NL2010974C2 - METHOD FOR TREATING WASTE MATERIAL - Google Patents

Abstract

Process for treating a waste containing non-inert heavy metals, according to which the first waste and a phosphating agent rich in phosphates and / or metal phosphites are introduced into a calcination furnace, and the first waste is calcined therein in the presence of the phosphating agent.

Description

METHOD FOR TREATING WASTE MATERIAL

The invention relates to a method in which a waste material is treated which contains heavy metals, such as certain types of sludge from a purification device.

In a particular embodiment, this method also makes it possible to valorise the product from the treatment of another waste material containing heavy metals, such as most sediments from waterway purification.

The problems caused by the ever-increasing quantities of waste to be treated, treated and stored are generally known. These waste materials come from multiple sources. They come, for example, from water treatment plants, from the dredging or purification of waterways or various industries and can contribute to soil contamination. Regarding sediment from waterway purification, this is particularly worrying given the quantities involved and their contamination with pollutants such as heavy metals and organic substances. An important part of the waterways of northern Europe is now blocked by sludge, which hinders shipping traffic. The economic and environmental consequences, directly or indirectly, are very large. On the other hand, it is well known that this worrying situation of the water network is mainly caused by the drawbacks of the current solutions for the treatment and storage of contaminated waste materials.

After all, a simple means of removing waste materials consists of discharging them by boat into the sea or transporting them to landfill sites. However, when the waste materials are contaminated with heavy metals or hazardous organic substances (which is generally the case with sediments from waterway purification), this agent is of course unacceptable. After all, before they can be stored, the waste materials must be treated in order to meet the non-toxicity tests. It is also important that they can be dried effectively and economically, so that processing and storage thereof is facilitated.

The invention relates to the provision of a method for treating waste materials that is economically more favorable and / or technically more competitive than the methods according to the state of the art, in particular the methods described in the patents of SOLYAY WO 02 / 32817, WO 04/035490, WO 2005/100261 and WO 2007/080179, the entire contents of which are incorporated herein by reference, where applicable.

In view of this, the present invention relates to a method for treating a waste material containing non-inert heavy metals (the "first waste material"), wherein the first waste material is added to a calcining furnace, in addition to which a phosphating agent is added to the calcining oven and the first waste material is calcined in the presence of the phosphating agent, the phosphating agent comprising: - at least one salt S, of at least one metal other than a heavy metal, the salt S being a salt, which is derived from phosphorus, wherein the salt S as such or at least partially is in its ionic form and wherein the salt S is selected from: (i) the salts S1 comprising at least a mono- or polyphosphate group which the general formula

where x is an integer positive number or zero and wherein the (3 + x) oxygen atoms marked with an asterix (O *) are independently of each other on a hydrogen atom or on a metal atom other than a heavy metal are bonded with the proviso that at least one of them is bonded to a metal atom other than a heavy metal (e.g., to a Na, Ca, Mg or Fe atom), (ii) the polymetaphosphate salts S2, which at least one ring that is of the formula

where y is an integer of at least 3, and wherein the y oxygen atoms marked with an asterix (O *) are attached to a metal atom other than a heavy metal and (iii) the salts S3 , comprising at least one mono- or polyphosphite group, that of the general formula

where z is an integer positive number or zero, in which one of the 2 oxygen atoms marked with an asterix (O *) is attached to a metal atom that differs from a heavy metal and the other with an asterix oxygen atom characterized either by a hydrogen atom or by a metal atom other than a heavy metal, and - if desired, moreover, at least one acid A, derived from phosphorus, as such or at least partially in an ionic form selected from: (i ') the mono- or polyphosphoric acids A1, those of the general formula

where x 'is an integer positive number or zero, and (ii) the mono- or polyphosphorous acids A2 which satisfy the general formula

where z 'is an integer positive number or zero, the total phosphorus content present in the at least one salt S relative to the total phosphorus content contained in the at least one salt S and the at least one acid A is present, is higher than 50% and can reach 100%, and wherein the total phosphorus content present in the at least one salt S and the at least one acid A, relative to the total phosphorus content contained in the phosphating agent present is higher than 75% and can reach 100%. Description of the phosphating agent

In the phosphating agent, the total phosphorus content that is present in the salt S, relative to the total phosphorus content that is present in the salt S and the acid A, is preferably higher than 75% and particularly preferably higher than 90% . The phosphating agent is particularly preferably free of acid A and most preferably contains essentially no, if not completely free of acid A.

Furthermore, the total phosphorus content that is present in the at least one salt S and the at least one acid A, relative to the total phosphorus content that is present in the phosphating agent, is preferably higher than 90%, with the optional remainder of the phosphating agent is, for example, a metal hypophosphite or phosphorus pentoxide. with particular preference the phosphating agent essentially consists of, and even exclusively consists of the salt S and the optional acid A.

The salts S1, S2 and S3 advantageously comprise calcium as a metal element. Preferably, the salts S1, S2 and S3 do not comprise any metal other than calcium.

The metal salt S is preferably selected from the salts S1. x can in particular be equal to 0 (a single atom P, monophosphate group) or is higher than 0 (multiple P atoms, polyphosphate group). The salts S1 preferably contain at least one monophosphate group; moreover, the salts S1 preferably do not have a polyphosphate group.

Good results have been obtained when the salt S is or includes a salt selected from calcium orthophosphate [Ca3 (PO4) 2], calcium monohydrogen phosphate (CaHPO / t), calcium dihydrogen phosphate [Ca (H2PO4) 2], "tricalcium TCP" phosphate [Ca9 (PO4) 6], the whitlockites [in particular the whitlockites corresponding to the formula Ca9 (Mg, Fe) (PO4) 6 (HP04)] and the apatites [in particular the apa tits that meet answer the formula Ca 10 (PO 4) 6 (OH, F, Cl, Br) 2, such as hydroxyapatite], the hydrated forms of said salts and mixtures thereof.

Excellent results have been obtained when the salt S is or comprises the anhydrous calcium monohydrogen phosphate (also referred to as monetite) and / or a hydrated calcium monohydrogen phosphate (in particular brushite (CaHPO 4 .2H 2 O)).

Excellent results have also been obtained when the salt S is or comprises a whitlocite corresponding to the formula Ca 9 (Mg, Fe) (PO 4) 6 (HPO 4).

Excellent results have also been obtained when the salt S hydroxyapatite [formula Ca 5 (PO 4) 3 (OH), which is also generally described as Ca 10 (PO 4) 6 (OH) 2 to indicate that the crystalline unit cell has two units of Ca 5 (PO 4) 3 (0H) includes].

The weight content of the phosphating agent, expressed in equivalent phosphorus relative to the dry matter content of the first waste material, is advantageously at least 0.35%, preferably at least 0.5%, particularly preferably at least 0.7%. Furthermore, the weight content of the phosphating agent, expressed as phosphorous equivalent and relative to the dry matter content of the first waste material, is advantageously at most 5%, preferably at most 3%, with particularly preferably at most 2%. More particularly preferably, it is 0.7 -2%.

Calcination (most important properties).

The calcination is advantageously carried out at a temperature of or in a temperature range of 450 ° C - 1000 ° C.

It is also sometimes useful to perform calcination in an oxidizing atmosphere, preferably using air as the oxidizing agent.

Description of the first waste material.

In general, more than 10% by weight, optionally more than 15% by weight or more than 20% by weight of the heavy metals present in the first waste material can be eluted in 0.5 M acetic acid.

The first waste material advantageously has a dryness of at least 85%, preferably at least 90% and in certain special cases at least 99%.

The first waste material is preferably a sludge of natural origin, which must be dried to achieve a dryness of at least 70%. The first waste material is particularly preferably a sludge from a purification device that has been dried to achieve a dryness of at least 80%, preferably at least 85%.

The first waste material can be a substantially dry natural waste material.

The first waste material can also be a non-natural waste material. For example, the first waste material may consist of parts and / or ground parts of cars in which plastic material is used.

The first waste material can be a substantially dry non-natural waste material.

Preferred embodiment of the invention, wherein a second waste material is used.

In a particular preferred embodiment of the invention, the phosphating agent is present at least in part in a second waste material containing inert heavy metals by a phosphating treatment. According to this special embodiment, the first waste material and the second waste material are added to the calcining oven, after which the first waste material and the second waste material are calcined together.

In accordance with this particular embodiment, the method according to the invention may furthermore comprise the step in which a waste material containing non-inert heavy metals is subjected to a phosphating treatment, which waste material, after having undergone this phosphating treatment, forms the second waste material.

Preferably, the phosphating agent is completely present in the second waste material.

Advantageously, a maximum of 10% by weight, preferably a maximum of 7% by weight and particularly preferably a maximum of 5% by weight of the heavy metals present in the second waste material can be eluted in 0.5 M acetic acid. Furthermore, the weight content of the eluable heavy metals present in the second waste material is advantageously at least 2 times lower and preferably at least 4 times lower than the weight fraction of the eluable heavy metals present in the first waste.

The second waste material advantageously has a dryness of at least 85%, preferably at least 90% and in certain special cases at least 99%.

The second waste material is advantageously a waste material that has been subjected to a phosphating treatment with phosphoric acid, preferably in a humid environment.

Moreover, the second waste material is advantageously a sludge of natural or non-natural origin; this sludge, in particular when it is of natural origin, may have to be dried to achieve a dryness of at least 70%.

The second waste material preferably consists of sediments that come from purifying an aqueous environment, such as a watercourse or a region with stagnant water.

In addition, the second waste material is preferably a sludge with an initial dryness of less than 70% (i) which has been converted into a foam to which is added at least one acid A selected from the acids A1 and acids A2 at preferably an acid A1 and particularly preferably phosphoric acid, (ii) which is matured so that the phosphation develops in the foam after which (iii) it is dried to achieve a dryness of at least 70%.

The sludge is preferably matured for a sufficient time t1 so that a sufficient fraction of the acid A is converted into the salt S, so that, for example, the total phosphorus content present in the salt S, compared to the total phosphorus content contained in the salt S and the acid A is present, is higher than 75%, higher than 90% or even better higher than 99%. The time t 1 is usually at least 5 minutes, preferably at least 15 minutes, particularly preferably at least 1 hour and very particularly preferably at least 3 hours.

The sludge is also preferably matured for a sufficient time so that the percentage by weight of the heavy metals that can be eluted in 0.5 M acetic acid containing the sludge is at least 2 times, preferably at least 4 times and particularly preferably at least becomes at least 6 times lower than the percentage by weight of the heavy metals that can be eluted in 0.5 M acetic acid present in the sludge before adding the acid A.

Still with particular preference the sludge is aged for a sufficient time so that the content of the heavy metals that can be eluted in 0.5 M acetic acid present in said sludge, relative to the total content of the heavy metals, which are present in said sludge is at most 10%, preferably at most 7% and particularly preferably at most 5%.

A particularly advantageous aspect of the invention, in connection with the preferred embodiment of the invention to be discussed, relates to the use of a waste material containing inert heavy metals by a phosphating treatment (the "second waste material" which is described in the present application) as an inerting agent in a calcining oven of another waste material containing non-inert heavy metals (the "first waste material" described in the present application).

Adding waste materials to the calcining oven. when the method comprises the second waste material.

The first waste material and the second waste material can be added together or separately or partially together and the remainder separately to the calcining oven.

In a preferred embodiment of the invention, the first waste material is added to the calcining oven separately from the second waste material. This embodiment can in particular be recommended when the two waste materials have the consistency of an aqueous slurry, but also when the two waste materials have the consistency of a solid and not an aqueous slurry.

In another embodiment of the invention, which has other advantages, the first waste material and the second waste material have the consistency of a solid and not an aqueous slurry, and the first waste material and the second waste material become virtually without adding water, even mixed without adding water, so that the homogeneous or heterogeneous mixture of the first waste material and the second waste material also has the consistency of a solid and not an aqueous slurry, after which the mixture is added to the calcining oven, preferably as soon as it is able to it is recordable, for example, less than 3 hours, less than 1 hour, less than 30 minutes, less than 15 minutes, less than 5 minutes, less than 1 minute even immediately after the formation of the mixture.

Amounts of the first waste material and the second waste material when the method comprises the second waste material.

The weight of the first waste material is advantageously at least 10%, preferably at least 20% and particularly preferably at least 40% of the weight of the second waste material.

Furthermore, the weight of the first waste material is advantageously at most 200%, preferably at most 100% and particularly preferably at most 60% of the weight of the second waste material.

Possibly self-combustible property when the process comprises the second waste material.

In a preferred embodiment of the method according to the invention, the first waste material and the second waste material together form a self-combustible mixture in the calcining oven which, in the absence of a third fuel with a much lower calorific capacity than that of the whole produced by the first waste material and the second waste material is formed, can be calcined, such as fuel oil.

In this regard, the applicant has found that the choice of sludge from water treatment plants as the first waste material usually permits the use of this preferred embodiment.

Description of the third waste material.

In general, calcining produces slag containing inert heavy metals and fly ash containing inert heavy metals, each of these two calcination products, individually or mixed, advantageously forming a waste material that can be valorized (the "third waste material" ").

Advantageously, a maximum of 10% by weight of the heavy metals present in the third waste, in particular in the slag and / or in the fly ash, can be eluted in 0.5 M acetic acid.

In addition, the elutable weight fraction of the heavy metals present in the third waste material is at most the elutable weight fraction of the heavy metals present in the second waste material and preferably it is at most half.

Post-treatment of the third waste material.

In a special and favorable embodiment of the invention, the third waste material is mixed with water, optionally a hydraulic binder is added, after which the whole comprising the third waste material, water and possibly hydraulic binder, is subjected to thickening and curing, in such a way way that a solid mass is formed.

The invention therefore also relates to a method for forming a solid mass which can be used for the construction of a road, the manufacture of a stone or for the production of a concrete, according to which method the third waste material with the water is mixed, optionally a hydraulic binder is added, after which the whole comprising the third waste material, water and possibly hydraulic binder, is subjected to thickening and hardening in such a way that a solid mass is formed.

The invention also relates to an end product, such as a road, brick or concrete, which comprises the solid mass formed by the particular method or method described in the two preceding paragraphs, respectively.

Other technical features relating to the present invention.

Further details of the heavy metals of the first waste material and possibly the second waste material.

The heavy metal content of a waste material is obtained by summing the levels of each of the heavy metals present in the waste material.

A heavy metal is understood to be any metal selected from metals whose specific weight is at least 5 g / cm 3 (such as cadmium, chromium, copper, mercury, nickel lead and zinc), as well as from beryllium, arsenic, selenium and antimony.

Ash content. The dry substances of the first waste material and the second waste material may independently contain at least 2 mg / kg, at least 10 mg / kg or at least 20 mg / kg As. It can contain a maximum of 500 mg / kg of As.

CD content. The dry substances of the first waste material and the second waste material may independently contain at least 1 mg / kg, at least 5 mg / kg or at least 10 mg / kg Cd. It can contain a maximum of 250 mg / kg of Cd.

Cr content. The dry substances of the first waste material and the second waste material may independently contain at least 5 mg / kg, at least 25 mg / kg or at least 50 mg / kg Cr. It can contain a maximum of 1000 mg / kg of Cr.

Hg --- content. The dry matter of the first waste material and the second waste material may independently contain at least 0.1 mg / kg, at least 0.5 mg / kg or at least 1 mg / kg Hg. It can contain a maximum of 25 mg / kg.

Cup stop. The dry matter of the first waste material and the second waste material may independently contain at least 5 mg / kg, at least 25 mg / kg, at least 100 mg / kg or at least 250 mg / kg Cu. It can contain a maximum of 1000 mg / kg Cu or a maximum of 10000 mg / kg Cu.

Pb content. The dry matter of the first waste material and the second waste material may independently contain at least 5 mg / kg, at least 25 mg / kg, at least 100 mg / kg or at least 250 mg / kg Pb. It can contain a maximum of 1000 mg / kg of Cu or a maximum of 10000 mg / kg of Pb.

Zn content. The dry matter of the first waste material and the second waste material can independently be at least 5 mg / kg, at least 50 mg / kg, at least 200 mg / kg, at least 500 mg / kg or at least 1000 mg / kg Zn contain. It can contain a maximum of 10000 mg / kg of Cu or a maximum of 50000 mg / kg of Zn.

Ni content. The dry substances of the first waste material and the second waste material may independently contain at least 5 mg / kg, at least 15 mg / kg or at least 30 mg / kg Ni. It can contain a maximum of 500 mg / kg of Ni.

The levels are advantageously measured with optical emission spectrometry on plasma with inductive coupling (ICP - OES).

Details of the dryness of a waste material.

The dryness of a sample of a waste material is determined by calculating the ratio of sample before and after a residence time of 4 hours in an autoclave, which is kept at 100 ° C.

Details of the nature of the first and any second waste material.

The first waste material and the second waste material can be independently of each other: from decanting used water of industrial or urban origin, from cleaning soil, such as that from certain industrial sites; residues from the grinding of cars ash from burning sediments, originating from the cleaning of rivers, fens, wells or sewers, and sediments, originating from the cleaning of waterways (eg harbors, lakes, rivers, canals).

Dredging is a special form of purification. The dredging must be understood as a treatment of a certain size, which is carried out with heavy tools (suction pump, dredger, etc.), whereby the purification refers to any treatment in an aqueous environment that releases material, even of vegetable origin. , implies, for example in a channel or in a low-water bed or the catchment area of a watercourse.

By fly ash is meant incineration ash, which is entrained by combustion gases.

Details of the sludge.

By sludge is meant any aqueous substance that contains suspended solids. It may be of natural origin or due to the addition of water to a powdered solid obtained, for example, by grinding. When the sludge is of natural origin, it advantageously contains weak clay, mud and suspended mineral materials (sand even gravel). The sludge from the cleaning of waterways or contaminated soil forms examples of natural sludge to which the invention can be applied. On the other hand, sludge that results from adding water to incineration ash or to car grinding residues is examples of non-natural sludge to which the invention can be applied. The size of the grain distribution of the suspended particles in the sludge can be very wide, for example from less than 1 micron to a few hundred microns, even a few millimeters. The sludge often contains a high content of very fine particles. Often 10% by weight of the dry sludge is formed by particles with a diameter smaller than 5 micrometers, while the content of particles with a diameter larger than 500 micrometers can reach a few percent. On the other hand, the histograms of the grain size distribution of certain types of sludge are multimodal, that is, they have multiple peaks.

Further details of the phosphating treatment with phosphoric acid of the possible second waste material.

The amount of phosphoric acid to be used depends on the precise composition of the second waste material to be treated and in particular on the content of heavy metals. In practice a weight amount of at least 1% (preferably 2%) relative to the dry matter content is used. It is preferred that the amount of phosphoric acid is less than 15%. Quantities of 2 - 6% are generally very suitable.

It is interesting to use highly dilute phosphoric acid in which a source of inexpensive phosphate is dissolved, such as certain phosphorus-containing minerals containing P2 O5, or calcining residues of animal meal, which is also rich in phosphates. For example, from an acid the concentration of which corresponds to 20 ml of phosphoric acid is diluted to 85% with 980 ml of water, and by adding this to phosphorus-containing minerals or calcined animal meal, an acid suitable for the process is obtained in a very economic manner. according to the invention. It has been observed that by phosphating the second waste material, a second waste material can be obtained in which toxic compounds present in the second waste material are rendered inert.

For treatment with the phosphoric acid in question, drynesses of less than 30% or in certain cases 40% are preferably avoided. When the dryness is higher than 70%, it is necessary in some cases to add water so that phosphating can be carried out optimally.

In a recommended variant of this treatment, the second waste material is converted into a foam, after which it is present in the form of a foam (with foam, for a particular starting product, is meant a condition of this product with a lower density than that of the starting product). Converting into a foam facilitates the later processing of the second waste material. After all, the inventors have observed that after a storage period, which typically ranges from 2-7 days, preferably 4-6 days, during which period the second waste material, originally in the state of a foam, is left at normal outside temperatures (but avoiding the gel), its consistency that approximates to a solid, which can easily be machined with construction equipment, such as excavators or bulldozers, while still containing a lot of water (typically up to 40% by weight). The low density foams were found to give rise to better consistency. The density of the foam must usually be less than 95% of that of the second waste material before treatment. Values lower than 90%, preferably lower than 85%, more preferably lower than 80%, are favorable. It is preferred that the density does not fall below 30%. Values of 60 - 75% are particularly suitable.

Foaming of the second waste material can be carried out with any known foaming technique, which is tailored to the second waste material to be treated. In general, phosphating the second waste material with the aid of phosphoric acid causes a sufficient development of gas to obtain foaming. If it is insufficient, the foaming can be achieved in particular chemically by the addition of reagents which cause the development of gas in situ. In a preferred embodiment, the reaction of an acid, such as hydrochloric acid, sulfuric acid or phosphoric acid, with, for example, a carbonate is used to cause gas release. It has been observed that the release of H 2 S gas during phosphating improves the conversion of the sludge into a foam. The addition or presence of surfactants that stabilize the foam is also beneficial. In this connection, it has been observed that certain humic acids present in the sludge obtained by the cleaning of waterways have a favorable effect on foaming, probably caused by their surface-active character. However, as a function of the waste to be treated, it will optionally be appropriate to add certain surfactants to obtain a foam with a density according to the invention. The selection of the most suitable surfactant and the amount thereof to be used will be made in a manner known per se from case to case. On the other hand, it is preferred that the second waste material is mechanically stirred to facilitate foaming. The stirring intensity is selected as a function of the particular conditions of use of the method according to the invention. It is favorable that the mechanical stirring is not too intense. The help of mixing screws should generally be avoided, since they usually impede the formation of the foam. The use of tubular reactors, which are segments of tubes, with or without static mixers, is recommended. They advantageously have dimensions such that a residence time of 2-10 seconds is obtained. In any case, the mechanical stirring is controlled such that the foaming according to the invention is favored. In certain cases, it is preferred that the reagent causing foaming be added to the second waste material after its passage through a pump that will cause the desired mechanical stirring. The use of static mixers can also be beneficial to obtain the optimum intensity of the mechanical stirring.

Foaming advantageously comprises a ripening period. After all, the reaction of the second waste material with phosphoric acid and / or any other reagent requires a certain time. It is recommended that the duration of the ripening period be sufficient so that 80%, preferably 90%, more preferably 95% of the reagents used. In general, a period of 2 days, preferably 3 days, is well suited.

According to a favorable variant, the method comprises a step of foaming and the resulting foam, which is advantageously matured, is dried. In the following description, "dried sludge" means the product obtained as a result of drying the foam. This product is no longer necessarily in the state of a foam because the foam tends to compact during drying. The foam is preferably subjected to an identical treatment as compost. Composting is a well-known technique for treating fermentable waste materials (which can be fermented), such as green waste. It consists essentially of storing the second waste material in contact with air for a long period of time at external ambient temperature, so that organic substances present in the second waste material are degraded and removed by calculating the liquid it contains. . The use, according to this embodiment of the invention, of techniques similar to composting, for drying the foamed sludge, which contains organic substances - even non-fermentable - and heavy metals, makes it possible for surprisingly high drynesses to be very eco-friendly. be obtained in an economic way. This reduces the use of energy during any subsequent calcining of the foam. Drying the foam with techniques that are similar to composting even make it possible to dispense with the calcining step because the degradation of organic substances obtained is sufficient.

During drying, the second waste material is advantageously stored for a sufficiently long period so that the water can be removed spontaneously, under the influence of gravity. A drying period of more than 24 hours is often necessary. The drying preferably lasts at least 48 hours. Drying for more than a month has not proved useful. Drying periods of one to two weeks have proven to be very suitable.

As explained above, when the second waste material is present in the form of a foam, drying is easier and more effective. After all, the improved consistency of the dried foam makes it possible to process its mass with conventional building tools and, in particular, makes it possible to manipulate it during composting. This ensures that the desired drynesses are achieved faster.

According to a recommended variant of this embodiment, drying is carried out under conditions such that after 12 days of drying, the dried foam reaches a dryness of more than 65%, preferably 70%.

Drying can also be carried out directly on the earth. In a favorable embodiment of the method according to the invention, however, the foam is applied to a layer of sand.

In this embodiment, it is preferable for the layer of sand itself to be applied to a water-impermeable membrane to avoid contaminating the earth with the heavy metals and thereby recovering the water from the phosphated sludge during composting , is possible. Membranes from plastic materials, for example from polyethylene or PVC, are very suitable.

Drying can take place outdoors, without protection against possible rain showers and large variations in temperature, on the understanding that it remains above 0 ° C. It is nevertheless preferred to use a closed drying system, such as a composting tunnel. Such composting tunnels are generally known in the field of the industrial treatment of organic waste materials that can be fermented. The composting tunnel is advantageously provided with air circulation systems and systems for collecting and treating emitted gases, such as hydrogen sulphide. The hydrogen sulfide is preferably recovered and, for example, treated on a biofilter or reinjected during a possible calcination. It is preferred that the composting tunnel comprises a layer of sand that is applied to a water-impermeable membrane.

Further details of calcination.

The calcination is intended to break down the organic material present in the first waste material and in the optional second waste material. The organic material may include, for example, non-polar hydrocarbons, aliphatic or aromatic (mono- or polycyclic) hydrocarbons and halogenated solvents. The calcining is generally carried out at a temperature higher than 450 ° C, so that the organic material is sufficiently degraded. It is convenient to avoid an excessive temperature that would result in the evaporation of a portion of the heavy metals. In practice, the calcining temperature is lower than 1000 ° C. Preferably, the calcination temperature is higher than 500 ° C and lower than 800 ° C. In order to break down the organic materials particularly well and to evaporate as little heavy metals as possible, it is particularly favorable that the calcining temperature is 550 ° C - 750 ° C.

It has been observed that calcination is advantageously carried out under controlled atmosphere.

With this in mind, in a particular embodiment of the method according to the invention, this atmosphere is oxidizing. This variant facilitates the thickening of the possibly adjoining mortar, as described below. In this case, for example, ambient air can be used. It must therefore be ensured that the air is available in the oven in sufficient quantity.

In another particular embodiment, the atmosphere is reducing. This embodiment is particularly advantageous because it inhibits the formation of chromium VI.

The duration of the calcination depends on the composition of the waste material to be treated and the distribution of the material in the calcining oven. It must also be sufficient to break down the organic material.

Details of the after-treatment of the third waste.

The product from the calcining step can be mixed with water and then thickened and cured. In this embodiment, a reducing additive is preferably included in the mixing water. As an example, this additive can be selected from iron, manganese, compounds of iron (II), compounds of manganese (II) and reducing salts of alkali metals. Sodium sulfite is preferred. The reducing agent is advantageously added in a weight amount of 0.1-1% by weight of the dry substance present in the sludge.

During calcination, certain sludge, in particular that that is rich in calcite, causes the formation of puzzolan earth. In this case, it is not necessary to add a hydraulic binder to cause thickening and hardening.

When a hydraulic binder is necessary to ensure thickening and curing, its precise composition is not critical. It usually consists of Portland cement. Puzzolane materials, such as carbon combustion ash, may also be suitable. A sufficient amount of mixed water must be added during mixing of the hydraulic binder with the calcining product intended to form a mortar to obtain a plastic slurry. The amount of the hydraulic binder to be used depends on various parameters, in particular on the chosen hydraulic binder, the composition of the sludge and the desired properties of the end product of the treatment method according to the invention, in particular its mechanical resistance. In practice it is often recommended to use a weight amount of binder in excess of 1% by weight of the calcining ash. According to the invention, it is desirable that the weight of the hydraulic binder is less than 50% and preferably does not exceed 30%.

In a favorable variant of the method according to the invention, a weight amount of hydraulic binder of more than 2% and less than 20% of the calcining product is used.

The shape of the solid mass obtained after curing, which can take several days, is that in which the mortar is produced. It may, for example, comprise bricks or spherical or prismatic blocks. It is compact, almost without gaseous inclusions and therefore has good mechanical properties, in particular a sufficient hardness and shock resistance, so that processing and storage thereof is possible without problems.

The solid and compact mass obtained after curing advantageously respects the standards of toxicity with regard to extracted leaching products according to heavy procedures, such as those defined by the "TL" or "NEN" regulations.

The French triple leaching "TL" test is described in the French regulation XPX 31 - 210. The test protocol consists of grinding the substance so that it can pass through a 4 mm sieve. This ground substance is leached three times with demineralized water, in a liquid / solid ratio of 10, with constant stirring. At the end of each leaching, the content of heavy metals in the liquid is measured.

The Dutch test "NEN" consists, for this test, of grinding the sample (smaller than 4 mm) and adding it to a water-solids ratio of 10. It is then kept at a pH for three hours of 7, then also for three hours at a pH of 4 (this is the minimum pH of rainwater). The pH is adjusted continuously with the aid of an IN nitric acid solution (non-complexing acid). The content of heavy metals in the liquid phase is then determined by analysis.

According to the American test TCLP (Toxicity Characteristic Leaching Procedure), 100 g of solid is taken, passed through a 9.5 mm sieve and the sample is contacted for 18 hours with 2000 ml of a solution of 5.7 g / l of CH3 COOH.

Claims (46)

A method for treating waste material containing heavy non-inert metals (the &quot; first waste material &quot;), according to which method the first waste material is added to a calcining oven, wherein also a phosphating agent is added to the calcining oven and the first waste material is calcined in the presence of the phosphating agent, the phosphating agent comprising: - at least one salt S of at least one metal other than a heavy metal, the salt S being a salt derived from phosphorus, the salt S is at least partially in its ionic form and the salt S is selected from: (i) the salts S1, comprising at least one mono- or polyphosphate group, which corresponds to the general formula <img img-format = "tif" img-content = "drawing" file = "NL2010974CC00221.tif" id = "icf0001" /> wherein x is an integer positive number or zero and wherein the (3 + x) oxygen atoms characterized by an asterix (O *) are independently bonded to a hydrogen atom or to a metal atom other than a heavy metal, with provided that at least one of them is bonded to a metal atom other than a heavy metal, (ii) the polymetaphosphate salts S2, comprising at least one ring corresponding to the formula <img img-format = "tif" img-content = "drawing" file = "NL2010974CC00231.tif" id = "icf0002" /> wherein y is an integer of at least 3, and wherein the y atoms of oxygen characterized by an asterix (O *) are bonded to a metal different from a heavy metal, and (iii) the salts S3, which comprise at least one mono- or polyphosphite group, which corresponds to the general formula <img img-format = "tif" img-content = "drawing" file = "NL2010974CC00232.tif" id = "icf0003" /> wherein z is an integer positive number or zero, wherein one of the 2 oxygen atoms marked with an asterix (O *) is bonded to a metal atom different from a heavy metal, and wherein the other oxygen atom labeled with an asterix is bonded to either a hydrogen atom or a metal atom other than a heavy metal, and - if desired additionally at least one acid A, derived from phosphorus, as such or at least partially in an ionic form selected from: (i ' the mono- or polyphosphoric acids A1 corresponding to the general formula <img img-format = "tif" img-content = "drawing" file = "NL2010974CC00241.tif" id = "icf0004" /> wherein x 'is an integer positive number or zero, and (ii) the mono- or polyphosphoric acids A2 corresponding to the general formula <img img-format = "tif" img-content = "drawing" file = "NL2010974CC00242.tif" id = "icf0005" /> wherein z 'is an integer positive number or zero, the total phosphorus content that is present in the at least one salt S, relative to the total phosphorus content that is present in the at least one salt S and the at least one acid A , is higher than 50% and can reach 100%, and wherein the total phosphorus content present in the at least one salt S and the at least one acid A, relative to the total phosphorus content present in the phosphating agent, more than 75% and can reach 100%. Method according to claim 1, characterized in that the total phosphorus content that is present in the salt S, compared to the total phosphorus content that is present in the salt S and the acid A, is higher than 90%. Method according to claim 1 or 2, characterized in that the phosphating agent is substantially free of acid A. Method according to one of the preceding claims, characterized in that the phosphating agent consists essentially of the salt S and the optional acid A. Method according to one of the preceding claims, characterized in that the salts S1, S2 and S3 comprise calcium as a metal element. Method according to one of the preceding claims, characterized in that the metal salt S is selected from the salts S1. Method according to claim 6, characterized in that the salts S1 contain at least one monophosphate group. The method according to claim 6 or 7, characterized in that the salts S1 do not contain a polyphosphate group. Process according to one of the preceding claims, characterized in that the salt S consists of a salt selected from calcium orthophosphate [Ca 3 (PO 4) 2], calcium monohydrogen phosphate (CaHPO 4), calcium dihydrogen phosphate [Ca (H 2 PO 4) 2], &quot; tricalcium phosphate &quot; TCP [Ca9 (PO4) 6], whitlockites and apatites, hydrated forms of said salts, and mixtures thereof, or include them. A method according to claim 9, characterized in that the salt S consists of, or comprises, the anhydrous calcium monohydrogen phosphate and / or a hydrated calcium monohydrogen phosphate. A method according to claim 9 or 10, characterized in that the salt S is or comprises a whitlockite which corresponds to the formula Ca 9 (Mg, Fe) (PO 4) 6 (HPO 4). A method according to claim 9, 10 or 11, characterized in that the salt comprises or comprises S hydroxyapatite [Ca 5 (PO 4) 3 (OH)]. A method according to any one of the preceding claims, characterized in that the weight of the phosphating agent, expressed in phosphorus equivalent and at least 0.35% with respect to the weight of the dry matter of the first waste material. A method according to any one of the preceding claims, characterized in that the weight of the phosphating agent, expressed in phosphorus equivalent and with respect to the weight of the dry matter of the first waste material, is a maximum of 5%. Method according to one of the preceding claims, characterized in that the calcination is carried out at a temperature or in a temperature range of 450 ° C to 1000 ° C. Process according to one of the preceding claims, characterized in that the calcination is carried out under an oxidizing atmosphere. A method according to any one of the preceding claims, characterized in that more than 10% by weight of the heavy metals present in the first waste material can be eluted in 0.5 M acetic acid. Method according to one of the preceding claims, characterized in that the first waste material has a dryness of at least 85%. A method according to any one of the preceding claims, characterized in that the first waste material is a sludge of natural origin, which must be dried to obtain a dryness of at least 70%, or a natural or non-natural substantially dry waste material. A method according to claim 19, characterized in that the first waste material is a sludge from a purification device that is dried to achieve a dryness of at least 80%. Method according to one of claims 1 to 19, characterized in that the first waste material consists of plastic parts and / or ground parts of used cars. A method according to any one of the preceding claims, characterized in that the phosphating agent is present at least in part in a second waste material containing inert heavy metals by a phosphating treatment, and in that the first waste material and the second waste material are added to the calcining oven after which the first waste material and the second waste material are calcined together. A method according to claim 22, characterized in that it furthermore comprises the step in which a waste material containing non-inert heavy metals is subjected to a phosphating treatment, which waste material, after being subjected to this phosphating treatment, forms the second waste material . The method of claim 22 or 23, wherein the phosphating agent is completely present in the second waste material. A method according to claim 22 or 23 or 24, characterized in that a maximum of 10% by weight of the heavy metals present in the second waste material can be eluted in 0.5 M acetic acid. A method according to claim 22 or one of claims 23 to 25, characterized in that the eluable weight fraction of the heavy metals present in the second waste material is at least 4 times lower than the eluable weight fraction of the heavy metal metals present in the first waste material. Method according to claim 22 or according to one of claims 23 to 26, characterized in that the second waste material has a dryness of at least 85%. A method as claimed in claim 22 or as claimed in any of the claims 23-27, characterized in that the second waste material is a sludge of natural or non-natural origin. A method according to claim 28, characterized in that the second waste material consists of sediments obtained by purifying an aqueous medium, such as a watercourse or a region of stagnant water. A method according to any one of claims 23 to 29, characterized in that the second waste material is a waste material with which a phosphating treatment with phosphoric acid in a moist environment has been carried out. A method according to any one of claims 23 to 30, characterized in that the second waste material is a sludge with an original dryness of less than 70% (i) converted into a foam to which at least one acid A is added, which acid is selected from the acids A1 and the acids A2, (ii) which is matured so that the phosphation develops inside the foam after which (iii) it is dried until a dryness of at least 70% is achieved. A method according to claim 31, characterized in that the sludge is matured for a sufficient time, so that a fraction of the acid A is converted into the salt S, which is according to claim 2 or 3, and preferably for at least 3 hours . A method according to claim 31 or 32, characterized in that the sludge is matured for a sufficient time so that the percentage by weight of the heavy metals that can be eluted in 0.5 M acetic acid containing said sludge is at least 4 times lower is then the percentage by weight of the heavy metals that can be eluted in 0.5 M acetic acid present in the sludge before the acid A is added to it. A method according to any one of claims 31 to 33, characterized in that the sludge is matured for a sufficient time so that the weight percentage of the heavy metals, directly in 0.5 M acetic acid, which are present in said sludge can be eluted , according to claim 25. The method according to any of claims 22 to 34, characterized in that the first waste material and the second waste material are added separately to the calcining furnace. A method according to any one of claims 22 to 34, characterized in that the first waste material and the second waste material have the consistency of a solid and not of an aqueous slurry, and that the first waste material and the second waste material without adding water so that the homogeneous or heterogeneous mixture of the first waste and the second waste also has the consistency of a solid and not an aqueous slurry, after which the mixture is added to the calcining oven as soon as it is able to and immediately after the formation of the mixture. A method according to any one of claims 22 to 36, characterized in that the weight quantity of the first waste material is at least 20% of the weight quantity of the second waste material. A method according to any one of claims 22 to 37, characterized in that the weight amount of the first waste material is at most 100% of the weight amount of the second waste material. A method according to any one of claims 22 to 38, characterized in that the first waste material and the second waste material together form a self-combustible substance in the calcining oven, which can be calcined in the absence of a third fuel with a much lower increase calorific capacity than that of the mixture formed by the first waste material and the second waste material. A method according to any one of the preceding claims, characterized in that the calcining produces slag containing inert heavy metals, and fly ash containing inert heavy metals, each of these two products of calcining, individually or mixed, a waste material that can be valorised (the &quot; third waste material &quot;). A method according to claim 40, characterized in that a maximum of 10% by weight of the heavy metals present in the third waste material can be eluted in 0.5 M acetic acid. A method according to claim 40 or 41, characterized in that the eluable weight fraction of the heavy metals present in the third waste material is at most half the eluable weight fraction of the heavy metals present in the second waste are. Method according to one of claims 40 to 42, characterized in that the third waste material is mixed with water, if desired a hydraulic binder is added, after which the mixture comprising the third waste material, water and any hydraulic binder is subjected becomes thickening and curing in such a way that a solid mass is formed. 44. Use of a waste material (called &quot; second waste material &quot;), containing inert heavy metals, by a phosphating treatment as an inerting agent in a calcining furnace of another waste material containing heavy non-inert metals (the &quot; first waste material &quot;). A method of forming a solid mass that can be used in the construction of a road, the manufacture of a stone or the production of a concrete, according to which method the waste material, which is claimed in any one of claims 40 to 42 ( &quot; third waste material &quot;) is produced, mixed with water, optionally a hydraulic binder is added, after which the mixture comprising the third waste material, water and any hydraulic binder is subjected to thickening and hardening in such a way that a solid mass is formed .. A finished product, such as a road, a brick or a concrete, which comprises the solid mass formed by the method according to claim 43 or by the method according to claim 45.