Electronic Grade Hydrofluoric Acid
The process description refers to the Process Block Diagram as shown below.
1. Plant Sections
The Plant consists of the following sections:
- AHF Oxidation and Reduction Reactions
- HF Distillation
- EG AHF Dilution
- EGHF Filtration
- EGHF Filling Station
- Ultra-Pure Water Generation
2. Batch Part of the Plant
2.1 Purification: Reaction
Raw AHF is filled into the reactor in the purification section.
The oxidation agent solution is prepared batch-wise by mixing ultra-pure water with the solid oxidation agent. This solution is then pumped into the reactor and mixed thoroughly with the HF.
Excess oxidation agent is destroyed using a reduction agent solution.
3. Continuous Part of the Plant
3.1 Purification: Distillation
The treated batch of HF is pumped to the distillation column.
The purified HF is collected at the top and is discharged to the Product Analysis Tank.
The sump liquid is collected with the reaction residues essentially dissolved in the solution (raw AHF has low levels of arsenic) and discharged intermittently to the aqueous HF section.
UP AHF will be analysed. If the quality is according to the specification, the UP AHF is pumped to the dilution section.
UP AHF is mixed with ultra-pure water and the mixture is cooled down. The concentration of the acid is kept constant by adjusting the UP water. The HF with a concentration of 49%-wt is fed continuously to the filtration unit and stored in the HF Day Tank, where a sample is taken for quality control (OSBL).
The waste water, including the dilute HF from the distillation column, will be pumped to the waste water treatment (OSBL).
The off-gases will flow to a wet scrubber (OSBL).
3.3 Ultra-Pure Water Generation
The UP water is used to dissolve the oxidation agent and for the dilution of the UP AHF. UP water is also used for cleaning purposes. It is prepared with raw water directly within the module.