FR2660829A1 - Method and installation for skinning particulate elements - Google Patents

Abstract

The method comprises the steps of applying to a volume of particulate elements, combined movements of agitation and translation along a first defined path (5), of applying (12) a given quantity of skinning composition to the moving volume in at least one zone of the first path, then of carrying out continuous drying of the skinned elements, conveyed substantially at the same translational speed along a second given path (6). Application particularly to the skinning of seeds with a high output rate.

Description

DESCRIPTION
The present invention relates to the methods of coating particulate elements, in particular seeds, by spraying a coating composition onto a moving volume of said elements, and drying the latter.

 Such a coating process, in particular for seeds, is described in document FR-A-2 603 154. In this document, the spraying of the coating composition and the drying of the particulate elements are carried out simultaneously on a compact volume of said particulate elements. in a rotary drum with a volume much higher than that of the compact volume of elements, after which the film-coated and dried elements are extracted from the drum. This procedure, consisting of treating discrete and reduced volumes of particulate elements (of the order of 15 kg per hour in the examples given), in a confined volume, is not suitable for the production in large quantity of film-coated elements. , especially cereal seeds.

 The present invention relates to a coating process for treating high flow rates of particulate elements while ensuring, with reduced installation costs, quality lamination and capable of numerous adaptations according to the elements to be treated.

 To do this, according to a characteristic of the invention, the method comprises the steps of applying to the volume of particulate elements combined movements of agitation and translation along a first defined path, of applying or of projecting a determined quantity of film-coating composition on the moving volume in at least one zone of the first path, then of carrying out continuous drying of the film-coated elements conveyed, substantially at the same translation speed, along a second defined path.

 With such a method, the combined movements of agitation and translation of the particulate elements during the reception phase of the film-coating composition allow the application of the necessary volumes, for high flow rates of particulate elements, of the film-coating composition and its suitable distribution, in a humid atmosphere, over the elements along the first path, the excess moisture being then easily and quickly extracted, in a controlled manner, in the second path, by modulating, if necessary, the steps of drying along this second path.

 Such a method makes it possible to film flow rates of particulate elements greater than 500 kg / hour, typically greater than 1,000 kg / hour and which can reach 5 tonnes / hour.

 Another object of the present invention is to propose an installation for implementing the above method, comprising a device for supplying particulate elements, an elongated filming tunnel comprising at least one rotary element and defining a first path, at at least one pouring head or a spray nozzle for applying a film-forming composition to at least one zone of the first path, conveyor means defining a second path following the first path, and drying means associated with the conveyor means.

 The present invention finds a preferred application for the continuous filming of large volumes of seeds, in particular of corn, but sweet, rapeseed, peas, sunflower, or even vegetable seeds.

Other characteristics and advantages of the present invention will emerge from the following description of embodiments, given by way of illustration, but in no way limiting, made in particular in relation to the appended drawing where:
the single plate represents an embodiment of an installation for implementing the coating process according to the invention.

 As shown diagrammatically in the single figure, a laminating installation according to the invention successively comprises a feed hopper (1), a belt conveyor (2) provided with at least one roller (3) associated with a device weighing machine, a flow control device with pivoting blades (4), a rotary film-coating drum (5) having an inclination downstream of between 5 and 10 degrees, and a rotary drying drum (6) having an inclination downstream between 5 and 10 degrees and placed in a drying enclosure (7) comprising a gas blowing device (8) blowing hot gas towards the lower half of the drum (6). More specifically, the enclosure (7) comprises a first hot gas extraction passage (9) surrounding the discharge zone at the outlet of the laminating drum (5) in the drying drum (6), and a second gas extraction passage hot (10) at the downstream outlet of the drum r drying (6) from which the dried film-coated elements flow in a discharge pipe (11).

 According to one aspect of the invention, the coating drum (5) is equipped with a series of nozzles (12) for spraying or spraying, in an upstream zone of the drum (5), a film-forming composition conveyed by a pump 13 from a tank (14). On the other hand, the drum (5) is provided, typically downstream of the nozzles (12), with a pouring device, typically a head (15) for spraying, via a tube (16), a powder of 'a substance, for example phytosanitary, used in the composition of the film to be formed on the particulate elements and contained in a reservoir (17).

 The drum (5) can be a conventional film-coating or coating drum, generally of greater length than the usual coating drums, the drying drum (6) being a similar drum but with a peripheral wall provided with perforations for the passage of hot gases As a variant, the drums (5) and (6) can each be replaced by a conveyor device of the type described in document FR-A-2 610 847 with injection of film-coating composition or hot gas.

 It will thus be noted that the first drum (5) constitutes a combined means of agitation and of translation along a first defined path of the particulate elements delivered by the flow control device (4) while the drying drum (6) defines, downstream of said first path, a second path for the film-coated elements delivered, continuously, at the outlet of the drum (5), the drying being able to be carried out from the exit of the particulate elements out of the drum (5) until their discharge in the exhaust duct (11).

 The installation also comprises means (not shown) for regulating the rotation of the drums (5 and 6) and for controlling the temperature and / or the humidity in the enclosure (7).

 As a variant, the conveying and drying means (6), (7) may consist of a vibrated fluidized bed drier, such as those sold under the name FOF by the company NEU.

 We will now give practical examples of the coating process according to the invention, applied to different seeds.

I - SWEET BUT SEED
The coating tunnel has a length of between 6 and 7 m equipped with 4 spray nozzles (12), each with a diameter of 1.5 mm projecting a flat jet in the axis of the drum (5) on the first 1.50 m from the latter. The transmission and drying means (6, 7) have a drying surface of the order of 6 to 7 m2 and a total heating capacity of the order of 800 therms. The coating composition consists of a slurry composed, for 1 liter of slurry, of - 20 g of methyl cellulose, - 40 g of titanium oxide, - 40 g of a red pigment marketed under the reference "Pigment
Red 112 ", - 40 g of a fungicide sold under the name THIRAM, - the balance of water.

 Such a composition is projected with a flow rate of 5 liters per quintal of seed, which makes it possible to treat 4.5 tonnes per hour of corn but for a consumption of 225 liters per hour of the aqueous composition described above. With a hot air inlet temperature of 50 "C the seeds leave in (11) dried on the surface, their humidity at the outlet being the same as that of the seeds at the entrance to the hopper (1). The seeds are completely covered in the convex parts and in all the concave parts with a continuous and homogeneous film.The residence time of the seeds in the installation is of the order of 10 min.

2 - COLZA SEEDS
The coating tunnel (5) is approximately 8 m long. and the conveyor and drying means (6, 7) has a useful area of approximately 10 m2 for a heating power of approximately 1,600 therms.

A coating composition is used here consisting of an aqueous dispersion comprising, per liter - 25 g of methyl cellulose, - 20 g of titanium oxide, - 4 g of a liquid dye sold under the name
RHODAMINE, - 16 g of an ethoxylated nonylphenol, - 340 g of an insecticide and fungicide compound sold under
the name OFTANOL T, - the water balance.

This composition, in the form of a viscous slurry, is brought by a pipe (12) to the entrance of the tunnel (5) while downstream of the pipe (12), at about half of the tunnel a drying powder, marketed by the plaintiff under the name
SEPIRET 08 and described in document FR-A-2 548 675, is poured onto the seeds.

 The installation allows the treatment of a rapeseed seed flow rate of the order of 4 t / hour with a filming composition flow rate of 480 1 / hour and a spraying of drying powder of 40 kg / hour. The seeds emerge from the installation covered with a homogeneous, porous and resistant film.

3 - SUNFLOWER SEEDS
The installation, of smaller dimensions, comprises a cylinder (5) with a diameter of 1 m. and a length of 5 m. rotating at 5 revolutions / min, the drying consisting of an identical cylinder (6) perforated over its entire surface with holes of diameter 2 mm.

Is used here, for projection by the nozzles (12), a film-forming, aqueous composition consisting, for 1 liter of composition, of - 105 g of a cellulose binder such as methyl hydroxy propyl cellulose, - 210 g of oxide titanium, - 21 g of a blue phthalocyanine pigment - 17 g of a phytosanitary composition sold under
the BENOMIL appellation, - the balance of water.

 Drying air at 70 ° C. is used, which makes it possible to remove around 25 liters of water per hour. Such an installation makes it possible to treat 1,000 kg / hour of seed with a flow rate of film-coating composition of the order of 60 l / hour. The residence time of the sunflower seeds in the drum (5) is approximately 3 min and approximately 9 min in the drum (6) (where the thickness of the seeds are higher.) The seeds emerge in (11) film-coated, uniformly colored blue, at a temperature of 25 "C, their humidity at the outlet being very slightly higher than their humidity at the entrance.

4 - SEEDS OF ONIONS
The lamination tunnel (5) is here inclined by 10 and has a length of approximately 1.50 m rotating at a speed of approximately 10 revolutions / minute. The dryer (6) offers a useful surface of 1 m2, the drying air flow being adjusted between 2 and 4 tonnes / hour with a heating capacity of the order of 4 kw / hour.

An aqueous film-coating dispersion is used here, made up for 1 liter of composition, of - 20 g of polyvinyl alcohol, - 20 g of the fungicidal composition sold under the name
THYRAM, - 50 g of clay, - 10 g of titanium oxide, - 10 g of blue dye, - the balance of water.

 This installation makes it possible to treat 500 kg / hour of onion seeds for a flow rate of aqueous film-coating dispersion of 40 l / hour. The residence time of the seeds in the installation is of the order of 10 min and the filming obtained is homogeneous and covers the entire seed well.

 Although the present invention has been described in relation to particular embodiments, it is not limited thereto but is on the contrary subject to modifications and variants which will appear to those skilled in the art. In particular, the method according to the invention is also applicable to the coating of pharmaceutical or food particulate elements.

Claims (10)

 1. A method of coating particulate elements, in particular seeds, by applying a coating composition to a moving volume of said elements and drying them, characterized in which comprises the steps of applying to the volume of elements of combined movements of agitation and translation along a first defined path (5), of applying a determined quantity of film-coating composition to the moving volume in at least one zone (12) of the first path, then of drying in continuous film-coated elements, routed at substantially the same translation speed, along a second defined path (6).  2 -A method according to claim 1, characterized in that it comprises the steps of applying to the volume of moving elements determined quantities of film-coating composition (12) and at least one other substance (15) entering the composition of the film, in at least two distinct zones of the first path.  3 -A method according to claim 1 or claim 2, characterized in that the flow rate of the particulate elements is greater than 500 kg per hour.  4 -A method according to claim 3, characterized in that the flow rate of the particulate elements is greater than 1,000 kg per hour.  5 -A process according to one of the preceding claims, characterized in that an aqueous dispersion of film coating is projected onto the volume of the particulate elements with a flow rate greater than 0.035 1 per kg of particulate elements.  6 -A method according to claim 5, characterized in that the aqueous coating dispersion comprises between 10 and 200 g per liter of film-forming component.  7 -A method according to one of claims 5 and 6, for the film coating of seeds, characterized in that it comprises the step of projecting onto the volume of seeds in motion a phytosanitary compound.  8 -A method according to claim 7, characterized in that the phytosanitary compound is mixed with the aqueous coating dispersion at a rate between 10 and 500 g per liter thereof.  9 - Application of the method according to one of the preceding claims to the coating of seeds chosen from the following varieties: but, but sweet, rapeseed, peas, sunflower, vegetable seeds.  an elongated lamination tunnel (5) comprising at least one rotary element and defining a first path - at least one device (12) for projecting a film-forming composition into at least one zone of the first path - a conveyor (6) defining a second path after the first trip; and - drying means (7, 8) associated with the conveyor (6).  10 -An installation for implementing the method according to one of claims 1 to 8, characterized in that it comprises - a device (1,3,4) for supplying particulate elements