Fuel from ash

Abstract

Coal ash, which also consists of fly ash, is a very fine granular solid residue obtained as a by-product of coal combustion. The invention relates to the surprising result that a fuel can be obtained from coal ash. The process involves a pneumatic separation of the coal ash at relatively low temperatures. The coal ash is separated into at least two size fractions. The size fractions obtained by the process of this invention include at least one with lower carbon and another containing increased levels of carbon in the range of 50% by weight and a heating value in the range of 4000 to 6000 Btu/lb.

1 . A process for producing a fuel from a coal ash having an initial carbon amount, comprising; 
 a pneumatic separation of the coal ash into at least two size fractions; 
 the separation taking place in a solid-gas contactor in association with a classifier means, wherein  
 the two size fractions comprise when separated, a major fine fraction, and 
 a minor coarse fraction, being the fuel, and containing at least 45% of the initial carbon fuel amount, and  
 
   a recovery of the fuel.    
     
     
         2 . The process according to  claim 1 , wherein the initial carbon amount is at least 5% by weight.  
     
     
         3 . The process according to  claim 1 , wherein the initial carbon amount is at least 10% by weight.  
     
     
         4 . The process according to  claim 1 , wherein the initial carbon amount is at least 14% by weight.  
     
     
         5 . The process according to  claim 1 , wherein the fine fraction has a particle size distribution of less than 45 μm and the coarse fraction has a particle size distribution of greater than or equal to 45 μm.  
     
     
         6 . The process according to  claim 1 , wherein the coarse fraction has a particle size distribution greater than or equal to 63 μm.  
     
     
         7 . The process according to  claim 1 , wherein the fuel has a heating value between 4000 and 6000 Btu/lb.  
     
     
         8 . The process according to  claim 1 , wherein the solid-gas contactor is selected from the group consisting of a fluidized bed, a circulating fluidized bed, a transport vessel and a classifying transport vessel.  
     
     
         9 . The process according to  claim 8 , wherein the classifying transport vessel is a Torbed™ toroidal vessel.  
     
     
         10 . The process according to  claim 1 , wherein the separation is conducted at ambient temperature or up to a temperature of 200° C.  
     
     
         11 . The process according to  claim 1 , wherein the classifying means is a cyclone or a bank of cyclones.  
     
     
         12 . The process according to  claim 11 , wherein the classifying means may be placed in series to obtain a number of different size fractions.  
     
     
         13 . A fuel which is derived from a coal ash having an initial carbon amount and produced by, 
 a pneumatic separation of the coal ash wherein the coal ash is separated into at least two fractions;    the separation taking place in a solid-gas contactor in association with a classifier means,    wherein the two size fractions comprising, a major fine fraction, and 
 a minor coarse fraction, being the fuel, and containing at least 45% of the initial carbon fuel amount, and  
   a recovery of the fuel.    
     
     
         14 . The process according to  claim 13 , w wherein the initial carbon amount is at least 5% by weight.  
     
     
         15 . The process according to  claim 13 , wherein the initial carbon amount is at least 10% by weight.  
     
     
         16 . The process according to  claim 13 , wherein the initial carbon amount is at least 14% by weight.  
     
     
         17 . A fuel according to  claim 13 , wherein the fine fraction has a particle size distribution of less than 45 μm and the coarse fraction has a particle size distribution of greater than or equal to 45 μm.  
     
     
         18 . The fuel according to  claim 13 , wherein the coarse fraction has a particle size distribution of greater than or equal to 63 μm.  
     
     
         19 . The fuel according to  claim 13 , wherein the fuel has a heating value between 4000 and 6000 Btu/lb.  
     
     
         20 . The fuel according to  claim 13 , wherein the circulating solid-gas contactor is selected from the group consisting of a fluidized bed, a circulating fluidized bed, a transport vessel and a classifying transport vessel.  
     
     
         21 . The fuel according to  claim 20 , wherein the classifying transport vessel is a Torbed™ toroidal vessel.  
     
     
         22 . The fuel according to  claim 13 , wherein the separation is conducted at ambient temperature or up to a temperature of 200° C.  
     
     
         23 . The fuel according to  claim 13 , wherein the classifying means is a cyclone or a bank of cyclones.  
     
     
         24 . The fuel according to  claim 13 , wherein the classifying means may be placed in series to obtain a number of different size fractions.  
     
     
         25 . A method of burning a fuel derived from a coal ash having an initial carbon amount and produced by, 
 a pneumatic separation of the coal ash wherein the coal ash is separated into at least two fractions, 
 the separation taking place in a solid-gas contactor in association with a classifier means,  
 wherein the two size fractions comprising, a major fine fraction, and 
 a minor coarse fraction, being the fuel, and containing at least 45% of the initial carbon fuel amount, and  
 
   a recovery of the fuel; and    a conveyance of the fuel to a combustion system.    
     
     
         26 . The method according to  claim 25 , wherein before the conveyance of the fuel to the combustion system there is an optional agglomeration step.  
     
     
         27 . The method according to  claim 26 , wherein the agglomeration step is a densification of the fuel into briquettes.  
     
     
         28 . The method according to  claim 27 , wherein the combustion system is selected from the group consisting of a coal fired heater, a coal fired boiler, a cement kiln and a coal burning power generating station.