FR2740059A1 - Inertisation of residues from waste incineration fumes using high vitrified ground furnace slag - Google Patents

Abstract

A method for inertising residues from waste incineration fumes consists of mixing residues with water and slag of high vitrified ground furnace, the slag activated by the elements constituting the residues. A solid material containing residues from waste incineration fumes, slag of high vitrified ground furnace and water is also claimed. Its composition is: (i) residues:slag ratio between 85:15 and 95:5. (ii) water content of 30-55 wt.% of solid residues-slag mixture, or 35-45 wt.% when compacted and 55 wt.% when vibrated. Its 28-day compression strength is at least 1MPa or preferably greater than 3 MPa.

Description

Process for inerting smoke purification residues
incineration of waste using high slag
vitrified vitrified vitrified furnace comprising said
residues.

 The invention relates to a process for inerting residue for purification of waste incineration fumes using ground vitrified blast furnace slag as well as the solidification comprising said residues.

 Waste, whether industrial or household waste, due to their ever increasing production, are the target of increasingly drastic legislation both in terms of their treatment and that of their storage .

 Indeed, waste may contain elements more or less toxic to humans and the environment and it is necessary to stabilize them by appropriate treatment before storage.

 Landfilling pure and simple has long been considered both a mode of treatment and a way of storing waste, which could be extremely harmful to the environment by pollution, especially underground, that could cause . Thus, the regulations in force now go in the direction of limiting the role of the landfill. Indeed, regulations tend to allow only the storage of so-called "ultimate" waste, ie "waste resulting or not from waste treatment, which are no longer likely to be treated under the conditions technical and economic aspects of the moment, in particular by extracting the recoverable part or by reducing their polluting or dangerous nature (Decree of 18 February 1994 - Article 3). "Most waste must therefore undergo appropriate treatment prior to their implementation. discharge.

Currently, there are essentially three main modes (excluding recycling or landfill) of waste treatment
- the physicochemical treatment,
- biological treatment,
- heat treatment or incineration.

 Physicochemical treatment consists in concentrating, separating, mitigating the toxicity, inerting and conditioning all or part of the toxic elements (mineral or organic) that make up the waste and is mainly intended for industrial waste, solid, liquid, or pasty, not fuels. ("Engineering Techniques" A8660C4260).

 Biological treatment consists of aerobic or anaerobic biological treatment of waste for the purpose of energy recovery (biogas, alcohol) or agricultural (composting) and is mainly intended for biodegradable organic waste. It usually requires pre-treatments.

 The heat treatment consists of a combustion of the waste and has two objectives: almost total elimination of the waste and recovery of the energy of the reaction. It is intended for all types of waste, provided that the calorific value of the waste is sufficiently high.

 Incineration, as the main method of heat treatment of waste, should be considered in a broad sense as it includes not only a stage of incineration itself waste in an incineration chamber, such as a boiler or a furnace at a temperature of about 8000 C, or by means of a plasma torch, but also a subsequent step of treating the fumes by washing with alkaline water (wet process), with lime milk (semi-wet process ) or by injecting pulverulent lime, previously or not cooled by water injection (semi-dry and dry processes), after which the purification residues are filtered using a bag filter or an electrostatic precipitator (except in the case of the wet process for which an upstream dust removal is performed).

 At present, the current regulations require incineration plants not only to treat fumes prior to the release of gases into the atmosphere, but also to stockpile residues for the purification of these fumes. incineration, with the imperative condition that these residues are stabilized before storage.

 As regards the treatment of the fumes, different purification residues are obtained according to the nature of the treatment used.

 In the case of a wet treatment, the electrostatic precipitator is placed before the flue gas treatment device and recovers the fly ash which may contain heavy metals. At the end of the scrubber, the other residues are recovered in the form of an aqueous cake and a filtrate and must undergo an additional treatment consisting of solidifying the cake obtained and treating the filtrate in order to stabilize the toxic elements of the cake before storage and to release the treated water in nature.

 In the case of a semi-wet, semi-dry or dry treatment, the filter is generally placed after the flue gas treatment zone, which is carried out by injection of lime in various forms. The electrostatic precipitator then captures the dry residues consisting of ash and salts including those of heavy elements.

 With regard to the inerting of the incineration flue-cleaning residues, it consists in particular of improving the mechanical and physical properties of the waste, limiting the exchange surface with the surrounding environment and minimizing the permeability to the water of the residues as well as their leachable fraction, that is to say the fraction of their constitutive chemical elements likely to come back into the wild by the effect of, for example, the runoff of water. The inerting thus comprises, in accordance with the legislation in force, a phase of solidification of said residues which, as they are recovered after incineration of the waste, are in pulverulent form, as well as a phase of stabilization.

Inerting or solidification / stabilization processes, residues of purification of household waste incineration fumes (REFIOM) have already been described. They consist in particular
- washing electrostatic precipitator ash with stirring at basic pH and solidifying the filter cake as well as the filtrate obtained by a hydraulic binder, lime and other additives, (SULZER process)
- to solidify electro-filter ash and chlorinated residues by means of two reagents rich in anhydrous aluminates and silicates such as slag and fly ash or pozzolans as well as liquid reagents and catalysts, (ASHROCK process)
- to stabilize residues by means of steel by-products or pozzolanic elements such as slag and fly ash, cements and other catalyst additives, (PETRIFIX process)
- to use special hydraulic binders, reagents acting on the species contained in the waste, additives and various additives to solidify / stabilize the REFIOM, (INERTEC process)
- to use silicates and setting agents, (CHEMFIX process)
- to carry out a pretreatment before solidification of the waste by food materials, (SEALOSA process
FE)
- to bring into play pozzolanic reactions by adding lime and fly ash, (IUCS process)
- to bring into play pozzolanic reactions (fly ash and lime), with the addition of sulphates helping to cure, (ENVIROSAFE SERVICE Inc.)
to use a molten aluminous cement in order to trap the heavy metals in the cementitious matrix, and in particular to incorporate them into the crystalline structure of ettringite (LAFARGE process).

 However, these processes have the disadvantage of being complex, by the treatments they make to the residues to be solidified and / or by the diversity of reagents and additives they implement, which are expensive and require moreover be used in large quantities to be effective.

 Moreover, most of these processes use Portland cement or clinker cements, often expensive, to effect the solidification in question and it should be emphasized that these are not durable in the presence of chlorides. Sewage residues contain a lot of chlorides, in particular residues resulting from dry and semi-dry or semi-wet fume treatments, which contain many more chlorides and lime than those resulting from wet treatments. It is precisely the case that the current regulation is in the sense of limiting wet treatment processes for fumes, in order to avoid the rejection of the filtrate, even if it is treated, in the soil.

 The present invention therefore proposes to overcome the drawbacks of the prior art and is intended to carry out the inerting by solidification of wastewater purification residues of incineration waste, so as to confer at least the minimum required resistance current legislation, namely 1 MPa, while stabilizing the said residues.

 Thus, the Applicant Company, after extensive studies, has developed a method to inert a maximum of residues in a minimum volume using a minimum of additive.

 In addition, it should be emphasized that the cost of such inerting is reduced not only by the fact that the amount of additive used is minimized, but also by the fact that said additive is itself a residue of the metallurgical industries: the ground vitrified blast furnace slag, which has the advantage of being inexpensive.

The slag is not and does not behave like a traditional cement in the sense that it needs, to make, an activator. In fact, several activators enter into the normal chemical constitution of the residues that the process according to the invention proposes to inert and may be in the form of: CaClOH, CaSO 4,
CaCl2, Ca (OH) 2 or CaO or compounds of these minerals. Of course, a minimal amount of activator is required to activate a certain amount of slag. It should be emphasized, however, that in the context of the present invention, no additional activator is necessary.

 It should be noted that other constituents of the residues such as NaCl or KCl can affect the conditions of the setting in the solidification phase.

 The process of inerting, or solidification / stabilization, of the residues of purification of waste incineration fumes is thus characterized by the fact that one uses ground vitrified blast furnace slag (latent hydraulic binder) and that it is activated by the constituent elements of wastewater treatment waste incineration waste.

The process of inerting the residues of purification of waste incineration fumes, using slag, according to the invention, is also characterized by the fact that it consists in mixing residues of purification of the fumes of incineration of waste, ground vitrified blast furnace slag, and water in such proportions that
the ratio of residues: slag is between 70:30 and 95: 5, preferably between 85:15 and 95: 5,
the overall quantity of water used represents from 30 to 55%, preferably from 35 to 45% by weight, relative to the solid mixture (slag and residues) for placing the material by compacting, and 55% order for vibration placement.

The residues comprise at least 10% by weight of calcium, (especially in the form of CaSO4, CaO, Ca (OH) 2,
CaCl 2), 2% by weight of sulphates (for example in the form of
CaSO4, Na2SO4) and 5% by weight of chlorides (for example in the form of CaCl2, NaCl or KCl).

According to an advantageous embodiment, the method according to the invention consists
to mix and mix the slag with 4/5 of the total quantity of water used,
to add to this mixture the residues of purification of waste incineration fumes and to continue mixing,
to add to the mixture thus obtained the remaining 1/5 of the total quantity of water used and to continue mixing,
to introduce the final mixture into molds,
- Store the molds before demolding in a humidity of less than 85%.

According to an even more advantageous embodiment, the process according to the invention consists
- Mixing the slag and 4/5 of the water at a speed between 40 and 200 revolutions / min, preferably of the order of 140 revolutions / min, for a period of between 20 and 60 seconds, preferably of the order of 30 seconds,
- Continue mixing after adding the residues to the previous mixture at the same speed for a period of between 20 and 60 seconds, preferably of the order of 30 seconds, then to continue the mixing for a period of between 50 seconds and 70 seconds preferably of the order of 60 seconds at a speed of between 100 and 350 rpm, preferably of the order of 285 rpm,
to continue mixing again after adding the 1/5 of remaining water at a speed of between 100 and 350 rpm, preferably of the order of 285 rpm, for a duration of between 50 seconds and 70 seconds; preferably of the order of 60 seconds.

 Advantageously, in order to facilitate the introduction of the material, to obtain a better workability or a better compactness of the material, during the inerting process according to the invention, one or more adjuvants chosen from water-reducing or fluidifying superplasticizers, setting retarders, antifoam agents.

 The aforesaid adjuvants may be added to the mixture either individually or in combination in an amount representing from 0.5 to 5% by weight of solid material, this amount being fixed depending on the residue to be treated and the conditions of implementation required.

 For an optimum result, the adjuvant or adjuvants are added to the mixture either during the first water incorporation phase or during the second water incorporation phase, depending on the residue. to be processed and the conditions of implementation required.

According to another advantageous embodiment of the invention, the introduction of the final mixture into the molds can be carried out
- by vibration, which allows a simple introduction by pouring the material into the molds,
by compacting, which makes it possible not only to provide, for the manufacture of the solidifiats to be compacted, a quantity of water which is much lower than that required for a traditional placement by casting, independently of the use of water reducers such as described above, but also an immediate release of solidifiat thus obtained, the compacting being preferably carried out at a pressure of the order of 1 MPa.

 Advantageously, the storage of the molds is carried out in an atmosphere having a moisture content of between 55 and 85%, preferably between 60 and 70%, and a temperature of between 15 and 30 C, preferably of the order of 20 to C.

 Apart from the REFIOMs or wastewater treatment residues of conventional industrial waste incineration, the process according to the invention is also applicable to the inerting of radioactive residues resulting for example from the incineration of radioactive waste themselves. , or other contaminated residues such as for example from the incineration of hospital waste.

 The invention also relates to the "bread" or solidifiat as it can be obtained by carrying out the inerting process described above.

The solidifiat according to the invention therefore comprises residues for the purification of waste incineration fumes, ground vitrified slag, and water, in which
the ratio of residues: slag is between 70:30 and 95: 5, preferably between 85:15 and 95: 5,
the water represents 30 to 55% relative to the weight of the solid phase, preferably 35 to 45% for placing the material by compacting and of the order of 55% for placing the material by vibration.

The residues comprise at least 10% by weight of calcium (in particular in the form of CaSO 4, CaO, Ca (OH) 2, Cal 2), 2% by weight of sulphates (for example in the form of
CaSO4, Na2SO4) and 5% by weight of chlorides (for example in the form of CaCl2, NaCl or KCl).

 According to this advantageous embodiment of the invention, the solidifat in question has a compressive strength at 28 days of at least 1 MPa and preferably greater than 3 MPa.

 The present invention is not limited to the description which is made above but encompasses all variants. In particular, in the case of a construction site, some modifications can be made. The following example illustrates the present invention and allows to better understand it but it can not be considered as limiting.

Example:
Waste from household waste incineration residues (REFIOM) was inerted from a dry process with a vitrified ground blast furnace slag in the following proportions
the residue / slag ratio was varied in the following proportions: 80/20; 85/15; 90/10; 95/5,
the total amount of water used represents 40% by weight relative to the weight of the solid phase (Refiom + slag).

The chemical composition in major elements of the
REFIOM is given in Table 1.

 The chemical composition of the slag and its characteristics are given in Table 2.

Table 1:
Chemical composition of the REFIOM from a dry process

<tb><SEP> ELEMENTS <SEP>% <SEP> ON <SEP> MASS <SEP> DRY
<tb><SEP> C <SEP> 1,3
<tb><SEP> C1 <SEP> 6.2
<tb><SEP> Ca <SEP> expressed <SEP> in <SEP> CaO <SEP> 50.5
<tb><SEP> If <SEP> expressed <SEP> in <SEP> SiO2 <SEP> 23.4
<tb><SEP> Al <SEP> expressed <SEP> in <SEP> A1203 <SEP> 13.4
<tb><SEP> Fe <SEP> expressed <SEP> in <SEP> Fe203 <SEP> 2.5
<tb><SEP> Mg <SEP> expressed <SEP> in <SEP> MgO <SEP> 2,3
<tb><SEP> S <SEP> expressed <SEP> in <SEP> S03 <SEP> 1.8
<tb><SEP> Na <SEP> expressed <SEP> in <SEP> Na2O <SEP> 0.5
<tb><SEP> K <SEP> expressed <SEP> in <SEP> K20 <SEP> 0.5
<tb> Surface <SEP> specific <SEP> Blaine <SEP>: <SEP> Mass <SEP> volumic <SEP> apparent
<tb><SEP> 9600 <SEP> cm2 / g <SEP>: <SEP> 0.4 <SEP> g / cm
<Tb>
Table 2
Chemical composition and physical characteristics of slag

<tb><SEP> ELEMENTS <SEP> EXPRESSES <SEP> IN <SEP>% <SEP><SEP> ON <SEP> MASS <SEP> DRY
<tb><SEP> OXYDES
<tb><SEP> SiO2 <SEP> 33.24
<tb><SEP> Fe203 <SEP> 0.99 <SEP>
<tb><SEP> A1203 <SEP> 10.38
<tb><SEP> CaO <SEP> 45.49
<tb><SEP> MgO <SEP> 6.13
<tb><SEP> K20 <SEP> 0.54
<tb><SEP> Na20 <SEP> 0.35
<tb><SEP> Mn203 <SEP> 0.34
<tb> Surface <SEP> specific <SEP> Blaine <SEP>: <SEP> Mass <SEP> volumetric <SEP> actual
<tb><SEP> 3030 <SEP> cm2 / g <SEP> 2.9 <SEP> g / ca3 <SEP>
<Tb>
This REFIOM was mixed with the slag according to a preferential mixing method
4/5 of the total amount of water is incorporated with the slag, kneaded at a speed of 140 rpm for a period of 30 seconds,
- REFIOM is incorporated, kneaded at a speed of 140 rpm for a period of 30 seconds,
the mixture described above is kneaded at a speed of 285 rpm for a period of 1 minute,
the 1/5 of the remaining water is incorporated, kneaded at a speed of 285 rpm for a period of 1 minute.

The mixture, the production of which has been described above, was incorporated into molds of dimensions 4x4 × 16 cm according to a preferred embodiment.
said mixture is incorporated in a mold of standardized dimensions in accordance with the standard EN 196-1 (mold provided for 3 test pieces 4x4x16 cm), by distributing the same mass of material in each of the 3 compartments,
a uniformly distributed pressure of 1 MPa is applied to the material,
the test pieces are demoulded 1 hour after being put in place, taking care not to apply bending thereto.

 Mechanical strength tests were carried out on solidifiats aged 35 days, according to EN 196.1. The results obtained are given in Table 3.

Table 3
Mechanical characteristics at 35 bears solidifiats of
REFIOM

<tb><SEP> Resistance <SEP> to <SEP> Resistance <SEP> Mass
<tb><SEP> Report <SEP><SEP> Pull <SEP> to <SEP><SEP> Volumetric
<tb> residue / slag <SEP> by <SEP> bending <SEP> apparent <SEP> compression
<tb><SEP> (MPa) <SEP> (MPa) <SEP> (g / cm3)
<tb><SEP> 80:20 <SEP> 2,17 <SEP> 8.25 <SEP> 1.41
<tb><SEP> 85:15 <SEP> 1.9 <SEP> 6.75 <SEP> 1.39
<tb><SEP> 90:10 <SEP> 1,17 <SEP> 5 <SEP> 1,30
<tb><SEP> 95: 5 <SEP> 1.3 <SEP> 4.75 <SEP> 1.12
<Tb>
Note: the minimum compressive strength required by law is 1 MPa.

 It should be pointed out that compressive strength tests carried out at 90 days have shown an increase in resistance over time of around 40%. The material described above, 95% residues, was subjected to the leaching test according to the X31-210 standard and it perfectly meets the stabilization criteria vis-à-vis the stabilization of heavy metals.

A significant increase in the apparent density of the REFIOMs can be noted, since it goes from 0.4 for the REFIOM alone to 1.12 for the 95% solidifiat of
REFIOM.

 It should be noted that the minimum normative value of 1 MPa is very largely achieved.

Claims (15)

 1. A process for inerting wastewater purification residues of waste incineration, characterized in that it consists in mixing said purification residues with water and ground vitrified blast furnace slag, the activation of the slag being carried out by the constitutive elements of said purification residues.  2. inerting process according to claim 1, characterized in that the mixture of the waste residues of waste incineration fumes, ground vitrified blast furnace slag and water is carried out in such proportions that  the ratio of residues: slag is between 70:30 and 95: 5, preferably between 85:15 and 95: 5,  the overall amount of water used represents from 30 to 55% by weight relative to the dairy solid-residue mixture, preferably from 35% to 45% in the case of compacted placement, and preferably of the order of 55% in the case of implementation by vibration.  3. inerting process according to either of claims 1 and 2, characterized in that the residues comprise at least 10% by weight of calcium, 2% by weight of sulfates, 5% chlorine.  4. Method of inerting according to any one of claims 1 to 3, characterized in that it consists of:  - mix and mix the slag with 4/5 of the total quantity of water used,  - add to this mixture the residues of purification of the waste incineration fumes and continue the mixing,  - add to the mixture thus obtained the remaining 1/5 of the total amount of water used and continue the mixing,  - introduce the final mixture into the molds,  - Store the molds before demolding in a humidity atmosphere of less than 85%.  Inerting process according to claim 4, characterized in that it consists in  - Mixing the slag and 4/5 of the water at a speed between 40 and 200 revolutions / minute, preferably of the order of 140 revolutions / minute, for a period of between 20 and 60 seconds, of preferably of the order of 30 seconds,  - Continue the mixing after adding the residues to the previous mixture at the same speed for a period of between 20 and 60 seconds, preferably of the order of 30 seconds, and then for a period of between 50 seconds and 70 seconds, at a speed of between 100 and 350 rpm, preferably of the order of 285 / min,  continue mixing again after adding the 1/5 of remaining water at a speed of between 250 and 350 rpm, preferably of the order of 285 rpm for a period of between 50 seconds and 70 seconds, of preferably of the order of 60 seconds.  6. Inerting process according to either of claims 1 to 5, characterized in that it further comprises a step during which one or more adjuvants selected from the superplasticizers or fluidizing reducing agents are added. water, retarders and antifoam agents.  7. inerting process according to claim 6, characterized in that the amount of the additive or adjuvants added represents from 0.5 to 5% by weight relative to the milk-residues solid material, this quantity being fixed as a function of characteristics of said residue.  Inerting process according to either of Claims 6 and 7, characterized in that the addition of the adjuvant (s) is carried out during the phases of incorporation of the water, the choice of the first or the second phase depending on the adjuvant and the residue.  9. inerting process according to any one of claims 1 to 8, characterized in that the introduction of the final mixture into molds is performed by vibration.  10. inerting process according to any one of claims 1 to 8, characterized in that the introduction of the final mixture into molds is carried out by compacting.  11. Inerting process according to claim 10, characterized in that the compacting is applied at a pressure of the order of 1 MPa.  12. Inerting process according to any one of claims 1 to 11, characterized in that the storage of the molds is carried out in an atmosphere having a humidity of between 55 and 85%, preferably between 60 and 70%, and at a temperature between 15 and 30 C, preferably of the order of 20 C.  13. A solidifiat comprising residues of purification of waste incineration fumes, ground vitrified blast furnace slag, and water, in which  the ratio of residues: slag is between 70:30 and 95: 5, preferably between 85:15 and 95: 5,  the water represents from 30% to 55% by weight of the dairy solid-residue mass, preferably from 35% to 45% in the case of compacting placement, and preferably of the order of 55% in the case of the case of vibration placement.  14. Solidifiat according to claim 13, characterized in that the residues comprise at least 10% of lime, 2% of sulphates and 5% of chlorine.  15. Solidifiat according to either of claims 13 and 14, characterized in that it has a compressive strength at 28 days of at least 1 MPa, preferably greater than 3 MPa.