Methods for removing impurities from coal including neutralization of a leaching solution

Abstract

A method for removing at least one impurity from coal is provided. The method comprises providing coal having a plurality of impurities and contacting the coal with a first leaching solution. The first leaching solution reacts with at least one of the impurities to produce one or more first products soluble in the first leaching solution. The method further comprises adding a neutralizing composition to the first leaching solution. The neutralizing composition reacts with the first leaching solution to form a precipitate. The method further comprises separating at least a portion of the first leaching solution from the coal and the precipitate and contacting the coal and the precipitate with a second leaching solution. The second leaching solution reacts with at least one of the impurities and the precipitate to form one or more second products and one or more third products, respectively, the second products and the third products being soluble in the second leaching solution. The method further comprises separating at least a portion of the second leaching solution from the coal.

1 . A method for removing at least one impurity from coal, the method comprising:
 providing coal having a plurality of impurities;   contacting the coal with a first leaching solution, wherein the first leaching solution reacts with at least one of the impurities to produce one or more first products soluble in the first leaching solution;   adding a neutralizing composition to the first leaching solution, wherein the neutralizing composition reacts with the first leaching solution to form a precipitate;   separating at least a portion of the first leaching solution from the coal and the precipitate; and   contacting the coal and the precipitate with a second leaching solution, wherein the second leaching solution reacts with at least one of the impurities and the precipitate to form one or more second products and one or more third products, respectively, the second products and the third products being soluble in the second leaching solution; and   separating at least a portion of the second leaching solution from the coal.   
     
     
         2 . The method of  claim 1 , wherein the neutralizing composition comprises calcium hydroxide, sodium hydroxide, or combinations thereof. 
     
     
         3 . The method of  claim 1 , wherein the neutralizing composition has a neutralizing reactant concentration ranging from about 1 M to about 10 M. 
     
     
         4 . The method of  claim 1 , wherein the first leaching solution comprises a hydrofluoric acid solution, the neutralizing composition comprises calcium hydroxide, the precipitate comprises a calcium fluoride, and the one or more third products comprise calcium ions, nitrate ions, or combinations thereof. 
     
     
         5 . The method of  claim 1 , wherein the first leaching solution comprises a hydrofluoric acid solution, a nitric acid solution, a hydrochloric acid solution, a hydrofluorosilicic acid solution, or combinations thereof. 
     
     
         6 . The method of  claim 1 , wherein the first leaching solution comprises a hydrofluoric acid solution having a hydrofluoric acid concentration ranging from about 3 M to about 10 M. 
     
     
         7 . The method of  claim 1 , wherein the neutralizing composition reacts with the first leaching solution to neutralize substantially all of the first leaching solution. 
     
     
         8 . The method of  claim 1 , wherein the second leaching solution comprises nitric acid, aluminum nitrate, ferric nitrate, fluoronitrate, hydroxide, hydroxyl fluoride, hydroxynitrate, ions thereof, or combinations thereof. 
     
     
         9 . The method of  claim 1 , wherein the second leaching solution comprises a nitric acid solution having a nitric acid concentration ranging from about 0.1 M to about 5 M. 
     
     
         10 . The method of  claim 1 , wherein the method is carried out in a batch reactor chamber. 
     
     
         11 . A method for removing at least one impurity from coal, the method comprising:
 providing coal having a plurality of impurities;   contacting the coal with a first leaching solution, wherein the first leaching solution reacts with at least one of the impurities to produce one or more first products soluble in the first leaching solution;   separating at least a portion of the first leaching solution from the coal as an unreacted first leaching solution;   adding a neutralizing composition to the unreacted first leaching solution, wherein the neutralizing composition reacts with the unreacted first leaching solution to form a precipitate;   separating at least a portion of the unreacted first leaching solution from the precipitate;   contacting the coal and the precipitate with a second leaching solution, wherein the second leaching solution reacts with at least one of the impurities and the precipitate to form one or more second products and one or more third products, respectively, the second products and the third products being soluble in the second leaching solution; and   separating at least a portion of the second leaching solution from the coal.   
     
     
         12 . The method of  claim 11 , wherein the neutralizing composition comprises calcium hydroxide, sodium hydroxide, or combinations thereof. 
     
     
         13 . The method of  claim 11 , wherein the neutralizing composition has a neutralizing reactant concentration ranging from about 1 M to about 10 M. 
     
     
         14 . The method of  claim 11 , wherein the first leaching solution comprise a hydrofluoric acid solution, the neutralizing composition comprises calcium hydroxide, the precipitate comprises a calcium fluoride, and the one or more third products comprise calcium ions, nitrate ions, or combinations thereof. 
     
     
         15 . The method of  claim 11 , wherein the first leaching solution comprises a hydrofluoric acid solution, a nitric acid solution, a hydrochloric acid solution, a hydrofluorosilicic acid solution, or combinations thereof. 
     
     
         16 . The method of  claim 11 , wherein the first leaching solution comprises a hydrofluoric acid solution having a hydrofluoric acid concentration ranging from about 3 M to about 10 M. 
     
     
         17 . The method of  claim 11 , wherein the neutralizing composition reacts with the unreacted first leaching solution to neutralize substantially all of the unreacted first leaching solution. 
     
     
         18 . The method of  claim 11  wherein the second leaching solution comprises nitric acid, aluminum nitrate, ferric nitrate, fluoronitrate, hydroxide, hydroxyl fluoride, hydroxynitrate, ions thereof, or combinations thereof. 
     
     
         19 . The method of  claim 11 , wherein the second leaching solution comprises a nitric acid solution having a nitric acid concentration ranging from about 0.1 Mto about 5 M. 
     
     
         20 . The method of  claim 11 , wherein the method is carried out in a batch reactor chamber.