高氮量硝化棉的脱硝反应动力学研究

用实时测定凝聚相分解产物的固体原位反应池／快速扫描傅立叶变换红外光谱热技术研究了高氮量硝化棉的脱硝反应动力学,该反应的动力学参数用改良的Ｃｏａｔｓ－Ｒｅｄｆｅｒｎ法计算,根据所得结果,提出了在４０３－４６５Ｋ温度范围内描述高氮量硝化棉脱硝反应的微分动力学方程。     

高氮量硝化棉的脱硝反应动力学研究(英文)

用实时测定凝聚相分解产物的固体原位反应池/快速扫描傅立叶变换红外光谱热技术研究了高氮量硝化棉(14.14%N)的脱硝反应动力学。该反应的动力学参数(活化能和指前因子)用改良的Coats-Redfern法计算。根据所得结果,提出了在403～465K温度范围内描述高氮量硝化棉脱硝反应的微分动力学方程。     

基于ADAMS的重载液压机械臂动力学建模与仿真

针对七自由度重载液压机械臂,建立精确、高效的重载液压机械臂系统逆动力学模型。利用牛顿-欧拉递推法、Spong柔性关节模型和Stribeck摩擦模型建立机械臂动力学模型;利用Creo完成机械臂三维模型搭建并导入ADAMS分析计算。与试验结果对比,确定系数均大于0.6,与无摩擦纯刚体模型计算结果相比有明显提升,验证了建模方法的准确性。     

Research on the dynamic characteristics of a turbine flow meter

In the hardware-in-loop simulation of aero-engine control system where the real fuel regulator is engaged, it's crucial to measure the real-time flow rate. In view of this, a flow meter with high precision and fast response is important. In this paper, modeling and experiments are conducted to verify the dynamic characteristics of a turbine flow meter (TFM). For the modeling part, driving torque and resistance torques are analyzed to derive the kinetic equation of TFM. Simulation with the kinetic equation shows good dynamic performance of TFM. In experiments, a workbench is designed to generate step-type flow and sine-type flow for identification in time domain and frequency domain. Results show that the settling time for TFM is no more than 100 ms and its band-with is over 4.61 Hz. Compared with the settling time of a main fuel valve and the band-width of a main fuel control loop, that is, 1.2 s and 2 Hz respectively, TFM is considered to be adaptive to measure the fuel of aero-engine.     

AC corrosion - Part 1: Effects on overpotentials of anodic and cathodic processes

AC-induced corrosion is a controversial subject and many aspects of it need to be clarified, first and foremost, the mechanism and relationship between AC density and corrosion rate. This paper (Part 1) presents and discusses the effects of AC interference on kinetics parameters; the effects on corrosion rate and corrosion mechanism will be discussed in Part 2. Polarisation curves were obtained in different solutions (soil-simulating solution, 35 g L⁻¹ NaCl, 1 M FeSO₄, 1 M CuSO₄ and 1 M ZnSO₄) on different metallic materials (carbon steel, galvanised steel, zinc and copper) in the presence of AC interference (30-1000 A/m²).     

Inhibitive effect of diethylcarbamazine on the corrosion of mild steel in hydrochloric acid

Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), weight loss measurements and atomic force microscopy techniques were used to investigate the inhibitory effect of diethylcarbamazine (DECM) on corrosion of mild steel in HCl solution. The inhibitor showed >90% inhibition efficiency at 5.01 × 10⁻⁴ M. Results obtained revealed that inhibition occurs through adsorption of inhibitor molecules on metal surface without modifying the mechanism of corrosion process. Potentiodynamic polarization studies suggested that it is a mixed type inhibitor, predominantly controls cathodic reaction. Activation parameters (E_a, ΔH and ΔS) and thermodynamic parameters (, and ) were calculated to investigate mechanism of inhibition.     

Kinetic analysis of catalytic hydrodechlorination process of polychlorinated biphenyls (PCBs)

Catalytic hydrodechlorination (HDCl) of 2,4,4′,6-tetrachlorobiphenyl and 2,3,4,5-tetrachlorobiphenyl has been studied in the presence of a sulphided Ni–Mo/γ-Al₂O₃ catalyst. The reaction runs were carried out at constant temperature and pressure in a stirred batch reactor using hexadecane as the reaction medium. Temperature levels of T=250°C and T=300°C at a hydrogen pressure of P_H2=20 bar were tested. The results demonstrate that the HDCl process proceeds via an irreversible stepwise pattern. The kinetic constants of all observed intermediate HDCl steps were evaluated. The selectivity of HDCl reactions has been interpreted on the basis of electrophilic aromatic substitution mechanism. It shows that the HDCl rate is slower when carbon atoms adjacent to a substituted chlorine atom are bonded to other chlorine atoms. This depends on the inductive effect of chlorine atoms. It also shows that ortho-substitution is slower than meta- and para-substitution. In this case, both steric and electronic effects are probably relevant.     

Development and application of gas hydrate reservoir simulator based on depressurizing mechanism

Natural gas hydrates are known to occur in vast quantities at the ocean floor or in permafrost regions. In-situ hydrate contains great volumes of methane gas, which indicates a potential future energy resource. In this study, we have developed a three-dimensional, multi-phase (gas, water, and hydrate) flow finite-difference model by using implicit pressure explicit saturation technique in order to investigate simultaneous flow through ice-liked hydrate reservoir. The developed model is based on the depressurizing method as producing mechanism. The model evaluates local gas generation dissociated from the hydrate with the aid of kinetic dissociation theory proposed by Kim-Bishnoi. The computation of kinetic dissociation uses the empirical dissociation rate as a function of specific surface area between phases and pressure difference. With the developed model, a one-dimensional system has been simulated for analyzing the production performance of a hydrate reservoir and for investigating the effect of hydrate saturation on absolute permeability and relative permeability characteristics. Also, for the three-dimensional field-scaled reservoir system, a number of numerical exercises have been conducted to understand the effect of mass transfer and to characterize the flowing mechanism under the conditions of increased permeability resulting from the dissociation hydrate.     

Non-isothermal degradation kinetics of poly (2,2′-dihydroxybiphenyl)

Catalytic oxidative polymerization of 2,2′-dihydroxybiphenyl (DHBP) was performed by using Schiff base polymer-Cu (II) complex and hydrogen peroxide as catalyst and oxidant, respectively. According to size exclusion chromatography (SEC) analysis, the number-average molecular weight (M _n), weight-average molecular weight (M _w) and polydispersity index (PDI) values of poly (2,2′-dihydroxybiphenyl) (PDHBP) were found to be 37,500, 90,000 g mol⁻¹ and 2.4, respectively. The thermal degradation kinetics was investigated by thermogravimetric analysis in dynamic nitrogen atmosphere at four different heating rates: 5, 10, 15 and 20 °C min⁻¹. The derivative thermogravimetry curves of PDHBP showed that its thermal degradation process had one weight-loss step. The apparent activation energies of thermal decomposition for PDHBP as determined by Tang, Flynn–Wall–Ozawa (FWO), Kissenger–Akahira–Sunose (KAS), Coats–Redfern (CR) and Invariant kinetic parameter (IKP) methods were 109.1, 109.0, 110.0, 108.4 and 109.8 kJ mol⁻¹, respectively. The mechanism function and pre-exponential factor were determined by master plots and Criado–Malek–Ortega method. The most likely decomposition process was a D _n Deceleration type in terms of the CR, master plots and Criado–Malek–Ortega results.     

Development and application of kinetic models for the primary biodegradation of non-ionic surfactants

The growing concern for the environment is promoting the use of surfactant products from renewable sources such as fatty alcohol ethoxylates. The high production and use of these products implies the need to develop models that enable predictions of their behaviour in biodegradation processes. The biodegradation tests were carried out according to the OECD 301 E test for ready biodegradability. In this work, kinetic models of general application to surfactant biodegradation are developed, both for substrates that do not support growth and for those that do, considering a residual substrate concentration as not being biodegraded. The models were applied to three commercial non-ionic surfactants, fatty alcohol ethoxylates with different carbon-chain lengths and degrees of ethoxylation, also analysing the initial surfactant concentration.