JP2011033636A - Device and method for analyzing siloxane in siloxane-containing gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for accurately and continuously analyzing siloxane concentration in biogas on the real time basis, and a method for analyzing siloxane using the device. <P>SOLUTION: An infrared siloxane analyzing device for analyzing siloxane concentration in the siloxane-containing biogas has an optical filter which passes only infrared rays of a wave number of 1,250-770 cm<SP>-1</SP>. A filter filled with an adsorbent for adsorbing siloxane is fixed in front of a sample gas introducing port, and a dehumidifier for keeping the water content in the biogas constant is fixed in front of the sample introducing port. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for analyzing siloxane in biogas for effectively using siloxane-containing biogas generated during biological treatment as an energy source.

  Biological treatment of organic waste generated in sewage treatment plants, food factories, beer factories, livestock breeding plants, etc. generates biogas containing carbon dioxide, moisture, hydrogen sulfide, etc. in addition to methane.

  In recent years, in order to effectively use such biogas as an energy source, for example, in a sewage treatment facility, concentrated sewage is concentrated to obtain sludge containing various organic substances, which is anaerobically digested by the action of microorganisms, A method for obtaining electric power by using a combustible gas (digestion gas) mainly containing methane obtained in this process to a power generation facility such as a gas engine and a gas turbine is becoming mainstream.

  However, as the penetration rate of sewage plants has improved and the lifestyle has changed, consumption of hair finishes such as shampoos and rinses and water repellents such as car wax has increased, and the siloxane compounds contained in these have increased. A large amount of water began to flow into sewage.

  Note that the siloxane compound refers to a compound having a chain or cyclic structure with a siloxane bond (Si—O—Si) as a basic skeleton. Examples of the chain compound include methoxytrimethylsilane, dimethoxydimethylsilane, hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, and dodecamethylpentasiloxane. Examples of the cyclic compound include hexamethylcyclohexane. Examples include trisiloxane (D3 form), octamethylcyclotetrasiloxane (D4 form), decamethylcyclopentasiloxane (D5 form), and dodecamethylcyclohexasiloxane (D6 form). In the compounds listed here, the functional group in the compound is composed of a methyl group, but a compound substituted with a hydrocarbon group similar to the methyl group or a compound substituted with fluorine, chlorine or the like instead of hydrogen is also available. There are also polypolymeric compounds which are included and which have a high molecular weight.

Most of the siloxane compounds are present in the sewage in the form of being adsorbed to sludge because they are insoluble in water, but volatilize to the digestion gas side in the subsequent digestion process. That is, the siloxane compound is present together with methane, which is a fuel gas for power generation, and flows into the gas engine at the subsequent stage. The siloxane compound that has flowed into the gas engine becomes silica (SiO ₂ ) in the combustion chamber in the engine, and adheres to and deposits on the cylinder head and other components in the engine. As a result, the engine is worn out and deteriorated.

Further, engine exhaust gas that has passed through a power generation facility such as a gas engine is introduced into a denitration catalyst tower for treatment, for example, for nitrogen oxide treatment, and silica (SiO ₂ ) is contained in the exhaust gas. Further, powdered silica (SiO ₂ ) in the exhaust gas is deposited on the surface of the catalyst. The powdery silica thus covers the surface of the catalyst, and a part of the silica penetrates into the inside of the catalyst, so that the catalyst activity is deteriorated and the desired nitrogen oxide removal cannot be achieved.

  In order to solve these problems, it is necessary to analyze the concentration of siloxane and appropriately treat it. As an analysis method therefor, for example, a method in which siloxane is once absorbed in a solvent and then analyzed by gas chromatography Is known (see Non-Patent Document 1).

  However, such an analysis method has a complicated sampling and is difficult to continuously analyze in the field. Furthermore, only an average value of several hours could be obtained. Because of this situation, the siloxane concentration in the untreated biogas containing the siloxane compound or the siloxane concentration in the treated biogas is analyzed substantially continuously on site, and the result Based on the above, it has not been possible to specify the operating specifications of the biogas purification apparatus (for example, the replacement time of the siloxane adsorption treatment agent). Therefore, despite the fact that sufficient adsorption performance remains, the problem that the siloxane adsorption treatment agent is discarded or subjected to regeneration treatment, or conversely, the siloxane adsorption treatment agent has already sufficiently reached breakthrough. Nevertheless, there is a danger that the operation is continued, causing problems such as wear and deterioration of the gas engine described above.

38th Sewerage Research Presentation, 2001, p. 695-697

  An object of the present invention is to provide an analyzer capable of continuously analyzing the siloxane concentration in biogas with high accuracy in real time and a method for analyzing siloxane using the device.

  As a result of intensive studies, the present inventor has found that a non-dispersed infrared siloxane analyzer having an optical filter that transmits infrared light of a specific wave number, a filter filled with an adsorbent that adsorbs siloxane, and a certain amount of water in biogas. It has been found that the above problem can be solved by mounting the dehumidifier in front of the sample gas inlet, and the present invention has been completed.

That is, the present invention provides an analyzer and an analysis method for siloxane in a siloxane-containing gas as shown below.
Item 1 An infrared siloxane analyzer for analyzing a siloxane concentration in a siloxane-containing biogas, having an optical filter that passes only infrared rays having a wave number of 1250 cm ^{−1 to} 770 cm ⁻¹ , and filled with an adsorbent that adsorbs siloxane A non-dispersive infrared siloxane analyzer, wherein a filter is mounted in front of a sample gas inlet, and a dehumidifier for mounting a constant amount of water in the biogas is mounted in front of the sample gas inlet.
Item 2. The non-dispersive infrared siloxane analyzer according to Item 1, wherein infrared rays having a wave number of less than 770 cm ^-1 are absorbed by an optical filter made of BaF ₂ .
Item 3. The non-dispersive infrared siloxane analyzer according to Item 1 or 2, wherein a gas filter for removing suspended particulates having a filter size of 10 μm or less is mounted in front of the sample gas inlet.
Item 4 A method for analyzing siloxane, wherein the siloxane concentration in the siloxane-containing biogas is continuously monitored using the non-dispersive infrared siloxane analyzer according to any one of Items 1 to 3.

  Hereinafter, the present invention will be described in detail.

  The configuration of the non-dispersive infrared siloxane analyzer includes, for example, a light source, a chopper, a sample cell, a comparison cell, an optical filter, a detection cell, an amplifier, a calculation unit, and a display unit as shown in FIG. Infrared light emitted from the light source becomes intermittent light by the rotating chopper, passes through the sample cell and the comparison cell, and then enters the detection cell through the optical filter. When the infrared rays that pass through the sample cell are absorbed by the sample gas, a difference in the amount of light occurs in the infrared rays that enter the detection cell. The difference is detected by the detection cell, and the siloxane concentration is measured.

  As the gas sealed in the comparison cell, any gas that does not absorb the measurement wave number can be used. Preferably, nitrogen, air, biogas containing no siloxane, or the like can be used.

  As a detection method, a generally used method can be applied, but a detection method by vibration of a thin film provided in a detection cell is particularly preferable. The detection cell based on the vibration of the thin film is composed of two chambers, and the space is partitioned by the thin film. Infrared rays that have passed through the sample cell and the comparison cell are incident on the respective rooms. The concentration of siloxane can be measured by the vibration of the thin film due to the difference in infrared absorption in each room.

  A reference gas is enclosed in the detection cell. As the reference gas, one having absorption in the measurement wave number can be used. Usually, a gas (for example, ammonia) having absorption at the absorption wave number of siloxane that is a measurement target gas or siloxane that is a measurement target gas is enclosed.

The optical filter, which does not transmit infrared rays other than the region of the analysis is the absorption range of the siloxane is a target gas 1150cm ^-1 ~1000cm ^-1 and / or 850cm ^-1 ~770cm ^-1 are preferred. Specifically, the optical filter allows only infrared rays having a wave number of 1250 cm ^{−1 to} 770 cm ⁻¹ to pass therethrough. In order to absorb infrared rays having a wave number of less than 770 cm ⁻¹ , for example, an optical filter made of BaF ₂ can be used. In order to absorb infrared rays having a wave number exceeding 1250 cm ⁻¹ , for example, an optical filter of a multilayer coating film used in an ammonia meter or the like can be used.

  If the sample gas contains a component whose absorption wave number partly overlaps the wave number of the measured component, an optical filter and a similar detection cell are provided after passing through the detection cell, if necessary. It is possible to avoid being affected by this.

Suspended particulates having absorption in 1250cm ^-1 ~770cm ^-1 measuring wavenumber range (e.g., metal oxides, phosphoric acid, etc.) in order to be unaffected in the analysis precision, the removal of suspended particles from the sample gas A gas filter may be mounted in front of the sample gas inlet in the non-dispersive infrared siloxane analyzer. The sample gas introduction port is an introduction port through which the sample gas is introduced into the sample cell as indicated by an arrow in FIG. As the gas filter for removing suspended particulates, a general gas filter not using a silicon-based substance can be used. The filter size is preferably 10 μm or less, more preferably 0.01 to 5 μm, and particularly preferably 0.01 to 1 μm.

When analyzing siloxane contained in a biogas containing moisture, there is a possibility that a problem of interference due to moisture may occur. Therefore, by making the amount of water in the biogas constant by a dehumidifier, the measured value of the siloxane concentration can be corrected by the amount of moisture that is an interference component of siloxane, and the concentration of siloxane can be accurately analyzed. Is possible.
Moreover, a general thing can be used as a dehumidifier. Preferably, it is a cooling type dehumidifier. The degree of dehumidification is not limited as long as the siloxane in the gas is not recondensed, and the water dew point is preferably from 0 ° C to 20 ° C, more preferably from 0 ° C to 10 ° C. In addition, the moisture dew point after dehumidification is preferably lower than the temperature of the analysis target gas. When the moisture dew point after dehumidification is higher than the analysis target gas temperature, it is preferable to bubble the moisture before the dehumidifier.

If a filter filled with an adsorbent that adsorbs siloxane is installed in front of the sample gas inlet in the infrared siloxane analyzer, zero point correction with higher accuracy is possible in that state, and the filter is removed. An infrared siloxane analyzer having a structure capable of accurately analyzing the concentration of siloxane can be obtained. By doing in this way, it is possible to suppress the influence on the analysis accuracy by the influence of the interference by carbon dioxide and moisture and the fluctuation of carbon dioxide and moisture at various sites. As the adsorbent, a general adsorbent capable of adsorbing siloxane can be used. When using activated carbon as an adsorbent has a specific surface area preferably has 500~2400m ² / g, it is more preferred 600~1800m ² / g. If the specific surface area is less than 500 m ² / g, the amount of adsorption per unit weight tends to be small. Moreover, when the specific surface area exceeds 2400 m ² / g, the packing density tends to be low, and the amount of adsorption per unit volume tends to be small. Also, for the same reason with respect to the pore volume is preferably a 0.2~1.5cm ³ / g, it is more preferred 0.3~1.0cm ³ / g. The average pore diameter is preferably 7 to 20 mm, more preferably 8 to 15 mm.

  Furthermore, by attaching a filter filled with an adsorbent that adsorbs siloxane in front of the sample gas inlet, in addition to highly accurate zero point correction, it is possible to correct the measured value of the siloxane concentration by the amount of water, It becomes possible to analyze the concentration of siloxane more accurately.

  Furthermore, in addition to mounting a filter filled with an adsorbent that adsorbs siloxane in front of the sample gas inlet, it is also possible to mount a dehumidifier in front of the sample gas inlet as described above. In addition to the zero point correction, it is possible to correct the measured value of the siloxane concentration by the amount of water, and the siloxane concentration can be analyzed more accurately.

In addition, as described above, a configuration in which a dehumidifier that makes the amount of water in biogas constant is mounted in front of the sample gas inlet, a filter filled with an adsorbent that adsorbs siloxane is placed in front of the sample gas inlet. As for the configuration to be mounted, it is preferable to provide an optical filter that allows only infrared rays having a wave number of 1250 cm ^{−1 to} 770 cm ⁻¹ to pass as described above. Even when an optical filter capable of passing infrared rays including infrared rays having a wave number of 1250 cm ^{−1 to} 770 cm ⁻¹ is provided, the concentration of siloxane can be accurately analyzed.

  The non-dispersion type infrared siloxane analyzer of the present invention (hereinafter sometimes simply referred to as “the analyzer of the present invention”) is used in the gas inlet of the adsorption biogas storage device or the adsorption biogas purification device, in the middle of the container. The siloxane concentration can be analyzed in real time by installing at the gas outlet or the like and introducing a part of the gas at the gas inlet, in the middle of the container, or at the gas outlet into the analyzer of the present invention. Therefore, troubles of the gas engine using biogas can be prevented and the time of breakthrough of the siloxane adsorption / removal device can be accurately grasped.

  Here, the adsorption-type biogas storage device uses a storage tank filled with an adsorbent such as activated carbon for biogas to absorb and store the generated biogas and reduce the pressure when using biogas. It is a storage device capable of desorbing and discharging biogas stored by adsorption. When this storage device is used, the siloxane contained in the biogas is adsorbed and removed, so that it is not necessary to separately install a conventional siloxane removal device. By installing the analyzer of the present invention, the siloxane concentration before and after the storage of biogas can be continuously analyzed, and the siloxane removal performance of the storage device can always be grasped.

  In addition, the adsorption-type biogas purification apparatus is contained in biogas by allowing siloxane-containing biogas to pass through a packed bed filled with a porous adsorbent and adsorbing siloxane to the porous adsorbent. This is a purifier capable of obtaining purified gas by removing siloxane. By installing the analysis device of the present invention, the siloxane concentration before and after biogas purification can be continuously analyzed, the performance of the purification device can be always grasped, and the adsorbent filled in the purification device can be appropriately selected. The time for replacement becomes clear.

  The analyzer of the present invention can also be used for analyzing siloxane-containing gas and the like generated in the semiconductor manufacturing process.

  If the analyzer of this invention is used, the siloxane density | concentration in biogas can be continuously analyzed in real time with a sufficient precision.

It is a figure which shows the outline of an example of the non-dispersion type | mold infrared siloxane analyzer of this invention. It is a figure which shows the relationship between the siloxane density | concentration in Example 2, and elapsed time. It is a figure which shows the relationship of the siloxane density | concentration in Example 3 and elapsed time.

  Next, the present invention will be described in more detail with reference to examples.

[Example 1]
A predetermined amount of cyclic octamethylcyclotetrasiloxane (D4) was mixed with a mixed gas of 35% carbon dioxide + methane balance to prepare a standard gas for analysis of each siloxane concentration shown in the left column of Table 1. This standard gas was introduced into the non-dispersed infrared siloxane analyzer shown in FIG. 1 at a flow rate of 500 ml / min, and the siloxane concentration was analyzed. The results are shown in the right column of Table 1. As is clear from Table 1, the concentration of siloxane can be analyzed with high accuracy by using the non-dispersive infrared siloxane analyzer of the present invention.

[Example 2]
The biogas from the sewage treatment plant was mixed with a specific surface area of 1207 m ² / g, an adsorbent of siloxane, a pore volume of 0.541 cm ³ / g, an average pore diameter of 9 mm, and a particle diameter of 0.212 to 4.75 mm (median diameter 1. 15 mm) of activated carbon was passed through, and the gas after siloxane was completely adsorbed and removed was calibrated as a zero point gas for non-dispersive infrared analysis. Thereafter, biogas was introduced into the non-dispersive infrared siloxane analyzer shown in FIG. 1 at a flow rate of 500 ml / min, and the siloxane concentration was continuously analyzed in real time. The result is shown in FIG. For reference, hydrophobic siloxanes and hydrophilic siloxanes in biogas were analyzed by a conventional analysis method consisting of solvent absorption (carbon tetrachloride and alkaline aqueous solution) and GC-MS. As a result, the hydrophobic siloxane was 4.30 ppm and the hydrophilic siloxane was 0 ppm.

  As can be seen from FIG. 2, by using the biogas that has passed through the adsorbent as a zero point gas, it is possible to accurately analyze even the actual biogas.

Example 3
The biogas in a state where water is saturated in a sewage treatment plant is first dehumidified through a dehumidifier so that the dew point is 5 ° C., and the amount of water is made constant. It was introduced into an analyzer and analyzed for siloxane concentration. The results are shown in Example 3-1 in FIG.
Further, a biogas saturated with the same water content was directly introduced into a non-dispersive infrared siloxane analyzer without passing through the dehumidifier, and the concentration of siloxane was analyzed. The results are shown in Example 3-2 in FIG.
For reference, siloxanes in biogas were analyzed by a conventional analysis method consisting of solvent absorption (carbon tetrachloride and alkaline aqueous solution) and GC-MS. As a result, the concentration of organic siloxane was 1.32 ppm.
As is clear from FIG. 3, if the amount of water in the biogas is reduced, interference due to water is removed, and the concentration of siloxane can be analyzed with relatively high accuracy. In addition, since the actual measurement values of Example 3-1 and Example 3-1 are shifted according to the moisture content with respect to the actual siloxane concentration, the actual measurement value of the siloxane concentration is corrected by the moisture content. For example, it is possible to accurately analyze the concentration of siloxane.

Claims (4)

An infrared siloxane analyzer for analyzing the concentration of siloxane in a siloxane-containing biogas, comprising an optical filter that passes only infrared rays having a wave number of 1250 cm ^{-1 to} 770 cm ^-1 , and a filter filled with an adsorbent that adsorbs siloxane A non-dispersive infrared siloxane analyzer, which is mounted in front of a sample gas inlet and is equipped with a dehumidifier for making the amount of water in biogas constant. The non-dispersive infrared siloxane analyzer according to claim 1, wherein infrared rays having a wave number of less than 770 cm ^-1 are absorbed by an optical filter made of BaF ₂ .   The non-dispersive infrared siloxane analyzer according to claim 1 or 2, wherein a gas filter for removing suspended particulates having a filter size of 10 µm or less is mounted in front of the sample gas inlet.   A method for analyzing siloxane, wherein the siloxane concentration in the siloxane-containing biogas is continuously monitored using the non-dispersive infrared siloxane analyzer according to claim 1.

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