Underground Coal Gasification and Associated Systems and Methods

The present application is a continuation of U.S. patent application Ser. No. 17/818,303, filed Aug. 8, 2022, which is a continuation of U.S. patent application Ser. No. 17/456,130, filed Nov. 22, 2021, which is a continuation application of U.S. patent application Ser. No. 17/468,649, filed Sep. 7, 2021, now abandoned, which is a continuation of U.S. patent application Ser. No. 17/200,334, filed Mar. 12, 2021, now U.S. Pat. No. 11,125,069, which claims the benefit of priority to U.S. Provisional Patent Application No. 63/139,044, filed Jan. 19, 2021, the disclosures of which are incorporated herein by reference in their entireties.

The present disclosure relates to the field of underground coal gasification.

Underground coal gasification (“UCG”) is an industrial process in which coal is used to generate a product gas at an underground coal seam. Generally, UCG involves supplying an oxidant and, if required, water and/or steam to an underground coal seam in order to ignite coal and sustain the gasification process. The oxidant and possibly other reagents are typically delivered to the underground coal seam via injection wells drilled from the surface. The gasification process generates product gases, which can then be brought to the surface using production wells drilled from the surface. The predominant product gases are hydrogen, carbon monoxide, methane and carbon dioxide. Alternatively, mined shafts and associated workings can be used to inject the oxidant and/or produce the product gas. The resultant extracted product gas may be commercially used in a number of ways, e.g., as combustion fuel for power generation, or as a chemical feedstock in the production of fuels, fertilizers, or other chemical products.

As described above, underground coal gasification (“UCG”) is a process in which one or more oxidants are injected into a coal seam to promote an in-situ gasification reaction. The gasification reaction produces a product gas, which can then be extracted and brought to the surface using one or more production wells extending from the coal seam to the surface. The product gases can comprise hydrogen, carbon monoxide, methane and/or carbon dioxide, and are sometimes referred to as “syngas” or synthesis gas. The specific composition of the product gas can vary based on a number of factors, such as formation pressure, depth of the coal seam, oxidant balance, and gasification conditions.

While UCG and other underground gas processing technologies have been used for decades to produce and extract syngas, the conventional UCG systems and methods have a number of deficiencies. For example, the UCG system typically includes an injection well and a production well that each have end portions disposed within a UCG reaction region of the coal seam at which the gasification reaction occurs. As the oxidant gas is injected via the injection well and the coal of the coal seam at the UCG reaction region is ignited, the injected oxidant gas reacts with carbon molecules of the coal to produce syngas. However, when the oxidant gas disperses from the injection well within the coal seam, there is no containment device outside the UCG reaction region or technique to prevent the oxidant gas from traveling in a direction away from the production well. As a result, not all of the oxidant gas is used by the gasification reaction and converted into syngas, and some of the oxidant gas can oxidize areas of the coal seam surrounding the UCG reaction region, which is generally undesirable. This in turn can cause low product gas yield, low hydrogen recovery, and increased costs for the operator. Relatedly, much of the product gas produced by the gasification reaction is not extracted by the production well for the same reason. That is, as the product gas is generated within the UCG reaction region, the product gas disperses in directions away from the production well, and thus not all of the product gas is extracted. This further contributes to the low yield, low hydrogen recovery, and increased costs. Additionally, the unextracted product gas can migrate to other regions of the coal seam and act as a contaminant.

Embodiments of the present technology address these and other issues by containing the oxidant gas, product gas, and/or other gases in the UCG reaction region, thereby inhibiting them from migrating to undesired areas. As an example, embodiments of the present technology can include an injection well extending from the ground surface to the UCG reaction region of the coal seam, a production well extending from the ground surface to the UCG reaction region, and a plurality of conduits each extending from the ground surface to areas of the coal seam that are laterally peripheral to the UCG reaction region. In some embodiments, end portions of the conduits are positioned in the coal seam to form a perimeter or a partial perimeter around the UCG reaction region, such that a primary fluid delivered via the conduits can form a pressurized primary region within the coal seam that at least partially surrounds the UCG reaction region. The primary region can effectively act as a barrier and/or operate at a pressure higher than that of the UCG reaction region to contain the gases associated with the gasification reaction. In doing so, embodiments of the present technology can better ensure (i) the oxidant gas is used by the gasification reaction occurring within the UCG reaction region, and/or (ii) the product gases are extracted via the production well to increase yield of the product gas and enhance hydrogen recovery, amongst other benefits.

illustrates a UCG systemand associated process. As shown in, the UCG systemincludes an underground coal seamhaving a UCG reaction region, an injection wellextending from a surfaceto the UCG reaction region, and a production wellextending from the UCG reaction areato the surface. The coal seamand/or UCG reaction regionis located a distance (e.g., 100 meters (m)-1600 m) below the ground surface, and is the site at which the in-situ gasification reaction occurs. The injection wellcan be configured to receive an oxidant (e.g., oxygen, air, or combinations thereof) and deliver it to the UCG reaction region, and the production wellcan be configured to receive a product gas(e.g., syngas) produced at the UCG reaction regionand deliver the product gasto the surface, where the product gascan undergo further processing. An end portionof the injection wellcan be positioned at a reaction regionof the UCG reaction area, and an end portionof the production wellcan be positioned at a production regionof the UCG reaction area. The distance between the end portionof the injection welland the end portionof the production wellcan be between 15-300 m, and can vary depending on various factors of the particular UCG reaction region.

The oxidantcan be supplied (e.g., pumped) from the surfaceat a generally high pressure and/or ambient (or higher) temperature. In some embodiments, the oxidantcan have a temperature of from 700° C.-1500° C. or any value therebetween (e.g., 800° C., 900° C., 1000° C., 1200° C., 1400° C., etc.) at the UCG reaction regionover the course of the gasification reaction. In some embodiments, water may also be supplied via the injection well, e.g., in conjunction with the oxidant, and can enable the gasification reaction to produce more product gas. In some embodiments, the coal seamincludes sufficient water, e.g., because it is located beneath a water table, and thus additional water does not need to be supplied via the injection well. In operation, the coal of the coal seamis ignited and the gasification reaction is initiated, enabling the injected oxidantand/or water to promote the in-situ gasification reaction and produce the product gas.

As previously described, the product gascan comprise a mixture of hydrogen, carbon monoxide, methane and carbon dioxide. In some embodiments, the product gascan also comprise contaminants including various organic compounds, ammonia, and hydrogen sulfide. The product gasis represented in simplified terms in Reaction 1 below as just hydrogen and carbon monoxide.

In practice, the product gasproduced via the gasification reaction flows toward the production regionand then to the surfacevia the production well. The extracted product gasmay then be treated (e.g., purified) and/or undergo further processing depending on the desired end use or commercial application.

As previously described, embodiments of the present technology include improvements to conventional UCG systems.is a schematic cross-sectional plan view of a representative UCG system, andis a schematic cross-sectional side view of the UCG systemshown in. Referring totogether, the systemincludes the injection welland the production well, each extending from the ground surface() to the coal seam, with the end portions,() of the respective injection welland production wellbeing positioned in or at the UCG reaction regionof the coal seam. As described with reference to, the injection wellis configured to deliver the oxidantto the coal seamand the production wellis configured to deliver product gasproduced at the UCG reaction regionto the ground surface().

With continuing reference to, the systemcan include a plurality of fluid conduits(e.g., wells, mining shafts, etc.). Each of the conduitscan extend from the ground surface() to an area of the coal seam, and have end portionspositioned laterally peripheral to (i) the UCG reaction regionand/or (ii) end portions,() of the respective injection welland production well. As shown in, the end portionsof the conduitscan surround the end portions,of the respective injection welland production well, such that the conduit end portionsform a perimeter around the well end portions,and/or the UCG reaction area. In some embodiments, the conduit end portionscan be arranged within the coal seamto form a generally circular, ovular, rectangular, or polygonal shape. Additionally or alternatively, in some embodiments the conduit end portionsdo not entirely surround the end portions,of the respective injection welland production well, but rather only partially surround the well end portions,.

The conduitscan be configured to receive a primary fluidand deliver the primary fluidfrom the ground surfaceto the coal seamvia the conduit end portions. The primary fluidcan comprise carbon dioxide (e.g., gaseous or liquid carbon dioxide), a supercritical fluid (e.g., supercritical carbon dioxide), water (e.g., steam), organic materials (e.g., organic solvents, polymers), inorganic materials, and/or combinations thereof. Once injected, the primary fluidcan disperse from each of the conduit end portionsinto the coal seamto generally saturate a surrounding area and form a primary region. The primary regioncomprises the coal or coal matrix of the coal seamand the primary fluid, in which the primary fluidcan comprise (i) at least 30%, 40%, 50%, 60%, 70%, or 80% by volume of the open fracture space and/or pore volume of the primary region, and/or (ii) at least 5%, 10%, 15%, 20%, 25% by weight of the primary region(e.g., via adsorption to the coal and filling the pore and open fracture space). As such, the primary fluidinjected to the coal seamvia individual ones of the conduitswill disperse from the corresponding conduit end portionsin multiple directions, such that the primary regionforms around the conduit end portionsof each of the conduits. Injecting the primary fluidcan cause (i) the coal, or coal matrix of the coal seam to increase in size, (ii) closure of cleat fractures of the coal seam, and/or (ii) voids or pore space between individual coal particles of the coal seamto be filled. Stated differently, whereas the coal seamcan have a first void or pore space between individual coal particles prior to the primary fluidbeing injected, the primary regioncan have a second pore space that is less than the first pore space after injecting the primary fluid.

The primary regionformed as a result of injecting the primary fluidaround the UCG reaction regioncan effectively contain the oxidant, product gas, and other gases present within the UCG reaction region. Stated differently, the primary regioncan create a low permeability or generally impermeable jacket or barrier zone that inhibits the migration of fluids from the UCG reaction regionto areas of the coal seamperipheral to the primary region. In doing so, the primary regioncan improve the overall yield of the product gasproduced via the system, improve conversion of the oxidant, enhance hydrogen recovery, and/or improve the quality of the product gas, amongst other benefits. As an example, in an actual trial wherein water was injected into a coal seam surrounding a UCG reaction region, hydrogen content of the product gas increased from 10-15% to 18-26% on a mol/mol basis.

Injecting the primary fluidand/or the oxidantcan occur at predetermined pressures, e.g., to create a pressure differential between the UCG reaction region, the primary region, and/or the surrounding coal seam. In some embodiments, the primary fluidis injected at a pressure of at least 100 bar, 110 bar, 120 bar, 130 bar, 140 bar, 150 bar, or 160 bar, or within a range of 100-160 bar or any incremental range therebetween (e.g., 145-155 bar). In some embodiments, the injection pressure of the primary fluidis controlled using compressors, pumps, or other regulating equipment located at the ground surface(). Additionally or alternatively, in some embodiments the injection pressure is controlled based on the product gas(e.g., the flow rate and/or composition of the product gasreceived via the production well). The pressure at which the primary fluidis injected can be generally above or equal to the pressure (P) of the primary region. In some embodiments, the oxidantis injected at a pressure of no more than 50 bar, 60 bar, 70 bar, or 80 bar, or within a range of 50-80 bar or any incremental range therebetween. The pressure at which the oxidantis injected can be generally above or equal to the pressure (P) of the UCG reaction region. For example, the pressure of the oxidantat the well end portionis less than the injection pressure at the top of the injection welldue to hydraulic resistance of the injection well. As such, the pressure (P) of the primary regionis higher than the pressure (P) of the UCG reaction region. A hydrostatic reservoir pressure (P) of untreated areas of the coal seamcan vary, but in some embodiments can be about 140 bar, 150 bar, or 160 bar, or within a range of 140-160 bar or any incremental range therebetween. The hydrostatic pressure (P) is always higher than the pressure (P) of the UCG reaction region. The pressures of the coal seam, primary region, and UCG reaction regioncreate a pressure profile in which the oxidant, product gas, and other gases present within the UCG reaction regionare contained within and/or inhibited from migrating laterally beyond the primary region. As a result, these gases are more effectively utilized as reactants and/or extracted via the production well.

In some embodiments, the injection pressure of the primary fluidand/or the injection pressure of the oxidant(and therein the pressure (P) of the UCG reaction region) is based on the depth of the coal seam, which in turn determines the hydrostatic pressure (P) of the coal seam. For example, the pressure (P) of the UCG reaction region(e.g., the gasification pressure) is a value between the injection pressure of the oxidantand the production pressure at which the product gasis extracted via the production well. The injection pressure of the primary fluid, and/or the pressure (P) of the primary region, is higher than the hydrostatic pressure (P) of the coal seam, which in turn is higher than the pressure (P) of the UCG reaction region, e.g., to maintain a hydraulic pressure gradient of fluids in the systemand direct the oxidantand/or product gastoward the UCG reaction region. The injection pressure of the primary fluidand/or the pressure (P) of the primary regionis set to be above the hydrostatic pressure (P) to ensure the primary fluidflows into the coal seam(e.g., the pore volume and/or fractures of the coal seam). The systemcan include one or more sensors within the coal seamthat are configured to measure pressures of the UCG reaction region, primary region, and/or coal seam.

In some embodiments, the primary fluidis injected to the injection wellat a flow rate that is proportional to the pressure differential between the primary regionand the coal seam(e.g., between the primary region pressure (P) and the hydrostatic pressure (P)). In operation, it can be beneficial to set a flow rate of the primary fluidthat maintains a minimum pressure differential (e.g., 10 bar, 15 bar, 20 bar, 30 bar, 40 bar, 50 bar, 75 bar, 100 bar, etc.) between the primary regionand the coal seam, while also keeping the injection pressure of the primary fluidand/or the pressure (P) of the UCG reaction regionrelatively low to minimize compression costs. Additionally or alternatively, in some embodiments the injection pressure of the primary fluidis set to be a predetermined percentage (e.g., 10%, 15%, 20%, or 25%) above the hydrostatic pressure (P). In some embodiments, the injection pressure of the primary fluid is between and/or based on the hydrostatic pressure (P) and a lithostatic pressure (e.g., pressure imposed by the weight of overlying material) of the coal seam at the depth of the UCG reaction region. In such embodiments, the lithostatic pressure can be at least 300 bar, 350 bar, 400 bar, etc.

As previously described, injecting the primary fluidinto the coal seamcan cause the corresponding coal to increase in size (e.g., swell). Without being bound by theory, this increase in size can be due to the higher affinity of the coal for the primary fluid(e.g., carbon dioxide) relative to other fluids (e.g., water and/or methane) commonly present in the coal seam. For example, the higher affinity for the primary fluidcan cause the carbon dioxide and/or other constituents of the primary fluidto attach or adsorb to the coal, and thereby cause the coal to swell. As a result of such swelling, the relative pore space between the adjacent coal particles of the coal seamis advantageously decreased and allows the primary regionto effectively act as a barrier to prevent or inhibit gases and fluids (e.g., the oxidant gas, water, methane, hydrocarbons, carbon monoxide, carbon dioxide, and hydrogen) present in the UCG reaction regionfrom migrating beyond (e.g., laterally peripheral to) the primary region. In doing so, a greater amount of these gases remains available to react within and/or be extracted from the UCG reaction region, and can thus (i) increase production of the product gas, (ii) enhance hydrogen recovery, and/or (iii) improve effectiveness of the systemgenerally.

The type of primary fluidinjected into the coal seamcan affect certain characteristics of the primary regionand produce different benefits. For example, in those embodiments for which the primary fluidcomprises carbon dioxide, injecting the primary fluidcan cause the coal matrix of the coal seamto swell, as previously described, and form a sequestration cap or barrier around the UCG reaction region. The sequestration cap can help contain the spread of groundwater in the coal seam region and thereby have one or more environmental benefits in addition to the production benefit(s) previously described. The sequestration cap can remain in place as a barrier for extensive periods of time (e.g., months, years, or decades), depending on the hydrostatic pressure (P) of an untreated area of that particular coal seam, and/or the pressure differential between the hydrostatic pressure (P) and the pressure (P) of the primary regionand/or sequestration cap. Stated differently, as long as there is groundwater saturation of the surrounding coal seamand the hydrostatic pressure (P) remains constant, the carbon dioxide will not desorb from coal and will continue to be stored at the same quantity. If the hydrostatic pressure decreases with time, carbon dioxide will partially desorb and continue to be stored in equilibrium with the hydrostatic pressure (P). Since the hydrostatic pressure (P) in deep coal seams tends to stay constant, and once disturbed by UCG operations tends to restore its original values with time, carbon can be stored in the coal seamfor an indefinite time. Additionally or alternatively, in such embodiments for which the primary fluidcomprises carbon dioxide, the carbon dioxide can react with (e.g., be reduced by) coal present in the UCG reaction regionto form carbon monoxide, as represented in Reaction 2 below. Additionally, carbon monoxide can further react with water vapor present in the UCG reaction regionaccording to the water-gas shift reaction, as represented in Reaction 3 below, to form additional hydrogen. As such, injecting the primary fluidcan enhance hydrogen recovery and improve yield of the product gas. In some embodiments, the carbon dioxide does not act as a reactant for the gasification reactions occurring within the UCG reaction region.

As another example of how the type of primary fluidinjected into the coal seamcan affect certain characteristics of the primary region, in those embodiments for which the primary fluidcomprises supercritical carbon dioxide, the adsorption of carbon dioxide by the coal matrix of the coal seamcan be enhanced relative to using non-supercritical carbon dioxide as the primary fluid, and the resultant pressure (P) of the corresponding primary regioncan be relatively higher. Using a supercritical fluid as the primary fluidcan be particularly beneficial when working at extreme depths, e.g., to ensure the pressure (P) of the primary regionis greater than the hydrostatic pressure (P) of the coal seam, and thus creates the pressure gradient, as described elsewhere herein, to establish containment of the oxidant, product gas, and other gases present within the UCG reaction regionand generally increase yield of product gasextracted via the production well.

As another example of how the type of primary fluidinjected into the coal seamcan affect certain characteristics of the primary region, in those embodiments for which the primary fluidcomprises water, injecting the primary fluidcan cause the coal matrix surrounding or at least partially surrounding the UCG reaction regionto become saturated or partially saturated with water. Without being bound by theory, the injected water of the primary fluidis expected to occupy the pore space and/or the fractures of the coal seam (e.g., between individual coal particles), and wets the coal to form forces (e.g., surface tension) that maintain the water in the pore space and/or fractures. As a result, the pore space of the coal matrix is decreased relative to that of a coal matrix of an untreated coal seam, and creates the impermeable barrier or jacket described elsewhere herein to inhibit the oxidant, product gas, and other gases present within the UCG reaction regionfrom migrating to areas peripheral to the primary region. Additionally or alternatively, the water vapor formed as the primary fluidenters the UCG reaction regioncan act as a reactant for the gasification reaction (Reaction 1) and the water-gas shift reaction (Reaction 3) occurring within the UCG reaction region. Accordingly, injecting water as part of the primary fluidcan improve the yield of the product gasand/or enhance hydrogen recovery.

In some embodiments, injecting the primary fluidinto the coal seamcan cause a secondary regionto form that is (i) peripheral to and/or partially surrounding the UCG reaction region, and (ii) at least partially surrounded by the primary region. As previously described, the higher affinity of the coal of the coal seamfor the primary fluidcan displace and/or cause the coal to release, other fluids present in the coal seam. This can occur in conjunction with the swelling of the coal of the coal seam, as previously described. For example, carbon dioxide of the primary fluidinjected into the coal seamcan attach or adsorb to the corresponding coal of the coal seamand cause the coal to displace a secondary fluidthat the coal has a lower affinity for. The secondary fluidcan comprise water, methane, other hydrocarbons, and/or combinations thereof. The pressure of the secondary regioncan be similar to the pressure (P) of the primary region, which can correspond to the injection pressure of the primary fluid. As such, the decreasing pressure differential in the direction from the primary regiontoward the UCG reaction regioncan drive the secondary fluidtoward the UCG reaction region. The secondary fluidcan act as a reactant to further promote the coal gasification reactions (e.g., Reactions 1 and 3) occurring within the UCG reaction region. As a result, releasing the secondary fluid, produced as a result of injecting the primary fluidperipheral to the UCG reaction region, can further promote the coal gasification reactions and thereby improve the yield of the product gasand/or enhance hydrogen recovery. In some embodiments, the amount of secondary fluid generated is controlled by the injection pressure of the primary fluid. Moreover, as the secondary fluid can affect the composition of the product gas, in some embodiments controlling the primary fluid(e.g., the composition, the injection pressure, etc.) can be used to adjust the yield and/or composition of the product gas.

An example test was conducted that corresponds to embodiments of the present technology. In the test, an air-blown UCG reactor was established in a coal seam at a depth of 225 meters that was saturated with groundwater. The hydrostatic pressure of the coal seam was approximately 1,550 kilopascals (kPa). The UCG reactor operated for 45 days with stable injection and production flow rates under a pressure of 700 kPa. The product gas contained approximately 15% hydrogen and 4.5% methane. Water was injected into the coal seam in the vicinity of the UCG reactor at the rate of 1.5 tons per hour at a pressure of 2,850 kPa on day 46, and continued under steady conditions for 10 days. The UCG reactor pressure during this period remained unchanged. On day 49, hydrogen and methane content of the product gas increased and remained elevated until day 61, with average concentrations of 21% hydrogen and 6.5% methane. During the same period (day 49 to day 61), the average dry product gas flow rate increased by 3.5%.

is a block flow diagram of a methodfor gasifying coal, in accordance with embodiments of the present technology. The methodcan comprise injecting, via a plurality of conduits (e.g., the conduits), a primary fluid (e.g., the primary fluid) to an area of a coal seam (e.g., the coal seam) beneath a ground surface (e.g., the ground surface) (process portion). Injecting the primary fluid can occur at a pressure of at least 100 bar, 110 bar, 120 bar, 130 bar, 140 bar, 150 bar, or 160 bar.

The methodcan further comprise injecting, via an injection well (e.g., the injection well), an oxidant (e.g., the oxidant) to a UCG reaction region (e.g., the UCG reaction region) of the coal seam to support or enable a gasification reaction to occur (process portion). The gasification reaction can include one or more of Reactions 1, 2, or 3 described herein, and can produce a product gas (e.g., the product gas) comprising at least two of hydrogen, carbon monoxide, or carbon dioxide. In some embodiments, injecting the primary fluid occurs before injecting the oxidant gas, e.g., to allow sufficient time for the primary fluid to saturate an area at least partially surrounding the UCG reaction region and thereby form a barrier zone (e.g., the primary region). In some embodiments, injecting the primary fluid occurs concurrently to injecting the oxidant gas.

The methodcan further comprise extracting, via a production well (e.g., the production well), at least a portion of the product gas from the UCG reaction region (process portion). In some embodiments, extracting the product gas can include monitoring the product gas (e.g., continuously or intermittently) to measure the composition and/or quality of the product gas and determine whether adjustments need to be made. For example, if the extracted product gas indicates that quality, purity, and/or yield is deteriorating over time, the process can include making adjustments to the injection of the primary fluid. For example, the primary fluid injection pressure, amount of injected primary fluid, and/or composition of the primary fluid can each be adjusted and affect the product gas.

The methodcan further comprise, wherein end portions (e.g., the conduit end portions) of the conduits are laterally peripheral to the UCG reaction regionand/or end portionsof each of the injection well and the production well (process portion). Disposing the end portions of the conduits laterally peripheral to the UCG reaction region can form a pressure profile configured to at least partially surround the UCG reaction region and/or contain the oxidant and product gas within the UCG reaction region.

It will be apparent to those having skill in the art that changes may be made to the details of the above-described embodiments without departing from the underlying principles of the present disclosure. In some cases, well known structures and functions have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments of the present technology. Although steps of methods may be presented herein in a particular order, other embodiments may perform the steps in a different order. For example, injecting the primary fluid can occur before, after, or concurrent with injecting the oxidant gas. Similarly, certain aspects of the present technology disclosed in the context of particular embodiments can be combined or eliminated in other embodiments. Furthermore, while advantages associated with certain embodiments of the present technology may have been disclosed in the context of those embodiments, other embodiments can also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages or other advantages disclosed herein to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein, and the invention is not limited except as by the appended claims.

Throughout this disclosure, the singular terms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise. The term “and/or” when used in reference to a list of two or more item is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Additionally, the term “comprising,” “including,” and “having” should be interpreted to mean including at least the recited feature(s) such that any greater number of the same feature and/or additional types of other features are not precluded.

Reference herein to “one embodiment,” “an embodiment,” “some embodiments” or similar formulations means that a particular feature, structure, operation, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present technology. Thus, the appearances of such phrases or formulations herein are not necessarily all referring to the same embodiment. Furthermore, various particular features, structures, operations, or characteristics may be combined in any suitable manner in one or more embodiments.

Unless otherwise indicated, all numbers expressing numerical values (e.g., pressures, temperatures, etc.) used in the specification and claims, are to be understood as being modified in all instances by the term “about” or “approximately.” The terms “about” or “approximately,” when used in reference to a value, are to be interpreted to mean within 10% of the stated value. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present technology. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Additionally, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a range of “1 to 10” includes any and all subranges between (and including) the minimum value of 1 and the maximum value of 10, i.e., any and all subranges having a minimum value of equal to or greater than 1 and a maximum value of equal to or less than 10, e.g., 5.5 to 10.

The disclosure set forth above is not to be interpreted as reflecting an intention that any claim requires more features than those expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in a combination of fewer than all features of any single foregoing disclosed embodiment. Thus, the claims following this Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment. This disclosure includes all permutations of the independent claims with their dependent claims.

The present technology is illustrated, for example, according to various aspects described below. Various examples of aspects of the present technology are described as numbered examples (1, 2, 3, etc.) for convenience. These are provided as examples and do not limit the present technology. It is noted that any of the dependent examples may be combined in any combination, and placed into a respective independent example. The other examples can be presented in a similar manner.