Analysis Of Hydrate-based Separation,storage And Transportation Technologies For Non-conventional Gases

With the increasing consumption of natural gas,the unconventional natural will gradually account 85%of the total natural gas consumption.However,the traditional technologies of gas separation,storage and transportation in unconventional natural gas supply chain do not have well economic performance.Recently,the exploitation technologies of hydrate reservoir were developed rapidly,as new technologies,hydrate-based technologies in gas separation,storage and transportation have been derived,which have the advantages of economic operating expense and low capital investment.Therefore,based on the natural gas supply chain,this dissertation proposed new processes for gas separation,storage and transportation of unconventional natural gas.Process simulation was applied and case studies were considered to explore the tech-economic performance of hydrate-based technologies in the unconventional natural gas supply chain through software.In the aspect of gas separation,the recovery of C₂H₆from oilfield associated gas in Caofeidian and recovery of CH₄from flooding exhaust gas were compared with traditional technologies.The sepecific energy consumption of C₂H₆recovery was taken as the key optimization objective to select the reaction pressure of hydrate-based separation at 274.15 K.The results show that the product with C₂H₆ concentration more than 90 mol%can be obtained by 9-stage hydrate-based separation in pure water.Among the proposed three hydrate-based processes,the lowest specific energy consumption of C₂H₆ recovery is 0.94 k Wh·kg^-1in pure water with gas recycle,which is lower than conventional cryogenic distillation.Additionly,recovering CH₄ from fire flooding exhaust gas was discussed between hydrate-based and pressure swing adsorption(PSA)processes.In terms of energy consumption for CH₄ recovery,the hydrate-based process shows advantage of sepecific energy consumption of CH₄recovery(0.65 k Wh·kg^-1)compared with PSA.In the aspect of gas storage,the second gas hydrate production in Shenhu Area of the South China Sea is analyzed as a basis of small-scale gas storage processes.Three kinds of gas storage technologies including hydrate-based(HNG),pressurized liquefied(PLNG),and compression(CNG)technologies,were simulated and optimized in terms of specific energy consumption(SPC),exergy efficiency,equipment weight and investment.The hydrate-based gas storage process is superior in SPC(0.21 k Wh·kg^-1),equipment investment($363273)and weight(33403 kg),and has high efficiency(64%)among the three processes,which provides a promising small-scale natural gas storage scheme in ship-based situation.Finally,the economic evaluation model(REC)of marine natural gas storage and transportation for HNG,PLNG,and CNG is established.Two key parameters including gas production rate and marine transportation distance were selected through sensitivity analysis.The economic storage and transportation intervals of the three storage and transportation modes are analyzed and calculated when the gas production and storage and transportation distance of hydrate gas wells change.HNG has economic advantages in the transportation distance range of 100-500 km.Compared with PLNG and CNG,HNG is found applicable for natural gas storage and transportation in the South China Sea.In present work,the hydrate-based technologies has tech-economic advantages compared with traditional processes through process simulation of software calculations.It is necessary to verificate its practical operability on a larger scale in the future.