Three indexing belt filters for the production of hydrofluoric acid

May 16, 2022
BHS-Sonthofen Process Technology has supplied three larger than average indexing belt filters for the production of hydrofluoric acid. The key requirement for the design of the belt filters was particularly high chemical resistance given the strong acidic product attributes of the source material. BHS employed acid-resistant metallic materials and special plastics which offer maximum safety combined with high product quality. The plant has been in operation since the end of 2021.

BUSS-ChemTech in Pratteln, Switzerland, is internationally known as a supplier of customized and innovative process technologies for the chemical and aluminum industries. The company supports customers worldwide with its holistic solutions for chemical reaction processes, for example in the production of halogen-containing basic chemicals such as hydrofluoric acid, aluminum fluoride, phosgene, and their by-products.
Recently, BUSS delivered the full process solution and the appropriate key-equipment for a project involving the production of hydrofluoric acid. In this case, a new, more environmentally friendly technology was used that converts fluorosilicic acid into silicon dioxide and valuable hydrofluoric acid. The latter can be further processed for profit, thus eliminating the need for costly neutralization and disposal.

Indexing belt filter enables maximum yield
To get this innovative project moving, BUSS relies on filtration technology from BHS. For the conversion process, the BHS experts provided the indexing belt filter of type BF 300, a continuously operating, horizontal vacuum filter. “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, the responsible project manager at BHS. Due to the highly corrosive nature of the acid, BHS used particularly acid-resistant metallic materials and special plastics during construction – for instance, for the vacuum tray and the feeding equipment.

Three-stage counter-current washing ensures high product quality
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 carefully and safely filtered off in the BHS filter subsequently. 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.

Efficient filtration technology is crucial for this new type of process, and the solution from BHS-Sonthofen has convinced BUSS. The plant went into operation at the end of 2021.