Solids handling: from powders to granules

Handling solids presents a variety of potential problems, including the need to contain toxic dusts and ensuring efficient transfer from one vessel to another for processing

Many parts of the pharmaceutical manufacturing chain involve handling solids, from dusty powders to granulated ingredients. Problems involved range from containment of toxic or irritants dusts, to preventing clogging.

Swiss manufacturer Anag, whose UK agents are S&B Process, has developed a modular discharge system to provide enhanced product containment while mixers, size reduction equipment and reactor vessels are being loaded. The Dosicon uses a pneumatically-operated cone valve to make the connection between process vessels below sacks, big bags or portable silos.

The cone valve can be adjusted to control product flow during discharge, allowing set feed rates to be applied to powders with different flow characteristics, particularly for applciations such as dosing into mixers. It can be automatically regulated via PC and load cells, on a gain-in-weight or loss-in-weight basis. Discharge can be stopped after a pre-set weight, and the parent container removed or exchanged.

The Dosicon system includes three types of discharge module. The big bag module and the sack/drum discharge module act as intermediate storage, while the Dosicon silo connects directly to the unloading station.

The new range of bag emptying stations from Spiroflow is intended to avoid problems associated with tipping 25kg bags of powders, pellets and other dusty bulk granular materials into process systems. They are fitted with integral dust collection or can be adapted to existing dust collectors. They include removable grate, gas spring assisted access door, removable filter cartridge, reverse pulse air filter cleaning, high capacity fan and bag support shelf. Reverse filter cleaning and optional quick detachable fittings decrease downtime.

quick-clean option

Made from mild or stainless steel and for hygienic use with a quick-clean option, stations include a no-weld perforated steel grate and food grade white neoprene gaskets. Discharge flanges are offered to suit vacuum, flexible screw or aero-mechanical conveyors. The equipment is claimed to be ideal for tipping material from 25kg bags into a process machine hopper, filling blenders, check screeners or feeding mills, and into mixing tanks.

The Charge Point transfer coupling from PSL was designed in collaboration with GlaxoWellcome for the safe transfer of powders and granules with containment down to 10µg/m3. The multifunctional equipment can be used to seed ractors using the company's SeedPoint, and also for CIP operations, including a deep extension option. It can also be used to aid in-process validation.

It is made from Hastelloy C22 or 316L stainless steel with a near-mirror hand-polished finish, and is also available in polypropylene. It has 2, 4 or 8-inch nominal bores, with either EPDN or PTFE seats.

For larger scale solids transfer, Flomat Bagfilla's Model S FIBC filling machine has been designed to improve efficiency. It can fill up to 24 FIBCs/hr with an accuracy of ±0.5kg. Its additional functions include hang weighing, bag stretching and product compaction. Its pallet location guides ensure the filled bags are positioned correctly on the pallets for removal, transportation and storage up to three high.

easier bag rigging

Longer trombone arms have made rigging an empty bag easier. These enable the two rear loop suspension points to slide further forward for ready connection. These are then slid back, leaving the bag ready for filling. The filling head has also been redesigned, and now can tilt forward to ease the installation of the FIBC liner's neck around the head's inflatable seal.

The Allgaier tumbling screen machine, available from Hosokawa Micron, is designed to mimic the three-dimensional sieving action of hand sieving. Part of a range that also includes a vibratory tumble screen, it uses ultrasonic vibrations from a generator, which are converted into mechanical vibrations and transferred to the screen fabric by a resonator ring. This vibration prevents the screen from becoming blocked to ensure the accurate screening of difficult bulk solids. The resonator ring ensures the vibration is uniformly distributed, making the entire screen area into an active ultrasonic screen to provide total screening performance.

Screens are available in sizes from 500mm to 2,600mm in diameter, with multideck units up to five decks for multiple fraction operation. A range of screen cleaning devices can be incorporated which include brush cleaning, air cleaning, combined brush and air, and top screen disagglomerators in various shapes and sizes. The company claims the range provides low power consumption, long screen fabric life and low, constant operating temperature with no localised heating. A special pharmaceutical version is available.

An improved remeshing service has been introduced by Plastok Meshes and Filtration, aimed at companies who need high product throughput from their meshes. The service, available for all makes of sieving equipment, is claimed to offer a cost-effective alternative to buying new meshes. It includes cleaning and preparation of frames prior to them being tension-bonded.

The company also offers a range of ultrasonic equipment that increases throughput by deblinding the screens. These can be retrofitted to existing vibratory machines.

The latest screening sieves from Endecotts are claimed to be ideal for use in pilot plants and other small scale screening applications. The stainless steel sieves have side outlets and can be fitted with a range of interchangeable meshes. Available frame diameters are 300, 315, 350, 400 and 450mm.

instantaneous dispersion

Ytron's ZC3 Powder Disperser is said to instantaneously disperse extremely difficult-to-wet powders, such as carbomers and starches, into a liquid stream. The ZC3 is a larger version of the company's ZC1 disperser. Powders are drawn into the reactor head via a vacuum created by a liquid seal. Complete dispersion of the powders is achieved by the interchangeable rotating and stationary elements providing the precise amount of shear to wet the powders prior to hydration. It is capable of concentrations up to 15% by weight at flow rates up to 100g/min at ambient temperature. It is claimed to eliminate the need for solvents or recirculation to disperse the powders resulting in increased productivity.

Stable measures flow

Stable Micro Systems" ManUmit powder rheometer is designed for accurately measuring the flow properties of dry and cohesive powders, granules and wet mixes. It is intended to help manufacturers avoid problems such as batch and source variation of ingredients, caking during storage and sticking during production and filling. It uses a rotary blade, similar to a boat's propeller, which rotates through the sample. By measuring the force, torque and energy profile necessary to rotate the blade through the sample, the rheometer provides highly sensitive data on the sample's flow properties. To ensure the data accurately mimic real-life applications, it can precondition the sample for testing in an aerated or compact state, and then cause flow by slicing, shearing, compacting or lifting. The user controls the test speed and the angle of the blade path to ensure the flow caused is complementary to the required sample characteristic and the process conditions. Testing can be performed on volumes as low as 10ml. These samples are placed in a stainless steel or boroslilcate sample vessel, and the data are presented graphically, simplifying the comparison of the properties of different samples.