The Treatment Of Waste Water Containing Fluoride And Ammonia Nitrogen In Tantalum And Niobium Smelting

Fluorine-containing waste water mainly comes from fluorine ore exploration and processing, metal smelting, aluminum electrolyzing, charcoal, glass, electroplating, fertilizer, pesticide and chemical industry, etc. The high concentration of fluorine usually causes pollution to the environment. Fluorine pollution is inviting more and more attention from the public. The investigation on the treatment technology of fluorine containing waste water has always been the major topic of the environmental protection filed at home and abroad. Ammonia and nitrogen containing waste water comes from extensive sources including fertilizer, oil refining, inorganic chemical, meat processing, feedstuff production, nonferrous metal smelting, agriculture, animal excretion and daily garbage liquids etc. It is harmful to the natural environment and people's health. In China, ammonia and nitrogen containing waste water treatment remains a problem. Therefore, this study of the treatment technology is of practical significance. The waste water discharged from the tantalum and niobium smelting and processing industry has a high concentration of fluorine, ammonia and nitrogen, and its disposal has been a problem in the industry.Based on his work experience, the author takes charge of carrying out the project of waste water treatment by probing into the treatment technology of fluorine and nitrogen containing waste water in a tantalum and niobium smelting plant in Hunan Province. This paper is focused on a systematic introduction of the approach, principle, technique process, technological parameter, engineering effect, economic analysis, existing problems and improvement measures in the light of the concrete examples of the project. Finally, a "combined treatment process" is proposed to effectively treat the waste water from the tantalum and niobium smelting industry, i.e., calcium carbide residue e-fluorine, blowing de-ammonia and nitrogen and ecological oxidation pond de-ammonia and nitrogen.In this project, the process of fluorine removing should be tried best to make the carbide slag water excessive and pH should be controlled above 11. Mixing reaction time is 30 min, and deposition time is 60 min. During the operation, three-stage reaction method will be adopted, each reaction stage should be controlled more than 10 min, and the whole reaction should be controlled more than 30min. Then it goes to basin radial sedimentation tank and the deposition time is more than 60 min. The pH of blowing de-ammonia and nitrogen process should be 11.0. Wastewater should be heated by steam to 50℃, blow-off gas liquid scale is 3200:1 (air blowing amount is 3380 m³/h), and the blow-off time is 2h.The slave ammonia-separating of the ecological oxidation pond, using local materials of the pollution defending belt of the tantalum and niobium smelting and processing factory which is a natural marsh of more than 90 Mu, utilize the bacterium and alga communal function to deal with the main pollutants for example organic pollutants and abio-ammonia. Heterotrophy bacteria in the pond reduce the organic pollutant in the water into CO₂ and H₂O. Ammonia nitrogen as nutrition for bacterium and algae intergrowth also consume the dissolved oxygen in water. Algae in the pond utilize solar energy to make photosynthesis, and use the carbon from CO₂ to compose itself and release oxygen so that to purify the water.The designed treatment capacity of this project is 350m³/d. In the process of its implementation, the amount of waste water was greatly reduced because of the improvement of the production processes and the actual treatment amount was about 200m³/d. The project expenses were saved and the treatment effect was guaranteed. The project consists of two large treatment systems: the ammonia blown system and the multipurpose treatment system.This waste water treatment project is the first case of complete and systematic treatment of ammonia and nitrogen waste water in the tantalum and niobium smelting industry. The removal proportions of major pollution elements such as fluorine ions, ammonia and nitrogen reach 99.5% and 94.7% respectively after the treatment, bringing about an outstanding effect and prominent environmental benefits. This sets a good example in the tantalum and niobium smelting industry in China.