Experimental Study On Formation Kinetics Of Methane Hydrate In Natural Active Biomass

As a cleaner forms of fossil energy,natural gas is widely used in industrial production and urban life.The large-scale application of natural gas is indispensable for efficient storage and transportation.Natural gas storage in the form of hydrate is recognized as an efficient technology with great potential.However,this technology’s application is critically challenged owing to its unsatisfactory practical formation rate and storage capacity.Therefore,how to enhance the formation kinetics of gas hydrate is important for the development of natural gas industry.Based this,this study is looking for a green environmental material to strengthen the formation kinetics of methane hydrate.Natural tobacco shred filtrates and tobacco granule filtrates with varying liquid to solid ratios（5–100）were made,and surface tension and active ingredient concentrations were determined.These solutions with surface activity were used in the experiment at8.0 MPa and 274.2 K to explore the kinetic characteristics of methane hydrate formation.Compared to pure water,the interface tension decreased by 38.5%–42.2%and 36.7%–47.5%in tobacco shred filtrates and tobacco granule filtrates.The content of active substance in tobacco shred solutions was significantly lower than that in tobacco granule solutions.When the liquid–solid ratio was low,tobacco shred solutions could store more gas in hydrate and had higher storage rate.When the liquid–solid ratio was large,tobacco granule solutions had better gas storage performance.Especially,the methane uptakes in tobacco granule solution with liquid–solid ratio of 50 reached 148.3cm³·cm^-3,and the rate up to 3.67 cm³·cm^-3·min^-1.In this study,a series of wet tobacco samples prepared by soaking different masses of tobacco shred/granules in water were used to store methane in the hydrate.Gas consumption experiments were conducted in an unstirred reactor to investigate the hydrate formation kinetics in the tobacco/water mixtures at 274.2 K and 8.0 MPa.The results demonstrated that the wet loose biomass materials provided abundant nucleation sites for gas to solid hydrates.Compared to pure water,the tobacco–water mixtures significantly shorten the induction time of nucleation and accelerate hydrate growth.The amount of methane stored in tobacco granule hydration systems ranged from 112.3to 160.3 cm³·cm^-3,and the storage rates reached 2.06–5.58 cm³·cm^-3·min^-1.The wet tobacco shreds exhibited higher gas uptakes(132.6–171.6 cm³·cm^-3)than the tobacco granule systems and tobacco shreds filtrates at the same liquid–solid ratio.The use of green wet tobacco samples to enhance of hydration should be helpful for the extension of hydrate-based technology.The tobacco filtrate with liquid–solid ratio of 5–200 and tobacco granule–water mixtures with liquid–solid ratio of 4–200 were filled into the honeycomb aluminum respectively,and hydrate methane storage experiments were conducted at 8.0 MPa.It was found that the effective thermal conductivity of the aluminum honeycomb/tobacco system was 5.524 W·m^-1·K^-1,which was 5.6 times higher compared to the tobacco filtrates.Compared the pure tobacco shred filtrates with liquid to solid ratio of 5–10 and the tobacco granule filtrates with liquid to solid ratio of 5–50,the methane hydrate formation kinetics in the composite system was increased.After filling the honeycomb aluminum with tobacco granule–water mixtures with liquid-solid ratio of 4–200,the composite system’s methane hydrate storage capacity improved by 0.4%–23.9%and the hydration rate increased by 2.6%–108.7%.Metals resulted in methane hydrate storage up to 113.6–130.7 cm³·cm^-3 and 123.4 cm³·cm^-3 in the tobacco shred filtrates（liquid–solid ratio of 20–100）and tobacco granule filtrates（liquid–solid ratio of 100）,respectively,with storage rates of 2.45–4.87 cm³·cm^-3·min^-1 and 4.28 cm³·cm^-3·min^-1,which had no gas absorption previously.The gas storage capacity was 155.5 cm³·cm^-3 at ratio of 200 and the storage rate up to 7.72 cm³·cm^-3·min^-1 in the honeycomb metal reinforced tobacco granule–water composite system’s.The surface active properties of natural tobacco solution effectively reduce the surface tension of water,and the rough and porous tobacco provides rich nucleation sites for gas–liquid crystallization and can effectively strengthen the nucleation and growth of methane hydrate.This discovery may help to explore effective environmental friendly biological accelerators and provide technical support for efficient gas storage of hydrate technology.