Method for estimating asbestos melting conditions

Abstract

In a first step (S101), a simulated sample is prepared by mixing a simulated substance for simulating asbestos and a base material of a building material in which asbestos is used. In a second step (S102), the prepared simulated sample is applied to a predetermined substrate and dried. In a third step (S103), the simulated sample prepared as described above is subjected to X-ray diffraction analysis to confirm the peaks in the structure of the simulated substance contained in the simulated sample that has been applied to the substrate and dried. In a fourth step (S104), laser irradiation conditions under which heating of the simulated sample by laser irradiation causes the simulated substance to melt are confirmed by the disappearance of the simulated sample peaks obtained by X-ray diffraction analysis.

Description

Method for estimating asbestos melting conditions

[0001] The present invention relates to a method for estimating asbestos melting conditions.

[0002] As asbestos has excellent insulating properties and chemical resistance, asbestos-containing building materials mixed into paints and spray-on materials have been used in many buildings, but it has been pointed out that the fibrous form of asbestos poses a risk of lung cancer, and its manufacture and use have been banned in Japan. Meanwhile, as buildings that use asbestos-containing building materials age, the number of demolition works for these buildings is increasing, and as a result, the number of works to remove asbestos-containing building materials is also increasing.

[0003] Generally, asbestos-containing building materials are removed using power tools, hand tools, or high-pressure water cleaning. Although the removed asbestos-containing building materials can be reused through heat treatment, there are few facilities capable of heat treatment, and most of the asbestos is disposed of by landfill. This necessitates the construction of more disposal sites, and even if disposed of by landfill, the fibrous form is retained, so the harmful properties do not disappear.

[0004] To solve the above problems, technologies have been developed to melt asbestos-containing building materials at building demolition sites to eliminate the fibrous structure, such as a technology that uses laser light to eliminate the fibrous structure in asbestos-containing building materials (Patent Document 1).

[0005] JP 2009-028717 A

[0006] As asbestos-containing building materials are used in a wide variety of forms, so in order to efficiently melt asbestos using a laser, it is desirable to identify through experiments the laser light conditions that are suitable for each building material, such as the wavelength and power of the laser light source. However, collecting asbestos-containing samples is time-consuming, and the number that can be collected is limited, making it difficult to carry out the above-mentioned experiments. Thus, in the past, there was a problem in that it was not easy to identify the laser light conditions that are suitable for asbestos-containing building materials to melt the asbestos.

[0007] The present invention has been made to solve the above problems, and aims to make it possible to easily identify the laser light conditions suitable for asbestos-containing building materials that melt asbestos.

[0008] The method for estimating asbestos melting conditions of the present invention comprises a first step of preparing a simulated sample by mixing a simulated substance for simulating asbestos with a melting point higher than that of asbestos and the base material of a building material in which asbestos is used; a second step of applying the simulated sample to a substrate and drying it; a third step of confirming, by X-ray diffraction analysis, the peaks of the structure of the simulated substance contained in the simulated sample that has been applied to the substrate and dried; and a fourth step of confirming, by the disappearance of the peaks in the simulated sample by X-ray diffraction analysis, the irradiation conditions under which the simulated substance melts when heated by laser irradiation of the simulated sample.

[0009] As explained above, according to the present invention, a simulated sample is used that is a mixture of a simulated substance for simulating asbestos and the base material of a building material in which asbestos is used, so that the conditions of laser light suitable for melting asbestos in asbestos-containing building materials can be easily identified.

[0010] FIG. 1 is a flowchart illustrating a method for estimating asbestos melting conditions according to an embodiment of the present invention. FIG. 2 is a configuration diagram showing an example of the configuration of a laser irradiation device for implementing the method for estimating asbestos melting conditions. FIG. 3 is a characteristics diagram showing the results of X-ray diffraction analysis before laser light irradiation (solid line) and the results of X-ray diffraction analysis after laser light irradiation (dotted line). FIG. 4 is a characteristics diagram plotting laser light irradiation conditions and quartz melting. FIG. 5 is a characteristics diagram showing the results of predicting laser light irradiation conditions under which chrysotile melts. FIG. 6 is a characteristics diagram plotting laser light irradiation conditions and iron melting. FIG. 7 is a characteristics diagram showing the results of predicting laser light irradiation conditions under which chrysotile melts.

[0011] Hereinafter, a method for estimating asbestos melting conditions according to an embodiment of the present invention will be described with reference to FIG.

[0012] First, in the first step S101, a simulated sample is prepared by mixing a simulated material for simulating asbestos with the base material of the building material in which asbestos is used. The simulated material has a higher melting point than asbestos. For example, the simulated material can be quartz or iron.

[0013] Next, in a second step S102, the prepared simulated sample is applied to a predetermined substrate and dried. The substrate can be made of, for example, concrete.

[0014] Next, in the third step S103, X-ray diffraction analysis is performed on the simulated sample prepared as described above to confirm the peaks of the structure of the simulated material contained in the simulated sample that has been applied to the substrate and dried. For example, if the simulated material is quartz, the X-ray diffraction analysis can confirm peaks indicating the crystalline structure of SiO. Furthermore, for example, if the simulated material is iron, the X-ray diffraction analysis can confirm peaks indicating the crystalline structure of Fe.

[0015] Next, in a fourth step S104, the laser irradiation conditions under which the simulated material melts when heated by laser irradiation are confirmed by X-ray diffraction analysis to determine whether the peak disappears in the simulated sample. For example, the laser is irradiated by changing irradiation conditions such as the power of the irradiated laser light and the scanning speed of the irradiated laser light. The laser is irradiated under each condition, and the irradiation conditions under which the peak disappears in the simulated sample as determined by X-ray diffraction analysis are confirmed (identified).

[0016] As described above, the irradiation conditions under which the simulated material melts, for which the disappearance of peaks in the simulated sample is confirmed by X-ray diffraction analysis, can be estimated as the melting conditions for asbestos in the building material being estimated (step 5).

[0017] The following will explain in more detail using examples.

[0018] Example 1 First, Example 1 will be described. In Example 1, the simulated material is quartz. The melting point of quartz (SiO2) is approximately 1600°C. On the other hand, the melting point of chrysotile, which is said to be the most widely used type of asbestos, is 1500°C. Therefore, if quartz in a simulated sample prepared using quartz as a simulated material melts when irradiated with laser light, it is thought that this suggests that chrysotile will also melt if a surface preparation material containing chrysotile is irradiated with laser light under the same irradiation conditions.

[0019] (Preparation of mock samples) First, the preparation of mock samples will be described. In Example 1, mock samples of a building material called a surface preparation material, which is one of the asbestos-containing building materials, are prepared. Surface preparation materials are building materials (plaster materials) used to smooth the surface of concrete walls before applying wallpaper to them, and are often made by mixing asbestos with cement.

[0020] Powdered quartz was weighed out so that the quartz concentration was approximately 1% by weight, added to the cement material, and mixed for 7 hours using a ball mill to prepare a simulated sample. A concrete piece was used as a substrate, and the simulated sample was applied to its surface. The simulated sample was applied so that the coating thickness of the coating film as a surface conditioner was 1 mm. A wooden frame with a depth of 1 mm was placed on the concrete piece, and the simulated sample was poured into the frame and then spread evenly with a spatula to form a coating film. In this way, a coating film of the simulated sample was formed on the surface of the concrete piece, and then dried.

[0021] (Laser Irradiation Experiment) Using the dried coating film of the above-mentioned simulated sample, the irradiation conditions of laser light that melts the quartz in the simulated sample were investigated.

[0022] As shown in Figure 2(a), the laser irradiation device used emitted laser light from a light source 101 that emitted continuous wave laser light with a wavelength of 1070 nm. The emitted laser light was guided through an optical fiber 102 and introduced into a fiber collimator 103. The laser light was converted into a parallel beam 104 with a beam diameter of 5.0 mm by the fiber collimator 103, and then transmitted through a convex lens 105 to become a condensed beam 106 with a spot diameter of 60 µm, which was then irradiated onto a coating film 107 of the simulated sample.

[0023] The concrete piece coated with the simulated sample was placed on an automatic moving stage (not shown), and the focused light was moved (scanned) and irradiated along the arrow line shown in Figure 2(b) by moving the automatic moving stage.

[0024] Figure 3 shows the results of X-ray diffraction analysis before laser irradiation (solid line) and after laser irradiation (dotted line). Before laser irradiation, peaks indicating the crystalline structure of quartz (SiO2), which is used as an asbestos simulant, can be confirmed. By appropriately selecting the laser irradiation conditions, it is possible to eliminate the X-ray diffraction peaks indicating the crystalline structure of quartz, as shown by the dotted line in Figure 2. The disappearance of the peaks indicates that the quartz has melted and lost its crystalline structure.

[0025] Figure 4 plots the laser light irradiation conditions used in the experiment and the melting of quartz. The horizontal axis represents the laser light power, and the vertical axis represents the laser light spot movement (scanning) speed. In Figure 4, the black circles represent cases where there is a quartz peak in X-ray diffraction analysis, and the white circles represent cases where there is no quartz peak in X-ray diffraction analysis. The same applies to Figures 5, 6, and 7 shown below. Figure 5 shows the results of projecting the laser light irradiation conditions (spot movement speed) under which chrysotile melts when the laser light power is increased, based on the results of Figure 4. The area indicated by the dotted line in Figure 4 represents the predicted irradiation conditions under which chrysotile melts.

[0026] Since quartz melted at power p1 and spot movement speed v1, it was predicted that chrysotile would also melt under the same conditions. Similarly, since quartz did not melt at p1 and v2, it was predicted that chrysotile would not melt either. Furthermore, if the laser light power was increased to p2, chrysotile would melt even at v2, but it was predicted that chrysotile would not melt at the combination of p2 and v3.

[0027] (Confirmation Experiment) An experiment was conducted to confirm the melting of chrysotile using the combination of irradiation conditions described above. Surface preparation materials containing chrysotile were collected from a building demolition site and used as samples. The combinations of laser light power and spot movement speed were p1-v1, p1-v2, p2-v2, and p2-v3. After irradiating the surface preparation materials with laser light under each irradiation condition, X-ray diffraction analysis and electron microscope observation were used to confirm whether chrysotile had melted. The results are shown in Table 1 below. As shown in Table 1, the melting of chrysotile was confirmed, as predicted in Figure 5.

[0028]

[0029] From the results of Example 1 described above, it was possible to efficiently estimate the irradiation conditions of laser light that melt chrysotile by using the simulated sample according to the embodiment.

[0030] Example 2 Next, Example 2 will be described. In Example 2, the simulated substance is iron. The melting point of iron (Fe) is approximately 1500°C. On the other hand, the melting point of chrysotile, which is said to be the most widely used type of asbestos, is also 1500°C. Therefore, if the iron in a simulated sample prepared using iron as a simulated substance melts when irradiated with laser light, it is thought that this suggests that chrysotile will also melt if a surface preparation material containing chrysotile is irradiated with laser light under the same irradiation conditions.

[0031] (Preparation of mock samples) First, the preparation of mock samples will be described. In Example 2, mock samples of a building material called a surface preparation material, which is one of the asbestos-containing building materials, are prepared. Surface preparation materials are building materials (plaster materials) used to smooth the surface of concrete walls before applying wallpaper to them, and are often made by mixing asbestos with cement.

[0032] Powdered iron was weighed out so that the iron concentration by weight was approximately 1%, and added to the cement material. The mixture was then mixed using a ball mill for 7 hours to prepare a simulated sample. A concrete piece was used as a substrate, and the simulated sample was applied to its surface. The simulated sample was applied so that the coating thickness of the coating was 1 mm as a surface conditioner. A wooden frame with a depth of 1 mm was placed on the concrete piece, and the simulated sample was poured into the frame and then evenly spread with a spatula to form a coating film. In this way, a coating film of the simulated sample was formed on the surface of the concrete piece, and then dried.

[0033] (Laser Irradiation Experiment) Using the dried coating film of the above-described simulated sample, the irradiation conditions of laser light that melt the iron in the simulated sample were investigated.

[0034] As shown in Figure 2(a), the laser irradiation device used emitted laser light from a light source 101 that emitted continuous wave laser light with a wavelength of 1070 nm. The emitted laser light was guided through an optical fiber 102 and introduced into a fiber collimator 103. The laser light was converted into a parallel beam 104 with a beam diameter of 5.0 mm by the fiber collimator 103, and then transmitted through a convex lens 105 to become a condensed beam 106 with a spot diameter of 60 µm, which was then irradiated onto a coating film 107 of the simulated sample.

[0035] The concrete piece coated with the simulated sample was placed on an automatic moving stage (not shown), and the focused light was moved (scanned) and irradiated along the arrow line shown in Figure 2(b) by moving the automatic moving stage.

[0036] As a result of X-ray diffraction analysis before irradiation with laser light, peaks indicating the crystalline structure of iron (Fe), which is used as an asbestos simulant, were confirmed. As in Example 1 described above, by appropriately selecting the irradiation conditions of the laser light, it is possible to eliminate the X-ray diffraction peaks indicating the crystalline structure of iron. The disappearance of the peaks indicates that the iron has melted and lost its crystalline structure.

[0037] Figure 6 plots the laser beam irradiation conditions used in the experiment and the melting of iron. The horizontal axis represents the laser beam power, and the vertical axis represents the laser beam spot movement (scanning) speed. Figure 7 shows the results of projecting the laser beam irradiation conditions (spot movement speed) under which chrysotile melts when the laser beam power is increased, based on the results of Figure 6. The area indicated by the dotted line in Figure 7 represents the predicted irradiation conditions under which chrysotile melts.

[0038] Since iron melted at power p1' and spot movement speed v1', it was predicted that chrysotile would also melt under the same conditions. Similarly, since iron did not melt at p1' and v2', it was predicted that chrysotile would not melt either. Furthermore, it was predicted that if the laser light power was increased to p2', chrysotile would melt even at v2', but would not melt with the combination of p2' and v3'.

[0039] (Confirmation Experiment) An experiment was conducted to confirm the melting of chrysotile using the combination of irradiation conditions described above. Surface preparation materials containing chrysotile were collected from a building demolition site and used as samples. The combinations of laser light power and spot movement speed were p1'-v1', p1'-v2', p2'-v2', and p2'-v3'. After irradiating the surface preparation materials with laser light under each irradiation condition, X-ray diffraction analysis and electron microscope observation were used to confirm whether chrysotile had melted. The results are shown in Table 2 below. As shown in Table 2, the melting of chrysotile was confirmed, as predicted in Figure 7.

[0040]

[0041] From the results of Example 2 described above, it was possible to efficiently estimate the irradiation conditions of laser light that melt chrysotile by using the simulated sample according to the embodiment.

[0042] As described above, according to the embodiment of the present invention, a simulated sample is used that is a mixture of a simulated substance for simulating asbestos and the base material of a building material in which asbestos is used, making it possible to easily identify the conditions of laser light that are suitable for asbestos-containing building materials to melt the asbestos.

[0043] Asbestos-containing building materials are used in a wide variety of forms, so in order to efficiently melt asbestos using a laser, it is desirable to identify through experiments the laser light conditions suitable for each building material, such as the wavelength and power of the laser light source. However, collecting asbestos-containing samples is time-consuming, and the number that can be collected is limited. According to an embodiment of the present invention, in order to efficiently conduct such experiments, the laser light conditions that melt asbestos are estimated from the results of experiments using samples that closely simulate asbestos-containing building materials, and then these are confirmed in experiments using actual samples that contain asbestos, which is convenient.

[0044] It should be noted that the present invention is not limited to the embodiments described above, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention.

[0045] 101...light source, 102...optical fiber, 103...fiber collimator, 104...parallel light beam, 105...convex lens, 106...condensed light, 107...coating film.

Claims

1. A method for estimating asbestos melting conditions, comprising: a first step of preparing a simulated sample by mixing a simulated substance for simulating asbestos, which has a melting point higher than that of asbestos, with the base material of a building material in which the asbestos is used; a second step of applying the simulated sample to a substrate and drying it; a third step of confirming, by X-ray diffraction analysis, the peak of the structure of the simulated substance contained in the simulated sample that has been applied to the substrate and dried; and a fourth step of confirming, by X-ray diffraction analysis, the irradiation conditions under which the simulated substance melts when heated by laser irradiation of the simulated sample, based on the disappearance of the peak in the simulated sample.

2. A method for estimating asbestos melting conditions as described in claim 1, further comprising a fifth step of estimating the irradiation conditions under which the simulated substance melts, confirmed by the disappearance of the peak in the simulated sample by X-ray diffraction analysis, as the melting conditions of the asbestos in the building material.

3. A method for estimating asbestos melting conditions according to claim 1 or 2, wherein the simulated material is quartz or iron.

Images