| The method of producing dibasic calcium phosphate by hydrochloric acid has many advantages. The application prospect is wide because of its high phosphorus recovery rate, fitting for low grade phosphate rock, limited requirements for ore’s purity and low energy consumption etc.In the process of extraction, phosphate rock was decomposed by hydrochloric acid(concentration is about 21%). Extraction was affected by several factors such as reaction temperature, reaction time and the ratio of hydrochloric acid adding into the phosphate ore. The results indicated that the extraction rate could reach to 99.02% when dosage of hydrochloric acid was 1.05 times to the amount of the theory at 35℃ while reaction for 0.5 hours.In our country, the fluorine content is high in phosphate rock, but national standard requires that F-content should be lower than 0.18%, thus deflourination is the key point in this experiment. Sodium chloride, potassium chloride, sodium carbonate, calcium hydroxide and calcium carbonate were selected as the defluorinate agents. The results indicated that the calcium hydroxide was the best defluorinate agent.Eventually, the process of circulating extraction without any defluorinating agents was designed. The results indicated that the extraction rate could reach to 95% when the ratio of liquid and solid was 2.15:1. The deflourination process was eliminated and the consumption of raw materials was reduced in this process.In the crystallization process, lime milk and calcium carbonate were selected as neutralizing agents. The results showed that the bigger and more uniform crystallization particles can be got via two-step neutralization.The carbonization agent was added into waste solution to prepare calcium carbonate and ammonium chloride. Qualified products were obtained by controlling the reaction conditions. |
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