Abstract: In order to concentrate the diluted sulfuric acid from the titanium dioxide (TiO₂) production of sulphate process, a new concentration process was proposed by coupling chemical dehydration and multi-effect evaporation. The ferrous sulfate monohydrate (FeSO₄·H₂O), as the dehydrant, was added to the diluted sulfuric acid to form ferrous sulfate heptahydrate (FeSO₄·7H₂O) according to the H₂SO₄-FeSO₄-H₂O phase diagrams, which partially removes the water. This process was named as Chemical Dehydration Process. The residual water was further removed by two-effect evaporation and finally 70 wt% sulfuric acid was obtained. The FeSO₄·H₂O can be regenerated through drying and dehydration of FeSO₄·7H₂O. The results show that FeSO₄·H₂O is the most suitable dehydrant, the optimal reaction time of chemical dehydration process is 30 min, and low temperature is favorable for the dehydration reaction. 45.17% of the entire removed water can be removed by chemical dehydration from the diluted sulfuric acid. This chemical dehydration process is also energy efficient with 24.76% saving compared with the direct evaporation process. Furthermore, 51.21% of the FeSO₄ dissolved originally in the diluted sulfuric acid are precipitated out during the chemical dehydration, which greatly reduces the solid precipitation and effectively alleviates the scaling in the subsequent multi-effect evaporation process.

Key words: Chemical dehydration, Multi-effect evaporation, Sulfuric acid, Titanium

摘要： In order to concentrate the diluted sulfuric acid from the titanium dioxide (TiO₂) production of sulphate process, a new concentration process was proposed by coupling chemical dehydration and multi-effect evaporation. The ferrous sulfate monohydrate (FeSO₄·H₂O), as the dehydrant, was added to the diluted sulfuric acid to form ferrous sulfate heptahydrate (FeSO₄·7H₂O) according to the H₂SO₄-FeSO₄-H₂O phase diagrams, which partially removes the water. This process was named as Chemical Dehydration Process. The residual water was further removed by two-effect evaporation and finally 70 wt% sulfuric acid was obtained. The FeSO₄·H₂O can be regenerated through drying and dehydration of FeSO₄·7H₂O. The results show that FeSO₄·H₂O is the most suitable dehydrant, the optimal reaction time of chemical dehydration process is 30 min, and low temperature is favorable for the dehydration reaction. 45.17% of the entire removed water can be removed by chemical dehydration from the diluted sulfuric acid. This chemical dehydration process is also energy efficient with 24.76% saving compared with the direct evaporation process. Furthermore, 51.21% of the FeSO₄ dissolved originally in the diluted sulfuric acid are precipitated out during the chemical dehydration, which greatly reduces the solid precipitation and effectively alleviates the scaling in the subsequent multi-effect evaporation process.

关键词: Chemical dehydration, Multi-effect evaporation, Sulfuric acid, Titanium