>5 (e.g., capture vessel TS3 in this example,) enters a turbocharger compressor 148 of the CO₂-turbocharger 138 via manifold 149, boosted in pressure (e.g., to 15-25 psi), raising the temperature of the CO₂gas to 300° F. or more. In other words, the manifold 149 connects capture vessel TS3, TS4, and TS5 to the turbocharger compressor 148 of the CO₂-turbocharger 138 to transport a CO₂stream of CO₂gas generated by a capture vessel set in the regeneration stage to the turbocharger compressor 148.

The heated CO₂gas from the turbocharger compressor 148 then enters the CO₂heat exchanger (CO₂HX) 118, and is heated to near raw exhaust temperature, typically 800-900° F., by a heat exchange process that uses the exhaust from the engine 112 for further heating the heated CO₂gas to produce hot CO₂gas. This hot CO₂gas is then expanded through an expander 150 (e.g., a decompressor) of the CO₂-turbocharger 138 (which causes the temperature of the hot CO₂to drop due to less pressure). However, due to the super-heating process performed by the turbocharger compressor 148 and the CO₂heat exchanger (CO₂HX) 118, the CO₂gas exiting the expander 150 still has a temperature equal to or greater than 600° F. that is sufficient for the regeneration process, and still at a pressure high enough to support a flow through the capture vessel TS3, TS4, or TS5 that is performing the regeneration (e.g., capture vessel TS3 in this example). For example, a pressure increase on a compressor side of the CO₂-turbocharger 138 significantly exceeds a pressure decrease on an expander side of the CO₂-turbocharger 138, such that a pressure of the CO₂gas exiting the expander 150 toward the capture vessel TS3, TS4, or TS5 is high enough to support the flow of the CO₂gas through the capture vessel TS3, TS4, or TS5 that is performing the regeneration. The expander 150 may be respectively coupled to the capture vessels TS3, TS4, TS5 via manifolds 152, 154, and 156 to provide a heated CO₂gas to a capture vessel that is set in the regeneration stage. At an end of the regeneration process, virtually no CO₂, and almost no water, remains in the capture vessel TS3, TS4, or TS5 that is performing the regeneration (e.g., the capture vessel TS3).

As a result of the regeneration process, the media (e.g., the mole sieve) of the capture vessel TS3, TS4, or TS5 is hot, typically with an average temperature of about 500° F., and must be cooled to prepare the capture vessel for a next CO₂adsorption cycle. A cooling process for the capture vessel TS3 is accomplished by opening valves T3C and T3X, while closing valves T3In, T3T, T3H, and T3D. In other words, the dry (warm) N₂gas that exits the capture vessel set in the adsorbing stage (e.g., capture vessel TS5 for cooling of capture vessel TS3) is directed into the capture vessel TS3 for cooling the media of the capture vessel TS3.

The cooling process need not return the media temperature fully to ambient temperature. Any temperature under 100° C. (212° F.) will provide some capacity for initial adsorption of CO₂, with temperatures near or below 50° C. (122° F.) being preferred. The cooling process may continue in parallel with the adsorption process to some extent since a raw exhaust stream from cooler P2T (e.g., a heat exchanger) is provided at nominally 10° C. (50° F.).

In addition, the carbon capture system 100 may include a coolant tank 158 or another coolant source or circulator that is configured to circulate coolant through a capture vessel (e.g., capture vessels TS3, TS4, or TS5) that is configured in an adsorption stage. The coolant may be circulated through a coil of an inter-exchanger of the capture vessel, as described further in connection with FIG. 5, while the capture vessel is performing CO₂adsorption. In some implementations, the inter-exchanger may be used to circulate the coolant in the capture vessel during the cooling stage.

FIG. 2 shows an example cycle timing diagram 200 of the CO₂-TSA process using capture vessels TS3, TS4, and TS5, including a state of each of the valves during each stage, including the adsorption stage, the cooling stage, and the regeneration stage of the batch sequence.

FIG. 3 shows an example diagram 300 showing flow directions of fluid flow and a process sequence in a capture vessel (e.g., capture vessel TS3). The directions of fluid flow correspond to directions in FIG. 1, where an upward flow corresponds to a flow from a bottom of the capture vessel to a top of the capture vessel (e.g., away from valves T3X, T4X, and T5X), and downward flow corresponds to a flow from the top of the capture vessel to the bottom of the capture vessel (e.g., toward valves T3X, T4X, and T5X).

FIG. 4 illustrates a carbon capture system 400 according to one or more implementations. The carbon capture system 400 is similar to the carbon capture system 100 described in connection with FIG. 1, with the exception that the capture vessels TS3, TS4, and TS5 are used for both adsorbing water for dehydration and for adsorbing (capturing) CO₂. Thus, the capture vessels TS3, TS4, and TS5 additionally perform the water dehydration process carried out by the adsorbent vessels TSA1 and TSA2 described in connection with FIG. 1.

FIG. 5 shows a cross-section of a capture vessel 500 according to one or more embodiments. For example, the capture vessel 500 may be used for CO₂adsorption during a CO₂-TSA process. In other words, the capture vessel 500 may correspond to any one of the capture vessels TS3, TS4, and TS5 described in connection with FIG. 1.

The top-down, the capture vessel 500 includes an upper flange 502, an upper perforated baffle 504, an upper guard 506 of dehydrating media, an upper capture media 508 (e.g., an upper bed), an inter-exchanger 510, a lower capture media 512 (e.g., a lower bed), a lower guard 514 of dehydrating media, a media support screen 516, a lower perforated baffle 518, and a lower flange 520. Thus, the inter-exchanger 510 is arranged between and in thermal contact with the upper capture media 508 and the lower capture media 512. The inter-exchanger 510 is configured to reduce temperature in the upper capture media 508 and/or the lower capture media 512 during CO₂adsorption and is configured to aid in cooling during CO₂adsorption. In some implementations, the inter-exchanger 510 may be enabled during the cooling stage. For example, the inter-exchanger 510 may be used to circulate the coolant in the capture vessel during the cooling stage to aid in cooling of the media.

For example, the upper guard 506 and the lower guard 514 include dehydrating media that has an affinity for water. The exhaust gas from the adsorption inlet 132 may flow into the capture vessel 500 via the upper flange 502 or via the lower flange 520. The upper guard 506 or the lower guard 514 that initially receives the exhaust gas from the adsorption inlet 132 removes water from the exhaust gas to dehydrate the exhaust gas going to the upper capture media 508 and/or the lower capture media 512. Assuming the lower guard 514 initially receives the exhaust gas from the adsorption inlet 132, the lower capture media 512 will start to capture CO₂before the upper capture media 508 starts to capture CO₂. Prior to adsorption the capture vessel 500 is cooled during the cooling stage to increase a capture capacity of the upper capture media 508 and the lower capture media 512. However, adsorption of CO₂causes the capture media 508 and 512 to release heat, causing a temperature of the capture media to rise. Since the lower capture media 512 will start to capture CO₂first and start to release heat, the heat released as a result of the CO₂adsorption at the lower capture media 512 may flow toward the upper capture media 508 and lower the capture capacity of the upper capture media 508 due to an increase in temperature at the upper capture media 508. This thermal wave associated with a heat of CO₂adsorption can decrease a capture efficiency of a CO₂capture system. For example, higher temperatures cause a capture efficiency of a capture media to decrease. High enough temperatures (e.g., temperatures exceeding a temperature threshold) may render a capture media inert for CO₂capture.

The inter-exchanger 510 may include at least one coil 522 or exchanger bundle configured to carry a coolant. For example, the coil 522 may circulate the coolant through the inter-exchanger 510 to absorb or otherwise take away heat generated in the lower capture media 512 and/or the upper capture media 508 during CO₂adsorption. The coolant may be a cool fluid (e.g., a cool gas, liquid, or fluid mixture) that flows from in inlet to an outlet of the inter-exchanger 510 to carry heat out of the capture vessel 500 during the adsorption stage. In other words, the coolant may be injected into the inter-exchanger 510 when it is desired to lower a temperature of the lower capture media 512 and/or the upper capture media 508. The coil 522 is configured to maintain separation of the coolant from the capture media such that the coolant does not physically interact with the capture media or the exhaust gas flowing through the capture vessel 500. In some implementations, the coil 522 is embedded in the capture media such that the lower capture media 512 and the upper capture media 508 are not physically separated from each other. Instead, the capture media may be filled around the coil 522.

The inter-exchanger 510 may be arranged to provide contact between individual bed media pellets and a heat transfer surface of the coil 522. The coil 522 of the inter-exchanger 510 may be made of stainless steel or another lightweight alloy construction, consistent with temperature excursions of the regeneration process. The inter-exchanger 510 may maintain temperatures in the lower capture media 512 and/or the upper capture media 508 below 150° F., which may be a temperature at which the capture capacity of the capture media is significantly reduced, made substantially inefficient, and/or made inert or substantially inert.

Even a small reduction in the temperature of the lower capture media 512 and/or the upper capture media 508, which is achievable by cooling the exhaust gas flowing through the capture vessel 500 via the inter-exchanger, may significantly increase the capture capacity of the capture vessel 500. Thus, the inter-exchanger 510, distributed internally within the capture vessel 500, is configured to manage the thermal wave associated with the heat of adsorption by lowering the temperature of the lower capture media 512 and/or the upper capture media 508 to increase the capture capacity of the capture vessel 500 during the adsorption stage.

The inter-exchanger 510 may assist in significantly reducing a carbon footprint of a gas turbine engine or a piston engine as a result of achieving a high CO₂capture percentage, generally greater than 95%. Greenhouse gases include CO₂, NO_x, and SO_xthat make part of acid rain and/or attack the ozone layer, as well as unburnt hydrocarbon HC (e.g., methane and non-methane), and any partial products of combustion, like aldehydes. Carbon monoxide, while not commonly considered a greenhouse gas, is a regulated pollutant that converts in the atmosphere quickly to form CO₂.

Other capture techniques, like conventional amine, do not address most of these gases. Other mole sieve capture techniques could address these gases, but gases like NOx will go into a capture vessel, but will not come out (in a pressure swing adsorption (PSA) process or a vacuum pressure swing adsorption (VPSA) process) resulting in reduced capture vessel (bed) performance over time. The CO₂-TSA described herein has a capability to also capture CO, HC, NOx with proper media choice, but, if those gases are captured, they must be tolerable as contaminants in the CO₂. CO and HC are allowed, but frequently NO_xand SO_xare not allowed at high concentration, since they could combine with other gases and create a corrosive mixture.

FIG. 6A illustrates a carbon capture system 600 according to one or more implementations. FIG. 6B illustrates a fluid flow path used during a CO₂adsorption stage of a CO₂-TSA process in the carbon capture system 600 and is similar to the CO₂adsorption stage described in connection with FIG. 1. FIG. 6C illustrates a fluid flow path used during a regeneration stage of the CO₂-TSA process in the carbon capture system 600. FIG. 6D illustrates a fluid flow path used during a drying stage of the CO₂-TSA process in the carbon capture system 600. FIG. 6E illustrates a fluid flow path used during a cooling stage of the CO₂-TSA process in the carbon capture system 600.

The carbon capture system 600 adds additional components and manifolds to the carbon capture system 400 described in connection with FIG. 4. For example, the carbon capture system 600 includes an N₂heat exchanger (N₂HX) 602, an N₂-turbocharger 604 that includes a compressor 606 and an expander 608, a valve HN2, a valve CN2, a valve CO2R, and a CO₂evaporative cooler (CO₂EVC) 610, a direct air capture (DAC) inlet fan 612, and a valve AC. These components may improve the performance of the carbon capture system 600 in terms of total CO₂percentage captured, system stability (e.g., both in terms of production rate and component duty), and system powering. The compressor 606 may be arranged at an inlet of the N₂-turbocharger 604 and is coupled to adsorption outlet 614 of the capture vessels TS3, TS4, and TS5 via manifold 616. The expander 608 may be arranged at an output of the N₂-turbocharger 604 and is coupled to an inlet 618 of the capture vessels TS3, TS4, and TS5 via manifold 620.

In addition, an ABS chiller heat exchanger (HX) 615 is provided to chill the exhaust exiting the CO₂heat exchanger (CO₂HX) 118. The CO₂evaporative cooler (CO₂EVC) 610 is arranged between valves T3D, T4D, and T5D and the CO2-turbocharger 138. In addition, optional valves P1in, P2in, P1V, P2V, P1D, P2D are added, as well as optional PSA vessels PS1 and PS2.

In the carbon capture system 600, a drying cycle (e.g., a hot drying cycle) is added after the regeneration stage and before the cooling stage of the batch sequence of the CO₂-TSA process described in connection with FIG. 1. Thus, once a capture vessel (e.g., TS3, TS4, or TS5) undergoes a regeneration process, the capture vessel undergoes a drying cycle before the capture vessel undergoes a cooling process. In addition, water may be used during the regeneration stage (e.g., a wet regeneration). In addition, a change in a regeneration flow direction may be reversed, as compared to the flow direction for regeneration shown in FIG. 3. For example, in FIG. 3, the flow direction for regeneration may be a flow from the top to the bottom of the capture vessel. In FIG. 6A, the flow direction for wet regeneration may be a flow from the bottom to the top of the capture vessel. This may be accomplished by reconfiguring a piping manifold and/or changing a state of one or more valves to achieve a desired flow direction through the capture vessel.

During operation of the carbon capture system 100 shown in FIG. 1, a temperature at a bed exit (e.g., valves T3D, T4D, or T5D), without temperature mitigation in a CO₂recirculation loop, may vary at an inlet of the CO₂-turbocharger 138 from about 100° F. to greater than 500° F. during the regeneration process. A rate of CO₂production may also change from a negative rate (e.g., capture vessel adsorbing CO₂early in the regeneration process) to a very high rate, over 1.5 times an average rate, through much of the regeneration process. In addition, about 10% of the captured CO₂may remain in the capture vessel TS3, TS4, or TS5, even after regeneration performed at greater than 600° F.

Referring to FIGS. 6A-6E, the CO₂-TSA process is a batch process. Whether using a three-stage adsorption, regeneration, and cooling process or a four-stage adsorption, regeneration, drying, and cooling process, the production of CO₂will not be constant, but will occur only during the regeneration process, and generally only later in the regeneration process, after the relevant capture vessel TS3, TS4, or TS5 has warmed up. However, a constant flowrate of CO₂is preferred over an uneven flowrate of CO₂. Accordingly, valve CO₂R may be provided to allow for recycling CO₂during regeneration. The valve CO₂R may function as a pressure regulator, opening to prevent the capture vessel TS3, TS4, and TS5 from going into a high vacuum condition during an instant when a capture value switches from adsorption to regeneration, and partial pressure of CO₂in the capture value increases dramatically.

While FIG. 6A shows a final dehydration via PSA after the capture process, it is also possible to replace the CO₂evaporative cooler (CO₂EVC) 610 with vessels PS1 and PS2, loaded with a ceramic like alumina, that will serve to both regulate the temperature at the inlet of the CO₂turbo and to dehydrate the product CO₂before returning to the CO₂heat exchanger (CO₂HX) 118 and the capture vessels TS3, TS4, and TS5.

CO₂Recycling During Regeneration

During an initial start of the regeneration stage, CO₂is lacking in a main regeneration loop (e.g., the CO₂recirculation loop) shown in FIG. 6C and it would take some time for enough CO₂to be present for the CO₂-turbocharger 138 in the main regeneration loop to become effective. The CO₂storage tank 146 may be used in a secondary regeneration loop to provide additional CO₂(e.g., auxiliary CO₂) to the CO₂-turbocharger 138 during the initial start of the regeneration stage. For example, valve CO₂R may be opened to allow CO₂stored in the CO₂storage tank 146 to be injected into a main regeneration loop. After a predetermined duration, valve CO₂R may be closed. At this time, more than a sufficient amount of CO₂is present in the main regeneration loop and a small percentage can be siphoned off from the main regeneration loop by the secondary regeneration loop at the cooler 140, and provided through the CO₂screw compressor 144, to a chiller 145, and ultimately to the CO₂storage tank 146 to replenish the CO₂supply in the CO₂storage tank 146. The replenished CO₂supply may be used for the initial start of a next regeneration stage (e.g., regeneration of the next capture vessel) by opening the CO₂R valve.

Thus, the secondary regeneration loop includes a CO₂source (e.g., the CO₂storage tank 146) that may be configured to inject the auxiliary CO₂into the CO₂stream of the main regeneration loop during an initial time interval of the regeneration stage. Additionally, the CO₂source may be configured to siphon off a portion of the CO₂stream from the main regeneration loop during a remaining time interval of the regeneration stage to replenish the CO₂supply that may be used for the initial start of a next regeneration stage (e.g., for a next capture vessel that enters into the regeneration stage).

Accordingly, valve CO₂R and the CO₂storage tank 146 may be used to increase an amount of CO₂in the main regeneration loop that flows into the CO₂evaporative cooler (CO₂EVC) 610 in order to decrease an amount of time until the CO₂-turbocharger 138 becomes effective for regeneration of a capture vessel.

CO₂Evaporative Cooler (CO₂EVC) for Wet Regeneration

The CO₂evaporative cooler (CO₂EVC) 610 may be used during the regeneration stage to provide wet regeneration of a respective capture vessel TS3, TS4, or TS5. The CO₂evaporative cooler (CO₂EVC) 610 may introduce water vapor into a CO₂stream in order to improve a CO₂release at the respective capture vessel by displacing adsorbed CO₂with adsorbed water vapor. Heat is created during the adsorption of the water vapor, which raises the bed temperature, and which further accelerates CO₂release from the respective capture vessel.

In addition, the CO₂evaporative cooler (CO₂EVC) 610 regulates a temperature of the CO₂flowing into the turbocharger compressor 148 by cooling the CO₂. By cooling CO₂flowing into the inlet of the CO₂-turbocharger 138 (e.g., into the turbocharger compressor 148), a temperature variation at the inlet of the CO₂-turbocharger 138 is reduced. Furthermore, temperatures exceeding 400° at the inlet of the CO₂-turbocharger 138 may not be acceptable and may cause failure. Thus, by cooling CO₂flowing into the inlet of the CO₂-turbocharger 138, a maximum temperature of the CO₂flowing into the inlet of the CO₂-turbocharger 138 may be reduced to be closer to 100° (e.g., to be less than 300° F.). Thus, the CO₂evaporative cooler (CO₂EVC) 610 provides temperature control for the inlet of the CO₂-turbocharger 138.

The CO₂evaporative cooler (CO₂EVC) 610 may be a DCC. As shown in FIG. 6C, a portion of the warm CO₂that exits a capture vessel (e.g., the capture vessel TS3) during regeneration is provided to the CO₂evaporative cooler (CO₂EVC) 610 as an inlet CO₂gas. A saturated gas mixture of CO₂and water vapor exits the CO₂evaporative cooler (CO₂EVC) 610 to the CO₂-turbocharger 138 for wet regeneration. The saturated gas mixture of CO₂and water vapor has a reduced temperature relative to the warm CO₂that exits the capture vessel.

A source of water for the CO₂evaporative cooler (CO₂EVC) 610, in cases where water is used for regeneration, can be condensed water from the engine exhaust stored in the water storage tank 124. When the CO₂evaporative cooler (CO₂EVC) 610 is operated with the water from the water storage tank 124 shut off, a temperature coming out of a capture vessel (e.g., the capture vessel TS3) may vary from 100-500° F. and is moderated based on a thermal capacity of a ceramic of the capture vessel. For a large ceramic load, approaching 50% of a mole sieve load per capture vessel, a peak temperature can be mitigated so that, even without water spray, an inlet temperature (e.g., less than 300° F.) of the CO₂-turbocharger 138 (e.g., an inlet temperature of the turbocharger compressor 148) is acceptable.

When the water from the water storage tank 124 is on continuously, the CO₂evaporative cooler (CO₂EVC) 610 acts as a very effective counter flow heat exchanger. Given a low temperature out of the CO₂evaporative cooler (CO₂EVC) 610, a percentage of water vapor in the saturated gas mixture of CO₂and water vapor will be low. For example, at 100° F., a water vapor percentage may be under 7% by volume and under 3% by weight. Nevertheless, the water vapor is present as the saturated gas mixture of CO₂and water vapor exits the expander 150 of the CO₂-turbocharger 138 and is provided to the capture vessel that is performing the regeneration (e.g., the wet regeneration). The CO₂-turbocharger 138 is configured to receive the saturated gas mixture of CO₂and water vapor from the evaporative cooler (CO₂EVC) 610, and heat the saturated gas mixture of CO₂and water vapor using the CO₂heat exchanger (CO₂HX) 118 in order to provide a hot mixed stream of CO₂and water vapor to the capture vessel that is configured in regeneration (e.g., a same capture vessel that produces the CO₂stream that is mixed with the water vapor by the evaporative cooler (CO₂EVC) 610).

The CO₂evaporative cooler (CO₂EVC) 610 can also be operated with water on only a percentage of a regeneration cycle. If the water is turned on late during regeneration, when a ceramic mass transfer media of the CO₂evaporative cooler (CO₂EVC) 610 is already hot, a large percentage of water vapor can be created, since a partial pressure of water vapor is 14.7 pounds per square inch absolute (PSIA) at 212° F. This water vapor and variable ability to create water vapor allows the regeneration process to be improved in two ways. First, water is adsorbed preferentially to CO₂in the media of the capture vessel (e.g., capture vessel TS3, TS4, or TS5) performing the regeneration. As a result, water is adsorbed by the media of the capture vessel, and a higher amount of CO₂is released (which is the objective during regeneration). Thus, the water vapor acts like a purge gas (e.g., a water vapor purge gas), but without reducing a dry purity of the CO₂gas that exits the capture vessel. Second, during a process of water vapor adsorption by the media of the capture vessel, heat is created, at nominally 1800 BTU/lb of water vapor. This heat increases the temperature of the capture vessel, which further aids in driving out CO₂from the capture vessel during regeneration. Thus, the water vapor purge derived from an output of the CO₂evaporative cooler (CO₂EVC) 610 is configured to increase a temperature associated with the wet regeneration stage. The net result is that the percentage of carbon captured during adsorption vs. released/produced during regeneration can be increased from nominally 90% (without the CO₂evaporative cooler (CO₂EVC) 610) to greater than 95% (with the CO₂evaporative cooler (CO₂EVC) 610).

Hot Drying Using N₂-Turbocharger

As shown in FIG. 6D, the N₂heat exchanger (N₂HX) 602 and the N₂-turbocharger 604 are provided for the drying stage (e.g., hot drying) of the CO₂-TSA process. The N₂-turbocharger 604 is associated with the N₂heat exchanger (N₂HX) 602 and is configured to reduce a power duty. During the drying stage, shown in FIG. 6D, a hot dry gas 622 is created from a gas 624 (e.g., the dry N₂gas) provided after CO₂adsorption, which exits the capture vessel TS3, TS4, or TS5 at valve T3T, T4T, or T5T, respectively. The dry N₂gas 624 is provided to the compressor 606 of the N₂-turbocharger 604 by opening valve HN2 and closing valve CN2. In other words, the compressor 606 is connected to the adsorption outlet 614 of the capture vessels TS3, TS4, and TS5 and is configured to receive the dry N₂gas 624 from the capture vessel set in the CO₂adsorption stage via manifold 616.

The dry N₂gas 624 enters the N₂-turbocharger 604, where the compressor 606 compresses the dry N₂gas 624 to produce compressed N₂gas. The N₂heat exchanger (N₂HX) 602 uses the hot exhaust from the engine 112 to heat the compressed N₂gas to produce heated (compressed) N₂gas. The expander 608 of the N₂-turbocharger 604 then expands the heated N₂gas, which results in a drop in temperature of the heated N₂gas, but the heated N₂gas remains sufficiently high with sufficient pressure to be used for hot drying of a respective capture vessel. The expander 608 is configured to output the hot dry gas 622 that is provided to the capture vessel that is set in the drying stage (e.g., capture vessel TS5). The hot dry gas 622 may be delivered from the expander 608 to the inlet 618 of the capture vessels TS3, TS4, and TS5 via manifold 620. The hot dry gas 622 is delivered to the capture vessel that is set in the drying stage.

Given that the exhaust temperature from the engine 112 can be near 900° F., and given the characteristics of the N₂-turbocharger 604 and the N₂heat exchanger (N₂HX) 602, it is possible to create a hot dry gas 622 that is mostly N₂gas and has a temperature that is greater than 600° F. for the drying process. The drying process may be used to dry the media of the capture vessel after wet regeneration. For example, in order for a capture vessel to again be able to sufficiently adsorb CO₂, the water adsorbed during wet regeneration should be released from the capture vessel. The drying process may be used to release the water as water vapor via evaporation and moving the water vapor out of the capture vessel. Importantly, the N₂-turbocharger 604 may be driven exclusively or mostly via engine waste heat (e.g., from the hot exhaust from the engine 112). As a result, little or no mechanical or electrical power is needed to sustain the drying process.

While the N₂heat exchanger (N₂HX) 602 and the CO₂heat exchanger (CO₂HX) 118 are shown in series, in some implementations, the exhaust flow from the engine could be split. As result, the N₂heat exchanger (N₂HX) 602 and the CO₂heat exchanger (CO₂HX) 118 could be provided in parallel, resulting in both the N₂heat exchanger (N₂HX) 602 and the CO₂heat exchanger (CO₂HX) 118 providing a respective hot gas (e.g., a CO₂turbo hot gas and an N₂turbo hot gas) at temperatures greater than 600° F.

In some implementations, a number of capture vessels need not align with a number of stages. For example, in the carbon capture system 600, three capture vessels TS3, TS4, and TS5 are used for the four-stage adsorption, regeneration, drying, and cooling process. As one capture vessel performs adsorption during a process time slot (e.g., during a batch), a second capture vessel can perform regeneration (e.g., wet regeneration) during the same process time slot. In addition, a third capture vessel can perform both drying and cooling during the same process time slot, with dying being performed during a first portion of the process time slot and cooling performed during a second portion of the process time slot. In some implementations, four capture vessels may be provided, with each capture vessel being allocated one of the four stages during a process time slot. In some implementations, five or six capture vessels may be provided with additional In, T, C, H, D, and X valving and manifolds. In addition, two capture vessels may be used simultaneously for a process that takes longer, such as adsorption or cooling, and only a single capture vessel used for a shorter process, such as regeneration or drying.

Valves HN2 and CN2 may allow the carbon capture system 600 to deliver either hot dry gas 622 for the drying process (valve HN2 open and valve CN2 closed) or deliver a cool mixture of N₂and air (e.g., cooled N₂gas 630) for the cooling process (valve CN2 open and valve HN2 closed). Thus, even if the number of capture vessels is three, the four stages can be accomplished, for example, by splitting a drying time and a cooling time for a single capture vessel.

Cooling

The cooling stage may be performed according to FIG. 1. Alternatively, the cooling stage may be performed according to FIG. 6E. In FIG. 6E, the dry N₂gas 624 that exits the capture vessel that is set in the adsorbing stage (e.g., capture vessel TS3) is circulated through the valve CN₂, through a chiller 626 for further cooling, though a cooler tank 628 by the TSA screw/blower 126 and to one of the capture vessels TS3, TS4, or TS5. In the cooling stage, valve HN2 is closed and valve CN2 is open to redirect the dry N₂gas 624 for cooling instead of for drying. The DAC inlet fan 612 is used to introduce outside air into the N₂flow. Thus, cooled N₂gas 630, that is mixed with outside air, is provided from the cooler tank 628, to the inlet 618, and passed through the capture vessel that is set in the cooling stage (e.g., capture vessel TS5) and exits though an exit valve (e.g., valve T5X).

FIG. 7 illustrates a carbon capture system 700 according to one or more implementations. The carbon capture system 700 is similar to the carbon capture system 600 described in connection with FIGS. 6A-6E, with the exception that a chiller 702 (e.g., a heat exchanger) and a valve N2R (N₂recycle) are provided between the TSA path 128 and the adsorption outlet 614 that is connected to valves T3T, T4T, T5T, HN2, CN2.

The SCC exhaust loop may be used to increase CO₂concentration for an adsorption bed (e.g., for capture vessels TS3, TS4, and TS5) via exhaust recirculation. The SCC has the purpose of concentrating the CO₂in the exhaust, to improve capture performance. In general, higher CO₂concentration reduces a size of capture equipment. There are limits, and in some cases, with higher water loading and/or with higher CO₂percentages like one might have in some reciprocating engines, a combination of heat of adsorption of water and heat of adsorption of CO₂can result in higher than desired temperatures in a bed (e.g., in a capture vessel) during the CO₂adsorption process. In these cases, reducing a bed temperature during adsorption will improve performance.

Valve N2R may be provided to divert some of the dry N₂gas 624 (e.g., the depleted flue gas) generated during CO₂adsorption from the capture vessel to the TSA screw/blower 126 in order to dilute the cold exhaust flowing into the TSA screw/blower 126 from the TSA path 128. The dry N₂gas 624, which is substantially depleted of CO₂, is added to the cold exhaust, which results in an amount of CO₂by volume to be decreased at the adsorption inlet 132. Thus, the dry N₂gas 624 may be used as a diluent gas (e.g., a cold diluent gas). As a result, the cold exhaust flowing into the adsorption inlet