Point Source Carbon Capture System

Abstract

In one aspect, described herein is a method for removing CO from flue gas or exhaust gas streams generated from point sources, including, but not limited to, power generation facilities, concrete manufacturing facilities, and chemical and food processing facilities. The method, in some embodiments, includes an adsorption cycle for removing at least 70 percent of CO from the exhaust gas stream. The adsorption cycle includes flowing the exhaust gas stream through at least one adsorbent bed formed from a monolithic adsorber having an outer peripheral wall and a plurality of inner partition walls that support organic or inorganic compounds that adsorb CO from the exhaust gas stream.

Description

[Technical Field]

[0001] This application relates to carbon capture technologies, and in particular to the removal and capture of carbon dioxide (CO2) from point source flue gas streams.

[0002] Related application data This application claims priority under Patent Cooperation Treaty Article 8 to U.S. Provisional Patent Application No. 63 / 425,549, filed November 15, 2022, the entire contents of which are incorporated herein by reference. The present claim priority under Patent Cooperation Treaty Article 8 is incorporated herein by reference in its entirety. [Background technology]

[0003] Global warming and associated climate change caused by human activities pose an existential threat to many ecosystems and human lifestyles as currently understood. The extraction and combustion of fossil fuels is a major contributor to global warming through the release of large amounts of greenhouse gases, including methane and CO2. CO2 accounts for the majority of greenhouse gas emissions, with CO2 concentrations exceeding the 400 ppm mark in recent years. Current CO2 concentrations are higher than at any time in the past 800,000 years.

[0004] Given this alarming trend in atmospheric CO2 concentrations, countries and industries have initiated various mitigation strategies to reduce CO2 and methane emissions. The electrification of vehicles and transportation systems has received significant attention, and the transition to green / renewable energy sources, including wind and solar, has received significant private and public investment. While promising, these mitigation strategies do not address the CO2 currently present in the atmosphere or the CO2 produced by current fossil fuel consumption. Therefore, current carbon dioxide concentrations are subject to time-consuming natural degradation processes. Summary of the Invention [Means for solving the problem]

[0005] In one aspect, described herein is a method for removing CO from flue gas or exhaust gas streams generated from point sources, including, but not limited to, power generation facilities, concrete manufacturing facilities, and chemical and food processing facilities. Such CO removal is commonly referred to as point source capture. In some embodiments, the method includes an adsorption cycle for removing at least 70 percent of CO from the exhaust gas stream. The adsorption cycle includes flowing the exhaust gas stream through at least one adsorption bed formed from a monolithic adsorber having an outer peripheral wall and a plurality of inner partitions supporting organic or inorganic compounds that adsorb CO from the exhaust gas stream, the exhaust gas stream having an inlet temperature of at least 60°C, a CO content of 3 to 20 percent, and a water vapor content of 2 to 22 percent. The adsorbent bed is isolated from the exhaust gas stream, and steam having a pressure of -14 kPa (-2 psig) to 14 kPa (2 psig) and a maximum temperature of 120°C is flowed through the adsorbent bed in a direction counter to the flow of the exhaust gas stream to provide the enthalpy of CO2 desorption and thereby desorb the CO2 captured in the adsorbent bed. A first portion of the steam is condensed within the pores of the monolithic adsorber, and a second portion of the steam sweeps the desorbed CO2 from the adsorbent bed, providing a mixture of the desorbed CO2 and the sweep steam. The CO2 is then separated from the mixture, thereby providing a product gas having at least 90 weight percent CO2. The adsorbent bed is then discontinued from isolation from the exhaust gas stream, and the exhaust gas stream re-enters the monolithic adsorber, vaporizing the condensed steam within the pores and cooling the adsorber to a temperature below 90°C to begin a new adsorption cycle.

[0006] In some embodiments, the methods described herein use at least two adsorbent beds, where at any one time, a first adsorbent bed removes CO from the exhaust gas stream and a second adsorbent bed is isolated from the exhaust gas stream and desorbs CO captured by the monolithic adsorbent. CO adsorption by the first adsorbent bed and CO desorption from the second adsorbent bed are carried out according to the procedures described above.

[0007] Additionally, in some embodiments, a condensing heat exchanger is positioned downstream of one or more of the adsorbent beds, which in some embodiments can be used to recover water vapor in the exhaust gas stream from the combustion process and / or condensed vapors evaporated from the monolithic adsorbent of the adsorbent beds. These and other embodiments are further described in the detailed description that follows. [Brief explanation of the drawings]

[0008] [Figure 1] 1 illustrates a honeycomb monolithic structure adsorbent according to some embodiments herein. [Figure 2] Illustrated are flow channels 12 defined by internal partitions 11 within a honeycomb-like monolithic structural catalyst body according to some embodiments herein. [Figure 3] A method for determining the average thickness of the outer peripheral wall 10 and the inner partition wall 11 will be described. [Figure 4] FIG. 1 illustrates a plan view of a module including a monolithic adsorbent according to some embodiments. [Figure 5] FIG. 1 is a schematic diagram illustrating the methods described herein according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0009] The embodiments described herein can be more readily understood by reference to the following detailed description and examples, as well as the preceding and following descriptions. However, the elements, devices, and methods described herein are not limited to the specific embodiments shown in the detailed description and examples. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Many modifications and adaptations will be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention.

[0010] In one aspect, a method for removing CO from a flue gas or exhaust gas stream generated from a point source, including, but not limited to, a power generation facility, a concrete manufacturing facility, and a chemical and food processing facility, is described herein. The method, in some embodiments, includes an adsorption cycle for removing at least 70 percent CO from the exhaust gas stream. The adsorption cycle includes flowing the exhaust gas stream through at least one adsorbent bed formed from a monolithic adsorbent having an outer peripheral wall and a plurality of inner partitions supporting organic or inorganic compounds that adsorb CO from the exhaust gas stream, the exhaust gas stream having an inlet temperature of at least 60°C, a CO content of 3 to 20 percent, and a water vapor content of 2 to 22 percent. The adsorbent bed is isolated from the exhaust gas stream, and steam having a pressure of -14 kPa (-2 psig) to 14 kPa (2 psig) and a maximum temperature of 120°C is flowed through the adsorbent bed in a direction counter to the flow of the exhaust gas stream to provide the enthalpy of CO desorption and thereby desorb the CO captured in the adsorbent bed. A first portion of the vapor is condensed within the pores of the monolithic adsorber, and a second portion of the vapor sweeps the desorbed CO2 from the adsorbent bed, providing a mixture of desorbed CO2 and the sweep vapor. The CO2 is then separated from the mixture, thereby providing a product gas having at least 90 weight percent CO2. The adsorbent bed is discontinued from isolation from the exhaust gas stream, and the exhaust gas stream re-enters the monolithic adsorber, vaporizing the condensed vapor within the pores and cooling the adsorber to a temperature below 90°C to begin a new adsorption cycle.

[0011] Turning now to specific components, the adsorbent bed used in the point source recovery method described herein employs a monolithic adsorbent. The monolithic adsorbent includes an outer peripheral wall and a plurality of inner partition walls that support an organic or inorganic compound that adsorbs CO from an exhaust gas stream. In some embodiments, the outer peripheral wall and the plurality of inner partition walls are dispersed throughout a support comprising an inorganic oxide composition. When dispersed throughout the outer peripheral wall and the inner partition walls, the support comprising the inorganic oxide composition forms the outer peripheral wall and the inner partition walls in some embodiments. The support may comprise any inorganic oxide not inconsistent with the technical objectives described herein. In some embodiments, the inorganic oxide comprises at least one of titania (TiO), alumina (AlO), and zirconia (ZrO). In some embodiments, the inorganic oxide composition is titania-based or alumina-based. The alumina of the inorganic oxide may include one or more polymorphs, including gamma-alumina. When titania- or alumina-based, the titania or alumina is the inorganic oxide present in the highest amount in the composition. In some embodiments, for example, an alumina-based inorganic oxide composition contains 40 to 100 wt% alumina, and similarly, in some embodiments, a titania-based inorganic oxide composition contains 40 to 100 wt% titania.

[0012] In some embodiments, the support comprises 50-100 wt. % of the inorganic oxide composition. In some embodiments, the inorganic oxide of the support is substantially free of tungsten, vanadium, and / or molybdenum oxides. For example, the inorganic oxide of the support comprises less than 5 wt. %, less than 3 wt. %, or less than 1 wt. % of tungsten, vanadium, and / or molybdenum oxides. In some embodiments, the inorganic oxide composition also comprises less than 100 ppm of iron or iron compounds, which can be used to oxidize and / or otherwise decompose CO2 capture functional groups, such as amine functional groups, associated with the support. The support can further comprise a filler and / or a reinforcing agent, as further described herein.

[0013] In some embodiments, the support exhibits a hierarchical pore structure with a macroporosity of at least 0.05 cc / g in pores with diameters ranging from 600 to 5,000 angstroms. In some embodiments, the macroporosity ranges from 0.05 to 0.3 cc / g or 0.08 to 0.2 cc / g in pores with diameters ranging from 600 to 5,000 angstroms. In some embodiments, the macroporosity of the support comprises a first porosity distribution of at least 0.08 cc / g in pores with diameters ranging from 600 to 5,000 angstroms and a second porosity distribution of at least 0.16 cc / g in pores with diameters ranging from greater than 5,000 to 50,000 angstroms, the sum of the first porosity distribution and the second porosity distribution falling within a total macroporosity range of 0.24 to 1.0 cc / g. In some embodiments, the macroporosity is bimodal or multimodal, and the sum of the individual modes yields the total macroporosity. The first porosity distribution, in some embodiments, is greater than the second porosity distribution of the macroporosity. Alternatively, the second porosity distribution of the macroporosity can be greater than the first porosity distribution.

[0014] In addition to macroporosity, the support may have a mesoporosity of at least 0.15 cc / g or at least 0.20 cc / g for pores ranging from 20 to 500 angstroms in diameter. In some embodiments, the support has a mesoporosity of at least 0.30 cc / g for pores ranging from 20 to 500 angstroms. The mesoporosity of the support may also have a value selected from Table 1.

[0015] [Table 1]

[0016] The ratio of mesoporosity to macroporosity of the support can be greater than 1, such as greater than 1.1 or greater than 1.2. In other embodiments, the ratio of mesoporosity to macroporosity of the support is less than 1, such as from 0.5 to 0.8. The macroporosity of the support can be measured by mercury intrusion porosity, and the mesoporosity can be measured by nitrogen (N2) adsorption.

[0017] As described herein, the support having the aforementioned hierarchical pore structure is dispersed throughout the outer peripheral wall and inner partition walls of the monolithic adsorbent. In some embodiments, the support comprising an inorganic oxide composition forms the outer peripheral wall and inner partition walls of the monolithic adsorbent. The inner partition walls are disposed within the dimensions defined by the outer peripheral wall, and a plurality of flow channels are defined by the inner partition walls, which extend longitudinally through the monolithic adsorbent. Figure 1 shows a honeycomb-shaped monolithic adsorbent according to some embodiments of the present disclosure. The honeycomb-shaped adsorbent in the embodiment of Figure 1 comprises an outer peripheral wall 10 and a plurality of inner partition walls 11. The inner partition walls 11 define a plurality of flow channels 12 extending longitudinally through the honeycomb-shaped monolithic adsorbent.

[0018] FIG. 2 illustrates flow channels 12 defined by inner partition walls 11 within a honeycomb-shaped monolithic catalyst body according to some embodiments of the present disclosure. The inner partition walls 11 and their junctions with the outer peripheral wall serve as boundaries between adjacent flow channels 12. When a portion of the outer peripheral wall 10 serves as a boundary between flow channels 12, that portion may be referred to as an outer peripheral wall segment 13. As shown in FIGS. 1 and 2 , the flow channels 12 define a flow channel density or cell density across the inlet and outlet faces of the monolithic adsorbent. The monolithic adsorbents described herein can have any desired cell or flow channel density. As discussed above, the monolithic adsorbent has a cell density of at least 85 cpsi. In some embodiments, the monolithic adsorbent has a cell density of 100 cpsi to 900 cpsi. For example, the monolithic adsorbent can have a cell density of 100 cpsi to 500 cpsi, 140 cpsi to 450 cpsi, or 170 cpsi to 500 cpsi. Additionally, the length of the flow channel or cell is, in some embodiments, at least 100 mm or at least 110 mm. In some embodiments, the length of the flow channel of a monolithic cell having a treatment body is at least 120 mm or at least 125 mm.

[0019] As described above, the thickness of the inner partition wall of the monolithic adsorbent is 0.1 mm to 0.3 mm. In some embodiments, the thickness of the inner partition wall can be 0.1 mm to 0.25 mm, 0.1 mm to 0.2 mm, 0.1 mm to 0.25 mm, 0.15 mm to 0.25 mm, or 0.15 mm to 0.2 mm. The thicknesses of the outer peripheral wall 10 and the inner partition wall 11 are measured using a vernier caliper or micrometer with a resolution of 0.01 mm. Figure 3 shows a method for determining the average thickness of the outer peripheral wall 10 and the inner partition wall 11. The thickness of the outer peripheral wall 10 is measured at 12 different positions on a catalyst body sample. The 12 measurement positions consist of three points on each side of the square outer peripheral wall, as shown in Figure 3. The average thickness of the outer peripheral wall 10 is calculated by averaging the values ​​obtained from the 12 measurements. Similarly, the average thickness of the inner partition wall 11 is determined by first measuring the thickness of the inner partition wall 11 at 12 different locations across the catalyst body. The inner partition wall 11 is measured in the horizontal and vertical directions, as shown in Figure 3. The average thickness of the inner partition wall 11 is calculated by averaging the values ​​obtained from the 12 measurements.

[0020] A thin inner partition can help achieve high cpsi without sacrificing the open frontal area of ​​the monolithic adsorbent and / or inducing undesirable pressure drops experienced by gas flow through the monolithic structure. The open frontal area (OFA) of a monolithic adsorbent is the portion of the body cross section available to gas flow in a cross section perpendicular to the direction of gas flow. Increasing the open frontal area can result in more efficient fluid flow characteristics within the monolithic body, which can reduce the pressure drop experienced by fluid flow through the monolithic adsorbent. The monolithic adsorbents described herein have an OFA of at least 65 percent. In some embodiments, the monolithic adsorbent has an OFA of at least 70 percent or at least 80 percent. The OFA of the monolithic adsorbent can range from 65 to 90 percent, 65 to 85 percent, 70 to 90 percent, 70 to 80 percent, 75 to 85 percent, or 80 to 90 percent in some embodiments.

[0021] As described above, the monolithic adsorbent also has a hydraulic diameter of at least 100 mm. The hydraulic diameter of the catalyst body is defined as the cross-sectional area of ​​the catalyst body perpendicular to the flow direction multiplied by 4 and divided by the circumference of the outer peripheral wall. If the monolithic adsorbent body has a circular cross-sectional shape, the hydraulic diameter is equal to the diameter of the circular cross-sectional area. If the monolithic adsorbent body has a square cross-sectional shape, the hydraulic diameter is equal to the length or width of the side. Thus, the hydraulic diameter characterizes the size of the monolithic adsorbent, with larger hydraulic diameters corresponding to larger monolithic adsorbents. In some embodiments, the monolithic adsorbent has a hydraulic diameter of at least 120 mm or at least 130 mm. The hydraulic diameter of the monolithic adsorbent can range from 100 mm to 150 mm, from 120 mm to 150 mm, or from 130 mm to 150 mm. In some embodiments, the hydraulic diameter of the monolithic adsorbent can be greater than 150 mm. The hydraulic diameter of the monolithic adsorber can have an upper limit of 300 mm in some embodiments.

[0022] In addition to the high porosity provided by the thin internal walls, high OFA, large hydraulic diameter, and hierarchical pore structure, the monolithic adsorbent also exhibits sufficient lateral compressive strength to enable its use in industrial gas processing applications. Insufficient lateral compressive strength may preclude the monolithic adsorbent from being placed or packed into modules and / or other configurations for industrial gas processing applications.

[0023] FIG. 4 shows a plan view of a module including monolithic adsorbents according to some embodiments. The module 20 includes an open metal framework 22 for supporting monolithic adsorbents 24 disposed therein. The monolithic adsorbents 24 are arranged side by side. In some embodiments, packing material, cement, or silicone is present between one or more sides of adjacent monolithic adsorbents to prevent gas flow around the monolithic adsorbents. Modules including monolithic adsorbents can be arranged to form adsorbent beds as described herein.

[0024] When arranged in a module, as shown in Figure 4, the monolithic adsorbents are subjected to compressive forces resulting from pressure between the adsorbents when they are assembled side-by-side, with or without sealant, and when they are stacked on top of each other, with or without sealant, to form an array large enough to process significant quantities of gas. In some embodiments, the monolithic adsorbents have a compressive force of at least 500 g / cm. 2 The lateral compressive strength of the monolithic adsorbent may also have a value selected from Table 2.

[0025] [Table 2]

[0026] The lateral compressive strength of the monolithic structural catalyst bodies of the present invention can be measured using a compression testing device such as the Tinius Olson 60,000 lb. Super "L" compression tester, which exhibits a maximum compressive load of 30,000 kg and is available from Tinius Olsen, Inc., Willow Grove, Pa. Samples for lateral compressive strength testing can be prepared by cutting the monolithic structural catalyst into sections, typically 150 mm long, and at least 50 mm long, with each section serving as an individual test sample.

[0027] A 6 mm thick ceramic wool is spread above and below the pressure surface of the specimen, and the specimen, wrapped in a plastic bag, is placed in the center of the pressure plate. The pressure plate used for the test can be stainless steel with dimensions of 160 mm x 160 mm. The lateral compressive strength is quantified at the lower side where a compressive load is applied in a direction parallel to the cross section of the honeycomb structure and perpendicular to the partition wall. Therefore, the compressive load is applied in a direction perpendicular to the direction of flow in the channel. The compressive load can be applied as specified in Table 3.

[0028] [Table 3]

[0029] The maximum lateral compressive load W (g) that the sample can withstand is recorded by the instrument. The lateral compressive strength is calculated from the maximum compressive load by dividing the value of the maximum compressive load in grams force (gf) by the surface area to which the load is applied.

[0030] When producing the monolithic sorbents described herein, lubricants and other extrusion aids are used to reduce shear stress and pressure during processing. Mixing energy can be monitored by motor amperage, and mixing cycles can be optimized to minimize mixing energy. Shear stress during extrusion can be minimized by maintaining extruder tolerances, minimizing flow transitions, and / or using an extruder with higher positive pressure. Dies can be designed to minimize internal pressure loss during extrusion, such as by tapering the entrance to the open channel at the die entrance. Die surfaces can also be designed to minimize friction within the die, such as by polishing the internal surfaces and using nickel plating. The conveying system downstream of the extruder can be designed to minimize forces on the extrudate to minimize batch stiffness, such as by using foam conveyor surfaces or air bearings.

[0031] In some embodiments, the monolithic adsorbents described herein can further include an inorganic binder and / or a reinforcing agent. In some embodiments, the inorganic binder and / or one or more reinforcing agents can be present in the monolithic adsorbent in an amount of 3 to 30 weight percent. Reinforcing agents can include reinforcing fibers, including glass (SiO2) fibers, carbide fibers, ceramic fibers, and mixtures thereof. In some embodiments, the reinforcing fibers have a diameter of 3 μm to 10 μm. The inorganic binder and / or reinforcing agent can be added to the inorganic oxide extrusion batch. The extrusion conditions described herein are carefully adjusted when using fibrous reinforcing agents, as such reinforcing agents can complicate or prevent the creation of the desired mesopores and macropores of the hierarchical pore structure. The extrusion system can include an extruder, a filter or screen, and an extrusion die. The filter or screen can be utilized to facilitate passage of the mixture through the die while minimizing shear stress. Particles that could clog the die are removed without removing fillers, binders, glass fibers, and / or other reinforcing agents, which provide advantageous product properties. In some embodiments, for example, a wedge-shaped screen is used to prevent or reduce the removal of fiber reinforcement from the mixture.

[0032] The monolithic adsorbents described herein contain one or more organic or inorganic species usable for CO2 capture from a gas stream flowing through the monolithic adsorbent. The inner and outer peripheral walls can support organic or inorganic species usable for CO2 capture. Thus, a monolithic adsorbent without one or more species usable for CO2 capture can be considered a substrate for one or more species usable for CO2 capture. One or more species usable for CO2 adsorption from an exhaust gas stream can be combined with a support exhibiting the above-described hierarchical pore structure. The one or more species for CO2 adsorption can be dispersed throughout the support and reside in mesopores, macropores, or a combination thereof of the hierarchical pore structure. When combined with a support, the species for CO2 adsorption can be dispersed throughout the inner walls. Such a structure is fundamentally different from a washcoat, in which a refractory oxide layer is coated on a substrate as a support for the adsorbent species.

[0033] The chemical species for CO2 adsorption can be organic or inorganic. In some embodiments, the chemical species includes one or more organic compounds containing amine functional groups for CO2 adsorption. For example, the chemical species can include one or more polymeric species containing amine functional groups. In some embodiments, the polymeric species includes polyalkyleneimine, including polyethyleneimine, polypropyleneimine, or a combination thereof. The polymeric species containing amine functional groups for CO2 adsorption can be linear, branched, or hyperbranched (dendrimer). The polymeric species containing amine functional groups for CO2 adsorption can include homopolymers, copolymers, and graft copolymers. The organic compound containing amine functional groups for CO2 adsorption can also include small molecules (non-polymeric molecules), such as tetra(ethylenepentamine) (TEPA).

[0034] As described herein, organic compounds containing amine functional groups for CO2 adsorption can be dispersed throughout the support and present in the mesopores, macropores, or a combination thereof of the hierarchical pore structure. In some embodiments, the ratio of organic compounds containing CO2-trapping functional groups present in the mesopores to organic compounds containing CO2-trapping functional groups present in the macropores is greater than 1. In some embodiments, this ratio ranges from 1.5 to 10 or from 2 to 5. Additionally, in some embodiments, at least 80 percent of the organic compounds containing CO2-trapping functional groups are present in the mesopores. In some embodiments, 80 to 90 percent of the organic compounds containing CO2-trapping functional groups are present in the mesopores. Additionally, in some embodiments, at least 75 percent of the organic compounds containing CO2-trapping functional groups are present in the mesopores, and the inclusion of the organic compounds reduces the total mesopore volume by less than 70 percent.

[0035] Organic compounds containing amine functional groups for CO2 adsorption can form one or more interactions with the inorganic oxide composition of the support. In some embodiments, the organic compounds form van der Waals and / or ionic interactions with the inorganic oxide composition of the support, forming mesopores and / or macropores. In other embodiments, the organic compounds can be covalently bonded to the inorganic oxide composition. The organic compounds can include one or more functional groups for reacting with surface functional groups of the inorganic oxide, such as hydroxide surface functional groups, oxide surface functional groups, and / or carboxyl surface functional groups. In some embodiments, chemical linkers can be used to covalently bond the organic compounds containing amine functional groups to the inorganic oxide composition of the support.

[0036] The organic compound containing amine functional groups for CO2 adsorption can partially fill the mesopores and / or macropores of the hierarchical pore structure of the support. Additionally, the organic compound can, in some embodiments, be uniformly or substantially uniformly dispersed within the mesopores and / or macropores along the entire length of the channels or cells of the monolithic adsorbent. In some embodiments, the organic compound containing amine functional groups for CO2 adsorption can be present in the monolithic adsorbent in an amount of at least 10 weight percent. In some embodiments, the organic compound is present in the monolithic adsorbent in an amount of 10 weight percent to 30 weight percent.

[0037] In some embodiments, the inclusion of organic compounds containing amine functional groups for CO adsorption in the hierarchical pore structure of the support increases the lateral compressive strength of the monolithic adsorbent body relative to the bare monolithic body. For example, in some embodiments, the inclusion of one or more organic compounds in at least 40 percent of the mesoporosity increases the lateral compressive strength of the monolithic body by at least 50 percent relative to the bare monolithic body.

[0038] To facilitate improved performance life of the monolithic adsorbents described herein, the inorganic oxide composition of the support can be free or substantially free of compounds containing metals that function to oxidize organic compounds containing amine functional groups for CO2 adsorption. In some embodiments, the inorganic oxide composition is free or substantially free of compounds containing oxides of metals selected from the group consisting of tungsten, vanadium, iron, chromium, and / or molybdenum. For example, the inorganic oxide of the support contains less than 5 wt%, less than 3 wt%, or less than 1 wt% of tungsten, vanadium, and / or molybdenum compounds. In some embodiments, the inorganic oxide composition also contains less than 100 ppm of iron or iron compounds that can be used to oxidize and / or otherwise decompose CO2 capture functional groups, such as amine functional groups, associated with the support.

[0039] As an alternative to organic compounds containing amine functional groups, the monolithic adsorbents described herein can include one or more alkali metal-based functional groups for CO adsorption. In some embodiments, the alkali metal-based functional groups include alkali metal oxides usable for CO adsorption. The alkali metal oxides can be dispersed throughout the inorganic oxide composition of the support and thus present in the mesoporosity and / or macroporosity of the hierarchical pore structure. Any alkali metal oxide compound can be used in the monolithic adsorbents described herein. In some embodiments, for example, the alkali metal oxide includes alkali metal carbonates, including sodium carbonate and / or potassium carbonate.

[0040] Monolithic adsorbents containing organic or inorganic compounds for CO2 capture can exhibit mesoporosity greater than 0.05 cc / g with pores ranging from 20 to 500 angstroms in diameter. The mesoporosity of monolithic adsorbents containing organic or inorganic compounds for CO2 capture is measured by nitrogen (N2) adsorption.

[0041] As described herein, an exhaust gas stream is passed through at least one bed formed of a monolithic adsorbent to remove at least 70 percent of CO from the exhaust gas stream, the exhaust gas stream having an inlet temperature of at least 60°C, a CO content of 3-20%, and a water vapor content of 2-22 percent. In some embodiments, the exhaust gas stream has an inlet temperature of 60-95°C. The exhaust gas stream can undergo upstream treatment before entering one or more adsorbent beds. For example, the exhaust gas stream can undergo selective catalytic reduction (SCR) treatment to remove nitrogen oxides and / or mercury from the exhaust gas stream. Additionally, the exhaust gas stream can be mixed with other gases, such as ambient air, to cool, dry, and / or dilute the CO content of the exhaust gas stream. In some embodiments, the exhaust gas stream is passed through one or more filters upstream of the inlet to one or more adsorbent beds. The filters can remove particulate matter harmful to the monolithic adsorbent, including metal oxide particles that accelerate degradation of the CO2 adsorbing functional groups and particles that clog the flow paths of the monolithic adsorbent or otherwise impede gas flow through the flow paths. In some embodiments, the one or more filters remove 20-95% of particles having a size of 0.3 μm or greater.

[0042] After flowing the exhaust gas stream through one or more adsorbent beds and adsorbing CO2 from the exhaust gas stream with the monolithic adsorbent, the adsorbent beds are isolated from the exhaust gas stream. The one or more adsorbent beds with adsorbed CO2 can be isolated from the exhaust gas stream by closing valves, louvers, or other panels through which the exhaust gas stream flows. The valves, louvers, or other panels can have fixed positions such that they do not move or change position within the CO2 removal system. In some embodiments, the adsorbent beds are also fixed and do not move. Figure 5, described below, further illustrates these principles.

[0043] Once isolated, steam at a pressure of -14 kPa (-2 psig) to 14 kPa (2 psig) and a temperature of 96-120°C is flowed through the adsorbent bed in a direction counter to the flow of the exhaust gas stream to provide the enthalpy of CO2 desorption and thereby desorb the CO2 trapped in the adsorbent bed. A first portion of the steam is condensed within the pores of the monolithic adsorbent, and a second portion of the steam sweeps the desorbed CO2 from the adsorbent bed, providing a mixture of desorbed CO2 and sweep steam. The CO2 is then separated from the mixture, thereby providing a product gas having at least 90 weight percent CO2. In some embodiments, the mixture of desorbed CO2 and sweep steam is cooled to condense the steam, thereby providing a product gas having at least 90 weight percent CO2. In some embodiments, the product gas comprises 90-99 weight percent CO2.

[0044] In some embodiments, at least 1 percent or at least 10 percent of the adsorbed CO2 remains in the monolithic adsorbent after the vapor desorption process. The remaining CO2 can protect the organic or inorganic CO2 adsorption functional groups of the monolithic adsorbent from degradation, thereby extending the life of the adsorbent. In some embodiments, 1 to 20 percent of the desorbed CO2 remains in the monolithic adsorbent after the vapor desorption process. Additionally, the change in ammonia concentration in the exhaust gas stream from the inlet to the outlet of the adsorbent bed averages less than 2 ppm during adsorption of CO2 from the exhaust gas stream. The ammonia content in the exhaust gas stream is measured using an FTIR multi-gas analyzer with ppb-level sensitivity in high-moisture gas streams. An increase in ammonia concentration at the outlet of the adsorbent bed may indicate decomposition or degradation of the amine CO2 adsorbent functional groups in the adsorbent bed.

[0045] The isolation of the adsorbent bed from the exhaust gas stream is discontinued, and the exhaust gas stream re-enters the monolithic adsorber, vaporizing the condensed vapor within the pores and cooling the adsorber to a temperature below 90°C to begin a new adsorption cycle.

[0046] In some embodiments, the methods described herein use at least two adsorbent beds, where at any one time, a first adsorbent bed removes CO from the exhaust gas stream and a second adsorbent bed is isolated from the exhaust gas stream and desorbs CO captured by the monolithic adsorbent. CO adsorption by the first adsorbent bed and CO desorption from the second adsorbent bed are carried out according to the procedures described above.

[0047] Figure 5 is a schematic diagram illustrating the methods described herein according to some embodiments. In the embodiment of Figure 5, a first adsorption bed (adsorption) having the structure and properties described herein is removing CO from an exhaust or flue gas stream. Cooled flue gas (70°C) enters the adsorption bed through a louver valve, where CO (black dots) is removed from the flue gas stream by adsorption by the monolithic adsorbent of the adsorption bed. A second adsorption bed (desorption) having the structure and properties described herein undergoes a CO desorption process by exposure to steam (gray circles). The louver valve allowing flue gas flow to the second adsorption bed is closed, thereby isolating the second adsorption bed from the flue gas stream during the CO desorption process. As described herein, steam enters the second adsorption bed in a direction opposite to the flue gas path through the second adsorption bed. The resulting mixture of desorbed CO2 and sweep vapor (black and gray circles) passes to a condenser for cooling, thereby condensing the vapor and providing a product gas having at least 90 weight percent CO2.

[0048] Additionally, in some embodiments, a condensing heat exchanger (not shown in FIG. 5) can be installed downstream of the adsorption bed to allow recovery of vapor condensed in the adsorption bed during desorption. The total amount of water recovered from the condensing heat exchanger, plus the amount removed during separation from the CO2 product resulting from desorption, represents at least 90% of the vapor introduced into the adsorption bed during desorption. In some embodiments, the heat exchanger also recovers at least 2 percent of the water vapor in the exhaust gas stream produced by the combustion process. These and other embodiments are further described in the non-limiting examples below.

[0049] Example 1 - Removal of CO2 from an Exhaust Gas Stream

[0050] To quantify the removal of CO2 from the exhaust gas stream, a monolithic adsorber having the parameters in Table 4 was placed in a test chamber.

[0051] [Table 4]

[0052] One CO2 adsorption / desorption cycle in the test system was carried out as follows: the simulated feed gas containing CO2 was fed for 2483 h. -1 The exhaust gas stream was injected into the monolithic adsorber at a space velocity of 0.05 sq. m / s. The average CO2 content at the inlet of the monolithic adsorber was 4.2%, the average moisture content at the inlet was 17.4%, and the average temperature at the inlet was 88.4°C. The CO2 capture efficiency was calculated by simultaneously measuring the CO2 concentrations at the inlet and outlet and calculating the CO2 recovery efficiency using the following equation:

number

[0053] After the adsorption step was completed, the feed gas was shut off (by redirecting it to the second adsorption chamber), and steam was passed through the monolithic adsorber from the opposite side of the adsorber section. This steam provided both the heat necessary to desorb CO2 from the monolithic adsorber and a sweep gas for recovering the desorbed CO2. The steam / CO2 mixture was passed through a condensing heat exchanger to remove water. The resulting CO2 stream was compressed and stored in a tank. A slipstream stream drawn from the transfer line between the compressor and the storage tank was analyzed by a high-concentration range CO2 analyzer to quantify CO2 purity. The output of this CO2 analyzer was fed back to the compressor inlet to recover the analyzed CO2. The test results showed a CO2 capture efficiency (CE) of 97.7% and a product gas containing 94.6% CO2 by weight.

[0054] Various embodiments of the present invention have been described to accomplish various objectives of the present invention. It should be recognized that these embodiments are merely illustrative of the principles of the present invention. Many modifications and adaptations of the present invention will be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. CO from the exhaust gas stream 2 A method for removing flowing an exhaust gas stream produced by a point source through at least one adsorbent bed formed of a monolithic adsorbent; isolating the adsorption bed from the exhaust gas stream; CO 2 CO captured in the adsorbent bed by providing enthalpy for desorption. 2 flowing steam having a pressure of -2 psig to 2 psig and a maximum temperature of 120°C through the monolithic adsorber in a direction counter to the flow of said exhaust gas stream to desorb condensing a first portion of the vapor within the pores of the monolithic adsorber; CO desorbed from the adsorption bed 2 with a second portion of the vapor to remove desorbed CO 2 and providing a mixture of sweep steam; The desorbed CO 2 from the mixture, thereby separating at least 90 weight percent of CO 2 providing a product gas comprising: interrupting isolation of said adsorption bed from said exhaust gas stream; Including, The monolithic adsorber removes CO from the exhaust gas stream. 2 an outer peripheral wall and a plurality of inner partition walls for supporting an organic or inorganic compound that adsorbs The exhaust gas stream has an inlet temperature of at least 60°C, 3 to 20 percent CO 2 content, and a water vapor content of 2 to 22 percent; The exhaust gas stream re-enters the monolithic adsorber to vaporize at least a portion of the first portion of the vapor condensed within the pores and cool the adsorber to a temperature below 90°C to begin a new adsorption cycle.

2. The at least one adsorption bed converts CO from the exhaust gas stream. 2 a first adsorbent bed for removing CO captured by the monolithic adsorber, while simultaneously a second adsorbent bed is isolated from the exhaust gas stream. 2 The method of claim 1 , wherein the

3. CO captured from the exhaust gas stream 2 10. The method of claim 1, wherein at least 1 percent of the total amount of the sorbent remains in the monolithic adsorbent after desorption and before discontinuing isolation of the adsorbent bed from the exhaust gas stream.

4. CO captured from the exhaust gas stream 2 4. The method of claim 3, wherein at least 1 to 10 percent of the total amount of the sorbent remains in the monolithic adsorbent after desorption and before discontinuing isolation of the adsorbent bed from the exhaust gas stream.

5. The method of claim 3 , wherein the organic compound is present on the monolithic adsorbent and comprises an amine functional group.

6. The method of claim 5 , wherein the organic compound comprises a polyalkyleneimine.

7. The method of claim 6 , wherein the polyalkyleneimine is polyethyleneimine.

8. The change in ammonia concentration in the exhaust gas stream from the inlet to the outlet of the adsorption bed determines whether CO 2 is removed from the exhaust gas stream. 2 6. The method of claim 5, wherein the average concentration of HCl is less than 2 ppm during adsorption of HCl.

9. 10. The method of claim 1, further comprising disposing at least one filter upstream of the adsorption bed, the filter removing at least 50 percent of particles having a size of 0.3 μm or greater.

10. 10. The method of claim 1, further comprising: installing a condensing heat exchanger downstream of the adsorption bed, the condensing heat exchanger recovering at least 2 percent of the water vapor in the exhaust gas stream produced by the combustion process.

11. and further comprising providing a condensing heat exchanger downstream of the adsorption bed to allow recovery of vapor condensed in the adsorption bed during desorption, wherein water recovered from the condensing heat exchanger is mixed with CO 2 resulting from desorption. 2 10. The method of claim 1, wherein the total amount plus the amount removed during separation from the product represents at least 90% of the vapor introduced into the adsorbent bed during desorption.

12. 10. The method of claim 1, wherein the monolithic adsorbent exhibits a mesoporosity of at least 0.05 cc / g with pores having diameters between 20 and 500 angstroms.

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