Research On Efficient Synthesis Technology Of Natural Gas Hydrate Enhanced By Spiral Agitation

Hydrate based solid natural gas(SNG)technology has the characteristics of mild storage conditions and low cost,which is a very promising way of natural gas storage and transportation.The key to the application of this technology is the rapid generation of hydrate with high gas storage ratio.Although the current strengthening methods can effectively enhance the dynamics of hydrates,they usually require a large driving force,which is extremely detrimental to the industrial production of hydrates.Therefore,it is the premise of SNG technology application and promotion to realize the rapid growth of hydrate and guarantee the equivalent gas storage under mild conditions.This paper designed a new type of spiral stirring reaction device,the two kinds of working system(backspin and topspin)of methane hydrate formation experiments,assessment of the spiral stirring reaction kettle hydrate induction period,reservoir volume,morphology,growth rate and hydrate explores the helical mixing under the incentive of hydrate nucleation and growth kinetics,The flow field distribution under spiral agitation in the reactor was simulated by computational fluid dynamics(CFD),and the dynamic mechanism of hydrate enhancement by spiral agitation was revealed.Furthermore,in order to achieve rapid hydrate formation under mild conditions,amino acids and nanosphere accelerators were introduced into the spiral agitation reaction system,and the synergistic promotion effect of L-methionine and L-leucine with spiral agitation was evaluated.Three kinds of nanospheres(-SO₃^-,-COO^-and-N(CH₃)₃⁺)accelerators were prepared by emulsion polymerization.Finally,the synergistic mechanism of spiral agitation and accelerant was determined by means of hydrate growth rate analysis,morphology evolution evaluation and torque comparison.The results show that the mass transfer and the nucleation and growth kinetics of hydrate are greatly enhanced by the mechanisms of high dispersion,bidirectional convection,double agitation,continuous interface impact,surface fragmentation and microbubbles induced by spiral agitation.In pure water system,under the extremely mild conditions of 3.5 MPa,275.15 K and 60 rpm,the average induction time of hydrate is 3.9 min and 2.76 min,respectively,under the mild conditions of 5 MPa,275.15 K and30 rpm.The final gas storage capacity of hydrate can reach 144 V/V.The introduction of amino acids further reduced the hydrate growth conditions,spiral agitation guaranteed the excellent nucleation and growth kinetics of hydrate at the early stage of reaction,while the"secondary absorption"of amino acids enhanced the hydrate growth kinetics at the later stage,and the synergistic effect of the two greatly enhanced the hydrate kinetics under mild conditions.Compared with pure water system,80%conversion rate can be achieved at 3.5 MPa with 0.3 mmol/L L-methionine solution,and the gas storage capacity can reach 145 V/V,which is about 80%higher.The nanospheres showed similar promoting effect to amino acids.The induction period of 1 mmol/L-SO₃^-@PSNS solution was only about 2min under the mild condition of 3.8 MPa and 30 rpm,and the final conversion rate was as high as 94.03%.Considering the characteristics of easy preparation and low cost of nanospheres accelerator,It has a broader application prospect.In conclusion,the synergistic promoting effect of spiral agitation and amino acid/nanospheres proposed in this paper makes the rapid growth of hydrate possible under mild conditions,which provides technical support for the application and promotion of hydrate based solid natural gas technology.