EP0908674A1 - Process for the combustion of refuse in an incinerator and for processing the residues from the incineration - Google Patents

Abstract

A rotating pipe oven is used as the incinerator and the fine ash fraction up to 2 mm in particle size is returned to the oven for incineration. Dry ash (9) is removed from the incinerator and immediately separated into at least two fractions, the first fraction with a particle size up to 32 mm being separated in a first screening step, and the material passing through this screen being supplied to a second sorting step where the fine fraction (14) with a particle size of up to 2 mm is separated. The fine fraction is then supplied to a sorting step. A rotating pipe oven (2) is used as the incinerator, and at least some of the fine fraction is returned to the air inlet side of the oven for incineration.

Description

Technical field

The invention relates to the field of thermal waste treatment. she relates to a method for incinerating waste in an incinerator and for the preparation of the slag from this waste incineration.

State of the art

Today, the grate combustion process is usually used to burn household waste used. The garbage is mechanically inclined horizontally or horizontally Level moves and at the same time with combustion air passing through from below the rust enters the garbage bed, flows through. The incombustible part of the waste will discharged from the incinerator as rust ash or slag. While the grate firing process for waste with a calorific value of over 6500 kJ / kg can be used excellently, it is for burning garbage not suitable with lower heating values, because in this case to dry the Garbage requires a high preheating of combustion air, which is disadvantageous high strength and corrosion problems of the rust coating.

EP 0 372 039 B1 describes a process for treating the slag from waste incineration plants known in which the slag dry from the incinerator is carried out, a rough cleaning (removing unburned Coarse goods and magnetic parts) is subjected, and then the coarse cleaned slag is separated into at least two fractions and one fraction all particles that are smaller than 2 mm are assigned. This procedure lies based on the knowledge that the fine fraction was largely the original contains pollutants contained in the slag. The fine fraction undergoes special treatment supplied while the coarse fraction z. B. is suitable as a building material.

A further development of this method is disclosed in ER 0 722 777 A1. There is a process for the treatment of slag from waste incineration plants claimed, in which the raw slag after passing through the grate directly and without quenching in a water bath in at least two Fractions is separated, and these two fractions treated separately the coarse fraction is fed to a wet slag remover. The The method is characterized in that the first fraction has a particle size less than 80 mm, preferably less than 32 mm, separated in a first screening stage is that the screen overflow of the wet purification is fed that the sieve diarrhea and, if applicable, the grate diarrhea of the grate a second sieving stage is fed in to separate the fine fraction 0 ... 2 mm that the screen overflow of the second stage, if necessary after sorting out is mechanically crushed by metallic and inert materials, and the sieve diarrhea the second stage of special treatment, e.g. B. fed to a melting furnace becomes. In this, for example, carried out in an arc furnace Melting process become a glassy, easy to deposit product and a Metal concentrate produced (see F.-G. Simon and K.-H. Andersson: InRec process - Recycling of residues from thermal waste treatment, ABB technology 9/1995, pp. 15-20). In practice, this processing method has been used for the slag from rust incinerators was used and has proven itself there.

The high costs resulting from the use of the arc furnace are disadvantageous surrender.

In addition to the rust incineration process for waste, it is also known that waste (predominantly Hazardous waste) in a rotary kiln. Rotary kilns exist essentially from a cylinder inclined in the conveying direction, the inside is lined with refractory material or has a cooled hollow jacket. The garbage can be of different consistency and texture can be put together in the DC process at the top of the rotary tube fed to the rotary tube with the combustion air and then in the rotary tube burned. The disadvantage of this method is that the combustion air does Can not flow through the garbage bed and thus a bad slag burnout is produced. This can be done by extending the waste disposal time or by a temperature increase in the rotary tube can be avoided, but that in turn has The following disadvantages: The first measure either leads to a large rotary kiln or too little throughput, and the second measure leads to Melting the slag with great wear on the lining material and thus too high treatment costs. For these reasons, in practice is mostly only hazardous waste burned in a rotary kiln, because of its different In turn, consistency cannot be treated in the grate.

The application is for low calorific value waste with a particularly high water content the countercurrent principle in the rotary kiln advantageous, d. H. the waste-slag path runs in the opposite direction to the combustion air / flue gas path. The vapors from the drying zone go directly into the combustion chamber derived without burdening the rest of the furnace of the rotary kiln. This means that the waste is ignited earlier, a shorter drum is sufficient for complete burnout. (K. J. Thomé-Kozmiensky: Thermal Waste treatment. EF publishing house for energy and environmental technology GmbH, 2nd edition, 1994, p. 240).

Another disadvantage of using rotary kilns for waste incineration is that there is poor mixing of slag and air he follows. Rotary kilns are operated with a large excess of air from 2.0 to 3.0 (K. J. Thomé-Kozmiensky: Thermal waste treatment. EF publishing house for Energie- und Umwelttechnik GmbH, 2nd edition, 1994, p. 239), which is too high NOx values, which are as low as possible for environmental reasons should be.

Presentation of the invention

The invention tries to avoid all of these disadvantages. You have the task based on an effective and inexpensive method of incinerating waste in an incinerator and to treat the slag from this waste incineration to create which with a robust and simple technique too is realized, which can also be used for waste with a low calorific value and at which only produces low NOx emissions. In addition, one of pollutants depleted slag is created, which should be processed so that the Residues can be used in other processes.

According to the invention, this is done in a method for incinerating waste an incinerator and to treat the slag from this waste incineration, in which the slag is discharged dry from the incinerator and is separated directly into at least two fractions, the first Fraction with a particle size up to about 32 mm separated in a first sieving stage and the sieve diarrhea is fed to a second classification stage to separate the fine fraction 0 ... 2 mm, and the fine fraction a special treatment is fed in that the garbage is in a rotary kiln is burned, and that the fine fraction 0..2 mm from the slag processing returned to the rotary kiln on the air inlet side and burned there becomes. The fine fraction can preferably be by means of a burner, but also be burned using a fluidized bed process.

The advantages of the invention are that during combustion in a rotary kiln typical low ash burnout is increased and the slag in one state depleted of pollutants. The mechanical complexity of the rotary kiln used for waste incineration is compared to the previously preferred combustion grates low. Through this simple The technique can also be used in developing and emerging countries without any problems deploy.

It is particularly useful if the rotary kiln with an air ratio smaller 1, i.e. sub-stoichiometric, is operated. This has the advantage that the Combustion produces only low levels of nitrogen oxides. At the same time, it turns out to be low Flue gas speed in the rotary tube, which prevents Dust and unburned light particles are carried away by the gas flow. This also means that the amount of flue gas at the end of the boiler is kept low can and therefore only smaller flue gas cleaning systems are necessary.

Furthermore, it is advantageous if the sieve diarrhea of the first sieving stage causes one Air classifier is fed and there into a carbon-rich light fraction (= Fine fraction) and an inert heavy fraction is separated. The high carbon The light fraction contains all particles <2 mm. It is returned to the rotary kiln and burned in a burner, causing a temperature increase at the cold air inlet end of the rotary kiln.

It is also advantageous if the rotary kiln with a waste incineration Calorific value <7 MJ / kg is operated in the counterflow principle. If the combustion air inserted into the rotary kiln at the opposite end for waste disposal then it causes the hot flue gases to heat up convection and radiation very efficiently to the rotary pipe lining and dispose of the garbage, be used very well to dry the wet garbage can and therefore good combustion is possible.

The method according to the invention is also excellent for combustion suitable for waste with a high calorific value (greater than 7 MJ / kg). In this case the rotary kiln is operated using the direct current principle.

Finally, it is advantageous when burning waste with a low calorific value Additional fuel is injected at the air-side end of the rotary tube, so that the combustion conditions are further improved. The same applies if the Combustion air introduced into the rotary kiln in the preheated state becomes. It is advisable to preheat the air through the hot flue gases, which are cooled, for example, in a radiation cooler or the previous one Use of the combustion air as cooling air to cool the outer casing of the rotary tube.

Furthermore, it is useful if the garbage through before entering the rotary tube mechanical pressing is pre-compressed.

Brief description of the drawing

Exemplary embodiments of the invention are shown in the drawing.

Fig. 1

ein Prinzipschema des erfindungsgemässen Verfahrens in einer ersten Ausführungsvariante (Drehrohrofen im Gegenstromprinzip);

Fig. 2

ein Detail von Fig. 1 (Schlackenaufbereitung);

Fig. 3

ein Prinzipschema des erfindungsgemässen Verfahrens in einer zweiten Ausführungsvariante (Drehrohrofen im Gegenstromprinzip).

Show it:

Fig. 1

a schematic diagram of the inventive method in a first embodiment (rotary kiln in the counterflow principle);

Fig. 2

a detail of Figure 1 (slag processing).

Fig. 3

a schematic diagram of the inventive method in a second embodiment (rotary kiln in the countercurrent principle).

Only the elements essential for understanding the invention are shown. The direction of flow of the media is indicated by arrows.

Way of carrying out the invention

The invention is explained below using exemplary embodiments and FIG. 1 to 3 explained in more detail.

1 shows a basic diagram of the method according to the invention in a first Design variant. Garbage 1 with a low calorific value (4.5 MJ / kg) be burned. In this exemplary embodiment, waste 1 consists of 28.5% flammable material, 46.9% water and 24.6% ash. Such a garbage composition is typical for Asian countries and developing countries, for example.

The garbage 1 is a rotary kiln via a feed device, not shown 2 fed. Optionally, the garbage 1 in a press 3 before entering the rotary kiln are mechanically precompressed, the press 3 being advantageous can be integrated into the loading device.

The rotary kiln 2 in this first embodiment has a length of 25 m and a diameter of 5 m. It is operated according to the countercurrent principle, that is to say the waste 1 is fed in at the upper end of the rotary tube inclined in the conveying direction of the waste 1 and the combustion air (primary air 4) is fed in via a fan 5 at the lower end of the rotary tube. The waste-slag path thus runs in the opposite direction to the combustion air-flue gas path. An afterburner chamber 6 connects to the upper end of the rotary kiln 2. The secondary air 8 is fed into the afterburning chamber 6 by means of a blower 7. While there is a maximum temperature of 1000 ° C in the rotary kiln 2, the temperature at the end of the afterburning chamber 6 is approximately 850 ° C. The rotary kiln 2 is operated sub-stoichiometrically, that is, with an air ratio <1. The amount of primary air 4 supplied is 39,000 Nm ³ / h, the amount of flue gas at the upper end of the rotary tube is 63,400 Nm ³ / h, and the amount of flue gas at the outlet of the afterburning chamber 6 98,000 Nm ³ / h.

The garbage 1 is continuously fed into the rotary kiln 2 and through the oven 2 transported. It is heated to a temperature of> 500 ° C and the flammable components are burned. At the lower end of the rotary kiln 2 the slag (ash) 9 becomes dry, i.e. without quenching in a water bath, carried out and a dry or semi-dry sorting and classification process subjected such as this, for example, in EP 0 722 777 A1, EP 0 691 160 A1 or EP 0372 039 B1 are described. These writings are expressly mentioned here related, so that the recovery process from recyclables Waste incineration slag cannot be described in detail here. With 10 are generally the various sorting, classifying and shredding devices referred to, on the one hand scrap iron 11, non-ferrous metals (especially Cu, Al) 12 and inert slag 13 can be obtained, which continues in the economy can be used, and on the other hand the fine fraction 0 ... 2 mm (carbon-rich Light fraction) 14 is obtained on the air inlet side in the rotary kiln 2 is returned. The carbon-rich light fraction 14 can either burned directly via a burner at the end of the rotary tube or it can optionally before returning them to the rotary kiln 2 in a further intermediate step be enriched with carbon 15. It is also possible to supply additional fuel 16 directly at the lower end of the rotary kiln in order to to improve combustion. An improvement is also achieved when preheated Combustion air is used, preheating the combustion air for example in a radiation cooler due to the hot flue gas can take place or the air first for cooling the outer tube of the rotary tube used and then used as combustion air.

Fig. 2 again illustrates the slag processing for the first embodiment in detail. The slag 9 leaving the rotary kiln 2 is in a first sieve stage 17 sieved on a roller grate, the sieve diarrhea <32 mm of a second classification stage 18, in this case a zigzag air classifier is fed. In the zigzag air classifier, the sieve diarrhea becomes the first sieving stage 17 into a carbon-rich light fraction (fine fraction 14) and an inert one Heavy fraction 19 separated. The light fraction 14 can now also with Carbon 15 can be enriched or returned directly to the rotary kiln become. Of course, only a part of the light fraction can be used as required 14 are returned to the furnace 2. The screen overflow> 32 mm is with the inert heavy fraction 19 from the zigzag wind sifter merged and by means of iron or non-ferrous metal separator 20 from its metallic components Cut. The screen overflow> 32 mm is after scrapping and crushing returned to the rotary kiln 2. The problem is unburned coarse particles, such as B. books and melons. You can either sort them out by hand and be recycled, or it will be the whole coarse fraction after crushing returned to the oven.

The inventive combination of waste incineration in a rotary kiln recycling and incineration of at least part of the fine fraction 14 the slag 9 leads to the elimination of the serious disadvantage of the rotary kilns (low ash burnout). In addition, the substoichiometric Combustion in the rotary kiln in connection with post-combustion at low Temperatures reduce NOx emissions compared to rust combustion. The robust and simple technology of the rotary kilns also represents a major one Advantage when using the inventive method in development and Emerging countries.

3 shows a basic diagram of the method according to the invention in a second Design variant. Garbage 1 with a high calorific value (> 7 MJ / kg) be burned, such as occurs in European countries. The procedure 3 differs from the embodiment variant shown in FIG. 1 only in that the rotary kiln 2 operated in the direct current principle will, d. H. at the upper end of the rotary tube inclined in the conveying direction of the waste 1 both the garbage 1 and the combustion air (primary air 4), the was previously compressed in a compressor 5, supplied. The waste-slag path thus runs in the same direction to the combustion air-flue gas path. According to the invention part or all of the fine part of the slag is here was previously carried out dry from the rotary kiln 2 and a dry one Sorting / classification has been made in the upper end of the rotary kiln returned. The advantages described above also occur here.

Further improvements in effectiveness of the method according to the invention are possible if, for example, the combustion air is preheated. That can e.g. B. happen in a radiation cooler through the hot flue gases, or Combustion air is first used to cool the Rotary tube outer jacket used and preheated.

Reference list

1

rubbish

2nd

Rotary kiln

3rd

Press

4th

Combustion air / primary air

5

Blower for item 4

6

Afterburner

7

Blower for pos. 8

8th

Combustion air / secondary air

9

slag

10th

Sorting, classic and shredding equipment

11

Scrap iron

12th

Non-ferrous metals

13

Inert material

14

Fine fraction / carbon-rich light fraction

15

carbon

16

Additional fuel

17th

first sieve stage

18th

second classification level

19th

inert heavy fraction from item 18

20th

Metal separator

Claims (10)

Process for the incineration of waste (1) in an incinerator and for the treatment of the slag (9) from incineration, in which the slag (9) is discharged dry from the incinerator and separated directly into at least two fractions, the first fraction having one Particle size up to about 32 mm is separated in a first sieving stage (17) and the sieve diarrhea is fed to a second classification stage (19) for the purpose of separating the fine fraction 0 ... 2 mm (14), and the fine fraction (14) is subjected to a special treatment, characterized, a) that the waste (1) is burned in a rotary kiln (2), b) that at least a part of the fine fraction 0..2 mm (14) from the slag treatment on the air inlet side is returned to the rotary kiln (2) and c) that said fine fraction (14) is burned there. A method according to claim 1, characterized in that the rotary kiln (2) is operated with an air ratio less than 1. Method according to one of claims 1 or 2, characterized in that that the sieve diarrhea of the first sieve stage (17) is fed to an air classifier and there into a carbon-rich light fraction (= fine fraction 14), which is returned to the rotary kiln (2) and burned, and in one inert heavy fraction (19) is separated, the light fraction (14) optionally in a further process step before their return to the furnace (2) is enriched with carbon (15). Method according to one of claims 1 to 3, characterized in that that the rotary kiln (2) has a calorific value when burning waste (1) <7 MJ / kg is operated in the counterflow principle. Method according to one of claims 1 to 3, characterized in that that the rotary kiln (2) has a calorific value when burning waste (1) > 7 MJ / kg is operated in the direct current principle. A method according to claim 4, characterized in that on the air side Rotary tube end (2) fuel (16) is injected. Method according to one of claims 1 to 6, characterized in that that the combustion air (4, 8) is preheated. A method according to claim 7, characterized in that the combustion air (4, 8) used to cool the outer casing of the rotary tube and is preheated. A method according to claim 7, characterized in that the combustion air (4, 8) preheated in a radiation cooler by the hot flue gas becomes. A method according to claim 1, characterized in that the garbage (1) before Entry into the rotary tube (2) is pre-compressed by mechanical pressing.

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