Patent Application
20100031570
This invention relates generally to partial oxidation gasifiers and gas coolers and, more particularly, to reducing wear on internal components of an integral gasifier and gas cooler combination.
At least some known gasification vessels include areas that are prone to elevated amounts of wear due to the flow characteristics of the raw effluent gas passing these areas and the adverse conditions of temperature, pressure, and chemistry these areas are exposed to. For example, but not limited to a gasifier bottom transition, a gasifier throat, and a syngas cooler throat are high wear zones for refractory linings because the narrow flow path increases the mass flow rates of molten slag along the lining wall. Although some attempts to mitigate the effects of the adverse conditions affecting the refractory have been tried, the attempts have tended to create other problems. For example, one known attempt to actively cool the affected areas resulted in a vertical expansion gap in the throat lining between the actively cooled and passively cooled section. The gap provides a potential leak path of syngas into the annular space behind the vertical tube cage. Another attempt used a vertical steel cylindrical gas barrier with a flanged bottom behind the throat refractory to prevent gas from escaping into the stagnant annular zone. However, the steel cylinder is not cooled, therefore leading to either overheating of metal or shorter refractory life. Further, in the known gasification vessels the inside diameter of the flow path in the throat is constrained by the inside diameter of the flanges of both the gasifier and syngas cooler. The flow path diameter cannot be changed without significantly altering the steel vessels.
Providing a gasifier having an integrated cooler formed integrally with the gasifier eliminates a forged flange on the gasifier vessel and a forged flange on the cooler vessel. Elimination of these two large flanges in the integrated gasifier/cooler significantly reduces the cost of the gasifier/cooler over the separate gasifier and cooler configuration. Elimination of the flange-to-flange joint between the gasifier and the syngas cooler permits the combined axial length of the two vessels to be significantly reduced. The reduced length reduces the thermal growth of the combined vessel, thus reducing the mismatch with the interconnecting piping (injectors, steam drum, steam piping, instrumentation) that are fixed to the support structure which is at ambient temperature with minimal thermal growth. Elimination of the flange-to-flange joint also improves the integrity of the vessel and facilitates eliminating components (flanges, supports, etc.) and reducing erection operations.
In one embodiment, an integrated gasifier and syngas cooler includes a gasifier including a reaction chamber, a syngas cooler integrally formed with the gasifier and including at least one heat exchanger element, and a transition portion integrally formed with the reaction chamber and the syngas cooler and extending therebetween, the transition portion further includes a throat extending between the reaction chamber and the syngas cooler and the transition portion further includes a heat exchanger circumscribing the throat.
In another embodiment, an integrated gasifier and syngas cooler system includes a first pressure vessel portion surrounding a gasifier reaction chamber wherein the first portion extends from a vessel head to a lower end. The system also includes a second pressure vessel portion surrounding a gas cooler configured to cool a hot raw effluent gas stream from the gasifier reaction chamber. The second portion extends from an upper end vertically downward towards a solids removal end. The system further includes a transition portion extending between the lower end and the upper end wherein each of the first portion, the second portion, and the transition portion are in substantial vertical coaxial alignment along a central longitudinal axis of each portion. The system includes a throat coaxially aligned with each portion and extending therebetween for the free passage of the hot raw effluent gas stream from the gasifier reaction chamber to the gas cooler, the throat is lined about a radially inner surface with a refractory material. The system further includes a concentric coaxial vertical tube cage surrounding the throat along at least a portion of a length of the throat, and a plurality of annular anchoring rings coupled to at least one of the first portion and the tube cage, the anchoring rings extending radially inward and are configured to support the throat refractory material.
In yet another embodiment, a method of assembling an integrated gasifier and syngas cooler includes providing a syngas cooler vessel that is integrally formed with a gasification vessel wherein the gasification vessel includes a reaction chamber and the syngas cooler vessel includes a heat exchanger. The method also includes coupling the reaction chamber and the syngas cooler vessel in flow communication using a throat lined with a refractory material wherein the refractory material is supported in the throat using one or more annular anchoring rings. The method further includes positioning a cooling tube cage surrounding the throat such that during operation the refractory material is cooled using the cooling tube cage.
It should be noted that although embodiments of the present invention are described with respect to an integral gasifier and syngas cooler combination, one of ordinary skill in the art should understand that the embodiments of the present invention are not limited to being used only with integral gasifier and syngas cooler combinations. Rather, embodiments of the present invention may be used with any integrated vessels.
The following detailed description illustrates embodiments of the invention by way of example and not by way of limitation. It is contemplated that the invention has general application to cooling internal components of vessels to extend their life in industrial, commercial, and residential applications.
As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. 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.
Transition portion 112 includes a tube cage comprising a membrane wall of cooling tubes 214 extending circumferentially around throat 114. A stagnant annular space 216 extending radially outward from cooling tubes 214 to transition portion 112 provides an area for risers and downcorners (both not shown) that supply water and remove water and steam from cooler 110. Throat 114 is lined with a throat layer 218 of refractory bricks that extends from a third annular anchoring ring 220 coupled to cooling tubes 214 upward to bottom exit passage 116. Anchoring ring 220 extends radially inward from cooling tubes 214 and supports throat layer 218. Between throat layer 218 and first layer 202, sloped layer 222 of refractory brick is supported by a fourth annular anchoring ring 224 coupled to and extending radially inward from cooling tubes 214. Because first layer 202 is supported by first annular anchoring ring 208, which is coupled to upper shell 104 and sloped layer 222 is supported by third anchoring ring 220, which is coupled to cooling tubes 214 during certain operations of vessel 200, first layer 202 and sloped layer 222 may move axially relative to each other due to differential expansion between upper shell 104 and cooling tubes 214. Accordingly, an abutting joint between first layer 202 and sloped layer 222 is vertically aligned such that first layer 202 and sloped layer 222 may slide past each other relatively freely during periods of differential expansion and contraction. Such slidable engagement facilitates avoiding compression of first layer 202 and sloped layer 222 which may cause cracking of first layer 202 and/or sloped layer 222 and to avoid forming gaps between first layer 202 and sloped layer 222.
Stagnant annular space 216 is positioned outside refractory lined transition throat cylinder 114 and inside transition portion 112 and has an increased volume compared to a flanged joint configuration. This increased volume permits an embodiment of the present invention with boiler feed water piping and support structure inside annular space 216. The embodiment reduces thermal stress of pipe components and joints with the vessel due to thermal expansion mismatch by permitting more flexible pipe routing. The embodiment also provides sufficient space to route a top header (not shown) into annular space 216 above a horizontal tube wall (not shown). The embodiment adds additional tube panel surface area inside the hot gas path under the horizontal tube wall that increases the heat recovery performance or reduces the total axial length of the syngas cooler assembly. Additionally, the embodiment simplifies the support structure for the vertical tube panels by permitting direct connection to the vessel wall, which frees up more annular space for better access and design flexibility.
A first layer 302 of refractory brick is stacked circumferentially about an outer periphery of reaction zone 106, and a second layer 304 of refractory brick stacked radially outward from first layer 302. First layer 302 is supported at a lower end 306 by a first annular anchoring ring 308 that extends radially inward from support skirt 301. A second annular anchoring ring 310 provides support to second layer 304 and also extends radially inward from support skirt 301 at a position spaced axially from first annular anchoring ring 308. First layer 302 and second layer 304 are stacked such that seams between adjacent bricks in first layer 302 do not align with seams between adjacent bricks in second layer 304. Such misalignment presents a labyrinthine path between reaction zone 106 and upper shell 104 that facilitates preventing hot raw effluent gas from reaction zone 106 from leaking from reaction zone 106 and entering space 212, where corrosive constituents of the hot raw effluent gas can attack upper shell 104.
Transition portion 112 includes a tube cage comprising a membrane wall of cooling tubes 214 extending circumferentially around throat 114. Stagnant annular space 216 extends radially outward from cooling tubes 214 to transition portion 112 to provide an area for risers and downcorners (both not shown) that supply water and remove water and steam from gas cooler 110. Throat 114 is lined with a throat layer 218 of refractory bricks that extends from a third annular anchoring ring 220 coupled to cooling tubes 214 upward to bottom exit passage 116. Anchoring ring 220 extends radially inward from cooling tubes 214 and supports throat layer 218.
A fourth anchoring ring 312 extends radially inward from support skirt 301 to a radially outer periphery of throat layer 218. Anchoring ring 312 supports a transition layer 314 of refractory brick and/or castable refractory material. Transition layer 314 provides for sliding engagement between first layer 302 and transition layer 314, and between throat layer 218 and transition layer 314 to account for differential expansion and contraction between cooling tubes 214 and upper shell 104.
Exemplary embodiments of systems and methods for an integral gasifier and syngas cooler combination are described above in detail. The systems and methods illustrated are not limited to the specific embodiments described herein, but rather, components of the system may be utilized independently and separately from other components described herein. Further, steps described in the method may be utilized independently and separately from other steps described herein. For example, step 508 shown in
Embodiments of the integral vessel that encloses the reactor, the syngas cooler, and the transition in between eliminate a flanged joint between the reactor, the syngas cooler, and the transition, thus separating the gas path transition (throat) 114 from the outer vessel transition 112. Such a configuration permits a shorter throat length than vessel configurations that include separate vessels with a flanged transition between them while maintaining the same or a larger annular space 216. The integral configuration also permits cooling throat refractory lining 218 along its entire length and/or cooling transition refractory 314.
Embodiments of the present invention provide for reducing overall vessel length, reducing piping length and pipe stress, reducing material and fabrication cost, and the following improvement concepts and benefits; a steam-cooled throat refractory lining, a steam-cooled transition portion and throat refractory lining, “drip points” in the throat flow path, which are only effective using the reduced length throat that embodiments of the present invention permit. Embodiments of the present invention also permit gas flow moderation and a longer life transition point, an expansion feature of the gasification portion-to-throat transition brick allowing thicker brick for longer life at a high wear point, a ship lap expansion joint, a steam cooled refractory brick lining, modified support features of gasifier sidewall, gasifier transition, gasifier throat and syngas cooler throat linings, an integral gasifier and syngas cooler vessel, and a flexible flow path diameter and shape in the refractory lined throat wherein the variable diameter can be realized using stepwise increase in lining thickness.
The steam cooled refractory lining in the transition and/or throat allows longer run life and less down times for refractory replacement, which increases the availability of gasification process and reduces operation cost. The steam cooled refractory lining also adds flexibility in adjusting syngas velocity and/or mass and momentum flux exiting the throat by means of variable diameter in the refractory lined throat. Active cooling of the refractory lining is accomplishing by extending the steam cooled tubes from the syngas cooler into the gasifier and/or tube cage. The integrated vessel and refractory lining permits the flexibility of varying the refractory lined throat flow path diameter and shape without alternating the steel vessel flanges. The throat shape could be cylindrical, conical, or flaring out with the diameter increasing as the flow approaches the downstream exit of the throat.
The above-described embodiments of a method and system for an integrated gasifier and syngas cooler system provides a cost-effective and reliable means for eliminating the horizontal flange-to-flange joint between the gasifier and the syngas cooler using instead a non-continuous and integral vessel that encloses the refractory-lined gasification reaction chamber and the syngas cooler heat exchanger internals together in the single vessel. Additionally, embodiments of the present invention provide sufficient internal volume in the gasifier-to-syngas cooler transition area to extend the throat tube cage to the bottom transition of the gasifier, which enables steam cooling of the refractory lining of the entire length of the throat, and/or of the entire throat plus the 45 degree bottom transition in the gasifier. The steam-cooled refractory lining has a longer life that without active steam cooling in the throat. Further, the supports of the refractory linings in the gasifier sidewall, transition, and throat sections accommodate the expansion and contraction of the gasifier sidewall, transition, and throat sections during periods of temperature changes. Accordingly, direct leak paths in the refractory lining for syngas to flow into the transition area are substantially eliminated. As a result, the methods and systems described herein facilitate gasification and cooling of a fuel in a cost-effective and reliable manner.
While the disclosure has been described in terms of various specific embodiments, it will be recognized that the disclosure can be practiced with modification within the spirit and scope of the claims.
