Fire tube

Abstract

A fire tube with three hollow tube sections, two of which are parallel to each other and one of which is perpendicular to and connects the ends of the first two tube sections. The bottom-most tube section, which contains the burner, has an inner ceramic liner that is made up of one or more separate ceramic tubular sections. An upper set of cooling fins surrounds the top part of the bottom-most tube section, and a lower set of cooling fins surrounds the bottom part of the bottom-most tube section.

Claims

1. A fire tube comprising: a. a first tube section comprised of a first length of hollow tube, a second tube section comprised of a second length of hollow tube, and a third tube section comprised of a third length of hollow tube, wherein the third tube section is situated at a rear end of each of the first and second tube sections and is oriented so that a longitudinal axis of the third tube section is perpendicular to a longitudinal axis of each of the first and second tube sections, wherein the first tube section comprises an open front end that terminates in a first flange, wherein the second tube section comprises an open front end that terminates in a second flange, and wherein the first, second and third tube sections are configured to provide a fluid channel through the open end of the first tube section at the first flange, through the first tube section, through the third tube section, through the second tube section, and out the open end of the second tube section at the second flange; and b. a tubular and hollow ceramic liner that is situated inside of the first tube section, the ceramic liner comprising one or more separate tubular sections, each of which comprises a front end with a circumferential recess and a rear end with a circumferential protrusion that is configured to fit into the circumferential recess on the front end of an adjacent tubular section.

2. A fire tube comprising: a. a first tube section comprised of a first length of hollow tube, a second tube section comprised of a second length of hollow tube, and a third tube section comprised of a third length of hollow tube, wherein the third tube section is situated at a rear end of each of the first and second tube sections and is oriented so that a longitudinal axis of the third tube section is perpendicular to a longitudinal axis of each of the first and second tube sections, wherein the first tube section comprises an open front end that terminates in a first flange, wherein the second tube section comprises an open front end that terminates in a second flange, and wherein the first, second and third tube sections are configured to provide a fluid channel through the open end of the first tube section at the first flange, through the first tube section, through the third tube section, through the second tube section, and out the open end of the second tube section at the second flange; and b. a tubular and hollow ceramic liner that is situated inside of the first tube section, the ceramic liner comprising one or more separate tubular sections, each of which comprises a front end with a circumferential recess and a rear end with a circumferential protrusion that is configured to fit into the circumferential recess on the front end of an adjacent tubular section, wherein at least one of said first tube section, said second tube section and said third tube section is comprised of a base layer and a nickel alloy layer bonded to said base layer, wherein said nickel alloy layer has a nickel content higher than said base layer.

3. The fire tube of claim 2 where said base layer is comprised of a carbon steel.

4. The fire tube of claim 3 further including a sealant layer bonded to said nickel alloy layer.

5. The fire tube of claim 2 wherein said nickel alloy layer is comprised of C-276.

6. A tire tube comprising: a. a first tube section comprised of a first length of hollow tube, a second tube section comprised of a second length of hollow tube, and a third tube section comprised of a third length of hollow tube, wherein the third tube section is situated at a rear end of each of the first and second tube sections and is oriented so that a longitudinal axis of the third tube section is perpendicular to a longitudinal axis of each of the first and second tube sections, wherein the first tube section comprises an open front end that terminates in a first flange, wherein the second tube section comprises an open front end that terminates in a second flange, and wherein the first, second and third tube sections are configured to provide a fluid channel through the open end of the first tube section at the first flange, through the first tube section, through the third tube section, through the second tube section, and out the open end of the second tube section at the second flange, and wherein at least one of said first tube section, said second tube section and said third tube section is comprised of a base layer of carbon steel and a nickel alloy layer bonded to said base layer, wherein said nickel alloy layer has a nickel content higher than said base layer; b. a plurality of cooling fins that are configured to surround at least a portion of a mid-section of the first tube section, wherein the plurality of cooling fins comprises an upper set of cooling fins that surrounds an upper part of the first tube section and a lower set of cooling fins that surrounds a lower part of the first tube section; c. a tubular and hollow ceramic liner that is situated inside of the first tube section, the ceramic liner comprising one or more separate tubular sections, wherein the ceramic liner has a length and a position within the first tube section, wherein the plurality of cooling fins has a length and position relative to the first tube section, and wherein the length and position of the ceramic liner within the first tube section corresponds to the length and position of the cooling fins surrounding the first tube section; and d. a sealant layer bonded to said nickel alloy layer.

7. A fire tube comprising: a first tube section comprised of a first length of hollow tube, a second tube section comprised of a second length of hollow tube, and a third tube section comprised of a third length of hollow tube, wherein the third tube section is situated at a rear end of each of the first and second tube sections and is oriented so that a longitudinal axis of the third tube section is perpendicular to a longitudinal axis of each of the first and second tube sections, wherein the first tube section comprises an open front end that terminates in a first flange, wherein the second tube section comprises an open front end that terminates in a second flange, and wherein the first, second and third tube sections are configured to provide a fluid channel through the open end of the first tube section at the first flange, through the first tube section, through the third tube section, through the second tube section, and out the open end of the second tube section at the second flange, and wherein at least one of said first tube section, said second tube section and said third tube section is comprised of a base layer of carbon steel and a nickel alloy layer bonded to said base layer, wherein said nickel alloy layer has a nickel content higher than said base layer, and a tubular and hollow ceramic liner situated inside of the first tube section, the ceramic liner comprising one or more separate tubular sections, each of which comprises a front end with a circumferential recess and a rear end with a circumferential protrusion that is configured to fit into the circumferential recess on the front end of an adjacent tubular section.

8. The fire tube of claim 7 further including a sealant layer bonded to said nickel alloy layer.

9. A fire tube comprising: a. a first tube section comprised of a first length of hollow tube, a second tube section comprised of a second length of hollow tube, and a third tube section comprised of a third length of hollow tube, wherein the third tube section is situated at a rear end of each of the first and second tube sections and is oriented so that a longitudinal axis of the third tube section is perpendicular to a longitudinal axis of each of the first and second tube sections, wherein the First tube section comprises an open front end that terminates in a first flange, wherein the second tube section comprises an open front end that terminates in a second flange, and wherein the first, second and third tube sections are configured to provide a fluid channel through the open end of the first tube section at the first flange, through the first tube section, through the third tube section, through the second tube section, and out the open end of the second tube section at the second flange; and b. a tubular and hollow ceramic liner that is situated inside of the first tube section, the ceramic liner comprising one or more separate tubular sections, each of which comprises a front end with a circumferential recess and a rear end with a circumferential protrusion that is configured to ft into the circumferential recess on the front end of an adjacent tubular section, wherein at least one of said first tube section, said second tube section and said third tube section is comprised of a base layer, said base layer having a sealant layer bonded to said base layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a rear perspective view of the present invention.

(2) FIG. 2 is a front perspective view of the present invention.

(3) FIG. 3 is a rear perspective view of the present invention with the second and third tube sections and the second flange removed.

(4) FIG. 4 is a rear view of the invention showing only the cooling fins and ceramic liner.

(5) FIG. 5 is a side view of the present invention.

(6) FIG. 6 is a front view of the present invention showing the section line for FIG. 7.

(7) FIG. 7 is a section view of the present invention.

(8) FIG. 8 is a perspective view of one of the sections of the ceramic liner of the present invention.

(9) FIG. 9 is a section view of the ceramic liner section taken at the section line shown in FIG. 8.

(10) FIG. 10 is a detail perspective view of the spray washer nozzle of the present invention.

(11) FIG. 11 is a cutaway view of the present invention installed on a heater treater.

(12) FIG. 12 is a rear perspective view of the present invention showing a first alternate embodiment of the cooling fins.

(13) FIG. 13 is a rear perspective view of the present invention showing a second alternate embodiment of the cooling fins.

(14) FIG. 14 is a rear perspective view of the present invention showing a third alternate embodiment of the cooling fins.

(15) FIG. 15 is a perspective view of one of the cooling fins shown in FIG. 14.

(16) FIG. 16 is a front perspective view of an embodiment of the invention with the cooling fins removed.

(17) FIG. 17 is a cross sectional view of the invention illustrated in FIG. 16 and taken along lines 17-17 thereof.

(18) FIG. 17A is an enlarged view of a portion of FIG. 17 and showing the tube material layers.

DETAILED DESCRIPTION OF THE INVENTION

(19) A. Overview

(20) The present invention overcomes the disadvantages of existing fire tubes by fabricating the fire tube out of a corrosion-resistant alloy and incorporating other structural features that extend the life of the fire tube and minimize maintenance requirements. These structural features include (1) cooling fins on the lower tube surrounding the burner to prevent the metal in this area of the tube from corroding and oxidizing anti (ii) a ceramic cylinder (or liner) inserted into the tube on the lower portion of the tube near the burner. The ceramic liner absorbs the heat from the burner and then transfers that heat outward to the lower portion of the fire tube and the cooling fins, thereby providing a more uniform distribution of the heat generated from the burner anti greater efficiency in heating the treater vessel.

(21) Other structural improvements include: (iii) a bar at the bottom of the lower tube to facilitate installation of the fire tube; (iv) a spray washer rail situated on top of the lower cooling fins and configured to direct high-pressure water into the fins for pressure washing; and (v) a threaded opening for insertion of a borescope to observe and inspect the upper portion of the lower fire tube without removing it. With these structural improvements, maintenance on the fire tube can be performed by draining the vessel, attaching the pressure washer for removal of the sludge around the cooling fins, inserting a borescope and conducting the visual inspection. The present invention is engineered for a life expectancy of five or more years without requiring removal of the fire tube.

(22) B. Detailed Description of the Figures

(23) FIG. 1 is a rear perspective view of the present invention. As shown in this figure, the invention 1 comprises two parallel tube sections 1a, 1b joined by a third tube section 1c that is situated at the rear end of each of the first and second tube sections 1 a, 1b. The third tube section 1 c is oriented so that its longitudinal axis is perpendicular to the longitudinal axes of the first and second tube sections 1a, 1 b. Each tube section 1 a, 1 b, 1 c is hollow. The tube sections 1 a, 1b, 1c are optionally coated on the outside with a layer of thermally conductive material such as copper or aluminum and/or a ceramic coating. Each of the first and second tube sections 1 a, 1b comprises an open front and that terminates in a flange 2a, 2b. The front end of each of the first and second tube sections 1a, 1b, is open (see FIG. 2). The three tube sections 1a, 1b, 1c are configured to provide a fluid channel through the open end of the first tube section 1 a at the first flange 2a, through the first tube section 1 a, through the third tube section 1 c, through the second tube section 1 b, and out the open end of the second tube section 1 b at the second flange 2b.

(24) In a preferred embodiment, the first tube section 1a is comprised of C276 alloy. The C276 alloy is a nickel-molybdenum-chromium-iron-tungsten alloy engineered to have excellent corrosion resistance in a wide range of severe environments. The high nickel and molybdenum contents make the alloy especially resistant to pitting and crevice corrosion in reducing environments, and the chromium imparts resistance to oxidizing media. The low carbon content minimizes carbide precipitation during welding to maintain corrosion resistance in as-welded structures. This alloy is resistant to the formation of grain boundary precipitates in the weld heat-affected zone, thus making it suitable for most chemical process applications in an as-welded condition. The C276 alloy is largely used in the most severe environments, such as chemical processing, pollution control, pulp and paper production, industrial and municipal waste treatment, and recovery of sour natural gas.

(25) The second tube section 1 b and third tube section 1c are preferably comprised of 316 L stainless steel, which is an austenitic chromium-nickel stainless steel that contains between two and three percent, molybdenum. The molybdenum content increases corrosion resistance, improves resistance to pitting in chloride ion solutions, and increases strength at high temperatures. Type 316 grade stainless steel is particularly effective in acidic environments. This grade of steel is effective in protecting against corrosion caused by sulfuric, hydrochloric, acetic, formic anti tartaric acids, as well as acid sulfates and alkaline chlorides. Although the 316L stainless steel is less expensive than the C276 alloy, the latter alloy is preferably used in the first tube section 1a because this is the hottest section of the fire tube (the burner assembly is located within this section of the fire tube).

(26) In a preferred embodiment, a plurality of cooling fins 3 surrounds at least a portion of the mid-section of the first tube section 1a; this is the portion of the tube that contains the burner assembly (not shown). In this context, the term “mid-section” refers to that part of the first tube section 1a that is between the main flange 2c and the third tube section 1 c. The cooling fins are shown in greater detail in FIG. 4. A dual-pronged spray washer rail 4 extends rearward from the main flange 2c across the top of the cooling fins 3 (see FIG. 3). The purpose of the cooling fins 3 is to help dissipate the heat created by the burner (not shown) within the first tube section 1a.

(27) FIG. 2 is a front perspective view of the present invention. As shown in this and the preceding figure, a main flange 2c comprises two apertures through which the front ends of the first and second tube sections 1a, 1b extend. The main flange 2c is situated behind the first and second flanges 2a, 2b but in front of the cooling fins 3 on the first tube section 1a. A burner lighting pipe 5 extends downwardly from the front end of the first tube section 1a between the first flange 2a and the main flange 2c. The purpose of the burner lighting pipe 5 is to allow access to light the burner (not shown). A threaded opening 6 on the main flange 2c is configured so that a borescope (not shown) can be attached to the threaded opening 6 for viewing of the fire tube behind the main flange 2c. In this particular embodiment, the threaded opening 6 is situated on one side of the main flange 2c between the first and second tube sections 1a, 1b. The spray washer valve 7 on the outside of the main flange 2c is connected to the spray washer rail 4 (see FIG. 3).

(28) FIG. 3 is a rear perspective view of the present invention with the second and third tube sections 1 b, 1c and second flange 2b removed. This figure shows the ceramic tube 9 or liner that is positioned inside of the first tube section 1a. A stepper 14 in the form of a rail extends forwardly from the rear end of the first tube section 1a and abuts up against the rear-most, surface of the ceramic liner 9. The stopper 14 may be attached to the inside of the first tube section 1a in any manner; however, in a preferred embodiment, it is welded to the inside of the first tube section 1a. The purpose of the stopper 14 is to prevent the ceramic liner 9 from being situated too far rearward within the first tube section 1a. The length and position of the ceramic liner 9 within the first tube section 1a preferably corresponds to the length and position of the cooling fins 3 on the outside of the first tube section 1a.

(29) As shown in this figure, the spray washer rail 4 preferably comprises a first extension member 4a that extends rearwardly of the main flange 2c across the top of one side of the cooling fins 3 and that is connected to the spray washer valve 7 (not shown in this view). The spray washer rail 4 further comprises a second extension member 4b that is parallel to the first extension member 4a and that extends rearwardly of the main flange 2c across the top of the other side of the cooling fins 3. A connection member 4c connects the first and second extension members 4a, 4b on the end of the spray washer rail 4 that is closest to the inside of the main flange 2c.

(30) FIG. 4 is a rear view of the invention showing only the cooling fins and ceramic liner. Note that there is a gap X between the cooling fins 3 and the ceramic liner 9 where the first tube section 1a (not shown) would be. This figure shows the relative size and shape of the cooling fins 3. In a preferred embodiment, the cooling fins 3 comprise an upper set of cooling fins 3a and a lower set of cooling fins 3b. The upper cooling fins 3a are preferably larger in size (height) than the lower cooling fins 3b; this extra height enables the upper cooling fins 3a to catch and contain debris and sludge that may collect on top of the first tube section 1a. Each set of cooling fins 3a, 3b is preferably crescent-shaped with the ends of the two crescents terminating on each side of the first tube section 1a. With this configuration, the cooling fins 3 provide the greatest cooling capacity at the top and bottom of the first tube section 1a where the crescents are the largest in diameter. In a preferred embodiment, the cooling fins 3 are comprised of stainless steel. In this particular embodiment, the cooling fins 3 are welded to the outside surface of the first tube section 1a.

(31) FIG. 5 is a side view of the present invention. In one embodiment of the present, invention, a bottom rail 8 extends downwardly from the lower cooling fins 3b. The purpose of this bottom rail 8 is to protect the lower cooling fins 3b from contact with the ground or another surface when the fire tube is being installed or removed; when the fire tube is installed within the heater-treater, it is suspended so that the lower cooling fins 3b do not come into contact with the bottom flange on the heater treater (see FIG. 11). There is preferably a space between the lower cooling fins 3b and this bottom flange.

(32) FIG. 6 is a front view of the present invention showing the section line for FIG. 7. FIG. 7 is a section view of the present invention. As shown in this figure, the upper cooling fins 3a are separated in the center (at the top of the first tube section 1 a) by a first center rail 3c that extends longitudinally along the length of the upper cooling fins 3a. The lower cooling fins 3b are separated in the center (at the bottom of the first tube section 1a) by a second center rail 3d that extends longitudinally along the length of the lower cooling fins 3b. The bottom rail 8 is attached (for example, welded) to the bottom of the second center rail 3d and extends beyond the second center rail 3d both forwardly and rearwardly, as shown.

(33) FIG. 8 is a perspective view of one of the sections of the ceramic liner 3 of the present invention. In a preferred embodiment, the ceramic liner 9 is comprised of four separate tubular sections 9a, one of which is shown in FIG. 8. FIG. 9 is a section view of the ceramic liner section taken at the section line shown in FIG. 8. As shown in this figure, the front end (right side of FIG. 9) of each ceramic liner section 9a preferably comprises a circumferential recess 9b into which the rear and of an adjacent ceramic liner section 9a fits. The rear end (left side of FIG. 9) of each ceramic liner section 9a comprises a circumferential protrusion 9c that fits into the circumferential recess 9b on the front end of an adjacent ceramic liner 9a. In a preferred embodiment, the angle shown as “Y” on. FIG. 9 is one hundred thirteen (113) degrees. This angle facilities the coupling of adjacent ceramic liner sections 9a.

(34) FIG. 10 is a detail perspective view of the spray washer nozzle 10 of the present invention. As shown in FIG. 3, each of the first and second extension members 4a, 4b of the spray washer rail 4 comprises a plurality of spray washer nozzles 10 spaced an equal distance apart along the length of the extension member. Each spray washer nozzle 10 is positioned to spray water onto the upper cooling fins 3a, thereby cleaning away the debris and sludge that has collected there. In a preferred embodiment, the spray washer nozzles 10 are wide-mouthed nozzles, as shown in FIG. 10.

(35) FIG. 11 is a cutaway view of the present, invention installed on a heater treater 15. When the present invention is installed on a heater treater 15, the first flange 2a (see FIG. 1) is bolted to the burner 11, and the second flange 2b (see FIG. 1) is bolted to the chimney 12. Although the first flange 2a is shown as extending further forward than the second flange 2b, the invention is not limited to such a configuration. The burner 11 extends from the first flange 2a through the main flange 2c and into the first tube section 1a. The burner 11 has been omitted from the previous figures.

(36) FIG. 12 is a rear perspective view of the present invention showing a first alternate embodiment, of the cooling fins 3. This embodiment is similar to that shown in FIG. 1 except that the cooling fins 3 fit over the first center rail 3c (in the case of the upper cooling fins 3a) and the second center rail 3d (in the case of the lower cooling fins 3b) rather than abutting up against them. Thus, there is a central notch in each of the upper and lower cooling fins 3a, 3b that is configured to accept the first or second center rail 3c, 3d. The shape of the cooling fins 3a, 3b is otherwise the same as described above in connection with the first embodiment. In this particular embodiment, the cooling fins 3a, 3b are press fit onto the center rails 3a, 3b, thereby minimizing the amount of welding required (as compared to the first embodiment, which requires the cooling fins 3 to be welded to the center rails 3a, 3b).

(37) FIG. 13 is a rear perspective view of the present invention showing a second alternate embodiment of the cooling fins 3. This embodiment is similar to the embodiment shown in FIG. 12 except that the upper cooling fins 3a are extended upward and configured to surround the lower half of the second tube section 1b, as shown. This particular embodiment provides more cooling fin surface area, which maximizes heat transfer, and reduces sludge buildup in the cooling fin area. The buildup of sludge in the cooling fin area may cause a loss of efficiency.

(38) FIG. 14 is a rear perspective view of the present invention showing a third alternate embodiment of the cooling fins 3. In this embodiment, the upper and lower cooling fins 3a, 3b are comprised of a plurality of concentric rings that are configured to fit around the outer circumference of the first tube section 1a. Each of these concentric rings is triangular in cross-section (see FIG. 15). This particular embodiment, when combined with a highly thermally conductive metal layer followed by a ceramic coating (to prevent corrosion) applied over the cooling fins 3a, 3b and first tube section 1a, allows for good heat transfer with less material use.

(39) FIG. 16 is a front perspective view of an embodiment of the invention with the cooling fins 3 removed. This Figure illustrates an alternative construction of the tube sections 1a, 1b, 1c. As will be discussed, the tube sections 1a, 1b, 1c shown in this view are fabricated from carbon steel 16 with a high nickel alloy layer 18, such as C-276, bonded to the carbon steel 16. The high-nickel alloy layer 18 is preferably bonded to the carbon steel 16 via electric arc spray (EAS), or other acceptable means. Known EAS process includes the use of two conductive wires (not shown) that are fed together through wire guides or contact tips in the head of an EAS gun (not shown). The wires are charged with opposite electrical charges from a direct current power supply. An arc is struck, between the two wires, causing them to melt. Compressed air from behind the arc is used to atomize the molten material and propel it through a nozzle, which shapes and accelerates the spray stream. The particles deposit onto the prepared surface where they instantly create the coating build-up. Tube sections 1a, 1b, 1c having the layers 16, 18 as shown in FIGS. 16-17A provide a significant cost savings over the tube sections 1a, 1b, 1c illustrated and discussed in previous views, since the amount of C-276 used in fabrication is greatly reduced. The tube sections 1a, 1b, 1c of the previously mentioned embodiment, are fabricated entirely from C-276, whereas the embodiment illustrated in FIGS. 16-17A require only the amount of C-276 necessary to coat the base carbon steel layer 16 with a C-276 layer 18.

(40) The views of FIGS. 17 and 17A more clearly illustrate the base carbon steel layer 16 with the EAS-bonded nickel alloy layer 18. As may be further seen, the EAS process may leave the nickel alloy layer 18 with some pitting 19 resulting in a degree of porosity (approximately 2%). As such, fabrication of the tube sections 1a, 1b, 1c preferably includes application of a further, sealant layer 20. The sealant layer 20 is applied in a known manner to the nickel alloy layer 18. An acceptable sealant layer 20 includes Dichtol, or other effective sealant. The sealant layer 20 obviates the porosity seen with this process. The application of a nickel alloy layer 18 and sealant layer 20 over the steel layer 16 is adequate for corrosion resistance while also using significantly less material. Moreover, the use of an alloy layer 18 and sealant layer 20 on the tube sections 1a, 1b, 1c also meets the engineering requirements of the pressure vessel. Further, the tube sections 1a, 1b, 1c having layers 18, 18, and 20 allows the user to make repairs and to use existing firetubes 1 rather than replacements, to thereby reduce waste.

(41) It is to be understood that the tube sections 1a, 1b, 1c having a base layer 16, alloy layer 18 and sealant layer 20 may be utilized with any of the previously described fin 3 arrangements.

(42) Although the preferred embodiment of the present invention has been shown and described, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention in its broader aspects. The appended claims are therefore intended to cover all such changes and modifications as fall within the true spirit and scope of the invention.