Study on Preparation of Feed Grade Defluorinated Tricalcium Phosphate from Yunnan Phosphate Mine 2
3.4 Discussion of the test results 3.4.1 Different CaO / P 2 O 5 molar ratio of the batching ratio of the test material is the key to the production process of the defluorinated calcium phosphate. It directly affects the quality of the product and the rationality of the technical economy. Choosing the right ratio of ingredients is beneficial to improving product quality and reducing product costs. The ratio of the CaO/P 2 O 5 molar ratio of the material is changed, that is, the amount of phosphoric acid added is changed to adjust the amount of CaO and P 2 O 5 in the ore, so that the reaction proceeds as completely as possible.
From the test results, it is known that the addition of phosphoric acid is beneficial to the defluorination of phosphate rock and the promotion of efficient phosphorus conversion. The general trend is that the phosphorus conversion rate and defluorination rate increase as the amount of phosphoric acid added increases. When the molar ratio of CaO/P 2 O 5 is less than 2.70, the defluorination rate of phosphate rock is >98%, the phosphorus conversion rate is >93%, and the molar ratio of CaO/P 2 O 5 is controlled to 2.50-2. At 60 o'clock, the fluorine content and phosphorus content of the product can meet the requirements of the superior product index of the product quality standard.
3.4.2 Batching test with different AMP dosages Phosphoric acid is added to the phosphate rock to promote the defluorination reaction of the phosphate rock and reduce the sintering temperature of the defluorination reaction, but the amount of phosphoric acid added is not as high as possible. Too much phosphoric acid not only affects the rationality of the ratio of the reaction materials, but also affects the normal reaction, affects the quality of the product, and increases the product cost due to the high acid consumption. Due to the high cost of phosphoric acid, in order to reduce its use, after years of research, a relatively economical and effective defluorination agent AMP has been screened out. The purpose of using the defluorination agent is mainly to improve the defluorination efficiency, shorten the time of the sintering defluorination reaction, and improve the process operating conditions. The results of different AMP dosage tests are shown in Table 5.
Through the test of the addition amount of different defluorination agents AMP, it can be known that the addition of the defluorination agent AMP promotes the defluorination reaction of the phosphate rock, and the effect is very remarkable. When the added AMP is zero, the F content in the product exceeds the standard, and the product is unqualified; when the AMP addition amount is 4% to 8% of the phosphate rock dosage, the defluorination rate is >97%, and the product P and F content can reach the superior product. Indicator requirements. There is also a relationship between the amount of AMP added and the conversion of phosphorus. Too much AMP is used, the material is easy to melt and stick, the phosphorus conversion rate is lowered, and the appearance of the product is gray, making it difficult to meet the quality requirements.
3.4.3 Test of different sintering temperatures The sintering temperature is the key factor in the sintering reaction process of phosphate rock. It directly affects the completeness of the sintering reaction of phosphate rock and the quality of the final product. The determination of the sintering temperature of phosphate rock is an important part of the process evaluation test. index. The test results of different sintering temperatures are shown in Table 6.
It can be seen from the test results that the defluorination rate and the phosphorus conversion rate are greatly increased as the temperature is increased. When the temperature is higher than 1 200 °C, the defluorination rate and phosphorus conversion rate are obviously improved. When the temperature is higher than 1 250 °C, the fluorine content and phosphorus content of the product can reach the requirements of superior products. However, if the temperature is too high, there are also unfavorable factors, the biggest influence on the material melting and sticking, the appearance of the product is red, the product quality is unstable, and the phosphorus conversion rate is decreased.
Many studies tricalcium phosphate conventional sintering method found mostly sintering temperature 1 300 ~ 1 500 ℃, the present process is sintered at 1 250 ℃ superior product can be obtained, showed good activity of Yunnan low thermal decomposition of heavy metals phosphorite The developed process formula is reasonable.
3.4.4 Tests with different reaction times After determining the ratio, the reaction time of the materials is an important factor to promote the complete reaction of the phosphate rock. The test results for different reaction times are as follows.
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