【作者】 冯雨；

【导师】 解利昕；

【作者基本信息】 天津大学 ， 膜科学与技术， 2010， 硕士

【摘要】 随着国内外经济的不断发展,纯碱产品需求增长,前景广阔。目前我国生产纯碱的方法主要有氨碱法、联碱法和天然碱加工法。在天然碱加工制纯碱时,为保证蒸发结晶过程的顺利进行,提高产品质量,需要排放适量母液;排放的母液中除含有大量的NaCl外,还含有较高浓度的Na₂CO₃和NaHCO₃。如果将排放母液中的NaCl分离出来,而保留Na₂CO₃和NaHCO₃,并将其返回到系统中利用,则可以减少母液排放量,提高经济效益。因此,本文采用纳滤过程对高盐度碱液的脱盐过程进行了详细研究,为实际应用提供依据。试验中采用DK1812C卷式纳滤膜元件,对含有NaCl:187.9g/L、Na₂CO₃:30.5g/L、NaHCO₃:7.4g/L的原料液,在不同进料流量、操作压力和料液浓度下,考察了纳滤膜对CO32-、HCO3-和Cl-三种离子的截留率、离子间分离系数、膜通量及回收率的变化情况。结果表明浓度和操作压力对纳滤膜性能具有较大影响。离子间分离系数、膜通量和回收率也都随着压力的增大和料液浓度的减小而增大。流量主要是通过改变膜表面附近的流动状况及浓差极化来影响结果,影响较其他因素不明显,随流量增大,离子截留率及膜通量呈微弱上升趋势。较优实验条件下分离系数CO32-/Cl-、HCO3-/Cl-分别达到25.7和1.8。当原料为碳酸钠-氯化钠两元物系时,相对于碳酸钠-盐酸氢钠-氯化钠三元物系,原料利用率较高。在料液组成为Cl-:0.622mol/L、CO32-:0.0646mol/L和压力12bar条件下,碳酸根和氯离子的截留率分别为93.5%和4.4%,此时两离子间的分离系数为14.9,较改变物料前碳酸根、碳酸氢根与氯离子间的总分离系数5.5提高幅度较大。因此将母液中HCO3-转化成CO32-后再进行纳滤处理,有利于提高原料利用率。更多还原

【Abstract】 With the continual development of international economic, the need of soda ash is increasing and has a well prospect. At present, the main methods of producing soda ash in China, include Solvay process, combined method and trona processing. In order to ensure the process of evaporation and crystallization smoothly and improve the quality of product when obtain soda ash from trona, we should discharge proper mother liquor during trona processing, which contains large amounts of NaCl and high concentration of Na₂CO₃ and NaHCO₃ also. If NaCl is separated from discharged mother liquor, while Na₂CO₃ and NaHCO₃ components are retained to return to the system, we can not only reduce emissions, but also increase the economic efficiency. In this paper, we made a detailed research on desalination effect of high salinity alkali solution by nanofiltration to provide the basis for practical application.The experiment use GE-DK1812C roll nanofiltration membrane to make research on the changes of rejections about nanofiltration membrane to CO32-, HCO3- and Cl-, separation coefficient, membrane flux and recovery rate at different feed flow, operating pressure and feed concentration; in experiment, the raw material solution is composed of NaCl:187.9g/L, Na₂CO₃:30.5g/L and NaHCO₃:7.4g/L. The experiment results indicate that feed concentration and operating pressure have greater impact to the performance of nanofiltration membrane. Ion separation factor, membrane flux and recovery rate are all increased with increase of operating pressure and decrease of feed concentration. Feed flow affects experiment results mainly by changing the flow conditions near the surface of membrane and the concentration polarization, the effect of which is less obvious than other factors; ion rejection and membrane flux are slightly increasing with the increase of feed flow. Under optimum conditions, separation factors of CO32-/Cl- and HCO3-/Cl- are 25.7 and 1.8.When the feed solution is two element system of sodium carbonate - sodium chloride, the raw material has a higher utilization rate compared to ternary system of sodium carbonate - sodium hydrochloride - sodium chloride. Under the conditions that feed solution is composed of Cl-:0.622mol/L and CO32-:0.0646mol/L and operating pressure is 12bar, the rejection of carbonate and chloride ions are 93.5% and 4.4%; meanwhile, the separation coefficient of carbonate and chloride ions is 14.9, which is larger than total separation coefficient 5.5 of carbonate, bicarbonate and chloride ions before feed solution changed. So changing HCO3- in mother liquor to CO32- and then making treatment by nanofiltration can improve utilization rate of raw material.更多还原