Method To Improve The Efficiency Of Removal Of Liquid Water From Solid Bulk Fuel Materials

Abstract

The invention provides methods to efficiently reduce the water concentration of raw solid fuels, including low rank coals such as brown coal, lignite, subbituminous coal, and other carbonaceous solids. Efficiently drying these materials at low temperatures significantly reduces greenhouse gas emissions and allows the production of low-rank coals for gasification and liquifaction.

1 . A method of treating a solid carbonaceous material comprising:
 compacting a solid carbonaceous material under a force of at least about 5000 lb/in 2  to form a compacted carbonaceous material; and,   contacting the compacted carbonaceous material with a working fluid, wherein the working fluid causes evaporative drying of the compacted carbonaceous material to form a dried carbonaceous material.   
     
     
         2 . The method of  claim 1 , wherein the solid carbonaceous material is selected from the group consisting of brown coal, lignite, subbituminous coal and mixtures of these materials. 
     
     
         3 . The method of  claim 1 , wherein the solid carbonaceous material has a top size between about 0.1 mm and about 6 mm. 
     
     
         4 . The method of  claim 1 , wherein the solid carbonaceous material has a moisture content between about 15 weight percent and about 65 weight percent. 
     
     
         5 . The method of  claim 1 , wherein the solid carbonaceous material has a temperature between about 17° C. and about 66° C. 
     
     
         6 . The method of  claim 1 , wherein the force is between about 5000 lb/in 2  and about 50000 lb/in 2 . 
     
     
         7 . The method of  claim 1 , wherein the working fluid is selected from the group consisting of unsaturated air, nitrogen, inert gas, flue gas, superheated steam and mixtures of these fluids. 
     
     
         8 . The method of  claim 1 , wherein the contacting comprises applying the working fluid to the compacted carbonaceous material in at least one of a stockpile of the compacted carbonaceous material and a rotary dryer containing the carbonaceous material. 
     
     
         9 . The method of  claim 1 , wherein the contacting comprises contacting the compacted carbonaceous material on a conveyor with a working fluid flowing past the conveyed material. 
     
     
         10 . The method of  claim 1 , further comprising collecting dust created in the contacting step and returning the collected dust to a solid carbonaceous material for the compacting step. 
     
     
         11 . The method of  claim 1 , further comprising compacting the dried carbonaceous material to form a shaped compacted material. 
     
     
         12 . The method of  claim 11 , wherein the shaped compacted material is a briquette of ovoid shape with a minor dimension between about 6 mm and about 100 mm. 
     
     
         13 . The method of  claim 11 , wherein the shaped compacted material has a moisture content between about 7 weight percent and about 17 weight percent.