example 1, the conduit 2 in FIG. 2 (a) is replaced with a glass tube extending in a wave shape in the longitudinal direction as shown in FIG. 2 (b), and the gas 11 is collected in the same manner. The mercury concentration was measured for each chemical form.

Example 4
In Example 1, the conduit 2 in FIG. 2 (a) is replaced with a glass tube having a portion that is spirally formed in the longitudinal direction as shown in FIG. 2 (c), and the gas 11 is collected in the same manner. Mercury concentration was measured by chemical form.

(Comparative Example 1)
In Example 2, the heating of the flexible heater 12 wound around the conduit 2 was stopped, the gas 11 was collected in the same manner, and the mercury concentration was measured for each chemical form.

(Comparative Example 2)
In Example 2, all the control temperatures of the flexible heater 12 wound around the conduit 2 are set to 120 ° C. so that the conduit 2 is kept warm without applying a temperature gradient. Concentration was measured by chemical form.

(Confirmation test for leaked mercury)
The method for measuring mercury concentration in the present invention aims to reliably collect mercury in a gas according to chemical form. Therefore, in order to clarify the effect of the present invention, a glass filter (manufactured by ADVANTEC, QR-100) is provided at the last stage of the sampling lines of Examples 1 to 4 and Comparative Examples 1 and 2 (before the suction pump 7). A holder was placed so that leaked mercury could be collected. The amount of mercury in the filter after sampling was measured by immersing the filter in 50 cc of potassium persulfate acidic acid (1.5 g / L). It was measured by absorption method.

In Examples 1 to 4 and Comparative Examples 1 and 2, the obtained mercury sampling analysis results and the leakage mercury content analysis results are summarized in Table 2. The numerical values in Table 2 indicate the amount of mercury measured in one gas sampling. (A) is the amount of mercury in the gas 11 on the inlet side of the packed bed 10, (B) is the amount of oxidized mercury absorbed in the solution 3 of the absorption bottle 4 and the amount of oxidized mercury adhering to the inner wall surface of the conduit 2. The total value, (C) is the amount of metallic mercury captured by the mercury collecting agent 5 in the collecting tube 6 or absorbed in the solution 21 of the absorption bottle 22, and the leaked mercury indicates the amount of mercury collected in the holder. The recovery rate (5) indicates the calculated value of (B + C) / A, and the mercury oxidation rate (%) indicates the calculated value of B / A. FIG. 4 shows the temperature transition in the gas flow direction in the conduit 2 from the high temperature layer 1 to the absorption bottle 4 when sampling is performed by the methods of Example 1 and Comparative Examples 1 and 2.

  As shown in Table 2, it can be seen that in Comparative Examples 1 and 2, the mercury recovery rate is as low as about 90%, and the remaining about 10% leaks without being collected by the sampling line. This is considered to be due to the fact that insoluble mercury is generated in the gas in the process in which the gas 11 collected from the high temperature layer 1 flows in the conduit 2.

The mercury oxidation rate is about 75% in Comparative Example 1 and about 64% in Comparative Example 2, which is about 10% despite evaluating the gas 11 that has passed through the same oxidation catalyst in the packed bed 10. There is a difference. This is because, in the case of Comparative Example 1, since the gas 11 exiting the high temperature layer 1 is not kept warm, the gas temperature rapidly dropped when flowing through the conduit 2, and a large amount of fine SO ₃ mist was generated. This is presumed to be due to this.

  On the other hand, in Comparative Example 2, in order to prevent condensation of water in the conduit 2, the gas 11 exiting the high temperature layer 1 is kept at 120 ° C., but in this case, the gas 11 at 120 ° C. has a normal temperature. Since the solution 3 is aerated, the temperature difference is large and the gas 11 is rapidly cooled. As a result, it is considered that a large amount of fine sulfuric acid mist was generated in the gas 11, and hardly soluble mercury was easily generated. Then, it is presumed that the mercury that was originally detected as oxidized mercury changed to poorly soluble mercury in the conduit 2, so that a part of the mercury was absorbed by the solution 21 and the amount of metal mercury detected increased. The

  From the above, it is clear that the heat insulation condition in the conduit 2 greatly affects the Hg recovery rate and Hg oxidation rate in the sampling line.

When the results of Examples 1 and 2 of the present invention (Table 2) are compared with Comparative Examples 1 and 2 above, the mercury recovery rate is 98 to 99%, and the leaked mercury is also very good. Yes. This is because the heating output of the flexible heater 12 is controlled so that the gas 11 flowing in the conduit 2 is cooled with a predetermined temperature gradient. That is, as shown in FIG. 4, the gas 11 flowing in the conduit 2 is gradually cooled, particularly at 200 ° C. or lower, and kept at a temperature higher than the dew point of water, thereby suppressing the formation of hardly soluble mercury. High mercury recovery rate and mercury oxidation rate can be obtained. Further, in Examples 3 and 4, as shown in FIGS. 2 (b) and 2 (c), since the conduit 2 is formed in a wave shape or a spiral shape (spiral type), the leakage mercury is almost zero. can do. This is because, because the flow of the gas 11 flowing in the conduit 2 is disturbed, the SO ₃ mist in the gas 11 is collected by inertial collision with the inner wall surface, so that the slight mercury accompanying can be recovered without missing. Guessed.

(Example 5)
Next, another embodiment for carrying out the present invention will be described with reference to FIG. FIG. 5 shows an example of a mercury concentration measuring device for carrying out mercury analysis in an actual boiler exhaust gas to which the present invention is applied. The sampling line of this mercury concentration measuring apparatus includes a conduit 101 for collecting exhaust gas flowing through the flue 111, a dust filter unit 102, a slow cooling control unit 103, an oxidized mercury absorption bottle 107 containing a KCl solution, a sulfuric acid acidic solution. It is composed of a metal mercury absorption bottle 108 containing a potassium manganate solution, a suction pump 109 and a gas meter 110. Moreover, although not shown in figure, the measurement means which each measures the amount of mercury absorbed by the absorption bottles 107 and 108 is provided.

  A plurality of heaters are attached in the longitudinal direction of the conduit 101 accommodated in the slow cooling control unit 103. A thermometer 104 is provided inside the slow cooling control unit 103 so that the surface temperature of the conduit 101 or the temperature of the exhaust gas flowing in the conduit 101 can be detected. The result detected by the thermometer 104 is displayed on the temperature monitor 105 as an electrical signal, and the detection result is processed by the computing unit 106. Thereby, the signal calculated from the signal intensity output from the thermometer 104 is returned to each heater of the slow cooling control unit, and the temperature of the conduit 101 in the unit is controlled to be cooled to the set temperature.

  Here, the temperature gradient at which the gas in the conduit 101 is gradually cooled is, for example, 5 ° C./cm or less with respect to the length of the conduit 101 in the slow cooling control unit 103 when the gas temperature is 200 ° C. or less. It is good to control. In addition, the gas temperature is maintained in the conduit 101 at a temperature higher than the dew point temperature of water. As the heater for keeping the conduit 101 warm, a plurality of flexible heaters and small electric furnaces are arranged, and the temperature is individually controlled, or the current flowing through the hot wire is controlled by winding the hot wire around the conduit 101. There is a way to set. If the amount of gas to be sampled is large and the temperature of the conduit 101 becomes too high due to heat dissipation of the gas, the conduit 101 may be cooled by using an electronic device such as a Peltier device.

  In this way, by controlling the temperature of the conduit 101 through which the exhaust gas flows, the inside of the conduit 101 can be moderately cooled even when the exhaust gas conditions and the outside air atmosphere fluctuate, and the water in the conduit 101 can be cooled. Since condensation can be prevented, it is possible to prevent the formation of hardly soluble mercury and the reduction of oxidized mercury during sampling of exhaust gas. Therefore, it is possible to always perform highly accurate mercury measurement by chemical form, and it is possible to cope with various exhaust gas conditions in a coal-fired boiler or the like.

DESCRIPTION OF SYMBOLS 1 High temperature layer 2 Conduit 3 Solution 4 Absorption bottle 5 Mercury collection agent 6 Collection pipe 7 Suction pump 8 Gas meter 9 Electric furnace 10 Packing layer 11 Gas 12 Flexible heater 21 Solution 22 Absorption bottle 104 Thermometer 105 Temperature monitor 106 Calculator

Claims (5)

In the mercury concentration measurement method that measures the mercury concentration in gas separately from oxidized mercury and metallic mercury,
A first step of collecting the oxidized mercury in the gas by bringing the gas collected by being introduced into the conduit into contact with a first solution that absorbs the oxidized mercury; and the first step in the first step. A second step of collecting the metal mercury in the gas by bringing the gas not collected in the solution into contact with a solid that captures the metal mercury or a second solution that absorbs the metal mercury; Measuring the concentration of the oxidized mercury collected in the first solution in the step and the concentration of the metallic mercury collected in the solid or the second solution in the second step, respectively. 3 processes,
In the first step, the gas flowing in the conduit is gradually cooled along the flow direction of the gas.   The method for measuring mercury concentration according to claim 1, wherein the third step includes measuring the concentration of the oxidized mercury adhering to the inside of the conduit.   The gas flowing in the conduit is gradually cooled with a temperature gradient of 5 ° C./cm or less in the flow direction in a gas temperature range of 200 ° C. or lower and maintained at a temperature higher than the dew point temperature of water. The method for measuring mercury concentration according to claim 1 or 2. In a mercury concentration measuring device that measures mercury concentration in gas separately from oxidized mercury and metallic mercury,
A conduit for introducing the gas; and a first reaction section for collecting the oxidized mercury in the gas by contacting the gas collected through the conduit with a first solution that absorbs the oxidized mercury; The gas not collected in the first solution of the first reaction section is brought into contact with a solid solution that captures metallic mercury or a second solution that absorbs metallic mercury to collect metallic mercury in the gas. A first reaction section that moves the oxidized mercury collected in the first solution in the first reaction section into the gas phase and measures the mercury concentration in the gas phase. Measuring means; and second measuring means for measuring the concentration of mercury in the gas phase by transferring the metal mercury collected in the solid or the second solution in the second reaction section into the gas phase. And
Mercury characterized in that the conduit is provided with a plurality of heaters along the longitudinal direction, and the heating temperature of the heater is set so as to decrease stepwise or continuously toward the gas flow direction. Concentration measuring device.   5. The mercury concentration measuring apparatus according to claim 4, wherein the conduit is formed so that components in the gas collide inertially with an inner wall of the conduit.

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