Separating components from gas streams

Abstract

The system and method separates a process fluid stream into a liquid-phase carbon dioxide stream and a carbon dioxide-depleted stream containing residual light gases. The system and method uses a dryer heat exchanger to contact the process fluid stream with a dryer contact liquid to remove moisture from the process fluid stream. The gaseous process fluid stream is separated from the wet dryer contact liquid stream and directed to an extractor heat exchanger where the gaseous process fluid stream is contacted with an extractor contact liquid such that carbon dioxide is removed from the process fluid stream and a treated process fluid stream and a carbon dioxide-enriched extractor contact liquid stream are formed.

Description

[Technical Field]

[0001] Priority claims

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 481,916, filed January 27, 2023, the contents of which are incorporated herein by reference.

[0002]

[0002] The present disclosure relates generally to systems and methods for gas purification, and more particularly to systems and methods for carbon capture. [Background technology]

[0003] Gas separation into distinct streams of different composition has long been a key component of industrial processes, and advances in climate change mitigation technologies are further increasing its importance. Carbon capture, or the separation of CO2 from other light gases, looms large among key new technologies. Typical streams requiring carbon capture include process fluid flows from industrial processes such as cement and lime production, iron and steel production, refinery operations, and heat plants, as well as utility power generation exhaust streams. Combustion fuel sources include coal, natural gas, liquid hydrocarbons, black liquor, biomass, industrial and municipal waste streams, and similar streams containing CO2 mixed with other light gases. These fuels and the technologies used to consume them produce combustion flue gases with varying compositions. Combustion using air leads to most of the flue gas consisting of nitrogen. Non-nitrogen flue gas consists primarily of carbon dioxide, water, and unconsumed oxygen. Small amounts of carbon monoxide, nitrogen oxides, sulfur oxides, and trace amounts of hundreds of other chemicals are also present, depending on the source. Entrained dust, ash, and soot will also be present in most combustion flue gas streams.

[0004]

[0004] The separation of carbon dioxide from other light gases, such as nitrogen, is called carbon capture and is important for reducing carbon dioxide emissions and their associated environmental impacts. Environmental and climate scientists identify this carbon dioxide as a major, if not the only, source of global climate change. Therefore, there is a clear need for an efficient method of capturing carbon dioxide from flue gas to produce a concentrated stream of carbon dioxide that can be easily transported to a safe storage site or for further use, preventing the release of carbon dioxide into the atmosphere.

[0005]

[0005] Carbon capture is conceptually similar to the removal of other more traditional pollutants, such as oxides of nitrogen and sulfur, ozone, and carbon monoxide, from emission sources. However, carbon capture requires much more energy, capital investment, and operating costs than these other processes, due, among other things, to the quantity and difficulty of its separation. Cost-effective carbon capture requires new systems and methods that improve the energy efficiency and / or provide other operational benefits for carbon capture technologies.

[0006]

[0006] Mixed gas streams, such as flue gas, synthesis gas, producer gas, natural gas, and refinery off-gas, tend to contain moisture in varying amounts, as do the vitiated flows discussed above. Moisture removal plays a key role in both traditional carbon capture and many further gas processing systems. For example, without water removal, the typical cryogenic temperatures of natural gas liquids recovery during natural gas processing can lead to ice formation in unit operations. Methods for water removal vary widely and include fixed-bed adsorption with molecular sieves, distillation, ice production, and even drying. All of these methods have one or several undesirable characteristics, including high energy use, batch operation, poor scaling to large systems, or high capital and operating costs. Summary of the Invention [Means for solving the problem]

[0007] There are several aspects of the present subject matter that may be embodied separately or together in the devices and systems described and claimed below. These aspects may be used alone or in combination with other aspects of the subject matter described herein, and the description of these aspects together is not intended to exclude the use of these aspects separately or the claiming of such aspects separately or in combinations other than as set forth in the claims appended hereto.

[0008] In one aspect, a system for separating carbon dioxide from a process fluid stream includes a process fluid feed line and a dryer contact liquid feed line. The dryer heat exchanger has a combined stream cooling passage and a refrigeration passage. The junction is configured to combine a process fluid from the process fluid feed line and a dryer contact liquid from the dryer contact liquid feed line such that a combined stream is formed and directed to the combined stream cooling passage. The combined stream cooling passage and the refrigeration passage are configured such that a coolant stream in the refrigeration passage lowers the temperature of the combined stream such that water condenses from the process fluid into the dryer contact liquid. The combined stream phase separator is configured to receive the combined liquid stream from the combined stream cooling passage and separate it into a gaseous process fluid stream and a wet dryer contact liquid stream. The extraction heat converter has a carbon dioxide extraction cooling passage and an extraction heat converter refrigerant warming passage. The carbon dioxide extraction cooling passage comprises two phases in direct contact: a gas phase that enters through the gaseous process fluid inlet and exits through the treated process fluid outlet; and a liquid phase in contact with the gas phase that enters through the extraction contact liquid inlet and exits through the carbon dioxide-enriched extraction contact liquid outlet. The extraction heat converter also includes an indirect contact refrigerant passage configured to receive a first or second refrigerant that controls the temperature profile within the extraction heat converter. The gaseous process fluid line is configured to direct the gaseous process fluid from the combined stream phase separator to the gaseous process fluid inlet of the carbon dioxide extraction cooling passage of the extraction heat converter. The carbon dioxide extraction cooling passage of the extraction heat converter is configured to contact the extraction contact liquid in the carbon dioxide extraction cooling passage with the gaseous process fluid so that carbon dioxide is extracted from the gaseous process fluid to form a treated process fluid and a carbon dioxide-enriched extraction contact liquid, the treated process fluid exiting the carbon dioxide extraction cooling passage through the treated process fluid outlet and the carbon dioxide-enriched extraction contact liquid exiting the carbon dioxide extraction cooling passage through the carbon dioxide-enriched extraction contact liquid outlet.

[0009] In another aspect, a system for separating carbon dioxide from a flue gas stream includes a process fluid feed line and an extraction heat exchanger having a carbon dioxide extraction cooling passage and an extraction heat exchanger refrigerant warming passage, the carbon dioxide extraction cooling passage having a process fluid inlet in fluid communication with the process fluid feed line, a treated process fluid outlet, an extraction contact liquid inlet configured to receive extraction contact liquid, and a carbon dioxide-enriched extraction contact liquid outlet.

[0010]

[0010] The carbon dioxide extraction cooling passage of the extraction heat exchanger is configured so that the extraction contact liquid in the carbon dioxide extraction cooling passage contacts the process fluid so that carbon dioxide is extracted from the process fluid to form a treated process fluid and a carbon dioxide-enriched extraction contact liquid, the treated process fluid exiting the carbon dioxide extraction cooling passage through a treated process fluid outlet and the carbon dioxide-enriched extraction contact liquid exiting the carbon dioxide extraction cooling passage through a carbon dioxide-enriched extraction contact liquid outlet.

[0011]

[0011] In yet another aspect, a method for separating carbon dioxide from a process fluid stream includes combining a process fluid stream and a dryer contact liquid stream to provide a combined stream; directing the combined stream through a drying heat exchanger; cooling the combined stream in the drying heat exchanger by warming a coolant stream; condensing water from the process fluid stream into the dryer contact liquid stream in the drying heat exchanger; separating the combined stream into a gaseous process fluid stream and a wet dryer contact liquid stream; contacting the gaseous process fluid stream with the extraction contact liquid stream in the extraction heat exchanger so that carbon dioxide is transferred from the gaseous process fluid stream to the extraction contact liquid and a treated process fluid stream and a carbon dioxide-enriched extraction contact liquid stream are produced; and warming first and second refrigerants in the extraction heat exchanger so that the contacting gaseous process fluid stream and extraction contact liquid stream are cooled in the extraction heat exchanger.

[0012] The following drawings are provided to illustrate certain embodiments described herein. The drawings are illustrative only and are not intended to limit the scope of the claimed invention, nor are they intended to depict every conceivable feature or embodiment of the claimed invention. The drawings are not necessarily drawn to scale, and in some cases, certain elements of the drawings may be enlarged relative to other elements of the drawings for illustrative purposes. Generally, flow diagrams follow common conventions: e.g., stream inlet and outlet temperatures in a heat exchanger increase with increasing vertical height of the exchanger; liquid flows in / out of a tower from top to bottom while gas flows in the opposite direction; and streams flow into the center of a pump and out from the periphery. Stream numbers increase in the direction of stream flow but are generally not strictly conservative (i.e., some numbers are routinely skipped) to allow for process modifications without significant renumbering of many of the streams. Typically, the first number of a three-digit stream number indicates the major flow loop or configuration of that stream, as explained below. However, these conventions are merely qualitative and not strictly imposed. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a process flow diagram illustrating a system for separating carbon dioxide from a process fluid stream. DETAILED DESCRIPTION OF THE INVENTION

[0014] The following description lists various aspects and embodiments of the invention disclosed herein. No particular embodiment is intended to define the scope of the invention. Rather, the embodiments provide non-limiting examples of various compositions and methods that fall within the scope of the claimed invention. The description is read from the perspective of one of ordinary skill in the art. Accordingly, information that is familiar to one of ordinary skill in the art is not necessarily included.

[0015] The following terms and phrases have the meanings indicated below, unless otherwise provided herein. This disclosure may use other terms and phrases not expressly defined herein. Such other terms and phrases shall have the meaning they would have to one of ordinary skill in the art within the context of this disclosure. In some cases, a term or phrase may be defined in the singular or in the plural. In such cases, it is understood that any term in the singular may include its plural counterpart, and vice versa, unless expressly indicated to the contrary.

[0016] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to "a substituent" includes a single substituent as well as two or more substituents, and the like.

[0017] As used herein, "for example," "for instance," "such as," or "including" means introducing an example that further clarifies a more general subject matter. Unless expressly indicated otherwise, such examples are provided only as an aid in understanding the embodiments set forth in this disclosure and are not meant to be limiting in any way. These phrases do not imply any kind of preference for the disclosed embodiments.

[0018] As used herein, the terms "communication," "communicating," and the like generally refer to fluid communication, unless otherwise specified.

[0019]

[0019] As used herein, the terms "high," "middle," "warm," "cold," etc. are relative to comparable streams, as is customary in the art.

[0020] As used herein, "condensing" is meant to refer to the process by which a vapor is cooled to a liquid. As used herein, "desublimating" is meant to refer to the process by which a vapor is cooled to a solid. As used herein, "cryogenic" is intended to refer to temperatures below about -50°C (-58°F).

[0021]

[0021] As used herein, "dried" or "dry" is meant to refer to a gas or liquid stream from which water has been removed, such as when a process fluid is dried to remove water vapor, resulting in a dried flue gas stream.

[0022] As used herein, "depleted" is meant to refer to a gas or liquid stream from which components such as carbon dioxide have been removed. A process fluid stream from which carbon dioxide has been at least partially removed is a depleted process fluid stream.

[0023]

[0023] As used herein, "wet" is meant to refer to a gas or liquid stream to which water has been added, such as when a contact liquid picks up water and becomes a wet contact liquid, or a stream that contains moisture that has not yet been removed, as in the case of a wet process fluid stream.

[0024]

[0024] As used herein, "enriched" is meant to refer to a gas or liquid stream to which a component has been added, such as when a contact liquid captures carbon dioxide and becomes an enriched contact liquid.

[0025] As used herein and as known in the art, a heat exchanger is a single device, multiple devices, or one or more areas within one or more devices, where heat exchange occurs between two or more streams of different temperatures or between a stream and the environment. A heat exchanger can be a direct contact device, where two different phase fluids are in physical contact, or an indirect contact device, where fluids exchange heat through a barrier that separates the fluid flows in different channels. As used herein, the terms "communicating," "communicating," and the like generally refer to fluid communication, unless otherwise specified.

[0026] Combustion flue gas comprises the pollutant flow from a fuel combustion device, which carries with it the products of at least partial oxidation of the fuel. The inlet gas is typically air, but this is not a limitation of the present invention; the oxidant can be pure oxygen, CO or H2O in producer or syngas, or other common oxidants. Combustion fuel sources include coal, hydrocarbons, natural gas, waste, black liquor, biomass, combinations of these, or these fuels combined with non-carbon-containing fuels such as hydrogen and ammonia. Combustion fuel gas varies significantly in composition depending on the combustion method and fuel. Combustion in pure oxygen produces little to no nitrogen in the flue gas. Combustion using air leads to a large amount of flue gas consisting of nitrogen. Non-nitrogen flue gas consists primarily of carbon dioxide, water, and occasionally unconsumed oxygen. Small amounts of carbon monoxide, nitrogen oxides, sulfur oxides, hydrogen sulfide, and trace amounts of many other chemicals are also present, depending on the source. Entrained dust and soot will also be present in most combustion flue gas streams. The disclosed method applies to any combustion flue gas. Dried combustion flue gas has had water removed.

[0027]

[0027] Synthesis gas consists of a mixture containing substantially hydrogen, carbon monoxide, water vapor, and carbon dioxide, possibly with additional nitrogen, argon, or other gases. Typically, synthesis gas is passed through a synthetic process to produce different products, such as Fischer-Tropsch synthesis, which produces liquid or waxy products.

[0028] Producer gas consists of fuel gas produced from materials such as coal, wood, black liquor, biomass, or similar fuels or synthesis gas. Producer gas contains essentially carbon monoxide, water, hydrogen, tar, and carbon dioxide, with possibly additional other gases present.

[0029] Steam reforming is a process for producing hydrogen, carbon monoxide, and other compounds from hydrocarbon fuels, including natural gas. The steam reformate gas referred to herein consists primarily of carbon monoxide and hydrogen, with varying amounts of carbon dioxide and water.

[0030] Light gases include gases that have a higher volatility than water, or more specifically, gases that do not condense at typical ambient pressures and temperatures. These include hydrogen, helium, carbon dioxide, nitrogen, argon, methane, ethane, and oxygen. This list is exemplary only and should not be implied to place limitations on the viability of other gases in the process. In particular, references in this document to CO2 in light gases refer to gases that are more volatile (lighter) than CO2. One skilled in the art will be able to evaluate any gas as to whether it is a light gas in the context of this document.

[0031] Refinery off-gases include gases produced by refining petroleum and other hydrocarbons or precious metals such as gold and silver. These off-gases may contain significant amounts of condensable materials, such as hydrocarbons with three or more carbon atoms, sulfur, nitrogen, chlorine, or trace contaminants, often including heavy metals, including, but not limited to, mercury and arsenic.

[0032] As used herein, a sensible heat exchanger / dryer (SHED) is a type of heat, mass, or heat and mass exchanger, embodiments of which are described in more detail below. Briefly, a contact liquid stream flows into a first channel of the exchanger such that the contact liquid stream wets the surfaces of the first channel but leaves an open volume within the first channel for the gas stream to flow through. Preferably, the contact liquid stream flow rate is sufficient to produce a ratio of contact liquid stream to water removed that is high enough so that the mixture of water and contact liquid does not form solids, although this is not a limitation and some solids formation is acceptable. Similarly, preferably, the contact liquid forms a continuous flow over all portions of the channel surface, although this is also not a limitation. The gas stream, flowing co-currently, counter-currently, or cross-currently with respect to the contact liquid, directly contacts the contact liquid, regardless of the contact pattern (co-current, counter-current, or cross-current). Preferably, the gas stream forms a continuous phase in the bulk flow, while the liquid stream forms a continuous phase on the surface, although intermittent gas phases in the bulk (bubble mode) are permitted, as is an intermittent liquid stream (spray mode). Heat, mass, or most typically, heat and mass are exchanged between the gas and the contact liquid stream. In particular, water and other vapors in the gas condense or absorb, or in some cases evaporate and desorb from, the contact liquid stream, changing the chemical composition of both the liquid and vapor. The second channel of the exchanger carries a cold liquid or refrigerant, which indirectly exchanges heat with the first channel and cools the contact liquid stream. The optional third channel carries a third stream, such as a refrigerant, any cold process stream, or an H2O- and CO2-depleted or gaseous return process fluid stream, which flows countercurrent to the wet process fluid stream and warms as the wet stream cools.Because the wet and gaseous process fluid streams generally have different flow rates, the optional fourth (or higher) streams help balance the heat exchanger so that it preferably maintains a nearly constant temperature difference between the warming and cooling streams, although non-constant temperature differences are acceptable. These streams help establish or maintain a desired temperature profile within the heat exchanger that regulates the temperatures of the gas and liquid streams and, in combination with gas at the contact liquid inlet temperature, facilitates drying or gas absorption.

[0033] As used herein, a latent heat and CO2 extractor (LHANCE) is a type of heat, mass, or heat and mass exchanger, embodiments of which are described in more detail below. Briefly, a contact liquid stream flows into a first channel of the exchanger such that the contact liquid stream wets the surfaces of the first channel but leaves a volume within the first channel for the gas stream to flow through. A gas stream, preferably flowing countercurrently to the liquid stream, engages in direct contact heat, mass, or heat and mass exchange with the contact liquid stream. Preferably, the contact liquid stream flow rate is sufficient to produce a ratio of contact liquid stream to CO2 removed that is high enough so that the mixture of CO2 and contact liquid does not form solids, although this is not a limitation and some solids formation is acceptable. Also preferably, the contact liquid forms a continuous flow over all portions of the channel surfaces, although this is also not a limitation. The gas stream, flowing cocurrently, countercurrently, or crosscurrently with respect to the contact liquid, directly contacts the contact liquid, regardless of the contact pattern (cocurrent, countercurrent, or crosscurrent). Preferably, the gas stream forms a continuous phase in the bulk flow, while the liquid stream forms a continuous phase on the surface, although an intermittent gas phase in the bulk (bubble mode) is acceptable. The second channel of the exchanger carries a cold liquid or refrigerant, which indirectly exchanges heat with the first channel. The second channel regulates the temperature of the device by indirect heat transfer with the first channel. While CO2 is the preferred reference gas for extraction, the present invention can also extract other gases, including acid gases, from other gas streams. The amount of gas removal depends on the physical characteristics of the exchanger (surface area, length, width, etc.), as well as the relative gas and liquid flow rates, operating temperature, and operating pressure.

[0034]

[0034] LHANCE and SHED share several characteristics, most notably involving both liquid and gas streams in a single passageway flowing cocurrently, countercurrently, or crosscurrently relative to one another. They differ in that, in typical embodiments, SHEDs utilize heat recovery to help cool the wet process fluid stream as it warms the gaseous process fluid stream, operating with a substantial temperature differential from warm end to cold end (from the wet process fluid inlet to its outlet) and with one primary design goal of removing moisture from the gas by condensation into a liquid, while LHANCEs can operate with a small temperature gradient in the direction of flow, perhaps nearly isothermally, with one primary design goal of selectively removing CO2 or some similar gaseous component from a gas stream. In some embodiments, both devices can be combined to form a single heat exchanger with appropriate routing of process fluid and contact liquid.

[0035]

[0035] Both LHANCE and SHED operate with solids formation. In these cases, solids will form within the contact liquid stream of the exchanger. The portion of the exchanger where this liquid exits the device optionally transitions from a series of channels to an open drop tower, through which the liquid falls either as droplets through a continuous gas phase or as a bubbler where gas bubbles through a continuous liquid phase. This allows solids to form on the liquid film / droplets / bubbles surface, and the solids are suspended in the liquid phase. The liquid and suspended solids exit the device together for further processing.

[0036]

[0036] Embodiments of the disclosed systems and methods separate a carbon dioxide-containing process fluid stream into a product standard purity liquid-phase carbon dioxide stream (such as beverage-grade carbon dioxide that is below some specifications for shipboard CO requiring 20 ppm H2O and 30 ppm O2, or less than 10 ppm O2), and a carbon dioxide-depleted stream containing residual light gases. The light gases may include N2, O2, or Ar when processing flue gas streams, H2, CO, or CH4 when processing producer gas streams, syngas streams, or natural gas streams, and H2 or additional gases depending on the particular application when processing hydrogen production streams.

[0037]

[0037] Most process fluid streams, such as flue gas and other gases listed, enter the process with some amount of moisture. A combination of water removal and carbon dioxide removal is also disclosed herein.

[0038] FIG. 1 illustrates a low temperature carbon capture process and system in one embodiment of the disclosed system and method in the form of a process flow diagram with stream numbers organized to indicate the main flow streams.

[0039] Process Flow Loop

[0040] In FIG. 1, streams 100-199 correspond to the CO2-laden process fluid loop, while streams 300-399 correspond to the CO2-depleted process fluid loop.

[0040]

[0041] The initial process fluid stream 101 is first cooled to near ambient temperature in a process fluid cooling tower CT1, most typically by direct contact using cooling water 701, although indirect contact systems are also acceptable. When liquid and gas flow countercurrently, as is common during process fluid cooling, a portion of the water condenses to the equilibrium amount of water at the temperature and pressure of the CT1 water inlet stream 701. Cocurrent or crosscurrent flow can also be used and may be preferred, for example, to mitigate the effects of acid gas condensation or solid particles. The process fluid cooling tower CT1 may be a heat exchanger or conventional spray tower, a packed column, or a similar device with a direct contact liquid stream or an indirect contact heat exchanger. The liquid is preferably water, although alternative cooling fluids may be used, including air, such as those used in facilities where water is unavailable or limited. Another alternative is to incorporate process fluid cooling into the heat source for the distillation column reboiler, either directly by using the bottoms flow from these columns, or indirectly by transferring heat to an intermediate fluid and using that fluid to heat the reboiler. The second arrangement has the disadvantage of lower overall heat transfer efficiency, but has the advantage of isolating the distillation column bottoms stream from the process fluid, which could be a safety, cost, or environmental issue if the bottoms stream is flammable / hazardous, expensive, or environmentally sensitive. The heat removed by the water or other cooling stream can be used in other parts of this or other processes, for example, to provide reboiler heat, or can be released in a cooling tower or some other water cooling system, such as the sea, lake, stream, district heating, or other heat absorption system.

[0041]

[0042] Process fluids from many sources contain contaminants such as particulates, NOx, SOx, HCl, NH3, Hg, and similar species that present corrosion and environmental problems. These problems can be mitigated through materials, design, operation, and treatment provisions. Acid gas heat exchangers are known in the industry and to those skilled in the art.

[0042]

[0043] The cooled and partially dried process fluid stream 103 enters blower B100, which increases the pressure sufficiently so that the gas can flow through the remaining equipment and be vented to the ambient atmosphere or to subsequent parts of the larger process. By way of example only, blower B100 can provide a pressure increase of 10,000 to 50,000 Pascals (0.1 to 0.5 bar), depending on the design details of the remaining equipment.

[0043]

[0044] Optionally, the cooled process fluid can be substantially pressurized, at a pressure above that required to flow through the rest of the system. This pressurization enhances the moisture and CO2 removal rate in subsequent steps and provides a pressurized clean gas stream that can then be expanded to generate energy near the end of the process. A significant advantage of pressurization is that the sub-ambient process stream can accumulate heat, including low-grade or waste heat, from other process steps or other processes and convert this heat to work in the expander. Expander T335 shown in the process flow diagram provides an example of where this expansion can occur.

[0044]

[0045] Pressurization of the process fluid by the blower generally raises the stream (stream 105) temperature slightly, and optional heat exchanger E100 can reduce the process fluid temperature to near ambient if desired.

[0045]

[0046] As will be explained in more detail below, process fluid stream 110 enters countercurrent direct contact heat exchanger CT2, which produces cooler gaseous stream 118 having a temperature, for example, slightly above 0° C., by direct contact with water stream 715. Liquid water stream 715 enters heat exchanger CT2 by pumping water stream 710 using pump P700.

[0046]

[0047] Water stream 710 originates from separate exchanger CT5, which is typically a direct contact countercurrent exchanger with stream 730 from heat exchanger CT2 along with return clean gas stream 315.

[0047]

[0048] As will be further explained in more detail below, both treated process fluid stream 315 and raw process fluid stream 110 exchange heat with water in a spray tower, packed tower, bubble column, or similar device (CT5 for treated gas and CT2 for raw gas, respectively). When the raw process fluid (stream 110) cools to approximately 0° C. (for example) to form stream 118, it loses moisture, as well as particulates, NO x , SO x , HCl, NH3, Hg, and similar species noted above, while the treated process fluid (stream 315) exiting CT5 as stream 320 gains a small amount of water when warmed by direct contact with water, up to the equilibrium limit at the process fluid outlet temperature and pressure.

[0048]

[0049] Established industry procedures, tailored to specific process fluid conditions, remove contaminants that accumulate in water stream 710 or 720, or both. These vary depending on the contaminant and are not shown in the flow diagram. Similarly, established procedures remove excess water that collects in CT1 and CT2 to provide make-up water for the water that evaporates in CT5. The diagram also does not show these streams.

[0049]

[0050] Stream 118 typically contains a small amount of water (e.g., about 0.6% at approximately 0°C and 100,000 Pascals (1 bar)) that must be removed. This may be achieved with a steady-state drying heat exchanger E118, which performs both cooling and drying. By way of example only, the drying heat exchanger E118 may be a brazed aluminum heat exchanger. In the case of incompatible materials between the exchanger, the process fluid, and the contact liquid, stainless steel or other materials may be used. As an alternative to the drying heat exchanger E118, a conventional molecular sieve or similar dryer followed by a cooler may be used.

[0050]

[0051] In the embodiment shown, heat exchanger E118 may include a sensible heat exchanger / dryer system or SHED (described above) that simultaneously dries and cools the process fluid. More specifically, and as shown in FIG. 1 , within E118, process fluid stream 118 combines with dryer contact liquid stream 830, which, as it cools, absorbs moisture from stream 118 and prevents or inhibits water freezing within the temperature range of the heat exchanger. Streams 118 and 830 combine within heat exchanger E118 and may flow cocurrently, countercurrently, or crosscurrently within the same channel, although cocurrent and countercurrent will be most common. In alternative embodiments, streams 118 and 830 may combine prior to entering heat exchanger 118 or within or near the heat exchanger header. In all cases, the system design encourages liquid to flow down the interior walls / surfaces or channel walls (preferably) of heat exchanger E118 while gas flows between the liquid-coated walls. This is done, for example, by spraying or otherwise introducing the liquid as a sheet directly onto the heat exchanger header or channel surfaces, by spraying the dryer contact liquid into the header or into stream 118 just before entering the exchanger, or by simply combining the liquid and gas streams without spraying. It is beneficial, and therefore preferably not required, that the dryer contact liquid not reach complete chemical or thermal equilibrium with the untreated process fluid stream before both streams begin to cool. This is achieved by minimizing the surface area and exposure time of gas stream 118 and dryer contact liquid stream 830 when they are combined. Injection of the dryer contact liquid 830 into the heat exchanger E118 should promote the dryer contact liquid to coat all surfaces of the channels of the heat exchanger E118 containing both the dryer contact liquid 830 and the process fluid 118 while minimizing evaporation of the dryer contact liquid in the raw process fluid stream.

[0051]

[0052] Examples of suitable dryer contact liquids include one or a combination of alcohols, including but not limited to methanol, ethanol, and propanol; ketones, including but not limited to acetone and methyl-ethyl ketone; ethers, including but not limited to dimethyl ether, diethyl ether, and methyl-ethyl ether; water in combination with these compounds; organic liquids miscible or immiscible with water; and inorganic fluids, including ammonia and low-melting-point amines. Of these, alcohols and ketones have several advantages when used similarly later in the process, while methanol and ethanol solutions have lower minimum melting points than pure or aqueous ketone solutions and may be preferred when the minimum process temperature is close to or below the ketone-based fluid melting point (nominally, −95°C to about −107°C). Typical large-scale applications may use commonly available materials, such as methanol or methanol-acetone mixtures, given their compatibility with subsequent process steps, the relative ease of obtaining such materials, and their low cost.

[0052]

[0053] While the process flow diagram of FIG. 1 shows the dryer alcohol liquid flowing cocurrently with the untreated process fluid stream through heat exchanger E118, an alternative is for the dryer alcohol liquid and the untreated process fluid to flow countercurrently within the same heat exchanger channel, with the liquid flowing substantially along the heat exchanger surfaces and the gas flowing between the liquid-coated surfaces. Cocurrent flow allows for higher gas velocities within the heat exchanger because velocity is not limited by potential entrainment of liquid. Countercurrent flow offers potential advantages for both heat and mass transfer. However, the majority of heat transfer within heat exchanger E118 may occur between process fluid stream 118 (which is cooled) and the cooling streams, which may include treated process fluid stream 301 and streams 690 and 805 (all three of which are warmed), making heat transfer between the moisture absorption dryer contact liquid stream and the untreated process fluid stream a minor consideration.

[0053]

[0054] In one embodiment, treated process fluid stream 301 provides much of the cooling required in heat exchanger E118, as shown in the process flow diagram. While this type of heat recovery provides such an embodiment with high energy efficiency, heat recovery can be managed in other ways. For example, streams that would otherwise provide heat integration in exchanger E600, including but not limited to streams 690, 805, and 405, can provide much or all of the cooling needed to cool stream 301, many of which have the advantage of being liquid streams, reducing the size of exchanger E118 and, if fewer streams are used, its complexity. Furthermore, treated return process fluid stream 301 typically has a lower flow rate than the incoming wet process fluid stream 118 and therefore cannot efficiently provide all of the cooling required. Therefore, additional streams may be provided to help balance this cooling demand. Another alternative, which is particularly attractive in large-scale applications, is to split heat exchanger E118 into two or more parallel heat exchangers, one of which (typically the larger exchanger) is balanced as just described, and the other of which incorporates an additional stream. The embodiments in this section provide examples of obtaining heat integration between several heat exchangers, but those skilled in the art will be able to find alternative ways to do so.

[0054]

[0055] The moisture absorption dryer contact liquid stream 830 also typically absorbs some CO2 as it cools and dries the process fluid within E118. As shown in Figure 1, the combined streams 118 and 830 are phase separated into a moisture-depleted (dry) gaseous stream 119 and a moisture-enriched and possibly CO2-enriched liquid stream 800. The diagram shows the streams separated internally in heat exchanger E118. They may alternatively, and perhaps more easily, be separated by an external flash vessel or tank F119. This phase separation may occur entirely within heat exchanger E118, in both heat exchanger E118 and flash tank F119 (shown in Figure 1), or phase separation may occur solely within flash tank F119. In embodiments in which phase separation occurs solely within heat exchanger E118, flash tank F119 may be omitted.

[0055]

[0056] The discussion will next follow the dryer contact liquid loop and then return to the process fluid stream. A short description of this loop is that the process distills the water and CO2 collected in stream 801 and recycles the dryer contact liquid to the process. The distillation column reboiler can use waste heat from the incoming process fluid stream 101 or the compressor, which are heated separately. Finally, column T815 may operate at a range of pressures, including subambient (vacuum) pressures, to optimize separation and heat integration. Heat integration may be provided to minimize cost and energy requirements in ways known to experts in heat integration and process engineering.

[0056]

[0057] Separated dryer contact liquid stream 801 increases in pressure as it flows through pump P801 and then re-enters illustrated heat exchanger E118, or alternatively E600, as stream 805 for warming (e.g., warming back to approximately 0°C or above), with the resulting liquid stream 810 illustratively exiting heat exchanger E118. Liquid stream 810 is further warmed in heat exchanger E800, with the resulting warm stream 815 entering distillation column T815. Distillation column T815 separates water from the dryer contact liquid stream, with HO exiting the column as stream 790. As shown in FIG. 1, water stream 790 warms stream 815 to reduce the load on the reboiler. Recovered dryer contact liquid stream 825 exits distillation column T815 and is recycled to heat exchanger E118 as stream 830 via pump P810, as described above, completing the loop. Vapor stream 820 exits the distillation column as a vapor and contains primarily contact liquid, but also CO2 collected in T118. While small amounts of CO2 are generally present, the CO2 can be recovered and purified by separating it from other possible impurities, typically N2, O2, and dryer contact liquid vapors. This purification uses techniques well known to those skilled in the art. T815 may flow through compressor C800 and can be combined with stream 830, or vented as vapor stream 821. In alternative embodiments, a liquid-liquid extraction process or a reverse osmosis system or some combination of these with distillation may be used in place of distillation column T815. This system also removes hydrocarbons, particulates, NO2, and other impurities. x , SO xThis results in the removal of several contaminants from many process fluids, including HCl, NH3, Hg, and all other compounds that condense or absorb in the exchanger at these low temperatures. These contaminants leave the condensed phase flow in dedicated purification systems or similar established separation processes common to the industry, such as filtration, ion exchange, sedimentation, chemical reaction, distillation, or in the CO2 purification system described later.

[0057]

[0058] Continuing with reference to FIG. 1, the cooled and dried process fluid stream 125 flows from the vapor outlet of flash tank F119 to extraction heat exchanger E125, which is in direct contact with the gas and extracts CO from the gas stream 125 into extraction contact liquid stream 255, which flows in the same channel as the gas. Heat exchanger E125 may take the form of a latent heat and CO extractor (LHANCE), as described above. This contact liquid stream 255 preferably flows countercurrently to the gas stream 125, as shown in FIG. 1. As these streams flow, contact liquid stream 255 extracts CO from the gas stream 125, possibly combining with solids that form in the contact liquid stream, but preferably without forming solids. A separate channel within heat exchanger E125 contains evaporating or otherwise cooling refrigerant 650, which carries away heat generated in contact liquid 255 as CO2 is transferred from gas stream 125 into refrigerant 650. The temperature profile of E125 can be controlled by stream 650, with an essentially constant temperature being particularly efficient and useful. The use of heat exchanger E125 or LHANCE performs unit operations that would typically be performed in adsorption, distillation, or similar columns. This heat exchanger in combination with stream 650 allows for independent control of the temperature profile within the exchanger, which allows the process to provide a nearly constant temperature profile, for example, in unit operations involving phase change and associated substantial heat transfer. In addition to managing the heat load of the phase change, this design allows a single-component refrigerant to provide cooling, simplifying refrigerant loop design and maintenance. Heat exchanger design, construction, and operation are all potentially simpler and less expensive than those of traditional columns. This heat exchanger is the subject of a separate patent, which is incorporated herein by reference.

[0058]

[0059] The outlet streams for heat exchanger E125 include gas stream 301, which has been depleted of water by CO2 and E118 with E125, contact liquid stream 401, which has been enriched with CO2, and warmed refrigerant stream 655. In the embodiment shown, the system operates as a nearly isothermal heat exchanger, with small temperature variations both from inlet to outlet and between streams within the exchanger. The temperature difference between refrigerant stream 650 and the combined contact liquid and gas streams (255 and 125, respectively) is a design choice. The minimum value within the exchanger is called the minimum temperature approach (MITA). MITA is sometimes less than 1°C, but can generally range from 1°C to 6°C. Typically, heat exchanger size decreases as MITA increases. The temperature variation from refrigerant inlet (650) to outlet (655) is also a design choice, but can be as low as about 1°C and is primarily driven by the pressure drop within the refrigerant channels, which slightly alters the refrigerant evaporation temperature. In other embodiments, the temperature change can be greater if the heat exchanger extracts a portion of the heat based on a sensible energy change, uses a refrigerant mixture, or receives and produces gas streams of different temperatures. This system also provides a means to remove hydrocarbons, particulates, NO x , SO x This results in the removal of several contaminants from many process fluids, including HCl, NH3, Hg, and all other compounds that condense or absorb in the exchanger at these low temperatures. These contaminants leave the condensed phase flow in dedicated purification systems or similar established separation processes common to the industry, such as filtration, ion exchange, sedimentation, chemical reaction, distillation, or in the CO2 purification system described later.

[0059]

[0060] The process fluid leaves heat exchanger E125 depleted of CO2 as stream 301 and other components less volatile than CO2 begin the warming process by flowing back to and through heat exchanger E118, where it helps cool incoming stream 119. Stream 301 remains cooler than stream 119 by some amount, an amount that affects the design and efficiency of the process. Designs can achieve a MITA as low as 1°C, sometimes slightly lower, that optimizes converter efficiency at the expense of larger size / heat transfer surface area. The MITA in heat exchanger E118 can reach this low value, or can be higher, preferably higher, to reduce heat exchanger size and pressure drop and possibly handle fluctuating process fluid flow rates, compositions, and pressures, making the overall process more robust to real-world operation.

[0060]

[0061] The treated process fluid stream exits heat exchanger E118 as stream 310, for example, at or near 0°C. Stream 310 is then split into streams 315 and 325, with stream 315 having sufficient flow to cool water stream 730 to a temperature slightly above 0°C in heat exchanger CT5, which may be a direct contact heat exchanger, a packed column, a spray tower, or a similar device, as indicated above. As indicated above, the resulting cold water stream 710 exits heat exchanger CT5 and then flows through pump P700, changing into stream 715, which enters heat exchanger CT2, which may be a direct contact heat exchanger, a packed column, a spray tower, or a similar device, as indicated above, where stream 715 cools untreated process fluid stream 110 to approximately 0°C, as described above.

[0061]

[0062] The remainder of treated process fluid stream 325 recombines with stream 370 to provide stream 330. Stream 330 may optionally be heated via heat exchanger 330 (to provide stream 335), for example, using low-grade heat from this or other processes, and then expanded via expansion device T335 to provide clean, light gas stream 340 suitable for venting to the atmosphere. This stream 340 is a dry, CO2-depleted, and otherwise very clean stream, but will often contain insufficient O2 released at ground level when the process processes the process fluid. Stream 340 is most typically vented into a stack or other device into which untreated stream 118 would generally be released. Sufficient pressure must still exist in stream 340 to exit this stack at an adequate velocity and disperse into the ambient air. When the process processes syngas, producer gas, natural gas, etc., stream 340 is a product stream that forms an inlet to a separate process.

[0062]

[0063] Contact Liquid and CO2 Loop

[0064] As explained above, the contact liquid stream 255 directly contacts the process fluid stream 125 in the heat exchanger E125, where the contact liquid stream 255 primarily extracts CO. In a preferred embodiment, the heat exchanger E125 includes at least one set of two-phase channels, with the process fluid and contact liquid flowing countercurrently to one another in at least one set of channels of a multi-stream heat exchanger. Temperature control in E125 is preferably maintained by separate refrigeration channels, and gas extraction often occurs by adsorption rather than condensation. The selection of the contact liquid 255 depends in part on its ability to absorb CO, particularly in operating scenarios that minimize solids formation, and in part on the material's compatibility, viscosity, and other practical considerations. As with E118 discussed above, the phase change in E125 will typically occur in an absorption or distillation column containing packing or trays, and the temperature profile will be governed by heat absorption in the column and heat exchange between the countercurrent liquid and gas streams. In the embodiment shown, a heat exchanger rather than a column performs this unit operation, with one set of channels within the exchanger containing two phases whose compositions change within the exchanger, and separate refrigerant channels within the same exchanger controlling the temperature profile. A similar effect can be achieved with a column containing a series of pump-around coolers, which is included in an alternative embodiment, although pump-around systems are more cumbersome than heat exchanger systems. This arrangement allows for independent control of composition and temperature profile, allowing, for example, operation of an essentially isothermal absorption column or any other temperature profile suitable for the process.

[0063]

[0065] The contact liquid stream 255 typically directly contacts the process fluid stream 125 inside the heat exchanger E125. In one embodiment, the liquid stream 255 enters near the top of the device and flows down the same channel as the process fluid stream 125 flows up. As the two flow past each other, CO2 transfers from the gas to the liquid, and the associated heat is released to the liquid phase. The liquid and gas streams separate either within the heat exchanger E125, as in the embodiment shown in FIG. 1, or just outside the exchanger. The heat exchanger E125 ideally operates with the contact liquid flowing countercurrently to the process fluid, although cocurrent flow is also possible and easier to implement, especially for streams with low initial CO2 content. Combinations of cocurrent, countercurrent, and crosscurrent flow patterns are also contemplated, especially when the exchanger includes different sections.

[0064]

[0066] The absorbed, possibly solid, CO accumulates in the contact liquid stream 255 as the contact liquid stream 255 and the process fluid stream 125 flow together. The solids that form will be primarily CO and can exit the device as a lightly-loaded slurry and be carried through the next part of the process to the point where the CO dissolves.

[0065]

[0067] The contact liquid stream absorbs some nitrogen and oxygen in heat exchanger E125, in addition to CO2, contaminants less volatile than CO2, and other compounds. Some of these compounds leave in the liquid phase, further reducing the harmful compounds in the process fluid stream. The contact liquid is also selected so that only a minimal amount evaporates in the process fluid stream where the contact liquid and process fluid contact each other. The operating temperature also affects the amount of material that accumulates in the liquid stream and the amount of contact liquid that evaporates in the process fluid stream. An optional flash separation device (not shown in Figure 1) into which the liquid stream enters after E125 removes some of these compounds absorbed or condensed in the contact liquid at ambient pressure, or optionally, at subambient pressure. Other options exist for removing these species later in the purification process, as described below.

[0066]

[0068] The contact liquid containing CO2 exits heat exchanger E125 as stream 401 and then increases its pressure in pump P400 to form stream 405, the pressure of which is high enough to maintain the CO2 as a liquid as stream 405 is warmed in E600 and exits at near ambient temperature as stream 425.

[0067]

[0069] Stream 425 enters one or more distillation columns T425 where the CO2 and contact liquid are separated to form CO2 product stream 470 and process recycle contact liquid stream 245. Stream 245 is cooled in heat exchanger E600 back to near the operating temperature of E125 to become stream 255, which completes the contact liquid cycle.

[0068]

[0070] Distillation column T425 can be equipped with a traditional staged, packed, or trayed column. In an alternative embodiment, distillation column T425 may be replaced by one or several combinations of at least a single, and possibly multiple, stage flash tanks, liquid-liquid extraction columns, reverse osmosis systems, or some combination thereof to purify CO2 to target specifications. In one embodiment, the feed and product streams of columns T425 and / or T815 flow through heat exchangers that modify their temperatures to within the lowest approach temperature of the feed stream, minimizing appreciable energy losses within the system and therefore its energy efficiency. Additionally, the feed stream may be split into two streams, with the two streams entering the column already partially separated and at the appropriate temperatures for the cold and warm ends of the column. This makes the column more efficient at separating components.

[0069]

[0071] Small amounts of contact liquid are carried over as vapor or fumes in the process fluid stream 301 exiting heat exchanger E125 and leave with the pure (or nearly pure) CO stream 470 from distillation column T425; these represent the major losses of contact liquid in the system, both of which are small. Make-up flow (not shown) compensates for these small losses.

[0070]

[0072] Pump P470 pressurizes CO2 stream 470 to a design pressure, typically 12,500,000 to 15,000,000 pascals (125 to 150 bar). Stream 475 exits pump P470 and is cooled in heat exchanger E600 to form cooled stream 455, which exits the system as a CO2 product stream.

[0071]

[0073] Ketones, alcohols, ethers, acetates, and blends of these, possibly with some water, are good candidates for contact fluids. In particular, acetone or methanol / ethanol / propanol do not freeze within the temperature range of typical operation, absorb water in addition to CO2, and have suitable volatility and viscosity for this process. Some mixtures of these chemicals with each other and with H2O or CO2 exhibit eutectic behavior, with melting points well below those of any single component, making them particularly suitable contact fluids. Acetone has a particularly good ability to absorb CO2, making it an excellent candidate for use in E125. Acetone mixtures with small amounts (0-15%) of methanol are also excellent candidates, allowing E125 to operate at temperatures somewhat lower (-90 to -100°C) than pure acetone, which freezes at approximately -95°C. Methanol mixtures with water have particularly low viscosities and freezing points, making them excellent candidates for use in E118. In particular, E118 is preferably operated with enough methanol vapor at its warm end slightly above 0°C before mixing with methanol so that the condensate that forms in the system contains enough methanol to remain above the freezing point of the condensate at all temperatures and compositions in the exchanger.

[0072]

[0074] Heat exchangers E118 and E600, as shown here, primarily separate the wet process fluid stream 118 from the refrigerant sensible heat exchanger stream (E600). This is because the process fluid stream 118 may contain certain trace components, such as condensable acids and mercury, that are incompatible with aluminum and other materials commonly used in E600. Furthermore, large-scale applications handle process fluid volumetric flows that may require these exchangers to be as large as, or perhaps larger than, those commonly available from manufacturers; splitting them reduces the size of the exchangers. However, for smaller applications, or when material issues do not exist, these exchangers may be combined or separated in different ways to minimize cost, maximize efficiency, simplify the process, or otherwise result in a flow diagram that differs from that shown here. These alternative combinations will be apparent to those skilled in that type of industrial or utility heat exchange.

[0073]

[0075] Refrigeration cycle

[0076] The system of Figure 1 uses a traditional refrigeration cycle for cooling. However, the system of Figure 1 is non-traditional in that it achieves cooling using only two refrigeration loops, both of which use a single-component refrigerant. This simplifies the process and reduces the capital and maintenance costs of the compressor and refrigeration loops. Alternatively, the system could use a similar refrigeration cycle using a mixed refrigerant, in which case the heat exchanger in this process flow diagram that primarily evaporates a single refrigerant could be combined with a heat exchanger that primarily performs sensible heat exchange.

[0074]

[0077] The following section describes one way to design a refrigeration loop for this system. Many alternative methods exist that will be apparent to those skilled in the art.

[0078] Heavy refrigerant loop (Loop 900)

[0079] The lowest volatility refrigeration loop preferably uses propane, propylene, or other fluids with similar volatility to the working fluid. In embodiments using propane as the refrigerant, liquid propane enters main refrigerant cooler E600 from compressor C900 as stream 955, where the temperature of stream 955 is dropped to approximately −40° C. to form stream 960. Compressor C900 is typically a multi-stage device with interstage cooling using cooling water, air, or other available means to carry away the heat of compression. This heat can be integrated into the distillation column reboiler.

[0075]

[0080] Stream 960 optionally splits to form stream 965 and optional stream 935, which flows through expansion valve V935 to form stream 940. Stream 965 flows through an expansion valve (as shown) or turbine expander V965, where the pressure of stream 965 drops to near the bubble point (slightly above 100,000 Pascals (1 bar)), and enters heat exchanger E635. Exchanger E635 partially evaporates stream 965 to form two-phase stream 970, while condensing the gas in stream 635 in another refrigeration loop to form single-phase liquid stream 637; both processes preferably occur at an essentially constant temperature with a minimum temperature approach (MITA) determined by the converter design. The most efficient designs generally operate with a MITA of approximately 1°C for these two well-characterized streams.

[0076]

[0081] The now combined vapor-liquid stream exits E635 as stream 970. Stream 970 provides cooling for the CO2 purification process by cooling condenser E426 of distillation column T425, forming stream 975, as shown in the process flow diagram. At this point, stream 975 contains primarily vapor but typically has a small amount of residual liquid, which aids in its ability to modify the temperature profile in exchangers E600 and E118 as stream 975 warms back to ambient temperature. The stream is split into one stream each for E600 and E118, forming streams 975 and 985.

[0077]

[0082] Stream 975 enters E600 with a small residual liquid portion and warms to ambient temperature—because stream 975 helps modify the temperature profile of E600 to maintain a low and reasonably constant minimum approach temperature within E600. Stream 975 exits E600 as stream 980.

[0078]

[0083] As indicated above, stream 960 is split to form stream 965 and optional stream 935, described above, which flows through expansion valve V935, and enters exchanger E600 as stream 940 at a pressure where stream 940 begins to evaporate, preferably modifying its temperature profile to maintain a small and consistent temperature difference or minimum approach temperature between the hot and cold streams in E600. The pressure of stream 940 is adjusted to match the pressure of one of the intermediate stages of compressor C900, which is higher than the inlet pressure of compressor C900, so that stream 940 enters E600 as stream 945 and evaporates at a somewhat higher temperature than stream 965 and at a downstream evaporation point. Stream 945 exits E600 at approximately ambient temperature.

[0079]

[0084] As noted above, stream 985 branches off from stream 970 and enters E118, where it modifies its temperature profile to maintain a reasonably small and consistent temperature differential. Stream 985 exits E118 at near ambient temperature as stream 990 and combines with stream 980 exiting heat exchanger E600, and the combined stream enters the low-pressure end of compressor C900 at (say) slightly above 100,000 Pa (1 bar), thereby producing stream 995 and terminating the heavy refrigerant loop.

[0080]

[0085] Some of the salient features of the 900 loop cycle include: (a) the loop cycle can contain a single refrigerant rather than a mixed refrigerant; (b) the loop cycle condenses to a liquid before entering the E600; (c) the pressure of the loop cycle never drops below ambient to avoid air leaking into the loop cycle; (d) the loop cycle provides cooling both for condensing the refrigerant from the 600 loop and for the CO2 purification process; and (e) the loop cycle helps shape the temperature profiles in both the E600 and E118 to maintain a constant and small temperature difference between the cold and hot streams within these exchangers.

[0081]

[0086] Cooling water that is below about 18°C ​​can provide the cooling needed to condense the CO2 in distillation column T425, reducing the amount of refrigerant needed in loop 900 and improving overall energy efficiency. This requires adjusting the pressure of T425 so that the CO2 condenses at the temperature of the cooling water, or more specifically, at a temperature that allows the cooling water to operate the condenser.

[0082]

[0087] Light Refrigeration Loop (Loop 600)

[0088] The lightest or most volatile refrigerant loop (loop 600) primarily provides cooling to absorb the heat of phase change associated with CO2 capture. This loop can be powered by one of several single refrigerants; the choice of refrigerant depends on the temperature requirements of exchanger E125, and more specifically, stream 650, but the refrigerant will generally be one of ethylene, ethane, or propylene. Compressor C600 is typically a multi-stage device with interstage cooling using cooling water, air, or other available means to carry away the heat of compression.

[0083]

[0089] Stream 325, preferably at a subambient temperature, near 0°C, can optionally have the final stage of C600 or C900 cooled to the subambient temperature to reduce the heat load within E600 and / or the required outlet pressure of at least one of the compressors. Stream 630 exits the compressor and enters E600 as a gas and is cooled to near its dew point to form stream 635. Stream 635 enters E635 near its dew point and exits E635 near its bubble point as stream 637, having substantially condensed to a liquid within E635 due to the minimum temperature change (as discussed above). The pressure drop of the stream within E635 changes the bubble and dew point temperatures as the stream progresses through the exchanger, but this is a small change, and E635 operates essentially as a constant temperature condenser.

[0084]

[0090] Stream 637 exits E635 as a liquid and is split into streams 640 and optionally 670.

[0091] Stream 640 is cooled in heat exchanger E600 to form liquid stream 645. The temperature of liquid stream 645 is a few degrees below the temperature at which CO2 conducts into contact liquid 255 in E125, typically between -80°C and -98°C. Stream 645 flows through an expansion valve (shown) or expansion turbine V645 to form stream 650, which has a pressure near its bubble point, which should be somewhat higher than ambient pressure. Stream 650 enters E125 as a substantially liquid stream and exits as a substantially vapor stream 655, with minimal change in temperature but significant phase change within E125. From this point, the stream warms to near ambient temperature by cooling other streams.

[0085]

[0092] Stream 655 splits to form streams 660 and 690, which flow through E600 and E118, respectively. The small amount of residual liquid in these streams helps establish the appropriate temperature differential within each heat exchanger as the liquid begins to evaporate. Within E600, stream 660 warms to ambient temperature as it exchanges heat with the cooled stream and exits as stream 665, which combines with stream 695 to form the cold inlet for C600. This completes the light refrigerant loop, except for a branch stream, which will be discussed next.

[0086]

[0093] Optional stream 670 branches off from stream 637 as a liquid stream near the condensation temperature of stream 635. The purpose of stream 670 and the rest of this branch is to help shape the temperature profile within E600 to maintain a constant and small temperature difference between the hot and cold streams. Stream 670 is cooled as a liquid within E600 and exits as stream 675, which is warmer than stream 645 and near the stream bubble point temperature at one of the interstage pressures of C600. Expansion valve or expander V675 reduces the pressure of stream 675 to approximately the exit pressure of this same stage to form substantially liquid stream 680. Stream 680 re-enters E600 and evaporates as stream 680 warms back to ambient temperature. Stream 680 exits E600 as a vapor at a pressure close to one of the intermediate stage pressures of C600 to form stream 685, which enters the compressor at the inlet pressure of one of the intermediate stages of C600.

[0087]

[0094] Optional stream 690 branches off from stream 655; stream 690 helps shape a narrow and consistent temperature profile between hot and cold streams within E118. Stream 690 is substantially, but not necessarily, completely vapor and enters E118 near the bottom of its temperature range. Stream 690 is warmed to approximately ambient temperature to form stream 695 as the exit stream from E118. Stream 695 mixes with stream 665 to form the low-pressure inlet stream for compressor C600.

[0088]

[0095] Some of the salient features of the 600 loop cycle include: (a) the loop cycle can contain a single refrigerant rather than a mixed refrigerant; (b) the loop cycle condenses to a liquid in E635 by exchanging heat with loop 900, particularly stream 965 and subsequent streams; (c) the pressure of the loop cycle never drops below ambient to avoid air leaking into the loop cycle; (d) the loop cycle provides primarily refrigeration for CO2 extraction from the process fluid streams; and (e) the loop cycle helps shape the temperature profiles in both E600 and E118 to maintain a constant and small temperature difference between the cold and hot streams in these exchangers.

[0089]

[0096] Waste Heat Recovery System

[0097] In some embodiments of the disclosed system, the major power consumers of the system are the blower (B100) and compressors (C600 and C900). The compressor provides the refrigerant, and the blower provides the process pressure to overcome the pressure drop. The efficiency with which the blower overcomes the process pressure drop increases as the blower inlet pressure increases. Similarly, if the blower raises the pressure more than needed, the blower can recover some of the energy by expanding the stream at the end of the process, as shown by T335. The amount of energy recovered increases when the expanding stream is hotter than the incoming stream for the same reason that a gas turbine or jet engine extracts more energy from the hot exhaust than is needed to compress the cold inlet air. This is a function of the heat exchanger E330. The amount of energy recovered depends on the details of the flow, including the fraction of the flow removed in the carbon capture process, the pressure drop of the unit operation, and the amount of heat recovered. The primary heat sources, capable of raising the gas temperature above the heat source inlet temperature, include the hot process fluid upstream of the process and three energy-consuming and heat-producing turbomachines B100, C600, and C900. The process flow diagram shows the heat recovery from each of the turbomachines, with dashed lines leading to a heat exchanger just before the expander. The warm and somewhat pressurized process fluid at this point exits through the expander, where it is cooled using low-grade heat available internally and externally in the process.

[0090]

[0098] Examples of systems that the present invention can treat include CO removal from process fluids such as air, flue gas, syngas, natural gas, biogas, and process gases; HO removal from most water-bearing gases; and SO removal from pollutant streams and other sulfur-containing gases. X This includes, but is not limited to, removal, and absorption / condensation of any gaseous components by a contacting liquid capable of absorbing some portion of the component.

[0091]

[0099] Embodiments of the present disclosure can produce up to 99.999% pure CO2.

[0100] All patents and published patent applications referenced herein are hereby incorporated by reference. The invention has been described with reference to various specific and preferred embodiments and techniques. Nevertheless, it will be understood that many variations and modifications may be made while remaining within the spirit and scope of the invention.

Claims

1. 1. A system for separating carbon dioxide from a process fluid stream, comprising: a. a process fluid feed line; b. a dryer contact liquid feed line; c. a dry heat exchanger having combined stream cooling and refrigeration passages; a junction configured to combine a process fluid from the process fluid feed line and a dryer contact liquid from the dryer contact liquid feed line such that a combined stream comprising a dryer contact liquid portion, a dryer contact vapor portion, and the process fluid is formed and directed into the combined stream cooling passage; e. the combined stream cooling passage and the refrigeration passage configured such that a coolant stream in the refrigeration passage reduces a temperature of the combined stream such that water from the process fluid and at least a portion of the dryer-contacted vapor portion condenses and combines with the dryer-contacted liquid portion to form a combined liquid stream; a combined stream phase separator configured to receive the combined liquid stream from the combined stream cooling passage and separate it into a gaseous process fluid stream and a wet dryer contact liquid stream; g. an extraction heat converter having a carbon dioxide extraction cooling passage and an extraction heat converter refrigerant warming passage, the carbon dioxide extraction cooling passage having a gaseous process fluid inlet, a treated process fluid outlet, an extraction contact liquid inlet configured to receive an extraction contact liquid, and a carbon dioxide-enriched extraction contact liquid outlet, the extraction heat converter refrigerant warming passage configured to receive a first refrigerant or a second refrigerant for cooling the carbon dioxide extraction cooling passage; a gaseous process fluid line configured to direct the gaseous process fluid from the combined stream phase separator to the gaseous process fluid inlet of the carbon dioxide extraction cooling passage of the extraction heat transformer; i. the carbon dioxide extraction cooling passage of the extraction heat transformer is configured so that the extraction contact liquid in the carbon dioxide extraction cooling passage contacts the gaseous process fluid such that carbon dioxide is extracted from the gaseous process fluid to form a treated process fluid and a carbon dioxide-enriched extraction contact liquid, the treated process fluid exiting the carbon dioxide extraction cooling passage through the treated process fluid outlet and the carbon dioxide-enriched extraction contact liquid exiting the carbon dioxide extraction cooling passage through the carbon dioxide-enriched extraction contact liquid outlet.

2. 10. The system of claim 1, The system wherein the carbon dioxide extraction cooling passages of the extraction heat transformer are configured such that the extraction contact liquid flows countercurrently to the gaseous flue gas within the extraction contact liquid.

3. 10. The system of claim 1, a wet dryer contact liquid line configured to direct a wet dryer contact liquid stream from the combined stream phase separator to the at least one refrigeration passage of the drying heat exchanger to provide cooling for the combined stream cooling passage.

4. 10. The system of claim 1, 10. The system of claim 1, further comprising: a treated process fluid line configured to direct treated process fluid from the treated process fluid outlet of the extraction heat transformer to the refrigeration passage of the dryer heat exchanger to provide cooling for the combined stream cooling passage.

5. 10. The system of claim 1, The system wherein the combined stream phase separator is integrated into the drying heat exchanger.

6. 10. The system of claim 1, The system wherein the combined stream phase separator is a flash vessel configured to receive the combined stream from the drying heat exchanger and separate the combined stream into a gaseous process fluid stream and a wet dryer contact liquid stream.

7. 10. The system of claim 1, the system further comprising a first feedstream cooling heat exchanger configured to receive a process fluid feedstream and a first cooling fluid stream such that the process fluid feedstream is cooled by the first cooling fluid stream, the first feedstream cooling heat exchanger having a first wet process fluid feedstream outlet in fluid communication with the process fluid feedline.

8. 8. The system of claim 7, a second feedstream cooling heat exchanger having a wet process fluid inlet and a cooled cooling water inlet in fluid communication with the first wet process fluid feedstream outlet of the first feedstream cooling heat exchanger, the cooled cooling water inlet configured to receive the cooled cooling water stream such that a flue gas feedstream is cooled by direct contact with the cooled cooling water stream in the second feedstream cooling heat exchanger to produce a warmed cooling water stream, the second feedstream cooling heat exchanger having a second wet process fluid feedstream outlet in fluid communication with the process fluid feed line; and a third feedstream cooling heat exchanger configured to receive the warmed cooling water stream from a treated process fluid stream inlet in fluid communication with the second feedstream cooling heat exchanger and the treated process fluid outlet of the extraction heat exchanger, and to directly contact and cool the received warmed cooling water stream to produce a cooled cooling water stream, the third feedstream cooling heat exchanger having a cooled cooling water stream outlet in fluid communication with the cooled cooling water inlet of the second feedstream cooling heat exchanger.

9. 9. The system of claim 8, 10. The system of claim 9, further comprising: a cooled cooling water pump configured to pump cooled cooling water from the cooled cooling water stream outlet of the second feedstream cooling heat exchanger to the cooled cooling water inlet of the second feedstream cooling heat exchanger.

10. 9. The system of claim 8, 10. The system further comprising: a cooled process fluid feedstream compressor having an inlet in fluid communication with the first wet process fluid feedstream outlet of the first feedstream cooling heat exchanger and an outlet in fluid communication with the wet process fluid inlet of the second feedstream cooling heat exchanger.

11. 10. The system of claim 1, j) a wet dryer contact liquid line configured to direct a wet dryer contact liquid stream from the combined stream phase separator to the refrigeration passage of the dryer heat exchanger to provide cooling for the combined stream cooling passage; k. A dryer distillation column having a distillation column inlet in fluid communication with the refrigeration passage outlet, the dryer distillation column also having a dryer distillation column treated contact liquid outlet and a dryer distillation column water outlet, the dryer distillation column configured to receive wet dryer contact liquid from the refrigeration passage outlet of the drying heat exchanger and separate it into a dryer contact liquid stream directed out the treated contact liquid outlet and a reboiler outlet stream directed out the dryer distillation column water outlet.

12. 12. The system of claim 11, The system further comprises a dryer distillation column heat exchanger configured to receive and cool a reboiler outlet stream from the dryer distillation column, to receive and warm a wet dryer contact liquid from the outlet of the refrigeration passage of the dryer heat exchanger, and to direct the warmed wet dryer contact liquid to the dryer distillation column inlet.

13. 12. The system of claim 11, The system, wherein the dryer distillation column further comprises a dryer contact vapor outlet, wherein dryer contact vapor is formed within the dryer distillation column and directed through the dryer contact vapor outlet.

14. 10. The system of claim 1, The system wherein the dryer contact liquid comprises an alcohol.

15. 10. The system of claim 1, The system wherein the dryer contact liquid comprises a component selected from the group consisting of water, methanol, ethanol, propanol, ketones, and inorganic fluids.

16. 16. The system of claim 15, The system, wherein the extraction contact liquid comprises a component selected from the group consisting of ketones, alcohols, ethers, and acetates.

17. 10. The system of claim 1, The system wherein the dryer contact liquid comprises an ether selected from the group consisting of dimethyl ether, diethyl ether, and methyl ethyl ether.

18. 10. The system of claim 1, The system wherein the dryer contact liquid comprises an inorganic fluid selected from the group consisting of ammonia and low melting point amines.

19. 10. The system of claim 1, The system, wherein the extraction contact liquid comprises a component selected from the group consisting of ketones, alcohols, ethers, and acetates.

20. 10. The system of claim 1, The junction is positioned within the dry heat exchanger.

21. 10. The system of claim 1, The system wherein the junction is positioned upstream from the dry heat exchanger.

22. 10. The system of claim 1, The system wherein the dry heat exchanger includes a header, and the junction is positioned within the header.

23. 10. The system of claim 1, the combined stream cooling passage of the dryer heat exchanger includes a combined stream cooling passage channel configured such that a dryer contact liquid stream wets surfaces of the combined stream cooling passage channel but leaves an open volume within the combined stream cooling passage channel for a process fluid stream to flow through.

24. 10. The system of claim 1, the coolant stream is selected from the group consisting of the wet dryer contact liquid stream from the combined stream phase separator, the treated process fluid from the treated process fluid outlet of the extraction heat exchanger, the first refrigerant, and a separate refrigerant.

25. 10. The system of claim 1, the carbon dioxide extraction cooling passage of the extraction heat exchanger comprises a carbon dioxide extraction cooling passage channel configured such that an extraction contact fluid stream wets surfaces of the carbon dioxide extraction cooling passage channel but leaves an open volume within the carbon dioxide extraction cooling passage channel for a gaseous process fluid stream to flow through.

26. 10. The system of claim 1, j) a refrigerant heat exchanger including a refrigerant cooling passage and an extraction heat exchanger refrigerant warming passage in fluid communication with the freezing passage of the drying heat exchanger, a carbon dioxide-enriched extraction contact liquid warming passage in fluid communication with the carbon dioxide-enriched extraction contact liquid outlet of the extraction heat exchanger, and an extraction contact liquid cooling passage in fluid communication with the extraction contact liquid inlet of the extraction heat exchanger; k. an extractive distillation column having a carbon dioxide-enriched extracted contact liquid inlet in fluid communication with the carbon dioxide-enriched extracted contact liquid warming passage of the refrigerant heat exchanger, a carbon dioxide liquid outlet, and an extracted contact liquid outlet in fluid communication with the extracted contact liquid cooling passage of the refrigerant heat exchanger; l. the extractive distillation column is configured to separate a warmed carbon dioxide-enriched extracted contact liquid stream received from the carbon dioxide-enriched extracted contact liquid warming passage of the refrigerant heat exchanger into a carbon dioxide liquid stream directed out of the extractive distillation column through the carbon dioxide liquid outlet and an extracted contact liquid stream directed out of the extractive distillation column through the extracted contact liquid outlet.

27. 27. The system of claim 26, the refrigerant heat exchanger includes a liquid carbon dioxide refrigeration passage, and the system further comprises a liquid carbon dioxide pump configured to pump liquid carbon dioxide from the carbon dioxide liquid outlet of the extractive distillation column to the liquid carbon dioxide refrigeration passage of the refrigerant heat exchanger.

28. 10. The system of claim 1, The system wherein the dryer contact liquid generates a sufficient dryer contact vapor fraction such that condensation of the dryer contact vapor fraction and at least a portion of the water vapor results in the combined liquid stream remaining above the melting point of the combined liquid stream for all temperatures present in the dryer.

29. 1. A system for separating carbon dioxide from a flue gas stream, comprising: a. a process fluid feed line; b. an extraction heat exchanger having a carbon dioxide extraction cooling passage and an extraction heat exchanger refrigerant warming passage, the carbon dioxide extraction cooling passage having a process fluid inlet in fluid communication with the process fluid feed line, a treated process fluid outlet, an extraction contact liquid inlet configured to receive an extraction contact liquid, and a carbon dioxide-enriched extraction contact liquid outlet; c) the carbon dioxide extraction cooling passage of the extraction heat exchanger is configured such that an extraction contact liquid in the carbon dioxide extraction cooling passage contacts the process fluid such that carbon dioxide is extracted from the process fluid to form a treated process fluid and a carbon dioxide-enriched extraction contact liquid, the treated process fluid exiting the carbon dioxide extraction cooling passage through the treated process fluid outlet and the carbon dioxide-enriched extraction contact liquid exiting the carbon dioxide extraction cooling passage through the carbon dioxide-enriched extraction contact liquid outlet.

30. 30. The system of claim 29, The system, wherein the extraction heat exchanger includes an extraction heat exchanger refrigerant warming passage configured to receive refrigerant for cooling the carbon dioxide extraction cooling passage.

31. 1. A method for separating carbon dioxide from a process fluid stream, comprising: a. combining a process fluid stream and a dryer contact liquid stream to provide a combined stream; b. directing the combined stream through a drying heat exchanger; c. cooling the combined stream in the dry heat exchanger by warming a coolant stream; d. condensing water from the process fluid stream into the dryer contact liquid stream in the dryer heat exchanger; e. separating the combined stream into a gaseous process fluid stream and a wet dryer contact liquid stream; f. contacting the gaseous process fluid stream with the extraction contact liquid stream in an extraction heat exchanger such that carbon dioxide is transferred from the gaseous process fluid stream to the extraction contact liquid to produce a treated process fluid stream and a carbon dioxide-enriched extraction contact liquid stream; and g. warming the first refrigerant or the second refrigerant in the extraction heat exchanger such that the contacting gaseous process fluid stream and the extracted contact liquid stream are cooled in the extraction heat exchanger.

32. 32. The method of claim 31 , wherein the coolant stream of step c. is selected from the group consisting of the treated process fluid stream, the wet dryer contact liquid stream, and the first refrigerant stream.

33. 32. The method of claim 31 , wherein the extraction contact liquid flows countercurrently to the gaseous process fluid in the extraction heat exchanger during step f.

34. 32. The method of claim 31 , The method wherein the dryer contact liquid comprises an alcohol.

35. 32. The method of claim 31 , The method wherein the dryer contact liquid comprises a component selected from the group consisting of water, methanol, ethanol, propanol, ketones, and inorganic fluids.

36. 36. The method of claim 35, The method, wherein the extraction contact liquid comprises a component selected from the group consisting of ketones, alcohols, ethers, and acetates.

37. 32. The method of claim 31 , The method wherein the dryer contact liquid comprises an ether selected from the group consisting of dimethyl ether, diethyl ether, and methyl ethyl ether.

38. 32. The method of claim 31 , The method wherein the dryer contact liquid comprises an inorganic fluid selected from the group consisting of ammonia and low melting point amines.

39. 32. The method of claim 31 , The method, wherein the extraction contact liquid comprises a component selected from the group consisting of ketones, alcohols, ethers, and acetates.

40. 32. The method of claim 31 , The method wherein the combining of the process fluid stream and the dryer contact liquid stream occurs within the dryer heat exchanger.

41. 32. The method of claim 31 , The method wherein the combining of the process fluid stream and the dryer contact liquid stream occurs upstream of the dryer heat exchanger.

42. 32. The method of claim 31 , Step e. occurs within said drying heat exchanger.

43. 32. The method of claim 31 , Step e. occurs in a flushing vessel.

44. 32. The method of claim 31 , The method further comprises the step of cooling said process fluid stream with a fluid prior to step a.

45. 45. The method of claim 44, The method further comprises cooling the process fluid stream using a fluid in a first feedstream cooling heat exchanger and a second feedstream cooling heat exchanger prior to step a.

46. 46. ​​The method of claim 45, The method further comprising compressing the process fluid stream between the first feedstream cooling heat exchanger and the second feedstream cooling heat exchanger.

47. 32. The method of claim 31 , The method further comprising separating the wet dryer contact liquid stream from the dry contact heat exchanger into the dry contact liquid stream and a wastewater stream.

48. 48. The method of claim 47, The method further comprising using the wastewater stream to cool the wet dryer contact liquid stream from the drying heat exchanger.

49. 32. The method of claim 31 , h. cooling the first refrigerant in a refrigerant heat exchanger; i. warming the carbon dioxide-enriched extraction contact liquid stream in the refrigerant heat exchanger; j. separating the warmed carbon dioxide-enriched extracted contact liquid stream into a carbon dioxide liquid stream and the extracted contact liquid stream in an extractive distillation column; k) cooling the extracted contact liquid stream from the extractive distillation column in the refrigerant heat exchanger and directing the cooled extracted contact liquid stream from the refrigerant heat exchanger to the extractor heat exchanger.

50. 50. The method of claim 49, The method wherein the liquid carbon dioxide is warmed in the refrigerant heat exchanger.

51. 32. The method of claim 31 , During step g., carbon dioxide from the gaseous process fluid stream is condensed into the extraction contact liquid.

52. 32. The method of claim 31 , During step f., carbon dioxide from the gaseous process fluid stream is absorbed within the extraction contact liquid.

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