Dynamics Study On The Formation Of Methane Hydrate In An Impinging Stream Reactor

Gas storage and transportation by hydrate method was a new type of natural gas storage and transportation technology,which has the advantages of large capacity,environmental protection,mild storage and transportation conditions.However,gas storage and transportation by hydrate method are still in the laboratory stage.The main reasons hindering its industrial application are slow hydrate formation,high energy consumption and difficult hydrate removal.The formation process of hydrate was mainly affected by two factors,one was the gas-liquid mass transfer rate in the hydration process,and the other was how to quickly derive the heat of the reaction process.The diffusion rate was usually increased by adding additives such as SDS,TBAB,THF and CP to the liquid.Impinging stream technology was a new method to enhance heat and mass transfer in recent decades.Compared with traditional mechanical methods such as stirring,spraying and bubbling,impinging stream technology can effectively enhance heat and mass transfer between different phases.It has been successfully applied in many chemical unit processes.In this paper,a vertical liquid continuous impinging stream hydration reactor was improved on the basis of the original laboratory equipment.By applying impinging stream technology to the field of methane hydrate formation,the characteristics of methane hydrate formation in liquid continuous impinging stream reactor were investigated.The temperature and pressure in the reactor during hydrate formation of pure water and SDS were obtained by data acquisition instrument.The dynamic parameters such as gas consumption,reaction rate constant and space velocity of methane hydration reaction in two systems are analyzed,which can provide technical reference for the application of impinging stream technology in hydrate formation.The following results were obtained through experimental research:?1?The pressure variation with time during the formation of methane hydrate in two systems at different temperatures was investigated.The results show that the influence of temperature on the hydration process in pure water system?temperature greater than 0??ranges from 0.01 to 0.1 MPa at the end of the reaction,and from 0.01to 0.1 MPa in SDS system?temperature greater than 4??.?2?The formation characteristics of methane hydrate under different initial pressures were investigated.The results show that with the increase of initial pressure,the pressure in the reactor decreases slowly in the pure water system,but rapidly in the additive system.The gas consumption and hydration rate constant of the two systems increase with the increase of initial pressure.In pure water system,with the increase of initial pressure?4.5⁹.0 MPa?,the hydration rate constant increases from 2.73×10^-8mol²/?s J?to 5.28×10^-8 mol²/?s J?.In the presence of SDS,with the increase of initial pressure?3.5⁶.5 MPa?,the rate constant of methane hydration increased from 2.41×10^-8 mol²/?s J?to 4.29×10^-8 mol²/?s J?.?3?The formation characteristics of methane hydrate under different rotational speeds of the two systems were investigated.The results show that the slope of the system pressure curve increases with the rise of the rotational speed.By comparing the two systems,it can be found that the addition of SDS greatly promotes the formation of hydrate.Compared with pure water,the addition of SDS system can promote the formation of hydrate better even when the impinging strength is small.The gas consumption in the pure water system increases with the increase of the rotational speed,and the gas consumption in the additive system increases first and then decreases.Under the pure water system,the hydration reaction rate constant first increases and then decreases,the maximum value was 3.68×10^-8 mol²/?s·J?,while in the additive system,the hydration reaction rate constant increases with the increase of impact strength,with a maximum value of 4.61×10^-8 mol²/?s·J?.?4?The optimal concentration of SDS was 600 mg/L,the minimum induction time was 59 min,and the rotational speed was 600 r/min?impinging strength was 0.21?.?5?The activation energy Ea of the methane hydrate formation process under different initial pressure conditions of pure water and additive system was calculated to be 14.26¹6.8 kJ/mol and 19.30³0.26 kJ/mol,respectively.Methane hydrate was controlled by diffusion in the pure water system,and both diffusion control and surface reaction control in the SDS system.