共查询到18条相似文献,搜索用时 187 毫秒
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测定了KOH-K3VO4-H2O体系的溶解度,结合KOH-K2CrO4-H2O体系的溶解度变化规律,研究了KOH-K2CrO4-K3VO4-H2O四元体系中蒸发结晶分离K2CrO4和冷却结晶分离K3VO4的方法. 针对钒渣钾系亚熔盐分解获得的溶出液组成,研究了该体系中K2CrO4和K3VO4结晶分离工艺参数对分离效果的影响. 结果表明,将溶出液蒸发至KOH浓度为630~670 g/L进行K2CrO4分离,K2CrO4结晶率达90%以上,晶体纯度达95%以上;将分离K2CrO4后的结晶母液继续蒸发至KOH浓度为800~850 g/L,从80℃到40℃自然降温,在搅拌速度200 r/min、晶种添加量2%(w)的优化结晶条件下,K3VO4结晶率为60%以上,晶体纯度达90%以上. 分离K2CrO4和K3VO4后的溶液返回钒渣亚熔盐分解反应过程循环使用. 相似文献
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二次(盐析)结晶技术在铬酸钾清洁生产中的应用研究 总被引:3,自引:0,他引:3
介绍了K2CrO4清洁生产中的二次(盐析)结晶工艺技术。根据0℃、30℃和60℃时K2O-CrO3-H2O体系的溶解度数据,拟合出了K2CrO4在KOH溶液中溶解度的解析式;并结合二次(盐析)结晶过程的物料平衡关系,推导出了各工艺参数的估算式。通过对工艺实验结果的分析与对比,验证了估算方法的可靠性以及二次(盐析)结晶工艺路线的可行性。表明二次(盐析)结晶技术在铬盐清洁生产中,具有良好的应用前景。 相似文献
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《无机盐工业》2017,(2)
针对白钠镁矾矿物加工分离困难的问题,对相关水盐体系相图做了研究,设计了以硫酸铵为盐析剂加工分离白钠镁矾的生产工艺。通过相图分析可以发现,当温度为60℃时Na_2SO_4-MgSO_4-(NH_4)_2SO_4-H_2O四元体系会形成较大的MgSO_4·(NH_4)_2SO_4·6H_2O复盐结晶区,0℃时则形成Na_2SO_4·10H_2O结晶区,所以调节混合体系温度和水量可以实现氮镁复肥和硫酸钠的循环生产。硫酸铵为盐析剂加工分离白钠镁矾的生产工艺具有反应时间短、操作简单等特点,此外还可制备得到氮镁复肥和硫酸钠。该工艺对于有效分离白钠镁矾矿物,实现白钠镁矾资源的综合利用具有重要的现实意义。 相似文献
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根据测定的Na^ ,NH4^ ∥CrO4^2-,HCO3^---H2O体系相图对铬酸钠碳氨转化过程中CrO4^2-析出形式进行分析,并结合实验研究提出相应的分离方法。结果表明铬酸钠碳氨转化过程中首先析出碳酸氢钠,铬会依次以铬酸铵钠和铬酸铵结晶形式析出,利用铬酸铵钠结晶与碳酸氢钠结晶的粒度和密度差别可用水力旋流器分离。 相似文献
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以90 ℃的Na2CrO4-NaOH-H2O体系相图为依据,采用蒸发盐析结晶的方法从体系中分离铬酸钠晶体,研究了搅拌强度、蒸发速度、结晶温度、晶种添加等因素对工艺过程的影响规律,得到最优工艺操作条件:搅拌强度为能使晶体离底悬浮所需的最小转速;每1 050 g原料的蒸发速率约为140 mL/h;结晶温度为90 ℃;并添加一定量的晶种。在以上操作条件下制备出的铬酸钠晶体粒度较大,尺寸均一。同时研究了不同氢氧化钠浓度下体系压力与沸点间的关系,为铬酸钠结晶过程的温度控制提供了基础数据。 相似文献
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利用阳离子膜,以K2CrO4电解结晶制备K2Cr2O7,考察了电流密度、温度、阴极液KOH浓度、阳极液K2CrO4浓度等因素对转化率、电流效率和直流能耗的影响;研究了K2Cr2O7不同浓度、不同转化率下的结晶纯度和收率及搅拌速率、降温速率和晶种加入量等对晶体粒度分布和形貌的影响. 结果表明,最佳电解工艺条件为:电流密度0.2 A/cm2,电解温度80℃,阴极液KOH浓度50 g/L,阳极液K2CrO4浓度400 g/L. K2Cr2O7转化率大于90%时,结晶纯度不低于99.8%. 优化的结晶条件为:溶液初始K2Cr2O7浓度500 g/L,搅拌速率300 r/min,降温速率0.5℃/min,不添加晶种. 所得产品符合GB 28657-2012要求. 相似文献
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采用等温溶解平衡法对川西平落坝地下卤水三元子体系KCl+K2B4O7+H2O进行研究,测定该体系平衡液相的溶解度及物化性质(密度、折光率)。结果表明:该三元体系属简单共饱型,无复盐或固溶体形成;平衡相图中单变度曲线AE和BE对应的平衡固相分别为K2B4O7.4H2O和KCl。对比该体系298 K和348 K稳定相图:氯化钾、硼酸钾结晶形式相同;在348 K下氯化钾的结晶区明显增大而硼酸钾的结晶区明显减小;随温度的升高,氯化钾对硼酸钾的盐析作用增强。 相似文献
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以铬酸钾中间体为原料,系统地研究了采用结晶分离等常规手段制备铬酸钠产品的清洁制备方法。应用等温法分别测定了KNO3在Na2CrO4水溶液中和Na2CrO4在KNO3水溶液中的相平衡数据,绘制了溶解度曲线,确定采用先冷却结晶后蒸发结晶的方法制备铬酸钠晶体产品。考察了冷却结晶终点温度和物料配比,分析了分步蒸发结晶产品,确定了结晶最佳操作条件:K2CrO4与NaNO3的质量比在1∶(0.9~1.2),冷却结晶的终点温度控制在4℃。提出铬酸钾通过结晶方式转化为铬酸钠的整体工艺流程,并进行了全流程循环实验。采用重结晶法对铬酸钠产品进行精制,获得高纯度的铬酸钠晶体,质量分数由81.4%提高到92.2%,且粒径较大,粒度均匀。 相似文献
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为了对苦卤结晶析出的Na(Cl,Br)固溶体中氯化钠组分和溴化钠组分进行分离,测定了NaCl–NaBr–CH3OH三元体系在273及323 K温度时的溶解度数据,根据测得的液相点和湿渣相点确定了对应的固相点,由此绘制出了两个温度下的相图。结果显示,273及323 K温度下该三元体系的相图特征相似,均只有一个共饱点、两条饱和溶解度曲线,对应的固相结晶区有三个:NaCl纯盐结晶区、NaCl和Na(Cl,Br)固溶体共结晶区、Na(Cl,Br)固溶体结晶区。NaBr在无水甲醇中溶解度的增大导致NaCl溶解度大幅减小,说明NaBr对NaCl产生了较强的盐析效应,273 K时两种溶质在甲醇中的溶解度均比323 K时的溶解度大。依据273和323 K的NaCl–NaBr–CH3OH体系相图及298 K的NaCl–NaBr–H2O体系相图设计了分离Na(Cl,Br)固溶体中氯化钠和溴化钠的工艺。 相似文献
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采用等温溶解平衡法研究了三元体系NaBr-Na2B4O7-H2O在373 K时的相平衡关系,并测定了饱和溶液的溶解度及密度。研究发现:该三元体系为简单共饱和型,无复盐及固溶体形成。根据溶解度数据绘制了相应的平衡溶解度曲线,相图中有1个共饱点,2条单变曲线,2个平衡固相分别为NaBr和Na2B4O7·5H2O;对不同温度条件下的溴化钠和硼酸钠的溶解度做了对比分析和讨论,结果表明,随着温度的增加,硼酸钠和溴化钠的溶解度均增大,但是在高温条件下,硼酸钠其溶解度数据增加明显;在该三元体系中溴化钠对硼酸钠有明显的盐析作用;并简要讨论了密度变化规律。 相似文献
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This paper focuses on struvite (MgNH4PO4·6H2O) crystallization in controlled supersaturation. Struvite can be used as a slow-release fertilizer. Crystallization experiments were conducted using supersaturated solutions. The secondary focus of this paper is the design of a struvite recovery system in fed-batch-controlled supersaturation mode. The design and commissioning of fed-batch struvite crystallization included the determination of operating supersaturation of struvite crystallization, suitable seed materials and the composition of feed solution. Determination of operating supersaturation of struvite crystallization was conducted by two steps including thermodynamic simulation using gPROMS2 (process simulation software) along with a set of batch experiments. Investigation of suitable seed materials was also conducted using set of batch experiments. Two types of seed materials including quartz sand and struvite seeds were used in the investigation of seed materials. Composition of feed solution included the investigation of struvite solution chemistry using PHREEQC3 thermodynamic modeling package. Based on the previously investigated design approach, struvite crystallization in fed-batch system was conducted using a 44-L of reactor with 15-L of initial reactant volume. 相似文献
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Crystallization in the presence of high pressure gas as antisolvent could be applied for the recovery of valuable compounds from liquid solution. A study of separation behavior is presented here for a mixture of anthracene (AN) and anthraquinone (AQ) in cyclohexanone (CX) expanded with a gaseous antisolvent, CO2. The pressure range was 0.1 to 12 MPa; the temperature was either 292 or 313K. Separation factors were obtained from the measured salted-out yields and the supersaturation of each solute could be also obtained for this pressure-tuning crystallization. The separation factor varies almost linearly with relative supersaturation ratio in the crystallization of anthracene-anthraquinone from cyclohexanone and CO2. 相似文献
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A systematic approach has been developed and applied to the preferential crystallization of 4-hydroxy-2-pyrrolidone in isopropanol. The concept of critical supersaturation control was introduced for preferential crystallization process. System thermodynamics, crystallization kinetics, optimal operation and in-situ monitoring were combined and integrated to establish the strategy for the critical supersaturation control. Subsequently, the solubility and metastable zone widths of 4-hydroxy-2-pyrrolidone with different compositions in isopropanol under different cooling rates were determined using an automatic lab reactor (Mettler Toledo LabMax) system equipped with Lasentec Focused Beam Reflectance (FBRM) probe. The crystal nucleation and growth kinetics were measured with s-plane analysis. A modified technique was proposed for size-dependent crystal growth. Based on the thermodynamics properties and crystallization kinetics, a simplified cooling profile was proposed and applied to the critical supersaturation control. The final product's high optical purity, good crystal size distribution, SEM imagines and the in-situ observations, all suggested that the critical supersaturation control was essential and the systematic approach was successful and applicable for preferential crystallization. 相似文献
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Na_2B_4O_7-Na_2SO_4-NaCl-H_2O四元体系323K相平衡研究 总被引:1,自引:2,他引:1
采用等温溶解平衡法研究了四元体系Na2B4O7-Na2SO4-NaC l-H2O在323 K的相平衡及平衡液相,测定了平衡液相的溶解度及密度。研究发现,该体系属于简单共饱和体系,无复盐和固溶体生成。根据实验数据绘制了相应的相图,相图中有一个共饱点E,3条单变曲线E1E,E2E和E3E;3个结晶区平衡固相分别为:NaC l,Na2B4O7.10H2O和Na2SO4。实验结果表明,NaC l对Na2B4O7.10H2O和Na2SO4有盐析作用,并简要讨论了密度变化规律。 相似文献