Experimental Study On The Synthesis Of Natural Gas Hydrate Under SDS System

Natural gas hydrate is characterized by green cleanliness and high gas storage capacity.It has wide application prospects in the fields of gas storage and transportation,desalination,petrochemical and cool storage,etc.At present,the key problem in hydrate technology is the high efficiency and rapid formation rates of natural gas hydrates.In the process of hydrate formation,there're a series of problems,sucn as,complex mass transfer,heat transfer,phase equilibrium,the lower formation rate and random nucleation.The study found that adding the sodium dodecyl sulfate(SDS)can significantly promote the formation of hydrates.And lower manufacturing costs are suitable for large-scale industrial production.Therefore,it is crucial that the phase equilibrium of methane hydrate formation conditions under SDS system is accurately predicted and the effect of solution concentration on the rate of hydrate formation and the capacity of gas storage is calculated.It is very important to study the thermodynamic conditions and kinetic parameters for the formation of natural gas hydrate under SDS system.This paper studied a series of thermodynamic equilibrium conditions experiments and the kinetic formation rate experiments of nature gas hydrate under the SDS system.The formation conditions of gas hydrate in submarine were simulated and hydrate device was designed by laboratory.The study of thermodynamics experiments based on the van der Walls-Platteeuw model and the method of dividing group contribution,and the contribution of different groups of Sodium dodecyl sulfate to the activity coefficient of water were calculated respectively by UNIFAC method and Aasberg-Petersen model.Therefore,a prediction model of methane hydrate formation conditions under SDS system was established.The maximum error of model is not more than 5%and the average error is less than 3%through experiment results.The good reliability of the model can provide accurate phase equilibrium data for hydrate dynamics research.It is found that SDS will affect the activity of water to improve hydrate formation condition by model calculation.When the concentration is 0.0015mol/L,the improvement is the best.Once the concentration is above 0.002mol/L,the hydrate formation condition will become difficult and hydrate formation will be inhibited.In the study of kinetic experiments,the dimensionless Gibbs free energy difference is used as the driving force and SDS concentration parameters is introduced,then put forward the growth rate model of hydrate growth which can accurately predict the hydrate growth rate and determine the application range.The experimental results show that compared with the pure water system,SDS can significantly shorten the induction time by solubilization and the induction time of hydrate formation is 20 times of the pure water system.However,when the concentration was too high,the induction period began to increase,it's not good for nucleation.During the rapid growth period,adding SDS can obviously accelerate the growth rate of hydrate in the rapid growth period.But it is not involved in the reaction process and does not affect its structural parameters.Calculated by the growth rate model,when the concentration of SDS is at 0.0015mol/L,the growth rate of the hydrate formation is the fastest.However,once the concentration exceeds this value,the growth rate is gradually inhibited.In addition,SDS can reduce the gap water,and the gas storage capacity of hydrates is increased from 70 to about 130.