Coal combustion residual based aggregate and method of making an aggregate

Abstract

Embodiments presented provide for a method of making aggregate from coal combustion residuals (CCR) compounds, which includes employing a significant amount of such coal combustion residuals in combination with a calciferous additive, sodium hydroxide, and water to cure the shape the same under the influence of controlled pressure and temperature for a predetermined time to create an aggregate which is characterized by a mineralogical crystalline phase.

Description

PATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] None. FIELD OF THE DISCLOSURE

[0002] Aspects of the disclosure relate to producing an aggregate material used in construction. More specifically, aspects of the disclosure relate to producing a coal combustion residual based aggregate as well as a method of making the aggregate for use in the construction industry. BACKGROUND

[0003] As time moves forward, the need for environmentally clean technologies grows. Surprisingly, the construction industry accounts for large percentages of carbon dioxide (designated as a greenhouse gas). Recently, governmental efforts on an international basis have been made to limit the amount of greenhouse gases produced. Therefore, innovation with conventional technologies is needed to develop structural products that meet their intended design specifications and that are environmentally friendly.

[0004] Many times, coal is used as a heat source in the production of electricity. Substantial amounts of coal are burned daily in the United States and other countries to provide a safe and secure electrical supply. Coal itself is not a homogenous material, and different types of coal may be used in the burning process. Some types of coal burn very efficiently, while others are not as efficient. The remaining products from the coal burning process often have remnants of combustible hydrocarbons left in a residue. This residue is considered waste, and large amounts of money are being spent on properly disposing of it.

[0005] Coal combustion residues include, but are not limited to boiler bottom ash, boiler slag, as well as flue gas desulfurization material. Boiler bottom ash is defined by the 1 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE Environmental Protection Agency (“EPA”) as a coarse angular particle that is too large to be carried up into a power plant’s smokestack. Boiler slag is defined as a molten bottom ash from a slag tap in the boiler as well as cyclone-type furnaces that turn into pellets that have a smooth, glassy appearance. In some electrical production plants, the flue gas is treated before release. The treatment entails taking sulfur components from the flue gas. The flue gas desulfurization material is the material leftover from the process of reducing sulfur dioxide emissions from a coal-fired boiler. The material may be a wet sludge consisting of calcium sulfite or calcium sulfate or a dry powdered material that is a mixture of sulfites and sulfates.

[0006] The coal combustion residue is typically placed into a surface impoundment or a landfill. Other disposal techniques include discharging the material into nearby waterways as controlled by the electrical plants' water discharge permit. Currently, over 130 million tons of coal combustion residual based materials are generated.

[0007] The EPA tightly controls coal combustion residue. Accidents involving coal combustion residue have produced significant economic damage to Kingston, Tennessee, and Eden, North Carolina communities, from large material spills. Since coal combustion residue contains contaminants such as mercury, cadmium, and arsenic, reuse of the material is avoided due to its toxicity. As of 2015, the EPA has put forth complex regulations for containing coal combustion wastes originating from electrical generation facilities. Technical requirements for the storage and handling of such coal combustion wastes are dictated by the Resource Conservation and Recovery Act. As the regulatory landscape has changed, previous potential uses of coal combustion residue have been altered. Uses previously acceptable before 2015, are now forbidden and severely limiting. In light of the increased regulations and regulatory environment, very few options exist for reusing some coal combustion residues. 2 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE

[0008] There is a need to make beneficial use of coal combustion residue. Current beneficial uses include incorporating flue gas desulphurization materials into grout or for use with wallboard products. Boiler slag and bottom ash currently have limited uses as mercury, cadmium, and arsenic toxicity may be present.

[0009] EPA regulations evaluate the potential environmental impacts associated with the coal combustion residue from both a regulatory and human health perspective. Unencapsulated beneficial uses are minimal for coal combustion residues. A large majority of coal combustion residues do have affixed mercury, cadmium, and arsenic, and widescale use of the material is prohibited unless the material is found to be non-toxic. As a result, a majority of the coal combustion residue cannot be used because of contamination risks.

[0010] Further problems exist for coal combustion residues in that, over time, the lack of toxicity of the overall material must be maintained. Thus, the material may be initially safe for use, but continued weathering may cause locked contaminants to flow out of the residue. Freezing and thawing of materials may break apart the residue, thereby liberating the contaminants. Current technologies do not address these long-term issues; thus, the overall use of coal combustion residues is minimal compared to the amount of waste generated.

[0011] There is a need to provide an apparatus and methods to enable the production of structural materials with ease compared to conventional apparatus and methods.

[0012] As described above, there is a further need to provide apparatus and methods that do not have the drawbacks of leakage of toxic materials over time. 3 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE

[0013] There is also a need to reduce the economic costs associated with the operations and apparatus described above for structural material fabrication.

[0014] There is a further need to provide a beneficial use for all types of coal combustion residues and not just isolated portions of such materials. Such beneficial uses should include the ability to use large quantities of material.

[0015] There is a further need to provide a beneficial use that meets the more complex regulatory requirements placed upon such materials from such regulations. SUMMARY

[0016] So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized below, may be had by reference to embodiments, some of which are illustrated in the drawings. It is to be noted that the drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments without specific recitation. Accordingly, the following summary provides just a few aspects of the description and should not be used to limit the described embodiments to a single concept.

[0017] In one example embodiment, a method to produce a coal combustion residual based aggregate is disclosed. The method comprises receiving a feedstock of coal combustion residue. The method further comprises separating the feedstock of coal combustion residue into a size of 35 microns or less to create a separated fraction of sized coal combustion residue. The method further comprises combining a weighed portion of at least one of a lye and a lime amount to a weighed portion of the separated fraction of sized coal combustion residue to create a mixture, wherein a mix ratio of 3 4 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE percent to 15 percent of one of calcium oxide and calcium hydroxide and 1 percent to 5 percent sodium hydroxide based on weight. The method further comprises dry mixing the mixture to create a mixed dry mixture. The method further comprises adding water to the mixed dry mixture to create a green mixture. The method further comprises hydraulically roller pressing the green mixture into a pre-shaped mold to directly form a green aggregate. The method further comprises thermally curing the green aggregate in an autoclave to form the coal combustion residual based aggregate and wherein the method occurs at a storage area for the coal combustion residue.

[0018] In another example embodiment, a method to produce a coal combustion residual based aggregate is disclosed. The method may comprise receiving a feedstock of coal combustion residue. The method may further comprise separating the feedstock of coal combustion residue into a size of 35 microns or less to create a separated fraction of sized coal combustion residue, wherein the coal combustion residue includes boiler slag. The method may further comprise combining a weighed portion of at least one of a calcium oxide, calcium hydroxide, and sodium hydroxide, to a weighed portion of the separated fraction of sized coal combustion residue to create a mixture, wherein a mix ratio of 3 percent to 15 percent of one of calcium oxide and calcium hydroxide and 1 percent to 5 percent sodium hydroxide, based on weight. The method may further comprise mixing the mixture with water to create a green mixture. The method may further comprise roller pressing the green mixture into a pre-shaped mold to directly form a formed shape. The method may further comprise thermally curing the formed shape in an autoclave at a temperature between 180 degrees Celsius and 225 degrees Celsius and a pressure of 140 pounds per square inch and 350 pounds per square inch. The method may further comprise crushing the formed shape to an aggregate-size material after thermal curing, wherein the method occurs in a storage area for coal combustion residue. 5 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE

[0019] In another embodiment, a construction material based upon a coal combustion residue is disclosed. The material may comprise a molded formed aggregate with a homogenous matrix of calcium silicate hydrates and sodium alumino-silicates with a stable crystalline structure formed into an aggregate shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the drawings. It is to be noted; however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not considered limiting of its scope, for the disclosure may admit to other equally effective embodiments.

[0021] FIG.1 is a systemized approach for producing a coal combustion residual based aggregate and a method of making an aggregate.

[0022] FIG.2 is a method for producing an aggregate from coal combustion residue in conformance with the systemized approach of FIG.1.

[0023] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures (“FIGS”). It is contemplated that elements disclosed in one embodiment may be beneficially utilized in other embodiments without specific recitation. DETAILED DESCRIPTION

[0024] In the following, reference is made to embodiments of the disclosure. It should be understood, however, that the disclosure is not limited to specific described embodiments. Instead, any combination of the following features and elements, whether 6 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE related to different embodiments or not, is contemplated for implementation and practice in the disclosure. Furthermore, although embodiments of the disclosure may achieve advantages over other possible solutions and / or over the prior art, whether or not a given embodiment achieves a particular advantage is not limiting the disclosure. Thus, the following aspects, features, embodiments, and advantages are merely illustrative and are not considered elements or limitations of the claims except where explicitly recited in a claim. Likewise, reference to “the disclosure” shall not be construed as a generalization of the inventive subject matter disclosed herein and should not be considered an element or limitation of the claims except where explicitly recited in a claim.

[0025] Although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer, or section from another region, layer, or section. When used herein, terms such as “first”, “second”, and other numerical terms, do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer, or section discussed herein could be termed a second element, component, region, layer, or section without departing from the teachings of the example embodiments.

[0026] When an element or layer is referred to as being “on”, “engaged to”, “connected to”, or “coupled to” another element or layer, it may be directly on, engaged, connected, coupled to the other element or layer, or interleaving elements or layers may be present. In contrast, when an element is referred to as being “directly on”, “directly engaged to”, “directly connected to”, or “directly coupled to” another element or layer, there may be no interleaving elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed terms. 7 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE

[0027] Some embodiments will now be described with reference to the figures. For consistency, elements in the various figures will be referenced with numbers. In the following description, numerous details are set forth to provide an understanding of various embodiments and / or features. It will be understood; however, by those skilled in the art that some embodiments may be practiced without many of these details and that numerous variations or modifications from the described embodiments are possible. As used herein, the terms “above” and “below”, “up” and “down”, “upper” and “lower”, “upwardly” and “downwardly”, and other like terms indicating relative positions above or below a given point are used in this description to more clearly describe certain embodiments.

[0028] Aspects of the disclosure provide a method for producing an aggregate that may be used in the construction industry. Embodiments of the method produce an aggregate with a significant amount of such coal combustion residuals in combination with a calciferous additive, sodium hydroxide, and water, to cure the shape under the influence of controlled pressure and temperature for a predetermined time to create an aggregate which is characterized by a mineralogical crystalline phase.

[0029] Embodiments of the disclosure provide for an aggregate that encapsulates toxic elements, such as mercury, arsenic, lead, and cadmium, so that these elements are not transported to the external environment. The resulting aggregate has been tested through an exhaustive number of established testing methods to determine the properties of the aggregate.

[0030] As described above, conventional materials have significant defects during freezing and thawing cycles. In testing, a 50-cycle thaw process is performed in conformance with AASHTO T 103. The test simulates the amount of weathering an 8 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE aggregate would undergo in field conditions, not the disintegration of the aggregate placed under such conditions. The resulting aggregate shows acceptable results.

[0031] As the coal combustion residue may have significant amounts of carbon that could cause ignition and subsequent fire, the aggregate produced was tested for a loss of ignition according to standard ASTM C 25. In the test, an aggregate sample is subjected to a specific temperature. The weight of the sample, before and after heating, is recorded. As the temperature is above the normal combustion temperature for materials, volatile organic matter, and water are driven off the sample. As provided in Table 1, the loss of ignition (LOI) is minimal.

[0032] Aggregate may be used in a variety of conditions. The aggregate may be used as road bedding material for grading purposes or in landscaping. In other instances, the aggregate may be used in conjunction with concrete to produce a concrete building structure, such as a block or a brick. In such uses, the aggregate may chemically react in the matrix of the block or brick. In the test, repeated immersion of the aggregate is performed in saturated sodium or magnesium sulfate solutions, followed by oven drying, to partially or completely dehydrate the salt precipitated in permeable pore spaces. The internal expansive force, derived from the rehydration of the salt upon re-immersion, simulates the expansion of water upon freezing. The test provides information that helps determine the soundness of aggregates when adequate information is not available from service records of the material exposed to actual weathering conditions. The results indicate sufficient soundness of the aggregate.

[0033] Aggregates used in the construction industry may be exposed to different mechanical force environments. As such, the aggregate may be subjected to abrasive forces, thus degrading the material. An abrasion test was conducted in conformance with ASTM C 131, where abrasive forces are placed upon the aggregate. The forces are 9 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE created using a standard Los Angeles testing machine. In this test, a load of aggregate approximately five pounds in weight is inserted into a drum that also incorporates steel balls. The mixture of steel balls and aggregate is raised or scooped up to the top of the drum and allowed to drop, creating an overall crushing force. This action is repeated a standardized number of times, and the aggregate is removed from the drum and weighed a second time. The amount of abrasion loss is then recorded. The resulting range for the tested aggregate shows little to no abrasion loss.

[0034] In some applications, the amount of lightweight particles in the aggregate is desired to be known. To ascertain the amount of lightweight particles in the aggregate, a sample of the aggregate was submersed in a high-gravity liquid (over a specific gravity of 2.0), and the amount of floating aggregate was determined. This may be used to determine the amount of coal or lignite remaining in the sample. As tested, the aggregate has little to no coal or lignite remaining in the material.

[0035] A standard petrographic analysis of the aggregate, as specified in ASTM C 295, is also performed. The petrographic examination establishes whether the aggregate contains chemically unstable minerals such as soluble sulfates or unstable sulfides that may form sulfuric acid. Other evaluations are also performed to analyze the potential distress the material may expose upon a surrounding concrete matrix. Temperatures also increase during such tests to determine viability in different temperature regimes. Unstable materials, such as smectites, are also determined, as well as the presence of swelling clay materials. The results of such petrographic examinations are acceptable.

[0036] As the amount of swellable clays and friable particles may be detrimental when the aggregate is incorporated into a concrete brick or block, a test in conformance with ASTM C 142 was performed. Clays and friable materials at or near the surface of a 10 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE structural element may result in the pitting of the surface through wear. Test results of the materials indicate a low percentage of clays and friable materials.

[0037] Other tests were also performed to identify the physical properties of the aggregate. These include determining bulk dry specific gravity, apparent specific gravity, and water absorption percentage. All tests recorded acceptable results. Test Parameter Test Method Result Range 50 cycle free thaw % AASHTO T 103 0 – 50Table 1

[0038] Referring to FIG. 1, a process for making a coal combustion residue based aggregate is illustrated. The method 100 entails receiving a shipment of material to be processed. The material can be received from an electrical generation facility that produces coal combustion residue based materials. As previously discussed, materials 11 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE include fly ash, boiler slag, bottom ash, and flue gas desulphurization materials. These materials, in embodiments, may be combined into a single non-homogenous mixture. The materials may be transported by rail, car, or truck in some embodiments. In other embodiments, the apparatus creating the coal combustion residual based aggregate is a mobile unit transported to the coal combustion residual storage area.

[0039] As will be understood, providing a mobile unit that processes the coal combustion residual based materials at a generation site provides advantages over conventional treatment methods. For example, trucking or transportation of materials over roads, rails, or ships is minimized. Permitting for transporting what may be hazardous waste is thereby eliminated. Other advantages include eliminating “double handling” of materials, where the hazardous materials are merely placed into the treating apparatus rather than handled, transported, unloaded, and then treated. Such elimination of double handling is not possible with conventional treatment processes.

[0040] Remediation of the coal combustion residual materials, when it occurs at the storage site, significantly reduces greenhouse gas emissions as transportation emissions are virtually eliminated. Permitting for the treatment site is also avoided as the treatment of the residual materials occurs at a site that was previously permitted to store coal combustion residue.

[0041] After receiving the materials at step 102, the method progresses to steps 104 and 106 as well as step 108. In step 104, fly ash materials or materials that are generally lightweight and small in diameter size are separated from bottom ash materials. The fly ash material at 104 is then placed into a silo at 110. Materials larger in diameter than fly ash, such as bottom ash, may be processed as noted in step 112. The bottom ash material at 106, because it is larger in diameter size than the fly ash components at 104, is screened at step 112. If the bottom ash size is considered to be acceptable, it is placed 12 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE in the silo at 110, along with the fly ash from step 104. If the bottom ash is too large at step 112, the material is sent to a grinder or crusher at 114 and then passes through the screening test again at step 112. If the material is acceptable in size then the material is stored at 110 in the silos. If the material is too large for the screens at 112, the material may be sent again to a grinder or crusher at 114 and then reprocessed through to the screening step at 112. As will be further understood, materials such as flue gas desulfurization materials and bottom slag from the boiler may also be screened, as in step 112, and then determined to be acceptable or not. If the material is considered to be acceptable, it is then placed in a silo at 110. If the material is rejected in the screening process at 112, the material may be sent to a grinder or crusher at 114 and reprocessed through the screening step 112. As will be understood, materials such as boiler slag and flue gas desulfurization materials are not conventionally recycled in this manner; therefore, the process illustrated incorporates materials into a final process that was previously not used by reclamation techniques.

[0042] As will be further understood, materials such as bottom ash at 106, flue gas desulphurization materials, and bottom slag do not have to be added to the same silo at 110. Each of the materials may be stored in their own respective silo. Further processing steps in the method may include fly ash or use bottom slag, bottom ash, or flue gas desulphurization materials exclusively or in combination. Conventional techniques for treatment are limited to fly ash and are thus limited.

[0043] Storage of the material constituents of the aggregate may be stored in a silo or other segregation method. Such methods may include bin storage and on-site open-pit storage. In some embodiments, the materials may come directly from the electrical generating equipment itself where the material is produced. This continual feed process eliminates storage requirements and may be applicable to electrical generating facility plants with small areas with limited storage capacity. 13 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE

[0044] At 108, lye material, as well as lime material at 116, may be stored in separate storage areas and then metered to a specific amount of lye and / or lime and added to the contents of the silo at 110. As will be understood, materials may be metered from the silo at 110 to a separate vat or container such that specific amounts of lye and / or lime may be added to the contents coming from the silo at 110. The resulting mixture is then weighed at 118.

[0045] Batch formulas may be previously determined with specifically defined amounts of sub-components by weight. Each of the sub-components; therefore, may be weighed prior to addition to a mixing vat. The dry materials may be mixed first to achieve a relatively uniform mixture of materials based on the dry batch formula. In some embodiments, a batch mixing process is performed where large amounts of each constituent are added to a hopper. The rotary motion of the hopper mixes the constituents. Other mixing forms, such as convective mixing, may also be performed. In such convective mixing processes, a base material travels along a beltway or other transportation mechanism, and other constituents are added to the base material, thereby arriving at the end of the process with a mixed material. Still, further types of mixing may be used, such as paddle mixers, industrial ribbon mixers, double cone blenders, drum blenders, or shear mixers.

[0046] After the mixing of the dry components, water may be added. As illustrated, the materials are mixed at 122 with water added at step 120. The resultant material is defined as a “green” mix or wet mix. The wet mix of material is then put into a press at step 124. As will be understood, a hydraulic press may be used at step 124. Additionally, to increase the efficiency of the process, a roller press may be used at step 124, thereby providing continuous processing ability for the method. The green mixture may be pressed to a specified value, such as processing through a 5000 pounds per square inch roller press. 14 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE The use of a roller press is considered a valuable alternative to other presses as the amount of energy used by the roller press may be substantially less than other conventional hydraulic presses. Therefore, the use of the roller press is significant as the overall amount of energy usage and emissions that occur during the process are reviewed and rated by governmental agencies, such as the EPA. A single roller cylinder may be used in one non-limiting embodiment as the green mix is held captive in a tray or mold. Other possibilities for a roller press include a dual action or dual roller system with top and bottom rollers.

[0047] While the material constituents of the green mixture are designated by the batch design, the use of a dual-action or dual roller system may allow for additional grinding of materials, such as bottom / boiler slag, if such a need arises. Therefore, a dual roller system is not present in conventional systems as pre-ground fly ash is used as a constituent for products like concrete. The use of a roller system is not performed because, in fact, the materials are pre-designated to fit a specific design requirement. As the current methods described use more rugged materials and additional processing steps, such as a roller press, this method has significant advantages over conventional systems. In the instance of a roller press, the amount of compressive force may be between 7000kN and 35,000kN.

[0048] Thicknesses of the green mixture, after compression, may vary. In some embodiments, the green product (prior to insertion into an autoclave for drying) may be 3 inches. Other values may be used. In some instances, thicknesses may be substantially decreased, thereby creating relatively thin strips of material. These strips may be easily converted through additional processing steps to make large or small aggregates.

[0049] The green mixture, after being pressed at 124, is then sent to an autoclave at step 130. Materials are placed in the autoclave for a specific amount of time and dried. In 15 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE the autoclave a humid atmosphere may be achieved by water, at 126, being added to a boiler, at 128, providing a steam atmosphere for the autoclave 130.

[0050] In some applications, the cured product from the autoclave may then be sent to a crusher to crush the material to a desired final size. The crushing may result in the desired size of aggregate. The material may also be tumbled, as necessary, in a tumbling machine if the final product to be achieved specifies a non-angular resultant product.

[0051] After completion of curing in an autoclave, samples of the material may be tested at 132 to see if they conform to expected standards. As will be understood, the testing may be related to any or all of the tests identified in Table 1. Additional tests, such as for size, specific gravity, angularity, or other features, may also be performed. If the testing at 132 is acceptable, packaging may be accomplished at 134. To this end, packaging may take many forms. The materials may be ordered in small batches or larger batches by a customer. Smaller batches may be placed in 20 to 50 pound bags for direct delivery to a consumer or retailer. Larger batches may be separated according to the size of the material. Material may be put into large freestanding piles that may be loaded onto railcars, trucks, ships, or other transportation devices. A unique feature of the method illustrated in FIG.1, is that if testing is not acceptable at 132, the method may return to step 114 for further grinding and crushing the material. In these embodiments, the material that fails the testing is related to the size component of the aggregate that has been produced. Thus, the overall size of the aggregate is too large for a specified diameter by a customer. To achieve the size of the material as specified by the customer or project engineer, the size of the aggregate may be altered by an additional grinding or crushing procedure at 114.

[0052] The use of lime at 116 involves the addition of an inorganic material composed primarily of calcium oxide and hydroxides. As will be understood, the type of hydroxides 16 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE that may be incorporated with the calcium oxides may vary. In one possible alternative, calcium hydroxide is the type of hydroxide used. The source material for lime may be limestone extracted from quarries or mines. As will be further understood, instead of directly using calcium hydroxide, a process may be used at the site or with equipment where quicklime is hydrated with water to produce calcium hydroxide. Thus, although the process at 116 shows a single step, the step may be subdivided by using quicklime with an addition of water to produce lime that is then weighed at 118 with material from the silos at 110.

[0053] As will be further understood, different types of lime with other features may be used for the lime function at 116. These types of lime include portlandite, brucite, magnesite, and other magnesium hydroxycarbonate compounds. Lime in the building industry can also be characterized into three subcategories. Each of these subcategories may be used in combination with the process. The three types of lime include pure, hydraulic, and poor lime. In embodiments, hydraulic lime, also called water lime, contains lime with silica or alumina, which is set by exposure to water. In embodiments, the amount of clay added to the hydraulic lime predicts the type of behavior of the hydraulic lime and the ultimate use of the materials. With greater use of clay materials, hydraulic lime can be used in more aggressive and freezing climates than limes with lesser amounts of clay added. Pure lime may be used in a variety of conditions. Pure lime consists primarily of calcium hydroxide, which is derived from quicklime with the addition of water, and may contain up to 5 percent of other ingredients. Pure lime may be used in areas where the material will ultimately be exposed to potential cracking due to loads or freeze-and-thaw conditions. The use of pure lime allows for a self-healing process to occur for the aggregate produced, thereby preventing further degradation of the aggregate due to the conditions that are being experienced. In some instances, poor lime may be used when the base material has little to no toxicity. Poor lime is characterized by comparatively longer set times and strength. To this end, poor lime may be used in low-quality 17 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE aggregates that do not need extensive encapsulation for toxic elements or materials and that also require a relatively cost-effective treatment process for aggregate production.

[0054] The addition of lye at 108 includes the addition of an alkali metal hydroxide. Different types of alkali metal hydroxides may be added, including sodium hydroxide or potassium hydroxide, as nonlimiting embodiments. The type of lye that may be added in the process may be in the form of flakes, pellets, powders, solutions, or beads. One of the purposes of adding lye to the matrix of the material being generated for aggregate production is to create an alkaline solution to prevent a potential acidic attack upon the aggregate produced. In embodiments where the aggregate may experience a hostile environment that is acidic in nature, greater amounts of lye may be added to combat acid attack.

[0055] As will be understood, the amount of lye at 108 and the amount of lime at 116 may vary when added to the materials obtained from the silos at 110. In some instances, no lye at 108 is used. In some further instances, no lime at 116 is used. Thus, the process may include various amounts of each component according to the aggregate type needed for end production.

[0056] Referring to FIG.2, a method 200, in accordance with one example embodiment of the disclosure, is illustrated. The method entails receiving materials at step 202. The receiving of materials includes materials derived from electrical production plants such as boiler slag, bottom ash, flue gas desulfurization materials, and fly ash. Any or all of these components may be received. A specification for the maximum size of aggregate may be submitted by a customer related to a specific project. To that end, the material is sized at 204 according to the maximum size range desired. If the material is not of the proper size at 204, the material may be resized at 222 through the use of a grinding or abrasion method. Alternatively, material that will pass the required size may be found; therefore, 18 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE resizing the material would not be necessary at 222. At 206, additives may be added to the sized materials. The additives may be lime, lye, or other materials. Percentages and weights of different lime and lye may be incorporated into the sized material arriving from 204. In embodiments, sand or other filler materials may be added to manufacture the green material. The addition of sand or other materials may be controlled such that the overall specifications required for the material are maintained. To ensure the proper mixture, each of the individual components may be weighed at 208. The materials may then be dry mixed at 210. After completion of the dry mix at 210, water may be added directly to the mixture, or the contents of the dry mixture may be emptied and placed into a wet mixture at 214, wherein water is added at 212 to the wet mixture at 214. The wet mix generated at 214 is then provided to a roller press at 216. The roller press compresses the green mixture to a desired thickness, and heat is applied at 218. Heat applied at 218 may be in a steam atmosphere in an autoclave. Heating sources other than an autoclave may be used. In embodiments, a mobile autoclave is used such that a sized material from 204 is treated at the electrical production facility directly, without the need for shipping. After the heating process at 218, the aggregate may be evaluated at 220. The sizing operation performed at 220 may be through the performance of dumping materials onto mechanical screens with separate fractions of material according to size. Acceptable sized material results in an end of the process. Material that is not sized appropriately may be resized at 222. After resizing at 222, a query is run if the process has been previously completed at 224. If the process has been previously completed at 224, then the resized material may be used, and the process ended. If the resized material has not been previously processed, the method may return back to 206, where additives of lime and lye are added. As will be understood, successive additions of additives such as lime and lye are prevented through the query run at 224. Thus, the batch process that creates the aggregate always maintains the correct chemical composition. 19 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE

[0057] As will be understood, the roller press at 216 may be a dual roller press or a single roller press that impacts material into a predefined mold. In the process of making small aggregate, a dual roller press may be used to provide small or thin-size aggregate as necessary. In instances where a larger aggregate is needed, then a single-sided roller press may be used at 216. In either embodiment, after heating the green mix at 218, an additional step of abrasive mechanical action at 220, for example, may be accomplished to size the heated material correctly. As will be further understood, the roller press at 216 may directly determine the aggregate size from the rolling action in one step prior to heating. For example, such a roller press action may include mechanically separating components of an area into desired sizes such as one-half-inch aggregate. A roller press or crusher chosen, for example, may directly make materials in various sizes such that a specific void ratio for the aggregate, placed in an embankment, is maintained below a specific threshold.

[0058] In embodiments of the disclosure, 50 tons or more of aggregate can be processed per hour. Although described as using a roller press, other processes are possible, including an extrusion process where the green mixture is cut or shaped directly into desired sizes.

[0059] In embodiments, a separate step of drying the green mix may occur after the roller press or extrusion process. The drying process may include holding the coal combustion based aggregate in trays for periods up to and possibly exceeding thirty-six hours. This drying process would be in addition to the firing at the autoclave at 130. Firing time at the autoclave may be determined by the aggregate size produced. Firing may take one-half-hour in the case of small aggregate to 10 hours for large-size material. Autoclave temperatures of between 180 degrees Celsius and 250 degrees Celsius may be used as a non-limiting temperature profile. After autoclave thermal treatment, a separate step of cooling may also occur prior to packaging at 134 or determining size 20 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE acceptance at 220. The cooling may be convective cooling, in one non-limiting embodiment.

[0060] The autoclave used at 130 may be equipped to handle toxic element vaporization, thereby capturing vaporized hazardous emissions. Such emissions may include those of mercury or other heavy metals. As such, ordinary kiln technology, which does not provide this environmental benefit, is not used, as the fugitive emissions would be considered to be a generated waste, impacting the overall environmental clean-up capability of the process. In further embodiments, the autoclave times may be minimized for small aggregate production, providing an economic benefit for greenhouse gas emissions. As such kilns are prohibited from such production methods, use of an autoclave allows the method to be performed. Kiln technology would be strictly forbidden due to environmental regulations.

[0061] The autoclave used at 130 also has the advantage of keeping a controlled humidity and pressure inside the unit during the heating process. Pressures up to 16 atmospheres may be exerted on the aggregate during the heating process, thereby chemically combining the lime and / or lye with the coal combustion residue to encapsulate toxic elements. Humidity levels up to 100 percent relative humidity may be used to provide a structurally sound final product.

[0062] Additives may be added to the green material in order to provide the desired architectural color. Additions of zinc and / or iron, as non-limiting possibilities, may be added to the green mix to produce the required color of the material.

[0063] The environmental process provided herein has several advantages over conventional aggregate production. Conventional aggregate production has at least three mechanical crushing steps that are undertaken to arrive at a finalized product. The 21 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE mechanical crushing processes are a primary jaw crusher, a secondary cone crusher, and a tertiary cone crusher. Each of these mechanical crushing steps involves the use of fuels, production of heat, and emissions that are not present in the present disclosure. Conventional aggregate is first mined and then provided to a main primary jaw crusher. This step is necessary because the overall size of the aggregate obtained from nature requires crushing large portions. This step is eliminated through the current process as the fly ash, bottom slag, bottom ash, and flue desulphurization products do not need treatment like natural products. Thus, the current process described is superior to conventional technologies.

[0064] Conventional technologies use a secondary cone crusher to crush medium sized pieces into more manageable sizes. Again, the current process does not use the secondary cone crusher process, saving on fuel, energy, and environmental emissions.

[0065] Conventional aggregate production does not ensure the absence of toxic materials in the materials placed. In the current process, any heavy metals not chemically combined during the mixing process and setting process with the lime / lye are driven off by the autoclave or are chemically combined with the lime and / or lye to render an inert product. In the event the heavy metals are driven off, such toxic materials may be captured. Conventional aggregate mining merely mechanically degrades the existing aggregate source. Thus, if the aggregate is incorporated with heavy metals in the surrounding soils, the heavy metals will continue to be present up to and after the placement of the aggregate in the final position. This is avoided through the current disclosure.

[0066] Conventional aggregate production does not take a defined waste and allow the waste to be used in an environmentally friendly manner. Conventional aggregate production merely takes a naturally occurring material and uses mechanical processes to 22 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE size the overall material. Such sizing and production occurs at the mine, as this is the most economical production method. Conventional aggregate output does not happen at a waste generating facility; thus, conventional aggregate production is not “mobile.” With the presence of thousands of coal combustion facilities around the world, potential coal combustion residual based aggregate production can happen in areas such as cities, wherein conventional aggregate production is limited to mine-mouth operations. Aspects of the present disclosure also eliminate the transportation step required for mine-mouth operations, thereby significantly benefiting overall greenhouse gas emissions compared to conventional activities.

[0067] Conventional aggregate production activities are also eliminated by the present disclosure. For example, conventional aggregate production involves significant production of construction dust that must be handled by a producer. Dust reduction often includes spraying down feedstock hills to minimize dust production to the local population. The current disclosure prevents the use of such water processes and the energy and emissions associated with providing the power for such wetting activities. The current disclosure provides an essentially sealed processing regime, where the processing footprint for the current method processes is limited. Due to the wetting requirements for conventional aggregate production, mining permits also require stormwater management and run-off management plans. These plans must be approved and verified by local officials. Such requirements are precluded under the disclosed process as raw materials enter the process, and only a finalized product is removed (other than emissions from the autoclave). Moreover, the emissions from the autoclave may be minimized and controlled such that greenhouse gas emissions are minimized, and toxic materials liberated by the process may be reused as feedstock for other processes and industries. To this end, the processes described herein present significant improvements over conventional aggregate production. 23 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE

[0068] Direct use of boiler slag and bottom ash as an aggregate is generally not permitted. Pyrite material in boiler slag and bottom ash may degrade, causing various toxic elements to leach into the environment. To this end, boiler slag and bottom ash are not used in such aggregate capacities because of the fear of contamination. Such fears of contamination are eliminated with embodiments of the disclosure. A beneficial use for boiler slag and bottom ash may be achieved through the process by adding lime and / or lye, thereby chemically encapsulating pyrites and other materials. The chemical changes occurring throughout the process are achieved through the various steps of the process, including the use of the humidity and pressure-controlled capabilities of the autoclave. The use of boiler slag as an aggregate has been desired for many years but has not been environmentally possible until the present methods disclosed herein.

[0069] The use of boiler slag, in fact, is specifically warned against by AASHTO, the American Association of State Highway and Transportation Officials. Documentation from 1993 indicates that boiler slag, used as a base material, produces or induces a chemically active environment. The use of slag, therefore, promotes corrosion, which may be detrimental to construction activities. As such, AASHTO recommends not using such materials due to the potential side effects. Embodiments of the current disclosure prevent these concerns by providing an aggregate that does not create a chemically active environment (either acidic or alkaline). Applications for backfilling may be performed under such regulations as the material is considered to be acceptable under the AASHTO and EPA regulations.

[0070] Different coal residues may have different chemical constituents. The methods are applied to the different chemical constituents of differing coal residues to treat these feedstock materials such that the resultant stream of products from the method is usable under current regulatory requirements. Conventional methods do not provide such 24 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE usable products, and, in some applications, such as boiler slag, the use of such materials is extremely limited or non-existent.

[0071] In the case of boiler slag, such material is rarely recycled. Recycling that does occur is limited to producing grit for sanding purposes. Conventional applications for boiler slag do not and cannot treat this material as an aggregate material.

[0072] In embodiments, the feed material is dried and screened from 35 to 500 microns. Any material larger than 35 microns will be rejected and ground down (using a ball mill) to an acceptable particle size. Screened and dry material is mixed with calcium oxide (lime) or calcium hydroxide (hydrated lime). An additional sodium hydroxide (lye) compound is added to the mix. The mix ratio of the blend is 100 percent material with 3 percent to 15 percent calcium oxide or calcium hydroxide and 1 percent to 5 percent sodium hydroxide, based on the total weight of the material. The material is thoroughly mixed, and the finished material is malleable to the touch but cannot lose shape after molding. The mixed material is transferred into a rolling press that applies a force of 5,000 pounds per square inch to 15,000 pounds per square inch to mold the green mix into aggregate or briquette shapes. Once the green mix has been formed to the desired shape, it becomes known as a green product. The green mix is transferred into a thermal curing treatment. Thermal curing is performed at 140 pounds per square inch to 350 pounds per square inch and 180 degrees Celsius to 225 degrees Celsius for 4 to 10 hours.

[0073] Embodiments may include the following alternatives or features. These include performing a preparation of the feedstock into the method. In one embodiment, the coal combustion residuals (CCR) are initially subjected to a drying process to remove moisture content. Subsequently, the dried material undergoes mechanical sieves screening to achieve a particle size distribution within the range of 35 to 500 microns. As will be 25 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE understood, the range of 35 to 500 microns is but one example embodiment. Finer diameter material may be used. In some instances, material larger than 500 microns may be used.

[0074] In embodiments, material particles exceeding the upper limit of 35 microns are identified and segregated for further processing, as illustrated at 112. These oversized particles are directed to a ball mill, where they undergo grinding operations until they reach the desired particle size distribution.

[0075] The material from the silos at 110 may be screened. Appropriately sized dry material is then introduced into a mixing chamber where it is blended with predetermined quantities of calcium oxide (lime) or calcium hydroxide (hydrated lime) and sodium hydroxide (lye). The proportions of these chemical compounds are adjusted to achieve the desired chemical composition and reactivity within the final product. The mixing process is carefully controlled to ensure uniform distribution of the chemical compounds throughout the material matrix.

[0076] Mixing at 122 is then performed. The blended material undergoes thorough mixing to homogenize the mixture and ensure even distribution of the chemical additives. The resulting mixture, known as the green mixed material, possesses specific physical properties, including malleability and cohesiveness, which render it suitable for subsequent forming processes. Precise control is maintained over the mixing parameters to achieve the final product's consistent quality and performance characteristics.

[0077] In embodiments, the green mixed material is then fed into a rolling press apparatus equipped with precision molds designed to impart the desired shape and dimensions to the final products. The material is subjected to controlled compression forces ranging from 5,000 pounds per square inch to 15,000 pounds per square inch, facilitating the formation of dense, uniform aggregates or briquettes. 26 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE

[0078] In these embodiments, the molding process applies meticulous attention to detail to ensure the accurate replication of mold geometry and prevent defects or inconsistencies in the finished products.

[0079] In some embodiments, following molding, the green products are transferred to a thermal curing chamber, where they undergo a curing process to enhance their mechanical strength and durability. In one embodiment, thermal curing is carried out under controlled conditions, typically at temperatures ranging from 180 degrees Celsius to 225 degrees Celsius, and pressures between 140 pounds per square inch and 350 pounds per square inch, for a specified duration lasting between 4 to 10 hours. Times for curing may vary according to the thickness and size of the aggregate produced. During thermal curing, chemical reactions occur within the material matrix, forming stable crystalline phases and developing interparticle bonds, thereby imparting structural integrity and dimensional stability to the final products. The thermal curing process achieves the desired performance characteristics, including compressive strength, abrasion resistance, and resistance to environmental degradation, in the finished aggregates or briquettes.

[0080] Within the autoclave, at 130, in embodiments, chemical reactions occur. The lime (calcium oxide or calcium hydroxide) and lye (sodium hydroxide) react with the clay minerals present in the mixture. These reactions form new compounds, such as calcium silicate hydrates and sodium alumino-silicates, through processes like pozzolanic reactions and alkali activation. In these embodiments, the high temperature and pressure conditions in the autoclave accelerate the hydration of lime and lye. Hydration reactions lead to the formation of calcium hydroxide and sodium hydroxide solutions, which act as activators for the clay materials, promoting their dissolution and re-precipitation into stable crystalline structures. For purposes of definition the clay materials may be the mechanically separated material or other fine materials added in for filler purposes. 27 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE

[0081] In embodiments, under the applied pressure and temperature within the autoclave, the clay-lime-lye mixture undergoes consolidation, forming a dense, homogenous matrix. The combination of chemical reactions and compaction leads to the development of mechanical strength and structural integrity in the cured product.

[0082] In embodiments, microstructural changes occur. The thermal curing process induces changes in the microstructure of the material, including the refinement of pore size distribution and the formation of interlocking crystals or mineral phases. These changes contribute to the enhancement of mechanical properties such as compressive strength and durability.

[0083] The combination of chemical reactions and physical compaction facilitates the setting and hardening of the material. During curing in the autoclave, the clay-lime-lye mixture undergoes a transition from a plastic or malleable state to a rigid and stable form, capable of withstanding external forces and environmental conditions.

[0084] Aspects of the methods described may be performed by computer-controlled equipment. These aspects include controlling mixing in batch mixers as well as timing for autoclave curing. As such, methos portions of the disclosure may be recorded onto a non-volatile memory system for control of these mechanical systems. For definitional purposes, a non-volatile memory system may be a memory system that does not wipe clean after the termination of electrical power to the system. Non-volatile memory systems may include compact disks, solid-state drives, and universal serial bus devices. These memory systems may be used to store program executable method steps for a computer, server, or computing arrangement. Control of such equipment and methods under the current disclosure are contemplated.

[0085] Different descriptions of the claims are recited. These descriptions should not be considered limiting. In one example embodiment, a method to produce a coal combustion residual based aggregate is disclosed. The method comprises receiving a 28 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE feedstock of coal combustion residue. The method further comprises separating the feedstock of coal combustion residue into a size of 35 microns or less to create a separated fraction of sized coal combustion residue. The method further comprises combining a weighed portion of at least one of a lye and a lime amount to a weighed portion of the separated fraction of sized coal combustion residue to create a mixture, wherein a mix ratio of 3 percent to 15 percent of one of calcium oxide and calcium hydroxide and 1 percent to 5 percent sodium hydroxide based on weight. The method further comprises dry mixing the mixture to create a mixed dry mixture. The method further comprises adding water the mixed dry mixture to create a green mixture. The method further comprises hydraulically roller pressing the green mixture into a pre- shaped mold to directly form a green aggregate. The method further comprises thermally curing the green aggregate in an autoclave to form the coal combustion residual based aggregate and wherein the method occurs at a storage area for the coal combustion residue.

[0086] In another example embodiment, the method may be performed wherein the roller press compresses the green mixture between 5,000 pounds per square inch to 15,000 pounds per square inch.

[0087] In another example embodiment, the method may be performed wherein the thermal curing is performed between 180 degrees Celsius to 225 degrees Celsius between 4 to 10 hours at a pressure of between 140 pounds per square inch to 350 pounds per square inch.

[0088] In another example embodiment, the method may be performed wherein a portion of the feedstock of coal combustion residue above 35 microns size is treated in a ball mill to create a ball mill treated fraction with a size of the portion to less than 35 29 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE microns size and adding the ball mill treated fraction to the separated fraction of sized coal combustion residue.

[0089] In another example embodiment, the method may be performed wherein the feedstock of coal combustion residue includes boiler slag.

[0090] In another example embodiment, the method may further comprise crushing the aggregate after the thermally curing of the green aggregate in the autoclave.

[0091] In another example embodiment, the method may be performed wherein the aggregate produced is characterized by a mineralogical crystalline phase.

[0092] In another example embodiment, the method may be performed wherein the lime is one of calcium oxide and calcium hydroxide and where the lye is sodium hydroxide.

[0093] In another example embodiment, the method may further comprise drying the feedstock prior to the separating.

[0094] In another example embodiment, the method may be performed wherein the aggregate has at least one of calcium silicate hydrates and sodium alumino-silicates.

[0095] In another example embodiment, the method may be performed wherein the separated fraction of sized coal combustion residue resembles a clay consistency.

[0096] In another example embodiment, a method to produce a coal combustion residual based aggregate is disclosed. The method may comprise receiving a feedstock of coal combustion residue. The method may further comprise separating the feedstock of coal combustion residue into a size of 35 microns or less to create a separated fraction 30 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE of sized coal combustion residue, wherein the coal combustion residue includes boiler slag. The method may further comprise combining a weighed portion of at least one of a calcium oxide, calcium hydroxide, and sodium hydroxide, to a weighed portion of the separated fraction of sized coal combustion residue to create a mixture, wherein a mix ratio of 3 percent to 15 percent of one of calcium oxide and calcium hydroxide and 1 percent to 5 percent sodium hydroxide based on weight. The method may further comprise mixing the mixture with water to create a green mixture. The method may further comprise roller pressing the green mixture into a pre-shaped mold to form a formed shape directly. The method may further comprise thermally curing the formed shape in an autoclave at a temperature between 180 degrees Celsius and 225 degrees Celsius and a pressure of 140 pounds per square inch and 350 pounds per square inch. The method may further comprise crushing the formed shape to an aggregate-size material after the thermal curing and wherein the method occurs at a storage area for the coal combustion residue.

[0097] In another example embodiment of the disclosure, the method may be performed wherein portions of the feedstock above the size of 35 microns are mechanically abraded to a new size of less than 35 microns prior to adding the new-sized portion to the separated fraction.

[0098] In another example embodiment of the disclosure, the method may further comprise mechanically separating the crushed aggregate size material into finalized size portions.

[0099] In another example embodiment of the disclosure, the method may be performed wherein the thermally curing to the formed shape includes forming at least one of silicate hydrate and sodium alumino-silicates. 31 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE

[0100] In another example embodiment of the disclosure, the method may further comprise bagging the final-sized portions.

[0101] In another example embodiment of the disclosure, the method may be performed wherein the roller pressing the green mixture into a pre-shaped mold to directly form the formed shape occurs at a pressure of between 5,000 pounds per square inch and 15,000 pounds per square inch.

[0102] In another example embodiment of the disclosure, the method may be performed wherein the separating the feedstock of coal combustion residue into a size of 35 microns or less to create a separated fraction of sized coal combustion residue is performed through mechanical sieves.

[0103] In another example embodiment of the disclosure, the method may further comprise storing the separated fraction in a silo prior to weighing.

[0104] In another example embodiment of the disclosure, a construction material based upon a coal combustion residue is disclosed. The material includes a molded-formed aggregate with a homogenous matrix of calcium silicate hydrates and sodium alumino- silicates with a stable crystalline structure formed into an aggregate shape.

[0105] The foregoing description of the embodiments has been provided for illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but where applicable, are interchangeable and can be used in a selected 32 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE embodiment, even if not specifically shown or described. The same may be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

[0106] While embodiments have been described herein, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments are envisioned that do not depart from the inventive scope. Accordingly, the scope of the present claims or any subsequent claims shall not be unduly limited by the description of the embodiments described herein. 33 CONFIDENTIAL INFORMATION

Claims

PATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE CLAIMS What is claimed is:

1. A method to produce a coal combustion residual based aggregate, comprising: receiving a feedstock of coal combustion residue; separating the feedstock of coal combustion residue into a size of 35 microns or less to create a separated fraction of sized coal combustion residue; combining a weighed portion of at least one of a lye and a lime amount to a weighed portion of the separated fraction of sized coal combustion residue to create a mixture, wherein a mix ratio of 3 percent to 15 percent of one of calcium oxide and calcium hydroxide and 1 percent to 5 percent sodium hydroxide based on weight; dry mixing the mixture to create a mixed dry mixture; adding water to the mixed dry mixture to create a green mixture; hydraulically roller pressing the green mixture into a pre-shaped mold to directly form a green aggregate; and thermally curing the green aggregate in an autoclave to form the coal combustion residual based aggregate, wherein the method occurs at a storage area for the coal combustion residue.

2. The method according to claim 1, wherein the roller pressing compresses the green mixture between 5,000 pounds per square inch and 15,000 pounds per square inch.

3. The method according to claim 1, wherein the thermal curing is performed between 180 degrees Celsius to 225 degrees Celsius between 4 to 10 hours at a pressure of between 140 pounds per square inch to 350 pounds per square inch. 34 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE 4. The method according to claim 1, wherein a portion of the feedstock of coal combustion residue above 35 microns size is treated in a ball mill to create a ball mill treated fraction with a size of the portion to less than 35 microns size and adding the ball mill treated fraction to the separated fraction of sized coal combustion residue.

5. The method according to claim 1, wherein the feedstock of coal combustion residue includes boiler slag.

6. The method according to claim 1, further comprising crushing the aggregate after the thermally curing of the green aggregate in the autoclave.

7. The method according to claim 1, wherein the aggregate produced is characterized by a mineralogical crystalline phase.

8. The method according to claim 1, wherein the lime is one of calcium oxide and calcium hydroxide and where the lye is sodium hydroxide.

9. The method according to claim 1, further comprising drying the feedstock prior to the separating.

10. The method according to claim 1, wherein the aggregate has at least one of calcium silicate hydrates and sodium alumino-silicates.

11. The method according to claim 1, wherein the separated fraction of sized coal combustion residue resembles a clay consistency.

12. A method to produce a coal combustion residual based aggregate, comprising: receiving a feedstock of coal combustion residue; 35 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE separating the feedstock of coal combustion residue into a size of 35 microns or less to create a separated fraction of sized coal combustion residue, wherein the coal combustion residue includes boiler slag; combining a weighed portion of at least one of a calcium oxide, calcium hydroxide, and sodium hydroxide, to a weighed portion of the separated fraction of sized coal combustion residue to create a mixture, wherein a mix ratio of 3 percent to 15 percent of one of calcium oxide and calcium hydroxide and 1 percent to 5 percent sodium hydroxide based on weight; mixing the mixture with water to create a green mixture; roller pressing the green mixture into a pre-shaped mold to directly form a formed shape; thermally curing the formed shape in an autoclave at a temperature between 180 degrees Celsius and 225 degrees Celsius and a pressure of 140 pounds per square inch and 350 pounds per square inch; and crushing the formed shape to an aggregate size material after the thermal curing and wherein the method occurs in a storage area for the coal combustion residue.

13. The method according to claim 12, wherein portions of the feedstock above the size of 35 microns are mechanically abraded to a new size of less than 35 microns prior to adding the new sized portion to the separated fraction.

14. The method according to claim 12, further comprising mechanically separating the crushed aggregate size material into finalized size portions.

15. The method according to claim 12, wherein the thermally curing to the formed shape includes forming at least one of silicate hydrate and sodium alumino-silicates. 36 CONFIDENTIAL INFORMATIONPATENT ATTORNEY DOCKET ECH-004 COAL COMBUSTION RESIDUAL BASED AGGREGATE AND METHOD OF MAKING AN AGGREGATE 16. The method according to claim 12, further comprising bagging the final sized portions.

17. The method according to claim 12, wherein the roller pressing the green mixture into a pre-shaped mold to directly form the formed shape occurs at a pressure of between 5,000 pounds per square inch and 15,000 pounds per square inch.

18. The method according to claim 12, wherein the separating the feedstock of coal combustion residue into a size of 35 microns or less to create a separated fraction of sized coal combustion residue is performed through mechanical sieves.

19. The method according to claim 12, further comprising storing the separated fraction in a silo prior to weighing.

20. A construction material based upon a coal combustion residue, comprising: a molded formed aggregate with a homogenous matrix of calcium silicate hydrates and sodium alumino-silicates with a stable crystalline structure formed into an aggregate shape. 37 CONFIDENTIAL INFORMATION

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