What good is reliable filtration of respirable, harmful or toxic dust and suspended matter if contamination risks arise for operators and the environment as soon as the dust is disposed of or the filter media replaced? The engineers at Infastaub asked themselves this question and came up with the Infa-Micron MPR self-cleaning cartridge filter for suspended matter.
The author: Jens Kampmeyer Head of Sales, Infastaub
Many industrial production processes demand high standards for the filtration of toxic dusts or powders containing active pharmaceutical ingredients (API). The list of dusts to be separated is long and ranges from explosive, toxic and carcinogenic solids through metals to pharmaceutical substances. Interest is growing not only in low-dust production but also in disposal technologies – especially if the substances involved are highly active. Aiming to meet the requirements of these production processes for dust removal efficiency, functionality and operational reliability, Infastaub developed an entire series for the filtration of respirable, harmful or toxic dusts and suspended matter. The result – the Infa-Micron MPR – is a self-cleaning cartridge filter for challenging processes.
The modularly expandable MPR is designed as a single-stage or two-stage filter system. The number of modules (filter chambers) required depends on the volume flow to be handled. The two-stage design achieves a residual dust content of <1 mg/m³ from raw gas dust concentrations of up to 10 g/m³. As the dust layer builds up, the filter cartridges in the first stage are cleaned regularly with a jet pulse and simultaneously regenerated. The pulse causes secondary air to be sucked into the cartridge while the patented Coanda annular-gap injector converts the air pressure energy optimally into flow energy inside the cartridges. The cleaning system of the Infa-Micron MPR cartridge filter is thus more efficient than the constant air-flow cleaning principle of conventional cassette filter systems. Good cleaning results with permanently low differential pres-sure are guaranteed even with very sticky dusts.
The contaminated raw gas flows via an exterior distribution duct into the filter and over the horizontally arranged cartridges. Owing to the optimised air flow inside the filter, the dust is uniformly distributed across all filter elements. A small, constant pressure drop is produced.
Cleaning and dust sedimentation into the discharge hopper are supported by the successive offline cleaning of each filter chamber. Whenever one chamber is in cleaning mode, the others take care of filtering the volume flow. A second, optional filter stage serves as a safety or policing filter and is not cleaned. If the saturation limit of the filter cartridge is reached due to the high dust load, it is replaced with a new one.
Dust removal with less contamination
In response to demands to eliminate contamination, both dust disposal and the replacement of the filter media are carried out with the help of the so-called safe change system. The cartridges are clamped in the filter case with compressed air while they are being inserted into the filter. Their bottom also forms the seal between the filter inside and outside. When a cartridge is replaced, it is removed without touching the interior of the filter. This is achieved with the help of the ‘safe change collar‘ mounted around the bottom of the cartridge on the outside of the filter casing. A plastic bag on this collar is pulled up tightly and the cartridges or the separated dust then emptied into it directly from the filter housing. All contact between the operator and contaminated materials inside the filter is effectively prevented. If multiple filter chamber units are used, the filter cartridges and dust bins can be changed without interrupting filtration.
The MPR system is optimally accessible for maintenance due to its exterior electrical system and pneumatic components; there are no mechanical wearing parts in the raw gas area of the filter. In addition to an intrinsically safe version consisting of antistatic filter media with all components completely earthed, the filter can also be supplied as an Atex compliant unit. The dust-tight standard design comprised of screwed sheets is rated for pressures of +/-50 mbar g. Reinforced versions up to +/-200 mbar g, gas-tight welded filter housings (for use with nitrogen or other gases) and pressure shock resistant designs (max. 1 bar g) are likewise possible as are filters with an explosion suppression system, mobile versions for laboratories and variants with stainless steel cladding to meet GMP requirements.
Infa-Micron MPR cartridge filters are delivered ready to use. They include an electronic control which analyses the operating parameters and cleans the filter cartridges with a jet pulse on demand. Various accessories round off the basic system and enable operation to be largely automated.
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