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  Emission control systems and methods thereofThe Patent Description & Claims data below is from USPTO Patent Application 20070297963. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001]This is a divisional application of application Ser. No. 11/474,794 filed Jun. 26, 2006. FIELD OF THE INVENTION [0002]This invention generally relates to systems and methods for emissions control and, more particularly, to nitrogen oxide and sulfur trioxide emission control systems and methods thereof. BACKGROUND [0003]Exhaust emission from coal fired furnaces or boilers such as those used in power plants, may contain a variety of different gases depending on the type of coal being burned. The amounts at which some of these gases could be emitted into the environment are regulated. For example, there are restrictions on the amount of nitrogen oxides which could be emitted into the atmosphere. [0004]To reduce the amount of nitrogen oxides emitted into the environment, selective catalytic reactors have been added into the exhaust systems of coal fired furnaces and boilers such as at power plants. Ammonia is injected into a selective catalytic reactor (SCR) and mixes with the nitrogen oxides in the exhaust emission to produce pure nitrogen and water, thus reducing the amount of emitted nitrogen oxides. [0005]Unfortunately, this retrofit of selective catalytic reactors to coal fired furnaces and boilers such as in power plants to reduce nitrogen oxides can also result in visible emissions known as "blue plume." This begins with the oxidation of a relatively small portion of the sulfur dioxides in the exhaust emissions to sulfur trioxide. Sulfur trioxide and water vapor readily combine to form an acid mist. Small amounts of water vapor, which may or may not be sufficient to convert enough sulfur trioxide to acid mist to become visible, are available in the exhaust gases both from humidity in the combustion air and products of combustion of the small amount of hydrogen in the coal. If there is insufficient water in the exhaust gases, blue plume may form downstream of the plant stack after the sulfur trioxide combines with atmospheric moisture. Finally, if the plant has a wet SO2 scrubber, there is abundant moisture present to convert a high fraction of the sulfur trioxide to acid mist and a substantial portion of this mist escapes the scrubber. The source of moisture merely controls where the acid mist is formed and, thereby, how visible it will be. [0006]In any case, sulfuric acid mist is formed which can come down to the surface of the earth as acid rain. The long term health effects of sulfur trioxide or blue plume are not well known. The amount of sulfur dioxide catalyzed to sulfur trioxide and thence to acid mist is a relatively small fraction of the total sulfur from the coal burned. Nevertheless, the problem of blue plume is of great concern as evidenced by the purchase of most of the town of Chesire, Ohio by American Electric Power Co. (AEP) because of blue plume emitted from AEP's power plant which was upwind of the town of Chesire. [0007]Several methods for essentially eliminating the acid mist and associated blue plume resulting from sulfur trioxide have been proposed. At least one has been reported successful. This method involves injecting ammonia (at much higher dosages than are used in the SCR) to the exhaust gas at a point where its temperature has been reduced to the range of about 250-300.degree. F. (although the injection is sometimes carried out at higher temperatures). At this temperature, the ammonia reacts readily with the sulfur trioxide to form a number of possible compounds, the most notable of which are ammonium sulfate and ammonium bisulfate. The formation of these compounds by this reaction can capture a very high fraction of the sulfur trioxide thereby eliminating the conversion to acid mist and formation of blue plume. [0008]This method of controlling blue plume, while highly effective, has several disadvantages. First, the large usage of ammonia constitutes a substantial expense. Second, if insufficient ammonia is injected, the reaction produces mostly ammonium bisulfate which is a very sticky, somewhat liquid substance at these temperatures. Ammonium bisulfate can quickly build up on downstream equipment and cause operational problems. Finally, even when sufficient ammonia is used to assure predominately ammonium sulfate (a dry powder) is formed, the ammoniated compounds are collected with and detrimental to the quality of the fly ash. The most advantageous use for fly ash (highest value and largest quantity) is in concrete as a partial replacement for Portland cement. Even the smaller quantities of ammoniated compounds that sometimes results from SCR use are problematic for this use of fly ash. The much larger amounts of these compounds from blue plume control by ammonia injection make the ash completely unusable. Unusable ash is typically disposed of in landfills. However, since many of the ammoniated compounds (such as ammonium sulfate) are water soluble, it is not clear that landfill disposal will be acceptable for ash containing large quantities of these compounds. SUMMARY [0009]A method for controlling one or more emissions in accordance with embodiments of the present invention includes introducing ammonia to react with at least a portion of sulfur trioxides in an exhaust emission and results in at least one or more ammoniated compounds. At least a portion of fly ash particles and the ammoniated compounds in the exhaust emission are precipitated. At least a portion of the ammonia from the precipitated ammoniated compounds is recovered with heat from the exhaust emission and the recovered ammonia is reused. [0010]A system for controlling one or more emissions in accordance with other embodiments of the present invention includes a first ammonia delivery system, the precipitator system, the recovery system, and the resupply system. The first ammonia delivery system is connected to an exhaust system to introduce ammonia that reacts with at least a portion of sulfur trioxides in an exhaust emission and results in at least one or more ammoniated compounds. The precipitator system precipitates at a least a portion of fly ash particles and the ammoniated compounds in the exhaust emission. The recovery system recovers at least a portion of the ammonia from the precipitated ammoniated compounds with heat from the exhaust emission. The resupply system supplies the recovered ammonia to the first ammonia delivery system. [0011]A method for making a system for controlling one or more emissions in accordance with other embodiments of the present invention includes connecting a first ammonia delivery system to an exhaust system to introduce ammonia that reacts with at least a portion of sulfur trioxides in an exhaust emission and results in at least one or more ammoniated compounds. A precipitator system is connected to the exhaust system to precipitate at a least a portion of fly ash particles and the ammoniated compounds in the exhaust emission. A recovery system is connected to the precipitator system and the exhaust system that recovers at least a portion of the ammonia from the precipitated ammoniated compounds with heat from the exhaust emission. A resupply system is connected to the first ammonia delivery system that supplies the recovered ammonia. [0012]The present invention provides a number of advantages including providing an effective system and method for controlling and reducing nitrogen oxides and sulfur trioxides in exhaust emission while recovering ammonia used to control these emissions. Additionally, the fly ash particles, from which the ammonia is recovered, could be used for other applications, such as a substitute for a portion of the cement in concrete. [0013]The present invention provides a system in which NH3 injection could be used for its very effective control of nitrogen oxides and also control of blue plume (along with partial capture of sulfur compounds from the exhaust gases). Additionally, the present invention is able to achieve this control by utilizing the high concentrations of ammonia necessary to avoid creating problems in downstream power plant equipment, but without the large increase in ammonia cost and without contaminating the resulting fly ash such that it cannot be beneficially used. Further, the present invention accomplishes this without creating substantial new emissions, such as the conversion of ammoniated compounds into oxides of nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS [0014]FIG. 1 is a block diagram of an emission control system in accordance other embodiments of the present invention. DETAILED DESCRIPTION [0015]An emission control system 10 in accordance with embodiments of the present invention is illustrated in FIG. 1. The emission control system 10 includes an exhaust system 12, a selective catalytic reactor 14 (SCR), heat exchangers 16 and 18, ammonia injection systems 20 and 22, an electrostatic precipitator 24 (ESP), an ammonia recovery system 26, and a collection bin 28, although the sulfur emission control system 10 can comprise other numbers and types of components in other configurations. The present invention provides an effective system and method for controlling and reducing nitrogen oxides and sulfur trioxides and for recapturing and reusing at least a portion of the injected ammonia used in reducing these emissions. [0016]Referring more specifically to FIG. 1, the exhaust system 12 comprises a number of lines, ducts or pipes 30(1)-30(6) and a chamber 32 which are used to transport and process the exhaust emission, although the exhaust system 12 can comprise other types and numbers of vessels for carrying and processing the exhaust emissions in other configurations. The line 30(1) of the exhaust system 12 is connected to the exhaust emission outlet of a coal power plant furnace 15, although the exhaust system 12 could be connected to other sources of exhaust emission, such as to a coal fired industrial furnace. The exhaust emission from the coal power plant 15 or other exhaust emission source which is input to the line 30(1) of the exhaust system 12 includes fly ash particles and one or more other gases, such as sulfur dioxides and nitrogen oxides, although the exhaust emission could include other elements. [0017]The heat exchanger 16 (called an economizer in a coal fired power plant or similar boiler) is connected between the line 30(1) from the coal power plant furnace 15 and the line 30(2) to the selective catalytic reactor 14, although the heat exchanger 16 could be connected to other components and in other configurations. The heat exchanger 16 reduces the temperature of the exhaust emission to between about 600 degrees to 750 degrees Fahrenheit which is a more optimal temperature for the removal of at least a portion of the nitrogen oxides in the selective catalytic reactor 14, although the temperature of the exhaust emission could be reduced to other temperatures. [0018]The selective catalytic reactor 14 is connected between the line 30(2) from the heat exchanger 16 and the line 30(3) to the heat exchanger 18 (called an air preheater in a coal fired power plant or similar boiler), although the selective catalytic reactor 14 could be connected to other components and in other configurations. An ammonia injection system 20 is connected to and injects the ammonia (NH.sub.3) into the selective catalytic reactor 14 which is used to react with and reduce the amount of nitrogen oxides in the exhaust emission. More specifically, the selective catalytic reactor 14 uses ammonia (NH.sub.3) to reduce nitrogen oxides (NO.sub.x) in the exhaust emission to nitrogen (N) and water (H.sub.2O) in a chemical reduction. By way of example, this reaction can be illustrated by the following generalized formula: 3NO+2NH.sub.3.fwdarw.5N.sub.2+3H.sub.2O Continue reading... Full patent description for Emission control systems and methods thereof Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Emission control systems and methods thereof patent application. Patent Applications in related categories: 20080292519 - Bifunctional catalysts for selective ammonia oxidation - Catalysts, methods, and systems for treating diesel engine exhaust streams are described. In one or more embodiments, the catalyst comprises platinum, a second metal from one of the groups VB, VIIB, VIIB, VIIIB, IB, or IIB of the periodic table, a refractory metal oxide, and a zeolite, the oxidation catalyst ... ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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