Catalyst – solid sorbent – or support therefor: product or process – Regenerating or rehabilitating catalyst or sorbent – Gas or vapor treating
Patent
1993-02-16
1995-04-11
McFarlane, Anthony
Catalyst, solid sorbent, or support therefor: product or process
Regenerating or rehabilitating catalyst or sorbent
Gas or vapor treating
502 20, 502 56, 502516, 502517, 423210, 423240R, 4232441, 422177, 422216, 422219, 96126, 96130, 96146, 96150, 588234, B01J 2034, B01J 808, B01D 5000
Patent
active
054058120
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method for purifying a carbon-containing absorption medium that has been spent in a flue gas scrubbing process and which has been removed from a flue gas treatment reactor wherein the removed adsorption medium is subjected to a desorption process in a separate thermal regeneration/desorption apparatus for separating and decomposing pollutants and wherein the pollutant-rich desorption gas is subjected to a further treatment. Furthermore, the invention relates to an arrangement for performing this method.
With the increasing number of flue gas scrubbing devices, with respect to number and capacity the amount of adsorption medium used within such scrubbing devices has also steadily increased, these adsorption media being partially heavily loaded with pollutants. A combustion of the carbon-containing adsorption medium is not feasible or feasible only with a considerable expenditure whereby it has not been possible to date to dispose of especially heavy metals and dioxin in a suitable manner.
From U.S. Pat. No. 4,500,501 a method is known in which the separation of SO.sub.2 and NO.sub.x by catalytic adsorption is performed in two serially connected moving bed reactors. The carbon-containing adsorption medium removed from the second moving bed reactor in line is regenerated in a regenerator arranged downstream, partially replaced and turned into the first flue gas treatment reactor. With this known process it is possible to reactivate the adsorption medium; on the other hand, the contents of toxic substances, especially dioxin, furane, and heavy metals, especially mercury, within the recycled adsorption medium can increase.
Under the given circumstances the pollutant-rich adsorption medium spent during flue gas scrubbing often must be disposed of at special hazardous waste depositories at a respective cost expenditure.
From German published document 3 426 059 a desorption method for carbon-containing adsorption media is known in which temperatures of more than 1000.degree. C. are deemed necessary. In the described method there is further the danger of introducing oxygen into the desorption apparatus.
It is therefore an object of the invention to dispose of heavily polluted carbon-containing adsorption media spend during flue gas scrubbing at comparatively low costs and in an environmentally safe manner.
SUMMARY OF THE INVENTION
According to the inventive method this object is solved by: subjecting the removed adsorption medium in a separate thermal regeneration apparatus to a desorption process whereby the treatment temperature is selected such that pollutants are separated from the adsorption medium, i.e., especially dioxins are decomposed, adsorbed SO.sub.2, HCl, HF, etc. are released, and mercury is vaporized; by guiding the pollutant-rich desorption gas into an adsorption apparatus and treating it by removing mercury from it; by guiding the essentially mercury-free desorption gas of the adsorption apparatus to further treatment, especially returning it into the flue gas scrubbing process.
The arrangement for performing this method is inventively characterized by providing a thermal regeneration apparatus downstream of the flue gas treatment reactor, the thermal regeneration apparatus provided with means for heating the adsorption medium, a removal unit at the bottom for removing the treated adsorption medium and a gas and steam removing device for removing the pollutant-rich adsorption gas, the gas and steam removal device connected to an adsorption apparatus which is designed to remove mercury from the desorption gas.
With the invention the adsorption medium loaded to a greater or lesser extent with pollutants is first substantially freed from pollutants in a desorption process performed by supplying heat. The thus treated adsorption medium can then be burned without further substantial expenditure or regenerated for reuse. Residues of the previously cleaned adsorption medium, after combustion, can be disposed of without problems and correspond to o
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Prof. Dr. Jurgen Falbe and Prof. Dr. Manfred Regitz; Rompp Chemic Lexikon; 1990; 996-998.
McFarlane Anthony
Steag Aktiengesellschaft
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