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Title:
SYSTEM AND METHOD FOR REMOVING ASH DEPOSITS WITHIN A BOILER
Document Type and Number:
WIPO Patent Application WO/2018/077729
Kind Code:
A1
Abstract:
A system for removing ash deposits within a boiler is provided. The system includes a soot blower disposed within the boiler, and a gas supply line in fluid communication with the soot blower and a gas source. The soot blower is operative to inject compressed gas from the gas source into the boiler to remove the ash deposits from a surface of the boiler.

Inventors:
LEVASSEUR, Armand (17 TINKER DRIVE, WINDSOR LOCKS, Connecticut, 06096, US)
ZHANG, Wei (125 CODY CIRCLE, SOUTH WINDSOR, Connecticut, 06074, US)
STALLMANN, Olaf (BÜTTENWEG 21, ESSENHEIM, 55270, DE)
NIASS, Tidjani (561 NAJMAH DRIVE, P.O. BOX 9208DHAHRA, ., 31311, SA)
YOUNES, Mourad (E221, SAUDI ARAMCO CAMPAbqaiq, 31311, SA)
JAMAL, Aqil (8006 CRESENT KNOLLS DRIVE, RICHMOND, Texas, 77406, US)
Application Number:
EP2017/076795
Publication Date:
May 03, 2018
Filing Date:
October 19, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
GENERAL ELECTRIC TECHNOLOGY GMBH (Brown Boveri Strasse 7, 5400 Baden, CH-5400, CH)
International Classes:
F22B37/48; F23J3/00
Domestic Patent References:
WO2012035777A12012-03-22
Foreign References:
US20110048295A12011-03-03
US20130244190A12013-09-19
US20060042525A12006-03-02
US20110168275A12011-07-14
CN105066113A2015-11-18
CN104930527A2015-09-23
Other References:
None
Attorney, Agent or Firm:
FOSTER, Christopher Michael (General Electric Technology GmbH, Global Patent Operation - EuropeBrown Boveri Strasse 7, 5400 Baden, CH-5400, CH)
Download PDF:
Claims:
WHAT IS CLAIMED IS:

1. A system for removing ash deposits within a boiler comprising:

a soot blower disposed within the boiler,

a gas supply line in fluid communication with the soot blower and a gas source; and

wherein the soot blower is operative to inject compressed gas from the gas source into the boiler to remove the ash deposits from a surface of the boiler.

2. The system of claim 1, wherein the compressed gas is carbon dioxide.

3. The system of claim 1 or 2, wherein the gas source is the boiler.

4. The system of claim 3, further comprising:

a compressor disposed downstream of the boiler for compressing a flue gas stream discharged from the boiler; and

wherein the flue gas stream is the compressed gas.

5. The system of claim 3, further comprising:

a compressor disposed downstream of the boiler for compressing a flue gas stream discharged from the boiler;

a separator disposed downstream of the compressor that is operative to separate carbon dioxide from the flue gas stream; and

wherein the separated carbon dioxide is the compressed gas.

6. The system of claim 5, further comprising:

a series of compressors disposed downstream of the separator and operative to compress the separated carbon dioxide prior to being injected into the boiler by the soot blower.

7. The system of claim 6, further comprising:

a heat exchanger for heating the separated carbon dioxide prior to being injected into the boiler by the soot blower; and

wherein the heat exchanger heats the separated carbon dioxide via cooling the flue gas stream.

8. The system of claim 7, wherein the heat exchanger is disposed downstream of the compressor and upstream of the separator.

9. The system of any one of claims 1 to 8, further comprising:

a heat recovery system that includes a particulate remover and a desulferizer, the heat recovery system operative to recover heat from a flue gas stream discharged by the boiler; and

wherein the compressed gas is heated by the flue gas stream between the particulate remover and the desulferizer.

10. The system of any one of claims 1 to 9, wherein the boiler is an oxy-fuel combustion boiler.

11. A method for removing ash deposits within a boiler comprising:

supplying a compressed gas from a gas source via a supply line to a soot blower disposed within the boiler;

injecting the compressed gas into the boiler via the soot blower so as to remove the ash deposits from a surface of the boiler.

12. The method of claim 11, wherein the compressed gas is carbon dioxide.

13. The method of claim 11 or 12, wherein the gas source is the boiler.

14. The method of claim 13 further comprising:

compressing a flue gas stream discharged from the boiler via a compressor disposed downstream of the boiler; and

wherein the flue gas stream is the compressed gas.

15. The method of claim 13 further comprising:

compressing a flue gas stream discharged from the boiler via a compressor disposed downstream of the boiler;

separating carbon dioxide from the flue gas stream via a separator disposed downstream of the compressor; and

wherein the separated carbon dioxide is the compressed gas.

16. The method of claim 15 further comprising:

compressing, via a series of compressors disposed downstream of the separator, the separated carbon dioxide prior to injecting the separated carbon dioxide via the soot blower into the boiler.

17. The method of claim 16 further comprising:

heating the separated carbon dioxide via a heat exchanger prior to injecting the separated carbon dioxide via the soot blower into the boiler; and

wherein the heat exchanger heats the separated carbon dioxide via cooling the flue gas stream.

18. The method of claim 17, wherein the heat exchanger is disposed downstream of the compressor and upstream of the separator.

19. The method of any one of claims 11 to 18 further comprising:

recovering heat from a flue gas stream discharged by the boiler via a heat recovery system that includes a particulate remover and a desulferizer; and

heating the compressed gas via the flue gas stream between the particulate remover and the desulferizer.

20. A system for removing ash deposits within a boiler comprising:

a soot blower disposed within the boiler;

a gas supply line in fluid communication with the soot blower and a carbon dioxide gas storage vessel; and

wherein the soot blower is operative to inject carbon dioxide gas received from the carbon dioxide gas storage vessel into the boiler to remove the ash deposits from a surface of the boiler.

Description:
SYSTEM AND METHOD FOR REMOVING ASH DEPOSITS WITHIN A

BOILER

BACKGROUND TECHNICAL FIELD

[0001] Embodiments of the invention relate generally to boilers, and more specifically, to a system and method for removing ash deposits within a boiler.

DISCUSSION OF ART

[0002] Many power plants utilize boilers that combust fuels, e.g., coal, oil, and/or gas, to generate steam which in turn is used to produce electricity via a steam turbine generator. Such power plants typically generate and heat steam by using heating surfaces, e.g., evaporators, superheaters, etc., to transfer thermal energy produced from combusting a fuel into water and/or steam.

[0003] In addition to producing a flue gas that contains carbon dioxide

("CO2"), combustion of a fuel may also produce dust and ash that accumulates on one or more heating surfaces within a boiler so as to form ash deposits. Ash deposits on heating surfaces of a boiler often act as insulators that restrict the ability of the heating surfaces to transfer heat into the water/steam. In other words, ash deposits usually result in less heat being transferred into the water/steam, and more heat leaving the boiler via a vented flue gas. Thus, ash deposits typically reduce a boiler's

performance/efficiency. As such, ash deposits usually lead to higher fuel

consumption by the boiler and/or other operational problems.

[0004] On-line, e.g., occurring during boiler operations, removal of ash deposits by "soot blowing" is a means to retain desired heat transfer rates by restoring boiler heating surface area, i.e., removing ash deposits. Many boilers often use steam for soot blowing because of its overall cost and availability. Steam, however, is expensive in countries/locations where water sources are costly (e.g., in

countries/regions where water is produced from desalination). Further, in many boilers, the steam utilized for soot blowing is often drawn/tapped from a supply of steam used to generate electricity, which in turn may reduce the amount of steam available to generate electricity and result in a power production loss in the encompassing power plant. [0005] What is needed, therefore, is an improved system and method for removing ash deposits within a boiler.

BRIEF DESCRIPTION

[0006] In an embodiment, a system for removing ash deposits within a boiler is provided. The system includes a soot blower disposed within the boiler, and a gas supply line in fluid communication with the soot blower and a gas source. The soot blower is operative to inject compressed gas from the gas source into the boiler to remove the ash deposits from a surface of the boiler.

[0007] In another embodiment, a method for removing ash deposits within a boiler is provided. The method includes: supplying a compressed gas from a gas source via a supply line to a soot blower disposed within the boiler; and injecting the compressed gas into the boiler via the soot blower so as to remove the ash deposits from a surface of the boiler.

[0008] In yet another embodiment, a system for removing ash deposits within a boiler is provided. The system includes a soot blower disposed within the boiler, and a gas supply line in fluid communication with the soot blower and a carbon dioxide gas storage vessel. The soot blower is operative to inject carbon dioxide gas received from the carbon dioxide gas storage vessel into the boiler to remove the ash deposits from a surface of the boiler.

DRAWINGS

[0009] The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below:

[0010] FIG. 1 is a schematic block diagram of a system for removing ash deposits within a boiler in accordance with an embodiment of the present invention;

[0011] FIG. 2 is another schematic block diagram of the system of FIG. 1 in accordance with an embodiment of the present invention;

[0012] FIG. 3 is yet another schematic block diagram of the system of FIG. 1 in accordance with an embodiment of the present invention; and

[0013] FIG. 4 is still yet another schematic block diagram of the system of

FIG. 1 in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0014] Reference will be made below in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings.

Wherever possible, the same reference characters used throughout the drawings refer to the same or like parts, without duplicative description.

[0015] As used herein, the terms "substantially," "generally," and "about" indicate conditions within reasonably achievable manufacturing and assembly tolerances, relative to ideal desired conditions suitable for achieving the functional purpose of a component or assembly.

[0016] The term "real-time," as used herein, means a level of processing responsiveness that a user senses as sufficiently immediate or that enables the processor to keep up with an external process.

[0017] As used herein, "electrically coupled", "electrically connected", and

"electrical communication" mean that the referenced elements are directly or indirectly connected such that an electrical current, or other communication medium, may flow from one to the other. The connection may include a direct conductive connection, i.e., without an intervening capacitive, inductive or active element, an inductive connection, a capacitive connection, and/or any other suitable electrical connection. Intervening components may be present.

[0018] As also used herein, the terms "fluidly connected" and "fluid communication" mean that the referenced elements are connected such that a fluid (to include a liquid, gas, and/or plasma) may flow along a flow path from one to the other.

[0019] The term "stream," as used herein, refers to the sustained movement of a substance, e.g., a gas, solid, liquid, and/or plasma.

[0020] Accordingly, the terms "upstream" and "downstream," as used herein, describe the position of the referenced elements with respect to a flow path of a gas, solid, liquid, and/or plasma flowing between and/or near the referenced elements.

[0021] As also used herein, the term "heating contact" means that the referenced elements are in proximity of one another such that heat/thermal energy can transfer between them.

[0022] Additionally, while the embodiments disclosed herein are described with respect to boilers, it is to be understood that embodiments of the present invention may be applicable to other systems and/or processes where accumulated ash needs to be removed from a surface.

[0023] As will be appreciated, disclosed herein is a system and method of using pressurized CO2 or flue gas in place of steam for soot blowing in a boiler. The system and method facilitate supplying a compressed gas, e.g., a flue gas and/ or CO2, to a soot blower from which it is discharged to remove ash deposits from the internal surfaces of a boiler, e.g., tubes, other parts of a combustion chamber, and/or evaporators, superheaters, etc. Thus, some embodiments of the present invention may reduce water consumption in power plants, which as stated above, is usually costly in dry regions or other locations where water is expensive.

[0024] Accordingly, FIGS. 1-4 show various embodiments of a system for conducting soot blowing in accordance with the present invention. For example, referring now to FIG. 1, a system 1 including a boiler 2 and a flue gas

processing/treatment system 3 is shown.

[0025] The boiler 2 includes a furnace 5 and conventional tube banks disposed downstream of the furnace 5. The boiler 2 has at least one soot blower 6 for facilitating soot blowing which is operative to receive gas via supply line 7 that is fluidly connected through conection 27 to a gas source, e.g, the boiler 2, such that the gas flows from the gas source/boiler 2 through the supply line 7 and into the blower 6 where it is injected into the boiler 2 via a port 11. In embodiments, the gas utilized by the blower 6 may be a flue gas generated by the boiler 2 and/or CO2 recovered from the flue gas via the flue gas treatment system 3. In embodiments, the gas may be compressed prior to being injected into the boiler 2.

[0026] As will be appreciated, in embodiments, the soot blower 6 and port 11 may be a single soot blower 6 port 11 pairing and/or a plurality of ports 11 fluidly connected to one or more soot blowers 6 disposed at different locations within the boiler 2. Additionally, in embodiments, the furnace 5 may be an oxy-fuel combustion furnace, i.e., a combustion furnace/system in which fuel is combusted with a mixture of recirculated flue gas and pure or substantially pure oxygen, that provides for the generation of a flue gas having a high CO2 content, such as between 75% to 85% or even more. Thus, in embodiments, the gas injected into the boiler 2 via the blower 6 may be pure, or substantially pure, CO2 gas, or a gas mixture containing CO2.

[0027] As further shown in FIG. 1, the flue gas treatment system 3 includes a compressor 15 disposed downstream of the furnace 5 which compresses the flue gas discharged from the furnace 5. While not shown, it will be understood that the system 1 may include various Environmental Control Systems ("ECS") and/or a heat recovery system 4 having a particulate remover 8 and/or a desulferizers 12, and/or nitrogen oxide removers (not shown), disposed downstream of the boiler 2 and upstream of the compressor 15. In embodiments, the flue gas treatment system 3 may further include a mercury removal unit 16 and a dryer 17 disposed downstream of the compressor 15. In such embodiments, one or more heat exchangers 18, 19 may also be disposed upstream of the mercury removal unit 16 and the dryer 17.

[0028] The flue gas treatment system 3 may further include a separation stage

20 that is disposed downstream of the compressor 15 which separates CO2 from other gases contained in the flue gas. The separation stage 20 may be fluidly connected to a line 21 for venting gas separated from the CO2, and further fluidly connected to a line 22 for supplying the separated CO2 into a compressor 23 (typically an intercooled, multistage compressor, and/or a series of compressors), a pump 24 (for supercritical CO2), and storage 25, e.g., a CO2 storage vessel and/or a pipeline.

[0029] As shown in FIG. 1, in embodiments, the connection 27 may be disposed downstream of the compressor 15 and upstream of the separation stage 20 such that the compressed gas is flue gas coming from the furnace 5. In such embodiments, the gas supply line 7 is connected immediately downstream of the compressor 15, i.e. without any components between the compressor 15 and the connection 27. In such embodiments, the flue gas diverted to supply line 7 may have a pressure of about 10 to 15 bar and a temperature of about 110°C. As will be further understood, compressed/pressurized gas for the blower 6 may also be drawn downstream from the pump 24 via gas supply line 9 or from the storage 25 via gas supply line 10. As will be appreciated, the gas drawn downstream from pump 24 and/or the storage 25 may be pure and/or nearly pure CO2. Accordingly, each of the gas supply lines 7, 9 and 10 may be fitted with valves (not shown) that permit the flow of the CO2 to the soot blower 6 from the connection 27, the pump 24, the storage 25, or from any two or more of these sources.

[0030] Referring briefly to FIG. 2, as will be appreciated, in some

embodiments wherein the compressor 15 is a multistage compressor, connection 27 may be disposed at an interstage section of the compressor 15, i.e., gas supply line 7 may draw flue gas from regions between stages of compressor 15. In such embodiments, a part of the flue gas at a pressure of about 10 to 15 bar is diverted through the gas supply line 7 to the soot blower 6. [0031] Turning now to FIG. 3, another embodiment of the system 1 is shown having two separation stages 20a, 20b. As will be appreciated, the separation stages 20a, 20b can be realised in different ways and according to different technologies. For example, each separation stage 20a and 20b may include a condensation step that includes a cooling process to facilitate separation of CO2 from the other gases contained in the flue gas.

[0032] Moving to FIG. 4, in embodiments, connection 27 may be downstream of the separation stage 20a, 20b such that the gas is substantially compressed pure, or near pure, CO2 coming from the separation stages 20a 20b. While FIG. 4 depicts two separation stages 20a and 20b, as stated above, embodiments may have a single separation stage 20 (FIG. 1). As further shown in FIG. 4, a heat exchanger 28 may be provided for heating the separated CO2 downstream of connection 27. For example, in embodiments, the heat exchanger 28 may be disposed downstream of the compressor 15 and upstream of the separation stages 20a, 20b with respect to the flue gas discharged by the boiler 2. In such embodiments, a part of the compressed CO2 at a pressure between about 10 to 15 bar is diverted through connection 27 and heated at the heat exchanger 28, via cooling of the flue gas passing from the compressor 15 to the mercury removal unit 16, before being forwarded to the blower 6 via gas supply line 7. In embodiments, the heat exchanger 28 may be disposed between the particulate remover 8 (FIG. 1) and the desulferizer 12 (FIG. 1), e.g., in the oxy boiler island.

[0033] Thus, in a method in accordance with embodiments of the present invention, flue gas produced at the furnace 5 of the boiler 2 is compressed at the compressor 15, treated at the mercury removal unit 16 and dryer 17 (after cooling in the heat exchangers 18, 19), and then supplied into the separation stage 20 (FIGS. 1 and 2) / 20a, 20b (FIGS. 3 and 4). From the separation stage 20 (FIGS. 1 and 2) / 20a, 20b (FIGS. 3 and 4), the CO2 is discharged and/or supplied to the compressor 23 and pump 24, and finally fed into a pipeline for use or storage 25, e.g., a CO2 storage vessel/container. In addition, the gas separated from the CO2, e.g., nitrogen, argon, etc., is vented via line 21.

[0034] Continuing, gas is diverted via connection 27 through the gas supply line 7 to the blower 6, which in embodiments, may be performed on demand, i.e., whenever it is desirable for accumulated ash to be blown away from surfaces of the boiler 2. As stated above, in embodiments, the gas may be flue gas or CO2 depending on the location of connection 27.

[0035] Additionally, in embodiments where trace impurities, e.g., hydrogen disulfide, in the flue gas at the connection 27 cause corrosion to the blower, or if higher pressures are desired, the high pressure CO2 stream exiting the compressor 23 may be recirculated, thus providing for a compressed high purity CO2 to be used in the soot blower 6. In such embodiments, the compressed high purity of CO2 may have a pressure between about 16 to 20 bar and be reheated using flue gas from the boiler 2 between to 60 to 90°C before being injected into the soot blower 6.

[0036] Finally, returning back to FIG. 1, it is also to be understood that the system 1 may include the necessary electronics, software, memory, storage, databases, firmware, logic/state machines, microprocessors, communication links, displays or other visual or audio user interfaces, printing devices, and any other input/output interfaces to perform the functions described herein and/or to achieve the results described herein. For example, the system 1 may include at least one processor 30, and system memory/data storage structures 31 in the form of a controller 32. The memory 31 may include random access memory (RAM) and readonly memory (ROM). The at least one processor 30 may include one or more conventional microprocessors and one or more supplementary co-processors such as math co-processors or the like. The data storage structures discussed herein may include an appropriate combination of magnetic, optical and/or semiconductor memory, and may include, for example, RAM, ROM, flash drive, an optical disc such as a compact disc and/or a hard disk or drive.

[0037] Additionally, a software application that provides for control, which may be in real-time, over one or more of the various components of the system 1, e.g., the boiler 2, blower 6, etc., may be read into a main memory of the at least one processor 30 from a computer-readable medium. The term "computer-readable medium," as used herein, refers to any medium that provides or participates in providing instructions to the at least one processor 30 of the system 1 (or any other processor of a device described herein) for execution. Such a medium may take many forms, including but not limited to, non- volatile media and volatile media.

[0038] While in embodiments, the execution of sequences of instructions in the software application causes the at least one processor 1 to perform the

methods/processes described herein, hard- wired circuitry may be used in place of, or in combination with, software instructions for implementation of the methods/processes of the present invention. Therefore, embodiments of the present invention are not limited to any specific combination of hardware and/or software.

[0039] It is further to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and/or aspects thereof) may be used in combination with each other. Additionally, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope.

[0040] For example, in an embodiment, a system for removing ash deposits within a boiler is provided. The system includes a soot blower disposed within the boiler, and a gas supply line in fluid communication with the soot blower and a gas source. The soot blower is operative to inject compressed gas from the gas source into the boiler to remove the ash deposits from a surface of the boiler. In certain embodiments, the compressed gas is carbon dioxide. In certain embodiments, the gas source is the boiler. In certain embodiments, the system further includes a

compressor disposed downstream of the boiler for compressing a flue gas stream discharged from the boiler. In such embodiments, the flue gas stream is the compressed gas. In certain embodiments, the system further includes a compressor disposed downstream of the boiler for compressing a flue gas stream discharged from the boiler; and a separator disposed downstream of the compressor that is operative to separate carbon dioxide from the flue gas stream. In such embodiments the separated carbon dioxide is the compressed gas. In certain embodiments, the system further includes a series of compressors disposed downstream of the separator and operative to compress the separated carbon dioxide prior to being injected into the boiler by the soot blower. In certain embodiments, the system further includes a heat exchanger for heating the separated carbon dioxide prior to being injected into the boiler by the soot blower. In such embodiments, the heat exchanger heats the separated carbon dioxide via cooling the flue gas stream. In certain embodiments, the heat exchanger is disposed downstream of the compressor and upstream of the separator. In certain embodiments, the system further includes a heat recovery system that includes a particulate remover and a desulferizer, and the heat recovery system is operative to recover heat from a flue gas stream discharged by the boiler. In such embodiments, the compressed gas is heated by the flue gas stream between the particulate remover and the desulferizer. In certain embodiments, the boiler is an oxy-fuel combustion boiler. [0041] Other embodiments provide for a method for removing ash deposits within a boiler. The method includes: supplying a compressed gas from a gas source via a supply line to a soot blower disposed within the boiler; and injecting the compressed gas into the boiler via the soot blower so as to remove the ash deposits from a surface of the boiler. In certain embodiments, the compressed gas is carbon dioxide. In certain embodiments, the gas source is the boiler. In certain

embodiments, the method further includes compressing a flue gas stream discharged from the boiler via a compressor disposed downstream of the boiler. In such embodiments, the flue gas stream is the compressed gas. In certain embodiments, the method further includes: compressing a flue gas stream discharged from the boiler via a compressor disposed downstream of the boiler; and separating carbon dioxide from the flue gas stream via a separator disposed downstream of the compressor. In such embodiments, the separated carbon dioxide is the compressed gas. In certain embodiments, the method further includes compressing, via a series of compressors disposed downstream of the separator, the separated carbon dioxide prior to injecting the separated carbon dioxide via the soot blower into the boiler. In certain

embodiments, the method further includes heating the separated carbon dioxide via a heat exchanger prior to injecting the separated carbon dioxide via the soot blower into the boiler. In such embodiments, the heat exchanger heats the separated carbon dioxide via cooling the flue gas stream. In certain embodiments, the heat exchanger is disposed downstream of the compressor and upstream of the separator. In certain embodiments, the method further includes: recovering heat from a flue gas stream discharged by the boiler via a heat recovery system that includes a particulate remover and a desulferizer; and heating the compressed gas via the flue gas stream between the particulate remover and the desulferizer.

[0042] Yet still other embodiments provide for a system for removing ash deposits within a boiler. The system includes a soot blower disposed within the boiler, and a gas supply line in fluid communication with the soot blower and a CO2 gas storage vessel. The soot blower is operative to inject CO2 gas from the CO2 gas storage vessel into the boiler to remove the ash deposits from a surface of the boiler.

[0043] Accordingly, by supplying compressed gas containing CO2 withdrawn from part of flue gas at an interstage during multistage compression and/or downstream of the compressor and/or upstream of the separator, and/or withdrawing at least a part of the separated CO2, some embodiments provide for the ability to blow accumulated ash off of surfaces in a boiler without the use of steam. Thus, some embodiments provide for a more efficient system and method for soot blowing in arid environments where it may be desirable to conserve water.

[0044] While the dimensions and types of materials described herein are intended to define the parameters of the invention, they are by no means limiting and are 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 respective terms "comprising" and "wherein." Moreover, in the following claims, terms such as "first," "second," "third," "upper," "lower," "bottom," "top," etc. are used merely as labels, and are not intended to impose numerical or positional 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 as such, unless and until such claim limitations expressly use the phrase "means for" followed by a statement of function void of further structure.

[0045] This written description uses examples to disclose several

embodiments of the invention, including the best mode, and also to enable one of ordinary skill in the art to practice the embodiments of invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to one of ordinary skill in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

[0046] 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 of said elements or steps, unless such exclusion is explicitly stated. 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," "including," or "having" an element or a plurality of elements having a particular property may include additional such elements not having that property.

[0047] Since certain changes may be made in the above-described invention, without departing from the spirit and scope of the invention herein involved, it is intended that all of the subject matter of the above description shown in the accompanying drawings shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the invention.