Boiler tube insert and boiler tubes having inserts

Abstract

Boiler systems having convection sections containing a set of boiler tubes having boiler tube inserts, boiler tubes for use in the convection section of a boiler system, and boiler tube inserts for boiler tubes for use in the convection section of a boiler system are provided herein. The boiler tube inserts are positioned in a first section of each boiler tube, where the first section extends from a front tube end the receives combustion gases from a furnace. The first section of the boiler tubes can be a plain tube section, and the boiler tubes can have a second section that includes a finned structure. The boiler tube inserts can be helical and can be made of a ceramic material.

Description

BOILER TUBE INSERTS AND BOILER TUBES HAVING INSERTS BACKGROUND OF THE INVENTION Technical Field of the Invention

[001] The present technology relates to boiler systems that employ combustion processes, and more specifically to such boilers, boiler tubes having inserts and boiler tube inserts. Background of the Related Technique

[002] Inserts are frequently added to radiant tubes in heated energy systems, such as furnaces, boilers, and other systems that utilize radiant tubes. The advantages provided by inserts generally include improved fluid channeling, uniformity of heat transfer and radiation, moderation of fluid flow and energy-producing reactions, control and improvement of energy-producing reactions, structural improvement of the system, and increased or augmented system efficiency.

[0003] Inserts have been manufactured in many shapes, although helical inserts are preferred in many applications. Helical inserts are typically placed within heated power systems to interact with and / or be exposed to the products of power generation, such as combusted or burned hydrocarbon fuel, steam, hydrogen, nitrogen, carbon dioxide, and the products of catalytic reactions, subjecting the inserts to high-temperature environments. Qzncnn / eznz / e / Yi

[0004] Radiant tube inserts used in boilers and other heated energy systems have been constructed from metallic materials, such as stainless steel and nickel-chromium alloys. One reason for this is that metals are easy to fabricate into coiled, braided, twisted, or helical shapes, especially for simple, low-twist geometries that allow for the efficient exchange of thermal energy to a heat exchange fluid flowing within the heat exchangers. However, metals exhibit much higher levels of thermal expansion and are limited in the temperatures at which they can operate.

[0005] Ceramics have also been used as a construction material for radiant tube inserts due to their natural ability to withstand high-temperature environments. Ceramic inserts tend to be advantageous in that they generally experience less thermal expansion than other materials when subjected to significant temperature changes. The reduced thermal expansion rates of ceramics can also improve an insert's ability to adapt and couple with other system components, reducing the thermal stresses that can be associated with intercomponent couplings during high-temperature operating conditions.

[006] The optimum configuration of radiant tube inserts, with respect to shape and material, depends heavily on the specific application. If the heat produced by the energy-generating reactions within a system is not adequately radiated, captured, or recycled due to an inefficiency of the inserted radiant tube or the system as a whole, an undue amount of energy may be lost and wasted, or possibly result in a lack of control, economy, or operability of the system. Accordingly, with respect to radiant tube inserts, characteristics such as material, length, shape, and placement within the radiant tube can all affect the operation or Qzncnn / eznz / e / Yi operation and the efficiency of the radiant tube insert. Regarding helical inserts, the specific characteristics of the shape also come into play, such as the number of channels, the depth of the channels, the twist angle, and the number of twists. In addition, the characteristics of the radiant tubes also affect the operation of the system.

[0007] In addition, tube inserts in other types of tubes in heated energy systems are not generally known, such as boiler tubes used for heat transfer by convection rather than heat transfer by radiation. Summary of the Invention

[0008] The present technology includes boiler tube inserts, boiler tubes having inserts, and boiler systems having boiler tubes that include boiler tube inserts.

[0009] In one aspect, a boiler system is disclosed that includes a housing, cover, or casing, a furnace within the housing, the furnace including a back wall, and a boiler tube assembly in a convection section of the boiler system. Each boiler tube in the boiler tube assembly includes a front tube end that receives combustion gases from the furnace, a back tube end through which combustion gases exit the boiler tube, and a first section extending from the front tube end along at least a portion of a length of the boiler tube. Additionally, the first section of each boiler tube includes a boiler tube insert.

[0010] In another aspect, a boiler tube configured for use in a convection section of a boiler system is provided. The boiler tube includes a front tube end configured to receive combustion gases from a furnace, and a rear tube end configured to allow combustion gases to exit the boiler tube. The tube The boiler section also includes a first section extending from the end of the front tube along at least a portion or part of a length of the boiler tube. Additionally, the first section includes a boiler tube insert.

[0011] In a third aspect, a boiler tube insert is provided that is configured to be retained in a boiler tube configured for use in a convection section of a boiler system. The boiler tube insert includes a solid central core extending the entire length of the boiler tube insert, and a plurality of projections each wrapping helically around the solid central core in less than a complete 360° rotation. Furthermore, the boiler tube insert is made of a ceramic material. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Specific examples have been selected for the purpose of illustration and description, and are shown in the accompanying drawings, which form part of the description.

[0013] Figure 1 is a schematic diagram of a boiler system in accordance with an example embodiment of the present technology.

[0014] Figure 2 is an end view of an example of a boiler tube of the present technology that can be used in the boiler system of Figure 1.

[0015] Figure 3 is a cross-sectional side view of a portion of the boiler tube of Figure 2, taken along line 3-3 of Figure 2.

[0016] Figure 4 is an external side view of a portion of the boiler tube from Figure 3. Qzncnn / eznz / e / Yi

[0017] Figure 5 is a front perspective view of a boiler tube insert of the present technology for use in a boiler tube, such as any of the boiler tubes in Figures 2-4.

[0018] Figure 6 is an end view of the boiler tube insert of Figure 5.

[0019] Figure 7 is a side view of the boiler tube insert from Figure 5. DETAILED DESCRIPTION OF THE INVENTION

[0020] This technology relates to boiler tube inserts, boiler tubes having inserts, and boiler systems having boiler tubes that include boiler tube inserts. This technology is particularly useful in boiler systems that have a furnace or heater and employ combustion processes, such as boiler systems for hot water and steam applications.

[0021] Boiler systems that employ combustion processes to generate heat are commonly used in a variety of environments. Fire-tube boilers, also known as fire-tube boilers or boiler furnaces, typically have a combustion chamber enclosed within a water vessel or tank and a convection section that includes a plurality of heat transfer tubes running through the vessel to conduct the heated combustion gases resulting from the combustion of an air-fuel mixture by means of a burner, typically located at the front of the boiler. The hot combustion gases are typically passed from the front of the boiler to the rear and back again. The boiler may have additional passes, using extra tubes, to achieve complete heat exchange. Qzncnn / eznz / e / Yi

[0022] Figure 1 shows an example of a boiler system 100 of the present technology. The boiler system 100 is a fire-tube boiler. The boiler system 100 has a housing, cover, or casing 102, which may generally be cylindrical in shape. The housing 102 may have a front end 104, a rear end 106, a top side 108, and a bottom side 110. The housing 102 may be mounted on a base 112. Extending longitudinally (and as shown horizontally) within the housing 102 and generally near the bottom side 110 of the housing 102 is a main fire tube or furnace 114, which provides a combustion chamber 116 (Figure 1). The combustion chamber 116 is generally enclosed by a casing structure 118, which may be cylindrical in shape.The housing structure 118 in the illustrated example extends longitudinally from a front wall 120 of the oven to a rear wall 122 of the oven.

[0023] On or near the front wall 120 of the furnace, the furnace 114 opens to accommodate a burner 124. On or near the rear wall 122 of the furnace, the furnace 114 opens to a boiler tube assembly 126 in a convection section of the boiler system 100, which may be located at the rear of the furnace 114 and further extends longitudinally (and as shown horizontally) within the housing 102 of the boiler system 100, towards the rear end 106.

[0024] Each boiler tube 128 of boiler tube assembly 126 is a convection boiler tube, configured to perform convection heat transfer to transfer heat from the combustion gases of the furnace 114 to a medium such as water or steam. Each boiler tube 128 of boiler tube assembly 126 may be straight. Each boiler tube 128 of boiler tube assembly 126 may have a front tube end 130 that receives combustion gases from the furnace 114, and a rear tube end 132 where the combustion gases exit the boiler tube 128. Each boiler tube 128 of boiler tube assembly 126 may also Qzncnn / eznz / e / Yi may have a first section 134 extending from the end of the front tube 130 along at least part of the length of the boiler tube 128. Each boiler tube 128 of the boiler tube assembly 126 may further have a second section 136 extending from the first section 134 to the end of the rear tube 132. In some examples, the first section 134 may be approximately half, or up to approximately half, the length of a boiler tube 128. In other examples, the first section 134 may be less than approximately half the length of a boiler tube 128, such as being approximately one-third, or up to approximately one-third, of the length of a boiler tube 128.

[0025] In at least some examples, the first section 134 of a boiler tube 128 may be structured as a flat or smooth tube section. In other examples, the first section 134 of the boiler tube 128 may have a fire-side surface, such as a rough, grooved, ribbed, or curled surface. In at least some examples, the second section 136 of the boiler tube 128 may include a finned or flapped structure extending along at least a portion of the length of the second section, and may extend to the entire length of the second section. The finned, flapped, or flapped structure may be formed of an aluminum alloy. In some examples, the entire tube, including the first section 134 and the second section 136, may be rough, grooved, ribbed, or curled.In other examples, the first section 134 may be flat or smooth and the second section 136 may be rough, striated, striped or curled.

[0026] After exiting furnace 114, the combustion gases enter the boiler tube assembly 126, where they are cooled by convective heat transfer to the water or steam medium. The combustion gases from furnace 114 enter each boiler tube 128 of the assembly. The combustion gases enter boiler tubes 126 through the front end of tube 130, travel through the first and second sections, and then exit boiler tube 128 through the rear end of tube 132. In the illustrated example, the combustion gases can leave each boiler tube 128 and exit the boiler system through a flue gas outlet 138. At the front tube end, the combustion gases can have a temperature in the range of approximately 1600°F (871.1111°C) to approximately 2000°F (1093.333°C), such as approximately 1800°F (982.2222°C).

[0027] As shown in Figure 1, the first section 134 of each boiler tube 128 includes a boiler tube insert 140. The boiler system 100 may then include a boiler tube insert 140 positioned within the first section 134 of each boiler tube 128. In at least some examples, each boiler tube insert 140 may be located on a front portion 142 of the first section 134 of the boiler tube 128. The front portion 142 of the first section of the boiler tube 128 begins at the end of the front tube 130 and extends along at least a portion of the length of the first section 134. In some examples, the front portion 142 may be approximately half, or up to approximately half, the length of the first section 134 of the boiler tube 128.In other examples, the front portion 142 may be less than approximately half the length of the first section 134 of a boiler tube 128, such as being approximately one-third, or up to approximately one-third of the length of the first section 134 of a boiler tube 128.

[0028] Figure 2 is an end view of an example of a boiler tube 200 of the present technology, which may be used as a boiler tube 128 in the boiler system 100 shown in Figure 1. Figure 3 is a cross-sectional view of a portion of the first section 202 of the boiler tube 200, taken along line 3-3 of Figure 2, and Figure 4 is an external side view of a portion of the first section 202 of the Qzncnn / eznz / e / Yi boiler tube 200. The boiler tube 200 has a front tube end 204, which is configured to receive combustion gases 300 from a furnace, such as furnace 114 in Figure 1. Although not shown in Figures 2 and 3, the boiler tube 200 also includes a rear tube end, such as rear tube end 132 in Figure 1, which is configured to allow combustion gases 300 to exit the boiler tube 200.

[0029] The first section 202 extends from the end of the front tube 204 along at least part of the length of the boiler tube and includes a boiler tube insert 206. As shown in the example illustrated in Figures 2 and 3, the first section 202 is a flat tube section, and the boiler tube insert 206 is located in a front portion 208 of the first section 202 of the boiler tube 200. The front portion 208 of the first section 202 of the boiler tube 202 extends from the end of the front tube 204 along at least part of the length of the first section 202, as discussed above with respect to the front portion 142 of the boiler tube 128. Although the exact position of the boiler tube insert within the front portion 208 may vary depending on the length and design of the boiler tube 200, the boiler tube insert is preferably placed near the end of the front tube 204.In some examples, the boiler tube insert can be positioned so that the first end 210 of the boiler tube insert is positioned within approximately, or up to approximately, one foot (30.48 cm) of the front end of tube 204, or within approximately, or up to approximately 6 inches (15.24 cm) of the front end of tube 204. In at least one example, the boiler tube insert can be positioned so that the first end 210 of the boiler tube insert is positioned within approximately, or up to approximately, 2 inches (5.08 cm) of the front end of tube 204. Qzncnn / eznz / e / Yi

[0030] During manufacturing or installation, the boiler tube insert 206 can be placed inside the boiler tube 200 by sliding the boiler tube insert 206 into the boiler tube 200. Accordingly, the boiler tube insert can have a diameter that is less than, or up to approximately, the inside diameter of the boiler tube 200, and can be configured to be slidably received inside the boiler tube 200. The boiler tube 200 can include at least one groove 212 configured to retain the boiler tube insert 206 in the desired location within the boiler tube 200. The groove 212, as shown in Figures 3 and 4, is a circumferential groove and extends around the entire circumference of the boiler tube 200.In some other examples, one or more slits of shorter length may be provided, extending along only a portion of the circumference of the boiler tube 200. Alternatively, the boiler tube may include at least one other type of retaining feature to retain the boiler tube insert 206 in the desired location within the boiler tube 200. Preferably, the at least one retaining feature is configured to retain the boiler tube insert 206 in the desired location within the front portion 208 of the first section 202 of the boiler tube 200 during operation, when the combustion gases 300 exert force against the boiler tube insert 206 as they flow downstream through the boiler tube 200.

[0031] Figures 5-7 illustrate an example of a boiler tube insert 400, which can be used as a boiler tube insert 140 in the boiler tube system 100, or as a boiler tube insert 206 of the boiler tube system 200. The boiler tube insert 400 is generally helical in shape and has a plurality of projections or lugs 402, which are formed projections that each extend radially outward from and longitudinally along the central core 404. Each of the projections 402 also wraps helically around, or bends around, the central core 404. The projections 402 form a channel Qzncnn / eznz / e / Yi helical 410, or duct, corridor, passage or passage, between each pair of projections 402, and combustion gases flowing through the boiler tube can flow along each of those channels 410.

[0032] The 400 boiler tube insert has a first end 406 and a second end 408, and a length extending from the first end 406 to the second end 408. The 400 boiler tube insert has a length L, which can be any suitable length, and in some examples is from approximately 1 inch (2.54 cm) to approximately 20 inches (50.8 cm), such as from approximately 4 inches (10.16 cm) to approximately 8 inches (20.32 cm). In at least one example, the length of the 400 boiler tube insert can be approximately 6 inches (15.24 cm). The boiler tube insert 400 has a diameter D that is less than the length of the boiler tube insert 400, and, as discussed above, may be less than, equal to, or up to approximately the inside diameter of the boiler tube 200. For example, the diameter of the boiler tube insert 400 may be approximately 1 inch (2.54 cm) to approximately 4 inches (10.16), for example, from approximately 3 inches (7.62 cm).

[0033] In the example illustrated in Figures 5-7, the boiler tube insert 400 has four 402 projections. In other examples, the boiler tube insert may have any suitable number of projections. For example, the boiler tube insert may have up to six projections, including having 2, 3, 4, 5, or 6 projections. Each of the 402 projections has a thickness or thickness T, which may be at least 0.25 inches (0.635 cm).

[0034] The central core 404 is solid and extends the entire length of the boiler tube insert 400. Each of the projections 402 can be helically wrapped, extended, or bent around the central core 404 in an arc. The angle of the arc may depend on the length of the boiler tube insert 400, and in at least some examples Qzncnn / eznz / e / Yi may be less than a full 360° arc. In the illustrated example, the arc formed by each projection 402 around the central core 404 is approximately 135° to approximately 225°, being, for example, approximately 180°, or up to approximately 180°. The pitch, or pitch P, which is the distance between any two consecutive peaks of the projections, may vary depending on the length of the boiler tube insert 400 and the number of projections 402.

[0035] The 400 boiler tube insert may be made of a ceramic material configured to withstand or endure combustion gas temperatures in the range of at least approximately 800°F (426.667°C) to at least approximately 2000°F (1093.333°C). The ceramic material may include silicon carbide (SiC) and may contain up to approximately 80% by weight of silicon carbide. The ceramic material may also include other materials such as aluminum oxide (Al₂O₃), silicon dioxide (SiO₂), calcium oxide (CaO), ferric oxide (Fe₂O₅), alkalis, and other materials. The ceramic material may be porous and may have a porosity of approximately 8.0% to approximately 14%, such as approximately 9% to approximately 10%, or approximately 13% to approximately 14%.

[0036] It should be understood that, although the boiler systems shown in the illustrated examples have horizontally oriented tubes, boiler tubes having inserts of the present technology may have any suitable orientation, such as horizontal, vertical, or inclined at any angle.

[0037] The use of boiler tube inserts in boiler tubes and boiler systems according to the present technology can provide advantages over other boiler systems and boiler tubes. For example, in a boiler system using boiler tubes that have a finned structure formed from an aluminum alloy, but without boiler tube inserts, the flow velocity of the combustion gases Qzncnn / eznz / e / Yi must be reduced to prevent overheating of the aluminum. In contrast, in boiler tubes of the present technology, the ceramic insert can increase or enhance the convective heat transfer of the boiler tube, particularly in the first section of the boiler tube. The increased heat transfer in the first section of the boiler tube can reduce the temperature of the combustion gases before they reach the aluminum fin structure sufficiently so that it is not necessary to reduce the velocity, flow rate, or flow rate of the combustion gases. For example, tests have indicated that the flow rate in boiler tubes of the present technology can be increased by approximately 50%, compared to identical boiler tubes that do not include a boiler tube insert of the present technology.Additionally, the increased convective heat transfer within the boiler tubes of this technology may allow boiler systems to have less space or a smaller footprint and reduce manufacturing, transportation, and installation costs.

[0038] It follows from the foregoing that, although specific examples have been described for illustrative purposes, various modifications may be made without departing from the spirit or scope of the present invention. Therefore, the description detailed above is intended to be illustrative rather than limiting, and it is understood that the following claims, including all equivalents, are intended to specifically address and clearly claim the subject matter claimed.

Claims

1. A boiler system comprising: a housing; a furnace within the housing, including a rear wall; and a boiler tube assembly in a convection section of the boiler system; wherein each boiler tube of the boiler tube assembly includes a front tube end receiving combustion gases from the furnace, a rear tube end from which combustion gases exit the boiler tube, and a first section extending from the front tube end along at least a portion of a length of the boiler tube, wherein the first section includes a boiler tube insert.

2. The boiler system according to claim 1, wherein each boiler tube of the boiler tube assembly is straight.

3. The boiler system according to claim 1, wherein the first section of each boiler tube of the boiler tube assembly is a flat tube section.

4. The boiler system according to claim 1, wherein each boiler tube of the boiler tube assembly further comprises a second section extending from the first section to the rear end of the tube; the second section includes a finned structure.

5. The boiler system according to claim 1, wherein the boiler tube insert is located in a front portion of the first section, wherein the front portion begins at the end of the front Qzncnn / eznz / e / Yi tube and extends along at least a portion of a length of the first section.

6. The boiler system according to claim 5, wherein the front part is approximately half the length of the first section.

7. The boiler system according to claim 1, wherein the boiler tube includes at least one slit configured to retain the boiler tube insert within the boiler tube.

8. The boiler system according to claim 1, wherein the boiler tube insert comprises: a solid central core extending the entire length of the boiler tube insert; and a plurality of projections each helically enveloping the solid central core in less than a full arc of 360°; wherein the boiler tube insert is made of a ceramic material.

9. The boiler system according to claim 1, wherein: the plurality of projections consists of between two and six projections; each of the plurality of projections helically envelops the solid central core in an arc between 135° and approximately 225°; and a length of the boiler tube insert is from approximately 1 inch (2.54 cm) to approximately 20 inches (50.8 cm).

10. A boiler tube configured for use in a convection section of a boiler system, the boiler tube comprising: a front tube end configured to receive combustion gases from a furnace; a back tube end configured to allow combustion gases to exit the boiler tube; and a first section extending from the front tube end along at least a portion of the length of the boiler tube, wherein the first section includes a boiler tube insert 11. The boiler tube according to claim 10, wherein the boiler tube is straight.

12. The boiler tube according to claim 10, wherein the first section of the boiler tube is a flat tube section.

13. The boiler tube according to claim 10, wherein the boiler tube further comprises a second section extending from the first section to the rear end of the tube, and the second section includes a finned structure.

14. The boiler tube according to claim 10, wherein the boiler tube insert is located in a front portion of the first section, wherein the front portion begins at the end of the front tube and extends along at least a portion of a length of the first section.

15. The boiler tube according to claim 14, wherein the front portion extends to approximately half the length of the first section. Qzncnn / eznz / e / Yi 16. The boiler tube according to claim 10, wherein the boiler tube includes at least one slit configured to retain the boiler tube insert within the boiler tube.

17. The boiler tube according to claim 10, wherein the boiler tube insert comprises: a solid central core extending the entire length of the boiler tube insert; and a plurality of projections each helically wraps around the solid central core in less than a complete 360° rotation; wherein the boiler tube insert is made of a ceramic material.

18. The boiler tube according to claim 17, wherein: the plurality of projections consists of from two to six projections; each of the plurality of projections helically envelops the solid central core in a rotation that is from 135° to approximately 225°; and the length of the boiler tube insert is from approximately 1 inch (2.54 cm) to approximately 20 inches (50.8 cm).

19. A boiler tube insert configured to be retained in a boiler tube configured to be used in a convection section of a boiler system, the boiler tube insert comprising: a solid central core extending the entire length of the boiler tube insert; and a plurality of projections each helically wrapping around the solid central core in less than a complete 360° rotation; Qzncnn / eznz / e / Yi wherein the boiler tube insert is made of a ceramic material.

20. The boiler tube insert according to claim 19, wherein: the plurality of projections consists of between two and six projections; each of the plurality of projections helically wraps around the solid central core in a rotation that is between 135° and approximately 225°; and the length of the boiler tube insert is from approximately 1 inch (2.54 cm) to approximately 20 inches (50.8 cm).