PURPOSE: To remove CO2 and simultaneously to reutilize CO2 by removing CO2 and then uitlizing the removed CO2 in the process for synthesizing hydrocarbonic compds.
CONSTITUTION: The waste gas generated from a factory, for example, is sent to a CO2 absorption tower 2 through a waste gas line 1. CO2 is separed from NOx and SOx in the tower 2 by a CO2 separation membrane and absorbed into NaOH. The absorbed material is sent to a CO2 recovery tank 6 as it is the form of a slurry though a pipeline 3, CO2 is liberated therein by electrolysis, and NaOH as the by-product is sent to the tower 2 and reutilized. The CO2 liberated in the tank 6 is immediately introduced into a decomposition tower 8 contg. photocatalyst, and CO2 is decomposed into CO utilizing the sunlight as the decomposition energy. The formed CO is introduced into a synthesis tower 10 contg. a hydrogen catalyst and converted into 1-6 C hydrocarbons.