Description: “HIGH PRESSURE FEED WATER HEATER FOR PARTLOADS IN THERMAL POWER PLANTS”

FIELD OF INVENTION
The present invention relates to High pressure feed water heater for partloads in thermal power plants. This invention involves De-superheating zone at part loads for flexible operation of High pressure feed water heaters.
BACKGROUND OF THE INVENTION
Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

Feed water heaters in a thermal power plant used to better the heat rate and efficiency of the plant by raising the feed water temperature thereby reducing the amount of coal consumed in the boiler.

High pressure feed water heater (HP heater) is a shell and U-tube Heat exchanger with steam on shell side and feed water on tube side. These HP heaters consist of three zones namely i) Desuperheating zone ii) Condensing zone and iii) Sub cooling zone on shell side.

First, Super-heated steam enters the shell side Desuperheating zone through steam inlet nozzle and gets desuperheated and enters condensing zone just above the saturation temperature. In the condensing zone, steam gets saturated and further goes to sub cooling zone. Finally, in the sub cooling zone saturated liquid further gets sub cooled and leaves the heater through drain out let nozzle.

In a power plant, full load or 100% Load means rated capacity of the plant.
Part load refers to ~80% of full load (or) ~60% of full load(or) ~50% of full load (or)~20% of full load.

Feed water heater design is as per Heat Exchange Institute (HEI), USA Standards and ASME.
The amount by which the tube wall metal temperature within the zone exceeds the saturated steam temperature at the corresponding steam pressure is referred to as “dry safety wall margin”. As per HEI Standards, this should be a minimum of 1.11 Deg C to avoid any wetness on the tube surfaces.
The performance of a feed water heater is guaranteed at one specific “design point” condition generally the 100% Load as per contract and heater performance is predicted at other possible operating conditions.
At part load conditions, like ~80% of full load (or) ~60% of full load(or) ~50%of full load (or)~20% of full load etc., Steam pressure, Steam temperature, and Steam quantity into feed water heater are less than that at full load.

At part load conditions also the superheat available in the extraction steam is less compared to “design point”. However, area available in Desuperheating zone is same as in design condition. As the less quantity of steam is exposed to a larger available area in the Desuperheating zone, steam condenses on the tube surfaces leading to wet tube condition.
Formation of wetness on the tube surface along with high velocity steam flow in Desuperheating zone leads to scooping of tube material and hence the tube punctures, damaging the heater internals.
At present, operating range of High pressure feed water heater is restricted at part load conditions due to possible tube punctures because of wetness on the tube surfaces.
Hence, the Present invention has been proposed which focuses on optimally designing the Desuperheating zone to maintain dry safety wall margin at all full load and part loads.
The present invention addresses formation of wetness on the tube surfaces problem and allows High pressure feed water heaters to operate at wide range of part load condition up to 20% of full load.
OBJECTIVES OF THE INVENTION:
An object of the invention is to provide High pressure feed water heater for thermal power plant application.
Principal objective of the present invention is to develop an optimized De-superheating zone to obtain performance at “designed condition” and avoid “formation of wetness on the tube surfaces” thereby allowing HP heaters to operate at part load conditions.
Another object of the invention is to provide High pressure feed water heater for thermal power plant application, which serves the purpose effectively.
These and other objects and advantages of the present invention will be apparent to those skilled in the art after a consideration of the following detailed description taken in conjunction with the accompanying drawings in which a preferred form of the present invention is illustrated.

SUMMARY OF THE INVENTION
One or more drawbacks of conventional systems and process are overcome, and additional advantages are provided through the apparatus/composition and a method as claimed in the present disclosure. Additional features and advantages are realized through the technicalities of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered to be part of the claimed disclosure.

According to the present invention, there is provided High pressure feed water heater for thermal power plant application, the High pressure feed water heater 1 comprises of: a shell 2 and a Hemi head 3 including a tube sheet 4 and forming a water chamber 5, wherein the water chamber 5 is divided into two portions by partitions 6 and 6a forming inlet water chamber and outlet water chambers 5a and 5b, in which a feed water inlet 7 and a feed water outlet 8 are provided in the Hemi head 3 and communicate with the inlet and outlet chambers 5a and 5b on two sides of the partition 6, wherein the shell 2 forms a compartment 12 including a sub-cooling zone 15 and a de-superheating zone 19.
This invention talks about optimized De-superheating zone design for a high pressure feed water heater to obtain performance at designed condition and avoid formation of wetness on the tube surfaces thereby allowing High Pressure heaters to operate at part load conditions.

Various objects, features, aspects, and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein, wherein:-

Fig. 1 shows: A longitudinal sectional view of a high pressure feed water heater.

Fig.2 shows: An enlarged view of De-superheating zone shroud details.

Fig.3 shows: View-X of De-superheating zone shroud details in Fig.2.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

Detail Description of Invention with reference to the Accompanying Drawings

While the embodiments of the disclosure are subject to various modifications and alternative forms, specific embodiment thereof have been shown by way of example in the figures and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

The present invention makes a disclosure regarding High pressure feed water heater 1, which includes a shell 2 and a Hemi head 3 including a tube sheet 4 and forming a water chamber 5. The water chamber 5 is divided into at least two portions by partitions 6 and 6a forming inlet water chamber and outlet water chambers 5a and 5b. A feed water inlet 7 and a feed water outlet 8 are provided in the Hemi head 3 and communicate with the inlet and outlet chambers 5a and 5b on two sides of the partition 6. Thus feed water entering the water chamber 5 through inlet 7 and chamber 5a passes through a plurality of U-shaped heat exchange tubes 9 having opposite end portions seated in the tube sheet 4. Thereafter the feed water passes into the outlet chamber 5b and out of the heat exchanger through the feed water outlet 8.
The shell 2 is provided with a steam inlet 10 and a drain outlet 11, and the shell 2 forms a compartment or condensing zone 12 in which the heat exchange tubes 9 are disposed. The shell 2 is preferably secured to the tube sheet 4 by means of a weld joint 13. The tubes 9 are provided with tube support means including support plates 14 which are spaced from each other at preferably equal intervals along the longitudinal axis of the shell 2.
The compartment 12 is divided into three portions including a subcooling zone 15 and a de-superheating zone generally indicated at 19. The sub cooling zone 15 is enclosed between a DC end plate 17 and tube sheet 4 as shown in Fig. 1. Sub cooling zone 15 extends from the tube sheet 4 to the lower U-bent portions of the tubes 9. The portions of the tubes 9 within the zone 15 are supported by spaced DC baffle plates 16. The subcooling zone 15 encloses the inlet end portions of some of the tubes, while the inlet portions of other tubes 9 extend directly through the condensing compartment 12, as illustrated in Fig. 1. The left end (Fig. 1) of the sub cooling zone 15 communicates with the condensing compartment 12 while the condensate outlet 11 communicates with the right end of the subcooling zone 15.
The de-superheating zone 19 is formed preferably as a box-like structure enclosing the outlet portions of the tubes 9 nearest the tube sheet 4, i.e., at the advanced zone of water flow nearest the water outlet 8. Steam entering through steam inlet 10 passes thorough chamber made of seal ring 30, outer shroud 29 inner shroud 31 and gets divided into two portions as DSH right portion 22 and DSH left portion 23. Further, Impingement plate 28 is provided on inner shroud 31.
Thus, the DSH left portion 23 and DSH right portion 22 enclose the portions of the U-tubes 9 through which the heated feed water passes immediately before leaving the shell of the heat exchanger. Only the outlet end portions of tubes 9 are enclosed in and pass through the DSH left portion 23 and DSH right portion 22, the outlet end of the tubes 9 as shown in Fig.1 extending from the tube sheet 4 and water chamber 5b successively through DSH left portion 23 and DSH right portion 22 and then into the condensing compartment 12.
When the superheated steam enters the DSH left portion 23 and DSH right portion 22, its flow is directed in intimate contact with the portions of the tubes 9 in the chambers by the DSH baffle plates 20 which create a zigzag course of travel for the steam and thereby assure maximum heat transfer to the tube portions within DSH left portion 23 and DSH right portion 22 by a continually moving stream of steam. Thereafter, the steam leaves the DSH left portion 23 and DSH right portion 22 through the outlets 24 and 25,27 respectively, whereupon the de-superheated steam enters the condensing zone 12 of the shell where the steam condenses and the feed water is heated practically to the saturated steam temperature before passing in the tubes 9 to the de-superheating zone. The condensate then passes through the sub-cooling zone 15 where it is further cooled and heats the cold incoming feed water and the condensate then passes out of the shell through the outlet 11.
The working of invention can be understood from the above discussion particularly by a person skilled in the art.
ADVANTAGES OF INVENTION
-Designing of the De-superheating zone to maintain dry safety wall margin at all full load and part loads;
-Avoids formation of wetness on the tube surfaces
-Allows High pressure feed water heaters to operate at wide range of part load condition up to 20% of full load.

Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases, it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all groups used in the appended claims.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

The above description does not provide specific details of manufacture or design of the various components. Those of skill in the art are familiar with such details, and unless departures from those techniques are set out, techniques, known, related art or later developed designs and materials should be employed. Those in the art are capable of choosing suitable manufacturing and design details.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. It will be appreciated that several of the above-disclosed and other features and functions, or alternatives thereof, may be combined into other systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may subsequently be made by those skilled in the art without departing from the scope of the present disclosure as encompassed by the following claims.

The claims, as originally presented and as they may be amended, encompass variations, alternatives, modifications, improvements, equivalents, and substantial equivalents of the embodiments and teachings disclosed herein, including those that are presently unforeseen or unappreciated, and that, for example, may arise from applicants/patentees and others.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
, Claims:We Claim
1. High pressure feed water heater for partloads in thermal power plants, the High pressure feed water heater 1 comprises of:
a shell 2 and a Hemi head 3 including a tube sheet 4 and forming a water chamber 5, wherein the water chamber 5 is divided into two portions by partitions 6 and 6a forming inlet water chamber and outlet water chambers 5a and 5b, in which a feed water inlet 7 and a feed water outlet 8 are provided in the Hemi head 3 and communicate with the inlet and outlet chambers 5a and 5b on two sides of the partition 6, wherein the shell 2 forms a compartment 12 including a sub-cooling zone 15 and a de-superheating zone 19.

2. The High pressure feed water heater as claimed in claim 1, wherein the feed water entering the water chamber 5 through inlet 7 and chamber 5a passes through a plurality of U-shaped heat exchange tubes 9 having opposite end portions seated in the tube sheet 4.
3. The High pressure feed water heater as claimed in claim 2, wherein the feed water passes into outlet chamber 5b and out of the heat exchanger through the feed water outlet 8.
4. The High pressure feed water heater as claimed in claims 1-3, wherein the shell 2 is provided with a steam inlet 10 and a drain outlet 11, and the shell 2 forms a compartment/condensing zone 12 in which the heat exchange tubes 9 are disposed.
5. The High pressure feed water heater as claimed in claims 1-4, wherein the shell 2 is preferably secured to the tube sheet 4 by a weld joint 13, in which the tubes 9 are provided with tube support means including support plates 14 which are spaced from each other at preferably equal intervals along the longitudinal axis of the shell 2.
6. The High pressure feed water heater as claimed in claims 1-5, wherein the compartment 12 is divided into multiple portions including a subcooling zone 15 and a de-superheating zone 19, in which the sub cooling zone 15 is enclosed between a DC end plate 17 and tube sheet 4.
7. The High pressure feed water heater as claimed in claims 1-6, wherein the Sub cooling zone 15 extends from the tube sheet 4 to the lower U-bent portions of the tubes 9, the portions of the tubes 9 within the zone 15 are supported by spaced DC baffle plates 16,
8. The High pressure feed water heater as claimed in claims 1-7, wherein the subcooling zone 15 encloses the inlet end portions of some of the tubes, while the inlet portions of other tubes 9 extend directly through the condensing compartment 12.
9. The High pressure feed water heater as claimed in claims 1-8, wherein the de-superheating zone 19.
10. The High pressure feed water heater as claimed in claims 1-9, wherein the High pressure feed water heater as claimed in claim 2, wherein steam entering through steam inlet 10 passes thorough chamber made of seal ring 30, outer shroud 29 inner shroud 31 and gets divided into DSH right portion 22 and DSH left portion 23, in which Impingement plate 28 is provided on inner shroud 31.