A large proportion of pharmaceutically active compounds is available in a solid state in the form of pills or tablets. Other drugs are sold as granulate or tablets to be dissolved in water before consuming. The journey from a pharmaceutically active compound in solution to a ready-to-serve solid product passes through several process stages, such as spray or fluidized bed drying, grinding, and mechanical separation stages, like sieving, sifting, or classifying.
Transport between different process steps is carried out pneumatically. Transport gases (air or nitrogen) that are in contact with products or auxiliaries must be free of solid impurities. Fluidized bed systems or wind sifters demand a subsequent filtration of the air/gas streams in use. Other processes are combined with the generation or fluidizing of dust, which must be retained by filters in order to prevent contamination of the surrounding environment, as well as product losses. Humid exhaust air from drying processes is filtered just as any air flowing into a process chamber.
All filters used in this environment must meet highest hygiene requirements. This is why they all are suitable for cleaning in place (CIP). Product losses must also be reduced to a minimum during intermediate cleaning during filtration processes. These requirements are met by a dead zone free filter design in combination with effective back-pulse cleaning.

 

Granulation

Granulation is commonly applied for making up powders in the pharmaceutical and food processing industry. It generates bulk quantities of flowable granules with narrow size distributions from fine powders or from substances that are suspended or dissolved in liquids.  Before the further processing of granulates generated by spray or fluidized bed drying or by dry granulation, unwanted undersized or oversized grains (agglomerates or individual grains) have to be separated out and recycled into the process. This is done by our granulation sieves and conical sieves, which are specially adapted to the process in question. The sieves are also used to separate undersized or oversized grains after pelletizing and prior to packing or a further treatment process like coating.

 

Coating

The Wurster spray coating process is commonly used to deposit active compounds on carrier particles or protective coatings on tablets and pills. In doing so the particles are fluidized in a vessel by air flowing upwards through a sieve at the bottom. The coating material (as solution, suspension, or melt) is then injected into the air flow at the bottom. The process is carried on until all particles are uniformly coated. The sieve at the bottom of the coating vessel is a device made by Seebach, which is especially adapted to the particle to be treated and the air volume flow.
Another important filtration process carried out with our products is cleaning solutions or melts before spraying. Here, the filter system has to ensure that no particles, like agglomerates, unsolved solids. or unmelted material, can block the nozzle. The air circulating in the coater is filtered to separate particles that have been carried away by the flow.

 

Classification

After granulation and grinding, additional processes like sieving or classification are indispensable for standardizing particle size distributions. To meet this requirement we supply sieves in different geometries with a large variety of holes with respect to their width and shapes. Depending on the form and size distribution of particles to be classified, sieves with rhombus-shaped, circular, or quadratic holes are used. A special application that we are able to support is the combination of grinding/rubbing and classifying by means of sieves with grater perforations.

 

Pelleting

In addition to coating particles by liquid deposition and subsequently drying, it is also possible to deposit active compounds or auxiliaries in the form of powders. This type of pelleting is not only used in the pharmaceutical production, but also to treat seeds in agriculture.
In the latter case, the addition of pesticides or herbicides is common. As well as enabling the adhesion of active compounds, fillings, or auxiliary substances, the resulting uniform particle size facilitates transport and dosing processes.
Again, the sieving of the product to remove powder residues or outsizes are tasks that are solved by Seebach sieves.

 

Drying

Depending on the form, in which a powder product occurs, whether it is in a highly concentrated solution, a humid powder, a diluted suspension, or in slurry, the appropriate drying process must be selected from a variety of possibilities. All drying processes, like spray drying, fluidized bed drying, or belt drying with or without vacuum, utilize hot air that is recycled during the process. Particles are removed from the circulating air by filtration; water vapour is condensed and the dry air is re-heated. In a fluidized bed dryer, the dry powder is carried out together with the air and recovered in a subsequent filtration step. Here, Seebach filters that are especially adapted to the respective processes are used The material and filter design employed ensures high filtration efficiencies, minimum product losses, and long working life
All Seebach filter elements can be cleaned in place (CIP). This means that they can be back-flushed, washed, and prepared for a new batch automatically. Seebach’s world-renowned design combines maximum active filter area with minimum dead zones in order to guarantee complete removal of all residues during the CIP process.