Fastway Inc.
Providing Environmental and Air Pollution Control Services since 1968



Precoating the bags in your baghouse has been proven to increase bag life and air volume, and decrease differential pressure and costs.  Fastway is able to supply your company with either the product or the service of applying the precoat.  Click Here for a free quote on our Fas-Kote or services.

Powder Precoating and Continuous Injection Field Test


S.Y. Gong, K.S. Hwang, and M.H. Lee- 1996




Powder precoating and continuous injection technology is useful for fabric filter systems which have problems such as high filtering resistance or particulate bleedthrough.  When new bags go into a filtration system, they draw more air flow than bags with an existing dustcake in place because the fabric's air passages are not clogged with particulate.  Consequently, the particulate being filtered actually accelerates as it is drawn into the filter bag surface.  This can lead to the bags blinding early as the particulate builds up around the air passages before a protective dustcake is formed on the surface of the fabric.  When powder is injected into the gas stream before the new bags are brought into service, it forms a "protective layer" over the filtration surface of the fabric.  The main function of the powder is to protect interstices of the new fabric by forming a porous, nonrestrictive structure that prevents dust from depth blocking. 


Proper Powder Materials


There are some acceptable precoat materials such as diatomaceous earth, various forms of alluminum silicate solid, PC flyash, and crushed limestone.  Preferential properties of the powder as a precoat material are low density, non-hygroscopic, non-reactive, irregular shaped particles greater than 5 um to form a protective, high porosity dustcake.  Calcium oxide and ash with spherical, nonagglomerating properties are not suitable.


Conclusion of Test


The effectiveness of powder precoating and continuous injection was investigated by the laboratory and field tests.  In the laboratory test, differential pressure was reduced up to 50% by powder precoating and continuous injection.  Optimum amount of continuous injection was 1-3% of dust concentration.  Field test results show that differential pressure was reduced more than 50% and air volume increased about 20%.  But precoating was more important than continuous injection of powder.  It is expected that bag life will increase and operating costs will be reduced by 30%.