Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture
Patent
1994-03-08
1996-01-02
Straub, Gary P.
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
4232421, 423240S, 42324407, 423481, 95 92, 55280, B01D 5314, B01D 5350, B01D 5368, B01D 5374
Patent
active
054806240
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of purification of waste gases which are produced in, for example, combustion, gasification, or some chemical or metallurgical processes. Sulfur dioxides, ammonia, chlorine and fluorine compounds and condensing hydrocarbon compounds are typical pollutants contained in these gases. The present invention especially relates to a method in which reagent and/or absorbent which reacts with pollutants contained in the gases is activated by leading the gases into a wetting reactor. The reagent and/or absorbent is added to the process itself or to the gases discharged from the process. The gases are introduced into the wetting reactor for wetting them with water or steam in order to activate the reagent contained in the gases. The gases are first fed to the lower section of the wetting reactor and then further upwards to the wetting zone of thereof, where a suspension formed of the gas and the reagent is wetted with water or steam. The reagent and/or absorbent particles which have reacted either completely or partially are separated from the gases by a filter in the upper part of the wetting reactor before the gases are discharged from the reactor. Carbonates, oxides or hydroxides of, e.g., either alkali metals or alkaline earth metals are used as reagents or absorbents.
As known, combustion of fossile fuels produces flue gases which contain sulfur oxide and cause environmental acidification. The sulfur content of the flue gases varies depending on the sulfur content of the fuel. Efforts are made to find means for employing fuels which contain more and more sulfur even though the restrictions on sulfur emissions become tighter and tighter. Waste incineration plants, the number of which is continuously increasing, also produce sulfur-containing flue gases which have to be purified so as to be within the set limits. The flue gases produced in waste incineration plants when, e.g., plastic compounds are burnt contain, besides SO.sub.2 and SO.sub.3 emissions, also hydrochloric and hydrofluoric acids and other harmful gaseous and solid compounds.
Process gases produced in various gasification processes may also contain harmful amounts of sulfuric or other compounds which have to be separated from the gases prior to further treatment thereof.
BACKGROUND OF THE INVENTION
Several methods have been developed for cutting down sulfur emissions of combustion plants. The most common method used so far is wet scrubbing in which method the gases are scrubbed with a water suspension of a reagent, such as lime, reacting with, e.g., sulfur oxides. The water suspension is sprayed into a gas flow in a scrubber arranged after a combustor, whereby sulfur is absorbed into the water suspension and sulfur dioxide reacts with lime, forming calcium sulphate or calcium sulphite
Water suspension is sprayed in such an amount that sulfur compounds thus formed have not enough time to dry, but they are discharged as a slurry from the lower section of the scrubber. The wet scrubbing process is complicated as it requires means for preparing water suspension and means for after-treatment thereof. Furthermore, the method usually requires additional energy for drying the produced slurry in a slurry after-treatment plant. Therefore, the water suspension is usually fed into the system as dry as possible in order to minimize the energy requirement. Due to the considerable amount of water suspension used, the gas may be cooled to a relatively low temperature in the scrubber and, consequently, the gas discharged from the scrubber may cause corrosion and clogging of filters. Further, energy is consumed for reheating the flue gases prior to leading them out of the system. In the wet scrubbing system, the separation degree of, for example, SO.sub.2, is about 95%.
During the last few years, semi-dry scrubbing methods have been developed, in which a fine alkali suspension, e.g., calcium hydroxide suspension is sprayed through nozzles into a hot flue gas flow in a contact reactor where sulfur oxides dissolve in water an
REFERENCES:
patent: 4305909 (1981-12-01), Willett et al.
patent: 4322392 (1982-03-01), Gleason et al.
patent: 4555390 (1985-11-01), Bhatia
patent: 4600568 (1986-07-01), Yoon et al.
patent: 4753785 (1988-06-01), Kisters
patent: 4768448 (1988-09-01), Nobilet et al.
patent: 4832936 (1989-05-01), Holter et al.
patent: 4834955 (1989-05-01), Mouche et al.
patent: 4908195 (1990-03-01), Wanner et al.
patent: 5186916 (1993-02-01), Nevels
patent: 5238657 (1993-08-01), Kuivalainen
patent: 5310528 (1994-05-01), Kuivalainen
A. Ahlstrom Corporation
Straub Gary P.
Vanoy Timothy C.
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