Methods for the manufacture of fuel pellets and other products from lignocellulosic biomass

Abstract

The present invention is directed to a method for producing products, such as fuel pellets, from lignocellulosic biomass. Lignocellulosic biomass having a moisture content of less than about 30% by weight is introduced into a reactor. A vacuum of less than about 500 torr is applied to the reactor. Steam having a temperature of between about 180° C. and about 235° C. is injected into the reactor. The biomass is maintained in the reactor between about 1 and about 12 minutes. The treated biomass having a moisture content less than about 30% by weight is removed from the reactor. Treated biomass is formed into a pellet.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]The present application claims benefit under 35 U.S.C. §119(e) of U.S. Provisional Application Ser. No. 61 / 352,579, filed Jun. 8, 2010, which is hereby expressly incorporated herein by reference in its entirety.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not applicable.FIELD OF THE INVENTION[0003]The present invention relates generally to a method for making fuel pellets, and more particularly, but not by way of limitation, to a method of making molding compounds and extruded parts, including fuel pellets, from lignocellulosic biomass.BACKGROUND OF THE INVENTION[0004]The high price of fossil fuels and the worldwide interest in replacing fossil fuels and products based upon them by others based upon renewable resources. These include extruded parts and moldings that would otherwise be based upon petrochemical derivatives such as thermoplastics and fuel pellets that can be burned in domestic stoves and that can repl...

AI Technical Summary

Benefits of technology

[0015]The present invention relates to a method for producing fuel pellets and a pellet used as a fuel source prepared by a process. Lignocellulosic biomass having a moisture content of less than about 30% by weight is introduced into a reactor. The moisture content of the lignocellulosic biomass may be less than about 15% by weight. Less than about 50 weight % of a carbon source may be added to the biomass. The carbon sources is coal dust, coke powder, or unprocessed biomass. A vacuum of less than 500 torr, preferably less than 200 torr, is applied to the reactor. Steam having a temperature of between about 180° C. and about 235° C. is injected into the reactor. The biomass is maintained in the reactor between about 1 and about 12 minutes. The treated biomass having a moisture content less than about 30% by weight is removed from the reactor. The treated biomass is formed into a pellet or briquette such that forming may be pelletizing, extruding, briquetting, or the like.

Problems solved by technology

White pellets need to be made from finely divided biomass, meaning that coarser materials need to be ground before pelletizing, an energy intensive step.

The pellets typically contain about 10% moisture and need to be stored under cover, as they absorb water easily and lose their cohesiveness.

They are also liable to create dust during transport and storage and thus, risk causing a dust explosion.

However, the pellets made from all of these sources suffer from the same shortcomings of those made from sawmill waste.

Thus, whereas pelletized biomass is well established as a fuel for small-scale heating purposes, its shortcomings have made it difficult to use as a straightforward replacement for coal in large-scale installations such as power stations.

However, this friability means that the process may need to be carried out immediately prior to the pellet being used.

These features also make this procedure totally unsuited to the manufacture of extruded and molded parts.

Torrefaction is not yet employed commercially to manufacture fuel pellets and has never been proposed for the manufacture of extruded or molded products.

One field of use where conventional white pellets are unsatisfactory is where the product needs to be stored outdoors, as is the case for many coal-fired power stations.