EP3301360B1 - Method and device for preparation of ash from refuse incineration plants - Google Patents

Description

The invention relates to a method and a plant for the treatment of ash from waste incineration plants. The ash is in particular domestic waste incineration ash (HMVA).

In the treatment of ash from waste incineration plants, the aim is to separate the ash so that several differently contaminated with pollutants fractions (fractions) of the ash. While highly polluted components must be disposed of in a costly manner, less heavily polluted and possibly unencumbered components can be profitably recycled. Of particular importance in the treatment of ash is the extraction of ferrous and non-ferrous metals from the ashes, which are particularly profitable.

The treatment of household garbage ash is carried out in a wet classification process. For this purpose, the ash is mixed with liquid.

Classification is understood as meaning a separation of a starting material consisting of particles with a given particle size distribution into a plurality of fractions of different particle size distribution. The classification serves, for example, to separate the ashes into different proportions of pollutants.

From the DE 10 2011 013 030 A1 A method of treating ash by wet classification is known in which the ash is first mixed with liquid in a slurry tank and, after screening a coarse fraction, is fed as a feed stream to a classifier having an upstream classifier and an upstream hydrocyclone. The feed stream comprises a particle size distribution between 0 and 4 mm. In the hydrocyclone Feinstteilchen be deposited. At the top of the fluidized bed produced in the upflow classifier, a residual fraction having a particle size between 0 mm and 0.25 mm is withdrawn as suspension. At the bottom of the fluidized bed a Gutfraktion with a grain spectrum between 0.25 mm and 4 mm is deducted. The good fraction can be landfilled without environmental requirements or possibly also be used economically. The residual fraction contains pollutants such as heavy metals. It must be disposed of in compliance with legal regulations.

From the DE 10 2014 100 725 B3 A process for the treatment of ash from waste incineration plants is known in which the classifying stage also has an upstream classifier and an upstream hydrocyclone plant. The good fraction is taken off at the bottom of the fluidized bed and dewatered by means of a sieve. The screen passage of the screening device is returned to the hydrocyclone plant.

The focus of the economic analysis of treatment plants so far has been the extraction of metals mentioned above and the separation of highly polluted fractions, which must be disposed of expensively, of less contaminated fractions, which can be recycled.

The invention has for its object to make the treatment of ash from waste incineration plants such that the treatment plants can be operated with an even higher economic efficiency.

• dass die Asche zur Verfügung gestellt wird,
• dass die Asche in einer ersten Klassierstufe in eine erste Grobfraktion und eine Feinfraktion unter Hinzugabe von Wasser klassiert wird, das in einem ersten Wasserkreislauf geführt wird,
• dass die erste Grobfraktion in einer zweiten Klassierstufe einer Kontrollklassierung unterworfen und dabei eine Restfraktion abgetrennt wird, und
• dass die Kontrollklassierung unter Hinzugabe von Wasser erfolgt, das in einem zweiten Wasserkreislauf geführt wird, der unabhängig von dem ersten Wasserkreislauf ist.

To solve this problem, the method mentioned above is characterized according to the invention by

• that the ashes are made available
• the ashes are classified in a first classification stage into a first coarse fraction and a fine fraction with the addition of water, which is conducted in a first water cycle,
• that the first coarse fraction is subjected to a control classification in a second classification stage and thereby a residual fraction is separated, and
• that the control classification is carried out with the addition of water, which is guided in a second water cycle, which is independent of the first water cycle.

In the first classification stage, the ash is classified into a first coarse fraction and a fine fraction. The classification is done for example by a sizing. Water is needed for the classification. In particular, the water provides the driving force required to drive the ashes through the first classifier stage.

The fine fraction is preferably fed to a further treatment.

The first coarse fraction is fed to a second classification stage and subjected there to a control classification. This classification is carried out with the addition of water, in which case the water provides the required driving force. In the control classification, a residual fraction is separated. The task of the control classification is to ensure that the first coarse fraction coming from the first classification stage actually has the desired particle size distribution. In practice, it often occurs that the first coarse fraction after the first classification stage still contains a (small) proportion of a smaller fraction. This proportion with the smaller fraction is undesirable. He can make sure that the first coarse fraction becomes less usable or even unusable.

According to the invention, the water of the first classification stage is conducted in a first water cycle and the water of the control classification in a second water cycle.

The invention is based on the following consideration. The operation of the first classification stage in a first water cycle is known. When the first coarse fraction is subjected to a control classification in a second classification step and the control classification is carried out with the water of the first water cycle, the first water cycle accumulates with salts. This salt accumulation is undesirable. With increasing operation of the treatment plant, the water, which is guided in the substantially closed first water cycle, reaches a critical limit of pollutants (salts). When the limit is reached, all the water must be changed and disposed of. This is a typical plant by an order of 200 cubic meters. In addition, the first coarse fraction is also enriched with pollutants, especially with salts. This leads to a limitation of the usability of the first coarse fraction up to a non-usability.

The invention is based on the finding that the first coarse fraction after the first classification stage through the water Chlorides and sulfates is largely purified. The already cleaned first coarse fraction should not - as in the prior art - be contaminated by renewed contact with polluted water. According to the invention a second water cycle is provided in a departure from known technologies for this purpose, which is independent of the first water cycle. As a result, the second water cycle, due to the already cleaned first coarse fraction, has to be replaced much later than the first water cycle. Preferably, the second water cycle is changed at most half as often as the first water cycle. Initial tests have shown that the second water cycle can be operated much longer without water exchange.

In addition to the above-described advantage of water that does not accumulate or hardly accumulates with pollutants in the second water cycle, a further advantage is that the quality of the remaining (thus reduced by the residual fraction) first coarse fraction is excellent. This applies to the particle size distribution and even more so for the low or nonexistent pollutant load of the remaining first coarse fraction. It is possible to easily recycle the remaining first coarse fraction. For this purpose, it is forfeited and later used, for example, for the construction of dams or in road construction.

The savings by the inventive method are significant and justified by the fact that less water must be replaced in larger cycles. Preferably in the second water cycle between 25% and 50% of the total amount of water of the first and the second water cycle included. This implies, conversely, that in the first water cycle between 75% and 50% of the total amount of water of the first and the second water cycle are included. Since the water of the first water cycle accumulates more quickly with pollutants, only 75% to 50% of the total amount of water must be disposed of when the limit value is reached. This results in a considerable saving. The water of the second water cycle can run longer and must be replaced less frequently. Preferably, the water of the second water cycle remains at least three times, preferably at least four times, as long in the circulation as the water of the first water cycle, before it is exchanged.

Economic factors also include the recovery of valuable materials contained in the ash. It has proved to be particularly advantageous if metal is deposited between the first classification stage and the second classification stage. The deposition can be done by an overband magnet. It is particularly advantageous at this point insofar as the first coarse fraction has been purified in the first classification stage.

Preferably, the water of the second classification stage is collected after the control classification and at least partially returned to the control classification. The collecting may take place in a collecting device such as a tub. In the tub, the residual fraction, the is pumped by a pump. In this case, the residual fraction preferably has a residual moisture content of about 6% to 8%. The remaining water is driven in the second cycle.

In an essential embodiment of the invention, it is proposed that after the second classification stage by means of a curved screen lightweight materials are removed before the water is returned to the Kontrollklassierung. The lightweight materials may be unburned organic substances, such as wood or small polystyrene particles. Such substances are lighter than water and can lead to undesirable foaming. By discharging the light materials after the second classification stage foaming is prevented, so that a guiding of the water in the second water cycle is easily possible.

Advantageously, after the bow screen, the water is collected before being pumped back to the second classification stage. In this case, a storage container can be used.

In the second classification stage, the residual fraction is separated from the first coarse fraction. This is a false grain portion. The remaining first coarse fraction can be fed directly into the appropriate grain size (without false grain) of the recovery.

A preferred embodiment of the invention is characterized in that in the second classification stage from the first coarse fraction at least a second Coarse fraction is deposited, which comprises only a lower particle size range of the first coarse fraction. It is thus separated from the first coarse fraction, a second coarse fraction having a smaller maximum grain size than the remaining first coarse fraction. For example, the coarse fraction comprises a particle size range between 4 mm and 60 mm. Then, the second classifying step can be set so that the grain size spectrum of the remaining first coarse fraction is, for example, 16 mm to 60 mm and that of the second coarse fraction is 4 mm to 16 mm. The separation of a second coarse fraction, which is smaller than the remaining coarse fraction, has the advantage of a more versatile recovery. This allows the different fractions to have different applications.

In the second classification stage, the residual fraction is separated off, which can also be referred to as a false fraction. Preferably, the residual fraction is collected in a collecting device and then fed to a first hydrocyclone, wherein the overflow of the first hydrocyclone is passed back into the collecting device. At the lower reaches of the first hydrocyclone, the residual fraction is discharged and taken out of the water cycle. The largely freed from the residual fraction overflow is passed back to the collection device. In this way, the second water cycle is advantageously freed from the residual fraction.

From an economic point of view, it is advantageous if the second classification stage has an iron deposition stage and / or a non-ferrous precipitation stage is / is downstream. As a result, economically valuable iron and non-ferrous metals can be obtained. At the same time, the first and possibly the second coarse fraction is freed from the iron and non-ferrous metals, whereby they each gain in purity.

In the first classification stage, a fine fraction is classified within the scope of the invention in addition to the first coarse fraction. The fine fraction preferably has a smaller average grain size than the first coarse fraction. In particular, the fine fraction may be such that its maximum grain diameter is smaller than the minimum grain diameter of the first coarse fraction. In this connection, it should be noted that, in the case of a classification, the separation section between a fine fraction and a coarse fraction is not always sharp due to the technology, so that partial intersections of the grain size spectra may also occur. Advantageously, the fine fraction is fed to a second hydrocyclone, wherein in the second hydrocyclone, a first Feinstfraktion is deposited as a sludge-water mixture and wherein the first Feinstfraktion is thed after thickening of the sludge-water mixture. The first ultrafine fraction advantageously has a spectrum with a smaller grain size than the fine fraction. Due to the second hydrocyclone, the first pollutant-contaminated first micro-fraction is withdrawn from the first water cycle, particularly advantageously immediately after the first classifying stage.

The thickening is preferably carried out in a thickener in which the sludge settles, and the water is supplied as clear water to the first classification stage. As a result, the first water cycle is advantageously closed. If necessary, additional water can be added to the clear water. In this context, it should be noted that in the context of the invention (and in the field of wet processing), such water cycles are considered to be closed, in which water must be added regularly. The make-up water compensates for the water loss that occurs, for example, in the removal of solids. For example, the sludge still has a residual moisture of about 30% after thickening of the sludge-water mixture. Also evaporation water must be supplemented.

Preferably, a Aufstromsortierer is downstream of the second hydrocyclone, in which a second Feinstfraktion is deposited. The second ultrafine fraction is also taken out of the first water cycle and disposed of. The ultrafine fraction preferably contains a solids content fraction between 0 mm and 0.25 mm. This fraction is contaminated with pollutants and must be disposed of. Preferably, the clear water is introduced as upstream water in the upstream sorter. The clear water fulfills two functions particularly advantageous, namely, on the one hand, the brewing of the ash in the first classification stage and, on the other, the provision of the upflow water in the upstream sorter.

As procedurally advantageous, it is considered when the first and the second ultrafine fraction are brought together before Verhaldung. They can then be thickened together and dewatered before being disposed of. Before disposal, they are preferably dumped.

An advantageous embodiment of the method according to the invention is characterized in that the fine fraction reduced by the first very fine fraction and possibly the second very fine fraction is dehydrated in at least one dehydration stage and purified in a purification stage. Then it can be spent on the landfill.

Preferably, the cleaning stage is followed by at least one metal separator. This achieves a high efficiency due to the purity of the metals and non-metals, which is also advantageous from an economic point of view.

Previously, the first hydrocyclone of the second water cycle was addressed. The overflow is preferably fed back into the collector. It is considered particularly advantageous if the underflow of the first hydrocyclone is fed to the dewatering stage.

• einer ersten Klassierstufe zur Herstellung einer ersten Grobfraktion und einer Feinfraktion,
• einer ersten Brausevorrichtung zur Bebrausung der Asche in der ersten Klassierstufe mit Wasser, das in einem ersten Wasserkreislauf geführt ist,
• einer zweiten Klassierstufe mit einer zweiten Brausevorrichtung zur Bebrausung der Grobfraktion mit Wasser, das in einem zweiten Wasserkreislauf geführt ist, wobei der erste und der zweite Wasserkreislauf unabhängig voneinander sind.

The object mentioned above is further solved by a plant for the treatment of ash from waste incineration plants, with

• a first classification stage for producing a first coarse fraction and a fine fraction,
• a first shower device for brewing the ash in the first classification stage with water, which is guided in a first water cycle,
• a second classification stage with a second shower device for brewing the coarse fraction with water, which is guided in a second water cycle, wherein the first and the second water cycle are independent of each other.

By brewing the ash with water, the ashes are driven through the respective classification stage. The advantages of the first and second water cycles have been discussed in the context of the method of the invention.

Preferably, the plant is designed so that in the second water cycle between 25% and 50% of the total amount of water of the first and second water circulation are included.

An advantageous embodiment is characterized in that a metal separator is arranged between the first classifying stage and the second classifying stage. This may be a Überbandmagnetabscheider.

It is considered particularly advantageous if the second classification stage is followed by a curved screen.

Further advantageous developments of the system according to the invention will become apparent from the dependent claims.

In the following the invention will be explained in more detail with reference to a preferred embodiment in conjunction with the attached drawings . The drawing shows a process scheme of a plant according to the invention for the treatment of ash.

The ash from a waste incineration plant is fed via a conveyor belt 1 into a mashing tank 2 in which the ash is mixed with water to form a water-ash mixture. The grain size of the abandoned ash is about 0 mm to 60 mm. The ash is fed as ash-water mixture of a first classification stage 3. Via a first effervescing device 4, the ash is driven through the classifying stage 3. This results in a first coarse fraction 5 and a fine fraction 6, as indicated in the drawing of the respective strand.

The first coarse fraction 5 is fed to a second classification stage 7. Between the first classifying stage 3 and the second classifying stage 7, a metal separator 8 is arranged. The metal separator 8 is designed as an overband magnet and arranged above a conveyor belt 9 which conveys the first coarse fraction from the first classifying stage 3 to the second classifying stage 7.

The second classification stage 7 has a second shower device 10. The from the shower device 10th originating water drives the first coarse fraction 5 through the classification stage 7.

For reasons of technology, it can not be ruled out that the first coarse fraction 5 does not contain a defective grain fraction with a smaller grain size when it comes from the first classification stage 3. For this reason, the second classifying stage 7 is provided. Here, a control classification takes place, which is to ensure that the second classification stage 7 leaving - cleaned - first coarse fraction actually has the desired particle size distribution and not additionally an undersize fraction. In the second classification stage 7, a residual fraction 11 is separated from the first coarse fraction 5 in the control classification (see the strand marked 11 in the drawing).

In the control classification, the first coarse fraction 5 is supplied with water, which also serves as a driving force. According to the invention, the water is conducted in a second circuit, which is independent of the first cycle in which the water of the first classification stage 3 is guided.

The second cycle is as follows: The water is added via the second shower device 10 to the first coarse fraction. Coming from the second classification stage 7, the water is collected in a collecting device 12 and from there via an optional curved screen 13, in which lightweight materials are removed, into a storage container 14, from which the water is pumped again via a pump 15 to the second shower device 10 becomes.

The residual fraction 11 collects in the collecting device in the lower section of the collecting device and is conducted via a pump 16 to a first hydrocyclone 17. The overflow 18 is advantageously performed back to the collector 12. So this cycle is closed.

The second classification stage 7 may be designed such that only the first coarse fraction 5 is freed from the residual fraction 11. Alternatively, the second classifying stage 7 is formed in two stages, as shown in the drawing. For this purpose, at least one second coarse fraction 19 is deposited in the second classification stage 7 from the first coarse fraction 5, which has only a lower particle size range of the first coarse fraction. Reference numeral 20 denotes the remaining first coarse fraction reduced by the second coarse fraction 19. For example, the first coarse fraction 5 has a particle size range of 4 mm to 60 mm (taking into account that the first coarse fraction also has a defective grain fraction), and the second coarse fraction has a particle size fraction between 4 mm and 16 mm. Then, the remaining grain size fraction 20 of the first coarse fraction is 16 mm to 60 mm.

Preferably, at least one metal deposition stage 21 (ferrous metals and / or non-ferrous metals) is connected downstream of the second classification stage 7. This is advantageous insofar as both the second coarse fraction 19 and the remaining first coarse fraction 20 have a high Have purity, which is advantageous for the efficiency of metal deposition.

In addition to the coarse fraction 5, a fine fraction 6 having a smaller particle size spectrum is deposited in the first classification stage 3, as indicated at the outset. The fine fraction 6 is passed by means of a pump 22 to a second hydrocyclone 23. The underflow 24 of the second hydrocyclone enters a Aufstromsortierer 25th

In the second hydrocyclone 23, a first ultrafine fraction 26 is deposited as a sludge-water mixture, which has a particle size fraction in the lowest range of the fine fraction 6. In particular, the grain size between 0 mm and a maximum of 0.1 mm, preferably between 0 mm and a maximum of 0.07 mm amount. The first ultrafine fraction 26 adheres to a large part of pollutants. It is subsequently dewatered in a dewatering stage 27 and thickened in a thickener 28 before it is dumped.

In the upstream sorter 25, a second ultrafine fraction 29 is withdrawn as an overflow and also dewatered and thickened. Preferably, the first ultrafine fraction 26 and the second ultrafine fraction 29 are combined before they are thickened and dehydrated. This can be done in a collecting device 30.

The thickening of the first ultrafine fraction 26 and advantageously also of the second ultrafine fraction takes place, as stated, preferably in a thickener 28. This may be a lap thickener. such Round thickeners can have diameters of 2 m to 3 m and beyond. In the round thickener, the finest fractions settle. This results in clear water 31, which is preferably fed as Aufstromwasser 32 the Aufstromsortierer 25 and / or shower water 33 of the shower device 4.

Via a line 34 supplementary water can be supplied to the first circuit. Via a line 35 supplementary water can be supplied to the second circuit.

The reference numeral 36 denotes a dehydration stage. In the dewatering stage of the lower reaches 37 of the Aufstromsortierers 25 is passed. The first hydrocyclone 17 has an underflow 38, which is advantageously also fed to the dehydration stage. The dehydration stage 36 may be followed by a post-purification stage 39, in which dehydration is also carried out. After the post-purification stage 39, at least one metal separator 40, in particular at least one iron metal separator and / or one iron metal separator, is advantageously arranged. <B> LIST OF REFERENCES </ b> 1 conveyor belt 21 metal separators 2 mash tank 22 pump 3 first classification level 23 second hydrocyclone 4 shower device 24 underflow 5 first coarse fraction 25 upstream sorter 6 fine fraction 26 overflow (first fine fraction) 7 second classification stage 27 Drainage stage 8 metal separators 28 thickener 9 conveyor belt 29 overflow (second fine fraction) 10 shower device 30 collection device 11 residual fraction 31 clear water 12 collection device 32 upstream water 13 curved screen 33 shower water 14 storage containers 34 pipe (supplementary water) 15 pump 35 line (supplementary water) 16 pump 36 Drainage stage 17 first hydrocyclone 37 underflow 18 overflow 38 underflow 19 second coarse fraction 39 post-purification stage 20 for the second 40 metal separators Coarse fraction reduced first coarse fraction

Claims (21)

1. Method for treating ash from waste incineration plants, wherein

   - the ash is provided,

   - the ash is, in a first classification stage (3), classified into a first coarse fraction (5) and a fine fraction (6) with addition of water which is conducted in a first water circuit,

   - the first coarse fraction (5) is, in a second classification stage (7), subjected to control classification, and in the process a residual fraction (11) is separated off, and wherein

   - the control classification is realized with addition of water which is conducted in a second water circuit, which is independent of the first water circuit.
2. Method according to Claim 1, characterized in that between 25% and 50% of the total quantity of water of the first and second water circuits is contained in the second water circuit.
3. Method according to Claim 1 or 2, characterized in that metal is separated off between the first classification stage (3) and the second classification stage (7).
4. Method according to one of Claims 1 to 3, characterized in that, after the control classification, the water of the second classification stage (7) is collected and at least partially fed again to the control classification.
5. Method according to one of Claims 1 to 4, characterized in that, after the second classification stage (7), light materials are removed by means of a curved screen (13) before the water is returned to the control classification, wherein preferably, after the curved screen (13), the water is collected before being pumped back to the second classification stage (7).
6. Method according to one of Claims 1 to 5, characterized in that, in the second classification stage (7), at least one second coarse fraction (19) is separated off from the first coarse fraction (5), which comprises only a lower grain-size range of the first coarse fraction (5).
7. Method according to one of Claims 1 to 6, characterized in that the residual fraction (11) is collected in a collecting device (12) and fed to a first hydrocyclone (17), and in that the overflow of the first hydrocyclone (17) is conducted back into the collecting device (12).
8. Method according to one of Claims 1 to 7, characterized in that at least one metal separation stage (21), in particular an iron separation stage and/or a non-iron separation stage, are/is arranged downstream of the second classification stage (7).
9. Method according to one of Claims 1 to 8, characterized in that the fine fraction (6) is fed to a second hydrocyclone (23), in that, in the second hydrocyclone (23), a first ultrafine fraction (26) is separated off as a sludge-water mixture, and in that the first ultrafine fraction (26) is heaped after thickening of the sludge-water mixture, wherein preferably the thickening is realized in a thickener (28) in which the sludge settles, and furthermore preferably the water is fed to the first classification stage (3) as clarified water (31).
10. Method according to Claim 9, characterized in that arranged downstream of the second hydrocyclone (23) is an upflow sorter (25), in which a second ultrafine fraction (29) is separated off and in which, preferably, the clarified water (31) is introduced as upflow water (32), wherein preferably the first ultrafine fraction (26) and the second ultrafine fraction (29) are brought together before the heaping.
11. Method according to Claim 9 or 10, characterized in that the fine fraction (6) reduced by the first ultrafine fraction (26) and, if appropriate, the second ultrafine fraction (29) is dewatered in at least one dewatering stage (36) and cleaned in a cleaning stage (39), wherein preferably at least one metal separator (49) is arranged downstream of the cleaning stage.
12. Method according to Claim 7 and Claim 11, characterized in that the underflow (38) of the first hydrocyclone (17) is fed to the dewatering stage (36).
13. Plant for treating ash from waste incineration plants, having

    - a first classification stage (3) for producing a first coarse fraction (5) and a fine fraction (6),

    - a first showering apparatus (4) for showering the ash in the first classification stage with water which is conducted in a first water circuit,

    - a second classification stage (7) having a second showering apparatus (10) for showering the first coarse fraction (5) with water which is conducted in a second water circuit,

    - wherein the first and second water circuits are independent of one another.
14. Plant according to Claim 13, characterized in that the plant is configured such that between 25% and 50% of the total quantity of water of the first and second water circuits is contained in the second water circuit.
15. Plant according to Claim 13 or 14, characterized in that a metal separator (8) is arranged between the first classification stage (3) and the second classification stage (7).
16. Plant according to one of Claims 13 to 15, characterized in that a curved screen (13) is arranged downstream of the second classification stage (7).
17. Plant according to one of Claims 13 to 16, characterized in that a collecting device (12) is arranged downstream of the second classification stage (7) and a first hydrocyclone (17) having an overflow (18) and an underflow (38) is arranged downstream of the collecting device, and in that the overflow is in line connection with the collecting device.
18. Plant according to one of Claims 13 to 17, characterized in that at least one metal separation stage (21), in particular an iron separation stage and/or a non-iron separation stage, are/is arranged downstream of the second classification stage (7).
19. Plant according to one of Claims 13 to 18, characterized in that, in the first water circuit, a second hydrocyclone (23) having an overflow (26) and an underflow (24) is arranged downstream of the first classification stage (3), and in that a thickener (28) is arranged downstream of the overflow, wherein preferably the thickener (28) has a discharge device for discharging clarified water (31) from the thickener and the discharge device is in line connection with the first showering apparatus (4).
20. Plant according to Claim 19, characterized in that arranged downstream of the second hydrocyclone (23) is an upflow sorter (25), which has an overflow (29) and an underflow (37) and in which, preferably, the clarified water (31) is introduced as upflow water (32), wherein preferably, between the second hydrocyclone (23) and the thickener (28), there is arranged a collecting device (30) in which the overflow (26) of the second hydrocyclone (23) and the overflow (29) of the upflow sorter (25) are brought together.
21. Plant according to Claim 17 and Claim 20, characterized in that the underflow (38) of the first hydrocylone (17) is fed to a dewatering stage (36), to which the underflow (37) of the upflow sorter (25) is also fed.

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