Experimental study on secondary air mixing along the bed height in a circulating fluidized bed with a multitracer-gas method

A multitracer-gas method was proposed to study the secondary air(SA)mixing along the bed height in a circulating fluidized bed(CFB)using carbon monoxide(CO),oxygen(O_(2)),and carbon dioxide(CO_(2))as tracer gases.Experiments were carried out on a cold CFB test rig with a cross-section of 0.42 m×0.73 m and a height of 5.50 m.The effects of superficial velocity,SA ratio,bed inventory,and particle diameter on the SA mixing were investigated.The results indicate that there are some differences in the measurement results obtained using different tracer gases,wherein the deviation between CO and CO_(2) ranges from 42%to 66%and that between O_(2) and CO_(2) ranges from 45%to 71%in the lower part of the fluidized bed.However,these differences became less pronounced as the bed height increased.Besides,the high solid concentration and fine particle diameter in the CFB may weaken the difference.The measurement results of different tracer gases show the same trends under the variation of operating parameters.Increasing superficial velocity and SA ratio and decreasing particle diameter result in better mixing of the SA.The effect of bed inventory on SA mixing is not monotonic.

Enhancing ammonia production rates from electrochemical nitrogen reduction by engineering three-phase boundary with phosphorus-activated Cu catalysts

Electrochemical N_(2) reduction reaction(eNRR) over Cu-based catalysts suffers from an intrinsically low activity of Cu for activation of stable N_(2) molecules and the limited supply of N_(2) to the catalyst due to its low solubility in aqueous electrolytes.Herein,we propose phosphorus-activated Cu electrocatalysts to generate electron-deficient Cu sites on the catalyst surface to promote the adsorption of N_(2) molecules.The eNRR system is further modified using a gas diffusion electrode(GDE) coated with polytetrafluoroethylene(PTFE) to form an effective three-phase boundary of liquid water-gas N_(2)-solid catalyst to facilitate easy access of N_(2) to the catalytic sites.As a result,the new catalyst in the flow-type cell records a Faradaic efficiency of 13.15% and an NH_(3) production rate of 7.69 μg h^(-1) cm^(-2) at-0.2 V_(RHE),which represent 3.56 and 59.2 times increases from those obtained with a pristine Cu electrode in a typical electrolytic cell.This work represents a successful demonstration of dual modification strategies;catalyst modification and N_(2) supplying system engineering,and the results would provide a useful platform for further developments of electrocatalysts and reaction systems.

Enhanced gas separation performance of mixed matrix hollow fiber membranes containing post-functionalized S-MIL-53

Mixed matrix hollow fiber membranes（MMHFMs）filled with metal-organic frameworks（MOFs）have great potential for energy-efficient gas separation processes,but the major hurdle is polymer/MOFs interfacial defects and membrane plasticization.Herein,lab-synthesized MIL-53 was post-functionalized by aminosilane grafting and subsequently incorporated into Ultem-1000 polymer matrix to fabricate high performance MMHFMs.SEM,DLS,XRD and TGA were performed to characterize silane-modified MIL-53（S-MIL-53）and prepared MMHFMs.Moreover,the effect of MOFs loading was systematically investigated first;then gas separation performance of MMHFMs for pure and mixed gas was evaluated under different pressures.MMHFMs containing post-functionalized S-MIL-53 achieved remarkable gas permeation properties which was better than model predictions.Compared to pure HFMs,CO2permeance of MMHFM loaded with 15%S-MIL-53 increased by 157%accompanying with 40%increase for CO2/N2selectivity,which outperformed the MMHFM filled with naked MIL-53.The pure and mixed gas permeation measurements with elevated feed pressure indicated that incorporation of S-MIL-53 also increased the resistance against CO2plasticization.This work reveals that post-modified MOFs embedded in MMHFMs facilitate the improvement of gas separation performance and suppression of membrane plasticization.

Synergistic Effect in Mixed Capillary Gas Chromatographic Stationap Phases Containing Heptakis(2,3,6-tri-o-pentyl)-β-cyclodextrin and Dibenzo-18-crown-6

used－silical capillary columns containing heptakis（2、3、6－tri－o－pentyl）-β-cyclodextrinand dibenzo-18-crown-6 were prepared．By studying the selectivity of mixed stationary phases forsome solute pairs.as well as comparing with the heptakis（2．3、6-tri-O-pentyl）-β-cyclodextrin and thedibenzo-18-crown-6 used as individual stationary phase、the synergistic effects were observed.These effects were affected by the column temperature．mixed ratio and linear velocity of carrier gas．

Design and analysis of dual mixed refrigerant processes for high-ethane content natural gas liquefaction

Recovery and purification of ethane has a significant impact on economic benefit improvement of the high-ethane content natural gas.However,current LNG-NGL integrated processes mainly focus on conventional natural gas,which are not applicable to natural gas with high ethane content.To fill this gap,three dual mixed refrigerant processes are proposed for simulation study of high-ethane content natural gas liquefaction.The proposed processes are optimized by a combination method of sequence optimization and genetic algorithm.Comparatively analysis is conducted to evaluate the three processes from the energetic and exergetic points of view.The results show that the power consumption of Process 3 which compressing natural gas after distillation is the lowest.For safety or other considerations,some common compositions of the mixed refrigerant may need to be removed under certain circumstances.Considering this,case studies of mixed refrigerant involving six composition combinations are carried out to investigate the effects of refrigerant selection on the process performance.

Synergistic Effect in Special Selectivity Mixed Gas Chromatographic Stationary Phase in the Separation of Aromatic Compounds

The gas chromatographic separations of aromatic compounds using special mixed stationary phases consisting of pp-beta-CD+AgNO3, pp-beta-CD+TINO3, pp-beta-CD+di-n-butly phthalate, pp-beta-CD+BPBHpB liquid crystalline, and bentone-34+AgNO3 were investigated. Besides pp-beta-CD+di-n-butyl phthalate, most of the separations deviated from the additivity and a synergistic effect was observed. The separation effects depend on the temperature and how mixing is accomplished.

Assembling ionic liquid into porous molecular filler of mixed matrix membrane to trigger high gas permeability,selectivity,and stability for CO_(2)/CH_(4) separation

As an emerging zero-dimensional nano crystalline porous material,porous organic cages(POCs)with soluble properties in organic solvents,are promising candidates as molecular fillers in mixed matrix membranes(MMMs).The pore structure of POCs should be adjusted to trigger efficient gas separation performance,and the interaction between filler and matrix should be optimized.In this work,ionic liquid(IL)was introduced into the molecular fillers of CC3,to construct the IL@CC3/PIM-1 membrane to effectively separate CO_(2) from CH_(4).The advantages of doping IL include:(1)narrowing the cavity size of POCs from 4.4 to 3.9Åto enhance the diffusion selectivity,(2)strengthening the CO_(2) solubility to heighten the gas permeability,and(3)improving the compatibility between filler and matrix to upgrade membrane stability.After the optimization of the membrane composite,the IL@CC3/PIM-1-10%membrane possesses the CO_(2) permeability of 7868 Barrer and the CO_(2)/CH_(4) selectivity of 73.4,which compared to the CC3/PIM-1-10%membrane,improved by 15.9%and 106.2%,respectively.Furthermore,the membrane has maintained a stable separation performance at varied temperatures and pressures during the long-term test.The proposed method offers an efficient way to improve the performance of POCs-based MMMs in gas separation.

The numerical simulation of a new double swirl static mixer for gas reactants mixing

For the nitrogen oxide removal processes,high performance gas mixer is deeply needed for the injection of NH3 or O3.In this study,a new type of double swirl static mixer in gas mixing was investigated using computational fluid dynamics(CFD).The results obtained using Particle Image Velocimetry(PIV)correlated well with the results obtained from simulation.The comparisons in pressure loss between the experimental results and the simulation results showed that the model was suitable and accurate for the simulation of the static mixer.Optimal process conditions and design were investigated.When L/D equaled 4,coefficient of variation(COV)was<5%.The inlet velocity did not affect the distributions of turbulent kinetic energy.In terms of both COV and pressure loss,the inner connector is important in the design of the static mixer.The nozzle length should be set at 4 cm.Taking both COV and pressure loss into consideration,the optimal oblique degree is 450.The averaged kinetic energy changed according to process conditions and design.The new static mixer resulted in improved mixing performance in a more compact design.The new static mixer is more energy efficient compared with other SV static mixers.Therefore,the double swirl static mixer is promising in gas mixing.

Numerical Simulation and Analysis of Migration Law of Gas Mixture Using Carbon Dioxide as Cushion Gas in Underground Gas Storage Reservoir

One of the major technical challenges in using carbon dioxide( CO2) as part of the cushion gas of the underground gas storage reservoir( UGSR) is the mixture of CO2and natural gas. To decrease the mixing extent and manage the migration of the mixed zone,an understanding of the mechanism of CO2and natural gas mixing and the diffusion of the mixed gas in aquifer is necessary. In this paper,a numerical model based on the three dimensional gas-water two-phase flow theory and gas diffusion theory is developed to understand this mechanism. This model is validated by the actual operational data in Dazhangtuo UGSR in Tianjin City,China.Using the validated model,the mixed characteristic of CO2and natural gas and the migration mechanism of the mixed zone in an underground porous reservoir is further studied. Particularly,the impacts of the following factors on the migration mechanism are studied: the ratio of CO2injection,the reservoir porosity and the initial operating pressure. Based on the results,the optimal CO2injection ratio and an optimal control strategy to manage the migration of the mixed zone are obtained. These results provide technical guides for using CO2as cushion gas for UGSR in real projects.

Effect of gas blowing nozzle angle on multiphase flow and mass transfer during RH refining process

A three-dimensional mathematical model was developed to investigate the effect of gas blowing nozzle angles on multiphase flow,circulation flow rate,and mixing time during Ruhrstahl-Heraeus(RH) refining process.Also,a water model with a geometric scale of 1:4 from an industrial RH furnace of 260 t was built up,and measurements were carried out to validate the mathematical model.The results show that,with a conventional gas blowing nozzle and the total gas flow rate of 40 L·min^(-1),the mixing time predicted by the mathematical model agrees well with the measured values.The deviations between the model predictions and the measured values are in the range of about 1.3%–7.3% at the selected three monitoring locations,where the mixing time was defined as the required time when the dimensionless concentration is within 3% deviation from the bath averaged value.In addition,the circulation flow rate was 9 kg·s^(-1).When the gas blowing nozzle was horizontally rotated by either 30° or 45°,the circulation flow rate was found to be increased by about 15% compared to a conventional nozzle,due to the rotational flow formed in the up-snorkel.Furthermore,the mixing time at the monitoring point 1,2,and 3 was shortened by around 21.3%,28.2%,and 12.3%,respectively.With the nozzle angle of 30° and 45°,the averaged residence time of 128 bubbles in liquid was increased by around 33.3%.

Effect of Welding Parameters on GTA Weld Shape for Pure Iron Plate under Ar-O_2 Mixed Shielding

Weld shape variation for different welding parameters is investigated on pure iron plate under gas tungsten arc （GTA） welding with argon-oxygen mixed shielding. Results showed that small addition of oxygen to the argon base shielding gas can effectively adjust the oxygen adsorption to the molten pool. An inward Marangoni convection occurs on the pool surface when the oxygen content in the weld pool is over the critical value, 80×10^-6, for pure iron plate under Ar-0.3%O2 mixed shielding. Low oxygen content in the weld pool changes the inward Marangoni to an outward direction under the Ar-0.1%O2 shielding. The GTA weld shape depends to a large extent on the pattern and strength of the Marangoni convection on the pool surface, which is determined by the content of surface active element, oxygen, in the weld pool and the welding parameters. The strength of the Marangoni convection on the liquid pool is a product of the temperature coefficient of the surface tension （dσ/dT） and the temperature gradient （dT/dr） on the pool surface. Different welding parameters will change the temperature distribution and gradient on the pool surface, and therefore, affect the strength of Marangoni convection and the weld shape.

New insight into prediction of phase behavior of natural gas hydrate by different cubic equations of state coupled with various mixing rules

Progress in hydrate thermodynamic study necessitates robust and fast models to be incorporated in reservoir simulation softwares. However, numerous models presented in the literature makes selection of the best,proper predictive model a cumbersome task. It is of industrial interest to make use of cubic equations of state(EOS) for modeling hydrate equilibria. In this regard, this study focuses on evaluation of three common EOSs including Peng–Robinson, Soave–Redlich–Kwong and Valderrama–Patel–Teja coupled with van der Waals and Platteeuw theory to predict hydrate P–T equilibrium of a real natural gas sample. Each EOS was accompanied with three mixing rules, including van der Waals(vd W),Avlonitis non-density dependent(ANDD) and general nonquadratic(GNQ). The prediction of cubic EOSs was in sufficient agreement with experimental data and with overall AARD% of less than unity. In addition, PR plus ANDD proved to be the most accurate model in this study for prediction of hydrate equilibria with AARD% of 0.166.It was observed that the accuracy of cubic EOSs studied in this paper depends on mixing rule coupled with them,especially at high-pressure conditions. Lastly, the present study does not include any adjustable parameter to be correlated with hydrate phase equilibrium data.

Forecast of natural gas supply and demand in China under the background of “Dual Carbon Targets”

As a kind of clean energy which creates little carbon dioxide, natural gas will play a key role in the process of achieving “Peak Carbon Dioxide Emission” and “Carbon Neutrality”. The Long-range Energy Alternatives Planning System(LEAP) model was improved by using new parameters including comprehensive energy efficiency and terminal effective energy consumption. The Back Propagation(BP) Neural Network–LEAP model was proposed to predict key data such as total primary energy consumption, energy mix, carbon emissions from energy consumption, and natural gas consumption in China. Moreover, natural gas production in China was forecasted by the production composition method. Finally, based on the forecast results of natural gas supply and demand, suggestions were put forward on the development of China’s natural gas industry under the background of “Dual Carbon Targets”. The research results indicate that under the background of carbon peak and carbon neutrality, China’s primary energy consumption will peak(59.4×10^(8)tce) around 2035, carbon emissions from energy consumption will peak(103.4×10^(8)t) by 2025, and natural gas consumption will peak(6100×10^(8)m^(3)) around 2040, of which the largest increase will be contributed by the power sector and industrial sector. China’s peak natural gas production is about(2800–3400)×10^(8)m^(3), including(2100–2300)×10^(8)m^(3)conventional gas(including tight gas),(600–1050)×10^(8)m^(3)shale gas, and(150–220)×10^(8)m^(3)coalbed methane. Under the background of carbon peak and carbon neutrality, the natural gas consumption and production of China will further increase, showing a great potential of the natural gas industry.

Multichannel Discharge Characteristics of Gas Switch Gap in SF_6-N_2 or SF_6-Ar Gas Mixtures Under Nanosecond Triggering Pulses

Experiments were carried out to ascertain multichannel discharge characteristics in a self-designed coaxial field-distortion gas switch filled with SFa-N2 or SF6-Ar gas mixtures of different mixing ratios. In these experiments, the pressure varied from 0.1 MPa to 0.2 MPa, the voltage pulse peak applied to the switch was in the range from 40 kV to 78 kV, and the pulse rise time was 11 ns. The static breakdown strength of the gas switch gap in the switch was also measured. The results show that in general the average number of discharge channels for SF6-Ar or SF6-N2 gas mixture which contains less SFa is larger than that for gas mixture which contains more SF6, however, the average number of channels almost keeps constant as the gas mixing ratio varies when the pulse rise rate is high enough. The static breakdown strength of the gas switch gap decreases slightly as the content of argon or nitrogen increases.

THE MIXING OF GAS-LIQUID FLOW WITH VAPOR AND GAS-SOLID FLOW

In the industrial production, the mixing of gas-liquid flow with vapor and gas-solid flow is a very common problem. In the process of the mixing, solid particle-clusters will form, and will have steady radii when the effect of the gathering of particles is balanced withthat of the breaking of particle-clusters. Then, the population distribution function of size of particles per unit length per unit volume is introduced, and its governingequation is derived on the analogy of the molecular kinetic theory. Finally, when the gas flow is very slow, the expression of steady average radius of particle-clusters is obtained.

Changes in China--Beijing is seeking less energy-intensive economic growth ＆ a less carbon-intensive energy mix and its impact over oil ＆ gas supply

Having experienced over 30 years of rapid growth,China’s economic development is entering a new normal featured by an ever optimizing economic structure shifting from high-speed to medium-high speed growth,and from factor-driven to innovation-driven pattern.In adapting

Quantitative research of the liquid film characteristics in upward vertical gas, oil and water flows

The study of liquid film characteristics in multiphase flow is a very important research topic, however,the characteristics of the liquid film around Taylor bubble structure in gas, oil and water three-phase flow are not clear. In the present study, a novel liquid film sensor is applied to measure the distributed signals of the liquid film in three-phase flow. Based on the liquid film signals, the liquid film characteristics including the structural characteristics and the nonlinear dynamics characteristics in three-phase flows are investigated for the first time. The structural characteristics including the proportion, the appearance frequency and the thickness of the liquid film are obtained and the influences of the liquid and gas superficial velocities and the oil content on them are investigated. To investigate the nonlinear dynamics characteristics of the liquid film with the changing flow conditions, the entropy analysis is introduced to successfully uncover and quantify the dynamic complexity of the liquid film behavior.

Coexistence of natural gas hydrate,free gas and water in the gas hydrate system in the Shenhu Area,South China Sea

Shenhu Area is located in the Baiyun Sag of Pearl River Mouth Basin,which is on the northern continental slope of the South China Sea.Gas hydrates in this area have been intensively investigated,achieving a wide coverage of the three-dimensional seismic survey,a large number of boreholes,and detailed data of the seismic survey,logging,and core analysis.In the beginning of 2020,China has successfully conducted the second offshore production test of gas hydrates in this area.In this paper,studies were made on the structure of the hydrate system for the production test,based on detailed logging data and core analysis of this area.As to the results of nuclear magnetic resonance(NMR)logging and sonic logging of Well GMGS6-SH02 drilled during the GMGS6 Expedition,the hydrate system on which the production well located can be divided into three layers:(1)207.8–253.4 mbsf,45.6 m thick,gas hydrate layer,with gas hydrate saturation of 0–54.5%(31%av.);(2)253.4–278 mbsf,24.6 m thick,mixing layer consisting of gas hydrates,free gas,and water,with gas hydrate saturation of 0–22%(10%av.)and free gas saturation of 0–32%(13%av.);(3)278–297 mbsf,19 m thick,with free gas saturation of less than 7%.Moreover,the pore water freshening identified in the sediment cores,taken from the depth below the theoretically calculated base of methane hydrate stability zone,indicates the occurrence of gas hydrate.All these data reveal that gas hydrates,free gas,and water coexist in the mixing layer from different aspects.

Effect of Mg/Al atom ratio of support on catalytic performance of Co-Mo/MgO-Al_2O_3 catalyst for water gas shift reaction

Co-Mo-based catalysts supported on mixed oxide supports MgO-Al2O3 with different Mg/Al atom ratios for water gas shift reaction were studied by means of TPR, Raman, XPS and ESR. It was found that the octahedral Mo species in oxidized Co-Mo/MgO（x）-Al2O3 catalyst and the contents of Mo^5＋, Mo^4＋, S^2- and S^2-2 species in the functioning catalysts increased with increasing the Mg/Al atom ratio of the support under the studied experimental conditions. This is favorable for the formation of the active Co-Mo-S phase of the catalysts. Catalytic performance testing results showed that the catalysts Co-Mo/MgO-Al2O3 with the Mg/Al atom ratio of the support in the range of 0.475-0.525 exhibited optimal catalytic activity for the reaction.

Design of two-stage membrane reactor for the conversion of coke-oven gas to H_2 and CO

The catalyst function was achieved in two regions in an oxygen permeation membrane reactor： H2 dissociated and reacted with lattice oxygen or oxygen ions to form H20 near the membrane surface. The H20 formed could react with the residual CH4 away from the membrane surface area.