Improvement on the Operation Management System of Vertical Pressure Filters

Polishing filtration is one of the most crucial step of the Bayer process present in alumina refineries. In Hydro Alunorte, five of the seven production lines use Vertical Pressure Filters (VPF) in the polishing filtration and an excessive consumption of filter cloth was observed. The aim of this paper is present the improvements in the VPF operation management system. The actions were done on the process parameters in order to gain durability of filter cloths used in VPF filters. Process control variables, such as solids in the filtered pregnant liquor, filtration rate and VPF pressure were evaluated and become the limiters for programming the filters operation cycles. An automatic preparation control of the caustic wash solution, used to wash filter cloth at the end of filtration cycle, was also done. The useful life of filter cloth increased by 25% and it means about 12% of reduce in operation costs.