REDUCING ENVIRONMENTAL FOOTPRINT OF FILTERS IN BAYER PROCESS: TRIALS OF USED BAGS RECYCLING

Parent, L. andTremblay, Y.

Polypropylene filter bags are used in Bayer process for security filtration. The bags service life depends of operational conditions but in all cases they have to be replaced periodically when the targeted filter flow cannot be reached anymore. After use, the polypropylene fabric is covered with a hard scale and must be disposed. Each year, an alumina plant produces many tons of used bags as a waste. In order to reduce the environmental footprint of used bags, recycling attempts have been made. It is necessary to go through some steps before getting a clean polymer able to be re-used. However even if after processing the polymer can be re-used for some applications, it cannot be used to remake new bags. The economics of the different applications shows that recycling is a possible solution only in countries where the cost disposal is high.