Showing papers in "CIESC Journal in 2012"

Supercooling and crystallization of water under DC magnetic fields

Abstract: The supercooling and crystallization of water are affected by many factors,the investigation of which is of great significance in the field of food frozen and conservation and low temperature preservation of biology.Experiments were carried out to investigate the supercooling and crystallization of water under DC magnetic fields with different intensity.The results show that the DC magnetic field can reduce the lowest unfrozen temperature and increase supercooling.The time that water remains supercooled increases with the increase of intensity of DC magnetic filed.The crystallization speed also increases obviously.This effect is considered to relate to the formation of water molecular hydrogen bonds.

Content determination of phenolic hydroxyl and carboxyl in lignin by aqueous phase potentiometric titration

Abstract: The potentiometric titration in aqueous phase is used for determination content of phenolic hydroxyl and carboxyl on alkali lignin(AL) and sodium lignosulphonate(SL).The results show that the content of phenolic hydroxyl and carboxyl are 2.81 mmol·g-1 and 1.72 mmol·g-1 for AL,and 1.32 mmol·g-1 and 0.86 mmol·g-1 for SL,respectively.A comparison with classical non-aqueous potentiometric titration indicates that the stability is more excellent for the measurement in aqueous phase.The dynamic light scattering(DLS) method is used for the study of hydrodynamic diameter distributions of AL and SL in DMF and water solvents.The results show that they have stronger aggregation in DMF than in alkaline water,indicating that there is better dissolubility in alkaline aqueous solution than in DMF solvent.Therefore,it can be considered that the aqueous potentiometric titration is more suitable for the quantitative determination of phenolic hydroxyl and carboxyl contents on lignin-based compounds and can be an option for quantitative determination of the functional groups on lignin.

Recovery of titanium from titanium-bearing blast furnace slag by ammonium sulfate melting method

Abstract: A melting reaction process was developed to transform the titanium in titanium-bearing blast furnace slag into water-soluble one,such as TiOSO4 by the treatment with ammonium sulfate and potassium bisulfate,to recover titaniumThe effects of quantities of ammonium sulfate and potassium bisulfate added,reaction temperature and holding time on the recovery rate of titanium were investigated systemicallyThe experimental results showed that reaction temperature and holding time have a great impact on the recovery of titaniumThe recovery rate of titanium was improved with an increase of reaction temperature and holding timeThe optimum conditions of titanium recovery from titanium-bearing blast furnace slag were as follows: the mass ratio of slag to ammonium sulfate 1∶6,reaction temperature 350℃,and holding time 27 minUnder such conditions the recovery rate of titanium was up to 917% and the evaporation loss rate of nitrogen from(NH4)2SO4 was 815%The residue obtained after recovery of titanium was mainly composed of CaSO4·H2O,CaSO4·05H2O,SiO2,a small amount of CaTiO3 and Ca2Al2SiO7This study promises significant economic benefits for smelting enterprise

Discussion on development of coal chemical industry using low-carbon concept

Abstract: Coal is an important fossil fuel with highest carbon content.Huge amount of CO2 emission caused by the use of coal has attracted high attention.In this paper,a new concept which is directed by low-carbon economy was proposed for the development of coal chemical industry in China.According to the actual situation in China,it is necessary and inevitable to choose the processes that can be highly effective multi-product as well as can combine coal chemical industry with petrochemical or metallurgical industry for utilizing effectively coal at different level.Besides,in order to lessen the dependence of oil imports and reduce the carbon emission intensity per unit GDP,we should take efforts to produce high value-added products from coal chemical industry instead of petrochemical industry,such as alkenes,aromatics especially benzene,toluene and xylene,methane and acetylene.Therefore,it is important to launch deeper research on crucial processes and new techniques like molecular tailoring and directional conversion.

Effect of three-phase structure of solid-state fermentation substrates on its transfer properties

Abstract: Solid matrix structure,which has significant effect on its transfer properties,has not been systematically studied.In this paper,steam-exploded rice straw(SERS)and inoculum were used as the solid phase and liquid phase of substrates,the change of water retention,permeability and thermal conductivity of substrate with the variation of its three-phase structure was investigated within the particle size range(6.5—0.4 cm)and moisture content range(60%—85%)which was employed in industry.The results showed that liquid phase dominated the phase structure variation,therefore,a three-phase structural index(TPSI)was proposed based on weighted variation coefficient.Water evaporation rate of substrate showed exponential increase with the rise of TPSI,and obvious fluctuation was accompanied,indicating that there were some other factors influencing the water retention of substrate.The effect of particle size on substrates' permeability weakened gradually with increase of water content,and its variation with TPSI accorded with Bidoseresp function(R2=0.9025).The thermal property of substrate,such as volumetric specific heat,thermal resistivity and thermal conductivity,varied with the increase of TPSI according to power exponent functions(R2=0.8991,0.9135,0.9053);small fluctuation indicated that the effect of water content was stronger than that of particle size.Statistical analysis also proved that the TPSI can reflect comprehensive influence of moisture content and particle size on substrates' transfer properties.Therefore,the TPSI can be applied to effectively characterize the effect of substrate structure on its transfer properties.

Bio-mimic transpiration cooling using temperature-sensitive hydrogel

Abstract: Temperature-sensitive hydrogel(TSHG),a smart macromolecular material releasing moisture automatically when its temperature exceeds the lower critical solution transition temperature(LCST),has been used for transpiration cooling,mimicking the thermoregulation mechanism of living creatures.The temperature and humidity distributions and heat dissipation characteristics of the TSHG transpiration cooling were measured experimentally using laser interference technique.A numerical model was established and verified with the experimental results.With the numerical model,the effects of environmental temperature,environmental humidity and LCST on the heat dissipation capability of TSHG were further studied.Results show that the cooling of TSHG can quickly lower the temperature of the specimen,with a heat transfer coefficient 15 to 25 times larger than that with common passive heat dissipation methods(natural convection and thermal radiation).The heat transfer coefficient can be significantly increased with the increase of environmental temperature and LCST,and may be slightly declined with the increase of environmental humidity.With the high heat dissipation rate without using a fan,the TSHG transpiration cooling is promising for the thermal management of mobile phones and other portable microelectronics.

A data-driven approach to chemical process alarm threshold optimization

Abstract: In order to improve the performance of chemical process alarm systems,it is imperative to optimize assignments of process alarm thresholds.In response to limitations of traditional threshold assignment methods,based on historical data,this paper firstly invokes kernel density estimation methods to identify process alarm states before an objective associated with alarm threshold optimization in terms of minimizing the probabilities of false and missed alarms is established along with enabling numerical solvers.Simulation results on TE process demonstrate that the proposed approaches can effectively reduce the number of false alarms as well as limit that of missed alarms.

Development on thermal contact resistance

Abstract: Thermal contact resistance(TCR)is a hot topic in electronics cooling,cryogenic superconducting thin films,etc.In this paper,the fundamental research method,metrology macro-and nanotechnology,and diminishing method for TCR are reviewed.In order to investigate the heat transfer mechanism of TCR,the scattering and radiation of phonon and electron should be considered besides the quantitative analysis in macro.For the experimental measurement,the accuracy is to be further improved.For reducing the contact resistance,in addition to the commonly used methods,producing new materials with high thermal conductivity(such as carbon nano-tubes)on the contact surface is a useful way.Based on the reported studies,the future researches are discussed.

Contact characterizations of end faces in mechanical seals running-in

Abstract: In order to study the change of contact characterizations of end faces in mechanical seal running-in,taking into account the difference between real micro contact area and micro contact cross-sectional area of end faces of mechanical seals,the expressions of the micro-contacting areas related to the critical elastic and plastic deformations were revised.The expressions of elastic contact area ratio,elastic-plastic contact area ratio and plastic contact area ratio for mechanical seals were derived.Running-in tests of B104a-70 mechanical seals were made with water as test medium.Test temperature was 20℃.Test pressure was 0.5 MPa.Spring pressure was 0.15 MPa.Rotating speed was 2900 r·min-1.The results showed that the end face of the soft ring tended to be smoothened rapidly and its wear rate decreased quickly in running-in.The contact characterizations between end faces of mechanical seals changed greatly.The normalized real contact area increased from 0.00348 to 0.00567.The elastic contact area ratio increased from 0.716 to 0.822.The elastic-plastic contact area ratio decreased from 0.231 to 0.128.The plastic contact area ratio decreased from 0.053 to 0.050.

Water to water heat transfer on shell-side of trisection helical baffle heat exchangers

Abstract: Experimental study was conducted in trisection helical baffle heat exchangers with three sector baffle schemes of tilt angles 10°,15° and 20°,an ellipse baffle scheme of tilt angle 15°,and an axial overlap sector baffle scheme of tilt angle 20°,in contrast to a segmental baffle heat exchanger.Each helix heat exchanger has 48 tubes with layout of one third division of shell cylinder for each baffle,while the segmental baffle heat exchanger has 49 tubes.The data of the shell side,Nusselt number Nuo,axial Euler number Euz,o,and comprehensive performance indicator Nuo/Euz,o are presented versus the shell side axial Reynolds number Rez,o.The results show that the heat exchanger with the scheme of periphery connected sector baffles with tilt angle of 20° has the best performance,whose average comprehensive performance indicator Nuo/Euz,o is 69.8% higher than that of segmental baffle heat exchanger,while the comprehensive performance indicator of the scheme with tilt angle 10° is lower than that of segmental baffle scheme.With the same tilt angle,the performance with the periphery connected connection baffle scheme is better than that with the axial overlap baffle scheme,and the performance with the sector baffle scheme is better than that with the ellipse baffle scheme.

Hydrolysis of sweet sorghum bagasse hemicellulose with liquid hot water and its mechanism

Abstract: Sweet sorghum bagasse(SSB)was hydrolyzed with liquid hot water in a flow-through reactor with the objective of achieving complete saccharification of hemicellulose of SSB and understanding the hydrolysis mechanism.The effect of reaction temperature(155—235℃)and flow rate(5—30 ml·min-1)on the concentration of xylose,glucose,arabinose,their total sugars and their degradation products(furfural,5-HMF,acetic acid,glucuronic acid,formic acid and glycolic acid)in the liquid fractions was investigated.The experimental results indicated that xylose was more sensitive to temperature and flow rate than arabinose and glucose.The concentration of total xylose including xylose monomer and xylose oligomer dropped dramatically when temperature was higher than 195℃.A lower flow rate(5 ml·min-1)resulted in a higher furfural yield due to longer residence time for xylose in the reactor.In contrast,a higher flow rate(30 ml·min-1)would reduce the thickness of stagnant fluid layer surrounding the solid particles and lower resistance to penetration of water into the solids for hydrolysis and diffusion of oligomers into solution.It was hypothesized that the major xylan in SSB hemicellulose was O-acetyl-4-O-methyl-glucuronoarabinoxylan.Xylose,arabinose,glucose and their oligosaccharides could be considered as the primary products.Glucuronic acid and acetic acid were produced from the decomposition of glucuronic and O-acetyl groups in the branched chain of hemicellulose.Furfural and 5-hydroxymethyl-2-furaldehyde(5-HMF)were the direct degradation products of sugars.Moreover,glucuronic acid would be further oxidatively degraded into glycolic acid.Low molecular weight organic acids,such as formic acid were the further degradation products.

Catalytic cracking of coal pyrolysis product for oil and gas upgrading over char-based catalysts

Abstract: Catalytic cracking upgrading of coal pyrolysis oil and gas products was conducted in a dual-stage reactor using char and Co-impregnated char(Co-char)as the catalyst.The tested coal was Fugu coal,and the upper stage of the dual-stage reactor was used for pyrolysis.During catalytic cracking of coal pyrolysis products,tar yield decreased,and gas yield and also light oil fraction content of(boiling points360℃) the tar increased,while the yield of light tar remained constant or increased slightly.For the pyrolysis with secondary cracking at 600℃ over a char layer of 20% the tested coal,its gas yield and light tar content increased respectively by 31.2%(vol)and 25%(mass)in comparison with the direct pyrolysis of coal at 600℃,whereas light tar yield varied little.When Co-char was used as the catalyst,cracking at 500℃ over the catalyst of 5% coal mass increased light oil yield and light oil content in the tar by 8.8%(mass),and 28.8%(mass),respectively.The corresponding increase in gas yield was 21.5%(vol).Catalytic secondary cracking in coal pyrolysis worked mainly to convert heavy oil components into light oil and pyrolysis gas.

Influence of tip clearance on heat transfer efficiency in staggered micro-cylinders-group

Abstract: De-ionized water,used as working fluid,flows through a staggered micro-cylinders-group,which is made up of micro-cylinders with hydraulic diameter of 500 μm and height of 500 μm,and an experimental study is performed on the influence of tip clearance on heat transfer efficiency in the staggered micro-cylinders-group.Using an electricity heater,the flow rate and the temperature difference between the inlet and the outlet of micro-cylinders-group are measured and the friction factor and Nusselt numbers can be obtained over Reynolds numbers ranging from 8 to 400.The relationship between heat transfer efficiency and Reynolds number is grasped.The experimental results indicate that the tip clearance has a little influence on flow resistance and Nusselt number at low Reynolds number and these influences become apparent with the increase of Reynolds number.The heat transfer efficiency of micro-cylinders-group heat sink increases rapidly with Reynolds number for a start,and it increases slowly with the increase of Reynolds number,even begins to drop with the further increase of Reynolds number.However,the existence of the tip clearance promotes heat transfer efficiency in the micro-cylinders-group heat sink,though it reduces Nusselt number based on the experimental results.

Non-Gaussian process fault detection method based on modified KICA

Abstract: Many fault detection methods based on kernel independent component analysis(KICA)only consider the extraction of non-Gaussian information,but the preservation of local neighborhood structure is usually ignored.Aiming at this problem,a fault detection method based on modified KICA is proposed.The criterion of negentropy maximization in KICA considering only the extraction of non-Gaussian information is converted to the criterion of entropy minimization.The criterion of entropy minimization is then combined with the criterion of similar local neighborhood structure in locality preserving projections(LPP),and a new objective function taking both the extraction of non-Gaussian information and the preservation of local neighborhood structure into account is constructed.The particle swarm optimization algorithm(PSO)is utilized to optimize the objective function globally,and the monitoring statistics are built to monitor the process.The simulation results on Tennessee Eastman process illustrate that,in contrast to fault detection methods based on KICA,the proposed method can extract the non-Gaussian information of dataset while keeping the local neighborhood structure,shorten the fault detection latency and improve the fault detection rate effectively.

Influence of port angle on performance of gas wave ejector and prediction for optimal angle

Abstract: The angle between high pressure port and middle pressure port is one of the most important structure parameters for gas wave ejector.In this study,the influence of this angle on the performance of gas wave ejector is analyzed by numerical simulation and experiment.The prediction method for the optimal angle is proposed.For any given conditions,there is an optimal angle ψopt.When the angle is greater than the optimal one,a reflected shock wave is generated and the isentropic efficiency of gas wave ejector decreases significantly;while the angle is less than the optimal one,the efficiency declines slightly for the case of lower middle pressure.However,if the middle pressure is higher than pM-extra,the pressure inside the channel after a cycle is lower than that at the middle pressure outlet.A compression wave is produced when the channel is exposed to the outlet,so the efficiency drops sharply as the port angle decreases.The calculation results agree well with the experimental data,so the model could predict the optimal angel effectively.When the temperature and pressure of the inflows are constant,the optimal angels at different middle pressures are almost the same,but increase linearly with the rotation speed.The above conclusions provide guidance for gas wave ejector design and optimization.

Heat transfer of porous metal foam wick heat pipe

Abstract: Using water as working medium,an experimental investigation on heat transfer performance of the nickel foam wick heat pipe and the mesh wick heat pipe was conducted under the conditions of natural cooling and water cooling.The wall temperature distribution and isothermal characteristic of the two heat pipes were discussed.The variation of the evaporation and condensation heat transfer coefficients in the nickel foam wick heat pipe with the heat flux with natural cooling were obtained.In a certain range,the evaporation and condensation heat transfer coefficients increased with the increase of the heat flux.Under the conditions of water cooling,the evaporation heat transfer coefficients in the nickel foam wick heat pipe first increased and then decreased with the increase of the heat flux when the cooling water flow rate was 0.01 m3·h-1.The experimental results indicate that the nickel foam wick heat pipe has a good start-up performance,and the mesh wick heat pipe is easier to reach the heat transfer limit than the nickel foam wick heat pipe.

Influence of hydrophobically modified silicon dioxide particles on stability of EOR flooding foam

Abstract: The surface of commercial silicon dioxide particles was hydrophobically modified.The aqueous foams were prepared by stirring mixtures of dodecyl sulfate sodium(SDS) and silicon dioxide particles before or after surface modification.Hydrophobicity of particles,particle additions,concentration of particles adsorbed on the air/water interface and stability of dynamic stretching liquid film were investigated.The results showed that the foamability and foam stability of the original silica/SDS dispersion was better than that of the modified silica particle/SDS dispersion.The foam stability increased with increasing particle addition and it reached a maximum with the particle addition of 0.05%(mass).However,in dynamic stretching conditions,the liquid film can be stabilized by hydrophobically modified silica particles.The stretch length of liquid film reached a maximum at the particles addition of 0.05%.

A stair-like generalized predictive control algorithm based on multiple models switching

Abstract: A stair-like generalized predictive control algorithm based on multiple models switching is proposed for systems with jumping parametersMultiple fixed models,a conventional adaptive model and an assigned initial value adaptive model are established to identify dynamic characteristic in parallelMultiple fixed models can improve transient performance,conventional adaptive model can ensure the stability of systems and assigned initial value adaptive model can further enhance transient performanceThe best sub-model is selected as global model according to the switching index,and a stair-like generalized predictive controller is designed for this modelConsequently,the full-range operation is achievedFinally,simulation shows that the control effect of proposed method is superior to a single controller

Molecular dynamics simulation for diffusion of organic molecules in polyethylene membranes

Abstract: The diffusion of benzene,toluene and ethylbenzene in amorphous polyethylene(PE) membrane was studied in this paper,and their diffusion coefficients were analyzed and calculated by molecular dynamics simulation.The diffusion coefficients were calculated with the clustering method.The calculated results have the same trend with experimental results: the diffusion coefficient decreases with increasing molecular weight of organic molecules at the same temperature and increases with temperature for the same organic molecule.It is shown that the diffusion coefficients are reasonable and reliable.The diffusion behavior of three kinds of molecules in polyethylene membrane in a long time(300 ps) scale was simulated and the tracks of molecules were obtained,which show that the molecule movement in the membrane is local vibration combined with prancing diffusion.

Impact of high-frequency pulse electric field parameters on polarization and deformation of water droplet

Abstract: Based on theoretical analysis,micro-experiment was carried out and the impact of high-voltage high-frequency pulsed electric field parameters on deformation of water droplet was investigated.The results showed that polarization relaxation time decreased with increasing electric field strength,while the deformation of droplet,migration velocity of polarization charge and electric field frequency corresponding to maximum degree of deformation of water droplet increased.The lower the electric field frequency,the larger the emulsion capacitance and the smaller the polarization voltage,the less the polarization deformation.With electric field frequency deviating from natural frequency of water droplet,resonance effect and drop deformation were suppressed.With increasing duty ratio,electric field acting on the droplet and deformation of water droplet increased.Part of the electric field energy leaked through the oil phase when duty ratio was large,which resulted in smaller deformation of water droplet.The interaction between parameters of high frequency pulse electric field acting on polarized deformation of the droplet cannot be ignored.The research results laid good foundation for further investigation of high-voltage high-frequency electrostatic emulsion-breaking mechanism.

Online learning soft sensor method based on recursive kernel algorithm for PLS

Abstract: An online learning soft sensor method based on PLS kernel algorithm is presented for industrial processes with time-varying characteristics.By recursively learning representative samples,this method,utilizing PLS kernel algorithm,could improve soft sensor model's ability of adaptation,which is more computationally efficient than NIPALS.And deleting one or more redundant samples according to a similarity-based criteria that takes both input and output information into consideration may build more effective training sample set.The foregoing scheme is applied to build an industrial polypropylene unit's melt index model.The results indicate that the proposed method can efficiently track the change of melt index during grades transition.

Extraction of ZnO from zinc oxide ore by alkali roasting method

Abstract: Zinc oxide ore was treated by roasting with NaOH.ZnO,SiO2 and PbO reacted with alkali first and then went into solution after digestion.In this paper,orthogonal experiment method was used to optimize conditions for extraction of ZnO from zinc oxide ore by roasting with alkali.The optimized conditions were mass ratio of ore and alkali 1∶6,holding temperature 400℃,holding time 4 h.Under these conditions,the extraction rate of ZnO was 82.4%.The main components of zinc extracted slag were stishovite,and Na2ZnSiO4,whose presence impeded further extraction of ZnO.The morphology of slag was irregular,and the particle size was non-uniform.

Evaluation on air conditioning's operating property of airport terminal based on hierarchal cluster

Abstract: Building energy simulation software-Energyplus was used to construct simulation model of an airport building and its air conditioning system in Hainan.Based on chiller system's whole year operating data,the paper proposes a method of hierarchal cluster to categorize chiller's operating condition by extracting operating parameters which have evident influence on chiller's operation as the cluster parameters.It analyzes the relationship between chiller's operation level and operating parameters,construct multivariate regression models in different clusters.By comparing every chiller's COP in different cluster centers with the calculated COP of regression model,it illustrates that chiller's operating property of a cluster center can be used as the representative of the cluster.It was found that hierarchal cluster can supply an effective and simple way to evaluate chiller's operation level.

Numerical analysis on thermal processes in coupled coking and combustion chambers of coke oven

Abstract: To describe fluid flow,combustion and heat transfer in coke oven,a three-dimensional transient mathematical model with coupled coking and combustion chambers was developed and solved numericallyThe calculated central temperature of the coke was compared with measured dataThree different evaporation models were comparedEffects of operational factors such as temperature,moisture content and density of charging coal were investigatedIt is shown that the proposed model is suitable for describing thermal processes in the coke ovenIt reveals whether the temperature distribution is uniform along the height of the chambers with coking evolution Some measures may be used to improve the production efficiency,such as preheat,adjustment of moisture content,and densification for charging coalThis work is theoretically valuable for the operation of coke oven

Formation mechanism of cyanobacteria bloom in urban lake reservoir

Abstract: The treatment and prevention of water bloom play a significant role in efficiently controlling water pollution,and the key to solve this problem is to understand formation mechanism of water bloomBased on a further analysis for the formation process of cyanobacteria bloom in urban lake reservoir,and the whole process is simulated in laboratory,orthogonal experiment and rough set theory are combined to get key factors(DO,TP,TN,temperature and illumination)that can impact formation of cyanobacteria bloom and used as input parameters in establishment of mechanism model for the formation of cyanobacteria bloom in urban lake reservoirChlorophyll a is adopted as a characterization index for the formation of cyanobacteria bloom,and based on mechanism of interaction,a model of the process applied to describe cyanobacteria bloom formation in urban lake reservoir is structuredMeanwhile,the parameters involved in this model,such as Gmax,Is,,K,Kab,Dmax,mp,can be estimated and nonlinearly optimized by improved PSO(particle swarm optimization),which can highly enhance the model applicability and validationThe method provides an efficient approach for further study on formation mechanism of cyanobacteria bloom

Process simulation for Huadian-type oil shale retorting system by Aspen Plus

Abstract: In this paper,a model of technological process is to be constructed for Huadian-type oil shale retorting system using Aspen Plus software,and the physical parameters in the model came from oil shale samples of Gonglangtou mine in Jilin province.The overall thermal efficiency and power consumption of the main auxiliary device of this system were analyzed by calculating the mass balance and thermal balance of the simulated oil shale retorting system and by simulating different heating temperature conditions of two-stage heater.The results show increase of heating temperature for semi-coke combustion furnace can reduce consumption of fuel gas in gas combustion furnace.Furthermore,rise of heating temperature for gas combustion furnace can cut down flow of hot circulating gas and reduce loss of condensation heat for retorting gas and oil vapor.So,the overall thermal efficiency of whole retorting system can be improved by simultaneous increase of heating temperature in the two-stage combustion furnace,and its economic benefit can be enhanced by increase of foreign supply amount of gas and semicoke.

An overview on lignocellulose pretreatment and recalcitrant characteristics

Abstract: Lignocellulose is the most abundant renewable biomass on the earthEnzymatic hydrolysis of cellulosic polysaccharide is key step of lignocellulose biorefineriesTo enhance efficiency of cellulose hydrolysis,pretreatment is necessary for effectively breaking its recalcitrant structureSo,great attentions have been paid for design of pretreatment technologies to crack recalcitrant characteristics of lignocelluloseIn this paper,the latest research progresses on lignocellulose pretreatment and recalcitrant characteristics were reviewed,focusing on the new pretreatment technologies and their main advantages,including combined pretreatment,cold pretreatment,green solvents pretreatment and electrochemical approachOtherwise,the influence of recalcitrant characteristics,such as lignin,crystallinity,accessibility,on cellulose hydrolysis was discussedThe new methods used for analysis of recalcitrant characteristics and the new insight obtained are highlighted in this reviewThese are useful for evaluation of pretreatment technologies,and identification of key factors that limit cellulose hydrolysis,and can also be a basis for design and screen of appropriate pretreatment technologies,as well as for understand of lignocellulose hydrolysis mechanism

Hydrogenation of nitrobenzene to aniline on amorphous Ni-Mo-P catalysts and mechanism of catalyst deactivation

Abstract: The process of nitrobenzene hydrogenation to aniline using an amorphous Ni-Mo-P alloy as the catalyst and the deactivation mechanism of the amorphous Ni-Mo-P alloy catalyst were studied.Investigation of the effects of reaction time,temperature,and hydrogen pressure on nitrobenzene hydrogenation to aniline using the Ni-Mo-P catalyst revealed optimum conditions as 90 min,383 K,and 1.8 MPa.Under these conditions,the yield of aniline reached 98.2% using the amorphous Ni-Mo-P catalyst after nitrobenzene hydrogenation for 15 h,indicating excellent activity stability of the amorphous Ni-Mo-P catalyst.Deactivation of the amorphous Ni-Mo-P catalyst was due mainly to nitrobenzene hydrogenation byproducts covering the catalyst activity sites,which made it difficult for reactant molecules to access the catalyst activity sites and was highly unfavorable to the catalytic reaction.

Simulation and optimization of acetylene converter with decreasing catalyst activity

Abstract: Since the activity and selectivity of acetylene hydrogenation catalyst change with time,the operating parameters need to be changed to maximize the profit.Therefore,we collected the industrial process data and estimated the parameters of kinetic model and deactivation model by genetic algorithm.We compared the selectivity and activity performance of two commonly used catalysts.For two reactors in series filled with different catalysts,we proposed the methods of combinatorial optimization and ratio assignment to optimal ethylene production rate.When these optimization strategies were implemented in the actual plant,ethylene production rate and the total selectivity increased significantly.

A 38-lumped kinetic model for reforming reaction and its application in continuous catalytic reforming

Abstract: Based on the lumping theory and catalytic reforming reaction mechanisms,a new kinetic model involving 38 lumped components and 86 reactions was developed for the industrial continuous catalytic reforming(CCR).In the proposed model the reactants were lumped into C6—C11+ according to the number of carbon atoms,the components with the same carbon atoms number were divided into normal-paraffin,iso-paraffin,5-cyclanes,6-cyclanes and aromatics respectively,and the cracking products were lumped into C1—C5 lumps.The reaction network of the model was on the basis of the reaction mechanism of bi-functional catalyst and related kinetic theory.As the detailed division of the lumped components,most of the reactants information could be covered,consequently the model could be more realistic.By making reasonable simplification,86 model parameters were identified and estimated using the hierarchical strategy and BFGS algorithm from literature data.The model developed was used for simulation of a refinery reformer to validate the effectiveness.The prediction error of each component in the outlet products of the last reactor was within 0.7%,and that of temperature drop for each reactor was below 5℃.So,the reliability and accuracy of the model could meet the requirements of industrial applications.The model was then applied to predict the aromatics yield,and the average prediction error was only 0.42%.The result showed that the trend and precision of the aromatics yield prediction were satisfied in a long period of time.Finally,the process optimization was implemented based on the proposed model,and an increase of 0.17% on aromatics yield was obtained by a slight tuning of each inlet temperature.The optimization result could provide a guideline for the optimization of the CCR unit.