Swirl Flow Generator for Uniform Particle Coating
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Solution Overview
Problem
Existing particle coating devices using fluidization technology face challenges in achieving uniform coat thickness and reducing agglomeration, especially for small particles (50-300 microns), due to issues like particle shading, 'dead spots,' and size-dependent coating times, leading to non-uniform film coatings and increased energy consumption.
Innovation Solution
Incorporating a swirl flow generator with a unique airflow design that creates a swirling flow within the draft tube, reducing the variability in air speed and particle movement, which enhances heat transfer, reduces agglomeration, and results in a narrower distribution of film coating thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If bottom spray process device is used, then coating efficiency is improved, but particle agglomeration increases
Solution Approach 1:
The device divides the processing chamber into distinct functional zones: a coating area where particles receive coating dispersion, and a drying area where particles are dried by heated air. This segmentation prevents agglomeration by ensuring particles are dried quickly after coating, reducing the time they remain wet and prone to sticking together.
Solution Approach 2:
A draft tube is introduced as an intermediary component that directs and controls the flow of particles and air. The draft tube creates a controlled circulation pattern that enhances the separation between coating and drying functions, improving particle movement control and reducing agglomeration while maintaining coating efficiency.
2Object-generated harmful factors
If draft tube is added to create circulating fluid bed, then particle speed increases reducing agglomeration, but coating uniformity deteriorates due to particle mutual shading and dead spots
Solution Approach 1:
The device creates different flow conditions in different spatial locations: in the coating area, particles move slowly allowing uniform coating deposition, while in the drying area, heated air creates upward flow that prevents agglomeration. The draft tube geometry is optimized to create appropriate local flow patterns in each zone, achieving both uniform coating and agglomeration prevention.
Solution Approach 2:
The draft tube introduces a vertical dimension to particle circulation, creating a three-dimensional flow pattern that enhances particle movement through the processing chamber. This vertical circulation component helps eliminate dead spots and improves coating uniformity by ensuring all particles pass through both coating and drying zones repeatedly.
3Area of moving object
If smaller particles (50-300 microns) are coated, then specific surface area increases, but coating uniformity decreases due to size-dependent acceleration and rising height
Solution Approach 1:
The device creates a fluidized bed environment where particles are suspended and moved by air flow rather than gravity alone. This equipotential condition reduces the effect of size-dependent acceleration, as all particles are carried by the gas flow rather than falling under gravity. The draft tube enhances this effect by creating a controlled circulation pattern that maintains similar residence times for particles of different sizes.
Solution Approach 2:
The device changes the flow parameters (air velocity, temperature distribution) to optimize coating uniformity across different particle sizes. By adjusting the fluidization air flow and heated air temperature in different zones, the device compensates for size-dependent behavior, ensuring consistent coating thickness distribution across the particle population.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The swirl flow generator achieves a 56-62% reduction in the relative standard deviation of film coating thickness and significantly reduces agglomeration, improving coating yield and uniformity across particle sizes, while minimizing energy consumption.
Implementation Method 1
the swirl flow generator (4) for medium (air) forms in the area of draft tube (5) horizontal cross-section a swirling flow (17) of air with an axial and tangential component
Implementation Method 2
Process devices for coating particles operating on the principle of fluidization technology
Implementation Method 3
If the fluidization medium (9) is heated (usually at 40 to 80 °C) before entering the processing chamber, and is in good contact with the solid particles, there is an effective evaporation of the solvent of the coating dispersions from the surface of particles
Implementation Method 4
there is an effective evaporation of the solvent of the coating dispersions from the surface of particles
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The subject of the invention is a process device for coating particles that falls within the field of chemical and pharmaceutical technology. It represents an improvement on the process equipment for coating particles by spraying from the bottom and works on the principle of fluidization technology. The process device for coating particles, according to the invention which has within the wall (1), one or more units placed, for which each unit consists of a swirl flow generator (4) with a perforated plate (3) and a draft tube (5) where centrally through the swirl flow generator (4) a single or multi-phase spraying nozzle (6) with a coating dispersion inflow (7) and inflow (8) of compressed air is installed, in which the swirl flow generator (4) has outward open and at an angle with regard to the vertical installed grooves (18). The process device for coating particles in the second implementation case, has within the wall (1), one or more units placed, for which each unit consists of a draft tube (5) and a single or multi-phase spraying nozzle (6), which is mounted centrally with regard to the draft tube (5) and penetrates the perforated plate (3a). The perforated plate (3a), which is in the outer area, between the wall of the draft tube (5), and the wall (1) of the device, in cross-section straight or curved and has a characteristic distribution of the size of round orifices with the largest cross sections in the area of the ground floor projection of the draft tube (5) and smaller orifices in the remaining part of the plate. The device for coating shall have along the periphery of the wall (1) and at the perforated plate (3a) the ring (21 ) with installed inflow slots (27) that are pressure powered from a common hollow ring (20) with a connector (22) for compressed air. The device for coating shall have along the periphery of the wall (1) above the perforated plate (3a) a radially installed circumferential inflow slot (24) and otherwise inclined to the horizontal plane, the slot (24) is pressure powered through the hollow ring (23) with a pressure connection (25).