Patent Application
20120151834
Pyrolysis is the chemical decomposition of organic substances carried out by heating the organic substances in the absence of air or oxygen. Pyrolysis reactions typically produce three classes of products: off gas having low heating value, potentially unstable liquid product, and char or residual carbon material having only a small content of hydrogen. Of these three classes of products, the liquid product is of the greatest value, as it can include low-weight hydrocarbon material that is useful as fuel or as an intermediate in the production of fuel.
Pyrolysis technology is currently used to process various materials, including biomass, coal, and certain waste materials, such as spent tires. However, none of these materials produce a significant amount of valuable liquid material when pyrolzed. Pyrolysis of biomass generally produces predominantly off gas and char, with very little or no liquid product. Pyrolysis of coal can result in the production of about 25% liquid product, and pyrolysis of waste materials such as tires can produce up to 45% liquid product, neither of which is a generally considered to be a favorable yield.
Another common problem with pyrolysis processes used to upgrade material into more useful products is the tendency of the pyrolysis machinery to overly soften or melt the material as it enters the pyrolysis machinery. Over-softening of material being processed through pyrolysis machinery becomes problematic when the softened material begins to interfere with or jam moving parts inside of pyrolysis machinery. For example, as shown in U.S. Pat. No. 4,439,209, a typical pyrolysis unit may comprise a rotary drum 2 into which material to be pyrolyzed is fed, and baffles 29 for providing satisfactory flow of the material inside the rotary drum 2. If excessive material softening occurs, the material may jam the rotary drum 2, the baffles 29, and any other moving components of the pyrolysis unit, thereby leading the pyrolysis unit to malfunction and break down.
Disclosed below are representative embodiments that are not intended to be limiting in any way. Instead, the present disclosure is directed toward novel and nonobvious features, aspects, and equivalents of the embodiments of the methods of use described below. The disclosed features and aspects of the embodiments can be used alone or in various novel and nonobvious combinations and sub-combinations with one another.
Methods for upgrading asphaltene compositions through pyrolysis are described herein. In some embodiments, a method of upgrading asphaltene compositions includes a step of providing an asphaltene composition and a step of pyrolyzing the asphaltene composition. The asphaltene composition includes from 50 wt % to 90 wt % asphaltene and from 10 wt % to 50 wt % inert material. The methods of these embodiments can lead to increased conversion of asphaltene molecules into valuable liquid product. The methods also tend to avoid or mitigate the issue of hydrocarbon over-softening within a pyrolysis unit. Additionally, the method provides for the upgrading of asphaltene compositions that have previously been disposed of as waste material, such as asphaltene recovered from by products of oil sand processing (e.g., TSRU tailings).
In some embodiments, a method for upgrading asphaltene compositions includes a step of providing an asphaltene composition, a step of forming asphaltene pellets from the asphaltene composition, and a step of pyrolyzing the asphaltene pellets. The asphaltene composition includes from 50 wt % to 90 wt % asphaltene and from 10 wt % to 50 wt % inert material. As with the previous embodiments, the method results in improved conversion rates, elimination or mitigation of asphaltene over-softening issues, and provides methods for upgrading asphaltene compositions that have previously been treated as waste material.
In some embodiments, a method of preparing asphaltene pellets for use in pyrolysis, combustion, and other processes includes a step of providing an asphaltene material, a step of preparing a mixture comprising the asphaltene material and a first organic binding agent, and a step of extruding the mixture. In some embodiments, the first organic binding agent is a highly aromatic hydrocarbon, such as Aromatic 100 and Aromatic 150. In some embodiments, the organic binding agent is biodiesel or a fuel oil. In some embodiments the binding agent is oil produced from pyrolysis of the asphaltenes, thereby making a combined pelletization and pyrolysis process self sustaining. Asphaltene pellets formed by this method can have good structure retention, can be readily handled, and can serve to sufficiently slow the softening of the asphaltene material undergoing a pyrolysis process. Additionally, use of the first organic binding agent can repel water content from the asphaltene material. Without the first organic binding agent, attempts to remove water content from asphaltene material by pressing the material will can be frustrated by the asphaltene immediately reabsorbing any repelled water.
In some embodiments, a method of preparing asphaltene pellets for use in pyrolysis, combustion, and other processes includes a step of providing an asphaltene material, a step of feeding the asphaltene material into a disc pelletizer, a step of rotating the disc pelletizer, a step of feeding a first organic binding agent into the disc pelletizer while the disc pelletizer rotates, and a step of removing asphaltene pellets from the disc pelletizer. Asphaltene pellets formed by this method can have good structure retention, can be readily handled, and can serve to sufficiently slow the softening of the asphaltene material undergoing a pyrolysis process. Additionally, use of the first organic binding agent can repel water content from the asphaltene material. Without the first organic binding agent, attempts to remove water content from asphaltene material by pressing the material can be frustrated by the asphaltene immediately reabsorbing any repelled water.
In some embodiments, a method of preparing asphaltene pellets for use in pyrolysis, combustion, and other processes includes a step of providing an asphaltene material, a step of mixing the asphaltene material with a first organic binding agent to form a mixture, a step of feeding the mixture into a balling drum, a step of operating the. balling drum, and a step of removing asphaltene pellets from the balling drum. Asphaltene pellets formed by this method can have good structure retention, can be readily handled, and can serve to sufficiently slow the softening of the asphaltene material undergoing a pyrolysis process. Additionally, use of the first organic binding agent can repel water content from the asphaltene material. Without the first organic binding agent, attempts to remove water content from asphaltene material by pressing the material can be frustrated by the asphaltene immediately reabsorbing any repelled water.
In some embodiments, a method of preparing asphaltene pellets for use in pyrolysis, combustion, and other processes includes a step of providing an asphaltene material, a step of mixing the asphaltene material with a first organic binding agent to form a mixture, a step of feeding the mixture into a briquette press, a step of operating the briquette press, and a step of discharging asphaltene pellets from the briquette press. The asphaltene pellets formed by this method can also be referred to as asphaltene briquettes. Asphaltene briquettes formed by this method can have good structure retention, can be readily handled, and can serve to sufficiently slow the softening of the asphaltene material undergoing a pyrolysis process. Additionally, use of the first organic binding agent can repel water content from the asphaltene material. Without the first organic binding agent, attempts to remove water content from asphaltene material by pressing the material can be frustrated by the asphaltene immediately reabsorbing any repelled water.
The foregoing and other features and advantages of the present application will become apparent from the following detailed description, which proceeds with reference to the accompanying figures. It is thus to be understood that the scope of the invention is to be determined by the claims as issued and not by whether a claim includes any or all features or advantages recited in this Brief Summary or addresses any issue identified in the Background.
The preferred and other embodiments are disclosed in association with the accompanying drawings in which:
With reference to
Step 100 of providing an asphaltene composition can be achieved in a variety of ways. For example, the asphaltene composition can be provided by purchasing the asphaltene compositions from a third party. Additionally, the asphaltene composition can be prepared by separately acquiring the components of the asphaltene composition and mixing the components together in proportions described in greater detail below. In some embodiments, the asphaltene composition is provided by performing various refinement processes that result in the production of asphaltene compositions.
The asphaltene composition provided in step 100 includes an asphaltene component and an inert material component. Other materials may also be included in the asphaltene compositions, although the asphaltene component and the inert material component will typically make up a majority of the asphaltene composition. Additional other components that can be included in the asphaltene composition include sulfur scavengers and catalysts, and are discussed in greater detail below.
In some embodiments, the asphaltene component is substantially the only hydrocarbon compound included in the asphaltene composition. In such embodiments, the asphaltene composition can still include inert material, sulfur scavengers, catalysts, and other materials, but the only hydrocarbon material present in the composition is the asphaltene component. More specifically, the asphaltene composition can include less than 1 wt % of non-asphaltene hydrocarbons. This is especially true where the asphaltenes have been precipitated from a hydrocarbon extraction or upgrading process.
In some embodiments, the asphaltene composition includes other naturally occurring solid (non-toluene soluble) hydrocarbon sources, such as lignite or coal. In some embodiments, the solid hydrocarbon fraction is up to about 50% of the asphaltene composition.
In some embodiments, the asphaltene composition includes from 50 wt % to 90 wt % asphaltene and from 10 wt % to 50 wt % inert materials. When the asphaltene composition contains asphaltene and inert materials in this amount, the asphaltene composition is better suited for being subjected to pyrolysis in order to upgrade the asphaltene material into lighter hydrocarbon material. The presence of the inert material in these amounts helps to ensure that the asphaltenes do not melt when subjected to the pyrolysis process. Melting of the asphaltene both prevents upgrading of the asphaltene into lighter hydrocarbon molecules and potentially leads to the jamming or interfering of moving parts within the pyrolysis unit.
As mentioned above, suitable asphaltene compositions for use in the methods described herein can be obtained by performing certain refinement processes. One such refinement process that can produce a suitable asphaltene composition is the separation of asphaltene material from tailings. The tailings can be any tailings that include asphaltene material, solvent, and inert material. In some embodiments, the tailings are the tailings produced when performing certain bitumen extraction processes on tar sands and the like. In one specific example, the tailings are the tailings produced when performing a hot water froth treatment on tar sands to extract bitumen.
Separation of asphaltenes from tailings can be carried out by any known method for separating asphaltenes from tailings. In some embodiments, the tailings are sent to a tailings recovery solvent unit (TSRU), which in addition to separating solvent from the tailings, is also capable of separating the precipitated asphaltenes from the tailings. Exemplary TSRU processes are disclosed in U.S. Pat. No. 7,585,407 and U.S. Published Application No. 20080156702, both of which are hereby incorporated by reference in their entirety. The TSRU processes can produce a concentrated asphaltene material that includes asphaltenes and inert materials in the proportions described above for the asphaltene composition suitable for use in the methods described herein. In some embodiments, the TSRU process can be specifically tailored to produce a separated asphaltene composition having inert material in the desired amount. Even to the extent the concentrated asphaltene material produced by the TRSU does not include asphaltene or inert material in the desired proportion, additional asphaltenes or inert material can be added to the asphaltene separated during the TSRU process to reach the desired proportion for an asphaltene composition.
Another manner in which the asphaltene composition for the methods described herein can be obtained includes collecting asphaltene-containing bottoms from any of a variety of refinement process. In some embodiments, the refinement process is a distillation process, such as an atmospheric distillation process or a vacuum distillation, both of which are processes that produce bottoms containing asphaltene material. In some embodiments, the bottoms produced will require adding additional inert material or asphaltene material in order to reach the desired proportions for the asphaltene composition suitable for us in the methods described herein. The inert material present in the asphaltene composition is not limited to any specific type or class of inert material. Typical inert materials that can be present in the asphaltene composition include sand (e.g., clays quartz- and aluminosilicates), dirt, and various types of clay, such as kaolinite and illite.
As discussed above, the asphaltene composition can include inert material due to the manner in which the asphaltene composition is provided (e.g., when the asphaltene composition is obtained by separating asphaltene material from tailings). Alternatively or in combination, the inert material can be added to asphaltene material to arrive at an asphaltene composition having the desired percentage of each component (e.g., when certain refinery bottoms are used as the asphaltene component of the asphaltene composition).
The presence of the inert material helps to ensure the asphaltene material is in a favorable form to undergo pyrolysis inside of a pyrolysis unit. Typically, the extreme heat used in pyrolysis tends to soften asphaltenes. If the asphaltenes excessively soften during the pyrolysis step (i.e., before the end of the residency time inside the pyrolysis unit), the asphaltene material can begin to melt, at which point the asphaltene material may be inhibited from breaking down into lighter weight hydrocarbon molecules. Additionally, the softening asphaltenes can begin to interfere with and jam the pyrolysis unit.
The presence of inert material in the asphaltene composition can slow down the softening of the asphaltenes enough to prevent the asphaltenes from jamming or interfering with the pyrolysis unit, while at the same time not interfering with the thermal decomposition of the asphaltenes to produce light oil and other pyrolysis products.
As mentioned above, additional components can be present in the asphaltene composition besides asphaltenes and inert material. In some embodiments, sulfur scavengers are present in the asphaltene composition. The sulfur scavenger can be added to the asphaltene composition prior to pyrolysis in situations where the asphaltene composition provided by any of the manners described above does not include sulfur scavengers or the desired amount of sulfur scavenger. The sulfur scavenger can be added to the asphaltene composition to capture hydrogen sulfide generated during the pyrolysis reaction. Any suitable sulfur scavenger may be added to the asphaltene composition. Exemplary sulfur scavengers include limestone and other alkali and earth alkali compounds. The sulfur scavenger can be added to the asphaltene composition in any suitable amount. In some embodiments, the sulfur scavenger is mixed with the asphaltene composition at a sulfur scavenger:asphaltene composition ratio of from 1:1 to 100:1 on a weight basis.
In some embodiments, catalyst is present in the asphaltene composition. Catalyst can be added to the asphaltene composition prior to pyrolysis in situations where the asphaltene composition provided by any of the manners described above does not include catalysts or the desired amount of catalysts. In some embodiments the catalyst can be naturally occurring and can be naturally present in some or all of the desired quantity. The catalyst can function to increase the rate at which the asphaltene thermally degrades into lighter hydrocarbons during the pyrolysis step. Any catalyst suitable for increasing the thermal degradation of the asphaltenes can be added to the asphaltene composition. Suitable catalysts include iron, iron oxide, titanium dioxide, iron titanium oxide (ilmenite), calcium titanate (perovskite), and manganese compounds. The catalyst can be added to the asphaltene composition in any suitable amount. In some embodiments, the catalyst is mixed with the asphaltene composition at a catalyst:asphaltene composition ratio of from 1:1 to 500:1 on a weight basis.
Both sulfur scavenger and the catalyst can be included in the asphaltene composition at the same time. Alternatiely, only one of the catalyst and the sulfur scavenger is added to the hydrocarbon residue.
In step 110, the asphaltene composition is pyrolyzed to form pyrolysis products. Pyrolyzing includes thermally degrading material in an oxygen free environment, or in an environment in which the oxygen content is too low for combustion or gasification to take place. The pyrolysis of step 110 can take place in any suitable pyrolysis unit, including screw conveyors adapted for carrying out pyrolysis. The dimensions of the pyrolysis unit are not limited, and can be adjusted based on the amount of material to be processed inside the pyrolysis unit. Other suitable pyrolysis units include, but are not limited to, a rotary kiln, a rotary hearth unit, and a fluidized bed unit. Specific pyrolysis units that can be used to carry out the method are described in U.S. Pat. Nos. 4,439,209, 4,374,704, and 4,308,103, and U.S. Pub. App. No. 2008/0053813, each of which is herein incorporated by reference in its entirety.
The operating conditions of the pyrolysis unit are not limited and can be adjusted according to the makeup of the asphaltene composition pyrolyzed therein. In some embodiments, the pyrolysis step is conducted at an operating temperature above 315° C. (600° F.), and more specifically, within a temperature range between 350° C. and 525° C. In some embodiments, the asphaltene composition is quickly heated to a temperature within this range, rather than slowly heating the asphaltene composition to a temperature within this range. Fast heating of the asphaltene composition can tend to result in greater liquid product production. In some embodiments, the asphaltene composition is heated to within the desired temperature range in from 400° C. to 475° C. Any suitable pressure under which pyrolysis can take place can be used inside the pyrolysis unit. In some embodiments, the pyrolysis step 110 is carried out in a vacuum. When pyrolysis step 110 is carried out in a vacuum, the pressure inside the pyrolysis unit can range from 1 to 100 millibar.
The residence time of the asphaltene composition inside the pyrolysis unit is not limited, and may be freely adjusted to accomplish higher rates of reaction. As discussed above, the presence of the inert material in the asphaltene composition can allow the asphaltene composition to remain within the pyrolysis unit for a longer period of time because the asphaltene composition is less likely to overly soften or melt. In some embodiments, the pyrolyzing step 110 is carried out for between 5 minutes and 4 hours.
The step 110 of pyrolyzing the asphaltene composition produces pyrolysis products. Pyrolysis products are the result of the thermal degradation of the asphaltene material. In some embodiments, the pyrolysis products include a liquid hydrocarbon product, a gaseous product, and a residual carbon product.
In some embodiments, the liquid hydrocarbon product produced by the pyrolysis reaction is light oil. The light oil is generally defined as hydrocarbon molecules having a molecular weight lower than that of the asphaltene material. In some embodiments, the light oil produced by the pyrolysis of the asphaltene composition has a specific gravity of less than 0.95. Exemplary light oils include but are not limited to naphthalene, limonene, toluene, benzene. The light oil can be useful as a refinery feed stock or as a feed stock to produce various organic chemicals and solvents.
The gaseous product that can result from the pyrolysis reaction can include an off gas. Exemplary off gas that can be produced by pyrolysis of the asphaltene composition includes hydrogen and various alkanes and alkenes, such as methane, ethane, propane, butane, ethylene, propylene, and butylene. In some embodiments, the off gas or gases produced by the pyrolysis step can be used to help generate the heat needed to drive the pyrolysis step. For example, the off gas can be used to generate the heat applied indirectly through the walls of a pyrolysis unit. In some embodiments, the off gas can be used as a natural gas additive (after clean up).
Off gas produced by the pyrolysis reaction can also be used to produce superheated steam. The superheated steam produced by using the off gas can then be used in several additional processing steps following the pyrolysis reaction and discussed in greater detail below. Superheated steam is created by burning the off gas in a boiler, which thereby produces steam. The steam can then be sent to a processing unit where the steam is burned and the water vapor is superheated to a desired temperature and pressure. The superheated steam can then be used in any of the manners described below.
The residual carbon resulting from the pyrolysis reaction can include carbon black. The carbon black product can be adhered to inert material of the asphaltene compositions. In some embodiments, amounts of the residual carbon can be reduced and converted into light oil products described above through a reaction with superheated steam, such as the superheated steam produced using the off gas as described above. The superheated steam can produce hydrogen radicals which are then used to adjust the C:H ratio of the residual carbon and form light oil. This hydrotreating of the residual carbon will also produce additional heat that, like the off gas produced by the pyrolysis step, may be used to drive the pyrolysis step.
The residual carbon can also be converted into hydrogen and carbon dioxide using the superheated steam. Hydrogen and carbon dioxide are formed from the reaction between residual carbon and superheated steam at 450° C. according to the following equation:
C+2H2O→2H2+C)2 (1)
Still another use of superheated steam, whether produced using the off gas or obtained in another fashion, is the in situ hydrotreatment of the hydrocarbon liquid/vapor. The in situ hydrotreating works in part because of catalysts that are reduced in the reductive environment in which the pyrolysis is carried out. The superheated steam reacts with the catalyst to re-oxidize the catalyst, which thereby produces hydrogen. For example, when iron oxide catalysts are present in the asphaltene composition, the reduced iron oxide is re-oxidized by the superheated steam according to the following equation:
FeO(n)+H2O→FeO(n+1)+2H radicals (2)
The hydrogen radicals will react with broken bonds formed as a result of the thermal degradation of the asphaltenes and provide in situ hydrotreating.
The residual carbon produced by the pyrolysis reaction can also include inert materials. The residual carbon can be upgraded into a high grade carbon product through such unit operations as mineral flotation. In mineral flotation, the carbon reports to the minerals concentrate while the inert material will make up a tailings phase, which in itself can be reused to form more asphaltene pellets of the correct composition.
In some embodiments, the pyrolysis step 110 includes removing the gaseous product from the pyrolysis unit as it produced. It can be beneficial to remove the gaseous product as it is produced because the presence of the gaseous product in the pyrolysis unit tends to impede formation of liquid product. Any suitable manner of removing the gasesous product can be used. In some embodiments, the gaseous product is swept from the pyrolysis unit by introducing a steam or nitrogen purge into the pyrolysis unit. When steam is used as the purge gas, the steam can participate in the pyrolysis process and result in the production of more paraffinic components.
The method described above can further includes steps to separate certain components from the pyrolysis products. More specifically, the inert material, sulfur scavenger, and/or catalyst can all be separated from the pryolysis products. The separation steps can be carried out using any suitable separation methods and any suitable separation apparatus known to those of ordinary skill in the art. In some embodiments, the inert material is separated from the pyrolysis products by feeding the pyrolysis products to an attritioning and fine screening unit operation. In some embodiments, the catalyst is separated from the pyrolysis products by feeding the pyrolysis products to a magnetic or electrostatic separator. In some embodiments, the sulfur scavenger is separated from the pyrolysis products by feeding the pyrolysis products to a sulfide flotation unit. Any of the materials separated from the pyrolysis products can be reused in the method described herein, such as adding any of these materials to further asphaltene compositions yet to undergo pyrolysis.
In some embodiments, the method of upgrading asphaltenes through pyrolysis includes forming the aphaltene material into solid shapes, such as pellets, prior to conducting a pyrolysis step. Forming solid shapes of the asphaltenes prior to pyrolysis aids transport into the pyrolysis unit and can further prevent the asphaltenes from over-softening during pyrolysis and possibly jamming the pyrolysis unit. As discussed above, asphaltenes fed into a pyrolysis unit can soften during the pyrolysis step. If the asphaltenes soften too much, it can jam the moving parts of the pyrolysis unit. Accordingly, steps can be taken to alter the form of the asphaltenes prior to its introduction into a pyrolysis unit to thereby avoid over softening of the asphaltene.
In some embodiments, the step of forming solid shapes of the asphaltenes prior to pyrolysis includes pelletizing the asphaltenes to form asphaltene pellets. The process of forming asphaltene pellets can be carried out using the asphaltene compositions as described above, but can also be carried out using asphaltenes that are not mixed with inert material. Regardless of whether the asphaltene composition is used in the pelletizing method, pelletizing the asphaltenes creates heat transfer limitations that will slow the softening of the asphaltenes and avoid the jamming of moving parts of .a pyrolysis unit by the asphaltenes. However, the pelletized asphaltene will still be capable of thermally degrading into pyrolysis product.
Pelletization of the asphaltenes can be accomplished according to any suitable method for making pellets from asphaltenes. hi some embodiments, the asphaltenes are formed into pellets by adding water to the asphaltenes and forming a slurry, shaping the slurry into balls or other shapes, and drying the material. In some embodiments, the asphaltenes are formed into pellets by using an extrusion press or die mold to condense and shape the material into individual units. In some embodiments, asphaltene pellets can be produced by utilizing a briquetting process. Birquetting processes typically utilize two rollers with indents that material is dropped into as the rollers rotate in a confluent direction. In each of the above-described methods of producing asphaltene pellets, the size of the pellets can be manipulated and controlled to provide the correct size for feeding and controlling the rate of reaction in the pyrolysis unit.
In some preferred embodiments, methods of pelletizing the asphaltenes include mixing the asphaltenes and an organic binding agent in preparation for creating asphaltene pellets. As shown in
In step 200, asphaltenes are provided. Any suitable asphaltenes can be used and the asphaltenes can be derived from any of a number of sources. In some embodiments, the asphaltenes are derived from oil sands or tar sands, and more specifically, from the bitumen content of the oil sands or tar sands. As discussed above, the asphaltenes can also be part of the asphaltene composition that includes inert material.
In some embodiments, the asphaltenes are asphaltenes obtained from the low grade bitumen product produced by solvent extraction processing performed on bituminous material such as oil sands. During solvent extraction, solvent is added to bituminous material to create a slurry. Various ratios of solvent to bitumen content in the bituminous material (i.e., the S:B ratio) can be used. At certain S:B ratios, asphaltene in the bituminous, material will precipitate.
The slurry produced in the solvent extraction processing can be subjected to separation processing to separate low grade product from high grade product. In some embodiments, the separation is carried out via gravity separation. The high value product typically includes less than 400 ppmw of solid or sediment material and less than 0.5 wt % water and solids. This high value product is sent into the pipelines because it has a quality specification of water and solids that exceeds downstream processing and pipeline transportation requirements. The low grade product is rich in precipitated asphaltene. In some embodiments, the low grade product is from 90 to 95% asphaltene. The low grade product also includes a high solid (i.e., fines) content. As a result, this low grade product is well suited as a source of asphaltene material to be used in the methods described herein.
In some embodiments, the asphaltenes are obtained from performing a deasphalting process on a hydrocarbon material such as bitumen. Any deasphalting process known to those or ordinary skill in the art can be used to obtain the asphaltenes. An exemplary deasphalting process includes the Residuum Oil Supercritical Extraction (ROSE) process.
In step 210, a mixture is prepared that includes the solid asphaltenes and one or more organic binding agents. Any suitable organic binding agents can be used to create the mixture. In some embodiments, the organic binding agent is a light aromatic compound. The light aromatic compound can be an aromatic compound having a boiling point temperature less than about 400 ° C. at atmospheric pressure. In some embodiments, the light aromatic compound used in step 110 is an aromatic having a boiling point temperature in the range of from about 75° C. to about 350° C. at atmospheric pressure, and more specifically, in the range of from about 100° C. to about 250° C. at atmospheric pressure. In some embodiments, the light aromatic compound has a boiling temperature less than about 200° C.
It should be appreciated that the organic binding agent mixed with the asphaltenes need not be 100% organic binding agent. For example, in embodiments where the organic binding agent comprises one or more light aromatic compounds, the organic binding agent can include a mixture of aromatic and non-aromatic compounds. For example, the organic binding agent can include greater than zero to about 100 wt % aromatic compounds, such as approximately 10 wt % to 100 wt % aromatic compounds, or approximately 20 wt % to 100 wt % aromatic compounds.
Any of a number of suitable aromatic compounds can be used as the organic binding agent. Examples of aromatic compounds that can be used as the organic binding agent include, but are not limited to, benzene, toluene, xylene, aromatic alcohols and combinations and derivatives thereof. The organic binding agent can also include compositions, such as kerosene, diesel (including biodiesel), light gas oil, light distillate, commercial aromatic solvents such as Aromatic 100, Aromatic 150, and Aromatic 200 (manufactured by ExxonMobil), oxygenated hydrocarbons, and/or naphtha. In some embodiments, the organic binding agent is fuel oil. In some embodiments, the binding agent is oil produced from the pyrolysis of asphaltene pellets. In such embodiments, a combined pelletization and pyrolysis process can be self sustaining after initial start up by virtue of the binding agent necessary for the pelletization being produced from the pyrolysis of previously formed asphaltene pellets. In some embodiments, the organic binding agent has a boiling point temperature of approximately 75° C. to 375° C.
Any manner of preparing the mixture of organic binding agent and asphaltenes can be used. In some embodiments, the organic binding agent is mixed together with the asphaltenes in a vessel. The organic binding agent and the asphaltenes can be added into the vessel in any order, including simultaneously. Physical mixing of the organic binding agent and the asphaltenes can be carried out manually or automatedly, such as through a motorized stirring rod or blades. In some embodiments, the organic binder is applied as a fine spray that partially covers the surface of the asphaltenes as it is charged to a mixing device or as it is rotating in a mixing or pelletizing device.
The amount of organic binding agent and asphaltenes used when preparing the mixture can be any suitable amount for preparing a mixture of the two materials. In some embodiments, the ratio of organic binding agent to asphaltenes used when preparing the mixture ranges from about 1:200 to about 40:200 on a weight basis. Utilizing organic binding agent and asphaltenes in these ratios can help to ensure that the prepared mixture has a proper consistency for extruding the material and forming asphaltene pellets.
Additional materials can also be included in the mixture prepared in step 210. One specific example is the inclusion of inert material such that organic binding agent is mixed with the asphaltene composition described in greater detail above. Any of the inert materials described above can be mixed with the asphaltenes and organic binding agent. In some embodiments, the inert material is sand.
Additional materials that can be added to the asphaltenes and organic binding agent include, but are not limited to, catalysts and sulfur scavengers. The additional materials can be added to the mixture by adding the additional materials into the vessel in which the organic binding agent and asphaltenes are being mixed together.
Any suitable sulfur scavenger may be added to the mixture. Exemplary sulfur scavengers include, but are not limited to, limestone and other alkali and earth alkali compounds. The sulfur scavenger can be added to the mixture in any suitable amount. In some embodiments, the sulfur scavenger is added to the mixture at a sulfur scavenger:asphaltenes ratio of from 5:100 to 30:100 on a weight basis.
Any suitable catalyst can be added to the mixture. Exemplary catalysts include, but are not limited to, iron, iron oxide, titanium dioxide, iron titanium oxide (ilmenite), calcium titanate (perovskite), and manganese compounds. Catalysts can be added to the mixture in any suitable amount. In some embodiments, the ratio of catalyst to asphaltenes ranges in the mixture from about 1:100 to about 5:100 on a weight basis.
Fillers may also be added to the mixture. The filler material added to the mixture can aid in controlling and limiting the rate of reaction. Specific examples of fillers that can be used in the mixture include wax and fly ash. These fillers can be added to the mixture in any suitable amount depending on the desired effect on the rate of reaction.
Wax can be added as a filler and/or a binder. The wax will typically be added to the mixture as a liquid and can serve to beneficially repel water from the asphaltene pellets. The wax can also aid the pyrolyzation process by adding H2 and H2-deficient products, which thereby reduces olefins and improves product stability. In some embodiments, the wax is produced from known processes that convert natural gas to liquids.
Fly ash or ground granulated blast furnace slag (GGBFS) fillers store large amounts of heat and also provides a large surface area for heat transfer during the pyrolysis process. The fly ash filler can also have a catalytic effect during the pyrolysis process. Fly ash can include silica, alumina, iron oxide, lime, and carbon. When pozzolanic fly ash is used, the fly ash filler can also add to the strength of the pellets.
In step 220, an extrusion process is carried out to extrude the mixture prepared in step 210. Any suitable extrusion process that will condense and compact the mixture can be used. Similarly, any suitable extrusion apparatus that will produce a condensed and compacted extrudate can be used to carry out step 120. Where the extrusion apparatus includes a die, the shape of die used in the extrusion process is not limited, and can include conventional shapes such as circles, ovals, and rectangles, or non-conventional shapes. The shape of the die will generally dictate the cross section of the asphaltene pellets being formed by the processes disclosed herein. In some embodiments, the extrusion process is carried out a temperature in the range of from 10° C. to 90° C.
The extruded material leaving the extrusion apparatus is generally in the form of a rope having a uniform cross section similar or equal to the shape of the die used in the extrusion apparatus. In some embodiments, this rope of extruded material is cut along its length into shorter segments which can ultimately serve as the asphaltene pellets. The length of each segment is not limited, and the rope can be cut or allowed to naturally break into pieces of uniform or varying length. Any suitable manner of cutting the rope along its length can also be used. In some embodiments, the rope has a circular cross section, and the rope is cut along its length at an interval that is smaller than the diameter of the circular cross section to thereby create disc-shaped pellets.
As mentioned above, the individual segments created after cutting the rope of extruded material along its length generally make up the asphaltene pellets that can then be subjected to upgrading, such as by pyrolysis. The shape and size of the pellets in not limited. In some embodiments, the die of the extrusion apparatus has a circular shape, thereby allowing for the formation of cylindrical asphaltene pellets. In some embodiments, the diameter of the asphaltene pellets is in the range of from about 0.5 to about 0.4 inches and the height of the asphaltene pellets is in the range of from about 0.25 to about 4 inches. In some embodiments, asphaltene pellets are formed using a disc pelletizer. More specifically and as shown in
The step 300 of providing asphaltenes can be similar or identical to the step 200 described in greater detail above. Asphaltenes can be any suitable asphaltenes and can be obtained from any suitable process, such as by separating precipitated asphaltenes from tailings produced during froth treatment of bitumen material or by deasphalting a bitumen material. The provided asphaltenes can also be the asphaltene composition described in greater detail above.
In step 310, the asphaltenes are fed into a disc pelletizer. Any disc pelletizer capable of agglomerating material and forming pellets can be used. Generally speaking, the disc pelletizer will include a large pan that is positioned at an angle. The large pan is connected to a mechanism that is capable of rotating the pan. The disc pelletizer further includes a port for the continuous addition of material to be pelletized and a port where binding agent can be introduced into the pan. The size of the pan, the angle of inclination of the pan, and the speed at which the pan is rotated are all variables that can be adjusted to effect the size of pellets formed. In some embodiments, these variables can be adjusted during the process to alter the type of pellet being formed.
The asphaltenes can be fed into the disc pelletizer at any suitable location on the disc pelletizer for adding material into the disc pelletizer. As mentioned above, the disc pelletizer will preferably include a port which allows for the introduction of material into the pan. In some embodiments, the disc pelletizer is operated continuously, and as such, the asphaltenes can be added into the disc pelletizer continuously.
After the asphaltenes are fed into the disc pelletizer and the pelletizer begins to rotate, step 330 includes feeding an organic binding agent into the disc pelletizer. The organic binding agent is fed into the disc pelletizer to aid in the agglomeration of the asphaltenes and the eventual formation of asphaltene pellets.
The organic binding agent can be similar or identical to the organic binding agent described in greater detail above. Accordingly, in some embodiments, the organic binding agent includes an aromatic compound having a boiling point temperature in the range of approximately 75° C. to 375° C. In preferred embodiments, the organic binding agent is Aromatic 100, Aromatic 150, fuel oil, biodiesel, or a combination thereof.
In some embodiments, the organic binding agent is fed into the rotating disc pelletizer by spraying the organic binding agent into the pan. The spray of organic binding agent can aid in the uniform distribution of the organic binding agent throughout the pan and improve asphaltene agglomeration.
Any suitable amount of organic binding agent can be fed into the disc pelletizer. In some embodiments, the organic binding agent:asphaltenes ratio used ranges from 1:200 to 40:200 on a weight basis.
Additional material may also be added into the disc pelletizer, either with the asphaltenes or as a separate feed added to the disc pelletizer. For example, a sulfur scavenger or a catalyst may be added to the asphaltenes. Any suitable sulfur scavenger can be used, including, but not limited to, limestone, alkali compounds, and earth alkali compounds. Any suitable amount of sulfur scavenger can be added. In some embodiments, the ratio of sulfur scavenger to asphaltenes ranges from about 5:100 to about 25:100 on a weight basis. Similarly, any suitable catalyst can be used. In some embodiments, the catalyst is selected from iron, iron oxide, titanium dioxide, iron titanium oxide (ilmenite), calcium titanate (perovskite), and manganese compounds. Any suitable amount of catalyst can be added. In some embodiments, the ratio of catalyst to asphaltenes ranges from about 1:100 to about 10:100 on a weight basis.
Once the necessary materials have been added to the disc pelletizer, the rotation of the disc pelletizer begins to work on the material to agglomerate and form asphaltene pellets. As discussed above, variables such as the rotational speed of the pan, the angle of inclination of the pan, and the residence time can all factor into the formation of the asphaltene pellets. In step 340, the asphaltene pellets formed in the disc pelletizer are removed from the disc pelletizer. The disc pelletizer can include an exit port out of which asphaltene pellets can be removed. In a continuous operation (i.e., where asphaltenes and organic binding agent are continuously added to the rotating pan), the pellets may be removed on a continuous basis. The configuration of the disc pelletizer may allow for this continuous removal, as the formed pellets are channeled towards the exit. The exit may contain a mesh screen or device for sizing the pellets, so that only pellets of the required size exit the disc pelletizer.
In some embodiments, asphaltene pellets are formed using a balling drum. More specifically and as shown in
The step 400 of providing asphaltenes can be similar or identical to the step 200 described in greater detail above. Asphaltenes can be any suitable asphaltenes and can be obtained from any suitable process, such as by separating precipitated asphaltenes from tailings produced during froth treatment of bitumen material or by deasphalting a bitumen material. The asphaltenes provided in step 400 can also be the asphaltene composition described in greater detail above.
In step 410, the asphaltenes are mixed with an organic binding agent to form a mixture. The manner of mixing the asphaltenes and the organic binding agent can be similar or identical to step 210 described in greater detail above. Similarly, the organic binding agent can be similar or identical to the organic binding agent used in step 210. Additionally, as described in greater detail above, the mixture can include further materials, such as sulfur scavengers or catalysts.
After formation of the mixture in step 410, the mixture is fed into the balling drum in step 420. Any balling drum capable of agglomerating material and forming pellets can be used. Generally speaking, the balling drum will include a hollow drum that is connected to a mechanism capable of rotating the drum about its axis. The balling drum can be aligned horizontally or may be inclined at an angle. The balling drum further includes a port for the continuous addition of material to be pelletized and a port where pellets formed therein can exit the balling drum.
The mixture can be fed into the balling drum according to any suitable location on the balling drum for adding material into the balling drum. As mentioned above, the balling drum will preferably include a port which allows for the introduction of material into the drum. In some embodiments, the balling drum is operated continuously, and as such, the mixture can be added into the balling drum continuously.
After the mixture is fed into the balling drum, the balling drum is, operated in step 430. Operation of the balling drum generally includes rotating the drum about its axis with the mixture contained therein. The balling drum can begin to rotate after the mixture is fed into the drum, although in preferred embodiments, the drum is rotating as the mixture is fed into the drum.
Operation of the balling drum causes the mixture to begin to form nuclei of asphaltene pellets. These nuclei are small asphaltene pellets that begin to grow larger and larger as the balling drum continues to operate and cause interaction between the nuclei and the free mixture that has not yet formed into a pellet. Unlike the disc pelletizer, the balling drum generally uses fixed operating conditions, such as rotational speed of the drum, and will result in a fixed size distribution of asphaltene pellets (but not in a fixed size of pellets).
After asphaltene pellets are formed in the balling drum, a step 440 of removing asphaltene pellets from the drum is performed. The balling drum can include an exit port out of which asphaltene pellets can be removed. In a continuous operation (i.e., where the mixture is continuously added to drum), the pellets may be removed on a continuous basis. In some embodiments, the balling drum can include a spiral screen which helps to remove the pellets from the drum. The mesh size of the spiral screen allows pellets of a sufficient size to move to the hollow shaft at the center of the spiral screen, where they are then diverted out of the drum.
In some embodiments, the balling drum may also include a screening mechanism for removing small fines or undersized pellets that exit the drum with formed product pellets. The small fines or undersized pellets separated from the product pellets can then be recycled back into the drum. The screening mechanism can also separate pellets that are too large. The oversized pellets can then be crushed and the resulting material can be recycled back into the drum.
In some embodiments, asphaltene pellets are formed using a briquette press. More specifically and as shown in
The step 500 of providing asphaltenes can be similar or identical to the step 200 described in greater detail above. Asphaltenes can be any suitable asphaltenes and can be obtained from any suitable process, such as by separating precipitated asphaltenes from tailings produced during froth treatment of bitumen material or by deasphalting a bitumen material. The asphaltenes provided in step 500 can also be the asphaltene composition described in greater detail above.
In step 510, the asphaltenes are mixed with an organic binding agent to form a mixture. The manner of mixing the asphaltenes and the organic binding agent can be similar or identical to step 210 described in greater detail above. Similarly, the organic binding agent can be similar or identical to the organic binding agent used in step 210. Additionally, as described in greater detail above, the mixture can include further materials, such as sulfur scavengers or catalysts.
After formation of the mixture in step 510, the mixture is fed into the briquette press in step 520. Any briquette press capable of forming briquettes can be used. Generally speaking, the briquette press will include at least two rollers with indents that rotate in a confluent direction. The mixture formed in step 510 is dropped into the rollers as they rotate in a confluent direction. The mixture can be fed into the briquette press according to any suitable location on the briquette press for adding material into the briquette press. Typical briquette presses include a funnel into which the mixture can be poured and that will guide the mixture into the rollers. In some embodiments, the briquette press is operated continuously, and as such, the mixture can be added into the briquette press continuously.
The briquette press is operated in step 530 as the mixture is fed into the briquette press. Operation of the briquette press generally includes rotating the rollers in a confluent direction. The added mixture travels between the rollers rotating in a confluent direction and into the indents in the rollers, which thereby compress the material into a briquette shape.
After asphaltene pellets (i.e., briquettes) are formed in the briquette press, a step 540 of removing asphaltene pellets from the press is performed. In some embodiments, the asphaltene pellets pass through the rollers and collect in a collection area. In a vertical configuration, the mixture is added above the rollers, and the formed asphaltenes pellets fall from rollers after having passed therethrough into a collection area. The asphaltene pellets can then be removed from the briquette press by removing the pellets from the collection area.
Once formed, the asphaltene pellets formed by any of the methods described herein may be subjected to a pyrolysis process as described in greater detail above. In some embodiments, the above described method is modified only in that asphaltene pellets are introduced into the pyrolysis unit rather then introducing non-pelletized asphaltene composition into the pyrolysis unit. In some embodiments, additional sand or other inert material is added into the pyrolysis unit with the asphaltene pellets.
In some embodiments the asphaltene pellets are subjected to drying prior to introduction to the pyrolysis unit to reduce any residual moisture content and improve pyrolysis. Drying of asphaltene pellets can be by any suitable drying method, including heating or natural solar drying or evaporative drying through an appropriate manner of storage. In some embodiments the drying stage is incorporated into and part of the pyrolysis unit and the evaporated water provides an internal source of steam in the pyrolysis unit.
As described in greater detail above, the pyrolysis step leads to the asphaltenes endothermically degrading into lighter hydrocarbon products. Use of the asphaltene pellets can reduce or eliminate concerns of the asphaltenes quickly softening within the pyrolysis oven and interfering with moving parts of the pyrolysis unit. This is especially true as the pellets formed by the methods described herein still contain some residual moisture content that can only be gradually removed from the pellets as they are heating up to the oven operating temperature.
In each of the methods described herein, the use of the organic binding agents advantageously allows for easier water removal from the pellets prior to being heated in a pyrolysis unit. Traditionally, moisture content of asphaltene pellets can run as high as 40% due to the very open card-house structure of the asphaltene agglomerates. The surface of these pellets is hydrophilic, meaning that even when water is pushed out of the pellets, the water can be taken back up by the pellets and little to no moisture reduction will be realized. However, when the organic binding agents as disclosed herein are used in the formation of the asphaltene pellets, the asphaltene surfaces become hydrophobic and will push water away. Consequently, moisture removal is more easily accomplished. Specific examples of the water expulsion phenomenon are described in the Examples section below.
The size and shape of the pellets formed by the pelletization step are not limited. The shape of, the pellets may be any suitable shape, including spheres, cubes, and rods. The size of 10. the pellets may be any suitable size and may be selected based on the size of the pyrolysis unit into which the asphaltene pellets are fed.
While asphaltene pellets formed according to any of the above described methods can be subjected to pyrolysis processing to upgrade the asphaltene pellets, the asphaltene pellets can also be used in other processes. In some embodiments, the asphaltene pellets are combusted to produce both power and steam. Combustion of the asphaltene pellets can take place in any suitable combustion unit, and in some embodiments, the asphaltene pellets are combusted in a boiler. Any suitable type of boiler capable of combusting the asphaltene pellets can be used. In some embodiments, the boiler is either a pulverized fuel (PF) boiler or a circulating fluidized bed (CFB) boiler. Asphaltene pellets are suitable for use in these types of boilers for similar reasons as described above with respect to the use of asphaltene pellets in pyrolysis units. That is to say, the asphaltene pellets help to ensure that the asphaltenes being subjected to combustion do not overly soften or melt to the point that the asphaltenes plug feed tubes into the boilers. The asphaltene pellets, having a lower moisture content, are less likely to soften and melt and can therefore enter into the combustion area of the boilers and undergo combustion for the production of power and steam. The asphaltene pellets having lower moisture content have a higher heating value (BTU/lb) and lower boiling off gas requirements, thus producing more power per unit of asphaltene pellet and reducing the size requirement to achieve a specified MW power production and reducing off gas handling.
In some embodiments, the asphaltene pellets are subjected to drying prior to introduction to the boiler. The drying can be similar or identical to the drying prior to introduction into a pyrolysis unit as discussed in greater detail above. Drying can reduce any residual moisture content and improve heating value (BTU/lb). Drying of asphaltene pellets can be by heating or natural solar drying or evaporative drying through an appropriate manner of storage.
When a CFB boiler is used, the asphaltene pellets preferably include limestone as discussed in greater detail above. The presence of limestone in the asphaltene pellets helps to achieve boiler fixation of sulfur as a means for flue gas desulfurization.
360 lbs of asphaltene concentrate recovered from tailings produced during the aliphatic froth treatment of Athabasca tar sands is mixed together with 360 lbs of inert sand. The mixture of asphaltene and sand, plus 36 lbs of steam, are fed into a pyrolysis oven operating at 450° C. The mixture of asphaltene, sand and steam is maintained in the pyrolysis oven for 18 minutes.
The output stream of the pyrolysis oven includes 122 lbs of gas oil, 562 lbs of carbon black and sand, 66 lbs of water, and 6 lbs of off gases. Sand is separated from the output stream by feeding the pyrolysis products to a crusher and flotation circuit.
918 lbs of asphaltene concentrate recovered from tailings produced during the aliphatic froth treatment of Athabasca tar sands is mixed together with 1,000 lbs of sand, 95 lbs of sulfur scavenger, and 10 lbs of a silica-alumina catalyst. The mixture is fed into a pyrolysis oven operating at 420° C. The mixture of asphaltene and sand is maintained in the pyrolysis oven for 17 minutes. The output stream of the pyrolysis oven includes 325 lbs of gas oil, 1,688 lbs of carbon black, and 10 lbs of off gases. The sand, catalyst, and sulfur scavenger are separated from the output stream by feeding the pyrolysis products to a crusher and flotation circuit.
50 kg of asphaltene recovered from tailings produced during the aliphatic froth treatment of Athabasca tar sands is, mixed together with 1500 cc of Aromatic 150 in a conventional industrial cement mixer. The Aromatic 150 is added to the asphaltene material progressively over a course of 5 minutes. The mixing of the Aromatic 150 and the asphaltene material in the cement mixer is carried out for 20 minutes to eventually produce a mixture. The mixture is then transported to an extrusion apparatus. The mixture is fed through the extrusion apparatus, which has a circular shaped die with a diameter of 1.375 inches. The extrusion process produces a rope of hardened and compressed material. The rope is cut along its length every 0.75 inches to ultimately produce a plurality of disc-shaped asphaltene pellets having a length of 0.75 inches and a diameter of 1.375 inches.
Example 3 is repeated, with the exception that a quantity of limestone is added into the cement mixer with the asphaltene material and the Aromatic 150. 7 kg of limestone is added into the cement mixer prior to the addition of the Aromatic 150. The resulting mixture is transported to the extrusion apparatus and disc-shaped asphaltene pellets are produced in the same manner as described in Example 3.
A feed material of asphaltene concentrate is provided. The asphaltene concentrate has an original moisture content of about 35-40%, with dried feed showing a loss upon ignition of ˜70% (at 800° C.). The ash fraction (˜30 wt %) of the concentrate is primarily quartz sand and some aluminosilicate clays. Dry concentrate contains approximately 5% sulfur, about half as pyrite and half as organic sulfur.
The concentrate is fed into an operating 3-ft disc pelletizer. Organic binder is also added into the 3-ft disc pelletizer. In one run, the organic binder is Aromatic 150. In a second run, the organic binder is biodiesel. The concentrate is continuously fed into the disc pelletizer while a fine mist of organic binder is sprayed over the concentrate as it enters the disc pelletizer. Small balls in the disc pelletizer are wetted by the organic binder and become enlarged as new concentrate added into the disc pelletizer coats the surface of the balls. Large balls are eventually formed, having diameters ranging from about ⅜ inches to 1 inch. The larger balls tend to stay on top of the smaller balls and the unballed concentrate that remains at the bottom of the disc pelletizer. Once the balls reach their critical size (as determined by the disc pelletizer speed and angle), an essentially constant pellet size is discharged over the lip of the disc pelletizer.
In both runs, the ratio of organic binder to moist asphaltene concentrate is about 25:1. Because the moist concentrate contains only about 44% LOI components at the time of pelletization, the ratio of organic binder to asphaltene organics is about 1:11.
While pellet feed material contained about 35-40% moisture, “wet” pellets have a significantly reduced moisture content of 22%, and upon further standing, the pellets will readily lose most of their moisture (down to <4% moisture) at ambient temperature given dry conditions and sufficient time.
2,315 lbs of asphaltene concentrate recovered from tailings produced during the aliphatic froth treatment of Athabasca tar sands is mixed together with 100 lbs of Aromatic 150 and then used to make asphaltene pellets as described in Example 5. The asphaltene pellets are allowed to dry in ambient conditions for 24 hours. The pellets and 320 lbs of inert sand are then fed into a pyrolysis oven operating at 425° C. The pellets are maintained in the pyrolysis oven for 17 minutes. The output stream of the pyrolysis oven includes 1,043 lbs of gas oil, 1,579 lbs of carbon black mixed with sand, and 113 lbs of off gases. The sand is separated from the pyrolysis products by feeding the pyrolysis products to a crusher and flotation circuit.
In an example of water expulsion in asphaltene pellets formed by the methods described above, a visual inspection of the asphaltenes being sprayed with organic binding agent in a disc pelletizer reveals that water is being expelled from the pellets forming therein. While the water stays on top of the pellet surface and thereby gives the appearance of wet material, the interior of the pellets is, in fact, very dry. After the surface moisture is allowed to evaporate off of the pellets, the pellets become hard and the moisture content drops to less then 20% (as compared to an original moisture content of more than 40%). The reduced moisture content in the pellets means that additional water removal steps do not need to be carried out, resulting in a significant cost savings.
When carrying out the extrusion process disclosed herein, water from the feed material (initially about 40% moisture content) is readily expelled and a pool of water forms on top of the press. When the expelled water is removed from the press and a small amount of biodiesel is added, a very dry and solid pellet is produced having a moisture content of around 15%. As a contrast, the same extrusion process performed without the use of the organic binding agent results in most of the expelled water being sucked back into the pellet. The result is a wet compact that was still solid, but that includes an estimated moisture content of about 35%.
In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that tomes within the scope and spirit of these claims.
This application claims priority to U.S. Provisional Application No. 61/419,319, filed Dec. 3, 2010, the entirety of which is hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61419319 | Dec 2010 | US |
