Experimental investigation on coal pore-fracture variation and fractal characteristics synergistically affected by solvents for improving clean gas extraction

Chemical solvents instead of pure water being as hydraulic fracturing fluid could effectively increase permeability and improve clean methane extraction efficiency.However,pore-fracture variation features of lean coal synergistically affected by solvents have not been fully understood.Ultrasonic testing,nuclear magnetic resonance analysis,liquid phase mass spectrometry was adopted to comprehensively analyze pore-fracture change characteristics of lean coal treated by combined solvent(NMP and CS_(2)).Meanwhile,quantitative characterization of above changing properties was conducted using geometric fractal theory.Relationship model between permeability,fractal dimension and porosity were established.Results indicate that the end face fractures of coal are well developed after CS2and combined solvent treatments,of which,end face box-counting fractal dimensions range from 1.1227 to 1.4767.Maximum decreases in ultrasonic longitudinal wave velocity of coal affected by NMP,CS_(2)and combined solvent are 2.700%,20.521%,22.454%,respectively.Solvent treatments could lead to increasing amount of both mesopores and macropores.Decrease ratio of fractal dimension Dsis 0.259%–2.159%,while permeability increases ratio of NMR ranges from 0.1904 to 6.4486.Meanwhile,combined solvent could dissolve coal polar and non-polar small molecules and expand flow space.Results could provide reference for solvent selection and parameter optimization of permeability-enhancement technology.

Chemical profiling of bioactive compounds in the methanolic extract of wild leaf and callus of Vitex negundo using gas chromatographymass spectrometry

BACKGROUND The investigation of plant-based therapeutic agents in medicinal plants has revealed their presence in the extracts and provides the vision to formulate novel techniques for drug therapy.Vitex negundo(V.negundo),a perennial herb belonging to the Varbanaceae family,is extensively used in conventional medication.AIM To determine the existence of therapeutic components in leaf and callus extracts from wild V.negundo plants using gas chromatography-mass spectrometry(GCMS).METHODS In this study,we conducted GC-MS on wild plant leaf extracts and correlated the presence of constituents with those in callus extracts.Various growth regulators such as 6-benzylaminopurine(BAP),2,4-dichlorophenoxyacetic acid(2,4-D),α-naphthylacetic acid(NAA),and di-phenylurea(DPU)were added to plant leaves and in-vitro callus and grown on MS medium.RESULTS The results clearly indicated that the addition of BAP(2.0 mg/L),2,4-D(0.2 mg/mL),DPU(2.0 mg/L)and 2,4-D(0.2 mg/mL)in MS medium resulted in rapid callus development.The plant profile of Vitex extracts by GC-MS analysis showed that 24,10,and 14 bioactive constituents were detected in the methanolic extract of leaf,green callus and the methanolic extract of white loose callus,respectively.CONCLUSION Octadecadienoic acid,hexadecanoic acid and methyl ester were the major constituents in the leaf and callus methanolic extract.Octadecadienoic acid was the most common constituent in all samples.The maximum concentration of octadecadienoic acid in leaves,green callus and white loose callus was 21.93%,47.79%and 40.38%,respectively.These findings demonstrate that the concentration of octadecadienoic acid doubles in-vitro compared to in-vivo.In addition to octadecadienoic acid;butyric acid,benzene,1-methoxy-4-(1-propenyl),dospan,tridecanedialdehyde,methylcyclohexenylbutanol,chlorpyrifos,n-secondary terpene diester,anflunine and other important active compounds were also detected.All these components were only available in callus formed in-vitro.This study showed that the callus contained additional botanical characteristics compared with wild plants.Due to the presence of numerous bioactive compounds,the medical use of Vitex for various diseases has been accepted and the plant is considered an important source of therapeutics for research and development.

Induced drill-spray during hydraulic slotting of a coal seam and its influence on gas extraction

Hydraulic slotting can induce drill spray in a gassy,low permeability coal seam.This then influences subsequent gas extraction.This paper describes the drill spray phenomenon from a mechanical perspective and analyzes the effects of water jet damage during slotting.A simulation of the stresses around the drill hole and slot was prepared using FLAC-3D code.It helps explain the induction of drill spray during hydraulic slotting.The stress concentration around the bore increases as the diameter of the hole increases.As the hole enlarges the variation in stress also increases,which introduces an instability into the coal.This allows easy breaking and removal of the coal.Destruction of the coal structure by the water jet is the major factor causing drill spray.Energy stored as either strain or gas pressure is released by the water jet and this causes the coal to fracture and be expelled from the hole.Field tests showed the effect on gas extraction after slotting with drill spray.The concentration of gas increases after drilling.Compared to conventional techniques,the hydraulic slotted bore gives a gas concentration three times higher and has an effective range twice as far.This makes the gas extraction process more efficient and allows reduced construction effort.

Volatile components of Rhizoma Alpiniae Officinarum using three different extraction methods combined with gas chromatography-mass spectrometry

Volatile components from Rhizoma Alpiniae Officinarum were respectively extracted by three methods including hydrodistillation, headspace solid-phase microextraction （HS-SPME） and diethyl ether extraction. A total of 40 （hydrodistillation）, 32 （HS-SPME） and 37 （diethyl ether extraction） compounds were respectively identified by gas chromatography-mass spectrometry （GC/MS） and 22 compounds were overlapped, including β-farnesene, 7-muurolene, 2,6-dimethyl-6- （4-methyl-3-pentenyl）bicyclo[3.1.1]hept-2-ene, eucalyptol and cadina-1（10）, 4-diene and so forth, varying in relative contents. HS-SPME is fast, sample saving and solvent-free and it also can achieve similar profiles as those from hydrodistillation and solvent extraction. Therefore, it can be the priority for extracting volatile components from medicinal plants.

Study of the Reservoir Damage during Cyclic Injection and Extraction Process in the Hutubi Gas Storage

During the injection and extraction process in gas storage,cyclic loading stress is applied to the reservoir pore structure,affecting the capacity and service life of gas storage. To study the influence of cyclic injection and extraction on reservoir physical property,a finite-element model of reservoir elastoplastic damage under the effect of pore pressure is established based on elastoplastic mechanics and fatigue-damage mechanics. Considering the mechanical property of the Hutubi reservoir and the injection-extraction mode of gas storage,the finite-element model is used to study the pore pressure and porosity change,fault safety,and ground surface deformation. The results show that the change in pore pressure and porosity,the deformation of the Hutubi fault,as well as the uplift and sink of the grounds surface are controlled by the fatigue damage of the reservoir pore structure during the injection-extraction process. After a 6-year service life, the cumulative deformation of the reservoir pore reaches its limit,causing pore structure collapse and porosity decrease. As a result,storage capacity declines and the ground surface starts to sink. Through this study,the safety of the Hutubi gas storage is evaluated,and some suggestions for field operations are offered.

Feature Extraction and Dimensionality Reduction of Arc Sound under Typical Penetration Status in Metal Inert Gas Welding

Arc sound is well known as the potential and available resource for monitoring and controlling of the weld penetration status,which is very important to the welding process quality control,so any attentions have been paid to the relationships between the arc sound and welding parameters.Some non-linear mapping models correlating the arc sound to welding parameters have been established with the help of neural networks.However,the research of utilizing arc sound to monitor and diagnose welding process is still in its infancy.A self-made real-time sensing system is applied to make a study of arc sound under typical penetration status,including partial penetration,unstable penetration,full penetration and excessive penetration,in metal inert-gas（MIG） flat tailored welding with spray transfer.Arc sound is pretreated by using wavelet de-noising and short-time windowing technologies,and its characteristics,characterizing weld penetration status,of time-domain,frequency-domain,cepstrum-domain and geometric-domain are extracted.Subsequently,high-dimensional eigenvector is constructed and feature-level parameters are successfully fused utilizing the concept of primary principal component analysis（PCA）.Ultimately,60-demensional eigenvector is replaced by the synthesis of 8-demensional vector,which achieves compression for feature space and provides technical supports for pattern classification of typical penetration status with the help of arc sound in MIG welding in the future.

Multiresidue Method for Determination of 67 Pesticides in Water Samples Using Solid-Phase Extraction with Centrifugation and Gas Chromatography-Mass Spectrometry

A new multi-residue method based on solid-phase extraction (SPE) with centrifugation was developed for determination and quantitation of 67 pesticides in water samples. Two SPE cartridges were tested: Chromabond C18 and Oasis HLB. Parameters that influence the extraction efficiency such as the eluent volume, the sample loading volume, the addition of organic solvent to water sample, sorbent drying and elute concentration were optimized. The innovation of this work was the examination of the use of a centrifugation technique in both the drying and elution steps. When combined with centrifugation, the volume of the elution solvent was reduced to 2 mL and the time for sorbent drying decreased also to 10 min under vacuum. Under the optimized conditions, this method showed good recoveries higher than 65% - 68% for the 67 analyzed pesticides using the C18 and HLB cartridges with relative standard deviations lower than 9.7% - 12.3%. Limits of quantification were between 2 and 20 ng.L–1. The simplicity of the described method, use of less of organic solvent, short procedure time, and good recoveries demonstrate the advantages of this environmentally friendly approach for routine analysis of numerous samples.

Coupling mechanism of THM fields and SLG phases during the gas extraction process and its application in numerical analysis of gas occurrence regularity and effective extraction radius

The analysis of the coupling mechanism of thermal-hydraulic-mechanical(THM)fields,and solid-liquidgas(SLG)phases during gas extraction process is of profound significance to explore its numerical application in the gas occurrence regularity and its effective extraction radius.In this study,the Hudi coal mine in Qinshui basin is taken as the research area,the influencing factors of gas occurrence were analyzed,the differences in overburden load for gas pressure distribution and the factors influencing the effective extraction radius were further discussed by using the COMSOL software.The results show that the derivation of mathematical model in gas extraction shows that the process is a process the THM fields restrict each other,and the SLG phases influence each other.The longer the extraction time,the larger the influencing range of borehole,and the better the extraction effect.The larger the diameter of borehole,the larger the effective extraction radius,and the influence on gas extraction effect is smaller in the early stage and larger in the late stage.The borehole arrangement should be flexibly arranged according to the actual extraction situation.The higher the porosity,the higher the permeability,the better the gas extraction effect.The larger the overburden load of reservoir,the stronger the effective stress,which will result in the more severe the strain,and the closure of pore and fracture,which in turn will lead to the decrease of permeability and slow down the gas extraction.The relationship among extraction time,borehole diameter,negative pressure of gas extraction,permeability with effective extraction radius is exponential.This study has important theoretical and practical significance for clarifying and summarizing the gas occurrence regularity and its engineering practice.

Helium extraction from natural gas using DD3R zeolite membranes

Helium(He)is commercially produced from natural gas by low-temperature condensation.The process is energy extensive because of the extremely low He concentration(<0.3%)and the operation at cryogenic temperature.Herein we demonstrated DD3R zeolite membrane was efficient to extract He from natural gas at atmosphere temperature.The membrane performance was evaluated in terms of temperature,pressure and molar fractions.The overall membrane performance was dominated by the diffusivity selectivity.The single He permeance and ideal He/CH_(4) selectivity were 5.8×10^(-9)mol·m^(-2)·s^(-1)·Pa^(-1)and 79 under a feed pressure of 1.3 MPa.Even though He concentration was as low as 0.22%,the He permeance and He/CH_(4) mixture selectivity were 3.0×10^(-9)mol·m^(-2)·s^(-1)·Pa^(-1)and 44 at 0.7 MPa.During the longterm operation(~130 h)the membrane performance was stable even the feed mixture containing3.6%ethane as contaminations.The results approved the feasibility of DD3R zeolite membranes for He extraction from natural gas.

Ultrasonic Nebulization Extraction Coupled with Gas Chromatography-Mass Spectrometry for Analysis of Volatile Components in Traditional Chinese Patent Medicine

The ultrasonic nebulization extraction（UNE） was developed and applied to the extraction of volatile components from traditional Chinese patent medicine Xiaoyao Pills. Several parameters of ultrasonic nebulization extraction including the sample particle size, solvent volume, extraction time and ultrasonic power were studied and selected. As a result, 2.4 g of sample with particle size of 80 mesh was extracted with 15 mL of n-hexane for 20 min at an ultrasonic power of 35 W. The volatile components were analyzed by gas chromatography-mass spectrometry （GC-MS） under the optimal conditions and 57 compounds were identified. The precision, repeatability and stability of the proposed method were also studied. Compared with ultrasonic-assisted extraction（UAE） and hydrodistillation（HD） extraction, the proposed method is more efficient, faster and easier to be operated at room temperature with smaller sample and energy consumption. It is suggested that the ultrasonic nebulization extraction can be used as a novel alternative method for the extraction of volatile components from traditional Chinese patent medicine.

Determination of an Organophosphorus Pesticide Chlorpyrifos in Seawater by Solid Phase Extraction-Gas Chromatography

Solid phase extraction(SPE) and gas chromatography(GC) were combined to establish a method for detecting traces of chlorpyrifos in seawater,and the effects of extraction column type,water sample pH and salinity,and eluant type on the recovery rate of chlorpyrifos were analyzed. The results show that the linear range of the method was 0.02-2.0 μg/ml,and the correlation coefficient was 0.9993; the recovery rate of chlorpyrifos in the seawater samples to which the standard sample of chlorpyrifos averaged 101%-114%; MDL was 0.00851μg/L,and the lower limit of determination for chlorpyrifos was 0.034μg/L; the relative standard deviation ranged from 1.52% to 6.21%(n = 6). The method is simple,sensitive and accurate and has good repeatability. It is suitable for the determination of traces of chlorpyrifos in seawater.

Gas-liquid-liquid extraction in a novel rotating microchannel extractor

In this work,a novel rotating microchannel extractor(RME)is designed and further used for the extraction of chromium(Ⅲ)from water.Unexpectedly,the micro-extraction had the same effect as carrying out 2.9-stage cross-flow extractions.Various factors,including the gas intake methods,gas intake quantity(Qg),distance between inner rotor and outer wall(D),rotational inner rotor speed(R)and volumetric flow rate(Qa,Qo),were selected to investigate their effect on the extraction efficiency(η)thoroughly.The relation map ofηwith Weaand We(o-g)for RME provides a comprehension for the gas–liquid–liquid extraction process in this RME system.

Influence of Water Injection Fracturing on Crack Damage in Soft Coal and Application in Gas Extraction

In order to study the hypotonic and rheological particularity of “three soft” coal seam in west Henan, China, this paper explored the stress and damage characteristics of crack in coal under condition of water injection fracturing based on ABAQUS platform;The cohesive element in T-P damage evolution criterion was used to describe the approximately linear relationship between crack width and extending distance in soft coal. The simulation results show that stress evolution and crack damage in soft coal is a gradually developing process under condition of water injection fracturing. When the static pressure is 4 - 10 MPa, and the injection time is about 1 - 2 hours, the damage range of crack in soft coal can basically reach an ideal data of 80 - 100 m, and then greatly improve the hypotonic performance of “three soft” coal seam.

Determination of 7 Indictor Polychlorinated Biphenyls (PCBs) Residues in Porphyra by Ultrasonic Extraction and Gas Chromatography (GC)

A method was developed for determination of 7 indictors the polychlorinated biphenyls (PCBs) residues in porphyra by gas chromatography (GC) with electron capture detector (ECD). The PCBs were extracted with hexane/methylene chloride (1:1, v/v) by ultrasonic extraction and the samples were cleaned up by concentrated sulfuric acid and Alumina-N solid phase extraction cartridge. The analytes were quantified by an internal standard method. Under optimal experimental conditions, good linearity was observed in the range of 5 - 200 ng/mL and the correlation coefficients were 0.9994 - 0.9998. The limit of quantitation (LOQ) for target analytes ranged from 6.0 to 10.0 μg/kg. At the spiked levels of 10, 50, 100 μg/kg, the average recoveries ranged from 90.9% to 102% with the relative standard deviations 2.12% - 6.32%. The result showed that the proposed method was rapid, and could be used for the determination of the PCBs in porphyra.

Hollow-Fiber Microporous Membrane Liquid-Liquid Extraction for Determination of Polybrominated Diphenyl Ethers at Trace Levels in Sewage Sludge with Gas Chromatography-Electron Capture Detection

A two-phase hollow-fiber (HF) liquid-phase microextraction (LPME) method followed by gas chromatography was developed for quantification of 8 major polybrominated diphenyl ethers at trace level in sewage sludge. In this method the porous polypropylene hollow fibers filled with a few microliters of organic solvent, were immersed in aqueous samples of wet sludge which were spiked with the PBDEs at ng/l level. Parameters such as salt concentration, stirring speed, extraction time and pH were optimized and the optimum extraction conditions were then applied to the determination of PBDEs in sewage sludge from K?llby sewage treatment plant in Lund. The optimized method allowed detection of 5.1 μg kg–1 and 0.43 μg kg–1 of BDE-47 and 183, respectively, in dried sludge. The findings were compatible with the results from recent research on PBDEs level in sewage sludge samples from Sweden. Although BDE-209 was expected to have the highest level, it was not detected. Limit of detection, photodegradation or/and biodegradation of BDE-209 during treatment or experiment are major reasons. Low organic solvent consumption, low sample volume requirement, high preconcentration factor, simplicity without using expensive instrument for extraction and excellent sample clean-up are some important factors that make this sample preparation technique very useful for determination of PBDEs in sludge.

Dynamic microwave-assisted extraction combined with liquid phase microextraction based on the solidification of a floating drop for the analysis of organochlorine pesticides in grains followed by GC

A convenient,cost-effective and fast method using dynamic microwave-assisted extraction and liquid phase microextraction based on the solidification of a floating drop was proposed to analyze organochlorine pesticides in grains including rice,maize and millet.Twelve samples can be processed simultaneously in the method.During the extraction process,10%acetonitrile-water solutions containing 110μL of n-hexadecane were used to extract organochlorine pesticides.Subsequently,1.0 g sodium chloride was placed in the extract,and then centrifuged and cooled.The n-hexadecane drops containing the analytes were solidifi ed and transferred for determination by gas chromatography-electron capture detector without any further filtration or cleaning process.Limits of detection for organochlorine pesticides were 0.97–1.01μg/kg and the RSDs were in the range of 2.6%–8.5%.The developed technology has succeeded in analyzing six real grains samples and the recoveries of the organochlorine pesticides were 72.2%–94.3%.Compared with the published extraction methods,the developed method was used to analyze organochlorine pesticides in grains,being more environmentally friendly,which is suitable for the daily determination of organochlorine pesticides.

Rapid determination of volatile constituents in safflower from Xinjiang and Henan by ultrasonic-assisted solvent extraction and GC-MS

The total volatile components were extracted from safflower by ultrasonic-assisted solvent extraction （USE） and their chemical constituents were analyzed by gas chromatographymass spectrometry （GC-MS） to provide scientific basis for the quality control of safflower. Five different solvents （diethyl ether, ethanol, ethyl acetate, dichloromethane and acetone） were used and compared in terms of number of volatile components extracted and the peak areas of these components in TIC. The results showed that USE could be used as an efficient and rapid method for extracting the volatile components from safflower. It also could be found that the number of components in the TIC of ethyl acetate extract was more than that in the TIC of other solvent ones. Meanwhile, the volatile components of safflower from Xinjiang Autonomous Region and Henan Province of China were different in chemical components and relative contents. It could be concluded that both the extraction solvents and geographical origin of safflower are responsible for these differences. The experimental results also indicated that USE/GC-MS is a simple, rapid and effective method to analyze the volatile oil components of safflower.

A Study on a Gas Agitated Extractor with Static Mixer

1 INTRODUCTIONMany chemical engineering operations involve the mass and heat transfer between two liquidphases in reactions.Mechanically agitated liquid-liquid extractor can be one of the examples forsuch operations.It has been well developed and used in the nuclear energy,petrochemical andother chemical industries.However,not much attention has been paid to the gas agitated liquid-

Analysis of Residual Solvents in Annatto Extracts Using a Static Headspace Gas Chromatography Method

An analytical method for the quantification of residual solvents in annatto extracts, natural food colorants, was established using a static headspace gas chromatography (HSGC) coupled with a flame ionization detector (FID). As a sample diluent in a headspace sampling, dimethylformamide (DMF) was selected owing to its high capacity for dissolving both bixin-based and norbixin-based annatto extracts. The quantification of residual solvents was performed using the external standard method. The linearity of the calibration curves was assured with relative coefficients (R2) that were greater than 0.999. The recoveries of all standard solvents spiked in the annatto extracts were in the range from 95.1% to 107.1% to verify the accuracy and the relative standard deviation (RSD%) values (n = 3) were in the range from 0.57% to 3.31%. The quantification limits (QL) were sufficiently lower than the limits specified by Joint FAO/WHO Expert Committee on Food Additives (JECFA). With the established HSGC method, six residual solvents (methanol, ethanol, 2-propanol, acetone, ethyl acetate, and hexane) in 23 commercial annatto-extract products that consist of seven bixin-based and 16 norbixin-based products were quantified. The levels of residual ethyl acetate and hexane in all products were lower than the specified limits of JECFA. However, three samples of bixin-based products showed higher levels of residual 2-propanol (approximately 313.9 - 427.7 ppm) than the specified limit. Other bixin products also showed higher concentrations of residual methanol (approximately 166.6 - 394.7 ppm) and residual acetone (approximately 75.2 - 179.8 ppm) than the limits of JECFA. In the case of norbixin-based products, nine samples showed higher levels of residual acetone (approximately 42.6 - 139.5 ppm) than the limits of JECFA. This is the first survey of residual solvents in annatto extracts using the validated HSGC method.

Response Surface Optimization of Nigella glandulifera Freyn Seed Oil Yield by Supercritical Carbon Dioxide Extraction

Supercritical carbon dioxide （SC-CO2） extraction was employed to extract oil from Nigella glandulifera Freyn seed in this study. Response surface methodology （RSM） was applied to evaluate the effects of the process parameters （pressure, temperature, and CO2 flow rate） on oil yield of N. glandulifera seed. A Box-Behnken design was used to optimize the extraction parameters. The analysis of variance indicated that the linear coefficients of pressure and CO2 flow rate, the quadratic term coefficients of pressure and temperature and the interactions between pressure and temperature, as well as temperature and CO2 flow rate, had significant effects on the oil yield （P〈0.05）. The optimal conditions to obtain the maximum oil yield from N. glandulifera seed were pressure 30.84 MPa, temperature 40.57°C, and CO2 flow rate 22.00 L h-1. Under these optimal conditions, the yield of oil was predicted to be 38.19%. The validation experiment results agreed with the predicted values. The fatty acid composition of N. glandulifera seed oil extracted using SC-CO2 was compared with that of oil obtained by Soxhlet method. The results showed that the fatty acid compositions of oil extracted by the two methods were similar. Identification of oil compounds with gas chromatography-mass spectrometry （GC-MS） showed that the contents of unsaturated fatty acids linoleic acid （48.30%）, oleic acid （22.28%） and saturated fatty acids palmitic acid （16.65%）, stearic acid （4.17%） were the most abundant fatty acids in seed oil from N. glandulifera.