GB2532493A

GB2532493A - Improvements in or relating to bulk fuel feeders

Info

Publication number: GB2532493A
Application number: GB1420723.7A
Authority: GB
Inventors: Brown Christopher; Jaques Colin; Wegerski Marcin
Original assignee: Crowle Wharf Eng Ltd
Current assignee: Crowle Wharf Eng Ltd
Priority date: 2014-11-21
Filing date: 2014-11-21
Publication date: 2016-05-25
Anticipated expiration: 2034-11-21
Also published as: GB2532493B; GB201420723D0

Abstract

A bulk conveyor 10 features a weight measuring device 47 featuring a flexible member or plate 49, which overlies a mass measuring element 52, on a support element 53. The apparatus may be used for the measurement of the mass of material, such as coal, fed into a coal feeding conveyor 10, which itself outputs to other apparatus. Also disclosed is a bulk conveyor 10 with a weight measuring device 47 which generates weight measurement signals, and a volumetric metering element. This apparatus may be used to generate measures of both mass and volume, so that characteristics such as density of material can be calculated.

Description

IMPROVEMENTS IN OR RELATING TO BULK FUEL FEEDERS

The invention concerns improvements in or relating to bulk fuel feeders.

Bulk fuel feeders are used in various installations such as power stations, boilers, incinerators and the types of yard in which bulk fuel is stored.

The term "bulk fuel" embraces any fuel that exhibits so-called "bulk flow". The most common form of bulk fuel of this kind is coal in nut or nugget form, although the term also includes e.g. various forms of biofuel such as but not limited to wood pellets; coal slag; and also some high-viscosity liquids. The invention is applicable in the case of feeders for all the aforementioned fuel types.

One particularly common form of bulk fuel feeder is a coal feeder installed in a coal-burning power station.

Coal remains the most extensively used source of fuel in electrical power generation worldwide. The burning of coal in power stations however is recognised as a major source of anthropogenic atmospheric carbon dioxide. There are as a result many initiatives having the aim of reducing the amounts of coal burned in the generation of power, and/or of improving the efficiency with which coal is used. The invention is of benefit in these areas of endeavour.

Both in connection with improving the efficiency of coal usage and generally, it is desirable for power station owners and operators to know both the mass and the density of coal burned during power generation. One reason for wishing to know in particular the density of coal burned is that this can indicate the purity of the coal. Account can then be taken of contaminants such as ash (in slag coal), water, rocks and other debris that can adversely affect both combustion efficiency calculations and in some cases the price paid for the bulk fuel.

For reasons explained below however existing apparatuses and methods for establishing such quanta are sub-optimal and associated with considerable compromise.

Figure 1 is a side elevational view of a prior art coal feeder 10 of a kind employed for conveying coal from a bunker to a pulverising mill of a coal-fired power station. Figure 2 is a cross-sectional view of the Figure 1 coal feeder, taken along line A -A.

Coal feeder 10 is constituted by an elongate hollow interior 11 of a rectangular cross-section that is defined by mutually orthogonal, interconnected top 12, bottom 13 and side 14, 16 walls formed of a rigid metal such as a steel and firmly secured together e.g. by welding. The ends of the hollow interior 11 are closed by perforated, rigid end walls 17, 18 as illustrated.

The hollow interior 11 is divided into upper and lower chambers 19, 21 by a rigid, wear-resistant deck plate 22. Deck plate 22 spans from one side of the interior 11 to the other over a major part of the length of the coal feeder 10. In the coal feeder illustrated the deck plate 22 is horizontal but this need not necessarily be so.

A similar wear-resistant deck plate 23 is mounted on and overlies bottom wall 13. The purpose of the deck plates is to support coal conveyed in the coal feeder by a conveyor mechanism described below.

At each lateral side each deck plate 22, 23 includes extending upwardly a respective chain guide channel 24, 26, 27, 28. The chain guide channels are formed as elongate angle irons one vertical limb 29 of which is secured to one of the side walls 14, 16 of the coal feeder 10 and the other limb 31 of which extends horizontally towards the centre of the chamber 19, 21 in which it overlies a short lateral extent of the adjacent deck plate 22, 23.

An endless chain represented schematically by chain line 32 is looped about respective chain wheels 33, 34 that are mounted externally at either end of the coal feeder so as to be rotatable about respective horizontal axes. As noted the end walls 17, 18 of the hollow chamber 11 are perforated and this permits the chain 32 to extend around the chain wheels 33, 34 even though these lie outside the hollow interior 11. The chain wheels 33, 34 include drive transferring features such as drive teeth or dogs such that rotation of the chain wheels causes movement of the chain.

In practice there are two chain wheels disposed in the aforesaid manner at each end of the coal feeder 10 and spaced laterally apart from one another such that each chain wheel supports a respective side of the chain 32.

The lateral extremities of the chain are received in and extend along the chain guide channels 24, 26, 27, 28. Thus at any given time the lateral extremities of approximately 50% of the length of the chain are received in the chain guide channels 24, 26 of the upper chamber 19; and the lateral extremities of approximately the other 50% are received in the chain guide channels 27, 28 of the lower chamber 21.

At least one set of the chain wheels at one or other end of the coal feeder 10 is capable of being powered to rotate so as to cause continuous motion of the chain 32 inside the hollow interior 11 with the aforesaid extremities of the chain sliding in the chain guides.

The chain 32 is constituted by respective lateral flexible loops of chain links some of which are interconnected in the transverse direction of the coal feeder 10 by rigid flight bars that are equally spaced from one another in the longitudinal direction of the coal feeder 10.

The result is a chain the lateral loops of which engage with the chain wheels as aforesaid and that when powered to move by reason of powering of the chain wheels cause the flight bars extending transversely across the hollow interior to travel seriatim inside the hollow interior.

The arrangement of the chain loops and flight bars is such as to define a series of rectangular spaces, between the lateral loops of the chain, that are delineated in the transverse direction by the flight bars. The pitch of the flight bars in some coal feeders is variable and can be altered from time to time. During movement of the chain 32 as described the flight bars slide along the deck plates 22, 23. The flight bars extend upwardly of the deck plates 22, 23 with the result that any coal contained inside the rectangular spaces is dragged along the deck plates 22, 23 by the moving flight bars.

In the coal feeder 10 illustrated in Figures 1 and 2 the direction of motion of the chain is as signified by the arrow 36. Thus in the upper chamber 19 the flight bars move from right to left in Figure 1, and in the lower chamber 21 they move from left to right. In other coal feeders however the reverse movement directions, or more complex movement paths, are possible.

The coal feeder 10 is arranged to lie beneath the chute or opening of a coal bunker that is omitted from the drawings. The top wall 12 of the coal feeder 10 includes formed therein an elongate feeder opening 37 defined by opening mouth walls, of which one labelled 38 is visible in Figure 1, defining a rectangular mouth extending most of the way along the top wall 12 from one end of the coal feeder 10 to the other.

Coal dispensed from the bunker falls as a result of the described arrangement via the opening 37 onto the upper deck plate 22. Assuming one or more sets of chain wheels 33, 34 is powered to rotate this causes motion of the chain 32 as described above. In turn this means that the flight bars drag the coal initially from right to left along the upper deck plate 22.

When the coal reaches the left hand end of the upper deck plate 22 the space between the end of the deck plate 22 and the end wall 17, together with the fact that the chain 32 is open between the described flight bars and lateral loops, means that the coal falls onto the lower deck plate 23.

Further movement of the chain 32 as described then causes the flight bars to drag the coal along the lower deck plate 23 towards a bottom aperture 39 formed in the bottom wall 13 approximately underneath the chain wheels 34. The coal falls from the bottom aperture 39 into e.g. a pulveriser that comminutes the coal to a size suitable for burning in the burners of the power station.

When the coal falls from the bunker onto the chain 32 and deck plate 22 in the upper chamber 19 it piles up, in a generally predictable manner, towards the top of upper chamber 19. The upper chamber 19 includes extending vertically downwardly from top wall 12 towards deck plate 22 a metering plate, in the form of a rigid, flat plate 41, that controls the height of the coal conveyed onto the lower deck plate 23.

Plate 41 extends from one side of upper chamber 19 to the other a short distance to the left (in Figure 1) of the extremity of feeder opening 37 and terminates in a free edge 42 at a chosen height above the deck plate 22. The effect of the metering plate 41 is to render uniform at a predetermined level the height of coal conveyed. The metering plate achieves this by knocking coal piled up above the free edge 42 off the coal pile and redistributing it on the deck plate 22 so that a uniform pile of coal of a height less than the space between the free edge 42 and the deck plate 22 is conveyed.

The metering plate 41 therefore regulates the volume of coal conveyed, and ensures that this volume is known with reasonable accuracy as long as the coal feeder 10 is continuously supplied with coal from the bunker.

In addition to the foregoing features the known coal feeder 10 includes a number of inspection and/or access doors 43 that for the sake of example are shown at various locations in side wall 16; a nitrogen accumulator 44 that automatically adjusts the tension in chain 32; and an explosion chute 46 that accommodates gaseous expansion in the event of a gas or particulate explosion as occasionally occurs in use of power station equipment. These features are of peripheral relevance to the basic structure and operation of the coal feeder 10 as set out above, and therefore are not described in detail herein.

Since the coal feeder 10 includes only a single, continuous conveyor constituted by the chain loops and flight bars this type of conveyor is referred to herein as a single-stage conveyor chain.

The coal feeder 10 of Figures 1 and 2 as noted is capable of consistently delivering a known volume of coal to the pulveriser, but it includes no means of establishing the mass or weight of the coal as delivered.

As indicated above however knowledge of the coal mass is important since this can be used to derive a density value for the supplied coal and thence various other variables such as the water or contaminant content, the calorific value and indeed the correct purchase price of the coal.

It is known to incorporate weighing elements in a bulk fuel feeder. However in the prior art the only such device known to the inventors requires a second conveyor chain to be installed beneath an upper conveyor belt that differs from the type described in relation to Figure 1. A load measuring device is connected to this upper conveyor such that load measurement signals may be generated. In one known arrangement the second conveyor operates to clear spilled coal. In another known arrangement the second conveyor conveys coal towards a pulveriser.

The presence of a second conveyor assembly in order to create a two-stage conveyor in a bulk fuel feeder however is associated with numerous disadvantages.

Aside from the fact that the inclusion of the components of the second conveyor stage adds significantly to the cost of the bulk feeder, this also increases the overall height of the device since the conveyor stages must be installed one beneath the other.

In some locations in power stations however there is insufficient headroom to permit the installation of a bulk feeder that is of greater height than the single stage device of Figures 1 and 2. A two stage conveyor arrangement in such circumstances is impractical.

Moreover the interior of a bulk fuel feeder is generally a harsh environment as a result of the heavy mass of bulk fuel that it must accommodate in addition to moisture, chemicals, dust and the deleterious effect of conveying hard, heavy materials using powerful motors. The installation of a second conveyor stage is believed adversely to affect the reliability of the feeder. Since the operational costs of power stations are very high any performance reduction caused by additional component complexity is generally regarded as strongly undesirable.

According to the invention in a first aspect there is provided a weight measuring device for to fuel in a bulk fuel feeder, the weight measuring device comprising a flexible member that overlies and is coupled to a mass measuring element supported on a support member that is fixable in a bulk fuel feeder such that the mass of bulk fuel conveyed in the feeder acts on the flexible member.

Such a weight measuring device may be manufactured cheaply from robust materials. It can be retrofitted to an existing bulk fuel feeder such as that of Figures 1 and 2, without increasing either the height of the device or, appreciably, its complexity. Alternatively a weight measuring device according to the invention may be installed as original equipment at the time of manufacturing of the bulk fuel feeder. The weight measuring device of the invention is useable in all the types of bulk fuel feeder described herein.

Preferably the flexible member is a metal plate that is insertable in an aperture formed in a deck plate of a bulk fuel path in a bulk fuel feeder. The aforesaid aperture may readily be fabricated in the upper deck plate 22 of a bulk fuel feeder of the kind shown in Figures 1 and 2 either during construction of the bulk fuel feeder 10 or after installation of the feeder in an operational location. The weight measuring device therefore may be easily retrofitted in existing bulk fuel feeders.

However it is also possible in some embodiments of the invention for the flexible plate to be part of or constituted by a deck plate such as deck plates 22 and 23 of Figures 1 and 2.

Conveniently the mass measuring element includes one or more elements from the list comprising a load cell or a spring balance.

Regardless of its precise type preferably the mass measuring element is capable of generating one or more electrical or electronic signals indicating a mass value of bulk fuel acting on the flexible member. Such signals conveniently can be transmitted, processed or converted to a form that can be displayed using e.g. a screen or LED indicator device.

Preferably the support member is or includes a beam, selected from a list comprising of an I-beam, a C-beam and a square-section beam, that is rigidly fixable at at least one end in a bulk fuel feeder. An I-beam, that typically is made from a rigid metal such as but not limited to a steel, may provide an immobile supporting datum for the mass measuring element. This is important in relation to some types of mass measuring element as their accuracy can depend on having an immobile support.

Furthermore an I-beam is well suited to withstanding the harsh environment of the interior 11 of a bulk fuel feeder 10 of the kind illustrated in Figures 1 and 2.

The invention further is considered to reside in a bulk fuel feeder including a weight measuring device according to the invention as defined herein.

The said support member optionally may be fixed underlying a deck plate of a bulk fuel path in the bulk fuel feeder.

In preferred embodiments the bulk fuel feeder of the invention includes a single-stage conveyor chain for conveying bulk fuel along a bulk fuel path.

The bulk fuel feeder also optionally may include a metering element for volumetric metering of slugs of bulk fuel. Such a metering element may be similar to metering plate 41 described above, or it may be of a different design.

Preferably therefore the metering element is or includes a rigid plate that overlies and is spaced vertically from a bulk fuel path in the bulk fuel feeder so as to limit the maximum height of slugs of conveyed along a bulk fuel path.

In a further broad aspect the invention resides in a bulk fuel feeder comprising a bulk fuel weight measuring device positioned to measure the weight of bulk fuel acting on the weight measuring device in a bulk fuel path and generating one or more signals indicative of the mass of fuel so acting; a single-stage conveyor chain for conveying bulk fuel along the bulk fuel path; and a metering element for volumetric metering of slugs of bulk fuel conveyed in the bulk fuel feeder.

Preferably the bulk fuel feeder is configured as a coal feeder. However the invention may be configured as another type of feeder. Non-limiting examples of such fuel feeder types are presented herein. One further, preferred type of bulk fuel feeder is a biofuel feeder.

According to a further aspect of the invention there is provided a method of measuring the weight of fuel conveyed in a bulk fuel feeder according to the invention as defined herein, the method including the step of conveying bulk fuel along a bulk fuel path so as to act on the weight measuring device; and generating in the weight measuring device one or more signals indicative of the weight of bulk fuel so acting.

Such a method optionally includes the step of processing, transmitting or displaying a signal that is indicative of the weight of bulk fuel acting on the weight measuring device.

In yet a further aspect of the invention there is provided a method of measuring the density of fuel conveyed in a bulk fuel feeder according to the invention as defined herein, the method including the step of conveying bulk fuel along a bulk fuel path so as to act on the weight measuring device; generating in the weight measuring device one or more signals indicative of the weight of bulk fuel so acting; and dividing the value of the said one or more signals by a measure of the volume of bulk fuel in order to generate a density measure for the bulk fuel.

Such a method preferably includes the step of processing, transmitting or displaying a signal that is indicative of the density of bulk fuel acting on the weight measuring device.

There now follows a description of preferred embodiments of the invention, by way of non-limiting example, with reference being made to the accompanying drawings in which: Figure 1 is a side elevational, partly schematic view of a prior art power station coal feeder; Figure 2 is a transverse cross-sectional view on arrows A -A of Figure 1; and 3o Figure 3 is a perspective view of a weight measuring device, according to the invention, that is shown incorporated into a bulk fuel feeder such as that of Figures 1 and 2 in order to form a bulk fuel feeder in accordance with the invention.

Referring to Figure 3 the top wall 12, side walls 14, 16, deck plates 22, 23, chain guide channels 24, 26, 27, 28, feeder opening 37 and mouth wall 38 of a coal feeder 10 such as that of Figures 1 and 2 are visible.

A weight measuring device indicated generally by reference numeral 47 is secured relative to deck plate 22 in a manner permitting the weighing of coal that is caused by the flight bars of a conveyor chain of the general type described above to move along the deck plate 22 in the direction of arrow 48.

Weight measuring device 47 comprises a flexible member that in the preferred embodiment shown is formed as a rectangular plate 49 that is secured in a through-going aperture 51 formed in deck plate 22. Welding or other fastening means may be employed to secure the plate 49 in position.

The rectangular plate 49 is preferably formed from a metal that is of lesser rigidity that that of deck plate 22, but that nonetheless is sufficiently robust as to withstand the effects of heavy masses of coal being conveyed over it.

As noted herein however in other embodiments of the invention the flexible member may be formed integrally with, and indeed may be part of, the deck plate 22. Moreover it is not essential that the flexible member adopts the rectangular shape shown; and on the contrary numerous other shapes are possible. Furthermore the location of the flexible member need not be as shown, it being sufficient merely that the flexible member is repeatedly contacted by the coal as it is conveyed through the feeder 10. Therefore a range of positions is possible within the scope of the invention.

Located underneath and in contact with plate 49 is a load cell 52 or a similar mass measuring element. If not configured as a load cell the mass measuring element may be configured in a variety of ways as would occur to the person of skill in the art. An example of a possible measuring element includes a spring balance.

The load cell 52 is supported from underneath by a rigid support member in the form (in the embodiment shown) of a metal (e.g. steel) I-beam 53.

As alternatives to the I-beam illustrated the support may be configured as e.g. a beam of C or square cross-section. One advantage of using I, C or square cross-section beams is that their intersecting walls can provide protection, against the harsh environment inside a coal feeder, for cabling extending along the support. Such cabling may if desired be further protected within conduits or trunking. Cabling may be desirable in the vicinity of the load cell 52 in order to permit the transmission of data signals to e.g. processing apparatus in the form of a computer or other programmable device.

For convenience the term I-beam is used in the remainder of this description. It is to be understood that this term embraces equivalent structures such as C-and square cross-section beams.

I-beam 53 spans the interior 11 of the coal feeder 10 and is secured at its ends respectively to the side walls 14, 16 of the coal feeder 10. I-beam 53 therefore provides a rigid support that acts as a datum for the load cell.

The weight measuring device 47 may be formed integrally with the remainder of the coal feeder 10, or it may readily be retrofitted to an existing coal feeder. In the latter case a relatively straightforward installation process involves cutting the aperture 51 in deck plate 22; welding the rectangular plate 49 in place; and securing (e.g. by welding or using fasteners) the I-beam 53 to the side walls 14, 16 at the correct height with the load cell 52 interposed between the rectangular plate 49 and the I-beam 53 in a manner permitting operation of the latter.

Whether the load measuring device is fitted at the time of manufacture of the coal feeder 10 or is subsequently retrofitted, typically the mass measuring element is of a type that generates a signal that is indicative of the mass of coal (or other bulk fuel) acting on the rectangular plate 49 (or in some cases a section of the deck plate 22 that substitutes for the rectangular plate 49).

The signal from the load cell may be transmitted e.g. using a cable connection or wirelessly to a display device or a processing device. Thus it is possible in use of the invention to display indicia representing the mass of bulk fuel travelling in the coal feeder.

When a processing device is included and the coal feeder additionally includes a metering plate 41 it is possible by way of a simple calculation to determine the density of the bulk fuel. The resulting density value may be displayed, transmitted of further processed.

One example of further processing involves calculating the calorific value of the fuel. From this a power station operator may acquire a value of e.g. carbon dioxide produced during operation of a power station burner.

Another processing example involves determining the purchase value of the fuel from the density value calculated as aforesaid. Thus if for instance the fuel has a high water content (as a result of being stored outdoors in wet weather) it may be possible for the power station operator to use data produced by the apparatus of the invention and/or according to the method of the invention to negotiate discounts and rebates in respect of the fuel price paid.

Preferences and options for a given aspect, feature or parameter of the invention should, unless the context indicates otherwise, be regarded as having been disclosed in combination with any and all preferences and options for all other aspects, features and parameters of the invention.

The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

Claims

CLAIMS1. A weight measuring device for fuel in a bulk fuel feeder, the weight measuring device comprising a flexible member that overlies and is coupled to a mass measuring element supported on a support member that is fixable in a bulk fuel feeder such that the mass of bulk fuel conveyed in the feeder acts on the flexible member.
2. A weight measuring device according to Claim 1 wherein the flexible member is a metal plate that insertable in an aperture formed in a deck plate of a bulk fuel path in a bulk fuel feeder.
3. A weight measuring device according to Claim 1 wherein the flexible member is part of or formed integrally with a deck plate in a bulk fuel path of a bulk fuel feeder.
4. A weight measuring device according to any preceding claim wherein the mass measuring element includes one or more elements from the list comprising a load cell, a spring balance or a pivoting plate bulk flow mass measuring element.
5. A weight measuring device according to any preceding claim wherein the mass measuring element is capable of generating one or more electrical or electronic signals indicating a mass value of bulk fuel acting on the flexible member.
6. A weight measuring device according to any preceding claim wherein the support member is or includes a beam selected from a list comprising of an I-beam, a C-beam or a square-section beam that is rigidly fixable at at least one end in a bulk fuel feeder.
7. A bulk fuel feeder including a weight measuring device according to any preceding claim.
8. A bulk fuel feeder according to Claim 7 wherein the support member is fixed underlying a deck plate of a bulk fuel path in the bulk fuel feeder.
9. A bulk fuel feeder according to Claim 7 or Claim 8 including a single-stage conveyor chain for conveying bulk fuel along a bulk fuel path.
10. A bulk fuel feeder according to any of Claims 7 to 9 including a metering element for volumetric metering of slugs of bulk fuel.
11. A bulk fuel feeder according to Claim 10 wherein the metering element is or includes a rigid plate that overlies and is spaced vertically from a bulk fuel path in the bulk fuel feeder so as to limit the maximum height of slugs of conveyed along a bulk fuel path. 5
12. A bulk fuel feeder comprising a bulk fuel weight measuring device positioned to measure the weight of bulk fuel acting on the weight measuring device in a bulk fuel path and generating one or more signals indicative of the mass of fuel so acting; a single-stage conveyor chain for conveying bulk fuel along the bulk fuel path; and a metering element for volumetric metering of slugs of bulk fuel conveyed in the bulk fuel feeder.
13. A bulk fuel feeder according to any of Claims 7 to 11 or Claim 12 when configured as a coal feeder.
14. A bulk fuel feeder according to any of Claims 7 to 11 or Claim 12 when configured as a biofuel feeder.
15. A method of measuring the weight of fuel conveyed in a bulk fuel feeder according to any of Claims 7 to 11, 12, 13 or 14, the method including the step of conveying bulk fuel along a bulk fuel path so as to act on the weight measuring device; and generating in the weight measuring device one or more signals indicative of the weight of bulk fuel so acting.
16. A method according to Claim 15 including the step of processing, transmitting or displaying a signal that is indicative of the weight of bulk fuel acting on the weight measuring device.
17. A method of measuring the density of fuel conveyed in a bulk fuel feeder according to any of Claims 7 to 11, 12, 13 or 14, the method including the step of conveying bulk fuel along a bulk fuel path so as to act on the weight measuring device; generating in the weight measuring device one or more signals indicative of the weight of bulk fuel so acting; and dividing the value of the said one or more signals by a measure of the volume of bulk fuel in order to generate a density measure for the bulk fuel.
18. A method according to Claim 15 including the step of processing, transmitting or displaying a signal that is indicative of the density of bulk fuel acting on the weight measuring device.
19. A weight measuring device generally as herein described, with reference to and/or as illustrated in the accompanying drawings.
20. A bulk fuel feeder generally as herein described, with reference to and/or as illustrated in the accompanying drawings.
21. A method generally as herein described, with reference to and/or as illustrated in the accompanying drawings.