Search

As a crucial component of the oil transportation system, the oil terminal (or oil tank farm) may often pose some serious threats and damage to the ecological environment and production safety for the oil leakage. An effective emergency management strategy is particularly significant, involving the accurate assessment of leakage time, oil migration path, volume distribution, etc. Therefore, the volume of fluid (VOF) and liquid phase leakage model were applied to investigate the migration and distribution characteristic after the accidental hole occurs in the tank wall, and influence factors including height and diameter of the hole were considered in our study. Results show that the lower the leaking hole position is, the faster the horizontal injection rate of the leakage hole, the increase of the accumulation area of the oil on the ground, and the difference in the overall pressure value at the leakage hole is nearly four times. Under different leakage diameters, the oil spill is symmetrical. The larger the leakage diameter, the higher the amount of oil leakage and the initial leakage speed, the maximum speed is 1.5 times the minimum speed, causing harm to safety and environmental pollution. These results can quickly locate the leakage location of the tank and provide valuable references for emergency management of the oil pipeline transportation system.

Desorption of activated carbon saturated with VOCs (volatile organic compounds) under supercritical CO2 is greatly affected by pressure and temperature, and the influence mechanism remains ambiguous. In this paper, toluene is considered as the representative of VOC, influence of pressure and temperature on the toluene desorption ratio is investigated by experimental and molecular dynamic simulation methods. The experimental results show that the toluene desorption ratio increases as pressure increases, but the influence of temperature on the toluene desorption ratio is affected by pressure. The desorption ratio decreases with increasing temperature at lower pressure, while the desorption ratio increases at the beginning but then decreases with increasing temperature at higher pressure. The mechanism analysis presents that the influence of pressure is governed by “density effect”, the influence of temperature is governed by “density effect” and “diffusion effect” together, the final result is determined by the competition between the two effects.

As the standards for emissions of organic waste gas become increasingly strict, the competitive adsorption of water vapor and organic waste gas is becoming the hot spot of research on treatment of organic waste gas. Therefore, three adsorbents (AdsFOV-1, AdsFOV-2 and AdsFOV-3) were used for the research, and their adsorption capacity and thermal effect were investigated through the static adsorption to the vapors of n-hexane, gasoline and water after structural characterization. In addition, dynamic adsorption experiments were performed with the vapors of n-hexane and gasoline under different relative humidity conditions, so as to study the influence of relative humidity on adsorption effect and temperature rising curve, as well as the stability of cyclic adsorption. Meanwhile, the kinetics behavior of the adsorption process was judged by kinetic fitting. The results show that: the adsorption capacity of the three adsorbents to the vapors of n-hexane and gasoline decreases with the increasing of relative humidity, but the thermal effect of adsorption becomes more obvious. Besides, AdsFOV-1 and AdsFOV-2 have good cyclic adsorption performances, specifically, when the inlet vapor mass concentration is set to 25 g/m3, the outlet vapor mass concentration of the adsorption tower can meet the emission requirements of less than 80 mg/m3. Further, the adsorption kinetics behavior of the three adsorbents on the vapor of n-hexane is consistent with the Bangham dynamic equation, which means the adsorption rate is mainly controlled by the pore diffusion. In general, the research results could provide theoretical basis for the treatment of industrial organic waste gas with high humidity.

Oil evaporation and vapor diffusion from storage tanks will have adverse effects on atmospheric environment, social economy and the safety of tank farm. In this study, the current status and achievement of the researches on oil evaporation and vapor diffusion were summarized in terms of theoretical analysis, experimental research and numerical simulation for tracing carbon emission from storage tanks. Specifically, the potential mechanism of vapor-liquid phase change, mass transfer of oil vapor in the tank gas space, and vapor diffusion were revealed through theoretical analysis. Meanwhile, the field test and wind tunnel experiment were reviewed, which show that most experimental researches are performed in the aspects of temperature variation characteristics of crude oil in tanks, oil vapor emission during vehicle and ship loading, and dynamic structural change of storage tanks. In addition, simulation methods like Direct Numerical Simulation (DNS), Reynolds Average Navier-Stokes (RANS), and Large Eddy Simulation (LES) were used to analyze the vapor-liquid mass transfer, dynamic tracing of oil-gas interface and the process of vapor diffusion and flow under the coupling of different factors, which could trace diffused substances in a wide range with lower costs and shorter time. Finally, based on the low-carbon development demand of oil and gas industry, suggestions and prospects for oil evaporation and vapor diffusion in storage tanks were put forward with the expectation to maximize the comprehensive benefits of environmental protection.

The difference of vapor cloud density and the variation of atmospheric turbulence caused by ambient temperature are the main factors influencing the leakage and diffusion of LNG. Hence, it is very necessary to study the influence of the variation of ambient temperature on the diffusion rules of LNG. With the component transport model and the Realizable k-ε turbulence model in Fluent software, a numerical model of vapor diffusion caused by the surface leakage of LNG was established to explore the influence of ambient temperature on the volume fraction distribution of methane, vapor cloud density and atmospheric turbulence intensity in the process of LNG leakage and diffusion. The results show that under the low ambient temperature, the volume fraction lines of methane in the LNG vapor cloud is in the shape of"sawtooth", resulting in the increase of the horizontal diffusion range of the Low Flammability Limit (LFL) and 1/2 LFL of the methane, while under the high ambient temperature, the maximum range of diffusion of methane at LFL is 115 m farther than that under the low ambient temperature which leads to the increase of the diffusion range of methane at 1/2 LFL in the horizontal downwind direction. In addition, the increment of the turbulence intensity increases with the rise of the temperature in the area where the volume fraction of methane is greater than 1/2 LFL, while it decreases with the rise of temperature in the area where the volume fraction is less than 1/2 LFL. In the range of 100-200 m around the source of leakage, the increment of the turbulence intensity resulted by "temperature inversion" can be up to 0.79 times. The research results could provide references for prediction on leakage region, safety storage and transportation and emergency rescue of LNG.

If the oil vapor from the tanks is discharged into the atmosphere, the environment pollution will be caused and the human health will be threated. Definitely, pressure and temperature changes are the main factors causing evaporation of oil products in the tank. As for the breathing loss of oil tanks, the formula concerning the minimal reduction rate of the breathing loss of pressure tanks was derived based on the API theoretical formula, so as to reduce the breathing loss, even to completely eliminate the small breathing loss, by controlling the pressure with a breather valve of oil tank. According to the analysis on influence of temperature change on expansion factor of monomer hydrocarbon (propane, n-butane, isobutene, n-pentane and n-hexane) and various oil products (93# gasoline, 97# gasoline, naphtha, kerosene, diesel oil and Panyu crude oil), the results show that when the storage pressure of the tanks is designed for oil products of different types and compositions, tank with different design pressure shall be adopted. In addition, appropriate type of breather valve can be used, or the tank wall can be thickened to increase the control factor, further to reduce the breathing loss of tank. The research results could be used as theoretical reference for oil tank design and oil depot management.

Study on the law of oil vapor leakage and diffusion in inner floating roof tanks is of great significance for strengthening environmental pollution control and ensuring tank farm safety. The wind tunnel test platform was established to test the effects of wind speed and floating plate position on evaporation loss rate of small inner floating roof tank, and the distribution laws of wind field and concentration field were investigated. Based on CFD numerical simulation, the UDF was used to introduce environmental wind, the numerical model of oil vapor leakage and diffusion from inner floating roof tank was established, and the feasibility of the simulation was verified by wind tunnel experimental data. The distribution law of wind field and wind pressure outside the inner floating roof tank, as well as the influence of wind speed on the flow field distribution and the diffusion concentration of oil vapor in the inner floating roof tank, was emphatically discussed. The results show that the lower the floating plate position and the higher the wind speed, the faster the evaporation rate will be. The static pressure distributed on the tank wall is as follows: highest on windward wall, medium on leeward wall and lowest on the two side walls. Under different wind speeds, the distribution of oil vapor on the tank is symmetrical. The lower the wind speed, the higher the oil vapor mass concentration will be. The oil vapor concentration at the gap between floating plates is the highest, leaving hidden dangers of safety and environmental pollution. The research results are of reference value for the design, operation and maintenance of the inner floating roof tank and environmental protection and safety management.

Abstract Reduced graphene oxide (RGO) and three-dimensional graphene networks (3DGNs) are adopted to improve the performance of thermal interface materials (TIMs). Therein, the 3DGNs provide a fast transport network for phonons, while the RGO plays as a bridge to enhance the phonon transport ability at the interface between the filler and matrix. The types of surface functional groups of the RGO are found to exert a remarkable influence on the resulting thermal performance; the carboxyl groups are found in the optimal selection to promote the transport process at the interface area because a strong chemical bond will form between the graphene basal plane and epoxy resin (ER) through this kind of group. The resulting thermal conductivity reaches 6.7 Wm−1 K−1 after optimizing the mass fraction and morphology of the filler, which is 3250% higher than that of the pristine ER. Moreover, the mechanical properties of these as-prepared TIMs are also detected, and the specimens by using the RGO(OOH) filler display the better performances.

To investigate the evolution process of LNG (Liquefied Natural Gas) liquid pool and gas cloud diffusion, the Realizable k-ε model and Eluerian model were used to numerically simulate the liquid phase leakage and diffusion process of LNG storage tanks. The experimental results showed that some LNG flashed and vaporized rapidly to form a combustible cloud during the continuous leakage. The diffusion of the explosive cloud was divided into heavy gas accumulation, entrainment heat transfer, and light gas drift. The vapor cloud gradually separated into two parts from the whole “fan leaf shape”. One part was a heavy gas cloud; the other part was a light gas cloud that spread with the wind in the downwind direction. The change of leakage aperture had a greater impact on the whole spill and dispersion process of the storage tank. The increasing leakage aperture would lead to 10.3 times increase in liquid pool area, 78.5% increase in downwind dispersion of methane concentration at 0.5 LFL, 22.6% increase in crosswind dispersion of methane concentration at 0.5 LFL, and 249% increase in flammable vapor cloud volume. Within the variation range of the leakage aperture, the trend of the gas cloud diffusion remained consistent, but the time for the liquid pool to keep stable and the gas cloud to enter the next diffusion stage was delayed. The low-pressure cavity area within 200 m of the leeward surface of the storage tank would accumulate heavy gas for a long time, forming a local high concentration area, which should be an area of focus for alert prediction.

Abstract With the development of microelectronic devices, the insufficient heat dissipation ability becomes one of the major bottlenecks for further miniaturization. Although graphene-assisted epoxy resin (ER) display promising potential to enhance the thermal performances, some limitations of the reduced graphene oxide (RGO) nanosheets and three-dimensional graphene networks (3DGNs) hinder the further improvement of the resulting thermal interface materials (TIMs). In this study, both the RGO nanosheets and 3DGNs are adopted as co-modifiers to improve the thermal conductivity of the ER. The 3DGNs provide a fast transport network for phonon, while the presence of RGO nanosheets enhances the heat transport at the interface between the graphene basal plane and the ER. The synergy of these two modifiers is achieved by selecting a proper proportion and an optimized reduction degree of the RGO nanosheets. Moreover, both the high stability of the thermal conductivity and well mechanical properties of the resulting TIM indicate the potential application prospect in the practical field.

Abstract High quality and naturally continuous structure of three-dimensional graphene network (3DGN) endow it a promising candidate to modify TiO2. Although the resulting composite photocatalysts display outstanding performances, the lacking of active sites of the 3DGN not only goes against a close contact between the graphene basal plane and TiO2 nanoparticles (weaken electron transport ability) but also limits the efficient adsorption of pollutant molecules. Similar with surface functional groups of the reduced graphene oxide (RGO) nanosheets, surface defects of the 3DGN can act as the adsorption sites. However, the defect density of the 3DGN is difficult to control (a strict cool rate of substrate and a strict flow of precursor gas are necessary) because of its growth approach (chemical vapor deposition method). In this study, to give full play to the functions of graphene, the RGO nanosheets and 3DGN co-modified TiO2 composite photocatalysts are prepared. After optimizing the mass fraction of the RGO nanosheets in the composite photocatalyst, the resulting chemical adsorption ability and yields of strong oxidizing free radicals increase significantly, indicating the synergy of the RGO nanosheets and 3DGN.

An experimental platform of gas cloud deflagration is built in this study, and the propane–air premixed gas blasting experiment was carried out in curved pipes with different lengths. The effect of pipe length on combustible gas explosion and the influence of explosion shock wave on thin-walled pipe loading were also studied. The experimental device included photoelectric, pressure, and strain sensors which were used to evaluate the explosion parameters and stress of the thin-walled pipe. The result was that the longer the pipeline, the higher the wall overpressure and the bigger the maximum tube wall. The pressure time curve was consistent with the thin-walled strain time–history curve. The pipe bend accelerates the flame propagation to a certain extent, and the pipe length influenced the law of flame ignition and explosion in pipe integrally; the longer the pipe, the greater the pressure and the speed of the flame. The maximum explosion pressure appears at the end of the pipe, and the loading of the shock wave on pipe wall belongs to dynamic response.

Graphene and its derivatives, with their unique two-dimensional structures and excellent physical and chemical properties, have been an international research hotspot both in the research community and industry. However, in application-oriented research in the oil and gas industry they have only drawn attention in the past several years. Their excellent optical, electrical, thermal and mechanical performance make them great candidates for use in oil and gas exploration, drilling, production, and transportation. Combined with the actual requirements for well working fluids, chemical enhanced oil recovery, heavy oil recovery, profile control and water shutoff, tracers, oily wastewater treatment, pipeline corrosion prevention treatment, and tools and apparatus, etc., this paper introduces the behavior in water and toxicity to organisms of graphene and its derivatives in detail, and comprehensively reviews the research progress of graphene materials in the upstream oil and gas industry. Based on this, suggestions were put forward for the future research. This work is useful to the in-depth mechanism research and application scope broadening research in the upstream oil and gas industry.

SiO _2 aerogels were prepared by sol-gel method and methyl alkylation reaction using TEOS as silicon sources. Silica-supported polyethylenimine (PEI/SiO _2 ) adsorbents for CO _2 adsorption were prepare by grafting techniques, in which mesoporous SiO _2 aerogel was loaded with PEI and organic compounds functionalized by hydroxyl or amino groups as dopants. CO _2 adsorption isotherms of PEI amine-modified SiO _2 aerogels were measured and the results show that the maximum CO _2 adsorption capacity (1.8 mmol g ^−1 ) was obtained over a doped SA-PEI-N-Y loaded with 45% PEI and 15% N-Y (N-[3-(Trimethoxysilyl)propyl]ethylenediamine, denoted as N-Y). In addition, SA-PEI-N-Y has stronger thermal stability than SA-PEI-60% in nitrogen from room temperature to 800 °C at a heating rate of 10 °C min ^−1 . It turns out that N-[3-(Trimethoxysilyl)propyl]ethylenediamine is the best dopant.

An ordinary silica gel (SG-1) was chosen as the raw material and hydrophobically modified with trimethylchlorosilane under different microwave exposure. The orthogonal experiment was designed to screen the optimized modification method. The hydrophobic properties modified silica gel (SG-2) was analyzed by comparing the difference changes of surface chemistries. Then, the adsorption capacities of SG-1 and SG-2 to the n -hexane vapor and water vapor, respectively, were investigated and compared with the capacities of activated carbon and SG-3 (hydrophobically modified using the same composite modifier without microwave exposure). Meanwhile, there cyclable adsorptions of SG-2 to the two vapors were conducted while the desorptions of vacuum and heat was observed. The results showed that the effect of hydrophobic modification to SG-1 under microwave exposure was obvious and SG-2 also had a very good effect of adsorption for the n -hexane vapor. The modified silica gel shows great potential and effect for the recovery of volatile organic compounds with high content of water.

Research on hydrate dissociation mechanisms is critical to solving the issue of hydrate blockage and developing hydrate slurry transportation technology. Thus, in this paper, natural gas hydrate slurry decomposition experiments were investigated on a high-pressure hydrate experimental loop, which was equipped with two on-line particle analyzers: focused beam reflectance measurement (FBRM) and particle video microscope (PVM). First, it was observed from the PVM that different hydrate particles did not dissociate at the same time in the system, which indicated that the probability of hydrate particle dissociation depended on the particle’s shape and size. Meanwhile, data from FBRM presented a periodic oscillating trend of the particle/droplet numbers and chord length during the hydrate slurry dissociation, which further demonstrated these micro hydrate particles/droplets were in a dynamic coupling process of breakage and agglomeration under the action of flow shear during the hydrate slurry dissociation. Then, the influences of flow rate, pressure, water-cut, and additive dosage on the particles chord length distribution during the hydrate decomposition were summarized. Moreover, two kinds of particle chord length treatment methods (the average un-weighted and squared-weighted) were utilized to analyze these data onto hydrate particles’ chord length distribution. Finally, based on the above experimental data analysis, some important conclusions were obtained. The agglomeration of particles/droplets was easier under low flow rate during hydrate slurry dissociation, while high flow rate could restrain agglomeration effectively. The particle/droplet agglomerating trend and plug probability went up with the water-cut in the process of hydrate slurry decomposition. In addition, anti-agglomerates (AA) greatly prohibited those micro-particles/droplets from agglomeration during decomposition, resulting in relatively stable mean and square weighting chord length curves.

Graphene modified TiO2 composite photocatalysts have drawn increasing attention because of their high performance. Some significant advancements have been achieved with the continuous research, such as the corresponding photocatalytic mechanism that has been revealed. Specific influencing factors have been discovered and potential optimizing methods are proposed. The latest developments in graphene assisted TiO2 composite photocatalysts are abstracted and discussed. Based on the primary reasons behind the observed phenomena of these composite photocatalysts, probable development directions and further optimizing strategies are presented. Moreover, several novel detective technologies—beyond the decomposition test—which can be used to judge the photocatalytic performances of the resulting photocatalysts are listed and analyzed. Although some objectives have been achieved, new challenges still exist and hinder the widespread application of graphene-TiO2 composite photocatalysts, which deserves further study.

Oil vapor emitted during refueling process has caused serious issues of air pollution, especially the environmental impact in surrounding residential areas. Most petrol stations have installed oil vapor recovery systems, but some stations did not properly maintain or switch on them. With the increasing emphasis on ecological environmental protection, it is more crucial to investigate the internal mechanism of vapor-air mass transfer. In this study, a computational fluid dynamic (CFD) model was developed and verified to analyze the effects of wind speed, vehicles number, and residential layout on oil vapor diffusion in residential areas. Simultaneously, the effectiveness of oil vapor recovery was assessed by comparing contamination before and after recovery. Results indicate that wind speed greatly affects the area and location of excess emission areas (EEAs). As the wind speed increases from 2 m/s to 4 m/s, highest concentration, distance to buildings and width of EEAs decreases by 49.1%, 43.8%, and 33.3%, respectively, and EEAs disappear at the wind speed of 6 m/s. Vehicles number has a more significant effect on the symmetry of EEAs, and EEAs become gradually symmetrical as the number increases from 3 to 12. Further, the enclosure layout proves to be an effective layout for protecting residential air, with a minimum concentration of 0.18 mg/m³ . Notably, the effectiveness of oil vapor recovery is remarkable, with a purification rate of 98.5%. These findings can offer a valuable guidance for controlling air pollution in residential areas and enhancing the environmental protection level of petroleum enterprises. [ABSTRACT FROM AUTHOR]

In order to study the effect of ignition position on the deflagration characteristics of oil mist in ship cabins, a self-constructed simulated cabin experimental platform was created to conduct experiments on the effect of ignition position on oil mist deflagration characteristics. The results indicate that the deflagration process of oil mist under various conditions can be divided into four stages, they are respectively deflagration, turbulent combustion, flame stretch and self-extinguishing. The peak velocity of flame propagation decreases with the increasing of the distance between the ignition position and the nozzle. When the distance increases from 13 cm to 83 cm, the peak velocity decreases by 6 m/s with a reduction of 57.14%. The peak temperature inside the cabin decreases with the increasing of the distance between the ignition position and the nozzle. When the distance increases from 13 cm to 83 cm, the peak temperature decreases by 118.2°C with a reduction of 13.94%. The pressure distribution inside the cabin after ignition increases first and then decreases. As the distance between the ignition position and the nozzle increases, the peak pressure at various positions also increases, and the maximum peak pressure is located at 110 cm in the cabin. At the ignition position of 83 cm, the peak pressure reaches the maximum value of 1.603 MPa, which increases by 0.858 MPa (115.17%) compared with the ignition position of 13 cm. [ABSTRACT FROM AUTHOR]

The pipe structures and opening conditions have an important influence on gas explosion, but little research has been done on the coupling analysis of the two. In order to reveal the effect of pipe structure on the flammability characteristics of hydrogen-air premixed gas under end-opening conditions, the flame structure, flame propagation velocity, explosion pressure and flow field distribution in the explosion process of hydrogen-air premixed gas in different pipe structures were analyzed by numerical simulation. The results show that the flame propagation velocity and pressure are less influenced by the end-opening structure in the initial ignition stage, however, when the flame propagates to the pipe end, the flame propagation velocity in each pipe structure is significantly enhanced. The 90° elbow has a certain inhibitory effect on the flame development, while the T-shaped bifurcation structure can effectively increase the degree of gas detonation. In pipe with large aspect ratio, due to the wall effect, the effect of acoustic oscillation disturbance on the flame front and the air-flow release effect of the end-opening, there are two peaks and two troughs in the pressure rise rate curve of each pipe-line structure. [ABSTRACT FROM AUTHOR]