Showing papers in "CIESC Journal in 2014"

Industrial development and prospect about comprehensive utilization of coal gangue

Abstract: Coal gangue as one of the largest industrial solid wastes in China brings about very serious environmental, social and economic problems. Comprehensive utilization of coal gangue is of importance to sustainable development of society and economy. China has made great progress in comprehensive utilization of coal gangue in the latest 40 years since the 1960—1970's. Circulating fluidized bed(CFD) power generation using coal gangue is at the advanced level of the world. The equipment and technology of sintered brick manufactured from coal gangue have also reached the world's advanced level. A single facility reaches million tons of coal gangue consumption annually. Large amounts of coal gangue as the major harmless methods are used in backfilling, road paving and land reclamation. The comprehensive treatment capacity of coal gangue increases significantly and exceeds 400 Mt annually at present. Due to large production of coal gangue, however, the existing utilizations cannot meet the demand of coal gangue treatment. Value-added utilization as one of the important supplementary ways will become the development direction of comprehensive utilization of coal gangue. It is of significance to further improve the utilization level and efficiency by establishing the circular economy routes of value-added utilization proposed in this paper based on the development situation of value-added utilization.

Preparation of potassium sulfate from K-feldspar by hydrothermal alkaline method:reaction principle and process evaluation

Abstract: To develop an efficient and clean technique for comprehensively utilizing potassic syenite resources exposed in the Eastern Qinling to Dabie area of China,a series of experiments were performed using a typical K-feldspar powder as raw material,with focus on the hydrothermal stability of microcline in KOH-H2O solution,reaction principle of preparing potassium sulfate,as well as processing by-products from alumina and silica residue.Microcline was easily transformed into kalsilite by dislodging 2/3 SiO2 of the K-feldspar in the solution,resulting in nearly hundred percent higher concentration of K2O in the solid product,from which nearly pure solution of potassium sulfate was then obtained by dissolution with sulfuric acid,and further potassium sulfate was crystallized by evaporation of the solution or by the alcohol precipitation method.The alkaline solution of mainly potassium silicate reacted with lime milk to precipitate calcium silicate hydrate,from which needle-shaped wollastonite powder was synthesized hydrothermally,and then by calcination.The alumina and silica residue were used to make calcined kaolin first by acidic washing,and then by calcination.The whole procedure developed in this research was simple and economical,with recovery ratio of K2O up to 94.0%.In such a way,the components of K2O,Al2O3,and SiO2 in K-feldspar of the ores were wholly transformed to valuable products,giving rise to maximum utilization of K-feldspar resources,and also minimum consumption of relevant mineral resources.The technique is noted for energy conservation,high efficiency and clean production.

Status quo and development prospect of magnetizing roasting via fluidized bed for low grade iron ore

Abstract: There is large reserve of low grade and complex iron ore in China, which cannot be beneficiated by conventional physically-based beneficiation methods. High-efficiency utilization of these low grade iron ores is crucial to alleviate the supply shortage of iron ore in China on the one hand and to improve iron ore supply security on the other hand. Magnetizing roasting coupled with magnetic separation is an important method for the beneficiation of low grade iron ores and recently much attention has been paid to fluidized bed magnetizing roasting. In the present review, the principle of the magnetizing roasting method is first introduced, and then the status quo and existing problems of shaft furnace magnetizing roasting technology and rotary kiln magnetizing roasting technology are summarized. The development history and technical status of fluidized bed magnetizing roasting are also introduced, with the emphasis on summarizing the progress of the newly-developed low-temperature fluidized bed magnetizing roasting technology, including reduction intrinsic kinetics, process intensification, simulation and modeling, technology development like preheating of iron ore powder, feeding/discharging, roasted ore cooling and stable combustion of roasting off-gas. The application prospect of the technology is analyzed for low grade hematite, limonite, siderite and iron-containing tailings.

Separation and recovery of chromium and vanadium from reduced vanadium-chromium precipitate by calcinations-alkaline leaching

Abstract: Separation and recovery of chromium and vanadium from reduced vanadium-chromium precipitate were implemented by calcination followed by alkaline leaching. The reaction process during calcination and the factors, such as temperature, time and alkaline medium, affecting leaching vanadium were investigated. Cr(Ⅲ) and V(Ⅳ) could form CrVO4, and then CrVO4 was decomposed into Cr2 O3 and V2 O5 during calcinations. The appropriate conditions for calcination were temperature of 950℃ and time of 1.0—3.0 h. Under the same molarity conditions, NaOH was better than Na2 CO3 for leaching V2 O5. Increasing NaOH concentration and time was favorable for leaching of V2 O5 while temperature had little effect on leaching of V2 O5. When reduced vanadium-chromium precipitate was calcined for 1.5 h at 850℃ and was treated for 1.5 h using 3 mol·L?1 NaOH, the content of Cr2 O3 in the residue was more than 96%, and leaching rates of vanadium and chromium were 87.3% and less than 1%, respectively. Additionally, 97% of vanadium in the filtrate could be precipitated by acidic ammonium salt.

Effect of temperature on methanogens metabolic pathway and structures of predominant bacteria

Abstract: Methanogens are strictly anaerobic archaea, which not only take part in the methanogenesis procedure but also limit this process Temperature plays a key role in the anaerobic fermentation Temperature could not only directly alter the community structure and function of methanogenic archaea,but also affect the supply of substrates for methanogens,which in turn indirectly regulates the pathways of methanogenic archaeaThere are three pathway for methanogenesis, and they are started from acetic acid, H2/CO2 and C-1 compound respetively Acetoclastic methanogenesis accounts for about two-thirds of the total methane production globally, while hydrogenotrophic methanogenesis accounts for about one third Methanol- and methyl amine-derived methanogensis is restricted in ocean and saline water Acetoclastic methanogenesis is the predominant methanogenesis at a low temperature, and methane is produced by acetoclastic and hydrogenotrophic methanogenesis at a medium temperature, while methane is exclusively produced by hydrogenotrophic methanogenesis at a high or ultra-high temperature

Chaotic mixing enhanced by rigid-flexible impeller in stirred vessel

Abstract: Flow field in a stirred vessel is usually divided into chaotic and regular mixing regions. It is an alternative way to improve mixing performance and lower the energy consumption by enlarging chaotic mixing region. Reasonable design of impeller is helpful to form appropriate flow condition and to improve the fluid mixing efficiency. Rigid-flexible combination can be designed by flexible body and rigid body with multiple-body motion behavior, intensifying the chaotic mixing. In this study, with the software Matlab, the largest Lyapunov exponent and multi-scale entropy in the tap water mixing system are investigated with double mechanical impellers. The difference between rigid and rigid-flexible impellers is analyzed in mixing performance. Results show that the rigid-flexible impeller enhances fluid movement and the fluid goes into chaotic mixing. At 210 r·min-1,the fluid is chaotic mixing, and the largest Lyapunov exponent is 0.041 for rigid impeller, while it is 0.048 for rigid-flexible impeller. The rigid-flexible impeller could transfer energy effectively and make the energy distribute uniformly. At agitation speed 150 r·min-1, the multi-scale entropy rate of rigid-flexible impeller is similar to that of rigid one at 210 r·min-1. Compared with rigid impeller system, the mixing time is shortened by about 26% with rigid-flexible impeller system. The rigid-flexible impeller could enhance the fluid chaotic mixing and save energy by changing the flow field structure and energy dissipation.

Application of entropy generation method for analyzing energy loss of cyclone separator

Abstract: In this paper,entropy generation analysis is applied to investigate cyclone separator.The Reynolds stress model is used to simulate the flow field in a cyclone separator with adiabatic wall.The energy loss predicted by pressure drop and exergy loss predicted by entropy generation analysis method and exergy analysis method for calculation results of computational fluid dynamics indicate the availability of the second law of thermodynamics for investigating the energy consumption in cyclone separator.The entropy generation due to turbulent dissipation,viscosity in turbulent core flows,fluid friction near the wall,and heat transfer are calculated with the computation of turbulent kinetic dissipation rate,velocity,wall shear stress and temperature.It is found that the fluid friction near the wall and turbulent dissipation are the main factors for energy loss of cyclone separator.The percent of entropy generation in the vicinity of finder vortex and dust exit with the volume ratio of 10% and 5.8% in the cyclone separator is over 14% and 16%,respectively.The result can serve as a direction to decrease energy loss of cyclone separator.

Resistance characteristics of micro pin fins with different cross-section shapes

Abstract: The de-ionized water,used as the working fluid,flowed through the channel fitted with staggered array of micro pin-fins in circular,diamond,and ellipse shapes and the resistance characteristics were investigated experimentallyThe investigation shows that the pressure drop increases with the flux with these three micro pin-fin groupsWhen the flux is very small,ellipse and diamond shape micro pin-fin groups present almost the same pressure drop because the influences of the shape of micro pin-fin on the flow is weakened by the laminar boundary layer,while the flow resistance of circular pin fins is maximal due to the longer flow distanceThe pressure drop of the ellipse shape micro pin-fin is minimal compared with other two shapes of pin fins when the Reynolds number is relatively largeAt low Re,the friction factor of diamond shape micro pin-fins with the same major axis and minor axis as the ellipse shape micro pin-fins is slightly smaller than that of ellipse shape pin-finThe study also shows that the calculation values from the correlation related to the diamond shape micro pin-fins agree with experimental data among the three shapes of micro pin-fins

Characteristics of multiphase flow, mixing and transport phenomena in airlift loop reactor

Abstract: Compared to bubble columns, the mixing performance in an airlift loop reactor is significantly improved due to the presence of regular fluid flow, which has been widely applied in many chemical processes, such as fermentation and crystallization. Therefore, it has become a hot research topic in recent years. The flow regimes, hydrodynamic characteristics(including phase holdup, circulation velocity, mixing time and segregation index) and mass/heat transfer characteristics are reviewed in this paper. The influence of dispersed holdups, especially that of solid on the key parameters in the reactor, such as circulation liquid velocity and chemical reaction rates, is analyzed. In addition, a perspective is given on multi-disciplinary study of multiphase flow, mass/heat transfer and chemical reactions with mechanistic models in order to promote the industrial application.

Recent progress on atmospheric and room temperature plasma mutation breeding technology and its applications

Abstract: Radio-frequency atmospheric pressure glow discharge(RF APGD) plasmas have outstanding features of no need of expensive and complicated vacuum system, low gas temperatures, high concentrations of reactive species, good discharge uniformity, strong controllability and diverse interactions with various biomolecules, which have attracted more and more attentions for their applications in biotechnology. Our research group introduced the RF APGD plasma jet into the mutation breeding field. Based on the study on the physical characteristics of RF APGD plasmas and their interaction mechanisms with bio-macromolecules and whole cells, a novel mutation breeding system, named as atmospheric and room temperature plasma(ARTP) mutation breeding machine was invented. The ARTP mutation breeding system has the features of high safety for the operators and environment, easy operation, rapid mutation capability, high mutation rate and genetic stability of targeted mutants, as demonstrated by successful mutation for more than 40 different microbes including bacteria, fungi and algae. This paper reviews the recent research progress of ARTP mutation breeding technology, hopefully contributing to the development of the life evolution study and the industrial strain modification as a powerful mutation tool.

Fault detection for chemical process based on LSNPE method

Abstract: Complex chemical processes often have multiple operating modes and the within-mode process data do not follow Gaussian or non-Gaussian distributions.To handle the problem of multiple operating modes and complex data distribution,a novel fault detection method,local standardized neighborhood preserving embedding(LSNPE) was proposed by applying local standardization(LS) strategy to the neighborhood preserving embedding(NPE) algorithm.Firstly,LSNPE algorithm was performed for dimensionality reduction and thus the main features of the collected data were extracted.At the same time,it could keep the neighborhood structure unchanged.Next,a monitoring statistics was established using the local outlier factor(LOF) of each sample in feature space and its control limit was determined.Instead of building multiple monitoring models for complex chemical process with different operating modes,the proposed LSNPE method built only one global model to monitor a multi-mode process without the support of any prior process knowledge.Finally,the feasibility and efficiency of the proposed method were illustrated through a numerical example and the Tennessee Eastman process.

Adsorption characters of ammonium-nitrogen in aqueous solution by modified corn cob biochars

Abstract: Biochars produced by pyrolysis of corn cob(600℃) which is agricultural waste, and modified with hydrochloric acid, hydrogen peroxide and nitric acid separately. Elemental analysis, BET-N2 surface area(SA), scanning electron microscopy, Boehm titration and FTIR spectra were used to characterized their physicochemical properties. Batch experiments were conducted to investigate ammonium adsorption process of corn cob biochars. The results revealed that acid modification can significantly improve biochars' specific surface area, which were 17.74, 212.89, 208.74 and 209.15 m2·g?1 for without modified and modified with HCl, HNO3 and H2 O2 samples, respectively; while the amounts of acidic functional groups were 0.11, 0.95, 5.73 and 2.15 mmol·g?1, respectively. The results for fitting experimental data of adsorption process with isotherm models showed that it is better for Freundlich isotherm model than Langmuir isotherm model. Moreover, the adsorption process can be well described by pseudo-second-order kinetic model. The results obtained demonstrated that biochars modified with nitric acid have the highest adsorption capacity because of more acidic functional groups.

Numerical simulation and experiments on submerged supersonic gas jets

Abstract: Underwater submerged supersonic gas jet is a gas jet from the orifice or nozzle into water at supersonic speed, which diffuses in water flow and causes complex gas-water mixing and interface instabilities. Firstly, the flow field of the 3-dimensional submerged supersonic gas jet was recorded by a high speed camera in the experiment. Secondly, Ax-symmetric model was established for the experimental case by the VOF method. The numerical and experimental results showed early evolution of bubble motion of the jet and evolution process of a bubble, including generating, growing, being broken by the next one, bulging and back-attack etc. The jet flow field structures, such as distribution of pressure and velocity, Mach number in the flow field during injection were analyzed by numerical simulation. Complex shock wave/expansion wave cell structures existed in the field of the submerged jets, influencing the parameters in the flow fields and leading to the phenomena, such as bulging, back-attack. The results of numerical simulation agreed well with the results of experiment.

Analysis of thermodynamic losses of heat transfer process in large-scale LT-MED desalination plant

Abstract: Based on correlations of flow resistance and sea water boiling point elevation(BPE) applicable to the low-temperature multiple effect distillation(LT-MED) desalination plant, the thermodynamic losses in a large-scale LT-MED desalination plant were calculated and analyzed, including the distribution and proportion of various thermodynamic losses caused by BPE and flow resistances. The effect of the number of evaporator/condenser on thermodynamic losses was studied. The result indicates that, for a large-scale LT-MED desalination plant with constant production capacity, the total thermodynamic losses increases with the number of effects. The thermodynamic loss caused by BPE constitutes the highest proportion while that by the flow resistances can not be ignored. According to the analysis on the loss, the operating characteristics of LT-MED desalination system are summarized as small temperature difference, low pressure drop, saturation states and high sensitivity.

Preparation and characterization of organic-inorganic hybrid flexible silica aerogel

Abstract: Monolithic silica aerogels were prepared via supercritical fluid drying of methanol gels, which were obtained using the sol-gel co-precursor method with methyltrimethoxysilane(MTMS) and tetraethoxysilane(TEOS) as precursors, methanol as solvent, oxalic acid and ammonia as catalysts. The microstructure, specific surface area, pore size distribution, bending and compressibility, and thermal stability of silica aerogels were studied by scanning electron microscopy, nitrogen adsorption/desorption tests, and thermogravimetric analysis. The properties of the silica aerogels, prepared with different mole ratios of MTMS/TEOS, varied obviously. The silica aerogel, prepared with mole ratio of MTMS/TEOS at 8/1, was a flexible material with density of 0.11 g·cm-3, porosity of 94.2%, specific surface area of 693.3 m2·g-1, maximal bending angle of 92o, maximal compression ratio of 41.2% and compression spring-back of 100%.

Extraction of praseodymium(III) and neodymium(III) in saponified P507-HCl-kerosene system

Abstract: The effect of initial aqueous pH, concentration of P507 and saponification degree of P507 was investigated for P507-HCl-kerosene system, not only for individual rare earth elements, but also for both praseodymium(Ⅲ) and neodymium(Ⅲ). Extraction in a membrane dispersion micro-extractor was performed after determining the product formed by saponification reaction and optimized separation conditions. Using membrane dispersion micro-extractor could increase mass transfer rate and shorten reaction time to 2.5 s with similar extraction rate and separation factor achieved by shake flask tests.

Microbial community compositions and diversity in pit mud of Chinese Luzhou-flavor liquor

Abstract: Pit mud(PM) plays a key role in controlling the quality of Chinese Luzhou-flavor liquor in anaerobic fermentation. Here, microbial community composition and diversity in PM samples using pyrosequencing technique were investigated. A total of 494293 valid sequences were obtained. The reads fell into 796 operational taxonomic units(OTUs) affiliated to 21 phyla. The predominant groups were Firmicutes(66.8% of total reads), Bacteroidetes(16.0%), Euryarchaeota(9.0%), Spirochaetes(2.2%), Actinobacteria(1.8%) and Chloroflexi(1.0%). Microbial diversity increased with cellar age until 25 years old, but kept relatively constant from 25 to 50 years. A large difference between microbial communities was observed in the pit muds with different cellar ages. Lactobacillus predominanted in 1-year pit mud(62.3%), but its abundance decreased remarkably in 10-year and older pit muds. In contrast, the abundances of Petrimonas, Clostridium IV and methanogens increased dramatically. In addition, Archaea in PM were mainly composed of hydrogenotrophic methanogens such asMethanobrevibacter, Methanoculleus, Methanobacterium, while the H2/acetate-utilizing Methanosarcina was more abundant in PM with cellar age of 25—50 years(3.1%—4.5%). This research supports the practical experience that old fermentation pits produce high quality Luzhou-flavor liquor.

Depressurizing dissociation of natural gas hydrate with different saturation

Abstract: Natural gas hydrate(NGH),a high quality,clean and efficient new energy,has received worldwide attention.Among the NGH dissociation methods,depressurization has been considered as an effective way.However,the result of depressurization dissociation is different for NGH with different saturations.A home-made one-dimensional experimental system is used for studying formation and dissociation behavior of NGH.At simulation marine geological conditions,NGH with different saturations is formed in the simulated porous media.Then they are dissociated by depressurizing slowly.Dissociation performance and saturation influence of NGH are analyzed.The results show that:the NGH dissociation by depressurization can be divided into three stages:free gas production in the early stage,gas release from hydrate dissociation in the second stage and surplus free gas release in the third stage.In the second stage,with NGH saturation increasing from 16% to 48%,the average rate of gas production increases first and then decreases.It shows that the effect of NGH saturation on gas production rate by NGH dissociation is of non-linear relation.Higher NGH saturation results in a large range of temperature decrease.Within the range of our experimental conditions,the dissociation rate of NGH with medium saturation(32%) is relatively larger,so depressurization is a appropriate method for NGH reservoirs with medium saturation.

PAHs thermal desorption behavior of coking plant soil and its effect on soil characteristics

Abstract: Soils contaminated by polycyclic aromatic hydrocarbons(PAHs) were sampled from a typical coking plant in southeast Beijing,China,and tested by thermal desorption under the controlled condition of 50—450℃heating temperature and 30 min constant residual time using an indirect rotary heating laboratory equipment.After each thermal desorption program,decontamination level,residual contamination of 16 EPA priority PAHs and changes in soil characteristics,i.e.total organic carbon(TOC),dissolved organic carbon(DOC),surface area(SA) and soil particle size distribution,were investigated for low PAHs concentration soil(S1) and high PAHs concentration soil(S2),respectively.The results showed that with increasing heating temperature,the decontamination level of LPAHs(low molecular weight PAHs,sum of Nap to Pyr),HPAHs(high molecular weight PAHs,sum of BaA to BgP) and total PAHs increased significantly(p0.01),which was governed successively by heating temperature,PAHs molecular weight and contaminant concentration due to the F values based on a multivariate analysis.The decontamination level began to increase significantly around the melting point and for the isothermal desorption the significant difference of decontamination level between LPAHs and HPAHs existed only below 300℃ for S1 and 400℃ for S2.It was revealed that the thermal desorption process were evidently associated with the form of PAHs in soils and the bioavailable PAHs were almost removed at 200—300℃.The decontamination level reached 91.3% and 98.4% at 450℃ heating temperature where the eight target residual PAHs concentration ranged from 0.07 mg·kg-1 to 0.71 mg·kg-1 for S1 and from 0.26 mg·kg-1 to 40.20 mg·kg-1 for S2,whereas several PAHs species still exceeded the corresponding screening levels for soil environmental risk assessment of residential land in Beijing.After thermal desorption at 450℃,it was also found that TOC decreased by 51.4%(p0.05) for S1 and by 23.1%(p0.05) for S2,simultaneously with an inverse change trend in DOC between S1 and S2.Moreover,surface areas of S1 and S2 after heating were smaller than that before heating,which coincided with the slight increase in soil particle size and agglomeration existing at an electron scanning program.

Improvement of structure design on swirl meter based on CFD

Abstract: In order to reduce the pressure loss of 150-caliber swirl meter,two programs of increasing the lead of swirler and the throat diameter of casing were adopted to improve the performance of swirl meter.In the flow range from 120 m3·h-1 to 2100 m3·h-1,numerical simulation and experiment were conducted to study the pressure loss characteristics and meter factor of the swirl meter before and after improvement,and internal flow characteristics of the section where piezoelectric sensors were located was analyzed.Through numerical simulation it was found that these two programs could reduce the pressure loss of swirl meter,but meter factor decreased with degraded precision.Small flow measurement could not be applicable because of the decrease of meter factor.If only considering the factor of pressure loss,program B(increasing the lead and the throat diameter) was better than the program A(only increasing the lead).The experiments were performed on sonic nozzle device to verify simulation results of two programs.The experimental results of pressure loss and meter factor basically agreed with numerical simulation results.

Basic research on utilization of stillage for biogas production

Abstract: Anaerobic digestion of stillage residue from the ethanol and wine industry is a promising method to provide energy and reduce waste. In addition, biogas slurry and biogas residue can be used as biological fertilizer after anaerobic digestion. In this study, anaerobic digestion of stillage was tested at medium temperature, meanwhile, the element changes and the feasibility of biogas slurry used as biological liquid fertilizer were investigated. The cumulative biogas yields from corn ethanol stillage, Maotai-flavor stillage, Luzhou-flavor stillage and cassava fuel ethanol stillage were 607.4, 578.7, 434.2, 122.3 ml·g?1(based on VS), respectively. The methane contents of biogas ranged from 60% to 70%. The biogas potential of stillage was proportional to degradation of substrates. The ions content of biogas slurry was in the range of the standard of biological liquid fertilizer.

Preparation of levoglucosenone by catalytic pyrolysis of cellulose over solid phosphoric acid

Abstract: Solid phosphoric acid supported on SBA-15 carrier was mechanically mixed with the cellulose, and then the mixture was subjected to fast pyrolysis to prepare levoglucosenone(LGO). Using Py-GC/MS(pyrolysis-gas chromatography/mass spectrometry) the effect of temperature and catalyst/cellulose ratio on pyrolytic products mainly LGO was examined. The results indicated that the presence of solid phosphoric acid could inhibit formation of levoglucosan(LG) and other byproducts, but promote greatly and selective formation of LGO, one of major pyrolytic products. The maximal LGO yield and relative content were obtained at the temperature of 350℃ and the catalyst/cellulose ratio of 1/1, having the relative peak area of 68.6%. Moreover, the solid phosphoric acid would also promote the dehydration of LG to form LGO.

Impact of gas distributor configuration on hydrodynamics in bubble column with pipe internals

Abstract: Gas holdup and liquid axial velocity profile were measured in a large scale bubble column with tube bundle internals with four different types of gas distributor configuration and were compared with results in the bubble column without internals. Gas distribution type directly determined gas holdup and liquid axial velocity profile in the bubble column with internals. With central distribution, gas holdup and liquid axial velocity profile showed much steeper than those in the bubble column without internals. With annulus or near wall distribution, they presented saddle profile, while with uniform distribution, both of them showed more flat than those in the bubble column without internals. The influence of gas distributor was local in the bubble column without internals and the well-developed region occupied a major part of the column, however, its impact was global in the bubble column with internals and the initial distributions of gas holdup and liquid velocity determined their distributions in the whole column. It was difficult to observe the existence of well-developed region in the bubble column with internals and therefore, designing gas distributor is more meaningful than the bubble column without internals.

Deformation and breakup of dispersed phase droplets in uniform electric field

Abstract: Through coupling hydrodynamics and electrostatics, a phase field method based on Cahn-Hilliard formulation was used to predict the deformation and breakup of dispersed phase droplets in a uniform electric field. The distribution of charge density, electric field strength and electric field force on the droplet surface as well as the distribution of flow field and electric field were studied from the micro-perspective. The micro-droplet deformation mechanism was established. The influence of electric field strength, droplet diameter and interfacial tension on the deformation was predicted by numerical simulation. The results showed that strong electric field intensity, large droplet diameter or small interfacial tension could cause larger degree of droplet deformation. The droplet mainly ruptured from its middle or the two ends. Rupture mainly depended on the physical properties of the continuous phase and dispersed phase. The above study would provide a theoretical basis for complex electric demulsification.

Molecular dynamics simulation of water molecules adsorbed at muscovite (001) surface

Abstract: As an important separation technique,microscopic phenomena of solid/liquid interface are crucial in flotation process.A molecular dynamics simulation is performed with PCFF_phyllosilicates force field to study the adsorption of water molecules on the muscovite surface,and atomic density profiles,hydrogen bond profiles,radical distribution function,mean squared displacement and density field are calculated.Results show that at a surface with water coverage larger than 1,the number of water molecules in the first three layers near the muscovite(001) surface will be stable with the increase of water molecules;water molecules closed to the surface represent much more ordering than those far from the surface;"solid effect" in the microscopic phenomena in the water solution is stressed by change trends of atomic density profiles and hydrogen bond profiles.It is found that K+ have poor mobility,especially in the z direction,and the stability of [Si4Al2]-K+ structure is proven via the density field of K+.

Numerical simulation on shell side fluid flow and heat transfer in heat exchanger with trefoil-baffles

Abstract: Heat exchangers with trefoil-baffle are a new type heat transfer device and are widely used in nuclear power system due to their special advantages, with the fluid flowing longitudinally on the shell side. In this study, to avoid the limitation of unit duct model, a whole model for the heat exchanger with trefoil-baffles is established including inlet and outlet nozzles. Based on the RNG k-e model, numerical simulation shell side fluid flow and heat transfer are conducted by using commercial CFD software FLUENT14.0. Characteristics of fluid flow and heat transfer performance on the shell side are analyzed. The results show that the fluid is fully developed after the first trefoil-baffle and the heat transfer coefficient and pressure drop vary periodically along the shell side. Fluid velocity increases gradually and the jet flow forms in the region near baffles. The secondary flow is also produced on two sides of baffles when the fluid flows through the trefoil-baffle. The jet flow and secondary flow can decrease the thickness of boundary layer and enhance the heat transfer.

Effect of waste heat recovery on net biogas yield in thermophilic biogas plants

Abstract: As a more productive process, themophilic digestion has not been popularized in China for the possibility of negative net biogas yield. A heat demand model based on the biogas plant at Alviksg?rden, Sweden was established to calculate the heating load so as to investigate energy consumption and net biogas yield. By comparing to the mesophilic biogas plant with the same scale in Jintan, Jiangsu, the results showed that despite the energy consumption of the thermophilic biogas plant at Alviksg?rden 2.1 times of the mesophilic one in Jintan, with a much higher biogas volumetric productivity as 2.3 m3·m-3·d-1, the biogas yield increment from increasing the digestion temperature from mesophilic to thermophilic was considerably larger than the energy consumption increment used for heating. Based on the current biogas productivity of the biogas plant at Alviksg?rden, if waste heat recovery was introduced to further decrease energy demand in substrate heating, net biogas yield could be increased from 82% to 90%. While without waste heat recovery, biogas productivity should be increased to 4.2 m3·m-3·d-1 to reach the same net biogas yield, suggesting that waste heat recovery was more efficient and economical than increasing biogas productivity via improvement of digestion technology to further increase net biogas yield.

Progress of smoothed particle hydrodynamics in complex flows

Abstract: As a fully mesh-less,Lagrangian numerical method,smoothed particle hydrodynamics(SPH) has notable advantages in problems of complex flows with free surface and/or moveable interfaceWith the improvement in its accuracy and stability,the SPH method has been extensively used in different areas of science and engineeringThe recent advances in SPH fundamentals are presented,with emphasis on interfacial flows,fluid-structure interaction,and non-Newtonian fluidsFinally,future development of the SPH method is prospected

Influence of crude oil composition on wax deposition on tubing wall

Abstract: The wax deposition was studied for man-made crude oil with various compositions(different contents of resin, asphaltene and wax) under various conditions in a rotary wax deposition facility. The influence of the compositions was explored by sediment sampling from tubing wall, analyzing with the differential scanning calorimetry(DSC) and using four components method. Combined with mechanism of the wax deposition initiated by resin and asphaltene, it was found that lower content resin and asphaltene in crude oil could have a synergistic effect with paraffin molecules on the wax deposition, while for higher content resin and asphaltene they were attached to the pipe wall in the form of paste, although the existence of resin and asphaltene could weaken the driving force for paraffin molecule migration and impede deposition of paraffin molecules. The results obtained from studying on the effect of various wax contents on wax deposition showed that higher average carbon number of paraffin molecules in man-made crude oil was, less content of wax in the wax layer deposited. But the paraffin molecules with more carbon number could take place eutectic roles with resin and asphaltene easily, due to they were of longer carbon chain, leading to they was easier to deposit on the pipe wall with resin and asphaltene together.

Jet flow pattern and its effects on mass transfer area and gas phase pressure drop in a water-sparged aerocyclone

Abstract: Water-sparged aerocyclone(WSA) is high efficiency gas-liquid mass transfer equipment,which takes the advantage of coupling effect of gas cyclone and liquid jet fields.In order to investigate the mechanism of jet-cyclone system of WSA and improve its mass transfer performance,jet flow pattern and its transformation was investigated by direct observation.Effective gas-liquid interfacial area per unit volume(a) of the WSA was also determined by chemical reaction method with CO2-NaOH solution system.The results show that jet flow pattern is mainly affected by jet velocity and air inlet velocity.There exists five jet flow patterns in the WSA,i.e.,steady state jet,deformed spiral jet,broken spiral jet,atomized spiral jet and total atomized spiral jet at jet velocity less than 4.42 m·s-1.At the jet velocity higher than 6.19 m·s-1 there exists only three jet flow patterns,i.e.deformed spiral jet,broken spiral jet and atomized spiral jet.The value of a is related to jet flow pattern,higher in atomized spiral jet than in other jets,and increases with liquid jet velocity because of the intense gas-liquid interaction in the WSA.