GB2093787A - Transport and distribution system for pulverised fuel - Google Patents

Abstract

A transport and distribution system for pulverised fuel comprises a storage tank 30, a ring conduit 40 which connects several receivers with the storage tank and which has one turbo-separator 10 per receiver, and a receiving tank 23 for the pulverised fuel arranged in the ring conduit and incorporating a filter 23'. The storage tank 30 and the receiving tank 23 are connected with each other at the outlet ends thereof by the ring conduit 40 and at the loading ends by a turbo- separator 43, in such manner that the storage tank 30 is connected to the outlet of the turbo-separator 43 and the pulverised fuel receiving filter tank 23 is connected to the overflow of the turbo-separator. <IMAGE>

Description

SPECIFICATION Transport and distribution system for pulverised fuel This invention relates to a transport and distribution system for pulverised fuel of the kind comprising at least one storage tank, a ring conduit which connects several receivers with the storage tank and which has one turbo-separator per receiver, and a receiving tank for the pulverised fuel arranged in the ring circuit and incorporating a filter.

A transport and distribution system for pulverised fuel is known in which coal dust is supplied to several individual burners via a central ring conduit. The withdrawal points in the ring conduit are formed by turbo-separators. These make it possible for the burners to receive coal dust simultaneously, without the coal dust having to be regulated accurately over the long conveying distance. The coal dust fed to the turbo-separators in the ring conduit is separated from the delivery air in a filter with a fuel dust receiving tank, and from this it is fed back into the ring conduit upstream of the withdrawal points. A storage tank is attached to the filer, which can inject coal dust into the ring conduit through a blast injector in the filter, via a bucket wheel feeder and a blast injector. The storage tank is filled by transporters on rails or rolling conveyors.

In the known arrangement, reloading of the dust contained in the filter back into the storage tank is not provided for and is not possible.

The object of the present invention is to produce a transport and distribution system for pulverised fuel which at least permits the volume of dust in the filter to be reloaded into the storage tank.

This object is achieved in that the storage tank and the receiving tank for the fuel dust are connected with each other at the outlet ends thereof by the ring conduit and at the loading ends by a turbo-separator, in such manner that the storage tank is connected to the outlet of the turbo-separator and the pulverised fuel receiving filter is connected to the overflow of the turboseparator.

By means of this arrangement it is possible for the fuel dust transported through the turboseparators attached to the individual receivers to be fed not only into the fuel dust receiving filter tank, but also back into the storage tank. It is thereby possible to reload the contents of the fuel dust receiving filter tank into the storage tank via the turbo-separators and the ring conduit.

Likewise, it is possible to load the fuel dust receiving filter tank from the storage tank.

The storage tank can not only be independently loaded by a bucket conveyor in a known manner, but it can also be connected to a fuel dust discharging device, for example, a turbo-separator connected at the outlet end thereof to the separator of a coal crusher. During continuous operation of a coal crusher, and if the burners are lacking in sufficient fuel dust, the volume received by the turbo-separator, the fuel dust receiving filter tank and the storage tank can be replenished.

However, it is also possible for the burners to be not directly connected to the outlets of the turbo-separators in the ring conduit, but for the receivers to be fuel dust storage tanks individually connected by their loading openings to the outlets of the turbo-separators, the outlets of these fuel dust storage tanks being connected on the one hand with the ring conduit and on the other hand with one or several fuel dust burners. This arrangement is of particular advantage if one or more storage tanks are attached to individual steam generators. Since receiving tanks for coal dust must be designed so as to be pressure resistant, a central fuel dust receiving tank which is too large is disadvantageous, since it can be produced only under highly economical manufacturing conditions.

Since a pressure loss can occur in the ring conduit which cannot be ignored, it may be provided that the ring conduit has a cross-section which increases in the conveying direction. Thus, for example, the conduit can be enlarged by degrees upstream of each turbo-separator inserted into the ring conduit.

Further sub-claims relate to advantageous embodiments of the transport and distribution system for pulverised fuel.

The following is a detailed description of two embodiments of the invention, reference being made to the accompanying drawings in which: Figure 1 is a transport and distribution system for pulverised fuel, in which the burners are individually connected to turbo-separators arranged one after the other in the ring conduit.

Figure 2 is a transport and distribution system for pulverised fuel, in which individual burners or groups of burners are connected to the outlets of storage tanks, and the storage tanks are connected to the outlets of individual turboseparators in the ring conduit.

In both embodiments it is possible for the fuel dust to be reloaded between the various storage tanks.

Figure 1 shows a first embodiment of a coal dust distribution system.

Raw coal is fed from a raw coal bunker 1 via a feeder device 2 into a crusher 3 provided with a separator. The coal dust is led through a coal dust conduit 4 to a distributor 5, which delivers the coal dust through several injection conduits 6 to main burners which are not shown.

Coal dust pilot burners, which are not shown, are attached to the main burners, these pilot burners being supplied by turbo-separators 10 arranged in a ring conduit 40. A shut-off device 11 is attached to the withdrawal opening of each turbo-separator 10, and a bucket wheel feeder 1 2 is attached to the shut-off device. A blast injector 13 is connected to the outlet of each bucket wheel feeder, which blows igniting coal dust into igniting coal dust pipes 14 leading to the pilot burners. The supporting air is fed to the injectors by a blower 16 via regulating valves 1 5. A filter 1 6' and a damper 1 6" are connected in series to the blower 1 6 and an injection air preheater 17 is connected to the outlet of the blower upstream of the regulating valves.

A dust extractor 20 is provided in the coal dust pipe 4 for the preparation of ignition dust. The drawn off dust is fed to a turbo-separator 21. A bucket wheel lock is provided in a grit return pipe 22 leading from the turbo-separator 21. The grit return pipe leads back into the coal dust pipe 4.

The separated material is fed from the turboseparator 21 into an open receiving tank 23, which is fitted with an attachment filter 23' and with a height adjuster. The grit return pipe 22 is provided with a shut-off device 24 adjacent the coal dust conduit 4.

The extraction hopper of the open tank 23 is connected via a shut-off device 25 and a bucket wheel feeder 26 to a blast injector 27, which blows the igniting coal dust withdrawn from the tank 23 into the igniting coal dust ring conduit 40.

A vapour return blower 28 is connected to the filter of the tank 23, this blower being connected at the outlet end with a vapour exhaust pipe which extends from the top of the grit return pipe upstream of the shut-off device 24. A shut-off device 24' is provided in the pipe between the dust exhaust and the turbo-separator.

A storage tank 30 (also with height adjuster) is provided next to the tank 23, which is provided with an attachment filter 31 with a gas and supporting air exhaust. The storage tank also has a safety device 32.

As can be seen on the left-hand side of Figure 1, a deactivator 33 is attached to the storage tank, which allows gas to be fed to the top or bottom of the storage tank.

As is shown by a dotted line on the left-hand side of Figure 1 , the storage tank is provided with a discharge device 34, consisting of a shut-off device, a bucket wheel feeder and an injection device, which enables the conveyor 37 shown in the figure or a transporting container to be loaded.

The storage tank 30 has a loading conduit 35 for loading via the ring conduit 40 and a loading conduit 35' for loading from the conveyors. Under certain conditions the loading conduits 35 and 35' can be combined.

In order to shut off the loading conduit 35 from the igniting coal dust ring conduit 40, a shut-off device 36 is provided.

As can be seen on the right-hand side of Figure 1, the turbo-separators 10 are connected in series in the ring conduit 40. The storage tank 30 can be connected to the ring conduit 40 via a shut-off device 36', and a bucket wheel lock 41 along with the blast injector also connected with the ring conduit 40. The ring conduit 40 leads from the turbo-separators 10 to the loading opening of a turbo-separator 43, for loading the storage tank. The shut-off device 36 is connected to the withdrawal opening of the turbo-separator 43, and a bucket wheel feeder 46 is connected to the outlet end of this shut-off device. The overflow opening of the turbo-separator 43 is connected by a further section of the ring conduit, through a shut-off device 25' to the tank 23.The igniting coal dust pipe 40 is pressurised by a blower 45 via the blast injector 42 and a device 44 regulating the amount of supporting air, a filter 45' and a damper 45" being connected in series to this blower. A preheater 47 for the supporting air is connected to the blower 45 at the outlet end thereof.

The individual components of the fuel dust distribution system can be operated independently from each other: Injection Combustion with Main Burners Procedure: Bunker 1 ,feeder 2, crusher 3 with separator, coal dust distributor 5, main burner 6.

Preparation of Igniting Coal Dust with Operation of the Crusher Procedure: Raw coal bunker 1, feeder 2, crusher 3, dust exhaust 20, turbo-separator 21, open tank 23, bucket wheel feeder 26, injector 27, coal dust ring conduit 40, turbo-separator 10, coal dust ring conduit 40, turbo-separator 43, bucket wheel lock 46, storage tank 30, vapour return via a vapour fan 28 in the coal dust pipe 4.

A proportion of the igniting coal dust transported by the ring conduit is filtered in the turbo-separators. When the receiving capacity of a turbo-separator is filled, the igniting coal dust is fed through the turbo-separator in its entirety. It is possible to place the igniting coal dust which has been fed into the storage tank in a conveyor 37 via the outlet 34.

Ignition Firing Procedure: Supply of supporting air 45, preheater 47, coal dust mixture from storage tank 30 through bucket wheel feeder 41 and injector 42, or from tank 23 through bucket wheel feeder 26 and injector 27, distribution of the igniting coal dust to the pilot burners via the turbo-separators 10 and the bucket wheel feeders 1 2. The primary air for the pilot burners comes from the injection air supply 16, whereby an adjustment can be made by the regulating valves 1 5. The remaining coal dust either passes through the turbo-separator 43 into the storage tank 30 via the bucket wheel feeder 46, or passes through the shut-off device 25 back into the tank 23. After filtering, the supporting air passes through the vapour fan 28 and the regulating valve 29 into the open air or, when the crusher is already loaded with air, through the shut-off device 24 into the coal dust pipe 4.

Emptying of the Coal Dust Igniting System Procedure in a continuous boiler: The tank 23 is discharged via the bucket wheel feeder 26 into the ring conduit 40. Turboseparator 10, bucket wheel feeder 12, injector 13, pilot burner 14.

By this means, the supporting air passes from the supporting air supply 45 over the preheater 47 through the injector 27, the coal dust ring conduit 40, the turbo-separators 10 and 43 into the tank 23, and from there through the filter and the vapour fan 28 into the coal dust pipe 4.

Procedure in a fixed boiler: The tank 23 is discharged through the bucket wheel feeder 26, the injector 27, the igniting coal dust ring conduit 40, the turbo-separator 10 and the turbo-separator 43, and the bucket wheel feeder 46 into the storage tank 30. The transporting air passes along the same route as in a continuous boiler, but it is conducted through the vapour discharge 29 into the open air.

Thus in the fuel dust distribution system shown, it is possible to conduct the igniting coal dust produced by the crusher 3 through the tank 23 to the turbo-separators 10 and thereby to the ignition, and to convey the surplus igniting coal dust into a storage tank. The storage tank also offers the possibility of being able to supply the pilot burners with separate igniting coal dust, should the preparation of igniting fuel dust break down, which is fed into the storage tank 30 by a suitable means of transport.On the other hand, it is possible during operation of the boiler plant, that is with a continuous crusher 3, to draw off igniting coal dust from the storage tank via the connector 35 (of course, several crushers can be added to the system, so that if one crusher breaks down then igniting coal dust can still be produced), so as to use it in other boilers of the same power plant or in another power plant.

In the embodiment according to Figure 2 the same reference numerals are used as in Figure 1.

The embodiment according to Figure 2 differs from that in Figure 1 in that a burner is not directly connected at the outlet end to each turboseparator 10, but a further storage tank 48 with its loader 48a is connected to the outlet end of each turbo-separator, an outlet 48b of this further storage tank being connected via a shut-off device 49 and a bucket wheel feeder 50 to the ring conduit 40 via an injector 51. A further outlet 48c is connected via shut-off device 52 and a bucket wheel feeder 53 to a blast injector 54, which is supplied by a blower 55. A ring conduit for individual pilot burners (see Figure 1) or a forced feeder for individual burners can be connected to the outlet end of the injector 54.

The arrangement according to Figure 2 offers the advantage that smaller storage tanks can be used, which can be attached to the individual steam generators. This is of considerable advantage since the coal dust tanks have to be resistant to pressure, and therefore the use of large tanks is of disadvantage.

The connection of the tank 48 to the ring conduit via the turbo-separators 10 makes it possible for the contents of the storage tank 48 to be unloaded in the whole system, consisting of the tank 48, the storage tank 30 and the tank 23. The tank 23 is given the reference numeral 23" in Figure 2, since it no longer has to perform the duty of an open tank, but primarily only has to receive the igniting coal dust separated from the supporting air for a short time when the system is in operation.

Of course a supply can also be held in the tanks 48. By suitable use of the shut-off devices 11 and the bucket wheel feeders 12 on the one hand and of the shut-off devices 49 and 50 on the other hand, it is possible to load or unload the tanks 48 as required, and thereby to distribute the igniting coal dust present in the system amongst the tanks 30, 48 and if necessary 23', and to empty individual tanks completely.

Heating the supporting air in the supporting air preheater 47, or a special supporting gas, before entry into the ring conduit 40, serves the purpose of preheating it according to the residual water content of the fuel dust to be transported. With the presence of residual water in the fuel dust, the interior of the transport system becomes damp with condensation. This leads to sticking and congestion. By using preheated air or dried, preheated inert gas, this difficulty can be avoided.

As already mentioned, inert gas such as nitrogen or carbon dioxide can also be used as transport gas. This is of particular advantage if it cannot be guaranteed that the fuel dust can be completely removed when the transport and distribution system is out of operation.

Spontaneous ignition can be avoided by using an inert gas, as the oxygen content within the ignition system remains below the concentration necessary for ignition.

So as not to use too much inert gas, it is appropriate to recycle this gas from the filter of the open tank 23 or of the tank 23' back to the blower 45, as is shown by a dotted line in Figure 2 (naturally this also applies to Figure 1). Since in a cycle of operation the gas accumulates water vapour from the residual water content of the fuel dust, it is appropriate to arrange a cooling trap 56 between the fuel dust filter 23' and the blower 45, in order to remove excess water from the transport gas. After compression and appropriate preheating, the inert gas at the beginning of the transport route is then sufficiently capable of absorbing water vapour again.

In order to keep the inert gas cycle sufficiently low in oxygen, and in order not to carry atmospheric oxygen from the first storage tank 48 into the others 48 and 30, the pressure in the transport system must be kept as high as in all the connected storage tanks, even when these are not filled and are out of action. In this way, leaking feeder and shut-off devices will not endanger the system. If it should be necessary to operate one or all the connected storage tanks under a higher pressure than that of the transport system, then it is appropriate for the feeder and shut-off devices to be placed between the transport system and the individual storage tank, coupled with intermediate unloading.When the individual burners are directly connected to the outlet ends of the turbo-separators, as is shown in Figure 1, then the question of atmospheric oxygen being carried along is of little significance, since then only the volume that has settled in the individual turbo-separators has to be taken into account.

In both figures, the ring conduit 40 is shown with a uniform cross-section. It is necessary that, on entry into the ring conduit, the speed of the supporting gas or supporting air is high enough to guarantee transport of the fuel dust. However, since the pressure loss in the pipe line is not small enough to be ignored, then it is a question of compressed air or gas.

Along the length of the pipe line, particularly in the separators 10, the pressure of the supporting gas is reduced, that is, the gas expands. In order to avoid on the one hand increased transport speeds and on the other hand to reduce the total pressure loss in the transport and distribution system, it is appropriate to widen the transport pipe in the transporting direction, so in this way to optimise the power requirements of the transport system.

Preferably, the cross-section of the ring conduit is widened by degrees behind the turbo-separators 10 and if necessary 43.

Claims (10)

1. A transport and distribution system for pulverised fuel with at least one storage tank, a ring conduit which connects several receivers with the storage tank and which has one turboseparator per receiver, and a receiving tank for the pulverised fuel arranged in the ring conduit and incorporating a filter, wherein the storage tank and the receiving tank are connected with each other at the outlet ends thereof by the ring conduit and at the loading ends by a turbo-separator, in such manner that the storage tank is connected to the outlet of the turbo-separator and the pulverised fuel receiving filter tank is connected to the overflow of the turbo-separator.

2. A system according to claim 1 , wherein the storage tank can be independently loaded via a tank conveyor.

3. A system according to claim 1 or 2, wherein the receiving tank for pulverised fuel is connected to a device for producing pulverised fuel.

4. A system according to any one of claims 1 to 3, wherein the receiving tank for pulverised fuel is in the form of a storage tank, and the receivers are fuel dust burners connected to the withdrawal openings of the turbo-separators respectively.

5. A system according to any one of claims 1 to 4, wherein the receivers are fuel dust storage tanks the loading openings of which are connected to the withdrawal openings of the turbo-separators respectively, the outlet of these fuel dust storage tanks being connected on the one hand with the ring conduit and on the other hand with single fuel dust burners or groups of such burners.

6. A system according to any one of claims 1 to 5, wherein the ring conduit has a cross-section which increases in the conveying direction.

7. A system according to any one of claims 1 to 6, wherein the ring conduit is supplied with preheated supporting gas.

8. A system according to any one of claims 1 to 7, wherein the ring conduit is supplied with an inert supporting gas.

9. A system according to any one of claims 1 to 8, wherein a cooling trap is arranged between the filter of the filter tank and a blower for the supporting air in the ring conduit.

10. A transport and distribution system for pulverised fuel, substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawings.