Proppant Material Incorporating Fly Ash and Method of Manufacture

Abstract

A relatively low density, high strength round proppant material having (i) a round core made of a sintered mixture of fly ash and clay or, in same instances, fly ash, clay, and bauxite; and (ii) an outer shell made of sintered bauxite, and a method of making the same.

What is claimed is: 
     
         1 . A round proppant material comprising:
 a core comprising fly ash, bauxite, and clay wherein the fly ash is the primary component by weight; and   a coating comprising bauxite surrounding the core.   
     
     
         2 . The proppant of  claim 2 , wherein the core comprises about 70% fly ash, about 15% bauxite, and about 15% clay. 
     
     
         3 . The proppant of  claim 2 , wherein an iron oxide content of the fly ash is 12% or less. 
     
     
         4 . The proppant of  claim 2 , wherein an iron oxide content of the fly ash is about 7% or less. 
     
     
         5 . The proppant of  claim 2 , wherein an iron oxide content of the fly ash is about 4% or less. 
     
     
         6 . The proppant of  claim 2 , wherein the clay comprises kaolin clay. 
     
     
         7 . The proppant of  claim 2 , wherein the coating comprises more than one layer of coating. 
     
     
         8 . A round proppant material comprising:
 a core comprising lignite fly ash and clay wherein the fly ash is the primary component by weight; and   a coating comprising bauxite surrounding said core.   
     
     
         9 . The proppant of  claim 8 , wherein an iron oxide content of the fly ash is 12% or less. 
     
     
         10 . The proppant of  claim 8 , wherein an iron oxide content of the fly ash is about 7% or less. 
     
     
         11 . The proppant of  claim 8 , wherein an iron oxide content of the fly ash is about 4% or less. 
     
     
         12 . The proppant of  claim 8 , wherein the clay comprises kaolin clay. 
     
     
         13 . The proppant of  claim 8 , wherein the coating content of the proppant is about 5% or less. 
     
     
         14 . A method for manufacturing a round proppant material comprising the steps of:
 forming round granules comprising lignite fly ash and clay wherein the fly ash is the primary component by weight;   coating the round granules with a coating comprising bauxite to form coated round granules;   heating the coated round granules to a temperature of at least 1080° C.   
     
     
         15 . The method of  claim 14 , wherein the coated round granules are heated to a temperature in a range between 1080° C. and 1100° C. 
     
     
         16 . The method of  claim 14 , wherein the heating step comprises:
 calcining said coated round granules at a temperature in a range between 900° C. and 1150° C.; and   sintering said coated round granules at a temperature of at least about 1200° C.   
     
     
         17 . The method of  claim 14  in which said coating comprising bauxite is applied in more than one layer. 
     
     
         18 . The method of  claim 14  in which said coating is applied in powder form. 
     
     
         19 . The method of  claim 14  in which said coating is applied in the form of a slurry containing powdered bauxite. 
     
     
         20 . The method of  claim 14  in which said coating is applied in the form of a slurry comprising powdered bauxite and a binder.