Patent Grant
11185811
This invention relates to a method and a system for separating liquid and solid phase substances from a gas stream and more specifically, this invention relates to a method and a system for separating liquid components (e.g. H2O, CO, CO2), and or solid components (e.g. H2O, CO, CO2) from effluent.
Removal and sequestration of CO2 and other moieties from gas streams continues to be researched. State of the art methods include adsorption monoliths such as those researched at Oak Ridge National Laboratories, membrane absorption, and cryogenic distillation.
The aforementioned techniques require special materials and/or high maintenance.
Other state of the art removal techniques, such as centrifugal stratification, compress the target moieties into a liquid or solid phase, then remove same from the gas stream. But during removal, the liquid/solid phases travel through flow fields and their viscous heating effects. This causes the liquid/solid phases to re-vaporize, therefore stymieing separation efforts.
A need exists in the art for a method and system to efficiently remove targeted moieties from gas streams, such as those generated at power plants. The method and system should be integrated so as to be modular and/or require a small footprint. The method and system should utilize low cost technology and not require special adsorbents or other proprietary substrates. Finally the method and system should remove from 50 percent to 100 percent of the target moieties depending on the aerodynamic design, geometrical design and operating conditions.
An object of the invention is to provide a system and method for removing targeted moieties from gas streams that overcomes many of the drawbacks of the prior art.
Another object of the invention is to provide a system and method for efficiently extracting target moieties from gas streams. More than one moiety may be removed simultaneously. A feature of the invention is combining supersonic expansion and oblique shock compression (SEOSC) to liquefy and/or solidify the target moieties to facilitate their removal from the gas streams. An advantage of the invention is that no specialty chemicals or training is necessary.
Yet another object of the invention is to provide a method for extracting condensed liquid and solid components, (e.g. H2O, CO, CO2) from a gas stream. A feature of the invention is imparting a ridged body rotation to an outward radial flow of gas which has an initial supersonic expansion followed by an oblique shock compression. An advantage of the method is that it maintains both the supersonic expansion and the oblique shock compression flow processes to be as nearly irrotational and inviscid as is possible. This is done to minimize any thermal heating effects and recompression effects caused by boundary layers. Another advantage is that the efficiency of the extraction is enhanced given a near instantaneous application of both fluid effects on the gas stream.
Still another object of the invention is to provide a method and system for separating CO2 from a bulk raw gas flow. For example, the invention may be applied to an effluent stream of a conventional power plant, particularly if that stream is pressurized. In such a case, H2O and/or CO2 and/or CO would precipitate out. A feature of the invention is the coaxial positioning of a circular array of supersonic expanders within a circular array of oblique shock inducers. An advantage of the invention is that the configuration produces a subsonic multi-phase radial and rotating flow in the outer collection vessel.
Another object of the invention is to provide a mechanical means for liquidizing or solidifying gaseous target molecules from a gas stream for separation. A feature of the invention is that no sorbent or solvent is necessary to implement the system or process. An advantage is that flue gas may not need to be pretreated (such as dried) prior to separation procedures. Another advantage is that solids handling is no longer a formidable task.
Another object of the invention is to provide a compact system and process for separating target molecules from a carrier gas stream. A feature of the invention is the encapsulation of a supersonic gas expander and an oblique shock diffuser within the confines of a particle separator. Another feature is the implementation of rigid body rotation to the expander and compressor. An advantage of the invention is that particle separation becomes an integral part of the expansion and compression processes.
Another advantage is that the integration of all three processes allows its implementation to be used as a recirculation pump for the carrier gas.
Briefly, the invention provides a method for removing target moieties from gas streams, the method comprising simultaneously subjecting the streams to supersonic expansion and oblique shock compression along with ridged body rotation.
Also provided is a system for removing target moieties from gas streams, the system comprising a supersonic expander coaxially positioned within an array of oblique shock inducers.
The invention together with the above and other objects and advantages will be best understood from the following detailed description of the preferred embodiment of the invention shown in the accompanying drawings, wherein:
The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings.
All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (e.g., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure.
The recitation of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).
The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.
As used herein, an element or step recited in the singular and preceded with the word “a” or “an” should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly stated. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
Furthermore, references to “one embodiment” of the present invention are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property.
The invention provides an inviscid irrotational process for separating target moieties from a gas stream. Multiple components could be made to condense or to solidify out. For example, a syngas stream comprised of H2O, CO, CO2 and H2 could be expanded, and recompressed so that the H2O, CO and CO2 would precipitate out leaving only enriched H2. The H2O would come out first, and the CO and CO2 would come out second.
The process could also be designed to selectively get only the H2O out but leave the CO, CO2 and H2 in a gaseous state.
The process and system may receive raw or scrubbed and dehydrated flue gas from a combustion process providing a gaseous stream comprised of N2, CO2, Hg, K, O2 and perhaps particulates, wherein the CO2 and/or other compounds and elements are targeted for removal.
The invented process and system is applicable for removal of H2O, CO, CO2, CH4 or any component of a syngas stream or any other gas mixture, while the carrier gas, which is the predominant component of the gas mixture, remains in gaseous state. For example, the invention can be applied to Integrated Gasification Fuel Cell (IGFC) systems to enrich H2 in a syngas stream by condensing out all of the other components leaving only H2 in a gaseous state.
Supersonic velocities are based on achieving phase change of the target compound, while maintaining non-target moieties in gas phase. As such, phase change diagrams are consulted to determine optimal pressures and temperatures for specific moiety separation.
Application areas for the invention include any gas separation process, high pressure gasification systems (in which case the pressurized process can be operated very efficiently), gas turbine fuel cell hybrid systems, gas recirculation pumps, and others. The raw or treated gas may be supplied to the expansion means at a first pressure range of about 50 atmospheres and below. The carrier gas may be N2 and the target constituent CO2.
In the context of a magnetohydrodynamic MHD generation topping cycle—this separator may remove potassium-salt seed particles for recovery. The temperatures at which K2CO3 reforms from K+ and combustion products is high, so the shocking design is adjusted accordingly. After seeded combustion-gases surrender heat first to open-cycle, and then closed-cycle MHD, the carbonates are removed to prepare the gas to drive a turbine. In the context of coal combustion Hg would drop out as well—especially if there are NOx molecules in the gas.
The fluid stream is then compressed 14 or decelerated to a subsonic velocity. (The expansion step upstream may be ongoing during this deceleration step.) This compression enables the liquefied/solidified target material to pass through the remaining gas stream without contacting the heated boundary layers inherent with such compression. The liquefied or solidified target material is subsequently separated from the stream via conventional means such as a solid separator (e.g., centrifugal, electrostatic impingement) 16.
The system 10 may be serially applied to the same gas stream source to independently separate multiple target moieties. Alternatively, a plurality of systems may be imposed on the same gas stream simultaneously to extract different moieties at the same time.
The gaseous target moiety and the carrier gas comprising the gaseous stream have comparative properties such that the target moiety changes phase from the gaseous state by desublimation or condensation at a higher temperature than the carrier phase, over a given pressure range where the separation operation is to be conducted. The gaseous mixture is accelerated to a supersonic velocity causing a pressure and temperature decrease, followed by a deceleration resulting in a pressure and temperature increase. The acceleration and deceleration provide a temperature and pressure profile such that the target moiety changes phase from the gaseous state by desublimation or condensation, thereby producing a non-gaseous collectible constituent. The carrier gas remains in the gaseous phase.
The temperature and pressure of the gaseous stream decrease during the acceleration to the specified supersonic velocity.
Expander/Nozzle Detail
With reference to
The expander 12 is a nozzle or an array of nozzles each of which are adapted to receive a gaseous mixture flow Go comprised of a carrier gas and a gaseous constituent (or several targeted constituents). The expander accelerates the flow to a specified supersonic velocity, producing supersonic flow Gs. For example, the expander 12 may be a converging-diverging nozzle designed to accelerate gaseous mixture flow Go from an initial subsonic velocity to a specified supersonic velocity.
Within this disclosure, supersonic flow Gs is comprised of the carrier gas in a gaseous phase, and either the gaseous constituent in a gaseous phase or the collectible constituent in a non-gaseous phase. Additionally, within this disclosure, when the supersonic flow achieves the acceleration temperature and acceleration pressure, this indicates that at least the gaseous phases of the supersonic flow are at the acceleration temperature and acceleration pressure condition. Any non-gaseous phases including the collectible constituent, if formed, may or may not have the equivalent temperature and pressure condition.
The acceleration temperature and acceleration pressure resulting from acceleration to a specified supersonic velocity may be predicted or otherwise determined by those skilled in the art for a given gaseous mixture and flow expander 12. As will be discussed infra, within this disclosure, the acceleration temperature and acceleration pressure must decrease sufficiently during the acceleration such that the gaseous constituent either crosses a phase boundary during the acceleration, or crosses a phase boundary during the subsequent deceleration, when the supersonic flow transits the deceleration temperature-pressure profile originating at the acceleration temperature and acceleration pressure.
As discussed supra, a means for rapidly expanding the gas stream may be a supersonic nozzle or a plurality of nozzles, the latter of which is arranged in a predetermined configuration, such as orthogonally extending from a common manifold, or circularly arranged about a common center.
A supersonic expansion nozzle has three district regions. There is a convergent section which has a continually decreasing cross-sectional area. In this section the flow accelerates from a subsonic speed of low Mach number to a near sonic speed at the end of the contraction section under the action of a pressure gradient. Although the flow at the end of the contraction section is near sonic speed it is still subsonic. This is followed by the throat section where the rate of change in the cross-sectional area changes from a contraction to an expansion. This causes the flow to make a transition from subsonic speed to supersonic speed. The throat is then followed by an expansion section were the cross-sectional area is continuously increased. Since the flow emerging from the throat area into the expansion section is slightly supersonic the expanding area in the expansion section causes the flow to accelerate to a much higher Mach number.
Either an axisymmetric nozzle where the cross-sectional area is typically circular, or a 2-D nozzle where the cross-sectional area is rectangular are suitable configurations. In an axisymmetric nozzle the diameter of the circular cross-section changes along the nozzle axis while in a 2-D nozzle the height of the rectangular cross-section changes along the nozzle axis while the width remains constant.
A plurality of supersonic nozzles are arranged to form a cylindrical array. Two different configurations of these arrays are shown in
Aerodynamic separation nozzles as are disclosed in U.S. Pat. Nos. 9,050,550; 8,313,547; and 8,016,901 cannot be used in the instant method and system given their propensity to create highly rotational flows. Such flows induce compression waves and shock waves on the inward turning wall and expansion waves on the outward turning wall. These complex flow structures interact and form a highly non-uniform rotational flow existing in the expansion section with significant production of shear stress and frictional heating. The result is that the entire axial direction of the flow field rotates along with the flow field itself. This allows the flow to be radially expanded and recompressed in a turning apparatus as an inviscid, irrotational flow without using shear stress forces that are generated from friction that is caused by swirl or turning of the side walls.
Thus, the flow field provided in the instant invention will not experience high shear stress, and thus not suffer frictional heating because the entire flow is rotated during both the expansion, and the compression. After the oblique shock diffusion process, the flow has been recompressed and it is in a subsonic state but it is still rotating with the same ridged body rotation of the apparatus. Therefore, in the annular region outside of the shock inducers, the flow will be rotational, but the very high shear stresses will not be a significant heating factor and mechanical particle separation can occur as it does in any cyclone separator.
In summary, preferably, any flow imposed by the supersonic nozzle remains inviscid and irrotational, with the bulk flow not having any shear strain.
A means for rapidly compressing the gas stream may be an oblique shock diffuser or a plurality of oblique shock diffusers. A plurality of oblique shock diffusers may be arranged in an cylindrical array or an axial array. After the radial flow passes through the oblique shock inducers, it has been shocked down to a subsonic state and so it may be treated as a subsonic multi-phase flow.
A salient feature of the invention is that the means for expanding the gas stream may be coaxially aligned and nested or otherwise positioned within the means for compressing the gas stream. This causes the simultaneous expansion and compression of a gas stream, thereby enabling immediate and long lasting separation of target compound from the gas stream for subsequent collection.
An exemplary nozzle is explained in U.S. Pat. No. 8,771,401, awarded to the applicant and incorporated herein in its entirety by reference.
The nozzle may be configured in a plurality of planar segments and arranged in a circular fashion so that the effluent of the carrier gas and the solid particles from the exit plane of the supersonic expander forms a radial flow. This radial flow is directed outward from the cylindrical expander exit plane.
A set of nozzles may be arranged in a circle with a first upstream end of each nozzle situated proximal to the center of the circle and a second downstream end situated proximal to the periphery of the circle. A plurality of circular arrays are collinearly arranged to form a cylindrical array. This cylindrical array therefore comprises a plurality of rows of nozzles each row defining a plane perpendicular to adjacent planes. The cylindrical array further defines a central shaft adapted to receive a fluid feed stream.
Each of the nozzles comprising the cylindrical array rotate about the axis of the array. All of the nozzles may turn in unison, which is to say a ridged body rotation is imparted to the entire array. Alternatively, some of the nozzles may not turn in unison with the rest of the nozzles. This serves to tune the system by optimizing pumping efficiency and adjust to any changes in the inlet-gas composition.
Both configurations do form radial supersonic nozzles with an initial contracting section, which accelerates a subsonic flow up to a sonic condition in the throat section where the change in cross-sectional area is zero, then followed by an expanding cross-sectional area where the flow passes from sonic speed to supersonic speed. Both configurations will form a radially expanding supersonic flow at the exit plane. They impart a radially directed supersonic flow, first subjecting raw fluid flow to a convergent region 22 (which is situated proximal to the center of the expander), then a throat region 24 (which is situated downstream from the convergent region, and then a divergent region 26 (which is situated proximal to the periphery of the expander.
Compressor Detail
The flow passing through both the cylindrical supersonic expander and the cylindrical oblique shock inducers with be directed radially outward. The flow comprises carrier gas which remains in the gaseous state and the solid or liquid particles of the target component that has changes phase from its original gaseous state.
As depicted in
The inventors have found that the formation and the separation of the precipitate is not just a function of pressure difference. It is also a strong function of aerodynamic design. Slight changes in diffuser geometry can significantly change the performance of the precipitation process.
The shock inducers are pointed up stream at the onset of the flow. They could define a straight surface like a wedge, in which case the inclination angle that the surface of the shock inducer makes with the radius is constant along the shock inducer. Alternatively, the inducers may define a more rounded apex (such as a bullet shape) in which case the inclination angle that the surface of the shock inducer makes with the radius continually decreases along the surface of the shock inducer. The best configuration may be a combination of these two extremes, and determined empirically.
The surface of the shock inducer may be formed by a series of straight line segments where each successive line segment in the series would make a smaller inclination angle with the radius. The crossing oblique shock pattern which is formed in this region of the flow would be maintained with a sequence of straight wall sections were the finite turning angle for each segment successively decreases and then remains constant until the next segment. The walls would have a finite turning angle at every point where the oblique shock waves reflects on the wall forming a new region.
For example, each of the oblique shock inducers are configured roughly as an elongated isosceles triangle stood on end with its tip or apex extending upstream or medially. The shock inducers are generally impermeable to the fluid with which they come in contact and are sufficiently rigid to impose their desired effect to the outwardly radially flowing fluid stream. A myriad of rigid materials are suitable as shock inducer constituents, including, but not limited to metals, plastics, carbon fiber, glass, composites, and combinations thereof.
The inducers may also be comprised of reversibly deformable materials such that the inducers reversibly deform during contact with radially directed fluids. Both passive and actively controlled deformable surfaces could be utilized. These deformable surfaces could be actively deformed in a controlled fashion, akin to ailerons on an air foil, or as a result of fluid flow inducing a torsional effect.
An embodiment of the compressor 14 comprises a plurality of oblique shock inducers 28 that are positioned as a columnar array.
The center space defined by the compressor may include a myriad of mounting features. The center space can have an axle, or a plurality of concentric axles which are rigidly connected to the rotating nozzle array either by spokes or by some other rigid substrate forming a connection. The high-pressure reservoir would be situated around the axle and could include the axle and also the rigid connections. The center of the nozzle array, around the axle and any other connecting hardware, defines a reservoir volume where high pressure gas is introduced in the device before it flows radially out into the initial contraction sections of the nozzles.
In the annular region 3R upstream of the shock inducers 28 and the fluid flow regions 4, 5, 6, etc between the inducers, the radial time constant will be much smaller than the angular time constant. If the reference frame is fixed in inertial space then the entire flow field will have an angular velocity which is very close to the angular rotation of the device. This angular velocity will be much less than the radial velocity of the supersonic flow. This is because the entire flow is rotating more or less as a ridged body at a speed which has to be very much less than the speed of sound.
As is shown in the figure with respect to a reference frame that is fixed to the rotating component, there is a very small, almost insignificant, angular velocity component to the flow field. This can be understood to be like the Coriolis force which arises in situations having a non-inertial reference frame. It is due to the acceleration force that is always observed in a rotating reference frame. As in the field of ballistics, this force is usually significantly smaller than the other forces that are acting. It only becomes important when the length and time scales become very large. So, in this situation the gas will expand and be recompressed without introducing significant shear forces, and without smashing particles or droplets into the nozzle walls or the shock inducers even though the entire flow field is being rotated.
In light of the foregoing, the supersonic flows in this region will be inviscid and irrotational. There will be no viscous heating in this region. As such, the liquid and/or precipitate will not re-gasify.
In the annular region outside the shock inducers the axial and radial time constants may be of the same order allowing for mechanical separation.
Inasmuch as the separated liquid- and/or solid-phase target material will settle to the lower portions of the remover 16, the lower half exterior surfaces of the remover 16 may be in thermal contact with a means for reducing the temperature of the surface so as to prevent regasification of the separated moieties. (The separated moieties are depicted in
A second means of egress 34 may be positioned superior to the position of the expander/inducer combination and formed with the inlet portal 30. This second means provides an exit ramp for the still gasified portion of the feedstream. Alternatively, the second means of egress 34 may be formed with a side wall of the remover housing, as shown. This side wall intersect configuration provides a means for preserving the swirling flow in the annular region of the containment vessel.
It is to be understood that the above description is intended to be illustrative, and not restrictive. The above-described embodiments (and/or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope.
While the dimensions and types of materials described herein are intended to define the parameters of the invention, they are by no means limiting, but are instead exemplary embodiments. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112, sixth paragraph, unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.
As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” “greater than,” “less than,” “more than” and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. In the same manner, all ratios disclosed herein also include all subratios falling within the broader ratio.
One skilled in the art will also readily recognize that where members are grouped together in a common manner, such as in a Markush group, the present invention encompasses not only the entire group listed as a whole, but each member of the group individually and all possible subgroups of the main group. Accordingly, for all purposes, the present invention encompasses not only the main group, but also the main group absent one or more of the group members. The present invention also envisages the explicit exclusion of one or more of any of the group members in the claimed invention.
The U.S. Government has rights in this invention pursuant to the employer-employee relationship of the Government to the inventors as U.S. Department of Energy employees and site-support contractors at the National Energy Technology Laboratory.
| Number | Name | Date | Kind |
|---|---|---|---|
| RE29128 | Sohre | Feb 1977 | E |
| 8771401 | VanOsdol | Jul 2014 | B2 |
| Entry |
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| Chen, G. et al., “The radial dimension of a supersonic jet expansion from conical nozzle,” American Institute of Physics, AIP Advances 6, (2016), pp. 11505-1 to 115015-7. |
