Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Patent
1997-03-20
1999-03-16
Phasge, Arun S.
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
20415761, 2041582, 588210, 588212, 588219, 588227, 134 1, H01L 21268, C25D 534, B05D 306
Patent
active
058824871
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB95/01393 filed Jun. 15, 1995.
The present invention relates to removing contaminating substances from surfaces such as those of buildings, structure, industrial plants, vessels, cabins and the like.
According to the present invention there is provided a method of removing from the surface of an object a contaminating substance buried in an organic substance on the surface of the object which includes directing a laser beam at the organic substances to cause chemical change of the organic material or direct removal of the organic material by laser generated chemical change.
The said object may be the surface of a building, structure, industrial plant, vessel, cabin or the like.
The said contaminating substance may be a radioactive, biological or chemical contaminant.
The said organic substance in which the contamination is embedded may include one or more of paint, epoxy resin, sealant, adhesive, plastics, cloth, moss, lichen, fungus or other plants.
The said surface to be treated may be the surface of a substrate comprising a building material such as concrete, mortar, rendering, cement, brick, tiles, plaster, stainless steels, mild steels, alloying materials or the like.
The said laser beam may be of ultraviolet, visible or infrared wavelength.
The laser beam may be generated by a laser generator such as a gas laser, eg a CO.sub.2 gas laser or a CO gas laser, a solid state laser, eg a Nd--YAG (Neodymium-Yttrium-Aluminium-Garnet) or a Ti-Sapphire laser, an Excimer laser, a dye laser, a free electron laser or a semiconductor laser.
The laser beam may be either pulsed or continuous.
The laser beam which preferably produces high power is used to generate photothermal energy at the surface to be treated. After absorption of such energy by the organic substance a series of chemical changes will occur to the organic substance in the following temperature ranges: materials will be driven out or broken and decomposition of C--H chains will result, forming charred material--carbon. oxidised--forming CO.sub.2 and CO gases through combustion, leaving ashes of other oxides. Flames can be seen at this stage if not controlled with additional gas(es). Carbon rich contamination like soot found on the surface of most buildings in industrial cities can be removed this way.
Under these applied temperatures the substrate material (inorganic) may not be melted, or damaged but certain heat effects may be caused.
By careful control of the laser parameters this effect on the substrate can be minimised to an acceptable level.
When the laser beam has a wavelength in the ultraviolet range, direct photo-induced chemical change, such a bond breaking, may occur with organic materials, which may result in ablation.
The typical operating conditions and procedures are described below and illustrated in the embodiment described below.
The invention provides an efficient and effective method for treating contaminated surfaces, eg in the decommissioning of buildings or industrial plant facilities.
Preferably, at least one gas may be delivered to a treatment region of the surface being treated. The gas may desirably be compressed air. The gas provides removal of ashes formed by blowing them off the surface, controls any flames formed in the chemical reactions and provides oxygen to the treatment region to assist the chemical reaction occurring.
The laser beam and gas may be delivered to the treatment region via an inner nozzle or shroud and waste materials formed may be extracted by an extraction arrangement comprising an outer nozzle or shroud. The waste materials may be extracted by suction.
Conveniently the laser beam may be provided from a laser source arranged on a mobile carrying means, eg trolley, which may be transported to a site of use.
A supply of gas and a pump required for extraction of waste materials may both be carried on the said mobile carrying means, eg trolley.
The laser beam may be applied from the laser source to the region of the surface to be treated via an operator handset which may
REFERENCES:
patent: 3941670 (1976-03-01), Pratt, Jr.
patent: 4898650 (1990-02-01), Wu et al.
patent: 5024968 (1991-06-01), Engelsberg
patent: 5151134 (1992-09-01), Boquillon et al.
Brochure entitled "Laser Technology," Urenco Deutschland GmbH, as early as 1994 (no month available).
Li Lin
Spencer Julian Timothy
British Nuclear Fuels, Plc.
Phasge Arun S,.
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