Switzerland’s BUSS, which supplies customised process technologies for the chemical and aluminium industries, recently delivered a full process solution for a project involving the conversion of fluorosilicic acid into silicon dioxide and valuable hydrofluoric acid.
BUSS used filtration technology from BHS-Sonthofen for the conversion process.
BHS-Sonthofen provided the indexing belt filter of type BF 300, a continuously operating, horizontal vacuum filter. Due to the highly corrosive nature of the acid, BHS-Sonthofen used acid-resistant metallic materials and special plastics, in particular for the vacuum tray and the feeding equipment.
“With a size of 4.5 x 23.5 m and 58.5 m2 of active filter surface, the filters hold an above-average volume,” explains Simone Ahlert, project manager at BHS-Sonthofen.
At the beginning of the conversion process, the toxic tetrafluorosilane is dissolved in water and initially reacts to form fluorosilicic acid and silicon dioxide. The silicon dioxide is precipitated in the reactor and then filtered off in the BHS filter. During this process step, a three-stage counter-current washing system ensures high quality and maximum yield. The now pure fluorosilicic acid serves as the base material for the final product requested from the customer - the hydrofluoric acid. The filter cake on the belt can be further treated in separate processes.
The plant went into operation at the end of 2021.