A flow sheet diagram for the process of converting of LNG of Krasnoyarsk region is considered. Process comprises reactors for oxidative methane coupling (OCM) and ethane dehydrogenation utilising heat of OCM reaction, products and reagent recycling and block of product separation, which operates at cryogenic temperature and atmospheric pressure. Mass and heat balances for different cases were calculated. It is shown that utilisation of LNG as a cooling agent has a beneficial effect on power consumption. Simulation shows that substantial increase of yield of ethylene (up to 50%) can be achieved even with a moderate performance catalyst of OCM.