Hot Gas Filtration with DuPont™ Nomex® Spunlaced Filters

Glass manufacturing companies which release lead-containing dust particles have been faced with new, tighter emission legislation. In 2007, EU standards for these and other industries changed, requiring emissions of dust containing lead (Pb) to be limited to a maximum of 1mg / Nm3 compared to < 5mg / Nm3 before.

To filter dust particles out of very hot gases, many companies needed to switch from historically scrim supported needle-felt filter media made of a standard Nomex® fibre to an alternative solution.

Improved Nomex® spunlaced filters
In 2008, one of these glass manufacturers decided to use the new Nomex® spunlaced structure with a glass scrim instead of the traditional Nomex® one.

The new filter medium has good temperature resistance to gases at continuous temperatures of up to 200°C and can withstand peaks of 240°C. After almost three years in use, dust particle emissions were recorded between 10-20mg / Nm3, down from approximately 30mg / Nm3, and lead-containing dust particle emissions were at an average of 0.3mg / Nm3, well below the required level of < 1mg / Nm3, compared to previously 3mg or more.

The new processing technology, which allows DuPont to make Nomex® spunlaced structures, helps improve filtration performance because the resulting filter media structure is homogeneous, tightly laced, and the pore size is very regular and fine.

Lighter and longer-lasting
As this new filter medium is also about 20 per cent lighter than its predecessor, it has the further benefit of contributing to reduced operating costs.

Another advantage is that the support fabric inside the spunlaced fibre structure can be made using an inorganic scrim such as glass, which helps render the filter media stronger and ensures greater dimensional stability.

Filtration bags made of Nomex® spunlaced can be expected to last longer than the needle-felt of Nomex®.

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