EP1359374A1 - Process for treating residues of an incineration plant - Google Patents

Abstract

Water together with finer parts taken up during washing operation are fed to a wet slag remover when adhered finer parts are separated off. Incinerated residues are divided into two fractions such as a coarse fraction and an oversize fraction.

Description

The invention relates to a method of treatment combustion residues of an incinerator, in particular Waste incineration plant where the fuel burned on a grate, and the resulting Combustion residue by appropriate regulation of Combustion be brought to an elevated temperature.

In a method of this kind, which is known from EP 0 667 490 B1 is known, the fuel on the firing grate so strongly heated, that the resulting slag before reaching one arranged outside the furnace grate Melting stage has a temperature close to below the melting point of this slag is. In this process Thus, the combustion is regulated so that the Slag at the end of the firing grate as high as possible Temperature has to reduce the energy consumption in the downstream To keep melting level low. But here is no sintering or melting of the slag takes place. To anyway To get the desired slag quality, that's why a downstream melting stage is required. This downstream Melting stage not only requires a corresponding one Device, but despite the aforementioned procedure also an increased energy expenditure.

Significant for the desired quality of the slag are the from the waste remaining inorganic and organic Pollutant components. As inorganic pollutant components are mainly heavy metals and salts, while the organic pollutants in particular to an incomplete Incineration are due. Essential for the assessment of slag quality remains as existing Eliminated pollutants in elution experiments become. In addition, mechanical properties are for assessment the structural suitability, e.g. in landfill, earth or Road construction of importance.

Due to the high temperatures in the treatment of Combustion residues in a smelting stage are molten Combustion residues due to low levels of organic Marked connections. While typical Slags from waste incineration plants still unburned, usually measured as loss on ignition, from 1 to 5% by weight show the loss on ignition of molten combustion residues at below 0.3 wt .-%. In addition, are molten Combustion residues due to small proportions characterized by leachable salts and heavy metals, because these either evaporated or in the case of cooling the Melt forming glass matrix are involved.

The object of the invention is to provide a method in the combustion process is so influenced and regulated will that a completely sintered slag with the desired Quality without the use of downstream Melting or glazing aggregates is obtained, and in a low expenditure on equipment, the disadvantages of dust development the air termination of the firebox avoided and low consumption of water becomes.

A "completely sintered slag" becomes a material understood that consists of sintered and / or melted chunks, typically a grain size of at least 2 to 8 mm. These chunks consist of combustion residues of garbage by complete or superficial Melting are agglomerated.

The sintered or smelted pieces may be due to gas release during sintering or melting quite a porous Have structure. The possible porosity of the fully sintered Slag is due to the fact that the temperature the molten slag in the fuel bed is not high is enough to have a sufficiently low viscosity and thus to cause expulsion of gas bubbles, which in the Glass technology is also referred to as Läutern. This is different the completely sintered slag of typical vitrified slags that are in downstream high-temperature process in crucible furnaces lined with refractory material or other melt aggregates.

In addition, the fully sintered slag can also constituents of waste, such as glass or metals, containing of the combustion process largely unaffected the Walk through grate, so in the narrower sense in the fuel bed neither melted nor sintered, but in terms of Burnout and leachable pollutants the desired properties have.

The term "sintering" is equivalent to Hämmerli (garbage and waste 31, Supplement Disposal of slags and other residues, Page 142, 1994) as a special case of melting and freezing. The following is the term Sintering is often used in science Application of this term as "superficial fusion or fusing together of particles. "The chunks of sinter The completely sintered slag can also be completely or partially melted.

The residual slag will be the slag constituents below not sintered and / or melted are. Residual slag is characterized by a comparison to completely sintered slag smaller grain size as well higher loss on ignition and proportion of leachable pollutants.

From DE 701 606 C it is known, the combustion residues in one, an inlet shaft and one Purification tank with rising Ausschubschurre to promote the use of detoxifiers and from there by means of a Herauszubefördern plunger. Here is the Purification tank the water to extinguish the slag fed, with only so much fresh water in these Purification tank is introduced, as with the Slag is discharged through the moistening. there represents an equilibrium concentration with respect to numerous in the residues of adhering substances and compounds, e.g. Salts, so a reduction in their concentration not possible. This results in unsatisfactory Properties of the slag with regard to landfill capability and further processing to building materials. This Disadvantage is also justified by the fact that a division or classification of combustion residues in fractions with better qualities and those with worse ones Properties does not take place, so that thereby the Total of combustion residues inevitably has unsatisfactory properties.

From DE 44 23 927 A1 it is known that from an oven coming incineration residues directly without prior Quenching in a water bath for rough cleaning. The dry and coarsely cleaned slag will be in at least two fractions separated. All particles which are smaller are assigned as 2mm to a first fraction, the remaining particles of a second fraction. In the further course this process becomes the second faction in turn Segregated into at least two fractions and all Particles smaller than 27 to 35 mm become one assigned to the third fraction, with the remaining particles of a assigned to the fourth parliamentary group. In this way receives one fractions of combustion residues with satisfactory Characteristics. Disadvantages of this method are the strong dust and problems with the air of the firebox.

The above object is based on the above explained method depending on the Composition of the fuel on two different Because of solved.

The first way according to the invention is that the Combustion control is conducted so that already in the Brennbett the main combustion zone a sintering and / or Melting of the combustion residues to Slag occurs that the resulting combustion residues deleted altogether in a wet slagger and off be brought out of this, that from the Wet slagger coming wet combustion residues first by a mechanical separation process in two Fractions are split, which is essentially a Coarse fraction and a major fraction containing oversize fraction with withdrawn from the wet slag water washed and thereby separated smaller parts separated and that the wash water with the Washing process recorded finer parts of the Wet slag is fed.

This process variant is always used if it is assumed that the main usable fraction a small proportion of leachable pollutants, such as For example, salts or heavy metals, has.

The invention comprises two main areas, one of which Main area in the combustion control and the second Main area in the mechanical processing of the by the Combustion process obtained combustion residues consists. This second main area comprises two process variants, which depend on the composition of the fuel.

The first main area is for both subsequent process variants in terms of mechanical processing Consistent and is the combustion process on the firing grate so influence that already one Sintering and / or melting process on the grate in the main combustion zone takes place and that each not yet sintered or molten combustion residues be traced back to the second or third pass the desired sintering and / or To experience melting.

The focus of the inventive concept is therefore the sintering and / or melting process of the combustion residues already in the fuel bed of the main combustion zone, which was not thought possible until now. It is namely for mechanical firing grates extremely harmful, if liquid slag between the individual grate bars or Other movable parts of the Feuerungsrostes arrives. Out For this reason one has a melting of the slag on the Avoided rust and made sure that in the fuel bed the Melting temperature of the slag is not reached.

In the process according to the invention, the sintering and / or Melting process in the upper part of the fuel bed instead, because from the top the largest heat effect by the Radiation of the flame body takes place and from below by supplying relatively cold primary combustion air the Temperature of the directly on the Feuerungsrost lying Material can be kept lower than on the top of the fuel bed. Because with such a combustion control not the entire incipient combustion residues in a completely sintered slag with the desired Quality can be converted, those are Combustion residue, which does not yet have the character of completely sintered slag, the combustion process fed again.

As the sintering and / or melting of the slag in the fuel bed The grate firing is achieved is no additional external Energy source required. The quality obtained corresponds as far as possible the products that the expert from the known downstream high-temperature thermal process knows about melting and glazing. in this connection come aggregates such as rotary kiln, crucible furnace and melting chamber for use. The main disadvantage of these known However, the process is the need for the very elaborate additional units and the high energy input, what by the present invention despite approximately similar Quality of the slag is avoided.

In the first variant of the method in terms of mechanical Preparation, there is a circulation of the from the Wet slagder originating water, in such a way that the Main fraction with good quality properties without Use of larger amounts of fresh water from the adherent Fine parts, which experience shows the quality of Main fraction worsen, be released, so that the Combustion residues as slag with good qualitative Properties for processing are present.

In the second way of process management, always then comes into use when in the accruing Combustion residues a higher proportion of leachable pollutants, such as salts or Heavy metals, it is expected, will do the job solved that the combustion control is conducted so that already in the fuel bed of the main combustion zone Sintering and / or melting process of the combustion residues to slag takes place that the resulting combustion residues deleted altogether in a wet slagger and be brought out of this, that out the wet slagger coming wet combustion residues first by a mechanical separation process in two Zones are split, whereupon the separated essentially a coarse fraction and oversize fraction Main fraction is subjected to a crushing process and then with withdrawn from the wet slagger Water is washed and that the washing water at the Washing process recorded finer parts of the Wet slag is fed. The crushing of the main fraction has the consequence that in the subsequent washing process those in the combustion residues in the larger ones Parts of trapped pollutants washed out and thus can be separated from the main recyclable fraction, whereby despite stronger load of these combustion residues with pollutants a large proportion of combustion residues be recovered as recyclable slag can, without later with the washing out of pollutants must be expected on a larger scale.

First, the first main area of the invention will be discussed, which deals with the combustion regulation.

An essential advantageous aspect of the combustion control according to the method of the invention, that an oxygen enrichment of the primary combustion air to about 25 vol .-% to 40 vol .-% is made. Another advantageous measure is that a preheating the primary air temperature to values of approx. 100 ° C to 400 ° C is performed. These measures may vary depending on Conditions are used separately or combined. Preferably, depending on the nature of the Burning the fuel bed temperature in the main combustion zone set to 1,000 ° C to 1,400 ° C.

All measures in the context of combustion regulation setting the desired conditions for which the Combustion residues in sintered and / or molten Slag to be converted, are chosen so that a Proportion of completely sintered slag of 25-75% by weight the entire combustion residues accumulates. At this Measure is ensured that in the fuel bed of the main combustion zone not enough on the firing grid melting material is present, which is the melting Slag surrounds, so these are the mechanical parts of the Firing grate can not affect.

In an advantageous further embodiment of the invention is Fly ash fed back to the combustion process. This Fly ash leaves the fuel bed with the combustion gases over the boiler and is in a downstream Exhaust filter deposited.

Hereinafter, the second main part of the invention will be described having come in the form of two variants mechanical treatment of combustion residues deals.

The resulting in the mechanical separation ultrafine fraction and fine fraction are in a further embodiment of the invention fed to the combustion process. These fractions are again subjected to a combustion process, thus reducing the possibility of melting and sintering consists of these fractions.

These measures avoid the disadvantages of the first explained Procedure in which the total combustion residues only then be recycled if, coincidentally, those shares with worse Properties were low. Opposite the second known Process becomes the disadvantage of dust generation and also avoided the disadvantage of sealing the firebox. In addition, in addition by the return of the with poorer quality properties Ultrafine fraction and fine fraction the proportion of recoverable Combustion residues increased because the recycled fine Parts after one or more returns the Opportunity to agglomerate combustion residues, which have the desired properties. This Advantage is because of the lack of feedback in the second known method also not available.

If in a further embodiment of the invention with water from the wet slag pre-washed main fraction with Fresh water is rinsed, it is with pollutants rinsed relatively heavily polluted Entschlackerwasser and man achieves a further improvement in the quality of combustion residues or the sintered slag. The usage of fresh water for rinsing the coarse fraction also has the advantage that at least one Part of the coming from the final rinse water of the emission control can be fed without this water should be pre-cleaned, because the proportion of pollutants is relatively low. Furthermore, it may be advantageous that at least part of the coming from the final rinse Water is fed to the wet slagger. hereby the level can be maintained in the wet slagger, because of the discharged amount of combustion residues always water is mitabgeführt, reducing the amount of water in the wet slag decreases and filled up anyway would have to be. Since the water coming from the final rinse has only low calcium and sulphate contents not the risk of clogging pipes or nozzles.

If in the first separation process according to the first method variant the main fraction still large proportions of an oversize fraction which usually has a high scrap content possesses, in a further embodiment of the invention the coarse fraction another mechanical separation process be subjected.

In the following, without limitation of the invention only by way of example to clarify the respective areas indicated that the ultrafine fraction is about one grain size from 0 to 2mm, the fine fraction at a grain size of 2 to 8mm, the coarse fraction with a grain size of 8 to 32mm and the oversize fraction are at a grain size over 32mm should. These values are only for better understanding of a Groborientierung provided, of course each fraction a certain proportion of the underlying may contain finer fraction, as long as the finer fraction is of secondary importance. Usually, the Fine fraction coming directly from the purifier and having a grain size of about 2-8 mm, those Proportion of combustion residues, preferably the Combustion process is fed back. At the second Process variant is, however, by the crushing process obtained a grain fraction, this fine fraction in the core distribution, but in terms of quality has a higher standard for reuse, so that this fine fraction called quality fine fraction can be.

If so, for example, starting from the first method variant at the first coarse separation a separation limit of 32mm is maintained, that is, if so the oversize fraction is deposited, so it is recommended to use a second mechanical Provide separation, which then for example at 8mm, with all parts that are smaller than 8mm, again be supplied to the combustion process.

To damage mechanical separators by avoiding large pieces of scrap, it is recommended that at the main fraction carried out a metal deposition becomes.

The main fraction, which is an oversize fraction and coarse fraction this way, not only from the big ones Scrap parts, but also from all other metal parts be released, which supplied to a separate recycling become.

Depending on the procedure and intended reuse the resulting combustion residues and in dependence from the composition of these combustion residues it may be useful in the oversize fraction and the coarse fraction separately from each other a metal deposit perform.

If, for example, the combustion residues in road construction should be used, so it is recommended, after the Metal deposition, the oversize fraction another crushing process to submit, as parts, for example larger than 32mm are little for this purpose are suitable.

Starting from the first process variant, it is in the sense the provision of the largest possible fraction for the Further use, that in a further embodiment of the invention the separated from the main fraction coarse fraction with the crushed combustion residues from the oversize crushing mixed to a first mixed fraction become. It may turn out to be appropriate that the mixed fraction a mechanical separation process is subjected, as in the crushing process, such Grain sizes incurred, which is undesirable for further utilization are and, for example, the combustion process should be returned.

If the combustion residues for a particularly interesting Field of application to be prepared, that in the production of roadbeds for road construction, so the material must be compressible, what without fines, the according to the above given coarse division between 2 and 8mm is, is possible badly. For this reason, recommends it turns out that part of the coarse fraction is a comminution process is deliberately subjected to this needed To obtain fine fraction, so that one on the coincidental Proportion of this grain size is not dependent. advantageously, You will about 30% of the coarse fraction this crushing process submit. The crushing of the Coarse fraction resulting fine fraction and ultrafine fraction mixed with the coarse fraction to a second mixed fraction. Preferably, the proportion of coarse fraction in this for the roadworks intended mixing fraction about 70%.

In this second mixed fraction outweighs a grain fraction of Greater than 8mm as these components experience shows the for have the re-use necessary quality, with a smaller fraction of a grain fraction between 2 and 8mm necessary is to the mentioned compressibility of these combustion residues to ensure road construction.

If in a further embodiment of the invention, the second Mixed fraction washed with water from the wet slagger and the ultrafine fraction is separated, it is ensured that the proportions below 2mm grain size, often particularly heavily polluted, of the recoverable Shares are separated.

This wash water can then again in an advantageous manner fed to the wet slagger, as well as in a another context has already been explained. The meaning and the purpose of such repatriation is, if possible to consume little fresh water.

It is recommended that the deposited metals of a wash with Water from the Entschlackerwasser to subjugate, so any adhering combustion residues washed off become.

Advantageously, as a mechanical separation process Sieving used.

Increasing the quality of the combustion residues obtained it is extremely helpful if the water of the wet slag precipitant for soluble heavy metals be added. This allows these heavy metals be separated.

The invention will be described below with reference to various flow charts explained in more detail, the embodiments of the invention Show procedure.

Figur 1:

ein Flussdiagramm eines Basisverfahrens;

Figur 2:

ein Flussdiagramm des Basisverfahrens mit zusätzlicher Nachspülung;

Figur 3:

ein Flussdiagramm einer Variante des Basisverfahrens mit zusätzlichen Verfahrensschritten; und

Figur 4:

ein Flussdiagramm des Basisverfahrens mit Zusatz von Fällungsmitteln.

In the drawing show:

FIG. 1:

a flowchart of a basic method;

FIG. 2:

a flow chart of the basic process with additional rinsing;

FIG. 3:

a flowchart of a variant of the basic method with additional method steps; and

FIG. 4:

a flow chart of the basic method with the addition of precipitants.

According to the illustrations in the flow charts 1,000 kg of waste with an ash content of 220kg abandoned a grate firing and burned it in a way that already a part of 25% -75% of accruing Combustion residues to completely sintered slag is converted. In this combustion process arise 800kg of exhaust gas and 300kg combustion residues. These arrive in a wet slag, from which due to wetting 315kg incineration residues or slag discharged become. These combustion residues become one mechanical separation, in this case a sieving at 8mm, subjected. Here are 215kg combustion residues or slag as main fraction with a grain size of over 8mm on the one hand and a fine fraction and Fine fraction <8mm separated in the order of 100kg. The slag with a grain size about 8mm which a coarse fraction and an oversized grain fraction becomes one Wet treatment and that will be 1000 liters Water taken from the wet slagger to this Slag to wash while fine proportions below 8mm in the Order of 15kg to wash off. This laundry can conveniently on a sieve with a sieve passage 8mm or smaller. The slag water in connection with these fines and fine steels is the Wet slag fed again. The washed slag is deducted and for recovery, for example in Road construction, used. The deposited during the screening Fine fraction with a mass of about 100kg usually becomes again given to the grate firing, to a more extensive To achieve sintering. But it is also possible this Contribute to other treatment methods. 40 liters Inlet water or fresh water are supplied to the To compensate for water loss in the wet slagger by it occurs that the combustion residues in the discharge Of course, liquid from the wet slagger carry.

In the modification of the method according to Figure 2 is carried out after the wet treatment of the main fraction with a grain size of about 8mm a final rinse with fresh water, which with a quantity of 80 liters the 200kg of the main fraction added in order to free them from adhering components, from the wet treatment by the water from the Wet slag originate. 40 liters of this rinse liquid be used for waste gas purification or other disposal, diverted, while another 40 liters the wet slagger be supplied to compensate for the loss of water. The way cleaned slag can be recycled become.

FIG. 3 shows a variant of the method according to the invention. In this modified process will be 1000kg of garbage an ash content of 220kg fed to a grate firing. When burning 800kg of exhaust gas and 320kg Combustion residues that enter a wet slagger. This wet slag becomes combustion residues deducted on the order of 336kg. The weight gain is due to fine particles that over the Slag water recycling fed to the wet slagger become. The wet slagger will be 40 liters of water as Balancing supplied for the discharged water. The 336kg Slag or incineration residues reach a sieve with a separation grain size of 32mm. The oversize fraction with a grain size of> 32mm is first a metal deposit fed. The accumulating slag enters a crusher to slag of the order of 8mm to obtain. This slag so obtained will be on another Sieve brought with a separation grain diameter of 8mm. Out this mechanical separation will be 100kg slag or Combustion residues with a grain diameter of <8mm deducted and preferably the grate firing again fed. The remaining coarse fraction becomes a metal deposit fed. The obtained metal parts and the metal parts of the metal deposit from that described above Process step are merged and a wet treatment fed to adhering slag parts rinse. This will be 20kg of ferrous and non-ferrous metals obtained, which are recycled. The scrapped Slag or coarse fraction with a grain size of 8 to 32mm has a weight of 215kg. 60kg of this are fed to a crusher and to a grain size> 2mm crushed. After crushing, the crushed Mass fed to the main stream of 155kg and a wet treatment on a sieve with 2mm cut size. The washing water is used in an amount of 1000 liters taken from the wet slagger. After this wet treatment 155kg slag with a grain size of 8 to 32mm and a finer proportion of 45kg with a grain diameter from 2 to 8mm in front. These two factions will be recycled, while fines, the one Diameter of less than 2mm, the wet slagger be fed again.

The flowchart of Figure 4 shows the basic variant, accordingly FIG. 1, in conjunction with the addition of a precipitant for soluble heavy metals. This precipitant is added to the wet slag to reduce the lead content of the Purifier water of usually 2mg / l to 0,05mg / l too reduce. This reduces the cargo of dissolved lead to 1mg, with about 20l adhering slag water 200kg of wet-treated slag is present. Get 400g of lead during combustion into the exhaust gas. In the mechanical separation process with a separation grain size of 8mm, the 400g Lead split so that 200g of lead in the slag of 200 kg which are recycled after wet treatment be while 200g of lead with the fine fraction below 8mm back to the grate firing.

Claims (24)

A method for the treatment of combustion residues from an incinerator, in particular a waste incineration plant, wherein the fuel burned on a grate and the resulting combustion residues are brought by appropriate control of combustion to an elevated temperature, characterized in that the combustion control is performed so that already in the fuel bed of the main combustion zone, a sintering and / or melting process of the combustion residues to slag takes place that the resulting combustion residues are deleted altogether in a wet slag and out of this, that the coming from the wet slag wet combustion residues are first divided by a mechanical separation process into two fractions , whereupon the main fraction, which essentially has a coarse fraction and an oversize fraction, is washed with water removed from the wet slagger and thereby adhering finer parts are separated, and that the washing water is supplied to the recorded during the washing process finer parts of the wet slagger. A method for the treatment of combustion residues from an incinerator, in particular a waste incineration plant, wherein the fuel burned on a grate and the resulting combustion residues are brought by appropriate control of combustion to an elevated temperature, characterized in that the combustion control is performed so that already in the fuel bed of the main combustion zone, a sintering and / or melting process of the combustion residues to slag takes place that the resulting combustion residues are deleted altogether in a wet slag and out of this, that the coming from the wet slag wet combustion residues are first divided by a mechanical separation process into two fractions , whereupon the separated main fraction, which essentially has a coarse fraction and oversize fraction, is subjected to a comminution process and connected d is washed with withdrawn from the wet slag water and that the washing water is supplied to the recorded during the washing process finer parts of the wet slagger. A method according to claim 1 or 2, characterized in that the combustion control comprises an oxygen enrichment of the primary combustion air to 25 vol .-% to 40 vol .-%. Method according to one of claims 1 to 3, characterized in that the combustion control comprises a preheating of the primary combustion air to 100 ° C to 400 ° C. Method according to one of claims 1 to 4, characterized in that the fuel bed temperature is set to 1000 ° C to 1400 ° C. Method according to one of claims 1 to 5, characterized in that the combustion control is adjusted so that a proportion of fully sintered slag of 25% to 75% of the total combustion residues is obtained. Method according to one of claims 1 to 6, characterized in that the resulting during the combustion process fly ash is returned to the combustion process. Method according to one of claims 1 to 7, characterized in that the resulting in the mechanical separation process finest fraction and fine fraction is fed to the combustion process. Method according to one of claims 1 to 8, characterized in that the prewashed with water from the wet slag main fraction is rinsed with fresh water. A method according to claim 9, characterized in that at least a part of the water coming from the final rinse is supplied to the exhaust gas purification. A method according to claim 9, characterized in that at least a portion of the water coming from the final rinse is fed to the wet slag remover. Method according to one of claims 1 to 11, characterized in that in the main fraction, a metal deposition is carried out. A method according to claim 1, characterized in that the main fraction is subjected to a further mechanical separation process. Method according to one of claims 1 to 13, characterized in that in the oversize fraction and the coarse fraction separated from each other, a metal deposition is performed. Method according to one of claims 1 to 14, characterized in that the oversize fraction is subjected to a comminution process. Method according to one of claims 14 or 15, characterized in that the coarse fraction separated from the main fraction is mixed with the comminuted combustion residues from the oversize comminution to form a first mixed fraction. A method according to claim 16, characterized in that the first mixed fraction is subjected to a mechanical separation process. Method according to one of claims 1 or 3 to 17, characterized in that a part of the coarse fraction is subjected to a crushing operation. A method according to claim 18, characterized in that the fine fraction and ultrafine fraction formed during the comminution of the coarse fraction is mixed with the coarse fraction to form a second mixed fraction. A method according to claim 19, characterized in that the second mixed fraction is washed with water from the Nassentschlacker and the ultrafine fraction is separated. A method according to claim 20, characterized in that the ultrafine fraction is supplied to the wash water to the wet slagger. A method according to claim 12 or 14, characterized in that the deposited metals are subjected to a wash with water from the Entschlacker. Method according to one of claims 1 to 22, characterized in that a sieving process is used as a mechanical separation process. Method according to one of claims 1 to 23, characterized in that precipitating agents for soluble heavy metals are added to the water of the wet slagger.

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