Kinetics Of Natural Gas Hydration Reaction Enhanced By NiMnGa Alloy Particles

Natural gas hydrate（NGH）is a potential clean energy and a new technology applied in the field of natural gas storage and transportation and gas separation.However,the slow mass and heat transfer properties of the gas-liquid system seriously restrict the rapid separation and storage of gas hydration.Based on the characteristics of large specific surface area and active Brownian motion,using Ni_52.5Mn_22.5Ga₂₅ alloy particles with both martensitic transformation and magnetic properties to accelerate the kinetic process of gas hydration reaction was proposed.In this paper,Ni_52.5Mn_22.5Ga₂₅ alloy particles were prepared.The microstructure,martensitic transformation behavior and magnetic properties of the particles were analyzed.The effects of system pressure,particle concentration,particle size and accelerator on the kinetic properties of NGH formation process were systematically studied.The hydration reaction rate equation containing the transformation latent heat of alloy particles was established.The mechanism of NiMnGa micro/nano fluid strengthening natural gas hydration reaction kinetics was revealed from the aspects of Ni_52.5Mn_22.5Ga₂₅ alloy particle characteristics and accelerator types.To solve the problem of slow heat and mass transfer in the process of rapid separation and storage of gas hydration.Considering the effects of pressure（0,6,10,15,20,40 MPa）,heat treatment temperature（800 or 700 ^oC）and composition（adding carbon element）on the phase transformation behavior,the microstructure,martensitic transformation and magnetic properties of Ni_52.5Mn_22.5Ga₂₅ alloy particles were systematically studied.The results indicate that the A_s and A_f of the three NiMnGa alloy particles are relatively stable under the condition of 0～15 MPa.Among them,when the pressure of P800 alloy particles increases to29 MPa,A_s,A_f,M_s and M_f all decrease by about 3 ^oC,andΔh shows a downward trend.The A_f of P700 alloy particles can be stabilized near 2 ^oC.When the pressure increases to 20MPa,A_f increases by about 4 ^oC,andΔh does not change much,about 3.5 J/g.The A_s and A_fof PC700 alloy particles decreased by 1 ^oC and 2 ^oC,respectively,after the pressure increased to 20 MPa.Compared with P700 alloy particles,A_s of P800 alloy particles increased and A_f decreased,A_s and A_f of PC700 alloy particles decreased andΔh increased.The results showed that the P700 alloy particles meet the condition that the reverse martensitic transformation temperature is closest to the NGH formation temperature（2 ^oC）at 6 MPa pressure.The martensitic transformation behavior of the particles has good thermal cycle stability.With the magnetic field increasing to 0.09 T,the reverse martensitic transformation temperature of the particles was stable.Before and after the formation of NGH,the structure of P700 alloy particles was stable.A dynamic rotating magnetic field gas hydration reaction experimental system was built independently.The system can collect the temperature and pressure change data of the hydration reaction process in real time.And the external rotating magnetic field enabled the NiMnGa alloy particles in the kettle to move in the base liquid,to realize the natural gas hydration reaction kinetics experiment enhanced by the NiMnGa alloy particles.The results indicate that NiMnGa-SDS system with different pressure,particle concentration and particle size can enhance the kinetic process of natural gas hydration reaction.Compared with SDS system,NiMnGa-SDS system can shorten the induction time of natural gas hydration process,increase gas consumption and gas consumption rate;with the increase of pressure,the effect of NiMnGa-SDS system on strengthening the kinetic process of natural gas hydration reaction is obvious.In the range of 0.1～3 wt.%,with the increase of particle concentration,the promotion effect is enhanced.The 3 wt.%NiMnGa-SDS system shortened the induction time of G1 gas hydrate by 98.4%,increased the gas consumption by50.7%and the gas consumption rate by 351.9%.With the increase of particle size,the average growth rate and induction time of the gas hydration process of NiMnGa-SDS system are enhanced to varying degrees.To further evaluate the synergistic strengthening effect of NiMnGa alloy particles with different accelerators,the kinetic experiments of NiMnGa-SDS,NiMnGa-TRP,NiMnGa-THF-SDS system enhanced natural gas hydration reaction were carried out under static and dynamic rotating magnetic fields.The results showed that the induction time of NiMnGa-SDS system was 84.9%shorter than that of NiMnGa-TRP system in static magnetic field,while the induction time of NiMnGa-TRP system was 85.2%shorter than that of NiMnGa-SDS system in dynamic magnetic field,and the gas consumption and gas consumption rate were increased by 7.3%and 49.5%,respectively.The induction time and gas consumption rate of NiMnGa-THF-SDS system is faster than those of other systems.The gas consumption rate of all systems under dynamic magnetic field conditions is faster than that of static magnetic field systems,and the dynamic rotating magnetic field NiMnGa-THF-SDS system enhances the kinetics of natural gas hydration reaction significantly.The effects of NiMnGa-SDS,NiMnGa-TRP,NiMnGa-THF-SDS and other systems on the kinetics of natural gas hydration reaction were evaluated.The results showed that NiMnGa micro/nano fluid had a significant strengthening effect.The latent heat of phase change of NiMnGa alloy particles was introduced into the rate equation of natural gas hydration reaction in the first growth stage of natural gas hydration reaction.The kinetic mechanism of strengthening natural gas hydration reaction was revealed from the aspects of latent heat of phase change,concentration,particle size and magnetic properties of NiMnGa alloy particles.The magnetic NiMnGa alloy particles can be used as a disturbance medium to increase the gas-liquid contact area under the action of dynamic magnetic field.The latent heat of martensitic reverse phase transformation of NiMnGa alloy particles provides a driving force for the hydration reaction process,thus strengthening the kinetic process of natural gas hydration reaction.