WO2010148527A1

WO2010148527A1 - Method for thermally processing combustion residues, in particular filter ash, from trash or waste incineration plants and for recovering metal

Info

Publication number: WO2010148527A1
Application number: PCT/CH2010/000156
Authority: WO
Inventors: Niklaus Seiler; Michel Seiler
Original assignee: Niklaus Seiler; Michel Seiler
Priority date: 2009-06-24
Filing date: 2010-06-15
Publication date: 2010-12-29
Also published as: CH701352B1; CH701352A2

Abstract

The invention relates to a method for thermally processing combustion residues (in particular filter ash) from waste incineration plants (WIP) (10), comprising the following steps: - heating the combustion residues to convert contents of the combustion residues containing harmful substances into the gas phase; - filtering out heavy metals during the gas phase; - filtering off mercury during the gas phase; - introducing residual gases containing dioxins and furans into a waste incineration plant (10); and - landfilling the processed combustion residues. Advantageous developments of the method provide for further processing of the combustion residues so that the processed combustion residues, which have been freed of harmful substances (dioxins, furans, mercury, and/or metal oxides), can eventually be landfilled above-ground.

Description

Process for the thermal treatment of combustion residues, in particular of filter ash, garbage or waste incineration plants and for metal recovery

The invention relates to a method for the thermal treatment of combustion residues, in particular filter ash, from refuse incineration plants (KVA) with the features of claim 1.

Flammable domestic and commercial waste has been disposed of for decades in waste or incineration plants (KVA). The waste incineration works perfectly in these modern plants. On the one hand, it has been possible on the one hand to continuously reduce the environmental impact and to improve the ecological balance through increased exhaust air purification and increasing metal recovery from the slag, and on the other to permanently increase electricity and heat production. Still unsatisfactory solved, however, is the disposal of contaminated with pollutants combustion residues in the form of filter ash, of which, for example, in Switzerland in 2007 about 60'0OO tons accrued and which is mainly burdened with soot, heavy metals, mercury, furan and dioxin ,

Part of this filter ash is still deposited today without pretreatment in underground landfills. Another part of the filter ash is placed in a so-called neutral wash to remove salts. The remaining material from this filter ash is then solidified with cement and can be disposed of in a landfill. In a further alternative treatment process, the filter ash first passes through an acidic wash with hydrochloric acid from the flue gas cleaning. Here, the heavy metals zinc, cadmium and lead are removed and the filter ash then deposited together with the slag from the KVA. Filter ash from the KVA contains up to 5 micrograms of dioxin per kilogram. Does this toxic substance come from improper storage? In contact with oil-contaminated seepage water, it can be mobilized and washed out. Due to their dangerousness, it is therefore necessary to reduce the dioxin emissions to a minimum. In order to reach the limit of 1 microgram dioxin per kilogram of filter ash laid down by the European Union in this context, there is a need to develop a method of effectively reducing the level of dioxin in the filter ash.

A device and a method of the same applicant relate to the mechanical treatment of the filter ash. The treated with this method filter ash from refuse or waste incineration plants is cleaned so far that a landfill of the resulting after this treatment residues can be carried out in underground landfills. By mechanical means, however, other components of the filter ash (eg dioxins (PCDD), furans (PCDF) and mercury (Hg)), some of which are particularly harmful to health and the environment, as well as recyclable metals can not be removed. The overnight storage of the remaining filter ash fractions is therefore out of the question due to the residual contents of pollutants. But also in the underground landfill the contaminated residues are problematic. In addition, mercury and metal oxides contained in the residues can not be recovered as raw materials and additionally problematize the landfill or prevent their economic recovery.

A disadvantage of the mechanically processed filter ash (a name which is also used in the following as a synonym for the combustion residues) is that the deposition must be due to the pollution in underground landfills. This goes hand in hand with much higher costs. In addition, the existing underground landfills are reaching their capacity limits. This necessitates the development of new deposits, resulting in further costs and acceptance problems. The object of the present invention is therefore to provide a method which improves the treatment of incineration residues from refuse or refuse incineration plants, in particular filter ash, to such an extent that landfill of the ash fractions remaining after the treatment can be carried out without difficulty in a subfloor Overground landfill can be done. Furthermore, mercury, salt and metal oxides (in particular also zinc) are to be separated from the filter ash and recycled or recycled into the material cycle.

The object is achieved by a method for the thermal treatment of combustion residues from waste or refuse incineration plants according to claim 1. Advantageous developments of the invention are the subject of the dependent claims.

In the process according to the invention for the treatment of such combustion residues, dioxin (PCDD), furan (PCDF), mercury and metals are first removed from the combustion residues so that the combustion residues treated in this way can be readily disposed of in the underground. Due to the thermal treatment, the specific weight of the ash is increased by about 20%, which is ecologically and economically very important. With an optional additional addition of a cement compound as a binder, the leaching of remaining in the filter ash pollutant residues is prevented and increases the compressive strength of the as pressed in block mold ashes, so that a Überertagdeponierung the filter ash after treatment in the inventive process is straightforward. The method also allows the deposition of the mercury contained in the filter ash and recyclable metals. The recyclable fractions of the filter ash thus obtained can either be separately landfilled or subsequently returned to the material cycle, if this makes more sense from an economic point of view. The same applies to metal oxides, which in the course of the temperature treatment of the filter Ashes are excreted from this. The inventive method can in conventional filter ash recovery, resp. Processing plants, including in those with a so-called. Acid laundry, preceded to improve the degree of purification of the ash.

The process according to the invention comprises process steps for the elimination of dioxin and furan and for the recovery of mercury and / or metals from the filter ash to be treated. In a first step, the filter ash is heated to temperatures between 238 ° C and 1000 ⁰ C (preferably between 356 ⁰ C and 600 ⁰ C, in particular 500 ⁰ C). In this process step, the filter ash passes through the heatable part of a treatment plant, in particular a heated screw or a heated rotary tube. Black particles in the filter ash are lighter and float up the product stream in the treatment plant. In particular, the heating of these black particles in the specified temperature range produces gases in a gasification process. In this case, dioxin, furan, mercury and possibly also parts of the metals present are converted into the gas phase or vaporized and thereby removed from the filter ash. This is done at specific temperatures in a step-by-step process. Thus vaporized mercury, for example, at 356, 6 ⁰ C, while chlorine evaporate at 238.5 ° C and sulfur at 444.7 ° C. With the heating to 500 ⁰ C thus evaporation of all aforementioned components to be eliminated can be achieved. By further increase in temperature up to 1000 ⁰ C and the metal components can be evaporated and then recovered as described above from the gas phase. The zinc economically well usable evaporated, for example, at 907 ⁰ C and is also recorded by heating to close to 1000 ⁰ C.

The pollutants (including chlorine and sulfur) and metal residues are transferred to the gas phase. The ash remaining after heating and degassing thus no longer contains pollutants (such as dioxin). In the other Process steps, the vaporized pollutants are recovered from the steam and recycled (in the case of mercury, metals and metal oxides).

The process can be carried out in any suitable reactor designed for the corresponding parameters. However, it is considered particularly favorable if the process is carried out in a pyrolysis reactor under exclusion of oxygen. The treatment of the residues is then depending on the starting material in indirect or direct pyrolysis. To control the pyrolysis and to achieve certain end products here is the ability to add certain pyrolysis excipients, as well as the pressure ratios, gas mixtures and the duration of treatment set exactly to achieve the best possible efficiency.

Preferably, in a further development of the method, a cooling of the hot gas takes place. For this purpose, this is passed through a heat exchanger and thereby cooled. The heat recovered in this case can be used to increase the energy efficiency of the system, to operate a heater or to generate electricity and the like. By cooling the gases before passing through the filter this is conserved and thus extends its service life. In a further step of the method according to the invention, it is provided to filter out the heavy metals from the gas in order to deposit them separately. It is considered to be advisable to place the filters and / or the heavy metals in a separate depot and store them in order to prevent contamination of the remaining fractions and thus of the environment. It is also possible to exploit the heavy metals, which can be used as an alternative to landfill.

The method according to the invention further provides for passing the gases which have formed during the heating of the filter ash and possibly cooled gases through an activated carbon filter in order to remove mercury and / or metals present in the gas phase. The mercury and / or the metals are thereby bound in the coal of the filter. The remaining after filtration gas now contains only still dioxins and furans. The acted upon with mercury and / or metals coal is recycled in an regarded as favorable, additional process step and the mercury and / or metals thereby recovered. For this purpose, for example, the retrieved from the vapor mercury, resp. the activated carbon, which has taken up mercury, collected in a mercury catch tank and fed to market and environmentally friendly mercury treatment. The same can be done for the collected metals. In a further step of the thermal treatment process according to the invention for filter ash, the gases, which are freed of mercury and / or metals and still containing dioxin and furan, are introduced into a combustion furnace.

Preferably, a further cooling of the treated filter ash. In this context, it is considered favorable to pass the ash (for example after the passage of the above-mentioned heated screw or the heated rotary tube or after treatment in a so-called rotary table process) through or via a heat exchanger in order to increase the energy consumption. Efficiency to recover more heat and to provide the waste heat for further uses.

It is regarded as favorable if separation of these substances from the treated combustion residues takes place by means of magnetic separation for a further separation of metal oxides and metals which were not or not completely evaporated due to excessively low treatment temperatures. The magnetic separation can take place immediately before landfilling. However, it is also possible that this is carried out once or several times in or before each of the abovementioned method sections. It can thus be carried out a further reduction in the burden of pending for landfill combustion residues with these substances. In addition, however, there is also the possibility of recovering economically recoverable residual constituents of the filter ash in order to increase the contribution margin. In a simple embodiment, the filter ash is not desalted or the metal oxide portion is removed only incompletely. While the original ash was more flaky, this is converted by the application of the inventive method in a sandy texture and at the same time increases their specific gravity. Since only mercury, metals, dioxin and furan were removed from the filter ash in the process according to the invention, this ash is suitable for underground deposit. It is therefore considered advisable to further treat the treated filter ash for overnight storage.

A preferred development of the process according to the invention provides desalination and additional recovery of metal oxides from the filter ash. This is done in further steps, which are arranged downstream of the method described above. After the filter ash has been cooled in the heat exchanger, it is not directly dumped, but transferred to a desalination plant and a separation tank. The filter ash, which still contains metal oxides and has not yet been desalted, is first added with water for desalination. To improve the reaction, the water is preferably heated, wherein for heating the water, for example, the heat recovered in the heat exchanger can be used. Subsequently, the thus treated filter ash is stirred in a separation vessel. As low is considered when the stirring of the water-ash mixture using a stirrer. By stirring it comes to a separation of the phases of the water-ash mixture. The heavier parts of the filter ash, which mainly contain metal oxides, settle in the lower part of the separation tank, while the lighter components form the upper phase and form a cementitious layer. The dioxin, which was originally bound in the salt, is released in the dissolution of the salt in the warm water-ash mixture, whereby a further liberation of the filter ash of dioxin is achieved. The upper, separated phase comprising cementitious material has a lower specific gravity than the remaining phase, which still contains heavy metals. loading Preferably, the cement-like material is removed mechanically (for example with a slide) from the separation tank and stored separately.

The method also includes a filtration step for the unpurified salt water resulting from the mixing of filter ash and water. The filtered salt water can then be further treated as purified salt water in downstream process steps. Preferably, the particles filtered out of the salt water are thermally dried with the filter ash or separately. The salt is in dissolved form in the water and can not be held back by the filter. As recommended is considered to dispose of the filtered, saline wastewater, since this is to be regarded as safe in terms of pollutant content.

After desalting the filter ash and removing the cement-like material portion, the heavier metal oxide-containing material remains in the separation vessel. The material is still moist and therefore preferably dried first. This is done in a favorable manner by dripping, for example, after spreading on a grid or sieve. The dripping water can also be disposed of as wastewater due to the safety of the residual content of pollutants. In a further process step, the complete thermal drying of the drained mass is carried out, which can be conveniently resorted to the waste heat from the or the heat exchanger (s).

After drying, the magnetic metal oxides are removed from the material by magnetic separation and thus recovered. Preferably, the dried mass is comminuted for this purpose in order to increase the efficiency of the magnetic separation. It is regarded as favorable if the recovered heavy metals are collected and further treated or separately landfilled. In a further step of the inventive method, the filter ash is collected. The filter ash is now treated and cleaned and contains no salt and almost no metal oxides. The filter ash is now suitable for the daytime Landfill and can be deposited here inexpensively and free of environmental concerns.

Further advantages, features and special features of the invention will become apparent from the following description of preferred (but not limiting) embodiments of the invention with reference to the schematic drawing. It shows:

Fig. 1 is a schematic representation of the sequence of the inventive method and

Fig. 2 shows an advantageous development of the inventive method.

The inventive method is used for the thermal treatment of combustion residues and in particular for the treatment of dioxin, furan, mercury and heavy metal contaminated filter ash from garbage or waste incineration plants (here generally designated by the numeral 10). The process can be preceded or followed by any existing filter ash processing plant. In this case, the upstream is preferable to the downstream, so that the dioxin and furan are removed right at the beginning. It follows thus first a mechanical or chemical treatment of the filter ash and then a thermal treatment. However, it is also conceivable that the thermal of the chemical or mechanical treatment is connected upstream.

In the method shown schematically in FIG. 1, dioxin (PCDD), furan (PCDF) and mercury are removed from the ash, which is taken from the investment filter 20 of a KVA 10 or a mechanical / chemical treatment plant 30. The filter ash treated in this way is capable of being disposed of underground after treatment. Due to the thermal treatment, the specific weight of the ash is increased by about 20%, which is ecologically and economically very important. The mercury is recirculated (as are all metal oxides excreted at this temperature). In the first step of the process, filter ash, which is taken from the (a KVA 10 or a mechanical / chemical treatment plant 30 associated) investment filter 20 is heated in a reactor 11 at 500 ⁰ C. This is done for example by a reactor 11 arranged in the heated screw or by a heated rotary tube (both not shown). The black particles in the filter ash are lighter, float up here and are therefore the most heated. This heating of the black particles to 500 ^° C. produces gases (gasification process). The dioxin, furan and mercury go into the gas phase during the gasification process or evaporate and are thereby removed from the filter ash. For example, at 356.6 ° C mercury evaporates away, but already at 238, 5 ° C chlorine and only at 444, 7 ° C sulfur. In order to achieve reliable evaporation of all relevant pollutants, a reactor temperature of about 500 ^° C. is selected in the process according to the invention. The dioxin-containing residues (including chlorine and sulfur) are thus transferred to the gas phase and in the reactor 11 remains only ash, which contains no dioxin more. In a further method step, the hot gas is introduced into a gas heat exchanger 2, cooled there and thus recovered heat. By this cooling of the gases before passing through the heavy metal filter 3 this is conserved. After the gas heat exchanger 2 heavy metals are filtered out of the gas in the heavy metal filter 3, which can then be spent in the depot 7 and stored.

The resulting in the first steps and subsequently cooled gases flow through the heavy metal filter 3, an activated carbon filter 4, which binds the mercury in the coal. This mercury-laden coal can later be reprocessed and the mercury recovered. The filtration through the activated carbon filter 4 can be further improved by chemical bonding of mercury. The gas is after filtration through the activated carbon filter 4 only dioxin and furanhaltig. The gaseous phase separated mercury or the activated carbon, which received the mercury has, is collected in a mercury catch tank 17 and can then be provided from the mercury catch tank 17 for umweit- and market fair mercury treatment. The liberated from mercury, but still dioxin and furan-containing gases are returned via a gas inlet 5 (for example, a valve) in the combustion furnace 12 of the KVA 10 and eliminated by the high temperatures prevailing there.

The ash heated to separate the pollutants is passed over or through an ash heat exchanger 8 and the filter ash is cooled in this case. The recovered heat can then be fed, for example, into the heat cycle of the KVA 10 and the efficiency of the system can be increased thereby.

After passing through the ash heat exchanger 8, the processed filter ash is collected in a bearing 9. Since the filter ash after removal of mercury, dioxin and furan is not desalted and since the metal oxides have been removed only incomplete, this ash is usually suitable only for underground landfill. Due to the treatment described above, the filter ash is sandy consistency while at the beginning of the process it was flaky. Also, the specific gravity of this recycled filter ash is higher.

FIG. 2 shows a further development of the method from FIG. 1 schematically. This was modified by additional method steps to the effect that desalination and recovery of metal oxides from the filter ash can now also take place. For this purpose, the method shown in Fig. 1 is extended to further process steps for the desalination and recovery of metal oxides.

The steps of the method described with reference to FIG. 1 are identical until the filter ash is cooled in the gas heat exchanger 2. After the filter ash has been cooled while passing through the ash heat exchanger 8, it is passed to a desalination plant 22. There, the filter ash, which still contains metal oxides and which has not yet desalted de, with warm water added for desalination. Subsequently, the thus treated filter ash is stirred in a separation vessel 23 by means of a stirrer 14. By stirring, the heavier parts of the filter ash, namely the metal oxides settle down in the separation vessel 23, while the lighter parts float up and form a white, cement-like layer. The cement-like material, which floats above in the separation vessel 23 under the influence of the agitator 14, has a lower specific gravity than the remainder of the filter ash in the separation vessel 23, which still contains heavy metal. This cement-like material is pushed out of the separation vessel with a slide 15 and stored in a storage container 18. The unpurified salt water from the separation tank 23 is filtered in an intermediate step 19 and then disposed of as purified salt water via a sewer line 13. The filtered out of the salt water particles are transferred with the remaining part of the filter ash from the separation vessel 23 in a drying plant 16.

After desalting the filter ash and removing the cementitious material, the heavier and metal oxide containing portions of the filter ash remaining in the separation vessel 23 are deposited in a drip tray 25 (e.g., on a screen or grate). The dripping water is also disposed of via the sewer 13. After draining, the drained mass is dried completely thermally in the drying unit 16. The dried mass is crushed and all magnetic metal oxides are recovered by magnetic separation 26. These are then provided for further processing 27. The prepared and cleaned filter ash, which contains no salt and only traces of metal oxides, can then be easily stored on an overground landfill 12.

Claims

claims

1. A process for the thermal treatment of combustion residues, in particular of filter ash, from refuse incineration plants (10), comprising the steps:

Heating the combustion residues to transfer harmful constituents of the combustion residues into the gas phase,

- filtering out heavy metals during the gas phase,

Filtering off mercury and / or metals during the gas phase,

- Introducing dioxin and furan-containing residual gases in a refuse incineration plant (10) and

- Landfill or reuse the processed combustion residues.

2. The method according to claim 1, characterized in that heating of the filter ash to temperatures between 238 ° C and 1000 ⁰ C is carried out (preferably between 356 ° C and 600 ⁰ C, in particular 500 ° C).

3. The method according to claim 1 or 2, characterized in that the heating takes place in the heatable part of a treatment plant (30) or in a reactor (11) with a heated screw or a heated rotary tube.

4. The method according to claim 3, characterized in that the reactor is designed as a pyrolysis reactor, wherein the process under oxygen occlusion is feasible.

5. The method according to any one of the preceding claims, further comprising the step:

- Cooling of the hot gases.

6. The method according to claim 5, characterized in that the gases are passed for cooling by a gas heat exchanger (2).

7. The method according to any one of the preceding claims, further comprising the steps:

- Spend the filtered heavy metals in a depot (7) and

- Storage or recycling of the filtered heavy metals.

8. The method according to any one of the preceding claims, characterized in that the filtering off of mercury and / or metals with an activated carbon filter (4).

9. The method according to claim 8, characterized in that treated with mercury and / or metals activated carbon filter (4) and / or the activated carbon and the mercury and / or the metals are recovered.

10. The method according to any one of the preceding claims, further comprising the step:

- Cooling of the treated combustion residues, in particular by means of passage through an ash heat exchanger (8).

11. The method according to any one of the preceding claims, characterized in that the deposition of residual metal oxides and / or metals from the treated combustion residues takes place by means of magnetic separation (26).

12. The method of claim 11, further comprising the step of:

- Prepare the treated incineration residues for underground disposal.

13. The method according to any one of the preceding claims, additionally comprising the steps:

Transferring the combustion residues into a desalination plant (22),

Adding water to the combustion residues to form a water-combustion residue mixture and to dissolve salts from the combustion residues to form salt water,

Separating the phases of the water-combustion residue mixture into an upper light phase and a lower heavy phase,

Separating the upper light phase from the lower heavy phase,

- removing and filtering the salt water,

Dry the lower heavy phase and

- depositing metal oxides from the dried heavy phase.

14. The method according to claim 13, characterized in that the water is heated.

15. The method according to claim 13 or 14, characterized in that for heating the water in the gas (2) and / or ash heat exchanger (8) recovered heat is used.

16. The method according to any one of claims 13 to 15, characterized in that the formation of the water-combustion residue mixture in a separation vessel (23).

17. The method according to claim 16, characterized in that in or on the separation vessel (23) an agitator (14) is provided.

18. The method according to any one of claims 13 to 17, characterized in that for the drying of the lower heavy phase in the gas (2) and / or ash heat exchanger (8) recovered heat is used.

19. The method according to any one of claims 13 to 18, characterized in that the drying is carried out by dripping.

20. The method according to any one of claims 13 to 19, characterized in that the deposition of metal oxides from the dried heavy phase by means of magnetic separation (26).

21. The method according to claim 20, characterized in that the dried heavy phase is comminuted prior to the deposition of the metal oxides.

22. The method according to any one of claims 13 to 21, further comprising the steps:

- collecting the heavy metals and

- Separate dumping of the recovered heavy metals.

23. The method according to any one of claims 13 to 22, further comprising the steps:

- collecting the treated combustion residues and

- Deposit the incineration residues in an over-day landfill.

24. The method according to any one of claims 13 to 23, characterized in that the mechanical separation of the light phase with a slide (15).

25. The method according to claim 24, characterized in that the separated light phase is stored separately.

26. The method according to any one of claims 13 to 15, further comprising the step:

- Landfill and / or discharge into the sanitation of the withdrawn and filtered salt water.

27. The method according to any one of claims 13 to 26, further comprising the step:

- Drying of the particles filtered out of the salt water.