Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Waste gas purifier
Patent
1992-07-31
1994-05-10
Warden, Robert J.
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Waste gas purifier
55222, 55260, 55269, 55305, 422168, 422261, 422267, 4232421, 42324401, 42324408, B01D 5000, B01D 1102
Patent
active
053105281
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 or absorbent which reacts with pollutants contained in the gases is activated by leading the gases into a wetting reactor. The reagent or absorbent is added to the process itself or to the gases discharged from the process. The reagent or absorbent particles which have reacted either completely or partially are separated from the gases. Carbonates, oxides or hydroxides of, e.g., either alkali metals or alkaline earth metals are used as reagents or absorbents.
The present invention also relates to an apparatus for purification of waste gases. Especially, it relates to a wetting reactor which is provided with an inlet for waste gases and for reagent and/or absorbent, with spray means for water or steam, said spray means forming a wetting zone for activating the absorbent, with a filter disposed above the wetting zone in the upper section of the wetting reactor, for separating solid particles from the gases, and a gas outlet connected to the filter, and with an outlet or outlet duct for particles separated from the gases, disposed in the lower section of the wetting reactor.
As known, combustion of fossile fuels produces flue gases which contain sulfur dioxide 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.
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 dioxides. 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 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
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A. Ahlstrom Corporation
Thornton Krisanne M.
Warden Robert J.
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