Determination of the gas compositions for direct coal liquefaction by gas chromatography

Via multi-dimensional gas chromatography, configured with parallel dual-channel, double detectors, valves switching and back flushing, rapid analysis of the gas compositions consisting of C1-C5 hydrocarbons and permanent gases, such as CO2, H2S, H2, and CO, for direct coal liquefaction has been realized. With four packed chromatographic columns, which are Hayesep-Q pre-column, Hayesep-Q column, molecular sieve 5A column and one PLOT A1203 S capillary column, the gas compositions for direct coal liquefaction are analyzed qualitatively and quantitatively by the external standard method. The determination method has such advantages as excellent separation, simple operation, rapid analysis and accurate results.

△P index with different gas compositions for instantaneous outburst prediction in coal mines

In this study we measured the △P(initial speed of gas emission) index with different gas concentrations of carbon dioxide(pure CO2,90% CO2+10% CH4,67% CO2+33% CH4,50% CO2+50% CH4,30% CO2+10% CH4 and pure CH4) of coal samples from the No.2 coal seam in the Yaojie Coal Mine,Gansu province,China.The effect of carbon dioxide concentration,gas composition,coal strength and particle size of coal samples on the △P index was investigated.The experimental results show that with gas of various compositions,the △P value of three samples were clearly different.The △P index of coal samples A,B and C(0.2～0.25 mm) were 4,6 and 7 with pure CH4 and 22,30 and 21 when pure CH4 was used.Carbon dioxide concentration affects the △P index markedly.The △P index increases with an increase in carbon dioxide concentration,especially for coal B.Hence,the △P index and K(another outburst index) values tested only with pure CH4 for prediction of the danger of outburst is not accurate.It is important to determine the initial speed of gas emission given the gas composition of the coal seam to be tested for exact outburst prediction.

Geochemistry and origins of hydrogen-containing natural gases in deep Songliao Basin,China:Insights from continental scientific drilling

The different reservoirs in deep Songliao Basin have non-homogeneous lithologies and include multiple layers with a high content of hydrogen gas.The gas composition and stable isotope characteristics vary significantly,but the origin analysis of different gas types has previously been weak.Based on the geochemical parameters of gas samples from different depths and the analysis of geological settings,this research covers the diverse origins of natural gas in different strata.The gas components are mainly methane with a small amount of C_(2+),and non-hydrocarbon gases,including nitrogen(N_(2)),hydrogen(H_(2)),carbon dioxide(CO_(2)),and helium(He).At greater depth,the carbon isotope of methane becomes heavier,and the hydrogen isotope points to a lacustrine sedimentary environment.With increasing depth,the origins of N_(2)and CO_(2)change gradually from a mixture of organic and inorganic to inorganic.The origins of hydrogen gas are complex and include organic sources,water radiolysis,water-rock(Fe^(2+)-containing minerals)reactions,and mantle-derived.The shales of Denglouku and Shahezi Formations,as source rocks,provide the premise for generation and occurrence of organic gas.Furthermore,the deep faults and fluid activities in Basement Formation control the generation and migration of mantle-derived gas.The discovery of a high content of H_(2)in study area not only reveals the organic and inorganic association of natural-gas generation,but also provides a scientific basis for the exploration of deep hydrogen-rich gas.

Noble Gas Isotopic Compositions of Cobalt-rich Ferromanganese Crusts from the Western Pacific Ocean and Their Geological Implications

Noble gas isotopic compositions of various layers in three-layered （outer, porous and compact layers） cobalt-rich ferromanganese crusts and their basaltic and phosphorite substrates from the western Pacific Ocean were analyzed by using a high vacuum gas mass spectrum. The analytical results show that the noble gases in the Co-rich crusts have derived mainly from the ambient seawater, extraterrestrial grains such as interplanetary dust particles （IDPs） and wind-borne continental dust grains, and locally formation water in the submarine sediments, but different noble gases have different sources. He in the crusts derives predominantly from the extraterrestrial grains, with a negligible amount of radiogenic He from the eolian dust grains. Ar is sourced mainly from the dissolved air in the seawater and insignificantly from radiogenic Ar in the eolian continental dust grains or the formation water. Xe and Ne derive mainly from the seawater, with minor amounts of extraterrestrial Xe and Ne in the IDPs. Compared with the porous and outer layers, the compact layer has a relatively high 4He content and lower 3He/4He ratios, suggesting that marine phosphatization might have greatly modified the noble gas isotopic compositions of the crusts. Besides, the 3He/4He values of the basaltic substrates of the cobalt-rich crusts are very low and their R/R. ratios are mostly 〈0.1 R., which are similar to that of phosphorite substrates （0.087 R.）, but much lower than that of fresh submarine MORB （8.75±14 Ra） or seamount basalts （3-43 Ra）, implying that the basaltic substrates have suffered strong water/rock interaction and reacted with radiogenic ^4He and P-rich upwelling marine currents during phosphatization. The trace elements released in the basalt/seawater interaction might favor the growth of cobalt-rich crusts. The relatively low ^3He/^4He values in the seamount basalts may be used as an important exploration criterion for the cobalt-rich ferromanganese crusts.

Influence of Pore Size,Salinity and Gas Composition upon the Hydrate Formation Conditions

An experimental device was set up to study the hydrate formation conditions.Effects of pore size,salinity,and gas composition on the formation and dissociation of hydrates were investigated.The result indicates that the induction time for the formation of hydrates in porous media is shorter than that in pure water.The decrease in pore size,by decreasing the size of glass beads,increases the equilibrium pressure when the salinity and temperature are kept constant.In addition,higher salinity causes higher equilibrium pressure when the pore size and temperature are kept constant.It is found that the effects of pore size and salinity on the hydrate equilibrium are quite different.At lower methane concentration,the hydrate equilibrium is achieved at lower pressure and higher temperature.

Three Stage Equilibrium Model for Coal Gasification in Entrained Flow Gasifiers Based on Aspen Plus

A three stage equilibrium model is developed for coal gasification in the Texaco type coal gasifiersbased on Aspen Plus to calculate the composition of product gas, carbon conversion, and gasification teml^erature. The model is divided into three stages including pyrolysis and combustion stage, char gas reaction stage, and gas p.hase reaction stage. Part of the water produced in thepyrolysis and combust!on stag.e is assumed to be involved inthe second stage to react with the unburned carbon. Carbon conversion is then estimated in the second stage by steam participation ratio expressed as a function of temperature. And the gas product compositions are calculated from gas phase reactions in the third stage. The simulation results are consistent with published experimental data.

Analysis of vacuum chamber suppressing gas explosion

In order to suppress the harm of gas explosion,the current study researched on the body of vacuum chamber.The previous studies verifed that it could obviously lower the explosion overpressure by reasonably arranging vacuum chamber on pipe.That is to say,the vacuum chamber has the effect of absorbing wave and energy.To further deeply analyze the vacuum chamber suppressing gas explosion,this research designed the L-type pipe of gas explosion,and compared the experimental results of gas explosion with vacuum chamber and without vacuum chamber.Besides,using the gas chromatograph,this study also investigated the gas compositions in the pipe before and after explosion.The results show that:(1)without vacuum chamber,the maximum value of explosion overpressure is 0.22 MPa,with60 ms duration,and after explosion,the concentration of oxygen drops to 12.07%,but the concentration of carbon monoxide increases to 4392.3 10à6,and the concentration of carbon dioxide goes up to7.848%,which can make the persons in danger suffocate and die;(2)with vacuum chamber,explosion overpressure drops to 0.18 MPa,with 20 ms duration or less,and after explosion,the concentration of oxygen still remains 12.07%,but the concentration of methane is 7.83%,however the concentration of carbon monoxide is only 727.24 10à6,and the concentration of carbon dioxide is only 1.219%,at the this moment the concentration ratio of toxic gas drops by more than 83%in comparison to be that without vacuum chamber.Consequently,the vacuum chamber can guarantee that most methane does not take part in chemical reaction,and timely quenches the deflagration reaction of gas and oxygen.Because of the two points mentioned above,it reduces the explosion energy,and lowers that the overpressure of blast wave impacts and damages on the persons and facilities,and also decreases the consumption of oxygen and the production of the toxic gas.Therefore,it is safe to conclude that the vacuum chamber not only absorbs wave and energy,but also prevents and suppresses explosion.

Plasma-assisted abatement of SF6 in a packed bed plasma reactor: understanding the effect of gas composition

The potential impact of SF6 as a potent greenhouse gas on the global climate is highly attractive.This paper studies the effect of H2O concentration,SF6 inlet concentration and pre-heating temperature on SF6 abatement in a packed bed plasma reactor in terms of the removal efficiency and products selectivity.The results showed that the best performance in SF6 abatement was obtained at 1%H2O and 100°C with 98.7%destruction and remove efficiency(DRE)at 2%SF6.Higher energy yields was obtained under higher SF6 inlet concentration.Moreover,the existence of water vapor weakened the micro-discharge and provided H and OH radicals for this system,which showed a close relationship to removal efficiency and products selectivity.Among four sulfur-containing products,SO2 F2 was more stable than SOF2,SOF4 and SO2.Meanwhile,SOF4 and SO2 were very susceptible to the above parameters.This article provides a better understanding of SF6 abatement in a view of both scientific and engineering.

Influence of the Feed Gas Composition on the Fischer-Tropsch Synthesis in Commercial Operations

Key technical challenges relating to the Fischer-Tropsch （F-T） synthesis applied in the commercialization of coal/gas-to-liquids （CTL/GTL） technologies have been reviewed. Based on the experiences accumulated from pilot plant, semi-work test and lab researches, the influences of the H2/CO ratio and the CO2 in the feed gas on the F-T process as well as on CTL/GTL complex in terms of product yields, energy efficiency and carbon utilization efficiency have been studied. Being contrary to the current design schemes for F-T process using the coal derived syngas and the iron-based cata lyst, it is suggested to feed the F-T synthesis unit with a syngas having a H2/CO ratio of 0.5 and then adjusting to 1.4 via the recycling process. As a result, the carbon efficiency of the whole plant could be reached to as high as 50%. For the issue of CO2 addition to the feed gas, it is proved that only a diluting role is played under the current commercial slurry phase F-T process.

The distribution and variation in the gas composition of macro-seeps on the near-shore Lingtou Promontory in the South China Sea

Natural hydrocarbon seeps in a marine environment are one of the important contributors to greenhouse gases in the atmosphere,including methane,which is significant to the global carbon cycling and climate change.Four hydrocarbon seep areas,the Lingtou Promontory,the Yinggehai Rivulet mouth,the Yazhou Bay and the Nanshan Promontory,occurring in the Yinggehai Basin delineate a near-shore gas bubble zone.The gas composition and geochemistry of venting bubbles and the spatial distribution of hydrocarbon seeps are surveyed on the near-shore Lingtou Promontory.The gas composition of the venting bubbles is mainly composed of CO_2,CH_4,N_2 and O_2,with minor amounts of non-methane hydrocarbons.The difference in the bubbles＇ composition is a possible consequence of gas exchange during bubble ascent.The seepage gases from the seafloor are characterized by a high CO_2 content（67.35%） and relatively positive δ^（13）C_（V_PDB） values（-0.49×10^（-3）-0.86×10^（-3））,indicating that the CO_2 is of inorganic origin.The relatively low CH_4 content（23%） and their negative δ^（13）C_（V-PDB） values（-34.43×10^（-3）--37.53×10^（-3）） and high ratios of C_1 content to C_（1-5） one（0.98-0.99）as well point to thermogenic gases.The hydrocarbon seeps on the 3.5 Hz sub-bottom profile display a linear arrangement and are sub-parallel to the No.1 fault,suggesting that the hydrocarbon seeps may be associated with fracture activity or weak zones and that the seepage gases migrate laterally from the central depression of the Yinggehai Basin.

Pressure transient analysis of a finite-conductivity multiple fractured horizontal well in linear composite gas reservoirs

Faulted gas reservoirs are very common in reality,where some linear leaky faults divide the gas reservoir into several reservoir regions with distinct physical properties.This kind of gas reservoirs is also known as linear composite(LC)gas reservoirs.Although some analytical/semi-analytical models have been proposed to investigate pressure behaviors of producing wells in LC reservoirs based on the linear composite ideas,almost all of them focus on vertical wells and studies on multiple fractured horizontal wells are rare.After the pressure wave arrives at the leaky fault,pressure behaviors of multiple fractured horizontal wells will be affected by the leaky faults.Understanding the effect of leaky faults on pressure behaviors of multiple fractured horizontal wells is critical to the development design.Therefore,a semi-analytical model of finite-conductivity multiple fractured horizontal(FCMFH)wells in LC gas reservoirs is established based on Laplace-space superposition principle and fracture discrete method.The proposed model is validated against commercial numerical simulator.Type curves are obtained to study pressure characteristics and identify flow regimes.The effects of some parameters on type curves are discussed.The proposed model will have a profound effect on developing analytical/semi-analytical models for other complex well types in LC gas reservoirs.

Gasification of Organic Waste:Parameters,Mechanism and Prediction with the Machine Learning Approach

Gasification of organic waste represents one of the most effective valorization pathways for renewable energy and resources recovery,while this process can be affected by multi-factors like temperature,feedstock,and steam content,making the product’s prediction problematic.With the popularization and promotion of artificial intelligence such as machine learning(ML),traditional artificial neural networks have been paid more attention by researchers from the data science field,which provides scientific and engineering communities with flexible and rapid prediction frameworks in the field of organic waste gasification.In this work,critical parameters including temperature,steam ratio,and feedstock during gasification of organic waste were reviewed in three scenarios including steam gasification,air gasification,and oxygen-riched gasification,and the product distribution and involved mechanism were elaborated.Moreover,we presented the details of ML methods like regression analysis,artificial neural networks,decision trees,and related methods,which are expected to revolutionize data analysis and modeling of the gasification of organic waste.Typical outputs including the syngas yield,composition,and HHVs were discussed with a better understanding of the gasification process and ML application.This review focused on the combination of gasification and ML,and it is of immediate significance for the resource and energy utilization of organic waste.

Application of Heterogeneous Composite Model with Consideration of Stress Sensitive in Low Permeability Gas Reservoir

Stress sensitivity is a key factor affecting the productivity of single wells in low permeability gas reservoirs. A well test model for heterogeneous composite gas reservoirs under the influence of stress-sensitive effects was established. Based on the theoretical model, the well test was designed by gradually increasing the pressure difference. The relationship between abnormal high pressure and reservoir stress sensitivity was analyzed. Theoretical research shows that stress sensitivity will cause permeability damage during the production process, and the pressure drop test curve shows that the physical properties of the reservoir have gradually deteriorated. The pressure recovery test curve shows that the physical properties of the reservoir are getting better. Field practice shows that stress sensitivity is related to the formation of abnormally high pressure in the formation without considering the micro-cracks in the formation. Stress-sensitive reservoirs are generally unbalanced and compacted due to overpressure, for fluid expansion/conduction overpressure in Ledong Area. For these reservoirs, there is almost no stress sensitivity. The research results have significance for guiding the design and data interpretation of stress-sensitive reservoir.

Resilience of gas interchangeability in hydrogen-blended integrated electricity and gas systems:A transient approach with dynamic gas composition tracking

Green hydrogen can be produced by consuming surplus renewable generations.It can be injected into the natural gas networks,accelerating the decarbonization of energy systems.However,with the fluctuation of renewable energies,the gas composition in the gas network may change dramatically as the hydrogen injection fluctuates.The gas interchangeability may be adversely affected.To investigate the ability to defend the fluctuated hydrogen injection,this paper proposes a gas interchangeability resilience evaluation method for hydrogen-blended integrated electricity and gas systems(H-IEGS).First,gas interchangeability resilience is defined by proposing several novel metrics.Then,A two-stage gas interchangeability management scheme is proposed to accommodate the hydrogen injections.The steady-state optimal electricity and hydrogen-gas energy flow technique is performed first to obtain the desired operating state of the H-IEGS.Then,the dynamic gas composition tracking is implemented to calculate the real-time traveling of hydrogen contents in the gas network,and evaluate the time-varying gas interchangeability metrics.Moreover,to improve the computation efficiency,a self-adaptive linearization technique is proposed and embedded in the solution process of discretized partial derivative equations.Finally,an IEEE 24 bus reliability test system and Belgium natural gas system are used to validate the proposed method.

Development of CO2 Selective Poly（Ethylene Oxide）-Based Membranes： From Laboratory to Pilot Plant Scale

Membrane gas separation is one of the most promising technologies for the separation of carbon dioxide （CO2） from various gas streams. One application of this technology is the treatment of flue gases from combustion processes for the purpose of carbon capture and storage. For this application, poly（ethylene oxide）-containing block copolymers such as Pebax or PolyActiveTM polymer are well suited. The thin-film composite membrane that is considered in this overview employs PolyActiveTM polymer as a selective layer material. The membrane shows excellent CO2 permeances of up to 4 m^3（STP）.（m^2·h·bar）^-1 （1 bar = 105 Pa） at a carbon dioxide/nitrogen （CO2/N2） selectivity exceeding 55 at ambient temperature. The membrane can be manufactured reproducibly on a pilot scale and mounted into fiat-sheet membrane modules of different designs. The operating performance of these modules can be accurately predicted by specifically developed simulation tools, which employ single-gas permeation data as the only experimental input. The performance of membranes and modules was investigated in different pilot plant studies, in which flue gas and biogas were used as the feed gas streams. The investigated processes showed a stable separation performance, indicating the applicability of PolyActiveTM polymer as a membrane material for industrialscale gas processing.

Synthesis, Characterization and Gas Sensing Properties of Graphene Oxide-Multiwalled Carbon Nanotube Composite

Graphene oxide （GO）-multiwalled carbon nanotube （MWCNT） composite was synthesized and characterized by X-ray diffraction, atomic force microscopy, scanning electron microscopy, micro Raman, Fourier transform infrared and ultraviolet-visible near infrared spectroscopy techniques. Spectral characteris- tics of cladding modified fiber optic gas sensors were studied for various concentrations of ammonia, ethanol and methanol at 27 ℃. Thickness of the gas sensing layer was controlled by varying the concentration of composite in ethanol medium （0.5 and 1 mg/mL） for three times dipping process. The O.S mg/ mL concentrated GO-MWCNT coated sensor showed 1.20, 1.40 and 1.15 times higher sensitivity than the GO coated sensor for ammonia, ethanol and methanol vapors, respectively. Furthermore, it exhibited 1.50, 1.80 and 1.80 times better sensitivity than 1 mg/mL concentrated GO-MWCNT coated sensor for ammonia, ethanol and methanol vapors, respectively. The presence of functional groups in GO increased the sen- sitivity. This is mainly attributed to the effective electron charge transfer between the composite materials and analytes.

Production of ammonia from plasma-catalytic decomposition of urea: Effects of carrier gas composition

Effects of carrier gas composition（N2/air） on NH3 production, energy efficiency regarding NH3 production and byproducts formation from plasma-catalytic decomposition of urea were systematically investigated using an Al2 O3-packed dielectric barrier discharge（DBD） reactor at room temperature. Results show that the presence of O2 in the carrier gas accelerates the conversion of urea but leads to less generation of NH3. The final yield of NH3 in the gas phase decreased from 70.5%, 78.7%, 66.6% and 67.2% to 54.1%, 51.7%, 49.6% and 53.4% for applied voltages of 17, 19, 21 and 23 kV, respectively when air was used as the carrier gas instead of N2.From the viewpoint of energy savings, however, air carrier gas is better than N2 due to reduced energy consumption and increased energy efficiency for decomposition of a fixed amount of urea. Carrier gas composition has little influence on the major decomposition pathways of urea under the synergetic effects of plasma and Al2 O3 catalyst to give NH3 and CO2 as the main products. Compared to a small amount of N2 O formed with N2 as the carrier gas, however,more byproducts including N2O and NO2 in the gas phase and NH4 NO3 in solid deposits were produced with air as the carrier gas, probably due to the unproductive consumption of NH3, the possible intermediate HNCO and even urea by the abundant active oxygen species and nitrogen oxides generated in air-DBD plasma.

Biodegradable Poly(propylene carbonate)/Layered Double Hydroxide Composite Films with Enhanced Gas Barrier and Mechanical Properties

Relatively well crystallized and high aspect ratio Mg-Al layered double hydroxides（LDHs） were prepared by coprecipitation process in aqueous solution and further rehydrated to an organic modified LDH（OLDH） in the presence of surfactant. The intercalated structure and high aspect ratio of OLDH were verified by X-ray diffraction（XRD） and scanning electron microscopy（SEM）. A series of poly（propylene carbonate）（PPC）/OLDH composite films with different contents of OLDH were prepared via a melt-blending method. Their cross section morphologies, gas barrier properties and tensile strength were investigated as a function of OLDH contents. SEM results show that OLDH platelets are well dispersed within the composites and oriented parallel to the composite sheet plane. The gas barrier properties and tensile strength are obviously enhanced upon the incorporation of OLDH. Particularly, PPC/2%OLDH film exhibits the best barrier properties among all the composite films. Compared with pure PPC, the oxygen permeability coefficient（OP） and water vapor permeability coefficient（WVP） is reduced by 54% and 17% respectively with 2% OLDH addition. Furthermore, the tensile strength of PPC/2%OLDH is 83% higher than that of pure PPC with only small lose of elongation at break. Therefore, PPC/OLDH composite films show great potential application in packaging materials due to its biodegradable properties, superior oxygen and moisture barrier characteristics.

Study of RPC gas composition using Daya Bay RPCs

This study uses Daya Bay RPCs operating in streamer mode to investigate gas mixtures of at least 50% argon, at most 6% isobutane, and with small amounts of SF6. Isobutane is reduced to 2% without degradation of performance, and SF6 reduces the noise rate and current, as well as the signal size. This study provides quantitative relationships between basic RPC operating parameters and various gas compositions.

Numerical Simulation of Thermal and Iron Ore Reduction Conditions in Pre-reduction Shaft Furnace Based on Reducing Gas Composition and Temperature

Based on the principles of mass,momentum and heat transfers between the reducing gas and the iron ore solid,a two-dimensional mathematical model for above two phases is established to study the influences of reducing gas composition on thermal and reduction conditions in pre-reduction shaft furnace with the temperature ranging from 1 023 to 1 223 K.Due to the strong endothermic effect of iron ore reduction participated by hydrogen （H2）,increasing the ratio of carbon monoxide（CO）to H2 enlarges high temperature zone under present calculation conditions,thus improves reduction efficiency inside the furnace.In addition,replacing of the reducing gas with an appropriate proportion of nitrogen（N2）featuring the same temperature has a potential to reduce fuel consumption by as much as 6.5%while the products of similar quality are yielded.