環境・エネルギー問題と膜 温暖化ガス削減技術と膜利用「カルド型ポリマーを用いる二酸化炭素分離膜の開発」

Abstract

Cardo polyimide hollow fiber membranes were developed as an alternative to existing commercial amine absorption for CO2 capture from flue gases. To investigate the relationship between chemical structures and CO2 separation properties, various cardo polyimides were synthesized to measure CO2 separation properties, and some chemical structure was found to give remarkable properties both in CO2 permeation and selectivity. An asymmetric hollow fiber membrane of a bromated cardo polyimide showed excellent CO2 separation properties; CO2 permeation rate : 1.3×10-3 cm3 (STP) / (cm2 sec cmHg) (=1300 GPU, =7.5×10-9 Nm3/ (m2 sec Pa)) and CO2/N2 selectivity : 40. The permeation rate in an order of 10-3 cm3 (STP) / (cm2 sec cmHg) would be the first accomplishment in polymeric membranes.An economic analysis was carried out for CO2 separation using the hollow fiber membrane followed by a liquefaction process. The total cost of CO2 separation and liquefaction from an exhausted gas were estimated at 4, 900 JPY/t-CO2 for a flue gas from steel works (CO2 concentration : 26.8%). The equivalent cost of an amine absorption was 5, 300 JPY/t-CO2 for steel works. In the CO2 concentration around 25% or more, membrane separation has an advantage in the CO2 separation and liquefaction cost. Energy required in CO2 separation and liquefaction was 0.28 kWh/kg-CO2 for steel works.