DESC:EXTENDED LIFE COAL NOZZLE TIP FOR TANGENTIAL COAL FIRED BOILERS

FIELD OF THE INVENTION:
[001] This invention is directed to extended life coal nozzle tip for tangential coal fired boilers. The present invention is applicable for Pulverized coal fired boilers in thermal power plants. This invention addresses solution to abrasion of coal nozzle tips, which is part of the burner in such coal fired power plants.

BACKGROUND OF INVENTION/PRIOR ART:
[002] 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.

[003] A general method of firing coal in a conventional coal-fired steam boiler is known as tangential combustion. In tangential firing method, pulverized coal is fed into the furnace in the form of primary airflow through a burner, sometimes referred to as a fuel-air ingress device, located at the corner of the furnace windbox. The pulverized coal carried by primary air is transported to furnace through coal pipes, coal nozzles and burner tips. The pulverized coal-air emitted from these burners is tangentially fed toward the imaginary circle in the center of the furnace to form a large flame called a fireball in the furnace.

[004] Pulverized coal consists of ash which erodes the components that it comes in contact with. As the ash content in the coal is higher, large amount of abrasion occurs in the coal path. In general, Indian origin high rank sub-bituminous coals contain high ash content. All the power plants using coal are subject to frequent changing of coal handling equipment due to this reason. And also the coal burners in the boilers. The coal burners are the fag end components in the coal firing system of any pulverized coal fired boilers. Due to the high exit velocity at the firing zone in the furnace, these burners are subjected to very harsh combinations of high temperature and erosion due to pulverized coal air mixture. This combination may aggravate the erosive phenomenon of the pulverized coal on the coal burner plates. Conventional coal burners may not last long operational hours because of this reason. This leads to frequent shutdown of the boilers for replacement, which is very time consuming and capital intensive exercise due to prolonged boiler shutdown periods. By increasing the life of the coal burners tips the increase in duration between shutdowns due to enlarged life burners will be a great relief to the boiler operators. Hence availability of the power plants can be improved.

[005] In the context of newly introduced stringent emission norms for the coal fired power plants, the thermal units have become capital intensive. This makes power plant availability an important factor to optimize the resources utilization and improve the return on investment. Coal burners in the windbox generally serves for operational life of little over a year. The operational life depends on the ash content in the coal being fired in the boilers and operating conditions. More the ash content, more is the coal required to generate the same megawatt. Therefore this loads the burners with more coal, which leads to lesser operational life of the burner nozzles.

[006] Normally pulverized coal burners are provided with wear protection on account of pulverized coal air mixture. This will be accomplished by providing surface hardening methods. These are limited in nature due to cost optimization. To further enhance the life of the coal burner tips, a detailed study was conducted to understand the wearing patterns on the coal burner nozzle tips. With better understanding of the wear patterns, better wear resistance protection can be offered to these coal burners.

[007] In general the protective layers are in the form of hard facing over the base material. The base metal is carbon steel or stainless steel (SS). Most cases stainless steel (SS) is being used as base due to its high resistance to erosion and high temperature withstanding capabilities. Studies over a period of time recommended for weld overlay due to cost economics. The hardness and the composition of the weld overlay gives the wear protection by sacrificial method. This weld overlay will be more resistant to erosion than the base material.

[008] By doing flow model study the flow patterns of the pulverized coal air mixture in the coal pipes and coal burners have been identified. The wear protective coating has been adopted wherever the propensity is more for erosion on account of the pulverized coal in the harsh environment. This protection is offered in two different levels. First level offers moderate erosion protection due to pulverized coal. This protection cover is given at locations wherever the erosion pattern observed is of low to moderate severity during flow study. This protection layer provided will withstand and improve the operational life.

[009] Wherever the severity of the erosion is moderately high to very high, a superior protective weld overlay is applied. This protective layer will have superior hardness and overlay material also will withstand erosion for prolonged operational time. This higher hard weld overlay will be of superior material composition and hardness being offered against the erosion. However, this incurs higher cost per unit area compared to the erosion protection offered at moderately eroding areas. This technique of dual material overlay will reduce the cost of wear protective coating by identifying the erosion prone areas precisely.

PRIOR ART:
[0010] Reference may be made to Korean patent KR20180118349A. The Korean invention relates to a burner nozzle tip including wear resistant splitter, and more particularly to a burner nozzle tip comprising an anti-wear splitter that effectively improves the abrasion resistance of the burner nozzle tip.

[0011] In the patent KR20180118349A, splitter plates are partially hard-faced in the leading edge. Whereas the invention described in our patent offers complete protection of divider plates in the coal nozzle tips against the pulverized coal air mixture fed from the pulverizers. The present invention addresses coal erosion both in the divider plates in the coal nozzle tips and the primary air casing inner surfaces.

[0012] Also there is a patent associated with wear resistant solid fuel burner nozzles, a patent from Canada CA2451088C is available in similar field for comparison. This invention relates to firing systems for use with pulverized solid fuel-fired furnaces, and more specifically, to a pulverized solid fuel nozzle tip with a ceramic component for use in such firing systems. Inventor in the Canadian patent used the principal of applying ceramic coating over the components subject to wearing. This method of applying ceramic coating is being employed in the coal burners. But the present invention is to provide weld overlay over the coal nozzle plates. This is more economical and offers reliability over time due to better chemical bonding over the base materials. Method and the location of weld overlay is discussed in details in the later section of the patent.

[0013] Another patent from Korea, KR870001683B1 regarding the nozzle tip includes a replaceable, hollow, open-ended end cap which is mounted to the discharge end of a similarly configured base body mountable to a furnace burner. A replaceable, hollow, open- ended, weld-free insert cast of a highly abrasion resistant material is disposed intermediate of the base body and end cap. In use, a pulverised coal and air stream passes from a coal delivery pipe, through the base body, through the insert and then through the end cap into the furnace.
[0014] Inventor in the Korean patent has given sacrificial inner hollow casting insert. This invention is not dealt with any hard facing over the coal nozzle tips. Inventor recommended to replace the inner part of the nozzles whenever required. But the present invention deals with the high resistant weld layers in the primary casing inner surfaces to extend the wear life of the coal nozzle tips, which can enhance life in harsh furnace operating conditions. The study and development led to employment of different weld overlay in the erosion prone zones in addition to economical advantage.

OBJECTS OF THE INVENTION:
[0015] An object of the invention is to provide extended life coal nozzle tip for tangential coal fired boilers, which is simple in construction.

[0016] Another objective of the invention is to enhance the tangential fired coal burner’s operational life by using surface hardening procedure of weld overlay, which can be achieved by obtaining the erosion pattern of the burners over prolonged operational hours and various tilt and other operating conditions.

[0017] 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:
[0018] 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.
[0019] According to the present invention, there is provided Extended life coal nozzle tip for tangential coal fired boilers comprising assembly of primary air casing, secondary air casing, stiffener plates and divider plates.

[0020] The Primary air casing is formed by assembling the part (4) side inner plates and (3) top and bottom of the primary air casing plates, in which bend plates (9) are placed at corners to make an inner air casing, wherein Pulverized coal air is being admitted into the furnace through the inner air casing.

[0021] The secondary air casing is an opening formed by assembling the outer top and bottom plates (12) with side plates (2), in which Corner bent plates (8) are provided and the hot secondary air is diverted to furnace through this annular space between the primary air casing and the secondary air casing.

[0022] Said Primary air casing and secondary air casing are joined by the stiffener plates (6) left hand side and right hand side to form a wear resistant coal nozzle tip (1), in which top and bottom sides of primary air casings and secondary air casings are joined with stiffeners plates (7), wherein the divider plates (5, 10, 11) are part of primacy air casing.

[0023] The top divider plate (5) is placed adjacent to the top of primary air casing and the divider plate (10) is placed at middle of the primary air casing vertically, in which the bottom divider plate (11) is placed adjacent to the bottom of the primary air casing.

[0024] 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.
[0025] 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.

[0026] 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:
[0027] 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:

[0028] Figure 1-3 shows: Perspective view of the coal nozzle tip according to the present invention.

[0029] Figure 4-9 shows: A coal nozzle tip with hard facing together with weld overlay of hardness of 52-70 in accordance with the invention, wherein

[0030] Figure 4 indicates:
Hardface at shown area only – A

[0031] Figure 5 indicates:
High abrasion resistant surfaces with hardness of 60-70 HRC – H
Moderately abrasion resistant surfaces with hardness of 52-60 HRC – M
Surfaces with no special protection – S
Area of hardfacing – B
[0032] Figure 6 indicates:
Primary air casing Top & Bottom – P

[0033] Figure 8 indicates:
Hardface at Top, Bottom and leading edges – C
Flow – F

[0034] Figure 9 indicates:
Hardface at Top, Bottom and leading edges – C
Flow – F
Hardface at Top and Bottom surface only - D

[0035] 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 THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:
[0036] 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.

[0037] The present invention makes a disclosure regrading a technology pertaining to an invention relating to extended life coal nozzle tip for tangential coal fired boilers.

[0038] Embodiment (1) represents the perspective view of the coal nozzle tip in the figs 1-3. It is formed by the assembly of primary air casing, secondary air casing, stiffener plates & divider plates. Primary air casing is formed by assembling the part (4) side inner plates and (3) top and bottom of the primary air casing plates. To complete the primary air casing, bend plates (9) are used at corners to make a complete rectangular inner air casing. Pulverized coal air is being admitted in to the furnace through this inner air casing. Hence the inner surfaces of the parts (3), (4) & (9) are subjected to coal erosion.

[0039] The secondary air casing is a rectangular opening formed by assembling the outer top and bottom plates (12) and side plates (2). Corner bent plates (8) are used to complete the rectangular secondary air casing. Only the hot secondary air is diverted to furnace through this annular space between the primary air casing and the secondary air casing. This secondary air is used as cooling air for the coal nozzle tips when they face the red hot furnace radiation. As there is no contact with erosive coal these surfaces are not envisaged for hard-facing

[0040] Primary air casing and secondary air casings are joined by welding the stiffener plates (6) left hand side and right hand side to from a wear resistant coal nozzle tip embodiment (1). Also top and bottom sides of primary air casings and secondary air casings are joined with stiffeners plates (7). All the plates are joined by welding. The divider plates (5), (10), (11) are part of primacy air casing. These plates can be bluff body like diversion plates also. Hence forth these plates are called divider plates. The top divider plate (5) is placed near the top of primary air casing. The divider plate (10) is placed exactly at middle of the primary air casing vertically. And the bottom divider plate (11) is placed near the bottom of the primary air casing. These divider plates count will vary based on the size of the nozzle. These plate are welded inside the primary air casings plates (4).

[0041] Various operating conditions in the tilting tangential or fixed tangential boilers results in various erosion patterns in association with physical orientation of the nozzles with respect to the incoming pulverized coal pipes. The erosion patterns are very different in these parts.

[0042] Pulverized coal air mixture traverses only through the inside of the primary air casing. Due to high abrasive nature of the pulverized coal, all the components of the primary air casing, side primary air casing plates (4), primary air casing top and bottom plates (3), three divider plates (5), (10), (11), and the corner plates (9) are subjected to the erosion. The observed erosion pattern was varying among the components from moderate to severe. At some locations the divider plates are completely consumed due to the coal erosion, while other components are affected moderately and vice versa at some other locations. In conventional coal nozzles the divider plates (5), (10), (11) are only given with some amount of wear resistant protection against the high erosive pulverized coal air mixture.

[0043] The wearing components in the coal path are protected as described above by applying an optimized weld overlay. This specificity of the weld overlay is different for all these components. The weld overlay is specified for the thickness and the hardness values. These values vary from 52 HRC to 70 HRC as shown in fig -05. And the chemical composition is also detailed based on the erosion pattern.

FEATURES OF THIS INVENTION:
• A coal nozzle tip with hard facing together with weld overlay of hardness of 52-70 as per the figs 04-09.
• The hardness for the divider plate (05) & (10) with higher hardness ranging 60-70 HRC weld overlay and divider plates (11) with 52-60 HRC lower hardness weld overlays.
• Bringing the higher hardness weld overlay on the components (5), (10) & (11) with varying electrode composites use on the coal nozzle tips.
• Bringing the moderate hardness weld overlay on the components (8) & (9) with appropriate electrodes use on the coal nozzle tips.
• Use of two different hardness weld overlays on the part (9).
• Use of any combination of the hardness as provided above in coal nozzle tips.
• Use of “two different hardness” patterns in the coal nozzle tips.
• The “pattern of selection” of two different hardness in the coal nozzle tips.

ADVANTAGES OF THE INVENTION:
- Increase in the life of the coal burners tips;
- Improvement in availability of the power plants;
- Extension in the wear life of the coal nozzle tips, which can enhance life in harsh furnace operating conditions;
- Cost effective.

[0044] 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.
[0045] 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.

[0046] 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”.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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. Extended life coal nozzle tip for tangential coal fired boilers comprising assembly of primary air casing, secondary air casing, stiffener plates and divider plates.

2. The Extended life coal nozzle tip for tangential coal fired boilers as claimed in claim 1, wherein the Primary air casing is formed by assembling the part (4) side inner plates and (3) top and bottom of the primary air casing plates, in which bend plates (9) are placed at corners to make an inner air casing, wherein Pulverized coal air is being admitted into the furnace through the inner air casing.

3. The Extended life coal nozzle tip for tangential coal fired boilers as claimed in claim 1, wherein the secondary air casing is an opening formed by assembling the outer top and bottom plates (12) with side plates (2), in which Corner bent plates (8) are provided and the hot secondary air is diverted to furnace through this annular space between the primary air casing and the secondary air casing.

4. The Extended life coal nozzle tip for tangential coal fired boilers as claimed in claim 1, wherein said Primary air casing and secondary air casing are joined by the stiffener plates (6) left hand side and right hand side to form a wear resistant coal nozzle tip (1), in which top and bottom sides of primary air casings and secondary air casings are joined with stiffeners plates (7), wherein the divider plates (5, 10, 11) are part of primacy air casing.

5. The Extended life coal nozzle tip for tangential coal fired boilers as claimed in claim 4, wherein the top divider plate (5) is placed adjacent to the top of primary air casing and the divider plate (10) is placed at middle of the primary air casing vertically, in which the bottom divider plate (11) is placed adjacent to the bottom of the primary air casing.