Coalescer for co-current contactors
10486100 ยท 2019-11-26
Assignee
Inventors
- Stephanie A. Freeman (Houston, TX)
- Edward J. Grave (Montgomery, TX, US)
- J. Tim Cullinane (Montgomery, TX, US)
- P. Scott Northrop (Spring, TX, US)
- Norman K. Yeh (Shenandoah, TX, US)
Cpc classification
B01D11/0419
PERFORMING OPERATIONS; TRANSPORTING
B01D53/18
PERFORMING OPERATIONS; TRANSPORTING
C10G21/00
CHEMISTRY; METALLURGY
B01D53/526
PERFORMING OPERATIONS; TRANSPORTING
C10L2290/541
CHEMISTRY; METALLURGY
C10L3/10
CHEMISTRY; METALLURGY
B01D53/1462
PERFORMING OPERATIONS; TRANSPORTING
International classification
B01D53/18
PERFORMING OPERATIONS; TRANSPORTING
C10G21/00
CHEMISTRY; METALLURGY
C10L3/10
CHEMISTRY; METALLURGY
Abstract
The disclosure includes a method, comprising passing a fluid into a co-current contactor, passing a solvent into the co-current contactor, dividing the solvent into solvent droplets having a first average droplet size, placing the fluid in contact with the solvent droplets to create a combined stream, coalescing at least a portion of the solvent droplets to create solvent droplets having a second average droplet size, wherein the second average droplet size is greater than the first average droplet size, and separating the fluid and the solvent.
Claims
1. A method, comprising: passing a fluid into a co-current contactor, the fluid including a hydrocarbon and a contaminant; passing a solvent into the co-current contactor, dividing the solvent into solvent droplets having a first average droplet size; placing the fluid in contact with the solvent droplets to create a combined stream; absorbing the contaminant into the solvent droplets; coalescing at least a portion of the solvent droplets to create solvent droplets having a second average droplet size, wherein the second average droplet size is greater than the first average droplet size; separating the fluid from the solvent droplets; collecting the solvent droplets in a boot; and recycling gas, collecting in the boot, to the co-current contactor via a recycle gas inlet.
2. The method of claim 1, wherein the first average droplet size is between less than about 1 micrometer (m) and about 1000 m.
3. The method of claim 1, wherein the second average droplet size is between about 2 micrometers (m) and about 10000 m.
4. The method of claim 1, wherein coalescing comprises electrically inducing coalescence, mechanically inducing coalescence, or both.
5. The method of claim 1, wherein coalescing takes between less than about 0.01 seconds and about 15 seconds of residence time.
6. The method of claim 1, wherein coalescing comprises passing the combined stream through a pre-coalescer to create solvent droplets having a third average droplet size, wherein the third average droplet size is greater than the first average droplet size and less than the second average droplet size.
7. The method of claim 1, wherein the fluid and the solvent are liquids.
Description
DESCRIPTION OF THE DRAWINGS
(1) So that the manner in which the present invention can be better understood, certain illustrations, charts and/or flow charts are appended hereto. It is to be noted, however, that the drawings illustrate only selected embodiments of the inventions and are therefore not to be considered limiting of scope, for the inventions may admit to other equally effective embodiments and applications.
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DETAILED DESCRIPTION
(7) As used herein, an acid gas means any gas that dissolves in water producing an acidic solution. Non-limiting examples of acid gases include hydrogen sulfide (H.sub.2S), carbon dioxide (CO.sub.2), sulfur dioxide (SO.sub.2), carbon disulfide (CS.sub.2), carbonyl sulfide (COS), mercaptans, or mixtures thereof.
(8) As used herein, the term atomize means to divide, reduce, or otherwise convert a liquid into minute particles, a mist, or a fine spray of droplets having an average droplet size within a predetermined range.
(9) As used herein, the term co-current contacting device or co-current contactor means an apparatus, e.g., a pipe, a vessel, a housing, an assembly, etc., that receives (i) a stream of gas (or other fluid stream to be treated) and (ii) a separate stream of solvent (or other fluid treating solution) in such a manner that the gas stream and the solvent stream contact one another while flowing in generally the same direction within the contacting device.
(10) As used herein, the term contaminant means an acid gas, water, another undesirable component, or a combination thereof absorbable by a selected solvent.
(11) As used herein, the term flue gas means any gas stream generated as a by-product of hydrocarbon combustion.
(12) As used herein, the term fluid refers to gases, liquids, and combinations of gases and liquids, as well as to combinations of gases and solids, and combinations of liquids and solids.
(13) As used herein, the term hydrocarbon refers to an organic compound that includes primarily, if not exclusively, the elements hydrogen and carbon. Hydrocarbons generally fall into two classes: aliphatic, or straight chain hydrocarbons, and cyclic, or closed ring, hydrocarbons including cyclic terpenes. Examples of hydrocarbon-containing materials include any form of natural gas, oil, coal, and bitumen that can be used as a fuel or upgraded into a fuel.
(14) As used herein, the term industrial plant refers to any plant that generates a stream containing at least one hydrocarbon or an acid gas. One non-limiting example is a coal-powered electrical generation plant. Another example is a cement plant that emits CO.sub.2 at low pressures.
(15) With respect to fluid processing equipment, the term inline may mean that two or more items are placed along a flow line such that a fluid stream undergoing fluid separation moves from one item of equipment to the next while maintaining flow in a substantially constant downstream direction, and/or that the two or more items are connected sequentially or, more preferably, are integrated into a single tubular device.
(16) As used herein, the terms lean and rich, with respect to the absorbent liquid removal of a selected gas component from a gas stream, are relative, merely implying, respectively, a lesser or greater degree of content of the selected gas component. The respective terms lean and rich do not necessarily indicate or require, respectively, either that an absorbent liquid is totally devoid of the selected gaseous component, or that it is incapable of absorbing more of the selected gas component. In fact, it is preferred, as will be evident hereinafter, that the so called rich absorbent liquid produced in a first contactor in a series of two or more contactors retains significant or substantial residual absorptive capacity. Conversely, a lean absorbent liquid will be understood to be capable of substantial absorption, but may retain a minor concentration of the gas component being removed.
(17) As used herein, the term natural gas refers to a multi-component gas obtained from a crude oil well (associated gas) or from a subterranean gas-bearing formation (non-associated gas). The composition and pressure of natural gas can vary significantly. A typical natural gas stream contains methane (C.sub.1) as a significant component. The natural gas stream may also contain ethane (C.sub.2), higher molecular weight hydrocarbons, one or more acid gases, and water. The natural gas may also contain minor amounts of contaminants such as nitrogen, iron sulfide, and wax.
(18) As used herein, the term non-absorbing gas means a gas that is not absorbed by a solvent during a gas treating or conditioning process, e.g., during co-current contacting.
(19) As used herein, the term solvent means a liquid phase fluid or a multiphase fluid (a fluid comprising both a liquid and gas phase) that preferentially absorbs one or more component over other components. For example, a solvent may preferentially absorb a contaminant, e.g., acid gas, thereby removing or scrubbing at least a portion of the contaminant from a contaminated stream, e.g., a contaminated natural gas stream.
(20) As used herein, the term sweetened gas stream refers to a fluid stream in a substantially gaseous phase that has had at least a portion of acid gas components removed. Further, the term sweetened may also refer to a fluid stream that has been subjected to a dehydration or other conditioning process.
DESCRIPTION OF SPECIFIC EMBODIMENTS
(21)
(22) The gas processing system 100 may employ a number of vertically oriented co-current contacting systems 104A-F. In some embodiments, each vertically oriented co-current contacting system 104A-F includes vertically oriented co-current contactor upstream of a separation system. In other embodiments, each vertically oriented co-current contacting system 104A-F includes a number of vertically oriented co-current contactors upstream of a single separation system. As would be apparent to those of skill in the art, any or all of the co-current contacting systems 104A-F may be either vertically oriented or horizontally oriented, depending on the details of the specific implementation, and such alternate embodiments are within the scope of this disclosure.
(23) The gas stream 102 may be a natural gas stream from a hydrocarbon production operation. For example, the gas stream 102 may be a flue gas stream from a power plant, or a synthesis gas (syn-gas) stream. If the natural gas stream 102 is a syn-gas stream, the gas stream 102 may be cooled and filtered before being introduced into the gas processing system 100. The gas stream 102 may also be a flash gas stream taken from a flash drum in a gas processing system itself. In addition, the gas stream 102 may be a tail gas stream from a Claus sulfur recovery process or an impurities stream from a regenerator. Furthermore, the gas stream 102 may be an exhaust emission from a cement plant or other industrial plant. In this instance. CO.sub.2 may be absorbed from excess air or from a nitrogen-containing flue gas.
(24) The gas stream 102 may include a non-absorbing gas, such as methane, and one or more impurities, such as an acid gas. For example, the gas stream 102 may include CO.sub.2 or H.sub.2S. The gas processing system 100 may convert the gas stream 102 into a sweetened gas stream 106 by removing the acid gases.
(25) In operation, the gas stream 102 may be flowed into a first co-current contacting system 104A, where it is mixed with a solvent stream 108. If the gas processing system 100 is to be used for the removal of H.sub.2S, or other sulfur compounds, the solvent stream 108 may include an amine solution, such as monoethanol amine (MEA), diethanol amine (DEA), or methyldiethanol amine (MDEA). Other solvents, such as physical solvents, alkaline salts solutions, or ionic liquids, may also be used for H.sub.2S removal. In embodiments used for other purposes, such as dehydration or reactions, other solvents or reactants, such as glycols, may be used. The solvent stream 108 may include a lean solvent that has undergone a desorption process for the removal of acid gas impurities. For example, in the gas processing system 100 shown in
(26) In various embodiments, the gas processing system 100 employs a series of co-current contacting systems 104A-F. In some embodiments, as shown in
(27) Before entering the first co-current contacting system 104A, the natural gas stream 102 may pass through an inlet separator 114. The inlet separator 114 may be used to clean the natural gas stream 102 by filtering out impurities, such as brine and drilling fluids. Some particle filtration may also take place. The cleaning of the natural gas stream 102 can prevent foaming of solvent during the acid gas treatment process.
(28) As shown in
(29) Once inside the first co-current contacting system 104A, the natural gas stream 102 and the solvent stream 108 move along the longitudinal axis of the first co-current contacting system 104A. As they travel, the solvent stream 108 interacts with the H.sub.2S, H.sub.2O, and/or other impurities in the natural gas stream 102, causing the H.sub.2S, H.sub.2O, and/or other impurities to chemically attach to or be absorbed by the amine molecules. A first partially-loaded, or rich, gas solvent or treating solution 118A may be flowed out of the first co-current contacting system 104A. In addition, a first partially-sweetened natural gas stream 120A may be flowed out of the first co-current contacting system 104A and into a second co-current contacting system 104B. This general arrangement may be referred to as arranging co-current contactors in a counter current configuration.
(30) As shown in the example illustrated in
(31) As the progressively-sweetened natural gas streams 120A-E are generated, the gas pressure in the gas processing system 100 will gradually decrease. As this occurs, the liquid pressure of the progressively-richer gas treating solutions 118A-F may be correspondingly increased. This may be accomplished by placing one or more booster pumps (not shown) between each co-current contacting system 104A-F to boost liquid pressure in the gas processing system 100.
(32) In the gas processing system 100, solvent streams may be regenerated by flowing the partially-loaded gas treating solutions 118A and 118B through a flash drum 121. Absorbed natural gas 122 may be flashed from the partially-loaded gas treating solutions 118A and 118B within the flash drum 121, and may be flowed out of the flash drum 121 via an overhead line 124.
(33) The resulting rich solvent stream 126 may be flowed from the flash drum 121 to the regenerator 110. The rich solvent stream 126 may be introduced into the regenerator 110 for desorption. The regenerator 110 may include a stripper portion 128 including trays or other internals (not shown). The stripper portion 128 may be located directly above a heating portion 130. A heat source 132 may be provided with the heating portion 130 to generate heat. The regenerator 110 produces the regenerated, lean solvent stream 112 that is recycled for re-use in the final co-current contacting system 104F. Stripped overhead gas from the regenerator 110, which may include concentrated H.sub.2S (or CO.sub.2), may be flowed out of the regenerator 110 as an overhead impurities stream 134.
(34) The overhead impurities stream 134 may be flowed into a condenser 135, which may cool the overhead impurities stream 134. The resulting cooled impurities stream 138 may be flowed through a reflux accumulator 140. The reflux accumulator 140 may separate any remaining liquid, such as condensed water, from the impurities stream 138. This may result in the generation of a substantially pure acid gas stream 142, which may be flowed out of the reflux accumulator 140 via an overhead line 144.
(35) In some embodiments, if the initial natural gas stream 102 includes CO.sub.2, and a CO.sub.2-selective solvent stream 108 is used, the acid gas stream 142 includes primarily CO.sub.2. The CO.sub.2-rich acid gas stream 142 may be used as part of a miscible EOR operation to recover oil. If the oil reservoir to be flooded does not contain a significant amount of H.sub.2S or other sulfur compounds, the CO.sub.2 to be used for the EOR operation may not contain significant H.sub.2S or other sulfur compounds. However, concentrated CO.sub.2 streams from oil and gas production operations may be contaminated with small amounts of H.sub.2S. Thus, it may be desirable to remove the H.sub.2S from the CO.sub.2, unless the acid gas stream 142 is to be injected purely for geologic sequestration.
(36) While a gas stream 102 is discussed herein, those of skill in the art will appreciate that generally the same principles may be applied to any fluid stream, including with respect to liquid-liquid contacting. Consequently, use of the phrases gas stream. gas inlet, gas outlet, etc. are to be understood as non-limiting and may optionally be replaced with fluid stream, fluid inlet. fluid outlet, and so forth in various embodiments within the scope of this disclosure. Use of the phrases gas stream, gas inlet, gas outlet, etc. are for the sake of convenience only.
(37) In some embodiments, if the initial natural gas stream 102 includes H.sub.2S, an H.sub.2S-selective solvent stream 108 may be used to capture the H.sub.2S. The H.sub.2S may then be converted into elemental sulfur using a sulfur recovery unit (not shown). The sulfur recovery unit may be a so-called Claus unit. Those of ordinary skill in the art will understand that a Claus process is a process that is sometimes used by the natural gas and refinery industries to recover elemental sulfur from H.sub.2S-containing gas streams.
(38) In practice, the tail gas from the Claus process, which may include H.sub.2S, SO.sub.2, CO.sub.2, N.sub.2, and water vapor, can be reacted to convert the SO.sub.2 to H.sub.2S via hydrogenation. The hydrogenated tail gas stream has a high partial pressure, a large amount of CO.sub.2. e.g., more than 50%, and a small amount of H.sub.2S, e.g., a few percent or less. This type of gas stream, which is typically near atmospheric pressure, is amenable to selective H.sub.2S removal. The recovered H.sub.2S may be recycled to the front of the Claus unit, or may be sequestered downstream. Alternatively, a direct oxidation of the H.sub.2S to elemental sulfur may be performed using various processes known in the field of gas separation.
(39) As shown in
(40) The lean solvent stream 112 may be at a low pressure. Accordingly, the lean solvent stream 112 may be passed through a pressure boosting pump 150. From the pressure boosting pump 150, the lean solvent stream 112 may be flowed through a cooler 154. The cooler 154 may cool the lean solvent stream 112 to ensure that the lean solvent stream 112 will absorb acid gases effectively. The resulting cooled lean solvent stream 156 is then used as the solvent stream for the final co-current contacting system 104F.
(41) In some embodiments, a solvent tank 158 is provided proximate the final co-current contacting system 104F. The cooled lean solvent stream 156 may be flowed from the solvent tank 158. In other embodiments, the solvent tank 158 is off-line and provides a reservoir for the lean solvent stream 156.
(42) The process flow diagram of
(43)
(44) Because the partially-loaded gas treating solution 118B received by the first co-current contacting system 104A in
(45) Alternatively, a semi-lean liquid stream could be taken from other sweetening operations in the gas processing system 160 and used, at least in part, as an amine solution for the first or second co-current contacting system 104A or 104B. In this respect, there are situations in which a single type of solvent is used for more than one service in the gas processing system 160. This is referred to as integrated gas treatment. For example, MDEA may be used both for high-pressure, H.sub.2S-selective acid gas removal, as well as in a Claus tail gas treating (TGT) process. The rich amine stream from the TGT process is not heavily loaded with H.sub.2S and CO.sub.2, owing to the low pressure of the process. Thus, in some embodiments, the rich amine stream from the TGT process is used as a semi-lean stream for the first or second co-current contacting system 104A or 104B. The semi-lean stream (not shown) may be pumped to a suitable pressure and injected into the first or second co-current contacting system 104A or 104B, possibly along with the partially-loaded gas treating solution from the succeeding co-current contacting system.
(46) Further, in the gas processing system 160 of
(47) The process flow diagram of
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(49) In operation, each contacting unit 202a-202d receives a natural gas stream 102 at an inlet section 220a-220d, where the inlet nozzles 208a-208d atomize a lean solvent stream 206 and expose it to the natural gas stream 102, creating a mixed, two-phase flow or combined stream (not depicted). The mixed, two-phase flow or combined stream passes through a mass transfer section 222 where absorption occurs. The mass transfer section 222 may comprise a tubular body having a substantially empty bore having one or more surface features, e.g., a hydrophobic surface, a superhydrophobic surface, a raised surface, a recessed surface, or any combination thereof, along an inner surface of the mass transfer section 222. A separation section 224 follows the mass transfer section. In the separation section 224, entrained liquid droplets are removed from the gas stream. e.g., using a cyclone inducing element, resulting in an at least partially dehydrated and/or decontaminated treated gas stream. In some embodiments, the inlet section 220 and the mass transfer section 222 may collectively be referred to as a contacting section. The length of the contacting section may be determined based on the residence time required to obtain a predetermined decontamination and/or dehydration level for the natural gas stream 102. e.g., in view of the intended flow rate, pressure drop, etc. The treated gas stream exits the contacting units 202a-202d through the outlet section 226. The contacting units 202a-202d may operate at about 400 psig to about 1,200 psig, or higher. Because the contacting units 202a-202d must be individually constructed so as to tolerate these pressures, weight and/or footprint increases linearly as the number of contacting units 202a-202d is increased.
(50) As co-current contactors become more compact, both in length and diameter, it is important to ensure as much solvent as possible reacts in the increasingly shortened mixing and/or mass transfer section. The H.sub.2S reaction is instantaneous relative to the CO.sub.2 reactions, lowering the residence time, i.e., the contact time between the vapor and liquid phases, will result in less CO.sub.2 being absorbed into the solvent. The design of the co-current contacting systems 104A-F enhances selective H.sub.2S removal due to the short contact time inherent in the equipment design. Disclosed herein are techniques for inhibiting or impeding an amount of liquid from propagating along a wall of the mass transfer section using a surface feature. By inhibiting or impeding liquid propagation along a wall of the mass transfer section, a comparatively greater amount of solvent is retained in the interior volume of the mass transfer section and, consequently, remains available for reaction.
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(53) In operation, the solvent entering the coalescing section 402 may have an average droplet size in a range from a first average droplet size to a second average droplet size, wherein the first average droplet size is any of: less than about 1 micrometer (m), about 1 m, about 5 m, about 10 m, about 25 m, about 50 m, about 75 m, about 100 m, about 250 m, about 500 m, or about 750 m, and wherein the second average droplet size is any of: about 2 m, about 5 m, about 10 m, about 25 m, about 50 m, about 75 m, about 100 m, about 250 m, about 500 m, about 750 m, or about 1000 m. After passing through the one or more coalescer(s) 404, the solvent may have an average droplet size in a range from a first average droplet size to a second droplet size, wherein the first average droplet size is any of: about 1 m, about 5 m, about 10 m, about 25 m, about 50 m, about 75 m, about 100 m, about 250 m, about 500 m, about 750 m, about 1000 m, about 2500 m, about 5000 m, about 7500 m, or about 9000 m, and wherein the second average droplet size is any of: about 2 m, about 5 m, about 10 m, about 25 m, about 50 m, about 75 m, about 100 m, about 250 m, about 500 m, about 750 m, about 1000 m, about 2500 m, about 5000 m, about 7500 m, or about 10000 m. In embodiments with a pre-coalescer, after passing through the pre-coalescer, the solvent may have an average droplet size in a range from a first average droplet size to a second droplet size, wherein the first average droplet size is any of: about 1 m, about 5 m, about 10 m, about 25 m, about 50 m, about 75 m, about 100 m, about 250 m, about 500 m, about 750 m, about 1000 m, about 2500 m, about 5000 m, about 7500 m, or about 9000 m, and wherein the second average droplet size is any of: about 2 m, about 5 m, about 10 m, about 25 m, about 50 m, about 75 m, about 100 m, about 250 m, about 500 m, about 750 m, about 1000 m, about 2500 m, about 5000 m about 7500 m, or about 10000 m.
(54) The average residence time in the coalescer for a gas-liquid contacting system may be in a range from a first average residence time to a second average residence time, wherein the first average residence time is any of: less than about 0.01 seconds (s), about 0.01 s, about 0.1 s, or about 0.2 s, and wherein the second average residence time is any of: about 0.01 s, about 0.1 s, or about 0.2 s. The average residence time in the coalescer for a liquid-liquid contacting system may be in a range from a first average residence time to a second average residence time, wherein the first average residence time is any of: less than about 0.1 seconds (s), about 1 s, about 5 s, or about 10 s, and wherein the second average residence time is any of: about 1 s, about 5 s, about 10 s, or about 15 s.
(55) While it will be apparent that the invention herein described is well calculated to achieve the benefits and advantages set forth above, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the spirit thereof.