WO2011094403A1

WO2011094403A1 - Fuel pellets, briquettes and fire logs

Info

Publication number: WO2011094403A1
Application number: PCT/US2011/022714
Authority: WO
Inventors: Michael R. Andrews; Michael A. Bilodeau; Susan Mackay
Original assignee: University Of Maine System Board Of Trustees
Priority date: 2010-01-27
Filing date: 2011-01-27
Publication date: 2011-08-04

Abstract

A manufactured fuel article comprising cellulosic material, thermoplastic material, and zeolite.

Description

TITLE

FUEL PELLETS, BRIQUETTES AND FIRE LOGS

CROSS-REFERENCE TO RELATED APPLICATION

[0001 ] This application claims the benefit of United States Provisional Application No. 61/298,642, filed January 27, 2010, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] This invention relates in general to manufactured fuel articles, and in particular to improved fuel pellets, briquettes and fire logs.

[0003] It is known to manufacture fuel articles such as fuel pellets, briquettes and fire logs. For example, some fuel articles are produced from cellulosic materials and, optionally, binders such as thermoplastics, starch, waxes, or asphalt, and high specific energy materials such as coal and char. Fuel pellets having different compositions of materials have been used for heating since the mid-nineteen eighties.

[0004] Although such fuel articles are known, there is an ongoing need to reduce or eliminate sulfur compounds released into the flue gas during combustion or gasification of the articles to comply with environmental permits and/or subsequent operations, such as biofuel production via catalysis, or electrical generation via turbines or internal combustion engines, particularly when the fuel pellets, briquettes, and fire logs contain sulfur compounds and/or are co-fired with sulfur containing fuels, such as coal or fuel oil.

[0005] Therefore, it would be desirable to provide improved fuel articles such as fuel pellets, briquettes and fire logs that have reduced emission of sulfur compounds.

SUMMARY OF THE INVENTION

[0006] The present invention relates to a manufactured fuel article comprising cellulosic material, thermoplastic material, and zeolite. [0007] Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present invention relates to manufactured fuel articles, such as fuel pellets, briquettes and fire logs, having the ability to reduce or eliminate the emission of sulfur compounds during combustion or gasification of the articles, from one or more components of the articles and/or other co-fired fuels, such as coal or fuel oil.

[0009] The combustible fuel articles include a zeolite to reduce the sulfur emissions. In certain embodiments, the zeolite has the capacity to absorb sulfur compounds released during combustion or gasification of the fuel articles, thereby providing an economical and effective method of sequestering sulfur in the flue gas. The sulfur is more easily disposed of as part of the residual ash. Also, in certain embodiments, the zeolite may reduce the emission of sulfur compounds by catalyzing the reaction of the sulfur compounds to other compounds that are not harmful; this catalysis function may occur at high combustion temperatures.

[0010] The term "zeolite" is used here in its generic sense and refers to crystalline inorganic molecular sieves such as aluminophophates, silicon aluminum phosphates, microporous borosilicates, titanosilicates and tatanioaluminosilicates, as well as microporous aluminosilicates and their silica analogs, having a framework structure consisting of nanopores and interconnected cavities which can be occupied by ions and/or water molecules, both of which have considerable freedom of movement permitting ion exchange and reversible dehydration. In contrast to amorphous materials these crystalline structures contain regular arrays of intracrystalline pores (nanopores) and voids of uniform dimensions. A typical naturally occurring zeolite is the mineral clinoptilolite with formula (Ca, Na, K)_2-3Al₃(Al,Si)₂Si₁₃0₃₆12(H₂0).

[0011 ] In certain embodiments, the zeolite is an ion exchanged zeolite. The use of an ion exchanged zeolite can improve the capacity of the zeolite to absorb sulfur compounds. As used herein, "ion exchanged zeolite" refers to a natural or synthetic zeolite that has been modified by an ion exchange process to increase the content of one or more metal ions in the zeolite. Any suitable metal ion(s) can be used, for example, Zn, Fe, Mg, and/or Mn.

[0012] Another method more commonly employed to form a zeolite catalyst is incipient wetness impregnation and refers to a technique by which a higher amount of a metal salt can be incorporated into the interior of the zeolite than the exchange capacity would typically allow. Once the zeolite is impregnated with the metal salt it can be heated in the presence of air to form a metal oxide from the metal salt which can then be used as a metal oxide catalyst material.

[0013] The zeolite can be included in the combustible fuel article in any suitable amount to reduce sulfur emissions. For example, in certain embodiments the fuel article includes zeolite in an amount within a range of from about 2% to about 20% by weight of the fuel article, and more particularly from about 2% to about 10%.

[0014] U.S. Patent No. 5,980,595 to Andrews, issued November 9, 1999, is incorporated by reference herein. This patent describes a fuel pellet made from cellulose, thermoplastics and coal. However, unlike the fuel articles of the present invention, the fuel pellet disclosed in the Andrews patent does not include a zeolite.

[0015] In addition to the zeolite, the combustible fuel articles include a cellulosic material. Any suitable cellulosic material or combination of different materials can be used. For example, the cellulosic material may comprise paper mill sludge, wood chips, paper fiber, herbaceous crops, such as hay or straw, and other naturally occurring cellulosic waste products, such as cherry pits, olive pits, sugar cane

(bagasse), grass clippings, and/or fir trees, ie. Christmas trees. Alternatively, the cellulosic material may comprise the material used in diapers, catamenial products, and/or sanitary napkins. The cellulosic material can be used in any suitable form. In certain embodiments, the cellulosic material is in particulate form and has been ground into particle sizes of at least 80 Mesh and as fine as 200 Mesh.

[0016] The cellulosic material can be included in the combustible fuel article in any suitable amount. For example, in certain embodiments the fuel article includes cellulosic material in an amount within a range of from about 10% to about 80% by weight of the fuel article, and more particularly from about 30% to about 70%. [0017] In another embodiment of the invention, the cellulosic material in the fuel article may be replaced, in part or completely, by coal, torrified biomass, char, asphalt, and/or lignin to further increase the specific energy content of the fuel. For example, when the cellulosic material is replaced in part, the fuel article may include the cellulosic material in an amount within a range of from about 10% to about 80% by weight of the fuel article, and one or more of these replacement materials in an amount within a range of from about 30% to about 70% by weight of the fuel article.

[0018] The combustible fuel articles optionally include a thermoplastic material. A thermoplastic can contribute to the high energy content of the fuel article and can provide improved toughness and water resistance. Any suitable type of thermoplastic material can be used. In certain embodiments, the material is a thermoplastic polymer. Such polymers are well known and include, for example, polypropylene, polyethylene, polylactic acid, polyethylene terephthalate, polyurethane, polystyrene, polyvinyl chloride, and polyamide. Cellulosic thermoplastic materials are also known. In certain embodiments, the thermoplastic is densified and in certain embodiments, the thermoplastic was in the form of a film. The above-described Andrews patent describes densified thermoplastics and films. The thermoplastic can be used in any suitable form. In certain embodiments, the thermoplastic is in particulate form before the manufacture of the fuel article and has been ground into particle sizes of at least 80 Mesh and as fine as 200 Mesh.

[0019] The thermoplastic can be included in the combustible fuel article in any suitable amount. For example, in certain embodiments the fuel article includes thermoplastic in an amount within a range of from about 0% to about 50% by weight of the fuel article, more particularly from about 5% to about 50%, and more particularly from about 10% to about 30%.

[0020] The combustible fuel article can include the cellulosic material, the zeolite and the thermoplastic in any suitable form. In certain embodiments, the fuel article is composed of a homogeneous mixture of cellulosic material, thermoplastic and zeolite. [0021 ] In addition to the cellulosic material, zeolite and thermoplastic, the fuel article can optionally include one or more additional materials. For example, the fuel article may include a binder such as a starch or wax in any suitable amount, for example, in an amount from about 0.5% to about 10% by weight of the fuel article.

[0022] The combustible fuel article can be manufactured by any suitable method. For example, the above-mentioned Andrews patent describes methods of molding fuel pellets. Methods of producing briquettes and fire logs are well-known in the art.

[0023] In certain embodiments, the fuel article has a high specific energy content. For example, a fuel pellet may provide a heat output of from about 10,000 BTU per pound to about 16,000 BTU per pound.

[0024] The fuel articles according to the invention can be produced in any suitable size and shape. For example, they can be produced in a wide range of sizes, from 1/8" to 12" in diameter and 1/8" to 24" in length, depending on the application and customer preference.

[0025] In an alternative embodiment, the zeolite in the fuel article is optional, and the article is manufactured in sizes that are larger than or smaller than the sizes disclosed in the Andrews patent. The Andrews patent describes fuel pellets that are smaller than 0.75 inches in diameter and smaller than 3 inches in length. Such pellets may be deficient in that some industrial boilers, residential fireplace, and campfire applications prefer larger fuel briquettes and fire logs for material handling and aesthetic reasons. Accordingly, the fuel articles according to the invention can have small sizes within a range of from 0.25 inch to 3 inches in diameter or larger sizes within a range of from 3 inches to 12 inches in diameter.

[0026] While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. A manufactured fuel article comprising cellulosic material, thermoplastic material, and zeolite.