System and method for preparation of solid biomass by torrefaction
First Claim
1. A method for preparing a torrefied biomass fuel, the method comprising:
- extracting moisture from a relatively wet biomass fuel in a dryer to produce a relatively dry biomass fuel;
extracting all remaining moisture from the relatively dry biomass fuel using steam at a temperature of about 482°
C. (900°
F.) to produce a dried biomass fuel;
conveying the dried biomass fuel downward using gravity for subsequent processing;
torrefying the dried biomass fuel to produce the torrefied biomass fuel and torrefaction gases;
venting a gaseous mixture of the steam and the torrefaction gases to a heat exchanger;
heating the gaseous mixture via heat exchange with a flue gas; and
using the heated gaseous mixture to support the extraction of the remaining moisture from the relatively dry biomass and the torrefaction of the dried biomass fuel.
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Accused Products
Abstract
Methods and systems for preparing a torrefied biomass fuel are disclosed. Moisture is initially extracted from relatively wet biomass fuel to produce a relatively dry biomass fuel. Remaining moisture is then extracted from the relatively dry biomass fuel in a final drying stage, using steam at a temperature of about 900° F. The resulting dried biomass fuel is conveyed downward using gravity and undergoes torrefaction, which produces torrefied biomass fuel and torrefaction gases. A gaseous mixture of steam and torrefaction gases is vented to a heat exchanger, where the gaseous mixture is heated by a flue gas, and the heated gaseous mixture is used to support the extraction of the remaining moisture in the final drying stage and to support the torrefaction of the dried biomass fuel. Embodiments disclosed herein efficiently use available energy resources to the benefit of manufacturers, consumers, and the environment.
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Citations
17 Claims
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1. A method for preparing a torrefied biomass fuel, the method comprising:
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extracting moisture from a relatively wet biomass fuel in a dryer to produce a relatively dry biomass fuel; extracting all remaining moisture from the relatively dry biomass fuel using steam at a temperature of about 482°
C. (900°
F.) to produce a dried biomass fuel;conveying the dried biomass fuel downward using gravity for subsequent processing; torrefying the dried biomass fuel to produce the torrefied biomass fuel and torrefaction gases; venting a gaseous mixture of the steam and the torrefaction gases to a heat exchanger; heating the gaseous mixture via heat exchange with a flue gas; and using the heated gaseous mixture to support the extraction of the remaining moisture from the relatively dry biomass and the torrefaction of the dried biomass fuel. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A torrefaction system comprising:
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a dryer configured to dry a relatively wet biomass fuel and provide a relatively dry biomass fuel; a torrefaction reactor comprising; an upper chamber configured to remove all moisture from the relatively dry biomass fuel in an environment containing steam at a temperature of about 482°
C. (900°
F.), anda lower chamber configured to torrefy dried biomass produced by the upper chamber at a temperature between about 250°
C.-300°
C. (482°
F.-572°
F.);a combustion unit configured to combust a portion of a gaseous mixture of steam and torrefaction gases vented by the torrefaction reactor to produce a flue gas; and a heat exchanger configured to exchange heat from the flue gas to the gaseous mixture to provide a heated gaseous mixture for provision to the torrefaction reactor. - View Dependent Claims (11, 12, 14, 15, 16, 17)
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13. The torrefaction system of claim 13, wherein the torrefaction reactor further comprises entry ports coupled to a damper system, the damper system configured to supply and maintain a gas mixture temperature into the upper chamber to remain at about 482°
- C. (900°
F.) and the temperature in the lower chamber to between about 250°
C.-300°
C. (482°
F.-572°
F.).
- C. (900°
Specification