AU2011300475B2

AU2011300475B2 - An assembly for fossil fuel distribution

Info

Publication number: AU2011300475B2
Application number: AU2011300475A
Authority: AU
Inventors: Sauren Banerjee; Dey Debashis; Aditya Krishnendu
Original assignee: General Electric Technology GmbH
Current assignee: General Electric Technology GmbH
Priority date: 2010-09-09
Filing date: 2011-08-29
Publication date: 2014-11-20
Anticipated expiration: 2031-08-29
Also published as: TWI540288B; EP2614307A2; CA2810965C; WO2012032382A3; TW201217711A; JP2013544343A; CN103403450A; ZA201301829B; AU2011300475A1; CN103403450B; CA2810965A1; JP5788004B2; WO2012032382A2

Abstract

The present invention relates to the field of fossil fuel combustion arrangement. It relates in particular to a fuel distribution assembly for equal and homogenous pulverized fuel distribution in pulverized fuel conduits throughout. It also relates to a system for providing an equal and homogenous pulverized fuel distribution.

Description

WO 2012/032382 PCT/IB2011/001982 AN ASSEMBLY FOR FOSSIL FUEL DISTRIBUTION FIELD OF INVENTION The present invention relates to the field of fossil fuel combustion 5 arrangement. It relates in particular to a fuel distribution assembly for equal and homogenous pulverized fuel distribution in pulverized fuel conduits throughout. It also relates to a system for providing an equal and homogenous pulverized fuel distribution. 10 BACKGROUND OF THE INVENTION Coal coming out of mines requires to be crushed first in a crushing device at power plant yards. Crushing device crushes coal with around 2-centimeter diameter. This crushed coal is then pulverized to powder in coal mills. This pulverization is required for better burning in a boiler. Burning of coal releases heat to produce steam 15 at boiler. This steam rotates turbine and alternator to produce electricity. Pulverized coal coming out from coal mill requires to be evenly distributed in all individual burners for better burning and desired boiler efficiency. Otherwise it results in unburnt coal and unequal temperature at different zones of the boiler. In a typical boiler, coal particle and a primary airflow are fed from a pulverizer to the 20 burners through a network of fuel lines. A single large diameter main conduit along with further branching of numerous small diameter conduits form a fuel line. Primary air helps the pulverized fuel to move towards the boiler. A single conduit is used in carrying pulverized fuel from the coal mill and further branches into smaller conduits to feed burners of the boiler. At branching of single conduit into numerous smaller 25 conduits a flow imbalance takes place. Many users complain about the phenomenon of unequal temperatures in side the boiler. Investigations revealed that unequal flow after the coal mill is a major cause of such imbalance. Coal has to travel a long path sometimes about 30 to 50 meters after outlet at coal mill. Because of differences in conduits lengths and numbers and types of elbows 30 in each fuel line, the different conduits from a pulverize mill usually have different flow resistances. 1 2 Sometimes an orifice is fitted in each fuel line coming out of the mill. Orifices help to reduce flow imbalance only. But these orifices or flow restrictors are not sufficient. The long travel increases possibility of unequal flow through conduits. Another phenomenon takes place with high velocity air (around 30 meter per 5 second) is the formation of concentrated flow in one side of large diameter conduit, which is called "rope formation". Imbalances in pulverized fuel flow through conduits also lead to maintenance problems associated with conduits erosion and /or clogging for example excessive localized coal accumulation, damage to burners and wind boxes, and accelerated water 10 wall wastage. Problems such as these reduce the operating flexibility of the boiler. Effort of equal flow to each burner thus gets impaired due to complexity of the situation. A burner imbalance leads to higher carbon monoxide emissions and high levels of unburned carbons. Large and old boilers thus suffer from lesser effectiveness of burners. Most of the boilers have numerous burners that are to be fed by a single coal 15 mill. Also lesser space to accommodate new device is a typical problem in existing boilers. Currently there is a need for a solution in industry for removal of imbalance in coal flow to burners. At the same time the boilers require homogeneous flow of pulverized fuel (crushed coal). The solution needs to be used in space constraints and it 20 should be cost effective. The problem arises when coal mill outlet branches out in several numbers of smaller diameter conduits or ducts to reach individual burner of boiler. The resistance of each branches being unequal due to different lengths and varieties of configuration causes unequal output of pulverized fuel. Concentrated flow of pulverized fuel (coal rope) inside 25 the conduit is another problem that causes erosion and unequal flow. Although here we described the problems due to coal, similar problems are also there when any other fuel is used. Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission 30 that any of the material formed part of the prior art base or the common general knowledge in the relevant art in Australia on or before the priority date of the claims herein.

3 It would be desirable to provide an assembly that provides equal pulverized fuel to the pulverized fuel conduits and homogenous flow of pulverized fuel through out the pulverized fuel conduits. It would also be desirable to provide an assembly that withstands the erosion effects of coal and increases the life of pulverized fuel conduits supplying 5 pulverized fuel. It would further be desirable to provide an assembly which maintains sufficient pressure drop across the pulverized fuel conduits which is necessary for the supply of pulverized fuel. 10 SUMMARY In accordance with a first aspect of the present invention, there is provided an assembly for pulverized fuel distribution from a mill to a boiler including: an outer tube: an inner tube disposed within the outer tube wherein the inner tube and outer tube have a common central axis; and a plurality of deflectors disposed circumferentially about the 15 central axis between the inner tube and outer tube to provide resistance to the pulverized fuel flow; wherein the pulverized fuel flow passing through the outer and the inner tube is converted into homogenous pulverized fuel flow prior to distribution of the pulverized fuel to the boiler. Each deflector preferably comprises a first and a second tapered side walls 20 attached to a base structure, each deflector may be positioned such that the base structure forms a passage for a zig zag movement of the pulverized fuel. The partition plate may be embedded inside the inner tube and the deflector can be circumferentially distributed between the inner tube and the outer tube. The partition plate provides partial resistance to the flow of pulverized fuel. 25 The base structures may be alternately attached to an inner surface of the outer tube and to an outer surface of the inner tube. The base structure can be angled with respect to the central axis of the at least one tube. The first and the second tapered side walls may be angled alternately towards and away respectively with respect to the central axis of the tube. 30 The partition plate may extend in a radial direction from the central axis of the tube. In accordance with another aspect of the invention, there is provided a system for pulverized fuel distribution from a mill to a boiler including: a heater that generates a 4 primary air; a mill that pulverizes the coal into pulverized fuel, the pulverized fuel being supplied with the help of primary air through a main pulverized fuel conduit; an assembly that converts the pulverized fuel into homogeneous pulverized fuel and provides the homogenous pulverized fuel into the main pulverized fuel conduit; the assembly 5 including: an outer tube: an inner tube disposed within the outer tube wherein the inner tube and outer tube have a common central axis; and a plurality of deflectors disposed circumferentially about the central axis between the inner tube and outer tube to provide resistance to the pulverized fuel flow; wherein the pulverized fuel flow passing through the outer and the inner tube is converted into homogenous pulverized fuel flow and a 10 distributor that furcated the main pulverized fuel conduit into smaller pulverized fuel ducts, the smaller pulverized fuel ducts feeding the homogenous pulverized fuel to the burners of a boiler. The assembly may be embedded inside the main pulverized fuel conduit. In another embodiment the assembly can be installed between the main conduit 15 and the distributor. Comprises/comprising and grammatical variations thereof when used in this specification are to be taken to specify the presence of stated features, integers, steps or components or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. 20 BRIEF DESCRIPTION OF THE DRAWINGS The invention, its further features, nature as well as its advantages, shall be described in more details with the aid of accompanying drawings. Referring to the drawings 25 Fig. 1 schematically shows an embodiment of an assembly installed in a power plant, Fig. 2 schematically shows a front exploded perspective view of an assembly, Fig. 2a and 2b schematically shows perspective view of two embodiments of the deflectors for the assembly, 30 Fig. 2c schematically shows a perspective view of partition plate of the assembly, Fig. 3 schematically shows a partial transverse view of an assembly, Fig. 4 schematically shows a plan view of an assembly, Fig. 5 schematically shows a bottom perspective view of an assembly, 4a DETAIL DESCRIPTION OF THE DRAWINGS AND THE INVENTION In Fig 1, reference numeral 1 denotes a coal mill that receives primary air 2 from air heater 3 and crushed coal from a crusher device 4 through a coal feeder 5. The coal mill 1 further pulverizes the coal to powder size. Pulverized fuel is moved with the help of 5 primary air 2 towards a boiler 6 through a main pulverized fuel conduit 21. The main pulverized fuel conduit 21 is connected with the coal mill 1. A distributor 20 is provided for furcating the main pulverized fuel conduit 21 into a branching of smaller pulverized fuel ducts 24. The distributor 20 is attached for example through flange or nut bolts with the main pulverized fuel conduit 21 from one side and to 10 the branching of smaller pulverized fuel ducts 24 from other side towards the burners of the boiler 6. An assembly 7 is embedded inside the main pulverized fuel conduit 21 in a non moveable way for example through welding. The assembly 7 provides equal and 15 THE REMAINDER OF THIS PAGE HAS BEEN INTENTIONALLY LEFT BLANK. THE NEXT PAGE IS PAGE 5.

WO 2012/032382 PCT/IB2011/001982 homogenous fuel to the distributor 20 for distributing it into branching of at least one smaller pulverized fuel duct 24. Alternatively the assembly 7 is installed between the main pulverized fuel conduit 21 and distributor 20. The branching of smaller pulverized fuel ducts 24 feeds equal and 5 homogenous pulverized fuel to the burners of the boiler 6. The emissions from boiler 6 after passing through an electrostatic precipitator 8 are discharged through a chimney 9. The assembly 7 comprises a support unit 22 and a resistance unit 23.The support unit 22 is configured to hold the resistance unit 23 and provides strength and 10 support to the fuel distribution assembly 7. The support unit 22 is attached to the main pulverized fuel conduit 21 for example through welding and flanges. The resistance unit 23 is configured to provide resistance to the pulverized fuel flow so that equal pulverized fuel is supplied to the branching of smaller pulverized fuel ducts 24 and also orients the pulverized fuel flow into homogenous pulverized 15 fuel flow through out the smaller pulverized fuel ducts 24. The resistance unit 23 is embedded inside and attached to the support unit 22 for example through welding and flanges. The support unit 22 comprises at least one tube. In one embodiment as represented in fig 2, the support unit comprises for example two concentric tubes: an 20 outer tube 10 and an inner tube 11. The inner tube 11 provides support, rigidity and toughness to whole assembly 7 during the online condition when boiler 6 is fully operational. The outer tube 10 protects the whole assembly 7 from the corrosion effects, which occurs due to movement of pulverized fuel through it and holds the whole assembly 7. The length of outer tube 10 and the inner tube 11 corresponds to 25 the length of the assembly 7. Means for attachment are provided in form of welding, flanges, zigs, fixtures nut bolts, rivets and any other type for attaching the assembly 7 to the main conduit 21. The outer tube 10 is attached to the main pulverized fuel conduit 21 for example through welding or joined by a flange. 30 The resistance unit 23 comprises at least one partition plate 12 attached for example through welding or flange inside the inner tube 11 and at least one deflector 13 equally circumferentially distributed between the inner tube 11 and the outer tube 10. The assembly for example can have only one tube 10,11 to which for example at least one partition plate 12 or at least one deflector 13 attached through 5 WO 2012/032382 PCT/IB2011/001982 welding or flange. The partition plate 12 provides partial resistance to the flow of pulverized fuel. The deflectors 13 provide optimum resistance to the movement of pulverized fuel flow leading to accumulation of pulverized fuel downstream at the entry point of the assembly 7. 5 Each of the deflectors 13 is attached for example through welding or flange to an outer surface 14 of the inner tube 11 and to an inner surface 16 of the outer tubelO. The deflectors 13 and partition plates 12 may be attached directly for example through welding or through flanges with main pulverized fuel conduit 21. Zigs, fixtures and nut bolts can also be provided with main pulverized fuel conduit 21 for 10 attachment. The resistance unit 23 is disposed inside the at least one tube for example the partition plates 12 inside the inner tube 11 and/or the deflectors inside the outer tube 10. The central axis of the tubes 10, 11 is denoted by A-A' and is parallel to the central axis of main conduit 21. 15 The partition plates 12 as shown schematically in Fig 2c are flat surfaced and rectangular in shape. The partition plates 12 are attached for example by welding along the circumference to an inner surface 15 of the inner tube 11 and orthogonally placed from each other. The partition plates 12 can have a curved surface and any shape including square. 20 The partition plates 12 are extending in a radial direction from the central axis A-A'. The main conduit 21, tubes 10, 11 and further smaller pulverized fuel ducts 24 can be of any shape including circular. Fig 2a, 2b shows perspective view of two embodiments of the deflectors 13. 25 The two embodiments of the deflectors 13 are symmetrical. The deflectors 13 comprise a first tapered side wall 17 and a second tapered side wall 18 attached along at one of their ends to a base structure 19 in between. The deflectors 13 are positioned such that the base structure 19 attached to the first tapered side wall 17 and the second tapered sidewall 18 forms a passage for the 30 movement of the pulverized fuel. The base structure 19 can have any shape including rectangular, square, parallelogram. The base structure 19 corresponds to the length of the assembly7, measured along the axis A-A'. 6 WO 2012/032382 PCT/IB2011/001982 The first 17 and the second 18 tapered sidewalls are angled alternatively towards and away respectively with respect to the central axis A-A'. The tapered sidewalls angle a, shown in fig2 is the angle of the tapered sidewalls with respect to central axis A-A'. The angle a is with in range of 0 degree to 180 degrees with 5 respect to the central axis or more preferably in the range of 10 to 20 degrees. The first 17 and the second 18 tapered side walls are angled to provide optimum resistance in the path of pulverized fuel so that maximum amount of air and pulverized fuel can pass through them. This optimum resistance helps in equal and homogenous distribution of pulverized fuel into the at least one smaller pulverized fuel duct for 10 feeding the burners of the boiler 6 through the deflector 20. The first tapered side wall 17 and the second tapered side wall 18 can have any shape including trapezium, rectangular, square, parallelogram The angling of first 17 and the second 18 tapered side walls also helps in maintaining a optimum velocity and minimum pressure drop which is necessary for 15 the flow of pulverized fuel, so that the assembly 7 does not become a hindrance in flow of pulverized fuel. In Figure 3 angled base structures 19 are shown in a transverse partial view of the assembly 7.The base structures 19 angle P is the angle of the base structure 19 with respect to central axis A-A'. The base structures 19 angle P is with in range of 0 20 degree to 90 degrees with respect to the central axis A-A' or more preferably in the range of 10 to 30 degrees. The angling of base structure 19 provides optimum resistance to break the rope formation and equal distraction, which leads to equal and homogenous distribution of pulverized fuel in the branching of the smaller pulverized fuel ducts 24. The equal and homogenous pulverized fuel move upstream 25 homogenously in central portions of the branching of the smaller pulverized fuel ducts 24. The geometrically symmetrical deflectors 13 are attached for example through welding between the inner tube 11 and the outer tube 10 in such a way that the base structures 19 of the deflectors 13 are alternatively attached to the inner surface 16 of 30 the outer tube 10 and to the outer surface 14 of the inner tube 11. Pulverized fuel moves towards the central axis A-A' along the deflector 3 angled towards the central axis A-A' through base structure 19 attached to the inner surface 16 of the outer tube 10 or alternatively towards periphery of outer tube 10 along the deflector13 angled 7 WO 2012/032382 PCT/IB2011/001982 away from central axis A-A' through base structure 19 attached to the outer surface 14 of the inner tube 11. Means for transporting the pulverized fuel through the assembly 7 are provided for example a main pulverized fuel conduit 21, numerous smaller pulverized 5 fuel ducts 24 concentric tubes 10,11 or conveyer belt or any similar type of arrangement. Means for supporting the assembly 7 are provided through the support unit 22 for example concentric tubes 10,11, and any other similar arrangement. Means for resistance are provided in form of deflector 13, tapered sidewalls 10 17,18 and angled base plates 19, structures, of any shape and size and any other type in the assembly 7 to the flow of pulverized fuel. The assembly 7 is used for a laminar flow, a periphery flow and a turbulent flow. Basically type of flow has no impact on the working of the assembly 7. The assembly 7 ensures an equal distribution of pulverized fuel and breaking of 15 concentrated flow of pulverized fuel to homogeneous one for any kind of flow. The assembly 7 provides low to high resistance through partition plates 12 and deflectors 13 respectively. Most of the pulverized fuel having laminar flow passes through partition plates 12 but in case of peripheral and turbulent flow high resistance is provided through deflectors13 for equal distribution and breaking of rope formation. 20 Due to resistance, pulverized fuel coming from coal mill 1 starts accumulating before the assembly 7. The pulverized fuel starts moving towards deflectors 13. The base structure 19 of the deflector 13 pushes the pulverized fuel towards the central axis A-A' and towards a periphery of the outer tube10. A zigzag movement results in of the down stream-pulverized fuel due to this particular arrangement. This zig zag 25 movement leads to equal distribution of the pulverized fuel and breaks the rope formation to a large extent. Rope formation occurs due to high concentration of pulverized fuel in one side or periphery regions of the main pulverized fuel conduit 21 supplying pulverized fuel from coal mill 1 to the assembly 7. After passing over the assembly 7, the pulverized fuel is converted in to a 30 homogenous equal upstream-pulverized fuel with a desired flow pattern. This homogenous equal upstream-pulverized fuel is supplied through the branching of the smaller pulverized fuel ducts 24 to the burners of the boiler 6. 8 WO 2012/032382 PCT/IB2011/001982 The pulverized fuel is directed preferentially towards the plurality of partition plates12 in case of a laminar flow. The pulverized fuel is directed preferentially towards the plurality of deflectors 13 in case of a periphery flow and turbulent flow. In another embodiment a system for pulverized fuel distribution from a mill to 5 a boiler comprising a heater that generates a primary air, a mill that pulverized the coal into pulverized fuel, the pulverized fuel being supplied with the help of primary air through a main pulverized fuel conduit, an assembly that provides pulverized fuel equally and homogenously into the main pulverized fuel conduit, a distributor that furcates the main pulverized fuel conduit into smaller pulverized fuel duct, the smaller 10 pulverized fuel ducts feeding equal and homogenous pulverized fuel to the burners of a boiler. The assembly 7 can be applicable to other fossil fuels including gas although the description is here regarding coal. By using the present assembly 7 imbalances in fuel distribution have been 15 greatly reduced resulting in for examples with in 2% variation from mean flow. The assembly 7 may be produced in any desired shape or size including circular, elliptical and cylindrical. It may be available singly, in multiples, or in a "set" of varying sizes and shapes to suite existing layouts or the proposed lay outs according to user needs. It may vary in shape and dimensions as determined by its 20 desired locality and can be designed for any length and size of the main conduit 21 as well as further smaller pulverized fuel ducts 24. The assembly 7 can be placed in a "set" in multiple outlets from multiple coal mills as well as in the further of the smaller pulverized fuel ducts 24. The assembly 7 is attachable vertically along the axis of vertically placed 25 conduits, horizontally along the axis of horizontally placed conduits and in inclination along the axis of inclined conduits. The assembly 7 is made of mild steel with hard faced steel conduit with internal fitments of specific designed numbers of plates. It can also be prepared through any similar material including stainless steel and cast iron. 30 The assembly 7 is preferably light in weight and may be dismantled and relocated in very short span of time. The assembly 7 is inexpensive, easily fit in the existing systems with minimum alteration of existing systems and needs very less space. 9 WO 2012/032382 PCT/IB2011/001982 Although the invention has been described and illustrated with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without parting from the spirit and scope of the present invention. 5 Accordingly, other embodiments are within the scope of the following claims. 10

Claims

1. An assembly for pulverized fuel distribution from a mill to a boiler including: an outer tube: an inner tube disposed within the outer tube wherein the inner tube and outer tube have a common central axis; and a plurality of deflectors disposed circumferentially about the central axis between the inner tube and outer tube to provide resistance to the pulverized fuel flow; wherein the pulverized fuel flow passing through the outer and the inner tube is converted into homogenous pulverized fuel flow prior to distribution of the pulverized fuel to the boiler.

2. The assembly according to claim 1, further including at least one partition plate within the inner tube.

3. The assembly according to either claim 1 or claim 2, wherein each deflector includes first and second tapered side walls attached to a base structure.

4. The assembly according to claim 2, wherein the at least one partition plate is a pair of partition plates.

5. The assembly according to claim 4, wherein the pair of partitions are orthogonal to each other.

6. The assembly according to claim 4, wherein the partition plates have a curved surface.

7. The assembly according to claim 3, wherein the base structures are alternately attached to an inner surface of the outer tube and to an outer surface of the inner tube.

8. The assembly according to claim 3, wherein the base structure is angled with respect to the central axis of the tube. 12

9. The assembly according to claim 3, wherein first and the second tapered sidewalls are angled alternately towards and away respectively with respect to the central axis of the tube.

10. The assembly according to claim 2, wherein the at least one partition plate is extending in a radial direction from the central axis of the tube.

11. The assembly according to claim 1, wherein a portion of the deflectors direct the pulverized fuel towards the central axis and a portion of the deflectors direct the pulverized fuel away from the central axis.

12. The assembly according to claim 1, wherein the deflectors alternately direct the pulverized fuel towards the central axis and away from the central axis.

13. A system for pulverized fuel distribution from a mill to a boiler including: a heater that generates a primary air; a mill that pulverizes the coal into pulverized fuel, the pulverized fuel being supplied with the help of primary air through a main pulverized fuel conduit; an assembly that converts the pulverized fuel into homogeneous pulverized fuel and provides the homogenous pulverized fuel into the main pulverized fuel conduit; the assembly including: an outer tube: an inner tube disposed within the outer tube wherein the inner tube and outer tube have a common central axis; and a plurality of deflectors disposed circumferentially about the central axis between the inner tube and outer tube to provide resistance to the pulverized fuel flow; wherein the pulverized fuel flow passing through the outer and the inner tube is converted into homogenous pulverized fuel flow and a distributor that furcated the main pulverized fuel conduit into smaller pulverized fuel ducts, the smaller pulverized fuel ducts feeding the homogenous pulverized fuel to the burners of a boiler.

14. The system for pulverized fuel distribution according to claim 13, wherein the assembly is embedded inside the main pulverized fuel conduit. 13

15. The system for pulverized fuel distribution according to claim 13, wherein the assembly is installed between the main conduit and the distributor.

16. The system for pulverized fuel distribution according to claim 13, wherein a portion of the deflectors direct the pulverized fuel towards the central axis and a portion of the deflectors direct the pulverized fuel away from the central axis.

17. The system for pulverized fuel distribution according to claim 16, wherein the deflectors alternately direct the pulverized fuel towards the central axis and away from the central axis.

18. The system for pulverized fuel distribution according to claim 16, further including at least one partition plate within the inner tube.

19. The system for pulverized fuel distribution according to claim 13, wherein each deflector includes first and second tapered side walls attached to a base structure.

20. The system for pulverized fuel distribution according to claim 19, wherein the at least one partition plate is a pair of partition plates.

21. The system for pulverized fuel distribution according to claim 20, wherein the pair of partitions are orthogonal to each other.

22. The system for pulverized fuel distribution according to claim 20, wherein the partition plates have a curved surface.

23. The system for pulverized fuel distribution according to claim 19, wherein the base structures are alternately attached to an inner surface of the outer tube and to an outer surface of the inner tube.

24. The assembly according to claim 19, wherein the base structure is angled with respect to the central axis of the inner tube. 14

25. The assembly according to claim 19, wherein first and the second tapered sidewalls are angled alternately towards and away respectively with respect to the central axis of the inner tube.

26. The assembly according to claim 16, wherein the at least one partition plate is extending in a radial direction from the central axis of the inner tube.

27. An assembly for pulverized fuel distribution from a mill to a boiler, substantially as herein before described with reference to the accompanying drawings. ALSTOM TECHNOLOGY LTD WATERMARK PATENT AND TRADE MARKS ATTORNEYS P37221AUOO