CN114072342A

CN114072342A - Simplified chain conveyor for bottom ash transfer

Info

Publication number: CN114072342A
Application number: CN202080049284.7A
Authority: CN
Inventors: A·T·利特尔; B·G·小斯宾格
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 2019-07-02
Filing date: 2020-07-01
Publication date: 2022-02-18
Also published as: KR20220025013A; WO2021003231A1

Abstract

An ash removal conveyor system includes a hopper and a chain conveyor having an elongated enclosed conduit separate from the hopper, a receiving section positioned for receiving ash from the hopper, and an internal chain within the elongated enclosed conduit. The chain conveyor has a bottom section and a top section, wherein the flights of the top section and the flights of the bottom section move in opposite directions within the elongated enclosed conduit, one of the top or bottom sections moving ash from the receiving section to the distal end. The conveyor system may not include a bottom door interposed in the ash flow path from the hopper to the chain conveyor; or may not include a pulverizer interposed in the ash flow path; or may not include any of a bottom door or grinder interposed in the ash flow path.

Description

Simplified chain conveyor for bottom ash transfer

This application claims the benefit of U.S. provisional application No. 62/869,738 entitled "simplified chain conveyor for bottom ash transfer" filed on 7/2/2019. U.S. provisional application No. 62/869,738, filed 2019, 7, 2, is incorporated herein by reference in its entirety.

Technical Field

The present invention relates to a system for processing ash, and in particular to a simplified chain conveyor system for removing bottom ash of large coal fired boilers. The disclosed ash handling system may be more generally used to remove ash produced by other types of combustion processes.

Background

U.S. patent No. 10,124,968, issued 11/13/2018, is incorporated by reference herein for its teachings of certain chain conveyor systems.

U.S. patent No. 5,775,237 issued on 7/1998 is incorporated herein by reference for its teachings of a dry bottom ash handling system.

The following description of the general background of the invention refers to the accompanying figures 1 to 4 which illustrate a prior art system. The combustion process of coal in electric utility boilers produces two types of waste: 1) ash particles small enough to be entrained in the flue gas, known as fly ash, and 2) larger ash particles that overcome the resistance in the combustion gases and fall to the bottom of the boiler, known as bottom ash. Typically, the bottom ash is collected either in a reservoir or in a dry bottom. The impoundment type ash, referred to as wet bottom ash, is typically collected in a separate water charging hopper as shown in fig. 1 showing a typical bottom impoundment ash system 10, or in a closed loop recirculation system 26 as shown in fig. 2, or in a water charging tank equipped with a submerged drag chain system 12 as shown in fig. 3. In the system of fig. 1, ash is discharged from the hopper 14 through a bottom door 16 on the side of the hopper 14 on each shift in the batch process. The ash crusher 18 is provided to reduce the ash particle size to less than about 3 inches (typically) to allow transport in a pipeline as an ash/water slurry. The slurry is discharged to a holding tank 20 where ash settles out over time. A surge tank 30 is provided to handle transient impacts in the flow of stock. A number of pumps 22 and valves 24 are provided for moving the slurry through the system 10 (these elements are also shown in fig. 2, 3 and 4).

The closed loop recirculation system 26 shown in FIG. 2 is a modified form of system 10 and provides a closed loop dewatering system and uses what applicants refer to as FIG. 2

The precipitation unit of unit 28. In the system 26 shown in fig. 2, the bottom ash 11 is discharged from the hopper 14 into the pulverizer 18 and then pumped as an ash-water slurry to a remotely located one

A dewatering box 28 which provides the necessary two-stage settling process to clarify the water sufficiently for recycling. The settled ash passes through a screen in the dewatering box 28 to drain the water. Surge tank 30 and settling tank 32 process the discharged water and provide further clarification and separation of the fly ash from the water. The clarified water is recycled back to deliver the next batch of mortar. The dewatered mortar is hauled off the plant area.

The systems 10 and 26 are so-called wet-flush systems which operate successfully but have a number of disadvantages, mainly a large amount of transport water requiring complex treatment and a large capital expenditure.

A submerged mechanical drag conveyor system 12 (or submerged chain conveyor or "SCC") is shown in fig. 3 and 4 and is typically used to provide continuous ash removal. The bottom ash continuously falls through hopper discharge port 42 into SCC 12 and settles onto a chain and flight conveyor system known as submerged drag chain unit 34. The unit 12 forms an open slot that is filled with water to cool the dry ash as it falls from the boiler into the unit. The chain of unit 34 continues to move and carry away ash that is dewatered as it moves along the inclined section 36 and is transported via conveyor 44 into the bottom ash bin 38 and then discharged into a truck to transport the material off site. Make-up water is added to offset the wet ash removed from the system and the water loss due to evaporation. A grinding hopper 40 is provided to handle material that is directed onto the chain conveyor inclined section 36 for processing with the bottom ash slurry flow. The submerged drag chain conveyor unit 34 is positioned directly below the boiler hopper discharge 42. The rectangular boiler throat requires that the submerged drag chain conveyor unit 34 and the boiler hopper discharge 42 be oriented substantially parallel to the major axis of the boiler throat. Another view of the submerged drag chain conveyor unit 12 is shown in fig. 4, which further illustrates a conveyor drive unit 46 and a take-up unit 48 that provide suitable conveyor chain tensioning. In this prior art system, one of the units 12 shown in FIGS. 3 and 4 is provided for each boiler hopper discharge 42.

Ash handling for large coal fired boilers is subject to increasingly stringent government regulations, including federal ELG (emission restriction guidelines) regulations for the U.S. EPA. These rules treat different forms of water flow in the bottom ash handling system in different ways. For example, these rules preclude ash transfer water, such as used in the sump system 10 shown in FIG. 1 and the closed loop hydraulic system 26 shown in FIG. 2, from being discharged into the environment as well as the ash pan. Water flow that is not (currently) constrained by these ELG requirements includes quench water and other minor effluents for the submerged chain conveyor system 12. Retrofitting existing coal fired boilers to modern ash handling systems often involves significant capital expenditures. Given the substantial costs associated with retrofitting, operators of these systems will typically disable boilers.

In view of the above, boiler operators are often faced with difficult decisions regarding continuing the useful life of existing equipment. Installation of a conventional submerged drag chain system 12 as shown in fig. 3 typically requires removal of the existing bottom ash hopper 14 and replacement with a rectangular chute hopper 42 that can receive a continuous flow of ash. As previously mentioned, make-up water must be added to offset the water loss. The water temperature in these systems is relatively high and therefore a cooling system is provided, such as by recirculation to a water sump or installation of a heat exchanger. The advantages of the existing SCC system 12 are that no water transport is required and the equipment costs are relatively low. Furthermore, maintenance and operating costs are relatively low compared to wet-scrubbing systems. However, significant drawbacks are associated with the above-described major modifications of boilers and the considerable space requirements of such systems, including orientation limitations. Since the system 12 is directly below the boiler without any isolation valves, a break in the SCC chain or other maintenance issues may require shutting down the boiler to repair the fault.

The present invention relates to embodiments of a simplified chain conveyor system (SCS) suitable for retrofit applications avoiding the aforementioned disadvantages. Several embodiments of the present invention are shown and described herein.

Disclosure of Invention

In some illustrative embodiments disclosed herein, a conveyor system for removing ash is disclosed. The conveyor system comprises a hopper for collecting ash and a chain conveyor. The chain conveyor comprises an elongated closed conduit, separate from the hopper, having a receiving section for receiving ash from the hopper. The chain conveyor further comprises an internal chain arranged within the elongated closed conduit for transporting ash from the hopper to the distal end of the chain conveyor for discharge from the chain conveyor. The chain conveyor has a bottom section and a top section, wherein the flights in the top section and the flights in the bottom section move in opposite directions within the elongated enclosed conduit, one of the top or bottom sections moving ash from the receiving section to the distal end. In some embodiments, the conveyor system does not include a bottom door inserted in the ash flow path from the hopper to the chain conveyor. In some embodiments, the conveyor system does not include a shredder inserted in the ash flow path from the hopper to the chain conveyor. In some embodiments, the conveyor system does not include a bottom door interposed in the ash flow path from the hopper to the chain conveyor, nor a shredder interposed in the ash flow path from the hopper to the chain conveyor. The conveyor system may be a wet ash conveyor system, in which at least the lower part of the elongated closed conduit is submerged in water, or a dry ash conveyor system, in which the elongated closed conduit is not submerged in water. The conveyor system can optionally further include a chain support configured to support the inner chain and a cooling apparatus in the chain support. In some embodiments, the chain conveyor comprises at least a first chain conveyor having a water-cooled housing. In some embodiments, the conveyor system further comprises an electronic controller configured to receive sensor readings indicative of a temperature of the chain conveyor and to control the temperature of the chain conveyor based on the received sensor readings by controlling at least one of: (i) a flow of ash from the hopper to the chain conveyor controlled by controlling a flow control device configured to control the flow of ash from the hopper to the receiving section of the chain conveyor, and/or (ii) a speed of the chain conveyor.

In some illustrative embodiments disclosed herein, in a conveyor system as described in the immediately preceding paragraph, the chain conveyor comprises a top-carrying chain conveyor comprising a floor below a flight moving in the top section and above a flight moving in the bottom section, wherein the top section moves ash from the receiving section to the distal end. Such a top-carrying chain conveyor system may be a wet ash conveyor system, wherein an elongated closed conduit is submerged to submerge the scraper in the top section and the scraper in the bottom section. In some illustrative embodiments disclosed herein, in the conveyor system as described in the immediately preceding paragraph, the chain conveyor comprises a bottom-carrying chain conveyor, wherein the bottom section moves ash from the receiving section to the distal end. In some bottom-carrying chain conveyors, where the conveyor system also does not include a crusher interposed in the ash flow path from the hopper to the chain conveyor, the spacing between adjacent flights is large enough to allow uncrushed ash to fall between the flights moving in the top section to reach the bottom of the elongated enclosed conduit, and/or the spacing between the flights moving in the top section and the flights moving in the bottom section is effective for the flights moving in the top section to contact and break down the ash moving by the bottom section.

In some illustrative conveyor systems as described in either of the two preceding paragraphs, the chain conveyor performs loading from the hopper from a single point input, allowing the conveyor system to rotate in either of 360 ° directions in a plane relative to the hopper. The conveyor system may optionally further comprise a lateral cooling section interposed between the ash discharge opening of the hopper and the receiving section of the chain conveyor, wherein the ash moving device is configured in the lateral cooling section. In some embodiments, the ash moving apparatus may comprise a mechanical screw configured in the lateral cooling section, optionally with a water cooled shaft. In some embodiments, the lateral cooling section comprises a water jacket.

Drawings

Fig. 1 shows a typical bottom ash impoundment ash handling system according to the prior art.

Figure 2 shows a typical closed loop recirculation system for the treatment of ash slurry according to the prior art.

Figures 3 and 4 show a typical bottom ash submerged drag chain conveyor system according to the prior art.

Fig. 5 shows SCS according to the invention.

Fig. 6 shows an embodiment of the SCS shown in fig. 5 operating in a dry hopper and gaseous injection configuration.

Fig. 7 shows the bottom carrying arrangement of the SCS.

Fig. 8 shows SCS comprising lateral cooling sections with cooled mechanical screws.

Fig. 9 shows SCS with multiple conveyors in series, where the first conveyor includes a fluid cooled housing.

Fig. 10 shows a cross-sectional view of a first conveyor with the fluid cooled housing of the SCS of fig. 9.

Fig. 11 shows the top carrying arrangement of the SCS.

FIG. 12 shows a simplified SCS, with the omission of a bottom door and shredder.

Fig. 13 shows a maintenance shutdown procedure suitably performed using the simplified SCS of fig. 12.

Fig. 14 shows a temperature control process of SCS.

Detailed Description

Referring now to fig. 5 to 14, embodiments of the present invention will be described. Fig. 5 shows the basic construction of an SCS according to the invention, generally designated by reference numeral 50. In describing the SCS 50, certain components are the same as the prior art systems previously described, and they are identified using the same reference numerals. The SCS 50 includes a receiving section 52 that is directly connected to the existing ash hopper 14. The bottom door 16 arranged in the door housing 17 can be opened or closed to connect or isolate the ash hopper 14 from the receiving section 52. An optional crusher 18 is provided to control the flow of ash out of the hopper 14. The comminutor 18 has the added benefit of reducing the particle size to less than about 2 inches (typically) to accommodate smaller conveyor cross sections (although in particular embodiments the comminutor is contemplated to provide larger or smaller particle grind sizes). The SCS 50 forms an elongated enclosed conduit 54 that extends from the receiving section 52. The conduit 54 has a generally horizontal section 56 and may include an inclined or declined portion. The horizontal section 56 is provided primarily to accommodate the system to existing facility installation space constraints. The inclined or declined portion enables transport of ash to a subsequent ash handling facility. For some embodiments of the operating configuration, the enclosed conduit 54 is completely hydraulically enclosed on all sides. The pipe 54 preferably has a generally rectangular cross-section, may be water-tight, with a removable cover with special seals in place, and a twin drag chain conveyor 60 that moves in an endless manner inside the pipe between a sprocket 62 near the receiving section 52 and a drive sprocket (not shown) at the end of the pipe. A mechanism is provided for adjusting the tension in the conveyor 60, which mechanism is operable at either the sprocket 62 or the drive sprocket. The drag chain conveyor 60 forms a lower load-bearing section 66 that moves accumulated ash from the receiving section 52 along the horizontal section 56, with an upper return section 68 completing the endless loop. The optional inclined section 58 typically extends at an angle of about 30 ° to 40 °, which is intended to provide optimal ash dewatering (in wet applications) while providing ash transport efficiency. The SCS 50 can be easily installed in existing boilers because existing hoppers 14 can be utilized and only the flush lines replaced (when replacing the hydraulic transport system). In some embodiments, the existing hopper 14 is modified by modifying the cross-sectional geometry and/or modifying the wall angle of at least one wall of the hopper and/or changing the location where the ash exits the hopper. A benefit of this may be, for example, that a steeper wall may improve the efficiency of gravity feeding (or gravity assisted feeding) of ash into the pulverizer 18. Similarly, the normally disposed bottom ash door 16 and shredder 18 may remain in place. Maintenance of the bottom ash door 16 provides maintenance isolation between the boiler and the SCS 50, allowing maintenance operations without requiring the associated boiler to be taken out of service. On the other hand, alternative options of not leaving the bottom door in place (but holding the shredder), or not leaving the shredder in place (but holding the bottom door), or not leaving the bottom door in place and not leaving the shredder in place provide benefits such as reducing the number of mechanical parts, avoiding the possibility of the door 16 being blocked from opening or the shredder 18 becoming jammed or otherwise malfunctioning, and providing more retrofit space in the case of retrofitting to incorporate the SCS 50. Another benefit of the disclosed embodiment is that the orientation of the SCS 50 may be rotated 360 ° in any direction from a plan view, since the ash is loaded into the conveyor at a single approximately square or circular point location 53 in the receiving section 52, rather than along a long rectangular opening below the boiler throat. One option is to pick up multiple single load points using a single conveyor arranged in the same manner as a conventional SCC. Alternatively, if pre-existing structures prevent conventional arrangements, multiple smaller conveyors may be used for each single load point. This provides great flexibility for retrofit applications with crowded spaces. Another advantage of the point-load configuration is that a secondary isolation valve may be installed between the pulverizer 18 and the conveyor 60 to provide an additional level of personnel safety when performing conveyor maintenance while the boiler remains in operation.

Under certain conditions, it may be desirable to limit ash entering the SCS 50 to prevent overfilling. The present invention accomplishes this by monitoring the conveyor drive torque during operation. Torque monitoring may be accomplished in a variety of ways, including but not limited to motor current or hydraulic output. At a predetermined high set point for output, simple logic can be used to close the upstream feed valve or stop the previous conveyor, stopping the feeding of additional ash. The conveyor whose drive has reached the high set point may continue to run until the ash is sufficiently emptied, as indicated by the low set point of the drive output parameter. At this point, the signal will initiate a reopening of the valve or a restart of the upstream conveyor to begin feeding ash again. Controlling torque in this manner also provides benefits for chain sizing and wear life. Because the amount of ash accumulated in the conveyor can be controlled, a smaller chain size can be used than in conventional SCCs where a large amount of ash can build up on top of the chain and scraper mechanism. In fact, the chain size of conventional SCCs depends on the amount of ash that may accumulate on top of the chain and flight mechanism, rather than the conveying capacity of the machine. Despite the accumulation of large piles of ash on the chains of conventional SCCs, the removal rate remains constant based on the size of the scraper bar. Thus, the SCS 50 described in the present invention can provide the same conveying capacity as a conventional SCC with a given scraper bar size, while using a smaller chain. The use of smaller chains provides a significant cost savings. In addition, the lower chain-to-chain stresses achieved by reducing ash loading extend the wear life of the chain.

The basic system described for SCS 50 may operate in a variety of configurations, each providing specific functionality to optimize for a particular facility application. In addition, the pipe width, flight design, flight distance, and chain speed are flexible and can be tailored to the requirements.

Referring now to fig. 6, another configuration for operating the SCS 50 is shown, referred to as a "dry hopper and gaseous medium sprayer" configuration 88. This configuration is essentially a dry system, as the ash is not submerged in water. In this case, some other mechanism can optionally be employed to cool the ash. For example, a series of gaseous medium sprayers 90 may be provided. The operation here is typically continuous, with the bottom door 16 open (or omitted entirely), while the SCS 50 is continuously operated. In one embodiment, ambient or chilled "dry" air is the gaseous medium. A gaseous medium vent 19 in the housing 17 (as shown) of the bottom door 16 and/or in the hopper 14 (more generally, in fluid connection with the hopper 14) may also introduce ambient or cooled dry air or another gaseous medium. The gaseous medium introduced by the vents 19 in the hopper and/or door housing may be the same or different from the gaseous medium introduced by the gaseous medium sparger 90 of the SCS 50.

Alternatively, the sprayers 90 (and/or vents 19) may be used to spray wet or dry compounds onto the ash for the purpose of treating the ash. The wet or dry compound may include halogen, hydrogen, or metallic materials. The treated ash can be reintroduced into the boiler for controlled discharge or for subsequent processes. Wet or dry chemicals may alternatively be injected into the hopper through a vent fluidly connected to the hopper.

In some cases, it may be desirable to monitor and/or control the temperature of the SCS 50. One such situation is when the SCS 50 is operating in an arrangement that does not utilize water or otherwise requires the use of water (e.g., such as the dry ash handling system of fig. 6). In these systems, ash may exit hopper 14 at an elevated temperature, for example in some embodiments, dry ash entering the hopper may be at 1500 ° F (815 ℃) or higher; however, while the precise maximum temperature design parameters will depend on the detailed design of the shredder 18, it may be desirable to maintain the components of the shredder 18 at a temperature of about 500F (260℃) or less. A gaseous medium vent 19 fluidly connected to hopper 14 (more specifically, fluidly connected to door 16 of hopper 14 in illustrative fig. 5 and 6) may introduce a gaseous medium, such as ambient air, into the system to cool the ash. A slipstream of process gas may also be used through gaseous medium vent 19. Cooling may also be performed by placing an optional cooling device in or in fluid communication with the hopper, for example, interposed between the ash discharge port of the hopper 14 and a point location 53 in the receiving section 52 of the SCS 50.

An alternative cooling device may take the form of a flow control device with associated cooling, such as a mechanical screw, wherein cooling can be provided by the shaft of the screw and/or the screw housing (e.g., fig. 8). More generally, the flow control device (with or without associated cooling) may also take the form of a gate 16, a valve, a saw-tooth, a plunger, a shredder 18, hydraulic jaws, various combinations thereof, or the like; each flow control device can be located partially, wholly within the hopper or downstream of the hopper. In some arrangements, more than one flow control device is used and may further include a rapper system to assist in the removal of ash that may accumulate within the hopper.

In some cases, it may be necessary to provide additional cooling in addition to that previously discussed, or as a separate system.

Fig. 7 shows a bottom-carrying arrangement, for example taken along section S1-S1 shown in fig. 5, in which the chain 65 of the twin strand drag chain conveyor 60 (see fig. 5) carries the

flights

66 and 68. The

scrapers

66, 68 are also sometimes referred to in the art as scrapers because on the lower channel of the bottom carrier's twin drag chain conveyor 60, the scraper or scraper 66 pushes or "scrapes" ash along the floor 67 of the conveyor 50.

Chain flights

66, 68 are directly supported by chain 65. The double strand chain 65 is guided in replaceable wear strips and guided by a "U" shaped channel 69. In other embodiments, some other type of chain support may be used in place of the "U" shaped channel 69, such as an idler pulley. It is also contemplated to omit the chain support altogether and rely on chain 65 suspended between

flights

66, 68. SCS 50 is an improvement because all runs of chain are included, and the optional submerged water bath is positioned to clean the return run of the chain and deposit ash into the bottom run by gravity. Illustrative fig. 7 is directed to the wet ash SCS of fig. 5, as shown by waterline WL (in some other wet ash processing embodiments, the waterline may be above upper scraper 68 so that they are also submerged with lower scraper 66; it is also noted that in some wet ash processing embodiments, the entire conduit 54 is submerged, in which case waterline WL is understood to represent a possible air pocket at the top of the submerged conduit 54). However, the disclosed cooling method is also applicable to the dry ash SCS of fig. 6. Fig. 7 further shows that the SCS 50 comprises a closed container with side walls 100, a bottom plate 102 and a top cover 104. A cooling device 691 may be placed in one or more of the channels 69 to control chain temperature. Cooling devices may also be placed within any of the plate 102, the cover 104, or the sidewalls to control the temperature within the conveyor 50. For example, as non-limiting illustrative examples, the cooling apparatus 691 may comprise a water jacket for the channel 69, water cooled channels drilled into a plate or other structure forming the channel 69, and/or the like. In an alternative embodiment where an idler replaces the channel 69, the cooling device 691 may be implemented as a cooling of the axle of the idler. Sensors (not shown) may be placed within the conveyor 50 to monitor temperature. By way of non-limiting illustrative example, the sensor may comprise: submerged temperature sensors (for wet ash SCS); a temperature sensor coupled to channel 69 (or to the axle of the idler, if so, the axle is used in place of channel 69) to (approximately) measure the temperature of chain 65; fluid flow rate sensors (for wet ash SCS); a torque sensor (e.g., measuring the output of motor current or the hydraulic pressure of the chain drive, as previously described); and/or the like.

The hopper 14 may deliver ash at an elevated temperature to the conveyor 50. Controlling the temperature within the conveyor 50 enables a longer service life. A method of controlling the temperature of SCS includes one or more of the following steps: establishing an operating temperature range for the conveyor; monitoring and/or measuring one or more of the temperature within the conveyor 50, the rate of discharge of ash from the hopper, the drive torque applied to the chain conveyor, the flow rate of the gaseous medium, the temperature of the gaseous medium and the cooling status of the cooling apparatus; one or more of the temperature within the conveyor 50, the discharge rate of the hopper, the drive torque applied to the chain conveyor, the flow rate of the gaseous medium, the temperature of the gaseous medium, and the cooling state of the cooling apparatus are adjusted to maintain the chain conveyor 50 within the operating temperature range. In the following, some further non-limiting illustrative examples.

Fig. 8 depicts a cooling apparatus that includes a lateral cooling section 110 interposed between an ash discharge port of the hopper 14 (e.g., the outlet of the pulverizer 18 that discharges ash from the hopper 14) and a point location 53 in the receiving section 52 of the SCS 50. As shown in cross-sections S2-S2 of the lateral cooling section 110 of FIG. 8, the lateral cooling section 110 includes a "U" shaped channel 112 having a hollow interior 114. The top of the "U" shaped channel 112 may be open or may be covered. The lateral cooling section 110 may be cooled by ambient air contacting the channel 112, or (as shown in cross-section S2-S2) may be water cooled by designing the channel 112 with a water jacket 116. In another contemplated embodiment (not shown), cooling of the "U" shaped channel 112 may be provided by a tube that is helically wound around the lateral cooling section 110 and carries water or another coolant. The lateral cooling section 110 provides a defined transport distance for the ash, which allows for some cooling of the ash by conduction to the ambient air (or by conduction to the water jacket 116 or spiral cooling pipes, if provided) before the ash enters the SCS 50 at point location 53 in the receiving section 52. The length and cross-sectional area of the "U" shaped channel 112 are designed based on design constraints such as: (i) providing sufficient cooling (biased toward longer lengths and smaller cross-sections, but may also or alternatively provide more cooling via the water jacket 116 or spiral cooling tubes, or by the cooled mechanical screw 120); (ii) minimizing the ash flow resistance introduced by the lateral cooling section 110 (biased toward shorter lengths and larger cross-sections); and (iii) ensure sufficient ash transport capacity (biased towards larger cross-sections).

The illustrative lateral cooling section 110 is oriented horizontally; however, in other embodiments, the lateral cooling sections may have some upward or downward inclination. For example, in the case of a retrofit SCS, an upward tilt may be useful to accommodate vertical spatial constraints. Conversely, if sufficient vertical space is available, the downward slope may reduce the ash flow resistance, which may allow the length of the lateral cooling section 110 to be longer. However, the space available for introducing a downward slope into the lateral cooling section 110 may be limited, particularly in retrofit designs and also possibly in new installations.

Fig. 8 also shows that the machine screw 120 is disposed within the hollow interior 114 of the "U" shaped channel 112. The machine screw includes screw windings 122 and a shaft 124, the shaft 124 optionally being water cooled to provide further cooling of the ash flowing through the lateral cooling section 110. See also section S2-S2 of FIG. 8. The addition of the mechanical screw 120 provides several benefits, including: (i) it rotates to provide power to move ash through the lateral cooling section 110; and (ii) a water cooled shaft 124 to provide cooling for the ash. The spiral winding 122 is preferably thermally conductive (e.g., made of steel, aluminum alloy, or some other metal) to effectively act as a heat sink for transporting heat from the ash to the water cooled shaft 124. While the machine screw 120 is shown as an illustrative ash movement device configured in the lateral cooling section 110 shown in fig. 8, other ash movement device embodiments are contemplated, such as a slat conveyor or a pan conveyor. Optionally, the ash moving equipment disposed in the lateral cooling section 110 is water cooled, for example by means of a water cooled screw shaft 124. The plate or disc conveyor may be water cooled by a cooling apparatus similar to the cooling apparatus 691 of fig. 7. As another contemplated variation, if the lateral cooling section 110 is short enough, no ash moving equipment may be configured within the lateral cooling section.

The embodiment of fig. 8 is illustrated with respect to a dry ash handling system embodiment. However, the lateral cooling section 110 of fig. 8 or 9 is also suitable for use in conjunction with a wet ash handling system such as that of fig. 5.

Referring now to fig. 9 and 10, another cooling apparatus is described. Fig. 9 shows SCS with multiple conveyors 50, 501 in series, where the first conveyor 501 comprises a fluid cooled housing. Fig. 10 depicts a cross-sectional view along section S3-S3 of the first SCS 501 of the dry ash handling system of fig. 9. In this embodiment, the closed duct 54 of the first SCS 501 includes the water jacket 154 or is surrounded by the water jacket 154. This advantageously provides for more efficient cooling of the dry ash flowing through the water jacket 154. In another contemplated embodiment (not shown), cooling of the tubes of the SCS 50 may be provided by tubing that is helically wound around the tubes 54 and carries water or another coolant. In fig. 9, both the first SCS 501 and the second SCS 50 are horizontally oriented, thus requiring (at least) twice the vertical space of a single conveyor. If, for example, in a retrofit design, lateral spatial constraints make such an arrangement impractical, the first SCS 501 may be tilted upward such that the second SCS 50 may be at the same vertical position as the first SCS 501 (or at least at a vertical position closer to the first SCS 501 than the arrangement shown in fig. 9). While this embodiment is particularly useful in the dry ash handling system of fig. 6, it is contemplated to be used in conjunction with a wet ash handling system such as that of fig. 5. In a wet ash handling system, cooling the conduit 54 by forming a water cooled conduit 154 or by a pipe helically wound around the conduit 54 may beneficially increase the heat transfer from the water carrying the wet ash inside the conduit to the ambient air.

As previously mentioned, fig. 7 depicts the bottom carrying arrangement of the SCS 50. In this arrangement, the scraper 66 on the lower channel of the twin drag chain conveyor 60 acts as a scraper to push or "scrape" ash along the floor 67 of the conveyor 50. The top scraper 68 serves as the return path for the twin drag chain conveyor and the top scraper 68 has no effect on the movement of the ash. This bottom bearing arrangement has certain advantages. For example, ash will fall under gravity through the top passage onto the floor 67. Furthermore, the waterline WL may be lower, and in fact may be lower than the height of the upper screed 68.

However, it is recognized herein that for some particular applications, the bottom carrier arrangement may have some disadvantages. In this arrangement, the shredder 18 is included to ensure that the ash is sufficiently reduced in size to pass between the upper scrapers 68 to fall onto the floor 67 of the conveyor 50. The pulverizer is a mechanical component exposed to raw ash and therefore requires relatively frequent maintenance.

To address these issues, fig. 11 shows an embodiment in which the SCS 50 employs a top-loading arrangement, while still maintaining the benefits of enclosing the duct 54. FIG. 11 shows the equivalent of cross-section S1-S1 of FIG. 5, but for the case of a top load bearing arrangement. To enable the top screed to scrape ash, a floor 160 is added below the top screed 68 and above the bottom screed 66. That is, the floor 160 is configured below the scraper 68 moving in the top section of the chain conveyor and above the scraper 66 moving in the bottom section of the chain conveyor, and the scraper 68 moving in the top section moves ash over the floor. Ash entering through the point location 53 in the receiving section 52 of the SCS 50 falls onto the floor 160 and is thereby prevented from reaching the floor 67, the bottom scraper 66 passing over the floor 67. The added floor 160 is suitably one (or more) steel panels or the like. In the top load-bearing part of fig. 11, the bottom scraper 66 now serves as the return path for the twin-strand drag chain conveyor, and the top scraper 66 has no influence on the movement of the ash. The cross-sectional area through which the ash moves in the top load bearing arrangement is limited by the addition of the floor 160, in order to maximise this cross-sectional area, the top scraper 68 (and hence the underlying floor 160) optionally moves downwardly closer to the bottom scraper 66 than in the bottom load bearing arrangement of figure 7.

As shown by waterline WL in fig. 11, the illustrative top carrier arrangement of fig. 11 is deployed in a wet ash handling system. The waterline WL must be above the added floor 160 (or the pipe may be completely flooded so that the waterline WL graphically indicates an air pocket that may occasionally occur at the top of the pipe). In some embodiments, the floor 160 seals against the side wall 100 of the pipe 54 such that water above the floor 160 cannot leak downward through the floor 160. In this way, the added space under floor 160 will not be flooded with water, and return bottom screed 66 will be properly situated in ambient air. However, if the lower space contains ambient air, the twin-strand drag chain conveyor will typically be raised at the point where the lower flight 66 transitions to the upper flight 68, so that the transition flight moves into the flooded upper space through which flight 68 travels. This height of SCS can be problematic if there are tight vertical spatial constraints.

In contrast to the foregoing, in the method shown in fig. 11, the lower space through which the lower blade 66 travels is flooded. This may be suitably accomplished by water flow at one or both transition ends of the conveyor, with the lower flight 66 moving up onto the upper track as the upper flight 68 and/or the upper flight 68 moving down onto the lower track as the lower flight 66. These transition ends provide fluid communication between the upper and lower spaces such that when the upper space is submerged, the lower space is also submerged, which simplifies the design of the chain conveyor with the elongated closed conduit 54.

As previously described, an advantage of the top carrying arrangement of fig. 11 is that ash entering through point locations 53 in the receiving section 52 of the SCS 50 does not have to fall through the space between the top scrapers 68 to reach the floor 67. The result of this is that the shredder 18 is optionally omitted, as it is no longer necessary to ensure that the ash is reduced in size sufficiently to pass between the upper scrapers 68 to fall onto the floor 67 of the conveyor 50.

Referring to fig. 12, a simplified SCS is shown in schematic side view, comprising a SCS 50 as already described with reference to fig. 11 with a top carrying arrangement, comprising a bottom blade 66 scraping the floor 67 of the duct 54, and a top blade 68 scraping off the added floor 67. Because it is not necessary to pulverize the ash to reduce its size sufficiently to pass between the upper scrapers 68, the pulverizer is omitted in the embodiment of fig. 12, which increases the headroom available to assist in retrofitting. Alternatively, the bottom door may be omitted. The embodiment of fig. 12, in which the shredder and bottom door are omitted, also eliminates most or all of the mechanical components in the area of connection from the hopper 14 to the point location 53 in the receiving section 52 of the SCS 50. The simplified SCS 50 of fig. 12 greatly reduces the likelihood of mechanical failure at this critical location as the hot ash passes through the region.

In another embodiment of the simplified SCS of fig. 12, a bottom carrier arrangement is employed. In this case, the floor 160 is omitted and the spacing d between adjacent blades is large enough to allow ash to pass between the upper blades 68 without crushing to reach the bottom of the duct 54 and be transported by the lower blades 66. Further, for this embodiment, the upper scraper 58 should be raised sufficiently above the top of the bottom scraper 66 to allow the bottom scraper to transport ash without crushing the ash and without the upper scraper 68 moving in the opposite direction to the lower scraper 66 to impact the un-crushed ash. Alternatively, in another contemplated variation, if the ash is sufficiently brittle (i.e., friable), the spacing between the upper and

lower blades

66, 68 may be intentionally made small enough so that the upper blade 68 contacts and breaks up the friable ash as the upper blade 68 moves in the opposite direction relative to the movement of the lower blade 66. In effect, the conveyor thus provides some ash grinding.

It may be considered that removing the bottom door would create problems during maintenance, as the bottom door is typically used to isolate the SCS 50 from the hopper 14. However, referring to fig. 13, a method of performing maintenance without a bottom door is described. In operation 200, the boiler that transfers the ash to the hopper 14 is taken off-line as the chain conveyor of the SCS 50 is running. In operation 202, after the boiler is taken off-line, the chain conveyor of the SCS 50 is run until all ash is removed. This requires continuing to run the chain conveyor to remove ash from the hopper and chain conveyor. In operation 204, water is discharged from the SCS 50. In operation 206, the shredder is de-energized. (if the shredder is omitted as in the simplified SCS of FIG. 12, then this operation 206 is suitably omitted). In operation 208, the downstream equipment, including at least stopping the chain conveyor of the SCS 50, is powered down. In operation 210, maintenance is performed. By following this procedure, hopper 14 no longer needs to have a bottom door.

The simplified SCS of fig. 12 is applicable to wet ash handling systems such as fig. 5, and this example is indicated in fig. 12 by illustrating the waterline WL included in the hopper 14 of fig. 12. However, the simplified SCS of fig. 12 is also applicable to dry ash handling systems, such as the system of fig. 6. In the case of a dry ash handling system, SCS discharge operation 204 is suitably omitted in the process of fig. 13.

Referring now to fig. 14, the temperature control procedure of SCS is described. The temperature control process may be implemented as an electronic controller (not shown, e.g., including at least one microprocessor or microcontroller and auxiliary electronics, such as flash memory, read-only memory, electronically programmable read-only memory and/or other non-transitory storage media, optionally implemented as a computer) programmed to control the flow control device (e.g., the illustrative shredder 18 and/or the mechanical screw 120 of fig. 8, or valves, saw-tooth trimmings, plungers, grinders, hydraulic jaws, various combinations thereof, etc.) and/or the speed of the twin drag chain conveyor 60 according to the method schematically shown in fig. 14. In operation 250, the temperature of the conveyor is measured. In operation 252, a material flow rate from the hopper is measured. In operation 254, a drive torque of the conveyor is measured. In operation 256, the temperature of the water or other cooling medium is measured. In operation 258, a temperature of a cooling device, such as the temperature of the cooling device 691 of fig. 7, the temperature of the lateral cooling section 110 of fig. 8, the temperature of the water cooled machine screw 120 of fig. 9, and/or the like, is measured. It will be appreciated that the order in which

operations

250, 252, 254, 256, 258 are performed may vary, and that these operations are repeated at a sensor sampling rate (which may be different for different sensors) to provide (near) real-time sensor readings. Further, in particular embodiments, more, fewer, and/or different sensors may be employed to monitor the thermal state of the SCS.

Based on the sensor readings, it is determined whether the ash temperature is too high or too low. The measured conveyor temperature 250 directly measures whether the conveyor temperature is too high or too low. The measured material flow rate from the hopper 252 allows indirect inferences to be made as to whether the ash temperature is too high or too low, because if the material flow rate is high, the cooling system may not be able to handle cooling with high material flow. (furthermore, high material flow rates may be a problem in and of themselves, as it may subject the twin drag chain conveyor 60 to excessive pressure). Also, the measured conveyor torque 254 allows indirect inference as to whether ash temperature is too high or too low, because if the torque is high, this means that more material is being conveyed and the cooling system may not be able to handle a large amount of material. (furthermore, high conveyor torque may itself be a problem as it manifests mechanical stress on the twin drag chain conveyor 60). The measured temperature of the cooling medium 256 and/or the measured temperature of the cooling device 258 is an indirect measure of whether the conveyor temperature is too high or too low. If one or more of the

sensor readings

250, 252, 254, 256, 258 are too high, the flow control device (e.g., shredder 18) is turned off (or operated to reduce the flow rate if the flow control device provides such adjustment of the flow rate) and/or the speed of the chain of the SCS 50 is reduced in operation 260. On the other hand, if one or more of the

sensor readings

250, 252, 254, 256, 258 are too low, the shredder 18 or other flow control device is opened (or operated to increase the flow rate) and/or the speed of the chain of the SCS 50 is increased in operation 262. Although this is a direct control method, more complex flow control is envisaged. For example, if the shredder 18 or other flow control device allows for continuous or multi-step adjustment of the flow rate (as opposed to just opening/closing as in the case of a bottom door), the adjustment operation 260 and/or the adjustment operation 262 may employ more complex adjustment formulas, e.g., scaling the flow rate adjustment amount based on how high (or how low) the sensor reading triggered the adjustment and/or whether two or more sensor readings triggered the adjustment simultaneously.

The system described herein may also be installed in retrofit applications. A method of replacing an existing system includes one or more of the following steps: removing the existing conveyor, replacing or maintaining the existing hopper, installing the SCS, changing the geometry of the existing hopper, changing the wall angle of the existing hopper, adding gas or liquid vents to the existing hopper, and repositioning the door opening to the bottom position of the existing hopper.

In the described embodiment, the cooling fluid is described as water. However, in certain installations, the ash may react with water. In this case, the cooling fluid may be propylene or some other cooling fluid. Further, the embodiments disclosed herein and the various aspects disclosed herein can be used in any combination and may be used with wet ash processing systems or dry ash processing systems, except as noted herein.

While the above description constitutes the preferred embodiment of the present invention, it will be understood that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.

Claims

1. A conveyor system for removing ash, the conveyor system comprising:

a hopper for collecting ash, an

A chain conveyor comprising an elongated closed conduit separate from a hopper, the elongated closed conduit having a receiving section positioned for receiving ash from the hopper, and further comprising an internal chain disposed within the elongated closed conduit for transporting ash from the hopper to a distal end of the chain conveyor for discharging ash from the chain conveyor, the chain conveyor having a bottom section and a top section, flights in the top section and flights in the bottom section moving in opposite directions within the elongated closed conduit, and wherein one of the top section or the bottom section moves ash from the receiving section to the distal end;

wherein the conveyor system does not include a bottom door interposed in the ash flow path from the hopper to the chain conveyor.

2. A conveyor system as in claim 1 wherein the conveyor system does not include a shredder interposed in the ash flow path from the hopper to the chain conveyor.

3. A conveyor system as in any one of claims 1-2 wherein the chain conveyor comprises a top-carrying chain conveyor comprising a floor below a flight moving in the top section and above a flight moving in the bottom section, and wherein the top section moves ash from the receiving section to the distal end.

4. A conveyor system as in claim 3 wherein the chain conveyor system is a wet ash conveyor system wherein the elongated enclosed conduit is flooded to submerge a scraper in the top section and a scraper in the bottom section.

5. A conveyor system as in any one of claims 1-2 wherein the chain conveyor comprises a bottom-carrying chain conveyor, wherein the bottom section moves ash from the receiving section to the distal end.

6. A conveyor system as in any one of claims 1-5 wherein the chain conveyor is loaded from the hopper from a single point input allowing the conveyor system to rotate relative to the hopper in either one of 360 ° directions in a plane.

7. The conveyor system of any one of claims 1-6, further comprising:

a lateral cooling section interposed between an ash discharge opening of the hopper and the receiving section of the chain conveyor, wherein an ash movement apparatus is configured in the lateral cooling section.

8. A conveyor system as in claim 7 wherein the ash moving apparatus comprises a mechanical screw disposed in the lateral cooling section.

9. The conveyor system of claim 8, wherein the mechanical screw comprises a water-cooled shaft.

10. A conveyor system as in any of claims 7-9 wherein the lateral cooling section comprises a water jacket.

11. A conveyor system as in any of claims 1-10 wherein the conveyor system is one of:

a wet ash conveyor system in which at least a lower portion of the elongated enclosed conduit is submerged in water; or

A dry ash conveyor system in which the elongated closed conduit is not submerged in water.

12. The conveyor system of any one of claims 1-11, further comprising:

a chain support configured to support an inner chain; and

a cooling device in the chain support.

13. Conveyor system according to any of the claims 1-12, characterized in that the chain conveyor comprises at least a first chain conveyor with a water-cooled housing.

14. The conveyor system of any one of claims 1-13, further comprising:

an electronic controller configured to receive sensor readings indicative of a temperature of the chain conveyor and to control the temperature of the chain conveyor based on the received sensor readings by controlling at least one of: (i) a flow of ash from the hopper to the chain conveyor controlled by controlling a flow control device configured to control the flow of ash from the hopper to a receiving section of the chain conveyor, and/or (ii) a speed of the chain conveyor.

15. A conveyor system for removing ash, the conveyor system comprising:

a hopper for collecting ash, an

wherein the conveyor system does not include a shredder interposed in the ash flow path from the hopper to the chain conveyor.

16. A conveyor system as in claim 15 wherein the chain conveyor comprises a top-carrying chain conveyor including a floor below a flight moving in the top section and above a flight moving in the bottom section, and wherein the top section moves ash from the receiving section to the distal end.

17. A conveyor system as in claim 16 wherein the chain conveyor system is a wet ash conveyor system wherein the elongated enclosed conduit is flooded to submerge a scraper in the top section and a scraper in the bottom section.

18. A conveyor system as in claim 15 wherein the chain conveyor comprises a bottom-carrying chain conveyor in which the bottom section moves the ash from the receiving section to the distal end and wherein the spacing between adjacent flights is large enough to allow uncrushed ash to fall between flights moving in the top section to reach the bottom of the elongated enclosed conduit.

19. A conveyor system as in claim 18 wherein the spacing between the flights moving in the top section and the flights moving in the bottom section is effective for the flights moving in the top section to contact and break down ash moving by the bottom section.

20. A maintenance method of a conveyor system for removing ash from a large coal fired combustion plant, the conveyor system comprising a hopper for collecting ash and a chain conveyor arranged to receive ash from the hopper and transport the received ash, wherein the conveyor system does not comprise a bottom door interposed in an ash flow path from the hopper to the chain conveyor, the method comprising:

-letting the boiler transferring ash to the hopper go off-line with the chain conveyor running;

after taking the boiler off-line, continuing to run the chain conveyor to remove ash from the hopper and the chain conveyor, and then stopping the chain conveyor.

21. A conveyor system for removing ash from a large coal fired combustion unit, the conveyor system comprising:

a hopper for collecting ash, an

A chain conveyor comprising a chain conveyor housing separate from a hopper, an elongated closed conduit having a receiving section positioned for receiving ash from the hopper, and having an internal chain for transporting ash from the hopper to a distal end of the chain conveyor for discharging ash from the chain conveyor, the chain conveyor having a bottom section and a top section, a flight moving in the top section and a flight moving in the bottom section moving in opposite directions, wherein one of the top section or the bottom section moves ash from the receiving section to the distal end;

wherein the hopper and the conveyor system are dry and the conveyor system further comprises a cooling device arranged in the hopper and/or the chain conveyor and/or interposed between an ash discharge outlet of the hopper and a receiving section of the chain conveyor.

22. A conveyor system as in claim 21 wherein the cooling apparatus comprises:

23. A conveyor system as in claim 22 wherein the ash moving apparatus comprises a mechanical screw disposed in the lateral cooling section.

24. A conveyor system as in claim 23 wherein the mechanical screw comprises a water cooled shaft.

25. The conveyor system of any one of claims 22-24, wherein the lateral cooling section comprises a water jacket.

26. A conveyor system as in any one of claims 21-25 wherein the lateral cooling section comprises a water jacket of the chain conveyor.

27. The conveyor system of any one of claims 21-26, further comprising:

a chain support for supporting an inner chain; and

a cooling device in the chain support.

28. The conveyor system of any one of claims 21-27, further comprising: