Research On Solubility And Kinetics For Methane And Carbon Dioxide Hydration Enhanced By Phase Change Slurry Of N-tetradecane

Gas hydrate is non-stoichiometric crystalline compounds formed by gas molecule and water molecules.With the considerable hydration heat released,so that the hydrate growth rate and water conversion to hydrate are inhibited severely.In our previous work,the phase change slurry?PCS?containing phase change material?PCM?of n-tetradecane was used to directly absorb the heat of the methane hydration in a semi-batch hydrator through the solid-to-liquid phase change of n-tetradecane.However,the limitations of data analysis and modeling were posed owing to the scarcity of phase equilibrium data of methane in n-tetradecane at low temperature.Therefore,a pressure-volume-temperature?PVT?setup is employed to measure the solubility of methane in n-tetradecane near hydration conditions through pressure drop method in this work.Meanwhile,the enhancement and kinetics of carbon dioxide hydration in phase change slurry?PCS?of n-tetradecane are also investigated.The following work is included in this paper:?1?The solubility of methane in n-tetradecane are experimentally measured at low temperatures of?279.15,283.15,288.15,293.15?K and pressures in the range of2.0-6.0 MPa by using a self-made PVT apparatus.The obtained solubility data are correlated with equations of state?EOS?of Peng-Robinson?PR?and Soave-Redlich-Kwong?SRK?combinedwiththetemperature-dependent one-parameter mixing rules,solubility equation based on K-K equation respectively.And COSMO-RS molecular simulation is employed to calculate the methane solubility theoretically for the purpose to check the experimental measurements.As the results of measurements and modelings show,the experimental data are regressed well.Then a comparison between the predicted results of the models and the data based on literature is performed,which demonstrates the reliability of our measurements for methane solubility in n-tetradecane.?2?CO₂ capture based on hydrate formation is intensified by oil-in-water phase change slurry?PCS?in which the n-tetradecane particles are taken as nucleation center and used to directly remove the hydration heat by their solid-to-liquid phase change.In this study,the experiments of hydration are conducted at the temperature277.6 K and under the isobaric pressures in the range of 2.1-2.4 MPa.All measurements are performed at a stirring speed of 450 rpm in the PCS of 25-45 wt%n-tetradecane.Two kinetics models,transport and reversible hydration,are established to regress and analyze the experimental data from the isothermal hydration of CO₂ in a semi-batch hydrator.For each model,the effects of pressure and composition are discussed in details.As the experimental results show,the induction time before the hydration initiates is less than 1 min for all runs,and the durations of the entire hydration are approximately 13-15 min for each measurement.Furthermore,the average hydration rate can reach 197 mol.m^-3.min^-11 at 2.3 MPa in oil-in-water PCS of45 wt%n-tetradecane,which demonstrates that the presence of n-tetradecane particles contributes significantly to the enhancement of hydrate formation rate.As the modeling results show,the parameters of the two models are determined by correlating the experimental data,and the interpretations of the measurements by the two models are satisfactory.