ABSTRACT
Integrated gasification combined cycles (IGCC) exhibit conditions favourable to CO₂ sequestration. In this article, the Integrated Gasification Zero Emission Plant (IGZEP) concept is presented. The idea behind this concept is to use oxygen produced in a Mixed Conducting Membrane (MCM) reactor in an IGCC. The core of the membrane reactor is a ceramic membrane, which separates oxygen from air exiting the gas turbine compressor. The reactor operates at temperatures around 900°C and is driven by a difference in oxygen partial pressure. The oxygen permeating the membrane is used in a Texaco gasifier, whereas the oxygen depleted air is sent to a high temperature combustor. The rest of the cycle is essentially similar to a "standard" IGCC. The performed simulations result in a net cycle efficiency of 32,5 % (LHV). Despite this quite low efficiency, the IGZEP concept is interesting since one of the main reasons for the low efficiency is the low efficiency of the Texaco gasifier model used. Other models for Texaco gasifiers with higher efficiency have been found in literature. Nevertheless, it should be more interesting to look at the CO₂ capture penalty, which is 6,4 % (LHV), and to compare IGZEP’s penalty for oxygen generation with existing competitors’. It is showed that the oxygen production penalty can be decreased from 4,9 %points in the reference case to 4,3 %points in IGZEP. That is, about 0,6 %points in net efficiency can be gained by replacing the standard cryogenic air distillation unit with a MCM reactor. Other studies have also shown that this strategy can bring lower investment and electricity production costs. However, a measure to increase the net efficiency much more than using an MCM reactor is to replace the Texaco gasifier used in the IGZEP simulations with the more efficient Shell gasifier. This is however not possible as the IGZEP is presented in this article, and hence its fruitfulness is questionable. But if a way can be found to combine the MCM reactor with a Shell gasifier, the profitability would increase considerably.