Method of preparing a synthetic fuel from coal

Details Method of preparing a synthetic fuel from coal Method of preparing a synthetic fuel from coal

2002-09-11

2003-11-04

Medley, Margaret (Department: 1714)

Fuel and related compositions

Particulate

C044S620000, C044S542000, C044S595000, C044S599000

Reexamination Certificate

active

06641624

ABSTRACT:

TECHNICAL FIELD
This invention concerns a method of preparing a synthetic fuel. More particularly, this invention is directed to a method of preparing a synthetic fuel from coal comprising reacting the coal with a reactive polymer and to a coal-derived synthetic fuel prepared by reacting coal with the reactive polymer.
BACKGROUND OF THE INVENTION
A synthetic fuel is a manmade material synthesized by the union of chemical elements, groups, or simpler compounds or by the degradation of a complex compound and is used to produce heat or power by burning. The majority of synthetic fuels are generated by the degradation of complex materials such as coal, oil shale, oil sand or natural gas. Synthetic fuel generation by the degradation of complex organic materials typically requires energy in the form of heat, as well as pressurized processing conditions, special chemical catalysts and highly reactive chemical reagents. Synthetic fuels produced through degradation of complex materials are often toxic flammable liquids or gases that require special storage and handling. Typical examples of synthetic fuels are synthetic oil produced from coal, synthetic gas (syngas) produced from coal, synthetic diesel fuel derived from natural gas, synthetic gasoline derived from natural gas, synthetic oil derived from oil shale and synthetic oil derived from oil sand.
A second means of producing a synthetic fuel is to react a complex organic material with a second reagent to yield a new material without degradation. Reactions of coal with numerous simple organic chemicals are well documented and are often used to study the various reactive chemical functional groups present in coal. Examples of reactions of coal with organic chemicals include acetylation with acetic anhydride and alkylation with benzyl bromide. Such reactions can impart beneficial properties to a fuel product and allow the production of coal derived solid synthetic fuels with lower toxicity and easier handling than traditional synthetic fuels. Although many reactions of organic reagents with coal are known, the products of such reactions do not demonstrate sufficiently advantageous fuel properties to justify the high cost of large-scale synthetic fuel production.
Coal-based synthetic fuels can conceivably be used in any application where coal is used, however, most coal-derived synthetic fuels are used in one of two industries, electric power generation and coke production. In electric power generation, coal-based synthetic fuels are typically burned alone or with coal in power generation facilities. In coke production, the synthetic fuel can be used alone or with metallurgical coal. In this case the coal used to produce synthetic fuel must be metallurgical grade coal.
Asphalt emulsions, oil emulsions and carboxylated styrene butadiene copolymers have been used as additives to generate synthetic fuels. Synthetic fuels made from these suffer from disadvantages in that their lower reactivity results in higher dosage requirements and the attendant cost. These materials also typically add significant moisture to the coal, giving the resulting material lower BTU value. In certain crushing and grinding operations where a particular particle size is desired, the particles have been shown to re-agglomerate due to the presence of the additive. Handling problems may result from the presence of the additive. These products may also have attendant environmental and health concerns due to the presence of volatile organic compounds. Some of the additives require acid treatment of the coal which raises health and liability concerns at synthetic fuel production sites. Potentially hazardous conditions arise due to the high temperatures needed to feed and maintain some synthetic fuel additives. Incompatibility of the synthetic fuel additives with synthetic fuel plant equipment such as conveyor belts has been observed at some sites.
An object of the invention is to provide a method of preparing a synthetic fuel from coal that has advantages over existing technology in the areas of handling, synthetic fuel milling and pulverizing, additive toxicity and environmental acceptability.
SUMMARY OF THE INVENTION
In its principal aspect, this invention is directed to a method of preparing a synthetic fuel from coal comprising reacting the coal with a polymer composition comprising an aqueous solution or an aqueous emulsion of one or more reactive polymers, the reactive polymers selected from the group consisting of ethylene/vinyl acetate copolymers, ethylene/vinyl alcohol copolymers, poly(acrylic acid), poly(vinyl alcohol), vinyl alcohol/vinyl acetate copolymers, poly(vinyl acetate), vinyl acetate/acrylic acid copolymers, poly(vinyl acetate/acrylic acid/ethylene), acrylic acid/acrylamide copolymers and poly(acrylamide).
One advantage of the present invention is that synthetic fuels made as described herein have a lower polymer composition dosage requirement with attendant cost savings.
Another advantage is that the polymer compositions described herein do not add appreciable moisture to the coal. Therefore, the synthetic fuel shows no reduction in BTU value when compared to the parent coal.
Another advantage is in improved control of dusting of the synthetic fuel product.
Another advantage is improved handling characteristics exhibited by synthetic fuel produced according to this invention. In common end-use operations, such as crushing and grinding to a desired particle size, the particles show no tendency to re-agglomerate due to the presence of the additive.
Another advantage is reduced safety, environmental and health concerns due to the absence of volatile organic compounds in synthetic fuel prepared as described herein.
Another advantage is that this invention does not require acid treatment of the coal, thereby lessening health and liability concerns at synthetic fuel production sites.
Another advantage is that the method of this invention does not require elevated temperatures, resulting in lower safety concerns compared to other synthetic fuel additives.
Another advantage is that synthetic fuel prepared as described herein is compatible with plant equipment such as conveyor belts.
DETAILED DESCRIPTION OF THE INVENTION
A synthetic fuel is produced from coal according to this invention by applying to the coal a requisite amount of a reactive polymer selected from ethylene/vinyl acetate copolymer, ethylene/vinyl alcohol copolymer, poly(acrylic acid), poly(vinyl alcohol), vinyl alcohol/vinyl acetate copolymer, poly(vinyl acetate), vinyl acetate/acrylic acid copolymer, poly(vinyl acetate/acrylic acid/ethylene), acrylic acid/acrylamide copolymer or poly(acrylamide), or a mixture thereof such that the polymer reacts with the coal. The resultant product can be shown by the analytical methods described herein to be chemically different from either the parent coal or the polymer additive.
Ethylene/vinyl acetate copolymer is commercially available from several sources including Reichhold Chemicals, Research Triangle Park, N.C. (Elvace 714); Air Products Inc., Allentown, Pa. (Airflex 315); and National Starch and Chemical, Bridgewater, N.J. (Dur-O-Set E-130). Commercially available ethylene/vinyl acetate copolymer has the following characteristics:
Ethylene: 1 to 75% by weight.
Polymer particle size distribution maximum: 1%>200 mesh.
pH: 4.00-7.00.
Percent solids: 5 to 80%.
Viscosity: 100 to 5000.
Preferred ethylene/vinyl acetate copolymer has 6 to 8% ethylene, a maximum of 500 ppm of particles>200 mesh, a molecular weight distribution of from about 190,000 to about 250,000, a pH of about 4 to about 5.5, about 54.5 to about 56 percent solids, a viscosity of from about 1500 to about 2700 and residual vinyl acetate monomer of less than about 0.1%.
Ethylene/vinyl alcohol copolymer is commercially available from Aldrich Chemical Company, Milwaukee, Wis.
Poly(acrylic acid) is commercially available from Air Products Inc.; Nalco Chemical Company, Naperville, Ill.; and Rohm & Haas Company, Philadelphia, Pa.
Poly(vinyl alcohol) is commercially available from Air Pro

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