Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
  • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
  • B07B1/00—Sieving, screening, sifting, or sorting solid materials using networks, gratings, grids, or the like
  • B07B1/18—Drum screens
  • B07B1/22—Revolving drums
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/02—Investigating particle size or size distribution
  • G01N15/0255—Investigating particle size or size distribution with mechanical, e.g. inertial, classification, and investigation of sorted collections
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/02—Investigating particle size or size distribution
  • G01N15/0272—Investigating particle size or size distribution with screening; with classification by filtering

Definitions

• the invention relates to the sector of devices and apparatus for determining the particle size of the powders, this characterization may especially be carried out online, that is to say during the manufacturing process of said powders.
• the powders in question are more particularly dry powders, that is to say powders having a moisture content of less than 3% by weight of water, as determined by differential weighing measurements before and after drying of said powders. .
• the powders in question are also powders having a large particle size range, that is to say with an average diameter of between 0.1 and 5 mm.
• the powders in question are even more particularly sugar crystal powders, laundry powders, ceramic powders, plastic powders, metal powders, or powders made of mineral materials, and more particularly powdered materials. minerals based on natural or precipitated calcium carbonate and / or dolomites, and even more particularly mineral powders based on a natural calcium carbonate which is marble or limestone or mixtures thereof.
• a first object of the invention is a powder particle size characterization device comprising a feed member, an evacuation member, a weighing member, a continuous vibration member, a sieving member, as well as optionally a control member, and characterized in that the sieving member is a rotatable member about a horizontal axis, and has at least 3 positions corresponding to 2 different mesh sieves and 1 more particle release space coarse particles (particles that have not passed through the largest mesh sieve).
• Another object of the invention is the use of such a device for the characterization of the particle size of powders, and in particular their characterization in line, that is to say during their manufacturing process.
• These include dry powders, that is to say powders whose moisture content is less than 5% by weight of water, as determined by differential weighing measurements before and after drying. said powder.
• powders based on sugar crystals laundry powders, ceramic powders, plastic powders, metal powders, or powders consisting of mineral materials, and even more particularly mineral-based powders.
• natural or precipitated calcium carbonate and / or dolomite and even more particularly mineral powders based on a natural calcium carbonate which is marble or limestone or mixtures thereof.
• a first object of the invention is a device enabling the on-line characterization of the particle size of various powders, such as in particular dry powders as defined above, having a large particle size as defined above, and especially powders containing sugar crystals, laundry powders, ceramic powders, plastic powders, metal powders, or powders made of mineral materials, and even more particularly mineral powders based on natural calcium carbonate or precipitate and / or dolomite, and even more particularly of powders based on a natural calcium carbonate which is marble or limestone or mixtures thereof.
• various powders such as in particular dry powders as defined above, having a large particle size as defined above, and especially powders containing sugar crystals, laundry powders, ceramic powders, plastic powders, metal powders, or powders made of mineral materials, and even more particularly mineral powders based on natural calcium carbonate or precipitate and / or dolomite, and even more particularly of powders based on a natural calcium carbonate which is marble or limestone or mixtures thereof.
• the Applicant intends the control of the particle size during the process of manufacture of said powders, and in particular during the process of particle size reduction of said powders in the case of powders composed of mineral materials.
• Another object of the invention is a device for characterizing at a single time different particle size classes for the aforementioned powders.
• a last object of the invention is a simple device to be implemented at a manufacturing site of said powders, and compatible with the industrial constraints of such a site.
• the control of the particle size thereof is a fundamental element for those skilled in the art, a generalist engineer in industrial processes and specialized in techniques relating to powdery materials. This control makes it possible to assess the quality of the product produced during the different stages of particle size reduction in the context of powders of mineral matter.
• a control also enables the person skilled in the art to ascertain the effectiveness. of its manufacturing process, while guaranteeing the final customer precise specifications in fineness and particle size.
• the particle size distribution of a calcium carbonate powder may have an influence on the flowability properties of said powder, or on the drying of ceramic materials containing said powder, such as 'described in "Influence of party size we mean key-drying shrinkage behavior of calcium carbonate slip cast bodies" (Proceedings of the China International Conference on High-Performance Ceramics, the st, Beijing, China, October 31 to November 3, 1998 (1999), Meeting Date 1998, pp 181-184).
• this particle size distribution plays a very important role in the flowability of said powders. The same goes for metal powders.
• the Applicant can cite the range of the Mastersizer TM laboratory laser particle size analyzer manufactured by Malvern TM, the range of particle size analyzers. Insitec TM line laser manufactured by the same company, and Sedigraph TM devices manufactured by Micromeritics whose technology is based on X-ray diffraction.
• Camsizer TM marketed by the company Retsch Technology TM, CP A TM marketed by the Haver and Boecker TM, or Part An TM marketed by Norske Hydro TM.
• the skilled person prefers to opt for characterization apparatus based on a selection of particles according to their size, from mechanical devices.
• US 4,184,944 discloses a cylindrical sieve device, rotating about its horizontal axis continuously, and for sieving dry or wet powders through the screen that surrounds said cylinder.
• the document EP 1 163 958 presents a cylindrical apparatus rotating on its horizontal axis in a continuous manner, said horizontal movement being completed by an induced vibration movement on the sieve which forms the cylinder: this apparatus is particularly intended for sieving materials clay-based.
• the Applicant indicates that the use of cylindrical cages covered with a sieve, driven by a rotational movement and / or vibration, thus allowing the sieving of mineral particles, are means well known to man of career.
• the Applicant has developed a new device that meets the expectations of those skilled in the art.
• said device does not have the disadvantages of the laboratory methods mentioned above, since it is inexpensive to manufacture, simple to integrate and to use and that the conditions of its implementation are perfectly compatible with the environment.
• industrial in which it is used atmosphere rich in pulverulent materials, shocks, vibrations, .
• it allows at one time (without sieve change or interruption of the cycle of measurement) to characterize several particle size classes.
• its simplicity makes it perfectly adaptable at any point in the process of manufacturing mineral materials, thus allowing online control of the particle size of said particles, which is the essential objective for those skilled in the art.
• the first object of the invention is therefore a device comprising:
• said device being characterized in that the sieving member: - is a rotatable member about a horizontal axis, and has at least 3 positions corresponding to 2 sieves of different mesh size and 1 space of release of the coarser particles (Particles that have not crossed the largest mesh sieve), thus allowing a sieving of the powder in steps, over successive positions taken by said member about its axis.
• the sieving member - is a rotatable member about a horizontal axis, and has at least 3 positions corresponding to 2 sieves of different mesh size and 1 space of release of the coarser particles (Particles that have not crossed the largest mesh sieve), thus allowing a sieving of the powder in steps, over successive positions taken by said member about its axis.
• Feeding, evacuating, weighing and continuous vibrating members may be made in any form or means well known to those skilled in the art.
• the sieving device provided that it is rotatable about a horizontal axis, and comprises at least 3 positions corresponding to 2 sieves of different mesh size and 1 space for releasing the coarser particles.
• This sieving member is characterized in that it can be made in different shapes such as cylindrical or polygonal.
• the device which is the subject of the invention may therefore optionally contain a control member whose function is to control the other members.
• Said control member may be on board or remote. It may be a computer, a programmable controller, or any other control device well known to those skilled in the art.
• another object of the invention is the use of the device described above for the determination of the particle size of powders.
• This use is characterized in that it applies to dry powders, that is to say powders whose moisture content is less than 5% by weight of water, and preferably less than 2% by weight. water mass, and very preferably less than 1% by weight of water, as determined by differential weighing, before and after drying of said powder.
• This use is also characterized in that it applies to powders having a particle size range, such that the average diameter of said powders is between 0.1 and 5 mm, and preferably between 0.2 and 2 mm.
• the powders in question are, more particularly, powders based on sugar crystals, laundry powders, ceramic powders, plastic powders, metal powders, or powders consisting of mineral materials, and even more more particularly mineral powders based on natural or precipitated calcium carbonate and / or dolomites, and even more particularly mineral powders based on a natural calcium carbonate which is marble or limestone or their mixtures.
• the use of the device according to the invention is primarily characterized in that it allows the determination of the particle size of the powders by means of the different successive positions taken by the sieving member around its horizontal axis.
• This use is also characterized in that it allows the determination of the particle size of powders in line, that is to say during their manufacturing process. This use is finally characterized in that it allows the determination of at least one grain size class in a single measurement cycle.
• Figure 1 shows a general view of the device and its 6 characteristic organs.
• FIG. 2 shows a side view of the device illustrating the sieving, evacuation and weighing members.
• FIG. 3 represents the cylindrical sieving device equipped with different sieves:
• FIG. 4 schematically represents the characterization cycle of a powder, when the device according to the invention comprises a cylindrical screening member, provided with 2 screens, and an evacuation space:
• the representation of the top represents said sieving member, with its release space at the top, its thinnest sieve at the bottom, and its widest sieve at the right,
• the bottom representation is that of the device according to the invention in the process of characterizing a powder, in 3 positions: in position 1 (left view), the finest screen of the device being oriented downwards, in position 2 ( central view) with the widest sieve facing downwards,
• the device is connected by its feed member to a pipe of the manufacturing unit in which circulates the mineral material to be analyzed.
• the feed member is provided with a device for automatic sampling of the powder by piston, or screw or by any other means well known to those skilled in the art, which allows it to close when a given quantity of powder has penetrated into the sieving member, this quantity being adjustable by the user by modifying the number of samples to be made.
• the sieving device which has at least 2 sieves of different mesh size, has been positioned beforehand so that the sieve corresponding to the finest mesh is located downwards, just above the sender. weighing: the powder arrives directly on this sieve (which will be called the first sieve).
• the particles whose diameter is smaller than that of the first sieve fall into the weighing member, where an automatic balance measures the mass of corresponding particles.
• the sieving member rotates (with the aid of the rotation member) about its axis so as to place down the sieve (second sieve) whose mesh is greater than that of the first sieve.
• the particles remaining in the cylinder, on the first sieve before rotation, are then found on this second sieve.
• the particles whose size is smaller than the mesh of the second sieve are poured into the weighing member.
• the sieving member is positioned in such a way that the space for releasing the coarsest particles is in the lower position (last position) so as to recover after rotation, the last remaining particles. in the cylinder on the largest mesh sieve. This makes it possible to obtain the total weight of the sample taken at the beginning of the cycle.
• the particles are brought to sieves of increasingly larger mesh: thus a classification of the particles according to their size is carried out.
• the weighing system associated with the device makes it possible to measure the masses of particles whose diameter is smaller than the mesh size of each sieve: this gives, by plotting each mass of particles as a function of the total weight of the sample, a particle size distribution of the particles. particles.
• the results obtained can be expressed as "passing” (percentage of particles passing through the sieves), "refusal” (percentage of particles remaining in the sieves, ie the inverse of the "pass") or by any other means expression of this type of results.
• This cleaning step is intended to evacuate the powder present in the weighing member, to clean the screens of the sieving device, to dust off the device as a whole and to reset the equipment (original position for start-up and / or initialization following a possible failure of the invention, or starting position waiting for a new cycle during the use of the invention). It consists of:
• the analyzed sample returns to the process via the evacuation device.
• a new characterization cycle can then begin.
• the rotation member is positioned in such a way that the release space is positioned downwards; the particles remaining in the cylinder are thus evacuated downwards.
• the number of sieves, the passage time of the particles on each of them, the total mass of the particles initially introduced into the sieving member are all parameters that the person skilled in the art will know how to adapt to the nature of the powders he wants to characterize.
• the invention allows, during a simplified cycle using only the largest mesh size and the release position of the coarser particles, to identify a pollution.
• These particles of diameter too large are generally present in small quantities, hence the need to use a simplified cycle, allowing the sampling of a large mass sample compared to the mass of the sample analyzed during the complete cycle.
• This example illustrates the implementation of the invention for the particle size characterization of a powder which is calcium carbonate manufactured by OMYA TM in its plant in Salses (France) and subsequently marketed under the name of Durcal TM 130.
• the device according to the invention was equipped with 4 sieves whose meshes are equal to 100 ⁇ m, 250 ⁇ m, 355 ⁇ m and 500 ⁇ m, meeting the analysis needs of the aforesaid powder (qualitative customer specifications). .) • The times of passage of the powder on each sieve are respectively equal to 06:00 minutes, 07:30 minutes, 04:00 minutes, 00:30 minutes and finally 00:25 minutes on the position of release of coarser particles.
• Table 1 refusal at 100 ⁇ m, 250 ⁇ m, 355 ⁇ m and 500 ⁇ m, determined from the device according to the invention, on a dry powder of calcium carbonate (Durcal TM 130 sold by the company OMYA TM)
• Table 1 thus demonstrates that it is possible, by means of the device according to the invention, to obtain the particle size distribution of a powder such as calcium carbonate.
• Example 2
• This example is intended to demonstrate the reliability of the device according to the invention, illustrating the correlation between the measurements it performs, and the measurements made manually in the laboratory on the same samples.
• This example uses a powder which is calcium carbonate manufactured by OMY A TM in its Salses (France) plant and subsequently marketed under the name of Durcal TM 130.
• FIGS. 5 and 6, at the end of this document, represent the value of the refusal measured according to the manual laboratory test (y-axis or y-axis) as a function of the measured refusal according to the invention (x-axis or axis of the x), respectively:
• FIGS. 5 and 6 demonstrates the excellent correlation between measurements made manually at 100 and 250 ⁇ m, and those obtained directly by the device according to the invention on the same samples (this correlation is of course possible for products other than Durcal TM 130 and for other grain size points such as 63 ⁇ m, 80 ⁇ m, 355 ⁇ m ).

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• 2005
  • 2005-05-17 FR FR0504917A patent/FR2886014B1/fr not_active Expired - Fee Related
• 2006
  • 2006-05-12 EP EP06764606A patent/EP1931965A1/de not_active Ceased
  • 2006-05-12 WO PCT/FR2006/001063 patent/WO2006123037A1/fr active Application Filing

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