Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/006—Coating of the granules without description of the process or the device by which the granules are obtained
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/16—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by suspending the powder material in a gas, e.g. in fluidised beds or as a falling curtain

Definitions

• the invention is an enhanced processing apparatus for particle coating using a new airflow vortex generator that will contribute to the field of chemical and pharmaceutical technology.
• the invention represents an improvement in particle processing equipment by spraying from beneath and functions on the principle of a vortex generator. More precisely, the invention can be regarded as a design solution to the essential features of a particle coating device that improves the quality of the coating.
• the invention falls within the A61J3/06 class in accordance with international patent classifications.
• the invented device solves the technical problem of effectively ensuring a narrow variation in coating thickness from particle to particle, for small as well as large particles.
• the functional coating of particles is a common technological process in chemical and pharmaceutical industries.
• the main problem is the coating of small particles (50-300 microns), which, due to a low mass and inertia, are more prone to the undesirable effect of agglomeration.
• Independent and coated small particles are important in pharmaceutical and chemical technology due to their larger surface area, compared to larger particles.
• coating particles by spray dispersion containing a therapeutic substance it is particularly important in the pharmaceutical industry to maximise the material efficiency of coating process, which is most often dependent on the location and angle of the nozzles and the density of particles around the nozzle.
• the known particle-coating processing devices which work on the fluidised bed principle are ideal for coating particles in the size range from 50 microns to 6 mm
• Processing devices for coating particles that use the vortex technology can be roughly divided into groups: those devices which spray from above; devices which spray tangentially; and devices which spray from below.
• the processing devices which spray from above are primarily intended for granulation, however, in the case of coating, due to the need for the dispersion of small droplets to achieve the desired coating quality, a stronger undesirable effect of spray drying of coating solution is achieved.
• the distance between the nozzle and particles is short, whilst at the same time the nozzle is aimed in the direction of airflow for fluidisation, or the particles.
• the known version of the device that sprays from below contains a separation cylinder - or so-called inner cylinder- positioned centrally above the nozzle and a little above the distribution plate.
• the processing chamber works according to the principles of a circulating fluid bed, a technology which is named after its inventor: a Wurster chamber.
• the advantage of this device is that the particle coating area is separate from the drying area, and further, due to the pneumatic transportation of particles within the cylinder and around the nozzle, the velocity of particles is relatively greater (0.7 - 2 m / s), thus reducing the possibility of particle agglomeration.
• the movement of particles is repetitive and circular, i.e. a form of controlled movement.
• the problems of coating using a classical Wurster chamber are demonstrated by the uneven deposits of coating film across the population of particles. This is a consequence of the effect of the particles shading one another in the dispersion of the coating spraying area, the effect of a "blind spot" in the flow of particles, and a consequence of the disproportionate acceleration of the smallest and largest particles in the population of particles undergoing the coating procedure.
• the volume share of the pellet in the spraying area and the effect of mutual shading depend on the through-flow medium of fluidisation (air or another inert gas) and on the adjusted height of the separation cylinder.
• the effect of the "blind spot" on the stream of particles occurs in the corner between the outer wall of the processing device and the distribution plate, since the particles located nearer to the outer wall of the separation cylinder previously repeatedly pass into the area of horizontal transportation, and into the area of coating and vertical transportation, and so repeatedly circuit through the cylinder during coating, and consequently receive more coating.
• agglomeration of particles in the size range of 50 to 300 microns can build up relatively quickly, in spite of drying, due the large localised through-flow of heated air.
• the invention presented solves the technical problem of reducing the distribution variation in coating film widths, the problem of reducing the agglomeration of particles, and also the problem of increasing the efficiency of the coating.
• This is achieved by using an innovative airflow vortex design (see figures 3, 4, 5), which gives a different profile of air speed at the entrance to the bottom part of the cylinder, than that which is characteristic of the vortex current performances known up until now.
• the reduction in the relative standard deviation (RSD) in coating film thickness is also greater in comparison to other known devices, and significantly so in comparison with the classical Wurster chamber (PWS Heng et al, International Journal of Pharmaceutics, 327, 2006, 26-35).
• the innovative design of our device also reduces the problem of dependence of the coating film thickness on the initial size of the particle being coated.
• the features of the two-phase particle-gas flow, which affect the coating quality, can to a large extent be influenced by altering certain components of the airflow vortex generator, allowing the device to be used for a wide range of products.
• figure 1 a schematic cross-section of the processing equipment invented for particle coating
• figure 2 detail of the processing device with the airflow vortex generator; vortex generator
• figures 3, 4, 5 the geometry of the vortex generator figures 6,7 schematic implementation of a semi-industrial or industrial device invented for particle coating
• Figure 1 presents a schematic cross-section of the particle coating processing device, which consists of an outer wall (1), which at the bottom part of the device is in the shape of a cylinder shell, or a truncated cone.
• the generator (4) for the vortex airflow with the gas distribution plate (3) in the outer part, by the outer wall (1) of the device.
• the gas distribution plate (3) which on the plan has the shape of a ring, can be flat, curved, inclined or stepped.
• the metal mesh with perforations of the order 10-100 microns is the spray nozzle (6) introduces the suspension or dispersion coating spray centrally.
• the twin-channel nozzle (6) for spraying (see figure 1) has a conduit (7) for the coating dispersion, and a conduit (8) for the compressed gas.
• the wall of the processing device (2) forms a space into which a fluidising medium (9) (usually air) is supplied.
• the pressure in this part of the processing device is high given the space of the processing device above the airflow vortex generator (4) and the gas distribution plate (3).
• the separation cylinder (5) is fastened centrally in the processing chamber, is tubular in shape and fixed on such a height, that it creates between the vortex generator (4) and the gas distribution plate (3) a slit (most often of 5 to 25 mm).
• particles were found to form a layer around the separation cylinder (5) above the flat or curved gas distribution plate (3). Whether this layer takes the form of a loose static build up, or a fluid (floating) state depends upon the number and the arrangement of perforations in the outer gas distribution plate (3), the vortex medium for fluidisation (9), and the size and density of particles.
• the centrally positioned airflow vortex generator (4) creates a vortex (17) with an axial and a tangential component.
• the airflow vortex (17) in the slit area, between the separation cylinder (5) and the outer gas distribution plate (3) creates a negative pressure, due to the large local variations in the movement velocities of the gas.
• Figure 2 shows a detail of the processing device in the vicinity of the airflow vortex generator (4), and the spraying nozzle (6) with the distribution and form of the local currents (15), (16), (17) of the fluidisation medium.
• Figures 3, 4 and 5 show the geometry of the airflow vortex generator (4).
• Barriers (18) for directing the gas are set between two rotationally symmetrical walls (19) and (20). Given the nature of the central plan of the walls, (19), (20), the barriers (18) to direct the airflow are positioned at an angle ⁇ , most often from 10 to 80 °.
• a horn-shaped frame (21) is mounted in the centre of the lower plate (19).
• the shape of the frame (21) directs the airflow coming from the area enclosed by plates (19) and (20), in which barriers are installed (18) to create a vortex, upwards through the annular slit (22) that is formed by the inner edge and the inner wall of the frame (23), located between the upper plate (20) and the gas distribution plate (3) on one hand, and the frame wall (21) on the other. This is what creates the vortex current.
• the flow properties of the gas depend upon the shape and positioning of the barriers (18) for directing airflow, on the shape of the frame (21), and on the available surface area of the annular slit (22) between bodies (21) and (23).
• the surface area of the annular slit can, for certain gas through- flows, influence the velocity of the gas underneath the separation cylinder (5). This speed is one of the parameters affecting the flow of pellets in the separation cylinder (5), and thus the structure of the dual-phase current within the separation cylinder (5). If we imagine the structure of the airflow vortex to be in the form of a helix, then the shape of the helix can be easily influenced by angling barriers (18) to direct airflow, the frame shape (21) and the inner walls of the frame (23). The design set-up makes it possible and easy to alter those parts which do the regulating, and in so doing to create the appropriate helix airflow structure for achieving optimum coating conditions, which may vary according to individual applications.
• the nozzle (6) for spraying the solution or coating dispersion is positioned centrally through the horn-shaped frame (21).
• the airflow vortex generator (4) reduces the relative standard deviation (RSD) in the thickness of coatings (compare the results of Table 2 and Table 3). This is because the subsequent circular motion of particles, following the airflow, reduces the incidents of particles shading one another; since the particles are simultaneously more uniformly distributed throughout the volume of the separation cylinder (5). Due to a higher total air velocity (axially and tangentially), the airflow vortex is more effective at sucking up the particles, which reduces the effect of the blind spot, thus also reducing the variations in coating thickness. Compared to the performance detailed in patent application no. P-200800295, the flow of particles within the separation cylinder (5) in the device that we have invented does not contain strings formations of particles, and is significantly more homogeneous.
• the coating efficiency and the uniform thickness of the coating film are increased. Due to the improved heat transfer (as a result of the longer path of particle motion, on its route through the cylinder and the expansionary part of the appliance), and the reduction in the local density and the pellet collisions against the cylinder wall, significantly less particles were observed to agglomerate in a processing device that uses a vortex generator (4), than in a conventional Wurster chamber. Due to the centrifugal particle movement, smaller particles fall towards the bottom of the device after passing through the cylinder. This reduces the problem of the coating thickness depending on the initial particle size, which is a characteristic of the classical Wurster chamber.
• Figures 6 and 7 indicate the implementation of a semi-industrial or industrial particle coating device with a vortex generator (4), in which an increase in the device capacity is achieved through an increase in the number of airflow vortex generators (4), spraying nozzles (6), and separation cylinders (5) within a single processing device, limited by the outer wall (1).
• the gas distribution plate (3) can be flat, curved, inclined or stepped.
• the perforation of the distribution plate (3) can consist of holes, slits or, for example, may involve a wide variety of punching methods.
• the upper edge (21 b) of the horn (21 ) and the nozzle (6) height can be located above, underneath or at the same height as the distribution plate (3).
• Airflow routers (18) can be straight or e.g. curved and can be made in the shape of a vane or e.g. a groove. It is also not necessary for the bottom surface of the bottom wall (19) to be flat. It can be produced, e.g., in the shape of a hemisphere, which helps reduce gas pressure loss as it passes through the airflow vortex generator (4).
• Results in Tables 2) and 3) represent the mean of six measurements.
• each pellet coating trial we coated 1000 g pre-sieved pellets in the 800 to 1000 ⁇ m size interval.
• the inlet-air relative humidity fluctuated between 30 and 34% and the ambient temperature was held at 17°C.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Glanulating (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Nozzles (AREA)

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• 2009
  • 2009-03-19 SI SI200900075A patent/SI22991A/sl not_active IP Right Cessation
• 2010
  • 2010-03-15 EP EP10726648A patent/EP2408547A2/de not_active Withdrawn
  • 2010-03-15 RU RU2011141325/05A patent/RU2542276C2/ru active
  • 2010-03-15 WO PCT/SI2010/000013 patent/WO2010107401A2/en not_active Ceased

Non-Patent Citations (1)

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