Optimization of a Membrane Process for CO sub(2) Capture in the Steelmaking Industry

Three different types of membranes were experimentally evaluated for CO sub(2) recovery from blast furnace effluents: semi-commercial adsorption selective carbon membranes, in-house tailored carbon molecular sieving membranes, and fixed site carrier (FSC) membranes with amine groups in the polymer backbone for active transport of CO sub(2). In the single gas experiments the FSC membranes showed superior selectivity for CO sub(2) over the other relevant gases (CO, N sub(2) and H sub(2)) and high CO sub(2) permeance (productivity). In addition, it is easy to process and handle, relatively inexpensive to produce and the water in the feed gas is an advantage rather than a problem, since the membrane must be humidified during operation. Based on these experiments a simulation study of a full scale process was performed. The technology showed notable low energy cost, even when converted to the thermal equivalent. Total costs for the CO sub(2) recovery unit (CO sub(2) prepared for pipeline transport) were estimated to be in the range 15.0-17.5 /tonnes CO sub(2).