The main method of simulation exploiting methane (CH₄)from natural gas hydrate (NGH)is external stimulation.By heat injection or depressurization,NGH dissociate and release CH₄,which causes easily geological slope hazard,however,because of NGH structure damage.The method,replacing CH₄ in hydrate with CO₂,can dramatically lower the risk due to the replacement occurs in hydrate,and its structure cannot be destroyed.In this paper,the research works on CO₂-CH₄ replacement is reviewed comprehensively,including feasibility of replacement,kinetics model,simulation and experimental studies,and direction of further research and development is proposed for technologies exploitating CH₄ from NGH by replacement method.

The solidification process of mixtures of glycerol and 1,6-hexanediol with three mole ratios are carried out using molecular dynamics method.Self-diffusion coefficient and the specific volume method are used to calculate glass transition temperature separately,and the results are in good agreement with the experimental data.The self-diffusion coefficients of glycerol and 1,6-hexanediol hydroxy in mixtures are less than that of glycerol and 1,6-hexanediol hydroxyl.The first peak values of radial distribution function of glycerol and 1,6-hexanediol hydroxy in the mixture are higher than that of pure glycerol or pure 1,6-hexanediol hydroxy.As the temperature decreases,the radius of gyration is shorter,smaller bond lengths appear more,and bond angles change little.

A thermal storage system using multiple phase change materials (PCMs)has much better heat transfer and thermodynamic properties than that using single PCM.The phase change temperatures of multiple PCMs have an important effect on the performance of the thermal storage system.To obtain generalized results,the analysis method for thermodynamic exergy is employed,with the type of heat exchanger and heat transfer process neglected.The theoretical equation for the optimum phase change temperature of each PCM is derived.The optimum exergy efficiency is calculated for different number of PCMs.The results indicate that the exergy efficiency could be up to 80% with 4 or more PCMs,which is about 50% higher than that using single PCM.With thermal energy at 573.15 K as example,the optimum temperatures and the maximum exergy efficiencies for one to four PCMs are calculated,and the optimum combination of multiple PCMs is given on the basis of theoretical results.

A design for modified planar passive micromixer based on the concept of vortex-generated structure enhanced mixing is described in this work.By using computational fluid dynamics CFD-ACE+,three-dimensional numerical simulation and structural optimization for mixing were performed in order to reveal the structural influence on the flow feature and mixing characteristics.Experimental data were used to validate the numerical analysis.The computational and experimental results for the concentration distributions and flow patterns demonstrate that the expansion vortices,separated vortices and Dean vortices appear in the curved channel of this modified micromixer,which is arranged to vortex-generated structures.The combination and enhancement of the vortex system increase the fluid disturbance,effectively improving the contact area of fluid and accelerating the mixing process.Based on comprehensive consideration of mixing efficiency and pressure drop distribution,the structural design adopts the vortex-generated structure with regular arrangement,and the gap width ratio W_d/W,thickness-width ratio B/W,and arrangement angle θ_a are equal to 1/4,3/10,and 120°,respectively.Significant mixing effect of fluid in the micromixer can be realized in a wide range of Reynolds number.

Importing hotwind to the direct-discharged chimney of flue gas desulphurization(FGD),in which secondary dehydration device is installed,could lower the outlet moisture content and solve the problem of chimney rain effectively.In order to examine the influence of hotwind on the flow characteristics and optimize the structure of the chimney dehydration device to match the dehydration capacity and running resistance,discrete phase model,RNG k-ε double-equation turbulence model and component transport model based on calculation fluid dynamics (CFD)were adopted to build a hydrodynamic model to describe the flow field inside the chimney.The variation of temperature,velocity,pressure and moisture content in the chimney with and without hotwind and the optimal angle of blade of the rotating-stream tray were obtained by the numerical simulation.With hotwind added,the outlet temperature rises 3 K,outlet velocity is increased 0.6 m·s^-1,outlet pressure is decreased 55 Pa,outlet moisture content is reduced 29 mg·m^-3,and the optimal angle of blade is 45°.Compared with the angle of 42° in applications,the optimal angle makes the running resistance decrease 108 Pa with negligible increase in moisture content. The simulation results are in the range for practical use,verifying the rationality and feasibility of the simulation.The simulation provides theoretical bases for optimizing the internal structure of chimney and directing the sample locations in the project.

Gas-liquid turbulent flow in a side-entering stirred tank with φ1.5 m×1.2 m was simulated with computational fluid dynamics (CFD).Three interface boundary conditions (pressure-outlet,velocity-inlet and degassing boundary)and two drag force models(standard S-N model and Brucato-Tsuchiya model)were presented and respectively coupled with the Euler-Euler model and dispersed two-phase k-ε turbulence model by using user define function (UDF).The impeller power number,total gas holdup and gas phase distribution in the tank were calculated and compared with the measurements of the cold model experiments to investigate the effect of boundary condition of gas-liquid interface and drag force model on prediction accuracy.The results indicated that the predicted results calculated with the CFD model coupled with the Brucato-Tsuchiya model and adopting the velocity-inlet or degassing boundary condition,were in agreement with the experimental results,much better than the pressure-outlet boundary condition.

The deflecting oscillation of planar opposed jets was numerically simulated by large-eddy simulation (LES)at 35≤Re≤145000 and 4≤L/h≤40(where L was the nozzles separation,and h was the height of the slit of the planar nozzle).The numerical results were validated by comparing with experimental results of planar opposed jets.The influencing factors of the deflecting oscillation of turbulent planar opposed jets,such as different work fluids,confinement of boundary and height-to-width ratio of nozzle exit,were investigated,and a map of the parameter space describing the deflecting oscillation of planar opposed jets was plotted.The results showed that various fluids had no significant influence on the periods of the deflecting oscillation,and the dimensionless periods of the deflecting oscillation increased with increasing confinement of boundary,but decreased with increasing height-to-width ratio of nozzle exit.

The energy consumption of heating and domestic hot water in China is very large.The heat supply system based on air source absorption heat pump (ASAHP)is a promising alternative solution in cold regions.However,the single-stage ASAHP cannot operate normally under very cold weathers. Compression-assisted absorption cycles,including high-pressure boosting and low-pressure boosting in terms of the position of the pressurizer in the cycle,are proposed to improve the performance of ASAHP under low ambient temperatures.Different kinds of compression-assisted ASAHP using NH₃-LiNO₃ as working fluid have been comparatively simulated and analyzed.The results indicate that both high-pressure and low-pressure boosting can effectively improve the performance of ASAHP in cold conditions.Energy saving rates as high as 20%—45% can be obtained with different outdoor temperatures,driving source temperatures and hot water temperatures.Besides,low-pressure boosting ASAHP can achieve a higher primary energy efficiency than high-pressure boosting cycle in the same condition.Taken energy efficiency as well as difficulty of realization together,it can be concluded that the low-pressure boosting is a better choice for the improvement of ASAHP in cold regions.

Corrosion is one of the main characters of Al microchannel heat exchanger.In the present study,standard seawater acidified test (SWAAT)was carried out in microchannel heat exchangers with folded tube and traditional extruded tube,then the performance test and electron metallography analysis were carried on the test samples before and after the corrosion.The result showed that the performance of the sample with folded tube was much better than that with traditional extruded tube after SWAAT.According to the electron metallography analysis,for the test sample with extruded tube,the connection of fins and tubes was damaged first in the SWAAT.Obvious fin debonding occurred after 14 d of SWAAT,and leakage happened on the tube at main body after 28 d of SWAAT.In contrast,the fins of the test sample with folded tube were damaged first in the SWAAT,and no any fin debonding or leakage on the tube occurred after 49 d of SWAAT.The long-term performance of folded tube is better than that of extruded tube.

For the new heat exchanger,self-support rectangle converging-diverging tube bundle heat exchanger,3-D numerical simulations were performed with FLUENT software for turbulent heat transfer and fluid flow characteristics in the heat exchanger.To obtain the optimal structure of converging-diverging tube,the rib length (l)and height (h)were examined while retaining converging length ratio.The effects on heat transfer performance of tube side,shell side and whole heat exchanger were studied.With constant rib length,the effect of rib height was examined.The numerical results indicate that smaller rib length and larger rib height lead to better performance of heat transfer and larger flow resistance on both shell side and tube side.Performance evaluation criteria (η)is adopted to evaluate the overall heat transfer performance.When l=16.5 mm,η is the largest on the shell side,while when l=9 mm it is the largest on the tube side.For rib length of 15 mm,the overall heat transfer performance is the best when h=0.5 mm on the shell side,while it is the best when h=1.25 mm on the tube side.The reason is that the recirculation region increases with the increase of rib length and height on both shell side and tube side. With the increase of recirculation region,the friction in the channel increases.However,the recirculation region reduces the average intersection angle between the velocity vector and the temperature gradient,which is one of the essential factors influencing heat transfer performance.For rib length of 15 mm and rib height of 0.75 mm,the performance evaluation criteria η of the whole heat exchanger is 1.136—1.155 against the Reynolds number of shell side in the range of 27900—41900 as compared with the smooth tube bundle heat exchanger.

In the range of pressure from 11.5 to 28 MPa,mass flow rate from 450 to 1550 kg·m^-2·s^-1,and heat flux at inner wall from 50 to 585 kW·m^-2,an experiment was conducted to investigate the heat transfer characteristics of water in vertical downward tubes.The temperature distribution in the tube wall was obtained.The effects of heat flux at inner wall on heat transfer coefficient and temperature at inner wall were analyzed and corresponding empirical correlations were presented.The heat transfer coefficient of vertical downward flow was compared with that of vertical upward flow.The experimental results show that at subcritical and near critical pressures,dryout and departure from nucleate boiling occur in vertical downward tube.With the increase of inner wall heat flux,heat transfer deterioration occurs ahead and the peak wall temperature increases obviously after heat transfer deterioration.At supercritical pressures,the wall temperature increases slowly with fluid enthalpy when the bulk temperature is lower than the pseudo-critical temperature and increases considerably when the bulk temperature is higher than the pseudo-critical temperature.In the pseudo-critical enthalpy region,the heat transfer is enhanced.

Zeotropic mixtures are considered to be popular alternatives to chlorofluorocarbons and hydrochlorofluorocarbons in refrigeration systems.It has been discovered that composition shift of multicomponent mixtures will have negative effect on system performance.In order to reveal the influence of gravity on composition shift,by varying mass fraction,temperature and standing time and using refrigerants Z1,Z2 and Z3 (R290/R600,25%/75%,50%/50% and 75%/25%,by mass fraction)as working fluids,an experimental study of composition shift was carried out in a vertical copper tube with internal diameter of 10 mm and length of 2 m.A chromatographic analysis test bench was used to make an analysis on the composition shift and bring forward research suggestions.The results show that composition shift is weakly dependent on the mass fractions of mixtures.At 28.0℃,prolonging the standing time from 3 h to 24 h,decline rate of propane in the liquid phase varies from "large—small—large" to "decrease gradually",and composition shift of propane increases by 70.13%.In 3 h of standing time,composition shift of propane decreases 61.25% as the temperature increases from 28.0℃ to 40.0℃.

The research on transcritical ejector refrigeration cycle with CO₂ is rarely reported.In this study,a thermodynamic model for a transcritical ejector refrigeration cycle is established.The changes of ejector entrainment ratio,the cycle performance coefficient (COP)and effective performance coefficient (COP_m)with cooler pressure,cooler outlet temperature,heater pressure,heater outlet temperature and evaporation temperature are presented.As the cooler pressure increases,the entrainment ratio of ejector decrease,the cycle COP and COP_m first increase and then decrease,with optimum values at some cooler pressures.As the outlet temperature of cooler increases,both values of COP and COP_m decrease.With the increase of heater pressure,heater outlet temperature and evaporation temperature,the ejector entrainment ratio,the cycle COP and COP_m are improved,while the cycle COP decreases with the increase of heater outlet temperature.

A three-dimensional numerical study was carried out to investigate effects of fin angle,fin length,and tube wall temperature in natural convection on heat transfer enhancement for a longitudinal externally-finned tube placed vertically in a closed space.The numerical results show that the heat transfer rate per unit mass increases with fin length.The maximum heat transfer rate per unit mass occurs when the fin angle is about 60° for all the fin angles investigated.With increasing tube wall temperature,the maximum ratio of the natural convection occurs in the temperature range studied.In order to consider the effect of fin angle on heat transfer enhancement,the dimensionless factor d/H is introduced.The natural convection heat transfer criterion of longitudinal externally-finned tube in vertical is fitted based on 65 computational cases and the mean error is 3.53% between the criterion and simulations.

Effects of inclination on radial distribution of interfacial parameters were investigated for air-water bubbly flow in a pipe with the diameter of 50 mm.The double optical fiber probe method was used for measuring the local parameters of void fraction,interfacial area concentration and bubble passing frequency.Air and water were used as working fluids,with the superficial velocities of 0.002—0.037 m·s^-1 and 0.072—0.569 m·s^-1,respectively.Three inclination angles of 5°,15° and 30° were selected for the experiments.Four classical distribution types of the core peak,wall peak,intermediate peak and transition appeared under vertical flow condition.While for the inclined condition,bubbles congregate toward the upper wall of the pipe,resulting in the asymmetrical distribution of these parameters.The central broad peak leaned to the upper part of the tube,with its peak value increasing as the inclination angle increased.In the meantime,the peak near the lower wall lowered gradually,even disappeared, while the other one near the upper wall escalated accordingly.The interfacial parameters increased diametrically from r_i/R=-0.84 to the peak location around the upper wall,with its variation rate increasing as the inclination angle increased.The Sauter mean diameter under inclined condition were larger than that of vertical flow.

In order to deeply understand the super fine crushing technology of rear-mixed high-speed water jet flow,the mixing and jetting behavior of gas-liquid-solid three phases in acceleration tube with various diameter were investigated by using numerical simulation and crushing experiment methods.Mixing mechanism and acceleration performance of multiphase mixture jet flow were explored,and particles distributions in acceleration space were obtained.The result showed that aeration and entrainment effects of jet flow turbulent motion were the inherent mechanism of mixed attached phase.There existed many partition zones in the rear-mixed jet flow for particle acceleration.Whereby the nearer to the potential flow zone,the stronger the impact energy.Accordingly,optimizing configuration of the optional nozzle diameter with the acceleration tube diameter could force the particles near or enter the potential flow zone,whereby effectively improving grinding yield efficiency.The particles in space distribution within the acceleration tube were in the highest contents in high-efficiency acceleration zones of the outer and inner layers.As a result,the nearer to the potential flow zone,the fewer the particles.The particle contents in the air flow zone increased with increasing acceleration tube diameter.It was difficult for the particles to enter the ideal acceleration zone so that most of the particles were accelerated by relying on the high-efficiency acceleration zone of the inner and outer layers.In the case of maintaining the flowing morphological state of free jet flow,the grinding yield efficiency decreased with increasing acceleration tube diameter.Accordingly small tube diameter was of better constraint and concentration functions for water jet flow energy and particle motion space.

The heat transfer and flow characteristics of square wave impinging jets under different duty cycles are studied by numerical simulation method.This paper presents the heat transfer characteristics of target varied with traditional variables such as Reynolds number,pulse frequency and jet to plate spacing.The heat transfer and flow characteristics in the stagnation area with different duty cycles are analyzed emphatically.The numerical result is verified with the experimental result of impinging jet and pulsating jet.The results show that in the stagnation area,with the duty cycles of 0.5 and 0.7,the Nusselt numbers are very closed to each other.In the wall jet region,the Nusselt number with duty cycle of 0.5 is improved by 10% than that with duty cycle of 0.7.The Nusselt number with duty cycle of 0.9 is improved by 3% than that of steady jet in the whole jet region.Under duty cycle of 0.7,the vortex structure movement is much stronger in the stagnation area,compared to that under duty cycles of 0.5 and 0.9,and steady jet.

The gas-solids flow behavior in a two-dimensional riser was numerically simulated by combining computational fluid dynamics (CFD)and discrete element method (DEM).In particular,gas turbulence was investigated by standard k-ε two-equation model,and van der Waals force and rolling friction between particles were also considered.In the present study,the flow behavior of particles and gas was analyzed,distribution of particle concentration,velocity,granular temperature and gas velocity were obtained,and the effect of operating conditions on solids flow was also studied.The results indicated that particles flow showed significant non-uniformity in the riser,clustering was observed near the wall.The typical core-annulus flow structure with a dense phase near the wall and a dilute phase in the center was formed.In the vertical direction,it was divided into a dilute region in the upper zone and a dense region near the bottom in the riser.The results showed a certain amount of some backmixing of both particle and gas phase.Furthermore,it was demonstrated that particle velocity increased and particle concentration decreased with increasing superficial gas velocity,and particles had more non-uniform distributions.Larger solids mass flux led to more non-uniform solids distributions and higher particle concentration,while particle velocity was insensitive to change of solids mass flux.Simulated results were in qualitative agreement with experimental observations.

To study the influence of solidification rates of double emulsions on the sphericity of the resulting poly(α-methyl styrene)(PAMS)capsules in the microencapsulation process of PAMS capsules,the diffusion rates of fluorobenzene from oil phase to outer water phase under different conditions were experimentally measured,and the curing process of double emulsions under corresponding curing conditions were investigated.The results showed that the concentration of fluorobenzene in the outer water phase had a significant effect on the diffusion rate of fluorobenzene,which directly determined the solidification rate of double emulsions and then the sphericity of the resulting PAMS capsules.During the key phase of the solidification process of double emulsions,keeping proper concentrations of fluorobenzene in the outer water phase could remarkably reduce the solidification rate of double emulsions and consequently improve the sphericity of PAMS capsules.By optimizing the concentration of fluorobenzene in the outer water phase,the batch percentages of PAMS capsules with out-of-round less than 1 μm increased from 1.9% to 30.4%.

The photocatalytic activity evaluation of submicron-sized pigmentary titania using the degradation of Rhodamine B under ultraviolet radiation in a slurry reactor was studied.The effects of titania concentration,Rhodamine B concentration,and wavelength and power of the light source on reaction rate were investigated.The optimal operation conditions for evaluating the photocatalytic activity of pigmentary titania particles were determined.The experimental results showed that the photocatalytic degradation of Rhodamine B by pigmentary titania was an apparent first order reaction.The photocatalytic reaction rate was high under the conditions of a titania concentration of 4 g·L^-1,Rhodamine B concentration in the range of 2—10 mg·L^-1,and the use of the main emission peak of the light source at 254 nm,which were suitable for evaluating the photocatalytic activity of pigmentary titania.The photocatalytic activity of titania particles with a dense silica coat was measured under these optimized reaction conditions,which showed that this method could be used to evaluate the photocatalytic activity of the pigmentary or film coated titania quantitatively and rapidly.

An attempt using self-regulating mesoporous titanium dioxide whisker as catalyst carrier of hydrogen desulfurization,was carried out to prepare MoO₃-NiO/TiO₂ catalyst by single-step incipient wetness impregnation.X-ray,N₂ absorption/desorption,SEM,Raman diffraction were adopted to characterize the carrier and catalyst.The effect of mesoporous TiO₂ whisker as catalyst carrier on the performance of dibenzothiophene (DBT)hydrogen desulfurization (HDS)was evaluated.The results showed that the mesoporous TiO₂ whisker had highly active anatase,whisker morphology and larger specific surface area as well as special pore structure.DBT conversion over mesoporous TiO₂ whisker could approach 100% under moderate conditions of reaction temperature 280℃,hydrogen partial pressure 2.0 MPa,hydrogen/oil volume ratio 400 and LHSV 4 h^-1.Under the condition of similar specific surface area,the sequence of the desulfurization effect of the tested catalysts was anatase> mixed crystals of TiO₂ >rutile.As anatase carriers are concerned,the desulfurization effect increased with the increase of the specific surface area of TiO₂ carrier.

For the purpose of studying the impact of vortex generator structure and arrangement on fouling of heat exchange surface,CaCO₃ crystallization fouling deposition was simulated and the inside of rectangular channel was decorated with wing type vortex generator.Under the condition of temperature 50 centigrade,velocity 0.2 m·s^-1 and CaCO₃ concentration about 1000 mg·L^-1,the influence of geometrical factors was calculated and analyzed,such as winglet type,attack angle and lengthways distance on surface fouling deposition.The results showed that,at the specific temperature and velocity,surface unit area fouling decreased with increasing angle of attack of the wing vortex generator,and increased with increasing arrangement distance of vortex generator.The fouling on the surface reached a maximum when the distance was 60 mm,and then declined beyond 60 mm.

Ni-W/Al₂O₃ catalysts for heavy oil hydrotreating were prepared with incipient wetness impregnation,and the effects of zirconium step-impregnated and co-impregnated on the catalytic performance were studied.The catalysts were characterized with H₂-TPR,HRTEM,UV-Vis and XPS techniques.The results showed that zirconium weakened the strong interaction between active metals and Al₂O₃ support,increased the stacked layers of WS₂ active phase,zirconium step-impregnated promoted the sulfidation of active metals and increased the dispersion of W species on catalysts surface.Ni-W catalysts prepared with zirconium step-impregnated had outstanding hydrodesulfidation and hydrodenitrogenation performance for Venezuelan deasphalted oil.

SBA-15 with short channels was employed as adsorbent for uranium ions.Different factors including contact time,initial pH value and initial concentration of solution were examined to investigate their effects on adsorption of uranium by SBA-15 with short channels.Adsorption kinetics,adsorption isotherms and changes of FT-IR spectra of SBA-15 with short channels before and after adsorption were also studied.According to the experiment,uranium adsorption on SBA-15 is strongly pH-dependent and the maximum adsorption occurs at pH of 6,the adsorption reaches equilibrium within 30 min and the maximum adsorption capacity is 311 mg·g^-1 for initial solution concentration of 100 mg·L^-1.Adsorption capacity increases but adsorption percentage decreases with the increase of initial uranium concentration. Adsorption isotherm follows both Langmuir and Freundlich models,and pseudo-second order rate equation is better to describe kinetic process.The Si—OH and Si—O—Si groups existing in SBA-15 are mainly responsible for the adsorption of uranium.

Glutaraldehyde crosslinked humic acid-immobilized sodium alginate was used to develop a novel porous composite membrane adsorbent (GA-HA/SA)for the removal of uranium(Ⅵ)ions from uranium-contained wastewater.The physicochemical properties of GA-HA/SA before and after adsorption were investigated by FTIR,SEM and EDX methods.To investigate the effects of experimental parameters on adsorption behavior,batch experiments were performed by changing solution pH,initial concentration of U(Ⅵ)ions,contact time and temperature.The experimental data fit the Langmuir and Dubinin-Radushkevich (D-R)isotherm models well.The adsorption process can be described by pseudo-second-order kinetic model and the correlation coefficient is more than 0.99.The adsorption rate is controlled mainly by intra-particle diffusion.The calculated thermodynamic parameters such as Gibbs free energy change,enthalpy change and entropy change indicate that the adsorption of U(Ⅵ)onto GA-HA/SA is feasible,spontaneous and endothermic in nature.FTIR and mean free energy of adsorption for D-R isotherm show that the adsorption of U(Ⅵ)ions onto GA-HA/SA involves an ion exchange process.

The synthesis and purification steps were controlled in preparation of thymosin α1 to obtain the product with high-purity.In the solid-phase peptide synthesis (SPPS)process,TBTU/HOBt/DIEA was employed as the coupling reagent.In the sites where α-helix or β-turn structure formed easily,re-coupling reagent of HOBt/DIC was used to ensure a complete reaction.In the separation and purification process,a multi-step method was employed,in which reversed-phase ion-pair liquid chromatography was used as the main means,combining the advantages of reversed-phase chromatography and ion chromatography.The results showed that through the re-coupling the crude peptide had a purity of 67.2% with the use of TBTU/HOBt/DIEA reagent in SPPS.The purity of the refined thymosin α1 was above 99.5% with a total yield of 17.2% with the reversed-phase ion-pair liquid chromatography.This separation process avoids complex chromatography separation process.The method may be an efficient way for preparation of peptides with high-purity.

A configuration of an intermediate heat-integrated sequence of distillation columns (IHISDC)is proposed in this paper.The IHISDC configuration is analyzed by applying it in a direct sequence of distillation columns for ternary mixture separation.In this configuration,heat is transferred from the rectifying section of the high pressure column to the stripping section of the low pressure column through intermediate heat exchangers.Comparing to the conventional heat integrated sequence of distillation columns,the proposed IHISDC system presents smaller pressure difference between the two heat-integrated columns in the sequence,and consequently saves the energy cost for the reboiler of the high pressure column or for the condenser of the low pressure column.It is also found that the heat duties of the reboiler of the high pressure column and the condenser of the low pressure column are higher,and that the investment cost increases with the increase of the number of heat exchangers.The IHISDC needs to be optimized in order to lower its total annual cost(TAC).

The hazard and operability (HAZOP)analysis information consists of content information and structure information.A scenario object model (SOM)based on ontology was proposed,which could be used to represent contents and structures of hazard evaluation information.It could solve the problems including information hidden and information loss,existing in traditional HAZOP methods.Computer-aided automatic hazard evaluation and transfer,auditing and sharing of safety information were realized on graphical SOM.According to industrial practice,graphical SOM could lay the foundation for the standardization of hazard information,and be helpful to achieve high quality and efficiency of process hazard analysis.

The interaction between Bacillus megaterium(also called big bacterium)and Ketogulonicigenium vulgare (also called small bacterium)was studied for 2-keto-L-gulonic acid (2-KGA)mixed culture fermentation.The following mechanisms were found.(1)Big bacterium might adjust its growth behavior by quorum sensing.(2)Metabolites and autolysis substances of big bacterium were beneficial to overcoming the metabolic defects of small bacterium and therefore accelerating the latter's growth.(3)Small bacterium released lysozyme to promote big bacterium's autolysis.(4)Big bacterium autolysis released specific protease substances to enhance sorbitol dehydrogenase (SDH)which might increase the synthesis rate of 2-KGA.Based on such mechanisms,a kinetic model of 2-KGA mixed fermentation was established.Model validation was carried out with four sets of experimental data under different cultivation conditions.The results demonstrated that the proposed model was able to well describe the growth of two bacteria and 2-KGA production.

Taking into consideration the high-dimensional,correlated and nonlinear process data in the injection molding process with multiple operating modes,an online product quality prediction method was developed based on offline clustering and online recognition of the operating modes.Firstly,a nonlinear dimension reduction method,Laplacian Eigenmap (LE),was used to project the high-dimensional process data onto a low-dimensional feature space,where a Mean Shift based clustering algorithm was used to obtain the underlying operating patterns in the injection molding process.Meanwhile,an online operating mode recognition algorithm was proposed by making use of the principle of Mean Shift.After that,a PLS-LSSVM prediction method,where the particle swarm optimization (PSO)method was used for parameter determination,was used to develop the soft-sensor model of product quality for each operating mode.A multi-mode quality prediction method was finally developed by combining LE,Mean-Shift clustering and PLS-LSSVM algorithms.The experimental results showed that the proposed method outperformed the standard PLS-LSSVM method,and it could become a useful tool for online quality prediction for the industrial injection molding process with multiple operating modes.

A rapid design method for water using network with multiple contaminants was developed by mathematical programming based on rules of thumb.One effective strategy to solve complex or large-scale water network is that to simplify the algebraic model.However,obtaining accurate sequence of water process orders,such as water source or water demand,is the key to eliminating unnecessary stream and simplifying mathematical model of water network.Therefore,according to the analysis of limiting data and the understanding of the water process,a new sorting method of water supply and acceptance was proposed,then the necessary water pinch rules,sequences and approximation rules,and mixing rules were also set in order to remove unnecessary water network structure,simplify mathematical models and reduce the dimension of network composition.Finally,the problem with NLP(nonlinear program)model was solved with the LINGO (linear interactive and general optimizer)language.Three literature examples were used to illustrate the proposed approach.The result showed that setting the rules could effectively reduce model scale and nonlinear variables,shorten solving time,and obtain optimal design.

More and more nonlinear distributed parameter model described by partial differential equations have been directly adopted in advanced control strategies to improve control performance.However,some model parameter is highly sensitive to the operating condition that regularly changes.A novel characteristics based identification algorithm was proposed for estimating the time-varying parameter for a class of hyperbolic distributed model.Based on the method of characteristics,the partial differential equation (PDE)was transformed into a system of ordinary differential equations (ODEs).According to the analytical expression of the state variable,the model parameter was optimized and updated iteratively based on the latest measurable data sequence.Simulation results showed that the proposed identification algorithm achieved good performance and the time-varying parameters could rapidly converge to its true values.The experimental application on a circulating fluidized bed scrubber achieved an average prediction error within ?6.5%,which provided the basis to implement advanced control strategies with mechanism model described by partial differential equations.

The electrochemical oxidation of zinc O,O,O',O'-tetrabutyl bis(phosphorodithioate)(ZBPD)on glassy carbon electrode in DMF-H₂O solution was studied by cyclic voltammetry and chronocoulometry. The influences of temperature,scan rate and ZBPD concentration on the electrochemical characteristics of ZBPD were also investigated.The results showed that the electrochemical oxidation of ZBPD in DMF-H₂O solution was an irreversible process with one electron transferred,which was controlled by diffusion.Charge-time curve for the electrochemical oxidation of ZBPD in DMF-H₂O solution at various temperatures were obtained by chronocoulometry.In terms of the Cottrell equation,diffusion coefficient was estimated for each temperature,and it increased with temperature.According to the Arrhenius equation,the activation energy of diffusion of ZBPD in DMF-H₂O solution was calculated to be 29.52 kJ·mol^-1.

Lithium-ion battery has become the new safe and pollution free green energy,and has the advantages of high work voltage,high energy density,low self discharge rate and long cycle life. Separator as an essential part of the battery plays a key role in the performance of the battery.Its main function is to keep the positive and negative electrodes apart to prevent electrical short circuit and at the same time allow rapid transport of ionic charge carriers needed to complete the circuit during the passage of current in an electrochemical cell.Despite the widespread use of separator,a great need still exists for improving performance,increasing life,and reducing cost.In this paper,the composite membrane based on poly(vinylidene fluoride)(PVDF)and a polyethylene terephthalate (PET)non-woven matrix was prepared by coating PVDF/NMP solution on the matrix under the optimal condition.The pore structure in the PVDF region was generated by immersion precipitation of the polymer solution.Physical properties and battery performance of composite membrane were compared with those of the Celgard separator.The results showed that the composite membrane had bigger pore size and better pore distribution,porosity of 48.5%,ionic conductivity of 0.346 mS·cm^-1 and tolerance of 250.8℃.The capacity of Li-ion battery made with the composite membrane was 48.7 mA·h and was maintained at about 77.9% of the initial value on the 100th cycle at room temperature.The battery also showed good performance at different discharge rates and could meet the requirements of practical application.

The reactivity and inhibition performance on Al (111)surface of three pyridine molecules (pyridine,3-methylpyridine and 4-methylpyridine)was studied by using the density functional theory (DFT).The results showed that the frontier orbitals of the three corrosion inhibitor molecules,including the highest occupied molecular orbital (HOMO)and lowest unoccupied molecular orbital (LUMO),were all distributed on the pyridine ring,and both the nucleophilic and electrophilic activity centers of the three molecules were mainly concentrated at the heteroatoms N atom.Moreover,all of the three corrosion inhibitor molecules could perpendicularly chemisorb on Al surface via N atom,and the order of adsorption energy agreed with the inhibition efficiency obtained by experiment.The strong effect of N-Al bonding resulted from the atomic orbits hybridization.Additionally,3-methylpyridine and 4-methylpyridine could also nearly parallel physisorb on the Al (111)surface.

Calcium carbide is a major coal-derived platform chemical with annual production of more than 15 Mt in China alone.It is used to generate acetylene,upon reacting with water,to start production of many commodity chemicals,such as vinyl chloride and vinyl acetic acid.Reactions of calcium carbide with alcohols were reported decades ago but received little attention.With the production of low cost alcohols from coal,natural gas as well as biomass,these reactions may become more important in the future.In this paper,reactions of calcium carbide individually with three alcohols,methanol,ethanol and isopropanol,at various temperatures and time in the presence and absence of a catalyst were studied batch-wise in a stirred autoclave.The products were analyzed with gas chromatography,mass spectroscopy,X-ray diffraction and infrared spectroscopy.The products mainly included acetylene,vinyl ethers,calcium alkoxides,and higher alcohols from decomposition of calcium alkoxides.One of the reaction pathway involved formation of acetylene and calcium alkoxides in the first step,reaction of acetylene with alcohols to produce vinyl ethers in the second step,and decomposition of calcium alkoxides to higher alcohols.

High temperature desulfurization of coal gas is a key step of integrated gasification combined cycle (IGCC)and direct reduced iron (DRI)production,which directly influences the global thermal efficiency.Manganese-based sorbents with different Mn-contents were prepared by coprecipitation method for the high temperature sulfur removal.Precipitation was conducted by neutralizing the mixed solution of manganese nitrate and alumina nitrate with 10% NH₃·H₂O at 50℃.And the pH value in precipitation was kept around 9.The sorbents prepared were tested in a fixed-bed reactor by sulfidation-regeneration cycles.XRD,SEM and BET were used to characterise the structural change of the sorbents during the cycles.The sorbents made by coprecipitation method have good Mn/Al dispersibility.The desulfurization reaction at 850℃ was rapid and quantitative.The sulfur capacity increased linearly with increase of manganese content in the sorbents.The S/Mn atomic ratio was within 0.90—0.95 after sulfurization.The sulfur capacity was not influenced by space velocity and H₂S content in feed gas.The sulfided sorbent was regenerated using diluted air containing 3% O₂ at 850℃.The sulfur capacity was stable after many cycles.So,the sorbents could be used as regenerable sulfur sorbents for high temperature H₂S removal.

An investigation into chemical-looping gasification (CLG)of coal with K₂CO₃ and NiO-decorated Fe₂O₃ oxygen carrier in a fluidized bed reactor,using steam as the gasification-fluidization medium,was carried out.The reactivity and regeneration of two kinds of Fe₂O₃ composite oxygen carriers in multi-cycles,as well as the mechanism and kinetics model of the gasification process,were presented.At 920℃,the reactivity order was as follow:Fe4Al6K1>Fe4Al6>Fe4Al6Ni1.X-ray diffraction (XRD)images showed that the Fe4Al6K1 composite oxygen carrier was completely regenerated after 6 cycle redox experiments,and potassium ferrites were formed during the calcinations process,whose structure could boost the reactivity of Fe-based oxygen carrier.Fe4Al6K1 particles were excellent oxygen carriers for chemical-looping gasification of coal.Finally,the peak fitting technique was used to analyze the gasification reaction rate curve describing the reaction mechanism of coal and Fe₂O₃ composite oxygen carrier.It indicated that complex reactions of CLG included three stages,the reaction between Fe₂O₃,coal char and steam,the gasification of coal char,and the reaction of Fe₃O₄ to FeO.

Ignition characteristics of coal powder airflow was investigated with a one dimensional furnace under various oxygen-enriched conditions,to get their changing laws.The results show that with oxygen concentration increases,ignition temperature of four kinds of coals decrease greatly and do faster for low volatile coals,and an obvious transformation is observed for ignition mode of pulverized coals,from homogeneous to heterogeneous,the oxygen concentrations corresponding to the transformation are about 40% for bitumite,50%—60% for lignite and about 30% for both lean coal and anthracite,respectively. With oxygen concentration increasing,the optimal coal powder concentrations increase first and then decrease for bituminous coal and lignite,but decrease slowly for lean coal and anthracite.

Desulfurizers CuO supported ATP were prepared using direct precipitation method and applied for sorbing H₂S at ambient temperature.XRD and TEM were employed to characterize the desulfurizes. The effects of calcination temperature,CuO loading,gas flow rate and reaction temperature on the desulfurization performance were investigated.The diffusion and thermodynamics data demonstrate that dispersion state of CuO on the support depends highly on calcination temperature and CuO loading.Over-calcination or over-loadings may result in serious destructive and different dispersion state of CuO,which cause rapid decline of desulfurizer activity.Low gas flow rates are benefit for sorption capacity and the usage ratios of the sorbents can reach to 97%.When reaction temperature is at 0℃,the desulfurizers still be of high capacity 33.17%.

A honeycomb SCR catalyst of V₂O₅/TiO₂ with WO₃ and MoO₃ was prepared and its deNO_x performance was investigated in a pilot plant test using flue gas of a coal-fired power plant.The results show that the larger catalyst volume is,the higher deNO_x efficiency,and SO₂ oxidation increases too,but increase ratio becomes smaller.When deNO_x efficiency is above 80%,the outlet NO_x concentration met the emission standards,and the efficiency improvement is not significant by further enlarging catalyst volume which led to higher construct cost.In order to obtain the best ratio of deNO_x efficiency to catalyst volume and avoid resources waste for single requirement of higher deNO_x efficiency,SCR catalyst volume should be adjusted for different boiler types,according to flue gas component of coal-fired power plant and national emission standards.The deNO_x efficiency reduces with soot increase deposited,and drops about 9.4% within 4 h of soot depositing.The outlet NO_x concentration can be at 198 mg·m^-3 after 8 h of soot depositing.At 0.031 kg·m^-3 of fly ash concentration,the soot deposited needed to be blown each 6 h to obtain a satisfied deNO_x efficiency (>80%).When run time prolongs,the deNO_x efficiency falls sharply first,and then reaches a relative stable level.Within 48—168 h,the deNO_x efficiency and SO₂ oxidation decline less than 1% and 0.1%,respectively.After continuous run for 3 months (2160 h),the NO_x concentration at outlet of SCR tower is 196 mg·m^-3.The deNO_x efficiency declines at a rate of 1% per 700 h for continuous 12 month run.

Extraction of iron from pyrite cinder by mixed acid of sulfuric acid and hydrochloric acid, and main factors influencing iron leaching rate were investigated.In order to analyze feasibility of extraction of iron from pyrite cinder,the main elements were determined by using X-ray fluorescence spectrum analyzer (XRF).The crystal type of iron oxide in the pyrite cinder was also analyzed by X-ray diffraction (XRD)to understand the presence forms of iron in pyrite cinder.First,10 g dried pyrite cinder were added to a 250 ml three-necked flask.Then,sulfuric acid and hydrochloric acid of specified concentration and quantity were gradually added into the flask under proper stirring,and were kept at a specific temperature for several hours.After filtration,the solution was diluted to 250 ml with distilled water.The diluted solution was used for determination of iron content in leacheate using the stannous chloride-mercury chloride-potassium dichromate method.At last extraction conditions were optimized.The results showed that the significances of each factor on iron extraction were as follows:concentration of sulfuric acid>hydrochloric acid amount>reaction time>sulfuric acid over-dose coefficient.Iron extraction rate increased with higher reaction temperature and increasing amount of hydrochloric acid.However,there existed an optimum combination of sulfuric acid concentration,reaction time and sulfuric acid over-dose coefficient.The optimal conditions were reaction temperature 118—125℃,reaction time 3 h,sulfuric acid concentration 50%—60%,and hydrochloric acid 0.25 ml·(g pyrite cinder)^-1,sulfuric acid over-dose coefficient 1.2.Under these conditions,the extraction yield of iron was 93.1%,much higher than that by a single acid.So,the process can improve utilization of iron resource.

Biochar samples were prepared by hydrothermal carbonization (HTC)from municipal sewage sludge (MSS)and textile dyeing sludge (TDS)at different temperatures ranging from 150℃ to 300℃.This study focused on carbon fixation in biochar.The results showed that carbon fixation was significantly affected by sludge type and hydrothermal temperature.The HTC process of MSS was based on decarboxylation,while that of TDS was based on dehydration.Atomic ratios of biochar from MSS varied more greatly with the rise of hydrothermal temperature than those from TDS.Carbon recoveries in biochar from MSS were mainly influenced by biochar yield and decreased from 68.0% to 49.0% as the temperature increased,while those dropped from 100.0% to 76.8% for TDS due to the dominating effect of carbon content.Furthermore,the stable carbon content and its yield,recalcitrant C/total OC (RIc)of MSS biochars increased from 4.19% to 6.62%,from 123.6% to 161.2% and from 48.02% to 64.34% respectively with a rise of temperature,respectively.But the data of those indexes decreased from 3.80% to 1.86%,from 103.0% to 46.5% and from 54.26% to 47.04% respectively for TDS.Raman spectroscopy indicated that polycyclic aromatic hydrocarbon,fused aromatic ring and graphite-like microcrystalline structures led to high stability of MSS biochar.It was obvious that carbon fixation in biochar from municipal sewage sludge was better than that from textile dyeing sludge.

The relationships between process performance of ANAMMOX,conductivity and ionic strength variations were investigated.The linear correlations were found not only between the conductivity and main ions' concentrations of substrate,but also between the conductivity and the concentration of synthetic wastewater.There is preferably agreement between conductivity variation and process performance of ANAMMOX.The conductivity could serve as an indicator that reflects volumetric loading rate,volumetric nitrogen removal rate,and concentrations of influent and effluent,and it is a suitable parameter for process performance variation and could assist process control of ANAMMOX.

In the pre-denitrification of anoxic-aerobic reaction process,nitrite accumulation and sludge performance at different phenol concentrations were investigated.The results showed that there were two obvious nitrite accumulations finally stabilized at 70%±5% when phenol varied from 0 to 90 mg·L^-1.At low phenol concentration (0 to 30 mg·L^-1),nitrite accumulation and recovery were caused by microbial structure varieties and secreting extracellular polymer.At high phenol concentration (60—90 mg·L^-1),nitrite accumulation was caused by microbial population changes of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria was caused by phenol inhibition.Ammonia oxidation rates and nitrogen oxide production rates varied from 10.85 mg N·(g MLSS)^-1·h^-1 and 10.12 mg N·(g MLSS)^-1·h^-1 to 2.79 mg N·(g MLSS)^-1·h^-1 and 2.32 mg N·(g MLSS)^-1·h^-1,respectively.Nitrite accumulation rate had a negative correlation with nitrogen oxide production rate,whereas a positive correlation to phenol concentration.Fluorescence in situ hybridization showed that nitrifying bacteria communities changed due to phenol inhibition,with AOB relative quantity increasing from 2.80% to 9.30%.As carbon source,phenol caused sludge concentration increase from 2500 mg·L^-1 up to 5870 mg·L^-1.When total extracellular polymeric substances declined from 67.20 mg·(g VSS)^-1 to 32.10 mg·(g VSS)^-1,sludge volume index (SVI)accordingly changed from 165 ml·g^-1 to 50 ml·g^-1.Nitrite accumulation,filamentous bacteria and extracellular polymer contributed to SVI changes in the activated sludge system,and nitrite accumulation was the main reason followed by filamentous bacteria.

In treating simulation coking wastewater in upflow blanket filter(UBF),addition of NaNO₃ in water for simulating backflow of nitrification liquid results in simultaneous methanogenesis and denitrification,along with COD removal rate 94%,and NO₃^--N removal efficiency 99%.In denitrification dynamics research of the sludge at the bottom of the UBF,double-substrates Monod model was adopted to fit the test data obtained under conditions of nitrite accumulation,NO₃^--N+0.6NO₂^--N as the electronic acceptor of denitrification.The results show that there is a good correlation between the fitting curve and the experimental measurement.Then differential model based on Monod model was used to fit the change in the concentration of NO₃^--N and NO₂^--N respectively,relevant parameters obtained were as follows:The maximum specific degradation rate and half-saturation constant are 1.13 d^-1 and 2.0 mg·L^-1 for NO₃^--N,and 0.66 d^-1 and 2.5 mg·L^-1for NO₂^--N.The half-saturation constant of organic substrate based upon NO₃^--N and NO₂^--N are 90.8 mg·L^-1 and 96.8 mg·L^-1.

In the present paper bamboo was hydrothermally treated to overcome biomass recalcitrance for enzymatic hydrolysis.The effects of pretreatment temperature,residence time,adding amount of cellulase and bamboo kinds on enzymatic hydrolysis of glucan/xylan were investigated.The result shows that hydrothermal treatment can significantly improve total monosaccharide yield.The optimal pretreatment temperature is 190℃ and residence time 10 min.Approximately 74.3% glucan and 54.0% xylan were transformed after 72 h enzymatic hydrolysis using 15 FPU·(g glucan)^-1 of cellulose (about 1% of glucan),which are 3.5-fold and 4.7-fold of untreated substrate respectively.Too high treating temperature and too long staying time can lead to degradation of xylose and glucose,so total yield of monosaccharide decreases.If cellulase amount adding increases from 15 FPU·(g glucan)^-1 to 60 FPU·(g glucan)^-1,the total sugar recovery goes up 21.5% and 9.9% for treated and untreated bamboo,respectively. To rise enzymatic digestibility of bamboo,it was more effective using hydrothermal pretreatment than increasing enzyme amount.Hydrothermal pretreatment was sensitive to raw biomass materials and significantly different results were obtained for different bamboo materials.

The equilibrium species and theoretical electromotive force of cells fed with NH₃ and 3% H₂O humidified H₂,CH₄,C₃H₈ and underground coal gasification(UCG)gas on the basis of minimum Gibbs free energy were calculated,whilst the open circuit voltage(OCV),V-I characteristics and long-term stability of NiO-GDC‖GDC‖Ba_0.9Co_0.7Fe_0.2Nb_0.1O_3-δ(B_0.9CFN)anode-supported cells operated in above five fuels were evaluated.The results showed that direct utilization of hydrocarbon fuels in anode could achieve a desirable electromotive force (EMF)no less than 1.05 V,while the OCV for ceria-based cells was comparatively poorer due to the presence of electronic conductivity.Besides,the synergy effect between stagnant kinetics of hydrocarbons reforming and the relatively sufficient O^2- supply due to fast migration of oxide ions suppressed carbon deposition at low operating temperatures for ceria-based SOFC. Furthermore,the UCG gas fed cell exhibited peak power densities as high as 0.151,0.299,0.537 and 0.729 W·cm^-2,respectively at 500,550,600 and 650℃,and showed no evident performance decay and carbon deposition on anode after discharging at 600℃ under a constant voltage of 0.6 V for 120 h,thereby demonstrating UCG gas is a promising fuel for direct utilization in SOFC.

Waterborne polyurethane (WPU)with 50% solid content were synthesized by using polyethylene glycol adipate diol (PBA),isophorone diisocyanate (IPDI)and hexamethylene diisocyanate (HDI)as main raw materials,N-(2-aminoethyl)-amino ethane sulphonated sodium (AAS)and dimethylol propionic acid (DMPA)as hydrophilic chain extender.The effects of AAS/DMPA molar ratio on crystallinity of WPU film were investigated by means of DSC,XRD and light transmittance measurement,and in turn the influence of crystallinity on water resistance and heat resistance was also studied by experiments of water absorption and thermal stability of WPU films.The results showed that with the increase of AAS/DMPA,relative crystallinity of the WPU films was enhanced.Consequently,to some degree,water resistance and heat resistance of WPU films were improved.

CeO₂-TiO₂/attapulgite (ATP)nanocomposites were prepared by the sol-gel method using ATP as support,cerium nitrate hexahydrate and tetrabutyl titanate as raw materials,glacial acetic acid as complexing agent.The microstructures of the as-prepared composites were characterized by thermogravimetric-differential scanning caloricity (TG-DSC)analysis,transmission electron microscopy (TEM),X-ray diffraction (XRD),and nitrogen adsorption-desorption measurements.The effects of Ce/Ti molar ratio on catalytic properties of the as-prepared composites for decomposing Rhodamine B solutions were investigated.The results indicated that when Ce/Ti was more than or equal to 5/5,CeO₂-TiO₂ solid solution oxide particles with cubic fluorite structure were uniformly coated on the surface of ATP with particle size of 5—10 nm.With the increase of Ti⁴⁺ content,CeO₂ nanoparticles tended to form a defective crystalline phase and existed as amorphous phase.When Ce/Ti was less than 3/7,a separated anatase TiO₂ was observed in the composites.A suitable amount of Ti⁴⁺ doping could promote the formation of structure defects,which contributed to increasing the content of oxygen vacancies and improving the catalytic activity.The catalytic efficiency of CeO₂-TiO₂/ATP (Ce/Ti=5/5)nanocomposite on Rhodamine B solution was higher than that of others,and the removal rate of chemical oxygen demand (COD)could reach over 96%.

Capped polyether macromonomers APES10 and APEC10 were synthesized from allyl polyethylene glycol sole ether APEO10,and their polycarboxylic acid type copolymers AA/APES10,AA/APEC10 as antiscalants were prepared from small molecule monomers acrylic acid AA.The products were characterized by FT-IR and ¹H NMR and the performance of their copolymers of calcium phosphate inhibition was evaluated by the static scale-inhibiting method.The studies indicated that when mass ratio of APES10 to AA was 1:1,APEC10 to AA was 2:3,both AA/APEC10 and AA/APES10 had much better ability to inhibit the precipitation of calcium phosphate than other mass ratios.It was also shown that both AA/APEC10 and AA/APES10 had superior ability to inhibit the precipitation of calcium phosphate when the dosage was 6 mg·L^-1,approximately showing 100%,92% inhibition,respectively. While compared to that of AA/APES10,AA/APEC10 had superior ability to control calcium-phosphate deposition.Furthermore,the synthesized AA/APEC10 is an environmentally friendly antiscalant,only containing four elements of carbon (C),hydrogen (H),oxygen (O),sodium (Na),without phosphorous (P)and nitrogen (N).AA/APEC10 is an excellent performance non-phosphorus inhibitor for calcium phosphate scaling in industrial recycling water systems.

A particle packing method was developed to prepare porous silica ceramics aggregated by sintering silica powder with methyl cellulose as binding agent at 1300℃ for 1 h.The result of electromagnetic wave absorption showed obvious electromagnetic wave absorption properties with a bandwidth of 9 GHz and-3 dB reflectivity.The electromagnetic wave absorption properties changed after graphene oxide (GO)layers were incorporated into the samples.When the mass fraction of graphene oxide impregnated samples was 0.004%,an increase of 75% in absorption was observed with the greatest reflectivity of-5 dB.The eddy current damping caused by these GO layers was responsible for the enhanced absorption efficiency.While excess GO made the porous sample to be a reflector for incident waves.

Preparation of α-calcium sulfate hemihydrate from phosphogypsum in hydrothermal electrolyte solutions under atmospheric pressure has been a promising way of effective utilization of phosphogypsum. In this paper preparation of α-calcium sulfate hemihydrate from phosphogypsum in Ca-Na-Cl solutions at 95℃was studied.Reaction time and solid products identification in 18.8% NaCl solution,24% CaCl₂ and CaCl₂+NaCl solutions were investigated through morphologic observation,water of crystalization determination and phase analysis methods.The results showed that NaCl solution was not favorable as the dehydration reaction medium of phosphogypsum though reaction time was only 20 min,because the dehydration product was α-calcium sulfate hemihydrate containing omangwaite (Na₂Ca₅(SO₄)₆·3H₂O)which had no hydration property of gypsum.In 24% CaCl₂ solution α-calcium sulfate hemihydrate phase could be obtained at reaction time of 240 min,reaction time was reduced obviously with increasing NaCl content in Ca-Na-Cl solution,but it was accompanied by increase of Na₂O content and irregular uncompleted crystal shapes in the reaction product.Therefore,Ca-Na-Cl solution could be a suitable medium for dehydration reaction of phosphogypsum to form α-calcium sulfate hemihydrate in hydrothermal electrolyte solution under atmospheric pressure.Meanwhile NaCl content should be limited to 2%.