Storage Of C1-C4 In Natural Gas By Forming Hydrate

Natural gas is an important clean energy resource which is widely distributed in the world.It arouses much attention in many fields for its advantages such as various sources,low price and convenience.The storage and transportation of natural gas are the most concerned problems to date.At present,the major storage technologies are classified as compressed natural gas(CNG),liquified natural gas(LNG),adsorbed natural gas(ANG)and natural gas hydrate(NGH).The technology of NGH possesses good application prospect following the development of ANG.From previous report,natural gas storage using method of hydrate formation in a porous material can overcome the difficulty of kinetics that hydrates formed in pure water.Gas hydrate could form in milder conditions,thus this technology has potential value in application in the future.The key problem for hydrate storage technology is to seek materials with appropriate pore size distribution.Activated carbon is widely used for its rich pore,high surface area,stable chemical properties and low price.Therefore,activated carbon prepared from coconut shell charcoal and activated by KOH has a good activation effect.It has a small amount of mesoporous and rich microporous with pore size centered into 1~1.5 nm.Pore size,however,suitable for storage of natural gas hydrate centered into 1.6~3 nm.Thus,the important procedure for preparing activated carbon is to form much optimal pore which is suit for forming hydrate.We chose method of physical activation associate with chemical activation to prepare activated carbon.A small amount of CO2 was injected to widen the pore size by activating activated carbon which was activated by KOH before.In this paper,the specific surface area of activated carbon reached 2768 m2/g,the pore volume was 1.87 cm3/g,the optimal pore volume was 0.7 cm3/g and the peak value of pore size distribution was at 3nm.C1-C4 is the major component in natural gas.Hence,studying the impacts of each alkane for storage amounts when all of them formed hydrate has an important significance for storage and transportation of natural gas hydrate.The equilibrium isotherms of pure methane,ethane,propane and butane on activated carbon were measured using a volumetric method respectively at different temperature(275 K-281 K)and water content.According to the gas liquified pressure at different temperatures,we set different experimental pressure of methane at 0-10 MPa,ethane at 0-2.5 MPa,propane at 0-0.5 MPa and butane at 0-0.1 MPa.The results show that each alkane can form hydrate in nano-space and the maximum amount can reach 36.9mmol/g,46.7 mmol/g,17.3 mmol/g and 11 mmol/g respectively.At the same time,the multi-component dynamic penetration experiment was conducted and the influence of bulk density for each component was analyzed.The results show that the storage amount for each alkane firstly increases and then decreases with the increase of bulk density.