DE102014214427A1 - Method and device for removing a coating from a surface of a base material - Google Patents

Abstract

The present invention relates to a method and apparatus for removing a coating (12) containing polychlorinated biphenyls, PCB, from a surface of a base material (13). The coating (12) is heated to a predetermined temperature by a first laser beam (4) so that the polychlorinated biphenyls are decomposed, the decomposition being monitored by laser-induced fluorescence by exposing a zone (15) above the heated coating (12). is irradiated by a second laser beam (10). In the zone (15), a chemical compound formed during the decomposition is excited by the second laser beam (10) to fluoresce, and the fluorescence is detected with an optical detector (11).

Description

The present invention relates to a method and apparatus for removing a coating containing polychlorinated biphenyls (PCBs) from a surface of a base material.

Polychlorinated biphenyls were used as component in paints until their prohibition in the Federal Republic of Germany. Concrete walls were sealed with these paints to protect them against contamination. In the course of renovation or demolition work, these paints whose PCB content exceeds a hazard threshold must be removed from the walls, packaged and disposed of in a separate operation in a hazardous waste incineration plant.

From the prior art, a manual-mechanical removal with subsequent thermal treatment in a hazardous waste incineration plant is known. These methods require a high safety effort to minimize or avoid secondary contamination by dust. Working under protective clothing with breathing mask represents an extremely high physical stress for the staff and is associated with significant health risks. Due to the low mechanical precision and concrete structures are removed, which have no toxic contamination, but are also fed to the thermal aftertreatment, which increases the cost accordingly.

In addition, a laser ablation of the paint is known as a further method. In the utility model DE 20 2009 009 514 U1 such a laser ablation is described. A disadvantage of such methods is that the paint is indeed removed, but no monitoring is carried out during the removal of a complete removal or on the formation of toxic decomposition products.

The present invention is therefore based on the object to propose a method and a device with which the mentioned disadvantages are overcome, d. H. Process monitoring takes place at the same time as the removal.

This object is achieved by a method according to claim 1 and a device according to claim 7. Advantageous embodiments and further developments are described in the subclaims.

In a method of removing a coating containing polychlorinated biphenyls (PCB) from a surface of a base material, the coating is heated to a predetermined temperature by a first laser beam so that the polychlorinated biphenyls are thermally decomposed. The thermal decomposition is monitored by laser induced fluorescence (LIF) by irradiating a zone above the heated coating from a second laser beam of at least one wavelength which can excite a characteristic chemical intermediate of the decomposition. In this case, a chemical compound formed during the thermal decomposition is excited in the zone as a characteristic chemical intermediate of the second laser beam to fluoresce and detects the fluorescence with an optical detector.

By heating the coating to a predetermined temperature, the coating, typically a paint, is detached from the surface of the base material and burned. The use of laser radiation for decontamination has the advantage of being able to generate very high temperatures very quickly locally. The thermal decomposition forms a reaction zone which is located above the previously irradiated area and can be easily examined there by the second beam with regard to the composition. Using the laser-induced fluorescence allows a fast and accurate real-time investigation of the reaction zone. The second laser usually stimulates fluorescence in the thermal decomposition of PCB-containing coatings resulting in chemical compounds, so that these components can be specifically investigated.

The power of the first laser beam can be increased if a concentration of the chemical compound determined by the laser-induced fluorescence with the optical detector falls below a predetermined limit value. By adjusting the laser power of the first laser, an energy input for thermal decomposition of the coating can be set and controlled as a function of the determined concentration of intermediate products. An optical observation system is particularly suitable for this because of the possibility of a non-contact measurement. An on-line process control, which increases the output below the limit for the intermediate product, so that the polychlorinated biphenyls are decomposed, unnecessary material removal can be avoided since only the coating, but not the uncontaminated base material, is removed becomes.

The second laser beam typically passes through the zone above the heated coating as a beam with a linear cross section, that is to say preferably as a light section with a vertically expanded, horizontally focused cross section. Through this also known as "Lightsheet" cross section of In the second laser beam, only a small but significant area of the combustion zone or reaction zone above the burning coating is examined, allowing the method to be used even in a limited space. The laser beam can also focus as a line process a single point and monitor the process, without realizing a spatial resolution.

Alternatively or additionally, the second laser beam may have at least one wavelength in the range from 271 nm to 279 nm, since this wavelength range can be used for the reliable excitation of resulting intermediates.

The chemical compound formed upon completion of the thermal decomposition may contain a radical, preferably CCI. The presence of this radical allows for a statement about a successful decontamination process. If no CCI can be detected, this is an indication that the removal process is not working properly and the polychlorinated biphenyls are not degraded. Alternatively or additionally, the chemical compound formed during the thermal decomposition can be a chemical compound contained in a material, in particular concrete, on which the coating is formed, or a chemical element contained in the material. By detecting substances that are typical for the replacement of the coating, can reliably on the successful replacement, d. H. Decontamination of the surface of the base material are closed.

It may be provided that the gaseous chemical components formed in the thermal decomposition thermally quenched to temperatures of less than 250 ° C, d. H. be cooled quickly. Alternatively or additionally, the predetermined temperature may be at least 1000 ° C. By such a high temperature followed by rapid cooling, the formation of polychlorinated dibenzodioxins (PCDD) and polychlorinated dibenzofurans (PCDF) is prevented by a recombination of decomposition products.

Typically, the first laser beam has a wavelength of 800 nm to 1100 nm, preferably 915 nm, 940 nm, 980 nm, and 1030 nm, and preferably a kilowatt continuous wave power, i. H. of at least 3 kW, more preferably at least 10 kW. This allows reliable heating of the coating so that it can be vaporized and examined by the laser-induced fluorescence. The four wavelengths mentioned can be present in each case one quarter in the first laser beam.

An apparatus for removing a coating containing polychlorinated biphenyls (PCB) from a surface of a base material includes a first laser configured to irradiate a first laser beam onto the coating and thereby thermally decompose the same. The device comprises a second laser, which is set up to irradiate a zone located above the coating with a second laser beam and thereby to excite fluorescence of a chemical compound formed during thermal decomposition. The device also includes an optical detector configured to detect the fluorescence.

Furthermore, a control unit may be provided which increases a power of the first laser when a concentration of the chemical compound falls below a predetermined limit value.

It can also be provided that the device has an aspirator which sucks up gaseous and particle-bound chemical compounds formed during the thermal decomposition. Preferably, the aspirator has at least one filter to bind toxic substances in aspirated volumes. Typically, the described cooling to temperatures of less than 200 C, so the thermal quenching takes place in front of the extractor.

The first laser can produce a laser spot having a size of 45 mm by 10 mm, which is preferably rectangular. In this way, the surface of the base material can be completely and quickly traversed while ensuring a sufficient homogeneous energy transfer to the coating.

Alternatively or additionally, the first laser may generate at least 220 kJ / m of track energy, preferably at least 225 kJ / m of track energy, more preferably at least 230 kJ / m of track energy, to reliably remove the polychlorinated biphenyls. Typically, the second laser is arranged to irradiate the zone above the coating with a second laser beam having at least one wavelength in the range from 271 nm to 279 nm.

The optical detector is typically set up to detect the fluorescence in temporal and spatial resolution. The optical detector may also be arranged to perform spot or line processes, for example via photomultipliers. It can also be provided that the optical detector is designed to carry out a line method without spatial resolution. The won by the optical detector Information can be used for a fine control of the first laser to control the removal in a defined manner.

The described method is typically carried out with the device described or the device described is suitable for carrying out the described method.

An embodiment of the invention is illustrated in the drawing and will be described below with reference to the 1 explained.

It shows:

1 a schematic view of a device for laser decontamination of PCB-containing coatings with process monitoring.

1 shows a schematic view of an apparatus for laser decontamination of PCB-containing paints with process monitoring. The device comprises a high-power laser aggregate 1 that has a fiber optic cable 2 with a laser optic 3 connected is. The high-power laser aggregate is a diode laser and emits a laser beam 4 with a power of 10 kW and a wavelength of 800 nm to 1100 nm, preferably 915 nm, 940 nm, 980 nm and 1030 nm via one or more optical fibers of the optical fiber cable 2 and the laser optics 3 on a paint layer 12 containing polychlorinated biphenyls (PCBs) and on a base material 13 that contains concrete, is applied. The four wavelengths mentioned are each one quarter in the laser beam 4 available. The base material 13 For example, it may be calzitic, quartzitic or mixed concrete. A thickness of the paint layer 12 is typically between 0.1 mm to 1 mm. A distance between the arbitrarily positioned laser aggregate 1 and the laser optics 3 This can be several hundred meters, resulting in contamination of the laser aggregate 1 can be avoided. The laser optics 3 shapes the laser beam 4 into a rectangular spot measuring 45 mm by 10 mm in order to allow a corresponding removal area in the square centimeter range.

The laser beam 4 is to a laser working head 5 coupled, which ensures complete combustion by supply air and a controlled removal of a resulting flue gas through an exhaust pipe 6 , The rectangular laser spot strikes a surface of the lacquer layer 12 and burns or degrade them at temperatures greater than at least 1000 ° C, causing complete decomposition of the PCB. The hot flue gas produced by the combustion is then sucked into a suction, ie through the exhaust pipe 6 , one after the exhaust pipe 6 arranged filters 7 , For example, a wet filter, and arranged at the end of the suction suction 8th passing the flue gas through the exhaust pipe 6 and the filter 7 aspirates to avoid recombination to polychlorinated dibenzodioxins (PCDD) and dibenzofurans (PCDF). Even if the filter 7 and the aspirator 8th in 1 spatially separated, the filter can 7 in further embodiments also directly on the suction 8th be arranged. The base material 13 , So typically a concrete block is not affected in this process, so performing the described method.

For paint thicknesses between 0.1 mm and 1 mm is for a complete removal of the paint layer 12 and the decomposition of the polychlorinated biphenyls through the laser aggregate 1 required path energy of at least 225 kJ / m required.

The laser working head 5 has optical accesses, typically windows, arranged at right angles to each other. This allows frontal one of a second laser unit 9 emitted laser sheet 10 , So a second laser beam with a line-shaped cross section, which is also referred to as a light sheet or laser disk, are irradiated with a wavelength between 271 nm and 279 nm, so that one above the current of the laser beam 5 machined area of the paint layer 12 combustion zone located 15 is irradiated. As a result, a laser-induced fluorescence measurement is possible. At the indicated wavelengths, the radical CCI is excited, whose presence allows a statement about the successful decontamination process. The excited CCI takes the energy of the laser sheet 10 and releases it again while emitting fluorescence. The fluorescence is detected by means of a detection system 11 detected perpendicular to the second laser aggregate 9 is arranged and sensitive to the wavelength range between 271 nm and 285 nm. Thus, already in the process, ie on-line, a statement about a decomposition of polychlorinated biphenyls and a possible formation of toxic products are made and monitoring in real time is given.

The detection system 11 transmits the received data to a computer 14 that is the laser aggregate 1 depending on the determined concentration of CCI, that is, if the concentration is too low, the performance is increased because the detection of CCI indicates that polychlorinated biphenyls are decomposed and at a high concentration lowers the output until the CCI concentration begins to decrease , If no CCI is detected, although polychlorinated biphenyls are present in the paint layer in a measurement made prior to performing the procedure 12 have been detected, the Lack of detection of CCI by the laser-induced fluorescence indicates that the decontamination process does not work and polychlorinated biphenyls are not burned.

By means of the described device or the described method, a renovation or a demolition of building structures can be carried out in a resource-saving manner with high efficiency and without the risk of contaminating carryover.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 202009009514 U1 [0004]

Claims (10)

Method for removing a coating ( 12 ) containing polychlorinated biphenyls, PCB, from a surface of a base material ( 13 ), in which the coating ( 12 ) by a first laser beam ( 4 ) is heated to a predetermined temperature such that the polychlorinated biphenyls are thermally decomposed, the decomposition being monitored by a laser-induced fluorescence by applying a zone ( 15 ) above the heated coating ( 12 ) from a second laser beam ( 10 ), whereby in the zone ( 15 ) a chemical compound formed in the thermal decomposition as a characteristic chemical intermediate of the decomposition of the second laser beam ( 10 ) are excited to fluorescence and the fluorescence is detected with an optical detector ( 11 ) is detected. Method according to claim 1, characterized in that the power of the first laser ( 4 ) is increased when one with the optical detector ( 11 ) determined by the laser-induced fluorescence concentration of the chemical compound falls below a predetermined limit. Method according to claim 1 or claim 2, characterized in that the second laser beam ( 10 ) as a beam with a linear cross-section (as a light sheet) or as a line the zone ( 15 ) above the heated coating ( 12 ) and / or has at least one wavelength in the range from 271 nm to 279 nm. A method according to claim 1 or claim 2, characterized in that the chemical compound formed during the thermal decomposition of a radical, preferably the radical CCI, and / or one in a material, in particular concrete, on which the coating ( 12 ), contained chemical compound or a chemical element. Method according to one of the preceding claims, characterized in that the gaseous chemical components formed in the thermal decomposition are thermally quenched to temperatures of less than 250 ° C and / or the predetermined temperature is at least 1000 ° C. Method according to one of the preceding claims, characterized in that the first laser beam ( 4 ) is operated at wavelengths from 800 nm to 1100 nm, preferably 915 nm, 940 nm, 980 nm and 1030 nm, and preferably has a continuous wave power of at least 10 kW. Device for removing a coating ( 12 ) containing polychlorinated biphenyls, PCB, from a surface of a base material ( 13 ) with a first laser ( 1 ), which is formed, a first laser beam ( 4 ) on the coating ( 12 ) and thereby thermally decomposing them, a second laser ( 9 ), which is set up, one above the coating ( 12 ) zone ( 15 ) with a second laser beam ( 10 ) and thus to excite fluorescence of a chemical compound formed on decomposition, and an optical detector ( 11 ), which is set up to detect the fluorescence. Device according to claim 7, characterized in that the device comprises a control unit ( 14 ), which is set up, a power of the first laser ( 1 ), if a concentration of the chemical compound falls below a predetermined limit. Apparatus according to claim 7 or claim 8, characterized in that a suction device ( 8th ) is provided for the extraction of formed during decomposition gaseous and particle-bound chemical components, wherein the suction device ( 8th ) preferably at least one filter ( 7 ) having. Device according to one of claims 7 to 9, characterized in that the first laser ( 1 ) generates a path energy of at least 220 kJ / m, preferably at least 225 kJ / m, particularly preferably at least 230 kJ / m, and / or the second laser ( 9 ) which is above the coating ( 12 ) zone ( 15 ) with a second laser beam ( 10 ) with at least one wavelength in the range from 271 nm to 279 nm.

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