Patent Grant
10969169
The devices and processes described herein relate generally to separation of gases.
Separating gases from other gases is a challenge in any industry. In some instances, such as in natural gas production, the gases to be removed can not only lower the value of the natural gas but can make it unusable unless purified. Many processes exist for stripping contaminants out of natural gas, but they suffer from a variety of downsides. Some are energy inefficient. Some have limited extraction capacity. Some are not feasible in remote locations, where natural gas is typically located. Energy efficient and cost-effective methods for purifying natural gas streams are needed.
In one aspect, the disclosure provides a method for separating components of a gas. A feed gas stream is passed into a vessel. The feed gas stream includes methane, carbon dioxide, and water. The feed gas stream is cooled in the vessel such that a portion of the methane, a first portion of the carbon dioxide, and a first portion of the water condense, resulting in a product stream and a depleted gas stream exiting the vessel.
The feed gas stream may also consist of a secondary component which may include carbon dioxide, NGLs, nitrogen, argon, hydrogen sulfide, mercaptans, hydrogen, or a combination thereof. The NGLs may include ethane, propane, butane, isobutane, pentane, natural gasoline, cyclic hydrocarbons, aromatic hydrocarbons, or a combination thereof.
Cooling the fed gas stream may condense a portion of the secondary component into the product stream, desublimate a portion of the secondary component into the product stream, or a combination thereof. The product stream may be separated into a liquid product stream and a solids stream. The solids stream may be separated into a water stream and a secondary component stream.
In a second aspect, cooling the feed gas stream desublimates a second portion of the carbon dioxide and a second portion of the water as a solid product stream.
In a third aspect, the disclosure provides a method for separating components of a gas. A feed gas stream is passed into a vessel. The feed gas stream consists of methane, carbon dioxide, and water. The feed gas stream is cooled in the vessel such that a first portion of the carbon dioxide and a first portion of the water condense, resulting in a product stream and a depleted gas stream.
Further aspects and embodiments are provided in the foregoing drawings, detailed description and claims.
The following drawings are provided to illustrate certain embodiments described herein. The drawings are merely illustrative and are not intended to limit the scope of claimed inventions and are not intended to show every potential feature or embodiment of the claimed inventions. The drawings are not necessarily drawn to scale; in some instances, certain elements of the drawing may be enlarged with respect to other elements of the drawing for purposes of illustration.
The following description recites various aspects and embodiments of the inventions 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 are included within the scope of the claimed inventions. The description is to be read from the perspective of one of ordinary skill in the art. Therefore, information that is well known to the ordinarily skilled artisan is not necessarily included.
The following terms and phrases have the meanings indicated below, unless otherwise provided herein. This disclosure may employ other terms and phrases not expressly defined herein. Such other terms and phrases shall have the meanings that they would possess within the context of this disclosure to those of ordinary skill in the art. In some instances, a term or phrase may be defined in the singular or plural. In such instances, it is understood that any term in the singular may include its plural counterpart and vice versa, unless expressly indicated to the contrary.
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” encompasses a single substituent as well as two or more substituents, and the like.
As used herein, “for example,” “for instance,” “such as,” or “including” are meant to introduce examples that further clarify more general subject matter. Unless otherwise expressly indicated, such examples are provided only as an aid for understanding embodiments illustrated in the present disclosure and are not meant to be limiting in any fashion. Nor do these phrases indicate any kind of preference for the disclosed embodiment.
As used herein, “natural gas” is meant to refer to a methane containing gas stream. Natural gas, as harvested in the field, contains at least water and carbon dioxide. In many instances, natural gas may also contain NGLs, nitrogen, argon, hydrogen sulfide, and hydrogen.
As used herein, the term “NGLs” is meant to refer to compounds selected from the group consisting of ethane, propane, butane, isobutane, pentane, natural gasoline, cyclic hydrocarbons, aromatic hydrocarbons, and combinations thereof.
As used herein, “cryogenic” is intended to refer to temperatures below about −58° F. (−50° C.).
As used herein, “desublimate” refers to the process of a gas changing to a solid state directly, without passing through the liquid phase. This is to distinguish it from the term, “condense,” which is used herein to refer to the process of a gas changing to a liquid state directly. The term “solidify” refers to the process of a liquid changing to a solid.
As used herein, “liquid-liquid” separators refer to a device that separates one liquid compound from another liquid compound. This includes decanters, centrifuges, settling tanks, thickeners, clarifiers, distillation columns, flash vessels, or similar devices used in the art.
Purifying natural gas can be complex and energy inefficient. The methods, devices, and systems disclosed herein overcome these limitations, as well as providing other benefits that will be apparent to those of skill in the art. A natural gas stream is cooled in an exchanger. This exchanger has the necessary temperature gradients and pressure to condense a portion of the methane and a portion of the carbon dioxide and to desublimate substantially all of the water and at least a portion of the carbon dioxide present in the natural gas stream, resulting in a solid. process individually, as detailed below.
The preferred methods, devices, and systems disclosed herein have advantages compared to some current technologies. These may include:
1. Avoiding the chemical hazards and costs associated with amine absorption technologies;
2. Combining natural gas sweetening (CO2 removal), drying (H2O removal), NGLs recovery, and trace gas mitigation (H2S and N2 removal) into a single process step and vessel;
3. Treating natural gas without reducing pressure, thereby decreasing repressurization equipment requirements and costs while also decreasing equipment size;
4. Improving NGLs recovery;
5. Enabling treatment of high-carbon dioxide natural gas streams;
6. Reducing treatment facility size, health and environmental hazards, and capital costs; and,
7. Reducing process energy consumption and cost.
The methods, devices, and systems disclosed are used to treat natural gas at typical plant delivery pressures of 60-100 bar, as well as other natural gas streams. The single step process simultaneously removes moisture, and carbon dioxide and methane. When NGLs are present, these are also removed in the single step. This may occur in a single vessel, such as in an indirect-contact exchanger or in a direct-contact exchanger configured as a counter-current spray column, packed column, staged column, or other vessels typically used for direct-contact exchange. As the gases condense, the volumetric flow rate and downstream equipment sizes decrease significantly. The products from the vessel, after solid-liquid separation, may be rewarmed to near the initial operating temperature by helping to pre-cool upstream flows.
In one embodiment, substantially all of the water is removed from the feed gas stream. In a preferred embodiment, “substantially all of the water” should leave no more than 1 ppm water in the depleted gas stream. In a more preferred embodiment, “substantially all of the water” should leave no more than 100 ppb water in the depleted gas stream. In an even more preferred embodiment, “substantially all of the water” should leave no more than 10 ppb water in the depleted gas stream. In a most preferred embodiment, “substantially all of the water” should leave no more than 1 ppb water in the depleted gas stream.
In one embodiment, substantially all of the NGLs is removed from the feed gas stream. In a preferred embodiment, “substantially all of the NGLs” should leave no more than 1 ppm NGLs in the depleted gas stream. In a more preferred embodiment, “substantially all of the NGLs” should leave no more than 100 ppb NGLs in the depleted gas stream. In an even more preferred embodiment, “substantially all of the NGLs” should leave no more than 10 ppb NGLs in the depleted gas stream. In a most preferred embodiment, “substantially all of the NGLs” should leave no more than 1 ppb NGLs in the depleted gas stream.
In one embodiment, substantially all of the carbon dioxide is removed from the feed gas stream. In a preferred embodiment, “substantially all of the carbon dioxide” should leave no more than 120,000 ppm carbon dioxide in the depleted gas stream. In a more preferred embodiment, “substantially all of the carbon dioxide” should leave no more than 50,000 ppm carbon dioxide in the depleted gas stream. In an even more preferred embodiment, “substantially all of the carbon dioxide” should leave no more than 1,000 ppm carbon dioxide in the depleted gas stream. In a most preferred embodiment, “substantially all of the carbon dioxide” should leave no more than 50 ppm carbon dioxide in the depleted gas stream.
In some embodiments, the NGLs comprise compounds selected from the group consisting of ethane, propane, butane, isobutane, pentane, natural gasoline, cyclic hydrocarbons, aromatic hydrocarbons, or combinations thereof.
In some embodiments, the contact liquid stream may consist of water, ethers, alcohols, hydrocarbons, liquid ammonia, liquid carbon dioxide, cryogenic liquids, or a combination thereof.
In some embodiments, the contact liquid stream may consist of a mixture of a solvent and an ionic compound. The solvent may be water, hydrocarbons, liquid ammonia, liquid carbon dioxide, cryogenic liquids, or a combination thereof. The ionic compound may be potassium carbonate, potassium formate, potassium acetate, calcium magnesium acetate, magnesium chloride, sodium chloride, lithium chloride, calcium chloride, or a combination thereof.
In some embodiments, the contact liquid stream may be a mixture of a solvent and a soluble organic compound. The solvent may be water, hydrocarbons, liquid ammonia, liquid carbon dioxide, cryogenic liquids, or a combination thereof. The soluble organic compound may be glycerol, ammonia, propylene glycol, ethylene glycol, ethanol, methanol, or a combination thereof.
In some embodiments, the hydrocarbons may consist of 1,1,3-trimethylcyclopentane, 1,4-pentadiene, 1,5-hexadiene, 1-butene, 1-methyl-1-ethylcyclopentane, 1-pentene, 2,3,3,3-tetrafluoropropene, 2,3-dimethyl-1-butene, 2-chloro-1,1,1,2-tetrafluoroethane, 2-methylpentane, 3-methyl-1,4-pentadiene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-methylpentane, 4-methyl-1-hexene, 4-methyl-1-pentene, 4-methylcyclopentene, 4-methyl-trans-2-pentene, bromochlorodifluoromethane, bromodifluoromethane, bromotrifluoroethylene, chlorotrifluoroethylene, cis 2-hexene, cis-1,3-pentadiene, cis-2-hexene, cis-2-pentene, dichlorodifluoromethane, difluoromethyl ether, trifluoromethyl ether, dimethyl ether, ethyl fluoride, ethyl mercaptan, hexafluoropropylene, isobutane, isobutene, isobutyl mercaptan, isopentane, isoprene, methyl isopropyl ether, methylcyclohexane, methylcyclopentane, methylcyclopropane, n,n-diethylmethylamine, octafluoropropane, pentafluoroethyl trifluorovinyl ether, propane, sec-butyl mercaptan, trans-2-pentene, trifluoromethyl trifluorovinyl ether, vinyl chloride, bromotrifluoromethane, chlorodifluoromethane, dimethyl silane, ketene, methyl silane, perchloryl fluoride, propylene, vinyl fluoride, or a combination thereof.
In one embodiment, cooling the feed gas stream condenses a portion of the carbon dioxide and a portion of the water, but none of the methane is condensed. This is useful when only some of the carbon dioxide and water need to be removed from the feed gas stream.
The invention has been described with reference to various specific and preferred embodiments and techniques. Nevertheless, it understood that many variations and modifications may be made while remaining within the spirit and scope of the invention.
This invention was made with government support under DE-FE0028697 awarded by the Department of Energy. The government has certain rights in the invention.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2528028 | Barry | Oct 1950 | A |
| 3376709 | Dickey | Apr 1968 | A |
| 3724226 | Pachaly | Apr 1973 | A |
| 20190128603 | Baxter | May 2019 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20200018547 A1 | Jan 2020 | US |
