Sieves and mills - Flexible use in (almost) every process situation
Nothing is more important in the production of pharmaceuticals than a precise process flow. Continuous processes and digital systems ensure the consistent quality of high-quality products and a high level of patient safety.
Cone mill / Conical Sieve:
Cone mills or conical sieves are used for the uniform size reduction of pharmaceutical ingredients. They can also be used for mixing, Sieving and dispersing. They are available in a variety of different sizes - from laboratory scale to high capacity equipment.
Compared to other size reduction technologies on the market, the sieve offers numerous advantages for production: lower noise levels, a narrow distribution of Particle Sizes, high design flexibility and higher capacity. For example, when processing low-density materials, such a screen can increase throughput by more than 50 per cent compared to conventional mills.
The patented Turbo Sieve BTS from L.B. Bohle Maschinen und Verfahren GmbH (Ennigerloh) is used to calibrate the Particle Sizes and thus guarantees optimum particle size distribution. By using different conical sieve inserts (perforated sieve and friction sieve), both dry and moist products can be processed at a speed of 150 to 1,500 rpm (revolutions per minute). Product capacities of two to three tonnes can be achieved within an hour.
Convenient operation is via a 7" (Sieving) touch panel, which enables user and recipe management as well as PDF batch print management and has a USB interface. The explosion-proof version of the Turbo Sieving can also be used in accordance with ATEX directives.
Cleaning the sieving unit manually is very easy thanks to the easy-to-clean design. The sieve container can be easily removed using the combination of bayonet lock and clamping ring.
The individual components are therefore easy to clean. As an option, the screen housing can be equipped with cleaning nozzles for simplified WIP cleaning, which quickly remove material residues from the inside of the screen container. Cleaning nozzles on the side of the screen insert and underneath the bevel gear are included in the scope of delivery and are supplied with cleaning medium via a central water connection.
Hammer Mills
Hammer mills or turbo mills are suitable for Research & Development as well as for batch production or continuous manufacturing. They crush powders, agglomerates and granulates. Hammer Mills are used particularly frequently when the user requires precise particle reduction of Active Pharmaceutical Ingredients (API) and other substances that are difficult to grind. Hammer Mills are also used to regrind broken tablets.
Tablets that have already been produced may not meet the customer's requirements during inspection for various reasons. Criteria for this are, for example, incorrect hardness, optical defects or a deviating weight. If the tablet does not meet the specification, the manufacturer can grind the tablets back into powder using the Hammer Mill and reuse the material. Grinding the tablets again and returning them to production ultimately reduces waste and increases productivity.
Hammer Mills, such as the BTM series (Bohle Turbo Mill) from L.B. Bohle, can produce up to 1,500 kg/h at speeds of 600 rpm to 6,000 rpm. To achieve this, the BTM is equipped with an automatic dosing device (rotary valve). This allows the operator to feed the grinding chamber with material evenly and without overfilling. In addition, such automatic feeding devices can control the flow of powder into the grinding chamber. Further advantages: Heat generation is reduced and the process can be repeated with the same parameters.
The rotor inside has two sides with different functions that support applications with moist or dry products. The so-called knife side crushes sticky products. The hammer side is used for Grinding hard, crystalline products.
With the Hammer Mill, the Particle Size is determined by the sieve size selected for the mill. In the BTM, the material size can be reduced down to 0.1 mm by using different sieve inserts.
An application example
In the past, cell culture developers used ball mills to reduce the Particle Size of initial mixtures. The ball milling process is time consuming and relies on ceramic balls in a tumbling vessel to grind the products into powder.
After Grinding a batch, the mill and hundreds of ceramic balls inside need to be cleaned. The cleaning process can take up to a week. During this time, the machine cannot be used and is not available if, for example, a customer requests a customised, fast powder batch.
A manufacturer of such cell cultures was looking for a mill that would enable it to fulfil the requirements of its biopharmaceutical customers more flexibly and efficiently. The grinder also needed to take up less space and be mobile. The device needed to be able to be removed from the original production room for cleaning to free up space for further production steps.
The customer also specified product-specific requirements for the mill in terms of temperature, particle and batch size. Cell cultures require a fine Particle Size for perfect dissolution rates. Up to 50 per cent of the batch must be smaller than 100 micrometres. In addition, the medium is very susceptible to temperatures above 37°C, as the powder loses its bioactivity at these temperatures.
After sounding out the market, the manufacturer turned to L.B. Bohle to carry out grinding trials. Using the BTM 150 turbo mill, L.B. Bohle achieved the desired product size at a Throughput of 375 kg/h in a closed container-to-container grinding setup (inline process). For the test, the Bohle experts selected a rotor speed of 6000 rpm with the hammer side of the rotor.
After a production cycle of 30 kg, a heat of approx. 30° C was measured. The grinding chamber was fitted with a cooling jacket in order to better control the temperature, dissipate the heat generated and thus fulfil the manufacturer's specifications. In order to prevent condensation in the grinding chamber caused by the cooling, nitrogen is introduced into the grinding chamber and also discharged again via filters.
In addition, a 1-millimetre sieve insert was used in the turbo mill to ensure an identical Particle Size as in the ball mill.
The precise results with the BTM convinced the manufacturer. He first ordered a Hammer Mill and later two more. After installing the mills, the manufacturer significantly increased processing efficiency. Several batches (e.g. 1000 kg batches) can now be ground in a week instead of just one or two batches (with the conventional ball milling method) because the BTM can be dismantled and cleaned very quickly with virtually no tools.
20. Februar 2019
