Rapid hydrate formation and efficient gas separation based on aqueous solid carrier

The long hydrate induction time and limited gas-liquid contact area leads to slow hydrate formation rate and low water-hydrate conversion rate.Porous media are often used to promote hydrate formation because of their large specific surface area.Consequently,we used 3A molecular sieve as a water-carrying solid in this work,and investigated the dynamic renewal of the gas-liquid interface and its effect on hydrate formation.The formation kinetics of ethane hydrate was first measured in an aqueous molecular sieve system.Then the separation of(H_(2)+CH_(4)+C_(2)H_(6)+C_(3)H_(8))gas mixture was conducted via hydrate formation.The results show that the formation rate and gas storage capacity of ethane hydrate can be greatly improved by using aqueous molecular sieve.Compared with a pure water system under the same temperature and pressure,aqueous molecular sieve has obvious advantages in separation effect and energy consumption for separating gas mixtures.

The Impact of Solid Waste Generation, Storage and Separation Practices among Households on the Environment in Freetown

As urbanization and population growth continue to increase in Freetown, due to changes in economic, social, environmental, political, and demographic factors, the municipal solid waste (MSW) generation also continues to increase, making its management difficult for the municipal authority. Efficient separation and storage of solid waste at the source of generation can boost resource and energy recovery from MSW. This study examines the municipal solid waste management (MSWM) process, focusing on generation, storage and separation practices among households and their impact on the environment in Freetown. It emphasizes the inclusion of MSWM programs in primary schools to raise public awareness, the implementation of effective waste management practices, and the enforcement of related policies to enhance the MSWM sector, contributing to sustainable MSWM in Freetown. By utilizing both qualitative and quantitative methods, 393 structured questionnaires were administered across three selected sections to collect data on household solid waste storage and separation practices. The analysis employed descriptive statistics, using Origin-Pro9 and MS Excel. The findings show that with a population of 1.53 million people in Freetown, the per capita solid waste generation is 0.58 kg per day. The findings also show that 97% of the households have storage facilities as a result of the increase in awareness and education about the proper storage of solid waste. However, 96% of respondents do not practice separation of solid waste at the source of generation, which has become a concern among researchers in Sierra Leone. Additionally, 88% of respondents are unaware of ISWM principles, with only 12% aware, most of whom have received some education on proper solid waste management. The study recommends improving MSWM in Freetown to protect public health and the environment.

CFD studies on the separation performance of a new combined gas–solid separator used in TMSR-SF

In order to comply with discharge standards, a gas–solid separator is used to remove solid particles from the thorium molten salt reactor-solid fuel (TMSR-SF) system. As a key component, it directly determines system energy efficiency. However, current gas–solid separators, based on activated carbon adsorption technology, result in high pressure drops and increased maintenance costs. In the present study, a new combined gas–solid separator was developed for the TMSR-SF. Based on a simplified computational fluid dynamics (CFD) model, the gas–solid twophase flow and the motion trajectory of solid particles were simulated for this new separator using commercial ANSYS 16.0 software. The flow and separation mechanism for this structure were also been discussed in terms of their velocity effects and pressure field distributions, and then the structure was optimized based on the influence of key structural parameters on pressure and separation efficiency. The results showed that the standard k–ε model could be achieved and accurately simulated the new combined separator. In this new combined gas–solid separator, coarse particles are separated in the first stage using rotating centrifugal motion, and then fine particles are filtered in the second stage, giving a separation efficiency of up to 96.11%. The optimum blade inclination angle and numbers were calculated to be 45° and four, respectively. It implicated that the combined separator could be of great significance in a wide variety of applications.

Separation Properties of a New Polysiloxane-Anchored β-Cyclodextrin Derivative as Gas Chromatography Stationary Phase

A new capillary gas chromatography stationary phase, monokis (2,6 di O benzyl 3 O propyl (3’)) hexakis(2,6 di O benzyl 3 O methyl) β CD bonded polysiloxane, was synthesized. It exhibited separation abilities to disubstituted benzene isomers and some chiral solutes. It was also found that the polarity of CD derivatives can be lowered both by chemically bonding it to polysiloxane and by diluting it in polysiloxane. The separation abilities of the polysiloxane anchored CDs (SP CD) are higher than that of the unbonded CDs (S CD) and the diluted S CD at lower column temperature. Hydrosilylation reaction is one of the best methods to lower the operating temperature of CDs.

Separation and Characterization of Nitrogen-Rich Components in Coker Gas Oils from Athabasca Bitumen

It is well known that gas oils from oilsands bitumen are difficult to hydrotreat. In order to develop the most appropriate flow sheet and operating conditions, a thorough knowledge of the molecular structure and behaviour of bitumen and its gas oil products is needed. In this work, the gas oil samples are fractionated in an attempt to isolate and identify the problematic molecular species for hydrotreating. It is found that the major nitrogen sources in coker gas oils are associated with relatively small pentane insoluble species and an even smaller, highly polar, hexane insoluble species. Structural information obtained for these fractions indicates that they are formed during the cracking of resin molecules. Nitrogen speciation shows that the pyrroles are the primary nitrogen type, with pyridines also being an important species. Both nitrogen species are undesirable in the hydrotreating process. Pyrroles in particular are subject to polymerisation, producing gums and sediments that foul filters and other equipment while pyridines can directly deactivate the hydrotreating catalyst.

Performance of Inner-core Supersonic Gas Separation Device with Droplet Enlargement Method

To improve the separation performance of a supersonic gas separation device for the treatment of gas mixture with a single heavy component, a novel structure with shorter settlement distance was constructed and a method of droplet enlargement was applied. A series of experiments were carried out in the improved separation device under various conditions, using air-ethanol vapor as the medium and micro water droplets as nucleation cen- ters. The effects of the inlet pressure, temperature and relative humidity, the swirling intensity, and mass flow rate of water on the separation performance were investigated. The separation was improved by increasing the inlet pressure and relative humidity. With the decrease of swirling intensity and mass flow rate of water, the separation efficiency increased first and then decreased. The inlet temperature had a slight effect on the separation. The results showed that the separation performance was effectively improved using the proposed structure and method, and the best separation in this study was obtained with the ethanol removal rate about 55% and dew point depression 27 K. The addition of water had little pollution to the air-ethanol vapor system since the water carry-over rate was within the range of -2 %-0 in most cases.

On the feasibility of variable separation method based on Hamiltonian system for plane magnetoelectroelastic solids

The eigenvalue problem of an infinite-dimensional Hamiltonian operator appearing in the isotropic plane magnetoelectroelastic solids is studied. First, all the eigenvalues and their eigenfunctions in a rectangular domain are solved directly. Then the completeness of the eigenfunction system is proved, which offers a theoretic guarantee of the feasibility of variable separation method based on a Hamiltonian system for isotropic plane magnetoelectroelastic solids. Finally, the general solution for the equation in the rectangular domain is obtained by using the symplectic Fourier expansion method.

Applications of metal–organic frameworks for green energy and environment: New advances in adsorptive gas separation, storage and removal

The separation of gas molecules with similar physicochemical properties is of high importance but practically entails a substantial energy penalty in chemical industry. Meanwhile, clean energy gases such as H_2 and CH_4 are considered as promising candidates for the replacement of traditional fossil fuels. However, the technologies for the storage of these gases are still immature. In addition, the release of anthropogenic toxic gases into the atmosphere is a worldwide threat of growing concern. Both in academia and industry, considerable research efforts have been devoted to developing advanced porous materials for the effective and energy-efficient separation, storage, or capture of the related gases. In contrast to conventional inorganic porous materials such as zeolites and activated carbons, metal–organic frameworks(MOFs) are considered as a type of promising materials for gas separation and storage. In this contribution, we review the recent research advance of MOFs in some relevant applications, including CO_2 capture, O_2 purification, separation of light hydrocarbons, separation of noble gases, storage of gases(CH_4,H_2, and C_2 H_2) for energy, and removal of some gaseous air pollutants(NH_3, NO_2, and SO_2). Finally, an outlook regarding the challenges of the future research of MOFs in these directions is given.

Economic Comparison of Three Gas Separation Technologies for CO2 Capture from Power Plant Flue Gas

Three gas separation technologies,chemical absorption,membrane separation and pressure swing adsorption,are usually applied for CO2 capture from flue gas in coal-fired power plants.In this work,the costs of the three technologies are analyzed and compared.The cost for chemical absorption is mainly from $30 to $60 per ton(based on CO2 avoided),while the minimum value is $10 per ton(based on CO2 avoided).As for membrane separation and pressure swing adsorption,the costs are $50 to $78 and $40 to $63 per ton(based on CO2 avoided),respectively.Measures are proposed to reduce the cost of the three technologies.For CO2 capture and storage process,the CO2 recovery and purity should be greater than 90%.Based on the cost,recovery,and purity,it seems that chemical absorption is currently the most cost-effective technology for CO2 capture from flue gas from power plants.However,membrane gas separation is the most promising alternative approach in the future,provided that membrane performance is further improved.

Effect of montmorillonite on hydrate-based methane separation from mine gas

Three types of mine gas samples were used in the solutions of tetrahydrofuran(THF),sodium dodecyl sulfate(SDS)and THF-SDS with/without MMT respectively to investigate the effect of montmorillonite(MMT)on separation characteristics of methane recovered from mine gas based on hydrate method.The partition coefficient,separation factor and recovery rate were used to evaluate the effects of MMT,and the selection factor was primarily proposed to define the selectivity of mine gas hydrate in the relative target gases.The experimental results indicate that MMT could improve the following factors including hydration separation factor,the selection factor,the partition coefficient,and the recovery rate.Furthermore,the effect of SDS on the function of MMT is analyzed in the process of hydration separation.Finally,due to the results of the experiment,it is concluded that MMT hydration mechanism explores the effect of MMT enrichment methane from mine gas.

The combination of 1-octyl-3-methylimidazolium tetrafluorborate with TBAB or THF on CO2 hydrate formation and CH4 separation from biogas

[C_8min] BF_4 was used in this work to combine with TBAB or THF for the investigation about thermodynamic and kinetic additives on CO_2 and CH_4/CO_2 hydrates. The results show that [C_8min] BF_4 has the inhibition effect on the equilibrium of hydrate formation. About the kinetic study, [C_8 min] BF_4 could improve the rate of CO_2 hydrate formation and increase the gas uptake in hydrate phase. At the same time, the combination of TBAB and [C8 min] BF_4 could increase the mole friction of CH_4 in residual gas comparing with the data in THF solution. CH_4 separation efficiency was strongly enhanced. Since that the size of CO_2 and CH_4 molecules are similar, CH_4 and CO_2 could form the similar hydrate, so the recovery of CH_4 from biogas decreases lightly. The CH_4 content in biogas can purified from 67 mol% to 77 mol% after one-stage hydrate formation. In addition, the combination of THF and[C_8 min] BF_4 do not have obvious promoting effect on CH_4 separation comparing with the gas separation results in pure THF solution.

Separation of Fine Particles by Using Colloidal Gas Aphrons

This paper presents a method of separation of fine particles, of the order of a few microns or less, from aqueous media by flotation using colloidal gas aphrons (CGAs) generated in aqueous solutions. More than 150 experiments were conducted to study the effects of surfactant type, surfactant concentration, CGAs flow rate, and particle concentration on the removal efficiency (fine particles of polystyrene were used as a target compound). The results indicate that CGAs, generated from cationic surfactant of hexdecyltrimethyl ammonicum bromide (HTAB) and anionic surfactant of sodium dodecylbenzne sulfonate (SDBS), are an effective method for the separation off ine particles of polystyrene from wastewater. The flotation yields are higher than 97%.

Performance assessment of an inline horizontal swirl tube cyclone for gas-liquid separation at high pressure

The application of swirl tube cyclone for gas-liquid separation is attractive due to its small size and weight. However, very scarce information on the performance of the swirl tube cyclone especially at high operating pressure emulating actual field condition was published in journals. Performance assessment was usually done at a low operating pressure using either air-water, air-fine particle mixtures or dense gas such as SF6 . This paper fills the existing gaps and reports the initial findings on the performance assessment of a horizontal swirl tube cyclone for gas-liquid separation operating at a flow rate of 5 MMSCFD at 40-60 bar operating pressure.

Capture and separation of CO_(2) from flue gas by coupling free and immobilized amines

A novel system was proposed for the capture and separation of CO 2 from flue gas. In this method, a resin was employed to regenerate the amine capturing CO 2 from flue gas at room temperature. The feasibility for the resin to regenerate amines such as MEA, MAE, TEA, and ammonia was demonstrated. It was also discovered that the resin could be regenerated by hot water.

Separation of primary solid phases from Al-Si alloy melts

The iron-rich solids formed during solidification of Al-Si alloys which are known to be detrimental to the mechanical,physical and chemical properties of the alloys should be removed.On the other hand,Al-Si hypereutectic alloys are used to extract the pure primary silicon which is suitable for photovoltaic cells in the solvent refining process.One of the important issues in iron removal and in solvent refining is the effective separation of the crystallized solids from the Al-Si alloy melts.This paper describes the separation methods of the primary solids from Al-Si alloy melts such as sedimentation,draining,filtration,electromagnetic separation and centrifugal separation,focused on the iron removal and on the separation of silicon in the solvent refining process.

Studies on Oxygen Characteristics of YBa_2Cu_3O_(7-x) and Its Applications to Air Separation and Gas Purification

Oxygen diffusion and oxygen selective adsorption properties of rare earths material YBa_2Cu_3O_(7-x) (YBCO) were investigated by thermogravimetric, oxygen static adsorption and selectivity adsorption experiments. The results show that YBCO is a very good deoxidizing material. The oxygen desorption of YBCO begins remarkably at about 400 ℃, mass loss can arrive at 1.2% of its original quantity at 800 ℃. Oxygen can be completely absorbed back into the sample again when temperature descends to 400 ℃. The oxygen adsorption selectivity, reproducibility and oxygen adsorption under very low oxygen partial pressure make the material desirable for air separation and gas purification. High purity nitrogen gas was produced with the YBCO molecular sieves in the air separation and gas purification experiments. 0.017 m^3 of high purity nitrogen (>99.9999%) can be obtained with 1 kg YBCO molecular sieve in one cycle. As a deoxidant, an obvious advantage of YBCO is that no hydrogen is needed in its applications.

Rapid and real-time analysis of multi-component dissolved gas in seawater by Raman spectroscopy combined with continuous gas-liquid separator

Rapid and sensitive detection of dissolved gases in seawater is quite essential for the investigation of the global carbon cycle.Large quantities of in situ optical detection techniques showed restricted measurement efficiency,owing to the single gas sensor without the identification ability of multiple gases.In this work,a novel gas-liquid Raman detection method of monitoring the multi-component dissolved gases was proposed based on a continuous gas-liquid separator under a large difference of partial pressure.The limit of detection(LOD)of the gas Raman spectrometer could arrive at about 14 μl·L^(-1)for N_(2)gas.Moreover,based on the continuous gas-liquid separation process,the detection time of the dissolved gases could be largely decreased to about 200 s compared with that of the traditional detection method(30 min).Effect of equilibrium time on gas-liquid separation process indicated that the extracted efficiency and decay time of these dissolved gases was CO_(2)>O_(2)>N_(2).In addition,the analysis of the relationship between equilibrium time and flow speed indicated that the decay time decreased with the increase of the flow speed.The validation and application of the developed system presented its great potential for studying the components and spatiotemporal distribution of dissolved gases in seawater.

A pillared-layer metal-organic framework for efficient separation of C_(3)H_(8)/C_(2)H_(6)/CH_(4) in natural gas

Metal-organic frameworks(MOFs)have great potentials as adsorbents for natural gas purification.However,the trade-off between selectivity and adsorption capacity remains a challenge.Herein,we report a pillared-layer metal-organic framework Ni(HBTC)(bipy)for efficiently separating the C_(3)H_(8)/C_(2)H_(6)/CH_(4) mixture.The experimental results show that the adsorption capacity of C_(3)H_(8) and C_(2)H_(6) on Ni(HBTC)(bipy)are as high as 6.18 and 5.85 mmol·g^(-1),while only 0.93 mmol·g^(-1) for CH_(4) at 298 K and 100 kPa.Especially,the adsorption capacity of C_(3)H_(8) at 5 kPa can reach an unprecedented 4.52 mmol·g^(-1) and for C_(2)H_(6) it is 1.48 mmol·g^(-1) at 10 kPa.The ideal adsorbed solution theory predicted C_(3)H_(8)/CH_(4) selectivity is as high as 1857.0,superior to most of the reported materials.Breakthrough experiment results indicated that material could completely separate the C_(3)H_(8)/C_(2)H_(6)/CH_(4) mixture.Therefore,Ni(HBTC)(bipy)is a promising material for separation of natural gas.

Evaluation of gas-liquid separation performance of natural gas filters

Fibrous filters are often used to remove contaminants including both dusts and liquid droplets from natural gas. This paper aims to evaluate the gas-liquid separation performance of three types of cartridge filters used in the West-East natural gas transmission project. The comparison of the original pressure drop of clean filters and the evolution of pressure drop as liquid droplets deposited in the filter media are described. The original pressure drops of these filters were similar but the pressure drops at a steady state were different. Fractional efficiency was used to study the separation performance of cartridge filters. Droplets at the outlet of the filters had small diameters, no more than 3 μm, but were very numerous. The effect of filtration velocity on gas-liquid separation performance was analyzed. Higher filtration velocity indicated better gas-liquid separation performance. Finally the quality factor related to pressure drop and filtration efficiency was applied to evaluate the gas-liquid separation performance.

Separation of methane from different gas mixtures using modified silicon carbide nanosheet: Micro and macro scale numerical studies

This research discusses the separation of methane gas from three different gas mixtures,CH4/H2 S,CH4/N2 and CH4/CO2,using a modified silicon carbide nanosheet(Si CNS)membrane using both molecular dynamics(MD)and computational fluid dynamics(CFD)methods.The research examines the effects of different structures of the Si CNSs on the separation of these gas mixtures.Various parameters including the potential of the mean force,separation factor,permeation rate,selectivity and diffusivity are discussed in detail.Our MD simulations showed that the separation of CH4/H2 S,and CH4/CO2 mixtures was successful,while simulation demonstrated a poor result for the CH4/N2 mixture.The effect of temperature on the diffusivity of gas is also discussed,and a correlation is introduced for diffusivity as a function of temperature.The evaluated value for diffusivity is then used in the CFD method to investigate the permeation rate of gas mixtures.