The energy used by the fan accounts for 60 - 80% of the baghouse operation costs and therefore, a stable and low differential pressure makes it worth considering investing in highly developed filter bag materials. This will have be done anyway, when production is restricted due to limited airflow through the filter. Maintenance costs must also be considered a cut back by 50% is achievable, not taking into account the possibility of reduced kiln downtime.
The current economic situation of the cement industry creates sensitivity regarding off-times and process stability. More stringent air-pollution laws, especially when using waste-derived fuels, are drawing more attention to the off-gas cleaning facilities, usually bag filters. This article does not deal with electrostatic precipitators - as even they have well known disadvantages. By using more sophisticated felts at a comparably low differential pressure, even in tougher operating conditions, bag life can be doubled. This usually justifies the higher price. Fine fibres and trilobal shaped cross-sections are, meanwhile, a common approach to produce felts with finer pores and a higher fibre surface. Furthermore, the blending of different materials appears to influence the filtration behaviour by changing the distribution of static charges.