Radiant syngas cooler

Abstract

A system for exchanging heat comprising a header oriented vertically within a pressure vessel, the header configured to receive a coolant stream from a coolant source or deliver a coolant stream to a coolant sink; one or more platen tubes in fluid flow communication with the header; wherein the one or more platen tubes comprise a vertical section and a non-vertical section; wherein the non-vertical section of the one or more platen tubes is configured to receive the coolant stream from or discharge the coolant stream to the header.

Description

RADIANT SYNGAS COOLERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application 63 / 539,362 filed September 20, 2024 and is incorporated herein by reference.BACKGROUND

[0002] The partial combustion or gasification of solid carbonaceous fuels to produce sythesis gases, or syngas, having value as residential and industrial fuels, as starting materials for synthesis of chemicals and fuels, and as an energy source for generations of electricity has long been recognized and practiced on varying scales throughout the world. The term “solid carbonaceous fuel” as used herein is intended to include various gas- carried combustible materials and mixtures thereof, and may be selected from the group of coal, coke from coal, coal liquefaction residues, petroleum coke, soot, biomass, and particulate solids derived from oil shale, tar sands and pitch. The coal may be of any type, including lignite, sub-bituminous, bituminous and anthracite.

[0003] A gasification reactor produces hot syngas comprising hydrogen and carbon monoxide which may be contacted with one or more heat exchangers to recover high quality heat as steam. One such heat exchanger is a radiant syngas cooler or RSC. An RSC is a large and complex piece of capital equipment that provides maximum heat exchange area within the pressure vessel.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The present invention will hereinafter be described in conjunction with the appended figures wherein like numerals denote like elements:

[0005] Fig. 1 is a schematic view of a cutaway profile of a radiant syngas cooler.

[0006] Fig. 2 is a schematic view illustrating a system delivering boiler feed water to a radiant syngas cooler and collecting steam and heated boiler feed water from the radiant syngas cooler.

[0007] Fig. 3 is a schematic view of a cutaway profile of a radiant syngas cooler zoomed in to show a tube cage and platens in greater detail.

[0008] Fig.4 is a schematic view depicting two embodiments for improving packing density of platens.

[0009] Fig. 5 is a schematic view of the structure of non-staggered platens in greater detail.

[0010] Fig. 6 is a schematic view of cross-sections of non-staggered platens and staggered platens at different elevations.

[0011] Fig. 7 is a plan view of a single platen with vertical top and bottom platen headers with vertically oriented platen tubes.

[0012] Fig. 8 is a schematic view of a single platen with vertical top platen header showing the connection to the top header in greater detail.

[0013] Fig. 9 is a schematic view depicting a modification of Fig. 8 in which platen tubes connect at or near the base of the vertical header.

[0014] Fig. 10 is a schematic view depicting a modification of Fig. 8 in which a vertical tube aligned with the vertical header is omitted.

[0015] Fig. 11 is a schematic view depicting a modification of Fig. 8 in which platen tubes are asymmetrically connected to the vertical header.

[0016] Fig. 12 is a schematic view of a top flange that connects the top of a radiant syngas cooler to the bottom of a gasifier.

[0017] Fig. 13 is a schematic view depicting a modification of Fig. 12 that eliminates the need for a forging ring.DETAILED DESCRIPTION

[0018] The ensuing detailed description provides preferred exemplary embodiments only, and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the ensuing detailed description of the preferred exemplary embodiments will provide those skilled in the art with an enabling description for implementing the preferred exemplary embodiments of the invention. Various changes may be made in the function and arrangement of elements without departing from the spirit and scope of the invention, as set forth in the appended claims.

[0019] Fig. 1 shows a cutaway profile of a radiant syngas cooler or RSC. Typically an RSC comprises a pressure vessel 101 to house heat tansfer surfaces, a waterwall liner made up of parallel tubes forming a tube cage 103 that pass a coolant stream such as boiler feed water (BFW), and a quench chamber 105 in the bottom portion to use direct contact with water 104 to cool and partially scrub the syngas 106 which exits via line 108.The tube cage 103 may form a roof 107 at the top of the tube cage, and may be supported by a load support ring, also known as a forging ring, near the top of the vertical section of the RSC vessel wall. The pressure vessel typically comprises a heavy ring at the top called a forging ring that supports the piping for steam generating in the RSC. The parallel tubes in the waterwall liner may be welded together to form a contiguous surface and may or may not include webbing between the tubes. Within the waterwall liner may be arranged one or more platens 109 that also pass a coolant stream such as BFW. Each platen comprises a horizontal inlet header, a horizontal outlet header, and platen tubes that typically extend for nearly the full axial length of the tube cage. The platens are supported by a “spider” support located between the dome of the RSC vessel and the roof. One or more downcomers 111 and risers 113 that pass coolant through the tube cage 103 and platens 109 must pass through the forging ring. When a large number of downcomers 111 and risers 113 must pass through the forging ring, this requires the forging ring to be thicker to provide mechanical support.

[0020] An annular space 115 between the pressure vessel and the waterwall liner may be purged with a seal media 117 such as nitrogen, carbon dioxide, clean recycled syngas, or superheated steam to limit the ingress of syngas into the annular space 115. The annular space 115 may be further sealed with a first seal 119 such as a bellows seal between the inlet throat and the top of the pressure vessel, and a second seal 121 such as a baffle seal near the bottom of the tube cage.

[0021] Fig. 2 shows a schematic diagram illustrating the system delivering BFW to the RSC and collecting steam and heated BFW from the RSC. A steam drum 201 supplies BFW to a circulation pump 203, although circulation of BFW may also be provided by thermosyphon or pumping with a thermosyphon assist. The mixture of steam and heated BFW returning via the risers 205 enters the steam drum 201 , where the steam 207 is separated and drawn off the top of the steam drum 201. Makeup BFW 209 may be added to the steam drum 201 as needed.

[0022] Fig. 3 shows a cutaway profile of an RSC zoomed in to show the tube cage 301 and platens 303 in greater detail. Water flows through one or more downcomers 305 into the top of the pressure vessel, down between the tube cage 301 and pressure vessel sidewall 307. Three connections are shown in Fig. 3, one for tube cage bottom header 309 and one each for the inner and outer platen bottom headers 311. The downcomer connections for the platen bottom headers 311 may pass through the tube cage 301 usingseals such as box seals to accommodate thermal expansion. Alternatively, the downcomer connections for the platen bottom headers 311 may be routed from the tube cage 301 itself and expansion joints used to accommodate thermal expansion. Any number of downcomers may be distributed radially around the RSC to connect to the platen 303 and tube cage bottom header 309. BFW is heated and boils as it travels up through the tube cage 301 and inner and outer platens 303 before being collected in the top platen headers 313 and top ring header 315. The top platen headers 313 may deliver steam and heated BFW to one or more risers 317 exiting the top of the pressure vessel via the top ring header 315 and / or direct connectors 318. Just as in the bottom headers 311 , the risers 317 may utilize expansion joints to accommodate thermal expansion. The top and bottom platen headers may curve to follow the desired profile of the platens, and must be of significantly larger diameter than the platen tubes. The increased size of the top and bottom platen headers therefore constrain the total number of platen tubes that can fit in an RSC of given size. The effect is amplified if the platen headers are insulated.

[0023] The distribution of platens within the RSC is a key constraint on the design of a gasification process. The platens typically are responsible for more than half of the heat exchange duty of the RSC, so maximizing the available surface area for heat exchange allows more throughput for a given size of RSC. For large projects the outer diameter of the pressure vessel is constrained by transportation regulations, so an attractive way to improve throughput is to increase the packing efficiency of the platens. Since the platen headers are larger in diameter than the platen tubes, packing the platen headers more efficiently reduces the space between adjacent platens, allowing more platens to be used in a given space.

[0024] Fig. 4 shows two embodiments for improving the packing density of the platens. The first, A, features platen tubes 401 of equal length with alternating platens staggered in the axial direction such that neighboring headers 403 are at different elevations. The second, B, features platen tubes 405 of alternating length such that the top platen headers 407 at a higher elevation than their neighbors are connected to bottom platen headers at a lower elevation than their neighbors.

[0025] Fig. 5 shows the structure of the non-staggered platens in greater detail. The top platen headers 501 and bottom platen headers 503 curve in a J shape, with the curved end closer to the pressure vessel wall and the straight end extending into the center of the RSC. The cross-section at the level of the headers is densely-packed compared to therelatively open cross-section at the level of the platen tubes 505. In at least some embodiments the top and bottom platen headers are insulated, further increasing both their diameter and the difficulty in packing more platens into the RSC. Insulation may be used for the top and bottom platen headers because the pipe walls are thicker, increasing the risk of overheating and failure without insulation. The platen tubes 505 are shown to extend radially away from and then move back towards the plane of the vertical tubes before connecting to the top and bottom header. This design enables closer packing of the tubes within the platen..

[0026] Fig. 6 shows cross-sections of non-staggered platens on the left and staggered platens on the right at different elevations. The top-left shows a first cross-section 601 of non-staggered platens at the level of the top and bottom headers and the bottom-left shows a second cross-section 603 at the level of the platen tubes. Open tubes represent the large diameter headers and the closed circles represent the smaller diameter platen tubes. The top-right shows a third cross-section 605 of staggered platens at the level of the higher elevation top headers, the bottom-middle shows a fourth cross section 607 of staggered platens at the level of the lower elevation top headers, and the bottom-right shows a fifth cross section 609 of staggered platens at the level of the platen tubes. Comparing the top-left to both the top-right and bottom-middle it can be seen that the staggered platen headers are less closely packed, allowing freer flow of syngas up through the RSC. The more open design of the staggered platens is seen both in the top-left, where only the risers from the lower elevation top headers are adjacent to the higher elevation top headers, and in the bottom-middle, where the smaller diameter platen tubes are adjacent to the lower elevation top headers. Rerouting the risers from the lower elevation top headers could open up even more space. Comparing the bottom-left to the bottom-right shows that the total number of platen tubes is unchanged. This shows that by utilizing staggered platens in the same size RSC, either more platens could be added, the size of the top and bottom headers could be increased, the thickness of insulation in the top and bottom headers could be increased, or any combination of the three. Similarly, more space is made available for top and bottom headers, downcomers, and risers.

[0027] Fig. 7 shows a plan view of a single platen with vertical top and bottom platen headers with vertically oriented platen tubes. Vertical top headers 701 and vertical bottom headers 703 may simplify the connection of vertical risers to the headers. Platen tubes 705 may bend away from the vertical direction, such as horizontally, to connect to the top and bottom platen headers. As in Fig. 1 , the platen tubes may have webbing 707 betweenthe tubes. Platen tubes may have partial webbing or no webbing between the tubes. For example, in superheated steam generation service, it may be desired to have spacing between the platen tubes. The platen tubes are shown with 90° bends, but any angle and radius of curvature could be chosen based on criteria such as flow characteristics, structural integrity of the platen tubes, desired spacing between adjacent tubes, or desired points of contact between adjacent tubes, or the manufacturing method. The vertical top and bottom headers may improve syngas flow circulation in the areas adjacent to the top and bottom headers. Fig. 8 shows the connection of the platen tubes to the top platen header in greater detail at a series of horizontal cross-sections. From the elevation of A- A looking down, the platen tubes can be seen curving away from the plane of the vertical tube sheet to connect into the top header. Comparing the cross sections at the elevation of B-B and C-C, the alternating directions of the curve away from the plane can be seen. Connecting on both sides of the top and bottom header allow a greater number of connections per unit length of header compared to a horizontal header, allowing a reduction in the length of the vertical top and bottom header. Finally, the cross section at the elevation of D-D shows that the platen tubes between the top and bottom headers are unchanged compared to the platen tubes with horizontal headers. In Fig. 8 the cross section of the platen tubes take the shape of an arc, but any shape suitable for heat transfer with the syngas may be used. The bottom platen header may be connected in the same way, reflected vertically. The vertical top and bottom headers may reduce in cross-sectional area as they approach the platen tubes to further improve spacing.

[0028] A person of skill in the art will appreciate that the vertical header may take on other embodiments as dictated by requirements of welding, distribution of BFW in the header, or the flow of syngas around the platen. One such modification is to have the platen tubes connect at or near the base of the vertical header as shown in Fig. 9. One or more vertical headers with a smaller diameter than the top vertical header distribute BFW to the platen tubes. The vertical header may have a short horizontal header 901 to accommodate the one or more distribution pipes. Fig. 10 shows a modification of the vertical header in which the vertical tube aligned with the vertical header is omitted. This may be desired to improve syngas flow around the platen. Fig. 11 shows a modification of the vertical header in which the platen tubes are asymmetrically connected to allow more independent positioning of the vertical header with respect to the top of the pressure vessel and the platen tubes within the pressure vessel. Positioning the vertical header further from the leading edge of the platen tubes may reduce the risk of overheating thevertical header. Vertical headers may also be staggered as shown in Fig. 6. Vertical headers may also be staggered in a direction such as radially relative to the centerline of the RSC. Any of the vertical headers described in this disclosure may be chosen independently for the top and bottom of the platen tubes. Similarly, any of the vertical headers described in this disclosure may be connected to the top of the platen tubes and a horizontal header as shown in Fig. 5 may be connected to the bottom of the platen tubes, or vice versa. A mixed header design can be implemented wherein a first portion of the platen tubes connect to a horizontal portion of the header located at the end of a vertical portion of the header and a second portion of the platen tubes connect to a vertical portion of the header. Multiple vertical headers for different platens may be connected to one another by a common horizontal header.

[0029] Fig. 12 shows a drawing of a top flange that connects the top of an RSC to the bottom of a gasifier. A forging ring 1201 reinforces the top of the RSC where downcomers 1203 and risers 1205 enter and exit the RSC. A downcomer is defined as a pipe bringing liquid water into the RSC to be indirectly heated by the syngas stream leaving the gasifier bottom. A riser is defined as a pipe bringing steam and liquid water out of the RSC to be utilized onsite or exported after being separated in a steam drum. The forging ring may form an integral part of the RSC vessel. The forging ring is much thicker than the top head and side wall of the RSC to support the large number of closely spaced penetrations required through the dome for the downcomers and risers.

[0030] Fig. 13 shows a drawing of the top section of an RSC that eliminates the need for a forging ring. At least a portion of the downcomers are relocated from the top head of the RSC to instead enter the RSC around the top of the sidewall of the RSC. And at least a portion of the risers 1301 are relocated to exit the top head of the RSC over a wider area of the top head. The downcomers 1403 may enter the RSC and the risers 1405 may exit the RSC at one or more elevation levels. This may eliminate the need for the forging ring in Fig. 12. Distributing the downcomers and risers in this fashion reduces the number of openings through the top head of the RSC. An increased spacing between the downcomer and riser openings makes it possible to use larger welding ligaments and reinforce the openings. The routing of the internal piping within the RSC is simplified due to the spacing, which also reduces piping congestion. These benefits are possible without sacrificing any best practices from known RSC design such as accomodating differential thermal expansion between the downcomer and riser piping, the methods and mechanical integrityof the structural supports, the distribution systems for boiler feed water and / or steam, and the throat, roof, tube cage, platens, and the vessel walls.

[0031] Aspects of this invention include, but are not limited to:

[0032] Aspect 1 : A system for exchanging heat comprising a header oriented vertically within a pressure vessel, the header configured to receive a coolant stream from a coolant source or deliver a coolant stream to a coolant sink; one or more platen tubes in fluid flow communication with the header; wherein the one or more platen tubes comprise a vertical section and a non-vertical section; wherein the non-vertical section of the one or more platen tubes is configured to receive the coolant stream from or discharge the coolant stream to the header.

[0033] Aspect 2: A system according to Aspect 1 , wherein the non-vertical section comprises a horizontal section.

[0034] Aspect 3: A system according to Aspect 1 or Aspect 2, wherein the non-vertical section deviates in the radial direction towards or away from the pressure vessel wall immediately before connecting with the header.

[0035] Aspect 4: A system according to Aspect 3, wherein the non-vertical section section deviates in the opposite radial direction as the next closest non-vertical section.

[0036] Aspect 5: A system according to any of Aspects 1 to 4, further comprising a vertical gap in the one or more platen tubes aligned with the header.

[0037] Aspect 6: A system according to any of Aspects 1 to 5, wherein the header decreases in cross-sectional area when traveling away from the source or sink of the coolant stream.

[0038] Aspect 7: A system according to any of Aspects 1 to 6, wherein the one or more platen tubes have a center in a horizontal plane and the header is offset in the horizontal plane with respect to the center.

[0039] Aspect 8: A system according to any of Aspects 1 to 7, wherein the one or more platen tubes are in thermal contact with one another to form a single heat exchange surface.

[0040] Aspect 9: A system for exchanging heat comprising a plurality of platens, each platen comprising a top header in fluid flow communication with a coolant source, one or more platen tubes in fluid flow communication with the top header, and a bottom headerin fluid flow communication with the one or more platen tubes; wherein each top header and each bottom header has a vertical elevation; wherein the vertical elevation of the top headers of adjacent platens are offset from one another by at least the thickness of the top headers; wherein the vertical elevation of the bottom headers of adjacent platens are offset from one another by at least the thickness of the bottom headers.

[0041] Aspect 10: A system according to Aspect 9, wherein the top header is vertically offset from the adjacent top header in the same vertical direction as the bottom header in fluid flow communication with the top header is vertically offset from the adjacent bottom header.

[0042] Aspect 11 : A system according to Aspect 9, whereinthe top header is vertically offset from the adjacent top header in the opposite vertical direction as the bottom header in fluid flow communication with the top header is vertically offset from the adjacent bottom header.

[0043] The articles "a" or "an" as used herein mean one or more when applied to any feature in embodiments of the present invention described in the specification and claims. The use of "a" and "an" does not limit the meaning to a single feature unless such a limit is specifically stated. The article “the” preceding singular or plural nouns or noun phrases denotes a particular specified feature or particular specified features and may have a singular or plural connotation depending upon the context in which it is used.

[0044] The term “and / or” placed between a first entity and a second entity includes any of the meanings of (1) only the first entity, (2) only the second entity, or (3) the first entity and the second entity. The term “and / or” placed between the last two entities of a list of 3 or more entities means at least one of the entities in the list including any specific combination of entities in this list. For example, “A, B and / or C” has the same meaning as “A and / or B and / or C” and comprises the following combinations of A, B and C: (1) only A, (2) only B, (3) only C, (4) A and B but not C, (5) A and C but not B, (6) B and C but not A, and (7) A and B and C.

[0045] The adjective “any” means one, some, or all, indiscriminately of quantity.

[0046] The phrase “at least a portion” means “a portion or all.” The “at least a portion of a stream” has the same composition, with the same concentration of each of the species, as the stream from which it is derived.

[0047] As used herein, “first,” “second,” “third,” etc. are used to distinguish among a plurality of steps and / or features, and is not indicative of the total number, or relative position in time and / or space, unless expressly stated as such.

[0048] While the principles of the invention have been described above in connection with preferred embodiments, it is to be clearly understood that this description is made only by way of example and not as a limitation of the scope of the invention.

Claims

CLAIMS1 . A system for exchanging heat comprising: a header oriented vertically within a pressure vessel, the header configured to receive a coolant stream from a coolant source or deliver a coolant stream to a coolant sink; one or more platen tubes in fluid flow communication with the header; wherein the one or more platen tubes comprise a vertical section and a non-vertical section; wherein the non-vertical section of the one or more platen tubes is configured to receive the coolant stream from or discharge the coolant stream to the header.

2. The system of claim 1 , wherein the non-vertical section comprises a horizontal section.

3. The system of claim 1 , wherein the non-vertical section deviates in the radial direction towards or away from the pressure vessel wall immediately before connecting with the header.

4. The system of claim 3, wherein the non-vertical section section deviates in the opposite radial direction as the next closest non-vertical section.

5. The system of claim 1 , further comprising a vertical gap in the one or more platen tubes aligned with the header.

6. The system of claim 1 , wherein the header decreases in cross-sectional area when traveling away from the source or sink of the coolant stream.

7. The system of claim 1 , wherein the one or more platen tubes have a center in a horizontal plane and the header is offset in the horizontal plane with respect to the center.

8. The system of claim 1 , wherein the one or more platen tubes are in thermal contact with one another to form a single heat exchange surface.

9. A system for exchanging heat comprising: a plurality of platens, each platen comprising a top header in fluid flow communication with a coolant source, one or more platen tubes in fluid flowcommunication with the top header, and a bottom header in fluid flow communication with the one or more platen tubes; wherein each top header and each bottom header has a vertical elevation; wherein the vertical elevation of the top headers of adjacent platens are offset from one another by at least the thickness of the top headers; wherein the vertical elevation of the bottom headers of adjacent platens are offset from one another by at least the thickness of the bottom headers.

10. The system of claim 9, wherein the top header is vertically offset from the adjacent top header in the same vertical direction as the bottom header in fluid flow communication with the top header is vertically offset from the adjacent bottom header.

11. The system of claim 9, wherein the top header is vertically offset from the adjacent top header in the opposite vertical direction as the bottom header in fluid flow communication with the top header is vertically offset from the adjacent bottom header.

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