Patent Application
20170321884
The present invention generally relates a spray nozzle assembly for steam-desuperheating, a steam-desuperheating device using the nozzle assembly, and a method of steam-desuperheating using the device.
Many industrial facilities operate with superheated steam that has a higher temperature than its saturation temperature at a given pressure. However, a high amount of heat (superheat) in the steam can damage turbines or other downstream components, and thus, it is necessary to control the temperature of the steam. Desuperheating refers to the process of reducing the temperature of the superheated steam to a lower temperature, permitting operation of the system as intended, ensuring system protection, and correcting for unintentional deviations from the setpoint.
A steam desuperheater can lower the temperature of superheated steam by spraying cooling water into a flow of superheated steam that is passing through a steam pipe. Once the cooling water is sprayed into the flow of superheated steam, the cooling water mixes with the superheated steam and evaporates, drawing thermal energy from the steam and lowering its temperature. If the cooling water is sprayed into the superheated steam pipe as very fine water droplets or mist, then the evaporation of the cooling water in the superheated steam is fast, which is desirable. Conventionally, therefore, much effort has been made to ensure that water droplets have sufficiently small sizes.
Another critical requirement for efficient evaporation is good mixing of injected cooling water in the steam flow. In conventional methods wherein cooling water is sprayed into the steam pipe in a uniform conical pattern, mixing occurs primarily because of turbulence in the steam flow. In search of ways to improve the desuperheating process, the present inventor has conceived segmenting the spray pattern, and means to achieve such effect, to increase the mixing of the steam flow and the injected cooling water, and completed the invention.
Any discussion of problems and solutions in relation to the related art has been included in this disclosure solely for the purposes of providing a context for the present invention, and should not be taken as an admission that any or all of the discussion was known at the time the invention was made.
Some embodiments provide an improved nozzle assembly for desuperheating. In an embodiment, a nozzle assembly is provided with a splitter member which cuts a spray pattern into multiple segments. In a first embodiment, the nozzle assembly is used in a probe-type desuperheater, and the segmentation of the spray pattern can entrain surrounding hot steam within the core of the spray pattern, i.e., hot steam flows through the gaps between the segments and is enveloped by the cooling fluid flow, improving the mixing of the steam and the sprayed cooling fluid and increasing the evaporation rate of the cooling fluid, which are desirable in desuperheaters. It also allows injection of cooling fluid against the steam or vapor flow (counter flow injection) with minimal potential for droplets of cooling fluid to hit the probe-type desuperheater, wherein droplets of cooling fluid flow in segments and go around the probe located between the segments.
In a second embodiment, a nozzle assembly is used in a multi-nozzle ring desuperheater, wherein injection of cooling fluid is performed in a direction perpendicular to the steam or vapor flow (radial flow injection). In the second embodiment, the segmentation of the spray pattern entrains surrounding hot steam within the core of the spray pattern in the same manner as in the first embodiment, improving the mixing of the steam and the sprayed cooling fluid and increasing the evaporation rate of the cooling fluid, which are desirable in desuperheaters.
For purposes of summarizing aspects of the invention and the advantages achieved over the related art, certain objects and advantages of the invention are described in this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
Further aspects, features and advantages of this invention will become apparent from the detailed description which follows.
These and other features of this invention will now be described with reference to the drawings of preferred embodiments which are intended to illustrate and not to limit the invention. The drawings are greatly simplified for illustrative purposes and are not necessarily to scale.
In this disclosure, “steam” may include vaporized liquid which may be constituted by a mist of minute liquid droplets in gas (e.g., air) and may be constituted by a single vapor or a mixture of vapors, and typically the liquid is water. Also, in this disclosure, “cooling fluid” refers to a substance which is able to easily flow and form a mist of minute liquid droplets by being sprayed for cooling steam, and which is typically the same liquid as that constituting “steam”; however, in some embodiments, “cooling fluid” may be different from liquid constituting steam. Additionally, in this disclosure, an article “a” or “an” refers to a species or a genus including multiple species. Further, in this disclosure, any two numbers of a variable can constitute a workable range of the variable as the workable range can be determined based on routine work, and any ranges indicated may include or exclude the endpoints. Additionally, any values of variables indicated (regardless of whether they are indicated with “about” or not) may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments. The terms “constituted by” and “having” refer independently to “typically or broadly comprising,” “comprising,” “consisting essentially of” or “consisting of” in some embodiments.
In the present disclosure where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in view of the present disclosure, as a matter of routine experimentation.
In all of the disclosed embodiments, any element used in an embodiment can be replaced with any elements equivalent thereto, including those explicitly, necessarily, or inherently disclosed herein, for the intended purposes. Further, the present invention can equally be applied to apparatuses and methods.
In this disclosure, any defined meanings do not necessarily exclude ordinary and customary meanings in some embodiments.
The embodiments will be explained with respect to preferred embodiments. However, the present invention is not limited to the preferred embodiments.
In some embodiments, a nozzle assembly for spraying cooling fluid in a steam-desuperheating device, comprises: (i) a nozzle body defining a seating area and having an opening defining a flow passage extending through the seating area; (ii) a plug element movably attached to the nozzle body in the opening and selectively movable between closed and open positions relative thereto, wherein the plug element is seated against the seating area to close the flow passage in the closed position, and the plug element is away from the seating area to open the flow passage in the open position; and (iii) a splitter member fixed to a front face of the plug element, said splitter member having at least one splitter arm extending across the flow passage as viewed from the front of the plug element to cut the conical flow pattern of fluid sprayed through the flow passage.
In some embodiments, the splitter arm has a cross section which is a triangle with an apex facing the flow passage. In some embodiments, an angle at the apex of the triangle is about 25° to about 60° or any other suitable angles. In some embodiments, the at least one splitter arm is constituted by two splitter arms symmetrically extending in opposite directions. In some embodiments, the at least one splitter arm is constituted by three or more (e.g., four) splitter arms symmetrically extending in three or more respective directions. The symmetrical arrangement (e.g., line symmetry or point symmetry) of the splitter arms can create symmetrical segments of flow of sprayed cooling fluid and improve steam entrainment to the sprayed cooling fluid. In some embodiments, the nozzle assembly further comprises a biasing member disposed with a stem of the plug element to continuously bias the plug element toward the closed position. In some embodiments, the plug element has an outer diameter equivalent to an outer diameter of the opening of the nozzle body. In some embodiments, the splitter member is fixed to the front face of the plug element with screws or any other fastening tools.
In another aspect of the present invention, a probe-type steam-desuperheating device comprises: (a) a feeding pipe for feeding cooling fluid, having a lower end and an upper end; (b) a nozzle holder attached to the lower end of the feeding pipe; (c) a cooling fluid inlet port disposed at the upper end of the feeding pipe; (d) a flange provided in the feeding pipe, for attaching the feeding pipe to a steam pipe; and (e) at least one of the nozzle assembly disclosed herein attached to the nozzle holder in a manner such that an axis of the plug element is parallel to an axis of the steam pipe, wherein a length of the feeding pipe between the flange and the nozzle holder is set such that the axis of the plug element is aligned with the axis of the steam pipe. Depending on the size of the steam pipe, two or more nozzle assemblies can be installed on the same plane or different planes perpendicular to the axis of the steam pipe.
In some embodiments, the nozzle holder is disposed in a direction such that the front face of the plug element faces an upstream direction of steam flowing through the steam pipe. Alternatively, in some embodiments, the nozzle holder is disposed in a direction such that the front face of the plug element faces a downstream direction of steam flowing through the steam pipe. In some embodiments, the splitter arm extends in a direction in which the feeding pipe extends from the nozzle holder.
In still another aspect of the present invention, a multi-nozzle ring-type steam-desuperheating device comprises: (A) a circular feeding pipe with multiple branches for feeding cooling fluid having multiple branch ends and an upper end; (B) multiple nozzle holders attached to the multiple branch ends of the feeding pipe, respectively; (C) a cooling fluid inlet port disposed at the upper end of the feeding pipe; and (D) a plurality of the nozzle assemblies of claim 1 attached to the nozzle holders, respectively, in a manner such that each nozzle assembly is configured to gas-tightly communicate with the interior of a steam pipe, and an axis of each plug element is perpendicular to an axis of a steam pipe.
In some embodiments, each nozzle body is configured to gas-tightly communicate with the interior of the steam pipe. In some embodiments, the nozzle arm extends along an axis of the steam pipe.
In yet another aspect of the present invention, a method of desuperheating steam using any of the probe-type steam-desuperheating device disclosed herein, comprises: (I) supplying superheated steam in the steam pipe upstream of the probe-type steam-desuperheating device; (II) feeding cooling fluid to the cooling fluid inlet port of the probe-type steam-desuperheating device and spraying the cooling fluid from the nozzle assembly against flow of the superheated steam, thereby desuperheating the superheated steam while the superheated steam is passing through the probe-type steam-desuperheating device, wherein the cooling fluid sprayed out of the flow passage of the nozzle assembly flows against the flow of the superheated steam, and deflects to the direction of the flow of the superheated steam, wherein the cooling fluid sprayed out of the flow passage of the nozzle assembly is split into two streams by the splitter arm, which streams pass through the feeding pipe without hitting the feeding pipe; and (III) obtaining the desuperheated steam downstream of the probe-type steam-desuperheating device. Alternatively, in some embodiments, a method of desuperheating steam using any of the probe-type steam-desuperheating devices disclosed herein, comprises: (I′) supplying superheated steam in the steam pipe upstream of the probe-type steam-desuperheating device; (II′) feeding cooling fluid to the cooling fluid inlet port of the probe-type steam-desuperheating device and spraying the cooling fluid from the nozzle assembly toward a downstream direction of the superheated steam, wherein the cooling fluid sprayed out of the flow passage of the nozzle assembly flows toward the downstream direction of the superheated steam, wherein the cooling fluid sprayed out of the flow passage of the nozzle assembly is split into two streams by each splitter arm, between which streams part of the superheated steam passes, thereby desuperheating the superheated steam while the superheated steam is passing through the sprayed cooling fluid; and (III′) obtaining the desuperheated steam downstream of the probe-type steam-desuperheating device.
In some embodiments, the at least one splitter arm is constituted by multiple splitter arms symmetrically extending in multiple directions, thereby creating symmetrical segments of flow of sprayed cooling fluid and improving steam entrainment to the sprayed cooling fluid. In some embodiments, the steam is water vapor, and the cooling fluid is water.
The embodiments will be further explained with reference to the drawings; however, the embodiments are not intended to limit the present invention.
The plug element 1 is provided with a splitter member 11 fixed by screws 13 to a front face 8 of the plug element 1, wherein the splitter member 11 has at least one splitter arm 12 extending across the flow passage as viewed from the front of the plug element 1 to deflect flow 10 of fluid sprayed through the flow passage. The splitter member 11 (also the screws 13) may be made of an erosion-resistant material such as hardened 400 series steel, nickel-based super alloy, etc., or can be made of the same material as that of the plug element 1 and/or the nozzle body. The length of each splitter arm is greater than the outer diameter of the plug element 1 so as to deflect and split the spray pattern into two or more streams (segmented flow). Typically, each splitter arm is longer than the outer diameter of the nozzle body 14.
The nozzle body 14 may be fabricated as a single component (or alternatively two separate components threadably attached to each other) comprising an upper portion and a lower portion. The upper portion 5 may be threadably attached to a nozzle holder.
In some embodiments, an angle at the apex of the triangle or other shapes is about 10° to about 90°, typically about 25° to about 60°, so that the splitter arm can effectively split the fluid sprayed out of the flow passage into two streams apart from each other by a distance slightly greater than a diameter of a feeding pipe to which the nozzle assembly is attached, when the bifurcated stream flows against the steam flow (counter flow injection) in a steam pipe, deflects to the direction of the steam flow, and passes through the feeding pipe, so as to avoid hitting the feeding pipe. The appropriate angle can be determined by a skilled artisan based on the velocity of steam, the velocity of spray, the mass of steam, the mass of spray, the width and thickness of the splitter arm, etc., through routine work. In some embodiments, the width (the size of the base of the triangle) of the splitter arm is about 10% to about 50% (typically 20% to 40%) of the outer periphery diameter of the aperture 19. In some embodiments, the width of the splitter arm is determined depending on the size of a fastening means, e.g., a screw, so as to securely fasten the splitter arm to the plug element. In some embodiments, the width (clearance) of the aperture when in operation is about 5% to about 20% (typically about 10%) of the outer periphery diameter of the aperture.
In
In this embodiment, two splitter arms 12 are used. Although the lower splitter arm is not used for avoiding hitting of the feeding pipe by the cooling fluid, it is useful for improving the mixing of the sprayed cooling fluid and the superheated steam (by drawing in additional superheated steam into regions where water droplets are concentrated) and increasing the evaporation rate of the sprayed cooling fluid so as to efficiently cool the superheated steam, wherein effective turbulence including eddies 17 occurs. When the splitter arms split the spray pattern, the spray pattern is divided into multiple segments, i.e., segmentation of the spray pattern. The segmentation of the spray pattern can entrain surrounding hot steam inside the core of the spray pattern, i.e., hot steam flows through the gaps between the segments and is enveloped by the cooling fluid flow, improving the mixing of the steam and the sprayed cooling fluid and increasing the evaporation rate of the cooling fluid, which are desirable in desuperheating devices.
In some embodiments, alternatively, the nozzle assembly can be used in concurrent flow injection (co-flowing with the steam), i.e., spraying the cooling fluid in the same direction as that of the steam so that the sprayed fluid will not hit the feeding pipe; however, cooling efficiency of the concurrent flow injection may not as good as that of the counter flow injection. In some embodiments, the velocity of steam in the steam pipe is about 8 m/s to about 100 m/s, whereas the initial velocity of spray is about 20 m/s to about 30 m/s, wherein the pressure difference between the steam flowing in the steam pipe and the fluid to be sprayed is about 1 bar or higher to ensure good atomization of the cooling fluid, but about 15 bar or less to prevent erosion of the nozzle assembly. In some embodiments, the velocity of spray is greater than that of steam.
In some embodiments, in
In some embodiments, the nozzle assembly structures and other structures associated therewith disclosed in U.S. Pat. No. 6,746,001, U.S. Pat. No. 7,850,149, and U.S. Pat. No. 8,931,717, and WO 2014/055691 can be employed to the full extent consistent with this disclosure, each disclosure of which is incorporated herein by reference in its entirety.
It will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the forms of the present invention are illustrative only and are not intended to limit the scope of the present invention.
