Bag house filters in the pharmaceutical industry

In the pharmaceutical industry, dosing, granulating, agglomerating, coating and mixing often release a lot of dust. In order to protect personnel, these types of contaminants are often removed with source extraction or extraction of air around certain processes. Air Solutions Holland uses bag house filters to clean these air streams that are used for extraction. A compressed air cleaned bag house filter is a very efficient dry filter system to purify air from suspended solids. A bag house filter has no problem with moist air or hygroscopic and sticky contaminants. The trick here is to realize a large filter surface. Partly thanks to the micro-perforated textile (possibly coated with Teflon) and the shape of the cylindrical bags, the harmful substances in the bag house filter are captured. The bags are supported by metal cages, which are attached to the filter housing and can be exchanged on the clean side at the top of the filter. The design of the installation (round or rectangular) allows the treatment of a wide range of pollutants and air volumes.

The aerodynamic filter inlet consists of a pre-chamber, which reduces the air velocity by widening and thus minimizes bag wear. A series of plates ensures that the larger coarse dust particles are separated immediately. Depending on the degree of contamination and particle size, a cyclone can also be used as a pre-separator. The air flow is distributed over the entire filter element surface and crosses it from outside to inside. The dust deposited on the external surface of the filter elements produces a uniform layer of dust that improves filtration efficiency. Once filtered and cleaned, the air is transported to the filter outlet. In order to achieve extra low dust emissions, the bag house filter can be additionally equipped with a HEPA (H13) absolute filter. A bag house filter in the pharmaceutical industry is therefore assembled and configured according to customer specific requirements.

The pressure drop will gradually increase due to the contamination, a sensor measures the differential pressure over the filter elements and controls the filter cleaning system. This periodic cleaning of the filter elements is done by a strong compressed air pulse, this way the differential pressure stays within the selected limits. This compressed air pulse cleaning system blows the bags clean from the inside out. As a result, less compressed air is consumed and the bags will last longer.

The dust is released from the filter element surface and falls by gravity to the bottom of the filter hopper where it is collected in a bin. This collection barrel has to be emptied periodically. Depending on the application, the hopper at the bottom of the filter is equipped with a rotating sluice to continuously discharge the powder and collect it, for example, in a big-bag. It is also possible to use a conveyor screw to continuously discharge the dust to a container.