Synthetic fuel pellet and methods

Abstract

The present invention includes a synthetic fuel pellet, the pellet comprising a compressed agglomeration 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.

Description

PRIOR APPLICATION DATA[0001]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.TECHNICAL FIELD OF THE INVENTION[0002]The present invention is in the field of synthetic fuels, and relates generally to the production of non-traditional fuels, often referred to as synthetic fuels prepared from waste products such as coal fines and waste cellulosic materials. More particularly, this invention relates to the creation of such fuels using existing stockpiles of coal fines, coal dust, and other similar small particles of virgin coal.DESCRIPTION OF THE PRIOR ART[0003]For centuries coal has been mined as a source of fuel. During these years, numerous improvements have been made to increase mining efficiency and safety, and to improve the overall quality and purity of the end product. However, one drawback of coal mining is the by-product of coal fines that frequently end u...

AI Technical Summary

Benefits of technology

[0061]One of the advantages of the present invention is that synthetic fuel pellet may be produced with acceptable stability by using reduced amounts of binder as compared to prior formulations. Higher amounts of binder may be used, as desired. Typically, the synthetic fuel pellet may be produced with acceptable stability by using binder in a range from about 2 to about 20 percent by weight of the overall coal fines/fibrous cellulosic material/binder mixture, typically depending upon the type of binder. For instance, starch binders typically are present in higher amounts while plastic binders are effective in lower amounts. For instance, wheat starch binders are typically required in greater amounts, while plastic binders require lesser amounts.

[0062]Still another aspect of

Problems solved by technology

However, one drawback of coal mining is the by-product of coal fines that frequently end up abandoned into waste pits scattered throughout the countryside.

This material has traditionally been abandoned to waste, deposited in the form of “coal tips,” because it has been economically inefficient to handle such sizes as they are brought to the point of being burned for their energy content.

As a result, literally millions of tons of such material have been produced over the years, and currently lay dormant at or near mining sites.

Not only does this non-use pose a great waste of valuable natural fuel resources, but it also poses a threat to the surrounding environment.

In addition to respiratory hazards presented by the dust-sized particles, the large surface area associated with stockpiles of such particles poses a high risk for spontaneous combustion such as the type known as a dust explosion.

Also, starches and sulfates have no apparent ability to completely fuse the coal fines.

Moreover, when rewetted, the bond weakens.

Thus, pellets made with starch and sulphate binders are neither strong nor waterproof.

Sulfates also add sulfur to the coal which produces undesirable sulfur oxides and stack gases, which is direct noncompliance with the clean air regulations.

However, they do not sufficiently prevent the bound material from absorbing water and they are not suitable for industrial use due to their soft and “gummy” characteristics.

These binders produce a product that fouls the feed lines to furnaces by clogging the inlets.

Regrettably these prior art binders are derived from useful and often expensive raw materials such as natural and synthetic polymer, thereby adding significantly to the overall cost of the briquette and making their use cost prohibitive.

Unfortunately, the heating value of coal decreases as moisture content increases.

Regardless, water in the final product is undesirable as it is useless weight, increasing transportation costs and, as a result, decreasing the BTU content per ton.

As a result, many examples of prior art have failed to produce synthetic fuels that have sufficient heating value.

Unfortunately, this process is extremely costly, primarily because of the required liquefaction process, which is carried out in an oxygen-free environment at elevated temperatures—between 450 degrees and 700 degrees F.—and elevated pressures, typically between 200 psi and 3,000 psi.

The resulting liquid is then sprayed on coal fines that have themselves been heated to at least 250 degrees F., after which the coal and the liquid are allowed to react at about 300-400 degrees F. Although this method serves to alleviate certain environmental concerns, the high costs of reclaiming coal using this process undercuts the basic usefulness of the invention itself.

Although this process is effective, its requirement of PVA, which must be separately created for this particular use, makes the Ford process economically and environmentally inefficient in comparison with a process founded entirely on the use of constituents that are already present, and which some of the constituents are not being devoted to any economical purpose.

Although this process does use various waste products of other industries in transforming coal fines into a more usable fuel source, the complexity of the binding material makes the process quite complex, thereby reducing the economic viability of the overall method.

Again, although the process of Dondelewski has as its feed stock predominantly industrial by-products, it is very process intensive, first requiring large vats to mix the coal slurry and tall oil mix, followed by further processing to remove excess water and tall oil mix followed by drying the end product.

Thus, the method of Dondelewski does not satisfy the condition of using industrial by-products to produce a synthetic fuel that is economically competitive with the fuels that the synthetic fuel is intended to supplant, or which in general is in competition with it as a fuel source.

It generally has a high BTU value but since it adds sulfur to the fuel, its use results in higher SOx emissions and the resulting need to purchase, rather than sell, priority air pollutant credits.

Notwithstanding decades of development, the pelletization and of synthetic fuels produced from coal fines continues to be plagued by several problems.

The synthetic fuel pellets of the prior art remain subject to disintegration during handling and transport.

One component of cellulose, hemicellulose, is especially susceptible to sorption and needs to be chemically converted or physically isolated to achieve waterproof briquettes.

In addition, synthetic fuel pellets of the prior art are often produced using relatively expensive binders, such as epoxies, and / or must be produced using relatively high pressures and temperatures (typically above 10,000 pounds / square inch and typically above 400 degrees Fahrenheit), in order to form a satisfactory pellet by removing water and compacting the pellet material blend.

The presence of water in the pelletizing mixture, its efficient removal during processing, and the uptake of water in finished pellet remains a challenge to the production, transport and combustion of stable synthetic fuel pellets.

In this same regard, the production of synthetic fuel pellets typically requires high pressures and temperatures when binders such as lignin is used, or relatively expensive plastic binders to achieve a pellet of acceptable stability.