Thermodynamic Evaluation of Membrane Based Oxyfuel Power Plants with 700°C Technology

Cryogenic air separation is the only available state-of-the-art technology for oxyfuel power plants and represents an important burden to the total plant efficiency. Nowadays, high temperature ceramic membranes, which are associated with significantly lower efficiency losses, are foreseen as the best candidate to challenge cryogenics for high tonnage oxygen production for this type of CCS power stations. In this study, two oxyfuel plant designs were developed, the first based on the state-of-the-art supercritical 600 degrees C hard coal plant Nordrhein-Westfalen and the second on the advanced ultra-supercritical 700 degrees C pulverized coal-fired power plant. The membrane-based air separation unit was modeled considering the three-end concept, where oxygen is transported across the membrane aided by a compressor at the feed side and by a vacuum pump at the permeate side. This paper analyzes the influence of both, the cryogenic and high temperature membrane air separation units on the net plant efficiency, considering the same boundary conditions and equivalent thermal integrations. Moreover, the oxygen permeation rate, heat recovery, and required membrane area are also evaluated at different membrane operating conditions. (C) 2011 Published by Elsevier Ltd.