Principle and Method of Preparation of Explosive Micro-particles Through the Supercritical Anti-solvent Process

In explosive research area, one of important trends is to study on the preparation technology of explosive microparticles. A new principle and method based on supercritical anti-solvent (SAS) process is put forward and discussed for the preparation of explosive micro-particles. The satisfactory micro-particles of explosives can be obtained easily by its particular mechanism of creating micro-particles, and operating conditions at normal temperature. This method is good for further study and development.

Preparation and characteristics of nano-crystalline Cu-Ce-Zr-O composite oxides via a green route: supercritical anti-solvent process

The nano-crystalline Cu-Ce-Zr-O composite oxides were successfully prepared by the supercritical anti-solvent （SAS） process. The physicochemical properties and catalytic performances were investigated by X-ray diffraction （XRD）, Raman spectroscopy, H2 temperature-programmed reduction （H2 -TPR）, oxygen storage capacity （OSC） measurement and catalytic activity evaluation. It was found that Cu2＋ ions incorporated into CeO2 -ZrO2 lattice to form Cu-Ce-Zr-O solid solution associated with the formation of oxygen vacancies. The Cu-Ce-Zr-O catalysts prepared via the SAS process with the Cu content 2.63 mol.% showed the highest OSC index of 636.9 μmol/g. Compared with the samples prepared by impregnation method, Cu doping using SAS process could improve the dispersion of Cu2＋ in the composite oxide, enhance the interaction between Cu2＋ and CeO2-ZrO2 , improve the reducibility of catalyst, and thus improve the OSC performance and increase the catalytic activity for CO oxidation at low temperature.

Structures and oxygen storage capacities of CeO_2-ZrO_2-Al_2O_3 ternary oxides prepared by a green route:supercritical anti-solvent precipitation

CeO2-ZrO2-Al2O3 ternary oxides were successfully prepared by a green route of supercritical anti-solvent precipitation with supercritical CO2 as anti-solvent and methanol as solvent. The structures and oxygen storage capacities of these ternary oxides were characterized by XRD, Raman spectra and oxygen storage capacity measurements. It was found that Al3＋ and Zr4＋ inserted into CeO2 lattice, forming CeO2-ZrO2-Al2O3 solid solution. The concentration of aluminium isopropoxide in the solution affected the concentration of oxygen vacancy and the distortion of oxygen sublattice which were responsible for the oxygen storage capacity. The rapidest oxygen uptake/release rate and maximum total oxygen storage capacity （122.0 mmolO2/molCeO2） were obtained with the aluminitun isopropoxide concentration at 0.2 wt.% in the solution.

Hollow nano-particles formation for CuO-CeO2-ZrO2 via a supercritical anti-solvent process

Hollow CuO-CeO2-ZrO2nano-particles were prepared with supercritical anti-solvent apparatus by using methanol as sol-vent and supercritical carbon dioxide as anti-solvent. Two key factors （i.e., pressure and temperature） were investigated to explore the effects of catalyst structure and physic-chemical properties （i.e., morphology, reducing property, oxygen storage capacity and specific surface area）. The resulting materials were characterized with X-ray diffraction （XRD）, high resolution transmission electron micros-copy （HRTEM）, Brunauer-Emmett-Teller （BET）,hydrogen temperature programmed reduction （H2-TPR） and oxygen storage capac-ity （OSC） measurement, respectively. The experimental results showed that lower temperatures promoted production of hollow struc-ture nano-particulates. The particle morphology also changed significantly, i.e. the solid construction was first transferred to hollow structure then back to solid construction. The optimal conditions for obtaining hollow nano-particles were determined at 45 °C, 18.0–24.0 MPa.

Micronization of curcumin with biodegradable polymer by supercritical anti-solvent using micro swirl mixer

Curcumin is a hydrophobic polyphenol compound exhibiting a wide range of biological activities such as anti-inflammatory, anti-bacterial, anti-fungal, anti-carcinogenic, anti-human immunodeficiency virus, and antimicrobial activity. In this employed to produce the work, a swirl mixer was micronized curcumin with polyvinylpyrrolidone （PVP） by the supercritical antisolvent process to improve the bioavailability of curcumin. The effects of operating parameters such as curcumin/PVP ratio, feed concentration, temperature, pressure, and CO2 flow rate were investigated. The characterization and solubility of particles were determined by using scanning electron microscopy, Fourier Transform Infrared spectroscopy, and ultra-violet-visible spectroscopy. The result shows that the optimal condition for the production of curcumin/PVP particles is at curcumin/PVP ratio of 1：30, feed concentration of 5 mg·mL^-1, temperature of 40 ℃, pressure of 15 MPa, and CO2 flow rate of 15 mL·min^-1. Moreover, the dissolution of curcumin/PVP particles is faster than that of raw curcumin.

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.

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.

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.

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.

Enhancing the stability of astaxanthin by encapsulation in poly (1-lactic acid) microspheres using a supercritical anti-solvent process

To improve the physicochemical properties of astaxanthin, it was encapsulated in poly (1-lactic acid)(PLLA) using a supercritical anti-solvent (SAS) process with dichloromethane/acetone mixture as the solvent, and supercritical CO2 as the anti-solvent. The effects of altering five SAS operating cond让ions, solvent ratio, temperature, pressure, concentration of carrier, and flow rate, on the microstructure of particles were investigated using an orthogonal experimental design. Under the optimal conditions, astaxanthin/PLLA particles were produced with an encapsulation efficiency of 91.5% and a mean particle size of 954.6 nm. SEM images showed that most astaxanthin/PLLA particles were uniform microspheres. FT-IR spectra showed that the chemical structure of astaxanthin was unchanged by the SAS process. The results of chromatic difference, X-ray diffraction, thermogravimetric, and differential scanning calorimetry analyses showed that astaxanthin had been encapsulated in the PLLA matrix in an amorphous state. Overall, astaxanthin/PLLA microspheres greatly enhanced the stability of astaxanthin during storage, and the levels of residual solvents were far lower than the ICH lim让s. This means that astaxanthin/PLLA microspheres prepared using SAS show great potential for use in many food, cosmetic, and pharmaceutical formulations.

PURIFICATION OF BILIRUBIN AND MICRO-PARTICLE FORMATION WITH SUPERCRITICAL FLUID ANTI-SOLVENT PRECIPITATION

1 INTRODUCTIONA supercritical fluid is one existing at temperatures and pressures above its criticalpoint values(T_c,p_c) [1].Supercritical fluid has unconventional thermophysical prop-erties,exhibiting higher density,greater compressibility,lower viscosity between the gasand liquid extremes.Its solute binary diffusion coefficient is considerably higher thanthat in liquids[2-4].Supercritical fluid extraction(SFE)has been suggested as a viablealternative to other separation technologies.

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.

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.

Numerical simulation of flow and heat transfer of n-decane in sub-millimeter spiral tube at supercritical pressure

The flow and heat transfer characteristics of n-decane in the sub-millimeter spiral tube(SMST) at supercritical pressure(p = 3 MPa) are studied by the RNG k-ε numerical model in this paper. The effects of various Reynolds numbers(Re) and structural parameters pitch(s) and spiral diameter(D) are analyzed.Results indicate that the average Nusselt numberNu and friction factorNu increase with an increase in Re, and decrease with an increase in D/d(tube diameter). In terms of the structural parameter s/d, it is found that as s/d increases, the Nu first increase, and then decrease. and the critical structural parameter is s/d = 4. Compared with the straight tube, the SMST can improve Nu by 34.8% at best, while it can improve Nu by 102.1% at most. In addition, a comprehensive heat transfer coefficient is applied to analyze the thermodynamic properties of SMST. With the optimal structural parameters of D/d = 6 and s/d = 4, the comprehensive heat transfer factor of supercritical pressure hydrocarbon fuel in the SMST can reach 1.074. At last, correlations of the average Nusselt number and friction factor are developed to predict the flow and heat transfer of n-decane at supercritical pressure.

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.

Micro-mechanical properties of shale due to water/supercritical carbon dioxide-rock interaction

To investigate the impacts of water/supercritical CO_(2)-rock interaction on the micro-mechanical properties of shale,a series of high-temperature and high-pressure immersion experiments were performed on the calcareous laminated shale samples mined from the lower submember of the third member of Paleogene Shahejie Formation in the Jiyang Depression,Bohai Bay Basin.After that,grid nanoindentation tests were conducted to analyze the influence of immersion time,pressure,and temperature on micro-mechanical parameters.Experimental results show that the damage of shale caused by the water/supercritical CO_(2)-rock interaction was mainly featured by the generation of induced fractures in the clay-rich laminae.In the case of soaking with supercritical CO_(2),the aperture of induced fracture was smaller.Due to the existence of induced fractures,the statistical averages of elastic modulus and hardness both decreased.Meanwhile,compaction and stress-induced tensile fractures could be observed around the laminae.Generally,the longer the soaking time,the higher the soaking pressure and temperature,the more significant the degradation of micro-mechanical parameters is.Compared with water-rock interaction,the supercritical CO_(2)-rock interaction caused a lower degree of mechanical damage on the shale surface.Thus,supercritical CO_(2)can be used as a fracturing fluid to prevent the surface softening of induced fractures in shale reservoirs.

Existence of Supercritical Hopf Bifurcation on a Type-Lorenz System

In this paper, a system of Lorenz-type ordinary differential equations is considered and, under some assumptions about the parameter space, the presence of the supercritical non-degenerate Hopf bifurcation is demonstrated. The technical tool used consists of the Central Manifold theorem, a well-known formula to calculate the Lyapunov coefficient and Hopf’s Theorem. For particular values of the parameters in the parameter space established in the main result of this work, a graph is presented that describes the evolution of the trajectories, obtained by means of numerical simulation.

Optimization of Supercritical Extraction Process of Laoshan Black Tea by Response Surface Methodology

[Objectives]Laoshan black tea was subjected to supercritical CO_(2) extraction. [Methods]The extraction conditions of Laoshan black tea were studied by an orthogonal experiment and optimized by response surface methodology. [Results] The optimum extraction conditions of black tea extract by supercritical CO_(2) extraction were as follows: extraction pressure 23.53 MPa, extraction time 1.73 h, and extraction temperature 49.75 ℃, with which the extract yield could reach 5.15% theoretically. [Conclusions] Based on the traditional extraction process, a supercritical extraction method optimized by response surface methodology and a unique extraction process were formed, which enriches the extraction processes and methods of natural raw materials.