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Cryogenic carbon capture removes CO2 and other pollutants from flue and waste stream gases produced from the combustion of fossil fuels such as coal, natural gas, and oil and the production of cement. A transient, 1-dimensional numerical model was developed to study the temperature profile within a counter-current surface CO2 desublimation-falling liquid or solid heat exchanger. Effects of desublimation heat and mass transfer as well as convective and conductive heat transfer relationships were taken into account. Experiments show that CO2 can be captured on a falling spherical particle when appropriate column operating conditions are met.

Anthropogenic emission of greenhouse gases has long been suspected to contribute to global warming and climate change. Most greenhouse gases are emitted in a mixture, so efficient methods and materials to separate and capture the gases are in demand in order to reduce emissions. A promising material group for this purpose is metal-organic frameworks (MOFs). This class of material have the ability to selectively adsorb green house gases due to its high porosity and high surface area. Zeolitic imidazolate frameworks (ZIFs) are a subclass of MOFs that are topologically similar to zeolites and are known for their good chemical and thermal stability.   The aim of this project was to investigate if the greenhouse gas (i.e. CO2 and SF6) capture performance of ZIFs could be improved and tuned using a mixed-linker approach with seven different imidazolate-based organic linkers of different sizes or with various functional groups. As well as to investigate the processability of MOFs using 3D printing. ZIFs composed of different ratios of 2-methylimidazolate as base linker and a second linker of imidazolate, benzimidazolate, 2-aminobenzimidazolate, 5,6-dimethylbenzimidazolate, and 4,5-dichloroimidazolate were succesfully made. The materials were all found to be crystalline, however, mixed-linker ZIFs containing 2-aminobenzimidazole, 5,6-dimethylbenzimidazole and dichloroimidazole were observed to contain more than a single phase. All samples showed to be somewhat porous towards CO2 and SF6, and there seem to be a trend where a low % of a bulkier linker (eg. bIm, ambIm) resulted in a higher uptake of SF6 whereas a high % resulted in a higher uptake of CO2. For dcIm it was the other way around, a low % showed a higher uptake for CO2  whereas a high % showed a higher uptake for SF6. For CO2, the ZIF containing 80% benzimidazolate showed the highest uptake of 9.81 wt%. For SF6, the 25% 4,5-dichloroimidazolate showed the highest uptake of 17.73 wt%. Furthermore, direct ink writing (DIW) 3D printing was also successfully utilized to process and structure a Mn-based MOF using carbopol as binder. The printed structure was found to have similar properties to the pristine MOF in regards to crystallinity and porosity.

Worldwide concern on reducing global warming consequences has motivated the development of power generation technologies to move towards renewable and sustainable energy. The process takes time and currently, a significant percentage of the world’s electricity systems are driven by fossil fuels. The transition phase from fossil fuel to renewable technology has allowed the combined cycle gas power plant to play an essential role in our global energy mix. This investigation aims to develop scenarios to improve its performance and reduce the carbon footprint during its operation. A baseline scenario of the natural gas combined cycle has been developed using Aspen Hysys software, and the simulation performance is validated with ASME PTC 4-4. The analytical validation results in a 1.13% difference in air and fuel flow rate of 642.95 kg/s compared with 650.28 kg/s as simulation input. Four scenarios are developed following the baseline scenario: seawater cooling and intercooling with LNG cold energy utilization, carbon capture, and hydrogen blending. Those scenarios are compared with three key performance indicators such as system efficiency (%), levelized cost of electricity (USD/MWh), and specific carbon dioxide emissions (gr-CO2/kWh). The analysis shows that sea water cooling with LNG cold energy achieves the highest efficiency of 56.46%, a 0.12% increase compared with the baseline scenario. Hydrogen blending with natural gas achieves the lowest LCOE and specific carbon dioxide footprint of 46.97 USD/MWh and 351.23 gr-CO2/kWh, respectively. The reduction of 12.58 kTon annual carbon dioxide is achieved by implementing 5% hydrogen blending by volume into the combined cycle power generation system. / Världsomfattande oro att minska konsekvenserna av den globala uppvärmningen har motiverat kraftgenereringsteknik att gå mot förnybar och hållbar energiutveckling. Processen tar tid och förnuvarande drivs en betydande andel av världens elsystem av fossila bränslen. Övergångsfasen från fossilt bränsle till förnybar teknik har gjort det möjligt för kombikraftverk att spela en viktig roll i vår globala energimix. Denna rapport syftar till att utveckla scenarier för att förbättra dess prestanda och minska koldioxidavtrycket under dess drift. Ett utgångsscenario för naturgasens kombinerade cykel har utvecklats med hjälp av Aspen Hysys programvara, och simuleringsprestandan är validerad med ASME PTC 4-4. Den analytiska valideringen resulterar i en skillnad på 1,13 % i luft- och bränsleflöde på 642,95 kg/s jämfört med 650,28 kg/s som simuleringsindata. Fyra scenarier utvecklas efter baslinjescenariot: havsvattenkylning och mellankylning med LNG kall energianvändning, kolavskiljning och väteblandning. Dessa scenarier jämförs med tre nyckeltal som systemeffektivitet (%), utjämnad kostnad för el (USD/MWh) och specifika koldioxidutsläpp (gr-CO2/kWh). Analysen visar att havsvattenkylning med LNG kall energi uppnår den största verkningsgraden på 56,46 %, en ökning med 0,12 % jämfört med utgångsscenariot. Vätgasblandning med naturgas uppnår lägsta LCOE och specifika koldioxidavtryck på 46,97 USD/MWh respektive 351,23 gr-CO2/kWh. Minskningen av 12,58 kTon årlig koldioxid uppnås genom att implementera 5 % vätgasblandning i volym i det kombinerade kraftgenereringssystemet.

The objective of this research was to determine an appropriate adsorbent for the separation of CH₄ from CO₂, N₂, and O₂. To screen different adsorbents for this purpose, pure component adsorption isotherms and gas mixture isotherms were measured. Adsorption isotherms are critical data for modeling adsorption processes. Thus, determining an accurate and reliable method of measuring gas adsorption isotherms is crucial. Concentration pulse chromatography can be used to measure the slope of the isotherm. In the case of pure component adsorption, the slope at different partial pressures of adsorbate can be integrated to determine the adsorption isotherm. The accuracy of the concentration pulse chromatography method was compared to that of gravimetric analysis to find an appropriate technique to obtain pure component gas adsorption isotherms by measuring CH₄ isotherms on activated carbon at 25°C and up to 6.3 atm. Isotherm results from concentration pulse chromatography were identical to gravimetric results, but the use of a sufficiently long column for concentration pulse chromatography was crucial. Afterwards, gravimetric analysis was used to determine the performance of activated carbon (AC A-C) and carbon molecular sieve (CMS A-D) adsorbents for adsorbing CO₂ and N₂. Additionally, O₂ adsorption isotherms were measured for CMS's. At 25°C and above atmospheric pressure, AC-B showed the highest CO₂ capacity and CO₂/N₂ selectivity. The isosteric heat of adsorption values of CO₂, N₂, and O₂ for the CMS's were calculated; CMS-A and CMS-C had high isosteric heat of adsorption values for CO₂, above 40 kJ mol⁻¹. Finally, the performance of activated carbon in separating a binary mixture of CO₂ and N₂ was experimentally measured by obtaining binary gas mixture adsorption isotherms using concentration pulse chromatography technique between 30-70°C and 1-5 atm total pressure. The OLC activated carbon showed selectivity for CO₂ over N₂, with the experimental results showing a slight deviation from theoretical predictions of the binary adsorption isotherms. Compared to other adsorbents in the literature, OLC had similar CO₂ and N₂ adsorption capacities but higher CO₂/N₂ selectivity.

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The present work deals with capture and storage of carbon dioxide from biogases by bond- ing to alkaline earth metals from power plant ashes. The aim is to achieve the feed-in standard in Germany for the natural gas grid by binding CO2 in a long-term stable and environmentally compatible manner. In addition, the ash quality is to be improved by reduced mobility of critical metals such as lead, zinc and cadmium, and calcium carbonate is to be recovered as a valuable material in addition to the biomethane. In several experimental setups from laboratory scale to pilot plant, it was shown that both carbon dioxide and hydrogen sulfide can be captured and stored in large quantities of ash residues. Both the use of a packed column to compensate for the poor absorption and reaction kinetics and the use of ammonium chloride as an extraction agent proved to be particularly effective for biogas upgrading to biomethane level. In contrast, both the absorption and reaction temperature, as well as gas-specific influencing factors such as carbon dioxide concentration and volume flow rate, had little to no influence. With regard to ash quality, an improvement of the landfill class from IV to 0 was achieved with respect to lead, from II to 0 for zinc and from III to I for cadmium. A significant improvement was also achieved for chlorine, but this did not result in a reduction of the landfill class. The ash quantity could be reduced by more than 50 %, among other things, by dissolving out the alkaline earth metals for the carbon dioxide reaction. As further research steps, it remains to further reduce the metal mobility with respect to the ash eluate in order to better optimize the process water quality. This could be achieved, for example, by a controlled pH value.