Kurzwegdestillation

Among serveral processes of vacuum distillation the so-called Short Path Distillation has proven as the most efficient process for laboratory, pilot plant and production use. Especially in pharmacy, cosmetics and plastic resins where sensitive mixtures have to be separated, the Short Path Distillation has made itself indispensable.     

Kurze Wege für große Moleküle

Short‐Path distillation, often also called incorrectly molecular distillation guarantees the advantages of a distillation at considerably reduced pressure and thus reduced evaporation temperature with the distillation rates of 100–200 kg per square meter of evaporator surface area and hour which can be achieved in the fine vacuum range, i.e. at a pressure range of 10⁻³ to 1 mbar and which are economical. Short‐Path Distillation is being applied whenever all other distillation methods lead to thermal product damages, or if the vapor pressures of the components to be separated are so small that an evaporation at atmospheric pressure or rough vacuum would required extremely high temperature. The article below describes the history and the basics of Short‐Path Distillation and is giving an typical example of nowadays applications.     

Study of thermally coupled distillation systems for energy-efficient distillation

Distillation is one of the most widely used separation unit operations in process industries, although it is quite energy intensive. In many cases, the enormous energy requirements for distillation make it economically infeasible to carry out the separation. Thermally coupled distillation system (TCDS) is an advanced distillation method that provides significant energy savings of about 30% as compared with conventional distillation column sequences. The most well-known TCDS sequence, the Petlyuk configuration, has some operational challenges due to bidirectional vapour flow, which makes its implementation difficult in two-column mode. To overcome these limitations, a number of unidirectional vapour flow configurations have been proposed in the literature. The work on simulation analysis for such configurations is limited. In this paper, simulation models for two such configurations are developed, analyzed and compared with the Petlyuk and conventional distillation column sequences for separation of equimolar mixture of benzene–toluene–ethylbenzene.     

硝酸羟胺的热稳定性评估及热分解机理研究

为评估氧化剂硝酸羟胺的热稳定性,使用标准液体铝皿于3K/min、4K/min、5K/min加热速率下进行热分析。借助非等温DSC曲线的参数值,应用Kissinger法和Ozawa法求得热分解反应的表观活化能和指前因子,根据Zhang-Hu-Xie-Li公式、Hu-Yang-Liang-Xie公式、Hu-Zhao-Gao公式以及Zhao-Hu-Gao公式,计算硝酸羟胺的自加速分解温度和热爆炸临界温度,并对热分解机理函数进行了研究。设计了7条热分解反应路径,采用密度泛函理论B3LYP/6-311++G(d,p)方法对硝酸羟胺的热分解进行了动力学和热力学计算。计算结果表明,硝酸羟胺热分解的自加速分解温度TSADT=370.05K,热爆炸临界温度Tbe0=388.68K,Tbp0=397.54K,热分解最可几机理函数的微分形式为f(α)=17×(1-α)18/17。硝酸羟胺热分解各路径中,动力学优先支持路径Path 6、Path 5、Path 4和Path 1生成NO和NO_2,其次是Path 2、Path 7和Path 3生成N2和N_2O。温度在373K以下时,Path 1′反应无法自发进行,硝酸羟胺无法进行自发的热分解。从热力学的角度来看,硝酸羟胺在370.05K以下储存是安全的。     

Equivalence of the LP relaxations of two strong formulations for the capacitated lot-sizing problem with setup times

The multi-item Capacitated Lot-Sizing Problem (CLSP) has been widely studied in the literature due to its relevance to practice, such as its application in constructing a master production schedule. The problem becomes more realistic with the incorporation of setup times since they may use up significant amounts of the available resource capacity. In this paper, we present a proof to show the linear equivalence of the Shortest Path (SP) formulation and the Transportation Problem (TP) formulation for CLSP with setup costs and times. Our proof is based on a linear transformation from TP to SP and vice versa. In our proof, we explicitly consider the case when there is no demand for an item in a period, a case that is frequently observed in the real world and in test problems in the literature. The equivalence result in this paper has an impact on the choice of model formulation and the development of solution procedures.     

一种精馏型油分离器的实验研究

精馏是利用气液混合物中各组分挥发度的差异进行分离.本文研制的精馏型油分离器结合了传统油分离器的分离原理和精馏原理,以塔内恒定压力1000 kPa、入口温度62℃、R134a和PAG的质量比为7:3的进料条件用Aspen软件进行模拟,模拟可得通过精馏过程可除去二元混合物中的润滑油.为验证该油分离器的实际可行性,搭建了测试...     

Some new insights on informational entropy for water distribution networks

Several researchers have studied the use of informational entropy as a surrogate measure for the reliability of water distribution networks. The hypothesis is that the numerical value of network entropy in some way reflects the reliability of water distribution networks, and this appears to be supported by the analysis of some example water distribution networks. However, the precise relationship between the entropy value and some measures of reliability has not been formally established. The primary objective in this paper is to present an alternative methodology to calculate the informational entropy of water distribution networks. This methodology is termed as the Path Entropy Method (PEM), which provides some insights into the entropy of branching-tree networks and maximum-entropy flows of single-source networks. In addition, a quick method of computing the maximum-entropy value of single-source networks is presented and termed as the Simplified Path Entropy Method (SPEM).     

An Improved General Path Order

We define a strong and versatile termination order for term rewriting systems, called theImproved General Path Order, which simplifies and strengthens Dershowitz/Hoot's General Path Order. We demonstrate the power of the Improved General Path Order by proofs of termination of non-trivial examples, among them a medium-scale term rewriting system that models a lift control.     

A k-SHORTEST PATHS ROUTING HEURISTIC FOR STOCHASTIC NETWORK EVACUATION MODELS

Stochastic-network evacuation models require an optimization process to determine the best evacuation routes for a building's occupants. The optimization process developed and applied below is a heuristic based on the K-th Shortest Path Algorithm.     

专家系统在精馏塔故障诊断中的应用

精馏是空气分离过程中非常重要的一步。简单介绍了精馏塔故障诊断的必要性,主要阐述了专家系统的具体实现,包括知识库、推理机、人机界面等。将故障诊断技术和专家系统结合起来,能够有效的预防和避免事故,这将是故障诊断的发展趋势。     

碳纳米管填充硅橡胶膜回收大豆油/正己烷混合油的溶剂

采用膜分离技术取代当前的蒸发工艺回收植物油浸取工艺中的浸取溶剂,这一新技术不涉及相变,节能效果明显.为此,研制了单壁碳纳米管填充聚二甲基硅氧烷/聚偏氟乙烯(PDMS/PVDF)复合膜,通过接触角和SEM等方法对复合膜的表面进行表征.将制备的复合膜应用于从大豆油/正己烷(质量比1∶3)混合油中回收溶剂正己烷,考察了碳纳米管填充量和高温纯化处理对复合膜分离性能的影响.结果表明,碳纳米管经高温纯化预处理后,所制成填充复合膜的分离性能得到了较大的提高.     

Atmospheric transmittance of an absorbing gas. 5. Improvements to the OPTRAN approach

Improvements to a fast and accurate transmittance-calculation procedure, Optical Path TRANsmittance (OPTRAN), are described. The previous version computed a transmittance ratio for an absorbing layer. It required special attention to the interpolation methodology. The new approach reported here computes the absorption coefficient for an absorbing layer. This modified approach is not only simpler but also runs in one twentieth the time of the original OPTRAN approach with the same accuracy.     

A New Method of Global Path Planning for AGV

Path planning is important in the research of a mobile robot （MR）. Methods for it have been used in different applications. An automated guided vehicle（ AGV） , which is a kind of MR, is used in a flexible manufacturing system （FMS）. Path planning for it is essential to improve the efficiency of FMS. A new method was proposed with known obstacle space FMS in this paper. FMS is described by the Augmented Pos Matrix of a Machine （ APMM ） and Relative Pos Matrix of Machines （ RPMM）, which is smaller. The optimum path can be obtained according to the probability of the path and the maximal probability path. The suggested algorithm of path planning was good performance through simulation result： simplicity, saving time and reliability.     

DNA biosensor for the detection of hydrazines

A double-stranded (ds) DNA-coated carbon paste electrode is employed as a remarkably sensitive biosensor for the detection of hydrazine compounds. The sensor relies on monitoring changes in the intrinsic anodic response of the surface-confined DNA resulting from its interaction with hydrazine compounds and requires no label or indicator. Short reaction times (1-10 min) are sufficient for monitoring part-per-billion levels of different hydrazines. Applicability to untreated natural water samples is illustrated. The response mechanism is discussed, along with prospects of using DNA biosensors for quantitaing other important molecules and elucidating DNA interactions and damage.     

Availability assessment of a two-unit stand-by pumping system

The paper aims at assessing the availability of a critical pumping system of the Crude Distillation Unit of a refinery with recourse to the Markovian model. Actual field data on failure and the repair times have been collected and analyzed by fitting exponential distribution. Also a simulation model has been developed for assessing the system availability. The availabilities based on both the analytical and the simulation models have been compared. The simulation model has been used for predicting system availability for varying failure and the repair rates. The repair strategies for the increasing failure rate in order to attain the desired availability have also been discussed in the paper.     

The lost art of short communications in academia

Scientometrics - Short communications are an integral part of academic journal publishing since they serve as a forum for scholarly debate on recently published journal articles. Their prestige and...     

Dual path independent integrals in the boundary-value problems of cracks

Path independent integral J in Rice's theory is expressible as the rate of decrease of strain potential energy P with respect to crack length. The dual integral I is path independent, and is expressible as the rate of decrease of potential energy Q for stress field. Approximate upper and lower bounds of integrals are obtained by variational principles.     

Path integral solution for nonlinear systems under parametric Poissonian white noise input

In this paper the problem of the response evaluation in terms of probability density function of nonlinear systems under parametric Poisson white noise is addressed. Specifically, extension of the Path Integral method to this kind of systems is introduced. Such systems exhibit a jump at each impulse occurrence, whose value is obtained in closed form considering two general classes of nonlinear multiplicative functions. Relying on the obtained closed form relation liking the impulses amplitude distribution and the corresponding jump response of the system, the Path Integral method is extended to deal with systems driven by parametric Poissonian white noise. Several numerical applications are performed to show the accuracy of the results and comparison with pertinent Monte Carlo simulation data assesses the reliability of the proposed procedure.     

Distillation separation sequence optimization synthesis based on application of adaptive parallel tabu search

Abstract

Distillation separation sequences can be described as binary tree data structures, because of the analogous structures of distillation separation sequences and binary trees, and then by applying graph theory, the change mechanism of neighborhood separation points based on binary trees is built, correspondingly a kind of highly effective, evolutionary neighborhood structure is constructed. For the purpose of researching further tabu search algorithms, adaptive mechanisms and parallel techniques are introduced. That is, according to memory frequency information, the tabu length and the number of candidates are adaptively adjusted, and multitask parallel technology is realized through the arrangement of the search assignments. The example shows that adaptive parallel tabu searches can solve, successfully, large‐scale distillation separation sequence synthesis problems.