JP4332083B2 - Microwave heat treatment analyzer - Google Patents

Description

  The present invention relates to an apparatus for analyzing desorbed material from a sample when a harmful substance is removed from the sample by irradiation with microwaves. The analyzer of the present invention is used for elucidating a mechanism for removing harmful substances from soil by microwave irradiation, for example.

  In recent years, soil contamination by harmful substances such as dioxins has become a social problem, and demands for soil analysis and removal of harmful substances are increasing.

  As a method for purifying soil containing toxic substances, a method has been proposed in which toxic substances contained in the soil are thermally decomposed by high-temperature heating using an incineration facility. However, high-temperature heating of soil using incineration equipment has a large burden on labor and equipment and tends to increase processing costs. Therefore, development of a method for reducing the soil purification cost is required.

  As a method for reducing the purification cost of soil, there is a method of removing harmful substances by mixing a sodium hydroxide aqueous solution having a concentration of 1 to 95% with soil and directly irradiating the mixture with microwaves having a frequency of 300 MHz to 30 GHz. It has been proposed (see Patent Document 1). According to Patent Document 1, polar molecules cause intense molecular vibrations in a very short time due to microwave energy, locally generate a high temperature, and oxidative decomposition removal by alkali occurs. When removing harmful substances using microwaves, it is assumed that the harmful substances are removed by a mechanism different from the removal of harmful substances by simple heating.

However, the mechanism of harmful substance decomposition by microwaves has not been fully elucidated at present, and in order to improve the removal method using microwaves and verify the effectiveness, it is not possible to elucidate the decomposition of harmful substances by microwaves. There is a need to develop analytical instruments that contribute.
JP 2003-47933 A

  An object of the present invention is to provide an analyzer that contributes to the elucidation of the mechanism of desorption of harmful substances during microwave heating.

  As a means for elucidating the mechanism of desorption of harmful substances by microwave heating, a means for observing a product from a sample at a predetermined temperature can be considered. In other words, it is a technique for analyzing the relationship between temperature and the product from the sample and elucidating the mechanism from the result. To elucidate the mechanism by this method, it is required to accurately control the temperature of the sample.

  However, there is a problem with accurately controlling the temperature of the sample. In order to remove harmful substances contained in the soil, the soil must be heated to a high temperature of several hundred degrees Celsius or higher. When the soil is heated using microwaves, the temperature of the soil rises due to microwave absorption by components in the soil. However, if the amount of the sample is too small, the calorific value is insufficient and the temperature of the sample is not sufficiently raised. On the other hand, if the amount of the sample is large, the calorific value is increased, but a temperature distribution is generated inside the sample, and it is difficult to accurately control the temperature of the sample. In addition, if the amount of the sample is large, the analyzer is increased in size, and the problem of the apparatus manufacturing cost and installation area is also caused.

  In the analyzer of the present invention, a heating element that absorbs microwaves and generates heat efficiently is disposed around the sample. For this reason, even when a small amount of sample is used, the sample temperature can be increased efficiently, and the temperature distribution generated in the sample can be reduced. The analyzer of the present invention having these effects contributes to the elucidation of the harmful substance desorption mechanism using microwaves.

  Specifically, preferred embodiments of the present invention are as follows.

(1) a sample holder made of CaO · _6Al 2 _{O 3} solid material, and irradiating a microwave to the sample holder, and the microwave irradiation device for heating the CaO · _6Al 2 _{O 3} solid material in the sample holder A temperature measuring device for measuring the temperature of the sample placed, and a component of gas generated from the sample when the sample placed on the sample holder is heated by irradiating the sample holder with microwaves to generate heat A gas analyzer for analyzing the gas .

(2) The analysis apparatus according to (1), further including a hot air supply device that supplies hot air to a pipe that conveys a gas generated from a sample disposed in the sample holder to the gas analysis apparatus.

  (3) The analysis apparatus according to (1) or (2), wherein the sample to be analyzed is soil.

  If the analyzer of the present invention is used, it is easy to control the sample to a desired temperature, and the analyzer of the present invention greatly contributes to elucidation of the harmful substance desorption mechanism during microwave heating.

The inventors of the present invention have examined heating using a microwave and found that a bulk solidified body having a composition of CaO.6Al ₂ O ₃ is effective as a microwave susceptor. Based on this finding, the present invention has been completed. Hereinafter, the present invention will be described in detail.

First, the outline | summary of the analyzer of this invention is demonstrated using drawing. FIG. 1 is a schematic cross-sectional view showing an embodiment of the analyzer of the present invention. The sample to be analyzed is placed in the sample holder 10. The composition of the solidified body constituting the sample holder 10 is CaO.6Al ₂ O ₃ , and in the upstream and downstream directions of the sample holder 10, a lid 12 having a hole for allowing gas to pass through the sample holder 10. Is arranged. The “upstream direction” and the “downstream direction” are upstream and downstream with respect to the flow of gas flowing through the sample holder. An analyzer described later is arranged in the downstream direction.

  The sample holder 10 is irradiated with a desired microwave from the microwave irradiation device 20. The sample is heated, the compound is desorbed from the sample, and the sample holder is heated by the microwave from the microwave irradiation device 20. The temperature of the sample placed in the sample holder is measured by the temperature measuring device 30. The gas flowing through the sample holder 10 is supplied to the sample holder 10 through the tube 40, and the gas flowing through the sample holder 10 is transported to the analyzer 50 through the tube 42. A gas collector 46 may be installed for analysis in the analyzer 50. In the analyzer 50, components derived from the sample that are mixed in the circulating gas are analyzed. It is preferable to take care so that other components are not mixed in the supply of the gas to the tube 40 and the discharge of the gas from the tube 42. For example, plugs 45 having gas tubes are arranged at the entrances and exits of the tubes 40 and 42.

  Other devices may be arranged in the analyzer as necessary. For example, a hot air supply device 60 for preventing condensation in the pipe 42 is disposed. Although the periphery of the sample holder 10 is heated to a high temperature by microwave irradiation, the temperature decreases as the distance from the sample holder 10 increases, and there is a possibility that condensation occurs inside the tube 42. When dew condensation occurs, the components flowing through the tube are dissolved, which may hinder accurate analysis. The hot air supply device 60 serves to prevent this problem. The tube 42 is heated by the hot air supplied from the hot air supply device 60 to prevent condensation. As shown in the figure, when the sample holder 10 is covered with the applicator 70, a discharge port 80 for discharging hot air may be formed in a part of the applicator 70. If there is a possibility that condensation in the vicinity of the plug 45 cannot be prevented with only hot air from the hot air supply device 60, a heater 90 such as a ribbon heater may be disposed on the tube.

In the analyzer of the present invention, a sample holder made of CaO.6Al ₂ O ₃ is used. Since CaO · 6Al ₂ O ₃ has high heating efficiency by microwaves, it is possible to effectively raise the temperature of the sample placed inside the sample holder, and the temperature of the sample placed inside the sample holder The distribution can be reduced. In addition, the temperature of the sample placed in the sample holder can be controlled to a desired temperature by controlling the microwave irradiation output. By using the analyzer of the present invention having these effects, it is possible to precisely analyze the components released from the sample during microwave heating.

  In the above description, the analysis apparatus of the present invention has been described with reference to FIG. 1, but the analysis apparatus of the present invention is not limited to the embodiment shown in FIG. Can be included in the technical scope.

  Then, the structure of the analyzer of this invention is demonstrated in detail for every member.

The sample holder 10 is made of a CaO.6Al ₂ O ₃ solidified body. The manufacturing method of CaO.6Al ₂ O ₃ is not particularly limited. CaO.6Al ₂ O ₃ can be produced, for example, by mixing CaO and alumina in a molar ratio of about 1: 6 and firing at 1500 ° C. or higher using a rotary kiln or the like. CaO.6Al ₂ O ₃ may be produced by electromelting a powder having a composition corresponding to CaO.6Al ₂ O ₃ . Commercially available CaO.6Al ₂ O ₃ may be used.

The solidified body means a bulk heating element made of CaO.6Al ₂ O ₃ . In view of ease of production and the like, the solidified body is preferably a sintered body. However, as long as a solidification method other than sintering is applicable, a method other than sintering may be used. For example, a method of mixing and solidifying CaO.6Al ₂ O ₃ powder and alumina cement may be used.

The solidifying method is not particularly limited. For example, when sintering CaO.6Al ₂ O ₃ , the sintering apparatus and the sintering time may be determined according to factors such as the type of material and the size of the solidified body.

  The shape of the solidified body is not particularly limited. The shape of the solidified body may be determined according to the arrangement form of the sample holder. When the embodiment as shown in FIG. 1 is adopted, the shape of the solidified body may be determined according to the shapes of the tube 40 and the tube 42. When the sample holder is manufactured by combining a plurality of solidified bodies, the solidified body may have a partial shape of the sample holder. For example, when the sample holder shown in FIG. 1 is manufactured by combining a plurality of solidified bodies, a cylindrical solidified body corresponding to the portion where the sample is arranged and a hole for gas to flow in the center are formed. What is necessary is just to prepare these 2 solidified bodies and to combine these.

  The size of the solidified body is not particularly limited. The size of the solidified body may be determined according to the amount of the sample to be measured. In consideration of downsizing of the analyzer, it is preferable that the sample holder is small. However, if there are too few samples to be analyzed, the measurement error tends to increase. For example, when analyzing the removal of harmful substances contained in soil, it is preferable that 20 g of soil has a size that allows placement. The thickness of the solidified body is not particularly limited, but if the solidified body is too thin, the amount of heat generation is reduced, which may make it difficult to raise the temperature of the sample. The thickness of the solidified body is generally about 10 to 25 mm.

In some cases, the sample holder may be combined with a material other than CaO.6Al ₂ O ₃ . For example, a heat insulating material that transmits microwaves may be disposed around a sample holder made of CaO.6Al ₂ O ₃ .

  The microwave irradiation device 20 is not particularly limited as long as it can irradiate the periphery of the sample holder with microwaves. For example, various frequencies such as a microwave having a frequency of 0.915 GHz using a magnetron as an oscillation tube, a microwave having a frequency of 2.45 GHz employed in a microwave oven, a microwave of 28 GHz using a gyratorron as an oscillation tube, etc. Of microwaves can be used. A microwave optical waveguide that guides the microwave to a desired site may be used.

  The temperature measuring device 30 is used to measure the temperature of a sample and analyze a compound released from the sample at a predetermined temperature. As long as the temperature of the sample can be measured, the specific mode of the temperature measuring device is not particularly limited. For example, a thermocouple may be arranged on the sample as shown in FIG. 1, or the temperature distribution in the sample holder may be observed by analyzing the heat distribution of the sample holder by image processing if possible.

  The tube 40 and the tube 42 are preferably formed from a heat-resistant material that does not deteriorate even when the sample holder 10 reaches a high temperature. An example of the constituent material of the tube is quartz glass.

  The tube is supplied with a gas for transporting the gas generated from the sample to the analyzer, and the gas is preferably an inert gas such as nitrogen gas. When supplying the gas to the pipe, it is preferable to take measures to prevent mixing of other components. For example, silicon stoppers equipped with inert gas introduction tubes are arranged at both ends of the tube. In order to analyze the generated gas, for example, a gas collector 46 that traps the gas in water is installed, and the gas collected by the gas collector is analyzed by gas chromatography or mass spectrometry (GC-MS). Analyze with device 50. The analyzer is not particularly limited as long as the generated component can be analyzed. Various commercially available analyzers may be used, and improvements suitable for the present invention may be applied.

  As described above, depending on the conditions, condensation may occur on the inside of the tube 42, which may cause a problem of reducing the analysis accuracy. As a means for solving this problem, there is a hot air supply device 60 that supplies hot air to a tube that conveys a gas generated from a sample placed in the sample holder 10 to the analyzer 50. The temperature of the hot air may be controlled according to the measurement temperature of the sample and the output of the microwave. When analyzing soil remediation using microwaves, the temperature of the hot air is usually controlled to about 100 to 300 ° C. As a system for producing high-temperature hot air, an electric hot air generator may be mentioned. However, the present invention is not limited to such a system. When a high-temperature process such as an incinerator or a heating furnace exists around the analyzer, the medium gas of hot air may be heated using these heats.

  The material of the applicator that is a constituent material of the analyzer is not particularly limited, but is preferably a material that is unlikely to deteriorate such as rust such as stainless steel.

  When a heater 90 such as a ribbon heater is installed, the temperature of the heater 90 may be controlled to about 120 to 150 ° C.

  An analysis of soil contaminated with dioxin components and dibenzofuran components was attempted using the analyzer shown in FIG. The configuration of the analyzer used is as follows.

6 parts by mass of alumina cement and 8 parts by mass of water were added to 100 parts by mass of the CaO.6Al ₂ O ₃ powder, and poured into a 230 mm × 40 mm × 114 mm mold. After curing for 24 hours, the compact was removed from the mold and fired at 1400 ° C. for 4 hours in an electric furnace. The obtained CaO.6Al ₂ O ₃ solidified body was wet processed into a cylindrical shape having an inner diameter of 20 mm, an outer diameter of 40 mm, and a length of 40 mm, and then dried to 150 ° C. to obtain a sample holder.

  After filling the sample holder with sample soil, on both sides of the sample holder, a lid having a hole with an inner diameter of 5 mm, an outer diameter of 40 mm and a thickness of 10 mm was arranged.

  The sample holder on which the soil is arranged is connected to a quartz glass tube (inner diameter 42 mm), and a silicon gas introducing polytetrafluoroethylene tube for introducing nitrogen gas is arranged at the upstream end and the downstream end of the quartz glass. The stopper was filled to prevent gas contamination. The sample temperature inside the sample holder was measured by placing a K thermocouple in the center of the soil.

Nitrogen gas (N ₂ ) was allowed to flow at a flow rate of 2 liters / min from a polytetrafluoroethylene tube disposed in the upstream silicon plug. The temperature of the ribbon heater was set to 150 ° C., and hot air at 300 ° C. was supplied to the analyzer at a flow rate of 1.48 m ³ / min using an electric hot air generator. As a microwave irradiation apparatus, in order to irradiate a microwave of 2.45 GHz, the microwave was irradiated to the applicator using a WRJ-2 type stainless steel waveguide.

  FIG. 2 shows the relationship between temperature change, microwave output, and sample temperature due to heating using microwaves. As shown in FIG. 2, the temperature of the sample could be gradually increased from room temperature to 510.degree. That is, by using the analyzer of the present invention, it is possible to accurately analyze the relationship between the temperature of the sample and the product from a low temperature to a high temperature. This effect is very useful in elucidating the mechanism of various reactions and achieving further improvements and improvements. For the purpose of investigating the temperature distribution inside the sample, thermocouples were installed at both ends and the center of the soil sample under the same conditions. When the temperature at the center was 510 ° C, the temperature at the upstream was 503 ° C, The downstream temperature was 506 ° C. Thus, in the analyzer of the present invention, the temperature distribution in the sample is small.

  For reference, Table 1 shows the contents of the dioxin component and dibenzofuran component contained in the soil before heating, and the contents of the dioxin component and dibenzofuran component contained in the soil after heating at 510 ° C. . It turns out that the harmful substance contained in soil is removed by heat-processing at 510 degreeC using a microwave. In addition, Shimadzu Corporation GCMS-QP2010 was used for the analyzer.

  The analyzer of the present invention contributes to elucidation of the mechanism during microwave heating. In addition, the analytical apparatus of the present invention can be applied to determine the optimum conditions for purifying soil by microwave heating.

It is a cross-sectional schematic diagram which shows one Embodiment of the analyzer of this invention. It is a graph which shows the relationship between the temperature change by a heating using a microwave, a microwave output, and sample temperature.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Sample holder, 12 ... Open lid, 20 ... Microwave irradiation apparatus, 30 ... Temperature measuring instrument, 40 ... Tube, 42 ... Pipe, 45 ... Plug, 46 ... Gas collector, 50 ... Analytical device, 60 ... Hot air supply device, 70 ... Applicator, 80 ... Discharge port, 90 ... Heater.

Claims (3)

A sample holder made of a solidified CaO.6Al ₂ O ₃ ;
The microwave irradiation device that irradiates the sample holder with microwaves and generates heat from the CaO.6Al ₂ O ₃ solidified body
A temperature measuring device for measuring the temperature of the sample placed in the sample holder;
A gas analyzer for analyzing a component of a gas generated from the sample when the sample placed in the sample holder is heated by irradiating the sample holder with microwaves to generate heat ;
Analytical apparatus having The analyzer according to claim 1, further comprising a hot air supply device that supplies hot air to a pipe that conveys a gas generated from a sample disposed in the sample holder to the gas analyzer.   The analysis apparatus according to claim 1, wherein the sample to be analyzed is soil.

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