JP2018025429A - Reduction filter of mercury concentration measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove an organic material in combustion exhaust gas input into a mercury concentration measuring apparatus.SOLUTION: A reduction filter is disposed on the pre-stage of a mercury concentration measuring apparatus, and is formed of a reduction catalyst, a combustion catalyst, a cylindrical body, and a heating member to achieve the above-mentioned objective. The reduction catalyst reduces mercury compounds in combustion exhaust gas, and the combustion catalyst promotes the combustion of an organic material in the combustion exhaust gas. The reduction catalyst and the combustion catalyst are filled into the cylindrical body, and the reduction catalyst is disposed on the upstream side and the combustion catalyst is disposed on the downstream side. The cylindrical body is heated by the heating member to a prescribed temperature. The combustion catalyst is at least one of copper oxide, cerium oxide, and cobalt oxide. The combustion catalyst is carried by a base material, and, at this time, is sometimes carried together with the reduction catalyst by the base material.SELECTED DRAWING: Figure 2

Description

  More particularly, the present invention relates to a reduction filter for combustion exhaust gas containing organic matter.

  As a device for detecting the concentration of mercury contained in combustion exhaust gas from an incineration facility such as a garbage incineration plant, a mercury concentration measuring device using, for example, atomic absorption spectrometry is used. Such a mercury concentration measuring device detects the amount of absorption of light of a specific wavelength (254 nm) by irradiating the sample gas introduced into the measuring device with ultraviolet light, and based on this amount of absorption, the concentration of mercury contained in the sample gas Is what you want.

  In the above measurement apparatus, since the mercury concentration is detected based on the absorbance of atomic mercury, it is necessary to reduce the mercury compound contained in the sample gas to atomic mercury in order to accurately measure the mercury concentration. is there. Therefore, a reduction filter for reducing the mercury compound to atomic mercury is provided in the introduction path for introducing the sample gas into the measuring apparatus.

  In combustion exhaust gas from an incineration facility or the like, the mercury compound is mainly mercury chloride, and a reduction filter is provided for reducing the mercury chloride.

  As the reduction filter, a cylindrical body in which a reduction catalyst is enclosed is used. As the reduction catalyst, for example, as disclosed in JP-A-2005-98713, an alkali metal or alkaline earth metal heated to a predetermined temperature is used. Basic compounds such as sodium carbonate are used.

  Related techniques include, as the reduction catalyst, Patent No. 554683 using two kinds of reduction catalysts, or Patent No. 5877540 using two kinds of diameters as the diameter of the reduction catalyst. Patent No. 5192562 using sodium, calcium, magnesium sulfite or phosphate.

JP 2005-98713 A Japanese Patent No. 5464883 Japanese Patent No. 5877540 Japanese Patent No.5192652

  Since municipal waste is based on the premise of complete combustion, organic substances are rarely contained in the combustion exhaust gas, but depending on the combustion conditions, organic substances may be temporarily included in the combustion exhaust gas. For example, this phenomenon appears during startup and shutdown of a combustion furnace where incomplete combustion is likely to occur.For example, it shows a high absorbance at startup, and it behaves as if mercury is contained in the combustion exhaust gas. is there.

  This phenomenon is not due to mercury being contained in the combustion exhaust gas, but due to the incomplete combustion containing organic matter in the combustion exhaust gas, but appears as mercury concentration in the mercury concentration meter.

  In addition, if organic substances are adsorbed on the gas contact part of the mercury gas measuring device, and then adsorbed organic substances are desorbed and flow into the detection part, there is a possibility that an incorrect mercury concentration is detected.

  Furthermore, the organic substance adsorbed on the gas contact part may trap the mercury compound in the combustion exhaust gas. In this case, the mercury concentration is detected as lower than the actual concentration.

  Examples of organic substances that are easily adsorbed by the gas contact part and can easily trap mercury compounds when adsorbed include bis (2-ethylhexyl) phthalate and tris (2-ethylhexyl) trimellitic acid. As a result, the amount of mercury contained in the fuel exhaust gas when using waste plastic and waste oil is high, and the mercury measurement accuracy of the combustion exhaust gas from these combustion facilities becomes a problem.

  The present invention has been proposed in view of the above-described conventional circumstances, and provides a reduction filter disposed in a preceding stage of a mercury concentration measuring apparatus capable of accurately measuring the mercury concentration even in the case of combustion exhaust gas containing organic matter. It is intended.

  The present invention is a reduction filter disposed in a preceding stage of a mercury concentration measuring device for quantifying the mercury concentration in combustion exhaust gas, and comprises a reduction catalyst, a combustion catalyst, a cylinder, and a heating member in order to achieve the above object. Is done.

  The reduction catalyst reduces mercury compounds in the combustion exhaust gas, and the combustion catalyst promotes the combustion of organic substances in the combustion exhaust gas. The reduction catalyst and the reduction catalyst are filled in a cylinder, and a reduction catalyst is disposed upstream and a combustion catalyst is disposed downstream thereof. The cylinder is heated to a predetermined temperature by a heating member.

  The combustion catalyst is at least one of copper oxide, cerium oxide, and cobalt oxide. The combustion catalyst is supported on a base material, and at this time, it may be supported on the base material together with the reduction catalyst.

  Further, the reduction catalyst comprises a first reduction catalyst having a reduction function for mercury and having an acid gas removal capability, and a second reduction catalyst having no acid gas removal capability but having a reduction capability for mercury, The combustion catalyst may be supported on a base material together with the second reduction catalyst.

  According to the above configuration, if the organic matter concentration in the combustion exhaust gas is less than several thousand ppm and the combustion exhaust gas flow rate is about several hundred ml / min, even a small amount of combustion catalyst shows high organic matter decomposition ability and durability for several months. Can maintain sex.

It is the schematic of a mercury measuring system. It is a longitudinal cross-sectional view of the filter used as the principal part of this invention.

  FIG. 1 is a schematic diagram of a mercury concentration measuring system including a mercury concentration measuring device.

  A probe 10 that guides combustion exhaust gas from the inside of the flue to the outside is installed on the wall of the flue of the combustion furnace. Combustion exhaust gas is led from a sampling tube 11 at the tip of the probe 10 to a reduction filter 20 described below, and is led from the downstream side of the reduction filter 20 to the outside of the flue, and further via a conduit 12. And input to the mercury concentration measuring device 30. The mercury concentration measuring device 30 includes a suction pump 35, and the exhaust gas from the reduction filter 20 is guided to the mercury concentration measuring device 30 by the suction of the suction pump 35.

  In the mercury concentration measuring device 30, the combustion exhaust gas from the conduit 12 is first removed from the moisture by the moisture trap 31, guided to the filter 32, passed through the filter 32, and further disclosed in JP-A-2005-77355. It is introduced into the detection unit 34 via the interference reduction mechanism 33. The interference reduction mechanism 33 has a function of reducing the influence of organic matter to several tenths, but the present invention is intended for removal of organic matter up to the interference reduction mechanism 33.

  The detection unit 34 measures the amount of absorption of light having a specific wavelength (for example, 254 nm) by mercury atomic absorption. In the detection unit 34, in order to obtain the true value of the mercury amount by the difference between the gas containing mercury and the gas not containing mercury, the interference reduction mechanism 33 is configured to use the gas containing mercury and the gas not containing mercury. Is supposed to make.

  The exhaust gas after measurement is discharged to the outside through the flow rate adjusting valve 36, the flow meter 37, and the mercury remover 38.

  FIG. 2 is a view showing a longitudinal section of the reduction filter 20 according to the invention.

  A conventionally used reduction catalyst 22 is disposed on the upstream side of the cylinder (quartz column) 21 and a combustion catalyst 23 for burning organic substances on the downstream side thereof. The upstream end and the downstream end are silica wool. In addition, a silica wool 24 is interposed between the reduction catalyst 22 and the combustion catalyst 23 as a separator. Further, a heater 25 is provided on the outer peripheral side of the cylinder 21 and is operated at 300 to 500 ° C.

  The reduction catalyst 22 is an alkali metal basic compound such as sodium carbonate or an alkaline earth metal basic compound as described above, and reduces a mercury compound such as mercury chloride in the combustion exhaust gas to a state of atomic mercury. . Further, the combustion exhaust gas contains acidic gases such as hydrogen chloride, sulfur dioxide, nitrogen oxides, etc. When these acidic gases come into contact with the mercury atoms, mercury is reoxidized to form mercury compounds again. In addition, the combustion catalyst of the present invention (including a second reduction catalyst described later) is poisoned. Therefore, when an alkali metal carbonate having an acid gas removing ability is used as the reduction catalyst 22, it is effective in preventing mercury from being reoxidized and preventing the combustion catalyst from being poisoned. Here, a granular reduction catalyst 22 is used.

  The combustion catalyst 23 works in the same temperature range as the reduction catalyst 22, does not capture mercury, efficiently decomposes organic substances, does not interfere with reduction of mercury compounds, or reduces reduced atomic mercury to mercury. It is selected on the condition that it does not return to the compound, and at least one of copper oxide, cerium oxide, and cobalt oxide is selected. The combustion catalyst 23 may be in the form of powder or granules, but is supported on a base material such as alumina, zeolite, or diatomaceous earth here. Although the shape of the base material is generally granular with a diameter of several millimeters, it is not limited to a granular shape, such as a honeycomb shape, if the ventilation resistance is low and the exhaust gas efficiency is high.

  By the way, in the presence of carbon dioxide gas, it is effective to use the alkali metal carbonate as the reduction catalyst (first reduction catalyst 22a). Further, when the alkali metal carbonate is used, Acid gas can also be removed. Therefore, a reduction catalyst (second reduction catalyst 22b) made of activated alumina or molecular sieves that has a reduction function but does not have resistance to acidic gas is disposed downstream of the first reduction catalyst to increase the reduction efficiency. It can be configured to be raised (Japanese Patent No. 5464883).

  Accordingly, as the combustion catalyst 23, a mixture of the material used for the second reduction catalyst 22b and the combustion catalyst 23 is supported on a base material, or the second combustion catalyst is used as a base material and the combustion catalyst is supported. Can be taken.

  In the above configuration, the combustion catalyst 23 needs to capture mercury atoms and not adversely affect the detected mercury concentration, and conversely, by placing the combustion catalyst 23 downstream, It is required that the reduction effect does not decrease.

  Further, the reduction filter having the above-described configuration is operated at 300 to 500 ° C. at which the reduction catalyst 22 works. When the temperature is within this temperature range, the combustion catalyst 23 selected as described above works effectively for removing organic substances by combustion decomposition. . Therefore, by adopting the above-mentioned type of combustion catalyst 23, there is no need to change the conventional reduction temperature range, or there is no need to change the heating temperature between the reduction catalyst portion and the combustion catalyst portion, and the packing can be reduced. All you have to do is change or add.

  Further, as the following experimental results show, the amount of mercury trapped by the combustion catalyst 23 made of the material selected as described above is zero, and the combustion catalyst does not adversely affect the measurement.

<Example 1>
Table 1 shows the experimental results of examining the organic substance removal rate and the presence or absence of mercury capture for substances that can be used as combustion catalysts.

  Catalyst shape is powder (no support), catalyst temperature is 400 ° C, organic substance concentration is 350ppm of toluene, gas flow rate is 0.03L / min (carrier gas is air), inner diameter is 3mm, packing length is 5mm ) And the amount of catalyst is about 0.2g.

  As shown in Table 1, cerium oxide, cobalt oxide, and copper oxide can be used as a combustion catalyst of the present invention because they efficiently remove organic substances and do not capture mercury. In particular, cobalt oxide and copper oxide are promising because of their high organic matter removal rate. It can be understood that platinum and palladium capture organic substances efficiently but also capture mercury and cannot be used as a combustion catalyst of the present application.

＜実施例２＞
表２は燃焼触媒として酸化銅を使用したときの各種の有機物の除去率を示す実験結果である。酸化銅は球形アルミナに担持、温度400℃、ガス流量0.3L／分（キャリアガスは空気）の条件下で、トルエン、フタル酸ビス、トリメリット酸トリスについて調べた。トルエン、フタル酸ビス（2−エチルヘキシル）、については効率よく除去されているが、粘着性の強いトリメリット酸トリス（2−エチルヘキシル）については除去率が多少落ちることになる。水銀と有機物が同じ濃度であるとき有機物の紫外線吸収量は水銀の１万分の１以下、ではあるが、燃焼排ガス中の有機物の量が多くなると当該有機物の紫外線吸収量による水銀濃度測定への干渉の影響は無視できなくなる。この場合であっても、当該実施例のように、５０％前後の除去率が達成できるとかなり水銀濃度の誤差は改善されることになる。

<Example 2>
Table 2 shows the experimental results showing the removal rates of various organic substances when copper oxide is used as the combustion catalyst. Copper oxide was supported on spherical alumina, and toluene, bisphthalate, and trimellitic acid tris were examined under conditions of a temperature of 400 ° C. and a gas flow rate of 0.3 L / min (the carrier gas was air). Toluene and bis (2-ethylhexyl) phthalate are efficiently removed, but the removal rate of trimellitic acid tris (2-ethylhexyl), which is highly tacky, is somewhat lowered. When mercury and organic matter have the same concentration, the amount of UV absorption of organic matter is 1 / 10,000 or less of mercury, but when the amount of organic matter in combustion exhaust gas increases, the amount of UV absorption of organic matter interferes with mercury concentration measurement. The effects of can not be ignored. Even in this case, if the removal rate of around 50% can be achieved as in this embodiment, the error in mercury concentration is considerably improved.

＜実施例３＞
表３は温度を変えての燃焼触媒の効果を確認する実験結果を示すものである。

<Example 3>
Table 3 shows experimental results for confirming the effect of the combustion catalyst at different temperatures.

  The experimental conditions are that organic substances are 500 ppm and 1000 ppm of toluene respectively, the combustion catalyst is copper oxide (6.8 g), the reduction catalyst (16.8 g), the gas flow rate is 0.3 g / min, and the catalyst temperature is changed to 300 to 500 ° C. I let you. Each catalyst is a weight including a carrier, and is used by mixing copper oxide and a reduction catalyst.

  It can be understood that organic matter (toluene) decomposes almost completely at 400 ° C. or higher. 50% or more can be removed even at 300 ° C, and organic substances can be decomposed even at low temperatures.

＜実施例４＞
表４は、還元触媒と燃焼触媒を組み合わせたときと燃焼触媒のみのときとでの塩化水銀の還元効率を確認した実験結果である。

<Example 4>
Table 4 shows the experimental results for confirming the reduction efficiency of mercury chloride when the reduction catalyst and the combustion catalyst are combined and when only the combustion catalyst is used.

The mercury concentration was 179 μg / m ³ , the catalyst temperature was 400 ° C., the combustion catalyst was copper oxide (20 g: no reduction catalyst), and the gas flow rate was 0.3 g / min. The reduction rate of 75% with the combustion catalyst is equivalent to thermal decomposition at 400 ° C, and the combustion catalyst has no mercury reduction ability. On the other hand, the reduction rate when the reduction catalyst and the combustion catalyst are combined is 100%, and it can be understood that the reduction catalyst works effectively and that the combustion catalyst does not hinder the reduction function of the reduction catalyst.

以上説明した構成によると、燃焼排ガス中の有機物濃度が数千ppm未満、燃焼排ガス流速が数百ml／分程度であれば、少量（例えば１０ｇ程度）の燃焼触媒でも、高い有機物分解能力を示すとともに、数ヶ月程度の耐久性を維持することが確認されている。

According to the configuration described above, if the organic matter concentration in the combustion exhaust gas is less than several thousand ppm and the combustion exhaust gas flow rate is about several hundred ml / min, even a small amount (for example, about 10 g) of the combustion catalyst exhibits high organic matter decomposition ability. In addition, it has been confirmed that the durability of about several months is maintained.

  As described above, the present invention is capable of decomposing organic matter while maintaining the conventional mercury compound reduction function even when organic matter is contained in the combustion exhaust gas. Errors can be suppressed.

DESCRIPTION OF SYMBOLS 10 Probe 11 Sampling pipe 12 Conduit 20 Reduction filter 21 Tube 22 Reduction catalyst 23 Combustion catalyst 30 Mercury concentration meter 31 Moisture trap 32 Filter 33 Interference reduction mechanism 34 Detection part 35 Suction pump 36 Flow control valve 37 Flow meter 38 Mercury remover

Claims (5)

In the reduction filter placed in the front stage of the mercury concentration measuring device to quantify the mercury concentration in the combustion exhaust gas,
A reduction catalyst for reducing mercury compounds in combustion exhaust gas,
A combustion catalyst that promotes the combustion of organic matter in the flue gas,
The reduction catalyst and a cylinder filled with the combustion catalyst on the downstream side of the reduction catalyst;
A heating member for heating the cylinder to a predetermined temperature;
A reduction filter comprising:   The reduction filter according to claim 1, wherein the combustion catalyst is at least one of copper oxide, cerium oxide, and cobalt oxide.   The reduction filter according to claim 2, wherein the combustion catalyst is supported on a base material.   The reduction filter according to claim 2, wherein the combustion catalyst is supported on a base material together with a reduction catalyst.   The reduction catalyst comprises a first reduction catalyst having a reduction function for mercury and having an acid gas removal capability, and a second reduction catalyst having no acid gas removal capability but having a reduction capability for mercury, and the combustion The reduction filter according to claim 2, wherein the catalyst is supported on a base material together with the second reduction catalyst.

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