Study On Purification Of Products Reclaimed From Sludge Phosphorus

As the energy supplying of every country have been intense in recent years. With the increase in electricity price and the continuous strengthen in the requirement of environmental protection, the scale and output of abroad yellow phosphorus have been decreased and the center of phosphorus chemical industry has began to shift to China. The reserves of phosphate rock in Yunnan Province ranks first in the country and it's the major producing areas of yellow phosphorus in our country and the word. The phosphorous chemical industry is one of the pillar of the economy in Yunnan province, and the yellow phosphorous as the main export products is the key raw material of the chemical industry. However, it produces residual substances-phosphorus sludge in the process for yellow phosphorous production. As the phosphorus sludge has large production capacity and its pollution is relatively serious, it becomes the primary goal of enviroment governnance at present. Now from the perspctive of sustainable development, using phosphorus sludge with alkali liquor to get sodium hypophosphite is an effective utilization way. And sodium hypophosphite as a reducing agent, which is widely used in galvanization, machinery, food processing, and has the very high economical value. Using this method is not only may enhance the returns-ratio of phosphorus, but also reduce the environment pollution.In this thesis, sodium hypophosphite liquor from phosphorus sludge with alkali solution was the object of study. The method of aeration+lime-iron was adopted to eliminate arsenic and florine in sodium hypophosphite, and the method of crystal+distillation-recrystal by ethanol was adopted to seperate sodium phosphite from sodium hypophosphite solution, so as to improve the purity of sodium hypophosphite and get the requirement of comprehensive utilization sludge phosphorus.The main research includes six aspects. Firstly, a feasiable and effective method was chosen, in order to arsenic as well as flouride all can be removed efficiently. Secondly, the amount of calcium hydroxide, the dosage of ferrous sulfate dosage, initial arsenic time and so on factors on arsenic and flouride removal rate were researched, in order to get the suitable experimental conditions by singal factor experiments. Thirdly, in terms of the content and property of sodium phosphite in sodium hypophosphite from phosphorus sludge, the enviromentally friendly and economically feasible method was chosen to futher enhance the recovery of phosphorus in phosphorus sludge availability. Forthly, the concentration of ethanol, the dosage of ethanol, the temperature of solventing, and ect on the purity of sodium phosphite and sodium hypophosphite were investigated, and the optimal experimental conditions were initially determined. Fifthly, four factors and three levels orthogonal experimental was designed according to the results of singal factor experiments, and verify the optimum experimental conditions. Sixthly, the mechanisms of the process of impurity and desperation were analysed.The suitable conditions while removing impurity were determined. When the dosage of calcium hydroxide was 1.6g, the ferrous sulfate was 0.7g, the time of first and secend aeration was 6h,12h respectively, the pH value was 8.6, the time of vibration was 40min,the standing time was 60min, the result showed that arenic and flouride removal rates can get 81.37%,96.12%respectively, the result also showed that the content of arsenic and fluorine droped 0.36%and 0.0008%in sodium phosphite solution.The suitable conditions of seperation experiment were determined. Under the conditons of the concentration of ethanol in 90%, the dosage of ethanol in 50mL, pH at 7.65, the solution temperaturen at 45℃, the crystallization temperature at 65℃, the recrystallization temperature at 70℃, the purities of sodium hypophosphite and sodium phosphite were better. After impurity and seperation, the purity of sodium hypophosphite and sodium phosphite could get to 98.77%,99.19%respectivly.Under the suitable conditions, arsenic and fluorine all were measured to less than 0.001%, the content of sodium hypophosphite was close to the level of technical grade (99%), and the content of sodium phosphite had reach 99.19%after impurity and desperation treatment. Moreover, the mechanisms of separation and impurity processes were analysed, and reaction equationreaction equation and reaction equationreaction impetus were deduced on the base of experimental conditions.