JP4054140B2 - Method and apparatus for analyzing mercury in gas - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mercury analysis method and apparatus for analyzing mercury contained in exhaust gas from a refuse incinerator.
[0002]
[Prior art]
To analyze mercury contained in waste gas from incinerators, treat mercury-containing gas with metallic tin as a reducing agent, reduce compound mercury in mercury-containing gas to metallic mercury, and analyze the metallic mercury (Patent No. 1567717 (Japanese Patent Publication No. 1-54655)) is known. That is, for example, exhaust gas from a garbage incinerator contains mercuric chloride generated by the reaction of metal mercury with hydrogen chloride gas in addition to metal mercury. In the analysis method, the mercuric chloride is converted into metal. Reduce to mercury and analyze with an analyzer such as a flameless atomic absorption mercury analyzer.
[0003]
[Problems to be solved by the invention]
The analysis method is effective for old type garbage incinerators but not for new type garbage incinerators. When the cause was investigated, the following was found. In other words, metal tin itself does not have a reducing ability, but in old garbage incinerators and the like, the content of hydrogen chloride (HCl) in the exhaust gas is relatively high. Tin becomes stannous chloride, and this stannous chloride reacts with the mercuric chloride as a reducing agent, whereby Hg ²⁺ in the mercuric chloride is reduced to metallic mercury (Hg ⁰ ). However, in the new type incinerator, since the content of hydrogen chloride in the exhaust gas is small, Hg ^{2 in the} mercuric chloride contained in the exhaust gas can be used even if metallic tin is used as in the conventional mercury analysis method described above. ⁺ Is not reduced to metallic mercury (Hg ⁰ ), and accurate mercury analysis cannot be performed.
[0004]
The present invention has been made on the basis of the above knowledge, and a method and apparatus for analyzing mercury in a gas capable of correctly analyzing mercury in a gas containing mercuric chloride such as exhaust gas from a garbage incinerator or the like. The purpose is to provide.
[0005]
[Means for Solving the Problems]
To achieve the above object, a method for analyzing mercury in a gas according to claim 1 of the present invention is a method for analyzing mercury in a gas containing mercuric chloride, wherein the surface of tin particles is chlorinated. A reducing agent formed by forming a stannous coating is prepared, and after the reduction of Hg ²⁺ in the mercuric chloride to Hg ⁰ by the reducing agent, analysis is performed.
[0006]
According to the mercury analysis method, even when the concentration of hydrogen chloride gas in the gas is low, Hg ^{2 in} mercuric chloride contained in the gas is formed by the coating of stannous chloride formed on the surface of the tin particles. ^{Since +} is reduced to Hg ⁰ , mercury in a gas containing mercuric chloride such as exhaust gas from a garbage incinerator can be correctly analyzed.
[0007]
In order to achieve the above object, a mercury analyzer according to claim 2 of the present invention is an apparatus for analyzing mercury in a gas containing mercuric chloride, wherein the surface of tin particles is coated with chloride. A reduction reactor having a reducing agent formed with a film of stannous, and the gas is passed through the reduction reactor to reduce Hg ²⁺ in the mercuric chloride to Hg ⁰ by the reducing agent. A reduction device and an analyzer for analyzing the reduced Hg ⁰ are provided.
[0008]
According to the mercury analyzer, gas containing mercuric chloride is allowed to pass through the reduction reactor by the reduction device, and by the stannous chloride on the surface of the tin particles as the reducing agent in the reduction reactor, Since Hg ^{2+ in} mercuric chloride contained in the gas is reduced to Hg ⁰ and the reduced Hg ⁰ is analyzed by an analyzer, it contains mercuric chloride such as exhaust gas from a garbage incinerator. Even if the concentration of hydrogen chloride gas in the gas is low, it can be analyzed correctly.
[0009]
According to a third aspect of the present invention, the mercury analyzer further comprises a heater for heating the reduction reactor to prevent condensation of water in the gas.
[0010]
If the temperature of the reducing agent is low, moisture in the gas may condense and the stannous chloride film may dissolve and flow out. According to the mercury analyzer, the condensation of the water is prevented, so that the reducing agent is protected. As a result, the mercury in the gas can be analyzed accurately and rapidly.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a conceptual diagram showing a schematic configuration of a mercury analyzer according to an embodiment of the present invention. This mercury analyzer 1 is an apparatus for analyzing mercury in a gas containing mercuric chloride, such as exhaust gas from a garbage incinerator or the like. As shown in a cross-sectional view in FIG. A reduction reactor 5 having a reducing agent 4 formed by forming a film 3 of stannous chloride on the surface of the particles 2.
[0012]
The reducing agent 4 having the stannous chloride coating 3 formed on the surface of the tin particles 2 is formed by immersing metallic tin in hydrochloric acid, and has a particle size of about 2 mmφ. The reduction reactor 5 is made of, for example, a quartz tube having a main part diameter of 12 mmφ, a both end diameter of 8 mmφ, and a main part length of 15 cm, and the main part is filled with a plurality of the reducing agents 4. In order to confine the reducing agent 4 in the main part of the reduction reactor 5, quartz glass wool 6 is packed at both ends.
[0013]
The gas containing mercuric chloride is reduced by passing through the reduction device 7 provided with the reduction reactor 5. This reduction device 7 is connected to the inlet of the reduction reactor 5 and has a pipe 9 having a filter 8 at the front end, and is connected to the outlet of the reduction reactor 5, with a cooler 10 in the middle, and a suction pump 11 at the rear end. It is comprised with the piping 12 which has this. When the gas is allowed to pass through the reduction reactor 5 by the reducing device 7, Hg ²⁺ in mercuric chloride contained in the gas is reduced to metallic mercury (Hg ⁰ ) by the reducing agent 4.
[0014]
The filter 8 is for removing dust and the like contained in the gas introduced into the pipe 9, and is made of, for example, quartz glass wool. The pipe 9 is a heating pipe that is heated to a constant temperature (for example, 150 ° C.), and moisture in the gas introduced thereby does not condense in the pipe.
[0015]
The reduction reactor 5 is heated to 100 to 130 ° C. by the heater 13. If the temperature of the reducing agent 4 is lower than the dew point of the moisture in the gas, the moisture in the gas may condense and the stannous chloride may dissolve and flow out. Moreover, although the upper limit of the same temperature is 232 ° C. or less of the melting point of metal tin, it is necessary to cool in order to analyze the metal mercury in the subsequent process, so that it is preferably 130 ° C. or less for rapid cooling. . At the rear end of the reducing device 7, an analyzer 14 for analyzing metallic mercury (Hg ⁰ ) contained in the gas derived from the reducing device 7 is provided. The analyzer 14 is composed of, for example, a flameless atomic absorption mercury analyzer.
[0016]
Next, processing steps in the case where mercury in a gas containing mercuric chloride is analyzed by the mercury analyzer 1 having the above-described configuration will be described.
In FIG. 1A, the gas containing mercuric chloride is, for example, exhaust gas discharged from a chimney 15 of a garbage incinerator, and the tip of a pipe 9 constituting the reduction device 7 is exposed to the chimney 15. However, by operating the suction pump 11, the exhaust gas is introduced from the pipe 9 and passes through the reduction reactor 5. The exhaust gas introduced from the chimney 15 into the pipe 9 contains mercuric chloride and metallic mercury as mercury components. As described above, the pipe 9 is composed of a heating pipe and has a predetermined temperature (for example, 150 ° C.). Therefore, moisture in the exhaust gas does not condense. As a result, it is possible to prevent mercuric chloride and metal mercury from adhering to the water droplets while passing through the pipe 9, and to avoid inaccurate mercury analysis due to adhesion to the water droplets.
[0017]
When exhaust gas passes through the reduction reactor 5, Hg ^{2+ in} mercuric chloride contained in the exhaust gas is converted to stannous chloride of the reducing agent 4 according to the following reaction formulas (1) and (2). (SnCl2) reacts with and is reduced to metallic mercury (Hg ^0).
HgCl ₂ + SnCl ₂ → Hg ⁰ + SnCl ₄ (1)
HgCl ₂ + SnCl ₂ + 2H ₂ O → Hg ⁰ + SnO ₂ + 4HCl (2)
That is, in this case, even when the hydrogen chloride gas concentration in the exhaust gas is low, the stannous chloride of the reducing agent 4 can reliably reduce Hg ²⁺ in mercuric chloride to metallic mercury (Hg ⁰ ). .
[0018]
Further, the reduction reactor 5 is heated to 100 to 130 ° C. by the heater 13 so that the inside thereof protects the reducing agent and has an advantageous atmospheric temperature for subsequent cooling of the metal mercury. Mercury analysis can be performed more accurately and quickly.
[0019]
The metal mercury thus reduced and the metal mercury originally contained in the exhaust gas are sent together with the exhaust gas to the analyzer 14 through the pipe 12 of the reduction device 7, and the analyzer 14 analyzes the metal mercury. Done. When the exhaust gas is sent to the analyzer 14 through the pipe 12, the exhaust gas is cooled to the ambient temperature or lower by the cooler 10 in the middle of the pipe 12, and moisture in the exhaust gas is removed. It is possible to prevent moisture from condensing on the analyzer, and the mercury analysis by the analyzer 14 can be performed more accurately.
[0020]
Note that the stannous chloride coating 3 on the surface of the tin particles 2 in the reducing agent 4 is consumed by the reducing action in the reduction reactor 5, but in the case of exhaust gas from a garbage incinerator, the concentration is about However, since some hydrogen chloride gas is contained, a new stannous chloride coating 3 is formed on the surface of the tin particles 2 by the reaction with the hydrogen chloride gas. As a result, the reducing agent 4 filled in the reduction reactor 5 does not lose its reducing ability in a short period of time and functions effectively as a reducing agent for a long period of time.
[0021]
In addition, when the gas contains both metallic mercury and compound mercury, if mercury analysis is performed in the gas without using the method of reducing the compound mercury of the present invention to metallic mercury, only metallic mercury is analyzed. The Therefore. By combining this with the present invention, it is possible to separate and determine metallic mercury and compound mercury not only in waste incineration flue with high hydrogen chloride gas concentration, but also in waste incineration flue exhaust gas with dilute hydrogen chloride gas. Become.
[0022]
【The invention's effect】
As described above, according to the inventions of claims 1 and 3, Hg ²⁺ in mercuric chloride contained in gas is reduced by forming a film of stannous chloride on the surface of tin particles. Since mercury is analyzed after reducing it to Hg ⁰ with an agent, mercury in the gas can be correctly analyzed even when the concentration of hydrogen chloride gas in the gas is low.
[Brief description of the drawings]
FIG. 1A is a schematic configuration diagram showing a mercury analyzer according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view of a reducing agent used in the mercury analyzer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Mercury analyzer, 2 ... Tin particle, 3 ... Stannous chloride coating, 4 ... Reducing agent, 5 ... Reduction reactor, 7 ... Reduction device, 13 ... Heater, 14 ... Analyzer

Claims (3)

A method for analyzing mercury in a gas containing mercuric chloride,
Prepare a reducing agent by forming a film of stannous chloride on the surface of the tin particles,
A method for analyzing mercury in a gas, wherein Hg ²⁺ in the mercuric chloride is reduced to Hg ⁰ by the reducing agent and then analyzed. An apparatus for analyzing mercury in a gas containing mercuric chloride,
A reduction reactor having a reducing agent formed by forming a film of stannous chloride on the surface of tin particles;
A reducing device that passes the gas through the reduction reactor and reduces Hg ²⁺ in the mercuric chloride to Hg ⁰ by the reducing agent;
An analyzer for analyzing the reduced Hg ⁰ ;
Mercury analyzer with 3. The mercury analyzer according to claim 2, further comprising a heater that heats a reducing agent in the reduction reactor to prevent condensation of moisture in the gas.

Images