Micronization is used routinely in many applications in solid oral and other dosage forms:
The spiral jet mill uses compressed gas (air/nitrogen) to micronize a dry powder into a final particle size distribution between 1 to 10 or 20 micrometers.
The raw material is introduced into an inlet cone by a feeding unit (screw or vibrating feeder). The combination of a venturi tube and a gas injection creates a vacuum that transports the particles of the raw material inside the milling chamber.
A second inlet of pressurized gas enters the milling chamber through a series of nozzles positioned on the perimeter, which’s aim is to transform the gas pressure into gas speed.
The high-speed gas accelerates the particles in a vortex, in which these collide against each other and they reduce in size.
The centrifugal force created by the high-speed gas keeps the large particles in the perimeter, where the product is micronized, while the small particles follow the gas stream, and through the classifier they proceed inside the final filtration and collection system.
The particle size distribution is determined and influenced by a combination of the two main process parameters: feed rate and gas pressure.
The opposite jet mill micronizes dry particles through frontal collision.
The powder is introduced from a feeder, through a double valve into the milling chamber. At the bottom of the milling chamber, three nozzles accelerate the particles and create the micronization effect. The fluidized bed generated by the nozzles transports the particles toward the top of the jet mill. Before being transported by air/nitrogen into the cyclone filter, the particles pass through a rotating classifier. The classifier separates the fine particles from the bigger ones, which by physic effect are rejected and they fall again into the gas stream, until being micronized.
Differently from the spiral jet mill, the final particle size distribution is determined by gas pressure and the rotation speed of the classifier. The higher is the rotation speed, the finer is the final particle size.
The jet mill is positioned on load cells, which regulate automatically the feeding of the jet mill, according to the weight set on the PLC by the operator or by the uploaded recipe.
The Pin / hammer mill is a mechanical mill used for gross milling of large particles >1mm.
The milling body predisposed for both PM100 and HM100. The material is introduced from the double screw electric feeder into the inlet cone.
After grinding through pins or hammers, the material is exhausted from the bottom discharge and conveyed into the cyclone filter.
The hammer mill is available with different mesh sizes according to customer request.
The dynamic classifier is used to separate fine or gross particles from a particle size distribution. This can be executed before or after a micronization / milling process.
The classifier is composed by a cylindrical chamber, with a rotating classifier mounted on top. The injection of the product is made through a venturi system, that transports the powder inside the classifier.
At the bottom part of the classifier there’s an injection of N2/compressed air to create the fluidized bed. The bottom part is equipped with a deflector and a collection bottle with a manual butterfly valve, for the collection of big particles. Small particles are selected by the dynamic classifier and proceed toward the cartridge filter.
Lonza’s focus is to provide high tech- highly tailored units to customers which are not satisfied by standard and modular solutions highly available on the market.
The engineering division has always been a key partner for the contract micronization department, with its capabilities on providing highly innovative solutions for customers looking not only for a simple micronization process, but for an optimized service, specifically tailored for their products.
Technical solutions can be developed or customized to reach the maximum available flexibility, with the latest technological standards or tailored on a specific product, with a particular look into process optimization in terms of performances, comfort for the operator and occupied space.
Ever since Lonza Monteggio started manufacturing glove boxes (1992), the demand for high containment and for more strict OEL (Operational Exposure Limit) levels increased significantly.
Micronization process is the most challenging to be contained into an isolator, due to its heavy creation of dust of ultra-fine particles.
Thanks to the latest technical innovations and the long know how and experience in containment and micronization solutions, Lonza can now provide contained jet mills reaching an OEL of up to 10ng/m³ and 1ng/m³ for other processes.