The Separation Research Of Acid-Insolude In Nitrophosphate

There are many impurities in the phosphate used in the production of nitric phosphate, which appear from forming or mining, and most of impurities do not dissolve in nitric acid to become acid-insoluble in the acid hydrolyzate. In China the separation of acid-insoluble in nitrate phosphate fertilizer production is more serious and prominent. Because even though China’s phosphate reserves are very rich, but the high-grade ore has a very small proportion and the vast majority is low-grade phosphate rock. The content of P2O5is low content but more impurities, but the content of acid-insoluble is as high as12%to14%. The acid-insoluble will arrive the each operation unit of the production process with following the materials, which comes from the decomposition solution got in process of decomposing phosphate ore with nitric acid, and have a very adverse effect on the equipment and products’quality. The transformation measures of acid-insoluble separation system in nitro phosphate production is mostly limited to the design of equipment structure, which have done by domestic and foreign research institutions and production units and almost are sedimentation separation and centrifugal sedimentation, etc. Although these methods have reduced the adverse effect of acid-insoluble in the production, they have not yet reached the desired effect and only achieve the separation rate of20%, which is far from the satisfactory result.By reading domestic and foreign literature and combining with the actual situation, we consider the flocculation method for the separation of acid-insoluble research. In the water treatment industry, the most widely used method is flocculation fettling, which is an economical, convenient, high treatment efficiency water treatment technology. The flocculant is a kind of substances, which makes suspended particles or colloid agglomerate together in the solution to form a visible flocculent precipitate. Flocculants can act on the surface electric charge of suspended particles or colloid in the water and make it lost the stability. Small colloids and dispersed particles will collide with each other to form flocs in water under the action of molecular forces, and as the dimensions and mass becomes larger, a large number of visible precipitate is formed under the action of gravity. The existing state of the smaller particle size of acid insoluble in acid hydrolyzate is the same as impurities in the wastewater, and colloid and suspended particles are the main components. So using chemical flocculation to separate the acid-insoluble in nitrophosphate process can achieve the desired results.The flocculant has a wide variety and the factors affecting the flocculation sedimentation effects are very diverse. Therefore, the main contents of this paper are based on the principle of chemical flocculation, and using various organic and inorganic flocculant for separation test to screen effective flocculant, then studying and improving effective flocculant to calculate the optimum amount of effective flocculant. There are three steps of experimental section, as follows the flocculant sea election experiment, the flocculant excellent selection test and the experiments of the optimum amount of flocculant. After the experimental screening and modification,7#,8#,9#and13flocculant have better separation effect, specifically7#and8#flocculant’ removal rate of acid-insoluble are more than90%. The further experiment shows that9#flocculants and13#flocculant still need more modification to meet the production requirements. The optimum amounts of8flocculant in200mL acid hydrolyzate at60℃is that the optimum addition amount is2mL and best preparation concentration is0.5%, and the optimum amounts of7#flocculants in200mL acid hydrolyzate at60℃is that the optimum addition amount is lOmL and best preparation concentration is0.1%. Based on good chemical flocculation sedimentation effect, the preliminary design is using the spiral centrifuge to improve acid-insoluble separation system, in order to reach the better actual separation effect.