Combustion, CO2 capture

Figure 11.9. Schematic representation of an NGCC power plant with post-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 . 

Keywords post-combustion, CO2 capture, regeneration, blends, heat of absorption. 

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. 

Another direction is towards the mixture of AMP and PZ, a solvent typically used for post-combustion CO2 capture. A model based on 52 calibration samples is currently being made and will be used and validated during several weeks of operation at an industrial pilot plant. 

Combinations of in-line measurement techniques with multivariate modelling show promising properties for nse as real-time monitoring applications of the liqnid composition in acid gas absorption processes. Both spectroscopic and non-spectroscopic analytical techniques can be nsed. Althongh the first developments were mostly aimed at predicting CO2 and amine concentrations in post-combustion CO2 capture processes, recent developments are also directing into applications involving acid gas removal from natural gas and the use of solvents that inclnde mixtures of two active components. 

To the best of our knowledge, up to now there is no experimentally reported CO2/N2 binary adsorption isotherms yet reported. So the calculated selectivity factors are useful for preliminary evaluations of MOFs in post-combustion CO2 capture. It was believed that for a high adsorption selectivity, the CO2 adsorption should be maximized at pressures near 0.15 bar. Theoretically, as the adsorbent for the post-combustion CO2 capture, it is expected that a MOF has such pore surface properties that can increase the adsorption selectivity and capacity toward CO2 yet... 

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. 

Besides tbe CO2/N2 selectivity and the CO2 uptake capacity, cyclability is another important factor in post-combustion CO2 capture. TSA and VSA are combined to test the cyclability of the polyamine-tethered PAFs. After 20 cycles, no capacity loss can be observed (Fig. 4.10). Although regeneration energy for PPN-6-CH2DETA with more primary amines species in the network are higher than those for mmen-CuBTTri [82] with only secondary amines, it is still lower than that for amine solution. 

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... 

CO2 capture from coal and natural gas fired power plants is important if the atmospheric CO2 levels are to be kept within accepted limits. Currently utilized commercial technology for CO2 separation from natural or synthesis gas is amine solvent-based absorption. But this process has its own drawbacks such as amine loss, handling of corrosive liquids, and removal of SO2 when applied to post-combustion CO2 capture [3]. Plus amine absorption process is not fiscally viable as the cost associated with it is around 80 % of the total CO2 sequestration cost [4]. Thus, efforts are being made to develop materials and methods that can significantly reduce the capture and storage costs along with efficient performance. 

M. Simmonds, P. Hurst, M. B. Wilkinson, C. Watt, C. A. Roberts, A study of very large scale post combustion CO2 capture at a refining petrochemical complex, 2003. www. CO 2captureproj ect. org. 

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... 

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. 

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. 

Goto, K., Yogo, K. and Higashii, T. (2013) A review of efficiency penalty in a coal-fired power plant with post-combustion CO2 capture. App/ted Energy, 111, 710-720. 

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. 

L. Hao, P. Li, T. Yang, T.-S. Chung, Room temperature ionic liquid/ZlF-8 mixed-matrix membranes for natural gas sweetening and post-combustion CO2 capture. Journal of Membrane Science 436 (2013) 221—231. 

In particular, the project is associated with a 25 tonnes per day COj capture plant, in which the flue gas is at atmospheric pressure and, apart from CO2 (about 11-12%), contains also other gases such as N2, O2, H2O, SO and NOj as well as particulate matter. For post-combustion CO2 capture, the project considers both the existing commercial separation techniques (solvent absorption with amino acid and potassium carbonate solvents) and also novel capture options, such as membrane and adsorption. With respect to the membranes, the programme includes the evaluation of the performance of module configurations under real flue gas conditions, and with respect to the membrane plant, two process options are available ... 

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. 

Combining post-combustion CO2 capture with CO2 utilization... 

For the near future, post-combustion CO2 capture will be one of the first options to be implemented. This will be based on retrofitting power-plants with an absorption-based process to separate the produced CO2 from the flue gas. The main cost for CO2 capture, and CCS in general, from large point sources, like power plants, refineries, and various industries (glass, cement) are associated with the thermal regeneration of the solvent. The solvent is used to remove selectively the CO2 from the gas stream, during the absorption step. The loaded solvent is regenerated thermally in the desorber. 

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