Synthetic coal and methods of producing synthetic coal from fermentation residue

Abstract

The invention herein describe a novel process for producing a novel synthetic coal product from fermentation residues, such as, the waste materials from fermentation based ethanol production. The fermentation residue is subject to a hydrothermal carbonization process in an aqueous solution at a temperature and at a pressure sufficient to form a synthetic coal solid and a liquid component. This process does not require drying of the fermentation residue which provides for a more energy efficient method of processing thereof. The synthetic coal solid has a high heat content combustive material. The liquid component has nutrient value so that it can be recycled thereby permitting the sustainable recycling of such nutrients and the water in which those nutrients are dissolved.

1 . A method of producing a synthetic coal from a fermentation residue having a low lignocellulosic content, the method comprising the steps of:
 subjecting the fermentation residue to hydrothermal carbonization in an aqueous suspending medium at a temperature of between about 170° C. and about 225° C., at a pressure of between about 0.8 and about 2.41 MPa, for a period of time of less than 4 hours, and separating the resulting synthetic coal from a liquid component.   
     
     
         2 . The method of  claim 1  and further including the step of adding an acidic buffer to the fermentation residue prior to subjecting said residue to hydrothermal carbonization. 
     
     
         3 . The method as defined in  claim 1  and wherein the fermentation residue is thin stillage obtained from the corn based ethanol manufacturing process. 
     
     
         4 . The method as defined in  claim 1  and wherein the fermentation residue is whole stillage obtained from the corn based ethanol manufacturing process. 
     
     
         5 . The method as defined in  claim 1  and wherein the lignocellulosic content is less than 20% by dry weight of the fermentation residue. 
     
     
         6 . The method of  claim 1  and the fermentation residue based synthetic coal produced thereby having an ash content less than both lignocellulosic substrate derived synthetic coals and fossil fuel bituminous coals. 
     
     
         7 . The method of  claim 1  and the fermentation residue based synthetic coal produced thereby having both a nitrogen and hydrogen content greater than both lignocellulosic substrate derived synthetic coals and fossil fuel bituminous coals. 
     
     
         8 . The method of  claim 1  and the fermentation residue based synthetic coal produced thereby having a heat of combustion greater than 10,000 BTU's per pound. 
     
     
         9 . The method of  claim 1  and the fermentation residue based synthetic coal produced thereby having a sulfur content less than both lignocellulosic substrate derived synthetic coals and fossil fuel bituminous coals. 
     
     
         10 . The method of  claim 1  and the fermentation residue based synthetic coal produced thereby having a macroporous structure. 
     
     
         11 . The method of  claim 1  and the liquid component thereof containing an amount of phosphorous comprising substantially all the phosphorous present in the fermentation residue. 
     
     
         12 . A method of producing a synthetic coal from a fermentation residue having a lignocellulosic content less than 20% by dry weight of the fermentation residue, the method comprising the steps of:
 subjecting the fermentation residue to hydrothermal carbonization in an aqueous suspending medium at a temperature of between about 170° C. and about 225° C., at a pressure of between about 0.8 and about 2.41 MPa, for a period of time of less than 4 hours, and   separating the resulting synthetic coal from a liquid component.   
     
     
         13 . The method of  claim 12  and further including the step of adding an acidic buffer to the fermentation residue prior to subjecting said residue to hydrothermal carbonization. 
     
     
         14 . The method as defined in  claim 12  and wherein the fermentation residue is obtained from a corn based ethanol manufacturing facility. 
     
     
         15 . The method of  claim 12  and the fermentation residue based synthetic coal produced thereby having an ash content less than both lignocellulosic substrate derived synthetic coals and fossil fuel bituminous coals. 
     
     
         16 . The method of  claim 15  and the fermentation residue based synthetic coal produced thereby having both a Nitrogen and Hydrogen content greater than both lignocellulosic substrate derived synthetic coals and fossil fuel bituminous coals. 
     
     
         17 . The method of  claim 16  and the fermentation residue based synthetic coal produced thereby having a heat of combustion greater than 10,000 BTU's per pound. 
     
     
         18 . The method of  claim 17  and the fermentation residue based synthetic coal produced thereby having a sulfur content less than both synthetic lignocellulosic substrate derived coals and fossil fuel bituminous coals. 
     
     
         19 . The method of  claim 18  and the fermentation residue based synthetic coal produced thereby having a macroporous structure. 
     
     
         20 . The method of  claim 12  and the liquid component thereof containing phosphorous comprising substantially all the phosphorous present in the fermentation residue.