Modelling-based Optimisation of the Direct Synthesis of Dimethyl Ether from Syngas in a Commercial Slurry Reactor

In the present study, we developed a multi-component one-dimensional mathematical model for simulation and optimisation of a commercial catalytic slurry reactor for the direct synthesis of dimethyl ether （DME） from syngas and CO2, operating in a churn-turbulent regime. DME productivity and CO conversion were optimised by tuning operating conditions, such as superficial gas velocity, catalyst concentration, catalyst mass over molar gas flow rate （W/F）, syngas composition, pressure and temperature. Reactor modelling was accomplished utilising mass balance, global kinetic models and heterogeneous hydrodynamics. In the heterogeneous flow regime, gas was distributed into two bubble phases： small and large. Simulation results were validated using data obtained from a pilot plant. The developed model is also applicable for the design of large-scale slurry reactors.

Dynamic corner frequency in source spectral model for stochastic synthesis of ground motion

The static comer frequency and dynamic comer frequency in stochastic synthesis of ground motion from fi- nite-fault modeling are introduced, and conceptual disadvantages of the two are discussed in this paper. Furthermore, the non-uniform radiation of seismic wave on the fault plane, as well as the trend of the larger rupture area, the lower comer frequency, can be described by the source spectral model developed by the authors. A new dynamic comer frequency can be developed directly from the model. The dependence of ground motion on the size of subfault can be eliminated if this source spectral model is adopted in the synthesis. Finally, the approach presented is validated from the comparison between the synthesized and observed ground motions at six rock stations during the Northridge earthquake in 1994.

Modeling and optimization of industrial Fischer–Tropsch synthesis with the slurry bubble column reactor and iron-based catalyst

To optimize industrial Fischer-Tropsch （IT） synthesis with the slurry bubble column reactor （SBCR） and iron- based catalyst, a comprehensive process model for IT synthesis that includes a detailed SBCR model, gas liquid separation model, simplified CO2 removal model and tail gas cycle model was developed. An effective iteration algorithm was proposed to solve this process model, and the model was validated by industrial demonstration experiments data （SBCR with 5.8 m diameter and 30 m height）, with a maximum relative error 〈 10% for predicting the SBCR performances. Subsequently, the proposed model was adopted to optimize the industrial SBCR performances simultaneously considering process and reactor parameters variations. The results show that C5＋yield increases as catalyst loading increases within 10-70 ton and syngas H2/CO value decreases within 1.3-1.6, but it doesn＇t increase obviously when the catalyst loading exceeds 45 ton （about 15 wt% concentration）. Higher catalyst loading will result in higher difficulty for wax/catalyst separation and higher catalyst cost. There- fore, the catalyst loading （45 ton） is recommended for the industrial demonstration SBCR operation at syngas H2/ CO = 1.3, and the C5 ＋ yield is about 402 ton＂ per day, which has an about 16% increase than the industrial dem- onstration run result.

Mathematical modeling of a slurry reactor for DME direct synthesis from syngas

In this paper,an axial dispersion mathematical model is developed to simulate a three-phase slurry bubble column reactor for direct synthesis of dimethyl ether（DME） from syngas.This large-scale reactor is modeled using mass and energy balances,catalyst sedimentation andsingle-bubble as well as two-bubbles class flow hydrodynamics.A comparison between the two hydrodynamic models through pilot plantexperimental data from the literature shows that heterogeneous two-bubbles flow model is in better agreement with the experimental data thanhomogeneous single-bubble gas flow model.Also,by investigating the heterogeneous gas flow and axial dispersion model for small bubblesas well as the large bubbles and slurry（i.e.including paraffins and the catalyst） phase,the temperature profile along the reactor is obtained.Acomparison between isothermal and non-isothermal reactors reveals no obvious performance difference between them.The optimum values ofreactor diameter and height were obtained at 7 m and 50 m,respectively.The effects of operating variables on the axial catalyst distribution,DME productivity and CO conversion are also investigated in this research.

Two-Bubble Class Model for Churn-Turbulent Regime in a Bubble Column Slurry Reactor of Fischer-Tropsch Synthesis

A model for a bubble column slurry reactor is developed based on the experiment of Rhenpreussen Koppers demonstration plant for slurry phase Fischer-Tropsch synthesis reported by Koelble et al. This model is applicable to the operation in the churn-turbulent regime and incorporates the information on the bubble size. The axial dispersion model is adopted to describe the flow characteristics of the Fischer-Tropsch slurry reactor. With the model developed, simulations are performed to identify the steady state behavior of a Fischer-Tropsch slurry reactor of commercial size. Predictions of the two-bubble class model is compared with that of the conventional single- bubble class model. The results show that under a variety of conditions, the two-bubble class model gives results different from those for the single-bubble class model.

Application of Cochlear Model in Speech Analysis/Synthesis Using Sinusoidal Representation

A sinusoidal representation of speech and a cochlear model are used to extract speech parameters in this paper, and a speech analysis/synthesis system controlled by the auditory spectrum is developed with the model. The computer simulation shows that speech can be synthesized with only 12 parameters per frame on the average. The method has the advantages of few parameters, low complexity and high performance of speech representation. The synthetic speech has high intelligibility.

Science Letters:Mask synthesis and verification based on geometric model for surface micro-machined MEMS

Traditional MEMS （microelectromechanical system） design methodology is not a structured method and has become an obstacle for MEMS creative design. In this paper, a novel method of mask synthesis and verification for surface micro-machined MEMS is proposed, which is based on the geometric model of a MEMS device. The emphasis is focused on synthesizing the masks at the basis of the layer model generated from the geometric model of the MEMS device. The method is comprised of several steps： the correction of the layer model, the generation of initial masks and final masks including multi-layer etch masks, and mask simulation. Finally some test resuhs are given.

Microchannel reactors for Fischer-Tropsch synthesis:Experimental investigation and mathematical modeling

The Fischer-Tropsch synthesis is a significant technology for converting coal,natural gas,and biomass into synthetic fuels.In recent years,the use of microchannel reactors for the Fischer-Tropsch synthesis has attracted significant attention.Fischer-Tropsch synthesis experiments were carried out in a microchannel reactor and the influences of reaction conditions on the experimental results were investigated in this study.Based on the experimental data,a dynamic multi-component pseudo-homogeneous variable-volume flow model of microchannel reactors for the Fischer-Tropsch synthesis was built to determine the pressure-,velocity-,conversion-and(component-wise)concentration-distributions in reaction channels.The model takes into account the combined effects of gas volume expansion caused by the frictional pressure drop and gas volume contraction caused by reaction consumption.A novel effective method for calculating the pressure and superficial gas velocity values in microchannel reactors was proposed in the model.Besides that,two sets of experimental data were selected from references to evaluate the validity and accuracy of the model.The reaction performances in the microchannels were analyzed carefully based on the calculated results.

Low Temperature One-Step Synthesis of Barium Titanate:Thermodynamic Modeling and Experimental Synthesis

A thermodynamic model has been developed to determine the reaction conditions favoring low temperature direct synthesis of barium titanate (BaTiO3). The method utilizes standard-state thermodynamic data for solid and aqueous species and a 0ebye-Huckel coefficients model to represent solution nonideality. The method has been used to generate phase stability diagrams that indicate the ranges of pH and reagent concentrations, for which various species predominate in the system at a given temperature. Also, yield diagrams have been constructed that indicate the concentration, pH and temperature conditions for which different yields of crystalline BaTiO3 can be obtained. The stability and yield diagrams have been used to predict the optimum synthesis conditions (e.g., reagent concentrations, pH and temperature). Subsequently, these predictions have been experimentally verified. As a result, phase-pure perovskite BaTiO3 has been obtained at temperature ranging from 55 to 85℃ using BaCl2, TiCl4 as a source for Ba and Ti, and NaOH as a precipitator.

Modelling of Microchannel Reactors for Fischer-Tropsch Synthesis

The Fischer-Tropsch synthesis is an important step in coal liquefaction,natural gas liquefaction,and biomass liquefaction.In recent years,the use of microchannel reactors for Fischer-Tropsch synthesis has received widespread attention.Since thermocouples and other sensors cannot be placed easily in a microchannel reactor,it is very vital to establish a model to provide calculated results highly compatible with the experimental data.This paper mainly introduces the establishment and solution of microchannel reactor models for Fischer-Tropsch synthesis.General mass transfer differential equations,heat transfer differential equations and related parameters(such as reaction rates,dispersion coefficient,and convective heat transfer coefficient)are listed.To solve the models,numerical solutions,such as the CFD simulation methods and the programming methods,are reviewed.It is recommended that a more accurate solution strategy is the combination of CFD simulation and programming methods.

Synthesis of Imidazole Cyclophane as Ligand of Binuclear Metalloprotein Models

Four imidazole cyclophanes have been synthesized by the oxidation of bis-imidazoline with barium manganate followed by cyclization with 2,6-bis(bromomethyl) pyridine in the presence of NaH. All the compounds were identified by IR, (HNMR)-H-1, MS and elemental analysis.

Synthesis and Characterization of Porphyrin-Trisbenzimidazole Dinucleating Ligand and Its Heterodinuclear Complex as CcO Active Site Model

A new dinucleating ligand having two metalbinding sites has been designed and synthesized as model ligand for Cytochrome c Oxidase. The corresponding heterodinuclear complex, as an active site model of Cytochrome c Oxidase, consisting of a porphyrinatocobalt compound covalently linked with a copper derivative of tris(2-benzimidazylmethyl) amine bearing three benzimidazole ligands for copper was synthesized and spectroscopically characterized. The spectra data suggest that there are interactions between the cobalt and copper coordination units. The cobalt is coordinated to four central nitrogens of the porphyrin and the copper has pentacoordinate geometry with the four tertiary amine nitrogens and a chloride.

In-Depth Study on Synthesis Load Modeling

Detailed procedures for the modeling of synthesis load models (SLM) of actual power network are presented, then the classification indices based on 1oad characteristics and the principle of load classification are expounded. Based on the results of general investigation of 220 kV and 330kV substations in China’s power grid, the load characteristics are classified, and detailed load characteristic investigation of selected different kinds of typical substations are carried out. By use of statistical synthesis, the SLM for typical substations, in which the distribution networks are taken into account, are built;and the modeling results are disseminated and applied to whole Chinese power grid. Besides, the load model parameters are evaluated and verified via post-disturbance simulation method. The effectiveness of the built SLM is validated by the fitting of some disturbance incidents.

3DV quality model based depth maps for view synthesis in FTV system

Depth maps are used for synthesis virtual view in free-viewpoint television （FTV） systems. When depth maps are derived using existing depth estimation methods, the depth distortions will cause undesirable artifacts in the synthesized views. To solve this problem, a 3D video quality model base depth maps （D-3DV） for virtual view synthesis and depth map coding in the FTV applications is proposed. First, the relationships between distortions in coded depth map and rendered view are derived. Then, a precisely 3DV quality model based depth characteristics is develop for the synthesized virtual views. Finally, based on D-3DV model, a multilateral filtering is applied as a pre-processed filter to reduce rendering artifacts. The experimental results evaluated by objective and subjective methods indicate that the proposed D-3DV model can reduce bit-rate of depth coding and achieve better rendering quality.

Biomedical overview of melanin.2.Updating molecular modeling,synthesis mechanism,and supramolecular properties regarding melanoma therapy

Melanins represent one of the most ancient and important group of natural macromolecular pigments.They have multiple biological roles in almost all organisms across the Phyla,examples being photoprotection,anti-oxidative action,radical scavenger activity,and heavy metal removal.From the biomedical point of view,melanocytes are involved in the origin of melanoma tumors,and the main therapeutic advances for their treatment have been revised in Part 1 of this review.The chemical structure of eumelanin is a biological concern of great importance,and therefore,exploring theoretical molecular models and synthesis mechanisms will be here described,as well as molecular orbital features and supramolecular organization,which are responsible for the key properties that make these biological pigments so important,and so fascinating.Ultimately,this updated overview is devoted to describe present structural models and physico-chemical characteristics of eumelanin,in order to explain and utilize melanin properties on which new photothermal and ultrasonic protocols for melanoma treatment can be devised and applied.

Modeling and simulation of tube-shell reactor for dimethyl-ether synthesis from coal-based synthesis ga

Mathematical simulation was performed on tube-shell reactor for dimethyl ether （DME） synthesis from coal-based syngas. The model was established based on kinetics of dimethyl-ether synthesis from syngas over a bifunctional catalyst, which is mixed by methanol synthesis catalyst and dehydration catalyst as 1：1 mass ratio. Methanol synthesis from CO and CO2 and methanol dehydration were selected as three-independent reactions, CO, CO2, and DME as key components to estab- lish the one-dimensional mathematical model of the reactor. The gas concentration and temperature profiles inside the reactor tubes were obtained. The operating conditions affecting DME synthesis were also discussed based on the model. The simula- tions indicate that higher pressure and lower temperature at the inlet and rich hydrogen in the reactant are favorable in direct DME synthesis in fixed-bed process, and the temperature of boiling water affect the reactor performance seriously.

THE SYNTHESIS AND CRYSTAL STRUCTURE OF B-(32) MODEL COMPOUND: 1-C_4H_9Co(salen)(Py)

The title complex i-C_4H_9Co(salen)(Py) (Py=pyridine. salen=dianion of disalicylideneethylenediamine) has been first synthesized. Its crystal structure has been determined by X-ray diffraction method. The crystsis are monoclinic with space group P2_1/ C. The unit cell parametes are presented. The structure has been refined to a final R of 0.038.

A New Type of Biomimetic Model: Design, Synthesis andCharacteriration of Imidazolium Bis-Estrogen

Two imidazolium bis-estrogens as a new type of biomimetic model, which possesspotential multiple biomimetic functions, were srnthesized in gcod yields by three steps fromestrogen. All new compounds were characterized by MS, 1HNMR and elemental analysis.

Structural Synthesis, Dynamic Modeling and Analysis of a 3-DOF Asymmetric Parallel Mechanism

Most research papers about parallel kinematic chainmechanisms investigate symmetric robot manipulators, in which all the limbs connecting the end-effector to the fixed based are composed by the same sequence of links and joints. Contrarily, in some manipulation tasks the velocity and stiffness requirements are anisotropic. In such cases, the asymmetric parallel kinematic chain mechanisms may offer advantages. This work objective is to present the synthesis, dynamic modeling and analysis of a 3-dof asymmetric parallel chain mechanism, conceived as a robot manipulator for pick-and-place operations. Firs＇t, a structural synthesis, resulting in a three translations end-effector, and a kinematic modeling are carried out. Then, the inverse dynamic modeling is developed by employing the virtual work principle. Based on the model equations and on the saturation of the mechanism actuators, a maximum acceleration analysis is performed and shows that although the mechanism has a parallel architecture its actuators influences on the 3-dof are quite decoupled.