Carbon capture simulation

T vo carbon-capture processes have been studied in this chapter. Both use a two-column absorber/stripper flowsheet. The low-pressure amine system presents more problems in dynamic simulation than does the high-pressure physical absorption system. The plantwide control structures that are effective for the two systems are quite sunilar. 

In an effort to accurately predict the thermodynamic and transport properties of CO2 in mixtures with other components, typically found in the carbon capture and sequestration process, both molecular simulation... 

Babarao R, Dai S, Jiang D (2012) Nitrogen-doped mesoporous carbon for carbon capture— a molecular simulation study. J Phys Chem C 116 7106-7110... 

Similarly to any separation problem, the definition of the system boundary conditions is an essential prerequisite before simulations are performed. In the case of post-combustion carbon capture, the boundary conditions will correspond to the flue gas composition at the inlet, and the target purity specifications for pipeline transport at the outlet (Figure 2.1). 

Figure 10. Stochastic simulations. In the starting structure (A) one C atom is attached to the catalyst only two events are possible propylene capture followed by the 1,2- or 2,1-insertion. For the structure B four events are taken into account isomerization to the tertiary carbon, 1,2- and 2,1-insertions, and a termination. For the structures C, D and E five events are considered two isomerizations, two insertions and a termination. The probabilities of these events are equal for the structures C and E (in both cases two different isomerizations lead to a primary or secondary carbon at the metal), and different for the structure D (for which both isomerizations lead to the structure with a secondary carbon attached to the metal). For clarity, the numbers [(1), (2), and (3)] labeling different atom types (primary, secondary, and tertiary, respectively) are shown.

Our research has shown that activated carbons can be used to selectively capture NO, (NO and NO2) from flue gases at typical combustion stack temperatures (70-120 C) (1-3). Temperature programmed desorption releases NO2 at temperatures near 140°C. It is necessary for O2 to be present for this selective and large NO, adsorption capacity, but CO2 and H2O do not interfere with adsorption nor are themselves adsorbed to any significant level. The NO, adsorption capacity can be as high as 0.15 g NO,/g carbon using a simulated combustion flue gas containing 5% O2,15% CO2,1% H20,2% NO, balance He... 

Comparison of the common electrolyte solvents (EC, propylene carbcaiate [PC], dimethyl carbonate [DMC], EMC, vinylene carbonate [VC], dimethoxyethane [DME]) oxidative stability with experiments was reported by Zhang et al. [3]. While trends of the oxidative stability were reasonably captured in this study, typical deviations between experiments and simulations were reported to be around 0.5-1.0 V. Note that Zhang et al. [3] did not use the value of 1.4 V to convert from the absolute to Li /Li potential scale, instead they used the Li/LF and M/M" cycles with a number of calculated/estimated quantities, resulting in the absolute potential versus LF/Li being around 2.2 V. Application of the value of 1.4 or 1.54 V derived from SHE potential in water and acetonitrile and using the standard LF/Li vs. SHE potential will result in an improved agreement between QC-based values reported by Zhang et al. [3] and experiments. 

Xiang Z, Cao D, Lan J, Wang W, Broom DP Multiscale simulation and modelhng of adsorptive processes for energy gas storage and carbon dioxide capture in porous coordination frameworks. Energy Environ Sd 3(10) 1469—1487, 2010. 

To capture more accurately the behavior of the adsorbates in micropores, it is often necessary to model them as non-spherical molecules with electrostatic interactions. Given the limited capabilities of DFT in this context, molecular simulation based on the Grand Canonical Monte Carlo (GCMC) technique has been established for the generation of adsorption isotherms in carbons [15,16, 17] and the determination of PSDs [18, 19, 20, 21, 22,23, 24, 25, 26]. A review on both methods is given in [27]. 

Wang et al. [162] did perform a numerical study of hydrogen production by the SE-SMR process with in-situ CO2 capture. The SMR- and adsorption of CO2 processes were carried out simultaneously in a bubbling fluidized bed reactor. Enhanced production of hydrogen was achieved in the SE-SMR process compared with the conventional SMR process. The hydrogen molar fraction in the gas phase was near the equilibrium composition. The effects of inlet gas superficial velocity and steam-to-carbon ratio (or mass ratio of steam to methane in the inlet gas) on the process performance were examined. The reactor system design parameters used in the numerical simulation are listed in Table 4.14. 

A general sketch of the inlet-outlet boundary conditions which will be defined for the carbon dioxide capture process, according to the previous analysis, is presented on Figure 2.1. The membrane process simulation framework will be presented in the next paragraph, based on a binary feed mixture in a first step, as explained above. 

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