钙钛矿型致密膜透氧过程的模拟研究

由于钙钛矿型致密膜的透氧机理十分复杂,影响因素较多,因此对过程进行数学模拟是实现其工业化应用的一个重要步骤,本文将影响其高温透氧过程的主体扩散和表面交换反应有机结合起来,同时考虑膜表面气固相交界层内的传递阻力,建立了钙钛矿型致密膜透氧过程的数学模型,并对模型的适用范围进行了理论分析,以便为钙钛矿型致密膜透氧过程的实验研究提供前瞻性预测。     

甲烷部分氧化制合成气膜反应实验与模拟

采用钙钛矿型致密透氧膜对甲烷部分氧化制合成气进行了膜反应实验研究，并建立了该膜反应的数学模型。模拟计算结果与实验结果吻合较好：通过该模型考察了绝热条件下的反应床层温度分布，以及恒温反应体系中温度、流量、反应器长度等因素对膜反应结果的影响。     

钙钛矿型混合导体BaCo_(0.7)Fe_(0.2)Nb_(0.1)O_(3-δ)的透氧性能

采用高温固相反应法制备钙钛矿型混合导体BaCo0.7Fe0.2Nb0.1O3-δ(BCFN)透氧膜,并通过SEM、XRD、O2-TPD等手段进行表征。实验考察了空气速率、氦气速率及温度对BCFN膜片透氧量的影响。研究发现膜的透氧量取决于两侧的氧分压差和氧离子在体相内的扩散。XRD的结果表明使用前后材料的相结构没有变化,证明BCFN作为透氧膜材料具有实际应用前景。     

钙钛矿型透氧膜及其在甲烷部分氧化中的应用

钙钛矿型透氧陶瓷膜是同时具有氧离子和电子导电性的功能无机膜,在纯氧分离和甲烷部分氧化膜反应器中具有重要的潜在应用.介绍了钙钛矿型透氧陶瓷膜的氧渗透原理、膜材料的结构性能及其在甲烷部分氧化制合成气中的应用研究进展,并对透氧膜所面临的挑战进行了论述.     

无机透氧膜的发展与应用

阐述了无机膜的优缺点及其透氧技术的研究与应用进展,并对无机膜透氧技术发展中存在和尚待解决的问题作了简要评述.     

管式致密透氧膜用于甲烷部分氧化制合成气的研究

采用钙钛矿型管式致密透氧膜反应器,在Ｎｉ／Ａｌ２Ｏ３催化剂上进行了甲烷部分氧化制合成气的实验研究,考察了进料气中甲烷的摩尔分数和反应温度对反应结果的影响,并对膜在反应条件下的稳定性作了分析     

亚油酸乳状液体系氧化模型与求解

研究了恒表面氧压静置式无限氧补偿条件下乳状液中亚油酸的氧化,通过综合考虑气液边界传质阻力、水相扩散、油水边界乳化剂膜边界层阻力、多不饱和脂肪酸(PUFA)自催化氧化反应动力学,建立了扩散-氧化数学模型。采用非对称正交配置法处理特殊边界,求解偏微分方程组,计算了氧化过程中乳状液中氧和亚油酸在垂直于液膜方向的浓度分布,计算方法快捷、有效;结合数学模拟试验和实验值,确定了气液界面氧的液膜传质系数和水相中氧的扩散系数。实验验证该模型能较好地拟合静置式无限氧补偿条件下乳状液中氧的扩散和亚油酸的氧化过程。     

无外界氧补偿条件下乳状液中多不饱和脂肪酸氧化模型

建立了在无外界氧补偿条件下乳状液中多不饱和脂肪酸(PUFA)氧化的数学模型。该模型综合考虑了乳化剂形成的液膜边界层阻力、PUFA自催化氧化反应以及油水相比表面积等因素的影响。实验验证了该模型能较好地拟合无外界氧补偿条件下乳状液中氧的扩散和亚油酸的氧化过程,并模拟计算了乳化剂膜传质系数和油水相比表面积等因素对扩散-氧化的影响程度。结果表明,乳化剂膜传质系数和油水相比表面积是影响乳状液中PUFA的氧化的主要因素。     

Ba_(0.9)Co_(0.7)Fe_(0.2)Nb_(0.1)O_(3–δ)–Gd_(0.1)Ce_(0.9)O_(2–δ)双相复合透氧膜的氧渗透性能

通过干压成型制备了Ba_(0.9)Co_(0.7)Fe_(0.2)Nb_(0.1)O_(3–δ)–Gd_(0.1)Ce_(0.9)O_(2–δ)(BCFN–GDC)双相复合透氧膜。研究了GDC掺入量对氧渗透性能的影响。结果表明:70%BCFN–30%GDC透氧膜的氧渗透速率最高。对70%BCFN–30%GDC透氧膜进行100 h稳定性测试,其透氧量稳定在0.33 mL/(cm~2·min),稳定性良好。进一步将70%BCFN–30%GDC透氧膜用于甲烷部分氧化重整(POM)研究,在900℃、(18 mL/min He+2 mL/min CH_4)的混合气吹扫下,100 h的稳定性测试过程中,CH_4转化率、CO选择性以及透氧量最终分别达到60%、84%和1.7 mL/(cm~2·min),并有缓慢增长的趋势。研究表明:70%BCFN–30%GDC透氧膜具有良好的透氧性能,在POM膜反应器方面具有重要的应用价值。     

富甲烷部分氧化制氢气混合导体材料的研究进展

综述了混合导体透氧膜材料用于富甲烷气体部分氧化制氢气的研究状况。介绍了混合导体材料用于富甲烷气体部分氧化制氢气的工作原理,BaCoO3基单相混合导体材料、及体相掺杂或使用催化剂对此类材料的改性研究,双相混合导体透氧膜材料。并对混合导体膜材料的应用前景和改进方向进行了展望。     

Protein biostimulant foliar uptake modeling: The impact of climatic conditions

Biostimulants are substances which promote plant metabolism and are able to increase yields of various crops. However, their efficiency at field can be affected by climatic conditions. A novel mathematical model based on diffusion transport mechanism is proposed to predict the biostimulant uptake at different climatic conditions. The main input model parameter is experimentally measured effective diffusion coefficient of the biostimulant. The model is applied to a biostimulant prepared from leather waste by enzymatic hydrolysis. Simulations show that climatic conditions have significant impact on biostimulant penetration and should not be neglected in biostimulant application and further research. The suggested model is able to explain observed differences between laboratory and field biostimulant investigations, as well as draw recommendations for protein biostimulant application. The model also shows that the theoretical tools of chemical engineering can be used for optimization of biostimulant performance. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

A Simple Model to Predict Formation of Bromate Ion and Hypobromous Acid/Hypobromite Ion through Hydroxyl Radical Pathway during Ozonation

A simple model is developed to predict the formation of bromate ion as well as hypobromous acid/hypobromite ion through the hydroxyl radical pathway. For simplicity of the model, hydroxyl radical concentrations are represented by the concentration ratio of hydroxyl radical to dissolved ozone under the different pH conditions. A kinetic analysis is conducted to evaluate the ratio under the different pH conditions based on the experimental data. The different extent of the ratio by one pH unit is found to be 3–4 times. This model can favorably simulate the formations of bromate ion as well as hypobromous acid/hypobromite ion in spite of the simplicity of the model. So it is likely that this model will be applicable to the prediction of bromate ion formation in water purification process such as drinking water treatment by introducing the concentration ratio of hydroxyl radical to dissolved ozone.     

Modeling of an industrial scale hydrodynamic cavitation multiphase reactor for Prileschajew epoxidation

The hydrodynamic cavitation multiphase reactor (HCMR) is emerging as a promising alternative for the intensification of liquid–liquid heterogeneous reactions, but research on HCMR modeling is lacking. In this article, an HCMR model was developed using Prileschajew epoxidation as the model system. First, based on experimental measurements of oil/water two-phase flow downstream of hydrodynamic cavitation devices, semiempirical correlations were proposed to describe the droplet size and droplet size distribution (DSD) as functions of flow conditions and geometry parameters. Then, with boundary conditions calculated by the DSD correlation, a droplet dynamics simulation in a reaction tank was performed by computational fluid dynamics coupled with population balance model to obtain the two-phase interfacial area. Finally, the acquired reactor model was substituted into an overall kinetic model, to simulate the epoxidation reaction in HCMR. Model predictions were verified by experimental results measured on an industrial scale HCMR.     

Spatial temperature profiles in an aluminum reduction cell under different anode current distributions

The development of a thermal model to estimate energy distribution in an aluminum reduction cell and its impact on local conditions based on anode current signals are presented. In the Hall–Héroult process, routine practices carried out during operation give rise to spatial energy imbalances and consequently temperature variation in the cell. This phenomenon has been ignored in thermal models developed to date as they are only concerned with overall process dynamics. Implementing anode current signals as model inputs along with the discretization method allows the change of spatial conditions caused by current distribution to be calculated. Simulation studies have been performed to investigate the cell thermal balance affected by anode shorting. The article shows the potential of using anode current signals as model inputs to compute spatial thermal conditions based on the proposed model structure that are not considered in traditional modeling approaches. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1544–1556, 2013     

Modelling of Inclusion Re‐entrainment During Filtration

During filtration, the release of deposited inclusions back to the main flow under certain conditions is called re‐entrainment. In this study, re‐entrainment was investigated experimentally in a pilot scale filter under continuous flow as well as interrupted flow conditions. Also, one‐dimensional mathematical model simulating the global behaviour of filter bed was developed and validated by comparing its predictions with the experimental results. This model solves the mass conservation equations for the inclusions. A deposition/re‐entrainment sub‐model was incorporated into the filter model. The model predictions were in good agreement with the experimental data.     

Influence of process parameters on extraction equilibria for the chiral separation of amines and amino‐alcohols with a chiral crown ether

Reactive extraction is studied as a promising chiral separation technique for commercial production scale. For chiral separation of amines and amino alcohols, a chiral crown ether was identified as a versatile enantioselective extractant. In this paper, the influence of various process conditions on the extraction performance is studied experimentally, and a predictive model is constructed based on the chemical and physical equilibria. It was found that the operational selectivity in one extraction step is mainly determined by the complexation constants between crown ether and enantiomers (which are dependent on solvent and temperature) and by the extractant concentration, whereas the distribution ratio is also strongly influenced by the pH. The model gives an excellent prediction of the operational selectivity and a good explanation for the system's responses to changes in process conditions. The model can be used as a basis for a multistage equilibrium extractor model and for conceptual process design. Under optimal process conditions, an operational selectivity >1.5 was obtained for five out of seven model compounds, with satisfying distribution ratios (D ～ 1–10). Copyright © 2006 Society of Chemical Industry     

An intrinsic kinetic model for liquid-phase photocatalytic hydrogen production

A kinetic study was accomplished to describe the photocatalytic production of hydrogen in liquid phase. A reaction mechanism and a kinetic model were proposed to predict the rate of hydrogen production, which is a function of light intensity, catalyst loading, substrate concentration, and time. To assess the capability of the proposed model, glycerol and ethanol were selected as representative hydrogen sources (substrates). The experimental data performed under different operating conditions, based on Box–Behnken experimental design, were used to train the developed kinetic model, optimize the parameters using genetic algorithms and check its accuracy. The analysis confirms the validity of the model under different operating conditions. In addition, the ability of the model to predict the rate of hydrogen production for other substrates, photocatalysts, and operating conditions was confirmed by comparing model predictions with experimental data from literature.     

振荡流反应器的物料停留时间分布模型研究

提出了一个基于马尔柯夫链（Markov chains）的考虑腔室间返混的振荡流反应器物料停留时间分布模型。通过对在内径50mm,长1．95m的振荡流反应器进行的理想脉冲示踪试验数据的统计分析,给出了模型的唯一参数回流比R的经验计算公式。发现在试验条件下,存在一个与最小回流比R相对应的振荡条件。这振荡条件可表示为振荡流雷诺数（Reo）与净流雷诺数（Ren）的比值ζ,其范围为1．6〈ζ〈2．5。     

Modeling Condensation and Evaporation on Fruit Surface

Rewarming of fruits and vegetables after cooling is characterized by heat and mass transfer processes, which leads commonly to condensation of water on the produce surface at temperatures below the dew point. This effect may affect the produce quality due to microbial growth at unfavorable environmental conditions. The amount of condensed water is a function of the produce surface temperature and of the surrounding conditions as air temperature, air humidity, and air flow. Under practical conditions, both the warming and the condensation are strongly affected by the packaging system used. Depending on the flow conditions close to the produce surface, parameters of heat and mass transfer under laboratory conditions were measured. A mathematical model was developed for the determination of the amount of condensed water on fruit surfaces, its reevaporation, and its total dwell time dependent on the environment air conditions. The model describes the heat and mass transfer processes on single fruits. The process of diffusion of humidity in air and proceed of surface temperature is the basis for the model.     

Process similarity and developing new process models through migration

An industrial process may operate over a range of conditions to produce different grades of product. With a data-based model, as conditions change, a different process model must be developed. Adapting existing process models can allow using fewer experiments for the development of a new process model, resulting in a saving of time, cost, and effort. Process similarity is defined and classified based on process representation. A model migration strategy is proposed for one type of process similarity, family similarity, which involves developing a new process model by taking advantage of an existing base model, and process attribute information. A model predicting melt-flow-length in injection molding is developed and tested as an example and shown to give satisfactory results. © 2009 American Institute of Chemical Engineers AIChE J, 2009