Study On Extraction Of Potassium Chloride And Silver From Sintered Soot In Ironmaking

As the world’s largest steel production country, it has produced a large amount of solid waste of China’s steel industry every year and bring the serious burden to the enterprise and society. Ironmaking and sintering dust ash is one of the major soild waste of iron and steel enterprises. The yield of steel is about 6 billion tons every year in China, and the yield of ironmaking and sintering dust ash is about 800 to 1000 million tons, in which rich potassium sintering dust ash is about 300 million tons. If the content of potassium is 20% in rich potassium sintering dust ash, this is equivalent to 60 million tons potassium chloride produced every year, and it is equivalent to the 10% of total production of potassium chloride in 2014 in China.At present, the potassium chloride are extracted mainly from potassium ore or salt lake and research on producing potassium chloride from ironmaking and sintering dust ash was fewer in domestic. As the same time, it is also contains many other valuable elements after extracting the potassium chloride and can be further extraction and utilization. According to analysis on sintering dust ash of one of steel company in Sandong Ponglai, content of its silver was high except the potassium chloride and had the value of extraction and utilization. In the paper, the extraction technology of the potassium and silver elements were studied with rich potassium sintering dust ash of a company in Penglai of Shandong as raw material. Study of the process of rich potassium sintering dust ash utilization may provide an effective way to achieve the comprehensive utilization of secondary resources and achieve the purpose of green circulation economy.In paper, it was studied that process of lenching ironmaking and sintering dust ash with water and make the alkali metal potassium into the solution in the form of potassium ions. Research showed that the optimal leaching conditions were as follows: reaction temperature was room temperature, the reaction time was 30 min, liquid-solid ratio (mL/g) was 2:1, stirring rate was 350r/min, and the leaching efficiency of potassium could reaches 95.59%. The purification process of potassium leaching solution was researched with sodium carbonate and its optimal technology conditions were as follows:the reaction time was 30 min, the amount of sodium added was 2.5g, the reaction temperature was room temperature, stirring rate was 300r/min. The removal efficiency of calcium was 82.50% and that of magnesium was 45.56%. After evaporation and crystallization purification solution, the yield and purity of KC1 product obtained could reach above 90%.The residue of which potassium was leached and dried was used as the raw material of extracting silver and the content of silver reach 0.072%(720g/t) in the residue. For extracting silver from the slag of leaching potassium, the exploratory test was studied by leaching the residue with ammonia, sodium chloride, sodium thiosulfate. Researches indicated that sodium thiosulfate has the best leaching rate and its leaching rate can reach 87.56%. Therefore, the sodium thiosulfate was selected as the best reagent to leach silver. Research results shows that the optimal leaching conditions were was follows:reaction time was 3h, the concentration of sodium thiosulfate was 20%, liquid-solid ratio (mL/g) was 6:1, the amount of sodium sulfite added was 7.5g, the amount of mmonia added was 5mL, reaction temperature was 65 ℃, stirring rate was 300r/min, the leaching efficiency of silver was 90.54%.Finally, the silver leaching solution of which leaching rate more than 80% is selected as the raw material liquid of reducing silver after mixing and stirring. From analysis, the content of silver in combined leaching solution can reach 0.1223g/L. For reducing silver in the solution, the exploratory test was carried outed with formaldehyde, hydrazine hydrate, modified activated carbon, sodium hyposulfite and founed as ruducting agent. The study indicated that dithionite has the best reducing rate and the reducing efficiency of silver can reach about 90%. Research results showed that the optimal reducing condition was as follows:the reaction temperature was room temperature, amount of sodium hyposulfite added was O.lg, the reaction time is 30 min, stirring rate is 350r/min. the reduction efficiency of silver could reach 91.02%.In order not to cause the waste of resources, the filtrate after extracting silver was returned to the leaching process to recycle in the course of leaching silver from slag in which potassium had been extracied. The four circulation experiment researches showed that the optimum technological conditions of the cycle use were 50 g potassium slag, the filtrate of sodium thiosulfate after extracting silver was 300 mL, ammonia water 5 mL, stirring speed of 300 r/min, the reaction temperature 65 ℃, reaction time 3h, sodium thiosulfate supplemented 30g and the addition quantity of sodium sulfite 7.5 g for cycling test of supplementary conditions, the silver leaching rate could reach more than 80% in the course of cycle use of extracting silver filtrate.