Treatment method

Abstract

According to the present invention, in a first step S101, a treatment region to be treated is divided into a plurality of divided regions. Next, in a second step S102, in the divided region, a laser beam is scanned and irradiated such that the entirety of the divided region is irradiated with the laser beam. For example, a spot beam of the laser beam focused to a desired beam diameter is raster-scanned and irradiated on a plane of the target divided region.

Description

Processing method

[0001] The present invention relates to a method for treating asbestos by thermal decomposition, melting, or evaporation.

[0002] Asbestos possesses excellent thermal insulation and chemical resistance, and asbestos-containing building materials, such as coatings and spray coatings, have been used in many buildings. However, it has been pointed out that the fibrous structure of asbestos poses a risk of lung cancer, and its manufacture and use are now prohibited in Japan. On the other hand, the aging of buildings that used asbestos-containing building materials has led to an increase in demolition work, and consequently, an increase in the removal of asbestos-containing building materials. Generally, asbestos-containing building materials are removed using power tools, hand tools, or high-pressure water, but these removal methods do not render the asbestos harmless.

[0003] To solve these problems, a method has been proposed that uses laser light to melt asbestos in asbestos-containing building materials, causing the fibrous structure to disappear, and also to instantly evaporate the asbestos in the building materials (Patent Document 1). This technology suggests the possibility of removing asbestos from asbestos-containing building materials using laser light and rendering the asbestos harmless by melting it.

[0004] Japanese Patent Publication No. 2009-028717

[0005] In the aforementioned technology, for example, asbestos is heated to its melting point to melt it. Therefore, to shorten the working time, it is necessary to increase the energy of the laser beam applied to the asbestos per unit time, i.e., the power. However, generally speaking, increasing the power of the laser beam leads to an increase in the price of the laser light source.

[0006] This invention was made to solve the above-mentioned problems, and aims to shorten the laser irradiation time in the treatment of asbestos or asbestos-containing materials using a laser, without relying on increasing the power of the laser beam.

[0007] The processing method according to the present invention is a method for thermally decomposing, melting, or evaporating asbestos or an asbestos-containing substance by scanning and irradiating it with laser light, and comprises a first step of dividing the processing area to be processed into a plurality of divided areas, and a second step of scanning and irradiating each of the plurality of divided areas with laser light so that the laser light irradiates the entire divided area.

[0008] As described above, according to the present invention, the processing area to be processed is divided into a plurality of divided areas, and laser light is scanned and irradiated in each of the divided areas. Therefore, in the processing of asbestos or asbestos-containing materials using a laser, the irradiation time of the laser light can be shortened without relying on increasing the power of the laser light.

[0009] Figure 1 is a flowchart illustrating the processing method according to the embodiment. Figure 2 is an explanatory diagram illustrating the scanning of laser light. Figure 3 is an explanatory diagram illustrating the principle of the effect of the embodiment. Figure 4 is an explanatory diagram illustrating the principle of the effect of the embodiment. Figure 5 is an explanatory diagram illustrating the effect of dividing the processing area of ​​the target to be processed into multiple divided areas. Figure 6 is an explanatory diagram illustrating the effect of dividing the processing area of ​​the target to be processed into multiple divided areas. Figure 7 is an explanatory diagram illustrating the effect of dividing the processing area of ​​the target to be processed into multiple divided areas. Figure 8 is an explanatory diagram showing a state in which processing is performed continuously for each adjacent divided area. Figure 9 is an explanatory diagram showing a state in which processing is performed continuously for each non-adjacent divided area.

[0010] The following describes a processing method according to an embodiment of the present invention with reference to Figure 1. This method involves scanning and irradiating asbestos or an asbestos-containing substance with laser light to thermally decompose, melt, or evaporate the asbestos.

[0011] First, in the first step S101, the processing area to be processed is divided into multiple sub-regions. For example, the processing area to be processed can be divided equally into multiple sub-regions. Alternatively, the processing area to be processed can be divided into multiple sub-regions with different areas. Next, in the second step S102, the laser beam is scanned and irradiated in the sub-regions so that the laser beam irradiates all of the sub-regions. For example, as shown in Figure 2, a spot beam 121 of laser light focused to a desired beam diameter is irradiated by raster scanning on the plane of the target sub-region 101.

[0012] For example, the system that performs the irradiation process described above includes a laser light source, a collimator that collimates the laser light emitted from the light source, a polygon mirror, a galvanometer mirror, and a MEMS (Micro Electro Mechanical Systems) for scanning the light in two dimensions, as well as a lens for focusing the laser light. The wavelength of the laser light can be 1.07 μm, the spot diameter 50 μm, the power 400 W, and the scanning speed 10 m / sec. As shown in Figure 2, the scanning distance in the x direction is approximately the same as the length of one side of the divided region 101, and for example, 20 μm is scanned in the negative y-axis direction.

[0013] Next, in the third step S103, it is determined whether or not irradiation processing has been performed on all divided regions. If there are still divided regions that have not been processed (no in step S103), the process moves to the next divided region to be processed in step S104. On the other hand, once the irradiation processing of all divided regions is completed (yes in step S103), the process ends. For example, if the processing region to be processed is divided into n parts, the process for each divided region is repeated n times before the process ends.

[0014] Here, the laser beam irradiation process by scanning (second step) can be performed consecutively for each non-adjacent divided region. For example, in the region movement of step S104, the system moves to an unprocessed divided region that is not adjacent to the previously processed divided region.

[0015] Next, the principle will be explained using Figures 3 and 4. The starting position for scanning the laser beam is defined as the origin O (scanning start position). The temperature of any measurement point 102 on the scanning path is measured. As the temperature is measured at measurement point 102, the temperature begins to rise as the laser beam is scanned and approaches measurement point 102, reaching a maximum value after a certain time τ seconds after passing measurement point 102, and thereafter the temperature decreases with a decay coefficient α.

[0016] When the laser beam is scanned again from the scanning start position O and passes through the measurement point 102, the temperature rises again, and then similarly, the temperature falls again. Since the laser beam passes through the measurement point 102 again after the scanning period of t1 seconds from the first time, the temperature reaches a maximum value τ seconds after the laser beam passes through the measurement point 102, just as in the first time, and then the temperature decreases with a decay coefficient α. By repeating this temperature change, the temperature rises as the number of scans increases, and the device is heated to the target temperature.

[0017] Here, using the following approximation, we obtain the maximum temperature T of the measurement point 102 at the nth scan. n It is expressed by the following equation. The temperature change when approximated is shown by the thick line in Figure 4.

[0018] (1) The temperature reaches a maximum value at the time the laser passes through measurement point 102, i.e., τ = 0 seconds. (2) The temperature rise at measurement point 102 occurs only when the laser beam passes through measurement point 102. (3) The temperature attenuation coefficient α is constant regardless of the area scanned by the laser beam, the number of scans, the scan period, and the temperature. (4) The temperature rise ΔT when the laser beam passes through measurement point 102 is constant regardless of the area scanned, the number of scans, the scan period, and the temperature.

[0019]

[0020] T n : The maximum temperature value of A reached after the nth scan. R : Room temperature. ΔT: Temperature rise as the laser beam is scanned and passes through measurement point 102. α: Temperature decay coefficient. t1: Scanning period (time from when the laser beam passes through measurement point 102 until it returns).

[0021] Next, the effects of dividing the processing area to be processed into multiple sub-regions will be explained with reference to Figures 5, 6, and 7.

[0022] (1) From equation (1), the smaller the scanning period t1, the lower the temperature T when the laser beam passes the measurement point 102 on the nth time. n The temperature will increase. Figures 5 and 6 schematically show the effect when the scanning range is divided into four regions: the first region 101a, the second region 101b, the third region 101c, and the fourth region 101d. By reducing the scanning area, the effect of temperature drop can be reduced. A smaller scanning area means a smaller scanning period t1. Therefore, the time required to heat up to the required temperature can be shortened without increasing the laser power.

[0023] Figure 7 shows the results when the damping coefficient α is 0.3 / sec, ΔT is 680°C, and T r This is an example of temperature change calculated using equation (1), with a temperature of 30°C, comparing the cases where t1 is 2.5 seconds and 1.8 seconds. By reducing t1, the temperature can be raised to, for example, 1400°C in a short time.

[0024] Table 1 shows the total laser irradiation time required to heat the target processing area to 1400°C, under two conditions: when the target processing area is 30 mm x 30 mm, and when the area is divided (equally divided) and when it is not divided. The results are in general agreement with the experimental results.

[0025]

[0026] The scanning time t1 is the same quantity as t1 in equation (1), and is determined by the performance of the galvanometer mirror and other components used in the scanning mechanism. The laser irradiation time required for processing asbestos in a 30 mm x 30 mm area could be reduced by up to approximately 51 seconds.

[0027] The length of one side of the smallest division area can be twice the spot diameter of the laser beam. For example, if the spot diameter is 50 μm, the smallest division area can be 100 μm × 100 μm.

[0028] Next, the effect of performing processing consecutively on each non-adjacent divided region will be explained with reference to Figures 8 and 9. Figure 8 shows an example where processing is performed consecutively on each divided region in the order (a) → (b) → (c) → (d) → (e), sequentially on adjacent divided regions. In this case, the temperature near the edges shared with adjacent divided regions tends to rise, which can, for example, melt concrete coated with asbestos. To avoid this situation, as shown in Figure 9, the next object to be processed is (a) → (b) → (c), avoiding adjacent divided regions.

[0029] Next, we will explain in more detail using examples.

[0030] [Example 1] In Example 1, the process of detoxifying asbestos was carried out at a building demolition site. In Example 1, a 400W CW laser was used. The wavelength was 1.07 μm. The light generated by the laser light source passed through a fiber and was collimated to a diameter of φ5 mm by a fiber collimator, and then guided to a galvanometer mirror unit that performs x-y biaxial scanning. The galvanometer unit is equipped with an Fθ lens with a focal length of 300 mm, and the laser light emitted from the galvanometer unit is focused to a spot diameter of 50 μm and irradiated onto the target object. The scanning speed was 10 m / sec.

[0031] The scanning process involved scanning a distance equal to the length of one side of the area to be scanned at 10 m / sec, followed by a 20 μm scan in a direction perpendicular to the scanning direction. This scanning was repeated (raster scanning) to process the desired area. In Example 1, the area of ​​the currently processed segmented region and the next segmented region to be processed were different. In Example 1, the processing area to be processed was divided into multiple segmented regions, and the area of ​​each region was made to differ within a predetermined range. Each segmented region was a square.

[0032] The material to be treated is a substrate preparation material containing asbestos. Area: 10 m² 2 When a 1 mm thick base coat material was divided into sections ranging from 30 mm x 30 mm to 35 mm x 35 mm and irradiated with laser light to neutralize it, the laser irradiation time required to heat it to 1500°C, the temperature necessary for neutralization, was 6 hours.

[0033] Area 10m 2 When a 1 mm thick base coat material was divided into sections ranging from 15 mm x 15 mm to 20 mm x 20 mm and irradiated with laser light to neutralize it, the laser irradiation time required to heat it to 1500°C, the temperature necessary for neutralization, was 5 hours.

[0034] Area 10m 2 When a 1 mm thick base coat material was divided into sections ranging from 5 mm x 5 mm to 10 mm x 10 mm and irradiated with laser light to neutralize it, the laser irradiation time required to heat it to 1500°C, the temperature necessary for neutralization, was 3 hours.

[0035] In summary, by dividing the area irradiated with laser light, it was possible to shorten the laser light irradiation time without increasing the laser light power. Furthermore, asbestos removal can be performed using a similar process.

[0036] [Example 2] In Example 2, asbestos removal work was carried out at a building demolition site. In Example 2, a 400W CW laser was used. The wavelength was 1.07 μm. The light generated by the laser light source passed through a fiber and was collimated to a diameter of φ5 mm by a fiber collimator, and then guided to a galvanometer mirror unit that performs x-y biaxial scanning. The galvanometer unit is equipped with an Fθ lens with a focal length of 300 mm, and the laser light emitted from the galvanometer unit is focused to a spot diameter of 50 μm and irradiated onto the target object. The scanning speed was 10 m / sec.

[0037] The scanning area was scanned at a speed of 10 m / sec over a distance equal to the length of one side of the scanning area, and then scanned for 20 μm in a direction perpendicular to the scanning direction. This scanning was repeated (raster scanning) to process the desired area. In Example 2, the area of ​​the currently processed segmented region and the next segmented region to be processed were made equal. In Example 2, the processing area to be processed was divided into multiple equally spaced segments, and the area of ​​each segment was made equal. Each segmented segment was a square.

[0038] The material to be treated is a substrate preparation material containing asbestos. To remove the substrate preparation material, it needs to be heated to 1500°C. Area: 10 m²2 In order to remove asbestos in the base adjustment material with a thickness of 1 mm, when laser light was irradiated after dividing it into equal areas of 30 mm × 30 mm, the laser light irradiation time required to heat it to 1500 °C, which is the temperature required for asbestos removal, was 5 hours.

[0039] In order to remove asbestos in the base adjustment material with an area of 10 m2 and a thickness of 1 mm, when laser light was irradiated after dividing it into equal areas of 15 mm × 15 mm, the laser light irradiation time required to heat it to 1500 °C, which is the temperature required for asbestos removal, was 4 hours.

[0040] In order to remove asbestos in the base adjustment material with an area of 10 m 2 、when laser light was irradiated after dividing it into equal areas of 5 mm × 5mm in order to remove asbestos in the base adjustment material with a thickness of 1 mm, the laser light irradiation time required to heat it to 1500 °C, which is the temperature required for asbestos removal, was 2 hours. <P <P

[0041] As described above, by dividing the range irradiated with laser light, it was possible to shorten the laser light irradiation time without increasing the power of the laser light. Further, by making the areas of the divided regions equal (equal division), no gap occurred between the adjacent divided regions in the vertical and horizontal directions, and the laser light irradiation time could be shortened compared to Example 1. In addition, by the same treatment, asbestos can be detoxified. <P <P

[0042] [Example 3] In Example 2, laser light is irradiated to each of the divided ranges. However, when laser light was irradiated in order to the adjacent ranges as (a) → (b) → (c) → (d) → (e) as shown in FIG. 8, the concrete, which is the framework of the base adjustment material, might be damaged due to excessive temperature rise near the side shared by the adjacent ranges. <P <P

[0043] Therefore, as shown in FIG. 9, by irradiating laser light in order to the non - adjacent ranges as (a) → (b) → (c) for processing, it was possible to shorten the laser light irradiation time without damaging the concrete. <P <P

[0044] As explained above, by dividing the processing area to be processed into multiple sub-regions and scanning and irradiating each sub-region with laser light, it becomes possible to shorten the laser irradiation time in the processing of asbestos or asbestos-containing materials using a laser without relying on increasing the power of the laser light.

[0045] 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 implemented within the technical concept of the present invention by those with ordinary skill in the art.

[0046] 101...Divided region, 101a...First region, 101b...Second region, 101c...Third region, 101d...Fourth region, 102...Measurement point, 121...Spotlight.

Claims

1. A processing method for thermally decomposing, melting, or evaporating asbestos or an asbestos-containing substance by scanning and irradiating it with laser light, comprising: a first step of dividing a processing area to be processed into a plurality of divided areas; and a second step of scanning and irradiating each of the plurality of divided areas with laser light so that the laser light irradiates the entire divided area.

2. The processing method according to claim 1, wherein the first step is a processing method that equally divides the processing area to be processed into the plurality of divided areas.

3. The processing method according to claim 1, wherein the second step is a processing method that is carried out sequentially for each non-adjacent divided region.

4. The processing method according to any one of claims 1 to 3, wherein the second step is a processing method in which laser light is irradiated by raster scanning.

Images