► CO–THF hydrate formation pressures are measured at different temperatures. ► We fit complete parameter values of CO required in Chen–Guo hydrate model for the first time. ► Hydrates formation ...conditions of different systems including CO are predicted by Chen–Guo model. ► The parameter values of CO fitted in this work are acceptable. The applied range of Chen–Guo hydrate model is extended.
With a fine accuracy and conciseness, Chen–Guo hydrate model has been widely applied to predict the hydrates formation conditions of different systems, including inhibitor containing systems and salt containing systems. However, the model could not predict the formation condition of carbon monoxide (CO) hydrates as the parameter values of CO required in the calculation are not available. In this work, CO hydrate formation pressures were measured at different temperatures in tetrahydrofuran (THF) solution first, then the parameter values of CO required in Chen–Guo model were fitted completely for the first time. On that basis, the hydrates formation conditions of different systems including CO were predicted by the model to verify the accuracy of the fitted values. The comparison between the predicted results and our experimental data (or literature data) shows that the absolute average deviation percentage (AADP) of structure I hydrates is no more than 1.481%, and the AADP of structure II hydrates is less than 6.796%. It is proved that the fitted parameter values of CO are credible, and Chen–Guo model is capable of predicting the formation conditions of CO hydrates. The experimental results and model modifications extend the applied range of Chen–Guo model and promote the development of CO hydrates thermodynamics research.
CO2 enhanced oil recovery has a great potential to improve the rate of oil production and store carbon dioxide emission. However, CO2 injection can destabilize the asphaltene-oil colloidal system and ...thus favor severe asphaltene particle deposition in porous reservoir formation. These block reservoir pores and change pore wetting condition, finally damage the porous reservoir formation and significantly reduce oil production. A good understanding on CO2-induced asphaltene deposition at a pore scale is of significance for CO2-EOR processes. Few studies have directly investigated the asphaltene deposition behavior and asphaltene-induced pore wetting alteration on a pore interior surface in a confined pore. In this study, we directly measured the CO2-induced asphaltene deposition behavior on the interior surface of a single pore under high pressure and temperature. The particle size and particle size distribution of CO2-induced asphaltene deposition on pore interior surfaces were directly measured and analyzed, by considering the influences of aging time and temperature. The results indicate that long aging period and elevated temperature could favor CO2-induced asphaltene flocculation and deposition on pore interior surfaces. Finally, the pore-scale wetting alteration caused by asphaltene deposition was quantified by direct pore contact angle measurements.
During oil recovery process, the equilibrium state of asphaltene–oil solution system and colloidal system in porous media is altered, which could cause asphaltene to precipitate from crude oil in ...rock pores. This severely results in the alteration of wettability, permeability, and porosity of formation and damages oil reservoir formation. Nanoparticles have recently been considered as effective asphaltene inhibitors. Several experimental works were carried out to study the impact of nanoparticles on asphaltene precipitation. The majority of these studies were performed using core-flooding experiments in bulk phase. However, few experimental investigations were performed to directly reveal the impact of nanoparticles on asphaltene aggregation based on the direct pore-scale visual evidence. In this work, a novel method was employed to make direct visualization and measurement on the kinetics of asphaltene aggregation in the presence of nanoparticles in a microcapillary. NiO, SiO2, and Fe3O4 nanoparticles were used. We directly measured the diameter and number and analyze size distribution of asphaltene aggregate particles in a microsized pore. The results indicate that the nanoparticles can significantly inhibit the aggregation of asphaltene particles in a microsized pore due to adsorption of asphaltene particles onto nanoparticle surfaces. The effect of nanoparticle concentration was investigated. Higher concentration of nanoparticles could contribute to the inhibition of aggregation of asphaltene particles. The asphaltene precipitation and aggregation can be prevented more effectively at higher concentration of asphaltene precipitant in the presence of nanoparticles.
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•Hydrate dissociation is directly studied and visualized using a microfluidic chip.•Dissociation manners of guest fluids (cyclopetane) are observed and investigated.•Size and size ...distribution of dissociated CP microdroplets are quantified.•Effects of salt and surfactant on hydrate dissociation are considered.
A concrete understanding of hydrate dissociation behavior is crucial for hydrate exploration and oil/gas transportation. A microfluidic chip has been used in this study to visualize cyclopentane (CP) hydrate dissociation. The results showed that during CP-pure water hydrate dissociation, the guest fluid (CP) released from the CP hydrate behaves like small CP microdroplets, forming a stable CP-in-water emulsion. The size and size distribution of the released CP microdroplets are quantified. The mean size of the microdroplets was around 5.3 μm, while the size distribution was within a narrow range of 4 to 9 μm. Fewer and less stable CP microdroplets were released from the CP-brine hydrate dissociation, while more significant coalescences of the CP microdroplets were observed at a higher salt concentration. For the CP-SDS system, a thick and stable emulsion layer was formed by the mass of tiny CP microdroplets released from the CP hydrate during hydrate dissociation.
The replacement process of CH4 from CH4 hydrate formed in NaCl solution by using pressurized CO2 was investigated with a self-designed device at temperatures of 271.05,273.15 and 275.05 K and a ...constant pressure of 3.30 MPa.The mass fraction of the NaCl solution was either 0.5 wt% or 1.0 wt%.The effects of temperature and concentration of NaCl solution on the replacement process were investigated.Experimental results showed that high temperature was favorable to the replacement reaction but high NaCl concentration had a negative effect on the replacement process.Based on the experimental data,kinetic models of CH4 hydrate decomposition and CO2 hydrate formation in NaCl solution were established.The calculated activation energies suggested that both CH4 hydrate decomposition and CO2 hydrate formation are dominated by diffusion in the hydrate phase.
•A novel hydrate-based gas separation model, namely the gas–water-hydrate three-phase flash model, was proposed.•The proposed model further considers the structural transitions of hydrates.•Four ...typical hydrate structure transformations are discussed through experiments.•The key parameters for calculating the degree of hydrate structural transitions were optimized.•The calculation results of the proposed model have an absolute average relative deviation of 8.00%.
The study introduces a pioneering model for hydrate-based gas separation technology, which enhances the prediction method for the coexistence of multiple structure hydrates. The calculated results demonstrate strong agreement with 96 sets of experimental data, exhibiting a lower average relative deviation of 8.00 % compared to the traditional model’s average relative deviation of 60.00 %. Furthermore, it offers a comprehensive discussion on the composition of hydrate structures in (H2 + CH4 + C2H6 + C3H8) during gas–water-hydrate equilibrium, providing a more precise depiction of hydrate structure evolution. Additional gas-hydrate equilibrium experiments were conducted for the (H2 + CH4 + C2H6 + C3H8) system to optimize the model parameters. The fitting goodness of the hydrate structure transformation formula (niI-Si formula) is enhanced from 0.9162 to 0.9816.
A pressure swing hydrate-membrane coupled separation (PSHMS) process was designed, and process simulation was conducted using a combination of Aspen Plus and Excel. PSHMS achieves continuous, highly ...efficient, and stable production of qualified gaseous products without thermodynamic promoters of hydrate or circulating working fluids. In hydrogen separation from diesel hydrogenation tail gas, PSHMS exhibits lower energy consumption and higher efficiency compared to hydrate-based separation technologies. Sensitivity analyses of various design parameters within PSHMS were performed through simulation, the results indicate that low temperature, high initial pressure, and high water content are all advantageous for improving separation efficiency. The selection of feed rates needs to be determined comprehensively based on the design parameters. The optimized unit energy consumption of PSHMS is merely 46.41 kJ/mol, significantly lower than the 117.94 kJ/mol of hydrate-based separation technology.
•Study of self-designed pressure swing hydrate-membrane coupled method (PSHMS).•The energy consumption of PSHMS is only 40% of that in hydrate-based separation method.•The operational approach of pressure swing separation mitigates hydrate blockage issues in pipelines.•Sensitivity analysis of design parameters in PSHMS was conducted.•Lower temperatures, higher pressures, and increased water content are conducive to effective performance.
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•Pretreatment could enhance cotton stalk (CS) hydrothermal conversion activity.•CS surface microstructure changed by pretreatments benefits hydrothermal bio generation.•The best ...bio-oil properties and CS conversion activity was realize by NaOH/EtOH pretreatment.•Pretreatment could be used as an important way to regulate the composition of bio-oil.
Conversion of agricultural and forestry waste biomass into high value-added bio-oil by mild hydrothermal method is of great significance to reduce the diesel consumption and alleviate the shortage of high-quality fuel oil supply. Most of the current research focuses on the parameter adjustment in the hydrothermal process, including temperature, time, catalyst and cosolvent, but the influence of the structure of raw materials on the hydrothermal conversion activity and the properties of hydrothermal oil is less. In this study, several typical pretreatment methods (including ball milling, alkali + ball milling, urea/NaOH and NaOH + ethanol) were used to change the structural characteristics of agricultural waste cotton stalks (CS), and the treated CS were used for hydrothermal conversion at low temperature (180–220 ℃). Taking the yield of hydrothermal bio-oil as index, the results show that various pretreatment can effectively improve the hydrothermal conversion activity of CS, improve the combustion performance of hydrothermal bio-oil and adjust the composition of hydrothermal oil. The hydrothermal bio-oil obtained by NaOH + EtOH pretreatment has the best properties, the yield is 7.41 % (wt, 220 ℃, 2 h), the calorific value is 24.16 MJ/kg, and the energy recovery is 10.98 %, which is higher than untreated CS bio-oil (with yield of 3.90 wt% at 220 ℃ and 2 h, calorific value is 23.32 MJ/kg and energy recovery of 10.98 %). The research will strengthen the role of lignocellulosic raw material structure in the hydrothermal process, which will play an important role in promoting the industrialization process of hydrothermal technology in the field of biomass, especially considering the optimization of operating parameters of various raw materials in the future industrialization.
Recovery of hydrogen from hydrogenation tail gas plays an increasingly important role as hydrogen is a clean and efficient energy source in petrochemical industry. Hydrate separation process is a ...high-efficiency and energy-saving hydrogen recovery technology. We are committed to the industrialization of hydrate separation process, and has completed a preliminary pilot test in Maoming Petrochemical Company. This work aims to conduct the process modeling and optimization of hydrate separation. The improved Chen-Guo model is used to simulate the mass transfer units (hydrate flash reactor, hydrate dissociation reactor), and the process simulation is realized by calling Excel in the Aspen Plus environment through the interface toolbox. After optimizing the key process operating parameters, the results show that decreasing flash temperature instead of increasing flash pressure can improve the energy utilization efficiency. Compared with the pilot test, the total energy consumption of optimization is reduced from 138.60 kW to 111.77 kW, saving 19.36% of energy consumption, and the energy consumption of optimization for rising hydrogen mole fraction by 1% per mol product gas is 2.277 kJ/mol, which is 15.88% lower than that of pilot test (2.707 kJ/mol).
•Modeling and optimization of hydrate-based gas separation process were established in Aspen plus.•The optimum operating conditions are obtained through sensitivity analysis of process parameters.•Decreasing operating temperature of hydrogen enrichment unit can improve the energy utilization efficiency.•The optimization reduces energy consumption by 19.36%.
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