黑北凹地富钾地下卤水自然蒸发实验研究

黑北凹地位于阿尔金山山前,其富钾地下卤水储量巨大,该卤水以钠、氯含量占绝对优势。富钾地下卤水化学组成简单,易于提取,具有很好的开发利用价值。以该富钾卤水为研究对象,在现场进行了自然蒸发实验。通过实验发现,卤水经过较长的石盐(NaCl)析出阶段后,分别达到光卤石(KCl·MgCl2·6H2O)和水氯镁石(MgCl2·6H2O)析出阶段,最后蒸干于南极石阶段,其析盐顺序为石盐—光卤石—水氯镁石—南极石;其中钾只以光卤石矿物析出,且析出阶段比较集中,在整个蒸发过程中氧化硼(B2O3)和锂则都在卤水中浓缩富集,没有析出。根据卤水蒸发过程中的析盐规律,其与K^+,Na^+,Mg^2+∥Cl^--H2O(25℃)介稳相图相符,蒸发过程中的体系变化趋势为液相体系点在石盐相区逐渐向远离石盐相点的方向移动,到达石盐与钾石盐共饱线后沿此线向石盐、钾石盐、光卤石共饱点移动,后沿石盐、光卤石共饱线移动,最终蒸干于石盐、光卤石、水氯镁石共饱点。经过对整个蒸发过程中卤水pH及密度的变化规律进行分析,指出可以通过pH及密度的变化来控制卤水的制卤过程。通过该蒸发实验研究,将为黑北凹地地下卤水的提钾工艺实验和后期开发提供科学依据。

Study on natural evaporation of underground potassium-rich brine in Heibei concave

With huge reserves of underground potassium-rich brine,the Heibei concave is located in the piedmont of the Altun Mountains.The ion species in the brine are few except for Na or Cl whose content accounts for absolute advantage.Be-cause of its simple chemical composition and easy extraction,the brine has a great value in industrial development and utiliza-tion.Taking the potassium-rich brine as the research object,the natural evaporation experiment was carried out on site.It was found through experiments that the brine reached the precipitation stage of carnallite（KCl·MgCl₂·6H₂O） and bischofite （MgCl₂·6H₂O） after a long period of halite precipitation of（NaCl）,and finally dried out at the antarctic stage,and the sequ-ence of the mineral crystallization during evaporation was halite,carnallite,bischofite and antarcticite.And potassium was only precipitated from carnallite minerals,and the precipitation stage was relatively concentrated.During the whole evaporation process,boron oxide（B₂O₃） and lithium were concentrated and enriched in the brine without precipitation.According to the crystallization law of brine during the evaporation process,it was consistent with the metastable phase diagram of K ⁺,Na ⁺,Mg ²⁺//Cl ^--H₂O（25 ℃）.The evolution trend of the brine during the evaporation process was that it moved from the NaCl point in the halite phase area to the sylvite and carnallite phase area and when reaching the univariant curve of halite and sylvite,it moved along the curve and arrives at the invariant point of halite,sylvite and carnallite.Then it moved along the univariant curve of halite and carnallite,and finally arrived at the invariant point of halite,carnallite and bischofite.After analyzing the variation of brine pH and density during the whole evaporation process,it was pointed out that the halogen production process of brine could be controlled by changes in pH and density.Through the evaporation experiment,it would provide a scientific basis for the potassium extraction process experiment and post-development of the underground brine in the Heibei concave.