Choosing The Optimal Filter Media for Dust Collector Bags

Selection criteria when choosing the optimal filter media for dust collector bags

Selection Criteria

Gas and Temperature
Dust Separation Procedure
Dust

All other criteria for the choice of the optimal filter medium must meet or exceed minimum emission control standards and service life.

Selection Criteria Gas and Temperature

The chemical and physical properties of the fibres have an essential influence on the efficiency and service life of the filter medium. Chemical, thermal and physical effects can impact the different kinds of fibres in many various ways. Knowing the fibre characteristics, we are able to provide optimal solutions with regard to efficiency and process conditions. The table below will be of assistance for fibre selection.

When operating a filter plant, the temperature must always be above the dew point. If the temperature drops below this limit, the water will condense and form droplets on the filter medium. Besides this, with existing corrosive gases, the development of aggressive acids is possible. Moreover, cleaning effectiveness will be reduced by the formation of a wet, sticky dust layer. As a direct consequence pressure drop problems may occur. If acids form, chemical degradation of the filter medium, supporting cage and dust collector will take place.

At Sefar we offer exclusively BWF needlona® felts that provide • Longer service life • Lower emission levels • Lower operating costs • Fewer bag changes • = Cost savings

Resistance of synthetic fibres to the influence of chemicals and temperature

Scrim & Fibre Types	Continuous operating temp °C	Max *operating temp°C	BWF Type	Resistance to Hydrolosyis	Resistance to Acids	Resistance to Alkalis**	Resistance to Oxidation
Polypropylene	90	95	PP	Excellent	Excellent	Excellent	Restricted
Polyamide	110	115	PA	Restricted	Restricted	Good	Restricted
Polyester	150	150	PE	Restricted	Good	Restricted	Good
Polyphenylene sulphide	190	200	PPS	Excellent	Excellent	Excellent	Restricted
M-Aramide	200	220	NO, NX	Restricted	Restricted	Restricted	Good
Polytretrafluourtheylene	250	280	PTFE, TFL	Excellent	Excellent	Excellent	Excellent

* Chemical gas stream conditions may require a lower continuous operating temperature to be maintained
** Especially in case of operation below the dew point and harmful impact of aerosols

Selection Criteria Dust Separation Procedure

Different dust separation procedures require different weights and air permeability values for filter media.

The Rule: The more effective the cleaning process, the more compact and heavier the filter medium can be.

Dust Separation Procedure

Dust Separation Procedure	Felt Weight g/m2	Air permeability l/dm2 min @ 200 Pa
Intermittent Shaking	300 – 350	400 – 600
Shaking and Reverse Air	350 – 450	250 – 400
Low-Pressure cleaning	400 – 500	150 – 350
Jet Pulse	500 – 650	50 – 150

Selection Criteria Dust

Besides the necessary knowledge about the dust source and the process conditions, the following criteria are of decisive importance for recommending the appropriate surface of the filter media:

1. Dust Concentration (Dust proportion in raw gas)
2. Dust Composition (Particle size, the chemical composition of the dust
3. Dust Characteristics (Electrostatic properties, a tendency to agglomerate, hygroscopic properties, settling rate, abrasiveness, bulk density

Typical dust properties with the appropriate surface finishes

Codes	Code 1	Code 4 Glaze	CS 17	CS 30/31	MPS	EPI as Excharge	PM-TEC	Food-Tec
Dust properties	Singed face side	Calendered face side	Full bath oil and water repellent finish	Full bath PTFE treatment	Micro pores by fine fibres	Permanent conductive matrix resistance	with ePTFE membrane	FDA compliant
Free Flowing	⊕
Agglomerating		⊕
Extremely Fine					⊕		⊕
Abrasive	⊕
Humid			⊕
Sticky		⊕	⊕	⊕
Electrostatic chargeability						⊕
Occasional spark flow
In contact with Food material								⊕

Please note that a combination of filter media and surface finishes are available – please contact one of our qualified and trained sales specialists for any assistance required!