MECHANICAL VAPOR RE-COMPRESSOR HEAT PUMP FOR SEPARATING CO2 FROM WATER VAPOR IN TEMPERATURE-VACUUM SWING ADSORPTION CYCLES

Abstract

Systems and methods for providing regeneration heat to a sorbent material and subsequently recovering a significant portion of the heat are provided. The systems and methods are useful, for example, for energy-efficient direct capture of carbon dioxide (CO.sub.2) from the atmosphere or flue gases. The systems and methods include introducing steam generated by an evaporator into a reactor of the system to directly heat sorbent material in the reactor and to purge desorbed CO.sub.2 from the reactor using the steam. Water condensing within the reactor is drained and returned to the evaporator. The purged steam and CO.sub.2 from the reactor are directed to a vapor re-compressor to lift their temperature and then to a condenser or re-boiler where the water is condensed and separated from the CO.sub.2 and latent heat transferred to the cooling water is recovered, optionally via use of a jet ejector.

Claims

1. A method of heat recovery in a carbon dioxide (CO.sub.2) capture and separation system, the method comprising: introducing steam generated by an evaporator 101 into a reactor 102 of the separation system; heating a sorbent material 103 in the reactor 102 using the steam, wherein the steam leaves condensed water, steam vapor, and CO.sub.2 within the reactor 102; in response to a temperature reaching a first predetermined threshold and pressure within the reactor 102 reaching a second predetermined threshold, opening an outlet valve 202 downstream from the reactor 102; directing, via the outlet valve 202, a product stream comprising the steam vapor and the CO.sub.2 from the reactor 102 to vapor re-compressor 111; cooling and condensing the directed product stream from the vapor re-compressor 111 in a condenser 105; and recovering latent heat from the product stream with the condenser 105 by directing a first portion of the vapor from the condenser 105 to the evaporator 101.

2. The method of claim 1, further comprising: directing the condensed water from the reactor 102 to a water treatment station 107; and introducing the treated condensed water from the water treatment station 107 into the reactor 102.

3. The method of claim 1, further comprising: condensing a second portion of the vapor to create liquid water; and directing the liquid water and the CO.sub.2 to a water treatment station 107.

4. The method of claim 3, further comprising: separating, by the water treatment station 107, the CO.sub.2 from the liquid water.

5. The method of claim 4, further comprising: introducing the liquid water separated by the water treatment station 107 into the reactor 102 to cool the sorbent material 103, wherein the liquid water converts to evaporated water as the sorbent material 103 cools.

6. The method of claim 5, further comprising: directing the evaporated water from the reactor 102 to the evaporator 101.

7. The method of claim 1, wherein the second predetermined threshold is 1.0 bar.

8. The method of claim 1, wherein the steam directly condenses onto the sorbent material 103.

9. The method of claim 1, wherein the steam provides substantially uniform temperature distribution within the reactor 102.

10. The method of claim 1, wherein the reactor 102 is evacuated and hermetically sealed before the steam is introduced into the reactor 102.

11. The method of claim 1, further comprising: before introducing the steam to the reactor 102, evacuating the reactor 102 to a pressure in the range of 0.05-0.3 bar.

12. The method of claim 1, wherein the separation system further includes a plurality of reactors connected in parallel, and wherein the outlet valve 202 is a single valve downstream of the plurality of reactors.

13. The method of claim 1, wherein the introducing of the steam generated by the evaporator 101 into the reactor 102 of the separation system comprises: removing air within the reactor 102 as the steam is introduced into the reactor 102.

14. The method of claim 13, wherein the ratio of the air and the steam changes over time, and wherein the method further comprises: when the air is removed from the reactor 102: restarting a steam purge to regenerate the sorbent material 103, or continuing to provide steam into the reactor 102 while leaving the reactor 102 open to permit the CO.sub.2 to exit a bed.

15. The method of claim 1, wherein the vapor re-compressor 111 increases the temperature and pressure of the mixture of steam and CO.sub.2 and directs the mixture to a condenser 105.

16. A carbon dioxide (CO.sub.2) capture and separation system comprising: an evaporator 101 configured to generate steam; a reactor 102 including sorbent material 103; an outlet valve 202 downstream from the reactor 102; a vapor re-compressor 111; and a condenser 105, wherein the steam generated by the evaporator 101 is introduced into the reactor 102, wherein the sorbent material 103 is heated using the steam and the steam leaves condensed water, steam vapor, and CO.sub.2 within the reactor 102, wherein the outlet value 202 is opened in response to a temperature and pressure within the reactor 102 reaching a predetermined threshold, wherein the steam vapor and the CO.sub.2 are directed from the reactor 102 to the vapor re-compressor 111 via the outlet valve 202, wherein the directed vapor and CO.sub.2 from the vapor re-compressor 111 is cooled and condensed in the condenser 105, and wherein latent heat from the vapor is recovered with the condenser 105 by directing a first portion of the vapor from the condenser 105 to the evaporator 101.

17. The system of claim 16, further comprises: a water treatment station 107, wherein the condensed water is directed from the reactor 102 to the water treatment station 107, and wherein the treated condensed water is introduced to the reactor 102 from the water treatment station 107.

18. The system of claim 17, further comprises: a plurality of reactors connected in parallel.

19. The system of claim 16, wherein the vapor re-compressor 111 increases the temperature and pressure of the mixture of steam and CO.sub.2 and directs the mixture to a condenser 105.

20. An energy-efficient method of capturing carbon dioxide (CO.sub.2) from the atmosphere, the method comprising: circulating atmospheric air containing an ambient concentration of CO.sub.2 over, through, or around a sorbent 103 provided within a sorbent container 102 that is capable of being hermetically sealed; hermetically sealing the sorbent container 102 using valves (403, 404) when adsorption is complete; removing residual air from the sorbent container 102 by evacuating the sorbent container 102 to a pressure in the range of 0.05-0.3 bar using a vacuum pump 109; admitting steam from an evaporator 101 into the sorbent container 102 to heat the sorbent 103 to a desired temperature; draining liquid condensate from the sorbent container 102 and returning the liquid condensate to the evaporator 101; purging the sorbent container 102 with additional steam to desorb CO.sub.2 from the sorbent and directing the resulting mixture of steam and CO.sub.2 out of the sorbent container 102 and into a vapor re-compressor 111; using the vapor re-compressor 111 to increase the temperature and pressure of the mixture of steam and CO.sub.2 and then direct the mixture to a condenser 105; using the condenser 105 to recover latent heat from the mixture of steam and CO.sub.2 and transfer the heat to convert cooling water in the condenser 105 to steam which is returned to the evaporator 101; further directing the mixture of steam and CO.sub.2 exiting the condenser 105 to a treatment station 107 where water vapor is cooled to near ambient temperature and condensed as liquid water and separated from gaseous CO.sub.2; stopping the steam purge and hermetically sealing the sorbent container 102 using the valves (403, 404) when desorption is complete; spraying a fine mist of the cooled liquid water from the treatment station 107 into the sorbent container 102 and evacuating the sorbent container 102 with the vacuum pump 109 to evaporate the water and cool the sorbent 103 and the sorbent container 102; returning the evaporated water to the evaporator 101, thereby recovering the sensible heat from the sorbent 103 and sorbent container 102; and returning the sorbent container 102 to atmospheric pressure after it has been cooled to a desired temperature to complete one cycle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] These and other objects, features, and advantages of the invention will be more fully appreciated or become better understood when considered in conjunction with the accompanying drawings, where:

[0042] FIG. 1 shows an exemplary system in accordance with the invention;

[0043] FIG. 2 shows exemplary process steps for adsorbing CO.sub.2 in a system in accordance with the invention;

[0044] FIG. 3 shows exemplary process steps for evacuating the sorbent container in a system in accordance with the invention;

[0045] FIG. 4 shows exemplary process steps for heating the sorbent in a system in accordance with the invention;

[0046] FIG. 5 shows exemplary process steps for regenerating the sorbent using a steam purge and recovering heat via recuperative heat exchange in a system in accordance with the invention;

[0047] FIG. 6 shows exemplary process steps for cooling the sorbent and recovering sensible heat in a system in accordance with the invention;

[0048] FIG. 7 shows exemplary CO.sub.2 capture process modules in accordance with the invention that can be operated in parallel and share common supply, treatment, and process lines;

[0049] FIG. 8 shows an example of CO.sub.2 capture process modules sharing common supply, treatment, and process lines;

[0050] FIG. 9 shows an exemplary system in accordance with the invention with multiple types of heat recovery process equipment;

[0051] FIG. 10 shows an exemplary system in accordance with the invention where the heat recovery process equipment serves multiple sorbent containers in parallel;

[0052] FIG. 11 shows an exemplary modular CO.sub.2 capture and heat recovery system in accordance with the invention where multiple sorbent containers are arranged in a module, which is combined with a process equipment module to form a cluster and which may be combined with other clusters that share common plant services;

[0053] FIG. 12 shows an exemplary system in accordance with the invention where drained condensate is returned to water treatment prior to reuse;

[0054] FIG. 13 shows an exemplary system in accordance with the invention where the evacuation step is replaced with a plug flow of steam to remove air from the sorbent container;

[0055] FIG. 14 shows an exemplary system in accordance with the invention where a jet ejector is utilized to recover heat;

[0056] FIG. 15 shows an exemplary system in accordance with the invention where a compressor is utilized along with a jet ejector to recover heat;

[0057] FIG. 16 shows an exemplary system in accordance with the invention where a compressor is utilized in a system with a source of high-pressure plant steam to recover heat;

[0058] FIG. 17 shows an exemplary system in accordance with the invention where multiple compressors are utilized to recover heat; and

[0059] FIG. 18 shows an exemplary system in accordance with the invention where a jet ejector is utilized with an accumulator to recover heat in a steady-state continuous fashion.

DETAILED DESCRIPTION

[0060] The various embodiments are described in detail with reference to the accompanying drawings. Whenever possible, the same reference numbers are used throughout the drawings to refer to the same or like parts. References made to particular examples, details, and representative materials, methods, and implementations are for illustrative purposes only, and thus do not, and are not intended to, limit the scope of the various embodiments of the claims.

[0061] In one example embodiment in accordance with the invention, a system includes several process variations from the general steam-assisted TVSA process described above. Adsorption and evacuation can use typical methods. The methods for heating the sorbent, however, are to introduce steam directly into the sorbent container (reactor) at a controlled rate and specified temperature and pressure. The term process steam is sometimes used herein to refer to such steam that enters the sorbent container at a controlled rate, temperature, and pressure. The terms sorbent container and reactor are used interchangeably herein to refer to a process vessel containing a sorbent and within which the adsorption and desorption processes take place. The sorbent container is capable of being hermetically sealed using valves. This steam is allowed to adsorb and condense directly onto the sorbent material; the heat of condensation and heat of adsorption raise the temperature of the sorbent. As the steam is introduced into the reactor, the pressure in the reactor increases. Once the temperature and pressure in the sorbent reaches a specified value (typically around 100? C. and just over 1.0 bar pressure, although other temperatures and pressures may be applicable depending upon the desorption characteristics of the particular sorbent material utilized), a downstream valve is opened, and the steam purge step can begin as described earlier.

[0062] Compared to other systems that may utilize internal surface heat exchangers embedded in the sorbent, allowing the steam to condense on the sorbent provides much faster, more even, and more efficient heating in a more compact and simpler overall sorbent container designs. Condensed water is drained using equipment built into the sorbent container and integrated into the rest of the systems. Some sorbents cannot be exposed to liquid water during operation due to leaching or degradation of the sorbent; however, the systems in accordance with the invention utilize a sorbent that withstands this process. Nonlimiting examples of such sorbents include solid-phase anion exchange resins, cross-linked polyamine materials, and the like.

[0063] Following steam heating, steam regeneration continues as described in the general process. The steam purge enhances desorption by lowering the partial pressure of CO.sub.2 in the space surrounding the sorbent and by providing a motive force to remove this CO.sub.2 from the sorbent container. Downstream of the sorbent container, product CO.sub.2 is separated from the steam by using a condenser to cool the outgoing stream, which causes most of the water to condense out from the outgoing gas stream. In general, process steam enters the sorbent container with a pressure around atmospheric pressure which is suitable for heating and purging of the sorbent. In one example embodiment, the steam purge enters the sorbent container at just over 1.0 barjust enough to overcome the pressure drop from steam injection to collection at ambient pressure. However, in other example embodiments, a higher or lower purge pressure may be desired. A lower pressure can be achieved using a vacuum pump to pull the steam through the reactor at a specified sub-ambient pressure. In some embodiments of the present invention, the process steam enters the sorbent container at a pressure between about 0.8-1.3 bar, 0.8-1.2 bar, 0.9-1.1 bar, 1.0-1.1 bar, 1.0-1.2 bar, 1.0-1.3 bar, 1.1-1.2 bar, 1.1-1.3 bar, or 1.2-1.3 bar. In some embodiments of the present invention, the process steam enters the sorbent container at a pressure between about 1.0-1.1 bar. In some embodiments of the present invention, the process steam enters the sorbent container at a pressure of about 1.1 bar.

[0064] The systems and methods in accordance with the invention provide process advantages by creating more process flexibility in the regeneration step. A typical process using internal surface heaters must avoid condensation of the steam to 1) protect the sorbent and 2) avoid flooding a container that is not designed to drain liquids. This presents a challenge as the incoming steam must be significantly superheated in order to provide the heat of desorption for CO.sub.2 without condensing within the sorbent container. The systems and methods of the invention do not have this requirement. There is no issue with providing desorption heat via condensation and a simpler saturated steam system can be used. As in heating, the water that is condensed in this step can be drained and collected for re-use. Although this condensed water will need to be reboiled to create new process steam, its temperature is still considerably higher than fresh makeup water, thereby retaining heat energy within the system.

[0065] Once regeneration is complete, the sorbent is cooled to near ambient temperature. Some sorbents are cooled by flowing in airflow using the same fan that is used during adsorption; however, some sorbents (including most amines) will degrade if exposed to atmospheric concentrations of oxygen at elevated temperatures. Another common method is to cool with cold fluid using embedded heat exchangers in the sorbent container. In the systems and methods in accordance with the invention, however, the direct contact of sorbent with water allows for cooling via evaporation. As with heating, this cooling method is fast and uniform and requires no embedded heat exchanger.

[0066] In evaporative cooling, the reactor pressure is lowered using a vacuum pump. This lowering of pressure causes water that is sitting on or adsorbed into the sorbent to evaporate. The evaporation of this water removes heat from the sorbent. Downstream of the sorbent container, the vapor is condensed to recover the water and to separate out remaining CO.sub.2 in the stream. In the case that there is not enough residual water to evaporate off the sorbent to provide adequate cooling, a liquid cooling spray can be injected into the reactor to supplement the process. Once the sorbent has reached a temperature that is safe and effective for airflow exposure, the reactor can be repressurized with air and a new adsorption can begin. In a typical process, the sorbent is cooled to about 40-50? C. before repressurization. In other embodiments, the sorbent is cooled to about 50-60, 60-80, or 70-80? C. before repressurization

[0067] In general steam-assisted TVSA processes, significant amounts of heat are required to generate the steam that is introduced into the reactor. The energy used to create this steam is consumed via several thermal sinks, including: [0068] Losses to ambient, due to imperfect insulation between the reactor space and the outside walls; [0069] Desorption heat, to release CO.sub.2 molecules that have been adsorbed into the sorbent; [0070] Sensible heat, required to raise the temperature of the sorbent, the inert substrate and/or binder, and surrounding reactor internal structure to the desorption temperature; and [0071] Purge heat, which is the energy required to generate the steam that sweeps out the CO.sub.2 but does not otherwise contribute heat to the desorption process.

[0072] As dictated by a system energy balance, all the heat inputted to the reactor must exit the reactor via some process. In theory, this heat can be recovered and used elsewhere in the process. Desorption heat and losses to ambient are difficult to recover. However, because of the direct steam injection and evaporative cooling methods used in the systems and methods of the invention, all of the purge heat energy and a significant amount of the sensible heat energy leaves the reactor in the form of water vapor mixed with some amount of CO.sub.2. The systems and methods of the invention provide efficient methods to accomplish this recovery by using the heat of condensation and sensible heat of the outgoing water vapor to create new, fresh steam which can be re-introduced into the reactor (or into a different reactor operating in parallel).

[0073] To achieve this recovery, a mechanical vapor recompression process is used where the temperature of the outgoing water vapor is lifted to 105-115? C. using a compressor. This provides the temperature differential required to effectively pass heat to an incoming water stream and boil new steam at close to 100? C. Work in the form of electrical energy into a motor is required to lift the temperature of the outgoing steam and CO.sub.2 mixture to enable this recovery. However, the required electrical energy is estimated to be 10 to 20 times less than the amount of thermal energy that is recovered using this method.

[0074] One embodiment of the system is illustrated in FIG. 1. An evaporator 101 containing saturated water vapor and liquid water supplies steam along path 301 to a sorbent 103 inside a container 102 by way of the motive vapor pressure inside evaporator 101. From sorbent container 102, vapor and CO.sub.2 flow through a condenser 105 before entering a treatment station 107 along path 303 by way of the motive force of a vapor re-compressor 111. Downstream of treatment station 107, a pump 108 supplies liquid water to condenser 105 along a path 305. Pump 108 can also supply liquid water to a sorbent spray manifold 104 inside sorbent container 102 along path 306. Water vapor inside sorbent container 102 can be returned to evaporator 101 along a path 307 through a multi-way valve 502 by way of the motive force of a mechanical vacuum pump 109. Air inside sorbent container 102 can be exhausted to atmosphere along path 501 through multi-way valve 502, also by way of the motive force of vacuum pump 109.

[0075] The process for capturing CO.sub.2 according to the example embodiment is presented in the context of the five basic steps previously described: 1) adsorbing, 2) evacuating, 3) heating, 4) regenerating, and 5) cooling.

[0076] FIG. 2 shows exemplary relevant aspects related to step 1, adsorbing. During the adsorbing step, atmospheric air containing an ambient concentration of CO.sub.2 is drawn into sorbent container 102 along a path 401, passing through an air filter 402, an air inlet valve 403, over sorbent 103, and through an air outlet valve 404 by way of the motive force of fan 405. At the end of step 1, fan 405 is shut off, and inlet valve 403 and outlet valve 404 are closed, thereby hermetically sealing the sorbent container 102. In some embodiments of the present invention, air filter 402 is located on the air inlet side of sorbent container 102 and the fan 405 is located on the air outlet side and pulls the air through sorbent container 102. In some embodiments of the present invention, a fan or blower may instead be located on the air inlet side in front of air filter 402 and push air through the air filter 402 and the sorbent container 102.

[0077] FIG. 3 shows exemplary relevant aspects related to step 2, evacuating. During the evacuating step, residual air in the hermetically sealed sorbent container 102 is exhausted to the atmosphere along a sorbent evacuation path 307 and vacuum exhaust path 501 through a sorbent evacuation valve 205 and multi-way valve 502 by way of the motive force of vacuum pump 109. During evacuation, a sorbent steam/CO.sub.2 outlet valve 202, a sorbent cooling water valve 204, and a sorbent steam inlet valve 201 are closed. The evacuating step is complete when the pressure in sorbent container 102 is reduced to a specified pressure, typically 0.05-0.3 bar. At the end of step 2, sorbent evacuation valve 205 is closed, and compressor 109 is shut off.

[0078] FIG. 4 shows exemplary relevant aspects related to step 3, heating the sorbent. Steam from evaporator 101 is admitted into sorbent container 102 along a path 301 through sorbent steam inlet valve 201 by way of the motive pressure in evaporator 101. The rate of steam admission can be regulated by controlling sorbent steam inlet valve 201. The steam pressure in evaporator 101 can be maintained by controlling the input power to an immersed heating element 110. The condensing of steam inside sorbent container 102 uniformly heats sorbent 103 to a final desired temperature. Liquid condensate drains back to evaporator 101 along path 301 by way of gravity.

[0079] FIG. 5 shows exemplary relevant aspects related to step 4, regenerating the sorbent. Steam is admitted to sorbent container 102 through sorbent steam inlet valve 201. The motive pressure in evaporator 101 can be maintained by controlling the input power to the immersed electrical heating element 110. A mixture of steam and CO.sub.2 flows out of sorbent container 102 and into vapor re-compressor 111 along path 302. The mixture of steam and CO.sub.2 flows through condenser 105 by way of the motive force of vapor re-compressor 111. The vapor re-compressor 111 increases the temperature of the steam and CO.sub.2 from the sorbent container 102 allowing more effective heat transfer to the fluid once it reaches the condenser 105. Cooling water enters the cold side of the condenser along path 305 by way of the motive force of pump 108. The rate of cooling water flow, and hence the condensation of vapor by direct contact with the cooling water, is regulated by controlling condenser cooling water valve 203. The condenser serves to recover the latent heat contained in the steam and re-introduce that energy as steam into evaporator 101 through multi-way valve 502. The mixture of water and CO.sub.2 from condenser 105 flows into treatment station 107, where water vapor is condensed, and gaseous CO.sub.2 is separated from the liquid water by way of gravity.

[0080] FIG. 6 shows exemplary relevant aspects related to step 5, cooling the sorbent. By way of the motive force of pump 108, liquid water from treatment station 107 at a temperature close to ambient enters sorbent container 102 through sorbent spray manifold 104 along path 306. The flow rate of cooling water, and hence the rate of cooling, can be regulated by controlling a sorbent cooling water valve 204. Cooling water manifold 104 distributes the water uniformly inside the sorbent container 102 as a fine mist. The evaporation of this water removes heat from sorbent 103 and sorbent container 102. The evaporated water is removed from sorbent container 102 through sorbent evacuation valve 205 along path 307 by way of the motive force of vacuum pump 109, from where the water enters evaporator 101 through multi-way valve 502, thereby recovering the sensible heat to the steam source.

[0081] In another embodiment, additional single CO.sub.2 capture modules 601, as shown in FIG. 7, may be connected to a common CO.sub.2 return manifold 605 and common water supply manifold 604, which are in turn connected to a common water treatment station 602, as shown in FIG. 8.

[0082] FIG. 9 shows an exemplary embodiment, where steam from evaporator 101 enters the sorbent container 102. The steam may enter from or be directed to the top of sorbent container 102 and flow down through the sorbent 103 in cases where vertical flow through the sorbent 103 is possible. Alternatively, the steam may enter from or be directed to a front side (e.g., air inlet side) or back side (e.g., air outlet side) of sorbent container 102 and flow through sorbent 103 in a horizontal direction. A condensate accumulator 112 is added to allow liquid to accumulate before being returned to evaporator 101 via the motive force of vacuum pump 109. Steam condenser 105 is split into separate heat exchangers, condenser 105 which recovers the latent heat of outgoing water vapor and a sub-cooler 106 which recovers the sensible heat of the condensate. CO.sub.2 is separated and removed from the gas stream via condenser 105.

[0083] FIG. 10 illustrates an exemplary embodiment in which additional sorbent containers 102, each containing sorbent 103, can utilize the equipment presented in FIG. 9 in parallel. These sorbent containers can be contained in a single larger module container 701. The process flows into and out of these sorbent containers is controlled using valves on inlet and outlet manifolds for each container. One advantage of this embodiment is that, by operating with multiple sorbent containers or modules in parallel, the process equipment such as compressor 111 can run in a mode that approaches steady-state operation.

[0084] As shown in FIG. 11, the module container 701 can be further arranged by coupling it with utilities container 702, which contains the process equipment for the proposed system such as the equipment shown in FIG. 9. Together, this unit forms cluster 704. Multiple clusters can be built to form a modular plant architecture. These clusters may each share common plant services such as water treatment station 107 or other units such as CO.sub.2 injection sites or on-site energy generation, generally represented by 703.

[0085] FIG. 12 shows an exemplary embodiment where liquid that is drained from sorbent container 102 returns to water treatment station 107 via pump 801 through line 802. Compared to the initial embodiment, this ensures that all water passing over sorbent 103 is treated before it is re-introduced to that or any other sorbent container. Heat exchangers can be used between outgoing condensate line 802 and incoming evaporator feedwater line 803 to recover the sensible heat contained in this relatively warm drainage liquid.

[0086] In other exemplary embodiments, alternative methods can be used to provide some or all of the reactor sensible heat requirement, using electric heaters or an embedded heat exchanger, for example, with superheated steam subsequently introduced to sweep out desorbed CO.sub.2. The energy recovery process described above can help recover the energy of this superheated steam purge. Other methods can be used to recover energy during the preheating and precooling step.

[0087] Alternatively, the process can occur without a significant purge step, involving only a heating period followed by an immediate evaporation period. In this embodiment, the evaporative period both removes desorbed CO.sub.2 and cools the sorbent. The sensible heat can be recovered using the methods described above; no purge heat recovery is necessary as there is no purge steam and therefore no purge heat to recover.

[0088] In other exemplary embodiments, the evaporator heating element 110 in FIG. 1 can be replaced with or used alongside of an external source of heat via a heat exchanger or direct injection of steam from an external supply. This external supply may include waste heat from another process internal to the DAC system or from an external partner.

[0089] In other exemplary embodiments, the processes can be modified to work at a range of desorption conditions, including temperature, pressure, time, and transients thereof. One example reduces or eliminates the purge step and removes the desorbed CO.sub.2 alongside H.sub.2O during the evaporative cooling step. Another example embodiment uses a steam purge but uses a vacuum system to maintain the reactor pressure at a point between 0.2 and 1.0 bar. A third example embodiment injects steam into the sorbent container at a higher pressure than 1.0 bar, which uses a corresponding compression from the outgoing stream to generate this higher-pressure steam using recovered energy.

[0090] In an exemplary embodiment, the evacuation step is reduced or eliminated and replaced with a method that uses a plug flow of steam to displace the dead air and remove it from the sorbent container. This method is shown in FIG. 13. At time t=0, marking the start of the heating step, steam enters the reactor and pushes out air. After time t=x, the dead air is removed and desorption continues, either by sealing the sorbent container to permit heating and pressurization and then restarting a steam purge to regenerate the sorbent or by continuing the steam flow while leaving the sorbent container open to permit CO.sub.2 to exit the bed as if performing a purge step.

[0091] In some example embodiments, the invention is not limited to using steam and uses other refrigerants at pressures that are ideal for the process equipment and fluid network. These alternative refrigerants condense onto the sorbent to provide heat and/or be condensed from the CO.sub.2 after sweeping through the reactor. The benefits of using different refrigerants other than steam include enabling customization of the temperature and pressure of condensation.

[0092] In some embodiments of the present invention, high-pressure steam (sometimes referred to herein as plant steam) may be available from a centralized source, such as a shared plant services unit 703, and that can service multiple modular sorbent containers 102, module containers 701, or clusters 704. The high-pressure plant steam can be circulated throughout a large-scale modular plant architecture. The plant steam pressure can be reduced to the desired process steam pressure at or near each point of use. In some embodiments of the present invention, the plant steam will have a pressure of about 2-10 bar, 3-8 bar, or 4-6 bar. In some embodiments of the present invention, the plant steam will have a pressure higher than about 4 bar.

[0093] A jet ejector can be used as an alternative to a mechanical vapor compressor in some embodiments of the present invention. FIG. 14 shows an exemplary embodiment where a jet ejector is used as an alternative to a mechanical vapor compressor (i.e., vapor re-compressor(s) described above) when, for example, a source of high-pressure plant steam 309 is available. The product stream of steam and CO.sub.2 can flow out of one or more sorbent containers (not shown) along path 302 into re-boiler 113, generating low-pressure steam (less than 1 bar and generally about 0.4-0.6 bar) from the water 206 present in the re-boiler. In an alternative embodiment, steam and CO.sub.2 can be introduced to re-boiler 113 from one or more sorbent containers 102. The low-pressure steam exits re-boiler 113 through pathway 308 to jet ejector 114. Pressure-sensing valve 209 diverts the flow of high-pressure plant steam through the jet ejector 114, creating motive force to pull the lower pressure steam through the jet ejector 114 and into process steam pathway 310. If the output from the jet ejector 114 is insufficient to provide the desired process steam pressure, the pressure-sensing valve 209 may allow some of the higher pressure plant steam 309 directly into the process steam pathway 310 to make up the difference in pressure. The cooled mixture of condensed steam and CO.sub.2 exits re-boiler 113 for further separation and processing through pathway 311. Makeup water is provided to the re-boiler 113 through pathway 312. Since the high-pressure plant steam 309 must be let-down to lower pressure process steam anyway, there is optimization in the system by utilizing the jet ejector 114 to capture waste heat as shown, for example, in FIG. 14 with little to no additional resources (e.g., energy, costs, etc.) being introduced into the system.

[0094] In some embodiments of the present invention, jet ejectors and vapor re-compressors may both be utilized. As a non-limiting example, FIG. 15 shows a system utilizing vapor re-compressor 111 to compress a product stream 302 to higher pressure and temperature stream 303 prior to passage through re-boiler 113. With the higher input pressure and temperature, a higher pressure steam (up to about 0.6-1.0 bar) can be provided to jet ejector 114 through pathway 308 from the heated re-boiler water 206. As it can be challenging to achieve high amounts of compression in any given single step, carrying out the compression over multiple steps can lead to overall process efficiencies.

[0095] In other exemplary embodiments, the jet ejector 114 in FIG. 14 or FIG. 15 can be replaced with a vapor re-compressor and utilized with a source of plant steam as shown in FIG. 16 and FIG. 17. In the exemplary embodiment shown in FIG. 16, the product stream of steam and CO.sub.2 flowing out of one or more sorbent containers along path 302 flows through re-boiler 113, generating low-pressure steam (less than 1 bar and generally about 0.4-0.6 bar) from the water 206 present in the re-boiler. The low-pressure steam exits re-boiler 113 through pathway 308 to vapor re-compressor 111 where it is compressed to a higher pressure steam that passes through pathway 304 and back into process steam pathway 310. Pressure-sensing valve 209 adjusts the flow of high-pressure plant steam into process steam pathway 310 to maintain the desired process steam pressure.

[0096] The exemplary embodiment shown in FIG. 17, utilizes vapor re-compressor 111a to increase the pressure of a product stream 302 into re-boiler 113 along with a second vapor re-compressor 111b to increase the pressure of the recovered steam stream 304 injected back into the process steam stream 310. As in the embodiment shown in FIG. 16, pressure-sensing valve 209 adjusts the flow of high-pressure plant steam into process steam pathway 310 to maintain the desired process steam pressure.

[0097] The systems stagger the adsorption/desorption cycles, and manage the process control thereof, to achieve the most efficient processes and lower equipment costs. For example, managing the number of reactors undergoing simultaneous desorption can reduce the needed size of steam pipes and valves. In some embodiments of the present invention, steam streams or product streams from different sources may be combined and collected in accumulators that can then provide a more constant stream to feed downstream processes. As a non-limiting example embodiment, FIG. 18 shows the product streams 302 from multiple sorbent containers 102 being combined and collected in accumulator 115. The accumulator 115 can then more easily provide a steady and constant supply of the product stream to re-boiler 113 for product separation and heat recovery as described above. In other embodiments, accumulators are utilized to combine and collect the low-pressure steam exiting multiple re-boilers 113 to provide a steady and constant supply of the low-pressure steam to downstream jet-ejectors or vapor re-compressors.

[0098] 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.