Boiler for natural gas firing and components thereof

Abstract

A bottom seal for a boiler is provided that includes a first refractory layer, a second refractory layer, a plurality of anchors, and an alloy plate. The first refractory layer is made of a castable refractory material. The second refractory layer is positioned below the first refractory layer. The anchors are configured to support the first and second refractory layers. The alloy plate is configured to be positioned below and support the first and second refractory layers. The first and second refractory layers are configured to seal a bottom opening of the boiler.

Description

701359-WO-l (GTV1020-0448WO) BOILER FOR NATURAL GAS FIRING AND COMPONENTS THEREOFBACKGROUND TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate generally to a boiler for natural gas firing and components thereof, more particularly, to an insert for a boiler.DISCUSSION OF ART

[0002] Solid fuel fired boilers, for example coal-fired boilers, are used to generate steam for many industrial purposes, for example to drive electric generating, steam powered turbines for the electric utility industry. All of the solid fuel is not combustible and as a result large quantities of ash are deposited within the furnaces of such boilers. Ash hoppers are adapted to receive this solid, combustion-produced material and dispose of the material without interruption to boiler operation.

[0003] The ash hopper may have a seal arrangement that consists of a combination of drip and seal plates to form a labyrinth with the seal plate extending into a water trough to maintain a positive barrier between the boiler furnace and the atmosphere.

[0004] Increasingly, natural gas fired boilers may be used as a more efficient and ecologically-friendly alternative to coal-fired boilers. Natural gas fired boilers do not produce ash or byproduct. As such, when converting a coal-fired boiler to a natural gas fired boiler, the hopper and water trough must still be maintained, even though no ash or byproduct is produced.

[0005] Existing coal fired boilers may have openings at the bottom of sloped coutant tube panels. The most common furnace bottom seals for coal firing units is a furnace bottom ash701359-WO-l (GTV1020-0448WO) hopper system with water seal troughs. The existing furnace bottom ash hoppers and water seal troughs are costly to maintain.

[0006] It may be advantageous to have a method and system for using a natural gas boiler with existing boiler types.BRIEF DESCRIPTION

[0007] Certain embodiments commensurate in scope with the originally claimed subject matter are summarized below. These embodiments are not intended to limit the scope of the claimed subject matter, but rather these embodiments are intended only to provide a brief summary of the possible embodiments. Indeed, the disclosure may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

[0008] The present invention relates methods and systems for natural gas fired steam generation units. The system can be easily adapted to existing units, including existing units that were previously coal fired units. Existing boilers have openings at the bottom of sloped coutant tube panels. The most common furnace bottom seals for coal firing units is a furnace bottom ash hopper system with water seal troughs. The existing furnace bottom ash hoppers and water seal troughs are costly to maintain. This present design provides for an easy to install and low maintenance method to seal the furnace bottom opening seal and allow the removal of the bottom ash hopper and water seal trough system.

[0009] The present system and method provides a design for sealing a furnace bottom for boilers, specifically boilers with coutant bottoms that originally fired coal but have been converted to natural gas firing. These converted boilers may generally still have a bottom ash hopper, water troughs, and / or submerged scrapers in place. The furnace bottom seal utilizes701359-WO-l (GTV1020-0448WO) layers of high strength castable refractory material and lightweight insulating castable refractory material across the coutant bottom throat opening.

[0010] The refractory layers may rest on top of an alloy plate that may be supported by a series of low alloy support beams. The support beams are supported by bracket plates at each end that attach to fin bars between slope panel tubes. The refractory layers may be held in place by a plurality of refractory anchors that are attached to the alloy support plate.

[0011] According to an aspect of the invention, a bottom seal for a boiler is provided. The bottom seal includes a first refractory layer, a second refractory layer, a plurality of anchors, and an alloy plate. The first refractory layer is made of a castable refractory material. The second refractory layer is positioned below the first refractory layer. The anchors are configured to support the first refractory layer and the second refractory layer. The alloy plate is configured to be positioned below and support the first refractory layer and the second refractory layer. The first refractory layer and the second refractory layer are configured to seal a bottom opening of the boiler.

[0012] In one embodiment, the bottom seal may include an openable drain.

[0013] In one embodiment, the boiler includes a coutant bottom.

[0014] In one embodiment, the first refractory layer may have a thickness between about 7 centimeters and about 30 centimeters.

[0015] In one embodiment, the second refractory layer may have a thickness between about 5 centimeters and about 30 centimeters.

[0016] In one embodiment, the castable refractory material of the first refractory layer may be stronger than the second refractory layer.701359-WO-l (GTV1020-0448WO)

[0017] In one embodiment, the second refractory layer may be an insulating castable refractory material that may be lighter than the first refractory layer.

[0018] In one embodiment, an upper refractory layer may be positioned above the first refractory layer. The upper refractory layer may include firebrick.

[0019] In one embodiment, the first refractory layer may include expansion joints lined with ceramic paper that are configured to allow for differential thermal growth.

[0020] According to an aspect of the invention, a method for converting a boiler from coal fired to natural gas fired is provided. The method may include inserting an alloy plate above a hopper of the boiler, inserting a lower refractory layer above the alloy plate, and inserting an upper refractory layer above the lower refractory layer. The method may further include securing the alloy layer, the lower refractory layer, and the upper refractory layer using a plurality of anchors. The method may include sealing a bottom opening of the boiler with the alloy plate, the lower refractory layer, and the upper refractory layer.

[0021] In one embodiment, the method may further include inserting an openable drain through the alloy plate, the lower refractory layer, and the upper refractory layer.

[0022] In one embodiment, the method may further include positioning the alloy plate, the lower refractory layer, and the upper refractory layer on a coutant bottom of the boiler.

[0023] In one embodiment, the method may further include inserting a third refractory layer positioned above the upper refractory layer. The third refractory layer may include firebrick.

[0024] In one embodiment, the method may further include inserting expansion joints lined with ceramic paper into the upper refractory layer, the expansion joints configured to allow for differential thermal growth.701359-WO-l (GTV1020-0448WO)

[0025] According to an aspect of the invention, a boiler having a coutant bottom is provided. The boiler has an insert that includes a first refractory layer, a second refractory layer, a plurality of anchors, and an alloy plate. The first refractory layer is made of a castable refractory material. The second refractory layer is positioned below the first refractory layer. The anchors are configured to support the first refractory layer and the second refractory layer. The alloy plate is configured to be positioned below and support the first refractory layer and the second refractory layer. The first refractory layer and the second refractory layer are configured to seal a bottom opening of the boiler.

[0026] In one embodiment, the boiler may further include an openable drain.

[0027] In one embodiment, the first refractory layer may include expansion joints lined with ceramic paper that are configured to allow for differential thermal growth.

[0028] In one embodiment, the first refractory layer may have a thickness between about 7 centimeters and about 30 centimeters.BRIEF DESCRIPTION OF THE FIGURES

[0029] The present invention will be better understood from reading the following description of non-limiting embodiments, with reference to the attached drawings, wherein below:

[0030] Fig. 1 is a cross-sectional view of a combustion apparatus with a bottom seal, according to one example.

[0031] Fig. 2 is a top view of the combustion apparatus with the bottom seal shown in Fig. 1, according to one example.

[0032] Fig. 3 is a cross-sectional view of a combustion apparatus with a bottom seal, according to one example.701359-WO-l (GTV1020-0448WO)

[0033] Fig. 4 is a flowchart illustrating a method for converting a boiler from coal fired to natural gas fired, according to one example.DETAILED DESCRIPTION

[0034] 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.

[0035] As used herein, the terms “approximately” and “about,” as applied to one or more values of interest refer to a value that is similar to a stated reference value. In some embodiments, the term “approximately” or “about” refers to a range of values that fall within, for example, 25%, 20%, 10%, 5%, 4%, 3%, 2%, 1%, or less in either direction (greater than or less than ) of the stated reference value unless otherwise stated or otherwise evident from the context (except where such number would exceed 100% of a possible value).

[0036] The present subject matter is advantageous because there is a minimal impact to the design of the existing system and allows a flexibility in operation. Other than the bottom seal being added, no additional components are required and no changes are required to existing coal fired boilers.

[0037] This arrangement can be implemented on existing coal fired steam generation units with minimal impact to the design. Besides the bottom seal / insert including the multiple refractory layers, no additional components are needed. As such, this improvement is cost and labor effective. This system allows the units to operate using natural gas on units originally intended to be used with coal. This reduces the cost of replacement, as well as reduces the maintenance costs for these systems.701359-WO-l (GTV1020-0448WO)

[0038] Fig. 1 illustrates a cross-section view of a combustion apparatus 100 with a bottom seal 102, according to one example. The combustion apparatus may be a furnace or a boiler. The combustion apparatus 100 may be provided in a conventional heating or steam boiler or a thermal power generator. The combustion apparatus 100 includes a fuel supply means for supplying a fuel. Combustion systems for boilers may use a variety of different types and qualities of fuels, including natural gas, pulverized fuels, such as coal, petroleum coke, bituminous coal, lignite, biomass, etc., and a broad range of mixed gas fuels, such as refinery and other waste gases.

[0039] The bottom seal 102 may be positioned and designed to provide a seal between sloped tube panels 104 of the combustion apparatus 100 or furnace. During use, the expected temperature of the bottom surface of the furnace when firing natural gas is approximately 1100 degrees Celsius. In order to provide an effective seal, the bottom seal 102 includes a refractory system and a support structure designed to seal the furnace bottom, keep the temperature at the bottom of the refractory (where the support system will be) at approximately 455 degrees Celsius or lower. The bottom seal 102 may accommodate the thermal differential growth of the components of the combustion apparatus 100.

[0040] In order to reduce the temperature to an acceptable range, a refractory system 110 is installed across an existing opening between the sloped tube panels 104. The refractory system 110 may be a multi-layered system having 2, 3, 4, 5, or more layers. The refractory layers are designed to be of a heat-resistant material, for example castables, bricks, ceramic wools, ceramic fibers, fireproof polymers, or the like.

[0041] The refractory system 110 may be supported by an alloy plate 116. The alloy plate 116 may have a thickness between about 0.5 centimeters and about 5 centimeters. The alloy701359-WO-l (GTV1020-0448WO) plate 116 may be attached with a plurality of refractory anchors 130. In one example, the alloy plate may be a stainless-steel support plate.

[0042] The refractory system 110 may include a lower layer 112. The lower layer 112 may be a lightweight refractory material having strong insulating properties. The refractory material may be castable. The lower layer 112 may have a thickness between about 5 centimeters and about 30 centimeters. The thickness may be selected based on one or more of the size and geometry of the combustion apparatus, the temperature requirements, the strength requirements, or the like.

[0043] The refractory system 110 may include an upper layer 114. The upper layer 114 may be a high strength refractory material. The upper layer 114 may have a thickness between about 8 centimeters and about 30 centimeters. The thickness may be selected based on one or more of the size and geometry of the combustion apparatus, the temperature requirements, the strength requirements, or the like.

[0044] In other embodiments, additional refractory layers may be included. For example, an additional layer may be coupled with an uppermost side of the upper layer. The additional layer may provide additional strength and insulating properties. The additional layer may be a firebrick material and may cover only a portion of the upper layer or the entirety of the upper layer.

[0045] Expansion joints may be coupled with one or more of the refractory layers, for example, the upper refractory layer 114. The expansion joints may be lined with ceramic paper to allow for the differential thermal growth of the sloped tube panels. The expansion joints may reduce or mitigate cracking of the upper refractory layer 114.701359-WO-l (GTV1020-0448WO)

[0046] The bottom seal 102 may be installed over the existing ash hopper and / or water trough system. By being installed over and sealing a bottom portion of the furnace, no particulate matter reaches the ash hopper, and, as such, no maintenance or cleaning of the ash hopper and / or water trough system is needed. Alternatively, when the bottom seal is installed, the existing ash hopper and / or water trough system may be removed to save space, as the ash hopper and / or water trough system is no longer used or needed. The size and shape of the bottom seal 102 may be adjusted to fit a desired existing furnace size and shape. As such, the bottom seal 102 allows a plug-and-play approach to converting a coal fired furnace to a natural gas fired furnace.

[0047] The bottom seal 102 may include an openable drain 120. The openable drain 120 is configured to extend through the refractory layers. When the boiler is in use, the openable drain 120 remains closed to maintain the seal of the bottom seal 102. However, the drain 120 may be opened and / or removed to facilitate cleaning and / or maintenance of the boiler or the bottom seal.

[0048] Fig. 2 illustrates a top view of the combustion apparatus with the bottom seal shown in Fig. 1, according to one example. Specifically, a top view of the lower refractory layer 112 is shown. A plurality of anchors 130 may be distributed throughout the lower refractory layer 112. The anchors provide additional support and connection between the refractory layers. The anchors may be attached to the pressure parts of the apparatus, for example the coutant sloped tube panels and / or the alloy plate. The number and spacing of the anchors may be varied based on the refractory material used and the boiler size and geometry. The anchors may be arranged substantially vertically, substantially horizontally, or arranged irregularly. The anchors may be arranged in uniform rows or spaced irregularly.701359-WO-l (GTV1020-0448WO)

[0049] Fig. 3 illustrates a cross-sectional view of a combustion apparatus with a bottom seal, according to one example. The cross-sectional view shows the sloped tube panels 104 discussed above with respect to Fig. 1. Additionally, the arrangement of the alloy plate 116 supporting the lower refractory layer 112 and the upper refractory layer 114 is also shown in Fig.3. Of note, the weight of the refractory layers may put stress on the supporting alloy plate 116. To prevent or reduce any unwanted bending or sagging, support beams 132 may be added between the refractory layers and the alloy plate. The number and placement of support beams 132 may be modified or adjusted based on the specific alloy plate and refractory layers used. The support beams may be evenly spaced apart from one another, as shown in Fig. 3, or may be spaced at irregular intervals.

[0050] Fig. 4 illustrates a flowchart of a method for converting a boiler from coal fired to natural gas fired, according to one example. At step 400, the method may include inserting an alloy plate above a hopper of a boiler. The alloy plate may have a thickness between about 0.5 centimeters and about 10 centimeters. The alloy plate may be made from stainless-steel or the like. To prevent or reduce any unwanted bending or sagging, support beams may be added to support the alloy plate.

[0051] At step 402, the method may include inserting a lower refractory layer above the alloy plate. Support beams may be included below the lower refractory layer and the alloy plate to help support the weight of the refractory layer. The lower refractory layer may have strong insulative properties and may have a thickness between about 5 centimeters and about 30 centimeters. The lower refractory layer may be made of castables, bricks, ceramic wools, ceramic fibers, fireproof polymers, or the like.701359-WO-l (GTV1020-0448WO)

[0052] At step 404, the method may include inserting an upper refractory layer above the lower refractory layer. The upper refractory layer may be a high strength refractory material having a thickness of between about 8 centimeters and about 30 centimeters. The upper refractory layer may be made of castables, bricks, ceramic wools, ceramic fibers, fireproof polymers, or the like.

[0053] At step 406, the method may include securing the alloy layer, the lower refractory layer, and the upper refractory layer using a plurality of anchors.

[0054] At step 408, the method may include sealing a bottom opening of the boiler with the alloy layer, the lower refractory layer, and the upper refractory layer.

[0055] All of the materials of the bottom seal arrangement may be selected based on desired use case. Of note, the materials should be selected to provide added thermal capacity and strength in case elevated temperatures are encountered.

[0056] In one embodiment, a bottom seal for a boiler is provided. The bottom seal includes a first refractory layer, a second refractory layer, a plurality of anchors, and an alloy plate. The first refractory layer is made of a castable refractory material. The second refractory layer is positioned below the first refractory layer. The anchors are configured to support the first refractory layer and the second refractory layer. The alloy plate is configured to be positioned below and support the first refractory layer and the second refractory layer. The first refractory layer and the second refractory layer are configured to seal a bottom opening of the boiler.

[0057] In one example, the bottom seal also includes an openable drain. The boiler may include a coutant bottom. In one example, the first refractory layer has a thickness between about 8 centimeters and about 30 centimeters. The second refractory layer may have a thickness between about 5 centimeters and about 30 centimeters.701359-WO-l (GTV1020-0448WO)

[0058] The castable refractory material of the first refractory layer may be stronger than the second refractory layer. The second refractory layer may be an insulating castable refractory material that is lighter than the first refractory layer. The refractory materials may include castables, bricks, ceramic wools, ceramic fibers, fireproof polymers, or the like and may be made from substances such as fireclay, silicon carbide, alumina, magnesite, zirconia, chromite, dolomite, bauxite, or the like. These materials contain high strength, chemical resistance, and heat-insulating properties.

[0059] The bottom seal may include a third refractory layer positioned above the first refractory layer. The third refractory layer may include firebrick. The first refractory layer may include expansion joints lined with ceramic paper that are configured to allow for differential thermal growth.

[0060] In one embodiment, a method is provided for converting a boiler from coal fired to natural gas fired. The method may include inserting an allow plate above a hopper of the boiler, inserting a lower refractory layer above the alloy plate, and inserting an upper refractory layer above the lower refractory layer. The method may further include securing the alloy layer, the lower refractory layer, and the upper refractory layer using a plurality of anchors. The method may include sealing a bottom opening of the boiler with the alloy plate, the lower refractory layer, and the upper refractory layer.

[0061] In one example, the method includes inserting an openable drain through the alloy plate, the lower refractory layer, and the upper refractory layer. The method may include positioning the alloy plate, the lower refractory layer, and the upper refractory layer above or on a coutant bottom of the boiler.701359-WO-l (GTV1020-0448WO)

[0062] The method may include inserting a third refractory layer positioned above the upper refractory layer. The third refractory layer may include firebrick. The method may further include inserting expansion joints lined with ceramic paper into the upper refractory layer. The expansion joints may be configured to allow for differential thermal growth.

[0063] In an embodiment, a boiler having a coutant bottom is provided. The boiler has an insert that includes a first refractory layer, a second refractory layer, a plurality of anchors, and an alloy plate. The first refractory layer is made of a castable refractory material. The second refractory layer is positioned below the first refractory layer. The anchors are configured to support the first refractory layer and the second refractory layer. The alloy plate is configured to be positioned below and support the first refractory layer and the second refractory layer. The first refractory layer and the second refractory layer are configured to seal a bottom opening of the boiler.

[0064] In one example, the boiler may include an openable drain. The first refractory layer may include expansion joints lined with ceramic paper that are configured to allow for differential thermal growth. The first refractory layer may have a thickness between about 7 centimeters and about 30 centimeters.

[0065] It is 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. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the inventive subject matter without departing from its scope. While the embodiments described herein are intended to define the parameters of the inventive subject matter, they are by no means limiting and are example embodiments.Many other embodiments will be apparent to one of ordinary skill in the art upon reviewing the701359-WO-l (GTV1020-0448WO) above description. The scope of the inventive subject matter 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, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical 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 based on 35 U.S.C. § 112(f), unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.

[0066] This written description uses examples to disclose several embodiments of the inventive subject matter, including the best mode, and also to enable one of ordinary skill in the art to practice the embodiments of inventive subject matter, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the inventive subject matter 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.

[0067] 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,701359-WO-l (GTV1020-0448WO)embodiments “comprising,” “comprises,” “including,” “includes,” “having,” or “has” an element or a plurality of elements having a particular property may include additional such elements not having that property.

[0068] 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.

[0069] Parts List:100 - combustion apparatus102 - bottom seal104 - sloped tube panels110 - refractory system112 - lower refractory layer114 - upper refractory layer116 - alloy plate120 - drain130 - anchors132 - support beams

Claims

701359-WO-l (GTV1020-0448WO)CLAIMS:

1. A bottom seal for a boiler comprising:a first refractory layer made of a castable refractory material;a second refractory layer positioned below the first refractory layer;a plurality of anchors configured to support the first refractory layer and the second refractory layer;an alloy plate configured to be positioned below and support the first refractory layer and the second refractory layer;wherein the first refractory layer and the second refractory layer are configured to seal a bottom opening of the boiler.

2. The bottom seal of claim 1, further comprising an openable drain.

3. The bottom seal of claim 1, wherein the boiler includes a coutant bottom.

4. The bottom seal of claim 1, wherein the first refractory layer has a thickness between about 7 centimeters and about 30 centimeters.

5. The bottom seal of claim 1, wherein the second refractory layer has a thickness between about 5 centimeters and about 30 centimeters.

6. The bottom seal of claim 1, wherein the castable refractory material of the first refractory layer is stronger than the second refractory layer.

7. The bottom seal of claim 1, wherein the second refractory layer is an insulating castable refractory material that is lighter than the first refractory layer.

8. The bottom seal of claim 1, further comprising an upper refractory layer positioned above the first refractory layer.701359-WO-l (GTV1020-0448WO)9. The bottom seal of claim 8, wherein the upper refractory layer includes firebrick.

10. The bottom seal of claim 1, wherein the first refractory layer includes expansion joints lined with ceramic paper that are configured to allow for differential thermal growth.

11. A method for converting a boiler from coal fired to natural gas fired, the method comprising:inserting an alloy plate above a hopper of the boiler;inserting a lower refractory layer above the alloy plate;inserting an upper refractory layer above the lower refractory layer;securing the alloy layer, the lower refractory layer, and the upper refractory layer using a plurality of anchors; andsealing a bottom opening of the boiler with the alloy plate, the lower refractory layer, and the upper refractory layer.

12. The method of claim 11, further comprising inserting an openable drain through the alloy plate, the lower refractory layer, and the upper refractory layer.

13. The method of claim 11, further comprising positioning the alloy plate, the lower refractory layer, and the upper refractory layer on a coutant bottom of the boiler.

14. The method of claim 11, further comprising inserting a third refractory layer positioned above the upper refractory layer.

15. The method of claim 11, wherein the third refractory layer includes firebrick.

16. The method of claim 11, further comprising inserting expansion joints lined with ceramic paper into the upper refractory layer, the expansion joints configured to allow for differential thermal growth.701359-WO-l (GTV1020-0448WO)17. A boiler having a coutant bottom, comprising:an insert including:a first refractory layer made of a castable refractory material;a second refractory layer positioned below the first refractory layer;a plurality of anchors configured to support the first refractory layer and the second refractory layer;an alloy plate configured to be positioned below and support the first refractory layer and the second refractory layer;wherein the first refractory layer and the second refractory layer are configured to seal a bottom opening of the boiler.

18. The boiler of claim 17, further comprising an openable drain.

19. The boiler of claim 17, wherein the first refractory layer includes expansion joints lined with ceramic paper that are configured to allow for differential thermal growth.

20. The boiler of claim 17, wherein the first refractory layer has a thickness between about 7 centimeters and about 30 centimeters.

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