Clean coal technology microbial wash

Abstract

Described herein are methods, apparatuses, and systems for reducing the sulfur content of coal. Coal is loaded into an apparatus comprising a vertically rotatable drum within a housing. The rotatable drum comprises a perforated cylindrical outer wall, a solid cylindrical inner wall, and a perforated, cylindrical central wall positioned between the outer wall and the inner wall, wherein the coal is loaded into a coal wash annulus between the central wall and the outer wall. A microbial wash fluid flows into a wash fluid annulus between the inner wall and the central wall, wherein the microbial wash fluid contains sulfur digesting bacteria and nutrients for the bacteria. The drum is rotated to cause the microbial wash fluid to migrate from the wash fluid annulus through the coal in the coal wash annulus and collect in a splash wash annulus between the outer wall and the housing.

What is claimed is: 
     
         1 . A method for reducing the sulfur content of coal, comprising the steps of:
 loading the coal into a coal cleaning apparatus comprising a vertically rotatable drum within a housing, the rotatable drum comprising a perforated cylindrical outer wall, a cylindrical inner wall, and a perforated, cylindrical central wall positioned between the outer wall and the inner wall, wherein the coal is loaded into a coal wash annulus between the central wall and the outer wall;   introducing a microbial wash fluid into a wash fluid annulus between the inner wall and the central wall, wherein the microbial wash fluid contains sulfur digesting bacteria and nutrients for the bacteria;   rotating the drum to cause the microbial wash fluid to migrate from the wash fluid annulus through the coal in the coal wash annulus and collect in a splash wash annulus between the outer wall and the housing; and   removing the coal from the coal cleaning apparatus, wherein the sulfur content of the coal is reduced.   
     
     
         2 . The method of  claim 1 , wherein the rotatable drum further comprises reinforcing bars extending radially from a center of the rotatable drum across an upper portion of the wash fluid annulus. 
     
     
         3 . A method for reducing the sulfur content of coal, comprising the steps of:
 loading the coal into a coal cleaning apparatus comprising a vertically rotatable drum within a housing, the rotatable drum comprising a perforated cylindrical outer wall, a cylindrical inner wall, and a perforated, cylindrical central wall positioned between the outer wall and the inner wall, wherein the coal is loaded into a coal wash annulus between the central wall and the outer wall;   introducing a wash fluid into a wash fluid annulus between the inner wall and the central wall, wherein the wash fluid contains bacterial nutrients including a source of nitrogen and phosphorus;   rotating the drum to cause the wash fluid to migrate from the wash fluid annulus through the coal in the coal wash annulus and collect in a splash wash annulus between the outer wall and the housing;   introducing a microbial wash fluid into the wash fluid annulus, wherein the microbial wash fluid contains sulfur digesting bacteria;   rotating the drum to cause the microbial wash fluid to migrate from the wash fluid annulus through the coal in the coal wash annulus and collect in a splash wash annulus between the outer wall and the housing; and   removing the coal from the coal cleaning apparatus, wherein the sulfur content of the coal is reduced.   
     
     
         4 . The method of  claim 3 , wherein the rotatable drum further comprises reinforcing bars extending radially from a center of the rotatable drum across an upper portion of the wash fluid annulus. 
     
     
         5 . A method for reducing the sulfur content of coal, comprising the steps of:
 loading the coal into a coal cleaning apparatus comprising a vertically rotatable drum within a housing, the rotatable drum comprising a perforated cylindrical outer wall, a cylindrical inner wall, and a perforated, cylindrical central wall positioned between the outer wall and the inner wall, wherein the coal is loaded into a coal wash annulus between the central wall and the outer wall;   introducing a microbial wash fluid into a wash fluid annulus between the inner wall and the central wall, wherein the microbial wash fluid contains sulfur digesting bacteria and nutrients for the bacteria;   removing the coal and the microbial wash fluid from the coal cleaning apparatus; and   allowing the bacteria to digest the sulfur during transportation or storage of the coal.