Studies on the inhomogeneous nature of the silent discharge reactor: Part 1. Experimental investigations

Commercial application of the silent discharge reactor is confined to its use for the manufacture of ozone. Free electron concentration in the reaction space is determined by the occurrence of electron avalanches between the dielectrics and generation of transient primary reaction zones (PRZ) where the electron –- molecule collision reactions take place. Experimental studies have been carried out in order to increase the frequency of occurrence of PRZs as well as to enhance the mean electron energy within an individual avalanche. The dielectric surface has been treated with P.T.F.E. to reduce the recombination rate of O-atoms. Results indicated that both methods of modifying the current pulse train have influenced the pattern of utilization of electrical energy. Similarly a P.T.F.E. coated dielectric has been found to be more efficient than an ordinary glass dielectric.     

Studies on the inhomogeneous nature of the silent discharge reactor: Part 3. A multi-zoned flow model

The reaction space of a silent discharge reactor consists of two distinct components, viz. (1) the collection of primary reaction zones (PRZ) or discharge streamers where, under the influence of free electron avalanches, primary electron molecule collisions take place and (2) the remaining reaction space which provides for secondary or quenching reactions between activated species and gas molecules. A flow model based on this concept has been proposed which accounts for the intrinsic chemical activity of the PRZs as well as their random distribution, spatial location, transient nature, and temperature field. Experimental results obtained on laboratory ozonizers have been examined to show the validity of the proposed model.     

Avalanching of granular material in a horizontal slowly rotating cylinder: PEPT studies

A detailed analysis of the motion af a single particle in a slowly rotating horizontal cylinder in the avalanching mode has been carried out using the positron emission particle-tracking technique to follow the motion of a tagged particle. Cylinders of diameters 240, 390, and 488 mm, and sand of mean diameter 500 μm were used; the tracer was an irradiated sand particle. It was found that a tracer particle rotates with the bed in rigid body motion and then traverses the active surface region in a series of discrete avalanches before being absorbed once again into the rigid body rotation. The mean number of avalanches required to traverse the active region decreased from 3.5 to 4 at low rotational speed to 1 at higher rotational speed at the transition to the rolling mode.     

Characterization of boron doped diamond epilayers grown in a NIRIM type reactor

Boron doped diamond layers have been grown on (100) single crystal substrates in a wide range of boron concentration. The boron doped layers have been electrically and optically characterized. Boron doped layers with Hall mobility closes to natural diamond holes mobility have been obtained. The films morphology has been observed by scanning electron microscopy and their purity has been assessed by cathodoluminescence. Fourier Transform Photocurrent spectroscopy results show the evolution of the photo-ionization onset and the excited states as boron concentration in the films increases.     

Interacting coalescence avalanches in a 2D droplet assembly

A 2D droplet assembly can undergo destabilization through a series of coalescence events that propagate like an avalanche. Multiple avalanches can get triggered during the course of an experiment, which interact as they propagate in the system. In this article, the avalanching phenomenon as a function of the number of avalanches triggered is investigated. The dynamics of interaction between the avalanches is studied as a function of the propensity for propagation of an avalanche and the proximity and asynchrony in triggering. This article shows that when the propagation propensity of avalanches is small, they are uncorrelated and independent allowing one to predict the effect of multiple triggers by a superposition of the results of the single-avalanche case. However, for large propagation propensities, the avalanches compete for droplets to coalesce due to the finite-sized nature of the droplet assembly and behave like a single autocatalytically propagating avalanche. © 2018 American Institute of Chemical Engineers AIChE J, 65: 1111–1118, 2019     

Characterization of nanofibrous carbon produced at pilot-scale in a fluidized bed reactor by methane decomposition

Carbon nanofibers (CNFs) production in the range of hundreds of grams per day has been achieved in a fluidized bed reactor (FBR) by methane decomposition using a nickel based catalyst. The characterization of the carbon produced at different operating conditions (temperature, space velocity and the ratio of gas flow velocity, u_o, to the minimum fluidization velocity, u_mf) has been accomplished by means of X-ray diffraction (XRD), N₂ adsorption, temperature-programmed oxidation (TPO), scanning electron microscope (SEM) and transmission electron microscopy (TEM). It has been concluded that the structural and textural properties of the CNFs obtained in the FBR are analogous to the ones obtained in a fixed bed reactor at a production scale two orders of magnitude lower. Thus, FBR can be envisaged as a promising reaction configuration for the catalytic decomposition of methane (CDM), allowing the production of high quantities of CNFs with desirable structural and textural properties.     

Modeling and numerical analyses of microwave plasmas for optimizations of a reactor design and its operating conditions

A model of MW plasmas has been developed, which prescribes distributions of electron temperature as well as electron number density under self-consistent electromagnetic field. In the proposed model, an energy balance equation is algebraically solved, and only electron continuity equation is essentially coupled to the Maxwell equations. Preliminary simulations are carried out and the results are compared with corresponding results obtained by using other model.     

Surface study of iridium buffer layers during the diamond bias enhanced nucleation in a HFCVD reactor

The BEN nucleation of diamond on iridium substrates has been studied in a hot filament reactor. Without a prior BEN stage, no diamond nucleation could be detected. Nucleation is promoted only if a BEN step is applied before the CVD growth with nucleation densities up to 5 10⁹ cm⁻². The present study focuses on the early stages of BEN to better understand its specific role. In this way, samples have been in situ characterized using electron spectroscopies (XPS, AES, ELS) and further investigated by HR-SEM, AFM, Nano-Auger and Raman spectroscopy. A very different behaviour in the interface formation has been observed, as compared to silicon. First, a substrate roughening takes place during the cleaning step. Second, the formation of a graphite layer was systematically observed, with or without the BEN stage, in the early stages of CVD synthesis. Its crystallinity has been studied from the Raman experiments. The study of the XPS Ir 4f peaks supports a weak chemical bonding between graphite and iridium. Finally, after the BEN stage, spatially resolved Nano-Auger and Raman measurements revealed the presence of diamond nanocrystals.     

三峡库区(湖北段)崩滑地质作用形成的地质背景

长江三峡库区地质灾害频繁发生与地质构造背景关系密切,崩滑地质作用是库区较为常见的地质灾害,大型崩滑体常常对生存环境造成极大破坏。崩滑地质作用主要受构造-岩性-地貌-气象水文等综合因素控制,其中,地质构造、岩性是崩滑地质作用发生和分布的内在控制因素,新构造运动及气象水文的变化是地质灾害发生的诱因。研究三峡库区地质背景特征是认识大型崩滑体分布规律的重要基础,查明区内崩滑地质作用与地质背景关系可以为崩滑地质灾害的防治提供基础资料。     

Reactions of benzene in a microwave discharge reactor

A study has been made of the reactions of benzene in a continuous-flow microwave-discharge reactor. The distribution of reaction products was found to depend on the reactor pressure and flow-rate. By accounting for all reaction products (solid, liquid and gas) an overall mass balance was obtained. The reactions are not the result of simple pyrolysis. The insertion of nickel wire into the reactor enhanced the reactions which proceed via a radical—radical mechanism. The addition of carbon dioxide to the benzene feed appeared to retard reactions which involve highly energetic ionisation processes. Thus, the presence of carbon dioxide changed the reaction selectivity. The carbon dioxide did not react chemically. Comparison with other work with benzene shows that the behaviour of this reactor system is significantly different from the behaviour of reactors which operate at a lower frequency. It is suggested that the distribution of electron energies in the microwave discharge is narrower than the energy distributions which are encountered in lower-frequency and d.c. discharges.     

流化床与沸腾床内部微生物群落演变与分析

用流化床反应器和沸腾床反应器处理焦化废水,对两种反应器运行效能及微生物群落变化进行对比研究。结果表明,提高污泥负荷后流化床COD去除率优于沸腾床反应器。提高进水污泥负荷对沸腾床内微生物的冲击更大,致使其种群丰富程度下降明显。研究结果证明,流化床在宏观去除率、维持菌种丰富度方面具有较大优势。     

Diffusion limitation effects in the washcoat of a catalytic monolith reactor

In monolith reactors with catalytic washcoat, intraphase diffusion effects have often been underestimated. This paper presents numerical simulations of diffusion/reaction in the washcoat of a catalytic monolith reactor. The problem is solved in two dimensions for the washcoat geometry obtained in a 1-mm square monolith channel, as revealed by scanning electron microscopy. For the oxidation of carbon monoxide, propane or methane diffusion limitation can be substantial at typical operating conditions. The two-dimensional solution is compared to a one-dimensional approximation. The latter approximation for the real washcoat is valid provided that the characteristic length is selected carefully. This value is different from the characteristic length of the two-dimensional washcoat. The characteristic length of a two-dimensional geometry is not sufficient in itself to describe all washcoat geometries. It is predicted that the application of a diffusion barrier of 4–6 μm of inactive washcoat may be used to lower the rate of reaction in the inlet region of the monolith reactor.     

Synthesis of ordered carbon replicas by using Y-zeolite as template in a batch reactor

Ordered carbon material that preserves the structural regularity of the parent zeolite template was synthesized by using ethylene as carbon source and HY-zeolite in a batch reactor. The obtained carbons exhibit a high degree of microporosity having BET surface areas between 1400 and 2400 m²/g. The morphology and structure of the prepared carbon materials were investigated by elemental analysis, X-ray diffraction measurements, scanning electron microscopy and nitrogen adsorption. The results were compared with the parent zeolite template. The carbonization procedure of precursor-encapsulated samples was investigated by thermal analysis and it has been found that the resulting quality of the ordered carbons strongly depends on the heat treatment of the composite material.     

Fuzzy control of a semi-batch copolymerization reactor

This study describes the development of a rule-based fuzzy controller for regulating the copolymer composition (F₁) in a semi-batch solution copolymerization s. The membership functions, fuzzy ranges for errors and the controller output are defined. A fuzzy rule base has been constructed relating error to controller output based on the operator's knowledge. The performance of the fuzzy controller has been evaluated by simulating the semi-batch copolymerization reactor by means of a mathematical model. The fuzzy controller developed at one operating condition has also been tested for other operating conditions.     

Mixing characteristics in the torus reactor

The hydrodynamic characteristics of propeller-induced toroidal flow in a loop reactor were investigated by performing an RTD analysis. The experimental determination of circulation time allows the calculation of the mean axial velocity with respect to the rotational speed of the impeller. RTD measurements are interpreted with the aid of the dispersion plug flow model, and it is shown that axial dispersion is relatively weak in the torus reactor. The mixing time was also determined experimentally and related to the circulation time. A direct relationship between mixing time and axial dispersion coefficient has been established, leading to a correlation for the mixing time in a torus reactor.     

Variable measurement structures for the control of a tubular reactor

The feasibility of the variable measurements structure is investigated within the framework of controlling a tubular chemical reactor. An on-line sequential analysis of the temperature measurements along the length of the reactor, allows a fast and time-adaptive selection of the best measurements to be used in a low order, simple and robust control scheme. The approach has been developed for both static and dynamic cases. It is based on a recursive computation of the state estimate errors. Its theoretical and computational simplicity makes it attractive for on-line implementation. The procedure has been applied for the adaptive tubular reactor under pseudo-steady state and dynamic conditions with very encouraging results.     

生物柴油连续化生产设备及工艺进展

“碳中和”目标提出后，各行各业都在寻求减少碳排放的方法，生物质能源的使用是实现碳中和目标的重要手段之一。生物柴油以其优良的燃烧性能及环保性能成为一种较为理想的生物质燃料，其生产工艺是近年研究热点。连续化生产工艺对生物柴油的规模化制备与推广有着重要意义。目前连续化制备生物柴油的反应装置主要有微反应器、固定床反应器、管式反应器、膜反应器。本文综述了近年来国内外采用连续化工艺制备生物柴油的研究进展。这些研究表明，通过优化反应器结构、使用助溶剂、提高催化剂活性等均可提高生物柴油的收率。最后本文还分析了各反应器存在的不足，并提出了相应的建议，对生物柴油连续化生产进行了展望，以期为低成本、低能耗的生物柴油生产提供参考。     

Performance comparison of ZnO photocatalyst in various reactor systems

BACKGROUND: Owing to difficulties in catalyst recovery from slurries the deposition of a catalyst on suitable supports has been investigated extensively in recent years. The support material and the method of coating influence the activity. Photocatalytic decolorization of methyl orange (MO) and Rem Red F3B (RRF3B) was conducted in various reactor systems including a slurry reactor, ZnO thin film coated tube reactor and fixed bed reactor filled with ZnO coated ceramic or glass supports of various geometries. RESULTS: ZnO coating was carried out by the ammonium zincate deposition method. ZnO thin films were quite stable in acidic and basic media and resistant to photocorrosion. Various methods including scanning electron microscopy (SEM) and X‐ray diffraction (XRD) were applied for the physical characterization of thin films. The XRD patterns of ZnO thin film exhibit a wurtzite (zincite) crystal structure. SEM analysis revealed the granular morphology of ZnO film with a particle size of 300–400 nm. CONCLUSION: Photocatalytic activities were determined kinetically by calculating first‐order rate constants, which were also related to process variables by regression analysis. From the viewpoint of decolorization efficiency, the coated tube reactor (6 mm i.d.) showed the highest activity, which was equal to that of a powder catalyst loading of 300 mg dm^?3 for MO and of 200 mg dm^?3 for RRF3B. Copyright © 2010 Society of Chemical Industry     

环管反应器轴流泵轴功率波动的分析

环管反应器轴功率波动,尤其为一环反应器轴流泵轴功率波动,此种现象在液相环管反应生产中表现尤为突出,并且一直困扰着聚丙烯行业,大庆30万t聚丙烯/年装置经首次开工成功后,至今已运行一年,期间多次出现环管轴功率波动现象,为此装置技术人员采取了多种措施,并进行了深入的分析.     

Catalytic reduction of nitrate on Pt-Cu and Pd-Cu on active carbon using continuous reactor: The effect of copper nanoparticles

The increasing pollution of natural sources of drinking water encourages the development of new emerging technologies and processes for water remediation. This work deals with the study of catalytic reduction of contaminated waters containing nitrates (60 ppm) in a continuous reactor working at room temperature and atmospheric pressure and using hydrogen as reducing agent. Optimal proportions of Pt-Cu and Pd-Cu in bimetallic catalysts on activated carbon, obtained by wetness impregnation, have been found. Besides, novel catalysts obtained from copper nanoparticles doped with Pd or Pt and supported on activated carbon, have also been studied. For all catalysts the Pt-Cu pair seems to be more selective in the transformation of the nitrates ions to nitrogen compared to Pd-Cu pair. Furthermore, considering the noble metal amount, the bimetallic nanosphere catalysts are more active (between 20 and 50) than the impregnated ones. The catalysts have been characterized by hydrogen chemisorption, BET, X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. During the reaction, a considerable amount of the noble metal in its oxidised form has been detected. Based on this result an additional step to the generally accepted reaction mechanism of the nitrate reduction has been proposed.