Patent Application
20070251143
In accordance with the foregoing summary, the following describes a preferred embodiment of the invention which is presently considered to be the best mode thereof.
To prepare a synthetic fuel pellet in accordance with one embodiment of the present invention, a mixture of: (a) coal fines; (b) a fibrous cellulosic material wherein the fibers of the fibrous cellulosic material have been substantially disintegrated; and (c) at least one binder, the binder adapted to form a pellet of the coal fines and the fibrous cellulosic material.
The fibrous cellulosic material is obtained by subjecting wood chips or other acceptable source of cellulosic material, such as that derived from waste digesters, to pneumatic shear so as to disintegrate the cellulosic fibers. This may be done by obtaining the mechanical or pneumatic shear-treated material commercially, such as the kinetic disintegration technology commercially available from Alternative Green Energy Systems Inc. (AGES) of Canada or First American Scientific Corporation of Bakersfield, Calif. Examples of devices capable of performing this method are the KDS Model 250 and KDS Model 3000 (in development), commercially available from First American Scientific Corporation of Bakersfield, Calif. Another source is municipal waste autoclaving, such as is commercially available from Estech USA LLC of Canal Winchester, Ohio.
The fibrous cellulosic material is typically first mixed with the cellulose binder in a suitable industrial charger as is known and used in the art. Mixing is continued until a uniform slurry is formed.
The coal fines are obtained from on-going or past coal mining operations, such as from waste ponds. The coal fines are collected and permitted to dry before being incorporated into the slurry. The coal fines are admixed to form a mixture with the coal fines binder that is prepared to be pelletized.
The mixture may be formed into pellets using machinery and methods known and used in the art, or which hereafter may be developed.
The pellets are articles of commerce that can be easily transported by rail or shipped from the palletizing operation to combustion chambers, such as for energy generation at electric generating plants. Because electric generating plants are often geographically separated from the mining operations, the pellets must be durable to provide stability during transport. The pellets are typically crushed just prior to feeding the combustion chamber.
It is essential that the binder be non-water-soluble. While there are numerous such binders commercially available, one of the less expensive options appears to be that of a highly-hydrolyzed grade of polyvinyl alcohol (PVOH) such as Elvanol 90-50 (commercially available from Dupont). This material provides a high degree of cold-water insolubility, and its use as a binder is well known.
Experimentation with PVOH show that water resistant briquettes can be made with PVOH alone, with addition rates in the range of 0.1-1% (solids ratio), and preferably in the range of 0.1-0.4%.
PVOH also crosslinks with a number of materials, and experiments with crosslinkers have shown that the PVOH does indeed insolubilize, but the crosslinked material has a tendency to gel. Various crosslinkers were tested, ranging from aldehydes to metals. Invariably, as gelation occurs, the structural integrity of the briquette diminishes.
Testing has confirmed that gelation does not occur in alkaline environments. As an example, briquettes were formed with PVOH (using 90-50 Elvanol as an example) at 0.4% addition, and a glyoxol-based crosslinker (Curesan, from BASF), at 0.1% addition. Sufficient alkalinity was added to raise the pH above 8 (with sodium hydroxide), and briquettes were formed at room temperature at about 9000 psi. The briquettes were heated to accelerate drying to ˜200 F. Upon drying, the PVOH and Curesan react and cure. The resulting briquettes were both physically durable and waterproof. The alkaline insolubility of PVOH and coal is described in U.S. Pat. No. 6,709,472, which is hereby incorporated herein by reference.
Several reaction pathways are available to produce “waterproof” cellulose. One pathway teaches that waterproof cellulose composites can be created using a thermoset binder extracted from (wood) cellulose by prescribed steam treatments: the steam hydrolyzes cellulose components which, after concentration, can be utilized as a glue or binder by thermosetting with heat and pressure.
Another pathway utilizes a Maillard reaction to bind “particulated” cellulose, such as that found in the preferred feedstocks of this patent. U.S. Pat. No. 5,582,682 to Ferretti (hereby incorporated herein by reference) regarding forming cellulose composites, teaches that the Maillard reaction resin is compatible with the surface of cellulose, and the particulation increases the binding site population with which the resin reacts. This patent also describes the ammoniation/protein (starch) binder for cellulose.
Indeed, experimentations have demonstrated that a water insoluble material can be formed from fibers derived from the autoclave processing of municipal waste (previously cited). In one experiment, a 50 gram sample of fiber (available from Estech USA LLC of Canal Winchester, Ohio) was combined with 50 grams of 2% ammonia (a commercial home product) and 20 grams of soy protein isolate, briquetted at under 100 psi, and heated cause the briquette core to rise to 350 F. The resulting briquette was porous, but insoluble.
A synthetic coal briquette was made using techniques identical or similar to those outlined above. 70 grams of coal, along with its binder, and 30 grams of cellulose, along with its binder, were combined and briquetted using standard briquetting techniques at a pressure of about 10,000 psi. The resulting briquette was heated briefly to 350 degrees F. While not wishing to be bound by theory, prior work with the coal/PVOH system has shown that heating a stronger briquette, and indeed, the resulting synthetic fuel briquette was strong and did not dissolve after in 24 hours in water.
Additional information regarding the formulation and production of synthetic fuel pellets is provided in the following patents and published patent applications which are hereby incorporated by reference:
The present application claims the benefit of provisional patent application Ser. No. 60/795,401, the entire disclosure of all of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 60795401 | Apr 2006 | US |
