Investigations On Fractional Crystallization Process Of High Salinity Wastewater From Coal Industry

The unique resources characteristic of china promotes the development of coal industry rapidly,which remits the energy crisis in a certain extent,which produces a large amount of high salinity wastewater.At present the treatment mainly are evaporation pond and evaporation crystallization,the product of both processes is mixed salt,with plenty of organic and heavy metals,so they are only handled as dangerous solid,which leads to environmental pollution and resource waste.At the same time,evaporation crystallization exists many problems,such as high cost,high consumption,poor stability,corrosion and scaling and so on.It is under the above background,we study systematically the fractional crystallization process of high salinity wastewater from coal industry.Firstly,the paper studies the effects of the typical organic impurities-phenol-in high salinity wastewater on the thermodynamic properties of sodium sulfate and sodium chloride.We measured solubility data of sodium sulfate and sodium chloride in water by the static method at different temperatures,and studies the influence of phenol on the solubility of sodium sulfate and sodium chloride;two empirical equations was used to fitting the solubility data,in addition,we compare the simulation results with the experimental data and study the applicability and accuracy of the model.What's more,we obtained the influence of phenol on thermodynamic data(dissolving enthalpy,entropy,and the gibbs free energy)of sodium sulfate in water by calculation and study the influence of phenol on thermodynamic data.Secondly,based on the measured data of thermodynamics,the paper studies the effects of phenol on the nucleation and growth of sodium sulfate.We measured metastable zone width and induction time of sodium sulfate in water by FBRM on-line detection technology,and study the influence of phenol,saturation temperature,cooling rate and supersaturation.Models was used to fit the data,we obtained the corresponding nucleation and growth parameters by calculation of different theoretical models.Combining with molecular dynamics simulation,we obtain the influence of phenol on the nucleation mechanism and growth mechanism of sodium sulfate.Finally,based on the above theoretical research,in order to obtain sodium sulfate and sodium chloride which have high purity,big granularity,uniform partical size distribution and meet the requirements of industrial product quality from high salinity wastewater,realizing the resource utilization of salt.The paper studies systematically the fractional crystallization technique of high salinity wastewater from coal industry,according to the feature of composition of high salinity wastewater,we determines the crystallization technique route,what's more,we study the influence of decoloring condition,stirring rate,cooling rate,evaporation rate,and pH on the product,and finally determine the optimized operating condition of crystallization process of sodium sulfate and sodium chloride.The electrodialysis high salinity wastewater was used to verify the stability and strong adaptability of fractional crystallization process,at the same time,it provides technology support for the comprehensive utilization of high salinity wastewater.