Patent Application
20240149246
The invention relates to methods for the efficient regeneration of sorbents such as those used for the direct capture and separation of carbon dioxide (CO2) and/or water from the atmosphere. Temperature responsive bimetallic alloy strips, gores, or sheets are utilized to guide heated gas or steam flows to cooler regions of adsorbent beds undergoing regeneration.
Global warming is posing devastating effects on our climate, health, and communities. Coastal flooding due to rising sea levels, extended wildfire seasons, as well as more destructive hurricanes are the direct impacts of climate change. Moreover, global food and water security are at stake. There is a consensus among scientists that global warming is directly linked to the increase in the level of greenhouse gases in the atmosphere. Carbon dioxide (CO2) is a major greenhouse gas and its concentration in the atmosphere has sharply increased over the past century due to the burning of fossil fuels. Although efforts are underway to move toward renewable energy sources that do not emit greenhouse gases, shifting our energy supply to completely renewable sources is not possible in the near term and requires further technological advancements and significant global investments. Therefore, there is a growing need for technologies that can efficiently capture carbon dioxide from the flue gas of power plants and other industrial processes and, increasingly, even from ambient air. The latter is known as direct air capture (DAC).
CO2 capture processes can utilize some type of regenerable adsorbent bed to capture the CO2 from a gas or air stream (see, for example, Sanz-Perez, et al., Chemical Reviews, 2016, 116, 11840-11876). In one approach, ambient air or flue gas is moved through a bed of a solid sorbent that is effective at selectively capturing a significant portion of the CO2 therein. Once the sorbent reaches a level of significant saturation of CO2, it needs to be regenerated in a separate step. During regeneration, the adsorbent bed is treated in some fashion to cause the CO2 to desorb from the sorbent. The released CO2 is subsequently captured, and the regenerated sorbent can then be returned to the first step and reused to capture more CO2. Due to the low concentrations (currently a little over 400 parts per million) of CO2 in ambient air, high volumes of ambient air need to be moved and processed in a DAC process, necessitating high efficiency to be practical.
Solid CO2 sorbents include various zeolites or molecular sieves; amine-functionalized silicious, inorganic, activated carbon, graphitic, metal organic framework (MOF) or polymeric supports; amine-functionalized carbon, glass, cellulosic, or polymeric fibers; and basic or weakly basic ion exchange resins (see, for example, Samanta, et al., Industrial & Engineering Chemistry Research, 2012, 51, 1438-1463). In some cases, the solid CO2 sorbents are utilized in powder or pellet form in packed bed configurations. In other cases, the solid CO2 sorbents are utilized in fibrous webs, mats, or woven fabrics through which air is passed. In still other cases, the solid CO2 sorbents are formed into structured monoliths or other structured forms such as sheets, films, membranes, or plates through or around which air may be passed.
Some of the sorbents utilized for CO2 capture also adsorb water vapor in a competitive fashion, especially since water is typically present in ambient air at a concentration higher than that of CO2. Therefore, in some DAC applications, separate sorbent beds including desiccants are utilized to dry the air before it passes through the CO2 sorbent and must also be regenerated by treating to release adsorbed water. In some cases, for example as described in U.S. Pat. No. 11,446,605, the desorbed water can be collected, purified, and utilized as drinking water or for other human uses since freshwater resources are becoming short due to growing demand and global warming. In fact, there has been a growing interest in harvesting water directly from the air—see, for example, Zhou, et al. in ACS Materials Letters, 2020, 2, 671-684 and Bagheri in Water Resources and Industry, 2018, 20, 23-28. One advantage is that it can potentially be located anywhere on earth, but, like DAC, must be highly efficient to be practical at large scale.
The captured water or CO2 is desorbed during the sorbent regeneration process, which usually involves purging with a heated gas or applying heat and vacuum to the adsorbent bed to desorb and remove the sorbate. There is great interest in being able to heat the adsorbent beds quickly and evenly to conserve energy and to optimize cycle times. Thermal jackets or surface heaters are common heating methods but offer poor performance (cycle time) with the bulky adsorbent beds filled with insulative sorbent materials typically utilized for water and/or CO2 capture. Uneven airflow, temperature distributions, and channeling can all reduce sorbent regeneration efficiency, therefore a method of mitigating these inefficiencies is needed.
This invention provides efficient ways to heat an adsorbent bed, allowing for faster and more even heat transfer. In some embodiments, heat responsive bimetallic alloy strips, gores, or sheets are utilized to guide heated gas or steam flows to cooler regions of adsorbent beds undergoing regeneration. The invention provides a passive system for reactor thermal or fluid flow and improves overall heating and regeneration efficiency.
In an embodiment, the invention relates to a system to heat and regenerate an adsorbent bed including one or more chemical moieties adsorbed onto the adsorbent bed, the system comprising:
In another embodiment, the invention relates to an adsorbent bed comprising:
In another embodiment, the invention relates to a method to evenly heat and regenerate an adsorbent bed including one or more chemical moieties adsorbed onto the adsorbent bed, the method comprising:
In another embodiment, the invention relates to a method of heating and regenerating a sorbent included in an adsorbent bed, where the adsorbent bed is sealed within a reactor and the adsorbent bed includes heat-responsive fins having a first configuration, the method comprising:
In another embodiment, the invention relates to a method to evenly heat and regenerate an adsorbent bed including one or more chemical moieties adsorbed onto the adsorbent bed, the method comprising:
In another embodiment, a method to evenly heat and regenerate an adsorbent bed including one or more chemical moieties adsorbed onto the adsorbent bed, the method comprising:
The accompanying drawings, which are incorporated herein and constitute a part of this specification, illustrate exemplary embodiments. These and other objects, features and attendant advantages of the present invention will be more fully appreciated or become better understood when considered in conjunction with the accompanying drawings, wherein:
In an embodiment, the invention relates to a system to heat and regenerate an adsorbent bed including one or more chemical moieties adsorbed onto the adsorbent bed, the system comprising:
In another embodiment, the invention relates to an adsorbent bed comprising:
In another embodiment, the invention relates to a method to evenly heat and regenerate an adsorbent bed including one or more chemical moieties adsorbed onto the adsorbent bed, the method comprising:
Air and other gases are processed through adsorbent beds to remove water, CO2, or other chemical moieties such as acid gases including hydrogen sulfide, hydrogen chloride, sulfur oxides (SOx) and nitrogen oxides (NOx). Fans, blowers, compressors, and other types of air- and gas-moving equipment are utilized to force the gas through the sorbent(s) included within the adsorbent beds during an adsorption step. Depending on the identity and selectivity of the particular sorbent utilized in the adsorbent bed, one or more of the various chemical moieties that may be present in the gas stream is captured (adsorbed) by the sorbent and held in the adsorbent bed while a purified gas stream exits the adsorbent bed. Once the sorbent becomes sufficiently saturated with the adsorbed chemical moieties, it is regenerated by desorption of the adsorbed chemical moieties.
One approach to regenerate an adsorbent bed is to heat the bed to a temperature at which the adsorbed chemical moieties desorb from the sorbent. This may be accomplished by using thermal jackets or surface heaters around the adsorbent bed or embedded heating elements within the adsorbent bed, although this adds significant complexity to the design and operation of the systems and suffers from poor performance as heat distribution is generally uneven. Heating can be more efficiently accomplished by using a gas moving device to flow a heated gas (e.g., dry air, nitrogen, etc.) or fluid (e.g., steam) stream through the adsorbent bed to heat the sorbent and to purge the desorbed chemical moieties out of the adsorbent bed. Methods and equipment that supply the needed heated gas or fluid streams to the adsorbent beds include, but are not limited to, heat exchangers, steam boilers, fans, blowers, and compressors. Depending on the system configuration, fans, blowers, or compressors are already present in the system to move air through the adsorbent bed during the adsorption step. Therefore, there just needs to be a source of heated purge gas that can be pushed or pulled through the adsorbent bed via the existing fan, blower, or compressor, as the case may be. In some embodiments of the present invention, steam may be utilized as the source of heat for the regeneration process. Steam is commonly available and serves as an efficient heat source. Steam is available at a variety of pressures and the pressure of the steam may serve as the motive force to move the steam through the adsorbent bed. Furthermore, the adsorbent beds are commonly evacuated to a low pressure using a vacuum pump after the adsorption step and prior to the regeneration to remove residual air from the adsorbent bed, both to provide a higher purity of the desorbed chemical moieties and to protect the sorbent from oxidation at the elevated regeneration temperatures. In some embodiments of the present invention, a vacuum pump is utilized to pull the heated gas or steam stream through the adsorbent bed.
As shown in
During the desorption stage, heated air, steam, or other desorption gas flows through the adsorbent bed. As shown in
Changing the composition of the thermo bimetallic material will allow tuning as different materials have different temperature responses. Some materials will activate at higher or lower temperatures with more or less fin force. Outside of the composition of the fin material, changing the thickness of the fin will increase or decrease the fin force and changing the length of the fin will change how quickly the fin closes or blocks the gas passageway. A longer fin will have to respond quicker or earlier relative to a shorter fin of the same properties and thickness. A fin having a smaller thickness will respond quicker or earlier relative to a fin having a greater thickness. Lastly, varying the fin depth embedded depth, while keeping the non-embedded length consistent between all fins, will tune the response as increased surface area in the sorbent will better transfer heat between the sorbent and the fin. This is advantageous as the fin will respond quicker to the temperature of the sorbent region it is embedded in.
In an exemplary embodiment, desorption can be performed either from a front or rear of the sorbent (101) in an adsorbent bed. That is, air flow may be directed such that the air or gas impacts a first surface of a fin when the flow is provided from the front of the sorbent (101) and the air or gas impacts a second surface, opposite the first surface of the fin when the flow is provided from a rear or the sorbent (101). In some embodiments, the direction of the air flow during the adsorption step is the same as the direction of the heated gas or steam flow during the desorption step. In some embodiments, the direction of the heated gas or steam flow is opposite to that of the direction of the air flow during the adsorption step.
The calculations shown in
In another example embodiment, mechanical gates can be added to prevent flow obstruction until the fin has reached a particular temperature and corresponding mechanical force to overcome the gate force. One such example of limiting fin deflection is with a torsional spring as shown in
In some embodiments of the invention, one or more zeolites are used as the sorbent in the adsorbent bed. Low-silica zeolites with the faujasite (FAU) framework topology are commercially available at a relatively low cost (e.g., 13X and Y) and are amongst the most commonly used adsorbents in industrial gas adsorption and separation processes. Thus, in some embodiments of the invention, the sorbent in the adsorbent bed is a 13X zeolite. In other embodiments of the invention, the sorbent in the adsorbent bed is an erionite zeolite, a chabazite zeolite, a mordenite zeolite, a clinoptilolite zeolite, a 4A zeolite, or a 5A zeolite. In yet other embodiments of the invention, the adsorbent bed may contain two or more sorbents selected from a 13X zeolite, an erionite zeolite, a chabazite zeolite, a mordenite zeolite, a clinoptilolite zeolite, a 4A zeolite, and a 5A zeolite.
In some embodiments of the invention, one or more desiccants are used as the sorbent in the adsorbent bed. Common desiccants include silica, alumina, calcium sulfate, zeolites, and various types of clays such as montmorillonite. The desiccants may be in the form of powders, pellets, beads, flakes, or granules. In some embodiments of the present invention, activated carbons or charcoals are used as the sorbent in the adsorbent bed.
In some embodiments of the present invention, one or more amine functionalized solid sorbents are used as the sorbent in the adsorbent bed, including (i) polyamines supported on inorganic oxides; (ii) polyamines supported on other materials; and (iii) polyamine sorbents that do not feature a support material. See the variety of solid amine-based sorbents described in Hamdy, et al., Materials Advances, 2021, 2, 5843-5880.
In some embodiments of the present invention, one or more solid sorbents are used in a structured adsorbent bed. In some embodiments of the present invention, the solid sorbents are coated onto a suitable structuring substrate such as a flat plate, fiber, fiber bundle, or monolith. In some embodiments of the present invention, the solid sorbents are coated onto or embedded into a fabric, felt, membrane, or mat. In an exemplary embodiment, the one or more solid sorbents may be used in reactor 100.
Sorbent-coated monoliths, such as shown in
As shown in
Any number of fins may be disposed on a face of the monolith. For example, one fin may be disposed to correspond to each channel. In an alternative embodiment, one fin may be disposed to correspond to a plurality of channels. For example, a single fin can correspond to an entire column of channels such that one fin, when activated and bent, covers a column of channels in the monolith. Alternatively, a single fin can correspond to an entire row of channels such that one fin, when activated and bent, covers a row of channels in the monolith. A plurality of fins may be disposed with respect to the rows or columns of the matrix. For example, a plurality of fins can be mounted on the monolith such that each of the plurality of fins corresponds to one row or column of the matrix where a total number of fins corresponds to a total number of rows or columns of the matrix, respectively.
In another embodiment, a plurality of fins may be disposed in a single row or a single column. That is, one row or one column can include a plurality of fins and the number of rows or columns may be the same or different for each fin. For example, a first fin may be provided in a first portion of a row of the channels of the matrix and the fin may correspond to three or four channels and a second fin in a second portion of the same row may correspond to seven or eight channels.
As regions of the monolith begin to warm, the local fins will begin to bend (403), thereby restricting gas flow in those regions as shown in
As those skilled in the art will appreciate, numerous modifications and variations of the present invention are possible in light of these teachings, and all such are contemplated hereby. All of the references cited herein are incorporated by reference herein for all purposes, or at least for their teachings in the context presented.
The foregoing detailed description of the certain exemplary embodiments has been provided for the purpose of explaining the principles of the invention and its practical application, thereby enabling others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use contemplated. This description is not necessarily intended to be exhaustive or to limit the invention to the precise embodiments disclosed. The specification describes specific examples of accomplishing a more general goal that also may be accomplished in another way. Those skilled in the art will appreciate that the features described above can be combined in various ways to form multiple variations of the invention.
In an exemplary embodiment, the invention relates to a method of heating and regenerating a sorbent included in an adsorbent bed, where the adsorbent bed is sealed within a reactor and the adsorbent bed includes heat-responsive fins having a first configuration, the method comprising:
In another exemplary embodiment, the invention relates to a method to evenly heat and regenerate an adsorbent bed including one or more chemical moieties adsorbed onto the adsorbent bed, the method comprising:
In another exemplary embodiment, a method to evenly heat and regenerate an adsorbent bed including one or more chemical moieties adsorbed onto the adsorbent bed, the method comprising:
This application claims benefit of priority from U.S. Provisional Application No. 63/382,215 filed on Nov. 3, 2022, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63382215 | Nov 2022 | US |
