Study On The Process Of Preparation Magnesium Sulfate By Medium Transformation And Low Temperature Freezing Crystation

The process technology of preparing magnesium sulfate heptahydrate by using China's western brine and sodium sulfate is studied.The whole craft process is composed of three stages which are medium temperature transformation,freezing crystallization at the low temperature,refining crude magnesium and recycling mother liquor.The impact in medium temperature transformation,the mass ratio of brine to sodium sulfate,the mass ratio of water to sodium sulfate,reaction time and the freezing crystallization temperature on the purity and yield of magnesium sulfate is studied.In medium temperature transformation stages,through four factors and four levels orthogonal experiment explored the reaction temperature,the mass ratio of sodium sulphate to old brine,the mass ratio of sodium sulphate to water,reaction time on the rate removing sodium chloride,the rate leaching magnesium and sulfuric acid root,then determined the order of experimental factors,at last showed the best reaction conditions.The next step through three factors and the levels orthogonal experimens and single factor test to confirm the best conditions.The experimens showed that the optimum temperature range from 55? to 60?;the mass ratio of sodium sulfate to old brine range from 1?5.0 to 1?5.5;the mass ratio of sodium sulfate to water range from 1?1.35 to 1?1.40;the reaction time is 60 mins.In this transformation process conditions within the scope showed the average rate of removing sodium chloride reaches 61.58%,the average rate leaching magnesium reaches 96.51%,the average rate leaching sulfuric acid root reaches 87.59%.Freezing the filtrate at ? 10 ?,the yield of magnesium sulfate could reach maxium,preparation crude products which purity is 78.3%,yiele is 79.6%.Washing crude products by frozen mother liquor and water with the mass ratio of 1?0.3?0.3,then washing the products gained in first washing with the mass ratio 1?0.3.The final products are characterized by XRD,shows that is magnesium sulfate;SEM characterization of product shows the size of magnesium sulfate is large,the nanlysis of chemical composition shows the products match the standar which industrial firstgrade.Improving the yield of magnesium sulfate,evaporating the mixture of frozen mother liquor,first washing liquid and second washing liquid to recycle magnesium sulfate precipitation,which gained the magnesium sulfate of purity 99.49%,then the yield of magnesium sulfate reaches 71.34% after a time recovery.