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.

Description

[0001]This application is related to pending U.S. patent application Ser. No. 12 / 763,355, filed Apr. 20, 2010. This application is also related to pending U.S. patent application Ser. No. 12 / 566,174, filed Sep. 24, 2009 (the '174 application“), which is a continuation-in-part of pending U.S. patent application Ser. No. 11 / 316,508, filed Dec. 22, 2005, which is a continuation-in-part of U.S. patent application Ser. No. 10 / 978,768 (the '768 application), now U.S. Pat. No. 7,537,622 filed Nov. 1, 2004, which is a continuation-in-part of abandoned U.S. patent application Ser. No. 09 / 974,320 (the '320 application), filed on Oct. 10, 2001, and a continuation-in-part of the '320 application. The '174 application also claims the benefit of pending U.S. Provisional Patent Application Ser. No. 61 / 212,668, filed Apr. 14, 2009. The entire disclosure of each of the identified patents and patent applications is incorporated by reference herein.FIELD OF THE INVENTION[0002]A multi-stage process for...

AI Technical Summary

Benefits of technology

[0013]It is another aspect of the present invention to both cool and add equilibrium moisture to the treated coal and / or biomass as it exits the second stage or the initial drying stage if no pre-drying is required. It is desirable to add moisture to the processed coal and biomass to reduce the probability of post-drying combustion of the coal portion. Thus, one embodiment employs a fluid spray that cools the coal exiting the drying stage. The water also replaces at least a portion of the coals equilibrium moisture.

Problems solved by technology

This moisture not only does not add to the fuel value, but also increases the transport cost of the material.

In addition, the '978 patent discloses a torrefaction residence time of 0.5 to 5.0 hours and does not disclose a specific cooling methodology.

The '331 application discloses combustion of vapors produced during torrefaction to supply the heat for torrefaction and the subsequent pelletizing of the torrefied product, but does not address product cooling.

With larger reactors, where the output(s) often exceed 1,000 tons per day, the process is often not as efficient.

Without being bound to any particular theory, it is believed that, as the size of the reactor increases, the gas velocity produced in the process increases geometrically, often to the point where the desired density of the fluidized bed used suffers.

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