AU2016273922A1

AU2016273922A1 - Good issue process and plant for continuous drainage of water, in particular for dewatering of brown coal

Info

Publication number: AU2016273922A1
Application number: AU2016273922A
Authority: AU
Inventors: Steffen AUMÜLLER; Michael SCHÖLER
Original assignee: Siempelkamp Maschinen und Anlagenbau GmbH and Co KG
Current assignee: Siempelkamp Maschinen und Anlagenbau GmbH and Co KG
Priority date: 2015-12-15
Filing date: 2016-12-15
Publication date: 2017-06-29
Also published as: DE102015121869A1; EP3181664A1

Abstract

Abstract: The subject is a method for the continuous dewatering 5 of material containing water, especially for the dewatering of brown coal, wherein the material to be dewatered is first of all preheated in a preheating device (9) and wherein the preheated material is dewatered in a continuously operating dewatering press 10 (1) using pressure and heat. The method is characterised in that the material to be dewatered in the continuous preheating device (9) is exposed to a throughflow of a steam-air mixture. 15 For publication with Fig.2 -, '3 t2~Z -_________ j

Description

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Method and plant for the continuous dewatering of material containing water, especially for the dewatering of brown coal

Description:

The invention relates to a method and a plant for the continuous dewatering of material containing water, especially for the dewatering of brown coal, wherein the material to be dewatered is first of all preheated in a preheating device and wherein the preheated material is dewatered in a continuously operating dewatering press using pressure and heat. 15 The material to be dewatered is especially preferably coal, especially brown coal which is treated in the course of a mechanically-thermal dewatering process (MTE) . Since as a rule raw brown coal has a high water content the firing of such moist brown coal in power 20 plants is energetically and ecologically unfavourable. Therefore, the dewatering or pre-drying of the brown coal before firing becomes especially important. The invention in this case preferably relates to a method for the dewatering of brown coal in a continuously 25 operating dewatering press which for example is designed as a double belt press, wherein the brown coal as a rule is first of all crushed and as a dispersed material mat is applied to or scattered onto a conveyor belt and this dispersed material mat is then first of 30 all guided through a preheating device and then through the dewatering press and is mechanically-thermally dewatered in the process. In the case of a double belt press it is a continuously operating press which in its basic construction consists of a lower heated press 35 plate or heating plate, an upper heated press plate or heating plate and also endlessly revolving press belts.

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(N (N σ^ m r- (N Ό O (N 10 15 20 25 -2- for example steel belts, in each case which with the interposition of rolling body elements, for example rolling bars, are supported against the press plates and form a press nip. A method and a plant of the type described in the introduction are known for example from DE 10 2014 016 867 B3. Upstream of the press, in which the dispersible material is exposed to pressure and heat application, provision can be made for a pre-treatment station. This can serve for smoothing, for trimming, for vaporizing, for preheating, for pre-compression and/or for equalizing the dispersed material mat. Consequently, slight unevenness during the dispersion is to be compensated with physically or chemically different dispersed materials.

Alternative methods for reducing the water content of brown coal or sludge are described in DE 195 35 315 A1 and DE 195 37 286 B4.

Apart from this, a method for the preparation of soft brown coal using screw presses, extruders or expanders is known from DE 10 2008 012 873 A1. DD 608 B2 describes a method for improving brown coal briquettes by the treatment of loose dry brown coal with a steam-air mixture.

Described in DE 196 06 152 A1 is a method for reducing 30 the water content of water-holding, granular brown coal with the influence of thermal energy and pressure on the material, distributed in flat bed form, in which the brown coal is exposed to a mechanically applied initial surface pressure which lies below the surface 35 pressure which occurs in the method and in which by means of steam thermal energy is fed to the brown coal

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(N (N σ^ m o (N o (N 10 -3- which by condensation heats the brown coal. After this, the surface pressure, without further feed of steam, is increased to such an extent that the water contained in the heated brown coal is pressed out. Before feeding steam, the brown coal is preheated by waste heat and the hot water which is pressed out of the brown coal during the process is used as the waste heat source. In this case, it is provided that the hot water is fed directly to the brown coal, distributed in flat bed form, with uniform application and is pressed through the brown coal. The dewatering is carried out in this case in a conventional plate press. A similar method is described in DE 196 35 086 Cl. 15 Alternatively, the preheating of brown coal by means of pure saturated steam is known in practice and used in power plant processes for drying. The known methods have certainly proved to be successful in the main but they are capable of further development with regard to 20 their efficiency and profitability. The invention is introduced at this point.

The invention is based on the object of creating a method for the continuous dewatering of material 25 containing water, especially for the dewatering of brown coal, which method is distinguished by particularly high efficiency and profitability.

For achieving this object, the invention instructs that 30 in a generic method of the type described in the introduction the material to be dewatered is exposed to a throughflow of a steam-air mixture in a continuously operating preheating device. 35 The invention in this case is based in the first instance on the basically known knowledge that the

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(N (N σ^ m o (N Ό o (N -4- material, especially brown coal, can be dewatered in a particularly efficient manner in a continuous process using a continuously operating dewatering press, wherein such a dewatering press is preferably designed 5 as a double belt press. In the course of the mechanically-thermal dewatering in the continuous double belt press the material to be dewatered, for example the brown coal, is to be heated to a defined temperature level at which the process runs in a 10 particularly efficient manner. This presumes a defined process time. The invention in this case is based on the knowledge that this process time in the continuous dewatering press can be shortened if the material to be dewatered, for example the brown coal, is preheated 15 before introduction into the dewatering press.

Therefore, the throughput capacity in the case of the same press length can be increased, or conversely the same throughput in the case of a smaller press length, can be achieved. 20

According to the invention, particularly efficient preheating is now carried out by the material being exposed to a throughflow of a steam-air mixture because in such a process the steam-air ratio can be varied and 25 consequently set and therefore the dew point of the steam-air mixture can be specifically predetermined.

The invention in this case has recourse to basically known knowledge from the field of production of wooden 30 composite boards because the preheating of composite wooden boards during the production of composite wooden boards with the aid of a steam-air mixture is known and has proved to be excellent in practice. In this case, the dispersed material is exposed to a throughflow of a 35 steam-air mixture and in the process is heated very quickly, thoroughly and uniformly. Corresponding ο (Ν Ο (υ Q m (Ν (Ν (Ν σ^ m r- (Ν Ό ο (Ν 10 35 5- methods are described for example in DE 196 35 410 Al, DE 102 42 770 A1, DE 10 2008 039 720 B4 and DE 197 01 596 C2. Such developments had no influence on the dewatering of brown coal, however.

In addition to the possibility of heating the brown coal or another material to be dewatered quickly, thoroughly and uniformly with the aid of a steam-air mixture, the possibility advantageously exists of varying the steam-air ratio and therefore of achieving in the described manner specifically defined dew points during condensation.

Distinguished by exceptional efficiency is a preferred 15 embodiment of the invention in which the press vapours (in this case a steam-air mixture) which accumulate in the dewatering press in the course of the dewatering are sucked out and fed to the preheating device as a steam-air mixture. Therefore, use can be made of 20 steam-air mixtures which, contingent upon concept, accumulate in the (open) dewatering press during the process. These press vapours are sucked out, possibly purified (for example by electrofilters and cyclones) and fed to the preheating device, which is also 25 designed as a continuous preheating device, so that a continuous process is realized overall. In this way, the thermal efficiency of the dewatering is further increased by thermal losses being avoided by utilising the steam-air mixtures which develop in the dewatering 30 press during the dewatering process.

The possibility of varying the composition of the steam-air mixture for setting the dew point is of particular importance. When utilising the press vapours, this can be carried out for example by the press vapours being mixed with (separate) steam, for Ο (Ν Ο <D Q (Τ) (Ν (Ν (Ν σ^ m r- (Ν Ό Ο (Ν -6- example live steam, for setting the dew point. In this case it can be saturated steam. However, mixing the press vapours with air, for example fresh air, for setting the dew point also optionally or additionally 5 lies within the scope of the invention.

During the continuous operation, the steam-air mixture consisting of press vapours and possibly admixed (live) steam and/or admixed air is as a rule therefore used 10 for the preheating. As an option, the possibility exists of operating with a steam-air mixture consisting of steam (for example live steam) and air during startup of the dewatering press. In this case, the invention is based on the knowledge that during the 15 start-up process significant quantities of press vapours are possibly still not available from the dewatering process. In this phase of the process, the preheating device is fed with a steam-air mixture independently of the press vapours, for example fed 2 0 with a pure live steam which in an upstream mixing chamber is set at the desired dew point by admixing of air. During the established operation, in this mixing chamber the press vapours which are sucked from the press are also added to the desired dew point, for 25 example by means of live steam feed.

An object of the invention is also a plant for the dewatering of material containing water, especially for the dewatering of brown coal, having a preheating 30 device by means of which the material to be dewatered is preheated, and having a continuously operating dewatering press, preferably with heatable press plates and endlessly revolving press belts, which form a press nip through which the material to be dewatered is 35 guided for dewatering by means of pressure and heat. This plant is preferably designed and adapted for ο (Ν Ο (υ Q m (Ν (Ν (Ν σ^ m (Ν Ό Ο (Ν -τ dewatering using the described dewatering method. The plant is characterised according to the invention by the preheating device being designed as a continuously operating preheating device in which the material which 5 passes through and is to be dewatered is exposed to a throughflow of a steam-air mixture.

The preheating device subsequently also operates continuously and it is preferably designed as a double 10 belt device similar to a double belt press. To this end, it has two conveyor belts which revolve endlessly around deflection rollers in each case and between which is formed a passage nip for the material to be preheated. These conveyor belts are designed so that 15 the steam-air mixture can penetrate through the conveyor belts. Therefore, they can be sieving belts, for example. The steam-air mixture subsequently penetrates through the mat of material to be preheated which passes through the passage nip in a direction 2 0 which in the main is perpendicular to the mat plane.

To this end, the preheating device, for example on the one side of the mat (for example above the mat), has one or more feed boxes and on the opposite side (for example beneath the mat) has one or more suction boxes. 25 As an option, both feed boxes and suction boxes can also be arranged on the one side and then corresponding suction boxes or feed boxes can be arranged on the opposite side. In any case, the steam-air mixture for preheating the mat can be sucked through the conveyor 30 belts, for example sieving belts, and through the material to be preheated (for example brown coal). In this case, the steam proportion in the mat condenses so that a particularly efficient preheating occurs. Via the mixture suction hood the air proportion of the 35 mixture is then especially sucked out. ο (Ν Ο ω Q m (Ν (Ν (Ν σ^ m (Ν Η Ο (Ν 10 15

Particularly advantageous in this case is an embodiment in which use is made of the press vapours which develop in the dewatering press. To this end, the dewatering press is equipped with at least one suction device for sucking out the press vapours, wherein the suction device is connected via a vapour line to a mixing device in which the press vapours can be mixed with steam and/or air. This mixing device, for example mixing chamber, can be connected via a mixture line to the preheating device so that the mixed steam-air mixture is fed via the mixture line to the preheating device for preheating. Since the press vapours are preferably mixed with steam, for example live steam, a steam feed line is preferably connected to the mixing device for the feed of steam, for example for the feed of live steam/saturated steam.

Furthermore, it is preferably provided that a bypass line is connected to the vapour line upstream of the 20 mixing chamber for discharging the press vapours. Unless sufficient quantities of press vapours are still not available, for example during the start-up process, and a steam-air mixture consisting of live steam and air is then used, the quantity of vapours which develop 25 in the press during start-up can be discharged, and disposed of for example, via this bypass line.

Overall, by dewatering in a continuous process the thermal efficiency of the subsequent brown coal firing 30 can be significantly improved. According to the invention, the dewatering is carried out in a particularly energy-efficient manner by means of heat recovery. The heat recovery is energetically therefore particularly efficient because the arising vapours can 35 be used directly as a steam-air mixture or for producing a steam-air mixture which flows through for

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(N (N σ^ m o (N 1—H o (N 10 15 -9- the purpose of preheating the brown coal (or another material to be heated).

The invention is explained in more detail below based on a drawing which represents only one exemplary embodiment. In the drawing

Fig. 1 shows in a simplified side view a plant according to the invention for the dewatering of brown coal.

Fig. 2 shows an enlarged detail of the plant according to Fig. 1,

Fig. 3 shows in a schematically simplified form a preheating device of the plant according to Figures 1 and 2 in a cross section through the mat M. 20 Shown in the Figures is a plant for the dewatering of material containing water, especially for the dewatering of brown coal. The key feature of such a plant is a continuously operating dewatering press 1 in which the brown coal is mechanically-thermally 25 dewatered using pressure and heat. Such a dewatering press 1 is designed in the exemplary embodiment as double belt press. It has an upper heatable press plate 2 in the press upper part and a lower heatable press plate 3 in the press lower part and also 30 endlessly revolving press belts 4, wherein these press belts 4 are guided around deflection rollers 5. The press belts 4 are supported on the press plates 2, 3 by the interposition of rolling body elements 6, for example rolling bars, so that a press nip 7 is formed 35 between the press belts. At least one of the press plates, for example the upper press plate 2, is acted ο (Ν Ο ω Q m (Ν (Ν (Ν σ^ m (Ν Ό ο (Ν 30 -10- upon by pressure elements, for example hydraulic press cylinders 8, which can be supported on the press frame of the press stand. Such continuously operating presses have been known for a long time, specifically 5 in conjunction with the production of composite wooden boards. Within the scope of the invention, they serve for the dewatering of for example brown coal, as is also described in DE 10 2014 016 867 B3. 10 Connected upstream to the dewatering press 1, with regard to the operating direction A, is a preheating device 9 by means of which the brown coal, or a mat scattered with brown coal, is preheated in order to optimise the subsequent dewatering process. The 15 preheating device 9 is designed as a continuously operating preheating device 9 in the style of a preheating press which operates with a steam-air mixture. In this case, the "ContiTherm Preheating" which is marketed by the applicant can be referred back 20 to. The preheating device has at least two endlessly revolving sieving belts 10 which are guided around deflection rollers 11, wherein a passage nip 12, through which the mat (consisting of for example brown coal) to be preheated is guided, is formed between the 25 sieving belts 10.

In this case, it is shown in Fig. 1 that for forming this mat the brown coal is first of all crushed in a crushing device 13 and then with the aid of a scattering station 14 is scattered onto the conveyor belt 15, wherein the thus formed mat is then fed to the preheating device 9.

In the preheating device 9, the brown coal or the brown 35 coal mat is exposed to a throughflow of a steam-air mixture. To this end, the preheating device 9 has on

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(N (N σ^ m o (N Ό O (N 10 -11- one side at least one feed device 16, or one feed box 16, and on the other side has a suction device 17, for example a suction box 17. Details can be seen in Figs. 2 and 3. In the exemplary embodiment, provision is made for a plurality of feed boxes 16 and suction boxes 17. The steam-air mixture D is fed via the feed box 16 and via the suction device, or the suction box 17, is sucked through the mat. In the process, the steam proportion condenses in the steam-air mixture and the air proportion L of the mixture is sucked out via the discharge hood 17. The air proportion L of the mixture or also a steam-air mixture D can also be discharged, and possibly sucked out, from the mat M at the side. 15 By corresponding mixing of steam on the one hand and air on the other hand the dew point of the steam-air mixture is set. For this, reference is made to Fig. 2.

According to the invention then, the press vapours 20 which accumulate in the dewatering press 1 are used for preheating. The dewatering press 1 is provided with (lateral) suction devices 18 via which the press vapours which develop in the dewatering press are sucked out. Via a vapour line 19, these press vapours 25 are fed to a mixing chamber 20. In this mixing chamber 20, the press vapours 19, which are formed as a steam-air mixture, are mixed with live steam which is fed via a live steam line 21. In this way, the possibility exists of varying the steam proportion in the steam-air 30 mixture and so of setting the dew point to the desired degree, specifically by the simultaneous utilisation of the press vapours which develop in the dewatering press 1. The thus mixed steam-air mixture is fed from the mixing chamber 20 via the mixing line 22 to the 35 preheating device 9. -12-

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Shown in Fig. 2 in this case is an embodiment in which the mat is exposed to a throughflow from the top downwards in a first section and from the bottom upwards is a second section. This means that a first feed box 16 is arranged above the mat and a first suction box 17 is arranged below the mat and then a second feed box 16 is arranged beneath the mat and a second suction box 17 is arranged above the mat. The gases/vapours which are sucked out of the preheating device 9 via the suction boxes 17 are fed to a cyclone 23 for water separation so that on the one hand residual condensate of the vapours which are sucked through the coal and on the other hand residual vapours are then discharged and can be re-used in the process . 20

According to the invention, the press vapours, which are mixed with steam and/or air for setting the dew point in the mixing chamber 20, are subsequently used for preheating in the preheating device 9. 25 30

If, however, sufficient quantities of press vapours are still not available in the dewatering press 1 during a start-up process a steam-air mixture consisting of pure live steam and air is used for preheating in the preheating device so that a steam-air mixture consisting of pure live steam is produced in the mixing chamber 20 by admixing of air. During this phase, the press vapours which therefore develop in the dewatering press 1 can be discharged via a bypass line 24. During established operation, the vapours, which are sucked out of the press, are admixed in the mixing chamber 20 to the desired dew point by means of live steam feed. 35 ο (Ν Ο ω Q m (Ν (Ν (Ν σ^ m (Ν Η Ο (Ν -13-

Furthermore shown in Fig. 2 in this case is that a control valve 25 and a shut-off valve 26, and also a fan 27 for the transporting of vapour, can be provided in the vapour line 19.

Further processing devices, for example a chain screen 28 and/or a crushing device 29 which for example can be arranged beneath the chain screen 28, can be connected to the press 1.

Claims

Patent Claims:

1. Method for the continuous dewatering of material containing water, especially for the dewatering of brown coal, wherein the material to be dewatered is first of all preheated in a preheating device (9) and wherein the preheated material is dewatered in a continuously operating dewatering press (1) using pressure and heat, characterised in that the material to be dewatered is exposed to a throughflow of a steam-air mixture in the continuous preheating device (9).
2. Method according to Claim 1, characterised in that the press vapours which accumulate in the dewatering press (1) in the course of the dewatering are sucked out and fed to the preheating device (9) as a steam-air mixture .
3. Method according to Claim 2, characterised in that the press vapours are mixed with steam, for example live steam, and/or air for setting the dew point of the steam-air mixture.
4. Method according to one of Claims 1 to 3, characterised in that the preheating device (9) is acted upon by a steam-air mixture consisting of live steam and air during start-up of the dewatering press (1) ·
5. Plant for the dewatering of material containing water, especially for the dewatering of brown coal, especially according to a method according to one of Claims 1 to 4, having a preheating device (9) by means of which the material to be dewatered is preheated and having a continuously operating dewatering press (1), preferably with heatable press plates (2, 3) and endlessly revolving press belts (4) which form a press nip (7) through which is guided the material to be dewatered for dewatering by means of pressure and heat, characterised in that the preheating device (9) is designed as a continuously operating preheating device (9) in which the material which is passing through and to be watered is exposed to a throughflow of a steam-air mixture.
6. Plant according to Claim 5, characterised in that the preheating device (9) is designed as a double belt device and has at least two conveyor belts (10), for example sieving belts, which revolved endlessly around deflection rollers (11) in each case, between which a passage nip (12) is formed for the material to be preheated.
7. Plant according to Claim 5 or 6, characterised in that the dewatering press (1) is equipped with at least one suction device (17) for sucking out the press vapours, wherein the suction device (17) is connected via a vapour line (19) to a mixing device (20) in which the pressure vapours can be mixed with steam and/or air .
8. Plant according to Claim 7, characterised in that the mixing device, for example mixing chamber, is connected via a mixture line (22) to the preheating device (9).
9. Plant according to Claim 7 or 8, characterised in that a steam feed line (21), for example for the feed of live steam, is connected to the mixing device (20).
10. Plant according to one of Claims 7 to 9, characterised in that a bypass line (24) for discharging the press vapours, for example during a start-up process, is connected to the vapour line (19), for example upstream of the mixing chamber (20).