Cloth

Filter media are available either in form of woven fabric or felt fabrics. The structure of these two filter media is shown as follows:

The characteristics of woven fabric are its system of warp and weft threads crossing one to another. Needle felts are “three-dimensional” filter media.

Most used filter media in the cement industry are needle felts due to a lower pressure drop and higher dust collection efficiencies compared to the woven fabric.

Selection criteria

The filter medium is the all-important central feature of any dust collector operating on the filtration principle. With the correct or incorrect choice of the filter material, the whole dust collection operation will stand or fall in actual practice.

Important selection criteria are:

• filter type, particularly cleaning principle

• moisture level

• gas temperature (average and peaks)

• composition and chemical properties of the gas

• raw gas dust load, particle size

• particulate abrasiveness

• allowed dust load in the clean gas

• physical and chemical properties of the dust

Furthermore, the filter medium must satisfy the following conditions:

• high air permeability (low pressure losses)

• good mechanical strength

• good thermal stability at operational temperature

• good dimensional stability at operational temperature