TECHNICAL FIELD
This disclosure relates to a spring-loaded system and method for maintaining compression on heat recovery or non-recovery ovens during thermal expansion and contraction of the ovens.
BACKGROUND
Coke is a solid carbon fuel and carbon source used to melt and reduce iron ore in the production of steel. In one process, known as the “Thompson Coking Process,” coke is produced by batch feeding pulverized coal to an oven that is sealed and heated to very high temperatures for approximately forty-eight hours under closely-controlled atmospheric conditions. Coking ovens have been used for many years to convert coal into metallurgical coke. During the coking process, finely crushed coal is heated under controlled temperature conditions to devolatilize the coal and form a fused mass of coke having a predetermined porosity and strength.
Because coke ovens cycle between very high temperatures during the coking process and lower temperatures between coking processes, the ovens often undergo expansion and contraction. To avoid damage to the oven, structures that can maintain compression on the oven during this expansion and contraction are needed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a cross-section view of a coke oven, according to one embodiment.
FIG. 1B is a front view of a coke oven.
FIGS. 2A-2C illustrate an example compression device for a coke oven.
FIGS. 3A-3B illustrate another example compression device.
FIGS. 4A-4B illustrate another example compression device.
FIGS. 5A-5C illustrate another example compression device.
FIGS. 6A-6E illustrate another example compression device.
FIGS. 7A-7C illustrate another example compression device.
FIGS. 8A-8B illustrate an example compression device that can be used while a coke oven or its components are being repaired.
FIG. 9 shows an example spring including two concentric springs.
DETAILED DESCRIPTION
The present technology is generally directed to systems and methods for maintaining compression on coke ovens during thermal expansion and contraction of the ovens. A coke oven, which can be any of a variety of types of heat recovery ovens or non-recovery ovens, can include an oven body, a foundation, and a plurality of beams separating the oven body from the foundation. A buckstay applies force to the oven body to maintain compression on the oven body as the oven body expands and contracts during thermal cycling. The coke oven further comprises a spring-loaded compression device, which can include a restraining device, an anchor coupled to the restraining device, and a spring coupled to the restraining device. The anchor can be attached to one or more of the beams, the foundation of the oven, to a similar compression device on an opposite side of the oven, or to another object outside the oven. The spring applies force between the restraining device and the one or more beams or foundation to compress the buckstay against the oven.
Embodiments of the compression device described herein beneficially allow for expansion and contraction of the oven body as the oven is heated and cooled while maintaining compression on the oven. The compression device can maintain structural stability of the oven over a plurality of thermal cycles. Because the compression device can be coupled to either the foundation or the beams supporting the oven, the compression device design described herein does not need to be coupled to an opposite side of the oven in order to maintain compression the oven. For example, if space under the oven fills in (e.g., due to a beam collapsing), components of the compression device do not need to be threaded through the collapsed region. Rather, embodiments of the compression device described herein can be coupled to a structure on the same side of the oven at which the compression device is located. Various embodiments described herein also reduce interference with machines that operate at either end of the oven body. For example, embodiments of the compression device described herein maintain a low profile so as not to be hit by a machine that cleans material (coal or coke) that falls out of the oven. The components of the compression device can also be visually inspected to discover structural problems before any of the structures fail. Furthermore, although embodiments of the spring-loaded compression device are described herein as being used to maintain compression on heat recovery ovens, similar devices may be used for other types of ovens such as non-recovery ovens.
Specific details of several embodiments of the technology are described below with reference to FIGS. 1A-8B. Other details describing well-known structures and systems often associated with coke ovens have not been set forth in the following disclosure to avoid unnecessarily obscuring the description of the various embodiments of the technology. Many of the details, dimensions, angles, and other features shown in the Figures are merely illustrative of particular embodiments of the technology. Accordingly, other embodiments can have other details, dimensions, angles, and features without departing from the spirit or scope of the present technology. A person of ordinary skill in the art, therefore, will accordingly understand that the technology may have other embodiments with additional elements, or the technology may have other embodiments without several of the features shown and described below with reference to FIGS. 1A-8B.
FIG. 1A is a longitudinal cross-section view of a heat recovery coke oven 100 in accordance with embodiments of the disclosure, and FIG. 1B is a front view of the heat recovery oven 100. As shown in FIGS. 1A-1B, the oven 100 can include an open cavity (referred to herein as an oven chamber 101) defined by a floor 105, two sidewalls 110 extending upwardly from the oven floor 105, and a crown 115 that forms a top surface of the open cavity. A first end of the crown 115 can rest on a first sidewall 110 while a second end of the crown 115 can rest on an opposing, second sidewall 110. The oven can have a front door 108 and a rear door 109, which can be closed to seal the oven chamber 101. The oven 100 can be adjacent to other similar heat recovery ovens. Each adjacent oven can share a common sidewall 110 with the oven 100.
In operation, volatile gases emitted from heated coal in the oven 100 collect in the crown 115 and are drawn downstream into a sole flue 120 positioned beneath the oven floor 105. The sole flue 120 includes a plurality of side-by-side runs that form a circuitous path beneath the oven floor 105.
Coke is produced in the oven 100 by first loading coal into the oven chamber, heating the coal in an oxygen-depleted environment, driving off the volatile fraction of coal, and then oxidizing the volatile matter within the oven 100 to capture and utilize the heat given off. The coking cycle begins when coal is charged onto the oven floor 105 through the front door 108. The coal on the oven floor 105 is known as the coal bed. Heat from the oven 100, due to the previous coking cycle, starts a carbonization cycle. Roughly half of the total heat transfer to the coal bed is radiated down onto the top surface of the coal bed from the luminous flame of the coal bed and the crown 115. The remaining approximately half of the heat is transferred to the coal bed by conduction from the oven floor 105, which is convectively heated from the volatilization of gases in the sole flue 120. In this way, a carbonization process “wave” of plastic flow of the coal particles and formation of high strength cohesive coke proceeds from both the top and bottom boundaries of the coal bed. At the end of the coking cycle, the coal has coked out and has carbonized to produce coke. The coke can be removed from the oven 100 through the rear door 109 opposite the front door 108 using a mechanical extraction system. Finally, the coke is quenched and sized before delivery to a user.
Primary air for combustion can be added to the oven chamber 101 to partially oxidize coal volatiles, but the amount of primary air can be controlled so that only a portion of the volatiles released from the coal are combusted in the oven chamber 101, thereby releasing only a fraction of their enthalpy of combustion within the oven chamber 101. The partially combusted gases pass from the oven chamber 101 into the sole flue 120, where secondary air can be added to the partially combusted gases. As the secondary air is introduced, the partially combusted gases are more fully combusted in the sole flue 120, thereby extracting the remaining enthalpy of combustion that can be conveyed through the oven floor 105 to add heat to the oven chamber 101. However, at least part of the heat produced by the combustion in the sole flue 120 is conveyed downward to structural components below the flue 120.
Beneath the sole flue 120 is a castable slab 125. The slab 125, comprising concrete, a ceramic, or other castable refractory, can form a bottom floor of the sole flue 120 and support the oven 100. The slab 125 can have a width that is approximately equal to the width of the oven 100, or the slab 125 can extend the width of multiple ovens.
The oven 100 is supported by a foundation 130, for example comprising concrete. Between the foundation 130 and the castable slab 125 are one or more beams 140 that form a plurality of air gaps 142 between the foundation and slab. The beams 140 an extend a length of the oven from a first end to a second end. For example, the beams 140 can extend from the front door 108 to the rear door 109. Each beam 140 can be a continuous structure extending the length of the oven 100, or two or more beams 140 placed end-to-end can together extend the length of the oven. The air gaps 142 can similarly extend the length of the oven 100. The air gaps 142 can be open at a first end of the oven 100 and a second end of the oven 100 opposite the first end, allowing air movement through the gaps 142 and around the beams 140. The beams 140 comprise a structural material capable of supporting the oven 100 while leaving air gaps 142 below the castable slab 125. In some embodiments, the beams 140 are manufactured out of a metal, such as steel.
As shown in FIG. 1B, the beams 140 in some embodiments can comprise I-beams. However, the beams 140 can take other shapes or configurations in other embodiments. For example, the beams 140 can include a hollow pipe with a rectangular cross-section, a solid tube with a rectangular cross-section, a brick, a combination of two or more of these structures (e.g., I-beams under some portions of the oven and bricks under other portions of the oven), or another structure that allows the beams 140 to be spaced apart from one another while supporting the weight of the oven 100 above the beams.
In various embodiments, the beams 140 can be between six inches and eighteen inches high (i.e., leaving a gap between the foundation 130 and the castable slab 125 that is between six and eighteen inches). For example, the beams 140 can have a height of eight inches or twelve inches. The height of the beams 140 may be selected based on material properties of the beams, as well as an amount of natural or forced air flow through the air gaps 142. For example, because taller beams allow more air to flow through the gaps 142 under natural airflow than shorter beams, taller beams can be used in circumstances where more natural cooling is desired. The beams 140 can have a distance between them that depends on structural capacity of each beam. The beams 140 may have uniform spacing under the ovens, or more beams can be placed under heavier components of the ovens while fewer beams are placed under lighter components. For example, the beams 140 can be closer together under the sidewalls 110 than they are under the sole flue 120. The air gaps created by the beams 140 can thermally isolate the oven body from the foundation 130 and/or improve heat dissipation from the oven body by allowing airflow under the oven body. The heat dissipation caused by the airflow reduces the temperature of the castable slab 125 and reduces heat transfer between the sole flue 120 and the foundation 130. Because the slab 125 or foundation 130 may fail at high temperatures, the dissipation of heat helps reduce the likelihood of failure of either component. Similarly, heat transferred to subgrade below the foundation 130, in particular if the subgrade includes a high proportion of slag, can cause the subgrade to become unstable. Reducing the heat transfer into the foundation 130 similarly reduces heat transfer to the subgrade and reduces the likelihood of the subgrade becoming unstable.
The air gaps created by the beams 140 enable air to flow around the beams 140 to reduce heat transfer between the slab 125 and the foundation and the cool the beams and other structures of the oven, such as a compression device. Depending on a location of the oven 100, natural air flow through the air gaps (e.g., due to wind) may be sufficient to cool the beams. However, in some embodiments, the oven 100 includes a forced cooling system that forces air a fluid can be forced through at least one of the air gaps between the beams 140 to increase convection and further reduce the amount of heat transfer from the sole flue 120 to the foundation 130. The forced cooling system can, for example, force air through an air gap using one or more fans, nozzles, air horns, air multipliers, air movers, or vacuums. Gases other than air may be forced through the air gaps instead of, or in addition to, air. As another example, the forced cooling system can include cooling pipes positioned in the air gaps, adjacent to the beams 140, or passing through the beams 140 or foundation 130. A cooling fluid can be pumped through the pipes continuously or on a periodic basis to dissipate heat from the beams 140.
Various other configurations of the beams 140 are described in U.S. patent application Ser. No. ______, filed ______ (Attorney Docket No. 84553-8052.US01), which claims the benefit of U.S. Provisional Patent Application No. 62/786,320, filed Dec. 28, 2018, both of which are incorporated herein by reference in their entirety.
The heat recovery coke oven 100 further includes buckstays 150. Each buckstay 150 comprises a mechanical structure that constrains movement of the oven 100, for example during thermal expansion and contraction. As shown in FIGS. 1A-1B, the oven 100 can include four buckstays 150: one on either lateral side of the front or “pusher” side of the oven, and one on either lateral side of the back or “coke” side of the oven. For example, the buckstays 150 can be positioned in front of or adjacent to the sidewalls 110 of the oven. Because adjacent ovens may share a sidewall 110, two buckstays 150 can be positioned in front of each sidewall. By way of example, during typical operation of some configurations of the heat recovery oven 100, the length of the oven can expand by about six inches between its lowest operating temperature and its highest operating temperature in a given thermal cycle. The buckstays 150 provide compression against the oven, reducing the likelihood of the oven failing as it expands and contracts.
Associated with each buckstay 150 is a spring-loaded compression device 155. The compression device 155 can be coupled to various components of the heat recovery oven 100, such as the foundation 130 or one or more beams 140, or to objects outside the oven 100, such as a flume. The compression device 155 applies force to the buckstay 150 to maintain compression of the buckstay against the oven. The compression device 155 can provide force against a single buckstay or multiple buckstays 150. For example, one compression device 155 can apply force to two adjacent buckstays 150 (e.g., a buckstay 150 positioned at the right sidewall 110 of a first oven, and a buckstay 150 positioned at a left sidewall 110 of a second oven to the right of the first oven). If the compression device 155 couples two buckstays 150, the compression device effectively can spring-load two adjacent ovens together. In some embodiments, the compression device 155 can be a bridle assembly.
The compression device 155 can include a restraining device, such as a bridle, and one or more springs. In some embodiments, the restraining device can pass over a buckstay 150 on an outside (away from the oven) or an inside (toward the oven) of the buckstay, without passing through the buckstay. Other embodiments of the restraining device can pass through the buckstay. The restraining device can be coupled to one more anchors that anchor the compression device, for example to the beams 140, the foundation 130, the castable slab 125, a compression device on an opposite side of the oven, or an object outside the oven. The restraining device and springs compress the buckstay 150 against the oven 100, while allowing the buckstay 150 to move as the oven expands or contracts. Various embodiments of the compression device 155 are illustrated in FIGS. 2A-8B.
In some embodiments, as shown for example in FIG. 1A, the oven 100 has a first compression device 155 at a first end of the oven 100 and a second compression device 155 at a second end of the oven. The second compression device 155 can be physically separate from the first compression device 155, such that the second compression device 155 is not connected to the first compression device 155. For example, there is no tie rod connecting the second compression device to the first compression device that applies force between the first and second compression devices. Rather, the first and second compression devices are each anchored to the beams 140 and/or foundation 130, allowing the beams 140 or foundation 130 to act as a structural element that resists horizontal expansion of the oven 100 in addition to supporting the weight of the oven 100. The arrangement of two physically separate compression devices shown in FIG. 1A can be advantageous, for example, because a tie rod does not need to pass through obstructed regions under the oven.
The first and second compression devices 155 can both be spring-loaded compression devices, in which a spring applies force to a component of the compression device to compress a the buckstay 150 against the oven body. In other cases, one compression device can be spring-loaded while the other compression device is fixed. For example, the fixed compression device can be welded or otherwise attached to the buckstay 150 while the buckstay 150 is welded or otherwise attached to a beam 140.
FIGS. 2A-2C illustrate top, side, and front views respectively of a first example compression device 155. As shown in FIGS. 2A-2C, the compression device 155 can include two springs 205, each positioned on an outside of a buckstay 150 (i.e., on a side away from the oven 100). The springs 205 are compressed against the buckstays 150 and are coupled to a restraining device 210 by a connecting rod 212. The restraining device 210 can pass through a hole in at least one beam 140 under the oven 100 and is anchored against the beam. A third spring 215 can compress the restraining device 210 against the beam 140. Other embodiments of the compression device 155 may omit the third spring 215, or may include an additional spring compressing the restraining device 210 against the beam 140 (e.g., opposite the spring 205A in FIG. 2A). The springs 205, 215 allow the buckstay 150 to move as the oven 100 expands and contracts, but provide force compressing the buckstay 150 against the oven 100.
FIGS. 3A-3B are a front elevation and side view of another example compression device 155. The compression device 155 shown in FIGS. 3A-3B can also include two springs 205 coupled to a restraining device 210 by a connecting rod 212. The restraining device 210 is positioned on an outside of the buckstays 150, and can be anchored to the foundation 130 to pull the compression device 155 against the buckstays 150. The springs 205 can be coupled to the restraining device 210 on opposite sides of one or more buckstays 150, such that one spring 205 is on each side of the one or more buckstays 150. In the example of FIG. 3A, the restraining device 210 is a bridle that passes over two adjacent buckstays 150 (e.g., each supporting an adjacent oven), and the springs 205 are positioned such that a first spring 205A is on a first side of a first buckstay 150A and a second spring 205B is on a second side of a second buckstay 150B. However, a similar structure for the compression device 155 can be used to constrain a single buckstay 150 against the oven body. An anchor 305, such as a plate, coupled to each spring can anchor the compression device 155 to the foundation 130. For example, the anchor 305 can be drilled into the foundation 130, or can be attached to a plate or rod that is drilled into or otherwise coupled to the foundation.
In the example compression device 155 configuration shown in FIGS. 3A-3B, the buckstays 150 can be approximately centered between the springs 205. However, the springs 205 can have different distances from the buckstays 150. For example, if the foundation 130 is cracked near a right side of the buckstays 150 shown in FIGS. 3A-3B but not cracked near the left side, an anchor coupling the right side of the compression device 155 to the foundation may be placed farther away from the buckstays 150 (where the foundation is not cracked) than the anchor coupling the left side of the compression device to the foundation. A length of the restraining device 210 may be extended toward the right side of the buckstays to accommodate the placement of the anchor.
FIGS. 4A-4B are a front elevation and side view of another example compression device 155. Like the example shown in FIGS. 3A-3B, the example shown in FIGS. 4A-4B can include two springs 205 coupled to a restraining device 210 on opposite sides of one or more buckstays 150, and the restraining device 210 can be positioned on an outside of the buckstays 150. The restraining device 210 can be anchored to a beam 140 by the connecting rod 212 to pull the compression device 155 against the buckstays 150. The restraining device 210 can be anchored to beams 140 adjacent to the buckstays 150 on either side of the buckstays, or to beams 140 some distance away from the buckstays 150. For example, if the beams 140 adjacent to the buckstay are damaged or structurally unsound, the restraining device 210 can be anchored into a structurally sound beam that is farther from the buckstays. The restraining device 210 can have a length that is approximately equivalent to a length between the beams 140 to which the restraining device is anchored. An anchoring beam 405 coupled to the restraining device 210 can extend downward from the restraining device 210 and can be anchored into the foundation 130 below the buckstay 150. For example, if the foundation 130 has cracked around or near the buckstay 150, the surface of the foundation may be unable to support the compression device 155. The anchoring beam 405 can anchor into an intact portion of the foundation 130 below the cracked portion to provide force to counteract the thermal expansion of the oven 100. The anchoring beam 405 can have any length sufficient to anchor into an intact region of the foundation 130.
FIGS. 5A-5C illustrate yet another example compression device 155. FIG. 5A shows a perspective view of a portion of the oven, FIG. 5B shows an expanded view of the example compression device 155, and FIG. 5C is a top view of the compression device 155 in the oven. The compression device 155 shown in FIGS. 5A-5C includes a restraining device 210 on the outside of one or more buckstays 150. Each end of the restraining device 210 is coupled to a plate 502 by the connecting rod 212. The spring 205, also coupled to the connecting rod 212, applies force against the plate 502 to compress the restraining device 210 against the one or more buckstays 150. One or more springs can be coupled to the connecting rod 212 at either end of the restraining device 210. As shown in FIGS. 5A-5C, the example compression device 155 also includes a J-hook 505 that can hook into a beam 140. For example, if the beams 140 are I-beams, the J-hook 505 can pass through a hole in the web of a beam 140. The J-hook 505 can be coupled to the plate 502. In some embodiments, a J-hook can be coupled to the plate 502 on either side of both springs 205. Alternatively, the compression device 155 can include fewer or additional J-hooks 505. For example, the compression device 155 can include two hooks 505, one positioned at either end of the restraining device 210.
FIGS. 6A-6E illustrate still another example compression device 155, in which the restraining device 210 is positioned behind one or more buckstays 150. FIG. 6A is a perspective view of a portion of the oven and FIG. 6B is a side view. FIG. 6C is a perspective view of the example compression device 155, FIG. 6D is a top view, and FIG. 6E is a front view of the compression device 155 with a portion of the oven. The restraining device 210 in the example of FIGS. 6A-6E can be coupled to the back of the one or more buckstays 150 by welds, nut bolting, and/or other connectors. For example, FIGS. 6A-6E show bolts 602 drilled into the restraining device 210 and a flange of two adjacent buckstays 150 to connect the restraining device 210 to the buckstays 150. The restraining device 210 can be anchored to one or more beams 140 by, for example, a bracket 605 that is attached to the restraining device 210 and a flange of the beams 140. Each end of the restraining device 210 can be coupled to the bracket 605 by a connecting rod 212 and a bolt 610 that applies force between the restraining device 210 and the bracket 605. FIGS. 6D-6E illustrate that both ends of the restraining device 210 can be coupled to the same bracket 605. However, in other embodiments, the ends of the restraining device 210 can each be coupled to a separate bracket 605. Furthermore, there may be additional connection points between the restraining device 210 and the bracket 605 in other embodiments. The spring 205 can be positioned in front of the restraining device 210 and coupled to the bracket 605 by the connecting rod 212, such that the spring applies force to resist expansion of the oven body by compressing the buckstays 150 against the oven body. Instead of or in addition to being coupled to the bracket 605, the restraining device 210 can pass through the beams 140.
A smaller example compression device 155 is shown in FIGS. 7A-7C. In FIGS. 7A-7C, a bracket 705 is used as the restraining device 210. The bracket 705 can provide counterforce against a single buckstay 150. In some embodiments, as shown in FIGS. 7A-7B, the bracket 705 is on a back side of the buckstay 150 (i.e., toward the oven). In other embodiments, as shown for example in FIG. 7C, the bracket 705 is on a front side of the buckstay 150. Alternatively, the compression device 155 can include a bracket and spring positioned on both the front and back side of the buckstay 150. The bracket 705 can be anchored to the beams 140, the foundation 130, or another component of the oven 100. For example, the bracket 705 can be attached to a top flange of a beam 140 by bolts or other connectors, or can be drilled into the foundation. The spring 205 is compressible between the bracket 705 and the buckstay 150 to compress the buckstay 150 against the oven 100. The connecting rod 212 passes through the buckstay 150 (e.g., through holes in the flanges of the buckstay 150) to couple the bracket 705 and spring 205 to the buckstay 150.
FIGS. 8A-8B illustrate an example compression device 155 that can be used while the restraining device, oven 100, buckstays 150, or other components are being repaired. The compression device 155 shown in FIGS. 8A-8B includes a first restraining device 210A positioned behind a first (old) buckstay 150A, a second restraining device 210B positioned behind a second (new) buckstay 150B, and a U-channel 805 coupling the first restraining device 210A to the second restraining device 210B. In the example of FIGS. 8A-8B, the old oven is hot (and therefore expanded) while the new oven is colder (and therefore not expanded). Accordingly, the front faces of the first buckstay 150A and second buckstay 150B are not aligned. However, depending on the temperature of the respective ovens, the first and second buckstays 150A, 150B may have different relative positions than shown. One or more springs can be used to compress the buckstays 150 against the restraining devices 210, using for example any of the example spring positions shown in FIGS. 2A-7C.
In various embodiments, any of the springs described with respect to FIGS. 2A-8B (such as the springs 205 or 215) can each comprise two or more concentric springs. FIG. 9 shows an example spring 205 that includes two concentric springs, in which a smaller-diameter spring 904 is positioned inside of a larger-diameter spring 902, both of which are concentric to the connecting rod 212. The larger spring 902 can have a different spring constant than the smaller spring 904, or the springs 902, 904 can have the same spring constant. The spring 205 can also include additional springs concentric to the springs 902, 904.
Any of a variety of other configuration of the spring-loaded compression device 155 may be used instead of those shown in FIGS. 2A-8B. The restraining device 210 and springs 205 can have different positions relative to the buckstays 150, or additional or fewer restraining devices or springs can be used with those shown in the example figures. The compression device 155 can anchor to any of a variety of structures on the oven 100. For example, the compression device 155 can anchor to one or more beams 140 by coupling to an anchor that passes through a hole in the beam, coupling to a support that is placed across two or more beams 140, coupling to a support or angle attached to a top flat part of one or more beams 140, or otherwise attaching or coupling to a beam 140. The compression device 155 can additionally or alternatively couple to an anchor that is anchored to the foundation 130, castable slab 125, or to a compression device 155 on an opposite side of the oven 100.
From the foregoing it will be appreciated that, although specific embodiments of the technology have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the technology. Further, certain aspects of the new technology described in the context of particular embodiments may be combined or eliminated in other embodiments. Moreover, while advantages associated with certain embodiments of the technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein. Thus, the disclosure is not limited except as by the appended claims.
Patent Application
20200208845
