Attention: Mr. Jonn McFarlen, P. Eng.
Reference: White Liquor Pressure Filter Performance – Gore- Tex™ Socks
Dear Mr. McFarlen;
Simpson Tacoma Kraft has been operating pressure filters in its recausticizing plant since 1991, utilizing heavy duty polypropylene filter socks supplied by McFarlen Engineering Ltd. for many of those years. Being pleased with the performance of these socks the mill has been reluctant to use anything else. As the old adage goes, “Why change if things are working well?”
In May, 2004 an operating excursion resulted in the emergency change of half the socks in the white liquor pressure filter. The only filter socks that were immediately available were Gore-Tex™. Your company rushed them to the mill but within a few days, the operators were struggling with the filter. The mill was about to perform an acid wash or water wash but after reviewing the timing sequence, it was decided that the filtration period be reduced. It was surprising to see the operation of the filter improve after only two hours and continue to run extremely well after that.
In the past, acid washing of the filters was necessary every 4-6 weeks but only one acid wash was performed in the summer of 2004. In September, the remaining polypropylene socks in the filter were replaced with Gore-Tex™. The filter ran well with no acid washes until the annual shut down in January of 2005. A full set of Gore-Tex™ was installed with anticipation that a full year of operation could be expected before the next sock change. The filter has now been running well for over nine months without an acid wash. The mill is very pleased with these results. Benefits include steady, uniform production of white liquor and zero acid wash material and labor costs.
I would like to thank you for your assistance with our recausticizing and pressure filter systems.
Randy Sousley, Area Manager