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Large Volume Inorganic Chemicals - Ammonia ... - ammk-rks.net

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Chapter 66.4.10 Fluosilicic acid processDescriptionHydrogen fluoride is produced by the decomposition of an aqueous solution of H 2 SiF 6 in thepresence of strong sulphuric acid in a reactor. Products of decomposition are SiF 4 and HF. TheHF leaves the reactor in the sulphuric acid solution and the HF is evaporated and purified toobtain the desired product quality. Next, the SiF 4 gas leaving the reactor is absorbed in theH 2 SiF 6 feed solution to generate additional H 2 SiF 6 and silica. For an overview, see Figure 6.4.Off-gasDiluteH 2 SiF 6Process waterVentscrubbingConcentratedH 2 SO 4SiF 4 gasSiO 2generationSiO 2filtrationH 2SO 4absorptionH 2SO 4absorptionHFpurificationSiF 4generationHFgenerationAnhydrousHFHFstrippingDiluteH 2 SO 4ConcentratedH 2 SiF 6Figure 6.4: Overview of the fluosilicic acid process[25, Davy, 2005]Achieved environmental benefits• recycling of the large scale by-product H 2 SiF 6 instead of natural resource consumption• if carried out on an integrated site with the production of phosphoric acid, the dilute H 2 SO 4can be recycled.280 <strong>Large</strong> <strong>Volume</strong> <strong>Inorganic</strong> <strong>Chemicals</strong> – <strong>Ammonia</strong>, Acids and Fertilisers

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