Treatment of waste from the purification of incineration fumes by means of a thermoplastic polymer with a view to storing same

Abstract

The present invention relates to a method for treating a powder material, such as waste from the purification of incineration fumes, in order to obtain a solid composite product that is storable. The method has a markedly improved ecological footprint.

Description

Description Title: Treatment of incineration fume purification residues with a thermoplastic polymer for storage Technical field

[0001] This disclosure relates to the field of treatment of products from waste incineration for storage, in particular the treatment of residues from the purification of incineration fumes for storage. Prior art

[0002] Managing waste from residential, institutional, and commercial sources, as well as agricultural waste and other wastes such as sewage sludge, is a challenging issue for which solutions are continually evolving.

[0003] Currently in France, incineration is the second most common method of waste disposal. The incineration process results in a reduction in the volume and mass of solid waste; however, incineration generates, among other things, smoke containing acid gases, fly ash, and wastewater treatment residues. The smoke must be purified before being released into the atmosphere, and the fly ash and wastewater treatment residues must be treated before being stored.

[0004] As illustrated in Fig. 1, an incineration plant comprises, among other things, an incineration furnace 1, a fly ash storage unit 3, a cooling tower 5, a flue gas treatment unit 7, a storage unit 10, an optional catalytic treatment unit and a chimney (not shown in Fig. 1).

[0005] Incineration furnace 1 incinerates waste, produces fly ash and emits smoke. The recovered fly ash is conveyed to fly ash storage unit 3 via fly ash pipeline 2.

[0006] The flue gas is conveyed via a pipe 4 to the cooling tower 5 to produce cooled flue gas. This cooled flue gas is conveyed via a cooled flue gas pipe 6 to the flue gas treatment unit 7, the objective of which is that the flue gas complies with the regulatory atmospheric discharge thresholds. In this flue gas treatment unit 7, the cooled flue gas is brought into contact with a flue gas treatment material, such as sodium bicarbonate or lime, in order to neutralize acid gases, such as SO2 and HCl, to produce purified flue gas and solid residues comprising soluble fractions such as NaCl, KCl, Na2SO4, K3Na(SO4)2 and CaCl(OH).

[0007] After separation with a bag filter, the purified smoke is recovered in the purified smoke pipe 8 to be discharged into the atmosphere via the chimney and the solid residues are conveyed via a solid residue pipe 9 to the storage unit 10.

[0008] Before being discharged into the atmosphere, the purified flue gas may undergo an additional purification step in the optional catalytic treatment unit to obtain highly purified flue gas which is discharged into the atmosphere via the stack and optional solid residues. These optional solid residues are then conveyed to the storage unit 10. The solid residues and, possibly, the optional solid residues, stored in the storage unit 10 are the incineration flue gas purification residues.

[0009] Thus, an incineration plant can produce the following two different powdered materials: - fly ash, produced in incineration furnace 1 and stored in fly ash storage unit 3, and - the residues from the purification of incineration fumes, produced in the smoke treatment unit 7 and optionally in the catalytic treatment unit and stored in the storage unit 10.

[0010] Table 1 below shows the weight content of major salts in the soluble fraction present in three examples of incineration flue gas purification residues obtained by treatment with sodium bicarbonate or lime and in one example of fly ash. Major salts are those whose weight content is greater than 4% relative to the total dry weight of the residue or fly ash.

[0011] Table 1 highlights that the composition of these two types of powdered materials is quite different. In fact, in a purification residue, the weight content of the soluble fraction relative to the total dry weight of said residue is greater than 30%. On the other hand, in fly ash, the weight content of the soluble fraction relative to the total dry weight of said fly ash is less than 20%. The weight content of the soluble fraction is calculated by adding the weight contents of each major salt present in said soluble fraction.

[0012] Furthermore, the person skilled in the art knows that K3Na(SO4)2 and a high NaCI content are markers of sodium bicarbonate treatment while CaCI(OH) is a marker of lime treatment.

[0013] [Table 1]

[0014] Two main directives constitute the second level of European waste legislation and focus on the treatment of incineration flue gas treatment residues: the Industrial Emissions Directive (Waste Incineration) and the Landfill (Storage) Directive. European Directive No. 1999 / 31 / EC of 26 / 04 / 99 on the landfill of waste introduces the concept of pre-storage treatment. The French ministerial decree of 30 / 12 / 2002, as amended, relating to the storage of hazardous waste imposes various limits at the storage entrance. For example, it imposes a limit of 10% in soluble fraction, a limit of 1000 mg / kg in Total Organic Carbon (TOC), a limit of 500 mg / kg for fluoride ions, a limit of 30 mg / kg in molybdenum, a limit of 70 mg / kg in chromium and a limit of 50 mg / kg in lead in the leachate obtained from the residues of incineration fume purification.

[0015] Thus, before storage, legislation requires that incineration flue gas purification residues be stabilized, i.e. treated to comply with the imposed limits. The resulting treated residues, commonly referred to as stabilized solid products, are then stored in specially designed cells at a temperature below 60°C, as required by current regulations.

[0016] These incineration flue gas purification residues are generally stabilized by mixing with a hydraulic binder, as described in "FNADE ADEME study - feedback on the French sector - stabilization / solidification - storage of hazardous waste" published in 2006. The hydraulic binder is generally a mixture of cement (approx. 15% by weight), meta kaolin (approx. 15% by weight), blast furnace slag (approx. 15% by weight) and water (approx. 55% by weight).

[0017] In France, the use of hydraulic binder by hazardous waste storage facilities requires more than 40,000 tonnes of cement per year, and therefore generates more than 26,000 tonnes of CO2. Indeed, the production of 1 tonne of cement generates 650 kg of CO2. Furthermore, meta kaolin, an artificial pozzolan resulting from the calcination of kaolite (AI2O3-2SiO2-2H2O), is obtained by flashing at 900°C in gas-fired furnaces. Blast furnace slag is a by-product of blast furnaces. Thus, the use of each of these three components in hydraulic binder generates significant quantities of CO2.

[0018] The current process using a hydraulic binder therefore has a poor carbon footprint. However, the constant increase in CO2 in the atmosphere is blamed for climate change and global warming through the greenhouse effect.

[0019] It is therefore easy to understand that reducing CO2 emissions is a constant concern.

[0020] Furthermore, the residues from the purification of incineration fumes contain soluble chemical elements considered to be pollutants, such as molybdenum, lead, arsenic, antimony, fluorine or selenium. The current process using a hydraulic binder does not effectively retain these polluting chemical elements.

[0021] There is therefore a need to provide a process for treating incineration flue gas purification residues, with a carbon footprint lower than the poor carbon footprint of the current process using a hydraulic binder, while optimally trapping soluble chemical elements considered to be pollutants. Summary

[0022] This disclosure improves the situation.

[0023] There is provided a method of treating a powdery material with a thermoplastic polymer to obtain a solid composite product, said powdery material comprising at least 30% by weight of a soluble fraction relative to the total dry weight of the powdery material, said method comprising the following steps: a) contacting the powdery material and the thermoplastic polymer at a temperature equal to or greater than the softening point of the thermoplastic polymer to obtain a mixture; b) shaping said mixture; and c) solidifying the mixture to obtain the solid composite product.

[0024] Advantageously, the method according to the present invention makes it possible to stabilize the powdery material by effectively encapsulating it in a thermoplastic polymer matrix while having a carbon footprint lower than the poor carbon footprint of the current method using a hydraulic binder.

[0025] Indeed, when the powdery material is a residue from the purification of incineration fumes, the inventors have calculated that the substitution of the hydraulic binder by the thermoplastic polymer makes it possible to avoid the emission of 1100 to 1700 kilograms of CO2 equivalent per tonne of powdery material encapsulated by the process of the present invention.

[0026] In addition, the method of the present invention makes it possible to recover thermoplastic polymers that would have been incinerated. Indeed, plastic packaging is the main source of thermoplastic polymers and is generally incinerated. According to studies, the incineration of plastic packaging generates around 2,400 kilograms of CO2 equivalent per tonne of plastic packaging. This recovery advantageously reduces the carbon footprint linked to the end of life of thermoplastic polymer packaging.

[0027] Furthermore, the stability of the solid composite product obtained by the method of the present invention is sufficiently high to: - avoid leaching of the soluble fraction of the powdered material, and - to effectively trap soluble chemical elements considered as pollutants such as molybdenum, lead and chromium and also fluoride ions. The solid composite product also has a TOC of less than 1000 mg / kg.

[0028] The solid composite product obtained by the process of the present invention can advantageously be stored in a storage cell because it complies with the storage entry limits imposed by the French ministerial decree of 30 / 12 / 2002, as amended, relating to the storage of hazardous waste.

[0029] Furthermore, the inventors have found that, for the same mass proportion of powdered material, the volume of the solid composite product obtained by the method of the present invention is less than the volume of a stabilized and solidified product obtained by the current method using a hydraulic binder. A storage cell can therefore contain a greater quantity of solid composite product obtained by the method of the present invention than of stabilized and solidified products obtained by the current method using a hydraulic binder, which reduces the excavation space consumed linked to the storage of hazardous waste. However, the preservation of the excavation space for hazardous waste storage is a major issue in the management of hazardous waste in France.

[0030] Furthermore, during step a), bringing the powdered material into contact with the thermoplastic polymer at a temperature equal to or greater than the softening point of the thermoplastic polymer allows the homogeneous dispersion of the powdered material in the thermoplastic polymer.

[0031] In fact, without wishing to be bound by any theory, the inventors are of the opinion that, thanks to its thermal conductivity, the soluble fraction of the powdered material plays the role of heat conductor ensuring homogeneous heating of the mixture of the powdered material and the thermoplastic polymer.

[0032] This homogeneous dispersion is very advantageous because, without the necessary addition of a third compound such as a wax, an anti-leaching agent, or a hydroabsorbent, it could confer its stability to the solid composite product obtained by the process according to the present invention and therefore makes it possible to store it in accordance with regulations.

[0033] The fact that the addition of a third compound is not necessary is also advantageous because it allows the proportion of powdered material in the solid composite product to be increased.

[0034] The method of the invention is also simple to implement on an industrial scale to treat a large quantity of waste. Indeed, the method of the invention can be implemented simply after or in parallel with a conventional waste storage installation.

[0035] The process of the invention is also economical. Indeed, it does not require heavy investment in equipment since it can be easily implemented in existing installations. Furthermore, the cost of the thermoplastic polymer is low or even zero.

[0036] According to another aspect, there is provided a method for purifying fumes from the incineration of waste implementing the treatment method as defined above and further comprising the following step: - bringing the incineration fumes into contact with a fume treatment material to form an incineration fume purification residue, said incineration fume purification residue then being used in step a) of the treatment process.

[0037] Such a flue gas treatment material can be sodium bicarbonate, lime or their mixtures.

[0038] According to another aspect, there is provided a solid composite product comprising particles of a powdery material dispersed in a thermoplastic polymer, said solid composite product comprising a leachable soluble fraction.

[0039] Such a product is advantageous in that it allows the long-term storage of a high proportion of powdered materials with a high content of soluble fraction while avoiding the leaching phenomenon and effectively trapping soluble chemical elements considered as pollutants such as molybdenum, lead and chromium and also fluoride ions. Brief description of the drawings

[0040] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analyzing the attached drawings, in which: Fig. 1

[0041] [Fig. 1] shows a simplified diagram of a waste incineration plant. Fig. 2

[0042] [Fig. 2] shows a photograph illustrating a solid composite product according to the invention. Detailed description

[0043] There is provided a method of treating a powdery material with a thermoplastic polymer to obtain a solid composite product, said powdery material comprising at least 30% by weight of a soluble fraction relative to the total dry weight of the powdery material, said method comprising the following steps: a) contacting the powdery material and the thermoplastic polymer at a temperature equal to or greater than the softening point of the thermoplastic polymer to obtain a mixture; b) shaping said mixture; and c) solidifying the mixture to obtain the solid composite product.

[0044] For the purposes of the present invention, the singular forms "a", "an", "the" and "the" also encompass the plural forms of the terms to which they refer, unless the content clearly indicates otherwise.

[0045] Weight values ​​are expressed in dry weight, unless otherwise stated.

[0046] For the purposes of the present invention, “powdery material” means a material in powder form.

[0047] For example, the powdered material may be a residue from the purification of incineration fumes.

[0048] For the purposes of the present invention, “incineration fume purification residue” means a material: - obtained by treating incineration fumes with a fume treatment material, such as sodium bicarbonate or lime, in particular sodium bicarbonate, and - comprising at least 40% by weight of a soluble fraction relative to the total dry weight of the incineration fume purification residue. In the present application, the incineration fume purification residue may be referred to as purification residue.

[0049] The composition of the purification residue obtained by treatment with sodium bicarbonate differs from the composition of the purification residue obtained by treatment with lime. Especially : - the weight content of the soluble fraction in the purification residue obtained by treatment with sodium bicarbonate is greater than the weight content of the soluble fraction in the purification residue obtained by treatment with lime, - the weight content of NaCI in the purification residue obtained by treatment with sodium bicarbonate is greater than 40% while the weight content of NaCI in the purification residue obtained by treatment with lime is less than 40%, - the purification residue obtained by treatment with sodium bicarbonate comprises K3Na(SO4)2 whereas the purification residue obtained by treatment with lime does not contain it, and - the purification residue obtained by lime treatment contains CaCI(OH) while the purification residue obtained by sodium bicarbonate treatment does not contain it.

[0050] For the purposes of the present invention, "solid composite product" means a material comprising particles of powdered material dispersed in a thermoplastic polymer, said powdered material comprising a soluble fraction. In the present application, the solid composite product may be referred to as a composite product.

[0051] For the purposes of the present invention, “soluble fraction” designates a fraction comprising at least one soluble salt chosen from the salts of which: - the anion is chloride, sulfate, hydroxychloride and their combinations, and - the cation is sodium, potassium, calcium and their combinations.

[0052] For example, the soluble fraction may comprise a salt selected from NaCI, KCI, Na2SO4, K3Na(SO4)2, CaCI(OH) and mixtures thereof, in particular a mixture of NaCI and KCI, a mixture of NaCI and Na2SO4, a mixture of NaCI and K3Na(SO4)2, a mixture of NaCI and CaCI(OH), a mixture of KCI and K3Na(SO4)2, a mixture of KCI and CaCI(OH), a mixture of Na2SO4 and K3Na(SO4)2 and mixtures thereof, particularly a mixture of NaCI, Na2SO4 and K3Na(SO4)2, a mixture of NaCI, KCI and K3Na(SO4)2 and a mixture of NaCI, KCI and CaCI(OH), more particularly still a mixture of NaCI, Na2SO4 and K3Na(SO4)2 and a mixture of NaCI, KCI and K3Na(SO4)2

[0053] The mixture of NaCI, Na2SO4 and K3Na(SO4)2 or the mixture of NaCI, KCI and K3Na(SO4)2 may be characteristic of a purification residue obtained by treatment with sodium bicarbonate.

[0054] The mixture of NaCI, KCI and CaCI(OH) may be characteristic of a purification residue obtained by lime treatment.

[0055] The powdered material may comprise at least 40% by weight of sodium chloride (NaCl) relative to the total dry weight of said powdered material, preferably between 45% and 75%, more preferably between 50 and 60%.

[0056] The powdery material may, for example, comprise between 1 and 50% by weight of KCI relative to the total dry weight of said powdery material, preferably between 1 and 15%, more preferably between 5 and 10%.

[0057] The powdery material may comprise between 1 and 50% by weight of Na2SO4 relative to the total dry weight of said powdery material, preferably between 1 and 15%, more preferably between 1 and 5%.

[0058] The powdery material may comprise between 1 and 50% by weight of K3Na(SO4)2 relative to the total dry weight of said powdery material, preferably between 1 and 25%, more preferably between 1 and 20%.

[0059] The powdery material may comprise between 1 and 50% by weight of CaCl(OH) relative to the total dry weight of said powdery material, preferably between 30 and 45%, more preferably between 35 and 40%.

[0060] The powdery material may comprise at least 40% by weight of NaCl relative to the total dry weight of said powdery material, preferably between 45% and 75%, more preferably between 50 and 60% and, optionally,: - between 1 and 50% by weight of KCI relative to the total dry weight of said powdered material, preferably between 1 and 15%, more preferably between 5 and 10%, - between 1 and 50% by weight of Na2SO4 relative to the total dry weight of said powdered material, preferably between 1 and 15%, more preferably between 1 and 5%, - between 1 and 50% by weight of K3Na(SO4)2 relative to the total dry weight of said powdered material, preferably between 1 and 25%, more preferably between 1 and 20%, or mixtures thereof.

[0061] The powdered material may include: - between 50% and 60% by weight of NaCl relative to the total dry weight of said powdered material, - between 1 and 20% by weight of K3Na(SO4)2 relative to the total dry weight of said powdered material, and - between 5 and 10% by weight of KCI relative to the total dry weight of said powdered material, or between 1 and 5% by weight of Na2SO4 relative to the total dry weight of said powdered material.

[0062] The powdered material may include: - between 10% and 15% by weight of NaCl relative to the total dry weight of said powdered material, - between 1 and 20% by weight of KCI relative to the total dry weight of said powdered material, preferably between 5 and 15% and - between 30 and 45%, by weight of CaCI(OH), more preferably between 35 and 40%, relative to the total dry weight of said powdered material.

[0063] The sum of the weight contents of the salt(s) of the soluble fraction, relative to the total dry weight of said powdered material, cannot exceed 100%.

[0064] The powdery material may comprise between 30% and 90% by weight of the soluble fraction relative to the total dry weight of said powdery material, preferably between 35% and 80%, preferably between 40% and 70%, preferably between 50% and 70%.

[0065] The soluble fraction content in the powdered material can be determined using the following protocol: - implementation of a leaching test of the powdered material according to standard NF EN 12 457-2 dated December 2002 to obtain an eluate, and - analysis of the eluate according to standard NF T 90-029 of August 2002 to determine the content of soluble fraction in the powdered material.

[0066] The content of each soluble salt present in the soluble fraction of the powdered material can be determined by this protocol and by analysis of the eluate according to standard NF EN ISO 11885 of November 2009 which measures the cations and anions Cl, S.

[0067] The solid composite product may have a soluble fraction content of between 20% and 80% relative to the total dry weight of the composite product, preferably between 25% and 70%, preferably between 30% and 65%.

[0068] A portion of the soluble fraction of the solid composite product is leachable. Thus, the solid composite product may have a leachable soluble fraction content which may be less than 10% by weight relative to the total dry weight of said solid composite product, in particular less than 7% by weight, more particularly at least 0.5%.

[0069] For the purposes of the present invention, "leachable soluble fraction" means the portion of the soluble fraction present in an eluate obtained by a leaching test of the solid composite product according to standard NF X 31-211:2012. The content of leachable soluble fraction in the solid composite product can be determined by analyzing the eluate according to standard NF T 90-029 of August 2002.

[0070] The maximum diameter of the volume distribution of 50% of the particles (d50) of the powdered material used in the method according to the invention may be less than or equal to 100 pm, preferably from 8 pm to 70 pm, more preferably from 25 pm to 60 pm. The d50 value can be determined by liquid laser granulometry in distilled water with a Malvern-Mastersizer 2000 laser granulometer equipped with a 120 ml “small volume” cell, the signal is processed with the Mie mathematical model.

[0071] Advantageously, a particle size in the above ranges makes it possible to increase the contact surface of the powdered material with the thermoplastic polymer. This facilitates the homogeneous mixing of these two compounds and therefore the obtaining of the composite product.

[0072] Advantageously, the method according to the invention can make it possible to obtain the composite product without the necessary addition of a third compound such as a wax, an anti-leaching agent, a hydraulic binder or a hydroabsorbent. Thus, the implementation of step a) of the method is facilitated because it may not require the management of a ternary mixture.

[0073] The composite product may comprise less than 1% by weight of wax relative to the total dry weight of the composite product, preferably less than 0.5% by weight of wax, preferably wax-free.

[0074] The composite product may comprise less than 1% by weight of an anti-leaching additive relative to the total dry weight of the composite product, preferably less than 0.5% by weight of anti-leaching additive, preferably may be free of anti-leaching additive.

[0075] The anti-leaching agent may be selected from calcium hydroxide, sodium hydroxide, magnesium hydroxide, sodium sulfide and mixtures thereof.

[0076] The composite product may comprise less than 1% by weight of water-absorbing agent relative to the total dry weight of the composite product, preferably less than 0.5% by weight of water-absorbing agent, preferably may be free of water-absorbing agent.

[0077] The water-absorbing agent can be chosen from clay, Na-Ca borosilicates, expanded silicates and their mixtures.

[0078] The method according to the invention is advantageous in that it allows the production of a composite product having a water content of less than 7% by weight relative to the total weight of the composite product, preferably less than 3% by weight, without adding a water-absorbing agent.

[0079] The composite product may comprise between 40% and 80% by weight of powdered material relative to the total dry weight of the composite product, preferably between 50% and 75%, preferably between 55% and 70%.

[0080] This quantity of powdered material is greater than or equal to the quantity introduced in the conventional process using a hydraulic binder. Thus, in the same alveolar volume, it is possible to store a greater mass of waste treated by encapsulation than by the conventional process using a hydraulic binder.

[0081] Without wishing to be bound by any theory, the inventors are of the opinion that for the same volume, the mass proportion of powdered materials contained in the composite product obtained by the process according to the invention is greater than the mass proportion of powdered materials contained in the stabilized and solidified product obtained by the conventional process using a hydraulic binder.

[0082] The composite product may comprise between 20% and 60% by weight of thermoplastic polymer relative to the total dry weight of the composite product, preferably between 25% and 50%, preferably between 30% and 45%.

[0083] In the composite product, the sum of the content of powdered material and thermoplastic polymer may not exceed 100% by weight relative to the total dry weight of the composite product.

[0084] The composite product may comprise between 20% and 80% by weight of soluble fraction relative to the total dry weight of the composite product, preferably between 25% and 70%, preferably between 30% and 65%.

[0085] The thermoplastic polymer may be a polymer having processing temperatures of between 80°C and 300°C, in particular between 100°C and 275°C, more particularly between 140°C and 250°C.

[0086] The polymer may be selected from polyolefins, polyvinyls, polystyrenes, poly(meth)acrylics, polyamides, polycarbonates, linear polyesters, fluoropolymers, polyacetals, polysulfones, cellulosic polymers and mixtures thereof. Preferably, the polymer may be selected from polyolefins, poly(meth)acrylics, polyvinyls, polyamides and linear polyesters.

[0087] Fluoropolymers can be polyfluorothenes.

[0088] An example of polysulfone can be polyphenylene sulfide.

[0089] For example, the polymer may be polyethylene (including high-density polyethylene (HDPE) and low-density polyethylene (LDPE)), polypropylene, acrylic, polyvinyl acetate, polyvinyl chloride (PVC), polystyrene, nylon, polybutadiene, and mixtures thereof.

[0090] Polyolefins are preferred because they are advantageously present in abundance in plastic waste.

[0091] All or part of the, in particular all of the thermoplastic polymer may be derived from plastic waste, preferably non-biodegradable plastic waste, non-recyclable plastic waste or non-biodegradable and non-recyclable plastic waste.

[0092] For the purposes of the present invention, "non-biodegradable plastic waste" means waste that does not spontaneously and naturally undergo degradation under the action of a natural environment, including for example living organisms and / or air and / or water, or which undergoes it too slowly. Non-biodegradable plastic waste is in particular unsuitable for entering into the formation of compost by composting the latter.

[0093] For the purposes of the present invention, "non-recyclable plastic waste" means waste that does not meet the criteria allowing it to be processed in a traditional recycling process. This waste is generally buried or incinerated, which is likely to produce CO2 and consume excavation space.

[0094] The process is therefore advantageous in that it allows waste to be recovered without producing CO2, which would not have been the case if it had been incinerated. Thus, the use of such a thermoplastic polymer makes it possible to further reduce the carbon footprint of the process of the present invention.

[0095] For example, the thermoplastic polymer may come at least partially or completely from waste, such as packaging, an object, or both. The waste may be clean or soiled.

[0096] The packaging can be a bag, a food tray, a yogurt pot, a cream pot, a can, a container or their mixtures.

[0097] The object can be disposable tableware, a food container, a piece of furniture, a tarpaulin or their mixtures.

[0098] In the composite product, the thermoplastic polymer may comprise one or more thermoplastic polymers.

[0099] The thermoplastic polymer may be supplied in ground form having a particle size of between 1 and 10 mm, preferably between 2 and 6 mm.

[0100] Such a particle size advantageously allows good mixing between the powdered material and the thermoplastic polymer, and therefore better dispersion of the powdered material during step a).

[0101] The contacting of the powdered material and the thermoplastic polymer of step a) of the process can be carried out at a temperature between 80°C and 300°C, in particular between 100°C and 275°C, more particularly between 140°C and 250°C.

[0102] A temperature below 80°C does not ensure proper dispersion of the purification residue in the thermoplastic polymer. A temperature above 300°C could degrade the thermoplastic polymer and alter its elastic and plastic properties.

[0103] The duration of contact between the purification residue and the thermoplastic polymer from step a) of the process depends on the purification residue and thermoplastic polymer, but a person skilled in the art will be able to adapt to it. For example, the duration may be between 3 min and 20 min, preferably between 5 min and 10 min.

[0104] A shorter duration would not allow the homogenization of the powdered material and the thermoplastic polymer; the resulting mixture could have heterogeneous areas. A longer duration would involve significant energy expenditure and a decrease in the profitability of the process.

[0105] Step a) can be carried out in a mixer.

[0106] Using a mixer is advantageous because it is a device that operates semi-continuously and allows for constant temperature and viscosity to be maintained during mixing. Furthermore, hot mixing in a mixer produces a paste that can then be easily shaped, for example, by extrusion. The mixer is mainly used to mix and homogeneize several materials. Preferably, mixing is done using a Z-arm mixer.

[0107] The powder material, the thermoplastic polymer, or their mixtures may be preheated to a temperature equal to or greater than the softening point of the polymer. In particular, the powder material and the thermoplastic polymer may be preheated to a temperature equal to or greater than the softening point of the polymer separately before mixing them.

[0108] The powdery material may be preheated before step a) of contacting to a temperature above room temperature and lower than or equal to the temperature at which step a) is carried out. For example, the powdery material may be preheated to a temperature between 50°C and 300°C, in particular between 60°C and 250°C, more particularly between 80°C and 200°C.

[0109] The thermoplastic polymer may be preheated before step a) of contacting to a temperature above room temperature and lower than or equal to the temperature at which step a) is carried out. For example, the thermoplastic polymer may be preheated to a temperature between 20°C and 100°C, in particular between 30°C and 90°C, more particularly between 40°C and 80°C.

[0110] Advantageously, this step of preheating the powdered material, the thermoplastic polymer or both allows good mixing between the powdered material and the thermoplastic polymer while avoiding the formation of a cold spot at the point of contact of the powdered material and the thermoplastic polymer during step a).

[0111] In addition, these preheating steps make it possible to reduce the contact time during step a) because at least one of the components of the mixture is at the temperature for implementing step a).

[0112] Step b) of shaping can be chosen from extrusion, injection, molding, thermoforming, rotational molding, compression, calendering, boilermaking, pultrusion and their combinations, preferably from extrusion, molding, calendering and their combinations.

[0113] Extrusion means the preparation of a polymer in a desired form from a material in the form of granules or powder, using an extruder.

[0114] The main function of the extruder is to allow, through the action of temperature and pressure, the passage of the mixture through a die which is located at its end. Typically, an extruder is composed of one or more heating barrels with different temperature grades, one or two Archimedean screws which will allow the material to be transported along the barrel, a hopper which allows the material to be extruded to be fed at different points, a more or less complex die which is located at the end of the barrel and which allows the desired shape and size to be given to the material which comes out continuously. Preferably, the extrusion step is carried out using a twin-screw extruder.

[0115] Carrying out step b) by extrusion is particularly suitable for a step a) carried out using a mixer. Indeed, this allows steps a) and b) to be carried out using a single device known to those skilled in the art and called a mixer / extruder.

[0116] Molding can be implemented by using an extruder screw, for example a worm screw, to inject the mixture into a closed mold.

[0117] The composite product obtained may have a cylindrical structure with a diameter of less than 100 mm and preferably 40 mm.

[0118] According to another aspect, there is also provided a method for purifying fumes from the incineration of waste implementing the treatment method as defined above and further comprising the following step: - bringing the incineration fumes into contact with a fume treatment material to form an incineration fume purification residue, said incineration fume purification residue then being used in step a) of the treatment process.

[0119] The flue gas treatment material can be sodium bicarbonate, lime or their mixtures.

[0120] The step of bringing the incineration fumes into contact with the fume treatment material is a step well known to those skilled in the art, who will know how to implement it.

[0121] Preferably, the incineration fumes are fumes from the incineration of household waste or industrial waste.

[0122] According to another aspect, there is provided a solid composite product comprising particles of a powdery material dispersed in a thermoplastic polymer, said solid composite product comprising a leachable soluble fraction.

[0123] The powdered material, the thermoplastic polymer and the leachable soluble fraction are as defined above in connection with the treatment method of the present invention.

[0124] For example, the content of leachable soluble fraction in the solid composite product may be less than 10% by weight relative to the total dry weight of said solid composite product, in particular less than 7% by weight, more particularly at least 2%.

[0125] Thus, according to the regulations in force, the solid composite product is waste, or even waste classified as hazardous waste which can be stored in a storage cell because it complies with the storage entry limits imposed by the French ministerial decree of 30 / 12 / 2002 amended relating to the storage of hazardous waste.

[0126] The powdered material and the thermoplastic polymer are as described above in connection with the treatment method of the invention.

[0127] The solid composite product can be obtained according to the treatment method of the invention as described above.

[0128] The solid composite product may have a density of between 1.5 and 2, preferably between 1.6 and 1.8.

[0129] The solid composite product may comprise between 20 and 60% by weight of thermoplastic polymer relative to the total dry weight of the solid composite product, preferably between 25 and 50%, preferably between 30 and 45%.

[0130] The solid composite product may comprise between 40 and 80% by weight of powdered material relative to the total dry weight of the solid composite product, preferably between 50% and 75%, preferably between 55% and 70%.

[0131] Advantageously, this allows better integration of the powdery material into the solid composite product whereas until now the prior art processes based on hydraulic binders did not allow the inclusion of more than 30% of powdery material with a high soluble fraction in a stabilized and solidified product.

[0132] According to another aspect, there is provided a solid composite product comprising particles of a powdery material dispersed in a thermoplastic polymer, said powdery material comprising a soluble fraction, said solid composite product having a soluble fraction content of between 20% and 80% relative to the total dry weight of the composite product, preferably between 25% and 70%, preferably between 30% and 65%. Examples

[0133] Example 1 - Obtaining composite solid products

[0134] Starting materials

[0135] Two different purification residues are implemented in this example.

[0136] The first, noted REF BICAR, comes from the treatment with sodium bicarbonate of fumes generated by the incineration of hazardous waste and has a d50 value of 32 pm.

[0137] The second, noted REF CALCIQ, comes from the lime treatment of fumes generated by the incineration of hazardous waste and has a d50 value of 56 pm.

[0138] Each of the two residues, REF BICAR and REF CALCIQ, is subjected to a leaching test according to standard NF EN 12 457-2 dated December 2002 to obtain an eluate.

[0139] Each eluate is analyzed according to standards NF T 90-029 of August 2002, NF EN ISO 11885 of November 2009, and NF ISO 10359-1 of December 1992 and NF EN 1484 of July 1997 to determine respectively: - the soluble fraction content of the residue, - the content of metals present in the eluate, - the content of fluoride ions present in the eluate, and - the Total Organic Carbon (TOC) value of the eluate.

[0140] Table 2 presents the results of these analyses.

[0141] [Table 2]

[0142] Three thermoplastic polymers are used in this example.

[0143] The first, called THERMO MOU, is a mixture of soft thermoplastic polymers from, for example, flexible tarpaulins and rolls of pallet film.

[0144] The second, called THERMO DUR, is a mixture of hard thermoplastic polymers coming, for example, from containers.

[0145] The third, called THERMO PEHD, is obtained from high-density polyethylene waste.

[0146] Operating Protocol

[0147] Different solid composite products, presented in Table 3 below, are obtained using the following operating protocol: The thermoplastic polymer is ground to a particle size of approximately 4 mm. The ground thermoplastic polymer is then introduced into a mixer. In the mixer, it is subjected to a temperature ranging from 220°C to 250°C, which allows it to soften. In the mixer, the purification residue is added to the softened thermoplastic polymer. The solid composite product is obtained at the outlet of the mixer equipped with an extrusion screw.

[0148] Figure 2 is a photograph of the solid composite product 3.

[0149] Example 2: Characterization of composite solid products.

[0150] Each of the different composite solid products obtained is subjected to a leaching test according to standard NF X 31 211:2012 to obtain an eluate.

[0151] Each eluate is analyzed according to standards NF T 90-029 of August 2002, NF EN ISO 11885 of November 2009, and NF ISO 10359-1 of December 1992 and NF EN 1484 of July 1997 to determine respectively: - the content of leachable soluble fraction of the composite solid product, - the content of metals present in the eluate, - the content of fluoride ions present in the eluate, and - the Total Organic Carbon (TOC) value of the eluate.

[0152] Table 3 presents the results of these analyses.

[0153] As highlighted in Table 3, all solid composite products present, in accordance with the regulations: - a leachable soluble fraction content of less than 10%, - no metal content exceeding the said regulations, - a fluoride ion content of less than 500 mg / kg, and - a Total Organic Carbon (TOC) value of less than 1000 mg / kg.

[0154] In accordance with current regulations, these solid composite products can therefore be stored. 0155] [Table 3]

Claims

Claims

1. A method of treating a powdery material with a thermoplastic polymer to obtain a solid composite product, said powdery material comprising at least 30% by weight of a soluble fraction relative to the total dry weight of the powdery material, said method comprising the following steps: a) contacting the powdery material and the thermoplastic polymer at a temperature equal to or greater than the softening point of the thermoplastic polymer to obtain a mixture; b) shaping said mixture; and c) solidifying the mixture to obtain the solid composite product.

2. The method of claim 1, wherein the soluble fraction comprises a salt selected from sodium chloride (NaCl), potassium chloride (KCl), sodium sulfate (Na2SO4), potassium sulfate (K3Na(SO4)2), calcium hydroxychloride (CaCl(OH)) and mixtures thereof.

3. A method according to either of claims 1 or 2, wherein the powdered material comprises at least 40% by weight of sodium chloride relative to the total dry weight of said powdered material.

4. Method according to one of claims 1 to 3, in which the powdery material is a residue from the purification of incineration fumes.

5. Method according to one of claims 1 to 4, in which the thermoplastic polymer is chosen from polyolefins, polyvinyls, polystyrenes, poly(meth)acrylics, polyamides, polycarbonates, linear polyesters, fluorinated polymers, polyacetals, polysulfones, cellulosic polymers and their mixtures.

6. Method according to one of claims 1 to 5, in which the shaping b) is chosen from extrusion, injection, molding, thermoforming, rotational molding, compression, calendering, boilermaking, pultrusion and their combinations.

7. A method of purifying fumes from the incineration of waste implementing the treatment method as defined in any one of claims 1 to 6 and further comprising the following step: - bringing the incineration fumes into contact with a fume treatment material to form an incineration fume purification residue, said residue incineration fume purification then being implemented in step a) of the treatment process.

8. A method according to claim 7, wherein the flue gas treatment material is sodium bicarbonate, lime or mixtures thereof.

9. A solid composite product comprising particles of a powdered material dispersed in a thermoplastic polymer, said solid composite product comprising a leachable soluble fraction.

10. A solid composite product according to claim 9 wherein the content of leachable soluble fraction in the solid composite product is less than 10% by weight relative to the total dry weight of said solid composite product.

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