Study On Ethylene/Ethane Separations By Absorption

Today,75%of the world ’s petrochemical products were produced from ethylene,ethylene the leading products in petrochemical industry, promote the development ofworld economy. At present, China has become the second only to the USA in ethyleneproduction.Ethylene recycling from types of industrial gas can alleviate the ethylene marketsupplying shortage and reduce the pollution to atmosphere. Among many separationprocesses, pressure swing adsorption separation（PSA） method gained widespreadattention with low energy consumption, flexible operation, low cost of investment andoperation.In present work, mechanism of C₂H₄and C₂H₆adsorption on activated carbonwere studied, the influences of the adsorbent pore size, specific surface area,adsorption pressure and other factors on the ethane/ethylene gas separation propertieswere investigated. Provide the basic data to PSA for ethane/ethylene, and guide toadsorbent selection. Through improving the traditional PSA craft and optimizing theexperimental conditions, the product gas purity and yield effectively improved.According to the10-4-3potential model, C₂H₄and C₂H₆adsorption potentialenergy with different carbon pore size were calculated. The results indicate that,ethane adsorption potential energy is minimum at0.82nm while ethylene at0.76nm.ethylene Priority adsorbed with pore size of0.64nm-0.76nm, when pore size greaterthan0.76nm, ethane Priority adsorbed. Ratio of potential energy C₂H₄/C₂H₆reachmaxim with pore size of0.90nm, then descent with pore size increasing, finallychange little when H>2nm.According to calculation results, five kinds of activated carbon samples wereprepared. Ethylane adsorption capacity on the activated carbon is superior to ethylene,so that ethylene became the top product witch is beneficial to obtain high purityethylene product gas.Through determination breakthrough curves of five samples, separation factorunder different pressure were calculated, the results show that the separation factor increased firstly and then decreased with specific surface area increasing. C3whichbelong the highest pore volume of pore size0.76-2.0nm, its separation factor reachedmaximum1.53under0.1Mpa,By adding replacement steps to C₂H₄/C₂H₆separation experiment. C₂H₄turn totop products successfully, ethylene concentration and recovery rate obtain improving.The optimal conditions for C₂H₄/C₂H₆separation were gained though experiments,optimum inlet time is270s, the best replacement rate was150ml.min^-1, the optimalconditions for regeneration10min vacuum then blowing8min.