Fuel slurry heating system and method

Abstract

The disclosed embodiments relate to systems and methods for heating a slurry to increase a solids concentration of the slurry while maintaining the viscosity of the slurry below a threshold viscosity. For example, in one embodiment, a system includes a fuel slurry preparation system having a slurry tank configured to hold a fuel slurry, the fuel slurry having a solid fuel and a liquid. The fuel slurry preparation system also includes a heat source and a controller configured to control the heat source to heat the fuel slurry to decrease a viscosity of the slurry below a threshold viscosity.

1 . A method for generating a fuel slurry for a gasification process, comprising:
 monitoring one or more parameters of the fuel slurry in a vessel with a controller, wherein the one or more parameters comprise a viscosity of the fuel slurry and a solids concentration of the fuel slurry, and the fuel slurry comprises a solid fuel and a liquid; and   maintaining the fuel slurry below an upper viscosity threshold by heating the fuel slurry in the vessel, wherein the upper viscosity threshold is at a transition between a pumpable viscosity and an unpumpable viscosity of the fuel slurry by a slurry pump configured to pump the fuel slurry.   
     
     
         2 . The method of  claim 1 , comprising removing a portion of the liquid from the fuel slurry to increase the solids concentration of the fuel slurry after heating the fuel slurry. 
     
     
         3 . The method of  claim 2 , wherein removing the portion of the liquid from the fuel slurry comprises removing the portion of the liquid from the fuel slurry via a liquid removal unit disposed downstream of the vessel. 
     
     
         4 . The method of  claim 1 , comprising adding additional fuel to the fuel slurry to increase the solids concentration of the fuel slurry after heating the fuel slurry. 
     
     
         5 . The method of  claim 3 , wherein adding the additional fuel to the fuel slurry comprises adding the additional fuel to the fuel slurry via a fuel supply unit disposed downstream of the vessel. 
     
     
         6 . The method of  claim 1 , wherein heating the fuel slurry comprises directing heat from a steam source in a gasification plant to the vessel. 
     
     
         7 . The method of  claim 6 , wherein directing the heat to the vessel comprises outputting a flow of steam into the vessel via a steam sparging applicator to directly contact the fuel slurry with the steam in the vessel. 
     
     
         8 . The method of  claim 6 , wherein directing the heat to the vessel comprises directing a flow of steam to an indirect heat exchanger disposed in the vessel to transfer heat from the flow of steam to the fuel slurry in the vessel. 
     
     
         9 . The method of  claim 6 , wherein directing the heat to the vessel comprises directing a flow of steam to a heating jacket at least partially surrounding the vessel. 
     
     
         10 . The method of  claim 1 , comprising receiving the solid fuel, reducing a particle size of the solid fuel, receiving the liquid, and mixing the solid fuel with the liquid within a mill to form a resulting mixture, and directing the resulting mixture to the vessel. 
     
     
         11 . A method, comprising:
 preparing a fuel slurry in a mill, wherein the fuel slurry comprises a solid fuel and a liquid, and the preparation of the fuel slurry comprises receiving the solid fuel, reducing a particle size of the solid fuel, receiving the liquid from a liquid supply, and mixing the solid fuel with the liquid;   heating the fuel slurry in a closed vessel disposed downstream of the mill, the heating comprising directing steam from a steam source in a gasification plant to the vessel;   monitoring a viscosity of the fuel slurry and a solids concentration of the fuel slurry with a controller; and   adjusting, with the controller, a flow of the steam from the steam source to maximize the solids concentration of the fuel slurry while maintaining the viscosity of the fuel slurry at a pumpable viscosity by a slurry pump configured to pump the fuel slurry.   
     
     
         12 . The method of  claim 11 , wherein the heating of the fuel slurry comprises outputting the flow of the steam from the steam source into the vessel via a steam sparging applicator to directly contact the fuel slurry with the steam in the vessel. 
     
     
         13 . The method of  claim 11 , wherein the heating of the fuel slurry comprises directing the flow of the steam from the steam source to an indirect heat exchanger disposed in the vessel to transfer heat from the flow of steam to the fuel slurry to form a cooled flow of steam. 
     
     
         14 . The method of  claim 11 , wherein the heating of the fuel slurry comprises directing the flow of the steam from the steam source to a heating jacket at least partially surrounding the vessel to form a cooled flow of steam. 
     
     
         15 . The method of  claim 13 , comprising directing the cooled flow of steam to the liquid supply. 
     
     
         16 . The method of  claim 14 , comprising directing the cooled flow of steam to the liquid supply. 
     
     
         17 . The method of  claim 11 , comprising adding, with the controller, an additional amount of solid fuel to the fuel slurry. 
     
     
         18 . A gasification method, comprising:
 using a controller to control a solids concentration of a fuel slurry, the controller comprising:
 one or more tangible, non-transitory, machine-readable media collectively storing one or more sets of instructions; and 
 one or more processors configured to execute the one or more sets of instructions, wherein controlling the solids concentration comprises:
 controlling a liquid supply to deliver liquid to a mill, wherein the liquid is mixed with a solid fuel in the mill to form the fuel slurry, wherein the fuel slurry is transferred to a vessel disposed downstream of the mill; 
 controlling a first flow of steam from a steam source in a gasification plant to heat the fuel slurry in the vessel; and 
 controlling a fuel supply unit disposed downstream of the vessel to add an additional amount of solid fuel to the fuel slurry. 
 
   
     
     
         19 . The gasification method of  claim 18 , wherein controlling the solids concentration comprises controlling a second flow of steam from the steam source to a liquid removal unit disposed downstream of the vessel to add an additional amount of liquid to the fuel slurry. 
     
     
         20 . The gasification method of  claim 18 , wherein controlling the solids concentration comprises controlling the fuel supply unit to add the additional amount of solid fuel to the fuel slurry in response to a signal, generated by a transducer coupled to a fuel slurry flow path coupling the vessel and a gasifier, representative of a solids concentration, a viscosity, a temperature, or a combination, of the fuel slurry in the fuel slurry flow path.