γ-氨基丁酸的生理作用与制备方法综述

简述了γ-氨基丁酸的基本性质与生理作用,另外比较了微生物发酵法,生物提纯法与化学合成法,同时又对化学合成法几种常用合成法作了比较,发现吡咯烷酮开环法中的吡咯烷酮与固体碱法比较占有优势,而且有较好的工业应用前景。     

电石法PVC透明片专用树脂的开发

对比了乙烯法与电石法氯乙烯单体的质量指标,找出了电石法单体的不足。通过采用固碱干燥法、分子筛脱水法提升单体质量,优化聚合工艺及配方体系,选用无毒环保的聚合助剂,生产出了电石法PVC透明片专用树脂,其性能与乙烯法PVC透明片专用树脂相当。     

化学共沉淀法制备陶瓷色料研究进展

综述了化学共沉淀法制备陶瓷色料工艺原理及流程,讨论了传统固相法制备陶瓷色料与化学共沉淀法制备陶瓷色料的优缺点,重点介绍了化学共沉淀法制备固溶体型陶瓷色料与包裹型陶瓷色料及其包裹模型,展望了化学共沉淀法的应用前景与研究方向。     

碳酸二苯酯生产技术进展

文章主要介绍了碳酸二苯酯的生产技术,重点介绍了光气法、苯酚氧化羰基化法、酯交换法三种方法。酯交换法包括碳酸二甲酯与苯酚酯交换法、草酸二甲酯与苯酚酯交换法和羧酸酯和碳酸二甲酯酯交换法三种方法。碳酸二甲酯与苯酚酯交换反应合成DPC法使用的原料及产物均无毒、无污染、无腐蚀性,被认为是最具有工业化前景的非光气合成路线。     

微孔-介孔复合分子筛的合成研究进展

概括了近几年微孔-介孔复合分子筛的合成研究工作,主要介绍了原位合成法、后合成法和纳米组装法。原位合成法主要包括单模板合成法与双模板合成法;后合成法主要包括孔壁晶化法、附晶生长法、水热重组法、碱处理法、机械混合法与包埋法。最后对微孔-介孔复合分子筛的发展远景进行了展望。     

纳米二氧化锰制备方法的研究进展

简单介绍了纳米二氧化锰晶型、各晶型的结构与性质及应用领域。主要介绍了水热法、固相法、共沉淀法、溶胶凝胶法与电化学法制备纳米二氧化锰的研究进展,并对纳米二氧化锰制备方法的发展进行了分析与探讨。     

KCA法脱硫与888法脱硫的应用比较

介绍了应用KCA法脱硫与888法脱硫装置状况和使用效果,并对KCA法脱硫与888法脱硫的应用进行比较,得出了在对高硫气体脱硫时,KCA法脱硫具有高效脱硫的能力和显著的经济效果。     

PBT技术经济分析及原料开发

本文分析了国外PBT发展快的原因及前景;对生产工艺路线(酯交换法与直接酯化法)与过程(间歇法与连续法)以及主要原料1.4—丁二醇的制法做了技术经济分析,同时提出了我国开发PBT的建议。     

我国酯交换法合成碳酸二苯酯技术研究进展

介绍了碳酸二甲酯与苯酚酯交换法、草酸二甲酯与苯酚酯交换法和羧酸酯和碳酸二甲酯酯交换法等合成碳酸二苯酯的技术进展,指出了其今后的发展方向。     

多种技术与Fenton法联合在废水处理中的应用

Fenton法是一种在处理难生物降解有机物废水方面有独特优势的废水处理技术。Fenton法、微波法、超声法、吸附法、混凝法、生物法,每种技术在废水处理方面都各有特点,Fenton法与这些技术联用时能有效提高废水的处理效果。Fenton法与多种技术联合处理废水是难降解废水研究的发展方向。文章介绍了Fenton法与多种技术联用在废水处理中的应用。     

Improved magnetic particle tracking technique in dense gas fluidized beds

Noninvasive monitoring of multiphase flow is rapidly gaining increased interest. More specifically noninvasive particle tracking techniques have received a lot of attention in recent years to study dense granular flow. However, these techniques are usually quite expensive and require strict safety measures. An improved magnetic particle tracking (MPT) technique for dense granular flow will be presented in this article. The improvements of the analysis technique for MPT will be demonstrated and rigorously tested with a three‐dimensional system and two‐dimensional sensor system. The strengths and limitations of the MPT technique will also be reported. Finally, the results of the MPT are compared with data obtained from a combined particle image velocimetry and digital image analysis technique. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3133–3142, 2014     

Modelling and simulation of particle re-suspension in a turbulent square duct flow

The ability of a Reynolds-averaged Navier-Stokes (RANS) approach, coupled with a Lagrangian particle tracking technique, to predict particle re-suspension rates in a high Reynolds number duct flow has been assessed for spherical particles over a range of sizes, with results compared with predictions based on large eddy simulation. In general, there is reasonable agreement between the two predictive techniques in regards to the locations where maximum re-suspension rates occur in the lower half of the duct, with both methods predicting the preferential re-suspension of smaller particles. The main difference between the approaches is in the magnitude of the re-suspension rate, with RANS predicting a greater variability across the duct. These differences are attributable to the method used to derive instantaneous fluid velocities, required by the Lagrangian particle tracking technique, from the RANS solutions, coupled with smaller inaccuracies due to the turbulence model employed as the basis of the RANS solutions.     

Magnetic monitoring of a single particle in a prismatic spouted bed

In this work a non-intrusive measuring technique for continuous tracking of a magnetic marked particle during fluidization in a prismatic spouted bed is presented. The magnetic monitoring system provides besides the spatial coordinates x, y and z the orientation of the particle, whereby the trajectory, the velocity, the acceleration as well as the rotation of the particle are obtained. It will be demonstrated that the characteristic particle trajectories and particle velocity distributions in dependency of the gas throughput and of the bed mass can be detected in this type of spouted bed. Furthermore, a calculated particle velocity distribution obtained by a CFD continuum simulation will be favorably compared with a measured distribution.     

Microstructure of some rubber-reinforced polystyrenes

An electron-microscope technique is presented to permit detailed examination of the fine structure of the rubber particles in reinforced polystyrenes. Several rubber-modified polystyrenes, prepared by different methods, have been examined by this technique, and the resulting photomicrographs compared with those of the previously used phase contrast method. Polymers produced by the agitated-solution process are examined in more detail. It is shown that the rubber particle fine structure is basically unaltered as the amount or type of rubber is changed or if the polymer is diluted by mechanically blending with polystyrene. It is characterized by the presence of numberous polystyrene occlusions within the particle.     

Comparison of Experimental and Computational Particle Trajectories in a Stirred Vessel

A particle trajectory in a turbulent flow is measured by a 3-dimensional tracking technique and compared with the pattern calculated by a Lagrangian model. The geometry chosen is a standard vessel provided with a Rushton turbine. First, the flow field is simulated using the commercial Fluent package. The impeller global performance is determined. The dimensionless numbers are calculated: t_c, N_QP, N_P. These results are validated by LDV data. The numerical particle trajectory is compared to the experimental trajectory, and the reliability of the numerical trajectory is proved. Finally, some news tools for analyzing the flow are presented. Useful information is included in the long particle trajectory, which enables one to compute a probability of presence. The fluid dynamic behavior is visualized by Poincaré sections.     

Hydrodynamic modelling of dense gas-fluidised beds: comparison and validation of 3D discrete particle and continuum models

A critical comparison of a hard-sphere discrete particle model, a two-fluid model with kinetic theory closure equations and experiments performed in a pseudo-two-dimensional gas-fluidised bed is made. Bubble patterns, time-averaged particle distributions and bed expansion dynamics measured with a nonintrusive digital image analysis technique are compared to simulation results obtained at three different fluidisation velocities. For both CFD models, the simulated flow fields and granular temperature profiles are compared. The effects of grid refinement, particle-wall interaction, long-term particle contacts, particle rotation and gas-particle drag are studied. The mechanical energy balance for the suspended particles is introduced, and the energy household for both CFD models is compared. The most critical comparison between experiments and model results is given by analysis of the bed expansion dynamics. Though both models predict the right fluidisation regime and trends in bubble sizes and bed expansion, the predicted bed expansion dynamics differ significantly from the experimental results. Alternative gas-particle drag models result in significantly different bed dynamics, but the gap between model and experimental results cannot be closed. In comparison with the experimental results, the discrete particle model gives superior resemblance. The main difference between both CFD models is caused by the neglect of particle rotation in the kinetic theory closure equations embedded in the two-fluid model. Energy balance analysis demonstrates that over 80% of the total energy is dissipated by sliding friction. Introduction of an effective restitution coefficient that incorporates the additional dissipation due to frictional interactions significantly improves the agreement between both models.     

Manufacture of submicron drug particles with enhanced dissolution behaviour by rapid expansion processes

In the case of pharmaceutical substances the particle size is quite important since it can limit the bioavailability of poorly soluble drugs. As an example we can refer to the data obtained for Griseofulvin. In 1962 Atkinson has studied the concentration of the drug in the blood, taken from healthy volunteers at given intervals of time after dosing, as a function of its specific area. The quantity absorbed for a particle size of 2.7 μm is twice as high compared with a particle size of 10 μm. The present article gives a survey of published knowledge about particle and product design with focus on the RESS process and some promising modifications of this technique. Experimental results confirm that each of these processes is a promising technique for the formation of submicron particles (≤100 nm) and that the improved dissolution behaviour is influenced by particle size, surface area, and wettability of the processed powders as well as by the pH-value of the dissolution media.     

Analysis of FBRM measurements by means of a 3D optical model

Continuous process monitoring is desirable for many particulate processes such as the crystallization of active pharmaceutical ingredients. Only an in-line measurement technique can achieve such a continuous monitoring.A popular in-line measurement technique, which can be applied without dilution, is the focussed beam reflectance measurement (FBRM). However, FBRM is at this point mainly used for qualitative measurements. The measured chord length distribution is different from a particle size distribution. For a quantitative measurement a sound understanding of the measurement principle is necessary. In this paper, an optical model of the FBRM probe and a three-dimensional simulation of the measurement are presented.A three-dimensional particle field is generated with a Monte-Carlo approach. The back scattered light intensity is calculated as a function of the position of the laser beam with respect to this particle field. A vector of scattering intensities is obtained for a given laser path. This vector is processed with the simulated electronics of the Lasentec FBRM system. The output of this processing step is a chord length distribution which can be compared to the output of the Lasentec FBRM system.Simulation studies with mono-disperse polystyrene particles of different sizes and concentrations are conducted and compared to measurements of a Lasentec D600L FBRM probe. With the presented model yet unexplained massive over-estimation of small particles and concentration-dependent changes in the chord length distribution can be described.     

Hydrodynamic modelling of dense gas-fluidised beds: Comparison of the kinetic theory of granular flow with 3D hard-sphere discrete particle simulations

A novel technique to sample particle velocity distributions and collision characteristics from dynamic discrete particle simulations of intrinsically unsteady, non-homogeneous systems, such as those encountered in dense gas-fluidised beds, is presented. The results are compared to the isotropic Maxwellian particle velocity distribution and the impact velocity distribution that constitute the zeroth-order Enskog approximation for the kinetic theory of granular flow. Excellent agreement with the kinetic theory is obtained for elastic particles. The individual particle velocity distribution function is isotropic and Maxwellian. A good fit of the collision velocity distribution and frequency is obtained, using the radial distribution function proposed by Carnahan and Starling (J. Chem. Phys. 51 (1969) 635). However, for inelastic and rough particles an anisotropic Maxwellian velocity distribution is obtained. It is concluded that the formation of dense particle clusters disturbs spatial homogeneity and results in collisional anisotropy. Analysis of the impact velocity shows that, in dense gas-fluidised beds, not all impact angles are of equal likelihood. The observed anisotropy becomes more pronounced with increasing degree of inelasticity of the particles.     

Influences on the Particle Size Distribution of Diesel Particulate Emissions

Particulates give great concern for mankind health. Especially the nano size particles are under discussion. Therefore, the particle size distribution from the combustion chamber to tail pipe emissions are of great interest. With the aim of scanning mobility particle sizer the number weighted particle size distributions were measured in the combustion chamber as well as in the exhaust gas up and downstream of aftertreatment systems. Using the identical particle measurement technique results can be compared without changing the particle size definition. The particles in the cylinder of a modern serious DI diesel engine were sampled with a time resolved fast gas sampling valve. The Soot particles formed in the cylinder during the early combustion phase are oxidized by about 99% in the late combustion/early expansion phase, whereas the soot particle sizes distribution in the cylinder at the end of the expansion phase are equal to that in the tail pipe. DI diesel engines with high pressure injection system emit less numbers of particle with in tendency greater sizes compared to IDI diesel engines. Oxidation catalysts do not influence particle size distribution but particulate traps reduce particle number by up to two orders of magnitude. Detail analysis shows that an increase of nano size particle number downstream of an aftertreatment device results from artifacts.