Hydrothermal liquefaction technology can convert lignocellulosic biomass such as straws into bio-oil, and it can be upgraded to produce liquid fuels and high value-added chemicals. But it is accompanied by inherent drawbacks, such as high oxygen content and high viscosity. Thus, it is crucial to develop upgrading method which can be suitable for bio-oils with variable composition. In recent years, the facile method for bio-oil upgrading by zero-valent metals (Al, Fe, Mg and Zn) as an international burgeoning technology is proposed, that has superiority in material adaptability, cost and efficiency. In this paper, the principle, classification and research progress of in-situ hydrogenation of bio-oils by metal hydrolysis are systematically reviewed. Combined with the numerical simulation method, the main problems of in-situ hydrogenation of bio-oils by metal hydrolysis are analyzed and the research directions are proposed. The role of active hydrogen and hydrogen gas in bio-oil in-situ hydrodeoxygenation upgrading is still not clear. The successful cooperation of hydrogenation catalyst and metal/metallic oxide plays an important role in in-situ hydrodeoxygenation upgrading process. The mechanism of hydrothermal liquefaction and upgrading should be further investigated by theoretical calculations, such as lumping kinetics and molecular simulation.

Critical heat flux (CHF) is one of the limiting parameters of flow boiling heat transfer in microchannels. When heat flux is greater than CHF, the heat transfer performance deteriorates sharply and the heat transfer equipment is prone to burn out and failure. Therefore, CHF has an important impact on the safe operation of microchannel heat transfer. At present, microchannel heat transfer is the mainstream technology of electronic cooling. However, in recent years, the heat flux of electronic equipment has been continuously improved, and CHF has become a key parameter to limit the application of micro-channel. Study progress of microchannel CHF is systematically discussed in this paper. Generating mechanism of CHF of microchannel is explained in details, impact of working conditions and channel size of microchannel on CHF is analyzed, prediction models of microchannel CHF are summarized, technical methods and principles for improving CHF of microchannel are discussed in details, differences of academic viewpoints and the future research direction are discussed. This process provides reference for the safe and reliable operation of microchannels under condition of high heat flux.

Using electrocatalytic methods to reduce CO₂ to high value-added chemicals under normal temperature and pressure is one of the ideal choices for solving the current energy shortage and environmental pollution problems. To date, copper based materials have been confirmed to be the most effective catalysts for reducing CO₂ to hydrocarbon products such as methane, ethene, and ethanol. Therefore, extensive attentions have been paid to explore Cu-based electrocatalyst for CO₂ reduction. In this paper, we reviewed the development of Cu-based catalysts for electrochemical CO₂ reduction, and mainly focused on the dependence of catalytic performance on catalyst morphology including grain boundaries, surface structures and open facets and testing conditions such as substrate transport and local pH. Finally, we offer some challenges and perspectives on the future outlook for electrochemical CO₂ reduction.

Thermal power generation is main power generation method in China. When burning solid fuels such as coal and biomass, it will face erosion and wear or corrosion problems on the heating exchange surface of the boiler, causing pipeline failure and shutdown of the boiler, seriously affecting the safe and stable operation of the power plant. As one kind of thermal spraying technology, high velocity oxy-fuel (HVOF) spraying can alleviate the erosion and corrosion problem by adding protective coatings on the surface of the heat exchange tubes. Coatings prepared by HVOF spraying have good applicability under erosion and corrosion environment in boilers since their excellent characteristics such as high bonding strength and low porosity. The development of HVOF technology, the spraying process and coating characteristics were reviewed in this article, and common anti-erosion/anti-corrosion coatings and environmental factors needed to be considered when applying different coating materials were summarized. According to various literatures, the adopted anti-erosion HVOF coatings are mainly NiCr alloys, stellite alloys, WC-Co, Cr₃C₂-NiCr and other metal or cermet coatings. Comprehensive consideration of fly ash composition, erosion angle, and erosion temperature is needed when selecting coating materials in boilers. The adopted anti-corrosion coating materials are mainly Ni-based or Fe-based alloys, of which Ni-based materials are particularly dominant. The tube wall temperature and corrosive substances are the main environmental factors affecting the application of anti-corrosion coatings. Different from various options in literatures, coating materials used in actual boilers are quite simple, mainly Cr₃C₂-NiCr and Inconel 625 for erosion and corrosion protection respectively. Moreover, HVOF is not a common coating preparation technology mainly due to its high cost. To bridge the gap between researches and practical applications of HVOF coatings, spraying process optimization, progress in coating materials and experimental method innovation is prospected in this article.

With the rapid development of cutting-edge industries such as electronics and materials, niobium has been regarded as a crucial strategic metal resource due to its unique physicochemical properties. The demand for niobium is increasing year by year, and the metallurgical extraction technologies of niobium have also received more and more attention. China's Bayan Obo region is rich in niobium resource, but it has not been effectively exploited and utilized yet as a result of the low-grade niobium, complicated ore phases, and difficulty in beneficiation and separation. Developing suitable niobium extraction technologies from low-grade niobium resources in China has important research value and strategic significance. In this review, the research status of main niobium extraction technologies from low-grade niobium resources including pyrometallurgical reduction, acid decomposition, alkali decomposition, chlorination, and combined pyrometallurgy-hydrometallurgy technology is summarized. The advantages and characteristics of various technical processes above are concluded. The effect of low-grade niobium on niobium extraction is discussed. Besides, the sub-melting salt method and the combined roasting-acid leaching method developed in recent years are also used to extract niobium from low-grade niobium resources. These two methods demonstrate great extraction effect and application value, and expansive prospects. The former has great potential owing to its high decomposition rate and light environmental burden. Existing studies have shown that the latter is able to decompose low-grade niobium ores more efficiently, and the leaching rate of niobium reaches 98%. Finally, the problems existing in the current technologies of niobium extraction from low-grade niobium resources and future research and development directions are summarized and previewed.

Meropenem is an effective and safe antibiotic with high clinical value and is also one of the candidate drugs for treatment of COVID -19. Meropenem hydrogenation can be achieved via two processes:one-pot reaction and two-step process. This paper investigated the involved technical processes. Since most physical properties of the chemicals in meropenem hydrogenation reaction cannot be obtained from handbook, we estimate the properties of these chemicals by the group contribution method (Joback method, Constantinous method, Benson method & Ma Peisheng method), including critical parameters, standard generation heat, standard generation Gibbs free energy, heat capacity, etc. Based on the basic principle of thermodynamics and the estimated properties, the reaction enthalpy change, Gibbs free energy and reaction equilibrium constant in the standard condition and different temperatures (273—323 K) were calculated. The results indicated that meropenem hydrogenation was an exothermic reaction with considerable release of heat, so it is necessary to pay attention to the heat removal during the reaction process, and reducing the operating temperature is conducive to the reaction in the favorable direction of thermodynamics. According to the Gibbs free energy and equilibrium constant of each reaction, hydrogenation is easy to carry out, and condensation reaction is the thermodynamic limiting step of meropenem hydrogenation system. Therefore, it should be emphasized to reduce the operating temperature and remove the reaction products in time to promote the condensation reaction to the thermodynamic direction. The conclusions obtained through the thermodynamic calculation are basically consistent with the industrial practice. The one-pot reaction process is thermodynamicly more favorable than the two-step process. Combining anti-poisoning surrounding catalysts with micro-interface reaction enhancement technology to optimize the one-pot hydrogenation process is a direction worth exploring for upgrading meropenem hydrogenation technology.

The density, viscosity and surface tension of the working pairs of lithium bromide (LiBr), 1-ethyl-3-methylimidazolium acetate ([EMIM][OAC]) and 1-butyl-3-methylimidazoliumthiocyanate ([BMIM][SCN]) aqueous solution for absorption refrigeration and heat pump were determined within the temperature from 283.15 K to 343.15 K and at ambient pressure in this work. The experimental density and viscosity were satisfactorily described with the linear model and the Vogel-Tammann-Fulcher type equation, respectively. The results show that the density of LiBr aqueous solution is higher than that of ionic liquid solution, but the viscosity of the former is lower than that of the latter. For the surface tensions, the values increase with the increasing of lithium bromide concentration in LiBr aqueous solution, while a small amount of ionic liquids can make the surface tension of water decrease rapidly under the same conditions. According to the experimental viscosity and surface tension, the energy barrier and surface entropy/enthalpy were obtained, indicating that the mobility of molecular or ion migration in each aqueous solution follows [EMIM][OAC] > [BMIM] [SCN] > LiBr and the surface orderings follow [BMIM][SCN]>[EMIM][OAC] > LiBr. The results of this work can provide reliable data support for the design and calculation of the absorption refrigeration or heat pump working pairs and low temperature waste heat recovery systems.

The solubility of DL- and D-penicillamine in ethanol-water mixed solvents with different mass ratios at 273.15—333.15 K was measured, and the appropriate crystallization solvent ratio was determined. The solubility curves of penicillamine at 273.15 K, 283.15 K, 293.15 K, 303.15 K, 313.15 K and 323.15 K were drawn. The width of the metastable zone of D- and DL-penicillamine and the solution with ee value of 87% was measured. The initial nucleation of saturated solutions with different ee values (saturation temperature of 313.15 K) under different initial subcooling, and the thermostatic crystallization process of saturated solutions with ee value of 87% under different initial subcooling and seed amount were studied. Finally, the crystallization resolution of raw materials with an ee value of 87%, different cooling rates and seed amounts were preliminarily investigated. The results show that, for the thermostatic crystallization process, as the crystallization progresses, the ee value of the product decreases, and the greater of initial subcooling, the more of seeds, the higher of the yield of the product with ee > 99%. For the cooling crystallization process, the ee value of the product decreases as the yield increases, and the slower of the cooling rate, the more of seeds, the higher of the yield of the product with ee> 99%.

For the ternary systems KCl+PEG10000/20000+ H₂O at 308.2 K, the composition of equilibrium liquid at solid-liquid equilibrium was measured by the isothermal dissolution method, and turbidimetric method was adopted for liquid-liquid equilibrium. Meanwhile, the density and refractive index of the equilibrated solution were also determined. According to the experimental data, the phase diagrams, comparison diagram of binodal curve, and tie-line diagrams were plotted. In terms of phase diagrams of both ternary systems mentioned above, they were all consisted of 6 regions which respectively were region of unsaturated liquid phase (L), two regions of one liquid and one solid phase KCl (L+S), region of two-liquids phase (2L), two liquids with one solid KCl (2L+S), and region of one liquid with two solids of KCl and PEG10000/20000 (L+2S). Among those regions, the area of (L+S) was the largest, and the area of (2L) was the smallest. Also, this paper compared phase diagrams of ternary systems KCl+PEG+H₂O where the molecular weight of PEG respectively was 1000, 4000, 6000, 10000, and 20000 at 308.2 K, respectively. The results showed that there was only solid-liquid equilibrium when the mixed solvents were composed of PEG1000, PEG4000, or PEG6000 in ternary systems at 308.2 K, while the solid-liquid equilibrium and liquid-liquid equilibrium coexisted in the systems containing PEG10000 or PEG20000 at 308.2 K. It also could be found that with an increase of the molecular weight of PEG, the binodal curve was closer to the original point, the region of two-liquids phase (2L) and two liquids with one solid KCl (2L+S) enlarged, while the region of unsaturated liquid phase (L) and two regions of one liquid and one solid phase KCl (L+S) shrank. The Chen-NRTL-PDH thermodynamic model is used to calculate the liquid-liquid equilibrium, and the calculated results are in good agreement with the experimental data.

In order to reveal the characteristics of different supercritical fluids (SCFs) from a micro perspective, molecular dynamics study on heterogeneous structure and phase change of supercritical argon and water under different pressures and temperatures were performed. The influence of temperature and pressure on the fluctuation of local density time series, physical clusters and the proportion of different density regions were analyzed. According to the simulation results, the physical parameters of different SCFs are strongly consistent. Firstly, the temperature corresponding to the maximum root mean square errors of local density time series always deviates from the pseudo-critical temperature. The “ridge” gradually weakens and even disappears with pressure increasing. At specified pressure, the radial distribution function (RDF) shows the characteristics of liquid-like transiting to gas-like with temperature increasing, where the liquid-like region is characterized by “short-range order and long range disorder”. While the gas-like region being “short and long range disorder”.And the number of physical clusters increases and the proportion of atoms in the largest cluster atoms decreases. With the pressure increasing, the opposite trend is shown at specified temperature. SCFs are continuous condensed medium in the liquid-like region, and a continuous network of molecules is broken by holes of different sizes. While the gas-like region seems to be vacuum-like clusters, and the system is filled with different sizes and isomer clusters. The number of physical clusters and the proportion of atoms in the largest clusters strongly depend on the system density. With the temperature increasing, the proportion of homogeneous region decreases first and then increases under different pressures. The overall uniformity gradually increases with the increase of pressure. Secondly, the start and termination temperature for two-phase region can be determined theoretically. Then, it can be found that phase transition enthalpy corresponding to liquid-like transiting to gas-like increases with the increase of pressure, and is a linear function of pressure. Finally, the effect of entropy on the order of SCFs is discussed according to the relationship between entropy and temperature. It is considered to be an important mechanism that entropy drives the supercritical phase transition. The results can provide theoretical support for engineering application of SCFs.

In this work, the hierarchically superhydrophobic surface was fabricated by the combination of CuO nanostructures and regular microgrooves. The deionized water and aqueous ethanol with 8% and 16% mass fractions were utilized as test liquids. The characteristics of confined growth of single droplet in microgroove and the coalescence-induced jumping between deformed droplet in microgroove and undeformed droplet outside microgroove were studied by the microdroplet deposition method to explore the role played by confined microstructure on the coalescence-induced droplet jumping with low surface tension. The results showed that the confinement of microgroove caused the deformation of growing droplet in microgroove. The self-jumping of deformed water droplet in microgroove occurred by the driving of Laplace pressure difference generating in droplet. However, the deformed droplets of aqueous ethanol with 8% and 16% mass fractions spontaneously moved upward and suspended on the microgroove instead of self-jumping, due to the increased surface adhesion caused by the decreased liquid surface tension. The increase of surface adhesion resulted in the increase of Laplace pressure difference for deformed droplet detachment from valley of microgroove, in turn causing larger degree of droplet deformation. Thus, the size of spherical droplet originated from deformed droplet recovering increased. The confined microstructures enabled the enhancement in coalescence-induced droplet jumping by regulating the morphologies of droplet and the interaction between coalesced droplet and surface. However, the enhancement reduced with the decreased liquid surface tension. Compared with the deionized water, the coalescence-induced jumping velocities between deformed and undeformed droplets of aqueous ethanol with 8% and 16% mass fractions respectively decreased by 26.7% and 75.9%, and the energy conversion efficiency has been reduced by 17.8% and 90%, respectively.

Based on the computational fluid dynamics (CFD) and experimental method, the cavitation characteristics of liquid nitrogen induced by ultrasonic waves with a frequency of 20 kHz are studied. The simulations were based on the mixture model with the Singhal cavitation model for phase change calculations, and the Realizable k-ε turbulence model was adopted for turbulence consideration. The sinusoidal oscillation of the vibrator was realized with the dynamic mesh method to simulate the ultrasonic generator. The periodic variation characteristics of the ultrasonic cavitation structure were obtained, which are in good agreement with the experimental observations. Based on the CFD models, the changes of pressure and temperature in the ultrasonic affected zone were obtained to make up for the lack of experimental conditions. It was found that the ultrasonic cavitation of liquid nitrogen had different characteristics due to the thermal effect compared with ultrasonic cavitation of water. The effects of different amplitudes, ultrasonic frequencies and pressures of cavitation were studied. The expression of the ultrasonic induced cavitation number was proposed, and the result proved that the smaller the cavitation number, the more likely to occur cavitation and the larger the cavity. The results reveal the mechanism of liquid nitrogen ultrasonic cavitation.

Burning high-alkali coal causes ash deposition on heat transfer surface. To visualize the deposit growth process, the numerical simulation of fouling process was carried out on fluidized-bed boiler convection super heater using sticky particle collision adhesion model based on discrete element method. The influences of gas velocity, particle diameter, gas temperature and wall temperature to ash deposition characteristics were studied and compared with existing research results. The simulation results indicated that the collision efficiency increased and capture efficiency decreased with the increase of gas velocity and the decrease of particle diameter. The increase of particle surface energy caused by the increase of gas and wall temperature led to the increase of capture efficiency while the influence of wall temperature was more obvious. The maximum deposition thickness and the shape of deposition under different working conditions have little change.

The VOF (volume of fluid) method was used to numerically simulate the free-rising process of bubble in still water, and the evolution of bubble wake with different initial diameters was studied. The results show that there are three motion states of bubble wake: symmetrical shedding, unstable shedding and periodic shedding during the bubble freely rising, and the unstable shedding is transitional state between symmetrical shedding and periodic shedding. The shape of bubble changes from spherical to ellipsoidal as it rises. The symmetric shedding of bubble wake occurs when the bubble is in the ellipsoidal shape state and rises straightly. As the bubble continues to rise, when the long axis of the bubble and the horizontal direction form an angle, the wake will change from symmetrical shedding to a transition state (unsteady shedding). Eventually, the bubble wake changes a motion state of periodic shedding. The critical Reynolds number of transition of the wake motion state of bubble with an initial diameter of 2.4－3.7 mm is difference and increases with the increase of the bubble initial diameter. The frequency of periodic shedding of the bubble wake with an initial diameter of 2.4－3.7 mm is 31－39 Hz, and the frequency decreases with the increase of the initial diameter of bubble.

Based on MATLAB program and by implementing the distributed parameter method, the 2-D model of reverse-flow plate fin heat exchanger(PFHE) was constructed. The numerical results were compared with the experimental results in a multi-stream PFHE used in liquefier in Claude cycle, and the numerical results were in good agreement with the experimental results. The effect of the axial conduction on heat transfer performance of PFHE was investigated, and it was observed that the effectiveness of PFHE considering axial conduction decreased by 21.8%, compared with that without considering axial conduction. Moreover, the influence of the adiabatic boundary condition on the cold and hot ends of separating plate of PFHE was transferred to the inner domain of PFHE by axial conduction effect, which resulted in the fluid temperature distortion in near-inlet domain. When the boundary conditions of constant wall temperature or constant heat flux were adopted on hot and cold ends of separating plate respectively, the fluid temperature distortion in near-inlet domain almost disappeared. When considering axial heat conduction, compared with the adiabatic boundary conditions at both ends of the partition, the effectiveness of the constant wall temperature boundary conditions increases by 35.8%({\epsilon }_{\mathrm{c}}) and 31.7%({\epsilon }_{\mathrm{h}}), and the effectiveness of the constant heat flow boundary conditions increases by 22.8%(\epsilon).

The tubular mixer-settler has a broad application prospect in industrial production. A tubular mixer settler was simulated by using computational fluid dynamics (CFD). The effects of dispersed phase droplet size (d₃₂ = 100—500 μm), oil-water ratio (O∶A = 1∶1—1∶5), inlet baffle position on the mixing and settle performance of tubular mixer-settler were systematically investigated. The simulation results were compared with those of traditional square mixer-settler. The results show that the flow field distribution in the tubular mixer chamber is better than that in the square mixer chamber, in which the flow dead zone is not easy to generate. In the tubular mixer chamber, a lower pressure zone is formed above and below the impeller, and the turbulent kinetic energy of the fluid is higher. The mixing performance can be improved by reducing d₃₂ of dispersed phase and oil-water ratio of feed. In the tubular settler, increasing the dispersed phase d₃₂ and reducing the feed oil-water ratio can improve the clarification performance, and the inlet baffle can effectively improve the clarification performance.

In this paper, vibration characteristics of the bench-scale flexible-blade Rushton impeller developed by our team previously were numerically studied. Experimental measurements using the Denmark Brüel & Kj?r and China Donghua vibration testing instruments were also carried out. It was found that the 1st to 6th and the 7th to 12th-order vibration mode of the flexible-blade impeller and shaft system was the bending and torsional type, respectively. The simulated natural frequencies agree well with the experimental results, both indicate the existence of frequency concentrating phenomenon. Compared with the dry-modal natural frequencies, the wet-modal natural frequencies are decreased. When exerted high-frequency alternating excitation load, there is clear stress and strain harmonic responses. Natural frequency of this system decreases with the increase of impeller rotational speed, and increases with the increase of fluid viscosity. The research results lay the foundation for the enlarged design and industrial application of flexible blade Rushton impeller.

Double torsion flow heat exchanger is a new type of shell-and-tube heat exchanger. The periodic full-section calculation models of trapezoidal baffle heat exchangers and new double torsion flow heat exchangers are established respectively. The computational fluid dynamics (CFD) method is used to numerically study the heat transfer coefficient, flow resistance and comprehensive performance of the shell side. The results show that at the same mass flow rate in the shell side, the heat transfer coefficient of the double torsion flow heat exchanger is reduced by 24.4%—27.9%, the pressure drop is reduced by 63.3%—71.0%, and the overall performance is increased 1.2%—4.1% compared with the trapezoidal baffle heat exchanger. The heat transfer and resistance reduction mechanism are analyzed through the principle of field synergy, and it is shown that the speed and pressure gradient of the double torsion flow heat exchanger are in good coordination, and the speed and temperature gradient of the torsion flow heat exchanger are in good coordination. The cold model test was carried out on the torsion flow heat exchanger, and the laser Doppler velocimeter (LDV) was used to measure the speed on the verification line, which verified the correctness and accuracy of the simulation method and results. The research models and conclusions in this paper can provide references for the structure development and performance research of heat exchangers.

The flow characteristics in a stirred tank equipped with traditional frame impellers, the traditional frame combined impeller and the new frame type combined impeller was investigated by particle image velocimetry (PIV) measurements. The velocity, flow pattern and turbulent kinetic energy of the three type of frame impellers in a stirred tank was compared under the same experimental and working condition. The results show that the fluid flow of the traditional frame impeller in stirred tank is mainly horizontal circulation, and fluid flow is insufficient in the upper and middle part of the frame impeller. Due to the two-fold-blade impeller, the fluid velocity in upper part of the traditional frame combined impeller is increased, the fluid flow in the upper and lower parts of the tank is strengthened, but there is still dead mixing zone at the center of the frame impeller. For the new frame type combined impeller, the connecting flow between the two layers of blades in the stirred tank is enhanced. The exchange of material and energy between the bottom and the middle area of the frame impeller is more sufficient. The comparison results show that the new frame type combined impeller has the best mixing performance among the three types of frame impellers. The research results can provide reference for the application of the new frame type combined impeller in the polyester synthesis industry.

To improve the heat transfer efficiency of traditional heat exchanger and heat transfer medium, TiO₂-water nanofluids with different mass fractions (ω=0.1%, 0.2%, 0.3%, 0.4%, 0.5%) were prepared by a two-step method, and the circular cylinders heat transfer systems with different micro-rib structures (vertical and annular fins) were developed, and the effects of the micro-rib structure types (vertical and circular ribs) and numbers (N₁₍₂₎=4, 6, 8) on cylindrical surfaces, the mass fraction of nanoparticles (ω=0, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%), and Reynolds number (Re=514—1205) on the circular cylinders heat transfer systems were studied experimentally. The results showed that the addition of nanoparticles and micro-rib structures can effectively improve the heat transfer efficiency, and the surface temperature of the cylinder decreases significantly. Among them, the nanofluid with a mass fraction of 0.4% shows better heat transfer performance when the number of vertical fins is 6.

Through experiments, the flow and heat transfer characteristics of pool boiling outside the vertical heat exchange tube under transient conditions were studied, and the visualization results of two-phase flow were obtained, showing the evolution process of pool boiling along the vertical tube flow pattern. The differences of pool boiling are analyzed between the large scale restricted space and the open space. Analysis of overall heat transfer in restricted space is superior to that in open space. However, the heat transfer coefficient ratio between the upper location and bottom position is less than that of the open space. The more heat load increases, the less time difference between open space and restricted space is. Meanwhile, numerical simulations corresponding to the experimental model are carried out to investigate the saturated pool boiling. The flow fields of pool boiling in the open space presents a hierarchical, progressive, and conductive circulation. The thermal stratification is formed in open space. While the setting of restricted space forms the circulation convection mechanism between the large pool and the restricted space.

The regenerative throttling structure has a decisive influence on the performance of the micro-channel J-T cooler. Considering the feature of low cooling capacity in micro channel J-T cooler, and the advantages of printed circuit board technology, such as multi layer, high heat transfer efficiency, etc., two types of printed circuit micro channel J-T cooler are designed and manufactured. The J-T coolers have six interleaved high-pressure and low-pressure channels each. The channel structure of the first cooler is composed of large and small rectangle microchannels to realize heat exchange first and then throttling. The equivalent diameters are 463 μm and 120 μm, respectively. The channel structure of second cooler is staggered micro cylindrical pin ribs with an equivalent diameter of 337 μm. Heat exchange and throttling are realized meanwhile in both the high and low pressure plates. The performance of the two coolers was experimentally investigated in the range of 2.02—5.20 MPa inlet pressure. The temperature at axial measuring points, mass flow rate and pressure drop are obtained. The results show that the temperature drop slope of the throttling section of the micro-channel structure refrigerator is significantly greater than that of the regenerative section; the temperature drop slope of the front section of the micro-needle rib structure has a slight increase trend. Due to the existence of axial heat conduction and parasitic heat load, the rear section temperature drop slows down. The tip temperature of first cooler is 210.9 K under 5.12 MPa when the mass flow rate is 4.52 g/s and pressure drop is 4.31 MPa; the second cooler can reach 165.2 K at 5.20 MPa when the mass flow rate is 8.70 g/s and pressure drop is 4.40 MPa. Compared with the order of heat exchange first and then throttling, heat exchange and throttling at the same tine have better temperature drop and different laws of heat transfer and thermodynamic process. It is the comprehensive result of the interaction of flow rate, pressure drop, heat transfer and thermal process. With the increasing application of microchannel technology in the field of gas throttling, heat transfer with throttling is more common, the comparative study of the coolers may provide some reference for such problems in the future.

This work is aimed at the non-azeotropic working fluid nonlinear and complex phase change heat transfer process, based on the advanced exergy analysis method, deduced the evaluation index model that characterizes the heat pump system performance—temperature matching degree (TMD), the heat transfer matching characteristics between the non-azeotropic working fluid and the heat exchange fluid are discussed, the accuracy and applicability of the model are verified by experiments. Three representative non-azeotropic working fluids with different temperature slip degrees (M1, M2, M3) are selected as objects, the relationship between TMD and heat exchange pinch point, system COP, exergy efficiency η and actual exergy loss ratio of heat exchanger ε were investigated. The results show that the smaller the TMD, the better the temperature matching between the heat exchange fluids, the greater the COP and exergy efficiency η of the system, the smaller the actual exergy loss of the heat exchanger, and vice versa; and when the TMD is the smallest, the pinch point in the heat exchanger always appears at the saturated gas point .

This paper aims at the heat dissipation and cooling of high heat flux chips, dry ice with huge sublimation latent heat and extremely low initial temperature is used as heat dissipation fluid. By establishing the model of dry ice cooling radiator, the heat flow fields of dry ice cooling process in the cooling space of radiator are simulated, and the characteristics of the dry ice cooling chip are analyzed. The results show that the best heat dissipation effect is that the radius of dry ice inlet is 6 mm, and the pin diameter of radiator is 2 mm and 11×11 is evenly distributed. With the increase of dry ice flow rate, it takes less time for the chip temperature to reach stability. When the flow rate is 0.20 m/s, the temperature of stability is 15.49℃, which is far lower than the junction temperature of the chip. The safe temperature of the chip can be obtained when the flow rate is 0.06 m/s. When the flow rate of dry ice is 0.20 m/s, the cooling space is filled with dry ice in only 10 s, so that better cooling effect can be obtained. When the power is 125 W, dry ice cooling can also stably control the temperature of the central measuring point (point A) of the chip below 49.47℃. Moreover, the cooling performance of water-cooled at P₀=65 W and dry ice-cooled at P₀=95 W are compared and analyzed. It is concluded that the stabilized temperature of water-cooled cooling chip is 74.2℃, and that of dry ice cooling chip is 15.49℃. The overall temperature distribution of the chip cooled by dry ice is more uniform and the cooling effect is better. The research results lay the foundation for further research on the dry ice cooling system of high heat flux chips.

The phase distribution characteristics of gas-liquid two-phase flow in conventional T-junction have been fully studied, but few literatures have paid attention to the distribution characteristics of two-phase flow in micro-channel flat T-junction. Using the two-phase refrigerant R134a as the working fluid, the phase distribution characteristics in the flat T-junction are studied experimentally. The results show that the increase of the liquid-phase inlet flow rate of the two-phase flow in the flat T-junction will decrease the liquid-phase separation ratio and increase the gas-phase separation ratio. The increase of the inlet quality will increase the liquid-phase separation ratio and decrease the gas-phase separation ratio. The gas inlet velocity has little effect on the phase distribution of the bubbly flow in the flat T-junction. It can be seen from the comparison between the predicted phase distribution model and the experimental value that the existing phase distribution model cannot accurately predict the gas-liquid separation ratio of the bubbly flow in the flat T-junction. In the experimental conditions, when the inlet dryness is 0.45—0.5, the refrigerant R134a in the flat T-junction has a relatively uniform gas and liquid distribution.

The vulcanization reaction process of rubber plays a decisive role in the final performance of the product, and the vulcanization of thick-walled rubber is a typical non-isothermal vulcanization process. It is usually difficult to directly determine the best vulcanization process of the product through the isothermal vulcanization curve measured by the experiment. Therefore, it is of great significance to study the vulcanization process of rubber molding by using numerical simulation technology.In view of this, based on the traditional cure kinetic modeling, an improved vulcanization model with higher accuracy was constructed by introducing initial vulcanization parameters and treating the order of reaction as a quadratic function of temperature. At the same time, the thermophysical parameters of rubber were regarded as a function of vulcanization degree and temperature. UDF(user defined function) subroutines were developed based on C language and FLUENT pre-defined macros, which realized the coupled simulation of heat transfer and vulcanization in the vulcanization process of rubber products. Aiming at the flat vulcanization molding of typical thick-walled rubber products, the reliability of the coupling algorithm for temperature field and vulcanization simulations is verified through temperature measurement experiments, product stretching of different vulcanization degrees, DSC testing and cross-sectional morphology observation. This method is more practical to guide the vulcanization molding of thick-walled and complex-structure rubber products.

With the deterioration of crude oil supply and the introduction of strict environmental regulations, fluidized bed residue hydrogenation technology has attracted widespread attention. Cylindrical and spherical Ni-Mo/Al₂O₃ catalysts were prepared by the extrusion molding method and the special molding method of STRONG fluidized bed, respectively, and the effect of the catalyst particle morphology on the active phase and residual oil hydrogenation performance was systematically studied. Multiple techniques, including X-ray diffraction (XRD), N₂ adsorption-desorption, H₂ temperature-programmed reduction (H₂-TPR), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and electron microprobe analysis (EMPA), were employed to determine the physico-chemical properties of the catalysts. It was found that spherical catalyst had more active Type Ⅱ MoS₂ phase, excellent textural properties and better fluidization characteristic,which made it exhibited superior hydrogenation activity than that in cylindrical catalyst. The weaker metal-support interaction in spherical catalyst is beneficial for a higher sulfidation degree and the formation of Ni-Mo-S Type Ⅱ active phase with a higher staking degree. Moreover, the spherical catalyst with a larger pore size and pore volume facilitates the diffusion of larger molecular impurities into the pore and adsorption on the catalyst active sites, which results in a uniform distribution of metal deposits in the spherical catalyst rather than concentrated distribution near the pore mouth. Finally, spherical catalyst with a smaller pore size may be easier to be fluidized, enhancing the mass transfer performance of the catalyst. The results provide new ideas for the design and development of more efficient industrial hydrogenation catalyst based on morphology effect.

The strontium waste residue left after the production of strontium carbonate from celestite is a secondary resource because it contains a large amount of strontium resources. At present, strontium celestite waste residue is mainly used to prepare SrCl₂ through a two-step method of carbonate conversion and hydrochloric acid leaching, and the preparation process is complicated. In the experiment, BaCl₂ was used as the leaching agent to extract SrSO₄ from the strontium lapis lazuli waste residue after acid pretreatment, and SrCl₂ was obtained by one-step leaching. The effects of leaching time, leaching temperature, BaCl₂/SrSO₄ molar ratio, and liquid-solid ratio on the leaching rate of strontium were investigated respectively. The results showed that when the leaching time was 120 min, the leaching temperature was 90℃, the molar ratio of BaCl₂/SrSO₄ was 2.0, and the initial liquid-to-solid ratio was 10 ml/g, the strontium leaching rate reached 68.79%. The leaching process conforms to the unreacted nuclear shrinkage model and is mainly controlled by the diffusion of the BaSO₄ product layer, and its apparent activation energy is 38.75 kJ/mol. Ba²⁺ partially or completely replaces the strontium in SrSO₄, so that the strontium in the strontium waste residue is leached in the form of SrCl₂.

Hydrate is widely used in gas separation, transportation and storage, sewage treatment, seawater desalination and cold storage. However, natural hydrate formation is extremely slow, requiring higher pressure and lower temperature to maintain stability. In this paper, the nucleation and growth of tetrabutylammonium bromide (TBAB) hydrate crystals in a 2 μl droplet is experimentally studied by a high-speed camera under different subcooling degrees and concentrations. The growth characteristics of TBAB hydrate crystals in droplet are analyzed and the corresponding mathematical model is established. The results show that the induction time of hydrate nucleation can be effectively shortened by dropping droplets on the supercooled solid surface, and the rapid formation of hydrate can be promoted. The research provides a new method for solving the problem of large-scale industrial application of hydrates.

Macroporous SiO₂ (Macro-SiO₂) with an open framework structure and MgCl₂ are used to form a composite carrier, and polysilsesquioxane (POSS) is introduced to form a spatially separated POSS/ MgCl₂ nano-aggregate, which is prepared after loading TiCl₄ modified Ziegler-Natta catalyst. The catalytic structure of POSS-free and modified catalysts was investigated by FTIR, TG, CO low-temperature IR spectroscopy, SEM and particle size analysis. The incorporated POSS contributed the formation of defect Mg_4c²⁺ sites and Lewis acidic sites, where the more defect Mg sites facilitated the effective loading of TiCl₄. The POSS-modified Ziegler-Natta catalyst exhibited exceptional activity reaching 1.03×10⁶ g?(mol·h)^-1 in ethylene/1-hexene copolymerization. Simultaneously, the ethylene-hexene copolymer with much higher comonomer contents (3.79%) and narrowed molecular weight distribution (MWD=3—6) was synthesized in the POSS modified catalyst.

In this paper, two structural models of three-phase horizontal screw decanter centrifuge for oil-water sand separation are proposed first. Through CFD numerical calculation, it is found that the structure model of three-phase decanter centrifuge with axial pipe flanges for fluid discharging has certain defects that there is sand blocking in pipe flanges and lower separation efficiency. Through the improved design, the structure model with adjustable overflow baffles is available. The model has high oil recovery rate and relatively drier solid phase, which is suitable for oil-water solid separation. The model also has several different fluid discharging methods such as water and oil-sand separation, oil-water and sand separation, or oil and water-sand separation. The three-phase decanter centrifuge was processed and manufactured, and an experimental platform was built. Through experimental research, it is found that the three-phase decanter centrifuge with this structure has a higher separation efficiency for the oil phase, and the distance from the center of the baffle arc to the center axis of the drum has different effects on the separation efficiency.

By designing an electrolytic cell containing a three-electrode system and strictly controlling the potential of the working electrode, an electro-oxidation method is proposed for the selective extraction of bromine resources in underground brine. The technical feasibility, the reaction kinetic model, the influence of co-existing Cl^- and the initial pH of the anolyte, and the optimal operating time has been discussed respectively. The results showed that the electro-oxidation was technically feasible for extracting bromine from underground brine, and the reaction of electro-oxidation for extracting bromine from underground brine followed the second-order reaction kinetic model. The bromide reaction rate constant increased first and then decreased with the increase of chloride concentration. The co-existing chloride had both promoting and inhibititing effects on the electro-oxidation of bromide. The promotion effect might result from the increase of total solution conductivity caused by the increase of chloride concentration. The inhibitition effect might be due to the adsorption competition between chloride and bromide on the graphite electrode surface. The energy consumption deceased with the increase of chloride concentration, and the current efficiency was changed little with the change of chloride concentration. In addition, the bromide reaction rate constant gradually increased as the initial pH of the anolyte decreased, and current efficiency and energy consumption were relatively unaffected by it. In the process of extracting bromine from underground brine by electro-oxidation, the extraction ratio of Br₂ grew more and more slowly with the time prolong, the current efficiency continued to decrease, and the energy consumption continued to rise and its growth rate was also increasing. Therefore, the optimal operating time might be 6—10 h.

Reasonable and efficient adsorption process is the key process link that determines the industrial feasibility of the adsorption method to purify and recover NO_x in flue gas. In this paper, a novel adsorption process (GVTSA) with NO_x desorption using multiple hot gas circulations (GC) within the enclosed fixed bed through extra gas replenishment was proposed. Based on Na-ZSM-5 zeolites as sorbents, experimental studies on NO_x adsorption and recycling from desulfurized iron-ore sintering flue gas of a steel plant were conducted. The results show that the GVTSA obtained a higher NO_x recovery compared with traditional adsorption processes (e.g. TSA, VSA), reaching 90% under the optimal conditions (220℃, -50 kPa). The concentration of desorbed NO₂ was more than 2%, significantly enhanced from merely 36 mg·m^-3 in the feed gas. The NO_x cyclic adsorption capacity reached 0.10 mmol·g^-1 for up to 16 cycles. This work can provide references for industrial engineering application of flue gas ultra-low emission control and resource utilization.

Aiming at the problem of high lignin content in the hemicellulose extracted by alkaline method and difficult purification, the hydrophobic resin adsorption-ultrafiltration is used for cooperative treatment. In this study, the effect of different methods on the purification and separation of hemicellulose was explored through the method of macroporous resin adsorption and ultrafiltration technology. Ion chromatography (IC), ultraviolet spectrophotometer (UV), gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) were used to analyze chemical composition, molecular weight, thermal stability and other characteristics of the separated and purified hemicellulose. The results show that the resin adsorption-membrane ultrafiltration treatment can effectively remove lignin and obtain hemicellulose with higher molecular weight. No significant changes are found in the molecular backbone structure, and the thermal stability is slightly improved. The side chain unit of hemicellulose after resin adsorption has obvious changes. The hemicellulose with smaller molecular weight has more side chain lignin unit structure, and is mostly connected to carbohydrates by phenyl glycosidic bonds (PhGlc). Through the cooperative treatment of resin adsorption and ultrafiltration, hemicellulose with different side chain units and lignin content can be obtained, which provides a basis for expanding the utilization value of hemicellulose.

In this paper, a solar thermal-photovoltaic membrane distillation of square cavity is designed to study the mechanism and optimization of the system. Firstly, the experiment adopted the feed inlet temperature, the feed flow rate and the solar irradiance as the influence factors, and the membrane flux and the energy consumption as the response values. The relationships between each influence factor and the corresponding response value were analyzed by response surface methodology. Secondly, the central composite design method is used for experimental design, and established the quadratic polynomial regression model of the response value and the influence factor. The reliability analysis of the established model was validated through analysis of variance and experimental results. Finally, the optimal operating conditions and the corresponding optimal membrane flux and energy consumption values of the system were obtained and validated by response surface optimization analysis and experiments. The results show that the best working conditions of the system are: the material liquid inlet temperature 63℃, the material liquid inlet flow rate 232 L/h, the solar irradiance 700 W/m². Under this working condition, the actual membrane flux reaches 7.28 L/(m²·h), which is higher than the predicted value of 6.39 L/(m²·h), the error between the two is 12.23%, and the corresponding energy consumption value is 10.40 L/(kW·h).

To address the problems of high energy consumption and substandard effluent quality in the wastewater treatment process, a multi-objective optimization control method for wastewater treatment process based on multi-strategy adaptive differential evolution algorithm is proposed. Firstly, the tracking control of the dissolved oxygen concentration of the 3rd and 4th units is added under the conventional differential tracking control framework, which aims to expand the optimal adjustment range of energy consumption and effluent water quality. Then, a multi-strategy adaptive differential evolution algorithm (MSADE) is proposed, which selects proper mutation strategy and random individuals to guide the population mutation by combining the multi-strategy fusion mutation technique and sorting optimization method. Further, the convergence of proposed algorithm and the diversity of the pareto solution can be greatly improved by updating the crossover rate adaptively according to the evolution process information. Finally, the MSADE algorithm and the PID controller are combined, and a novel multi-objective optimization method is built with a good balance of energy consumption and effluent quality, realizing the dynamic optimization process and the tracking control of setting values of dissolved oxygen and nitrate nitrogen concentration. The simulation results on the international benchmark simulation platform BSM1 show that the proposed method can effectively reduce energy consumption and improve effluent quality in the wastewater treatment process.

In view of the shortage of process data and the strong nonlinear and multi-scale characteristics of the new batch process, a product quality prediction method based on multi-scale kernel JYMKPLS (Joint-Y multi-scale kernel partial least squares) transfer learning is proposed, which combines the advantages of transfer learning and multi-scale kernel learning. First, the new batch process modeling efficiency and quality prediction accuracy are improved by using the old process data in the similar source domain through transfer learning. Then, in order to solve the problem of non-linear and multi-scale characteristics of the data, multi-scale kernel method is used to better fit the data features, so as to improve the prediction accuracy of the model. In addition, the online update and data elimination of the model are proposed to continuously improve the matching degree of the transfer model to the new batch process, so as to eliminate the adverse effects of the differences between similar processes on the transfer learning, so as to continuously improve the prediction accuracy. Finally, the effectiveness of the proposed method is verified by simulation. The results show that, compared with traditional data-driven modeling methods, the method proposed in this paper can effectively improve modeling efficiency and prediction accuracy.

The dry gas seal working condition at the inlet of the supercritical CO₂ compressor is near the critical point. The strong nonlinear physical properties and high Reynolds number flow make the sealing characteristics different from conventional dry gas seals. Based on the steady-state film pressure calculation model considering the real gas effect, centrifugal inertia effect, turbulent effect and choked effect, a multi variables perturbation numerical model by considering perturbed film pressure, density, viscosity, Reynolds number, turbulence coefficient and inertia coefficient for calculating dynamic characteristics of dry gas seal is established based on perturbation method. The dynamic characteristics of supercritical CO₂ and N₂ dry gas seals were compared and analyzed. The influences of actual fluid effects and variable perturbation models on the axial and angular dynamic characteristics coefficients of supercritical CO₂ dry gas seals under different conditions were obtained. The results show that the stiffness and damping coefficient of supercritical CO₂ dry gas seal are reduced by more than 50% compared with N₂ dry gas seal under high frequency disturbance. Turbulent effect and real gas effect have significant influence on dynamic characteristics of dry gas seal. The calculation deviations of dynamic characteristics calculated by classical variable perturbation and ignoring turbulence coefficient perturbation are relative large under low frequency disturbance, while the prediction accuracy of the classical variable perturbation model is acceptable under high frequency disturbance.

Local corrosion defects on the inner surface of natural gas pipelines will induce sudden changes in the local flow field and affect the local corrosion process. The high-shear stress corrosion test device is used to conduct on-line electrochemical corrosion testing under the flow, and the influence of local corrosion pits on the local corrosion process is studied. The interfacial corrosion electrochemical signal of the specimens during the corrosion process is analyzed by electrochemical impedance spectroscopy (EIS). The composition and characteristics of the corrosion scale are characterized by scanning electron microscope (SEM),energy diffraction spectrum (EDS) and X-ray diffraction(XRD). The influence of flow field parameters on the corrosion mass transfer process is calculated and analyzed. The results show that surface defects will induce changes in the flow field and enhance the mass transfer at local locations. Therefore, the corrosion scale on the surface will show different microscopic forms with the change of flow velocity. In a high-intensity flow field, the locally enhanced wall shear stress will peel off part of the dense corrosion product film, resulting in the formation of electrochemical distribution of large cathodes and small anodes on the test surface, which promotes the corrosion process at local locations and accelerates the occurrence of local corrosion.

Based on the gas lubrication theory, the steady-state and transient-state theoretical models of the spiral groove, upstream pumping spiral groove and double-row spiral groove dry gas seal(DGS) were established, and were solved by using the finite difference method, and then the steady and transient seal performance parameters of the three typical spiral groove DGSs were obtained. The mechanism of difference in steady performance of the three typical spiral groove DGSs and the evolution rule of transient performance of the DGSs under different film thickness disturbances were studied. On this basis, the change rates of transient performance parameters and its time average values relative to steady values were defined. The influence of nonlinear effect under film thickness disturbance on performance of the DGSs and the suitable range of steady theory were explored. The results show that upstream pumping spiral groove has a significant improvement on the sealing performance, but has a certain weakening on the opening performance. The influence of nonlinear effect increases with the increase of film thickness disturbance, and the average value of performance parameters of the DGSs calculated based on transient theory is obviously larger than that of steady value under large film thickness disturbance, at this time, the error of calculation results based on steady theory is large. Ordinary spiral groove DGS is least affected by nonlinear factors, and within the acceptable performance error range of its steady-state theory, the permissible film thickness disturbance is greater than that of the other two spiral groove DGS.

The emergence of drug-resistant Staphylococcus aureus (S. aureus) and the lack of high-efficiency antibiotics have threatened food quality and public safety. Therefore, it is urgent to find new treatment strategies to resist the increasingly severe bacterial challenge. In this work, dihydromyricetin (DMY) was obtained by using a hydrothermal extraction technology from Ampelopsis grossedentata. Then, the multivesicular dihydromyricetin-coated liposomes (DMY-lips) were prepared by using liposomes as drug carriers and polyethylene glycol 4000 as modifiers. The successful formation of DMY-lips was determined by UV-vis spectrophotometer, Fourier infrared spectrometer, X-ray powder diffractometer and simultaneous thermal analyzer. Moreover, the multivesicular structure of DMY-lips was confirmed by transmission electron microscope and dynamic light scattering. The obtained DMY-lips exhibited a uniform particle size with an average particle size of 155 nm and a drug loading rate of 42.93%. In addition, antibacterial experiments found that DMY coated liposomes will improve drug antibacterial activity and antibacterial time, which due to liposomes increase the degree of hydrolysis and membrane permeability of DMY. The minimum inhibitory concentration of DMY-lips against S. aureus is 0.05 mg/ml. Noteworthy, the results of biological scanning electron microscopy and electrical conductivity test displayed that DMY-lips can destroy the cell barrier of S. aureus, causing intracellular materials leaked, resulting in bacterial cell death. Therefore, the multivesicular dihydromyricetin-coated liposomes have great potential in the pharmaceutical industry and are expected to reduce the medical system's dependence on chemical antibiotics.

To improve the slurryability of lignite and make it meet the demand of coal water slurry gasification, the coal blending with petroleum coke and kerosene as surface modifier were used to study the influence of modification methods on the slurryability of lignite. The results show that: (1) Due to the strong hydrophobicity of petroleum coke, the slurry concentration of lignite can be increased by adding petroleum coke, and the slurry concentration is positively correlated with the mass fraction of solid particles α of petroleum coke. (2) The surface modification of kerosene mixed particles can enhance the hydrophobicity of kerosene particles and increase the concentration of coal coke slurry. The viscosity decreases at first and then increases with β. The optimum dosage of kerosene is negatively related to α (α > 10.0%). (3) When a small amount of petroleum coke is added (α < 1.0%), the surface roughness of lignite can be increased within a certain range, kerosene modification effect can be improved, and the viscosity of coal coke slurry can be reduced.

In this paper, P1/Ti2-15@AC natural minerals are blended to modify activated coke to simulate the combined desulfurization and denitrification reaction process of activated coke in a moving bed reactor system. The results indicate that the low-temperature, highly efficient and low-cost flue gas desulfurization and denitrification process could be well combined by the natural mineral blending modified activated coke integrate thermal regeneration method. The NO conversion of the P1/Ti2-15@AC-Rn was improved significantly after the desulfurization-regeneration process. The P1/Ti2-15@AC-R1 and P1/Ti2-15@AC-R2 had almost 100.0% NO conversion, and it kept relative stable at 85.0% after the third regeneration cycles. The enhanced NO removal performance is mainly because the acidic C—O, C—S and other acidic functional groups on the surface of activated coke increase after desulfurization regeneration, which enhances the adsorption process of NH₃ on the surface of activated coke during denitration, thereby improving the efficiency of denitration reaction.

To save space and improve the integration of equipments, a novel process combining the liquid dehumidification and wet electrostatic precipitator (WESP) is proposed in this paper for both dehumidification and dust removal of flue gas. Through the numerical simulation and experiment of the falling film dehumidification process of the wet electric flat plate, the influence of the flue gas and solution parameters on the water heat recovery performance is explored. The results show that the model can agree with the process quite well and the highest water and thermal efficiency is 37.5% and 35% respectively. Most of the latent heat is transferred to the solution. The dehumidification process has almost no effect on dust removal of WESP. Through the analysis of psychrometric chart and visual comparison, it is proved that the falling-film dehumidification in WESP can reduce even eliminate white smoke.

Rice straws and cotton stalks were selected as raw materials. After torrefaction pretreatment, the fixed-bed combustion experiment and HSC Chemistry thermodynamic equilibrium calculations were conducted to obtain the release and migration characteristics of alkali metal K during the combustion of torrefied biomass. The results showed that there was a small amount of water-soluble K release and its conversion to ammonium acetate dissolved K during torrefaction, and its conversion and release capacity was positively correlated with Cl/K. The ash formation rate of torrefied biomass decreased with the increase of combustion temperature, while the release rate of K changed with the temperature on the contrary; K was released in the form of water-soluble K, ammonium acetate dissolved K and acid-soluble K,and its main release form was K chloride and KOH. In addition, water-soluble K and ammonium acetate dissolved K were mainly converted to char-K at 600℃, and mainly converted to K silicate at 700—900℃. As the temperature rose, its conversion volume continued to increase. Compared with the raw biomass, torrefied biomass had a higher ash formation rate; in addition, torrefaction promoted the conversion of ammonium acetate dissolved K to acid-soluble K or potassium silicate during the combustion of biomass, and at the same time inhibited the release of water-soluble K. Therefore, the release rate of K during the combustion of torrefied biomass was lower. The inhibition of K release during the combustion of biomass by torrefaction is positively correlated with the release rate of Cl during the torrefaction.

Biomass is an ideal raw material for renewable energy, and it is difficult to use effectively because of its hard lignin shell protection. Ionic liquid (IL) was a green solvent which could be used in pretreating and improving the use efficiency of the biomass. To investigate the effects of IL on the pyrolytic char structure and its reactivity, eucalyptus powder was pyrolyzed in quartz reactor under 650℃. After being pretreated by IL ([Bmim]Cl, [Bmim]OAc and [Bmim]H₂PO₄) with a concentration of 2%, 4%, 8% at 120℃ for 2 h, the structure of char obtained was characterized by SEM, FTIR, XRD and Raman spectrum. The reactivity of char with air at 450℃ was also evaluated with thermal gravimetric analysis (TGA). The results showed that the yield of the char decreased with the increasing of the IL concentration, while the crystallinity was enhanced. The decrease in I_D1/I_G and an increase of I_G/I_all in Raman spectrum indicated an improvement in the order of the char structure, and the promotion of the transformation of small aromatic ring system into the large one, which led to a decrease reactivity of the biochar. IL pretreatment can adjust the reactivity of the pyrolytic biochar conveniently, and can provide effective way in using biomass with high value added.

To study the freezing characteristics of the water-containing gas diffusion layer (GDL) and the law of water migration, a visual observation system of the freezing process of the water-containing GDL was designed and built. The freezing process of the water-containing GDL was studied by visual experiment research. The temperature change during the freezing process of the water-containing GDL was analyzed. The influence of wettability and supercooling degree on freezing probability were analyzed. Experimental results show that the sudden freezing at a nucleation point of the GDL causes the release of the supercooled state of the water inside the entire GDL, and then the supercooled water is squeezed out of the GDL pores under the volume expansion force of liquid-solid phase change. Water inside the hydrophobic GDL freezes at higher supercooling degree. With the decrease of GDL temperature, the freezing probability of supercooled water inside GDL increases continuously. This study explores the freezing characteristics of the water-containing GDL, which can lay a foundation for solving the problem of the water-containing GDL freezing during the cold start-up of the proton exchange membrane fuel cell (PEMFC) in the future.

A carbon film (Fe₂C /N-C) co-doped with Fe₂C and nitrogen was prepared by the directional freezing-carbonization method as an integrated electrode for lithium-sulfur batteries. Due to its regular conductive networks and well-connected ion diffusion channels, it can effectively alleviate the poor conductivity of the active substance sulfur and the final discharge products, meanwhile, the microporous structure can effectively buffer the volume expansion effect during the charging/discharging process. This membrane structure is conducive to electron transfer and lithium ion diffusion, coupled with the addition of Fe₂C which can provide the adsorption of lithium polysulfides (LiPSs) and the catalytic conversion of LiPSs to the final discharge products, the synergistic effect can effectively inhibit the “shuttle effect”, increase the sulfur utilization rate, and significantly improve the comprehensive performances and cycling stability of the batteries. Therefore, the Li-S batteries with Fe₂C/N-C/S as cathodes exhibit a high specific capacity of 833.0 mA·h·g^-1 at 1.0 C after 100 cycles with the coulombic efficiency of 99.3% and an extended cycling stability of 0.02% per cycle capacity decay at sulfur loading of 1.1 mg·cm^-2, even at a higher sulfur loading of 3.8 mg·cm^-2, the specific capacity of 714.3 mA·h·g^-1 can be obtained at 0.2 C after 100 cycles.

In this study, silicon carbide (SiC) porous ceramic supports were prepared via dry pressing method with the sintering temperature of 1150℃. Isodium dodecyl benzene sulfonate (SDBS), sodium hydroxide (NaOH) and NaA molecular sieve residue were used as sintering additives, carbon powder was employed as pore forming agent, respectively. The effects of additives on microstructure, average pore size, porosity and thermal shock resistance were investigated. The low-temperature sintering mechanism of additives was analyzed. The research results showed that the ceramics have an enhanced gas permeance, bending strength and thermal shock resistance. Ceramics doped with NaA molecular sieve residue possesses the best gas permeance of 1300 m³/(m²·h·kPa), bending strength of 27 MPa, and good thermal shock resistance.

Using tire semi-coke as carbon source and silicon sand as silicon source,silicon carbide(SiC) was prepared by carbothermal reduction method at 1520℃. XRD, SEM and FTIR spectrometer were used to characterize the SiC prepared under different raw material particle size conditions. The influence law of raw material particle size on the phase, morphology, particle size and reaction degree of the synthesized SiC was investigated. The results show that the size of the raw material has a very important influence on the degree of synthesis reaction and the phase composition, morphology and size of the product.Within a certain particle size range, with the decrease of silicon sand particle size, SiC crystal type becomes complete and SiC whisker decreases gradually, while the SiC particle size distribution does not change significantly.With the increase of semi-coke size of tire, the product phase gradually becomes single, and the proportion of SiC particle size and whisker decreases gradually. In addition, by measuring the C/Si ratio in the product and confirming the presence of the intermediate product SiO, it is inferred that the formation mechanism of SiC particles is gas-solid (VS) reaction, while the formation mechanism of SiC whiskers is gas-gas(VV) reaction.

Paraffin wax emulsion is a new functional fluid integrating heat storage and heat transfer, and has broad application prospects. However, when the paraffin emulsion is cooled down, there will be obvious supercooling phenomenon, which reduces its heat storage and heat transfer performance. In the present work, O/W type paraffin Pickering emulsion was prepared via high mechanical shear, using magnesium-aluminum double-layer metal hydroxide (Mg-Al LDHs) instead of chemical surfactant. The microscale morphology, particle size distribution, viscosity, stability, and thermal properties of the as-prepared paraffin Pickering emulsion were characterized by using scanning electron microscope, laser diffraction particle size analyzer, rheometer, multiple light scatterometer and differential scanning calorimeter, respectively. The results show that, with the increase of Mg-Al LDHs content from 1%(mass) and 5%(mass), the mean particle size of paraffin Pickering emulsion decreased, while the viscosity increased significantly, resulting in better long-term stability of the emulsion. The subcooling of paraffin Pickering emulsion was suppressed completely via heterogeneous nucleation of paraffin, which was induced by Mg-Al LDHs nanoparticles absorbed at the water-paraffin interface. Latent heat of as-prepared paraffin Pickering emulsion was around 56.6 J·g^-1, while the mean apparent specific heat capacity was 6.08 J·g^-1·K^-1 in the temperature range concerned (30—70℃), which was about 1.45 times of the value of water.

Using 1, 2-bis(triethoxysilyl)ethane (BTESE) and boric acid as precursors, a boron-doped silica (B-BTESE- SiO₂) hybrid membrane was successfully prepared by the sol-gel method. The boron element was confirmed to be successfully doped into silica frameworks during the sol-gel procedure by various characterizations of FTIR, XRD, XPS, TEM and SEM, which would form hydrothermally stable Si—O—B bonds. It could significantly influence membrane surface microstructure, hydrophilicity and pore size of B-BTESE-SiO₂ hybrid membranes, and then improve their desalination performance and stability. The B-BTESE-SiO₂ membranes prepared under the optimized condition of H₃BO₃/BTESE ratio as 0.25 in the sols, exhibited the strongest hydrophilicity, lowest mass transfer resistance (lowest activation energy during desalination process) and applicable pore size of 0.61 nm, thus demonstrating the highest desalination performance. The high water flux up to 16.5 kg·m^-2·h^-1 and NaCl rejection of nearly 100% were achieved for this SiO₂ membrane towards 3.5%(mass) NaCl feed solution at 60℃. Moreover, this membrane showed excellent long-term stability (>168 h) and desalination performance for high-salinity [4.2%—15.0%(mass) NaCl] solutions, which had promising potential applications in seawater desalination and high-salinity wastewater treatment.

To realize the reliability evaluation of safety-critical equipment under incomplete maintenance conditions, the traditional reliability evaluation model does not consider the data difference between multiple fault samples and the complex problem of solving model parameters. This paper proposes a hybrid Kijima Ⅰ Virtual service age model. Firstly, the cumulative failure intensity function is used to describe the failure trend of the system on the time diagram. The appropriate reliability evaluation model is selected based on the AIC and BIC information criteria, and the non-linear constraint programming method is used to transform the estimated value of the distributed parameter under imperfect repair. Then, for the multi-category sample failure data caused by different reasons, the hybrid Kijima Ⅰ model is established by considering the difference between failure data. The case analysis of the ship unloading system of an LNG receiving station shows that this model is more effective than the commonly used mixed sample distribution model in actual reliability evaluation. At the same time this helps to achieve a balance between differentiated maintenance and high equipment availability.