Data-based real-time petrochemical gas diffusion simulation approach on virtual reality

Background Petrochemical products possess a high risk of flammability,explosivity,and toxicity,making petrochemical accidents exceedingly destructive.Therefore,disaster analysis,prediction,and real-time simulations have become important means of controlling and reducing accident hazards.Methods This study proposes a complete real-time simulation solution of gas diffusion with coordinate and concentration data,which was mainly aimed at simulating the types of harmful gas leakage and diffusion accidents in the petrochemical industry.The rendering effect was more continuous and accurate through grid homogenization and trilinear interpolation.This study presents a data processing and rendering parallelization process to enhance simulation efficiency.Gas concentration and fragment transparency were combined to synthesize transparent pixels in a scene.To ensure the approximate accuracy of the rendering effect,improve the efficiency of real-time rendering,and meet the requirement of intuitive perception using concentration data,a weighted blended order-independent transparency(OIT)with enhanced alpha weight is presented,which can provide a more intuitive perception of the hierarchical information of concentration data while preserving depth information.This study compares and analyzes three OIT algorithms-depth peeling,weighted blended OIT,and weighted blended OIT with enhanced alpha weight-in terms of rendering image quality,rendering time,required memory,and hierarchical information.Results Using weighted blended OIT with an enhanced alpha weight technique,the rendering time was shortened by 53.2%compared with that of the depth peeling algorithm,and the texture memory required was significantly smaller than that of the depth peeling algorithm.The rendering results of weighted blended OIT with an enhanced alpha weight were approximately accurate compared with those of the depth peeling algorithm as the ground truth,and there was no popping when surfaces passed through one another.Simultaneously,compared with weighted blended OIT,weighted blended OIT with an enhanced alpha weight achieved an intuitive perception of the hierarchical information of concentration data.

A general solution and approximation for the diffusion of gas in a spherical coal sample

The square root relationship of gas release in the early stage of desorption is widely used to provide a simple and fast estimation of the lost gas in coal mines. However, questions arise as to how the relationship was theoretically derived, what are the assumptions and applicable conditions and how large the error will be. In this paper, the analytical solutions of gas concentration and fractional gas loss for the diffusion of gas in a spherical coal sample were given with detailed mathematical derivations based on the diffusion equation. The analytical solutions were approximated in case of small values of time and the error analyses associated with the approximation were also undertaken. The results indicate that the square root relationship of gas release is the first term of the approximation, and care must be taken in using the square root relationship as a significant error might be introduced with increase in the lost time and decrease in effective diameter of a spherical coal sample.

Effect of an electrostatic field on gas adsorption and diffusion in tectonic coal

The characteristics of adsorption, desorption, and diffusion of gas in tectonic coal are important for the prediction of coal and gas outbursts. Three types of coal samples, of which both metamorphic grade and degree of damage is different, were selected from Tongchun, Qilin, and Pingdingshan mines. Using a series of experiments in an electrostatic field, we analyzed the characteristics of gas adsorption and diffusion in tectonic coal. We found that gas adsorption in coal conforms to the Langmuir equation in an electrostatic field. Both the depth of the adsorption potential well and the coal molecular electroneg- ativity increases under the action of an electrostatic field. A Joule heating effect was caused by changing the coal-gas system conductivity in an electrostatic field. The quantity of gas adsorbed and AP result from competition between the depth of the adsorption potential well, the coal molecular electronegativ- ity, and the Joule heating effect. △P peaks when the three factors control behavior equally. Compared with anthracite, the impact of the electrostatic field on the gas diffusion capacity of middle and high rank coals is greater. Compared with the original coal, the gas adsorption quantity,△P, and the gas diffusion capacity of tectonic coal are greater in an electrostatic field. In addition, the smaller the particle size of tectonic coal, the larger the△P.

Gas diffusion in a cylindrical coal sample – A general solution,approximation and error analyses

The analytical mathematical solutions of gas concentration and fractional gas loss for the diffusion of gas in a cylindrical coal sample were given with detailed mathematical derivations by assuming that the diffusion of gas through the coal matrix is concentration gradient-driven and obeys the Fick’s Second Law of Diffusion.The analytical solutions were approximated in case of small values of time and the error analyses associated with the approximation were also undertaken.The results indicate that the square root relationship of gas release in the early stage of desorption,which is widely used to provide a simple and fast estimation of the lost gas,is the first term of the approximation,and care must be taken in using the square root relationship as a significant error might be introduced with increase in the lost time and decrease in effective diameter of a cylindrical coal sample.

Electrochemical disinfection using the gas diffusion electrode system

A study on the electrochemical disinfection with H202 generated at the gas diffusion electrode （GDE） from active carbon/poly- tetrafluoroethylene was performed in a non-membrane cell. The effects of Pt load and the pore-forming agent content in GDE, and operating conditions were investigated. The experimental results showed that nearly all bacterial cultures inoculated in the secondary effluent from wastewater treatment plant could be inactivated within 30 min at a current density of 10 mA/cm^2. The disinfection improved with increasing Pt load. Addition of the pore-forming agent NH4HCO3 improved the disinfection, while a drop in the pH value resulted in a rapid rise of germicidal efficacy and the disinfection time was shortened with increasing oxygen flow rate. Adsorption was proved to be ineffective in destroying bacteria, while germicidal efficacy increased with current density. The acceleration rate was different, it initially increased with current density. Then decreased, and finally reached a maximum at a current density of 6.7 mA/cm^2. The disinfection also improved with decreasing total bacterial count. The germicidal efficacy in the cathode compartment was approximately the same as in the anode compartment, indicating that the contribution of direct oxidation and the indirect treatment of bacterial cultures by hydroxyl radical was similar to the oxidative indirect effect of the generated H2O2.

Numerical simulation to evaluate gas diffusion of turbulent flow in mine ventilation system

Tracer gas technique is a method to analyze the airflow path, measure the airflow quantity, and detect any recirculation or leakages in underground mine. In addition, it is also possible to evaluate the axial gas diffusion of gas in turbulent bulk flow by utilizing the tracer gas data. This paper discussed about the measurement using tracer gas technique in Cibaliung Underground Mine, Indonesia and the evaluation of effective axial diffusion coefficient, E, by numerical simulation. In addition, a scheme to treat network flow in mine ventilation system was also proposed. The effective axial diffusion coefficient for each airway was evaluated based on Taylor's theoretical equation. It is found that the evaluated diffusion coefficient agrees well with Taylor's equation by considering that the wall friction factor, f, is higher than those for smooth pipe flow. It also shows that the value of effective diffusion coefficient can be inherently determined and the value is constant when matching with other measurements. Furthermore, there are possibilities to utilize the tracer gas measurement data to evaluate the airway friction factors.

A Study of Gas Diffusion Electrodes for the Coupled Reaction of Water Electrolysis and Electrocatalytic Benzene Hydrogenation

Gas diffusion electrodes are applied to the coupled reaction of water electrolysis and electrocatalytic benzene hydrogenation. The effects of the preparation conditions of electrodes, electrolyte acidity, the concentration of benzene and water vapor, and the flow rate of N2 are investigated by evaluating the efficiency of the current. Furthermore, the optimal operational conditions have been ascertained. The results of our experiment show that gas diffusion electrodes have good performance when the content of PTFE is 10% (wt) and that of Nafion is 0.75mg/cm2. The optimal operational conditions are as follows: The temperature of electrolysis is 70℃, acidity 0.5mol/L, the concentration of benzene 26%, the concentration of vapor 10%, the flow rate of N2 80mL/min-240mL/min. The efficiency of the current can reach 35% under optimal operational conditions. Then, a conclusion can be drawn that gas diffusion electrodes can improve the rate of the coupled reaction effectively.

Influence of gas-diffusion-layer current collector on electrochemical performance of Ni(OH)_(2) nanostructures

We report the electrochemical performance of Ni(OH)_(2) on a gas diffusion layer(GDL).The Ni(OH)_(2) working electrode was successfully prepared via a simple method,and its electrochemical performance in 1 M NaOH electrolyte was investigated.The electrochemical results showed that the Ni(OH)_(2)/GDL provided the maximum specific capacitance value(418.11 F·g^(−1))at 1 A·g^(−1).Furthermore,the Ni(OH)_(2) electrode delivered a high specific energy of 17.25 Wh·kg^(−1) at a specific power of 272.5 W·kg^(−1) and retained about 81%of the capacitance after 1000 cycles of galvanostatic charge–discharge(GCD)measurements.The results of scanning electron microscopy(SEM)coupled with energy-dispersive X-ray spectroscopy(EDS)revealed the occurrence of sodium deposition after long-time cycling,which caused the reduction in the specific capacitance.This study results suggest that the light-weight GDL,which can help overcome the problem of the oxide layer on metal–foam substrates,is a promising current collector to be used with Ni-based electroactive materials for energy storage applications.

Fractal Analysis of Gas Diffusion Layer in PEM Fuel Cells

The aim of this study is to show how fractal analysis can be effectively used to characterize the texture of porous solids. The materials under study were carbon papers, the backing material of the gas diffusion layer （GDL） in Proton Exchange Membrane Fuel Cell （PEMFC）. The fractal dimensions were calculated by analyzing data from mercury porosimetry. The polytotrafluoroethylene （PTFE） treated carbon paper shows a significantly high fractal dimension value than pare sample, and the high fractal dimension signifies that the physical complexity of the pore surface is enhanced. The fractal dimension can be used as a valid parameter to monitor the textural evolution of the samples as the treatment progresses, as this behaves in a similar way to other textural parameters. The use of fractal analysis in conjunction with the results of classical characterization methods leads to a better understanding of textural modificatious in the processing of materials.

HIGH-PERFORMANCE GAS DIFFUSION POROUS STARVED OF ELECTROLYTE SOLUTION

The performance of gas diffusion porous electrode starved of electrolyte solution can be significantly increased by decreasing the thickness of uneven liquid film covering the catalyst agglomerates.

SELECTIVE SULFUR DIOXIDE DETERMINATION BY GAS DIFFUSION FLOW INJECTION ANALYSIS WITH CHEMILUMINESCENT DETECTION

Sulfur dioxide has been found to decrease the chemiluminescence of luminol-iodine system.A new determination method for sulfur dioxide in atmosphere is developed by applying this reaction to a flow injection gas diffusion separation system.This permits the determination of sulfur dioxide selectively and rapidly.

Electrocatalytic CO_(2) reduction to C_(2)H_(4): From lab to fab

The global concerns of energy crisis and climate change,primarily caused by carbon dioxide(CO_(2)),are of utmost importance.Recently,the electrocatalytic CO_(2) reduction reaction(CO_(2)RR) to high value-added multi-carbon(C_(2+)) products driven by renewable electricity has emerged as a highly promising solution to alleviate energy shortages and achieve carbon neutrality.Among these C_(2+) products,ethylene(C_(2)H_(4))holds particular importance in the petrochemical industry.Accordingly,this review aims to establish a connection between the fundamentals of electrocatalytic CO_(2) reduction reaction to ethylene(CO_(2)RRto-C_(2)H_(4)) in laboratory-scale research(lab) and its potential applications in industrial-level fabrication(fab).The review begins by summarizing the fundamental aspects,including the design strategies of high-performance Cu-based electrocatalysts and advanced electrolyzer devices.Subsequently,innovative and value-added techniques are presented to address the inherent challenges encountered during the implementations of CO_(2)RR-to-C_(2)H_(4) in industrial scenarios.Additionally,case studies of the technoeconomic analysis of the CO_(2)RR-to-C_(2)H_(4) process are discussed,taking into factors such as costeffectiveness,scalability,and market potential.The review concludes by outlining the perspectives and challenges associated with scaling up the CO_(2)RR-to-C_(2)H_(4) process.The insights presented in this review are expected to make a valuable contribution in advancing the CO_(2)RR-to-C_(2)H_(4) process from lab to fab.

Gas diffusion in catalyst layer of flow cell for CO_(2) electroreduction toward C_(2+) products

The use of gas diffusion electrode(GDE)based flow cell can realize industrial-scale CO_(2) reduction reactions(CO_(2)RRs).Controlling local CO_(2) and CO intermediate diffusion plays a key role in CO_(2)RR toward multi-carbon(C_(2+))products.In this work,local CO_(2) and CO intermediate diffusion through the catalyst layer(CL)was investigated for improving CO_(2)RR toward C_(2+)products.The gas permeability tests and finite element simulation results indicated CL can balance the CO_(2) gas diffusion and residence time of the CO intermediate,leading to a sufficient CO concentration with a suitable CO_(2)/H_(2)O supply for high C_(2+)products.As a result,an excellent selectivity of C_(2+)products~79%at a high current density of 400 mA·cm^(-2) could be obtained on the optimal 500 nm Cu CL(Cu500).This work provides a new insight into the optimization of CO_(2)/H_(2)O supply and local CO concentration by controlling CL for C_(2+)products in CO_(2)RR flow cell.

Characteristics and accumulation mechanism of tight sandstone gas reservoirs in the Upper Paleozoic, northern Ordos Basin, China

The Ordos Basin is a significant petroliferous basin in the central part of China.The Carboniferous and Permian deposits of transitional and continental facies are the main gas-bearing layers in the north part of the basin.The Carboniferous and Permian natural gas reservoirs in the northern Ordos Basin are mainly tight sandstone reservoirs with low porosity and low permeability,developing lots of ＂sweet spots＂ with comparatively high porosity and permeability.The tight sandstones in the study area are gas-bearing,and the sweet spots are rich in gas.Sweet spots and tight sandstones are connected rather than being separated by an interface seal.Sweet spot sand bodies are vertically and horizontally overlapped,forming a large gas reservoir group.In fact,a reservoir formed by a single sweet spot sand body is an open gas accumulation.In the gentle dipping geological setting and with the source rocks directly beneath the tight reservoirs over a large area,the balance between gas charging into tight reservoirs from source rocks and gas loss from tight reservoirs through caprock is the key of gas accumulation in tight sandstones.Both the non-Darcy flow charging driven by source-reservoir excess pressure difference and the diffusion flow charging driven by source-reservoir gas concentration difference play an important role in gas accumulation.The results of mathematical modeling indicate that the gas accumulation cannot be formed by just one of the above mechanisms.The diffusion of gas from source rocks to reservoirs is a significant mechanism of tight sandstone gas accumulation.

Analysis of factors affecting vent system for underground gas storage

The operating conditions of vent system for underground gas storage was introduced. The numerical simulation of the diffusion process of natural gas was conducted using process hazard analysis software tool （PHAST） with gas release velocity greater than 40 000 m^3/h. The effects of release velocity, atmospheric stability and wind speed on the diffusion area, flash fire, explosion and spray fire of natural gas were analyzed. The results show that the higher release velocity is, the bigger explosive area is; the stabler atmosphere is, the less natural gas diffuses; the lower wind speed is, the less natural gas diffuses, and the lower diffusion speed is, the bigger dangerous area is. Moreover, wind speed also has an effect on flash fire and heat radiation. In order to ensure safety of vent process of natural gas storage, the release velocity should be controlled and atmospheric conditions should be considered at the same time.

Molecular Simulation of Oxygen Sorption and Diffusion in the Poly （lactic acid）

Grand canonical Monte Carlo and molecular dynamics simulation methods are used to simulate oxygen sorption and diffusion in amorphous poly（lactic acid） （PLA）. The simulated solubility coefficient of oxygen is close to experimental data obtained from the quartz crystal microbalance but much higher than those from the time-lag method. This discrepancy is explained by using the dual-mode sorption model. It is found that oxygen sorotion in PLA is predominantly Langmuir type controlled, i.e., through the process of filling holes. The time--lag method only takes into account oxygen molecules that participate the diffusion process whereas a large proportion of oxygen molecules trapped in the void have little chance to execute hopping due to the glassy nature of PLA at room temperature. The simulated diffusion coefficient of oxygen is reasonably close to the data obtained from the time-lag method. The solubility coefficient of oxygen decreases linearly with increasing relative humidity while its diffusion coefficient firstly decreases and then increases as a function of relative humidity.

Ice-Shielding Models for Self-Preservation of Gas Hydrates

The self-preservation of methane hydrate is a key process in its engineering applications because the hydrate can survive for a significant period under atmospheric pressure and moderate temperature. Some experiments have predicted that the shielding ice formed on the hydrate surface after initial dissociation of the hydrate plays an important role in the self-preservation effect. We propose ice-shielding models of gas hydrates to investigate the dissociation rates quantitatively, including the self-preservation process, at temperatures below the ice-melting point and at atmospheric pressure. Three general models are constructed for two temperature ranges The rate-determining process for the lower temperature range is hydrate dissociation, and those for the higher range are gas diffusion through ice or hydrate layers, which depend on the thickness of the shielding-ice layer. Our models suggest that the extent of self-preservation depends on temperature, original hydrate size, and guest substances, which can explain the experimental results.

A generalized formula for two-dimensional diffusion of CO in graphene nanoslits with different Pt loadings

Catalytic performance of supported metal catalysts not only depends on the reactivity of metal,but also the adsorption and diffusion properties of gas molecules which are usually affected by many factors,such as temperature,pressure,properties of metal clusters and substrates,etc.To explore the impact of each of these macroscopic factors,we simulated the movement of CO molecules confined in graphene nanoslits with or without supported Pt nanoparticles.The results of molecular dynamics simulations show that the diffusion of gas molecules is accelerated with high temperature,low pressure or low surface-atom number of supported metals.Notably,the supported metal nanoparticles greatly affect the gas diffusion due to the adsorption of gas molecules.Furthermore,to bridge a quantitative relationship between microscopic simulation and macroscopic properties,a generalized formula is derived from the simulation data to calculate the diffusion coefficient.This work helps to advise the diffusion modulation of gas molecules via structural design of catalysts and regulation of reaction conditions.

Advances and challenges of electrolyzers for large-scale CO_(2) electroreduction

CO_(2) electroreduction(CO_(2) ER)to high value-added chemicals is considered as a promising technology to achieve sustainable carbon neutralization.By virtue of the progressive research in recent years aiming at design and understanding of catalytic materials and electrolyte systems,the CO_(2) ER performance(such as current density,selectivity,stability,CO_(2) conversion,etc.)has been continually increased.Unfortunately,there has been relatively little attention paid to the large-scale CO 2 electrolyzers,which stand just as one obstacle,alongside series-parallel integration,challenging the practical application of this infant technology.In this review,the latest progress on the structures of low-temperature CO_(2) electrolyzers and scale-up studies was systematically overviewed.The influence of the CO_(2) electrolyzer configurations,such as the flow channel design,gas diffusion electrode(GDE)and ion exchange membrane(IEM),on the CO_(2) ER performance was further discussed.The review could provide inspiration for the design of large-scale CO_(2) electrolyzers so as to accelerate the industrial application of CO_(2) ER technology.

Multi-stage gas diffusion and its implications for the productivity of coalbed methane in the southern Qinshui Basin, north China

The behavior of coalbed methane(CBM)diffusion considerably influences gas productivity.Based on the multi-porous diffusion model and on-site CBM desorption data of coal cores,the behavior of CBM diffusion and its implications on the gas productivity of No.3 coal seam in the southern Qinshui Basin(SQB)were elaborately analyzed.Results indicate that CBM diffusion of No.3 coal seam demonstrates noticeable three-stage characteristics,including the fast diffusion,transitional diffusion,and slow diffusion stages.During the gas diffusion process,the gas content and/or the degree of developed pores and fractures/cleats in coal seams can affect the desorption of CBM and the amount of diffused CBM by influencing the changes in gas pressure in pores,thus controlling the behavior of gas diffusion in different stages.Because gas content and the developed degree of pores and fractures/cleats are closely associated with the deformation degree of the coal seams,variably deformed coal seams exhibit unique characteristics of gas diffusion.The low-deformation degree of the coal seams have a relatively uniform distribution of gas production over the history of a well.By contrast,the moderate-deformation degree of the coal seams have a relatively high rate and amount of gas diffusion in the fast and transitional diffusion stages,producing most of the gas in the early-to-intermediate stages of the wells.Finally,the high-deformation degree of the coal seams has a high rate and amount in the fast diffusion stage,indicating that most of the production stage occurs during the early stage of the gas production history of a well.In summary,the behavior of gas diffusion can be used for predicting gas production potential.