Pre-combustion CO2 capture

Coal gasification, which is used intensively in parts of the world, is also based on partial oxidation. Often the hydrogen is, however, not separated from the syngas, e.g. in the production of synthetic fuels. Coal gasification plays a role as a sub-process especially for the so called Pre-Combustion CO2 Capture . 

The design case is a case simulation CO2 capture to LNG specifications. As a secondary case, pre-combustion CO2 capture can be operated as well. In table 1, these cases are summarized. 

The base case (A) for the design of the equipment shall be based on capturing CO2 down to 50 ppm in de product stream, LNG specifications, from the synthetic natural gas feed. The other case (B) is capturing 90% of the CO2 from gas mixture that models the gas when pre-combustion CO2 capture is applied. The maximum absolute amount of CO2 captured in both cases is the same. 

At high temperature and pressure, a mixture of mostly H2, CO, CO2, and H2O is named synthesis gas (syn gas), which is produced by the steam reforming and partial oxidation of hydrocarbons or a combination of both processes (tandem reforming) in chemical industry [104]. The syn gas will produce H2 and CO2 through the water gas shift reaction at high pressure and slightly elevated temperature (5-40 bar and 313 K). In order to obtain pure H2 for further utilizations, pre-combustion CO2 capture, which refers to the separation of CO2 from H2 within the gas mixture, is required. 

Because its internal surface imparts little CO2/H2 selectivity, MOF-177 is thus a bad pre-combustion CO2 capture material. These two examples also indicated that the MOFs with high-surface area and CO2 capacity, however, may not be suitable for the pre-combustion CO2 capture. 

Martin CF, Stockel E, Clowes R et al (2011) HypercrossUnked organic polymer networks as potential adsorbents for pre-combustion CO2 capture. J Mater Chem 21 5475-5483... 

Merkel T.C., Zhou M., Thomas S., Lin H. and Serbanescu A. (2010), Novel Polymer Membrane Process for Pre-Combustion CO2 Capture From Coal-Fired Syngas, AIChE spring meeting 2010, San Antonio TX, paper 60b... 

More information about the power production is illustrated in the energy balance shown in Table 5.7. Here the CLC configurations are compared with an IGCC without CO2 capture and an IGCC with conventional Selexol pre-combustion CO2 capture. It is demonstrated that in the packed beds, more energy is produced by the gas turbine, because of the lower C02/H20-temperature, but this is for a large extent compensated by the higher electricity production by the steam turbines. 

Figure 6.1 Natural gas combined cycle with pre-combustion CO2 capture on the basis of the SERF concept [5, 6]. (Source Reproduced from Ref [5], with permission from Elsevier and reproduced with permission from Ref [61, Copyright 2006, american chemical society)...

Cobden, P.D., Van Beurden, R, Reijers, H.T.J. et al. (2007) Sorption enhanced hydrogen production for pre-combustion CO2 capture Thermodynamic analysis and experimental results. International Journal of Greenhouse Gas Control, 1,170-179. 

Wright, A., White, V, Hufton, J. et al. (2009) Reduction in the cost of pre-combustion CO2 capture through advancements in sorption-enhanced water-gas-shift. Energy Pro-cedia, 1, 707-714. 

The hydrogen plants described above serve as excellent platforms for pre-combustion CO2 capture because most of the feedstock carbon has been already converted to CO2 and separated as a relatively pure stream, ready for dehydration, compression, pipeline transport and geologic storage. The result is fossil fuel-derived hydrogen that has been decarbonized via pre-combustion CO2 capture. 

Since H2 is a good fuel for generating power, replacing the PSA with a combined cycle yields fossil fuel-derived electricity that has been decarbonized via pre-combustion CO2 capture. 

As discussed in Section 10.2.1, ATR is used today for large-scale production of syngas from natural gas, and is a promising basis for future power plants with pre-combustion CO2 capture. The same configuration described for IGCC plants (Fig. 10.7) can be adopted to integrate OTM into an 02-blown ATR-based power generation plant with pre-combustion capture. 

Hydrogen separation membranes can be used to produce H2-rich streams for either H2 production or power generation with pre-combustion CO2 capture. In the latter case, high purity H2 is not required since it is used to fuel a combustion turbine in fact, dilution with membrane sweep gases such as steam and N2 actually reduces NO, formation by reducing the stoichiometric combustion temperature. In H2 production, high purity H2 (>99.9%) is generally required and only steam, which is easily separated by condensation, can be used as a sweep gas. 

Damen K, Gnutek R, Kaptein J, Nannan NR, Oyarzun B, Trapp C, et al. Developments in the pre-combustion CO2 capture pilot plant at the Buggenum IGCC. Energy Procedia 2011 4 1214-21. 

Nord LO, Anantharaman R, BoUand O Design and offtdesign analyses of a pre-combustion CO2 capture process in a natural gas combined cycle power plant, Int J Greenh Gas Con 3 385-392, 2009. 

Figure 39.4 General scheme of a process based on two sequential steam reforming units implemented with proton-conducting membranes for pre-combustion CO2 capture. (Image adapted from Ref. [64].)...

Table 39.4 Summary of H2 permeation properties of perovskite membranes under pre-combustion CO2 capture conditions in the temperature range of 850-900°C,...

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