SAMENBEHANDLUNGSVERFAHREN

Description

TECHNICAL FIELD

[0001] The present invention relates to seed treatment and more particularly, but not exclusively, to a process and installation for preparing a mixture intended for treating, in particular coating, seeds. BACKGROUND

[0002] In agriculture, seed treatment is a well-known practice. It facilitates handling, improves the environment in which seeds will develop or their germination properties, and protects them from pests, mold, harsh weather conditions, or deterioration during aging. Various treatment methods exist for this purpose, such as simple surface treatment (seed dressing), seed coating, or seed pelletizing.

[0003] Seed coating generally involves depositing a thin polymer film, containing various agrochemicals, onto the surface of the seeds. The shape and size of the seeds are only slightly altered during this process.

[0004] Encapsulation generally involves modifying the size and shape of seeds by adding a significant amount of inert material, for example, to facilitate the use of conventional mechanical seed drills that struggle with very small seeds. Several plant protection products can thus be more precisely localized within the different layers of the coating.

[0005] In the following, "coating" will refer to "film coating" or "encapsulation".

[0006] Typically, the treatment formulations used are: liquid formulations typically include a water-dispersed fungicide, pigments and binder polymers, or powder formulations, which accelerate drying, decrease stickiness and improve seed fluence.

[0007] Typically, liquid formulations are applied to seeds by processes such as spraying, spray-drying, mixing, churning, or any other means well known to those skilled in the art.

[0008] In the case of powder formulations, the formulation adheres to the seeds by adding water, as described in patent application GB 2 025 200.

[0009] More specifically, the most common method involves premixing the powder and water to create a dispersion, which is then applied to the seeds. Alternatively, the following methods can be used: either the seeds are moistened and the powder is then applied to them, or the powder is mixed with the seeds and then water is added.

[0010] However, some treatment compounds remain difficult to apply to seeds. This is particularly true of hydratable compounds that develop significant viscosity upon contact with water and which are intended to be used in substantial proportions. Typically, for field crop seeds, the target proportion is between 0.1% and 1%, this proportion corresponding to the mass of the treatment formulation by dry weight, after water removal, relative to the seed mass.

[0011] In the case of a liquid formulation, these hydratable compounds result in a viscosity that is too high to handle and apply the formulation under normal conditions. Furthermore, the option of diluting the formulation (to decrease the compound concentration and thus limit the formulation's viscosity) is not satisfactory. This option would lead to the introduction of a significant amount of water relative to the mass of seeds treated. However, the amount of water is limited by a maximum value acceptable to the seeds in the absence of drying, which is the norm for field crop seeds.Beyond this acceptable threshold, the seed may germinate spontaneously during storage, rapidly lose its germination capacity after a short period of storage, or the water may cause the seed to swell and only very slowly return to its original shape. These volume variations can lead to crumbling or even cracking of the encapsulation or coating film, or cause clumping of treated seeds. Therefore, diluting the formulation would only be satisfactory if the seeds were used immediately after treatment, which is not feasible for field crop seeds due to their large volumes.

[0012] In the case of a powder formulation, it was observed that the aforementioned hydratable compounds caused problems of inhomogeneity in seed treatment, and residues which in turn caused problems of material loss and fouling of mixing equipment.

[0013] Various installations allowing the dispersion of a powder in a liquid medium have been proposed.

[0014] US 2014 / 0269153 describes an industrial installation for performing a mixture in which a powder is introduced by vacuum into a mixing tank.

[0015] EP 1 165 874 discloses an installation in which a powder is introduced into a mixing tank via a dip tube. However, such an installation is not suitable for preparing a composition based on hydratable compound(s), given its rheological behavior. In particular, the use of hydratable compounds would cause a problem of rapid fouling of the dip tube and the deposition of residues on the tank walls that are difficult to remove.

[0016] Publications CN 202105636, CN 203329707, CN104607091 and CN201880505 describe other installations also unsuitable for the automatic preparation of several successive batches of mixture, with relatively low variability in the formulation of the mixture between batches.

[0017] There is therefore a need for a new treatment process that allows for the automated and cyclical application of powdered substances, including hydratable compounds, to seeds in a significant proportion.

[0018] There is also a need for a facility to implement such a process on an industrial scale and at a reasonable cost.

[0019] There is also a need for a facility that allows for the combined implementation of different types of seed treatments using a single installation.

[0020] There is also a need for a new seed treatment process, and an installation for the implementation of such a process, which can be integrated into an industrial seed treatment line without significantly impacting its size and / or rate (typically at least 20kg of seeds treated per minute, in particular at least 100kg of seeds treated per minute, in particular at least 150kg of seeds treated per minute, in particular at least 200kg of seeds treated per minute, or even at least 300kg of seeds treated per minute). GENERAL PRESENTATION

[0021] The invention meets all or part of the aforementioned needs through a seed treatment process, using a composition obtained extemporaneously by mixing at least one powdered substance and an aqueous medium, comprising the steps of claim 1.

[0022] The invention allows automated operation over several treatment cycles, advantageously limiting tank fouling problems related to the rheological behavior of the dispersion, the powdered substance being a hydratable compound.

[0023] Injecting the powdered substance into the liquid in the tank using a vacuum proves to limit the emission of dust and the deposition of the powdered substance on the exposed walls of the tank, while ensuring good dispersion of the powdered substance within the liquid.

[0024] The invention is therefore particularly well suited to a powdery substance being a hydratable compound.

[0025] The invention is particularly suitable for a mixture which has a viscosity which increases significantly over time.

[0026] The volume of the mixture in the tank is preferably less than or equal to 151 liters, ideally 101 liters, and preferably at least 0.1 L, especially at least 0.5 L. Such a volume is well-suited to seed treatment and allows the use of a standard-sized tank without any special reinforcement of its mechanical strength, which would not be the case with a larger tank, given the pressure or vacuum levels encountered. It is worth noting that, surprisingly, despite this relatively small volume, the injection of the powdered substance can be carried out without clogging the tank or causing a significant emission of dust, even after several repeated cycles without manual intervention inside the tank, thanks to the automation.

[0027] In examples of implementations of the invention, the process does not include a drying step between the mixing step and the application of the mixture to the seeds. Thus, the contents of the tank applied to the seeds are not a dry powder, but rather an aqueous dispersion of the powdered material in an aqueous medium.

[0028] The contents of the tank can be evacuated in one or more compressed gas flushes, preferably in a single compressed gas flush.

[0029] The first flush can be carried out at the latest 60s after the end of the introduction of the powdered substance into the tank, better at the latest 30 s after this, and the last flush can be carried out, if necessary, at the latest 30 min after the end of the introduction of the powdered substance into the tank, better at the latest 15 min after this, even better at the latest 5 min after this and even better at the latest 75s after this, or even at the latest 60s after this.

[0030] When the evacuation of the contents of the tank is carried out in a single blast of compressed gas, this is preferably carried out no later than 5 min after the end of the introduction of the powdered substance into the tank, better no later than 2 min, even better no later than 75s after this, preferably no later than 45s after this, preferably no later than 30s after this, for example no later than 20s after this, or even no later than 10s after this.

[0031] Such a short time between the end of the powder's introduction and the emptying of the tank allows for the processing of a large quantity of seeds in a short period. Furthermore, in the case of an aqueous dispersion that undergoes rheological changes over time, particularly becoming increasingly viscous, this time between the end of the powder's introduction and the emptying of the tank ensures that the aqueous dispersion has the appropriate viscosity for application to the seeds.

[0032] Preferably, the application of the contents of the tank to the seeds is carried out immediately after the contents of the tank have been emptied, preferably less than 5 minutes after emptying, better less than 1 minute after emptying, even better, less than 30 seconds after emptying.

[0033] Preferably, the process does not involve a step of storing the contents of the tank between emptying the tank and applying the contents of the tank to the seeds.

[0034] The powdered substance is injected into the tank through a nozzle with an internal diameter of 17 mm or less, for example between 3 and 17 mm, preferably between 5 and 15 mm. Such a diameter helps to limit dead volume and reduce the risk of fouling.

[0035] The mixture can be subjected to agitation according to at least two different agitation regimes.

[0036] In particular, the mixture can be agitated at a lower rate (typically by a factor of 0.05 to 0.9, or even zero) during at least partial emptying, compared to the sequence from the end of the powder's introduction to the beginning of emptying. This reduces the risk of gas pockets forming in the discharge line. It also decreases the flow stress at the discharge connection.

[0037] According to a preferred embodiment, the agitation regime in the tank can be identical from the end of the introduction of the powdered substance into the tank until the start of emptying.

[0038] According to this embodiment, the mixture can be subjected to agitation at a lower rate, typically by a factor of 0.05 to 0.9, or even zero, at the time of at least partial emptying, compared to the sequence from the beginning of the introduction of the powdered substance to the beginning of emptying.

[0039] In another embodiment, the mixture can be agitated at least twice, using two different non-zero agitation regimes, from the introduction of the powder into the tank until the start of emptying. One of these regimes is more vigorous (typically by a factor of 1.1 to 4) between the end of the powder's introduction and the start of emptying than the intensity at the time the powder was introduced into the tank. This reduces the risk of the powder being projected above the liquid in the tank during the introduction step.

[0040] For example, the mixture can be subjected to agitation ranging from 300 to 2000 rpm, for example from 400 to 1000 rpm between the start of the introduction of the powdered substance and the start of emptying, or even between the end of the introduction of the powdered substance and the start of emptying.

[0041] The aqueous medium may contain at least one plant protection product, which is injected into a water pipe connected to the tank. The aqueous medium may also contain several plant protection products injected separately through respective connections in said pipe. Such separate injection facilitates traceability and maintenance. It also significantly reduces the space required in the immediate vicinity of the tank. The invention enables the separate injection of these different plant protection products into the pipe, and their introduction into the tank can be carried out either simultaneously or sequentially.

[0042] This pipeline may include a direct line opening directly into the tank and at least one branch opening into it via at least one wash head, and at least one valve to selectively send the water possibly carrying at least one phytosanitary active ingredient into the tank, either via the direct line or via the branch.

[0043] In particular, water can be sent directly to the tank when it contains the plant protection product(s). This avoids excessive exposure of the spray head to the plant protection product(s), thus reducing the risk of corrosion and preventing the potential sedimentation of plant protection product(s) from leading to progressive fouling of the spray head.

[0044] Preferably, a certain quantity of water is sent back into the tank after it has been emptied. This water circulates through the bypass and the wash head and is used both for rinsing the tank and for preparing the aqueous medium for the next preparation cycle. This limits the amount of waste and the cost of treating the effluent generated by the installation, since the rinse water can be reused as is in the very next preparation cycle. Experience has shown that even with this method, the variability in the mixture formulation remains within acceptable limits because the composition of this rinse water is almost constant from one cycle to the next.

[0045] The minimum vacuum level in the tank just before the aspiration of the powdered substance can be between -0.05 and -1 bar, specifically between -0.1 and -0.8 bar, and preferably between -0.3 and -0.5 bar. This minimum vacuum level is preferably maintained in the tank throughout the entire injection of the powdered substance.

[0046] The overpressure level in the tank during at least a partial draining operation can be between 0.05 and 2 bar, specifically between 0.1 bar and 1 bar. For example, the overpressure level in the tank during at least a partial draining operation can be less than or equal to 0.5 bar, for example, between 0.1 and 0.5 bar.

[0047] The process according to the invention may include bringing the tank to atmospheric pressure by means of a vent during the injection of water, possibly loaded with active ingredient(s), into the tank.

[0048] The contents of the tank can be immediately emptied automatically into a dedicated container in the event of an emergency stop, this emergency emptying being triggered in particular by manually pressing a corresponding button.

[0049] The process according to the invention is advantageously implemented using at least two tanks operating in cycles that are out of phase with each other. These tanks are preferably connected to the same source of water and active ingredient(s) and to the same source of powdered substance. According to this embodiment, each tank can be connected to the same seed treatment device or, alternatively, to separate seed treatment devices. In other words, the emptying of each tank can be carried out either to the same seed treatment device or to separate seed treatment devices.

[0050] The invention also relates to an installation for preparing a seed treatment composition, for implementing the process according to the invention as defined above, comprising the characteristics of claim

[0051] A single branch connection can be linked to several different supply / supply points. Alternatively, as many branch connections are used as there are different supply / supply points.

[0052] The installation according to the invention allows the introduction of the powdered substance below the level of the aqueous medium in the tank, by means of a tap and a depression created in the tank by the vacuum source.

[0053] This method of introducing the powdered substance is advantageous compared, for example, to introduction via a dip tube, since the powdered substance is a hydratable compound. This method effectively reduces the risk of fouling the means of introducing the powdered substance.

[0054] Preferably, the connection point for the powdered substance inlet is below the level of the aqueous medium when the latter is at rest.

[0055] The connection to the powdered substance inlet may nevertheless be above the level of the aqueous medium when the latter is at rest, when it is planned to agitate the aqueous medium during the introduction of the powdered substance, the agitation causing the liquid to rise on the walls above the connection to the powdered substance inlet so that the latter is introduced into the aqueous medium during the agitation.

[0056] The vacuum source can be a device comprising a venturi. The installation according to the invention can comprise at least one washing head in the tank, connected to the tank's water supply line via a branch.

[0057] The installation according to the invention may include a tank having a capacity less than or equal to 50 l, better at 20 l, even better at 10 l, and a capacity greater than or equal to 0.1 l, better at 0.5 l, even better at 11. The size of the tank may be fixed according to the quantity of seeds to be treated per cycle and the possible number of successive flushes of a compressed gas fixed to empty it completely.

[0058] Preferably, the installation of the invention comprises conical tanks. This promotes the flow of the mixture during the emptying stage, which helps to limit the risk of settling of the dispersion containing the powdered substance, particularly at the end of the cycle.

[0059] The installation according to the invention may include an automated control system for solenoid valves, motors and / or pumps allowing for the cyclical control of the filling, including dosing, of the tank with liquid, the dosing and then the injection of the powdered substance into the tank, the emptying of the tank, and the agitation therein.

[0060] The installation according to the invention may include two mixing tanks, adapted to be used in a phased manner, so that a mixture can be prepared in one of the tanks while a ready-to-use mixture is discharged from another tank.

[0061] The seed treatment device can be directly connected to the discharge outlet, in particular by a tube.

[0062] The installation may lack a storage area such as a tank, for the contents of the tank between emptying and the seed treatment device.

[0063] According to a method not in accordance with the invention, the installation can still be used without adding powdered substance to the tank to treat seeds with one or more active ingredients. In this case, the powdered substance inlet is not used, and the corresponding solenoid valve remains closed.

[0064] The term "seed" should not be understood in a restrictive sense.

[0065] Thus, the term "seed(s)" refers to any organ or fragment of a plant that is placed in a culture medium (generally soil) to allow the formation of another plant of the same type. This can include, in particular, a seed. A seed can be formed from such an organ or fragment of a plant agglomerated with other substances, or from several organs or fragments agglomerated together. Furthermore, the seed to which the treatment process is applied may have undergone prior treatment. In particular, this seed may already have been treated and, for example, be coated with one or more layers of a coating. Conversely, this seed may be in its natural state.

[0066] The expression "aqueous medium" refers to a medium comprising water as a solvent, and "dispersion" refers to a heterogeneous system in which a finely divided material, here the powdered material, is distributed in another material, here the aqueous medium.

[0067] A "hydratable compound" is defined as a compound, for example a polymer, which, when dispersed in distilled water at 25°C, with stirring for 2 hours, at a concentration of up to 5% by weight relative to the total weight of the dispersion, leads, in less than 48 hours under gentle stirring, to a formulation with a viscosity (measured by a Rheomat RM300 at 25°C, at a shear rate of 10⁻¹ s⁻¹) greater than 8000 cP. In this sense, formulations for which no viscosity measurement is possible (for example, fully gelled formulations) are considered to have a viscosity (measured by a Rheomat RM300 at 25°C, at a shear rate of 10⁻¹ s⁻¹) greater than 8000 cP.

[0068] For this measurement, the pH value of the dispersion can be adjusted to improve the hydration conditions of the hydratable compound. The pH value can thus typically vary from 3 to 12, particularly from 5 to 10, depending on the hydratable compound in question; the appropriate pH ranges for each type of hydratable compound are known to those skilled in the art.

[0069] The hydratable compound is present in the mixture used to treat the seeds at a maximum concentration of 70% by weight, relative to the weight of the mixture. Advantageously, this concentration is between 4.5 and 70% by weight, for example between 5 and 65% by weight, better between 7.5 and 65% by weight, especially between 10 and 60% by weight.

[0070] According to the invention, the mixture is brought into contact with the seeds before the viscosity of the mixture (measured at 25°C at a shear rate of 10⁻¹ s⁻¹ using a Rheomat RM300) reaches a maximum value. This maximum value can be greater than or equal to 10,000 cP (centipoise), or 10,000 mPa·s (millipasca·seconds), and in particular greater than or equal to 50,000 cP, or 50,000 mPa·s. The contact step can thus be carried out before the viscosity of the mixture (measured at 25°C at a shear rate of 10⁻¹ s⁻¹ using a Rheomat RM300) reaches a maximum value of 50,000 mPa·s.

[0071] According to the invention, the hydratable compound is selected from the following compounds: cellulose or one of its derivatives, for example hydroxycellulose, alkylcellulose, such as methylcellulose, hydroxyalkylcellulose such as hydroxyethylcellulose, or hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxyalkylcellulose, such as carboxymethylhydroxyethylcellulose, sodium carboxymethylcellulose, synthetic polymers such as polyvinylpyridine, polyvinylpyrrolidone, polyethylene glycol, polyethylene oxide, polyamide, polyacrylamide, polymethacrylic acid, polyvinyl alcohol, polyglycerol, polytetrahydrofuran, polyacrylic acid, polyacrylate, alginic acid and its derivatives, such as alginate, pectin, galactomannans and their derivatives, such as guar gum, hydroxypropyl guar gum, carboxymethyl guar, carboxymethyl hydroxypropyl guar, cationic guars, gelatin, Starch and its derivatives, such as cationic starch, corn starch,Wheat starch, rice starch, potato starch, tapioca, waxy maize, sorghum, waxy sorghum, dextrin, chitin, chitosan, xanthan gum, carrageenan gum, karaya gum, a derivative of any of the above-mentioned compounds, or a combination thereof.

[0072] According to one embodiment, the hydratable compound is chosen from celluloses and their derivatives.

[0073] According to another embodiment, the hydratable compound is chosen from galactomannans and their derivatives.

[0074] According to another embodiment, the hydratable compound is chosen from polyacrylamides and their derivatives.

[0075] According to another embodiment, the hydratable compound is chosen from starch and its derivatives.

[0076] According to another embodiment, the hydratable compound is chosen from xanthan gum and its derivatives.

[0077] The hydratable compound is, for example, a naturally derived agropolymer marketed under the brand name AgRHO WR 30 or AgRHO GSB 30 by the company SOLVAY.

[0078] It should be noted that the mixture may advantageously include other compounds besides the hydratable compound such as, for example, pesticides, fungicides, herbicides, molluscicides, bactericides, bacteriostatics, repellents, nutrients, fertilizers, growth stabilizers, latexes (for example, selected from vinyl acetate, polyurethane, styrene butadiene or acrylic polymers, possibly in the form of core-shell structures), surfactants, antioxidants, plasticizers, colorants, fillers (for example, a fluence powder (or drying powder) of the silica type (in particular precipitated or pyrogenated silicas), kaolin or talc), biological additives (for example, inoculants of the bacteria or fungi type (in particular mycorrhizal)) or a mixture thereof. These additional compounds can be added in quantities typically used by a person skilled in the art.As an example, latexes can typically be introduced in amounts ranging from 2 to 60 g (in dry extract), in particular from 3 to 30 g (in dry extract) per quintal of seed to be treated.

[0079] The invention allows for good distribution of the dispersion achieved during the mixing operation on the seeds. This process is applicable to seed coating and, in particular, seed film coating.

[0080] When the dispersion covers a seed, it has a positive influence on the seed's development. It appears that the dispersion helps maintain the seed it covers in a moist environment, favorable to seed development. However, this positive influence is only observed if the concentration of hydratable compounds in the dispersion is sufficiently high and, in particular, exceeds the aforementioned minimum concentration.

[0081] A high concentration of the hydratable compound, however, has the drawback of increasing the viscosity of the dispersion. In practice, after adding the hydratable compound to the aqueous medium, the viscosity of the dispersion increases very rapidly. Bringing the hydratable compound into contact with the seeds before the dispersion's viscosity reaches the aforementioned maximum value and / or within a certain timeframe helps to limit, or even prevent, the formation of aggregates. Such aggregates are undesirable because the amount of dispersion clumped together is useless for seed treatment and represents a loss. Conversely, if there are few or no aggregates, a more homogeneous treatment is achieved: the dispersion is better distributed over the seeds, and each seed is more thoroughly covered.By limiting or avoiding the formation of aggregates in the invention, the risk of fouling of the tank and mixing bowl of the seed treatment device, for example of the coating machine, in which the dispersion is mixed with the seeds, is reduced.

[0082] According to one embodiment, the mass of mixture put in contact with the seeds can be between 0.5 and 10% of the mass of the seeds.

[0083] In some embodiments, the mass of the mixture brought into contact with the seeds is greater than or equal to 0.5% of the seed mass. Below this minimum value of 0.5%, the quantity of mixture per seed, and therefore the effect of the mixture on the seeds, may not be sufficient. Typically, the mass of the mixture brought into contact with the seeds may be greater than or equal to 0.75% of the seed mass, and in particular greater than or equal to 1% of the seed mass.

[0084] Furthermore, the mass of the mixture in contact with the seeds is typically less than or equal to 10% of the seed mass, specifically less than or equal to 8%, and particularly less than or equal to 6%. Beyond this maximum value, a saturation effect may occur. In other words, the excess mass of the mixture has little or no effect and constitutes a loss. Also, beyond a ratio of 10% between the mass of the mixture and the mass of the seed, specifically beyond 8%, and particularly beyond 6%, there is a risk that the amount of water in the mixture will exceed the threshold acceptable for the seed. Above this acceptable threshold, the seed may germinate spontaneously during storage, or rapidly lose its germination capacity after a short storage period.

[0085] Advantageously, the implementation of the treatment process of the invention does not cause excessive hydration of the seeds. Furthermore, the implementation of the treatment process of the invention does not alter the germination capacity of the seeds.

[0086] Preferably, the hydration resulting from the application of the tank contents to the seeds is low enough that the treated seeds cannot clump together or germinate during storage.

[0087] The minimum and maximum mass ratios between the mass of the mixture and the mass of the seed can vary between the aforementioned ranges depending on the nature of the seed and the formulation of the mixture, and in particular the nature of the hydratable compound.

[0088] In addition to the characteristics mentioned above, the proposed process may exhibit one or more of the following characteristics, considered individually or in technically feasible combinations: Upon contact with the seeds, the hydratable compound must already be at least partially hydrated. This partial hydration improves its adhesion to the seed. Advantageously, the process of the invention does not require the introduction of additional adhesive solutions to ensure the adhesion of the hydratable compound to the seed.

[0089] As previously mentioned, the concentration of the hydratable compound is preferably between 4.5 and 70% by weight, particularly between 5 and 65% by weight, relative to the weight of the mixture. This concentration can also be between 10 and 45% by weight, particularly between 15 and 35% by weight. These concentration ranges provide a good compromise, for most hydratable compounds, between the observed viscosity rise kinetics and the amount of compound and water in the dispersion.

[0090] Optionally, a drying step can be implemented after the seeds have been contacted with the mixture to reduce the amount of water absorbed by the mixture. This drying can be achieved, for example, by heating at a moderate temperature, such as 20 to 40°C, for a few minutes to a few hours, so that the moisture gain in the seeds resulting from the process of the invention does not exceed approximately 3% by weight, preferably approximately 2% by weight.

[0091] Advantageously, the process of the invention does not, however, include an additional drying step.

[0092] Seeds can be processed in batches ranging from 1 to 500 kg, specifically from 10 to 350 kg, and from 20 to 300 kg, with each batch processing cycle in the seed treatment device taking less than 1 minute. Furthermore, the proposed process can be integrated into a seed processing chain. In other words, this process can be implemented on seeds before or after one or more other seed processing steps.

[0093] The invention also relates to treated seeds, in particular coated seeds, obtained according to the process described above.

[0094] A non-limiting example of implementation of the invention will now be described, with reference to the attached drawing, on which the figures 1 to 4 represent a processing installation according to the invention, and the Figure 5a detail of the realization of a variant of the supply tapping for powdered substance. DETAILED DESCRIPTION

[0095] The method according to the invention can be implemented using an installation such as is schematically represented in the figures 1 to 4 .

[0096] This installation includes at least one preparation tank, 10 or better, as illustrated in the figures 1 And 2 , two tanks 10 and 10'.

[0097] Each 10 or 10' tank preferably has a capacity less than or equal to 50 l, better 20 l, even better 10 l, and a capacity greater than or equal to 0.1 l, better 0.5 l, even better 11.

[0098] Each 10 or 10' tank has various connections 11 to 14 in the upper part, and a connection 15 on its side wall.

[0099] In the example considered, each tank 10 and 10' is for example made of stainless steel which may include for example an internal coating of the Teflon type and has a cylindrical body 16 closed at the bottom by a bottom wall 17, conical and at the top by a lid 19.

[0100] An agitation device 23 is associated with each tank 10 and 10', this device comprising a shaft 22 driven in rotation on itself by a motor 20. One or more mixing elements 21, identical or different, are mounted on the shaft 22 so as to be driven in rotation by it.

[0101] The mixing organ(s) 21 can be chosen in particular from among the Intermig type deflocculators or agitators.

[0102] The connection 12 supplies at least one 60-360° rinse water spray nozzle into the tank. In the example shown, the connection 12 supplies a rotating spray ball 24.

[0103] The branch 12 is connected via a solenoid valve 50 to a pipe 25 supplied by a water network 27, for example a municipal water network, shown in the figure 4 .

[0104] As seen on this figure 4 , the pipes 25 connected to the taps 12 of the two tanks 10 and 10' join downstream of a section 40 supporting various taps 30 to 34 for active supply, these taps being for example arranged close together in a so-called "clarinet" arrangement.

[0105] Returning to figures 1 And 2 , we see that the tap 13 of each tank 10 or 10' is connected, via a branch 42 comprising a solenoid valve 51, to the corresponding pipe 25, upstream of the solenoid valve 50 and downstream of the section 40.

[0106] Each branch 14 is connected, on the one hand, via a solenoid valve 54, to a vent 55, and on the other hand, to a compressed air source 57, via a solenoid valve not shown. The branches 11 of tanks 10 and 10' are each connected, via a solenoid valve 58, to a vacuum source 59, notably including a venturi.

[0107] According to one embodiment, each branch 14 can be connected simultaneously to a vent 55 via a solenoid valve 54, to a compressed air source 57 via a solenoid valve not shown, and to a vacuum source 59, in particular comprising a venturi, via a solenoid valve 58. Such an embodiment makes it possible in particular to reduce the size of the installation.

[0108] The connections 30 to 34 of section 40 are connected via respective solenoid valves 60 to 64 to sources of active ingredients that may be present in the final mixture.

[0109] The connections 30 to 34 can be supplied by dosing pumps through respective flow meters 70 to 74 allowing precise knowledge of the quantity of active ingredient distributed.

[0110] Alternatively, flow meters 70 to 74 are not considered to be part of the installation according to the invention, as they may in fact be pre-existing and linked to the dosing pumps.

[0111] Section 40 can be supplied selectively by a compressed air network 82 or by the city water network 27, via solenoid valves 80 and 81 respectively.

[0112] Each port 15 opens into the corresponding tank 10 or 10', below the nominal liquid level in the tank during the mixing operation. This means that each port 15 opens into the corresponding tank 10 or 10', below the liquid level in the tank, taking into account any agitation vortex. This allows the powdered substance to be injected below the liquid level.

[0113] The branch 15 opens, for example, as illustrated, approximately at the junction between the cylindrical body 16 of the tank and its bottom wall 17.

[0114] The 15th branch can be, as illustrated on the figures 1 And 2 oriented roughly horizontally or, as illustrated in the Figure 5with a non-zero angle α with the horizontal. The branch 15 is, for example, oriented obliquely downwards, specifically at 45° to the axis of the tank. In this case, it will preferably open onto the cylindrical body 16. The branch 15 can also be oriented obliquely upwards. In this case, it will preferably open onto the bottom wall 17. Preferably, the branch 15 is oriented obliquely downwards, specifically at 45° to the axis of the tank.

[0115] The branching is preferably of an internal diameter less than or equal to 17 mm, for example between 3 and 17 mm, better between 5 and 15 mm.

[0116] Each branch 15 is connected via a solenoid valve 95 to a line 100 for introducing the powdered substance into the tank 10 or 10'. This line 100 is connected, as illustrated in the figure 3, to a powder dosing system 122 including a hopper 120 feeding a powder transfer system 105 of the screw type (for example twin screw) or vibrating plate, all of which can be mounted on a load cell 121 in order to know by difference the quantity delivered.

[0117] According to one embodiment, each 10 or 10' tank can also be mounted on a load cell (not shown) in order to measure the quantity of liquid and / or powdered substance introduced into it.

[0118] Pipe 100 is advantageously constructed, for at least part of its length, of a flexible hose 106, preferably at least partially transparent. This facilitates maintenance in case of blockage of pipe 100.

[0119] Compressed air can be injected into the section between solenoid valve 95 and powder feed tank 123, via a solenoid valve (not shown) connected to a compressed air network (not shown), to purge line 100 between two introductions of powdered substance. Compressed air can also be continuously injected into the section between solenoid valve 95 and the corresponding tank 10 or 10', to limit liquid backflow in this section.

[0120] The solenoid valve 95 preferably includes a full bore ball valve, the outlet of which can be fixed a short distance away on the wall of the tank so as to limit the dead volume.

[0121] In the embodiment in which the 15th branch is oriented substantially horizontally, as illustrated in the figures 1 And 2 , solenoid valve 95 can be of the piston type.

[0122] The contents of each tank 10 or 10' are evacuated via a drain orifice 126 at the lowest point of the bottom wall 17, this orifice opening via a solenoid valve 130 onto a drain pipe 135. The solenoid valve 130 is preferably equipped with a ball-type valve.

[0123] Pipe 135 is connected to a three-way solenoid valve 140, which allows the pipe 135 to be selectively connected either to a waste collection container 145 or to a supply line 150 for a treatment device such as a coating machine (not shown in the drawing). Preferably, as illustrated, the connection of the solenoid valve 140 to the container 145 and to the treatment device is made via flexible hoses 147 and 148 respectively, advantageously made of stainless steel braided PTFE, which facilitates the drainage of the spillage. A non-drip valve (not shown) can be installed at the end of the flexible hose 148.

[0124] The 140 three-way solenoid valve is preferably equipped with a ball-type valve.

[0125] A non-intrusive flow meter (not shown) can be installed downstream of the three-way solenoid valve 140 (i.e., between the seed treatment device and the three-way solenoid valve 140) to control the valve and interrupt the emptying of the corresponding tank 10 or 10' at the end of each feeding cycle of the treatment device from one of the tanks. The flow meter indicates the quantity of mixture sent to the treatment device. This non-intrusive flow meter is not required when the tank contents are completely emptied using a single flush of compressed gas.

[0126] Compressed air can be injected into the section between solenoid valves 130 and 140 via a solenoid valve 170, connected to the compressed air network, to purge the pipes at the end of use.

[0127] The shaft 22 of the stirring device can be centered or off-center with respect to the axis of the tank.

[0128] The system operates as follows. The various solenoid valves, pumps, and motors are controlled by a programmable logic controller (PLC). This PLC receives information from the system's various sensors, including pressure, flow rate, and weight readings.

[0129] Tanks 10 and 10' are preferably used in parallel, with a phase shift, where the mixture is prepared in one tank while the mixture in the other tank is being sent to the processing unit, and vice versa. The following process is described for tank 10 only; the process is the same for tank 10', but with a time shift.

[0130] Tank 10 is first supplied with active ingredients via connection 13, then with water via connection 12, until the liquid level in the tank corresponds to a predefined quantity depending on the final concentration of powdered material to be obtained in the mixture. This liquid level is sufficient for connection 15 to be submerged, taking into account the agitation vortex if necessary. The volume of the mixture is preferably less than or equal to 151, ideally 101. During filling, solenoid valve 54 is opened to allow communication to vent 55. The water inlet through the wash head 24 cleans the exposed part of the tank of any deposits left by the previous preparation cycle.

[0131] Then, with solenoid valves 50, 51, and 54 closed, solenoid valve 58 is opened to create a vacuum in the tank via connection 11. Once sufficient vacuum is reached, solenoid valve 95 is opened to allow the injection of at least one powdered substance, previously weighed and stored in the powder feed tank 123 below the liquid level, taking into account the agitation vortex of the latter during injection. The minimum vacuum level in the tank just before the powdered substance is drawn in is preferably between -0.05 and -1 bar, specifically between -0.1 and -0.8 bar, and ideally between -0.3 and -0.5 bar. Such a level of depression allows satisfactory suction of the powdery substance while preventing it from being sucked in too violently and passing through the liquid towards the lid, which would cause fouling of the emerged walls and the emission of dust.During the injection of the powdered substance, the vacuum is maintained at a sufficient value. The mixture is then subjected to agitation according to a first regime.

[0132] Next, solenoid valves 58 and 95 are closed, and the mixture undergoes a second agitation regime. This second regime is stronger, typically by a factor of 1.1 to 4, than the first. This second regime can continue until the tank 10 begins to empty.

[0133] Once the mixture is ready to be sent to the seed treatment device, which is for example a coating machine, compressed air is sent through the tapping 14 and then the solenoid valve 130 is opened.

[0134] Once the planned quantity has been delivered, solenoid valve 130 is closed.

[0135] The mixture can be subjected during the evacuation of tank 10 to agitation according to a third weaker regime, typically by a factor of 0.05 to 0.9 (or even zero), than the second.

[0136] The tank contents can be completely emptied either by a single flush of compressed gas or by several consecutive flushes of compressed gas. Preferably, the tank contents are completely emptied by a single flush of compressed gas.

[0137] The tank contents can thus be emptied intermittently to prevent an excessive influx of the mixture into the treatment system. In this case, solenoid valve 130 is opened intermittently.

[0138] The first flush can be carried out no later than 60 seconds after the end of the introduction of the powdered substance into the tank, better at the latest 30 seconds after this, and the last flush can be carried out, if necessary, no later than 30 minutes after the end of the introduction of the powdered substance into the tank, better at the latest 15 minutes after this, even better at the latest 5 minutes after this and even better at the latest 75 seconds after this, or even at the latest 60 seconds after this.

[0139] The overpressure level in tank 10 during at least partial emptying is preferably between 0.05 and 2 bar, in particular between 0.1 bar and 1 bar. For example, the overpressure level in the tank during at least partial emptying may be less than or equal to 0.5 bar, for example between 0.1 and 0.5 bar.

[0140] When the tank is emptied in stages, that is, when it is carried out via several consecutive flushes of compressed gas, the volumes emptied during each flush may be identical or different. These volumes are determined according to the quantity of seeds to be treated.

[0141] Once tank 10 is substantially emptied, the next preparation cycle can be started, while the mixture prepared in tank 10' can be sent to the seed treatment device.

[0142] Of course, the invention is not limited to the example just described.

[0143] The installation may consist of only one preparation tank, or alternatively more than two tanks.

[0144] The installation can also be used, if necessary, to prepare a mixture without powdery substance, by introducing one or more active ingredients through the connections 30 to 34, and optionally mixing them with water sent into tank 10 or 10'.

[0145] Several powder dosing systems can be used to feed the tank with different powdered substances. Thus, the mixture can contain different powdered substances.

Claims

1. A method for treating seeds, using a composition obtained extemporaneously by mixing at least one powdered substance and an aqueous medium, comprising the following steps: - automatically and cyclically mixing in at least one first tank (10; 10') by first introducing at least part of the aqueous medium and then the powdered substance, the latter being sucked into the aqueous medium within the tank due to a vacuum created in the tank, the injection of the powdered substance into the tank being carried out through a tapping point located below the level of the aqueous medium in the tank, if necessary taking into account the vortex of agitation of the aqueous medium, and connected to an inlet for the powdered substance, the tapping point having an internal diameter less than or equal to 17 mm, the powdered substance being a hydratable compound, the hydratable compound being chosen from the following compounds: a cellulose or one derivatives thereof, for example hydroxycellulose, alkylcellulose, such as methylcellulose, hydroxyalkylcellulose such as hydroxyethylcellulose, or hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxyalkylcellulose, such as carboxymethylhydroxyethylcellulose, sodium carboxymethylcellulose, synthetic polymers such as polyvinylpyridine, polyvinylpyrrolidone, polyethylene glycol, polyethylene oxide, polyamide, polyacrylamide, polymethacrylic acid, polyvinyl alcohol, polyglycerol, polytetrahydrofuran, polyacrylic acid, polyacrylate, alginic acid and derivatives thereof, such as alginate, pectin, galactomannans and derivatives thereof, such as guar gum, hydroxypropylated guar gum, carboxymethyl-guar, carboxymethylhydroxypropyl-guar, cationic guars, gelatin, starch and derivatives thereof, such as cationic starch, corn starch, wheat starch, rice starch, potato starch, tapioca, waxy corn, sorghum, waxy sorghum, dextrin, chitin, chitosan, xanthan gum, carrageenan gum, karaya gum, a derivative of any of the aforementioned compounds, or a combination of these compounds, the hydratable compound being present in the mixture used to treat the seeds at a concentration between 4.5 and 70% by weight, - at least partially draining, using at least one flushing with compressed gas, its content towards a mixing bowl of a seed treatment device where the mixture is brought into contact with the seeds and in which the dispersion is mixed with the seeds before the viscosity of the mixture reaches a maximum value.

2. Method according to Claim 1, the volume of the mixture in the tank being less than or equal to 151, preferably 10l.

3. Method according to any of preceding claims, the first flushing being carried out at the latest 60s after the end of the introduction of the powdered substance into the tank, preferably at the latest 30s after it, and the last flushing taking place, if applicable, at the latest 30 min after the end of the introduction of the powdered substance into the tank, preferably at the latest 15 min after it, further preferably at the latest 5 min after it, even further preferably at the latest 75s after it, even at the latest 60s after it.

4. Method according to any of preceding claims, the injection of the powdered substance into the tank being carried out through a tapping point with an internal diameter between 3 and 17 mm, preferably between 5 and 15 mm.

5. Method according to the preceding claim, the mixture being subjected to agitation at a lower rate, typically a factor of 0.05 to 0.9, or even nil, at the time of the at least partial draining, compared to the sequence from the beginning of the introduction of the powdered substance to the start of the draining.

6. Method according to any of preceding claims, the minimum level of vacuum in the tank just before the aspiration of the powdered substance being between -0.05 and -1 bar, particularly between -0.1 and -0.8 bar, preferably between -0.3 and -0.5 bar.

7. Method according to any of preceding claims, the minimum level of vacuum being maintained in the tank throughout the entire duration of the injection of the powdered substance.

8. Method according to any of preceding claims, the level of overpressure in the tank during the at least partial draining operation being between 0.05 and 2 bar, particularly between 0.1 and 1 bar.

9. Method according to any of preceding claims, the evacuation of the tank content being performed at the latest 5 min after the end of the introduction of the powdered substance into the tank, preferably at the latest 75s after it.

10. Method according to any of preceding claims, the hydration resulting from the application of the tank content to the seeds being sufficiently low so that the treated seeds do not clump together, nor germinate during storage.

11. Installation for the preparation of a seed treatment composition, for the implementation of the method according to any of preceding claims, comprising at least one tank comprising: ∘ at least one tapping point (15) located below the level of the aqueous medium in the tank, if necessary taking into account the vortex of agitation of the aqueous medium, and connected to an inlet for the powdered substance, the tapping point having an internal diameter less than or equal to 17 mm, ∘ one or more tapping points (11-14) connected to: ▪ a water supply pipe of the tank, this pipe having one or more tapping points allowing the injection of active ingredient(s) into it, ▪ a vent (55), ▪ a vacuum source (59), ▪ a compressed air source (57), and ∘ a draining outlet (126) of the tank towards a treatment device where the mixture is brought into contact with the seeds to be treated, the compressed air source (57) being configured to allow a compressed air flush in the tank to empty the content of the tank through the draining outlet.

12. Installation according to Claim 11, comprising a washing head (24) in the tank, connected to the water supply pipe of the tank via a bypass.

13. Installation according to any of Claims 11 or 12, the tank having a capacity less than or equal to 501, preferably 201, further preferably 101, and a capacity greater than or equal to 0.11, preferably 0.51, further preferably 11.

14. Installation according to any of Claims 11 to 13, comprising a control device for solenoid valves, motors and / or pumps allowing the cyclic control of filling, including dosing, the tank with liquid, dosing and then injecting the powdered substance into the tank, draining the tank, and agitating within it.