Burnout of residual carbon in coal fly ash using air cyclones

Abstract

This patent application is for the novel utilization of an air cyclone combustion unit (CCU) for burnout of residual carbon from burning of fly ash resulting from coal and/or coke in electric power plants or from natural pozzolans. In some cases, residual carbon and/or moisture is too high in fly ash or pozzolans to meet market conditions for quality or ASTM C 618 Specification for Natural Pozzolans and Coal Fly Ash. Heat treating the coal fly ash or natural pozzolan to remove sufficient amounts of carbon renders the remaining pozzolan capable of meeting specifications and being sufficient in quality to perform as a cementitious material in concrete and mortars. Use of an air cyclone, with suitable mechanical adjustments and heat either from an external source or with the inherent heat value from the residual carbon will be claimed.

1 . A cyclonic combustion unit consisting of one or more cyclones or combustion chambers outfitted with a feed mechanism to feed one or more materials, two or more sources of fuel combustion utilizing added fuel sources, a means of cooling the resulting exit gasses and materials, a dust collecting system for collecting the product of the unit and a fan for moving gasses through the system. 
     
     
         2 . The combustion unit described in  claim 1  wherein said material fed into the system consists of coal fly ash, natural pozzolan, cement, cement kiln dust, slag, kaolin, bentonite, salts of metallic carbonates such as calcium, potassium, sodium, etc, hydrated lime, quicklime, clay burned lime, dirt, compost and mineral or feed stocks with compositions to modify the composition of the fed materials either chemically or mineralogically. 
     
     
         3 . The combustion unit according to  claim 1  which further comprises a chamber connected to a feed system that has been heated with externally supplied fuel. 
     
     
         4 . The combustion unit according to  claim 1  that is outfitted with a system that conveys the feed from the feed and initial fueled heat system by air into the main body of the cyclone. The configuration of the combustion can be cylindrical, square or other geometric configuration. 
     
     
         5 . The combustion unit according to  claim 1  that is outfitted with an internal pipe or “thimble” reaching down into the cyclone and attached to the exhaust section of the cyclone. 
     
     
         6 . The combustion unit according to  claim 5  in which the internal thimble connected to the exhaust section of the cyclone is adjustable in length. 
     
     
         7 . The cyclonic combustion unit in  claim 3  in which is outfitted with a source of external fueled heat. 
     
     
         8 . The combustion unit described in  claim 1  in which the fuel may be feed into the cyclone at its periphery or near the adjustable internal pipe. 
     
     
         9 . An embodiment of the cyclonic combustion system described in  claim 1  in which the primary initial combustion zone fuel is from different points of ignition and/or made up of different fuels, including natural gas, liquefied petroleum gasses such as propane or butane, coal, coke, fuel oil, waste automotive oil or waste cooking grease or oil. 
     
     
         10 . An embodiment of the cyclonic combustion system described in  claim 1  in which the primary flame(s) at the secondary combustion zone fuel in the cyclone is from different points of ignition and/or made up of different fuels, including natural gas, liquefied petroleum gasses such as propane or butane, coal, coke, fuel oil, waste automotive oil or waste cooking grease or oil. 
     
     
         11 . An embodiment of the cyclonic combustion system described in  claim 1  in which heat may be from a tertiary source such as waste heat from another system. 
     
     
         12 . The cyclonic combustion system described in  claim 1  in which the exhaust from the cyclone is outfitted with a duct in which there is a water spray, air, water jacket or product cooling system. 
     
     
         13 . An embodiment of the cyclonic combustion system described in  claim 1  in which there is a dust collection system consisting of a second cyclone, set of cyclones, baghouse or electrostatic precipitator to collect the product from the cyclone and heat treatment therein. 
     
     
         14 . An embodiment of the cyclonic combustion system described in  claim 1  in which there is a fan to induce either heated or ambient air, oxygen in part or in total to support combustion of the fuels used for heating the materials. 
     
     
         15 . An embodiment of a Cyclonic Combustion Unit capable of heat treating coal fly ash or natural pozzolan to remove sufficient amounts of carbon and/or moisture and render the resultant fly ash capable of exhibiting pozzolanic or cementitious properties. The resulting minerals will be sufficient in quality to competitively perform as a cementitious material in concrete, mortars or cementitious products. 
     
     
         16 . A cyclonic combustion unit according to  claim 15  in which valves are inserted in the areas at the lower end of the cyclone(s) and primary feed section to remove coarse fractions of minerals that form during combustion and handling. 
     
     
         17 . An embodiment of the cyclonic combustion system described in  claim 15  in which a device is inserted into the exhaust portion of the cyclone to capture mercury vapors. 
     
     
         18 . An embodiment of the cyclonic combustion system described in  claim 15  in which the fuel is provided to the heating zones of the CCU are outfitted with pipes to which is attached a means of increasing turbulence within the flame, enabling increased oxygen in contact with heated air for improved combustion of carbon or other organic materials in the feed material. 
     
     
         19 . An embodiment of the cyclonic combustion system of the invention in which sulfates and sulfites in the CCP could be reacted with lime containing material added other materials at the feed inlet and minerologically converted during the combustion process to render them harmless and become part of the mineralogy of the CCP materials product. 
     
     
         20 . An embodiment of the cyclonic combustion system described in  claim 19  in which the heated air in the stream (downstream) coming from the cyclone exhaust duct is fitted with an outer shell in which water inlet and outlet ducts are fitted. The purpose of the outer shell is to provide a water-cooling jacket to cool the exhaust air and to some degree the heated product carried by the exhaust air.