Micro segment analysis of supercritical methane thermal-hydraulic performance and pseudo-boiling in a PCHE straight channel

The printed circuit heat exchanger(PCHE) is receiving wide attention as a new kind of compact heat exchanger and is considered as a promising vaporizer in the LNG process. In this paper, a PCHE straight channel in the length of 500 mm is established, with a semicircular cross section in a diameter of 1.2 mm.Numerical simulation is employed to investigate the flow and heat transfer performance of supercritical methane in the channel. The pseudo-boiling theory is adopted and the liquid-like, two-phase-like, and vapor-like regimes are divided for supercritical methane to analyze the heat transfer and flow features.The results are presented in micro segment to show the local convective heat transfer coefficient and pressure drop. It shows that the convective heat transfer coefficient in segments along the channel has a significant peak feature near the pseudo-critical point and a heat transfer deterioration when the average fluid temperature in the segment is higher than the pseudo-critical point. The reason is explained with the generation of vapor-like film near the channel wall that the peak feature related to a nucleateboiling-like state and heat transfer deterioration related to a film-boiling-like state. The effects of parameters, including mass flow rate, pressure, and wall heat flux on flow and heat transfer were analyzed.In calculating of the averaged heat transfer coefficient of the whole channel, the traditional method shows significant deviation and the micro segment weighted average method is adopted. The pressure drop can mainly be affected by the mass flux and pressure and little affected by the wall heat flux. The peak of the convective heat transfer coefficient can only form at high mass flux, low wall heat flux, and near critical pressure, in which condition the nucleate-boiling-like state is easier to appear. Moreover,heat transfer deterioration will always appear, since the supercritical flow will finally develop into a filmboiling-like state. So heat transfer deterioration should be taken seriously in the design and safe operation of vaporizer PCHE. The study of this work clarified the local heat transfer and flow feature of supercritical methane in microchannel and contributed to the deep understanding of supercritical methane flow of the vaporization process in PCHE.

Layered Structural PBAT Composite Foams for Efficient Electromagnetic Interference Shielding

The utilization of eco-friendly,lightweight,high-efficiency and high-absorbing electromagnetic interference(EMI)shielding composites is imperative in light of the worldwide promotion of sustainable manufacturing.In this work,magnetic poly(butyleneadipate-coterephthalate)(PBAT)microspheres were firstly synthesized via phase separation method,then PBAT composite foams with layered structure was constructed through the supercritical carbon dioxide foaming and scraping techniques.The merits of integrating ferroferric oxideloaded multi-walled carbon nanotubes(Fe3O4@MWCNTs)nanoparticles,a microcellular framework,and a highly conductive silver layer have been judiciously orchestrated within this distinctive layered configuration.Microwaves are consumed throughout the process of“absorption-reflection-reabsorption”as much as possible,which greatly declines the secondary radiation pollution.The biodegradable PBAT composite foams achieved an EMI shielding effectiveness of up to 68 dB and an absorptivity of 77%,and authenticated favorable stabilization after the tape adhesion experiment.

Demonstration of a small‐scale power generator using supercritical CO_(2)

The supercritical CO_(2)(sCO_(2))power cycle could improve efficiencies for a wide range of thermal power plants.The sCO_(2)turbine generator plays an important role in the sCO_(2)power cycle by directly converting thermal energy into mechanical work and electric power.The operation of the generator encounters challenges,including high temperature,high pressure,high rotational speed,and other engineering problems,such as leakage.Experimental studies of sCO_(2)turbines are insufficient because of the significant difficulties in turbine manufacturing and system construction.Unlike most experimental investigations that primarily focus on 100 kW‐or MW‐scale power generation systems,we consider,for the first time,a small‐scale power generator using sCO_(2).A partial admission axial turbine was designed and manufactured with a rated rotational speed of 40,000 rpm,and a CO_(2)transcritical power cycle test loop was constructed to validate the performance of our manufactured generator.A resistant gas was proposed in the constructed turbine expander to solve the leakage issue.Both dynamic and steady performances were investigated.The results indicated that a peak electric power of 11.55 kW was achieved at 29,369 rpm.The maximum total efficiency of the turbo‐generator was 58.98%,which was affected by both the turbine rotational speed and pressure ratio,according to the proposed performance map.

Multi-objective optimization and evaluation of supercritical CO_(2) Brayton cycle for nuclear power generation

The supercritical CO_(2) Brayton cycle is considered a promising energy conversion system for Generation IV reactors for its simple layout,compact structure,and high cycle efficiency.Mathematical models of four Brayton cycle layouts are developed in this study for different reactors to reduce the cost and increase the thermohydraulic performance of nuclear power generation to promote the commercialization of nuclear energy.Parametric analysis,multi-objective optimizations,and four decision-making methods are applied to obtain each Brayton scheme’s optimal thermohydraulic and economic indexes.Results show that for the same design thermal power scale of reactors,the higher the core’s exit temperature,the better the Brayton cycle’s thermo-economic performance.Among the four-cycle layouts,the recompression cycle(RC)has the best overall performance,followed by the simple recuperation cycle(SR)and the intercooling cycle(IC),and the worst is the reheating cycle(RH).However,RH has the lowest total cost of investment(C_(tot))of$1619.85 million,and IC has the lowest levelized cost of energy(LCOE)of 0.012$/(kWh).The nuclear Brayton cycle system’s overall performance has been improved due to optimization.The performance of the molten salt reactor combined with the intercooling cycle(MSR-IC)scheme has the greatest improvement,with the net output power(W_(net)),thermal efficiencyη_(t),and exergy efficiency(η_(e))improved by 8.58%,8.58%,and 11.21%,respectively.The performance of the lead-cooled fast reactor combined with the simple recuperation cycle scheme was optimized to increase C_(tot) by 27.78%.In comparison,the internal rate of return(IRR)increased by only 7.8%,which is not friendly to investors with limited funds.For the nuclear Brayton cycle,the molten salt reactor combined with the recompression cycle scheme should receive priority,and the gas-cooled fast reactor combined with the reheating cycle scheme should be considered carefully.

Conventional Geothermal Systems and Unconventional Geothermal Developments: An Overview

This paper provides an overview of conventional geothermal systems and unconventional geothermal developments as a common reference is needed for discussions between energy professionals. Conventional geothermal systems have the heat, permeability and fluid, requiring only drilling down to °C, normal heat flow or decaying radiogenic granite as heat sources, and used in district heating. Medium-temperature (MT) 100°C - 190°C, and high-temperature (HT) 190°C - 374°C resources are mostly at plate boundaries, with volcanic intrusive heat source, used mostly for electricity generation. Single well capacities are °C - 500°C) and a range of depths (1 m to 20 Km), but lack permeability or fluid, thus requiring stimulations for heat extraction by conduction. HVAC is 1 - 2 m deep and shallow geothermal down to 500 m in wells, both capturing °C, with °C are either advanced by geothermal developers at <7 Km depth (Enhanced Geothermal Systems (EGS), drilling below brittle-ductile transition zones and under geothermal fields), or by the Oil & Gas industry (Advanced Geothermal Systems, heat recovery from hydrocarbon wells or reservoirs, Superhot Rock Geothermal, and millimeter-wave drilling down to 20 Km). Their primary aim is electricity generation, relying on closed-loops, but EGS uses fractures for heat exchange with earthquake risks during fracking. Unconventional approaches could be everywhere, with shallow geothermal already functional. The deeper and hotter unconventional alternatives are still experimental, overcoming costs and technological challenges to become fully commercial. Meanwhile, the conventional geothermal resources remain the most proven opportunities for investments and development.

Proppant transport in rough fracture networks using supercritical CO_(2)

Proppant transport within fractures is one of the most critical tasks in oil,gas and geothermal reservoir stimulation,as it largely determines the ultimate performance of the operating well.Proppant transport in rough fracture networks is still a relatively new area of research and the associated transport mechanisms are still unclear.In this study,representative parameters of rough fracture surfaces formed by supercritical CO_(2) fracturing were used to generate a rough fracture network model based on a spectral synthesis method.Computational fluid dynamics(CFD)coupled with the discrete element method(DEM)was used to study proppant transport in this rough fracture network.To reveal the turning transport mechanism of proppants into branching fractures at the intersections of rough fracture networks,a comparison was made with the behavior within smooth fracture networks,and the effect of key pumping parameters on the proppant placement in a secondary fracture was analyzed.The results show that the transport behavior of proppant in rough fracture networks is very different from that of the one in the smooth fracture networks.The turning transport mechanisms of proppant into secondary fractures in rough fracture networks are gravity-driven sliding,high velocity fluid suspension,and fracture structure induction.Under the same injection conditions,supercritical CO_(2)with high flow Reynolds number still has a weaker ability to transport proppant into secondary fractures than water.Thickening of the supercritical CO_(2)needs to be increased beyond a certain value to have a significant effect on proppant carrying,and under the temperature and pressure conditions of this paper,it needs to be increased more than 20 times(about 0.94 m Pa s).Increasing the injection velocity and decreasing the proppant concentration facilitates the entry of proppant into the branching fractures,which in turn results in a larger stimulated reservoir volume.The results help to understand the proppant transport and placement process in rough fracture networks formed by reservoir stimulation,and provide a theoretical reference for the optimization of proppant pumping parameters in hydraulic fracturing.

CO_(2)-Induced Modulation of Si-O Bonds for Low Temperature Plastic Deformation of Amorphous Silica Nanoparticles with Enhanced Photoluminescence

Modulation of Si-O bonds under mild conditions has been a challenging issue in the field of material science,which is critical to manufacture highperformance silica-based optical and photonic devices.Herein,we introduce a nondestructive technique to achieve Si-O bond rearrangement,leading to plastic deformation and photoluminescence enhancement of amorphous silica nanoparticles using supercritical carbon dioxides in EtOH/H_(2)O solution under mild temperature.Specifically,plastic deformation is achieved by treating hollow mesoporous silica nanospheres using supercritical CO_(2)at 40°C under 20 MPa.Experimental and theoretical studies revealed the critical role of supercritical CO_(2)in the plastic deformation process,which can be intercalated into the hollow mesoporous silica nanospheres with anisotropic stresses and induces the rearrangement of Si-O bonds and transformation of ring structures.This work suggests a novel approach to engineer high-performance nano-silica glass components for numerous optical and photonic devices under mild condition.

Parametric resonance of axially functionally graded pipes conveying pulsating fluid

Based on the generalized Hamilton's principle,the nonlinear governing equation of an axially functionally graded(AFG)pipe is established.The non-trivial equilibrium configuration is superposed by the modal functions of a simply supported beam.Via the direct multi-scale method,the response and stability boundary to the pulsating fluid velocity are solved analytically and verified by the differential quadrature element method(DQEM).The influence of Young's modulus gradient on the parametric resonance is investigated in the subcritical and supercritical regions.In general,the pipe in the supercritical region is more sensitive to the pulsating excitation.The nonlinearity changes from hard to soft,and the non-trivial equilibrium configuration introduces more frequency components to the vibration.Besides,the increasing Young's modulus gradient improves the critical pulsating flow velocity of the parametric resonance,and further enhances the stability of the system.In addition,when the temperature increases along the axial direction,reducing the gradient parameter can enhance the response asymmetry.This work further complements the theoretical analysis of pipes conveying pulsating fluid.

Experimental investigation on pyrolysis products and pore structure characteristics of organic-rich shale heated by supercritical carbon dioxide

The efficient pyrolysis and conversion of organic matter in organic-rich shale,as well as the effective recovery of pyrolysis shale oil and gas,play a vital role in alleviating energy pressure.The state of carbon dioxide(CO_(2))in the pyrolysis environment of shale reservoirs is the supercritical state.Its unique supercritical fluid properties not only effectively heat organic matter,displace pyrolysis products and change shale pore structure,but also achieve carbon storage to a certain extent.Shale samples were made into powder and three sizes of cores,and nitrogen(N_(2))and supercritical carbon dioxide(ScCO_(2))pyrolysis experiments were performed at different final pyrolysis temperatures.The properties and mineral characteristics of the pyrolysis products were studied based on gas chromatography analysis,Xray diffraction tests,and mass spectrometry analysis.Besides,the pore structure characteristics at different regions of cores before and after pyrolysis were analyzed using N_(2) adsorption tests to clarify the impact of fracturing degree on the pyrolysis effect.The results indicate that the optimal pyrolysis temperature of Longkou shale is about 430℃.Compared with N_(2),the oil yield of ScCO_(2) pyrolysis is higher.The pyrolysis oil obtained by ScCO_(2) extraction has more intermediate fractions and higher relative molecular weight.The ScCO_(2) can effectively improve the pore diameter of shale and its effect is better than that of N_(2).The micropores are produced in shale after pyrolysis,and the macropores only are generated in ScCO_(2) pyrolysis environments with temperatures greater than 430℃.The pore structure has different development characteristics at different pyrolysis temperatures,which are mainly affected by the pressure holding of volatile matter and products blocking.Compared to the surface of the core,the pore development effect inside the core is better.With the decrease in core size,the pore diameter,specific surface area,and pore volume of cores all increase after pyrolysis.

Control system design for a pressure-tube-type supercritical water-cooled nuclear reactor via a higher order sliding mode method

Nuclear power plants exhibit non-linear and time-variable dynamics.Therefore,designing a control system that sets the reactor power and forces it to follow the desired load is complicated.A supercritical water reactor(SCWR)is a fourth-generation conceptual reactor.In an SCWR,the non-linear dynamics of the reactor require a controller capable of control-ling the nonlinearities.In this study,a pressure-tube-type SCWR was controlled during reactor power maneuvering with a higher order sliding mode,and the reactor outgoing steam temperature and pressure were controlled simultaneously.In an SCWR,the temperature,pressure,and power must be maintained at a setpoint(desired value)during power maneuvering.Reactor point kinetics equations with three groups of delayed neutrons were used in the simulation.Higher-order and classic sliding mode controllers were separately manufactured to control the plant and were compared with the PI controllers speci-fied in previous studies.The controlled parameters were reactor power,steam temperature,and pressure.Notably,for these parameters,the PI controller had certain instabilities in the presence of disturbances.The classic sliding mode controller had a higher accuracy and stability;however its main drawback was the chattering phenomenon.HOSMC was highly accurate and stable and had a small computational cost.In reality,it followed the desired values without oscillations and chattering.

Solubility of iron(Ⅲ) and nickel(Ⅱ) acetylacetonates in supercritical carbon dioxide

As a common precursor for supercritical CO_(2)(scCO_(2))deposition techniques,solubility data of organometallic complexes in scCO_(2)is crucial for the preparation of nanocomposites.Recently,metal acetylacetonates have shown great potential for the preparation of single-atom catalytic materials.In this study,the solubilities of iron(Ⅲ)acetylacetonate(Fe(acac)3)and nickel(Ⅱ)acetylacetonate(Ni(acac)2)were measured at the temperature from 313.15 to 333.15 K and in the pressure range of 9.5–25.2 MPa to accumulate new solubility data.Solubility was measured using a static weight loss method.The semi-empirical models proposed by Chrastil and Sung et al.were used to correlate the solubility data of Fe(acac)3 and Ni(acac)2.The equations obtained can be used to predict the solubility of the same system in the experimental range.

Numerical Predictions of Laminar Forced Convection Heat Transfer with and without Buoyancy Effects from an Isothermal Horizontal Flat Plate to Supercritical Nitrogen

Numerical predictions are made for Laminar Forced convection heat transfer with and without buoyancy effects for Supercritical Nitrogen flowing over an isothermal horizontal flat plate with a heated surface facing downwards.Computations are performed by varying the value ofΔT from5 to 30 K and P_(∞)/P_(cr)ratio from1.1 to 1.5.Variation of all the thermophysical properties of supercritical Nitrogen is considered.The wall temperatures are chosen in such a way that two values of Tw are less than T∗(T*is the temperature at which the fluid has a maximum value of Cp for the given pressure),one value equal to T∗and two values greater than T∗.Three different values of U∞are used to obtain Re∞range of 3.6×10_(4)to 4.74×10^(5)for forced convection without buoyancy effects and Gr_(∞)/Re^(2)_(∞)range of 0.011 to 3.107 for the case where buoyancy effects are predominant.Six different forms of correlations are proposed based on numerical predictions and are compared with actual numerical predictions.It has been found that in all six forms of correlations,the maximum deviations are found to occur in those cases where the pseudocritical temperature TT∗lies between the wall temperature and bulk fluid temperature.

Modeling Blood Flow in Veins of Uniform Properties (Giraffe Jugular Vein)

This paper models the giraffe’s jugular veins as a uniform collapsible tube from a rigid skull. The equations governing one-dimensional steady flow through such a tube for various conditions have been developed. The effects of inertial and inclination angles that have not been discussed previously have been included. It has been shown that different flows for a uniform tube (vein) are possible. However, this flow matches that of a jugular vein which is supercritical, and the steady solution has been given by the balance between the driving forces of gravity and the viscous resistance to the flow at the right atrium of the heart must be sub-critical for a fixed right-atrium pressure which means that an elastic jump is required to return the flow to sub-critical from the supercritical flow upstream this type of relationship gives rise to flow limitation at the same time given any right atrium fixed pressure there exists a maximum flow rate which when exceeded the boundary conditions of the flow do not hold boundary conditions at the right atrium are not satisfied hence making the steady flow impossible this mechanism of flow limitation is slightly different from the other one in that causes airways through forced expiration from the observation made it is clearly shown that there is an intravascular pressure difference with a change in height.

Simulation Modelling and Techno-Economics of Supercritical Carbon Dioxide Recompression Closed Brayton Cycle

In recent years, there has been global interest in meeting targets relating to energy affordability and security while taking into account greenhouse gas emissions. This has heightened major interest in potential investigations into the use of supercritical carbon dioxide (sCO2) power cycles. Climate change mitigation is the ultimate driver for this increased interest;other relevant issues include the potential for high cycle efficiency and a circular economy. In this study, a 25 MWe recompression closed Brayton cycle (RCBC) has been assessed, and sCO2 has been proposed as the working fluid for the power plant. The methodology used in this research work comprises thermodynamic and techno-economic analysis for the prospective commercialization of this sCO2 power cycle. An evaluated estimation of capital expenditure, operational expenditure, and cost of electricity has been considered in this study. The ASPEN Plus simulation results have been compared with theoretical and mathematical calculations to assess the performance of the compressors, turbine, and heat exchangers. The results thus reveal that the cycle efficiency for this prospective sCO2 recompression closed Brayton cycle increases (39% - 53.6%) as the temperature progressively increases from 550˚C to 900˚C. Data from the Aspen simulation model was used to aid the cost function calculations to estimate the total capital investment cost of the plant. Also, the techno-economic results have shown less cost for purchasing equipment due to fewer components being required for the cycle configuration as compared to the conventional steam power plant.

Experimental Research on Supercritical Carbon Dioxide Fracturing of Sedimentary Rock:A Critical Review

Supercritical carbon dioxide(ScCO_(2))fracturing has great advantages and prospects in both shale gas exploitation and CO_(2)storage.This paper reviews current laboratory experimental methods and results for sedimentary rocks fractured by ScCO_(2).The breakdown pressure,fracture parameters,mineral composition,bedding plane angle and permeability are discussed.We also compare the differences between sedimentary rock and granite fractured by ScCO_(2),ultimately noting problems and suggesting solutions and strategies for the future.The analysis found that the breakdown pressure of ScCO_(2)was reduced 6.52%–52.31%compared with that of using water.ScCO_(2)tends to produce a complex fracture morphology with significantly higher permeability.When compared with water,the fracture aperture of ScCO_(2)was decreased by 4.10%–72.33%,the tortuosity of ScCO_(2)was increased by 5.41%–70.98%and the fractal dimension of ScCO_(2)was increased by 4.55%–8.41%.The breakdown pressure of sandstone is more sensitive to the nature of the fracturing fluid,but fracture aperture is less sensitive to fracturing fluid than for shale and coal.Compared with granite,the tortuosity of sedimentary rock is more sensitive to the fracturing fluid and the fracture fractal dimension is less sensitive to the fracturing fluid.Existing research shows that ScCO_(2)has the advantages of low breakdown pressure,good fracture creation and environmental protection.It is recommended that research be conducted in terms of sample terms,experimental conditions,effectiveness evaluation and theoretical derivation in order to promote the application of ScCO_(2)reformed reservoirs in the future.

Mesoporous poly(ionic liquid)s with dual active sites for highly efficient CO_(2)conversion

Atmospheric CO_(2)concentrations are soaring due to the continued use of fossil fuels in energy production,an anthropogenic activity that is playing a leading role in global warming.Thus,research aimed at the capture and conversion of CO_(2)into value-added products,such as cyclic carbonates,is booming.While CO_(2)is an abundant,cheap,non-toxic,and readily accessible Cl feedstock,its thermodynamic stability necessitates the development of highly efficient catalysts that are able to promote chemical reactions under mild conditions.In this work,a novel mesoporous poly(ionic liquid)with dual active sites was synthesized through a facile method that involves co-polymerization,post-synthetic metalation,and supercritical CO_(2)drying.Due to a high density of nucleophilic and electrophilic sites,the as-prepared poly(ionic liquid),denoted as P2D-4BrBQA-Zn,offers excellent performance in a CO_(2)cycloaddition reaction using epichlorohydrin as the substrate(98.9%conversion and 96.9%selectivity).Moreover the reaction is carried out under mild,solvent-free,and additive-free conditions.Notably,P2D-4BrBQA-Zn also efficiently promotes the conversion of various other epoxide substrates into cyclic carbonates.Overall,the catalyst is found to have excellent substrate compatibility,stability,and recyclability.

Carbon dioxide capture, enhanced-oil recovery and storage technology and engineering practice in Jilin Oilfield, NE China

This paper systematically presents the established technologies and field applications with respect to research and engineering practice of CO_(2) capture,enhanced oil recovery(EOR),and storage technology in Jilin Oilfield,NE China,and depicts the available series of supporting technologies across the industry chain.Through simulation calculation+pilot test+field application,the adaptability of the technology for capturing CO_(2) with different concentrations in oilfields was confirmed.The low energy-consumption,activated N-methyl diethanolamine(MDEA)decarburization technology based on a new activator was developed,and the operation mode of CO_(2) gas-phase transportation through trunk pipeline network,supercritical injection at wellhead,and produced gas-liquid separated transportation was established.According to different gas source conditions,liquid,supercritical phase,high-pressure dense phase pressurization technologies and facilities were applied to form the downhole injection processes(e.g.gas-tight tubing and coiled tubing)and supporting anti-corrosion and anti-blocking techniques.In the practice of oil displacement,the oil recovery technologies(e.g.conical water-alternating-gas injection,CO_(2) foam flooding,and high gas-oil ratio CO_(2) flooding)and produced fluid processing technologies were developed.Through numerical simulation and field tests,three kinds of CO_(2) cyclic injection technologies(i.e.direct injection,injection after separation and purification,and hybrid injection)were formed,and a 10×10^(4) m^(3)/d cyclic injection station was constructed to achieve"zero emission"of associated gas.The CO_(2) storage safety monitoring technology of carbon flux,fluid composition and carbon isotopic composition was formed.The whole-process anti-corrosion technology with anticorrosive agents supplemented by anticorrosive materials was established.An integrated demonstration area of CO_(2) capture,flooding and storage with high efficiency and low energy-consumption has been built,with a cumulative oil increment of 32×10^(4) t and a CO_(2) storage volume of 250×10^(4) t.

Anti-Melanogenesis Activity of Supercritical Carbon Dioxide Extract from Perilla frutescens Seeds

Perilla frutescens seed (PFS) oil is reported to inhibit skin photoaging;however, its effect on melanogenesis has not yet been investigated. Herein, we tested the anti-melanogenesis activity of an oil-based extract from PFS with supercritical carbon dioxide (scCO2). In a cell culture system, B16 mouse melanoma cells were treated with the PFS scCO2 extract and other samples. The PFS scCO2 extract decreased melanin production by approximately 90% in B16 mouse melanoma cells without cytotoxicity at 100 μg/mL. This effect was greater than that of the well-known melanogenesis inhibitor, kojic acid. Although a hexane-extracted PFS oil and a squeezed PFS oil also decreased melanin production in the B16 cells, the inhibitory effect of the PFS scCO2 extract was higher than both of these. Chemical analysis of the PFS scCO2 extract and squeezed PFS oil showed that almost 90% of the components of both oils were α-linolenic acid, linoleic acid, and oleic acid. Furthermore, the ratio of those three fatty acids across both samples was almost the same. When the three fatty acids were mixed in the same ratio as in the PFS scCO2 extract, the IC50 of the mixture for melanin production in B16 melanoma cells was identical to that of the PFS scCO2 extract. However, the IC50 of the squeezed PFS oil was approximately 6.6 times higher than that of the mixture. Although those fatty acids are the main inhibitory ingredients against melanin production in all of the extracts, some factor(s) in the squeezed PFS reduce their affinity with the cells. These results indicated that the PFS scCO2 extract could be a superior melanogenesis inhibitor. Although its main ingredients are probably the same as those of the squeezed PFS oil, it is necessary to extract with scCO2 for stronger anti-melanogenesis activity.

Adsorption of methane onto mudstones under supercritical conditions: Mechanisms, physical properties and thermodynamic parameters

Since the mechanisms of methane-mudstone interactions are important for estimating shale gas reserves,methane adsorption under supercritical conditions of 30 MPa pressure and 303.15,333.15,363.15 K temperatures was studied to measure the excess methane adsorption in two mudstone samples from Yanchang Formation,Ordos Basin.Excess adsorption features inflection points where the amount of adsorbed gas changes from increasing to decreasing concentrations.Three methods(fixed,slope,and freely fitted density)were applied to calculate the adsorbed-phase density(rad),which was then used to fit the measured excess adsorption.Two criteria,the goodness-of-fit and whether the fitting can obtain reasonable absolute adsorption,were applied to determine the most accurate model.Results indicated that the supercritical Dubinin-Radushkevich(SDR)model with freely fitted rad was the most reasonable model.The volume of adsorbed methane at 363.15 K is close to the micropore(d<2 nm)volume of the corresponding mudstone.Considering the actual geological conditions,the adsorbed gas should be predominantly stored in micropores.Thermodynamic parameters reveal that the methane adsorption on mudstone is a physisorption process that is jointly controlled by the heterogeneity of,and interaction forces between the methane molecule and,the rock surface.

Numerical simulations of supercritical carbon dioxide fracturing:A review

As an emerging waterless fracturing technology,supercritical carbon dioxide(SC-CO_(2))fracturing can reduce reservoir damage and dependence on water resources,and can also promote the reservoir stimulation and geological storage of carbon dioxide(CO_(2)).It is vital to figure out the laws in SC-CO_(2)fracturing for the large-scale field implementation of this technology.This paper reviews the numerical simulations of wellbore flow and heat transfer,fracture initiation and propagation,and proppant transport in SC-CO_(2)fracturing,including the numerical approaches and the obtained findings.It shows that the variations of wellbore temperature and pressure are complex and strongly transient.The wellhead pressure can be reduced by tubing and annulus co-injection or adding drag reducers into the fracturing fluid.Increasing the temperature of CO_(2)with wellhead heating can promote CO_(2)to reach the well bottom in the supercritical state.Compared with hydraulic fracturing,SC-CO_(2)fracturing has a lower fracture initiation pressure and can form a more complex fracture network,but the fracture width is narrower.The technology of SC-CO_(2)fracturing followed by thickened SC-CO_(2)fracturing,which combines with high injection rates and ultra-light proppants,can improve the placement effect of proppants while improving the complexity and width of fractures.The follow-up research is required to get a deeper insight into the SC-CO_(2)fracturing mechanisms and develop cost-effective drag reducers,thickeners,and ultra-light proppants.This paper can guide further research and promote the field application of SC-CO_(2)fracturing technology.