Oxy-combustion CO2 capture

Soundararajan, R. (2011) Efficiency loss analysis for oxy-combustion CO2 capture process, Norwegian University of Science and Technology - NTNU, Department of Energy and Process Engineering, Trondheim, Norway. 

Pre-, Post-, and Oxy-combustion CO2 Capture High- versus Low-Temperature Membrane Technologies... 

Table 39.3 Summary of O2 permeation properties of perovskite membranes under oxy-combustion CO2 capture conditions in the temperature range of 900-950°C.

Schematically, CO2 capture can be achieved following three main strategies (Figure 39.1) [12] (1) oxy-combustion (or oxy-fuel combustion) where the fuel combustion is performed with pure or enriched O2 instead of air, so that a CO2/ H2O mixture is produced (2) pre-combustion, where the carbon from the fuel is removed prior to combustion (decarbonization) either as CO2, as coke, or in other forms, and whereby the primary fuel heating value is transformed into H2 through partial oxidation, steam reforming, or autothermal reforming with subsequent water-gas shift (WGS) reaction and (3) post-combustion, where CO2 recovery is performed at the end of pipe from a wet exhaust flue gas, usually at 10-30% (v/v) CO2 concentration. The target separations to achieve in these processes to make them feasible are O2/N2 for oxy-combustion, CO2/H2 for precombustion, and CO2/N2 for post-combustion CO2 capture.

Table 39.1 Classification of inorganic membranes for oxy-, pre-, and post-combustion CO2 capture as a function of the operation temperature.

Given the unique MIEC properties of perovskites, these materials can be employed in the design of membrane-based solutions for CO2 capture. A general view of possible membrane implementation potentials is provided in Figure 39.1. We compile below the current developments of perovskite-based or -containing membranes for oxy-, pre-, and post-combustion CO2 capture scenarios, including membrane reactor applications. 

Until now, the reports of adsorptive separation of CO2 and other gases in a mixture by using MOFs, conducted by experimental separation process, are limited. Among various characterization methods in separation, the breakthrough experiment and gas chromatographic separation are simple and straightforward in the evaluation of the separation performance of a MOF toward a gas mixture. On the other hand, as previously mentioned, reported CO2 separation in MOFs mainly includes CO2/N2 separation for post-combustion capture, CO2/H2 from synthesis gas for pre-combustion capture, and O2/N2 and CO2/CO separation for oxy-combustion capture, which will be detailed as following. 

Figure 2.2 Pathways to CO2 capture (a) conventional combustion process without capture, (b) post-combustion, (c) pre-combustion, (d) oxy-fuel...

Figure 4.1 Block diagrams illustrating a membrane-based oxy-fuel combustion system for CO2 capture with ceramic membranes for oxygen separation from air integrated with the combustion process. (Source Reproduced with permission from Ref [6], Copyright 2011, The...

In this book, we have collected, in 11 chapters, information on novel possible intensified methods and reactors for sustainable energy conversion, including-but not limited to - novel concepts for chemical looping combustion, PI concepts for CO2 capture, oxy-ftiel and oxygen permeable membranes, blue energy and biomass conversion. 

Oxy-fuel combustion for power generation and carbon dioxide (CO2) capture... 

In Fig. 10.6, it can be seen that the plant modifications required to implement CO2 capture via oxy-combustion affect only the boiler and exhaust treatment units the steam cycle is largely untouched. This suggests that oxy-firing is well suited to retrofitting existing coal-fired power plants. 

Oxygen transport membranes have been proposed for plants using high purity O2 for fuel conversion. These include both plants that partially oxidize feedstocks to produce syngas, and power plants with CO2 capture based on oxy-fuel combustion. 

The cryogenic process is used on a large scale for air separation but cryogenic distillation does not seem to be currently considered as an alternative for CO2 capture, probably because of anticipated high costs when diluted streams are used [7]. However in the case oxy-fuel combustion technique where cryogenic air separation unit is implemented, it may be conveniently integrated with c ondensation units for separating water from CO2. 

Fossil fuels, such as carbon burning in a nearly pure O2 will produce a relatively small number of CO2, so capture CO2 from this system was defined as oxy-fuel combustion capture. So the gas separation in the oxy-fuel combustion capture is essentially of an O2/N2 separation to get pure O2. 

---