EP0921352B1 - Process for waste incineration and fly ash treatment, and apparatus for carrying out the process - Google Patents

Description

The invention relates to a method for processing fly ash entrained by the fumes emitted during the incineration of household and / or industrial waste, to a household waste incineration process and / or manufacturers including such a process for processing entrained fly ash, and a device for the implementation of these methods.

During the incineration of waste, whether domestic (or assimilated) or industrial, and whatever the incineration process (on a grid, in a fluidized bed, or even in thermolysis), the gases from combustion or thermolysis leads to "fly ash". These fly ash are pulverulent solids made up unburnt particles, silicates and silico-aluminates calcium, inorganic chlorides in particular of heavy metals and alkaline earths such than sodium and potassium chlorides, oxides, sulfates and calcium carbonates as well as metals heavy. These fly ash are collected throughout along the smoke circuit from which they are separated, particular, by filters.

These ashes contain many elements soluble and must therefore be stabilized before dump. The purpose of stabilization is to reduce the soluble fraction which brings with it many pollutants.

We know a method of treating these ashes which consists of washing them in order to dissolve the soluble fraction, the resulting solid then being free pollutants. But in this case, the problem is only moved and then resides in the treatment of liquids polluted resulting from this washing.

It has also been proposed to coat fly ash in plastics or bitumen.

We currently know methods of stabilizing fly ash by hydraulic binders.

However, these methods require the implementation a device or a special installation not integrated into the waste incineration system household and / or industrial themselves. They require more to bring to the site and use reagents such that hydraulic binder, plastic, bitumen or other to achieve their coating.

We also know a vitrification technique of these fly ash which has a drawback additional to the coating or stabilization described above which is a high cost due when using a high temperature.

It has also been proposed to hydrolyze these fly ash but again, you have to use a device or a special installation not integrated in the incineration furnace garbage.

In addition, all of these methods have the disadvantage of always require storage, in landfills of special industrial waste, treated ash or stabilized. However, this storage is expensive and the ashes cannot be used and therefore valued for example in road techniques.

WO-A-8,909,253 describes a reduction method acid gas emissions by reducing agents put in contact with fly ash, this process involving the disposal of said ashes by their transformation into bottom ash in the incinerator.

The invention aims to overcome the drawbacks of the methods of the prior art by proposing a treatment method fly ash entrained by the fumes emitted during the incineration of household waste and / or industrialists by transforming these ashes into bottom ash by clinkérisation.

• collecte desdites cendres le long du circuit des fumées,
• formation d'une pulpe par apport d'eau à ces cendres,
• introduction de la pulpe ainsi obtenue dans le foyer de l'incinérateur de déchets pour transformer les cendres en mâchefers par hydrolyse des chlorures inorganiques contenus dans les cendres, et clinkérisation,
• récupération en sortie de l'incinérateur, par l'extracteur des mâchefers ainsi formés.

To this end, the invention provides a method for treating fly ash entrained by the fumes emitted during the incineration of household and / industrial waste, characterized in that it comprises the steps of:

• collection of said ashes along the smoke circuit,
• formation of a pulp by adding water to these ashes,
• introduction of the pulp thus obtained into the hearth of the waste incinerator to transform the ashes into bottom ash by hydrolysis of the inorganic chlorides contained in the ashes, and clinkering,
• recovery at the outlet of the incinerator, using the bottom ash extractor thus formed.

The invention uses a reverse reaction to WO-A-8,909,253 allowing the elimination of inorganic chlorides and leading to the formation of hydrochloric acid.

According to a variant of the invention, said supply of water is made by adding water alone.

According to another variant of the invention, said contribution water is made by adding wet sludge water, organic matter and mineral matter such as sludge from stations water purification or black liquors from paper mills.

According to a feature of the method of the invention said pulp has a dryness of between 20 and 40% by weight.

According to an embodiment of the method of the invention, a mixture of said pulp is produced with household and / or industrial waste before introduction of this mixture by the normal means of introducing household and / or industrial waste.

According to another embodiment of the method of the invention, household and / or industrial waste is introduced by normal means of waste introduction and the pulp is introduced by means of introduction separate located upstream and in the cold zone of the the incinerator.

According to yet another embodiment of the method of the invention, the pulp and household waste and / or manufacturers are introduced by separate means, the household and / or industrial waste being introduced by the normal way of introducing waste and pulp being introduced directly into the hearth of the incinerator.

The invention also relates to an incineration process household and / or industrial waste, characterized in that that he understands the treatment of fly ash driven by the fumes emitted during this incineration by the process described above.

• un moyen d'introduction des déchets dans le foyer d'un incinérateur,
• un extracteur situé en sortie basse du foyer, pour récupérer les mâchefers ainsi formés,
• un moyen de séparation des cendres volantes des fumées, pour épurer ces fumées,
• un moyen d'extraction et d'évacuation des fumées épurées,

caractérisé en ce qu'il comprend de plus :

• au moins un moyen de récupération des cendres volantes le long du circuit des fumées, relié à un malaxeur,
• un moyen d'alimentation en eau relié au malaxeur,
• un moyen de transport de la pulpe formée dans le malaxeur, reliant la partie basse du malaxeur, directement ou indirectement, au foyer de l'incinérateur pour amener la pulpe dans le foyer afin de transformer les cendres en mâchefers par hydrolyse des chlorures inorganiques contenus dans les cendres et clinkérisation.

It also relates to a device for implementing the methods described above comprising:

• a means of introducing waste into the hearth of an incinerator,
• an extractor located at the bottom outlet of the hearth, to recover the clinkers thus formed,
• a means for separating fly ash from the smoke, to purify this smoke,
• a means of extracting and evacuating the purified smoke,

characterized in that it further comprises:

• at least one means for recovering fly ash along the smoke circuit, connected to a mixer,
• a water supply means connected to the mixer,
• a means of transporting the pulp formed in the mixer, connecting the lower part of the mixer, directly or indirectly, to the hearth of the incinerator to bring the pulp into the hearth in order to transform the ashes into bottom ash by hydrolysis of the inorganic chlorides contained in ash and clinkering.

According to a characteristic of the device of the invention, said means of transport is connected to the household by the means of introduction opening into the chute located under the normal hopper for the introduction of household waste and / or industrial.

According to a variant of the device of the invention, said means of transport is connected to the household by the hopper normal introduction of household waste and / or industrial.

According to another variant of the device of the invention, said introduction means is connected directly to the fireplace, in hot zone.

According to another characteristic of the the invention, the means of transporting the pulp is a pump associated with a conduit.

According to yet another characteristic of the device the invention, the means of transporting the pulp is consisting of bulk mechanical conveyors, with belts or bucket.

The invention will be better understood, and other advantages and purposes of it will appear better on reading the explanatory description which will follow and which is given in reference to the attached single figure which represents a device for implementing the method of the invention.

First, the waste incineration process household and / or industrial of the prior art will be described with reference to the attached single figure.

The waste to be incinerated is introduced through the hopper 11 and the chute 9 in a combustion hearth 10 where they are cremated.

The incinerator used in this process can be either a oven without heat recovery, in which case all ash is collected under filter 2, i.e. a furnace-boiler that is to say an oven equipped with the hearth 10 and a heat recovery means constituted by the boiler 1, in which case the ashes are recovered from a partly under the boiler 1 and partly under the filter 2.

During this incineration, on the one hand, clinkers which are evacuated at the bottom of the hearth 10 by a extractor 12, and on the other hand, combustion gases or fumes in which fine particles are entrained called fly ash. These fumes are evacuated by the top of the hearth 10 and cooled. They then pass by a filter 2 to separate the solid particles from the gas phase and the gas phase purified in the smoke treatment 16 is released to the atmosphere by a fan 13 and a chimney 14. The ashes retained in filter 2 are collected under this filter and are routed, for example by screws 3, 4, for storage, for example in a container not shown.

The fly ash is then further processed in another device, before storage.

In contrast to this classic process, the invention proposes to process the fly ash continuously and in the same installation as that planned for the treatment of waste themselves.

To this end, the invention proposes to collect the all of the ashes, and mix them in a mixer 5 with water from an introduction means 6. In the mixer 5, a pulp is formed which is then injected by a means of transport 7, 8, into the hearth 10. This reintroduction of ashes, in the form of pulp in focus 10 can be done either directly in the hearth 10 and in the hot zone, by a device sludge injection known per se, either with waste to be incinerated, in a cold zone. In this case, the pulp may either be mixed with the waste to be incinerated before introduction of this pulp / waste mixture through the hopper 11, either injected by a separate introduction means, in the chute 9.

Introducing recycled ashes directly in the hearth, in the form of pulp, advantageously avoids the immediate ash entrainment by the gases of combustion.

In foyer 10, regardless of the introduction site pulp, hydrolysis of chlorides, in particular of sodium and potassium in the ashes product, when the pulp is brought to a temperature high of about 850 ° C, in hearth 10. In the same time, the ashes are clinkerized and turned into clinkers.

Thus, with the method of the invention, there is no longer need to process or store fly ash circulating in the incineration plant.

Indeed, the fly ash turns into clinkers under the effect of the heat brought directly by burning waste.

The process for handling fly ash from the invention is therefore particularly advantageous because it transforms ash into bottom ash, which is easily recyclable and therefore recoverable. In addition, this process directly uses the thermal energy of the household and / or industrial waste incinerator and minimizes the thermal energy required to process ash which only affects the surface of the grains of ashes and not the whole mass of these grains, and this without addition of reagent. In addition, the chlorine present in these ash is removed as hydrochloric acid by hydrolysis of alkali and alkaline earth chlorides and heavy metals, this hydrochloric acid then being retained in the smoke treatment system including the incineration plant is regulated equipped. This process also removes unburnt from carbon in the form of carbon dioxide. So putting in the form of fly ash pulp, besides the fact to bring the water necessary to obtain a mass of easily transportable ash, more particularly easily pumpable, to simplify the process injection into the incinerator, advantageously allows hydrolysis of the chlorides contained in these ashes.

Water to make an easily transportable pulp, preferably by a pump, and to hydrolyze the chlorides is supplied by either water alone or, advantageously, by the water contained in sludge wet from water treatment plant. In the latter case, we save the water that should have been used to make the pulp. In addition, the clinkerization of ash and incineration of sludge from water treatment plants are performed in a single operation.

In the process of the invention, it should be noted that more heavy metals entrained and fixed on the ashes are themselves thus fixed in the silico-aluminous matrix ash by substitution of calcium atoms during clinkering. Indeed, clinkering is a surface vitrification which allows reactions between particles of silicates and silico-aluminates of calcium and molten sodium and potassium oxides. then of this operation at high temperature (800 to 1000 ° C) the particles agglomerate, become larger and heavier and are not driven by the flow of smoke: they remain in bottom ash, the physical or chemical characteristics are identical.

So because of this clinkering or vitrification of surface heavy metals are fixed in silico-aluminates of calcium and are not soluble.

In order to better understand the invention, we will describe now as purely illustrative examples several modes of implementation.

Example 1

As described with reference to the appended figure, the waste is introduced through the hopper 11 and the ashes are collected under the boiler 1 and under the filter 2 and are routed by screws 3 and 4 to a mixer 5. For 1 tonne of waste, the ash represents approximately a weight of 20 kg of dry matter.

The mixer 5 is supplied with water by the means introduction 6. Water is dosed by a system volumetric or classical mass so as to obtain out of the mixer a pulp having a dryness, that is to say a dry matter content, which allows it to be easily pumped by a pump 7 known per se. Preferably the pump 7 is volumetric. She sends the pulp through the conduit 8 and the introduction means 15 located in the chute 9 in the hearth 10.

The pulp is introduced into the hearth 10 at the same time that the waste and we will make sure to distribute the pulp on the entire width of the chute 9.

Arrival in the hearth, the pulp is subjected to reactions hydrolysis and clinkerization described above and is integrated into clinkers of which it has the same physico-chemical characteristics.

In the case where part of the pulp is re-driven by the fumes, because containing too many particles particles will be stopped again by the filter 2 and recycled to the hearth 10 via the mixer 5 and the reformed pulp. Thus, the invention allows a continuous treatment and complete elimination of the need to dispose of fly ash.

Example 2

In the same way as in Example 1, 20 kg of ash from the incineration of 1 ton of waste are collected under the boiler 1 and under the filter 2 and are routed by screws 3 and 4 to the mixer 5.

Unlike example 1, the mixer 5 is fed, by the introduction means 6, with wet sludge from water treatment plants. In that case, 150 kg of sludge at 20% by weight of materials are used dry, which gives a pulp with a dryness of 30% which is still easily transportable, for example by pumping. However, a means of transport is used here mechanical consisting of a series of mass conveyors or belt and bucket elevator. The pulp is mixed with the waste to be incinerated before introduction of this mixing by hopper 11. The pulp / waste mixture to to be cremated is then sent to hearth 10 where the fly ash undergoes hydrolysis reactions and of clinkering described above and are integrated clinker resulting from waste incineration themselves.

As in Example 1, the clinkerized ashes have then the same physico-chemical characteristics as clinkers.

Example 3

The procedure is as in Example 1, except that the pulp is directly introduced into the hearth 10. Again, the pulp will be hydrolyzed and clinkered and integrated into the clink as in examples 1 and 2.

As can be seen from the above, while in the processes of the prior art, the ashes are considered as special waste and disposed of after costly stabilization, in waste landfills special industrial, thanks to the invention, these ashes are free of the chlorine they contain and they are thermally stabilized by clinkering and transformed into valuable bottom ash.

The ash treatment process and device flying driven by the fumes from the incineration of household and / or industrial waste according to the invention and as described above, can of course be integrated into a process and a waste incineration device, respectively industrial and / or household goods of the prior art.

Therefore, the invention also encompasses all of the household waste and / or incineration processes manufacturers that include the processing step ash entrained by the fumes from the incineration of household and / or industrial waste and which consists of collecting these ashes, transforming them into aqueous pulp and to recycle them, in the incinerator of waste, to clinkerize it and integrate it into clinkers produced in this incinerator.

In the same way, any device for the incineration of household and / or industrial waste which includes the ash treatment device entrained by fumes from the incineration of household waste and / or industrial and which includes a means of transformation, recovery and transformation of ash into pulp aqueous and a means of injection and recycling of this aqueous pulp in the incinerator is encompassed by the invention.

The method and the device of the invention are not limited to injection means, pulp transport, obtaining pulp and recycling this pulp in the fireplace described and illustrated here, as long as these means are used to recycle the ash entrained in the gases from the incineration of household waste and / or industrial, in the form of aqueous pulp, in the incinerator itself.

Claims (13)

1. A process for the treatment of fly ash carried by the flue gases emitted during incineration of household and/or industrial waste, characterised in that it comprises the stages of:

   collecting said ash along the flue gas circuit.

   forming a pulp by admixture of water to the ash,

   introducing the pulp thus obtained into the furnace (10) of the waste incinerator (1) to convert the ash into clinker by hydrolysis of the inorganic chlorides contained in the ash, and clinkering,

   recovering the clinker thus formed at the outlet of the incinerator (1) by means of the extraction apparatus (12).
2. A treatment process according to Claim 1, characterised in that said admixture of water is realised by the addition of water alone.
3. A treatment process according to Claim 1, characterised in that said admixture of water is effected by adding moist sludges constituted by water, organic matter and mineral matter, such as the sludges produced by water purification plants or the black liquors produced by paper-making plants.
4. A process according to any one of the preceding claims, characterised in that said pulp has a dry content of between 20% and 40% by weight.
5. A process according to any one of the preceding claims, characterised in that a mixture of said pulp with household and industrial waste is produced before the introduction of this mixture via the introduction means (11) for the industrial and/or household waste.
6. A process according to any one of Claims 1 to 4, characterised in that said household and/or industrial waste is introduced via the normal introduction means (11) and in that said pulp is introduced via a separate introduction means (15) located upstream of and in the cold zone of the furnace (10).
7. A process according to any one of Claims 1 to 4, characterised in that said pulp and said household and/or industrial waste are introduced via separate introduction means, the household and/or industrial waste being introduced via the normal introduction means (11) and the pulp being introduced directly into the furnace (10) of the incinerator (1).
8. A process for incineration of household and/or industrial waste, characterised in that it comprises the treatment of the fly ash carried by the flue gases emitted during this incineration by the process according to any one of Claims 1 to 7.
9. An apparatus for carrying out the process according to any one of the preceding claims, comprising:

   a means (11) of introduction of the waste into the furnace (10) of an incinerator (1),

   an extraction apparatus (12) located at the low outlet of the furnace (10) for recovering the clinker thus formed,

   means (2) for separating the fly ash from the flue gas, in order to clean said flue gas,

   means of extraction (13) and discharge (14) of the cleaned flue gas,

   characterised in that the apparatus additionally comprises:

   at least one means (3, 4) for recovering the fly ash along the flue gas circuit connected to a mixer (5),

   a means for supplying aqueous solution (6) connected to the mixer (5),

   means (7, 8) for transporting the pulp formed in the mixer (5) which connect the lower portion of the mixer (5) directly or indirectly to the furnace (10) of the incinerator (1) in order to feed the pulp into the furnace (10) in order to convert the ash into clinker by hydrolysis of the inorganic chlorides contained in the ash, and clinkering.
10. An apparatus according to Claim 9, characterised in that the transport means (7, 8) is connected to the furnace (10) via the introduction means (15) which opens into the chute (9) located below the hopper (11) for the normal introduction of household and/or industrial waste.
11. An apparatus according to Claim 9, characterised in that the transport means (7, 8) is connected to the furnace (10) via the hopper (11) for the normal introduction of household and/or industrial waste.
12. An apparatus according to Claim 9, characterised in that the transport means (7, 8) is connected directly to the furnace (10) in the hot zone.
13. An apparatus according to any one of claims 9 to 12, characterised in that the transport means (7, 8) is a pump (7) associated with a pipe (8).

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