Study On The Effect And Mechanism Of Nanomaterials On Hydrate Formation

Hydrates have many potentials for commercial applications,such as natural gas storage and transportation,CO₂ capture and storage,gas separation,seawater desalination,cooling media for air conditioning systems,etc.However,due to their harsh production conditions,low temperature and high pressure are required and the generation rate is slow.This greatly limits its commercial applications.Therefore,it is necessary to strengthen the formation process,speed up the formation rate,increase the gas storage capacity,and alleviate the formation conditions.At present,the effective means of promotion is the addition of promoter.The main traditional additives are THF,TBAB,and SDS.Although these promoters have great promotion effects,they are chemical additives,and the use of chemical additives will increase the difficulty of industrial wastewater treatment.Nanomaterials are insoluble in water,providing nucleation seeds for hydrate formation and promoting hydrate formation.Therefore,the effect of multi-walled carbon nanotubes on methane hydrate was studied.Two kinds of multi-walled carbon nanotubes were used for experiments,which are strong polar hydrophilicity MWCNT-NH₂ and non-polar hydrophobic MWCNT.The results of thermodynamic experiments show that multi-walled carbon nanotubes do not affect the thermodynamic conditions of hydrate.Kinetic data indicate that the promotion effect of hydrophilic MWCNT-NH₂ more significant.Comparing the promotion effects at different concentrations,it was found that the multi-walled carbon nanotubes had an optimum concentration?400 ppm?,promotion effect was less significant when the concentration was above or below 400ppm.Multi-walled carbon nanotubes are prone to aggregation due to the large specific surface area and excess surface energy.Meanwhile the effect of the combination with the micro-surfactant SDS has also been studied.It is found that the addition of multi-walled carbon nanotubes weakens the promotion effect of SDS.In order to explain the promotion effect on the hydration process from the perspective of carbon tube aggregation,carbon nanotube aggregation experiments at a microscale were carried out,and it was found that MWCNT-NH₂ has better dispersibility than MWCNT.The greater the concentration of multi-walled carbon nanotubes,contributes to the more severe the agglomeration.The addition of SDS will enhance the dispersion stability of multi-walled carbon nanotubes in water.In order to explore the effect of multi-walled carbon nanotubes on hydrate gas separation,a coalbed methane gas separation experiment was carried out,and it was found that the overall separation effect was not good,but the addition of multi-walled carbon nanotubes also has a weak promotion effect.Finally,based on the kinetic experiments,the kinetic model of methane hydrate growth was established.The results show that the model can describe the dynamic growth process of methane hydrate in the experimental system.