SIMULA在Cu/ZnO/Al_2O_3催化剂上进行甲醇部分氧化蒸气重整制备氢气的模拟研究(英文)

两个大气压下 ,对管状填充床反应器中在Cu ZnO Al2 O3催化剂上甲醇部分氧化蒸气重整制备氢气进行了实验研究。在Cu ZnO Al2 O3催化剂上进行该反应体系动力学研究的基础上 ,建立了该反应器内的稳态质量和热量衡算方程 ,同时考虑了颗粒内的扩散限制。模型的预测结果与实验结果吻合较好。

PEO-PPO嵌段共聚物反胶束的形成及其热力学行为

通过对嵌段聚合物 PE62 0 0和 2 5R4有机溶液的加溶水量 WO 与温度关系的实验 ,确定了不同温度下反胶团形成的临界浓度 ( CMC) ,分析了聚合物在对二甲苯中形成反胶团的热力学行为 .结果表明 ,提高温度 ,有利于对二甲苯对聚合物的溶解 ,导致 CMC值上升 .ln XCMC与温度 T成线性关系 ,胶团化过程中体系的标准吉布斯自由能变、焓变和熵变皆为负值 ,表明该过程是一个自发的放热过程 ,并且是一个混乱度降低的熵减过程 .

焙烧的P-25TiO_2微结构特性和光催化活性

The microstructural characteristics of P-25 TiO2 photocatalysts calcined at 600, 650,700, 750, 800, 900 and 1000℃ have been studied using XRD, TEM and BET. The photocatalytic activity of the samples were also examined using the degradation of phenol as a model reaction.The results indicate that the calcination significantly affects both microstructural characteristics and photoactivity, and there is an apparent relationship between photocatalytic activity and centain mocrostructural characteristics.Over the range of calcination temperatures and durations studied, the sample calcined at 650℃ for 3 h revealed the highest photoreactivity, which can be ascribed to an improvement in crystallinity on calcination.The increase in the rutile content and grain size caused by the calcination at higher temperatures were observed to decrease the photocatalytic activities of the TiO2 samples.

原位漫反射红外分析水分对煤中氢键形成的作用规律

采用原位漫反射红外技术测定了煤中水分的-OH含量和加热脱水过程中由氢键引起的焓变,并与TG和DSC的测定结果进行了对比。证明该技术是定量研究煤中氢键的有效方法。

鼓泡床中的气泡尺寸分布

根据气泡聚并和破裂速率模型,提出一个描述鼓泡床中气泡尺寸分布的总体平衡(Population Balance)模型。该模型可预计鼓泡床中气泡尺寸分布随床高的变化。对空气-水体系的模拟结果与实测结果吻合较好。

N_2-C_2H_6-CO_2三元系统汽液平衡的实验测定

在低温条件下测定了N_2C_2H_6CO_2系统的汽液平衡。所测数据的温度范围为220.00～253.15K,压力范围为2.00～5.00MPa。实验数据以常用的几个状态方程RKS、PR以及LKP来检验,结果令人满意,实验结果并被用来对以上3个状态方程中二元相互作用系数进行了优选。对于全部105个测量点的汽相组成,实验值和计算值之差的算术平均值分别为0.0064（N_2）,0.0039(C_2H_6）,0.0050（CO_2）,压力实验值和计算值的算术平均相对误差为1.7％。

Study on Optimal Strategy of Grade Transition in Industrial Fluidized Bed Gas-Phase Polyethylene Production Process

A model of grade transition is presented for a commercialized fluidized bed gas-phase polyethylene production process. The quantity of off-specification product and the time of grade transition can be minimized by the optimization of operating variables, such as polymerization temperature, the ratio of hydrogen to ethylene, the ratio of co-monomer to ethylene, feed rate of catalyst, and bed level. A new performance index, the ratio of melt flow (MFR), is included in the objective function, for restraining the sharp adjustment of operation variables and narrowing the distribution of molecular weight of the resin. It is recommended that catalyst feed rate and bed level are decreased in order to reduce the grade transition time and the quantity of off-specification product. This optimization problem is solved by an algorithm of sequential quadratic programming (SQP) in MATLAB. There is considerable difference between the forward transition and reverse transition of grade with regard to the operating variables due to the non-linearity of the system. The grade transition model is extended to a high space time yield (STY) process with the so-called condensed model operation. In the end, an optimization strategy for multi-product transition is proposed with two-level optimization of the objective function J(x,u) on the basis of the optimal grade transition model. A sequential transition of six commercial polyethylene grades is illustrated for an optimal multi-product operation.

Influence of nonionic surfactant on the solubilization and biodegradation of phenanthrene

Phenanthrene was solubilized in two different nonionic surfactants, Tween80 and Triton X-100. The bioavailability of phenanthrene to the bacteria isolated from the petroleum contaminated soils was studied based on the rotary flasks experiments. The results showed that the concentration of nonionic surfactants above the critical micelle concentration(CMC) can increase the solubility of phenanthrene in water and were innoxious to the phenanthrene-degrading bacteria; phenanthrene solubilized in the micelles of Tween80 was bioavailable and biodegradable. The research demonstrated the potential of surfactant-enhanced bioremediation of soils contaminated by hydrophobic organic compounds(HOCs).

Enhancement Factors in Ozone Absorption Based on the Surface Renewal Model and its Application

Based on the Danckwerts surface renewal model, a simple explicit expression of the enhancement factor in ozone absorption with a first order ozone self-decomposition and parallel second order ozonation reactions has been derived. The results are compared with our previous work based on the film theory. The 2,4-dichlorophenol destruction rate by ozonation is predicted using the enhancement factor model in this paper.

The Structure and Protective Properties of Zinc and Nickel Alternate Electrodeposits

The electrodeposition of coatings consisting of alternate zinc and nickel deposits produced by successive deposition from a revised zinc sulphate electrolyte and a new developed nickel bath has been investigated. Coated samples have been evaluated in terms of surface appearance, surface morphologies and cross-sectional morphologies using scanning electron microscopy (SEM). The corrosion resistance of laminar coatings has been studied by means of salt spray accelerated testing and anodic polarization measurement. The results obtained showed that the corrosion performance of zinc-nickel laminar coatings was better than that of a single-layer zinc or nickel deposit with the same thickness, and the coatings with nickel sublayer adjacent to the steel substrate and zinc as the top layer had the best corrosion resistance. These results were in good agreement with the characteristics indicated in the morphologies of zinc-nickel laminar coatings after anodic polarisation measurement.

The Physical Models of Cyclone Diplegs in Fluidized Beds

In most industrial fluidization units, two- or three-stage cyclone systems are used to clean the product gases. To return the solids to the bed, these cyclones are fitted with diplegs. By pass of gas from the bed through the dipleg is partially overcome by the back pressure build-up in the dipleg and by adding a trickle valve at the bottom of the dipleg. Diplegs of primary cyclones, operating at a high solid loading behave differently from diplegs of secondary and tertiary cyclones which operate at low solid loading. Both types have been investigated by pressure drop measurements, visual observation and by measurements of the air flow rate flowing up the riser. The primary dipleg was also studied using electrical capacitance tomography. The results are reported hereafter and will give a first indication towards the right design of the dipleg and the selection of the trickle valve. The influence of gas flow in the dipleg on the conversion in a catalytic fluidized bed reactor is found to be negligible.

Catalyst-Packed Non-Thermal Plasma Reactor for Removal of Nitrogen Oxides

A single-stage plasma-catalytic reactor in which catalytic materials werepacked was used to remove nitrogen oxides. The packing material was scoria being made of variousmetal oxides including Al_2O_3, MgO, TiO_2, etc. Scoria was able to act not only as dielectricpellets but also as a catalyst in the presence of reducing agent such as ethylene and ammonia.Without plasma discharge, scoria did not work well as a catalyst in the temperature range of 100 ℃to 200 ℃, showing less than 10% of NOx removal efficiency. When plasma is produced inside thereactor, the NOx removal efficiency could be increased to 60% in this temperature range.

Liquid Circulation in a Multi-tube Air-lift Loop Reactor

A multi-tube air-lift loop reactor (MT-ALR) is presented in this paper. Based on the energy conservation, a mathematical model describing the liquid circulation flow rate was developed, which was determined by gas velocity, the cross areas of riser and downcomer, gas hold-up and the local frictional loss coefficient. The experimental data indicate that either increase of gas flow rate or reduction of the downcomer diameter contributes to higher liquid circulation rate. The correlation between total and the local frictional loss coefficients was also established.Effects of gas flowrate in two risers and diameter of downcomer on the liquid circulation rate were examined. The value of total frictional loss coefficient was measured as a function of the cross area of downcomer and independent of the gas flow rate. The calculated results of liquid circulation rates agreed well with the experimental data with an average relative error of 9.6%.

Vapor-phase elemental mercury adsorption by residual carbon separated from fly ash

The adsorption capacity for vapor-phase elemental mercury(Hg0) of residual carbon separated from fly ash was studied in an attempt for the control of elemental mercury emissions from combustion processes. At low mercury concentrations(<200 μg/m3), unburned carbon had higher adsorption capacity than commercial activated carbon. The adsorbality of unburned carbon was also found to be source dependent. Isotherms of FS carbon(separated from fly ash of a power plant of Shishi in Fujian Province) were similar to those classified as typeⅡ. Isotherms of XJ carbon(separated from fly ash of a power plant of Jingcheng in Shanxi Province) were more like those classified as type Ⅲ. Due to the relatively low production costs, these residual carbons would likely be considerably more cost-effective for the full-scale removal of mercury from combustion flue gases than other technology.

Intrinsic Kinetics of Dimethyl Ether Synthesis from Syngas

The intrinsic kinetics of dimethyl ether (DME) synthesis from syngas over amethanol synthesis catalyst mixed with methanol dehydration catalyst has been investigated in atubular integral reactor at 3-7 MPa and 220-260℃. The three reactions including methanol synthesisfrom CO and H_2, CO_2 and H_2, and methanol dehydration were chosen as the independent reactions.The L-H kinetic model was presented for dimethyl ether synthesis and the parameters of the modelwere obtained by using simplex method combined with genetic algorithm. The model is reliableaccording to statistical analysis and residual error analysis. The synergy effect of the reactionsover the bifunctional catalyst was compared with the effect for methanol synthesis catalyst underthe same conditions based on the model. The effects of syngas containing Na on the reactions werealso simulated.

Surface State of Carbon Fibers Modified by Electrochemical Oxidation

Surface of polyacrylonitrile (PAN)-based carbon fibers was modified by electrochemical oxidation. The modification effect on carbon fibers surface was explored using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Results showed that on the modified surface of carbon fibers, the carbon contents decreased by 9.7% and the oxygen and nitrogen contents increased by 53.8% and 7.5 times, respectively. The surface roughness and the hydroxyl and carbonyl contents also increased. The surface orientation index was reduced by 1.5% which decreased tensile strength of carbon fibers by 8.1%, and the microcrystalline dimension also decreased which increased the active sites of carbon fiber surface by 78%. The physical and chemical properties of carbon fibers surface were modified through the electrochemical oxidative method, which improved the cohesiveness between the fibers and resin matrix and increased the interlaminar shear strength (ILSS) of carbon fibers reinforced epoxy composite (CFRP) over 20%.

Biodegradation of methanol vapor in a biofilter

Volatile organic compounds (VOCs) are a new class of air pollutants posing threat to the environment. Newer technologies are being developed for their control among which biofiltration seem to be most attractive. Biofiltration of methanol vapor from air stream was evaluated in this study. Experimental investigations were conducted on a laboratory scale biofilter, containing mixture of compost and polystyrene inert particles as the filter materials. Mixed consortium of activated sludge was used as an inoculum. The continuous performance of biofilter for methanol removal was monitored for different concentrations and flow rates. The removal efficiencies decreased at higher concentrations and higher gas flow rates. A maximum elimination capacity of 85 g/(m 3·h) was achieved. The response of biofilter to upset loading operation showed that the biofilm in the biofilters was quite stable and quickly adapted to adverse operational conditions.