Method of co-producing activated carbon in a circulating fluidized bed gasification process

Abstract

A method of co-producing activated carbon in a circulating, fluidized bed gasification process includes gasifying carbonaceous fuel in a fluidized bed to form syngas and char, activating the char to form particles of activated carbon, discharging syngas and particulate solids entrained with the syngas from the reactor, separating entrained solids from the syngas with a particle separator and returning at least a portion of the separated solids to the reaction chamber, but allowing a solids product, including activated carbon and having an average size smaller than a predetermined size, to exit the particle separator with the syngas. The solids product is separated from the syngas in a dust separator to form cleaned syngas, and both the cleaned syngas and the solids product are discharged from the gasifier.

1 . A method of co-producing activated carbon in a circulating fluidized bed gasification process, the method comprising the steps of: 
 (a) feeding carbonaceous fuel to a reaction chamber of a gasifier to form a particle bed in the reaction chamber;    (b) fluidizing the particle bed with oxygenous gas to partially oxidize the fuel to form syngas and char;    (c) feeding an activation agent comprising at least one of steam and carbon dioxide to the reaction chamber to activate the char to form particulate of activated carbon;    (d) discharging syngas and particulate solids entrained with the syngas from the reaction chamber;    (e) separating entrained solids from the syngas with a particle separator and returning at least a portion of the separated solids through a return duct to the reaction chamber, but allowing a solids product, comprising entrained solids of activated carbon and having an average size smaller than a predetermined size, to exit the particle separator with the syngas;    (f) separating the solids product from the syngas in a dust separator to form cleaned syngas;    (g) discharging the cleaned syngas from the dust separator;    (h) discharging the solids product from the dust separator;    (i) supplying the cleaned syngas to a location for use in at least one of a combustion process and a chemical process; and    (j) supplying the separated solids product to a location for use in removing contaminants from a fluid.    
     
     
         2 . The method of  claim 1 , further comprising the step of utilizing the separated solids product to remove contaminants from a fluid.  
     
     
         3 . The method of  claim 2 , wherein the separated solids product is used to remove contaminants in at least one of a water purification process, a wastewater treatment process, a sugar refining process, a beverage filtration process, and an air pollution control process.  
     
     
         4 . The method of  claim 2 , wherein the separated solids product is used in capturing mercury from the flue gases of a combustion process.  
     
     
         5 . The method of  claim 1 , wherein the gasifier is operated at a pressure of between about 2 bar and about 70 bar.  
     
     
         6 . The method of  claim 5 , wherein the gasifier is operated at a pressure of between about 10 bar and about 20 bar.  
     
     
         7 . The method of  claim 1 , wherein the predetermined size is less than about 60 μm.  
     
     
         8 . The method of  claim 7 , wherein the predetermined size is less than about 45 μm.  
     
     
         9 . The method of  claim 1 , further comprising the step of activating the char with at least one of steam and carbon dioxide in a fluidized bed in a hot loop of the gasifier.  
     
     
         10 . The method of  claim 9 , wherein the fuel comprises bituminous coal.  
     
     
         11 . The method of  claim 1 , wherein the average activation time for the solids product is at least about twenty (20) minutes.  
     
     
         12 . The method of  claim 11 , wherein the average activation time for the solids product is at least about forty (40) minutes.  
     
     
         13 . The method of  claim 9 , wherein the average activation time for the solids product is at least about one (1) hour.  
     
     
         14 . The method of  claim 9 , wherein the fluidized bed in the hot loop is maintained at a temperature of at least about 800° C.  
     
     
         15 . The method of  claim 14 , wherein the fluidized bed in the hot loop is fluidized with oxygenous gas.