共查询到18条相似文献,搜索用时 234 毫秒
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熔融结晶技术是利用被分离物质各组分间凝固点的差异,通过控制热量的输入和移出,使被分离组分从熔融液中结晶析出,经洗涤、发汗等操作,实现目标组分分离纯化的一种结晶技术。熔融结晶分离纯化技术由于具有不需要使用溶剂、能耗低、设备体积小、能得到高纯产品等优点,在有机化合物的分离纯化领域得到了广泛应用。本文简述了熔融结晶的方式,介绍了熔融结晶器的类型,综述了熔融结晶技术分离纯化有机同分异构体、有机化工原料、日用品、食品和药品的研究进展,分析了熔融结晶技术分离纯化有机化合物过程中存在的问题,展望了熔融结晶技术分离纯化有机化合物的发展方向。文中指出:随着熔融结晶技术的发展,以提高产品质量,减小能耗和降低成本为目的的耦合熔融结晶技术已成为熔融结晶技术发展的方向。以包含熔融结晶设备、工艺、晶体成核和生长动力学、发汗机理以及传热传质模型的系统工程将会成为熔融结晶分离纯化有机化合物的研究热点。 相似文献
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动态层熔融结晶技术净化磷酸,具有分离效率高、能耗低、无污染等优点,绿色环保。采用程序冷冻法研究了动态层熔融结晶净化磷酸过程中的传质、传热、结晶动力学和杂质分布。研究表明,磷酸晶层生长速率随磷酸熔体起始浓度和冷端降温速率的增加而增加,达结晶平衡态时,晶层平均厚度随磷酸熔体起始浓度的增加和降温终点温度的降低而增加,研究建立了晶层的增长速率和平均厚度与过程操作参数的关联模型;晶层传热能力和杂质的分离效率随着磷酸熔体起始浓度和降温终点温度的降低而增加;采用优化的工艺条件,通过一次结晶纯化,可将质量分数为86.79%的磷酸溶液纯度提高至90.8%,杂质氟离子的质量分数由3×10~(-5)下降到4.5×10~(-6),杂质去除率达85%。 相似文献
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熔融结晶技术及其应用 总被引:1,自引:0,他引:1
介绍了熔融结晶技术的发展现状、原理、特点、装置、优势以及应用。认为熔融结晶技术不需溶剂、耗能小、设备简单,对难精馏、高沸点有机化舍物分离提纯有独特功能。但结晶过程的耦合传质、传热理论研究还不够透彻;应加强结晶器和结晶分离技术的研究,提高分离效率,从而加快熔融结晶精制技术的发展应用。满足工业新材料应用的需要。 相似文献
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在液相氧化法铬盐清洁生产工艺中,中间产品铬酸钠的结晶相分离为重要的组成部分,采用真空蒸发结晶的方法可从Na2CrO4-NaOH-H2O体系中分离得到铬酸钠晶体。文中研究了Na2CrO4在NaOH溶液中晶体成核与生长动力学规律。采用间歇动态法中的矩量变换法建立了结晶过程的动力学模型,用最小二乘法对动力学实验数据进行多元线性回归,得到了动力学参数,并验证了动力学模型的可靠性。结果表明:在粒度大于50μm的范围内,铬酸钠晶体的生长符合粒度无关生长模型;晶浆的悬浮密度、搅拌强度和过饱和度对成核速率均有显著影响;溶液过饱和度对成核速率的影响大于对生长速率的影响。结晶动力学的研究为液相氧化法铬盐清洁生产工艺中铬酸钠和氢氧化钠的分离工艺优化提供了理论基础。 相似文献
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结晶作为一种传统的分离和提纯工艺,广泛运用于医药、化工、材料等领域。随着对结晶工艺的深入研究和对晶体产品质量越来越高的要求,结晶不再仅仅用于物质的分离和提纯,更重要的是根据产品功能的需要,制备特定结构的晶体。作为结晶的重要组成部分,溶析结晶因其操作简单、能耗相对较低、适用于热敏性物质等优势受到了广泛的关注。本文从溶析结晶相较于其他溶液结晶的不同点出发,重点介绍了溶析结晶热力学、溶析结晶动力学和工艺过程的研究,以及与溶析结晶相关的超临界流体技术和球形结晶技术。溶析结晶热力学关注了溶解度的测定方法和如何通过相图来确定合适的操作条件;溶析结晶动力学,详细描述了间歇、连续溶析结晶动力学模型的建立;工艺过程的研究,包括溶析剂与含有待结晶物质混合、结晶过程的控制和优化。同时本文对溶析结晶目前存在的问题进行了总结,并对未来的发展作了展望。 相似文献
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Gerard Arkenbout 《化学,工程师,技术》1991,63(4):336-348
Ultrapurification of organic chemicals by melt crystallization. The need for ultrapure organic compounds is increasing fast. Purities up to 99.999 wt% are required for compounds like caprolactam and phenol. Ultrapurification by melt crystallization is promising from a cost-efficiency point of view, provided that the desired separation can be achieved in a single crystallization operation. When growing the crystals in a suspension a large solid-liquid interface can be made available, permitting a small rate of crystal growth and reducing the rate of solute incorporation. As a consequence, however, complete separation between crystals and melt has to be established. An efficient crystal-liquid separation can be attained using so-called crystal separation columns. Two types can be distinguished: non-packed and packed columns. In a packed column crystal transport is accomplished using a force like pressure. The separation efficiency of a single crystallization operation could be improved further by recrystallization. When procedures become available which are based not only on experimental experience but mainly on physical and technology knowledge, a broad application of suspension crystallization may be expected. 相似文献
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Numerous organic products which are commercially refined by crystallization exhibit wide metastable zones, for example, xylene, bisphenol‐A, isocyanates, or pyridine derivatives. The practical meaning for layer crystallization processes is that a high degree of subcooling on crystallization surfaces is necessary to start nucleation at the beginning of a crystallization stage. The subsequent crystallization runs then uncontrolled, at much higher rates than designed until the subcooling has been dissipated. As a consequence dendritic crystal growth sets in, which is disadvantageous in terms of the separation efficiency of the crystallization process. A practicable countermeasure is seeding which, however, requires more complex equipment and generates additional process steps, resulting in additional costs. In this work an alternative way of reducing the negative impact of subcooling on crystallization, which is based on the reduction of the metastable zone itself rather than on the bypassing it, has been investigated. The width of the metastable zone depends on the activation energy for nucleation which in turn depends on the interfacial surface tension between the melt and the surface of the crystallization element. It has been shown in this work that the activation energy for nucleation and so the supercooling in a xylene isomer mixture can be considerably reduced when replacing stainless steel by PTFE as a material for the crystallization surface. In follow‐up trials it was found that the crystallization surfaces do not need to be wholly covered by PTFE but that just small PTFE nucleation zones on steel surfaces have the same positive effect on the separation by crystallization. Applied in industrial equipment such nucleation zones might contribute to the cost optimization of commercial layer crystallization processes. 相似文献
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The present work investigates the energy consumption of a solids production process. Such a process consists of three different operation units: crystallization/precipitation, solid-liquid separation by centrifuges or filters and drying of wet crystals. Each unit is analyzed with the objective of minimizing the energy consumption. Operating conditions, process design and other characteristic parameters (crystal size, porosity and physical proporties) are discussed with the aim to evaluate their influence on the process. 相似文献
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Innovative hybrid processes offer significant cost savings, particularly for azeotropic or close-boiling mixtures. Hybrid separation processes are characterized by the combination of two or more different unit operations, which contribute to the separation task by different physical separation principles. Despite of the inherent advantages of hybrid separation processes, they are not systematically exploited in industrial applications due to the complexity of the design and optimization of these highly integrated processes. In this work we study a hybrid distillation/melt crystallization process, using conventional and thermally coupled distillation sequences. The design and optimization were carried out using, as a design tool, a multi-objective genetic algorithm with restrictions coupled with the process simulator Aspen Plus™, for the evaluation of the objective function. The results show that this hybrid configuration with thermally coupled arrangements is a feasible option in terms of energy savings, capital investment and control properties. 相似文献
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尼龙6/聚酯(PET)共混体系结晶相分离的研究 总被引:2,自引:0,他引:2
用差示扫描量热(DSC)考察尼龙6/聚酯(PET)共混体系的结晶行为,表明是结晶相分离的。不同条件下,结晶相分离的过程和形成的结晶态不同,反映在热行为上,如熔融过程和相应特征参数值,便随着处理的条件、组成比等而改变。研究结果还表明,当尼龙6组分的质量分数W PA-6< 0.1 时,它被PET 阻隔而不再结晶,因两者形成部分氢键,酯基对尼龙6 结晶影响的结果,尼龙6/聚酯(PET)共混体系中尼龙6 的熔融峰温,随组成比的变化呈现波浪形曲线。 相似文献