FR2746034A1 - New process for the re-treatment of incineration fumes - Google Patents

Abstract

A new process for the re-treatment of incineration fumes from household waste treated with quicklime, comprises: (i) densifying the fumes with acetic acid (with a degree of hydrolysis); and (ii) thermal treating by submitting the mixture to a temperature higher than the evaporation point of the heavy metals in aqueous phase. Also claimed, is the product obtained by the above process.

Description

 The present invention relates to a process for the reprocessing of household waste incineration fumes.

 So far, the garbage is incinerated which generates smoke, posing a problem, since it is polluted with scrap and clinkers, which are reintroduced into the industrial circuit.

 These fumes are generally buried permanently in cells which are very expensive on the right-of-way surface, in partitioning materials, in bondage, etc.

In fact, a concrete enclosure is generally made, which will contain the fumes, in order to isolate the dangerous elements contained therein. These dangerous elements are essentially derived from oxides, such as SiO2, Au203, Fe203, CaO,
MgO, Na20, K20, S03, MnO, P20s, TiO2, anions, such as Cl-, and heavy metals, such as As, Ba, Cd, Cr, Cu, Hg, Ni, Pb, St, V,
Zn.

 Another method of processing these incineration products is to use pyrometallurgical techniques. These techniques consist in isolating the dangerous elements by incorporating them inside a stable material in the glass state which is chemically inert. In this case, the polluting elements are trapped inside the vitrified molecular structure.

 To meet this priority of general interest, these toxic ultimate residues from, in particular, household waste incinerators will now be stored, in accordance with new European standards, according to a regulatory burial protocol costly in volume, in costs of installation and maintenance (sealed cells with geotextile membranes, etc.).

In France, this is the final landfill of around 200,000 tonnes per year plus at least a factor of 2 (200,000 tonnes of stabilization reagents), or a total of 400,000 tonnes for the only toxic ultimate residues from incinerators. household waste at a prohibitive cost per tonne buried. In a few years, the current centers will be saturated.

 Document EP-A-0.455.873 proposes the transformation of a dangerous residue into a non-dangerous aggregate without leaching by the introduction of the material into a rotary kiln where the large solid masses are, at least partially, burned to form a primary aggregate . Gaseous combustion by-products and pulverulent residues of the residue materials are introduced into at least one oxidation device having water-cooled metal walls. Some of the powdery residue is melted to form a molten milk-like material, which is removed from the apparatus and cooled to form a non-hazardous aggregate. The part of the material in the oxidation device which is not melted is cooled, neutralized and subjected to a gas-solid separation. The solid is reintroduced into the oxidation device with the primary aggregate where they are either melted or entrained inside the molten material and become an integral part of the non-hazardous aggregate.

 Despite the incineration, heavy metals still remain in the smoke, the toxicity of which is troublesome.

 The document EP-A-O.547.923 relates to a process for stabilizing and solidifying household waste incineration products, products resulting from the process and products for its implementation. This invention relates to a process for stabilizing and solidifying ash or dechlorination residues of smoke resulting from the incineration of household waste, which consists in incorporating them into an aqueous binder formed mainly by a powder of a product to blast furnace slag base, while putting them in the presence of magnesium oxide, and a sulfate or a carbonate or a combination of the two at a pH between 8 and 13 and preferably between 9 , 5 and 12.5.

 This process is used to treat ash and smoke. It combines chemicals with these substances. These additives are numerous (two or three) and basic conditions must be met. The process is therefore expensive to implement.

 The present invention eludes these drawbacks by proposing a process which requires only one adjuvant and which eliminates all of the heavy metals contained in the fumes due to the incineration of household waste.

 To this end, the invention provides a process for the reprocessing of household waste incineration fumes treated with quicklime, characterized in that it consists in densifying and heating the fumes by mixing them with acid. more or less hydrolyzed acetic acid, then heat treatment of the mixture by subjecting it to a temperature above the point of evaporation of heavy metals in the aqueous phase.

 The heat-treated mixture is ground in the presence of clay and is then heat-treated at a temperature above the point of evaporation of the heavy metals in the aqueous phase, in order to give a neutral, downgraded product.

 According to a mode of use, the heat-treated mixture is ground in the presence of water in order to give a cement.

 The vapors, coming from at least one of the heat treatments, are captured and sent to an incineration site to be burned there.

 In addition, each heat treatment is carried out by short infrared rays with penetration.

 More precisely, the infrared rays have a wavelength between 0.8 and 1.5 microns (p) at nominal voltage.

 The product obtained by the process is characterized in that it contains a mixture of fumes and more or less hydrolyzed acetic acid.

 The concentration of acetic acid, reacting with the fumes, is between 4 and 8%.

 In addition, the mass of dilute acetic acid is 300 to 400 grams per kilogram of treated fumes.

 In the case where the method consists in mixing the heat-treated mixture with clay, on the one hand the mass of heat-treated mixture is between 35 and 50% and, on the other hand the mass of clay is between 50 and 65%.

 The present invention relates to a process for the reprocessing of household waste incineration fumes.

 Up to now, all household waste has been burned inside ovens.

 This action generates waste of different kinds.

 First there are the clinkers, then the ashes and finally the fumes.

 If the bottom ash is easily reusable, the same does not apply to smoke or ash.

 The reprocessing method according to the invention therefore resides in the reprocessing of these fumes only, in order to allow their reuse in the form of a neutral and downgraded product.

 Also conventionally, these household waste incineration fumes are treated with quicklime.

pour donner l'anion de l'acide acétique également appelé "alcool acétique".The invention will therefore consist in densifying and heating the fumes treated with quicklime by mixing them, via a mixer, with acetic acid: CH3-COOH,
Of course, acetic acid is a weak acid, it is easily hydrolyzed in the presence of water, depending on the reaction

to give the anion of acetic acid also called "acetic alcohol".

 During this operation, the density of the fumes goes from 0.5 to the value of 1.2. Of course, this mixture contains a lot of very polluting heavy metals. The mixture is in the form of a flexible paste which forms a puddle containing heavy metals and which hardens on cooling.

 Thereafter, the mixture is then heat treated by subjecting it to a temperature above the point of evaporation of heavy metals in the aqueous phase, inside a tunnel at a temperature of approximately 300 Celsius ('C).

 Part of these heavy metals will therefore evaporate and will be able to be taken up in the form of oxide via a sheath which will once again direct them towards an incineration hearth, in order to be burned there.

 The rest of the heavy metals will end up crystallized in aggregates which are the final result of the heat treatment.

 In a first embodiment of the process, the acidified mixture, which has just been heat treated, is ground in the presence of clay, for example a bricklayer or a potter, in order to obtain a very fine sand, then be new heat-treated, always at a temperature above the point of evaporation of heavy metals in the aqueous phase, but preferably around 800 C, in order to give a neutral downgraded product.

 Of course, the vapors resulting from this second heat treatment can again be directed via a sheath towards an incineration hearth, in order to be burned there.

 In a second embodiment of the process, the acidified mixture, which has just been heat treated, is ground in the presence of water to form an inert cement.

 These heat treatments are due to short penetration infrared rays whose wavelength is between 0.8 and 1.5 p at nominal voltage.

 More specifically, the wavelength of the infrared rays used is 1.2%.

 The product, which we will be able to obtain by the process, therefore consists of a mixture of smoke and acetic acid.

 The concentration of acetic acid, which reacts with the fumes, is between 4 and 8%.

 This mixture of pure acetic acid with distilled water is carried out in order to allow the wetting of the fumes. In fact, the goal is to get as much acetic acid as "acetic alcohol".

In a preferred mode of composition, the acid constitutes 3% of the substance to be kneaded and the "alcohol" also 3% of this substance. The balance, that is to say 94%, consists of demineralized water.

 It is this wetting operation which will allow the evaporation of the heavy metals, the said heavy metals transforming into oxides, then, under the effect of the heat treatment, into vapor.

 It is also necessary that the mass of diluted acetic acid is proportional to the mass of treated fumes.

 The ratio is substantially one third.

 In practice, 350 grams of acetic acid, diluted as indicated above, will be used per kilogram of fumes.

 When the product uses a mixture of the heat-treated product combined with clay, the proportion of the product is between 35 and 50%, while the proportion of clay is between 50 and 65%.

 The neutral product thus obtained is downgraded, therefore it can be reused, for example to serve as embankment or be mixed with bottom ash or loaded in concrete.

Claims (10)

 1. Process for the reprocessing of household waste incineration fumes treated with quicklime, characterized in  that it consists in densifying and heating the fumes by mixing them with more or less hydraulic acetic acid, then in carrying out a heat treatment of the mixture by subjecting it to a temperature higher than the point of evaporation of the heavy metals in phase aqueous.  2. Method according to claim 1, characterized in that  that the heat-treated mixture is ground in the presence of clay and is then heat-treated at a temperature above the point of evaporation of heavy metals in the aqueous phase, in order to give a neutral product which has been downgraded.  3. Method according to claim 1, characterized in that  that the heat treated mixture is ground in the presence of water to give a cement.  4. Method according to any one of claims 1 or 2, characterized in that  that the vapors, coming from at least one of the heat treatments, are captured and sent to an incineration hearth to be burned there.  5. Method according to any one of claims 1, 2 or 4, characterized in that  that each heat treatment is carried out by short infrared rays with penetration.  6. Method according to claim 5, characterized in that  that infrared rays have a wavelength between 0.8 and 1.5 p at nominal voltage.  7. Product obtained by the method according to claim 1, characterized in that  that it contains a mixture of fumes and more or less hydraulic acetic acid.  8. Product according to claim 7, characterized in that  that the concentration of acetic acid, reacting with the fumes, is between 4 and 8%.  9. Product according to claim 8, characterized in that  that the mass of diluted acetic acid is 300 to 400 grams per kilogram of treated fumes.  10. Product obtained by the process according to claim 2, characterized in that  that the mass of heat-treated mixture is between 35 and 50%, and  that the mass of clay is between 50 and 65%.