Gas separation is useful in many industries and can typically be accomplished by flowing a mixture of gases over an adsorbent that preferentially adsorbs one or more gas components while not adsorbing one or more other gas components. The non-adsorbed components are then recovered as a separate product.
One particular type of gas separation technology is swing adsorption, such as temperature swing adsorption (TSA), pressure swing adsorption (PSA), partial pressure swing adsorption (PPSA), rapid cycle pressure swing adsorption (RCPSA), rapid cycle partial pressure swing adsorption (RCPPSA), and not limited to but also combinations of the fore mentioned processes, such as pressure and temperature swing adsorption. As an example, PSA processes rely on the phenomenon of gases being more readily adsorbed within the pore structure or free volume of an adsorbent material when the gas is under pressure, i.e., the higher the gas pressure, the greater the amount readily-adsorbed gas adsorbed. When the pressure is reduced, the adsorbed component is released, or desorbed.
PSA processes may be used to separate gases of a gas mixture because different gases tend to fill the micropore of the adsorbent to different extents. If a gas mixture, such as natural gas, is passed under pressure through a vessel containing a polymeric or microporous adsorbent that is more selective towards carbon dioxide than it is for methane, at least a portion of the carbon dioxide is selectively adsorbed by the adsorbent, and the gas exiting the vessel is enriched in methane. When the adsorbent reaches the end of its capacity to adsorb carbon dioxide, it is regenerated by reducing the pressure, thereby releasing the adsorbed carbon dioxide. The adsorbent is then typically purged and repressurized and ready for another adsorption cycle.
TSA processes rely on the phenomenon that gases at lower temperatures are more readily adsorbed within the pore structure or free volume of an adsorbent material compared to higher temperatures, i.e., when the temperature of the adsorbent is increased, the adsorbed gas is released, or desorbed. By cyclically swinging the temperature of an adsorbent bed, TSA processes can be used to separate gases in a mixture when used with an adsorbent that is selective for one or more of the components of a gas mixture.
In these swing adsorption processes, various adsorbent bed assemblies are coupled together with conduits and valves to manage the flow of fluids. Orchestrating these adsorbent bed assemblies involves coordinating the cycles for each of the adsorbent bed assemblies with other adsorbent bed assemblies in the system. A complete cycle can vary from seconds to minutes as it transfers a plurality of gaseous streams through the adsorbent bed assembly.
However, swing adsorption systems do not properly manage the void space within the conduits of the system. Typically, these systems are distributed with various conduits being different lengths for the different adsorbent bed assemblies. This void space has a gas from the previous stream, which has to be displaced as part of the process. Accordingly, the conventional systems for swing adsorption are inefficient in managing the streams passing through the system in the various steps of the cycle.
There remains a need in the industry for apparatus, methods, and systems that are more efficient and that can be constructed and employed on a smaller footprint than conventional equipment. The more efficient management of the streams along with more compact designs are beneficial when the swing adsorption apparatus is to be deployed in remote locations, such as off-shore production platforms, arctic environments, or desert environments.