Method of Simultaneously Drying Coal and Torrefying Biomass

Abstract

A process for simultaneously drying coal and/or torrefying biomass is provided in which coal and/or biomass are passed into a fluidized bed reactor and heated to a predetermined temperature. The dried coal and/or biomass is then fed to a cooler where the temperature of the product is reduced to approximately 200 degrees Fahrenheit and water is added to further passivate the coal.

1 . A method for drying coal, comprising:
 charging coal to a fluidized bed reactor, said coal having an average moisture content of from about 15 to about 50 percent, and said fluidized bed reactor is comprised of a fluidized bed with a fluidized bed density of from about 20 to about 50 pounds per cubic foot;   charging air to said fluidized bed reactor at a velocity of from about 4 to about 8 feet per second;   subjecting said coal to a temperature of from about 230 to about 350 degrees Centigrade; and   removing water from said coal wherein said fluidized bed reactor is comprised of a fluidized bed with a fluidized bed density of from about 20 to about 50 pounds per cubic foot.   
     
     
         2 . The process of  claim 1 , wherein said coal charged to said fluidized bed reactor is under about 3 inches in size. 
     
     
         3 . The process of  claim 1 , wherein said coal charged to said fluidized bed reactor is classified as bituminous, sub-bituminous or lignite. 
     
     
         4 . The process of  claim 1 , wherein said coal in said fluidized bed reactor is maintained at said temperature of from about 400-650 degrees Fahrenheit. 
     
     
         5 . The process of  claim 1 , wherein said fluidized bed is maintained at a fluidized bed density of from about 20 to about 50 pounds per cubic foot. 
     
     
         6 . The process of  claim 1 , wherein said coal has a residence time in the reactor of about 2 to about 5 minutes. 
     
     
         7 . The process of  claim 1 , further comprising heating said air prior to introduction into said fluidized bed reactor using heat recovered from heated gas taken from said fluidized bed reactor or from the downstream emissions control device. 
     
     
         8 . The process of  claim 1  further comprising a cooler that employs at least one of a mixing screw conveyor, hollow flight screw conveyor, a rotary drum and a rotary tube. 
     
     
         9 . The process of  claim 1 , wherein said reactor comprises at least one water spray to aid in the control of reactor temperature. 
     
     
         10 . The process of  claim 1 , further comprising feeding said dried coal into a cooler where it is cooled to a temperature below 100 degrees Centigrade and mixed with water to restore a portion of the product's equilibrium moisture. 
     
     
         11 . The process of  claim 10  wherein the application of water is continuous. 
     
     
         12 . A process for biomass torrefaction, comprising:
 charging biomass to a fluidized bed reactor, said biomass charged to said fluidized bed reactor has an average moisture content of from about 15 to about 50 percent, and said fluidized bed reactor is comprised of a fluidized bed with a fluidized bed density of from about 20 to about 50 pounds per cubic foot;   charging air to said fluidized bed reactor at a velocity of from about 3 to about 8 feet per second;   subjecting said biomass to a temperature of from about 230 to about 350 degrees Centigrade wherein said air is heated using heat recovered from heated gas taken from said fluidized bed reactor, heated gas taken from the reactor associated with drying coal, or heated gas taken from the process emissions control device; and   torrefying said biomass wherein:
 said biomass charged to said fluidized bed reactor has an average moisture content of from about 15 to about 50 percent, and 
 said fluidized bed reactor is comprised of a fluidized bed with a fluidized bed density of from about 20 to about 50 pounds per cubic foot. 
   
     
     
         13 . The process of  claim 12 , wherein said biomass charged to said fluidized bed reactor has a minimum dimension of about 3 mm to about 10 mm. 
     
     
         14 . The process of  claim 12 , wherein said biomass charged to said fluidized bed reactor is wood, plant material or agricultural waste. 
     
     
         15 . The process of  claim 12 , wherein said biomass has a residence time in the reactor of 2 to 15 minutes. 
     
     
         16 . The process of  claim 12  further comprising a cooler that employs at least one of a mixing screw conveyor, hollow flight screw conveyor, a rotary drum and a rotary tube. 
     
     
         17 . The process of  claim 12 , wherein said reactor comprises at least one water spray to aid in the control of reactor temperature. 
     
     
         18 . The process of  claim 12 , further comprising feeding said dried biomass into a cooler where it is cooled to a temperature below 100 degrees Centigrade and mixed with water to restore up to 3% of the product's moisture. 
     
     
         19 . The process of  claim 18  wherein the application of water is continuous. 
     
     
         20 . A process for biomass torrefaction, comprising:
 charging biomass to a fluidized bed reactor, charging air to said fluidized bed reactor at a velocity of from about 4 to about 8 feet per second, subjecting said biomass to a temperature of from about 230 to about 350 degrees Centigrade, and removing the water from said biomass by torrefying said biomass, wherein:   said biomass charged to said fluidized bed reactor has an average moisture content of from about 15 to about 50 percent,
 said fluidized bed reactor is comprised of a fluidized bed with a fluidized bed density of from about 20 to about 50 pounds per cubic foot, whereby a dried, torrefied biomass is produced; and 
   wherein heat used for said single stage process is taken from exhaust associated with a coal drying process.