CA2665350A1 - Method for treating mineral sludge and installation for carrying out same - Google Patents
Method for treating mineral sludge and installation for carrying out same Download PDFInfo
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- CA2665350A1 CA2665350A1 CA002665350A CA2665350A CA2665350A1 CA 2665350 A1 CA2665350 A1 CA 2665350A1 CA 002665350 A CA002665350 A CA 002665350A CA 2665350 A CA2665350 A CA 2665350A CA 2665350 A1 CA2665350 A1 CA 2665350A1
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- sludge
- flocculating agent
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F11/00—Treatment of sludge; Devices therefor
- C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
- C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
- C02F11/147—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using organic substances
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/001—Runoff or storm water
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/10—Nature of the water, waste water, sewage or sludge to be treated from quarries or from mining activities
Abstract
A method for treating sludge from the mining or mineral industry, whereby, before spreading above ground, the sludge is subjected to an upward movement during which it is contacted with a flocculating agent.
Description
METHOD FOR TREATING MINERAL SLUDGE AND INSTALLATION FOR
CARRYING OUT SAME
The present invention relates to a method for treating mineral sludge and an installation for implementing the method. It applies, inter alia, to the treatment of effluents from the mining or mineral industry, dredging processes, or public works operations generating large quantities of mineral sludge, for their dehydration and solidification above the ground.
Due to their substantial volume, these sludges raise a major storage problem insofar as they are indestructible.
Conventionally, they were mainly stored by spreading the sludge in closed areas where the sludge settled and was then abandoned:
- construction of a dam on entrenched valleys, - use of the excavations produced by the removal of the materials, - more or less natural lagoons (basins), - construction of border strips with embankments.
While certain coarse sludges (sand, gravel, etc.) can dry and reconstitute a soil usable in agriculture for example, most effluents, containing large quantities of suspended matter in colloidal form (clay, silt, etc.), are particularly stable and difficult to settle out and do not dehydrate.
~, In the context of the present invention, the terms "sand", gravel , "clay"
and "silt"
designate the size of the grain rather than its composition. Sand is a material passing through a No. 4 sieve (4.76 mm), but not through a No. 200 sieve (0.074 mm).
Gravel is a granular material that does not pass a No. 4 sieve and can be as large as 9 cm.
The finest colloidal material passing through the No. 200 sieve iscalled clay or silt.
Stored in this way, these sludges constitute risk zones in the long term, particularly said sludge basins in case of dam break. Moreover, with a more or less dry surface crust, covering a soft "colloidal layer", these storage areas cannot withstand the weight of animals, pedestrians, or vehicles.
Since conventional storage solutions have proved inadequate or even dangerous, a growing body of national regulations had been published prohibiting the abandonment of these zones, accompanied by a remediation obligation, that is treatment and consolidation.
For this purpose, various techniques have been tested in order to facilitate the removal of the trapped water: vibration, porous cores, drains, high-evaporation trees, but the layers are so thick (3 to 150 meters) and the quantity of trapped water so large that these treatments have all failed.
A first improvement was obtained by thickening the effluents before sending them to the basins. The thickening (or conditioning) consists of a flocculation of the sludge aimed to promote, with slow mixing, the contact between the colloidal particles, which then gather together to form more bulky aggregates (flocs).
The application of this technique has made it possible to double the dry matter concentration of the sludges treated, but in most cases (colloidal clays, red sludge, tar sand sludge, dredging with high silt, etc.) the results have been inadequate.
In particular, it has turned out that the transport of these sludges by pipeline before storage resulted in the destruction of the flocs, thereby at least partially returning the sludge to its original colloidal structure.
In 1979-1980 Alsthom Atlantique and SNF (US 4347140) developed a multistep flocculation system designed for the special treatment of clay lagoons created by phosphate production in Florida.
In a first step, the method applied consisted in using flocculents to condition the sludges (originating either from a phosphate washery, or from dredging lagoons where they had been stored), in a settler, or a settlerfollowed by a thickener.
The thickened sludge was then pumped to a zone above the ground, where it was then deposited after a piped addition at one or more points of an additional quantity of flocculent. This overflocculation in the line had the result of enabling the sludge to constitute a flow slope, thereby allowing storage above the ground and not in a border strip. The water which escaped from the sludge thus overflocculatedwas recycled via a peripheral ditch and repumped to the phosphate washery and/or to a flocculent dilution unit, in order to increase its effectiveness. It was also demonstrated that a ballast layer, located under the storage zone, allowed drainage of the bore water and sharply decrease the drying time. Similarly, the addition of the flocculent at several points had the effect of improving its effectiveness and allowing a partial reduction of its consumption.
Simultaneously, some tests with flocculent injection from a pressure chamber incorporated in the piping allowed a significant but very limited iinprovement of the system.
The Alsthom method, although innovative, has many drawbacks:
- the need to dilute the flocculent (usually to under 1 g/1) so that it can be mixed with the sludge flow within a few seconds, thereby increasing the volume of sludge by 30 to 40%, - moreover, due to the pumping speed usually applied in the piping (about 2 to 3 m/sec), a high overbatching of the flocculent is necessary so that the flocs are not destroyed as they are formed.
The invention overcoines all the drawbacks described above.
Description of the invention It is therefore the object of the present invention to develop a method and an installation for treating effluents from the mining or mineral industry for their dehydration and subsequent solidification above the ground, so that the storage location again becomes usable.
According to the invention, it has been found surprisingly that the upward movement of a sludge issuing from the mining or mineral industry in a vertical tank serving as a flocculator, placed at the pipe outlet just before the spreading operation, and in which a flocculating agent is introduced via one or more telescopic injection pipes, served to significantly improve the settling of the fine solid particles present in the sludges during their storage above the ground for the remediation of the areas used.
A primary object of the invention is therefore a method for treating sludge from the mining or mineral industry, whereby, before spreading above ground, the sludge is subjected to an upward movement during which it is contacted with a flocculating agent.
In the rest of the description and in the claims, "sludge" means an effluent issuing from the mining or mineral industry, from dredging processes or public works operations. The inventive method therefore consists in inserting, before the spreading step, a specific flocculation step during which the sludge undergoes an upward movement.
According to a first feature, the upward speed of the sludge is higher than its settling rate. The upward speed is between 0.1 and 0.5 m/s in practice.
Advantageously, the upward movement is duplicated by a centrifugal movement entraining the mixture of the sludge and the flocculating agent at a speed of between 0.2 and 0.8 m/s. This produces a uniform mixture. It is also possible to accelerate the sludge in the tank through the presence of deflectors obscuring part of the surface and changing the direction of the currents, thereby improving the mixing and flocculation.
According to the invention, the flocculating agent is introduced into the sludge in a concentration of between 50 and 500 g per tonne of solid according to the type and composition of the sludge to be treated.
In practice, the contact time between the sludge and the flocculating agent is between.
1 and 10 minutes, advantageously between 2 and 5 minutes.
According to another feature, the flow angle of the sludge at the time of spreading is preferably between 2 and 20% (i.e. level difference per 100 meters at the horizontal).
A further object of the present invention is an installation for implementing the method.
This installation is characterized in that it comprises a vertical tank fed at its base by a sludge intake line.
According to another feature, the tank is preferably provided in the upper part with a 30, ramp suitable for removing the sludge.
In practice:
a) the tank:
- has a diameter for maintaining an upward speed higher than the settling rate of the flocculated sludge, - has an inlet pipe for the sludge to be treated, either via an immersion tube or a line, located in the bottom part of the tank and shaped so as to create a centrifugal effect allowing a mixing at low speed (0.2 to 0.8 m/sec), - and is dimensioned so that the sludge has a residence time of between 1 and 5 10 minutes, preferably between 2 and 5 minutes, b) the flocculating agent:
- is introduced via one or more - telescopic - injection pipes or distributed on the height of the tank for controlling the flocculation time. For example, with a tank and a residence time of 4 minutes, the mixing can take place in I to 4 minutes, depending on the height of the flocculent injection into the sludge, - and is preferably injected in dilute form, in a water solution or in a dispersion in a solvent medium (or brine) in which the flocculent is insoluble or not completely soluble, c) the flocculated sludge:
- is removed via the top of the tank, due to the upward speed, or is deposited on its storage area above the ground via a ramp consisting: - of one or more chutes, optionally perforated (curved grids), preferably made from steel or wood, or - via a riprap under the flocculation tank or - via large pipes at low speed (less than 0.2 m/sec).
This method serves both to very significantly reduce the consumption of flocculent in comparison with a direct addition of the same flocculent in the line, and also to sharply increase the flow angle of the sludge, which is usually 2 to 7% and can be raised to 8 to 20%.
It is also observed that the steeper the slope, the lower the pore water and the faster its drainage, despite the pressure exerted by the height of the sludge.
According to the invention, to obtain large storage volumes, it is necessary to construct relatively high flocculation tank supports (10, 20 up to 50 meters).
Similarly, once this treated and discharged sludge reaches the bottom of the tank, the tank has to be moved or another one reconstructed when it is positioned in a central pivot and impossible to recover.
In addition to the above arrangements, the invention also comprises other alternative embodiments. Among them, mention can be made of the following in a nonlimiting manner:
- the addition of sand, lime and/or calcium sulfate to the sludge, - the introduction of the flocculent at 2 points in the tank, or at one point in the line and the second in the tank according to the invention, or the use of 2 types of flocculents according to the abovementioned 2 introduction modes, - the presence of a cleaning opening at the bottom of the tank to remove the heavy gravel or sand that accumulates therein, - the use of a tank on wheels or rails, enabling it to move on the embankment, - the use of the angle created by the embankment as a ramp.
The invention has the following main advantages:
- sharp reduction in flocculent consumption, - significant improvement in dehydration and solidification of the sludge, - and considerable adaptability to the requirements associated both with the type of sludge to be treated (in terms of composition: quantities of fines/sand, specific surface area, etc.), to the flow rate and to the conditions associated with the storage site itself (no electricity, relatively inaccessible, etc.).
Typically and without limitation, the sludgy effluents from the industry and treated according to the invention originate from dredging processes, public works operations, effluents issuing from ore extraction (coal, alumina, platinum, phosphate, iron, diamonds, gold, copper, etc.), tar sands, or any type of aqueous sludge consisting of clays or silts.
According to the invention, the flocculating agents used include all types of organic polymers soluble in water, including cationic, anionic, nonionic or amphoteric (co)polymers. The most appropriate flocculating agent for the sludge is first selected in the laboratory after routine tests. Preferably, it is selected from the group comprising:
- anionic (co)polymers, - cationic or amphoteric (co)polymers, generally for the most organic sludges, such as canal dredging sludge, - polyacrylates, polyhydroxamates, or even natural polymers such as dextran, generally for red alumina sludge, - polyamines or polydiallyldimethylamonium chloride (polydadmac), generally for drilling muds.
In practice, the polymer used consists preferably of at least one monomer selected from:
a) anionic monomers having a carboxylic function (e.g.: acrylic acid, methacrylic acid, and salts thereofJ, having a sulfonic acid function (e.g.: 2-acrylamido-
CARRYING OUT SAME
The present invention relates to a method for treating mineral sludge and an installation for implementing the method. It applies, inter alia, to the treatment of effluents from the mining or mineral industry, dredging processes, or public works operations generating large quantities of mineral sludge, for their dehydration and solidification above the ground.
Due to their substantial volume, these sludges raise a major storage problem insofar as they are indestructible.
Conventionally, they were mainly stored by spreading the sludge in closed areas where the sludge settled and was then abandoned:
- construction of a dam on entrenched valleys, - use of the excavations produced by the removal of the materials, - more or less natural lagoons (basins), - construction of border strips with embankments.
While certain coarse sludges (sand, gravel, etc.) can dry and reconstitute a soil usable in agriculture for example, most effluents, containing large quantities of suspended matter in colloidal form (clay, silt, etc.), are particularly stable and difficult to settle out and do not dehydrate.
~, In the context of the present invention, the terms "sand", gravel , "clay"
and "silt"
designate the size of the grain rather than its composition. Sand is a material passing through a No. 4 sieve (4.76 mm), but not through a No. 200 sieve (0.074 mm).
Gravel is a granular material that does not pass a No. 4 sieve and can be as large as 9 cm.
The finest colloidal material passing through the No. 200 sieve iscalled clay or silt.
Stored in this way, these sludges constitute risk zones in the long term, particularly said sludge basins in case of dam break. Moreover, with a more or less dry surface crust, covering a soft "colloidal layer", these storage areas cannot withstand the weight of animals, pedestrians, or vehicles.
Since conventional storage solutions have proved inadequate or even dangerous, a growing body of national regulations had been published prohibiting the abandonment of these zones, accompanied by a remediation obligation, that is treatment and consolidation.
For this purpose, various techniques have been tested in order to facilitate the removal of the trapped water: vibration, porous cores, drains, high-evaporation trees, but the layers are so thick (3 to 150 meters) and the quantity of trapped water so large that these treatments have all failed.
A first improvement was obtained by thickening the effluents before sending them to the basins. The thickening (or conditioning) consists of a flocculation of the sludge aimed to promote, with slow mixing, the contact between the colloidal particles, which then gather together to form more bulky aggregates (flocs).
The application of this technique has made it possible to double the dry matter concentration of the sludges treated, but in most cases (colloidal clays, red sludge, tar sand sludge, dredging with high silt, etc.) the results have been inadequate.
In particular, it has turned out that the transport of these sludges by pipeline before storage resulted in the destruction of the flocs, thereby at least partially returning the sludge to its original colloidal structure.
In 1979-1980 Alsthom Atlantique and SNF (US 4347140) developed a multistep flocculation system designed for the special treatment of clay lagoons created by phosphate production in Florida.
In a first step, the method applied consisted in using flocculents to condition the sludges (originating either from a phosphate washery, or from dredging lagoons where they had been stored), in a settler, or a settlerfollowed by a thickener.
The thickened sludge was then pumped to a zone above the ground, where it was then deposited after a piped addition at one or more points of an additional quantity of flocculent. This overflocculation in the line had the result of enabling the sludge to constitute a flow slope, thereby allowing storage above the ground and not in a border strip. The water which escaped from the sludge thus overflocculatedwas recycled via a peripheral ditch and repumped to the phosphate washery and/or to a flocculent dilution unit, in order to increase its effectiveness. It was also demonstrated that a ballast layer, located under the storage zone, allowed drainage of the bore water and sharply decrease the drying time. Similarly, the addition of the flocculent at several points had the effect of improving its effectiveness and allowing a partial reduction of its consumption.
Simultaneously, some tests with flocculent injection from a pressure chamber incorporated in the piping allowed a significant but very limited iinprovement of the system.
The Alsthom method, although innovative, has many drawbacks:
- the need to dilute the flocculent (usually to under 1 g/1) so that it can be mixed with the sludge flow within a few seconds, thereby increasing the volume of sludge by 30 to 40%, - moreover, due to the pumping speed usually applied in the piping (about 2 to 3 m/sec), a high overbatching of the flocculent is necessary so that the flocs are not destroyed as they are formed.
The invention overcoines all the drawbacks described above.
Description of the invention It is therefore the object of the present invention to develop a method and an installation for treating effluents from the mining or mineral industry for their dehydration and subsequent solidification above the ground, so that the storage location again becomes usable.
According to the invention, it has been found surprisingly that the upward movement of a sludge issuing from the mining or mineral industry in a vertical tank serving as a flocculator, placed at the pipe outlet just before the spreading operation, and in which a flocculating agent is introduced via one or more telescopic injection pipes, served to significantly improve the settling of the fine solid particles present in the sludges during their storage above the ground for the remediation of the areas used.
A primary object of the invention is therefore a method for treating sludge from the mining or mineral industry, whereby, before spreading above ground, the sludge is subjected to an upward movement during which it is contacted with a flocculating agent.
In the rest of the description and in the claims, "sludge" means an effluent issuing from the mining or mineral industry, from dredging processes or public works operations. The inventive method therefore consists in inserting, before the spreading step, a specific flocculation step during which the sludge undergoes an upward movement.
According to a first feature, the upward speed of the sludge is higher than its settling rate. The upward speed is between 0.1 and 0.5 m/s in practice.
Advantageously, the upward movement is duplicated by a centrifugal movement entraining the mixture of the sludge and the flocculating agent at a speed of between 0.2 and 0.8 m/s. This produces a uniform mixture. It is also possible to accelerate the sludge in the tank through the presence of deflectors obscuring part of the surface and changing the direction of the currents, thereby improving the mixing and flocculation.
According to the invention, the flocculating agent is introduced into the sludge in a concentration of between 50 and 500 g per tonne of solid according to the type and composition of the sludge to be treated.
In practice, the contact time between the sludge and the flocculating agent is between.
1 and 10 minutes, advantageously between 2 and 5 minutes.
According to another feature, the flow angle of the sludge at the time of spreading is preferably between 2 and 20% (i.e. level difference per 100 meters at the horizontal).
A further object of the present invention is an installation for implementing the method.
This installation is characterized in that it comprises a vertical tank fed at its base by a sludge intake line.
According to another feature, the tank is preferably provided in the upper part with a 30, ramp suitable for removing the sludge.
In practice:
a) the tank:
- has a diameter for maintaining an upward speed higher than the settling rate of the flocculated sludge, - has an inlet pipe for the sludge to be treated, either via an immersion tube or a line, located in the bottom part of the tank and shaped so as to create a centrifugal effect allowing a mixing at low speed (0.2 to 0.8 m/sec), - and is dimensioned so that the sludge has a residence time of between 1 and 5 10 minutes, preferably between 2 and 5 minutes, b) the flocculating agent:
- is introduced via one or more - telescopic - injection pipes or distributed on the height of the tank for controlling the flocculation time. For example, with a tank and a residence time of 4 minutes, the mixing can take place in I to 4 minutes, depending on the height of the flocculent injection into the sludge, - and is preferably injected in dilute form, in a water solution or in a dispersion in a solvent medium (or brine) in which the flocculent is insoluble or not completely soluble, c) the flocculated sludge:
- is removed via the top of the tank, due to the upward speed, or is deposited on its storage area above the ground via a ramp consisting: - of one or more chutes, optionally perforated (curved grids), preferably made from steel or wood, or - via a riprap under the flocculation tank or - via large pipes at low speed (less than 0.2 m/sec).
This method serves both to very significantly reduce the consumption of flocculent in comparison with a direct addition of the same flocculent in the line, and also to sharply increase the flow angle of the sludge, which is usually 2 to 7% and can be raised to 8 to 20%.
It is also observed that the steeper the slope, the lower the pore water and the faster its drainage, despite the pressure exerted by the height of the sludge.
According to the invention, to obtain large storage volumes, it is necessary to construct relatively high flocculation tank supports (10, 20 up to 50 meters).
Similarly, once this treated and discharged sludge reaches the bottom of the tank, the tank has to be moved or another one reconstructed when it is positioned in a central pivot and impossible to recover.
In addition to the above arrangements, the invention also comprises other alternative embodiments. Among them, mention can be made of the following in a nonlimiting manner:
- the addition of sand, lime and/or calcium sulfate to the sludge, - the introduction of the flocculent at 2 points in the tank, or at one point in the line and the second in the tank according to the invention, or the use of 2 types of flocculents according to the abovementioned 2 introduction modes, - the presence of a cleaning opening at the bottom of the tank to remove the heavy gravel or sand that accumulates therein, - the use of a tank on wheels or rails, enabling it to move on the embankment, - the use of the angle created by the embankment as a ramp.
The invention has the following main advantages:
- sharp reduction in flocculent consumption, - significant improvement in dehydration and solidification of the sludge, - and considerable adaptability to the requirements associated both with the type of sludge to be treated (in terms of composition: quantities of fines/sand, specific surface area, etc.), to the flow rate and to the conditions associated with the storage site itself (no electricity, relatively inaccessible, etc.).
Typically and without limitation, the sludgy effluents from the industry and treated according to the invention originate from dredging processes, public works operations, effluents issuing from ore extraction (coal, alumina, platinum, phosphate, iron, diamonds, gold, copper, etc.), tar sands, or any type of aqueous sludge consisting of clays or silts.
According to the invention, the flocculating agents used include all types of organic polymers soluble in water, including cationic, anionic, nonionic or amphoteric (co)polymers. The most appropriate flocculating agent for the sludge is first selected in the laboratory after routine tests. Preferably, it is selected from the group comprising:
- anionic (co)polymers, - cationic or amphoteric (co)polymers, generally for the most organic sludges, such as canal dredging sludge, - polyacrylates, polyhydroxamates, or even natural polymers such as dextran, generally for red alumina sludge, - polyamines or polydiallyldimethylamonium chloride (polydadmac), generally for drilling muds.
In practice, the polymer used consists preferably of at least one monomer selected from:
a) anionic monomers having a carboxylic function (e.g.: acrylic acid, methacrylic acid, and salts thereofJ, having a sulfonic acid function (e.g.: 2-acrylamido-
2-methylpropane sulfonic acid (AMPS) and salts thereof), b) and/or nonionic monomers: acrylamide, methacrylamide, N-vinyl pyrrolidone, vinylacetate, vinyl alcohol, acrylate esters, allyl alcohol, N-vinyl acetamide, N-vinylformamide, c) and/or cationic monomers: in particular and in a nonlimiting manner, mention can be made of dimethylaminoethyl acrylate (ADAME) and/or dimethylaminoethyl methacrylate (MADAME) quaternized or salified, dimethyldiallylammonium chloride (DADMAC), acrylamido propyltrimethyl ammonium chloride (APTAC) and/or methacrylamido propyltrimethyl ammonium chloride (MAPTAC).
In combination with these monomers, it is also possible to use monomers insoluble in water, such as acrylic, allyl or vinyl monomers, comprising hydrophobic group.
During their use, these monomers are employed in very small quantities, less than mol %, preferably less than 10.mo1 %, and they are preferably selected from the 20 group comprising derivatives of acrylamide such as N-alkylacrylamide for example, N-tert-butylacrylamide, octylacrylamide and the N,N-dialkylacrylamides such as N,N-dihexylacrylamide, derivatives of acrylic acid such as alkyl acrylates and methacrylates.
The flocculating agents may optionally be branched using a branching/crosslinking agent, optionally in the presence of a transfer agent. A nonlimiting list of branching/crosslinking agents is given below: methylene bisacrylamide (MBA), ethylene glycol di-acrylate, polyethylene glycol dimethacrylate, diacrylamide, cyanomethylacrylate, vinyloxyethylacrylate or methacrylate, triallylamine, formaldehyde, glyoxal, compounds of the glycidylether types such as ethyleneglycol diglycidylether, or epoxy or any other means well known to a person skilled in the art for crosslinking.
Similarly, the (co)polymers may also:
- issue from the family of polycondensates: epichlorhydrin resin, dicyandiamide resin, - or have undergone one (or more) post-modification reactions such as hydrolysis, Hoffman degradation, Mannich product, hydroxamation reaction.
The present invention is aimed particularly at installations for treating mining or mineral sludge suitable for the implementation of the invention, but also the implementation and treatment processes in which these apparatus are included.
Obviously, the following examples are only provided to illustrate the subject matter of the invention, but without in any way whatsoever constituting limitation thereof.
Figure 1 is a schematic representation of the invention of the installation according to a first embodiment.
Figure 2 is an alternative of Figure 1.
Figure 3 is a schematic representation of the tank in a first embodiment.
Figure 4 is a schematic representation of the tank in a second embodiment.
Figure 5 is a schematic representation of the installation of the invention according to a third embodiment.
Figure6 is a schematic representation of the installation of the invention applied to dredging.
Example 1 (counter-example) The effluents from a phosphate washery, after separation of the sand, are flocculated in a settler with an anionic flocculent (acrylamide/sodium acrylate 70/30, molecular weight 18 million) enabling the sludge thus treated to reach a concentration of 150 g/liter of dry matter.
The sludge is then pumped at a rate of 300 m3/h via a line to an embankment 20 meters high constructed on a bed ""of drained sand.
The same flocculent as the one used in the settler is introduced into the line after dilution to a concentration of 0.05 gLliter:
- at a first point 100 meters from the end of the line, - and at a second point 15 meters from the end of the line.
The quantities of flocculent required are then varied in order to create the maximum slope of the sludge thus flocculated (value of 5.5%).
The quantities of flocculating agent required are:
- about 200 g/tonne of sludge at the first injection point, - and 300 g/tonne of sludge at the second point, making a total of 500 g/tonne.
A sample of spread sludge is taken two days after the end of pumping. It contains 480 g/liter of solid matter. After 12 months of storage, the surface of the spreading site is cracked and sufficiently consolidated to permit the passage of alight vehicle.
Example 2 Example 1 above is reproduced. The effluents from a phosphate washery, after separation of the sand, are flocculated in a settler (1) with an anionic flocculent (acrylamide/sodium acrylate 70/30, molecular weight 18 million) enabling the sludge thus treated to reach a concentration of 150 g/liter of dry matter.
The sludge is then pumped at a rate of 300 m3/h via a line (3) to an embankment (2) 20 meters high constructed on a bed of drained sand.
A vertical cylindrical tank (4) with the useful volume of 6 m3 and a diameter of 1.20 meters, is installed after the line (3). A flocculation pipe (5.1) (Figure 2) is lowered into the tank in order to visually obtain the best flocculation both at the overflow and at the bottom of the ramp (6). The flocculation pipe must be immersed by about 4 meters. In an alternative shown in Figure 3, three side flocculation pipes (5.2) are used. The optimal quantity of flocculating agent required is g/tonne of sludge. The ramp has an angle of 20 to the ground. The flow slope (7) obtained is 9%.
After two days, the concentration of the spread sludge is 640 g/liter of solid matter.
The surface tracking is considerable after one morith of storage with very deep cracks.
After seven months, the sludge supports a light vehicle.
In the embodiment shown in Figure 4, the slope (2) is used as a ramp (6).
Example 3 A suction dredge (8) is used for the construction of a port in low level dunes consisting of about:
- 85 % of very fine sand with a maximum grain size of 1 mm.
- and silts consisting of very fine clays and a small quantity of organic matter.
Pumping is carried out on a 12 meter high dam via a 60 cm diameter pipe at an average flow rate of 1500 m3/h.
The tank, which is placed on an embankment (2), has a diameter of 2 meters and a 5 height of 6 meters. The ramp (6) has an angle of 20 to the ground.
The flocculent pipe (5) is introduced at the bottom of the tank (4) and the flocculent rate is determined visually (ditto example 1) to obtain good flocculation and a perfectly clear pore water.
The quantity of flocculent required is about 90 g/tonne of dry matter. Due to the variations in flow rate and composition, the average steady state consumption is about 110 g/tonne of treated sludge.
The slope obtained is very steep, on average 16%. The tank must therefore often be moved. The sand-silt mixture obtained is completely uniform. After one month, it is possible to level the treated surfaces by bulldozer and construct the storage buildings of the port within 6 months.
By way of comparison, when the same flocculent is introduced into a line 10 meters before the exit, about 180 g/tonne is needed to obtain a flocculation that is partially broken by the height of fall. Similarly,with an introduction at 2 points (at 100 meters and 10 meters from the exit) the consumption remains high at about 150 g/tonne. In this case, due to the partial breakage of the flocs, part of the silts is dispersed in the recovery water, therefore requiring passage through a settling lagoon before being discharged in the sea.
Example 4 In this embodiment, the tank.(4) is mounted on a support (9) at a height of about 20 meters. The tank is provided on its whole periphery with a ramp (6). It follows that the treated sludge is dumped on either side of the tank, above the ground. When the level of the treated sludge reaches the base of the tank, it is replaced or buried.
The invention and the advantages thereof clearly appear from the above description.
Particularly noteworthy is the significant improvement in the settling of the fine solid particles present in the sludge during its storage above the ground, to permit the remediation of the surfaces used.
In combination with these monomers, it is also possible to use monomers insoluble in water, such as acrylic, allyl or vinyl monomers, comprising hydrophobic group.
During their use, these monomers are employed in very small quantities, less than mol %, preferably less than 10.mo1 %, and they are preferably selected from the 20 group comprising derivatives of acrylamide such as N-alkylacrylamide for example, N-tert-butylacrylamide, octylacrylamide and the N,N-dialkylacrylamides such as N,N-dihexylacrylamide, derivatives of acrylic acid such as alkyl acrylates and methacrylates.
The flocculating agents may optionally be branched using a branching/crosslinking agent, optionally in the presence of a transfer agent. A nonlimiting list of branching/crosslinking agents is given below: methylene bisacrylamide (MBA), ethylene glycol di-acrylate, polyethylene glycol dimethacrylate, diacrylamide, cyanomethylacrylate, vinyloxyethylacrylate or methacrylate, triallylamine, formaldehyde, glyoxal, compounds of the glycidylether types such as ethyleneglycol diglycidylether, or epoxy or any other means well known to a person skilled in the art for crosslinking.
Similarly, the (co)polymers may also:
- issue from the family of polycondensates: epichlorhydrin resin, dicyandiamide resin, - or have undergone one (or more) post-modification reactions such as hydrolysis, Hoffman degradation, Mannich product, hydroxamation reaction.
The present invention is aimed particularly at installations for treating mining or mineral sludge suitable for the implementation of the invention, but also the implementation and treatment processes in which these apparatus are included.
Obviously, the following examples are only provided to illustrate the subject matter of the invention, but without in any way whatsoever constituting limitation thereof.
Figure 1 is a schematic representation of the invention of the installation according to a first embodiment.
Figure 2 is an alternative of Figure 1.
Figure 3 is a schematic representation of the tank in a first embodiment.
Figure 4 is a schematic representation of the tank in a second embodiment.
Figure 5 is a schematic representation of the installation of the invention according to a third embodiment.
Figure6 is a schematic representation of the installation of the invention applied to dredging.
Example 1 (counter-example) The effluents from a phosphate washery, after separation of the sand, are flocculated in a settler with an anionic flocculent (acrylamide/sodium acrylate 70/30, molecular weight 18 million) enabling the sludge thus treated to reach a concentration of 150 g/liter of dry matter.
The sludge is then pumped at a rate of 300 m3/h via a line to an embankment 20 meters high constructed on a bed ""of drained sand.
The same flocculent as the one used in the settler is introduced into the line after dilution to a concentration of 0.05 gLliter:
- at a first point 100 meters from the end of the line, - and at a second point 15 meters from the end of the line.
The quantities of flocculent required are then varied in order to create the maximum slope of the sludge thus flocculated (value of 5.5%).
The quantities of flocculating agent required are:
- about 200 g/tonne of sludge at the first injection point, - and 300 g/tonne of sludge at the second point, making a total of 500 g/tonne.
A sample of spread sludge is taken two days after the end of pumping. It contains 480 g/liter of solid matter. After 12 months of storage, the surface of the spreading site is cracked and sufficiently consolidated to permit the passage of alight vehicle.
Example 2 Example 1 above is reproduced. The effluents from a phosphate washery, after separation of the sand, are flocculated in a settler (1) with an anionic flocculent (acrylamide/sodium acrylate 70/30, molecular weight 18 million) enabling the sludge thus treated to reach a concentration of 150 g/liter of dry matter.
The sludge is then pumped at a rate of 300 m3/h via a line (3) to an embankment (2) 20 meters high constructed on a bed of drained sand.
A vertical cylindrical tank (4) with the useful volume of 6 m3 and a diameter of 1.20 meters, is installed after the line (3). A flocculation pipe (5.1) (Figure 2) is lowered into the tank in order to visually obtain the best flocculation both at the overflow and at the bottom of the ramp (6). The flocculation pipe must be immersed by about 4 meters. In an alternative shown in Figure 3, three side flocculation pipes (5.2) are used. The optimal quantity of flocculating agent required is g/tonne of sludge. The ramp has an angle of 20 to the ground. The flow slope (7) obtained is 9%.
After two days, the concentration of the spread sludge is 640 g/liter of solid matter.
The surface tracking is considerable after one morith of storage with very deep cracks.
After seven months, the sludge supports a light vehicle.
In the embodiment shown in Figure 4, the slope (2) is used as a ramp (6).
Example 3 A suction dredge (8) is used for the construction of a port in low level dunes consisting of about:
- 85 % of very fine sand with a maximum grain size of 1 mm.
- and silts consisting of very fine clays and a small quantity of organic matter.
Pumping is carried out on a 12 meter high dam via a 60 cm diameter pipe at an average flow rate of 1500 m3/h.
The tank, which is placed on an embankment (2), has a diameter of 2 meters and a 5 height of 6 meters. The ramp (6) has an angle of 20 to the ground.
The flocculent pipe (5) is introduced at the bottom of the tank (4) and the flocculent rate is determined visually (ditto example 1) to obtain good flocculation and a perfectly clear pore water.
The quantity of flocculent required is about 90 g/tonne of dry matter. Due to the variations in flow rate and composition, the average steady state consumption is about 110 g/tonne of treated sludge.
The slope obtained is very steep, on average 16%. The tank must therefore often be moved. The sand-silt mixture obtained is completely uniform. After one month, it is possible to level the treated surfaces by bulldozer and construct the storage buildings of the port within 6 months.
By way of comparison, when the same flocculent is introduced into a line 10 meters before the exit, about 180 g/tonne is needed to obtain a flocculation that is partially broken by the height of fall. Similarly,with an introduction at 2 points (at 100 meters and 10 meters from the exit) the consumption remains high at about 150 g/tonne. In this case, due to the partial breakage of the flocs, part of the silts is dispersed in the recovery water, therefore requiring passage through a settling lagoon before being discharged in the sea.
Example 4 In this embodiment, the tank.(4) is mounted on a support (9) at a height of about 20 meters. The tank is provided on its whole periphery with a ramp (6). It follows that the treated sludge is dumped on either side of the tank, above the ground. When the level of the treated sludge reaches the base of the tank, it is replaced or buried.
The invention and the advantages thereof clearly appear from the above description.
Particularly noteworthy is the significant improvement in the settling of the fine solid particles present in the sludge during its storage above the ground, to permit the remediation of the surfaces used.
Claims (9)
1. A method for treating sludge from the mining or mineral industry, whereby, before spreading above ground, the sludge is subjected to an upward movement during which it is contacted with a flocculating agent, characterized in that the flow angle of the sludge at the time of spreading is between 8 and 20%.
2. The method as claimed in claim 1, characterized in that the upward speed of the sludge is higher than its settling rate.
3. The method as claimed in one of the preceding claims, characterized in that the upward movement is duplicated by a centrifugal movement entraining the mixture of the sludge and the flocculating agent at a speed of between 0.2 and 0.8m/s.
4. The method as claimed in one of the preceding claims, characterized in that the contact time between the sludge and the flocculating agent is between 1 and 10 minutes, advantageously between 2 and 5 minutes.
5. The method as claimed in one of preceding claims, characterized in that the flocculating agent is introduced into the sludge in a concentration of between 50 and 500 g per tonne of sludge.
6. The method as claimed in one of the preceding claims, characterized in that the flocculating agent is selected from the group comprising a) anionic monomers having a carboxylic function or a sulfonic acid function;
b) and/or nonionic monomers: acrylamide, methacrylamide, N-vinyl pyrrolidone, vinylacetate, vinyl alcohol, acrylate esters, allyl alcohol, N-vinyl acetamide, N-vinylformamide;
c) and/or cationic monomers: dimethylaminoethyl acrylate (ADAME) and/or dimethylaminoethyl methacrylate (MADAME) quaternized or salified, dimethyldiallylammonium chloride (DADMAC), acrylamido propyltrimethyl ammonium chloride (APTAC) and/or methacrylamido propyltrimethyl ammonium chloride (MAPTAC);
d) copolymers issuing from the family of polycondensates: epichlorhydrin resin, dicyandiamide resin;
e) anionic or cationic (co)polymers issuing from one (or more) post-modification reactions such as hydrolysis, Hoffman degradation, Mannich product, hydroxamation reaction;
f) or natural polymers such as dextran.
b) and/or nonionic monomers: acrylamide, methacrylamide, N-vinyl pyrrolidone, vinylacetate, vinyl alcohol, acrylate esters, allyl alcohol, N-vinyl acetamide, N-vinylformamide;
c) and/or cationic monomers: dimethylaminoethyl acrylate (ADAME) and/or dimethylaminoethyl methacrylate (MADAME) quaternized or salified, dimethyldiallylammonium chloride (DADMAC), acrylamido propyltrimethyl ammonium chloride (APTAC) and/or methacrylamido propyltrimethyl ammonium chloride (MAPTAC);
d) copolymers issuing from the family of polycondensates: epichlorhydrin resin, dicyandiamide resin;
e) anionic or cationic (co)polymers issuing from one (or more) post-modification reactions such as hydrolysis, Hoffman degradation, Mannich product, hydroxamation reaction;
f) or natural polymers such as dextran.
7 An installation for implementing the method as claimed in one of claims 1 to 7.
8. The installation as claimed in claim 8, characterized in that it comprises a vertical tank fed at its base by a sludge intake line.
9. The installation as claimed in claim 9, characterized in that the tank is provided in the upper part with a ramp suitable for removing the sludge.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR0853997 | 2008-06-17 | ||
| FR0853997A FR2932470B1 (en) | 2008-06-17 | 2008-06-17 | PROCESS FOR TREATING MINERAL SLUDES AND EQUIPMENT FOR IMPLEMENTING THE METHOD |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2665350A1 true CA2665350A1 (en) | 2009-12-17 |
| CA2665350C CA2665350C (en) | 2018-07-03 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2665350A Active CA2665350C (en) | 2008-06-17 | 2009-05-06 | Method for treating mineral sludge and installation for carrying out same |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA2665350C (en) |
| FR (1) | FR2932470B1 (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8721896B2 (en) | 2012-01-25 | 2014-05-13 | Sortwell & Co. | Method for dispersing and aggregating components of mineral slurries and low molecular weight multivalent polymers for mineral aggregation |
| US9068776B2 (en) | 2009-10-30 | 2015-06-30 | Suncor Energy Inc. | Depositing and farming methods for drying oil sand mature fine tailings |
| US9150442B2 (en) | 2010-07-26 | 2015-10-06 | Sortwell & Co. | Method for dispersing and aggregating components of mineral slurries and high-molecular weight multivalent polymers for clay aggregation |
| US9404686B2 (en) | 2009-09-15 | 2016-08-02 | Suncor Energy Inc. | Process for dying oil sand mature fine tailings |
| US9663388B2 (en) | 2013-08-09 | 2017-05-30 | Exxonmobil Upstream Research Company | Method of using a silicate-containing stream from a hydrocarbon operation or from a geothermal source to treat fluid tailings by chemically-induced micro-agglomeration |
| US9909070B2 (en) | 2009-09-15 | 2018-03-06 | Suncor Energy Inc. | Process for flocculating and dewatering oil sand mature fine tailings |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2965007B1 (en) | 2010-09-20 | 2012-10-12 | Snf Sas | IMPROVED PROCESS FOR ASSISTED OIL RECOVERY USING THE ASP TECHNIQUE |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL6804893A (en) * | 1968-04-05 | 1969-10-07 | ||
| US4626345A (en) * | 1984-09-04 | 1986-12-02 | Lenox Institute For Research, Inc. | Apparatus for clarification of water |
| US4775468A (en) * | 1985-08-19 | 1988-10-04 | Peterson Filters Corporation | System for mineral slurry flocculation and vacuum filtration |
| US5800717A (en) * | 1996-10-02 | 1998-09-01 | Microsep International Corporation | Water and wastewater treatment system with internal recirculation |
| AU2004228573A1 (en) * | 2003-04-11 | 2004-10-21 | Sang Hun Hong | Sludge concentration system and process which have functions for automatically charging a coagulant and for automatically controlling the concentration of a sludge |
| US7276154B1 (en) * | 2004-02-25 | 2007-10-02 | Vav Technologies, Inc. | Settling grid separator |
-
2008
- 2008-06-17 FR FR0853997A patent/FR2932470B1/en not_active Expired - Fee Related
-
2009
- 2009-05-06 CA CA2665350A patent/CA2665350C/en active Active
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9404686B2 (en) | 2009-09-15 | 2016-08-02 | Suncor Energy Inc. | Process for dying oil sand mature fine tailings |
| US9909070B2 (en) | 2009-09-15 | 2018-03-06 | Suncor Energy Inc. | Process for flocculating and dewatering oil sand mature fine tailings |
| US10590347B2 (en) | 2009-09-15 | 2020-03-17 | Suncor Energy Inc. | Process for flocculating and dewatering oil sand mature fine tailings |
| US9068776B2 (en) | 2009-10-30 | 2015-06-30 | Suncor Energy Inc. | Depositing and farming methods for drying oil sand mature fine tailings |
| US9150442B2 (en) | 2010-07-26 | 2015-10-06 | Sortwell & Co. | Method for dispersing and aggregating components of mineral slurries and high-molecular weight multivalent polymers for clay aggregation |
| US9540469B2 (en) | 2010-07-26 | 2017-01-10 | Basf Se | Multivalent polymers for clay aggregation |
| US8721896B2 (en) | 2012-01-25 | 2014-05-13 | Sortwell & Co. | Method for dispersing and aggregating components of mineral slurries and low molecular weight multivalent polymers for mineral aggregation |
| US9090726B2 (en) | 2012-01-25 | 2015-07-28 | Sortwell & Co. | Low molecular weight multivalent cation-containing acrylate polymers |
| US9487610B2 (en) | 2012-01-25 | 2016-11-08 | Basf Se | Low molecular weight multivalent cation-containing acrylate polymers |
| US9663388B2 (en) | 2013-08-09 | 2017-05-30 | Exxonmobil Upstream Research Company | Method of using a silicate-containing stream from a hydrocarbon operation or from a geothermal source to treat fluid tailings by chemically-induced micro-agglomeration |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2932470B1 (en) | 2011-10-28 |
| CA2665350C (en) | 2018-07-03 |
| FR2932470A1 (en) | 2009-12-18 |
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