EP2495518A2 - Fluidised bed drier system - Google Patents

Abstract

The fluidized bed dryer assembly has heating assembly (22) comprising several parallel heating tubes or plates, and nozzle plate (28) comprising several nozzles to produce a fluidized bed. The fluid velocity of fluid flow emerging from different nozzles of the nozzle plate is varied. An independent claim is included for method for operating fluidized bed dryer assembly.

Description

Technical area

1. (a) einen Behälter;
2. (b) eine Heizungsanordnung mit einer Vielzahl von parallelen Heizrohren oder - platten; und
3. (c) einen Düsenboden mit einer Vielzahl von Düsen zur Erzeugung einer Wirbelschicht.

The invention relates to a fluidized-bed dryer arrangement for drying coal containing

1. (a) a container;
2. (b) a heater assembly having a plurality of parallel heating tubes or plates; and
3. (C) a nozzle plate having a plurality of nozzles for generating a fluidized bed.

Coal, in particular raw lignite, contains a high proportion of water. Before burning in a power plant process, the coal is ground and dried. For drying, a fluidized bed dryer can be used. A fluidized bed dryer comprises a container into which the raw coal is introduced via a coal manhole in the upper area. In the lower part of the container, a nozzle bottom is arranged. The nozzle bottom has a plurality of upwardly directed nozzles. From the nozzles, a fluid, such as vapor (vapors) exits with pressure. The coal is blown up and forms a fluidized bed with quasi-fluid properties. In the fluidized bed a heating arrangement is provided with a plurality of parallel heating tubes. The heating pipes are traversed by heating steam and transfer heat to the fluidized bed.

State of the art

A fluidized-bed dryer arrangement is disclosed, for example, on the Internet at www.kohletrocknung.de.

DE 196 20 047 C2 (RWE Rheinbraun AG) discloses a fluid bed dryer in atmospheric operation. The fluidized-bed dryer has an elongate, substantially cylindrical container with a nozzle bottom and a heating arrangement. The longitudinal axis of the container is vertical. The heating arrangement consists of a plurality of parallel heating pipes or heating plates. The heating pipes or plates extend in the horizontal direction. The longitudinal axis of the container is perpendicular to it in a vertical direction. The heating pipes are held in vertical holders in the form of a steam distributor or condensate collector. The heating pipes extend over the entire circular cross-section of the container. In the middle area, the heating pipes are correspondingly longer than in the edge area.

In known arrangements, there is a risk of floe formation. This effect occurs when very wet coal, for example, raw coal with 50-60% water content glued from the coal manhole and gets as a lump on the surface of the fluidized bed. The wet coal has a high surface moisture. The lumps of coal that form, settle on the upper heating pipes and form "floes". These are unfavorable for the fluidized bed.

Disclosure of the invention

It is an object of the invention to provide a fluidized bed dryer of the type mentioned without additional distribution device, in which the fluidized bed is protected in a simple manner against floe formation.

According to the invention the object is achieved in that the emerging from different nozzles of the nozzle bottom fluid flow is different. In places where the danger the floes formation, a higher fluid flow can be used. At a higher fluidization of the fluidized bed, the incoming raw coal is mixed very well. A stable and homogeneous fluidized bed can be operated with high heat transfer rates. A higher fluidization means that the loosening point of the fluidized bed is significantly exceeded according to the particle size. As the fluidizing volume flow through the exiting coal vapor increases, there must be a superficial velocity at the top of the fluidized bed, which provides sufficient turbulence to intermix the wet raw coal. This process is supported by a higher coverage of the heating tubes by the fluidized bed. By appropriate selection of the nozzles, the fluidized bed is influenced accordingly so that the clods do not even form. A separate distribution device is no longer required.

Using higher flow rates for fluidization requires more steam. The adaptation of the fluid flow therefore has the advantage that only at the points a stronger fluid flow or higher flow velocities are used, where this is really necessary. That's especially economical.

By separating the nozzle base and a separate supply of the fluidization medium, the individual zones in the fluidized bed (mixing zone and drying zone) can be fluidized differently. The different amounts of fluidization are adjusted via valves in the supply lines.

In particular, the fluid flow of several nozzles of the nozzle plate may be the same zone-wise and different in different zones. In a particularly preferred embodiment of the invention, the zones comprise at least one mixing zone in the edge region of the dryer arrangement and a drying zone in the central region of the dryer arrangement. In a particularly preferred embodiment of the invention, a mixing zone is provided under each coal manhole.

Then, high flow velocities are generated in the zones where the wet coal meets the fluidized bed. This is then pre-dried before it enters the dryer zone.

In a further embodiment of the invention, the fluid flow exiting from different nozzles of the nozzle base has a different fluid velocity.

Preferably, separating plates are arranged between the zones. Then the zones are physically separated. The coal can only enter the dryer zone if it is already pre-dried. In this way, floe formation is avoided even in the dryer zone. The dividing plates can also be used to mechanically hold heating pipes.

It can be provided with a Brüdenfilter Brüdenabzug and a return for coal particles from the vapor filter in the container, the return opens in the region of the mixing zone.

The arrangement is particularly suitable when the heating tubes are elongated and form a Heizflächenpaket which is substantially wider than at least in one direction.

In a method according to the invention for operating such a fluidized-bed dryer arrangement, it is provided that a fluid for producing a fluidized bed emerges from the nozzles of a nozzle base, wherein the fluid emerges in a mixing zone at a higher speed than in a dryer zone.

The velocity of the fluid flow in the mixing zone is preferably adjustable and is between 0.05 and 0.2 m / s, preferably 0.09 to 0.11 m / s higher than in the dryer zone. Thus, a higher fluidized bed is produced with higher turbulence and realized a flow of the particle mixture of wet and dry coal in the dryer zone. The drying zone is centrally located in the dryer and is fluidized near the loosening point. This is a safe overrun of Losening point sought to avoid the collapse of the fluidized bed or parts thereof.

Embodiments of the invention are the subject of the dependent claims. An embodiment is explained below with reference to the accompanying drawings.

Brief description of the drawings

Fig.1

is a front view of a fluidized bed dryer.

Fig.2

is a side view of the fluidized bed dryer from the left in FIG. 1 ,

Figure 3

is a rear view of the fluidized bed dryer FIG. 1 ,

Figure 4

is a longitudinal section along the section plane CC in FIG. 2 ,

Figure 5

is a cross section along the section BB in FIG. 1 ,

Figure 6

is a cross section along the cutting plane AA in FIG. 1 ,

Description of the embodiment

The figures show a fluidized bed dryer arrangement. The arrangement is used to dry raw lignite. The fluidized bed dryer assembly comprises a container with a container shell 1 in a saddle bearing 18. The container is formed substantially cylindrical. At the end faces of the container is curved outward. The container is heated with a container heater 16, which has a condensate collector 17. The container is under a pressure of 4 bar. The container heater 16 is fed from a distributor 15 with heating steam.

In the upper part of the container two coal manholes 2 are provided. Through the coal manholes 2, the wet raw coal is introduced into the container. For this purpose, suitable locks, such as a rotary valve, are provided which allow the introduction of coal in the standing under a pressure of 4 bar container.

In the area between the coal manholes 2, two vapor withdrawals 3 are arranged with a static separator 31. About the vapor exhausts 3 loaded with coal dust steam is discharged from the container interior. During the start-up process of the pressure-charged fluidized-bed drying, dry lignite is fed via the feed 4 into the dryer. Dry lignite, which has been filtered from the vapors by means of a vapor filter, is returned via a return 5 in the container interior.

In the area of the vapor withdrawal 3, part of the pulverized coal is separated by a static separator 31, which then remains in the fluidized-bed dryer. Thus, the proportion of coal dust in the withdrawn vapor is reduced.

For maintenance of the arrangement outside the operation at atmospheric pressure, a boarding door 6 is provided in the central region of the container shell. Laterally next to the access door 6, a sootblower 7 is provided for Heizflächenreinigung during the Abfahrprozesses and the destruction of coal floes. The sootblower is a cleaning device which, during draining of the dryer, i. during the shutdown prevents dry carbon deposits on the Heizflächenrohren. The sootblower 7 is operated with steam as a cleaning medium. At the same time, floe formation (coal lumps) occurring during operation due to targeted steam pulses can be destroyed on the fluidized bed surface.

Furthermore, a rinsing device 30 is provided. The rinsing device 30 is a rinsing nozzle, with which carbon deposits are eliminated on the dryer floor during emptying of the dryer.

Just above the container bottom, a nozzle bottom 28 is arranged. From the nozzles of the nozzle plate 28 exits pressurized steam. With this steam, a fluidized bed of coal is produced. Part of the fluidization steam can be introduced via side nozzles 32 in the upper region of the fluidized bed in order to support the turbulence and thus the interference of the moist raw carbon.

The nozzles of the nozzle bottom are charged with different amounts of steam. In the edge regions of the nozzle bottom, a larger amount of steam exits the nozzles than in the middle region. This defines mixing zones in the edge area and a dryer zone in the middle area. Basically too high steam quantities are uneconomical. It is therefore desirable to produce the fluidized bed with as little steam as possible. However, the raw coal has a high water content in the range of, for example, 50-60%. The surface moisture therefore leads to bonding. If the raw coal from the coal manholes 2 comes down, there is a risk of floe formation. A higher amount of steam from the nozzles of the nozzle bottom 28 below the coal manholes 2 increases the particle velocity and avoids the risk of floe formation. In the dryer zone in the middle area of the nozzle bottom, this high amount of steam is not required. There you can work with usual amounts of steam. In this way, it continues to work with a minimum of steam.

In the lower, central region of the container above the nozzle bottom, a condensation heating surface 22 is arranged. The Kondensationsheizfläche 22 consists of a plurality of parallel heating tubes of equal length. It extends over the entire length of the substantially cylindrical part of the container. The heating pipes are held by a support 26. The longitudinal axis of the heating pipes runs from right to left in FIG. 4 parallel to the longitudinal axis of the container. In cross section in FIG. 6 It can be seen that the heating pipes almost extend to the container wall zoom. As a result, the dead volume is kept low.

The heating tubes of the condensation heating surface 22 are welded to a perforated plate 27. The perforated plate 27 is part of a partition wall between the fluidized bed and a laterally arranged antechamber. Together with the perforated plate 27 forms a hemispherical shell an inlet chamber 21. On the output side, the corresponding perforated plate with a hemispherical shell forms an outlet chamber 23. The inlet chamber 21 is connected via connecting tubes 20 with a heating steam inlet 9. The inlet chamber 21 has a condensate drain 25. The outlet chamber 23 has a condensate drain 24. Heating steam enters via the Heizdampfeintritt 9 and the connecting pipes 20 in the inlet chamber 21 a. This forms a distributor. The heating steam passes through the holes in the perforated plate 27 in the welded thereto heating tubes the Kondensationsheizfläche 22. On the output side, the Heizdampfkondensat passes through the holes of the perforated plate 27 in the outlet chamber 23. This forms a collector. Due to the condensate drain 24 occurs water, which is condensed in the fluidized bed in the heating tubes, again from.

The coal entering through the coal manhole 2 enters the fluidized bed. At the Kondensationsheizfläche the fluidized bed is heated and dried. The dry lignite is transported via a connection shaft 29 in the bottom of the container to a screw conveyor. There it is available for further use.

Since there is sufficient space at the side of the heating pipes, the inlet and outlet chambers 21 and 23 can be hemispherical in shape. The monitoring of the arrangement is done with measuring instruments. These include thermocouples, which are arranged at temperature measuring points 11 and pressure gauge for measuring the pressure at pressure measuring points 12. A visual monitoring of the drying process via a sight glass 13 with flushing.

The condensation heating surface 22 has a continuous, vertical lane 14 in the longitudinal direction of the container 1. There are no heating pipes in it. The vertical lane is directly below the coal manholes 2 in the center of the vessel. With the lane 14 improved mixing of the raw coal is achieved in the dry coal. The raw coal is better distributed and can not remain above the coal bed of the fluidized bed. The coal top edge is not too close above the condensation heating surface to avoid floe formation. A gap in the dry area leads to a good introduction of the raw coal.

Claims (10)

Fluidized bed dryer arrangement for drying coal, containing (a) a container (1); (b) a heater assembly (22) having a plurality of parallel heating tubes or plates; and (c) a nozzle plate (28) having a plurality of nozzles for producing a fluidized bed;
characterized in that (d) the fluid flow exiting from different nozzles of the nozzle bottom (28) is different. Fluidized-bed dryer arrangement according to claim 1, characterized in that the fluid flow of several nozzles of the nozzle plate (28) is the same zone-wise and different in different zones. Fluidized-bed dryer arrangement according to claim 2, characterized in that the zones comprise at least one mixing zone in the edge region of the dryer arrangement and a drying zone in the central region of the dryer arrangement. Fluidized-bed dryer arrangement according to claim 3, characterized in that under each coal manhole (2) a mixing zone is provided. Fluidized-bed dryer arrangement according to one of the preceding claims, characterized in that the fluid flow exiting from different nozzles of the nozzle base (28) has a different fluid velocity. Fluidized-bed dryer arrangement according to one of the preceding claims 2 to 5, characterized by separating plates between the zones. Fluidized-bed dryer arrangement according to one of the preceding claims 3 to 6, characterized in that a vapor withdrawal is provided with a vapor filter and a return for coal particles from the vapor filter in the container, wherein the return opens in the region of the mixing zone. Fluidized-bed dryer arrangement according to one of the preceding claims, characterized in that the heating tubes are elongated and form a Heizflächenpaket which is substantially wider than at least in one direction. Method for operating a fluidized-bed dryer arrangement according to one of the preceding claims, characterized in that a fluid for generating a fluidized bed emerges from the nozzles of a nozzle plate, wherein the fluid emerges in a mixing zone at a higher speed than in a drying zone. A method according to claim 9, characterized in that the speed of the fluid flow in the mixing zone is adjustable and between 0.05 and 0.2 m / s, preferably 0.09 to 0.11 m / s higher than in the dryer zone.

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