Method of drying biomass

Abstract

A process for torrefaction of biomass is provided in which biomass are passed into a fluidized bed reactor and heated to a predetermined temperature in an oxidizing environment. The dried biomass is then fed to a cooler where the temperature of the product is reduced to approximately 100 degrees Fahrenheit.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application is a Continuation In Part of U.S. patent application Ser. No. 13 / 084,697 filed on Apr. 12, 2011, which issued as U.S. Pat. No. 8,956,426 on Feb. 17, 2015, which is a Continuation In Part of U.S. patent application Ser. No. 12 / 763,355, filed Apr. 20, 2010, the entire disclosures of which are incorporated by reference herein.FIELD OF THE INVENTION[0002]Embodiments of the present invention generally relate to thermal processing of biomass “torrefaction” so that it can be used instead of, or in addition to, coal for energy production. In one embodiment of the present invention, the biomass is “roasted” in the presence of oxygen wherein heat generated by the combustion of biomass and hot gases associated with biomass combustion provide the heat required to support the torrefaction process, all in a single reactor.BACKGROUND OF THE INVENTION[0003]Many states have adopted Renewable Portfolio Standards (RPS) that require electrici...

AI Technical Summary

Benefits of technology

The present invention is about a process for torrefying biomass to produce a material that can be handled and burned like coal. The process involves adding biomass to a reactor, adding enriched gas, controlling the oxygen content, and initiating heating of the biomass. The biomass is then maintained at a high temperature for a predetermined time. During this process, water is removed, volatile organic compounds are vaporized, and the biomass is torrefied. The torrefied biomass is then combusted to help maintain the temperature of the reactor. The process results in a biomass material with improved grindability and handling characteristics, reduced moisture content, increased heating value, and improved energy density. The process can be used in existing coal burning power plants without needing major modifications. The patent also describes an alternative method for starting combustion in the reactor using excess heat. Overall, the invention provides a more efficient and economical way to process biomass for energy production.

Problems solved by technology

The trapped moisture cannot be used as fuel and increases costs associated with transportation of the biomass.

Thus biomass is a low grade, high cost fuel that cannot compete economically with the fuel most commonly used to generate electricity—coal.

Further, biomass has a low bulk density, is very hydrophilic, is seasonal, is variable, and has a limited shelf life.

In addition, during the torrefaction process, molecules of biopolymers (cellulose, hemicelluloses and lignin) contained in the biomass decompose.

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