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In this work, CO2 conditioning processes for ship-based CCS sequestration are modelled using the software APSEN HYSYS V11. This study uses the captured CO2 gas from the 3D project as the feed. The feed stream contains water, H2S, and CO as contaminants. The purification processes for dehydration, desulfurization, and CO removal are reviewed. Two liquefaction approaches, the open-cycle and the closed-cycle liquefaction, are modelled and compared for transport pressures 7 and 15 bar. It is found that the energy requirement of the open-cycle process is higher than that of the closed-cycle liquefaction process. For the closed-cycle design, two refrigerants, ammonia and propane, are considered. Results show that the energy requirement of the process using ammonia is lower than that of propane. When comparing the two transport pressures, it is found that liquefaction at 15 bar requires less energy than 7 bar. On top of that, both refrigerants are unsuited for the liquefaction of CO2 at 7 bar, as their operating pressures are below 1 atm. Several optimization concepts are tested on the closed-cycle liquefaction design. The net power consumption of the closed-cycle liquefaction is reduced when CO2 is precooled using the intermediate pressure ammonia streams and the cold from the CO stripper. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide is essentially removed from the raw natural gas to meet the process, health, safety and environmental standards. Alkanolamine based absorption process remains the prevalent technique for hydrogen sulfide removal due to ease of operation and economic considerations. The design of such gas separation systems is a critical factor in meeting the stringent process requirements and optimizing operations. To achieve precise design, determination of vapor–liqid equilibrium for the system is indispensable while maintaining efficacy and simplicity. This study presents a simple model for estimating hydrogen sulfide solubility in aqueous alkanolamines and their blends in the high pressure-high gas loading region. The model equation is developed by considering and combining amine protonation and bi-sulfide formation reactions, assuming ideal liquid properties. Satisfactory correlated values of hydrogen sulfide loadings (0.21–3.15 mol gas/mole solvent) are obtained over a wide range of temperature (298.15–393.15 K), pressure (60–7027 kPa) and alkanolamine concentration (1.12–14.27 molal). Parameters are given for the hydrogen sulfide solubility in aqueous solutions of monoethanolamine, diethanolamine, N-methyldiethanolamine, 2-amino-2-methyl-1-propanol, piperazine, diglycolamine, di-isopropylamine, 1-amino-2-propanol and their selected blends. The model shall be useful for the design of alkanolamine based natural gas sweetening systems, operating at high pressure and high hydrogen sulfide gas loadings. [ABSTRACT FROM AUTHOR]

Direct catalytic methanation of CO2 (from CO2/CH4 biogas mixture) to produce biomethane was conducted in a pilot demonstration plant. In the demonstration project (MeGa-StoRE), a biogas desulfurization process and thermochemical methanation of biogas using hydrogen produced by water electrolysis were carried out at a fully operational biogas plant in Denmark. The main objective of this part of the project was to design and develop a reactor system for catalytic conversion of CO2 in biogas to methane and feed biomethane directly to the existing natural gas grid. A process was developed in a portable container with a 10 Nm3/h of biogas conversion capacity. A test campaign was run at a biogas plant for more than 6 months, and long-time operation revealed a stable steady-state conversion of more than 90% CO2 conversion to methane. A detailed catalytic study was performed to investigate the high activity and stability of the applied catalyst. [ABSTRACT FROM AUTHOR]