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  Use of manganese compounds to improve the efficiency of and reduce back-corona discharge on electrostatic precipitatorsUSPTO Application #: 20060219096Title: Use of manganese compounds to improve the efficiency of and reduce back-corona discharge on electrostatic precipitators Abstract: Manganese is added to a combustion fuel, combustion air, or the resulting combustion exhaust gas in order to improve the efficiency of an electrostatic precipitator in collecting the resulting fly ash. Further, manganese or other flame suppressant is added to a fuel, and/or combustion air, or combustion exhaust gas stream in order to reduce back-corona discharge that could otherwise occur in an electrostatic precipitator. (end of abstract)
Agent: New Market Services Corporation (formerly Ethyl Corporation) - Richmond, VA, US Inventors: Allen A. Aradi, Michael W. Adams, Stephen A. Factor USPTO Applicaton #: 20060219096 - Class: 095058000 (USPTO) Related Patent Categories: Gas Separation: Processes, Electric Or Electrostatic Field (e.g., Electrostatic Precipitation, Etc.), With Addition Of Solid, Gas, Or Vapor The Patent Description & Claims data below is from USPTO Patent Application 20060219096. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF THE INVENTION [0001] The present invention relates to improving the efficiency and operation of electrostatic precipitators in utility and industrial furnace systems. Specifically, the addition of manganese in fuel, in the combustion air, or in combustion exhaust gas (flue gas) increases the efficiency of an electrostatic precipitator in collecting the fly ash from the combustion gas. Further, the addition of manganese or other flame suppressant materials into fuel, into combustion air, or into combustion exhaust gas reduces back-corona discharge in electrostatic precipitators, thus also improving fly ash collection efficiency. BACKGROUND OF THE INVENTION [0002] The environmental issues and concerns with respect to smoke stack emissions are well recognized. One of the combustion exhaust gas products that receives considerable attention is fly ash. Much technology and effort has been dedicated to reducing fly ash emissions that are the result of the combustion of hydrocarbonaceous fuel in a combustion unit. [0003] Electrostatic precipitators are one significant type of technology used to reduce fly ash emissions. The basic process used in electrostatic precipitators includes the creation of an electric field in a pipe or passage through which a combustion exhaust gas, including fly ash, flows. When the gas flows through the electric field, particles in the gas (fly ash) pick up a negative charge from the electrons given off by an emitter source. These particles in the gas build up a negative charge and are then attracted to the positive charge on a grounded collector plate. Those particles are then collected there. The fly ash is subsequently collected from the plates by physically rapping the plates and collecting the fly ash that falls off into hoppers where it is then removed. [0004] The efficiency of electrostatic precipitators is affected by several basic factors, one of which is the resistivity of the fly ash particles that the system is trying to collect. For normal operation, the resisitivity of the fly ash should lie between about 1.times.10.sup.8 and 1.times.10.sup.4 Ohm-cm. Values above this range lead to back corona discharge, and below this range lead to re-entrainment of the fly ash back into the exhaust stream because the particles of very low resistivity loose their negative charge very easily. Carbon in the fly ash lowers the resitivity so much that efficient collection in the ESP is impeded. If the particles are highly conductive (i.e., have an excessively low resistivity), then the particles give up there charges very easily and are relatively difficult to retain on a collector plate. An example of this is high carbon content in fly ash, which is known to contribute to electrostatic precipitator inefficiency. On the other hand, very high resistivity particles will retain their charge even after being collected on the collector plates. These high resistivity particles, while initially easy to collect, may form an insulating layer on the collection plates of a system. After a relatively short period of time, the build up of those particles may block the electric flow necessary for the efficient operation of systems. [0005] This build up of high resistivity particles on collector plates also presents other performance problems. One of these problems is referred to as "back-corona" discharge which is a spark or arc across the electric field as a result of the voltage gradient build-up across the collected particle layer on the collector plate. If the electrostatic precipitator voltage becomes too large because of excessively high resistivity of the fly ash (above 10.sup.9 Ohm cm), gas trapped in this particle layer can ionize and break down, thereby causing a spark or flare that substantially reduces the efficiency of the electrostatic precipitator. Every time this event occurs, there is a "puff" of increased smoke out of the exhaust chimney that is recorded as a transient increase in flue gas opacity. To inhibit this event, ESP controls back off on the potential between the electrodes (reduce the voltage to the electrodes), thereby leading to performance inefficiency and an increase in steady state exhaust opacity. [0006] Particle resistivity can be manipulated and improved by modifying the fuel to be combusted or by modifying the combustion gas before it flows through an electrostatic precipitator. Blending fuels that give off high and low resistivity particles is one way to obtain a desired resistivity in a combustion gas. Alternatively, a combustion gas may be modified or conditioned to make it have the desired resistivity. One of the most recognized methods of modifying or conditioning a combustion exhaust gas is to add sulfur trioxide (SO.sub.3) vapor into a combustion exhaust gas stream. The addition of SO.sub.3 lowers resistivity. The amount of SO.sub.3 can be varied depending on a particular fuel combustion exhaust gas and other operating parameters. Drawbacks of sulfur-type emissions are also recognized, so other types of treatments are desired. SUMMARY OF THE INVENTION [0007] Accordingly, it is an object of the present invention to add a source of manganese to a combustion fuel or to the combustion air, or to the resulting combustion exhaust gas in order to improve the efficiency of an electrostatic precipitator in collecting the resulting fly ash. Further, it is an object of the present invention to add a source of manganese or other flame suppressant to a fuel or combustion air, or combustion exhaust gas stream in order to reduce back-corona discharge that could otherwise occur in an electrostatic precipitator. [0008] In one embodiment, the invention includes a method for improving the efficiency of an electrostatic precipitator used to collect fly ash from a combustion exhaust gas resulting from the combustion of a fuel in a combustion unit. The method comprises adding to the fuel an effective amount of a source of manganese. Alternatively, the method comprises adding to the combustion exhaust gas an effective amount of a source of manganese. [0009] In a further alternative, the invention includes a method of reducing back-corona discharge in electrostatic precipitators used to collect fly ash from a combustion exhaust gas resulting from the combustion of a fuel in a combustion unit. This method comprises adding to the fuel an effective amount of a source of manganese. Alternatively, the method comprises adding to the combustion exhaust gas an effective amount of a source of manganese. Still further alternatively, the method comprises adding to the combustion exhaust gas an effective amount of an additive selected from the group consisting of inorganic and organic compounds of transition metals, actinides, lanthanides, alkali and alkaline earth metals, metalloids, halogens, phosphorus, and sulfur. Also alternatively, the method may include adding to the combustion exhaust gas an effective amount of an oxygenate. [0010] In connection with any of the foregoing methods, a combustion unit may be selected from the group consisting of any and all burners, stationary burners, waste incinerators, diesel fuel burners, gasoline fuel burners, power plant generators, power plant furnaces, any and all internal and external combustion devices, boilers, furnaces, evaporative burners, plasma burner systems, plasma arc, and devices that can combust or in which can be combusted a hydrocarbonaceous fuel. [0011] Also with respect to any of the foregoing methods, the fuel may be selected from the group consisting of diesel fuel, biodiesel, biodiesel-derived fuel, synthetic diesel, jet fuel, alcohols, ethers, kerosene, low sulfur fuels, synthetic fuels, Fischer-Tropsch fuels, liquid petroleum gas, fuels derived from coal, coal, genetically engineered biofuels and crops and extracts therefrom, natural gas, propane, butane, unleaded motor and aviation gasolines, reformulated gasolines which contain both hydrocarbons of the gasoline boiling range and fuel-soluble oxygenated blending agents, gasoline, bunker fuel, coal (dust or slurry), crude oil, refinery "bottoms" and by-products, crude oil extracts, hazardous wastes, yard trimmings and waste, wood chips and saw dust, agricultural waste, fodder, silage, plastics, organic waste, and mixtures thereof, and emulsions, suspensions, and dispersions thereof in water, alcohol, and other carrier fluids. [0012] Also alternatively, the source of manganese may be selected from the group consisting of methyl cyclopentadienyl manganese tricarbonyl, cyclopentadienyl manganese tricarbonyl, bis- cyclopentadienyl manganese (manganocene), bis-alkyl cyclopentadienyl manganese, manganese sulfonate, manganese phenate, manganese salicylate, alkyl cyclopentadienyl manganese tricarbonyl, organic manganese tricarbonyl derivatives, alkyl cyclopentadienyl manganese derivatives, neutral and overbased manganese salicylates, neutral and overbased manganese phenates, neutral and overbased manganese sulfonates, manganese carboxylates, and combinations and mixtures thereof. [0013] In a still further embodiment, a fuel is adapted to be combusted in a combustion unit to result in a combustion exhaust gas, said fuel improving the efficiency of an electrostatic precipitator used to collect fly ash from the combustion gas. The fuel comprises an effective amount of a source of manganese. Alternatively, the invention is an additive for a fuel wherein the fuel additive comprises an effective amount of a source of manganese. Alternatively, the additive may be adapted to be injected into the combustion exhaust gas, said additive comprising an effective amount of a source of manganese. [0014] In a still further embodiment, a fuel that is adapted to be combusted in a combustion unit to result in a combustion exhaust gas reduces back-corona discharge in an electrostatic precipitator used to collect fly ash from the combustion exhaust gas. The fuel comprises an effective amount of a source of manganese. Alternatively, an additive for a fuel may comprise an effective amount of manganese. Still further, an additive comprising an effective amount of a source of manganese; or organic and inorganic compounds of transition metals, actinides, lanthanides, alkali or alkaline earth metals metalloids, halogens, phosphorous, or sulfur; or an oxygenate may be injected into the combustion exhaust gas resulting from the combustion of a fuel in a combustion unit. [0015] In another alternative embodiment, the invention includes a method for improving the efficiency of an electrostatic precipitator used to collect fly ash from a combustion exhaust gas resulting from the combustion of a fuel and combustion air in a combustion unit. The method comprises adding to the combustion air an effective amount of a source of manganese. [0016] In another further embodiment, the invention includes a method of reducing back-corona discharge in an electrostatic precipitator used to collect fly ash from a combustion exhaust gas resulting from the combustion of a fuel and combustion air in a combustion unit. The method comprises adding to the combustion air an effective amount of a source of manganese or an effective amount of an inorganic or organic compound of transition metals, actinides, lanthanides, alkali or alkaline earth metals, metalloids, halogens, phosphorous or sulfur. BRIEF DESCRIPTION OF THE DRAWINGS [0017] FIG. 1 is a graph demonstrating comparative fly ash resistivities of a combustion gas during a trial experiment. [0018] FIG. 2 is a graph demonstrating the fly ash mineral composition change as a result of the addition of a manganese source to the fuel in the trial experiment. [0019] FIG. 3 demonstrates that an increase in resistivity during the trial experiment did not result in back-corona discharge. (See FIG. 4). [0020] FIG. 4 is a graph demonstrating the oil usage versus stack opacity of a portion of the trial run of the present invention. Continue reading... Full patent description for Use of manganese compounds to improve the efficiency of and reduce back-corona discharge on electrostatic precipitators Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Use of manganese compounds to improve the efficiency of and reduce back-corona discharge on electrostatic precipitators patent application. ###  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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