EP0862019A1 - Method and device for thermal treatment of fly ash from grate incinerators - Google Patents

Abstract

The process removes fly ash (10) and if appropriate, particles of grate end ash (19) entrained from waste incineration. The waste is burned on the grate (4) in a incinerator furnace (1). From this arises grate ash (19) and flue gases carrying fly ash (10). The incinerator (1) comprises primary (7) and secondary (8) combustion chambers. The flue gases are withdrawn for further treatment in the boiler (2) and the dust filtration plant (3) where precipitated fly ash is extracted. At least some of the fly ash is melted or sintered. Some the fly ash (10) is recycled back to the high temperature region of the combustion chamber. Here the maximum temperature exceeds the melting point or the sintering temperature of the fly ash. The residence time is sufficient that the ash becomes glassified or sintered. Also claimed is the corresponding plant for this process.

Description

Technical field

The invention relates to the field of waste incineration. It affects one Method and device for the thermal treatment of airborne dust and possibly fine ash from rust incineration plants.

State of the art

A large number of processes are known for the thermal treatment of waste / refuse, where the garbage is gassed, caked or burned. The resulting solid reaction products can be used in different ways, e.g. B. thermal, further processed and then the no longer usable products to be deposited. The quantities of fly ash to be deposited should be as small as possible because they have a high proportion of heavy metals.

For example, a method is known from DE 38 11 820 A1, in which waste in a pyrolysis reactor in carbonization gas and in essentially non-volatile pyrolysis residues is converted. The carbonization gas is then a separate one Afterburner supplied, as well as the fine fraction (smoked coke and Fine dust) of the residues and those in the dust filter system or in the heat recovery steam generator accruing fly ash (dust). The dust and the fine particles are burned in this high temperature chamber and the solid parts melted. The molten slag is then removed from the combustion chamber passed a water container, where it solidifies into a glass-like granulate.

However, such a solution requires processing of the smoldered material and a separate afterburning chamber, which results in an increased space requirement and expresses in high costs.

This also applies to the combustion-melting plant described in EP 0 446 888 B1 for urban waste disposal. There is a melting furnace for the incinerator downstream for melting the ashes from the incinerator, whereby the ashes are transported to the melting furnace via a dry conveyor. Special dust is also used to filter dust from the dust separator into the Melting furnace introduced, so that ashes from the incinerator in the melting furnace and flue dust from the dust collector melted together will.

Another way to reduce the amount of fly ash is e.g. B. in the incineration process for waste incineration plants To be connected off-line. Such a method is described in F.-G. Simon and K.-H. Andersson: "In-rec process - recycling of residues from the thermal Waste treatment ", ABB Review 9/1995, pp. 15-20. The fine fraction the grate ash is common in this process, called the AshArc process melted with the filter ash in a direct current arc furnace. The high temperatures immediately decompose organic compounds. Metal chlorides are evaporated, and heavy metal compounds become Element reduces and then either sink into the metal bath to form one Alloy, or they leave the furnace in a gaseous state. The exhaust gas undergoes post-combustion for CO and rapid cooling with water and lots of air to especially the formation of toxic organic compounds to prevent. Evaporated metal chlorides sublime and are on a Bag filter separated. This heavy metal concentrate can be smelted.

Since the AshArc furnace is designed for very large throughputs, it is possible to the fine fraction of the grate ash (approx. 8% of the waste used) together with the filter ash from the particle separation of the flue gas cleaning (approx. 2.5% of waste used).

The disadvantage of this prior art is that an external furnace unit is built which must be 100% externally heated. It is also included The resulting glassy product is not part of the rust ash.

Presentation of the invention

The invention tries to avoid all of these disadvantages. You have the task based, a method and an apparatus for the thermal treatment of Fly dusts and possibly fine ash from waste incineration plants develop with those in a simple manner and at low cost Product is generated, which either slammed into the grate ash or else can be recycled separately and thus the remaining amount of fly ash is reduced becomes.

According to the invention, this is achieved in that in a method according to the preamble of claim 1 at least part of the dusts in the High temperature range of the incinerator is fed back, the Temperature in said high temperature range above the melting temperature or sintering temperature of the airborne dusts, and that the airborne dusts are in the high temperature range of the incinerator remain sufficiently long so that they at least partially glazed or sintered. These products can then added to the grate ash or recycled separately.

According to the invention, this is the case with a device according to the preamble of Claim 13 achieved in that the ash conveyor up to close the high temperature area of the incinerator extends that of the ash conveyor there a metering device for introducing at least one Part of the returned dusts in the high temperature area of the incinerator is connected downstream and that in the high temperature area of the incinerator Means to ensure a sufficient dwell time of the ashes are arranged.

The advantages of the invention include the elimination of separate ones High-temperature combustion chamber or the external furnace unit, which were previously used Melting of the fly ash was necessary. This can save costs will. The product can be added to the grate ash so that the remaining amount of fly ash with a high proportion of pollutants compared to State of the art is reduced. Another advantage of the invention is that existing systems can be easily retrofitted.

It is particularly expedient if the entire amount of the dust in the High temperature range of the incinerator is traced because of this The way a product is created that does not have to be disposed of as special waste.

Furthermore, it is advantageous if, in the case of only a partial return of the fly dusts in the high temperature area of the incinerator the dusts after discharge from the boiler or the dust filter system, first into a low-pollutant and a pollutant-rich fraction are separated and only that Low pollutant fraction of the airborne dust in the high temperature area of the incinerator is recycled because it produces a low-pollutant product and the risks of corrosion problems from increased concentrations Heavy metals in the boiler area can be reduced.

Finally, the dusts are removed after discharge from the boiler or the dust separator with the fine fraction (<2 mm), for example According to the DryEx / DryRec process (dry discharge and dry sorting) prepared grate ash mixed and this mixture then in the High temperature range of the incinerator is returned. That has the The advantage that the pollutant-rich fraction of the rust ash is treated in a targeted manner can. At the same time, the melting properties, e.g. B. viscosity, Melting temperature, the liquid slag improves, and it becomes a dry, but hardly any dusty rust ash.

Further advantageous embodiments of the invention are in the further subclaims described.

Brief description of the drawing

Several exemplary embodiments of the invention are shown in the drawing.

Fig. 1

eine schematische Darstellung einer erfindungsgemässen Müllverbrennungsanlage nach einem ersten Ausführungsbeispiel, bei welchem die Gesamtmenge der Flugstäube in die Primärbrennkammer zurückgeführt wird;

Fig. 2

eine schematische Darstellung einer erfindungsgemässen Müllverbrennungsanlage nach einem zweiten Ausführungsbeispiel, bei welchem die Gesamtmenge der Flugstäube nach Zwischenlagerung und Pelletiesierung in die Sekundärbrennkammer zurückgeführt wird;

Fig. 3

eine schematische Darstellung einer erfindungsgemässen Müllverbrennungsanlage nach einem dritten Ausführungsbeispiel, bei welchem nur ein Teil der Flugstäube in die Primärbrennkammer zurückgeführt wird;

Fig. 4

eine schematische Darstellung einer erfindungsgemässen Müllverbrennungsanlage nach einem vierten Ausführungsbeispiel, bei welchem die Flugstäube gemeinsam mit der Feinfraktion der Rostasche in die Primärbrennkammer zurückgeführt werden;

Fig. 5

ein Detail des Hochtemperaturbereiches des Ofens mit einer speziellen Ausführungsform eines Mittels zur Gewährleistung einer für die rückgeführten Flugstäube ausreichenden Verweilzeit in diesem Bereich;

Fig. 6

eine schematische Darstellung einer erfindungsgemässen Müllverbrennungsanlage nach einem fünften Ausführungsbeispiel, bei welchem die geschmolzene Asche separat von der Rostasche ausgetragen wird.

Show it:

Fig. 1

is a schematic representation of a waste incineration plant according to the invention according to a first embodiment, in which the total amount of dusts is returned to the primary combustion chamber;

Fig. 2

is a schematic representation of a waste incineration plant according to the invention according to a second embodiment, in which the total amount of dusts after intermediate storage and pelletization is returned to the secondary combustion chamber;

Fig. 3

is a schematic representation of a waste incineration plant according to the invention according to a third embodiment, in which only part of the dusts are returned to the primary combustion chamber;

Fig. 4

is a schematic representation of an inventive waste incineration plant according to a fourth embodiment, in which the dusts are returned together with the fine fraction of the grate ash in the primary combustion chamber;

Fig. 5

a detail of the high temperature area of the furnace with a special embodiment of a means for ensuring a sufficient dwell time for the returned dust in this area;

Fig. 6

is a schematic representation of an inventive waste incineration plant according to a fifth embodiment, in which the molten ash is discharged separately from the grate ash.

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

Way of carrying out the invention

The invention is explained below using exemplary embodiments and the figures 1 to 6 explained in more detail.

Fig. 1 shows schematically a waste incineration plant according to a first embodiment the invention.

The waste incineration plant essentially consists of an incinerator 1, a boiler 2 and a dust collector 3, z. B. an electrostatic filter, are connected downstream. A combustion grate 4 is arranged in the incinerator 1, on which the waste 5, for example household waste, with the supply of primary air 6 in the primary combustion chamber 7 is burned. The combustion takes place in the secondary combustion chamber 8 further completed due to the supply of secondary air 9. In the Combustion of household waste creates flue dusts 10, which are associated with the flue gas 11 via the primary combustion chamber 7, the secondary combustion chamber 8, the radiation train 12 and the contact trains 13 of the boiler 2 in the boiler 2 and in the filter 3 be shipped. The fly dusts 10 (boiler ash and fly ash) are on the boiler tube walls, not shown here, and the E-filter plates. After tapping, discharge devices, also not shown here, such as cellular wheel locks or double flaps that Airborne dusts 10 from an ash conveyor system 14, preferably a trough chain conveyor, a pneumatic conveyor or a screw conveyor. According to the invention the ash conveyor 14 extends close to the high temperature area of the incinerator 1. There the ash conveyor 14 is one Dosing device 15, for. B. a plug screw or a piston pump, downstream. The total dust 10 discharged is in this first Embodiment of the invention via the ash conveyor 14, if necessary with the addition of additives 16, for example water or melting point lowering Substances supplied to the metering device 15.

Via the device 15, the additives 16, if any, are mixed Airborne dusts 10 metered into the high temperature range of the incinerator 1. If the ash (flue dust 10) was added to water 1 before being returned to the oven, so the already cooling effect of the recycled ash is on the surrounding refractory bricks of the incinerator 1 are reinforced. In order to a contribution is made to reducing corrosion. As can be clearly seen in FIG. 1 is in this primary embodiment, the dust 10 in the primary combustion chamber 7 returned.

Of course, it is also possible in another embodiment, the Airborne dusts 10 can be traced back to the high temperature region of the secondary combustion chamber 8 (see Fig. 2). It is crucial that the temperature in this area is higher than the melting temperature or the sintering temperature of the dusts 10 or the mixture of dusts 10 and additives 16, and that the residence time the dusts 10 or the mixture of dusts 10 and additives 16 is so large in this high-temperature region of the incinerator 2, that glazing or sintering of at least some of the dusts 10 takes place. It is particularly favorable if the entire proportion of the returned Product is melted or sintered. Shouldn't the temperatures may be sufficient, via support burner 17 (not shown here), which by means of Oil, gas or waste operations are operated, an additional amount of heat supplied will.

In the high temperature area of the incinerator 1 are according to the invention Means 18 arranged to ensure a sufficient residence time of the ashes. These means 18 can, for example, channels, crucibles, baffles and or Slabs, but also specially shaped refractory bricks.

Then the products created during glazing / sintering slammed the grate ash 19, either dry or over a water bath is discharged wet from the incinerator 1. When the discharge is dry it is important that the ash discharge provides an airtight seal for the combustion chamber forms what is guaranteed in conventional systems by a water lock is. The grate ash 19 is then via methods known per se, for. Legs Dry sorting, further processed.

Fig. 2 shows a second embodiment of the invention. It differs from the first embodiment only in that the dusts 10 after their Discharge from the boiler 2 and the filter 3 via the ash conveyor 14 in one Bunker 20 temporarily stored, then transported to a pelletizing plant 21 and then the pelletized dusts 10, if necessary again mixed with additives 16, in the high temperature range of the secondary combustion chamber 8 can be introduced in doses. The schematically indicated in Fig. 2 external temperature source 17 (burner, burner lance) can the secondary combustion chamber 8 additionally supply thermal energy. This will in everyone If a temperature is guaranteed that is above the melting or sintering temperature the dusts 10 or the mixture of dusts 10 and additives 16 lies, so that the melting / sintering of the ash is supported.

In the third embodiment of the invention shown in Fig. 3 is only a part of the discharged from the boiler 2 and the dust removal system 3 Airborne dusts 10 are returned to the high-temperature region of the primary combustion chamber 7. Before being introduced into the combustion chamber 7, the flying dust 10 gets in a separation chamber 22, in which the dust 10 in a low-pollutant fraction 10.1 and be separated into a pollutant-rich fraction 10.2. Only the low pollutant Fraction 10.1 is on the ash conveyor 14 and the metering device 15 returned to the high temperature area of the incinerator 1 and slammed after the glazing of the grate ash 19.

In Fig. 4 an embodiment of the invention is shown schematically, the differs from the first exemplary embodiment described in FIG. 1 only as a result distinguishes that the dusts 10 after discharge from the boiler 2 and the Filter 3 together with a fraction of the grate ash 19.1, which is smaller than 2 mm and was separated from the rest of the grate ash 19.2 in the sorting system 23 (e.g. at approx. 2 mm grain size), in the high temperature area of the incinerator 1 can be returned.

5 shows a possible embodiment of the in the high temperature range in the primary combustion chamber 7 or arranged in the secondary combustion chamber 8 Means 18 for ensuring a sufficient dwell time of the dusts 10. The stuffing screw 15 is followed by a channel 18 in which the dusts 10 can stay under high temperature conditions for so long that at least partly melt and glaze or sinter and these products can then be slammed into the grate ash 19 or else be recycled separately.

6 shows a further exemplary embodiment. There the firebox is 7.8 Afterburner 26 downstream, which is designed so that the melted Ash 25 can be discharged separately from the grate ash 19. Like the Embodiments already described above can also be used with this type a mixture or a single fraction of the ash (boiler ash, Filter ash, fine fraction of the rust ash) with or without the addition of additives 16 in the combustion chamber 7,8 or the afterburning chamber 26 can be returned.

Another advantage of this design is the ability to get the dust over the nozzles for the secondary air 9 and / or tertiary air 24 in the hot area attributed. In addition, by means of a non-concentric transition between the combustion chamber and the afterburner 26 and / or by tangential Injection of the secondary air 9 or the tertiary air 24 into the afterburning chamber 26 a vortex flow can be generated in the afterburning chamber 26. The vortex leads to better separation of the ash particles on the walls of the afterburner 26. The recycled ash, which by means of the secondary air 9 or Tertiary air 24 is introduced into the afterburner 26 is against the walls thrown, where an ash melt flow caused by the very high temperatures arises. The molten ash 25 flows through the walls of the high temperature afterburner 26 down and is about a specially designed Device 27 removed from the afterburner 26.

Reference list

1

Incinerator

2nd

boiler

3rd

Dust collector

4th

Burn grate

5

rubbish

6

Primary air

7

Primary combustion chamber

8th

Secondary combustion chamber

9

Secondary air

10th

Flying dust
(10.1 low-pollutant fraction from item 10)
(10.2 pollutant-rich fraction of item 10)

11

Flue gas

12th

Radiation train from item 2 13 Touch of pos. 2

14

Ash conveyor

15

Dosing device

16

Additives

17th

Support burner

18th

Means to ensure a sufficient dwell time of the dusts

19th

Rust ash
(19.1 Fraction 1 of item 19)
(19.2 Fraction 2 of item 19)

20th

bunker

21

Pelletizing plant

22

Separation chamber

23

Sorting system

24th

Tertiary air

25th

melted ashes

26

Afterburner

27

Device for discharging item 25 from item 26

Claims (16)

Process for the thermal treatment of fly dusts (10) and optionally Parts of the grate ash (19) from waste incineration plants where the garbage on a combustion grate (4) in an incinerator (1) is burned, with rust ash (19) and flue dust (10) containing Flue gas (11) arise, the grate ash (19) from which a primary (7) and a combustion furnace (1) having a secondary combustion chamber (8) is drawn off and is further processed and which is in a downstream Boiler (2) and settling in a downstream dust filter system (3) Dusts (10) are discharged and at least part of the dusts (10) is melted or sintered, characterized in that that at least some of the dusts (10) are in the high temperature range of the incinerator (1) is returned, the temperature in said high temperature range above the melting temperature or Sintering temperature of the airborne dusts (10) is at least one Part of the dusts (10) in the high temperature area of the incinerator (1) lingers long enough so that it is at least partially is glazed or sintered. A method according to claim 1, characterized in that in the high temperature range of the incinerator (1) glazed or sintered Airborne dusts (10) are then added to the grate ash (19). Method according to claim 1 or claim 2, characterized in that that the total amount of dusts (10) in the high temperature range of the incinerator (1) is returned. Method according to one of claims 1 to 3, characterized in that that the dusts (10) in the high temperature area of the primary combustion chamber (7) can be returned. Method according to one of claims 1 to 3, characterized in that that the dusts (10) in the high temperature area of the secondary combustion chamber (8) can be returned. A method according to claim 1 or 2, characterized in that in the case a partial return of the dusts (10) to the high temperature range of the incinerator (2) the dusts (10) after discharge from the boiler (2) or the dust filter system (3) first into a low-pollutant (10.1) and a pollutant-rich fraction (10.2) are separated and only the low-pollutant fraction (10.1) of the dusts (10) in the High temperature range of the incinerator (1) is returned. Method according to one of claims 1 to 6, characterized in that that the high temperature area of the incinerator (1) in addition Heat is supplied via a support burner (17). Method according to one of claims 1 to 7, characterized in that that the dusts (10) after discharge from the boiler (2) or the Dust separator (3) with a fraction 19.1 of the processed grate ash (19), preferably <2 mm, mixed and then this mixture returned to the high temperature area of the incinerator (1) becomes. Method according to one of claims 1 to 8, characterized in that that the dusts (10) after discharge from the boiler (2) or the Dust removal system (3) transported by means of an ash conveyor system (14) are optionally stored, pelletized and / or moistened and then metered into the high temperature range using suitable means (18) of the incinerator (1). Method according to one of claims 1 to 9, characterized in that that before the introduction of the dusts (10) or the mixture Fly dusts (10) and fine fraction of the grate ash (19) in the high temperature range the incinerator (1) additives (16), preferably water and / or substances which lower the melting point. Method according to one of claims 1 to 10, characterized in that that the returned to the high temperature area of the incinerator (1) Ash by means of secondary and / or tertiary air injection into the Primary combustion chamber (7) or the afterburner (26) is introduced. Method according to one of claims 1 to 11, characterized in that that a vortex flow of the flue gases (11) in the afterburner (26) is produced. Device for the thermal treatment of fly dusts (10) and, if appropriate, parts of the grate ash (19) from waste incineration plants, essentially consisting of a primary furnace (7) and a secondary combustion chamber (8) having a combustion furnace (1) with a combustion grate (4) and one Discharge device for slag and grate ash (19), a boiler (2) downstream of the incinerator (1) with radiation (12) and contact trains (13), and a dust separator system (3) downstream of the boiler (2), the boiler (2 ) and discharge devices for the airborne dusts (10) are arranged on the dust separation system (3) and said discharge devices are assigned to an ash conveyor system (14), characterized in that a) the ash conveyor system (14) extends close to the high-temperature area of the incinerator, b) the ash conveyor system (14) is followed by a metering device (15) for introducing at least part of the returned flue dust (10) into the high-temperature region of the incinerator (1), and c) in the high temperature area of the incinerator (1) means (18) are arranged to ensure a sufficient residence time of the ash. Apparatus according to claim 13, characterized in that as an ash conveyor (14) a trough chain conveyor, a pneumatic conveyor or a screw conveyor can be used. Apparatus according to claim 13, characterized in that as a metering device (15) a stuffing screw or a piston pump will. Device according to claim 13, characterized in that as a means (18) to ensure a sufficient dwell time of the ashes in the High temperature range of the incinerator (1) channels, crucibles, baffles and / or plates are used.

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