ABSTRACT
It is commonly accepted that the increase of greenhouse gas emissions in the last century is at least one of the main reasons for global warming. Although carbon dioxide (CO₂) has, compared to other greenhouse gases, a low global warming potential (GWP), the large amount of CO₂ emissions accounts for 64% of all greenhouse gas emissions.
Various methods of carbon dioxide capture and storage (CCS) in fossil fuel power generation processes are proposed in the literature. The different methods can be classified into: pre-combustion CO₂ capture, oxyfuel combustion (integrated CO₂ capture), and post-combustion CO₂ capture. An example of a coal-based cycle with pre-combustion capture is an Integrated Gasification Combined Cycle (IGCC) with CO₂ capture. Semi-closed gas turbine combined cycles, oxyfuel-fired boiler and chemical looping combustion (CLC) processes belong to the cycles with integrated CO₂ capture.
Both, fuel decarbonisation and oxyfuel cycles, require oxygen enriched air or technically pure oxygen as an oxidant in the combustion process. Conventionally, the oxygen is produced by a cryogenic air separation unit (ASU). A major drawback of the ASU is its high demand of electrical or mechanical power. This leads to a high penalty in the efficiency of the power generation process. On this account, there is a need to develop new technologies for producing oxygen which can be utilised in power generation processes. High-temperature membranes seem to be a very promising option for this.
In this paper, the integration of membranes into an IGCC process is described. Computational simulations of an oxygen transport membrane (OTM) are carried out; operating conditions of the membrane are varied and their impacts on membrane performance with respect to oxygen permeation flow as well as implications regarding the steam power cycle are discussed