精馏节能过程非平衡热力学分析——模型方程的建立

通过对精馏过程进行热力学分析,建立了通用性较强的非平衡热力学数学模型.该模型可对精馏过程中用能情况进行非平衡热力学分析和熵均分分析,也可用于评价塔板性能.模型建立的基础只适用于线性非平衡热力学区,即近平衡区,有较大的局限性.     

化工专业综合性实验“分离乙醇水溶液”的探究

化工专业综合性实验对于培养学生的创新精神和工程实践能力至关重要。以分离乙醇水溶液为例,将气液相平衡测定实验和萃取精馏过程模拟相结合形成综合性实验,涉及到了三元体系的气液相平衡测定方法、实验数据采用不同热力学模型的回归及评价、萃取精馏过程模拟、各因素对分离效果的影响评价等。加深了学生对理论知识的理解,使学生对萃取精馏工业应用有了一定的认识,提高了学生的实验操作水平和工程实践能力,为应用型人才的培养提供了有力保障。     

金属的溶剂萃取热力学研究 2:In~2(SO~4)~3+Na~2SO~4+D~2EHMTPA+n-C~8H~18+H~2O体系

在温度278.15-303.15K和离子强度=为0.1-2.0mol/kg范围内,在萃取体系In~2(SO~4)~3+Na~2SO~4+D~2EHMTPA+n-C~8H~18+H~2O体系中,本文测定了萃取平衡的In^3+的平衡浓度和水相pH值,其中Na~2SO~4为支持电解质.根据Pitzer电解质溶液理论,估算了平衡水相中的真实离子强度值,并用直线外推法和多项式拟合法确定了萃取过程的热力学平衡常数K^ ,进而计算了这个萃取过程的各个热力学量.     

金属的溶剂萃取热力学研究 2:In~2(SO~4)~3+Na~2SO~4+D~2EHMTPA+n-C~8H~18+H~2O体系

在温度278.15—303.15K和离子强度为0.1—2.0mol/kg范围内,在萃取体系In_2(SO_4)_3+Na_2SO_4+D_2EHMTPA+n-C_8H_(18)+H_2O体系中,本文测定了萃取平衡的In_(3+)的平衡浓度和水相pH值,其中Na_2SO_4为支持电解质.根据Pitzer电解质溶液理论,估算了平衡水相中的真实离子强度值,并用直线外推法和多项式拟合法确定了萃取过程的热力学平衡常数K(?),进而计算了这个萃取过程的各个热力学量.     

有机溶剂脱水的相平衡研究

根据精馏分析原理可知用精馏的方法不能获得含水量低于7%的有机溶剂,用溶液的热力学处理盐影响恒沸物气液平衡的数据,证实了加入无水氯化钙使有机溶剂脱水是有效的.文章讨论了无水氯化钙脱水的机理,并提出了有机溶剂脱水的合适工艺.     

伯胺N1923从HCl溶液中萃取Zn(Ⅱ)的机理研究

本文研究了仲碳伯胺N_(1923)从HCl介质中萃取Zn(Ⅱ)的平衡规律,通过IR、NMR的测定和斜率法、饱和法得出了不同酸度下的萃取平衡反应,并分别计算了萃取过程的热力学函数。     

CuSO4-氨化P507-n-C6H14体系平衡常数的计算

用热力学方法研究了酸性磷萃取剂与金属体系间的平衡计算模型,萃取体系的水相采用Pitzer半经验公式求算γCu²⁺,有机相用热力学关系求出了水、正已烷和萃取剂的活度系数.实验结果用Scatchard-Hildebrand模型关联,并经回归处理,得到了萃取反应热力学平衡常数(K=1.26×10^-7～5.26×10^-7)及萃合物的活度系数.     

非平衡化学反应的热力学

化学现象是由反应速率表征的,只有在非平衡条件下化学反应过程才会呈现出非零的反应速率.因此化学现象本身是一种非平衡现象,化学热力学应属于非平衡态热力学(也称不可逆过程热力学)的范畴.但是传统的化学热力学主要限于研究平衡态和可逆过程,其主要原因是长期以来整个非平衡态热力学缺乏一个较为令人满意的理论.但在最近二、三十年间非平衡态热力学取得了巨大的进展.本文简要讨论与化学反应有关的非平衡态热力学的进展.     

异丙醇-水分离技术研究新进展

介绍了萃取精馏法、吸附蒸馏法和膜分离法等用于异丙醇-水分离的新进展,并对这几种方法进行了简单评述,具体分析了各种方法的优缺点,展望了异丙醇-水分离新工艺的前景,认为以乙二醇为萃取剂的萃取精馏技术具有推广价值.     

Gaussian与Aspen Plus在化工原理课程设计中的应用*

在化工原理课程设计中将某药厂委托的科研项目“二甲硫醚、甲醇和水分离设计项目”转化为典型教学案例,结合现代计算机辅助技术,引入量化计算软件Gaussian和化工模拟软件Aspen Plus分别从微观和宏观上进行萃取精馏分离共沸物的设计。通过Gaussian软件,基于密度泛函理论证实了待分离体系中已有的组分水可改变二甲硫醚与甲醇二元共沸物的相对挥发度,消除2者之间的共沸。继而采用Aspen Plus软件对待分离混合液进行萃取精馏工艺模拟与优化,最后开展工业设计与设备选型。上述实际案例的设计过程,创造性地使用了混合液已有的组分作为萃取剂,通过萃取精馏工艺实现共沸物的分离,弥补了传统萃取精馏因引入萃取剂导致产品携带少量第三组分的缺点,极大地激发了学生学习的兴趣,丰富了课程教学内容,将复杂的萃取精馏过程讲解透彻,促进教学质量的提升,增强学生的工程设计能力,学生多次参加全国大学生化工设计竞赛并取得了优异成绩。     

加碱萃取精馏制取无水乙醇

乙醇-水体系存在共沸点,难以通过普通精馏方法制取高纯度乙醇,萃取精馏是分离共沸体系的有效途径。目前常用的萃取溶剂是乙二醇。在分离乙醇-水体系的过程中,将适当的盐类(醋酸钾)溶于乙二醇形成溶盐萃取剂,会有效提高溶剂的选择性。本文用萃取精馏方法并加入乙二醇分离效果更明显。     

Design of extractive distillation process with mixed entrainer

The separation of two systems containing minimum boiling azeotropes (acetone—methanol and tetrahydrofuran (THF)—water) was performed using extractive distillation with a heavy boiling mixed entrainer consisting of two compounds. The entrainer constituents did not form new azeotropes with each other and with the components of the original mixture. An analysis of the mixed entrainer influence on the vapor-liquid equilibrium (VLE) and relative volatility provides an understanding of the cases in which the separation by extractive distillation (ED) in the presence of the mixed entrainer revealed energy benefits over their individual constituents. New results for application of the mixed entrainer monoethanolamine (MEA)—ethylene glycol (EG) and dimethyl-sulphoxide (DMSO)—glycerol for the separation of THF—water and acetone—methanol, respectively, are presented for the first time. The individual selective agents were chosen from the efficient entrainers discussed in the literature. The calculations were performed using the platform Aspen Plus 7.3. Different extractive distillation flowsheets are provided for the zeotropic mixed agents, viz. with two or three columns. For the ED of the binary mixtures investigated, the structures of the different separation schemes, the operating parameters of the columns, and the energy consumptions are presented and compared. The application of the mixed entrainer MEA—EG fed into the ED column with pre-mixing can be recommended, providing up to 1.7 % of energy saving for acetone—methanol separation. In the case of THF—water, the mixed entrainer DMSO—glycerol provides 0.8 % of energy saving. The separate inputs of the individual constituents of the mixed entrainer led to a significant increase in the energy consumptions of the flowsheet because of the third regeneration column, hence this flowsheet cannot be recommended for use in the separation of both mixtures.     

The separation potential of pervaporation : Part 2. Process design and economics

Pervaporation is a relatively complex process compared to other membrane processes like reverse osmosis for two reasons:— the process is sensitive to pressure losses at the permeate side— the evaporation enthalpy has to be transferred to the membrane surface (permeate side).Selectivity and flux can decrease markedly in case of hindered permeate flow. This is demonstrated by numerical design calculations of hollow-fiber modules. The calculations indicate that optimal fiber dimensions of hollow-fiber pervaporation modules should be much larger than those employed in RO and gas permeation modules.In principle, several alternatives exist for the supply of the evaporation enthalpy. The most economical solution seems to be to draw this energy from the liquid and to maintain the operating temperature level by a combination of modules and heat-exchangers in series. An alternative is the sweeping of the permeate by a partially condensing, and with respect to the permeate immiscible, carrier vapor. Since the latent heat of the carrier vapor can be utilized only partially, this concept will not be economically competitive.Pervaporation has a wide range of possible applicatio for this reasons it is impossible to discuss the economics of pervaporation in general. In this paper the separation of benzene/cyclohexane, an azeotropic system with similar vapor pressures of the components, has been chosen as an example. But even such a limited discussion reveals tendencies which seem to be generally valid:1.Pervaporation processes consisting of several stages (cascade) cannot compete with conventional separation processes like extractive distillation.2. Hybrid processes like a combination of extractive distillation, pervaporation are very promising, especially in cases where high product purities required     

On the integration of jet ejectors into hybrid dehydration processes

Hybrid processes of distillation and membrane separation are considered as promising alternatives to azeotropic and extractive distillation. However, the membrane process, which is basically pervaporation or vapor permeation, is still a niche operation with a limited number of applications. The relatively high cost of the membrane units, and the lack of long time industrial experience are the main obstacles. Great efforts are being undertaken to improve the membrane properties and to optimize the membrane process. Additional savings in the effective cost of the membrane unit could be achieved by its proper integration into the overall process. In this work, the use of steam jet ejectors as a process integration alternative for hybrid dehydration processes is investigated. Favorable implementation regions are defined. Advantages and limitations of this modification are discussed.     

RETRACTED ARTICLE: Purification of phenol from hydroxyacetone and 2-methylbenzofuran by rectification

This paper presents structural relationships of phase equilibrium diagrams and azeotropic properties, and resulting evaluation of optimum process conditions for removal of hydroxyacetone (HA) and 2-methylbenzofuran (2-MBF) from phenol. It is demonstrated that the concentration region of HA separation from phenol is absolutely different from that for 2-MBF, which makes the task of HA and 2-MBF removal from phenol by distillation requiring installation of at least two highly selective extractive distillation columns operating with significant steam consumption.     

超临界CO_2萃取-分子蒸馏对大蒜化学成分的提取与分离

采用超临界CO2流体萃取技术和分子蒸馏对大蒜化学成分进行萃取与分离，用气相色谱－质谱联用技术测定其化学成分；从超临界CO2萃取物中鉴定出16种成分，经分子蒸馏后，得到4种主要成分：二烯丙基二硫、3－乙烯基－1，2－二硫代环己－5－烯、2－乙烯基－1，3－二硫代环己－5－烯及二烯丙基三硫。     

Computer simulation of the dartmouth process for separation of dilute Ethanol/Water mixtures

High energy costs are associated with the recovery of ethanol from fermentation broths. This paper discusses a computer simulation of the Dartmouth Process, which aims to reduce these costs by the use of IHOSR distillation, extensive heat integration, and extractive distillation using a salt. To resolve the uncertainty in modeling alcohol-water-salt vapor-liquid equilibrium, a new and more accurate activity coefficient model was used. An Aspen™ model was used to generate capital and energy costs for a range of ethanol concentrations in the feed. Simulation results show that the Dartmouth Process offers substantial economic advantages over benzene azeotropic distillation, particularly at low feed concentrations.     

色谱法筛选C_9芳烃萃取精馏溶剂

将萃取精馏溶剂作为气相色谱固定液,利用气－液色谱法对Ｃ９芳烃所用溶剂进行了选择。共测试环丁砜、邻苯二甲酸二甲酯等７种溶剂。其中邻苯二甲酸二甲酯对Ｃ９芳烃异构体的分离效果较好。方法省时省力,消耗少,结果可靠。