| Natural Gas Hydrate(known as "flammable ice")has large reserves,high energy density,and clean combustion.It is expected to dominate the global energy supply in the future.The success of the continuous and stable trial production of "flammable icet" in the South China Sea waters indicates that China’s natural gas hydrate research has entered a new stage.However,how to economically and effectively transport the shattered hydrate slurry from the bottom of the sea to the sea surface has always been an important issue for researchers.In order to study the influence of flow parameters on pipe transport and determine the economic flow parameters of natural gas hydrate slurry transport to achieve goal for the minimum energy consumption required for the pipeline to transport unit gas hydrates.Therefore,the study on the characteristics of natural gas hydrate slurry transportation in pipeline was carried out.In this paper,numerical calculation methods were used to study the characteristics of the transmission for natural gas hydrate slurry.The research contents mainly include:the study on characteristics of hydrate slurry in the solid-liquid transportation section;the study on gas-liquid-solid section of hydrate slurry;the analysis of the optimal flow parameters based on response surface methodology.The results of the study are as follows:(1)In the solid-liquid transportation section of hydrate slurry,the critical velocity is judged based on the variation coefficient of uniformity in the horizontal tube,which is 26.52%.And the relationship between the critical flow rate and particle volume fraction,particle diameter,and solid-liquid density ratio were be fitted based on the different conditions.And the pressure loss increases with the increase of the flow rate in the horizontal pipe;The pressure loss increases linearly with the increase of the volume fraction of the solid particles.Besides,the pressure loss shows a decreasing change law with the increase of the particle diameter.As to the vertical pipe slurry,the pressure loss shows non-uniformity increases with the increase of the flow rate.The ratio of pressure loss first decreased when it is 3.5 m/s,which increased.The pressure loss exhibited the law of first increase and then decrease as the volume fraction of hydrate increased,when the volume fraction was 0.25,where is a minimum value for pressure drop.And the pressure loss decreases with increasing particle diameter.(2)In the hydrate-dissociation section of hydrate slurry,the mass fraction of gas produced from the hydrates decomposition presents a circular distribution rule with "less middle and more sides" along the cross-section in the pipeline.With increasing elevation,both the velocity distribution and the volume distribution of the particles appear to be firstly disturbed and then changed more smoothly.In addition,the gas generated by hydrate decomposition has a lifting effect on the slurry pipeline transportation,and the lifting flow velocity of the decomposition section should not be less than 2.5m/s.(3)During the analysis of the optimal flow parameters based on response surface methodology,the flow rate,the volume fraction of hydrate particles,and the particle diameter were the influencing factors.The pressure drop was an indicator.And optimal parameters of the horizontal pipeline were obtained:the initial flow rate was 4.02 m/s,and the volume of the hydrate particles was 0.2,the particle diameter was 4.94mm,the min total pressure drop was 0.562MPa;the optimal flow parameters of the vertical pipeline also be obtained,that was,the initial flow rate was 1.5m/s,the volume fraction was 0.23,the particle diameter is 5mm,the pressure of the natural gas hydrate slurry rises from the sea bottom to the sea surface need 15.48 MPa at least. |
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