Effect of nozzle diameter and its orientation on the flow pattern and plume dimensions in gas-liquid jet reactors

Gas-liquid jet reactors are widely used in chemical industries in various applications such as feed-water heaters, metal processing, and thermal energy sources, etc. In all these applications, the principal requirement for the design is a prior knowledge of jet shape and dimensions, which primarily depend upon the nozzle type, size, submergence and its orientation. In the present study, CFD simulations of non-reacting (steam-water) and reacting (SF₆-Li) jets have been carried out to understand the variation in plume dimensions of gas-liquid jet reactors. For condensation jet and reaction jet, the criteria have been developed to identify the plume boundary based on the hold-up profile of steam/SF₆ gas and the evaporated fuel. The effect of nozzle diameter and its orientation, nozzle gas velocity and bath temperature on the plume dimensions have been studied for both the types of jets. It was observed that the extent of increase in the plume length is always higher in the case of reaction jet as compared to the condensation jet for all the cases. The analyses also proved that, the availability of reactant is much better with the horizontal orientation which leads to stable plume length. The CFD model has been extended for the prediction of the flow pattern and its effect on the rate of condensation/reaction and plume dimensions for both the jet systems.     

表面活性剂协同作用下湿式过滤除尘实验研究

选取无烟煤粉为对象,对表面活性剂的相关性能以及无烟煤粉的润湿性进行研究,在此基础上设计并搭建了湿式纤维栅除尘系统,研究不同风速、喷雾压力、纤维栅目数以及复配表面活性剂的种类对除尘效率的影响。实验结果表明,表面活性剂可以有效降低水的表面张力,使得煤粉更容易被湿润;在除尘系统还未添加表面活性剂时,干式纤维栅对粉尘的单一过滤效率较低;添加喷雾装置后,除尘效率随喷雾压力的增大先提高,后趋于稳定,且总体效率均明显高于单一纤维栅除尘条件下的效率;纤维栅目数和除尘效率呈正相关,而当风速大于0.7 m/s后,由于纤维网上形成的水膜较多,会对风速产生一定的阻力,此时,风速对除尘效率的变化影响不明显;添加表面活性剂之后,发现LAB-35和X-100混合表面活性剂溶液的除尘效率最高,达到97.03%。     

Influence of temperature on the compaction of an organic powder and the mechanical strength of tablets

The purpose of this work consists in following the dependence of physical properties on the temperature during the compaction of an organic component. A special thermo-regulated die has been developed to realize uniaxial compression at different constant temperatures. This study has shown that a temperature change modifies the microstructures and the mechanical behaviour of the tablets. The measurement of the tablet porosity during the compression cycle allows us to conclude that temperature influences mainly the phenomena occurring during the isobaric stage of the compression cycle and not the ones during the pressure increase. On the other hand, during the pressure increase, the acoustical activity of the powder is reduced when temperature increases. The tensile strength of tablets realized at different temperatures was also studied and shows a maximum around 60 °C that can be explained by the SEM analysis of the microstructure of the tablets.     

Killing Effect of Ozone on House Dust Mites,the Major Indoor Allergen of Allergic Disease

This study examined whether ozone could kill house dust mites (HDMs), one of the most common causes of allergic diseases, and if an ozone application might be helpful in the environmental control of allergic patients. The experiments were performed in a small chamber (50 cm³), in which the continuous contact between the gaseous ozone and 40–60 live HDMs could be maintained during the reaction time (temperature=25°C and relative humidity=75%). Within the ozone range of 0.19–10.62% (v/v), the higher concentration dose resulted in a more rapid inactivation of the live HDMs. The CT value of ozone showed a linear relationship with the inactivation efficiency (%) of the live HDMs. From our results, it was found that a CT value 400 mg-min/L was required to obtain an almost 100% removal efficiency of the 40–60 live HDMs.     

Discrimination limit between mean gray values for the prediction of powder concentrations

Powder mixing is one of the most impacting steps in the handling of pharmaceutical powders for tablet production due to its strong effect in the properties and potency of the tablets. The monitoring of this process to detect the required mixing end point so that adequate properties and potency on the tablets are achieved requires continuous analysis of the powder concentration. However, its complex dynamics requires fast and accurate methods to determine the concentrations.Image analysis has already been shown to be suitable for this application. The objectives of this work were to further demonstrate its applicability to bright as well as dark powders, to determine the discrimination limit of the used vision system between powder's Mean Gray Values (MGV) in mixtures, and to develop a mathematical model to accurately predict calibration curves with minimum adjustable parameters. The study was emphasized for bright powders in the region of MGV between 255 and 140 and for dark powders in the region between 139 and 0. Mixtures of powders with difference in density greater than 0.3 g/cm³ showed considerably deviation in the prediction of concentrations. The discrimination limit between MGV attained was between 21 and 17 for both bright and dark powders. Below this range, unacceptable residuals larger than 8% w/w were obtained.     

Determination of sodium in biodiesel by flame atomic emission spectrometry using dry decomposition for the sample preparation

This work reports a method for sodium determination in biodiesel fuel by flame atomic emission spectrometry (FAES) using the dry decomposition for the sample preparation. Two calibration methods for the sodium quantification were evaluated: the standard addition and the external standard. In either cases significant matrix effects or loss of sensibility were not observed. For all determination, the external standard was chosen as a calibration method and the limit of detection (LOD) and limit of quantification (LOQ) were 1.3 and 4.3 mg Na kg⁻¹ of biodiesel, respectively. The accuracy method was checked by means of addition and recovery tests and recovered results varied from 93% to 110%. The relative standard deviations of the results were less than 4.0% in all cases. Afterwards, the performance method was checked in different biodiesel samples from vegetable and animal matrices collected in Mato Grosso State, Brazil. The sodium concentration in these samples varied from below LOQ to 28.7 mg Na kg⁻¹ of biodiesel. The simplicity, accuracy and precision of the proposed method suggest that it can be a good alternative for sodium determination in biodiesel samples.     

Method for the evaluation of the degree of pigment dispersion in powder coatings

The quantitative method for the evaluation of the degree of pigment dispersion in powder coatings is described here. The quantitative information is obtained using selective oxygen plasma etching, scanning electron micrography and image analysis. This procedure was used in order to analyse the influences of the input power of the extrusion equipment on the pigment dispersion in powder coatings. The correlation between the particle size distribution graphs and the energy input during the extrusion process is discussed and compared to the colorimetric analysis.     

利用声发射技术测量搅拌釜的淤浆悬浮高度

根据颗粒运动碰撞搅拌釜壁面产生声波的机理,结合声信号的频谱分析、小波分解和R/S分析,获得了代表颗粒运动的特征信号频段（d1、d2频段）。同时,基于声波特征信号频段能量沿搅拌釜轴向的规律性变化,提出了声波法测量搅拌釜淤浆悬浮高度的判据,即当声波特征信号频段能量或声波特征信号频段能量比出现阶跃性变化时的高度为淤浆悬浮高度。以水-玻璃珠体系为例,研究发现,无论是盘式涡轮还是桨式叶轮的搅拌桨,基于声信号测定淤浆悬浮高度的判据都能较好地得到验证,与目测法相比,其平均相对误差小于10 %,具有较高的精度。由此,获得了一种简单快捷、灵敏准确、非侵入式的搅拌釜淤浆悬浮高度测量技术,能够实现淤浆悬浮高度的实时监控。     

Impacts of wind velocity on sand and dust deposition during dust storm as inferred from a series of observations in the northeastern Qinghai-Tibetan Plateau, China

The monthly sand and dust deposition flux and modern dust storms were monitored in the northern Qaidam Basin of the Qinghai-Tibetan Plateau. The monthly sand and dust flux varied between 0.57 and 18.12 mg cm^− 2 month^− 1 from June 2003 to April 2005, and was well correlated with the monthly extreme wind velocity (V_extr) (r² = 0.60, n = 23). Sand and dust was mainly deposited in spring and early summer in the study area. The weight of settled sand and dust collected during dust storms exhibited a positive correlation with the mean 10-min wind velocity (r² = 0.60, n = 16) during the dust storms. For the typical dust storms, the weight and flux of settled sand and dust will linearly increase with the increasing wind strength and fluctuation amplitude of wind velocities. The coarse fraction (> 63 μm) also increases with them, in contrast, the fine-grained fraction (< 63 μm) decreases. It is plausible to assume that most of the fine-grained dust particles are lifted and transported far from the region under dust storm conditions, especially under the stronger and more variable wind conditions. The results demonstrate that the wind regime (strength and variability) is a key control on the sand and dust deposition during dust storm; dust can be emitted from the Qaidam Basin as one of dust source areas in China.     

Influence of electric field and emission current on the configuration of nanotubes in carbon nanotube layers

The influence of applied electric field (E_av) and emission current (I_FE) on the configuration of conical layers carbon nanotubes (CLNTs) grown by CVD on the edge of Ni foil has been investigated. TEM profile imaging revealed a high concentration of nanotubes near the foil edge surface, whereas on the nanotube layers’ outer surfaces single, non-oriented nanotubes with open ends free of catalytic particles, were observed. After sufficient electric field application many nanotubes became oriented towards the anode, but one or two of them were found to be always a few microns more extended. In situ SEM investigation showed that below E_av = 3.2–3.9 V/μm, emission was achieved at the expense of originally existing free nanotube ends. Configuration changes began at larger electric fields. On the observed foil edge length (14.6–17.8 μm, with an edge thickness of 200 μm) one or two nanotubes extended towards the anode and probably became the main emitters. Upon further increasing the field to E_av = 5.7–8 V/μm and at an emission current I_FE = 2 × 10⁻⁵ A these tubes disappeared (or essentially shortened). At E_av = 8 V/μm and higher and at an exposure time up to 40 min, several tens of extended nanotubes appeared, with one or two extended well beyond the others. This nanotube configuration pattern is connected with electrostatic screening between the nanotubes. Our interpretation of the data suggests that in the investigated range of E_av and I_FE, a limited number of nanotubes are emitting and these nanotubes are constantly changing as E_av, I_FE and exposure time increase.     

污水处理厂运行工况对温室气体排放的影响

市政污水处理厂是城市的重要基础设施之一,其因在运行过程中产生大量的CO₂、CH₄和N₂O等气体而被视为温室气体（GHGs）的重要来源之一,同时又因其减排潜力较大,引起了各界学者的广泛关注。GHGs减排需求正推动着污水处理厂朝着优化核心运行参数及资源能源回收的低碳方向发展。本文简述了污水处理厂中GHGs直接排放的主要环节和产生机理以及目前常用核算方法中存在的主要问题,并总结了污水处理厂运行工况的变化,包括温度、pH、进水C/N、污泥停留时间（SRT）、亚硝酸盐浓度、溶解氧（DO）浓度对其直接排放的GHGs的影响。分析表明进水C/N、DO浓度、pH和亚硝酸盐浓度对GHGs的排放影响较为明显且它们的变化更易于进行人为干预,人为减排潜力较大。最后总结了目前已有相关研究存在的主要问题以及对未来研究方向的展望,以期为污水处理厂优化运行工况和GHGs减排提供参考。     

Influence of water content in sub-flooring materials using adhesive on chemical compounds emission

Indoor air pollution is caused predominantly by emission of primary pollutants from building materials or finishing materials. Recently, there has been increasing interest in the new secondary pollutants caused by chemical reaction of the primary pollutants. In this study, the pollutants emitted from poly(vinyl chloride) (PVC) flooring material were measured, and 2-ethyl-1-hexanol (2E1H) and volatile organic compounds (VOCs) emitted from composite building materials made of PVC flooring material used as a self-leveling flooring were measured to identify the mechanism of emission of 2E1H. The moisture sorption isotherm was measured with a Magnetic Suspension Balance to examine the moisture content of the self-leveling flooring material and its effect on emission of 2E1H. 2E1H was emitted from the PVC flooring material through hydrolysis or oxidation of di-2-ethylhexyl phthalate (DEHP). The composite building material including the self-leveling flooring material emitted more 2E1H through hydrolysis over time. It was determined that liquid prevails in the self-leveling flooring material when the water content is higher than 4% and vapor prevails when the water content is lower than 4%. The prevailing liquid in the flooring material contributes to the increased emission of 2E1H and the prevailing vapor in the material did not cause increase in emission of 2E1H. It is considered that control of water in the self-leveling flooring material or concrete slab is very important in order to inhibit emission of 2E1H through hydrolysis of DEHP on the floor.     

脱硫除雾器对烟尘排放影响的研究

除雾器出口雾滴含固量影响烟尘排放达标值,本文通过对实验数据的分析,得出雾滴含固量约7.5%的结论,改变了国内业界一直认为除雾器出口雾滴含固量等同于塔内石膏含固量的观点。本文还针对国内外雾滴测量标准存在差异易引起误解的问题,对两种测量标准进行了对比,得出国标收集称重法测量值较VDI3679撞击法测量值约高10-20 mg/Nm3左右的结论。     

Shrinkage and Deformation of Agave atrovirens Karw Tissue during Convective Drying: Influence of Structural Arrangements

The influence of structural arrangements of Agave discs cut transversally (ADCT) and longitudinally (ADCL) on moisture loss, shrinkage, and shape was evaluated during convective drying by physical and image parameters.

ADCT showed lower drying and shrinkage rates than ADCL. The fractal exponent (d) relating volume and thickness of samples rose from 1.552 ± 0.126 to 2.394 ± 0.128 and from 1.662 ± 0.111 to 1.848 ± 0.070 for ADCT and ADCL, respectively, which indicates that shrinkage was nonisotropic for both cases.

Parameters considered for evaluating the changes of size and shape of Agave discs at macro- and microscopic levels during drying were projected area (PA), major length (ML), shape factor (SF), and fractal dimension of contour (FD_C). The values obtained for these parameters demonstrated that changes in shrinkage and shape of both samples were dependent on structural arrangements of the samples. During the drying of ADCT samples, which have short and rigid structures, pronounced creasing was observed compared to ADCL materials, which are mainly formed by long and rigid structures. Also, it was observed that orientation of fibers influenced shrinkage and deformation.     

Use of acoustic emission in the analysis of polypropylene failure caused by photodegradation

Photodegradation is among the most frequent causes for the low performance of polypropylene (PP) products during service. This type of failure has been investigated extensively throughout the years using conventional methods including infrared spectroscopy and molar mass measurements. The use of acoustic emission, conversely, is not a common technique to evaluate polymer behavior, even though showed to be very useful to detect and locate damage during loading, contributing to the understanding and, hence, to the prevention of failure. In this investigation, injection molded tensile bars were exposed to the ultraviolet radiation in the laboratory for periods of up to 35 weeks and then characterized by Fourier transform infrared spectroscopy, X-ray diffraction, tensile properties, and scanning electron microscopy. During tensile testing, the acoustic emission technique was applied to monitor parameters like intensity of hits, events, and energy released during deformation. The results confirmed the high efficiency of hindered amines light stabilizers to inhibit chemical degradation of PP and the high sensitivity of the neat polymer toward UV exposure. The several steps of polymer failure were detected by acoustic emission, being a very important tool to understand the differences in mechanical behavior of the types of samples under investigation. It showed the beginning of the failure process as well as significant events that occurred during the test, such as the formation of shear bands, cracking, and material fracture. These observations, combined with the traditional degradation monitoring procedures, allowed a good understanding of the effect of UV radiation on PP failure mechanism. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46943.     

水泥行业无组织排放粉尘治理现状研究

本文介绍了水泥厂内无组织排放粉尘的种类,危害及治理难点,进而提出相应的治理措施：生产工艺优化设计,产尘环节封闭处理,收尘器收集处理,水雾喷淋处理,云雾（干雾）抑尘处理,生物纳膜抑尘处理等新型技术处理方式。与传统的除尘方式相比,以新型技术为核心的综合治理方式节电可达75%,节水可达95%,抑尘率达到98%以上。     

基于声发射信号递归分析的气固流化床流型转变

利用声发射技术采集不同流化气速下流化床内颗粒与壁面碰撞的声信号,结合声能量及递归分析法研究不同流型下颗粒运动特征,得到鼓泡流态化到湍动流态化的临界转变速度及流型转变规律。特别是针对声能量分析无法准确区分不同床层高度处流型转变的不足,利用递归分析可有效预测系统周期性的特点,将声信号进行递归分析,研究了流化床不同位置的流型转变性质。结果表明,鼓泡流态化下颗粒运动的周期性较湍动流态化强,并能够清晰地检测到由鼓泡流态化向湍动流态化的流型转变速度,而且床层较低处的流型转变速度比床层较高处大。由此获得了一种便捷灵敏、安全环保的非侵入式流化床流型转变速度的测量技术,可用于对整个流化床内不同位置流型转变过程的实时在线监控。