Coal is playing a major role as a reductant and as an energy source in the present world steel production due to its low cost and widespread distribution around the world. At the same time, being the largest contributor to global CO2 emissions, coal faces significant environmental challenges in terms of air pollution and global warming. Hydrogen is a promising alternative for coal in lowering the steel industry's CO2 footprint, but the availability of green hydrogen is currently limited by its high production cost. This research study focuses on developing a pressure swing adsorption (PSA) technology that will allow for continued use of coal for a smooth transition towards green hydrogen-based steel production, by better utilisation of its by-product coke oven gas to produce high purity hydrogen. A generic, fast and robust simulation tool for simulating a variety of PSA processes considering both equilibrium and kinetic effects using a detailed non-isothermal and non-isobaric model is developed in the study. The adsorption equilibrium data required for the model are calculated from experimental results using the non-linear regression data fitting method. A series of rigorous parametric studies and breakthrough tests are performed using the developed mathematical model for better understanding of the effects of different factors on the PSA process performance. With the better understanding obtained from the above-mentioned parametric studies, the model is optimised by performing several simulation tests to achieve a high process performance in terms of purity and recovery of the H2 product, productivity of the adsorbents and energy consumption for compression of gases. The optimised 14-step multi-bed PSA cycle developed in this study allows for an improved energy efficiency of coal usage by better utilisation of its by-product coke oven gas by converting it into valuable high purity (>99.999%) hydrogen product with a recovery of over 75%.

A molecular modeling study was carried out on linear polyethyleneimine (LPEI) to determine the CO2 capturing process taking into account structural changes of the material at various amounts of H2O. Until now, CO2 capture by LPEI was described as a combination of carbamic and carbonic acid formation. It was found that humidification below the melting point of LPEI leads to the formation of an LPEI/0.5H2O type of phase. Such a type of phase leads to CO2 capture exclusively via carbonic acid formation, stabilized by secondary amines via ammonium bicarbonate and H-bridged amine carbonic acid complexes. Both the strong physisorption CO2 complex and the low activation barrier for carbonic acid formation contribute to the overall process. Only in the absence of H2O, carbamic acid formation is possible. Thus, under CO2 capturing process conditions, carbonic acid formation seems to be the only option as H2O will be present in flue gas.

Since 2012, Lewatit R VP OC 1065 was reported as a promising material for direct air capture of CO₂. However, deactivation at a high pressure of CO₂ at 120 °C was reported with detrimental effects on its application. In this study, using density functional theory calculations, a quantitative description of the deactivation mechanism in the presence of CO₂ is presented. Deactivation by CO₂ follows a three-step mechanism. The first step in deactivation of the resin is self-catalyzed formation of a carbamic acid from an amine group and CO₂. The second step is decomposition of a carbamic acid to an isocyanate as the rate-determining step with an activation barrier of 144.4 kJ/mol. The third step is the H₂O-catalyzed addition of a benzyl amino group to the isocyanate, yielding an urea species, responsible for deactivation. However, the process can be made reversible by optimizing H₂O and CO₂ concentration and temperature. The identified deactivation mechanism quantitatively explains the differences between experimental CO₂ sorption data and the earlier reported dual site Langmuir model. ©

Carbon dioxide (CO₂) can electrochemically be converted to a range of products including formic acid (HCOOH) and acetic acid (CH₃COOH). The yield of the products in an electrolysis cell depends on the solubility of CO₂ in the (aqueous) mixture. In absence of experimental data, Monte Carlo simulations in the Gibbs ensemble are used to compute the VLE of the binary systems, CO₂-H₂O, CO₂-HCOOH and CO₂-CH₃COOH, and the ternary systems, CO₂-HCOOH-H₂O and CO₂-CH₃COOH-H₂O. In addition, the PC-SAFT equation of state (EoS) is used to model the VLE of these strongly associating mixtures. Both methods correctly predicts the liquid-phase compositions, but the gas-phase compositions are less accurately described. The challenges to model these systems are related to the simultaneous formation of dimers, rings, and chains, which requires accurate force fields and advanced biasing schemes in MC simulations, and association theories that can account for this effect.

Natural gas, synthesis gas, and flue gas typically contain a large number of impurities (e.g., acidic gases), which should be removed to avoid environmental and technological problems, and to meet customer specifications. One approach is to use physical solvents to remove the acidic gases. If no experimental data are available, the solubility data required for designing the sweetening process can be obtained from molecular simulations. Here, Monte Carlo (MC) simulations are used to compute the solubility of the gas molecules, i.e., carbonyl sulfide, carbon disulfide, sulfur dioxide, hydrogen sulfide, methyl mercaptan, carbon dioxide, and methane in the commercial solvents tetraethylene-glycol-dimethyl-ether (Selexol), n-methyl-2-pyrrolidone, propylene carbonate, methanol (Rectisol), and the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf₂N]). Henry coefficients of the gases in the investigated solvents are obtained from the computed solubilities. The ratio of Henry coefficients is used to compute ideal selectivities of the solvents. The solubilites and selectivities computed from MC simulations are compared with available experimental data. Some guidelines are provided to remove acidic gases using the investigated solvents. Rectisol is the best solvent for acid gas removal, but it should be used at low temperatures. Selexol and the ionic liquid have similar selectivity of sulfur compounds with respect to methane and may be used at elevated pressures and temperatures since both have low vapor pressures. The solubility of carbon disulfide, sulfur dioxide, and methyl mercaptan in these solvents is the highest. Hence, these components can be removed easily prior to hydrogen sulfide, carbonyl sulfide, and carbon dioxide in a pre-absorber.