Liquid hydrogen receiving terminal (LHRT) is exposed to great hydrogen-leakage threat due to the frequent operation and complex components. The evaluation of the consequences resulting from a potential liquid hydrogen (LH2) leakage is therefore essential. Numerical simulation of LH2 leakage based on a pseudo-source model was conducted at the operational Kobe LHRT in Japan. The consequences of leakage duration and rate under the current station structure were assessed in terms of both dispersion and explosive overpressure hazards. The results show that considering the prevailing northerly winds in the city of Kobe, leakage from a downwind jet was expected to produce the most serious hazard, with the hazard of leakage and the risk of explosion overpressure increasing sharply in the first 100 s after leakage and stabilising thereafter. It is also discovered that leakage rate has a bigger influence on accidents than leakage duration. Furthermore, the global maximum explosion pressure exceeds 0.3447 bar. The administrative buildings will be substantially affected if the leaking diameter exceeds 15 mm and the duration exceeds 100 s.
In order to reveal the enhancement effect of the hydrophilic-hydrophobic composite structure surface on condensation heat transfer and the effects of dynamic behavior characteristics of condensate droplets, an experimental system and a mathematical model of condensation on the hydrophilic-hydrophobic composite surface was established. The model is based on the theories of dropwise condensation (DWC) and filmwise condensation (FWC), in combination with the effects of droplets nucleation, coalescence, detachment, and sliding sweeping. The effects of surface structure size, wettability, operating temperature and droplet dynamic behavior on condensation efficiency were analyzed by the model. The surface has circular hydrophobic patterns with a diameter of WDWC and hydrophilic channels separated by WFWC. The results show that under the same conditions, the condensation heat transfer coefficient increases first and then decreases with the increase of WDWC, and there is only one optimal WDWC corresponding to WFWC, which maximizes the condensation heat transfer coefficient. Moreover, the optimal WDWC is only affected by WFWC and is insensitive to other factors. The average condensation heat transfer coefficient of the optimal structure size can be increased by 78.8 % and 316.6 % compared with that of the completely hydrophobic surface and hydrophilic surface. The results illustrate the possibility of enhanced condensation with composite surfaces, which provide guidance for the design and preparation of composite surfaces with hydrophobic patterns for enhanced heat transfer in steam condensation.
Water-gas shift reaction (WGSR) is key to the supercritical water gasification (SCWG) of coal in hydrogen production, but it has not been considered in studies inside pores where coal conversion occurs. Here, to investigate the impact of intrapore WGSR on the SCWG of single irregular-shaped coal particle, a three-dimensional multi-species reaction–diffusion model is proposed and validated through experiments. We observe that the intrapore WGSR inhibits the SCWG of coal by slowing down the fluid diffusion and retarding the fixed-carbon steam reforming heterogeneous reaction (FSRR). Increasing gasification temperature enhances the inhibition by WGSR while increasing mole fraction of H2O weakens the inhibition. The area and volume of pores have little effect on the inhibition because increasing area enhances the FSRR but retards the diffusion while increasing volume facilitates the WGSR but promotes the diffusion. An analytical model is thereby proposed to quantify the inhibition, and to characterize the prolonged gasification time.
Process intensification has become the research focus in recent years.The high gravity technology is one new way for process intesification.This review summarized the researches on the stuctures of bulk and structured packings for high gravity field,and discussed their hydrodynamics and mass transfer properties.Compared with bulk packings,structured packings will be the di-rection of future research and development.
The separation of aromatic hydrocarbons from straight-run naphtha is crucial for the optimal utilization of naphtha resources in the petrochemical industry. Bimetallic halides exhibit excellent performance in aromatic separation from straight-run naphtha. Therefore, it is highly significant to investigate the complexation mechanism and aromatic separation mechanism for bimetallic halide selection and further separation performance enhancement. In this study, CuAlCl4 and Sn(AlCl4)(2 )were used in the separation of aromatics from naphtha and exhibited excellent performance. The complexation mechanism of bimetallic halide-aromatic complexes was elucidated by XAFS, FT-IR, and density functional theory. The results unveiled that bimetallic halides could coordinate with only one aromatic ring. The geometric structures, bonding characteristics, and weak interaction between bimetallic halides and hydrocarbons were analyzed by a series of wavefunction analysis methods. The results indicated that there was pi complexation between bimetallic halides and aromatics, in which s and d orbitals of Cu(I) ion and s and p orbitals of Sn(II) ion played an important role. Meanwhile, there was weak hydrogen bonding interaction between bimetallic halides and aliphatic hydrocarbons. The directional complexation between bimetallic halides and aromatics was the essential reason for aromatic separation.
A hydrothermal method was used to synthesize ZSM-22 molecular sieve and prepare a catalyst carrier.By loading precious metal Pt,a highly dispersed Pt/H-ZSM-22 hydroisomerization catalyst was prepared.Using n-C12 as feedstock,the hydroisomerization performance of the catalyst was investigated.By introducing a certain amount of nitrogen-containing species in the reaction process,the acid of catalyst was adjusted in the hydroisomerization reactor,and the change of the catalyst performance was investigated.The results showed that,as the reaction temperature increased,the liquid yield of Pt/N-ZSM-22 decreased slowly,and the isomerization selectivity of Pt/N-ZSM-22 were about 3 percentage points higher than Pt/H-ZSM-22 under the same conversion rate above 85%.The acid sites of Pt/N-ZSM-22 catalyst which was absorbed by the nitrogen-containing species can also be restored during raising the reaction temperature.The catalyst after acid regulation was used for hydroisomerization of the hydrocracking UCO,and the base oil yield was significantly higher than the catalyst before regulation.
To probe into the separation process of coarse and fine particles in the classifiers,based on the particle-eddy interaction model and the discrete element soft sphere model,the influence of turbulent fluctuation in the turbo air classification flow field on particle motion and cut size d50 are investigated.The distribution laws of particles in the classification process are also explored.Turbulent fluctuation mainly influences the trajectory of small particles.It has little effect on the trajectory of large particles,and has no significant effect on cut size d50.At an inlet air velocity of 12 m·s-1 and a rotor cage rotating speed of 1200 r·min-1,for the radial distribution,the fine particles less than 20 μm are mainly distributed in the rotor cage area,particles with size near d50 move with swirling flow in the annular region,and the coarse particles larger than 25 μm gather in the area near the guide blade.Due to the interaction between particles,some fine particles may be mixed with the coarse particles,resulting in a"fish-hook effect".For the axial distribution,the fine particles less than 20 μm are mainly distributed in the classifier near the top area,the coarse particles gradually settle downward and the larger the particle size the faster the settlement.
The rising behavior of bubbles in different liquid media(deionized water,ionized water,5#white oil and water-white oil solution)was observed by using high-speed photography.Three air-injection nozzles with different outlet diameters were employed.A comprehensive comparison of the rising velocity,equivalent diameter,aspect ratio,and drag coefficient of bubbles obtained under different operating conditions was implemented.The results demonstrated that the trajectory and kinetic characteristics of the bubble varied considerably in different single mediums.The viscosity and surface tension of the medium exerted a significant effect on shape and size of the bubble.Additionally,behavior of the bubble passing through the water-white oil interface was investigated.It was observed that when the bubble was away from the interface,its motion resembled that observed in corresponding single medium.However,when the bubble crossed the interface,it was enveloped by a liquid film,which subsequently detached from the bubble.After passing through the water-white oil interface,small-sized bubbles exhibited the geometric and kinetic characteristics similar to those in single white oil.In contrast,large-sized bubbles were characterized by a zigzag trajectory after passing through the water-white oil interface.Meanwhile,the bubble aspect ratio varied considerably.
Biomass chemical looping pyrolysis(BCLPy)employs oxygen carriers to decompose the pyrolysis-gasification reaction of biomass into a two-stage reaction at different temperatures,yielding simultaneously both high quality bio-oils/chemicals and clean syngas.In this work,six iron-based composite oxygen carriers were prepared by sol-gel method by adopting alkali earth metals such as Ca,Sr,Ba and transition metals such as Co,Ni,Cu,respectively.The oxygen-carrying and catalytic properties of six iron-based oxygen carriers during chemical looing pyrolysis of corn stalk were studied.The results show that six iron-based composite oxygen carriers have excellent catalytic cracking,ketonization and hydrodeoxygenation ability for liquid products during biomass pyrolysis stage,significantly reducing the content of oxygen compounds in bio-oils and increasing the generation of hydrocarbon compounds.At the gasification stage,oxidize pyrolytic char can be oxidized to syngas with CO as main components.Among them,the Ca-Fe composite oxygen carrier reduces the content of acid compounds from 29.4%without oxygen carrier to 0.3%,and the CO yield in syngas reaches 330 L/kg biomass.Under the optimal condition of 650℃and the mass ratio of biomass to oxygen carrier 3∶6,ten pyrolysis-gasification cycles were investigated by using Ca-Fe composite oxygen carrier.The results indicate that the Ca-Fe composite oxygen carrier exhibits excellent catalytic,deoxygenation and oxidation properties,however,phase separation and agglomeration of iron was observed during the 10 cycles.It is imperative to focus on the development of iron composite oxygen carrier with enhanced reactivity and a stable structure in the future research of biomass chemical looping pyrolysis.
Distillation and absorption,as typical nonlinear processes,have a large number of state variables that describe the characteristics of the system during their operation.In order to reconstruct and predict these state variables and realize the real-time digital twin of the distillation and absorption process,this paper obtains an approximate linearized model of the nonlinear system by the dynamic mode decomposition method(DMD),which is used to quickly obtain the state variables such as concentration,flow rate,temperature and holding capacity at each tray of the distillation and absorption process.Based on this,a Kalman filter is applied to correct the linear model generated by DMD in real time,which makes it possible to predict the state variables of absorption or distillation effectively without retraining the model even under off-design and limited measurement conditions.
Hydrogen energy,as an important carrier for achieving sustainable development,is of great significance for building a clean,low-carbon,and efficient energy system and achieving the"dual carbon"goals.This article designs a complete process for hydrogen separation,which is simulated and analyzed using software Aspen Plus.By proposing a coupled hydrogen separation system consisting of pressure swing adsorption(PSA),rectisol,and membrane separation,and using software such as Aspen Plus for simulation and analysis,the advantages of various separation technologies were combined.The integration of multiple separation processes has broken the purity bottleneck of single membrane separation,resulting in a product hydrogen concentration of up to 99.67%.In addition,it achieves the enrichment of CO2 and the recycling of CH4,reducing the loss of hydrogen production raw materials.The entire system has better separation performance compared to existing single technology,providing new insights and application potential for other gas separation problems.
In order to study the scale-resisting properties and scale-resisting mechanism of spirals inserted in tubes,the effects of three spirals inserted into heat exchange tubes at different flow rates on fouling thermal resistance and total heat transfer coefficient were experimentally studied.Meanwhile,the particle size and porosity of fouling were quantitatively characterized from a microscopic perspective to obtain the microstructure distribution of fouling.The results show that,under the experimental conditions,with the increase of flow velocity,the fouling resistance of the interpolation spiral decreases by 63%,the heat transfer coefficient decreases by more than 20%,and the interpolation spiral with a pitch of 20 mm has the best scaling performance.The particle size and porosity of dirt gradually increase from the near wall area to the surface area,and there is a clear crystal transition feature between the dirt layers.The porosity of the surface area and transition area of the fouling layer increases with the increase of flow velocity,and the change of the internal structure of the fouling by the characteristics of the interpolation spiral flow field is the fundamental reason for the difference in scale-resisting properties.
Trans-TXA,as the main active component in the isomers of tranexamic acid,has coagulation function and is widely used in the pharmaceutical industry.Its synthesis is mainly achieved through isomerization of cis-TXA.In the actual industrial production process,it involves kilogram level synthesis.Therefore,the most commonly used method is to use tranexamic acid as raw material to obtain a mixture of cis-tranexamic acid and trans-tranexamic acid through catalytic hydrogenation.Then,cis-tranexamic acid is converted to trans-tranexamic acid by isomerization reaction.The reaction conditions of cis-tranexamic acid isomerization are harsh,requiring high temperature,high pressure,and the participation of noble metal catalysts.By consulting the literature at home and abroad,it was found that some preparation studies are conditional experiments,however,there are few reports on the kinetics of the reaction system.How to obtain the isomerization reaction kinetic data and provide reliable data for industrial production design has become the focus of research.The purpose of this work is to determine the reaction mechanism and kinetics of tranexamic acid isomerization reaction under alkaline conditions.This study uses first principles simulation to obtain theoretical data such as the enthalpy change of isomerization raction,Gibbs free energy,and structural changes in the reaction process.The simulation results show that the data obtained by different calculation methods are different.Among them,the Gibbs free energy and reaction enthalpy data calculated by GGA+PBE method were the largest(ΔHr =14.5 kJ∙mol-1,ΔGr =16.0 kJ∙mol-1),and the minimum(ΔHr= 11.2 kJ∙mol-1,ΔGr=10.7 kJ∙mol-1)was calculated by GGA+BLYP method.In addition,the reaction barrier is calculated by the transition state search to be 46.86 kJ∙mol-1.Then,under the actual situation of experimental investigation,the reaction process of cis-TXA isomerization into trans-TXA at 453.15-513.15 K,the reaction kinetic model was established,and the reaction kinetic parameters were obtained.The positive reaction activation energy was 64.9 kJ∙mol-1,the pre-exponential factor was 2.15×105 s-1,the reverse reaction activation energy was 53.8 kJ∙mol-1,the pre-exponential factor was 4.72×103 s-1,and the reaction enthalpy value was 10.4 kJ∙mol-1 and 11.0 kJ∙mol-1.The average reaction enthalpy value of 10.7 kJ∙mol-1 obtained by experimental calculation is basically consistent with the value of 11.2 kJ∙mol-1 obtained by the simulation of GGA+BLYP method and the value of 12.1 kJ∙mol-1 obtained by the simulation of GGA+BLYP method of transition state search.Experimental and simulation data provide theoretical data and basis for the industrial design of the substance.
In order to study the performance of upstream pumping mechanical seal under high-pressure conditions,a thermal elasto-hydrodynamic lubrication model(TEHD)was established considering the fluid-solid thermal coupling between the sealing ring and the lubricating film.Based on the finite element method,the liquid film lubrication equation,the heat conduction equation of the sealing ring and the thermal deformation equation were solved.The triple iteration algorithm was used to obtain the coupling solution between film pressure,film thickness,temperature and deformation of the seal rings.The influence of rotational speed,sealing pressure and medium temperature on the deformation of the end face of the upstream pumping mechanical seal were investigated.And the upstream pumping capacity of the seal under mechanical and thermal deformation were analyzed.The research results indicate that under high pressure conditions,a liquid film gap converges along the upstream pumping direction at the sealing end face,and force deformation under high sealing pressure is the main reason,while thermal deformation partially offsets the impact of pressure deformation.With the increase of rotational speed,the convergence degree of liquid film along the upstream pumping direction decreases,the upstream pumping rate and the friction coefficient increases.With the increase of sealing medium pressure,the convergence degree of liquid film increases,the friction coefficient and the upstream pumping rate decreases greatly.With the increase of the temperature of the sealing medium,the convergence degree of the liquid film and the friction coefficient decreases,and the upstream pumping rate increases.The results can provide a theoretical reference for the structural optimization and design of the upstream pumping mechanical seals for high-pressure conditions.
Zr-based metal organic framework MOF-808 is used as the carrier and is functionalized with polyethylenimine(PEI)to obtain PEI@M-808 composite material,which is used to selectively capture humid flue gas(10%CO2 + 90%N2 + 10 kPa H2O).The physicochemical properties of the sorbents are characterized by XRD,FT-IR,SEM,and BET techniques,and the effectiveness of the modification scheme is assessed.The sorption performance of PEI300-30@M-808 at trace CO2 with moisture is dramatically enhanced due to the abundant amine groups on the surface of PEI@M-808 corresponding to the loading of PEI molecules.The adsorption performance of the composite adsorbent at trace CO2 concentration is greatly enhanced by the introduction of abundant amine functional groups on the surface of MOF-808 due to the loading of PEI.The PEI300-30@M-808 could trap 0.89 mmol/g at 343 K and 0.1 bar while the MOF-808 manifests sorption capacity of approximately 0.052 mmol/g under the same condition.Furthermore,the sorption selectivity of PEI300-30@M-808 is 5524.65 at 10/90 CO2/N2 at 0.1 bar and 343 K,which is about 56 times larger compared to that of MOF-808.Additionally,per gram of PEI300-30@M-808 could react with 1.47 mmol/g at the sorption condition with 5%RH,indicating that the moisture has a positive effect for CO2 capture with PEI-based materials.After 5 cycles,the CO2 saturated adsorption capacity of PEI300-30@M-808 can still be maintained at 90.7%.Therefore,the PEI300-30@M-808 feature great potential for trace carbon capture in moist flue gas.
Chemical looping combustion(CLC)is an important research orientation of clean energy processing and efficient conversion in the period of profound global changes.The reaction between solid fuels such as coal and oxygen carriers are one of the core scientific issues in CLC research.However,the evolution rules and the transformation mechanism are still unclear,especially the microscale description of the molecular structure evolution and functional group transformation of coal and other macromolecular solids in the fuel reactor from the atomic and molecular scale is lacking.Based on the macromolecular structure of coal and ReaxFF MD simulation,we study the chemical looping combustion process of Ningxia QH and YCW coal and nickel oxide oxygen carrier.Through the CLC process analysis of QH-NiO and YCW-NiO systems,the rules of total energy,total molecular number,product distribution and gas conversion are obtained.Based on the ReaxFF MD simulation process,the dynamic evolution process of coal macromolecular structure in CLC process is directly obtained.As the CLC reaction progresses,the macromolecular structure of coal gradually dissociates due to the breaking of old bonds and the generation of new bonds,resulting in various intermediate products,small molecules such as COx and H2O.The regulation and mechanism of quantity and rate of oxygen release from oxygen carrier during CLC in QH-NiO and YCW-NiO systems are revealed.The results show that compared with QH coal,YCW coal has lower metamorphism and higher reactivity.Therefore,the YCW-NiO system has lower total potential energy,generates more molecular fragments and more non-hydrocarbon gas,which can attribute to the oxygen carrier release lattice oxygen earlier.With the progress of CLC reaction,the oxygen vacancy formed on oxygen carrier surface leads to the migration and release of lattice oxygen in the secondary outer and inner lattice to the surface.
The condensing flow and heat-transfer characteristics around dentate-fin tubes were investigated using numerical and experimental methods.Using the examined computational model,the film flow characteristics and condensing heat-transfer coefficient of the dentate-fin tubes in the circumferential and axial directions were analyzed.Comprehensive information regarding the condensation process in high-performance tubes was provided.The results showed that the circumferential and axial film thicknesses of the dentate-fin tubes increased with increasing fin density.The liquid film distribution of dentate-fin tubes with a low fin density was relatively uniform,and condensate drainage was easy.The special heat-transfer structure of dentate-fin tubes was examined,and it was found that the complex heat-transfer structure led to variations in the surface tension,which changes the liquid-film distribution.The local condensing heat-transfer coefficient of the dentate-fin tubes was very sensitive to the liquid-film distribution.The optimal fin density corresponding to the maximum total heat-transfer coefficient was obtained,indicating that the enhanced heat transfer mechanism of dentate-fin tubes is the combined effect of heat transfer area and liquid film thickness.
In order to solve the problem that the waste heat generated by biomass aerobic fermentation is difficult to be effectively recovered,with corn straw as the main raw material and using heat exchange method,a 100 L scale fermentation device and heat recovery system were built to recover the apparent heat and latent heat in the compost steam.The electric heating method is used to simulate aerobic fermentation heat production.The waste heat recovery process was optimized from the aspects of fluid flow,equipment insulation,water storage and heat transfer area.The heat production and heat recovery effect of the optimized system were tested.The results indicate that fluid flow rate,water tank insulation,and storage capacity have a significant impact on the heat recovery performance of the system.In the simulated heat production mode,the tank temperature can rise from 17℃ to more than 40℃.Finally,through the intermittent heat recovery method,the balanced heat recovery efficiency of the system reaches more than 57％,and the average heat recovery power reaches more than 274 kJ/h,realizing the efficient recovery of fermentation waste heat.
The inorganic and resource disposal technology of tributyl phosphate(TBP)organic hazardous waste is an important environmental protection demand.Based on the principle of chemical looping combustion(CLC)and the mechanism of alkaline hydrolysis of TBP,a reaction system of alkali-assisted thermal oxidation TBP by Mn3O4 was constructed.A process of TBP degradation with simultaneous phosphorus recovery was developed.Under an optimal feed ratio of TBP,NaOH and Mn3O4(1 ml∶6 g∶13 g),the conversion rate of P from TBP to inorganic phase could reach 77.47%,and the non-methane hydrocarbon(NMHC)concentration of gas products was only 27.28 mg/m3,which was lower than the relevant environmental standard limit.Inorganic phosphorus products were separated and recovered by ethanol precipitation.X-Ray diffraction(XRD)analysis showed that the main components of phosphorus-containing products included Na3PO4,NaPO3,Na2HPO4 and Na3PO4·8H2O.According to mass spectrometry analysis of TBP degradation intermediates,the possible pathways of TBP degradation and phosphorus migration were proposed.Electron paramagnetic resonance(EPR)analysis revealed that hydroxyl radical(·OH)and superoxide radical(·O-2)played important roles in promoting the degradation of TBP.
The production process of corn deep processing to produce fructose has problems of outdated control and lack of refinement in production and processing.However,due to the complexity of the process,it is difficult to establish and optimize mechanism based models.Big data technology offers an effective solution by utilizing a substantial volume of production data to uncover process insights and identify key points.Initially,crucial target variables of this process were selected.Using big data technology,the original production data underwent preprocessing steps such as handling missing values,addressing outliers,noise reduction,and dimensionality reduction.Subsequently,three machine learning models—random forest(RF),extreme gradient boosting(XGBoost),and artificial neural network(ANN)were constructed,all achieving R2 values exceeding 0.90.Lastly,the SHAP method is used to explain different machine learning models,validate the credibility of the models,obtain the contribution levels of different features to the prediction results,and integrate the results of explanations from different models.This process generates a ranking of the importance of different points in the production process.Combining this with production experience,a mechanistic analysis is conducted to obtain the final key point table.
