二元有机混合液体闪点的实验研究

纯物质的闪点一般可通过查取文献获得,混合物的闪点则很难查到。由于混合液体在实际生产中有着广泛的应用,因此,掌握混合液体闪点的变化规律对于其在生产、储存和使用场所中的风险评估有重要意义。文中采用MINIFLASH FLPL全自动闪点测试仪,对由16种纯物质(包含醇类、酸类、酯类、酮类、醚类、烷烃类)组成的14组不同组成和配比的二元混合液体(含完全互溶和部分互溶)的闪点进行实验研究。用图示法分析了不同研究体系的二元有机混合物其闪点随配比和组分变化的经验规律,将二元混合液体闪点的变化规律大致划分为4类,并对每一类的闪点变化特征和机理进行了探讨。研究结果不仅为工程上提供了二元混合液体闪点的可靠实验数据,还为混合液体在生产、储存和使用过程中的火灾风险评估与安全管理提供了重要参考。     

三元互溶混合液体闪点预测研究

闪点是评价易燃液体火灾危险性重要指标。文中基于定量结构-性质相关性(QSPR)原理对三元互溶混合液体的闪点与其结构信息间的内在定量关系(M-QSPR)开展了理论研究。从结构信息角度计算混合物描述符,并采用"Kay's mixing rule"混合规则对混合液体的结构特征进行表征,应用遗传-多元线性回归(GA-MLR)算法,优化筛选出与混合体系闪点最密切的结构参数作为输入参数,分别采用多元线性回归(MLR)和支持向量机(SVM)算法建立三元互溶混合液体闪点的理论预测模型,并将其与文献已有模型比较。研究结果表明:预测模型不仅有较好的预测能力,还可揭示影响三元互溶混合液体闪点的主要结构因素及其影响规律。     

混合液闪点的计算方法

提出根据液体混合物种类,采用适当的活度系数公式计算混合液闪点的方法,活度系数公式中的参数可由气液平衡数据或由文献得到。     

闪点预估及其在航空危险品货物鉴定领域的应用

闪点是确定液态易燃危险品的航空运输条件的重要依据,但其数值很难直接查到。在危险品航空运输中,易燃液体的水溶液体系非常常见,因此掌握该类易燃液体水溶液体系的闪点预估方法对确保航空运输安全具有重要意义。文中选择UNIFAC模型对3种有机物水溶液体系[水(1)+乙醇(2)/水(1)+1-丙醇(2)/水(1)+2-丙醇(2)]的闪点进行预估,同时设计二元水溶液体系的闪点预估流程。结果表明:预估结果与闪点实验结果比较吻合,但这3种体系中,预估值与实验值之间的差异随水含量的增加而变大,文中同时就3种体系的预估结果和共同规律进行了讨论。最后,列举了该预估闪点方法在航空危险品货物鉴定领域方面的应用,表明该项技术在实际工作中是非常有效的手段。     

两种特性的涂料类有机混合物闪点模型预测

为了简化与扩展热力学推导的闪点预测模型,提出由UNIFAC活度系数模型与二元汽液平衡的实验得出二元互溶溶液的超额Gibbs自由能,评判区分溶液的理想与非理想性的方法。选择实用的2种涂料类有机混合物配方成分的二元与三元混合溶液,实验研究闪点变化规律,并与Raoult定律、活度系数模型(Wilson、NRTL、UNIQUAC)和UNIFAC模型的预测值比较。结果表明:理想性物系可直接由Raoult定律预测闪点(平均绝对误差AAD1.0℃);而非理想性物系适宜用3种活度系数模型(AAD2.5℃)或UNIFAC模型(AAD1.0℃)预测闪点。可为涂料类有机混合物的火灾爆炸危险性控制提供可靠闪点预测数据。     

三元可燃性液体水溶液闪点的理论预测

为了预测三元互溶可燃性液体水溶液的闪点,分析确定了影响混合溶液闪点的主要因素,如沸点、相对分子质量、相对密度、饱和蒸汽压、表面张力等。将这些因素作为输入变量,应用支持向量机算法对混合溶液闪点与其对应理化参数之间的内在定量相关性进行了研究,建立了三元互溶可燃性液体水溶液闪点的理论预测模型。对预测模型进行了验证,讨论了模型的有效性和可靠性;解释了模型反映的机制,明确了混合溶液闪点的主要影响因素及其重要程度。     

降液管内液体混合的模拟计算

<正>自五十年代末以来,塔板效率的模拟计算工作已有了长足的进展.但迄今的模拟工作都是在降液管内液体完全混合的假定下进行的.在大直径塔板上,由于液流不匀和二维返混,沿塔板出口堰的液体浓度是不相等的.由于假定液体在降液管内完全混合,则进入塔板的液体为均一的浓度,这对模型的求解和逐板计算都大为简便.八十年代初才见到Weiler和Lockett等关于降液管混合研究的报道.他们在矩形冷模装置上实测了降液管内液体的混合,并用涡流扩散模型求出了涡流扩散系数D’_e,证实在垂直方向上混合剧烈,可以为完全混合;但沿堰长则更接近于完全不混.工业上广泛应用弓形降液管的塔板,本研究在冷模塔弓形降液管内测得大量反映液体混合状态的数据,并运用混合池和涡流扩散两种模型,对降液管内的液体混合进行了模拟计算.     

计算混合液体导热系数新方法

根据液体微观结构的特点，提出了一种计算混合液体导热系数的新方法。对３１９种含水混合液体和非水混合液体２２９９个数据点的计算结果表明，计算值与实验值基本一致，平均误差分别为０７５８％和０７６７％，计算精度优于文献方法。据此发展了一种根据纯物质导热系数预测混合液体导热系数的有效方法     

液体危险化学品鉴定的方法研究

介绍了液体危险化学品的鉴定方法,并对MINIFLASH全自动闭口闪点仪与现行国标测定法测定各种不同外观的危险品闪点的结果进行了比较,结果显示MINIFLASH全自动闭口闪点仪法鉴定液体危险化学品是一种较有效的手段。     

计算有机混合液体粘度的新型方程

在Ｅｙｒｉｎｇ的反应速率理论基础上，引用ＮＲＴＬ方程的　表达式，得到一个计算有机混合液体粘度的新型方程，该方程不但适用于非理想程度不大的体系，而且对极性的和缔合性的醇水、酸水体系均取得了较好的关联结果。经对１９个二元体系和２个三元体系，共１２１０个数据点的检验，与文献值相比总的平均误差仅为１．３１％。     

Calculation of mixture equilibrium binary interaction parameters using closed cup flash point measurements

Proper design and operation of separation processes are highly dependent on phase equilibrium calculations. The common method to treat polar/nonpolar systems, and also mixtures of normal compounds where the sizes are significantly different is to use binary interaction parameters. This paper presents a method to calculate mixture binary interaction parameters using closed cup flash point measurements. The measured and literature closed cup flash points of different binary mixtures (ethanol + n-octane, 1-propanol + n-octane, 1-propanol + n-decane, n-octane + n-decane, 1-propanol + water, 1-butanol + n-octane, 2-butanol + n-octane, and water + propionic acid) are used to calculate binary interaction parameters. These binary interaction parameters together with common activity models are then used to calculate vapor–liquid equilibrium compositions of different binary mixtures considered in this study. The validity of the proposed method was successfully approved by comparing the calculated equilibrium compositions with experimental data.     

Estimation of flash point

A general correlation has been obtained for estimation of closed-cup flash point of organic compounds from their normal boiling points. Estimated flash points are within a deviation of about 10% of reported values. However, separate correlations have been obtained and recommended for acids and alcohols for estimation of flash points for more accurate results.     

具有最低共沸点难分离物系变压精馏分离

变压精馏是根据物系压力改变引起液体混合物共沸点组成变化,进而使共沸物系得以分离的一种有效分离方法。具有最低共沸点的液体混合物分离是化工过程中常见的分离难题。本文在热力学分析基础上研究了四氢呋喃与乙醇、环己烷与苯混合物这类典型的最低共沸液体混合物的变压精馏可行性,提出变压精馏分离四氢呋喃-乙醇液体混合物工艺流程,以NRTL-RK为物性计算方法,利用Aspen Plus模拟软件对变压精馏分离工艺过程进行分析及模拟,并对工艺参数进行优化。结果表明:在常压塔和8atm高压塔组成的双塔流程中变压精馏能将四氢呋喃-乙醇最低共沸混合物进行较好的分离,指出本文提出的研究方法可为具有最低共沸点液体混合物分离工艺的建立提供更加有效的指导。     

Calculating the composition of pitch-coke mixture

The basic principles in formulating pitch-coke mixtures for the production of large graphitized electrodes are considered. With unchanging technological requirements, a mathematical model for calculating the basic characteristics of the blank (prior to graphitization) is proposed, taking account of the subsequent thermodynamic transformations of the mixture and steeping processes; the model is adapted to the particular technological cycle and to the requirements on the prediction and optimization of the mixture composition.     

Effect of liquid temperature on spray flash evaporation

To complement the authors' previous experimental study of spray flash evaporation pursued at 60°C jet inlet temperature, an additional experimental study has been made of the effect of liquid temperature on the spray flash evaporation by changing jet inlet temperatures to 40 and 80°C.From the experimental results, a more general empirical equation suitable for predicting the variation of liquid temperature in the center of jet with residence time was deduced, and the recommendable operating conditions were proposed. Furthermore, an expedient method for prediction of the liquid temperature drop along the length of jet was devised for the recommendable operating conditions.It was realized that, even at lower liquid temperatures, the spray flash evaporation still has higher evaporation performance and extremely faster evaporation rate than the flash evaporation occurring in other systems.     

High flash point electrolyte for use in lithium-ion batteries

The high flash point solvent adiponitrile (ADN) was investigated as co-solvent with ethylene carbonate (EC) for use as lithium-ion battery electrolyte. The flash point of this solvent mixture was more than 110 °C higher than that of conventional electrolyte solutions involving volatile linear carbonate components, such as diethyl carbonate (DEC) or dimethyl carbonate (DMC). The electrolyte based on EC:ADN (1:1 wt) with lithium tetrafluoroborate (LiBF₄) displayed a conductivity of 2.6 mS cm⁻¹ and no aluminum corrosion. In addition, it showed higher anodic stability on a Pt electrode than the standard electrolyte 1 M lithium hexafluorophosphate (LiPF₆) in EC:DEC (3:7 wt). Graphite/Li half cells using this electrolyte showed excellent rate capability up to 5C and good cycling stability (more than 98% capacity retention after 50 cycles at 1C). Additionally, the electrolyte was investigated in NCM/Li half cells. The cells were able to reach a capacity of 104 mAh g⁻¹ at 5C and capacity retention of more than 97% after 50 cycles. These results show that an electrolyte with a considerably increased flash point with respect to common electrolyte systems comprising linear carbonates, could be realized without any negative effects on the electrochemical performance in Li-half cells.     

An experimental study of flash evaporation from liquid pools

The objective of this study is, based on experiments, to improve the understanding of flash evaporation from pools, and to develop empirical correlations of the total quantity of vapor released and the rate of vapor generation (both in non-dimensional form) as a function of the primary nondimensional parameters which govern the process: the Jakob number (Ja_p), Prandtl number (Pr), a dimensionless hydrostatic head (Δp/H), and the salt concentration (C). The work was done in the range of parameters characteristic to desalination plants and to open-cycle ocean-thermal energy conversion. Experiments were performed with fresh water and with saline water (3.5% NaCl concentration), for initial temperatures from 25°C – 80°C, flash-down temperature differences from 0.5°C – 10°C, and pool depths of 6.5″ (165 mm), 12″ (305 mm) and 18″ (457 mm). The prediction of flashed mass as a function of the nondimensional parameters is accurate to within 7.5%. A new time scale τ = (σ/Δp)²/α₁, (where σ = surface tension, α₁ = thermal diffusivity of the liquid, and Δp = pressure difference between the liquid and the vapor space) was employed. The expressions for the rate of flashed steam using this time scale show a scatter of ± 68%. The asymptotic value of the flashed mass increases with Jakob number, increases slightly with pool depth, and decreases with increasing liquid Prandtl number. The comparisons show very good agreement with the experimental values, but underpredict the data obtained from other experiments.     

Determining the residual alcohol in biodiesel through its flash point

A simple low cost method is proposed for the quantitative analysis of residual alcohol in biodiesel through determination of the flash point, with which it is correlated. Methyl ester biodiesels from vegetable oils such as corn, soy and sunflower were prepared. The ethyl ester was obtained from soy oil and methyl biodiesel was also synthesized from bovine fat. In all cases it became very evident that there is a direct correlation between the flash point and the residual alcohol content in the prepared biodiesel. Therefore this parameter can be used to directly determine the residual alcohol content of the product.     

新型拓扑电负性指数模拟烃类物质闪点的标度

在距离矩阵的基础上采用原子的平衡电负性和相对键长校正含有多重键的化合物提出了两个新颖的拓扑电负性指数Y_C、W_C,结合路径数P3对92个碳氢化合物的局部化学微环境进行结构表征,并对化合物的闪点进行了QSPR研究。采用线性回归得到模型的复相关系数R和标准偏差S分别为0.9924和5.1799,模型实验值与计算值的平均绝对误差仅3.86K,相对误差1.46%。同时采用内部及外部双重验证的办法对所建模型进行检验,留一法（LOO）检验和训练集、检验集闪点的预测值和实验值较为吻合,结果表明模型具有良好的内部稳定性和外部预测能力。