Alternative fuel comprising combustible solids and by-products or waste material from industrial processes   

This invention relates to alternative fuels comprising by-products or waste material from industrial processes and methods of using the fuels. More particularly, this invention concerns alternative fuels comprising liquid hydrocarbons derived from biomass and combustible solids. The biomass liquid hydrocarbons can include sugar solutions, tall oil, black liquor, vegetable oils, animal fats, triglycerides, methyl esters, ethyl esters glycerin and fatty acids. The liquid hydrocarbon is mixed with coal or other combustible solids to prepare the alternative fuel.

The current US economy is dominated by technologies that rely on fossil energy (coal, petroleum, and natural gas) to produce fuels. Biomass presents a promising renewable energy source that could provide an alternative to the use of fossil resources. Biomass includes crops, trees, grasses, crop residues, forest residues, animal wastes, and municipal wastes. There are many reasons to increase the use biomass for energy, including lessening dependence upon foreign oil, utilizing green chemistries from a renewable source, creating less toxic pollution, and improving the domestic agricultural economy.

A fuel product formed from vegetable oil and dried cellulosic powder is disclosed in U.S. Pat. No. 6,818,027 B2 and Published Patent Application No. 2005/0055873 A1.

A fuel product formed by homogenizing, heating, pressurizing and removing water from organic waste products of industrial processes and then separating a selected constituent from the product into a waste stream and blending the waste stream with a fuel is disclosed in Published Patent Application Publication No. 2005/0142250 A1.

U.S. Pat. No. 6,890,451 B2 discloses an anti-icing or deicing fluid comprising by-products of triglyceride processing and its application to surfaces including particulate materials such as coal. A method of preventing the agglomeration of coal in subfreezing temperatures comprising applying an anti-agglomerating amount of by-product glycerin containing up to 5 percent methanol by weight to the coal is disclosed in U.S. Pat. No. 7,108,800. A method of preventing the agglomeration of coal in subfreezing temperatures comprising applying an anti-agglomerating amount of by-product sugar solution to the coal is disclosed in U.S. Pat. No. 6,878,308 B2.

This invention relates to a novel and cost effective fuel and methods of preparing and using the fuel. The fuel comprises biomass liquid hydrocarbons mixed or blended with existing fuels such as coal and/or other combustible solids. Some of the biomass hydrocarbon liquids of this invention are by-products of current processes. For example, fatty acids and glycerin are by-products of a biodiesel manufacturing process.

Accordingly, in an embodiment, this invention is an alternative fuel comprising one or more combustible solids and one or more liquid hydrocarbon components selected from a group consisting of sugar solutions, tall oil, black liquor, vegetable oils, animal fats, triglycerides, methyl esters, ethyl esters, glycerin and fatty acids, provided that when the liquid hydrocarbon component is vegetable oil, the combustible solid is other than a cellulosic powder and further provided that when the combustible solid is coal, the liquid hydrocarbon component is other than sugar solutions.

In another embodiment, this invention is method of preparing a alternative fuel comprising applying one or more liquid hydrocarbon components selected from a group consisting of sugar solutions, tall oil, black liquor, vegetable oils, animal fats, triglycerides, methyl esters, ethyl esters, glycerin and fatty acids to one or more combustible solids, provided that when the liquid hydrocarbon component is vegetable oil, the combustible solid is other than a cellulosic powder and further provided that when the combustible solid is coal, the liquid hydrocarbon component is other than sugar solutions.

The invention uses biomass liquids such as sugar solutions, tall oil, black liquor, vegetable oils, animal fats, triglycerides, methyl esters, ethyl esters, glycerin and fatty acids mixed with coal or other combustible solids to create alternative fuels. The sugar solutions, vegetable oils, animal fats, triglycerides, methyl esters, glycerin and fatty acids described herein are “green”, i.e. non-hazardous, non-toxic, biodegradable, environmentally friendly, and/or derived from renewable sources.

“Combustible solids” means any solid combustible material which can be mixed with one or more biomass liquids as described herein to prepare the alternative fuel of the invention. In an embodiment, the combustible solid is selected from coal, wood chips, coke, and garbage. In another embodiment, the combustible solid is coal. “Coal” includes fine coal from stockpiles, fine coal from impoundments, run of mine coal washed, run of mine coal unwashed and waste coal. Coke is derived from coal. Garbage includes municipal and/or industrial garbage.

“Sugar solutions” refers to by-products of sugar beet or sugar cane processing which can comprise one or more components selected from raffinose, glutamine, betaine, lactate, glucose and/or fructose. Other components can include sodium, potassium, chloride, nitrate, nitrite, acetate, ammonia and magnesium. The by-products are also commonly referred to as “de-sugared” solutions.

“Black liquor” refers to the liquor resulting from the sulfate or kraft paper processes. Black liquor comprises lignin and tall oil.

“Tall oil” refers to a mixture of rosin acids, fatty acids including oleic and linoleic acids and other organic material including sterols and long chain alcohols resulting from acid treatment of black liquor as described above.

“Triglycerides” refers to esters of glycerol, a trihydric alcohol, with different fatty acids of varying molecular weight associated with a particular fat or oil. Triglycerides are the principal components of animal fats and vegetable oils. The most common fatty acids sourced from natural fats and oils include palmitic, stearic and linoleic acid.

“Fatty acids” means carboxylic acids derived from or contained in an animal or vegetable fat or oil. Fatty acids comprise a terminal COOH group and a long chain saturated or unsaturated alkyl chain. Representative fatty acids include butyric acid, lauric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and the like.

“Glycerin” and “glycerol” means 1,2,3-propanetriol.

Glycerin and fatty acids can be derived as by-products from transesterification reactions involving triglycerides including transesterification reactions involving biodiesel manufacturing processes as described herein.

“Methyl esters” and “ethyl esters” means methyl and ethyl esters of fatty acids as described herein.

“Vegetable oil” means triglycerides extracted from the seeds, fruit or leaves of plants including corn oil, soybean oil, canola oil, palm oil, coconut oil, rapeseed oil, and the like.

In an embodiment, methyl esters, ethyl esters, glycerin and fatty acids are derived from transesterification reactions involving triglycerides.

“Transesterification reactions involving triglycerides” refers to the splitting of triglyceride esters derived from vegetable oils and/or animal fats in the presence of base and a monohydroxy alcohol such as methanol or ethanol to produce monoesters of the fatty acids comprising the original triglycerides.

Representative fats and oils used in the transesterification reactions described herein include tallow, crude tall oil, virgin vegetable oils, soy, mustard, canola, coconut, rapeseed, palm, poultry offal, fish oils, used cooking oils, and/or trap grease, and the like.

In an embodiment, the glycerin, fatty acids, ethyl esters and methyl esters are derived from a biodiesel manufacturing process.

Biodiesel is a cleaner-burning diesel replacement fuel made from natural, renewable sources. For example, biodiesel can include fatty acid alkyl esters used as a cleaner-burning diesel replacement fuel made from sources such as new and used vegetable oils and animal fats.

According to the American Fuel Data Center of the U.S. Department of Energy, approximately 55% of the biodiesel is currently produced from recycled fat or oil feedstock, including recycled cooking grease. The other half of the industry is limited to vegetable oils, the least expensive of which is soy oil. The soy industry has been the driving force behind biodiesel commercialization because of excess production capacity, product surpluses, and declining prices. Similar issues apply to the recycled grease and animal fats industry, even though these feedstocks are less expensive than soy oils. Based on the combined resources of both industries, there is enough of the feedstock to supply 1.9 billion gallons of biodiesel.

Biodiesel is typically made through a chemical process called transesterification in which vegetable oil or animal fats are converted to fatty acid alkyl esters and glycerin by-products. Fatty acids and fatty acid alkyl esters can be produced from oils and fats by base-catalyzed transesterification of the oil, direct acid-catalyzed esterification of the oil and conversion of the oil to fatty acids and subsequent esterification to biodiesel.

The majority of fatty acid alkyl esters are produced by the base-catalyzed method. In general, any base may be used as the catalyst used for transesterification of the oil to produce biodiesel, however sodium hydroxide or potassium hydroxide are used in most commercial processes.

In the biodiesel manufacturing process, the oils and fats can be filtered and preprocessed to remove water and contaminants. If free fatty acids are present, they can be removed or transformed into biodiesel using special pretreatment technologies, such as acid catalyzed esterification. The pretreated oils and fats can then be mixed with an alcohol and a catalyst (e.g. base). The base used for the reaction is typically sodium hydroxide or potassium hydroxide, being dissolved in the alcohol used (typically ethanol or methanol) to form the corresponding alkoxide, with standard agitation or mixing. It should be appreciated that any suitable base can be used. The alkoxide may then be charged into a closed reaction vessel and the oils and fats are added. The system can then be closed, and held at about 71° C. (160° F.) for a period of about 1 to 8 hours, although some systems recommend that the reactions take place at room temperature.

Once the reactions are complete the oil molecules (e.g. triglycerides) are hydrolyzed and two major products are produced: 1) a crude fatty acid alkyl esters phase (i.e. biodiesel phase) and 2) a glycerin by-product phase. Typically, the crude fatty acid alkyl esters phase forms a layer on top of the denser glycerin by-product phase. Because the glycerin by-product phase is denser than the biodiesel phase, the two can be gravity separated. For example, the glycerin by-product phase can be simply drawn off the bottom of a settling vessel. In some cases, a centrifuge may be employed to speed the separation of the two phases.

The glycerin by-product phase typically consists of a mixture of glycerin, methyl esters, methanol, mong and inorganic salts and water. Mong is “matiere organique non glycerol”. Mong normally consists of soaps, free fatty acids, and other impurities. Methyl esters are typically present in an amount of about 0.01 to about 5 percent by weight.

Methanol can be present in the glycerin and fatty acids in an amount greater than about 5 weight percent to about 30 weight percent. The methanol can be a valuable component in the alternative fuels because of its low flash point which can help ignite the fuel.

In certain instances, it may be necessary to further refine the glycerin by-product prior to use, for example by washing, acidulation or distillation to adjust the glycerin concentration and/or remove impurities. Methanol may also be added to the desired concentration.

In an embodiment, the glycerin-containing by-product comprises about 30 to about 95 weight percent of glycerin.

In an embodiment, the combustible solid is coal and the liquid hydrocarbon component is by-product glycerin.

The fatty acid by-products can originate from the refining of the crude fatty acid alkyl esters phase and/or the crude glycerin phase during the biodiesel manufacturing process. For example, the crude fatty acid alkyl esters phase typically includes a mixture of fatty acid alkyl esters, water and a fatty acid salts component. These fatty acid salts component generally form a solution with the water phase (e.g. soap water) where they can be further separated from the fatty acid alkyl esters component. Once separated from the fatty acid alkyl esters component, any suitable acid such as, for example, hydrochloric acid can be added to the water phase containing the fatty acid salts component to produce the fatty acid by-products of the present invention.

The fatty acid by-product may be in a wax or solid form. It can also contain fatty acid esters. The esters are beneficial components in the alternative fuel mixture.

Similarly, the crude glycerin phase typically includes a mixture of glycerin, water and a fatty acid salts component. This fatty acid salts component forms a solution or suspension with the water phase where it can be further separated from the glycerin component by adding any suitable acid to recover the fatty acid by-products suitable for the present invention.

It should be appreciated that the fatty acid by-products of the present invention can be derived from the acidulation of any of the biodiesel manufacturing process streams/stages that contain the fatty acid salts component (e.g. soap water) including, for example, the wash water. These fatty acid by-products derived from any of the different stages/streams of the biodiesel manufacturing process can be used as a component in alternative fuel.

The alternative fuels are prepared by applying the desired amount of liquid hydrocarbon component to the combustible solid, for example by spraying onto piles of the combustible solid or by means of showers oriented over conveyors used to transport the combustible solid. If desired, the liquid hydrocarbon component-combustible solid mixture may be mixed to ensure even distribution of the liquid hydrocarbon in the combustible solid.

In the case of loose or finely divided combustible solids, the alternative fuel may be prepared by applying the liquid hydrocarbon component to the combustible solid and pressing the resulting material into briquettes or ingots.

In an embodiment, about 0.1 to about 49 weight percent of said liquid hydrocarbon component is applied to the combustible solid.

In an embodiment, about 0.1 to about 25 weight percent of said liquid hydrocarbon component is applied to the combustible solid.

The alternative fuel of this invention may be used as a substitute for, or additive to conventional combustible solids for combustion in boilers or furnaces.

Changes can be made in the composition, operation, and arrangement of the method of the invention described herein without departing from the concept and scope of the invention as defined in the claims.